JP5315793B2 - Security devices and labeled items - Google Patents

Description

  The present invention relates to a forgery prevention technique.

  A latent image may be used to prevent forgery. The latent image can be formed using a liquid crystal material as described in Patent Document 1. For example, a layer including a plurality of regions made of a solidified liquid crystal material and having different slow axis directions is formed. Then, a reflective layer is provided on the back side of the liquid crystal layer.

  When the security device thus obtained is observed with the naked eye from the liquid crystal layer side, the previous regions cannot be distinguished from each other. When this security device is observed through the polarizer, the brightness of the previous region varies depending on the angle formed by the slow axis and the light transmission axis of the polarizer. That is, the latent image formed by the previous region is visualized by observing through a polarizer.

A latent image formed using a liquid crystal material is difficult to realize. In addition, this latent image is not only machine readable, but can also be visualized by using a polarizer such as a polarizing film, i.e. without using a large device. For this reason, anti-counterfeiting technology using a liquid crystal material has attracted high interest.
JP 2003-251643 A

  Such a security device is desired to have a special visual effect. Further, such a security device is required to be able to distinguish a visualized image with high accuracy. For example, if a bright image can be displayed on the security device, high discrimination accuracy can be achieved.

  An object of the present invention is to provide a security device that has a special visual effect and displays a bright image when a latent image is visualized.

According to the first aspect of the present invention, the plurality of grooves each made of a solidified liquid crystal material, including the first and second main surfaces, having the same length direction and adjacent to each other in the direction intersecting the length direction are provided. wherein the plurality of unit regions provided first main surface viewed contains a first liquid crystal portion corresponding to one of said plurality of unit regions, the second liquid crystal corresponding to the other one of said plurality of unit areas The portion is a liquid crystal layer having a different length direction and thickness, a light transmission layer covering the first main surface, and facing the first main surface with the light transmission layer interposed therebetween, or ; and a reflective layer of the volume hologram beam which faces the second major surface, the reflective layer, the white light as the reference light for reproduction, the spread angle and the incident angle is, the spread angle of the reference light for reproduction and when irradiated to be equal to the incident angle, of the reflective layer, versus the first liquid crystal portion Portion will emit red light, the portion corresponding to the second liquid crystal portion security device, characterized in that for emitting the green light is provided.

  According to a second aspect of the present invention, there is provided a labeled article comprising the security device according to the first aspect and an article supporting the security device.

  According to the present invention, there is provided a security device that has a special visual effect and displays a bright image when a latent image is visualized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same referential mark is attached | subjected to the component which exhibits the same or similar function through all drawings, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a plan view schematically showing a security device according to an aspect of the present invention. 2 is a cross-sectional view taken along the line II-II of the security device shown in FIG.

  1 and 2, the X direction is a direction parallel to the main surface of the security device 10. The Y direction is a direction parallel to the main surface of the security device 10 and perpendicular to the X direction. The Z direction is a direction perpendicular to the X direction and the Y direction.

  The security device 10 is, for example, a display body that is supported by an article to be confirmed to be a genuine product. The security device 10 includes a base material 11, a reflective layer 12, an intermediate layer 13, a liquid crystal layer 14, and a protective layer 15. The front surface of the security device 10 is a surface on the protective layer 15 side.

  The substrate 11 is a film or sheet made of a resin such as a polyethylene terephthalate (hereinafter referred to as “PET”) film. The substrate 11 may or may not have light transmittance. Moreover, the base material 11 may have a single layer structure, and may have a multilayer structure. The substrate 11 can be omitted.

  The reflective layer 12 covers the entire front surface of the substrate 11. The reflective layer 12 may cover only a part of the front surface of the substrate 11. Alternatively, the reflective layer 12 may at least partially cover the back surface of the substrate 11. In this case, the base material 11 is light transmissive at at least a part of the position corresponding to the reflective layer 12. In this case, typically, the substrate 11 is transparent at least at a part of the position corresponding to the reflective layer 12.

  The reflective layer 12 may have a light scattering property or may not have a light scattering property. The reflective layer 12 may have a single layer structure or a multilayer structure.

  The reflective layer 12 includes a hologram or a diffraction grating. The reflective layer 12 may include only one of the hologram and the diffraction grating, or may include both of them.

  The hologram is, for example, a volume hologram, that is, a Lippmann hologram, or a surface relief hologram. The diffraction grating is, for example, a planar grating or a blazed grating.

  When the reflective layer 12 includes a volume hologram, the reflective layer 12 may be a layer in which interference fringes are recorded three-dimensionally as a distribution of optical characteristics such as refractive index and transmittance. Alternatively, the reflective layer 12 may include a light transmission layer in which such interference fringes are recorded three-dimensionally and a metal layer facing the back surface thereof.

  When the reflection layer 12 includes a hologram or a diffraction grating having a relief structure, the reflection layer 12 may be a metal layer having a relief structure on the surface. Alternatively, the reflective layer 12 may include a dielectric multilayer film having a different refractive index between adjacent dielectric layers and having a relief structure at the interface.

  The reflective layer 12 may have uniform optical characteristics throughout. Alternatively, the reflective layer 12 may include a plurality of portions that are adjacent to each other in the direction perpendicular to the Z direction and have different optical characteristics.

  Here, as an example, it is assumed that the reflective layer 12 includes a volume hologram, and the optical characteristics are uniform throughout. A method for manufacturing such a volume hologram will be described later.

  The liquid crystal layer 14 faces the front surface of the reflective layer 12. The liquid crystal layer 14 is formed by solidifying a liquid crystal material. Typically, the liquid crystal layer 14 is a polymer birefringent layer formed by curing a polymerizable liquid crystal material having fluidity with ultraviolet rays or heat.

  The liquid crystal layer 14 includes a plurality of liquid crystal portions 141 to 143 having different mesogen alignment states. Here, as an example, it is assumed that the mesogen is aligned substantially parallel to the X direction in the liquid crystal portion 141, aligned substantially parallel to the Y direction in the liquid crystal portion 142, and not aligned in the liquid crystal portion 143.

  The liquid crystal portions 141 to 143 form a latent image, and the latent image is visualized when observed under a specific condition using a polarizer. A method of forming a liquid crystal layer including portions with different alignment states and the visual effect of the latent image will be described later.

  The intermediate layer 13 is interposed between the reflective layer 12 and the liquid crystal layer 14. The intermediate layer 13 has optical transparency and is typically transparent. The intermediate layer 13 is typically optically isotropic.

  The intermediate layer 13 includes, for example, a resin. The intermediate layer 13 plays a role of improving the adhesion between the reflective layer 12 and the liquid crystal layer 14.

  As the material of the intermediate layer 13, for example, a resin such as a thermoplastic resin can be used. As resin or the material which the intermediate | middle layer 13 contains, an acrylic resin, a urethane resin, an epoxy resin, a polyester resin, or a vinyl resin can be used individually or in combination, for example.

  The intermediate layer 13 may have a single layer structure or a multilayer structure. The intermediate layer 13 can be omitted.

  The protective layer 15 covers the front surface of the liquid crystal layer 14. The protective layer 15 is a light transmissive layer having light transparency, and is typically transparent. In this case, the protective layer 15 may be colorless and transparent, or may be colored and transparent. The protective layer 15 is typically optically isotropic.

  The protective layer 15 plays a role as a protective layer that makes it difficult to cause damage and light degradation of the liquid crystal layer 14 and suppresses degradation of an image displayed by the security device 10. The protective layer 15 may have a single layer structure or a multilayer structure.

  The protective layer 15 is made of resin, for example. Examples of the material of the protective layer 15 include thermoplastic resins such as acrylic resin, urethane resin, vinyl chloride resin-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin, polystyrene resin, and polyimide resin, and thermosetting resin. , Or UV or electron beam curable resins can be used alone or in combination.

  This security device 10 can be manufactured, for example, by the following method. First, a method for manufacturing the reflective layer 12 will be described.

FIG. 3 is a diagram schematically illustrating an example of a volume hologram manufacturing apparatus.
The manufacturing apparatus 20 includes a light source (not shown) such as a laser and an optical system. The optical system includes a beam splitter (not shown), a mirror and / or a prism (not shown), lenses 21 and 22, and a diffusion plate 23.

Beam splitter splits the laser beam laser was discharged into two laser beams L _0. The mirror and / or the prism guide these laser beams L ₀ to the lenses 21 and 22, respectively.

The lens 21 faces the front surface of the photosensitive material layer 12 ′ where interference fringes are to be recorded. The optical axis of the lens 21 and the normal line of the photosensitive material layer 12 ′ make an angle α. The lens 21 converts one of the laser beams L ₀ into recording reference light L _ref 1 that is diverging light, and the reference light L _ref 1 illuminates the front surface of the photosensitive material layer 12 ′.

The lens 22 faces the back surface of the photosensitive material layer 12 ′ with the diffusion plate 23 interposed therebetween. The optical axis of the lens 22 and the normal line of the photosensitive material layer 12 ′ form an angle β. The lens 22 converts the other laser beam L ₀ into divergent light, and illuminates one main surface of the diffusion plate 23 with the divergent light. The diffuser plate 23 emits object light L _obj which is scattered light from the other main surface, and illuminates the back surface of the photosensitive material layer 12 ′ with this object light L _obj .

  The reflective layer 12 can be obtained, for example, by recording interference fringes three-dimensionally on the photosensitive material layer 12 ′ using this apparatus 20. Here, as an example, a photosensitive material layer 12 ′ is formed on the base material 11, and a laminate of the base material 11 and the reflective layer 12 is manufactured using the apparatus 20 shown in FIG. 3.

  Next, a laminate of the liquid crystal layer 14 and the protective layer 15 is manufactured. For example, first, the protective layer 15 having one main surface including the regions A1 to A3 is formed. The regions A1 to A3 correspond to the liquid crystal portions 141 to 143, respectively.

  Each of the regions A1 and A2 is provided with a plurality of grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction. In the region A1, the length direction of the groove is substantially parallel to the X direction. In the region A2, the length direction of the groove is substantially parallel to the Y direction. Region A3 is a flat surface. When such a structure is employed, as will be described in detail later, a liquid crystal layer 14 in which mesogens are aligned along the length direction of the grooves at positions corresponding to the regions A1 and A2 is obtained.

Here, a structure that can be employed in each of the regions A1 and A2 and a method for forming the structure will be described in detail.
For each of the regions A1 and A2, for example, a structure in which a plurality of grooves are arranged in parallel in the width direction at equal intervals can be employed.

  These grooves may not be parallel to each other. However, the closer these grooves are to parallel, the easier the long axes of mesogens are aligned in each of the liquid crystal portions 141 and 142. The angle formed by these grooves is, for example, 5 ° or less, and typically 3 ° or less.

  In each of the regions A1 and A2, these grooves may be arranged vertically and horizontally. The lengths of the grooves may be equal to each other or different from each other. Further, the distance between adjacent grooves in the length direction may be uniform or non-uniform. Furthermore, the distance between adjacent grooves in the width direction may be uniform or non-uniform. For example, in each of the regions A1 and A2, grooves having the same length may be arranged vertically and horizontally. Alternatively, grooves having various lengths may be randomly arranged in each of the regions A1 and A2.

  The protective layer 15 can be formed, for example, on a photosensitive resin material by a method of recording a hologram pattern using a two-beam interference method or a method of drawing a pattern by an electron beam. Alternatively, it can be formed by pressing a mold provided with a plurality of linear protrusions against the resin, as is done in the manufacture of surface relief holograms. For example, the protective layer 15 is a method in which an original plate provided with a plurality of linear protrusions is pressed against a thermoplastic resin layer formed on a base material (not shown) while applying heat, that is, a heat embossing method. Is obtained. Alternatively, the protective layer 15 is formed by applying an ultraviolet curable resin on a substrate (not shown) and irradiating the ultraviolet ray from the substrate side while pressing the original to cure the ultraviolet curable resin, and then removing the original. It is also possible to form.

  According to these methods, a plurality of regions having different groove length directions can be formed in one plane. Further, according to these methods, a plurality of regions having different groove depths, widths, and / or grooves can be formed in one plane.

  The original plate can be obtained, for example, by performing electroforming of a mother die obtained by a method of recording a hologram pattern using a two-beam interference method, a method of drawing a pattern by an electron beam, or a method of cutting by a cutting tool. It is done. When the protective layer 15 does not have such a variety as described above, an alignment process such as a rubbing process may be performed.

  The depth of these grooves is, for example, in the range of 0.05 μm to 1 μm. The length of the groove is, for example, 0.5 μm or more. The pitch of the grooves is, for example, 0.1 μm or more, and typically 0.75 μm or more. The pitch of the grooves is, for example, 10 μm or less, and typically 2 μm or less. In order to orient mesogens with a high degree of order, it is advantageous that the pitch of the grooves is small.

  The liquid crystal layer 14 is formed on the protective layer 15 formed by the method described above, for example. The liquid crystal layer 14 is formed by solidifying a liquid crystal material.

  For example, a photopolymerizable nematic liquid crystal material having fluidity is applied on the protective layer 15. When a liquid crystal material is applied to the protective layer 15, mesogens of the liquid crystal material are arranged along the length direction of the groove. If necessary, the orientation of the mesogen is promoted by heating. Next, the liquid crystal material is solidified while maintaining the alignment state of the mesogen. For example, the liquid crystal material is irradiated with ultraviolet rays to cause polymerization thereof.

  When the liquid crystal material is solidified with the mesogen alignment state substantially maintained, liquid crystal portions 141 to 143 having different mesogen alignment states are obtained. In this example, a liquid crystal portion 141 in which mesogens are aligned in the X direction, a liquid crystal portion 142 in which mesogens are aligned in the Y direction, and a liquid crystal portion 143 in which mesogens are not aligned are obtained.

Refractive index for alignment direction of the mesogens is extraordinary refractive index n _e, the refractive index in the direction orthogonal to the orientation direction is the ordinary index n _o. Then, the refractive index n _e is greater than the refractive index n _o. Therefore, the slow axis of the liquid crystal portion 141 is parallel to the X direction, and the fast axis is parallel to the Y direction. Further, the slow axis of the liquid crystal portion 142 is parallel to the Y direction, and the fast axis is parallel to the X direction. The liquid crystal portion 143 is optically substantially isotropic.

  Further, on the surface of the liquid crystal layer 14 obtained by such a method facing the protective layer 15, a plurality of linear convex portions are provided corresponding to the plurality of grooves provided on the surface of the protective layer 15. Yes. When a structure in which a plurality of grooves are arranged substantially in parallel at equal intervals in the width direction is employed in the regions A1 and A2, the difference in refractive index between the liquid crystal layer 14 and the protective layer 15 is sufficiently increased, so that the liquid crystal A diffraction grating can be constituted by linear protrusions or grooves provided on the surface of the layer 14. When a structure in which a plurality of grooves are arranged in parallel at irregular intervals in the width direction is employed in the regions A1 and A2, the difference in refractive index between the liquid crystal layer 14 and the protective layer 15 is sufficiently increased. The unidirectional diffusion pattern can be constituted by linear protrusions or grooves provided on the surface of the liquid crystal layer 14. In this unidirectional diffusion pattern, the diffusivity in the plane perpendicular to the length direction of the linear protrusions or grooves is perpendicular to the main surface of the liquid crystal layer 14 and the length of the linear protrusions or grooves. It is a pattern showing a larger light diffusion characteristic, that is, light scattering anisotropy, compared with the diffusivity in a plane parallel to the vertical direction.

  Here, as an example, each of the regions A1 and A2 adopts a structure in which a plurality of grooves are arranged substantially in parallel at equal intervals in the width direction. Here, the difference in refractive index between the liquid crystal layer 14 and the protective layer 15 is sufficiently small, and the linear protrusions or grooves provided in each of the liquid crystal portions 142 to 144 are diffraction gratings and unidirectional diffusion patterns. None of these are configured.

  As described above, the liquid crystal layer 23 in which the orientation of the major axis of liquid crystal molecules or mesogens is fixed is obtained. Here, a nematic liquid crystal material is used as the material of the liquid crystal layer 23, but a cholesteric liquid crystal material or a smectic liquid crystal material may be used. Further, the material of the liquid crystal layer 23 may be thermally polymerizable. In this case, the liquid crystal material may be cured by heating.

  Next, the laminate of the liquid crystal layer 14 and the protective layer 15 is bonded to the laminate of the substrate 11 and the reflective layer 12. For example, an adhesive layer is formed on at least one of the liquid crystal layer 14 and the reflective layer 12, and the previous laminate is bonded with the adhesive layer interposed therebetween. Thereby, while forming the intermediate | middle layer 13, the security device 10 shown in FIG.1 and FIG.2 is obtained.

  Next, an image displayed by the security device 10 will be described. First, a phenomenon that occurs when the reflective layer 12 is illuminated will be described.

  FIG. 4 is a diagram schematically showing how a volume hologram manufactured by the method shown in FIG. 3 reproduces an image by illuminating with a reference light for reproduction.

In FIG. 4, reference numeral 31 indicates a light source that emits white light as the reproduction reference light L _ref 2. Moreover, in FIG. 4, the reflective layer 12 is a volume hologram manufactured by the method shown in FIG.

The front surface of the reflective layer 12 is illuminated with the reproduction reference light L _ref 2 as follows. That is, the spread angle and the incident angle of the reproduction reference light L _ref 2 are made equal to the spread angle and the incident angle of the recording reference light L _ref 1 described with reference to FIG. Thus, the reflective layer 12 emits the reproduction light L _rpr substantially equal to the object light L _obj described with reference to FIG.

As is clear from this, the reflective layer 12 exhibits a high reflectance under specific conditions and has a low reflectance under other conditions. In other words, the illumination conditions for the reflective layer 12 exhibiting high reflectivity are limited, and the angle range in which the reproduction light L _rpr as reflected light can be observed when illuminated under these conditions is limited.

The angle range in which the reproduction light L _rpr can be observed varies depending on the size of the diffusion plate 23 shown in FIG. 3 and the distance between the diffusion plate 23 and the photosensitive material layer 12 ′. When the angle range in which the reproduction light L _rpr can be observed is reduced, the reproduction light L _rpr becomes higher in intensity.

Further, the emission angle β of the reproduction light L _rpr is equal to the incident angle β of the object light L _obj shown in FIG. That is, the exit angle β of the reproduction light L _rpr can be controlled by the incident angle β of the object light L _obj .

  Next, an image that is visible when the security device 10 shown in FIGS. 1 and 2 is irradiated with white light and observed with the naked eye will be described. Here, it is assumed that the reflectances of the front surface and the back surface of the reflective layer 12 and the objects located on the back surface side thereof are sufficiently small so that the reflection by them can be ignored. For example, the security device 10 further includes a colored layer having a high absorption rate, for example, a black layer on the back side of the reflective layer 12, or the security device 10 is supported by an article having a low reflection rate.

  White light is light composed of non-polarized light having all wavelengths in the visible region. 1 and 2 and other drawings, reference numerals 101 to 103 denote display units obtained by dividing the security device 10 along a boundary parallel to the Z direction. Specifically, in the security device 10, the part corresponding to the liquid crystal part 141 is the display unit 101, the part corresponding to the liquid crystal part 142 is the display unit 102, and the part corresponding to the liquid crystal part 143 is the display unit 103. It is.

  When the security device 10 is irradiated with white light and observed with the naked eye, the display units 101 to 103 cannot or cannot be distinguished from each other as shown in FIG. This will be described in more detail.

  White light as illumination light incident on the display unit 101 passes through the protective layer 15 and the liquid crystal portion 141 shown in FIG. 2 in this order. A plurality of grooves are provided on the front surface of the liquid crystal portion 141, but the difference in refractive index between the liquid crystal layer 14 and the protective layer 15 is sufficiently small. Therefore, this incident light is ideally transmitted through the protective layer 15 and the liquid crystal portion 141 in this order without causing any scattering or diffraction.

The light transmitted through the liquid crystal portion 141 passes through the intermediate layer 13 and enters the reflective layer 12. The reflection layer 12 generates the reproduction light L _rpr described with reference to FIG. 4 from a part of the light incident in the oblique direction, and transmits the remaining light. The light transmitted through the reflective layer 12 is absorbed by an object located on the back side of the reflective layer 12.

The reproduction light L _rpr passes through the intermediate layer 13, the liquid crystal portion 141, and the protective layer 15 in this order. The observer perceives the reproduction light L _rpr when the observation angle is within a specific range, and does not perceive the reproduction light L _rpr when the observation angle is outside the previous range.

Therefore, the display unit 101 looks like a color derived from the reproduction light L _rpr within an angular range in which the reproduction light L _rpr can be observed. Within the angle range where the reproduction light L _rpr cannot be observed, the display unit 101 looks dark, for example, black.

  The display unit 102 differs from the display unit 101 in the orientation of mesogens, but the observer cannot perceive the difference. Further, the display unit 102 is different from the display unit 101 in the length direction of the groove, but as described above, the difference in refractive index between the liquid crystal layer 14 and the protective layer 15 is sufficiently small. Therefore, the display unit 102 looks the same color as the display unit 101.

  The display unit 103 is different from the display unit 101 in that no groove is provided and the mesogen is not oriented. The observer cannot perceive the difference in the orientation state of the mesogen. Therefore, the display unit 103 looks the same color as the display unit 101.

  In this way, the display units 101 to 103 look the same color. Accordingly, when the security device 10 is irradiated with white light and observed with the naked eye, the display units 101 to 103 cannot or cannot be distinguished from each other as shown in FIG.

  Next, an image seen when the security device 10 is observed through a polarizer will be described. Here, as an example, a linearly polarizing film is used as the polarizer.

  FIG. 5 is a plan view schematically showing an example of an image that can be observed when the security device shown in FIGS. 1 and 2 and a linearly polarizing film are overlaid.

  In FIG. 5, when the security device 10 and the absorption type linearly polarizing film 50 shown in FIGS. 1 and 2 are viewed from the polarizing film 50 side, the transmission axis of the polarizing film 50 is in the X direction. Are stacked in a clockwise direction at an angle of 45 °. In FIG. 5, it is assumed that the front surface of the polarizing film 50 is illuminated from a direction perpendicular to the X direction and inclined with respect to the Z direction, and the security device 10 is observed from the Z direction through the polarizing film 50. ing. In this case, as shown in FIG. 5, the display units 101 to 103 cannot or cannot be distinguished from each other. This will be described in more detail.

  When the polarizing film 50 is irradiated with white light as illumination light, the linear polarizing film 50 transmits linearly polarized light having a polarization plane parallel to its transmission axis (vibration plane of the electric field vector), and a polarization plane perpendicular to the transmission axis. Absorbs linearly polarized light having

  The linearly polarized light incident on the display unit 101 passes through the protective layer 15 and the liquid crystal portion 141 shown in FIG. 2 in this order. In the liquid crystal portion 141, mesogens are aligned substantially parallel to the X direction. That is, when viewed from the polarizing film 50 side, the slow axis of the liquid crystal portion 141 is parallel to the direction rotated 45 ° counterclockwise with respect to the transmission axis of the polarizing film 50. Therefore, the previous linearly polarized light is converted into right circularly polarized light or right elliptically polarized light by passing through the liquid crystal portion 141.

  These right circularly polarized light and right elliptically polarized light are transmitted through the intermediate layer 13 and are incident on the reflective layer 12. The reflective layer 12 does not reflect light incident from a direction perpendicular to the X direction and inclined with respect to the Z direction. Therefore, the display unit 101 looks dark, for example, black.

  The display unit 102 and the display unit 101 are different only in that the length direction of the groove is different by 90 ° and the orientation direction of the mesogen is different by 90 °. Accordingly, the display unit 102 looks dark, for example, black, like the display unit 102.

  The display unit 103 is different from the display unit 101 only in that no grooves are provided and mesogens are not oriented. Accordingly, the display unit 103 looks dark, for example, black, like the display unit 102.

  Thus, the display units 101 to 103 appear dark, for example, black. Therefore, as shown in FIG. 5, the display units 101 to 103 are impossible or difficult to distinguish from each other.

  In addition, when the reflective layer 12 shows a high reflectance regardless of which direction is illuminated, when the polarizing film 50 and the security device 10 are overlapped and observed as described with reference to FIG. And 102 can be easily distinguished from the display unit 103. For example, it is assumed that the reflective layer 12 has a mirror surface, illuminates the polarizing film 50 from the Z direction, and observes the security device 10 from the Z direction through the polarizing film 50. In this case, the display units 101 and 102 appear to be colored in the same color, and the display unit 103 looks silvery white.

  FIG. 6 is a perspective view schematically showing another example of an image that can be observed when the security device shown in FIGS. 1 and 2 and a linearly polarizing film are overlaid.

  FIG. 6 shows the same conditions as those described with reference to FIG. 5 except that the observation direction is tilted in the direction perpendicular to the Z direction in the plane perpendicular to the X direction. I draw an observable image. Also in this case, the reflective layer 12 does not reflect incident light. Accordingly, the display units 101 to 103 appear dark, for example, black. Therefore, the display units 101 to 103 are impossible or difficult to distinguish from each other.

  FIG. 7 is a perspective view schematically showing still another example of an image that can be observed when the security device shown in FIGS. 1 and 2 and a linearly polarizing film are overlaid.

  In FIG. 7, the security device 10 and the polarizing film 50 can be observed under the same conditions as described with reference to FIG. 6 except that the security device 10 and the polarizing film 50 are rotated by 90 ° around their normals. I'm drawing a statue. Under such observation conditions, when the incident angle of the illumination light is appropriately set, the reflective layer 12 diffracts the incident light and emits the diffracted light as reflected light. Therefore, as will be described below, the latent images formed by the display units 101 to 103 are visualized.

  When the polarizing film 50 is irradiated with white light as illumination light, the linear polarizing film 50 transmits linearly polarized light having a polarization plane parallel to the transmission axis and absorbs linearly polarized light having a polarization plane perpendicular to the transmission axis. .

  The linearly polarized light incident on the display unit 101 passes through the protective layer 15 and the liquid crystal portion 141 shown in FIG. 2 in this order. This linearly polarized light is converted into right circularly polarized light or right elliptically polarized light by passing through the liquid crystal portion 141.

  These right circularly polarized light and right elliptically polarized light are transmitted through the intermediate layer 13 and are incident on the reflective layer 12. The reflective layer 12 diffracts light incident at an incident angle α from a direction perpendicular to the Y direction, and emits diffracted light as left circularly polarized light and left elliptically polarized light at an exit angle β in a direction perpendicular to the Y direction.

  The left circularly polarized light and the left elliptically polarized light as the reflected light are transmitted through the intermediate layer 13, the liquid crystal portion 141, and the protective layer 15 in this order. The reflected light passes through the liquid crystal portion 141 and is converted into linearly polarized light, elliptically polarized light, or circularly polarized light according to the wavelength.

  Accordingly, only the light component in a part of the wavelength range of the reflected light from the display unit 101 is transmitted through the polarizing film 50, and the observer perceives this transmitted light. Therefore, the display unit 101 appears colored.

  In the display unit 102, like the display unit 101, the liquid crystal layer 14 has birefringence. Therefore, as is clear from the description regarding the display unit 101, the display unit 102 also appears colored. However, the display unit 102 differs from the display unit 101 in the orientation of mesogens. Therefore, the display unit 102 looks a different color from the display unit 101.

  In the display unit 103, unlike the display units 101 and 102, the liquid crystal layer 14 does not have birefringence. Therefore, the display unit 103 emits linearly polarized light having a polarization plane parallel to the transmission axis of the polarizing film 50 as reflected light. Therefore, for example, when the diffracted light emitted from the reflective layer 12 is white light, the display unit 103 looks white.

  In this way, the display units 101 to 103 look different colors. Therefore, the display units 101 and 102 can be easily discriminated from the display unit 103 under the observation conditions shown in FIG. 7, and in addition, the display unit 101 can be discriminated from the display unit 102.

  As described above, the security device 10 visualizes the latent image only when observed under special conditions. That is, the security device 10 has a special visual effect, and it is difficult to realize that a latent image is recorded.

  In addition, the security device 10 displays a bright image when the latent image is visualized. Therefore, the visualized image can be determined with high accuracy.

  The optical characteristics described with reference to FIG. 7 can be confirmed by visual observation if, for example, the polarizing film 50 is used. Further, the optical characteristics described with reference to FIG. 7 can be confirmed by using, for example, the following apparatus.

FIG. 8 is a diagram schematically illustrating an example of the determination device.
The determination device 30 includes a light source 31, a polarizer 50, an image sensor 32, and a processing unit and an output unit (not shown). In FIG. 8, a security device 10 is depicted as an example of a discrimination target.

The light source 31 irradiates the polarizer 50 with illumination light L _ref 2 that is reference light for reproduction. The illumination light L _ref 2 is white light as natural light, for example.

The polarizer 50 is a linearly polarizing film, for example. The polarizer 50 emits linearly polarized light toward the entire security device 10 or the display units 101 and 102 and their surrounding portions. Then, the polarizer 50 emits part of the reflected light from the security device 10 toward the image sensor 32 as reproduction light L _rpr .

The image sensor 32 reads a reproduction image formed on the light receiving surface by the reproduction light L _rpr and outputs the image data to the processing unit.

  For example, the processing unit processes the image data and generates a control signal for controlling the operation of the output unit. For example, the processing unit performs image processing on the image data output from the image sensor 32 as necessary, and compares it with reference data stored in advance. The processing unit outputs the first control signal to the output unit when the image data matches the reference data, and outputs the second control signal to the output unit when they are different. Output. Alternatively, the processing unit outputs a video signal as a control signal or a part thereof from the image data output from the image sensor 32 to the output unit.

The output unit outputs information that can be perceived by the operator under the control of the processing unit. The output unit is, for example, a display that displays an image corresponding to the reproduction image formed by the reproduction light L _rpr on the light receiving surface of the image sensor 32, or matches and / or mismatches between the image data and the reference data. A lamp or buzzer that informs the operator. Based on this information, the operator confirms whether or not the discrimination target is the security device 10.

  The security device 10 or the security device 10 and the polarizer 50 may be rotated by 90 ° around an axis parallel to the Z direction, and in this state, the reproduction image may be further read out. In this state, the security device 10 displays the image described with reference to FIG. Therefore, for example, the image data output by the image sensor 32 in this state is subjected to image processing as necessary, and compared with reference data stored in advance, whether or not the determination target is the security device 10. Can be determined with higher accuracy.

  In the above description, it is assumed that the reflective layer 12 includes a volume hologram, and the optical characteristics are uniform throughout. When the optical characteristics are made different between a part of the reflective layer 12 and another part, it can be determined whether or not the determination target is the security device 10 by the following method.

In the following description, as an example, the reflective layer 12 is positioned in the display unit 101 of the reflective layer 12 when the reference light L _ref 2 is irradiated under the conditions described with reference to FIG. It is assumed that the portion thus designed emits red light as the reproduction light L _rpr and the portion of the reflective layer 12 positioned in the display unit 102 is designed to emit green light as the reproduction light L _rpr . The spectrum of the reproduction light L _rpr optimizes the recording wavelengths of the object light L _obj and the reference light L _ref 1 described with reference to FIG. 3 in consideration of shrinkage or expansion of the photosensitive material used for the reflective layer 12. Can be controlled.

FIG. 9 is a diagram schematically illustrating another example of the determination device.
The discriminating device 30 shown in FIG. 9 is substantially the same as the discriminating device 30 shown in FIG. 8 except that it includes two photodetectors 32 a and 32 b instead of the image sensor 32. The photodetector 32a detects the reproduction light L _rpr a corresponding to the reflected light from the display unit 101. The photodetector 32b detects the reproduction light L _rpr b corresponding to the reflected light from the display unit 102.

  For example, the processing unit compares the color data output from the photodetectors 32a and 32b with first and second reference data stored in advance. And based on the result of these comparisons, the 1st or 2nd control signal mentioned above is outputted to an output part. In this way, for example, it is determined whether or not the determination target is the security device 10.

In the discrimination device 30 shown in FIG. 9, among the illumination light L _ref 2 emitted from one light source 31, a part L _ref 2a is used for illumination of the display unit 101 and another part L _ref 2b is displayed. It is used for illumination of the unit 102. The discriminating apparatus 30 may include a light source that emits the illumination light L _ref 2a and a light source that emits the illumination light L _ref 2b, instead of the light source 31.

  FIG. 10 is a graph showing an example of a spectrum detected by one photodetector of the determination device shown in FIG. FIG. 11 is a graph showing an example of a spectrum detected by the other photodetector of the determination device shown in FIG.

10 and 11, the horizontal axis indicates the wavelength, and the vertical axis indicates the luminance. In FIG. 10, a solid line La1 shows an example of the spectrum of the reproduction light L _rpr a detected by the photodetector 32a when white light is irradiated as illumination light. The broken line La2 is the light detected by the photodetector 32a when the intermediate layer 13, the liquid crystal layer 14, and the protective layer 15 are omitted from the security device 10 in the arrangement shown in FIG. An example of the spectrum is shown. In FIG. 11, a solid line Lb1 shows an example of a spectrum of the reproduction light L _rpr b detected by the photodetector 32b when the previous white light is irradiated as illumination light. The broken line Lb2 is the light detected by the photodetector 32b when the intermediate layer 13, the liquid crystal layer 14, and the protective layer 15 are omitted from the security device 10 in the arrangement shown in FIG. An example of the spectrum is shown.

The spectrum of the reproduction light L _rpr a detected by the photodetector 32 a depends on the reflection characteristics of the portion of the reflective layer 12 located in the display unit 101 and the absorption characteristics of the combination of the liquid crystal portion 141 and the polarizer 50. doing. Similarly, the spectrum of the reproduction light L _rpr b detected by the light detector 32 b includes the reflection characteristics of the portion of the reflective layer 12 located in the display unit 102 and the absorption characteristics of the combination of the liquid crystal portion 142 and the polarizer 50. And depends on.

  In this example, at each position corresponding to the display units 101 and 102, a design is adopted in which the absorptance in the wavelength region where the reflective layer 12 exhibits a large reflectance is smaller than the absorptance in other wavelength regions. Yes. Therefore, the photodetector 32a detects high luminance red light as shown in FIG. 10, and the photodetector 32b detects high luminance green light as shown in FIG. Therefore, the discrimination device 30 shown in FIG. 9 can detect colors peculiar to the display units 101 and 102 even when the sensitivity of the photodetectors 32a and 32b is low.

  In the discrimination device 30 shown in FIG. 9, the image sensor 32 described with reference to FIG. 8 may be used instead of the photodetectors 32a and 32b. Further, in the determination device 30 shown in FIG. 8, the photodetectors 32 a and 32 b described with reference to FIG. 9 may be used instead of the image sensor 32.

Various modifications can be made to the security device 10 described above.
For example, instead of providing the above-described groove in the regions A1 and A2, the groove may be provided at the interface between the intermediate layer 13 and the liquid crystal layer 14 as a light transmission layer. In this case, the protective layer 15 can be omitted. Alternatively, the security device 10 may employ the following structure.

FIG. 12 is a cross-sectional view schematically showing a security device according to a modification.
This security device 10 has the same configuration as the security device 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, in this security device 10, the length direction of the groove provided in the region A2 is substantially parallel to the X direction, and therefore the slow axis of the liquid crystal portion 142 is substantially parallel to the X direction. The liquid crystal portion 142 is thinner than the liquid crystal portion A1. That is, in this security device 10, the liquid crystal portions 141 and 142 have the same slow axis direction and different retardations.

  When the security device 10 is observed with the naked eye and under the conditions described with reference to FIGS. 5 and 6, the latent image formed by the display units 101 to 103 is visualized. There is no. When the security device 10 is observed under the conditions described with reference to FIG. 7, the display units 101 to 103 are formed due to the difference in retardation of the liquid crystal portions 141 to 143. The latent image is visualized. Specifically, the display units 101 to 103 look different colors.

  Here, the reason why the display units 101 and 102 look different colors will be described with reference to mathematical expressions.

The retardation Re of the liquid crystal layer depends on the film thickness d of the liquid crystal layer and its birefringence Δn, as shown in the following equation (1).
Re = Δn × d (1)
Here, a Δn = n _e -n _o.

A pair of linearly polarizing films face each other so that their transmission axes are perpendicular to each other, and a liquid crystal layer is interposed between them so that the optical axis forms an angle θ with respect to the transmission axis of the linearly polarizing film. When one linearly polarizing film is illuminated with light having a wavelength λ from its normal direction, the intensity of light incident on the liquid crystal layer is I ₀ and the intensity of light passing through the other linearly polarizing film is I. I can be represented by the following equation (2).
I = I ₀ × sin ² (2θ) × sin ² (Re × π / λ) (2)
As is apparent from equation (2), the wavelength λ at which the intensity I of the transmitted light is maximum depends on the retardation Re. As shown in equation (1), the retardation Re depends on the film thickness d of the liquid crystal layer and its birefringence Δn. That is, the wavelength λ at which the transmitted light intensity I is maximum depends on the film thickness d of the liquid crystal layer. Accordingly, the display units 101 and 102 appear to have different colors.

  The structure described with reference to FIG. 12 may be combined with the structure described with reference to FIGS.

  As described above, since the security device 10 visualizes a latent image only when observed under special conditions, it is difficult to realize that the latent image is recorded. Since the security device 10 displays a bright image when the latent image is visualized, the visualized image can be distinguished with high accuracy. That is, the security device 10 is not easily counterfeited and can be easily identified. Therefore, the security device 10 provides an excellent anti-counterfeit effect.

For example, when a labeled article including the security device 10 and an article that supports the security device 10 is an authentic product, if an article whose authenticity is unknown does not exhibit one or more of the above-described features, It can be determined that the article is non-genuine. That is, it is possible to discriminate an article whose authenticity is unknown between a genuine product and a non-authentic product. Therefore, for example, forgery of securities, banknotes, identification cards and other high-quality items such as printed matter such as credit cards and fine arts can be prevented or suppressed.
The invention described in the original claims is appended below.
[1]
One or more unit regions each made of a solidified liquid crystal material, having first and second main surfaces, each having a plurality of grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction A liquid crystal layer including the first main surface;
A light transmission layer covering the first main surface;
A security device comprising a reflection layer including a hologram or a diffraction grating facing the first main surface or facing the second main surface with the light transmission layer interposed therebetween.
[2]
The first main surface includes a plurality of the unit regions, and a first liquid crystal portion corresponding to one of the plurality of unit regions in the liquid crystal layer corresponds to the other one of the plurality of unit regions. The security device according to [1], wherein the length direction and / or the thickness is different from that of the two liquid crystal portions.
[3]
The security device according to [2], wherein a plurality of portions of the reflective layer respectively corresponding to the plurality of unit regions have the same optical characteristics.
[4]
The security device according to [2], wherein a portion of the reflective layer corresponding to the first liquid crystal portion has a reflection spectrum different from that of the portion corresponding to the second liquid crystal portion.
[5]
The security device according to any one of [1] to [4], wherein the reflective layer includes a volume hologram as the hologram or diffraction grating.
[6]
The security device according to any one of [1] to [4], wherein the reflective layer includes a relief structure as the hologram or diffraction grating.
[7]
[1] An article with a label comprising the security device according to any one of [6] and an article that supports the security device.

The top view which shows roughly the security device which concerns on 1 aspect of this invention. Sectional drawing along the II-II line of the security device shown in FIG. The figure which shows schematically an example of the manufacturing apparatus of a volume hologram. The figure which shows a mode that the volume hologram manufactured by the method shown in FIG. 3 reproduces | regenerates an image by illuminating with the reference light for reproduction | regeneration. The top view which shows roughly an example of the image which can be observed when the security device shown in FIG.1 and FIG.2 and a linearly polarizing film are piled up. The perspective view which shows schematically the other example of the image which can be observed when the security device shown in FIG.1 and FIG.2 and the linearly polarizing film are piled up. The perspective view which shows schematically the further another example of the image which can be observed when the security device shown in FIG.1 and FIG.2 and the linearly polarizing film are piled up. The figure which shows an example of a discrimination device schematically. The figure which shows the other example of a discrimination device schematically. The graph which shows an example of the spectrum which one photodetector of the discrimination device shown in FIG. 9 detects. The graph which shows an example of the spectrum which the other photodetector of the discrimination device shown in FIG. 9 detects. Sectional drawing which shows schematically the security device which concerns on one modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Security device, 11 ... Base material, 12 ... Reflective layer, 12 '... Photosensitive material layer, 13 ... Intermediate | middle layer, 14 ... Liquid crystal layer, 15 ... Protective layer, 20 ... Manufacturing apparatus, 21 ... Lens, 22 ... Lens , 23 ... Diffuser, 30 ... Discriminating device, 31 ... Light source, 32 ... Image sensor, 32a ... Photo detector, 32b ... Photo detector, 50 ... Polarizing film, 101 ... Display unit, 102 ... Display unit, 103 ... Display Department, 141 ... liquid crystal portion, 142 ... liquid crystal portion, 143 ... liquid crystal portion, A1 ... area, A2 ... area, A3 ... area, L ₀ ... laser beam, La1 ... solid line, La2 ... broken lines, Lb1 ... solid line, Lb2 ... broken lines , L _obj ... object light, L _ref 1 ... reference light for recording, L _ref 2 ... reference light for reproduction, L _ref 2a ... illumination light, L _ref 2b ... illumination light, L _rpr ... reproduction light, L _rpr a ... reproduction Light, L _rpr b ... reproducing light, α ... angle, β ... angle.

Claims (2)

A plurality of unit regions each made of a solidified liquid crystal material, having first and second main surfaces, each having a plurality of grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction; viewed first main surface including a first liquid crystal portion corresponding to one of said plurality of unit regions, the longitudinal and thickness and the second liquid crystal portion corresponding to the other one of said plurality of unit areas Liquid crystal layers with different
A light transmission layer covering the first main surface;
Comprising a said optical transmitting layer interposed therebetween or facing the first major surface or reflective layer of the volume hologram beam which faces the second major surface, the reflective layer, white as the reference light for reproduction light, the divergent angle and the incident angle, when irradiated to equal the divergence angle and the incident angle of the recording reference beam, of the reflective layer, the portion corresponding to the first liquid crystal portion red light security device emitted to the portion corresponding to the second liquid crystal portion, characterized in that for emitting green light. An article with a label, comprising the security device according to claim 1 and an article supporting the security device.

Images