JP4154933B2 - Printing method and printing machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a printing method of a pattern in which a gradation pattern and a gradation-free pattern (solid pattern) coexist, and can be suitably used to maintain a stable expression and a coating amount particularly in continuous printing of a long lot. is there.
[0002]
[Prior art]
Generally, gravure printing is not only widely used as the most excellent method for expressing gradation patterns, but also a method for imparting a function of concealment or adhesion because a high coating amount can be easily obtained. As a prize.
[0003]
However, this method uses a doctor to scrape excess ink on the plate surface, so that wear of the plate is unavoidable due to friction between the plate surface and the doctor, and there is a limit to the stability in continuous printing of long lots. It was. One of the limitations of stability is a decrease in the coating amount, and there is a problem that the performance is deteriorated particularly in a solid pattern portion for the purpose of providing concealability and adhesiveness. Another limitation of stability is a phenomenon called “fogging” in which ink remains in the non-image area due to uneven wear of the doctor, which is a typical problem as a defect in printed expression. This phenomenon is particularly noticeable when water-based ink is used, and has been a problem in switching from organic solvent ink to environmentally friendly water-based ink.
[0004]
A typical example of when a gradation pattern and a solid pattern coexist is to print the gradation pattern on a transparent film, to make the gradation pattern stand out, and to attach it to a film that protects the contents It is printing of a film for food packaging which also prints a white solid pattern having concealability and adhesiveness. In such a case, it is empirically that the fog and the change in the coating amount in continuous printing become a problem in the solid pattern portion where the pattern area is large and the coating amount is large, especially containing a lot of hard pigments such as titanium oxide. In aqueous inks, it is known that the above phenomenon appears at an early stage.
[0005]
By the way, flexographic printing, which is one of the letterpress printing methods, is a method that does not cause fogging in principle, and ink is once transferred from a solid intaglio plate called anilox roll to a flexographic plate with a patterned pattern. After that, it will be transferred from the flexographic plate to the original fabric. Although this method is effective in preventing fogging, since it is a relief printing method, there is a limit to gradation expression, and since it is difficult to express with fine and light and sharp, it is difficult to use in Japan. It was.
[0006]
Moreover, although there is little in pattern printing, there is a system called gravure offset as a coating system mainly used for the entire surface coating. In this method, the ink is once transferred from the gravure plate to a smooth roll called an offset roll, and then transferred from the offset roll to the original fabric. The coating amount can be changed depending on the peripheral speed difference between the gravure plate and the offset roll.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to stabilize the printing of a long lot by preventing fluctuations in coating amount and occurrence of fog during continuous printing.
[0008]
[Means for Solving the Problems]
In order to achieve the above object in the present invention, first, the invention of claim 1 is a printing method characterized in that a gradation pattern is performed by gravure printing and a solid pattern is performed by flexographic printing.
[0010]
In the invention of claim 3, the printing method according to claim 1 or 2 is characterized in that water-based ink is used as the printing ink.
[0011]
The invention of claim 4 is a printing machine comprising gravure printing means for performing gravure printing and flexographic printing means for performing flexographic printing,
The printing machine is characterized in that the gradation pattern is printed by gravure printing and the solid pattern is printed by flexographic printing.
[0013]
The invention according to claim 6 is the printing machine according to claim 4 or 5, wherein water-based ink is used as the printing ink.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0015]
FIG. 1 is an outline of the configuration of a printing press, and FIG. 2 is an example of the configuration of a flexographic printing unit.
[0016]
The substrate to be printed (original fabric) is supplied from the original fabric unwinding 1, and is wound around the printed material winding 6 after the printing in the gravure printing unit and the flexographic printing unit is completed.
[0017]
The first unit of the gravure printing unit is composed of the ink pan 2, the gravure plate 11, the doctor 7, and the impression cylinder 15. The original fabric is dried by the dryer 20 after completion of the ink transfer and enters the next printing unit. The configuration of the next printing unit is the same as that of the first unit, and printing with the pattern plate is repeated for each color as many times as necessary. Printing with process colors is generally four colors including black in addition to the three primary colors. Here, an example of three colors is shown.
[0018]
The original fabric that has completed printing in the gravure printing unit enters the next flexographic printing unit. The flexographic printing unit is composed of an ink pan 5, an anilox roll 14, a doctor 10, a flexographic plate 18, and an impression cylinder 19. The original fabric is dried by a dryer 23 after completion of ink transfer and wound by a printed material winding 6. .
[0019]
At this time, the peripheral speed of the flexographic plate 18 is basically the same as that of the gravure plates 11, 12, and 13, and the flexographic plate 18 is printed in register with the pattern printed on the gravure plate.
[0020]
The peripheral speed of the anilox roll 14 is normally set to a speed different from the peripheral speed of the flexographic plate 18. FIG. 2 shows a configuration example when the anilox roll 14 is driven from the same drive source as the flexographic plate 18. The initial setting of the peripheral speed of the anilox roll 14 is performed by setting a specific value in accordance with the target value of the coating surface and the coating amount. When the anilox roll 14 is worn during continuous printing, the rotational speed of the anilox roll 14, that is, the circumferential speed is set by the transmission in accordance with the printing length (m) set in advance so as to keep the ink transfer amount constant. To change. Even if the drive system is not the same drive source, each unit independent drive sectional drive system also changes the rotational speed, that is, the peripheral speed of the anilox roll 14 corresponding to the preset printing length (m). It is the same.
[0021]
【Example】
Printing by the method of the present invention and printing by only gravure printing were performed, and the change in the degree of fogging and the solid coating amount was examined.
[0022]
As an example, continuous printing was performed by using a red and black indigo plate having an area ratio of 5 to 30% in the gravure printing unit and each color ink and using a white plate having an area ratio of 96% in the flexographic printing unit. In addition, as a comparative example, continuous printing was performed by using a white plate having the same specifications and using only a white method (gravure printing).
[0023]
In the comparative example, white fog was clearly generated in continuous printing of 50,000 m, and the amount of white ink applied was reduced to 80% of the initial value. In the method of the example, continuous printing at 100,000 m was performed under the condition that the peripheral speed of the anilox roll was increased by 2% every 10,000 m, but there was no white fog, and the amount of white ink applied was 3% of the initial value. The fluctuation was within. Further, continuous printing was performed up to 200,000 m by the method of the example, but the results were the same.
[0024]
As a result, the printing press of the present invention uses a flexographic printing method to prevent fogging on the solid pattern portion, and uses a gravure printing method excellent in gradation expression on the pattern portion, so that even a long lot continuous printing is stable. In addition, it is possible to maintain stable concealment and adhesiveness by changing the rotation speed of the anilox roll in response to a decrease in the coating amount in the flexographic printing part. It was proved to be.
This effect is particularly remarkable when water-based ink is used as printing ink.
[0025]
【The invention's effect】
According to the present invention, it is possible to perform printing with less fogging and less change in coating amount in continuous printing. As a result, the frequency of exchanging plates and doctors is reduced, and the productivity is improved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a configuration example of a printing machine according to the present invention.
FIG. 2 is an explanatory diagram of a configuration example of a flexographic printing unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Original roll unwinding 2, 3, 4, 5 ... Ink pan 6 ... Print winding 7, 8, 9, 10 ... Doctor 11, 12, 13 ... Gravure plate 14 ... Anilox roll 15, 16, 17, 19 ... Pressure Body 18 ... Flexo plate 20, 21, 22, 23 ... Dryer

Claims (4)

A printing method characterized by performing a gradation pattern by gravure printing and performing a solid pattern by flexographic printing.   The printing method according to claim 1, wherein water-based ink is used as the printing ink. A printing machine comprising gravure printing means for performing gravure printing and flexographic printing means for performing flexographic printing,
A printing machine characterized by performing gravure printing by gravure printing and solid printing by flexographic printing.   The printing machine according to claim 3, wherein water-based ink is used as the printing ink.

Images