JP2838541B2 - Method of desensitizing lithographic printing plate - Google Patents

Description

The present invention relates to a method for desensitizing a lithographic printing plate formed by an electrophotographic process.

[Conventional technology]

Nowadays, as a flat plate offset printing plate, a PS plate using a positive photosensitive agent mainly containing a diazo compound and a phenol resin or a negative photosensitive agent mainly containing an acrylic monomer or a prepolymer has been put into practical use. . On the other hand, with advances in computer image processing, large-capacity data storage, and data communication technology, in recent years, computer operations have been consistently performed from document input, correction, editing, layout to page layout, and real-time remote control via high-speed communication networks and satellite communications. An electronic editing system that can output to the end plotter on the ground has been put into practical use. In particular, in the newspaper printing field where immediacy is required, there is a strong demand for directly outputting electronically edited data to a lithographic printing plate.

However, direct-type printing plates, which create printing plates directly from the output of the terminal plotter, have hardly been put to practical use, and even when the electronic editing system is running, the output is made on silver halide photographic film and based on this. PS indirectly
The reality is that a printing plate is prepared by contact exposure to the plate. This is the output plotter light source (eg, He-Ne
(Laser, semiconductor laser, etc.), because it is difficult to develop a direct type printing plate having high sensitivity enough to prepare a printing plate within a practical time.

An electrophotographic photoreceptor is considered as a photoreceptor having high photosensitivity capable of providing a direct printing plate.

Conventionally, printing plate material using electrophotography (printing plate)
As, for example, JP-B-47-47610, JP-B-48-40002,
JP-B-48-18325, JP-B-51-15766, JP-B-51-25761
Japanese Patent Application Publication No. JP-A-2005-64103 and the like, known are zinc oxide-resin dispersion type offset printing plate materials, which use a harmful cyanide compound as a desensitizing liquid and have a printing durability of 5,000 to 1
It is low, on the order of ten thousand sheets, and does not necessarily have sufficient characteristics for general printing.

No. 37-17162, No. 38-7758, No. 46-
39405, JP-B-52-2437, JP-A-57-147656, JP-A-59-147335, JP-A-59-152456, JP-A-59-168462
In the organic photoconductor-resin printing plate material described in JP-A-58-145495, for example, a photoconductive material obtained by binding an oxazole or oxadiazole compound with a styrene-maleic anhydride copolymer is used. 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.

However, the substance in the electrophotographic photosensitive layer is adsorbed on the non-image portion of the printing plate prepared using the electrophotographic photoreceptor, and the non-image portion is contaminated, so that the ink adheres to the non-image portion of the printed matter, Since "dirt" occurs, it cannot be used as a printing plate.

Excessive elution of the non-image area in order to remove the dirt causes a problem that the image area is eroded and the image quality deteriorates.

On the other hand, as described in JP-A-60-159755 and JP-A-60-107042, a lithographic printing plate is prepared by transferring and fixing a toner image formed on an electrophotographic photosensitive member to a printing substrate. Has been proposed. The feature of this method is that a high-sensitivity photoconductor used for a conventional PPC or printer can be used, and the photoconductor can be reused. Further, as described above, there are many advantages such as no elution process of the photosensitive layer and a simplified process of preparing a printing plate. However, when a grained or anodized aluminum plate commonly used in PS plates is used as a substrate, there is a problem that printing stains occur.

By the way, in a PS plate using a photosensitive resin, a stain on a non-image area during printing can be improved by applying a photosensitive layer after treating an anodized aluminum substrate with an alkali metal silicate. No. 3,181,461. However, a printing plate that uses toner transferred to a substrate surface-treated with an alkali metal silicate as described above has poor printing durability, and it is extremely difficult to achieve both printing durability and prevention of printing stains. Met.

[Problems to be solved by the invention]

An object of the present invention is to prevent printing stains on a lithographic printing plate formed by transferring a toner image formed by an electrophotographic process or the like, and to create a printing plate with improved printing durability. An object of the present invention is to provide a useful method for desensitizing lithographic printing plates.

Another object of the present invention is that a lithographic printing press can be easily applied to a plate by using a sponge, a cotton tampon, an automatic gum coater, or the like, and can be easily washed from water or by contact with a humidifying roller of the printing press. Desensitizing treatment of a lithographic printing plate formed by transferring a toner image formed by an electrophotographic process or the like using a desensitizing solution that can be removed and retains the hydrophilicity of the non-image area Is to provide a way.

[Means for solving the problem]

According to the present invention, the silicate removes the stain-causing substance on the plate, desensitizes the non-image area at the same time, and by using a water-soluble resin in combination, the plate surface is not directly exposed to the air, so that an oxidation phenomenon occurs. Prevents the desensitization of the non-image part from being reduced by the like, and furthermore, has the effect of increasing the desensitization.
It is based on the knowledge that it prevents stains from adhering to the plate surface before printing on the printing machine after plate making and becomes print stains, and it is difficult to scratch when stored repeatedly or hit by foreign matter It is.

That is, the present invention provides a lithographic printing plate in which an image portion is formed of a toner image directly formed on a substrate whose surface is mainly made of aluminum, and a non-image portion is the substrate, by the following (1)
Alternatively, there is provided a method for desensitizing a lithographic printing plate, wherein the desensitization is performed by the method (2).

(1) General formula mSiO ₂ / nM ₂ O (M: alkali metal atom, m / n
= 0.5 to 8.5) and desensitization by treatment with an aqueous solution containing a silicate and a water-soluble polymer.

(2) At least (a) treatment with an aqueous solution containing a silicate represented by the general formula mSiO ₂ / nM ₂ O (M: alkali metal atom, m / n = 0.5 to 8.5), and (b) water-soluble polymer Desensitization by treatment with dissolved aqueous solution.

In the present invention, sodium silicate, potassium silicate, lithium silicate and the like can be used as the silicate. Molar ratio m / n of mSiO ₂ / nM ₂ O used in the present invention is preferably 0.5 to 8.5.

In the aqueous solution of a silicate and a water-soluble polymer or an aqueous silicate solution used in the present invention, the silicate is present in an amount of about 0.4% to about 40% by weight, preferably about 0.8% to about 40% by weight of the total composition.
It is good to use in the range of 25% by weight.

Examples of the water-soluble polymer that can be used in the present invention include the following.

For example, natural polymers include potato starch, potato starch, tapioca starch, starches such as wheat starch and corn starch, carrageenan, laminaran, sea sour mannan, fungi, Irish moss, agar and those obtained from algae such as alginate and sodium alginate, Tropical mallow, mannan, quince seed, pectin, tragacanth gum, karaya gum, xanthin gum, guaingham, locust bingham, gum arabic, carbox gum, benzoin gum, etc. And the like, denatured mucus using fermentation of microorganisms such as heteropolysaccharides, glue, proteins such as gelatin, casein and collagen. Fibers such as viscose, methylcellulose, ethylcellulose, methylethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxypropylethylcellulose, and hydroxypropylmethylcellulose phthalate, in addition to propylene glycol alginate, which is a semi-natural product (semi-synthetic product) Derivative and modified starch. The processed starch is white dextrin, roasted starch such as yellow dextrin and British gum, enzyme-modified dextrin such as enzyme dextrin and shardinger dextrin, acid-decomposed starch shown in solubilized starch,
Oxidized starch shown in dialdehyde starch, pregelatinized starch such as modified pregelatinized starch and unmodified pregelatinized starch, phosphate starch, fat starch, sulfate starch, nitrate starch,
Esterified starch such as xanthate starch and carbamic acid starch, carboxyalkyl starch, hydroxyalkyl starch, sulfoalkyl starch, cyanoethyl starch,
Allyl starch, benzyl starch, etherified starch such as carbamylethyl starch and dialkylamino starch, crosslinked starch such as methylol crosslinked starch, hydroxyalkyl crosslinked starch, phosphate crosslinked starch and dicarboxylic acid crosslinked starch, starch polyacrylamide copolymer, Starch polyacrylic acid copolymer, starch polyvinyl acetate copolymer, starch polyacrylonitrile copolymer, cationic starch polyacrylic acid ester copolymer, cationic starch vinyl polymer copolymer,
And starch graft copolymers such as starch polystyrene maleic acid copolymer and starch polyethylene oxide copolymer. Synthetic products include polyvinyl alcohol, partially acetalized polyvinyl alcohol, allyl-modified polyvinyl alcohol, polyvinyl methyl ether,
Modified polyvinyl alcohol such as polyvinyl ethyl ether and polyvinyl isobutyl ether, sodium polyacrylate, saponified polyacrylate,
Polyacrylic ester copolymer partially saponified product, polyacrylic acid derivative and polymethacrylic acid derivative such as polymethacrylate and polyacrylamide, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, copolymer of polyvinylpyrrolidone and vinyl acetate Carboxyvinyl polymer, styrene-maleic acid copolymer, styrene-crotonic acid copolymer, and the like.

In the aqueous solution of a silicate and a water-soluble polymer or an aqueous solution of a water-soluble polymer used in the present invention, the water-soluble polymer is
It may be used in the range of about 1% to about 30%, preferably about 3% to about 25% by weight of the total composition. As the content becomes less than 1% by weight, the effect of the use thereof decreases, and as the content becomes more than 30% by weight, the oil sensitivity of the image area decreases, and at the start of printing, satisfactory results are obtained. By the time a print having an ink density is obtained, a large number of prints must be printed. These water-soluble polymers may be used alone or in combination of two or more.

In the step of desensitizing the lithographic printing plate of the present invention, the treatment liquid in each step may contain various known components as necessary.

For example, the surface condition of the coating layer is improved by adding a surfactant. Surfactants that can be used include anionic surfactants, nonionic surfactants, amphoteric surfactants,
There are cationic surfactants.

Examples of the anionic surfactant include fatty acid salts, alkylbenzene sulfonates, linear alkylbenzene sulfonates, alkyl sulfates, α-olefin sulfonates, alkyl phosphate esters, dialkyl sulfosuccinate salts, and polyoxyethylene alkyl ethers. , Sulfates, polyoxyethylene alkyl ether phosphates, alkyl naphthalene sulfonates, N
-Lauroyl sarcosine salts, sulfonic acids of naphthalene formalin condensate, diphenyl ether disulfonates and the like. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenol ethers, polyoxyethylene, polyoxypropylene block polymers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyethylene glycol fatty acid Esters, polyoxyethylene fatty acid amines, fatty acid monoglycerides, sorbitan fatty acid esters, pentaerythritol fatty acid esters, sucrose fatty acid esters, amine oxides and the like.

Examples of the amphoteric surfactant include alkyl carboxy betaines, alkyl amino carboxylic acids, and alkyl imidazolines. Examples of the cationic surfactant include tetraalkylammonium salts, trialkylbenzylammonium salts, and alkylimidazolinium salts. Other examples include a fluorine-based surfactant and a silicon-based surfactant.

In particular, among surfactants, anionic surfactants and / or nonionic surfactants are effective. These surfactants can be used in combination of two or more. The amount used is not particularly limited, but the preferred range is 0.01% of each treatment solution.
~ 10% by weight.

Water functions as a solvent for each processing solution. As the water, distilled water, deionized water, water from which solids have been removed by filtration,
Tap water or the like can be used. Water accounts for the remainder of the content of the other components, and the range of the content is not specified, but is generally preferably used in the range of 40 to 95% by weight.

The pH of the treatment solution containing the silicate of the present invention is 8 to 14,
In particular, the range of 9 to 13 can be preferably used.

Method of Desensitizing Lithographic Printing Plate The method of desensitizing a lithographic printing plate of the present invention to a lithographic printing plate prepared by a process described below will be described. When a silicate and a water-soluble resin are simultaneously contained in the treatment liquid, an appropriate amount of the treatment liquid is poured onto the plate surface, and the treatment liquid is rubbed with a sponge so as to be applied to the entire plate, and then dried. This can be achieved by an automated, commercially available PS plate gum coater. When the treatment liquid is divided into an aqueous solution of a silicate and an aqueous solution of a water-soluble polymer, the lithographic printing plate is immersed in the aqueous silicate solution for an appropriate time, and then, if necessary, washed with water. Next, an appropriate amount of an aqueous solution of a water-soluble polymer is poured onto the plate surface, rubbed with a sponge so as to coat the entire plate, and then dried. The same purpose can be achieved by an automated commercial PS plate developing machine or gum coater.

Since the treatment with the silicate aqueous solution differs depending on the silicate concentration, the aqueous solution temperature, and the treatment time, it cannot be stated unconditionally, but generally speaking, treatment from room temperature to 100 ° C. for about 5 seconds to 5 minutes is preferable, 20 ° C to 80 ° C, 20 seconds to 2
Minutes can be more preferably used.

When printing is started, generally, the water-soluble polymer on the plate surface is washed off with water (so-called rubber removal), and then printing may be performed according to a normal procedure, or in the desensitization method of the present invention. Can also start printing immediately without doing so-called gum removal. At the time of printing, it is possible to obtain a sufficiently satisfactory clear print immediately after printing without producing many defective prints as in the past, and one non-image area retains strong hydrophilicity. Thus, a good printed matter free of printing stains can be obtained.

 Hereinafter, the present invention will be described in more detail.

The lithographic printing plate of the present invention is prepared by transferring a toner image formed by a conventionally known electrophotographic method, electrostatographic method or the like onto a substrate having a surface mainly composed of aluminum, which will be described later. be able to. The electrophotographic process is based on “ELECTROP HOTOGRAPHY” (RMSchafferrt; Focal
Press, 1980), "Basics and Applications of Electrophotographic Technology" (edited by the Electrophotographic Society of Japan; Corona, 1988), and various methods are described, and any of them can be used. Method is briefly described.

First, an electrophotographic photosensitive member is charged substantially uniformly in a dark place, and an electrostatic latent image is formed by image exposure. Examples of the exposure method include scanning exposure using a semiconductor laser, a He-Ne laser, or the like, reflection image exposure using a xenon lamp, a tungsten lamp, a fluorescent lamp, or the like as a light source, and contact exposure through a transparent positive film. Next, the electrostatic latent image is developed with toner. As the developing method, various conventionally known 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 particularly suitable for preparing a printing plate.

The toner image formed as described above is printed on a substrate for printing by an electrostatic transfer method such as corona transfer or bias roller transfer, a pressure transfer method, an adhesive transfer method via an intermediate transfer body having adhesiveness and releasability. Transfer to the top. The transferred image is fixed by a heat roller, a radiant, a flash, an open, a pressure, or the like, and can be subjected to offset printing by subjecting it to the above-described insensitive fatting treatment.

Electrophotographic photoreceptors include a-Se, a-Se-Te, a-S
Photoconductors in which inorganic crystal such as amorphous chalcogenide type such as e-As, ZnO (dye if necessary) and CdS are dispersed in resin, photoconductive polymer such as amorphous silicon type, polyvinyl carbazole derivative, polyvinyl pyrene derivative, etc. Organic photoconductors including polymer dispersions such as oxadiazole derivatives, polyarylalkane derivatives, arylamine derivatives, hydrazone derivatives, etc. and resin dispersion composites of low molecular weight organic compounds (for higher sensitivity and selection of photosensitive wavelength region) And sensitizing dyes such as azo pigments, phthalocyanine pigments and perylene pigments, and sensitizing dyes such as pyrylium dyes and cyanine dyes).

As a toner, a dry developer and a wet developer are mainly used. Examples of the dry developer include a magnetic or non-magnetic one-component developer and a magnetic or non-magnetic two-component developer containing a carrier. Since a wet developer has toner particles dispersed in a highly insulating liquid, the particle size can be made smaller than that of a dry developer. Therefore, it can be said that a wet developer is advantageous for forming a fine image.
As the toner particles, it is necessary to contain a resin component having an ink affinity required for printing and sufficient printing durability. As the resin, acrylic resin using (meth) acrylic acid, (meth) acrylic acid ester, etc., vinyl acetate resin, polyethylene resin, polypropylene resin, chlorinated product such as polyethylene resin or polypropylene resin, vinyl chloride Resin, vinylidene chloride resin, vinyl acetal resin such as polyvinyl butyral, polystyrene, styrene resin composed of styrene and (meth) acrylic acid or butadiene, polyester resin, polyamide resin, phenol resin, xylene Resins, alkyd resins, vinyl-modified alkyd resins, cellulose ethers, waxes, polyolefins, waxes and the like. Among them, JP-A-61-180248, JP-A-62-135842, JP-A-62-266566, JP-A-62-223584, and JP-A-62-223584
-223585, Japanese Patent Application Nos. 63-41272, 63-41273, etc., ethylene / carboxylic acid copolymer, ethylene / alkyl (meth) acrylate / carboxylic acid copolymer, ethylene / vinegar A wet developer using a copolymer such as a bi-copolymer has good transfer efficiency and quality of a transferred image,
Preferably it can be used.

Examples of the printing substrate (transfer object) of the present invention include an aluminum plate, a bimetal plate such as a copper-aluminum plate, a trimetal plate such as a chromium-copper-aluminum plate, a plastic sheet or paper, and especially a solvent-impermeable material. A substrate having a hydrophilic surface, such as a substrate obtained by depositing or laminating a metal mainly composed of aluminum on a prepared paper is used, and the thickness thereof is preferably 0.1 to 3 mm, particularly preferably 0.1 to 0.5 mm.
Among these substrates, an 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 a different atom, and the composition thereof is not specified, and conventionally known and publicly available materials are appropriately used. Can be used.

This aluminum plate can be used after graining and anodizing by a conventionally known method. Prior to the graining treatment, a degreasing treatment with a surfactant or an alkaline aqueous solution is performed, if desired, to remove the rolling grease on the surface of the aluminum plate, and the graining treatment is performed. 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 of mechanically roughening the surface,
Known methods called a ball polishing method, a brush polishing method, a blast polishing method, a buff polishing method and the like can be used.
Further, as an electrochemical surface roughening method, there is a method of performing an alternating or direct current in a hydrochloric acid or nitric acid electrolyte. Also,
As disclosed in JP-A-54-63902, a method in which both are combined can also be used.

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

The aluminum plate thus treated is anodized. As the electrolyte used for the anodizing treatment, sulfuric acid,
Phosphoric acid, oxalic acid, chromic acid, or their mixed acids are used, and their electrolytes and their concentrations are appropriately determined depending on the type of electrolyte. Since the anodizing treatment conditions vary depending on the electrolyte used, they cannot be specified unconditionally. In general, the concentration of the electrolyte is 1 to 80% by weight, and the solution temperature is 5 to 70%.
° C, current density 5-60A / dm ² , voltage 1-100V, electrolysis time 10
It is preferable to be in the range of seconds to 50 minutes. The amount of anodic oxide film is
0.1 to 10 g / m ² is suitable, but more preferably 1 to 6 g / m ²
Range.

〔Example〕

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 the examples, all parts are parts by weight.

Example 1 Preparation of Photoreceptor A photosensitive solution having the following composition was applied to a 100 μm-thick polyethylene terephthalate film having an indium oxide vapor-deposited layer using a wire bar and dried to prepare a 6 μm-thick electrophotographic photoreceptor. .

Preparation of Aluminum Substrate A JIS1050 aluminum sheet was grained with a rotary nylon brush using a Pumice-water suspension as an abrasive. At this time, the surface roughness (center line average roughness) was 0.5 μm. After washing with water, it was immersed in a 10% aqueous solution of caustic soda 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% aqueous nitric acid solution for 1 minute, and washed thoroughly with water. Then, electrolytic roughening was performed 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, the substrate was subjected to anodizing treatment in a 20% sulfuric acid aqueous solution so that the weight of the anodized film became 3.0 g / m ² , washed with water, and dried to prepare a substrate.

Preparation of Wet Developer The following components were added to a kneader (PBV-01 bench kneader manufactured by Irie Shokai) and kneaded at 95 ° C. for 2 hours. After the mixture was cooled and solidified by water cooling in a kneader, the kneader was continuously rotated and pulverized.

Next, the following components were wet-dispersed for 12 hours using a paint shaker (manufactured by Toyo Seiki Co., Ltd.) using glass beads having a diameter of 3 to 4 mm as media, and the toner solid content was controlled to 1 g per liter of the carrier liquid. By diluting with G, a wet developer was prepared.

Preparation of printing plate After the above photoreceptor is corona-charged to +350 V in a dark place, image exposure is performed through a positive original document to form an electrostatic latent image. The photoreceptor was immersed in the above-mentioned wet developer, developed with toner, superposed on the above-mentioned printing substrate, and corona-discharged to transfer the toner to the substrate side. next,
The substrate was placed in a hot-air dryer at 140 ° C. and left for 10 minutes to fix the toner. Next, the treatment liquid A is applied to the surface of the printing plate.
Was applied to obtain a plate-making printing plate.

Comparative Example 1 The same non-greasy fitting treatment as in Example 1 was performed using the treatment liquid except for the potassium silicate solution of the treatment liquid A in Example 1.

Comparative Example 2 The same desensitization treatment as in Example 1 was performed using the treatment liquid of Example 1 except that the hydroxypropyl etherified starch of the treatment liquid A was excluded.

Comparative Example 3 The printing plate on which the toner was transferred and fixed on the substrate was not subjected to any desensitizing treatment.

These four printing plates were simultaneously printed by Oliver 52 (Kikuhan Mosai Molton Printing Machine). Ink is DIC CAPS-G
Ink (Dainippon Ink Co., Ltd.) and EU-3 (Fuji Photo Film Co., Ltd.) diluted with a fountain solution at a volume ratio of 1: 100 (water) were used. As a result, the sample of Example 1 did not generate print stains up to 50,000 sheets, whereas the sample of Comparative Example 1 had about 10
Smearing began to occur from about 00 sheets and did not disappear until the end. The sample of Comparative Example 2 had stains such as fingerprints generated from the beginning of printing, and the sample of Comparative Example 3 had more severe stains, which was judged to be impractical.

Example 2 A printing plate was produced in the same manner as in Example 1, except that the following processing solution B was used instead of the processing solution A.

Comparative Examples 4 and 5 Printing plates were prepared in exactly the same manner as in Example 2, except that a substrate treated with the following potassium silicate solution was used as the substrate for printing. That is, potassium silicate (SiO ₂ / K ₂ O molar ratio 2.0) with the printing substrate of Example 1 kept at 70 ° C.
Was immersed in a 5% aqueous solution for 30 to 60 seconds, washed with water, dried and pretreated (Comparative Example 4).

Further, this aqueous solution of potassium silicate was used for treating solution B of Example 2.
Instead, it was immersed, washed with water, dried and pretreated (Comparative Example 5). Example 2 is a process after toner formation, and Comparative Examples 4 and 5 are processes before toner formation.

These three types of printing plates were simultaneously printed on 50,000 sheets by an Oliver 52 (Kikuhan half-length Molton printing machine). Ink is DIC
CAPS-G black ink (Dainippon Ink Co., Ltd.), dampening water EU-
3 (Fuji Photo Film Co., Ltd.) diluted 1: 100 (water) and used. As a result, the samples of Example 2 and Comparative Example 4 did not have print stains to the end, but the samples of Comparative Examples 4 and 5 began to suffer from missing image areas without reaching approximately 5,000 sheets,
The printed matter was not practical. Example 2 as described above
Can be said to be a printing plate having no stain on the non-image portion and excellent in printing durability.

Example 3 In Example 1, Canon NPT was used as a wet developer.
A printing plate was prepared by exactly the same operation except that ype3 / 5/6 (manufactured by Canon Inc.) was used. This is 5 under the conditions of Example 1.
As a result of printing 10,000 sheets, a printed matter having a good image with no stain on the non-image area was obtained.

Example 4 A printing plate was prepared in the same manner as in Example 1, except that the following processing solution C was used instead of the processing solution A, and the following developing solution was used as a wet developer.

When this was printed on 50,000 sheets under the conditions of Example 1, a printed matter of a good image with no stain on the non-image area was obtained.

Preparation of Wet Developing Solution The following composition was added to TK Loss Double Planetary Mixer 130LPM (manufactured by Tokushu Kika Co., Ltd.), and the mixture was stirred at 95 ° C. and 50 rpm for 1 hour.

Under these conditions, 9 parts of Isopar L were added in portions over 2 hours. Next, the mixture was discharged into a stainless steel bucket and cooled to room temperature to obtain a sponge-like solid. Next, 1 part of the above mixture and 6 parts of Isopar H were wet-dispersed for 20 minutes by a paint shaker using glass beads having a diameter of 3 to 4 mm as a medium.
Dynomill KDL with 75-1mm glass beads as media
4500 depending on the type (Shinmaru Enterprises Co., Ltd.)
The mixture was wet-dispersed at rpm for 6 hours. This was diluted with Isopar G so that the toner solid content was 1 g per liter of the carrier liquid, and 0.1 g of basic barium petronate was added to prepare a wet developer.

Example 5 A printing plate was produced in the same manner as in Example 4, except that the following processing solution D was used instead of the processing solution C. When this was printed on 50,000 sheets under the conditions of Example 1, a printed matter of a good image with no stain on the non-image area was obtained.

Example 6 A printing plate was prepared according to Example 1. This was immersed in the treatment solution E heated to 70 ° C. for 30 seconds, and then thoroughly washed with running water. The following treatment liquid F was applied to the surface of the treated printing plate and dried.

Treatment solution E Potassium silicate (SiO ₂ / K ₂ O molar ratio 2) 50 parts Pure water 950 parts Treatment solution F Hydroxypropyl etherified starch (degree of substitution 0.05) 60 parts Sodium butylnaphthalene sulfonate 5 parts Pure water 935 parts Comparative example 6 In Example 1, the prepared aluminum substrate was heated to 70 ° C.
After being immersed in the treatment liquid E heated to 60 ° C. for 60 seconds, it was sufficiently washed with running water. On this aluminum base plate, a toner image was formed and fixed in exactly the same manner as in Example 1. Next, the treatment liquid F was applied on the printing plate and dried.

These two printing plates were printed in the same manner as in Example 1. As a result, the samples of Example 6 and Comparative Example 6 did not cause printing stains to the end, but the sample of Comparative Example 6 was approximately
At around 5,000 sheets, the image area began to drop, and the printed matter was not practical. As described above, the sixth embodiment can be said to be a printing plate having no stain on the non-image portion and having excellent printing durability.

Example 7 A printing plate was prepared according to Example 1. This was immersed in the treatment liquid G at 25 ° C. for 60 seconds, and then sufficiently washed with running water. The following treatment liquid H was applied to the surface of the treated printing plate and dried.

Treatment liquid G Sodium silicate (SiO ₂ / Na ₂ O molar ratio 3) 25 parts (JISK1408-1973 standard No. 53 product) Pure water 975 parts Treatment liquid H Arabic gum 10 parts Sodium butylnaphthalene sulfonate 5 parts Pure water 985 parts Compare Example 7 A printing plate was prepared in the same manner as in Example 7, except that the process using the treatment liquid G was not performed.

The two printing plates prepared as described above were printed in the same manner as in Example 1. The printing plate of Example 7 obtained a good printed matter without any stain on the non-image portion after printing 50,000 sheets, but the printing plate of Comparative Example 7 showed stain on the non-image portion from about 3,000 sheets. It wasn't practical.

Example 8 A printing plate was prepared according to Example 1. This was immersed in the treatment liquid G at 25 ° C. for 60 seconds, and then sufficiently washed with running water. The following treatment liquid I was applied to the surface of the treated printing plate and dried.

Treatment liquid J Carboxymethylcellulose (Cellogen 7A, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 15 parts Sodium butylnaphthalene sulfonate 5 parts Pure water 980 parts Comparative Example 8 In Example 8, except that the process using the treatment liquid G was not carried out, A printing plate was created by the same operation.

Comparative Example 9 A printing plate was prepared in the same manner as in Example 8, except that the process using the treatment liquid J was not performed.

The three types of printing plates prepared as described above were printed in the same manner as in Example 1. The printing plate of Example 7 obtained a good printed matter without stain on the non-image area even after printing 50,000 sheets, but the printing plate of Comparative Example 9 had stains such as fingerprints generated from the beginning of printing. In addition, the printing plate of Comparative Example 8 had stains on the non-image area on about 3,000 sheets after the start of printing, and was not practical.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-61-264040 (JP, A) JP-A-61-63497 (JP, A) JP-B-58-5798 (JP, B2) (58) Field (Int.Cl. ⁶ , DB name) B41N 3/08 G03G 13/28

Claims (2)

(57) [Claims] An image portion comprises a toner image directly formed on a substrate whose surface is mainly made of aluminum, and a non-image portion is a lithographic printing plate having the general formula mSiO ₂ / nM ₂
A method for desensitizing a lithographic printing plate, comprising treating with a water solution containing a silicate represented by O (M: alkali metal atom, m / n = 0.5 to 8.5) and a water-soluble polymer. 2. A method for desensitizing a lithographic printing plate, wherein the image area is formed directly on a substrate whose surface is mainly made of aluminum, and the non-image area is at least A desensitizing method comprising the steps of a) and (b). (A) General formula mSiO ₂ / nM ₂ O (M: alkali metal atom, m / n
= 0.5-8.5) with an aqueous solution containing a silicate. (B) a step of treating with an aqueous solution in which a water-soluble polymer is dissolved.