JP4273507B2 - Authentic printed material - Google Patents

Description

  The present invention relates to a printed matter capable of authenticating authenticity applied to valuables such as banknotes, passports, securities, cards, stamps, product tags, toll roads and various valuable tickets.

  With the recent development of digital devices such as scanners, printers, color copiers, etc., it has become possible to easily produce elaborate copies of precious printed matter. As one of the countermeasures, many methods using a metameric pair ink applying metamerism as a visual identification method have been tried. The method of visual discrimination of precious printed matter using metameric pair ink utilized the characteristic that the ink looks the same color or looks different due to the type of illumination light source and the filter that transmits a specific wavelength. Is. In the printed matter that requires anti-counterfeiting technology, a method of utilizing the optical characteristics due to the ink metamerism is conventionally performed.

  Usually, a printed matter printed with colored metameric pair ink has two wavelengths, a wavelength region A which is a visible total wavelength of 400 to 700 nm and a wavelength region B which is a predetermined wavelength transmitted by a predetermined filter or the like to be used. Observed in the area.

  The printed matter A1 shown in FIG. 1A forms a visible image 2 on the substrate 1, and the visible image 2 is printed with the first region 3 printed with the first ink and the second ink. 2 regions 4. When the printed matter A1 is observed with the naked eye under normal light such as sunlight, a fluorescent light, or an incandescent light bulb, as shown in FIG. The second region 4 printed with the second ink is visually recognized in the same color, and only the visible image 2 can be confirmed. When the printed matter A1 is observed with the naked eye through a predetermined filter or the like, as shown in FIG. 1C, the first region 3 printed with the first ink and the second printed with the second ink are used. Since the color of the region 4 is visually recognized differently, it can be confirmed as a latent image. The printed matter A1 is determined to be genuine when a color difference between the first region 3 and the second region 4 occurs through the predetermined filter 10 or the like with respect to the visible image 2, and when the color difference does not occur, it is a fake. It is judged.

  As another method for determining the authenticity of a printed material using another metameric pair ink, there is a method that uses a change in contrast between the pair inks. In this method, since the specific wavelength region is set to a region limited to a range of about several tens of nanometers, the hue changes only slightly, but there is a difference in reflection and absorption characteristics in the specific wavelength region between the paired inks. Since it appears more conspicuously, only the density of the first region 3 in FIG. 1 is reduced, the second region 4 in FIG. 1 is emphasized, and the second region 4 appears to appear as a latent image. As described above, there is also a method for authenticating whether a latent image appears through a filter and performing authenticity determination.

  In any case, in each method of authenticating the presence or absence of a hue change or the appearance of a latent image, authenticity determination using a metameric pair ink can be performed by measuring differences in ink reflection and absorption characteristics in a specific wavelength region. It is what you use.

  For example, it looks the same color under normal light such as sunlight, fluorescent light or incandescent light bulb, but it is viewed under a light source having a predetermined spectral energy distribution, through a predetermined filter, or passed through a predetermined filter. An image forming body characterized in that a pattern is formed on a substrate so that a pattern can be observed in contrast to each other by two kinds of colorants that have metallic properties that appear to have different hues when viewed under bright light. It is disclosed (see Patent Document 1).

  In addition, the present applicant assigns metameric pair inks with different near-infrared characteristics, and prints using the two types of metameric pair inks can reflect or transmit light of two different wavelengths in the near-infrared region. An application has been filed for a true / false discrimination method and apparatus for reading in terms of voltage (see Patent Document 2).

Japanese Examined Patent Publication No. 60-58711 (page 1-4, FIG. 1-11) Japanese Patent No. 3709539 (page 1-6, FIG. 1-6)

  However, the printed matter printed with the conventional metameric pair ink is generally printed with a solid printing pattern when authenticating the presence or absence of a hue change or a latent image, and FIG. As shown in the figure, the latent image is given by using a so-called "extract" configuration in which a part of the visible image is blanked and the latent image is superposed and replaced with the blanked portion. Therefore, there is a risk that the latent image embedded in the visible image will be visible under normal light, and the degree of freedom of design. However, a visible image that appears to be the same color under normal light and a latent image that appears when observed through a predetermined filter or the like are simple characters or marks. That is, there is no one that forms a visible image having a density gradation or a latent image having a density gradation. Japanese Patent Publication No. 60-58711 and Japanese Patent No. 3709539 do not describe the formation of density gradation.

  Assuming that the visible image 2 printed with the metameric pair ink, which is visually recognized under normal light, is used for the printed material using the metameric pair ink, at least two images, not just the solid image. In the case of the printed matter A2 having two density gradations, for example, a density gradation as shown in FIG. 2A, a highlight area, a halftone area, and a shadow area, the second area 4 appears through a predetermined filter 10 or the like. There is a problem that the visibility of the latent image consisting of is inferior as shown in FIG. This means that the gradation of the visible image 2 needs to be reflected in the latent image composed of the second region 4 in order to express the gradation in the visible image 2 that is visually recognized under normal light. For this reason, when the image is observed through a predetermined filter 10 or the like, the gradation of the visible image 2 appears in the latent image formed of the second region 4, and the latent image formed of the second region is light. A region is formed and the visibility is inferior. In addition, the visible image 2 itself is often changed to such an extent that the gradation representation area is slightly lost when the filter is passed through, so that the gradation of the visible image 2 itself appears to the extent that it can be visually observed. Mixing with the latent image composed of the region 4 is also one of the causes of poor visibility of the latent image when the visible image 2 is given gradation.

  An object of the present invention is to solve such a conventional problem. Under visible light, a plurality of first regions and second regions are alternately arranged adjacent to each other. A visible image having a density gradation in which the second region is arranged by hair removal is visually recognized, and further, under visible light, the second region is concealed by the first region, and a latent image composed of the second region Is in a state where it is difficult to be visually recognized or is not visually recognized. However, when observed with the naked eye through a predetermined filter or the like, the latent image composed of the second area is visually recognized, and the latent image reflects the density gradation of the area having the density gradation visible under visible light. In addition, since the latent image formed of the second region is visually recognized with a clear density difference from the first region, it is possible to easily determine whether the image is true or false. Further, it is possible to give density gradation to the latent image composed of the second region as needed, and there is no design restriction.

  An object of the present invention is to propose a printed matter printed with a metameric pair ink having the above-described gradation image and capable of authenticating authenticity.

  In the present invention, a visible image having a density gradation is formed by arranging a plurality of first regions and second regions on a substrate, and the second region is formed by tweezing in the first region. Arranged to form a latent image, and an image obtained by removing the second region for constructing the latent image from the visible image having the density gradation by the first region is formed; Are printed with the first printing ink, the second area is printed with the second printing ink, and the spectral reflectances of the first printing ink and the second printing ink are the first and second spectral inks in the visible region. The printed matter is characterized by being printed with a metameric pair ink having a different value in the range of the second wavelength in the visible region and different values in the second wavelength range in the visible region.

  In the present invention, the halftone dot area ratio of the visible image having the density gradation is formed at 40 to 80% or less, and the halftone dot area ratio of the latent image is formed at 40% or less. It is a printed matter that is characterized by authenticity.

  In the present invention, the integral value of the spectral reflection spectrum of the first printing ink between 640 and 700 nm is more than twice the integral value of the spectral reflection spectrum of the second printing ink between 640 and 700 nm. The integral value of the spectral reflection spectrum of the first printing ink between 400 and 600 nm is substantially the same as the integral value of the spectral reflection spectrum of the second printing ink between 400 and 600 nm. It is a printed material that can be checked for authenticity.

  The present invention is the printed matter capable of authenticating authenticity, wherein the latent image has a density gradation.

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a printed material having a gradation image that can be applied to a valuable product printed with a metameric pair ink that is not restricted by a design, and that has a gradation image. Of course, it can be applied to printed materials other than valuables.

  A visible image having a density gradation is visually recognized on the authenticity determination printed matter under visible light. Further, under visible light, the latent image is in a state where it is difficult to see or not visible. However, when observed with the naked eye through a predetermined filter or the like, the latent image is visually recognized. The latent image does not reflect the density gradation of the area having the density gradation, and the latent image is visually recognized with a clear density difference between the latent image and other areas. Therefore, it is possible to easily determine whether or not the latent image is visually recognized, and to determine whether the latent image is true or false.

  The first region and the second region formed with the metameric pair ink are paired with each other, and the concealability of the latent image under visible light is improved as compared with the conventional case by making the overall density constant. In addition, by appropriately setting the minimum halftone dot area ratio and the maximum halftone dot area ratio of the first region and the second region, the concealability of the latent image under visible light is improved, and through a predetermined filter or the like When observed with the naked eye, the latent image is clearly visible.

  Further, it is possible to give density gradation to both the visible image and the latent image. Furthermore, a camouflage pattern is formed on a visible image with at least one color ink (for example, magenta ink and / or yellow ink) having a high reflectance with a spectral reflectance between 640 and 700 nm, thereby giving a plurality of colors. Therefore, the concealability of the latent image under visible light can be improved.

  The best mode for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the best mode for carrying out the invention described below, and includes various other embodiments within the scope of the technical idea described in the scope of claims.

  Usually, the image formed by the metameric pair ink has two wavelength regions, a wavelength region A which is a visible total wavelength of 400 to 700 nm and a wavelength region B which is a predetermined wavelength transmitted by a predetermined filter to be used. Observed at. The printed matter capable of authenticating in the embodiment of the present invention is produced by printing on a substrate using two or more kinds of ink.

  FIG. 3 (a) shows a printed matter B that can be determined authenticity. As shown in FIG. 3A, a plurality of first regions 2 and second regions 3 are arranged on the substrate 1 to form a visible image 4 having a density gradation. The second area 3 is arranged in the first area 2 by tweezers. In this hair removal, the second region 3 is formed in the non-printing region 2a of the first region 2 as shown in FIG. Furthermore, as shown in FIG. 4, the position where the second region 3 is formed in the non-printing region 2 a of the first region 2 is not particularly limited. Further, as shown in FIG. 5, the boundary between the first region 2 and the second region 3 is printed in an overlapped state as shown in FIG. 5 (a) or as shown in FIG. 5 (b). The first region 2 and the second region 3 may have a region 6 in which a part thereof overlaps. In the partially overlapped area 6, the second area 3 may be printed on the first area 2, or the first area 2 may be printed on the second area 3. In this case, it is preferable to adjust the density such as gradation in the region where one or both of the first region 2 and the second region 3 overlap.

  As shown in FIG. 6, an image 6 is formed by removing the second region 3 for forming the latent image 5 from the visible image 4 having the density gradation by the first region 2. A latent image 5 is formed. Further, as shown in FIGS. 2, 3, 4, and 5, a latent image is formed in the first region 2 at the boundary between the first region 2 and the second region 3. A camouflage area 7 is provided to conceal 5.

  An image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation composed of the first region 2 is formed with the first printing ink, and the second region 3 The resulting latent image is printed with the second printing ink.

  The relationship between the first printing ink and the second printing ink will be described. The spectral reflectances of the first printing ink and the second printing ink are approximated in the first wavelength range in the visible region, and are different values in the second wavelength range in the visible region. That is, the first printing ink and the second printing ink have a relationship of metameric pair ink. Further, the integral value of the spectral reflection spectrum between 640 and 700 nm of the first printing ink has more than twice the integral value of the spectral reflection spectrum between 640 and 700 nm of the second printing ink. The integral value of the spectral reflection spectrum between 400 and 600 nm of the ink is preferably substantially the same as the integral value of the spectral reflection spectrum between 400 and 600 nm of the second printing ink.

  FIG. 7 is an example of a spectral reflectance curve of the first printing ink and the second printing ink that are the metameric pair ink used in the present invention. As shown in FIG. 7, the relationship between the spectral reflectances of the first printing ink and the second printing ink is designed to produce a spectral reflectance difference of 30% or more between 640 to 700 nm, and 20% at 400 to 600 nm. The first printing ink and the second printing ink are produced with a design that produces the following spectral reflectance difference. The first printing ink and the second printing ink having the spectral reflectance curve shown in FIG. 7 are tea-based colors. However, in the present invention, the description is given using a metameric pair ink of tea color, but the metameric which is excellent in color matching under normal light and excellent in color difference in a specific wavelength range. If it is assumed that pair ink is used, there is no restriction on the color.

  The relationship between the first printing ink and the second printing ink, which are the metameric pair inks shown in FIG. 7, is designed so that a large difference occurs in the spectral reflectance of 640 nm or more, and the wavelength region B is the highest visible from 640 nm. The wavelength range is 700 nm. In FIG. 7, a more remarkable difference in spectral reflectance is observed at 660 nm or more. However, when a sharp cut filter or the like that transmits light of 660 to 700 nm is used, the amount of light transmitted through the indoor light source is insufficient. No matter how excellent the reflection and absorption characteristics are, the entire image itself will darken and become almost invisible, so a strong light source is often required. From the above, the wavelength region B is set to 640 to 700 nm. Regarding the setting of the wavelength region B, it is only necessary to determine the authentication wavelength desired by the user, select an ink material according to the authentication wavelength, and produce a metameric pair ink, and is not particularly limited to this wavelength region. .

  Next, the halftone dot area ratio of the image 6 excluding the second region 3 for constituting the latent image 5 from the visible image 4 having the density gradation composed of the first region 2, and the halftone image 5. The relationship between the dot area ratio and the halftone dot area ratio of the camouflaged area 7 in order to conceal the latent image 5 in the first area 2 will be described.

  The visible image 4 having the density gradation printed by the first area 2 and the second area 3 is printed with a halftone dot area ratio in the first predetermined range, and the density scale printed by the first area 2 is printed. The image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having a tone is printed with the halftone dot area ratio in the second predetermined range, and is printed by the second region 3. The latent image 5 is printed with a halftone dot area ratio in the third predetermined range. In order to conceal the latent image 5 in the first region 2, the camouflaged area 7 has a halftone dot in the fourth predetermined range. It is necessary to print at the area ratio.

  The visible image 4 having the density gradation composed of the first region 2 and the second region 3 printed with the first printing ink and the second printing ink is printed with a halftone dot area ratio in the first predetermined range. Thus, the latent image 5 composed of the second region 3 printed with the second printing ink needs to be printed with a minimum halftone dot area ratio of the visible image 4 having a density gradation.

  The halftone dot area ratio of the first predetermined range of the visible image 4 having the density gradation printed by the first region 2 and the second region 3 is printed at 40 to 80% or less. The halftone dot area ratio of the second predetermined range of the image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation to be printed is 0 to 80% or less. In order to conceal the latent image 5 in the first region 2, the halftone dot area ratio of the third predetermined range of the latent image 5 printed by the second region 3 is 40% or less. The halftone dot area ratio of the fourth predetermined range of the camouflage region 7 is preferably printed at 40% or less.

  Next, the visible image 4 having the density gradation composed of the first region 2 and the second region 3 printed with the first printing ink and the second printing ink is printed with the second printing ink. The relationship between the latent image 5 formed of the second region 3 and the density gradation region of the camouflage region 7 in order to hide the latent image 5 in the first region 2 printed with the first printing ink. 8 will be used for explanation.

  As a means for concealing the latent image, the halftone dots of the second region 3 printed with the second printing ink forming the latent image 5 and the first region 2 printed with the first printing ink are used. In order to conceal the latent image 5, the total dot area ratio obtained by combining the halftone dots of the camouflage region 7 is set to a constant value.

  In the wavelength region A, the region printed with the first printing ink and the region printed with the second printing ink expressed by a specific reflection density are good in each other region in the wavelength region B. A density difference can be obtained. A maximum dot area ratio for obtaining a high density difference in the wavelength region B is defined as a dot area ratio A. This is because if the density of the visible image 5 having density gradation is too high, the visible image 5 having density gradation will be visually recognized even in the wavelength region B, so that it is preferable to provide a certain gradation restriction.

  As shown in FIG. 8, in the wavelength region A, a visible image 4 having a density gradation composed of the first region 2 and the second region printed with the first printing ink and the second printing ink, In order to conceal the latent image 5 consisting of the second area 3 printed with the second printing ink and the latent image 5 in the first area 2 printed with the first printing ink, The relationship between the density gradation areas will be described with reference to FIG.

  The visible image 4 having the density gradation composed of the first region 2 and the second region 3 printed with the first printing ink and the second printing ink is converted into a latent image 5 composed of the second region 3. A latent image composed of a second area 3 that is printed with the second printing ink and that has a halftone dot area ratio (for example, 40%) or more and a halftone dot area ratio A (for example, 80%) or less. The density gradation area 5 is configured to be equal to or less than the lowest halftone dot area ratio of the visible image 4 having the density gradation, for example, 0 to 40%. In order to conceal the latent image 5 in the first region 2 printed with the first printing ink, the density gradation region of the camouflage region 7 has a dot area ratio A (for example, 80%) or less, for example, 0 to Consists of 40%. The halftone dot area ratio of the camouflage area 7 is a constant value (for example, 40%) of the total dot area ratio obtained by combining the halftone dots constituting the latent image 5 and the halftone dots of the camouflage area 7 paired with the halftone dots. ). For example, when the halftone dot area ratio of the latent image 5 is 0, the halftone dot area ratio of the camouflage region 7 to be paired is 40, and when the halftone dot area ratio of the latent image 5 is 20, it becomes a pair. When the halftone dot area ratio of the camouflage area 7 is 20 and the halftone dot area ratio of the latent image 5 is 40, the halftone dot area ratio of the camouflage area 7 to be paired is zero.

  When using the metameric pair ink, the latent image viewed with a filter or the like uses only the light in the wavelength region B out of the light existing in the observation environment. Even in an image that feels like this, in the wavelength region B, the amount of light itself is greatly reduced. Therefore, the reflection and absorption characteristics of the light in the wavelength region B are reflected more strongly, and the density is higher than the density obtained in the wavelength region A. It can be made to feel visually. That is, when the reflection and absorption characteristics of the ink in the wavelength region B are excellent, even if the concentration is only visible as a highlight level in the wavelength region A, the concentration of shadow from the middle when observed through a filter. It is possible to make the observer recognize.

  The printed material B capable of authenticating authenticity is a visible image 4 having a density gradation as shown in FIG. 9 (a) under normal light such as sunlight, fluorescent light or incandescent light having a specific wavelength A, and a latent image. Image 5 cannot be confirmed. The latent image 5 is arranged in the visible image with a fine structure that is invisible to the visible image with a reflection density equal to or lower than that of the visible image 4 having the density gradation. It is completely hidden inside.

  When the printed material B capable of authenticating authenticity is observed through different light sources in the wavelength region B or through a predetermined filter 10, the latent image 5 is confirmed as shown in FIG. 9B. The image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation printed with the first printing ink appears as if erased, and the latent image It appears that only 5 is visible. The latent image 5 has a reflection density equal to or lower than that of the image 6 obtained by removing the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation printed with the first printing ink. However, the image obtained by removing the second region 3 for forming the latent image 5 from the visible image 4 having the density gradation composed of the first region 2 printed with the first printing ink in the wavelength region B. 6 is converged to a constant density, so that the density difference between the latent image 5 and the image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having density gradation is high. As a result, it can be expressed as a latent image with high visibility. The image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation composed of the first region 2 and the latent image 5 overlap with each other in terms of design. When observed in the region B, the density of the image 6 excluding the second region 3 for forming the latent image 5 from the visible image 4 having the density gradation composed of the first region 2 in the latent image 5. The gradation is hardly reflected, and there is a clear density difference between the latent image 5 and the image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation. Therefore, it is possible to easily determine authenticity.

  Excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation composed of the first region 2 printed by the first printing ink used for the print B for authenticity discrimination. As an easy procedure for producing the second plate surface 14 of the latent image 5 consisting of the first plate surface 13 of the image 6 and the second region 3 printed with the second printing ink, FIG. In order to conceal the latent image 5 in the first area 2 shown in (a), the camouflage area 7 and the latent image 5 shown in FIG. 10B are formed, and the camouflaged area 7 and the latent image 5 are formed. An image 11 having a constant density is formed as shown in FIG. In this case, the density is lowered to a level equal to or lower than the minimum halftone dot area ratio of the visible image 4 having density gradation. Next, only the camouflage area 7 is extracted from the latent image 5 and the camouflage area 9 shown in FIG. 10C with respect to the image 12 having the density gradation shown in FIG. Is added to the image 12 having the dot ratio and lowered to the halftone dot area ratio A to produce the first printing plate 13 forming the first region 2 shown in FIG. For the second printing plate 14, only the latent image 5 is extracted from the latent image 5 and the camouflaged region 7 shown in FIG. 10C to produce the second printing plate 14. However, it goes without saying that the present invention is not limited to this procedure.

  In a printed matter with authenticity discrimination, a camouflage pattern is formed on a visible image 4 having a density gradation with at least one color ink (for example, magenta ink and / or yellow ink) having a high spectral reflectance between 640 and 700 nm. By overprinting, a plurality of colors can be provided. Even with such a configuration, the above-described operation when observed with a filter or the like is not impaired. This is because when a visible image 4 having a density gradation is overprinted with ink (for example, magenta ink and / or yellow ink) having a wavelength longer than that of a predetermined filter (for example, SC64 manufactured by FUJI FILM), the filter is applied to the printed matter. This is because the overprinted ink cannot be visually recognized even if it is repeatedly observed. Further, the latent image 5 embedded in the visible image 4 having the density gradation is not visually recognized under normal light.

  The halftone dot shape used in the present invention is not limited to a circular dot, but a random dot or a special halftone dot generation method proposed in Japanese Patent Application Laid-Open No. 11-268228 filed earlier by the present applicant. It is also possible to use a special halftone dot shape having a degree of freedom obtained by converting an input image taking design characteristics into a continuous tone halftone dot composed of a halftone screen.

  The first area 2 and the second area are preferably printed at 60 to 700 line / inch.

  Moreover, the base material used for the printed matter capable of authenticating authenticity of the present invention is not particularly limited, and paper sheets or films such as high-quality paper, coated paper, and art paper can be used.

    The printing method of the printed matter capable of authenticating authenticity of the present invention is not particularly limited, such as an offset printing method, a gravure printing method, a screen printing method, a flexographic printing method, an ink jet printer, or a laser printer. The offset printing method is particularly preferable because it is often required. When actually producing printed matter, in most printing methods, the dot area ratio is expected to increase due to dot gain between the printed matter and the plate surface. It goes without saying that there is a need to do.

  It should be noted that the visible image and the latent image having the density gradation may be a simple binary image such as a character, a number, or a symbol, or may be a gradation image.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, the content of this invention is not limited to the range of these Examples.

  The printed matter of the Example was produced using the 1st printing ink and the 2nd printing ink which have the spectral reflectance curve shown in FIG. The image 6 excluding the second region 3 for constituting the latent image 5 from the visible image 4 having the density gradation shown in the embodiment is printed with the first printing ink, and the latent image 5 is the second image. The printing ink was used.

  In carrying out the invention, the halftone dot area ratio A, the latent image 5 and the combined density of the camouflage region 7 are first determined according to the characteristics of the first printing ink and the second printing ink shown in FIG. went. First, the gradation scales of the first printing ink and the second printing ink to be used were respectively printed, and the reflection density characteristics of both inks in the wavelength region A were confirmed as shown in FIG. In the wavelength region A, it is important that the halftone dot area ratio and the reflection density of the first printing ink and the second printing ink are in a substantially proportional relationship, and as a result of the measurement, it was confirmed that they are in a proportional relationship. Next, in the wavelength region B, the density difference between the first printing ink and the second printing ink was determined by visual inspection through a sharp cut filter. It is also possible to calculate the integral value in the wavelength region B of the spectral spectrum based on the dot area ratio of each of the first printing ink and the second printing ink.

  It was confirmed that the latent image 5 has sufficient gradation in the wavelength region B when it is printed with the second printing ink in a range where the dot area ratio is 0 to 40% or less. The camouflage area 7 printed with the first printing ink is formed with a dot area ratio of 0 to 40% or less, and halftone dots constituting the latent image 5 and the camouflage area 7 paired with the halftone dots. The total of the dot area ratios combining the halftone dots was set to a constant value (40%). The halftone dot area ratio printed with the first printing ink was confirmed to be within the range where 80% or less continuous gradations are within a certain gradation in the wavelength region B, so printing with the first printing ink is possible. The region to be formed was formed in a range where the dot area ratio was 80% or less. Therefore, the visible image 4 having the density gradation printed with the first printing ink and the second ink was formed with a dot area ratio of 40 to 80% or less.

  The image 6 obtained by removing the second area 3 for constructing the latent image 5 from the latent image 5 and the visible image 4 having density gradation has a gradation expression range of 25% or more due to the difference in the dot area ratio. Is preferably reached.

  Using the first printing ink and the second printing ink, a printed material C that can be determined by an offset proofing printing machine was prepared.

  As shown in FIG. 12, the printed material C capable of authenticating authenticity includes a plurality of first regions 2 and second regions 3 which are alternately adjacent to each other on the substrate 1, and a third region 3 in the second region 3. The visible image 4 having the density gradation is formed by arranging the regions 4 by hair removal. The dot area ratio of the visible image 4 having the density gradation is formed in the range of 40 to 80% or less. The first region 2 forms an image 6 excluding the second region 3 for constructing the latent image 5 from the visible image 4 having the density gradation, and the second region 3 forms the latent image 5. The camouflaged area 7 was formed in the first area 2 at the boundary between the first area 2 and the second area 3 in order to conceal the latent image 5. The halftone dot area ratio of the latent image 5 is formed in a range of 0 to 40% or less, and the halftone dot area ratio of the camouflage area 7 is formed in a range of 0 to 40% or less. The halftone dot area ratio of the composite region 5 was adjusted to 40%.

  As shown in FIG. 13 (a), only the visible image 4 having a density gradation is confirmed in the printed material C that can be determined as authenticity under normal light from a specific wavelength A such as sunlight, fluorescent light, or incandescent light bulb. . The latent image 5 could not be confirmed.

  As shown in FIG. 13B, the printed material C capable of authenticating authenticity has a density gradation when observed with light in the wavelength region B (640 nm to 700 nm) through the sharp cut filter 10 (SC64 manufactured by FUJI FILM). A latent image 5 was confirmed.

It is a figure which shows the conventional metameric pair printed matter. It is a figure which shows the problem of the conventional metameric pair printed matter. This is a printed matter B of the present invention capable of authenticating authenticity. It is a figure which shows the positional relationship of tweezers. FIG. 3 is a diagram illustrating a boundary between a second region 3 and a third region 4. It is explanatory drawing of the printed matter B which can authenticate authenticity of this invention. It is a figure which shows an example of the spectral reflectance curve of the 1st printing ink which is a metameric pair ink used by this invention, and a 2nd printing ink. A visible image 4 having a density gradation composed of a first area 2, a second area 3 and a third area 4 printed with the first printing ink and the second printing ink, and the first printing ink. It is explanatory drawing about the relationship between the camouflage area | region 7 which consists of the 2nd area | region 3 printed, and the density gradation area | region of the latent image 5 which consists of the 3rd area | region printed with 2nd printing ink. It is explanatory drawing about the effect | action of the printed matter B which can authenticate authenticity of this invention. It is explanatory drawing which shows the method for producing the 1st printing plate and the 2nd printing plate. It is a figure which prints the gradation scale of 1st printing ink and 2nd printing ink, respectively, and shows the reflection density characteristic in the wavelength range A. FIG. It is explanatory drawing of the printed matter C which can authenticate authenticity of an Example. It is a figure which shows the effect | action of the printed matter C which can authenticate authenticity of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 1st area | region 3 2nd area | region 2a Non-printing area | region 4 Visible image 5 which has a density gradation The latent image 6 The 2nd for comprising the latent image 5 from the visible image 4 which has a density gradation The image excluding the area 7 The camouflaged area 10 The filter 11 The image having a constant density 12 The image having the density gradation 13 The first printing plate 14 The second printing plate A Printed matter B, C Printed matter with authenticity discrimination

Claims (4)

A plurality of first regions and second regions are arranged on the substrate to form a visible image having a density gradation, and the second region is arranged in the first region by hair removal and is latent. An image image is formed, and an image obtained by excluding the second region for forming the latent image from the visible image having the density gradation is formed by the first region, and the first region is the first region. The first region is printed with the second printing ink, and the spectral reflectance of the first printing ink and the second printing ink is within the first wavelength range within the visible region. A printed matter capable of authenticating authenticity, which is printed with a metameric pair ink having a different value in the second wavelength range in the visible region. 2. The halftone dot area ratio of the visible image having the density gradation is formed at 40 to 80% or less, and the halftone dot area ratio of the latent image is formed at 40% or less. Printed material that can be checked for authenticity. The integral value of the spectral reflection spectrum between 640 and 700 nm of the first printing ink has at least twice the integral value of the spectral reflection spectrum between 640 and 700 nm of the second printing ink. The integral value of the spectral reflection spectrum between 400 and 600 nm of the printing ink is substantially the same as the integral value of the spectral reflection spectrum between 400 and 600 nm of the second printing ink. Printed material that can be distinguished. 4. The printed matter capable of authenticating authenticity according to claim 1, wherein the latent image has a density gradation.

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