JP5604860B2 - Anti-counterfeit paper - Google Patents

Description

  The present invention relates to a type of paper that requires anti-counterfeiting, and more particularly, to an anti-counterfeit paper that can easily determine the authenticity of a display body that causes an optical change applied to the anti-counterfeit paper.

  Conventionally, as a means for preventing counterfeiting, a fine structure or color tone change that cannot be easily imitated, or an optical phenomenon that is only in combination with another optical functional film as a discriminator is observed. Various aspects have been put into practical use with the advancement of technology, such as a configuration such that a certain pattern or the like can be read only by a dedicated reader.

Among them, a hologram that is an OVD (optical variable element: an abbreviation of “Optical (ly) Variable Device”) that causes an optical change is used as the most used anti-counterfeiting display body because of its practical convenience. And diffractive structures. A hologram is produced by providing a fine concavo-convex pattern and a refractive index distribution by an optical imaging method such as two-beam interference, and the diffractive structure is a diffraction grating with a diffraction grating arranged in a small area as a pixel. An image is created.
Both the hologram and diffractive structure are difficult to counterfeit, difficult to copy with a color copier, etc., and excellent in design, so they are widely used for credit cards, ID cards, various securities, certificates, etc. ing.
However, in actual operation, the authenticity of holograms and diffractive structures is left to the human eye, so even if it is a microscopically poor counterfeit product, all people can accurately and accurately authenticate with the naked eye. It is not easy to make a false determination.

Further, as the holograms and diffractive structures as described above are distributed and popularized, forgery technology also advances, so that a display body that is more difficult to forge is required.
For example, a hologram or diffractive structure having a surface relief structure may be duplicated by contact exposure.
In order to prevent forgery, for example, Patent Document 1 describes that a fine pattern having a diffraction effect is devised. This display body makes it difficult to know the presence or absence of security information so that the information cannot be read visually. Therefore, since it is difficult to determine whether or not the product is genuine, a reading machine is used for the determination.
In addition, holograms and diffractive structures replicated by the contact exposure method can be confirmed to have reduced accuracy compared to the original, but usually replicas are distributed only as replicas, so for ordinary people who are not experts There is a problem that it is difficult to determine whether the product is genuine.

It is known that a substrate provided with fine irregularities suppresses reflection of incident light. For example, some types of anti-reflection films have a fine distribution of the refractive index of the film by embossing fine irregularities on the surface of the film base material, or by adding a filler to the film-forming resin itself. Unevenness is formed.
In recent years, it has been disclosed that the unevenness can be made finer and the period of the protrusions can be made equal to or less than the wavelength of light to prevent light reflection and control incident light (see, for example, Patent Document 2). In this technique, the period of the convex portion is set to be equal to or less than the wavelength of light, particularly about 50 to 250 nm, so that reflection of light is suppressed and applied to the light control sheet (hereinafter referred to as the wavelength of such light). The concavo-convex structure having the following convexity period is referred to as a fine relief).
Further, it is disclosed that a reflective body is provided on a fine relief to control a diffracted light and to make a display body capable of observing the diffracted light. (For example, see Patent Document 3)
However, a display body with a reflective layer on such a fine relief is more effective in preventing counterfeiting because it requires more precise manufacturing technology than conventional diffractive structures and is difficult to counterfeit. Since diffracted light is not generated unless observed from an angle close to the horizontal direction, there is a problem that it is difficult to observe the diffracted light with the conventional method for observing a diffractive structure.

  Further, it is disclosed that a transparent portion and an opaque portion that are specially processed are provided on one anti-counterfeit paper, and moire appears when these are overlapped. (For example, refer to Patent Document 4) Although it is described in this technique that a diffractive structure is used in an opaque part, this diffractive structure alone is for expressing the effect of a convex lens, and is like an OVD for preventing forgery. A visual effect is obtained only when the transparent portion is overlaid on the transparent display.

JP-T-2002-505774 JP 2007-48688 A JP 2008-275740 A Special table 2008-513816 gazette

  The present invention aims to solve the above problems. That is, an object of the present invention is to provide an anti-counterfeit paper that can grasp the characteristics with human vision and easily determine the authenticity without changing the advanced visual effects of the OVD.

  In the present invention, in order to achieve the above object, first, in the invention of claim 1, in the anti-counterfeit paper having an OVD that causes an optical change, the anti-counterfeit paper is separate from the OVD in or on the base material of the anti-counterfeit paper. This part is a forgery prevention sheet characterized by having a prism structure that changes the incident angle and reflection angle of reflected light and diffracted light expressed by OVD.

According to the second aspect of the present invention, in the forgery prevention paper having an OVD that causes an optical change, a transparent portion is provided in a portion different from the OVD in the base material of the forgery prevention paper or on the base material. The anti-counterfeit paper according to claim 1, wherein the portion includes a prism structure for changing an incident angle and a reflection angle of reflected light and diffracted light expressed by OVD.

  The invention of claim 3 is characterized in that there are at least two types of OVD, and there are also at least two types of transparent prism structures for changing the incident angle and reflection angle of reflected light and diffracted light of OVD. Item 1 or 2 is forgery prevention paper.

  According to a fourth aspect of the present invention, at least one of the OVDs comprises a diffractive structure that expresses diffracted light, and the diffractive structure further includes a distance between centers of adjacent convex portions in a range of 200 nm to 400 nm and a depth of the concave portion. The anti-counterfeit paper according to any one of claims 1 to 3, wherein the anti-counterfeit paper is 100 nm or more.

  Since this invention is the above structure, there exist the following effects.

That is, the anti-counterfeit paper of the present invention does not incline the anti-counterfeit paper at various angles or tilt it to a deep angle when observing reflected light or diffracted light by OVD authenticity determination for anti-counterfeiting. It is possible to easily observe a plurality of types of reflected light and diffracted light simply by superimposing the prism structures.

FIG. 3 is a plan view showing a first example of a forgery prevention sheet according to the invention. Sectional drawing which shows the 1st example of the forgery prevention paper which concerns on this invention, and the model figure of incident light in OVD at the time of normal time, reflected light, and diffracted light (AA cross section of FIG. 1). The top view at the time of the authenticity determination of the forgery prevention paper of FIG. Sectional drawing at the time of authenticity determination of the forgery prevention paper of FIG. 1, and a model diagram of incident light, reflected light, and diffracted light at the time of authenticity determination. (B-B cross section of FIG. 3). FIG. 5 is an enlarged cross-sectional view of an OVD and a prism structure portion and a model diagram of incident light, reflected light, and diffracted light at the time of authenticity determination of the anti-counterfeit paper of the present invention (enlarged portion C in FIG. 4). The top view which shows the 2nd example of the forgery prevention paper which concerns on this invention. Sectional drawing which shows the 2nd example of the forgery prevention paper which concerns on this invention (DD cross section of FIG. 6). Sectional drawing which shows the 2nd example of the forgery prevention paper which concerns on this invention (EE cross section of FIG. 6). The top view which shows the 3rd example which concerns on this invention. Sectional drawing which shows the 3rd example of the forgery prevention paper which concerns on this invention (FF cross section of FIG. 9). Sectional drawing which shows the 3rd example of the forgery prevention paper which concerns on this invention (GG cross section of FIG. 9). FIG. 10 is a plan view at the time of authenticity determination of the forgery prevention paper of FIG. FIG. 10 is a cross-sectional view of the anti-counterfeit paper shown in FIG. 9 when authenticity is determined, and model diagrams of incident light, reflected light, and diffracted light when authenticity is determined (cross-section F′-F ′ in FIG. 9). FIG. 10 is a cross-sectional view of the anti-counterfeit paper in FIG. 9 when authenticity is determined, and model diagrams of incident light, reflected light, and diffracted light during authenticity determination (cross section G′-G ′ in FIG. 9).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing a first example of an anti-counterfeit paper according to the present invention.
In the anti-counterfeit paper 1 of FIG. 1, an OVD 12 that is an optical variable element is pasted on a base material 11 in a band shape. As long as the optical change of the OVD 12 can be directly visually observed, the OVD 12 may be inserted into the base material 11 in a window shape or may be affixed to another shape other than a belt shape. The OVD 12 is composed of a display whose pattern, color, brightness, etc. vary depending on the viewing angle. In FIG. 1, for example, the letters “OVD” surrounded by broken lines are OVD 121, and FIG. Therefore, the brightness of the OVD 121 of “OVD” in the center is dark, and the OVD 121 close to the edge of the sheet changes its angle rather than directly in front, so the brightness is slightly increased.
A base material 11 of the anti-counterfeit paper 1 of FIG. 1 has a perforated part 13, and a prism sheet 14 is attached so as to cover the perforated part 13. In the prism sheet 14, as shown in a cross-section in FIG. 2, the surface with prism irregularities is the substrate 11 side, and the opposite surface is a plane.

FIG. 2 is a cross-sectional view of the anti-counterfeit paper 1 shown in FIG. 1, and illustrates optical characteristics when the OVD 12 is a diffractive structure.
When the illumination light 121a is incident on the diffractive structure 121 of the OVD 12, regular reflected light 121b and diffracted light 121c are generated, and the observer can tilt the forgery prevention paper 1 or face so that it can be observed from the angle 121c. 121c can be observed.

  FIG. 3 is a plan view showing a state when authenticity determination of the anti-counterfeit paper 1 of the present invention is performed, and the OVD 12 is observed from the perforated portion 13 while the anti-counterfeit paper 1 is bent and the prism sheet 14 is closely attached to the OVD 12. Indicates the state.

FIG. 4 shows the BB cross section of FIG. 3 and the optical characteristics of the diffractive structure 121. OVD
When the illumination light 121a is incident on the twelve diffractive structures 121, the specularly reflected light 121b and the diffracted light 121c are generated, and the prism sheet 14 changes the angles of the incident light, the reflected light, and the diffracted light. .

FIG. 5 is an enlarged cross-sectional view of a portion C where the prism sheet 14 and the diffractive structure 121 in FIG. 4 are in contact, and shows details of the light refraction effect by the prism. The prism sheet 14 has a V-shaped prism structure with an apex angle α on the observation surface side, and the opposite surface has a flat shape so as to be in close contact with the diffraction structure portion 121. On the other hand, the diffractive structure 121 has a flat surface in contact with the prism sheet 14, and a relief that is a diffractive structure is formed on the opposite surface.
The refractive effect of such a structure is that when the illumination light 121a is incident on the prism sheet 14 at an angle θ1, the incident angle of the illumination light 121a changes to θ2 due to the difference in refractive index between air and the prism sheet. It enters into 121. As a result, reflected light 121b and diffracted light 121c are generated in the diffractive structure 121, and the exit angle of the reflected light 121b changes from θ2 to θ1 and the exit angle of the diffracted light 121c changes from θ4 to θ3 due to refraction of the prism sheet. And then injected. The refraction phenomenon at this time is expressed by the difference between the refractive index of air and the refractive index of the prism sheet. Generally, the refractive index of air is about 1.0, and glass or resin that is a transparent material that can be used for the prism sheet. Is approximately 1.5 to 2.5, and thus becomes larger than 1.0 of air. According to Snell's law (n ₁ Sinθ ₁ = n ₂ Sinθ ₂ ), θ1> θ2 and θ4> θ3. Become.

  FIG. 6 is a plan view showing a second example of the forgery prevention paper according to the present invention. The anti-counterfeit paper 2 in FIG. 6 is provided with a transparent portion 15 so as to cover the perforated portion 13, and the upper half of the transparent portion 15 is a prism having a V-shaped structure for changing the direction of light incidence and emission. The lower half of the transparent portion 15 is a flat portion 152 having a transparent and flat shape.

  7 is a cross-sectional view taken along the line DD of FIG. 6, and FIG. 8 is a cross-sectional view showing a cross-section taken along the line EE of FIG. 6.

  FIG. 9 is a plan view showing a third example of the anti-counterfeit paper according to the present invention. The OVD 12 of the anti-counterfeit paper 3 of FIG. 9 is formed with a diffractive structure 121 and a diffractive structure 122 as two types of diffractive structures having different incident angles for expressing diffracted light. An apex angle prism structure portion 153 corresponding to the diffractive structure portion 121 and an apex angle prism structure portion 154 corresponding to the diffractive structure portion 122 are formed to cover the perforated portion 13. 10 is a cross-sectional view taken along the line FF in FIG. 9, and FIG. 11 is a cross-sectional view taken along the line GG in FIG.

  FIG. 12 is a plan view showing a state of authenticating the anti-counterfeit paper 3 according to the present invention, in which the anti-counterfeit paper 3 is bent and the OVD 12 is observed from the perforated portion 13 while the prism sheet 14 is in close contact with the OVD 12. Thus, FF and GG in FIG. 9 are in a state like F′-F ′ and G′-G ′ in FIG. 12 when authenticity is determined. When the diffractive structure 121 is observed through the prism structure 153 as shown in FIG. 12, diffracted light like the diffractive structure 121 ′ is observed with a small inclination angle, and the diffractive structure 122 also passes through the prism structure 154. When observed, diffracted light such as the diffractive structure 122 ′ can be observed at an angle closer to the front.

  13 is a cross-sectional view taken along line F′-F ′ in FIG. 12, and FIG. 14 is a cross-sectional view taken along line G′-G ′ in FIG. 12, and further passes through the prism structure 153 and prism structure 154. An optical path when incident and reflected light and diffracted light are generated is shown. An optical path with a at the end of the number is incident light, an optical path with b at the end of the number is reflected light, and an optical path with c at the end of the number is diffracted Showing light

  Hereinafter, the configuration of the anti-counterfeit paper of the present invention will be described in detail.

(Base material)
The base material 11 is a base material of the anti-counterfeit papers 1 to 4, such as a single piece of paper or resin or a laminate thereof, a composite single piece or laminate of paper or resin, or a synthetic paper manufactured using a resin as a main material, Any material may be used as long as it is a material used for anti-counterfeit paper.

(OVD)
The OVD 12 can use a resin film as a base material. As the resin film, a polyethylene terephthalate resin film, a polyethylene naphthalate resin film, a polyimide resin film, a polyethylene resin film, a polypropylene resin film, a heat-resistant vinyl chloride film, or the like can be used. Among these resins, since the heat resistance is high and the thickness is stable, a polyethylene terephthalate resin film can be preferably used.

  As the OVD provided on the substrate, it is possible to see different colors depending on the diffractive structure provided with a metal reflection layer, an optical multilayer interference film that is a multilayer thin film, a layer of cholesteric liquid crystal, and an observation angle. Ink containing powder can be used, but a diffractive structure that can change greatly the angle at which a plurality of images are switched or the color changes depending on the observation angle is desirable. Moreover, you may provide the contact bonding layer for affixing on the base material 11 of a forgery prevention paper.

  The relief type diffraction grating has a diffraction grating recorded in the form of a fine uneven pattern on the surface thereof. Such a concavo-convex pattern is obtained by, for example, irradiating the surface of the photosensitive resin with two coherent light beams using the two-beam interference method to generate an interference pattern on the surface of the photosensitive resin. Can be formed by recording in a photosensitive resin in the form of irregularities. The interference fringes formed by this two-beam interferometry are also diffraction gratings, and an arbitrary three-dimensional image can be recorded as a diffraction grating pattern by selecting the two light beams, depending on the observation angle. It is possible to record so that different images (hereinafter referred to as changing images) can be seen.

  About the method of recording the image pattern expressed by the diffraction grating structure used in the present invention, in addition to the two-beam interference method, production of conventionally known holograms such as image holograms, rainbow holograms, integral holograms, etc. It can be produced by a method.

  Further, the concavo-convex pattern of the relief type diffraction grating can form a diffraction structure by irradiating the surface of the electron beam curable resin with an electron beam and exposing it to a striped pattern to be a diffraction grating. In this case, since the interference fringes can be controlled for each line, any three-dimensional image or changing image can be recorded in the same manner as the hologram. It is also possible to divide the image into dot-like pixel areas, record different diffraction gratings for each pixel area, and express the entire image with a set of these pixels. The pixel may be a circular dot or a star-shaped dot.

It is also possible to form the concavo-convex pattern by an induced surface relief forming method. That is, by irradiating an amorphous thin film of a polymer having azobenzene on the chain side with a relatively weak light of about several tens mW / cm ² having a certain wavelength ranging from blue to green, several μm scale As a result, movement of polymer molecules can be caused, and as a result, relief by unevenness can be formed on the surface of the thin film.

Then, by forming a metal film on the surface of the relief-type master plate having the uneven pattern formed in this way by electroplating, the uneven pattern of the relief-type master plate is duplicated and used as a press plate. And OVD for forming the diffraction structures 121 and 122
A diffractive structure is formed by thermocompression-bonding this press plate to the forming layer and transferring a relief composed of a concavo-convex pattern to the surface of the thin film.

  As a resin used for such an OVD forming layer, a thermoplastic resin, a thermosetting resin, an ultraviolet ray, an electron beam curable resin, or the like can be used. For example, acrylic resins include acrylic resins, epoxy resins, cellulose resins, vinyl resins, and the like. In addition, urethane resins, melamine resins, phenol resins, and the like obtained by adding polyisocyanate as a crosslinking agent to an acrylic polyol or polyester polyol having a reactive hydroxyl group and crosslinking can be used. Further, as the ultraviolet ray or electron beam curable resin, epoxy (meth) acryl, urethane (meth) acrylate, or the like can be used.

  When the OVD 12 is a diffractive structure, a reflective layer is provided so as to be in contact with the diffractive structure. As the reflective layer in this case, a metal thin film can be preferably used in terms of high reflection luminance. Examples of the metal used for the metal thin film include Al, Sn, Cr, Ni, Cu, Au, and brass. And this metal thin film can be formed using a vacuum film-forming method. As the vacuum film formation method, a vacuum deposition method, a sputtering method, or the like can be applied, and the thickness may be controlled to about 5 to 1000 nm.

  Alternatively, a thin film may be formed by printing ink containing metal powder or transparent material powder. In this case, the powder preferably has a particle diameter of 500 nm or less. The thickness of the thin film is preferably 0.1 to 20 μm, and a known printing method such as a gravure printing method, a flexographic printing method, or a screen printing method can be used as a printing method.

  The reflective layer may be processed into an arbitrary pattern to form a partially reflective layer. As a method for forming the partial reflection layer, the following method is used.

  That is, the first method is a method using the above-described printing method. The second method is a method of forming a film in an image pattern by stacking a mask having an image pattern-shaped opening on the diffractive structure and partially depositing the reflective layer in a vacuum in each step. is there.

  In the third method, first, a solvent-soluble resin layer is provided in a negative pattern on the diffractive structure, and this solvent-soluble resin layer is coated to form a uniform reflection layer on the entire surface. The solvent-soluble resin layer is dissolved and removed, and at the same time, the reflective layer superimposed on the solvent-soluble resin layer is removed to partially reflect the reflective layer remaining in the image pattern on the diffraction structure. It is a method to make a layer.

  In the fourth method, first, a resin layer that is easily peeled off from the OVD forming layer is provided on the OVD 12 in a negative pattern, and the reflective layer is uniformly formed on the entire surface by covering the resin layer. This is a method in which a negative pattern is transferred to and removed from an adhesive roll or adhesive paper by pressing against a roll or adhesive paper, and as a result, the reflective layer remains in an image pattern and becomes a partially reflective layer.

  Next, in the fifth method, a reflective layer is uniformly formed on the entire surface of the OVD forming layer, a chemical resistant resin layer is provided on the reflective layer in an image pattern, and an alkaline or acidic etching solution is applied. In this method, the reflective layer exposed by application is dissolved and removed to form a partially reflective layer. In this case, after the reflective layer is processed into an image pattern, the chemical-resistant resin layer may be removed, but it remains on the partial reflective layer as it is, as a protective layer for imparting chemical resistance. It can also be used.

Next, in the sixth method, a photosensitive resin layer is formed on the reflective layer uniformly formed on the entire surface of the OVD forming layer, exposed and developed into an image pattern, and then an alkaline or acidic etching solution is applied. Then, the exposed reflective layer is dissolved and removed. Also in this case, the remaining photosensitive resin layer can be left as it is, and can be used as a protective layer for imparting chemical resistance.

  The seventh method is a method in which the reflective layer formed uniformly on the entire surface is removed by irradiating with a laser beam, so that the remaining reflective layer becomes an image pattern as it is as a partial reflective layer.

(Adhesive layer)
As the adhesive layer, any adhesive layer may be used as long as it adheres to the substrate 11 that is a transfer object by heat and pressure, and a known heat-sensitive adhesive material can be used.

(Other layers)
Although not shown in the figure, as other layers, an anchor layer is provided in order to further strengthen the adhesion between the layers, a colored layer that colors the entire surface or a part of the OVD 12 is provided, and characters and designs are provided. A print layer can be added for printing. As these inks, known adhesion improvers and adhesives, colorants using dyes and pigments, printing inks, and the like can be used.

(Prism sheet)
As a base material used for the prism sheet 14, a resin film can be used. As the resin film, a polyethylene terephthalate resin film, a polyethylene naphthalate resin film, a polyimide resin film, a polyethylene resin film, a polypropylene resin film, a heat-resistant vinyl chloride film, or the like can be used. Among these resins, since the heat resistance is high and the thickness is stable, a polyethylene terephthalate resin film can be preferably used.

As a resin for constituting the V-shaped prism structure portion in the prism sheet 14, a thermoplastic resin, a thermosetting resin, an ultraviolet ray or an electron beam curable resin may be used as long as it has transparency capable of transmitting visible light. Etc. can be used. For example, acrylic resins include acrylic resins, epoxy resins, cellulose resins, vinyl resins, polycarbonate resins, and the like.
In addition, urethane resins, melamine resins, phenol resins, and the like obtained by adding polyisocyanate as a crosslinking agent to an acrylic polyol or polyester polyol having a reactive hydroxyl group and crosslinking can be used. Among them, epoxy (meth) acryl, urethane (meth) acrylate, etc. can be used as ultraviolet or electron beam curable resin, and V-shaped prism-shaped processing is performed by cutting, hot-press embossing by metal plate, injection molding, etc. Can be produced. In addition, in this invention, if it can produce in a desired shape using transparent resin, it will not be specifically limited to the said resin and a preparation method.

  The prism sheet has a flat surface on the side in contact with the OVD 12 and a regular V-shaped structure on the opposite surface. Each light, such as incident light, diffracted light, and reflected light, follows Snell's law, and when light enters and exits the V-shaped interface of the prism sheet 14 at an angle within a critical angle, air and prism respectively. Since the refraction angle proceeds by being refracted at the interface with the sheet, and the refraction angle is determined by the refractive index n and the apex angle α of the material constituting the prism sheet 14, the refractive index n and the apex angle α are appropriately designed to be diffracted. The light emission angle can be set arbitrarily.

Next, the present invention will be described by way of examples.
<Example 1>

The anti-counterfeit paper which is the first example of the present invention will be described.
First, a polyethylene terephthalate (commonly known as PET) film having a thickness of 25 μm was used as the base material of the prism sheet. An ultraviolet curing acrylic resin is uniformly applied to this substrate to a film thickness of 5 μm by a bar coating method, and a V-shaped groove having an apex angle of 79 ° is arranged at regular intervals. While pressing the embossed plate made of the material, it was cured by irradiating with ultraviolet rays to produce a desired prism sheet.

Next, softwood pulp, which is a raw material for anti-counterfeiting paper, was beaten in water to produce a slurry to which a sizing agent (starch) and filler (calcium carbonate) were added, and it was designed into an arbitrary shape using a hand mill. The paper sheet was poured into the paper layer so that the prism sheet was exposed from the window opening, dehydrated and dried to prepare a base material for anti-counterfeit paper having a weight of 150 g / m ² .

  Next, a 12 μm PET film is used as a base material for OVD, and an ink composed of the following composition is applied and dried on one side of the base material to form an OVD forming layer having a film thickness of 1.5 μm. The press plate was hot-pressed to form unevenness on the surface for generating a diffractive structure at the same time.

  Next, an aluminum vapor deposition film was uniformly formed with a film thickness of 50 nm on the entire surface of the OVD formation layer by vacuum vapor deposition to form a reflective layer.

  On this reflective layer, the ink which consists of the following composition was apply | coated and dried, and the hot melt type contact bonding layer with a film thickness of 3 micrometers was formed.

  Finally, a forgery-preventing paper according to the first example of the present invention is affixed to a base material by a hot roll heated to 160 ° C. at a position on the base material away from the prism sheet into which the sheet is inserted. Was made.

"OVD forming layer ink composition"
Acrylic resin 20.0 parts by weight Reactive silicone 1.0 part by weight Methyl ethyl ketone 50.0 parts by weight Ethyl acetate 30.0 parts by weight

"Adhesive layer ink composition"
Vinyl chloride vinyl acetate copolymer resin 15.0 parts by weight Acrylic resin 10.0 parts by weight Silica 1.0 part by weight Methyl ethyl ketone 44.0 parts by weight Toluene 30.0 parts by weight

<Example 2>
Next, as a second embodiment, a forgery prevention sheet which is a fourth example of the present invention will be described.
First, a polyethylene terephthalate (commonly known as PET) film having a thickness of 25 μm was used as a prism sheet substrate. An ultraviolet curable acrylic resin was uniformly applied to a film thickness of 5 μm by a bar coating method on this substrate, and the angle was 50 A desired prism sheet was prepared by irradiating and curing ultraviolet rays while pressing an Ni embossed plate having a shape in which V-shaped grooves having apex angles of ° were arranged at regular intervals.

Next, softwood pulp, which is a raw material for anti-counterfeiting paper, was beaten in water to produce a slurry to which a sizing agent (starch) and filler (calcium carbonate) were added, and it was designed into an arbitrary shape using a hand milling device. The paper sheet was poured into the paper layer so that the prism sheet was exposed from the window opening, dehydrated and dried to prepare a base material for anti-counterfeit paper having a weight of 150 g / m ² .

  Next, a 12 μm PET film is used as the OVD base material, and an ink composed of the following composition is applied and dried on one side of the base material by a bar coating method to form an OVD forming layer having a thickness of 2.5 μm. After the formation, the diffractive structure has two types of diffractive structures: a concavo-convex structure with a concave portion depth of 400 nm and a concave portion pitch (center-to-center distance) of 360 nm and a wavy concavo-convex structure with a height of 500 nm and a pitch of 1 μm. The Ni plate was pressed against the OVD forming layer, and the desired diffractive structure was formed by irradiating ultraviolet rays toward the OVD forming layer from the PET film surface side to cure the ink.

  Next, an aluminum vapor deposition film was uniformly formed with a film thickness of 50 nm on the entire surface of the OVD formation layer by vacuum vapor deposition to form a reflective layer.

  On the reflective layer, an ink comprising the following composition was applied and dried to form a hot melt type adhesive layer having a thickness of 3 μm.

  Finally, a strip-shaped OVD is attached to the base material with a hot roll heated to 160 ° C. at a position away from the prism sheet inserted on the base material, and the anti-counterfeit paper according to the fourth example of the present invention is produced. did.

"OVD forming layer ink composition"
UV curable acrylic resin 20.0 parts by weight Methyl ethyl ketone 50.0 parts by weight Ethyl acetate 30.0 parts by weight

"Adhesive layer ink composition"
Vinyl chloride vinyl acetate copolymer resin 15.0 parts by weight Acrylic resin 10.0 parts by weight Silica 1.0 part by weight Methyl ethyl ketone 44.0 parts by weight Toluene 30.0 parts by weight

<Comparative example>
As a comparative example, anti-counterfeit papers having the same layer configuration and materials were prepared except that the prism sheets in Examples 1 and 2 were not used.

  When the anti-counterfeit paper produced in Example 1 was bent near the center, the prism sheet was brought into close contact with the OVD, and the OVD was observed through the prism sheet, diffracted light could be observed at an angle of 30 ° from the front. Further, when the OVD is observed with the prism sheet portion being shifted by hand without covering the OVD, the diffracted light is not observed at this angle, and the angle is set so that the angle is further increased. Diffracted light was observed. As described above, in the anti-counterfeit paper manufactured in Example 1, it is possible to determine whether the OVD diffracted light is present or not by changing the observation angle by simply moving the prism sheet up and down or left and right by hand. Yes, thanks to the prism sheet, it was possible to observe the diffracted light at an angle closer to the front than the anti-counterfeit paper produced in the comparative example without the prism sheet.

Next, when the anti-counterfeit paper produced in Example 2 was bent near its center and the prism sheet portion was closely attached to the OVD and the OVD was observed, the color of the characters changed in a state inclined at an angle of 15 ° from the front. Then, the diffracted light can be observed, and when the angle is further changed to 22 °, the green diffracted light can be further observed. On the other hand, in the anti-counterfeit paper prepared in the comparative example without the prism sheet, the diffracted light cannot be observed at 15 ° and 20 ° from the front, and the diffracted light is observed by tilting to a deeper angle. Some people were unaware of the diffracted light from near-horizontal angles. Therefore, when diffracted light of two types of OVD is observed by overlapping the prism sheets, observation can be performed with a small change in observation angle, and further, the diffracted light can be observed by shifting the prism sheet part back and forth or left and right. Therefore, even if a plurality of types of OVD are mixed, it is easy to determine the authenticity.

  As described above, the anti-counterfeit paper of the present invention can easily observe diffracted light not only with one type of diffractive structure but also with anti-counterfeit paper having a plurality of types of diffractive structures by providing a prism sheet. It was found that this paper is an anti-counterfeit paper that can be easily checked for authenticity.

DESCRIPTION OF SYMBOLS 1 ... Anti-counterfeit paper which is 1st example which concerns on this invention 2 ... Anti-counterfeit paper 3 which is 2nd example which concerns on this invention 3 ... Example 3 based on this invention Anti-counterfeit paper 11 shown..Base material 12 of anti-counterfeit paper showing first to fourth examples according to the present invention .... OVD (optical variable element)
13 .... perforated part 14 ... prism sheet 15 ... transparent part 121 ... diffractive structure 122 ...... diffractive structure 121a ... incident light 121b ... reflected Light 121c ... Diffraction light 122a ... Incoming light 122b ... Reflected light 122c ... Diffraction light 151 ... Prism structure part 152 ... Flat part 153 ... Prism Structure portion 154... Prism structure portion

Claims (4)

  In an anti-counterfeit paper having an OVD that expresses an optical change, an incident angle and a reflection angle of reflected light and diffracted light expressed by the OVD are set in a portion of the base material of the anti-counterfeit paper or different from the OVD on the base material. Anti-counterfeit paper characterized by a prism structure that changes. In anti-counterfeit paper having an OVD that expresses optical changes, a transparent part is provided in a part of the base material of the anti-counterfeit paper or different from the OVD on the base material, and at least a part of the transparent part is expressed by the OVD. forgery preventing paper you characterized in that it comprises a prismatic structure for varying the angle of incidence and the angle of reflection of the reflected light or diffracted light.   The said OVD consists of at least 2 types, The transparent prism structure for changing the incident angle and reflection angle of the reflected light and diffracted light of the OVD also consists of at least 2 types. Anti-counterfeit paper.   At least one of the OVDs comprises a diffractive structure that expresses diffracted light, and further, the distance between centers of adjacent convex parts of the diffractive structure is 200 nm to 400 nm, and the depth of the concave part is 100 nm or more. Item 4. The anti-counterfeit paper according to any one of items 1 to 3.