JPH03281249A - Prevention of offset in offset printing - Google Patents

Abstract

PURPOSE:To prevent the occurrence of offset in a simple manner without using special ink and requiring any manual operation by spraying ozone against the printed surface of a printed paper to accelerate the drying of ink. CONSTITUTION:An offset printing machine 1 consists of four printing units 2 and a paper supply part 3 and a paper removing part 4 are provided at both ends thereof. A spray pipe 14 is provided extending from a paper removing cylinder 12 to a pallet 7 along the passageway through which to convey printed matter 5' in order to direct a spray against the moving printed matter 5' from above. An ozone environment producing device 13 is provided with an ozonizer 15, a transfer pipe 16 and an air blower 17 connected to an intermediate part of the transfer pipe 16. The ozone produced by the ozonizer 15 is sent through the transfer pipe 16 to the air blower 17 to be mixed with air and such mixture is thereafter sent through the transfer pipe 16 to the spray pipe 14, whereby the mixture is sprayed against the printed surface of the printed matter 5'. In this way the oxidative polymerization of the ink adhered to the printed matter 5' is accelerated to harden the ink momentarily and, therefore, no offset occurs, even when a large number of sheets of the printed matter 5' are laid one upon another immediately after printing.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for preventing ink set-off when a large number of sheets of paper printed by offset printing are stacked.

(Prior art) Sheet-fed offset printing machines usually have a paper feed section and a paper ejection section at both ends of a plurality of printing units arranged in a line for each color, and a large number of sheets are stacked in the paper feed section. The structure is such that one sheet of paper is sequentially guided to each printing unit, where each color is printed, and then the printed matter is sent to a paper discharge section where a large number of sheets are stacked.

By the way, when a large number of printed materials printed by an offset printing machine such as the one described above are stacked at the paper output section, a phenomenon (blocking) occurs in which the weight of the printed material causes the ink on the surface of the printed material to transfer to the back surface of another printed material that comes into contact with it. was.

In order to deal with this phenomenon, conventionally, the height of the printed matter was 10 to 50 cx (paper 200 to 3
Each time a board is stacked (approximately 00 sheets), a board is inserted between the printed materials, and a support rod is used to support the space between the two bottom boards inserted so that the weight of the two printed materials is not applied to the printed material below. I was doing it.

Furthermore, since it is not possible to completely prevent set-off by just removing the boards, it is also common practice to create a physical space between each print by sprinkling a large amount of powder onto the printed surface of the print. Ta.

Other methods have also been proposed that use ultraviolet curing ink and perform ultraviolet irradiation.

(Problem to be Solved by the Invention) When a conventional boarding method is used to prevent ink set-off, at the paper discharge section of an offset printing machine, each time a certain number of printed materials are piled up, manual intervention is required. In addition to the work of inserting plates and support rods, it is also necessary to manually reload the printed matter after the ink on the printed surface has hardened after a certain period of time (approximately 5 to 72 hours) while the printed matter is stacked. It is necessary to remove the board.

In addition, the method of scattering powder on the printing surface of printed matter,
Since the ink and powder mix together and the surface of the printed matter becomes rough, there is a problem that the printed surface loses its luster when surface processing such as resin coating or film application is performed on the printed surface in a subsequent process.

On the other hand, using UV-curable ink eliminates the need for board removal and powder scattering as described above, but in this case, the ink itself is expensive and it is necessary to install UV irradiation equipment, etc. There is a problem in that it is expensive and high costs are unavoidable.

The present invention was made to solve the above-mentioned problems, and it is possible to eliminate set-off in offset printing by a simple method without using special ink, and without requiring any manual labor. The purpose is to obtain a method that can prevent this.

(Means for Solving the Problems) The present invention is based on the finding that ink can be dried in a short time by promoting oxidative polymerization of ink with ozone. That is, the method for preventing set-off in offset printing according to the present invention is characterized in that ozone is sprayed onto the printed surface of the printed paper to accelerate the drying of the ink.

(Function) When ozone is sprayed onto the printing surface of a printed material printed by offset printing just before it reaches the paper discharge section, oxidative polymerization of the ink on the printing surface is promoted and the printing material dries instantly.

Therefore, even if printed materials are piled up immediately after printing, set-off will not occur.

(Example) Examples will be described below based on the drawings.

FIG. 1 is an overall structural diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of essential parts of the apparatus.

In this embodiment, the offset printing press 1 is constituted by four printing units 2 arranged in a negative row, and a paper feed section 3 and a paper discharge section 4 are disposed at both ends of the four printing units 2, respectively. A large number of sheets of paper 5 are stacked in the paper feed section 3, and are guided from above to the printing unit 2 one by one via the feeder board 6, and in each printing unit 2, the paper 5 is sequentially processed with black, eye, red, and black marks. After each color is printed, the sheets are sent to a paper discharge section 4 and stacked on a pallet 7.

The plate cylinder 8 provided in each printing unit 2 includes the following:
Ink and fountain solution are supplied. The ink supplied to the surface of the plate cylinder 8 is once transferred to the surface of the blanket cylinder 9 in contact with the plate cylinder 8, and then transferred to the paper 5 passing between the blanket cylinder 9 and the impression cylinder 10. Printing is done. In the figure, reference numeral 11 indicates an intermediate cylinder, which is disposed between the feeder board 6 and the impression cylinder 10 closest to the paper feed section 3, and between the impression cylinders 10 of each printing unit 2.

A paper discharge cylinder 12 is provided in contact with the impression cylinder 10 of the printing unit 2 closest to the paper discharge section 4, and the printed material 5' is discharged from the paper discharge cylinder 12 by a gripper chain (not shown). The sheets are transferred to the paper section 4 and sequentially stacked on a pallet 7'' arranged in the paper discharge section 4.

In the middle of the transport path of the printed matter 5' from the paper delivery cylinder 12 to the pallet 7, there is a spray pipe 14 located above the transported printed matter 5 and forming part of the ozone atmosphere creating device 13.
is installed. This ozone atmosphere creation device I3 is
It includes an ozone generator 15, a transfer pipe I6 connected to the ozone generator 15, and a blower 17 connected to the middle of the transfer pipe 16. And ozone generator 1
The ozone generated in step 5 is transferred to the blower 17 by a transfer pipe 16, where it is mixed with air, and then transferred to the pipe 14 by the transfer pipe 16, where it is sprayed onto the printed surface of the printed material 5. It will be done.

In this way, by spraying ozone onto the printed matter 5' stacked up after printing is completed, the oxidative polymerization of the ink adhering to the printed surface of the printed matter 5' is promoted, and the ink instantly hardens. I will do it. therefore,
Immediately after printing, there is no set-off even when a large number of 5" or more printed materials are stacked, so they can be stacked in a bar.

Note that using the ozone atmosphere creation device 13 of this example,
As a result of a bar stacking test using 38 g/h of ozone generated by the ozone generator 15, there was almost no tendency for set-off to be observed even when 2,000 sheets of printed matter were stacked in a bar, and the gloss of the printed matter was not impaired. It was confirmed that there was no such thing.

(Effects of the Invention) The present invention is configured as described above, and set-off of printed matter can be prevented by a simple method of spraying ozone onto the printed matter. In addition, this makes it possible to completely eliminate the complicated work that is conventionally done, such as board cutting.
Moreover, since there is no need to use expensive special ink,
Does not lead to high costs.

[Brief explanation of the drawing]

FIG. 1 is an overall structural diagram of an apparatus according to an embodiment of the present invention;
FIG. 2 is a perspective view of the main parts of the device. 1 Offset printing machine, 5' ・Printed matter, 13 Ozone atmosphere creation device, 14 Spraying tube.

Claims (1)

[Claims] (1) A method for preventing set-off in offset printing, characterized by spraying ozone onto the printed surface of printed paper to accelerate ink drying.