JP2004291282A - Method for gravure printing and gravure printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for gravure printing by which a problem of insufficient concentration caused when an FM screen is employed can be avoided by changing the screen to an AM screen, and a problem of insufficient ink transfer at a highlight portion occurred when the AM screen is employed or unclear contour of tilting fine lines or curved lines/ generation of moire can be avoided by changing the screen to the FM screen, and to provide a gravure printed matter. <P>SOLUTION: In the gravure printing method for performing overlap printing in plural colors by using plural printing rolls, a cell for a gravure printing roll for printing in Japanese ink or white color necessary for thick ink concentration is formed on the AM screen, while a cell for the gravure printing roll for printing in indigo blue, red, yellow or the like other than Japanese ink and white color is formed on the FM screen, for which a thick ink concentration is not required in particular, but expression in rather highly precise gradation and printing hard to generate moire are required, even if the overlap printing is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a gravure printing method in which a plurality of colors are overprinted using a plurality of printing rolls. In the case of black or white printing, the gravure printing roll cells that perform the printing are formed so that a dark ink density is obtained. For the printing of indigo, red, yellow, etc., the gravure printing roll that performs the printing is capable of performing high-definition gradation printing and gravure printing that can perform moire-free printing even when overprinting is performed Method and gravure print.
[0002]
[Prior art]
FIG. 4 shows a normal gravure version of an AM screen (Amplitude Modulation Screen). In the gravure plate, the gradation expression is represented by the size of a halftone dot, and it is necessary to put the ink into a cell with a doctor and scrape off excess ink, so that the area of the screen line at the shadow portion becomes 20% to 30%. That is, the gravure plate is configured as a plate that expresses the gradation of the printed matter at about 0 to 75% with respect to the gradation of the printed matter of 0 to 100%.
The gravure plate includes a method of forming cells by engraving and a method of forming cells by applying, exposing, developing, and etching a photosensitive film (hereinafter, referred to as an etching method). Since it is formed in the shape of a pyramid, the transfer of the ink in the highlight portion is good. In the etching method, since the cells are formed in shallow dish-shaped concave portions, the transfer of the ink is inferior to the engraving method due to the ink being clogged in the cells in the highlight portion where the cells are very small. On the other hand, there is an advantage that the ink can be reliably transferred to the intersection by cutting off the intersection of the screen lines of the uppermost shadow portion so that the ink flows, and the outline of the character can be made an outline without jagged. Since the cells in the shadow area are also shallow, they are suitable for printing using water-based ink.
[0003]
FIG. 5 shows an AM screen of an offset printing plate or a flexographic printing plate. An AM screen such as an offset printing plate also expresses a gradation expression by the size of a halftone dot, but unlike a gravure plate, a screen line is not required. Therefore, the gradation of a printed matter is approximately 0 to 100%, and the gradation of a plate is approximately 0 to 100%. Corresponds exactly.
[0004]
In recent years, in the field of offset printing and flexographic printing, as shown in FIG. 5, an FM screen method, which expresses a gradation expression by the number of small halftone dots, mainly in Europe and the United States, instead of the conventional AM screen method shown in FIG. It is starting to be put to practical use. Since the FM screen technology can obtain the resolution of the minimum drawing dot that uses the fine structure expression power, the image quality is expected to be improved even in the output from a low-resolution output device such as a printer or an on-demand printer. In gravure printing, there has been no attempt to apply the gravure printing because there is no screen line for putting ink into a cell with a doctor and scraping off excess ink.
[0005]
The following is an excerpt of the advantages of the FM screen method applied in the fields of offset printing and flexographic printing, which are published on the Internet by the Japan Printing Industry Federation.
(1) Since the halftone dots are not regularly arranged in the FM screen as in the AM screen (FIG. 4), it is possible to avoid occurrence of moiré which may be an obstacle. In the AM screen, the screen angle is set for each plate so that the output moire is minimized. However, in the FM screen, the output moire does not occur because dots are scattered. The FM screen does not generate a rosette pattern. On the AM screen, a pattern of a turtle pattern appears from the highlight to the middle, but this does not occur on the FM screen. No line break occurs even when printing five or more colors.
(2) The FM screen can reduce the halftone dot size over all gradations from highlight to shadow, so that high-resolution print reproduction can be performed. The screen is distributed without the minimum dots sticking up to about 30% density.
(3) Density jumps are not noticeable on FM screens. Density jumps (steps in density) occurring at halftone dots near 50% on the AM screen are inconspicuous on the FM screen. This is because the halftone dots near the middle of the screen make random contact with the adjacent points, so that the density step is reduced.
(4) The color tone of the FM screen is vividly expressed. Colors close to the primary colors and colors with high saturation can be reproduced with the four process colors, and a more realistic expression effect can be exhibited.
(5) The FM screen can have a higher resolution than the AM screen if the output data capacity is the same. Since the interval between the halftone dots can be reduced, if the output data capacity is the same, the resolution can be made higher than that of the AM screen by reducing the dot diameter. Since the minimum drawing dot has a physical resolution in the FM screen, it can be expected that image data (32 to 51% of the screen) is smaller than that of the screen. Since the dot diameter can be increased to obtain the same resolution as that of the 175-line AM screen, the FM screen created from the same input data amount requires a relatively small image data amount. For this reason, if the quality equivalent to the screen of 175 lines can be realized with an FM screen having a large dot diameter, the processing time and waiting time of the plate making / outputting step can be reduced, and the productivity can be improved.
(6) In the FM screen, the minimum drawing dot becomes the physical resolution, and it is easier to obtain a higher resolution than the AM screen. As for the number of gradations, the number of gradations decreases at a high screen line number in order to realize high definition on an AM screen, but the FM screen does not have such a case.
(7) The tone of the middle to shadow parts of the FM printed matter is higher than that of the AM printed matter, and the highlight to the middle part is almost equal to or lower than AM. The FM value of the K value representing the contrast on the shadow side is generally small. Regarding the ink solid density, in a high definition FM screen using a small dot diameter, it is difficult to obtain a high density in a halftone portion similarly to an AM screen having a high screen ruling.
[0006]
Conventional gravure printing rolls are all formed of AM screen cells, and none of the gravure printing rolls are formed of FM screen cells. With the engraving method, it is impossible to engrave an FM screen, but with the photolithography method there is a possibility.
In the specification of the present application, the cell of the AM screen is made by laser plate making including the steps of photosensitive film coating-laser exposure / latent image formation-development-etching, the arrangement pitch is constant, and the cell size changes. Refers to both cells and cells made with a diamond stylus of an electronic engraving machine and having a constant arrangement pitch and varying cell size and depth, and other cells having a constant arrangement pitch. .
[0007]
Conventionally, a gravure plate that requires sharpness of the outline of a character or a gravure plate that requires a sufficient density in a shadow portion has a laser plate consisting of a photosensitive film coating-laser exposure / latent image formation-development-etching process. Gravure plate making by an electronic engraving machine, which causes less transfer failure due to ink dropout, is often used for images that are frequently used and have many photographic portions.
Also, in making a plate for multi-color printing gravure printing, there are cases where a character / thin line plate is used for a net gravure and a plate having a photographic portion is used for an electronic engraving machine, taking advantage of the features of each plate making.
However, there is an image in which moiré occurs when the engraving plate and the net gravure plate making are combined carelessly, and there is a limitation on use.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and in a gravure printing method of performing overprinting in a plurality of colors using a plurality of printing rolls, for black and white printing, a gravure printing roll cell for performing the printing. The composition is formed so as to obtain a dark ink density, and for the printing of indigo, red, yellow, etc., the gravure printing roll cell that performs the printing can perform high-definition gradation printing and perform overprinting. It is possible to provide a gravure printing method and a gravure printed matter that can perform printing in which moiré is unlikely to occur and can obtain high-definition gravure printing as compared with a conventional gravure printing roll having AM screen cells. The purpose is.
According to the present invention, the problem of insufficient density that occurs when an FM screen is used can be avoided by using an AM screen. In addition, poor transfer of ink in a highlight portion, a thin inclined line, or a contour of a curve that occurs when an AM screen is used. It is an object of the present invention to provide a gravure printing method and a gravure printed matter that can avoid the problem of indistinctness and moire generation by using an FM screen and can enjoy the advantages of the FM screen described above.
[0009]
[Means for Solving the Problems]
The invention of the present application is a gravure printing method in which a plurality of colors are overprinted using a plurality of printing rolls. In a printing roll that performs black and white printing, cells are formed on an AM screen, and indigo, red, and yellow printing are performed. The present invention provides a gravure printing method in which cells are formed of an FM screen for a printing roll.
According to the invention described in [Claim 2], a gravure printed matter printed by the gravure printing method described in [Claim 1] can be provided.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
For example, in the case of gravure printing in which five colors of black, indigo, red, yellow, and white are overprinted using five printing rolls, a gravure printing method as shown in FIG. Attach the printing roll R1 to print black ink, attach the gravure printing roll R2 to the second printing station to print indigo, attach the gravure printing roll R3 to the third printing station to print red, and The gravure printing roll R4 is attached to the printing station of No. 5 to print yellow, and the gravure printing roll R5 is attached to the fifth printing station to print white.
For printing in black and white, a dark ink density can be obtained because the configuration of the cells forming the plate image 1 or 5 of the gravure printing roll for printing is made of the AM screen shown in FIG.
In addition, in the blue, red, and yellow printings, since the configuration of the cells that form the plate image 2 or 3 or 4 of the gravure printing roll that performs each printing is made of the FM screen shown in FIG. Can be performed, and even when overprinting is performed, printing in which moire is unlikely to occur can be performed.
Therefore, characters and lettering images that require a high ink density are printed in black and white, or, although not shown, printed with a special color and rolls composed of AM screen cells. When a photographic image and a thin line expressed by gradation are printed in a color other than black and white, printing is performed as a roll composed of cells of an FM screen.
[0011]
The AM screen shown in FIG. 2 may be formed by any of a method of forming a cell using an electronic engraving machine and a method of forming a cell by applying, exposing, developing, and etching a photosensitive film.
[0012]
In FIG. 3, A1 represents digital information of an FM screen obtained by performing FM screening using an FM screening program when a gradation of 0% to 100% is prepared as plate information before forming a plate. It is. B1 is a screen line of the most shadow portion of the AM screen obtained by performing AM screening on the plate information before forming the plate and corresponding to the shadow region from the shadow region or the shadow portion of the halftone portion. This is a display of the displayed AM screen information. C1 displays digital version information in which digital information of the FM screen shown in A1 and digital information of only the screen lines of the AM screen shown in B1 are superimposed.
[0013]
Accordingly, the plate C1 performs FM screening of the region from the highlight to the shadow with respect to the plate information before the plate is formed, so that the minimum cell has a required size for performing good ink transfer. In the area from the shadow portion of the halftone portion to the shadow portion of the FM screen information A1 (illustrated as optical information), information B1 (optical information) of only the screen line of the most shadow portion of the gravure AM screen is displayed. (Shown as information) are superimposed on each other, so that the area from the highlight area to the halftone area is purely an FM screen and has no graininess. The size of the screen is regulated to the required size which is satisfactorily performed. In the area of the part are completely become a gravure printing plate will AM screen.
[0014]
The FM screen shown as plate C1 in FIG. 3 is formed by a method of forming cells by applying a photosensitive film, laser exposure, development, and etching, or by a method of forming cells by laser engraving. .
Since an FM screen cannot be made by an electronic engraving machine, a plate in which an AM screen and an FM screen are mixed is formed by a method of forming a cell by applying a photosensitive film, laser exposure, development, etching, or laser engraving. It is preferable that the cell is formed by any of the cell forming methods by the method because no man-hour is required.
[0015]
This gravure printing plate is a mesh-shaped AM screen required for gravure printing in the shadow area, and the FM density of the screen is in the grid, and the optical density is uneven. In the area that shifts from the halftone area to the halftone area, the mesh-shaped AM screen gradually disappears and shifts to the dots of the FM screen. From the halftone area to the highlight area, the shadow area of the gravure version of the AM screen has the highest shadow area. Since the screen is not superimposed, the screen is purely an FM screen. In addition, since the minimum cells are regulated to a required size that allows good ink transfer, the ink transfer is good and the FM screen is excellent. Points are obtained.
[0016]
In the plate making method, the digital plate information is separated into three colors of Y, M and C, and the area from the highlight part to the shadow part is reduced to a required size so that the minimum cells can transfer ink well. The FM screening is performed by the improved program which is regulated to obtain plate information, and the AM screening is performed by the improved AM screening program, and from the shadow portion to the shadow portion of the halftone portion, the highest shadow portion of the gravure AM screen is obtained. The plate information indicated by the screen is obtained, the two plate information are superimposed, and the plate is made based on the plate information.
[0017]
【The invention's effect】
As is clear from the above description, the present invention
In the gravure printing method of overprinting a plurality of colors using a plurality of printing rolls, for black and white printing, the configuration of the cells of the gravure printing roll performing the printing is formed so as to obtain a dark ink density, indigo, For the printing of red, yellow, etc., the structure of the cell of the gravure printing roll that performs the printing can perform high-definition gradation printing, and can perform printing in which moire does not easily occur even when overprinting is performed, and the conventional AM screen A gravure printing method and a gravure printed matter that can obtain a high-definition gravure printing as compared with a case where printing is performed by a gravure printing roll having cells of
In addition, the present invention can avoid the problem of insufficient density caused by using an FM screen by using an AM screen. In addition, poor transfer of ink in a highlight portion, slanted thin lines or curved lines caused by using an AM screen can be avoided. The present invention can provide a gravure printing method and a gravure printed matter which can avoid the problem of blurred outline and occurrence of moiré by using an FM screen and can enjoy the advantages of the FM screen described above.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a gravure printing method according to an embodiment of the present invention in the case of gravure printing in which five colors of black, indigo, red, yellow, and white are overprinted using five printing rolls.
FIG. 2 is a view showing a conventional AM screen of a gravure plate used conventionally and used in the present invention.
FIG. 3 is a diagram showing gradation of an FM screen used in the present invention.
FIG. 4 is a diagram showing a normal AM screen used for conventional offset printing and the like.
FIG. 5 is a diagram showing an FM screen used for conventional offset printing and the like.

Claims (2)

In a gravure printing method in which a plurality of colors are overprinted using a plurality of printing rolls, for a printing roll performing black and white printing, cells are formed on an AM screen, and for a printing roll performing indigo, red, and yellow printing, A gravure printing method, wherein the cells are formed by an FM screen. A gravure printed matter printed by the gravure printing method according to claim 1.

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