JP5315258B2 - Identification medium, identification medium identification method, and optical apparatus for observing the identification medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an identification medium whose image being observed looks changing in visually recognized size, looks three-dimensionally standing out or sinking and, at the same time, looks changing in colors. <P>SOLUTION: The identification medium includes: a nematic liquid crystal layer 103 which is constituted at least of one layer of nematic liquid crystal wherein the product of birefringence and helical pitch of a liquid crystal molecule with respect to visible light viewed from the observing side is at least more than 3.5 times larger than the wavelength of the visual light and selective reflection by Bragg reflection does not occur; and a reflection pattern 104 which overlaps the nematic liquid crystal layer 103 and constitutes a light reflection layer whereon a light reflection pattern is formed so that a pattern appears repeatedly at predetermined pitches. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an identification medium, an identification medium identification method, and an optical apparatus for observing the identification medium.

  Patent Document 1 discloses an identification medium that has a configuration in which a reflective layer is provided on a twisted nematic liquid crystal and changes color when observed by rotating a linear polarizing filter. Patent Document 2 discloses a display means in which the visual size of a pattern appears to change by shifting the plano-convex lens and the pattern of the printed pattern in a three-dimensional moire that combines a plano-convex lens assembly and a fine pitch printed pattern. ing. Patent Document 3 describes a configuration in which a three-dimensional moire pattern can be observed by rising or sinking by adjusting the pitch of the convex lens in a three-dimensional moire pattern using a convex lens assembly and a fine pitch printing pattern. Patent Document 4 describes a configuration in which a plurality of display patterns are provided in a configuration for displaying moire by a combination of a diffraction grating and a lens sheet.

JP 2008-129421 A Japanese Patent No. 3338860 JP 2008-12870 A JP 2009-186544 A

  With the technique of Patent Document 1, it is possible to observe a change in color, but it is impossible to observe a phenomenon in which the visual size of the image being observed changes, or the phenomenon that the image is three-dimensionally raised or submerged. In the techniques described in Patent Documents 2 to 4, the visual size of the image being observed can be changed, or the phenomenon of three-dimensionally rising or sinking can be observed, but the color change can be observed. I can't.

  In such a background, the present invention recognizes how the color of the image changes in appearance at the same time that the visual size of the image being observed changes or appears three-dimensionally lifts or sinks. The purpose is to provide a medium.

  According to the first aspect of the present invention, the product of the birefringence of the liquid crystal molecules and the helical pitch with respect to the visible light is larger than at least 3.5 times the wavelength of the visible light when viewed from the observation side, and A nematic liquid crystal layer composed of at least one layer of nematic liquid crystal that does not cause selective reflection due to Bragg reflection, and a light reflection layer that overlaps with the nematic liquid crystal layer and is provided with a light reflection pattern in a pattern that repeatedly appears at a predetermined pitch. It is an identification medium characterized by having a laminated structure.

  According to the first aspect of the present invention, in the observation through the viewer in which the linear polarizing filter and the microlens array are overlapped, the nematic liquid crystal layer and the linear polarizing filter are obtained when the viewer is rotated with respect to the identification medium. The color observed is changed by the combined optical function. Further, due to the optical function in which the light reflection pattern and the microlens array are combined, when the viewer is rotated, the visual size of the pattern is changed, and the pattern is three-dimensionally raised or submerged. And, by combining the former optical function and the latter optical function, when the viewer is rotated, the color of the reflection pattern changes, and the visual size changes or appears three-dimensionally. The optical function is obtained. This appearance is a peculiar appearance, and it can be used to determine authenticity.

  A second aspect of the present invention is the first aspect of the present invention, comprising the first area and the second area in which the light reflection pattern is formed, and the nematic in a portion overlapping the first area. The liquid crystal layer region and the region of the nematic liquid crystal layer in a portion overlapping with the second region are subjected to alignment treatment in different directions.

  According to the second aspect of the present invention, the alignment directions of the nematic liquid crystal in the first image region and the second image region are different. For this reason, in the observation through the viewer in which the linear polarization filter and the microlens array are overlapped, when the viewer is rotated relative to the identification medium, the first region and the second region show different colors, And the color changes. In addition, a phenomenon is observed in which the visual recognition size of the pattern in the first region and the second region is changed, or the pattern is lifted or submerged. Note that the number of images may be two or more.

  The invention according to claim 3 is the invention according to claim 1 or 2, further comprising a first region and a second region in which the light reflection pattern is formed, and the light reflection in the first region. The arrangement direction of the pattern is different from the arrangement direction of the light reflection pattern in the second region. According to the third aspect of the present invention, the size of the pattern and the stereoscopic effect appear different depending on the difference in the arrangement direction of the light reflection patterns. As a result, higher discrimination can be obtained.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the light reflecting layer is constituted by a diffraction grating. According to the fourth aspect of the present invention, since an image is formed using reflection from the diffraction grating, it is possible to use a hologram image due to a diffraction phenomenon as an identification target. Since the hologram image can form a three-dimensional image, a higher identification function can be obtained.

  According to a fifth aspect of the present invention, the identification medium according to any one of the first to fourth aspects has a lens disposed at an interval corresponding to the linearly polarizing filter layer that selectively transmits linearly polarized light and the pitch. An identification medium identification method characterized by observing with an optical device in which a lens array layer is laminated.

  Invention of Claim 6 is an optical apparatus for observing the identification medium as described in any one of Claims 1-4, Comprising: The linearly-polarized-light filter layer which selectively permeate | transmits linearly polarized light, The said, An optical device for observing an identification medium, comprising a structure in which a lens array layer in which lenses are arranged at intervals corresponding to a pitch is laminated.

  According to the first aspect of the present invention, the visual size of the image being observed changes, or the three-dimensional image rises or sinks, and at the same time, the color of the image changes. An identification medium is provided.

  According to the second aspect of the present invention, since two images showing different color changes can be observed, higher discrimination can be obtained.

  According to the invention described in claim 3, since two images showing changes in different sizes and changes in stereoscopic effect can be observed, higher discrimination can be obtained.

  According to the fourth aspect of the present invention, since an image using a diffraction grating can be used as an identification target, a higher identification function can be obtained.

  According to the fifth aspect of the present invention, there is provided a method for observing an identification medium having the superiority according to any one of the first to fourth aspects.

  According to invention of Claim 6, the optical apparatus for observing the identification medium as described in any one of Claims 1-4 is provided.

It is sectional drawing (A), front view (B), and (C) of the identification medium of embodiment. It is sectional drawing (A) and a front view (B) of a viewer. It is a conceptual diagram which shows how an identification medium looks.

(Configuration of the embodiment)
FIG. 1 shows an identification medium 100 of the embodiment. 1A is a cross-sectional view, and FIGS. 1B and 1C are front views as viewed from the observing side. The identification medium 100 has a structure in which a nematic liquid crystal layer 103, a base film 102, and an adhesive layer 101 are laminated in order from the observed side.

  The adhesive layer 101 has a function of fixing the identification medium 100 to an object, and is made of an adhesive material. Although not shown, release paper is attached to the exposed surface side of the adhesive layer 101 before the identification medium 100 is attached to the object. When the identification medium 100 is attached to the object, the release paper is peeled off from the adhesive layer 101 and the adhesive layer 101 is brought into contact with the object to fix the identification medium 100 to the object.

  The base film 102 is made of a resin film such as PET. A reflective pattern 104 is formed on the base film 102 on the nematic liquid crystal layer 103 side. The reflection pattern 104 is configured by printing an aluminum vapor deposition layer or ink having a reflection function. The reflection pattern 104 constitutes two types of patterns described below.

  The first pattern is the pattern shown in FIG. The first pattern is composed of a quadrangular reflection pattern 104a. The second pattern is the pattern shown in FIG. The second pattern is composed of a round reflection pattern 104b. In FIG. 1, the first pattern and the second pattern are shown separately in FIGS. 1B and 1C for the sake of clarity, but actually, these two patterns are Are formed on the same plane. The first pattern and the second pattern are in a state in which the reflection patterns are regularly arranged in a matrix form vertically and horizontally at predetermined intervals.

  The first pattern and the second pattern shown in FIGS. 1B and 1C are formed using the technique described in Japanese Patent No. 3338860. That is, in the first pattern shown in FIG. 1B, rectangular reflective patterns are arranged vertically and horizontally at a determined pitch (interval). In the second pattern shown in FIG. 1C, round reflection patterns are arranged vertically and horizontally at the same pitch (interval) as the first pattern. The pitch is the same in the vertical and horizontal directions.

  Here, the arrangement direction of the first pattern shown in FIG. 1B and the second pattern shown in FIG. 1C are shifted by 45 degrees. That is, the first pattern shown in FIG. 1B is arranged in the vertical and horizontal directions in FIG. 1, but the second pattern shown in FIG. 1C is 45 degrees from the vertical and horizontal directions in FIG. Arranged in the rotated direction. The diameters of the reflective patterns 104a and 104b (in the case of not being circular, the diameter converted into a circle) are about 0.1 μm to 1 mm, and the values are the nematic liquid crystal layer 103, the protective layer on the nematic liquid crystal layer 103 not shown, In addition, it is set to be 1/2 or less with respect to the sum of the thicknesses of the viewers described later. The pitch (interval between adjacent patterns) R1 of the reflection patterns 104 (104a, 104b) is selected from a range of about 0.05 mm to 2 mm. As will be described later, the pitch R1 of the reflection patterns 104 (104a, 104b) is slightly larger than the pitch R2 of the macro lens array of the viewer (the difference is about 20 μm at the maximum). The optimum values of the specific values of these parameters vary depending on the design of the pattern and the material used, and may be determined experimentally.

  Next, the nematic liquid crystal layer 103 will be described. The nematic liquid crystal layer 103 has at least one layer in which the product of the birefringence of the liquid crystal molecules constituting the liquid crystal layer and the helical pitch is at least 3.5 times the wavelength of the light and does not cause selective reflection by Bragg diffraction. It has a structure. Hereinafter, a liquid crystal layer having this configuration is referred to as a “twisted nematic liquid crystal layer” (or a liquid crystal layer whose color changes).

  Twisted nematic liquid crystals are distinguished from cholesteric liquid crystals as follows. A twisted nematic liquid crystal is a liquid crystal molecule that has the target axis direction spontaneously aligned in a certain direction and is macroscopically anisotropic, and the liquid crystal molecule has a spiral structure with the layer normal direction as a spiral axis. A liquid crystal having an alignment structure and having an alignment structure that substantially satisfies the Morgan condition for visible light having a wavelength of 400 nm to 800 nm and does not cause Bragg reflection.

  Cholesteric liquid crystal is an orientation in which the direction of the target axis of the liquid crystal molecules is spontaneously aligned and macroscopically anisotropic, and the liquid crystal molecules have a helical structure with the layer normal direction as the helical axis. Although it has a structure, it refers to a liquid crystal having an alignment structure that does not satisfy the Morgan condition for visible light having a wavelength of 400 nm to 800 nm and generates Bragg reflection.

  Accordingly, the twisted nematic liquid crystal and the cholesteric liquid crystal are distinguished from each other in that they have different optical properties while having the same helical alignment structure.

  The helical pitch refers to the length in the layer normal direction required for the twisted nematic liquid crystal molecules or the cholesteric liquid crystal molecules to rotate 360 ° with the layer normal direction as the helical axis.

  Mauguin Condition means that when the product of birefringence of liquid crystal molecules (difference between extraordinary ray refractive index and ordinary ray refractive index) and helical pitch is sufficiently large with respect to the wavelength of light, the major axis of liquid crystal molecules This is a condition under which linearly polarized light incident in parallel or perpendicularly can propagate along the helical structure of liquid crystal molecules while maintaining the polarization state.

  In general, it is known that a birefringent medium having optical anisotropy is placed on a reflecting plate and colored when observed through a polarizing filter. This is because when light that has passed through a polarizing filter and has become linearly polarized light is converted into elliptically polarized light due to a phase difference between the two intrinsic polarized light when passing through the birefringent medium, the wavelength of the light is reduced. This is because the phase difference generated differs from one to another, and the ellipticity of elliptically polarized light is different.

  In this case, the coloration (color) produced is determined by the optical film thickness (retardation) of the birefringent medium used, and the color shading (saturation) is determined by the fast axis (slow axis) of the birefringent medium and the polarization filter. It depends on the angle formed by the transmission (absorption) axis. According to Japanese Patent Laid-Open No. 2000-019323, when the fast axis (slow phase axis) of the birefringent medium and the transmission (absorption) axis of the polarizing filter are parallel or orthogonal, the saturation is the highest, which is 45 degrees. In some cases it is known to be the thinnest. That is, when the polarizing filter is rotated, a phenomenon that a specific color can be seen at a certain angle is observed. However, no color change (eg, red → green) is observed. It just means that a certain color is visible or invisible, and the color does not change.

  No means other than changing the optical film thickness of the birefringent medium is known in order to change the color with the configuration of the reflector / birefringent medium / polarizing filter. However, in an identification medium used as a seal or a label, it is practically impossible to change the optical film thickness of the birefringent medium after being attached to an article or the like.

  Analyzes why the color does not change regardless of the angle formed by the fast axis (slow axis) of the birefringent medium and the transmission (absorption) axis of the polarizing filter in the above-described reflector / birefringent medium / polarizing filter configuration. As a result, it has been found that although the ellipticity of elliptically polarized light varies depending on the wavelength of light depending on the birefringent medium, the major axis orientation is constant regardless of the wavelength. Therefore, based on this knowledge, if not only the ellipticity but also the major axis direction can be changed for each wavelength, the angle formed by the fast axis (slow axis) of the birefringent medium and the transmission (absorption) axis of the polarizing filter. It came to invent that it became possible to change a color by changing.

  Employing a twisted nematic liquid crystal layer provides an identification medium that can observe color changes according to this principle. Hereinafter, this function will be described in detail. Here, as a premise, a structure in which a twisted nematic liquid crystal layer and a light reflection layer are laminated from the observation side is considered. Here, the twisted nematic liquid crystal layer functions as a polarization conversion rotation layer.

  In the above configuration, a case is considered where non-polarized light passes through a linear polarizing filter and becomes linearly polarized light and enters the twisted nematic liquid crystal layer. This linearly polarized light becomes elliptically polarized light when transmitted through the twisted nematic liquid crystal layer, and the ellipticity changes according to the optical film thickness of the twisted nematic liquid crystal layer. Moreover, the major axis direction of this elliptically polarized light rotates according to the twist angle. The change in the ellipticity and the rotation angle vary depending on the wavelength of light. The light emitted from the twisted nematic liquid crystal layer is reflected by the reflection layer, and enters the twisted nematic liquid crystal layer again through a reverse path.

  Then, the light emitted from the surface first incident on the twisted nematic liquid crystal layer passes through the linear polarization filter and is observed. At this time, since the ellipticity differs depending on the wavelength of the light, the intensity of the light transmitted through the linear polarization filter differs for each wavelength. Thereby, coloring is observed. That is, since light with a deviated wavelength distribution is observed, a specific color is visually recognized.

  Furthermore, since the major axis direction differs for each wavelength, rotating the linear polarizing filter increases the amount of transmission of light having a wavelength near which the transmission axis of the polarizing filter and the major axis direction of the elliptically polarized light are parallel. The closer the wavelength, the less transmitted. As a result, the coloring color (color) changes due to the rotation of the polarizing filter. That is, it is observed that the color changes by rotating the linear polarizing filter with respect to the twisted nematic liquid crystal layer.

  As described above, it is important that the twisted nematic liquid crystal layer changes not only the ellipticity of the passing polarized light but also the major axis direction. Here, as a desirable condition for the rotation in the long axis direction, that is, the optical rotation ability, it can be mentioned that the Morgan condition is substantially satisfied. That is, the product of the birefringence of liquid crystal molecules (difference between extraordinary ray refractive index and ordinary ray refractive index) and the helical pitch needs to be sufficiently large with respect to the wavelength of light. According to experiments, the product of the birefringence of liquid crystal molecules (difference between extraordinary ray refractive index and ordinary ray refractive index) and the helical pitch is preferably at least three times the wavelength of visible light used for identification, more preferably It has been found that it is desired to be 3.5 times or more. When the number is less than three times, the optical rotation ability is lost as light with a shorter wavelength in particular, the polarization cannot be rotated along the helical axis of the twisted nematic liquid crystal, and the tendency that the above-described optical function cannot be obtained accurately increases. That is, the phenomenon that the coloring color (color) changes due to the rotation of the polarizing filter is not clear.

  Next, a method for obtaining the nematic liquid crystal layer 103 will be described. For the nematic liquid crystal layer 103, a method of fixing a liquid crystal molecule alignment structure after applying a solution containing a liquid crystal material on an alignment substrate and performing twisted nematic alignment in a liquid crystal state can be employed. Such a liquid crystal material may be any material as long as the liquid crystal molecules have a twisted nematic alignment structure, and both high-molecular liquid crystals and low-molecular liquid crystals can be used. Further, as a method for fixing the alignment structure of the liquid crystal molecules in this way, when a polymer liquid crystal having a glass transition temperature of 70 ° C. or higher is used as the liquid crystal material, the liquid crystal is rapidly cooled after being twisted nematically aligned. A method is mentioned. In the case of using a low molecular liquid crystal as the liquid crystal material, there is a method in which twisted nematic alignment is performed in a liquid crystal state and then, for example, crosslinking is performed by energy beam irradiation.

  Examples of such polymer liquid crystals include main chain polymer liquid crystals such as polyester, polyamide, polycarbonate, and polyimide, polyacrylate, polymethacrylate, polymalonate, and polysiloxane side chain type Molecular liquid crystals can be mentioned. Further, preferred examples of the structural unit of the polymer include an aromatic or aliphatic diol unit, an aromatic or aliphatic dicarboxylic acid unit, and an aromatic or aliphatic hydroxycarboxylic acid unit.

  Such low-molecular liquid crystals include saturated benzene carboxylic acid derivatives, unsaturated benzene carboxylic acid derivatives, biphenyl carboxylic acid derivatives, aromatic oxycarboxylic acid derivatives, Schiff base derivatives, bisazomethine compound derivatives. , Azo compound derivatives, azoxy compound derivatives, cyclohexane ester compound derivatives, sterol compound derivatives, etc., compounds exhibiting liquid crystallinity having reactive functional groups introduced at the ends thereof, and liquid crystal properties among the above compound derivatives The composition etc. which added the crosslinkable compound to the compound are mentioned.

  Furthermore, when the alignment structure formed in the liquid crystal state is fixed by thermal crosslinking or photocrosslinking, it is preferable to include a liquid crystal material having a functional group or a site that can undergo a crosslinking reaction by heat or light. Examples of such functional groups include acryl groups, methacryl groups, vinyl groups, vinyl ether groups, allyl groups, allyloxy groups, glycidyl groups and other epoxy groups, isocyanate groups, isothiocyanate groups, azo groups, diazo groups, azide groups, Examples thereof include a hydroxyl group, a carboxyl group, and a lower ester group, and an acrylic group and a methacryl group are particularly preferable. Further, the site capable of crosslinking reaction includes a site structure including a maleimide, maleic anhydride, cinnamic acid and cinnamic acid ester, alkene, diene, allene, alkyne, azo, azoxy, disulfide, polysulfide and the like. Etc. These cross-linking groups and cross-linking reaction sites may be contained in the liquid crystal material itself constituting the liquid crystal material, but a non-liquid crystalline material having a cross-linkable group or site may be separately added to the liquid crystal material.

  Moreover, it is preferable that the solution containing such a liquid crystal material further contains an optically active compound for twisting nematic alignment of liquid crystal molecules in a liquid crystal state. Examples of such optically active compounds include optically active low molecular compounds and high molecular compounds. Any compound having optical activity can be used in the present invention, but from the viewpoint of compatibility with a polymer liquid crystal, an optically active liquid crystalline compound is desirable.

  In addition, a known surfactant may be appropriately added to the solution containing the liquid crystal material in order to facilitate application. Furthermore, in order to improve the heat resistance and the like of the liquid crystal layer to be obtained, a crosslinking agent such as a bisazide compound or glycidyl methacrylate is added to the solution containing the liquid crystal material, It can also be crosslinked in the process.

  In addition, the solvent used for the preparation of the solution containing such a liquid crystal material is not particularly limited. And a polar solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, sulfolane, and cyclohexane. These solvents can be appropriately selected and used depending on the type of liquid crystal material to be used, etc., and may be appropriately mixed and used as necessary. Further, the concentration of such a solution can be appropriately selected according to the molecular weight or solubility of the liquid crystal material.

  In addition, such alignment substrates include polyimide, polyamide, polyamideimide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyarylate, triphenyl. Films of acetyl cellulose, epoxy resin, phenol resin, etc., or uniaxially stretched films of these films can be used. Some of these films exhibit a sufficient alignment ability for liquid crystal materials without performing a treatment for expressing the alignment ability again depending on the production method, but the alignment is insufficient or the alignment ability is not exhibited. In such a case, the film is stretched under moderate overheating, the film surface is rubbed in one direction with a rayon cloth or the like, and the alignment film is made of a known alignment agent such as polyimide, polyvinyl alcohol or silane coupling agent on the film. A film that is appropriately subjected to a rubbing treatment, a diagonal vapor deposition treatment such as silicon oxide, and a combination of these appropriately may be used as necessary.

  The application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method can be appropriately employed. Examples of such a coating method include a roll coating method, a die coating method, a dip coating method, a curtain coating method, and a spin coating method. Moreover, you may put the solvent condition (drying) process by methods, such as a heater and hot air blowing, after application | coating.

  In addition, after fixing the liquid crystal molecules on the alignment substrate, it was immersed in a poor solvent for all structural materials, a method of mechanically peeling using a roll or the like at the interface between the alignment substrate and the liquid crystal layer whose color changes. A method of peeling mechanically afterwards, a method of peeling by applying ultrasonic waves in a poor solvent, a method of peeling by giving a temperature change using the difference in thermal expansion coefficient between the alignment substrate and the liquid crystal layer whose color changes, A single liquid crystal layer whose color changes can be obtained by, for example, a method of dissolving and removing the alignment substrate itself or the alignment film on the alignment substrate. The nematic liquid crystal layer 103 peeled from the alignment substrate is fixed to the base film 102 with an adhesive.

  Note that the nematic liquid crystal layer 103 is in a state in which the direction of the alignment treatment is 45 degrees different between the region 105 and the region 106 in FIG. This angle is not limited to 45 degrees, and may be another angle such as 30 degrees. Note that a light-transmitting protective layer is provided on the upper surface of the nematic liquid crystal layer 103, but is not shown in FIG.

(Viewer configuration)
An example of the viewer (observation optical device) used when observing the identification medium 100 shown in FIG. 1 will be described. 2A is a cross-sectional view, and FIG. 2B is a front view seen from the lens array side. A viewer 200 is shown in FIG. The viewer 200 has a structure in which a linear polarization filter layer 201 and a plano-convex lens sheet 202 are laminated from the side facing the identification medium 100.

  The linear polarizing filter layer 201 is configured by a linear polarizing filter that selectively transmits linear polarized light. The plano-convex lens sheet 202 is made of a resin material (for example, TAC) that does not disturb the polarization state of transmitted light, and has a structure in which a plurality of plano-convex lenses 203 are arranged vertically and horizontally in a matrix. The distance R2 between the adjacent plano-convex lenses 203 is a dimension satisfying R1> R2 and R1-R2 ≦ 20 μm with the pitch R1 of the reflection pattern 104. The pitch R2 is the same in the vertical and horizontal directions as the pitch R1 of the reflective pattern 104.

  By setting R1> R2, in the observation of the identification medium 100 using the viewer 200, it is possible to obtain a visually recognized state in which the pattern is lifted up and viewed three-dimensionally. On the other hand, when R1 <R2 (where R2-R1 ≦ 20 μm), a visually observable state is obtained in which the pattern sinks and looks three-dimensional.

(Optical function)
Hereinafter, the optical function of the identification medium 100 will be described. Here, the optical function obtained when the viewer 200 of FIG. 2 is superimposed on the identification medium 100 of FIG. 1 and the viewer 200 is rotated relative to the identification medium 100 in that state will be described. Here, the identification medium 100 is observed from the nematic liquid crystal layer 103 side. At this time, the linear polarizing filter layer 201 of the viewer 200 is brought into contact with the nematic liquid crystal layer 103 side of the identification medium 100 and the identification medium 100 is observed through the viewer 200.

  FIG. 3 is a conceptual diagram showing a state in which the viewer of the embodiment is superimposed on the identification medium of the embodiment and observed from the viewer 200 side. FIG. 3 shows the identification medium 100 and the viewer 200 superimposed thereon. FIG. 3A shows a case where the relative rotation angle between the identification medium 100 and the viewer 200 is the first angle. FIG. 3B shows a case where the relative rotation angle is shifted by 45 degrees from the first angle. This is the case where the angle is 2. That is, FIG. 3B shows a state where the viewer 200 is rotated 45 degrees from the state of FIG.

  In the state of FIG. 3A, the quadrangular reflection pattern 104a is enlarged and emerges and looks three-dimensional, and the round reflection pattern 104b appears to be small (or small and difficult to see). Further, in the state of FIG. 3A, the reflection patterns 104a and 104b in the area 105 look like a specific first color, and the reflection patterns 104a and 104b in the area 106 look like a specific second color. .

  Then, when the viewer 200 is rotated 45 degrees from the state shown in FIG. 3A to the state shown in FIG. 3B, the square reflection pattern 104a is reduced, and the round reflection pattern 104b is enlarged and emerges three-dimensionally. Change to visible state. Further, in the state of FIG. 3B, the reflection patterns 104a and 104b in the area 105 look like a specific third color, and the reflection patterns 104a and 104b in the area 106 look like a specific fourth color. . The change from the state of FIG. 3A to the state of FIG. 3B occurs continuously.

  The reason why such a unique appearance can be obtained will be described below. First, in the state of FIG. 3A, the viewer 200 is set to the first intersection angle with respect to the identification medium 100. Here, the crossing angle is an angle of deviation between the arrangement direction of the plano-convex lenses in the viewer 200 and the arrangement direction of the reflection pattern 104 of the identification medium 100. The crossing angle can also be understood as the relationship between the angular positions of the identification medium 100 and the viewer 200 when the identification medium 100 and the viewer 200 are overlapped. By setting the first intersection angle, the quadrangular reflection pattern 104a is enlarged and floated to appear three-dimensionally, and the round reflection pattern 104b appears to be small.

  This phenomenon uses the technique described in Japanese Patent No. 3338860, and the detailed principle is not clear. However, the pitch of the plano-convex lenses 203 periodically arranged in the vertical and horizontal directions and the periodic arrangement in the vertical and horizontal directions are the same. This is caused by a slight deviation from the pitch of the reflection pattern 104 and a shift (intersection angle) between the two in the arrangement direction.

  In the case of the second intersection angle in FIG. 3B, the rectangular reflection pattern 104a is reduced, and the round reflection pattern 104b is enlarged and floated so as to be stereoscopically viewed.

  For the above reasons, the size of the reflection patterns 104a and 104b and the change in stereoscopic effect accompanying the change in the crossing angle are observed. That is, enlargement of one reflection pattern and reduction of the other reflection pattern (or the reverse phenomenon) are observed.

  On the other hand, linearly polarized light transmitted through the viewer 200 enters the portion of the identification medium 100 viewed through the viewer 200. This is because the viewer 200 includes the linear polarization filter layer 201.

  Here, the angles formed by the polarization direction of light transmitted through the viewer 200 and incident on the nematic liquid crystal layer 103 and the orientation direction of the nematic liquid crystal layer 103 are different between the regions 105 and 106.

  As described above, when linearly polarized light is transmitted through the twisted nematic liquid crystal layer, it becomes elliptically polarized light, and the ellipticity changes according to the optical film thickness of the twisted nematic liquid crystal layer. The major axis direction rotates according to. At this time, the state of elliptically polarized light generated in the nematic liquid crystal layer differs depending on the relationship between the polarization direction of the linearly polarized light incident on the nematic liquid crystal layer 103 and the alignment direction of the liquid crystal molecules on the incident surface of the twisted nematic liquid crystal layer 103.

  For this reason, in the areas 105 and 106, light having different elliptical polarization states enters the viewer 200 from the identification medium 100, and different colors are observed in the areas 105 and 106. This is the reason why the colors of the reflection patterns 104a and 104b are different between the regions 105 and 106 in FIG.

  When the viewer 200 is rotated with respect to the identification medium 100 and the crossing angle is changed, the polarization direction of the linearly polarized light incident on the nematic liquid crystal layer 103 and the alignment direction of the liquid crystal molecules on the incident surface of the twisted nematic liquid crystal layer 103 are changed. The angular relationship changes, and the colors of the reflected patterns 104a and 104b being observed change. At this time, for the reasons described above, the regions 105 and 106 have different color changes.

  Note that the colors of the reflection patterns 104a and 104b in the areas 105 and 106 in FIG. 3A may be the same as the colors of the reflection patterns 104a and 104b in the areas 105 and 106 in FIG. This depends on the design conditions and the crossing angle.

(Superiority)
As described above, the identification medium 100 has a product of birefringence of liquid crystal molecules and a helical pitch with respect to visible light as viewed from the observation side, which is at least 3.5 times the wavelength of the visible light, In addition, a nematic liquid crystal layer 103 composed of at least one layer of nematic liquid crystal that does not cause selective reflection due to Bragg reflection, and a light reflection pattern are provided so as to overlap the nematic liquid crystal layer 103 and repeatedly appear at a predetermined pitch. And a reflection pattern 104 constituting the light reflection layer.

  According to this configuration, by rotating the viewer 200 with respect to the identification medium 100, it is possible to obtain an optical function in which different patterns appear and appear three-dimensionally, and these patterns show different color changes. Since this optical function cannot be reproduced unless various conditions are the same, forgery is difficult, and high authenticity determination can be performed.

  Further, the identification medium 100 includes a first region 105 and a second region 106 where the light reflection patterns 104a and 104b are formed, and a region of the nematic liquid crystal layer 103 in a portion overlapping the first region 105; The alignment treatment in a direction different from that of the region of the nematic liquid crystal layer 103 in the portion overlapping with the second region 106 is performed. According to this configuration, it is possible to observe a phenomenon in which the change in hue varies depending on the location.

  The identification medium includes a first region shown in FIG. 1B where the light reflection pattern 104a is formed and a second region shown in FIG. 1C where the light reflection pattern 104b is formed. The arrangement direction of the light reflection pattern 104a in the first region is different from the arrangement direction of the light reflection pattern 104b in the second region. According to this configuration, when the viewer 200 is rotated with respect to the identification medium 100, it is possible to observe two types of patterns showing different size changes and changes in how they emerge.

(Other)
The reflection pattern may be constituted by a diffraction grating having a periodic pitch. If a diffraction grating is used, it is possible to provide a reflective pattern with a finer shape. Further, by using a diffraction grating, a hologram image due to a diffraction phenomenon can be used as an identification target. Since the hologram image can form a three-dimensional image, a unique visual effect is generated due to a synergistic effect with the effect that the reflection pattern is enlarged to make it appear three-dimensional, and a higher discrimination function can be obtained. The reflection pattern may be composed of cholesteric liquid crystal. The cholesteric liquid crystal reflects light having a specific center wavelength, so that even when viewed directly, the color can be observed and a higher discrimination function can be obtained.

  In addition, a hologram can be used for displaying a symbol. The layer for forming the hologram is not limited, and a nematic liquid crystal layer 103 which is a reflective pattern layer or a liquid crystal layer whose color changes can be selected. The number of layers of the nematic liquid crystal layer 103 is not limited, and a configuration in which multiple layers are provided may be used.

  The lens array of the viewer 200 may be formed directly on the linear polarization filter layer 201. Further, the lens array of the viewer 200 may be configured by a hologram lens. The shape of the reflective pattern 104 constituting the pattern in the identification medium 100 is not limited to the illustrated rectangular shape and round shape, and various shapes such as a polygonal shape, a star shape, and an elliptical shape can be employed. The difference in the direction of the arrangement of the two patterns is not limited to 45 degrees, and may be another angle such as 30 degrees. Moreover, you may comprise a pattern, a character, etc. by making a reflective pattern into a dot.

  The types of patterns shown in FIG. 1 are not limited to two types, and may be one type or three or more types. FIG. 1 illustrates a configuration in which two types of patterns arranged in two directions are illustrated, but a configuration in which a plurality of patterns arranged in three or more directions is also possible. Further, a configuration in which a finer reflection pattern or hologram is formed in one reflection pattern constituting the pattern is also possible.

  In the viewer 200 shown in FIG. 2, the plano-convex lens sheet 202 may be fixed to the identification medium side, the plano-convex lens sheet may be integrated on the identification medium 100 side, and the viewer may be a linear polarization filter only. However, in this case, since the change in the crossing angle cannot be performed, the change in the image size and the stereoscopic effect cannot be observed, and the change can be observed only in the color change.

  The article to which the identification medium 100 is affixed is not particularly limited as long as it is necessary to identify a counterfeit product (identification of authenticity). Examples of such articles include credit cards, passports, securities, product packages, licenses, ID cards, clothing, accessories, electronic devices, and various consumables.

  The present invention can be used in a technique for identifying authenticity.

  DESCRIPTION OF SYMBOLS 100 ... Identification medium, 101 ... Adhesive layer, 102 ... Base film, 103 ... Nematic liquid crystal layer, 104 ... Reflection pattern, 104a ... Rectangular reflection pattern, 104a ... Round reflection pattern, 105 ... 1st orientation area | region, 106: second alignment region, 200: viewer, 201 ... linearly polarizing filter layer, 202 ... plano-convex lens sheet, 203 ... plano-convex lens.

Claims (6)

Seen from the observing side,
For visible light, the product of birefringence of liquid crystal molecules and helical pitch is at least 3.5 times the wavelength of the visible light, and is composed of at least one layer of nematic liquid crystal that does not cause selective reflection by Bragg reflection. A nematic liquid crystal layer,
A discriminating medium characterized by having a structure in which a light reflecting layer provided with a light reflecting pattern is laminated on a pattern that overlaps with the nematic liquid crystal layer and repeatedly appears at a predetermined pitch. A first region and a second region in which the light reflection pattern is formed;
A region of the nematic liquid crystal layer in a portion overlapping with the first region and a region of the nematic liquid crystal layer in a portion overlapping with the second region are subjected to alignment treatment in different directions. The identification medium according to claim 1. A first region and a second region in which the light reflection pattern is formed;
3. The identification medium according to claim 1, wherein an arrangement direction of the light reflection pattern in the first area is different from an arrangement direction of the light reflection pattern in the second area.   The identification medium according to claim 1, wherein the light reflection layer is formed of a diffraction grating.   5. The identification medium according to claim 1, wherein a linearly polarizing filter layer that selectively transmits linearly polarized light and a lens array layer in which lenses are arranged at intervals corresponding to the pitch are stacked. The identification method of the identification medium characterized by observing with an optical device. An optical device for observing the identification medium according to any one of claims 1 to 4,
A linear polarizing filter layer that selectively transmits linear polarized light;
An optical apparatus for observing an identification medium, comprising a structure in which a lens array layer in which lenses are arranged at intervals corresponding to the pitch is laminated.

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