JP2771908B2 - Electrophotographic lithographic printing original plate - Google Patents

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 precursor, and more particularly to an electrophotographic lithographic printing plate precursor which is excellent in printability, provides a high quality printed matter, and has good printing workability. is there.

[0002]

2. Description of the Related Art As a method of manufacturing a lithographic printing original plate by an electrophotographic method, conventionally, a photoconductive layer of an electrophotographic lithographic printing original plate is uniformly charged, image-exposed, and wet-developed with a liquid toner. A method of obtaining a toner image, fixing the toner image, and then treating the toner image with a desensitizing liquid (etching liquid) to hydrophilize a non-image portion having no toner image is generally adopted. As a support for the lithographic printing plate precursor, paper or the like to which conductivity has been conventionally used has been used, but the permeation of water into the support has affected printing power and photographic performance. That is, the above-mentioned etching solution or immersion water during printing penetrates and the support elongates, and sometimes the separation occurs between the support and the photoconductive layer to lower the printing durability. The moisture content of the support changed depending on the temperature and humidity conditions, and as a result, the conductivity of the support changed, adversely affecting photographic performance. Further, if there is no water resistance, wrinkles occur during printing. In order to solve such a problem, for example, an epoxy resin or a copolymer of ethylene and acrylic acid having water resistance may be applied to one or both surfaces of the support (see JP-A-50-138904 and JP-A-55-138904). 105
580, 59-68753, etc.) or a laminated layer of polyethylene or the like (Japanese Patent Laid-Open No. 58-5 / 1983).
No. 7994) has been proposed. The layer provided as a backing layer on the surface of the support opposite to the surface having the photoconductive layer (printing surface, top) is referred to as a backing layer. In addition, improvements have been made to maintain various functions.

Incidentally, the present inventors have changed the method of developing a printing original plate for electrophotographic type plate making to a conventional method in which a master is passed while a developing solution is flowing between electrodes, and the side opposite to the printing surface is changed. A so-called direct power supply type wet development method has been developed in which a conductor is used in place of the electrode and development is performed while power is supplied directly from the conductor to the back side of the support.
3-89373. As an improved method, a back layer of a support having a polyolefin laminate layer on both sides of the support has a surface electric resistance of 1 × 10
By providing a layer with a friction resistance of ¹⁰ Ω or less and higher than the polyolefin laminate layer, winding and fixing to the printing machine drum are accurate, preventing printing misalignment and enabling good electrophotographic plate making. (Japanese Unexamined Patent Publication No. 2-84665).
Further, an under layer and a photoconductive layer are provided on the surface of the support, and a back layer is provided on the back surface, and the surface resistivity of the under layer is 1 × 10 ^8.
By setting the back layer to 1 × 10 ¹⁴ or less and 1 × 10 ¹⁰ or less, accurate, good and quick, no pinholes are generated on a solid screen, regardless of the conventional or direct power supply wet development. An original plate capable of forming a uniform image and a method of developing the same have been proposed (Japanese Patent Application Laid-Open No. 2-132264).

[0004]

By the way, since the lithographic printing plate precursor is usually wound into a roll, the back layer and the printing surface (top layer) come into contact with each other. Substances for application are transferred to the top layer. The water resistance improver is a problem that occurs dirt (rubbing referred to as dirt) on printed materials when attached to a portion (non-image portion) having no toner image. If the amount of waterproofing agent added to the back layer is reduced to prevent this, the waterproofness naturally declines.For example, while nipping in a plate making machine, the support expands due to the absorption of moisture in the atmosphere and deforms into a wavy shape. and, coming out is a problem that such a linear portion When you print a master from being printed wavy. That is, both of waterproof and securing rubbing stain prevention (prevention of the support modified by environmental changes) has been difficult. In addition, the back layer needs to have a function of ensuring printing workability and printing suitability such as easy attachment to the plate cylinder (fitting property) and no deviation from the plate cylinder. Satisfaction is required. Therefore, an object of the present invention is to have good characteristics against stains and prevent problems such as the original plate being stretched and wavy due to environmental changes in the plate making machine, and the ruled line being bent and printed as a real harm. An object of the present invention is to provide an electrophotographic lithographic printing plate precursor that simultaneously solves printing performance such as the ability to do so. Further, another object of the present invention is to apply the method to the development of a normal electrophotographic plate making and the development of a direct power supply method, and furthermore, the above-mentioned spot stain and the electrophotographic lithographic printing which can satisfy both printing performance. To provide the original.

[0005]

According to the present invention, there is provided an electrophotographic lithographic printing plate precursor comprising a support having at least a photoconductive layer on one side and a back layer on the other side. An outer layer in which the back layer contains a hydrophilic polymer and an inner layer having a dehumidification speed of 0.03 g / m ² · min or less (provided that the water absorption by the Cobb method is 25 g / m ² / min).
m ² (45 minutes value) or less].

[0006]

According to the present invention, the back layer is composed of a plurality of layers, and the outermost layer and the inner layer have different functions to achieve both waterproofness and hydrophilicity, which have been difficult in the past. That is, the back layer of the present invention is the outermost layer containing a hydrophilic polymer (hereinafter referred to as A layer).
And an inner layer (hereinafter referred to as layer B) having a dehumidification speed of 0.03 g / m ² · min or less.

Here, the dehumidification speed in the present invention will be described as follows. The dehumidification speed is an index relating to the ease of removal of water contained in the layer and the permeability of H ₂ O to the support. Specifically, an electrophotographic lithographic printing plate precursor having a water content adjusted to 5.5% is faced to the photosensitive layer side, and four sides are tightly adhered to each other with a self-adhesive tape to prevent moisture from entering and exiting from the side. This is 3
The sample was left in an atmosphere of 0 ° C. and 20% RH for 60 minutes, the weight before and after dehydration was measured, and the value converted per minute per 1 m ² was defined as the dehumidification speed. Usually, the size of the original plate for measurement is 280 mm × 400 mm. The measuring method and calculating method of the above “moisture value” are as follows. The weight measurement of the electrophotographic lithographic printing plate precursor and a _1. This is placed in an oven at 140 ° C. for 15 minutes, dried, and then dried at 20 ° C.
/ 65% RH and take out the weight after 5 seconds. This measurement and a _2. The value (%) calculated from this value by the following equation is defined as the moisture value. Moisture value (%) = [(a ₁ −a ₂ ) / a ₁ ] × 100 Incidentally, the size of the original plate for measurement is usually 280 mm × 4.
Perform at 00 mm.

The layer B of the present invention has a dehumidification speed of not more than 0.03 g / m ² · min and excludes a water absorption of 25 g / m ² (45 minutes value) by the Cobb method. . Here, the Cobb method is JIS P-8140 "Method of testing water absorbency of paper and paperboard (Cobb method)", and measures the water absorbency when one side of non-absorbable paper and paperboard is in contact with water for a certain period of time. The contact time is 45 minutes in the present invention. Further, the water absorption by this method is not directly related to the water repellency of the paper.

In the present invention, since the outermost layer A contains a hydrophilic polymer, a large amount of the hydrophilic polymer is transferred to the top even if the back layer surface is in contact with the top layer in a roll state. If it is a layer that is formed , it is possible to prevent the occurrence of stains. For the purpose of further enhancing the ability to prevent stiffness, hydrophilic colloid particles and the like may be added to the layer A. The B layer of the back layer of the present invention has a dehumidification speed of 0.0.
By providing an inner layer as low as 3 g / m ² · min or less (excluding those having a water absorption of 25 g / m _{2 ■} (45 minutes value) or less by the cup method), the support is retained even when the environment changes. Humidity is hardly affected, sufficient water resistance and waterproofness can be secured, and the deformation of the support during the plate making process and thereby the printing of straight lines such as ruled lines can be prevented. The layer A is mainly intended to prevent the occurrence of stains, but the layer B can maintain the required performance as a printing plate. The B layer may have a single layer structure, but may have a plurality of layers. In addition, a hydrophilic polymer binder, for example, an organic titanium compound or the like may be added to one or both layers for the purpose of improving the adhesion between the layer A and the layer B. As described above, according to the present invention, it is possible to achieve both conflicting functions of preventing stains and waterproofing.

Hereinafter, the back layer of the present invention will be described in more detail. The layer A of the present invention is a layer containing a hydrophilic polymer. FIG. 1 shows a composition (not containing a hydrophilic polymer) of a formulation (A-2) of Example 2 described below, in which a layer B according to the present invention is formed on a support, and the layer A is (A-2). Each of the compositions was prepared by changing the thickness of each of the compositions in which 2, 5, and 10% of the 53% acrylic weight composition ratio was replaced with polyvinyl alcohol (abbreviated as PVA) which is a hydrophilic polymer. For the sample, a photoconductive layer was further formed with a common composition, and the obtained electrophotographic printing plate precursor was printed to examine the occurrence of stains. In FIG. 1, ○ means no occurrence, Δ means slight occurrence, and × means occurrence. As is clear from FIG. 1, as the PVA replacement amount (S) increases, the occurrence of blurring stains decreases. Also, it can be seen that the A layer is effective even if it is extremely thin, and that if it exceeds 1 μm, the effect hardly changes even if it is made thicker.

As the hydrophilic polymer for the layer A of the present invention, any of known hydrophilic polymers, natural or synthetic, may be used. Specifically, for example, in addition to ordinary lime-treated gelatin, acid-treated gelatin, modified gelatin, gelatins such as derivative gelatin, albumins, sodium alginate, gum arabic, latex, celluloses such as cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, etc. And one or more of hydrophilic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, and styrene-maleic anhydride copolymer. The addition of hydrophilic colloid particles further improves the ability to prevent kossure.

The layer A of the present invention comprises the above hydrophilic polymer and another A
And a layer forming material. As the material for forming the A layer, for example, one or more of various water-resistant materials, water-resistant organic solvent-resistant materials, and synthetic emulsions can be used. Examples of the water-resistant material include water-resistant film forming materials such as polyvinyl chloride, acrylic resin, polystyrene, polyethylene, alkyd resin, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, and organic solvent-resistant films. Examples of the forming material include starch, oxidized starch, PVA, methylcellulose, hydroxyethylcellulose, and CMC. As the water-resistant and organic solvent-resistant material, for example, ethylene-vinyl alcohol copolymer, high polymerization degree polyester, high polymerization degree polyurethane and the like are used. Also, a cross-linking agent such as starch, PVA, an acrylic resin (a reactive acrylic resin, which may be an organic solvent solution type or an O / W emulsion type), an alkyd resin (however, an air-curable type) and a melamine resin. Can be used in combination as a water-resistant organic solvent-resistant material. As the synthetic emulsion, monomers or prepolymers such as acrylates, methacrylates, vinyl chloride, vinylidene chloride, vinyl acetate, polyurethane, prepolymers, acrylonitrile, butadiene, styrene-butadiene, etc. are emulsion-polymerized or emulsified. Examples thereof include those obtained by polymerization. These A layer forming materials can be used in combination. Note that a dispersant, a leveling agent, a crosslinking agent, and the like can be added to the A layer as needed. The proportion of the hydrophilic polymer in the total amount of the composition for forming the A layer is preferably in the range of 3 to 40% by weight.

The layer B of the present invention has a dehumidifying speed of 0.03 g.
/ M^Two・ Cobb among those satisfying the condition of min or less
Water absorption by the method is 25g / m^Two(45 minutes value)
Anything other than can be used. The value of this dehumidification speed is B
It depends not only on the composition of the layer, but also on the thickness of the B layer. Same composition
If so, the dehumidification speed decreases as the layer thickness increases.
FIG. 2 shows the removal of the B layer formed on the support to a thickness of 7 μm (dry thickness).
Wet speed and the degree of deformation when printing straight lines (ruled lines)
The result of examining the relationship is shown. Each layer B has the following formula
In (B-1), SBR is replaced with acrylic, and
Adjust the clay / binder ratio to change the dehumidification speed
And a water absorption of 85 g / cm on each layer B ^TwoA layer of
It was provided with a common composition. A photoconductive layer is formed on this support to
A photographic printing plate precursor was used at 25 ° C and 30% R
Deformation when left in the nip for 15 hours under H
Judgment was made based on the wavy state of the ruled line (straight line) at the time of printing. Ruled line
And draw a tangent to the undulating valley from this tangent
If the distance to is 0 to 0.2 mm or less, it is practically acceptable
Since it could not be obtained, it was judged as pass (（). Also, 0.2 mm
Judgment of a bend that can be seen even by visual inspection is rejected (x)
did. More than 0.2mm and a slight bend can be seen
It was △. As is clear from FIG. 2, the dehumidification speed
0.03 g / m^Two・ Wave evaluation becomes ○ when min or less
You can see that.

As the material for forming the layer B, the various water-resistant materials, water-resistant organic solvent-resistant materials, and synthetic emulsions described above as the material for forming the layer A can be used, and a water-soluble polymer compound can also be used. . Examples of the water-soluble polymer compound include starch or a water-soluble derivative thereof, a water-soluble cellulose derivative, casein, polyvinyl alcohol, a styrene-maleic anhydride copolymer, and a vinyl acetate-maleic anhydride copolymer. . Also in this case, the amount of use is selected so that the water absorption of the layer B is 25 g / m ² or less. These B layer forming materials can be used in combination, and a dispersing agent, a leveling agent, a cross-linking agent, and the like can be added as necessary, as in the case of the A layer. Further, as described above, the adhesion between the two layers can be improved by adding a hydrophilic polymer binder such as an organic titanium compound to one or both of the A layer and the B layer.

In the present invention, the thickness of the layer A is not particularly limited as long as it can exhibit its performance, and is not particularly limited, but is about 0.5 to 10 μm. The thickness of the layer B is about 2 to 25 μm. When the B layer has a multilayer structure, the total thickness may be within this range. The thickness of the entire back layer including the A layer and the B layer of the present invention is generally 3 to 25 μm, preferably 8 to 15 μm.

As the support of the present invention, any of the known supports used in this type of electrophotographic lithographic printing plate precursor can be used. For example, a substrate such as a metal, paper, or plastic sheet, or a substrate subjected to conductive treatment by impregnating the substrate with a low-resistance substance, or a substrate provided with a water-resistant adhesive layer or at least one precoat layer on the surface of the support. A material obtained by laminating a substrate conductive plastic on which Al or the like has been deposited on paper can be used. Specific examples of the conductive substrate or the conductive material include Yukio Sakamoto, "Electrophotography" 14, (No. 1), pp. 2-11 (1975), Hiroyuki Moriga, "Chemistry of Introductory Special Paper", Polymer Publishing Association. (1975),
MF Hoover, J. Macromol. Sci. Chem., A-4
(6), and those described in pages 1327 to 1417 (1970) and the like are used.

The photoconductive layer of the present invention contains at least a photoconductor and a binder, and the photoconductor may be an inorganic material or an organic material. As the inorganic photoconductive material, for example, Si, Ge, zinc oxide, cadmium sulfide, titanium oxide, selenium, cadmium selenide, zinc selenide or lead oxide, Se—Te alloy, As ₂ S ₃ , As
Chalcogen alloys such as ₂ Se ₃ can be cited. Examples of the organic photoconductive material include photoconductive cyanine pigments, photoconductive quinoline pigments, photoconductive phthalocyanine pigments, photoconductive pyrylium salt pigments, substituted vinyl oxazoles, triphenylamine derivatives, anthracene, and benzo condensation. Heterocyclic, pyrazoline or imidazole derivatives, oxadiazole derivatives, vinyl aromatic polymers and their copolymerized products, fluorenone derivatives,
Polyarylalkanes such as triarylmethane leuco dye and squaric acid derivative dye, perylene, tetracene, carbazole, tetrabenzyl-p-phenylenediamine, squarium, indigo, dimethylperimide, polyenyltetracene, polyzenylperylene , Acylhydrazone derivatives, benzthiazole derivatives, tetracyanopyrene, chlorocyan blue and the like. These may be used in combination. As the binder, use a silicone resin, polystyrene, polyacrylic acid or polymethacrylic acid ester, polyvinyl acetate, polyvinyl chloride, polyvinyl butyral and derivatives thereof and other materials known as binders for photoconductive layers. Can be. The amount of the photoconductor in the photoconductive layer is such that the ratio of the photoconductive substance to the binder is, for example, in the range of 3: 1 to 20: 1 by weight, but is not particularly limited in the present invention. . If necessary, a sensitizer, a coating aid used when performing coating, and other additives can be added. The thickness of this photoconductive layer is usually about 5 to 30 μm, but is not particularly limited in the present invention. Further, in order to improve the adhesive strength between the photoconductive layer and the under layer, the surface of the under layer is previously prepared, for example, in US Pat.
As described in the specification of Japanese Patent No. 1,908, surface treatment such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet treatment, ozone treatment, and plasma treatment is preferably performed.

The preparation of the lithographic printing plate precursor according to the present invention may be carried out according to a technique known in the field of this type of electrophotographic lithographic printing plate precursor. For example, a ball mill, a colloid mill, an ultrasonic disperser, This roll mill, grain mill,
Usual ones such as a homogenizer and a homomixer can be used. In addition, air knife coater,
Trailing grade coaters, wire bar coaters, reverse roll coaters, kiss roll coaters, fountain coaters and the like can be used.

The above-mentioned original plate of the present invention is made into a lithographic printing plate through ordinary steps such as charging, image exposure and development. Also,
It is also suitable for performing the above-described direct power supply type development.

[0020]

The present invention will be described below with reference to examples.
The present invention is not limited to this. Example 1 A high-quality paper of 85 g / m ² was used as a support, and a composition (B-1) prepared according to the following formulation (B-1) was first applied as an inner layer as a back layer using a wire bar, and then heated. By drying at 140 ° C. for 1 minute, an inner layer having a thickness of 7 μm was formed. Next, the composition (A-1) prepared according to the following formulation (A-1) was similarly applied with a wire bar, and then dried at a temperature of 140 ° C. for 1 minute to have a thickness of 3 μm.
A back layer was formed as the outermost layer of m. Outer layer formulation (A-1) [Solid content weight ratio] Clay 58 Acrylic 34 (from emulsion) Polyvinyl alcohol 9 Melamine cross-linking agent 4.3 Water is added in advance so that the total solid content is finally 30% by weight. Dissolved or dispersed in Inner layer formulation (B-1) [Solid content weight ratio] Clay 45 SBR (Tg 30 ° C) 18 (from emulsion) The above was dissolved or dispersed in water in advance so that the total solid content was finally 30% by weight. . Next, after applying a 5% aqueous solution of polyvinyl alcohol (PVA) to the surface of the support with a wire bar so as to have a dry film thickness of 8 μm, the following composition is further provided as a photoconductive layer Photoconductive layer composition (parts by weight): Photoconductive oxidation Zinc (trade name: SAZEX 2000) 100 parts Acrylic resin (manufactured by Fuji Photo Film Co., Ltd.) 20 parts Rose Bengal 0.1 parts Toluene 190 parts is applied and dried, and a dry coating material 23 g / m ² is provided to provide an electronic material of the present invention. A lithographic printing original plate was obtained.

When the dehumidifying speed of each layer of the back layer of the obtained electrophotographic lithographic printing plate precursor was measured, the outermost layer was 0.047 g / m ² · min, and the inner layer was 0.011 g / m 2.
It was ² min. Two pieces of this original plate (sample) are placed on top of each other, and a bottom area of 5 cm ² and a weight of 20
g of aluminum metal piece was placed, the upper sample was fixed so as not to move, and only the lower sample was slid so as to be forcibly distorted. Next, after making a plate using the ELP-310 electrophotographic plate making machine manufactured by Fuji Photo Film Co., Ltd. using the extracted sample as a master, the surface is subjected to an etching treatment by dipping the etching solution E2 manufactured by Fuji Photo Film Co., Ltd. in cotton. Then, printing was carried out using a Ryobi AD80 printing machine (manufactured by Ryobi Co., Ltd.), and no stain was observed. The ripple evaluation (shown in the same manner as in FIG. 2) was acceptable (○).

Comparative Example 1 In Example 1, the formulation of the outermost layer of the back layer was as follows (A-
A lithographic printing original plate was prepared in the same manner as in Example 1, except that the hydrophilic polymer was not included in 2). At this time, the dehumidification speed of the outermost layer is 0.050 g / m ² · min,
The inner layer was 0.011 g / m ² · min. Outer layer formulation (A-2) [Solid content weight ratio] Clay 58 Acrylic 43 Melamine crosslinker 4.3 or more was dissolved or dispersed in water in advance so that the total solid content was finally 30% by weight. Inner layer formulation (B-1) When the obtained original plate was printed and evaluated in the same manner as in Example 1, as shown in Table 1, kore stain was generated.
The ripple evaluation was passed.

Comparative Example 2 In Example 1, the formulation of the inner layer of the back layer was as follows (B-
Example 1 except that the dehumidifying speed was changed to 2).
A lithographic printing original plate was prepared in the same manner as described above. At this time, the dehumidification speed of the outermost layer was 0.047 g / m 2. min, inside
The layer was 0.042 g / m ² · min. The above was dissolved or dispersed in water in advance so that the total amount of the solid content finally became 30% by weight. When the obtained original plate was printed and evaluated in the same manner as in Example 1, as shown in Table 1, there was no occurrence of stains as shown in Table 1, but the waving evaluation was x.

Comparative Example 3 On the same support as in Example 1, the following formulation (C
A composition prepared from a material obtained by mixing (A-1) and (B-1) as in -1) is applied, dried at a temperature of 135 ° C. for 1 minute, and has a thickness of 10 μm and a dehumidifying speed of 0.035. g /
A lithographic printing original plate was prepared in the same manner as in Example 1 except that only one back layer of m ² · min was used. The above was dissolved or dispersed in water in advance so that the total amount of the solid content finally became 30% by weight. When printing and evaluation were performed on the obtained original plate in the same manner as in Example 1, as shown in Table 1, slight stains were generated, but corrugation evaluation was x.

Example 2 In Example 1, the outermost layer had a dry thickness of 5 μm.
(Dehumidification speed 0.038 g / m _{2 ■} · min), the inner layer is 5 μm in dry thickness (dehumidification speed 0.016 g / m ²
Min) of the present invention in the same manner as in Example 1 except that
A lithographic printing plate was created. Outer layer prescription (A-1) Inner layer prescription (B-1) When the obtained original plate was printed and evaluated in the same manner as in Example 1, as shown in Table 1, no stain was generated and the waving evaluation was passed. there were.

Example 3 In Example 1, the thickness of the outermost layer was 6 μm in dry thickness.
(Dehumidification speed 0.035 g / m ² · min), the inner layer was 4 μm in dry thickness (dehumidification speed 0.025 g / m ² · min).
except that the min) in the same manner as in Example 1 flat of the present invention
An original plate for plate printing was created. Outer layer prescription (A-1) Inner layer prescription (B-1) When the obtained original plate was printed and evaluated in the same manner as in Example 1, as shown in Table 1, no stain was generated and the waving evaluation was passed. there were.

[0027]

[Table 1] Evaluation Criteria ○: No scrap stains generated △: Slight stains slightly generated ×: Scratches stains generated

From the results of the above Examples and Comparative Examples, the back layer was made into a multilayer and the outermost layer contained a hydrophilic polymer,
Only by the configuration of the present invention in which the inner layer has a dehumidifying speed of 0.03 g / m ² · min or less, it is possible to achieve both the opposite effects of preventing the occurrence of stains and preventing waving (curving of a ruled line) even if the environment changes. It will be appreciated.

Examples 4 to 6 and Comparative Examples 4 to 6 The outermost layer of the back layer was prepared according to the following formulations (A-3) and (A-4)
And each of the following formulations (B
-3) or (B-4), or as a back layer having a single-layer constitution according to the following formula (C-1), for electrophotographic lithographic printing having a dry thickness and a dehumidifying speed shown in Table 2. An original plate was prepared by a method according to Examples 1 to 3 and Comparative Examples 1 to 3. Denthol WK-100W manufactured by Otsuka Chemical Co., Ltd. was used as the conductive fine powder. The dry layer thickness and dehumidifying speed of each layer were as shown in Table 2. Outermost layer formulation (A-3) [Solid content weight ratio] Clay 58 Conductive fine powder 14 Acrylic 34 (from emulsion) Starch 9 Melamine cross-linking agent 4.3 The final solid content becomes 30% by weight. As described above. Inner Layer Formulation (B-3) [Solid Content Weight Ratio] Clay 45 SBR (Tg 30 ° C.) 18 (from emulsion) The above was dissolved or dispersed in water in advance so that the total solid content was finally 30% by weight. . Outer layer formulation (A-4) [Solid content weight ratio] Clay 58 Conductive fine powder 14 Acrylic 43 (from emulsion) Melamine cross-linking agent 4.3 More than final amount of solid content is 30% by weight It was previously dissolved or dispersed in water. Inner Layer Formulation (B-4) [Solid Content Weight Ratio] Clay 58 Acrylic 43 Melamine Crosslinking Agent 4.3 or more was dissolved or dispersed in water in advance so that the total solid content was finally 30% by weight. One-layer mixed back layer formulation (C-1) [Solid content weight ratio] Clay 103 Conductive fine powder 14 Acrylic 34 SBR resin (Tg 30 ° C.) 18 Polyvinyl alcohol 9 Melamine cross-linking agent 4.3 Was previously dissolved or dispersed in water so that the total amount was 30% by weight.

The obtained electrophotographic lithographic printing original plates of Examples 4 to 6 and Comparative Examples 4 to 6 were evaluated in the same manner as in Example 1. Table 2 shows the results.

[0031]

[Table 2]

From the results shown in Table 2, it can be seen that the original plate having the back layer having the two-layered structure of the A layer and the B layer within the limited range of the present invention can satisfy both the characteristics of preventing stain contamination and passing the evaluation of wavy. . Thus, the type in which the conductive fine powder is added to the layer A of the back layer is also suitable for the direct power supply type development.

As described above, according to the present invention, it is possible to produce a printing original plate for electrophotographic plate making without producing stains during manufacturing, and when printing using the original plate of the present invention, it is possible to obtain a wavy shape. It is possible to print a large number of sheets without (bending of ruled lines). Further, the original plate of the present invention is very suitable for development by a direct power supply system in addition to the development by a normal electrophotographic method.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the thickness of the outermost layer of the back layer of the present invention and occurrence of stains on the back layer.

FIG. 2 is a graph showing the relationship between the dehumidification speed of an inner layer of a back layer and waving (curving of a ruled line) of the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 5/14 G03G 13/28

Claims (1)

(57) [Claims] 1. An electrophotographic lithographic printing plate precursor comprising a support having at least a photoconductive layer on one surface and a back layer on the other surface, wherein the back layer is separated from the outermost layer containing a hydrophilic polymer. Inner layer having a wet speed of 0.03 g / m ² · min or less (provided that the water absorption by the Cobb method is 25 g / m ² (4
Excluding the following): an electrophotographic lithographic printing plate precursor.