JPH05204193A - Production of planographic printing plate - Google Patents

Abstract

PURPOSE:To elucidate the method for solving the problem of so-called side etching by which even the photosensitive layer on the lower side of a toner image is etched in the production of a photosensitive planographic printing plate for so-called direct plate making to form the toner image by an electrophotographic system. CONSTITUTION:The toner image 3 is formed larger than an original image 4 in the process for production of the planographic printing plate consisting in forming the toner image 3 by the electrophotographic system on the planographic printing plate provided with a photoconductive layer 2 on a conductive base 1, then eluting away the photoconductive layer 2 of the non-image parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lithographic printing plate, more specifically, a toner image is formed on a lithographic printing plate precursor having a photoconductive layer provided on a conductive support by an electrophotographic method, The present invention relates to a method of manufacturing a lithographic printing plate that solves the problem of so-called side etching when a non-image area is eluted by an etching process.

[0002]

BACKGROUND OF THE INVENTION A lithographic printing plate precursor of the type in which a support is a metal plate such as aluminum and a photoconductive layer is applied on the surface thereof, and a toner image is formed on the surface thereof by an electrophotographic method. A method for preparing a lithographic printing plate by eluting the non-image area by an etching treatment step using an etching solution which is an alkaline aqueous solution is described in, for example, JP-A-58.
No. 25477, No. 58-80659 and the like.

The above-mentioned technique has attracted attention because it enables direct plate making because it does not require a film original for exposure, but a conductive metal plate such as an aluminum plate is used as a support, and this support is used. For example, a photoconductive layer in which an organic pigment-based organic photo-semiconductor (OPC) is dispersed in a resin such as a phenol resin, particularly a photoconductive layer in which copper-phthalocyanine is dispersed in a novolac resin is applied. By using the original plate produced, various methods which make the principle the same as the development processing method of the conventional type so-called PS plate or waterless planographic printing original plate which requires a film original, The elution process is performed.

However, all the conventional developing (etching) methods cannot be directly applied to the etching treatment of the lithographic printing original plate by the electrophotographic method, and the problems peculiar to the treatment of the lithographic printing original plate by the electrophotographic method remain. There is.

Particularly, in the case of the electrophotographic method, there is a problem of so-called side etching in the etching process. In the electrophotographic lithographic printing plate precursor, the toner image formed on the surface of the photoconductive layer is used as a resist to elute and remove the non-image portion in the etching step.However, during the etching process, the etching liquid is removed from the edge portion of the toner image. , It penetrates into the photoconductive layer located under the toner image and elutes the edge part, and the ink inking part becomes smaller than the toner image, and printing is performed using such a lithographic printing plate. This is a phenomenon in which the line becomes thin when performing. In particular, in the case of color printing, halftone dot reproducibility deteriorates, which causes a problem in color reproducibility.

In order to avoid the above-mentioned situation, when the elution treatment is performed so that the side etching is reduced, conversely, the elution defective portion is generated in the non-image portion, and so-called stain occurs when printing is performed. It will be.

In order to satisfy the conflicting problems described above,
Considering that it is very difficult to specify the degree to which side etching occurs at an intermediate value, and in consideration of the fact that a large number of original plates must be running processed by an automated processing device, the amount of side etching is controlled. However, it is actually very difficult to process.

The inventors of the present application have conducted researches on the etching process of the lithographic printing original plate by the electrophotographic method,
For example, Japanese Patent Application No. 1-168641 proposes improvements, but the present invention has been completed as a part of such research, and the first purpose thereof is to perform the side etching described above. The second purpose is to improve the electrophotographic method by solving the problem, and the second purpose is to improve the dissolution latitude by effectively improving the electrophotographic method. The point is to clarify the manufacturing method of the planographic printing plate.

[0009]

The method for producing a lithographic printing plate according to the present invention comprises the steps of forming a toner image by an electrophotographic method on a lithographic printing plate precursor having a photoconductive layer provided on a conductive support. In the method for producing a lithographic printing plate in which the photoconductive layer in the non-image area is eluted and removed, a toner image is formed larger than the original image, or after the photoconductive layer in the non-image area is eluted and removed, the toner is removed. Is carried out.

[0010]

In order to solve the above-mentioned problems caused by side etching, the present invention is to form a toner image larger than the original image when forming a toner image on the plate surface of a lithographic printing original plate. In other words, the toner image is enlarged and formed so that an enlarged portion is formed in at least a part of the periphery of the edge portion of the original image, in other words, the toner image is thickened in at least one direction. Adopted.
To enlarge (thicken), the toner image is a character / line drawing, or
Even if it is a halftone dot, it is not necessary to extend it to the entire edge portion (entire periphery) of the toner image. For example, even if it is enlarged (thickened) only in a certain direction, the effect of the present invention can be sufficiently obtained. .. Especially in the shadow part of the halftone image,
When the image is enlarged over the entire periphery, the halftone dots are crushed. Therefore, the shape of the halftone dots is changed so that the area of the toner image is larger than the area of the halftone dots (for example, square) of the original image.

Here, the original image is an image formed on a master copy original used in a normal printing process, a positive or negative silver salt photographic film or an original of photographic paper, or, for example, a computer. Controlled digital image of data, C
An image displayed on the RT screen, etc. means a halftone dot / line drawing,
Including characters. In particular for digital images, characters are original font data, line images are data read by a scanner, halftone images are original documents scanned by a scanner with a dot generator, or they are the desired printed matter. The images converted according to the above are referred to as original images.

As a method for enlarging (thickening) the toner image, various methods can be adopted depending on the medium on which the original image is formed or the means for forming the toner image. For example, bias potential, developing time Control in the development process, dry etching in close contact exposure of the original film, image operation on the original film, adjustment of exposure amount by camera exposure and image operation on the original, digital image by laser, LED, etc. In the scanning direction and the sub-scanning direction, image processing such as output of halftone dot data obtained by converting an original image by an LUT (lookup table), beam diameter during reversal development, increase in light amount, etc. are adopted. ..

Which of the above methods is adopted is arbitrary, but the greatest merit of producing a lithographic printing plate by an electrophotographic method is that of a so-called computer to plate, which is capable of directly recording a digital image on a plate surface. In terms of enabling plate making, it is preferable that the electrostatic latent image is enlarged (thickened) in such a plate making step. To do this, there are a method of processing and converting the digital information of the image and outputting the digital information, and a method of directly converting the digital information without any conversion and performing conversion by an optical system at the output stage. Examples of the former method include a method described below and a method combining these methods, but methods other than these methods are not excluded.

A method of adjusting the modulation timing in the scanning direction to enlarge the original image. In this method, it is possible to control not more than 1 dot but not more than 1 dot by selecting the timing of the clock.

A method of taking in pixels which are in contact with the original image in the sub-scanning direction as an image, a method of adjusting the output halftone dot through an LUT (look-up table) when the original image is formed of halftone dots, An example of enlargement of the image by and is shown in FIG. The right diagonal line shows the original image, and the left diagonal line shows the enlargement by 1 dot in the scanning direction by and by 1 dot in the sub scanning direction by.

According to the above method, since side etching proceeds evenly in any part, the density of each halftone dot is changed so as to form an ideal resist image on the plate surface in consideration of dot gain in printing. Need to be converted accordingly. In color printing, it is preferable to change the conversion curve for each color of yellow, magenta, cyan, and violet.

It is also possible to employ a method in which an image is output on a monochrome photographic film or photographic paper using the data converted by the above-mentioned method and the image is read by an image reading apparatus used in a facsimile. Is.

When the toner image is enlarged and comes into contact with the surrounding image and the image is crushed, the following method is used.

When the distance between the image portions is one dot, the image is not enlarged.

When the distance between the image portions is 2 dots, one of the images is enlarged by 1 dot.

In the above and above, when it is not possible to enlarge in the scanning line direction or the sub-scanning line direction, the opposite side is enlarged in the same direction.

FIG. 2 shows an example of the enlarging method in the shadow portion.
Shown in. That is, in the halftone dot of the shadow portion, the space between the halftone dots is only one scanning line, and when it is enlarged, it becomes completely solid, and when neither portion can be enlarged, as shown in (B). The problem is solved by making a part of the non-image part. Further, in a region where the halftone dot density of the original image is 90% or more, it is preferable to prevent the shadow collapse in the toner image by reducing the screen ruling, that is, the resolution as shown in FIG.

The above-described toner image enlargement method by digital image processing can be applied to both the normal development in which toner is attached to the unexposed portion and the reversal development method in which toner is attached to the exposed portion.

Further, in the case of the reversal development method, a laser,
The circumference of the toner image can be enlarged by a method such as increasing the light intensity of the LED or the like, increasing the beam diameter, or the like. Further, the toner image can be enlarged depending on the exposure condition in contact exposure of a positive or negative film original and projection exposure from a master original instead of direct recording. An example of the method is shown below.

Contact exposure of a positive film (regular development) For example, in the step of making a positive film by exposing a negative film by contact exposure, the exposure amount is increased, a spacer is interposed, and the like. An image is formed on the positive film. Further, in the case of a digital image, it is possible to obtain a positive film of an enlarged image by writing the enlarged image with a plotter. This method is possible as a method of writing a magnified image on a negative film and making a positive film based on the image.

Negative film contact exposure (reverse development) A magnified latent image can be obtained simply by increasing the exposure amount or interposing a spacer.

An image is formed on a positive photographic printing paper by a method similar to the method of projection exposure (normal development) from a positive block original.

Projection exposure (reversal development) from a negative original document An enlarged image can be formed by a method such as increasing the exposure amount.

The above is the method of adjusting the size of the electrostatic latent image by exposure to adjust the toner image. In addition to these methods, the bias potential in the developing section, the interval between the developing electrodes, the adjustment of the developing time, and the developer are used. It is also possible to enlarge the toner image by adjusting the characteristics of the photoconductive layer and by pressure bonding or fusing in the toner fixing step.

The amount of side etching depends on the number of screen lines and the halftone dot reproduction range of a desired printed matter, but as shown in FIG. 3, the lower limit of side etching is 5 which is related to the film thickness of the photoconductive layer 2. It is equal to the sum of the target side etch amount 6. The lower limit amount 5 of side etching is almost equal to the film thickness of the photoconductive layer 2. If the amount of side etching is less than this, it becomes impossible to remove the photoconductive layer in the non-image area, and as a printing plate. Becomes impossible to use. The minimum lower limit amount of the side edge can be experimentally obtained under elution conditions with the minimum etching time for removing the photoconductive layer in the non-image area, for example. The film thickness of the photoconductive layer is 0.5 to 30 μm, and in order to maintain the resolution after the elution treatment, the film thickness of the photoconductive layer is 10 μm.
m or less, the photoconductive layer thickness is 1 μm for printing durability and sensitivity.
It is preferably m or more. In order to increase the amount of side etching, the activity of the etching solution can be increased and the etching time can be increased.

The resist image formed of the photoconductive layer which is the ink inking layer is preferably smaller than the original image 4. Therefore, by intentionally advancing the etching on the side by a minimum etching amount of 5 (corresponding to the film thickness of the photoconductive layer 2) or more, for example, 0 to 30 μm, preferably 5 to 15 μm. The side etch amount is 6. Such a setting is preferable for preventing adhesion of residual components of the photoconductive layer, and particularly for absorbing fluctuations in the activity of the etching solution.

Even if the intentional side-etching amount 6 is set to 0 μm and the image is enlarged, the reproducibility of the image can be obtained, but in comparison with the example of intentionally side-etching, Experiments have shown that it is inferior in terms of stain generation.

As described above, the resist image formed by the photoconductive layer is set smaller than the original image 4 because
This is also because we considered the dot gain during printing,
The toner image and the side etch amount are adjusted so that the side etch progresses in the range of 0 to 20 μm, preferably 5 to 10 μm from the peripheral portion of the original image 4 to obtain the intentional side etch amount 6.

The expansion amount is 0.5 to 40 μm, preferably 1
Is about 15 μm. This depends on the following three factors. d: Minimum amount of side etching (≈photoconductive layer film thickness) D: Intentional side etching 1: Reduction amount from original image to resist image of photoconductive layer Expansion amount L is shown by L = d + D-1 ..

Further, the reason for the above setting will be described with reference to FIG. FIG. 4 shows halftone dot reproducibility, and when the reproducibility accurately corresponding to the halftone dot density of the original image is obtained, the halftone dot reproduction curve is indicated by B, but in the present invention, The toner image is set so that the curve A is dot gained more than the curve B, and the side etch amount is set so that the halftone dot reproducibility in the resist image formed of the photoconductive layer becomes the curve C in the etching process. However, the dot gain of ink occurs at the time of printing, and the printed image is reproduced so as to have the curve B. Even if the toner image is set to have the curve B and processed to have the curve C in the elution step by the conventional technique, it is inevitable that the non-image portion is stained or the shadow is crushed.
Furthermore, even if a reproducibility curve having a larger dot loss than the curve C is set and processed, it is impossible to faithfully reproduce the curve B at the printing stage.

As for the reproducibility, the curve shown in FIG.
If B (straight line) is included in the present invention, C may be formed as B. However, if printing without dot gain is performed under these conditions, the amount of ink adhering is not sufficient, and the ink density, especially the density in solid areas, decreases, which is not preferable. Therefore, the preferred mode is A> B (straight line)> C.

The preferable halftone dot reproduction curves of A and C vary depending on the screen ruling, but are 5 in the original image B.
%, 50% and 95% halftone dots are preferably converted in A and C as follows.

5% 50% 95% A 6-20 55-75 96-99.9 C 2-4 35-45 90-94 The reproducibility curve concept described above is exactly the same for characters and line drawings. Is applicable to.

The lithographic printing plate material to which the method of the present invention is applied includes a photoconductive substance having a photoconductive pigment as an organic photoconductor of the photoconductive layer and / or a solvent which completely dissolves it (of a dissolution type). A photoconductive layer containing a photoconductive substance) in a binder resin is included. The effect of the present invention is particularly high for a lithographic printing plate material having a photoconductive layer using a pigment-based organic photoconductor. Examples of such organic photoconductive pigments include JP-B Nos. 40-2780 and 44-1267.
1, No. 46-30035, No. 44-16474,
48-30513, 50-7434 and JP-A-4
No. 7-18543, No. 47-18544, No. 47-3
No. 0330, No. 47-37543, No. 49-1113
No. 6, No. 49-99142, No. 51-109841.
No. 54-134632, No. 55-11715,
55-105254, 55-153948, 55-161250, 56-1944, 56-56.
No. 2352, No. 56-9752, No. 56-19063.
No. 56, No. 56-29250, No. 56-69644, No. 56-50050, No. 59-125751, No. 59.
-176756, 60-17751, 60-1
No. 7752, No. 60-17753, No. 60-1775
No. 4, No. 60-17755, No. 60-17756,
No. 60-17757, No. 60-17758, and No. 60
-17759, 60-17760, 60-17.
No. 761, No. 60-17762, No. 60-35750
Nos. 61-67869, 61-67870 and the like, perylene pigments, quinacridone pigments, bisbenzimidazole pigments, aromatic polycondensed ring compounds, monoazo pigments, disazo pigments, trisazo pigments, metal- or metal-free phthalocyanine pigments. , Zinc oxide, and other photoconductive pigments.
Among the pigment-based organic photoconductors, the effect of the present invention is particularly large with respect to a lithographic printing plate material having a photoconductive layer using a phthalocyanine pigment.

The binder resin of the photoconductive layer of the lithographic printing plate material to which the method of the present invention is applied is preferably a polymer compound soluble or dispersible in the above-mentioned etching solution.

Specifically, for example, copolymers of styrene and maleic anhydride, copolymers of styrene and monoalkyl maleic anhydride, methacrylic acid / methacrylic acid ester copolymers, styrene / methacrylic acid / methacrylic acid. Ester copolymers, acrylic acid / methacrylic acid ester copolymers, styrene / acrylic acid / methacrylic acid ester copolymers, vinyl acetate / crotonic acid copolymers, vinyl acetate / crotonic acid / methacrylic acid ester copolymers, etc. Acrylic acid, methacrylic acid, styrene, acrylic acid such as vinyl acetate, methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride,
A copolymer or methacrylic acid amide with a carboxylic acid-containing monomer such as fumaric acid or an acid anhydride group-containing monomer,
Copolymers containing monomers having vinylpyrrolidone, phenolic hydroxyl groups, sulfonic acid groups, sulfonamide groups, sulfonimide groups, phenol resins, partially saponified vinyl acetate resins, xylene resins, vinyl acetal resins such as polyvinyl butyral. Can be raised.

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. , Can be used with good results.

As a copolymer containing a monomer having an acid anhydride group as a copolymerization 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. Further, vinyl acetate and crotonic acid copolymer, and terpolymer of vinyl acetate and vinyl ester of carboxylic acid having 2 to 18 carbon atoms and crotonic acid are also preferable examples. Among the phenolic resins, a novolak resin obtained by binding phenol, o-cresol, m-cresol or p-cresol with formaldehyde or acetaldehyde under acidic conditions can be mentioned as a particularly preferable one. The binding resins may be used alone or in combination of two or more.

Examples of the above-mentioned phenol resin include phenol, o-cresol, m-cresol, p-cresol, ethylphenol, isopropylphenol and t-cresol.
Butylphenol, t-amylphenol, hexylphenol, t-octylphenol, cyclohexylphenol, 3-methyl-4-chloro-6-t-butylphenol, isopropylcresol, t-butylcresol, t-amylcresol, hexylresole, t
-A resin obtained by condensing an aliphatic or aromatic aldehyde such as formaldehyde, acetaldehyde, acrolein, crotonaldehyde, furfural, etc. of at least one substituted phenol such as octylcresol and cyclohexylcresol is used as a representative resin. be able to. Further, a polyhydroxyphenol resin obtained by polycondensation of pyrogallol or resorcinol and acetone can also be used.

Among these phenol resins, preferred are phenol, o-cresol, m-cresol and p-cresol.
It is a novolac-type phenol resin obtained by condensing at least one of cresol and formaldehyde or acetaldehyde under acidic conditions.

The average molecular weight of this phenol resin is 350
Is about 20,000, preferably about 350 to 6000. These phenolic resins include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, glycol ethers such as dioxane, butyl acetate and ethyl acetate. Those that are soluble in organic solvents such as esters are desirable.

To produce a lithographic printing plate material to which the method of the present invention is applied, for example, 1 part by weight of a photoconductive material and 0.01 to 100 parts by weight of a phenol resin as a binder (preferably photoconductive material) are used. Layer is dissolved and removed by an alkaline solution) is mixed in the above organic solvent, and if necessary, an electron accepting compound or an electron donating compound is added in an amount of 0.01 to 100 mol (preferably 0.01) based on the pigment. -10
(Mol) and then uniformly dispersed by a ball mill, an ultrasonic disperser or the like. The obtained photosensitive solution is applied on a conductive support described below in a thickness of 1 to 50 μm, preferably 1 to 10 μm.
It is obtained by coating and drying to a thick thickness and heat-treating at 70 ° C. or higher to increase the solubility of the photoconductive layer in the photoconductive layer removing solution as described above.

The support of the lithographic printing plate material according to the present invention is an aluminum plate, a resin laminated with aluminum, or a bimetal plate such as a zinc plate, a copper-aluminum plate, a copper-stainless plate, a chrome-copper plate, or the like. A conductive support having a hydrophilic surface such as a trimetal plate such as a chrome-copper-aluminum plate, a chrome-lead-iron plate, and a chrome-copper-stainless plate is used.

Further, particularly in the case of a support having an aluminum surface, surface treatment such as graining treatment, anodic oxidation treatment, immersion treatment in an aqueous solution of sodium silicate, potassium fluorozirconate, phosphate or the like is carried out. Preferably. Further, as described in U.S. Pat. No. 2,714,066, an aluminum plate which has been grained and then dipped in an aqueous sodium silicate solution, JP-B-47-5.
It is also preferable to use an aluminum plate which has been subjected to anodizing treatment as described in Japanese Patent Publication No. 125, and then subjected to immersion treatment in an aqueous solution of an alkali metal silicate. The anodizing treatment is, for example, an inorganic acid such as phosphoric acid, chromic acid, sulfuric acid or nitric acid, or an organic acid such as oxalic acid or sulfamic acid or an aqueous solution or a non-aqueous solution of these salts, or an electrolysis combining two or more kinds. It is carried out by passing an electric current in a liquid using an aluminum plate as an anode.

Further, silicate electrodeposition as described in US Pat. No. 3,658,662 is also effective.
The treatment with polyvinylphosphonic acid described in West German Patent Publication No. 16214278 is also suitable.

These hydrophilic treatments are carried out for the purpose of preventing harmful reaction with the photoconductive layer provided thereon, and for performing the photoconductive layer except that the surface of the support is rendered hydrophilic. It is applied to improve the adhesion with.

In the present invention, an alkali consisting of casein, polyvinyl alcohol, ethyl cellulose, phenol resin, styrene-maleic anhydride copolymer, polyacrylic acid or the like is optionally provided between the conductive support and the photoconductive layer. A soluble intermediate layer may be provided for the purpose of improving the adhesion between the support and the photoconductive layer or the electrostatic properties of the light.

On the photoconductive layer of the photosensitive lithographic printing plate precursor to which the method of the present invention is applied, if necessary, the electrostatic property of the photoconductive layer, the developing property during toner development, or the image property is improved. Thus, it is possible to provide an overcoat layer which dissolves when the photoconductive layer is removed. The developer (toner) used in the method of the present invention is preferably hydrophobic and ink-receptive, and examples thereof include polystyrene resin, polyester resin (amino group-containing acrylic ester, long chain acrylic ester, etc.), acrylic resin. Resin (resin having phenolic hydroxyl group or sulfone group, etc.), epoxy resin, vegetable oil modified alkyd, cyclized rubber, asphalt,
Includes polymeric substances such as vinyl chloride. Further, colorants such as carbon black, nigrosine-based pigment, Carmine 6B, and
Phthalocyanine blue, benzidine yellow, phthalocyanine green, and the like, and a charge control agent such as a metal salt of fatty acid or naphthenic acid, a metal-containing pigment, and a sulfonate can be contained.

The means for forming a toner image by the electrophotographic method is not limited, and a commonly used means can be adopted. However, for developing a toner, a colorant (carbon) is added to a carrier liquid composed of an electrically insulating liquid. (Black, copper phthalocyanine, etc.), a coating agent and a charge control agent, and particularly, as a coating agent, one or more of polyethylene, polypropylene, ethylene copolymer, and propylene copolymer are used to control the charge. It is preferable to use an electrophotographic liquid developer using a negative charge control agent composed of a phosphate ester type surfactant as a material.

The etching solution used in the method of the present invention includes an alkali metal hydroxide, an alkali metal silicate, an alkali metal phosphate, or an alkali metal aluminate, water and, if necessary, a surfactant or other. PH 12 consisting of additives
The above strong alkaline aqueous solution is included.

The etching solution used in the method of the present invention is, for example, JP-A-51-77401 and JP-A-51-8.
0228, 53-44202 and 55-520.
An aqueous solution of an anionic surfactant as described in JP-A No. 54, an organic solvent having a solubility in water of 10% by weight or less at room temperature, an alkaline agent, water and, if necessary, an antifouling agent. Also, JP-A-60-13
A developer for both negative PS plate and positive PS plate described in JP-A-0741 may be used.

In order to improve the coating property of the etching solution, a surface active agent is added to have a surface tension of 45 dyn.
It is adjusted to be e / cm or less, preferably 35 dyne / cm or less.

As the rinse liquid, Japanese Patent Application No. 3-17835 is used.
In addition to those described in the above specification, water or an aqueous solution containing an alkaline agent can be used. In the aspect in which the etching process and the rinsing process are continuously performed, it is obvious that the etching solution is brought into the rinsing step and the rinsing solution becomes alkaline.

When printing, stains due to toner may occur, and it is preferable to remove the toner before printing.

To remove the toner, for example, Japanese Patent Laid-Open Publication No.
No. 6-66863, No. 56130766, No. 62-2
80769, etc., a method of removing by rubbing using an organic solvent-containing aqueous solution (the organic solvent is preferably an alcohol-based one having a solubility in water at 20 ° C. of 10 wt /% or less, and various interfaces). It is also preferable to use an activator together), and a method of removing the hydrocarbon solvent while rubbing it with a treating agent in which water is dispersed is used.

[0061]

EXAMPLES The present invention will be illustrated by the following examples. still,
"Parts" means "parts by weight" unless otherwise specified. Example 1: A, photosensitive lithographic printing plate precursor used 3 parts of phenolic resin having the following structural formula and 0.1 part of maleic anhydride

[0062]

[Chemical 1] Is dissolved in 20 parts of propylene glycol monomethyl ether, and then copper phthalocyanine Lionol manufactured by Toyo Ink Co., Ltd.
1 part of Blue-ER (ε-type copper phthalocyanine) was added and glass beads were dispersed for 30 minutes to obtain a dispersion liquid. Next, an aluminum plate of 1100 mm x 400 mm is grained by electrolytic polishing in a hydrochloric acid bath, and further anodized,
After the pores were sealed with hot water, the above dispersion liquid was applied so as to have a dry film thickness of 5 μm and dried to obtain a lithographic printing original plate.

B. Formation of Latent Image After the above-mentioned photosensitive lithographic printing plate precursor was charged to a plate surface potential of +200 V, a non-image portion was scanned and exposed by a semiconductor laser system writing plotter having a resolution of 2000 DPI to form an electrostatic latent image. Formed. This plotter performs image recording (electrostatic latent image) based on the image signal sent from the connected computer. The power of the laser beam on the plate surface is 1 mW and the beam diameter is the maximum value of the light intensity. It was 13 μm at 1 / e ² .

Enlargement processing of the electrostatic latent image by laser exposure was performed by the following method. Line drawings and characters were expanded by 1 dot around the original image. For the halftone image, LUT conversion was performed as shown in the reproduction curve A shown in FIG. By this LUT conversion, each halftone dot density of the original image is 5
%, 50% and 95% are 9%, 59% and 98, respectively.
Converted to%.

C, Development / Fixation of Latent Image The gap between the developing electrodes is uniformly 2 mm, a bias potential of +40 V is applied to the plate surface, and the developing time is 7 while continuously supplying the liquid developer at 10 l / min to the electrode tube. Then, the plate surface was heated to 150 ° C. by an infrared heater and a fixing process was performed for 5 seconds.

As the developer, a liquid developer produced by the method described below was used. Octadecyl methacrylate / methacrylic acid copolymer (90: 5) 10% Isopa G solution 10 parts MA-100 (carbon black: manufactured by Mitsubishi Kasei) 1 part The above mixture was dispersed with glass beads for 5 hours.

Further, to the above mixture, sun wax 151
P (polyethylene average molecular weight 2000: manufactured by Sanyo Kasei Co., Ltd.)
1 part was added, and the mixture was dispersed for 3 hours while heating at 80 ° C.
This dispersion was diluted 80 times to obtain a liquid developer.

D, Etching Treatment The photosensitive lithographic printing original plate on which the toner image was formed as described above was transferred with a conveying width 1 shown in FIG. 1 of Japanese Patent Application No. 3-171648.
An etching treatment for eluting the non-image area was performed by an etching treatment device having a thickness of 150 mm. The side etch amount was adjusted to 10 μm by adjusting the etching time.

An etching solution having the following composition was used and diluted so that the volume ratio was 1: 5 (water).

Benzyl alcohol 6.0 parts Propylene glycol 6.0 parts pt-Butylbenzoic acid 5.0 parts Benzoic acid 2.0 parts 2-Hydroxy-3naphthoic acid 2.0 parts KOH 50% aqueous solution 26.3 parts potassium silicate solution (Sio _2: 26 wt%) 29.0 parts (Nippon chemical Co., Ltd., A potassium silicate) Pelex NBL 0.2 parts (Kao Atlas Co., sodium alkyl naphthalene sulfonate) EDTA (ethylenediaminetetraacetic acid ) 0.3 parts water 24.0 parts The above etching solution was adjusted to 27 ° C., and 400 cc / m
It was supplied as in and the transport speed was adjusted so that the etching time was 15 seconds.

The etching liquid applied on the plate surface of the photosensitive lithographic printing plate precursor was set to 180 cc / m ² .

Before printing, the plate surface was rubbed with a sponge containing Einper G (manufactured by Exxon) to remove the toner layer.

According to the above method, 100 plates were continuously treated, and as shown in Table 1, adhesion of photoconductive layer components to the grain, a resist image formed from the photoconductive layer on the plate surface,
We evaluated the reproducibility during printing and stains on non-image areas during printing.A good printing plate was obtained, and fine lines and halftone dots were reproduced well even on printing, and stains on non-image areas were also seen. There wasn't.

Other Examples and Comparative Examples: Experiments were conducted by changing the mode of toner image enlargement as shown below and in Table 1.

In the second and third embodiments, a method of enlarging an electrostatic image of a character / line image by one dot in the scanning direction and the sub-scanning direction is adopted as a method of enlarging the character / line drawing.
The conversion and side etch widths were set as shown in Table 1.

In Example 4, the halftone dot density of the original image is 90%.
In the above area, the screen ruling was converted as shown in FIG.

In Examples 5 and 6 and Comparative Example 5, Table 1
In addition to the conditions shown in (1), the image area was exposed, and reversal development was performed using a power toner manufactured by Chemco Co. as a liquid developer. In Example 6, the beam diameter of the laser was changed so that it was 18 μm at 1 / e ² of the maximum value of the light intensity.

In Example 7, as in Example 1, the printing original plate on which the toner image was fixed was subjected to the elution treatment using the apparatus disclosed in Japanese Patent Publication No. 1-60825. As the etching solution, a 6-fold diluted solution prepared by adding 5 liters of water to 1 liter of SDR-1, manufactured by Konica Corporation, and adjusting the temperature to 30 ° C. was used. Water was used as the rinse liquid.

After the etching time was set so that the width of the side etch was 15 μm, a 4-fold diluted solution of the etching solution (SDR-1R manufactured by Konica Corp.) with water was added per plate.
A continuous process of 200 plates was performed while replenishing each with 0 cc.

The maximum and minimum values of side etch and the corresponding evaluations for these plates are shown in Table-1.

In Comparative Example 6, the same as in Comparative Example 1, the printing original plate on which the toner image was fixed was subjected to continuous processing with the side etch width set to 7 μm, as in Example 7.

In Comparative Example 7, the width of side etching was set to 15 μm by the same process as in Comparative Example 6. In Example 9, the amount of ink was reduced and printing without dot gain was tried.
Only a solid image having a low solid density and a low density in the details as a whole and having a poor reproducibility was obtained.

Table 1 shows the experimental results of the above Examples and Comparative Examples. Here, the stain on the non-image area during printing was evaluated as follows. ○ ・ ・ The supply amount of dampening water is 30 to 100 during normal printing.
No stain was generated even when the change was made within the range of%. ○ △ ・ ・ Smear was generated when the supply of dampening water was reduced to 40% of normal printing. △ ・ ・ Smear was generated when the supply amount of dampening water was reduced to 70% of that in normal printing.

Further, the reproduction range of the halftone dots at the time of printing is a range in which the small dots of the highlight do not skip and the shadow is not crushed.

Example 10: An experiment was carried out under the conditions of Example 1 to print without removing the toner. In the printed matter evaluation, up to the first 300 sheets, 5%, 50%, and 95% of each halftone dot of the original image were 6%, 52%, and 96%, and the reproducibility was deteriorated. The reproduction range was 1 to 98%. Fine wire is 50 μm
Met. Dirt on the non-image area did not occur even when the dampening water supply was reduced to 40%.

When the edge of the toner image on the plate was observed with an optical microscope before printing, a part of the toner layer where the photoconductive layer was removed by side etching remained on the grain of the support as fringes. Was. Further, when printing was continued, the toner was gradually transferred from the plate surface to the printed matter on the next 300 sheets, and a slight turbidity was generated in the color ink. After that, the same good printed matter as in Example 1 was obtained.

Comparative Example 8 (Comparative Example of Example 10) An experiment was conducted under the conditions of Example 1 to print without removing the toner. Evaluation of printed matter is 5% up to the first 300 sheets,
The halftone dots of 50% and 95% were 3%, 42% and 93%, respectively. The reproduction range was 3 to 98%, and the fine line was 40 μm. The stain on the non-image area did not occur as in Example 10.

Further, when printing was continued, color turbidity due to toner transfer was confirmed on the next 300 sheets as in Example 10, but thereafter the same results as in Comparative Example 1 were obtained.

[0089]

[Table 1]

[0090]

As is apparent from the above experimental results, the method for manufacturing a lithographic printing plate according to the present invention can solve the problems caused by side etching and solve the above-mentioned problems.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an enlarged example of an image,

FIG. 2 is a schematic diagram showing an enlarged example of an image,

FIG. 3 is a conceptual diagram showing the method of the present invention,

FIG. 4 is a graph showing dot reproducibility,

FIG. 5 is a graph showing the number of screen lines,

[Explanation of symbols]

 1 Support 2 Photoconductive Layer 3 Toner Image 4 Original Image 5 Side Etch Lower Limit 6 Intentional Side Etch

Claims (2)

[Claims] 1. A lithographic printing plate which comprises forming a toner image on a lithographic printing plate precursor having a photoconductive layer provided on a conductive support by an electrophotographic method and then eluting and removing the photoconductive layer in the non-image area. The method for producing a lithographic printing plate as claimed in claim 1, wherein the toner image is formed larger than the original image. 2. After the photoconductive layer in the non-image area is eluted and removed,
The step of removing toner is performed.
The method for producing a lithographic printing plate described in.