JP2015221523A - Forgery prevention medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forgery prevention medium which visualizes a latent image when a determination sheet is superimposed at a specified angle and visualizes another latent image when the determination sheet is superimposed at another angle, by using a forgery prevention measure which utilizes a double refractive index material.SOLUTION: In a sheet-like forgery prevention medium having two kinds of latent image patterns, a first latent image pattern is constituted with a latent image pixel and a background pixel belonging to a background of the latent image pixel, the background pixel 22 is arrayed on parallel lines, a latent pixel 21 is arrayed on a position removed from the parallel line, a second latent image pattern is constituted with a transparent double refractive index material layer 41 which is laminated on a light-reflective surface, the light-reflective surface is divided into a patterned latent image region 4a which constitutes the second latent image pattern and the background region 4b of the second latent image pattern and, on the latent image region, the transparent double refractive index material layer is arranged and the background region has an optical property different from the transparent double refractive index material layer.

Description

  The present invention relates to a sheet-form forgery prevention medium having two types of latent image patterns. Both of the two types of latent image patterns according to the present invention can be visualized by overlapping dedicated determination sheets. That is, one latent image pattern can be visualized by overlaying a determination sheet at a specific angle on the anti-counterfeit medium of the present invention, and the other latent image pattern can be visualized by overlapping a determination sheet at another angle. can do.

  Conventionally, various forgery prevention measures have been taken for securities such as banknotes and gift certificates in order to prevent forgery. In addition to securities, various forgery prevention measures have been taken on identification cards such as passports. For example, forgery prevention measures such as attaching a forgery prevention label.

  Some of these anti-counterfeiting measures can be recognized by the naked eye. For example, a label formed with a diffraction grating. Since the diffraction grating has a characteristic brightness, its existence is obvious. In addition, the brightness cannot be reproduced by color copying or the like, and advanced technology and equipment are required for counterfeiting. For this reason, it is difficult to counterfeit, and a counterfeit product can be distinguished from a genuine product by the presence or absence of a diffraction grating.

  On the other hand, there are anti-counterfeiting measures that cannot be recognized by just observing with the naked eye. For example, in Patent Document 1, when a birefringent retardation layer is formed in a pattern on the surface of a light-reflective substrate and the pattern is used as a latent image, a polarizing plate is superimposed on the surface. In addition, a forgery prevention measure that can visualize the latent image only when the images are superimposed at a specific angle is disclosed.

JP 2008-183832 A

  However, the anti-counterfeiting measure described in Patent Document 1 has a problem that since only one latent image is visualized, the power of appealing to the eye during verification is weak, and it cannot be distinguished at a glance. Nor does it mean that it is impossible to counterfeit, even if it is difficult.

  Therefore, the present invention uses the counterfeit prevention measure described in Patent Document 1 to visualize a latent image when a determination sheet is overlapped at a specific angle, and to display another latent image when overlapped at a different angle. An object of the present invention is to provide a forgery prevention medium to be visualized.

That is, the invention according to claim 1 is a sheet-form anti-counterfeit medium having two types of latent image patterns composed of a first latent image pattern and a second latent image pattern.
The first latent image pattern is composed of a set of a large number of pixels, and the large number of pixels are divided into a latent image pixel constituting the first latent image pattern and a background pixel belonging to the background. The pixels are arranged at positions on parallel lines with a specific pitch and the latent image pixels are arranged at positions deviating from the parallel lines,
The second latent image pattern is composed of a light reflective surface and a transparent birefringence material layer laminated on the light reflective surface, and the light reflective surface constitutes the second latent image pattern. The patterned latent image region and the background region are divided into the transparent birefringence material layer in the latent image region and the background region has different optical properties.
This is a medium for preventing forgery.

  Next, the invention described in claim 2 is characterized in that the angle formed by the fast axis of the birefringent material layer and the parallel line is 15 degrees or less. Is a forgery prevention medium.

  The invention according to claim 3 is the anti-counterfeit medium according to claim 1 or 2, wherein the birefringent material layer comprises a λ / 4 retardation layer.

  The invention according to claim 4 is the forgery prevention medium according to any one of claims 1 to 3, wherein a large number of the pixels are formed of a diffraction grating.

  The invention according to claim 5 is the anti-counterfeit medium according to claim 4, wherein the diffraction grating is composed of irregularities on the surface of the light reflective substrate.

  The invention according to claim 6 is the anti-counterfeit medium according to any one of claims 1 to 5, wherein a large number of the pixels are constituted by dot-like pixels.

  According to a seventh aspect of the present invention, the first latent image pattern and the second latent image pattern are provided at a position where they overlap each other. The forgery prevention medium described.

  The anti-counterfeit medium according to the present invention uses a dedicated determination sheet, and the first latent image pattern can be visualized by overlapping this determination sheet at a specific angle, or by overlapping at another angle. The second latent image pattern can be visualized. The dedicated determination sheet used for visualization is, for example, one in which a striped light shielding film is formed on a polarizing plate. Moreover, what provided the retardation layer in the polarizing plate and also formed the stripe-shaped light shielding film may be used as a determination sheet. The stripe-shaped light shielding films of the determination sheet are arranged at the same pitch as the parallel lines on which the background pixels of the first latent image pattern of the forgery prevention medium are arranged. Then, the angle formed between the transmission axis of the polarizing plate of the appropriate judgment sheet and the striped light shielding film is also determined according to the angle formed between the phase advance axis of the birefringence material layer of the anti-counterfeit medium and the parallel line. The If the relationship between these angles is not appropriate, the first latent image pattern and the second latent image pattern cannot be distinguished and visualized.

  For example, when the angle between the phase advance axis and the parallel line of the anti-counterfeit medium is 0 degree, that is, when the direction of the phase advance axis and the parallel line is the same, the transmission axis of the polarizing plate and the stripe shape The first latent image pattern and the second latent image pattern can be distinguished and visualized by using a determination sheet in which the angle formed with the light shielding film is 0 degree.

  Hereinafter, in this case, that is, for a forgery prevention medium in which the angle between the fast axis and the parallel line is 0 degree, a determination sheet having an angle between the transmission axis of the polarizing plate and the striped light shielding film is 0 degree. A method for visualizing the first latent image pattern and the second latent image pattern separately will be described.

  First, the angle formed between the fast axis of the birefringence material layer of the anti-counterfeit medium and the direction of the parallel lines for arranging the background pixels (hereinafter referred to as “background pixel parallel lines”) is 0 degrees, and is therefore parallel. In addition, since the angle between the transmission axis of the polarizing plate of the judgment sheet and the striped light shielding film is 0 degree, the transmission axis of the polarizing plate (that is, the direction of the striped light shielding film) and the birefringence material layer of the anti-counterfeit medium When this judgment sheet is stacked on the anti-counterfeit medium so that the fast axis (that is, the direction of the background pixel parallel lines) is parallel, the background pixel parallel lines of the anti-counterfeit medium and the striped light shielding film of the judgment sheet are parallel. Since the pitch of the background pixel parallel lines and the pitch of the light shielding film are the same, the background pixels arranged at positions on the background pixel parallel lines are concealed by the striped light shielding film. Then, latent image pixels can be observed from the gap between the stripe-shaped light shielding films. A first latent image pattern constituted by the set of latent image pixels can be recognized.

  On the other hand, when this determination sheet is overlaid so that the transmission axis of the polarizing plate and the fast axis of the birefringence material layer of the anti-counterfeit medium are parallel as described above, the second latent image pattern is visualized. I can't. That is, in this case, since the plane of polarization of the linearly polarized light transmitted through the polarizing plate is the same as the fast axis of the birefringent material layer, the plane of polarization of the linearly polarized light incident on the latent image region is maintained. The birefringent material passes through and is reflected by the light-reflecting surface, and the reflected light passes through the birefringent material layer and the polarizing plate again while maintaining the polarization plane. For this reason, the latent image area is observed brightly. Since there is no birefringent material layer in the background region, the linearly polarized light incident on the background region is reflected by the light-reflecting surface while maintaining its polarization plane, and passes through the polarizing plate. For this reason, the background area is also observed brightly. Thus, since both the latent image area and the background area are observed brightly, it is difficult to recognize the latent image pattern.

  Thus, if the transmission axis of the polarizing plate and the phase advance axis of the birefringence material layer of the anti-counterfeit medium are overlapped, the second latent image pattern cannot be recognized, and the first Only the latent image pattern can be recognized.

  Next, the transmission axis of the polarizing plate (that is, the direction of the striped light shielding film) and the fast axis of the birefringent material layer of the anti-counterfeit medium (that is, the direction of the background pixel parallel lines) intersect at 45 degrees. In this case, a part of the background pixels and a part of the latent image pixels are observed in a mixed manner from the gap between the striped light shielding films on the determination sheet. For this reason, it is difficult to recognize the first latent image pattern.

  By the way, when the transmission axis of the polarizing plate and the fast axis of the birefringence material layer of the anti-counterfeit medium are overlapped so as to intersect at 45 degrees in this way, the linearly polarized light that has passed through the polarizing plate and entered the latent image region Is separated into ordinary light having a polarization plane on the fast axis and extraordinary light having a polarization plane on the slow axis by the birefringent material layer, and is emitted as a circularly polarized light or an elliptically polarized light obtained by synthesizing them. When the birefringent material layer is a λ / 4 retardation layer, it is circularly polarized. If this circularly polarized light is right-handed circularly polarized light, the reflected light is left-handed circularly polarized light because the phase is reversed and reflected by the light-reflecting surface. Then, the reflected light is incident on the birefringence material layer again, and is changed into linearly polarized light by the birefringence material layer. Since the plane of polarization of this linearly polarized light is perpendicular to the transmission axis of the polarizing plate, it cannot pass through the polarizing plate. For this reason, the latent image area is observed dark. Since the background region is observed brightly, the second latent image pattern can be recognized by the contrast between the two.

The contrast C between the latent image area and the background area can be expressed by the following equation. In the formula, C _max is a constant indicating the maximum value of contrast, and θ is an angle formed by the transmission axis of the polarizing plate and the fast axis of the birefringence material layer of the anti-counterfeit medium.

C = C _max sin ² (2θ)
As is apparent from this equation, when θ = 0 degree or 90 degrees, the contrast C is 0, and the second latent image pattern cannot be visualized. On the other hand, when θ = 45 degrees, the contrast C shows the maximum value C _max and the second latent image pattern can be visualized.

As can be seen from the above description, the second latent image pattern should be visualized when the transmission axis of the polarizing plate and the fast axis of the birefringence material layer of the anti-counterfeit medium are overlapped at 45 degrees. But the first latent image pattern cannot be visualized.

  If the transmission axis of the polarizing plate and the fast axis of the birefringence material layer of the anti-counterfeit medium are superimposed so as to be orthogonal, both the first latent image pattern and the second latent image pattern are visualized. It is difficult to do. That is, in this case, a part of the background pixels and a part of the latent image pixels are observed mixedly from the gap between the stripe-shaped light shielding films, and the latent image region and the background region constituting the second latent image pattern are observed. Since the contrast between and is 0, neither is visualized.

  Thus, according to the forgery prevention medium of the present invention, only the first latent image pattern can be visualized or only the second latent image pattern can be visualized according to the angle at which the dedicated determination sheet is overlapped. .

  Further, when the angle formed by the phase advance axis of the birefringence material layer of the anti-counterfeit medium and the parallel line is not 0 degrees, the transmission axis of the polarizing plate and the stripe-shaped light shielding film according to the size of the angle By using a determination sheet in which the angle formed between and the first latent image pattern is an appropriate angle, the first latent image pattern and the second latent image pattern can be visualized separately. In this case, that is, even when the angle formed between the fast axis and the parallel line is not 0 degrees, the angle formed between the fast axis and the parallel line, the transmission axis of the polarizing plate, and the striped light shielding film It is desirable that the angle formed by is the same. In this case, if the parallel lines of the anti-counterfeit medium are overlapped so that the direction of the striped light-shielding film of the determination sheet coincides, the fast axis and the transmission axis of the polarizing plate also coincide. Only the image pattern can be visualized. On the other hand, if the angle between the direction of the parallel lines of the anti-counterfeit medium and the direction of the striped light-shielding film of the determination sheet is 45 degrees, the fast axis of the anti-counterfeit medium and the transmission axis of the polarizing plate Since the formed angle is 45 degrees, only the second latent image pattern can be visualized. Even if the angle formed by the phase advance axis of the anti-counterfeit medium and the parallel line is not the same as the angle formed by the transmission axis of the polarizing plate and the striped light shielding film, the difference between the two angles should be 15 degrees or less. It is enough.

  In addition, even when the birefringence material layer of the anti-counterfeit medium is not a quarter wavelength plate, by using a determination sheet with an appropriate angle formed by the transmission axis of the polarizing plate and the stripe-shaped light shielding film The first latent image pattern and the second latent image pattern can be visualized separately. This angle may be appropriately designed according to the retardation of the birefringent material layer.

FIG. 1A is a plan view showing a first specific example of the forgery prevention medium of the present invention, and FIG. It is a principal part enlarged plan view of the said 1st example. FIG. 3A is a plan view of a determination sheet applied to the anti-counterfeit medium according to the first specific example, and FIG. 3B is a cross-sectional view thereof. It is a top view which shows the state which visualized the 1st latent image pattern which concerns on a said 1st example. It is a top view which shows the state which visualized the 2nd latent image pattern which concerns on a said 1st example. It is sectional explanatory drawing which shows the modification 1 of the forgery prevention medium of this invention. It is a section explanatory view showing modification 2 of the forgery prevention medium of the present invention. It is sectional explanatory drawing which shows the modification 3 of the forgery prevention medium of this invention. It is a section explanatory view showing modification 4 of the forgery prevention medium of the present invention. FIG. 9 is an explanatory cross-sectional view showing a fifth modification of the forgery prevention medium of the present invention.

(Description of anti-counterfeit media)
Hereinafter, specific examples of the present invention will be described with reference to the drawings. FIG. 1A is a plan view showing a first specific example of the forgery prevention medium of the present invention, and FIG. FIG. 2 is an enlarged plan view of the main part.

  As can be seen from FIGS. 1 (a) and 1 (b), the anti-counterfeit medium 1 has a light-reflective substrate 10 as the light-reflective surface, and a transparent birefringence material layer 41 on the surface. Laminated. The anti-counterfeit medium 1 shown in the drawing has the transparent birefringence material layer 41 oriented between the light reflective substrate 10 and the transparent birefringent material 41 in addition to the light reflective substrate 10 and the birefringent material layer 41. And a transparent protective layer 5 that covers the transparent birefringence material layer 41.

  The light reflective base material 10 is configured by laminating a light reflective film 12 on a base body 11 serving as a structural support of the anti-counterfeit medium 1, and on the light reflective surface of the light reflective film 12. Are provided with pixels composed of a large number of dot-like irregularities. These dot-like irregularities constitute a relief type diffraction grating, and have a brightness feeling peculiar to the diffraction grating. And since many point-like unevenness | corrugations are arrange | positioned widely in the light reflection film 12, the almost whole surface of the forgery prevention medium 1 seems to shine brightly. Further, by changing the observation angle, the color changes, for example, it appears to shine in rainbow colors.

  By the way, a large number of these concavo-convex portions are divided into a latent image pixel 21 constituting the first latent image pattern 2a and a background pixel 22 belonging to the background 2b. The first latent image pattern formed by the latent image pixels is the letter “A”, and for convenience of explanation, FIG. 1A shows the latent image pattern and its background separately. As described above, almost the entire surface of the anti-counterfeit medium 1 appears to shine, and it is difficult to observe this latent image pattern without using a determination sheet.

FIG. 2 is an enlarged plan view of a region indicated by x in FIG. As can be seen from FIG. 2, the background pixels 22 are arranged at positions on the virtual parallel lines 20. The virtual parallel lines 20 are obtained by arranging straight lines at a specific pitch P. In FIG. 2, the virtual parallel lines 20 are drawn with two-dot chain lines as virtual parallel lines 20. The virtual parallel lines 20 are not drawn on the prevention medium 1. Since the background pixels 22 are arranged at positions on the virtual parallel lines 20 having the specific pitch P, the stripe-shaped light shielding film having the same pitch P is aligned with the direction 2 _A of the virtual parallel lines 20. In such a case, the background pixels 22 are hidden by the stripe light shielding film and cannot be observed. Incidentally, in FIG. 1 (a) and 2, reference numeral 2 _A indicates the direction of imaginary parallel lines 20 extend.

On the other hand, the latent image pixels 21 are arranged at positions deviating from the virtual parallel lines 20. Thus exposed, the stripe-shaped light-shielding film having the same pitch P, even when the direction of the stripe is superimposed so as to coincide with the direction 2 _A virtual parallel line 20, the latent image pixel 21 from the gap of the stripe-shaped light shielding film Can be observed.

Thus, the stripe-shaped light-shielding film having the same pitch P to the anti-counterfeit medium 1, when the direction of the stripe is superimposed so as to coincide with the direction 2 _A virtual parallel line 20, the background pixel 22 is blocked, latent The image pixel 21 can be observed from the gap. Since the first latent image pattern 2a is composed of a set of latent image pixels 21, the image that can be observed from the gap between the stripe-shaped light shielding films is the first latent image pattern 2a.

The surface of the light reflecting film 12 is divided into a patterned latent image region 4a constituting the second latent image pattern and a background region 4b, and the transparent birefringence material layer 41 is formed in the latent image region 4a. Are arranged in a pattern. On the other hand, the background region 4b has the transparent birefringence material layer 21.
Have different optical properties. In this example, a λ / 4 retardation layer is used as the transparent birefringence material layer 41, and this λ / 4 retardation layer is disposed in the latent image area 4a, and nothing is disposed in the background area 4b. Although the transparent protective layer 5 is directly provided on the light reflecting film 12, a transparent material having optical properties different from that of the λ / 4 retardation layer may be disposed in the background region 4b. It is also possible to arrange a λ / 4 retardation layer having a fast axis in a direction intersecting with the fast axis of the λ / 4 retardation layer arranged in the latent image region 4a in the background region 4b.

  In this example, the second latent image pattern is “BC”. The second latent image pattern is arranged at a position overlapping the first latent image pattern. In FIG. 1A, for convenience of explanation, the outline of the second latent image pattern is indicated by a broken line, but the second latent image pattern is configured by arranging a transparent birefringent material 41. Therefore, it is difficult to observe this latent image pattern without using a determination sheet. As described above, since the point-like pixels 21 and 22 made of a diffraction grating are arranged on the entire surface of the light reflecting film 12, the transparent birefringence material layer 41 and the protective layer 5 can be used beautifully. Looks shining. Therefore, even if the gloss and light reflectance of the latent image area 4a are slightly different from those of the background area 4b, it is difficult to determine the second latent image pattern from the difference in gloss and reflectance.

When a polarizing plate is stacked on the anti-counterfeit medium 1, the polarizing plate is stacked such that the transmission axis of the polarizing plate and the fast axis n _{A of the} transparent birefringence material layer 41 form an angle of 45 degrees. The background area 4b appears bright and the latent image area 4a appears dark. Since the latent image area 4a constitutes a second latent image pattern, the second latent image pattern is thus visualized. When the polarizing plates are stacked such that the transmission axis of the polarizing plate and the fast axis n _{A of the} transparent birefringent material layer 41 form an angle of 0 °, or the polarizing plate forms an angle of 90 °. When the images are overlaid, both the background area 4b and the latent image area 4a appear bright, and therefore it is difficult to recognize the first latent image pattern. When the images are overlapped at an angle between them, the contrast between the background region 4b and the latent image region 4a changes according to the angle. As described above, this contrast is expressed by the following equation.

C = C _max sin ² (2θ)
Incidentally, in this embodiment, as shown in FIG. 1 (a), the direction 2 _A of the fast axis n _A and the virtual parallel line 20 of the transparent birefringent material layer 41 in the same direction. For this reason, if a judgment sheet is formed by forming a striped light-shielding film on a polarizing plate and the transmission axis of the polarizing plate coincides with the direction of the striped light-shielding film, the judgment sheet is used as the judgment sheet. Are overlapped so that the transmission axis n _A (that is, the direction of the striped light shielding film) and the fast axis of the birefringent material layer 41 of the anti-counterfeit medium (that is, the direction 2 _A of the background pixel parallel lines) coincide with each other. The first latent image pattern can be visualized. On the other hand, the second latent image pattern can be visualized by superimposing them so that the angle formed by these is 45 degrees.

In this example, the fast axis n _A of the transparent birefringent material layer 41 and the direction 2 _A of the virtual parallel line 20 are the same, but the angle formed by these fast axes n _A and the virtual parallel line 20 is the same. 15 degrees or less is sufficient. That is, in this case, the determination sheet in which the transmission axis of the polarizing plate coincides with the direction of the striped light shielding film is used, and this determination sheet is used as the transmission axis n _{A of the} polarizing plate (that is, the direction of the striped light shielding film). ) And the transparent birefringence material layer 41 of the anti-counterfeit medium, the second latent image pattern can be visualized by overlapping so that the fast axis (that is, the direction 2 _A of the background pixel parallel lines) coincides, On the other hand, if the angles formed by these are 45 degrees, the second latent image pattern can be visualized, although there is a slight decrease in contrast.

When the angle between the fast axis n _{A of} the transparent birefringent material layer 41 and the direction 2 _A of the virtual parallel line 20 exceeds 15 degrees, this angle, that is, the fast axis n _A And the direction 2 _A of the imaginary parallel line 20 is α, and the angle between the transmission axis of the polarizing plate and the direction of the stripe-shaped light shielding film is β, and the difference between α and β is 15 ° or less. Can be used. Desirably, the difference between α and β is zero.

(Description of judgment sheet)
Next, the determination sheet applied to the forgery prevention medium 1 according to this example will be described. The determination sheet according to the present invention is dedicated for the forgery prevention medium.

  FIG. 3A is a plan view of a determination sheet applied to the anti-counterfeit medium according to this example, and FIG. 3B is a cross-sectional view thereof.

As can be seen from these drawings, the determination sheet 6 according to this example is obtained by forming a striped light shielding film 62 on a polarizing plate 61. 3 (a), the reference numeral OP denotes the transmission axis of the polarizer 61, reference numeral 6 _A indicates the direction in which stripe-shaped light-shielding film 62 extends. In this example, the direction 6 _A of the transmission axis OP and stripe light shielding film 62 are the same. Further, the pitch of the straight lines constituting the stripe-shaped light shielding film 62 is the same as the pitch P of the virtual parallel lines 20 in which the background pixels 22 of the first latent image pattern of the anti-counterfeit medium 1 are arranged. The width of the straight line constituting the stripe-shaped light shielding film 62 is preferably the same as or larger than that of the background pixel 22. For example, when the background pixel 22 has a size of 10 μm, the width of the straight line constituting the stripe-shaped light shielding film 62 is 10 to 15 μm. Then, the first latent image pattern can be visualized by superimposing the determination sheet 6 on the anti-counterfeit medium 1 at a specific angle (see FIG. 4), and the second latent image pattern can be visualized by overlapping at another angle. Can be visualized (see FIG. 5).

(Description of manufacturing method of forgery prevention medium 1)
Next, the manufacturing method of the forgery prevention medium 1 shown in this example will be described together with the material.

(Description of forming method of dot-like pixels 21 and 22 including light-reflecting substrate 10 and diffraction grating)
The light reflective substrate 10 serves as a structural support for the anti-counterfeit medium 1 and also serves to reflect incident light by making its surface light reflective. As the light-reflective substrate 10, any substrate can be used as long as the surface thereof is a sheet having light reflectivity. For example, a metal foil such as an aluminum foil. Further, as shown in FIG. 1, the base body 11 serving as a structural support for the anti-counterfeit medium 1 and the light reflecting layer 12 constituting the light reflecting surface are separated and laminated. It may be a thing. As will be described later, when the anti-counterfeit medium according to the present invention is configured as a transfer sheet, a peeling layer is formed on the surface as a structural support for the anti-counterfeit medium instead of the light-reflective substrate 10. It is desirable to use the transferred transfer substrate.

  By the way, as the base-material main body 11, a plastic film or a plastic sheet can be used, for example. Any of an unstretched plastic film, a uniaxially stretched plastic film, and a biaxially stretched plastic film can be used as the substrate body 11. For example, cellophane, triacetyl cellulose film, polycarbonate film, polyethylene film, polypropylene film, ethylene-vinyl alcohol film, polyvinyl alcohol film, polyvinyl chloride film, polyethylene terephthalate film, polyethylene naphthalate film, nylon film, acrylic resin film, etc. is there. Moreover, the film of the multilayer structure which laminated | stacked these plastic films may be sufficient. The surface of the substrate body 11 may be subjected to mat processing or emboss processing entirely or partially.

Next, a thin metal film can be used as the light reflecting layer 12. This metal thin film can be provided on the surface of the base body 11 using a vacuum deposition method or a sputtering method. Examples of the metal include aluminum, tin, chromium, nickel, copper, gold, inconel, stainless steel, and duralumin. Further, as the light reflecting layer 12, a light reflecting ink containing a metal powder can be used. In addition, although the light reflection layer 12 may be provided in the whole surface of the base-material main body 11, you may provide it partially in a required site | part. Further, the surface thereof may have light scattering properties.

  The dotted pixels 21 and 22 made of a diffraction grating can be formed by embossing the light reflecting layer 12 using a stamper. Moreover, after embossing the surface of the base-material main body 11, you may provide by forming a metal thin film in this embossed surface. The metal thin film formed using the vacuum deposition method or the sputtering method is formed along the embossed surface of the base body 11 as a base, and this metal thin film surface can reproduce the unevenness of the base body 11. .

(Description of Method for Forming Transparent Birefringence Material Layer 41)
Next, the transparent birefringence material layer 41 can be formed by orienting an optically anisotropic material. A nematic or smectic liquid crystal material can be used as the optically anisotropic material. Preferably, it is a curable liquid crystal material that is cured by heat or ultraviolet rays. This liquid crystal material can be mixed with a dichroic dye or a fluorescent dichroic dye.

  In order to align this liquid crystal material, for example, as shown in FIG. 1, an alignment film 3 is formed on a light-reflective substrate 10 and the surface of the alignment film 3 is linearly fine along the alignment direction. After forming the grooves, the liquid crystal material may be applied. The liquid crystal material is aligned along the groove. For example, the direction of the groove is the fast axis or the slow axis of the transparent birefringent material layer 41.

  As the alignment film 3, for example, polyimide or polyimide amide can be used. Then, by rubbing the alignment film 3, it is possible to form linear fine grooves on the surface.

  Further, it is possible to form a linear fine groove by using a synthetic resin as the alignment film 3 and embossing the surface thereof. Alternatively, the alignment film 3 having linear fine grooves on the surface can be formed by obliquely depositing a transparent inorganic material or polymer material on the surface of the light reflective substrate 10.

  Further, it is possible to form the transparent birefringence material layer 41 made of the aligned liquid crystal material directly on the surface of the light reflective substrate 10 without using the alignment film 3. For example, the liquid crystal material can be aligned by applying linearly polarized light after the liquid crystal material is applied to the surface of the light-reflecting substrate 10. In this case, the polarization plane of linearly polarized light becomes the fast axis or slow axis of the transparent birefringence material layer 41.

  In addition, after aligning the liquid crystal material, it is desirable to cure the liquid crystal material in order to fix the alignment state. For example, when the liquid crystal material is a thermosetting type, it can be cured while maintaining the alignment state by heating the liquid crystal material after it is aligned. In the case where the liquid crystal material is an ultraviolet curable type, the liquid crystal material can be aligned and then cured by irradiating a randomly polarized ultraviolet ray having no polarization plane while maintaining the alignment state.

  It is also possible to use a birefringent film as the transparent birefringent material layer 41 and to bond the birefringent film to the light reflective substrate 10.

(Description of forming method of protective layer 4)
The protective layer 4 plays a role of preventing physical damage to the anti-counterfeit medium 1 and photodegradation of the liquid crystal material. As such a protective layer 4, an optically isotropic transparent material can be used. It may be colorless and transparent, or may be colored and transparent.

  Examples of the material constituting the protective layer 4 include acrylic resin, urethane resin, vinyl chloride-vinyl acetate copolymer resin, polyester resin, melamine resin, epoxy resin, polystyrene resin, and polyimide resin. It may be a thermoplastic resin, a thermosetting resin, a resin curable with ultraviolet rays or an electron beam. Moreover, the protective layer 4 may be comprised with the mixed resin which mixed these resin, and it is good also as a multilayered structure. Then, these resins may be applied to form the protective layer 4, or a film made of these resins may be adhered to form the protective layer 4.

(Description of manufacturing method of judgment sheet)
Next, the manufacturing method of the determination sheet 6 shown in this example will be described together with its material.

As described above, as the determination sheet 6 used in the forgery prevention medium 1 according to the present invention, a sheet in which a stripe light shielding film 62 is formed on a polarizing plate 61 can be used. The angle formed between the transmission axis OP of the polarizing plate 61 and the direction of the stripe-shaped light shielding film 62 is between the fast axis n _A of the transparent birefringence material layer 41 of the anti-counterfeit medium 1 and the direction 2 _A of the background pixel parallel line. Designed according to the angle. The pitch of the striped light shielding film 62 is the same as the pitch P of the background pixel parallel lines. For this reason, the determination sheet 6 is dedicated to each forgery prevention medium 1.

  As the polarizing plate 61, an absorptive polarizing plate or a reflective polarizing plate can be used.

  Examples of the absorbing polarizing plate include an absorbing polarizing plate in which a polyvinyl alcohol film is impregnated with iodine or a dichroic dye and then uniaxially stretched to align the iodine or dichroic dye. Moreover, you may use the absorption type polarizing plate which orientated the dichroic dye in the film form.

  A wire grid polarizer can be illustrated as a reflective polarizing plate. The wire grid polarizer is a linear ultrafine conductor arranged in parallel lines at a pitch of about the wavelength of light. For example, it can be produced by embossing the surface of the transparent resin film in the shape of the parallel lines, forming linear convex portions and concave portions on the surface, and vacuum-depositing the metal. In the vacuum vapor deposition method, unlike the sputtering method, the evaporated metal goes straight in the vacuum, so that this metal is mainly deposited on the linear protrusions and arranged in parallel lines. The wire grid polarizer reflects linearly polarized light having a polarization plane in a direction in which the linear protrusion extends, and transmits linearly polarized light having a polarization plane in a direction orthogonal to the linearly polarized portion.

  Next, the striped light shielding film 62 can be formed by printing using a printing ink having a high optical density. For example, black ink.

(Description of modification)
As described above, the case where the pixels 21 and 22 constituting the first latent image pattern are provided on the surface of the light-reflecting base material 10 and are formed of a point-like diffraction grating has been described as an example. It is also possible to constitute the forgery prevention medium of the present invention depending on the structure.

  That is, first, the pixels 21 and 22 constituting the first latent image pattern can be constituted by a point-like diffraction grating provided on the surface of the transparent birefringence material layer 41. FIG. 6 of the drawing is a cross-sectional view showing such an example (Modification 1), and this anti-counterfeit medium is obtained by embossing the surface of the transparent birefringence material layer 41 to provide a point-like diffraction grating. Is the same as the first specific example shown in FIG. In this case, the first latent image pattern is provided in the latent image area 4a constituting the second latent image pattern.

FIG. 7 of the drawings is a cross-sectional view of a forgery prevention medium (Modification 2) in which the pixels 21 and 22 constituting the first latent image pattern are formed by printing ink instead of the dotted diffraction grating. As is apparent from the figure, this anti-counterfeit medium is provided with dot-like pixels 21 and 22 with printing ink on the light reflecting film 12 of the light reflecting substrate 1 without providing a diffraction grating. Others are the same as the 1st example shown in FIG.

  Moreover, FIG. 8 of drawing is the thing which provided the dotted | punctate pixels 21 and 22 by printing ink on the protective layer 5 (modification 3). Others are the same as those of the second modification shown in FIG.

  Note that the pixels constituting the first latent image pattern are not limited to dot shapes, and may be linear pixels arranged on the virtual parallel lines 20.

  Next, the anti-counterfeit medium according to the present invention can be used as a label by applying an adhesive to the surface of the light reflective substrate 1. FIG. 9 of the drawings is a cross-sectional view showing this example (Modification 4). As the adhesive, for example, a polyester-based adhesive, a polyamide-based adhesive, a butyl rubber-based adhesive, a natural rubber-based adhesive, a silicon-based adhesive, a polyisobutyl-based adhesive, or the like can be used. It is also possible to use a vinyl chloride-vinyl acetate copolymer as an adhesive. Moreover, additives such as an aggregating component, a modifying component, a polymerization initiator, a plasticizer, a curing agent, a curing accelerator, and an antioxidant can be added to these adhesives. For example, alkyl methacrylate, vinyl ester, styrene, vinyl monomer, unsaturated carboxylic acid, hydroxy group-containing monomer, acrylonitrile and the like. The adhesive can be formed by a known gravure printing method, offset printing method, screen printing method, bar coating method, gravure coating method, roll coating method or the like.

  This label can be used, for example, by attaching it to the aforementioned securities or identification card. Then, when the first latent image pattern and the second latent image pattern are visualized when the dedicated determination sheets are overlapped and overlapped at a predetermined specific angle, it can be determined to be authentic. On the other hand, if either of the first latent image pattern and the second latent image pattern is not visualized, it is a counterfeit product.

  In addition, this label can be affixed by peeling off the separator when affixing a separator to the adhesive surface and affixing it to a securities or identification card. In addition, it is desirable to provide a cut or a perforation in the light-reflective substrate 10 in order to prevent it from being peeled off from securities or identification cards and pasted on counterfeit products. In this case, the label is broken when it is peeled off from the securities or the identification card, and it becomes difficult to reattach.

  Next, the anti-counterfeit medium of the present invention can be used as a transfer sheet. In the case of a transfer sheet, the anti-counterfeit medium (first specific example) shown in FIG. 1 is bonded to the transfer base material via a release layer, and an adhesive is applied on the anti-counterfeit medium. .

  However, when the anti-counterfeit medium of the present invention is used as a transfer sheet, it is desirable to change the order of the layers of the anti-counterfeit medium (first specific example) shown in FIG. FIG. 10 of the drawings is a cross-sectional view of a transfer sheet (Modification 5) formed by changing the order of the layers.

  That is, this transfer sheet uses a transfer substrate having a release layer formed on the surface instead of the substrate body 11 as the structural support, and the protective layer 5 and the alignment film are sequentially formed on the release layer. 3. A transparent birefringence material layer 41, a diffraction grating forming layer, a light reflecting layer 12, and an adhesive layer are formed.

  The transfer sheet can be formed through the following steps.

  That is, first, the protective layer 5 is formed by applying an optically isotropic transparent resin on the release layer of the transfer substrate. Subsequently, polyimide or the like is applied on the protective layer 5, and the alignment film 3 is formed by rubbing or embossing the surface to form linear fine grooves. Alternatively, the alignment film 3 may be formed by obliquely depositing a transparent inorganic material or polymer material on the protective layer 5.

  Then, a liquid crystal material having optical anisotropy is applied to the latent image region 4a on the alignment film 3 so as to align the liquid crystal material along the fine linear grooves, and then heated or irradiated with ultraviolet rays. The transparent birefringence material layer 41 is formed by fixing the orientation state by irradiating with an electron beam and curing.

  Next, the transparent birefringence material layer 41 in the latent image region 4a is covered, and a transparent resin is applied to form a diffraction grating forming layer. Further, the light reflecting layer 12 is formed, and then the light reflecting layer 12 is embossed. As a result, fine dot-like pixels 21 and 22 made of a diffraction grating are formed on the surface of the light reflecting layer 12. In addition, the order of the embossing step and the light reflecting layer 12 forming step is changed, and after embossing the surface of the diffraction grating forming layer to form fine dot pixels 21 and 22 made of the diffraction grating, the light reflecting layer 12 is formed. May be.

  As the transparent resin constituting the diffraction grating forming layer, any resin can be used as long as it is an optically isotropic transparent resin. It may be a colorless transparent or colored transparent resin. For example, acrylic resin, polyolefin resin, polyester resin, polyamide resin, polyvinyl chloride resin, or the like can be used. Moreover, a cellulose resin may be sufficient.

  The transfer sheet can be completed by applying an adhesive on the light reflecting layer 12 to form an adhesive layer. As the adhesive, a heat-sensitive adhesive can be used in addition to the pressure-sensitive adhesive.

  This transfer sheet is, for example, laminated with the adhesive layer facing the securities or identification card, and after being bonded by pressing or heating from the back side of the transfer sheet, the transfer substrate and the release layer are peeled and removed. Can be transferred. The securities and identification cards obtained by the transfer include an adhesive layer, a light reflecting layer 12 having a dot-like latent image pixel 21 and a background pixel 22 made of a fine diffraction grating, a diffraction grating forming layer, and a latent image region. The birefringence material layer 41, the alignment film 3, and the protective layer 5 arranged in the above are stacked in this order. And when the first latent image pattern and the second latent image pattern are visualized when a dedicated determination sheet is superimposed on this securities or identification card and superimposed at a predetermined specific angle, , It can be determined to be authentic. On the other hand, if either of the first latent image pattern and the second latent image pattern is not visualized, it is a counterfeit product.

  Then, it is difficult to peel off the light reflection layer 12 and the birefringence material layer 41 from the surface of the securities and identification cards obtained by transferring in this way. This is because if the layer is forcibly peeled off, these layers will be destroyed. For this reason, the light reflecting layer 12 and the birefringence material layer 41 cannot be peeled off and re-applied to a counterfeit product.

DESCRIPTION OF SYMBOLS 1 ... Anti-counterfeit medium 10 ... Light reflective base material 11 ... Base-material main body 12 ... Light reflection layer 2a ... 1st latent image pattern 20 ... Virtual parallel line 21 ... Latent image pixel 22 ... Background pixel 3 ... Orientation film 41 ... Transparent birefringent material 4a Latent image area 4b Background area 5 Protective layer 6 Determination sheet 61 Polarizing plate 62 Striped light-shielding film 2 _{A A} direction of imaginary parallel line n _{A A} fast axis of transparent birefringent material 6 _A ... Direction of stripe-shaped light shielding film OP ... Transmission axis of polarizing plate

Claims (7)

In the sheet-form anti-counterfeit medium having two types of latent image patterns composed of the first latent image pattern and the second latent image pattern,
The first latent image pattern is composed of a set of a large number of pixels, and the large number of pixels are divided into a latent image pixel constituting the first latent image pattern and a background pixel belonging to the background. The pixels are arranged at positions on parallel lines with a specific pitch and the latent image pixels are arranged at positions deviating from the parallel lines,
The second latent image pattern is composed of a light reflective surface and a transparent birefringence material layer laminated on the light reflective surface, and the light reflective surface constitutes the second latent image pattern. The patterned latent image region and the background region are divided into the transparent birefringence material layer in the latent image region and the background region has different optical properties.
An anti-counterfeit medium characterized by that.   2. The medium for preventing forgery according to claim 1, wherein the anti-counterfeit medium is arranged so that an angle formed by the fast axis of the birefringent material layer and the parallel line is 15 degrees or less.   The anti-counterfeit medium according to claim 1, wherein the birefringent material layer is a λ / 4 retardation layer.   The anti-counterfeit medium according to any one of claims 1 to 3, wherein a large number of the pixels are formed of a diffraction grating.   The forgery prevention medium according to claim 4, wherein the diffraction grating is constituted by irregularities on the light reflective surface.   The anti-counterfeit medium according to any one of claims 1 to 5, wherein a large number of the pixels are constituted by dot-like pixels.   The forgery prevention medium according to claim 1, wherein the first latent image pattern and the second latent image pattern are provided at positions where they overlap each other.

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