JPH05155167A - Electrophotographic plate making material - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic plate making material reduced in tensile stress and the elongation due to the deformation of a plate attaching hole, in a support formed by coating both surfaces of paper with a water- resistant resin, by forming the waterresistant resin layer at least on the side coated with a photoconductive layer from an ionomer resin. CONSTITUTION:A support consisting of a paper substrate and the waterresistant resin layers applied to both surfaces of the paper substrate and the photoconductive layer formed on the surface of the support are provided. The surface water-resistant resin layer carrying the photoconductive layer of the support is formed from an ionomer resin. As a result, an electrophotographic plate making material capable of producing a planographic printing plate not generating elongation due to water absorption during printing and reduced in tensile stress or the elongation due to deformation can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic plate-making material capable of making a lithographic printing plate by an electrophotographic method. More specifically, the present invention is
The present invention relates to an electrophotographic plate-making material suitable for color printing, which has little elongation due to water absorption and mechanical deformation.

[0002]

2. Description of the Related Art A method for making a lithographic printing plate by an electrophotographic method is known, and generally, this method involves uniformly charging a photoconductive layer of an electrophotographic plate-making material, exposing it to an image, and then applying a wet or dry method. The toner image is developed to form a toner image, and the toner image is fixed and then treated with a desensitizing solution to make the non-image portion hydrophilic.

As such an electrophotographic plate-making material, one having a photoconductive layer provided on a paper support has been conventionally known. However, a problem with such a conventional lithographic printing plate is that it has a paper support. It was the elongation of the plate due to water absorption. That is, the lithographic printing plate is exposed to the action of dampening water for a long time during printing. The paper support is usually provided with a water-resistant coating layer on both sides, but since the waterproofness of the coating layer cannot be perfect, water permeates into the paper layer of the lithographic printing plate during printing. As a result, the planographic printing plate grows.

The degree of this elongation varies depending on the number of printed sheets, but it is large in the direction perpendicular to the paper making direction and reaches 1 to 2% of the plate size. A printing plate having such elongation cannot be used for color printing requiring color superposition.

As a support for an electrophotographic plate-making material which is less likely to grow due to water absorption, a support in which both surfaces of paper are coated with a polyethylene resin mixed with a conductive substance is known. A printing plate having such a support is known. JP-A-59-64395
No. 59-188661 and the like. A lithographic printing plate obtained from an electrophotographic plate-making material using such a support has little elongation during printing due to water absorption and can be sufficiently used for color printing. However, this lithographic printing plate material is used for a printing press having a large pulling force when the lithographic printing plate is attached to the printing press or when the lithographic printing plate is attached to the plate cylinder with a hole formed in the lithographic printing plate. When it is used in a printing machine in which the hook of the plate cylinder is hooked, there is a problem that it cannot be used for color printing due to stress elongation or elongation due to deformation of holes.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of conventional electrophotographic plate-making materials, does not cause elongation of the lithographic printing plate due to absorption of water during printing, and is free from tensile stress and holes. It is intended to provide an electrophotographic plate-making material capable of producing a lithographic printing plate which is less likely to be stretched due to deformation.

[0007]

As a result of various studies, the present inventors have found that among the water-resistant resin layers that cover both sides of paper, at least the resin that constitutes the resin layer on the side to which the photoconductive layer is applied is
The present invention has been completed by finding that the above problems can be solved by using an ionomer resin.

That is, the electrophotographic plate-making material of the present invention is
A paper base, and a support comprising front and back water-resistant resin layers that cover both front and back surfaces of the paper base, and a photoconductive layer formed on the surface of the support, wherein the support comprises: The surface water-resistant resin layer supporting the photoconductive layer is formed of an ionomer resin.

The ionomer resin used in the present invention generally has a structure in which an acid group is contained in the polymer skeleton of the resin and the acid group is neutralized with a metal ion, and the polymer skeleton is ethylene-methacryl. It is made of an acid copolymer, an ethylene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, a sulfonated polystyrene or the like, and its metal ions include Na, Zn, Mg and Ka.
Generally, from the viewpoint of processability in extrusion lamination for resin coating of paper, it is preferable to use a Na or Zn salt of an ethylene-acrylic acid copolymer or an ethylene-methacrylic acid copolymer.

As an example of such an ionomer resin, when the metal ion is Zn, Himilan H-1652 (trademark) manufactured by Mitsui DuPont Polychemical, AM-60 is used.
04 (trademark), and when the metal ion is Na, manufactured by Mitsui DuPont Polychemical, Himilan AM-7902-1
(Trademark), H-1601 (trademark) and the like.

The ionomer resin has a tough property because it has a cross-linking structure by metal ions at room temperature, but at high temperatures, the cross-linking structure disappears and fluidity occurs, so that the ionomer resin has a normal processing temperature. It is easy to carry out extrusion lamination.

If the surface water-resistant resin layer is formed of, for example, a polyethylene terephthalate resin, since the resin is tough, but has a high melting temperature, a preformed film is laminated on paper with an adhesive. Since the processing method is inevitable, the surface water-resistant resin layer made of the ionomer resin of the present invention is inferior in terms of productivity and cost.

The water resistant resin layer on the surface side (the side on which the photoconductive layer is applied) and the back surface side of the support used in the present invention are preferably ionomer resins, but the water resistant resin layer on the back surface side is preferable. In the case of using an ionomer resin,
Depending on the type of plate-making machine, if a hot plate, hot roll, etc. are used in the drying section, the water-resistant resin layer on the back side will come into direct contact with this, and the ionomer resin will exhibit tackiness at high temperatures, and therefore the support will be It may stick to the dry part of the plate making machine. In such a case, it is preferable that the water resistant resin layer on the back side is formed of high density polyethylene or a mixture of high density polyethylene and low density polyethylene.

The support used for the electrophotographic plate-making material must have electroconductivity as a whole in order to impart electrophotographic property to the electrophotographic plate-making material, and for that reason, the front surface side and the back surface side. A conductive material is mixed in the water-resistant resin layer of, and thereby the volume electric resistance of the support is 1 × 10.
Adjusted to ¹⁰ ohms or less.

The conductive substance for the water resistant resin layer can be selected from metal oxides of metals such as zinc, magnesium, tin, barium, molybdenum and titanium, and carbon black. A particularly preferred conductive material is
It is a conductive carbon black. This substance has the advantage that it is possible to obtain conductivity even in a small amount and is easily miscible with an ionomer resin or a polyethylene resin. When the conductive carbon black is taken as an example, the amount of such a conductive substance added is appropriately in the range of 10 to 30%. If it is less than 10%, the conductivity is not sufficient, and if it exceeds 30%, the waterproof property of the resin layer is deteriorated.

The water-resistant resin layer on the front surface side and the back surface side of the support used in the present invention is coated on both sides of the paper substrate by the extrusion laminating method. The appropriate thickness of the resin layer to be laminated is 5 to 30 μm. If it is thinner than 5 μm, the waterproof property of the obtained support will be insufficient, and if it is thicker than 30 μm, the cost will only increase and the advantage will be less.

Further, in order to enhance the adhesive strength between the paper base and the water resistant resin layer, the surface of the paper base is preliminarily treated with ethylene.
A vinyl acetate copolymer, an ethylene-acrylic acid ester copolymer or the like can be applied as a primer, or the surface of a paper substrate can be subjected to corona discharge treatment.

As the paper base used in the present invention, any conductive paper conventionally used for electrophotographic plate-making materials can be used. Usually used, bleached chemical pulp, a paper made by adding a sizing agent such as alkyl ketene dimer, modified rosin, polyacrylamide, polyamide polyamine epichlorohydrin resin and the like,
It is manufactured by impregnating a conductive agent such as salt or polystyrene sulfonic acid. The basis weight of the paper base is preferably 50 to 150 g / m ² .

The photoconductive layer provided on the support as described above is composed of a photoconductive substance and a binder. As the photoconductive substance, an inorganic photoconductive agent such as zinc oxide or titanium oxide, or an organic photoconductive agent such as phthalocyanine or polysilane is used. As the binder, silicone resin, polyacryl- or methacrylic acid resin, polyvinyl chloride resin and the like and their derivatives are used alone or in combination.

In order to increase the adhesive strength between the photoconductive layer and the support, the surface of the surface water-resistant resin layer coated with the photoconductive layer may be previously subjected to corona discharge treatment or ozone treatment.

The support used in the present invention is 1 × 10 ^10.
It has a volume electric resistance of ohms or less. To measure this volume electric resistance, the electrophotographic plate-making material support is sandwiched between two metal disk-shaped electrodes having a radius of 2.5 cm, and a DC voltage V is applied. The current value A at this time is read and calculated from the following equation. Volume electric resistance Rv = V / A (ohm)

[0022]

EXAMPLES The present invention will be explained in more detail by the following examples, but these examples do not limit the present invention. In the text, “%” and “part” represent “% by weight” and “part by weight” unless otherwise specified.

Example 1 Stock 1 obtained by mixing bleached hardwood pulp and bleached softwood pulp in a ratio of 2: 1 and beaten to a Canadian Deness of 350 ml.
In 00 parts, 0.3 parts of anionic polyacrylamide (manufactured by Arakawa Chemical Co., Ltd., Polystron 191), 2.5 parts of cationic starch (manufactured by Oji National, Kate F), polyamide polyamine epichlorohydrin resin (manufactured by Dick Hercules, Kamen 557H) 0.3 parts, alkyl ketene dimer (Dick Hercules, Harcon 40)
0.5 part was added, and paper having a basis weight of 110 g / m ² was made from the pulp slurry with a paper machine. Then, a calcium chloride solution was applied to the paper by a size press on a paper machine so that the dry application amount of calcium chloride was 1 g / m ² .

On both sides of the base paper thus obtained, conductive acetylene black 15%, zinc stearate 0.
Ionomer resin (Himilan H-1652 (trademark) manufactured by Mitsui DuPont Polychemical), which was previously melt-kneaded with 8% and 0.05% of 4,4′thiobis (3-methyl-6-tert-butylphenol), was extruded and laminated. Was used to laminate to a coating weight of 24 g / m ² to prepare a support. Before laminating, both sides of the base paper were subjected to corona discharge treatment.

On one side of the support thus obtained,
Corona discharge treatment was performed, and a photoconductive layer having the following composition was applied thereon by a bar coating method so that the coating weight was 25 g / m ² . Photoconductive zinc oxide (Sakai Chemical Co., SAZEX2000) 100 parts Silicone resin (Shin-Etsu Chemical KR = 211) 30 parts

The obtained electrophotographic plate-making material was placed in a dark room for 24 hours.
After acclimation for time, a printing plate having an image of a predetermined pattern was prepared using an ITEC 235 plate making machine.
Round holes each having a diameter of 5 mm were formed on the two opposite sides of the printing plate at intervals of 2.95 cm by using a printing punch. The printing plate thus treated was etched using a desensitizing treatment solution manufactured by Aitec Co., Ltd., and then mounted on a Hamada Star 500 printing machine manufactured by Hamada by a method in which a hook of a plate cylinder was hung in a round hole of the printing plate. , 3000 sheets were printed with blue ink.

Next, a second printing plate was prepared with the same pattern, and the last one of the previously printed products was used as the top, and overprinting was carried out with the red ink. The pattern displacement of the obtained printed matter was measured, and the maximum value thereof was taken as the pattern displacement value. The measurement results are shown in Table 1.

Example 2 The resin used for the water resistant resin layer on the back side of the support was high density polyethylene (density 0.946, MI = 3.2) and low density polyethylene (density 0.923, MI = 8. An electrophotographic plate-making material was prepared in the same manner as in Example 1 except that the 2: 1 mixture of 6) was used, and then a printing plate was prepared and subjected to printing. The measurement results are shown in Table 1.

Comparative Example 1 An electrophotographic plate-making material was prepared in the same manner as in Example 1 except that the same polyethylene resin mixture as in Example 2 was used as the resin used for the water resistant resin layers on both sides of the support.
Then, a printing plate was prepared and used for printing. Table 1 shows the measurement results
Shown in.

[0030]

[Table 1]

As described above, in Examples 1 and 2, the deviation of the pattern of the printed matter was small and the color printing was possible, but in Comparative Example 1, the deviation of the pattern was large, and it was used for color printing. It was inappropriate.
When the printed printing plate was examined, it was determined that most of the above deviations were caused by deformation of holes in the printing plate.

[0032]

According to the present invention, it becomes possible to obtain an electrophotographic plate-making material having a small elongation due to tensile stress and deformation of holes. The plate-making material of the present invention is useful for popularizing electrophotographic plate-making materials.

Claims (1)

[Claims] 1. A paper substrate, and a support comprising a front and back waterproof resin layer covering both front and back surfaces of the paper substrate, and a photoconductive layer formed on the surface of the support. An electrophotographic plate-making material, characterized in that the surface water-resistant resin layer carrying the photoconductive layer of the support is formed of an ionomer resin.