JP2001113676A - Method for flexographic printing for rainbow printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for flexographic printing for rainbow printing even by a flexographic printing type not adapted to a rainbow printing due to a fault of mixing of inks by transmitting along an anilox roller to widely utilize a forgery preventing technique using the rainbow print on each type of printing medium. SOLUTION: The method for flexographic printing for rainbow printing in a rainbow printer having inks of different hues in a plurality of ink fountains and anilox rollers set to change densities of ink transfer amounts at respective ink fountains, comprises the steps of transferring the inks of the respective fountains to the rollers, then transferring the inks mixed from the rollers to one plate cylinder, and then printing on a printing sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexographic printing method capable of performing rainbow printing on various printing media by using flexographic printing.

[0002]

2. Description of the Related Art Conventionally, as one of the printing techniques, there is a method in which printing paper is printed in a plurality of colors, and a rainbow color is expressed by blurring between adjacent colors. The printing expressed in a rainbow color is called rainbow printing, and the printed matter subjected to the rainbow printing is often used for the purpose of preventing forgery because it is difficult to reproduce. In this rainbow printing method, since a weir is provided in the ink fountain of the printing machine, it is necessary to provide inks of different hues in a section parted by the weir without being mixed with ink. Not suitable for use in offset printing presses.

Therefore, in a printing method such as flexographic printing, in which the ink is low in viscosity and the ink is merely provided with a weir inside the ink fountain, the ink is likely to be mixed along the anilox roll. However, it is very difficult to produce a printed material subjected to rainbow printing because of discoloration. Also, if physical obstacles are provided near the surface of the anilox roll to prevent the ink from being mixed along the anilox roll, the notches on the surface of the anilox roll will be worn away. There is a problem that proper maintenance of the anilox roll cannot be performed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preventing forgery using rainbow printing on various printing media so that inks can be transferred along an anilox roll. Provided is a flexographic printing method capable of rainbow printing, which can use a rainbow printing method even in a flexographic printing method that is not suitable for rainbow printing because of problems such as mixing.

[0005]

A flexographic printing method capable of performing rainbow printing according to the present invention is a flexographic printing method capable of performing rainbow printing, wherein a plurality of ink fountains are provided with inks having different hues, respectively. Anilox rolls set so that the density of the ink transfer amount changes for each ink fountain are provided, and the ink for each ink fountain is transferred to each anilox roll, and then each anilox roll is placed on one plate cylinder. And printing on printing paper after the ink is transferred in a mixed state.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a printing unit using the flexographic printing method of the present invention, and FIG.
FIG. 3 is a perspective view of a printing unit using the flexographic printing method of the present invention, and FIG. 3 is a perspective view of two kinds of anilox rolls set so that the density of the ink transfer amount changes.

Hereinafter, an embodiment of a flexographic printing method capable of rainbow printing according to the present invention will be described. As shown in FIG. 1, in the method of the present invention, a plurality of ink fountains 1a and 1b are provided, and inks 2a and 2b having different hues are put into these ink fountains 1a and 1b. Each of the ink fountains 1a and 1b is separately provided with a fountain roll 3a and 3b, respectively, and each of the inks 2a and 2b placed in each of the ink fountains 1a and 1b.
Is temporarily transferred to the fountain rolls 3a and 3b. The fountain rolls 3a, 3b are provided with anilox rolls 4a, 4b, respectively, which are set so that the density of the ink transfer amount is changed, and the inks 2a, 2b having different hues are supplied to the fountain rolls 3a, 3b, respectively. 3b is transferred to each anilox roll 4a, 4b.

The anilox rolls 4a and 4b have a large number of small holes called cells formed on the surface of a cylinder plated and coated with chromium or ceramics, and are transferred by putting ink into the cells. Is transferred to the surface of the plate cylinder 5. Each of the inks 2a, 2 transferred to the anilox rolls 4a, 4b is provided on each anilox roll 4a, 4b.
One commonly used plate cylinder 5 for transferring b is provided. Therefore, for the plate cylinder 5, the inks 2 having different hues from the respective anilox rolls 4a and 4b.
a and 2b are transferred.

Further, each of the anilox rolls 4a, 4
b is provided with doctor blades 9a and 9b for scraping off the ink that has excessively adhered to the surfaces of the anilox rolls 4a and 4b, and adjusting the ink so that a stable amount of ink is always supplied to the plate cylinder 5. Instead of the doctor blades 9a and 9b, a rubber roll called a doctor roll may be provided to adjust the ink that has excessively adhered to the surfaces of the anilox rolls 4a and 4b. Also,
In the case of the two-roll system described above, the doctor blade 9
a, 9b, doctor roll, etc.
Since the inks on the surfaces of the anilox rolls 4a and 4b are adjusted by a and 3b, they need not always be provided.

A rubber plate 6 is attached to the plate cylinder 5, and each ink 2a, 2b is transferred onto the rubber plate 6. An impression cylinder 7 for pressing the printing paper 8 against the rubber plate 6 of the plate cylinder 5 during printing is provided near the outer periphery of the plate cylinder 5.
And prints on the printing paper 8 by sandwiching the printing paper 8 while rotating the plate cylinder 5 and the impression cylinder 7.

As the flexographic printing method, a doctor blade method, a two-roll method, and the like are known technologies. As described above, the fountain rolls 3a, 3b are provided between the anilox rolls 4a, 4b and the ink fountains 1a, 1b.
The anilox rolls 4a, 4b are directly immersed in the inks 2a, 2b of the ink fountains 1a, 1b without providing the fountain rolls 3a, 3b.
A doctor blade system in which the doctor blades 9a and 9b scrape off excessive ink on the surfaces of the anilox rolls 4a and 4b and adjust so that a stable amount of ink is always supplied to the plate cylinder 5 may be used in the present invention. . In any case, in the present invention, anilox rolls 4a and 4b for separately supplying ink to one plate cylinder 5 are provided, and inks 2a and 2b having different hues are applied to the anilox rolls 4a and 4b, respectively. It is provided with a plurality of ink fountains 1a and 1b containing inks 2a and 2b having different hues provided for supply.

Each anilox roll 4a, 4b has
As shown in FIGS. 3A and 3B, the surfaces of the anilox rolls 4a and 4b are adjusted so that the density of the ink transfer amount changes. In the case of the two-roll system, the density of the ink transfer amount of the anilox rolls 4a and 4b can be adjusted by the number of engraving lines, the cell depth and shape of the anilox rolls 4a and 4b, and the fountain rolls 3a and 3b.
The ink supply amount is controlled by the strength of the nip pressure between the ink and the anilox rolls 4a and 4b. Then, the anilox rolls 4a and 4b are adjusted between the anilox rolls 4a and 4b and the plate cylinder 5 so as to transfer to the one commonly used plate cylinder 5 with a different density of the ink transfer amount. Have been. The concentration of the ink transfer amount is adjusted, for example, by providing a small hole called a cell 10 in the one anilox roll 4a shown in FIG. Further, the other anilox roll 4b shown in FIG.
Contrary to the hole of the cell 10a, the hole of the cell 10 is provided gradually smaller from the right side to the left side.

The cells 10 of the anilox rolls 4a and 4b
Because the smaller the cell 10 is provided, the smaller the amount of ink supplied from the fountain rolls 3a, 3b to the anilox rolls 4a, 4b depends on the shape and volume of the hole.
Therefore, the density of the ink transfer amount changes on the surface of each anilox roll 4a, 4b, and as a result, each of the anilox rolls 4a, 4b uses a common one.
When the ink is transferred to one of the plate cylinders 5, the ink can be transferred in a state where the density of the ink transfer amount is changed in the ink supply to the rubber plate 6 of the plate cylinder 5.

Moreover, each anilox roll 4a,
In the case 4b, the anilox rolls 4a, 4b are provided on the rubber plate 6 of the plate cylinder 5 in such a manner that the portions where the density change of the ink transfer amount of the anilox roll 4a is high and the portions where the density changes are low are reversed. When the inks 2a and 2b having different hues are transferred from the rubber plate 6 of the plate cylinder 5, the inks 2a and 2b having different hues are mixed at an appropriate concentration on the rubber plate 6 of the plate cylinder 5, and are transferred onto the rubber plate 6 of the plate cylinder 5. An area having an intermediate color of two different hue inks can be provided.

Then, on the rubber plate 6 of one plate cylinder 5, two inks 2a and 2b having different hues transferred from the respective anilox rolls 4a and 4b are mixed to form a region having an intermediate color. Then, printing is performed on the printing paper 8 by sandwiching the printing paper 8 while rotating the plate cylinder 5 and the impression cylinder 7. The printed printing paper 8 is mixed with the inks 2a and 2b having different hues of the plate cylinder 5 to transfer the ink of the area having the intermediate color to the area of the printing paper 8,
It is possible to perform a display in which the colors of two adjacent hues having different hues 2a and 2b are blurred like a rainbow color.

[0016]

As described above, according to the flexographic printing method capable of rainbow printing of the present invention, even if the rainbow printing method is used, the inks may be mixed together through the anilox roll even if flexographic printing is used. Since there is no problem, it is possible to use the rainbow printing method that has been used only in offset printing in flexographic printing, so it is possible to widely use forgery prevention technology using rainbow printing for various printing media. became.

[0017]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a printing unit using a flexographic printing method of the present invention.

FIG. 2 is a perspective view of a printing unit using the flexographic printing method of the present invention.

FIG. 3 is a perspective view of two kinds of anilox rolls set so that the density of the ink transfer amount changes.

[Explanation of symbols]

 1a, 1b Ink fountain 2a, 2b Ink 3a, 3b Fountain roll 4a, 4b Anilox roll 5 Plate cylinder 6 Rubber plate 7 Impression cylinder 8 Printing paper 9a, 9b Doctor blade 10 cells

Claims (1)

[Claims] 1. A flexographic printing method capable of performing rainbow printing, wherein a plurality of ink fountains are provided with inks having different hues, and a setting is made such that the density of the ink transfer amount changes for each of the ink fountains. Each anilox roll is provided, and the ink for each ink fountain is transferred to each anilox roll. Then, the ink from each anilox roll is transferred to one plate cylinder in a mixed state, and then printed on printing paper. A flexographic printing method capable of rainbow printing.