JPS6044652B2 - Net gravure plate making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes a carhon tissue and a halftone positive for lithography or letterpress printing to give differences in the size of halftone dots and the depth of each halftone dot through a simple process, thereby creating a pattern. The present invention relates to a net gravure plate making method that can easily and satisfactorily reproduce density gradations.

The present invention adjusts the density gradation of a picture by the size of halftone dots.
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p-mouth/reco Z-shoulder field positive (The same applies to letterpress net positives, so below I will describe lithographic net positives, but letterpress net positives are also included), and the size of the halftone dots is almost the same. A gravure white line screen with a desired number of lines in which approximate continuous tone positives and white lines intersect in a lattice pattern, expressing the density gradation of an image by approximately continuous changes in density that are blurred to an unrecognizable degree. The density gradation of the image is reproduced by selecting an appropriate number of dots and printing them in close contact with the sensitized carbon material, thereby giving the gravure printing cylinder the size of halftone dots and the depth of each halftone dot. This is a net gravure plate making method that can improve the quality.

To explain the present invention more specifically, first, a white line screen for gravure vias with a desired number of lines is closely printed on a sensitized carbon sheet to prevent ink from flowing from the middle part to the dark part of the gravure plate. Then, a lithographic or letterpress net positive is adhered to the carbon tissue on which this gravure white line screen has been printed, to express the density gradation of the image by varying the size of the halftone dots. By printing, the size of the halftone dots can be changed, and then the size of the halftone dots is blurred to the extent that the size of the halftone dots can hardly be distinguished on the same carbon tissue. 5. Approximate continuous tone positive that expresses the density gradation of the pattern through continuous density changes is closely printed to produce changes in halftone dot depth,
Finally, the carpon stock printed in this way is transferred to an ordinary gravure printing cylinder, developed and eroded to make a plate, and the pattern is created by changing the size of the halftone dots and the depth of each halftone dot. There is a net gravure plate making method that reproduces density gradation. To explain each step of the present invention in detail, the first step is to closely print a gravure white line screen D having a desired number of lines onto a sensitized carpon tissue E (FIG. 2).

Commercially available carpon chips E may be used, and sensitization can be obtained by soaking the carpon chips in a potassium dichromate solution and drying them.

The printing is carried out by placing the white line screen D for gravure and the carpon chisel E in a printing frame in close contact with each other in a vacuum, and using an arc lamp, mercury lamp, xenon lamp, metal halide lamp, etc. as a light source.

In addition to the commonly used carpon resists E, photoresists made from known photosensitive resins can also be used.

This fourth process of printing the white line screen D for gravure is performed when using a halftone positive with continuous halftone dots from the dark part to the middle part, such as halftone positive A for planography or letterpress printing. A screen is formed at that location to prevent ink from flowing. Next, the second step is to flatten the carpon chip E onto which the white line screen D for gravure has been printed in the first step. There is a process of contact-printing a mesh positif for printing plates or letterpress printing (Figure 3).

The halftone positive A to be printed at this time expresses the density gradation of the picture by the size of the halftone dots, and the printing may be carried out in the same manner as in the first step. In other words, this second step is net positive baking. ” is for forming halftone dots and changing the size of the halftone dots.Next, the third step is to create an approximately continuous gradation on the carpon tissue E printed with halftone positive in the second step. Z (Fig. 4) is the process of closely baking the positive C.

In this third step, not only the size of each halftone dot changes, but also the depth changes by printing a positive C image having approximately continuous gradation.

In other words, halftone positive plate making is performed by combining the size of the halftone dots and the change in plate depth. The following method is available for producing this approximate continuous tone positive C.

In this method, a lithographic printing net positive A prepared by a conventional method is closely printed on a photosensitive film to form a net positive 1, and this net negative 1 is transferred to a photosensitive material 2 as shown in FIG.
An approximation in which a blurring spacer 3 such as a diffusion sheet is inserted between the two and printed in close contact, and the size of the halftone dots is almost indistinguishable due to the effect of the spacer 3 such as a diffusion sheet. Create continuous tone positive C.

The subsequent fourth step is the 11th second, 93rd, and 3rd steps described above.
There is a step in which the printed carpon tissue is transferred to a gravure cylinder, developed and etched to obtain a net gravure plate.

In this fourth step, it is sufficient to obtain a plate in the same manner as in the conventional method, and the printed carton film is attached and transferred to a gravure cylinder prepared in advance while adding moisture.

After transferring, soak in warm water to dissolve unhardened gelatin.
Develop and dry. Here, the size and thickness of the halftone dots of the gelatin register are made depending on the density gradation of the halftone positive. Next, the cylinder surface is corroded through the gelatin film with an etchant mainly composed of ferric chloride solution, and after the corrosion has reached a predetermined depth, chromium plating is sometimes performed to increase printing durability.

As described above, after printing a white line screen for gravure, the present invention expresses the density gradation of the image by the size of the halftone dots by printing a halftone positive screen. By printing a tone positive and giving a change in depth to each halftone dot, it is expressed by a combination of the size of the halftone dot and the change in depth.
It is possible to easily obtain a half-tone gravure plate with rich image density gradations and excellent reproducibility.

As the net positive used in the present invention, a net positive for planography and letterpress printing can be used.

For this purpose, for example, if a lithographic halftone positive film taken directly from the original through a contact screen is used, the process is simpler and faster than the process of obtaining halftone positives using the conventional halftone gravure method using two positives. It is also possible to reduce material costs and manufacturing costs. Furthermore, according to the present invention, a lithographic or letterpress net positive A1 used for printing a carpon
and approximate continuous tone positive C shift can be easily produced individually and corrected appropriately each time.
A well-corrected positive can always be used for printing the carpon stock E, and therefore a net gravure plate can be made to obtain a net gravure print in which the density gradation of the image is reproduced satisfactorily. It is possible.

[Brief explanation of the drawing]

FIG. 1 illustrates a method of obtaining an approximate continuous tone positive with close contact printing by exposing it to a light source in the direction of the arrow using a diffusion sheet as a spacer based on a halftone positive for lithographic printing in the present invention. 2 is a sectional view illustrating the state of contact baking in the first step, and FIG. 3 is a sectional view illustrating the state of contact baking in the second step.
FIG. 4 is a sectional view illustrating the state of contact printing in the third step, and both are views exposed to the printing light in the direction of the arrow. A: Net positive for planography or letterpress, C...
...Approximate continuous tone positive, D...White line screen for gravure, E...Carpon chitshi,
1... Net positive for lithography, 2... Carpon stitch, 3... Spacer like diffusion sheet.

Claims (1)

[Claims] 1. In the production of a net gravure plate using a net positive for lithography or letterpress printing, the first step is to closely print a white line screen for gravure with a desired number of lines onto a sensitized carbon tissue, and then the white line screen for gravure is A step of closely printing a net positive for planography or letterpress printing on the baked carbon tissue, and further inverting the net positive for planography or letterpress printing onto a photosensitive film to create a net negative, and obscuring the net negative. a step of closely printing an approximate continuous tone positive created by printing onto another photosensitive film through a spacer, and transferring the carbon tissue printed by these steps to a gravure cylinder; A net gravure plate making method consisting of the steps of printing, developing, and etching.