JP4905053B2 - OVD medium and card-like information medium including OVD medium - Google Patents

Description

  The present invention relates to an OVD (Optically Variable Device) medium having a concavo-convex pattern for displaying an image by light diffraction or interference, and in particular, an image due to the concavo-convex pattern is not recognized under normal illumination conditions. The present invention relates to an OVD medium that can display an image when illuminated from a specific direction and has a high eye-catching effect and a high anti-counterfeit effect.

  In recent years, for the purpose of preventing counterfeiting of securities such as gift certificates and checks, cards such as credit cards, cash cards, ID cards, and identification cards such as passports and licenses, diffraction grating patterns, relief holograms, An OVD medium including an uneven pattern that displays an image by light diffraction and / or interference, such as an interference fringe pattern, is applied to the surface of the securities, cards, certificates, and the like.

  The concave / convex pattern that displays an image by light diffraction or interference can change the display image according to the direction / angle to be observed by controlling the direction, angle, brightness, etc. of light diffraction, Can be displayed. Such a concavo-convex pattern has a directional gloss that cannot be expressed by a normal printing technique, and is therefore widely used for printed information products that require anti-counterfeiting measures.

  In addition, the directional gloss of the concavo-convex pattern changes to a rainbow color depending on the viewing direction, so it is highly eye-catching, and it can also be used for covers such as covers for books and magazines, promotional posters, toys, sweets, etc. Widely used.

As parameters such as diffraction grating,
(1) Spatial frequency of diffraction grating (pitch of grating line)
(2) Direction of diffraction grating (direction of grating line)
(3) There are three drawing areas of the diffraction grating,
In accordance with (1), the color at which the diffraction grating pattern appears shining with respect to a fixed point changes,
In accordance with (2), the direction in which the diffraction grating pattern appears shining changes,
In accordance with (3), a display image (picture, character, symbol, etc.) is determined.

  As a relief type diffraction grating, a diffraction grating 27 having a rectangular cross section as shown in FIG. 15 or a diffraction grating 28 having a sinusoidal cross section as shown in FIG. 16 is generally used for ease of processing. The typical lattice line pitch is about 0.5 to 2 μm, and the lattice depth is about 0.1 to 1 μm. A diffraction grating having a rectangular or sinusoidal cross-sectional shape is called a binary grating. When illumination light 06 enters these diffraction gratings, for example, from vertically above, diffracted light 02 by reflection and diffracted light 03 by transmission are emitted. The light quantity ratio between the diffracted light 02 by reflection and the diffracted light 03 by transmission changes depending on the grating depth. However, if a light reflection layer made of metal or the like is provided on the concave and convex surface of the diffraction grating, the light quantity of diffracted light by reflection is large. Thus, if the uneven surface is a light-transmitting material, the amount of diffracted light due to transmission increases.

  A blazed grating 29 shown in FIG. 17 is also known as a relief type diffraction grating. The blazed grating has a typical grating pitch and grating depth equivalent to those of the binary grating, but its cross-sectional shape is sawtooth, and the diffraction angle and the light reflection angle by the inclined surface with respect to the illumination light 06 from the vertical direction. , Diffracted light 02 having theoretically 100% diffraction efficiency is generated in that direction, and there is an optical action that light is not emitted in the other directions. In other words, the blazed grating has a feature that it can obtain a very high diffraction efficiency compared to the binary grating and that the traveling direction of light can be strictly controlled. Therefore, the blazed grating has high visibility and is used for security applications. Is even more suitable. The cross-sectional shape of the blazed grating is not only a sawtooth shape as shown in FIG. 17, but also a stepped blazed grating 30 as shown in FIG. The stepped blazed grating has a characteristic that the amount of diffracted light increases as the number of steps increases.

  Further, as shown in FIG. 19, when the light 01 of the light source 09 is incident from the end face 21 of the light transmissive diffraction grating pattern forming layer 11 on which the diffraction grating 12 is formed, the incident light 01 is formed into the diffraction grating pattern. The inside of the layer 11 advances while repeating total reflection, is diffracted by the diffraction grating 12, and is emitted to the outside. As described above, the diffraction grating pattern can emit light propagating through the inside to the outside, and can confine light from the outside to the inside. The diffraction grating pattern having such a configuration is used as a component of an optical pickup element or a waveguide.

  As a method for producing an original plate such as a diffraction grating pattern, a planar substrate on which a photosensitive resist is applied by computer control using an electron beam exposure apparatus as disclosed in Patent Document 1 and Patent Document 2 There is a method of forming a diffraction grating pattern on the surface of a substrate by moving an XY stage on which is mounted.

  Also in the production of the original blazed grating, a method is used in which the shape of the blazed grating is formed on a flat substrate placed on a stage by using an electron beam exposure apparatus and by computer control. In order to form the sawtooth cross-sectional shape of the blazed grating, for example, by changing the irradiation time of the electron beam or adjusting the irradiation intensity according to the irradiation position of the electron beam, the depth of the groove to be processed Patent Document 3 discloses a method for changing the thickness and obtaining the shape of the blazed grating. The blazed grating is more difficult to manufacture than the binary grating, and is suitable for use in security applications in terms of manufacturing technology.

  Further, as another method for producing an original plate such as a concavo-convex pattern, a method of exposing interference fringes by two-beam interference of a laser as shown in Non-Patent Document 1 is known.

A metal stamper is produced from the concavo-convex pattern original plate produced by the method as described above by a method such as electroforming, and a thermoplastic resin or photocuring is applied to a film such as PET using the metal stamper as a matrix. A metallic resin is applied, a metal stamper is brought into close contact, and the resin is cured by applying heat and light to replicate the diffraction grating pattern. Since the replicated diffraction grating pattern is usually transparent, a light reflecting layer is formed by a method such as vapor deposition of a metal or dielectric thin film layer such as aluminum, and then adhered to a substrate such as paper or a plastic plate. Affixed through layers. When the diffraction grating pattern is affixed to securities or cards, a protective layer for preventing the printed layer or the diffraction grating pattern layer from being stained or scratched is provided as necessary.
Japanese Patent Laid-Open No. 2-72315 US Patent 5,058,992 JP 2000-39508 A Junhei Takiuchi's “Holography” first edition, published by Maruzen Co., Ltd. (1993)

  The concave / convex pattern for displaying an image by light interference and / or diffraction enables image display that cannot be realized by a normal printing technique by emitting diffracted light having a gloss that shines in a unique rainbow color. It is widely used for printed information products that require security and for packages such as toys and confectionery for the purpose of catching the eye. However, as many articles using uneven patterns are distributed and the technology is widely recognized, there is a tendency for the generation of counterfeit products to increase in the information printed matter that requires security. The visual effect is generalized for the purpose, and the effect of attracting attention is reduced only by displaying an image with a simple uneven pattern.

  The present invention does not recognize an image due to a concavo-convex pattern under normal illumination conditions, and can display an image by making light incident from a predetermined direction. It is an object of the present invention to provide an OVD medium having a high diffraction grating pattern and a card-shaped information medium including such an OVD medium.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a light-transmitting concavo-convex pattern forming layer having a concavo-convex pattern for displaying an image on the surface by light interference and / or diffraction, A light control layer provided on the image observation side of the concavo-convex pattern forming layer and having a region where the light transmittance is smaller than the light absorptivity, and a part or all of the concavo-convex pattern displaying the image has a frequency The OVD is characterized in that it is formed with blazed gratings of 2000 lines / mm or more and 4000 lines / mm or less with different spatial frequencies and lattice line directions, and the end face of the concavo-convex pattern forming layer constitutes an incident light receiving part. Provide media.

  In the OVD medium according to the second aspect, the region where the light transmittance is smaller than the light absorption rate preferably has a light absorption rate of 50% or more and a light transmittance of 10% or more.

  In the present invention, a light shielding layer can be provided on the opposite side of the concavo-convex pattern forming layer from the side on which the light control layer is provided.

In the present invention, the concavo-convex pattern forming layer, on the surface of the light transmitting plate member are molded one body, that one or more of the end faces of the light transmitting plate member constitutes the incident light receiving portion Can do.

  In the present invention, the thickness of the light-transmitting flat plate member is preferably 0.3 mm or more and 1.2 mm or less.

According to a second aspect of the present invention, a card-shaped information medium including the OVD medium of the present invention is provided.

  In the present invention, the “concave / convex pattern for displaying an image by light diffraction or interference” includes a relief diffraction grating pattern, a relief hologram pattern, an interference fringe pattern, and the like.

  The OVD medium of the present invention has the following effects.

  (1) The concavo-convex pattern forming layer has a region where the light transmittance is smaller than the light reflectance or light absorption rate on the image viewing side (the viewer viewing the display; hereinafter referred to as the “displayed image viewing side”). Since the light control layer is provided, an image due to the uneven pattern is not observed under normal illumination conditions, and the image can be displayed only when light is incident from a predetermined direction. With such a function, the display / non-display of the image can be clearly switched between normal illumination conditions and when the incident light is turned on, compared with the conventional diffraction grating pattern that only shines in rainbow colors, The authenticity determination can be performed more reliably, and the effect of catching the eye can be improved.

  In particular, by using a light control layer having a light reflectance of 50% or more and a light transmittance of 10% or more, an image with a diffraction grating pattern is sufficiently concealed under normal illumination conditions, and an incident light source An image can be displayed only when is turned on. Further, the same image display / non-display can be switched by using a light control layer having a light absorption rate of 50% or more and a light transmittance of 10% or more.

  (2) By providing a light-shielding layer on the side opposite to the side on which the light control layer is provided of the concavo-convex pattern forming layer, the diffraction grating pattern is formed when observed from the side on which the light control layer is not provided. The image formed by the diffraction grating formed in the layer can be prevented from being visually recognized by outside light or the like when the incident light is not lit, the display image concealing effect is enhanced, and the forgery prevention effect is further improved. It becomes possible.

  (3) The diffraction grating pattern forming layer is attached to or integrally formed with a light-transmitting flat plate member, and the end surface of the flat plate member serves as an incident light receiving portion, so that light can be efficiently applied to the concavo-convex pattern. Can be guided, and an image with higher luminance can be displayed when the incident light is lit.

  In addition, by setting the thickness of the light transmissive flat plate member to 0.3 mm or more and 1.2 mm or less, it is possible to efficiently use light from a small light source such as a light emitting diode (LED) while suppressing an increase in the thickness of the entire OVD medium. It can guide light well.

  (4) By using a diffraction grating pattern including a diffraction grating having a spatial frequency of 2000 to 4000 lines / mm, the amount of light that has passed through the light control layer from the display image observation side returns to the display image observation side again is reduced. It is possible to prevent the display image by the diffraction grating pattern from being recognized under normal illumination conditions. Further, even when light is incident from a direction substantially parallel to the image display surface of the diffraction grating pattern forming layer, it is possible to diffract the light to the display image observation side and display an image.

  (5) By using the blazed grating, incident light can be efficiently emitted in the direction of display image observation, so that an image with higher luminance can be displayed when the incident light is lit.

  (6) By including the OVD medium of the present invention in the card base of a card-like information medium that requires security such as a credit card, cash card, ID card, etc., the magnetic stripe attached on the card base Since not only an IC chip, an RFID (Radio Frequency Identification) tag, etc., but also a card substrate can be provided with security, a card-like information medium having a higher anti-counterfeit effect can be realized.

  Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, like members and elements are given like reference numerals.

  FIG. 1 is a view showing an example of a relief type diffraction pattern forming layer that can be used in the present invention, FIG. 1 (A) is a plan view, and FIG. 1 (B) is a partially enlarged view thereof. is there.

  On the light transmissive diffraction grating pattern forming layer 11, a diffraction grating 12 with various changes in spatial frequency and grating line direction is formed, and a display image 13 is displayed.

  The relief type diffraction pattern forming layer that can be used in the present invention is not limited to the one in which the diffraction grating 12 having different spatial frequency and grating line direction is formed in an arbitrary region as shown in FIG. -What provided the some division | segmentation element (cell) divided | segmented and each formed with the diffraction grating pattern can also be used. In that case, the spatial frequency and grating line direction of the diffraction grating change for each cell. FIG. 2 is a view showing an example of a relief type diffraction pattern forming layer having such a cell, FIG. 2 (A) is a plan view, and FIG. 2 (B) is a partially enlarged view thereof.

  The pattern forming layer 11 is formed with a diffraction grating 12 whose spatial frequency and grating line direction are changed for each cell 111 divided in a matrix.

  When illumination light enters the diffraction grating pattern forming layer 11 as shown in FIG. 1 or FIG. 2, light of various colors is emitted from the diffraction grating in various directions, and is displayed on the predetermined display image observation side. An image is observed. The image display by the diffraction grating is as described with reference to FIGS. 15 and 16.

  Here, as shown in a cross section in FIG. 3, a configuration in which a light control layer 14 having a region in which the light transmittance is smaller than the light reflectance is provided on the display image observation side 07 of the diffraction grating pattern forming layer 11 according to the present invention. When the OVD medium 22 is observed under normal illumination conditions, most of the normal illumination light 06 is reflected by the surface of the light control layer 14 having light reflectivity and becomes reflected light 05. The light 04 transmitted through the light control layer 14 becomes light 02 diffracted in a direction other than the display image observation side 07 by the diffraction grating, or becomes light 04 returning to the display image observation side 07. Since the light 04 returning to the display image observation side 07 is transmitted through the light control layer 14 twice in a reciprocating manner, the amount of light is greatly reduced. Therefore, it is difficult to recognize the display image by the diffraction grating pattern forming layer 11. For example, if the light reflectance of the light control layer is 80% and the light transmittance is 20%, the light control layer 14 is transmitted through, reflected by the surface of the diffraction grating pattern forming layer 11, and the light control layer 14 again. The amount of light that passes through and returns to the display image viewing side is 20% × 20% = 4% (0.2 × 0.2 = 0.04) at the maximum. Insufficient value.

  Note that “normal illumination conditions” refer to conditions for observing an OVD medium under a general indoor light source such as a fluorescent lamp or ambient light, as well as conditions such as outdoor sunlight. The “normal illumination light” refers to the illumination light under the normal illumination conditions, such as observing the OVD medium.

  Here, a light source (image display light source for displaying the image 13) 09 different from the normal illumination light is provided on the back side of the OVD medium on the OVD medium 22 configured as shown in FIG. FIG. 4 is an explanatory diagram of a state in which light is incident. The image display light source 09 is installed on the back side of the OVD medium 22 and emits light having a higher luminance than the normal illumination light 06. That is, in this OVD medium, the back surface of the pattern forming layer 11 constitutes a light receiving portion for image display light. In this case, the light 01 from the image display light source 09 passes through the diffraction grating pattern forming layer 11 and reaches the diffraction grating, and the transmitted diffracted light 03 passes through the light control layer 14 and is emitted to the display image observation side 07 side. The The light of the image display light source 09 has high brightness and the number of times of transmission through the light control layer 14 is one. Therefore, a decrease in the amount of light by the light control layer 14 can be suppressed, and the diffracted light 03 on the display image observation side 07 is suppressed. An image can be recognized. For example, if the amount of light of the image display light source is twice that of the normal illumination light on the display image viewing side, 20% × 2 = 40% (0.2 × 2 = 0.4), and the image by the diffraction grating is recognized. The value is sufficient to

  Thus, the display image by the diffraction grating is hidden and difficult to observe under normal illumination conditions, and an OVD medium in which an image is observed only when illuminated from the back surface of the OVD medium can be realized. .

  The light transmissive diffraction grating pattern forming layer 11 can be formed of a thermoplastic resin, a photocurable resin, or the like.

  The light control layer 14 having a light transmittance smaller than the light reflectance is prepared by thinly applying a metal material such as mercury, silver, or aluminum to a transparent substrate, or forming a thin film by sputtering or vapor deposition. A so-called magic mirror or the like is suitable.

  The light control layer 14 preferably has a high light reflection function with a light reflectance of 50% or more and a light transmittance of 10% or more. If the light control layer has a light reflectance of 50% or more, normal illumination light such as outside light and ambient light can be efficiently reflected to the display image observation side under normal illumination conditions, and the image by the diffraction grating pattern is sufficiently concealed. be able to. When the light reflectance is less than 50% and the light transmittance is more than 50%, the brightness of normal illumination light such as outside light or ambient light is low, and the spatial frequency of the diffraction grating pattern is low ( In the case where the diffraction pitch of the diffraction grating pattern is low and the reflected light from the surface of the diffraction grating pattern is easy to return to the display image observation side, etc. There is a possibility that the image by the diffraction grating pattern may be recognized without being sufficiently concealed. In addition, when a light control layer having a light transmittance of less than 10% is used, light that passes through the light control layer and reaches the display image observation side is not sufficient unless an image display light source having sufficiently high luminance is used. The image by the diffraction grating pattern observed on the display image observation side becomes dark.

  As the light control layer, instead of the light control layer 14 having a region where the light transmittance is smaller than the light reflectance, a light absorbing light control layer 15 having a region where the light transmittance is smaller than the light absorption rate may be used. it can. An OVD medium 22 'having such a configuration is shown in FIG. In the OVD medium 22 ′, most of the light from the illumination light 06 is absorbed by the light control layer 15 under normal illumination conditions. Further, the light 04 transmitted through the light control layer 15 and reflected or diffracted by the diffraction grating is also transmitted through the light control layer 15 again and returned to the display image observation side 07 side. Therefore, it is difficult to recognize the display image. Then, as shown in FIG. 6, when light enters from the image display light source 09 located below the OVD medium 22 ', an image that cannot be observed under normal illumination conditions can be observed.

  The light control layer 15 having a light transmittance smaller than the light absorptance is formed by applying a film in which a plurality of films that absorb visible light or ultraviolet light are superposed, or a pigment or dye having a light absorbing pigment. This is also used as a sunshine adjustment sheet and a line-of-sight cut sheet for residential windows and car windows.

  The light control layer 15 is preferably a light control layer having a high light absorption function that has a light absorption rate of 50% or more and a light transmittance of 10% or more. If the light control layer has a light absorptance of 50% or more, normal illumination light such as outside light and ambient light can be efficiently absorbed under normal illumination conditions, and the image by the diffraction grating pattern can be sufficiently concealed. If the light absorptivity is less than 50% and the light transmittance exceeds 50%, the brightness of normal illumination light such as outside light or ambient light is high, and the spatial frequency of the diffraction grating pattern is high. When the design is low (the grating pitch is coarse) and the diffracted light easily returns to the display image observation side, the diffraction efficiency of the diffraction grating pattern is low, and the reflected light from the surface of the diffraction grating pattern easily returns to the display image observation side, etc. In this case, there is a possibility that the image by the diffraction grating pattern is recognized without being sufficiently concealed. In addition, when a light control layer having a light transmittance of less than 10% is used, light that passes through the light control layer and reaches the display image observation side is not sufficient unless an image display light source having sufficiently high luminance is used. The image by the diffraction grating pattern observed on the display image observation side becomes dark.

  As a configuration of the OVD medium of the present invention, a light shielding layer 16 may be provided on the side of the diffraction grating pattern forming layer 11 opposite to the side on which the light control layer 14 or 15 is provided, as shown in FIG. The presence of the light shielding layer 16 can prevent the image from the diffraction grating from being recognized under normal illumination conditions due to the wraparound of the normal illumination light 06. When the light shielding layer 16 is provided, as shown in FIG. 7, the end face 21 of the diffraction grating pattern forming layer 11 is used as a light receiving portion for image display light, and the light 01 from the image display light source 09 is used as the diffraction grating pattern forming layer 11. It is good to make it the structure which advances the inside.

  As the diffraction grating pattern forming layer, there is a diffraction grating pattern formed of a thermoplastic resin or a photocurable resin on the surface of a light-transmitting flat plate member having one or a plurality of end faces serving as a light receiving portion for incident light. It is desirable that it is affixed or the diffraction grating pattern is integrally formed on the surface of the flat plate member. As shown in FIG. 8, when image display light 01 is incident from a plurality of end surfaces 21 of a flat plate member 18 having a diffraction grating pattern forming layer, the incident light 01 is repeatedly totally reflected on the front surface 19 and the back surface 20 of the flat plate member 18. The light loss is small and the diffraction grating pattern 11 is reached, and a bright image can be displayed. Actually, a component of light 10 leaks outside the flat plate member 18 without being totally reflected by the front surface 19 and the back surface 20 of the flat plate member 18, so that the light is covered so as to cover the flat plate member. When the reflective layer 17 is provided, the loss of light amount is further reduced, and a brighter image can be displayed.

  When image display light is incident from the end face of the planar member, the thickness of the flat member is preferably 0.3 mm or more and 1.2 mm or less. When the thickness of the member is less than 0.3 mm, the image display light does not sufficiently enter from the end face, and it becomes difficult to obtain a high brightness image. If the thickness of the member exceeds 1.2 mm, the light component that does not satisfy the total reflection condition when reaching the front and back surfaces 19 and 20 of the member as shown in FIG. As the light travels, it is emitted as leaked light 10 to the outside of the member, the number of reflections on the front and back surfaces increases, and the amount of light reaching the diffraction grating decreases due to absorption of the material constituting the member. In the present invention, as an image display light source, an LED or a cold cathode tube (CCFL) light source used in a small mobile device is suitable because it is inexpensive and easily available.

  In the present invention, the spatial frequency of the diffraction grating formed in the diffraction grating pattern forming layer is preferably 2000 / mm or more and 4000 / mm or less (the grating pitch corresponds to 0.25 μm or more and 0.5 μm or less). ing. A diffraction grating having a spatial frequency of 2000 lines / mm or more and 4000 lines / mm or less has a large emission angle of diffracted light, and as shown in FIG. The amount of light emitted from the diffraction grating returning to the display image observation side 07 can be reduced. Further, incident light from a light source installed on the end face of the diffraction grating pattern forming layer can be emitted to the display image observation side vertically above with a large emission angle. As shown in FIG. 11, when the spatial frequency is about 500 lines / mm, for example, when the grating interval is rough, the diffracted light 02 emitted from the diffraction grating easily returns to the display image observation side 07. There is a risk of observing the image.

  In the present invention, a blazed grating (sawtooth blazed grating, stepped blazed grating) as described with reference to FIGS. 17 and 18 is suitable as the diffraction grating formed in the diffraction grating pattern forming layer. Since the blazed grating can emit diffracted light with high diffraction efficiency in any one direction, it is possible to display a bright image on the display image observation side. In addition, since the blazed grating is difficult to manufacture as compared with the binary grating, it is highly advantageous in terms of security.

  Next, FIG. 12 shows a configuration example of a card-like information medium such as a credit card, a cash card, or an ID card having the OVD medium of the present invention. In this card-shaped information medium, a diffraction grating pattern (not shown) is formed on a part of the base material 23 made of a material such as PET or polycarbonate, and the light control layer 14 or the upper part of the card-like information medium covers the diffraction grating pattern. 15 is placed. In addition, a magnetic stripe 24 is formed on another part of the substrate 23. FIG. 13 shows a cross-sectional view of the card-like information medium 26 in the X-X ′ direction. The front and back surfaces of the base material 23 are printed layers 25. The print layer 25 also functions as a light-shielding layer that restricts the passage of light between the outside and the region of the base material 23 where the diffraction grating pattern 11 is not formed. In addition, a light reflection layer may be provided between the base material 23 and the print layer 25 separately. By providing the light reflecting layer, the light incident from the end face can be efficiently propagated to the diffraction grating pattern, and the display image can be brightened. With such a configuration, a new forgery prevention function can be imparted to the substrate itself without impairing the read / write function of the magnetic stripe. Until now, the base material itself did not have anti-counterfeiting functions, so counterfeit products with illegally falsified magnetic stripe information were also rampant. The improvement of sex can be expected. It is possible to mount this OVD medium on a card-like information medium provided with an IC chip or RFID tag other than the magnetic stripe.

  Furthermore, as shown in FIG. 14, when another diffraction grating pattern 11 ′ is provided on the light control layers 14 to 15, the image by the upper diffraction grating pattern 11 ′ can always be observed under normal illumination conditions. When the image display light source 09 is turned on, the upper diffraction grating pattern 11 ′ and the lower diffraction grating pattern 11 of the light control layer 14 or 15 each display an image, so both patterns are displayed simultaneously. If meaningful information is displayed by combining the images of the upper diffraction grating pattern and the lower diffraction grating pattern, the design and security can be further enhanced.

  In the above description, the diffraction grating pattern forming layer is provided on the upper surface of the light transmissive flat plate member. However, the diffraction grating pattern forming layer is provided on the lower surface of the light transmissive flat plate member. In addition, the above-described functions can be exhibited even if they are provided on both the upper and lower surfaces of the light-transmitting flat plate member.

  In addition, the diffraction grating pattern forming layer and the light control layer described so far are the minimum necessary components constituting the OVD medium of the present invention. The OVD medium of the present invention can include a layer having an optical function such as a light shielding layer, a retardation film, and a polarizing film. Further, a gap may be provided between the layers by providing a spacer, or the layers may be tightly fixed to each other via an adhesive layer or the like.

  Furthermore, in the various embodiments described above, the lattice pattern for displaying an image by diffraction is used as the concave / convex pattern for displaying an image by light diffraction and / or interference. However, the image is displayed by light diffraction and / or interference. Needless to say, a relief hologram pattern or interference fringe pattern can be used as the concavo-convex pattern.

The figure which shows an example of the relief type | mold diffraction pattern formation layer which can be used for this invention. The figure which shows another example of the relief type | mold diffraction pattern formation layer which can be used for this invention. 1 is a schematic cross-sectional view showing an example of an OVD medium of the present invention. FIG. 4 is a schematic cross-sectional view for explaining an image display method in the OVD medium shown in FIG. 3. FIG. 3 is a schematic cross-sectional view showing another example of the OVD medium of the present invention. FIG. 5 is a schematic cross-sectional view for explaining an image display method in the OVD medium shown in FIG. 4. The schematic sectional drawing which shows another example of the OVD medium of this invention. The schematic sectional drawing which shows another example of the OVD medium of this invention. The figure for demonstrating the relationship between the thickness of a flat member, and image display light. The figure for demonstrating the relationship between the spatial frequency of a diffraction grating, and incident light. The figure for demonstrating the relationship between the spatial frequency of a diffraction grating, and incident light. The top view which shows the structure of card-like information provided with the OVD medium of this invention. FIG. 13 is a cross-sectional view taken along line X-X ′ in FIG. 12. The schematic sectional drawing which shows the structure of another card-like information provided with the OVD medium of this invention FIG. 3 is a schematic cross-sectional view for explaining a diffraction grating having a rectangular cross section. The schematic sectional drawing for demonstrating the diffraction grating of a cross-sectional sine wave shape. The schematic sectional drawing for demonstrating a serrated blazed diffraction grating. The schematic sectional drawing for demonstrating a step-like blazed diffraction grating. The schematic sectional drawing for demonstrating the advancing state of light at the time of entering light from the end surface of a diffraction grating pattern formation layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 01 ... Incident light 02 ... Diffracted light by reflection 03 ... Diffracted light by transmission 04 ... Transmitted light 05 ... Reflected light 06 ... Normal illumination light 07 ... Display image observation side 08 ... Light from diffraction grating pattern 09 ... Image display light source 10 ... Leakage light 11, 11 '... Diffraction grating pattern forming layer 12 ... Diffraction grating 13 ... Display image 14 ... Light reflecting light control layer 15 ... Light absorbing light control layer 16 ... Light shielding layer 17 ... Light reflecting layer 18 ... Flat plate member DESCRIPTION OF SYMBOLS 19 ... Surface of flat member 20 ... Back surface of flat member 21 ... End surface of flat member 22, 22 '... OVD medium 23 ... Base material 24 ... Magnetic stripe 25 ... Printing layer 26 ... Card-like information medium 27 ... Rectangular shape Binary grating 28 ... Sine-wave binary grating 29 ... Sawtooth blazed grating 30 ... Stair blazed grating

Claims (6)

A light-transmitting concavo-convex pattern forming layer having a concavo-convex pattern for displaying an image by light interference and / or diffraction on the surface, and the light transmittance provided on the observation side of the concavo-convex pattern forming layer Is provided with a light control layer having a region smaller than the light absorptance, and a part or all of the concavo-convex pattern for displaying the image differs depending on the blazed grating having a frequency of 2000 lines / mm to 4000 lines / mm. The OVD medium is formed in a lattice line direction, and an end face of the concavo-convex pattern forming layer forms an incident light receiving unit . The OVD medium according to claim 1 , wherein the region where the light transmittance is smaller than the light absorption rate has a light absorption rate of 50% or more and a light transmittance of 10% or more. The unevenness of the pattern formation layer, on the side opposite to the side where the light control layer is provided, OVD medium according to claim 1 or 2, characterized in that the light-shielding layer is provided. The concavo-convex pattern forming layer, and characterized in that the surface of the light transmitting plate member are molded one body, one or more of the end faces of the light transmitting plate member is in the incident light receiving portion The OVD medium according to any one of claims 1 to 3 . The OVD medium according to claim 4, wherein the thickness of the light-transmitting flat plate member is 0.3 mm or greater and 1.2 mm or less. Card-like information media comprising OVD medium according to any one of claims 1 to 5.

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