JP4397450B2 - Multicolor stencil printing method and multicolor stencil printing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multicolor stencil printing method and a multicolor stencil printing apparatus for performing multicolor printing using a master wound around an outer peripheral surface of a porous cylindrical plate cylinder.
[0002]
[Prior art]
Conventionally, an emulsion ink (hereinafter simply referred to as ink) supplied from an ink supply mechanism provided inside a plate cylinder by winding a master made using a thermal head around the outer peripheral surface of a porous cylindrical plate cylinder. 2. Description of the Related Art A stencil printing apparatus that prints on a printing paper using a printer is widely known.
[0003]
Further, in such a stencil printing apparatus, those capable of performing multicolor printing or color printing have been developed. For example, JP-A-2-245373, JP-A-6-135113, JP-A-7- No. 17121, JP-A-10-297073, JP-A-8-197827 and the like are known.
[0004]
The multicolor stencil printing apparatus described in JP-A-2-245373 and JP-A-6-135113 uses a single plate cylinder, and the inside of the plate cylinder is radially directed from the axis of the plate cylinder. The extended partition plate is partitioned into a plurality of regions, and different color inks are stored in each region. Two or more masters made according to the image data for each color are formed in a connected form.
[0005]
The multicolor stencil printing apparatus described in JP-A-7-17121 and JP-A-10-297073 has a plurality of plate cylinders, and inks of different colors are stored in each plate cylinder. A master made from a plate based on image data of an image corresponding to the color of the stored ink is wound around the outer peripheral surface of each plate cylinder.
[0006]
The multicolor stencil printing apparatus described in JP-A-8-197827 prints one color using a master, and the other colors using an ink jet recording apparatus.
[0007]
In each of the above-described multicolor stencil printing apparatuses, after an original image is read by a scanner or the like, the image is color-separated for each color, and image data of each color is input to a storage unit such as a RAM, and the input image data is converted into the input image data. The master is made by driving the thermal head accordingly.
[0008]
[Problems to be solved by the invention]
In multi-color stencil printing, when the ink printed in the first (first color) is dried to some extent (after water has evaporated), and the second (second color) printing is overprinted, the pigment of the first color ink As the ink penetration due to the capillary force of the printing paper is slightly lower in the second color than in the first color due to changes in properties (wetting properties) due to the adhesion of oil and oil to the paper fibers, the second color ink transfer Although the amount is slightly decreased, there is a sufficient amount of ink transfer as compared with the case of continuous printing (overprinting the second color before the first color ink is dried), and there is no particular problem in image quality.
[0009]
However, when a master is made according to the color-separated image data and multicolor stencil printing is performed continuously using the master, overprinting is performed in an area where two or more colors of ink are overprinted. As a result, the color of the synthesized color largely deviates toward the ink printed earlier, and the reproducibility of the color of the overprinted area decreases.
[0010]
The reason for this is that an experiment conducted by the inventor of the present application shows that, under predetermined printing conditions, the ink that has been previously printed and transferred to the printing paper is insufficiently penetrating and dried. It was found that even when printing was attempted, the amount of transfer of the next ink onto the printing paper was reduced. Furthermore, the amount of ink transfer is determined by the amount of ink extruded from the printing section of the stencil printing machine and the amount of ink penetration due to the capillary force of the printing paper. It was found that the amount of ink penetrating due to the capillary force of the printing paper of the ink increased.
[0011]
Then, it was found that the ink transfer amount is controlled by correcting the image density, and as a result, it is possible to prevent a decrease in color reproducibility.
[0012]
Therefore, in the case where the inks of different colors are overprinted, the present invention shifts the color of the synthesized color toward the previously printed ink side by changing the image density of the previously printed ink. It is an object of the present invention to provide a multicolor stencil printing method and a multicolor stencil printing apparatus capable of preventing the above-described problem and improving the reproducibility of the color of an overprinted region.
[0013]
[Means for Solving the Problems]
According to the first aspect of the present invention, two or more masters for each color are made in accordance with the image data for each color input to the storage unit, and these masters are formed on the outer peripheral surface of the plate cylinder that is rotatable about the axis. In a multicolor stencil printing method for performing multicolor printing by wrapping and overprinting images of different color inks printed using the respective masters on a single printing paper, input to the storage unit When the image data for each color is compared to identify an area in which images of different colors are overprinted, and the image density of the image data of the previously printed image in the overprinted area is input to the storage unit Correction was made to a value lower than the image density.
[0014]
Therefore, in the area where the image density of the image data used when making the master for the image to be printed first is differently printed, the image of the image data first input to the storage unit Since the correction is made to a value lower than the density, the transfer amount of the ink used for printing the previously printed image onto the printing paper is suppressed in this overprinted region. Thereby, from the relationship of the amount of ink penetration described above, the amount of transfer onto the printing paper of the ink used for printing the image to be printed later in the region to be overprinted is larger than before the correction, The master transfer amount is balanced in the overprinted area, and the color of the synthesized color is not shifted to the previously printed ink side, improving the color reproducibility of the overprinted area. .
[0015]
The invention according to claim 2 is the invention according to claim 1, wherein the correction of the image density of the image data of the image printed earlier is performed according to the type of ink used, the type of master, the type of printing machine, and the like. The calculation is performed for each pixel based on a set mathematical formula and a variable is the image density for each pixel of the image data.
[0016]
Therefore, the correction of the image density of the image data used when making the master for the image to be printed first is performed according to the image density of each pixel of the image data, so that the accuracy is high. Correction is performed, and the color tone of the synthesized color in the overprinted area does not shift to the ink side printed earlier, and the color reproducibility of the overprinted area is improved. In addition, when the type of ink used, the type of master, the type of printing machine, etc. change, it is the case where the printing work conditions have changed by obtaining mathematical formulas for performing corrections accordingly. In addition, the color tone of the synthesized color in the overprinted region does not shift to the ink printed on the previously printed region, and the color reproducibility of the overprinted region is improved.
[0017]
According to the third aspect of the present invention, two or more masters for each color are made in accordance with the image data for each color input to the storage unit, and these masters are formed on the outer peripheral surface of the plate cylinder that is rotatable around the axis. In a multicolor stencil printing apparatus that performs multicolor printing by wrapping and printing images of different color inks printed using the respective masters on a single printing paper, the image is input to the storage unit The image data of each color is compared, and an overprint area specifying means for specifying an area in which images of different colors are overprinted, and the image density of the image data of the image printed earlier in the overprint area are stored in the memory Image density correction means for correcting the image density to a value lower than the image density when it is input to the unit.
[0018]
Therefore, in the area where the image density of the image data used when making the master for the image to be printed first is differently printed, the image of the image data first input to the storage unit Since the correction is made to a value lower than the density, the transfer amount of the ink used for printing the previously printed image onto the printing paper is suppressed in this overprinted region. Thereby, from the relationship of the amount of ink penetration described above, the amount of transfer onto the printing paper of the ink used for printing the image to be printed later in the region to be overprinted is larger than before the correction, The ink transfer amount is balanced in the overprinted area, and the color tone of the synthesized color is not shifted to the previously printed ink side, improving the color reproducibility of the overprinted area. .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing a schematic structure of a main part of the multicolor stencil printing apparatus, FIG. 2 is a block diagram showing a control configuration of the multicolor stencil printing apparatus, and FIG. 3 is an image printed first in a region to be overprinted. FIG. 4 is a graph showing the relationship between the image density of the first color image (first printed image) and the ink transfer amount, and FIG. 5 is the image of the first color image. Regarding data, a graph showing the relationship between the image density at the time of input to the RAM and the corrected image density, FIG. 6 is a schematic diagram for explaining the image density correction of the image data of the first color image performed in units of pixels. .
[0020]
The multicolor stencil printing apparatus includes two porous cylindrical cylinders 1 and 1a which are provided so as to be rotatable about an axis and are arranged so that the axes are parallel to each other. A press roller 2, 2 a, which is provided so as to be movable to a position close to and away from the outer peripheral surface of 1 a and is rotatable around an axis parallel to the axis of the plate cylinder 1, 1 a, is wound around the outer peripheral surface of the plate cylinder 1, 1 a. Plate making sections 4 and 4a for making the masters 3 and 3a, a moving mechanism (not shown) for moving the press rollers 2 and 2a to a position where they come into contact with and away from the plate cylinders 1 and 1a, and used masters 3 and 3a for the plate cylinders 1, 1 a, and a platen unit 5, 5 a that accommodates the printing paper 6, a paper feeding table 7 that accommodates the printing paper 6, and a resist that controls the feeding timing of the printing paper 6 fed between the plate cylinder 1 and the press roller 2. Printing paper that has been printed on the roller 8, plate cylinder 1, 1a side Transport mechanism 9, 9a for transporting the printing paper 6 to the downstream side in the transport direction, the paper discharge tray 10 on which the printing paper 6 transported by the transport mechanism 9a is discharged after the printing on the plate cylinder 1a side is finished, etc. Is provided.
[0021]
The plate making sections 4 and 4a are platen rollers 11 and 11a, thermal heads 12 and 12a, cutters 13 and 13a, master guide plates 14 and 14a, which are provided with a large number of heating elements and pressed against the outer peripheral surface of the platen rollers 11 and 11a. The auxiliary rollers 15 and 15a are configured. The platen rollers 11 and 11a and the auxiliary rollers 15 and 15a are rotationally driven by a stepping motor (not shown). When the platen rollers 11 and 11a are rotationally driven, the master base papers 16 and 16a wound in a roll state are pulled out, and the heating elements of the thermal heads 12 and 12a are heated according to the image data, and the master base papers 16 and 16a are heated. Are heated and melted (perforated) to produce masters 3 and 3a. The masters 3 and 3a are conveyed on the master guide plates 14 and 14a toward the plate cylinders 1 and 1a by the driving force from the platen rollers 11 and 11a and the auxiliary rollers 15 and 15a, and the outer peripheral surfaces of the plate cylinders 1 and 1a. Wrapped around. The cutters 13 and 13a are driven at a predetermined timing corresponding to the number of steps of the stepping motor, and the masters 3 and 3a are cut to a predetermined length by driving the cutters 13 and 13a.
[0022]
On the outer peripheral surface of the plate cylinders 1 and 1a, clampers 17 and 17a connected to an opening / closing mechanism (not shown) are provided so as to be freely opened and closed. The clampers 17 and 17a that have been opened at positions facing the front ends of the master guide plates 14 and 14a are rotated to a closed position at a predetermined timing according to the number of steps of the stepping motor, so that the plate making units 4 and 4a The leading ends of the masters 3 and 3a that have been transported are sandwiched between the clampers 17 and 17a.
[0023]
Inside the plate cylinder 1, 1 a are ink pipes 18, 18 a that are located on the axis of the plate cylinder 1, 1 a and also serve as support shafts for rotatably supporting the plate cylinder 1, 1 a, and plate cylinders 1, 1 a. Ink rollers 19 and 19a that are driven to rotate in the clockwise direction indicated by arrows with a small clearance between the inner peripheral surface and doctor rollers 20 and 20a that are disposed with a small clearance are provided between the outer peripheral surfaces of the ink rollers 19 and 19a. It has been. Ink reservoirs 21 and 21a for storing ink supplied from the ink pipes 18 and 18a are formed in a portion sandwiched between the outer peripheral surfaces of the ink rollers 19 and 19a and the outer peripheral surfaces of the doctor rollers 20 and 20a. .
[0024]
The plate discharging portions 5 and 5a are configured by plate discharging rollers 23 and 23a for feeding the plate discharging storage boxes 22 and 22a, the masters 3 and 3a peeled from the plate cylinders 1 and 1a into the plate discharging storage boxes 22 and 22a, and the like.
[0025]
The transport mechanism 9, 9a includes a pair of transport rollers 24, 25, 24a, 25a, at least one of which is rotationally driven, and transport belts 26, 26a wound around these transport rollers 24, 25, 24a, 25a, It comprises suction fans 27, 27a and the like for sucking the printing paper 6 onto the conveyor belts 26, 26a. In addition, on the downstream side of each plate cylinder 1, 1 a along the conveyance direction of the printing paper 6, peeling claws 28, 28 a for peeling the printing paper 6 from the plate cylinder 1, 1 a are provided.
[0026]
FIG. 2 is a block diagram showing the control configuration of the multicolor stencil printing apparatus. The CPU 29 is a storage unit in which various data such as a ROM 30 storing fixed data such as a control program and image data are input. RAM 31, work area 32, scanner 34 via input image data processing unit 33, various loads 35 such as motors, various sensors 36, operation unit 37 having various operation keys and display units, thermal head image processing unit 38 Thermal heads 12, 12a, etc. are connected via
[0027]
The scanner 34 reads a document image, the input document data processing unit 33 separates the read document image into two colors, and the color-separated images of the respective colors (first color and second color). Data is input to the RAM 31.
[0028]
In the work area 32, the image data of the first color image and the image data of the second color image input to the RAM 31 are called and compared, whereby the first color image and the second color image are overprinted. An area is identified. Further, the image density of the image data when the master 3 for the image to be printed first is made from the master base paper 16 is corrected to a value lower than the image density when input to the RAM 31 in the overprinted area. Image density correction is performed. Note that this image density correction is performed based on mathematical expressions described later.
[0029]
In such a configuration, the basic operation of this multicolor stencil printing apparatus is as follows. First, an original image is read by the scanner 34, and the read original image is color-separated into two colors (first color and second color) in the input image data processing unit 33, and the color-separated image data of each color is obtained. The masters 3 and 3a are made by the plate making units 4 and 4a, and the masters 3 and 3a thus made are wound around the outer peripheral surface of the plate cylinders 1 and 1a. After the winding of the masters 3 and 3a around the outer peripheral surfaces of the plate cylinders 1 and 1a is completed, a printing start key (not shown) provided on the operation unit 37 is pressed, thereby printing on the sheet feeding table 7. The paper 6 is fed, and the printing paper 6 is fed between the plate cylinder 1 and the press roller 2 so that an image of the first color (for example, cyan) is printed. The printing paper 6 on which the image of the first color has been printed is conveyed to the plate cylinder 1a side by the conveyance mechanism 9, and is fed between the plate cylinder 1a and the press roller 2a to thereby generate the second color (for example, magenta). The printing paper 6 on which the second color image has been printed is transported by the transport mechanism 9a and discharged onto the paper discharge tray 10, whereby multicolor printing with two colors of ink is performed. Ends.
[0030]
Here, in the area where the first color image and the second color image are overprinted, the ink used for printing the second color image as described above in the section “Problems to be solved by the invention”. There is a problem in that the amount of transfer to the printing paper 6 decreases, and the color of the color synthesized by the overprinting shifts to the ink side used for printing the first color image. In order to solve this problem, it is necessary to perform correction to lower the image density of the image data of the first color image in the overprinted area, and this image density correction process will be described based on the flowchart of FIG. To do. First, it is determined whether the image data of the first color image and the image data of the second color image are input to the RAM 31 (step S1). If input, the image data of the first color image and the image data of the second color image are compared to identify the area to be overprinted (step S2), and the overprint area identification means executes here. Is done.
[0031]
When the area to be overprinted is specified in step S2, the image density of the image data of the first color image in the specified overprint area is set to a value lower than the image density of the image data when first input to the RAM 31. Image density correction to be corrected is performed based on mathematical expressions described later (step S3), and image density correction means is executed here.
[0032]
When the image density is corrected in step S3, the corrected image density image data is re-input to the RAM 31 as the image data of the first color image (step S4). The master making for the first color image master 3 performed by the plate making unit 4 is performed based on the re-input image data.
[0033]
In actual printing, after performing the image density correction described in the present application, so-called halftone processing for halftone reproduction is performed, and perforation / non-perforation is performed for each pixel in accordance with the color resolution of the thermal head. In the determined and overprinted region, the image density of the first color image is corrected to be low, and as a result, the number of perforations is reduced compared to before correction, and the amount of ink transfer is suppressed.
[0034]
When printing is performed using the master 3 for the first color image made in this way, the first color image is printed in an area where the first color image and the second color image are overprinted. The amount of ink transferred onto the printing paper 6 can be suppressed. For this reason, from the relationship of the ink penetration amount, the ink transfer amount between the first color and the second color is balanced in the region where the overprinting is performed, and the ink for printing the second color image onto the printing paper 6 is obtained. The amount of transfer is larger than before the correction, and the color of the color synthesized by the ink for the first color image and the ink for the second color image is used for printing the first color image. Displacement is prevented, and the color reproducibility in the overprinted area is improved.
[0035]
Next, in a region where the first color image and the second color image are overprinted, a correction formula for correcting the image density of the image data of the first color image necessary for obtaining good color reproducibility An experiment conducted to obtain the above will be described below. In this experiment, Ricoh Co., Ltd. Preport Master VT-6 (commercial product) was used as the master, and ink (cyan, magenta) was used in comparison with Ricoh Co., Ltd. black ink VT600II (commercial product). An ink with a slightly higher viscosity was prototyped and the transfer amount was 3 g / m. ² Used under the conditions before and after. The printing machine used was a prototype capable of A3 size and capable of two-color printing, and the printing speed was 90 sheets / minute. The environmental conditions were normal temperature and humidity. Then, a master which makes the image data of the first color image and the image data of the second color image the same and makes the master is a 1-pass 2-color machine (a printing machine capable of printing two colors by one paper pass). Printing was performed by wrapping around individual plate cylinders, and the amount of transfer of the ink used for printing the second color image onto the printing paper was measured. In this experiment, the image density of the image data of the first color image is changed to a different image density (9%, 20%, 32%, 49%, 100%), and the first density image for each image density of the first color image. The case of different image densities (9%, 20%, 32%, 49%, 100%) of the second color image was performed. The amount of ink transferred to the printing paper was measured by printing the number of sheets and then measuring the weight of the entire plate cylinder including residual ink.
[0036]
FIG. 4 shows the results of the experiment and the ink transfer when printing the first color image with the image data density changed to a different image density (9%, 20%, 32%, 49%, 100%). It is the graph which showed quantity. In this graph, the horizontal axis represents the image density of the image data of the first color image, and the vertical axis represents the ink transfer amount. From this graph, it can be seen that as the image density of the first color image increases, the ink transfer amount (ink transfer rate) of the second color image decreases accordingly.
[0037]
Next, based on the graph of FIG. 4, the ink transfer amount at a predetermined image density of the second color image in which the ink transfer amount of the first color image and the ink transfer amount of the second color image are the same is obtained. A value obtained by dividing the first color image by the ink transfer amount at the predetermined image density was obtained as a correction factor of the image density of the first color image. For example, when the image density of the second color image is 100%, 2.5 (the ink transfer amount graph of the first color image and the ink transfer amount graph of the 100% image density of the second color image in FIG. (Intersection point) /3.2 (Ink transfer amount at 100% image density of the first color image in FIG. 4) = 0.78. Similarly, as the respective correction factors when the image density of the second color image is 49%, 32%, 20%, 9%, 0.83 (1.57 / 1.9), 0.86 ( 1.16 / 1.35), 0.92 (0.85 / 0.92), and 0.97 (0.58 / 0.6) were obtained.
[0038]
FIG. 5 is a graph showing the relationship between the first input image density (horizontal axis) to the RAM 31 in the image data of the first color image and the corrected image density (vertical axis) corrected with the above-described correction rate. is there. From the graph of FIG. 5, a correction formula “Y = −0.0013X for correcting the image density of the first color image in the region where the first color image and the second color image are overprinted. ² + 0.9045X ″ was obtained. In this correction equation, X is the input image density, and Y is the corrected image density.
[0039]
Next, the correction equation “Y = −0.0013X” described above. ² The correction of the image density based on + 0.9045X ″ is performed for each pixel of the image data of the first color image, and the correction content will be described based on FIG. 6. FIG. 6A shows, for example, the first color. The image density at the time of the first input to the RAM 31 for the four pixels of the image data of the image is represented by a level of 0 to 63 (6 bit display), and Fig. 6B shows the second color image in the same region. FIG. 6A shows the image density of the image data. By comparing this information with the information of FIG. 6A, two of the four pixels are printed in an overlapping area. The other two pixels 6 (c) shows the image density of the image data of the first color image after correction, and the pixels that are overlapped and printed with the second color image. (Image density level is 1 to 63 Above-described correction formula things) "Y = -0.0013X ² + 0.9045X ”is corrected, and the image density levels of the two pixels overlapping the second color image are corrected as“ 60 → 51 ”and“ 24 → 22 ”, while the second color image is colorless ( Since the image density level is 0), correction is not performed on the two pixels that are not overlapped with the second color image and the image density level is maintained at “60 → 60” and “24 → 24”.
[0040]
Here, the ink transfer amount varies depending on the type of ink, the type of master, the type of printing press, and the like. For this reason, the above-described correction formula “Y = −0.0013X ² Since + 0.9045X ″ also changes according to the ink type, master type, printing machine type, etc., a correction formula corresponding to the type of ink to be used, the type of master, the type of printing machine, etc. is obtained.
[0041]
In the present embodiment, the color tone and the image density are expressed, but the hue and color at the a * b * coordinate in the L * a * b color system generally used to represent the color of the object. Can be thought of as equivalent to degrees.
[0042]
In the present embodiment, the multicolor stencil printing apparatus having the two plate cylinders 1 and 1a has been described as an example. However, the multicolor stencil printing apparatus to which the present invention can be applied is of this type. The number of ink colors that use the inside of a plate cylinder as described in JP-A-2-245373, JP-A-6-135113, etc. The present invention can also be applied to a multicolor stencil printing apparatus of a type divided according to the above.
[0043]
In this embodiment, the image data has been described as an example of color separation by reading a document image by the scanner 34, but may be input from a personal computer or the like.
[0044]
Furthermore, in the present embodiment, a multicolor printing apparatus that includes two plate cylinders 1 and 1a and performs two-color printing has been described as an example. However, the present invention uses three or four color inks. The present invention can also be applied to a color printer to be used. In that case, the correction formula for how much the image density of the image data of the color to be printed first should be reduced in the area where the color to be printed later is printed in an overlapping manner is as described in FIG. It is obtained by performing an experiment, and the image density of the color printed first is reduced according to the correction formula.
[0045]
【The invention's effect】
According to the multicolor stencil printing method of the first aspect of the present invention, when making a master for an image to be printed first, an image density of an area to be printed is input to the storage unit in an overlapping manner with an image to be printed later. Since the plate is made based on the image data corrected to a value lower than the image density of the first image data, the ink used for printing the image to be printed first is printed on the printing paper in this overprinted area. The amount of transfer can be suppressed, so that the amount of transfer of ink used for printing an image to be printed later in the overprinted area in relation to the amount of ink penetration is less than before correction. It is possible to prevent the color of the synthesized color in the overprinted area from shifting to the previously printed ink side, and to improve the reproducibility of the color of the overprinted area.
[0046]
The invention according to claim 2 is the invention according to claim 1, wherein the correction of the image density of the image data of the image printed earlier is performed according to the type of ink used, the type of master, the type of printing machine, and the like. Since it is performed for each pixel based on a set mathematical formula and the image density for each pixel of the image data as a variable, correction of the image density of the image data of the first printed image is performed with high accuracy. This can be performed, and the color reproducibility of the overprinted area can be improved.
[0047]
According to the multicolor stencil printing apparatus of the invention described in claim 3, the overprint area is specified by the overprint area specifying means, and the overprint area specifying means is used when making the master for the image to be printed first. Since the image density of the overprint area specified in (2) has been corrected to a low value by the image density correction means, the transfer amount of the ink used for printing the image to be printed first on the print paper is changed in the overprint area. As a result, the amount of transferred ink used to print the image printed in the overprinted area is larger than before correction due to the amount of ink penetration, and synthesis is performed in the overprinted area. It is possible to prevent the color of the printed color from deviating toward the previously printed ink, and to improve the color reproducibility of the overprinted region.
[Brief description of the drawings]
FIG. 1 is a front view showing a schematic structure of a main part of a multicolor stencil printing apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a control configuration of the multicolor stencil printing apparatus.
FIG. 3 is a flowchart for explaining image density correction of image data of a previously printed image in a region to be overprinted.
FIG. 4 is a graph showing a relationship between an image density of a first color image and an ink transfer amount.
FIG. 5 is a graph showing the relationship between the image density at the time of input to the RAM and the corrected image density for the image data of the first color image.
FIG. 6 is a schematic diagram illustrating image density correction of image data of a first color image performed in units of pixels.
[Explanation of symbols]
1,1a Plate cylinder
3,3a Master
6 Printing paper
31 Memory unit

Claims (3)

Two or more masters for each color are made according to the image data for each color input to the storage unit, and these masters are wound around the outer peripheral surface of a plate cylinder that is rotatable around an axis, and each master is used. In a multicolor stencil printing method for performing multicolor printing by overprinting images of different color inks to be printed on one printing paper,
The image data for each color input to the storage unit is compared to specify an area in which images of different colors are overprinted, and the image density of the image data of the first printed image in the overprinted area is determined. A multicolor stencil printing method, wherein the image density is corrected to a value lower than that inputted to the storage unit. The correction of the image density of the image data of the previously printed image is a mathematical formula set according to the type of ink to be used, the type of master, the type of printing machine, etc., and the image for each pixel of the image data 2. The multicolor stencil printing method according to claim 1, wherein the method is performed for each pixel on the basis of a mathematical expression having density as a variable. Two or more masters for each color are made according to the image data for each color input to the storage unit, and these masters are wound around the outer peripheral surface of a plate cylinder that is rotatable around an axis, and each master is used. In a multicolor stencil printing apparatus that performs multicolor printing by overprinting images of different color inks to be printed on one printing paper,
Overprint area specifying means for comparing the image data for each color input to the storage unit and specifying an area in which images of different colors are overprinted;
Image density correction means for correcting the image density of the image data of the image printed earlier in the overprinted area to a value lower than the image density when input to the storage unit;
A multicolor stencil printing apparatus comprising:

Images