JP5181850B2 - Verifier - Google Patents

Description

  The present invention relates to a verifier that determines the authenticity of an object using polarized light.

  Conventionally, there are various anti-counterfeit technologies for determining the authenticity of an object using polarized light. For example, Patent Document 1 proposes a method of confirming a latent image by using a cholesteric liquid crystal and observing through a polarizer.

  Patent Document 2 proposes a method in which a latent image is developed by aligning and solidifying a nematic liquid crystal on a fine structure, adhering it to a reflective layer, and observing it through a polarizer.

  These methods have the advantage of high designability, difficulty in counterfeiting, and high discrimination. Furthermore, these methods not only produce a latent image when polarizers are superimposed, but also have the effect that the color tone changes by observing the security medium while tilting the polarizers. Therefore, not only authenticity determination based on a latent image but also authenticity determination based on a change in latent image color is possible.

  However, the authenticity determination method based on such a change in the color tone of the latent image is not common, and when performing authenticity determination by a plurality of authenticity determination methods, the determiner needs special knowledge, so the determiner There is a problem that education is necessary.

Japanese Patent Laid-Open No. 11-42875 JP 2003-251643 A

  It is an object of the present invention to easily perform not only authenticity determination based on confirmation of a latent image but also a plurality of authenticity determinations including changes in the color of a latent image in an object verifier that performs authenticity determination using polarized light. Is to provide a verifier.

The verifier according to the invention of claim 1 is a verifier that performs authenticity determination using polarized light, and is laminated on a polarizing element that transmits only specific polarized light and a partial region on a surface portion of the polarizing element. And a light path changing element having transparency that changes the traveling direction of light in a specific direction and having a surface portion having an area smaller than the area of the surface portion of the polarizing element, and the light path changing elements are not stacked. A region having only a polarizing element is a single region, and a region in which the polarizing element and the optical path changing element are stacked is a stacked region .

  The verification device according to a second aspect of the invention is the verification device according to the first aspect, wherein the light path changing element changes the traveling direction of light by performing at least one of light refraction, reflection and diffraction. It is characterized by that.

  A verification device according to a third aspect of the present invention is the verification device according to the second aspect, wherein the optical path changing element has a diffraction grating structure.

  A verification device according to a fourth aspect of the present invention is the verification device according to the second aspect, wherein the optical path changing element has a lens structure.

  A verification device according to a fifth aspect of the invention is the verification device according to any one of the first to fourth aspects, wherein the optical path changing element is one of wavelength selective reflectivity and polarization selective property. It is formed by the material which has this.

  The verification device according to a sixth aspect of the invention is the verification device according to any one of the first to fifth aspects, wherein the optical path changing element has a plurality of regions in which traveling directions of light to be changed are different. It is characterized by.

  A verification device according to a seventh aspect of the present invention is the verification device according to any one of the first to sixth aspects, wherein the polarizing element has a transmission axis that transmits only the linearly polarized light in a specific direction. It is characterized by being a child.

  The verification device according to an eighth aspect of the invention is the verification device according to the seventh aspect, wherein the polarizing element has a plurality of regions having different transmission axis directions.

  The verification device according to the invention of claim 9 is the verification device according to any one of claims 1 to 6, wherein the polarizing element transmits only clockwise circularly polarized light or counterclockwise circularly polarized light. It is a circular polarizer.

  According to a tenth aspect of the present invention, in the verification device according to the ninth aspect, the polarizing element has a plurality of regions having different rotation directions of the circularly polarized light that is transmitted.

  The verifier according to an eleventh aspect of the present invention is the verifier according to any one of the first to sixth aspects, wherein the polarizing element includes a region having a transmission axis that transmits only linearly polarized light, and a clockwise direction. A region that transmits only the circularly polarized light or the counterclockwise circularly polarized light.

According to the present invention, in a verifier for an object that performs authenticity determination using polarized light, a polarizing element that transmits only specific polarized light and a transparency that is stacked on the polarizing element and changes the traveling direction of light to a specific direction. The optical path changing element is provided as a single area, and the area where the polarizing element and the optical path changing element are laminated is a laminated area . In addition to authenticity determination by confirmation, a plurality of authenticity determinations including a change in latent image color can be easily performed.

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

  FIG. 1 is a schematic cross-sectional view showing a verifier according to Embodiment 1 of the present invention. A verifier 10 according to Embodiment 1 of the present invention includes a polarizing element 1, an adhesive layer (adhesive layer) 2, and an optical path changing element 3. A partial region of the polarizing element 1 and the optical path changing element 3 are bonded and laminated by an adhesive layer (adhesive layer) 2.

  FIG. 2 is a schematic cross-sectional view showing the security medium according to Embodiment 1 of the present invention. The security medium 20 is verified by the verifier 10 according to the first embodiment of the present invention. The security medium 20 includes a liquid crystal layer 5 and a reflective layer 4. The liquid crystal layer 5 is formed of nematic liquid crystal. The security medium 20 is fixed or fixed to a part of an object (not shown). This object is, for example, a passport, a card, a certificate, a gift certificate, or a ticket.

  The polarizing element 1 has a function of transmitting only specific polarized light and a function of verifying the presence or absence of a latent image on the security medium 20. In the first embodiment, since the security medium 20 that performs authenticity determination includes the liquid crystal layer 5 and the reflective layer 4 made of nematic liquid crystal, the polarizing element 1 may be a linearly polarizing element or a circularly polarizing element. Even if it exists, the latent image of the security medium 20 can be confirmed.

  In the security medium 20, a liquid crystal layer 5 in which nematic liquid crystal is aligned and solidified is formed on the reflective layer 4. The reflective layer 4 maintains the polarization of light incident on the interface, that is, reflects the light without disturbing the polarization.

  In the first embodiment, the reflective layer 4 is formed by mixing resin with metal particles that do not disturb the deflection, and imparts the property of imparting scattering properties to incident light. That is, as a result, the reflective layer 4 has a scattering property to scatter light without disturbing the deflection.

  The liquid crystal layer 5 is formed by aligning and fixing nematic liquid crystals. Due to the alignment of the liquid crystal molecules, an image that can be observed by the verification device 10 according to the first embodiment of the present invention is formed.

  In the first embodiment, when the polarizing element 1 is positioned on the security medium 20 side when the security medium 20 is observed, there is no problem even if the adhesive layer 2 is formed of a material that disturbs the polarization. However, when the optical path changing element 3 is located on the security medium 20 side when the security medium 20 is observed, it is desirable that the adhesive layer 2 be formed of a material that does not disturb polarization.

  In the first embodiment, the optical path changing element 3 has a lens structure in which a fine prism-shaped lens is formed on a sheet, and changes the traveling direction of light by reflection and refraction.

  When the security medium 20 is observed from a certain angle by changing the angle of light incident on the liquid crystal layer 5 made of nematic liquid crystal, the optical path changing element 3 is observed from the same angle through the single polarizing element 1. It presents a different latent image color.

Here, the difference in color resulting from the difference in the optical path length of the light passing through the liquid crystal will be described. This is because the phase difference caused by the birefringence of the liquid crystal depends on the optical path length and wavelength of the light passing through the liquid crystal, and is clear from the following equations (1) and (2).
Re = Δnd (1)
(Δn = ne−no)
I = I0 sin2 (2θ) sin2 (Reπ / λ) (2)
Where Re: phase difference, Δn: birefringence, d: optical path length of light passing through the liquid crystal, ne: refractive index of ordinary light, no: refractive index of extraordinary light, I: incident light intensity, I0: transmitted light Intensity, θ: liquid crystal alignment direction and polarizer transmission axis angle, λ: wavelength.

  Here, a difference in optical path between the case where the security medium 20 is observed using only the normal polarizer 1 and the case where the security medium 20 is observed using the verifier 10 of the first embodiment will be described.

  When only the normal polarizer 1 is used, as shown in FIG. 3, the light incident from above is reflected upward again by the reflective layer 4.

On the other hand, when the verifier 10 according to the first embodiment is used, as shown in FIG. 4, when light enters the optical path changing element 3 from above, the light path 6 is set by a fine prism-shaped lens. The light is incident on the security medium 20 from an oblique direction. Light incident from an oblique direction is reflected by the reflecting layer 4, the path of the light is changed again by the optical path changing element 3. When the thickness of the liquid crystal layer 5 is equal, compared with the optical path length in the case of using only the normal polarizer 1, the optical path length in the case of using the verifier first embodiment becomes longer.

  Therefore, as shown in the equations (1) and (2), the latent image of the security medium 20 in the verifier 10 of the first embodiment is observed through the single area of the polarizing element 1. In the case and when observed through the area | region where the polarizing element 1 and the optical path changing element 3 are laminated | stacked, a different coloration is shown. In other words, by observing the security medium 20 from a certain angle, it is possible to obtain the same effect as that observed from two different angles.

  Further, as shown in the formula (2), it is apparent that the color appearance changes even when the alignment direction of the liquid crystal of the liquid crystal layer 5 and the angle of the transmission axis of the polarizer 1 are changed.

  Therefore, when the polarizing element 1 according to the first embodiment is formed by a plurality of regions having different transmission axes, different latent image colors are exhibited in the respective regions, and a plurality of authenticity determinations can be performed. desirable.

  For example, when the transmission axis direction of the polarizing element 1 is 0 °, 45 °, and 90 °, the security medium 20 in which the liquid crystal alignment direction of the liquid crystal layer 5 is 45 ° is observed from the front. In the single region of the polarizing element 1, the color is purple in the region where the transmission axis direction is 0 ° and 90 °, and white in the region of 45 °. On the other hand, the color observed in the region where the optical path changing element 3 is formed on the polarizing element 1 is red in the region where the transmission axis direction is 0 °, white in the region of 45 °, and 90 °. The area is green. This color is the same as the color when observed from an oblique direction in a single region of the polarizing element 1.

(Embodiment 2)
Next, a second embodiment of the invention will be described in detail with reference to the drawings.
FIG. 5 is a schematic cross-sectional view showing a verifier according to Embodiment 2 of the present invention. In the second embodiment of the present invention, the same components as those in the first embodiment of the present invention are designated by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, the verifier 30 according to Embodiment 2 of the present invention includes a polarizing element 11, an adhesive layer (adhesive layer) 2, and an optical path changing element 3. A partial region of the polarizing element 11 and the optical path changing element 3 are bonded and laminated by an adhesive layer (adhesive layer) 2. The polarizing element 11 is formed of a circular polarizer.

  FIG. 6 is a schematic sectional view showing a security medium according to Embodiment 2 of the present invention. This security medium 40 is verified by the verifier 30 according to Embodiment 2 of the present invention. The security medium 40 includes a black layer 7 and a liquid crystal layer 8. The liquid crystal layer 8 is formed of cholesteric liquid crystal. The security medium 40 is formed by forming a liquid crystal layer 8 on which a cholesteric liquid crystal is aligned and solidified on a black layer 7.

  The liquid crystal layer 8 is a layer including a cholesteric liquid crystal that reflects reflected light of only one of left circularly polarized light and right circularly polarized light to generate reflected light. Further, the average spiral axis orientation of the cholesteric liquid crystal is perpendicular to the film surface.

  The black layer 7 absorbs incident light to make the latent image formation of the liquid crystal layer 8 by cholesteric liquid crystal clear. In the second embodiment, the black layer 7 is formed of a resin containing a black dye.

Here, reflection of a polarized light component having a specific wavelength by the cholesteric liquid crystal of the liquid crystal layer 8 will be described.
The alignment structure of the molecules of the cholesteric liquid crystal has a regular twist so as to draw a spiral in the film thickness direction. Cholesteric liquid crystal exhibits selective reflectivity and circularly polarized light selectivity when pitch P is the film thickness necessary for liquid crystal molecules to rotate 360 ° and pitch P is substantially equal to wavelength λ of incident light. It is known.

  Selective reflectivity refers to the property of strongly reflecting light in a specific wavelength band of incident light. Since it is expressed limited to a specific wavelength band, reflection is achieved by appropriately selecting the pitch P of the cholesteric liquid crystal. Light becomes a chromatic color with high color purity.

Specifically, assuming that the center wavelength of the wavelength band in which selective reflection occurs is λs and the band width is Δλ, λs and Δλ are the pitch P (= λ / nm) and the average refractive index nm (= √ ((no ² + Ne ² ) / 2)) is determined as shown in equations (3) and (4). Here, Δn is (Δn = ne−no).
λs = nm · P (3)
Δλ = Δn · P / nm (4)

  The center wavelength λs and the wavelength band Δλ shown in the equations (3) and (4) are defined when the incident light to the selective reflection layer is perpendicularly incident, but when the incident light is obliquely incident, the pitch Since P apparently decreases, the center wavelength λs shifts to the short wavelength side, and the bandwidth Δλ decreases. Therefore, as the viewing angle is increased from the vertical, the observed color becomes a short wavelength side color.

  The circularly polarized light selectivity is a property of transmitting only circularly polarized light in a specific rotation direction and reflecting circularly polarized light having the opposite rotation direction. For example, in the case of a cholesteric liquid crystal having a right twist structure, right circularly polarized light is reflected, reflected light remains right circularly polarized light, and left circularly polarized light is transmitted.

  Here, the difference in optical path between the case where the security medium 40 is observed using the normal polarizer 11 and the case where the security medium 40 is observed using the verifier 30 in the second embodiment will be described.

  When only the normal polarizer 11 is used, as shown in FIG. 7, a part of the light incident from above is reflected by the liquid crystal layer 8, and the remaining wavelength is absorbed by the black layer 7.

  On the other hand, when the verifier 30 according to the second embodiment is used, as shown in FIG. 8, when light enters the optical path changing element 3 from above, the light path 6 is set by a fine prism-shaped lens. The light is incident on the security medium 40 from an oblique direction. A part of the wavelength of light incident from an oblique direction is reflected by the liquid crystal layer 8, and its path is changed again by the optical path changing element 3. The remaining wavelengths are absorbed by the black layer 7.

  Therefore, since the apparent pitch changes as the angle of the incident light changes, the latent image of the security medium 40 uses only the ordinary polarizer 11 as shown in the equations (3) and (4). Different coloration is shown when observing 40 and when observing using the verifier 30 of the second embodiment.

(Embodiment 3)
Next, a third embodiment of the invention will be described in detail with reference to the drawings.
FIG. 9 is a schematic cross-sectional view showing a verifier according to Embodiment 3 of the present invention. In the third embodiment of the present invention, the same components as those in the first and second embodiments of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 9, the verifier 50 according to Embodiment 3 of the present invention includes a polarizing element 11, an adhesive layer (adhesive layer) 2, and an optical path changing element 12. A partial region of the polarizing element 11 and the optical path changing element 12 are laminated by being adhered by an adhesive layer (adhesive layer) 2. The polarizing element 11 is formed of a circular polarizer. The optical path changing element 12 has a transmissive diffraction grating structure, and changes the angle of incidence on the liquid crystal layer by light diffraction.

(Embodiment 4)
Next, a fourth embodiment of the invention will be described in detail with reference to the drawings.
FIG. 10 is a schematic cross-sectional view showing a verifier according to Embodiment 4 of the present invention. In the fourth embodiment of the present invention, the same components as those in the first, second, and third embodiments of the present invention are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 10, the verifier 50 according to Embodiment 4 of the present invention includes a polarizing element 11, an adhesive layer (adhesive layer) 2, and an optical path changing element 13. A part of the polarizing element 11 and the optical path changing element 13 are stacked. The polarizing element 11 is formed of a circular polarizer. In the optical path changing element 13, two types of triangular members 13a and 13b having different refractive indexes are bonded together by an adhesive layer. In this case, the member 13b is formed so that the refractive index of the member 13b is larger than the refractive index of the member 13a.

  In the present embodiment, only one type of light travel direction is changed. However, in the case where an optical path changing element that can be changed to a different travel direction in a plurality of regions is formed, one light travel direction is formed. Even when observed from an angle, the same effect as when observed from a plurality of different angles is confirmed, which is desirable.

  As mentioned above, although the best form for implementing this invention was demonstrated referring an accompanying drawing, this invention is not limited only to this structure. The present invention includes various variations and modifications within the scope of the technical idea of the claimed invention, and these also belong to the technical scope of the present invention.

It is a schematic sectional drawing which shows the verification device which concerns on Embodiment 1 of this invention. It is a schematic sectional drawing which shows the security medium which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the optical path at the time of observing a security medium only using a normal polarizer. It is a figure for demonstrating the optical path at the time of observing a security medium using the verification device which concerns on Embodiment 1 of this invention. It is a schematic sectional drawing which shows the verification device which concerns on Embodiment 2 of this invention. It is a schematic sectional drawing which shows the security medium based on Embodiment 2 of this invention. It is a figure for demonstrating the optical path at the time of observing a security medium only using other normal polarizers. It is a figure for demonstrating the optical path at the time of observing a security medium using the verification device which concerns on Embodiment 2 of this invention. It is a schematic sectional drawing which shows the verification device which concerns on Embodiment 3 of this invention. It is a schematic sectional drawing which shows the verification device which concerns on Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11 Polarizing element 2 Adhesive layer 3 Optical path changing element 4 Reflective layer 5, 8 Liquid crystal layer 7 Black layer 10, 30, 50, 60 Verifier 20, 40 Security medium

Claims (11)

A verifier that performs authenticity determination using polarized light,
A polarizing element that transmits only specific polarized light;
Optical path change having a surface layer that is laminated on a part of the surface of the polarizing element and has a transparency that changes the traveling direction of light in a specific direction and has an area smaller than the area of the surface of the polarizing element. Comprising an element,
A region where only the polarizing element where the optical path changing element is not stacked is a single region, and a region where the polarizing element and the optical path changing element are stacked is a stacked region.
A verifier characterized by that.   The verifier according to claim 1, wherein the optical path changing element changes the traveling direction of light by performing at least one of light refraction, reflection, and diffraction.   The verifier according to claim 2, wherein the optical path changing element has a diffraction grating structure.   The verifier according to claim 2, wherein the optical path changing element has a lens structure.   5. The verifier according to claim 1, wherein the optical path changing element is made of a material having any one of wavelength selective reflectivity and polarization selectivity. .   The verifier according to any one of claims 1 to 5, wherein the optical path changing element has a plurality of regions in which traveling directions of light to be changed are different.   The verifier according to claim 1, wherein the polarizing element is a linear polarizer having a transmission axis that transmits only linearly polarized light in a specific direction.   The verifier according to claim 7, wherein the polarizing element has a plurality of regions having different transmission axis directions.   The verifier according to any one of claims 1 to 6, wherein the polarizing element is a circular polarizer that transmits only clockwise circularly polarized light or counterclockwise circularly polarized light.   The verifier according to claim 9, wherein the polarizing element has a plurality of regions having different rotation directions of transmitted circularly polarized light.   The said polarizing element has the area | region which has a transmission axis which permeate | transmits only linearly polarized light, and the area | region which transmits only clockwise circularly polarized light or counterclockwise circularly polarized light, The Claims 1-6 characterized by the above-mentioned. The verifier according to any one of the above.

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