JPS63227340A - Plate making method - Google Patents

Abstract

PURPOSE:To make a printing plate having good printability without generating doctor stripe, by carving an image in the surface of a printing plate material by mechanical carving and subsequently applying an etching solution to the entire surface thereof to etch the same so as to obtain such a state that acute-angle parts are not present on at least the surfaces of the carved parts. CONSTITUTION:Copper plating is applied to the surface of a cylinder for gravure printing and, subsequently, an image is carved in the plated surface according to a usual method. Next, an etching solution is applied to the entire surface of the cylinder using a roller. As the etching solution, a ferric chloride solution is used and the temp. thereof is held to a range of 20-30 deg.C and etching is performed for 20-30 sec under a humidity condition of 40-60%. The finish point of etching is set to the point of time when acute-angle parts are removed from the carved parts. A state free from the acute-angle parts 2 means such a state that the diameter of the upper part of the protruding part 1 of each acute-angle part becomes 2-4mum and, when the diameter is 2mum or less, smoothness is insufficient and, when the diameter is 4mum or more, effect is exerted on an image or on the coating amount in the case of a solid plate. After etching is finished, the etching solution is immediately washed off and, subsequently, puff polishing is applied to the cylinder and chromium plating is applied to the entire surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is a method for producing an image by mechanical engraving such as a gravure plate.
This invention relates to a method for making a printing plate that forms an image.

(Prior art) As a plate-making method for forming one image by mechanical engraving, there is one.
The method used is to engrave the ℃ 1 design on a gravure cylinder whose surface is plated with copper using a Seiko engraving machine.

However, the surface engraved using this method has countless convex portions including acute angle portions.

When the applied ink is scratched with a doctor, doctor streaks are likely to occur in these convex portions, causing printing defects.

(Problem that the invention attempts to solve) The present invention solves the above-mentioned drawbacks of the prior art.

The present invention aims to provide a method for producing a printing plate that does not generate doctor's streaks and has good printability.

(Means for solving the problem) Doctor's lines occur during printing because the engraved surface has convex parts including acute angles.
It would be possible to remove this acute angle part and leave only a smooth convex part, but it is difficult to remove the acute angle part without damaging the 51 iron by physical means.

Therefore, the present invention has devised a method for etching the entire surface of a machine-engraved printing plate using an etchant that has conventionally been used for partial etching.

That is, the etching liquid is not used to form #J formations, but is intended to be used to smooth the surface of the first printing plate.

The following is an example of plate making for gravure cylinders.

The method of the present invention will be explained in detail.

(Example) Copper plating was applied to the surface of a cylinder for gravure printing,
Next, ryotsu are engraved in the usual manner using a single engraving machine equipped with a diamond engraving needle.

Next, use a roller to apply etchant "C" to the entire surface of the cylinder.

A ferric chloride solution is used as the corrosive solution, and the temperature of the solution is 20 to 50℃.
Corrosion for 20-60 seconds under 40-60% humidity.

The end point of corrosion is when there are no sharp edges in the engraved part, and the time required will vary depending on the type of etchant, the temperature of the etchant, the humidity in the room, etc.

In addition to the corrosive solution or the ferric chloride solution mentioned above.

Alkaline corrosive solutions such as ferric nitrate and caustic soda can also be used.

Immediately after the etching is completed, the tK etching solution is washed away and then buffed to keep the surface where the artist is to be formed clean.

Then, the entire surface is plated with chrome to obtain a gravure printing plate.

If we show an example in a drawing in which an acute angle part does not exist due to corrosion, a convex part including an acute angle part formed by mechanical engraving becomes serrated, for example, as shown in Fig. 1, and this surface If the surface is smooth due to corrosion, the upper part of the convex portion (1) is rounded as shown in Figure 2.

Or it is made up of acute angles.

The state where the acute angle portion (2) does not exist refers to the state where the diameter of the upper part of the convex force portion (1) is 2 to 4μ.

If it is less than 2μ, the smoothness will be insufficient, and if it is more than 4μ, it will affect the image quality or, in the case of a solid plate, the coating type, which is not preferable.

(Effects of the Invention) The plate surface, which has an acute angle due to full-surface corrosion, reduces friction with the doctor, and the occurrence of doctor streaks due to damage to the doctor is extremely reduced. This is especially effective when using ink containing metal powder, etc.

Doctor's streaks etc. do not occur and the ink adheres smoothly.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view showing the state of the engraved surface of the plate material after mechanical engraving, and FIG. 2 is an enlarged cross-sectional view showing the condition of the engraving surface of the plate material after the corrosion process has been performed and the sharp edges have been removed. (1)...Convex part (2)...Acute angle part (3)...Plating layer (4)...Plate material

Claims (1)

[Claims] Images are engraved on the surface of printing plates by mechanical engraving,
A plate-making method characterized in that an etching solution is then applied to the entire surface of the plate to etch it to the point where there are no acute angles on at least the surface portion of the engraved portion.