JP2549547B2 - How to make a planographic printing plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for making a lithographic printing plate, and more specifically, electrophotography on a photoconductor layer provided with an image portion on a conductive substrate. The present invention relates to a method of producing a lithographic printing plate which is a lithographic printing plate including a toner image formed by a process and which has been subjected to a washing step in which washing water is circulated and reused after removing a non-image portion.

[Conventional technology]

Today, as a lithographic offset printing plate, a positive type photosensitive agent mainly composed of a diazo compound and a phenol resin, and a PS plate using a negative type photosensitive agent mainly composed of an acrylic monomer or a prepolymer have been put to practical use. However, since all of these methods have low sensitivity, a silver halide photographic film master on which an image has been recorded in advance is subjected to close contact exposure for plate making. on the other hand,
Due to advances in computer image processing, large-capacity data storage, and data communication technology, in recent years, computer operations have been consistently performed from manuscript input, correction, editing, layout, and page grouping, and high-speed communication networks and satellite communications enable immediate remote access. An electronic editing system that can output to end plotters is in practical use. In particular, there is a high demand for electronic editing systems in the field of newspaper printing, where immediacy is required. Also, in fields where the originals are stored in the form of original films and the printing plates are duplicated as necessary, the originals are stored on these recording media with the development of ultra-high capacity recording media such as optical disks. It will be stored as digital data.

However, direct type printing plates, which directly produce printing plates from the output of the end plotter, have hardly been put into practical use, and even when the electronic editing system is in operation, the output is performed on silver halide photographic film and based on this. Indirectly PS
The actual situation is that a printing plate is produced by contact exposure to the plate. This is the output plotter light source (eg, He-Ne
Lasers, semiconductor lasers, etc.) makes it difficult to develop a direct type printing plate having a high sensitivity enough to make a printing plate in a practical time.

An electrophotographic photoreceptor is considered as a photoreceptor having high photosensitivity that can provide a direct printing plate.

Conventionally, printing plate materials using electrophotography (printing plate)
For example, JP-B-47-47610, JP-B-48-4002
No., JP-B-48-18325, JP-B-51-15766, JP-B-51
Zinc oxide-resin dispersion offset printing plate materials described in JP-25761-A and the like are known, which are made of a desensitizing solution (e.g., For example, it is used after wetting with an acidic aqueous solution having a ferrocyanide salt or a ferricyanate salt). The offset printing plate thus treated has a printing durability of about 5,000 to 10,000 sheets and is not suitable for printing more than this, and if the composition is suitable for desensitization, the electrostatic characteristics deteriorate. In addition, there are drawbacks such as deterioration of image quality. It also has the drawback of using a harmful cyanide compound as a desensitizing solution.

JP-B-37-17162, JP-B-38-7758, JP-B-46-3
No. 9405, JP-B No. 52-2437, etc., an organic photoconductor-resin printing plate material includes, for example, a photoconductive material obtained by binding an oxazole or oxadiazole compound with a styrene-maleic anhydride copolymer. Electrophotographic photoreceptor with an electrically conductive insulating layer provided on a grained aluminum plate is used. After forming a toner image on the photoreceptor by electrophotography, the non-image part is dissolved and removed with an alkaline organic solvent and printed. A plate is formed.

JP-A-57-147656 discloses an electrophotographic photosensitive member containing a hydrazone compound and barbituric acid or thiobarbituric acid. In addition,
59-147335, JP-A-59-152456, JP-A-59-168462
And a dye-sensitized electrophotographic photosensitive member described in JP-A-58-145495 and the like.

When making a lithographic printing plate using these electrophotographic photoreceptors, after forming a toner image by an electrophotographic process and removing the non-image area (etching treatment), it is usually washed with a large amount of running water, A method of treating with a rinse liquid containing a surfactant and the like and treating with a plate surface protective agent (so-called gumming) is generally used. However, it is not only costly to use a large amount of rinsing water, but since such rinsing water contains harmful components such as an etching solution composition and a synthetic resin eluted from the lithographic printing plate,
There are many problems such as strong concern about environmental pollution due to wastewater.

Therefore, a treatment method in which such a washing step is omitted can be considered.

However, when the rinse treatment and the gumming treatment are immediately performed without passing through the water washing step after the development, the rinse liquid and the gum liquid gradually become fatigued as the number of processed printing plates increases. The term fatigue used here is brought into the rinse liquid and gum liquid by the printing plate that is treated with the etching liquid component in the etching liquid, the dissolved resin component, the atmospheric component, the etching replenishing liquid, the defoaming agent, etc. This indicates that the processing capacity of the processing liquid is reduced due to the decrease in the amount. Exhaustion of rinse liquid or gum liquid Exceeding a certain limit may cause stains during printing, or may cause an unexpected trouble such as poor ink deposition on the image area.

In such a case, a new etching liquid, a new rinse liquid or a gum liquid is usually added to the processing device in order to prevent the loss of the printing plate, the printing paper or the fatigue generated due to the fatigue of the rinse liquid or the gum liquid as described above. A method to calculate the number of processed printing plates, processing area, etc. from the time of preparation, and update the etching solution etc. when the value reaches a certain numerical value or from the period from the time of preparation Can be taken.
However, as described above, since the rinse liquid and the gum liquid in the treatment method without washing with water cause fatigue rapidly,
It has been found that the service life is short, and therefore the treatment liquid needs to be frequently updated, the amount of the fatigue waste liquid and the new liquid to be prepared increases, the labor is remarkably consumed, and stable treatment cannot be performed for a long time.

On the other hand, there is a method of rinsing with rinsing water repeatedly used after the etching treatment, and after the circulating water rinsing step, the treatment with the above-mentioned rinsing liquid or gum liquid can be performed.

However, in the above-mentioned method, when the washing water is relatively new, that is, when the pH is about 10 or less, the etching solution containing the elution component of the photosensitive layer is brought into the washing water to remove the undesirable components for removing the photosensitive layer. This produces precipitates and insoluble silicate chlorides, which adhere to the non-image areas of the printing plate,
It has been found that there is a drawback that the printed matter is stained.
Furthermore, since the pH of the etching solution is high, the pH of the washing water used repeatedly increases rapidly, and as a result, the above-mentioned various problems resulting from fatigue of the processing solution cannot be sufficiently solved.

[Problems to be solved by the invention] Therefore, the object of the present invention, in the first washing bath after etching, there is no generation of insoluble matter by bringing in the etching solution, the amount of washing water is small, and the life of circulating washing water The object of the present invention is to provide a method for making an electrophotographic lithographic printing plate which has been prolonged.

[Means for solving the problem]

The above-mentioned object of the present invention is to remove a non-image part (etching) in a lithographic printing plate comprising a toner image formed by an electrophotographic process on a photoconductor layer having an image part provided on a conductive substrate. , (A) Adjust the pH of the first washing bath after etching to 11.0 to 12.5, (b) circulate and reuse at least part of the washing water, and (c) This is achieved by replenishing the washing treatment step with an amount of water corresponding to the amount and discharging the overflowing washing water from the washing treatment step to adjust the pH of the washing bath within the above range.

The automatic developing machine used in the present invention is preferably of a type that conveys a photosensitive printing plate and has an electrophotographic process zone, an etching zone, a water washing zone, a rinse zone, a gas coating zone and a drying zone.

In the present invention, the first washing bath after etching is
In the washing bath after forming the image portion by the toner image by the electrophotographic process and then removing the non-image portion (etching treatment), the first washing bath after the etching treatment when there are a plurality of washing baths, and thus the first bath Means

In the present invention, in order to maintain the pH of the first washing bath within the above range, at the start of the treatment, the pH is adjusted to 11.0 to 12.5 by adding alkaline components of the etching solution or etching solution to fresh water, such as sodium hydroxide. It needs to be adjusted. For example, about 100 ml of the etching liquid used for the etching treatment of a normal printing plate may be added to 1 fresh water. If this washing water is simply repeatedly used for circulation, the pH of the washing water will be
Since the pH value rises and exceeds pH 13, the amount of fresh water corresponding to the amount of etching solution brought in is replenished, and the amount of water corresponding to this replenishment amount is discharged by, for example, overflow. Thereby, according to the present invention, the washing water is recirculated and the pH of the first washing bath after etching is set to 11.0 to
Can be adjusted to 12.5.

Further, the rinsing water to be circulated and used is a water which has been used for rinsing at least once at least once in total or almost all because it is continuously circulated for use. Therefore, as described above, the inconveniences such as the rise of pH and contamination due to the bringing in of the etching solution or the like occur, but these can be prevented by the method of replenishing fresh water of the present invention. This replenishment amount is determined depending on the amount of the printing plate processed, particularly the area thereof, and is preferably 3 to 300 cc, and more preferably 10 to 100 cc per 1 m ^{2 of} the printing plate area. Further, this replenishment can be performed by the area detection signal of the printing plate to be processed, or naturally, the replenishment can be made based on the determination of the replenishment amount. Further, as the water washing method as described above, a method of immersing the printing plate in a water washing tank, a method of spraying a large number of nozzles with washing water, a method of applying and cleaning with a roller, and the like are possible. Since the purpose is to remove the remaining adhering etching liquid, it is preferable to carry out the water washing in a state where the flow velocity of the water for washing is increased, as in the method of spraying from a large number of nozzles. The flow rate of the rinsing water is appropriately determined depending on the number of nozzles and the processing state of the printing plate. The used washing water is returned to the washing tank, circulated again by a generally known circulation pump or the like, and repeatedly used for washing. It is also possible to carry out such washing with water continuously in two or more tanks which are substantially separated and in multiple stages. For example, rinsing may be performed using two or more rinsing baths connected so that the rinsing water is sequentially overflowed from the subsequent rinsing bath to the rinsing bath of the previous bath. In this case, fresh water may be replenished in the final washing bath, the washing water may be overflowed to the preceding bath successively, and the washing water may be discharged from the first washing bath after etching, for example, by overflow. Furthermore, it is also possible to use a method of purifying the circulating water by a conventionally known solid-state filtering device or a device for separating charged substances.

The electrophotographic plate-making printing plate used in the present invention can be prepared by a known process using the electrophotographic photoreceptor described below. That is, it is charged substantially uniformly in the dark,
An electrostatic latent image is formed by image exposure. Examples of the exposure method include scanning exposure using a semiconductor laser, He—Ne laser, or the like, reflection image exposure using a xenon lamp, tungsten lamp, fluorescent lamp, or the like as a light source, contact exposure through a transparent positive film, and the like. Next, the electrostatic latent image is developed with toner. As the developing method, conventionally known methods, for example, various methods such as cascade development, magnetic brush development, powder cloud development, and liquid development can be used. Among them, liquid development is capable of forming a fine image and is suitable for making a printing plate. The formed toner image can be fixed by a known fixing method, for example, heat fixing, pressure fixing, solvent fixing and the like. A printing plate can be prepared by causing the toner image thus formed to act as a resist and removing the photoconductive layer in the non-image area with an etching solution.

As the etching liquid for removing the photoconductive insulating layer in the non-image area after toner image formation, any solvent can be used as long as it can remove the photoconductive insulating layer, and is not particularly limited. The etching solution to which the plate making method of the present invention can be preferably applied is an alkaline solvent. As used herein, the alkaline solvent is an aqueous solution containing an alkaline compound, an organic solvent containing an alkaline compound, or a mixture of an aqueous solution containing an alkaline compound and an organic solvent. Examples of the alkaline compound include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, sodium phosphate, potassium phosphate, ammonia, and monoethanolamine, diethanolamine, and triethanolamine. Examples thereof include organic and inorganic arbitrary alkaline compounds such as amino alcohols such as ethanolamine, but silicates are preferable. The amount of silicate in the etching solution is generally about 1-10% by weight, more preferably 1-8% by weight, most preferably 2-6% by weight, based on the total weight of the etching solution.
Is. As described above, water or many organic solvents can be used as a solvent for the etching solution, but an etching solution mainly containing water is preferably used from the viewpoint of odor and pollution. If necessary, various organic solvents can be added to the etching solution mainly containing water.
Preferred organic solvents include methanol, ethanol,
Lower alcohols such as propanol, butanol, benzyl alcohol, phenethyl alcohol and aromatic alcohols and ethylene glycol, diethylene glycol,
Examples thereof include triethylene glycol, polyethylene glycol, cellosolves, and amino alcohols such as monoethanolamine, diethanolamine and triethanolamine. Further, a solution containing a surfactant, an antifoaming agent, and other various additives as necessary is used as the etching solution.

As a method of removing the non-image portion of the printing plate on which the toner image is formed with the above-mentioned etching liquid, various conventionally known methods can be used. Specifically, a method of immersing a printing plate on which a toner image is formed in an etching solution, a method of ejecting the etching solution from a large number of nozzles to the photosensitive layer of the printing plate, and a sponge wet with the etching solution are used. Examples thereof include a method of wiping the photosensitive layer of the printing plate and a method of roller-coating the surface of the photosensitive layer of the printing plate with an etching solution. Further, after applying the etching solution to the photosensitive layer of the printing plate in this manner, the surface of the photosensitive layer can be lightly rubbed with a brush or the like. The etching treatment conditions can be appropriately selected according to the above treatment method. As an example, for the treatment method by immersion, for example, a method of immersing in an etching solution at about 10 to 35 ° C. for about 5 to 80 seconds is selected. As described above, the lithographic printing plate obtained by subjecting the printing plate to image exposure, development, fixing, and further etching treatment by an electrophotographic process and then washing with water is treated with a rinse liquid or a gas liquid containing a surfactant.

As the surfactant contained in such a rinse liquid,
Polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan aliphatic partial esters, pentaerythritol fatty acid partial esters , Propylene glycol monofatty acid ester, sucrose fatty acid partial ester, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester, polyethylene glycol fatty acid ester, polyglycerin fatty acid partial ester, polyoxyethylenated castor oil , Polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides,
Nonionic surfactants such as N, N-bis-2-hydroxyalkylamines, polyoxyethylenealkylamines, triethanolamine fatty acid esters, trialkylamine oxides, fatty acid salts, abietic acid salts, hydroxyerkane sulfonic acid salts , Alkane sulfonates, dialkyl sulfosuccinate salts, linear alkyl benzene sulfonates, branched chain alkyl benzene sulfonates, alkyl naphthalene sulfonates,
Alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkylsulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salts, N-alkylsulfosuccinic acid monoamide disodium salts, petroleum sulfonates, sulfated castor oil,
Sulfated cattle foot oil, fatty acid alkyl ester sulfate ester salts, alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, fatty acid monoglyceride sulfate ester salts, polyoxyethylene alkylphenyl ether sulfate ester salts, polyoxyethylene styryl phenyl ether Sulfate ester salts, alkyl phosphate ester salts, polyoxyethylene alkyl ether phosphate ester salts, polyoxyethylene alkylphenyl ether phosphate ester salts, partially saponified styrene-maleic anhydride copolymers, olefin-maleic anhydride Partial saponification products of copolymers, anionic surfactants such as naphthalene sulfonate formalin condensates, alkylamine salts, quaternary ammonium salts,
Examples thereof include cationic surfactants such as polyoxyethylene alkylamine salts and polyethylene polyamine derivatives, and amphoteric surfactants such as carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfates and imidazolines. Among the above-mentioned surfactants, those with polyoxyethylene can be read as polyoxyalkylenes such as polyoxymethylene, polyoxypropylene, and polyoxybutylene, and those surfactants are also included. The same applies to the description of.

The above-mentioned surfactants can be used alone or in combination of two or more, and about 0.001% by weight in an aqueous solution.
To about 10% by weight, more preferably 0.01% to 5% by weight.

The pH of the rinse liquid, that is, the aqueous solution containing a surfactant in the present invention is preferably 1 to 12. In order to adjust the aqueous solution to this pH, it is preferable to include either or both of an acid and a water-soluble salt as a buffer. As a result, when the aqueous solution is applied to the planographic printing plate, the etching liquid component remaining on the plate is neutralized, and the non-image area becomes more hydrophilic. For details of the buffer, see, for example, "Chemical Handbook Basic Edition".
II ”edited by The Chemical Society of Japan, 5th edition, February 20, 1972, published by Maruzen Co., Ltd., pages 1312 to 1320, and these can be applied as they are. Suitable acids and water-soluble salts include inorganic acids such as molybdic acid, boric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, acetic acid, oxalic acid, tartaric acid, benzoic acid, succinic acid, citric acid, malic acid, lactic acid, p-lactic acid. -Acids such as water-soluble organic acids such as toluenesulfonic acid and salts thereof.
More preferred salts are water-soluble alkali metal salts and ammonium salts, and particularly preferred are molybdate salts such as ammonium monobudenate, phosphate salts such as sodium phosphate, potassium tetrapolyphosphate, polyphosphate salts such as sodium trimetaphosphate, sodium oxalate. Such as oxalate salt, tartrate salt such as potassium tartrate, succinate salt such as sodium succinate, and citrate salt such as ammonium citrate. These acids and water-soluble salts can be used alone or in combination of two or more.

The more preferable pH of the rinse liquid is 2-8. The most preferable pH is 2.5 to 7.5, and in this case, the desensitizing performance of the non-image area of the lithographic printing plate is higher. Further, in the plate-making method according to the present invention, since the etching solution component is brought into the aqueous solution, in order to neutralize the solution, an amount of salt and / or acid corresponding to the intended processing area of the printing plate is previously contained. It is preferable to set. The addition amount of the acid and the salt contained in the aqueous solution is not particularly limited, but the total amount of the acid and the salt is preferably about 10% by weight or less based on the total weight of the aqueous solution. It is more preferably used in the range of 0.01 to 6% by weight.

The rinsing solution in the present invention may further contain preservatives such as sorbic acid and p-oxybenzoic acid ester, antifungal agents, propyl gallate, 2,6-di-t-butyl-4-ethylphenol, 2,6-diphenol. An antioxidant such as -t-butyl-4-methylphenol may be included. By adding a small amount of these preservatives, antifungal agents, and antioxidants as preservatives, it is possible to prevent alteration of the aqueous solution due to storage, and the preferable addition amount is 0.001 to 5% by weight.
Is.

It is preferable that the rinse liquid in the present invention contains a lipophilic substance. As a result, not only the image area of the planographic printing plate becomes more oil-sensitive and development ink buildup becomes easier, but also after treatment with the aqueous solution,
When the plate surface protective agent treatment is carried out, it is possible to strongly suppress deterioration of the oil sensitivity of the image area. Preferred lipophilic substances include
For example, organic carboxylic acids having 5 to 25 carbon atoms such as oleic acid, lauric acid, valeric acid, nonyl acid, capric acid, myristic acid, palmitic acid, and castor oil are included. These lipophilic substances can be used alone or in combination of two or more. The lipophilic substance contained in the rinse liquid of the present invention is in the range of 0.005% by weight to about 10% by weight, more preferably 0.05 to 5% by weight, based on the total weight of the lipophilic substance.

In the present invention, it is preferable to squeegee so that the amount of the etching liquid on the surface of the lithographic printing plate after etching and washing with water and the amount of washing water used repeatedly are minimized. This is because the squeegee of the lithographic printing plate is squeegeeed to reduce the amount of the rinsing liquid, and the squeegee of the rinsing liquid is squeegeeed to reduce the amount of the washing water on the plate. This is because the contamination is prevented as much as possible, and the treatment capacity of the wash water and the rinse solution is increased. Therefore, the residual amount of the preferred etching solution and washing water on the lithographic printing plate after being squeegeeed is preferably 20 ml / m ² or less, more preferably 10 ml / m ² or less, and most preferably 5 ml / m ² or less. is there.

The treatment method with the rinse liquid can be various methods such as a dipping method similar to the washing method, a roller coating method, a method of spraying from a number of nozzles and spraying onto a lithographic printing plate or a roller, but the rinse solution is repeatedly used. By using it, it becomes possible to greatly reduce the amount of the rinse liquid used per printing plate to be subjected to the plate making process.

The replenishment of the rinsing liquid is carried out in the same manner as the replenishment of washing water according to the treatment amount of the lithographic printing plate, preferably the treated area.
It is preferably carried out in the range of 1 to 400 cc for 1 m ² .

The gum solution also contains a polymer compound, a lipophilic substance, a surfactant and water.

Natural polymers include starches such as cane starch, potato starch, tapioca starch, wheat starch, and corn starch, those obtained from algae such as carrageenan, laminaran, sea soup mannan, fungus, Irish moss, agar, and sodium alginate, Troloois. , Mannan, quince seed, pectin, tragacanth gum, karaya gum, xanthine gum, guar bingham, locust bingham, gum arabic, carob gum and benzoin gum, and other vegetable mucilages, dextran,
Examples include microbial mucilages such as homopolysaccharides such as glucan and levan, and heteropolysaccharides such as succinoglucan and xanthan gum, and proteins such as glue, gelatin, casein and collagen. Semi-natural products (semi-synthetic products) include propylene glycol alginate, viscose, methyl cellulose, ethyl cellulose, methyl ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl ethyl cellulose and hydroxypropyl methyl cellulose phthalate. And the like, as well as processed starch and the like. Processed starch includes white dextrin, yellow dextrin and British gum, and other baked starch, enzyme-modified dextrin such as enzyme dextrin and Schardinger dextrin, acid-decomposed starch such as solubilized starch, oxidized starch such as dialdehyde starch, and modified starch. Alpha starch such as alpha starch and non-denatured alpha starch,
Esterified starch such as starch phosphate, fatty starch, starch sulfate, starch nitrate, starch xanthate and starch carbamic acid, carboxyalkyl starch, hydroxyalkyl starch, sulfoalkyl starch, cyanoethyl starch, allyl starch,
Etherified starch such as benzyl starch, carbamyl ethyl starch and dialkylamino starch, methylol cross-linked starch, hydroxyalkyl cross-linked starch, cross-linked starch of phosphoric acid cross-linked starch and dicarboxylic acid cross-linked starch, starch polyacrylamide copolymer, starch polyacrylic acid Copolymer, Starch Polyvinyl Acetate Copolymer, Starch Polyacrylonitrile Copolymer, Cationic Starch Polyacrylic Ester Copolymer, Cationic Starch Vinyl Polymer Copolymer, Starch Polystyrene Maleic Acid Copolymer and Starch Examples thereof include starch graft copolymers such as polyethylene oxide copolymers. Synthetic products include polyvinyl alcohol other than partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, modified polyvinyl alcohol such as polyvinyl methyl ether, polyvinyl ethyl ether and polyvinyl isobutyl ether, sodium polyacrylate, partially saponified polyacrylate ester, poly Acrylic ester copolymer partially saponified,
Polyacrylic acid derivatives and polymethacrylic acid derivatives such as polymethacrylic acid salts and polyacrylic amides,
Examples thereof include polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, a copolymer of vinylpyrrolidone and vinyl acetate, a carboxyvinyl polymer, a styrene maleic acid copolymer, a styrene crotonic acid copolymer. Of these, those obtained from algae,
Vegetable mucilages, fibrin derivatives, modified starches, propylene glycol alginates and synthetic products are preferably used because they have good film forming properties on printing plates. Examples of lipophilic substances include plasticizers, fatty agents, fatty oils, monohydric alcohols and waxes, as well as lipophilic resins used as vehicles for lithographic printing inks. Preferred lipophilic resins include novolac type phenol resins such as phenol formaldehyde resin, cresol formaldehyde resin and t-butylphenol formaldehyde resin, xylene resins obtained by condensing phenol and xylene with formaldehyde, resins obtained by condensing phenol and mesitylene with formaldehyde. , Polyhydroxystyrene, brominated polyhydroxystyrene, cashew resin, partial esterification product of copolymer of styrene and maleic anhydride, melamine resin, alkyd resin, polyester resin, epoxy resin, rosin, hydrogenated rosin and rosin ester, etc. Examples include petroleum resins such as modified rosin and gilsonite.

Preferred plasticizers include, for example, dibutyl phthalate, di-
n-octyl phthalate, di- (2-ethylhexyl)
Phthalates such as phthalate, dinonyl phthalate, didecyl phthalate, dilauryl phthalate, butylbenzyl phthalate, etc., such as dioctyl azelate, dioctyl adipate, dibutyl glycol adipate, dibutyl sebacate, di- (2-ethylhexyl) sebacate, dioctyl. Aliphatic dibasic acid esters such as sebacate, for example epoxidized triglycerides such as epoxidized soybean oil, for example tricresyl phosphate, trioctyl phosphate, phosphoric acid esters such as trischloroethyl phosphate, for example benzoic acid. Benzoic acid esters such as benzyl are included.
Preferred fatty acids include caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecyl acid, palmitic acid, heptadecyl acid, stearic acid, nonadecanoic acid, arachidic acid, Behenic acid, lignoceric acid,
Cerotic acid, heptacosanoic acid, montanic acid, melissic acid, laxeric acid, saturated fatty acids such as isovaleric acid and acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetrainic acid, erucic acid, brassic acid, There are unsaturated fatty acids such as sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearolic acid, sardonic acid, tariphosphoric acid and licanoic acid. Monohydric alcohols are classified into aliphatic saturated monohydric alcohols, aliphatic unsaturated monohydric alcohols, aromatic alcohols, alicyclic alcohols, heterocyclic alcohols and the like. The monohydric alcohol may have a substituent, and examples of the substituent include a halogen atom such as chlorine and bromine, an alkoxy group such as methoxy and propoxy, and an aryloxy group such as phenoxy.

The gum solution used in the present invention can be produced in any manner such as an emulsion type gum solution, a suspension type gum solution, a non-emulsion type non-suspension type gum solution, etc. by appropriately selecting a surfactant to be contained, a lipophilic substance, etc. However, the emulsion type gum solution and the suspension type gum solution are preferably used because of their high ability to prevent deterioration of the oil sensitivity of the image area of the lithographic printing plate. Further, the emulsion type gum liquid is preferable because it can strongly suppress the generation of suspensions and generate less insoluble matter in the plate-making method according to the present invention.

The method of treating with a gum solution is various, such as a dipping method similar to the cleaning method, a method of applying with a roller, a method of spraying from a number of nozzles and spraying onto a lithographic printing plate or a roller, and the like. By repeatedly using it, it is possible to greatly reduce the amount of gum solution used per printing plate to be subjected to plate making. The amount used in the processing method of supplying the plate surface protective agent onto the lithographic printing plate is preferably 0.1 / min or more and 40 / min or less. More preferably 3 to 20
/ Min. In addition, a method of processing with increased agitation on a lithographic printing plate, such as a method of spraying from a number of nozzles, has the advantage that the residue adhering to the lithographic printing plate can be washed with a gum solution, It is more preferable because the liquid can be made uniform.

The replenishment of the gum solution is performed in the same manner as the replenishment of the rinse solution according to the processing amount of the planographic printing plate, preferably the processing area.
It is preferably carried out in the range of 1 to 400 cc for 1 m ² .

 The present invention will be described in more detail.

As the conductive substrate used in the electrophotographic photoreceptor, a plastic sheet having a conductive surface or paper made especially solvent-impermeable and conductive, an aluminum plate, a zinc plate, or a copper-aluminum plate, a copper-stainless plate, A conductive substrate having a hydrophilic surface such as a bimetal plate such as a chromium-copper plate, or a trimetal plate such as a chromium-copper-aluminum plate, a chromium-lead-iron plate, or a chromium-copper-stainless plate is used. Is preferably from 0.1 to 3 mm, particularly preferably from 0.1 to 0.5 mm. Among these substrates, the aluminum plate is preferably used. The aluminum plate used in the present invention is a plate-like body such as pure aluminum containing aluminum as a main component or an aluminum alloy containing a trace amount of heteroatoms, and its composition is not specified, and a publicly known and publicly used material is appropriately used. You can do it.

This aluminum plate can be used by graining and anodizing by a known method. Prior to the graining treatment, a degreasing treatment with a surfactant or an alkaline aqueous solution is carried out, if desired, in order to remove the rolling fingers on the surface of the aluminum plate, and the graining treatment is carried out. The graining method includes a method of mechanically roughening the surface, a method of electrochemically dissolving the surface, and a method of chemically selectively dissolving the surface. As a method for mechanically roughening the surface, a known method called a ball polishing method, a brush polishing method, a blast polishing method, a buff polishing method or the like can be used. Further, as an electrochemical surface roughening method, there is a method of carrying out alternating current or direct current in a hydrochloric acid or nitric acid electrolytic solution. Further, as disclosed in JP-A-54-63,902, a method of combining the two can be used.

The aluminum plate thus roughened is subjected to an alkali etching treatment and a neutralization treatment as necessary.

The aluminum plate thus treated is anodized. Sulfuric acid, phosphoric acid, oxalic acid, chromic acid, or a mixed acid thereof is used as the electrolyte used in the anodizing treatment, and the electrolyte and the concentration thereof are appropriately determined depending on the kind of the electrolyte. The treatment conditions for anodic oxidation vary depending on the electrolyte used, and therefore cannot be specified unconditionally, but generally, the electrolyte concentration is 1 to 80 wt% solution, and the liquid temperature is 5 to 70%.
℃, current density 5-60A / dm ² , voltage 1-100V, electrolysis time 10
It is suitable if it is in the range of seconds to 50 minutes. The amount of anodized film is
Although 0.1 to 10 g / m ² is official, more preferably 1 to 6 g / m ²
Range.

By providing a known electrophotographic photosensitive layer (photoconductive layer) on the conductive substrate thus obtained, an electrophotographic photosensitive member can be obtained.

Many conventionally known organic or inorganic compounds can be used as the photoconductive material used for the photoconductive layer. For example, as the known dispersible photoelectric material, inorganic photoconductive materials such as selenium, selenium-tellurium, cadmium sulfide and zinc oxide can be cited. Also,
Examples of the organic photoconductive compound include 1) triazole derivatives described in US Pat. No. 3,112,197, 2) oxadiazole derivatives described in US Pat. No. 3,189,447, and 3) JP-B-37. Imidazole derivatives described in, for example, JP-A-16,096, 4) U.S. Pat. Nos. 3,615,402, 3,820,989, and 3,542,54
No. 4, Japanese Patent Publication No. 45-555, No. 51-10, 983, JP-A-51-9
3,224, 55-108,667, 55-156953, 56-3
6,656, polyarylalkane derivatives described in gazettes, etc. 5) U.S. Patent Nos. 3,180,729 and 4,278,746;
-88,064, 55-88,065, 49-105,537, 55
-51,086, 56-80,051, 56-88,141, 57-
No. 45,545, No. 54-112,637, No. 57-74,546,
Pyrazoline derivatives and pyrazolone derivatives described in gazettes, etc. 6) U.S. Pat. No. 3,615,404, JP-B Nos. 51-10,105 and 4
6-3,712, 47-28,336, JP-A-54-83,435,
54-110,836, 54-119,925, phenylenediamine derivatives described in publications, 7) U.S. Pat. Nos. 3,567,450, 3,180,703, 3,240,
Nos. 597, 3,658,520, 4,232,103, 4,175,961
No. 4,012,376, West German Patent (DAS) 1,110,518,
JP-B-49-35,702, JP-B-39-27,577, JP-A-55-144,
250, 56-119, 132, 56-22, 437, arylamine derivatives described in gazettes, 8) amino-substituted chalcone derivatives described in U.S. Pat. No. 3,526,501, 9) U.S. Pat. No. 3,542,546 N, N-bicarbazyl derivative described in, for example, 10) Uxazole derivative described in U.S. Pat. No. 3,257,203, 11) Styrylanthracene derivative described in JP-A-56-46,234, 12) Fluorene derivatives described in JP-A-54-110,837, 13) U.S. Pat.No. 3,717,462, JP-A-54-59,143 (corresponding to U.S. Pat.No.4,150,987), 55-52,063, 55
-52,064, 55-46,760, 55-85,495, 57-
No. 11,350, No. 57-148,749, No. 57-104,144,
Hydrazone derivatives described in gazettes, etc. 14) U.S. Pat. Nos. 4,047,948, 4,047,949, 4,265,
No. 990, No. 4,273,846, No. 4,299,897, No. 4,306,008 and other benzidine derivatives, 15) JP-A-58-190,953, No. 59-95,540, No. 59-97,14
No. 8, No. 59-195,658, No. 62-36,674 and the like include stilbene derivatives and the like.

In addition to the low molecular weight photoconductive compound as described above, the following high molecular compounds can also be used.

16) Polyvinylcarbazole and its derivatives described in JP-B-34-10966, 17) Polyvinylbylene, polyvinylanthracene, poly-2-, described in JP-B-43-18,674 and JP-B-43-19192
Vinyl-4- (4'-dimethylaminophenyl) -5-
Vinyl polymers such as phenyloxazole and poly-3-vinyl-N-ethylcarbazole, 18) Polymers such as polyacenaphthylene, polyindene, and copolymers of acenaphthylene and styrene described in JP-B-43-19193. ) Condensation resins such as pyrene-formaldehyde resin, prompyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin described in JP-B-56-13940, 20) JP-A-56-90,883, 56-161,550 Various pigments, dyes and the like can be used for the purpose of improving the sensitivity of the photoconductor and providing a desired photosensitive wavelength range. Examples of these are: 1) U.S. Pat. Nos. 4,436,800 and 4,439,506;
-37543, 58-123,541, 58-192,042, 58
-219,263, 59-78,356, 60-179,746, 61
-148,453, 61-238,063, JP-B-60-55941,
Monoazo, bisazo, trisazo pigments described in 60-45,664 and the like 2) Phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine described in U.S. Pat. Nos. 3,397,086 and 4,666,802 3) Described in U.S. Pat. No. 3,371,884 4) Indigo and thioindigo derivatives described in British Patent No. 2,237,680, etc. 5) Quinacridone pigments described in British Patent No. 2,237,679, etc. 6) British Patent No. 2,237,678, JP-A-59-184,348, and the same
Polycyclic quinone pigments described in 62-28,738 and the like 7) Bisbenzimidazole pigments described in JP-A-47-30,331 and 8) Squarium salt pigments described in U.S. Pat. Nos. 4,396,610 and 4,644,082 9) Azurenium salt-based pigments described in JP-A Nos. 59-53,850 and 61-212,542, etc. Further, as a sensitizing dye, "sensitizer", page 125, Kodansha (1
987), "electrophotographic" 12 9 (1973), "Synthetic Organic Chemistry" 24 No.11 1010 (1966) can be used known compounds described in, and the like. For example, 10) U.S. Pat.Nos. 3,141,770, 4,283,475, Japanese Patent Publication No. 48-25,658 and Japanese Patent Laid-Open No. 62-71,965, etc. 11) Applied Optics Supplement 3 50 (1969, JP Sho 5
0-39,548, etc. triarylmethane dyes 12) U.S. Pat. No. 3,597,196, etc., cyanine dyes 13) JP-A-60-163,047, 59-164,588, 60-25
Styryl dyes described in 2,517, etc. These organic photoconductive materials may be used alone or in combination of two or more.

In the photoconductive layer of the present invention, for the purpose of improving sensitivity,
For example, electron-withdrawing compounds such as trinitrofluorenone, chloranil, and tetracyanoethylene;
39, 58-102,239, 58-129,439, 62-71,9
No. 65 and the like.

In a photoreceptor for electrophotographic plate making, the photoconductive compound itself may have a film property, but when the photoconductive compound does not have a film property, a binding resin can be used.
As the binding resin, a resin known in the field of electrophotography can be used. In order to make a printing plate using a photoconductor for electrophotographic plate making, it is necessary to finally remove the photoconductive layer in the non-image area. Since it is determined by the relative relationship between the image and the etching liquid, such as the resist property, it cannot be generally stated. As the binding resin,
A polymer compound that is soluble or dispersible in the above-mentioned etching solution is preferable.

Specifically, for example, a copolymer of styrene and maleic anhydride, a copolymer of styrene and monoalkyl maleic anhydride, a copolymer of methacrylic acid / methacrylic acid ester, and a copolymer of styrene / methacrylic acid / methacrylic acid ester Copolymer, acrylic acid / methacrylic acid ester copolymer, styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate / crotonic acid copolymer, vinyl acetate /
Acrylic acid such as crotonic acid / methacrylic acid ester copolymer, methacrylic acid ester, styrene, vinyl acetate, etc. and acrylic acid, methacrylic acid, itaconic acid,
Crotonic acid, maleic acid, maleic anhydride, copolymers with carboxylic acid-containing monomers such as fumaric acid or acid anhydride group-containing monomers and methacrylamide, vinylpyrrolidone, phenolic hydroxyl groups, sulfonic acid groups, sulfonamide groups, A copolymer containing a monomer having a sulfonimide group, a phenol resin, a partially saponified vinyl acetate resin,
Examples thereof include vinyl acetal resins such as xylene resin and polyvinyl butyral.

A copolymer containing a monomer having an acid anhydride group or a carboxylic acid group as a copolymerization component, and a phenol resin have high charge retention of the photoconductive layer when used as a photoconductor for electrophotographic plate making, and have good results. Can be used.

As a copolymer containing a monomer having an acid anhydride group as a copolymer component, a copolymer of styrene and maleic anhydride is preferable. Further, a half ester of this copolymer can also be used. As a copolymer containing a monomer having a carboxylic acid group as a copolymerization component, there is a binary copolymer of acrylic acid or methacrylic acid and an alkyl ester, an aryl ester or an aralkyl ester of acrylic acid or methacrylic acid. preferable. Also preferred are vinyl acetate and crotonic acid copolymers, and terpolymers of vinyl acetate and vinyl esters of carboxylic acids having 2 to 18 carbon atoms and crotonic acid. A particularly preferred phenol resin is a novolak resin obtained by condensing phenol, o-cresol, m-cresol or p-cresol with formaldehyde or acetaldehyde under acidic conditions. The binding resins may be used alone or in combination of two or more.

When a photoconductive compound and a binding resin are used, the sensitivity is reduced when the content of the photoconductive compound is small, so that the photoconductive compound is at least 0.05 part by weight, more preferably at least 1 part by weight of the binding resin. It can be used in a range of 0.1 part by weight or more. Further, the thickness of the photoconductive layer is too thin to be charged with the electric charge necessary for development, and if it is too thick, a good image cannot be obtained due to etching in the plane direction called side etching during etching, 30μ, more preferably 0.5
Can be used at ~ 10μ.

The electrophotographic printing plate of the present invention can be obtained by applying a photoconductive layer on a conductive substrate according to a conventional method. In producing the photoconductive layer, a method of including the components constituting the photoconductive layer in the same layer, or a method of separately including two or more layers, for example, different charge carrier generating material and charge carrier transport material A method of separating the layers and using the layers is known, and any method can be used.
The coating solution is prepared by dissolving each component constituting the photoconductive layer in an appropriate solvent. When a component insoluble in the solvent such as a pigment is used, a dispersion machine such as a ball mill, a paint shaker, a dyno mill or an attritor is used. To be used after being dispersed in a particle size of 5 μ to 0.1 μ. The binder resin used in the photoconductive layer and the pigment such as other additives can be added during or after the dispersion. The coating liquid thus prepared is applied by rotation coating, blade coating, knife coating, reverse roll coating,
A known printing method such as dip coating, rod bar coating or spray coating can be applied onto the substrate and dried to obtain a printing plate for electrophotographic plate making. As a solvent for preparing the coating liquid,
Halogenated hydrocarbons such as dichloromethane, dichloroethane and chloroform, alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, glycol ethers such as ethylene glycol monomethyl ether and 2-methoxyethyl acetate, tetrahydrofuran and dioxane. And ethers such as, and esters such as ethyl acetate and butyl acetate.

For the purpose of improving the film physical properties such as the photoconductive compound, the bonding resin, the flexibility of the photoconductive layer, and the coated surface state,
If necessary, a plasticizer, a surfactant and other additives can be added. Examples of the plasticizer include biphenyl, biphenyl chloride, o-terphenyl, p-terphenyl,
Dibutyl phthalate, dimethyl glycol phthalate,
Dioctyl phthalate, triphenyl phosphoric acid and the like can be mentioned.

It is preferable that the toner forming the image portion contains a resin component having a resist property with respect to the etching liquid. Examples of the resin component include acrylic resins using methacrylic acid and methacrylic acid esters, vinyl acetate resins, copolymers of vinyl acetate and ethylene or vinyl chloride, vinyl chloride resins, vinylidene chloride resins, vinyl such as polyvinyl butyral. Acetal resins, polystyrene, copolymers of styrene and butadiene, methacrylic acid esters, etc., polyethylene, polypropylene and chlorinated products thereof, polyester resins (eg polyethylene terephthalate, polyethylene isophthalate, polycarbonate of bisphenol A), polyamide resins (eg , Polycipramide, polyhexamethylene adipamide, polyhexamethylene sebacamide), phenol resin, xylene resin, alkyd resin, vinyl modified alkyd resin, gelatin, carboxymethyi Cellulose ester derivatives such as cellulose, waxes, polyolefins, and the like waxes.

In the electrophotographic plate making photoreceptor used in the present invention,
Casein between the conductive substrate and the photoconductive layer if necessary,
Polyvinyl alcohol, ethyl cellulose, phenolic resin, styrene-maleic anhydride copolymer, polyacrylic acid, monoethanolamine, diethanolamine, trimethanolamine, tripropanolamine, triethanolamine and their hydrochlorides, oxalates, phosphates,
Monoaminomonocarboxylic acids such as aminoacetic acid and alanine;
Oxyamino acids such as serine, threonine and dihydroxyethylglycine; amino acids containing sulfur such as cysteine and cystine; monoaminodicarboxylic acids such as aspartic acid and glutamic acid; diaminomonocarboxylic acids such as lysine; Amino acids having an aromatic nucleus such as glycine, phenylalanine and anthranilic acid; amino acids having a heterocyclic ring such as tryptophan and proline;
Aliphatic aminosulfonic acids such as cyclohexylsulfamic acid; for example ethylenediaminetetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, hydroxyethyliminodiacetic acid, hydroxyethylethylenediaminetriacetic acid, ethylenediaminediacetic acid, cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid , (Poly) aminopolyacetic acid such as glycol ether diamine tetraacetic acid; and an intermediate layer in which some or all of the acid groups of these compounds are composed of sodium salt, potassium salt, ammonium salt, etc., for adhesion between the substrate and the photoconductive layer. Properties, the electrostatic properties of the photoconductive layer, the elution properties and / or the printing properties can be improved.

Also, if necessary on the photoconductive layer, the electrostatic properties of the photoconductive layer,
An overcoat layer which can be dissolved at the time of removing the photoconductive layer can be provided for the purpose of improving the developing characteristics at the time of toner development or the image characteristics. The overcoat layer may be a mechanically matted one or a resin layer containing a matting agent. Silicon dioxide as a matting agent,
Zinc oxide, titanium oxide, zirconium oxide, glass particles, alumina, starch, polymer particles (for example, particles of polymethylmethacrylate, polystyrene, phenol resin, etc.) and US Pat. No. 2,710,245, US Pat. No. 2,992,101. The matting agents described in 1. are included. These can be used in combination of two or more. The resin used for the resin layer containing the matting agent is appropriately selected depending on the combination with the etching solution used. Specifically, for example, gum arabic, glue, gelatin, casein, celluloses (for example, viscose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropinimethyl cellulose, carboxymethyl cellulose, etc.), starches (for example, soluble starch, Modified starch, etc.), polyvinyl alcohol, polyethylene oxide, polyacrylic acid, polyacrylamide, polyvinyl methyl ether, epoxy resin, phenol resin (particularly preferably novolac type phenol resin), polyamide, 1-vinylvinyl butyral and the like. These can be used in combination of two or more.

The preferred embodiments of the present invention are as follows.

(1) The method according to the claims, characterized in that a protective gum solution is applied after washing with water.

(2) The method according to the claims, characterized by treating with a rinse solution after washing with water.

(3) Claims characterized by supplementing with an amount of washing water corresponding to the treatment amount of the photosensitive lithographic printing plate and discharging an amount of washing water corresponding thereto or the above (1) to
The method according to any one of (2).

(4) Rinsing water is performed by two or more rinsing baths connected so that the rinsing water overflows sequentially from the subsequent rinsing bath to the preceding rinsing bath, and the rinsing water is circulated and reused in each rinsing bath. The method according to any one of claims (1) to (3), characterized in that

(Examples) The present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In Examples, all parts or percentages indicate parts by weight or percentage by weight.

Example 1 The surface of a JIS1050 aluminum sheet was grained with a rotating nylon brush using a Pumice-water suspension as an abrasive. At this time, the surface roughness (center line average roughness) was 0.5 μ. After the water was roughened, it was immersed in a 10% caustic soda aqueous solution at 70 ° C. and etched so that the amount of aluminum dissolved was 6 g / m ² . After washing with water, it was neutralized by immersion in a 30% nitric acid aqueous solution for 1 minute, and washed thoroughly with water. Thereafter, electrolytic roughening was performed for 20 seconds in a 0.7% nitric acid aqueous solution for 20 seconds using a rectangular alternating waveform having a voltage of 13 volts at the anode and a voltage of 6 volts at the cathode (described in JP-B-55-19,191). The surface was washed by immersion in a 50 ° C. solution, and then washed with water. Further, a substrate was prepared by performing anodization treatment in a 20% aqueous solution of sulfuric acid so that the weight of the anodized film would be 3.0 g / m ² , washing with water and drying.

The following photoconductive layer coating liquid was applied onto this substrate with a bar coater and dried at 120 ° C. for 10 minutes to prepare a photoconductor for electrophotographic plate making.

Coating solution for photoconductive layer 25 parts of hydrazone compound shown below Copolymer of benzyl methacrylate and methacrylic acid (methacrylic acid 30 mol%) 75 parts The following thiopyrylium salt compound 1.18 parts Methylene chloride 510 parts Methylcellosolve acetate 150 parts The electrophotographic photoconductor thus prepared had a dry film thickness of 4 μm.

Next, the sample was charged to a surface potential of +400 V by a corona charger in a dark place, exposed to tungsten light, and developed with a liquid developer Ricoh MRP (Ricoh Co., Ltd.).
It was possible to obtain a clear positive image. Further, the formed image was heated at 120 ° C. for 2 minutes to fix the toner image.

Next, treatment was carried out with an automatic processor, an etching solution and washing water as shown below.

(1) Automatic processor A driving device consisting of an etching bath followed by a washing bath-rinsing bath, which horizontally conveys the electrophotographic development-processed lithographic printing plate, and a storage tank for each processing bath → pump → spray → This is an automatic processor having a device that circulates from a nozzle to a storage tank and a replenishment device for each processing bath, and the storage tank of each processing bath has a mechanism for discharging excess processing liquid due to overflow.

(2) Etching solution The following etching solution was put into the etching bath.

Potassium silicate 40 parts Potassium hydroxide 10 parts Ethanol 100 parts Pure water 800 parts (3) Rinsing water Rinsing water (pH 11.5) 8 consisting of the following composition is charged into the rinsing bath and each printing plate of 1003 mm × 800 mm is processed. Was replenished with 40 ml of water (the storage tank of the washing bath is structured to overflow at 8).

(Composition) Sodium metasilicate: 10g Pure water: 10000g (4) Rinse solution containing surfactant A rinse solution (pH approx. 6.0) 8 consisting of the following composition was placed in a rinse bath to produce a 1003mm x 80mm printing plate. 40 each time one version is processed
Replenished with ml of water (the rinse bath also has a structure that overflows at 8).

(Composition) Sodium dodecyl phenyl ether disulfonate (40
6 wt% sodium dioctylsulfosuccinate ………… 1 g Phosphoric acid (85 wt% aqueous solution) ………… 1 g Sodium hydroxide ………… 2.4 g Silicon defoamer AST-731 ……… 0.01g Water ………… 985g Lithographic printing plate with a size of 1003mm × 800mm 80g
No debris or gel was formed in the washing bath even when the sheets were continuously treated.

When the same process was repeated 60 times each day,
After 5 days, the pH of the rinsing water reached 12.0 and the pH of the rinse solution reached 6.8, after which the treatment could be continued for 1 month with almost no change. The printing results were all good.

In addition, the replenisher having the following composition was replenished with the etching solution by 50 ml each time one plate treatment was performed.

(Composition) Potassium silicate 40 parts Potassium hydroxide 20 parts Ethanol 100 parts Pure water 800 parts Comparative Example 1 All were treated under the same conditions as in Example 1 except that tap water was used as the washing water and no additional water was added. However, after treating 10 sheets, insoluble matter began to float in the washing water and adhered to the non-image area on the 15th printing plate to cause printing stains.

Next, when 60 sheets were treated daily as in Example 1, the pH of the rinsing water was 12.5 or higher after 2 days, and the pH of the rinse solution was 9.8 after 2 weeks. When a printing plate treated at such a high pH was printed using a printing machine, not only was thin ink adhered to the non-image area from the start of printing to stain it, but also until a satisfactory ink density was obtained in the image area. It required printing 30 sheets.

Example 2 In Example 1, the treatment was performed under the same conditions as in Example 1 except that washing water having a pH of 11.2 in which 100 ml of the etching liquid shown in Example 1 was added to water 8 was used. 1
Similar satisfactory results were obtained.

Example 3 A washing water A having the following composition was prepared, and while vigorously stirring, B having the following composition was gradually added to form an emulsion, which was further emulsified with a homogenizer to obtain a protective gum solution.

Aqueous solution A Pure water 750 g Gum arabic 40 g Dextrin 160 g Phosphoric acid (85%) 2 g Aqueous solution B Sodium dilaurylsulfosuccinate 10 g Rosin ester (Arakawa Chemical Co., Ltd.) 5 g Dibutyl phthalate 30 g Rinsing solution containing surfactant in Example 1 Instead of the above, the above protective gum solution was used, and the treatment was carried out in exactly the same manner as in Example 1 while replenishing 40 ml of the protective gum solution each time one plate treatment was carried out. Reached 4.6 and could be treated for one hour with almost no change. Also in printing, satisfactory results were obtained with respect to ink receptivity and stain resistance.

Comparative Example 2 When tap water was used as the washing water and the treatment was carried out under the same conditions as in Example 3 except that the water was not replenished, when 10 sheets were treated, insoluble matter began to float in the washing water. It adhered to the printing plate and smeared the print.

Then, when 60 sheets were treated daily as in Example 3, the pH of the washing water became 12.5 or higher after 2 days, and the pH of the protective gum solution reached 10 after about 10 days, and the emulsion was separated. And the sludge of the sludge was generated, and further treatment could not be continued.

〔The invention's effect〕

According to the method of the present invention, it was possible to greatly reduce the amount of washing water and prolong the life of the circulating washing water without generating insoluble matter in the washing bath. As a result, it was possible to reduce the amount of rinsing water containing harmful substances and minimize the occurrence of pollution. Further, it is not necessary to use a large amount of washing water, so that the amount of wastewater treated can be reduced, and the treatment cost can be reduced.

Further, it has become possible to prevent deterioration of the rinse liquid and the gum liquid and to extend the life of the rinse liquid and gum liquid, thereby enabling stable treatment for a long period of time. Therefore, when using the lithographic printing plate by the electrophotographic process obtained by the present invention,
It became possible to print a large number of sheets without causing inconveniences such as stains and defective ink deposition on the image area during printing.

Claims (1)

(57) [Claims] 1. A lithographic printing plate comprising a toner image formed by an electrophotographic process on a photoconductor layer having an image portion provided on a conductive substrate, after removing (etching) the non-image portion, washing with water. (B) Adjusting the pH of the first washing bath after etching to 11.0 to 12.5, (b) Recycling and reusing at least a part of the washing water, and (c) Amount of the treated photoreceptor. The lithographic printing plate is characterized in that the pH of the washing bath is adjusted within the above range by replenishing the washing treatment step with an amount of water corresponding to the above and discharging the overflowed washing water from the washing treatment step. Plate making method.