JPH026060B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a base plate for lithographic printing, and more specifically, the conductive treatment layer on the back side of the support base paper is coated with a specific pigment, a binder,
The photosensitive layer made of a mixture of a conductive agent and a wax has particularly good storage stability, and even when multiple sheets are stacked and transported one by one, the photosensitive layer does not deteriorate due to misalignment between the front photosensitive layer and the back conductive treatment layer. A zinc oxide-binder resin type lithographic plate that can prevent property deterioration, is suitable for electrophotographic plate making, and can produce a large number of high-quality prints from the master (lithographic printing plate) created by the plate making. Regarding printing plates. Currently, the planographic printing master plates used in office printing include (1) direct printing type with a hydrophilic layer (water-resistant layer) on a base paper, and (2) a photoconductive layer on a conductive support. (3) A photosensitive resin layer or a diazo photosensitive layer provided on a base paper, etc. are typical examples. However, in order to form an image on the original plate described in 1 above, it is necessary to handwrite or type-print with lipophilic ink on the hydrophilic layer, or to adopt the xerography method, and therefore, the above 2.
It is difficult to form an image area that is faithful to the original document compared to the conventional method. In addition, the original plate in 3 above is, for example,
PS plates have the disadvantage of high manufacturing costs, and diazo photosensitive original plates have the disadvantage of being somewhat lacking in sharpening properties even after being made into a plate. Reflecting these circumstances, the above-mentioned 2 original plates for electrophotographic printing are increasingly being used. This base plate for electrophotographic lithography is generally produced by coating a subbing layer (precoat layer) on the surface of a base paper, and if higher printing durability is required, a water-resistant layer is provided on top of this, and then oxidation is performed. It is manufactured by coating a photosensitive layer (photoconductive layer) containing a zinc/resin dispersion system and providing a conductive treatment layer on the back surface of the support. By the way, in recent years, the automation of plate-making printing machines has progressed, and the quality required of planographic printing master plates (hereinafter sometimes simply referred to as "master plates") or printing plates (masters) obtained by plate-making has become multi-functional. And it has become more sophisticated. In particular, the properties of the conductive treatment layer on the back side of the original plate or master include (a) the electrical resistance value of the conductive treatment layer at low humidity (30%
Ground fog will occur if the resistance (RH) is not maintained at around 10 ¹⁰ Ωcm. (b) If the water resistance of the conductive treatment layer is poor, curling toward the photosensitive layer after passing through the etching treatment liquid (desensitization treatment liquid) will be large, resulting in poor handling and plate feeding properties of automatic plate feeding printers. , problems such as clamping errors may occur. (c) The above properties (a) and (b) are in a contradictory relationship; therefore, if a large amount of a conductive agent is added to improve conductivity, water resistance decreases and curling after etching increases. (d) When printing by stacking a large number of etched masters on an automatic plate-feeding printing machine and continuously feeding and discharging the plates, various problems occur because the back layer (conductive treatment layer) and photosensitive layer are in contact with each other. Ru. For example, plate feeding errors such as double feeding (multiple plate feeding) or non-feeding, deterioration of the hydrophilicity (desensitization) of the photosensitive layer due to misalignment between the back layer and the photosensitive layer, or printing stains due to transfer of oil-sensitive substances, etc. It is an occurrence. (E) The photosensitive layer may deteriorate due to misalignment between the back layer and the photosensitive layer during cutting and finishing in the master manufacturing process, automatic plate feeding by using a cassette in the original plate feeding device of the plate making machine, or when removing the plate from the bag. This may cause scratches, plate-making stains, image fading, etc. (c) If the frictional resistance of the back layer is too low, it will slip easily, resulting in poor workability during cutting and finishing, and slips will occur in the plate feeding and conveying system of the plate making machine. On the other hand, if the frictional resistance is too high, double feeding or non-feeding will occur when feeding cassettes to a plate-making machine, and also double feeding or non-feeding will occur in the case of automatic plate feeding printing machines. A plate defect occurs. (g) When storing or transporting masters or original plates in layers, the photosensitive layer and back layer are in contact with each other, so temperature, pressure, moisture, etc. may cause discoloration of the sensitizing dye in the photosensitive layer and photosensitivity. This may cause problems such as a decrease in the printing quality, stains on the plate making area, failure to take out the master when using the master due to blocking, stains on the plate, printing stains, and transfer of the back layer material to the photosensitive layer. etc. can be mentioned. The conductive treatment layer in conventional electrophotographic lithographic printing plates is composed of suitable conductive agents, pigments, and waxes.
(i) A water-soluble binder such as polyvinyl alcohol, starch, carboxymethylcellulose, methylcellulose, etc., or a binder formed by combining these with a crosslinking agent such as melamine resin, polyamide, glyoxal, etc., (ii) Polyacrylic acid ester, polychloride, etc. A binder based on emulsion resin such as vinyl, polyvinyl acetate, styrene-butadiene copolymer, acrylic-styrene copolymer, or (iii) a binder based on a combination of (i) and (ii) above. It is formed. However, when a water-soluble binder is used as a binder in the conductive treatment layer for a lithographic printing original plate having a conventional zinc oxide/resin dispersion photosensitive layer, the water resistance is unsatisfactory, and the crosslinking agent When water resistance is achieved by using a conductive agent in combination, the electrical resistance becomes high, and if a large amount of a conductive agent is added to lower the electrical resistance, crosslinking does not proceed, making it difficult to achieve water resistance. On the other hand, when an emulsion-type resin is used as the binder for the conductive treatment layer, the ionicity of the emulsion resin is determined by the ionicity of the conductive agent used. The electrical resistance is highly dependent on moisture and the resistance value is high at low humidity. Blocking tends to occur when emulsion type resins are used. In other words, resins with a minimum film forming temperature (MFT) of approximately 50°C or less are used. As mentioned above, if the original plates are stored in a stack, blocking may occur and the photosensitive layer (photoconductive layer) of the original plate may deteriorate.
Furthermore, when using an emulsion resin with a high MFT, the film cannot be formed well unless a fairly high temperature is applied during coating and drying, and the original plates produced in this way are stacked and coated with the conductive treatment layer and the photosensitive layer. When the layers rub against each other, the photosensitive layer deteriorates as described above, which in turn causes problems such as plate making stains and printing stains. As inferred from these studies, it is more advantageous to use a cationic conductive agent than an anionic conductive agent for the conductive treatment layer, and emulsion resins are generally anionic, and especially
None have high MFT and are cationic. In addition, conventional pigments include kaolin clay and calcium carbonate (heavy calcium carbonate, precipitated calcium carbonate, etc.), and water repellents include wax emulsions. Note that an emulsion resin with a low MFT (e.g. polyvinyl acetate emulsion) and an emulsion resin with a high MFT (e.g. polystyrene emulsion) are used in combination, and a cationic polymer conductive agent and/or wax emulsion (e.g. polyethylene emulsion) is used in combination. ) is combined in JP-A-53-
No. 46736 (back coating formulations No. 2 and 5 in Examples), in the case of these conductive treatment layers, even if the mixing ratio of both resins and the amount of conductive agent and wax used are appropriate, Contains no pigments. Pigments are used to prevent plate feeding errors by optimizing the frictional resistance of the conductive treatment layer, and to prevent deterioration of the photosensitive layer due to scratches or contact with the photosensitive layer during plate loading/unloading, storage (especially when stored at high temperatures), etc. is necessary. However, in the case of the conventional example, these points are not considered at all. As mentioned above, it is known that pigments are used in the conductive treatment layer, but it is necessary to select an appropriate pigment for the above purpose. However, as described above, in the conventional electrophotographic printing plates or masters, one that simultaneously satisfies the above conditions (A) through (G) has not yet been obtained. The present inventor discovered and proposed that a good original plate could be obtained by first forming a conductive treatment layer by combining a specific conductive agent and a binder (Japanese Patent Application No. 1986-
No. 23882 (Japanese Unexamined Patent Publication No. 57-138990)). but,
Even with this master plate, it was observed that plate feeding errors sometimes occurred. The present invention is a further improvement of the original plate proposed above. Therefore, the first object of the present invention is to provide a lithographic printing original plate with good storage stability (prevention of discoloration of the photosensitive layer, prevention of blocking, prevention of plate printing stains). A second object of the present invention is to provide a lithographic printing original plate that prevents plate-making fog in a low-humidity atmosphere (ie, a conductive layer with low electrical resistance and reduced humidity dependence). A third object of the present invention is to provide a lithographic printing original plate which has improved water resistance and is prevented from curling after etching. A fourth object of the present invention is to provide a lithographic printing original plate in which the photosensitive layer does not deteriorate even when the conductive treatment layer and the photosensitive layer come into contact with each other or are rubbed against each other. A fifth object of the present invention is to provide a lithographic printing original plate in which plate feeding errors do not occur, or even if they occur, the occurrence thereof is extremely small. That is, one of the present inventions is a lithographic printing plate in which a subbing layer, an optional waterproof layer, and a zinc oxide/resin dispersion photosensitive layer are provided on the surface of a base paper support, and a conductive treatment layer is provided on the back surface. In the original plate,
The conductive treatment layer includes (a) a mixture of 70 to 95 parts by weight of clay as a pigment and 5 to 30 parts by weight of calcium carbonate and/or zinc oxide (component A), (b) weak anions as a binder, respectively. 1 part by weight of a nonionic or nonionic emulsion resin with a minimum film forming temperature (MFT) of 0 to 30°C and 60 to 110°C
(component B) (c) A cationic polymer electrolyte (component C) as a conductive agent, the amount of which is 10% of the total resin amount (components B, C and D). and (d) the wax emulsion as a water repellent (component D), the amount of which is added to the total resin amount (component B,
It is characterized in that the main component is in the range of 5 to 40% by weight based on C and D). In this way, the lithographic printing original plate of the present invention has the above-mentioned A,
The combination of components B, C, and D simultaneously satisfies the conditions (a) to (g) above required for a lithographic printing original plate or master. The original plate of the present invention (original plate for electrophotographic lithography) is shown below.
will be described in more detail based on the accompanying drawings. FIGS. 1 and 2 show cross-sectional views of two examples of the original plates of the present invention, and the numbers assigned therein are 1 for the support base paper, 2 for the undercoat layer (precoat layer), 3 for the water-resistant layer, 4 represents a photosensitive layer (photoconductive layer), and 5 represents a conductive treatment layer. The support base paper 1 used in the base plate of the present invention is generally plain paper, but other materials include synthetic paper, metal-deposited paper, and the like. The undercoat layer 2 is made of a water-soluble resin such as polyvinyl alcohol (PVA), starch, carboxymethyl cellulose (CMC), or methyl cellulose (MC), or a combination of these water-soluble resins and an emulsion resin such as vinyl acetate, vinyl chloride, or acrylic ester. The mixture is used as a binder, and if necessary, a pigment such as clay or calcium carbonate, a polymer electrolyte as a conductive agent (for example, a quaternary ammonium-based polymer conductive agent, etc.), and a melamine resin or polyamide as a crosslinking agent are added. ,
It is formed by a mixture of glyoxal, etc. It should be noted that if a wax such as paraffin wax (polyethylene wax) or montan wax is further blended with these, it is advantageous in that water elongation and wrinkles of the master can be significantly prevented during printing. The water-resistant layer 3 is formed by coating a self-crosslinking type or thermosetting emulsion resin, or a solvent type crosslinking type or thermosetting resin. Specific examples of resins for forming this water-resistant layer include emulsions of polyol and polyisocyanate condensates, epoxy resins, isobutylene-maleic anhydride copolymer resins, ethylene, α- or β-olefinic unsaturated carboxylic acids. Or its salts, ethylene copolymer emulsions mainly containing vinyl group-containing compounds, O-coated with water-soluble polymer substances (polyvinyl alcohol, starch, gum arabic, etc.) and acrylic acid ester resins, vinyl acetate resins, styrene-butadiene resins, etc. /W type or W/O type emulsion can be mentioned. The surface photosensitive layer (photoconductive layer) 4 is the same as the photoconductive layer in general electrophotographic photosensitive materials, and is made of, for example, polybutyl methacrylate, acrylic ester, polyvinyl chloride, polyvinyl acetate, polystyrene, or silicone resin. , to lipophilic resins such as polyvinyl butyral, or to polyvinyl alcohol, carboxymethyl cellulose, casein,
It has a form in which zinc oxide is dispersed in a hydrophilic resin such as gelatin. In the base plate of the present invention, a conductive treatment layer 5 having the most characteristic structure of the present invention is provided on the back surface of the support base paper 1. As mentioned above, the conductive treatment layer 5 contains the component A,
The main components are B, C, and D. In the present invention, in order to optimize the frictional resistance of the back conductive treatment layer and to prevent deterioration of the photosensitive layer due to scratches or contact with the photosensitive layer, 70 to 95 parts by weight of clay and calcium carbonate and/or oxide are added as a pigment (component A). A mixture containing 5 to 30 parts by weight of zinc is used. Instead of clay, kaolin or a mixture of clay and kaolin is also effective. Now, when the appropriate range of the frictional resistance of the back conductive treatment layer was investigated in relation to the incidence of plate feeding errors in the master automatic overlapping printing machine, the results were measured as shown in Table 1. In addition, "plate feeding error" referred to here means double feeding,
It means sending multiple editions or not sending them.

[Table] As inferred from Table 1, plate feeding errors will not occur if the friction coefficient (frictional resistance value) is 0.85 or less. However, if this value is too low, the plate becomes slippery, resulting in decreased workability such as cutting, finishing, or load collapse, and slipping in the conveyance system of the plate making machine, resulting in poor plate passing. Considering these points,
It is desirable that the frictional resistance value is in the range of about 0.7 to 0.85. In addition, as shown in Table 2, the inventor's experiments have shown that the degree of deterioration and frictional resistance of the photosensitive layer depend on the pigment used in the conductive treatment layer, and that the deterioration of the photosensitive layer during high-temperature storage depends on the type of pigment. It was also found that there were differences in the degree of deterioration, and furthermore, there were large differences in properties such as a decrease in fat resistance due to wrinkles when a large number of etched masters were stacked and fed. In Table 2, ◯ indicates good, △ indicates fair, and × indicates poor.

[Table] Furthermore, Figure 3 shows the relationship between the pigment blending ratio and discoloration of the photosensitive layer when stored at 45°C, and Figure 4 shows the relationship between the pigment blending ratio and staining during automatic overlapping plate feeding. The relationship between the blending ratio and the friction coefficient was measured as shown in FIG. In addition, in these figures 3, 4, and 5
UW-90 is clay (Ultra White 90). Judging comprehensively from the results in Table 1, Table 2, and Figures 3, 4, and 5, the mixing ratio of pigment is 70 to 95 parts by weight of clay to 5 to 30 parts by weight of calcium carbonate.
By adding parts by weight, (i) the initial electrophotographic properties that do not cause discoloration or deterioration of the photosensitive layer during high-temperature storage are maintained; (ii) Even when etched masters are stacked and fed, no scratches occur. (iii) The coefficient of friction is approximately 0.80, so plate feeding errors do not occur, and since the friction coefficient is not too low, there are no conveyance errors due to slips, and there is no occurrence of load collapse during finishing. The following effects were observed. Such an effect is observed when zinc oxide is used instead of calcium carbonate, and when calcium carbonate and zinc oxide are mixed. It was confirmed that this effect remained unchanged even when the name of the pigment (calcium carbonate, zinc oxide) was changed. A weakly anionic or nonionic emulsion resin as a binder (component B) with a minimum film forming temperature (MFT) of 0 to 30°C - "Resin A" for convenience.
Specific examples of resins with MFT of 60 to 110°C (referred to as "resin B" for convenience) include polyvinyl acetate, polyvinyl chloride, polyacrylic acid ester, SBR, and vinyl acetate-acrylic copolymer as resin A. Examples of the resin B include emulsions of styrene-acrylic copolymers, acrylonitrile, polyacrylic acid esters, and the like. However, since MFT is determined by the types of resin A and resin B as well as the degree of polymerization of those resins, it is not appropriate to define it unconditionally. Resin A and resin B
Both can be used together. A suitable mixing ratio of resin A and resin B is 0.4 to 0.8 parts by weight of resin B to 1 part by weight of resin A.
If the amount is less than 0.4 part by weight, the conductive treatment layer 5 tends to block, and it is not preferable because it will have a negative effect on the photosensitive layer during high temperature storage or high temperature pressurized storage by stacking.On the other hand, if it is more than 0.8 part by weight, the film formation The conductive treatment layer 5
is too hard, so if it comes into contact with or rubs against the photosensitive layer, it will deteriorate the photosensitive layer, which is undesirable. FIG. 6 is a graph showing an example of the apparent MFT when a low MFT resin (resin A) and a high MFT resin (resin B) are mixed. Furthermore, Fig. 7 shows the relationship between the apparent MFT, the degree of deterioration of the photosensitive layer, and blocking when a binder made of a mixture of resin A and resin B is used. Curve b shows the blocking state. In FIG. 7, the values on the vertical axis are shown in stages from 5, which is good, to 1, which is bad. As can be seen from these graphs, the mixture of Resin A and Resin B draws a much flatter curve compared to the one in Figure 8 below.
Film formation can be sufficiently performed at a temperature corresponding to the normal coating and drying temperature. FIG. 8 shows the relationship between the apparent MFT of a single binder, the degree of deterioration of the photosensitive layer, and blocking when a single binder is used. Here, the curve a′ is the deterioration state of the photosensitive layer, and the curve
b' indicates a blocking state, which means that both properties cannot be simultaneously satisfied using a single binder. Also, here, the values on the vertical axis are shown in stages from 5 for good to 1 for bad. In the original plate of the present invention, the conductive treatment layer 5 is preferably made by using a low MFT resin and a high MFT resin together.
is formed. Although a detailed study has not yet been carried out as to why such good results are brought about, in any case, the advantages of the two types of resins work together to further improve the film-forming properties. It seems that the defects such as blocking and photosensitive layer deterioration mentioned above have been eliminated. As the cationic polymer electrolyte as the conductive agent (component C), any of those known in the field of electrophotographic photoreceptors can be used, and a typical example is a quaternary ammonium salt. The appropriate amount of the conductive agent (cationic polymer electrolyte) in the conductive treatment layer 5 is 10 to 30% by weight based on the total resin content (components B, C, and D). If it is less than 10% by weight, the surface electrical resistance value at low humidity (30%RH) will decrease.
If it exceeds 10 ^{to 11} Ωcm, background fog will occur during plate making, and conversely, if it exceeds 30% by weight, the water resistance and water repellency of the conductive treatment layer 5 will decrease and it will curl toward the photosensitive layer when passed through an etching solution. Operability and plate feeding performance deteriorate, contamination and deterioration occur due to elution into the etching solution, and furthermore, deterioration of the etching solution is accelerated. Petroleum-based waxes and modified wax emulsions (paraffin waxes, polyethylene waxes, microcrystalline waxes, etc.) can be used as the wax emulsion as the water repellent (component D), and modified wax emulsions are particularly suitable. is valid. The amount of this wax emulsion in the conductive treatment layer 5 is suitably 5 to 40% by weight based on the total resin content (components B, C and D). If it is less than 5% by weight, the water repellency will be poor and curling will occur after etching treatment, resulting in poor operability and plate feeding properties.On the other hand, if it is more than 40% by weight, the binding properties of the conductive layer 5 will decrease and friction will increase. Various problems occur, such as a decrease in resistance, an increase in surface gloss, and transfer during high-temperature storage. In the original plate of the present invention, when the conductive treatment layer 5 is formed by containing MFT exceeding 110°C, the film is formed at a temperature somewhat higher than the normal drying temperature (110 to 130°C). It is necessary to do this. Also,
In such a case, it may be considered to add a small amount of water-soluble resin to form the conductive treatment layer 5. Therefore, another aspect of the present invention is to combine component B of the above original plate with 70 to 90 parts by weight of an emulsion resin and 10 to 30 parts by weight of a water-soluble resin, and each of the emulsion resins 1 part by weight of weakly anionic or nonionic material with a minimum film forming temperature of 0 to 30°C and 60 to
It is characterized by being made of a mixture of 0.4 to 0.6 parts by weight of 110°C. In this manner, when component B is a combination of an emulsion resin and a water-soluble resin, as shown in FIG. 9, the wear resistance of the photosensitive layer is significantly improved. Note that the symbol c in FIG. 9 represents wrinkle deterioration, and d represents curl after etching. Although it has not been strictly elucidated why this improvement is made, it is important to note that when water-soluble resins are used to prepare and dry coating liquids, emulsion resin particles, surfactants, polymeric conductive agents, waxes, pigments, etc. The water-soluble resin acts as a protective colloid and improves the compatibility of emulsion particles, polymer electrolytes, surfactants, wax emulsion particles, etc. even if it rubs against the photosensitive layer. In order to obtain a good and uniform mixed solution, it is thought that even if the mixture is rubbed, adverse effects such as transfer and scratches will be reduced. To actually make the base plate of the present invention, support base paper 1
Undercoat layer 2 (solid content adhesion amount 5-10g/
m ² ), and after providing a conductive treatment layer 5 (solid content adhesion amount 5 to 15 g/m ² ) on the back side of the base paper 1,
Waterproof layer (not essential, solid content coverage 1-3g/
m ² ) and photosensitive layer 4 (solid content adhesion amount 20 to 25 g/m ² )
may be formed sequentially by a conventional method. In order to make an offset printing plate (master) using this original plate, the photoconductive layer is uniformly charged in a dark place and then subjected to image exposure (light image irradiation) using a normal dry or wet electrophotographic method. to form an electrostatic latent image, which is developed with a lipophilic toner developer to fix the toner image. Next, this may be treated with a desensitizing solution. Such plate making can be easily carried out using a dry or wet electrophotographic plate making machine. The lithographic printing original plate thus produced and the lithographic printing plate (master) using the same can fully achieve the intended purpose. Next, examples will be shown. Note that all parts are solid content weight ratios. Example 1 Polyvinyl alcohol (PVA-HC, Kuraray KK) was applied to the surface of the base paper (90 g/ ^m2 plain paper).
40 parts acrylic ester emulsion (HA-16, manufactured by Nippon Acrylic KK) 40 parts polyethylene wax emulsion (GIX-
0056, manufactured by Showa Kobunshi KK) A mixture consisting of 20 parts was adjusted so that the solid content was approximately 15% by weight, and then applied and dried.
A subbing layer of g/m ² was applied. Next, on the back side of this base paper, 45 parts of clay (Ultra White 90), 45 parts of calcium carbonate (Heavy Carbon Cal SSB, manufactured by Shiraishi Calcium KK), 5 parts of polyethylene wax emulsion (GIX-
0056, manufactured by Showa Kobunshi KK) 15 parts polyacrylic ester emulsion (weakly anionic, MFT approx. 25°C) 10 parts acrylic ester-styrene copolymer emulsion (weakly anionic, MFT approx. 70°C) 15 parts cationic A mixed solution consisting of 10 parts of polyelectrolyte with a solid content of approximately 40% was applied with a wire bar and dried at 110°C for 2 minutes to form a conductive treatment layer of approximately 8 g/ ^m2 . . Next, a layer of isoptylene-maleic anhydride copolymer resin (approximately 2g/
^m2 ) to form a water-resistant layer, and on top of this water-resistant layer, 6 parts of zinc oxide, 1 part of acrylic resin, and a sensitizing agent are added.
A photoconductive layer (approximately 25 g/m ² ) consisting of 0.07 parts was provided to prepare an original plate for electrophotographic printing. Example 2 Example 1 except that the composition of the conductive treatment layer was changed to the following.
In the same way, I made an original plate for electrophotographic printing. Clay (Ultra Hoite 90) 45 parts Calcium carbonate (Light fine carbon Cal, Brilliant
15, manufactured by Shiraishi Calcium KK) 5-part polyethylene wax emulsion (GIX-
0056, ) 15 parts polyacrylic acid ester emulsion (nonionic, MFT approx. 10°C) 10 parts acrylonitrile polymer emulsion (weak anionic, MFT approx. 100°C) 15 parts cationic polymer electrolyte 15 parts Example 3 Conductive treatment An original plate for electrophotographic lithography was prepared in the same manner as in Example 1, except that 5 parts of polyvinyl alcohol (PVA-HC, manufactured by Kuraray KK) was further added to the composition of the layer. Example 4 An original plate for electrophotographic printing was prepared in the same manner as in Example 2 except that 5 parts of starch was further added to the composition of the conductive treatment layer. Comparative Example Same as Example 1 except that 30 parts of nonionic vinyl acetate emulsion was used instead of 10 parts of polyacrylic ester emulsion and 15 parts of acrylic ester-styrene copolymer emulsion in Example 1. A comparative electrophotographic printing plate was prepared in the same manner. Plate making (KK Ricoh's S
-1 using a plate-making machine, fixing with a Ricof user, and desensitizing with a Ricoh etching processor) to create five types of offset masters, and print these masters on a commercially available offset printing machine (AP-1310,
(manufactured by KK Ricoh) to perform the actual printing.
The dampening solution used in this printing was the Ricoh Etching Processor diluted with 5 times the amount of water. In this plate-making process, curling was observed in the master using the original plate of the comparative example, and more than 5,000 clear prints were obtained when printing with the master using the original plate of the present invention. Furthermore, 1000 sheets of each of these original plates were stacked 40 times.
When examined after being left for 5 days under conditions of ℃ and 80% RH, no deterioration was observed in the original plates obtained in Examples 1 to 4, but blocking occurred in the comparative examples. Moreover, deterioration of the photosensitive layer was observed, and a master with good image quality could not be obtained. In addition, using these original plates, KK Ricoh's S
-3 Plate making machine (dry electrophotographic plate making machine) and FE
-2 (KK Ricoh, heat fixing machine), the master after etching was stacked with 30 plates and continuously printed on AP-2600 (KK Ricoh, automatic printing machine) (Examples 1 to 4 and Comparative Example) Good results with no plate feeding errors.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of two examples of planographic printing original plates according to the present invention, and Figure 3 shows the relationship between the pigment blending ratio of the conductive treatment layer and the discoloration of the photosensitive layer when stored at 45°C. The graph, Figure 4, is a graph showing the relationship between the pigment blending ratio of the conductive treatment layer and the scratch stain during automatic overlapping plate feeding, and Figure 5 is the graph showing the relationship between the pigment blending ratio of the conductive treatment layer and the coefficient of friction. Graph, Figure 6 is a graph showing the apparent minimum film forming temperature of a mixture of a resin with a low film forming temperature and a resin with a high film forming temperature, and Figure 7 is a graph showing a binder mixed with a resin with a low film forming temperature and a resin with a high film forming temperature. A graph showing the relationship between the minimum film forming temperature of the binder, the degree of deterioration of the photosensitive layer, and blocking when a single binder is used. A graph showing the relationship between the minimum film forming temperature, the degree of deterioration of the photosensitive layer, and blocking, and Figure 9 shows the relationship between the deterioration of scratches and the curling after etching when an emulsion resin and a water-soluble resin are used together as a binder. This is a graph showing the following. DESCRIPTION OF SYMBOLS 1...Support base paper, 2...Undercoat layer (precoat layer), 3...Waterproof layer, 4...Photosensitive layer (photoconductive layer), 5...Electroconductive treatment layer.

Claims (1)

[Scope of Claims] 1 A subbing layer, an optional waterproof layer, and a zinc oxide/resin dispersion photosensitive layer are provided on the surface of a base paper support, and a conductive treatment layer is provided on the back surface. , the conductive treatment layer comprises the following component A,
A planographic printing original plate characterized by containing component B, component C, and component D as main components. (Component A) A pigment prepared by mixing 70 to 95 parts by weight of clay and 5 to 30 parts by weight of calcium carbonate and/or zinc oxide. (Component B) A binder prepared by mixing 1 part by weight of a weakly anionic or nonionic emulsion resin with a minimum film forming temperature of 0 to 30°C and 0.4 to 0.8 part by weight of a weakly anionic or nonionic emulsion resin having a minimum film forming temperature of 60 to 110°C. (Component C) A cationic polymer electrolyte in an amount of 10 to 30% by weight based on the total amount excluding component A. (Component D) A wax emulsion containing 5 to 40% by weight based on the total amount excluding component A. 2 An undercoat layer, an optional water-resistant layer, and a zinc oxide/resin dispersion photosensitive layer are provided on the surface of the base paper support, and a conductive treatment layer is provided on the back surface, and the conductive treatment layer is The following ingredient A,
A planographic printing original plate characterized by containing component B, component C, and component D as main components. (Component A) A pigment prepared by mixing 70 to 95 parts by weight of clay and 5 to 30 parts by weight of calcium carbonate and/or zinc oxide. (Component B) Consists of a combination of 70 to 90 parts by weight of an emulsion resin and 10 to 30 parts by weight of a water-soluble resin, and each emulsion resin is weakly anionic or nonionic and has a minimum film forming temperature of 0 to 30°C. A binder made of a mixture of 1 part by weight and 0.4 to 0.8 parts by weight of a binder at 60 to 110°C. (Component C) A cationic polymer electrolyte in an amount of 10 to 30% by weight based on the total amount excluding component A. (Component D) A wax emulsion containing 5 to 40% by weight based on the total amount excluding component A.