JP6120025B2 - Anti-counterfeit paper - Google Patents

Description

  The present invention relates to the prevention of counterfeiting of securities consisting of paper such as banknotes, stock certificates, bonds, gift certificates, lottery tickets, and more specifically, when an attempt is made to counterfeit or tamper with an electronic copying machine. The present invention relates to anti-counterfeit paper that becomes extremely difficult.

  At present, paper is widely used as securities with monetary value, such as banknotes, stock certificates, bonds, gift certificates, lottery tickets, etc., and paper used for such securities can be easily counterfeited or In order to prevent alteration, watermarks are applied to the paper itself, or special printing such as micro letters, intaglio, hidden letters, and fluorescent printing is performed, foil with metallic luster such as gold foil or silver foil, or light interference In general, a foil having a diffractive structure such as a hologram or a diffraction grating that can express a stereoscopic image or a special decorative image is applied by transfer or sealing (for example, Patent Document 1 and Patent Document 2). reference).

Among these methods, the watermarking method and configuration include a white watermark method and a black watermark method that form a pattern by changing the thickness of the paper using a special paper machine, and a method in which a watermark pattern is printed in advance. By creating a material and adhering a paper base material to the front and back of the base material, applying a color former in advance to the base material, adhering the paper base material to the front and back of the base material, and finally irradiating the laser A method for obtaining a watermark image has been proposed in the past (see, for example, Patent Document 3 and Patent Document 4).
The prior art documents are shown below.

Japanese Patent No. 1615000 JP-A-4-149585 JP 2002-67470 A Japanese Patent No. 4391287

  However, the diffraction structure as a forgery prevention measure as described above is processed into a sticker or transfer foil and then attached to the object to be pasted. Forgery, such as attaching a diffractive structure, is increasing, and recently, there is a problem that its anti-counterfeiting effect is fading.

  In addition, when the general public makes authenticity judgments on securities and banknotes, the paper watermark is still effective, so the watermark is used for actual anti-counterfeit paper. Is limited to only two gradations called the white watermark method, and watermark paper using a black watermark method having a plurality of gradations is used only for banknotes.

  Further, since such a watermark paper forms a watermark using a change in light transmittance due to a change in the thickness of the paper base material, the paper base material must be made thin in order to obtain a bright watermark. In order to reduce the strength or improve the contrast effect of the watermark, the difference in the surface paper thickness of the watermark must be increased, resulting in unevenness in the watermark paper itself and the printing of the watermark There is a problem of poor aptitude.

  Therefore, the present invention solves the problems of the related art, and the problem is that a watermark paper having a plurality of gradations can be produced by a method different from the watermark method, and the strength and smoothness of the surface are improved. It is an object of the present invention to provide a forgery-preventing paper that is difficult to falsify and counterfeit because it has a structure in which the intermediate layer that has been encased is exposed at a part of the paper and further an optical change is developed at the exposed portion.

In the present invention, in order to achieve the above object, in the first invention, the paper sheet includes an intermediate layer including an intermediate layer substrate made of a transparent polymer resin film, and the intermediate layer is an intermediate layer. It has a base material and a concavo-convex forming layer, and the concavo-convex forming layer is laminated on a part or the entire surface of the intermediate layer base material , and this intermediate layer changes in thickness due to a change in the thickness of the intermediate layer base material. The paper base has a thickness change that counteracts the change in the thickness of the intermediate layer, and the thickness of the intermediate layer is the difference between the thickness of the paper base and the watermark paper The light transmission density difference of the light passing through the surface of the paper substrate is changed, thereby changing the light transmission density difference as a watermark pattern, and a part of the intermediate layer is formed on one side or both sides of the paper substrate. exposed and, in the part exposed from the sheet base material of the intermediate layer, the diffractive structure irregularities forming layer formed And the change in the thickness of the intermediate layer substrate is smaller than the portion where the difference in light transmission density occurs, and the thickness of the intermediate layer substrate in the portion where the difference in light transmission density occurs. The change is larger than the change in the thickness of the concavo-convex forming layer due to the concavo-convex forming the diffractive structure, and the thickness of the intermediate layer base material changes in a visible pattern so that the difference in light transmission density appears as a watermark pattern This is a forgery prevention paper characterized by

  Next, in the second invention, a part or the whole of the intermediate layer contains a multilayer thin film of an optical multilayer interference film, a layer of cholesteric liquid crystal, and a powder capable of seeing different colors depending on an observation angle. The anti-counterfeit paper is characterized by laminating any one of the printing layers.

According to a third aspect of the present invention, there is provided a forgery prevention paper characterized in that a light reflection layer is provided on a part of the intermediate layer.

According to a fourth aspect of the present invention, there is provided an anti-counterfeit paper characterized in that fine irregularities of 0.01 μm to 5 μm are formed on a part or the entire surface of the irregularity forming layer.

According to a fifth aspect of the present invention, the anti-counterfeit paper is characterized in that the light reflecting layer is provided only in a portion where the intermediate layer is exposed from the paper base material.

According to a sixth aspect of the invention, there is provided a forgery prevention paper characterized in that the light reflecting layer is provided in an arbitrary pattern.

In the seventh invention, the light reflection layer is a forgery-preventing paper characterized in that the visible light transmittance is 20% to 90%.

According to an eighth aspect of the present invention, there is provided a multilayer thin film or a cholesteric liquid crystal layer provided in the intermediate layer, a printed layer containing a powder that can show different colors depending on the viewing angle, a diffractive structure, and a light reflecting layer However, the anti-counterfeit paper is provided only in a portion exposed from the paper base material.

According to a ninth aspect of the invention, there is provided an anti-counterfeit paper characterized in that a printing layer is provided on at least a part or the whole of the intermediate layer.

According to a tenth aspect of the invention, there is provided an anti-counterfeit paper characterized in that an adhesive layer is provided on one side or both sides of the intermediate layer to strengthen the adhesion between the paper substrate and the intermediate layer. is there.

Further, in the eleventh invention, in order to further strengthen the adhesion between the intermediate layer and the paper substrate, the counterfeit is characterized in that two layers of an adhesive layer and an adhesion auxiliary layer are provided on at least one side of the intermediate layer. It is a prevention paper.

  Since this invention is the above structure, there exists an effect shown below.

  In other words, by directly forming irregularities such as letters, pictures, and figures on a transparent polymer resin film as an intermediate layer, this intermediate layer is inserted into the paper layer. The thick part of the layer becomes lighter and brighter than the paper base. On the other hand, the thinner part of the intermediate layer becomes thicker and darker, so that a watermark image having continuous gradation can be obtained.

  In addition, the presence of the intermediate layer makes it possible to make a strong anti-counterfeit paper regardless of the brightness of the watermark, and even if the thickness of the intermediate layer changes, the thickness of the portion where the intermediate layer is inserted is Because it is constant (the exposed part is slightly thinner), the entire paper surface is smooth, and the intermediate layer is exposed on one or both sides of the paper. High anti-counterfeit paper can be obtained.

  Next, a part of the intermediate layer in which the multilayer thin film of the optical multilayer interference film, the layer of cholesteric liquid crystal, and the printing layer made of ink containing powder is laminated is exposed on one side or both sides of the paper, thereby providing a watermark effect. By using different colors depending on the viewing angle, or looking through a special film, it is possible to obtain a forgery-preventing paper in which the colors and patterns change.

  In addition, the intermediate layer is a watermark paper comprising two layers of a base material made of a transparent polymer resin film and a transparent unevenness forming layer, and the intermediate layer is inserted into a paper layer. Therefore, it is possible to obtain a forgery-preventing paper having a watermark effect, which can change the thickness more easily and greatly.

  Further, by providing the light reflecting layer in a part of the intermediate layer, the color gamut of the dark color in the light and dark of the watermark is widened, so that it is possible to obtain a forgery prevention paper with a further enhanced contrast of the watermark.

  Further, by forming fine unevenness of 0.01 to 5 μm on a part or the entire surface of the unevenness forming layer, it is possible to obtain a forgery prevention paper having a smoother gradation watermark.

  In addition, it is possible to observe a part or the entire surface of the concavo-convex forming layer as a plurality of different colors and image patterns according to colors and images or observation angles within a certain range of angles, and watermarking. An anti-counterfeit paper having an effect can be obtained.

  In addition, by providing a light reflecting layer on the portion of the intermediate layer exposed from the paper substrate, the portion where the intermediate layer is exposed from the paper substrate has an effect of causing an optical change. A portion inserted into the base material can be a forgery prevention paper having a watermark effect.

  In addition, since the light reflection layer is provided in an arbitrary pattern, the anti-counterfeit paper can further improve the anti-counterfeit effect.

  Further, by setting the visible light transmittance of the light reflecting layer to 20% to 90%, the anti-counterfeit paper having an effect of developing an optical change while maintaining transparency in the intermediate layer exposed from the paper base material. Can be.

  In addition, the multilayer thin film or the cholesteric liquid crystal layer, a printing layer made of ink containing powder that can see different colors depending on the viewing angle, a single layer of a diffraction structure, a light reflection layer, or a plurality of layers Because it is provided only in the intermediate layer exposed from the paper base material, the part with the paper base material has a gradation effect with rich gradation, and the same printability as paper without general watermarks. In addition, the window opening part where the intermediate layer is exposed from the paper substrate can be made into an OVD that expresses optical changes, and this OVD part is integrated with the paper as the intermediate layer Thus, it is possible to make a forgery-preventing paper that is difficult to tamper with.

In addition, since the printing layer is provided on at least one part or the whole of the intermediate layer, in addition to the watermark effect due to the thickness of the paper base material, the design property by printing is given, and the watermark due to the density of printing is given. It can be set as the forgery prevention paper which can also obtain an effect.
In addition, since it has an adhesive layer on at least one surface of the intermediate layer to strengthen the adhesion between the paper base and the intermediate layer, the intermediate layer and the paper base have good adhesion and are not easily counterfeited. Can be paper.

  In addition, in order to strengthen the adhesion between the intermediate layer and the paper base material, the adhesive layer and the adhesion auxiliary layer are provided on at least one side of the intermediate layer. It can be made of anti-counterfeit paper that is strong and difficult to falsify.

  Therefore, according to the present invention, it is possible to obtain a watermark having an arbitrary continuous gradation by controlling the thickness of the intermediate layer inserted into the paper layer, and the strength and smoothness are high regardless of the brightness of the watermark. Since it is possible to improve the processability of printing and transfer, and further, a part of the intermediate layer is exposed from the paper layer, and an optical change can be expressed in the exposed part. The paper has a high level of anti-counterfeiting effects.

The top view which shows a state when the anti-counterfeit paper which concerns on the 1st Embodiment of this invention is observed in normal normal light environment. The top view which shows the state when observing the forgery prevention paper in a backlit environment. Sectional drawing in alignment with the AA in FIG. The top view which shows a state when the anti-counterfeit paper which concerns on the 2nd Embodiment of this invention is observed in normal normal light environment. The top view which shows the state when observing the forgery prevention paper in a backlit environment. Sectional drawing which follows the BB line in FIG. The top view which shows a state when the anti-counterfeit paper which concerns on the 3rd Embodiment of this invention is observed in normal normal light environment. The top view which shows the state when observing the forgery prevention paper in a backlit environment. Sectional drawing which follows the CC line | wire in FIG. The top view which shows a state when the forgery prevention paper which concerns on the 4th Embodiment of this invention is observed in normal normal light environment. The top view which shows the state when observing the forgery prevention paper in a backlit environment. Sectional drawing which follows the DD line | wire in FIG.

  Hereinafter, embodiments of the structure and the like of the anti-counterfeit paper of the present invention will be described in detail with reference to the drawings.

  1 to 3 show an anti-counterfeit paper 11 according to the first embodiment of the present invention, and FIG. 1 shows a state when the anti-counterfeit paper 11 is observed in a normal light-lit environment. 2 is a plan view showing a state when the anti-counterfeit paper 11 is observed in a backlight environment, and FIG. 3 is a cross-sectional view taken along the line AA in FIG.

  As shown in FIG. 3, the anti-counterfeit paper 11 is a watermark paper in which an intermediate layer base 3 made of a transparent polymer resin film is inserted as an intermediate layer 2 in the paper layer of the paper base 1. ing. Part of the intermediate layer base material 3 is an intermediate layer exposed portion 21 exposed on the front and back sides of the paper base material 1 through, for example, an elliptical window opening formed in the paper base material 1.

  As shown in FIG. 1, when the anti-counterfeit paper 11 is observed in a normal follow light environment, the watermark due to the difference in thickness of the paper base material 1 is not visible.

  On the other hand, as shown in FIG. 2, when viewed in a backlight environment, it can be observed that a difference in light transmission density due to a difference in thickness of the paper substrate 1 appears as a striped watermark pattern.

  As shown in FIGS. 1 and 2, a part of the intermediate layer base material 3 is exposed as an intermediate layer exposed portion 21 in the opening portion of the elliptical window opening formed in the paper base material 1, and the intermediate portion Since the layer base material 3 is transparent, the other side of the intermediate layer exposed portion 21 can be seen through in both the forward light state and the back light state.

  As shown in FIG. 3, the intermediate layer base material 3 is encased in the paper base material 1, but the thickness of the intermediate layer base material 3 is equal to the paper layer while the total thickness of the anti-counterfeit paper 11 is constant. The thickness of the paper base material 1 is also changed by the gentle change therein, and therefore, the light transmission density of the forgery prevention paper 11 is also partly changed. FIG. 3 shows a case where both the front and back sides of the paper base material 1 are in a window open state, but in the present invention, the intermediate layer exposed portion 21 is exposed only on either the front or back side of the paper base material 1. It may be the case.

  4 to 6 show an anti-counterfeit paper 12 according to the second embodiment of the present invention, and FIG. 4 shows a state when the anti-counterfeit paper 12 is observed under a normal light-promoting environment. FIG. 5 is a plan view showing a state when the anti-counterfeit paper 12 is observed in a backlight environment, and FIG. 6 is a cross-sectional view taken along the line BB in FIG.

  As shown in FIG. 6, the anti-counterfeit paper 12 has an uneven layer 4 laminated on one side of an intermediate layer base material 3 made of a transparent polymer resin film as an intermediate layer 2 in the paper layer of the paper base material 1. It is a watermark paper that has been inserted in the state of being printed. For example, an elliptical window opening is formed in a part of the paper base 1, and the intermediate layer base 3 and a part of the concavo-convex forming layer 4 are exposed to the front and back sides of the paper base 1 through the opening. The intermediate layer exposed portion 21 is formed. A fine uneven pattern 33 is formed on the unevenness forming layer 4 in the exposed portion of the intermediate layer 21. The fine uneven pattern 33 is exposed on the back side of the paper substrate 1.

  As shown in FIG. 4, when this anti-counterfeit paper 12 is observed in a normal light-promoting environment, the watermark due to the difference in thickness of the paper substrate 1 is not visible, but the fine irregularities provided on the intermediate layer exposed portion 21 are not visible. With the pattern 33, it is possible to thinly observe a pattern that optically changes depending on the viewing angle.

  On the other hand, as shown in FIG. 5, when the anti-counterfeit paper 12 is viewed in a backlight environment, it is clear that a difference in light transmission density due to a difference in thickness of the paper base material 1 appears as a watermark pattern. Although it can be observed, the pattern by the fine unevenness pattern 33 of the intermediate layer exposed portion 21 is hardly visible.

  As shown in FIG. 6, the intermediate layer 2 composed of the intermediate layer base material 3 and the concavo-convex forming layer 4 is inserted into the paper base material 1, but the intermediate layer base material 3 in the portion of the intermediate layer exposed portion 21 is Since the diffractive structure 32 having a substantially constant thickness and a fine unevenness of 0.01 μm to 5 μm is formed on the unevenness forming layer 4, an optical change can be observed depending on the viewing angle. Although FIG. 6 shows a case where both the front and back windows are open, in the present invention, the intermediate layer exposed portion 21 may be exposed on only one of the front and back sides of the paper substrate 1.

  7 to 9 show an anti-counterfeit paper 13 according to a third embodiment of the present invention, and FIG. 7 is a plan view showing a state when the anti-counterfeit paper 13 is observed in a normal light-promoting environment. 8 is a plan view showing a state when the anti-counterfeit paper 13 is observed in a backlight environment, and FIG. 9 is a cross-sectional view taken along the line CC in FIG.

  As shown in FIG. 9, the anti-counterfeit paper 13 is formed by laminating a concavo-convex forming layer 4 on one side of an intermediate layer base material 3 made of a transparent polymer resin film as an intermediate layer 2 in the paper layer of the paper base material 1. It is a watermark paper that has been inserted in the state. For example, an elliptical window opening is formed in a part of the paper base 1, and the intermediate layer base 3 and a part of the concavo-convex forming layer 4 are exposed to the front and back sides of the paper base 1 through the opening. The intermediate layer exposed portion 21 is formed. In the portion of the intermediate layer exposed portion 21, the intermediate layer base material 3 has a substantially constant thickness, and the concavo-convex forming layer 4 is formed with a diffractive structure 32 composed of fine unevenness. Further, the light reflecting layer 5 is laminated so as to be in contact with the diffractive structure 32. The light reflecting layer 5 is exposed on the back side of the paper substrate 1.

  As shown in FIG. 7, when this anti-counterfeit paper 13 is observed in a normal direct light environment, the watermark due to the difference in thickness of the paper substrate 1 is not visible, but the diffractive structure provided on the intermediate layer exposed portion 21. It can be observed that the diffracted light image 33 by 32 changes at the viewing angle.

  On the other hand, as shown in FIG. 8, when viewed in a backlight environment, it can be clearly observed that the difference in light transmission density due to the difference in thickness of the paper substrate 1 appears as a watermark pattern of horizontal stripes. The diffractive structure 32 of the intermediate layer exposed portion 21 is provided with the light reflecting layer 5 having the same shape as the diffracted light image 33 on the back surface, so that the pattern is hardly seen behind the light reflecting layer 5.

  As shown in FIG. 9, the intermediate layer 2 made up of the intermediate layer base material 3 and the concavo-convex forming layer 4 is inserted into the paper base material 1, but the intermediate layer base material 3 in the portion of the intermediate layer exposed portion 21 is Since the diffractive structure 32 having fine irregularities is formed on the concavo-convex forming layer 4 and the light reflecting layer 5 is laminated so as to be in contact with the diffractive structure 32, the thickness is substantially constant. When the intermediate layer exposed portion 21 is viewed, the diffracted light image 33 that optically changes depending on the viewing angle can be observed. Although FIG. 9 shows a case where both the front and back windows are open, in the present invention, only the opposite surface of the intermediate layer 2 opposite to the surface where the light reflecting layer 5 is laminated is exposed from the paper substrate 1. It may be.

  10 to 12 show an anti-counterfeit paper 14 according to the fourth embodiment of the present invention, and FIG. 10 shows a state when the anti-counterfeit paper 14 is observed in a normal light-promoting environment. FIG. 11 is a plan view showing a state when the anti-counterfeit paper 14 is observed in a backlight environment, and FIG. 12 is a cross-sectional view taken along line DD in FIG.

  As shown in FIG. 12, the anti-counterfeit paper 14 includes an intermediate layer base material 3 and a concavo-convex forming layer 4 made of a transparent polymer resin film as the intermediate layer 2 in the paper layer of the paper base material 1, a printing layer 6, It is a watermark paper in which the adhesive layer 7 is inserted. For example, an elliptical window opening is formed in a part of the paper substrate 1, and the intermediate layer base material 3, the unevenness forming layer 4, and a part of the adhesive layer 7 pass through the openings to the front and back surfaces of the paper base material 1. It becomes the intermediate | middle layer exposure part 21 exposed to the side. In the portion of the intermediate layer exposed portion 21, the intermediate layer base material 3 has a substantially constant thickness, and the concavo-convex forming layer 4 is formed with a diffractive structure 32 composed of fine concavo-convex portions, and is further in contact with the diffractive structure 32. 5 is laminated, and the adhesive layer 7 is formed on the entire front and back surfaces of the intermediate layer 2 after providing the light reflecting layer 5, and the intermediate layer 2 is firmly in close contact with the paper substrate 1.

  As shown in FIG. 10, when the anti-counterfeit paper 14 is observed in a normal direct light environment, the watermark due to the difference in the thickness of the paper base material 1 is not visible, but the intermediate layer 2 inserted into the paper base material 1 is visible. Since there is the printing layer 6 on the upper side, the character pattern “◯ △ □ GIFTCARD” by the printing layer 6 looks thin, and the diffraction structure 32 provided on the elliptical intermediate layer exposed portion 21 makes it optical at the viewing angle. The diffracted light image 33 that changes to can be observed.

  On the other hand, as shown in FIG. 11, when the anti-counterfeit paper 14 is observed in a backlight environment, the difference in light transmission density due to the difference in thickness of the paper substrate 1 is caused by the horizontal stripe watermark pattern or the print layer 6. The character pattern “GIFTCARD” can be clearly observed, but the diffracted light image 33 is seen because the diffractive structure 32 of the intermediate layer exposed portion 21 is behind the light reflecting layer 5 having the same shape provided on the back surface thereof. I can't do anything.

  As shown in FIG. 9, the intermediate layer 2 made up of the intermediate layer base material 3 and the concavo-convex forming layer 4 is inserted into the paper base material 1, but the intermediate layer base material 3 in the portion of the intermediate layer exposed portion 21 is Since the diffractive structure 32 composed of fine irregularities is formed on the concavo-convex forming layer 4 and the light reflecting layer 5 is laminated so as to be in contact with the diffractive structure 32, the thickness of the concavo-convex forming layer 4 is increased. From this, it is possible to observe the diffracted light image 33 that optically changes depending on the viewing angle. In FIG. 12, both the front and back windows are shown open. However, in the present invention, only the opposite surface of the intermediate layer 2 from the surface on which the light reflecting layer 5 is laminated is exposed from the paper substrate 1. In addition, the adhesive layer 7 may be formed only on either one of the front and back surfaces of the intermediate layer 2.

  Below, the material of each layer which comprises the forgery prevention paper of this invention, a formation method, etc. are demonstrated.

(Paper substrate)
Examples of the raw material for the paper substrate 1 of the present invention include conifers, hardwoods, cotton, rice, esparto, bagasse, hemp, flax, kenaf, cannabis, and other plant pulps, polyethylene terephthalate, polypropylene, polyacrylate, polyvinyl chloride, and the like. Synthetic fibers made from plastic are used.

  In forming the paper base material 1, plant pulp or synthetic fiber is beaten in water to obtain a water-lean raw material, which is entangled and then dehydrated and dried. At this time, the strength of the paper is obtained by water bonding between the hydroxyl groups of cellulose as a raw material. Fillers used for paper include clay, talc, calcium carbonate, titanium dioxide, and sizing agents include rosin, alkyl ketene dimer, stearic anhydride, alkenyl succinic anhydride, wax, etc. Examples of the agent include modified starch, polyvinyl alcohol, polyacrylamide, urea-formaldehyde, melamine-formaldehyde, polyethyleneimine and the like, and these materials are appropriately added to the water-diluted raw material as necessary.

  The paper making method of the anti-counterfeit paper according to the present invention may be an existing method of combining plant fiber papers, and the raw material concentration is sufficiently swollen with a water dilute raw material of 0.5% to 10%, preferably 1% to 2%. It is made by kneading the fibers well, pouring them on the wire / mesh wire part, and evaporating the water by heating after squeezing. At this time, before the squeezing, the upper side of the paper substrate 1 and the paper The intermediate layer 2 is disposed between the lower side of the base material 1 and squeezed and heated while superimposing the three layers, so that the intermediate layers 2 are combined while the three layers are in close contact with each other.

  In the case of paper mixed with, for example, synthetic fibers other than plant fibers, a binding agent is often required because there is no binding force such as hydrogen bonding between the synthetic fibers. It is desirable to determine appropriately so as not to reduce the strength of the paper.

(Middle layer)
The intermediate layer 2 includes an intermediate layer base material 3 made of a transparent polymer resin film. If necessary, the intermediate layer base material 3 may be provided with an unevenness forming layer 4, a light reflecting layer 5, a printing layer 6, an adhesive layer 7, or the like. An adhesion auxiliary layer is sequentially laminated.

(Intermediate layer base material)
As the intermediate layer base material 3, a film-like plastic made of a polymer material such as polyethylene terephthalate, polyvinyl chloride, or polyacrylate having excellent transparency and mechanically strong flexibility and flexibility is used as necessary. Used. In the case of the present invention, if the intermediate layer base material 3 is too thin, the strength is lowered, and it breaks during uneven processing, or the difference in unevenness is too small and the watermark gradation is lost. On the other hand, if it is too thick, the suitability of the anti-counterfeit paper is impaired. Therefore, considering the thickness of the anti-counterfeit paper, the thickness of the intermediate layer base material 3 is preferably between 6 μm and 100 μm in the present invention.

(Unevenness forming layer)
In the intermediate layer 2, when the unevenness is precisely formed, the unevenness forming layer 4 is laminated on the intermediate layer base material 3, and a fine uneven structure is formed by heat or pressure. Further, when the fine concavo-convex structure is formed by a relief type diffraction grating, a volume type diffraction grating or the like, the diffraction structure 32 is obtained.

  The relief type diffraction grating that can be used for the diffraction structure 32 is a diffraction grating recorded in the form of a fine concavo-convex pattern on its surface. For example, two-beam interferometry is used to allow interference on the surface of the photosensitive resin. The interference fringes are formed on the surface of the photosensitive resin by irradiating the two light beams, and the interference fringes are recorded on the photosensitive resin in the form of irregularities. The interference fringes formed by the 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. It is also possible to record so that different images (hereinafter referred to as changing images) can be seen depending on the viewing angle.

  As for the method of recording an image pattern to be a diffraction grating structure used in the present invention, in addition to the two-beam interference method, conventionally known holograms such as an image hologram, a Lippmann hologram, a rainbow hologram, and an integral hologram It can be manufactured by this manufacturing method.

  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. Then, the press plate is thermocompression-bonded to the concavo-convex forming layer 4, and the fine concavo-convex pattern is transferred to the surface of the resin layer, whereby the diffractive structure 32 can be obtained.

  As the resin applied to the unevenness forming layer 4, 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.

  The intermediate layer 2 can be laminated with an optical multilayer interference film which is a multilayer thin film, a layer of cholesteric liquid crystal, an ink containing a powder capable of seeing different colors depending on the viewing angle, and the like.

  The optical multilayer interference film may be a metal thin film, a ceramic thin film, or a composite thin film formed by combining them with an appropriate number of layers stacked depending on the relationship between the optical characteristics of each layer and the layer combination. For example, when thin films having different refractive indexes are stacked, a high refractive index thin film and a low refractive index thin film may be combined, or a specific combination may be stacked alternately. An optical multilayer interference thin film that exhibits a desired optical effect (here, a structural color) can be obtained by an appropriate combination that satisfies the optical conditions of these layers.

  Examples of materials used for such an optical multilayer interference film are given below. In addition, the numerical value in the parenthesis following the chemical formula indicates each refractive index n.

First, as ceramics, Sb ₂ O ₃ (3.0), 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), 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), Si ₂ O ₂ (1.5), MgF ₂ (1.4), CeF ₃ (1.6), CaF ₂ (1.3 to 1.4), AlF ₃ (1.6) _{, Al 2 O 3 (1.6)} , GaO (1.7), there is an equal and, as the material of the metal-based, Al, Fe, Mg, Zn , Au, Ag, Cr, Ni, Cu, Si It includes single metal or alloy and the like.

  Moreover, as a low refractive index material, for example, among organic polymers, polyethylene (1.51), polypropylene (1.49), polytetrafluoroethylene (1.35), polymethyl methacrylate (1.49), Polystyrene (1.60) and the like. However, the numerical value in parenthesis shows each refractive index n here. At least one kind is selected from these high refractive index materials or metal thin films having a light transmittance of 20 to 70%, and at least one kind is selected from low refractive index materials. Only a specific wavelength is absorbed or reflected.

  A multilayer thin film that generates optical wavelength interference is formed by laminating as a thin film by selecting from the above materials based on optical properties such as refractive index, reflectance, and transmittance, weather resistance, and interlayer adhesion. To do. As a forming method, a known method capable of controlling the film thickness, the film forming speed, the number of stacked layers, the optical film thickness and the like can be used. For example, a vacuum deposition method, a sputtering method, a CVD method, or the like. The optical film thickness is an amount given by n · d, where n is the refractive index and d is the film thickness.

  In addition, the cholesteric liquid crystal layer has a helical structure in which the constituent molecules are optically active and nematically uniaxially oriented in the thin layer, but are twisted at a certain angle in a certain direction between adjacent layers. doing. The pitch is distributed from several hundred nm to infinity. Due to this helical structure, the cholesteric liquid crystal selectively reflects light having a wavelength corresponding to the helical pitch and has a brilliant color from blue to red.

  Next, examples of the powder capable of seeing different colors depending on the observation angle include layered substances such as mica. A powder obtained by coating this mica with reduced titanium dioxide or iron oxide can be used. These exhibit chromatic dispersion performance by the so-called flip-flop effect. These powders can be converted into inks, and a layer having wavelength dispersion performance can be formed by a known printing method or coating method.

(Light reflecting layer)
As the light reflection layer 5, a metal thin film can be preferably used because of its high reflection luminance, easy film thickness control, and easy removal. Examples of such a metal 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 it is sufficient that the thickness can be controlled between 5 nm and 1000 nm, and the thickness is 20 nm to 100 nm in terms of visible light reflectivity and vacuum film formation. Is preferred.

  In addition, a transparent thin film having a high refractive index can be used as the light reflecting layer 5. This transparent thin film desirably has a refractive index greater than or equal to 0.2 than the refractive index of the diffractive structure forming layers 2 and 5, for example, a thin film made of a transparent material having a refractive index of 2.0 or more, and visible light. It is desirable that the transmittance is 20% to 90%. This is because when the visible light transmittance is less than 20%, the amount of visible light transmitted is too small, so that the transparent effect as a transparent thin film is weakened, while the visible light transmittance is larger than 90%. In this case, the light reflection effect is weakened.

Examples of the transparent material for the light reflecting layer 5 include Sb ₂ O ₃ (refractive index n = 3.0), Fe ₂ O ₃ (n = 2.7), TiO ₂ (n = 2.6), Cds ( n = 2.6), CeO ₂ (n = 2.3), ZnS (n = 2.3), PbCl ₂ (n = 2.3), CdO (n = 2.2), Sb ₂ O ₃ ( n = 2.0), WO ₃ (n = 2.0), SiO (n = 2.0), Si ₂ O ₃ (n = 2.5), In ₂ O ₃ (n = 2.0), PbO (n = 2.6), Ta ₂ O ₃ (n = 2.4), ZnO (n = 2.1), ZrO ₂ (n = 2.0), and the like can be given. Then, the thin film can be formed using a vacuum film forming method. The thickness of the thin film may be controlled between 5 and 1000 nm.

  Alternatively, the light reflecting layer 5 may be printed 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, and the thickness is preferably 0.1 to 20 μm. As the printing method, a known printing method such as a gravure printing method, a flexographic printing method, or a screen printing method is used. it can.

  The light reflecting layer 5 can be processed into an image pattern by the following method.

  That is, the first method is a method using the above-described printing method. The second method is a method in which the light reflecting layer 5 is formed into an image pattern by depositing a mask having an image pattern-shaped opening on the concavo-convex forming layer 4 and vacuum-forming the light reflecting layer 5. .

  In the third method, first, a solvent-soluble resin layer is provided in a negative pattern, and the light-reflective layer 5 is uniformly formed on the entire surface by coating the solvent-soluble resin layer. In this method, the remaining light reflecting layer 5 is formed into an image pattern by removing the light reflecting layer 5 superimposed on the solvent soluble resin layer at the same time as dissolving and removing the soluble resin layer.

  In the fourth method, first, a resin layer that is easily peeled off is provided on the concavo-convex forming layer 4 in a negative pattern, and the light reflecting layer 5 is uniformly formed on the entire surface by covering the resin layer. This is a method in which the light reflecting layer 5 is left in an image pattern shape by being transferred to an adhesive roll or a pressure sensitive paper sheet by being pressed against the adhesive paper or the like and removed in a negative pattern.

  In the fifth method, the light reflecting layer 5 is uniformly formed on the entire surface, and a chemical-resistant resin layer is provided on the light reflecting layer 5 in an image pattern, and exposed by applying an alkaline or acidic etching solution. In this method, the light reflecting layer 5 is dissolved and removed. In this case, the light-reflective layer 5 may be processed into an image pattern, and then the chemical-resistant resin layer may be removed. Alternatively, the light-reflective layer 5 may be left as it is and used as a protective layer for imparting chemical resistance. it can.

In the sixth method, a photosensitive resin layer is formed on the light reflecting layer 5 formed uniformly on the entire surface, exposed and developed into an image pattern, and then exposed to light by applying an alkaline or acidic etching solution. In this method, the reflective layer 5 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 remaining light reflection layer 5 is formed into an image pattern by directly removing the light reflection layer 5 formed uniformly on the entire surface by irradiating the laser beam.

  As a method of forming the light reflecting layer 5 in a pattern while continuously changing the film thickness, a metal thin film layer is uniformly formed on the entire surface, and a chemical-resistant resin layer is patterned on the metal thin film layer. The exposed metal thin film layer is dissolved and removed by applying an alkaline or acidic etching solution. However, in this case, the chemical resistance of the resin layer is such that the resin layer is gradually peeled off from the metal thin film layer while being immersed in an alkaline or acidic etching solution. However, a resin layer that does not peel at all from the metal thin film layer cannot be used.

  The second method for forming the light reflecting layer 5 in a pattern while continuously changing the film thickness is that after the structure depth and the structure width of the fine unevenness formed on the unevenness forming layer 4 are arbitrarily changed. A metal thin film layer is formed by a vacuum film forming method. In this method, the film thickness of the metal thin film layer changes according to the structure depth and structure width of the fine structure.

  In the present invention, the method of forming the light reflecting layer 5 in a pattern or changing the thickness continuously is not limited to the above method. In addition, these patterns may be random patterns having no clear meaning, but information that can be recognized by the observer may be given as patterns such as patterns, figures, patterns, letters, numbers, symbols, etc. .

(Print layer)
The printing layer 6 may be any printing method such as a known printing method, such as an offset printing method, a screen printing method, or a gravure printing method. In the present invention, the printing place is printed on any layer of the intermediate layer 2. May be.

(Adhesive layer)
For adhesion between the resin of the intermediate layer 2 and the paper substrate 1 as the adhesive layer 7, starch-based, methylcellulose-based, carboxylated cellulose-based, hydroxyethylcellulose-based, polyvinylalcohol-based, polyvinylpyrrolidone-based, vinylethylether-anhydrous maleate An acid copolymer system, a polyacrylic acid-based polyethylene oxide system, or the like can be used. However, since it is necessary to be suitable as a watermark paper, it is desirable that the adhesive layer 7 has a high light transmittance.

(Adhesion auxiliary layer)
For the adhesion auxiliary layer, known materials and forming methods can be used as long as they improve the adhesion between the respective layers. For example, for adhesion between resins, a vinyl chloride resin or an acrylic resin having good adhesion, Adhesive materials and adhesive materials based on resin materials such as urethane resin, epoxy resin, and silicon resin, and heat or photo-curable resin materials can be used. However, since the adhesion auxiliary layer also needs to be suitable as a watermark paper, a layer having high light transmittance is desirable.

  In addition, the printing process on the anti-counterfeit paper of the present invention can print characters and designs by the same method as that of conventional paper, that is, the printing method such as the offset printing method, the screen printing method, and the gravure printing method. It is also possible to perform small-cut processing using a cutting machine, transfer processing using a transfer foil or a pasting process, and pasting processing.

  Next, the present invention will be described by way of examples.

Example 1
First, the anti-counterfeit paper 11 according to the above-described first embodiment, in which the intermediate layer base material 3 is subjected to gentle uneven processing and the intermediate layer 2 having a continuously changing thickness is inserted.

  As the intermediate layer substrate 3, a transparent polyethylene terephthalate film having a thickness of 50 μm is used, and a metal roll having desired unevenness is heated to 180 ° C. and pressed from the front surface of the intermediate layer substrate 3, and at the same time on the opposite side Formed an uneven intermediate layer 2 by pressing a smooth metal roll.

Next, after coniferous pulp is beaten in water to a raw material concentration of 1.5%, once using a transparent net and a hand-working device processed with metal so that it becomes a partially oval window opening opening A book with a thickness (about 0.1 mm) equivalent to a weigh of 100 g / m ² by placing the intermediate layer 2 on the sown and sown softwood pulp, further squeezing it again, dehydrating and drying An anti-counterfeit paper 11 of the invention was produced (corresponding to the anti-counterfeit paper shown in FIGS. 1 to 3).

  In the anti-counterfeit paper 11 manufactured in this way, a transparent intermediate layer 2 having a continuously changing thickness is inserted into the paper base material 1, and a part of the intermediate layer 2 passes through a window-like opening. Since it is exposed to the outside of the material 1, when the anti-counterfeit paper 11 is observed in a normal light state, the intermediate layer exposed portion 21 is transparent so that the other side of the anti-counterfeit paper 11 can be seen through. All the parts other than the exposed part 21 have a smooth surface and no irregularities due to the watermark, so that the printability is good over the entire surface of the paper, and the characters and designs printed on the paper are not disturbed by the watermark. It was. On the other hand, a watermark pattern with rich gradation could be observed in a backlight environment.

(Example 2)
In the second embodiment described above, the uneven layer 4 is laminated on one side of the intermediate layer base material 3, and the diffraction structure 32 is formed on a part of the uneven layer 4 to form the intermediate layer 2. The anti-counterfeit paper 12 encased in the paper base 1 will be described.

  A transparent polyethylene terephthalate film with a thickness of 50 μm is used as the intermediate layer base material 3 and a metal roll having desired irregularities is heated to 180 ° C. and pressed from the front surface of the intermediate layer base material 3, and at the opposite side, The smooth irregularities were formed by pressing a smooth metal roll.

  Next, an ink having the following composition was applied to one surface of the intermediate layer base material 3 using a knife coater, and then dried by placing in a hot air drier kept at 100 ° C. for 40 seconds, and having a film thickness of 5 μm. After forming the concavo-convex forming layer 4, a press plate for forming a diffraction grating was hot-pressed by a roll embossing method to form a diffractive structure 32 on the surface thereof, thereby forming the intermediate layer 2.

Acrylic resin 30.0 parts by weight Silicon additive 0.2 parts by weight Methyl ethyl ketone 70.0 parts by weight Next, after conifer pulp was beaten in water to a raw material concentration of 1.5%, it was processed with metal and partially In order to form a window in a circle, it is once sown using a net that has been processed with metal and a hand milling device, and the intermediate layer 2 is placed at a desired position on the sown conifer pulp, and further squeezed again. By dehydrating and drying, the anti-counterfeit paper 12 of the present invention having the same thickness (about 0.1 mm) as the weighing 100 g / m ² was prepared (corresponding to the anti-counterfeit paper shown in FIGS. 4 to 6). To do).

In the anti-counterfeit paper 12 thus produced, the transparent intermediate layer 2 composed of the intermediate layer base material 3 and the unevenness forming layer 4 is encased in the paper base material 1, so , The front and back paper surfaces are smooth like the paper without the watermark, and the diffractive structure 32 is formed in the intermediate layer exposed portion 21. Therefore, the diffracted light image 33 that changes optically depending on the viewing angle is obtained. Although it appeared, it was observed as a thin image because there was no light reflecting layer.
On the other hand, under a backlight environment, a watermark pattern rich in gradation could be observed on the paper substrate 1, and the intermediate layer exposed portion 21 could observe bright transmitted light.

(Example 3)
In the third embodiment described above, the concavo-convex forming layer 4 is laminated on one side of the intermediate layer base material 3, and the diffractive structure 32 is formed on a part of the concavo-convex forming layer 4, and then a part on the diffractive structure 32 is formed. The anti-counterfeit paper 13 in which the light reflecting layer 5 having a metallic luster is provided to form the intermediate layer 2 in the paper base 1 will be described.

  As the intermediate layer substrate 3, a transparent polyethylene terephthalate film having a thickness of 50 μm is used, and a metal roll having desired unevenness is heated to 180 ° C. and pressed from the front surface of the intermediate layer substrate 3, and at the same time on the opposite side Formed smooth irregularities by pressing a smooth metal roll.

  Next, an ink having the following composition was applied to one surface of the intermediate layer base material 3 using a knife coater, and then dried by placing in a hot air drier kept at 100 ° C. for 40 seconds, and having a film thickness of 5 μm. After forming the concavo-convex formation layer 4, a press plate for forming a diffraction grating was hot-pressed by a roll embossing method to form a diffractive structure 32 on the surface.

Acrylic resin 30.0 parts by weight Silicone additive 0.2 parts by weight Methyl ethyl ketone 70.0 parts by weight Next, vacuum is applied in a state where a mask plate having a circular window opening is placed on top of the concavo-convex forming layer 4. Vapor deposition was performed, and an aluminum vapor deposition film having a film thickness of 40 nm was formed as the light reflection layer 5 at a desired position where the diffraction structure 32 was formed on the concave / convex formation layer 4 to produce the intermediate layer 2.

Next, beaten the coniferous pulp in water to a raw material concentration of 1.5%, and then use a net and a hand-working device that is processed with metal and processed with metal so that the window opens partially in a circle The intermediate layer 2 is placed at a desired position on the sown softwood pulp, and then squeezed again, dehydrated, and dried, so that the thickness is about the same as the weighed 100 g / m ² (about 0. 0. 1) was prepared (corresponding to the anti-counterfeit paper shown in FIGS. 7 to 9).

  In the anti-counterfeit paper 13 thus manufactured, the light reflecting layer 5 is provided on the diffractive structure 32, so that when the diffractive structure 32 formed on the intermediate layer exposed portion 21 is observed in the forward light state, depending on the observation angle, The diffracted light image 33 in which the color changes can be clearly observed, and the surface other than the intermediate layer exposed portion 21 has a smooth surface like a paper without a watermark. On the other hand, in the backlit state, the pattern and color of the diffracted light image 33 become invisible behind the light reflecting layer, but the transparent intermediate layer 2 engraved inside the paper substrate 1 makes the watermark pattern rich in gradation. I was able to observe.

Example 4
In the fourth embodiment described above, the concavo-convex forming layer 4 is laminated on one surface of the intermediate layer base material 3, and the diffractive structure 32 is formed on a part of the concavo-convex forming layer 4, and then a part on the diffractive structure 32 A light reflecting layer 5 having a metallic luster is provided on the substrate, and a printing layer 6 is provided on the concavo-convex forming layer 4 and then an adhesive layer 7 is laminated on the front and back to form an intermediate layer 2. The anti-counterfeit paper 14 inserted inside will be described.

  As the intermediate layer substrate 3, a transparent polyethylene terephthalate film having a thickness of 50 μm is used, and a metal roll having desired unevenness is heated to 180 ° C. and pressed from the front surface of the intermediate layer substrate 3, and at the same time on the opposite side Formed smooth irregularities by pressing a smooth metal roll.

  Next, an ink having the following composition was applied to one surface of the intermediate layer base material 3 using a knife coater, and then dried by placing in a hot air drier kept at 100 ° C. for 40 seconds, and having a film thickness of 5 μm. After forming the concavo-convex formation layer 4, a press plate for forming a diffraction grating was hot-pressed by a roll embossing method to form a diffractive structure 32 on the surface.

Acrylic resin 30.0 parts by weight Silicone additive 0.2 parts by weight Methyl ethyl ketone 70.0 parts by weight Next, with the concavo-convex forming layer 4 on the front, a mask plate having a circular window opening is placed A vacuum vapor deposition process was performed, and an aluminum vapor deposition film having a thickness of 40 nm was formed as the light reflecting layer 5 at a desired position where the diffraction structure 32 was formed on the unevenness forming layer 4.

  Next, the letter “◯ △ □ GIFTCARD” is printed in light gray on the unevenness forming layer 4 by a gravure printing method, and then ink having the following composition is printed on both the front and back surfaces by the gravure printing method. The adhesive layer 7 having a film thickness of 5 μm was formed by coating and drying.

Polyvinyl alcohol resin 20.0 parts by weight Isopropyl alcohol 40.0 parts by weight Distilled water 40.0 parts by weight Next, after conifer pulp was beaten in water to a raw material concentration of 1.5%, it was processed with metal and part In order to form a window in a circular shape, it is once sown using a net and a hand-working device processed with metal, and the intermediate layer 2 is placed at a desired position on the sown conifer pulp and further squeezed again. The anti-counterfeit paper 14 of the present invention having the same thickness (about 0.1 mm) as the weighing 100 g / m ² was produced by dehydration and drying (the anti-counterfeit paper shown in FIGS. 10 to 12). Corresponding).

  In the anti-counterfeit paper 14 thus manufactured, the printing layer 6 is provided on the intermediate layer 2, so that in addition to the effect of the anti-counterfeit paper 13, the printing layer 6 can pass through the paper base material 1 regardless of whether it is in a normal light state or a backlight state. Since the adhesive layer 7 is provided on the front and back of the intermediate layer 2, the intermediate layer 2 and the paper base material 1 are more firmly adhered to each other. It was found that the paper base material 1 was broken when it was peeled off, and the intermediate layer 2 and the paper base material 1 were difficult to tamper with.

  As described above, the anti-counterfeit paper of the present invention has the effect of the “watermark with gradation”, which is an anti-counterfeit technology that has been used only for banknote paper in the past, and the thickness change and surface of the anti-counterfeit paper itself. It can be confirmed that it is achieved by the unevenness of the transparent intermediate layer that has been engraved, and unevenness due to changes in the thickness of the paper has occurred on the front and back of the conventional watermark paper, In the anti-counterfeit paper of the present invention, both the front and back sides of the paper are smooth, and the paper has excellent processability and printability. Further, the intermediate layer is exposed by providing a window opening on the paper base material. The anti-counterfeit paper of the present invention has a high anti-counterfeit effect by forming a structure that expresses an optical change in the exposed part. I found it difficult.

DESCRIPTION OF SYMBOLS 1 ... Paper base material 2 ... Intermediate | middle layer 3 ... Intermediate | middle layer base material 4 ... Unevenness formation layer 5 ... Light reflection layer 6 ... Printing layer 7 ... Adhesive layer 11, 12, 13, 14 ... Forgery prevention paper 21 ... Intermediate layer exposure part 32 ... Diffraction structure 33 ... Diffraction light image

Claims (11)

A watermark paper including an intermediate layer including an intermediate layer base material made of a transparent polymer resin film in the paper layer of the paper base material,
The intermediate layer has the intermediate layer base material and the concavo-convex forming layer, and the concavo-convex forming layer is laminated on a part or the entire surface of the intermediate layer base material,
The intermediate layer includes a portion where the thickness is changed due to a change in the thickness of the intermediate layer base material ,
The paper substrate has a change in thickness that offsets a change in thickness of the intermediate layer;
As for the thickness of the intermediate layer, the difference in thickness in the paper base causes a difference in light transmission density of light transmitted through the watermark paper, thereby expressing the difference in light transmission density as a watermark pattern. Has changed so that
A part of the intermediate layer is exposed on one side or both sides of the paper substrate ,
In the portion of the intermediate layer exposed from the paper base material, a diffractive structure is formed in the concavo-convex forming layer, and the thickness of the intermediate layer base material is greater than the portion where the difference in light transmission density occurs. Change is small,
The change in the thickness of the intermediate layer base material in the portion where the difference in the light transmission density occurs is larger than the change in the thickness of the unevenness forming layer due to the unevenness forming the diffractive structure. The counterfeit prevention paper is characterized in that the thickness of the material changes in a visually recognizable pattern so as to express the difference in light transmission density as a watermark pattern .   A multilayer thin film of an optical multilayer interference film, a layer of cholesteric liquid crystal, or a printing layer containing a powder that can display different colors depending on the viewing angle is laminated on a part or the entire surface of the intermediate layer. The anti-counterfeit paper according to claim 1, wherein The anti-counterfeit paper according to claim 1 or 2 , wherein a light reflecting layer is provided on a part of the intermediate layer. The anti-counterfeit paper according to any one of claims 1 to 3 , wherein fine unevenness of 0.01 to 5 µm is formed on a part or the entire surface of the unevenness forming layer. The anti-counterfeit paper according to claim 3 , wherein the light reflection layer is provided only on a portion of the intermediate layer exposed from the paper base material. The anti-counterfeit paper according to claim 3 or 5 , wherein the light reflection layer is provided in an arbitrary pattern. The light reflecting layer is, according to claim 3, 5, 6 anti-falsification paper according to any one of which is a 20% to 90% visible light transmission. A multilayer thin film or a cholesteric liquid crystal layer provided in the intermediate layer, a printed layer containing a powder that can see different colors depending on the viewing angle, a diffractive structure, and a light reflecting layer are the sheets of the intermediate layer The anti-counterfeit paper according to any one of claims 1 to 7 , wherein the anti-counterfeit paper is provided only on a portion exposed from the base material. The anti-counterfeit paper according to any one of claims 1 to 8 , wherein a printing layer is provided on at least a part of or at least one side of the intermediate layer. One surface of the intermediate layer or on both sides, according to any one of claims 1 to 9 adhesive layer for intensifying the adhesion between the intermediate layer and the paper base material, characterized in that it is provided Anti-counterfeit paper. The two layers of an adhesive layer and an adhesion auxiliary layer are provided on at least one side of the intermediate layer in order to further strengthen the adhesion between the intermediate layer and the paper base. The forgery prevention paper in any one of 10 .