JP3102452B2 - Blanket sheet for offset printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blanket sheet for offset printing, and more particularly to a blanket sheet for offset printing having a surface layer having excellent hydrophilicity.

[0002]

2. Description of the Related Art A printing unit in an offset printing press will be described. A general printing unit, as shown in FIG. 1, includes an inking device 2 for supplying ink to a plate cylinder 1 on which a printing plate is mounted, and a dampening solution. And a blanket cylinder 4 provided with a printing blanket sheet. The blanket sheet is attached by bringing the blanket cylinder 4 into contact with the lowermost support with the surface printing layer facing the printing plate. When using this, first, dampening water is supplied from the water supply device 3 to the printing plate, and then ink is supplied from the inking device 2,
The ink image on the plate is transferred to a blanket sheet mounted on the blanket cylinder 4, and the image is printed on printing paper passing between the blanket cylinder 5.

In such offset printing, a hydrophilic portion and a lipophilic portion are provided on the printing plate of the plate cylinder 1, and water is adhered to the hydrophilic portion to prevent ink from adhering.
Prevents water from adhering to lipophilic parts and allows ink to adhere. Then, the ink is transferred from the printing plate onto the blanket sheet, and further transferred from the blanket sheet to printing paper. Accordingly, the blanket sheet is used for the surface layer with a rubber which is good for ink adhesion and good for ink release (ink transferability).

[0004]

As described above, since the surface layer has been particularly emphasized as being ink-resistant, that is, oil-resistant, the balance between ink reception and transfer has been maintained. , Ie, hydrophilicity was not regarded as important. The print quality is evaluated based on the reproducibility of whether or not the state of the ink adhering on the printing plate and the state of the ink transferred to the printing paper are equivalent. That is,
The determination is made based on how the state of the halftone dot on the printing plate changes on the printing paper and whether the halftone dot is enlarged or reduced.

[0005] If the water deposited on the plate is not well received on the blanket sheet, the water on the plate will be crushed when pressure transfers to the blanket sheet and will be larger than on the plate. State. As a result, the ink image on the printing plate is transferred to the blanket sheet in a distorted state.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a blanket sheet having an improved halftone dot reproducibility of ink on a printing plate and having excellent hydrophilicity.

[0007]

In order to achieve the above object, the present invention has the following arrangement. That is, in a blanket sheet having at least one support and a surface layer serving as a printing surface, the surface layer was formed of oil-resistant rubber mixed with fine powder of natural collagen fibers. The surface layer to be the printing surface was prepared by mixing natural collagen fiber fine powder into oil-resistant rubber to balance water absorption and water discharge. It is desirable that the size of the natural collagen fiber fine powder is 5 μm to 100 μm. If the particle size is smaller than 5 μm, the dispersibility becomes worse because the particle size is too small, and the cohesive force increases. Further, even if the particle size is larger than 100 μm, the dispersibility is deteriorated, or the particle size is too large for the halftone dot (printed image). Further, the amount of the natural collagen fiber fine powder to be mixed is desirably 5 phr to 100 phr. If the amount is less than 5 phr, no effect on hydrophilicity can be obtained. On the other hand, if the amount is more than 100 phr, the physical properties are deteriorated.

[0008]

The mixed natural collagen fiber fine powder acts to absorb the water on the printing plate, so that the blanket sheet can have appropriate hydrophilicity.

[0009]

Since the blanket sheet according to the present invention has hydrophilicity, a good blanket which does not impair the dot reproducibility can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a blanket sheet according to the present invention will be described below. In the examples, natural collagen fiber fine powder having an average particle diameter of 20 μm was used, and the mixing amount was changed. Example 1 having a mixing amount of 3 phr
5 phr for Example 2, 10 phr for Example 3, 50 phr for Example 4, 90 phr for Example 5, 100 phr for Example 6, 110 phr
The sample with r was designated as Example 7, and the sample with 120 phr was designated as Example 8. On the other hand, a conventional blanket sheet in which the natural collagen fiber fine powder was not mixed was used as a comparative example. The blanket sheet prepared in this manner was mounted on an offset printing machine (manufactured by Komori Printing Machine Co., Ltd., Lithrone 26). The ink used was Mark V New (red) manufactured by Toyo Ink Co., Ltd., and the printing paper was art paper (70.5 kg). Pressure 0.10mm, printing pressure 0.
A dot image was printed under the condition of 15 mm, and the dot enlargement ratio was measured.

The dot enlargement rate was determined by using cromarin for the test chart, setting the solid density to 1.40 using a COSER 61J densitometer, and setting the 50% halftone portion of 150 lines / inch to COSER 61J.
It was measured with a densitometer. The smaller the measured value is, the smaller the dot enlargement is, which means that the dot reproducibility is excellent.

[0012]

[Table 1]

As is clear from the above results, when 5 phr or more of natural collagen fiber fine powder is mixed, the dot enlargement ratio decreases. Therefore, in order to maintain excellent halftone dot reproducibility, it is desirable to mix 5 phr or more of natural collagen fiber fine powder.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a printing unit in an offset printing press.

[Explanation of symbols]

 Reference Signs List 1 plate cylinder 2 inking device 3 water supply device 4 blanket cylinder 5 impression cylinder

Claims (2)

(57) [Claims] 1. An offset printing method comprising: a blanket sheet having at least one layer of a support and a surface layer serving as a printing surface, wherein the surface layer is formed of an oil-resistant rubber mixed with a natural collagen fiber fine powder. Blanket sheet. 2. The size of the natural collagen fiber fine powder is 5
μ to 100 μ and the amount of contamination is 5 phr to 100 phr.
2. The blanket sheet for offset printing according to claim 1, wherein: