JPS6357777B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gravure plate making method, and particularly to a gravure plate making method for making a gravure printing plate using a gravure original plate prepared from a net original plate for offset or letterpress printing.

There are various types of printing such as lithographic printing, letterpress printing, and gravure printing, each of which uses its own printing press and plate, but the current state of the printing industry is as follows:
In order to keep all printing presses running without interruption, if necessary, we may change what was originally planned to be offset printing or letterpress printing to gravure printing, and to do so, it is necessary to use a common original plate for each plate type. It is hoped that it will be used for

In the prior art, there is a net gravure plate making method (for example, see Japanese Patent Application Laid-Open No. 50-26603), which uses a screen original plate for planography or letterpress for gravure plate making.
This technique consists of the steps of printing a white line screen for gravure onto a carbon tissue, printing a screen original, and printing the screen original through a diffusion sheet. However, with this technology, it is natural that moiré may occur between the white line screen and the netting of the halftone plate, and in order to avoid this problem, it is necessary to spend a lot of effort in setting the screen angle and screen angle. This is especially complicated when printing in color.
Furthermore, when a single original plate is produced by pasting, it is necessary to precisely match the mesh angles of each pasted portion, which is an extremely difficult task. For this reason, in order to perform the net gravure plate making method,
From the beginning, we had no choice but to process the net gravure plate with the assumption that it would be net gravure plate making.

Other gravure platemaking methods include conventional gravure platemaking and platemaking using an electronic engraving machine, but the former requires a continuous tone manuscript, and the latter requires a continuous tone manuscript (e.g. , heliomanuscript using opal film) was necessary, and it was impossible to reuse lithography and letterpress printing plates.

For these reasons, a unique original plate is required for each plate type or one plate type that performs special plate making, making it impossible to share the original plate smoothly.

This invention focuses on the problems in the above-mentioned prior art when creating an original plate, and as a result of intensive research to improve the drawbacks, by effectively utilizing a scanner,
This invention was completed by discovering a method for creating original plates for conventional gravure and electronic engraving machines from original plates for planography and letterpress.

That is, the gravure plate making method of the present invention is characterized by converting a screen original plate for planography or letterpress into a continuous tone original plate using a scanner, and then making a plate using the continuous tone original plate as a gravure original plate.

The details of this invention will be explained below with reference to the drawings showing one embodiment.

In FIG. 1, numeral 1 is a screen printing plate for offset or letterpress printing. The halftone plate 1 is an original plate that expresses the shading of an image by the size of halftone dots. When performing gravure printing based on this screen original plate, it is necessary to convert the screen original plate 1 into a continuous tone original plate to obtain a gravure original plate, and this conversion is performed by the scanner 2. As the scanner 2, a commercially available scanner as shown in FIG. 2 can be used. That is, as shown in FIG. 2, the scanner 2 includes an original cylinder 3 and an original cylinder 4 that rotate synchronously, and also includes a scanning head 5, a computer unit 6, and an exposure head 7. The screen original plate 1 is set in the original cylinder 3 of this scanner 2, and the photosensitive film 8' is set in the original cylinder 4. The screen printing plate 1 is scanned with a light spot by a scanning head 5, and the transmitted light is guided to a phototube in the scanning head 5 to form a photocurrent. The strength of this photocurrent varies depending on the size of the halftone dots on the screen original 1, and this photocurrent is input to the computer unit 6. In the computer unit 6, the input photocurrent is modified to a current suitable for obtaining a continuous tone image, and the current is sent to the exposure head 7. This corrected current causes the exposure head 7 to emit light and expose the photosensitive film 8', so that a continuous tone image is expressed on the photosensitive film 8'. This exposed photosensitive film 8' is used as a gravure original plate 8 (FIG. 1). That is, as shown in FIG. 1, a halftone original plate 1 is converted into a continuous tone gravure original plate 8 by erasing halftone dots by a scanner.

Next, the gravure original plate 8 obtained in this way
A gravure printing plate is obtained using a conventional plate-making method. That is, as shown in FIG. 1, a gravure printing plate 12 is obtained by stacking a gravure original plate 8 and a carbon tissue 9, baking and developing them, and then etching the plate material 11 using the carbon tissue 9, or
Alternatively, the gravure printing plate 12 is obtained using the gravure original plate 8 using a gravure engraving machine 13 typified by a heliocrysiograph.

In addition, when converting the halftone plate 1 into a continuous tone gravure master plate 8, before applying it to the scanner 2, the halftone plate 1 is converted to a black and white halftone positive 14 made of non-stretchable paper or film, and then,
The black-and-white halftone positive 14 may be applied to the scanner 2 and the reflected light may be guided to a phototube in the scanning head to erase the halftone dots and obtain a continuous-tone gravure original plate 8.

In the gravure plate making method configured in this way, it is possible to easily convert a screen original plate for offset or letterpress into a continuous tone gravure original plate,
Therefore, the original version can be used in common for each version. Moreover, when making a gravure printing plate from a conventional offset master plate or letterpress master plate,
In contrast, the gravure printing method of this invention converts the screen printing plate into continuous tone using a special set of scanners, whereas it was necessary to use a screen printing plate with uniform angles of the flat screens used for each individual pattern and half tone part. Therefore, there is no need to align the screen angles of the screen original plates, making the screen making work extremely easy.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram showing the process of gravure plate making according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a scanner. 1... Net printing plate, 2... Scanner, 8... Gravure original plate, 9... Carbon stock, 11... Plate material, 12... Gravure printing plate, 13... Gravure engraving machine, 14... Black and white net positive .

Claims (1)

[Scope of Claims] 1. A gravure plate making method, which comprises converting a screen original plate for planography or letterpress into a continuous tone original plate using a scanner, and making a plate using the continuous tone original plate as a gravure original plate. 2. The gravure plate making method according to claim 1, wherein the plate making is performed by an electronic engraving machine. 3. The gravure plate making method according to claim 1, wherein the plate making is performed by a conventional gravure plate making method.