JPH0453966A - Method for developing electrophotographic planographic printing plate by wet process - Google Patents

Abstract

PURPOSE:To develop the halftone images of a high line density with a high resolving powder by specifying the hardness of the roll on the side in contact with the toner image forming surface of the planographic printing plate formed by development of roll bodies. CONSTITUTION:The hardness of the roll 9 on the side in contact with the toner image forming surface 1a of the original plate 1 for planographic printing formed by the development of paired squeezing rolls 9, 10 is specified to >=20 deg. and <=70 deg. in the case of the development, by the wet process, of the electrophotographic planographic printing plate 1 for which a metallic base is used, by passing the printing plate through a developing device having the rolls 9, 10. A roll made of the material having the same hardness is usually used for the paired roll 10 in contact with the rear surface of the planographic printing plate of the squeezing rolls 9, 10, but the hardness thereof is not particularly limited. The uniform development with the high resolving power and the excellent fine line and halftone reproducibility particularly at the time of reversal development is executed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a wet developing method for electrophotographic lithographic printing plates.

[Conventional technology]

Many methods for producing lithographic printing plates are already known. For example, a manuscript made of silver halide film is brought into close contact with a printing master plate, and the photosensitive layer of the master plate is directly exposed to ultraviolet rays, etc., whereby hardened portions corresponding to the image areas of the original and uncured portions corresponding to non-image areas are formed. This is a plate-making method in which the uncured portions are washed away with alkali or water, and the cured portions are made ink receptive. A printing plate produced by this method is called a PS plate, and is widely used.

On the other hand, with the establishment of mechanical image processing technology and the development of large-capacity data memory and transmission technology, electronic editing systems have come to be adopted in the newspaper field. This system can input, correct, edit, etc. images such as text, figures, and photographs all under computer control, and can also output film instantly to terminal plotters in remote locations using high-speed communications networks or satellite communications. Because it can be done by printing, it has become possible to produce printing plates in a shorter time than before. However, in the printing field such as newspaper printing, where this electronic editing system is currently employed, it is an important issue to further shorten the time required to produce a printing plate.

Therefore, a direct plate making system is required in which the image information modulated light emitted from the light source of the output plotter is written directly onto a PS plate (not a silver halide film).However, the PS plates currently in use have low sensitivity. Therefore, exposure using a light source with short wavelength and strong energy such as ultraviolet rays is required, and the light source of the output plotter (for example, Ar
A printing plate cannot be produced within a practical time using a long wavelength laser light source such as a laser He-Ne laser or a semiconductor laser. Therefore, an electrophotographic lithographic printing plate is being developed that has higher sensitivity than a PS plate to the light source of an output plotter.

Electrophotographic lithographic printing plates are made from electrophotographic photoreceptors having a photoconductor layer containing a photoconductive material deposited on an electrically conductive support such as aluminum. The material constituting the photoconductor layer of this electrophotographic photoreceptor is
No. 62, No. 38-7758, No. 46-39405,
JP-A-522437, JP-A No. 57-161863, JP-A No. 5
No. 8-2854, No. 58-28760, No. 58-11
No. 8658, No. 59-12452, No. 59-4955
No. 5, No. 62-217256, No. 63-226668
Organic photoconductive compound/binder resin materials such as those described in Japanese Patent Application Laid-Open No. 1-261659 have a practical sensitivity,
Excellent printing durability.

In the process of making an electrophotographic lithographic printing plate, a predetermined charging process is first performed on the photoconductor layer of the electrophotographic photoreceptor to place a negative charge thereon. Exposure then forms an electrostatic latent image corresponding to the image. Subsequently, development and fixing using an electrophotographic developer are performed to form a toner image corresponding to the electrostatic latent image. This non-image area other than the toner image is dissolved and removed (eluted) with a solution containing an alkaline agent, etc., and then the apparent pH of the plate surface is adjusted by washing with water or an acidic rinsing liquid, and if necessary, Processing such as application of a plate surface protection liquid (protective gum liquid) is performed to obtain the final printing plate.

Incidentally, in a printing plate making system using such an electrophotographic method, development using a liquid developer is advantageous due to its good resolution. When a wet development method is used, it is necessary to remove excess liquid developer as uniformly as possible after forming an electrostatic latent image with toner as an image in order to obtain high resolution. Removal methods include a squeezing roll method in which the plate is sandwiched between upper and lower rolls to prevent excess liquid developer on the plate surface from being carried out of the developing device, and a squeezing roll method in which the plate is sandwiched between upper and lower rolls to prevent excess liquid developer on the plate surface from being carried away from the developing device.Air is blown onto the plate surface to push the liquid developer back. There are a drawing method using an air knife, a drawing method using corona charging, etc., but the drawing roll method is effective because of its simplicity, good squeezing effect, and uniformity in the drawing width direction. FIG. 1 is a schematic cross-sectional view of main parts showing an example of an electrophotographic lithographic printing plate wet-type developing device employing a squeeze roll system. The electrophotographic planographic printing plate 1 is carried into the developing section by a pair of carrying rolls 2.3 with the plate surface 1a facing upward, and passes between the developing electrode 4 and the guide 8. At this time, the liquid developer is supplied to the surface of the printing plate 1a from the developer supply port 5 via the developer introduction pipe 7 and the developer rectification chamber 6, and the developed printing plate 1 passes through the nip of the squeeze roll pair 9.10. During this passage, excess liquid developer is removed from the printing plate. A rubber roll is extremely effective as this squeezing roll pair 9, 10.

It is well known that the material of the rubber roll used must be resistant to the components of the liquid developer used. However, it is not known that the hardness of the roll, along with the pressure of the roll, is extremely important in enhancing the squeezing effect, and that it also affects the quality of the image formed, and is not considered much. Ta. In the normal development method, as seen in Japanese Utility Model Publication No. 1-43723 and Japanese Patent Publication No. 52-47331, a hard material such as a metal roll or polycarbonate with no elasticity is used on the plate side of the squeeze roll. There are also examples.

As a result of various experiments, it has been found that the hardness of the roll tends to affect the image quality, especially when forming a high line density halftone image by reversal development.

In reversal development, the image area developed by toner particles is the area where the surface potential has disappeared due to exposure, and the adhesion force of the charged toner particles to the plate surface is mainly present in the non-image area in the fine line area. This is a Coulomb repulsive force from the surface potential, and if more dispersion medium exists after development than necessary and the repulsive force from the non-image area decreases, toner particles will scatter from the image area. For example, when light hits the photoconductive layer after development, the charge held in the non-image area disappears, and the electrical contrast with the image area also disappears, resulting in the toner being retained in the image area. I lose my strength. Furthermore, if there is more dispersion medium than necessary due to poor aperture, there will be considerable repulsion between charged toner particles, and the toner will inevitably move.
The image collapses. Furthermore, even if there is no light, the potential of the non-image area may decrease due to dark decay of the photoconductive layer due to the time taken from the developing process to the fixing process, so the above-mentioned phenomenon may occur. There is also.

In the system for making an electrophotographic printing plate according to the present invention, the support of the electrophotographic printing plate is generally a surface-treated metal plate such as aluminum. Therefore, it is preferable to use straight horizontal transportation from exposure to elution process. In addition, fixing using radiant heat is advantageous since it can be set so that there is little temperature variation for each plate even if a large number of plates are processed, and since it does not come into contact with the toner-developed plate surface, it does not have a physical effect. However, in this case, since the conveyance line is horizontal, there is a possibility that light from a halogen lamp or the like which is a heat source of radiant heat may be unintentionally irradiated onto the plate surface on which an image is formed immediately after development.

In this way, if the hardness of the roll itself is not appropriate, it will not be possible to squeeze out the excess liquid developer even if the roll nip pressure is adjusted, and the image will easily collapse, making it difficult to form an image that is faithful to the electrostatic latent image. In the end, an image with poor resolution is formed. This is an extremely important problem especially in toner development for making printing plates that require high resolution, such as those for color printing.

[Purpose of the invention]

An object of the present invention is to provide an electrophotographic wet development method that is uniform, has high resolution, and is particularly excellent in reproducibility of fine lines and halftone dots during reversal development.

[Means for solving problems]

As a result of extensive studies, the inventors of the present invention have found that the hardness of the aperture roll has a large effect on the final image formation in wet development of electrophotographic lithographic printing plates using metal supports, especially in reversal development. I found out.

In other words, if the hardness is high, the squeezing performance will be reduced and image blurring will occur, and if the roll presser pressure is increased to improve the squeezing performance, the formed toner image will be crushed, resulting in an image with poor resolution. Furthermore, if the nip width is too narrow, the end portion of the sales channel cannot be completely squeezed, and the image at the rear end portion will be disturbed.

If the hardness is too low, the contact area between the rolls, the so-called nip width, increases, deforming the rolls and applying stress to the image, which also causes image blurring.

In order to prevent the above-mentioned problems, the exit-side squeeze roll is held down with at least a force greater than the force required to prevent it from lifting up when the plate enters the plate, and in particular, the hardness of the squeeze roll must be adjusted to JIS (
If the hardness is measured using a spring-type hardness tester type A specified in K6301), and the hardness is in the range of 20 degrees to 70 degrees, more preferably in the range of 40 degrees to 60 degrees, there is no so-called aperture failure and the image has high resolution. It was found that high-quality printed materials could be obtained.

That is, the present invention is a method of wet-developing an electrophotographic lithographic printing plate using a metal support by passing it through a developing device having a pair of aperture rolls, the lithographic printing plate formed by the development of the pair of rolls. This is a wet developing method for an electrophotographic lithographic printing plate, characterized in that the hardness of the roll on the side that contacts the toner image forming surface of the original plate is 20 degrees or more and 70 degrees or less.

In carrying out the present invention, the hardness of the squeeze roll that contacts the back side of the lithographic printing plate is usually the same, but is not particularly limited.

- Percoll hardness, Rockwell hardness, Vickers hardness, etc. are known for measuring the hardness of plastics used in boat fishing. For measuring rubber rolls and blankets for printing machines, etc., the spring-type hardness tester type A mentioned above is very simple and portable, and is used for boat fishing and is also easily available. This was also used to measure the roll hardness related to the present invention.

The method of measuring roll hardness according to the present invention is to place the roll to be measured horizontally, press the needle of the hardness meter perpendicularly to the tangent of the roll and the longitudinal direction of the roll, and press with a constant force. Read the maximum value indicated by the hardness tester. The value at that time is defined as the roll hardness here, but preferably, this measurement is repeated several times at arbitrary points in the longitudinal direction of the roll, and the average value is taken as the hardness of the roll.

The nip pressure of the roll on the developing device varies depending on the roll's own weight, material, shape, thickness of the printing plate, etc., but if the hardness is within the above range, Ig/cm per roll width direction length. As long as it is within the range of ~100 g/cm, there is no practical problem. According to this method, since it is simple, anyone can easily measure it with some training as long as it is calibrated. It is also possible to measure the squeezing roll while it is still installed in the developing device, so the elasticity of the squeezing roll may change depending on the material used, such as rubber, depending on the material used, such as rubber, due to long-term use. However, by managing the rolls by measuring the roll hardness according to the present invention, it is possible to prevent image defects caused by deteriorated rolls.

Still, the squeezing roll according to the present invention may be made of a material having elasticity, such as rubber, in its entire cylindrical portion, or may include a core ring made of metal or the like in the center to provide strength and increase squeezing pressure. ” may exist. Also, the total roll diameter including the core ring etc. depends on the size of the developing device, the size of the electrophotographic printing plate, the amount of liquid, and many other factors, so it is difficult to say more, but the diameter ranges from 10 mm to 100 mm.
It is generally about mm. The so-called range of rubber in such a roll is not particularly defined, and it is sufficient as long as at least the surface layer of the roll is made of rubber and the hardness of the roll is within the above range.

The elastic material of the squeezing roll according to the present invention may be any material as long as it has resistance to the components of the liquid developer, does not swell easily, and has a certain degree of abrasion resistance, aging resistance, weather resistance, etc. Synthetic rubbers made from components with low solubility in hydrocarbons and solvents are preferred, and particularly preferred are acrylonitrile-butadiene copolymer rubbers (NBR
), isoprene-acrylonitrile copolymer rubber, chloroprene rubber (CR), acrylic rubber (ACM-ANM)
, chlorosulfonated polyethylene rubber (C8M), silicone rubber (Q), fluorocarbon rubber (FKM), polysulfide rubber (TR), and the like. Among these, NBR with a high content of acrylonitrile is excellent in terms of processability, durability, solvent resistance, cost, etc. In addition, additives such as reinforcing fillers, extender fillers, dispersibility improvers, adhesion improvers, heat-resistant additives, antioxidants, colorants, crosslinking agents, and curing catalysts are added to the rubbers. It can also be contained within a range that does not affect the solvent properties and the like.

It is desirable that the rolls according to the present invention be used as a pair of upper and lower rolls as squeezing rolls on the exit side of the developing device in order to prevent generation of static electricity due to frictional charging. Of course, there is no problem in using it as a roll in the plate entrance part of the developing device used.

The electrophotographic lithographic printing plate used in the present invention has at least one photoconductive layer on a conductive substrate.

As the conductive substrate, a metal plate such as an aluminum plate or a zinc plate is used, and its thickness is preferably 0.1 to 3 mm, particularly preferably 0.1 to 0.5 mm. Among these substrates, an aluminum plate that is polished and has an anodic oxide film is preferable.

Furthermore, the composition, surface treatment, etc. of the aluminum plate applied to the present invention are not limited; conventionally known and publicly used materials for printing plates can be used as appropriate.

A conventionally known electrophotographic photosensitive layer is provided on such a conductive substrate. As the photoconductive material used in the electrophotographic photosensitive layer, many conventionally known inorganic or organic compounds can be used. For example, inorganic photoconductive materials include selenium and selenium alloys, amorphous silicon, Cd5CdSe, Cd5Se, ZnO1Z
nS etc. can be raised. In addition, examples of organic photoconductive materials include a) triazole derivatives described in U.S. Pat. No. 3,112,197, etc., b) oxadiazole derivatives described in U.S. Pat. d) Imidazole derivatives described in US Pat. No. 3,542,544, US Pat. No. 3,615,402, US Pat.
No. 5-108667, No. 55-156953, No. 56
Polyarylalkane derivatives described in -36656, etc., e) U.S. Patent No. 3180729, U.S. Patent No. 42787
Specification No. 46, JP-A-55-88064, JP-A No. 55-8
No. 8065, No. 49-105537, No. 55-510
86, No. 56-80051, No. 56-88141, No. 57-45545, No. 54-112637, No. 55-74546, etc., f) U.S. Patent No. 3615404 Specification, Special Publication No. 1971-
No. 10105, No. 46-3712, No. 47-2833
No. 6, JP-A-54-83435, JP-A No. 54-11083
6, No. 54-119925, etc., g) U.S. Pat. No. 3,567,450,
No. 3180703, No. 3240597, No. 3658
No. 520, No. 4232103, No. 4175961,
Specification No. 4012376, West German Patent (DAS) 11
No. 10518, Special Publication No. 49-35702, No. 39-2
No. 7577, JP-A-55-144250, JP-A No. 56-1
Arylamine derivatives described in US Pat. No. 19132, No. 56-22437, h) Amino-substituted chalcone derivatives described in US Pat. No. 3,526,501, i) N% described in US Pat. No. 3,542,546, etc.
N-bicalbasil derivatives, j) Oxazole derivatives described in US Pat. No. 3,257,203, etc., k) Styryl anthracene derivatives, described in JP-A-56-46234, etc., (2) JP-A-54-110837, etc. Fluorenone derivatives described in m) U.S. Pat.
No. 59143 (corresponding to U.S. Pat. No. 4,150,987),
No. 55-52063, No. 55-52064, No. 55
-46760, 55-85495, 57-11
No. 350, No. 57-148749, No. 57-1041
Hydrazone derivatives described in US Pat. No. 44, etc., n) US Pat. No. 4,047,948, US Pat.
Benzidine derivatives described in JP-A-58-190953 and JP-A-59-95540, etc.
No. 59-97148, No. 59-195658,
stilbene derivatives described in Japanese Patent Publication No. 62-36674, p) polyvinylcarbazole and its derivatives described in Japanese Patent Publication No. 34-10966, q) polyvinyl described in Japanese Patent Publication No. 43-18674 and Japanese Patent Publication No. 43-19192. Vinyl polymers such as pyrene, polyvinylanthracene, poly-2-vinyl-4-(4'-dimethylaminophenyl)-5-phenyloxazole, poly-3-vinyl-N-ethylcarbazole, r) Tokkosho Polymers such as polyacenaphthylene, polyindene, acenaphthylene/styrene copolymer, etc. described in Japanese Patent Publication No. 43-19193, S) Pyrene/ as described in Japanese Patent Publication No. 13940/1983, etc.
Formaldehyde resin, condensation resin such as ethyl carbazole/formaldehyde resin, t) JP-A-56-9088
Various triphenylmethane polymers described in U.S. Patent No. 3, No. 56-161550, etc.) Examples include metal-free or metal (oxide) phthalocyanine and naphthalocyanine, and derivatives thereof, as described in No. 64-4389.

The organic photoconductive compound is not limited to the compounds listed in a) to U), and any conventionally known organic photoconductive compound can be used. Two or more types of these organic photoconductive compounds can be used in combination, if desired.

Furthermore, various pigments, dyes, etc. can be used in combination for the purpose of improving the sensitivity of the photoconductor or imparting sensitivity to a desired wavelength range.

In photoreceptors for electrophotographic printing plates, the photoconductive compound itself may have film properties, but if the photoconductive compound alone does not have film properties, a binder resin may be used in combination. I can do it. In the electrophotographic photoconductive layer, it is necessary to finally remove the photoconductive layer in the non-image area, but this step depends on the relative relationship between the solubility of the photoconductive layer in the eluent and the resistivity of the toner image in the eluent. Although it cannot be expressed generally, at least as the binder resin, a polymer compound that is soluble or dispersible in the eluent described below is preferable. Copolymers containing monomers having acid anhydride groups or carboxylic acid groups and phenol resins have a high charge retention ability when used as photoreceptors for electrophotographic printing plates, and therefore can be advantageously used.

As the monomer-containing copolymer having an acid anhydride group, a copolymer of styrene and maleic anhydride is preferred. Examples of copolymers containing monomers having carboxylic acid groups include copolymers of styrene and maleic acid monoester, and copolymers of two or more acrylic acid or methacrylic acid and their alkyl esters, aryl esters, or aralkyl esters. Combination is preferred. A copolymer of vinyl acetate and crotonic acid is also good. Among the phenol resins, particularly preferred are novolak resins obtained by condensing phenol, O-cresol, m-cresol, or p-cresol with methanal or ethanal under acidic conditions. The binder resin may be used alone or in combination of two or more types.

The electrophotographic lithographic printing plate used in the present invention is obtained by coating a photoconductive layer on a conductive support according to a conventional method. In producing the photoconductive layer, the components constituting the photoconductive layer may be contained in the same layer, or separately contained in two or more layers, for example, a charge carrier generating substance and a charge carrier transporting substance may be contained. There are known methods for separating and using different layers, and any method can be used to create the layer. The coating solution is prepared by dissolving each component constituting the photoconductive layer in an appropriate solvent, but when using components such as pigments that are insoluble in the solvent, it can be prepared using a dispersing machine such as a ball mill, paint shaker, or dyno mill. It is used after being dispersed to an average particle size of 0.01 to 5 μm.

The binder resin and other additives used in the photoconductive layer can be added during or after dispersing the pigment. An electrophotographic lithographic printing plate can be obtained by applying the coating solution thus prepared onto a support by a known method such as spin coating, blade coating, dip coating, rod bar coating, or spray coating and drying.

In addition to the photoconductive compound and the binder resin, plasticizers, surfactants, and other additives may be added to the photoconductive layer as necessary to improve the physical properties of the photoconductive layer, such as its flexibility and coating surface condition. You can add things.

An intermediate layer may be provided between the conductive support and the photoconductive layer, if necessary, in order to improve adhesion, electrophotographic properties, and the like.

The electrophotographic printing plate created in this way is cut to a desired size and used as a printing plate by the plate-making method described below. In order to prevent ink stains caused by the side surface of the cut electrophotographic lithographic printing plate, a layer that maintains potential during the charging process may be provided on the side surface of the cut electrophotographic lithographic printing plate.

Further, in order to promote elution of the layer, an intermediate layer or the like having higher hydrophilicity than the potential holding layer may be provided below the potential holding layer.

The electrophotographic lithographic printing plate used in the present invention can be produced by a known operation using the above-mentioned electrophotographic lithographic printing plate. That is, it is charged substantially uniformly in a dark place, and an electrostatic latent image is formed by imagewise exposure. Exposure methods include reflective image exposure using a xenon lamp, tungsten lamp, fluorescent lamp, etc. as a light source, contact exposure through a transparent positive film, and scanning exposure using laser light, light emitting diodes, etc. When performing scanning exposure, He-Ne laser, He-Cd laser, argon ion laser, krypton ion laser, ruby laser, YAG laser, nitrogen laser, dye laser, excimer laser, GaAs/G aAIAs, InGaAs
Semiconductor laser alexandrite laser, such as P
Exposure can be performed by scanning exposure using a laser light source such as a copper vapor laser, or scanning exposure using a light emitting diode or liquid crystal shutter (including a line printer type light source using a light emitting diode array, liquid crystal shutter array, etc.).

Next, the electrostatic latent image is developed by a wet reversal development method using the roll according to the present invention, which is suitable for forming a fine image and producing a printing plate with good reproducibility.

The range of the bias voltage to be applied cannot be further specified because it varies depending on the surface potential of the non-image area of the printing master plate, the electrical properties of the toner used, etc., but it is usually between 5V and several 100V.
If it is within this range, it is suitable.

In the case of reversal development, the polarity of the toner used is the same as the polarity with which the original printing plate used is charged, and as long as the polarity of the applied bias voltage is also the same, both + and - can be used without problems. .

The toner image can be fixed by known fixing methods, such as heat fixing, pressure fixing, and the like. Using the toner image thus formed as a resist, the non-image area photoconductive layer and the side surface area potential holding layer are removed using an eluent, and a printing plate can be prepared by processing such as gumming.

〔Example〕

Examples 1 to 3, Comparative Examples 1 to 3 JIS1050 aluminum sheet at 60°C, 10%N
Immersed in aOH aqueous solution, aluminum dissolution amount is 6g/l
I etched it so that it looked like d. After washing with water, it was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize it, and then thoroughly washed with water. Then 0
．． Electrolytic surface treatment was carried out for 20 seconds in a 7% nitric acid aqueous solution,
The surface was washed by immersing it in a 20% aqueous sulfuric acid solution at 50°C, and then washing with water. Furthermore, a support for a printing plate was prepared by performing anodization treatment in a 20% aqueous sulfuric acid solution, washing with water, and drying.

On the surface-treated surface of this support, the following photoconductive layer composition was dispersed in a paint shaker for 1 hour, coated with a bar coater, and dried at 90° C. for 5 minutes to prepare an electrophotographic lithographic printing plate. At this time, the coating amount of the photoconductive layer was 4.5 g/m.

Photoconductive layer coating liquid composition: Butyl methacrylate/methacrylic acid copolymer (40% methacrylic acid): 18 parts: Polymer phthalocyanine: 4 parts: Butyl acetate
60 Part 2-Proper Tools
18 copies The printing master plate thus prepared was charged with a corona discharge in a dark place so that the surface potential (vo) was about +300V, and then a semiconductor laser (7
80 nm), and immediately subjected to wet reversal development (developing bias voltage 90 ■) using a positively charged liquid developer (manufactured by Mitsubishi Paper Industries, Ltd., LOM-EDm) using the wet developing device shown in Figure 1. I did it.

At this time, a stainless steel core ring 9 is used as the squeezing roll 9.10.
Six types of roll pairs (roll pressure: 50 g/an) having rubber coating layers 9a, 10a having the hardness shown in Table 1 on the peripheral surfaces of b and 10b were used.

After development, the plate was left to stand at room temperature until the dispersion medium of the liquid developer remaining on the plate surface dried naturally, and then heat fixing was performed to obtain a toner image on the photoconductive layer. Table 1 shows the results of observing this toner image.

In all of the rolls used in the Examples and Comparative Examples, the elastic body part was made of NBR and the core ring (diameter 18 mm) was made of stainless steel. 706).

(Margin below) Table 1 "None" indicates that an image faithful to the exposed image was formed, and "toner collapse" indicates a fogging condition in which toner in the image area is scattered around the image formed by toner. "Image drift" indicates a state in which the toner image collapses from the rear edge of the image toward the rear in the direction of advance of the plate.

As described above, there are differences in the toner images formed depending on the hardness of the aperture roll of the developing device, and in all of the toner images formed according to Examples 1 to 3, the toner image collapses even after processing such as elution. However, in all of the toner images formed in Comparative Examples 1 to 3, even after treatment such as elution,
As with the toner image, only a printing plate with a distorted image and poor resolution was obtained.

Comparative Example 4.5 In the developing device of FIG.
Using the same electrophotographic original plate as in Example 1 except that EPDM) (roll hardness 45) was used, similar plate making was performed continuously for 5 hours.In the initial stage, the image was not disturbed. However, the occurrence of image defects such as toner collapse gradually increased, and the printing master plate made after 5 hours had severe image distortion and was not suitable for practical use.At this point, the roll was swollen and It was deformed and the roll hardness was measured to be about 15.

Comparative Example 6 In the developing device shown in FIG. 1, toner development and fixing processing were performed in accordance with Example 1 except that the elastic layer 9a of the roll 9 was made of polycarbonate (roll hardness: 97). The resulting toner image on the lithographic printing plate had image defects such as toner collapse, and the image was very blurred, especially in the area of about 30 mm from the rear edge of the plate due to poor squeezing of the liquid developer, which caused the plate-made print to deteriorate. The version was not of practical use.

[Effects of the Invention] According to the present invention, an electrophotographic lithographic printing plate having a metal support is subjected to electrophotographic wet development, particularly electrophotographic wet reversal development processing, by directly exposing a high linear density halftone dot image to five... Agent supply port, 6...Developer rectification chamber, 7...Developer introduction pipe, 8...Guide, 9...Exit side squeezing roll (a: elastic layer, b: core ring)
, 10...Exit side squeezing roll (a: elastic layer, b: core ring) FIG. 1 is a schematic cross-sectional view of an example of a developing device to which the present invention is applied.

DESCRIPTION OF SYMBOLS 1... Electrophotographic lithographic printing plate, 1a... Plate surface of electrophotographic lithographic printing plate, 2... Carry-in roll (a: elastic layer, b: core ring), 3... Carry-in roll (a: Elastic layer, b: core ring), 4... development electrode,

Claims (1)

[Claims] 1. A method of wet developing an electrophotographic lithographic printing plate using a metal support by passing it through a developing device having a pair of aperture rolls, the toner of the lithographic printing plate formed by the development of the pair of rolls. A wet development method for an electrophotographic lithographic printing plate, characterized in that the hardness of the roll on the side in contact with the image forming surface is 20 degrees or more and 70 degrees or less.