JP6213039B2 - Security sheet and polymer bill - Google Patents

Description

  The present invention relates to a security sheet that is difficult to counterfeit and that is easy to authenticate even if counterfeited, and more particularly to a polymer bill.

  Banknotes include those printed on durable paper, such as Japanese banknotes, and those based on polymer films (hereinafter referred to as polymer banknotes). Paper can generally be procured by anyone, and it is relatively easy to forge based on the progress of copy technology. On the other hand, polymer bills are first introduced in Australia as bills with improved security that are difficult to counterfeit and imitate, and then used in more than 20 countries.

  A polymer banknote is obtained by printing a white ink on a transparent synthetic resin film to make it opaque, and then printing a desired pattern by a regular printing method, and coating a protective film that makes it difficult to wear. In addition, OVD (special hologram, optical variable device) can be arranged in various places, such as processing that cannot be directly realized on paper, so that design and security can be improved (Patent Document 1). When the OVD portion does not have a printed layer, a complicated visual effect can be exhibited such that the other side can be seen through.

  This paper made of synthetic resin is a non-resinous and non-porous material that is durable and waterproof, has a long service life, is easy to machine, and is difficult to tear. However, there is a problem that initial investment is increased, but it is advantageous in the long run, and it is expected that the introduction will increase in the future.

  Polymer bills are often provided with a transparent window portion through which a transparent synthetic resin portion can be seen without providing a printing layer having shielding properties on the front and back as means for improving security. It is apparent that the transparent portion is a copy product because it is not seen through because the copy paper is exposed as it is even when the polymer banknote is copied onto the copy paper. The presence of this transparent part is the point of deterrence that prevents counterfeiting and counterfeiting. However, the counterfeit suppression effect of the transparent window itself is low, and the entire polymer bill including the transparent window can be counterfeited or imitated.

JP 2012-78447 A

  Therefore, the present invention has an object to provide a sheet configuration in which the security of a security sheet including a polymer banknote is further improved.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a light-shielding printing layer is formed on the front and back of the light-transmitting film so that a light-transmitting window portion of a predetermined size is formed. A security sheet characterized in that a label or foil having a moth-eye structure is affixed to one side of the transparent window part so that the moth-eye structure is exposed, and a watermark pattern is printed on the other side. is there.

According to a second aspect of the present invention, a light-shielding printing layer is formed on the front and back sides of the light-transmitting film so that a light-transmitting window portion having a predetermined size is formed. The security sheet is characterized in that the moth-eye structure is exposed on the surface of the paper and the watermark design is printed on the other surface.

  The invention according to claim 3 is the security sheet according to claim 1 or 2, characterized in that a portion other than the moth-eye structure is covered with a protective layer.

  The invention according to claim 4 is a polymer banknote characterized by having the security sheet structure according to any one of claims 1 to 3.

  In the security sheet according to the present invention, a translucent film having a moth-eye structure on the surface is attached to a transparent window portion which is a non-printing portion of the film base material. The moth-eye structure film has a structure in which conical projections such as a cone or a quadrangular pyramid are two-dimensionally arranged on the film with a period of a submicron order. Therefore, when copying, the portion becomes black and has a copy suppression function. In addition, a special fine processing technique is required for manufacturing, and imitation is difficult in the first place.

  Even if it is imitated, the moth-eye structure will be reflected off of the black color when the viewing angle is changed from oblique to low. Setting and controlling this angle is difficult, and forgery can be determined by determining this angle.

  Furthermore, if the design is printed on the back of the moth-eye structure, it looks black with no reflection when viewed from the front, but the design is not visible, but when viewed through the back of the moth-eye film, the design appears due to the translucency of the moth-eye film. Can be confirmed. It is difficult to forge including this effect, and an effect that authentication can be easily performed can be expected.

It is a perspective view explaining the structure of the security sheet which becomes this invention. It is a figure of the sectional view explaining a moth eye structure. (A)-(c) It is a perspective view explaining three conditions for the authenticity determination of the security sheet which becomes this invention. It is a figure of the cross sectional view explaining the structure of a polymer banknote.

  As shown in FIG. 3 or FIG. 1, a polymer bill or generally a security sheet is a printed layer in which a synthetic resin such as a transparent polyester resin, polyethylene resin, or polypropylene resin is used as a base substrate 3 and necessary patterns are printed on both sides. 2 and 4, and the transparent protective layer 13 is further coated thereon for the purpose of improving the wear resistance of the printed layers 2 and 4.

  The printing layers 2 and 4 are coated with white ink on the front and back surfaces of the base substrate 3 to make it opaque, and then a regular gravure printing method or the like is applied to print a desired pattern or pattern in multiple layers. Since it is overcoated, it has moderate unevenness. At this time, a portion that is not printed is provided on a part of the front and back sides so that the portion can be seen through as a transparent window portion 6. This transparent window 6 is for preventing counterfeit bills because nothing is copied even if copied. Alternatively, processing such as OVD that cannot be directly formed on paper is possible on the window portion, which helps to improve security.

Polyester resin used as a base substrate is one of very strong resins, and does not change in strength even when wet, and is resistant to wear and relatively resistant to heat. The strength remains almost the same even when exposed to sunlight for a long time. In addition, it has low hygroscopicity and does not stretch even when washed, and drying is fast. Although it is thermoplastic, it does not lose its shape and is resistant to chemicals, insects and mold. Polypropylene resin has similar properties, but its heat resistance is inferior to that of polyester.

  For the polymer banknote with the above structure, the present invention is a film or foil that has a special visual effect that is more than OVD and is extremely difficult to manufacture, or is formed directly on the base substrate. is there. This film or foil has a moth-eye structure on the surface.

  A film having a moth-eye structure on the surface has a very low reflectivity with respect to incident visible light, and almost absorbs incident light, so that the appearance is black. The reason why light propagating in the air is reflected when it enters the glass or film is that the refractive index (air = 1) in the traveling direction of the light changes at the interface to a refractive index of 1.45. When the refractive index changes continuously as slowly as possible, the generation of reflected light can be suppressed.

The moth-eye structure or moth-eye film is a film formed by artificially forming a continuous change in the refractive index on the surface of a substrate using a high-level microfabrication technique.
Specifically, as shown in FIG. 2, a conical or pyramidal projection 12 whose tip 15 is sharp and has a diameter increasing toward the base 14 is periodically arranged on the substrate, or a hemispherical shape (not shown). Bumps are disposed (the substrate and the protrusion desirably have the same refractive index). That is, the needle-like projection group or hemispherical projection group whose diameter decreases toward the tip is arranged on a plane.

  In such a structure, the volume occupied by the projection group 12 is small at the tip and the refractive index is the same as that of air. However, as the diameter increases, the volume occupied by the projection group 12 in the air gradually increases. As a result, the refractive index gradually increases so as to interpolate the refractive indexes of air and the projection material. There is no jump of refractive index like the air-glass interface. Therefore, there is no reflection and the appearance looks black.

  The protrusions need to be two-dimensionally arranged at a pitch sufficiently shorter than the wavelength of visible light, for example, a pitch of 0.3 μm or less, so that interference does not occur in the visible region. The height of the protrusion is preferably as high as possible so that the refractive index change becomes gentle. However, since the pitch of the base portion is limited by the above-described value, it is about several times or less of the pitch in actual processing. Moreover, if the thickness of the base film 11 portion is set to be thin, it can be made semi-transmissive to transmit light.

As a manufacturing method for forming a moth-eye structure on a film, a molding method is preferable in which a stamper having a concave surface structure with inverted conical protrusions is manufactured, and after being pressed against molten resin, it is cooled and peeled off. It may be peeled by being thermally cured after being in pressure contact with the precursor resin before being thermally cured.
As an example of a stamper manufacturing method, for example, a chromium vapor deposition film is formed on a silicon wafer, and a columnar array of chromium with a submicron pitch is formed by a regular photolithography method.

  Thereafter, by subjecting the columnar pattern to dry etching, a silicon original plate having a conical chrome pattern can be formed. An electroless plating layer is formed on this surface, and then a nickel electrolytic plating layer is formed. Then, if the silicon wafer is taken out, a matrix made of nickel can be obtained. From now on, the inversion is repeated to produce a practical version as a stamper.

As the thermoplastic resin, polyethylene resin, polypropylene resin, polystyrene resin, polycarbonate, polyethylene terephthalate and the like can be used. A sheet made of any of these and having a thickness of about 100 μm is prepared, placed on the stage, the stage is heated to the glass transition temperature or higher, the practical plate is pressed, the resin is molded, and then cooled. When the practical version is peeled off, a fine protrusion arrangement is transferred onto the resin sheet. The resin may be poured between the plate and the stage and then cured. In this way, a moth-eye structure or a film having a moth-eye structure on the surface can be produced.

  In order to form bumps having a hemispherical surface, first, a deposited film having a thickness of about 500 angstroms is formed on a film substrate such as PET. A resist is applied to the deposited film, and a circular pattern with a period of about 1 μm is formed by photolithography. Thereafter, when the temperature is raised, the resist melts and the surface becomes hemispherical. When the temperature is further raised from this state, the resist is solidified while maintaining the hemispherical state. Next, when the entire surface is dry etched, the resist pattern is removed and at the same time a hemispherical pattern is transferred to the aluminum layer. In this way, irregularities on the order of submicrons can be formed. When this aluminum vapor deposition film is seen from the front, light is absorbed and it looks black (Asterium, registered trademark, letterpress printing). Since this deposited film is formed to be thin, it has a semi-transparency that can be seen through when light is applied from the back.

  The structure of the polymer banknote which is an example of the security sheet 1 according to the present invention is shown in FIG. Print layers 2 and 3 are formed on the front and back of a light-transmitting base substrate 3 made of polyester resin, and a transparent window 6 is formed on a part of the front and back without providing the print layers 2 and 3. . On one surface of the transparent window 6 is attached the label 5 or foil having the above-described moth-eye structure on the surface. A desired pattern 7 is printed on the other surface of the window portion 6 when the back surface is printed. Although the protective layer 13 is omitted in the drawing, it can be coated on a portion other than the moth-eye structure.

The above-mentioned polymer bill has three authenticity determination conditions.
First, as shown in FIG. 3A, the moth-eye label is colored in front view. The moth-eye structure looks non-reflective black when viewed from the front. If the part does not appear black, it is a counterfeit. Usually, it is transparent or transparent to the back, or a rainbow-colored band by the OVD effect, and the difference is clear.

  The second condition is the presence of reflected light when viewed obliquely from the front as shown in FIG. As for the moth-eye structure, if the viewing angle is deepened, unique reflected light can be seen. The angle at which the reflected light is seen and the color of the band can be controlled depending on the shape arrangement conditions of the protrusions. As long as the predetermined reflected light is not observed within a range where the predetermined observation condition is satisfied, it can be determined that the product is a counterfeit product.

  The third condition is a watermarked design that can be seen obliquely so that light enters the window from behind as shown in FIG. There is no way to put a watermark because it is light-shielding except for the window. In the present invention, since the moth-eye portion is semi-transparent, it can be seen by putting a thin pattern on the back surface.

  Therefore, unless all the three conditions are satisfied, the polymer money or the security sheet is a counterfeit / counterfeit product. It can be said that the anti-counterfeiting effect is high.

1, polymer bill 2, surface printed layer 3, base substrate 4, back printed layer 5, moth eye structure sheet 6, window 7, pattern 11, film substrate 12, protrusion 13, protective layer 14, base 15, Protrusion tip 20, conventional polymer banknote

Claims (4)

  A light-shielding printing layer is formed on the front and back of the light-transmitting film so that a light-transmitting window portion of a predetermined size is formed, and a label or foil having a moth-eye structure is formed on one surface of the light-transmitting window portion. A security sheet, wherein the moth-eye structure is affixed so as to be exposed, and a watermark pattern is printed on the other surface.   A light-shielding printing layer is formed on the front and back of the light-transmitting film so that a light-transmitting window portion of a predetermined size is formed, and the moth-eye structure is formed to be exposed on one surface of the light-transmitting window portion. And a watermark sheet printed on the other side.   The security sheet according to claim 1 or 2, wherein a portion other than the moth-eye structure is covered with a protective layer.   A polymer bill having the security sheet structure according to any one of claims 1 to 3.