JPH10254188A - Plate making method of electrophotographic lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithographic printing plate in which minute black spot defects, especially easily produced in a nonimage part, can be suppressed without damaging a good image having no fog or thinning of lines which is characteristic to reverse development. SOLUTION: An electrophotographic lithographic printing plate produced by forming a photoconductive layer on a conductive base body is subjected to electrification, exposure and reverse development to form an image, and then the nonimage part is removed by dissolving to obtain a lithographic printing plate. In this method, the surface potential (V) of the photoconductive layer during electrification, the center line height Rp(μm) of the conductive base body calculated from the measurement of the surface profile with a tracer type surface roughness meter, and the film thickness T(μm) of the photoconductive layer are controlled to satisfy 10<V<(T/Rp)×100+100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic lithographic printing plate having a photoconductive layer provided on a conductive support, forming a toner image by charging, exposing, and reversal developing, and then eluting and removing a non-image portion. More particularly, the present invention relates to a plate making method for an electrophotographic lithographic printing plate that suppresses minute black spot defects that easily occur in a non-image area.

[0002]

2. Description of the Related Art Many methods for preparing a lithographic printing plate are already known. For example, a silver halide film original is brought into close contact with a printing original, and the photosensitive layer of the original is directly exposed to ultraviolet light or the like,
This is a plate making method in which a cured portion corresponding to the image portion of the document and a non-cured portion corresponding to the non-image portion are formed, the non-cured portion is washed and removed with alkali or water, and the cured portion is made ink-receptive. . The printing plate obtained by this method is called a so-called PS plate, and is widely used.

On the other hand, due to advances in computer image processing technology, memory development of large-capacity data, and data communication technology, in recent years, computer operation has been consistently performed from document input, correction, editing, layout to page set, and a high-speed communication network has been developed. An electronic editing system that can immediately output to a remote terminal plotter by satellite communication or satellite communication has been put to practical use. In particular, not only electronic editing systems but also plate making systems in which printing plates are directly obtained from data therefrom are being put into practical use in the newspaper printing field and the like, where immediacy is required. At present, in such a plate making system, a system using an electrophotographic process and exposing with a laser light source (semiconductor laser, He-Ne laser, etc.) is expected from various aspects.

In such a system, an elution-type electrophotographic lithographic printing plate as described below can be advantageously used because it can be printed under the same printing conditions as a conventionally used PS plate. . The main plate-making process involves charging, exposing, and developing the printing original plate, forming an image with toner, removing the non-image area where toner does not adhere with an eluent, and subjecting the support surface to hydrophilic treatment in advance. To make a printing plate. Here, since the image area protected by the toner is lipophilic, offset printing can be performed.

[0005] An electrophotographic lithographic printing plate is prepared from an electrophotographic photosensitive member in which a photoconductive layer containing a photoconductive compound is adhered on a conductive support such as aluminum. The material constituting the photoconductive layer of the electrophotographic photoreceptor is disclosed in
No. 17162, No. 38-7758, No. 46-3940
No. 5, JP-A Nos. 52-2437 and 57-161863.
No. 58-2854, No. 58-28760, No. 5
Nos. 8-118658, 59-12452, 59-
No. 49555, No. 62-217256, No. 63-22
No. 6,668, JP-A 1-261659, etc., an organic photoconductive compound / binder resin material is excellent in practical sensitivity, printing durability and the like.

In the process of making an electrophotographic lithographic printing plate,
First, a predetermined charging step is performed on the photoconductive layer of the electrophotographic photosensitive member, and a uniform charge is applied. Next, an electrostatic latent image corresponding to the image is formed by exposure. Subsequently, development and fixing using an electrophotographic developer are performed, and a toner image corresponding to the electrostatic latent image is formed. The non-image area other than the toner image is dissolved and removed (eluted) by a solution containing an alkaline agent or the like, and then the apparent pH of the plate surface is adjusted by washing with water or an acidic rinsing liquid.
If necessary, a process such as application of a plate surface protecting solution (protective gum solution) is performed to obtain a final printing plate.

If a toner image is obtained by so-called reversal development in the developing step, a good image free from fog and line thinning can be obtained from the development characteristics. Recently, particularly high resolution and high quality image reproducibility are required, and a method for producing an electrophotographic lithographic printing plate by reversal development is a method that meets this quality requirement.

In the case of performing reversal development, first, light is irradiated to a portion (image portion) where toner is to be adhered in an exposure process, and the potential of the light irradiated portion is substantially 0V.
To be attenuated. At this time, the portion where light irradiation is not performed (the portion corresponding to the non-image portion) maintains the initial charging potential as it is. On the other hand, in the developing process region, a predetermined developing bias is applied between the electrode and the electrophotographic lithographic printing plate via the electrode filled with the liquid developer. In this case, the toner particles in the developer have a charge of the same polarity as the photoconductive layer side charged by a predetermined method. In such a state, when the photoconductor having an electrostatic latent image is carried in the developing electric field in the developing process area, the toner particles are migrated to the photoconductive layer side by the developing electric field, and the light is irradiated. The toner particles adhere to the 0V portion of the photoconductor. At this time, the portion corresponding to the non-image portion where the initial charge potential remains remains repelled by the toner particles, so that adhesion of the toner particles is avoided.

However, when a toner image is formed by reversal development and then a non-image portion is removed by elution to form a printing plate, a black spot defect may occur in the non-image portion although it is extremely small.

Japanese Patent Publication No. Hei 7-31424 discloses that, when a printing plate is produced by an electrophotographic method, there is a problem that a pinhole is generated particularly in a solid portion or a shadow portion of an image.
As a means of eliminating this pinhole, a cutting line provided in parallel with the center line at 2.0 μm above the center line in the measurement of profile R using a stylus type surface roughness measuring device It is described to use a conductive support having a surface having a number of peaks substantially exceeding 0.
However, this pinhole is a defect that occurs during a normal development method in which development is performed using toner particles having a polarity opposite to the charge on the photoconductive layer, and is different from a black spot defect that occurs during reversal development.

As a result of the present inventors' examination of the black spot defect, it has been found that this defect is much more likely to occur in reversal development than in normal development and reversal development, depending on the development method. Therefore, even the method described in the publication has not completely solved the problem. The reason is presumed as follows.

In the reversal development, even if the surface potential of the image portion, that is, the portion irradiated with light does not decrease to around 0 V, if the surface potential is lower than the bias voltage, the toner tends to adhere.
In particular, in a case where an image portion of a minute point has a non-image portion around the image portion, this tendency is further enhanced by the edge effect. Similarly, even if there is no light irradiation or leaking part in the non-image part area, if there is uneven surface potential, locally where the surface potential is lower than the bias voltage,
The toner adheres as if irradiated with light, and a black spot defect occurs.

As described above, up to now, the elimination of black spot defects by reversal development has not been achieved only by controlling the local potential leak caused by the surface of the support.

[0014]

SUMMARY OF THE INVENTION According to the present invention, an electrophotographic lithographic printing plate having a photoconductive layer provided on a conductive support is charged, exposed to light, and formed into a toner image by reversal development. The present invention relates to a method for making an electrophotographic lithographic printing plate as a lithographic printing plate, wherein a fine black spot defect occurring in a non-image portion is suppressed without impairing a good image free from fog and line thinning which are characteristics of reversal development. The purpose is to:

[0015]

Means for Solving the Problems As a result of intensive studies by the present inventors on the above-mentioned problems, it has been found that the problems can be achieved by the following method. That is, an electrophotographic lithographic printing plate in which a photoconductive layer is provided on a conductive support is charged, exposed, and after forming a toner image by reversal development, a non-image portion is eluted and removed to form a lithographic printing plate. A method of making a printing plate, comprising: a surface potential V (v) of the photoconductive layer during charging;
The relational expression 10 <V <(T) is obtained by determining the height Rp (μm) of the center line of the conductive support and the thickness T (μm) of the photoconductive layer, which are obtained from the measurement of the surface shape using a stylus type surface roughness meter. / Rp) × 1
This is a method for making an electrophotographic lithographic printing plate satisfying 00 + 100.

This will be described in more detail below. It has been found that the degree of occurrence of the black spot defects depends on the surface shape of the conductive support and the thickness of the photoconductive layer, and also varies depending on the value of the surface potential of the photoconductive layer during charging. Initially, as a mechanism for the generation of black spot defects, the non-image area must maintain the initial charging potential until the development process is completed, but the charge is locally charged depending on the conditions of the coating liquid for the photoconductive layer and the surface shape of the conductive support. However, it was thought that the local part would be in the same situation as when the light was exposed, and that the toner would adhere during reversal development,
It cannot be suppressed only by local charge leakage,
It is necessary to eliminate unevenness in surface potential over a certain wide range.

The unevenness of the surface potential of the photoconductive layer is closely related to the unevenness of the surface of the conductive support. If the unevenness is large, the unevenness of the surface potential of the photoconductive layer tends to increase accordingly. It is in. In particular, unevenness of the surface potential due to the shape of the convex side of the irregularities on the surface of the conductive support tends to greatly affect the occurrence of black spot defects. When the thickness of the photoconductive layer is small, the surface of the conductive support is more susceptible to irregularities. Moreover, as the surface potential of the photoconductive layer increases, the unevenness of the surface potential increases, and black spot defects tend to occur. The number of occurrences of black spot defects also increases as the surface potential of the photoconductive layer increases, and the rate of increase in the number increases. However, the upper limit of the surface potential of the photoconductive layer is
By selecting within the range of (T / Rp) × 100 + 100, unevenness of the surface potential is prevented, and as a result, generation of black spot defects is suppressed.

The lower the surface potential of the photoconductive layer is, the more the occurrence of black spot defects is suppressed. However, the contrast of the electrostatic latent image after exposure is reduced, and as a result, a sharp toner image cannot be obtained. I will. Therefore, the lowermost limit of the surface potential of the photoconductive layer is preferably higher than 10v.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The value of the surface potential of a photoconductive layer according to the present invention is a value obtained by measuring the amount of charge accumulated on the surface of a photoconductive layer by charging as an electrostatic potential. For the measurement of such an electrostatic potential, a known measurement method can be used.
When measuring the photoreceptor, it is preferable to use a non-contact type electrometer generally called a surface electrometer. The value of the surface potential of the present invention is more important than a value of a very small area at several μm × μm, and a value averaged over a certain area such as several mm × mm. What satisfy | fills should just be used. As an example, a surface electrometer model 362A manufactured by Trek Corporation and a high-precision surface electrometer model S-21 manufactured by Kawaguchi Electric Works, Ltd.
1, S-213 and the like can be suitably used.

The center line peak height Rp according to the present invention will be described. The center line peak height Rp is a kind of surface roughness parameter, and can be determined by a stylus type surface roughness meter. In the measurement of the stylus type surface roughness meter, the parameter value is slightly affected by the stylus diameter and the scanning speed used for the measurement. In the measurement of the surface shape of the present invention, the stylus diameter is 1 μm.
Then, a condition that the scanning speed is 0.15 mm / sec is adopted.

The center line peak height Rp is obtained by extracting a portion of the reference length from the extracted curve, and determining the distance between the extracted curve center line and a straight line parallel to the extracted line and passing through the highest peak height, by calculating the vertical magnification of the extracted curve. Direction, and the value is expressed in μm.
The invention adopts the provisions of the German standard DIN 4762. As described above, the generation of black spot defects can be suppressed by selecting the optimum surface potential of the photoconductive layer using the center line peak height Rp representing the maximum value of the projections of the irregularities on the surface of the conductive support. .

The thickness of the photoconductive layer according to the present invention will be described. Since the thickness of the photoconductive layer is microscopically affected by the unevenness of the surface of the conductive support, the value differs depending on the measurement location. However, in the present invention, an averaged film thickness value obtained by measurement at several places is more important than a microscopic film thickness value. Known measurement methods can be used for measuring such a film thickness value. Further, in the present invention, from the meaning of an averaged value, the relationship between the film thickness and the coating amount may be checked and calibrated in advance from a cross-sectional photograph of an electron microscope, and then the film thickness value may be calculated from the coating amount.

The conductive support used in the present invention may be a plastic sheet having a conductive surface, impermeable and conductive paper, or aluminum, zinc, copper or the like.
A conductive support having a hydrophilic surface such as a metal plate such as a bimetal such as aluminum, copper-stainless steel, and chromium-copper, and a trimetal such as chromium-copper-aluminum, chromium-lead-iron, and chromium-copper-stainless steel. Is mentioned. Their thickness is 0.07 to 2 mm, more preferably 0.1 to 2 mm.
0.5 mm is good. Among these supports, an aluminum plate is preferably used. This aluminum plate may contain a small amount of a different element with aluminum as a main component,
Conventionally known / public materials can be appropriately used.

The electrophotographic planographic printing plate according to the present invention comprises at least a conductive support and a photoconductive layer.

The conductive support according to the present invention may have at least a surface on which a photoconductive layer is provided, if necessary, subjected to a surface treatment to finally obtain a center line average roughness which is a surface roughness parameter of the photoconductive layer side surface of the support. Ra is 0.1 to 1.5 μm, especially 0.1 μm.
Those having a thickness of about 3 to 1.0 μm are preferred.

As a method for surface treatment, known methods, for example, graining and anodic oxidation can be used. Prior to the graining treatment, if necessary, a degreasing treatment with a surfactant or an aqueous alkali solution is performed. Graining methods include mechanical surface roughening, electrochemical surface roughening, and chemical surface selective dissolution. As the mechanical surface roughening method, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, and a buff polishing method can be used. In addition, the electrochemical surface roughening method includes:
There is a method in which an alternating current or a direct current is used in a hydrochloric acid or nitric acid electrolyte. Further, as disclosed in Japanese Patent Application Laid-Open No. 54-63902, a method combining the two can be used.

In the present invention, a method for improving the water retention of the surface of the support and forming a dense and uniform grain having a depth of more than a certain level, particularly, an electrochemical roughening process using an electrolyte mainly containing a mineral acid. Surface treatment is preferred.

The depth of the grain is, for example, the Japanese Patent Publication No. 55-342.
As disclosed in Japanese Patent Publication No. 40, it can be arbitrarily set within a specific range by controlling electrolysis conditions and the like. The aluminum plate thus roughened is used after being subjected to an alkali etching treatment and a neutralization treatment as necessary.

The aluminum plate subjected to the above treatment is subjected to anodizing treatment. As the electrolyte used for the anodizing treatment, sulfuric acid, phosphoric acid, oxalic acid or the like or a mixed acid thereof is used, and the electrolyte and the concentration thereof are appropriately determined depending on the type of the electrolyte. The anodizing conditions vary greatly depending on the electrolyte used and cannot be specified unconditionally, but generally the electrolyte concentration is 1.0 to 80% by weight, the liquid temperature is 5.0 to 70 ° C, and the current density is 5%. 0.0 to 60 A / dm ² , a voltage of 1.0 to 100 V, and an electrolysis time of 10 to 3000 seconds. The amount of the anodic oxide film thus obtained is preferably 0.10 to 10 g / m ² , and more preferably 1.0 to 6.0 g / m ^2.
A range of g / m ² is preferred.

Further, as described in JP-B-47-5125, an anodizing treatment followed by treatment with an aqueous alkali metal silicate solution is also suitable. Also, U.S. Pat.
The electrodeposition of silicate described in Japanese Patent No. 662 is also effective.
The treatment with polyvinyl sulfonic acid described in West German Patent Application No. 162478 is also suitable.

If necessary, casein, polyvinyl alcohol, ethyl cellulose, phenolic resin, styrene / maleic anhydride copolymer may be used between the conductive support and the photoconductive layer to improve adhesion and electrophotographic properties. , Maleic acid / acrylic acid copolymer, acrylic acid / methacrylic acid copolymer, polyacrylic acid, polymaleic acid, poly-α
-Hydroxyacrylic acid, polyitaconic acid, and alkali metal and / or ammonium salts of these polymer electrolytes, amino alcohols such as ethanolamine, and amines such as ethylenediamine, propanediamine and triethylenetetramine, and their hydrochlorides and phosphates , Organic ammonium salts such as oxalate, phosphate esters such as inosit hexaphosphate and salts thereof, malic acid, citric acid, and hydroxycarboxylic acids such as tartaric acid, and salts thereof, or glycine, alanine, Monoaminocarboxylic acids, such as serine, threonine, oxyamino acids such as dihydroxyethylglycine, cysteine, S-containing amino acids such as cystine, aspartic acid, monoaminodicarboxylic acids such as glutamic acid, diaminomonocarboxylic acids such as lysine, p-hydroxy Phenylglycine, phenylalanine, aromatic amino acids such as anthranilic acid, tryptophan, amino acids having a heterocyclic ring such as proline, sulfamic acid, aliphatic aminosulfonic acids such as cyclohexylsulfamic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, (Poly) aminopolyacetic acid such as hydroxyethylethylenediaminetriacetic acid, di (hydroxyethyl) ethylenediaminediacetic acid, ethylenediaminediacetic acid, diethylenetriaminepentaacetic acid, and triethylenetetraminehexaacetic acid; aminotri (methylenephosphonic) acid;
(Poly) aminopoly (methylene phosphonic acid) such as -hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), hexamethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and the like And an intermediate layer in which at least a part of the acid groups of these compounds are made of an alkali metal salt or an ammonium salt.

By providing the intermediate layer, the influence of the unevenness on the surface of the conductive support of the photoconductive layer is reduced, so that the surface potential of the photoconductive layer is set to (T / Rp) × 100 + 10
It can be higher than zero. In this case, the sum of the thicknesses of the photoconductive layer and the intermediate layer is 10 <V <(T /
The surface potential of the photoconductive layer may be selected within the range of (Rp) × 100 + 100.

The photoconductive layer according to the present invention contains at least an organic photoconductive compound and a binder resin, is provided on the above-mentioned conductive support, and can form a toner image by a usual electrophotographic developing method. It is.

As the photoconductive material, known organic compounds can be used. Examples of the organic photoconductive material include a) a triazole derivative described in U.S. Pat. No. 3,121,197, etc., b) an oxadiazole derivative described in U.S. Pat. No. 3,189,447, and c) Japanese Patent Publication No. 37-16096. D) US Patent Nos. 3,542,544 and 3,615,402.
No. 382089, JP-B-45-555
No. 51-10983, JP-A-51-93224
No. 55-108667, No. 55-156953
E) U.S. Pat. Nos. 3,180,729 and 4,278,746, JP-A-55-88064, and 55-8806.
No. 5, No. 49-105537, No. 55-51086
No. 56-80051, No. 56-88141, No. 57-45545, No. 54-112637, No. 55
Pyrazoline derivatives and pyrazolone derivatives described in JP-A-74546; f) U.S. Pat. No. 3,615,404;
No. 10105, No. 46-3712, No. 47-2833
No. 6, JP-A-54-83435 and JP-A-54-11083.
6, phenylenediamine derivatives described in JP-A-54-119925 and the like; g) U.S. Patent Nos. 3,567,450 and 3,180,703
Nos. 3240597, 3658520, 42
Nos. 32103, 417,961 and 401,376
JP-A No. 11-105518, JP-B-49-35702, JP-A-39-27577, JP-A-55-144250, JP-A-56-119132, JP-A-56-22437 and the like. Arylamine derivatives, h) amino-substituted chalcone derivatives described in U.S. Pat. No. 3,526,501, i) N, N-substituted derivatives described in U.S. Pat. No. 3,542,546, etc.
N-bicarbazyl derivatives; j) oxazole derivatives described in U.S. Pat. No. 3,257,203; k) styryl anthracene derivatives described in JP-A-56-46234; 1) JP-A-54-110837; M) U.S. Pat. No. 3,717,462;
No. 59143 (corresponding to U.S. Pat. No. 4,150,987),
No. 55-52063, No. 55-52064, No. 55
No. 46760, No. 55-85495, No. 57-11
No. 350, No. 57-148749, No. 57-1041
No. 44, etc., hydrazone derivatives; n) US Pat.
Nos. 4,265,990, 4,273,846, 42
No. 99897, No. 4306008, etc .; benzidine derivatives; o) JP-A-58-90953, JP-A-59-95540.
No. 59-97148, No. 59-195658,
Stilbene derivatives described in JP-B-62-36674, p) Polyvinylcarbazole and derivatives thereof described in JP-B-34-10966, and q) Polyvinyl described in JP-B-43-18874 and 43-19192. Vinyl polymers such as biylene, polyvinylanthracene, poly-2-vinyl-4- (4'-dimethylaminophenyl) -5-phenyloxazole, and poly-3-vinyl-N-ethylcarbazole; r) JP-B-43-19193 And polymers such as polyacenaphthylene, polyindene and acenaphthylene / styrene copolymer described in JP-B-56-13940.
Condensed resins such as formaldehyde resin and ethylcarbazole / formaldehyde resin; t) JP-A-56-90883 and 56-161550.
U) U.S. Pat. Nos. 3,397,086 and 4,666,802; Japanese Patent Publication Nos. 44-121671, 46-300.
No. 35, No. 49-17535, JP-A-49-11113
No. 6, No. 57-148745, No. 64-2061,
And metal-free or metal (oxide) phthalocyanines and naphthalocyanines described in JP-A-64-4389, and derivatives thereof.

Incidentally, the organic photoconductive compound according to the present invention is not limited to the compounds listed in a) to u), and any known organic photoconductive compound can be used. If desired, two or more photoconductive compounds can be used in combination. In the present invention, phthalocyanine is advantageously used.

As phthalocyanines, α, β, γ,
π, χ, τ, η, X, and ε-type metal-free phthalocyanines,
Alternatively, metal phthalocyanine such as copper, cobalt, lead, zinc, indium, gallium, germanium, and vanadium, or titanyl phthalocyanine is preferable. In particular,
From the standpoints of electrophotographic characteristics such as sensitivity and dark decay, the most suitable phthalocyanine as a photoconductive compound for electrophotographic lithographic printing plates is a χ-type metal-free phthalocyanine.

Various pigments, dyes and the like can be used in combination for the purpose of improving the sensitivity of the photoconductive layer and giving sensitivity to a desired wavelength range.

Examples of these are: 1) US Pat. Nos. 4,436,800 and 4,439,506, JP-A-47-37543, and JP-A-58-1235.
No. 41, No. 58-192042, No. 58-21926
No. 3, 59-78356, 60-179746
Nos., 61-148453, 61-238063
And monoazo, bisazo and trisazo pigments described in JP-B-60-5941 and JP-B-60-45664, and 2) metal phthalocyanines or metal-free phthalocyanines described in U.S. Patent Nos. 3,970,086 and 4,666,802. 3) Perylene pigments described in US Pat. No. 3,371,884, etc. 4) Indigo and thioindigo derivatives described in British Patent No. 2,237,680, etc., 5) British Patent No. 2,237,679 etc. 6) British Patent No. 2237678;
Nos. 184348 and 62-28738, polycyclic quinone-based pigments described in JP-A Nos. 47-30331, and 7) Bisbenzimidazole-based pigments described in JP-A-47-30331, etc. 8) U.S. Pat. Nos. 4,396,610 and 4,64,082. Squarium salt pigments described in the specification, etc. 9) JP-A-59-53850, JP-A-61-212542
And the azulenium salt pigments described in JP-A No. 6-1980.

As the sensitizing infection fee, “electrophotography” 1
2 9 (1973), "Synthetic Organic Chemistry" 24 No.
Known compounds described in 11 1010 (1966) and the like can be used.

[0040] Examples thereof, 10) Applied Optics Supplement 3 50 (196
9), triarylmethane dyes described in JP-A-50-39548, etc. 11) Cyanine dyes described in U.S. Pat. No. 3,597,196, 12) JP-A-59-164588, 60- 16304
No. 7, 60-252517 and the like.

These sensitizing dyes may be used alone or in combination of two or more.

In the photoconductive layer according to the present invention, compounds such as trinitrofluorenone, chloranil, tetracyanoethylene and the like are disclosed in JP-A-58-65439 in order to improve sensitivity and the like.
Compounds described in JP-A-58-102239, JP-A-58-129439, and JP-A-60-71965 can be used in combination.

The photoconductive layer according to the present invention comprises at least an organic photoconductive compound and a binder resin. However, it is necessary to finally remove the non-image portion photoconductive layer from this photoconductive layer. This step is determined by the relative relationship between the solubility of the photoconductive layer in the eluate and the resist properties of the toner image in the eluate, and cannot be expressed in a straightforward manner. A soluble or dispersible polymer compound is preferred.

Specific examples include styrene / maleic anhydride copolymer, styrene / maleic acid monoester copolymer, methacrylic acid / methacrylic ester copolymer, styrene / methacrylic acid / methacrylic ester copolymer, acrylic Styrene and methacrylic acid esters such as acid / methacrylic acid ester copolymer, styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate / crotonic acid copolymer, vinyl acetate / crotonic acid / methacrylic acid ester copolymer; Acrylic acid ester, vinyl acetate,
A copolymer or methacrylamide of a carboxylic acid-containing monomer or an acid anhydride group-containing monomer such as vinyl benzoate or the like with acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride, or fumaric acid; Vinyl pyrrolidone, acryloyl morpholine, phenolic hydroxyl group,
Copolymers containing a monomer having a sulfonic acid group, a sulfonamide group, and a sulfonimide group, phenol resins, partially saponified vinyl acetate resins, xylene resins, and vinyl acetal resins such as polyvinyl butyral can be exemplified.

A monomer-containing copolymer having an acid anhydride group or a carboxylic acid group and a phenol resin have a high charge retention when used as a photoreceptor for an electrophotographic printing plate, and can therefore be advantageously used.

As the monomer-containing copolymer having an acid anhydride group, a copolymer of styrene and maleic anhydride is preferable. As the monomer-containing copolymer having a carboxylic acid group, a copolymer of styrene and maleic acid monoester,
Binary or more copolymers of acrylic acid or methacrylic acid and their alkyl esters, aryl esters or aralkyl esters are preferred. Also, vinyl acetate and crotonic acid are good. Particularly preferred phenol resins include phenol, o-cresol, m-cresol,
Or a novolak resin obtained by condensing p-cresol with methanal or ethanal under acidic conditions. The binder resin may be used alone or in combination of two or more.

When only the photoconductive compound and the binder resin are used, if the content of the photoconductive compound is small, the sensitivity becomes low, so that the photoconductive compound (P) is used with respect to the binder resin (B). ) Is preferably used in a mixture of P / B (weight conversion) of 1/20 or more, more preferably 1/6 or more. However, even if the content of the photoconductive compound is too large relative to the binder resin, not only the sensitivity cannot be expected to be improved as compared to the content increase, but also the balance with other electrophotographic characteristics and the like cannot be obtained. The mixing ratio (P / B) of the binder resin and the photoconductive compound is preferably in the range of 1/6 to 1/3.

The electrophotographic lithographic printing plate according to the present invention can be obtained by coating a photoconductive layer on a conductive support according to a conventional method. In producing the photoconductive layer, a method of including the components constituting the photoconductive layer in the same layer, or a method of separately including two or more layers, for example, a charge carrier generation material and a charge carrier transport material A method of separating and using different layers is known, and it can be manufactured by any method.
The coating liquid is prepared by dissolving each component constituting the photoconductive layer in an appropriate solvent, but when using a component insoluble in a solvent such as a pigment, a ball mill, a paint shaker, a dyno mill,
The average particle size is 0.01 to 5 using a disperser such as an attritor.
μm, more preferably 0.05 to 0.2 μm. The binder resin and other additives used in the photoconductive layer can be added during or after the dispersion of the pigment or the like. Spin coating, blade coating,
An electrophotographic lithographic printing plate can be obtained by coating and drying on a support by a known method such as knife coating, reverse roll coating, dip coating, rod bar coating, spray coating, or extrusion coating. Examples of the solvent for the coating solution include halogenated hydrocarbons such as dichloromethane, dichloroethane and chloroform; alcohols such as methanol, ethanol, 2-propanol and 1-butanol; ketones such as acetone, 2-butanone and cyclohexanone;
Glycol ethers such as -methoxyethanol and 2-methoxyethyl acetate; cyclic ethers such as oxolane, oxane and dioxane; esters such as propyl acetate and butyl acetate; and the like, and the electrophotographic lithographic printing plate according to the present invention. Particularly preferred as a solvent (dispersion medium) for a photoconductive layer is a solvent having at least one of nitrogen and oxygen atoms in a solvent molecule, at least two atoms in which water is dissolved by 5% by weight or more, and specific gravity (25 ° C.) Is a solvent having a property of 0.95 or more. Examples of such solvents include 2-methoxyethanol, methyl formate, 2-ethoxyethyl acetate, 2- (2-ethoxyethoxy) ethanol, acetamide, morpholine, N-methylformamide,
(2-ethoxyethoxy) ethyl acetate, 2-methoxyethyl acetate, 1,3-butanediol, 2-
(2-methoxyethoxy) ethanol, ethyl lactate, 1
-Methyl-2-pyrrolidinone, 1,4-dioxane, 1,
2-propanediol, 2-oxolanmethanol,
1,3-propanediol, ethyl cyanoacetate, methyl acetoacetate, ethylene glycol diacetate,
2-pyrrolidinone, 1,2-ethanediol, diethylene glycol, γ-butyrolactone, 2-furanmethanal and the like.

In the photoconductive layer according to the present invention, if necessary,
Flexibility of the photoconductive layer in addition to the photoconductive compound and the binder resin,
A plasticizer, a surfactant, and other additives can be added for the purpose of improving the film properties such as the coated surface state. As a plasticizer,
Biphenyl, biphenyl chloride, o-terphenyl, p-
Terphenyl, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid and the like can be mentioned.

On the other hand, if the photoconductive layer is too thin, the charge required for toner development cannot be charged. 0.1 to 30 μm
However, it is more preferably 0.50 to 10 μm.

The electrophotographic lithographic printing plate according to the present invention may be charged by corona charging using a corotron, scorotron, or the like. Alternatively, a contact-type charging device using a known charging brush, charging roll, charging blade, or the like may be used. You may use it. The amount of charge with respect to the applied voltage and the like differs depending on the device using corona charging, contact charging, or the like.
When the height of the center line peak of the conductive support obtained from the measurement of the surface shape using a stylus type surface roughness meter is Rp (μm) and the thickness of the photoconductive layer is T (μm), 10 <V <
The applied voltage and the like may be selected within a range of (T / Rp) × 100 + 100.

The exposure according to the present invention forms an electrostatic latent image on the surface of a charged photoconductive layer. The exposure method includes a reflection image exposure using a xenon lamp, a tungsten lamp, a fluorescent lamp or the like as a light source. Examples include contact exposure through a transparent positive film, and scanning exposure using a laser beam, a light emitting diode, or the like. When performing scanning exposure, use He-Ne
Laser, He-Cd laser, argon ion laser, krypton ion laser, ruby laser, YA
G laser, nitrogen laser, dye laser, excimer laser, GaAs / GaAlAs, InGaAsP
Such as semiconductor lasers, alexandrite lasers,
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 a liquid crystal shutter (including a line printer type light source using a light emitting diode array, a liquid crystal shutter array, or the like).

In the reversal development according to the present invention, the electrostatic latent image is developed with toner.
Any of dry development methods (cascade development, magnetic brush development, powder cloud development) and liquid development can be used. In particular, the liquid developing method is suitable for producing a printing plate with which a fine toner image can be formed and which has good reproducibility. The formed toner image can be fixed by a known fixing method such as heat fixing, pressure fixing, and solvent fixing. Using the toner image thus formed as a resist, the non-image portion photoconductive layer is removed with an eluent to produce a printing plate.

The toner according to the present invention needs to contain a resin component having a resist property against the eluate. As the resin component, for example, methacrylic acid,
Acrylic acid and acrylic resin composed of these esters, vinyl acetate resin, copolymer of vinyl acetate and ethylene or vinyl chloride, vinyl chloride resin, vinylidene chloride resin, vinyl acetal resin such as polyvinyl butyral, polystyrene, Copolymers of styrene and butadiene, methacrylic acid esters, etc., polyethylene, polypropylene and its chlorides, polyethylene terephthalate, polyethylene isophthalate, and polyester resins such as polycarbonate of bisphenol A, polycapamide and polyhexamethylene adipamide Polyamide resins, phenolic resins, xylene resins, alkyd resins, vinyl-modified alkyd resins, gelatin, cellulose ester derivatives such as carboxymethylcellulose, other waxes, waxes, etc. It is below. In addition, the toner may contain a dye or a charge controlling agent as long as the toner does not adversely affect development and fixing.

The electrophotographic lithographic printing plate after the toner development can be prepared by using the toner image as a resist and treating the photoconductive layer in the non-image area with a plate-making treatment liquid.

The plate-making processing solution and the processing method according to the present invention will be described below.

As the eluate for dissolving and removing the non-image area photoconductive layer according to the present invention, any solution that at least solubilizes the binder resin can be used, and is not particularly limited. And those having a buffering capacity. As the alkaline agent, the general formula SiO ₂ / M
Representative examples include inorganic alkali agents such as silicates, alkali metal hydroxides, alkali metal and ammonium salts of phosphoric acid and carbonic acid represented by ₂ O (M = Na, K), and amines such as ethanolamine and propanediamine. Organic alkaline agent,
And a mixture thereof. Particularly, the above silicate is advantageously used because it exhibits a strong buffering capacity. In terms of formulation, it is desirable to add an alkali metal hydroxide to this.

When the above silicate is used as the alkali agent, SiO ₂ / M ₂ O is preferably 0.5 to 8.5 (in terms of mol). The pH of the eluate is preferably from 11.5 to 14.0, more preferably from 12.0 to 13.5. In the case of a large number of prints or a change in pH over time, a desired replenisher may be added as needed. It is desirable to improve the elution activity.

The eluate according to the present invention contains a surfactant in order to improve the wettability of the eluate on the surface of the photoconductive layer, thereby improving the elution ability and expanding the elution conditions. Is preferred. Examples of preferred surfactants include alkyl benzene sulfonates (the alkyl group has 8 to 18 carbon atoms, more preferably 12 to 16 carbon atoms), and alkyl naphthalene sulfonates (the alkyl group has 3 to 3 carbon atoms).
10) Formalin condensate of naphthalenesulfonic acid, dialkylsulfosuccinates (the alkyl group has 2 carbon atoms)
To 18), anionic surfactants such as dialkyl amide sulfonates (the alkyl group has 11 to 17 carbon atoms), imidazoline derivatives, carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfates, and imidazolines. And other amphoteric surfactants.

The eluate further includes ionic compounds described in JP-A-55-25100, water-soluble cationic polymers described in JP-A-55-95946, and JP-A-56-1.
Water-soluble amphoteric polymer electrolyte described in JP-A-42528, a neutral salt described in JP-A-58-75152,
Chelating agents described in JP-A-190952, JP-A No. 1-17
No. 7541, a liquid viscosity modifier described in JP-A-63-22
No. 6657, preservatives and bactericides, US Pat.
50727 and 3545970, British Patent No. 138
Known components such as antifoaming agents described in JP-A Nos. 2901 and 1387713, and natural and synthetic water-soluble polymers can be contained as necessary.

The solvent in the eluate is not particularly limited as long as it can stably disperse and dissolve the above components, but water, more preferably, ion-exchanged water is advantageously used. Further, an appropriate amount of an organic solvent may be contained in order to further stabilize the above components or adjust the elution rate.

The water washing solution that can be used in the present invention has such a property that the excess eluate and the solubilized photoconductive layer can be quickly diffused and dissolved in the solution. The washing solution finally contains a compound having an acid dissociation index (pKa) of at least 7.0 to 10.5, and its pH is adjusted to 10.5.
It is desirable to keep below. This compound (hereinafter, unless otherwise specified, is added to the washing solution, at least 7.
A compound having an acid dissociation index (pKa) of 0 to 10.5 is simply referred to as a compound. ) Can be sufficiently washed at first even with water that does not contain at least a compound.
It may be added later and "finally" included in the washing solution,
It may be added to the washing liquid prior to plate making. In the case of the former (post-addition), the pH of the washing solution is 8.5-
A range of 10.5, more preferably 9.5 to 10.0 is desirable. In particular, if the plate size is constant, unless the area of the non-image portion (eluted portion) is largely different, the pH rise of the washing liquid is almost proportional to the amount of printing (number of sheets). Can be added.
In the latter case (first addition), it can be further added to the multi-sheet printing in accordance with the rise in the pH of the washing solution. When a compound is added prior to plate-making, the compound may be added alone, or a compound previously dispersed or dissolved in water may be used. When preparing an aqueous solution, dissolution may be promoted with a small amount of an organic solvent. In particular, if the compound is a water-soluble solid, it may be immersed in a washing tank so that the compound is gradually dissolved by the liquid flow during printing and the pH fluctuation. The pH of the washing solution must always be 10.5 or less, but at least 7.5 in the compound-containing washing solution.
It is desirable to keep in the range of from 10.5 to 10.5, more preferably in the range of from 8.0 to 10.0.

The compound added to the washing solution is 7.0 to 10.5.
If the compound has multiple dissociation stages depending on the compound, at least the acid dissociation index (pKa)
It is sufficient that one of (pKa) is between 7.0 and 10.5. 7.0-1
Examples of compounds having an acid dissociation index (pKa) at 0.5 include:
For example, "Chemical Handbook. Basics II" edited by The Chemical Society of Japan, Showa 59
3rd edition, published by Maruzen Co., Ltd., II-339 to II-34
All of the compounds described on page 2 having the pKa defined in the present invention can be used. Among these, amino acids such as aspartic acid, alanine, glycine, and glutamic acid, and salts thereof are particularly preferable. These compounds may be added as a mixture of two or more kinds, or different compounds may be used for the first addition and the second addition. These compounds may be used as a mixture (salt) with a suitable acid or basic compound.
May be used, or an appropriate acid or basic compound may be used in combination for preparing an aqueous solution (aqueous dispersion) for pH adjustment and dissolution promotion. In particular, when the compound-containing solution is added later, it is desirable that the pH be adjusted to 6.0 to 9.5, more preferably 7.0 to 8.0, and then added. The amount of the compound added to the washing solution is 0.040 to 10% by weight.
More preferably, the content is 0.10 to 5.0% by weight.

When the washing solution is recycled and reused for washing, bacteria in the air are mixed in with the passage of time, which not only deteriorates the washing effect but also produces an unpleasant odor. It is desirable to include an agent and / or a bactericide.

In order to make the electrophotographic lithographic printing plate of the present invention, an automatic elution machine is preferable, and a lithographic printing plate having at least an elution portion and a washing portion and further having a plate surface protective agent coating portion is preferable. It is sufficient that the plate is automatically conveyed and at least elution and rinsing (washing) can be performed, and the specifications of each part are not particularly limited. However, considering the aging of the eluate, depending on the method of supplying the eluate to the photoconductive layer surface, a large amount of the solubilized photoconductive layer flows into the eluate from the plate in the eluate to reduce the deterioration. It is desirable that the eluate be supplied as softly as possible, since it may accelerate. As a method for softly supplying the elution portion, a method is preferable in which the liquid discharged from the eluate supply pipe is uniformly supplied to the photoconductive layer through another member, for example, a rectifying plate, a plate transport upper roll, or the like. The discharge amount of the eluate at this time may be the minimum amount that can be uniformly supplied to the printing plate, but is preferably 1.5 to 100 times the liquid amount taken out of the printing plate when transported to the washing section, more preferably 5.0 to 50 times is good. It is preferable that the amount of eluate carried out is as small as possible, and it is desirable to mechanically adjust the amount to be 10 g / m ² or less.

The washing section must have a mechanism capable of completely removing the solubilized photoconductive layer and excess eluate by supplying the washing liquid onto the plate and quickly. The liquid may be directly supplied to the solubilized photoconductive layer as long as the mechanism can suppress the scattering, or the elution promoting member described in JP-A-60-76395 may be applied to the water washing mechanism. In the washing section,
The solubilized photoconductive layer can be scraped off by directly contacting the rotating brush with the photoconductive layer, but usually the solubilized photoconductive layer can be easily removed without mechanical scraping, and the side-etch Its use is not desirable because it may accelerate deterioration.

The electrophotographic lithographic printing plate subjected to the water washing treatment is treated with a rinsing liquid containing an acidic substance, if necessary.

The rinsing liquid that can be used in the present invention is:
It is desirable that the pH of the solution is adjusted so that the binder resin in the electrophotographic lithographic printing plate photoconductive layer to be subjected to plate making does not re-aggregate. In other words, unless the initial pH of the rinsing liquid at least promotes the insolubilization of the binder resin, the binder resin flowing in with the washing liquid having a neutral or higher liquid pH at least during the liquid circulation pass is in a solubilized state. Therefore, the above-mentioned trouble due to the re-insolubilization of the binder resin can be prevented. However, since the rinsing liquid flows into the protective gum solution for plate surface protection, which is usually performed after that, even if slightly, if the pH of the rinsing solution is high, the pH of the protective gum solution necessarily rises early, and Since the effect is also attenuated, it is desirable to maintain the pH of the rinsing liquid at 7 or less.

Various test materials can be added to the rinsing liquid to adjust the pH of the rinsing liquid. In particular, in order to more stably process a large number of electrophotographic lithographic printing plates with an automatic dissolution machine or the like, it is desirable that the pH of the rinsing solution does not fluctuate during the plate making of at least the rinsing solution. It is desirable to include at least one of a water-soluble salt as an agent. Thereby, when the rinsing solution according to the present invention is applied to an electrophotographic lithographic printing plate, a basic component caused by an eluate remaining on the plate is neutralized, and the non-image portion becomes more hydrophilic. The electrophotographic lithographic printing plate from which the non-image portion photoconductive layer has been removed is subjected to a protective gum treatment for the purpose of improving the scratch resistance of the plate surface and desensitizing the non-image portion.

The protective gum solution that can be used in the present invention contains a polymer compound, a lipophilic substance, a surfactant and the like, and all of these reagents can be used.

[0071]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

Example 1 A JIS1050 aluminum sheet was heated at 60 ° C. and 10% N
immersed in an aOH aqueous solution to dissolve aluminum in an amount of 6 g / m
Etched so as to be ² . After washing with water, it was immersed in a 30% aqueous nitric acid solution for 1 minute to neutralize, and sufficiently washed with water. Thereafter, electrolytic surface roughening was performed in a 2.0% aqueous nitric acid solution containing boric acid for 25 seconds, and the surface was immersed in a 20% aqueous sulfuric acid solution at 50 ° C. to wash the surface, and then washed with water. Furthermore, by performing anodizing treatment in a 20% sulfuric acid aqueous solution, washing with water, and drying,
A support for a printing plate was prepared. SURFCOM 5 made by Tokyo Seimitsu
When measured using a 70A stylus type surface roughness meter, the center line peak height Rp was 2.1 μm.

The following photoconductive layer composition dispersed in a paint shaker for 1 hour was applied to the surface treated surface of the conductive support with a bar coater so that the thickness T of the photoconductive layer was 4.0 μm. After drying at 90 ° C. for 5 minutes, an electrophotographic lithographic printing plate was prepared.

Composition of coating liquid for photoconductive layer Butyl methacrylate / methacrylic acid copolymer (40 mol% of methacrylic acid) 18 parts by weight χ type metal-free phthalocyanine 4 parts by weight 1,4-dioxane 60 parts by weight 2-propanol 18 parts by weight

The obtained printing plate precursor was positively charged in a dark place with a corona charger at an applied voltage of 5.0 kv. The surface potential V of the photoconductive layer is measured using a surface potentiometer Mod manufactured by Trek Corporation.
el362A and probe Model362 for surface electrometer
7, it was 250v. Then, a positively charged toner (ODP-TW, manufactured by Mitsubishi Paper Mills, Ltd.)
, Liquid reversal development was performed, and the toner was thermally fixed, and the entire surface of the plate was made a non-image portion. Next, the eluate (OD, manufactured by Mitsubishi Paper Mills, Inc.)
The photoconductive layer was eluted using (P-DW) and washed with tap water to obtain a printing plate having a non-image area on the entire surface. The obtained plate was visually checked, but no black spot defect was found.

Examples 2-3 An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 200 V and 280 V. Then, a printing plate having a non-image area on the entire surface was obtained. The number of black spot defects was visually observed on the obtained printing plate. Table 1 shows the results. The number of black spot defects indicates the number in a range of 10 cm × 10 cm. In the table, the center line peak height of the conductive support is Rp (μm),
(T / Rp) when the thickness of the photoconductive layer is T (μm)
The value of × 100 + 100 is shown as Vm.

Comparative Example 1 An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 320 V. A printing plate of the image portion was obtained. The number of black spot defects was visually observed on the obtained printing plate. Table 1 shows the results. The number of black spot defects is 10cm
The number in the range of × 10 cm is shown. In the table, (T / Rp) × 100 + 1 where the center line peak height of the conductive support is Rp (μm) and the thickness of the photoconductive layer is T (μm).
The value of 00 is shown as Vm.

[0078]

[Table 1]

From Table 1, the value of the surface potential of the photoconductive layer at the time of charging is V (v), and the height of the center line peak of the conductive support is Rp.
(Μm), and when the thickness of the photoconductive layer is T (μm), it is apparent that the selection within the range of 10 <V <(T / Rp) × 100 + 100 suppresses the occurrence of black spot defects. It is.

Examples 4 and 5 JIS1050 aluminum sheet was heated at 60 ° C. and 10% N
immersed in an aOH aqueous solution to dissolve aluminum in an amount of 6 g / m
Etched so as to be ² . After washing with water, it was immersed in a 30% aqueous nitric acid solution for 1 minute to neutralize, and sufficiently washed with water. Thereafter, in an aqueous 2.0% nitric acid solution containing boric acid, electrolytic surface roughening was performed by changing the electrolysis time and voltage, and the surface was immersed in a 20% aqueous sulfuric acid solution at 50 ° C. to wash the surface and then washed with water. . Furthermore,
An anodizing treatment was performed in a 20% aqueous sulfuric acid solution, followed by washing with water and drying to prepare a printing plate support. The center line peak height Rp was 1.6 μm when measured using a probe-type surface roughness meter of Surfcom 570A manufactured by Tokyo Seimitsu.
A 5 μm conductive support was obtained.

Using this conductive support, an electrophotographic lithographic printing plate was prepared in the same manner as in Example 1, except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 250 V. After processing, a printing plate having a non-image area on the entire surface was obtained. The number of black spot defects was visually observed on the obtained printing plate. Table 2 shows the results. The number of black spot defects indicates the number in a range of 10 cm × 10 cm. In the table, the height of the center line peak of the conductive support is Rp (μm), and the thickness of the photoconductive layer is T (μm).
The value of (T / Rp) × 100 + 100 when Vm is
As shown.

Example 6 The same procedure as in Example 4 was carried out except that the conductive support having a center line peak height Rp of 1.6 μm was used and the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer was 320 V. An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 to obtain a printing plate having a non-image portion on the entire surface. The number of black spot defects was visually observed on the obtained printing plate. Table 2 shows the results. The number of black spot defects indicates the number in a range of 10 cm × 10 cm. In the table, the center line peak height of the conductive support is Rp (μm),
(T / Rp) when the thickness of the photoconductive layer is T (μm)
The value of × 100 + 100 is shown as Vm.

Comparative Example 2 The same procedure as in Example 5 was carried out except that the conductive support having a center line peak height Rp of 2.5 μm was used, and the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer was 320 V. An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 to obtain a printing plate having a non-image portion on the entire surface. The number of black spot defects was visually observed on the obtained printing plate. Table 2 shows the results. The number of black spot defects indicates the number in a range of 10 cm × 10 cm. In the table, the center line peak height of the conductive support is Rp (μm),
(T / Rp) when the thickness of the photoconductive layer is T (μm)
The value of × 100 + 100 is shown as Vm.

[0084]

[Table 2]

From Table 2, the value of the surface potential of the photoconductive layer at the time of charging is V (v), and the height of the center line peak of the conductive support is Rp.
(Μm), and when the thickness of the photoconductive layer is T (μm), it is apparent that the selection within the range of 10 <V <(T / Rp) × 100 + 100 suppresses the occurrence of black spot defects. It is.

Examples 7 and 8 The conductive support having the center line peak height Rp of 2.1 μm in Example 1 and the conductive support having the center line peak height Rp of 2.5 μm in Example 5 were used. The applied amount of the photoconductive layer coating liquid used in the above was changed so that the thickness T of the photoconductive layer became 5.0 μm, and the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 280 V. Except for the above, an electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 to obtain a printing plate having a non-image area on the entire surface. The number of black spot defects was visually observed on the obtained printing plate. Table 3 shows the results. The number of black spot defects is 10 cm x 1
The number in the range of 0 cm is shown. In the table, (T / Rp) × 100 + 100 when the height of the center line peak of the conductive support is Rp (μm) and the thickness of the photoconductive layer is T (μm).
Is shown as Vm.

Comparative Examples 3 and 4 Electrophotographic lithographic printing plates were prepared and processed in the same manner as in Examples 7 and 8, except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 380 V. Then, a printing plate having a non-image area on the entire surface was obtained. The number of black spot defects was visually observed on the obtained printing plate. Table 3 shows the results. Number of black spot defects is 10
The number in the range of cm × 10 cm is shown. In the table, (T / Rp) × 100 when the height of the center line peak of the conductive support is Rp (μm) and the thickness of the photoconductive layer is T (μm).
The value of +100 is shown as Vm.

[0088]

[Table 3]

From Table 3, the value of the surface potential of the photoconductive layer at the time of charging is V (v), and the height of the center line peak of the conductive support is Rp.
(Μm), and when the thickness of the photoconductive layer is T (μm), it is apparent that the selection within the range of 10 <V <(T / Rp) × 100 + 100 suppresses the occurrence of black spot defects. It is.

Examples 9 to 10 Using the conductive support having the center line peak height Rp of 2.1 μm in Example 1 and the conductive support having the center line peak height Rp of 2.5 μm in Example 5, The coating amount of the photoconductive layer coating liquid used in the above was changed so that the thickness T of the photoconductive layer became 3.0 μm, and the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 200 V. An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 except for the above, to obtain a printing plate having a non-image portion on the entire surface. The number of black spot defects was visually observed on the obtained printing plate. Table 4 shows the results. The number of black spot defects is 10cm ×
The number in the range of 10 cm is shown. In the table, (T / Rp) × 100 + 10 where the height of the center line peak of the conductive support is Rp (μm) and the thickness of the photoconductive layer is T (μm).
The value of 0 is indicated as Vm.

Comparative Examples 5 to 8 Examples 9 to 1 were performed except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 280 V and 320 V.
An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example No. 0 to obtain a printing plate having a non-image portion on the entire surface. The number of black spot defects was visually observed on the obtained printing plate. Table 4 shows the results. The number of black spot defects indicates the number in a range of 10 cm × 10 cm. In the table, when the height of the center line peak of the conductive support is Rp (μm) and the thickness of the photoconductive layer is T (μm), (T / R
The value of p) × 100 + 100 is indicated as Vm.

[0092]

[Table 4]

From Table 4, the value of the surface potential of the photoconductive layer at the time of charging is represented by V (v), and the height of the center line peak of the conductive support is represented by Rp.
(Μm), and when the thickness of the photoconductive layer is T (μm), it is apparent that the selection within the range of 10 <V <(T / Rp) × 100 + 100 suppresses the occurrence of black spot defects. It is.

Comparative Example 9 An electrophotographic lithographic printing plate was prepared and processed in the same manner as in Example 1 except that the applied voltage of the corona charger was changed so that the surface potential of the photoconductive layer became 7 V. A printing plate of the image portion was obtained. When the resulting plate surface was visually observed, the entire non-image portion was slightly fogged, and a good printing plate was not obtained.

[0095]

According to the present invention, an electrophotographic lithographic printing plate having a photoconductive layer provided on a conductive support is charged, exposed, and subjected to reversal development to form a toner image. In the method of making an electrophotographic lithographic printing plate as a printing plate,
In particular, black spot defects occurring in non-image portions are suppressed.

Claims (1)

[Claims] An electrophotographic lithographic printing plate having a photoconductive layer provided on a conductive support is charged, exposed, and subjected to reversal development to form a toner image, and then a non-image portion is eluted and removed to form a lithographic printing plate. A plate making method for an electrophotographic lithographic printing plate, wherein a surface potential V (v) of the photoconductive layer at the time of charging and a center line peak height of the conductive support obtained from measurement of a surface shape by a stylus type surface roughness meter. Sa R
p (μm) and the thickness T (μm) of the photoconductive layer are expressed by the following relational expression 1.
A plate making method for an electrophotographic lithographic printing plate, wherein 0 <V <(T / Rp) × 100 + 100 is satisfied.