JP5040334B2 - Anti-counterfeit medium and discrimination method - Google Patents

Description

  The present invention relates to a forgery prevention technique that can be used to prevent forgery of securities such as stock certificates, bonds, checks, and gift certificates, lotteries, and ID cards.

  In recent years, copiers using electrophotographic technology have become widespread, and anyone can easily copy documents using this. In particular, according to a recent color digital copying machine, even a copy that is extremely difficult to determine whether it is a manuscript or a copy can be easily produced.

  A general color digital copying machine performs copying by the following method. First, the original is irradiated with light, and the reflected light is detected by a CCD line sensor. The CCD line sensor generates a digital signal corresponding to the intensity of the reflected light and transmits it to a memory in the copying machine. This reading is performed for three colors of red (R), green (G), and blue (B), and digital signals obtained for the respective colors are stored in the memory. Next, based on the stored digital signal, an electrostatic latent image is drawn on the photosensitive drum with a laser beam. Subsequently, a toner image corresponding to the electrostatic latent image is formed on the photosensitive drum using electrostatic force. Thereafter, the toner image is transferred to a sheet, and the transferred toner image is fixed on the sheet. For example, by carrying out this process for four colors of yellow (Y), magenta (M), cyan (C), and black (Bk), an elaborate color copy can be obtained.

  While such color copying is convenient, it facilitates the forgery of securities such as stock certificates, bonds, promissory notes, checks, and printed materials such as admission tickets and boarding passes. For this reason, various proposals have been made to take measures to prevent duplication of printed matter so that they cannot be easily copied.

  As one of such measures, there is a technique for making the color of a copy by color copying different from the color of an original. For example, a technique for coloring a document such as securities with a very light color has been proposed. It is difficult to accurately reproduce this light color by copying. In addition, a technique for forming halftone dots of different sizes has been proposed. In these copies, the reproducibility of small halftone dots tends to be insufficient. Further, a technique for printing in a color that is not found in toner of color copiers such as green, purple, orange, gold, and silver has been proposed. In addition, reflection and / or absorption characteristics are almost equal in the wavelength range of light that can be easily perceived by humans, and reflection and / or absorption in wavelength ranges of light that are difficult for humans to perceive, for example, wavelength ranges of 380 nm to 450 nm and 650 nm to 780 nm. Techniques using two types of inks having different characteristics have been proposed. The two areas formed using these inks are visually the same color, but can be reproduced in different colors when copied on a color copier.

  However, the color copying machine can correct the output color. Also, digital presses that correct digital data read by a color scanner with a computer and output the data with a color printer are becoming widespread. Therefore, if a little effort is required, it is possible to precisely reproduce the color of the document, and it is difficult to prevent forgery with the above-described technique.

  In addition, for example, a technique has been proposed in which securities are provided with special parts that cannot be reproduced by a color copying machine. Among these, the technique of providing an OVD (Optical Variable Device) such as a hologram foil described in Patent Documents 1 and 2 on the surface of securities or the like has already been put into practical use. According to this technique, since the silver surface of the hologram specularly reflects light, the reflected light does not enter the CCD line sensor, and the silver surface portion of the original is reproduced in black on the copy. Patent Document 3 describes a technique using an optical thin film in which ceramic layers having different refractive indexes are stacked and the color changes depending on the viewing angle. Since this color change cannot be obtained with a copy, it is possible to easily determine the authenticity. Furthermore, it has also been proposed to perform printing by crushing the thin film formed by this method and mixing fragments into ink.

  However, due to the development of embossing technology, the formation of a reflective layer including a relief type diffraction grating is becoming more difficult than before. In addition, multilayer thin film has begun to be sold as a general packaging film. As a result, the effect of preventing forgery of holograms has been reduced.

Patent Document 4 discloses a liquid crystal multilayer composite including a patterned polymer liquid crystal layer and a diffractive structure layer as a continuous film. In this composite, the diffractive structure layer covers the polymer liquid crystal layer and embeds the openings of the pattern formed by it.
JP-A-6-259013 Japanese Patent Laid-Open No. 7-089293 JP-T-2004-505158 JP 2006-142599 A

  The present invention is to achieve a higher anti-counterfeit effect.

A first invention for solving the above-described problems is a light-reflective layer, facing only a part of the front surface of the light-reflective layer, made of a nematic liquid crystal material or a smectic liquid crystal material, and having a relief type on one main surface look including a diffraction grating is formed retardation layer, the diffraction grating is a medium for preventing forgery, characterized in that formed on the entire surface of the main surface.

In the second invention, the light reflecting layer faces only a part of the front surface of the light reflecting layer and is made of a nematic liquid crystal material or a smectic liquid crystal material, and a relief type diffraction grating is formed on one main surface. and a retardation layer, said diffraction grating is a counterfeit prevention medium you characterized in that it is formed only on a part of the major surface.

  The third invention is the anti-counterfeit medium according to the first or second invention, further comprising a light-transmitting colored layer positioned in front of the light reflecting layer and facing the retardation layer. is there.

  The fourth invention is the anti-counterfeit medium according to any one of the first to third inventions, wherein the light reflecting layer includes a reflecting layer exhibiting an interference color.

  A fifth invention is a method for discriminating an article whose authenticity is unknown between a genuine article and a non-authentic article, and the authentic article is any one of the first to fourth inventions. If an article that supports two anti-counterfeit media and whose authenticity is unknown does not contain a latent image that can be visualized by observation through a polarizer, it is authentic or unknown It is a discrimination method characterized in that the article includes judging that the article is an unauthentic product.

  According to the present invention, a higher forgery prevention effect can be achieved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to components that exhibit the same or similar functions, and duplicate descriptions are omitted.

  FIG. 1 is a plan view schematically showing a forgery prevention medium according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of the forgery prevention medium shown in FIG. The anti-counterfeit medium 10 is supported on an article to be confirmed to be genuine.

  The anti-counterfeit medium 10 includes a base material 21 shown in FIG. Examples of the base material 21 include films of synthetic resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, and polystyrene. Resin films, paper such as synthetic paper, glass plates, aluminum foil, or combinations thereof can be used. The thickness may be appropriately selected according to the purpose of use of the forgery prevention medium.

  A light reflection layer 22 is formed on the substrate 21. The material of the light reflection layer 22 is not particularly limited as long as light reflectivity is obtained. The light reflection layer 22 is, for example, a mirror reflection layer such as a metal vapor deposition layer. As a material of this light reflection layer, for example, a metal or an alloy such as aluminum, gold, silver, or copper can be used. These materials can be used alone or laminated. The light reflecting layer 22 can be formed using, for example, a vapor deposition method such as vacuum evaporation or sputtering.

  The light reflection layer 22 may be a light reflection pigment layer containing a reflection pigment. As a material for the light reflective pigment layer, for example, a material obtained by dispersing a light reflective pigment in a resin or the like can be used. The light reflecting layer 22 may give an interference color to the reflected light. Such a light reflecting layer 22 can be obtained by using, for example, a finely pulverized material whose color changes according to the viewing angle as the light reflecting pigment. This material is formed, for example, by laminating a plurality of layers made of ceramics having different refractive indexes and appropriate film thicknesses. In addition, a bright pigment called a pearl pigment can also be used as the light reflective pigment.

The front surface of the light reflecting layer 22 is partially covered with a λ / 4 retardation layer 23. The λ / 4 retardation layer 23 has a _fast axis along a direction indicated by an arrow n _A23 in FIG. 1 and a slow axis (not shown) perpendicular to the _fast axis n _A23 . The λ / 4 phase difference layer 23 has a wavelength of λ and a polarization plane (oscillation plane of the electric field vector) that is obliquely incident on the fast axis n _A23 makes the polarization plane parallel to the slow axis. The first linearly polarized light and the second linearly polarized light whose plane of polarization is parallel to the _fast axis n _A23 and whose phase has advanced by λ / 4 from the first linearly polarized light are emitted.

  The wavelength λ is a design wavelength. The design wavelength λ is typically a wavelength of green light in which natural human light cells have high sensitivity, for example, about 550 nm. The retardation of the λ / 4 retardation layer 23 at the design wavelength λ may not be as designed due to variations in the thickness thereof. Even in such a case, if the deviation of the retardation from the design value is about 10% or less of the design value, the verification described later is not greatly affected.

  The λ / 4 retardation layer 23 is made of a nematic or smectic liquid crystal material. This liquid crystal material is, for example, a thermotropic liquid crystal material. The λ / 4 retardation layer 23 is formed using, for example, an ink containing this liquid crystal material. For this printing, for example, a gravure printing method can be used.

  A solvent may be added to the previous ink. Moreover, you may introduce | transduce functional groups, such as an acryl group, into the terminal of a liquid crystal molecule. When such a liquid crystal material is used, the liquid crystal molecules can be crosslinked by irradiating active energy rays after completing the alignment of the liquid crystal molecules. Accordingly, the λ / 4 retardation layer 23 having excellent physical strength can be obtained.

  The λ / 4 retardation layer 23 may contain a dye such as a direct dye, a disperse dye, and a dichroic dye, or a pigment. In this case, the content of the colorant is such that the lightness L * in the ULCS (uniform lightness chromaticness scale) color system of the first light reflection region 11 described later is preferably 10 or more, more preferably 15 or more. Adjust to.

  A relief type diffraction grating 24 is formed on the front surface of the λ / 4 retardation layer 23.

  The diffraction grating 24 is, for example, a relief hologram. Holograms include a relief type that records light interference fringes as a fine uneven pattern on a flat surface, and a volume type that records interference fringes in the volume direction. Among these, relief holograms are generally used because they are preferable in terms of mass productivity and cost. The term “diffraction grating” means a structure that generates a diffracted wave when irradiated with illumination light, and includes not only a hologram but also a normal diffraction grating in which a plurality of grooves are arranged in parallel and at equal intervals, for example.

  Various images can be displayed on the diffraction grating 24. For example, the diffraction grating 24 can display a three-dimensional image, an image that causes a color shift in which the color changes depending on the viewing angle, an image that has a unique glittering shine, and the like. Alternatively, the diffraction grating 24 can display a figure such as a star or a character such as a so-called micro character that cannot be distinguished with the naked eye. In addition, the diffraction grating 24 can display a multicolor image, or can display a different image depending on an observation angle or the like.

  A pixel structure may be adopted for the image displayed on the diffraction grating 24. That is, a plurality of pixels each including a diffraction grating and having different visual effects may be arranged in a matrix on the front surface of the λ / 4 retardation layer 23. If the visual effect of each of these pixels is known, the prediction of the image obtained by reordering them is easy. Therefore, the structure to be adopted for each pixel can be easily determined from the digital image data.

  Typically, an alignment film is interposed between the light reflection layer 22 and the retardation layer 23 (not shown). The alignment film has a function of controlling the alignment direction of the mesogenic groups of the liquid crystal molecules included in the liquid crystal layer formed thereon. The alignment film is made of a resin such as polyvinyl alcohol (PVA).

  The alignment film is formed by the following method, for example. First, a resin solution obtained by dissolving the above resin in a solvent is applied onto a reflective substrate using a coating method such as wire bar, gravure, or microgravure, and the coating film is dried. Thereafter, a rubbing process is performed by rubbing the alignment film surface with a rubbing cloth to obtain an alignment film. For the rubbing cloth, for example, materials such as cotton and velvet can be used.

  The anti-counterfeit medium 10 can include a light absorption layer 25 on the surface opposite to the surface on which the light reflection layer 22 of the base material 21 is formed. When the light reflecting layer 22 includes a light reflecting pigment, the light absorbing layer 25 plays a role of clarifying the reflected color. The light absorption layer 25 may be interposed between the base material 21 and the light reflection layer 22. Further, the light absorption layer 25 can be omitted.

  Hereinafter, in this forgery prevention medium 10, a region composed of the λ / 4 retardation layer 23 and a portion facing the same is referred to as a first light reflection region 11, and the other region is referred to as a second light reflection region 12.

  Next, an image that is seen when natural light is irradiated onto the anti-counterfeit medium 10 and observed with the naked eye will be described.

  First, light reflection by the first light reflection region 11 will be described.

  The λ / 4 retardation layer 23 reflects a part of the irradiated natural light. Since the diffraction grating 24 is formed on the front surface of the λ / 4 retardation layer 23, at least a part of the reflected light is diffracted light. Hereinafter, this diffracted light is referred to as diffracted reflected light. The observer perceives the visual effect by the diffraction grating 24 by looking at the diffracted reflected light.

  On the other hand, the natural light incident on the λ / 4 retardation layer 23 is transmitted through the λ / 4 retardation layer 23. The light reflection layer 22 reflects this transmitted light.

  This reflected light is transmitted through the λ / 4 retardation layer 23. Hereinafter, this transmitted light is referred to as transmitted reflected light. Since the diffraction grating 24 is formed on the front surface of the λ / 4 retardation layer 23, at least a part of the transmitted / reflected light is diffracted light. The observer perceives the visual effect provided by the light reflection layer 22 and the visual effect provided by the diffraction grating 24 at the same time by looking at the transmitted / reflected light.

  As described above, the first light reflection region 11 has a visual effect by the diffraction grating 24 and a visual effect by the light reflection layer 22.

  Next, light reflection by the second light reflection region 12 will be described.

  The light reflection layer 22 reflects the irradiated natural light. The observer perceives the visual effect of the light reflecting layer 22 by looking at the reflected light. Therefore, the second light reflection region 12 has a visual effect due to the light reflection layer 22.

  As described above, the first light reflection region 11 and the second light reflection region 12 have different visual effects. That is, when the anti-counterfeit medium 10 is observed with the naked eye, these form a visible image that can be distinguished from each other.

  Next, a verification tool used for confirming that the article supporting the forgery prevention medium 10 is a genuine product will be described.

  The verification tool used here includes a linearly polarizing film and a λ / 4 retardation layer.

  The linearly polarizing film is, for example, an absorptive polarizing film. In this case, the linearly polarizing film transmits linearly polarized light having a polarization plane parallel to the transmission axis and absorbs linearly polarized light having a polarization plane perpendicular to the transmission axis.

  As the absorbing polarizing film, for example, a PVA-iodine type film or a dichroic dye type film in which iodine is absorbed in a stretched film made of PVA can be used. Since these polarizing films have low physical strength, they may be used by being sandwiched between films made of triacetylrose (TAC).

  The λ / 4 retardation layer faces one main surface of the linearly polarizing film. The fast axis of the λ / 4 retardation layer is oblique to the transmission axis of the linearly polarizing film. As an example, when the λ / 4 retardation layer is viewed from the linearly polarizing film side, the fast axis direction of the λ / 4 retardation layer is rotated 45 ° counterclockwise from the direction parallel to the transmission axis. Suppose that In this case, the verification tool functions as a left circular polarizer.

  Next, a method for verifying that the article supporting the forgery prevention medium 10 is an authentic product using this verification tool will be described.

  FIG. 3 is a plan view schematically showing an example of an image that can be observed when the anti-counterfeit medium 10 shown in FIGS. 1 and 2 and the verification tool described above are overlapped.

In FIG. 3, the anti-counterfeit medium 10 and the verification tool 50 are arranged such that the λ / 4 retardation layer of the verification tool 50 faces both the light reflection regions 11 and 12. Further, the transmission axis OP of the linearly polarizing film and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 are made parallel. In this case, as shown in FIG. 3, the second light reflection region 12 appears as a dark part, and the first light reflection region 11 appears brighter than the second light reflection region 12. The reason for this will be described below. Here, for simplification, only light having a wavelength equal to the design wavelength λ and perpendicularly incident on the forgery prevention medium 10 is considered.

  When the linearly polarizing film of the verification tool 50 is irradiated with natural light, the verification tool 50 emits left circularly polarized light toward the first light reflection region 11 and the second light reflection region 12.

  In the first light reflection region 11, the λ / 4 retardation layer 23 shown in FIG. 2 reflects a part of the left circularly polarized light and converts it into right circularly polarized light. Since the diffraction grating 24 is formed on the front surface of the λ / 4 retardation layer 23, at least a part of the right circularly polarized light is diffracted reflected light.

  The λ / 4 retardation layer of the verification tool 50 converts the right circularly polarized light into linearly polarized light. The plane of polarization of this linearly polarized light is orthogonal to the transmission axis OP of the linearly polarizing film of the verification tool 50. Therefore, the light reflected by the λ / 4 retardation layer 23 cannot pass through the verification tool 50.

On the other hand, the other part of the left circularly polarized light emitted from the verification tool 50 toward the first light reflection region 11 is transmitted through the λ / 4 retardation layer 23. The λ / 4 retardation layer 23 converts the left circularly polarized light into linearly polarized light. The plane of polarization of this linearly polarized light is inclined 45 ° counterclockwise with respect to the fast axis n _A23 when viewed from the observer side.

  The light reflection layer 22 reflects this linearly polarized light without changing the direction of the polarization plane.

  This linearly polarized light is transmitted through the λ / 4 retardation layer 23. The λ / 4 retardation layer 23 converts this linearly polarized light into left circularly polarized light.

  The λ / 4 retardation layer of the verification tool 50 converts the left circularly polarized light into linearly polarized light. The plane of polarization of this linearly polarized light is parallel to the transmission axis OP of the linearly polarizing film of the verification tool 50. Therefore, the light transmitted through the λ / 4 retardation layer 23 can be transmitted through the verification tool 50.

  For the above reasons, when the first light reflection region 11 of the anti-counterfeit medium 10 is observed through the verification tool 50, the observer cannot perceive the light reflected by the λ / 4 retardation layer 23, but λ / 4. The light transmitted through the retardation layer 23 can be perceived.

  Next, light reflection by the second light reflection region 12 will be described. The verification tool 50 emits left circularly polarized light toward the second light reflection region 12. The light reflection layer 22 reflects this left circularly polarized light and converts it into right circularly polarized light.

  The λ / 4 retardation layer of the verification tool 50 converts the right circularly polarized light into linearly polarized light. The plane of polarization of this linearly polarized light is orthogonal to the transmission axis OP of the linearly polarizing film of the verification tool 50. Therefore, the reflected light cannot pass through the verification tool 50.

  For the above reasons, when the anti-counterfeit medium 10 is observed through the verification tool 50, the observer cannot perceive the reflected light from the second light reflection region 12.

  As described above, when the anti-counterfeit medium 10 is observed through the verification tool 50, the observer can perceive the reflected light from the first light reflecting area 11, but perceives the reflected light from the second light reflecting area 12. Can not. Accordingly, the first light reflection region 11 appears as a bright portion, and the second light reflection region 12 appears as a dark portion. That is, by using the verification tool 50, the latent image formed by the birefringence of the λ / 4 retardation layer 23 can be visualized.

  Therefore, even when the article supporting the anti-counterfeit medium 10 and a non-authentic product such as a counterfeit product cannot be discriminated with the naked eye, they are discriminated by using a polarizer such as the verification tool 50. be able to. That is, when an article whose authenticity is unknown does not include a latent image that is visualized by observing through a polarizer, it can be determined that the article is non-authentic.

  Such a change in display image cannot be reproduced with a copy of the forgery prevention medium 10. In addition, the diffraction image formed by the diffraction grating 24 cannot be reproduced with a copy of the anti-counterfeit medium 10. And it is difficult to copy the forgery prevention medium 10.

  In addition, since the anti-counterfeit medium 10 has the diffracted image and the latent image completely overlapped with each other, the anti-counterfeiting measure by the diffraction grating 24 can only be taken even if the enlarged image is observed. can not see. In addition, in the forgery prevention medium 10, both the diffraction image and the latent image are formed in only one layer, that is, the λ / 4 retardation layer 23. Therefore, compared with the case where the diffraction image and the latent image are formed in separate layers, the difference between the thickness corresponding to these images and the thickness of the other portions is small. Therefore, it is difficult for the forgery prevention medium 10 to realize the existence of the latent image.

  Therefore, when the anti-counterfeit medium 10 is used, a higher anti-counterfeit effect can be achieved.

  In this anti-counterfeit medium 10, the λ / 4 retardation layer 23 is patterned to form a latent image, but the latent image can be formed by other methods.

  For example, a plurality of retardation layers that are patterned and have different retardations may be arranged in the same plane. However, it is difficult and expensive to form such a structure.

  Alternatively, it is possible to form a latent image by forming a λ / 4 retardation layer as a continuous film and providing regions having different retardations in the λ / 4 retardation layer. For example, the retardation of the heating portion can be changed by forming a λ / 4 retardation layer as a continuous film and heating a part thereof. Alternatively, the retardation of the coating part can be changed by forming a λ / 4 retardation layer as a continuous film and applying an organic solvent to a part thereof. However, the latent image formed on the λ / 4 retardation layer as a continuous film does not necessarily have high thermal stability. In particular, when the retardation is changed using an organic solvent, it is difficult to form a latent image having a fine and complicated shape.

  In the anti-counterfeit medium 10 shown in FIGS. 1 and 2, a latent image is formed only by the λ / 4 retardation layer 23 without using a plurality of retardation layers having different retardations. Therefore, a latent image can be formed easily and at low cost. In the forgery prevention medium 10 shown in FIGS. 1 and 2, the shape of the λ / 4 retardation layer 23 corresponds to the shape of the latent image. Therefore, the anti-counterfeit medium 10 is excellent in the thermal stability of the latent image. The λ / 4 retardation layer 23 can be formed by a printing method, for example. Therefore, a latent image having a fine and complicated shape can be formed.

  Next, another embodiment of the present invention will be described.

  FIG. 4 is a plan view schematically showing a forgery prevention medium according to the second embodiment of the present invention.

  The forgery prevention medium 20 is substantially the same as the forgery prevention medium 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, in the anti-counterfeit medium 20 of FIG. 4, the first light reflection region 11 includes a region 11 a where the diffraction grating 24 is formed and a region 11 b where the diffraction grating 24 is not formed.

  When the forgery prevention medium 20 is irradiated with natural light and observed with the naked eye, the region 11a shows a visual effect by the diffraction grating 24 and a visual effect by the light reflecting layer 22. The region 11b does not show the visual effect due to the diffraction grating, but shows only the visual effect due to the light reflecting layer 22. The second light reflection region 12 shows a visual effect by the light reflection layer 22.

  Therefore, when the forgery prevention medium 20 is observed with the naked eye, it is difficult to determine the boundary between the region 11b of the first light reflection region 11 and the second light reflection region 12. Moreover, the area | region 11a, the area | region 11b, and the 2nd light reflection area | region 12 form the visible image which can discriminate | determine from each other.

  Next, an image that appears when the forgery prevention medium 20 is observed through the verification tool will be described.

  FIG. 5 is a plan view schematically showing an example of an image that can be observed when the anti-counterfeit medium shown in FIG. 4 and the verification tool are overlapped.

In FIG. 5, the anti-counterfeit medium 20 and the verification tool 50 similar to that described in the first embodiment are arranged so that the λ / 4 phase difference layer of the verification tool 50 faces both the light reflection regions 11 and 12. is doing. Further, the transmission axis OP of the linearly polarizing film and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 are made parallel. In this case, as described in the first embodiment, the second light reflection region 12 appears as a dark portion, and the first light reflection region 11 appears as a bright portion.

  As described above, the second embodiment is the same as the first embodiment except that a diffraction image is formed only on a part of the first light reflection region 11, that is, the region 11a. Therefore, according to the present embodiment, although the effect associated with completely superimposing the diffraction image and the latent image cannot be obtained, substantially the same effect as described in the first embodiment can be obtained.

  Various modifications can be made to the forgery prevention media 10 and 20 described above.

  For example, a configuration in which the λ / 4 retardation layer 24 is provided on the entire front surface of the anti-counterfeit medium and a diffraction grating is provided on at least a part of the λ / 4 retardation layer 24 may be employed. In addition, in the anti-counterfeit media 10 and 20, the diffraction grating 24 is formed on the front surface of the λ / 4 retardation layer 23, but the diffraction grating 24 faces the light reflection layer 22 of the λ / 4 retardation layer 23. You may form in. Instead of the λ / 4 retardation layer 23, a retardation layer having a retardation other than λ / 4 may be used. For example, a λ / 2 retardation layer or a λ / 8 retardation layer can be provided on the light reflection layer 22. In that case, the verification tool used for verification is appropriately changed according to the provided retardation layer. In addition, a light-transmitting colored layer can be provided on the front surface or the back surface of the λ / 4 retardation layer 23.

  The light reflecting layer 22 may be patterned. For example, the light reflecting layer 22 may form a figure and / or a character pattern. Such a light reflection layer 22 is obtained, for example, by depositing metal on the substrate 21 by a vapor deposition method using a mask. The anti-counterfeit medium including the patterned light reflection layer exhibits a higher anti-counterfeit effect than the anti-counterfeit medium in which the light reflection layer is a continuous film.

  A protective layer can also be provided on the front surfaces of the anti-counterfeit media 10 and 20 for the purpose of protection from ultraviolet rays and physical impact. For example, if a light-transmitting protective layer is provided on the front surface of the anti-counterfeit medium 20 of FIG. 4, it becomes more difficult to determine the boundary between the region 11b of the first light reflection region 11 and the second light reflection region 12. Can do.

  The back surface of the anti-counterfeit media 10 and 20, here, the surface of the two main surfaces of the base material 21 on which the reflective layer 22 is not formed, may be subjected to adhesion or adhesion processing. That is, an adhesive label that can be used as an anti-counterfeit label may be formed using the anti-counterfeit medium 10 or 20.

  The anti-counterfeit media 10 and 20 can be applied to printed matter in various ways. For example, you may affix said adhesive label on printed matter. In this case, the base material 21 may be provided with cuts or perforations. In other words, a structure may be employed in which the base material 21 is broken from the notch or at the position of the perforation when the label is to be peeled off. Of course, the anti-counterfeit media 10 and 20 can also be affixed to articles other than printed matter.

  A transfer foil including the anti-counterfeit medium 10 or 20 may be formed, and the anti-counterfeit medium 10 or 20 may be transferred to the article using the transfer foil.

  When the anti-counterfeit medium 10 or 20 is applied to a printed material, the medium may be cut into paper in a form called a thread (also referred to as a strip, a filament, a thread, a safety band, or the like).

  A general material can be used as an adhesive for applying the anti-counterfeit medium 10 or 20 to a printed matter or the like. For example, an adhesive such as vinyl chloride-vinyl acetate copolymer, polyester polyamide, acrylic, butyl rubber, natural rubber, silicon, polyisobutyl, etc. can be used alone, or these adhesives can be used. Aggregating components such as alkyl methacrylates, vinyl esters, acrylonitrile, styrene, vinyl monomers, unsaturated carboxylic acids, hydroxy group-containing monomers, modifying components such as acrylonitrile, polymerization initiators, plasticizers, curing agents, curing What added additives, such as an accelerator and antioxidant, as needed can also be used. For the formation of the adhesive layer, for example, a printing method such as a gravure printing method, an offset printing method, a screen printing method, or a coating method such as a bar coating method, a gravure method, or a roll coating method can be used. Or you may use the separator which formed the adhesion layer in one main surface. That is, the adhesive layer may be attached to the anti-counterfeit medium 10 or 20 together with the separator, and then only the separator may be peeled off from the anti-counterfeit medium 10 or 20. You may affix the release paper and release film which performed the release process to the adhesion layer. This facilitates handling of the anti-counterfeit medium 10 or 20 that has been subjected to adhesive processing.

  Next, a reference example will be described.

  FIG. 6 is a plan view schematically showing a forgery prevention medium of a reference example. 7 is a cross-sectional view of the forgery prevention medium shown in FIG. 6 taken along the line VII-VII. This anti-counterfeit medium 30 is supported on an article to be confirmed to be genuine.

  The anti-counterfeit medium 30 shown in FIG. 6 is the same as the anti-counterfeit medium 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, the forgery prevention medium 30 of FIG. 6 further includes the diffraction grating forming layer 26 and the liquid crystal alignment film 27. The diffraction grating forming layer 26 is interposed between the base material 21 and the light reflecting layer 22. The liquid crystal alignment film 27 is interposed between the light reflection layer 22 and the λ / 4 retardation layer 23. The diffraction grating 24 is not formed on the front surface of the λ / 4 retardation layer 23 but on the front surface of the light reflecting layer 22 at a position corresponding to the region adjacent to the λ / 4 retardation layer 23. Is formed.

  On the front surface of the diffractive structure forming layer 26, irregularities having a shape corresponding to the diffraction grating 24 are provided. The diffraction grating forming layer 26 is obtained, for example, by forming a polymer resin layer on the substrate 21 and pressing an original plate having fine irregularities on the polymer resin layer.

  The light reflecting layer 22 is formed on the diffraction grating forming layer 26. The front surface of the light reflecting layer 22 is provided with unevenness corresponding to the unevenness provided on the front surface of the diffraction grating forming layer 26. This unevenness forms a diffraction grating 24.

  The alignment film 27 covers the light reflecting layer 22. The alignment film 27 can be formed, for example, by the method described in the first embodiment.

  Hereinafter, in the forgery prevention medium 30, a region composed of the λ / 4 retardation layer 23 and a portion facing the same is referred to as a first light reflection region 11 b, and the other region is referred to as a third light reflection region 13.

  When the forgery prevention medium 30 is irradiated with natural light and observed with the naked eye, the first light reflection region 11b looks similar to the region 11b of the forgery prevention medium 20 described with reference to FIG. That is, the first light reflection region 11 b has the visual effect of the light reflection layer 22.

  In the third light reflecting region 13, the light reflecting layer 22 reflects natural light. Since the diffraction grating 24 is formed on the front surface of the light reflecting layer 22, at least a part of the reflected light is diffracted light. That is, the third light reflection region 13 has a visual effect by the light reflection layer 22 and a visual effect by the diffraction grating 24.

  Thus, the 1st light reflection area | region 11b and the 3rd light reflection area | region 13 have a different visual effect. That is, when the forgery prevention medium 30 is observed with the naked eye, the first light reflection region 11b and the third light reflection region 13 form a visible image that can be distinguished from each other.

  Next, a verification tool used for confirming that the article supporting the forgery prevention medium 30 is a genuine product will be described.

  The verification tool used here is a linearly polarizing film. This linearly polarizing film is the same as the linearly polarizing film included in the verification tool 50 described above.

  Next, a method for verifying that the article supporting the forgery prevention medium 30 is an authentic product using this linearly polarizing film will be described.

  FIG. 8 is a plan view schematically showing an example of an image that can be observed when the anti-counterfeit medium 30 shown in FIGS. 6 and 7 and the linearly polarizing film are overlapped.

In FIG. 8, the anti-counterfeit medium 30 and the linearly polarizing film 51 are arranged such that the transmission axis OP of the linearly polarizing film and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 are parallel to each other. In this case, the observer can perceive both the reflected light from the first light reflecting region 11 b and the reflected light from the third light reflecting region 13. The reason for this will be described below.

  When the linearly polarizing film 51 is irradiated with natural light, the linearly polarizing film 51 emits linearly polarized light toward the first light reflecting region 11 b and the third light reflecting region 13.

In the first light reflection region 11b, this linearly polarized light is transmitted through the λ / 4 retardation layer 23 shown in FIG. Since this linearly polarized light has a polarization plane parallel to the fast axis n _A23 of the λ / 4 retardation layer 23, it passes through the λ / 4 retardation layer 23 without changing the polarization plane.

The light reflection layer 22 reflects this linearly polarized light without changing the direction of the polarization plane, and this linearly polarized light is transmitted through the λ / 4 retardation layer 23. Since this linearly polarized light has a polarization plane parallel to the fast axis n _A23 of the λ / 4 retardation layer 23, it passes through the λ / 4 retardation layer 23 without changing the polarization plane.

  Since this linearly polarized light has a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51, it passes through the linearly polarizing film 51. Therefore, when the anti-counterfeit medium 30 is observed through the linearly polarizing film 51 in the arrangement shown in FIG. 8, the observer perceives the reflected light from the first light reflection region 11b.

  Next, light reflection by the third light reflection region 13 will be described.

  The linearly polarized light emitted from the linearly polarizing film 51 toward the third light reflecting region 13 is applied to the light reflecting layer 22 shown in FIG. The light reflecting layer 22 reflects the incident linearly polarized light without changing the direction of the polarization plane. Since this linearly polarized light has a polarization plane parallel to the transmission axis OP of the linearly polarizing film 51, it passes through the linearly polarizing film 51. Therefore, when the anti-counterfeit medium 30 is observed through the linearly polarizing film 51 in the arrangement shown in FIG. 8, the observer perceives the reflected light from the third light reflection region 13.

  That is, when the forgery prevention medium 30 is observed through the linearly polarizing film 51 in the arrangement of FIG. 8, the first light reflection region 11b and the third light reflection region 13 appear bright.

FIG. 9 is a plan view schematically showing another example of an image that can be observed when the forgery prevention medium 30 and the linearly polarizing film 51 shown in FIGS. 6 and 7 are overlapped. FIG. 9 illustrates a state in which only the linearly polarizing film 51 is rotated clockwise by 45 ° from the state shown in FIG. That is, in the arrangement of FIG. 9, the optical axis OP of the linearly polarizing film 51 and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 form an angle of 45 °. In this case, the 1st light reflection area | region 11b becomes a dark part, and the 3rd light reflection area | region 13 looks bright compared with the 1st light reflection area | region 11b. The reason for this will be described below.

  First, light reflection by the first light reflection region 11b will be described.

The linearly polarized light emitted from the linearly polarizing film 51 toward the first light reflecting region 11b is transmitted through the λ / 4 retardation layer 23 shown in FIG. This linearly polarized light has a polarization plane inclined by 45 ° clockwise as viewed from the observer side with respect to the _fast axis n _A23 of the λ / 4 retardation layer 23. Accordingly, the λ / 4 retardation layer 23 converts this linearly polarized light into left circularly polarized light.

  The light reflection layer 22 reflects this left circularly polarized light and converts it into right circularly polarized light. The λ / 4 retardation layer 23 converts the right circularly polarized light into linearly polarized light.

  Since this linearly polarized light has a polarization plane orthogonal to the transmission axis OP of the linearly polarizing film 51, it cannot be transmitted through the linearly polarizing film 51.

  For the above reason, when the anti-counterfeit medium 30 is observed with the arrangement of FIG. 9 through the linearly polarizing film 51, the observer cannot perceive the reflected light from the first light reflection region 11b.

Next, light reflection by the third light reflection region 13 will be described.
Light reflection by the third light reflection region 13 is the same as that in the arrangement of FIG. That is, when the anti-counterfeit medium 30 is observed with the arrangement of FIG. 9 through the linearly polarizing film 51, the observer perceives the reflected light from the third light reflection region 13.

  For the above reasons, when the anti-counterfeit medium 30 is observed through the linearly polarizing film 51 in the arrangement shown in FIG. 9, the first light reflection region 11b appears as a dark portion, and the third light reflection region 13 is the same as the first light reflection region 11b. Looks brighter.

9, when only the linearly polarizing film 51 is rotated 45 ° clockwise as viewed from the observer side, the transmission axis OP of the linearly polarizing film and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 are obtained. Since they are orthogonal, the image displayed by the forgery prevention medium 30 is the same as that shown in FIG. When only the linearly polarizing film 51 is further rotated 45 ° clockwise as viewed from the observer side from this state, the transmission axis OP of the linearly polarizing film and the _fast axis n _{A23 of the} λ / 4 retardation layer 23 are 45 °. Therefore, the image displayed by the forgery prevention medium 30 is the same as that shown in FIG. That is, every time when only the linearly polarizing film 51 is rotated 45 ° clockwise as viewed from the observer side, the brightness of the first light reflection region 11b is switched. On the other hand, the brightness of the third light reflection region 13 does not change even when the linear film is rotated.

  Therefore, even when the article supporting the forgery prevention medium 30 and a non-authentic product such as a counterfeit product cannot be discriminated with the naked eye, they can be discriminated by using a polarizer such as the verification tool 51. it can. For example, when an article whose unknown whether or not the first light reflection region 11 and the third light reflection region 13 whose contrast ratio changes by observing through the verification tool 51 is authentic is not included, It can be determined that the article is non-genuine.

  The change in the display image according to the arrangement of the forgery prevention medium 30 and the verification tool 51 cannot be reproduced with a copy of the forgery prevention medium 30. Further, it is difficult to copy the anti-counterfeit medium 30. Therefore, when the anti-counterfeit medium 30 is used, a high anti-counterfeit effect can be achieved.

  Examples of the present invention will be described below.

(Example)
A polyethylene terephthalate film having a thickness of 25 μm was prepared. Next, in order to form a light reflective pigment layer, pearl ink having the following composition was applied to one side of the film by a printing method using a silk screen method.

Pigment (trade name: Iriodin 201 manufactured by Merck Ltd.) 8% by weight
Varnish (trade name: SS66 manufactured by Toyo Ink Co., Ltd.) 50% by weight
Solvent (trade name: S718 solvent, manufactured by Toyo Ink Co., Ltd.) 42% by weight
Next, in order to form a λ / 4 retardation layer, a liquid crystal layer ink having the following composition was subjected to gravure printing on the light reflective pigment layer so that the cured film thickness was about 0.5 μm.

Liquid crystal (trade name: Paliocolor LC242 manufactured by BASF Corp.) 30% by weight
Polymerization initiator (trade name: Irgacure 184, manufactured by Ciba Geigy Co., Ltd.) 1.5% by weight
Solvent (mixture of 50 parts by weight toluene and 50 parts by weight methyl ethyl ketone) 68.5% by weight
After this coating film was dried at 100 ° C. for 1 minute, it was irradiated with light of 500 mJ / cm ^{2 with} a high-pressure mercury lamp to cure the coating film. Thereby, a λ / 4 retardation layer was obtained.

  Next, a hologram relief pattern was formed on the λ / 4 retardation layer using a roll embossing method.

  Next, in order to form a light absorption layer, a black ink of the following composition was gravure-printed on the surface opposite to the surface on which the light-reflecting pigment layer of the polyethylene terephthalate film was formed so that the cured film thickness was about 2 μm. .

Black ink (trade name: Finestar R Conch ink, manufactured by Toyo Ink Co., Ltd.)
Next, this coating film was subjected to drying at 80 ° C. for 30 seconds. This obtained the light absorption layer.

  The anti-counterfeit medium was manufactured as described above.

  When this anti-counterfeit medium was observed with the naked eye while irradiating white light, a golden hue was confirmed from the entire surface. Further, a hue gradation due to interference could be confirmed from the region where the λ / 4 retardation layer was formed.

  Next, this anti-counterfeit medium and the verification tool 50 described in the first embodiment are overlapped so that the λ / 4 retardation layer of the verification tool 50 faces the anti-counterfeit medium, and in this state, the verification tool 50 is white. The anti-counterfeit medium was observed while irradiating light. As a result, the region where the λ / 4 retardation layer was formed in the anti-counterfeit medium appeared as a bright portion, and the region where the λ / 4 retardation layer was not formed appeared as a dark portion.

  Next, this anti-counterfeit medium was color-copied, and this copy was also observed using the verification tool 50 in the same manner as described above. As a result, no change in brightness could be confirmed.

(Reference example)
A polyethylene terephthalate film having a thickness of 25 μm was prepared. Next, in order to form a diffraction grating forming layer, the ink for a diffraction grating forming layer having the following composition was applied to one side of the film by gravure printing. This coating film was formed so as to have a dry film thickness of 3 μm.

Acrylic polyol (trade name: Dianal LR209, manufactured by Mitsubishi Rayon Co., Ltd.) 80% by weight
Isocyanate curing agent (trade name: Duranate 24A-100 manufactured by Asahi Kasei Corporation) 20% by weight
Next, this coating film was subjected to drying at 80 ° C. for 1 minute. As a result, a diffraction grating forming layer was obtained.

  Next, an aging treatment was performed at 40 ° C. for 3 days, and a hologram relief pattern was formed on the diffraction grating forming layer using a roll embossing method.

  Next, an aluminum vapor deposition layer having a thickness of 50 μm was formed as a light reflection layer on the entire surface of the diffraction grating formation layer using a vacuum vapor deposition method.

  Next, in order to form a liquid crystal alignment film, the alignment film ink was applied to the entire surface of the aluminum vapor deposition surface using a bar coating method. This coating film was formed so as to have a dry film thickness of 3 μm. The composition of this alignment film ink is shown below.

PVA resin (trade name: Poval 117, Kuraray Co., Ltd.) 10% by weight
Solvent (mixture of 95 parts by weight of water and 5 parts by weight of isopropyl alcohol) 90% by weight
After the coating film was dried at 100 ° C. for 2 minutes, the coating film was rubbed. As the rubbing cloth, FINE PUFF YA-20-R manufactured by Yoshikawa Chemical Co., Ltd. was used. Thereby, an alignment film was obtained.

  Next, in order to form a λ / 4 retardation layer, the liquid crystal layer ink was gravure-printed only on the surface of the liquid crystal alignment film corresponding to the portion of the diffraction grating forming layer where the hologram relief pattern was not formed. . The same material as that used in the example was used as the material of the λ / 4 retardation layer. Further, the same method as in the example was used to form the λ / 4 retardation layer.

  The anti-counterfeit medium was manufactured as described above.

  When this anti-counterfeit medium was observed with the naked eye while irradiating white light, a hue gradation due to interference could be confirmed in the region where the λ / 4 retardation layer was not formed. The region where the λ / 4 retardation layer was formed appeared white.

  Next, the anti-counterfeit medium and the linear polarizing film as the verification tool are superposed so that the transmission axis of the linear polarizing film and the fast axis of the λ / 4 retardation layer included in the anti-counterfeit medium are parallel, In this state, the forgery prevention medium was observed while irradiating the linearly polarizing film with white light. As a result, the reflected light could be perceived from the entire surface of the anti-counterfeit medium.

  Next, the anti-counterfeit medium was observed under the same conditions as above except that only the linearly polarizing film was rotated 45 ° clockwise as viewed from the observer side. As a result, the reflected light could be perceived in the region where the λ / 4 retardation layer was not formed, but the reflected light could not be perceived in the region where the λ / 4 retardation layer was formed.

  Subsequently, the anti-counterfeit medium was observed under the same conditions as described above except that only the linearly polarizing film was further rotated 45 ° clockwise as viewed from the observer side. As a result, the reflected light could be perceived from the entire surface of the anti-counterfeit medium.

  Thereafter, each time the linearly polarizing film alone was rotated 45 ° clockwise as viewed from the observer side, the brightness of the region where the λ / 4 retardation layer was formed was switched.

  Next, this anti-counterfeit medium was color-copied, and this copy was also observed using the verification tool in the same manner as described above. As a result, no change in brightness could be confirmed.

The top view which shows roughly the forgery prevention medium of 1st Embodiment of this invention. Sectional drawing along the II-II line of the forgery prevention medium shown in FIG. The top view which shows roughly an example of the image which can be observed when the forgery prevention medium shown in FIG. 1 and FIG. The top view which shows roughly the forgery prevention medium of 2nd Embodiment of this invention. The top view which shows roughly an example of the image which can be observed when the forgery prevention medium shown in FIG. 4 and a verification tool are piled up. The top view which shows schematically the forgery prevention medium of a reference example. Sectional drawing along the VII-VII line of the forgery prevention medium shown in FIG. The top view which shows roughly an example of the image which can be observed when the forgery prevention medium shown in FIG.6 and FIG.7 and a linearly polarizing film are piled up. The top view which shows roughly the other example of the image which can be observed when the forgery prevention medium shown in FIG. 6 and FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Anti-counterfeit medium, 11 ... 1st light reflection area | region, 12 ... 2nd light reflection area | region, 13 ... 3rd light reflection area | region, 20 ... Anti-counterfeit medium, 21 ... Base material, 22 ... Light reflection layer, 23 ... (lambda) / 4 retardation layer, 24 ... diffraction grating, 25 ... light absorption layer, 26 ... diffraction grating formation layer, 27 ... liquid crystal alignment film, 30 ... anti-counterfeit medium.

Claims (5)

And the light reflection layer, only facing part of the front surface of the light reflecting layer made of a nematic liquid crystal material or smectic liquid crystal material, seen including a retardation layer in which the diffraction grating is formed in a relief-type on one main surface, The anti-counterfeit medium , wherein the diffraction grating is formed on the entire main surface . A light reflection layer, and a retardation layer that faces only a part of the front surface of the light reflection layer, is made of a nematic liquid crystal material or a smectic liquid crystal material, and has a relief type diffraction grating formed on one main surface thereof, grating, forgery prevention medium you characterized in that it is formed only on a part of the major surface.   The anti-counterfeit medium according to claim 1 or 2, further comprising a light-transmitting colored layer positioned in front of the light reflection layer and facing the retardation layer.   The anti-counterfeit medium according to any one of claims 1 to 3, wherein the light reflection layer includes a reflection layer exhibiting an interference color. It is a method for discriminating between an authentic product and an unauthentic product for an article whose authenticity is unknown,
The genuine product is an article that supports the forgery prevention medium according to any one of claims 1 to 4,
If the article that is unknown whether or not it is authentic does not include a latent image that can be visualized by observation through a polarizer, it is determined that the article that is authentic or unknown is non-authentic. A distinction method characterized by including performing.

Images