JPH06104389B2 - Method for forming printing surface of printing blanket - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing blanket, and more particularly to a method for forming a rubber layer surface which is the uppermost printing surface. (Prior Art) As a printing blanket used in a high-speed offset printing machine, a compressible printing blanket provided with a compressible layer and an incompressible printing blanket having no compressible layer are used. In either case, since offset printing transfers ink from a printing plate to a blanket and then prints it on a paper surface, the printing surface of the blanket is formed with a certain roughness in order to improve the ink application. The roughness of this printed surface is usually 2 μm on average with 10 points using a stylus roughness meter.
It is formed to be about 15 μm. Conventionally, there are a method of using talc and a method of polishing or grinding as a method for forming a printing surface of a blanket on a rough surface. In the method of using talc, after the surface rubber layer is applied, talc is further applied to the surface rubber layer and vulcanization is performed as it is.
After vulcanization, excess talc is removed to form a printed surface roughness of 2 to 15 μm depending on the particle size of talc. On the other hand, the method of polishing is to apply a surface rubber layer and vulcanize it, and then polish the surface of the rubber layer with a sandpaper grinder to form a printed surface having a roughness of 2 to 15 μm. (Problems to be Solved by the Invention) The conventional method of forming the printing surface of the printing blanket as described above has the following problems. That is, in the method using talc, it is ideal to completely remove talc after vulcanization, but it was difficult to completely remove talc. Therefore, talc often remains attached to the printed surface, and talc hinders ink transfer. Therefore, in order to stabilize the print quality, it is necessary to print a considerable number of sheets. Moreover, when talc is used, since the surface roughness of the printed surface is formed by the particle size of talc, so-called whisker due to scratches such as when polishing is not possible. Therefore, although the dot reproducibility is excellent because the ink is poorly deposited, sufficient print quality cannot be obtained for so-called solid printing of one color. On the other hand, when the surface roughness of the printing surface is formed by polishing with a grinder, the number of polishing steps increases and the cost increases accordingly. Further, the polishing method has a problem that unevenness is formed on the printed surface and so-called beards are formed, so that the ink is deposited well, which is good for solid printing, but poor in reproducibility of halftone dots. That is, in the past, satisfactory printing characteristics could not be obtained regardless of which method was used to form the printing surface. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for forming a printing surface of a printing blanket which is excellent in both halftone dot reproducibility and solid printing by a simple method. (Means for Solving Problems) In order to achieve the above-mentioned object, the structure of the present invention is a method for forming a printing surface of a printing blanket having at least one support and a surface rubber layer, and the uppermost layer of the support is used. After applying a rubber layer to be a printed surface on, the surface of a surface forming sheet having a surface roughness of 2 μm to 15 μm is pressure-bonded to the upper surface of the rubber layer by vulcanization. After vulcanization, the surface forming sheet is peeled off to form a printed surface having a surface roughness of 2 μm to 15 μm. (Example) The printing blanket in the present invention includes both a compressible printing blanket and an incompressible printing blanket, and the structure itself is not changed. Therefore,
It can be used for all known blankets. The printing surface of the present invention is formed by using a surface-forming sheet whose surface is finished to be a rough surface having a constant roughness and press-bonding the surface-forming sheet to a surface rubber layer coated with the surface-forming sheet. The material of the surface forming sheet is not particularly limited, and a plastic sheet, a rubber sheet, a paper sheet or the like can be appropriately selected and used. Polyester resin sheet as plastic sheet,
A polyamide resin sheet or the like is preferable, and in the case of a rubber sheet, it is preferable to back it with a base cloth in order to prevent the extension. The surface of the surface forming sheet has a surface roughness of 2 μm to 15 μm, preferably 5 μm to 5 μm with a stylus type roughness meter by polishing with a grinder, embossing, roughening of the surface using printing such as gravure printing, or sandblasting. 6 μm
To finish. FIG. 1 shows a rubber sheet 4 in which a rubber 2 is applied to a base fabric 1 and vulcanized, and a surface 3 of the rubber 2 is polished by a sandpaper grinder to finish it to a predetermined roughness. Next, a method for manufacturing a printing blanket according to the present invention will be described. First, the compressive layer 6 is provided on the support 5, and the surface rubber 8 to be the printing surface is applied via the support 7. The supports 5 and 7 are made of, for example, woven cloth such as cotton cloth, rayon cloth, polyester cloth, etc., and the compressive layer 6 is formed by a foaming method using a foaming agent, a so-called salt leaching method using elution powder, hollow microsphere mixing. It may be formed by any method. As the surface rubber 8, an oil resistant rubber such as acrylonitrile butadiene rubber or chloroprene rubber is used. After sequentially stacking the respective components in this manner, the surface rubber layer 8
Then, the surface of the surface forming sheet 4 is pressure bonded (see FIG. 2). Next, this may be vulcanized, and after the vulcanization is completed, the surface forming sheet 4 may be peeled off. When the surface forming sheet 4 is peeled off, the surface rubber layer 8 is 2 to 15 μm due to the sheet 4.
It can be formed on a surface having a roughness of m. The surface forming sheet 4 can be repeatedly used, and the printed surface can be manufactured more easily and cheaply as compared with the conventional manufacturing method. Next, examples will be described. <Example 1> The surface forming sheet was manufactured as follows. First, a blanket woven fabric was used as a backing base fabric, and ethylene propylene rubber was applied to the base fabric to a thickness of 0.2 mm and vulcanized to prepare a rubber sheet having a JIS hardness of 80 degrees. The surface of this rubber sheet was polished and finished by a sandpaper grinder with a stylus type roughness meter so as to have a roughness of 5 μm to 6 μm. The surface of this rubber sheet was pressure-bonded to a surface rubber layer constituting a blanket for vulcanization, and after vulcanization, the rubber sheet was peeled off to produce a printing blanket having a printed surface with a roughness of 5 to 6 μm. The printing blanket thus produced exhibited excellent printing characteristics in both dot reproducibility and solid printing. The results of comparison with the conventional product are as follows. <Example 2> A polyester resin sheet having a thickness of 0.2 mm was provided with a sandpaper grinder to obtain a surface roughness of 5 with a stylus type roughness meter.
The surface was polished so as to have a thickness of 6 μm. A printing blanket was produced from this plastic sheet in the same manner as in Example 1. As a result of the printing test, it was possible to obtain excellent reproducibility of halftone dots and excellent print quality for both solid printing as in Example 1. Example 3 A matted paper sheet having a thickness of 0.2 mm and a surface roughness of 5 to 6 μm using a stylus roughness meter was used. The unvulcanized surface rubber layer is coated with powder such as zinc stearate that melts during vulcanization to prevent adhesion or sticking to paper and does not impair printability, and then press-bonds the paper sheet. After vulcanization, the paper sheet was peeled off after vulcanization to produce a printing blanket. As a result of the printing test, it was possible to obtain excellent reproducibility of halftone dots and excellent print quality for both solid printing as in Example 1. <Example 4> A 0.2 mm-thick polyester resin sheet was surface-polished by sandblasting so as to have a surface roughness of 5 to 6 m using a stylus roughness meter. A printing blanket was manufactured using a plastic sheet in the same manner as in Example 1. The print test results are shown in Example 1.
Similar to the above, it was possible to obtain excellent dot reproducibility and excellent print quality for solid printing. (Effects of the Invention) As described above, according to the present invention, the so-called beard cannot be produced as in the case of polishing with a grinder, so that the dot reproducibility is excellent, and the printing quality can be improved even in solid printing of one-color printing. It is possible to improve. Further, the surface forming sheet is economical because it can be reused, and it is extremely easy to manufacture because the printed surface layer can be formed only by pressing the coated surface rubber layer.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of the surface forming sheet, and FIG. 2 is an explanatory sectional view showing a state in which the surface forming sheet is pressure-bonded to a printing blanket before vulcanization. 4 is a surface forming sheet, 5 and 7 are supports 6 are compressible layers, 8 is a surface rubber layer

Claims (4)

[Claims] 1. A method of forming a printing surface of a printing blanket having at least one support and a surface rubber layer, the method comprising:
After applying the rubber layer to be the printing surface on the uppermost layer of the support,
The surface of the surface forming sheet having a surface roughness of 2 μm to 15 μm was pressure-bonded to the upper surface of the rubber layer by a stylus type roughness meter to vulcanize the surface forming sheet, and after the vulcanization, the surface forming sheet was peeled to 2 μm.
A method for forming a printing surface of a printing blanket, which comprises forming a printing surface having a surface roughness of ˜15 μm. 2. The method for forming a printing surface of a printing blanket according to claim 1, wherein the surface forming sheet is a rubber sheet. 3. The method for forming a printing surface of a printing blanket according to claim 1, wherein the surface forming sheet is a plastic sheet. 4. The method for forming a printing surface of a printing blanket according to claim 1, wherein the surface forming sheet is a paper sheet.