JP5211474B2 - Laminated body, adhesive label, recording medium, and labeled article - Google Patents

Description

  The present invention relates to a discrimination technique for discriminating an article between a genuine product and a non-genuine product.

  It is desired that counterfeiting is difficult for authentication media such as cash cards, credit cards and passports, and securities media such as gift certificates and stock certificates. Therefore, conventionally, a label that is difficult to forge is attached to such a medium in order to prevent the forgery.

  In recent years, the distribution of counterfeit products has been regarded as a problem for articles other than authentication media and securities media. Therefore, the opportunity to apply the above-described anti-counterfeiting technology for authentication media and securities media to such articles is increasing.

The forgery prevention technology can be classified into an overt technology and a covert technology.
The overt technique is an anti-counterfeiting technique that allows a general user to easily recognize application to an article and easily determine whether it is authentic. In a typical overt technique, a diffractive structure such as a hologram or a multilayer interference film such as Optically Variable Ink (OVI) is used.

  The covert technique is an anti-counterfeiting technique aimed at making it possible for only a specific user who knows the application of the covert technique to an article to make an authenticity determination because it is difficult for a general user to apply to the article. Typical covert techniques use fluorescent printing or line moire.

  Patent Document 1 describes a forgery prevention technique using both an overt technique and a covert technique. In this anti-counterfeiting technology, for example, a label including a multilayer film formed by alternately laminating a birefringent first light-transmitting layer and second light-transmitting layers having optical characteristics different from the first light-transmitting layer is used. In this multilayer film, the first light transmissive layer and the second light transmissive layer have the same refractive index in the first direction in the first plane perpendicular to the main surface of the first light transmissive layer. The refractive indexes in the second direction in the second plane perpendicular to the main surface and the first plane are different. Therefore, the interface between the first light transmissive layer and the second light transmissive layer does not reflect linearly polarized light whose polarization plane (vibration plane of the electric field vector) is parallel to the first plane, and the polarization plane is the second plane. Reflects some of the parallel linearly polarized light. Therefore, when the multilayer film is observed through a linear polarizer, the brightness of the multilayer film changes according to the direction of the transmission axis of the linear polarizer. In addition, when the multilayer film is observed without passing through a polarizer, a blue shift is caused by increasing the angle formed by the observation direction and the normal line of the multilayer film. That is, the interference color is shifted to the short wavelength side. Using these optical characteristics, genuine products and non-genuine products are discriminated.

The label used in this anti-fake technology can achieve low cost and high durability. However, the optical characteristics described above can be reproduced without using the multilayer film. For example, the above optical characteristics can be reproduced with a laminate of a general color shift film and an absorbing polarizing layer. Therefore, this label is relatively easy to counterfeit.
JP 2004-354430 A

  An object of the present invention is to make it difficult to forge a label used for discrimination between genuine products and non-genuine products.

According to the first aspect of the present invention, the reflective polarized light obtained by alternately laminating the birefringent first light transmissive layer and the second light transmissive layer having different optical characteristics from the first light transmissive layer. A first portion facing a portion of the front surface of the polarizing layer, a first portion facing the front portion of the polarizing layer, and the other portion of the front surface of the polarizing layer and the first portion.
A convex pattern or a concave pattern as a diffractive structure that includes a birefringent layer including a second portion having a slow axis direction different from the portion, and diffracts the light transmitted through or reflected by the polarizing layer There is provided a discriminating laminate characterized by comprising:

  According to the 2nd side surface of this invention, the adhesive label characterized by having comprised the laminated body which concerns on a 1st side surface, and the adhesion layer supported by the back surface of the said laminated body is provided.

  According to a third aspect of the present invention, there is provided a paper, a pressure-sensitive adhesive layer supported on one main surface of the paper, and a lamination according to the first side surface embedded in the paper so that a back surface faces the pressure-sensitive adhesive layer. An adhesive label characterized by comprising a body is provided.

  According to a fourth aspect of the present invention, there is provided a recording medium comprising paper and a laminate according to the first side surface embedded in the paper.

  According to a fifth aspect of the present invention, there is provided a label comprising: an article whose authenticity is to be confirmed; and a laminate according to the first side surface supported by the article whose authenticity is to be confirmed. Articles are provided.

  According to the present invention, it is possible to make it difficult to forge a label used for discrimination between a genuine product and a non-genuine product.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the component which exhibits the same or similar function, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a plan view schematically showing a layered product for identification according to one embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II of the laminate shown in FIG. 3 and 4 are perspective views schematically showing a reflective polarizing layer included in the laminate shown in FIGS. 1 and 2. FIG. 5 is a cross-sectional view schematically showing a part of the reflective polarizing layer shown in FIGS. FIG. 6 is an exploded perspective view schematically showing a part of the reflective polarizing layer shown in FIGS. 3 and 4.

  As shown in FIG. 2, the identification laminate 10 includes a reflective polarizing layer 11, an alignment film 17, a birefringent layer 12, a light absorbing layer 13 a, and an overcoat layer 14.

  Here, the term “polarizing layer” means a layer functioning as a linear polarizer unless otherwise specified. The term “polarizer” includes “linear polarizer”, “elliptic polarizer”, and “circular polarizer”, and does not include the concept of shape.

The reflective polarizing layer 11 is a layer whose reflectance changes when the polarization plane of linearly polarized light as incident light is rotated. As shown in FIG. 3, the reflective polarizing layer 11 is ideally linearly polarized L when the transmission axis _AT of the reflective polarizing layer 11 and the polarization plane of the linearly polarized light L _LP as incident light are parallel to each other. Transmits _LP without reflecting. When the angle formed by the polarization plane of the linearly polarized light L _LP with respect to the transmission axis _AT is increased, the light component reflected by the reflective polarizing layer 11 increases. As shown in FIG. 4, when the polarization plane of the linearly polarized light L _LP and the transmission axis _AT are orthogonal, the reflective polarizing layer 11 reflects the most light component.

  As shown in FIG. 5, the reflective polarizing layer 11 has a structure in which first light transmissive layers 11a and second light transmissive layers 11b are alternately stacked. When the number of the first light transmissive layers 11a and the number of the second light transmissive layers 11b included in the reflective polarizing layer 11 are increased, the above-described change in reflectance is increased. However, if these numbers are increased, the reflective polarizing layer 11 becomes thicker. Typically, the sum of the number of the first light transmissive layers 11a and the number of the second light transmissive layers 11b is, for example, in the range of 2 to 1000, and typically in the range of 100 to 500. .

  The first light transmissive layer 11a has birefringence. The first light transmissive layers 11a are arranged so that their slow axes are substantially parallel.

  The second light transmissive layer 11b is different in optical characteristics from the first light transmissive layer 11a. The second light transmissive layer 11b may be optically isotropic, or may have birefringence. The second light transmissive layers 11b are arranged so that their slow axes are substantially parallel when they have birefringence.

For the first linearly polarized light incident on the reflective polarizing layer 11 from the normal direction, substantially equal to the refractive index n _b1 of the refractive index n _a1 indicated by the first light transmitting layer 11a indicated by the second light transmissive layer 11b . Therefore, each interface between the first light transmissive layer 11a and the second light transmissive layer 11b transmits the first linearly polarized light. In addition, for the second linearly polarized light that is incident on the reflective polarizing layer 11 from the normal direction and has a polarization plane perpendicular to the polarization plane of the first linearly polarized light, the refractive index _na2 indicated by the first light transmitting layer 11a. Is different from the refractive index n _{b2 of} the second light transmissive layer 11b. Therefore, each interface between the first light transmissive layer 11a and the second light transmissive layer 11b reflects a part of the second linearly polarized light. For this reason, the reflection-type polarizing layer 11, is transmitted through the first linear polarized light having a polarization plane parallel to the transmission axis A _T shown in FIG. 6, the plane of polarization parallel to the reflection axis A _R shown in FIG. 6 The second linearly polarized light is reflected.

The absolute value of the difference between the refractive index n _a1 and the refractive index n _b1 is smaller than the absolute value of the difference between the refractive index n _a2 and the refractive index n _b2, and is typically almost zero. When this absolute value is reduced, the reflectance of the first linearly polarized light at each interface between the first light transmissive layer 11a and the second light transmissive layer 11b is reduced.

The absolute value of the difference between the refractive index n _a2 and the refractive index n _b2 is, for example, 0.03 or more, and typically 0.05 or more. When this absolute value is increased, the reflectance of the second linearly polarized light at each interface between the first light transmitting layer 11a and the second light transmitting layer 11b increases.

As the first light transmissive layer 11a, for example, a stretched film imparted with birefringence by uniaxial stretching or biaxial stretching can be used. As a material for the stretched film, for example, polystyrene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, or the like can be used. A birefringent inorganic layer may be used as the first light transmissive layer 11a. However, when a stretched film is used, the refractive indexes _na1 and _na2 can be easily adjusted. For example, a polyvinyl chloride film has a higher refractive index when stretched. The polymethyl methacrylate film has a low refractive index when stretched. And the refractive index of a stretched film changes according to a stretch ratio and / or stretch temperature.

  For example, a stretched film can be used as the second light transmissive layer 11b. As the material of the stretched film, for example, the same material as exemplified with respect to the first light transmissive layer 11a can be used. A birefringent or optically isotropic inorganic layer may be used as the second light transmissive layer 11b. However, when a stretched film is used as the first light transmissive layer 11a, the reflective polarizing layer 11 can be easily manufactured by using a stretched film as the second light transmissive layer 11b. That is, a laminated film obtained by alternately laminating first and second films having different materials is prepared, and the laminated film is uniaxially or biaxially stretched. By using appropriate materials for the first and second films and appropriately setting the stretching ratio and the stretching temperature, the reflective polarizing layer 11 having the above-described optical characteristics can be obtained.

  The optical thicknesses of the first light transmissive layer 11a and the second light transmissive layer 11b are, for example, in the range of 0.09 μm to 0.70 μm. For example, when the optical thickness is set to 0.38 μm, it looks blue-purple, and when the optical thickness is set to 0.68 μm, it looks red. In addition, when such a reflective polarizing layer 11 is observed without using a polarizer, a blue shift is caused by increasing the angle formed by the observation direction and the normal line of the reflective polarizing layer 11. That is, the interference color is shifted to the short wavelength side.

  When the liquid crystal material is used for the birefringent layer 12, the alignment film 17 is used for controlling the alignment of the mesogenic group. When the birefringent layer 12 is formed on the reflective polarizing layer 11, the alignment film 17 is positioned between the reflective polarizing layer 11 and the birefringent layer 12 as shown in FIG. 2. In this case, the alignment film 17 may be in direct contact with the front surface of the reflective polarizing layer 11. Alternatively, a transparent layer may be interposed between the alignment film 17 and the reflective polarizing layer 11. Further, the alignment film 17 may be omitted.

  The alignment film 17 includes a first alignment portion 17a and a second alignment portion 17b that are adjacent to each other in the in-plane direction. Before the birefringent layer 12 is formed, the first alignment portion 17a and the second alignment portion 17b are subjected to alignment treatment using, for example, a photo alignment method or a rubbing method. The first alignment portion 17a and the second alignment portion 17b differ in the direction in which the mesogenic groups of the liquid crystal material are aligned (hereinafter referred to as the alignment direction).

  In the photo-alignment method, the film is irradiated with light having anisotropy such as polarized light to induce molecular rearrangement or chemical reaction in the film. For example, photoisomerization of azobenzene derivatives, photodimerization or crosslinking of derivatives such as cinnamic acid ester, coumarin, chalcone, and benzophenone, and photolysis of polyimide and the like are caused. Thereby, anisotropy is imparted to the film.

  In the rubbing method, polymer layers such as a polyimide layer and a polyvinyl alcohol layer are formed, and the surface is rubbed with a rubbing cloth. The mesogenic groups of the liquid crystal material are aligned in the direction rubbed with the rubbing cloth, that is, the rubbing direction.

  When utilizing the photo-alignment method, the alignment film 17 can be formed, for example, by the following method. First, a film made of the above material is formed. This film can be formed using, for example, a gravure coating method or a micro gravure coating method. A portion of the film is then exposed with linearly polarized light. Then, the other part of the previous film is exposed with linearly polarized light having a different polarization plane (vibration plane of the electric field vector). Thereby, the alignment film 17 including the first alignment portion 17a and the second alignment portion 17b having different alignment directions is obtained.

  When the photo-alignment method is used, the alignment film 17 can be formed by other methods. First, a film made of the above material is formed, and a part of the film is exposed with natural light from an oblique direction. Next, the light irradiation direction is rotated around the normal of the film surface, and the other part of the film is exposed with natural light from an oblique direction. Thereby, the alignment film 17 including the first alignment portion 17a and the second alignment portion 17b having different alignment directions is obtained.

  When the rubbing method is used, the alignment film 17 can be formed by the following method, for example. First, a polymer film is formed. The polymer film can be formed using, for example, a gravure coating method or a micro gravure coating method. Next, the entire surface of the polymer film is rubbed in one direction with a rubbing cloth. Next, a mask is placed on the polymer film, and this is rubbed in another direction with a rubbing cloth. Thereafter, by removing the mask from the polymer film, the alignment film 17 including the first alignment portion 17a and the second alignment portion 17b having different alignment directions can be obtained.

  The birefringent layer 12 includes a first birefringent portion 12a and a second birefringent portion 12b that are adjacent in the in-plane direction. The first birefringent portion 12a faces a part of the front surface of the reflective polarizing layer 11 with the first orientation portion 17a interposed therebetween. The second birefringent portion 12b faces the other part of the front surface of the reflective polarizing layer 11 with the second orientation portion 17b interposed therebetween.

  The first birefringent portion 12a has substantially uniform optical characteristics in the plane. Similarly, the second birefringent portion 12b also has substantially uniform optical characteristics within the plane. The first birefringent portion 12a and the second birefringent portion 12b have different slow axis directions.

For example, the first birefringent portion 12a and the second birefringent portion 12b are arranged so that their slow axes are orthogonal to each other. In this case, each of the first birefringent portion 12a and the second birefringent portion 12b may be a quarter-wave plate. When this structure is adopted, the reflective polarizing layer 11 and the birefringent layer 12 are such that the transmission axis _AT of the reflective polarizing layer 11 is the slow axis of the first birefringent portion 12a and the second birefringent portion. It arrange | positions so that it may become diagonal with respect to each of the slow axis of 12b. For example, the angle formed by the transmission axis _AT of the reflective polarizing layer 11 with respect to each of the slow axis of the first birefringent portion 12a and the slow axis of the second birefringent portion 12b is about 45 °. .

Alternatively, the first birefringent portion 12a and the second birefringent portion 12b may be arranged such that their slow axes form an angle of 45 °. In this case, each of the first birefringent portion 12a and the second birefringent portion 12b may be a half-wave plate. When this structure is employed, the angle formed by the transmission axis _AT of the reflective polarizing layer 11 with respect to each of the slow axis of the first birefringent portion 12a and the slow axis of the second birefringent portion 12b is Is optional.

  In addition, the laminated body 10 is usually designed in consideration of light having a wavelength in the range of 400 nm to 700 nm among visible light. Therefore, a quarter-wave plate is usually used that provides a retardation of λ / 4 at at least one wavelength λ within the above range. In general, a half-wave plate that provides a retardation of λ / 2 at at least one wavelength λ within the above range is used.

  The front surface of the laminate 10 includes a region AA1 corresponding to the first birefringent portion 12a and a region AA2 corresponding to the second birefringent portion 12b. Each of the areas AA1 and AA2 forms a latent image that is difficult to distinguish from each other. That is, when the front surface of the laminate 10 is directly observed without using a polarizer, it is difficult to find the difference between the area AA1 and the area AA2. When the front surface of the laminated body 10 is observed through the polarizer, a difference in brightness occurs between the area AA1 and the area AA2. Thereby, the latent image is visualized.

  As each of the 1st birefringent part 12a and the 2nd birefringent part 12b, a birefringent stretched film can be used, for example. In this case, the alignment film 17 may be omitted. As the stretched film, for example, a uniaxially or biaxially stretched polyolefin film and polyester film can be used.

  A liquid crystal material may be used as the material of the first birefringent portion 12a and the second birefringent portion 12b. As this liquid crystal material, for example, a liquid crystal material that is solid in the use temperature range of the laminate 10 and exhibits a nematic phase or a smectic phase, typically a polymer liquid crystal material, can be used. In this case, for example, an alignment film 17 including a plurality of portions 17a and 17b having different alignment directions is formed, a thin film pattern made of a low molecular weight liquid crystal material is formed on the alignment film 17, and polymerization of the liquid crystal material is performed. Thus, the birefringent layer 12 including the first birefringent portion 12a and the second birefringent portion 12b can be obtained.

  The light absorption layer 13 a faces the back surface of the reflective polarizing layer 11. The light absorption layer 13a may face the entire back surface of the reflective polarizing layer 11, or may face only a part thereof. Further, the light absorption layer 13a may be omitted.

  The light absorption layer 13 a may be in direct contact with the back surface of the reflective polarizing layer 11. Alternatively, a transparent layer may be interposed between the light absorption layer 13a and the reflective polarizing layer 11.

  The light absorption layer 13a is obtained, for example, by applying an ink containing a pigment and / or a dye and a resin to the back surface of the reflective polarizing layer 11. Or the light absorption layer 13a is obtained by apply | coating the previous ink on a base material. In this case, the light absorption layer 13a can be attached to the back surface of the reflective polarizing layer 11 together with the base material.

  The light absorption layer 13a may be black or other colors. The light absorption layer 13a may include a plurality of portions having different colors and arranged in the in-plane direction.

  When the light absorption layer 13a is black and the latent image is not visualized, the colors of the areas AA1 and AA2 are white due to the light reflection of the reflective polarizing layer 11. When the latent image is visualized, one of the areas AA1 and AA2 changes to black. If the light absorption layer 13a is black, the contrast ratio of these regions is maximized when the latent image is visualized.

  When the light absorbing layer 13a that absorbs only a part of visible light and reflects the other part is used, the colors of the areas AA1 and AA2 are reflected by the reflective polarizing layer 11 when the latent image is not visualized. This is a color generated by additive color mixing of the white color caused by the color and the color caused by the reflection by the light absorption layer 13a. When the latent image is visualized, the intensity of the colored light due to the reflection by the light absorption layer 13a is weak in one of the areas AA1 and AA2, and the intensity of the white light due to the reflection by the reflective polarizing layer 11 is weak on the other. Become.

  The overcoat layer 14 covers the birefringent layer 12. The overcoat layer 14 is an optically isotropic transparent layer, typically a transparent resin layer. When the birefringent layer 12 has an uneven surface, the overcoat layer 14 plays a role of flattening the surface. This makes it difficult to understand the presence of the birefringent layer 12 and the alignment film 17. The overcoat layer 14 may be omitted.

  The overcoat layer 14 is obtained, for example, by applying a transparent printing ink to the birefringent layer 12. For the application of the printing ink, for example, a coating method such as gravure and microgravure can be used.

Next, the visualization of the latent image will be described.
FIG. 7 is a diagram schematically illustrating an example of a method for visualizing a latent image held by the stacked body illustrated in FIGS. 1 and 2.

The laminate 10 shown in FIG. 7 includes half-wave plates as the first birefringent portion 12a and the second birefringent portion 12b. In the laminate 10, the angle formed by the slow axis A _{S of} the first birefringent portion 12a and the slow axis A _S of the second birefringent portion 12b is 45 °. Then, the slow axis A _S and angle formed with the reflection axis A _R of the reflective polarizing layer 11 of the first birefringent portion 12a is 45 °, the slow axis A _S of the second birefringent portion 12b the reflection axis a _R of the reflective polarizing layer 11 are parallel.

In the method illustrated in FIG. 7, the front surface of the stacked body 10 is observed through the verification tool 200 while irradiating the front surface of the stacked body 10 with natural light. Here, as an example, an absorptive polarizing layer such as a polarizing layer in which a stretched polyvinyl alcohol layer is impregnated with iodine is used as the verification tool 200. Further, in this method, the laminate 10, the light source 300, and the observer 400 are arranged so that the observer 400 can observe the reflected light when the laminate 10 specularly reflects the light from the light source 300. The transmission axis A _T ′ of 200 is arranged so as to be perpendicular to the reflection axis A _R of the reflective polarizing layer 11.

Natural light L _N from the light source 300 enters the birefringent layer 12. The birefringent layer 12 transmits this natural light _LN .

Natural light L _N emitted from the birefringent layer 12 enters the reflective polarizing layer 11. Reflective polarizing layer 11, of the natural light L _N, the plane of polarization is transmitted through the first linearly polarized light L _L1 parallel to the transmission axis A _T, the second linearly polarized light the polarization plane is parallel to the reflection axis A _R L _L2 To reflect.

The first linearly polarized light L _L1 transmitted through the reflective polarizing layer 11 enters the light absorbing layer 13a. The light absorption layer 13a absorbs the first linearly polarized light L _L1 .

The second linearly polarized light L _L2 reflected by the reflective polarizing layer 11 is incident on the first birefringent portion 12 a or the second birefringent portion 12 b of the birefringent layer 12. The first birefringent portion 12a converts the second linearly polarized light L _L2 into the first linearly polarized light L _L1 . The second birefringent portion 12b transmits the second linearly polarized light L _L2 without rotating its polarization plane.

The first linearly polarized light L _L1 and the second linearly polarized light L _L2 emitted from the birefringent layer 12 _enter the verification tool 200. The verification tool 200 ideally transmits the first linearly polarized light L _L1 without absorbing it, and absorbs the second linearly polarized light L _L2 .

  That is, the verification tool 200 transmits the reflected light from the portion corresponding to the first birefringent portion 12a in the stacked body 10, and reflects from the portion corresponding to the second birefringent portion 12b in the stacked body 10. Absorbs light. Therefore, the viewer 400 perceives the first area AA1 corresponding to the first birefringent part 12a as a bright part, and perceives the second area AA2 corresponding to the second birefringent part 12b as a dark part. As described above, the latent image can be visualized.

Incidentally, the transmission axis A _T validation tool 200 'varies the angle formed with respect to the reflection axis A _R of the reflective polarizing layer 11, the bright portion and the dark portion of the position are interchanged. For example, when the transmission axis A _T ′ is parallel to the reflection axis A _R , the positions of the bright part and the dark part are opposite to those described with reference to FIG.

  FIG. 8 is a diagram schematically illustrating another example of a method for visualizing the latent image held by the stacked body illustrated in FIGS. 1 and 2.

The laminate 10 shown in FIG. 8 includes quarter-wave plates as the first birefringent portion 12a and the second birefringent portion 12b. In the laminate 10, the angle formed by the slow axis A _{S of} the first birefringent portion 12a and the slow axis A _S of the second birefringent portion 12b is 90 °. Then, the direction of the slow axis A _S of the first birefringent portion 12a, when viewed from the front side, rotated by 45 ° clockwise from the direction parallel to the reflection axis A _R of the reflective polarizing layer 11 Direction. The direction of the slow axis A _S of the second birefringent portion 12b, when viewed from the front side, 45 ° rotated counterclockwise from the direction parallel to the reflection axis A _R of the reflective polarizing layer 11 Direction.

In the method illustrated in FIG. 8, the front surface of the stacked body 10 is observed through the verification tool 200 while irradiating the front surface of the stacked body 10 with natural light. Here, as an example, as the verification tool 200, a laminated body of an absorption-type polarizing layer 201 and a quarter-wave plate 202 is used. When the verification tool 200 is viewed from the absorption polarizing layer 201 side, the direction of the transmission axis A _T ′ of the polarizing layer 201 is counterclockwise from the direction parallel to the slow axis A _S ′ of the quarter-wave plate 202. This is a direction rotated around 45 °. That is, the verification tool 200 is a left circular polarizer. In this method, the verification tool 200 and the laminated body 10 are arranged so that the quarter-wave plate 202 faces the front surface of the verification tool 200. Further, in this method, the laminated body 10, the light source 300, and the observer 400 are arranged so that the observer 400 can observe the reflected light when the laminated body 10 specularly reflects the light from the light source 300, and the polarizing layer. The transmission axis A _T ′ of 201 is arranged so as to be perpendicular to the reflection axis A _R of the reflective polarizing layer 11.

Natural light L _N from the light source 300 enters the birefringent layer 12. The birefringent layer 12 transmits this natural light _LN .

Natural light L _N emitted from the birefringent layer 12 enters the reflective polarizing layer 11. Reflective polarizing layer 11, of the natural light L _N, the plane of polarization is transmitted through the first linearly polarized light L _L1 parallel to the transmission axis A _T, the second linearly polarized light the polarization plane is parallel to the reflection axis A _R L _L2 To reflect.

The first linearly polarized light L _L1 transmitted through the reflective polarizing layer 11 enters the light absorbing layer 13a. The light absorption layer 13a absorbs the first linearly polarized light L _L1 .

The second linearly polarized light L _L2 reflected by the reflective polarizing layer 11 is incident on the first birefringent portion 12 a or the second birefringent portion 12 b of the birefringent layer 12. The first birefringent portion 12a converts the second linearly polarized light L _L2 into the right circularly polarized light L _RC . The second birefringent portion 12b converts the second linearly polarized light L _L2 into the left circularly polarized light L _LC .

The right circularly polarized light L _RC and the left circularly polarized light L _LC emitted from the birefringent layer 12 are incident on the quarter-wave plate 202. The quarter-wave plate 202 converts the right circularly polarized light L _RC into the second linearly polarized light L _L2 and converts the left circularly polarized light L _LC into the first linearly polarized light L _L1 .

The first linearly polarized light L _L1 and the second linearly polarized light L _L2 emitted from the quarter-wave plate 202 are incident on the polarizing layer 201. The polarizing layer 201 ideally transmits the first linearly polarized light L _L1 without absorbing it, and absorbs the second linearly polarized light L _L2 .

  That is, the verification tool 200 absorbs reflected light from the portion corresponding to the first birefringent portion 12a in the multilayer body 10, and reflects from the portion corresponding to the second birefringent portion 12b in the multilayer body 10. Transmit light. Therefore, the viewer 400 perceives the first area AA1 corresponding to the first birefringent part 12a as a dark part, and perceives the second area AA2 corresponding to the second birefringent part 12b as a bright part. As described above, the latent image can be visualized.

In this way, the transmission axis A _T of the polarizing layer 201 'is also by changing the angle formed with respect to the reflection axis A _R of the reflective polarizing layer 11, the bright portion and the dark portion of the positions are not interchanged. However, when the right circular polarizer is used instead of the left circular polarizer as the verification tool 200, the positions of the bright part and the dark part are opposite to those described with reference to FIG.

As described above, in the laminate 10, the reflective polarizing layer 11 and the birefringent layer 12 are combined. The birefringent layer 12 includes a first birefringent portion 12a and the second birefringent portion 12b directions are different from each other in the slow axis A _S, to form them with the latent image. Therefore, the laminate 10 is difficult to counterfeit.

  Further, as described above, the light applied to the stacked body 10 for visualizing the latent image need not be linearly polarized light. Therefore, it is not necessary to position the verification tool 200 in the vicinity of the stacked body 10. Therefore, this technique makes it easier to visualize the latent image as compared with the case where the laminated body 10 must be irradiated with linearly polarized light in order to visualize the latent image.

  In the method described with reference to FIGS. 7 and 8, natural light is used as light applied to the laminate 10 in order to visualize the latent image, but linearly polarized light, elliptically polarized light, or circularly polarized light is used instead. May be. For example, the verification tool 200 may be positioned in the vicinity of the stacked body 10 and the stacked body 10 may be irradiated with the polarized light transmitted by the verification tool 200.

  In the method described with reference to FIGS. 7 and 8, the verification tool 200 including the polarizing layer is used. However, the verification tool 200 may not include the polarizing layer. For example, the verification tool 200 may include a linear polarizer such as a polarizing prism.

  In the method described with reference to FIGS. 7 and 8, a polarizer is used as the verification tool 200 for visualizing the latent image. However, the structure described with reference to FIG. In this case, the latent image can be visualized without using a polarizer. This will be described below.

  FIG. 9 is a diagram schematically illustrating another example of a method for visualizing the latent image held by the stacked body illustrated in FIGS. 1 and 2.

In this method, a transparent body 200 ′ such as a transparent plate is used as a verification tool. Specifically, the natural light L _N emitted from the light source 300 is irradiated onto the laminated body 10, and the light reflected by the laminated body 10 is incident on the transparent body 200 ′. Here, as an example, the reflected light from the area AA1 is linearly polarized light (hereinafter referred to as S wave) L _S whose polarization plane is perpendicular to the main surface of the transparent body 200 ′, and the reflected light from the area AA2 is polarized light. It is assumed that the plane is linearly polarized light (hereinafter referred to as P wave) L _P perpendicular to the plane of polarization of the S wave L _S.

The incident angle θ of the S wave L _S and the P wave L _P with respect to the transparent body 200 ′ is made substantially equal to the Brewster angle. For example, when a glass plate having a refractive index of about 1.5 is used as the transparent body 200 ′, the incident angle is set to about 56 °.

In this way, most of the light reflected by the transparent body 200 ′ becomes the S wave L _S. That is, the reflected light from the area AA1 among the reflected light from the stacked body 10 reaches the observer 400, but the reflected light from the area AA2 hardly reaches. Therefore, the viewer 400 perceives the areas AA1 and AA2 as a bright part and a dark part, respectively. As described above, the latent image can be visualized.

  In the arrangement shown in FIG. 9, when the laminate 10 is rotated by 90 ° around the normal line, the regions AA1 and AA2 appear as dark portions and bright portions, respectively.

  A light absorption layer can be provided on the back side of the transparent body 200 ′. Employing this configuration improves the contrast ratio of the visible image.

  The transparent body 200 'is typically a transparent plate, but may not be a transparent plate as long as it has a smooth surface. The transparent body 200 ′ may be used only for the visualization, or may be used for other purposes such as a display cover plate mounted on a portable device. Good.

  Since the laminate 10 described above includes the reflective polarizing layer 11, when the front surface of the laminate 10 is directly observed without using the verification tool 200, the front surface of the laminate 10 looks bright. Therefore, a highly visible print pattern can be formed on the front surface of the laminate 10.

  FIG. 10 is a plan view schematically showing a modification of the laminate shown in FIGS. 1 and 2. FIG. 11 is a cross-sectional view taken along line XI-XI of the stacked body shown in FIG.

  The laminate 10 shown in FIGS. 10 and 11 is the same as the laminate 10 described with reference to FIGS. 1 and 2 except that the laminate 10 further includes a printed pattern 15 formed on the overcoat layer 14. It has a structure. Thus, the printing pattern 15 can be formed on the overcoat layer 14.

  The print pattern 15 may be interposed between the overcoat layer 14 and the birefringent layer 12. Alternatively, the print pattern 15 may be interposed between the overcoat layer 14 and the reflective polarizing layer 11. Alternatively, the print pattern 15 may be interposed between the birefringent layer 12 and the reflective polarizing layer 11.

The laminated body 10 described above may include a diffractive structure.
FIG. 12 is a plan view schematically showing another modification of the laminate shown in FIGS. 1 and 2. FIG. 13 is a cross-sectional view taken along line XIII-XIII of the laminate shown in FIG. The stacked body 10 has the same structure as the stacked body 10 described with reference to FIGS. 1 and 2 except that the stacked body 10 further includes a diffraction structure forming layer 18 and a reflective layer 13b.

  The diffractive structure forming layer 18 is interposed between the reflective polarizing layer 11 and the light absorbing layer 13a. In this example, the diffractive structure forming layer 18 is formed on the main surface of the reflective polarizing layer 11 facing the light absorption layer 13a. The main surface of the diffraction structure forming layer 18 on the light absorption layer 13 side includes a convex pattern or a concave pattern. The diffractive structure forming layer 18 is made of a transparent resin such as a thermoplastic resin, for example.

  The reflective layer 13b is interposed between the reflective polarizing layer 11 and the light absorbing layer 13a. In this example, the reflective layer 13b is formed on the main surface of the diffractive structure forming layer 18 facing the light absorbing layer 13a. The front surface of the reflective layer 13 b includes a convex pattern or a concave pattern corresponding to the convex pattern or the concave pattern of the diffractive structure forming layer 18. This convex pattern or concave pattern forms a hologram or a diffraction grating as a diffractive structure. This diffraction structure forms a diffraction image on the front surface of the laminate. FIG. 11 shows a diffraction image HG formed by holography as an example.

  The hologram can be formed by the following method, for example. First, a relief master plate composed of a fine convex pattern or a concave pattern is produced by using an optical photographing method. Next, by using an electroplating method, a nickel press plate in which a concave pattern or a convex pattern is duplicated from the master plate is produced. Thereafter, the press plate is pressed against the diffraction structure forming layer 18 while heating. Thereby, the convex pattern or the concave pattern is transferred to the diffractive structure forming layer 18. Further, the reflective layer 13 b is formed on the diffractive structure forming layer 18. As described above, a hologram can be formed.

The hologram can be formed by other methods. That is, first, the reflective layer 13 b is formed on the flat diffractive structure forming layer 18. Next, the press plate is pressed against the reflective layer 13b while heating. Thereby, the convex pattern or the concave pattern is transferred to the reflective layer 13 and the diffractive structure forming layer 18. As described above, a hologram can be formed.
This type of hologram is called a relief hologram.

  The diffraction grating can be formed by a method similar to that described for the hologram, except that no optical imaging method is used. In the case of forming a diffraction grating, an image called a grating image or a dot matrix (pixelgram or the like) may be displayed by arranging a plurality of pixels each including a diffraction grating.

  The reflective layer 13b is, for example, a metal layer, an alloy layer, or a high refractive index layer. As the material for the metal layer, for example, aluminum, tin, silver, chromium, nickel, and gold can be used. As a material of the alloy layer, for example, nickel-chromium-iron alloy, bronze, and aluminum bronze can be used. As a material for the high refractive index layer, for example, an inorganic dielectric such as titanium dioxide, zinc sulfide, and ferric trioxide can be used. As the reflective layer 13b, a dielectric multilayer film in which high refractive index layers and low refractive index layers are alternately stacked may be used.

  The reflective layer 13b may have a light transmission property or may not have a light transmission property.

  In the case where the reflective layer 13b does not have optical transparency, the light absorption layer 13a may be omitted. In this case, if the reflectance of the light reflecting layer 13b is high, the latent image cannot be visualized or the visualized latent image is difficult to see. For example, if a light-transmitting colored layer is provided in front of the light reflecting layer 13b, it is possible to prevent the latent image from being visualized and to prevent the visualized latent image from being difficult to see.

  In the case where the reflective layer 13b is light transmissive, the visibility of the visualized latent image can be increased by providing the light absorbing layer 13a. When providing the light absorption layer 13a, the light absorption layer 13a may face the whole back surface of the reflection layer 13b, or may face only a part of the back surface of the reflection layer 13b. The light absorption layer 13a can be formed by, for example, printing or a coating method.

  The reflective layer 13b can be formed by, for example, vapor deposition, sputtering, or ion plating. In this case, the thickness of the reflective layer 13b is, for example, in the range of about 10 nm to about 100 nm. The reflective layer 13b can be formed as a layer patterned by using, for example, paster processing, water-washed celite processing, or laser processing. That is, the reflective layer 13b may face the entire main surface of the reflective polarizing layer 11, or may face only a part thereof.

  The reflective layer 13b may be formed on the diffractive structure forming layer 18 as described above, or may be formed on a base material (not shown). For example, a base material including a convex pattern or a concave pattern on one main surface is prepared. Next, the reflective layer 13b is formed on the main surface by the above method. Then, this base material and the reflective polarizing layer 11 are bonded together through an adhesive layer. When the substrate is not transparent, the substrate and the reflective polarizing layer 11 are bonded so that the reflective layer 13 b faces the reflective polarizing layer 11. When the substrate is transparent, the substrate and the reflective polarizing layer 11 are bonded so that the reflective layer 13b faces the reflective polarizing layer 11, or the base material faces the reflective polarizing layer 11. Paste together. The reflective layer 13b may be supported on the reflective polarizing layer 11 by such a method.

  As the reflective layer 13b, a material that can be handled by itself, such as a metal foil, may be used. In this case, for example, a transparent adhesive layer is interposed between the reflective layer 13 b and the reflective polarizing layer 11 instead of the diffraction structure forming layer 18. In this case, typically, the light absorption layer 13a is omitted.

  The diffractive structure may be installed in front of the reflective polarizing layer 11. For example, the diffraction structure forming layer 18 may be formed on the front surface of the reflective polarizing layer 11, and the reflective layer 13b having light transmittance may be formed thereon.

  The diffraction structure forming layer 18 can be omitted. For example, when the above-described convex pattern or concave pattern can be formed on the surface of the reflective polarizing layer 11, the diffractive structure forming layer 18 is not necessary.

  The laminate 10 described above is supported directly or indirectly on an article whose authenticity is to be confirmed. And when discriminating an article whose authenticity is unknown between a genuine product and a non-authentic product such as a counterfeit product, the laminate 10 can be used as described below.

  As described above, the laminate 10 has a latent image that is visualized by observation through a polarizer. That is, at least a partial region of the article supporting the laminated body 10 has a latent image that is visualized by observing through the polarizer. Therefore, if an article with unknown authenticity does not have such a latent image, it can be determined that the article is non-authentic.

  In addition, when the laminate 10 is observed without using a polarizer, a blue shift is generated by increasing an angle formed by the observation direction and the normal line of the main surface of the reflective polarizing layer 11. Therefore, when an article whose authenticity is unknown does not include a region that causes such a blue shift, it can be determined that the article is non-authentic.

  If an article of unknown authenticity holds the previous latent image, the shape and / or size of the visualized latent image may be compared with that of the authentic product. If the shape and / or size of the visualized latent image is different from that of the genuine product, it can be determined that the article is non-genuine.

  For the determination of an article, only one of the above-described methods may be used, or a plurality of methods may be used in combination. This technique may be combined with other determination techniques. Increasing the number of methods used to determine an article decreases the probability of erroneously determining a non-authentic product as a genuine product.

The laminate 10 can be used in various forms as described below.
FIG. 14 is a cross-sectional view schematically showing an example of an adhesive label including the laminate shown in FIGS. 1 and 2. The pressure-sensitive adhesive label 20 includes a laminate 10 and a pressure-sensitive adhesive layer 21 provided on the back surface thereof. For example, the adhesive label 20 is attached to an article whose authenticity is to be confirmed, or is attached to another article such as a tag to be attached to the article. If it carries out like this, the authenticity of goods can be confirmed by the method mentioned above.

  The adhesive label 20 may be brittle. Such an adhesive label 20 is obtained, for example, by forming a cutout and / or a perforation in the laminate 10. When the pressure-sensitive adhesive label 20 is brittle, the laminate 10 is easily broken when the pressure-sensitive adhesive label attached to an article whose authenticity is to be confirmed is peeled off. Therefore, it becomes difficult to replace the adhesive label 20.

  FIG. 15 is a cross-sectional view schematically showing an example of a recording medium including the laminate shown in FIGS. 1 and 2. The recording medium 30 includes a paper 31 and a laminated body 10 embedded therein. An opening is provided in a portion of the paper 31 that covers the front surface of the laminate 10. Thereby, the visibility of the visualized latent image is enhanced. If the latent image can be visualized, the paper 31 does not have to be provided with the previous opening.

  The recording medium 30 can be used as a sheet for an authentication medium such as a cash card, a credit card and a passport, or a securities medium such as a gift certificate and a stock certificate, for example. Alternatively, the recording medium 30 can be used as a part of an adhesive label described later. Alternatively, the recording medium 30 can be used as a tag or a part thereof to be attached to an article whose authenticity is to be confirmed. Alternatively, the recording medium 30 can be used as a package or a part thereof for containing an article whose authenticity is to be confirmed.

  The recording medium 30 is obtained, for example, by sandwiching the laminate 10 between fiber layers during papermaking. The recording medium 30 obtained by such a method is difficult to forge.

  16 is a cross-sectional view schematically showing an example of an adhesive label including the recording medium of FIG. The adhesive label 40 includes a recording medium 30 and an adhesive layer 41 provided on the back surface thereof. For example, the adhesive label 40 is attached to an article whose authenticity is to be confirmed, or is attached to another article such as a base material of a tag to be attached to the article.

  FIG. 17 is a cross-sectional view schematically showing an example of a labeled article including the laminate shown in FIGS. 1 and 2. This labeled article 100 includes an article 101 and a laminate 10.

  The article 101 is an article whose authenticity is to be confirmed. The article 101 is, for example, an authentication medium such as a cash card, a credit card, and a passport, or a securities medium such as a gift certificate and a stock certificate. The article 101 may be an article other than the authentication medium and the securities medium. For example, the article 101 may be a craft or a work of art. Alternatively, the article 101 may be a packaged product including a package and contents contained therein.

  The laminate 10 is supported by the article 101. For example, the laminate 10 is attached to the article 101. In this case, for example, the laminate 10 can be supported by the article 101 by attaching the adhesive label 20 shown in FIG. 14 or the adhesive label 40 shown in FIG. 16 to the article 101.

The laminate 10 may be supported on the article 101 by other methods.
For example, when the article 101 includes paper, the laminate 10 may be embedded in the paper. In this case, the labeled article 100 is obtained, for example, by sandwiching the laminate 10 between fiber layers during papermaking, and then performing printing or the like on the paper as necessary. In order to facilitate visualization of the latent image, an opening may be provided in a portion of the paper covering the front surface of the laminate 10. Moreover, there is no restriction | limiting in particular in the shape of the laminated body 10 embedded in paper. For example, the thread-like laminate 10 may be embedded in paper.

  The laminate 10 may be supported by the article 101 by attaching a tag including the laminate 10 to the article 101. If it is difficult for a general user to replace the tag on the article 101, the laminate 10 is sufficiently useful for confirming the authenticity of the article 101.

Examples of the present invention will be described below.
DBEF manufactured by 3M (Minnesota Mining & Manufacturing) was prepared as a reflective polarizing layer.

Next, Daiichi Ink Manufacturing Co., Ltd. photo-alignment agent IA-01 was apply | coated to the thickness of 0.1 micrometer on the front surface of the reflective polarizing layer with the gravure coating method. Next, the entire surface of this coating film was exposed with an illuminance of 1 J / cm ² using linearly polarized light having a wavelength of 365 nm. The linearly polarized light was irradiated so that its polarization plane forms an angle of 45 ° with respect to the transmission axis of the reflective polarizing layer. Thereafter, the previous coating film was pattern-exposed with an illuminance of ² J / cm ² using linearly polarized light having a wavelength of 365 nm. A photomask was used for this pattern exposure, and linearly polarized light was irradiated so that the plane of polarization was parallel to the transmission axis of the reflective polarizing layer. As described above, an alignment film including first and second alignment portions having different alignment directions was obtained.

Next, UV curable liquid crystal UCL-008 (manufactured by Dainippon Ink Co., Ltd.) was printed on the alignment film by a gravure coating method. After heating at 65 ° C. for 60 seconds, this coating film was exposed to ultraviolet light at an illuminance of 0.5 J / cm ^{2 in} a nitrogen atmosphere to cure the coating film. As a result, a birefringent layer including first and second birefringent portions whose slow axis directions differ by 45 ° was obtained. The thickness of the birefringent layer was 1.5 μm, and the difference between the ordinary light refractive index and the extraordinary light refractive index in each of the first and second birefringent portions was 0.18. That is, each of the first and second birefringent portions is a half-wave plate that transmits a pair of linearly polarized light having a wavelength λ of 540 nm and gives a phase difference of λ / 2 to the linearly polarized light.

  Next, an adhesive layer having a thickness of 30 μm containing a black dye and an acrylic adhesive was formed on the back surface of the reflective polarizing layer. Further, a color shift ink containing a pearl pigment was printed on the birefringent layer. An adhesive label was obtained as described above.

  Next, this adhesive label was affixed on the base material. And while irradiating natural light to an adhesive label, the front surface of the adhesive label was observed first, without using an absorption type polarizing film. As a result, the region corresponding to the birefringent layer and the other region could not be distinguished. Next, the front surface of the pressure-sensitive adhesive label was observed through the absorption polarizing film while irradiating the pressure-sensitive adhesive label with natural light. As a result, the region corresponding to the birefringent layer and the other region could be seen as the bright part and the dark part, respectively. That is, the latent image could be visualized.

The top view which shows roughly the laminated body for identification which concerns on 1 aspect of this invention. Sectional drawing along the II-II line of the laminated body shown in FIG. FIG. 3 is a perspective view schematically showing a reflective polarizing layer included in the laminate shown in FIGS. 1 and 2. FIG. 3 is a perspective view schematically showing a reflective polarizing layer included in the laminate shown in FIGS. 1 and 2. FIG. 5 is a cross-sectional view schematically showing a part of the reflective polarizing layer shown in FIGS. 3 and 4. FIG. 5 is an exploded perspective view schematically showing a part of the reflective polarizing layer shown in FIGS. 3 and 4. The figure which shows schematically an example of the method of visualizing the latent image which the laminated body shown in FIG.1 and FIG.2 hold | maintains. The figure which shows schematically the other example of the method of visualizing the latent image which the laminated body shown in FIG.1 and FIG.2 hold | maintains. The figure which shows schematically the other example of the method of visualizing the latent image which the laminated body shown in FIG.1 and FIG.2 hold | maintains. The top view which shows roughly the modification of the laminated body shown in FIG.1 and FIG.2. Sectional drawing along the XI-XI line of the laminated body shown in FIG. The top view which shows roughly the other modification of the laminated body shown in FIG.1 and FIG.2. Sectional drawing along the XIII-XIII line of the laminated body shown in FIG. Sectional drawing which shows schematically an example of the adhesive label containing the laminated body shown in FIG.1 and FIG.2. FIG. 3 is a cross-sectional view schematically showing an example of a recording medium including the laminate shown in FIGS. 1 and 2. Sectional drawing which shows schematically an example of the adhesive label containing the recording medium of FIG. Sectional drawing which shows roughly an example of the labeled article containing the laminated body shown in FIG.1 and FIG.2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Discrimination laminated body, 11 ... Reflective polarizing layer, 12 ... Birefringent layer, 12a ... 1st birefringent part, 12b ... 2nd birefringent part, 13a ... Light absorption layer, 13b ... Reflective layer, DESCRIPTION OF SYMBOLS 14 ... Overcoat layer, 15 ... Print pattern, 17 ... Orientation film, 17a ... 1st orientation part, 17b ... 2nd orientation part, 20 ... Adhesive label, 21 ... Adhesion layer, 30 ... Recording medium, 31 ... Paper, 40 DESCRIPTION OF SYMBOLS ... Adhesive label, 41 ... Adhesive layer, 100 ... Labeled article, 101 ... Article, 200 ... Verification tool, 200 '... Transparent body, 300 ... Light source, 400 ... Observer, AA1 ... Area, AA2 ... Area, _AF ... Fast axis, A _F '... Fast axis, A _R ... Reflection axis, A _S ... Slow axis, A _S ' ... Slow axis, A _T ... Transmission axis, A _T '... Transmission axis, L _L1 ... Linear polarization, L _L2 ... linearly polarized light, L _LC ... left-handed circularly polarized light, L _LP ... linearly polarized light, L _N ... natural light, L _P ... P-wave, L _RC ... right circularly polarized light, _S ... _S wave.

Claims (8)

A reflective polarizing layer formed by alternately laminating a birefringent first light-transmitting layer and second light-transmitting layers having different optical characteristics from the first light-transmitting layer;
A first portion facing a part of the front surface of the polarizing layer and a second portion facing the other part of the front surface of the polarizing layer and having a slow axis direction different from that of the first portion. A refractive layer,
A discriminating laminate comprising a convex pattern or a concave pattern as a diffractive structure for diffracting the light transmitted or reflected by the polarizing layer. A light reflecting layer facing the back surface of the polarizing layer, the diffractive structure being provided on one main surface, and having light transparency;
The laminate according to claim 1, characterized in that further comprising a <br/> the light absorbing layer facing the rear surface of the polarizing layer is sandwiched between the light reflective layer. The laminate according to claim 2, further comprising a light-transmitting colored layer disposed in front of the light reflecting layer.   An adhesive label comprising: the laminate according to any one of claims 1 to 3; and an adhesive layer supported on a back surface of the laminate.   The adhesive label according to claim 4, wherein the laminate is provided with a notch and / or a perforation.   The laminate according to any one of claims 1 to 3, wherein the laminate is embedded in the paper, an adhesive layer supported on one main surface of the paper, and a back surface facing the adhesive layer. An adhesive label characterized by comprising:   A recording medium comprising paper and the laminate according to any one of claims 1 to 3 embedded in the paper.   A labeled article comprising: an article whose authenticity is to be confirmed; and a laminate according to any one of claims 1 to 3 supported by the article whose authenticity is to be confirmed. .

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