Holographic structure and method for manufacturing the same

Abstract

To provide a hologram structure that is difficult to counterfeit, machine-readable, and does not compromise the design aesthetics of the hologram. [Solution] The hologram structure of the present invention comprises at least an embossed layer having a surface structure that modulates incident light, and a metallic reflective layer covering at least a part of the surface structure of the embossed layer, wherein a first image is reproduced by the reflected light modulated by the surface structure, and a second image is displayed depending on the presence or absence of the metallic reflective layer, the smallest unit of the first image is a pixel, and a pixel includes a coded area and an uncoded area.

Description

Technical Field

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[0001] The present invention relates to a hologram structure and a method for manufacturing the same.

Background Art

[0002] Currently, personal authentication media such as ID cards and passports for personal authentication display facial images capable of identifying the individual, and furthermore, identification by machines using image authentication is also becoming widespread.

[0003] Personal authentication media need to record and manage their data on demand for each individual. In addition, if the personal authentication media can be decorated with a hologram or the like, the security and appearance of the operation of the object will be improved.

[0004] Therefore, Patent Document 1 proposes a method of processing a hologram and a code on demand on a personal authentication medium.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the prior art, a technique for providing a hologram and a code for authenticating them on a medium at the same time has been disclosed. However, when a decorative hologram image and a JAN code or QR code (registered trademark) lacking in design for machine reading are adjacent to each other, the design of the hologram is impaired.

[0007] Based on the above circumstances, the present invention aims to provide a hologram structure and a method for manufacturing the same that is difficult to counterfeit, can be read by machine, and does not impair the design qualities of the hologram. [Means for solving the problem]

[0008] A first aspect of the present invention is a hologram structure comprising at least an embossed layer having a surface structure that modulates incident light and a metallic reflective layer covering at least a portion of the surface structure of the embossed layer, wherein a first image is reproduced by the reflected light modulated by the surface structure, and a second image is displayed depending on the presence or absence of the metallic reflective layer, the smallest unit of the first image is a pixel, and a pixel includes a coded region and an uncoded region.

[0009] A second aspect of the present invention is a hologram structure of the first aspect, in which the second image is formed on demand.

[0010] A third aspect of the present invention is a hologram structure according to the first aspect, wherein the first image is composed of a plurality of pixels that are squares with sides of 1 μm or more and 1 mm or less.

[0011] A fourth aspect of the present invention is a hologram structure according to the first aspect, further comprising a stacked scattering reflective layer that functions as a reflective surface for isotropically dispersing incident light.

[0012] A fifth aspect of the present invention is a hologram structure according to the first aspect, further comprising a translucent or transparent spacer layer on which a third image can be written by laser.

[0013] A sixth aspect of the present invention is a hologram structure according to the fourth aspect, wherein a light-transmitting or transparent protective layer is further laminated on the outermost layer opposite the scattering reflective layer.

[0014] A seventh aspect of the present invention is a hologram structure of the third aspect, wherein the code region is formed by at least straight lines, curves, and pointillisms, the area ratio in the pixels is 5% or more and 50% or less, and includes code information created by encoding at least one of a string and a number, and when the code information is decoded, the string and number contained in the code information are reproduced.

[0015] An eighth aspect of the present invention is a hologram structure according to the seventh aspect, wherein the code information includes personally identifiable information.

[0016] A ninth aspect of the present invention is a hologram structure of the seventh aspect, wherein a portion of the metallic reflective layer is demetallized in order to display a second image in color.

[0017] A tenth aspect of the present invention is a hologram structure according to the ninth aspect, wherein the loss due to demetallation of pixels in the code region is 50% or less, so that the code information can be decoded even when a part of the metal reflective layer is demetallated.

[0018] An eleventh aspect of the present invention is a hologram structure according to the ninth aspect, wherein a portion of the metal reflective layer is demetallated, and when the loss due to demetallation of the pixels in the code region is 50% or more and 80% or less, the information formed in the second image is also used for decoding so that the code information can be decoded.

[0019] A twelfth aspect of the present invention is a hologram structure of the first aspect, wherein a portion of the metal reflective layer is demetallated, and when the loss due to demetallation of the pixels in the code region is 50% or more and 80% or less, the code information becomes decodeable, and further information formed in the third image is also used for decoding.

[0020] The 13th aspect of the present invention is a method for manufacturing a hologram structure, including at least: a forming step of laminating an embossed layer and a metal reflection layer to form a pre-structure of the hologram structure; and a removing step of removing a part of the metal reflection layer by laser to form a drawing pattern for displaying a visible hologram image on the pre-structure.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a hologram structure that is difficult to forge, can be read by a machine, and does not impair the designability of the hologram. Further, it is possible to provide a manufacturing method for manufacturing such a hologram structure.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view of a hologram structure according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of an image observed when the hologram structure shown in FIG. 1 is viewed in a plan view from the upper side in the figure. [Figure 3] FIG. 3 is a plan view illustrating a code area in which code information is determined according to the change in the area ratio. [Figure 4] FIG. 4 is a diagram for explaining an example of a dither pattern. [Figure 5] FIG. 5 is a diagram for explaining an example of forming code information by a dither pattern. [Figure 6] FIG. 6 is a diagram for explaining another example of forming code information by a dither pattern. [Figure 7] FIG. 7 is a diagram for explaining the principle of signal 0, 1 conversion. [Figure 8] FIG. 8 is a flowchart showing the flow from encoding to decoding of code information using the hologram structure according to the first embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view of a hologram structure according to the second embodiment. [Figure 10]Figure 10 is a schematic cross-sectional view of a hologram structure according to the third embodiment. [Figure 11] Figure 11 shows an example of an image observed when the hologram structure shown in Figures 10(a) and 10(b) is viewed from above in a planar view. [Figure 12] Figure 12 is a schematic cross-sectional view of a hologram structure according to the fourth embodiment. [Figure 13] Figure 13 is a cross-sectional view of a prestructure illustrating an example of a method for manufacturing a hologram structure according to the fifth embodiment. [Figure 14A] Figure 14A is a cross-sectional view of a prestructure illustrating the correlation between the power of the laser beam and the removal effect of the metal reflective layer. [Figure 14B] Figure 14B is a cross-sectional view of a prestructure illustrating the correlation between the laser beam power and the removal effect of the metal reflective layer. [Figure 15] Figure 15 is a plan view showing an example of a card according to the sixth embodiment. [Figure 16] Figure 16 is a schematic cross-sectional view conceptually illustrating the cross-sectional structure along line BB in Figure 15. [Modes for carrying out the invention]

[0023] The embodiments of the present invention are a group of embodiments based on a single, original invention from the background. Furthermore, each embodiment of the present invention is a form of a group of embodiments based on a single invention. Each configuration of the present invention may have each of the embodiments of the present disclosure. Each feature of the present invention is combinable and can form each configuration. Therefore, each feature of the present invention, each configuration of the present invention, each configuration of the present disclosure, and each embodiment of the present invention can be combined, and such combinations can have synergistic functions and produce synergistic effects.

[0024] In this specification and in each figure, elements similar to those described above for previously shown figures are denoted by the same reference numerals, and detailed explanations or redundant explanations are omitted as appropriate.

[0025] [First Embodiment] The first embodiment of the present invention will be described below.

[0026] (Holographic structure) Figure 1 is a schematic cross-sectional view of a hologram structure 1a according to the first embodiment of the present invention.

[0027] As shown in Figure 1, the hologram structure 1a is formed by laminating an embossed layer 30 having a relief structure (hereinafter also referred to as "relief structure") that modulates the incident light I incident on the hologram structure 1a from the upper side in the figure, and a metallic reflective layer 40 that covers at least a part of the embossed layer 30.

[0028] In this embodiment, the stacking direction of each layer, i.e., the Z direction in the figure, is referred to as the thickness direction. Also, the base of the arrow on the Z axis in the figure is referred to as the lower side, and the arrow side as the upper side. Furthermore, viewing the hologram structure 1a from the thickness direction side is called a plan view, and viewing the hologram structure 1a in a cross-section along the thickness direction is called a cross-sectional view. The relief surfaces are arranged along the XY plane.

[0029] (metal reflective layer) The metal reflective layer 40 has a specular reflection structure that functions as a reflective surface that specularly reflects incident light I. The metal reflective layer 40 is made of metal. The main component of the metal reflective layer 40 can be an inorganic substance. The inorganic substance can be a metal, a metal compound, or silicon oxide.

[0030] Examples of metals include aluminum, silver, tin, chromium, nickel, copper, and gold. The purity of these metals can be 99% or higher. Alternatively, the purity can be 99.99% (4N) or higher. As will be described later, the metal reflective layer 40 is partially removed by the laser beam, but by making the purity of the metal in the metal reflective layer 40 4N or higher, defects during removal by the laser beam can be reduced.

[0031] Examples of metallic compounds include titanium oxide, aluminum oxide, and zinc sulfide. Metallic compounds generally have high refractive indices.

[0032] The metallic reflective layer 40 can be formed by deposition or printing. For deposition, physical deposition or chemical deposition (CVD) can be applied.

[0033] Physical deposition may be performed by vacuum deposition or sputtering. The target metal in this case may be various metal targets with a purity of 4N or higher.

[0034] The ink used to form the metal reflective layer 40 by printing can be offset ink, silkscreen ink, letterpress ink, or gravure ink, depending on the printing method. The ink can be resin ink, oil-based ink, water-based ink, etc. Depending on the drying method, it can also be, for example, oxidation polymerization ink, penetration drying ink, evaporation drying ink, or UV curing ink. The ink can also be pigment ink, dye ink, or a mixture thereof.

[0035] An example of a pigment ink is a magnetic ink. Magnetic inks can form patterns through magnetism. Because these patterns are unique, they tend to be difficult to counterfeit.

[0036] An example of a dye ink is a liquid crystalline ink. An example of a liquid crystalline ink is a cholesteric liquid crystal ink. Cholesteric liquid crystals reflect light of specific wavelengths. Therefore, the metal reflective layer 40 becomes colored. Also, the reflectivity changes depending on the direction of rotation of circularly polarized and elliptically polarized light. Alternatively, a functional ink whose color changes depending on the illumination angle or observation angle may be used as the metal reflective layer 40. Examples of such functional inks include optically variable inks, color-shift inks, and pearl inks.

[0037] (Embossed layer) The embossed layer 30 has a relief structure 31 on at least one surface. Figure 1 shows an example in which the relief structure 31 is provided on the lower surface of the embossed layer 30. The embossed layer 30 is formed from, for example, an ultraviolet curing resin, a thermoplastic resin, or a thermosetting resin.

[0038] UV-curable resins can be monomers, oligomers, or polymers having ethylenically unsaturated bonds or ethylenically unsaturated groups that are curable resins. Examples of monomers having ethylenically unsaturated bonds or ethylenically unsaturated groups include 1,6-hexanediol, neopentyl glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0039] The oligomer having an ethylenically unsaturated bond or ethylenically unsaturated group can be an oligomer or co-oligomer of epoxy acrylate, urethane acrylate, or polyester acrylate.

[0040] The polymer can be a urethane-modified acrylic polymer or epoxy-modified acrylic copolymer.

[0041] The UV-curing resin can be any of the following: acrylic resin, acrylic acrylate resin, epoxy acrylate resin, urethane acrylate resin, polyester acrylate resin, or ethylene methacrylate resin; a copolymer resin of any of these; a composite resin of any of these; or a composite resin of any of these copolymer resins.

[0042] The thickness of the embossed layer 30 can be between 1 μm and 25 μm.

[0043] When a thermoplastic resin is used as the material for the embossed layer 30, it can be any of acrylic resin, epoxy resin, cellulose resin, vinyl resin, copolymer resin of any of them, composite resin of any of them, or composite resin of any of them. The thermosetting resin for the embossed layer 30 can be any of urethane resin, melamine resin, epoxy resin, phenolic resin, copolymer resin of any of them, composite resin of any of them, or composite resin of any of them.

[0044] The embossed layer 30 may be colored. Coloring can be achieved by adding pigments or dyes to the resin of the embossed layer 30. The pigments can be inorganic pigments or organic pigments. Alternatively, the pigments can be fluorescent pigments, pearl pigments, or magnetic pigments. The dyes can be natural dyes or synthetic pigments. Alternatively, the dyes can be fluorescent dyes.

[0045] The embossed layer 30 may have a relief structure 31 formed on the surface that is in contact with the metal reflective layer 40.

[0046] The relief structure 31 may be formed by transferring (embossing) the uneven relief structure formed on the surface of the metal stamper onto the object.

[0047] The relief structure 31 has optical effects such as optical diffraction, anti-reflection, isotropic or anisotropic scattering, lensing, and polarization-selective reflection. These optical effects allow for visual verification of authenticity. In other words, the relief structure 31 is visible and verifiable by sight. The metal reflective layer 40 on the relief surface having the relief structure 31 is also visible and verifiable by sight. In other words, the metal reflective layer 40 adjacent to the relief surface having the relief structure 31 can also be visually verified for authenticity. This provides an anti-counterfeiting and tampering effect. Furthermore, these optical effects can also impart an aesthetic appeal. In other words, these optical effects allow the hologram structure 1a to possess a visual effect.

[0048] The desired optical effect can also be obtained by combining one or more relief structures 31 having optical effects. The regions having each optical effect may be placed touching, adjacent, close together, at regular intervals, or alternately. In this way, a relief surface having multiple relief structures 31 having multiple optical effects can produce complex visual effects, thereby enhancing the effectiveness of preventing counterfeiting and tampering. It can also enhance the aesthetic appearance of the hologram structure 1a.

[0049] The relief structure 31 has recesses and protrusions, and imparts optical properties to the hologram structure 1a such as diffraction, light reflection suppression, isotropic or anisotropic light scattering, refraction, polarization, and wavelength-selective reflection, transmission, and light reflection suppression.

[0050] The relief structure 31 may have regions of diffraction grating structure with a pitch of 0.5 μm or more and 2 μm or less, and a depth of 0.05 μm or more and 0.5 μm or less. This imparts the function of diffracting light to the hologram structure 1.

[0051] As the relief structure 31, for example, a moth-eye structure or a deep lattice structure may be provided with a pitch of 0.1 μm or more and 0.5 μm or less, and a depth of 0.25 μm or more and 0.75 μm or less. In this case, the relief structure 31 provides the function of suppressing light reflection, or polarized or wavelength-selective reflection, transmission, or suppression of light reflection to the hologram structure 1.

[0052] The relief structure 31 may have, for example, regions of a non-periodic linear or dot-like repeating structure with an average pitch of 0.5 μm or more and 3 μm or less, and a depth of 0.05 μm or more and 0.5 μm or less. This imparts to the hologram structure 1a the function of emitting isotropic or anisotropic scattered light.

[0053] The relief structure 31 may have an average pitch greater than 3 μm and a region of structure deeper than 0.5 μm. This makes it possible to have a refractive index different from that of adjacent layers, and the relief structure 31 imparts a refractive function to the hologram structure 1a.

[0054] Furthermore, the relief structure 31 may include a relief surface (recording surface) as disclosed in Patent Document 2, which will be described below.

[0055] In other words, the relief surface in this embodiment may have a phase angle recording region and a phase angle non-recording region as described in Patent Document 2. Here, the region of the relief surface other than the phase angle recording region becomes the phase angle non-recording region. In one example, the phase angle non-recording region is a mirror surface.

[0056] (Reproduction image) Figure 2 shows an example of an image observed when the hologram structure 1a shown in Figure 1 is viewed from above in a plan view.

[0057] In the hologram structure 1a, as illustrated in Figure 1, the reflected light R1 and R2, which are modulated by the uneven structure 31 of the embossed layer 30 when incident light I is emitted, reconstructs the first image (reconstructed image 70 as illustrated in Figure 2).

[0058] In other words, when incident light I emitted from a point light source (not shown) is incident from a direction that intersects with a relief surface arranged along the XY plane, the incident light I is modulated by the relief surface, thereby obtaining a reconstructed image 70.

[0059] However, since the incident light I originates from a point source, the reconstructed image 70 disappears under diffuse illumination.

[0060] The reconstructed image 70 is an image formed by multiple reconstruction points. The reconstruction points are realized at positions spaced apart in the Z direction from the relief plane.

[0061] The reconstructed image 70 can be a pre-designed image, as exemplified by the moon and stars in Figure 2. Therefore, the reconstructed image 70 is verifiable and can be used for visual verification of the authenticity of the hologram structure 1a.

[0062] The angular range in which the reconstructed image 70 is reconstructed when the relief surface is viewed from the point of interest is called the field of view angle θ. Therefore, the direction of the field of view angle θ is either the X direction or the Y direction. If the hologram structure 1a is tilted beyond a certain point and observed from an angle exceeding the field of view angle θ, the reconstructed image 70 disappears.

[0063] On the relief surface, calculation element sections are defined according to the field of view angle θ from each reproduction point where the reproduced image 70 is reproduced (see Patent Document 2). In this way, the calculation element sections are defined independently of the phase angle recording area and the phase angle non-recording area, and therefore usually overlap with the phase angle recording area and the phase angle non-recording area individually.

[0064] Furthermore, there are multiple regeneration points. Therefore, there are as many calculation element partitions as there are regeneration points, corresponding to each of the multiple regeneration points.

[0065] Furthermore, the regeneration point is positioned at a distance from the relief surface. The distance of the regeneration point from the relief surface in the Z direction is preferably 5 mm or more and 25 mm or less; that is, the regeneration point is preferably regenerated at a distance of 5 mm or more and 25 mm or less from the relief surface. Note that the regeneration point may be regenerated on the observer side (upper side in Figure 1) from the relief surface, or on the opposite side from the observer (lower side in Figure 1) from the relief surface. In either case, the distance of the regeneration point from the relief surface can be defined similarly.

[0066] The field of view angle θ from the playback point is defined by equation (1) below.

[0067] θ < (A / m) ... (1) Here, if (λ / 2d) ≤ 1, then A = asin(λ / 2d), where λ is the wavelength of light, d is the spacing between unit blocks in the field of view direction, and m is a real number greater than or equal to 3. Specifically, the wavelength of light λ can be 555 nm, which is the maximum relative luminous efficiency for humans among visible light. The spacing d can be the distance between the centers of the unit blocks. The spacing between the central unit blocks can be between 10 nm and 200 nm.

[0068] As described in Patent Document 2, the field of view angle θ is determined by the range in the X direction when viewing the relief surface from the point of interest, and is half of the angle 2θ formed by the minimum value Xmin in the X direction and the maximum value Xmax in the X direction between the point of interest and the relief surface. Note that the X and Y directions correspond to the X and Y coordinate axes of Euclidean coordinates, where the direction in which the relief surface extends is the X direction and the direction perpendicular to the X direction is the Y direction.

[0069] The field of view angle θ is similarly defined when the field of view direction is the Y direction. That is, the field of view angle θ is determined by the range in the Y direction when viewing the relief surface from the point of interest, and is half of the angle 2θ formed by the minimum value Ymin in the Y direction and the maximum value Ymax between the point of interest and the Y direction. Therefore, the arrangement interval d of the unit block corresponds to the arrangement interval dx in the X direction of the unit block when the field of view direction is the X direction, and corresponds to the arrangement interval dy in the Y direction of the unit block when the field of view direction is the Y direction.

[0070] Therefore, the calculation element area is generally a square or rectangle. However, the calculation element area may be a polygon other than a quadrilateral, or it may be a circle or ellipse instead of a polygon. Among polygons, hexagons are particularly suitable in addition to squares and rectangles. If the calculation element area is not a square or rectangle, the minimum value (lower limit) in the X direction of the calculation element area is set to Xmin, and the maximum value (upper limit) in the X direction of the calculation element area is set to Xmax. Similarly, the minimum value in the Y direction of the calculation element area is set to Ymin, and the maximum value in the Y direction of the calculation element area is set to Ymax.

[0071] When the shape of a unit block is a square or rectangle, it actually becomes a rounded rectangle with rounded corners. Unit blocks may also be fused with adjacent unit blocks. In this case, even if the shape of each unit block is a rounded rectangle, the shape of the fused unit blocks will not be a rounded rectangle but will be deformed, but the optical effect will not change even if it is deformed by fusion. It is preferable that the unit blocks are arranged in an orderly manner. An orderly arrangement can be an arrangement with a certain range of intervals or an arrangement with equal intervals. Typical orderly arrangements are a square arrangement or a hexagonal arrangement.

[0072] As can be seen from equation (1) above, the field of view angle θ is less than A. When incident light I passes through this phase component and is diffracted, theoretically, diffraction exceeding A will not occur. Therefore, when performing hologram calculations using a computer, the calculation range can be limited to the field of view angle θ as the upper limit.

[0073] In this way, limiting the calculation range can reduce the calculation time. Furthermore, even if calculations were performed for a range beyond the field of view angle θ, it would only be performing a calculation of diffraction that does not theoretically exist, and the result would only contribute as noise. However, in the calculation described above, calculations are not performed for a range beyond the field of view angle θ, so no noise is superimposed when the reproduced image 70 at the reproduction point is reproduced.

[0074] Both the phase angle recording area and the phase angle non-recording area each contain multiple unit blocks. Within the phase angle recording area, the computer calculates the phase angle based on the phase component for the unit blocks included in the area that overlaps with the calculation element section (overlapping area), and the calculated phase angle is recorded in the corresponding unit block in the overlapping area.

[0075] The field of view θ is preferably 5° or greater from the viewpoint of visibility of the reproduced image 70, and preferably 15° or less from the viewpoint of the reproduction point being prone to disappearance.

[0076] Thus, when a hologram structure 1a, which is equipped with a relief surface as a relief structure 31, is observed from a field of view angle θ, the relief structure 31 can reproduce the reconstructed image 70. The reconstructed image 70 is perceived as the first image.

[0077] Furthermore, the reconstructed image 70 may be perceived as an image exhibiting optical effects such as general optical diffraction effects, anti-reflective effects, isotropic or anisotropic scattering effects, lensing effects, and polarization-selective reflection effects.

[0078] (Code area) The reconstructed image 70 consists of a relief structure 31, with the smallest unit being a pixel G. As shown in the partially enlarged view of Figure 2, each pixel G has a non-coded region 100 and a coded region 101. The reconstructed image 70 consists of multiple pixels G. Each pixel G has a size, for example, 1 μm or more and 1 mm or less on one side, and preferably 10 to 150 μm in size.

[0079] The code region 101 is formed by at least straight lines, curves, and pointillisms, and its area ratio in pixel G is between 5% and 50%, and it contains code information created by encoding at least one of a string and a number. The code information may contain personally identifiable information (personal information). The strings and numbers contained in the code information are reconstructed when the code information in code region 101 is decoded.

[0080] The code region 101 does not need to be recognized in the reconstructed image 70 at the time of observation, and may only be observed by a scanner or microscope.

[0081] The non-coded region 100 is the region in the reconstructed image 70 that fulfills the elements of the image in terms of visual perception, and occupies 10-100% of the pixel G.

[0082] The code information contained in the code region 101 is encoded code information. The code information can be decoded using the code region 101 with multiple pixels.

[0083] Code information consists of numbers, characters, and symbols, and can be used to identify or authenticate an individual, similar to personal information. Therefore, the code information held in code area 101 can be used to verify the authenticity of the hologram structure.

[0084] Examples of code area 101 include, for example, JAN codes, two-dimensional codes, Morse code, binary encryption, symmetric-key encryption schemes, and so on.

[0085] Examples of image formation in the code region 101 include, for example, a reflected image of the metal reflective layer 40, a latent image of 100 lines, a UV / IR ink image, and a moiré image.

[0086] The code area 101 contains data representing defects and fluctuations that are accidentally formed during manufacturing, such as burrs, pinholes, etching, and printing bleed, and can be decoded to obtain meaningful information.

[0087] The code area 101 can have both a two-dimensional arrangement of encryption when viewed as a whole, and a one-dimensional arrangement of encryption obtained by cutting in the vertical, horizontal, and diagonal directions.

[0088] Examples of one-dimensional encryption include generating binary-format encryption such as barcodes and Morse code by adjusting the area containing the code, and storing numerical information depending on the presence or absence of a code area in the reading direction.

[0089] Examples of two-dimensional ciphers include the generation of a two-dimensional code by combining one-dimensional ciphers.

[0090] (Drawing image) The hologram structure 1a receives incident light I, and depending on the presence or absence of the metal reflective layer 40, it returns reflected light R1 and R2 with different light intensities. Based on the contrast of these intensities, it forms a second image (image 90 as exemplified in Figure 2).

[0091] The demetallized pattern of the metal reflective layer 40 when forming the second image 90 can be generated and reproduced by image or calculation.

[0092] As illustrated in Figure 1, a metallic reflective layer 40 is laminated on at least a portion of the surface of the embossed layer 30. A portion of this metallic reflective layer 40 is removed (demetalized), for example, by irradiation with a laser beam. In this specification, demetalization may hereafter be referred to as "demeta". Depending on the presence or absence of the metallic reflective layer 40 due to demeta, the second image, image 90, is drawn and displayed in color.

[0093] The image 90 formed by removing a portion of the metal reflective layer 40 can consist of square pixels ranging from 10 μm to 300 μm, and particularly from 10 μm to 150 μm. In this case, the size of the pixels can be equal to the size of the calculation element section of the reproduction point that constitutes the reconstructed image 70, or an integer multiple of the calculation element section. Furthermore, grayscale levels from 0 to 255 exist within the pixels. The size and grayscale levels of the pixels are determined by the laser beam, and the desired conditions can be experimentally searched and reproduced by conducting preliminary experiments.

[0094] Image 90 is pre-designed and viewed on demand, such as the human face exemplified in Figure 2. Therefore, Image 90 can also be used for visual verification of the authenticity of the hologram structure 1a.

[0095] The information contained in image 90 and code area 101 can also be used to verify the authenticity of the hologram structure 1a.

[0096] Figure 3 is a plan view illustrating a code region where code information is determined according to changes in area ratio.

[0097] The information contained in image 90 and code region 101 may be different. For example, as illustrated in Figure 3(a), numerical information such as "1,0,0,0,0,1,1,1,0,1,1,0,·····" can be hidden within the face image 90, as indicated by the arrow in the face image 90. Alternatively, as illustrated in Figure 3(b), numerical information can be hidden as information contained in code region 101, which is determined according to the change in area ratio. This makes it possible to create a code by setting a threshold value that is a percentage of the pixel size and setting the scan direction parallel to the direction of region division. Furthermore, it is possible to change the code by changing the threshold value without changing the appearance.

[0098] Furthermore, by partially removing the metallic reflective layer 40, the image 90 can be displayed in color or its aesthetic appearance can be improved. The intended outline created by the partially formed metallic reflective layer 40 can be used as a security motif.

[0099] Security motifs can be authentication motifs or verification motifs. Security motifs can be line drawings, geometric patterns, text, or calligraphy.

[0100] Examples of geometric patterns include guilloche. Examples of text include microtext. Examples of calligraphy include Western calligraphy, Islamic calligraphy, Georgian calligraphy, Chinese calligraphy, Japanese calligraphy, Korean calligraphy, Filipino Suyat, Thai calligraphy, Indian Odia script, and Nepalese calligraphy.

[0101] Furthermore, the relief structure described above may have multiple relief structure regions. This makes it possible to display the image 90 not only as a single relief structure region, but also as a combination of multiple regions.

[0102] This allows image 90 to further be a portrait, a landmark motif, art, a nature motif, a geometric pattern, a sign, a symbol, an emblem, a coat of arms, or a single or combined text.

[0103] Symbols and emblems can be motifs such as 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 mythical goddesses.

[0104] Landmarks can include, for example, heritage sites, ruins, historical buildings, mountains, valleys, rocks, and monuments. Nature can include living things, stars, the moon, the sky, mountains, valleys, and rocks.

[0105] Living organisms can include, for example, flowers, leaves, grains, fruits, birds, wings, fish, arthropods, mammals, reptiles, and amphibians.

[0106] Legendary creatures can include, for example, unicorns, dragons, and phoenixes.

[0107] Furthermore, these motifs can also represent symbols, which can represent countries, regions, states, groups, councils, treaties, alliances, unions, or the Axis.

[0108] Furthermore, these motifs can be used not only for visual authentication but also as one-dimensional or two-dimensional codes for machine authentication.

[0109] In this case, the information contained in code area 101 may be similar to the information contained in code area 101, or confidential information using either of these as a key.

[0110] Furthermore, in pixels where the non-coded area 100 occupies 90% or more of the pixel, the digit pattern 102 may be treated as the coded area 101 and used accordingly. In this case, the digit pattern 102 is a pattern created by encoding information, similar to the coded area 101, and can be decoded using any algorithm.

[0111] Furthermore, even if a portion of the metal reflective layer 40 is demetallated, the loss due to demetallation of pixels G in the code region 101 is set to 50% or less so that the code information can be decoded.

[0112] Furthermore, even if the demetallation loss of pixels G in the code region 101 is set to 50% or more and 80% or less, decoding of the code information can still be made by further using the information formed in the second image 90.

[0113] Figure 4 illustrates an example of a demata pattern.

[0114] The dimensional pattern is formed by a femtosecond to millisecond pulsed laser, with the smallest processed marks being circular. Image 90 is formed by continuously oscillating the pulsed laser, as illustrated in Figure 4(a). The continuous oscillation pattern can be not only diagonal, as shown in Figure 4(a), but also horizontal, as shown in Figure 4(b), and vertical, as shown in Figure 4(c).

[0115] Figures 5 and 6 illustrate examples of code information formation using digit patterns.

[0116] In Figure 5(a), as in Figure 4(a), an image is formed by continuously oscillating a pulsed laser.

[0117] As shown in Figure 5(b), by combining a continuously oscillating (1) reference sequence and a (2) code sequence 1 with half the resolution, and further converting them into 0s and 1s, (3) barcode-usable code information can be incorporated into the entire image 90.

[0118] Figure 7 is a diagram illustrating the principle of signal 0 / 1 conversion.

[0119] To convert signals to 0 or 1, as shown in Figure 7(a), a "1" is assigned to signal values ​​above a predetermined threshold, and a "0" is assigned to signal values ​​below the threshold.

[0120] In Figure 5(b), an example is shown where (1) the code sequence 1 is arranged at half the density in the horizontal direction. However, this is just one example, and it may also be achieved by forming (2) the reference sequence by continuous oscillation in the vertical direction, and arranging (1) the code sequence 1 accordingly at half the density in the vertical direction.

[0121] Furthermore, as shown in Figure 6(b), the speed and oscillation of the pulsed laser may be controlled so that each pulse can be distinguished during drawing. This allows the pulses to be viewed at different resolutions, and numerical values ​​can be encoded and inserted into the XY columns and vertices of image 90, as shown in Figure 6(a).

[0122] Furthermore, when the digit pattern is defined as the code region 101, the image 90 that a person sees and the information in the code region 101 may be different. In this case, the image 90 contains the code region 101, but the code region 101 will have additional information.

[0123] The added information can be decoded using known algorithms such as JAN codes or Morse code, or it may be decoded using any algorithm.

[0124] Thus, since the hologram structure 1a has a reconstructed image 70 and a code region 101, it becomes more difficult to forge by querying the visual information and the code information.

[0125] Furthermore, within the observable field of view Φ (not shown) of the hologram structure 1a, image 90 is visible and recognizable. That is, when observed from the field of view Φ, image 90 can be seen, but when the hologram structure 1a is tilted beyond a certain angle and observed from outside the range of the field of view Φ, image 90 becomes unrecognizable.

[0126] In this case, in order to observe the image 90 superimposed on the reconstructed image 70 of the relief structure 31, the field of view Φ is preferably 5° or more and 15° or less, similar to the field of view θ described above.

[0127] Figure 8 is a flowchart showing the flow from encoding to decoding of code information using the hologram structure 1a according to this embodiment.

[0128] In the design of the hologram structure 1a (S1), the first step is to create the design of image 90 (S2). The design of image 90 can be, for example, a face image as illustrated in Figure 2.

[0129] Next, calculations are performed on the fine relief structure 31 so that the desired optical effect can be imparted to the hologram structure 1a (S3).

[0130] Next, code information is created by encoding strings, numbers, etc., that contain personal information (S4).

[0131] Furthermore, the metal reflective layer 40 is demetallated to add code information (S5). In this way, the encoding of the code information is completed (S6).

[0132] Next, we will describe how to decode the encoded code information in this way (S7).

[0133] For decoding, first the reflection contrast of the pixels is measured (S8). Then, a threshold is set (S9), the binary information is restored (S10), and decoding is performed using the code information algorithm (S11). As a result, the code information is obtained, and decoding is completed (S12).

[0134] As described above, the hologram structure 1a, which displays both the reconstructed image 70 and the image 90, can be used as a personal information medium, for example, as a security pass for the owner of the personal information medium.

[0135] The metal reflective layer 40 can also be composed of multiple layers, particularly two layers. The two metal reflective layers 40 may be in direct contact or superimposed on each other via a resin. When the metal reflective layer 40 consists of two layers, each layer can display a different image 90.

[0136] Furthermore, the metal reflective layer 40 may have a brittle structure that breaks when peeled off. This makes it more difficult to tamper with the hologram structure 1a.

[0137] As described above, according to the first embodiment, it is possible to provide a hologram structure 1a that is difficult to forge and has code information encoded in the code area 101, thereby providing high readability, aesthetics, and information.

[0138] [Second Embodiment] Next, a second embodiment of the present invention will be described. In the following description, components common to those described in the first embodiment will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0139] Figure 9 is a schematic cross-sectional view of a hologram structure according to the second embodiment.

[0140] The hologram structure 1b shown in Figure 9(a) is constructed by placing the scattering reflection layer 10 on the lower side when the metal reflection layer 40 is on the upper side, as is the hologram structure 1a shown in Figure 1.

[0141] The hologram structure 1c shown in Figure 9(b) is constructed by placing the scattering reflection layer 10 on the underside of the hologram structure 1a shown in Figure 1, with the embossed layer 30 facing upwards.

[0142] (Scattered reflective layer) The scattering reflective layer 10 functions as a reflective surface that isotropically disperses the incident light I. The scattering reflective layer 10 may be a white resin layer.

[0143] Examples of materials for the scattering reflective 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 thereof; and thermoformable materials having radically polymerizable unsaturated groups.

[0144] The scattering reflective layer 10, made of polycarbonate, has high heat resistance and can prevent discoloration caused by laser engraving.

[0145] The scattering reflective layer 10 can also be formed by arranging light-opaque reflective ink in layers 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 optical variable ink, color shift ink, pearl ink, etc. In this configuration, the substrate may be transparent.

[0146] Furthermore, considering the impact on the scattering reflective layer 10 due to the removal of the metal from the metal reflective layer 40, it is preferable to ensure a distance of 10 μm or more between the metal reflective layer 40 and the scattering reflective layer 10.

[0147] As described above, according to the hologram structures 1b and 1c of the second embodiment, the scattering reflection layer 10 allows the incident light I to be dispersed isotropically, so that the images 70 and 90 can be displayed without uneven brightness.

[0148] [Third Embodiment] Next, a third embodiment of the present invention will be described. In the following description, components that are common to those described in the first and second embodiments will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0149] Figure 10 is a schematic cross-sectional view of a hologram structure according to the third embodiment.

[0150] The hologram structure 1d shown in Figure 10(a) is constructed by placing a spacer layer 20 between the embossed layer 30 and the scattering reflection layer 10 of the hologram structure 1b shown in Figure 9(a).

[0151] The hologram structure 1e shown in Figure 10(b) is constructed by placing a spacer layer 20 on top of the embossed layer 30 of the hologram structure 1c shown in Figure 9(b).

[0152] Figure 11 shows examples of images observed when the hologram structures 1d and 1e shown in Figures 10(a) and 10(b) are viewed from above in a planar view.

[0153] The image shown in Figure 11 displays a third visible image (code) 80, in addition to the image shown in Figure 2.

[0154] (Spacer layer) The spacer layer 20 is translucent or transparent. The required translucency or transparency of the spacer layer 20 is such that incident light I, incident from the metal reflection layer 40 side, reaches the scattering reflection layer 10, and the light reflected by the scattering reflection layer 10 can be transmitted. The spacer layer 20 may be colored. The spacer layer 20 may be a layer that transmits visible or infrared laser beams.

[0155] The spacer layer 20 is configured to be laser-writable with a visible code 80, as shown in Figure 11. That is, the visible code 80 is formed by partially carbonizing the spacer layer 20 with a laser. The material of the spacer layer 20 can be polycarbonate or polyester, which are resistant to the heat generated during laser writing. Alternatively, a material with some light scattering properties can be used for the spacer layer 20. In this case, the transmittance is preferably 40% or more, more preferably 60% or more, in the visible range from 380 nm to 780 nm. Typically, the transmittance at a laser beam wavelength of 1064 nm is preferably 30% or more.

[0156] The material for the spacer layer 20 can be polyolefin or polymer having an aryl group. Polyolefin and polymer having an aryl group are translucent or transparent polymers.

[0157] Polymers containing aryl groups can be polycarbonates or polyester terephthalates. Polyolefins can be polyethylene or polypropylene, modified versions thereof, or copolymers thereof.

[0158] Furthermore, because polyolefins have a simple main chain structure and are thermally stable, they undergo little chemical change when irradiated with a laser beam below a certain energy. Therefore, even when irradiated with a laser beam with energy sufficient to remove the metal reflective layer 40, discoloration of the spacer layer 20 is unlikely to occur. In addition, since polyethylene, polypropylene, their modified products, or their copolymers are crystalline polymers, a certain amount of heat is required for the phase transition during melting, resulting in little change when irradiated with a laser beam below a certain energy.

[0159] The spacer layer 20 may be made of a polymer. If the spacer layer 20 is made of the same type of material as the scattering and reflecting layer 10, the two can be easily joined together by thermal fusion.

[0160] The thickness of the spacer layer 20 is preferably 10 μm or more, taking into consideration the effect on the scattering reflection layer 10 due to the impact when the metal reflection layer 40 is removed by the laser beam, and preferably 25 μm or more from the viewpoint of thermal conductivity.

[0161] If the thickness of the spacer layer 20 is 25 μm or more, damage to the scattering reflection layer 10 is less likely to be prevented, and if it is 200 μm or less, the protrusion of the hologram structure 1 during bonding or embedding is less likely to be perceived, making it easier to obtain the tolerance of the spacer layer 20. Therefore, the thickness of the spacer layer 20 can be in the range of 25 μm or more and 200 μm or less. However, considering the tolerance range in which the laser beam does not focus on the scattering reflection layer 10 from the focusing size, it is preferable to set the thickness to 50 μm or more and 200 μm or less.

[0162] Furthermore, aryl aromatic hydrocarbons have excellent heat resistance because they form resonance hybrids, making it easier to suppress deformation when irradiated with a laser beam that has enough energy to remove the metal reflective layer 40. On the other hand, aromatic hydrocarbons have a high carbon ratio in their molecules, so they are easily carbonized, and when carbonized with sufficient heat, they can produce a sufficiently black color even in thin layers.

[0163] Therefore, if the material of the spacer layer 20 is a polymer having an aryl group, and 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.

[0164] Furthermore, the scattered reflection layer 10 in the carbonized portion of the spacer layer 20 does not need to be removed. It is also possible to carbonize the spacer layer 20 by moving the laser beam's focal point away from the scattered reflection layer 10 (depending on the laser beam's irradiation energy and focal depth, the distance should be between 50 μm and 350 μm), or by providing a metal reflection layer 40 after carbonizing the spacer layer 20, and then not removing the metal reflection layer 40 in the carbonized portion.

[0165] This carbonized area offers excellent visibility. Therefore, it can record additional images or portions of image 90. This image can be a sequence of symbols, letters, numbers, facial images, or combinations thereof. This allows for both information processing by the code area 101 and visual verification.

[0166] The information recorded in these areas may also be used as a key to decode the information written in the code area 101. For example, if a portion of the metal reflective layer 40 is demetallized and the loss of pixels in the code area 101 due to demetallization is 50% or more and 80% or less, then information formed in the third image 80 can also be used to decode the code information.

[0167] Thus, when the information recorded in the carbonized region of the spacer layer 20 is used as a decoding key, the security is further enhanced because each piece of information is paired.

[0168] As described above, the hologram structure according to the third embodiment includes a spacer layer 20, which allows for the recording of additional images or a portion of the image 90 on the spacer layer 20. Furthermore, security can be enhanced by using the image recorded on the spacer layer 20 as a decoding key.

[0169] [Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. In the following description, components common to those described in the first, second, and third embodiments will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0170] Figure 12 is a schematic cross-sectional view of a hologram structure according to the fourth embodiment.

[0171] The hologram structure 1f shown in Figure 12(a) is constructed by placing a protective layer 50 on top of the hologram structure 1d shown in Figure 10(a).

[0172] The hologram structure 1g shown in Figure 12(b) is constructed by placing a protective layer 50 on top of the hologram structure 1e shown in Figure 10(b).

[0173] In this embodiment, the hologram structure further has a protective layer 50 laminated on the outermost layer opposite the scattering reflection layer 10.

[0174] (protective layer) The protective layer 50, like the spacer layer 20, is translucent or transparent and can 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 with a glass transition temperature of 90°C or higher and 130°C or lower.

[0175] The thermoplastic resin can be any of acrylic resin, polyester resin, or polyamide resin, a copolymer resin of any of these, a composite resin of any of these copolymer resins, or a composite resin of any of these copolymer resins.

[0176] The surface modifier may be a powder, wax, or oil. The powder may be a heat-resistant powder. The heat-resistant powder may be silica powder, polyethylene powder, fluorine-based powder, or silicone-based powder. The wax may be paraffin wax, silicone, or carnauba wax. The oil may be silicone oil.

[0177] The protective layer 50 protects the planar shape of the hologram structure 1 and maintains the machine-readable state of the aforementioned code 80.

[0178] 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 curing resin. When the protective layer 50 is formed from the same type of material as the spacer layer 20, all layers can be easily joined together by heat fusion. The difference in softening temperature between the protective layer 50 and the spacer layer 20 can be within 30°C. This makes it easier to join each layer together by heat fusion. The thickness of the protective layer 50 is preferably 50 μm or more and 400 μm or less.

[0179] In this way, the same material as the embossed layer 30 can be applied to the protective layer 50.

[0180] (adhesive layer) Although not shown in the diagram, an adhesive layer mainly composed of acrylic resin may be provided adjacent to the side of the metal reflective layer 40 opposite to the embossed layer 30. Acrylic resin has low heat resistance, but its thermal decomposition is of the depolymerization type, so as long as it has a certain molecular weight, the molecular structure can remain 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. Also, if 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 higher, the molecular weight is sufficiently large, and even if the metal reflective layer 40 is irradiated with a laser beam to the extent that it is removed, the performance as a spray adhesive can be maintained. The thickness of the adhesive layer can be 0.1 μm or more and 10 μm or less.

[0181] As described above, according to the hologram structure of the fourth embodiment, a protective layer 50 is further laminated on the outermost layer opposite the scattering reflection layer 10. Therefore, the protective layer 50 protects the planar shape of the hologram structure 1 and maintains the machine-readable state of the code 80.

[0182] [Fifth Embodiment] Next, a fifth embodiment of the present invention will be described. This embodiment relates to a method for manufacturing a hologram structure, and this manufacturing method is applicable to the manufacturing of hologram structures according to the first, second, third, and fourth embodiments. In the following description, components common to those described in the first, second, third, and fourth embodiments are denoted by the same reference numerals, and redundant descriptions are omitted.

[0183] Figure 13 is a cross-sectional view of a prestructure 2 illustrating an example of a method for manufacturing a hologram structure according to the fifth embodiment.

[0184] Note that the configurations of prestructure 2a shown in Figure 13(a) and prestructure 2b shown in Figure 13(b) are merely examples. In the following, when describing prestructures collectively, they will be referred to as prestructure 2.

[0185] The method for manufacturing a hologram structure according to this embodiment includes a forming step of forming a prestructure 2 by laminating at least an embossed layer 30 and a metallic reflective layer 40, and a removal step of removing a portion of the metallic reflective layer 40 with a laser.

[0186] In the removal process, the metal reflective layer 40 is partially removed by irradiating it with a laser beam L in order to create a drawing pattern for displaying a visible image depending on the presence or absence of the metal reflective layer 40.

[0187] Figure 13(a) shows a pre-structure 2a having a layered structure similar to that of the hologram structure 1f, but before a portion of the metal reflective layer 40 is removed.

[0188] The stacking order of the prestructure 2 can be arbitrary and is not limited to the stacking order shown in Figure 13(a). For example, the stacking order shown in Figure 13(b) can also be used.

[0189] Figure 13(b) shows a pre-structure 2b that has a layered structure similar to the hologram structure 1g, but before a portion of the metal reflective layer 40 is removed.

[0190] In the removal process for the pre-structure 2a illustrated in Figure 13(a), a laser beam L is irradiated from the protective layer 50 side to remove a portion of the metal reflective layer 40 and to manufacture the hologram structure 1f.

[0191] In the removal process for the pre-structure 2b illustrated in Figure 13(b), a laser beam L is irradiated from the protective layer 50 side to remove a portion of the metal reflective layer 40 and produce the hologram structure 1g.

[0192] In both Figure 13(a) and Figure 13(b), the power of the laser beam L is set to remove only the metal reflective layer 40 in the irradiated area, without causing discoloration or alteration to the spacer layer 20 and the reflection / scattering layer 10 located beneath the irradiated area. The specific type of laser beam L can be a pulsed laser beam.

[0193] Figures 14A and 14B are cross-sectional views of a prestructure illustrating the correlation between laser beam power and the removal effect of the metal reflective layer.

[0194] In Figure 14A, prestructure 2a, shown in Figure 13(a), is shown as prestructure 2 to explain 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 Figure 14B, prestructure 2b, shown in Figure 13(b), is shown as prestructure 2 to explain the correlation between the power of the laser beam L and the removal effect of the metal reflective layer 40.

[0195] Figures 14A and 14B both show (a) a state where the laser beam L has insufficient power, (b) a state where the laser beam L has appropriate power, and (c) a state where the laser beam L has excessive power. In these figures, the area removed by irradiation with the laser beam L is schematically shown as the removed area J.

[0196] As shown in Figures 14A(a) and 14B(a), if the power of the laser beam L is insufficient, only a small removal area J is formed, and the metal reflective layer 40 in the irradiated area is not completely removed. Therefore, even if incident light I is incident from the protective layer 50 side, it will not sufficiently reach the scattering reflective layer 10.

[0197] On the other hand, as shown in Figures 14A(c) and 14B(c), if the power of the laser beam L is excessive, the removal area J extends to the embossed layer 30, the spacer layer 20, and the scattering reflection layer 10. The embossed layer 30, the spacer layer 20, and the scattering reflection layer 10 are damaged by the laser beam L or by the heat generated by the laser beam L, resulting in discoloration and other damage.

[0198] Thus, both insufficient and excessive power of the laser beam L negatively affect the formation of the hologram structure 1 and the visibility of the reconstructed image 70.

[0199] Therefore, as shown in Figures 14A(b) and 14B(b), the removal process involves irradiating the area with a laser beam L at an appropriate power level that completely removes the metal reflective layer 40 at the desired location without damaging the embossed layer 30, the spacer layer 20, and the scattering reflective layer 10.

[0200] The optimal power range for the laser beam L can be easily determined through preliminary experiments using pre-structure 2.

[0201] A pulsed laser beam can be used for the laser beam L. The power of the laser beam L can be modulated by changing the oscillation frequency of the pulsed laser.

[0202] The light source for a pulsed laser can be a solid-state laser. The solid-state laser can be a YVO4 or YAG laser. The wavelength of the pulsed laser beam L can be 1064 nm, 532 nm, or 355 nm. These are the oscillation wavelength of the YAG laser, and its second and third harmonics.

[0203] The oscillation frequency (Q-switch frequency) of the pulsed laser is preferably 1 kHz or higher and 1 MHz or lower. The pulse width of the pulsed laser is preferably 1 ns or higher and 100 ns or lower.

[0204] The energy of one pulse of the pulsed laser is preferably between 0.02 mJ and 20 mJ. The laser output is preferably between 1 W and 20 W. For the pulsed laser light source, for example, a DPSS YAG wavelength of 1064 nm can be used. For the laser light source, for example, a YVO4 laser from Keyence's MD-V series can be used. Pulsed lasers allow for easy power adjustment and sharp irradiation.

[0205] As described above, the manufacturing method according to the fifth embodiment can be used to manufacture the hologram structures according to the first to fourth embodiments.

[0206] [Sixth Embodiment] Next, a sixth embodiment of the present invention will be described. This embodiment relates to a card to which a hologram structure is applied and a method for manufacturing the same. Here, the hologram structure is as described in the first, second, third, and fourth embodiments. Therefore, in the following description, components common to those described in the first, second, third, and fourth embodiments will be denoted by the same reference numerals and redundant descriptions will be omitted.

[0207] Figure 15 is a plan view showing an example of a card according to the sixth embodiment.

[0208] Card 110 is an example realized by hologram structure 1. Hologram structure 1 is a general term for the hologram structures 1a to 1g that have been exemplified so far.

[0209] The 110th surface of card 1 contains a first region A-1, which is realized by the hologram structure 1. The 110th surface of card 1 also contains a second region A-2, which does not contain the hologram structure 1.

[0210] In other words, from the first region A-1, as explained with reference to Figure 2, a human image 90 formed by the removal of the metal reflective layer 40 and a reconstructed image 70 formed by reflected light R modulated by the relief structure 31 of the embossed layer 30 are displayed.

[0211] Meanwhile, in the second area A-2, text and facial images are written by the laser beam L. These text and facial images are visible and can be used as identifiers, individual information, and in particular, owner information of card 110.

[0212] Card 110 can be applied to a single page of a booklet, such as a passport booklet or visa booklet.

[0213] Figure 16 is a schematic cross-sectional view conceptually illustrating the cross-sectional structure along line BB in Figure 15.

[0214] As shown in Figure 16, the card 110 has its upper surface side covered by the protective layer 50.

[0215] Furthermore, the card 110 has a spacer layer 20 laminated on top of the white core layer 106. The material of the spacer layer 20 is a polymer having aryl groups, and a visible code 80 can be written to it by irradiating it with a laser beam L. The polymer having aryl groups is the same as the polymer having aryl groups described in the first embodiment. That is, the spacer layer 20 is configured to be laser-writable with a visible code 80. The thickness of the spacer layer 20 is preferably 50 μm or more and 400 μm or less.

[0216] In the first region A-1 of card 110, a transfer foil 200 equipped with a metallic reflective layer 40 is placed between the spacer layer 20 and the protective layer 50.

[0217] On the other hand, in the second region A-2 of card 110, the protective layer 50 is located on the spacer layer 20, and the metal reflective layer 40 is absent.

[0218] The transfer foil 200 comprises, from the top in Figure 16, a release layer 201, a metallic reflective layer 40 laminated below the release layer 201, an embossed layer 30 laminated below the metallic reflective layer 40, and an adhesive layer 202 laminated below the embossed layer 30 and bonded to the top of the spacer layer 20. The adhesive layer 202 is bonded to the embossed layer 30 on its upper surface and to the spacer layer 20 on its lower surface.

[0219] The adhesive layer 202 can be mainly composed of acrylic resin. Although acrylic resin has low heat resistance, its thermal decomposition is of the depolymerization type, so as long as it has a certain molecular weight, the molecular structure can be preserved and its performance maintained by irradiation with the laser beam L.

[0220] The molecular weight of the acrylic resin is preferably 100,000 or more. Furthermore, a larger molecular weight also increases the glass transition temperature; therefore, if the glass transition temperature is above a certain level, the molecular weight is generally large. Thus, an acrylic resin with a glass transition temperature of 40 degrees Celsius or higher has a sufficiently large molecular weight, and can maintain its performance as an adhesive even when irradiated with a laser beam L to the extent that it removes the metal reflective layer 40.

[0221] The thickness of the adhesive layer 202 can be between 0.1 μm and 10 μm.

[0222] Furthermore, an anchor layer (not shown) may be provided at any location between the embossed layer 30 and the adhesive layer 202. Additionally, a mask layer (not shown) may be provided at any location between the anchor layer and the metal reflective layer 40.

[0223] The embossed layer 30 is formed of resin or the like and may have an optical relief structure with fine irregularities on the surface facing the adhesive layer 202. This optical relief structure is the same as the relief structure 31 described in the first embodiment.

[0224] As mentioned above, the adhesive layer 202 of the transfer foil 200 can be bonded to the spacer layer 20. In this case, the embossing layer 30 can be placed between the protective layer 50 and the metallic reflective layer 40 in the lamination direction (Z direction in the figure).

[0225] Alternatively, the adhesive layer 202 of the transfer foil 200 may be bonded to the protective layer 50. In this case, the embossing layer 30 is positioned between the spacer layer 20 and the metal reflective layer 40 in the lamination direction.

[0226] With the above configuration, the transfer foil 200 can produce predetermined optical effects such as holograms and diffraction gratings.

[0227] (How to manufacture cards) Next, the manufacturing method of card 110 will be described.

[0228] To manufacture card 110, first, a transfer foil 200 is prepared as illustrated in Figure 16.

[0229] The transfer foil 200 is formed by laminating a release layer 201, a metallic reflective layer 40, an embossed layer 30, and an adhesive layer 202 on a plastic film (not shown) in this order.

[0230] Next, a card 110 is formed by placing a transfer foil 200 on a card base material in which a spacer layer 20 is laminated on a scattering reflective layer 10, with the plastic film facing it.

[0231] Then, heat and pressure are applied to the transfer foil 200 from above the plastic film, and the plastic film is peeled off to bond the transfer foil 200 to the card base material.

[0232] Subsequently, the card base material and transfer foil 200 are covered with a plastic film that will serve as a protective layer 50, and laminated by applying heat and pressure to produce a card 110 having a first region A-1 and a second region A-2, as illustrated in Figure 15.

[0233] The release layer 201 may be colored. Coloring can be achieved by adding pigments or dyes to the resin of the release layer 201. The pigments may be inorganic pigments, organic pigments, or mixtures of inorganic and organic pigments. The pigments may be fluorescent pigments, pearl pigments, magnetic pigments, individual pigments, blends of the same type, mixtures of different types, or mixtures of different types of the same type. The dyes may be natural dyes, synthetic dyes, or mixtures of natural and synthetic dyes. The dyes may also be fluorescent dyes.

[0234] The release layer 201 can be formed on a plastic film by printing or coating. 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 accept a printed layer (not shown). The release layer 201 may be mainly composed of acrylic resin. Acrylic resin readily accepts printed layers.

[0235] Immediately after manufacturing, the card 110 has no information written in the second area A-2. By irradiating the second area A-2 with a laser beam L, the spacer layer 20 is carbonized to form a laser mark 105, and information can be written to it. The information written as the laser mark 105 can be personal data, a biometric identifier, or a code. An example of a biometric identifier is a facial image.

[0236] The metal reflective layer 40 of the first region A-1 of card 110 can be used to form a personal information area, similar to the metal reflective layer 40 described in the first embodiment. As a result, card 110 has the same effect as the hologram structure 1 described in the first embodiment. Furthermore, security can be further enhanced by combining the individual information written in the first region A-1, the information written in the second region A-2, and the optical effect produced by the transfer foil 200. In addition, in card 110, the second image 90 formed by removing the metal reflective layer 40 is covered by the protective layer 50, making tampering difficult.

[0237] Note that the first region A-1 is not limited to a configuration comprising a transfer foil 200. For example, if the optical effect of the embossed layer 30 is not to be applied to the first region A-1, the metallic reflective layer 40 may be formed only in the portion designated as the first region A-1, and an identifier may be formed using the same procedure as in the first embodiment.

[0238] Thus, according to the sixth embodiment, it is possible to manufacture a card that is difficult to counterfeit and achieves both high readability and aesthetic appeal.

[0239] As described above, the present invention provides a hologram structure and a method for manufacturing the same that is difficult to counterfeit, machine-readable, and does not impair the design of the hologram.

[0240] The best mode for carrying out the present invention will be described above with reference to the accompanying drawings. However, the present invention is not limited to such configurations. Within the realm of imagination, a person skilled in the art could conceive of various examples of changes and modifications. It is understood that these examples of changes and modifications also fall within the technical scope of the present invention. ru. [Explanation of Symbols]

[0241] 1. Holographic structure 2 Prestructure 10 Scattering reflective layer 20 Spacer layer 30 embossed layers 31. Relief structure 40 Metal reflective layer 50 protective layer 70 First image, reconstructed image 80 Third image, code 90. Second image, face image 100 Non-code areas 101 Code Area 102 Dimeta Patterns 105 Laser Mark 106 White core layer 110 cards 200 Transfer Foils 201 Exfoliation layer 202 Adhesive layer A-1 1st area A-2 Second area BB Line G pixels I incident light J removal part L laser beam R Reflected light

Claims

1. A holographic structure, at least, An embossed layer having a surface structure that modulates incident light, The embossed layer is laminated with a metallic reflective layer that covers at least a portion of the uneven structure of the embossed layer, The first image is reconstructed by the reflected light, which is modulated by the uneven structure, from the incident light. A second image formed by the presence or absence of the aforementioned metal reflective layer is displayed. The smallest unit of the first image is a pixel, The aforementioned pixel includes a coded region and a non-coded region. Holographic structure.

2. The hologram structure according to claim 1, wherein the second image is formed on demand.

3. The first image is a hologram structure according to claim 1, comprising a plurality of pixels that are squares with sides of 1 μm or more and 1 mm or less.

4. The hologram structure according to claim 1, further comprising a stacked scattering reflective layer that functions as a reflective surface for isotropically dispersing the incident light.

5. The hologram structure according to claim 1, further comprising a translucent or transparent spacer layer on which a third image can be written by laser.

6. The hologram structure according to claim 4, wherein a light-transmitting or transparent protective layer is further laminated on the outermost layer opposite the scattering reflective layer.

7. The code region is formed by at least straight lines, curves, and pointillisms, and the area ratio of the pixels is 5% or more and 50% or less, and includes code information created by encoding at least one of a string and a number. The hologram structure according to claim 3, wherein when the code information is decoded, the string and numerical values ​​contained in the code information are reproduced.

8. The hologram structure according to claim 7, wherein the code information includes information that can identify an individual.

9. The hologram structure according to claim 7, wherein a portion of the metal reflective layer is demetallized in order to display the second image in color.

10. The hologram structure according to claim 9, wherein the loss of the pixels in the code region due to demetallation is 50% or less, so that the code information can be decoded even if a part of the metal reflective layer is demetallated.

11. The hologram structure according to claim 9, wherein a portion of the metal reflective layer is demetallated, and if the loss of the pixels in the code region due to the demetallation is 50% or more and 80% or less, the information formed in the second image is also used for decoding so that the code information can be decoded.

12. The hologram structure according to claim 11, wherein a portion of the metal reflective layer is demetallated, and when the loss of the pixels in the code region due to the demetallation is 50% or more and 80% or less, the information formed in the third image is also used for decoding so that the code information can be decoded.

13. A method for manufacturing a hologram structure, At a minimum, the process includes a forming step of laminating an embossed layer and a metallic reflective layer to form a prestructure of the hologram structure, A manufacturing method comprising a removal step of removing a portion of the metal reflective layer by laser in order to form a drawing pattern on the prestructure for displaying a visible holographic image.

Images