JP3652487B2 - Medium for identifying object, identification structure and identification method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an identification medium for identifying authenticity for the purpose of preventing forgery of flat objects or various three-dimensional objects such as passports, cards, certificates, gift certificates, pictures, tickets, public competition voting tickets, etc. In particular, the present invention relates to a structure and a method for identifying the authenticity of an identification medium provided on an object by visual or mechanical recognition.
[0002]
[Prior art]
Conventionally, for example, as a method for preventing forgery of cards and certificates, a method is generally used in which a hologram is attached to the surface of an object, and the authenticity is determined by visual recognition. In addition, there has also been proposed a technique in which a hologram having specific diffraction characteristics is used to eliminate visual ambiguity, light of a predetermined wavelength is irradiated on the hologram, and authenticity is determined based on the light receiving position of the diffracted light.
[0003]
[Problems to be solved by the invention]
However, with the recent popularization of hologram manufacturing technology, hologram manufacturing becomes easier, and in particular, a reproduction hologram that is indistinguishable from an authentic hologram can be manufactured relatively easily. It has become. Therefore, it cannot be denied that the anti-counterfeit effect by the hologram is low. In addition, since other anti-counterfeiting techniques are expensive, there are few that are suitable for articles in general distribution, and the development of new anti-counterfeiting techniques has been desired.
[0004]
The present invention has been devised to solve the problems of the prior art as described above, and is an object identification structure suitable for commonly circulated articles that is extremely difficult to counterfeit and has high identification characteristics. It is another object of the present invention to provide an identification medium and an identification method used therefor.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in a medium for identifying an object having a hologram forming layer for optically identifying the authenticity of the object, a polymer cholesteric is formed on the reflecting surface of the hologram forming layer. A liquid crystal reflective layer was provided. Further, a polarizing filter and a wave plate are provided in this order from the incident light source side in an optical path through which incident light to the reflecting layer made of polymer cholesteric liquid crystal and outgoing light from the reflecting layer pass. It was decided to provide an object identification structure. Further, as a method for identifying an object having a hologram forming layer for optically identifying the authenticity of the object, a reflective layer of a polymer cholesteric liquid crystal is provided on the reflecting surface of the hologram forming layer, and an external light source is provided on the reflecting layer. Light is irradiated through a polarizing filter and a wave plate, and the reflected light is received by a light receiving means through the wave plate and the polarizing filter, or an object or object by visually recognizing an image or pattern recorded on a hologram It was decided to identify the authenticity of.
[0006]
In general, the cholesteric liquid crystal has a layered structure, and the molecular long axis directions in each layer are parallel to each other and parallel to the layer surface. Each layer is rotated and overlapped little by little and has a three-dimensional spiral structure. Selectable for circularly polarized light of wavelength λ represented by λ = n · p from the distance until this directional factor rotates 360 °, that is, the pitch p and the average refractive index n in each layer It has the characteristic of reflecting. Therefore, if the direction of the liquid crystal in each layer is counterclockwise with respect to the incident light, the left circularly polarized light having the wavelength λ is reflected and the right circularly polarized light is transmitted. All other wavelengths of light are transmitted. For example, if a cholesteric liquid crystal that reflects the red wavelength λ _R is placed on a material such as black paper that absorbs visible light, and if random light such as sunlight is applied, all transmitted light is absorbed, and the wavelength λ _R Since only the left circularly polarized light is reflected, the cholesteric liquid crystal looks bright red.
[0007]
Further, cholesteric liquid crystal has a feature that the color changes depending on the viewing angle. When the incident angle with respect to the liquid crystal surface is θ, the optical path difference reflected between the surface and bottom surface of the liquid crystal, that is, the pitch p is 2 pcos θ. When this optical path difference becomes equal to an integral multiple of the wavelength λ (2p · cos θ = nλ n is an integer), the reflected lights of both overlap and strengthen each other. Therefore, the strengthening wavelength is shorter as the incident angle becomes shallower, that is, changes from red to blue.
[0008]
On the other hand, in general, a hologram forming layer is a diffraction grating with various pitches and a metal reflection layer is attached to the surface of the hologram. The angle of diffraction of the light reflected from the surface varies depending on the pitch, so that the appearance of the light varies depending on the angle, the color changes, or the image looks three-dimensional. Therefore, in the present invention, the hologram reflection layer is formed of cholesteric liquid crystal, and the discriminating property is synergistically improved by utilizing the optical characteristics of the both.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
[0010]
As shown in FIG. 1, one or two or more hologram foils 1 to which the present invention is applied are attached to an appropriate place or the whole of an object A such as a card, passport, securities, and gift certificate by, for example, a hot stamp method. Here, hot stamping is a method of transferring a decorative thin film to the surface of an object by instantaneous heat and pressure. Further, as shown in an enlarged view in FIG. 2, the hologram foil 1 is formed by laminating an adhesive layer 2 to the surface of the object A, a polymer cholesteric liquid crystal layer 3 as a reflective layer, a hologram forming layer 4 and a protective layer 5. When the hot stamp is pressed, the protective layer 5 serving also as a release layer is separated from the base film (not shown) by the pressure and heat, and the hologram foil 1 is transferred to the object A.
[0011]
Thus, the hologram foil 1 provided on the object is read or recognized visually or by a machine.
[0012]
In addition, as a method of sticking the hologram foil 1 as an identification medium to an object, there are a heat sealing method, a roll-type hand sticking seal and the like in addition to the hot stamp.
[0013]
Here, the cholesteric liquid crystal reflects only one direction of circularly polarized light (for example, right circularly polarized light) of a specific wavelength (for example, green (λ1)), and other wavelengths of light or λ1 of circularly polarized light (left circle). (Polarized light) is transmitted as it is. By using this cholesteric liquid crystal layer 3 as a hologram reflection layer, if a pattern such as a letter is recorded as a hologram, the light irradiated on the hologram foil 1 from a light source (for example, a fluorescent lamp) is diffracted, and from a specific angle. When viewed, the pattern appears to be pale in λ1 (green) color. The authenticity can be determined by this phenomenon. Further, the amount of light diffracted by the cholesteric liquid crystal layer 3 is small. For example, if there is a pattern on the surface of the object A under the hologram foil 1, only the pattern is usually visible as it is. That is, the hologram foil 1 is usually almost transparent.
[0014]
Therefore, although the design of the object (such as a gift certificate) can be seen as it is with a substantially transparent foil, the authenticity can be confirmed by visual observation because the hologram pattern appears in λ1 color when the angle is changed.
[0015]
On the other hand, as another embodiment of the present invention, in order to improve the accuracy of authenticity determination, as shown in FIG. 3, in the optical path of incident / exited light of the hologram foil 1, a bandpass filter 7, polarizing filters 8 and 1 A detection device composed of the / 4 wavelength plate 9 may be arranged from the light source side. By arranging these on the hologram foil 1, natural light (sunlight, fluorescent lamps, etc.) is transmitted through the band-pass filter 7 only for the light of λ1 (green), and then the polarizing filter 8 and the quarter-wave plate 9. It becomes right circular polarization. This λ1 · right polarized light enters the foil, and the cholesteric liquid crystal of the hologram reflects only the right circularly polarized light having the wavelength of λ1. Then, it becomes the original linearly polarized light again by the quarter wavelength plate 9 and is emitted through the polarizing filter 8 and the band pass filter 7. By visually recognizing this (hologram image) from a specific angle, a clearer image can be obtained. At this time, light of other wavelengths and polarized light in other directions are cut by the bandpass filter 7 and the polarization filter 8 and do not reach the hologram. Therefore, when this detection element is placed, a specific wavelength, for example, λ1 (green) ) Only the color hologram pattern will be clearly visible. Even if the bandpass filter 7 is not provided, substantially the same operation and effect can be obtained, but the pattern becomes clearer when the bandpass filter is interposed.
[0016]
Here, the reflection of circularly polarized light differs between, for example, a normal surface such as a mirror and a cholesteric liquid crystal. In the normal plane, right circularly polarized light is reflected to become left circularly polarized light, but cholesteric liquid crystal becomes the same right circularly polarized light when the right circularly polarized light is reflected. Therefore, for example, even if a hologram is forged and a film that reflects the same color as the cholesteric liquid crystal is provided, the light is cut by the polarizing filter 8 shown in FIG.
[0017]
On the other hand, as still another embodiment of the present invention, automatic determination may be performed by a determination device. As shown in FIG. 5, a light source 11 such as an LED element is used, and a light receiving element 12 such as a photodiode is provided at a position where a hologram image is obtained by the hologram foil 1. A filter 13 and a quarter-wave plate 14 are provided. Then, the authenticity of the hologram foil 1 as the identification medium may be determined based on the light receiving intensity of the light receiving element 12. However, in this structure, even if the total reflection surface is formed by the cholesteric liquid crystal, although the intensity is slightly weakened, there is a possibility that a similar detection result may be obtained. Therefore, as shown in FIGS. 6 (a) and 6 (b). As described above, the light receiving element 16 having a large number of light receiving portions 16a to 16h made of photodiodes or the like that are divided into multiple portions so as to surround the light source 15 is arranged, and a specific light receiving portion corresponding to the hologram image by the hologram foil 1 is arranged. If the authenticity of the hologram foil 1 as an identification medium is discriminated based on the received light intensity (for example, 16c and 16g), the discriminability is improved. Also in this case, it goes without saying that the same polarizing filter and quarter wave plate (not shown) are provided on the front surfaces of the light source 15 and the light receiving element 16. However, the band-pass filter is not necessary if the emitted light from the light source is monochromatic light having a wavelength that is reflected by the cholesteric liquid crystal. Therefore, light of other wavelengths is not necessarily required because most of the light is cut by the polarizing filter.
[0018]
In each of the above embodiments, the reflection wavelength of the cholesteric liquid crystal has been described as light having a wavelength of λ1 (green). For example, the hologram is visually transparent, and the presence of the identification medium can be confirmed only by using the detection device, and the identification of the object is further improved.
[0019]
In addition, the hologram foil described above makes the cholesteric liquid crystal and the hologram forming layer weaker than the adhesive layer, so that the hologram forming layer or the cholesteric liquid crystal layer is destroyed when it is peeled off once and cannot be reused. Can prevent fraud.
[0020]
【The invention's effect】
As is clear from the above description, according to the object identification medium, the identification structure, and the identification method according to the present invention, the incident light and the emitted light of the identification medium composed of a hologram provided with a polymer cholesteric liquid crystal in the reflection layer are emitted. If necessary, a polarizing filter and a wave plate are provided in this order from the incident light source side in the passing optical path, and the hologram image by the emitted light is confirmed visually or by a detection device. It is possible to discriminate in combination with the diffraction characteristics by the method, and the discriminability is improved. Further, since this identification medium uses only a specific polarization component of a specific wavelength of incident light for identification, that is, it is usually almost transparent in the visible region, it does not hinder the degree of design freedom of the surface of the object. In addition, since a plurality of identification methods (for example, visual observation only, polarizing filter, wave plate + visual observation, machine reading, etc.) are possible, identification according to use and cost is possible, and its versatility is high.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a basic configuration of an object provided with an identification medium according to the present invention.
FIG. 2 is an enlarged sectional view showing the structure of an identification medium according to the present invention.
FIG. 3 is a side view showing one configuration of an object identification structure according to the present invention.
4 is a side view similar to FIG. 3 showing the operation of the identification structure of FIG. 3;
FIG. 5 is a side view showing another configuration of the object identification structure according to the present invention.
6A is a side view showing still another configuration of the object identification structure according to the present invention, and FIG. 6B is a plan view of the light source and the light receiving element of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Hologram foil 2 Adhesion layer 3 Polymer cholesteric liquid crystal layer 4 Hologram formation layer 5 Protective layer 7 Band pass filter 8 Polarization filter 9 1/4 wavelength plate 11 Light source 12 Light receiving element 13 Polarization filter 14 1/4 wavelength plate 15 Light source 16 Light reception Element 16a-16h Light-receiving part A Object

Claims (5)

A medium for identifying an object having a hologram forming layer for optically identifying the authenticity of the object,
A medium for identifying an object, wherein a reflection layer of a polymer cholesteric liquid crystal is provided on a reflection surface of the hologram forming layer . 2. The medium for identifying an object according to claim 1, wherein a part or all of the hologram is destroyed when peeled off. An object identification structure having a hologram forming layer to optically identify the authenticity of the object,
A reflective layer of polymer cholesteric liquid crystal is provided on the reflective surface of the hologram forming layer, and a polarizing filter and a wave plate are provided from the incident light source side in the optical path through which incident light to the reflective layer and outgoing light from the reflective layer pass. An object identification structure characterized by being provided in this order. Object according to claim 3, characterized in that the band-pass filter to the position of the incident light source closer is further provided than the incident light and the polarization filter and the wavelength plate in an optical path emitted light passes Identification structure. A method for identifying an object having a hologram forming layer to optically identify the authenticity of the object,
The reflective layer of the high polymer cholesteric liquid crystal disposed on the reflecting surface of the hologram forming layer, irradiating light through a polarizing filter and a wave plate from an external light source to the reflective layer, via the reflected light and the wavelength plate and a polarizing filter A method for identifying an object, wherein the authenticity of the object is identified by recognizing an image or a pattern recorded on the hologram by light reception by a light receiving means or by visual observation.

Images