JP5121680B2 - Identification medium, identification method, and identification apparatus - Google Patents

Description

  The present invention includes a passport, a document, various cards, a pass, a banknote, a cash voucher, a security, a certificate, a gift certificate, a picture, a ticket, a public competition voting ticket, a recording medium on which music and video are recorded, and a recording on which computer software is recorded The present invention relates to an identification medium for identifying the authenticity (authenticity) of a medium, a package of various products, and the like, and more particularly, to an identification medium in which a color shift due to multilayer film interference occurs in the opposite direction.

  When light is incident on the multilayer film, interference occurs because the reflected light has an optical path difference due to the difference in film thickness and refractive index of each film (multilayer film interference). Usually, when the incident angle of light incident on the multilayer film is increased (the viewing angle is increased), the optical path difference is reduced, so that light of shorter wavelengths is intensified. Therefore, when the multilayer film is gradually tilted from the state perpendicular to the line of sight (viewing angle 0) (the viewing angle is increased), the color of the multilayer film gradually changes to a short wavelength color. (Blue shift).

  As a technique for identifying the authenticity of an article, a technique using the above multilayer film as an identification medium is known (for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-085094

  However, against the background of increasing forgery technology, there is a need for an identification medium using a multilayer film that is more difficult to counterfeit and has high discrimination.

  Therefore, the present invention has an object to provide an identification medium having a unique color shift different from that of a general multilayer film, and having high visibility and security and difficult to forge or tamper with a color copying machine. And

The identification medium of the present invention reflects the first color shift layer that reflects the wavelength region near the ultraviolet region and the light reflection characteristics shift to the ultraviolet region as the viewing angle increases, and reflects the wavelength region near the infrared region. The first color shift layer and the second color shift have a structure in which a second color shift layer whose light reflection characteristic shifts from the infrared region to the visible light region as the viewing angle increases is stacked. A printing pattern of a specific color is provided on at least one part of the layer, and from the side where observation is performed, the printing pattern composed of the first color shift layer and the first light absorption layer, It has a structure in which a second color shift layer and a second light absorption layer overlapping with the first light absorption layer are stacked .

  The operation of the present invention will be described with reference to FIG. As shown in FIG. 1, a configuration in which the first color shift layer A is laminated on the surface of the second color shift layer B is assumed. In the first color shift layer A, the wavelength region near the ultraviolet region is reflected, and the light reflection characteristic shifts from the visible light region to the ultraviolet region as the viewing angle increases. Therefore, when the viewing angle θ is 0 °, it is visible. When light having a short wavelength in the light region is reflected and the viewing angle θ is increased, light in the ultraviolet region (invisible light) is reflected. On the other hand, in the second color shift layer B, the wavelength region closer to the infrared region is reflected, and the light reflection characteristic shifts from the infrared region to the visible light region as the viewing angle increases. Reflects light in the outer region (invisible light), and reflects light having a long wavelength in the visible light region when the viewing angle θ is large.

  Therefore, when the viewing angle θ is 0 ° and the configuration of FIG. 1 is viewed, the short wavelength reflected light of the first color shift layer A can be seen, and when the viewing angle θ is increased, the short wavelength that is visible light is reduced. It becomes invisible from light to ultraviolet light. On the other hand, in the second color shift layer B, the reflected light is invisible in the infrared region when the viewing angle θ is 0 °. However, as the viewing angle θ is increased, the reflected light having a long wavelength that is visible light is increased. Can be seen. Therefore, when the viewing angle θ is increased from 0 °, the reflected light having the long wavelength which is the visible light from the second color shift layer B is changed from the reflected light having the short wavelength which is the visible light by the first color shift layer A. The phenomenon opposite to the blue shift, that is, the red shift occurs.

  In the present invention, even when the positions of the first color shift layer A and the second color shift layer B are reversed from those shown in FIG. The first and second color shift layers A and B are optional as long as the light reflection characteristics are different from each other in the viewing angle.

  That is, at least one of the first color shift layer and the second color shift layer can be a multilayer film layer in which light transmissive thin films having different refractive indexes are stacked in multiple layers. Alternatively, a cholesteric liquid crystal layer having circular polarization selectivity that reflects circularly polarized light in a specific wavelength region can be used instead of or together with the multilayer film layer.

  Here, the principle that a blue shift occurs in the multilayer film will be described. FIG. 2 is a diagram illustrating a state in which light incident on the multilayer film is reflected by each layer. When white light is applied to the multilayer film layer, incident light is reflected at the interface of optical media having different refractive indexes according to Fresnel's reflection law. At this time, a part of the incident light is reflected at the interface between the A layer and the B layer, and the other is transmitted. Since the interface between the A layer and the B layer appears repeatedly, the reflected light generated at each interface interferes. At that time, it appears that the light in the wavelength range that interferes and strengthens is strongly reflected.

  When the incident angle of incident light is gradually increased, the optical path difference of reflected light generated at each interface is gradually reduced, and light of shorter wavelengths interferes and strengthens each other. Therefore, as the multilayer film layer irradiated with white light is viewed more obliquely (an angle more parallel to the surface), it appears that light having a shorter wavelength is more strongly reflected.

  The intensifying wavelength range can be arbitrarily set according to the refractive index and thickness of the material such as a polymer forming each layer, the number of layers, and the like. Therefore, by appropriately setting these conditions, the wavelength ranges of the reflected light of the first color shift layer and the second color shift layer can be set as described above.

  For example, the reflected color of a multilayer film layer that is colored red, for example, when viewed from the normal incident light (that is, viewed from the front) is orange, yellow, as the viewing angle increases (that is, as the multilayer film layer is tilted) Observed to change in order of green, blue-green, and blue (blue shift).

  Next, the principle of causing a color shift in the cholesteric liquid crystal layer will be described. First, the cholesteric liquid crystal will be briefly described. FIG. 3 is a conceptual diagram conceptually showing the structure of the cholesteric liquid crystal layer, and FIG. 4 is a conceptual diagram for explaining optical properties of the cholesteric liquid crystal layer. FIG. 4 shows that when natural light is incident, clockwise circularly polarized light having a specific wavelength is reflected, and counterclockwise circularly polarized light and linearly polarized light, and further clockwise light having other wavelengths are transmitted through the cholesteric liquid crystal layer 201. Has been.

  The cholesteric liquid crystal layer has a layered structure. When attention is paid to one layer, the molecular long axes of the liquid crystal molecules are aligned in the layer and are aligned parallel to the plane of the layer. The orientation direction is slightly shifted in the adjacent layers, and as a whole, the layers are stacked while the orientation rotates in a three-dimensional spiral shape.

  In this structure, considering the direction perpendicular to the layers, the distance from the molecular major axis rotating 360 ° to returning to the original is assumed to be a pitch P, and the average refractive index in each layer is n. In this case, the cholesteric liquid crystal layer exhibits a property of selectively reflecting circularly polarized light having a center wavelength λs that satisfies λs = n × P. That is, when white light is incident on the cholesteric liquid crystal layer, clockwise or counterclockwise circularly polarized light having a specific wavelength as a center wavelength is selectively reflected. In this case, the circularly polarized light having the same turning direction as that of the reflected circularly polarized light but having a wavelength that is not λs, the circularly polarized light in the reverse direction of the reflected circularly polarized light, and the linearly polarized light component are transmitted through the cholesteric liquid crystal layer. Therefore, by appropriately setting n and P, the wavelength range of the reflected light of the first color shift layer and the second color shift layer can be set as described above.

  The turning direction (rotation direction) of the reflected circularly polarized light can be determined by selecting the spiral direction of the cholesteric liquid crystal layer. That is, as viewed from the incident direction of light, draw a spiral in the direction of the right-hand screw and the molecular long axis in each layer is oriented, or draw a spiral in the direction of the left-hand screw and the molecular long axis in each layer is oriented, By selecting, the turning direction (rotation direction) of the reflected circularly polarized light can be determined.

  Here, when light is incident on a light-transmitting multilayer film layer having a different refractive index between adjacent layers, the light is reflected at each interface of the multilayer structure. This reflection is caused by the difference in refractive index between the light-transmitting layers adjacent in the vertical direction. When the interface of one layer is seen, what is reflected is a part of the incident light, and most of the incident light is transmitted. That is, incident light that has entered the interfaces stacked in multiple layers is reflected little by little at each interface. Since the reflected light generated at each interface is basically reflected in the same direction, they cause interference due to the optical path difference.

  The more the incident light is incident from a direction closer to the plane, the smaller the optical path difference. Therefore, light of shorter wavelengths interferes and strengthens each other. From this principle, when the viewing angle is increased, the reflected light with shorter wavelengths interfere with each other and strengthen each other. As a result, when the multilayer film layer is viewed under white light, the multilayer film layer that appears to have a predetermined hue at a viewing angle of 0 ° has a gradually bluish color as the viewing angle increases. The phenomenon of changing the color of is observed. This phenomenon is a blue shift.

  In the present invention, the multilayer film layer can be formed by any method. For example, the light transmissive thin film can be composed of a film. Alternatively, the multilayer film layer can be formed by forming a light transmissive thin film by vapor deposition. Alternatively, the multilayer film layer can be formed by applying a light interference pigment as a light transmissive thin film.

  Hologram processing or embossing can be performed on a part or the entire region of at least one of the first color shift layer and the second color shift layer. In addition, a design can be provided on a part of at least one of the first color shift layer and the second color shift layer. By adopting such an aspect, forgery becomes more difficult. Furthermore, an interlayer delamination structure or delamination fracture structure that is broken by applying an external force can be provided. In addition, if the third color shift layer in which the light reflection characteristic is blue-shifted depending on the viewing angle is arranged side by side on the identification medium as described above, the structure becomes complicated and further counterfeiting becomes difficult. Furthermore, it is possible to arrange the print layers side by side on the identification medium having the above configuration. In such an embodiment, the visibility can be improved by comparing the color of the printed layer whose light reflection characteristics are not different from the viewing angle and the color shift of the identification medium.

  Next, the present invention is an identification medium identification method, wherein a cholesteric liquid crystal layer having circular polarization selectivity that reflects circularly polarized light in a specific wavelength region is used as a first color shift layer and / or a second color shift. A method of identifying an identification medium as a layer, characterized in that the identification medium is irradiated with circularly polarized light in a predetermined turning direction and the reflected light is observed.

  The present invention is also an identification medium identification device, wherein a cholesteric liquid crystal layer having circular polarization selectivity that reflects circularly polarized light in a specific wavelength region is used as a first color shift layer and / or a second color shift layer. An identification device for identifying the identification medium is characterized by comprising an irradiating means for irradiating the identification medium with circularly polarized light in a predetermined turning direction and a detecting means for detecting reflected light from the identification medium. .

  According to the present invention, by having a unique color shift different from general multilayer interference, it is possible to provide an identification medium that has high visibility and security and is difficult to forge or tamper with a color copying machine or the like. In addition, it is possible to provide a technique that can be easily and reliably identified.

(1) Description of Embodiment FIG. 5 is a cross-sectional view of an identification medium according to an embodiment of the present invention. FIG. 5 shows the identification medium 1 in a state (unused state) before being attached to an article. In FIG. 5, reference numeral 10 denotes the light absorption layer 10. The light absorption layer 10 is colored in a dark color such as black. A second multilayer film layer (second color shift layer) 11B is laminated on the surface of the light absorption layer 10, and the first multilayer film is formed on the surface of the second multilayer film layer 11B via the adhesive layer 12. A film layer (first color shift layer) 11A2 is laminated. The multilayer layers 11A and 11B are configured by laminating light transmissive thin films having different refractive indexes in multiple layers. An adhesive layer 13 is laminated on the back surface of the light absorption layer 10. The adhesive layers 12 and 13 may be adhesive layers. Further, when the adhesive layer 13 is light absorbing, the light absorbing layer 10 can be omitted.

  The first multilayer film layer 11A is configured to reflect a wavelength region (for example, green to blue) close to the ultraviolet region, and the light reflection characteristics shift to the ultraviolet region as the viewing angle increases. The second multilayer film layer 11B is configured to reflect a wavelength region (for example, red to yellow) closer to the infrared region, and the light reflection characteristics shift to the infrared region as the viewing angle decreases.

  In the first multilayer film layer 11A, the wavelength region near the ultraviolet region is reflected, and the light reflection characteristic shifts to the ultraviolet region as the viewing angle increases. Therefore, when the viewing angle θ is 0 °, the visible light region is short. Reflects light of a wavelength (for example, green to blue), and reflects ultraviolet light (invisible light) when the viewing angle θ increases. On the other hand, in the second multilayer film layer 11B, the wavelength region closer to the infrared region is reflected, and the light reflection characteristic shifts from the infrared region to the visible light region as the viewing angle increases, so when the viewing angle θ is 0 °, In the infrared region, light (invisible light) is reflected, and when the viewing angle θ increases, long-wavelength light (for example, red to yellow) in the visible light region is reflected.

  Accordingly, when viewing the identification medium 1 in FIG. 5 with a viewing angle θ of 0 °, the short wavelength reflected light (for example, green to blue) of the first multilayer film layer 11A can be seen and the viewing angle θ is increased. The reflected light becomes invisible from blue to ultraviolet light. On the other hand, in the second multilayer film layer 11B, the viewing angle θ is 0 ° and the reflected light is invisible in the infrared region, but when the viewing angle θ is increased, the reflected light having a longer wavelength (for example, red to yellow). ) Will be visible. Therefore, the reflected light in the visible light region of the identification medium 1 is secondly reflected from the short wavelength reflected light (for example, green to blue) by the first multilayer film layer 11A when the viewing angle θ is increased from 0 °. Transition to long-wavelength reflected light (for example, red to yellow) by the multilayer film layer 11B.

(2) Description of modification of embodiment First Modified Example A cholesteric liquid crystal layer can be used in place of the first multilayer film layer 11A and the second multilayer film layer 11B. In this case, an aspect in which the two cholesteric liquid phase layers are clockwise circularly polarized light or counterclockwise circularly polarized light, or an aspect in which either one is clockwise circularly polarized light and the other is counterclockwise circularly polarized light. Can be adopted.

  The light-transmitting thin films constituting the first and second multilayer layers 11A and 11B can be formed, for example, by vapor-depositing ceramics, or can be formed by applying a light interference pigment. it can. Vapor deposition can be used for one of the first and second multilayer layers 11A and 11B, and a light interference pigment can be used for the other. In this case, the adhesive layer 12 can be omitted by using vapor deposition for the multilayer film layer.

B. Second Modified Example As shown in FIG. 6, the multilayer film layers 11A and 11B can be subjected to hologram processing or embossing processing. FIG. 6A is an example in which hologram processing or embossing is performed on the first multilayer film layer 11A, and FIG. 6B is an example in which hologram processing or stamping is performed on the second multilayer film layer 11B. FIG. 6C shows an example in which hologram processing and embossing of different designs are performed on the first and second multilayer layers 11A and 11B. Note that the hologram processing and the embossing processing may be formed on either the front surface or the back surface of the first and second multilayer layers 11A and 11B.

  In the mode of FIG. 6 (A), when the viewing angle [theta] is 0 [deg.], A pattern by hologram processing or embossing can be seen, and the pattern disappears as the viewing angle [theta] is increased. This is because, since a hologram or the like is formed on the first multilayer film layer 11A, when the viewing angle θ is increased, ultraviolet light (invisible light) is reflected from the first multilayer film layer 11A. Because. For the same reason, in the embodiment shown in FIG. 6B, when the viewing angle θ is 0 °, the design by hologram processing or embossing is not visible, but when the viewing angle θ is increased, the design is visible. Further, in the mode of FIG. 6C, when the viewing angle θ is changed, the design that is visible together with the color of the identification medium 1 changes.

C. Third Modified Example As shown in FIG. 7, symbols can be printed on the first and second multilayer layers 11A and 11B. In the embodiment shown in FIG. 7A, the surface A of the first multilayer film layer 11A is printed with a color A similar to the color when the viewing angle θ is 0 ° (for example, bluish green). In this case, when the viewing angle θ is 0 °, the print A cannot be seen in the background, but when the viewing angle θ is increased, the background is red-shifted so that the print A can be seen.

  Further, the surface B of the first multilayer film layer 11A is printed with a color B similar to a color when the viewing angle θ is large (for example, orange). In this case, the print B can be seen when the viewing angle θ is 0 °, but if the viewing angle θ is increased, the background will be red-shifted and will not be seen in the background.

  Furthermore, the printing C which is a light absorption layer is given to the surface of the 2nd multilayer film layer 11B. In this case, when the viewing angle θ is 0 °, visible light is reflected by the first multilayer film layer 11A, and infrared light (invisible light) is emitted from the second multilayer film layer 11B, which is the lower layer of the print C. The print C cannot be seen. On the other hand, when the viewing angle θ is increased, ultraviolet light (invisible light) is reflected from the first multilayer film layer 11A, and visible light is reflected from the second multilayer film layer 11B, which is the lower layer of the print C. , Print C is visible.

  In FIG. 7B, the positions of the first multilayer film layer 11A and the second multilayer film layer 11B are interchanged in FIG. 7A, and printing that is a light absorption layer is performed on the surface of the first multilayer film layer 11A. An example in which C ′ is applied is shown. In this case, when the viewing angle θ is 0 °, infrared light (invisible light) is reflected by the second multilayer film layer 11B, and from the first multilayer film layer 11A, which is the lower layer of the print C ′, The printed C ′ is visible because it reflects visible light. On the other hand, when the viewing angle θ is increased, visible light is reflected from the second multilayer film layer 11B, and ultraviolet light (invisible light) is reflected from the first multilayer film layer 11A below the print C ′. The print C ′ is not visible.

D. Fourth Modification Example When one or both of the first and second multilayer layers 11A and 11B are formed of cholesteric liquid crystal instead of the multilayer layer, the optical system selectively transmits right / left circularly polarized light. It is possible to determine authenticity using a filter. That is, the first cholesteric liquid crystal layer is configured to reflect a wavelength region close to the ultraviolet region (for example, bluish green), and the light reflection characteristic shifts to the ultraviolet region as the viewing angle increases. The liquid crystal layer is configured to reflect a wavelength region close to the infrared region (for example, orange), and the light reflection characteristics shift from the infrared region to the visible light region as the viewing angle increases.

(A) In the above aspect, the first cholesteric liquid crystal layer and the second multilayer film layer 11B can be used so that the first cholesteric liquid crystal layer selectively reflects right circularly polarized light. When the identification medium 1 is viewed through an optical filter that selectively transmits right circularly polarized light (hereinafter referred to as “right filter”), it looks blue-green when the viewing angle θ is 0 °. When the angle θ is increased, it looks orange. When the identification medium 1 is viewed through an optical filter that selectively transmits left circularly polarized light (hereinafter referred to as “left filter”), the light absorption layer is visible when the viewing angle θ is 0 °, When viewing angle θ is increased, it looks orange.

(B) In the above aspect, the first multilayer film layer 11A and the second cholesteric liquid crystal layer may be used so that the second cholesteric liquid crystal layer selectively reflects right circularly polarized light. When the identification medium 1 is viewed through the right filter, it looks blue-green when the viewing angle θ is 0 °, and looks orange when the viewing angle θ is increased. Further, when the identification medium 1 is viewed through the left filter, it looks blue-green when the viewing angle θ is 0 °, and the light absorption layer can be seen when the viewing angle θ is increased.

(C) The first and second cholesteric liquid crystal layers can be configured to selectively reflect right circularly polarized light. When the identification medium 1 is viewed through the right filter, it looks blue-green when the viewing angle θ is 0 °, and looks orange when the viewing angle θ is increased. When the identification medium 1 is viewed through the left filter, the light absorption layer can be seen when the viewing angle θ is 0 °, and the light absorption layer can be seen even when the viewing angle θ is increased.

(D) The first cholesteric liquid crystal layer can be configured to selectively reflect right-handed circularly polarized light, and the second cholesteric liquid crystal layer can be configured to selectively reflect left-handed circularly polarized light. When the identification medium 1 is viewed through the right filter, it looks blue-green when the viewing angle θ is 0 °, and the light absorption layer is visible when the viewing angle θ is increased. When the identification medium 1 is viewed through the left filter, the light absorption layer can be seen when the viewing angle θ is 0 °, and it looks orange when the viewing angle θ is increased.

  When a cholesteric liquid crystal layer is used on at least the lower layer side of the two color shift layers, the multilayer film layer or the cholesteric liquid crystal layer on the surface layer side transmits light reflected from the lower cholesteric liquid crystal layer. It is necessary to be isotropic so as not to disturb the polarization state.

E. Fifth Modification The identification medium 1 can be provided with an interlayer delamination structure or delamination fracture structure that is broken when an external force is applied. When an external force that peels the identification medium 1 from the article is applied, for example, the identification medium 1 is divided by breaking in one or both of the first and second multilayer layers 11A and 11B. (Delamination structure). Or it can also comprise so that the layer adjacent to 11 A of 1st multilayer films, etc. may peel (peeling destruction structure). By facilitating delamination and delamination, fraud in which the identification medium is peeled off and reused can be prevented.

F. Sixth Modification A cut can be made in a part of the identification medium 1. As a result, when the identification medium 1 is forcibly removed from the article for reuse, the identification medium 1 is torn from the cut and cannot be reused. Such an embodiment can be applied to an opening identification seal for identifying whether or not a package is opened.

G. Seventh Modification As shown in FIG. 8, the third color shift layer 15 (region A) in which the light reflection characteristic is blue-shifted depending on the viewing angle is arranged on the identification medium 1 (region B) having the above-described configuration. Can be arranged. In such an aspect, when the viewing angle θ is 0 °, the first multilayer film layer 11A looks blue, for example, in the region B, and yellow, for example, in the region A. When the viewing angle θ is increased, the region A is blue-shifted and looks blue, for example, and the region B is red-shifted and looks orange, for example. In this aspect, the structure becomes complicated and it is further difficult to forge. Note that the third color shift layer 15 may be a multilayer film layer or a cholesteric liquid crystal layer. The cholesteric liquid crystal layer can be configured to selectively reflect right circularly polarized light or left circularly polarized light. It is desirable that the red shift in region A and the blue shift in region B are completely reversed. For example, if region A looks blue-green, for example, when the viewing angle θ is 0 °, and looks orange, for example, when the viewing angle θ is increased, region B looks orange when the viewing angle θ is 0 °, When viewing angle θ is increased, it is desirable to look blue-green. Thus, visibility can be improved by reversing the color shift behavior of each region.

H. Eighth Modification As shown in FIG. 9, a printing layer (region D) in which the light reflection characteristic does not depend on the viewing angle can be arranged side by side on the identification medium 1 (region C) having the above configuration. If the color of the printing layer (region D) is the color of the identification medium 1 when the viewing angle θ is 0 °, the region C and the region D look the same color when the viewing angle θ is 0 °, and the viewing angle θ When is increased, the difference in color between the region C and the region D can be visually recognized (see FIG. 9A). Further, if the color of the print layer (region D) is the color of the identification medium 1 when the viewing angle θ is large, the color difference between the region C and the region D can be visually recognized when the viewing angle θ is 0 °. However, when the viewing angle θ is increased, the region C and the region D look the same color. In such an aspect, the visibility can be improved by comparing the color of the printed layer that does not differ from the viewing angle and the color shift of the identification medium 1 (see FIG. 9B).

It is a conceptual diagram which shows a part of principle of this invention. It is a conceptual diagram which shows a part of principle of a multilayer film layer. It is a conceptual diagram which shows a part of principle of a cholesteric liquid crystal. It is a conceptual diagram which shows a part of principle of a cholesteric liquid crystal. It is sectional drawing which shows the schematic structure of the identification medium of embodiment of this invention. It is sectional drawing which shows the schematic structure of the identification medium of the example of a change of this invention. It is sectional drawing which shows the general | schematic structure of the identification medium of the other modification of this invention, and a figure which shows notionally how it looks. It is a figure which shows notionally sectional drawing and the appearance which show the general | schematic structure of the identification medium of the further another modification of this invention. It is a figure which shows notionally the appearance of the identification medium of the further another modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Identification medium 10 Light absorption layer 11A 1st multilayer film layer (1st color shift layer)
11B Second multilayer film layer (second color shift layer)
12 Adhesive layer 13 Adhesive layer

Claims (12)

A first color shift layer that reflects a wavelength region close to the ultraviolet region and whose light reflection characteristics shift to the ultraviolet region as the viewing angle increases;
A second color shift layer that reflects a wavelength region closer to the infrared region and whose light reflection characteristics shift from the infrared region to the visible light region as the viewing angle increases;
A printing pattern of a specific color is provided on a part of at least one of the first color shift layer and the second color shift layer ,
From the observation side
The first color shift layer;
A printing pattern composed of a first light absorption layer;
The second color shift layer;
A second light absorbing layer overlapping the first light absorbing layer;
An identification medium characterized by having a structure in which layers are stacked .   2. The multilayer film layer according to claim 1, wherein at least one of the first color shift layer and the second color shift layer is a multilayer film in which light-transmitting thin films having different refractive indexes are stacked in multiple layers. Identification medium.   The identification medium according to claim 2, wherein the light transmissive thin film is a film.   The at least one of the first color shift layer and the second color shift layer is a cholesteric liquid crystal layer having circular polarization selectivity that reflects circularly polarized light in a specific wavelength range. The identification medium described.   4. The identification medium according to claim 2, wherein the multilayer film layer is formed by vapor deposition of the light transmissive thin film.   The identification medium according to claim 2 or 3, wherein the multilayer film layer is formed by applying a light interference pigment as the light-transmitting thin film.   7. A hologram process or an embossing process is performed on a part or the entire area of at least one of the first color shift layer and the second color shift layer. The identification medium described. The identification medium according to any one of claims 1 to 7, further comprising a delamination structure or a delamination structure that is broken when an external force is applied. An identification medium according to any one of claims 1 to 8 , wherein a third color shift layer whose light reflection characteristics are blue-shifted depending on a viewing angle is arranged side by side. The identification medium according to any one of claims 1 to 9 identification medium characterized in that arranged side by side a printed layer.   5. A method for identifying an identification medium according to claim 4, wherein the identification medium is irradiated with light containing circularly polarized light in a predetermined turning direction and the reflected light is observed. . 5. An identification apparatus for identifying an identification medium according to claim 4, wherein an irradiation means for irradiating the identification medium with light including circularly polarized light in a predetermined turning direction, and a detection means for detecting reflected light from the identification medium. An identification medium identification device comprising:

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