JP4287684B2 - Gravure printing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of the present application is a gravure printing method in which a plurality of printing rolls are used to overprint a plurality of colors. For black and white printing, the cell structure of the gravure printing roll that performs printing is formed so as to obtain a dark ink density. Gravure printing that can print indigo, red, yellow, etc., so that gravure printing roll cells can be printed with high-definition gradation and are less likely to cause moire even when overprinting is performed. The present invention relates to a method and a gravure print.
[0002]
[Prior art]
FIG. 4 shows a normal gravure AM screen (Amplitude Modulation Screen). In the gravure version, the gradation expression is represented by the size of halftone dots, and it is necessary to put ink into the cell by the doctor and scrape off the excess ink, so the area of the screen line at the most shadow portion is 20% to 30%. That is, the gravure plate is configured as a plate that expresses the gradation of the plate at about 0 to 75% with respect to the gradation of the printed material of 0 to 100%.
The gravure plate has a cell formation method by engraving and a cell formation method (hereinafter referred to as etching method) by photosensitive film coating / exposure / development / etching. Since it is formed in a pyramid, the ink transfer at the highlight portion is good. In the etching method, the cell is formed in a shallow dish-shaped recess, and the ink transfer is inferior to the engraving method due to the fact that the ink is clogged in the cell in the highlight portion where the cell is very small. On the other hand, there is an advantage that ink can be surely transferred to the intersection by lacking the intersection of the screen line of the shadow part so that the ink flows, and the outline of the character can be made an outline without jaggedness. Since the shadow cell is shallow, it is suitable for printing using water-based ink.
[0003]
FIG. 5 shows an AM screen of an offset printing plate or a flexographic printing plate. AM screens such as offset printing plates also express gradation in halftone dots, but unlike gravure plates, screen lines are abbreviated as 0 to 100% for printed gradations and 0 to 100% for printed gradations. Corresponds accurately.
[0004]
In recent years, in the field of offset printing and flexographic printing, an FM screen system that expresses gradation expression by the number of minute dots as shown in FIG. 5 is used mainly in Europe and the United States, instead of the conventional AM screen system shown in FIG. It is starting to be put into practical use. The FM screen technology is capable of obtaining the resolution of the minimum drawing dots that use the fine structure expressive power. Therefore, the image quality is expected to be improved even when outputting from a printer or an on-demand printing machine that is a low-resolution output machine. In gravure printing, there was no screen to apply ink to the cell with a doctor and there was no screen for scraping off excess ink, so there was no attempt to apply it at all.
[0005]
Below, the FM screen methods applied in the fields of offset printing and flexographic printing are listed below with the merits published by the Japan Printing Industry Federation on the Internet.
(1) In the FM screen, the halftone dot shape is not regularly arranged unlike the AM screen (FIG. 4), so that it is possible to avoid the occurrence of moiré that becomes an obstacle. In the AM screen, the screen angle is set for each plate so that the output moiré is minimized, but in the FM screen, since the dots are scattered, the output moiré does not occur. Also, the FM screen does not generate a rosette pattern. On the AM screen, a tortoiseshell pattern appears from the highlight to the middle, but this does not occur on the FM screen. Line breaks do not occur even when printing more than 5 colors.
(2) Since the FM screen can reduce the dot size over all gradations from highlight to shadow, high-resolution printing reproduction is possible. The screen is distributed with the smallest dots not sticking up to about 30% density.
(3) On the FM screen, the density jump is inconspicuous. Density jumps (concentration steps) that occur at halftone dots around 50% on AM screens are not noticeable on FM screens. This is because, in the halftone dot near the middle of the screen, the contact with the adjacent point is random, and the density step is reduced.
(4) The FM screen is vividly expressed in color. Colors close to primary colors and colors with high saturation can be reproduced with four process colors, enabling more realistic expression effects.
(5) The FM screen can have higher resolution than the AM screen if the output data capacity is the same. Since the distance 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. The FM screen can be expected to require less image data (32 to 51% of the screen) than the screen because the minimum drawing dots have a physical resolution. Moreover, since the dot diameter can be increased to obtain the same resolution as that of the 175-line AM screen, an FM screen created from the same input data amount requires a relatively small amount of image data. For this reason, if an FM screen with a large dot diameter can realize the quality equivalent to the screen 175 lines, it can be expected to shorten the processing time and waiting time of the plate making / output process and improve the productivity.
(6) The FM screen is easier to obtain a higher resolution than the AM screen because the minimum drawing dots have a physical resolution. In order to achieve high definition with an AM screen, the number of gradations decreases with the number of high screen lines, but FM screens do not.
(7) Compared with AM prints, FM prints have a higher tone in the middle to shadow portions, and highlights to middle portions appear almost the same as AM, but lower. The FM value representing the contrast on the shadow side is generally small in FM. In the high-definition FM screen using a small dot diameter, it is difficult to obtain a high density at the halftone area in the same manner as an AM screen having a high screen line number.
[0006]
All conventional gravure printing rolls have AM screen cells, and none of them are FM screen cells. With the engraving method, it is impossible to engrave the FM screen, but with the photolithography method, there is a possibility.
In the specification of the present application, the AM screen cell is made by laser plate making comprising the steps of photosensitive film coating-laser exposure / latent image formation-development-etching, and the arrangement pitch is constant and the cell size changes. Both cells and cells made of diamond engraving machine stylus with constant pitch and varying cell size and depth, other cells with constant pitch .
[0007]
Conventionally, for gravure printing that requires sharpness of the outline of characters and for gravure printing that requires a sufficient density in the shadow area, laser plate making comprising the steps of photosensitive film coating-laser exposure / latent image formation-development-etching is used. Gravure plate making using an electronic engraving machine with little transfer failure due to ink dropout was often used for images with many photographic parts.
Further, when making multicolor gravure printing, there were cases where the character / thin line plate was used as a screen gravure and the plate with a photo part was used separately from an electronic engraving machine, taking advantage of the characteristics of each plate making.
However, there is an image in which moire occurs when the engraving plate and the net gravure plate making are carelessly combined, and there is a limit to the use.
[0008]
[Problems to be solved by the invention]
The present invention has been devised in view of the above-described points. In a gravure printing method in which a plurality of printing rolls are used to overprint a plurality of colors, black or white printing is performed on a cell of a gravure printing roll that performs printing. The ink composition is formed so that a dark ink density can be obtained, and for the printing of indigo, red, yellow, etc., the cell structure of the gravure printing roll that performs the printing can perform high-definition gradation printing and overprinting is performed. It is possible to provide a gravure printing method and a gravure print that can perform printing that hardly causes moiré and can obtain high-definition gravure printing as compared with the case of printing with a gravure printing roll having cells of a conventional AM screen. It is aimed.
In 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, ink transfer failure, slanted fine lines, and contours of highlights that occur when an AM screen is used. An object of the present invention is to provide a gravure printing method and a gravure printed matter that can avoid the problem of ambiguity and moire generation by using an FM screen and that can enjoy the advantages of the above-described FM screen.
[0009]
[Means for Solving the Problems]
In the present invention, in a gravure printing method in which a plurality of printing rolls are used to overprint a plurality of colors, cells are formed on an AM screen for printing rolls that perform black and white printing, and indigo, red, and yellow printing is performed. With respect to the printing roll, a gravure printing method is provided in which cells are formed by FM screens.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
For example, a gravure printing method in the case of gravure printing in which five printing rolls are used to overprint five colors of black, indigo, red, yellow, and white is shown in FIG. The printing roll R1 is attached to print black, the gravure printing roll R2 is attached to the second printing station to print indigo, the gravure printing roll R3 is attached to the third printing station, and red is printed. The gravure printing roll R4 is attached to the printing station of No. 1 to print yellow, and the gravure printing roll R5 is attached to the fifth printing station to print white.
In the printing of 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 on which the printing is performed is made of the AM screen shown in FIG.
In the blue, red, and yellow printing, the structure of the cells forming 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. Thus, even if overprinting is performed, it is possible to perform printing that hardly causes moire.
Therefore, characters and lettering images that require a high ink density are printed in black and white, or, although not shown, are printed as a roll made up of AM screen cells with special colors. In addition, when printing a photographic image and a thin line expressed in gradation with colors other than black and white, it is printed as a roll composed of FM screen cells.
[0011]
The AM screen shown in FIG. 2 may be formed by either a cell forming method using an electronic engraving machine or a cell forming method using photosensitive film coating / exposure / development / etching.
[0012]
In FIG. 3, A1 displays digital information on an FM screen obtained by FM screening using an FM screening program when gradation of 0% to 100% is prepared as plate information before forming a plate. It is. B1 is the screen line of the most shadow part of the AM screen obtained by AM screening the plate information before forming the plate and corresponding to the shadow part region from the shadow part region or the shadow part of the halftone part. The AM screen information to be displayed is displayed. C1 displays digital version information in which the digital information of the FM screen shown in A1 and the digital information of only the screen line of the AM screen shown in B1 are superimposed.
[0013]
Therefore, the plate C1 performs FM screening on the region from the highlight portion to the shadow portion so that the minimum cell has a required size for good ink transfer with respect to the plate information before forming the plate. In the area from the shadow portion of the halftone portion of the FM screen information A1 (shown as optical information) to the shadow portion, information B1 (optical) of only the screen line of the most shadow portion of the gravure AM screen. (Indicated as information), the area from the highlight area to the halftone area is purely an FM screen, and there is no occurrence of roughness, and the smallest cell has no ink transfer. It is regulated to the required size to be performed well, and a grid-like AM screen gradually occurs from the halftone part on the base of the FM screen. In the area of the part it is completely become a gravure printing plate will AM screen.
[0014]
The FM screen shown in the plate C1 in FIG. 3 is formed by either a cell formation method by photosensitive film coating, laser exposure, development, or etching, or a cell formation method 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 cell forming method by photosensitive film coating, laser exposure, development, etching, or laser engraving. It is preferable that it is formed by any of the cell forming methods by the method because the number of man-hours does not take.
[0015]
This gravure printing plate is a grid-like AM screen necessary for gravure printing in the shadow area, and FM screen dots are present in the grid and the optical density is deviated, so that a sufficient optical density can be obtained in the printed matter. In the transition from the halftone area to the halftone area, the grid-like AM screen gradually disappears and shifts to the dots on the FM screen. From the halftone area to the highlight area, the most shadow area of the gravure AM screen appears. Since the screen is not superposed, the screen is purely an FM screen, and the minimum cell is regulated to a required size that allows the ink to be transferred well, so that the ink transfer is good and the FM screen is excellent. Points are earned.
[0016]
In the plate making method, digital plate information is separated into three colors Y, M, and C, and the area from the highlight portion to the shadow portion is reduced to the required size that allows the ink to be transferred well. The FM screen is obtained by the improved and regulated program to obtain the plate information, and the AM screen is obtained by the improved AM screening program and the shadow portion of the gravure AM screen from the shadow portion to the shadow portion is corrected. The plate information displayed by the screen line is obtained, the two plate information is superimposed, and the plate is made based on the plate information.
[0017]
【The invention's effect】
As apparent from the above description, the present invention
In a gravure printing method in which a plurality of printing rolls are used to overprint a plurality of colors, the cell structure of the gravure printing roll that performs printing for black and white 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 that hardly causes moiré even if overprinting is performed. The gravure printing method and gravure printed matter which can obtain high-definition gravure printing compared with the case where it prints with the gravure printing roll which has this cell can be provided.
Further, in 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, ink transfer failure, inclined fine lines, and curves that occur when an AM screen is used are highlighted. It is possible to provide a gravure printing method and a gravure printed matter that can be avoided by using an FM screen and can enjoy the advantages of the above-described FM screen.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a gravure printing method in the case of gravure printing according to an embodiment of the present invention, in which five printing rolls are used to overprint in five colors of black, indigo, red, yellow and white.
FIG. 2 is a diagram showing a conventional AM screen of a gravure plate that is conventionally used 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 or the like.
FIG. 5 is a diagram showing an FM screen used for conventional offset printing or the like.

Claims (1)

  In a gravure printing method in which a plurality of printing rolls are used to overprint a plurality of colors, a cell is formed on an AM screen for a printing roll that performs black and white printing, and a printing roll that performs indigo, red, and yellow printing. A gravure printing method, wherein the cell is formed of an FM screen.

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