JP5141108B2 - Optical element, labeled article, optical kit, and discrimination method - Google Patents

Description

  The present invention relates to a display technology that provides, for example, an anti-counterfeit effect, a decorative effect, and / or an aesthetic effect.

  A latent image may be used to prevent forgery. The latent image can be formed using, for example, line moire or intaglio printing.

  A latent image using line moire is obtained by superimposing an image to be a latent image and a large number of lines arranged at high density. When this image is observed with the naked eye, many lines make it difficult to identify, and hiding these lines facilitates identification.

  A latent image using intaglio printing is obtained by providing a concave pattern and / or a convex pattern in the ink layer. The image formed by the concave pattern and / or the convex pattern is difficult to identify when viewed from the front, and is visualized by observing from an oblique direction.

  Forgery prevention technology using line moiré or intaglio printing is relatively easy to determine authenticity. However, images formed by these methods are not necessarily indistinguishable when observed with the naked eye. Therefore, these latent images are easy to realize their existence.

  The latent image can also be formed using special inks such as fluorescent ink and infrared absorbing ink. The fluorescent ink is an ink that emits light when irradiated with ultraviolet rays, and a latent image formed using the fluorescent ink is visualized when irradiated with ultraviolet rays. The infrared absorbing ink is an ink having a high infrared absorption rate, and a latent image formed using the infrared absorbing ink is visualized by observing with an infrared camera, for example.

  Latent images formed using special inks are difficult to realize. However, the visualization requires a device such as an ultraviolet lamp or an infrared camera.

  The latent image can also be formed using a liquid crystal material. For example, a thin film pattern made of a solidified liquid crystal material such as a polymer liquid crystal material is formed on a substrate having light reflectivity. The mesogenic groups of the liquid crystal molecules are aligned in approximately one direction by, for example, performing an alignment process such as a rubbing process or a photo-alignment process on the base of the thin film pattern.

  This thin film pattern looks like an optically isotropic layer when viewed with the naked eye. Therefore, a latent image can be formed with this thin film pattern. Since this thin film pattern functions as a retardation layer, when observed through a polarizer, a change in brightness according to the angle formed by the slow axis and the light transmission axis of the polarizer occurs. That is, the latent image formed by the thin film pattern is visualized by observing through a polarizer.

  A latent image formed using a liquid crystal material is difficult to realize. In addition, the latent image can be visualized with a polarizer such as a polarizing film, and a large apparatus is not required. For this reason, anti-counterfeiting technology using a liquid crystal material has attracted high interest.

  For example, Patent Document 1 describes that an OVD (optically variable device) layer and a latent image forming layer are stacked. The latent image forming layer is made of, for example, a polymer liquid crystal material. The OVD layer is, for example, a hologram.

  When this laminate is observed with the naked eye, the visual effect of the hologram, that is, the rainbow color and the color change corresponding to the observation angle can be confirmed. The latent image formed by the latent image forming layer is visualized by observing through a polarizer. As described above, when the liquid crystal material and the hologram are combined, an image that changes variously can be formed. Therefore, a higher forgery prevention effect can be achieved as compared with the case where only the liquid crystal material is used.

However, progress in counterfeiting technology is significant. Therefore, further progress is desired in anti-counterfeiting technology.
JP 2001-63300 A

  An object of the present invention is to increase the variety of changes according to viewing conditions of an image displayed by an optical element including a solidified liquid crystal material.

  According to the first aspect of the present invention, one main surface includes one or more recess forming regions each having a plurality of first grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction. A light-transmitting concave portion forming layer, a liquid crystal layer made of a liquid crystal material supported and solidified by the main surface, and the first main surface facing the other main surface of the concave portion forming layer and having light scattering properties. A reflective layer; and a second reflective layer interposed between the concave portion forming layer and the liquid crystal layer and covering a part of the one or more concave portion forming regions. An optical element is provided in which a plurality of second grooves are provided corresponding to the plurality of first grooves on a surface of a portion covering the recess forming region.

  According to a second aspect of the present invention, there is provided a labeled article characterized by including the optical element according to the first aspect and an article supporting the optical element.

  According to the 3rd side surface of this invention, the optical kit characterized by including the optical element and polarizer which concern on a 1st side surface is provided.

  According to a fourth aspect of the present invention, there is provided a method for discriminating an article whose authenticity is unknown between an authentic product and a non-authentic product, wherein the authentic product supports the optical element according to the first aspect. An article of which the authenticity is unknown is observed with respect to the one main surface without the polarizer when observed from a direction inclined with respect to the one main surface without the polarizer. The same color as that observed from a direction perpendicular to the main surface is displayed, and when viewed from a direction perpendicular to the main surface through the polarizer, the light is perpendicular to the one main surface without the polarizer. A color different from that observed when viewed from the direction is displayed, and when viewed from a direction inclined with respect to the one principal surface through the polarizer, the color is perpendicular to the one principal surface without the polarizer. When observed from the direction and perpendicular to the main surface through the polarizer Whether or not it is authentic when it does not include a first display unit that displays a color different from that observed when it is observed and a second display unit that displays an interference color or exhibits light scattering anisotropy A determination method is provided that includes determining that an unknown article is a non-authentic item.

  According to the present invention, it is possible to increase the variety of changes according to the viewing conditions of the image displayed by the optical element including the solidified liquid crystal material.

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

  FIG. 1 is a plan view schematically showing an optical element according to the first embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II of the optical element shown in FIG. FIG. 3 is a plan view showing an example of a structure that can be employed in the recess formation region of the optical element shown in FIG. FIG. 4 is a plan view showing another example of a structure that can be employed in the recess forming region of the optical element shown in FIG. FIG. 5 is a plan view showing still another example of a structure that can be employed in the recess forming region of the optical element shown in FIG. FIG. 6 is a plan view showing still another example of a structure that can be employed in the recess forming region of the optical element shown in FIG. 1 and 2, the X direction is a direction parallel to the main surface of the optical element 10, and the Y direction is a direction parallel to the main surface of the optical element 10 and perpendicular to the X direction. The Z direction is a direction perpendicular to the X direction and the Y direction.

  The optical element 10 shown in FIG.1 and FIG.2 is a display body supported on the article | item which should be confirmed that it is a genuine product, for example. The optical element 10 includes a substrate 11, a first reflective layer 12, a recess forming layer 13, a second reflective layer 14, and a liquid crystal layer 15. The front surface of the optical element 10 is a surface on the liquid crystal layer 15 side.

  The base material 11 is, for example, a film or sheet made of a resin such as polyethylene terephthalate (PET). Fine irregularities are provided on the front surface of the substrate 11. The base material 11 may or may not have optical transparency. Moreover, the base material 11 may have a single layer structure, and may have a multilayer structure.

  The first reflective layer 12 is a reflective layer having light scattering properties, and covers the entire surface of the substrate 11. The first reflective layer 12 may cover only a part of the substrate 11.

  The front surface of the reflective layer 12 has a fine concavo-convex structure corresponding to the structure of the front surface of the substrate 11. The concavo-convex structure provided on the front surface of the reflective layer 12 irregularly reflects incident light in various directions.

  The reflective layer 12 is a metal layer, for example. As a material for the metal layer, for example, aluminum, silver, or an alloy thereof can be used. The metal layer can be formed, for example, by a vapor deposition method such as a vacuum evaporation method or a sputtering method.

The reflective layer 12 may be a single-layer or multilayer dielectric film having a fine uneven structure on the front surface. For example, when a single-layer dielectric film made of ZnO is used as the reflective layer 12, the color of the substrate 11 can be perceived when the optical element 10 is observed with the naked eye. Further, when the optical element 10 is observed through a polarizer, the visual effect given by the color of the substrate 11 can be added to the visual effect given by the liquid crystal layer 12 or the like. When a multilayer dielectric film is used as the reflective layer 12, the optical element 10 can be given wavelength selectivity. Therefore, it is possible to obtain a visual effect different from the case where a metal vapor deposition layer or a single-layer dielectric film is used as the reflective layer 12. The multilayer dielectric film is obtained by alternately depositing a high refractive index material such as zinc sulfide and a low refractive index material such as magnesium fluoride on the substrate 11.
Here, as an example, it is assumed that the reflective layer 12 is a metal layer.

  The recess forming layer 13 is light transmissive and covers the reflective layer 12. A plurality of first grooves are provided on the front surface of the recess forming layer 13. In this example, the front surface of the recess forming layer 13 includes three regions 131 to 133 each having a plurality of grooves, as shown in FIG.

  Each of the regions 131 to 133 is a recess forming region. Each of the regions 131 to 133 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. The regions 131 to 133 may have different groove length directions or may be the same. One or two of the regions 131 to 133 may be omitted. Alternatively, the front surface of the recess forming layer 13 may further include another region provided with a plurality of grooves.

  Here, as an example, the region 131 is provided with a groove whose length direction is substantially parallel to the X direction, and the region 132 is provided with a groove whose length direction is substantially parallel to the Y direction. The longitudinal direction of the groove provided in the region 133 is arbitrary, but here, as an example, it is assumed that an angle of 45 ° is formed with respect to the X direction.

  As shown in FIG. 2, the front surface of the recess forming layer 13 further includes a region 134 where no groove is provided. Region 134 can be omitted.

  Various structures can be employed for the recess forming regions 131 to 133. For example, as shown in FIG. 3, a structure in which a plurality of grooves are arranged in parallel in the width direction at equal intervals can be adopted for each of the recess forming regions 131 to 133.

  These grooves need not be parallel to each other, as shown in FIG. However, the closer these grooves are to parallel, the easier it is for the major axes of the liquid crystal molecules or their mesogenic groups to be aligned in the respective portions of the liquid crystal layer 15 corresponding to the recess forming regions 131 and 132. The angle formed by these grooves is, for example, 5 ° or less, preferably 3 ° or less.

  In each of the regions 131 to 133, 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 the grooves adjacent in the width direction may be uniform or non-uniform. For example, as shown in FIG. 5, grooves having the same length may be arranged vertically and horizontally in each of the recess forming regions. Or you may arrange | position the groove | channel of various length at random as shown in FIG.

  When the structure shown in FIGS. 3 to 5 is employed, the diffraction grating can be configured by these grooves by setting the grooves to be substantially parallel and appropriately setting the pitch. When the structure shown in FIG. 6 is adopted, a unidirectional diffusion pattern can be formed by these grooves. In this unidirectional diffusion pattern, the diffusivity in a plane perpendicular to the length direction of the groove is perpendicular to the main surface of the recess forming layer 13 and in a plane parallel to the length direction of the groove. It is a pattern showing a larger light diffusion characteristic, that is, light scattering anisotropy, compared with the diffusion capacity. Here, as an example, it is assumed that the grooves provided in each of the regions 131 to 133 constitute a diffraction grating.

  The recess forming layer 13 can be formed by, for example, a method of recording a hologram pattern on a photosensitive resin material using a two-beam interference method or a method of drawing a pattern with an electron beam. Alternatively, as is done in the manufacture of surface relief holograms, it can be formed by pressing a mold provided with fine linear projections onto the resin. For example, the recess forming layer 13 is a method in which a master plate provided with linear protrusions is pressed against a thermoplastic resin layer formed on a laminate of the base material 11 and the reflective layer 12 while applying heat. That is, it is obtained by a hot embossing method. Alternatively, the recess forming layer 13 is formed by applying an ultraviolet curable resin on the laminate of the base material 11 and the reflective layer 12, and curing the ultraviolet curable resin by irradiating ultraviolet rays from the base material 11 side while pressing the original. Then, it can be formed by a method of removing the original plate.

  According to these methods, it is possible to form a plurality of recess formation regions having different groove length directions in one plane. In addition, according to these methods, a plurality of recess formation 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 above-described diversity is not given to the recess forming layer, the groove may be formed by rubbing.

  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 align the liquid crystal molecules or their mesogenic groups with a high degree of order, it is advantageous that the pitch of the grooves is small.

  The second reflective layer 14 is a metal vapor deposition layer such as an aluminum vapor deposition layer, for example. The reflective layer 14 covers the entire recess forming region 133 of the main surface of the recess forming layer 13 and does not cover other regions.

  The reflective layer 14 may cover only a part of the recess forming region 133. Alternatively, the reflective layer 14 may further cover a part of the recess forming regions 131 and 132. The reflective layer 14 may further cover part or all of the region 134. In this case, the reflective layer 14 may further cover a part of the recess forming regions 131 and 132.

  The surface shape of the reflective layer 14 corresponds to the shape of the underlying surface. Here, a plurality of second grooves are provided on the surface of the reflective layer 14 in correspondence with the plurality of first grooves provided in the recess formation region 133. When the plurality of first grooves provided in the recess forming region 133 constitutes a diffraction grating, the second groove also constitutes a diffraction grating. Moreover, when the several 1st groove | channel provided in the recessed part formation area | region 133 comprises the unidirectional diffusion pattern, a 2nd groove | channel also comprises a unidirectional diffusion pattern.

  The liquid crystal layer 15 covers the recess forming layer 13 and the reflective layer 14. Hereinafter, portions of the liquid crystal layer 15 formed on the regions 131 to 134 are referred to as liquid crystal portions 151 to 154, respectively. In addition, regions of the optical element 10 corresponding to the liquid crystal portions 151 to 154 are referred to as display units 101 to 104, respectively.

  The liquid crystal layer 15 is made of a solidified liquid crystal material. That is, the liquid crystal layer 15 is formed by non-fluidizing a liquid crystal material having fluidity.

  The liquid crystal layer 15 is typically a polymer liquid crystal layer formed by curing a polymerizable liquid crystal material having fluidity with ultraviolet rays or heat. The polymer liquid crystal layer can be formed, for example, by the following method. First, a nematic liquid crystal material having photopolymerizability is applied on the recess forming layer 13 and the reflective layer 14. The liquid crystal material is then irradiated with ultraviolet light to cause their polymerization. Thereby, the liquid crystal layer 15 in which the orientation of the major axis of the liquid crystal molecules or their mesogenic groups is fixed can be obtained. A cholesteric liquid crystal material or a smectic liquid crystal material may be used as the material of the liquid crystal layer 15.

  Each of the recess forming regions 131 and 132 aligns the liquid crystal molecules included in the liquid crystal portion 151 or the mesogenic groups thereof along the length direction of the groove. Here, as an example, in each of the liquid crystal portions 151 and 152, the major axes of the mesogenic groups are aligned in substantially one direction. That is, here, the mesogenic group is aligned in the X direction in the liquid crystal portion 151 and is aligned in the Y direction in the liquid crystal portion 152.

The liquid crystal portions 151 and 152 have birefringence because the mesogenic groups are aligned. Since mesogenic groups in the liquid crystal portion 151 are oriented in the X direction, the refractive index for X-direction is the extraordinary ray refraction index n _e, the refractive index in the Y direction is the ordinary index n _o. Since the refractive index n _e is greater than the refractive index n _o, the slow axis of the liquid crystal part 151 is parallel to the X direction, fast axis is parallel to the Y direction. The slow axis of the liquid crystal portion 152 is parallel to the Y direction, and the fast axis is parallel to the X direction.

  Typically, in the liquid crystal portion 153, the mesogenic groups are not or are not oriented with as much order as the liquid crystal portions 151 and 152. Also, typically, the liquid crystal portion 154 is not aligned with a higher degree of order than the liquid crystal portion 153 or is not aligned. Here, as an example, in the liquid crystal portions 153 and 154, mesogenic groups are not aligned. That is, the liquid crystal portions 153 and 154 are assumed to be optically isotropic. Note that in the liquid crystal portion 154, for example, by performing an alignment process such as a rubbing process on the region 134, mesogenic groups can be aligned with a relatively high degree of order.

  Next, an image seen when the optical element 10 is irradiated with white light and observed with the naked eye will be described. White light is light composed of non-polarized light having all wavelengths in the visible region.

FIG. 7 is a plan view illustrating an example of an image displayed by the optical element illustrated in FIGS. 1 and 2.
When the optical element 10 is irradiated with white light and observed with the naked eye from the front, the display units 101, 102, and 104 cannot be distinguished from each other as shown in FIG. Is easily discriminated from the display units 101, 102, and 104. This will be described in more detail.

  White light as illumination light incident on the display unit 101 passes through the liquid crystal portion 151 shown in FIG. 2 and enters the region 131. Since the grooves provided in the region 131 constitute a diffraction grating, a part of the incident light enters the concave portion forming layer 13 as diffracted light. The diffracted light transmitted through the recess forming layer 13 is reflected by the reflective layer 12. Since the reflective layer 12 has light scattering properties, the reflected light is scattered light. This scattered light is transmitted through the recess forming layer 13. Although a diffraction grating is provided on the front surface of the recess forming layer 13, in addition to the reflected light from the reflective layer 12 being scattered light, the incident angle of illumination light varies in a normal environment. Therefore, the reflected light from the reflective layer 12 enters the liquid crystal portion 151 as scattered light. Thereafter, the scattered light passes through the liquid crystal portion 151, and the observer perceives the scattered light as display light. Therefore, the display unit 101 looks silvery white.

  The display unit 102 and the display unit 101 differ only in the length direction of the grooves constituting the diffraction grating, except for the planar shape. As is clear from the above description, when the display unit 101 is observed with the naked eye, the diffraction grating does not affect the display color or brightness. Therefore, the display unit 102 also looks silvery white.

  White light as illumination light incident on the display unit 103 passes through the liquid crystal portion 153 and enters the reflection layer 14. Since the grooves provided in the reflective layer 14 constitute a diffraction grating, the light reflected by the reflective layer 14 is diffracted light. The diffracted light passes through the liquid crystal portion 153, and the observer perceives the diffracted light as display light. Therefore, the display unit 103 looks rainbow. In other words, the display unit 103 displays the interference color.

  The display unit 104 is different from the display unit 101 only in that a groove is not provided in a corresponding portion of the recess forming layer 13 except for the planar shape, and the mesogen group is not oriented. As is clear from the above description, when the display unit 101 is observed with the naked eye, the diffraction grating does not affect the display color or brightness. Therefore, the display unit 104 also looks silvery white.

  In this way, the display units 101, 102, and 104 appear silver-white, and the display unit 103 appears rainbow. The display units 101, 102, and 104 have substantially the same brightness. Therefore, when the optical element 10 is irradiated with white light and observed with the naked eye from the front, the display units 101, 102, and 104 cannot be distinguished from each other as shown in FIG. The unit 103 can be easily distinguished from the display units 101, 102, and 104.

  When the optical element 10 is irradiated with white light and observed with the naked eye, the display colors of the display units 101, 102, and 104 remain silver white even when the observation angle is changed. The display color changes according to the observation angle. Further, when the optical element 10 is rotated around the normal line while the observation angle is tilted, the display colors of the display units 101, 102, and 104 remain silver white and the display color of the display unit 103 is rotated. It changes according to the angle.

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

  FIG. 8 is a plan view schematically showing an example of an image that can be observed when the optical element shown in FIGS. 1 and 2 and a linearly polarizing film are overlapped.

  In FIG. 8, when the optical element 10 and the absorption 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. In order to make an angle of 45 ° counterclockwise. When such an arrangement is adopted and this is observed from the front, as shown in FIG. 8, the display units 101 to 103 can be easily distinguished from the display unit 104, and the display units 101 and 102 are separated from the display unit 103. Discrimination is easy and discrimination from each other is impossible or difficult. This will be described in more detail.

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

The linearly polarized light incident on the display unit 101 is transmitted through the liquid crystal portion 151 shown in FIG. In the liquid crystal portion 151, the mesogenic groups 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 151 is parallel to the direction rotated 45 ° counterclockwise with respect to the transmission axis of the polarizing film 50. Therefore, for example, in the previous linearly polarized light, a light component having a certain wavelength λ ₀ is converted to right circularly polarized light by transmitting through the liquid crystal portion 151, and the remaining light component is transmitted through the liquid crystal portion 151. As a result, it is converted into right elliptical polarized light.

  These right circularly polarized light and right elliptically polarized light are incident on the region 131. Since the grooves provided in the region 131 constitute a diffraction grating, a part of the incident light enters the concave portion forming layer 13 as diffracted light.

  The right circularly polarized light and the right elliptically polarized light as the diffracted light transmitted through the recess forming layer 13 are reflected by the reflective layer 12. The right circularly polarized light and the right elliptically polarized light are respectively converted into left circularly polarized light and left elliptically polarized light by being reflected by the reflective layer 12. Moreover, since the reflective layer 12 has light scattering properties, this reflected light is scattered light.

  The left circularly polarized light and the left elliptical polarized light as the scattered light are transmitted through the recess forming layer 13. Although a diffraction grating is provided on the front surface of the recess forming layer 13, in addition to the reflected light from the reflective layer 12 being scattered light, the incident angle of illumination light varies in a normal environment. Therefore, the reflected light from the reflective layer 12 enters the liquid crystal portion 151 as scattered light.

Since this incident light is scattered light, it includes a light component traveling in the front direction and a light component traveling in an oblique direction. Of the light component traveling in the front direction, the left circularly polarized light having the specific wavelength λ ₀ is converted into linearly polarized light whose polarization plane is perpendicular to the transmission axis of the polarizing film 50 by passing through the liquid crystal portion 151. Then, the remaining light component is converted into left elliptically polarized light or left circularly polarized light, right elliptical polarized light or circularly polarized light by transmitting through the liquid crystal portion 151.

  That is, when focusing only on the light component having a polarization plane parallel to the transmission axis of the polarizing film 50, the ratio of the intensity of the light component emitted by the display unit 101 to the intensity of the light component incident on the display unit 101 is It has wavelength dependency. In other words, the ratio of the intensity of display light emitted from the polarizing film 50 to the intensity of illumination light incident on the polarizing film 50 has wavelength dependency. Therefore, the display unit 101 appears colored. The reason why the display unit 101 appears colored will be described later with reference to mathematical expressions.

  The display unit 102 and the display unit 101 are different only in that the length directions of the grooves constituting the diffraction grating are different by 90 °, except for the planar shape. Therefore, the display unit 102 behaves in the same manner as described for the display unit 101 except that the rotation direction of the polarization plane of circularly polarized light or elliptically polarized light is reversed. Therefore, the display unit 102 looks colored in the same manner as the display unit 101.

  The liquid crystal portion 153 of the display unit 103 is optically isotropic. Therefore, the light emitted from the display unit 103 is ideally transmitted through the polarizing film 50 without being absorbed by the polarizing film 50. Therefore, the display unit 103 looks rainbow.

  The display unit 104 is different from the display unit 101 only in that a groove is not provided in a corresponding portion of the recess forming layer 13 except for the planar shape, and the mesogen group is not oriented. That is, in the display unit 104, the region 134 does not include a diffraction grating, and the liquid crystal portion 154 is optically isotropic. Therefore, the light emitted from the display unit 104 is ideally transmitted through the polarizing film 50 without being absorbed by the polarizing film 50. Therefore, the display unit 104 looks silvery white.

  Typically, in the liquid crystal portions 153 and 154, the mesogenic groups are slightly aligned. That is, typically, the liquid crystal portions 153 and 154 are slightly optically anisotropic. The reason will be described below.

  When grooves are provided on the front surface of the recess forming layer 13, the grooves may affect the orientation of the mesogenic group at the upper part of the grooves. In addition, when the base of the liquid crystal layer 15 is flat and the alignment treatment is not performed, the method of forming the liquid crystal layer 15 may affect the alignment of the mesogenic groups. For example, when the material of the liquid crystal layer 15 is applied in one direction, the mesogenic group may be slightly aligned even when the base of the liquid crystal layer 15 is flat and not subjected to alignment treatment.

  For this reason, the mesogenic groups are slightly aligned in the liquid crystal portions 153 and 154, and as a result, the liquid crystal portions 153 and 154 may be slightly optically anisotropic. In this case, however, the display units 103 and 104 may be slightly colored, but this does not affect the appearance of the display units or the discrimination between the display units.

  Thus, the display units 101 and 102 appear colored, the display unit 103 appears rainbow, and the display unit 104 appears silvery white. The display units 101 and 102 have substantially the same brightness. Therefore, when the polarizing film 50 is superimposed on the optical element 10 and irradiated with white light and observed from the front, as shown in FIG. 8, it is easy to discriminate from the display units 101 to 103. 102 are easy to distinguish from the display unit 103 and are impossible or difficult to distinguish from each other.

  At this time, it is theoretically impossible to distinguish the display units 101 and 102 from each other. However, due to the accuracy of the grooves provided in the polarizing film 50 and the recessed portion forming layer 3, the display light spectrum differs between the display portions 101 and 102, and as a result, they can be distinguished from each other. There is.

Here, the reason why the display unit 101 appears colored will be described with reference to mathematical expressions. The liquid crystal portion 151 serves as a quarter-wave plate for light having a wavelength λ ₀ .

It can be considered that the linearly polarized light having the wavelength λ ₀ emitted from the polarizing film 50 in the normal direction is the sum of the linearly polarized light component whose polarization plane is perpendicular to the X direction and the linearly polarized light component whose polarization plane is perpendicular to the Y direction. it can. As described above, the refractive index in the X direction of the liquid crystal part 151 is extraordinary refractive index n _e, the refractive index in the Y direction is the ordinary index n _o. Thus, the liquid crystal part 151, these linear polarization component, providing a phase difference of lambda _0/4 in each of the forward path and the backward path. That is, the liquid crystal part 151 gives a phase difference of lambda _0/2 in total of these linearly polarized light components. Therefore, the light with the wavelength λ ₀ emitted from the display unit 101 in the normal direction cannot pass through the polarizing film 50.

By the way, the retardation Re 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 orthogonal to each other, and a liquid crystal layer is interposed between them so that the optical axis forms an angle of 45 ° 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 (Re × π / λ) (2)
The birefringence Δn has wavelength dependence, and the birefringence Δn and the wavelength n are not in a proportional relationship. Therefore, as is clear from equation (2), the spectrum of transmitted light has a different profile from the spectrum of incident light.

  Thus, when the liquid crystal layer is sandwiched between a pair of linearly polarizing films, transmitted light having a spectrum profile different from that of incident light can be obtained. Similarly, when the liquid crystal layer is sandwiched between the linearly polarizing film and the reflective layer, reflected light having a spectrum profile different from that of the incident light can be obtained. For this reason, the display unit 101 appears colored.

FIG. 9 is a perspective view showing another example of an image displayed by the optical element shown in FIGS.
As shown in FIG. 9, when the observation direction is tilted in the plane perpendicular to the X direction from the state shown in FIG. 8, the display color of the display unit 103 derived from the diffraction grating changes, and the display units 101 and 102 Display colors change to different colors. As a result, the display units 101 and 102 can be easily distinguished from each other. For example, if the display units 101 and 102 look orange when observed from the normal direction, the display unit 101 changes to red by tilting the observation direction in a plane perpendicular to the X direction. The part 102 changes to green. The reason for the color change that occurs in the display units 101 and 102 will be described below.

When the observation angle θ is tilted, the effective birefringence Δn ′ of the liquid crystal layer changes from the birefringence Δn, and the effective film thickness d ′ of the liquid crystal layer shown in the following equation (3) is It becomes larger than twice the actual film thickness d of the liquid crystal layer.
d ′ = 2d / cos θ (3)
That is, the retardation Re shown in the above equation (1) changes according to the observation angle, and therefore the intensity I shown in the above equation (2) changes. As a result, the spectrum profile of the display light changes according to the observation angle.

  The birefringence Δn ′ depends on the incident angle of the illumination light and the angle formed by the projection onto the principal surface of the liquid crystal layer, which is parallel to the propagation direction of the illumination light, with respect to the optical axis of the liquid crystal layer. Specifically, the birefringence Δn ′ of the liquid crystal portion 151 does not change even when the observation direction is tilted in a plane perpendicular to the X direction because its optical axis is parallel to the X direction. On the other hand, the birefringence Δn ′ of the liquid crystal portion 152 changes as the observation direction is tilted in a plane perpendicular to the X direction because its optical axis is parallel to the Y direction.

  As described above, the display unit 101 causes a color change due to an effective change in the film thickness d ′ when the observation direction is tilted in a plane perpendicular to the X direction. On the other hand, when the viewing direction is tilted in a plane perpendicular to the X direction, the display unit 101 changes color due to an effective change in film thickness d ′ and an effective change in birefringence Δn ′. Produce. Therefore, when the observation direction is tilted in a plane perpendicular to the X direction, the display colors of the display units 101 and 102 change to different colors, and as a result, the display units 101 and 102 can be easily distinguished from each other. Become.

FIG. 10 is a perspective view showing still another example of an image displayed by the optical element shown in FIGS.
FIG. 10 shows an image that can be observed when the optical element 10 is rotated by 90 ° around the normal line from the state shown in FIG. When the optical element 10 is rotated 90 ° around the normal line together with the polarizing film 50 while the observation direction is oblique, the display color is switched between the display unit 101 and the display unit 102. When the rotation angle is increased, the display color of the display unit 103 derived from the diffraction grating is changed within the range of 0 ° to 45 ° with an increase in the effective grating constant of the diffraction grating, which is 45 °. In the range of up to 90 °, the opposite change occurs. Therefore, the display colors of the display unit 103 are the same before and after the rotation. The color change described with reference to FIG. 10 also occurs when only the optical element 10 is rotated by 90 ° around the normal from the state shown in FIG.

  As described above, the image displayed by the optical element 10 shown in FIGS. 1 and 2 changes variously according to the observation conditions as illustrated below.

The display units 101 and 102 display the same color when viewed from the normal direction without the polarizing film 50.
The display units 101 and 102 display the same color when observed from the normal direction without the polarizing film 50 and when observed from the oblique direction without the polarizing film 50.
The display units 101 and 102 display substantially the same color when viewed from the normal direction through the polarizing film 50.

The display units 101 and 102 display different colors when observed from an oblique direction through the polarizing film 50.
The display units 101 and 102 display different colors when observed from the normal direction through the polarizing film 50 and when viewed from an oblique direction through the polarizing film 50.
The display units 101 and 102 cause a color change when the position and orientation of the polarizing film 50 are fixed and the optical element 10 is observed from an oblique direction through the polarizing film 50 while rotating around the normal line.

The display units 101 and 102 cause a color change when the position and orientation of the optical element 10 are fixed and the polarizing film 50 is observed from an oblique direction while rotating the polarizing film 50 around the normal line.
The display units 101 and 102 fix the position and orientation of the polarizing film 50, and the display color changes when the optical element 10 is observed from an oblique direction through the polarizing film 50 while rotating around the normal line. Change.
When the display units 101 and 102 are observed from an oblique direction through the polarizing film 50 while fixing the relative arrangement of the optical element 10 and the polarizing film 50 and rotating them around the normal line. The display color changes.

The display unit 103 displays the interference color. In addition, when the groove | channel provided in the recessed part formation area 133 comprises the unidirectional diffusion pattern, the display part 103 shows light scattering anisotropy.
The display unit 103 changes in color and brightness according to the observation angle.
The display unit 103 causes a color change when observed from an oblique direction while rotating the optical element 10 around its normal line.

  -The display part 103 does not produce a color change, when it observes from the diagonal direction through this, rotating the polarizing film 50 around the normal line. However, when the liquid crystal portion 153 is not completely optically isotropic, the display unit 103 is slightly observed when viewed from an oblique direction through the polarizing film 50 while rotating the polarizing film 50 around the normal line. Causes a color change.

The display unit 104 displays the same color as the display units 101 and 102 when observed from the normal direction without the polarizing film 50.
The display unit 104 displays the same color when observed from the normal direction without the polarizing film 50 and when observed from the oblique direction without the polarizing film 50. However, when the liquid crystal portion 154 is not completely optically isotropic, the display unit 104 is observed when viewed from the normal direction without the polarizing film 50 and when viewed from an oblique direction without the polarizing film 50. Display a slightly different color.

  The display unit 104 does not cause a color change when observed from an oblique direction while rotating the optical element 10 around its normal.

  -The display part 104 does not produce a color change, when rotating from the diagonal direction through the polarizing film 50 around the normal line, and observing it. However, when the liquid crystal portion 154 is not completely optically isotropic, the display unit 104 is slightly observed when viewed from an oblique direction through the polarizing film 50 while rotating the polarizing film 50 around the normal line. Causes a color change.

  As described above, since the image displayed by the optical element 10 shown in FIGS. 1 and 2 changes variously depending on the observation conditions, the optical element 10 has, for example, excellent anti-counterfeiting effects, decorative effects, and / or Provide an aesthetic effect.

  For example, when a labeled article including the optical element 10 and an article that supports the optical element 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 between an authentic product and an unauthentic product for an article whose authenticity is unknown. Therefore, forgery of, for example, certificates such as securities, banknotes, identification cards, and printed materials such as credit cards, and luxury items such as art can be prevented or suppressed. Further, the optical kit including the optical element 10 and the polarizing film 50 can be used as a toy, a learning material, or an ornament in addition to being usable for the previous authenticity determination.

Next, the second aspect of the present invention will be described.
FIG. 11 is a cross-sectional view schematically showing an optical element according to the second aspect of the present invention.

  The optical element 10 has the same structure as the optical element 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, in this optical element 10, the portion corresponding to the recess formation region 131 of the recess formation layer 13 is thicker than the portion corresponding to the recess formation region 132 of the recess formation layer 13. Further, the liquid crystal portion 151 is thinner than the liquid crystal portion 152. And the length direction of the groove | channel provided in the recessed part formation area | region 131 is parallel to a Y direction.

  The optical element 10 displays the same image as described with reference to FIG. 7 when observed with the naked eye. However, the optical element 10 displays an image different from the optical element 10 described with reference to FIGS. 1 and 2 when observed through a polarizer.

  FIG. 12 is a plan view schematically showing an example of an image that can be observed when the optical element shown in FIG. 11 and a linearly polarizing film are overlaid. FIG. 13 is a perspective view showing another example of an image displayed by the optical element shown in FIG. FIG. 14 is a perspective view showing still another example of an image displayed by the optical element shown in FIG.

  12 to 14, when the optical element 10 and the absorption linear polarizing film 50 shown in FIG. 11 are viewed from the polarizing film 50 side, the transmission axis of the polarizing film 50 is in the X direction. In order to make an angle of 45 ° counterclockwise. When such an arrangement is adopted and this is observed from the front, the display units 101 to 104 can be easily distinguished from each other as shown in FIG. This will be described in more detail.

  As is clear from the description using equations (1) and (2), the colors displayed on the display units 101 and 102 when the optical element 10 and the polarizing film 50 are overlapped and these are observed from the front are liquid crystals. Depends on the thickness d of the portions 151 and 152. Since the liquid crystal portion 151 and the liquid crystal portion 152 have different thicknesses, the display units 101 and 102 display different colors. For example, one of the display units 101 and 102 appears red and the other appears yellow.

  Thus, when the polarizing film 50 is overlapped on the optical element 10 and observed from the front, the display units 101 and 102 display different colors. Therefore, when the viewing direction is tilted in a plane perpendicular to the X direction from the state shown in FIG. 12, the color displayed by the display unit 101 is the same as that shown in FIG. The color displayed on the display unit 102 is different from that displayed when rotated 90 ° around the normal. Similarly, when the observation direction is tilted in a plane perpendicular to the X direction from the state shown in FIG. 12, the color displayed by the display unit 102 is the same as that shown in FIG. The color displayed on the display unit 101 is different from that displayed when rotated 90 ° around the normal.

  That is, this optical element 10 does not have the following features, unlike the optical element 10 described with reference to FIGS.

The display units 101 and 102 display substantially the same color when viewed from the normal direction through the polarizing film 50.
The display units 101 and 102 fix the position and orientation of the polarizing film 50, and the display color changes when the optical element 10 is observed from an oblique direction through the polarizing film 50 while rotating around the normal line. Change.
When the display units 101 and 102 are observed from an oblique direction through the polarizing film 50 while fixing the relative arrangement of the optical element 10 and the polarizing film 50 and rotating them around the normal line. The display color changes.
Instead, the optical element 10 has the following characteristics.

The display units 101 and 102 display different colors when observed from the normal direction through the polarizing film 50.
The display units 101 and 102 have different colors when they are observed from an oblique direction through the polarizing film 50 while fixing the position and orientation of the polarizing film 50 and rotating the optical element 10 around the normal line. A color change occurs while displaying.
The display units 101 and 102 are fixed when the relative arrangement of the optical element 10 and the polarizing film 50 is fixed, and the polarizing film 50 is rotated around its normal line and is observed from an oblique direction through this. The color change occurs while displaying different colors.

  Therefore, this optical element 10 also provides, for example, an excellent anti-counterfeiting effect, a decoration effect, and / or an aesthetic effect, like the optical element 10 described with reference to FIGS. 1 and 2. Therefore, when a labeled article including the optical element 10 and an article that supports the optical element 10 is a genuine article, when an article whose identity 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 between an authentic product and an unauthentic product for an article whose authenticity is unknown. Further, the optical kit including the optical element 10 and the polarizing film 50 can be used as a toy, a learning material, or an ornament in addition to being usable for the previous authenticity determination.

  When the liquid crystal portion 151 and the liquid crystal portion 152 have different thicknesses, the difference in thickness is, for example, in the range of 0.1 μm to 5 μm. When this difference is small, it is difficult to distinguish the display unit 101 and the display unit 102 from each other when observed through the polarizing film 50. When this difference is large, it becomes difficult to align mesogenic groups with a high degree of order in a thicker liquid crystal portion. As a result, it becomes difficult to display the designed color when observed through the polarizing film 50.

Various modifications can be made to the optical element 10 described above.
For example, a part of the front surface of the reflective layer 12 may be a flat mirror surface that does not have a fine uneven structure. In this case, a plurality of grooves constituting the diffraction grating may be provided in at least a part of a region corresponding to the mirror surface of the reflective layer 12 in the front surface of the recess forming layer 13. In this way, even when observed with the naked eye, it is possible to distinguish this portion from other portions.

  The optical element 10 may further include an optically substantially isotropic transparent or translucent layer between the reflective layer 12 and the recess forming layer 13. When such an intermediate layer is used, the adhesion between the reflective layer 12 and the concave portion forming layer 13 is improved, and the concavo-convex structure provided on the front surface of the reflective layer 12 affects the shape of the front surface of the concave portion forming layer 13. Can be prevented.

The optical element 10 may further include a protective layer and an adhesive layer described below.
FIG. 15 is a cross-sectional view showing a modification of the optical element shown in FIG.
The optical element 10 shown in FIG. 15 has the same structure as the optical element 10 described with reference to FIGS. 1 and 2 except that it further includes a protective layer 16 that covers the liquid crystal layer 15. . When the protective layer 16 is provided, the liquid crystal layer 15 or the like can be hardly damaged or light-degraded, and therefore degradation of an image displayed by the optical element 10 can be suppressed.

  As a material of the protective layer 16, for example, a hard coat material having excellent scratch resistance can be used. Moreover, as a material of the protective layer 16, a highly transparent material is typically used. The protective layer 16 may be colorless and transparent, or may be colored and transparent.

FIG. 16 is a cross-sectional view showing another modification of the optical element shown in FIG.
The optical element 10 shown in FIG. 16 has the same structure as the optical element 10 described with reference to FIG. 15 except that the optical element 10 further includes an adhesive layer 17 covering the back surface of the substrate 11. This optical element 10 is suitable for an application to be used by being attached to an article. The adhesive layer 17 may be covered with release paper.

  Instead of using the polarizing film 50 as the polarizer, other types of polarizers such as a plate-like polarizer may be used. Moreover, you may use a circular polarizer or an elliptical polarizer instead of a linear polarizer. In this case, a color change different from that when the linear polarizer is used can be observed. Therefore, a more complicated visual effect can be obtained.

The top view which shows roughly the optical element which concerns on the 1st aspect of this invention. Sectional drawing along the II-II line of the optical element shown in FIG. The top view which shows an example of the structure employable as the recessed part formation area of the optical element shown in FIG. The top view which shows the other example of the structure employable as the recessed part formation area of the optical element shown in FIG. The top view which shows the further another example of the structure employable as the recessed part formation area of the optical element shown in FIG. The top view which shows the further another example of the structure employable as the recessed part formation area of the optical element shown in FIG. The top view which shows an example of the image which the optical element shown in FIG.1 and FIG.2 displays. The top view which shows roughly an example of the image which can be observed when the optical element shown in FIG.1 and FIG.2 and a linearly polarizing film are piled up. FIG. 3 is a perspective view showing another example of an image displayed by the optical element shown in FIGS. 1 and 2. The perspective view which shows the further another example of the image which the optical element shown in FIG.1 and FIG.2 displays. Sectional drawing which shows schematically the optical element which concerns on the 2nd aspect of this invention. The top view which shows roughly an example of the image which can be observed when the optical element shown in FIG. 11 and a linearly-polarized-light film are piled up. FIG. 12 is a perspective view showing another example of an image displayed by the optical element shown in FIG. 11. FIG. 12 is a perspective view showing still another example of an image displayed by the optical element shown in FIG. 11. Sectional drawing which shows the modification of the optical element shown in FIG. Sectional drawing which shows the other modification of the optical element shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical element, 11 ... Base material, 12 ... 1st reflection layer, 13 ... Recess formation layer, 14 ... 2nd reflection layer, 15 ... Liquid crystal layer, 16 ... Protection layer, 17 ... Adhesion layer, 50 ... Polarizing film, DESCRIPTION OF SYMBOLS 101 ... Display part, 102 ... Display part, 103 ... Display part, 104 ... Display part, 131 ... Area, 132 ... Area, 133 ... Area, 134 ... Area, 151 ... Liquid crystal part, 152 ... Liquid crystal part, 153 ... Liquid crystal part 154 ... Liquid crystal part.

Claims (16)

  Formation of a light-transmitting recess having one main surface including one or more recess-forming regions each having a plurality of first 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 made of a liquid crystal material supported and solidified by the main surface, a first reflective layer facing the other main surface of the concave portion forming layer and having light scattering properties, and the concave portion forming layer, A second reflective layer that is interposed between the liquid crystal layer and covers a part of the one or more recessed portions, and a portion of the second reflective layer that covers the recessed portions The optical element is provided with a plurality of second grooves corresponding to the plurality of first grooves.   2. The one main surface includes a plurality of the recessed portion forming regions, and at least one of the recessed portion forming regions is different in length direction from the other recessed portion forming region. The optical element described.   The one main surface includes a plurality of the recessed portion forming regions not covered with the second reflective layer, and at least one of the recessed portion forming regions has a different length direction from the other recessed portion forming regions. The optical element according to claim 1.   The optical element according to any one of claims 1 to 3, wherein the one main surface further includes a region where no groove is provided.   The optical element according to claim 4, wherein the second reflective layer further covers at least a part of a region where the groove is not provided.   The optical element according to claim 1, wherein the liquid crystal layer includes a plurality of portions having different film thicknesses.   7. The optical element according to claim 1, wherein the plurality of grooves form a diffraction grating in at least one of the recessed portion forming region or the plurality of recessed portion forming regions.   The at least one of the recessed portion forming region or the plurality of recessed portion forming regions has the plurality of grooves forming a unidirectional diffusion pattern. Optical element.   The optical element according to claim 1, wherein the first reflective layer includes a metal reflective layer.   The optical element according to claim 1, wherein the first reflective layer includes a single-layer or multilayer dielectric film.   The optical element according to claim 1, wherein the second reflective layer includes a metal reflective layer.   The optical element according to claim 1, wherein the second reflective layer includes a single-layer or multilayer dielectric film.   A labeled article comprising the optical element according to any one of claims 1 to 12 and an article supporting the optical element.   An optical kit comprising the optical element according to any one of claims 1 to 12 and a polarizer. It is a method for discriminating between an authentic product and an unauthentic product for an article whose authenticity is unknown,
The genuine product is an article that supports the optical element according to any one of claims 1 to 12,
When the article of which the authenticity is unknown is observed from a direction inclined with respect to the one principal surface without a polarizer, the article is not perpendicular to the one principal surface without the polarizer. When the same color as that observed is displayed, and when viewed from a direction perpendicular to the principal surface through the polarizer, when observed from a direction perpendicular to the one principal surface without the polarizer When displaying from a direction perpendicular to the one main surface without the polarizer when displaying from a direction inclined with respect to the one main surface through the polarizer And a first display unit that displays a color different from that observed from a direction perpendicular to the main surface through the polarizer, and a second display that displays an interference color or exhibits light scattering anisotropy If it is not included, it is unknown whether it is authentic or not Discriminating method characterized by including be determined to be non-authentic.   In the case where an article whose unknown or not authentic includes the first and second display units, the article whose unknown or not is unknown is defined as a normal line of the one main surface. Whether the image is authentic when the color displayed by the first display unit does not change when observed from a direction inclined with respect to the one main surface through the polarizer while rotating around. The determination method according to claim 15, further comprising determining that an article whose unknown is unknown is a non-genuine product.

Images