Color display body, authentication medium, and method for determining authenticity of color display body

Abstract

In the color display body according to an embodiment of the present invention, a high-refractive-index layer and a protective layer are formed in order on an embossed layer, the refractive index of the high-refractive-index layer is the highest among the layers, the embossed layer has a first region (A) having a periodic structure shorter than at least the central wavelength of visible light, and, in the first region (A), longitudinal end sides of strip shapes are alternately connected and separated in the direction orthogonal to the longitudinal direction on a display surface, and the periodic direction of the periodic structure is arranged in the longitudinal direction.

Description

[Technical field]

[0001] An embodiment of the present invention relates to a color display body, an authentication medium, and a method for determining the authenticity of a color display body. [Background technology]

[0002] An optical device using guided mode resonance has been proposed. This optical device is equipped with a sub-wavelength grating, which is a diffraction grating arranged at a period smaller than the wavelength of visible light. When light is incident on the sub-wavelength grating, reflection of the diffracted light is suppressed toward the space on the side where the light is incident, while reflection of the light occurs due to guided mode resonance. Guided mode resonance is a phenomenon in which light in a specific wavelength range is caused by multiple reflections propagating within an optical device, causing resonance, and as a result, the light in that wavelength range is reflected by the optical device as reflected light with high intensity. Such optical devices are used as color display bodies that impart at least one of the difficulty of counterfeiting and designability to an object (see, for example, Japanese Patent Application Laid-Open No. 2018-063305).

[0003] In addition, a technology known as "changing" is also used, in which the direction of diffraction is arbitrarily controlled from the arrangement of a diffraction grating, and the pixel area in which a diffraction phenomenon occurs according to the observation angle is determined, so that the image changes depending on the observation angle (see, for example, Japanese Patent Application Laid-Open No. 4-136810).

[0004] Using this technology, pixels are arranged in a matrix, a lattice structure is formed that generates diffraction at multiple pixels for any angle of incidence, and a color display is used in which the image changes continuously depending on the observation angle (see, for example, JP 2011-170178 A). Summary of the Invention

[0005] Incidentally, a color display is required to reflect light having a specific wavelength and to emit a plurality of lights having mutually different wavelengths depending on the use of the color display, the environment in which the color display is applied, the functions expected of the color display, etc. Such a demand is increasing in recent years as the uses, environments, and functions described above become more diverse.

[0006] A highly designable color display body with rich color expression that emits multiple light beams by providing multiple pixels with arbitrary structures is applied, but because a different structure is assigned to each pixel, the reflectance is reduced, resulting in a color display body with low visibility.

[0007] Moreover, in order to increase the reflectance per unit pixel, it is necessary to increase the pixel size. However, when the pixel size is increased, the resolution decreases, resulting in a color display with low visibility. As such, it is difficult to realize a color display having both high resolution and rich color expression. Therefore, there is a demand for a color display having both high resolution and rich color expression.

[0008] The present disclosure aims to provide a color display body, authentication medium, and method for determining the authenticity of a color display body that has high resolution and rich color expression by increasing the intensity of reflected light and diversifying the wavelengths through guided mode resonance.

[0009] A color display device for solving the above problems has an embossed layer, a high refractive index layer, and a protective layer formed in that order, and among the layers, the high refractive index layer has the highest refractive index, and the embossed layer has a first region (A) having a periodic structure that is at least shorter than the central wavelength of visible light, and the first region (A) has rectangular longitudinal end sides connected to each other on the display surface and spaced apart in a direction perpendicular to the longitudinal direction, and the periodic direction of the periodic structure is arranged in the longitudinal direction.

[0010] The authentication medium for solving the above problem includes the above color display body and a support for supporting the color display body.

[0011] In a color display formed of an embossed layer, a high refractive index layer, and a protective layer, the high refractive index layer that conforms to the surface of the embossed layer serves as a waveguide layer, and waveguide mode resonance occurs.

[0012] Since the light propagating due to the waveguide mode resonance is diffracted light generated by the periodic structure, the reflected light generated by the waveguide mode resonance increases or decreases depending on the direction in which the periodic structures arranged in the region having the major axis and minor axis are arranged.

[0013] Therefore, according to the above configuration, the guided mode resonance effect can be controlled in the region having the major axis and the minor axis.

[0014] In the above color display device, zero-order diffracted light is emitted in the first region (A) due to resonance with the periodic structure of the high refractive index layer deposited on the periodic structure.

[0015] According to the above configuration, the high refractive index layer propagates as a waveguide layer and penetrates locally into the embossed layer or protective layer, which serves as the incident space, and the penetrated light and the incident light interfere with and reinforce each other with the light reflected on the surface of the embossed layer or protective layer, and can be emitted as zero-order diffracted light.

[0016] In the above color display device, the periodic structure included in the first region (A) has a longitudinal dimension that is an integer multiple of the value obtained by dividing the least common multiple of the multiple periods that are selectively used by the dividend and the greatest common divisor of the multiple periods that are selectively used by the divisor.

[0017] According to the above configuration, when a plurality of periodic structures are arranged in the first region (A), the period is not locally disturbed due to the relationship between the longitudinal dimension of the first region (A) and the period, and the light can be emitted as zero-order diffracted light without loss.

[0018] In the above color display, a plurality of rectangular first regions (A) composed of a first periodic structure and a plurality of second regions (B) composed of a second periodic structure in which a plurality of periods are mixed are alternately arranged in the embossed layer at least in the longitudinal direction or the orthogonal direction, and the dimensions of the second regions (B) are smaller than the dimensions of the first regions (A).

[0019] According to the above-mentioned configuration, since the optical effect produced by the first region (A) is different from the optical effect produced by the second region (B), it is possible to provide a color display device with excellent design.

[0020] In the above color display device, first-order diffracted light is emitted in the second region (B) due to interference with the mixed periodic structure of the high refractive index layers deposited on the second periodic structure.

[0021] According to the above configuration, the first region (A) emitting zero-order diffracted light can be visually recognized at a reflection angle that depends on the incident angle. Meanwhile, the second region (B) emitting first-order diffracted light can emit light at the same angle as the zero-order diffracted light or at a different angle because the reflection angle can be controlled, thereby providing a color display with excellent design.

[0022] In the above color display, the angle formed by the display surface and a plane including the line of sight of an observer observing the color display is the observation angle. The observation angles of the zeroth-order diffracted light emitted from the first region (A) and the first-order diffracted light emitted from the second region (B) are different.

[0023] According to the above configuration, the angle at which the first region (A) can be observed is different from the angle at which the second region (B) can be observed, so that a color display with high visibility can be provided.

[0024] In the color display device, a color image is formed at an observation angle of the zeroth-order diffracted light emerging from the first region (A), and a grayscale image is formed at an observation angle of the first-order diffracted light emerging from the second region (B).

[0025] According to the above configuration, color images and grayscale images can be observed from different angles, so that by recognizing changes in the images and the appearance or disappearance of colors, a high level of design can be achieved and can be used as a criterion for determining authenticity.

[0026] In the above color display, each image constituted by at least either the first region (A) or the second region (B) can be used as a machine-readable authentication code for determining authenticity.

[0027] According to the above configuration, an image constituted by the first area (A) or the second area (B), or color elements or grayscale elements that are image elements, can be stored as an authentication code, and therefore can be applied to authenticity determination.

[0028] In the above color display, the first periodic structure includes a convex surface and a concave surface, the distance between the convex surface and an adjacent concave surface is the height between the convex and concave surfaces, the first region (A) includes a first sub-region (A1) in which at least one of the height between the convex and concave surfaces, the dimensional ratio between the convex and concave surfaces, and the period is locally different, and the authentication code formed by the first sub-region (A1) can be used as a machine-readable authentication code for determining authenticity.

[0029] According to the above configuration, the reflected light generated by the waveguide mode resonance can have a wavelength and intensity that can be changed by the height between the projections and recesses, the dimensional ratio between the projections and recesses, and the period. Therefore, the first region (A) and the first sub-region (A1) can have different color information, and the first sub-region (A1) can be stored as an authentication code, which can be used for authenticity determination.

[0030] In the above color display body, the position of the viewpoint for observing the color image formed by the first region (A) is the observation position. The color display body has a first position and a second position with the normal to the plane on which the color display body spreads as the rotation axis. The second position is a position where the color display body is rotated by 90° from the first position around the rotation axis. When the color display body is located at the first position, it displays a first color image (1) having a first color with respect to the observation position. Also, when the color display body is located at the second position, it displays a second color image (2) having a second color with respect to the observation position. The first region (A) includes a second sub-region (A2) that locally includes a plurality of periods. The second sub-region (A2) is formed as an authentication code having the same color at both the first position and the second position. The authentication code can be applied as a machine-readable authentication code for authenticity determination.

[0031] According to the above configuration, the color information of the emitted reflected light differs depending on whether the observation position is the first position or the second position in the waveguide mode resonance. Therefore, by controlling the color information generated at the first position and the second position, it is possible to give the same color information at both positions, as in the second sub-region (A2), and by storing the second sub-region (A2) as an authentication code, it can be used for authenticity determination.

[0032] In the above color display, the second region (B) includes a plurality of periods of the second periodic structure, and includes a third sub-region (B1) locally composed of one period. The authentication code composed of the third sub-region (B1) can be used as a machine-readable authentication code for authenticity determination.

[0033] According to the above configuration, the third sub-area (B1) can have color information in contrast to the grayscale information reflected in the second area (B). Therefore, by storing the third sub-area (B1) as an authentication code, it can be used for authenticity determination.

[0034] In the color display device, the second region (B) includes a fourth sub-region (B2) in which the relationship between the multiple periods included in the second periodic structure is locally different. Therefore, the authentication code formed by the fourth sub-region (B2) can be used as a machine-readable authentication code for authenticity determination.

[0035] According to the above configuration, the emission angle can be controlled by the periodic information included in the second region (B). Therefore, the fourth sub-region (B2) that is different from the emission angle in the second region (B) can be stored as an authentication code and applied to authenticity determination.

[0036] In the color display device, the second region (B) includes a fifth sub-region (B3) in which the direction in which the convex and concave surfaces of the second periodic structure are arranged varies locally. Therefore, the authentication code formed by the fifth sub-region (B3) can be used as a machine-readable authentication code for authenticity determination.

[0037] According to the above configuration, the fifth sub-region (B3) can have grayscale gradation information in contrast to the grayscale information reflected in the second region (B). Therefore, the authentication code formed by the fifth sub-region (B3) can be used to determine authenticity.

[0038] In the above color display, the authentication code formed by the first area (A), the second area (B) and the third area (C) different from the first area (A) can be read by a machine and applied to authenticity determination.

[0039] According to the above configuration, by providing a new third area (C), it is possible to have different information in the first area (A) and the second area (B). Therefore, the authentication code formed by the third area (C) can be used for authenticity determination.

[0040] According to the present disclosure, it is possible to provide a color display body, an authentication medium, and a method for determining the authenticity of a color display body that have high resolution and rich color expression by using guided mode resonance to increase the intensity of reflected light and diversify the wavelength. [Brief description of the drawings]

[0041] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic diagram of the structure of a color display device according to a first embodiment, together with an observer and a light source. [Diagram 2] FIG. 2 is a schematic diagram showing the behavior of light in the color display shown in FIG. [Diagram 3] FIG. 3 is a schematic diagram of a color display device for explaining guided mode resonance. [Figure 4] FIG. 4 is a schematic diagram showing the behavior of light for further explanation of guided mode resonance. [Diagram 5] FIG. 5 is a schematic diagram showing the behavior of light for further explanation of guided mode resonance. [Figure 6] FIG. 6 is a schematic diagram for explaining the relationship between the azimuth angle of the uneven surface and the line of sight of the observer. [Figure 7] FIG. 7 is a graph showing the relationship between the azimuth angle of the uneven surface and the spectrum of reflectance for each wavelength. [Figure 8] FIG. 8 is a graph showing the relationship between the inclination of a color display and the reflectance. [Figure 9] FIG. 9 is a graph showing the relationship between the inclination of a color display and the reflectance. [Figure 10] FIG. 10 is a schematic diagram for explaining a region including a concave-convex surface in the color display device of the first embodiment. [Figure 11] FIG. 11 is a schematic diagram for explaining the region A. As shown in FIG. [Figure 12] FIG. 12 is a schematic diagram for explaining the orientation of the uneven surface included in the region. [Figure 13] FIG. 13 is a schematic diagram for explaining the regions of a color display device. [Figure 14]FIG. 14 is a graph showing the relationship between the layout of the regions of a color display device and the reflectance. [Figure 15] FIG. 15 is a schematic diagram showing a state in which an observer observes a color display medium. [Figure 16] FIG. 16 is a schematic diagram showing an example of the effect of a color display body. [Figure 17] FIG. 17 is a flow chart for explaining the procedure for manufacturing a color display. [Figure 18] FIG. 18 is a schematic diagram for explaining regions in a color display device according to the second embodiment. [Figure 19] FIG. 19 is a graph showing the relationship between the arrangement density of the mixed periodic structure and the diffraction angle. [Figure 20] FIG. 20 is a diagram showing reflected light spectra in nine color display devices with different r values. [Figure 21] FIG. 21 is a diagram showing the colors of light reflected by nine color displays on the xy chromaticity diagram. [Figure 22] FIG. 22 is a plan view showing the structure of a color display. [Diagram 23] FIG. 23 is a schematic diagram showing the relationship between a first range and a second range of observation angles. [Figure 24] FIG. 24 is a schematic diagram showing a state in which an observer is observing a color display medium. [Diagram 25] FIG. 25 is a plan view showing an image displayed by an authentication medium having a color display. [Figure 26] FIG. 26 is a diagram for explaining the first position and the second position in a color display body. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] [First embodiment] A first embodiment of a color display body, an authentication medium, and a method for determining the authenticity of a color display body will be described with reference to the drawings. The structure of the color display body, the shape of the uneven surface, the azimuth angle of the uneven surface, the function of the color display body, and the manufacturing method of the color display body will be described below in order.

[0043] (Structure of color display body) The structure of a color display device according to a first embodiment will be described with reference to FIGS.

[0044] FIG. 1 is a cross-sectional view showing a schematic diagram of the structure of a color display device according to a first embodiment, together with an observer and a light source.

[0045] 1, the color display body 10 includes an embossed layer 11, a high refractive index layer 12, and a protective layer 13. In the color display body 10, the embossed layer 11, the high refractive index layer 12, and the protective layer 13 are laminated in the order shown. Each of the layers 11, 12, and 13 is light-transmitting.

[0046] The embossed layer 11 has a refractive index n1, the protective layer 13 has a refractive index n3, and the high refractive index layer 12 has a refractive index n2. The refractive index n2 is higher than the refractive indexes n1 and n3. The refractive index n1 can be the same as or different from the refractive index n3.

[0047] The embossed layer 11 includes an uneven surface 11S1 in at least a part of the surface 11S in contact with the high refractive index layer 12. In the example shown in FIG. 1, the entire surface 11S is the uneven surface 11S1. The period d of the uneven surface 11S1 can be equal to or less than the central wavelength of visible light. The period d of the uneven surface 11S1 can be equal to or more than half the lower limit wavelength of visible light. Specifically, the period d of the uneven surface 11S1 is in the range of 250 nm to 500 nm. In the direction in which the concave and convex surfaces included in the uneven surface 11S1 are arranged, that is, in the example shown in FIG. 1, in the left-right direction of the paper, one period includes one concave surface and one convex surface. In one period, one concave surface and one convex surface can be arranged alternately. The uneven surface 11S1 has a wave shape in a cross section perpendicular to the plane in which the color display 10 spreads. On the uneven surface 11S1, the corrugated shape continues along the depth direction of the paper.

[0048] The high refractive index layer 12 has a thickness that can follow the surface 11S of the embossed layer 11. The high refractive index layer 12 can have a thickness of several nm or more and less than one hundred and several tens of nm. In a cross section perpendicular to the plane in which the color display body 10 extends, the high refractive index layer 12 has a wave shape that follows the uneven surface 11S1. In the high refractive index layer 12, the wave shape continues along the depth direction of the paper.

[0049] Light is incident on the color display body 10 from a light source LS located on the opposite side of the embossed layer 11 from the high refractive index layer 12. The light source LS can be, for example, the sun or a lighting fixture. The color display body 10 is observed by an observer OB from the opposite side of the embossed layer 11 from the high refractive index layer 12. An observation position OP, which is the position of the viewpoint of the observer OB, is an arbitrary position in space on the opposite side of the embossed layer 11 from the high refractive index layer 12. The direction in which the observer OB views the color display body 10 from the observation position OP is the line of sight direction DOB of the observer OB.

[0050] In this embodiment, the observation angle is defined as the angle formed between a plane including the line of sight DOB and a plane on which the color display 10 spreads. In the embossed layer 11, the surface opposite the above-mentioned surface 11S has a sufficiently high flatness and can be considered to be a flat surface. Note that when the roughness of the surface is sufficiently small relative to the wavelength, typically 1 / 10 or less, it can be considered to be a flat surface. Therefore, the observation angle can be defined as the angle formed between a plane including the line of sight DOB and the surface of the embossed layer 11 opposite the surface 11S.

[0051] Next, the guided mode resonance occurring in the color display 10 will be described with reference to FIGS.

[0052] FIG. 2 is a schematic diagram showing the behavior of light in the color display shown in FIG.

[0053] As shown in Fig. 2, the guided mode resonance occurs in a color display 10 having at least three layers as described above. In these three layers, the essential condition for generating the guided mode resonance is that the layer with the highest refractive index is located in the center and that the central layer is sandwiched between two layers having refractive indices different from that of the central layer. That is, in the color display 10, the above-mentioned high refractive index layer 12 needs to be sandwiched between the embossed layer 11 and the protective layer 13.

[0054] In the color display 10, the high refractive index layer 12 is included in the waveguiding layer. A part of the light diffracted by the high refractive index layer 12 among the incident light IL incident on the color display 10 is totally reflected at the boundary between the embossed layer 11 and the high refractive index layer 12 and at the boundary between the high refractive index layer 12 and the protective layer 13, and propagates through the high refractive index layer 12. Such light propagation occurs because the refractive index n2 of the high refractive index layer 12 is higher than the refractive index n1 of the embossed layer 11 and higher than the refractive index n3 of the protective layer 13. Note that, among the incident light IL, only light having a wavelength that satisfies the propagation condition of the waveguiding described below propagates through the high refractive index layer 12 as propagating light LG, and as a result of the propagation, is reflected by the color display 10 as reflected light RL having high brightness. The reflected light RL is reflected in the direction of regular reflection. On the other hand, light having a wavelength that does not satisfy the propagation condition exits the color display 10 as transmitted light TL that passes through the color display 10.

[0055] FIG. 3 is a schematic diagram of a color display for explaining the waveguide mode resonance.

[0056] 3, a color display 10 is shown in schematic form to explain the propagation conditions of a guided wave. The color display 10 has a structure in which parts of the high refractive index layer 12 and parts of the embossed layer 11 or protective layer 13 are alternately arranged in the direction in which the concave and convex surfaces of the high refractive index layer 12 are arranged, as viewed from the light propagating through the color display 10. That is, high refractive index portions and low refractive index portions are alternately arranged in the direction in which the concave and convex surfaces are arranged.

[0057] The propagation conditions can be expressed by the following formulas (1) to (6) using the occupancy rate F of the high refractive index layer 12 in the period d, the wavelength λ of the incident light IL, the period d of the uneven surface, the wave number k, and the reciprocal lattice vector K.

[0058]

number

[0059]

number

[0060]

number

[0061] Where: k = 2π / λ … Equation (4) K = 2π / d … Equation (5) β = (2π / λ) n eff … Formula (6) It is.

[0062] In formula (3), the incident angle θ of the incident light IL and the diffraction order m are integers. Also, in formula (3), the propagation constant β of the waveguiding layer, i.e., the high refractive index layer 12, is determined by the wavelength λ of the incident light IL and the effective refractive index n of the high refractive index layer 12. eff Equation (1) depends on the effective refractive index n eff and the formula (2) expresses the effective refractive index n eff The effective refractive index n eff is the effective refractive index n for TE waves when the period d of the concave-convex surface is shorter than the wavelength λ of the incident light IL. eff and the effective refractive index for TM waves, n eff Each effective refractive index n eff is determined by the occupancy rate of the high refractive index layer 12 in the period d.

[0063] FIG. 3 is a schematic diagram of a color display for explaining the waveguide mode resonance.

[0064] 3, the width of high refractive index layer 12 is a, and the width of embossed layer 11 or protective layer 13 is b. Therefore, the occupancy rate of high refractive index layer 12 in period d is the ratio of width a to period d, and the occupancy rate of embossed layer 11 or protective layer 13 in period d is the ratio of width b to period d.

[0065] The waveguide conditions that satisfy the above formulas (1) to (6) can be expressed by the following formula.

[0066] n eff >n1,n3 … Equation (7) λ>d … Equation (8) As mentioned above, the effective refractive index n eff is determined by the occupancy rate (a / d) of the high refractive index layers 12 in the period d, the following relationship can be derived:

[0067] n2>n1,n3 … Equation (9) In addition, the effective refractive index n eff By applying the above formula, the wavelength of light guided through the color display 10 and the reflectance of light having that wavelength can be obtained. That is, the effective refractive index n eff By adjusting the wavelength of the guided mode resonance, it is possible to reflect chromatic light having high brightness to the color display body 10. The reflection of chromatic light using the guided mode resonance can also be expressed as zero-order diffracted light.

[0068] For example, by simply modulating the period d, it is possible to change the wavelength of the guided light that satisfies the above formulas (1) to (6). In addition, by including uneven surfaces 11S of color display body 10 each having a different period, it is possible to display the colors r, g, and b, thereby providing a full-color color display body 10 with excellent design.

[0069] In addition, as is clear from the above formula, the effective refractive index n effThe wavelength and reflectance of light reflected by the guided mode resonance can be controlled by changing the parameters included in the equations for deriving and propagation constant β, namely, the refractive indexes n1 to n3, the period d, and the occupancy rate F. Furthermore, the light reflected by the guided mode resonance also depends on the incidence angle θ of the incident light IL incident on the color display 10. Therefore, a color display applying the guided mode resonance determines its reflected light by these parameters, and the light reflected by the color display can be read by a sensor and easily compared with the light determined by the parameters. Therefore, the color display can be applied to judgment by machine reading.

[0070] In addition, the effective refractive index n eff and the difference between the refractive index n1 and the effective refractive index n eff The greater the difference between the effective refractive index n and the refractive index n3, the higher the reflectance of the light reflected by the guided mode resonance. That is, the greater the occupancy rate F of the high refractive index layer 12, the higher the reflectance of the light. eff and the difference between the refractive index n1 and the effective refractive index n eff The reflectance of light is determined according to the difference between the effective refractive index n and the refractive index n3. Therefore, when the materials applicable to the embossed layer 11 and the protective layer 13, in other words the refractive index, are fixed, the effective refractive index n eff This is useful for diversifying the wavelengths of light reflected by the color display 10.

[0071] FIG. 4 is a schematic diagram showing the behavior of light to further explain the guided mode resonance.

[0072] 4, in order to facilitate understanding of waveguiding, it is assumed that high refractive index layer 12, embossed layer 11, and protective layer 13 are each a flat laminate. As described above, a part of the light diffracted by high refractive index layer 12 becomes propagating light LG that propagates through high refractive index layer 12 while being totally reflected at the boundary between embossed layer 11 and high refractive index layer 12 and at the boundary between high refractive index layer 12 and protective layer 13.

[0073] For example, when the propagating light LG travels to the interface of the embossed layer 11, if the incident angle θ of the propagating light LG is equal to or greater than the critical angle resulting from the relationship between the refractive index n1 of the embossed layer 11 and the refractive index n2 of the high refractive index layer 12, total reflection occurs at the interface between the embossed layer 11 and the high refractive index layer 12.

[0074] However, since the component of the wave number perpendicular to the boundary surface of the propagating light LG is an imaginary number, the propagating light LG penetrates into the embossed layer 11, which has a low refractive index. This penetrating light is called evanescent light, and appears as evanescent light LE shown in FIG. 4. The evanescent light LE cannot propagate long distances, and the propagation distance h only penetrates by about the wavelength. Furthermore, since the intensity of the evanescent light LE attenuates exponentially with distance from the interface, the evanescent light LE cannot be seen by the observer OB. However, the light that is the result of interference between the evanescent light LE and the incident light IL becomes propagating light, and is recognized by the observer OB.

[0075] When the incident angle of the incident light IL and the thickness of the high refractive index layer 12 are fixed, the intensity of the evanescent light LE increases because a waveguide mode is excited in a specific wavelength band. Therefore, the high refractive index layer 12 can have a uniform thickness.

[0076] FIG. 5 is a schematic diagram showing the behavior of light to further explain the guided mode resonance.

[0077] FIG. 5 shows a schematic diagram of the behavior of light to further explain the propagating light LG in FIG. 4. The intensity of the evanescent light LE increases as the intensity of the propagating light LG increases. The propagating light LG propagates while being multiple-reflected at the interface between the embossed layer 11 and the high refractive index layer 12 and at the interface between the protective layer 13 and the high refractive index layer 12, and is excited when the phases of the reflected plane waves are aligned. For example, when the propagating light LG is at point P and when it is reflected at point Q, the optical path length reflected in the waveguide of the high refractive index layer 12 is an integer multiple of 2π, so that the phases are aligned, excitation occurs, and the intensity of the propagating light LG increases. In this way, the more times the light in the waveguide of the high refractive index layer 12 is multiple-reflected, the higher the intensity of the evanescent light LE, and the better the visibility of the color display 10.

[0078] 4 and 5, the behavior of light is explained typically, but the color display body 10 has a periodic structure with concaves and convexes, and the diffracted waves due to the periodic structure become the propagating light LG. As explained above, the intensity of the evanescent light LE increases as the number of multiple reflections increases, so it is desirable to enlarge the area in which the periodic structure is arranged.

[0079] (azimuth angle of uneven surface) Next, the azimuth angle of the uneven surface 11S1 will be described with reference to FIGS.

[0080] FIG. 6 is a schematic diagram for explaining the relationship between the azimuth angle of the uneven surface and the line of sight of the observer.

[0081] Fig. 6 shows the relationship between the line of sight DOB of the observer OB and the azimuth angle of the uneven surface 11S1. In Fig. 1, the direction in which the wavy shape of the uneven surface 11S1 illustrated in the color display device 10 continues along the depth direction of the paper is the extension direction of the convex surface S1A.

[0082] As shown in FIG. 6(a), the convex surface S1A of the color display body 10 extends along one direction. In the example shown in FIG. 6(a), the convex surface S1A extends along the vertical direction of the paper. The azimuth angle of the uneven surface 11S1 is the angle formed between the direction in which the convex surface S1A extends and a reference direction, which is an arbitrary direction along the plane on which the color display body 10 spreads. In this example, the reference direction is the horizontal direction of the paper. In this case, the angle formed between the reference direction and the direction in which the convex surface S1A extends is 90°. Therefore, the azimuth angle of the uneven surface 11S1 is 90°. The projection direction of the line of sight DOB of the observer OB projected onto the plane on which the color display body 10 spreads is the vertical direction of the paper. The projection direction is parallel to the direction in which the convex surface S1A extends. That is, the uneven surface 11S1 is vertical to the observer OB.

[0083] In the example shown in FIG. 6(b), the convex surface S1A extends along the left-right direction of the paper. Since the left-right direction of the paper is the reference direction, the angle formed between the reference direction and the extending direction of the convex surface S1A is 0°. Therefore, the azimuth angle of the uneven surface 11S1 is 0°. The projection direction of the line of sight DOB of the observer OB projected onto the plane on which the color display body 10 spreads is the up-down direction of the paper. The projection direction is perpendicular to the extending direction of the convex surface S1A. In other words, the uneven surface 11S1 is oriented horizontally with respect to the observer OB.

[0084] FIG. 7 is a graph showing the relationship between the azimuth angle of the uneven surface and the spectrum of reflectance for each wavelength.

[0085] Fig. 7 shows the relationship between the wavelength and reflectance of the reflected light RL reflected by the color display body 10. In Fig. 7, the spectrum shown by the solid line is the spectrum obtained by the color display body 10 in which the uneven surface 11S1 is vertically oriented, and the spectrum shown by the dashed line is the spectrum obtained by the color display body 10 in which the uneven surface 11S is horizontally oriented. When obtaining the spectrum of the reflected light RL, the direction from the light receiving element of the measuring device toward the color display body 10 is set as the measurement direction, and the measurement direction is regarded as the line of sight direction DOB described above.

[0086] As shown in FIG. 7, the color display 10 in which the uneven surface 11S is arranged vertically and the color display 10 in which the uneven surface 11S is arranged horizontally can reflect red light represented by spectrum r, green light represented by spectrum g, and blue light represented by spectrum b. However, in each of the spectra r, g, and b, the peak intensity in the spectra r, g, and b represented by the solid lines is higher than the peak intensity in the spectra r, g, and b represented by the dashed lines. Therefore, the color display 10 can have the uneven surface 11S oriented vertically with respect to the observer OB. In other words, the color display 10 can display the intended image recorded on the uneven surface 11S with respect to the observer OB when the uneven surface 11S is oriented vertically.

[0087] FIG. 8 is a graph showing the relationship between the inclination of a color display and the reflectance.

[0088] FIG. 9 is a graph showing the relationship between the inclination of a color display and the reflectance.

[0089] 8 and 9 show the relationship between the wavelength of the reflected light RL reflected by the color display body 10 and the reflectance, as in FIG. 7. In both FIG. 8 and FIG. 9, a spectrum SP1 when the color display body 10 is tilted from a reference position by 20° is shown by a solid line, a spectrum SP2 when the color display body 10 is tilted by 30° is shown by a dashed line, and a spectrum SP3 when the color display body 10 is tilted by 40° is shown by a dashed line. Note that the position of the color display body 10 when it is placed on a horizontal plane is the reference position. Also, FIG. 8 shows a spectrum obtained by the color display body 10 arranged vertically. Meanwhile, FIG. 9 shows a spectrum obtained by the color display body 10 arranged horizontally.

[0090] As shown in Figure 8, when the color display 10 is arranged vertically, the difference in wavelength at the peak between spectrum SP1 when the color display 10 is tilted 20° with respect to the reference position and spectrum SP3 when the color display 10 is tilted 40° with respect to the reference position is less than 50 nm.

[0091] On the other hand, as shown in Figure 9, in a color display device 10 in which the uneven surface 11S is oriented horizontally, the difference in wavelength at the peak between spectrum SP1 when the color display device 10 is tilted 20° with respect to the reference position and field spectrum SP3 when the color display device 10 is tilted 40° with respect to the reference position is 50 nm or more and less than 100 nm.

[0092] In this way, when the color display body 10 is tilted with respect to the reference position, in order to suppress a change in the color of the reflected light RL reflected by the color display body 10, the color display body 10 can have the uneven surface 11S oriented vertically with respect to the observer OB. In other words, the color display body 10 can be configured to display an intended image recorded on the uneven surface 11S to the observer OB when the uneven surface 11S is oriented vertically.

[0093] The reflected light RL of the color display body 10 may include 1st-order diffracted light. The 1st-order diffracted light is reflected on a plane perpendicular to the direction in which the convex surface S1A extends and perpendicular to the plane on which the color display body 10 extends. Therefore, when the uneven surface 11S1 of the color display body 10 is oriented horizontally with respect to the observer OB, the observer OB can visually recognize the 1st-order diffracted light reflected by the color display body 10. In addition, the observer OB may mistakenly recognize the 1st-order diffracted light visually recognized by himself / herself as 0th-order diffracted light, that is, the reflected light RL due to the waveguide mode resonance. When the uneven surface 11S1 of the color display body 10 is oriented vertically with respect to the observer OB, the possibility that the observer OB will mistakenly recognize the 1st-order diffracted light as 0th-order diffracted light can also be reduced.

[0094] (Function of color display) The operation of the color display device 10 will be described with reference to FIGS.

[0095] FIG. 10 is a schematic diagram for explaining a region including a concave-convex surface in the color display device of the first embodiment.

[0096] As shown in Fig. 10, the motif 20 is formed in an area A including a concave-convex surface 11S1 having a periodic structure in a portion of the surface 11S of the embossed layer 11. As described above, the color of reflected light can be controlled by the period, so the formed motif 20 can be displayed in color, and if the periodic structure included in area A is formed with multiple periods, a colorful motif 20 can be displayed. Furthermore, the color can be changed, although the amount of change is small, by the height of the concave-convex surface where the convex and concave surfaces of the concave-convex surface 11S1 are adjacent, and a colorful motif 20 with a high degree of freedom can be displayed by the concave-convex information of the concave-convex surface 11S1 included in area A or the concave-convex information of the concave-convex surface 11S1 included in a different area A, so a color display 10 with high designability can be provided.

[0097] Furthermore, as explained above, when the uneven surface 11S is oriented vertically, the possibility that the observer OB will mistakenly recognize the first-order diffracted light as the zeroth-order diffracted light when viewing the motif 20 can be reduced.

[0098] FIG. 11 is a schematic diagram for explaining the region A. As shown in FIG.

[0099] In FIG. 11, the region A is explained in more detail. In FIG. 11(a), the region A has a long and short direction of a strip, and the uneven surface 11S is arranged vertically in the long direction. This is to increase the number of multiple reflections of the propagating light LG generated from the periodic structure. If the number of reflections is increased, the evanescent light LE is enhanced and the reflectance of the zeroth order diffracted light is improved, and a color display body 10 with high visibility can be provided to the observer OB. The short direction is directly connected to the pixel of the motif, and in order to reproduce a fine motif, it is preferable that the dimension is not resolved by the observer, and it can be at least 100 μm or less, and more preferably 60 μm. In addition, in order to enhance the evanescent light LE, it is preferable that the dimension is larger than the short direction. If the dimension ratio is at least twice or more, an increase in the reflectance of the zeroth order diffracted light is confirmed, and it can be 30 times or less in consideration of the degree of freedom of motif formation when used as a pixel.

[0100] Furthermore, the short side direction, which is perpendicular to the long side direction of region A, is separated from each other, and the separated region 11S2 can be the surface 11S of the embossed layer 11 or can include other elements. For example, if region 11S2 is an area containing colored ink, the zeroth order diffracted light can only be observed at a specific angle in region A. On the other hand, region 11S2 can be observed without any angle dependency, so that the color of motif 20 or the motif itself can change depending on the angle, and the change can be used as a criterion for determining authenticity.

[0101] Although colored ink has been given as an example of region 11S2, it may also include not only colored ink, but also optically variable elements such as a periodic structure different from the periodic structure of uneven surface 11S1 constituting region A, a scattering structure that has no periodicity, or other optically variable elements such as liquid crystal materials or magnetic pigments.

[0102] Furthermore, as shown in FIG. 11(b), when the period of the uneven surface 11S1 constituting region A is the same, the longitudinal end edges can be connected to each other. This connection can increase the number of multiple reflections of the propagating light LG resulting from the periodic structure, thereby enhancing the evanescent light LE and improving the reflectance of the zeroth-order diffracted light, thereby providing the observer with a color display 10 with high visibility.

[0103] When the longitudinal edges of the regions A are connected to each other at least 20 μm or more, more preferably 50 μm or more, the multiple reflection of the propagating light LG is not hindered, and the evanescent light LE can be enhanced. Furthermore, when the above values ​​are satisfied, the effect of the embodiment of the present invention can be obtained even if the positions of the major axes of each region A are slightly misaligned as shown in FIG. 11(b). This misalignment can be within 50% of the length of the edge. As a result, the evanescent light LE can be sufficiently enhanced. It may even be 10% or less. As a result, the enhancement of the evanescent light LE can be comparable to that in a state where there is no misalignment.

[0104] The contour line in the longitudinal direction of the region A can be a straight line, a curved line, or a combination thereof. The contour line in the lateral direction of the region A can be a straight line, a curved line, or a combination thereof. The contour shape of the region A can be a rectangle, a rectangle with rounded corners, or an octagon. The contour line in the longitudinal direction of the region A can be a curved line, and the contour line in the lateral direction of the region A can be a straight line. Since the region A is directly connected to the pixel, the degree of freedom of the motif to be displayed can be increased by emphasizing the boundary between the region A and the region 11S2, or conversely, by not emphasizing it and making the boundary ambiguous. The boundary can be emphasized by making the contour line of the region A that is the boundary of the region 11S2 a straight line, whereas the boundary can be not emphasized by making the contour line of the region A that is the boundary of the region 11S2 a curved line. The curve can be a semicircle, a semiellipse, or a free curve. The radius of curvature of the curve can be constant or variable. The radius of curvature can be shorter than the length of the end side and 1% or less of the length of the end side.

[0105] The short-side dimension of region A does not have to be the same for the entire region, and the dimension of the end side can be shorter than the other dimensions. Also, the short-side dimension can be shorter as it approaches the mutually connected portion.

[0106] In this way, it is possible to change the reflection spectrum of the zero-order diffracted light that appears in the motif's region A by changing the short-side dimension in region A. Therefore, even if the wavelength is the same, even within region A, the saturation changes depending on the reflectance, allowing for a richer color expression.

[0107] Furthermore, in the color display body 10, the longitudinal dimension of the region A can be an integer multiple of the value obtained by using the least common multiple of the multiple periods of the periodic structure of the uneven surface 11S1 arranged in the region A as the dividend and the greatest common divisor of the multiple periods as the divisor.

[0108] As explained above, the diffracted waves of the periodic structure of the uneven surface 11S1 are ultimately emitted as zero-order diffracted light, and therefore when the periodic structure of the uneven surface 11S1 is disposed in the region A, the period at the end is shifted depending on the dimension in the longitudinal direction, resulting in a decrease in the intensity of the zero-order diffracted light. However, by restricting the above dimensions, no period shift occurs in the region A for all of the multiple periods used, and it is possible to provide a color display 10 with high visibility and no decrease in intensity.

[0109] According to the above configuration, even if the concave-convex surfaces 11S of the connecting regions A have different periods, no misalignment occurs at the connecting portion, and a color display body 10 with no reduction in strength can be provided.

[0110] FIG. 12 is a schematic diagram for explaining the orientation of the uneven surface included in the region.

[0111] FIG. 12 shows a schematic diagram of the periodic structure of the uneven surface 11S1 arranged in the region A.

[0112] As explained above, the color display 10 can be arranged so that the periodic structure of the uneven surface 11S1 is aligned vertically in the long axis direction of the region A. In FIG. 12(a), the uneven surface 11S1 is arranged at an azimuth angle of 90°, as in FIG. 6(a), and in FIG. 12(b), the uneven surface 11S1 is arranged at an azimuth angle of 45°. In order to increase the intensity of the propagating light LG, the inside of the waveguide needs to be long; if it is short, the intensity of the propagating light LG decreases. The inside of the waveguide in the cross sections SLa1, SLa2, and SLa3 in FIG. 12(a) has the same length, and in FIG. 12(a), the inside of the waveguide has the same length no matter which cross section SLa is viewed.

[0113] On the other hand, the lengths of the waveguide in the cross sections SLb1, SLb2, and SLb3 in Fig. 12(b) are all different, and in Fig. 11(b), the lengths of the waveguide are different depending on the cross section viewed, and the intensity of the propagating light LG is reduced. Therefore, in order to increase the intensity of the propagating light LG, it is preferable to set the azimuth angle of the uneven surface 11S1 to 90° or 0°. Also, as described above, if the azimuth angle of the uneven surface 11S1 is set to 0°, first-order diffracted light may be included, so it is more preferable to set the azimuth angle of the uneven surface 11S1 to 90°.

[0114] FIG. 13 is a schematic diagram for explaining the regions of a color display device.

[0115] According to FIG. 13, the effect of the present disclosure is explained using a color display 10. In particular, in FIG. 13(a), the motif 25 in the color display 10 is composed of an area A, and the area A has a long side and a short side in a rectangular shape, and the uneven surface 11S1 is arranged vertically in the long side direction. The short side direction is dimension S, and the area is spaced apart by the dimension S. The spaced apart area 11S2 is composed of an uneven surface 11S1 that reflects the zeroth order diffracted light of the area A at an angle different from that of the area A. On the other hand, in FIG. 13(b), the area is divided into a square lattice shape of dimension S, and the uneven surface 11S1 and the spaced apart area 11S2 are arranged alternately to form the motif 25. Note that the surface areas of the area A and the spaced apart area 11S2 used in FIG. 13(a) and FIG. 13(b) are equal.

[0116] FIG. 14 is a graph showing the relationship between the layout of the regions of a color display device and the reflectance.

[0117] Fig. 14 shows the relationship between the reflectance and wavelength of the zeroth-order diffracted light due to the guided mode resonance for the motif 25 of the color display 10 described in Fig. 13. Fig. 14 shows the result of measuring the spectral reflectance spectrum of a color display 10 fabricated by using a sinusoidal curve structure with a period of 300 nm on the uneven surface 11S1 of the embossed layer 11, forming the uneven surface with adjacent convex and concave surfaces at a height of 110 nm, forming the high refractive index layer 12 from TiO2 with a refractive index of 1.95, and setting the refractive index of the embossed layer 11 and protective layer 13 to 1.45. In Fig. 14, the spectrum SP4 shown by the solid line corresponds to that of the color display 10 described in Fig. 13(a), and the spectrum SP5 shown by the dashed line corresponds to that of the color display 10 described in Fig. 13(b). Comparing the reflectance of the zeroth order diffracted light, it can be seen that even though the surface area is the same, the color display 10 in FIG. 13(a) has a higher reflectance, approximately 30% higher than the color display 10 in FIG. 13(b).

[0118] As explained above, the color display 10 in Fig. 13(a) can increase the number of multiple reflections of the propagating light LG caused by the periodic structure more than the color display 10 in Fig. 13(b), thereby achieving an increase in the evanescent light LE and an improvement in the reflectance of the zeroth-order diffracted light. If the reflectance of the zeroth-order diffracted light is increased, the visibility for the observer OB is improved, and the ease of authenticity determination is also increased.

[0119] The dimension S of the region A in the short direction is the resolution for forming the motif 25, and is therefore preferably a dimension that is not noticeable when observing the color display 10, and can be at least 100 μm or less, more preferably 60 μm or less.

[0120] FIG. 15 is a schematic diagram showing a state in which an observer observes a color display medium.

[0121] 15, when an observer OB observes the color display device 10, the observer OB can observe the zero-order diffracted light reflected by the guided mode resonance generated in the region A in the direction of regular reflection. The incident angle α of the incident light IL from the light source LS is equal to the reflection angle β of the zero-order diffracted light, which is the reflected light RL. The wavelength of the reflected light RL is included in the range of visible light, which allows the color display device 10 to display a chromatic color image.

[0122] FIG. 16 is a schematic diagram showing an example of the effect of a color display body.

[0123] FIG. 16 shows an example of the effect of the color display 10 having the region A and the region 11S2 containing colored ink. In the region A, the zero-order diffracted light can be observed at an angle β, whereas the region 11S2 can be observed without any angle dependency, so that the appearance of the motif 28 can be changed depending on the observation angle. For example, when the incident light IL is incident at an incident angle α, the motif 28 displayed on the color display 10 when observed at an angle different from the reflection angle β is as shown in FIG. 16(a), whereas the motif 29 when observed at the reflection angle β can be as shown in FIG. 16(b). By utilizing the characteristics of each region, a new motif 29 can be displayed by combining the elements of the region A with the motif 28 displayed in the region 11S2. This allows the observer OB to recognize the change in the motif by changing the observation angle, so that the change in the motif can be used as a criterion for determining authenticity. In addition to the combination of regions, for example, by forming an uneven surface 11S1 that reflects the region 11S2 at an angle different from that of the region A, a completely different motif can be displayed depending on the observation angle.

[0124] (How to determine authenticity) 15, when observer OB observes color display body 10, observer OB can observe the zero-order diffracted light reflected by the waveguide mode resonance in the direction of regular reflection. In other words, from the viewpoint of observer OB, when observer OB observes color display body 10, chromatic reflected light appears in the direction of regular reflection and chromatic reflected light disappears in a direction different from the direction of regular reflection. This can be used as a method for determining the authenticity of color display body 10.

[0125] On the other hand, the reflected light of the first-order diffracted light is dispersed and reflected in various directions, so if the observer OB changes the observation direction, the color transition becomes visible. However, it is not possible to determine which direction the observer OB is facing and which color is the genuine product. For this reason, the zeroth-order diffracted light can be used to determine the authenticity. Also, as described above, by setting the azimuth angle of the uneven surface 11S1 at 90°, the first-order diffracted light of the uneven surface 11S1 is not visible to the observer OB, which is effective not only as a design but also as a method of determining authenticity.

[0126] (Manufacturing method of color display body) A method for producing the color display device 10 will be described with reference to FIG.

[0127] FIG. 17 is a flow chart for explaining the procedure for manufacturing a color display.

[0128] As shown in FIG. 17, the manufacturing method for the color display device 10 includes a master creating process (step S11) for creating a stamper, a first layer forming process (step S12) for forming an embossed layer 11, a second layer forming process (step S13) for forming a high refractive index layer 12, and a third layer forming process (step S14) for forming a protective layer 13.

[0129] In the master creation process for creating a stamper, first, a master is created by lithography using electron beam lithography. When creating the master, a positive resist material is prepared. Next, a resist layer is formed using the resist material. Then, the resist layer is irradiated with an electron beam according to the shape of the surface 11S of the embossed layer 11. Since the resist layer is formed using a positive resist, the electron beam is irradiated to a portion of the resist layer that is to be removed from the resist layer after development. When a positive resist material is used, the portion irradiated with the electron beam is removed from the resist layer after development.

[0130] Furthermore, a stamper is produced from the formed master by electroforming to transfer the concave-convex shape of the master to the embossed layer 11. Then, the concave-convex shape of the stamper is transferred to a resin layer for forming the embossed layer 11, thereby forming the embossed layer 11.

[0131] In the first layer forming step of forming the embossed layer 11, first, a synthetic resin for forming the embossed layer 11 is prepared. The synthetic resin for forming the embossed layer 11 can be a thermoplastic resin, a thermosetting resin, or a photocurable resin. The synthetic resin is, for example, an acrylic resin, a urethane resin, or a urethane acrylic resin. Then, after applying a coating film containing the synthetic resin for forming the embossed layer 11, the uneven shape of the transfer plate is transferred to the coating film, thereby forming the embossed layer 11.

[0132] In the second layer forming process for forming the high refractive index layer 12, first, the high refractive index layer 12 is formed so as to cover the surface 11S of the embossed layer 11. The dielectric material for forming the high refractive index layer 12 can be a metal compound, silicon oxide, or the like. The metal compound can be a metal oxide, a metal sulfide, or a metal fluoride. The metal compound can be, for example, zinc oxide, titanium oxide, niobium oxide (NbO2), or zinc sulfide.

[0133] By changing the degree of oxidation of the metal oxide from a first value to a second value, the refractive index of the metal oxide can be changed from the first value to the second value. Among metal oxides, titanium oxide has a high refractive index and is therefore suitable as a material for forming the high refractive index layer 12. The refractive index of titanium oxide can be changed from the first value to the second value by changing the volume density of titanium oxide from the first value to the second value. In general, the higher the volume density of titanium oxide forming the high refractive index layer 12, the higher the refractive index of the high refractive index layer 12.

[0134] The high refractive index layer 12 can be formed by applying a deposition method. The deposition method for forming the high refractive index layer 12 can be a chemical deposition method or a physical deposition method. The physical deposition method can be, for example, a sputtering method or a vacuum deposition method.

[0135] In the third layer formation step of forming the protective layer 13, first, a synthetic resin for forming the protective layer 13 is prepared. The synthetic resin for forming the protective layer 13 can be a synthetic resin that can be used to form the embossed layer 11. After preparing a coating film containing the synthetic resin for forming the protective layer 13, the coating film is applied to the high refractive index layer 12 so as to cover the high refractive index layer 12. Next, the coating film is cured to obtain a color display body 10 having the protective layer 13.

[0136] As described above, according to the first embodiment of the color display medium, the authentication medium, and the method for determining the authenticity of a color display medium, the following effects can be obtained.

[0137] (1) In a structure in which an embossed layer 11, a high refractive index layer 12, and a protective layer 13 are laminated in this order, when an uneven surface 11S is present on a surface 11S of the embossed layer 11, wavelength components that satisfy the waveguiding conditions are reflected from light incident on the color display body 10.

[0138] (2) The guided wavelength can be controlled by the period d of the uneven surface 11S. When the periods d of the uneven surface 11S of the color display body 10 include different periods, it becomes possible to display the colors r, g, and b, thereby realizing a full-color, highly aesthetically pleasing color display body 10.

[0139] (3) When the light source LS is incident on the color display 10, part of the light diffracted by the high refractive index layer 12 has a wavelength that satisfies the waveguiding condition, and propagating light LG is generated in the high refractive index layer 12, and by fully filling the length of the waveguide, the phases of the light that is multiple-reflected in the propagating light are aligned, excitation occurs, and the propagating light LG is enhanced. This increases the intensity of the light reflected in the region A, and a color display 10 with high visibility can be provided.

[0140] (4) The direction in which the periods of the periodic structure arranged in the region A are aligned corresponds to the major axis direction of the region A, so that the intensity of the propagating light LG is increased, and a color display device 10 with high brightness can be provided.

[0141] (5) The color display device 10 can be used as a method for determining authenticity because the observer OB can observe the zeroth-order diffracted light reflected by the waveguide mode resonance in the direction of specular reflection and cannot see it in any direction other than the direction of specular reflection.

[0142] [Second embodiment] A second embodiment of a color display body, an authentication medium, and a method for determining the authenticity of a color display body will be described with reference to the drawings. The color display body of the second embodiment differs from the color display body 10 of the first embodiment in that the display area of ​​the motif 25 displayed on the color display body 10 of the first embodiment includes an area B different from the area A constituting the motif 25. Therefore, the following will describe in detail the differences between the color display body of the second embodiment and the color display body 10 of the first embodiment. Meanwhile, in the color display body of the second embodiment, the same reference numerals as the color display body 10 of the first embodiment are used for the components common to the color display body 10 of the first embodiment, and detailed description of the components will be omitted. The following will describe the configuration of the color display body and the method for determining the authenticity of the color display body in order.

[0143] (Color display configuration) The configuration of a color display device according to the second embodiment will be described with reference to FIGS.

[0144] FIG. 18 is a schematic diagram for explaining a region including an uneven surface in a color display device according to the second embodiment.

[0145] In the color display 20 of Fig. 18, a motif 35 is formed in a display area where the motif 25 displayed by the color display 10 of Fig. 13(a) is formed, the motif 35 including an area B different from the area that constitutes the motif 25. The areas B are arranged alternately at least in the longitudinal direction or lateral direction of the areas A, and are configured to have smaller dimensions than the areas A.

[0146] In region B, a mixed periodic structure 11S3 with a mixture of multiple periods is arranged, and diffracted light is generated by the periodic structure. In this configuration, unlike the effect of the guided mode resonance in region A, simple diffracted light can be emitted to the display surface, so it can be designed without considering multiple reflections of the propagating light LG, and as a result, a sufficient effect can be obtained even if the dimensions are smaller than those of region A. In addition, since the 0th order diffracted light can be emitted at an angle different from that of region A, a different motif with an appearance different from that of motif 35 formed in region A can be formed.

[0147] The display area of ​​the color display body 20 can include a spaced apart area 11S2 in addition to area A and area B, and can further include the elements described for the color display body 10.

[0148] The mixed periodic structure 11S3 in which a plurality of periods are mixed and arranged in region B can emit first-order diffracted light due to interference with the mixed periodic structure of the deposited high refractive index layer 12. In addition, since it is easiest to design first-order diffracted light to emit strong diffracted light, it can be used as first-order diffracted light.

[0149] When using the first-order diffracted light, it can be set based on the following formula (10).

[0150] mλ = d(sinγ+sinΔ) … Equation (10) In equation (10), d is the period of the periodic structure, λ is the wavelength of light reflected by the periodic structure, γ is the angle of incidence of the incident light, and Δ is the diffraction angle of light diffracted by the periodic structure.

[0151] When the periodic structure has the same period d, the reflected first-order diffracted light is dispersed. As a result, when the region B is observed by an observer OB, the observer OB can visually recognize an image having rainbow colors displayed by the periodic structure. In particular, when the period d is 500 nm or more and 20,000 nm or less, the periodic structure exhibits a noticeable rainbow color.

[0152] On the other hand, achromatic light can also be reflected by designing as follows. First, the period d calculated by applying the above-mentioned formula (10) is set as the reference period dr. Next, multiple periods d are discretely set in the positive direction with respect to the reference period dr, i.e., in a range larger than the reference period dr, and multiple periods d are discretely set in the negative direction with respect to the reference period dr, i.e., in a range smaller than the reference period dr. Periodic structures corresponding to each of the multiple periods d thus set are designed.

[0153] According to this configuration, light of a plurality of wavelengths is mixed, so that at a particular angle, an achromatic color, that is, an area B formed by white light, is visually recognized.

[0154] In addition, when designing the above-mentioned multiple periods d, the period d capable of reflecting light of a wavelength with high relative luminosity can be set as the reference period dr. The light of a wavelength with high relative luminosity is, for example, green light having a wavelength in the range of 540 nm or more and 560 nm or less. In this case, the light reflected by the mixed periodic structure 11S3 contains green light with high relative luminosity and light with a relative luminosity equivalent to that of green light. Therefore, the area B displayed by the mixed periodic structure 11S3 is easily visible. In addition, the light reflected by the mixed periodic structure 11S3 can contain red light having a longer wavelength and blue light having a shorter wavelength based on green light. This makes it easy to make the light reflected by the mixed periodic structure 11S3 achromatic light.

[0155] In the mixed periodic structure 11S3, the density of the multi-stage surface S2A having the reference period dr is the highest, and the density in the mixed periodic structure 11S3 can be reduced as the period d of the periodic structure is shifted more from the reference period dr. This reduces the intensity of the first-order diffracted light reflected at an observation position other than the specific observation position described above.

[0156] It is preferable that the mixed periodic structure 11S3 capable of reflecting achromatic light satisfies the following formulas (11) to (13). In the following formula (11), the r value is within the range θ R ' is a parameter that contributes to

[0157]

number

[0158]

number

[0159]

number

[0160] FIG. 19 is a graph showing the relationship between the arrangement density of the mixed periodic structure and the diffraction angle.

[0161] In FIG. 19, a curve that satisfies the above formulas (11) to (13) is shown. As shown in FIG. 19, in the above formulas (11) to (13), θ R θ' is the range of the diffraction angle θ. θ' is the discrete interval, i.e., the difference between the diffraction angle θ of the first-order diffracted light in a periodic structure and the diffraction angle θ of the first-order diffracted light in a periodic structure having the next larger or smaller period d than that periodic structure. θ n ρ′ is the discrete angle, i.e., the difference between the diffraction angle θ of the first-order diffracted light in a periodic structure and the diffraction angle θ of the first-order diffracted light in a periodic structure having a reference period dr. n ' is a specific discrete angle θ nThe r value is the density of the periodic structures having the ' in the entire mixed periodic structure 11S3. R The r value is an important parameter for realizing that the light reflected by the mixed periodic structure 11S3 is achromatic, and can be set to 221 or less.

[0162] In the mixed periodic structure 11S3 satisfying the formulas (11) to (13), the first-order diffraction angle of the periodic structure is set to 0° corresponding to the reference period dr, and the discrete angle θn', which is the diffraction angle θ at each multi-stage surface S2A, changes in discrete intervals θ'. In the mixed periodic structure 11S3, the density of the periodic structure having the reference period dr has a maximum value, and the discrete angle θ n The larger ', the lower the density of the periodic structure.

[0163] In this way, the mixed periodic structure 11S3 satisfying formulas (11) to (13) includes multiple values ​​in the period d of the periodic structure, and therefore it is more difficult to counterfeit the mixed periodic structure 11S3 or the color display device 20 including the mixed periodic structure 11S3 than a periodic structure in which the period d includes only one value.

[0164] Moreover, by forming the mixed periodic structure 11S3 as a blazed diffraction grating structure, the diffracted light is focused in the positive or negative direction, and can be selectively used depending on the motif to be expressed by the color display body 20. A general diffraction grating only reflects light at a diffraction angle that satisfies formula (10), but the mixed periodic structure 11S3 that satisfies formulas (11) to (13) can control the reflection angle by the relationship between multiple periods and densities. In addition to the diffraction grating, a scattering structure having directionality is generally used as a structure for controlling the reflection angle. However, although this can control the azimuth direction of reflection, it cannot control the elevation angle direction, and therefore it is impossible to realize an optical effect like that of the mixed periodic structure 11S3 that satisfies formulas (11) to (13).

[0165] FIG. 20 is a diagram showing reflected light spectra in nine color display devices with different r values, where the horizontal axis indicates the light receiving angle and the vertical axis indicates the received light intensity.

[0166] 20 shows spectra S1 to S9 obtained by a color display element 20 based on a mixed periodic structure 11S3 that diffracts light having a wavelength of 540 nm at a first order angle of 25° when the light is incident at an angle of 0°, i.e., directly above. The r value is set to any one of 255, 238, 221, 204, 187, 170, 153, 136, and 119.

[0167] 20, when the r value is set to 255, spectrum S1 is obtained, when the r value is set to 238, spectrum S2 is obtained, and when the r value is set to 221, spectrum S3 is obtained. When the r value is set to 204, spectrum S4 is obtained, when the r value is set to 187, spectrum S5 is obtained, and when the r value is set to 170, spectrum S6 is obtained. When the r value is set to 153, spectrum S7 is obtained, when the r value is set to 136, spectrum S8 is obtained, and when the r value is set to 119, spectrum S9 is obtained.

[0168] As is clear from the spectra S1 to S9, the smaller the r value, the wider the range of the receiving angle of the light reflected from the color display body 20, in other words, the first-order diffraction angle. On the other hand, the larger the r value, the higher the intensity of the light received at 25°, i.e., the intensity of the first-order diffracted light reflected at 25°.

[0169] FIG. 21 is a diagram showing the colors of light reflected by nine color displays on the xy chromaticity diagram.

[0170] 21, the reflected light having spectrum S1 and the reflected light having spectrum S2 have a green color. In contrast, the reflected light having any of spectra S3 to S9 has a white color. Therefore, the r value in the above formula (8) can be set to 221 or less. Furthermore, the r value can be set to a range of 204 or more and 221 or less. This can suppress a decrease in the intensity of the reflected light.

[0171] In FIG. 21, the area surrounded by the dashed line is a white area indicating the white point WP (x=0.33, y=0.33).

[0172] The mixed periodic structure 11S3 in this embodiment is configured to display an achromatic second motif by satisfying the above formulas (11) to (13). Therefore, the motif formed by region A can be a chromatic image, and the motif formed by region B can be an achromatic image, thereby enhancing the eye-catching nature of the motif that changes depending on the observation angle.

[0173] A chromatic image is an image that uses chromatic colors. A chromatic image can be an image that uses differences in hue. A chromatic image can have two regions in which the color difference ΔE*ab=√(Δa*)^2+(Δb*)^2) at a*b* other than the lightness L* is 5 or more among the color values ​​L*a*b* according to CIE1976. In this case, the color value L*a*b* can be the color value L*a*b* in a range with a diameter of 3 mm.

[0174] An achromatic image is an image that uses achromatic or light colors. An achromatic image can be a grayscale image with gradations of light and dark. An achromatic image can be colorless or monochromatic. In a chromatic image, the higher the saturation an image has, the greater the color variety can be even if the color difference in two areas is the same. This allows the chromatic image to have the appearance of an intricate pattern. Also, the higher the saturation an image has, the greater the external aesthetics of the chromatic image can be.

[0175] In the mixed periodic structure 11S3, the periodic direction in which the periods are arranged is set to be the same in the region B, and the periodic direction may be different in multiple regions B. The achromatic light described above is recognized by the observer as light having different intensities depending on the periodic direction, and a motif formed by the region B having multiple directions can be formed as a grayscale image with gradation.

[0176] FIG. 22 is a plan view showing the structure of a color display.

[0177] The relationship between region A and region B will be described with reference to FIG. 22. In the color display 30 shown in FIG. 22(a), region A is disposed at a position including the center of the surface 11S when viewed from the direction opposite to the plane on which the color display 30 spreads. Similarly to region A, region B is disposed at a position including the center of the surface 11S. In this embodiment, the contour of region A has a shape representing the sun, while the contour of region B has a shape representing a heart. However, the contours of region A and region B can be shapes other than these shapes. When viewed from the direction opposite to the plane on which the color display 30 spreads, the area defined by region A overlaps with the area defined by the contour of region B. However, when viewed from the direction opposite to the plane on which the color display 30 spreads, region A and region B do not overlap with each other.

[0178] As shown in FIG. 22(b), there are cases where region A does not overlap region B when viewed from the direction opposite to the plane on which the color display body 30 extends.

[0179] FIG. 23 is a schematic diagram showing the relationship between a first range and a second range of observation angles.

[0180] 23, the observation angle θOB is the angle formed by the plane on which the color display 30 is located and the plane including the line of sight DOB of an observer OB observing the color display 30. Area A displays a first motif that is observed within a range θOB1 at the observation angle θOB. Area B displays a second motif that is observed within a range θOB2 at the observation angle θOB.

[0181] The range θOB1 includes observation angles other than the observation angle θOB included in the range θOB2, and the range θOB2 includes observation angles other than the observation angle θOB included in the range θOB1.

[0182] As a result, the observation angle θOB of the color display 30 includes an observation angle θOB at which only the first motif is displayed and an observation angle θOB at which only the second motif is displayed. Therefore, at a specific observation angle θOB, the observer OB can view each image without being obstructed by the other images.

[0183] In this embodiment, the range θOB2 is different from the range θOB1 at the observation angle θOB. Also, the color display 30 does not display both the first motif and the second motif in a range θOB3 (not shown) at the observation angle θOB. The range θOB3 includes the observation angle θOB between the range θOB1 and the range θOB2.

[0184] Since region A reflects the light from the light source LS in the direction of specular reflection, the range θOB1 includes the direction of specular reflection. The observation angle θOB at which region B reflects light is determined by the period d of the periodic structure of the mixed periodic structure 11S3 and the direction in which the periods are arranged.

[0185] In this embodiment, the range θOB2 is different from the range θOB1, but the range θOB2 can include a part of the range θOB1 and a range different from the range θOB1. When a range θOB3 (not shown) is set for the observation angle θOB, the range θOB3 can include the following range in addition to the observation angle θOB between the above-mentioned range θOB1 and range θOB2. That is, the range θOB3 can include a range between the plane on which the color display body 30 spreads and the range θOB2, and does not include the range θOB1. Alternatively, the range θOB3 can include a range between the plane on which the color display body 30 spreads and the range θOB1, and does not include the range θOB2.

[0186] (Function of color display) The operation of the color display body 30 will be described with reference to Figures 24 to 26. Note that the operation of the color display body 30 when applied to an authentication medium will be described below.

[0187] FIG. 24 is a schematic diagram showing a state in which an observer is observing a color display medium.

[0188] As shown in Fig. 24, an observer OB of the authentication medium 40 can observe the authentication medium 40 while holding the authentication medium 40 in his / her hand. In the example shown in Fig. 24, the observer OB observes the authentication medium 40 while tilting the authentication medium 40 at an angle θ1 with respect to a reference plane Ph1 along the horizontal direction. Alternatively, the observer OB observes the authentication medium 40 while tilting the authentication medium 40 at an angle θ2 with respect to the reference plane Ph1. Alternatively, the observer OB observes the authentication medium 40 while tilting the authentication medium 40 at an angle θ3 with respect to the reference plane Ph1. The angle θ1 is greater than the angle θ2, and the angle θ2 is greater than the angle θ3.

[0189] FIG. 25 is a plan view showing an image displayed by an authentication medium having a color display.

[0190] FIG. 25 shows the state of the authentication medium 40 visually recognized by the observer OB according to the inclination of the authentication medium 40. As shown in FIG.

[0191] In the example shown in FIG. 25(a), the authentication medium 40 includes a color display body 30 and a support body 31 that supports the color display body 30. In this embodiment, the authentication medium 40 further includes an information recording medium 32 supported by the support body 31. The support body 31 is, for example, a sheet made of synthetic resin. Various information can be recorded on the support body 31. The various information can be, for example, the type of the authentication medium 40, biometric information of the owner of the authentication medium 40, non-biometric information, or both. Examples of the biometric information can be the owner's face photo, the owner's signature, and the owner's fingerprint. Examples of the non-biometric information can be the owner's name, the owner's nationality, the owner's date of birth, the owner's nationality code, and the owner code. The information recording medium 32 can be, for example, an IC chip. Note that the authentication medium 40 does not necessarily have to have the information recording medium 32.

[0192] The authentication medium 40 has a state where, relative to the observation position OP of the observer OB, the area A does not display the first motif and the area B does not display the second motif. As described above, in this embodiment, when the observation angle θOB is within a range θOB3 (not shown), the authentication medium 40 does not display both the first motif and the second motif. That is, when the observer OB tilts the authentication medium 40 at an angle θ2, the authentication medium 40 does not display both the first motif and the second motif.

[0193] When the authentication medium 40 does not display the first motif and the second motif, the information recorded on the support 31 is easily visible to the observer OB. In this manner, the color display body 30 is observed by the observer OB within a range θOB3 (not shown) at the observation angle θOB, so that the observer can easily grasp the state of the color display body 30 other than the first motif and the second motif displayed by the color display body 30.

[0194] On the other hand, in the example shown in FIG. 25(b), the authentication medium 40 has a state in which, relative to the observation position OP of the observer OB, area A displays a first motif PIC1 (hereinafter simply referred to as "motif PIC1"), while area B does not display a second motif. As described above, in this embodiment, when the observation angle θOB is within the range θOB1, the authentication medium 40 displays the motif PIC1, but does not display the second motif. That is, when the observer OB tilts the authentication medium 40 at an angle θ1, the authentication medium 40 displays the motif PIC1, but does not display the second motif.

[0195] 25(c), the authentication medium 40 has a state in which, with respect to the observation position OP of the observer OB, the region A does not display the motif PIC1, while the region B displays a second motif PIC2 (hereinafter simply referred to as "motif PIC2"). As described above, in this embodiment, when the observation angle θOB is within the range θOB2, the authentication medium 40 does not display the motif PIC1, but displays the motif PIC2. That is, when the observer OB tilts the authentication medium 40 at an angle θ3, the authentication medium 40 does not display the motif PIC1, but displays the motif PIC2.

[0196] FIG. 26 is a diagram for explaining the first position and the second position in a color display body.

[0197] FIG. 26 shows a state in which the color display body 30 is rotated around a rotation axis Z while the observation position OP of the observer OB and the position of a light source (not shown) are fixed.

[0198] 26(a), the normal to the plane on which the color display body 30 extends is the rotation axis Z. The color display body 30 is disposed at an arbitrary position along a plane parallel to the horizontal plane, for example. The arbitrary position is the first position of the color display body 30.

[0199] 26(b), the color display body 30 has a second position different from the first position. The second position is a position obtained by rotating the color display body 30 by 90° from the first position around the rotation axis Z. In this embodiment, the second position is a position obtained by rotating the color display body 30 located at the first position by 90° counterclockwise, but the second position can also be a position obtained by rotating the color display body 30 by 90° clockwise.

[0200] When the color display 30 is located at the first position, the region A displays a motif PIC1 having a first color with respect to the observation position OP. For example, the motif PIC1 described above with reference to Fig. 26(b) is the motif PIC1 having the first color. The first color is a color included in chromatic colors.

[0201] On the other hand, as shown in FIG. 26(a), when the color display body 30 is located at the second position, the area A displays a motif PIC1 having a second color with respect to the observation position OP. The second color is different from the first color. Like the first color, the second color is also a color included in the chromatic colors. By rotating the color display body 30, the apparent effective refractive index n eff becomes a different value from before the rotation. Therefore, the motif PIC1 is visually recognized by the observer OB such that the color of the motif PIC1 when the color display body 30 is located at the first position and the color of the motif PIC1 when the color display body 30 is located at the second position are different from each other.

[0202] When the color display 30 is located at the first position, the region B displays the motif PIC2 having a first luminance with respect to the observation position OP. For example, the motif PIC2 described above with reference to Fig. 25(c) is the motif PIC1 having the first luminance. The first luminance is a luminance at which the observer OB can visually recognize that the color display 30 is displaying the motif PIC2.

[0203] On the other hand, as shown in FIG. 26(b), when the color display body 30 is located at the second position, the area B displays the motif PIC2 having a second luminance with respect to the observation position OP. The second luminance is different from the first luminance. In this embodiment, the second luminance allows the observer OB to visually recognize that the color display body 30 is displaying the motif PIC2. However, the second luminance is lower than the first luminance. Note that the second luminance can also be higher than the first luminance.

[0204] By rotating the color display body 30, the direction in which the periods of the mixed periodic structure 11S3 constituting the region B as seen by the observer OB are arranged changes from the direction before the rotation. Therefore, the proportion of light that can be observed by the observer OB out of the light reflected in the region B changes. As a result, the motif PIC2 is visually recognized by the observer OB such that the luminance of the motif PIC2 when the color display body 30 is located at the first position differs from the luminance of the motif PIC2 when the color display body 30 is located at the second position.

[0205] In this way, the color display body 30 can have two states for the motif PIC1 that can give different impressions to the observer OB, and also has two states for the motif PIC2 that can give different impressions to the observer OB.

[0206] As explained above, since it is possible to change the appearance of each motif by changing the observation angle and rotation angle of the authentication medium 40, this can be easily used as a method for an observer to determine authenticity.

[0207] As described above, according to the second embodiment of the color display medium, authentication medium, and color display medium authenticity determining method, the following effects can be obtained.

[0208] (6) Since surface 11S of embossed layer 11 has periodic structure 11S1 formed in region A and mixed periodic structure 11S3 formed in region B, counterfeiting of a color display device having embossed layer 11 is more difficult than when surface 11S of embossed layer 11 has only periodic structure 11S1.

[0209] (7) The eye-catching nature of the color display unit 30 is increased compared to when both the motif PIC1 and the motif PIC2 are chromatic images and when both the motif PIC1 and the motif PIC2 are achromatic images.

[0210] (8) The observation angle θOB of the color display 30 includes an observation angle θOB at which only the motif PIC1 is displayed and an observation angle θOB at which only the motif PIC2 is displayed. Therefore, at a specific observation angle θOB, the observer OB can view each image without being obstructed by other images.

[0211] (9) By observing the color display body 30 by the observer OB within the range θOB3 of the observation angle θOB, the state of the color display body 30 other than the motifs PIC1 and PIC2 displayed by the color display body 30 can be easily grasped by the observer.

[0212] (10) The color display body 30 can have two states for the motif PIC1 that give different impressions to the observer OB, and can also have two states for the motif PIC2 that give different impressions to the observer OB.

[0213] [Modification of the second embodiment] The above-described second embodiment can be modified as follows.

[0214] (Mixed periodic structure 11S3) The mixed periodic structure 11S3 can display the motif PIC2 having the same luminance when located at the first position and when located at the second position. Even in this case, when the periodic structure 11S1 displays a chromatic image and the mixed periodic structure 11S3 displays an achromatic image, the same effect as described above can be obtained.

[0215] (observation angle) The first range of the periodic structure 11S1 and the second range of the mixed periodic structure 11S3 can be the same range. That is, the minimum value in the first range can be equal to the minimum value in the second range, and the maximum value in the first range can be equal to the maximum value in the second range. Even in this case, when the periodic structure 11S1 displays a chromatic image and the mixed periodic structure 11S3 displays an achromatic image, the same effect as described above can be obtained.

[0216] [Application examples of the first and second embodiments] Further application examples of the first and second embodiments described so far will be described. Up to now, the explanation has been centered on visual effects, but below, in addition to visual effects, mechanical reading utilization and authenticity determination methods will be explained. Of course, a color display body allows an observer to determine authenticity based on visual effects, but it is also possible to determine authenticity by mechanically reading complex information that an observer cannot read or fine information that cannot be separated by the observer's eyes at high resolution.

[0217] The display surface of the color display body 30 has a color image of a first motif formed in area A and a grayscale image of a second motif formed in area B, so that either the color or the grayscale, or both, can be stored as an authentication code, which can be used for machine reading and for authenticity determination.

[0218] In addition, since the observation angle of the motif PIC1 and the motif PIC2 can be controlled, the motif information obtained depending on the observation angle can be recorded as an authentication code. This authentication code is machine-readable and can be used to verify the authenticity.

[0219] Furthermore, since the effect of the guided mode resonance described in formulas (1) to (6) can change the resonating wavelength depending on the height between the convex and concave surfaces of the periodic structure of the concave-convex surface 11S1, the dimensional ratio between the convex and concave surfaces, and the period, if a sub-region A1 in which at least any of these has been changed is included in region A, the sub-region A1 can be recorded as an authentication code. This authentication code is machine readable and can be used to verify authenticity.

[0220] 26, the color of region A changes depending on the observation position. For example, assuming that region A can be observed as blue at a first position and red at a second position, if at least a part of region A includes sub-region A2 that is red at the first position and blue at the second position, region A and sub-region A2 will be mixed to display the same color (purple) at both the first and second positions, and the region whose color does not change between the first and second positions can be recorded as an authentication code. This authentication code is machine-readable and can be used to verify authenticity.

[0221] Furthermore, when region B has a mixed periodic structure 11S3 that includes multiple periods, but includes a sub-region B1 that is locally composed of a single period, it is possible to locally have color in the achromatic region B, and therefore the color sub-region composed of sub-region B1 can be recorded as an authentication code. This authentication code is machine-readable and can be used to verify authenticity.

[0222] Furthermore, if the mixed periodic structure 11S3 in region B includes a region B2 in which the relationship between the multiple periods varies locally, the reflection angle or the achromatic color information can be locally changed, so that the subregion B2 can be recorded as a machine-readable authentication code and used to determine authenticity.

[0223] In addition, when the mixed periodic structure 11S3 in the region B includes a sub-region B3 in which the direction in which the convex and concave surfaces are arranged varies locally, the achromatic grayscale information can be locally changed, and the sub-region B3 with different grayscale information formed by the sub-region B3 can be recorded as an authentication code. This authentication code is machine-readable and can be used to verify the authenticity.

[0224] Furthermore, if area C, which is different from area A and area B, is included, an effect different from the optical effects of area A and area B can be recorded as an authentication code. This authentication code is machine-readable and can be used to verify the authenticity. Area C here can be area 11S2 or another newly provided area.

[0225] The method of authenticity verification can utilize the machine-read result of the recorded authentication code. The verification can be performed on the machine side, or the machine can be connected to a computer and the computer can make a judgment based on the machine-read result sent from the machine, or the computer can be connected to the machine and a verification server, the computer can send the machine-read result sent from the machine to the server, and the server can send the judgment result to the computer.

[0226] (Authentication code) The machine-readable authentication code is not particularly limited, and can be, in addition to the motif image described above, letters, numbers and symbols, or a combination of these. Alternatively, it can be a one-dimensional barcode or a two-dimensional barcode.

[0227] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made in the implementation stage without departing from the gist of the invention. The embodiments may be implemented in combination as appropriate as possible, and in that case, the combined effects can be obtained. Furthermore, the above-mentioned embodiment includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the disclosed constituent elements.

Claims

1. a high refractive index layer and a protective layer are successively formed on an embossed layer, the high refractive index layer having the highest refractive index among the layers, the embossed layer having a first region having a periodic structure having a wavelength shorter than at least a central wavelength of visible light, the first region has rectangular longitudinal end sides connected to each other on a display surface, the end sides are spaced apart in a direction perpendicular to the longitudinal direction, and the periodic direction of the periodic structure is arranged in the longitudinal direction, In the embossed layer, a plurality of rectangular first regions having a first periodic structure and a plurality of second regions having a second periodic structure in which a plurality of periods are mixed are alternately arranged at least in the longitudinal direction or the perpendicular direction, and the second regions have a smaller dimension than the first regions; A color display device, wherein in the second region, first-order diffracted light is emitted due to interference with the mixed periodic structure of the high refractive index layer deposited on the second periodic structure.

2. 2. The color display according to claim 1, wherein in the first region, zero-order diffracted light is emitted by resonance with the periodic configuration of the high refractive index layer deposited on the periodic structure.

3. 3. The color display device according to claim 1, wherein the periodic structure included in the first region has a longitudinal dimension that is an integer multiple of a value obtained by dividing the least common multiple of the multiple periods selectively used by a dividend and the greatest common divisor of the multiple periods selectively used by a divisor.

4. 2. The color display body according to claim 1, characterized in that the angle formed by the display surface and a plane including the line of sight of an observer observing the color display body is an observation angle, and the observation angle is different between the zeroth-order diffracted light emitted from the first region and the first-order diffracted light emitted from the second region.

5. 5. The color display device according to claim 1, wherein a color image is formed at an observation angle of the zeroth-order diffracted light emitted from the first region, and a grayscale image is formed at an observation angle of the first-order diffracted light emitted from the second region.

6. 6. The color display device according to claim 1, wherein each image constituted by at least one of the first region and the second region is used as a machine-readable authentication code for determining authenticity.

7. 7. The color display body according to claim 1, wherein the first periodic structure includes a convex surface and a concave surface, a distance between the convex surface and an adjacent concave surface is a height between the convex and concave surfaces, the first region includes a first sub-region in which at least one of the height between the convex and concave surfaces, a dimensional ratio between the convex and concave surfaces, and a period is locally different, and an authentication code formed by the first sub-region is used as a machine-readable authentication code for determining authenticity.

8. 6. The color display body according to claim 5, wherein a viewpoint position for observing the color image constituted by the first region is an observation position, the color display body has a first position and a second position with a normal to a plane on which the color display body extends as a rotation axis, the second position is a position obtained by rotating the color display body by 90° from the first position around the rotation axis, when the color display body is located at the first position, a first color image having a first color is displayed for the observation position, and when the color display body is located at the second position, a second color image having a second color is displayed for the observation position, the first region includes a second sub-region including a plurality of periods locally, and the second sub-region is formed as an authentication code having the same color at both the first position and the second position, and the authentication code is utilized as a machine-readable authentication code for determining authenticity.

9. 6. The color display body according to claim 1, wherein the second region includes a third sub-region that is locally constituted by one period of the second periodic structure, and an authentication code formed by the third sub-region is used as a machine-readable authentication code for determining authenticity.

10. 6. The color display body according to claim 1, wherein the second region includes a fourth sub-region in which the relationship between the multiple periods included in the second periodic structure is locally different, and an authentication code formed by the fourth sub-region is utilized as a machine-readable authentication code for determining authenticity.

11. 6. The color display body according to claim 1, wherein the second region includes a fifth sub-region in which the direction in which the convex and concave surfaces of the second periodic structure are arranged varies locally, and an authentication code formed by the fifth sub-region is used as a machine-readable authentication code for determining authenticity.

12. 5. The color display body according to claim 1, wherein an authentication code constituted by a third area different from the first area and the second area is used as a machine-readable authentication code for determining authenticity.

13. An authentication medium comprising the color display body according to any one of claims 1 to 12.

14. A method for determining authenticity of a color display body according to any one of claims 1 to 5, comprising: Each image composed of at least one of the first area and the second area is authenticated with an authentication code; A machine reading of the authentication code is performed; The authenticity of the color display body is determined based on the result of the machine reading. A method for determining the authenticity of a color display.

Images