JPH1120116A - Method for gravure printing and gravure printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain gravure printed matter having an image quality being close falsely to the one of the gravure printed matter according to an etching method, adopting a physical engraving method. SOLUTION: Character-line drawing data LW and gradation image data CT are prepared, a logocombine device 100 divides them into four engravings of CMYK and executes a combine processing for synthesizing the two data after a face bonding processing and a filter processing (sharpness processing) and thereby divided-engraving synthesis data C1, M1, Y1 and K1 are obtained. After conversion of resolution is conducted, in succession, noise addition is conducted by a noise addition device 200, cell engraving is conducted by a cell engraving device 300 and thereby engravings of four colors are obtained. Since a noise component increasing or decreasing in a period being about 2-3 times the period of a pixel pitch is added in the noise addition device 200, the noise component having a spatial frequency being about 2-3 times the pitch of a halftone dot appears in a spatial distribution of the size of the individual halftone dot.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gravure printing method and a gravure printed matter, and more particularly, to driving an engraving needle (diamond needle) or a laser based on an electric signal.
The present invention relates to a technique for producing a gravure print by forming an intaglio using a so-called electronic engraving method of engraving a large number of cells on a plate cylinder surface and performing printing using the intaglio.

[0002]

2. Description of the Related Art Gravure printing is a printing method using an intaglio printing, and is mainly used for producing high-quality printed matter including photographic images. A plate used for gravure printing has a large number of concave cells, and the ink filled in the cells is transferred to the paper surface. Therefore, in a gravure print, an image is formed by a large number of cellular inks (dots). In other words, the image formed on the paper by gravure printing is
It is composed of a number of halftone dots arranged in a vertical and horizontal direction at a predetermined pitch, and shades are expressed by the ink amount of each halftone dot.

When performing gravure printing, an original image composed of a large number of pixels is prepared, and the pixel values (density values) of the pixels on the original image are converted into the size of a cell.
An intaglio in which one pixel is represented by one cell is created. Pixels having large pixel values are converted to large cells, and pixels having small pixel values are converted to small cells. The size of this cell is reflected in the amount of ink on the paper surface, and a light and shade pattern corresponding to the density distribution of the original image is reproduced on the paper surface.

[0004] As a method for forming an intaglio for gravure printing, a physical engraving method and a chemical corrosion method are generally known. The physical engraving method is a method in which cells are formed by a physical method. Usually, cells are engraved by driving an engraving needle (diamond needle) or a laser based on an electric signal. It is also called a method. The most common physical engraving method is a method using an engraving needle called a mechanical engraving method. The mechanical engraving method employs a method in which individual cells are physically engraved one by one with diamond needles. Normally, engraving is performed while scanning the plate surface with multiple diamond needles. Become. By controlling the distance between the diamond needle and the plate surface during embossing,
The size of the cell formed by embossing can be adjusted. By controlling the scanning process and the embossing process by the cell engraving device based on the pixel arrangement and pixel value of each pixel on the original image, a plate corresponding to the original image can be created.

On the other hand, the chemical corrosion method is generally called a "net gravure method", and a large number of cells are collectively formed on a plate surface by a chemical treatment using a corrosive liquid. Usually, based on the information of each pixel on the original image,
An image of the cell array is output on the halftone film, and a plate is created by a photolithography process using the halftone film. That is, an image on a halftone dot film is printed on the resist layer formed on the plate surface, and through a developing step and an etching step, the area inside the cell is removed by corrosion to form a concave portion.

[0006]

As described above, there are two known methods for forming an intaglio for gravure printing. Recently, however, a physical engraving method represented by a mechanical engraving method has been known. Methods are becoming mainstream. Since the corrosion method involves chemical treatment, the state of corrosion varies depending on the temperature of the etchant and the degree of fatigue, and there is a problem that it is difficult to ensure reproducibility. Further, even on the same plate surface, there is a possibility that a difference in the corrosion rate occurs between the portions depending on the flow of the etching solution, and the size of the cells formed is not uniform among the portions. Therefore, in order to prepare a plate by the corrosion method, it is necessary for a skilled technician to work while making full use of unique know-how. On the other hand, in the mechanical engraving method, the performance of the electronic cell engraving apparatus has been improved, and reproducibility has been relatively easily ensured. In addition, the corrosive method has been pointed out as a problem of environmental pollution due to chemical treatment. In particular, in most European countries, most gravure printing is performed by a mechanical engraving method.

[0007] However, many designers and photographers still support the image quality of gravure prints of the corrosion type. Of course, it is not appropriate to compare and evaluate the image quality of the gravure print by the mechanical engraving method and the image quality of the gravure print by the corrosion method on an objective scale. The difference between the two is merely a matter of subjective taste, and the evaluation often depends on the sensitivity of the viewer. However, according to such a subjective evaluation, the gravure printed matter of the corrosion method is "rich in three-dimensional feeling", "excellent in expressing human skin", and "unpleasant" compared to the gravure printed matter of the mechanical engraving method. It is said that the muscle is hard to be observed. " Further, in a gravure printed matter by a mechanical engraving method, when a pixel value exceeds a predetermined threshold value, ink between adjacent cells is combined, and a phenomenon called a tone jump in which a density value rapidly increases occurs, thereby deteriorating image quality. It is also known.

Accordingly, an object of the present invention is to realize a gravure print having an image quality close to that of a gravure print of a pseudo chemical corrosion type while employing a physical engraving method represented by a mechanical engraving method. I do.

[0009]

[Means for Solving the Problems]

(1) A first aspect of the present invention is a method for producing an intaglio by engraving a plurality of cells arranged at a predetermined pitch, and performing printing using the intaglio, an image to be printed. A step of preparing character / line drawing data representing a character and a line drawing part; a step of preparing gradation image data representing a gradation image part of an image to be printed; Performing combine processing for combining with the gradation image data to create combined data composed of a large number of pixels, and adding correction data by adding a noise component to the pixel value of each pixel constituting the combined data. Creating an intaglio by engraving a cell having a size corresponding to the pixel value of each pixel constituting the correction data; and performing printing using the intaglio. That's how it works.

(2) The second aspect of the present invention is the above-mentioned first aspect.
In the gravure printing method according to the aspect, a color separation process of dividing character / line image data for each predetermined color component, and a color separation process of dividing gradation image data for each predetermined color component are performed.
Combine processing is performed on the separated data for each color component, and a process of independently adding a noise component to each of the composite data for each color component is performed.

(3) A third aspect of the present invention is the above-mentioned first aspect.
Alternatively, in the gravure printing method according to the second aspect, a filtering process for increasing or decreasing a predetermined spatial frequency component is performed on one or both of the character / line drawing data and the gradation image data. After performing the combine process, a process of adding a noise component is performed.

(4) The fourth aspect of the present invention is the above-mentioned first aspect.
In the gravure printing method according to the third aspect, after performing the combine process, the process of converting the resolution of the pixels constituting the composite data is performed, and a noise component is added to the composite data after the resolution conversion. The processing is performed.

(5) The fifth aspect of the present invention is the above-mentioned first aspect.
-The gravure printing method according to the fourth aspect,
Line drawing data is prepared in the form of run-length data composed of a set of data indicating a predetermined pixel value and the length of a pixel column having the pixel value, and the gradation image data has a predetermined pixel value. It is prepared in the form of bitmap data composed of a pixel array.

(6) The sixth aspect of the present invention is the above-mentioned first aspect.
In the gravure printing method according to the fifth to fifth aspects, correction data is created by adding a noise component having a cycle of 2 to 5 times the pitch of each pixel constituting the composite data to each pixel value. It was made.

(7) The seventh aspect of the present invention is the above-mentioned first aspect.
In the gravure printing method according to the fifth to fifth aspects, a cell engraving apparatus having an embossing controller for mechanically engraving a cell by supplying a voltage corresponding to given digital data to a needle driving unit, A voltage variation device having a function of varying the voltage to be supplied is prepared, a correction data is created by adding a noise component to the synthesized data, and instead of the process of engraving a cell based on the correction data, The combined data is supplied to the embossing controller, and the voltage variation device performs a process of changing the voltage supplied by the embossing controller, thereby adding a noise component.

(8) The eighth aspect of the present invention is the above-mentioned first aspect.
A gravure print is created by the gravure printing method according to the seventh to seventh aspects.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS §1. Difference in Cell between Mechanical Engraving Method and Corrosion Method Hereinafter, the present invention will be described based on an embodiment shown in the drawings.
First, the difference in cell configuration between a general mechanical engraving type gravure print and a corrosion type (net gravure type) gravure print will be described. FIG. 1 is a partially enlarged view of a gravure printing plate created in a process of a mechanical engraving method, and FIG. 2 is a partially enlarged view of a gravure printing plate created in a process of a corrosion method. The original image data has a dot density of 60%
, And the area of the cell (the area hatched in the figure) is approximately 60% of the whole. The width shown is about 900 μm, and the presence of individual cells cannot be generally recognized when visually observed. However, when this is enlarged and observed, it can be seen that there is a large difference in the shape and distribution of the cells in the plates prepared by both methods.

As shown in FIG. 1, cells having the same shape and size are regularly arranged at the same pitch on a plate prepared by a mechanical engraving method. this is,
As described above, this is because regular engraving is performed while scanning the plate surface with a plurality of diamond needles. Therefore, in the case of a flat screen image as in the example shown here, cells having the same shape and the same area are regularly arranged. The above-mentioned phenomenon of tone jump is a phenomenon caused by such a regular arrangement of cells. That is, when the halftone dot density exceeds a certain threshold, the area of each cell exceeds a critical value, and the ink between adjacent halftone dots on a printed material is mutually bonded, and the borderline of halftone dots is lost. As a result, the density value increases rapidly.

On the other hand, as shown in FIG. 2, cells having different shapes and sizes are arranged on the plate prepared by the corrosion method, even though the original image is a flat screen. I have. The individual cells vary in shape and shape, ranging from tiny ones to quite large ones. However, this is because corrosion is performed based on a combined pattern obtained by combining a so-called “white line pattern” with a normal cell pattern. When the pattern shown in FIG. 2 is carefully observed, a white line pattern (a grid-like pattern that divides cells) overlaps a cell pattern (a pattern shown by hatching) arranged at a predetermined pitch. Can be recognized. Generally, the pitch of the grids constituting the white line pattern is set smaller than the pitch at which the cells are arranged, and the individual cells are divided in various ways by the white line pattern. In the example shown in FIG. 2, traces of cells divided into four, three, or two can be recognized in some places. Since there are various division modes by the white line pattern, individual cells after division have various shapes and sizes.

In the end, when the plate is prepared by the corrosion method, the original image pattern prepared on the halftone film is a composite pattern of a cell pattern arranged at a predetermined pitch and a white line pattern, This means that the cell is composed of many cells having different shapes and sizes. In addition, in the actual corrosion process, the temperature, fatigue level, flow rate, etc. of the corrosive liquid fluctuate from part to part, and the shape and size of each cell formed on the plate may vary from part to part. Elements will be added. Eventually, the individual cells on the plate created by the corrosion method have various shapes and sizes due to the synergistic effect of the fluctuation element based on the division mode by the white line pattern and the fluctuation element based on the conditions during the corrosion process. Become something.

As described above, since cells having various shapes and sizes are formed in the plate prepared by the corrosion method, the phenomenon of tone jump does not occur on a gravure print using this plate. FIGS. 1 and 2 show an example in which the original image is a flat screen image. However, when the original image is a gradation image, it may be considered that there is a difference in image quality for the same reason. In other words, in general, the advantages of the corrosion method expressed by words such as "rich in three-dimensional effect", "excellent expression of human skin", and "unpleasant muscles are hard to be observed" depend on the shape and size of the cell. It can be considered that a fluctuation element (fluctuation of division by the white line pattern and fluctuation of corrosion condition) is added.

§2. Basic concept of the present invention The object of the present invention is to realize a printed material having an image quality similar to a gravure printed material of a pseudo chemical corrosion type while employing a physical engraving method which is easy to work and has no problem of environmental pollution. Is to do. For this purpose, the above-described fluctuation element may be added in a pseudo manner. The basic concept of the present invention is to prepare an original image composed of an array of pixels having a predetermined pixel value, and add a noise component to the pixel value of each pixel constituting the original image, thereby causing a fluctuation element. Creates a gravure printing plate by engraving a cell of a size corresponding to the pixel value of each pixel constituting this modified image, and adopts a physical engraving method. Another object of the present invention is to simulate a printed matter having an image quality close to that of a gravure printed matter of a corrosion type.

Now, in order to compare the size distribution of the cells between the plate prepared by the mechanical engraving method shown in FIG. 1 and the plate prepared by the corrosion method shown in FIG. Consider a graph. In this graph, the horizontal axis indicates the spatial spread, and the vertical axis indicates the cell size. Here, the dashed line in the graph indicates the cell size distribution for the plate of the flat screen image created by the mechanical engraving method, and the solid line of the graph indicates the plate for the plate of the flat screen image created by the corrosion method. 9 shows a cell size distribution. As shown in the figure, in the case of the mechanical engraving method, the size of the cell is spatially constant, whereas in the case of the corrosion method, the size of the cell varies spatially and randomly.

The size of each cell stamped by the diamond stylus is determined according to the pixel value of the corresponding pixel. Therefore, the pixel value of each pixel constituting the original image is
If a corrected image is created by adding a noise component, the size of the cell will be spatially fluctuated on the plate created based on the corrected image. For example, the graph shown in FIG. 4 shows the spatial distribution of pixel values for an original image consisting of a flat screen image and a corrected image obtained by adding a noise component to the original image. Here, the pixel value is an amount corresponding to the size of the cell, and the cell on the plate created based on this corrected image also has a spatially varying size. When the original image is a gradation image, as shown in the graph of FIG. 5 (in this example, a graph for a monotonous gradation image), the pixel value in the original original image also varies spatially. In addition, the pixel value of the corrected image to which the noise component has been added shows more minute fluctuation.

§3. Of the gravure printing method according to the present invention
One embodiment Figure 6 is a block diagram showing a system configuration example for implementing the gravure printing method according to the present invention. To perform gravure printing using this system, first, characters and line drawings representing characters and line drawings in the image to be printed
Line drawing data LW and gradation image data CT representing a gradation image portion are prepared. Character / line drawing data LW (data about the part generally called Line Work)
Is image data of a character portion having no gradation and a portion drawn by a line having no gradation in the entire image, whereas the gradation image data CT (generally, Continuous Ton)
e) is image data of a portion having continuous tone generated mainly based on a photographic original. In the gravure printing process,
Usually, the character / line drawing data LW and the gradation image data CT are separately prepared as described above.

Each of the data is data representing an image in a so-called raster format (a format composed of a large number of pixels). In the present embodiment, the character / line drawing data LW is used.
Are composed of run-length data, whereas the gradation image data CT is composed of bitmap data. The run-length data is data indicating a predetermined pixel value and the length of a pixel column having the pixel value. For example, the unit data of (a, b) causes a pixel having a pixel value a to be continuous for b pixels. Can be shown. Since an image represented by the character / line drawing data LW does not have a continuous tone, a plurality of pixels having the same pixel value are often arranged continuously. For this reason,
With respect to the line drawing data LW, the data amount can be reduced by adopting a run-length data format. On the other hand, since the image represented by the gradation image data CT is an image having continuous gradation like a photographic image, it takes the form of bitmap data composed of a pixel array having a predetermined pixel value. (Of course, it is possible to adopt a format compressed using data compression technology).

The character / line drawing data LW and the gradation image data CT prepared in this way are stored in the logo combine device 100.
And necessary processing is performed based on the operation of the operator. This logo combine device 100 itself,
This is a known device used in general gravure printing. The logo combine device 100 shown in FIG. 6 includes a separation processing unit 110, an imposition processing unit 120, a filter processing unit 1
30, combine processing unit 140, resolution conversion processing unit 15
It has 0.

The separation processing unit 110 stores the character / line drawing data L
W is divided for each color component of CMYK, and separated character / line image data LW (C), LW (M), LW (Y), L
The process of generating W (K) and converting the gradation image data CT to C
A process of generating divided tone image data CT (C), CT (M), CT (Y), and CT (K) which are divided for each of the MYK color components. The subsequent steps are performed for each of the separation data (for each color component).

The imposition processing section 120 has a function of performing imposition processing for each piece of separation data. For example, when printing four pages of printed matter using one plate, four-sided layout is performed in which image data for four pages are arranged on the same plane. Subsequently, the filter processing in the filter processing unit 130 is performed for each of the separation data. This filter processing is processing for increasing or decreasing a predetermined spatial frequency component of image data. The most typical filter processing is a so-called “sharpness processing” that enhances a contour line. Since such a filtering process is a known technique, a detailed description is omitted here. Next, in the combine processing unit 140, a combine process of combining the separated character / line drawing data and the separated gradation image data for each color component is performed, and the separated combined data C1, M1, Y1 and K1 are created. For example, the separated composite data C1 is combined data relating to the color component C, and is obtained by combining separated character / line drawing data LW (C) and separated gradation image data CT (C). Can be In this embodiment, the character / line drawing data LW and the gradation image data CT are prepared in the form of raster data having the same pixel arrangement. This is performed by a process of superimposing the data CT on the upper surface of the layer. That is, the gradation image data CT appears only in a transparent portion in the image corresponding to the character / line drawing data LW.

Subsequently, in the resolution conversion processing section 150, resolution conversion is performed on each of the separated composite data C1, M1, Y1, and K1. This separation composite data C1, M
1, 1, and 1 are data obtained by separating the character / line drawing data LW and the gradation image data CT in the first place, and therefore have the same resolution at this time.
However, in performing gravure printing, if the color separation images have the same resolution, the halftone dot pitch of each color component becomes the same, which may cause adverse effects such as generation of moire fringes due to interference. Therefore, a resolution conversion process is performed for each of the separated images of each color component so that different resolutions can be obtained. This resolution conversion processing is, specifically,
This is performed by a process of thinning out the number of pixels at predetermined intervals. For example, if a process is performed in which four pixels are replaced with one pixel and the average of the original four pixel values is used as the new pixel value, an image having a resolution of 1/4 can be obtained. Can be. The separated composite data C2, M2, Y2, and K2 are image data after the resolution conversion is performed.

As a result, when the character / line drawing data LW and the gradation image data CT are given to the logo combine device 100, finally, the color separation combined data C2, M2, Y2, K2 having their own resolutions are obtained. Will be done.
In the conventional general gravure printing method, based on the color separation composite data C2, M2, Y2, and K2 thus obtained,
The cell engraving operation is performed, but in the present invention, a noise adding process is performed before that. That is,
Separated composite data C2, M2, Y2, and K2 output from the logo combine device 100 are input to the noise adding device 200, and after adding a noise component, the separated composite data C3, M3, Y3, and K3. And output to the cell engraving apparatus 300. The process of adding a noise component is performed separately and independently for each separation data. The cell engraving apparatus 300 separates the separated composite data C including the noise component.
3, M3, Y3, and K3 (image data corresponding to the corrected image shown in FIG. 4 or FIG. 5), a stamping operation using a diamond stylus is performed, and a C plate, an M plate, a Y plate,
A process for creating each gravure printing plate of the K plate is performed. That is, a cell having a size corresponding to the pixel value of each pixel is formed on the plate at a pitch indicated by the pixel array of each image data.

§4. Here the spatial frequency of the noise component to be added in advance to consider the spatial frequency of the noise component to be added at the noise adding unit 200 in the system shown in FIG.

The simplest way to add a noise component is
A method of randomly generating an increment value and a decrement value within a predetermined variance range, and adding a generated increment value to the pixel value of each pixel or performing a correction to reduce the generated decrement value. is there. For example, using a normal distribution having a predetermined variance as shown in FIG. 7, a reference value 0 is defined at the center position indicating the average, an increment value is defined on the right side of this reference value, and a decrement value is defined on the left side. I do. Then, a computer generates a random number, randomly generates an increment value or a decrement value at a frequency according to the normal distribution, and increases or decreases the pixel value of each pixel. More specifically, each separated composite data C output from the logo combine device 100
For each of 2, 2, M2, Y2, and K2, a process of adding a predetermined increment value to the pixel value of each pixel or reducing the decrement value may be performed. If cells are formed based on the separated composite data C3, M3, Y3, and K3 to which noise components have been added by such a method, random noise components are added to the spatial distribution of cell sizes. Will be.

However, the method of increasing or decreasing the pixel value completely at random does not always provide a sufficient effect. For example, for pixels in a certain area,
If the correction by the increment value happens to be performed in a concentrated manner, and the pixels in another area happen to be corrected by the decrement value in a concentrated manner, density unevenness will occur in each area. . To avoid such adverse effects,
It is preferable to prepare a noise component that increases or decreases at a predetermined spatial frequency and make the correction. For example, consider the noise component shown in the graph of FIG. Here, the horizontal axis of the graph indicates the spatial spread, and the vertical axis indicates the increment or decrement of the noise component. In this example, the noise component increases and decreases spatially with a period L. In other words, if a certain area indicates an increment value, an adjacent area indicates a decrement value. As described above, when a noise component that repeatedly increases and decreases at a predetermined spatial frequency is used,
A more sufficient effect can be expected as compared to a case where a noise component that increases and decreases at all is used.

The present inventor has found that it is effective to use a noise component having a period of 2 to 5 times the cell pitch. In particular, it is very effective to add a noise component having a period of two to three times the cell pitch. For example, assuming that the period L of the noise component shown in FIG. 8 is about twice the cell pitch, one cell becomes larger than the reference value, and cells adjacent thereto become smaller than the reference value. As described above, a cell configuration in which the size is alternately repeated is very effective for obtaining the effects of the present invention. According to an experiment conducted by the inventor of the present application, when the spatial frequency of the noise component to be added is low, a so-called rough feeling is seen in an image reproduced on a printed matter. That is, it is preferable that the spatial frequency of the noise component to be used is as close as possible to the spatial frequency of the cell arrangement, and the more the noise component having a lower spatial frequency is used, the more grainy the image quality becomes. This is thought to be related to the fact that in normal gravure printing, the cell pitch is set to a value that makes it difficult to observe individual cells with the naked eye, for example, (1/175) mm. Can be
In other words, if the spatial frequency of the noise component is made substantially equal to the spatial frequency of the cell, the noise component will not be recognized by the naked eye, and a natural image can be reproduced.
If the spatial frequency of the noise component is lowered, the noise component will be recognized by the naked eye, and it is considered that a rough feeling is generated.

In the gravure printing method according to the present invention, as shown in the system of FIG. 6, the separated composite data C2, M output from the logo combine device 100.
The noise adding device 200 performs a noise adding process on the noise adding device 2, Y2, and K2. In other words, after various image processing by the logo combine device 100 is completed,
A noise component is added. in this way,
It is important to perform the processing of adding a noise component after performing the processing by the logo combine apparatus 100, since it does not adversely affect the various processing by the logo combine apparatus 100.

Of course, it is also possible to perform a process of adding a noise component to the character / line drawing data LW and the gradation image data CT before inputting to the logo combine device 100. However, as described above, the noise component to be added preferably has a cycle of about 2 to 3 times, or about 2 to 5 times the cell pitch. Therefore, the character / line drawing data LW and the gradation image data CT are preferable. If a noise component is added in advance to the image combiner, the noise component may affect image processing in the logo combine device 100. For example, the filter processing (particularly, sharpness processing) in the filter processing unit 130 and the resolution conversion processing in the resolution conversion processing unit 150 are processings that change the spatial frequency of image data. If it is included, it will be affected by this noise component in some way, and the processing as expected may not be performed. From this viewpoint, as shown in the system of FIG.
After all the processing at 0 is completed, it is preferable to perform a noise component addition processing as a final step.

§5. Specific Noise Component Addition Processing Here, a specific method for adding a noise component to an original image is proposed. Now, consider a case where an original image P is prepared as a pixel array of M rows and N columns as shown in FIG. A predetermined pixel value is defined for each pixel constituting the original image P. Here, the pixel value of the pixel in the m-th row and the n-th column on the original image P is P (m,
n). For such an original image P,
A correction noise image A as shown in FIG. 9B is prepared.
The noise image A for correction has M rows N as in the original image P.
For example, a pixel value A (m, n) is defined for a pixel in the m-th row and the n-th column. If such a correction noise image A can be prepared, the pixel value of each pixel on the original image P is converted to the correction noise image A.
By correcting with the pixel value of the pixel at the corresponding position above, a corrected image P ^{* including} a pixel array of M rows and N columns can be obtained as shown in FIG. 9C. The pixel value of the pixel in the m-th row and the n-th column on the corrected image P ^* is P ^* (m,
n), this pixel value P ^* (m, n)
Can be determined, for example, by the following equation: P ^* (m, n) = P (m, n) + A (m, n). Of course, the pixel value P
The expression for defining ^* (m, n) is not limited to the above expression, and P ^* (m, n) = f (P (m, n), A (m , N)) may be used.

The modified image P obtained by such a method
The characteristics of ^* largely depend on what correction noise image A was used. The inventor of the present application initially considered using the most typical white noise image as the correction noise image A. For example, as shown in FIG. 10, if a pixel array of M rows and N columns is defined and a completely random value is defined as a pixel value of each pixel (for example, a random number generated for each pixel is directly converted to a pixel value ), A white noise image W is obtained. In the white noise image W, the pixel value W (m, n) of the pixel in the m-th row and the n-th column is a noise value defined completely independently of the pixel values of the other pixels. Such a spatial distribution of pixel values of the white noise image W includes all spatial frequency components. For example, in FIG. 10, when the pixel values of a plurality of pixels arranged in the m-th row are taken as a one-dimensional distribution and a graph showing the spatial variation of the pixel values is subjected to Fourier transform, a theoretical value determined based on the resolution of the pixels is obtained. A substantially uniform spatial frequency distribution is obtained over the entire range of possible spatial frequencies.

However, when such a white noise image W is used as it is as the correction noise image A, a so-called rough feeling is observed in the finally obtained gravure print, which is not always a preferable result. As described above, it is preferable that the spatial frequency of the noise component added in the present invention be as close as possible to the spatial frequency of the cell arrangement. The inventor of the present application has noticed that a noise image having a frequency component close to the spatial frequency of a cell can be generated by performing a filtering process using a predetermined spatial filter on the white noise image W,
It has been found that by using the noise image after the filtering process as the noise image A for correction, a favorable result as the present invention can be obtained.

For example, a spatial filter F of 3 rows and 3 columns as shown in FIG. 11 is defined for application to a white noise image W having a pixel array of M rows and N columns shown in FIG. Here, the rows of the spatial filter F are represented by α = −1,
0,1 and the column is represented as β = -1,0,1.
The filter value defined at the position of α row and β column is φ (α, β)
Will be expressed as Such a spatial filter F is shown in FIG.
As shown in FIG. 2, the method is applied to the pixel on the m-th row and the n-th column on the white noise image W, and A (m, n) = Σ (φ (α, β) · W (m + α, n +
β)) (where Σ is the sum of α = −1, 0, 1 and β = −1, 0, 1) to obtain a new pixel value A (m, n). The correction noise image having the pixel value A (m, n) may be used as the correction noise image A shown in FIG. Since the noise image for correction A obtained after such filtering processing is a noise image having a frequency component close to the spatial frequency of the cell, the original image P is converted to the corrected image P ^* using the noise image for correction A.
When converted to gravure, a gravure print having a natural image quality without a rough feeling can be obtained.

FIG. 13 is a diagram showing a specific example of the filter value of the spatial filter F actually used by the present inventor. When such a spatial filter F is used, the pixel value A (m, n) at the m-th row and the n-th column is A (m, n) = (− 3/16 · W (m−1, n−
1)) + (− 5/16 · W (m−1, n)) + (− 1 /
16 · W (m-1, n + 1)) + (− 7/16 · W
(M, n-1)) + (1 · W (m, n)).

Note that when performing the above-described calculation, usually, a first pixel array for storing the white noise image W,
A second pixel array for storing the correction noise image A is prepared, and while the pixel value W (i, j) in the first pixel array is read and referred to, the right side of the above expression is calculated. , The resulting pixel value A (i, j) is written into the second pixel array.

In the system shown in FIG. 6, if the noise addition processing based on the above-described method is to be performed, the color separation combined data C output from the logo combine device 100 is used.
2, M2, Y2, and K2 are used as the original images P shown in FIG. 9A, respectively, and a correction noise image A shown in FIG. The obtained corrected image P ^* becomes the separation composite data C3, M3, Y3, and K3 to be given to the cell engraving device 300.

§6. Adding analog noise components
The noise adding device 200 shown in FIG. 6 is a device that digitally adds a noise component. That is, in the noise adding device 200, a noise component is added to digital image data composed of many pixels by increasing or decreasing the pixel value of each pixel. However, the addition process of the noise component in performing the gravure printing method according to the present invention is not necessarily performed digitally,
It is also possible to carry out in an analog manner. In this case, instead of using the noise adding device 200 shown in FIG. 6, when the cell engraving device 300 performs the embossing operation, means for adding a noise component in an analog manner may be provided.

FIG. 14 shows a general cell engraving apparatus 300.
FIG. 13 is a block diagram showing a configuration example in which a voltage variation device 400 is added to realize analog noise component addition processing. In the cell engraving device 300, an embossing controller 310 for supplying a voltage corresponding to the given digital data, a needle driving unit 320 operated by a supply voltage from the embossing controller 310, and a needle driving unit 320 A diamond needle 330 that is driven and performs an embossing operation is provided. (In addition, a mechanism that scans the plate surface to be embossed with the diamond needle 330 is provided. Is omitted).
The needle driving unit 320 controls the pivot 335 of the diamond needle 330 according to the voltage given from the embossing controller 310.
It has the function of adjusting the distance between the plate and the printing plate, and the function of embossing by swinging the diamond needle 330 in the direction of the arrow at a predetermined cycle. More specifically, if the supply voltage from the embossing controller 310 is large, the diamond needle 3
The control is performed such that the pivots 335 of the 30 are brought closer to the printing plate, and the control is performed to move the pivots 335 away from the printing plate if the supply voltage is small. As a result, when a large voltage is supplied, a large cell is stamped, and when a small voltage is supplied, a small cell is stamped.

The embossing controller 310 has a function of supplying a voltage of a magnitude corresponding to the given digital data (pixel value) to the needle driving section 320. That is, when large digital data is given to the cell engraving apparatus 300, a large cell is stamped, and when small digital data is given, a small cell is stamped. Therefore, if data having a digitally added noise component is given to the cell engraving apparatus 300, cells having a noise distribution added to the size distribution are formed on the printing plate.

However, if the voltage supplied by the embossing controller 310 is changed in an analog manner by the voltage fluctuation device 400, a noise component can be added at the time of embossing by the cell engraving device 300. In this case, the digital data given to the cell engraving device 300 is
It is not necessary to include a noise component. That is, in the system shown in FIG. 6, the color separation combined data C2, M2, Y2, and K2 output from the logo combine device 100 are
What is necessary is just to give to the cell engraving apparatus 300 as it is. As described above, the noise component to be added in the present invention preferably has a period of 2 to 5 times the cell pitch.
Preferably, the period is up to three times. Therefore, as the voltage fluctuation device 400, 1
In consideration of the stamping cycle of one cell, a circuit that generates a voltage fluctuation having a cycle of about 2 to 5 times or about 2 to 3 times thereof may be used.

§7. Above gravure printed matter according to the present invention, the gravure printing method according to the present invention has been described,
Here, the features of the gravure printed matter obtained by such a printing method will be described.

FIG. 15 is a partially enlarged view showing an example of a gravure printing plate prepared by the above-described method. The example shown here shows the cell configuration of a portion corresponding to a flat screen having a halftone dot density of 60%, similarly to the example shown in FIG. As is apparent from comparison with the plate shown in FIG. 1 made by the conventional machine engraving method, in the plate shown in FIG. 15 made by the machine engraving method of the present invention, the size of each cell varies spatially. doing.

When printing is performed using such a gravure printing plate, a printed matter having an image quality close to that of a gravure printed matter prepared by the corrosion method can be obtained. FIG. 16 is a partially enlarged view of a printed matter created by using the gravure printing plate shown in FIG. 1, and FIG. 17 is a partially enlarged view of a printed matter created by using the gravure printing plate shown in FIG. The shape of each halftone dot on the gravure printing material is slightly different from the shape of each cell on the gravure printing plate, but this is because the ink accumulated in the concave cells is transferred to the paper and It is based on the physical behavior of the ink when formed.

As described above, although the individual cells and the individual halftone dots have slightly different shapes, the positions and the sizes are in a mutually corresponding relationship. 16 and 17, the halftone dot pitch is the same for both, but there is a great difference in the size of each halftone dot. That is, in the conventional gravure printed matter shown in FIG. 16, the size (area) of each halftone dot is almost constant, while
In the gravure print of the present invention, a noise component having a period of about two to three times the pitch of the halftone dots is added to the spatial distribution of the size of each halftone dot. For example, to examine the one-dimensional spatial distribution, as shown in FIG.
When an arbitrary coordinate axis Z is defined and attention is paid to the size distribution of the halftone dots arranged on the coordinate axis Z, the size of the halftone dot increases with a period of about two to three times the arrangement pitch of the halftone dots. It can be seen that the size has changed or has become smaller. That is,
This means that randomness is added to the size of the halftone dot.

Here, for the sake of convenience of explanation, an example of a plain halftone portion (portion indicated by character / line drawing data LW) has been described, but a gradation portion (portion indicated by gradation image data CT) may also be used. A similar effect that the size of each cell varies spatially is obtained. In particular, for the gradation portion, by applying the method of the present invention, features of the corrosion method such as "rich in three-dimensional feeling", "excellent in human skin expression", and "unpleasant streaks are hard to be observed". Can be reproduced, and an image quality very close to that of a gravure print produced by the corrosion method can be obtained despite the gravure print produced by the mechanical engraving method.

Although the present invention has been described based on the illustrated embodiments, the present invention can be implemented in various other forms. In particular, the method of adding a noise component is not limited to the method described in the above embodiment, and various other methods can be adopted.

In the above-described embodiment, a description has been given of an example of a mechanical engraving method in which a large number of cells are formed on the plate body surface by engraving using an engraving needle (diamond needle) to form an intaglio. However, the gravure printing method according to the present invention,
It is not always premised that intaglio printing is performed by a mechanical engraving method. The basic technical idea of the present invention is to obtain image quality close to that of gravure printing in which cells are formed by a chemical method, even though gravure printing in which cells are formed by a physical method. Therefore, the cell forming method in the present invention is not limited to the mechanical engraving method, and any method may be adopted as long as the cells can be formed by a physical method. The present invention
For example, the present invention is also applicable to a gravure printing method of engraving cells using a laser, and is widely applicable to a gravure printing method of forming cells by a so-called electronic engraving method.

[0056]

As described above, according to the gravure printing method according to the present invention, after combining character / line drawing data and gradation image data, a cell is formed by adding a noise component to the combined data. Therefore, it is possible to obtain a printed matter having an image quality similar to that of a gravure printed matter of a pseudo chemical corrosion type while employing a physical engraving method.

[Brief description of the drawings]

FIG. 1 is a partially enlarged view of a gravure printing plate created in a process of a mechanical engraving method.

FIG. 2 is a partially enlarged view of a gravure printing plate prepared in a corrosion-based process.

FIG. 3 is a graph for comparing cell size distributions of a plate prepared by a mechanical engraving method and a plate prepared by a corrosion method.

FIG. 4 is a graph showing a spatial distribution of pixel values of an original image composed of a flat screen image and a corrected image obtained by adding a noise component to the original image.

FIG. 5 is a graph showing a spatial distribution of pixel values of an original image composed of a gradation image and a corrected image obtained by adding a noise component to the original image.

FIG. 6 is a block diagram showing an example of a configuration of a system used to execute a gravure printing method according to the present invention.

FIG. 7 is a graph showing noise components of a normal distribution used in the gravure printing method according to the present invention.

FIG. 8 is a graph showing noise components having a predetermined spatial frequency used in the gravure printing method according to the present invention.

FIG. 9 is a diagram showing a basic principle of a noise component adding process based on the method of the present invention.

FIG. 10 is a diagram showing a white noise image W used to generate the correction noise image A shown in FIG. 9 (b).

11 is a diagram showing an example of a spatial filter F applied to the white noise image W shown in FIG.

FIG. 12 shows a white noise image W shown in FIG.
FIG. 3 is a diagram showing a state in which the spatial filter F shown in FIG. 1 is applied.

FIG. 13 is a diagram illustrating an example in which specific numerical values are defined for the spatial filter F illustrated in FIG. 11;

FIG. 14 is a block diagram illustrating a configuration example for adding a noise component in an analog manner.

FIG. 15 is a partially enlarged view showing an example of a gravure printing plate created by the gravure printing method according to the present invention.

16 is a partially enlarged view of a gravure print printed using the conventional mechanical engraving gravure printing plate shown in FIG.

17 is a partially enlarged view of a gravure print printed using the gravure printing plate of the mechanical engraving system according to the present invention shown in FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 logo combination device 110 separation processing unit 120 imposition processing unit 130 filter processing unit 140 combine processing unit 150 resolution conversion processing unit 200 noise adding device 300 cell engraving device 310 embossing controller 320 Needle drive unit 330: Diamond needle 335: Axis 400: Voltage fluctuation device A: Noise image for correction A (m, n): Pixel values of pixels constituting the noise image for correction C1, C2, C3: Separated composite data CT ... gradation image data CT (C), CT (M), CT (Y), CT (K) ... separated gradation image data F ... spatial filter K1, K2, K3 ... separated synthesized data L ... noise Component period LW: Character / line drawing data LW (C), LW (M), LW (Y), LW (K): Separated character / line drawing data M1, M2, M3 ... Separation Forming data P ... original image P (m, n) ... image pixel value P * ^... modification of the pixels constituting the original image P * ^(m, n) ... pixel value W ... white noise image W of the pixels constituting the corrected image (M, n)... Pixel values of pixels constituting the white noise image Y1, Y2, Y3.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshiaki Kudo 1-1-1 Ichigaya Kagacho, Shinjuku-ku, Tokyo Inside Dai Nippon Printing Co., Ltd.

Claims (8)

[Claims] 1. A gravure printing method in which an intaglio is created by engraving a plurality of cells arranged at a predetermined pitch, and printing is performed using the intaglio. Preparing character / line drawing data representing a line drawing portion; preparing gradation image data representing a gradation image portion of an image to be printed; and providing the character / line drawing data and the gradation image Performing combined processing for combining the data with the data to create combined data comprising a set of a large number of pixels; and creating corrected data by adding a noise component to the pixel value of each pixel constituting the combined data. Forming an intaglio by engraving a cell having a size corresponding to the pixel value of each pixel constituting the correction data; and performing printing using the intaglio. And a gravure printing method comprising: 2. The printing method according to claim 1, wherein a separation process for separating character / line drawing data for each predetermined color component and a separation process for separating gradation image data for each predetermined color component are performed. A gravure printing method comprising: performing a combine process on the separated data for each color component; and separately and independently adding a noise component to each of the composite data for each color component. . 3. The printing method according to claim 1, wherein a filtering process for increasing or decreasing a predetermined spatial frequency component is performed on one or both of the character / line drawing data and the gradation image data. A gravure printing method characterized by performing a process of adding a noise component after performing a combine process on subsequent data. 4. The printing method according to claim 1, wherein after performing the combine process, a process of converting the resolution of the pixels constituting the combined data is performed, and the combined data after the resolution conversion is converted to the combined data. A gravure printing method characterized by performing a process of adding a noise component. 5. The printing method according to claim 1, wherein the character / line drawing data is constituted by a set of data indicating a predetermined pixel value and a length of a pixel row having the pixel value. A gravure printing method comprising preparing in the form of run-length data, and preparing gradation image data in the form of bitmap data composed of a pixel array having a predetermined pixel value. 6. The printing method according to claim 1, wherein a noise component having a cycle of 2 to 5 times the pitch of each pixel constituting the composite data is added to each pixel value. A gravure printing method characterized in that correction data is created by the method. 7. The printing method according to claim 1, wherein a cell corresponding to the applied digital data is supplied to a needle driving unit to mechanically engrave the cell. An engraving device and a voltage fluctuation device having a function of fluctuating a voltage supplied by the embossing controller are prepared, correction data is created by adding a noise component to the synthesized data, and a cell is generated based on the correction data. Instead of performing the process of engraving, adding a noise component by providing synthesized data to the embossing controller and performing a process of changing the voltage supplied by the embossing controller by the voltage fluctuation device. Gravure printing method. 8. A gravure printed matter produced by using the gravure printing method according to claim 1.