JPH11277957A - Discriminative structure of papery object and method for discrimination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discriminative structure being very hard to forge, having high discriminative properties and being suitable for papery articles circulating generally, and a method for discrimination. SOLUTION: A discriminative medium having a macromolecular cholesteric liquid crystal film 1 is integrated with a papery object when this is manufactured. Thereby the discrimination making use of the characteristics of polarization by a cholesteric liquid crystal is made easily available and the discriminative properties are improved. Since the object and the discriminative medium are integrated, besides, an unfair practice of peeling off the discriminative medium from the object and sticking it to another object can be prevented. Moreover, the discriminative properties are further improved by providing a polarizing plate and a wave plate in this sequence from the incident light source side, as occasion demands, in an optical path through which an incident light on the discriminative medium and an emission light therefrom pass and by confirming the emission light visually or by a detecting device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an identification structure for identifying authenticity of paper-like objects such as passports, cards, certificates, gift certificates, paintings, tickets, public competition voting tickets, etc. More particularly, the present invention relates to a structure and a method for visually or mechanically recognizing an identification medium provided on an object to identify its authenticity.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing forgery of a card or a certificate, for example, a method of attaching a hologram to the surface of an object and visually or mechanically identifying the hologram to judge the authenticity thereof is generally used. It was a target. Further, there is a thread hologram as a hologram which is formed during paper production. This is used, for example, for gift certificates and bills.

[0003]

However, with the spread of hologram manufacturing technology in recent years, hologram manufacturing has become easier. In particular, visual (hologram) holograms that cannot be distinguished from genuine holograms have been produced. It is relatively easy to manufacture. Therefore, it cannot be denied that the forgery prevention effect of the hologram is low. In addition, other forgery prevention technology is expensive, such as commonly distributed articles,
In particular, there are few articles suitable for paper-like articles that are inexpensive and have a small number of circulations, such as gift certificates and tickets, and the development of a new forgery prevention technology has been desired.

The present invention has been devised in order to solve the above-mentioned problems of the prior art, and is extremely difficult to forge, has high discriminability, and is a paper-like article generally distributed. It is an object of the present invention to provide an object identification structure and an identification method suitable for the object.

[0005]

According to the present invention, there is provided a polymer cholesteric liquid crystal film for optically recognizing a paper-like object and identifying the authenticity of the object. A polarizing plate and a quarter-wave plate from an incident light source side in an identification structure of an object or an optical path through which incident light and reflected light of the identification medium pass, wherein the identification medium is embedded in the object. Are provided in this order, the object is identified by visually or mechanically recognizing the reflected light, and the identification structure of the object and a polymer embedded in the object A polarizing plate and a 1 /
The authenticity of the object is identified by irradiating light through a four-wavelength plate and receiving the reflected light by light-receiving means via the wavelength plate and the polarizing plate, or by visually recognizing the identification medium. The object is achieved by providing a method for identifying an object.

In general, a cholesteric liquid crystal has a layered structure, and the molecular long axis directions in each layer are parallel to each other.
And it is parallel to the layer plane. In addition, each layer is rotated and overlapped little by little to form a three-dimensional spiral structure. Selective for circularly polarized light of wavelength λ represented by λ = n · p, based on the distance until this direction factor rotates 360 ° and returns to its original state, that is, the pitch p and the average refractive index n in each layer. It has the characteristic of reflecting light. Therefore, if the direction of the liquid crystal in each layer is counterclockwise with respect to the incident light, the left circularly polarized light of the wavelength λ component is reflected and the right circularly polarized light is transmitted. In addition, all light of other wavelengths is transmitted. For example, a cholesteric liquid crystal that reflects a red wavelength λ _R is placed on a material such as black paper that absorbs visible light, and when random light such as sunlight is applied, all transmitted light is absorbed and the wavelength λ _R Since only left circularly polarized light is reflected, the cholesteric liquid crystal looks bright red.

[0007] The cholesteric liquid crystal has a characteristic that the color changes depending on the viewing angle. This is because, assuming that the incident angle with respect to the liquid crystal surface is θ, the optical path difference reflected between the surface and the bottom surface of the liquid crystal, that is, between the pitches p is 2 pcos θ.
This optical path difference becomes equal to an integral multiple of the wavelength λ (2p · co
sθ = nλ: n is an integer), and the reflected light of both overlaps and strengthens. Therefore, as the incident angle becomes shallower, the constructive wavelength becomes shorter, that is, changes from red to blue.

On the other hand, a hologram generally has a hologram forming layer formed of diffraction gratings having various pitches, and a metal reflection layer is provided on the surface. The light reflected on the surface has different angles of diffraction depending on the pitch, and thus the light looks different, the color changes, or looks three-dimensional depending on the angle. By forming the reflection layer of the hologram from cholesteric liquid crystal, the discriminability can be synergistically enhanced by utilizing the optical characteristics of both.

[0009]

Preferred embodiments of the present invention will be described below.

As shown in FIG. 1, a polymer cholesteric liquid crystal film 1 to which the present invention is applied is, for example, a card,
1 in place of paper-like object A such as passport, securities, gift certificate, etc.
One or two or more pieces are provided integrally.

Thus, the liquid crystal film 1 provided on the object is read or recognized visually or by a machine.

Here, the cholesteric liquid crystal reflects only one-directional circularly polarized light (for example, right circularly polarized light) of a specific wavelength (for example, green (λ1)), and reflects light of other wavelengths or circularly polarized light (for example, λ1) in the other direction. Left circularly polarized light) is transmitted as it is. By embedding the film 1 made of the cholesteric liquid crystal into the object A, only a certain portion of the liquid crystal film 1 out of the light from the light source (for example, natural light) has a reflected light of λ1 (green) when viewed from a specific angle. It will look like a color. Needless to say, even if an ordinary colored film is formed, a change in the color of the reflected light due to a change in the incident angle of light cannot be obtained.

Therefore, the design of the object (gift certificate, etc.) is usually visible as it is with a substantially transparent foil, but when the angle is changed, the λ1 color pattern can be seen, so that the authenticity can be confirmed visually. .

Here, in the case where the liquid crystal film 1 is formed in a strip shape, as shown in FIG. 2, for example, a slit is previously provided in the upper layer of a paper having a three-layer structure in order to cut the liquid crystal film 1. What is necessary is just to adhere | attach both layers by crimping etc. in a strip | belt shape between an intermediate | middle layer and an upper layer.

On the other hand, as another embodiment of the present invention, in order to improve the accuracy of authenticity judgment, as shown in FIG. A plate 2a and a quarter-wave plate 3a are arranged as a filter, and a polarizing plate 2 that passes only left circularly polarized light adjacent thereto.
b and the quarter-wave plate 3b may be arranged as a filter. By arranging these on the hologram foil 1, as shown in FIG. 4, the light entering the polarizing plate 2a side from the light source becomes right circularly polarized light by the polarizing plate 2a and the 波長 wavelength plate 3a. The light enters the liquid crystal film 1, is reflected by the cholesteric liquid crystal, becomes the original linearly polarized light again by the quarter-wave plate 3a, is emitted through the polarizing plate 2a, and looks bright from the outside. Further, the light entering the polarizing plate 2b side from the light source becomes left circularly polarized light by the polarizing plate 2b and the 波長 wavelength plate 3b, enters the liquid crystal film 1, passes through the cholesteric liquid crystal, and looks dark from the outside. . By viewing this from a specific angle, a clearer image can be obtained.

Here, the reflection of circularly polarized light differs between a normal surface such as a mirror and a cholesteric liquid crystal. In a normal plane, right-handed polarized light is reflected and becomes left-handed polarized light, but cholesteric liquid crystal becomes the same right-handed circularly polarized light when right-handed polarized light is reflected.
Therefore, for example, even if a film reflecting the same color as the cholesteric liquid crystal is forged, the film is cut by the polarizing plate 2a and there is no difference in contrast.

As shown in FIG. 5, the liquid crystal film 1 is a strip-shaped liquid crystal film 1a that reflects only left circularly polarized light.
And a band-shaped liquid crystal film 1b that reflects only right-handed circularly polarized light may be laid in parallel on paper, and the reflected light of both may be viewed directly or via a polarizing plate and a quarter-wave plate. In that case, it goes without saying that one band looks bright and the other band looks dark.

On the other hand, as still another embodiment of the present invention,
Automatic determination may be performed by the determination device. FIG.
As shown in FIG. 1, a light source 11 such as an LED element and a light receiving element 12 such as a photodiode are provided in an optical path of light reflected by the liquid crystal film 1, and a polarizing plate 13 similar to the above is provided on the front surface of the light source 11 and the light receiving element 12. , 1/4 wavelength plate 14 are provided. Then, the authenticity of the identification medium may be determined based on an electric signal corresponding to the light receiving intensity of the light receiving element 12.

Here, it is preferable that the liquid crystal film 1 is made of a liquid crystal that reflects infrared rays, and the light source 11 emits an infrared laser. Since infrared light does not reflect visible light and is transparent by visual observation, design restrictions are reduced. In addition, when a transparent film is simply used, the reflection of infrared rays is small, and even if a film having high reflection efficiency is used, the reflected light is converted into circularly polarized light opposite to the incident light. Since it is cut by the 波長 wavelength plate and the polarizing plate, the forgery prevention effect is enhanced.

As still another embodiment of the present invention, a hologram foil 21 using a cholesteric liquid crystal as a reflection layer may be used as an identification medium, and this may be sunk into a paper-like object A in the same manner as described above. As shown in FIG.
Are an adhesive layer 22 to the middle layer of the object A, a polymer cholesteric liquid crystal layer 23 as a reflection layer, and a hologram formation layer 24
And the protective layer 25 are laminated.
Acts as an adhesive layer to the upper layer. Thus, the hologram foil 21 provided on the object is read and recognized visually or by a machine.

In practice, if a pattern such as a character is recorded as a hologram, the light applied to the hologram foil 21 from a light source (for example, a fluorescent lamp) is diffracted, and the pattern becomes λ1 when viewed from a specific angle. (Green) color. The authenticity can be determined by this phenomenon. Further, the light diffracted by the cholesteric liquid crystal layer 23 is small. For example, if there is a pattern in the middle layer below the hologram foil 21, only the pattern is normally visible. That is, the hologram foil 21 is usually almost transparent.

Here, similarly to FIG. 3, a polarizing plate 2a and a quarter-wave plate 3a which pass only right-circularly polarized light are arranged as filters in the optical path of the incoming and outgoing light of the hologram foil 21, and are adjacent to the polarizing plate. If the polarizing plate 2b and the quarter-wave plate 3b that pass only the left circularly polarized light are arranged as filters, the hologram image can be clearly seen on the polarizing plate 2a side and the hologram image can be seen on the polarizing plate 2b side, as shown in FIG. It is almost invisible and dark. By viewing this from a specific angle, the authenticity of the identification medium can be determined.

In addition, as shown in FIGS. 9 (a) and 9 (b), a large number of light receiving sections 26a to 26h each composed of a multi-divided photodiode or the like surrounding the light source 27.
A light receiving element 26 having a specific light receiving portion (for example, 26c,
If the authenticity of the hologram foil 21 as the identification medium is determined based on the received light intensity of 26g), the identification is improved. Also in this case, needless to say, the same polarizing plate and quarter-wave plate (not shown) are provided on the front surface of the light source 27 and the light receiving element 26.

In the above embodiments, the reflection wavelength of the cholesteric liquid crystal has been described as light of wavelength λ1 (green).
Light of another wavelength may be used.

[0025]

As is apparent from the above description, according to the object identification structure and the identification method according to the present invention, the identification medium having the polymer cholesteric liquid crystal is slabbed into the paper-like object, thereby obtaining the cholesteric object. Discrimination using the polarization characteristics of the liquid crystal can be easily performed, and the discrimination property is improved. In addition, since the object and the identification medium are integrated, it is possible to prevent an unauthorized act of peeling the identification medium from the object and attaching the identification medium to another object. Furthermore, a polarizing plate and a wave plate are provided in this order from the incident light source side as needed in the optical path through which the incident light and the outgoing light pass to the identification medium, and the outgoing light is confirmed visually or by a detection device. In addition, the discriminability is further improved. In addition, since this identification medium uses only a specific polarization component of a specific wavelength of incident light for identification, that is, it can be generally almost transparent in the visible region, it also hinders the design freedom of the surface of the object. Absent. Further, there are a plurality of identification methods (for example, visual only, polarizing plate,
(Wave plate + visual observation, machine reading, etc.) is possible, so that identification according to the use and cost is possible, and its versatility is high.

[Brief description of the drawings]

FIG. 1 is a plan view showing one configuration of an object identification structure according to the present invention.

FIG. 2 is a perspective view simply showing a manufacturing process of an object having an identification structure according to the present invention.

FIG. 3 is a sectional view showing another configuration of the object identification structure according to the present invention.

FIG. 4 is a plan view showing another configuration of the object identification structure according to the present invention.

FIG. 5 is a plan view showing another configuration of the object identification structure according to the present invention.

FIG. 6 is a perspective view showing another configuration of the object identification structure according to the present invention.

FIG. 7 is a cross-sectional view of an object showing another configuration of the object identification structure according to the present invention.

FIG. 8 is a plan view showing the operation of the configuration shown in FIG. 7;

9A is a side sectional view showing another configuration of the object identification structure according to the present invention, and FIG. 9B is a plan view of the light source and the light receiving element of FIG. 9A.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid-crystal film 1a Strip-shaped liquid-crystal film which reflects only left circularly polarized light 1b Strip-shaped liquid-crystal film which reflects only right circularly polarized light 2a, 2b Polarizer 3a, 3b Quarter-wave plate 11 Light source 12 Light-receiving element 13 Polarizer 14 1 / 4 wavelength plate 21 hologram foil 22 adhesive layer 23 polymer cholesteric liquid crystal layer (reflective layer) 24 hologram forming layer 25 protective layer 26 light receiving elements 26 a to 26 h light receiving section 27 light source A target

Claims (5)

[Claims] 1. An identification medium having a high-molecular cholesteric liquid crystal film is embedded in said object in order to optically recognize a paper-like object and identify the authenticity of said object. Object identification structure. 2. A polarizing plate and a 1/4 light source from an incident light source side in an optical path through which incident light of the identification medium and reflected light thereof pass.
The object identification structure according to claim 1, wherein a wave plate is provided in this order, and the object is identified by visually or mechanically recognizing the reflected light. 3. The object identification structure according to claim 1, wherein the identification medium comprises a hologram in which a polymer cholesteric liquid crystal is provided on a reflection layer. 4. An identification medium having a polymer cholesteric liquid crystal embedded in an object is irradiated with light from an external light source via a polarizing plate and a quarter-wave plate, and the reflected light is reflected by the wavelength plate and the polarized light. A method for identifying an object, characterized in that the authenticity of the object is identified by recognizing the identification medium by receiving light with a light receiving means via a plate or visually. 5. The identification medium comprises a hologram in which a polymer cholesteric liquid crystal is provided on a reflection layer, and the reflected light is received by a light receiving unit via the wave plate and the polarizing plate, or is visually observed on the hologram. A method for identifying an object, characterized by identifying authenticity of the object by recognizing a recorded pattern or image. The method for identifying an object according to claim 4, characterized in that: