JP2006043978A - Method for preventing ovd medium from being forged, forgery-proof ovd medium and sticker using ovd medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method, for preventing an OVD medium from being forged, which enhances a forgery-proof effect on the OVD medium, enables a genuineness judgement to be made a multiple number of times, is not restricted in terms of resistance and image fineness and can easily judge whether the OVD medium is genuine or not by using a very simple tool. <P>SOLUTION: In this method, a latent image formation layer 14 and an OVD layer 15 are formed on a base material 13, and a latent image part which is formed utilizing an orientation phenomenon making it possible to recognize by viewing through a polarization film and impossible or difficult to recognize by viewing not through the polarization film, is formed on the latent image formation layer 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a forgery prevention method and a medium using a latent image for the purpose of displaying hidden characters and patterns, and in particular, when performing a true / false determination of whether or not a forgery is easy. The present invention relates to a method for preventing forgery of an OVD medium capable of visually confirming a latent image using the above verification medium, an OVD medium subjected to forgery prevention, and an OVD sticker using the OVD medium.

Conventionally, there are various methods using a latent image for preventing forgery.
For example, you can insert hidden characters, etc. using the gaps between the pitches of the lines, and print line drawings in which hidden characters appear by concealing the line parts, or those with fillers in transparent ink media, and use pencils to print them. There is pencil drawing printing (deco-matting) in which hidden characters appear when the part is rubbed and the pencil powder adheres to the printed part. Since these latent images are known when viewed closely, they are used for play rather than full-scale latent images.

  Next, there is a method of forming a latent image using halftone dots or moiré (interference fringes). In this method, by partially changing the pitch or angle of halftone dots and lines, moire is generated by superimposing neatly arranged halftone dots or lines of transparent film on the latent image, and an image appears. In this case, since it is a simple display medium, it can be used repeatedly, but there is a problem that a complicated image cannot be formed.

  In addition, fluorescent inks and infrared absorbing inks are functional inks that are difficult to see under visible light but can confirm a printed image only under certain conditions. The fluorescent ink is an ink issued by irradiating ultraviolet rays, and is used as a latent image because of the presence of white or colorless and transparent ink. There are organic and inorganic types of fluorescent inks, and the organic type can be confirmed to emit light when contained in a very small amount in the printing ink, but its application is limited because of its low light resistance. Further, it is necessary to put a large amount of inorganic type in the printing ink (about 10 to 20%), and since the latent image is known visually, it is necessary to devise the design and the like.

There is a latent image in which an image is formed with ink that absorbs infrared light using an infrared region, and the image is concealed so that it cannot be seen, and a layer that transmits light in the infrared region is provided. However, in order to display this latent image, an infrared camera or the like is required, which is large in apparatus. In addition, there are inks (IV inks) that are white or colorless in the visible light range but have absorption in the infrared range, and this also requires an infrared camera or the like.
As described above, the above method can be repeatedly displayed, but a specific detection device is required for displaying a latent image.

In recent years, there is a latent image forming method using an optical function of a material. This is a method in which a phase difference is generated by applying a heat treatment or a solvent treatment to a part of the retardation film, and a partial difference in the retardation is visualized and visually recognized through a polarizing plate. However, in the above method, since a partial difference in phase difference can be visually recognized, it is necessary to devise a design or the like (for example, see Patent Document 1).
There is also a latent image forming method using the birefringence of a liquid crystal material. This is because a thermotropic liquid crystal material is partially aligned to form a latent image, and the aligned portion can be visually recognized as a latent image by passing a polarizing plate thereon ( For example, see Patent Document 2.)

  On the other hand, OVDs (Optical Variable Devices) such as holograms, diffraction gratings, or multilayer thin films that cause a color change (color shift) depending on the viewing angle have been used to produce stereoscopic images and special decorative images using light interference. It can be expressed. These OVDs have an excellent decorative effect in order to give a special impression such as a stereoscopic image and color shift, and are used for general printed materials such as various decoration materials, picture books, catalogs and the like. Furthermore, since these OVD manufacturing methods require advanced manufacturing techniques, they are used as a medium for preventing forgery as a means for preventing counterfeiting such as credit cards, securities, certificates, etc. ing.

  An OVD such as a hologram or a diffraction grating has a diffractive structure such as a fine uneven pattern or a striped pattern having a different refractive index, and an angle viewed by light interference and diffraction (that is, an angle supporting a hologram). Accordingly, a unique image or color change (color shift) occurs. An OVD such as a multilayer thin film has a structure in which ceramics and metals having different optical properties are laminated in layers. This multi-layered thin film uses the interference effect of light obtained by the optical characteristics and film thickness of the constituent materials, and has reflection / transmission characteristics in a specific wavelength range, so that color shift may occur depending on the viewing angle. It will occur. Hereinafter, a hologram, a diffraction grating, a multilayer thin film, and the like using the interference of these lights will be collectively referred to as OVD.

  Holograms are classified into relief holograms and volume holograms according to the manufacturing method. First, a relief type hologram is produced by producing a relief type master hologram having a fine uneven pattern by an optical imaging method, and then replicating a nickel press plate by copying the uneven pattern by an electroplating method. It is a hologram manufactured by a known method of heating and pressing on the hologram forming layer. Next, there is a volume hologram that records interference fringes in the volume direction using a recording material such as a photosensitive resin. In this type of hologram, a so-called Lippmann hologram is generally used, and a reflection hologram is obtained by changing the refractive index of the photosensitive resin in the volume direction.

  Furthermore, unlike a hologram that can reproduce such a three-dimensional image, a diffraction grating that uses a diffraction grating arranges a plurality of types of simple diffraction gratings in a small area to form a pixel, and an image called a grating image or a pixelgram. To express. An image using such a diffraction grating is mass-replicated in the same manner as a relief hologram.

In recent years, as an anti-counterfeiting technology combining a latent image technology utilizing the birefringence of liquid crystal material and a light interference image such as a hologram, only a holographic image can be visually observed, and a latent image can be obtained through a polarizing plate. A latent image medium having an OVD layer that can confirm the above has been proposed (see, for example, Patent Document 3).
JP-A-9-81062 JP 2001-39100 A JP 2001-63300 A

As described above, since the manufacture of these OVDs requires advanced technology, it is affixed to a part of credit cards, securities, certificates, etc. as an effective means of preventing forgery, or on the entire surface. Although it is used as a medium that has been formed and has been subjected to anti-counterfeiting, the present invention further enhances the anti-counterfeiting effect of these OVD media and solves the above-mentioned problems when using latent images for anti-counterfeiting The latent image is added to the OVD medium.
That is, according to the present invention, when adding a latent image to an OVD medium to further enhance the anti-counterfeit effect, the authenticity determination can be performed many times, and is not constrained in terms of durability and image definition, and is very simple. It is an object of the present invention to provide a method for preventing forgery of an OVD medium that can easily determine whether a forgery or not by using a simple tool. It is another object of the present invention to provide an OVD medium in which such forgery prevention is performed and a sticker using the OVD medium.

  In the present invention, a latent image forming layer and an OVD layer are provided on a base material, and the latent image forming layer can be visually recognized through a polarizing film, and cannot be viewed or visually recognized through a polarizing film. An anti-counterfeiting method for an OVD medium, characterized in that a latent image portion formed using difficult orientation is provided to prevent forgery of the OVD medium.

  In the present invention, a latent image forming layer and an OVD layer are provided on a base material, and the latent image forming layer can be visually recognized through a polarizing film and cannot be visually observed through a polarizing film. Alternatively, the present invention is an OVD medium with anti-counterfeiting characterized in that a latent image portion formed using an orientation that is difficult to visually recognize is provided.

  The present invention also relates to a polymer material capable of providing a latent image portion that can be formed by aligning the material of the latent image forming layer by an external force in the OVD medium subjected to forgery prevention according to the above invention. This is an OVD medium that is provided with anti-counterfeiting.

  The present invention also provides forgery prevention characterized in that in the OVD medium subjected to forgery prevention according to the above invention, the material of the latent image forming layer is a lyotropic liquid crystal material comprising a dichroic dye that self-assembles. The applied OVD medium.

  The present invention also provides forgery prevention characterized in that in the OVD medium subjected to forgery prevention according to the above invention, the latent image portion formed in the latent image forming layer is provided by being oriented by printing or coating. OVD media.

  Further, the present invention provides forgery prevention characterized in that the latent image portion is a pattern-shaped latent image having information such as characters and patterns in the OVD medium subjected to forgery prevention according to the above invention. OVD media.

  In addition, the present invention is the OVD medium with anti-counterfeit, wherein the latent image forming layer is provided with a protective layer in the anti-counterfeit OVD medium according to the above invention.

  Further, the present invention is the OVD medium with anti-counterfeit characterized in that in the OVD medium with anti-counterfeit according to the invention, a light reflecting layer made of a metal material is provided on the OVD layer.

  The present invention is also an OVD medium with anti-counterfeiting characterized in that in the OVD medium with anti-counterfeit according to the above invention, the polarizing film is a linear polarizing film.

  Moreover, this invention is a sticker using the OVD medium characterized by being the sticker using the OVD medium which performed the forgery prevention of any one of Claims 2-9.

As described above, the present invention uses the orientation characteristics of the lyotropic liquid crystal material to prevent counterfeiting, so that an OVD medium provided with a latent image forming layer and an OVD layer on a substrate has an image pattern that is not visually observed. An unknown latent image is obtained, and the latent image can be confirmed by a simple verification method through a polarizing film.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a plan view of an embodiment of an OVD medium with anti-counterfeit according to the present invention, and FIG. 2 shows a latent image that appears when the polarizing plate 12 is superimposed on the OVD medium with anti-counterfeit of FIG. It is explanatory drawing of the image image 11. FIG. 3 is a cross-sectional view of the OVD medium with anti-counterfeit of the present invention shown in FIG. 1 taken along the line XX shown in FIG. 4 is a perspective view showing an embodiment of an image forming body in which the OVD medium with forgery prevention according to the present invention is attached to cardboard, and FIG. 5 is a view taken along line YY of the image forming body in FIG. It is sectional drawing.

  FIG. 6 is a plan view showing another first example of the OVD medium subjected to the forgery prevention according to the present invention. FIG. 7 is an explanatory diagram of a latent image 32 that appears when the polarizing plate 31 is overlaid on the OVD medium subjected to counterfeiting in FIG. FIG. 8 is an explanatory diagram of another latent image that appears when a polarizing plate is superimposed on the OVD medium with anti-counterfeiting shown in FIG. 6 at a different angle. FIG. 9 is a cross-sectional view of the OVD medium with anti-counterfeit of the present invention shown in FIG. 6 taken along the line ZZ shown in FIGS. FIG. 10 is a cross-sectional view showing another second example of the OVD medium subjected to the forgery prevention according to the present invention. FIG. 11 is a cross-sectional view showing another third example of the OVD medium subjected to the forgery prevention according to the present invention.

  In the plan view of the OVD medium 1 with anti-counterfeiting shown in FIG. 1, the latent image cannot be confirmed by visual observation, and can only be seen as a holographic image medium. However, as shown in FIG. 2, the latent image 12 appears when the polarizing film 11 is superimposed on the OVD medium 1 on which forgery is prevented. Hereinafter, an OVD medium with forgery prevention according to the present invention will be described with reference to FIG.

  The substrate 13 is selected from synthetic resins such as polyethylene terephthalate, polyvinyl chloride, polyester, polycarbonate, polymethyl methacrylate, polyacrylic acid, polystyrene, natural resin films, synthetic paper, paper, glass, etc. Alternatively, a composite selected from the above and combined can be used.

  The latent image forming layer 14 is formed of a lyotropic liquid crystal material made of a dichroic dye that self-assembles. Examples of dichroic dyes that self-assemble include bisazo dyes, trisazo dyes, benzidine dyes, diphenylurea dyes, dinaphthylamine dyes, and the like.

  A polymer material that does not destroy or break the liquid crystal phase of the liquid crystal material can be added to the latent image forming layer 14 as a binder. For example, there are polyamide, polyimide, polyester copolymer and the like.

  The latent image forming layer 14 made of a lyotropic liquid crystal material is applied by a known application means such as a gravure printing method, a micro gravure coater method, a die coater method, or a nozzle coater method. When the latent image forming layer 14 is applied under the special coating conditions and the coating means is used, the liquid crystal molecules are aligned in a certain direction.

The OVD formation layer 15 is a layer on which a hologram, a diffraction grating, a multilayer thin film, or the like using light interference is formed, and is sometimes called an OVD layer. As OVDs such as holograms and diffraction gratings, there are a relief type for recording light interference fringes on a plane as a fine uneven pattern and a volume type for recording interference fringes in the volume direction. Moreover, as an OVD such as a multilayer thin film that causes a color change (color shift) depending on the viewing angle, there is a laminate of ceramics or metal thin films having different optical characteristics. In addition to this, it is not limited to these as long as it causes a unique image or color change utilizing light interference. Among these OVDs, a relief hologram (diffraction grating) or a multilayer thin film is preferable in view of mass productivity and cost.

  Relief type hologram (diffraction grating) is a nickel press that produces a relief type master hologram consisting of fine concavo-convex patterns by an optical imaging method, and then duplicates the concavo-convex pattern from this master hologram by electroplating. Make plates and mass-produce them. That is, this press plate is heated and pressed against the OVD forming layer to replicate the uneven pattern. Therefore, the OVD forming layer needs to be a material that has good moldability by heat, is less likely to cause press unevenness, and is capable of obtaining a bright reproduced image. For example, a heat-resisting material such as polycarbonate resin, polystyrene resin, or polyvinyl chloride resin. A thermosetting resin such as a plastic resin, an unsaturated polyester resin, a melamine resin, or an epoxy resin, or an ultraviolet ray or electron beam curable resin having a radical polymerizable unsaturated group can be used alone or in combination. In addition, materials other than those described above can be used as long as they are stable materials capable of forming an uneven pattern as the OVD formation layer.

As shown in FIG. 3, when a relief hologram (diffraction grating) is used for the OVD forming layer 15, a light reflecting layer (OVD effect) having a refractive index different from that of the polymer material constituting the relief surface in order to increase the diffraction efficiency. (Layer) 16 is preferably provided.
Providing this light reflecting layer (OVD effect layer) 16 improves the diffraction efficiency, resulting in clearer images and color changes. Materials used include high refractive index materials such as TiO ₂ , Si ₂ O ₃ , SiO, Fe ₂ O ₃ , and ZnS having different refractive indexes, and Al, Sn, Cr, Ni, Cu, Au, and the like having higher reflection effects. These materials can be used, and these materials can be used alone or in layers. These materials are formed by a well-known thin film forming technique such as a vacuum deposition method or sputtering, and the film thickness is about 5 to 1000 nm although it varies depending on the application.

  Other than the above, the material constituting the light reflecting layer (OVD effect layer) 16 has a refractive index higher than that of the polymer material (refractive index n = 1.3 to 1.5) used in the OVD forming layer 15. As long as the material is high, an organic material other than the above-described inorganic material, an organic-inorganic composite, or a material in which an inorganic filler is dispersed in an organic material can be used. These materials are formed to a thickness of about 0.1 μm to 10 μm by a known coating method such as gravure coating, die coating, or screen printing, or a printing method. Furthermore, even materials other than those described above can be used as appropriate as long as they have reflectivity.

  On the other hand, as shown in FIG. 5, the multilayer thin film OVD layer 20 in which the OVD is formed from the multilayer thin film is composed of thin film layers 26, 27, and 28 having different optical aptitudes. The composite thin film is formed and laminated. For example, when thin films having different refractive indexes are laminated, a high refractive index thin film and a low refractive index thin film may be combined, and a desired multilayer thin film can be obtained by a specific combination.

This multilayer thin film is made of a material such as ceramics or metal, and a high refractive index material having a refractive index of about 2.0 or more and a low refractive index material having a refractive index of about 1.5 are laminated with a predetermined film thickness. Is. An example of the material used below is given. First, as ceramics, for example, Sb ₂ O ₃ (3.0 = refractive index: the same shall apply hereinafter), Fe ₂ O ₃ (2.7), TiO ₂ (2.6), CdS (2.6), CeO. ₂ (2.3), ZnS (2.3), PbCl ₂ (2.3), CdO (2.2), Sb ₂ O ₃ (2.0), WO ₃ (2.0), SiO (2 0.0), Si ₂ O ₃ (2.5), In ₂ O ₃ (2.0), PbO (2.6), Ta ₂ O ₃ (2.4), ZnO (2.1), ZrO ₂ (2.0), MgO (1.6) , SiO 2 (1.5), MgF 2 (1.4), CeF 3 (1.6), CaF 2 (1.3~1.4), AlF ₃ (1.6), Al ₂ O ₃ (1.6), GaO (1.7) and the like.

Examples of the simple metal or alloy thin film include Al, Fe, Mg, Zn, Au, and Ag.
, Cr, Ni, Cu, Si and the like. Examples of the low refractive index organic polymer include polyethylene (1.5), polypropylene (1.49), polytetrafluoroethylene (1.35), polymethyl methacrylate (1.49), polystyrene (1). .60) and the like. By selecting at least one kind from these high refractive index materials or metal thin films having a transmittance of 30 to 60% and at least one kind from a low refractive index material and alternately laminating them at a predetermined thickness, it is possible to detect visible light of a specific wavelength. A multilayer thin film exhibiting absorption or reflection is obtained.

  From the above materials, materials are appropriately selected based on optical properties such as refractive index, reflectance, and transmittance, weather resistance, chemical resistance, interlayer adhesion, etc., and a multilayer thin film is formed by laminating as a thin film. . A known method can be used as the formation method, and it is possible to control the film thickness, film formation speed, number of layers, optical film thickness (= n * d, n: refractive index, d = film thickness), etc. It is possible to use a physical vapor deposition method such as a vacuum vapor deposition method or a sputtering method, or a chemical vapor deposition method such as a CVD method. In addition, as a method for forming a low refractive index organic polymer, a known gravure printing method, offset printing method, screen printing method, or other coating method, or a bar coating method, a gravure method, a roll coating method, or the like may be used. Can do. In the present invention, any material having the same or similar refractive index and reflectance as those of ceramics and metals can be used.

The layer thickness of the multilayer thin film layer is specifically in the range of 5 to 2000 nm, and the layer structure of the thin film is a thin film made of the above-described high refractive index material or metal material, for example, ZnS, TiO ₂ , In _2. O ₃ , SnO, ITO, CeO ₂ , ZnO, Ta ₂ O ₃ , Al, Fe, Mg, Zn, Au, Ag, Cr, Ni, Cu, Si, and the like, and a thin film made of the low refractive index material, For example, it is a combination with MgF ₂ , SiO ₂ , CaF ₂ , MgO, Al ₂ O _3, etc., which are alternately laminated, and the number of lamination is 2 or more, preferably 2 to 9 layers. Spectral characteristics vary depending on the number of layers. Note that the optical characteristics of the multilayer film differ depending on the materials and combinations used, and the present invention is not limited to these.

  In the OVD medium of the present invention, by providing a colored layer such as a colored transparent ink so as to be positioned on the latent image forming layer or the OVD layer, the observed OVD color change becomes more diverse and easy to see, The confirmation becomes easy and the forgery prevention effect can be further improved.

  As shown in FIG. 10, the protective layer 41 has a role of protecting the latent image forming layer 42 and the OVD forming layer 43 from external damage. Examples of resins used include acrylic resins, urethane resins, Conventionally known thermoplastic resins such as vinyl chloride resin-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin, polystyrene resin, polyimide resin, etc., thermosetting resin, ultraviolet ray or electron beam curable resin alone Or it is used as a mixture. Further, a curing agent that crosslinks the resin, waxes such as polyethylene wax, carnauba wax, and silicon wax, or extender pigments such as calcium carbonate, zinc stearate, silica, alumina, and talc, and fats and oils such as silicone oil and fat. It can be added as long as the transparency is not impaired. The resin used for the protective layer 41 is applied by known coating means such as gravure printing, screen printing, and nozzle coater, and printing means such as offset printing and flexographic printing.

  As shown in FIG. 11, the adhesive layers 54 and 55 are required to have a performance of adhering the OVD effect layer 53 and the latent image forming layers 56 and 57. As the material, a thermoplastic resin is preferable, and an acrylic resin, a urethane resin, an epoxy resin, a polyester resin, a vinyl resin or the like can be used alone or in combination, It is not limited to this. These adhesive layer materials are applied by known application means such as a gravure printing method, a screen printing method, and a nozzle coater method.

  The polarizing film 12 in FIG. 2 may be a polymer polycrystalline type such as a PVA-iodine type in which iodine is absorbed in a PVA stretched film, a dichroic dye type, a metal or metal compound-containing type, or a polyene type. PVA-iodine type and dichroic dye type films are used.

  A latent image forming layer material ink comprising the following [latent image forming layer composition] was printed on a 50 μm thick acrylic substrate by a screen printing method at a drying temperature of 60 ° C. and a coating thickness of 500 nm. Further, the same latent image forming layer material ink was subjected to reverse pattern printing by a screen printing method at a drying temperature of 60 ° C. and a coating thickness of 500 nm. On top of that, an OVD forming layer material ink composed of the following [OVD forming layer composition] was applied by a roll coating method at a drying temperature of 80 ° C. and a thickness of 1.0 μm.

Next, an OVD relief pattern was formed on the OVD formation layer by heating a nickel OVD image mold having an OVD relief pattern to 100 ° C. and pressing it onto the OVD formation layer by a known roll embossing method. In this example, a rainbow hologram photographed by the two-step method was used for the OVD image.
Next, on the OVD forming layer on which the OVD relief pattern is formed by the above method, an Al vapor-deposited thin film layer having a film pressure of 0.05 μm is formed using a vacuum vapor deposition method, and a light reflection layer (OVD effect layer) is provided. Thus, an anti-counterfeit OVD medium having a cross-sectional laminated structure as shown in FIG.

[Composition of latent image forming layer]
-80 parts by weight of lyotropic liquid crystal aqueous solution-20 parts by weight of polyester emulsion [composition of OVD forming layer]
-15 parts by weight of vinyl chloride-vinyl acetate copolymer-10 parts by weight of urethane resin-50 parts by weight of methyl ethyl ketone-25 parts by weight of toluene.

  The obtained OVD medium with anti-counterfeiting cannot visually recognize the latent image at all, but looks like a simple hologram film. However, by overlapping the polarizing film, the latent image appears clearly as shown in FIG. 7, and by overlapping the polarizing film by changing the angle of the polarizing film, the black and white of the latent image is displayed as shown in FIG. An OVD medium with good anti-counterfeiting was obtained by reversing the display.

  The back surface of the OVD medium with anti-counterfeit obtained in Example 1 was subjected to adhesive processing, and a release paper was attached to obtain a sticker.

  The present invention is applied, for example, to an intrinsic product display medium excellent in anti-counterfeiting property capable of visually confirming a latent image using a dedicated verification medium, for example, a display medium affixed to a product or a package. Is mentioned.

It is a top view of one Example of the OVD medium which performed the forgery prevention of this invention. It is explanatory drawing of the latent image image which appears when a polarizing plate is piled up on the OVD medium which performed the forgery prevention of FIG. It is a cross section in the XX line shown in FIG. 1 is a perspective view showing an embodiment of an image forming body in which an OVD medium subjected to forgery prevention according to the present invention is attached to cardboard. FIG. 5 is a cross-sectional view taken along line YY of the image forming body in FIG. 4. It is a top view which shows the other 1st example of the OVD medium which gave the forgery prevention of this invention. It is explanatory drawing of the latent image image which appears when a polarizing plate is piled up on the OVD medium which performed the forgery prevention of FIG. It is explanatory drawing of the other latent image image which appears when a polarizing plate is piled up on the OVD medium which performed the forgery prevention of FIG. 6 from a different angle. It is sectional drawing in the ZZ line shown in FIG. It is a top view which shows the other 2nd example of the OVD medium which gave the forgery prevention of this invention. It is a top view which shows the other 3rd example of the OVD medium which gave the forgery prevention of this invention.

Explanation of symbols

1, 2, 3, 4, 5 ... Anti-counterfeit OVD media 11, 32, 33 ... Latent image images 12, 31 ... Polarizing films 13, 22, 34, 44, 59 ... Substrate 14, 23, 35, 36, 42, 43, 56, 57 ... latent image forming layer 15, 37, 49, 52 ... OVD forming layer 16, 38, 45, 53, 58 ... light Reflective layer (OVD effect layer)
20 ... Multilayer thin film OVD layer 21 ... Substrate (cardboard)
24 ... 1st OVD forming layer 25 ... 2nd OVD forming layer 26, 27, 28, 29 ... Thin film layer 29 ... Adhesive layer 41 ... Protective layer 46 ... Adhesive layer 47 ... Release paper 51 ... release protective layers 54, 55 ... adhesive layer

Claims (10)

  The substrate is provided with a latent image forming layer and an OVD layer, and the latent image forming layer is visually observable through a polarizing film and is invisible or difficult to visually recognize through a polarizing film. An anti-counterfeiting method for an OVD medium, comprising providing a latent image portion formed by utilizing the anti-counterfeiting of the OVD medium.   The substrate is provided with a latent image forming layer and an OVD layer, and the latent image forming layer is visually observable through a polarizing film and is invisible or difficult to visually recognize through a polarizing film. An anti-counterfeit OVD medium characterized in that a latent image portion formed by use is provided.   3. The forgery-preventing OVD according to claim 2, wherein the material of the latent image forming layer is a polymer material capable of providing a latent image portion that can be formed by being oriented by an external force. Medium.   3. The forgery-preventing OVD medium according to claim 2, wherein the material of the latent image forming layer is a lyotropic liquid crystal material made of a dichroic dye that self-assembles.   5. The forgery-preventing OVD medium according to claim 4, wherein the latent image portion formed in the latent image forming layer is provided by being oriented by printing or coating.   6. The forgery-prevented OVD medium according to claim 2, wherein the latent image portion is a pattern-shaped latent image having information such as characters and pictures.   7. The forgery-preventing OVD medium according to claim 2, wherein a protective layer is provided on the latent image forming layer.   The OVD medium with anti-counterfeiting according to any one of claims 2 to 7, wherein a light reflecting layer made of a metal material is provided on the OVD layer.   The OVD medium with anti-counterfeiting according to any one of claims 2 to 8, wherein the polarizing film is a linear polarizing film.   A sticker using an OVD medium, which is a sticker using an OVD medium subjected to forgery prevention according to any one of claims 2 to 9.

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