Hologram structure and method of manufacturing the same

Abstract

To provide a hologram structure capable of forming an image which is hardly forged and has both high visibility and beautiful appearance.SOLUTION: According to the embodiment, the hologram structure is laminated with an embossed layer having an uneven structure that modulates incident light and a metal reflection layer that covers at least a part of the embossed layer, and displays a first image reproduced by reflected light obtained by modulation of the incident light by the uneven structure and a second image drawn by the presence or absence of the metal reflection layer, the first image and the second image being visible.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE The present invention relates to a hologram structure and a method for manufacturing the same. [Background technology]

[0002] Currently, various objects used for personal authentication, such as ID cards and passports, carry facial images that can identify the individual, and machine-based identification using image recognition is also becoming more common.

[0003] The facial images to be mounted must be recorded and managed on demand for each individual. Also, if the object can be decorated with holograms or other decorations, the security and appearance of the object can be improved.

[0004] Therefore, Patent Document 1 proposes a method for processing a hologram object on demand. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 015198 [Patent Document 2] International Publication No. 2017 / 209113 [Non-patent literature]

[0006] [Non-Patent Document 1] “Rapid Object Detection using a Boosted Cascade of Simple Features”, ACCEPTED CONFERENCE ON COMPUTER VISION AND PATTERN RECOGNITION 2001, Paul Viola, Michael Jones Summary of the Invention [Problem to be solved by the invention]

[0007] In the prior art, there have been inventions for superimposing a hologram and a barcode. However, when superimposing a facial image with complex black and white shading on a hologram, the prior art has a problem that the facial image is difficult to view.

[0008] In view of the above circumstances, an object of the present invention is to provide a hologram structure capable of forming an image that is difficult to counterfeit and has both high visibility and aesthetic appeal, and a method for manufacturing the same. [Means for solving the problem]

[0009] A first aspect of the present invention is a hologram structure comprising an embossed layer having a concave-convex structure that modulates incident light and a metal reflective layer covering at least a portion of the embossed layer, and displays a first image reproduced by reflected light modulated by the concave-convex structure from the incident light, and a second image drawn depending on the presence or absence of the metal reflective layer, and the first image and the second image are visible.

[0010] A second aspect of the present invention is a hologram structure of the first aspect, wherein the second image includes a personal information area containing personal identification information used to identify an individual, and a non-personal information area containing no personal identification information.

[0011] A third aspect of the present invention is a hologram structure of the second aspect, in which the personal information area includes an important area containing a personal identification image used to identify an individual as personal identification information, and a non-important area not containing the personal identification image.

[0012] A fourth aspect of the present invention is the hologram structure of the third aspect, wherein the second image is an image of a person and the important area includes an image of at least one of the eyebrows, pupils, nose and mouth of the person's face as an image for personal identification.

[0013] A fifth aspect of the present invention is the hologram structure of the third or fourth aspect, wherein the brightness of the important area is greater than the brightness of the first image.

[0014] A sixth aspect of the present invention is a method for manufacturing a hologram structure, comprising a formation step of forming a pre-structure by stacking an embossed layer having a concavo-convex structure that modulates incident light and a metal reflective layer covering the embossed layer, and a removal step of partially laser-removing the metal reflective layer in the pre-structure so as to create a drawing pattern for displaying a visible image depending on the presence or absence of the metal reflective layer.

[0015] A seventh aspect of the present invention is the method for producing the hologram structure of the sixth aspect, wherein in the removing step, the metal reflective layer is partially removed by irradiating the metal reflective layer with a laser beam. Effect of the Invention

[0016] The hologram structure and the manufacturing method thereof of the present invention can form an image that is difficult to counterfeit and has both high visibility and good appearance. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view for conceptually explaining the structure of a hologram structure according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing an example of an image observed when the hologram structures 1a and 1b shown in FIGS. 1(a) and 1(b) are viewed in plan from the upper side in the figure. [Diagram 3] FIG. 3 is a schematic cross-sectional view for conceptually explaining the structure of the hologram structure according to the second embodiment. [Figure 4] FIG. 4 is a diagram showing an example of an image observed when the hologram structures 1c and 1d shown in FIGS. 3(a) and 3(b) are viewed in plan from the upper side in the figure. [Diagram 5] FIG. 5 is a cross-sectional view of a pre-structure for explaining an example of a method for manufacturing a hologram structure according to the third embodiment. [Figure 6A]FIG. 6A is a cross-sectional view of a pre-structure for explaining the correlation between the power of a laser beam and the removal effect of a metal reflective layer. [Figure 6B] FIG. 6B is a cross-sectional view of a pre-structure for explaining the correlation between the power of the laser beam and the removal effect of the metal reflective layer. [Figure 7] FIG. 7 is a cross-sectional view showing an example of a hologram structure for explaining the behavior of incident light that is incident on the hologram structure from the protective layer side, which is the upper side in the figure. [Figure 8] FIG. 8 is a cross-sectional view showing another example of a hologram structure for explaining the behavior of incident light that is incident on the hologram structure from the protective layer side, which is the upper side in the figure. [Figure 9] FIG. 9 is a plan view showing an example of a card according to the fourth embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view conceptually illustrating the cross-sectional structure taken along line II in FIG. [Figure 11] FIG. 11 is a top view showing a card made according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The embodiments of the present invention are a group of embodiments based on a single unique invention from the background. Also, each aspect of the present invention is an aspect of a group of embodiments based on a single invention. Each configuration of the present invention may have each aspect of the present disclosure. Each feature of the present invention can be combined to form each configuration. Therefore, each feature of the present invention, each configuration of the present invention, each aspect of the present disclosure, and each embodiment of the present invention can be combined, and the combination has a synergistic function and can exhibit a synergistic effect. In the present specification and each figure, elements similar to those described above with respect to the previous figures are given the same reference numerals, and detailed explanations and duplicated explanations are omitted as appropriate.

[0019] [First embodiment] A first embodiment of the present invention will now be described.

[0020] (Hologram structure) FIG. 1 is a schematic cross-sectional view for conceptually explaining the structure of a hologram structure according to a first embodiment of the present invention.

[0021] As shown in Figure 1(a), the hologram structure 1a is formed by laminating an embossed layer 30 having a concave-convex structure (hereinafter also referred to as a "relief structure") 31 that modulates incident light I entering the hologram structure 1a from the upper side in the figure, a metal reflective layer 40 that covers at least a portion of the embossed layer 30, and a scattering reflective layer 10 provided on the opposite side of the metal reflective layer 40 (the lower side in the figure) of the embossed layer 30.

[0022] The layer structure of the hologram structure is not limited to the structure of hologram structure 1a illustrated in FIG. 1(a), and may be, for example, as in hologram structure 1b shown in FIG. 1(b), in which an embossed layer 30, a metal reflective layer 40, and a scattering reflective layer 10 are laminated in this order from the side where incident light I is incident (the upper side in the figure).

[0023] Thus, the configurations of the hologram structures 1a and 1b are merely examples. In the following, when hologram structures are described generically, they will be referred to as a hologram structure 1.

[0024] In this embodiment, the stacking direction of each layer, i.e., the Z direction in the figure, is referred to as the thickness direction. When the scattering reflection layer 10 is disposed as the bottom layer as in Figures 1(a) and (b), the scattering reflection layer 10 side is referred to as the lower side, and the opposite side is referred to as the upper side. Viewing the hologram structure 1 from above in the thickness direction is referred to as a planar view, and viewing the hologram structure 1 at a cross section along the thickness direction is referred to as a cross-sectional view. The relief surface is disposed along the XY plane.

[0025] (metal reflective layer) The metal reflective layer 40 has a mirror reflection structure that functions as a reflection surface that specularly reflects the incident light I. The metal reflective layer 40 may be made of a metal. The main component of the metal reflective layer 40 may be an inorganic substance. The inorganic substance may be a metal, a metal compound, or silicon oxide.

[0026] Examples of metals include aluminum, silver, tin, chromium, nickel, copper, and gold. The purity of these metals can be 99% or more. They may also have a purity of 99.99% (4N) or more. By making the purity 4N or more, defects when removing the metal with a laser beam are easily reduced.

[0027] Examples of metal compounds are titanium oxide, aluminum oxide, and zinc sulfide. Metal compounds generally have a high refractive index.

[0028] The metal reflective layer 40 can be formed by deposition or printing. The deposition can be performed by physical deposition or chemical vapor deposition (CVD).

[0029] The physical deposition may be performed by vacuum deposition or sputtering. The target metal may be any of various metal targets having a purity of 4N or higher.

[0030] The ink used for printing may be offset ink, silk screen, letterpress ink, gravure ink, etc., depending on the printing method. The ink may be resin ink, oil-based ink, water-based ink, etc. Also, depending on the drying method, it may be, for example, oxidative polymerization type ink, penetration drying type ink, evaporation drying type ink, ultraviolet curing type ink, etc. The ink may further be pigment ink, dye ink, or a mixture thereof.

[0031] An example of pigment ink is magnetic ink, which can form a pattern due to its magnetism. This pattern is unique and therefore tends to increase the difficulty of counterfeiting.

[0032] An example of a dye ink is a liquid crystal ink. An example of a liquid crystal ink is a cholesteric liquid crystal ink. Cholesteric liquid crystal reflects light of a specific wavelength. This results in a colored reflective layer. The reflectance changes depending on the rotation direction of circularly polarized light or elliptically polarized light. A functional ink whose color changes depending on the illumination angle or observation angle may also be used as the reflective layer. Examples of such functional inks include optical variable ink, color shift ink, and pearl ink.

[0033] (embossed layer) The embossed layer 30 has a relief structure 31 on at least one surface. Fig. 1(a) shows an example in which the relief structure 31 is provided on the upper surface of the embossed layer 30 in the figure. The embossed layer 30 is formed of, for example, an ultraviolet curing resin, a thermoplastic resin, or a thermosetting resin.

[0034] The ultraviolet curable resin may be a curable resin, a monomer, oligomer, or polymer having an ethylenically unsaturated bond or an ethylenically unsaturated group. The monomer having an ethylenically unsaturated bond or an ethylenically unsaturated group may be 1,6-hexanediol, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, or dipentaerythritol hexaacrylate.

[0035] The oligomer having an ethylenically unsaturated bond or an ethylenically unsaturated group may be an oligomer or cooligomer of an epoxy acrylate, a urethane acrylate, or a polyester acrylate.

[0036] The polymer may be a urethane modified acrylic or epoxy modified acrylic polymer or copolymer.

[0037] The ultraviolet curable resin may be any one of acrylic resin, acrylic acrylate resin, epoxy acrylate resin, urethane acrylate resin, polyester acrylate resin, and ethylene methacrylate resin, any one of copolymer resins, any one of composite resins, and any one of composite resins of copolymer resins.

[0038] The thickness of the embossed layer 30 can be set to be not less than 1 μm and not more than 25 μm.

[0039] When a thermoplastic resin is used as the material of the embossed layer 30, it may be any one of acrylic resin, epoxy resin, cellulose resin, vinyl resin, any of copolymer resins, any of composite resins, or any of composite resins of copolymer resins. The thermosetting resin of the embossed layer 30 may be any one of urethane resin, melamine resin, epoxy resin, phenol resin, any of copolymer resins, any of composite resins, or any of composite resins of copolymer resins. The embossed layer 30 may be colored. It can be colored by adding a pigment or dye to the resin of the embossed layer 30. The pigment can be an inorganic pigment or an organic pigment. Alternatively, the pigment can be a fluorescent pigment, a pearl pigment, or a magnetic pigment. The dye can be a natural dye or a synthetic pigment. Alternatively, the dye can be a fluorescent dye.

[0040] The embossed layer 30 may have a relief structure 31 formed on the surface in contact with the metal reflective layer 40 .

[0041] The relief structure 31 may be formed by transferring (embossing) a relief structure having projections and recesses formed on the surface of a metal stamper onto the target object. The relief structure 31 has optical effects such as an optical diffraction effect, a non-reflective effect, an isotropic or anisotropic scattering effect, a lens effect, and a polarization selective reflection effect. This optical effect allows the authenticity to be verified visually. That is, the relief structure 31 is visible and can be authenticated visually. The metal reflective layer 40 on the relief surface having the relief structure 31 is also visible and can be authenticated visually. In other words, the metal reflective layer 40 adjacent to the relief surface having the relief structure 31 can also be verified visually. This provides an anti-counterfeiting and tampering effect. This optical effect can also provide an aesthetic appearance. That is, this optical effect allows the hologram structure 1 to have a visual effect. The desired optical effect can be obtained by combining relief structures 31 having one or more optical effects. The areas having the respective optical effects may be arranged in contact, adjacent, close proximity, at regular intervals, or alternately. In this way, the relief surface having the relief structures 31 having a plurality of optical effects can exhibit complex visual effects, thereby enhancing the effect of preventing counterfeiting and tampering. In addition, the aesthetic appearance of the hologram structure 1 can be improved. The relief structure 31 has recesses and protrusions, and provides the hologram structure 1 with optical properties such as diffraction, light reflection suppression, isotropic or anisotropic light scattering, refraction, polarization, and wavelength-selective reflection, transmission, and light reflection suppression.

[0042] For example, a diffraction grating structure region may be provided with a pitch of 0.5 μm to 2 μm and a depth of 0.05 μm to 0.5 μm as the relief structure 31. This provides the hologram structure 1 with a function of diffracting light.

[0043] For example, a moth-eye structure or a deep grating structure having a pitch of 0.1 μm to 0.5 μm and a depth of 0.25 μm to 0.75 μm may be provided as the relief structure 31. In this case, the relief structure 31 provides the hologram structure 1 with a function of suppressing light reflection, and polarized light or wavelength selective reflection, transmission, and light reflection suppression.

[0044] The relief structure 31 may have a region of a non-periodic linear or dot-like repeating structure with an average pitch of, for example, 0.5 μm to 3 μm and a depth of 0.05 μm to 0.5 μm. This provides the hologram structure 1 with the function of emitting isotropic or anisotropic scattered light.

[0045] The relief structure 31 may have regions with an average pitch larger than 3 μm and a structure depth of more than 0.5 μm, which allows it to have a refractive index different from that of the adjacent layers and thus confers a refractive function on the hologram structure 1. The relief structure 31 may also comprise a relief surface (recording surface) as disclosed in US Pat. No. 5,399,321 and described below.

[0046] As an example, the relief surface in this embodiment has a phase angle recorded region and a phase angle non-recorded region. In the relief surface, a region other than the phase angle recorded region is a phase angle non-recorded region. In one example, the phase angle non-recorded region is a mirror surface.

[0047] (Scattered reflective layer) The scattering reflective layer 10 has a scattering reflector that functions as a reflective surface that isotropically scatters the incident light I. The scattering reflective layer 10 may be a white resin layer.

[0048] Examples of materials for the scattering reflection layer 10 include thermoplastic resins such as urethane resin, polycarbonate resin, polystyrene resin, and polyvinyl chloride resin, thermosetting resins such as unsaturated polyester resin, melamine resin, epoxy resin, urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, and triazine (meth)acrylate, or mixtures of these, and further, thermoformable materials having radically polymerizable unsaturated groups.

[0049] The scattering reflective layer 10 made of polycarbonate has high heat resistance and can prevent discoloration due to laser engraving.

[0050] The scattering reflective layer 10 can also be formed by arranging a light-impermeable reflective ink in a layer on a sheet-like substrate. The reflective ink is a functional ink whose color changes depending on the illumination angle or observation angle, and includes optically variable ink, color shift ink, pearl ink, etc. In this configuration, the substrate may be transparent.

[0051] In addition, taking into consideration the effect on the scattering reflective layer 10 of the impact caused when the metal of the metal reflective layer 40 is removed, it is preferable to ensure that the distance between the metal reflective layer 40 and the scattering reflective layer 10 is 10 μm or more.

[0052] (Reproduction image) FIG. 2 is a diagram showing an example of an image observed when the hologram structures 1a and 1b shown in FIGS. 1(a) and 1(b) are viewed in plan from the upper side in the figure.

[0053] In the hologram structure 1, incident light I is modulated by the relief structure 31 of the embossed layer 30 to produce reflected light R, which forms a first image (reconstructed image 70).

[0054] When incident light I emitted from a point light source is incident from a direction intersecting a relief surface arranged along the XY plane, the incident light I is modulated by the relief surface, thereby obtaining a reconstructed image 70.

[0055] However, since the incident light I is generated from a point light source, the reconstructed image 70 disappears under diffuse illumination.

[0056] The reconstructed image 70 is an image of a plurality of reconstruction points, which are obtained at positions spaced apart from the relief surface in the Z direction.

[0057] The reconstruction 70 can be a pre-designed image, as exemplified by the moon and stars in Fig. 2. The reconstruction 70 is therefore authentic and can be used to visually verify the authenticity of the holographic structure 1.

[0058] The angular range in which the reconstructed image 70 is reconstructed when the relief surface is viewed from a reconstruction point of interest is called the viewing angle θ. Therefore, the direction of the viewing angle θ is the X direction or the Y direction. When the hologram structure 1 is tilted by a certain amount or more and observed from an angle exceeding the viewing angle θ, the reconstructed image 70 disappears.

[0059] On the relief surface, calculation element sections are defined according to the viewing angle θ from each reconstruction point at which the reconstruction image 70 is reconstructed (see Patent Document 2). In this way, the calculation element sections are defined independently of the phase angle recorded region and the phase angle non-recorded region, and therefore usually overlap with the phase angle recorded region and the phase angle non-recorded region, respectively.

[0060] In addition, there are a plurality of regeneration points, and therefore there are the same number of computational element partitions as the number of regeneration points, corresponding to each of the plurality of regeneration points.

[0061] Moreover, the reproduction point is disposed at a distance from the relief surface. The distance of the reproduction point from the relief surface in the Z direction is preferably 5 mm or more and 25 mm or less, that is, the reproduction point is reproduced at a distance of 5 mm or more and 25 mm or less from the relief surface. The reproduction point may be reproduced on the observer side from the relief surface (upper side in FIG. 1) or on the opposite side from the observer from the relief surface (lower side in FIG. 1). In either case, the distance of the reproduction point from the relief surface can be specified in the same way.

[0062] The viewing angle θ from the reproduction point is defined by the following equation (1). θ<(A / m) (1)

[0063] Here, when (λ / 2d)≦1, A=asin(λ / 2d), λ is the wavelength of light, d is the arrangement interval of the unit blocks in the viewing angle direction, and m is a real number of 3 or more. Specifically, the wavelength of light λ can be 555 nm, which is the maximum relative luminosity of humans among visible light. The arrangement interval d can be the center-to-center distance of the unit blocks. The arrangement interval of the central unit blocks can be 10 nm or more and 200 nm or less.

[0064] The viewing angle θ is determined by the range in the X direction when the relief surface is viewed from a focused reproduction point, and is 1 / 2 the angle 2θ formed by the minimum value Xmin in the X direction, the maximum value Xmax in the X direction, and the focused reproduction point. Note that the X and Y directions correspond to the X and Y coordinate axes of a Euclidean coordinate system in which the direction in which the relief surface extends is the X direction, and the direction perpendicular to the X direction is the Y direction.

[0065] The viewing angle θ when the viewing angle direction is the Y direction is also defined in the same way. That is, the viewing angle θ is determined by the range in the Y direction when the relief surface is viewed from the focused reproduction point, and is 1 / 2 the angle 2θ formed by the minimum value Ymin in the Y direction, the focused reproduction point, and the maximum value Ymax in the Y direction. Therefore, the arrangement interval d of the unit blocks corresponds to the arrangement interval dx of the unit blocks in the X direction when the viewing angle direction is the X direction, and corresponds to the arrangement interval dy of the unit blocks in the Y direction when the viewing angle direction is the Y direction.

[0066] For this reason, the computational element partition is generally a square or a rectangle. However, the computational element partition may be a polygon other than a rectangle, or a circle or an ellipse. As for polygons, in addition to squares and rectangles, hexagons are also suitable. When the computational element partition is other than a square or rectangle, the minimum value (lower limit value) of the computational element partition in the X direction is set to Xmin, and the maximum value (upper limit value) of the computational element partition in the X direction is set to Xmax. Similarly, the minimum value of the computational element partition in the Y direction is set to Ymin, and the maximum value of the computational element partition 16 in the Y direction is set to Ymax.

[0067] When the shape of the unit block is a square or a rectangle, the corners of the square or rectangle are actually rounded to form a rounded rectangle. The unit block may be fused with an adjacent unit block. In this case, even if the shape of each unit block is a rounded rectangle, the shape of the fused unit blocks is not a rounded rectangle and is deformed, but the optical effect does not change even if the shape is deformed by fusion. The unit blocks are preferably arranged in an orderly manner. The orderly arrangement can be an arrangement at intervals within a certain range or an arrangement at equal intervals. Typical orderly arrangements are a square arrangement and a hexagonal arrangement.

[0068] As can be seen from equation (1) above, the viewing angle θ is less than A. When incident light I passes through this phase component and is diffracted, theoretically, diffraction beyond A does not occur. Therefore, when performing hologram calculations using a computer, the calculation range can be limited to an upper limit of the viewing angle θ.

[0069] In this way, limiting the calculation range shortens the calculation time. Even if calculations were performed for a range exceeding the viewing angle θ, the calculation would only involve calculation of diffraction that does not theoretically exist, and the results would only contribute as noise. However, in the above calculations, since calculations for a range exceeding the viewing angle θ are not performed, noise is not superimposed when reconstructing the reconstructed image 70 at the reconstruction point.

[0070] Each of the phase angle recording area and the phase angle non-recording area includes a plurality of unit blocks. For unit blocks included in an area (overlapping area) of the phase angle recording area that overlaps with the calculation element partition, a phase angle is calculated by a computer based on the phase component, and the calculated phase angle is recorded in the corresponding unit block included in the overlapping area.

[0071] The viewing angle θ is preferably 5° or more from the viewpoint of visibility of the reconstructed image 70, and is preferably 15° or less from the viewpoint that the reconstructed point tends to disappear easily.

[0072] In this way, when the hologram structure 1 having the relief surface as the relief structure 31 is observed from the viewing angle θ, a reproduced image 70 can be reproduced by the relief structure.

[0073] (Drawing image) 1(a) and (b), a metal reflective layer 40 is laminated on at least a portion of the surface of the embossed layer 30. A portion of this metal reflective layer 40 is removed, for example, by irradiation with a laser beam. A second image (image 90) is drawn and viewed depending on the presence or absence of the metal reflective layer 40.

[0074] The image 90 formed by removing a part of the metal reflective layer 40 can be composed of square pixels of 10 μm or more and 300 μm or less, particularly 10 μm or more and 150 μm or less. In this case, the pixel can be equal in size to the computational element section of the reconstruction point constituting the reconstruction image 70, or an integer multiple of the computational element section. In addition, within the pixel, there is a gradation of light and shade in steps of 0 to 255. The size and gradation of the pixel are determined by the laser beam, and the target condition can be experimentally found by performing a preliminary experiment, and is reproducible.

[0075] The image 90 can be pre-designed and viewed on demand, such as the image of a person illustrated in Fig. 2. The image 90 can therefore also be used for visual verification of the authenticity of the holographic structure 1.

[0076] Image 90 includes personal information region 61, which contains personally identifiable information that can be used to identify an individual, and non-personal information region 62, which does not contain personally identifiable information.

[0077] The personal information area 61 includes an important area 63 that includes an image for identifying an individual that can be used to identify an individual as personal identification information, and a non-important area 64 that does not include an image for identifying an individual.

[0078] If the image 90 is an image of a person, the important area 63 may include at least one image of the eyebrows, pupils, nose, and mouth of the person's face as an image for identifying the individual. For example, the important area 63 may be an area surrounded by straight lines connecting the outline of the eyebrows and the outline of the mouth.

[0079] Using a known machine learning model, feature points can be easily detected from each component of the important region 63. Therefore, the important region 63 is an area that can be used for mechanical personal identification.

[0080] For example, in face recognition using machine learning, Non-Patent Document 1 shows that an image can be recognized as a face by extracting each feature point on the face.

[0081] In this way, the important area 63 includes the characteristic points of the eyebrows, pupils, nose, and mouth, and is therefore also preferable for machine authentication.

[0082] The more metal reflective layer 40 there is, the more easily the hologram structure 1 is visible. On the other hand, the more the metal reflective layer 40 is removed by demetallization or the like, the more easily the facial image is visible. For this reason, the more metal reflective layer 40 there is, the more the design is based on the face, and the less metal reflective layer 40 there is, the more the design is based on the hologram structure 1. Since the important area 63 is the part of the facial image that has characteristics such as the eyes, nose, and mouth, it is set as wide as possible to express gradations depending on the presence or absence of the metal reflective layer 40, the non-personal information area 62 is set so that the hologram structure 1 remains, and the non-important area 64 is set to be somewhere in between.

[0083] Taking the above into consideration, the important area 63 is set so that the area having the metal reflective layer 40 is a minimum of 0% and a maximum of 80%, the non-important area 64 is set so that the area having the metal reflective layer 40 is a minimum of 10% and a maximum of 60%, and the non-personal information area 62 is set so that the area having the metal reflective layer 40 is a minimum of 70% and a maximum of 100%.

[0084] Within the angular range of the viewing angle θ described above, the image 90 and the reconstructed image 70 can be simultaneously recognized adjacently or overlapping each other. The principle behind this will be explained below using mathematical expressions.

[0085] The luminance at a viewing angle θ is expressed by the following formula.

[0086]

number

[0087] Where, dS: area of ​​the light source dI θ : Luminous intensity in the θ direction It is.

[0088] In this case, the luminance of the superimposed image 90 and the reproduced image 70 at the viewing angle θ is expressed as L 60 and L 70 Then, the relative brightness ratio can be expressed as follows:

[0089]

number

number

[0090] When the relative ratio of the above brightnesses is greater than 0.8 and smaller than 1, the image 90 and the reconstructed image 70 can be clearly and simultaneously recognized even when they are superimposed on each other.

[0091] As for the brightness, the brightness of the important area 63 in the image 90 can be made greater than the brightness of the reconstructed image 70. The principle behind this will be explained below using mathematical expressions.

[0092] Luminance of important area 63 is L 63 Then, the relative ratio to the brightness of the reconstructed image 70 can be expressed as follows:

[0093]

number

number

[0094] Here, when the above formula (1) is satisfied, the relative ratio of luminance is greater than 0.9 and less than 1. On the other hand, when the above formula (2) is satisfied, the relative ratio of luminance is greater than 0.7 and less than 1. When the above relationship is satisfied, the luminance of important area 63 in image 90 is greater than the luminance of reconstructed image 70. This is preferable because it makes it easier to recognize important area 63 that includes parts that are used to recognize a person's face.

[0095] Incidentally, the aesthetics of the image 90 can be improved by partially removing the metal reflective layer 40. The intended shape of the partially formed metal reflective layer 40 can be a security motif.

[0096] The security motif may be an authentication motif or a verification motif. The security motif may be line art, a geometric pattern, text, or calligraphy.

[0097] An example of a geometric pattern is guilloche. An example of a text is microtext. Examples of calligraphy are Western calligraphy, Islamic calligraphy, Georgian calligraphy, Chinese calligraphy, Japanese calligraphy, Korean calligraphy, Philippine Suyat, Thai calligraphy, Indian Oriya, Nepali calligraphy.

[0098] Furthermore, the relief structure described above may comprise a number of relief structure regions, which allows the image 90 to be displayed not only as a single one, but also as a combination of a number of relief structure regions.

[0099] This further allows image 90 to be a portrait, a landmark motif, art, a nature motif, a geometric pattern, a sign, a symbol, an emblem, a coat of arms, or text, either alone or in combination.

[0100] Symbols and emblems may be, for example, flags, shields, swords, spears, crowns, stars, moons, hearts, logos, ribbons, lines, flowers, leaves, grains, fruits, birds, wings, fish, arthropods, mammals, reptiles, amphibians, mythical creatures, mythical gods and goddesses.

[0101] The landmarks can be, for example, heritage sites, ruins, historical buildings, mountains, valleys, rocks, and monuments. The nature can be living things, stars, moon, sky, mountains, valleys, and rocks.

[0102] The living thing can be, for example, a flower, a leaf, a grain, a fruit, a bird, a wing, a fish, an arthropod, a mammal, a reptile, or an amphibian.

[0103] The mythical creature may be, for example, a unicorn, a dragon, or a phoenix.

[0104] Additionally, these motifs may represent symbols, which may represent countries, regions, states, groups, councils, treaties, alliances, unions, and axes.

[0105] Note that the image 90 is visible and can be authenticated within the viewing angle Φ at which the hologram structure 1 can be observed. That is, the image 90 can be seen when observed from the viewing angle Φ, but when the hologram structure 1 is tilted beyond a certain angle and observed from outside the range of the viewing angle Φ, the image 90 cannot be recognized.

[0106] In this case, in order to observe the image 90 superimposed on the reconstructed image 70 of the relief structure 31, the viewing angle Φ is preferably 5° or more and 15° or less, similarly to the viewing angle θ.

[0107] As described above, the hologram structure 1 in which both the reconstructed image 70 and the image 90 are displayed can be used as a personal information medium, for example, as a security pass for the owner of the personal information medium.

[0108] When a group of two or more pixels forming the personal information medium 60 is defined as a segment, the area of ​​the metal reflective layer 40 in the segment varies depending on the region. The segment includes a personal information region 61 and a non-personal information region 62 that constitute the personal information medium 60, and the personal information region 61 can include an important region 63 and a non-important region 64.

[0109] The metal reflective layer 40 may be composed of multiple layers, particularly two layers. The two metal reflective layers 40 may be in direct contact with each other, or may be stacked with a resin interposed therebetween. When the metal reflective layer 40 is composed of two layers, each of the two layers can display a different image 90.

[0110] As described above, the hologram structure 1 according to this embodiment makes it possible to form a personal information area 61 that is difficult to counterfeit and that is both highly readable and aesthetically pleasing.

[0111] Furthermore, the metal reflective layer 40 may have a brittle structure that breaks when peeled off, which makes it more difficult to tamper with the hologram structure 1.

[0112] [Second embodiment] Next, a second embodiment of the present invention will be described. In the following description, the same components as those described in the first embodiment will be denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0113] FIG. 3 is a schematic cross-sectional view for conceptually explaining the structure of the hologram structure according to the second embodiment.

[0114] The hologram structure 1c shown in FIG. 3(a) is constructed by placing a protective layer 50 on the upper side of the hologram structure 1a shown in FIG. 1(a) and placing a spacer layer 20 between the embossed layer 30 and the scattering reflection layer 10.

[0115] The hologram structure 1d shown in Figure 3(b) is constructed by placing a protective layer 50 on the upper side of the hologram structure 1b shown in Figure 1(b) and placing a spacer layer 20 between the metal reflective layer 40 and the scattering reflective layer 10.

[0116] FIG. 4 is a diagram showing an example of an image observed when the hologram structures 1c and 1d shown in FIGS. 3(a) and 3(b) are viewed in plan from the upper side in the figure.

[0117] In the image shown in FIG. 4, in addition to the image shown in FIG.

[0118] (Spacer layer) The spacer layer 20 has light-transmitting or transparency. The required light-transmitting or transparency of the spacer layer 20 may be at a level that allows incident light I incident from the protective layer 50 side to reach the scattering reflection layer 10 and allows light reflected by the scattering reflection layer 10 to be transmitted. The spacer layer 20 may be colored. The spacer layer 20 may be a layer that transmits visible or infrared laser beams.

[0119] As shown in FIG. 4, the spacer layer 20 is configured so that a visible code 80 can be written by laser. That is, the visible code 80 is formed by partially carbonizing the spacer layer 20 by a laser. The material of the spacer layer 20 can be polycarbonate or polyester, which is resistant to heat during laser writing. A material having some light scattering properties can also be used for the spacer layer 20. In this case, the transmittance is preferably 40% or more, and more preferably 60% or more, in the visible range of wavelengths from 380 nm to 780 nm. Typically, the transmittance at a laser beam wavelength of 1064 nm is preferably 30% or more.

[0120] Polyolefin and polymers having an aryl group can be used as the material of the spacer layer 20. Polyolefin and polymers having an aryl group are light-transmitting or transparent polymers.

[0121] The aryl-containing polymer may be a polycarbonate or a polyester terephthalate. The polyolefin may be either polyethylene or polypropylene, or a modified version thereof, or a copolymer thereof.

[0122] In addition, polyolefin has a simple main chain structure and is stable to heat, so that it undergoes little chemical change when exposed to a laser beam with a certain energy or less. Therefore, even if it is irradiated with a laser beam with an energy sufficient to remove the metal reflective layer 40, the spacer layer 20 is unlikely to discolor. Furthermore, since either polyethylene or polypropylene, or modified products thereof, or copolymers thereof are crystalline polymers, a certain amount of heat is required for phase transition when melted, and so there is little change when exposed to a laser beam with a certain energy or less.

[0123] The spacer layer 20 may be made of a polymer. If the spacer layer 20 is made of the same material as the scattering reflection layer 10, the two can be easily bonded together by thermal fusion.

[0124] The thickness of the spacer layer 20 is preferably 10 μm or more, taking into consideration the effect on the scattering reflection layer 10 of the impact when the metal reflective layer 40 is removed by the laser beam, and from the viewpoint of thermal conduction, is preferably 25 μm or more.

[0125] If the thickness of the spacer layer 20 is 25 μm or more, damage to the scattering reflection layer 10 can be easily prevented, and if it is 200 μm or less, protrusions of the hologram structure 1 during lamination or embedding are less noticeable, making it easier to obtain flexibility for the spacer layer 20. Therefore, the thickness of the spacer layer 20 can be set in the range of 25 μm or more and 200 μm or less. Note that, taking into consideration the allowable range in which the laser beam is not focused on the scattering reflection layer 10 from the focused light size, it is preferable that the thickness be 50 μm or more and 200 μm or less.

[0126] In addition, aromatic hydrocarbons of aryl groups are excellent in heat resistance because they are resonant hybrids, and therefore deformation and the like can be easily suppressed when irradiated with a laser beam of energy sufficient to remove the metal reflective layer 40. On the other hand, aromatic hydrocarbons are easily carbonized because of the high ratio of carbon in the molecule, and when carbonized with a sufficient amount of heat, they can produce a sufficiently black color even in a thin layer.

[0127] Therefore, when the material of the spacer layer 20 is a polymer having an aryl group, if the irradiation energy of the laser beam is sufficiently high, the metal reflective layer 40 can be removed and the spacer layer 20 can be carbonized to produce a black color.

[0128] It is not necessary to remove the scattering reflection layer 10 from the carbonized portion of the spacer layer 20. By moving the focal point of the laser beam away from the scattering reflection layer 10 (50 μm or more and 350 μm or less, depending on the irradiation energy and focal depth of the laser beam), or by providing the metal reflection layer 40 after carbonizing the spacer layer 20, it is also possible to carbonize the spacer layer 20 and not remove the metal reflection layer 40 from the carbonized portion.

[0129] This carbonized area has excellent visibility. Therefore, a further image or a part of the image 90 can be recorded. This image can be a string of symbols, alphabets, numbers, face images, or a combination of these. This allows for both face image discrimination processing by the metal reflective layer 40 and visual confirmation.

[0130] (protective layer) The protective layer 50 may be, for example, a layer containing a thermoplastic resin and a surface modifier. The thermoplastic resin of the protective layer 50 may be a resin having a glass transition temperature of 90° C. or higher and 130° C. or lower.

[0131] The thermoplastic resin may be any one of acrylic resin, polyester resin, and polyamide resin, any one of copolymer resins, any one of composite resins, and any one of composite resins of copolymer resins.

[0132] The surface modifier may be a powder, a wax, or an oil. The powder may be a heat-resistant powder. The heat-resistant powder may be a silica powder, a polyethylene powder, a fluorine-based powder, or a silicone-based powder. The wax may be a paraffin wax, a silicone, or a carnauba wax. The oil may be a silicone oil.

[0133] The protective layer 50 has the same light-transmitting or transparent properties as the spacer layer 20, and protects the planar shape of the hologram structure 1, thereby maintaining the above-mentioned code 80 in a machine-readable state.

[0134] The protective layer 50 can be formed from various resins. The resin of the protective layer 50 can be polycarbonate resin or acrylic resin. The resin of the protective layer 50 can be thermoplastic resin or cured resin. When the protective layer 50 is formed from the same type of material as the spacer layer 20, all layers can be easily bonded together by thermal fusion. The difference in softening temperature between the protective layer 50 and the spacer layer 20 can be within 30°C. This makes it easy to bond each layer together by thermal fusion. The thickness of the protective layer 50 is preferably 50 μm or more and 400 μm or less.

[0135] In this manner, the same material as that of the embossed layer 30 can be used for the protective layer 50 .

[0136] (Adhesive layer) Although not shown, an adhesive layer mainly composed of acrylic resin may be provided adjacent to the surface of the metal reflective layer 40 opposite to the embossed layer 30. Although acrylic resin has low heat resistance, its thermal decomposition is of the depolymerization type, so that if it has a certain molecular weight, its molecular structure remains and its performance can be maintained by irradiation with a laser beam. The molecular weight of the acrylic resin is preferably 100,000 or more. In addition, if the molecular weight is large, the glass transition temperature also increases, so if the glass transition temperature is above a certain level, the molecular weight is generally large. Therefore, if the acrylic resin has a glass transition temperature of 40 degrees or more, the molecular weight is sufficiently large, and even if it is irradiated with a laser beam to the extent that it removes the metal reflective layer 40, its performance as a radiation adhesive can be maintained. The thickness of the adhesive layer can be 0.1 μm or more and 10 μm or less.

[0137] [Third embodiment] Next, a third embodiment of the present invention will be described. This embodiment relates to a method for manufacturing a hologram structure, and this manufacturing method is applied to both the hologram structure according to the first embodiment and the hologram structure according to the second embodiment. In the following description, the same reference numerals are used for configurations common to those described in the first and second embodiments, and duplicated descriptions are omitted.

[0138] FIG. 5 is a cross-sectional view of a pre-structure for explaining an example of a method for manufacturing a hologram structure according to the third embodiment.

[0139] Note that the configurations of the pre-structure 2a shown in Fig. 5(a) and the pre-structure 2b shown in Fig. 5(b) are merely examples. In the following, when the pre-structures are collectively described, they will be collectively referred to as the pre-structure 2.

[0140] The manufacturing method of the hologram structure in this embodiment includes a formation process of forming a pre-structure 2 by stacking an embossed layer 30 having a concave-convex structure 31 that modulates incident light I and a metal reflective layer 40 covering the embossed layer 30, and a removal process of partially laser removing the metal reflective layer 40 so as to create a drawing pattern for displaying a visible image depending on the presence or absence of the metal reflective layer 40.

[0141] In the removing step, the metal reflective layer 40 is irradiated with a laser beam L to partially remove the metal reflective layer 40.

[0142] In the lamination process, in addition to the embossed layer 30 and the metal reflective layer 40, layers such as the scattering reflective layer 10, the spacer layer 20, and the protective layer 50 may be further laminated. The order of lamination may be arbitrary, and the order of lamination shown in Figures 5(a) and 5(b) is merely an example.

[0143] FIG. 5(a) shows a pre-structure 2a which has a laminated structure similar to that of the hologram structure 1c, and in which a part of the metal reflective layer 40 has not been removed.

[0144] In the removal step, the pre-structure 2a is irradiated with a laser beam L from the protective layer 50 side to remove a part of the metal reflective layer 40, thereby producing a hologram structure 1c.

[0145] FIG. 5(b) shows a pre-structure 2b which has a laminated structure similar to that of the hologram structure 1d, and in which a portion of the metal reflective layer 40 has not been removed.

[0146] In the removal step, the pre-structure 2b is irradiated with a laser beam L from the protective layer 50 side to remove a part of the metal reflective layer 40, thereby producing a hologram structure 1d.

[0147] 5(a) and 5(b), the power of the laser beam L is set to a level that removes only the metal reflective layer 40 in the irradiated area and does not cause discoloration or deterioration of the spacer layer 20 and the reflective scattering layer 10 below the irradiated area. An example of the laser beam L may be a pulsed laser beam.

[0148] 6A and 6B are cross-sectional views of a pre-structure for explaining the correlation between the power of a laser beam and the removal effect of a metal reflective layer.

[0149] 6A shows a pre-structure 2a shown in FIG. 5(a) as a pre-structure 2 for explaining the correlation between the power of the laser beam L and the removal effect of the metal reflective layer 40. On the other hand, in FIG. 6B, a pre-structure 2b shown in FIG. 5(b) is shown as a pre-structure 2 for explaining the correlation between the power of the laser beam L and the removal effect of the metal reflective layer 40.

[0150] 6A and 6B both show (a) a state in which the power of the laser beam L is insufficient, (b) a state in which the power of the laser beam L is optimal, and (c) a state in which the power of the laser beam L is excessive.

[0151] As shown in Figures 6A(a) and 6B(a), if the power of the laser beam L is insufficient, the metal reflective layer 40 in the irradiated area will not be completely removed, and even if incident light I is incident from the protective layer 50 side, it will not sufficiently reach the scattering reflective layer 10.

[0152] On the other hand, as shown in Figures 6A(c) and 6B(c), if the power of the laser beam L is excessive, the embossed layer 30, the spacer layer 20, and even the scattering reflection layer 10 will be damaged by the laser beam L or by the heat generated by the laser beam L, resulting in discoloration, etc.

[0153] Thus, whether the power of the laser beam L is insufficient or excessive, it adversely affects the formation of the hologram structure 1 and the visibility of the reproduced image 70.

[0154] Therefore, as shown in FIG. 6A(b) and FIG. 6B(b), in the removal step, it is necessary to irradiate the laser beam L with an optimal power.

[0155] The optimum range of the power of the laser beam L can be easily determined by a preliminary experiment using the pre-structure 2, or the like.

[0156] A pulsed laser beam can be used as the laser beam L. The power of the pulsed laser can be modulated by changing the oscillation frequency.

[0157] The light source of the pulsed laser can be a solid-state laser. The solid-state laser can be a YVO4 or YAG laser. The wavelength of the laser beam L of the pulsed laser can be 1064 nm, 532 nm, or 355 nm. This is the oscillation wavelength of the YAG laser, its second harmonic, and its third harmonic.

[0158] The oscillation frequency (Q switch frequency) of the pulsed laser is preferably 1 kHz or more and 1 MHz or less, and the pulse width of the pulsed laser is preferably 1 ns or more and 100 ns or less.

[0159] The energy of one pulse of the pulse laser is preferably 0.02 mJ or more and 20 mJ or less. The laser output is preferably 1 W or more and 20 W or less. For example, a DPSS YAG wavelength of 1064 nm can be used as the light source of the pulse laser. For example, a YVO4 laser of the MD-V series manufactured by Keyence Corporation can be used as the laser light source. The power of the pulse laser is easy to adjust, and sharp irradiation is possible.

[0160] Next, the behavior of incident light I incident on the completed hologram structures 1c and 1d from the protective layer 50 side will be described with reference to FIGS.

[0161] 7 and 8 are cross-sectional views of the hologram structure for explaining the behavior of incident light that is incident on the hologram structure from the protective layer side, which is the upper side in the figure.

[0162] Figures 7(a) and (b) show cross-sectional views of hologram structures 1c and 1d, illustrating the behavior of incident light I1 that enters hologram structures 1c and 1d from the upper protective layer 50 side in the figure, when the incident light I1 is not reflected by the metal reflective layer 40 and reaches the scattering reflective layer 10.

[0163] In this case, in both cases of Figures 7(a) and (b), the incident light I1 that reaches the scattering reflection layer 10 is scattered and reflected at the scattering reflection layer 10, and a portion I1a of the incident light I1 is specularly reflected and emitted in a scattered manner from the protective layer 50 to the outside of the hologram structures 1c and 1d.

[0164] Figures 8(a) and (b) also show cross-sectional views of hologram structures 1c and 1d, similar to Figures 7(a) and (b), and illustrate the behavior of incident light I1 entering hologram structures 1c and 1d from the protective layer 50 side, which is on the upper side in the figure, being reflected by the metal reflective layer 40.

[0165] In this case, the incident light I2 that reaches the metal reflective layer 40 is specularly reflected by the metal reflective layer 40 that conforms to the relief structure 31, travels mainly in the direction of specular reflection, and is emitted to the outside of the hologram structures 1c, 1d via the protective layer 50. In this manner, the reproduced image 70 is reproduced by emitting the light modulated by the relief structure 31.

[0166] In addition, due to the difference in reflectance between the metal reflective layer 40 and the scattering reflective layer 10, a reflectance contrast occurs at the viewing angle Φ. m , R d Then, R m >R d Due to this relationship, the metal reflective layer 40 is made a white region and the scattering reflective layer 10 is made a black region. As a result, an image 90 is formed by the removal pattern of the metal reflective layer 40.

[0167] When recognized by humans, the reflection contrast in the visible light region R m -R d A minimum value of 70% and a maximum of 99% is preferred.

[0168] Also, in the infrared and ultraviolet regions, if the reflectance contrast is within the above range, it is possible to recognize the image 90 using an appropriate measuring device.

[0169] The viewing angle Φ is preferably ±10° from the specular reflection region of the incident light I.

[0170] As described above, the method for manufacturing a hologram structure according to this embodiment makes it possible to manufacture a hologram structure capable of forming a code that is difficult to counterfeit and that is both highly readable and aesthetically pleasing.

[0171] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described. This embodiment relates to a card to which a hologram structure is applied and a manufacturing method thereof. Here, the hologram structure is as described in the first and second embodiments. Therefore, in the following description, the same reference numerals are used for the configurations common to those described in the first and second embodiments, and duplicated descriptions are omitted.

[0172] FIG. 9 is a plan view showing an example of a card according to the fourth embodiment.

[0173] Card 101 is an example of a personal information medium 60 realized by hologram structure 1. Accordingly, a first area 102 realized by hologram structure 1 is arranged on the surface of card 101. A second area 103 where hologram structure 1 is not arranged is also arranged on the surface of card 101.

[0174] That is, from the first area 102, as described using Figure 2, an image 90 of a person formed by removing the metal reflective layer 40 and a reconstructed image 70 formed by reflected light modulated by the relief structure 31 of the embossed layer 30 are displayed.

[0175] Image 90 includes a personal information area 61 that contains personally identifiable information that can be used to identify an individual, such as the owner of card 101, and a non-personal information area 62 that does not contain any personally identifiable information.

[0176] The personal information area 61 includes an important area 63 (e.g., an area surrounded by straight lines connecting the outline of the eyebrows and the outline of the mouth) that contains an image for identifying an individual that can be used to identify an individual as personal identification information, and a non-important area 64 that does not contain an image for identifying an individual.

[0177] On the other hand, text and a facial image are written in the second area 103 by the laser beam L. These text and facial images are visible and can be used as an identifier, individual information, and in particular, information about the owner of the card 101.

[0178] The card 101 may apply to a page of a booklet, for example a passport booklet or a visa booklet.

[0179] FIG. 10 is a schematic cross-sectional view conceptually illustrating the cross-sectional structure taken along line II in FIG.

[0180] As shown in FIG. 10, the upper side of the card 101 in the figure is covered with a protective layer 50.

[0181] Furthermore, in the card 101, a spacer layer 105 is laminated on the white core layer 106. The material of the spacer layer 105 is a polymer having an aryl group, and a visible code can be written by irradiating the laser beam L. The polymer having an aryl group is the same as the polymer having an aryl group described in the first embodiment. That is, the spacer layer 105 is configured such that a visible code can be written by laser. The thickness of the spacer layer 105 is preferably 50 μm or more and 400 μm or less.

[0182] In the first area 102 of the card 101, a transfer foil 200 having a metal reflective layer 40 is disposed between the spacer layer 105 and the protective layer 50.

[0183] On the other hand, in the second region 103, the protective layer 50 is located on the spacer layer 105, and the metal reflective layer 40 is not present.

[0184] The transfer foil 200 includes, from the top in the figure, a peeling layer 201, a metal reflective layer 40 laminated on the underside of the peeling layer 201, an embossed layer 30 laminated on the underside of the metal reflective layer 40, a metal reflective layer 40 laminated on the underside of the embossed layer 30, and an adhesive layer 202 attached below the metal reflective layer 40 and above the spacer layer 105. The adhesive layer 202 is bonded to the metal reflective layer 40 on its upper surface and to the spacer layer 105 on its lower surface.

[0185] The adhesive layer 202 may be mainly composed of acrylic resin. Although acrylic resin has low heat resistance, its thermal decomposition is of the depolymerization type, so that if it has a certain molecular weight, the molecular structure remains after irradiation with the laser beam L, and the performance can be maintained.

[0186] The molecular weight of the acrylic resin is preferably 100,000 or more. In addition, when the molecular weight is large, the glass transition temperature also rises, so if the glass transition temperature is above a certain level, the molecular weight is generally large. Therefore, if the acrylic resin has a glass transition temperature of 40 degrees or more, the molecular weight is sufficiently large and the performance as a photo-sensitive adhesive can be maintained even if the laser beam L is irradiated to the extent that the metal reflective layer 40 is removed.

[0187] The thickness of the adhesive layer 202 can be greater than or equal to 0.1 μm and less than or equal to 10 μm.

[0188] Also, an anchor layer (not shown) may be provided at any location between the embossed layer 30 and the adhesive layer 202. Furthermore, a mask layer (not shown) may be provided at any location between the anchor layer and the metal reflective layer 40.

[0189] The embossed layer 30 is made of resin or the like, and can have an optical relief structure including fine irregularities on the surface on the adhesive layer 202 side. This optical relief structure is similar to the relief structure 31 described in the first embodiment.

[0190] As described above, the adhesive layer 202 of the transfer foil 200 can be attached to the spacer layer 105. In this case, the embossed layer 30 can be disposed between the protective layer 50 and the metal reflective layer 40 in the stacking direction (Z direction in the figure).

[0191] Moreover, the adhesive layer 202 of the transfer foil 200 may be attached to the protective layer 50. In this case, the embossed layer 30 is disposed between the spacer layer 105 and the metal reflective layer 40 in the stacking direction.

[0192] With the above-mentioned configuration, the transfer foil 200 exhibits a predetermined optical effect such as a hologram or a diffraction grating.

[0193] (Card manufacturing method) Next, a method for manufacturing the card 101 will be described.

[0194] To manufacture the card 101, first, a transfer foil 200 as shown in FIG. 10 is prepared.

[0195] The transfer foil 200 is formed by laminating a release layer 201, a metal reflective layer 40, an embossed layer 30, another metal reflective layer 40, and an adhesive layer 202 in this order on a plastic film (not shown).

[0196] Next, the transfer foil 200 is placed with the plastic film facing up on the card base material in which the spacer layer 105 is laminated on the white core layer 106, thereby forming the card 101.

[0197] Then, heat and pressure are applied to the transfer foil 200 from above the plastic film, and the plastic film is then peeled off, thereby bonding the transfer foil 200 to the card base material.

[0198] The card base material and transfer foil 200 are then covered with a plastic film that serves as the protective layer 50, and laminated using heat and pressure to produce a card 101 having a first area 102 and a second area 103, as illustrated in Figures 9 and 10.

[0199] The release layer 201 may be colored. Coloring can be achieved by adding a pigment or dye to the resin of the release layer 201. The pigment may be an inorganic pigment, an organic pigment, or a mixture of inorganic and organic pigments. The pigment may be a single fluorescent pigment, a pearl pigment, or a magnetic pigment, or a homogeneous blend, a heterogeneous blend, or a homogeneous blend of heterogeneous pigments. The dye may be a natural dye, a synthetic dye, or a mixture of natural and synthetic dyes. The dye may be a fluorescent dye.

[0200] The release layer 201 can be formed by printing or coating on a plastic film. Coating can be gravure coating, microgravure coating, or die coating. Printing can be gravure printing or screen printing. From the viewpoint of processability, the thickness of the plastic film can be 10 μm or more and 50 μm or less. The thickness of the release layer 201 is preferably 0.5 μm or more and 5 μm or less. The release layer 201 can receive a printed layer (not shown). The release layer 201 may be mainly composed of acrylic resin. Acrylic resin easily receives a printed layer.

[0201] Immediately after manufacture, the card 101 has no information written in the second area 103. By irradiating the second area 103 with a laser beam L, the spacer layer 105 is carbonized to form a laser mark 105a, and information can be written. The information written as the laser mark 105a can be personal data, a biometric identifier, or a code. An example of a biometric identifier is a face image.

[0202] A personal information area can be formed in the metal reflective layer 40 in the first area 102 of the card 101, similarly to the metal reflective layer 40 according to the first embodiment. As a result, the card 101 according to this embodiment has the same effect as the hologram structure 1 according to the first embodiment. Furthermore, by combining the individual information written in the first area 102, the information written in the second area 103, and the optical effect produced by the transfer foil 200, it is possible to further improve security. In addition, in the card 101, the personal information area 61 formed by removing the metal reflective layer 40 is covered with the protective layer 50, making it difficult to tamper with.

[0203] The first region 102 is not limited to a configuration including the transfer foil 200. For example, when the optical effect of the embossed layer 30 is not imparted to the first region 102, the metal reflective layer 40 may be formed only on the portion to be the first region 102, and the identifier may be formed in the same manner as in the first embodiment.

[0204] As described above, the card and manufacturing method thereof according to the present embodiment make it possible to form a code that is difficult to counterfeit and that is both highly readable and aesthetically pleasing. EXAMPLES

[0205] Next, an embodiment of the present invention will be described. FIG. 11 is a top view showing a card made according to the embodiment.

[0206] 11 has a metal reflective layer 40 only in the first area 102. The metal reflective layer 40 is an aluminum vapor deposition layer, and has a thickness of 0.05 μm. To create such a card 101, a hologram structure including a metal reflective layer 40 was fused and integrated with a polycarbonate sheet by thermal lamination. In this way, a card before laser processing having a metal reflective layer 40 was first created. At this time, the first area 102 including the face image 90 has not yet been formed on the card, and the card is in a blank state.

[0207] Next, the created card was irradiated with a laser to generate a second area 103 on the polycarbonate surface and a first area 102 on the metal reflective layer 40, thereby creating a card 101 as shown in FIG. 11(a).

[0208] When observing the card 101 shown in Figure 11(a), when the relationship between the light source, card 101, and observer is tilted at an angle of 0° or more and 10° or less from the card normal, facial image 90 and reproduced image 70 could be observed simultaneously, as shown in Figure 11(b), and when the angle was 10° or more and 80° or less, only facial image 90 could be observed, as shown in Figure 11(c).

[0209] Although the best mode for carrying out the present invention has been described above with reference to the attached drawings, the present invention is not limited to such a configuration. Within the scope of the technical idea of ​​the invention defined in the claims, a person skilled in the art may conceive of various modifications and alterations, and it is understood that such modifications and alterations also belong to the technical scope of the present invention. [Explanation of symbols]

[0210] 1 Hologram structure 2 Pre-structure 10 Scattering reflective layer 20 Spacer layer 30 Embossed Layer 31 Relief structure 40 Metal reflective layer 50 protective layer 60 Personal information medium 61 Personal information area 62 Area outside of personal information 63 Important areas 64 Non-critical areas 70 Reproduction image 80 Code 90 images 101 Cards 102 1st area 103 Second area 105 Spacer layer 105a Laser mark 106 White core layer 200 Transfer foil 201 Peeling layer 202 Adhesive layer I incident light L Laser beam θ viewing angle Φ Viewing angle (observable angle)

Claims

1. 1. A hologram structure comprising: an embossed layer having a concave-convex structure that modulates incident light; a metal reflective layer covering at least a portion of the embossed layer; a first image reproduced by reflected light modulated by the concave-convex structure; and A second image is displayed based on the presence or absence of the metal reflective layer. The first image and the second image are visible. A hologram structure comprising:

2. The second image includes a personal information area including personal identification information used to identify an individual, and a non-personal information area not including the personal identification information.

2. The hologram structure according to claim 1,

3. The personal information area includes an important area including an image for identifying an individual used to identify an individual as the personal identification information, and a non-important area including no image for identifying an individual.

3. The hologram structure according to claim 2, wherein the hologram structure is a hologram structure having a thickness of 100 nm or less.

4. the second image is an image of a person; The important area includes at least one image of the eyebrows, pupils, nose, and mouth of the person's face as the image for identifying the individual.

4. The hologram structure according to claim 3, wherein the hologram structure is a hologram structure having a thickness of 100 nm or less.

5. The brightness of the important region is greater than the brightness of the first image.

5. The hologram structure according to claim 3 or 4.

6. A method for manufacturing a hologram structure, comprising the steps of: a forming step of forming a pre-structure by laminating an embossed layer having a concavo-convex structure that modulates incident light and a metal reflective layer that covers the embossed layer; a removal step of partially removing the metal reflective layer in the pre-structure with a laser so as to create a drawing pattern for displaying a visible image depending on the presence or absence of the metal reflective layer; A method for manufacturing a hologram structure, comprising:

7. In the removing step, the metal reflective layer is partially removed by irradiating the metal reflective layer with a laser beam.

7. The method for producing a hologram structure according to claim 6.

Images