JP2002137353A - Gravure printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gravure printing plate by which time for processing and cost for processing are not increased and direct processing from digitized data of a manuscript onto a gravure cylinder is possible and the most of excellent color reproducibility being a merit of an electron engraving plate processing is made and deficiency of reprodicibility (resolution) on small-sized line such as letters and generation of partial color shading can be solved. SOLUTION: In the gravure printing plate consisting of a plurality of plates obtained from the digitized data of the same manuscript, at least one plate containing the small-sized lines such as letters among them is obtained by a plate processing system by means of a laser beam and other plates are the gravure printing plates obtained by an engraving system by means of a diamond needle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravure printing plate comprising a plurality of plates for multi-color (color) printing. More specifically, the present invention relates to high-quality color reproduction and reproduction of fine lines such as characters. The gravure printing plate that enables it.

[0002]

2. Description of the Related Art The gravure printing method is a method in which ink is put into cells (dents) of a printing plate and is transferred to a printing medium such as paper. The printing method is suitable for magazines and weekly magazines with a large number of copies because the printing speed is high, and the ink is evaporated and dried so that it does not penetrate plastic film etc. This printing method is suitable for printing on a printed body, and is mostly used in the field of flexible packaging material printing.

Conventionally, there are various methods for producing a printing plate for obtaining a gravure print as described above (hereinafter referred to as a plate making method). First, the most common method is to apply a sensitized carbon tissue to a gravure white line screen. There is a so-called conventional gravure method in which a continuous tone positive film is baked, transferred to a gravure cylinder and developed, and the cylinder is chemically corroded. This plate-making method requires many steps such as the use of carbon tissue and chemical corrosion, and requires a lot of time, and there are a lot of unstable elements. As a result, color unevenness etc. occurs partially on a large area printed matter. This is a plate-making method that is likely to be done, and has not been used recently.

As a method of improving these unstable elements, there is a dot gravure plate making method. As an example of such a method, a gravure cylinder coated with a negative type photosensitive agent is exposed through a dot positive film for gravure. It is a plate making method that develops and chemically corrodes, and because it does not use unstable carbon tissue or continuous tone positive film, a relatively stable plate can be obtained, and the problem of color unevenness at least partially occurs. However, there is a problem that color tone reproducibility is poor.

On the other hand, with the development of electronics in recent years, the cell (ce) is directly mounted on a gravure cylinder rotated by a diamond needle without the need for unstable chemical corrosion.
11: A method of engraving a gravure plate (a depression serving as an image portion) (hereinafter referred to as an electronic engraving method) has emerged, which has a stable color tone reproducibility, a small number of steps, a short plate making time, and the like. In addition to that, it has become the current mainstream because it can easily handle digitized manuscript data in the prepress section, which is a pre-process of plate making.

[0006]

However, in the prior art of the above-described electronic engraving method, the edge of a thin line such as a character becomes jagged from the shape of a cell (a diamond shape having a vertex in a cutting direction because the cell is cut). Reproducibility (resolution)
This is a phenomenon caused by the angle of the cell shape of the engraved rhombus (hereinafter referred to as screen angle).
There is a problem that partial color unevenness (a kind of moiré phenomenon) may occur due to expansion and contraction of the image.

In order to solve the above-described problem of insufficient reproducibility of thin lines such as characters and partial color unevenness, Japanese Patent Laid-Open Publication No.
As disclosed in Japanese Patent No. 284, the gravure printing method is performed using a plurality of plates, and among the plurality, the Sumi plate is a method (chemical corrosion method) similar to the net gravure plate making method described above. There is a gravure printing method in which the other plate is formed by an electronic engraving process.

However, in the plate making method using the combination of the net gravure plate making method and the electronic engraving plate making method, insufficient reproducibility of fine lines such as characters and partial color unevenness are eliminated. Since the number of processes is large and digital data from the prepress section cannot be handled, there has been a problem that plate making time and plate making cost are increased.

[0009] On the other hand, recently, for the purpose of solving all of the above problems, a plate making method using a laser beam has been developed and put into practical use, directly or indirectly to a rotating gravure cylinder. This is a method of forming a round cell. The feature of this plate making method is that the digitized original data can be easily taken in, and the cell forming speed (engraving speed) by the laser beam is high, so that the number of scanning lines of the beam (hereinafter referred to as engraving line number) can be increased. It is excellent in reproducibility of thin lines such as characters. On the other hand, there is a problem that stable color reproducibility is inferior to the above-mentioned electronic engraving method.

The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention that plate making time and plate making cost are not increased, and plate making can be directly performed from digitized original data to a gravure cylinder. Another object of the present invention is to provide a gravure printing plate that eliminates the lack of reproducibility (resolution) of thin lines such as characters and the occurrence of partial color unevenness by utilizing the excellent color reproducibility that is an advantage of the electronic engraving plate making method.

[0011]

In order to achieve the above object, the present invention provides a gravure printing plate comprising a plurality of plates obtained from the same digitized original data. At least one plate including a thin line such as a character is obtained by a plate making method using a laser beam, and the other plate is obtained by a gravure printing plate obtained by an engraving method using a diamond needle.

Further, in the invention of claim 2, the plate making method using the laser beam may be an engraving method in which cells are formed directly on the surface of the gravure cylinder, or an exposure method in which cells are formed indirectly on the surface of the gravure cylinder via a photosensitive agent. developing·
A gravure printing plate according to claim 1, which is of a corrosion type.

According to the first or second aspect of the present invention, of a plurality of plates (four plates of yellow, magenta, cyan, and black for reproducing a normal color), one plate (normal black) containing fine lines such as characters is included. Plate) using a laser beam capable of a high number of scanning lines, it is possible to improve the reproducibility (resolution) of fine lines such as characters, which is a drawback of the engraving method using a diamond stylus. The plate (usually yellow, magenta, and cyan) is engraved with a diamond needle (electronic engraving method) to produce a screen angle that is excellent in color reproducibility and free from moiré-like phenomena. Since setting and engraving can be performed, a gravure printing plate free from partial color unevenness due to expansion and contraction of paper can be obtained. In addition, any plate can correspond to digitized document data, and the plate making time and process can be shortened, so that a gravure printing plate with low plate making cost can be provided.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. The gravure printing plate of the present invention is a color gravure printing plate composed of, for example, four plates of yellow, magenta, cyan, and black. Of those, the black plate containing fine lines such as characters is a laser plate that has been recently developed and put into practical use. The remaining plates of yellow, magenta and cyan are obtained by a plate making method using a beam, and are obtained by a so-called electronic engraving plate making method using a mechanical engraving method using a diamond needle.

As the plate making method using the laser beam, a cell is formed directly on the surface of a gravure cylinder. For example, an engraving method of engraving a cell by irradiating a rotating gravure cylinder surface with a YAG laser beam (hereinafter referred to as laser engraving). Or indirectly forming cells on the surface of a gravure cylinder, for example, irradiating a carbon dioxide laser beam onto a gravure cylinder surface coated with a rotating negative photosensitive agent, exposing it to light, developing it, and developing it. A gravure printing plate obtained by two methods of a method of corroding a copper surface (hereinafter referred to as a laser etching plate making method) is applied.

As described above, the plate including fine lines such as characters is the black plate. In most cases, the plate is the black plate. In some cases, the plate may be the cyan plate or the magenta plate. The gravure printing plate obtained by engraving or laser erosion can be used, and when the remaining yellow, magenta, and cyan plates are represented by pseudo-colors with similar characteristics, A gravure printing plate obtained by a plate making method can also be used.

As described above, it can be obtained by the electronic engraving plate making method, the laser engraving plate making method or the laser erosion plate making method, and can correspond to the manuscript data digitized in the prepress section, that is, it can be obtained in a short time and at low cost. By using a gravure printing plate, color reproducibility and reproducibility of fine lines such as characters are excellent, and for example, as shown in the development view of the gravure cylinder surface in FIG. When a large number of one pattern (20) is arranged (hereinafter, referred to as multi-imposition), a phenomenon in which colors are different depending on the imposition position as in the related art does not occur, and each of the multi-imposition patterns (20) does not occur. Is also excellent in color reproducibility and can obtain a high-quality gravure printed matter without variation due to the imposition position.

In the following, a description will be given of factors such as a difference in color of a moire-like phenomenon and a lack of reproducibility of thin lines such as characters, which are disadvantages of the electronic engraving plate making method. The method will be described, and the features of the gravure printing plate of the present invention will be described in detail.

First, a cell mechanically engraved with a diamond stylus by an electronic engraving method is shown in FIG. 2 (b) as a plan view of FIG.
The planar shape of the cell (22) is a rhombus having two vertices in the rotation direction (P) of the cylinder (10), and forms a pyramid in the depth direction. Engraving lines (cells (22) arranged in the rotation direction (P)
The number of lines per cm) is constant, and the gradation from the dark part to the bright part of the image is reproduced according to the area and depth of the rhombus.

In contrast to the cell (22) of the above-described electronic engraving method, the cell obtained by the laser engraving method and the laser erosion method is a plan view of FIG. 3 (a) and a sectional view taken along the line AA of FIG. As shown in b), the planar shape of the cell (24) is substantially round, and a cylindrical shape is formed in the depth direction. In this case, the gradation reproduction of the image is performed by using this cell (2
4) The number of engraved lines is made constant, and this is achieved by the size of the area and depth. Thus, each cell (22, 2
From the shape of 4), in the electronic engraving method, the edges of thin lines such as characters are jagged, and the edges are not flat. From the viewpoint, the number of engraving lines can be increased in the laser engraving method or the laser engraving method, so that fine lines such as characters with high resolution can be obtained. Incidentally, for example, the engraving speed in a heliocrissograph as an electronic engraving method is about 8 in a laser star (manufactured by MDC, Switzerland) as a laser engraving method.
From this, the engraving line number in the electronic engraving method is about 70 lines / cm on average, whereas the laser engraving method is twice as much as 140 lines / cm in practical use. The laser method can still make a plate in a shorter time. The laser engraving method has almost the same performance as the laser engraving method. Specifically, a laser stream (manufactured by Think Laboratory Co., Ltd.) has been put to practical use.

As an electronic engraving method, for example, a screen angle of a diamond-shaped cell by a Heliocrissograph manufactured by Deutsche Hell, as shown in the plan view of FIG.
There are three types: a horizontal diamond (angle code 0) in (a), a square diamond (angle code 1) in (b), and a vertical diamond (angle code 2) in (c), generally a yellow plate. The angle code 0 is used for the cyan and black plates, the angle code 2 is used for the magenta plate, and the angle code 1 is not used for tone reproducibility and the like. As described above, the angle code 0 and the angle code 2 are used to make the moiré-like unevenness less noticeable when superimposed by printing as much as possible. However, since the screen angle (shape) and the number of engraving lines of the yellow plate, cyan plate, and black plate are the same, yellow, cyan, and black are partially registered due to expansion and contraction of the printed material (paper, film, etc.). Misregistration occurs, and in particular, misregistration of dark cyan and black is conspicuous, and this appears as a color difference in printed matter. For this reason, it is possible to prevent the above-mentioned color difference portion from appearing, for example, by obtaining only the black plate by laser engraving or laser engraving having different cell shapes (round shapes) and engraving lines. You can do it.

[0022]

Next, the present invention will be described in detail with reference to examples. Embodiment 1 As shown in FIG. 1, a copper-plated rotating gravure cylinder (10) having a plate cylinder circumference (W) of 600 mm and a plate length (L) of 1100 mm was used as an electronic engraving machine for heliocrishing. Using a graph (manufactured by Hell, Germany), the number of engraving lines: 70 line / cm, screen angle: yellow plate = angle code 0, magenta plate = angle code 2, cyan plate = angle code 0, digitized Engraved color original data, 150x1
A gravure printing plate (yellow plate, magenta plate, and cyan plate) in which 28 surfaces of a 50 mm picture (20) were multi-faced was obtained.

On the other hand, a galvanized rotating gravure cylinder of the same dimensions as above was used with a laser engraving machine, Laser Star (MDC, Switzerland).
The digitized color document data including characters was engraved under the conditions of the number of engraving lines: 100 line / cm to obtain a black plate of a gravure printing plate.

Using the four gravure printing plates (yellow plate, magenta plate, cyan plate, and black plate) obtained above, a thickness of 12
It was printed on a μm polyethylene terephthalate film to obtain a color gravure print containing characters.

The color gravure printed matter obtained in Example 1 has no variation in any of the multi-faced patterns (20), has excellent color reproducibility, and has excellent character reproducibility (resolution). It was a high quality gravure print.

Comparative Example 1 A color gravure print was obtained in the same manner as in Example 1 except that the black plate was obtained under the conditions of the electronic engraving process.

The color gravure printed matter obtained in Comparative Example 1 was excellent in color reproducibility, but had jagged character edges, lacked the reproducibility (resolution), and was multifaceted. Variations due to different colors were observed in the left side pattern (20) and the right side pattern (20).

[0028]

As described above, the present invention has the following effects. That is, in a gravure printing plate composed of a plurality of plates obtained from the same digitized original document data, one of the plurality of plates including a thin line such as a character is made a plate-making method using a laser beam, thereby making it possible to use a diamond plate. It is possible to improve the reproducibility (resolution) of fine lines such as characters, which is a drawback of the engraving method using a needle.
In addition, the other plate is engraved with a diamond needle (electronic engraving method) to provide excellent color reproducibility,
And since these plates can be set to a screen angle that does not cause moire-like phenomena related to the cell shape,
A gravure printing plate free from partial color unevenness can be obtained.

Further, since both the electronic engraving plate making method and the laser plate making method can deal with digitized original data, the plate making time and process can be shortened. Can be provided.

Accordingly, the present invention provides an excellent practical gravure printing plate as a gravure printing plate that enables high-quality color reproduction with rich gradations and improved reproducibility of fine lines such as characters in printing of magazines and flexible packaging bags. It is effective.

[Brief description of the drawings]

FIG. 1 is a development view of a gravure cylinder for explaining an embodiment of a gravure printing plate of the present invention.

FIGS. 2A and 2B are examples of the shape of a cell formed by electronic engraving making up the gravure printing plate of the present invention, wherein FIG. 2A is a plan view thereof, and FIG. 2B is an AA plane of FIG. FIG.

3A and 3B are examples of the shape of a cell formed by laser engraving making up the gravure printing plate of the present invention, wherein FIG. 3A is a plan view thereof, and FIG. 3B is a BB plane of FIG. FIG.

FIGS. 4A and 4B are plan views illustrating a screen angle related to the shape of a cell formed by electronic engraving making up the gravure printing plate of the present invention, wherein FIG.
Indicates an angle code 1 and (c) indicates an angle code 2.

[Explanation of symbols]

 1 gravure printing plate 10 gravure cylinder 20 pattern 22 cel by engraving plate 24 cel by laser engraving plate L gravure cylinder plate length P cylinder rotation direction W ‥ Circumferential length of gravure cylinder

Claims (2)

[Claims] In a gravure printing plate composed of a plurality of plates obtained from the same digitized original data, at least one plate including thin lines such as characters is obtained by a plate making method using a laser beam. Is a gravure printing plate obtained by engraving with a diamond needle. 2. The plate making method using a laser beam is an engraving method in which cells are formed directly on the surface of a gravure cylinder or an exposure, development, and corrosion method in which cells are formed indirectly on a surface of a gravure cylinder via a photosensitive agent. The gravure printing plate according to claim 1, wherein: