JP2789461B2 - Method of forming printing surface of printing blanket - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a printing blanket, and more particularly to a method for forming a rubber layer surface which is a top printing surface. (Prior Art) Compressible printing blankets provided with a compressible layer and non-compressible printing blankets not provided with a compressible layer are used as printing blankets used in high-speed offset printing presses. In any case, since the offset printing transfers the ink from the printing plate to the blanket once and then prints it on the paper surface, the printing surface of the blanket is formed with a fine uneven surface in order to improve the ink coverage. The unevenness of this printing surface is usually 10 points average roughness 2μ with a stylus type roughness meter.
The unevenness has a significant effect on the amount of transferred ink and the reproducibility of the image. 2. Description of the Related Art Conventionally, there are a method using talc and a method using polishing or grinding as a method of forming a printing surface of a blanket to a rough surface with a certain unevenness. In the method using talc, after applying a surface rubber layer, talc is further applied to the surface rubber layer and vulcanized as it is. After vulcanization, excess talc is removed to form a printed surface having a roughness of 2 to 15 μm depending on the particle size of the talc. On the other hand, in the polishing method, a surface rubber layer is applied and vulcanized, and then the surface of the rubber layer is polished with a sandpaper grinder or the like to form a printed surface having a roughness of 2 to 15 μm. (Problems to be Solved by the Invention) The method for 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 is difficult to completely remove talc. Therefore, talc often remains with being attached to the printing surface, and the talc has hindered the transfer of the ink. Therefore, it was necessary to print a considerable number of sheets until the printing quality was stabilized. When talc is used, so-called mustaches, such as scratches caused by polishing, cannot be formed because unevenness of the printed surface is formed by the particle size of talc.
Therefore, although the reproducibility of halftone dots is excellent, sufficient print quality cannot be obtained for one-color so-called solid printing due to poor ink coverage. On the other hand, when the unevenness of the printing surface is formed by polishing with a grinder, the number of polishing steps increases and the cost increases accordingly. Also, in the polishing method, directional irregularities are formed on the printing surface. For this reason, the ink placement is good, which is good for solid printing, but the contour of the halftone dot tends to collapse in a certain direction due to the directionality of the unevenness, and there is a problem that the halftone dot reproducibility is poor. Was. It is necessary that the printing surface of the printing blanket be a printing surface having unevenness with no directionality, which is excellent in both reproducibility of halftone dots and solid printing. The present invention has been made in view of such a situation, and provides a method for forming a printing surface of a printing blanket having an uneven surface with no directionality, which is excellent in both dot reproducibility and solid printing by a simple method. The purpose is to provide. (Means for Solving the Problems) The configuration of the present invention has the following configuration to achieve the above object. That is, at least one layer of the support is provided,
After applying a rubber layer to be the printing surface on the uppermost layer, this is semi-vulcanized to obtain a blanket semi-finished product, and then a plate cylinder having fine irregularities without directionality, or blasting, engraving, etc. Using a roll having fine irregularities with no directionality, transferring a liquid elastomer or resin to the rubber layer by a printing method to make the rubber layer surface a fine irregular surface, and finally the rubber layer surface is fine. The semi-finished blanket having a rough surface is crosslinked. Hereinafter, the configuration of the present invention will be described in detail, but the printing blanket of the present invention includes both a compressible blanket and a non-compressible blanket, and the internal structure thereof is not changed. Therefore, the blanket printing surface in the present invention, which can be used for all blankets having a known structure, is formed by a printing method using a roll having a surface with a roughness having a uniform roughness and no directionality. First, a printing method 1 will be described. In order to make the surface of the roll a rough surface with a uniform roughness and no directionality, form the created plate by winding it around the roll surface, or use a blasting process or engraving process on the roll surface directly with a rough-finished roll. Alternatively, a metal plate or a plastic plate roughened by blasting or engraving may be wound around a roll to obtain a roll having a fine uneven surface. The plate may be letterpress or intaglio, but intaglio includes both engraved intaglio and gravure. The method of making a plate is the same as the method of making a normal printing plate, and a plate having a pattern such as a fine halftone dot or a grid may be created. The plate thus prepared is wound around a roll surface to form a plate cylinder. Using a solution of an elastomer or a resin or a liquid elastomer or a resin instead of the printing ink on the plate cylinder, unevenness having no direction is transferred to the blanket surface by a printing method. As a printing method, any printing method such as gravure printing, offset printing, flexographic printing, and convex plate printing can be used. The blanket is formed by sequentially laminating a compressible layer, a support and the like by a known manufacturing method, applying a rubber layer to be a printing surface on the uppermost layer, and then half vulcanizing. As described above, the semi-vulcanization can prevent deformation of the rubber layer when forming the uneven surface by the printing method. In this way, a blanket semi-finished product is manufactured, and a solution of an elastomer or a resin, or a liquid elastomer or a resin is transferred to the surface by the printing method using the plate cylinder to form irregularities on the rubber layer surface, Crosslinking is carried out by heating or by means of electron beam, UHF, radiation or the like. The liquid elastomer or resin transferred by this crosslinking is solidified at the same time as the liquid elastomer or resin is solidified, so that a printing surface with certain irregularities is formed. FIG. 1 shows a printing surface forming method 1 by a gravure printing method.
It is an explanatory view showing an example and using a plate cylinder made of intaglio. A method of forming a surface by this printing method will be described with reference to the drawings. A part of a pre-manufactured plate cylinder 10 is immersed in a rubber solution 12 in a solution tank 11, and a doctor is
13 is arranged. Surface roughness of plate cylinder 10 is 2μ with a stylus type roughness meter.
m to 15 μm, preferably 5 μm to 6 μm. Guide rollers between the plate cylinder 10 and the impression cylinder 14 provided above
Pass the blanket semi-finished product 16, guided by 15,15. Since the rubber layer serving as the printing surface of the blanket semi-finished product 16 passes while being pressed against the plate cylinder 10 by the impression cylinder 14,
The rubber solution attached to the concave portion 17 of the plate cylinder 10 is transferred to the surface of the rubber layer, and a fine uneven surface having no direction is formed. Next, a blanket semi-finished product having a rough printing surface is rolled up on the other side, and this is crosslinked to form a rough surface. Next, the printing method 2 will be described. In this method, a roll having a fine uneven surface can be used in place of the plate cylinder 10 in the above method. That is, a blasting or engraving process is directly performed on the roll surface to form a roll having a uniform rough surface with no directionality, or a blasting or engraving process is performed on a metal plate or plastic with a uniform rough surface having no directionality. A roll having an uneven surface may be formed by winding a plate or the like around the roll. FIG. 2 shows a method of forming a printing surface by a gravure coater using the above-described roll. That is, the plate cylinder 10
Instead, a gravure roll 20 having a rough surface is used.
Except for using the gravure roll 20 in place of the plate cylinder 10, the printing method is the same as in the case of the first printing method, and therefore the description is omitted for simplification. Next, examples will be described. <Example 1> A compressible layer having a thickness of 0.6 mm was provided on a support, and further,
A rubber layer serving as a printing surface was applied to a thickness of 0.4 mm via the support, and this was semi-vulcanized to obtain a blanket semi-finished product. On the other hand, a rubber solution was prepared by dissolving rubber of the same quality as the surface rubber instead of the printing ink. The rubber solution was transferred to the surface of the rubber layer by a gravure printing machine equipped with a round screen having a 250 dot line, a concave portion having a depth of 5 to 6 μm, and a plate cylinder, according to one of the above printing methods. As a result, a fine uneven surface was formed. Next, this was vulcanized to produce a printing blanket having unevenness of 5 to 6 μm in which the rubber layer had no direction. The printing blanket of Example 1 manufactured in this manner exhibited excellent printing characteristics in both the outline of halftone dots and solid printing. The results of comparison with the conventional product are as shown in Table 1. Comparative Example 1 is a polished product using a grinder, and Comparative Example 2 is a non-polished product using talc. <Example 2> In Example 2, a blanket semi-finished product similar to that of Example 1 was obtained. Further, liquid urethane was applied to the surface rubber of this semi-finished product. On the other hand, the surface of a metal roll as a gravure roll of a gravure coater was subjected to a sandblast treatment to finish the surface roughness to 5 to 6 μm. The liquid urethane prepared in advance using this gravure roll was printed and transferred to the surface rubber by the method 2 of the above printing method. Furthermore, this is heat-cured to obtain 5-6 having no directivity on the printing surface.
A printing blanket having irregularities of μm was obtained. The printing blanket of Example 2 manufactured in this manner exhibited excellent printing characteristics in both the halftone dot outline and solid printing as in Example 1. (Effects of the Invention) As described above, according to the present invention, so-called whiskers cannot be formed as in the case of grinding with a grinder, so that the reproducibility of halftone dots is excellent, and printing is also possible in solid printing of one color printing. The quality can be improved. Further, since the roll can be reused, it is economical, and the processing time can be reduced as compared with the conventional case, so that the cost of the printing blanket can be reduced as a whole.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment according to the present invention, FIG. 1 is a side view for explanation showing a printing method using a plate cylinder, and FIG.
It is an explanatory side view showing a printing method when a gravure roll of a gravure coater is used. 10 Plate cylinder 11 Solution tank 12 Rubber solution 13 Doctor 14 Pressure cylinder 15 Guide roller 16 Semi-finished blanket 17 Depressed part 20 Gravure roll

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-52-147103 (JP, A)                 JP-A-60-116494 (JP, A)                 JP-A-50-125810 (JP, A)                 JP-A-58-92588 (JP, A)                 JP-A-59-156755 (JP, A)

Claims (1)

(57) [Claims] At least one layer of a support is provided, a rubber layer serving as a printing surface is applied to the uppermost layer, and then semi-vulcanized to obtain a blanket semi-finished product. Alternatively, using a roll with fine irregularities with no directionality on the surface by blasting, engraving,
Transferring a liquid elastomer or resin to the rubber layer by a printing method to make the rubber layer surface a fine uneven surface, and finally crosslink a blanket semi-finished product with the rubber layer surface having a fine uneven surface. Of forming a printing surface of a printing blanket.