JP2011099888A - Identification medium and identification method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an identification medium which has simple structure and in which images can be changed and seen. <P>SOLUTION: The identification medium 101 includes a star type pattern 202 displayed by cholesteric liquid crystals. The star type pattern 202 is constituted of two or more dot-shaped patterns, and the dot-shaped patterns include a first dot-shaped pattern group and a second dot-shaped pattern group having different central wavelengths of reflection. Then, the first dot-shaped pattern group constitutes the star type pattern 202 of first color, and the second dot-shaped pattern group constitutes the star type pattern 202 of second color. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  An identification medium using cholesteric liquid crystal is known. For example, Patent Document 1 describes an identification medium having a structure in which a hologram and a cholesteric liquid crystal are combined. Patent Document 2 describes a technique for forming a cholesteric liquid crystal layer by printing using a cholesteric liquid crystal component that has been granulated and dispersed in ink. Patent Document 3 describes a configuration in which a diffractive structure constituting a hologram is used for displaying a hologram by orientation of a liquid crystal material and an optical diffraction effect. Patent Document 4 describes a configuration in which an image is formed using a liquid crystal region having a property of rotating a polarization direction and a liquid crystal region having a circular polarization property.

JP 2006-145688 A Japanese Patent No. 4278731 JP-T-2006-525139 (paragraphs “0066” to “0076”) JP-T 2007-532959 (“0021” paragraph, “0022” paragraph)

  The configuration described in Patent Document 1 requires an alignment film or an alignment process. This complicates the structure and complicates the manufacturing process. In the configuration described in Patent Document 2, since the cholesteric liquid crystal component is dispersed in a granular form, the transmitted light is dispersed and lacks in transparency (appears cloudy). In the configuration described in Patent Document 3, since the diffraction structure also serves as the alignment film, the structure is simplified in that respect. However, the image cannot be changed such that the color is switched, and the discrimination function is lacking. The configuration described in Patent Document 4 also lacks an identification function because an image change that changes colors is not obtained.

  In such a background, an object of the present invention is to provide an identification medium that has a simple structure and can be switched and viewed.

  The invention described in claim 1 includes a cholesteric liquid crystal layer composed of a plurality of dot-like patterns, and the plurality of dot-like patterns are first dot-like shapes having different turning directions or center wavelengths of reflected light. An identification medium including a pattern group and a second dot-shaped pattern group.

  According to the first aspect of the present invention, the first image formed by the first dot-shaped pattern group and the second dot-shaped pattern group are configured by the difference in the turning direction of the reflected light. A second image is formed. These two images can be separated and observed by a circularly polarizing filter that selectively transmits one of the rotation directions. In addition, since an image can be formed using dots, it is possible to display an image with high identification while having a simple structure. For this reason, an identification medium capable of performing identification using switching of images while having a simple structure is provided.

  According to a second aspect of the present invention, in the first aspect of the invention, the first dot-shaped pattern group and the second dot-shaped pattern group have a turning direction and a center wavelength of reflected light to be reflected. Both are different. According to the second aspect of the present invention, since the colors of the two images that are observed separately by the difference in the turning direction are different, a higher identification function can be obtained. For example, a red image is visually recognized by using an optical filter that selectively transmits right-turn circularly polarized light, and a blue image is visually recognized by using an optical filter that selectively transmits left-turned circularly polarized light. An identification medium is provided. In addition, since the color is given by the difference in the center wavelength of the reflected light from the cholesteric liquid crystal, a color image is not required, but a simple configuration can be obtained while the configuration can observe a color image.

  According to a third aspect of the present invention, in the second aspect of the present invention, the first dot-shaped pattern group forms a first image, and the second dot-shaped pattern group is a second image. The first image and the second image are the same image, and are formed at overlapping positions.

  According to the third aspect of the present invention, a color obtained by combining the colors of the first image and the second image is observed by direct viewing. For example, if the first image is red and the second image is blue, a magenta color image is observed. Then, by observing the circularly polarized light in the first turning direction through a circularly polarizing filter that selectively transmits, the image of the first color can be observed, and the circularly polarized light in the second turning direction is selectively transmitted. The second color image can be observed by observing through the circular polarizing filter. That is, it is possible to observe an image whose color changes depending on whether or not the circularly polarizing filter is used and the difference in the turning direction.

  According to a fourth aspect of the present invention, the plurality of dot-like patterns reflect light having a central wavelength different from the reflected light from the first dot-like pattern group and the second dot-like pattern group. A third dot-shaped pattern group, and each of the first dot-shaped pattern group, the second dot-shaped pattern group, and the third dot-shaped pattern group has three primary colors of RGB. The identification medium according to claim 3, wherein the corresponding central wavelength light is reflected.

  According to the fourth aspect of the present invention, a color image using the three primary colors of RGB can be used for identification. In particular, color gradation display can be used for identification by adjusting the ratio of RGB. According to this mechanism, color gradation display is possible, so that a fine color image can be used for identification.

  The invention according to claim 5 is the invention according to claim 1, wherein the reflected light from the first dot-shaped pattern group and the reflected light from the second dot-shaped pattern group are in the turning direction. And the first image composed of the first dot-shaped pattern group is shifted from the second image composed of the second dot-shaped pattern group. To do. According to the fifth aspect of the present invention, two images at different positions can be distinguished and visually recognized due to the difference in the turning direction. Note that the two images located at different positions may or may not overlap.

  The invention according to claim 6 is the invention according to claim 5, wherein the first image constitutes an image for the right eye, the second image constitutes an image for the left eye, and the first image A stereoscopic image is constituted by the image and the second image. According to the invention described in claim 6, a stereoscopic image can be used for identification.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, further comprising a diffraction grating layer provided in contact with the cholesteric liquid crystal layer, wherein the diffraction grating layer is subjected to an alignment treatment. It is applied or serves also as an alignment layer, and a hologram image is formed by the diffraction grating layer. According to the seventh aspect of the present invention, since the cholesteric liquid crystal is aligned using the diffraction grating layer for forming the hologram image, the structure is simplified.

  The invention described in claim 8 is characterized in that in the invention described in any one of claims 1 to 7, the cholesteric liquid crystal layer is subjected to hologram processing. According to the eighth aspect of the present invention, a hologram formed by hologram processing applied to the cholesteric liquid crystal layer can be used for identification.

  According to a ninth aspect of the present invention, the first dot is obtained by observing the identification medium according to any one of the second to fifth aspects by an optical filter that selectively transmits right-handed or left-handed circularly polarized light. It is an identification medium identification method characterized by selectively observing a first image composed of a group of patterns. According to the ninth aspect of the present invention, the second image constituted by the second dot-shaped pattern group cannot be seen by observing using the optical filter that transmits the circularly polarized light in one turning direction. In addition (or difficult to see), a first image constituted by the first dot-like pattern group can be seen. Further, by observing without using the optical filter, the first image and the second image can be seen together. Identification is performed by utilizing the difference in color at this time.

  The invention according to claim 10 is an optical filter in which the identification medium according to claim 6 is observed with the right eye by an optical filter that selectively transmits the first turning direction and selectively transmits the second turning direction. The method for identifying the identification medium is characterized in that a stereoscopic image is observed by observing with the left eye. According to the tenth aspect of the present invention, an identification medium capable of identification using a stereoscopic image is provided.

  According to the present invention, there is provided an identification medium that has a simple structure and can be switched and viewed.

It is a conceptual diagram which shows the cross-sectional structure of the identification medium of embodiment. It is a front view at the time of seeing the identification medium of embodiment directly from the front. It is the front view (A) of an optical filter, and sectional drawing (B) of a circularly-polarizing filter part. It is a front view of the identification medium of the embodiment observed through a circular polarization filter. It is a front view of the identification medium of the embodiment observed through a circular polarization filter. It is a front view of the identification medium of the embodiment observed through a circular polarization filter. It is a front view of the identification medium of the embodiment observed through a circular polarization filter. It is a front view of the identification medium of the embodiment observed through a circular polarization filter. It is a conceptual diagram which shows the dot structure of the liquid crystal layer in the identification medium of embodiment. It is a conceptual diagram which shows the dot structure of the liquid crystal layer in the identification medium of embodiment. It is a conceptual diagram which shows the cross-sectional structure of the identification medium of embodiment. It is a front view which shows how the identification medium of embodiment is visible.

(1) First embodiment (identification medium)
FIG. 1 shows an identification medium 101. The identification medium 101 has a structure in which a protective layer 102, a hologram forming layer 103, a cholesteric liquid crystal layer 105, and an adhesive layer 106 are laminated from the observation side. In a state where it is not attached to the article to be identified, a release paper is attached to the exposed surface of the adhesive layer 106 (not shown in FIG. 1).

  The protective layer 102 has a light-transmitting property that transmits light used for identification, and is made of a material that does not disturb the polarization state of the transmitted light. As a material of the protective layer 102, for example, a TAC (Triacetylcellulose) film is used.

  The hologram forming layer 103 functions as a diffraction grating layer on which a diffraction grating is formed. The hologram forming layer 103 is a thermoplastic or thermosetting resin layer having optical transparency. A diffraction grating 104 (hologram type) for displaying a hologram is formed on the hologram forming layer 103 by hot pressing. The pitch of the diffraction grating 104 is preferably 100 nm to 1500 nm, and the depth of the diffraction grating is preferably about 100 nm to 500 nm, but is not particularly limited. The diffraction grating 104 also functions as an alignment layer for the cholesteric liquid crystal layer 105.

  The cholesteric liquid crystal layer 105 is formed using an ink jet method. The state of the cholesteric liquid crystal layer 105 viewed from the front will be described later. The adhesive layer 106 is made of an adhesive material to which a black or dark pigment or dye is added. The adhesive layer 106 may be made of an adhesive material that does not lose its adhesiveness. Further, the adhesive layer 106 may be light transmissive.

  Hereinafter, an example of a method for manufacturing the identification medium 101 will be described. First, the protective layer 102 is prepared, and the hologram forming layer 103 is formed using the protective layer 102 as a base material. Next, the hologram mold is pressed against the exposed surface of the hologram forming layer 103 by a hot press method to form the diffraction grating 104. At this time, an alignment layer is also formed at the same time. Note that the alignment process may be performed on the hologram forming layer 103 in a separate step, and the diffraction grating 104 may be provided with a function as an alignment layer.

  Next, a starting material (stock solution) of cholesteric liquid crystal is sprayed on the diffraction grating 104 by an ink jet printing method. Here, in an inkjet printing apparatus known as a printing method, a stock solution of cholesteric liquid crystal is used instead of ink, and this stock solution of cholesteric liquid crystal is sprayed onto the surface to be formed (on the diffraction grating 104) to adhere in the form of dots. Let At this time, the amount of the chiral agent in the cholesteric liquid crystal layer to be attached is adjusted according to the print pattern described later, and the center wavelength of the reflected light from the obtained cholesteric liquid crystal layer is adjusted. Thereby, colors composed of a plurality of colors are displayed in a predetermined pattern.

  A cholesteric liquid crystal has a layered structure, in which the directions of molecular long axes in each layer are parallel to each other and parallel to the layer surface. Each layer rotates and overlaps little by little and has a three-dimensional spiral structure (spiral structure). The distance p in the direction perpendicular to the layer until the direction of the molecular long axis in this helical structure rotates 360 ° (one rotation) and returns to the original is called the pitch. The central wavelength λ of the circularly polarized light reflected by λ = n · p is determined from the pitch p and the average refractive index n in each layer. Here, n is substantially determined by the type of cholesteric liquid crystal, and p is adjusted by the amount of addition of a chiral agent (additive material for spirally aligning liquid crystal molecules). Further, the turning direction of the reflected circularly polarized light is determined by the turning direction of the spiral structure.

  Therefore, by adjusting the amount of the chiral agent in the starting material of the cholesteric liquid crystal material sprayed by the ink jet, the distribution of the pitch p in the cholesteric liquid crystal layer 105 can be adjusted for each dot, and the center wavelength of the reflected light is set. . The turning direction of the reflected light is determined by the type of additive that determines the twist direction of the spiral structure.

  After the cholesteric liquid crystal stock solution is deposited on the diffraction grating 104 by the ink jet method, the alignment state of the liquid crystal molecules is grown under a predetermined temperature condition to obtain the cholesteric liquid crystal layer 105. Thereafter, an adhesive layer 106 is provided to obtain the identification medium 101 shown in FIG.

(Display pattern)
FIG. 2 is a front view showing a state in which the identification medium 101 is directly seen from the protective layer 102 side under natural light. Reference numeral 201 denotes a background color (background pattern). The background color 201 is constituted by a print pattern of the cholesteric liquid crystal layer 105 that reflects right-turn circularly polarized light having a center wavelength that looks green.

  Reference numeral 202 denotes a star pattern constituting an outer star shape of a double star shape, and is composed of two types of dot groups arranged in a matrix. FIG. 9 is a conceptual diagram in which a part of the star pattern 202 is enlarged. As shown in FIG. 9, the star pattern 202 is composed of two types of dot groups 202a and 202b that are alternately arranged in a matrix.

  The dot group 202a is composed of cholesteric liquid crystal dots that reflect right-handed circularly polarized light with a red wavelength. The dot group 202b is composed of cholesteric liquid crystal dots that reflect left-handed circularly polarized light with a blue wavelength. The dot groups 202a and 202b are formed by an ink jet method using a cholesteric liquid crystal stock solution as ink. Selection of a color and a turning direction is performed by adjusting the quantity and kind of an additive as mentioned above.

  The image formed by the dot group 202a and the image formed by the dot group 202b are the same star-shaped image 202. These two images overlap, and when viewed directly, red and blue appear to be mixed and appear magenta. When viewed with the right-turn circular polarization filter, the red star pattern 202 created by the dot group 202a is selectively viewed, and when viewed with the left-turn circular polarization filter, the blue star pattern 202 created by the dot group 202b is selected. Looks like.

  Returning to FIG. 2, the symbol 203 is a star pattern arranged inside the star pattern 202. The star pattern 203 is a pattern of the cholesteric liquid crystal layer 105 that reflects right-turn circularly polarized light having a center wavelength that looks green. The star pattern 203 is also composed of a set of cholesteric liquid crystal dots. Reference numeral 204 in FIG. 2 is a character display using a hologram. The hologram display 204 is generated by interference of diffracted light caused by the diffraction grating 104. This diffracted light becomes circularly polarized diffracted light because the cholesteric liquid crystal is used as a reflective layer.

(Identification function)
Hereinafter, the identification function of the identification medium 101 will be described. Table 1 below summarizes how the identification medium 101 looks.

  First, when the identification medium 101 is directly observed without using an optical filter to be described later, a magenta star pattern 202 and a green star pattern 203 inside the magenta star pattern 202 are observed with the green background color 201 as a background. In addition, the hologram 204 is observed.

  FIG. 3 is an example of an optical filter for viewing the identification medium 101. In FIG. 3, an optical filter 300 is shown. The optical filter 300 selectively transmits right-turning circularly polarized light and blocks other polarized light, and a left-turned circularly polarizing filter unit 301 that selectively transmits left-turned circularly polarized light and blocks other polarized light. A circular polarization filter unit 302 is provided.

  The right-turning circularly polarizing filter part 301 and the left-turning circularly polarizing filter part 302 have a structure in which a quarter-wave plate 311 and a linearly polarizing plate 312 that selectively transmits linearly polarized light are stacked. The turning direction of the transmitted light in the right turn circular polarization filter unit 301 and the left turn circular polarization filter unit 302 is determined by the angular relationship around the optical axis of the quarter-wave plate 311 and the polarizing plate 312.

  Hereinafter, a case where the identification medium 101 is observed through the right-turning circularly polarizing filter unit 301 that transmits right-turning circularly polarized light will be described. FIG. 4 is a front view when the identification medium 101 is observed through a right-turn circularly polarizing filter.

  In this case, right-handed circularly polarized light from the background color 201 and the star pattern 203 is transmitted through the right-handed circularly polarizing filter unit 301, so that the background color 201 and the star pattern 203 appear green. Then, the blue left-handed circularly polarized light from the star pattern 202 is blocked by the right-handed circularly polarizing filter unit 301, and the red right-handed circularly polarized light from the star-shaped pattern 202 passes through the right-handed circularly polarizing filter unit 301. Since it is transmitted, the star pattern 202 appears red (FIG. 4).

  Next, a case where the identification medium 101 is observed through the left-turning circularly polarizing filter unit 302 that transmits left-turning circularly polarized light will be described. FIG. 5 is a front view when the identification medium 101 is observed through the left-turn circular polarization filter.

  In this case, the right-handed circularly polarized light from the background color 201 and the star pattern 203 is blocked by the left-handed circularly polarizing filter unit 302, so that the background color 201 and the star pattern 203 appear black (the adhesive layer 106). Black color is visible). Then, the blue counterclockwise circularly polarized light from the star pattern 202 is transmitted through the counterclockwise circular polarization filter unit 302, and the red clockwise circularly polarized light from the star pattern 202 is blocked by the counterclockwise circular polarization filter unit 302. Therefore, the star pattern 202 looks blue. Further, the hologram 204 cannot be read (or is difficult to read) because it is diffracted light of right-turning circularly polarized light in portions other than the star pattern 202. The setting of the color of the identification medium 101 is an example, and the combination of the color and the turning direction is not limited as long as it is within the range described in the claims.

(Superiority)
The identification medium 101 includes a diffraction grating 104 that has been subjected to an alignment process, and a cholesteric liquid crystal 105 that is formed in contact with the diffraction grating 104. A hologram image is formed by the diffraction grating 104, and the star pattern 202 of the cholesteric liquid crystal 105 Is composed of a plurality of dot-shaped patterns shown in FIG. 9, and these dot-shaped patterns are a first dot-shaped pattern group 202a and a second dot-shaped pattern group that are different in the central wavelength to be reflected. 202b.

  Further, the first dot-shaped pattern group 202a forms a red first image, the second dot-shaped pattern group 202b forms a blue second image, and the first dot-shaped pattern group 202a The turning direction (right turn) of the reflected light from the pattern group 202a and the turning direction (left turn) of the reflected light from the second dot-shaped pattern group 202b are opposite, and the first image and the second image. Are the same star-shaped patterns 202 and are formed at overlapping positions.

  In this configuration, the star pattern 202 has an image formed by a set of two types of dots having different turning directions and different center frequencies of reflected light. Therefore, the direct pattern and the observation using the left and right circular polarizing filters have different shades. Looks like. Identification is performed using this fact. In this example, since a change in color is used, a high identification function can be obtained. Also, since the uncomfortable feeling caused by the difference in hue is easy to recognize, an identification medium that is difficult to obtain by camouflaging can be obtained. In addition to this, a high discrimination function can be obtained by observing a phenomenon in which the hologram changes visible and invisible by the circular polarization filter. Further, since the hologram formed in the cholesteric liquid crystal layer is difficult to duplicate, an identification medium that is difficult to forge can be obtained.

(Other examples of color display)
FIG. 10 is a conceptual diagram showing an example of a dot structure applicable to the star pattern 202 of FIG. FIG. 10 shows six pixels 10 to 60 arranged in a matrix. Actually, an image is displayed by a larger number of pixels. Here, an example constituted by six pixels will be described in order to simplify the description.

  The six pixels 10 to 60 have the same basic structure. Hereinafter, the pixel 10 will be described as a representative. The pixel 10 has dots 11, 12, and 13 made of cholesteric liquid crystal formed by an ink jet method. The shape of the dots 11 to 13 is arbitrary, but is an elliptical shape here. In this example, the dots 11 are assigned to the three primary colors R (red), the dots 12 are G (green), and the dots 13 are B (blue).

  The color is set by adjusting the pitch of the cholesteric liquid crystal constituting the dots. Specifically, the pitch is adjusted by adjusting the addition amount of the chiral agent, and the center wavelength of the reflected light is adjusted. That is, the addition amount of the chiral agent is adjusted so that the dot 11 has a pitch that reflects the center wavelength corresponding to red (R), and the dot 12 reflects the center wavelength corresponding to green (G). The addition amount of the chiral agent is adjusted so as to be a pitch, and the addition amount of the chiral agent is adjusted so that the dot 13 has a pitch reflecting the center wavelength corresponding to blue (B).

  In addition, the area of the dots 11 to 13 is adjusted to adjust the blending ratio of the three primary colors, thereby adjusting the color indicated by the pixel 10. This adjustment is performed by adjusting the ejection amount of the raw material of the cholesteric liquid crystal ejected in the ink jet printing, or by adjusting the number of ejections with a constant ejection amount. In FIG. 10, the area of each dot is the same, and an example of a uniform color as a whole is shown. The dots 11 and 12 reflect right-turning circularly polarized light, and the dot 13 reflects left-turning circularly polarized light.

  The above points are the same for the pixels 20, 30, 40, 50 and 60. Thus, the six pixels 10 to 60 form a color image that is observed when viewed directly (actually, a color image is formed by more pixels). According to this configuration, it is possible to display the gradation of the color, and it is possible to use a color image with shading for identification.

  Further, by adjusting the combination of the sizes of the dots 11 to 13, a desired color can be obtained, so that the color can be easily set.

  In this example, when observation is performed using a circularly polarizing filter that selectively transmits right-turn circularly polarized light, reflected light from the dots 11 and 12 can be seen, that is, a color in which red and green are overlapped is seen. Then, when observation is performed using an optical filter that selectively transmits counterclockwise circularly polarized light, the reflected light from the dots 13 can be seen, and the blue color can be seen. Further, when viewing directly without using a circular polarizing filter, a color image in which the three primary colors of the dots 11 to 13 are synthesized is observed.

(Other)
In the configuration shown in FIG. 9, by adjusting the area ratio of the dot group 202a and the dot group 202b, the ratio of red and blue can be adjusted, and the hue when directly viewed can be adjusted. In this case, the area of the dots may be adjusted by adjusting the amount of the cholesteric liquid crystal stock solution to be ejected in forming the dots by the inkjet method. Further, by adjusting the area ratio of red dots and blue dots in each region 202c, a color image having a gradation (light / dark) can be displayed.

  In the above example, the first image formed by the dot group 202a and the second image formed by the dot group 202b are the same star pattern 202, but the first image and the second image are separated from each other. It is good also as a simple shape. Further, the positions may be such that the two images partially overlap (that is, partially shift) or are completely shifted. By doing so, in observation using the left and right circularly polarizing filters, a function of switching not only the color but also the shape and position of the image can be obtained.

  In the configuration illustrated in FIG. 1, a hologram of the cholesteric liquid crystal layer 105 may be formed by pressing a hologram shape against the cholesteric liquid crystal layer 105 before the adhesive layer 106 is provided. In this case, a hologram different from the hologram by the diffraction grating 104 is formed on the side of the cholesteric liquid crystal layer 105 that is in contact with the adhesive layer 106.

(2) Second Embodiment FIG. 6 is a front view showing an identification medium according to another embodiment. 7 and 8 are front views showing a case where the identification medium of FIG. 6 is observed through a circular polarizing filter.

  FIG. 6 shows an identification medium 400. The sectional structure of the identification medium 400 is the same as that in the first embodiment. In this example, a cholesteric liquid crystal that reflects green right-handed circularly polarized light is selected as the background color 401. A cholesteric liquid crystal that reflects red right-handed circularly polarized light is selected as the pattern 402. In addition, “SECURITY” is also formed by a hologram.

  Here, the character pattern 403 “GENUINE” is composed of cholesteric liquid crystal that reflects the reflected light having the same color as the background and the direction of turning opposite. That is, “GE” and “NE” are made of cholesteric liquid crystal that reflects left-turning circularly polarized light having the same green color as the background color 401 and having a reverse turning direction, and the “NUI” part is the same as the pattern 402. It is composed of cholesteric liquid crystal that reflects left-turning circularly polarized light that is red and has a reverse turning direction. The background color 401, the design 402, and the character pattern 403 are configured by a set of cholesteric liquid crystal dots.

  In FIG. 6, the character pattern 403 “GENUINE” is displayed. However, since the character pattern 403 is the same color as the background as described above, when the character pattern 403 is viewed directly without using the circular polarization filter, Invisible (or difficult to see).

  When the identification medium 400 is viewed through a circular polarization filter that selectively transmits right-handed circularly polarized light, left-handed circularly polarized light reflected from the character pattern 403 “GENUINE” cannot be observed, and the character pattern 403 appears black (see FIG. 7). At this time, a character “SECURITY” is visually recognized as a hologram image.

  On the other hand, when the identification medium 400 is viewed through a circular polarizing filter that selectively transmits left circularly polarized light, left-turn circularly polarized light reflected from the character pattern 403 “GENUINE” is observed, and right-handed rotation from other regions is observed. Circularly polarized light cannot be observed (or is difficult to observe). For this reason, the character pattern 403 appears in the background color, and the other areas appear black (or appear darker) (FIG. 8).

  According to this example, a latent image effect is obtained in which the character pattern 403 “GENUINE” which is not visible (or difficult to see) in FIG. 6 appears as a color image as shown in FIG. 8 by using the circular polarization filter. It is done.

(3) Third Embodiment After forming a cholesteric liquid crystal layer, a configuration in which hologram processing is performed on the cholesteric liquid crystal layer is also possible. FIG. 11 is a conceptual diagram illustrating a cross-sectional structure of the identification medium according to the embodiment. FIG. 11 shows an identification medium 500. The identification medium 500 includes a protective layer 501, a cholesteric liquid crystal layer 502, and an adhesive layer 503.

  The protective layer 501 is made of a material (for example, TAC) that transmits light having a wavelength used for identification and does not disturb the polarization state of transmitted light. The cholesteric liquid crystal layer 502 is configured by a dot-like pattern formed by an inkjet method, like the cholesteric liquid crystal layer 105 of FIG. The adhesive layer 503 is made of an adhesive material or a pressure-sensitive adhesive material mixed with a dark color pigment or dye such as black. The adhesive layer 503 functions as a light absorption layer that absorbs light transmitted through the cholesteric liquid crystal layer 502 in addition to the function of attaching the identification medium to an article to be identified.

  Hereinafter, an example of a method for manufacturing the identification medium 500 will be described. First, a protective layer 501 is prepared, one surface thereof is subjected to alignment treatment, and a cholesteric liquid crystal layer 502 is formed by an ink jet method. As the symbol constituted by the cholesteric liquid crystal layer 502, the one shown in FIG. 2 can be adopted. When the cholesteric liquid crystal layer 502 is formed, a diffraction grating (embossed pattern) 504 for forming a hologram image by light interference is formed by hot pressing the hologram mold. Thereafter, the adhesive layer 503 is formed, and the identification medium 500 is obtained.

(4) Fourth Embodiment By separating the images formed by two types of dot groups for the right eye and for the left eye, and separating the images for the right eye and the left eye depending on the turning direction, the images are viewed separately. A three-dimensional image can also be used for identification. Hereinafter, an example of an identification medium that uses this stereoscopic image for identification will be described.

  FIG. 12 is a front view illustrating an example of an identification medium that uses a stereoscopic image for identification. FIG. 12A shows the appearance when directly observed without passing through the optical filter, and FIG. 12B shows the state observed through the optical filter.

  FIG. 12 shows an identification medium 600. The identification medium 600 has the same cross-sectional structure as the identification medium 101 shown in FIG. The identification medium 600 has a hologram display “SECURITY”, and a star shape R601 for the right eye and a star shape L602 for the left eye are formed. The star shape R and the star shape L are constituted by a set of dots of cholesteric liquid crystal. This is the same as in the case of the first embodiment. Here, the star R601 is constituted by a collection of dot patterns of cholesteric liquid crystal that reflects a red center wavelength, and the star L602 is constituted by a collection of dot patterns of cholesteric liquid crystal that reflects a blue center wavelength. Details of the dot pattern are the same as those shown in FIG.

  The star R601 is an image that forms an image for the right eye, and is formed of cholesteric liquid crystal dots that selectively reflect right-turning circularly polarized light. The star L602 is an image that forms an image for the left eye, and is composed of cholesteric liquid crystal dots that selectively reflect left-turn circularly polarized light. The star shape R and the star shape L are formed at positions slightly deviated by the parallax of both eyes (exaggerated in the figure), and the star shape R601 is visually recognized by the right eye, and the star shape L602 is By viewing with the left eye, a stereoscopic image is recognized.

  When the identification medium 600 is directly viewed, the star shape R601 and the star shape L602 are visually recognized by both the left and right eyes. For this reason, as shown in FIG. 12 (A), both the star shape R601 and the star shape L602 at the shifted positions can be seen at the same time, and the star-shaped symbol that is double-blurred is recognized. At this time, a portion where only the star shape R601 is visible appears red, and a portion where only the star shape L602 is visible appears blue. The portion where the star shape R601 and the star shape L602 overlap is mixed with red and blue and appears magenta.

  Next, a case where a stereoscopic image is viewed will be described. In this case, the identification medium 600 is viewed with the right eye through a right-turning circularly polarizing filter that selectively transmits right-turning circularly polarized light. Further, the identification medium 600 is viewed with the left eye through a left-turning circularly polarizing filter that selectively transmits left-turning circularly polarized light. Then, the right-handed circularly polarized light reflected from the star R601 is visible with the right eye but not with the left eye. Conversely, the left-turn circularly polarized light reflected from the star L602 is visible with the left eye but not with the right eye. That is, the star shape R601 is selectively visually recognized by the right eye, and the star shape L602 is selectively visually recognized by the left eye. Accordingly, a stereoscopic image is obtained as a virtual image in the visual center, and the star-shaped stereoscopic image 603 shown in FIG. 12B is recognized. The stereoscopic image 603 looks magenta in which red and blue are combined.

  The identification medium 600 is identified by the difference in appearance between FIG. 12 (A) and FIG. 12 (B). In other words, identification is performed by using a phenomenon in which a stereoscopic image appears when viewed through an optical filter and a phenomenon in which the color changes at this time.

  In the example shown in FIG. 12, the image for the right eye and the image for the left eye are configured with a cholesteric liquid crystal dot pattern. And by making the turning direction of reflected light into the opposite direction in both images, in observation using a circular polarizing filter, each image is separated and visually recognized by the left and right eyes so that a stereoscopic image can be observed. Furthermore, by changing the colors of the left and right images, it is possible to perceive a change in color between when viewed as a stereoscopic image and when viewed directly. For this reason, a high identification function can be obtained.

  Note that the left-handed circularly polarized light may be viewed with the right eye, and the right-turned circularly polarized light may be viewed with the left eye. Also, the color setting is not limited to this example, and other colors can be selected. Also, the dot pattern shown in FIG. 10 can be used.

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

  DESCRIPTION OF SYMBOLS 101 ... Identification medium, 102 ... Protective layer, 103 ... Hologram formation layer, 104 ... Diffraction grating, 105 ... Cholesteric liquid crystal layer, 106 ... Adhesive layer, 201 ... Background color, 202 ... Star pattern, 202a ... Dot group, 202b ... Dot group, 203 ... Star pattern, 204 ... Hologram display, 300 ... Optical filter, 301 ... Right-turn circular polarization filter section, 302 ... Left-turn circular polarization filter section, 311 ... 1/4 wavelength plate, 312 ... Linear polarization Plate 400 ... Identification medium 401 ... Background color 402 ... Pattern 403 ... Character pattern 500 ... Identification medium 501 ... Protective layer 502 ... Cholesteric liquid crystal layer 503 ... Adhesive layer 504 ... Diffraction grating 600 ... Identification Medium, 601 ... Star R, 602 ... Star L, 603 ... Star-shaped stereoscopic image.

Claims (10)

Provided with a cholesteric liquid crystal layer composed of a plurality of dot-like patterns,
The plurality of dot-shaped patterns include a first dot-shaped pattern group and a second dot-shaped pattern group having different turning directions or center wavelengths of reflected light, and an identification medium.   2. The identification medium according to claim 1, wherein the first dot-shaped pattern group and the second dot-shaped pattern group differ in both a turning direction and a center wavelength of reflected light to be reflected. . The first dot-shaped pattern group forms a first image;
The second dot-shaped pattern group forms a second image;
The identification medium according to claim 2, wherein the first image and the second image are the same image and are formed at overlapping positions. The plurality of dot-shaped patterns include a third dot-shaped pattern group that reflects light having a central wavelength different from the reflected light from the first dot-shaped pattern group and the second dot-shaped pattern group. In addition,
Each of the first dot-shaped pattern group, the second dot-shaped pattern group, and the third dot-shaped pattern group reflects light having a central wavelength corresponding to the three primary colors of RGB. The identification medium according to claim 3. The reflected light from the first dot-shaped pattern group and the reflected light from the second dot-shaped pattern group have different turning directions,
The first image composed of the first dot-shaped pattern group and the second image composed of the second dot-shaped pattern group are in a shifted position. 2. The identification medium according to 1.   The first image constitutes a right-eye image, the second image constitutes a left-eye image, and the first image and the second image constitute a stereoscopic image. The identification medium according to claim 5, characterized in that: A diffraction grating layer provided in contact with the cholesteric liquid crystal layer;
The diffraction grating layer is subjected to an alignment treatment, or doubles as an alignment layer,
The identification medium according to claim 1, wherein a hologram image is formed by the diffraction grating layer.   The identification medium according to claim 1, wherein the cholesteric liquid crystal layer is subjected to hologram processing.   An optical filter that selectively transmits right-handed or left-handed circularly polarized light is used to observe the identification medium according to any one of claims 2 to 5, and is configured by the first dot-shaped pattern group. A method for identifying an identification medium, wherein one image is selectively observed.   The identification medium according to claim 6 is observed with the right eye using an optical filter that selectively transmits the first turning direction, and is observed with the left eye using an optical filter that selectively transmits the second turning direction. An identification medium identification method characterized by observing an image.

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