JP2003062965A - Gravure plate-making method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gravure plate-making method enabling attainment of both of the merit of a gravure plate to be formed by an etching method and that of a screen, by adding screen lines to the screen applicable to offset printing or the like. SOLUTION: The digital information as to the screen obtained by screening conducted so that the minimum cell may have a required size enabling excellent transfer of ink and the digital information only as to the screen lines of the darkest shadow part of the gravure plate in the screen are superposed on the gravure information given before the gravure plate is formed. Based on the superposed digital information as to the gravure plate, the surface whereon a photosensitive film is formed and whereon the plate is to be formed is exposed and developed, or the surface whereon a film applicable to laser ablation is formed and whereon the plate is to be formed is subjected to the laser ablation. Then, the metal surface developed or exposed by the laser ablation is etched, a resist is peeled off and then a hard chromium plating is provided thereon.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen (Frequency Modulati) applicable to offset printing or the like.
gravure plate making method for adding a screen line to the on screen). FIG. 3 shows a conventional gravure 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 the ink into the cell with a doctor and scrape off the excess ink,
The area of the screen line at the shadow portion is 20% to 30%. That is, in the gravure plate, the gradation of the printed material is 0 to 75%, while the gradation of the plate is 0 to 75%.
It is composed as a version expressed in about%. The gravure version is
There are a cell forming method by an engraving method and a cell forming method by applying, exposing, developing, and etching a photosensitive film (hereinafter referred to as an etching method). Therefore, 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] Therefore, there is a demand for an improvement in ink transferability in a highlight portion having a very small cell in an etching method. FIG. 4 shows a screen of an offset printing plate or a flexographic printing plate. On a screen such as an offset printing plate, the gradation expression is represented by the size of a halftone dot. However, unlike a gravure plate, a screen line is not required.
The gradation of the plate corresponds almost exactly to 100% to 0-100%. In recent years, in the field of offset printing and flexographic printing, a screen system in which the gradation expression is represented by the number of small halftone dots as shown in FIGS. It has begun to be put to practical use mainly in Europe and the United States. Since screen technology can obtain the resolution of the minimum drawing dot that uses fine structure expression power, image quality is expected to be improved even in output from low-resolution output machines such as printers and on-demand printing machines, In gravure printing, there has been no attempt to apply gravure printing because there is no screen line for putting ink into cells with a doctor and scraping off excess ink. [0006] The following is an excerpt of the advantages of the screen method applied in the fields of offset printing and flexographic printing, which are published by the Japan Printing Industry Federation on the Internet. (1) Since the halftone dots are not regularly arranged on the FM screen as in the screen (FIG. 4), it is possible to avoid the occurrence of moiré which may be an obstacle. On the screen, the screen angle is set for each plate so that the output moire is minimized. However, on the screen, output moire does not occur because dots are scattered. Also, the screen does not generate a rosette pattern. On the screen, from the highlight to the middle, the pattern of the turtle pattern appears, but on the screen, this does not occur. No line break occurs even when printing five or more colors. (2) The FM screen can reduce the dot size over all gradations from highlights to shadows, enabling high-resolution print reproduction. The screen is distributed without the smallest dots sticking up to about 30% density. (3) Density jump is not noticeable on the FM screen. Density jumps (steps of density) occurring at halftone dots near 50% on the screen are inconspicuous on the 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 highly saturated colors can be reproduced with the four process colors, and more realistic expression effects can be exhibited. (5) The FM screen can achieve higher resolution than the screen with the same output data capacity. Since the interval between the halftone dots can be reduced, if the output data capacity is the same, the resolution can be higher than that of the screen by reducing the dot diameter.
The screen has less image data than the screen (32
~ 51%). Further, since the dot diameter can be increased to obtain the same resolution as that of a 175-line screen, a screen created from the same input data amount requires a relatively small image data amount. For this reason, if a screen with a large dot diameter can achieve a quality equivalent to 175 lines of the screen, shortening of the processing time and waiting time in the plate making / outputting process and improvement in productivity can be expected. (6) FM screens are easier to obtain higher resolution than screens because the minimum drawing dot is the physical resolution. Although the number of gradations decreases with a high screen line number in order to realize high definition on a screen, the screen does not have such a case. (7) Compared to AM prints, FM prints have a higher middle-to-shadow tone, and highlights-middle portions are almost equivalent to AM-
Get low. The FM value of the K value representing the contrast on the shadow side is generally small. Regarding the ink solid density, it is difficult to obtain a high density in a halftone portion of a screen for high definition use using a small dot diameter, like a screen having a high screen ruling. (8) As with the high screen ruling, the highlight expression power of FM screens is disadvantageous because it is easily affected by dampening water in film output, plate printing, and offset lithographic printing. In forming the calibration image, the screen theoretically has more adaptation means than the high screen ruling screen. (9) To use FM screens for high-quality printing,
It is said that quality control is not successful at the standard screen 175 line level, and quality control of plate making and printing using screens is completed only after strict control of the control level. [0007] The present invention has been made in view of the above-mentioned point, and a cell of a gravure plate screen formed by an etching method by adding a screen line to a screen applicable to offset printing or the like can be extremely improved. Overcoming the disadvantage of poor ink transfer due to clogging of the cells in the small highlight area, and the intersection where the ink flows at the intersection of the screen lines at the shadow end. In addition to the advantages that the ink can be transferred to the surface reliably and that the outline of the character can be contoured without jagged edges, the cells in the shadow area are shallow, making them suitable for printing using water-based ink, and highlights The advantage that the screen is superior to the screen from the part to the halftone part is that the moire can be avoided. Rukoto, that does not occur missing line in the printing of five or more colors, it can print reproducing the high resolution,
It is an object of the present invention to provide a gravure plate making method that can enjoy advantages such as inconspicuous density jump. According to the present invention, screening is performed on plate information before forming a plate so that the minimum number of cells has a required size for good ink transfer. Plate digital information obtained by superimposing the digital information of the screen obtained on the screen and the digital information of only the screen line at the shadow portion of the gravure plate of the screen, and forming a photosensitive film based on the superimposed digital plate information. Is exposed and developed, or laser ablation is performed on the plate forming surface on which a coating that can be laser ablated is formed, then the metal surface exposed by development or laser ablation is etched, the resist is peeled off, and hard chrome plating is provided. And a gravure plate-making method characterized by comprising: DETAILED DESCRIPTION OF THE INVENTION The gravure plate making method of the present invention is as follows.
Digital information of the screen obtained by screening the plate information before forming the plate so that the minimum cell has a required size for good ink transfer, and the shadow of the gravure plate of the screen. Digital information of only the screen line of the part is superimposed, and based on the superimposed digital version information, the surface on which the photosensitive film is formed is exposed and developed, or a coating that can be laser ablated is formed. Then, the metal surface exposed by development or laser ablation is etched, the resist is peeled off, and hard chromium plating is provided. The required size at which the minimum cell can transfer ink well is, specifically,
It is about 25 μm square. Embodiment 1 In FIG. 1, A1 is a digital screen of a screen obtained by performing screening by a screening program when a gradation of 0% to 100% is prepared as plate information before forming a plate. Information is displayed. B1 displays digital information of only the screen line of the shadow portion of the gravure version of the screen, irrespective of the version information before forming the version. C2 is the digital information of the screen shown in A1,
This is a display of digital version information in which digital information of only the screen line of the screen shown in B1 is superimposed. Second Embodiment In FIG. 2, when a gradation of 0% to 100% is prepared as plate information before forming a plate, A2 performs screening by a screening program different from that of the first embodiment. This is a display of the digital information on the screen obtained by the execution. B2 displays digital information of only the screen lines at the shadow portion of the gravure plate on the screen, regardless of the plate information before the plate is formed. C2 displays digital version information in which digital information of the screen shown in A2 and digital information of only the screen lines of the screen shown in B2 are superimposed. The digital version information shown in C2 of FIG.
The three colors M and C were prepared. In this case, the minimum cell is required to have good ink transfer.
By a laser exposure device manufactured by CreoScitex of Canada, a laser beam that forms a square cell with a side of 28 μm by arranging four laser beams of 7 μm square in the vertical and horizontal directions so that the unit output can be performed, And corresponding to this, the minimum cell is square and one side is 28μ.
The screen information before forming the plate was screened by inputting numerical values necessary for the screening program so as to obtain m, and digital information on the screen was obtained. Then, based on the digital color plate information of one color, the surface on which the positive type photosensitive film is formed is exposed and alkali-developed, and then the exposed metal surface (copper-plated surface) is treated with a cupric chloride solution. After etching, the resist was stripped off with a strong alkaline solution, and then a gravure plate having hard chromium plating was prepared for three colors and mounted on a gravure rotary printing machine to perform overprinting. The jump was not noticeable. High-resolution print reproduction was achieved. Drying load was small and drying was performed smoothly. The outline of the character could be made an outline without jaggedness. The present invention includes a planographic plate in addition to a roll as a plate forming surface. The photosensitive film may be either a positive type or a negative type. As described above, the gravure plate making method of the present invention has the following effects. (1) Since the minimum number of cells is of a required size for good transfer of ink, ink is contained in the cells at the very small highlights of the gravure plate screen formed by the etching method. It is possible to overcome the conventional disadvantage that the transfer of the ink due to the clogging is poor. (2) The intersection of the screen lines in the shadow area can be a free flow cell that lacks ink so that the ink flows, and the outline of the character can be transferred to the intersection without fail and the outline of the character has no jagged edges. Can do,
Since the cell in the shadow portion is also shallow, it can continue to enjoy the conventional advantage that it is suitable for printing using water-based ink. In addition, the advantages of the screen that can be enjoyed by offset printing or the like can also be enjoyed by the gravure version. (3) The advantages that the screen is superior to the screen from the highlight part to the halftone part are that moiré can be avoided, that line breaks do not occur even when printing five colors or more, and that high-resolution print reproduction can be performed. Benefits such as inconspicuous density jump can be enjoyed. (4) Since a conventional large cell is formed by being divided into a plurality of minimum cells, the ink film thickness is reduced, the drying load is reduced, and higher-speed printing is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 relates to a gravure plate making method of the present invention, and superimposes digital information A1 of an FM screen and digital information B1 of only a screen line of an AM screen of a gravure plate to obtain digital version information C1. FIG. 7 is a diagram for explaining that it is obtained. FIG. 2 relates to the gravure plate making method of the present invention, and is intended to explain that digital information A2 of an FM screen and digital information B2 of only a screen line of a gravure AM screen are superimposed to obtain digital plate information C2. FIG. FIG. 3 is a view showing a conventional AM screen of a conventional gravure plate. FIG. 4 shows a normal AM used for conventional offset printing and the like.
The figure which shows a screen. FIG. 5 is a diagram showing an FM screen used for conventional offset printing and the like. FIG. 6 is a diagram showing another FM screen used for conventional offset printing or the like.

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[Procedure amendment] [Date of submission] August 30, 2001 (2001.8.3
0) [Procedure amendment 1] [Document name to be amended] Description [Item name to be amended] Full text [Amendment method] Change [Content of amendment] [Document name] Specification [Title of invention] Gravure plate making method [Claims] An FM screen obtained by performing FM screening so that a minimum cell has a required size for performing good ink transfer with respect to plate information before a plate is formed. , Superimposing the digital information of only the screen line of the most shadow part of the gravure version of the AM screen, and based on the superimposed digital version information,
Expose and develop the plate-forming surface on which the photosensitive film has been formed, or
A gravure printing plate characterized in that a laser ablation is performed on a plate forming surface on which a coating that can be laser ablated is formed, then a metal surface exposed by development or laser ablation is etched, a resist is peeled off, and hard chrome plating is provided. Method. Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM screen (Frequency Modu
gravure plate making method that adds a screen line to the lation screen. 2. Description of the Related Art FIG. 3 shows a normal gravure version of an 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 the ink into the cell with a doctor and scrape off the excess ink. Therefore, the area of the screen line in the shadow portion is 20% to 30%.
become. That is, in the gravure plate, the gradation of the plate is 0 to 100%, while the gradation of the plate is 0 to 100%.
It is configured as a version that expresses around 75%. 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] Therefore, there is a demand for an improvement in ink transferability in a highlight portion having a very small cell in an etching method. FIG. 4 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, does not require a screen line, so that the gradation of the printed material is 0 to 100% and the gradation of the plate is 0 to 100.
It corresponds almost exactly to%. In recent years, in the field of offset printing and flexographic printing, instead of the conventional AM screen system shown in FIG. 4, an FM screen which expresses a gradation expression by the number of minute dots as shown in FIGS. The system has been put to practical use mainly in Europe and the United States. Since the FM screen technology can obtain the resolution of the minimum drawing dot where the fine structure expression power is used,
Although image quality is expected to improve in the output from low-resolution printers and on-demand printers, gravure printing does not have screen lines for inserting ink into cells with a doctor and scraping excess ink. So there was no attempt to apply. 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 by the Japan Printing Industry Federation on the Internet. (1) Since the FM screen is not regularly arranged in a halftone dot shape unlike the 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. 5
Line breaks do not occur even when printing more than colors. (2) Since the FM screen can reduce the dot size over all gradations from highlight to shadow, high-resolution print reproduction can be performed. The screen is distributed without the smallest 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 AM screens are not noticeable on FM screens. 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 FM screen has a vivid color tone. Colors close to the primary colors and highly saturated colors can be reproduced with the four process colors,
A more realistic expression effect can be exhibited. (5) The FM screen can have a higher resolution than the 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 the physical resolution of the FM screen, it can be expected that image data (32 to 51% of the screen) is smaller than that of the screen. Also, since the dot diameter can be increased to obtain the same resolution as that of an 175-line AM screen, the FM created from the same input data
The screen requires a relatively small amount of image data. For this reason, if a quality equivalent to 175 lines of a screen can be realized with an FM screen having a large dot diameter, shortening of the processing time and waiting time in the plate making / outputting step and improvement in productivity can be expected. (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 portions of the FM printed matter is higher than that of the AM printed matter, and the highlight to the middle portion is almost equal to or lower than the AM. K representing shadow side contrast
The value is generally small for FM. 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. (8) As with the high screen ruling, the highlight expressive power of FM screens is disadvantageous because it is easily affected by dampening water in film output, plate printing, and offset lithographic printing. In forming a calibration image, FM screens theoretically have more adaptation means than high screen ruling AM screens. (9) In order to use FM screens for high-quality printing, quality control is not successful at the normal 175-line AM screen level, and FM control must be rigorously scrutinized.
It is said that quality control of plate making and printing using screens will be completed. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and is directed to a cell of a gravure AM screen formed by an etching method by adding a screen line to an FM screen applicable to offset printing or the like. In the very small highlight area, the ink transfer is poor due to the clogging of the ink in the cells, and the ink is lacking so that the ink flows at the intersection of the screen lines in the shadow area. The advantage that the ink can be transferred to the intersection reliably and the outline of the character can be an outline without jaggedness, and the cells of the shadow area are shallow so that they are suitable for printing using water-based ink, The advantage that FM screen is superior to AM screen from highlight to halftone is It is an object of the present invention to provide a gravure plate-making method that can avoid the occurrence of gravure, that it has the advantages of preventing line breaks even when printing five or more colors, that it can reproduce high-resolution prints, and that the density jump is inconspicuous. And According to the present invention, an FM screening is performed on plate information before forming a plate so that the minimum cell has a required size for performing good ink transfer. The digital information of the FM screen obtained by performing the above process is superimposed on the digital information of only the screen line of the shadow portion of the gravure plate of the AM screen, and a photosensitive film is formed based on the superimposed digital plate information. Expose and develop the plate forming surface, or laser ablate the plate forming surface on which a coating that can be laser ablated is formed, then etch the exposed metal surface by development or laser ablation, strip the resist, and remove the hard chrome It is intended to provide a gravure plate-making method characterized by providing plating. DETAILED DESCRIPTION OF THE INVENTION The gravure plate making method of the present invention is as follows.
For the plate information before forming the plate, FM so that the minimum cell is the required size for good ink transfer.
The digital information of the FM screen obtained by performing the screening is superimposed on the digital information of only the screen line of the most shadow part of the gravure version of the AM screen,
Based on the superimposed digital plate information, the plate-forming surface on which the photosensitive film is formed is exposed and developed, or laser-ablated on the plate-formed surface on which a film that can be laser ablated is formed, and then developed or The metal surface exposed by laser ablation is etched, the resist is stripped, and hard chrome plating is provided. The required size at which the minimum cell can transfer ink well is
Specifically, it is about 25 μm square. Embodiment 1 In FIG. 1, A1 indicates a case where a gradation of 0% to 100% is prepared as plate information before forming a plate.
This is a display of digital information on an FM screen obtained by performing M screening. B1 indicates digital information of only the screen line of the shadow portion of the gravure plate of the AM screen, regardless of the plate information before the plate is formed. C2 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. Second Embodiment In FIG. 2, when A2 prepares a gradation of 0% to 100% as plate information before forming a plate, the gradation is converted to FM by an FM screening program different from that of the first embodiment. This is a display of digital information on an FM screen obtained by performing screening.
B2 is AM irrespective of the plate information before forming the plate.
This is a display of digital information of only the screen line at the shadow portion of the gravure version of the screen. C2 is A2
Digital information of the FM screen shown in FIG.
This is a display of digital version information in which digital information of only the screen lines of the M screen is superimposed. The digital version information shown at C2 in FIG.
The three colors M and C were prepared. In this case, the minimum cell is required to have good ink transfer.
By a laser exposure device manufactured by CreoScitex of Canada, a laser beam that forms a square cell with a side of 28 μm by arranging four laser beams of 7 μm square in the vertical and horizontal directions so that the unit output can be performed, And corresponding to this, the minimum cell is square and one side is 28μ.
In order to obtain m, digital information of an FM screen was obtained by performing FM screening on plate information before forming a plate by inputting numerical values necessary for the FM screening program. Then, based on the digital color plate information of one color, the surface on which the positive photosensitive film is formed is exposed and alkali-developed, and then the exposed metal surface (copper-plated surface)
Was etched with a solution of cupric chloride, the resist was stripped with a strong alkaline solution, and a gravure plate having hard chromium plating was prepared for three colors, attached to a gravure rotary printing machine, and overprinted. 50
The density jump was not conspicuous at a concentration of about%. High-resolution print reproduction was achieved. Drying load was small and drying was performed smoothly. The outline of the character could be made an outline without jaggedness. The present invention includes a planographic plate in addition to a roll as a plate forming surface. The photosensitive film may be either a positive type or a negative type. As described above, the gravure plate making method of the present invention has the following effects. (1) Since the minimum number of cells is of a required size for good transfer of ink, the ink is filled in the cells in the very small highlight areas of the gravure AM screen formed by the etching method. The conventional disadvantage of poor transfer of ink due to clogging can be overcome. (2) The intersection of the AM screen lines in the uppermost shadow area can be a free flow cell that lacks ink so that ink flows, and the ink can transfer to the intersection reliably, and the outline of the character is an outline without jagged edges. It is possible to continue to enjoy the conventional advantage that it is suitable for printing using water-based ink because the cells in the shadow portion are shallow. In addition, the advantages of the screen that can be enjoyed by offset printing or the like can also be enjoyed by the gravure version. (3) The advantages of the FM screen from the highlight area to the halftone area compared to the AM screen are that moiré can be avoided, line breaks do not occur even when printing five or more colors, and high-resolution print reproduction is achieved. You can enjoy the advantages of being able to do it and making the density jump inconspicuous. (4) Since a conventional large cell is formed by being divided into a plurality of minimum cells, the ink film thickness is reduced, the drying load is reduced, and higher-speed printing is possible. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 relates to a gravure plate making method according to the present invention, and digital version information C1 is superimposed on digital information A1 of an FM screen and digital information B1 of only a screen line of a gravure AM screen. FIG. 7 is a diagram for explaining that it is obtained. FIG. 2 relates to a gravure plate making method of the present invention, and is intended to explain that digital information A2 of an FM screen and digital information B2 of only screen lines of a gravure AM screen are superimposed to obtain digital plate information C2. FIG. FIG. 3 is a diagram showing a conventional AM screen of a conventional gravure plate. FIG. 4 shows a normal A used for conventional offset printing and the like.
The figure which shows an M screen. FIG. 5 is a diagram showing an FM screen used for conventional offset printing and the like. FIG. 6 shows another FM used for conventional offset printing and the like.
The figure which shows a screen.

Claims (1)

Claims: 1. A screen obtained by performing screening on plate information before forming a plate such that a minimum cell has a required size for performing ink transfer favorably. Digital information is superimposed on digital information of only the screen line of the shadow part of the gravure version of the screen,
Based on the superimposed digital plate information, the plate-forming surface on which the photosensitive film is formed is exposed and developed, or laser-ablated on the plate-formed surface on which a film that can be laser ablated is formed, and then developed or A gravure plate making method comprising etching a metal surface exposed by laser ablation, stripping a resist, and then providing hard chromium plating.