JP2793020B2 - Manufacturing method of electrophotographic lithographic printing plate - Google Patents

Description

The present invention relates to a method for producing an electrophotographic lithographic printing plate in which a dispersion for forming a photoconductive layer is applied to a conductive support. The present invention relates to a method for producing an electrophotographic lithographic printing plate having improved coating properties, good resolution of an image of a produced printing plate and the like, no occurrence of background stain, and high printing durability.

(B) Conventional technology and its problems In recent years, with the establishment of mechanical image processing technology and storage and transmission technology of large-capacity data, computer control of image input, correction, editing, layout, page combination, etc. of characters and figures, etc. However, an electronic editing system capable of instantaneously outputting data to a remote terminal plotter via a high-speed communication network or satellite communication is operating.
In particular, the demand for this electronic editing system is high in the field of newspaper printing, which relies on immediacy.

However, lithographic offset printing plates, also known as PS plates, which have been conventionally used in the newspaper printing field, generally have low sensitivity because image formation involves at least a chemical structural change due to actinic radiation of a photosensitive agent, and the The recorded silver halide photographic film master is subjected to close contact exposure for plate making.
Therefore, even in the place where the electronic editing system is operating, the image output is once performed on the silver halide photographic film, and based on this, the printing plate is produced indirectly by close contact exposure to the PS plate. . This is the output plotter light source (eg,
This is because it is difficult to develop a direct-type printing plate having a sensitivity high enough to produce a printing plate within a practical time using a He-Ne laser, a semiconductor laser, or the like.

Therefore, an electrophotographic photosensitive member is considered as a photosensitive material having high photosensitivity capable of providing a direct printing plate. Conventionally,
As a printing plate material (original plate for printing) using electrophotography,
For example, JP-B-47-47610, JP-B-48-18325, JP-B-48-4000
No. 2, photoconductive zinc oxide described in JP 51-15766, etc.
Resin-dispersed offset printing plate material and Japanese Patent Publication No. 37-17162
Nos. 38-7758, 41-2426, 46-39405, JP-A-50-19509, 52-2437, 54-134632
No. 54-145538, No. 55-153948, No. 57-147656, No.
Organic photoconductive compound / binder resin-based printing plate materials as described in, for example, JP-A-57-161863 are known.

The former photoconductive zinc oxide / resin dispersion type offset printing plate material has a zinc oxide-rich photoconductive layer based on paper having water resistance and conductivity, and after forming a toner image by electrophotography, the After the non-image area is wetted with a desensitizing solution (for example, an acidic aqueous solution containing hexacyanoferrate or inosit hexaphosphate) to make it non-sensitive, it is subjected to printing. Offset printing plates that have been treated in this way have a maximum number of printings of about 10,000 from the viewpoint of good print image reproducibility. Have.

Since the photosensitive region of photoconductive zinc oxide has a shorter wavelength, sensitivity is usually increased by using a dye sensitizer such as rose bengal or bromophenol blue. Without a practical photosensitive area
At present, it has not reached practical use until drawing with a semiconductor laser.

On the other hand, in the latter organic photoconductive compound / binder resin-based printing plate material, since the electrophotographic photoreceptor is generally provided on an aluminum substrate, the aluminum substrate and the photoconductive layer are firmly adhered to each other. If it is, it has essentially the same or higher printing durability as the PS version. Further, organic photoconductive compounds having a practical sensitivity of 800 nm or more are already known, and the practical use of the above printing plates using these compounds is also in progress.

In these general plate making methods, after a toner image is formed by an electrophotographic image forming method, non-image portions other than the toner image portion are treated with a liquid containing an alkaline agent or the like, so that a non-image Dissolves part of photoconductive layer (so-called elution)
More generally, the excess eluate and the solubilized photoconductive layer are removed from the plate with a washing solution having a neutral or higher pH, and if necessary, a plate surface protecting solution (protective gum solution). Is applied for plate making.

In the plate making method according to this method, the image portion includes not only the toner image portion but also the photoconductive layer under the toner image portion. Even if the toner image portion is worn, the photoconductive layer retains the function of the image portion. Excellent in nature.

As a result of further studies on these lithographic printing plates, if the surface roughness of the conductive support in these lithographic printing plates was too large, halation was likely to occur, and the plate resolution such as image resolution and sharpness was high. Not only is not preferable from the point of view, but the elution of the non-image area is not completely performed, so that an elution failure called a so-called pigment residue occurs, and it is preferable in terms of printability that a printing background stain occurs when used as a printing plate. No adverse effects were found.

It has also been found that, if the surface roughness of the lithographic printing plate conductive support is too small, the adhesion of the photoconductive layer to the support is insufficient, resulting in insufficient printing durability.

The present invention further relates to a method for producing an electrophotographic lithographic printing plate, in which a dispersion for forming a photoconductive layer is coated on a conductive support. As a result of examining the relationship with the viscosity of the liquid, if the viscosity of the dispersion for forming a photoconductive layer is absolutely high, coating unevenness occurs regardless of the surface roughness of the conductive support, and coating unevenness does not occur Even if the coating can be applied in such a way, if the surface roughness of the support becomes too large, the coating liquid is not filled in the valleys and the adhesiveness between the photoconductive layers of the support becomes insufficient, resulting in plate making such as image reproducibility and poor elution. -It has an adverse effect on printability. Conversely, if the viscosity of the dispersion for forming a photoconductive layer is too low, the valley of the support is sufficiently filled with the coating solution, and thus the adhesiveness is improved as the surface roughness is increased. Due to the provision on the conductive support having the surface roughness, microscopically, the photoconductive layer itself has thickness unevenness, and the migration of the binder resin is easily induced during the coating liquid drying. It was also found that electrophotographic characteristics such as charging potential and the like, and that the image was thinned due to the infiltration of the eluate from the side surface of the photoconductive layer during the elution, called a side etch, resulted in unevenness.

(C) Object of the Invention An object of the present invention is to provide an electrophotographic lithographic printing plate having a photoconductive layer comprising at least a phthalocyanine and a binder resin on a conductive support, having excellent phthalocyanine dispersibility, An object of the present invention is to provide a method for producing an electrophotographic lithographic printing plate capable of obtaining a printing plate having improved coating properties without occurrence of coating unevenness and excellent image resolution and sharpness.

Another object of the present invention is to provide a method for producing an electrophotographic lithographic printing plate having a high printing durability, free from background stains on printed matter, and capable of obtaining a printing plate with good water retention.

(D) Means for Achieving the Object The object of the present invention is to provide an electrophotographic lithographic printing plate in which a photoconductive layer containing at least phthalocyanine and a binder resin is provided on a conductive support coated with aluminum oxide. In the production method, the viscosity of the dispersion for forming a photoconductive layer having a solid concentration of 4 to 10% by weight on a conductive support having a center line average roughness (Ra) of 0.3 to 0.8 μm is in a range of 5 to 22 cp. It is achieved by preparing and applying the solution.

The dispersion for forming a photoconductive layer to which the present invention is applied (hereinafter, referred to as a dispersion) has a thixotropic behavior.
When specifying the viscosity, it is necessary to specify measurement conditions. The viscosity of the dispersion in the present invention is a value obtained by measuring the viscosity of the dispersion at 25 ° C. and 20 rpm with a cone A using an E-type viscometer manufactured by Tokyo Keiki Co., Ltd.

Phthalocyanine is used as the photoconductive compound for a photoconductive layer according to the present invention. Phthalocyanine is 50-27
No. 80, No. 45-8102, No. 45-11021, No. 46-42511,
No. 46-42512, No. 48-163, No. 49-17535, No. 50-5
No. 059, and JP-A Nos. 64-569, 64-17066, 64-4
No. 5474, JP-A-1-144057, JP-A-1-153757, JP-A-1
217362, 1-22259, 1-252967, 1-28
5952, 1-32-1551, 2-8256, 2-16570
Phthalocyanine described in Japanese Unexamined Patent Publication (Kokai) No. H10-209, which is represented by the general formula (C ₈ H ₄ N ₂ ) ₄ Rn, wherein R is hydrogen, lysium, sodium, potassium, copper, silver, beryllium, magnesium, calcium, Zinc, cadmium, barium, mercury,
Aluminum, indium, lutetium, titanium, tin,
Hafnium, lead, vanadium, antimony, chromium, molybdenum, manganese, iron, cobalt, nickel, rhodium, palladium, osmium, and platinum;
~ 2.

Of these, α, β, γ, π, τ, χ, and ε-type metal-free phthalocyanines, or metal phthalocyanines such as copper, magnesium, cobalt, lead, zinc, and titanyl (TiO) are preferable, and a He-Ne laser is more preferable. Χ-type metal-free phthalocyanine, ε-type copper phthalocyanine, which has practical photosensitivity even in a long wavelength region corresponding to a light source such as a semiconductor laser,
And titanyl phthalocyanine are preferred.

The photoconductive layer for an electrophotographic lithographic printing plate according to the present invention comprises at least phthalocyanine and a binder resin.
In this electrophotographic photoconductive layer, it is necessary to finally remove the non-image portion photoconductive layer, but this step is based on the relative solubility of the photoconductive layer in the eluate and the resistability of the toner image in the eluate. It is determined by the relationship and cannot be expressed unconditionally, but at least the binder resin is preferably a polymer compound soluble or dispersible in the above-mentioned eluate.

Specific examples include styrene / maleic anhydride copolymer, styrene / maleic acid monoester copolymer, methacrylic acid / methacrylic acid ester copolymer, styrene /
Methacrylic acid / methacrylic acid ester copolymer, acrylic acid / methacrylic acid ester copolymer, styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate /
Styrene such as crotonic acid copolymer, vinyl acetate / crotonic acid / methacrylic acid ester copolymer, methacrylate, acrylate, vinyl acetate, vinyl benzoate and the like, and acrylic acid, methacrylic acid, itaconic acid, crotonic acid, Copolymers with carboxylic acid-containing monomers such as maleic acid, maleic anhydride and fumaric acid, or copolymers with monomers containing acid anhydride groups, methacrylamide, vinylpyrrolidone, acryloylmorpholine, phenolic hydroxyl groups, sulfonic acid groups, sulfonamides And vinyl acetal resins such as phenolic resins, partially saponified vinyl acetate resins, xylene resins, and polyvinyl butyral.

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 electrophotographic printing, and can therefore be advantageously used.

The binder resin may be used alone or in combination of two or more.

When using only phthalocyanine and a binder resin,
If the content of phthalocyanine is small, the sensitivity becomes low,
Phthalocyanine (P) is P / B with respect to binder resin (B)
It is preferable to use a mixture of 1/20 or more (in terms of weight), 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 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 1/2. When the thickness of the photoconductive layer is too small, the electric charge required for toner development cannot be charged. 0.10-30 μm because it cannot be obtained
However, it is more preferably 0.5 to 10 μm. The electrophotographic lithographic printing plate according to the present invention is obtained by coating a photoconductive layer on a conductive support. 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 method in which the lower layer has a higher acid value and / or There is known a method in which a low molecular weight alkali-soluble binder resin is filled and the upper layer is separated into a layer having a higher phthalocyanine content and used, and any method may be used.

The dispersion is prepared by dissolving or dispersing the components constituting the photoconductive layer in an appropriate solvent. The phthalocyanine is dispersed using a dispersing machine such as a ball mill, paint shaker, dyno mill, and attritor to have an average particle size of 0.01 to 5 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 phthalocyanine is dispersed. The coating solution prepared in this manner is applied to a support by a known method such as spin coating, blade coating, knife coating, reverse roll coating, dip coating, rod bar coating, spray coating, extrusion coating, and then dried. Photolithographic printing plates can be obtained. 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; acetone;
Butanone, ketones such as cyclohexanone, 2-methoxyethanol, glycol ethers such as 2-methoxyethyl acetate, oxolane, oxane, cyclic ethers such as dioxane, propyl acetate, esters such as butyl acetate, and the like, Particularly preferred as the solvent (dispersion medium) for the photoconductive layer of the electrophotographic lithographic printing plate according to the present invention has at least one of nitrogen and oxygen atoms in the solvent molecule and at least 5% by weight of water. A solvent that has the property of being dissolved and having a specific gravity (25 ° C.) of 0.95 or more. Examples of such solvents include 2-methoxyethanol, methyl formate, 2-ethoxyethyl acetate,
(2-ethoxyethoxy) ethanol, acetamide,
Morpholine, N-methylformamide, 2- (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,
Examples thereof include 2-ethanediol, diethylene glycol, γ-butyrolactone, and 2-furanmethanal.

In the photoconductive layer according to the present invention, if necessary, in addition to the photoconductive compound and the binder resin, for the purpose of improving the film properties such as the flexibility of the photoconductive layer and the coated surface state, a plasticizer, a surfactant, And other additives can be added.

The solvent may be appropriately selected depending on the solubility of the binder resin to be used and the dispersibility of the phthalocyanine. However, two or more solvents may be mixed and used in consideration of coatability, dry film forming property and the like. When two or more kinds are mixed, it is particularly desirable to design a dispersion mainly using a solvent having the above properties.

The viscosity of the dispersion significantly affects the coatability and the like, but it is important that the viscosity of the dispersion according to the present invention be in the range of 5 to 22 cp. If the viscosity of the dispersion is lower than 5 cp, drying unevenness such as color unevenness is likely to occur during drying, and it becomes difficult to maintain a desired film thickness after drying and to apply the film uniformly in the width direction. Conversely, if the viscosity of the dispersion is higher than 22 cp, coating streaks and the like are likely to occur, and the thixotropic properties of the dispersion are more manifested, making it difficult to control uniform coating. A more preferred range of the viscosity of the dispersion is from 8 to 20 cp.

The above viscosity range is preferably adjusted when the solid content of the dispersion is in the range of 4 to 10% by weight. If the solid content is too low, the phthalocyanine pigment tends to aggregate, while if it is too high, the pigment dispersion tends to take a long time, which is not preferable.

Next, the conductive support used in the electrophotographic lithographic printing plate according to the present invention will be described.

Examples of the conductive support known in the present invention include a conductive support having an aluminum oxide surface such as a metal plate of aluminum, copper-aluminum or the like. Their thickness is preferably 0.07 to 2.0 mm, more preferably 0.1 to 0.5 mm. Among these supports, an aluminum plate is preferably used. This aluminum plate may contain aluminum as a main component and contain a trace amount of a different element, and conventionally known and publicly available materials can be appropriately used.

The conductive support according to the present invention has a surface provided with at least a photoconductive layer if necessary, and finally has a centerline average roughness (Ra) of 0.3 to 0.8 μm on the photoconductive layer side surface of the support.
m.

The center line average roughness (Ra) expressing the surface roughness can be determined by various measuring methods. The surface shape of the conductive support photoconductive layer side surface according to the present invention is determined by the scanning length and the surface roughness. In consideration of the level of contact, a stylus-type contact type device is used.

The center line average roughness Ra is obtained by extracting a portion of the measurement length L in the direction of the center line from the extraction curve, setting the center line of the extracted portion as the X axis, the direction of the vertical magnification as the Z axis, and extracting the extraction curve. Z =
When represented by f (x), it is given by the following equation and is expressed in μm.

That is, Ra represents the standard deviation obtained by dividing the area of the portion surrounded by the extraction curve and the center line by the measured length.

The center line average roughness Ra in the present invention is JI as in the above equation.
It is defined by SB 0601.
The value measured under the conditions of 0.08 mm, measurement length of 0.5 mm, and scanning speed of 0.06 mm / sec is adopted.

As a method of surface treatment, a known method, for example, graining or 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. As the electrochemical surface roughening method, 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, it is a method of improving the water retention of the surface of the support, making a dense and uniform grain with a certain depth or more,
In particular, an electrochemical surface roughening method using an electrolyte mainly containing a mineral acid is preferable.

The depth of the grain can be arbitrarily set within a specific range by controlling electrolytic conditions and the like as disclosed in, for example, Japanese Patent Publication No. 55-34240.

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

The aluminum plate that has been subjected to the above-described processing is anodized. 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. Anodizing conditions are not specified unconditionally to vary considerably with the electrolyte used, the amount of anodized film has good 0.10~10g / m ^2, more preferably in the range of 1.0~6.0g / m ² is there.

The surface shape of the conductive support having a center line average roughness (Ra) of 0.3 to 0.8 μm thus obtained is more preferably a bearing length (R tp) defined by ISO 4287/1 of 70. It is desirable for the surface to be as rough as 85%. When the bearing length of the electrophotographic lithographic printing plate support according to the present invention is less than 70%, the anchoring effect of the photoconductive layer on the support is reduced by half, and conversely the bearing length is 85%.
%, The possibility that the photoconductive layer remains without being removed in the concave portion on the surface of the support during elution increases, and the background stain easily occurs during printing. A more preferred bearing length range is 73-82%.

As required between the conductive support and the photoconductive layer, for improving adhesion and electrophotographic properties, see JP-A-1-185668.
And an intermediate layer described in JP-A No. 1-186967 and the like.

An electrophotographic lithographic printing plate can be obtained by providing the above electrophotographic photoconductive layer on the conductive support thus obtained.

(E) 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 present invention.

The viscosity of the dispersion was measured at 25 ° C. and 20 rpm with a cone A using an E-type viscometer manufactured by Tokyo Keiki Co., Ltd.

Example 1 * conductive support Preparation of JIS1050 aluminum sheet 60 ° C., and immersed in 10% NaOH aqueous solution, the amount of dissolved aluminum was etched so as to become 6 g / m ^2. After washing with water, it was immersed in a 30% nitric acid aqueous 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 for 25 seconds, and the surface was washed by immersion in a 20% aqueous sulfuric acid solution at 50 ° C., followed by washing with water. In addition, 20%
An anodizing treatment was performed in an aqueous sulfuric acid solution, followed by washing with water and drying to prepare a printing plate support (support No. 1). At this time, the center line average roughness of the surface treated surface of the support (Ra)
Was 0.52 μm.

* Preparation and application of photoconductive layer coating liquid The following photoconductive layer composition was dispersed for 1 hour using a paint shaker to prepare a photoconductive layer forming coating liquid. At this time, the liquid viscosity was 14 cp. This coating liquid is applied to the surface treated surface of the support by an extrusion coater so that the solid content is applied.
After coating and drying at 4.5 g / m ² , the mixture was further heated at 90 ° C. for 5 minutes to prepare an electrophotographic lithographic printing plate.

Photoconductive layer coating liquid 1 composition Butyl methacrylate / methacrylic acid copolymer (methacrylic acid 35% by weight) 5 parts by weight χ type metal-free phthalocyanine 1 part by weight 1,4-dioxane 60 parts by weight 2-ethoxyethyl acetate 14 parts by weight 2 -Propanol 10 parts by weight * Toner development The obtained printing plate precursor is charged in a dark place by corona discharge so that the surface potential (V ₀ ) becomes approximately +300 V, and then a semiconductor laser (780 nm) is used. After scanning image exposure, liquid reversal development was performed immediately with positive charge toner (Mitsubishi Paper Corp., LOM-ED III) and the toner was thermally fixed. A toner image with a resolution of 50 lines / mm was reproduced on the photoconductive layer. It was obtained well. The sharpness of the image was also good.

* Plate making process Next, an automatic elution machine, eluate, washing solution,
And a plate-making process using a rinsing liquid.

1) Automatic dissolution machine A dispensing device that has a dissolution tank, a subsequent washing tank, and a rinsing tank, and that transports the electrophotographic lithographic printing plate after toner development, and a storage tank, a pump, and a spray nozzle for processing liquid in each processing tank. → An automatic machine having a device for circulating in the storage tank cycle and a replenishing device for each processing tank was used.

2) eluent 1 Composition aqueous solution of sodium silicate (SiO ₂ minutes 30 wt%, SiO ₂ / Na ₂ 0 mole ratio of 2.5) 20 parts by weight of potassium hydroxide, 1 part by weight of pure water 79 parts by weight 3) wash solution 1 composition (20 dm ³ ) 0.1 part by weight of dioctylsulfosuccinate sodium 0.1 part by weight of 2-methyl-3-isothiazolone is dispersed and dissolved in pure water to make up to 100 parts by weight, and the solution is charged into a washing tank. Every 10 plate treatments, 15 ml of a 5% by weight aqueous glycine solution was added.

4) Rinse solution 1 composition (30 dm ³ ) Succinic acid 0.5 parts by weight Phosphoric acid (85% aqueous solution) 0.5 parts by weight Decaglyceryl monolaurate 0.05 parts by weight 2-methyl-3-isothiazolone 0.01 parts by weight Sodium hydroxide is added to this The solution was adjusted to pH 4.7, and then adjusted to 100 parts by weight with pure water.

When plate making was performed using the above-mentioned processing solution (elution time was set to 8 seconds), the side etch was only about 3 μm on one side and the fluctuation was slight. No failure such as pigment remaining) was observed.

Next, when this printing plate was used for printing with an offset printing machine (Hamaduster 600 CD), at least
Up to 100,000 sheets, good printed matter was obtained with less generation of stain on the printed matter.

Example 2 A support having the surface shape shown in Table 1 was obtained by changing the electrolytic surface roughening time during the preparation of the conductive support of Example 1.

The photoconductive layer coating solution 1 was applied to each of the above supports under the same conditions as in Example 1 and dried. When all the obtained electrophotographic lithographic printing plates were developed and subjected to plate making under the same conditions as in Example 1, the printing plate obtained from the support No. 1 (outside the present invention) had a resolution of 50 lines / mm.
Was obtained with good reproducibility and the sharpness of the image was good, but the printing durability was poor and the photoconductive layer peeled off during printing. On the other hand, the printing plates obtained from the supports Nos. 6 and 7 (outside the present invention) also have a large center line average roughness of the surface of the photoconductive layer, the toner image resolving power is deteriorated, and the elution is caused by the support surface. On the other hand, the photoconductive layer remains in the valley without elution
Side etch greatly fluctuated, and toner thin line jump occurred in part.

The printing plates obtained from Support Nos. 3, 4, and 5 had good toner image quality, elution properties, and good printability such as background stain and printing durability.
No problem occurred.

Example 3 A JIS1050 aluminum sheet was immersed in a 10% NaOH aqueous solution at 60 ° C., and was etched so that the amount of aluminum dissolved was 6 g / m ² . After washing with water, it was immersed in a 30% nitric acid aqueous solution for 1 minute to neutralize, and sufficiently washed with water. Thereafter, electrolytic surface roughening was performed in a 3.0% hydrochloric acid aqueous solution at 35 A / dm ^{2 for} 50 seconds, the surface was immersed in a 20% sulfuric acid aqueous solution at 50 ° C. to wash the surface, and then washed with water. Furthermore, anodizing treatment is performed in a 20% sulfuric acid aqueous solution,
By drying, a support for a printing plate (Support No. 8) was prepared. At this time, the center line average roughness (Ra) of the surface treated surface of the support was 0.55 μm.

The following photoconductive layer composition was dispersed in a paint shaker for 1 hour to prepare a coating liquid for forming a photoconductive layer. At this time, the liquid viscosity was 12 cp. This coating liquid is applied to the surface treated surface of the support by an extrusion coater so that the solid content is applied.
After coating and drying at 4.5 g / m ² , the mixture was further heated at 90 ° C. for 5 minutes to prepare an electrophotographic lithographic printing plate.

Photoconductive layer coating liquid 2 composition Butyl methacrylate / methacrylic acid copolymer (methacrylic acid 30% by weight) 5 parts by weight Titanyl phthalocyanine 1 part by weight 2-methoxyethyl acetate 70 parts by weight 2-propanol 10 parts by weight 2-furanmethanal 6 Parts by weight The obtained printing plate precursor was charged in a dark place by corona discharge to charge the surface potential (V ₀ ) to about +300 V, and then subjected to scanning image exposure using a semiconductor laser (780 nm). When the toner was thermally fixed by performing a liquid reversal phenomenon with a positively charged toner (LOM-ED III, manufactured by Mitsubishi Paper Mills), a toner image having a resolution of 50 lines / mm was obtained with good reproducibility on the photoconductive layer. The sharpness of the image was also good.

Next, a plate making process was performed using an eluate, a washing solution, and a rinse solution as described below.

Eluent 2 composition Potassium silicate aqueous solution (SiO ₂ content 20% by weight, SiO ₂ / K ₂₀ molar ratio)
3.5) 30 parts by weight Sodium hydroxide 1 part by weight Pure water 69 parts by weight Washing liquid 2 composition (20 dm ³ ) 0.1 parts by weight of sodium dioctyl sulfosuccinate 0.01 parts by weight of butyl p-hydroxybenzoate is dispersed and dissolved in pure water to obtain 100 parts. The liquid in parts by weight was charged into a washing tank, and after the plate making for 100 plates, 15 ml of a 5% by weight glycine aqueous solution was added every time the printing plate (A2 size) was processed for 10 plates.

Rinse solution 2 composition (20 dm ³ ) Succinic acid 0.2 parts by weight Citric acid 0.3 parts by weight Sorbitan monolaurate 0.05 parts by weight 2-Methyl-3-isothiazolone 0.01 parts by weight Sodium hydroxide was added to adjust the solution pH to 4.7. Then, it was adjusted to 100 parts by weight with pure water.

When plate making was performed using the above-mentioned processing solution (elution time was set to 8 seconds), the side etch was only about 3 μm on one side and the fluctuation was slight. No failure such as pigment remaining) was observed.

Next, when this printing plate was used for printing with an offset printing machine (Hamaduster 600 CD), at least
Up to 100,000 sheets, good printed matter was obtained without generation of stain on the printed matter.

Example 4 The support prepared in Example 3 was dispersed and dissolved in a mixed solvent of 1,4-dioxane / 2-propanol = 10/3, using the following phthalocyanine and the following binder resin in an amount of 5 times by weight. , Prepared so as to have the liquid viscosity shown in Table 2 (Coating liquids Nos. 3 to 7)
Then, an electrophotographic lithographic printing plate was prepared under the same conditions as in Example 3.

* Photoconductive layer composition Butyl methacrylate / butyl acrylate / methacrylic acid copolymer (monomer weight ratio 35:30:35) χ-type metal-free phthalocyanine The obtained printing plate precursor was subjected to corona discharge in a dark place to give a surface. After being charged so that the potential (V ₀ ) becomes about +300 V, it is exposed to a scanning image using a semiconductor laser (780 nm), and immediately liquid inverted with a positively charged toner (manufactured by Mitsubishi Paper Mills, LOM-ED III). Development was performed and the toner was thermally fixed.

Table 2 shows the relationship between the liquid viscosity and the surface properties of the obtained printing plate photoconductive layer and the toner image.

As described above, liquid viscosity is low (coating liquid NO.3, outside the present invention)
Then, the phthalocyanine was liable to agglomerate during drying, the surface of the photoconductive layer was pale and color unevenness occurred, and the image reproducibility was poor. Conversely, when the liquid viscosity is high (coating liquid No. 7, outside the present invention), coating streaks are generated, and when the liquid viscosity is further increased, the liquid runs out, and only a printing plate having no commercial value can be produced visually.

On the other hand, the printing plate manufactured within the viscosity range of the present invention (coating liquids Nos. 4 to 6) had both good photoconductive layer surface properties and good toner image reproducibility.

Example 5 The following photoconductive layer composition (coating liquids 8 to 11) was applied to the surface-treated surface of the printing plate support prepared in Example 3 under the same conditions as in Example 1 to prepare an electrophotographic lithographic printing plate. Produced.

Photoconductive layer coating composition 8 (liquid viscosity: 12 cp) Vinyl acetate / crotonic acid copolymer (crotonic acid 3% by weight) 5 parts by weight χ-type metal-free phthalocyanine 1 part by weight 1,4-dioxane 70 parts by weight 2-propanol 16 parts by weight Photoconductive layer coating liquid 9 composition (liquid viscosity: 13 cp) Styrene / butyl acrylate / acrylic acid copolymer (weight ratio 45:20:35) 5 parts by weight χ type metal-free phthalocyanine 1 part by weight Xylene 60 parts by weight 1,4-Dioxane 10 parts by weight 2-Propanol 15 parts by weight Photoconductive layer coating liquid 10 composition (liquid viscosity: 11 cp) Styrene / monooctyl maleate copolymer (weight ratio 50:50) 5 parts by weight χNo mold Metal phthalocyanine 1 part by weight Xylene 45 parts by weight Oxolan 25 parts by weight 15 parts by weight 2-propanol 5 composition of photoconductive layer coating liquid 11 (liquid viscosity: 11 cp) Benzyl methacrylate / methacrylic acid copolymer (molar ratio 70:30) 5 parts by weight Type I metal-free phthalocyanine 1 part by weight 2-ethoxyethyl acetate 60 parts by weight 1,4-dioxane 15 parts by weight 2-propanol 12 parts by weight Each of the obtained electrophotographic lithographic printing plates was subjected to toner development in the same manner as in Example 1. All had the same resolution and image quality as the printing plate developer of Example 1.

Next, a plate making process was performed using an eluate, a washing solution, and a rinse solution as described below.

Eluent 3 composition Monoethanolamine 0.5 parts by weight Triethanolamine 6 parts by weight Benzyl alcohol 1.5 parts by weight EDTA-4H 0.4 parts by weight Potassium hydroxide 2 parts by weight Pure water 89.6 parts by weight Washing liquid 3 composition (20 dm ³ ) Polyoxyethylene ( 6) 0.15 parts by weight of monooleate Dissolve and dissolve 0.20 parts by weight of hot ethanol solution of 5% by weight of dehydroacetic acid in pure water to make up to 100 parts by weight. Put the solution in a washing tank, and after printing 100 plates, make 10 plates (A2 size). For each treatment, 10 ml of a 4% by weight aqueous solution of ammonium bicarbonate was added.

Rinse liquid 3 composition (20 dm ³ ) Citric acid 0.2 parts by weight Adipic acid 0.2 parts by weight Phosphoric acid (85% aqueous solution) 0.4 parts by weight Sorbitan monolaurate 0.05 parts by weight Sodium hydroxide was added to adjust the solution pH to 5.0. Then, it was adjusted to 100 parts by weight with pure water.

Plate making was performed using the above processing solution (elution time was set so that the side etch was eluted to about 3 μm on one side)
No elution failure such as elution delay in the non-image area (pigment remaining) was observed in all the printing plates.

Next, when this printing plate was used for printing on an offset printing machine (Hamaduster 600 CD), all printed plates were printed, and at least up to 100,000 sheets were printed without any stains on the printed matter. A printed matter was obtained.

(F) Effects of the Invention According to the method for producing an electrophotographic lithographic printing plate of the present invention, phthalocyanine dispersibility and coatability were improved. as a result,
The image resolution was good, and there was no background smearing or plate skipping, and a high-quality printed image was obtained.

Claims (2)

(57) [Claims] 1. A dispersion for forming a photoconductive layer containing at least phthalocyanine and a binder resin and having a solid content of 4 to 10% by weight, is coated with aluminum oxide and has a center line average roughness (Ra) of at least one. When producing an electrophotographic lithographic printing plate by coating on a conductive support having a thickness of 0.3 to 0.8 μm, the electrophotographic lithographic printing plate is characterized in that the dispersion is applied within a range of 5 to 22 cp. Production method. 2. The phthalocyanine is χ-type metal-free, ε-type copper,
And at least one of titanyl phthalocyanine,
2. The production of an electrophotographic lithographic printing plate according to claim 1, wherein the weight ratio (P / B) between the binder resin (B) and the phthalocyanine (P) contained in the photoconductive layer is 1/6 to 1/2. Method.