JPH04319962A - Electrophotographic lithography plate - Google Patents

Abstract

PURPOSE:To reduce the occurrence of fog on the surface of the reverse side coat layer of a zinc oxide electrophotographic lithography plate by keeping the surface smoothness of the layer within 300 to 600 seconds as per Beck's smoothness. CONSTITUTION:The surface smoothness of the reverse side coat layer of a zinc oxide electrophotographic lithography plate is set within the range of 300 to 600 seconds as per Beck's smoothness. In this case, if the Beck's smoothness is less than 300 seconds, the surface of the reverse side coat layer is roughened, thereby generating the pitting of pressure fog on the surface of a zinc oxide photosensitive layer. On the other hand, if the Beck's smoothness exceeds 600 seconds, abraded fog tends to occur, due to slippage at coating, winding and finishing processes. The composition of the reverse side coat layer consists of latex as binding material, water soluble polymer, a waterproofing agent, a conductive agent or the like. Furthermore, pigment containing sericite and 30% or more of sericite component is used as pigment.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an electrophotographic lithographic printing plate, and in particular, it is obtained by dispersing zinc oxide as a photoreceptor in a resin as a binder and coating it on a conductive support. This invention relates to zinc oxide lithographic printing plates.

0002

[Prior Art] The electrophotographic copying method is the so-called electrofax method, in which an electrophotographic photosensitive layer is coated on a conductive support, and this photosensitive material is charged, exposed, and
This is a method of obtaining copies through the steps of development and fixing. An electrophotographic lithographic printing plate is an application of this method to an offset printing plate. After development and fixation of this electrophotographic lithographic printing plate, the non-image area is made hydrophilic with a desensitizing liquid (etching liquid), and printed matter can be obtained by applying it to an offset printing machine, but the printed matter may be smeared. It is necessary that there be no.

The cause of stains on printed matter is not only insufficient desensitization of the photosensitive layer itself, but also local scratches that occur on the surface of the photosensitive layer of the lithographic printing plate, and these scratched areas become desensitized. This may result in a shortage and stains on printed matter. Such scratches on the photosensitive layer are called fog.
In particular, conventional electrophotographic lithographic printing plates are more prone to fogging than other printing plates, and cannot be said to be lithographic materials that can be used with confidence.

[0004] There are many types of fog on electrophotographic lithographic printing plates, but the fog that is more noticeable compared to other printing plates is fog caused by so-called mechanical stress, called abrasion fog or pressure fog. This type of fogging can occur if the person handling the printing plate accidentally hits the printing plate against another object or drops it on the floor, but it can also occur during the manufacturing process of the printing plate, such as the application of the electrophotographic photosensitive liquid. -Various mechanical stresses are applied during each process such as drying, winding, cutting, and finishing, which can leave scratches and pressure marks and cause fogging, and sometimes such fogging occurs in the product. There were cases where things got mixed in. During the manufacturing process, measures are taken to prevent these fogs from occurring on the mounting surface or work surface, but it is difficult to completely eliminate fogs. In order to eliminate such fogging, the production efficiency may be lowered, and the yield may also be lowered.

[0005] As a method to solve these problems,
JP-A-57-185 as a method for improving the surface of zinc oxide
No. 441, JP-A-57-186756, JP-A-60-
250362, and Japanese Patent Application Laid-open Nos. 59-170860 and 62-468 as methods for specifying the material of the backing layer.
Although Publication No. 54 and the like have been proposed, they are not necessarily satisfactory in completely preventing the occurrence of fogging.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method for electrophotographic lithographic printing plates in which fogging is less likely to occur on the surface of the zinc oxide photosensitive layer. . That is, an object of the present invention is to provide a method for producing a zinc oxide lithographic printing plate that causes less staining during printing.

[0007]

[Means for Solving the Problems] As a result of intensive studies to achieve the above object, the present inventor discovered the following method and completed the present invention. That is, the present invention is characterized in that the surface smoothness of the backing layer of the zinc oxide lithographic printing plate falls within the range of 300 seconds to 6000 seconds in terms of Beck smoothness (JIS-P8119). The reason why the inventor of the present invention focused on the surface smoothness of the backing layer is that the backing layer is applied until the photosensitive layer of the zinc oxide lithographic printing plate is coated, wound up, finished, transported, stored, and used. This is because when mechanical stress is applied to the photosensitive layer, most of the mechanical stress is applied through the backing layer, and it is thought that this is the coating layer that has the most influence.

[0008] In order to investigate the influence of the backing layer, the present inventor prepared several types of zinc oxide lithographic printing plates with a constant photosensitive layer and different backing layer surface smoothness, and each Stack two sheets at a time, with the photosensitive layer side and the backing layer side in contact, and apply mechanical stress by rubbing or hitting the two sheets together, then plate making and printing to compare the degree of fogging. I tried an experiment to do this. It was found that the influence of the surface smoothness of the backing layer on scratch fog and pressure fog was greater than expected. The present invention was made based on the facts discovered through these experiments.

As mentioned above, the surface smoothness of the backing layer of the zinc oxide lithographic printing plate needs to be in the range of 300 seconds to 600 seconds in terms of Bekk smoothness.
If the heating time is less than 0 seconds, the surface of the backing layer becomes rough, resulting in small spot-like pressure fogging on the surface of the zinc oxide photosensitive layer, which is not preferable. On the other hand, if the Bekk smoothness exceeds 600 seconds, it is undesirable because it becomes slippery during the coating, winding, and finishing steps, which tends to cause scratching and fogging.

[0010] As a method of adjusting the surface smoothness of the above-mentioned backing layer, it is generally carried out in a process called calendering. Zinc oxide lithographic printing plate original plates, which are coated with a backing layer or undercoat layer on a support such as paper, are processed using super calenders, machine calenders, soft calenders, etc. for the purpose of imparting surface smoothness and adjusting thickness. The calender will be passed through the calendar, but the pressure of the calender at this time,
The surface smoothness of the backing layer can be adjusted by changing the number of passing stages, passing speed, etc.

The composition of the backing layer in this case consists of a pigment, a binder latex, a water-soluble polymer, a waterproofing agent, a conductive agent, and the like. As pigments, kaolin clay, calcium carbonate, aluminum hydroxide, titanium oxide, plastic pigments, etc., and mixtures thereof are used, but sericite (sericite) described in Japanese Patent Publication No. 62-46854 is particularly preferred. and a pigment containing 30% or more of a sericite component. This is because sericite's hexagonal plate-like shape and ``lubricity'' prevent local excess binder from forming in the zinc oxide photosensitive layer, or because the composition other than the pigment in the backing layer, which is an oleophilic substance, This is because it is less likely to be transferred and adhered to the fogged portion of the zinc oxide photosensitive layer. However, when such a sericite pigment is used in the backing layer, in order to fully utilize the characteristics of sericite described above, the smoothness of the backing layer must be 300 seconds to 600 seconds in Bekk smoothness as described above. It is necessary to fall within the range of If the Bekk smoothness is less than 300 seconds, the surface of the zinc oxide photosensitive layer may be roughened into a hexagonal plate shape, and if it is more than 600 seconds, it will become more slippery due to its "lubricity" and cause scratching. There is a risk that it may cause

Examples of the binder latex include styrene-butadiene latex, (meth)acrylate-butadiene latex, polyvinyl acetate latex, polyvinylidene chloride latex, vinyl acetate-acrylic copolymer latex, acrylonitrile-butadiene copolymer latex, and chloride. Vinyl-vinyl acetate copolymer latex, ethylene vinyl acetate latex, etc. are used. Various starches, casein, polyvinyl alcohol, cellulose derivatives, etc. are used as water-soluble polymers, melamine-formalin resin, urea-formalin resin, polyamide resin, epoxy resin, etc. are used as water-resistant agents, and as conductive agents, 4
Class salt type polymer compounds, polymer electrolytes, inorganic salts, etc. are used. After thoroughly mixing and dispersing these materials in an aqueous solution, they are coated onto a support such as paper using a coating device such as an air knife, blade, or metabar, and dried to form a backing layer.

The present invention is characterized by the surface smoothness of the backing layer of the zinc oxide lithographic printing plate, and other known supports, undercoat layers, and zinc oxide photosensitive layers can be used. For example, the support to which the backing layer of the present invention is applied may include paper,
Paper laminated with aluminum, synthetic paper, paper laminated with plastic, plastic sheet, aluminum plate, etc. are suitable, and each is used depending on the purpose. The undercoat layer can be made of the same material as the backing layer described above. In addition to photoconductive zinc oxide, the zinc oxide photosensitive layer is made of resin, sensitizing dye, various additives, etc. The resin is acrylic resin,
Silicone resin, polyester resin, alkyd resin, vinyl chloride resin, vinyl acetate resin, etc. are used, and sensitizing dyes include rose bengal, fluorescein, bromophenol blue, rhodamine, methylene blue, and cyanine dyes, and various additives are used. Agents include acid anhydride, p
-Chloroanil, p-benzoquinone, iodine, etc. are used. The acid-zinc lithographic printing plate of the present invention may have an intermediate layer between the undercoat layer and the zinc oxide layer or between the support and the undercoat layer.

[0014]

[Examples] The present invention will be explained below using specific examples.

Example 1 Kaolin 1 was applied to the surface of water-resistant base paper with a basis weight of 100 g/m2.
50 parts by weight, 100 parts by weight of styrene-butadiene resin,
An undercoat layer coating solution consisting of 15 parts by weight of Poval, 5 parts by weight of sodium sulfamate, and 1 part by weight of melamine-formalin resin was applied at a coating amount of 10 g/m2 (solid content). Next, 150 parts by weight of sericite and styrene were added to the back side.
A backing layer coating solution consisting of 100 parts by weight of butadiene resin, 15 parts by weight of POVAL, 1 part by weight of melamine-formalin resin, and 10 parts by weight of polyvinylbenditrimethylammonium chloride was applied at a coating amount of 15 g/m2 (solid content). . This was subjected to super calendering to prepare two types of samples such that the surface smoothness of the back side was 300 seconds and 400 seconds in Bekk smoothness. Further, on the undercoat layer, 100 parts by weight of photoconductive zinc oxide, 20 parts by weight of acrylic resin, 0.1 part by weight of rose bengal, and 0.0 parts by weight of phthalic anhydride were added.
A zinc oxide lithographic printing plate was prepared by thoroughly mixing and dispersing 1 part by weight of 0.01 parts by weight in a toluene solvent solution, and then coating the mixture in a coating amount of 25 g/m2 (solid content).

These lithographic printing plates are stacked in two layers so that one photosensitive surface is in contact with the backing surface of the other, and after rubbing them together while applying a constant load or pressing them with a pressure machine, the photosensitive surface in contact with the backing surface is A zinc oxide lithographic printing plate with
Desensitize with etchant Diafax LOM-OH (manufactured by Mitsubishi Paper Mills) for electrophotographic offset master,
When printed using a printing machine Ryobi 3200MCD (manufactured by Ryobi), there was hardly any rubbing or fogging in the extruded areas. In addition, the platemaking image quality and printing durability were also good.

Example 2 The same procedure was used as in Example 1 except that 150 parts by weight of sericite, the pigment component in the backing layer coating solution of Example 1, was replaced with Zeeklite (sericite content: 35%, manufactured by Zeeklite) pigment. Two types of zinc oxide lithographic printing plates were prepared in the same manner. This was subjected to super calendering, and the surface smoothness of the backing layer was adjusted to Bekk smoothness of 450 seconds and 600 seconds. Further, when mechanical stress was applied in the same manner as in Example 1 and then plate printing was performed, almost no fogging was observed. In addition, the platemaking image quality and printing durability were also good.

Example 3 The same undercoat layer coating liquid and backing layer coating liquid as in Example 1 were applied to the front and back sides of a paper made by laminating aluminum foil with a thickness of 10 U to a waterproof base paper with a basis weight of 100 g/m2. Then, this was subjected to machine calendering so that the surface smoothness of the back side was 500 seconds and 600 seconds in Beck smoothness. Furthermore, Example 1
A zinc oxide lithographic printing plate was prepared in the same manner as above by providing a zinc oxide photosensitive layer on the undercoat layer. After applying mechanical stress to this in the same manner as in Example 1, plate making printing was performed, and almost no fogging was observed. In addition, the platemaking image quality and printing durability were also good.

Comparative Example 1 A lithographic printing plate was prepared in the same manner as in Example 1, except that the surface smoothness of the backing layer was changed to Bekk smoothness of 100 seconds and 250 seconds, and the same mechanical process as in Example 1 was carried out. When the plates were printed after applying stress, fogging was observed in areas where they rubbed or were pressed.

Comparative Example 2 When the same test as in Example 2 was carried out except that the surface smoothness of the backing layer was changed to 650 seconds and 800 seconds in terms of Bekk smoothness, fogging was observed in the rubbed or pressed areas. It was done. These results are summarized in Table 1 below.

[0021] Evaluation ◎...There is no fogging at all.○...There is almost no fogging.△...There is some fogging, but it is practically acceptable.□...There is fogging and it is not practical.×... There is fogging all over the surface.

[0021]

Effects of the Invention As described in the present invention in the zinc oxide lithographic printing plate, by regulating the surface smoothness of the backing layer to a value within a certain range, fogging on the surface of the photosensitive layer is made less likely to occur. It is possible to provide a zinc oxide lithographic printing plate with less staining during printing.

Claims (2)

[Claims] Claim 1: In an electrophotographic printing plate comprising a zinc oxide photosensitive layer on a conductive support and a backing layer on the opposite side, the surface smoothness of the backing layer is determined by Bekk smoothness (J
IS-P8119) electrophotographic lithographic printing plates ranging from 300 seconds to 600 seconds. 2. The electrophotographic printing plate according to claim 1, wherein a pigment containing a sericite component is used in the backing layer.