JP2011123257A - Identification medium and identification method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an identification medium in which images different in color can be observed depending on a viewing angle by rotating a polarization filter for observation with respect to the identification medium. <P>SOLUTION: An optical anisotropic layer 105 showing a birefringent effect is provided on an alignment layer having alignment regions with different alignment directions in a lattice pattern. The optical anisotropic layer 105 includes regions having two types of optical anisotropy formed in a dot pattern, and first and second images are formed by being drawn with the dot pattern. The first image is constituted of dots having a first alignment direction and a first birefringent effect while the second image is constituted of dots having a second alignment direction and a second birefringent effect. The structure gives such a visual effect that in an observation through a polarization filter, images different in colors can be switched and observed by differences in the alignment direction and in the birefringent effect. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an identification medium and an identification method thereof.

  Patent Document 1 describes a configuration in which an alignment layer is a laminate of a liquid crystal layer, the alignment layer can be photo-aligned, and the alignment direction changes locally. Patent Document 2 describes an identification medium in which latent images of different colors are observed in observation through a polarizing filter by providing regions having different phase differences.

Japanese Patent No. 4054071 JP 2009-175208 A

  In an identification medium in which a reflection layer and a retardation layer are laminated as described in Patent Document 2, when a polarizing filter is pressed against the identification medium, a latent image is observed due to a difference in phase difference. In this structure, by varying the phase difference depending on the location, a plurality of colors can be observed at a rotation angle when the polarizing filter is rotated. However, multiple colors appear simultaneously at an angle, and as the polarizing filter is rotated, an image of the first color is observed at the first angle, and then the second color at the second angle. The appearance that the image is observed cannot be obtained.

  In such a background, an object of the present invention is to provide an identification medium that can be observed by switching images of different colors.

  The invention according to claim 1 includes a light reflecting layer and an optically anisotropic layer provided at a position overlapping the light reflecting layer and exhibiting birefringence, wherein the optically anisotropic layer includes A plurality of first regions having an orientation direction and having a first birefringence, and a plurality of second regions having a second orientation direction and having a second birefringence The first image is constituted by the plurality of first regions, the second image is constituted by the plurality of second regions, and the first image and the second image overlap each other. The identification medium is provided at a different position.

  According to the first aspect of the present invention, an identification medium showing a display in which the colors of the images at the overlapping positions are switched is obtained.

  The invention according to claim 2 is the invention according to claim 1, wherein the light reflecting layer reflects light in a specific polarization state. According to the second aspect of the present invention, the light reflected from the light reflecting layer is light in a specific polarization state (linear polarization in a specific direction, right circular polarization, or left circular polarization). The optical function is not lost even if observation is performed in a state where the polarizing filter is separated from the identification medium. Note that the polarizing filter for observation can also be observed by bringing it into contact with the identification medium.

  The invention according to claim 3 is the invention according to claim 1 or 2, further comprising an alignment layer for aligning the optically anisotropic layer, wherein the alignment layer includes a region having the first alignment direction. A structure in which the regions having the second alignment direction are alternately provided in a stripe shape, or the regions having the first alignment direction and the regions having the second alignment direction are provided in a lattice shape. It is characterized by having a structure.

  According to a fourth aspect of the invention, in the second aspect of the invention, the light reflecting layer is constituted by a structure in which a metal reflecting layer and a linearly polarizing filter layer are laminated or a cholesteric liquid crystal layer. Features.

  The invention according to claim 5 is a method of observing the identification medium according to any one of claims 1 to 4 through a polarizing filter that selectively transmits a specific polarization state, the identification medium In the observation with the rotation of the polarizing filter relative to the first image, the first image having the first color is selectively observed at the first rotation angle, and the second image at the second rotation angle. An identification medium identifying method, wherein the second image having two colors is selectively observed.

  According to the fifth aspect of the present invention, a latent image of a specific color is recognized at a specific rotation angle by rotating the polarizing filter for observation relative to the identification medium. A latent color image is recognized. For this reason, high discrimination is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the identification medium which can switch and observe the image of a different color is provided.

It is sectional drawing which shows the cross-section of the identification medium of embodiment. It is a front view which shows typically the state of the orientation of an orientation layer. It is a front view which shows the mode of distribution of the birefringence state of an optically anisotropic layer. It is a front view which shows an example of how an identification medium looks. It is a front view which shows an example of how an identification medium looks. It is a front view which shows typically the state of the orientation of an orientation layer. It is a front view which shows the mode of distribution of the birefringence state of an optically anisotropic layer. It is a front view which shows an example of how an identification medium looks. It is a front view which shows an example of how an identification medium looks. It is sectional drawing which shows the cross-section of the identification medium of embodiment.

1. First Embodiment FIG. 1 shows an identification medium 100 according to an embodiment. The identification medium 100 has a configuration in which an optically anisotropic layer 105, an alignment layer 104, a linearly polarizing filter layer 103, a metal reflective layer 102, and an adhesive layer 101 are laminated from the observation side.

  The adhesive layer 101 is a layer of an adhesive material for attaching the identification medium 100 to an article to be identified. The metal reflection layer 102 is a metal layer that reflects light in the visible light region. In this example, an example of the metal reflection layer 102 using a metal vapor deposition layer as the light reflection layer is shown. However, the material is not limited to this as long as it is a material that reflects a wavelength serving as observation light. The linear polarizing filter layer 103 is a polarizing filter layer that selectively transmits linearly polarized light in a specific direction. The alignment layer 104 is a layer obtained by performing an alignment process on a layer made of a resin material.

  The alignment layer 104 has an alignment structure in which two types of alignment treatment regions having directions different by 45 ° are arranged in a lattice pattern (checkered pattern or check pattern). FIG. 2 conceptually shows the state of the alignment state when the alignment layer 104 is viewed from the side where the identification medium 100 is observed. The alignment layer 104 has a structure in which a first alignment region having an alignment direction A and a second alignment region having an alignment direction B are arranged alternately in a lattice pattern. Here, the alignment direction A and the alignment direction B are shifted by 45 ° in the direction of alignment treatment. Note that the orientation direction shift is preferably an angle of 45 ° in order to clearly switch between the two regions, but other angles are also possible.

  The optically anisotropic layer 105 is made of an oriented polymer material having birefringence, and the orientation state is determined by the orientation layer 104. Further, birefringence is set in a pattern described below. FIG. 3 conceptually shows the optically anisotropic layer 105 viewed from the direction of observing the identification medium 100. As shown in FIG. 3, the optically anisotropic layer 105 includes a first region having a first birefringence anisotropy, a second region having a second birefringence anisotropy, and birefringence. It has other areas which are not shown and are merely light transmission.

  In this example, when observing using the linear polarizing filter, when the linear polarizing filter is set to a certain rotation angle position with respect to the identification medium 100, the first region looks preferentially in a specific color, The birefringence of each region is adjusted so that the second region looks preferentially another specific color when it is changed to another rotational angle position.

  Hereinafter, an example of a method for manufacturing the identification medium 100 will be described. First, the linearly polarizing filter layer 103 is attached to one side of the reflective layer 102 composed of a metal layer. The linear polarizing filter layer 103 is a polarizing filter layer that selectively transmits linearly polarized light in a specific direction. After the linear polarizing filter layer 103 is provided, a resin layer is formed thereon and an alignment process is performed. In the figure, a resin layer that has been made into an alignment layer 104 by performing an alignment treatment is described. As described with reference to FIG. 2, this alignment process is performed so that two regions whose directions of alignment differ by 45 ° are arranged in a lattice shape. In order to obtain this alignment state, a lattice-like mask is used and the resin layer (the layer denoted by reference numeral 104) is subjected to an alignment process in two stages. The orientation treatment is performed by rubbing with a friction member such as a cloth in a specific direction to form fine streaks (unevenness) physically extending in a specific direction. Note that the alignment layer 104 can be obtained by aligning the resin layer with light irradiation.

  Although not shown in the drawings, the metal reflective layer 102 is provided with an embossed pattern constituted by a fine concavo-convex structure, and a hologram display is performed by this embossed pattern. The hologram display may not be provided.

  When the alignment layer 104 is obtained, the optically anisotropic layer 105 is formed on the exposed surface. The optically anisotropic layer 105 is made of an oriented polymer material having birefringence, and is made of a material that undergoes a polymer polymerization reaction when irradiated with light and whose orientation state is determined. The polymer in the optically anisotropic layer has an unreacted reactive group. Unreacted reactive groups react upon exposure to cause cross-linking of the polymer chains, and the degree of cross-linking of the polymer chains varies depending on exposure under different exposure conditions. As a result, the retardation value changes, resulting in a birefringence pattern. It is formed.

  The optically anisotropic layer 105 may have a retardation of 5 nm or more at 20 ° C., preferably 10 nm or more and 10,000 nm or less, and most preferably 20 nm or more and 2000 nm or less.

  In this example, as a method for producing the optically anisotropic layer 105, a solution containing a liquid crystalline compound having at least one reactive group is applied and dried to form a liquid crystal phase, and then irradiated with ionizing radiation to be polymerized and fixed. The production method is adopted. This method is described in JP2009-175208A. The thickness of the optically anisotropic layer 102 is preferably 0.1 to 20 μm, and more preferably 0.5 to 10 μm.

  Hereinafter, an example of the formation process of the optically anisotropic layer 105 will be described. First, a composition (for example, a coating solution) containing a liquid crystal compound is applied onto the alignment layer 104 that has been subjected to an alignment treatment. In this example, a liquid crystal compound containing a rod-like liquid crystal, a horizontal alignment agent, a cationic photopolymerization initiator, a polymerization controller, and methyl ethyl ketone is used. And after setting it as the orientation state which shows a desired liquid crystal phase, this orientation state is fixed by irradiation of ionizing radiation.

In this example, the alignment state of the aligned liquid crystal compound is fixed by a photopolymerization reaction. The irradiation energy for light irradiation is selected from 25 to 800 mJ / cm ² . As the irradiation wavelength, ultraviolet light having a peak at 250 to 450 nm is used.

  At this time, light drawing is performed on the pattern shown in FIG. 3, and the phase difference of transmitted light (birefringence effect) generated in the first region of FIG. 3 and the phase difference of transmitted light generated in the second region (birefringence effect). ) To be in a different state. This adjustment is performed by changing the amount of light to be irradiated (exposure amount). In addition, the area | region where birefringence does not arise is formed by not performing light irradiation.

  Thereafter, by applying heat treatment at a temperature of 200 ° C., the fixed state of the alignment state according to the amount of light irradiated is determined, thereby obtaining the optically anisotropic layer 105 partially different in birefringence state. . If light is not applied, the orientation state is disturbed during heat treatment, and the birefringence of the region disappears (a simple light transmission layer). Said heat processing can be performed at the temperature selected from the range of 50 to 400 degreeC.

  In this way, the optically anisotropic layer 105 is obtained in which regions having different birefringence are provided in the lattice-like pattern shown in FIG.

(Optical function)
The identification medium 100 shown in FIG. 1 is observed from the optically anisotropic layer 105 side. First, a case will be described in which the identification medium 100 is directly observed without using an observation linear polarization filter. In this case, natural light is incident on the identification medium 100. Of the incident natural light, linearly polarized light in a specific direction is transmitted through the polarizing filter layer 103, and the transmitted light is reflected in the upper direction in FIG. The reflected light passes through the polarizing filter layer 103 in the upper direction in FIG. 1 and further passes through the alignment layer 104. Then, the light passes through the optical anisotropic layer 105 from the bottom to the top in FIG.

  This transmitted light is subjected to a birefringence effect when it passes through the first region showing the first birefringence and the second region showing the second birefringence in FIG. In addition, the region that is not birefringent transmits as it is without being affected by the polarization state.

  When this transmitted light is directly observed from the optically anisotropic layer 105 without passing through a polarizing filter, the human eye cannot identify the state of polarization, so that the uniform reflected light (regardless of the pattern of FIG. Reflected light of metallic luster from the metal reflective layer) is observed. At this time, a hologram image (not shown) provided on the metal reflection layer 102 is observed.

  Next, a case where the identification medium 100 is observed through a linear polarization filter that selectively transmits linear polarized light in a specific direction will be described. In this case, when the linear polarizing filter is rotated about the normal direction of the identification medium 100, the first region of FIG. 3 looks like a specific color (for example, green) at a certain angular position (first angular position). . This is shown in FIG. FIG. 4 shows a state where the green letter “A” is visually recognized.

  This is due to the following reason. First, the change in the polarization state in the optically anisotropic layer is caused by the difference in refractive index in the in-plane orthogonal direction of the optically anisotropic layer, and has wavelength dependency. Therefore, the difference in the polarization state caused by passing through the optically anisotropic layer affects the wavelength distribution (wavelength spectrum) of the polarized light when a certain polarized light is selectively viewed. In this case, the first region of FIG. 3 is set to appear green at a certain angle at a rotation angle position of the linear polarizing filter for observation with respect to the identification medium 100.

  On the other hand, since the second region in FIG. 3 is shifted from the first region by 45 ° in the direction of orientation (that is, the axis giving the phase difference), under the condition that the first region appears to be selectively green, It deviates from the condition that it looks like a specific color, it is difficult to see a specific color, and it is difficult to see.

  Then, when the linear polarizing filter for observation is further rotated from the angular position where the green image of FIG. 4 is visible, the image of FIG. 4 becomes invisible, and at a certain angular position (second angular position) Two areas appear to have a certain color. FIG. 5 shows an image formed by the second region. FIG. 6 shows a state where a red letter “B” is visually recognized.

  This appears because the phase difference (refractive index anisotropy) in the second region is such that, at the second angular position, the light from the second region of FIG. ) Is set. Note that, at this second angular position, the light from the first region deviates from the condition that the specific color is visible, and therefore the first region is not visible (or difficult to see).

  Thus, when the identification medium 100 is observed through the observation linear polarization filter, when the linear polarization filter is rotated with respect to the identification medium 100, the green letter A is selectively seen at the first angular position. The red letter B is selectively visible at the second angular position. That is, the latent images A and B of different colors can be switched and viewed by rotating the optical filter for observation.

  The optical function described above can be obtained in the same manner whether the linear polarizing filter is brought into contact with the identification medium 100 or separated from the identification medium 100. This is because the polarization state of light transmitted through the optically anisotropic layer 105 from the bottom to the top in FIG. 1 depends on the function of the polarization filter layer 103 and is in a specific polarization state (in this case, the state of linear polarization). This is because the state of polarization is not related to the distance between the optical filter for observation and the identification medium 100.

  If the polarizing filter layer 103 is not present, the optical function similar to that described above can be obtained in the observation with the linear polarizing filter for observation in contact with the identification medium 100. However, when the linear polarizing filter for observation is separated from the identification medium 100, the ratio of the natural light incident on the identification medium 100 increases, and the natural light included in the light transmitted through the optical anisotropic layer 105 from the bottom to the top of the figure. The proportion of increases. Even if natural light passes through the optically anisotropic layer 105, the influence of the phase difference does not appear. Therefore, as the linear polarizing filter for observation is separated from the identification medium 100, the function of observing the latent image described above decreases. Specifically, the clarity of the latent image is lost, and the function of observing the latent image from a certain stage is lost.

(Superiority)
As described above, in the identification medium 100, the optically anisotropic layer 105 exhibiting the birefringence effect is provided on the alignment layer having alignment regions in different directions in a lattice shape. In the optically anisotropic layer 105, two regions having optical anisotropy are formed in a dot pattern, and a first image and a second image are formed by drawing with the dot pattern. Here, the first image is composed of dots having a first orientation direction and a first birefringence effect, and the second image is provided with a second orientation direction and a second birefringence effect. It is made up of dots. Further, in the observation through the polarizing filter, a visual effect is obtained in which images of different colors can be switched and observed due to the difference between the orientation direction and the birefringence effect.

  That is, the identification medium 100 can display two latent images of different colors at different angular positions as shown in FIGS. 4 and 5 by rotating the linear polarizing filter for observation. These two latent images are in an overlapping position, and can be switched and displayed by rotating the polarizing filter. Further, when the identification medium 100 is viewed directly, these latent images cannot be observed. As described above, when the polarizing filter for observation is rotated with respect to the identification medium, an identification medium capable of observing images of different colors depending on the angle is obtained.

  This optical function can be obtained in the same manner whether the linear polarizing filter for observation is brought into contact with the identification medium 100 or separated from the identification medium 100 without making contact. For this reason, the degradation of the identification function due to the use of the polarizing filter for observation and the disadvantage that the identification function cannot be obtained do not occur.

2. Second Embodiment Another variation of how to give an alignment state to the optically anisotropic layer will be described. FIG. 6 shows an alignment state of the alignment layer 104 different from that in FIG. In the example shown in FIG. 6, alignment treatment regions in directions different by 45 ° are arranged alternately on the stripes. Here, the alignment direction A and the alignment direction B are misaligned by 45 °. Such an alignment process is also performed by an alignment process using a mask.

  FIG. 7 shows an example of a pattern of regions showing different birefringence effects given to the optical anisotropic layer 105 when the configuration of FIG. 6 is adopted. Hereinafter, the optical function of the identification medium 100 when the configuration shown in FIGS. 6 and 7 is employed will be described.

  In this case, when the identification medium 100 is directly viewed, the pattern of FIG. 7 is not visually recognized, and the whole appears to have a uniform metallic luster. When the identification medium 100 is observed with respect to the identification medium 100 via the observation linear polarization filter, the image shown in FIG. 8 is observed at the first angular position. The image shown in FIG. 9 is observed at the second angular position.

  That is, when the linear polarizing filter for observation is set to a specific first angular position, the image (first image) shown in FIG. 8 appears in the first color (for example, green). Then, when the linear polarizing filter for observation is rotated from the specific first angular position, the image (second image) shown in FIG. 9 appears in the second color (for example, red). In this way, as in the case of the first embodiment, by rotating the optical filter, an identification function capable of individually observing latent images of different colors is obtained.

3. Third Embodiment A cholesteric liquid crystal can also be used as reflecting means for reflecting light in a specific polarization state. Hereinafter, this example will be described. FIG. 10 shows an identification medium 200 of the embodiment. The same reference numerals in the identification medium 200 as those of the identification medium 100 are the same as those described with reference to FIG.

  The identification medium 200 includes a cholesteric liquid crystal layer 203 as reflecting means for reflecting light in a specific polarization state. Hereinafter, an example of a method for manufacturing the identification medium 200 will be described. First, a material that transmits observation light and does not disturb the polarization state of the transmitted light (in this case, a TAC (triacetyl cellulose) film is used) is prepared as a base material layer 201, and an adhesive layer is provided on one surface thereof. 101 is formed.

  Next, the film prepared separately is rubbed and a cholesteric liquid crystal layer is grown on the film. Then, the cholesteric liquid crystal layer is transferred onto the base material layer 201 to obtain a cholesteric liquid crystal layer 203. The cholesteric liquid crystal layer 203 has, for example, a layer having a green center wavelength and a characteristic of selectively reflecting circularly polarized light in the clockwise direction. In addition, a hologram image (not shown) is formed on the cholesteric liquid crystal layer 203 by embossing the embossed pattern.

  On the other hand, a base material layer 204 made of the same material as that of the base material layer 201 is prepared, the alignment layer 104 is formed on one surface thereof, and the optical anisotropic layer 105 is formed thereon. The alignment layer 104 and the optically anisotropic layer 105 are the same as those shown in FIG. Next, the cholesteric liquid crystal layer 203 and the base material layer 204 are bonded with a light-transmitting resin adhesive to obtain the identification medium 200 shown in FIG. In this example, black and dark color pigments and pigments are added to the adhesive layer 101, and the adhesive layer 101 also functions as a light absorption layer.

  When light is incident on the identification medium 200 from the optically anisotropic layer 105 side, circularly polarized light (with a specific center wavelength (in this case, a center wavelength corresponding to green) from the cholesteric liquid crystal layer 203 and in a specific turning direction ( In this case, circularly polarized light in the right turn direction) is selectively reflected, and the other light components are absorbed by the adhesive layer 101.

  Green right circularly polarized light reflected upward from the cholesteric liquid crystal layer 203 is transmitted through the base material layer 204 and the alignment layer 104 and further through the optically anisotropic layer 105. At this time, the green right-handed circularly polarized light is subjected to different birefringence effects in each of the first region (see FIG. 3) and the second region of the optical anisotropy 105 and is given a different phase difference. Thereby, the reflected light from the cholesteric liquid crystal layer 203 transmitted through the optically anisotropic layer 105 becomes elliptically polarized light corresponding to the phase difference in the first region and the second region. In a region where no birefringence effect is exhibited, the birefringence effect does not occur and green right-handed polarized light is transmitted as it is.

  When the identification medium 200 is directly viewed, the above birefringence effect is not observed, and the entire identification medium 200 looks green. In addition, a hologram image formed on the cholesteric liquid crystal layer 203 can be seen.

  When the identification medium 200 is observed through a right circular polarization filter that selectively transmits right-turn circularly polarized light, the light from the first region in FIG. 3 appears in the first color and the light from the second region The light appears in the second color. Other areas (background) appear green.

  When the identification medium 200 is observed through a left circularly polarizing filter that selectively transmits left-turning circularly polarized light, a component of circularly polarized light in the reverse turning direction as in the case of using right-turning circularly polarized light is seen. The first image and the second image can be seen in colors different from those when the right circular polarizing filter is used. That is, the color of the image is switched. Such a phenomenon appears because the phase difference generated in the optically anisotropic layer 105 is wavelength-dependent, and by observing different polarization components, light of different central wavelengths is observed. is there.

  Here, an example is shown in which the cholesteric liquid crystal layer selectively reflects right-turn circularly polarized light having a green center wavelength. However, the value (color) of the reflected center wavelength is not limited, and the reflected light swirls. The direction may be a left turn direction.

4). Other Embodiments In the above-described example, the example in which the alignment layer 104 is used as a method for aligning the optically anisotropic layer 105 has been described. However, the alignment layer 104 is not used and light having a specific polarization state is irradiated. Thus, the state of orientation of the optically anisotropic layer 105 can be controlled using a technique for controlling the orientation direction of the polymer. In this case, the orientation control is performed in the polarization state of the irradiated light, and the phase difference control (birefringence control) is performed by controlling the irradiation light amount.

  In the above description, the case where the linear polarization filter that selectively transmits linearly polarized light is used as the polarization filter for observing the identification medium 100 has been described. However, the identification medium 100 can also be observed through the circular polarization filter. It is also possible to observe the identification medium 200 through a linear polarization filter.

  In the above example, an example of an identification medium that shows the colors of two types of areas by switching them has been described, but three or more types of areas are used, for example, the first character at the first angle and the first at the second angle. It is also possible to use an identification medium in which the second character and the third character at a third angle can be seen in different colors.

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

  DESCRIPTION OF SYMBOLS 100 ... Identification medium, 101 ... Adhesive layer, 102 ... Metal reflecting layer, 103 ... Polarizing filter layer, 104 ... Orientation layer, 105 ... Optically anisotropic layer.

Claims (5)

A light reflecting layer;
An optically anisotropic layer provided at a position overlapping the light reflecting layer and exhibiting birefringence,
The optically anisotropic layer is
A plurality of first regions having a first orientation direction and having a first birefringence;
A plurality of second regions having a second orientation direction and having a second birefringence,
A first image is constituted by the plurality of first regions,
A plurality of second regions form a second image;
An identification medium, wherein the first image and the second image are provided at a position where they overlap each other.   The identification medium according to claim 1, wherein the light reflecting layer reflects light having a specific polarization state. An alignment layer for aligning the optically anisotropic layer,
The alignment layer has a structure in which regions having the first alignment direction and regions having the second alignment direction are alternately provided in stripes, or regions having the first alignment direction, and The identification medium according to claim 1, wherein the identification medium has a structure in which the regions having the second alignment direction are provided in a lattice pattern.   The identification medium according to claim 2, wherein the light reflection layer is configured by a structure in which a metal reflection layer and a linear polarization filter layer are laminated or a cholesteric liquid crystal layer. A method of observing the identification medium according to any one of claims 1 to 4 via a polarizing filter that selectively transmits a specific polarization state,
In observation by rotating the polarizing filter relative to the identification medium,
Selectively observing the first image having a first color at a first rotation angle;
A method for identifying an identification medium, wherein the second image having a second color is selectively observed at a second rotation angle.

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