Printing method and program

Abstract

To provide a method for creating printed matter and a program which improve concealment of a latent image by changing the density of the latent image according to a visible image, and improve concealment of the latent image even when printed matter is used under different light sources or different base materials are printed.SOLUTION: A method for creating printed matter includes: a patch printing step of performing printing on a sample base material on the basis of patch printing data combined by superposing reference coordinates of visible original image data and latent original image data; an evaluation table creation step of creating an evaluation table in which a latent image for a combination of pixels and densities of a visible image and a latent image under a plurality of different visible light sources indicates a concealment state, for patch printed matter; and a selection step of selecting a combination of densities in which the latent image can be concealed using the evaluation table, and performing printing on the base material on the basis of printed matter data obtained by combining latent image data and visible image original data.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method and program for creating printed matter that requires anti-counterfeiting and anti-tampering functions in the field of security printed matter such as banknotes, passports, securities, identification cards, cards, and travel tickets that require anti-counterfeiting effects. [Background technology]

[0002] In recent years, with the improvement of image quality of color copying machines and the computerization of color plate making technology, the means of counterfeiting gift certificates and securities have tended to become more diverse. In particular, the resolution of image input / output devices used in the printing industry has improved significantly, making it relatively easy to extract thin lines and minute characters used on securities.

[0003] As a result, it has become possible to extract with high accuracy using input / output devices such as scanners the background patterns, color patterns, relief patterns, and other patterns that are composed of thin lines and are used in many of the current securities. As a result, there has been an increase in more authentic counterfeit products that make extensive use of spot color plates, rather than simply counterfeits made using general commercial printing methods that consist of four-color CMYK halftone dots.

[0004] Therefore, as an anti-counterfeiting measure for high-resolution hard copies, the applicant has filed a patent application for a halftone print characterized by having a visible image formed on a substrate by a first halftone area (1) consisting of a first halftone dot area using a first ink having a first characteristic, a latent image consisting of a second halftone dot area using a second ink having a second characteristic different from the first characteristic, and a second halftone area (2) consisting of a visible image formed by a third halftone dot area using a first ink of the same color as the second ink having the first characteristic, formed adjacent to the first halftone area (1) (see, for example, Patent Documents 1 to 3).

[0005] The applicant has also filed a patent application for a method and program for creating the aforementioned halftone print, which includes an image input means for inputting a first image that is the basis for a first continuous tone image to be recognized as a visible image and a second image that is the basis for a second continuous tone image that is recognized as a latent image only under specific viewing conditions, a setting item setting means for setting the resolution, coloring, and halftone shape of the halftone data for each setting item, and a calculation means for generating a first continuous tone image and a second continuous tone image from the first image and the second image input by the image input means, respectively, and synthesizing the generated first continuous tone image and second continuous tone image, as well as a program for executing the same (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3544536 [Patent Document 2] Patent No. 4461234 [Patent Document 3] Patent No. 5707595 [Patent Document 4] Patent No. 4958117 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technologies of Patent Documents 1 to 4, there existed conditions under which the latent image would not be concealed by the second halftone region (2) composed of a second ink (e.g., an infrared-absorbing ink (K (black)) (2a)) and a first ink (e.g., an ink not having infrared absorption (CMY (cyan, magenta, yellow) (2b)) depending on the combination of printing conditions (halftone resolution, halftone processing method, type of ink), design and print density of the visible image and latent image. Therefore, there was a problem that the latent image would be visible when a part of the visible image with flat density was combined with a part of the latent image with large changes in density.

[0008] Furthermore, in order to conceal the latent image so that it cannot be seen by the naked eye, it was necessary to repeat a process of adjusting the density of the visible image, adjusting the density of the latent image, printing, and visually checking the image, through trial and error. As a result, there were problems such as poor concealment of the latent image and limitations on the design of the visible image and latent image.

[0009] Furthermore, even when optimal conditions are obtained through the above-mentioned trial and error, the latent image may not be concealed if the conditions of use of the printed matter, such as the light source when viewed or the type of substrate, are different.

[0010] The present invention aims to solve the above-mentioned problems, and provides a method and program for creating a printed matter having good concealment of a latent image by changing the density of the latent image according to the visible image, and having good concealment of a latent image even when the printed matter is used under different light sources or printed on different substrates. [Means for solving the problem]

[0011] The present invention is a method for producing a printed matter on which a latent image visible under a predetermined observation condition and a visible image visible under a visible light source formed so as to conceal the latent image are formed, the same corner of the visible image and the latent image are set as reference coordinates, and the coordinate diagonal to the reference coordinates is set as the final coordinates. Visible original image data and latent original image data are produced by regularly adding pixels and densities from the reference coordinates for an area from the reference coordinates to the final coordinates, and the coordinates of at least three points that are common positions of the visible original image data and the latent original image data are set as reference points, and a sample is produced based on patch print data synthesized by overlapping the reference points. The method for producing a printed material comprises a patch printing step of printing on a substrate to produce a patch print; an evaluation table creation step of creating, for the patch print, an evaluation table showing whether or not the latent image is concealed for combinations of pixels and densities of the visible image and the latent image image under a plurality of different visible light sources; and a selection step of using the evaluation table to select a combination of densities at which the latent image can be concealed by the visible image, creating latent image data based on the densities of the selected latent image original image data, and printing on the substrate using print data that is a combination of the latent image image data and the visible original image data.

[0012] The present invention is a print production program for causing a computer to execute a print production method. Effect of the Invention

[0013] By changing the density of the latent image according to the visible image, the present invention improves the visibility of the latent image and can create a print with good concealment of the latent image even when the print is used under different light sources or printed on a different substrate. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of a halftone print to be produced according to the present invention. [Diagram 2] 1 is a diagram illustrating an example of a method for producing a printed matter and a program for producing a printed matter according to the present invention; [Diagram 3]FIG. 13 is a diagram illustrating an example of a patch printing process. [Figure 4] FIG. 2 is a diagram showing an example of visible original image data. [Diagram 5] FIG. 2 is a diagram showing an example of original latent image data; [Figure 6] FIG. 13 is a diagram showing an example of a patch print in which a visible image and a latent image are combined. [Figure 7] FIG. 13 is a diagram illustrating an example of an evaluation table creation process. [Figure 8] FIG. 13 is a diagram illustrating an example of a table. [Figure 9] An example showing the density of a patch print [Figure 10] FIG. 13 is a diagram illustrating an example of a selection process. [Figure 11] FIG. 2 is an example diagram showing visible original image data according to the first embodiment. [Figure 12] FIG. 2 is a diagram showing an example of original latent image data according to the first embodiment; [Figure 13] FIG. 4 is an example diagram showing patch print data according to the first embodiment. [Figure 14] FIG. 13 is a diagram illustrating an example of an evaluation table according to the first embodiment. [Figure 15] FIG. 1 is an example showing data of Example 1. [Figure 16] 13 shows images of a halftone print observed under two different light sources. [Figure 17] FIG. 1 is a diagram illustrating an example of a printed matter. [Figure 18] FIG. 13 is a diagram illustrating an example of synthesis using a reference point. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The following describes an embodiment of the present invention with reference to the drawings. However, the present invention is not limited to the embodiment described below, and includes various other embodiments within the scope of the technical idea described in the claims.

[0016] The present invention can be applied to various printed matter (10) in which a latent image (14) and a visible image (13) are formed adjacent to each other, as shown by diagonal lines for convenience in Figures 17(a) and (b) as an example, but will be described using a halftone dot printed matter (A1) shown in Figure 1 as an example. Figure 1(a) is a schematic diagram of the halftone dot printed matter (A1), and Figure 1(b) is a partially enlarged diagram showing the configuration of the halftone dots in the halftone dot printed matter (A1). The configuration of the halftone dots shown in Figure 1(b) will be described below. Note that adjacent in this specification means that at least a portion of two adjacent areas, images, or halftone dots are in contact with each other.

[0017] (Dot Composition) The halftone dot configuration is such that a first region, a first halftone region (1), and a second region, a second halftone region (2), are used as basic units, and a plurality of first halftone regions (1) are regularly arranged so that the first halftone regions (1) surround the second halftone region (2). When a plurality of first halftone regions (1) and second halftone regions (2) are arranged, the shapes of the regions may be the same or different, and it is sufficient that at least a portion of the regions is arranged adjacent to each other. In consideration of the visibility of the latent image, it is more preferable that the regions have the same shape and are arranged adjacent to each other without any gaps.

[0018] (First Halftone Area) The first halftone regions (1) are all of the same shape, and may be polygonal, circular, or geometric, but are more preferably square or rectangular. The first halftone region (1) is composed of an image forming portion (1a) and a first background portion (1b). By arranging a plurality of first halftone regions (1), a first continuous tone image is formed that is recognized as a visible image on the printed matter.

[0019] (Second Halftone Area) The second halftone regions (2) are all of the same shape, and may be polygonal, circular, or geometric, but are preferably square or rectangular. The second halftone regions (2) are composed of an image portion (2a) and a second background portion (2b). By arranging a plurality of second halftone regions (2), a second continuous tone image is formed that is recognized as a latent image on the printed matter only under specific viewing conditions.

[0020] The inks used to form the halftone print (A1) are inks having different characteristics for each of the image forming portion (1a) and first background portion (1b) of the first halftone region (1) and the image portion (2a) and second background portion (2b) of the second halftone region (2). For example, when the image forming portion (1a) and the first background portion (1b) of the first halftone region (1) and the second background portion (2b) of the second halftone region (2) are formed with CMY inks that do not absorb infrared light, and the image portion (2a) of the second halftone region (2) is formed with black ink (K) that absorbs infrared light, a halftone print (A1) is obtained in which a first continuous tone image (8) formed by the image forming portion (1a) and the first background portion (1b) of the first halftone region (1) appears under a visible light source as shown in Figure 16(a), and a second continuous tone image (9) formed by the image portion (2a) of the second halftone region (2) appears under an infrared light source, which is a different observation condition, as shown in Figure 16(b). The technology used in this halftone print (A1) is "ImageSwitch (Trademark Registration No. 4718813)". The different characteristics in this specification include the presence or absence of infrared absorbing characteristics, the presence or absence of luminescent characteristics, the presence or absence of solvent characteristics, and the like.

[0021] First Embodiment As shown in FIG. 2, the method and program for creating a printed matter of the present invention comprises a patch printing process (S1) in which the density of each of the visible original image data (3) and the latent original image data (4) is changed, and a patch print (5) is created by combining the density-changed visible original image data (3) and the latent original image data (4), an evaluation table creation process (S2) in which an evaluation table is created from the patch print (5) that evaluates whether or not the latent image is concealed when viewed for combinations of the densities of the visible image and the latent image, and a selection process (S3) in which a density at which the latent image can be concealed is selected from the density of the visible image using the evaluation table, and printing is performed.

[0022] In this specification, an embodiment is shown in which the visible original image data (3) is a printed matter in gray scale, but it can be applied to color as well. As shown in Fig. 1, an image in this invention is expressed with the upper left corner of the image as the origin (0,0), the horizontal (width) direction as X, and the vertical (height) direction as Y, and the coordinates (position) are expressed as X, Y. An image is composed of pixels, which are the smallest units that can be expressed by a computer, and each pixel has brightness, which is expressed as density in this specification.

[0023] Density (brightness) is expressed as a gradation value of 0 to 255, with 255 being brighter (whiter, paler). Color is expressed as RGB (red, green, blue) density (0 to 255), and in the case of gray gradation, the RGB gradation values ​​are all the same value. Furthermore, the CMYK density in an image is expressed as 0 to 100%, with the higher the percentage value, the darker it is. For K, 0% is white and 100% is black. Furthermore, density is basically expressed as RGB density, and in the case of CMYK, it is expressed as %. Next, each process will be explained in detail.

[0024] (Patch printing process) The patch printing step (S1) is a step of creating patch printing data by combining the visible original image data (3) and the latent original image data (4) in which the densities of the visible original image data (3) and the latent original image data (4) are changed, and printing the created patch printing data on a sample substrate such as medium-quality paper, fine paper, or coated paper to create a patch printed matter (5) for checking whether the latent image is concealed from the visible image under a plurality of different visible light sources such as LED, fluorescent lamp, incandescent lamp, etc. The sample substrate is a known material such as medium-quality paper, fine paper, or coated paper for forming the patch printed matter (5), and is a material that serves as an optimum substrate for evaluating the patch printed matter (5) as described below based on the sample substrate and forming the final printed matter based on the sample substrate.

[0025] The process (S1-1) of creating the original visible image data (3) secures the area (width, height) of the original visible image data (3) that forms the visible image, and initializes the coordinates (X, Y), density, and density step (change) in the Y direction. After initialization, the original visible image data (3) is converted from the reference coordinates (X0, Y0) to the coordinates (X Z , Y n ) is filled with a solid density (0). The reference coordinates (X0, Y0) are one corner of the visible original image data (3), and in FIG. 4, the upper left corner is set as the reference coordinates (X0, Y0). Next, the pixel (+n) and density (+m) are regularly added to the Y-coordinate (Y0) to change the filling density, and the coordinates (X0, Y 0+n ) to a given coordinate (X Z , Y 0+n ) is filled with a solid color with density (T+m). Z , Y Z ), it is possible to obtain visible original image data (3) in which the density changes stepwise in the vertical direction (Y), as shown in FIG. 4. The size of the area to be filled in is set appropriately. Z , Y Z ) is a corner that is diagonally opposite the reference coordinates (X0, Y0) on the visible original image data (3).

[0026] Next, the process (S1-2) of creating the latent image original image data (4) will be described. In this first embodiment, for the sake of convenience, characters will be used as images to distinguish them from the visible original image data (3), but there is no particular limitation to patterns, symbols, etc. The process (S1-2) of creating the latent image original image data (4) first secures an image area of ​​the same size as the visible original image data (3) (width, height), and initializes the coordinates (X, Y), density, and density step (change) in the X direction. After initialization, the reference coordinates (X0, Y0) of the latent image original image data (4) are changed to the coordinates (X Z , Y n ), characters are created with a density of 0 within the area up to the pixel value (X0). The reference coordinates (X0, Y0) of the latent original image data (4) are the same as the reference coordinates (X0, Y0) of the visible original image data (3) described above. For example, in FIG. 5, the reference coordinates (X0, Y0) are the same upper left corner as the visible original image data (3). The number of characters is created so that they fit within a solid portion of the same density in the visible original image data (3). The density within a character is the same density. Next, the coordinates (X 0+n , Y0) to a given coordinate (X Z , Y n ) and create characters with density (T+m) in the area up to the final coordinate (X Z , Y Z ), it is possible to obtain original latent image data (4) whose density changes in the horizontal direction (X direction) as shown in FIG. 5. Note that the final coordinates (X Z , Y Z ) is a corner that is diagonally opposite to the corner at the reference coordinates (X0, Y0) on the original latent image data (4).

[0027] In the synthesis step (S1-3), the created visible original image data (3) and latent original image data (4) are synthesized to create patch print data, and the created patch print data is used to print a visible image with a first ink visible under a visible light source and a latent image with a second ink that is the same color as the first ink under a visible light source and is visible under a non-visible light source (infrared, ultraviolet) on a sample substrate, to create a patch print (5) shown in FIG. 6 (S1-4). Note that the synthesis of the visible original image data (3) and the latent original image data (4) is performed by moving the coordinates (X0, Y0) that are common to each data to the coordinates (X Z , Y n 18, the coordinates of at least three arbitrary points from the original visible image data (3) and the original latent image data (4) are used as reference points in the original visible image data (3) and the original latent image data (4), and the reference points are superimposed and synthesized. For example, as shown in FIG. 18, the reference points (P1, P2, P3) in the original visible image data (3) and the reference points (P1', P2', P3') in the original latent image data (4) are synthesized.

[0028] In addition, when forming the halftone dot configuration shown in FIG. 1(b), data for the image forming portion (1a) and the first background portion (1b) of the first halftone region (1) and data for the image portion (2a) and the second background portion (2b) of the second halftone region (2) are formed by the latent image original image data (4), and the coordinates (X0, Y0) which are common positions in the data forming the first halftone region (1) and the data forming the second halftone region (2) by the latent image original image data (4) are converted to coordinates (X Z , Y n ) are used as reference points in the visible original image data (3) and the latent original image data (4), and the reference points are overlapped and synthesized so that a plurality of them are regularly arranged so that the first halftone area (1) surrounds the second halftone area (2), thereby creating patch print data.

[0029] Next, using the created patch print data, an image forming portion (1a) and a first background portion (1b) of a first halftone area (1), and a second background portion (2b) of a second halftone area (2) are formed using CMY inks that do not absorb infrared light, and an image portion (2a) of the second halftone area (2) is printed on the aforementioned sample substrate using black ink (K) that absorbs infrared light to create a patch print (5).

[0030] The patch printing step (S1) shown in Fig. 3 shows a method in which there is one patch printed matter (5), but when increasing the number of gradations of black or when there are many colors, the patch printing step (S1) is performed multiple times to create multiple patch printed matters (5) for each color. Note that when there are many types of sample substrates, a patch printed matter (5) is created for each type of sample substrate.

[0031] (Evaluation table creation process) In the evaluation table creation step (S2), as shown in Fig. 7, the created patch print (5) is checked visually or with an optical device such as a camera for the latent image (one character at a time in this embodiment) under a plurality of different visible light sources such as the above-mentioned LED, fluorescent lamp, incandescent lamp, etc., to check whether the latent image is concealed by the visible image at each density and under each light source, evaluate the density combinations for concealment or not, and input the evaluation results into the evaluation table (6) shown in Fig. 8. Furthermore, when a patch print (5) is created for each type of sample substrate, an evaluation table (6) is created for each type of sample substrate.

[0032] The evaluation table (6) inputs the numerical values ​​of the density combinations where the latent image can be confirmed, that is, the density combinations where the latent image is not concealed by the visible image. For example, as shown in Fig. 9, the numerical values ​​are assigned points for each type of visible light source such as LED and fluorescent light, and the sum of the numerical values ​​indicates that the latent image is not concealed. The dotted area (7') where the number is 1 or more is the density (7') where the latent image is not concealed, and the thick area (7) where the number is 0 means that the latent image is concealed under all of the multiple light sources.

[0033] In addition, the patch print (5) in the evaluation table creation step (S2) may be checked using an optical device such as a color camera instead of a human. When checking with a color camera, one patch print (5) is imaged by switching between multiple light sources in the same way as with visual inspection, and the average value of the gradation value of a certain area of ​​an area without a latent image and the average value of the gradation value of a certain area of ​​an area with a latent image are calculated for the imaged images, and the average values ​​are compared.

[0034] If the comparison results in a difference of a certain gradation value or more, it is determined that the image is not concealed (is visible to the human eye) and is recorded in the evaluation table (6). The recording method is the same as for visual inspection, and the evaluation table creation step (S2) may be automated by processing the method by a program. It is also possible to use average values ​​and correlation coefficients as a comparison method for evaluation.

[0035] (Selection process) In the selection step (S3), as shown in Fig. 10, the evaluation table (6) is used to select the density at which the latent image is concealed relative to the density of the visible image, and printing is performed. In detail, as shown in Fig. 9, the evaluation table (6) is searched for combinations in which the latent image is concealed by the visible image under all visible light sources and / or on all sample substrates, and these are selected (S3-1) as the density of the visible image concealed under all light sources and the maximum density (A) of the latent image.

[0036] Next, latent image data in which the latent image has the maximum density (A) is created, or latent image data in which the original latent image data (4) is density converted to the selected maximum density (A) is created (S3-2). There are density conversion methods such as a method using a tone curve and a method using a lookup table, but in this first embodiment, linear density conversion in which the tone curve is a straight line is used. Note that linear density conversion is a process in which the density (tone value) of an image is converted from a specific range to a different range, and is expressed by the following formula 1.

[0037]

number

[0038] Here, X is the value of one pixel in the source image, Y is the value of one pixel in the destination image, Ymax is the maximum pixel value in the source image, Xmin is the minimum pixel value in the source image, Ymax is the maximum pixel value in the destination image (A in the first embodiment), and Ymin is the minimum pixel value in the destination image (0 in the first embodiment).

[0039] In the first embodiment, as an example of the selection step (S3), the density of the latent image is converted to the maximum density (A) using a density conversion method, but a known method may also be used to calculate the average value of one pixel of the visible image corresponding to the same position (coordinate) as one pixel of the latent image and / or its surrounding pixels, search for the maximum density (A) at which the latent image is concealed, and change it to the maximum density (A) of the latent image.

[0040] Alternatively, as another known method, blurring may be performed only on the portion of the latent image that is not concealed, and the density of the latent image may be changed to the maximum density (A) depending on the intensity of the edge image obtained by blurring the density of the latent image. Alternatively, edge extraction may be performed on the visible image, and the density of the latent image may be changed to the maximum density (A) depending on the intensity of the edge image obtained by blurring the density of the visible image.

[0041] In the first embodiment, the density of the latent image is changed in accordance with the density of the visible image, but the density of the visible image may be changed in accordance with the density of the latent image.

[0042] Next, in the same manner as in the above-mentioned method of combining the visible original image data (3) and the latent image data (4), the latent image data converted to density (A) is combined with the visible original image data (3) to create print data (S3-3), and the created print data is used to create a print on a substrate that can conceal the latent image, similar to the sample substrate.

[0043] Similarly, when forming the halftone dot configuration shown in Figure 1 (b), print data is created by combining data that forms a first halftone area (1) using visible original image data (3) with data that forms a second halftone area (2) converted to density (A), and the halftone dot print (A1) shown in Figure 1 is created on a substrate.

[0044] (program) The present invention also provides a program for causing a computer to execute the method for producing a printed matter.

[0045] Hereinafter, an example will be described in which a halftone dot print (A1) shown in Fig. 1 was specifically created based on the print creation method according to the above embodiment. However, the content of the present invention is not limited to the scope of the following example.

[0046] Example 1 In Example 1, a digital color copier RICOH Pro7100S (printing resolution 600 DPI) manufactured by RICOH Corporation was used as the printer, and high-quality paper was selected as the sample substrate and substrate. The inks forming the halftone print (A1) were CMY inks that do not absorb infrared rays for the image forming portion (1a) and the first background portion (1b) of the first halftone region (1) and the second background portion (2b) of the second halftone region (2), and black ink (K) that absorbs infrared rays for the image portion (2a) of the second halftone region (2).

[0047] The visible original image data (3) was created by regularly adding density from the reference coordinates (0,0) of the origin to the reference coordinates and the final diagonal coordinate (2349,105) to create the visible original image data (3) shown in Fig. 11. Similarly, the latent original image data (4) was created by regularly adding density from the reference coordinates (0,0) of the origin to the reference coordinates and the final diagonal coordinate (2349,105) to create the latent original image data (4) shown in Fig. 12.

[0048] In the synthesis process (S1-3), first halftone area data that forms the image forming portion (1a) and first background portion (1b) of the first halftone area (1) is created using the visible original image data (3), and second halftone area data that forms the image portion (2a) and second background portion (2b) of the second halftone area (2) is created using the latent image original image data (4). The coordinates of three points that are common positions in each data are used as reference points in the first halftone area data and the second halftone area data, and the reference points are superimposed and synthesized to create patch printing data (not shown).

[0049] Next, the image forming portion (1a) and the first background portion (1b) of the first halftone region (1) were created using CMY inks, and the second background portion (2b) of the second halftone region (2) was created with 100% CMY concentration using CMY inks that do not absorb infrared rays. The image portion (2a) was created using black ink (K) that absorbs infrared rays. Next, the first halftone regions (1) were regularly arranged so as to surround the second halftone region (2), and a patch print (5) as shown in Figure 13 was created on high-quality paper, which is a sample substrate.

[0050] Next, the evaluation table (6) is created by checking each character of the created patch print (5) visually or with an optical device such as a camera under three different visible light sources: a D65 light source, an LED light source, and a fluorescent light, and extracting density combinations in which the latent image is not concealed by the visible original image.

[0051] The rating number indicates the sum of all visible values, with 0 being invisible under all light sources, 1 being visible under D65 light source, 2 being visible under LED light source, and 4 being visible under fluorescent light.

[0052] As shown in Figure 14, the evaluation results are as follows: if it is visible with all light sources, the total value will be a maximum of 7; if it is visible with both LED light sources and fluorescent lights, it will be rated as 6; if it is visible with both D65 light sources and fluorescent lights, it will be rated as 5; if it is visible with both D65 light sources and LED light sources, it will be rated as 3; and the numerical values ​​for each of the other individual light sources will also be evaluated.

[0053] Next, the maximum density (A) of the latent image is selected by using the evaluation table (6) shown in FIG. 14 to search for an area where the density of the latent image is concealed in all visible image densities, and the area (7) surrounded by a dotted line where the density is 244 to 255, which is a value of 0 and therefore invisible to all light sources, is determined to be the maximum density (A).

[0054] Next, the latent image original image data (4) is converted using a linear density conversion with a tone curve so that the density of the latent image original image data (4) becomes the maximum density (A) from 244 to 255, and the latent image original image data (4) converted to the maximum density (A) is used to create the second halftone area data (15) shown in Figure 15(a).

[0055] Next, the first halftone area data (16) shown in Fig. 15(b) was created using the visible original image data (3), and the second halftone area data (15) converted to density (A) was synthesized and embedded to create print data (not shown), and the halftone dot print (A1) shown in Fig. 1 was printed on high-quality paper and confirmed with a D65 light source, an LED light source, and a fluorescent light. It was confirmed that the latent image was not visible under any of the light sources, and that it was concealed. When confirmed under an infrared light source, only the latent image was visible. [Explanation of symbols]

[0056] A1 halftone print 1 First halftone area 1a Image forming section 1b First background section 2 Second Halftone Area 2a Image section 2b Second background section 3. Visible raw image data 4. Original latent image data 5 Patch Print 6 Evaluation Table 7 Area where latent image is concealed 7´ Area where latent image is not hidden 8. First Continuous Tone Image 9 Second continuous tone image 10 Printed matter 11 Visible image data 12 Latent image data 13 Visible images 14 Latent Image 15 Second Halftone Area Data 16 First halftone area data

Claims

1. A method for producing a printed matter on which a latent image visible under a predetermined observation condition and a visible image visible under a visible light source formed so as to conceal the latent image are formed, comprising the steps of: a patch printing step of setting the same corner of said visible image and said latent image as a reference coordinate, setting the coordinate diagonally opposite to said reference coordinate as a final coordinate, creating visible original image data and latent original image data by regularly adding pixels and densities from said reference coordinate for an area from said reference coordinate to said final coordinate, setting the coordinates of at least three points that are common positions of said visible original image data and said latent original image data as reference points, and printing on a sample substrate based on patch print data that is synthesized by overlapping said reference points to create a patch print; an evaluation table creation step of creating an evaluation table showing whether the latent image is concealed or not for a combination of the pixels and densities of the visible image and the latent image under a plurality of different visible light sources for the patch print; a selection step of using the evaluation table to select the combination of densities that enables the latent image to be concealed by the visible image, creating latent image data based on the selected densities of the latent image original image data, and printing on a substrate using print data that is a combination of the latent image data and the visible original image data.

2. 2. A program for producing a printed matter, which causes a computer to execute the method for producing a printed matter according to claim 1.

Images