JP4441632B2 - Authentic printed material - Google Patents

Description

  The present invention relates to a printed matter capable of authenticating authenticity that can be applied to valuables such as banknotes, passports, securities, cards, stamps, product tags, coupon tickets for toll roads, and various 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 light source to illuminate and the filter that transmits a specific wavelength. Is. Conventionally, a method of utilizing optical properties due to ink metamerism in printed matter that requires anti-counterfeiting technology has been used.

  Usually, a printed matter printed with a colored 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 or the like to be used. Observed in the wavelength region.

  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 from sunlight, a fluorescent light, an incandescent light bulb, or the like, 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 ink printed with the second ink are used. Since the color of the area 4 of 2 is visually recognized differently, it can be confirmed as a latent image. The printed matter A1 is determined to be genuine when the 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 the color difference does not occur. Judgment of authenticity is performed by determining that the object is fake.

  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 or 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 decreases, the second region 4 is emphasized, and the second region 4 appears to appear as a latent image. As described above, there is also a true / false discrimination method that authenticates the presence / absence of a latent image through a filter and performs true / false discrimination.

  In any case, in each of the above-described methods for authenticating the presence or absence of a hue change or the appearance of a latent image, the authenticity determination using the metameric pair ink is based on the reflection / absorption characteristics of the ink in a specific wavelength region. The difference is used.

  For example, it looks the same color under normal light from sunlight, fluorescent lamps, incandescent lamps, etc., but it is viewed under a light source having a predetermined spectral energy distribution, through a predetermined filter, or passed through a predetermined filter. Anti-counterfeiting, characterized in that two types of colorants, which have metallic properties that look different when viewed under bright light, are formed on a substrate so that the patterns can be compared with each other. An image forming body with a countermeasure 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, the latent image may be given by using a so-called simple “drop” configuration in which a part of the visible image is blanked as it is and the latent image is superposed and replaced with the blanked portion. Is almost. Therefore, since colors of a plurality of colors are not used, the colors are poor, and there is a possibility that the latent image embedded in the visible image is visually recognized under normal light. In addition, a visible image that does not have a degree of design freedom and 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 and marks. That is, there is no one that forms a visible image having a density gradation or a latent image having a density gradation. Neither Patent Document 1 nor Patent Document 2 describes the formation of density gradation.

  Assuming that the above-described “pull out” configuration is used for a printed matter using a metameric pair ink, the visible image 2 printed with the metameric pair ink that is normally viewed under light is not limited to a solid image, but at least two. A second area that appears through a predetermined filter 10 or the like when the printed matter A2 has two density gradations, for example, a density gradation as shown in FIG. 2A, a highlight area, a halftone area, and a shadow area. There is a problem that the visibility of the latent image consisting of 4 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 formed of the region 4 is also one of the causes of poor visibility of the latent image when the gradation is given to the visible image 2.

  An object of the present invention is to solve such a conventional problem. An image in which a plurality of image lines are formed by the second region and the third region, and the first region has a density gradation. In the printed matter on which a visible image having a density gradation composed of a first region, a second region, and a third region is visible under visible light, the third region is visible under visible light. The latent image formed of the third area is concealed by the second area, and is hardly visible or is not visually recognized. When observed with the naked eye through a predetermined filter or the like, the latent image formed of the third area is visually recognized, and the latent image does not reflect the density gradation of the area having the density gradation visible under visible light. In addition, since the latent image formed of the third area is visually recognized with a clear density difference from the first area and the second area, 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 third region as necessary, 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.

  The present invention is a printed matter in which a visible image having a density gradation is formed by three areas on a substrate, and an image having a density gradation is formed by a plurality of first areas, and the second area And the third region form a plurality of image lines, and the first region, the plurality of image lines composed of the second region and the third region are alternately arranged, and the latent image is formed by the third region. Formed, the second area becomes a camouflaged area of the latent image, the first area and the second area are printed with the first printing ink, the third area is printed with the second printing ink, The spectral reflectances of the printing ink and the second printing ink were approximated in the first wavelength range in the visible region, and were printed with a metameric pair ink having a different value in the second wavelength range in the visible region. It is a printed matter capable of authenticating authenticity.

  Further, the present invention is a printed matter capable of authenticating authenticity, wherein a plurality of image lines are formed at a predetermined pitch.

  In the present invention, the image area ratio corresponding to one pitch in a predetermined pitch is 0 to 40% or less, and the dot area ratio corresponding to one pitch of an image having a density gradation is 0 to 80% or less. It is a printed matter that can be determined whether it is authentic or not.

  Further, according to the present invention, 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 first 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. It is a printed material that can be checked for authenticity.

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

  According to the present invention, a printed matter having a gradation image that can be applied to a valuable printed with a metameric pair ink that is not restricted by the design can be obtained. 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, the latent image is hardly visible or is not visually recognized under visible light. 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 density gradation, and the latent image and other areas are visually recognized with a clear density difference. 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 second region and the third 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. Further, by appropriately setting the minimum image area ratio or the minimum halftone dot area ratio and the maximum image area ratio or the maximum halftone dot area ratio of the first region, the second region, and the third region, visible light is set. The concealability of the underlying latent image is improved, and the latent image is clearly visible when observed with the naked eye through a predetermined filter or the like.

  It is possible to give density gradation to both the visible image and the latent image. Further, a camouflage pattern is formed on a visible image 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, and a plurality of colors. And 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. The image area ratio described in the best mode for carrying out the invention is a ratio of a surface line in one pitch composed of an image line and a non-image line.

  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 or the like 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.

(Embodiment 1)
FIG. 3 (a) shows a printed matter B that can be determined authenticity. As shown in FIG. 3A, a visible image 5 having a density gradation is formed on the substrate 1 by three regions (first region 2, second region 3, and third region 4). In the visible image 5 having density gradation, an image 7 having density gradation is formed by the first region 2 as shown in FIG. A plurality of first regions 2 are arranged in a strip shape. As shown in FIG. 3C, a plurality of image lines 6 are formed by the second region 3 and the third region 4, a latent image 8 is formed by the third region 4, and the second region 3 The camouflaging area 9 of the latent image 8 is set. As shown in FIG. 3A, a plurality of image lines composed of the first region 2 and the second region 3 and the third region 4 are alternately arranged. The image 7 having density gradation is divided and arranged in a plurality of non-image areas, which are image lines. The first region 2 and the second region 3 are printed with the first printing ink, and the third region 4 is printed with the second printing ink.

  As shown in FIG. 4 (a), the plurality of image lines 6 are composed of the second region 3 shown in FIG. 4 (b) and the third region 4 shown in FIG. 4 (c). . The hair removal referred to here is the formation of the third region 4 in the non-printing region 3 a of the second region 3 for forming the plurality of image lines 6. Alternatively, the second region 3 is formed in the non-printing region 4 a of the third region 4 for forming a plurality of image lines 6.

  Further, the boundary between the second region 3 and the third region 4 is printed without overlapping as shown in FIG. 5A, or the second region 3 as shown in FIG. 5B. The third region 4 may have a region 11 where a part of the third region 4 overlaps, but it is preferable that the region 11 where the part overlaps is not visible. In the region 11 that partially overlaps, the third region 4 may be printed on the second region 3 or the second region 3 may be printed on the third region 4. In this case, it is desirable to limit the overlapping area of one or both of the second area 3 and the third area 4 to a size that is not visually recognized. It is preferable to adjust the density.

  The plurality of image lines 6 formed by the second region 3 and the third region 4 are preferably formed at a predetermined pitch. The line width of the line 6 is preferably about 80 to 1000 μm. The pitch of the image line 6 is preferably about 240 to 3000 μm. When the second area 3 and the third area 4 are line drawing lines, the image 7 having a density gradation is formed by being divided into non-line drawing areas of the line drawing lines.

  FIG. 6 explains the relationship between the second region 3 and the third region 4 of the plurality of image lines 6. The relationship between the second region 3 and the third region 4 of the plurality of image lines 6 can be implemented in various forms. For example, FIG. 6A shows a predetermined pitch w1 of the first image line 12 formed by the second region 3 and a predetermined pitch w2 of the second image line 13 formed by the third region 4. Are substantially the same. That is, in this example, the first image line 12 and the second image line 13 have substantially the same image line width and non-image line width. In FIG. 6B, the second image line 13 formed by the third region 4 is surrounded by the first image line 12 formed by the second region 3. That is, the image line width of the first image line 12 is an example larger than the image line width of the second line 13. In FIG. 6C, the second image line 13 formed by the third region 4 is not surrounded by the first image line 12 formed by the second region 3, but FIG. ) Is an example in which the image line width of the first image line 12 is larger than the image line width of the second line 13. In FIG. 6D, the image line width of the second image line 13 formed by the third region 4 is not constant but is different, and the latent image 4 having density gradation is formed.

  It is preferable that the image area ratio corresponding to one pitch of image lines formed by the second region 3 and the third region 4 is 0 to 40% or less. The halftone dot area ratio of the image 7 having density gradation is preferably 0 to 80% or less. Thereby, the visibility and non-visibility of the latent image 3 of the present invention described later are improved. Note that the image 7 having the density gradation can express the density gradation with a thick image line. In this case, it is preferable that the image area ratio corresponding to one pitch of the image 7 having the density gradation is 0 to 80% or less.

  The image 7 having the density gradation composed of the first region 2 and the camouflaged region 9 composed of the second region 3 are made of the first printing ink, and the latent image composed of the third region 4 is made of the second printing ink. Printed.

  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 range of the first wavelength in the visible region, and have different values in the range of the second wavelength in the visible region. That is, the first printing ink and the second printing ink have a relationship of metameric pair ink. In addition, 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 printing 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 color inks. However, in the present invention, the description is described using a brownish-colored metameric pair ink, but the metameric pair is excellent in color matching under normal light and excellent in color difference in a specific wavelength range. If it is assumed that 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, a normal indoor light source has insufficient light amount to transmit. Thus, no matter how excellent the reflection or absorption characteristics of the ink 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 this wavelength region B, it is sufficient to decide the authentication wavelength desired by the user, select an ink material according to the authentication wavelength, and produce a metameric pair ink. It is not limited.

  Next, the halftone dot area ratio or image area ratio of the image 7 having the density gradation formed by the first area 2, the image area ratio of the latent image 8 formed by the third area 4, and the first The relationship of the line area ratio of the camouflaged area 9 of the latent image 8 formed by the area 3 of 2 will be described.

  The visible image 5 having the density gradation printed by the first region 2, the second region 3, and the third region 4 is printed with the image area ratio and / or the dot area ratio within the first predetermined range. The image 7 having the density gradation printed by the first region 2 is printed with a halftone dot area ratio or image area ratio within a second predetermined range, and the camouflage region 9 printed by the second region 3 is It is necessary to print the latent image 8 printed with the third predetermined range of the image area and printed with the third region 4 with the image area ratio of the fourth predetermined range.

  The visible image 5 having the density gradation composed of the first region 2, the second region 3, and the third region 4 printed with the first printing ink and the second printing ink has an image area within a predetermined range. The latent image 8 comprising the third region 4 printed with the rate and / or the dot area rate and printed with the second printing ink is equal to or less than the minimum dot area rate of the visible image 5 having a density gradation. It is necessary to print at an area ratio or less.

  The image area ratio and / or halftone dot area ratio of the first predetermined range of the visible image 5 having the density gradation printed by the first area 2, the second area 3, and the third area 4 is 40 The halftone dot area ratio and / or halftone dot area ratio in the second predetermined range of the image 7 having a density gradation printed by the first region 2 printed at ˜80% or less is 0 to 80% or less. The image area ratio of the third predetermined range of the camouflage area 9 printed by the second area 3 is printed at 40% or less, and the latent image 8 printed by the third area 4 is printed. The image area ratio in the fourth predetermined range is preferably 40% or less.

  Next, a visible image 5 having a density gradation composed of a first region 2, a second region 3, and a third region 4 printed with the first printing ink and the second printing ink, FIG. 8 shows the relationship between the camouflaged area 9 composed of the second area 3 printed with the printing ink and the density gradation area of the latent image 8 composed of the third area 4 printed with the second printing ink. I will explain.

  As a means for concealing the latent image, the image line of the third region 4 printed with the second printing ink that forms the latent image 8 and the camouflage region 9 paired with the image line are formed. The sum of the line area ratios of the combinations of the lines in the second region 3 printed with the first printing ink 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 with a specific reflection density are good in each region in the wavelength region B. A difference can be obtained. The maximum dot area ratio or the highest image area ratio for obtaining a high density difference in the wavelength region B is defined as the image area ratio A or the 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.

  The visible image 5 having the density gradation composed of the first region 2, the second region 3, and the third region 4 printed with the first printing ink and the second printing ink is obtained from the third region 4. It is composed of a maximum image area ratio (for example, 40%) or more and an image area ratio A or an image area ratio A (for example, 80%) that represents the latent image 8 and is printed with the second printing ink. The density gradation area of the latent image 8 composed of the third area is configured to be equal to or less than the lowest halftone dot area ratio or the lowest image area ratio of the visible image 5 having the density gradation, for example, 0 to 40%. . The camouflage area 9 composed of the second area 3 printed with the first printing ink is composed of the image area ratio A or the image area ratio A (for example, 80%) or less, for example, 0 to 40%. The density gradation region of the image 7 having the density gradation composed of the first region 2 printed with the first printing ink is configured with the image area ratio A or the image area ratio A (for example, 80%) or less. As for the line area ratio of the camouflage area 9, the sum of the line area ratios of the combination of the image lines constituting the latent image 8 and the image lines of the camouflage area 9 paired with the above-mentioned image lines is constant (for example, 40%). For example, when the image area ratio of the latent image 8 is 0, the image area ratio of the camouflaging region 9 to be paired is 40, and when the image area ratio of the latent image 8 is 20, it becomes a pair. When the image area ratio of the camouflage area 9 is 20 and the image area ratio of the latent image 8 is 40, the image area ratio of the camouflage area 9 to be paired is 0.

  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. In the wavelength region B, the amount of light itself is greatly reduced. Therefore, the reflection or absorption characteristics of the light in the wavelength region B are more strongly reflected, and the density is higher than that obtained in the wavelength region A. It can be made to feel visually. In other words, when the reflection or 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 that can be identified as authenticity is a specific wavelength A under normal light from sunlight, fluorescent light, incandescent light bulb, etc., and a visible image 5 having a density gradation is confirmed as shown in FIG. The latent image 8 cannot be confirmed.

  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 8 is confirmed as shown in FIG. As if the image 7 having the density gradation composed of the first region 2 printed with the first printing ink and the camouflaged region 9 composed of the second region 3 printed with the first printing ink were erased. Thus, it appears that only the latent image 8 is visually recognized. The latent image 8 is composed of the first printing ink in the wavelength region B, although the latent image 8 is composed of a reflection density equal to or lower than the visible image 5 having the density gradation composed of the first region 2 printed with the first printing ink. Since the image 7 having the density gradation to be printed and the camouflage area 9 having the second area 3 are converged to a constant density, the latent image 8 and the first area 2 are By increasing the density difference between the image 7 having the density gradation and the camouflaging area 9 composed of the second area 3, it is possible to develop a latent image having high visibility. When observed in the wavelength region B, the latent image 8 has almost no density gradation of the image 7 having the density gradation composed of the first region 2 and the latent image 8 and the image having the density gradation. 7 and the camouflaged area 9 are visually recognized with a clear density difference, so that it is possible to easily determine whether the image is true or false.

  In a printed matter capable of authenticating authenticity, a camouflage pattern is formed on the visible image 5 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. It is possible to give a plurality of colors by overprinting. 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 5 having a density gradation is overprinted with an 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 8 embedded in the visible image 5 having the density gradation is not visually recognized under normal light.

  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 materials, in most printing systems, the line area ratio or dot area ratio is expected to increase due to dot gain between the printed material and the plate surface. Needless to say, the line area ratio or the dot area ratio is required.

  It should be noted that the visible image having the density gradation, the image having the density gradation, and the latent image may be a simple binary image such as letters, numbers, or symbols, 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 7 and the camouflaged area 9 having the density gradation shown in the example were printed with the first printing ink, and the latent image 8 was printed with the second printing ink.

(Example)
In carrying out the invention, the image area ratio A or the dot area ratio A, the camouflage area 9 and the latent image 8 are first selected according to the characteristics of the first printing ink and the second printing ink shown in FIG. The concentration of the synthesis region was determined. 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 line area ratio or halftone dot area ratio of the first printing ink and the second printing ink and the reflection density are substantially proportional, and it was confirmed that they are proportional. . 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 at the line area ratio or the dot area ratio of each of the first printing ink and the second printing ink.

  It was confirmed that the latent image 8 has sufficient gradation in the wavelength region B when printed with the second printing ink in the range of the line area ratio of 0 to 40% or less. The camouflage region 9 printed with the first printing ink is formed in the range of the image area ratio of 0 to 40% or less. The image line constituting the latent image 8 and the camouflage region 9 paired with the image line are formed. The total of the line area ratios of the image line combinations was set to a constant value (40%). It was confirmed that the line area ratio or halftone dot area ratio printed with the first printing ink was within a range where 80% or less continuous gradations were within a certain gradation in the wavelength region B. The image 7 having a tone was formed with a dot area ratio of 80% or less. Therefore, the visible image 5 having the density gradation printed with the first printing ink and the second ink was formed in the range of the line area ratio and the dot area ratio of 40 to 80% or less.

  The latent image 8 and the image 7 having density gradation preferably have a difference of halftone dot area ratio or image area ratio for the gradation expression area reaching 25% or more.

  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. 11A, the printed material C capable of authenticating authenticity formed a visible image 5 having a density gradation by three regions on the substrate 1. A visible image 5 having a density gradation is obtained from an image 7 having a density gradation composed of a plurality of first areas 2 shown in FIG. 11B and a plurality of second areas 3 shown in FIG. The latent image 8 is composed of a camouflaged area 9 of the latent image 8 and a latent image 8 composed of a plurality of third areas 4 shown in FIG. By combining the camouflaged area 9 of the latent image 8 consisting of the second area 3 shown in FIG. 11B and the latent image 8 consisting of the third area 4 shown in FIG. 6 was formed. An image 7 having a density gradation composed of the first region 2 was formed in a non-image region of the plurality of image lines 6. The first region 2 and the second region 3 were printed with the first printing ink, and the third region 4 was printed with the second printing ink. The halftone dot area ratio and the image area ratio of the visible image 5 having a density gradation were formed in the range of 40 to 80% or less. The image area ratio of the latent image 8 is formed in a range of 0 to 40% or less, and the image area ratio of the camouflage region 9 is formed in a range of 0 to 40%. The print area C of the composite area of No. 8 was adjusted to be 40%, and a printed material C capable of authenticating authenticity was obtained.

  As shown in FIG. 12 (a), only the visible image 5 having a density gradation is confirmed in the printed matter C that can be determined as authenticity under normal light from sunlight, a fluorescent light, an incandescent light bulb, or the like having a specific wavelength A. . The latent image 8 could not be confirmed.

  As shown in FIG. 12B, 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 8 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 explanatory drawing of the hair removal of the 2nd area | region 3 and the 3rd area | region 4. FIG. FIG. 3 is a diagram illustrating a boundary between a second region 3 and a third region 4. FIG. 4 is a diagram illustrating a relationship between a second area 3 and a third area 4 of a plurality of image lines 6. 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 5 having a density gradation composed of a first region 2, a second region 3, and a third region 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 9 which consists of the 2nd area | region 3 printed, and the density gradation area | region of the latent image 8 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 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 2a Non-printing area | region 3 2nd area | region 3a, 3b Non-printing area | region 4 3rd area | region 5 Visible image 6 with a density gradation 6 Plural image lines 7 Image 8 with a density gradation Image image 9 Camouflaged area 10 Filter 11 Overlapping area 12 First image line 13 Second image lines A1, A2 Printed material B, C Printed material with authenticity determination

Claims (4)

A printed matter in which a visible image having a density gradation is formed by three areas on a substrate, and an image having a density gradation is formed by a plurality of first areas, and the second area and the third area A plurality of image lines are formed by the areas, and a plurality of image lines including the first area, the second area, and the third area are alternately arranged, and the latent image is formed by the third area. The second area is formed as a camouflaged area of the latent image, the first area and the second area are printed with the first printing ink, and the third area is printed with the second printing ink. The first printing ink and the second printing ink are normally color-matched under light,
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, Authenticity discrimination printed with a metameric pair ink in which the integrated value of the spectral reflection spectrum between 400 and 600 nm of the printing ink is substantially the same as the integrated value of the spectral reflection spectrum between 400 and 600 nm of the second printing ink Possible prints,
The printed matter capable of authenticating authenticity is that the latent image is confirmed when a visible image having a density gradation is confirmed without observing the latent image under normal light and is observed with light between 640 and 700 nm. A printed matter that can be checked for authenticity.   2. The printed matter capable of authenticating authenticity according to claim 1, wherein the plurality of image lines are formed at a predetermined pitch.   The image area ratio corresponding to one pitch of the predetermined pitch is 0 to 40% or less, and the dot area ratio corresponding to one pitch of the image having the density gradation is printed to be 0 to 80% or less. The printed matter capable of authenticating authenticity according to claim 1 or 2.   4. The printed matter capable of authenticating authenticity according to claim 1, wherein the latent image has a density gradation.

Images