JPS6143708B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a master plate for net gravure plate making. This invention relates to a method of creating an original plate for net gravure plate making, which is expressed by the depth and depth of cells.

In the conventional net gravure plate making method, when using a photoresist such as carbon tissue or photosensitive resin, a gravure net positive is used.
The depth of the cells on the plate is approximately constant, and the density of the image is expressed only by the difference in the size of the halftone dots.The other method uses two positives, a halftone positive for gravure and a continuous tone positive, and the halftone The so-called 2.
There is a positive sheet method.

A method in which the depth of the cell of the plate is kept approximately constant and the shading of the image is expressed only by the size of the halftone dots has the drawback of insufficient tone reproduction. On the other hand, with a method that combines the size of halftone dots and the depth of cells on the plate, even if depth errors occur due to variations in corrosion work, because the dots are large and small, variations in tone are less likely to occur, and It has the advantage of being easier to reproduce, but
In the above-mentioned so-called two-sheet positive method, a gravure net positive is printed on the carbon tissue to give halftone changes, then a continuous tone positive is printed to give a change in cell depth, and the plate is made by performing transfer, development, and corrosion. It requires quite advanced technology to laminate halftone positives and continuous tone positives in perfect register, and to print them onto carbon tissue.

The purpose of the present invention is to eliminate the drawbacks of the conventional two-sheet positive method, and instead of performing printing work using two types of positives on a carbon film, which is difficult to manage, To provide a method for creating a manuscript for net gravure plate making, which makes it possible to easily perform the printing process on carbon tissue by creating density changes corresponding to the size of halftone dots and the depth and depth of cells on a plate making film that is easy to manage. .

That is, the present invention provides a method for adjusting the density of the original by copying the original to create a continuous-tone negative and a halftone negative of desired dimensions, and then printing these two types of negatives in close contact with an unsensitized material and developing them. The gist of this paper is a method for creating a master plate for halftone gravure plate making that has corresponding halftone dot sizes and density changes.

Hereinafter, the above-mentioned present invention will be explained in detail.
First, explanation will be given with reference to the process diagram shown in FIG. To copy the original and create continuous tone negatives and halftone negatives of the desired dimensions, the first step is to create continuous tone negative 2 from original 1 using a prepress camera or electronic plate making machine in the usual manner. do. As a second step, a gravure net positive 3 is created from the continuous tone negative 2 by close contact hatching exposure using a gravure contact screen.Next, as a third step, a gravure net positive 3 is bonded. A net negative 4 is created by inversion exposure. Using the continuous tone negative 2 and halftone negative 4 thus produced, as a fourth step, a halftone gravure plate-making manuscript plate 5 having both the size of halftone dots and density change can be produced. In this fourth step constituting the present invention, the continuous tone negative 2
A gravure net positive 4 is pasted together with the registration of the net negative 4, printed on an unexposed continuous tone film using the contact exposure method, and developed to have halftone dot size and density changes corresponding to the shading of the image, that is, An original plate 5 for net gravure plate making is obtained. In the above, it is preferable to arrange the net negative on the side that is in close contact with the unexposed continuous tone film. This is to ensure that the sharpness of the image is not impaired.

A net gravure plate can be obtained by printing the document 5 thus obtained on a carbon tissue, transferring it to a gravure cylinder, and etching it. This manufacturing process can be performed in the same way as gravure plate making using a normal carbon tissue.

Furthermore, in the above process, changes in size and density of halftone dots (depth and shallowness of cells) corresponding to the shading of the image on the original document 1 are shown and explained in FIG. 2. First, FIG. show. b shows the density change of continuous tone negative 2. c indicates the size of the halftone dots on the positive halftone screen 3, and d indicates the size of the halftone dots on the negative halftone dot 4. Reference numeral e indicates a halftone gravure prepress original 5, which has both the size of halftone dots and a change in density. f is printing on carbon tissue using original plate 5;
FIG. 3 is a cross-sectional view showing the surface condition of a gravure cylinder 6 obtained through transfer, development, and corrosion. g is a cross-sectional view showing a printed matter produced by gravure printing by supplying ink to the cylinder 6, where 7 indicates ink and 8 indicates paper.

As is clear from the above description, the present invention provides an extremely excellent method for producing a halftone gravure plate-making original plate having both the size of halftone dots and density variation. According to the present invention, there is an excellent advantage that registration accuracy can be maintained extremely easily since the original plate is created using a contact printing method. By using the original plate obtained by the method of the invention, there is no need to perform the synthesis work on a carbon tissue as in the conventional method.
Since the size of halftone dots and changes in density can be recorded in advance on the plate-making film, which is easy to control in the process, work instability during carbon printing can be reduced and efficiency can be improved.

[Brief explanation of the drawing]

Figure 1 is a process diagram for explaining the present invention, Figure 2 is a process diagram for explaining the present invention.
The figure is an explanatory diagram of the size of halftone dots and changes in density (depth and shallowness of cells) corresponding to the shading of the image of a document in halftone gravure plate making including the method of the present invention. 1...Original, 2...Continuous tone negative, 3...
Net positive, 4... Net negative, 5... Net gravure plate-making manuscript, 6... Gravure cylinder, 7...
...Ink, 8...Paper.

Claims (1)

[Claims] 1. A method of producing halftone dots corresponding to the shading of the original, which is characterized by copying an original, creating a continuous tone negative and a halftone negative of the desired size, and then printing these two types of negatives in close contact with an unsensitized material and developing them. A method for creating an original plate for net gravure plate making that has both size and density changes.