JP2009073103A - Information recording medium and information reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily configure alignment of recording identification information in a small region and to reduce the risk of illegal reading of the identification information. <P>SOLUTION: This information recording medium 10 comprises a scattering reflection layer 120 and a latent image forming layer 150 facing the scattering reflection layer 120, composed of a solidified liquid crystal material, and holding a latent image as first information, a light-transmissive orientation layer 140 facing the latent image forming layer 150 in which a main surface facing the latent image forming layer 150 includes a plurality of unit orientation regions and the plurality of unit orientation regions form a latent image in the latent image forming layer 150, and an image forming layer 130 facing a portion of the scattering reflection layer 120 by sandwiching or not sandwiching at least one of the latent image forming layer 150 and the orientation layer, including a plurality of light absorbing parts arranged corresponding to a portion of the plurality of unit orientation regions, wherein the alignment of the light absorbing parts configures second information different from first information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an information recording technique that can be used, for example, to prevent forgery.

  An information recording medium such as an ID (identification) card may be provided with an array of a plurality of diffraction gratings in order to prevent forgery.

  For example, Patent Document 1 describes an information recording medium including a plurality of diffraction grating groups each composed of a plurality of diffraction gratings designed so that diffracted light is collected at one point under specific conditions. Yes. It is possible to determine whether or not this information recording medium is a genuine product by confirming the visible image displayed by these diffraction grating groups.

  In this information recording medium, identification information for determining whether or not it is a genuine product is recorded using a diffraction grating. When a diffraction grating is used, recorded information may be perceived by observation with the naked eye. Therefore, in order to make it difficult to realize that the identification information is recorded, for example, it is necessary to make the diffraction grating have a small size. Further, in order to conceal the portion where information is recorded, it is necessary to consider the arrangement of the diffraction grating.

Patent Documents 2 and 3 describe information recording media using a cholesteric liquid crystal material. In order to determine whether or not these information recording media are genuine products, a circular polarizing filter is used.
JP 2006-155292 A Japanese Patent Laid-Open No. 11-42875 Japanese Patent Laid-Open No. 2000-211300

  When recording identification information using one kind of cholesteric liquid crystal material, information “0” and “1” are assigned to a portion including the cholesteric liquid crystal material and a portion not including the cholesteric liquid crystal material, respectively. Become. When such binary recording is performed, it is easy to read the identification information, but there is a high risk that the identification information is illegally read.

  It is also possible to record the identification information by using two kinds of cholesteric liquid crystal materials having different twist directions of the helical structure formed by the mesogenic group. In this case, identification information can be recorded using the difference in the twist direction of the helical structure in addition to the presence or absence of the cholesteric liquid crystal material. However, it is extremely difficult to accurately coat a plurality of types of cholesteric liquid crystal materials in a fine region. Therefore, according to this technique, it is difficult to make individual regions sufficiently small. When recording identification information using an array of a plurality of regions, if the size of each region is large, the identification information is likely to be read illegally.

  The present invention has been made in view of the above circumstances, and it is easy to configure an array for recording identification information in a small area and to reduce the risk that the identification information is illegally read.

  According to the first aspect of the present invention, when one of the main surfaces is irradiated with light having polarization, a scattering reflection layer that emits scattered light having polarization from the main surface; A latent image forming layer that holds a latent image as first information, and faces the latent image forming layer, and has a plurality of main surfaces facing the latent image forming layer. A plurality of unit alignment regions between the light-transmissive alignment layer forming the latent image in the latent image forming layer and at least one of the latent image forming layer and the alignment layer. Or a plurality of light absorbing parts arranged in correspondence with a part of the plurality of unit orientation regions, facing a part of the scattering reflection layer with or between them And an image forming layer constituting second information different from the first information. Information recording medium, characterized in that the is provided.

  According to a second aspect of the present invention, there is provided an information reading device for reading information held by the information recording medium according to the first aspect, wherein the illumination device emits illumination light, an imaging device, and the illumination light is polarized. To the information recording medium, and thereby an optical system for guiding one linearly polarized light of the reproduction light emitted from the information recording medium to the imaging device, and information obtained from the output of the imaging device. There is provided an information reading apparatus comprising a processing unit that performs processing based on a difference in color and reproduces the first information.

  According to the present invention, it is possible to easily configure an array for recording identification information in a small area, and to reduce the risk that the identification information is illegally read.

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

  FIG. 1 is a plan view schematically showing an information recording medium according to an aspect of the present invention. FIG. 2 is a sectional view taken along line II-II of the information recording medium shown in FIG. 3 to 6 are plan views schematically showing unit alignment regions of the alignment layer included in the information recording medium shown in FIG. FIG. 7 is a plan view schematically showing the arrangement of the unit orientation regions shown in FIGS. 3 to 6 on the information recording medium shown in FIG. FIG. 8 is a plan view schematically showing an image forming layer included in the information recording medium shown in FIG.

  As shown in FIG. 2, the information recording medium 10 includes a substrate 110, a scattering reflection layer 120, an image forming layer 130, an alignment layer 140, and a latent image forming layer 150. This information recording medium 10 is irradiated with illumination light from the latent image forming layer 150 side to display an image, which is observed from the latent image forming layer 150 side. In the following description, the observer side is called the front side, and the opposite side is called the back side. 1 to 8, the directions that are parallel to the main surface on the front side of the substrate 110 and intersect each other are the X direction and the Y direction, and the directions perpendicular to them are the Z direction.

  The base material 110 has, for example, a layer shape. The base material 110 may have a light transmittance or may not have a light transmittance. That is, it is not necessary to consider birefringence when selecting the material of the substrate 110. Therefore, for example, a relatively inexpensive material such as polyethylene terephthalate (PET) can be used as the material of the equipment 110.

  The scattering reflection layer 120 is provided on the front surface of the substrate 110. The scattering reflection layer 120 emits scattered light having polarization from one main surface when light having polarization is irradiated on one main surface. In other words, the scattering reflection layer 120 reflects incident light by imparting scattering properties while substantially maintaining the polarization properties thereof.

  The scattering reflection layer 120 is, for example, a metal layer having a fine uneven structure on the surface. Such a scattering reflection layer 120 can be obtained, for example, by vapor-depositing a metal such as aluminum on a base provided with a fine uneven structure. For example, the scattering reflection layer 120 can be obtained by providing a fine uneven structure on the front surface of the substrate 110 and depositing a metal such as aluminum thereon.

  As the scattering reflection layer 120, a single or multilayer dielectric layer provided with a fine uneven structure may be used. When a multilayer dielectric layer is used as the scattering reflection layer 120, for example, a fine concavo-convex structure is provided on the base material such as the base 110, and a high refractive index material such as zinc sulfide and magnesium fluoride are provided thereon. The scattering reflection layer 120 can be obtained by alternately depositing the low refractive index material.

  The image forming layer 130 is provided on the front surface of the scattering reflection layer 120. The image forming layer 130 faces only a part of the front surface of the scattering reflection layer 120. In other words, the image forming layer 130 is provided with an opening.

  As shown in FIG. 8, the image forming layer 130 includes a plurality of light absorbing portions 130a. The opening provided in the image forming layer 130 includes a plurality of light transmission portions 130b. The arrangement of the light absorbing portions 130a forms a “B” -shaped pattern. The arrangement of the light transmitting portions 130b forms the inverted pattern. The light absorption part 130a and the light transmission part 130b are arranged corresponding to the plurality of unit alignment regions 140a to 140d shown in FIG.

  Hereinafter, in the information recording medium 10, each of a plurality of regions defined by the unit orientation regions 140a to 140d is referred to as a unit region or a pixel. In FIG. 1, reference numerals PX11 to PX16, PX21 to PX26, PX31 to PX36, PX41 to PX46, PX51 to PX56, and PX61 to PX66 are attached to these unit areas.

  The light absorption part 130a is typically a light-shielding layer having light absorption and light reflection, or a colored transparent layer. Here, as an example, it is assumed that the light absorbing portion 130a is a light shielding layer having light absorptivity and light reflectivity.

  The light absorption part 130a is obtained by printing colored ink on the scattering reflection layer 120, for example. For this printing, for example, an offset printing method, a relief printing method, or a screen printing method can be used.

  The image forming layer 130 may be interposed between the alignment layer 140 and the latent image forming layer 150. Alternatively, the image forming layer 130 may be provided on the latent image forming layer 150. In the latter case, typically, the light absorber 130a is light transmissive.

  The alignment layer 140 covers the image forming layer 130 and the scattering reflection layer 120. The alignment layer 140 is transparent and typically optically isotropic. The alignment layer 140 is made of a resin such as an acrylic resin, for example.

  The front surface of the alignment layer 140 includes a plurality of unit alignment regions 140a to 140d shown in FIGS. Each of the unit orientation regions 140a to 140d is provided with a plurality of grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction. Each of the unit alignment regions 140a to 140d controls the alignment direction of the mesogen group in the latent image forming layer 14 to be substantially parallel to the length direction of the groove.

  The length direction of the groove provided in the unit alignment region 140a and the length direction of the groove provided in the unit alignment region 140b are substantially orthogonal. The length direction of the groove provided in the unit alignment region 140c is substantially orthogonal to the length direction of the groove provided in the unit alignment region 140d. The length direction of the groove provided in the unit alignment region 140c and the length direction of the groove provided in the unit alignment region 140d are the same as the length direction of the groove provided in the unit alignment region 140a and the unit alignment region 140b. It is inclined with respect to the length direction of the provided groove.

  Specifically, in the unit alignment region 140a shown in FIG. 3, the length of the groove is substantially parallel to the Y direction. In the unit alignment region 140b shown in FIG. 4, the length direction of the groove is substantially parallel to the X direction. In the unit orientation region 140c shown in FIG. 5, the groove has an angle of about 45 ° counterclockwise with respect to the Y direction when viewed from the front side. In the unit orientation region 140d shown in FIG. 6, the groove has an angle of about 45 ° in the clockwise direction with respect to the Y direction when viewed from the front side.

  The unit orientation regions 140a to 140d are two-dimensionally arranged as shown in FIG. The arrangement of the unit alignment regions 140a and 14b forms an “A” -shaped pattern. The arrangement of the unit alignment regions 140c and 14d forms the inverted pattern. The unit orientation regions 140a to 140d may be arranged one-dimensionally instead of two-dimensionally.

  In each of the unit alignment regions 140a to 140d, the grooves may or may not be parallel to each other. However, the closer these grooves are to be parallel, the easier it is for the long axes of those mesogenic groups to be aligned in each portion of the latent image forming layer 150 corresponding to the unit alignment regions 140a to 140d. The angle formed by these grooves is, for example, 5 ° or less, and typically 3 ° or less.

  In each of the unit alignment regions 140a to 140d, the lengths of the grooves may be equal to each other or different from each other. Further, the distance between adjacent grooves in the length direction may be uniform or non-uniform. Furthermore, the distance between adjacent grooves in the width direction may be uniform or non-uniform.

  By making the grooves substantially parallel and appropriately setting the pitch, the diffraction grating can be constituted by these grooves. Alternatively, for example, when grooves having various lengths are arranged to be arranged in one direction on average while being somewhat random, a unidirectional diffusion pattern can be formed by these grooves. This unidirectional diffusion pattern has a diffusion capability in a plane perpendicular to the length direction of the groove, and diffusion in a plane perpendicular to the main surface of the alignment layer 140 and parallel to the length direction of the groove. It is a pattern showing a larger light diffusion characteristic, that is, light scattering anisotropy than the performance. Here, for simplification, it is assumed that the grooves provided in the unit alignment regions 140a to 140d do not constitute a unidirectional diffusion pattern.

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

  The cross section perpendicular to the length direction of each groove of the unit alignment regions 140a to 140d has, for example, a triangular wave shape. The cross section may have other shapes such as a sine wave shape, a square wave shape, a rectangular wave shape, a trapezoidal wave shape, and a sawtooth wave shape.

  Instead of providing grooves in each of the unit alignment regions 140a to 140d, each of the unit alignment regions 140a to 140d may be subjected to an alignment process such as a photo alignment process. For example, by performing an alignment process using a mask, mesogenic groups can be aligned in different directions in regions adjacent to the unit alignment regions 140a to 140d of the latent image forming layer 150.

  However, when grooves are provided in each of the unit alignment regions 140a to 140d, the alignment layer 140 can be formed using transfer.

  The planar shape of each of the unit alignment regions 140a to 140d is, for example, a parallelogram such as a square and a rectangle. In this case, the length of one side of each of the unit orientation regions 140a to 140d is typically 1 mm or less, for example, about 0.5 mm. Each of the unit alignment regions 140a to 140d may have another planar shape. For example, the planar shape of each of the unit alignment regions 140a to 140d may be circular or elliptical. In this case, the length of the circular diameter or the long axis of the ellipse is, for example, 1 mm or less.

  The alignment layer 140 can be formed by, for example, a method of recording a hologram pattern on a photosensitive resin material using a two-beam interference method or a method of drawing a pattern with an electron beam. Alternatively, as is done in the manufacture of surface relief holograms, it can be formed by pressing a mold provided with fine linear projections onto the resin. For example, the alignment layer 140 is a method in which a master plate provided with linear protrusions is pressed against a thermoplastic resin layer formed on a laminate of the substrate 110 and the scattering reflection layer 120 while applying heat. That is, it is obtained by a hot embossing method. Alternatively, the alignment layer 140 is formed by applying an ultraviolet curable resin on the laminate of the substrate 110 and the scattering reflection layer 120, and irradiating the substrate 110 side with ultraviolet rays while curing the ultraviolet curable resin. Then, it can be formed by a method of removing the original plate.

  Usually, a reverse plate is manufactured by transferring the uneven structure of the original plate, and a duplicate plate is manufactured by transferring the uneven structure of the reverse plate. Then, if necessary, a reversal plate is manufactured using the copy plate as an original plate, and the uneven structure of the reversal plate is transferred to further manufacture a copy plate. In actual production, a copy obtained in this way is usually used.

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

  The original plate can be obtained, for example, by performing electroforming of a mother die obtained by a method of recording a hologram pattern using a two-beam interference method, a method of drawing a pattern by an electron beam, or a method of cutting by a cutting tool. It is done.

  The latent image forming layer 150 covers the alignment layer 140 as shown in FIG. The latent image forming layer 150 is made of a solidified liquid crystal material.

  The latent image forming layer 150 is made of, for example, a polymer nematic liquid crystal or a smectic liquid crystal material. In this case, the latent image forming layer 150 is obtained by applying a photopolymerizable liquid crystal material on the alignment layer 140 and irradiating the coating film with energy rays such as ultraviolet rays.

  In each of the regions adjacent to the unit alignment regions 140a to 140d of the latent image forming layer 150, the mesogenic groups are aligned substantially parallel to the groove length direction. That is, in each region, the latent image forming layer 150 is composed of four types of birefringent regions having different mesogenic group orientation directions. These birefringent regions are arranged corresponding to the unit alignment regions 140a to 140d shown in FIG. 7, and form a latent image to be visualized by using a polarizer. The slow axis of each birefringent region is substantially parallel to the length direction of the groove.

  As described above, the arrangement of the unit alignment regions 140a and 14b forms an “A” -shaped pattern, and the arrangement of the unit alignment regions 140c and 14d forms an inverted pattern thereof. The latent image forming layer 150 includes four birefringent regions corresponding to the unit orientation regions 140c and 140d, respectively, and these birefringent regions form a latent image. That is, the latent image forming layer 150 holds character information “A” as the first information in the form of a latent image. The first information may be character information other than the character information “A”. The first information may be information other than character information such as a one-dimensional code, a two-dimensional code, and graphic information.

  Further, the arrangement of the light absorbing portions 130a forms a “B” -shaped pattern, and the arrangement of the light transmitting portions 130b forms an inverted pattern thereof. That is, the image forming layer 130 holds character information “B” as second information different from the first information. The second information may be character information other than the character information “B”. The second information may be information other than character information such as a one-dimensional code, a two-dimensional code, and graphic information.

  In the information recording medium 10, the orientation direction of the mesogen group is controlled by the unit orientation regions 140 c and 140 d provided in the image forming layer 130. The unit alignment regions 140c and 140d can be formed by embossing or an optical technique. Therefore, in this information recording medium 10, it is easy to configure an array for recording identification information in a small area. Therefore, the information recording medium 10 is to reduce the risk that the identification information is illegally read.

  The pattern formed by the arrangement of the light absorbing portions 130a and the pattern formed by the arrangement of the light transmitting portions 130b, the pattern formed by the arrangement of the unit alignment regions 140a and 140b, and the arrangement of the unit alignment regions 140c and 140d Are superposed on the pattern formed. Therefore, it is difficult to realize that the information recording medium 10 holds a latent image.

  Next, an image displayed by the information recording medium 10 will be described. First, an image displayed by the information recording medium 10 when observed from the normal direction will be described.

  FIG. 9 is a plan view showing an example of an image displayed on the information recording medium shown in FIG. 1 when observed from the normal direction using a polarizer.

In FIG. 9, as an example, a linear polarizing plate 220 is used as a polarizer. The information recording medium 10 and the polarizing plate 220 are arranged such that the front surface of the information recording medium 10 faces the polarizing plate 220 and the transmission axis _AT of the polarizing plate 220 is 45 ° clockwise with respect to the Y direction when viewed from the front side. The viewing direction is substantially perpendicular to the front surface of the information recording medium 10.

  When the information recording medium 10 is observed from a substantially vertical direction under such observation conditions, the information recording medium 10 displays, for example, an image shown in FIG. The reason for this will be described below.

When the linear polarizing plate 220 is irradiated with white light as illumination light, the polarizing plate 220 transmits linearly polarized light having a polarization plane (vibration plane of the electric field vector) parallel to the transmission axis _AT and is perpendicular to the transmission axis. Absorbs linearly polarized light having a polarization plane. Here, white light means continuous spectrum light including all wavelength components in the visible light range.

The linearly polarized light incident on the first unit region including the unit alignment region 140a and the light transmission part 130b is transmitted through the latent image forming layer 150 shown in FIG. In the first unit region, the slow axis of the latent image forming layer 150 forms an angle of 45 ° with respect to the X direction. Therefore, for example, the light component having a certain wavelength λ _{0 in} the previous linearly polarized light is converted into right circularly polarized light by passing through the latent image forming layer 150, and the remaining light component is converted into the latent image forming layer. By passing through 150, it is converted into right elliptically polarized light.

These right circularly polarized light and right elliptically polarized light are incident on the alignment layer 140.
The right circularly polarized light and the right elliptically polarized light as the diffracted light transmitted through the alignment layer 140 are reflected by the scattering reflection layer 120. The right circularly polarized light and the right elliptically polarized light are respectively converted into left circularly polarized light and left elliptically polarized light by being reflected by the reflective layer 120. Further, since the scattering reflection layer 120 has light scattering properties, the reflected light is scattered light.

  The left circularly polarized light and the left elliptical polarized light as the scattered light are transmitted through the alignment layer 140. A diffraction grating is provided on the front surface of the alignment layer 140. In addition to the reflected light from the scattering reflection layer 120 being scattered light, the incident angle of illumination light varies in a normal environment. Therefore, the reflected light from the scattering reflection layer 120 enters the latent image forming layer 150 as scattered light.

Since this incident light is scattered light, it includes a light component traveling in the front direction and a light component traveling in an oblique direction. Among the light components traveling in the front direction, the left circularly polarized light having the specific wavelength λ ₀ is transmitted through the latent image forming layer 150 to be linearly polarized light whose polarization plane is perpendicular to the transmission axis _{AT of the} polarizing plate 220. Converted. Then, the remaining light component is converted into left elliptically polarized light, left circularly polarized light, right elliptically polarized light, or circularly polarized light by transmitting through the latent image forming layer 150.

That is, when attention is paid only to a light component having a polarization plane parallel to the transmission axis _AT of the polarizing plate 220, the first unit region including the unit alignment region 140a and the light transmission part 130b includes the unit region. The ratio of the intensity of the light component emitted from the unit region to the intensity of the incident light component has a wavelength dependency. In other words, the ratio of the intensity of the display light emitted from the polarizing plate 220 to the intensity of the illumination light incident on the polarizing plate 220 has wavelength dependency. Therefore, the first unit region appears colored. The reason why the first unit area appears colored will be described later with reference to mathematical expressions.

  The second unit region including the unit alignment region 140b and the light transmission part 130b, and the first unit region including the unit alignment region 140a and the light transmission part 130b are the lengths of the grooves constituting the diffraction grating. The only difference is that the directions differ by 90 °. Therefore, the second unit region behaves in the same manner as described for the first unit region except that the rotation direction of the polarization plane of circularly polarized light or elliptically polarized light is reversed. Therefore, the second unit region appears colored in the same manner as the first unit region.

In the third unit region including the unit alignment region 140 c and the light transmission part 130 b, the slow axis of the latent image forming layer 150 is perpendicular to the transmission axis _AT of the polarizing plate 220. Therefore, ideally, all light components incident on the third unit region are transmitted through the polarizing plate 220 without being absorbed. Therefore, the third unit region looks silvery white.

  The fourth unit region including the unit alignment region 140d and the light transmission part 130b is the same as the third unit region except that the slow axis of the latent image forming layer 150 is different by 90 °. Therefore, the fourth unit region looks silvery white.

  When the light absorption part 130a is a light-shielding layer having light absorption and light reflection, the scattering reflection layer 120 does not contribute to display in the unit region including the light absorption part 130a. That is, in the unit region including the light absorbing portion 130a, only the reflected light from the light absorbing portion 130a can contribute to the display.

  Accordingly, the fifth unit region including the unit alignment region 140a and the light absorption unit 130a looks darker than the first unit region including the unit alignment region 140a and the light transmission unit 130b, and the unit alignment region 140b. The sixth unit region including the light absorbing portion 130a appears darker than the second unit region including the unit alignment region 140b and the light transmitting portion 130b. That is, the fifth unit region and the sixth unit region have substantially the same brightness, hue, and / or saturation. That is, the fifth unit region and the sixth unit region appear to be almost the same color. For example, the fifth and sixth unit regions appear gray to black.

  In addition, the seventh unit region including the unit alignment region 140c and the light absorption unit 130a looks darker than the third unit region including the unit alignment region 140c and the light transmission unit 130b, and the unit alignment region 140d. The eighth unit region including the light absorbing portion 130a appears darker than the fourth unit region including the unit alignment region 140d and the light transmitting portion 130b. The seventh unit area and the eighth unit area appear to have almost the same color. For example, the seventh and eighth unit regions appear to be almost the same color as the color of the light transmission part 140d itself.

  As is clear from the above description, when observed using the polarizing plate 220, the information recording medium 10 displays an image composed of four types of regions having different colors, that is, the image shown in FIG.

Here, the reason why the first unit region including the unit alignment region 140a and the light transmission portion 130b and the second unit region including the unit alignment region 140b and the light transmission portion 130b appear to be colored is expressed by a mathematical formula. The description will be given with reference. In these unit regions, the latent image forming layer 150 serves as a quarter-wave plate for light having a wavelength λ ₀ .

It can be considered that the linearly polarized light having the wavelength λ ₀ emitted from the polarizing plate 220 in the normal direction is the sum of the linearly polarized light component whose polarization plane is perpendicular to the X direction and the linearly polarized light component whose polarization plane is perpendicular to the Y direction. it can. As described above, in the first or second unit region, the refractive index in the X-direction of the latent image forming layer 150 is extraordinary refractive index n _e, the refractive index in the Y-direction is the ordinary refractive index n _o . Thus, the latent image formation layer 150, these linear polarization component, providing a phase difference of lambda _0/4 in each of the forward path and the backward path. That is, the latent image formation layer 150 provides a phase difference of lambda _0/2 in total of these linearly polarized light components. Therefore, the light with the wavelength λ ₀ emitted from the first or second unit region in the normal direction cannot pass through the polarizing plate 220.

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

A pair of linear polarizing plates face each other so that their transmission axes are perpendicular to each other, and a liquid crystal layer is interposed between them so that the optical axis forms an angle of 45 ° with respect to the transmission axis of the linear polarizing plate. When one linear polarizing plate is illuminated with light having a wavelength λ from its normal direction, the intensity of light incident on the liquid crystal layer is I _0, and the intensity of light transmitted through the other linear polarizing plate is I. I can be represented by the following equation (2).
I = I ₀ × sin ² (Re × π / λ) (2)
The birefringence Δn has wavelength dependence, and the birefringence Δn and the wavelength n are not in a proportional relationship. Therefore, as is clear from equation (2), the spectrum of transmitted light has a different profile from the spectrum of incident light.

  Thus, when the liquid crystal layer is sandwiched between a pair of linear polarizing plates, transmitted light having a spectrum profile different from that of incident light can be obtained. Similarly, when the liquid crystal layer is sandwiched between the linearly polarizing plate and the reflective layer, reflected light having a spectrum profile different from that of the incident light can be obtained. For this reason, the first and second unit regions appear colored.

  As described above, when the information recording medium 10 is observed using the polarizing plate 220, the information recording medium 10 displays an image composed of four types of regions having different colors, that is, the image shown in FIG. For example, the character information “A” can be read from the reproduced image by the following method.

FIG. 10 is a plan view showing information that can be read from the image shown in FIG.
When the information recording medium 10 is observed without using the polarizing plate 220, the information recording medium 10 displays an image including the character information “B” formed by the arrangement of the light absorbing portions 130a shown in FIG. When the information recording medium 10 is observed without using the polarizing plate 220, as shown in FIG. 9, the information recording medium 10 displays an image composed of four types of regions having different colors. Accordingly, the character information “A” shown in FIG. 10 can be read out by performing image processing using these images.

  For example, an image displayed on the information recording medium 10 when the polarizing plate 220 is used is compared with an image displayed on the information recording medium 10 when the polarizing plate 220 is not used. An image is composed of an array of unit areas having different colors and an array of unit areas having almost no change in color. Thereby, the character information “A” shown in FIG. 10 can be read.

  Alternatively, the unit region including the unit alignment region 140a or 140b and the light absorption unit 130a may be displayed when the polarizing plate 220 is used, and the unit region including the unit alignment region 140c or 140d and the light absorption unit 130a. The color displayed when the polarizing plate 220 is used is checked in advance. Then, referring to the image displayed on the information recording medium 10 when the polarizing plate 220 is used, the unit area exhibiting these colors is selected. When an image is constituted by an array composed of the selected unit areas and an array composed of other unit areas, the character information “A” shown in FIG. 10 can be read out.

  Alternatively, the unit region including the unit alignment region 140a or 140b and the light transmission unit 130b may be displayed when the polarizing plate 220 is used, and the unit region including the unit alignment region 140c or 140d and the light transmission unit 130b. The color displayed when the polarizing plate 220 is used is checked in advance. Then, referring to the image displayed on the information recording medium 10 when the polarizing plate 220 is used, the unit area exhibiting these colors is selected. When an image is constituted by an array composed of the selected unit areas and an array composed of other unit areas, the character information “A” shown in FIG. 10 can be read out.

  Next, an image displayed on the information recording medium 10 when observed from an oblique direction using the polarizing plate 220 will be described.

  When the observation direction is tilted in a plane perpendicular to the X direction from the observation conditions described with reference to FIG. 9, the optical path length of the latent image forming layer 150 is increased in each unit region, and the unit alignment regions 140a, 140c, and 140d are formed. In the included unit region, the birefringence Δn further changes. That is, when the observation direction is tilted, the retardation of the latent image forming layer 150 changes in each unit region.

  As a result, when the information recording medium 10 is observed from the normal direction using the polarizing plate 220, unit regions that appear to be the same color may display different colors by tilting the observation direction. For example, the first unit region including the unit alignment region 140a and the light transmission unit 130b displays red, and the second unit region including the unit alignment region 140b and the light transmission unit 130b displays green.

  However, when the information recording medium 10 is observed from the normal direction using the polarizing plate 220, the unit areas that appear different colors display different colors even when the observation direction is tilted. Therefore, when observing from an oblique direction, the character information “A” can be read out by a method almost the same as that when observing from the normal direction.

  In addition, the amount of information recorded in the latent image forming layer 150 can be increased by using the fact that the same color appears when viewed from the front direction using the polarizing plate 220 and that the color looks different when the viewing direction is tilted. Can do. Therefore, in this case, it is possible to achieve a higher level of forgery prevention effect.

For example, the following information reading device can be used for reading the information.
FIG. 11 is a diagram schematically illustrating an example of an information reading apparatus.
The information reading device 20 includes an illumination device, an optical system, an imaging device 230, and a processing unit 240.

The lighting device includes one light source 210. The light source 210, as illumination light L _i to illuminate the front of the information recording medium 10, for example, white light is emitted in an oblique direction with respect to the information recording medium 10. The light source 210 is sufficiently separated from the information recording medium 10 so that the entire front surface of the information recording medium 10 can be illuminated.

  The light source 210 may be a point light source, a line light source, or a surface light source. As the light source 210, for example, a halogen lamp, a light emitting diode, or a fluorescent tube can be used.

The optical system includes a polarizer 220. Polarizer 220, where is a linear polarizer, illumination light L _i where the light source 210 is emitted from the natural light is converted into linearly polarized light guided to the information recording medium 10, thereby the information recording medium 10 is emitted An optical system is formed that converts the reproduction light L _r into linearly polarized light and then guides it to the imaging device 230. The polarizing plate 220 faces the front surface of the information recording medium 10. The transmission axis _AT of the polarizing plate 220 forms an angle of 45 ° clockwise with respect to the Y direction when viewed from the light source 210 side.

The imaging device 230 receives the reproduction light L _r converted into linearly polarized light by the polarizing plate 220. The imaging device 230 is a color imaging device and includes, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Imaging device 230 and light source 210 is typically the surface of the information recording medium 10 the image pickup apparatus 230 illumination light L _i which regularly reflected is arranged so as not to light.

  The processing unit 240 is connected to the imaging device 230. The processing unit 240 processes the image information output from the imaging device 230 and reproduces the character information “A” held in the information recording medium 10.

  The information reading device 20 typically further includes an output device connected to the processing unit 240. The output unit outputs the information reproduced by the processing unit 240 so that the operator can perceive, for example, optically or acoustically. As the output unit, for example, a display device that displays the character information “A” reproduced by the processing unit 240 can be used.

  In the information reading device 20, the imaging device 230 detects, for example, the following image. That is, the portion corresponding to the first unit region including the unit alignment region 140a and the light transmission portion 130b is red, and the portion corresponding to the second unit region including the unit alignment region 140b and the light transmission portion 130b is It is green. A portion corresponding to the fifth unit region including the unit alignment region 140a and the light absorption unit 130a is a color obtained by subtractive color mixture of red and the color of the light absorption unit 130a. The unit alignment region 140b and the light absorption unit 130a The portion corresponding to the sixth unit area including the color is a color corresponding to the subtractive color mixture of the green color and the light absorbing portion 130a. The portions corresponding to the third, fourth, seventh, and eighth unit regions including the unit orientation region 140b are different in color from the portions corresponding to the first, second, fifth, and sixth unit regions. is there. Therefore, if these colors are stored as reference information in the processing unit 240, image information corresponding to the character information “A” can be obtained from the image information output from the imaging device 230 and the reference information.

  The information reading apparatus 20 may be provided with a drive mechanism that rotates the information recording medium 10 around its normal line. That is, when reproducing the character information “A” held in the information recording medium 10, the information recording medium 10 may be rotated around the normal line. Image information corresponding to the character information “A” can be obtained by using the rotation angle of the information recording medium 10 and the change in display color. For example, from the state shown in FIG. 11, only the information recording medium 10 is rotated by 90 ° around an axis parallel to the Z direction. In this way, the display color is switched between the portion corresponding to the first unit region and the portion corresponding to the second unit region, and between the portion corresponding to the fifth unit region and the portion corresponding to the sixth unit region. The display color does not change in the portions corresponding to the third, fourth, seventh, and eighth unit regions. That is, the display color is changed in the portion corresponding to the unit alignment region 140a or 140b, and the display color is not changed in the portion corresponding to the unit alignment region 140c or 140d. Therefore, based on this, image information corresponding to the character information “A” can be obtained.

FIG. 12 is a diagram schematically illustrating another example of the information reading apparatus.
This information reading apparatus 20 is the same as the information reading apparatus 20 described with reference to FIG. 11 except that the following configuration is adopted.

  In other words, in the information reading apparatus 20 shown in FIG. 12, the illumination device and the optical system include a plurality of light sources 210 a and 210 b and a plurality of polarizers 220 a to 220 c instead of the light source 210 and the polarizer 220.

Each of the light sources 210a and 210b, as the illumination light L _i to illuminate the front of the information recording medium 10, for example, emits white light. The light sources 210a and 210b are sufficiently separated from the information recording medium 10 so that the entire front surface of the information recording medium 10 can be illuminated. As the light sources 210a and 210b, for example, those exemplified for the light source 210 can be used.

Polarizer 220a to 220c here is a linear polarization plate, the illumination light L _i of the light source 210a and 210b is emitted from the natural light is converted into linearly polarized light guided to the information recording medium 10, thereby recording medium 10 constitutes an optical system that guides the reproduction light L _r emitted by the light 10 to the image pickup device 230 after converting it into linearly polarized light.

Polarizer 220a is the illumination light L _i where the light source 210a is emitted from the natural light is converted into linearly polarized light guided to the information recording medium 10. For example, the polarizer 220a transmits linearly polarized light whose polarization plane is perpendicular to the Z direction and forms an angle of + 45 ° with respect to the Y direction.

Polarizer 220b is illumination light L _i where the light source 210b is emitted from the natural light is converted into linearly polarized light guided to the information recording medium 10. For example, the polarizer 220b transmits linearly polarized light whose polarization plane is perpendicular to the Z direction and forms an angle of −45 ° with respect to the Y direction.

The polarizer 220 c converts the reproduction light L _r emitted from the information recording medium 10 into linearly polarized light and guides it to the imaging device 230. For example, the polarizer 220c transmits linearly polarized light whose polarization plane is perpendicular to the Z direction and forms an angle of + 45 ° with respect to the Y direction.

  The information reader 20 reads information held by the information recording medium 10 by the following method.

  When reading information held by the information recording medium 10 with the information reading device 20, first, the light source 210a is turned on with the light source 210b turned off. At this time, the image detected by the imaging device 230 is equal to the image captured by the imaging device 230 of the information reading device 20 shown in FIG.

  Next, the light source 210a is turned off and the light source 210b is turned on. At this time, the image detected by the imaging device 230 includes a portion corresponding to the first unit region including the unit alignment region 140a and the light absorption unit 130b, and a second unit including the unit alignment region 140b and the light transmission unit 130b. The color is switched between the portion corresponding to the unit region, and the portion corresponding to the fifth unit region including the unit alignment region 140a and the light absorbing portion 130a, the unit alignment region 140b, and the light absorbing portion 130a is included. The color is exchanged with the portion corresponding to the sixth unit region, and the portions corresponding to the third, fourth, seventh and eighth unit regions including the unit orientation region 140c or 140d are changed to black. .

  That is, by switching the illumination light source from the light source 210a to the light source 210b, the display color is changed in the portion corresponding to the unit alignment region 140a or 140b, and the display color is black in the portion corresponding to the unit alignment region 140c or 140d. And change. Therefore, for example, the image information output from the imaging device 230 is displayed on the processing unit 240 in a portion where the unit color constituting the latent image switches the illumination light source from the light source 210a to the light source 210b and causes a change in display color. That the unit area constituting the latent image corresponds to a portion where the display color does not change to black by switching the illumination light source from the light source 210a to the light source 210b, or both. By performing processing based on this, image information corresponding to the character information “A” can be obtained.

  Here, an arrangement is adopted in which the polarization plane of the linearly polarized light transmitted by the polarizer 220a and the polarization plane of the linearly polarized light transmitted by the polarizer 220c are parallel to each other. It may be adopted.

  The information reading apparatus 20 uses the two light sources 210a and 210b and the two polarizers 220a and 220b. However, even when the light source 210b and the polarizer 220b are omitted, the same method as described above is used. Thus, the character information “A” can be reproduced. For example, the information reader 20 is provided with a drive mechanism that rotates the transmission axis of the polarizer 220a or 220c. When the transmission axis of the polarizer 220a or 220c is rotated, the display color changes to black in the portion corresponding to the unit orientation region 140c or 140d, so that image information corresponding to the character information “A” can be obtained.

  In addition, although the structure which irradiates linearly polarized light to the information recording medium 10 was demonstrated here, you may add the structure which can irradiate the information recording medium 10 with natural light. In this way, it is possible to read the image information corresponding to the character information “B” even without this, but if natural light can be irradiated, the image information corresponding to the character information “B” can be easily obtained. it can. This image information can be used, for example, to confirm that the information recording medium 10 is genuine in combination with image information corresponding to the character information “A”. This image information can also be used for alignment of the information recording medium 10.

As described above, the case where the structure described with reference to FIGS. 1 and 2 is adopted as the information recording medium 10 has been described as an example, but the information recording medium 10 can be variously modified.
For example, in the above description, the information recording medium 10 is configured by 36 unit areas, but the information recording medium 10 may be configured by more or less unit areas. The information recording medium 10 may employ a configuration in which a latent image is visualized by using a circular polarizer or an elliptical polarizer instead of adopting a configuration in which the latent image is visualized by using a linear polarizer.

  The information recording medium 10 may further include a protective layer that covers the latent image forming layer 150 and / or a support that supports the substrate 150. Further, the thickness of the latent image forming layer 150 may be non-uniform.

  FIG. 13 is a cross-sectional view schematically showing an information recording medium according to a modification.

  This information recording medium 10 has the same structure as the information recording medium 10 described with reference to FIGS. 1 and 2 except that the following configuration is adopted. That is, in the information recording medium 10, the unit region PX34 has a thicker alignment layer 140 than the unit regions PX14, PX24, PX44, PX54, and PX64. The unit region PX34 has a thinner latent image forming layer 150 than the unit regions PX14, PX24, PX44, PX54, and PX64.

  The thickness of the latent image forming layer 150 affects the retardation. Therefore, when non-uniformity is introduced into the thickness of the latent image forming layer 150 in this way, the amount of information recorded in the latent image forming layer 150 can be increased.

1 is a plan view schematically showing an information recording medium according to one embodiment of the present invention. Sectional drawing along the II-II line of the information recording medium shown in FIG. The top view which shows roughly the unit orientation area | region of the orientation layer which the information recording medium shown in FIG. 1 contains. The top view which shows roughly the unit orientation area | region of the orientation layer which the information recording medium shown in FIG. 1 contains. The top view which shows roughly the unit orientation area | region of the orientation layer which the information recording medium shown in FIG. 1 contains. The top view which shows roughly the unit orientation area | region of the orientation layer which the information recording medium shown in FIG. 1 contains. 7 is a plan view schematically showing the arrangement of the unit orientation regions shown in FIGS. 3 to 6 in the information recording medium shown in FIG. FIG. 2 is a plan view schematically showing an image forming layer included in the information recording medium shown in FIG. 1. The top view which shows an example of the image which the information recording medium shown in FIG. 1 displays when it observes from a normal line direction using a polarizer. The top view which shows the information which can be read from the image shown in FIG. The figure which shows an example of an information reader roughly. The figure which shows the other example of an information reader roughly. Sectional drawing which shows schematically the information recording medium which concerns on one modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Information recording medium, 20 ... Information reader, 110 ... Base material, 120 ... Scattering reflection layer, 130 ... Image forming layer, 130a ... Light absorption part, 130b ... Light transmission part, 140 ... Orientation layer, 140a thru | or 140d ... Unit orientation region, 150 ... latent image forming layer, 210 ... light source, 210a ... light source, 210b ... light source, 220 ... polarizer, 220a to 220c ... polarizer, 230 ... imaging device, 240 ... processing unit, _AT ... transmission axis , L _i ... illumination light, L _r ... reproduction light, PX11 to PX16 ... unit area, PX21 to PX26 ... unit area, PX31 to PX36 ... unit area, PX41 to PX46 ... unit area, PX51 to PX56 ... unit area, PX61 to PX66 unit area.

Claims (15)

A scattering reflection layer for emitting scattered light having polarization from the principal surface when light having polarization is irradiated on one principal surface;
A latent image forming layer made of a liquid crystal material facing the main surface and solidified, and holding a latent image as first information;
The main surface that faces the latent image forming layer and faces the latent image forming layer includes a plurality of unit alignment regions, and the plurality of unit alignment regions form light that forms the latent image in the latent image forming layer. A transparent alignment layer;
At least one of the latent image forming layer and the alignment layer is sandwiched or faced with a part of the scattering reflection layer without sandwiching them, and arranged corresponding to a part of the plurality of unit alignment regions An information recording medium comprising: an image forming layer including a plurality of light absorbing portions, wherein the arrangement of the plurality of light absorbing portions constitutes second information different from the first information.   The plurality of unit alignment regions each include one or more first unit alignment regions for aligning mesogenic groups of the liquid crystal material in a first direction, and each of the plurality of unit alignment regions being substantially orthogonal to the first direction. One or more second unit alignment regions that are aligned in a second direction, and one or more third unit alignment regions that each align a mesogenic group of the liquid crystal material in a third direction obliquely intersecting the first direction. A pattern including the unit alignment region, and the pattern formed by the one or more first unit alignment regions and the one or more second unit alignment regions, and the inverted pattern thereof constitute the latent image. The information recording medium according to claim 1, wherein:   The plurality of unit alignment regions further include one or more fourth unit alignment regions that each align a mesogen group of the liquid crystal material in a fourth direction substantially orthogonal to the third direction, and the one or more first unit alignment regions. A pattern formed by one unit alignment region and the one or more second unit alignment regions, the one or more third unit alignment regions, and the one or more fourth unit alignment regions are formed. The information recording medium according to claim 1, wherein the pattern corresponding to the pattern corresponds to a pattern constituting the latent image.   The plurality of unit alignment regions are each provided with a plurality of grooves that are aligned in the length direction and are adjacent to each other in a direction intersecting the length direction. The information recording medium according to item.   The information recording medium according to claim 4, wherein the plurality of grooves form a diffraction grating in at least one of the plurality of unit orientation regions.   6. The information recording medium according to claim 4, wherein the plurality of grooves form a unidirectional diffusion pattern in at least one of the plurality of unit orientation regions.   The plurality of unit alignment regions are each composed of one or more unit alignment regions having the same length direction, and form a plurality of alignment region groups having different length directions. Item 7. The information recording medium according to any one of Items 4 to 6.   The plurality of unit alignment regions are each composed of one or more unit alignment regions having the same height from the main surface of the alignment layer, and form a plurality of alignment region groups having different heights. The information recording medium according to claim 1, wherein the information recording medium is a recording medium.   9. The scattering reflection layer according to claim 1, wherein the scattering reflection layer is a metal reflection layer provided with a concavo-convex structure, or a single or multilayer dielectric layer provided with a concavo-convex structure. Information recording medium. An information reading device that reads information held by the information recording medium according to any one of claims 1 to 9,
An illumination device that emits illumination light;
An imaging device;
An optical system that converts the illumination light into polarized light and directs it to the information recording medium, thereby guiding one linearly polarized light of the reproduction light emitted from the information recording medium to the imaging device;
An information reading apparatus comprising: a processing unit that processes information obtained from an output of the imaging apparatus based on a difference in color and reproduces the first information.   The imaging apparatus includes a first pattern as one of the patterns constituting the latent image, a second pattern as an inverted pattern thereof, a third pattern as a pattern formed by the plurality of light absorbing portions, and an inverted pattern thereof. Is the fourth pattern, the overlapping portion of the first pattern and the third pattern, the overlapping portion of the first pattern and the fourth pattern, the overlapping portion of the second pattern and the third pattern And the display color of the overlapping part of the second pattern and the fourth pattern can be distinguished from each other, and the processing unit reproduces the first information based on the difference of the display colors. The information reading device according to claim 10.   The plurality of unit alignment regions each include one or more first unit alignment regions for aligning mesogenic groups of the liquid crystal material in a first direction, and each of the plurality of unit alignment regions being substantially orthogonal to the first direction. One or more second unit alignment regions that are aligned in a second direction, and one or more third unit alignment regions that each align a mesogenic group of the liquid crystal material in a third direction obliquely intersecting the first direction. A pattern formed by the one or more first unit alignment regions and the one or more second unit alignment regions, and an inverted pattern thereof correspond to the first pattern. 12. The information reading apparatus according to claim 11, wherein the information reading apparatus is configured such that the information recording medium emits the reproduction light in an oblique direction with respect to a front surface thereof.   The information recording medium further includes a driving mechanism for rotating the information recording medium around an axis perpendicular to the main surface, and the processing unit uses the rotation angle of the information recording medium and a change in display color to change the first information. The information reading apparatus according to claim 10, wherein the information reading apparatus reproduces the information.   The illumination device includes a plurality of light sources, and the optical system includes a plurality of linear polarizers that respectively convert illumination light emitted by the light sources into linearly polarized light having different polarization planes, and one straight line of the reproduction light. The information reading apparatus according to claim 10, further comprising a linear polarizer that transmits polarized light toward the imaging device.   The illumination device includes first and second light sources, and the optical system includes a first linear polarizer that converts illumination light emitted by the first light source into first linearly polarized light and guides the light to the information recording medium. A second linear polarizer that converts the illumination light emitted from the second light source into a second linearly polarized light having a polarization plane different from that of the first linearly polarized light and guides it to the information recording medium; The information reader according to claim 10, further comprising: a third linear polarizer that transmits a third linearly polarized light parallel to the polarization plane of the first linearly polarized light toward the imaging device. .

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