JPH07429B2 - Rubber blanket for printing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a rubber blanket for printing.

[Prior Art and its Problems] The rubber blanket for offset printing is mainly required to have the following performances in order to improve print quality and operating rate.

(1) The surface rubber layer of the rubber blanket is
Since it is always in contact with the fountain solution that forms the ink and the non-image area, it is necessary to withstand these inks and fountain solution. From this viewpoint, conventionally, nitrile rubber having excellent oil resistance is used as a material for the surface rubber layer, except for using a special ink.

(2) From the viewpoint of improving print quality, it is necessary to ensure the uniformity of the ink film, which is called solid crushing, and the sharpness of each dot, which is called dot reproducibility.
In order to meet this requirement, it is necessary to make the surface roughness of the rubber blanket as smooth as possible to at least the surface roughness of the plate.

(3) From the viewpoint of improving workability, printing is completed by transferring the ink from the plate to the rubber blanket, and then transferring the ink again to the printing medium such as paper. When the rubber blanket comes into contact with the paper, the ink is transferred to the paper, and when the paper peels from the rubber blanket, a large adhesive force is generated. This causes the paper to stick to the rubber blanket, causing the paper to curl, or
There is a problem of tearing the paper. These trebles are
It frequently occurs when the surface roughness of the rubber blanket is fine, when printing is performed at high speed, or when the surface of a printing medium such as art paper or coated paper is smooth. These are described as having poor paper discharge properties (paper separation). Other than this,
Slur (dot flow) or double (dot printing double) is induced.

Such poor paper discharge property is more troublesome in an offset rotary press. That is, when the roll paper is cut, it is wrapped around the rubber blanket cylinder in multiple layers and the rubber blanket is destroyed. In that case, it must be replaced with a new one, which causes a decrease in productivity and a decrease in economic efficiency due to the stoppage of the machine.

Thus, the conventional rubber blanket for printing sacrifices the quality of the printed matter, that is, the reproducibility of the dots and the uniformity of the solid in the above-mentioned background, and attaches importance to the workability of the surface rubber. The surface roughness of the layer is set to 6 μm or more. In other words, it was difficult to achieve both print quality and paper discharge. Among such technical backgrounds, there is also one in which the surface rubber layer is cured by ultraviolet treatment to improve the paper discharge property, as in Japanese Utility Model Publication No. 36562 / SHO. However, there are problems that the cost is increased by adding one step, the working environment is deteriorated by using ultraviolet rays, and the surface rubber layer is easily scratched when it is shocked due to curing. Further, there is also one such as Japanese Patent Publication No. 47-51729, which intends to obtain the same effect as that described above as a chlorinated rubber layer by treating the surface rubber layer with chlorine water. However, in this case, there are problems that the working environment is deteriorated by using chlorine water and cracks are easily generated due to the decrease in elongation rate due to the formation of the chlorinated rubber layer. In addition, as in JP-A-56-75896, in order to improve the releasability from the material to be printed, a blanket is coated with a mixture of urethane resin and aluminum powder to form an uneven surface for high-speed printing. Some have been made available. However, in this case, there is a problem that the cost is increased by adding one step, the abrasion and life of the plate is reduced by mixing the metal powder, and further the reproducibility is reduced.

The present invention has been made in view of the above points, and provides a printing rubber blanket that exhibits good dot reproducibility and has good paper release properties.

[Means for Solving Problems] In the present invention, the surface of the substrate has at least a surface roughness (Rz) of 0.
A rubber blanket for printing, comprising a surface rubber layer made of a kneading type urethane rubber having a thickness of 5 to 2 μm.

That is, in order to improve the dot reproducibility and the solid uniformity which are the essence of print quality, it is preferable to make the surface roughness of the surface rubber layer fine so as to approach the plate surface roughness. However, when the surface roughness is made fine, the paper separation property (paper discharge property) is deteriorated. However, the inventors of the present invention have shown from a number of experiments that, in the case of a surface rubber layer formed of a kneading type urethane rubber, a sufficient paper discharge force can be exhibited even if the surface roughness (Rz) is reduced to about 0.5 μm. confirmed. That is, about 1/4 of the conventional surface rubber layer mainly composed of nitrile rubber etc.
It was confirmed by experiments that the paper can be ejected sufficiently with the paper ejection force below. The scientific basis for the kneading type urethane rubber having such a remarkable paper discharge property as compared with that of other materials has not been sufficiently clarified. From this viewpoint, the present invention provides a surface rubber layer made of a kneading type urethane rubber having a surface roughness (Rz) of 0.5 to 2 μm on a substrate. Further, the upper limit of the surface roughness (Rz) is set to 2 μm because the paper discharge amount is not sufficiently improved even if the surface roughness (Rz) is further increased, and the deterioration of the print quality becomes more remarkable.

As a means for forming a surface rubber layer made of a kneading type urethane rubber having a surface roughness (Rz) of 0.5 to 2 μm, for example, an extremely smooth plastic film (for example, Lumirror, a product of Toray Industries, Inc.) at the time of manufacturing a rubber blanket. There is a method in which (name) is applied to a rubber surface and vulcanized and then peeled off, or a method in which after vulcanization, it is ground with sandpaper having an extremely fine particle surface.

In the present invention, the kneading type urethane rubber refers to "liquid casting type, millable type, millable type," in the section of urethane rubber in the polymer dictionary (Taiseisha Publishing Department, published in September, 1970, p35).
It is a solid urethane rubber that corresponds to the millable type and is a solid urethane rubber in which a compounding chemical is kneaded with a so-called kneading roll.

[Operation] According to the printing rubber blanket of the present invention, since the surface rubber layer made of the kneading type urethane rubber having the surface roughness (Rz) of 0.5 to 2 μm is provided, good dot reproducibility is obtained. It is possible to exhibit the above-mentioned properties and, in addition, it is possible to exhibit a good paper release property.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

Example 1 Three cotton cloths are stuck together with nitrile rubber cement according to a conventional method to obtain a base material having a thickness of 1.3 mm. A predetermined adhesive was applied to one surface of this substrate with a doctor knife. Then, the materials for the surface rubber layer are sufficiently kneaded and mixed by a kneading roll according to the following formulation. Then, the obtained compound is dissolved in a solvent (for example, methyl ethyl ketone), and glued on a cotton cloth of the above-mentioned substrate with a doctor knife. Next,
After the solvent is dried, the polyester film lumirror is aligned with the rubber surface and placed in a vulcanizer to complete vulcanization. Then, the lumirror was peeled off to obtain a printing rubber blanket having a thickness of 1.65 mm. When the average surface roughness (Rz) of this rubber blanket for printing was measured, as shown in FIG.
It was 0.1 μm. The measuring instrument used was a universal surface profile measuring instrument SE-3F manufactured by Kosaka Laboratory.

After cutting this printing rubber blanket to a predetermined size,
It was attached to a double-sided printing machine (manufactured by Mitsubishi Heavy Industries, Ltd.) and coated paper was used as a printing paper, and printing was performed at a speed of 220 rpm for 1 minute. As a result, the paper discharge property was 10 (g / cm), so-called double, slur and register were not hindered, and the dot reproducibility and the crushing of the solid were very close to those of the proof print. .

Notes Material formulation of surface rubber layer Weight part Millathane76 (manufactured by TSE, USA) 100 Sulfur 2 Axel DM (vulcanization accelerator, Kawaguchi Chemical Co., Ltd. trade name) 1 Curacene (activator, Thiokol company trade name) 1 Stavaxol (hydrolysis) Inhibitor) 2 Stearic acid 0.5 Precipitable calcium carbonate 35 TP-90B (Plasticizer, trade name of Thiokol Company) 10 Accel M (vulcanization accelerator, trade name of Kawaguchi Chemical Co., Ltd.) 4 Comparative Example 1 Mainly composed of the following nitrile rubbers A rubber blanket for printing was produced in the same manner as in Example 1 based on the material formulation of the surface rubber layer. When a predetermined printing was attempted on the paper using this printing rubber blanket as in Example 1, the paper stuck to the printing rubber blanket and could not be printed at all. The paper discharge property was 40 g / cm.

Material formulation of surface rubber layer Weight part Nipol 1042 (Nitrile rubber, manufactured by Nippon Zeon Co., Ltd.) 100 Sulfur 2 Axel DM 1 Zinc white 5 Stearic acid 1 Precipitable calcium carbonate 40 TP-90B 10 Axel M 1 Nocrac 224 1 Example 2 Implementation Organic foaming agent Neocerbon P.1000 on the base material of Example 1
Nitrile rubber cement mixed with 10 parts by weight of (Eiwa Chemical Co., Ltd.) was applied, and a cotton cloth was further adhered onto the cement to prepare a base material composed of a total of four cotton cloths. The compound used in Example 1 was calendered on this base material with an adhesive.
The sheets were laminated to form a 0.4 mm sheet, and release paper was applied to the surface of the sheet to vulcanize it. After vulcanization, the rubber surface on the surface was polished with No. 800 sandpaper to obtain a rubber blanket for printing with a thickness of 1.95 mm. When the average surface roughness (Rz) of this printing rubber blanket was measured in the same manner as in Example 1, it was Rz = 2 μm as shown in FIG.

After cutting this rubber blanket for printing to a predetermined size, it was mounted on a BB type offset rotary press and 750 per minute.
Printed on coated paper at speed of rotation. The printing paper had a smooth running property, and the discharging property was 5 g / cm, which was extremely good. Further, the dot reproducibility in printing and solid crushing were of satisfactory quality.

Comparative Example 2 The printing rubber blanket produced in Comparative Example 1 was ground on its rubber surface in the same manner as in Example 2 to produce the printing rubber blanket of Comparative Example 2, and its surface roughness was measured. , Rz = 3.7 μm as shown in FIG. The paper discharge property was 20 g / cm.

[Effects of the Invention] As described above, according to the printing rubber blanket of the present invention, good dot reproducibility is exhibited, and
It is possible to achieve good paper release properties.

[Brief description of drawings]

1 to 3 are characteristic diagrams showing the surface roughness of a printing rubber blanket.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Fumio Koshiji 1-324 Osaki, Shinagawa-ku, Tokyo In-house Kinyo Co., Ltd. (56) References JP-A-58-42495 (JP, A) JP-A-58 -167197 (JP, A) JP-A 61-43596 (JP, A) Actually developed Shou 58-125070 (JP, U)

Claims (1)

[Claims] 1. A substrate having at least a surface roughness (Rz) on its surface.
A printing rubber blanket comprising a surface rubber layer made of a kneading-type urethane rubber having a thickness of 0.5 to 2 μm.