JP2004117682A - Optical diffraction structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical diffraction structure which is viewed normally as a transparent film, but makes it possible to view an image by the optical diffraction structure when viewed through a linear polarizing plate. <P>SOLUTION: This optical diffraction structure has an optical diffraction structure 3 formed of an uneven relief pattern, and the optical diffraction structure 3 is formed on a layer surface of a transparent medium 1 which has refractive index anisotropy and a layer of an isotropic transparent medium 2 having a refractive index nearly equal to the refractive index of the transparent medium 1 in a specified direction is provided on the optical diffraction structure 3. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light diffraction structure, and more particularly to a light diffraction structure such as a hologram and a diffraction grating used for forgery prevention.
[0002]
[Prior art]
Conventionally, holograms have excellent design properties and are difficult to forge or falsify even in color copiers, so they are often used in personal certificates, guarantees, certificates, etc., such as various vouchers and ID cards. Has been used. However, in recent years, forgery of holograms has been increasing, and the effect of preventing forgery of holograms has been reduced.
[0003]
[Problems to be solved by the invention]
The present invention has been made in view of such a problem of the prior art, and has an object to provide an image formed by a light diffractive structure when viewed through a linearly polarizing plate, although it appears as a transparent film when viewed normally. Is to provide a light diffraction structure that can be visually recognized.
[0004]
Another object of the present invention is to allow an image of a reflection type light diffraction structure to be visually recognized when viewed normally, and to visually recognize an image formed by another new light diffraction structure when viewed through a linear polarizer. It is an object of the present invention to provide a light diffractive structure.
[0005]
[Means for Solving the Problems]
The light diffractive structure according to the present invention that achieves the above first object is obtained by embossing a light diffractive structure on a film having a refractive index anisotropy, and then refracting the film in a specific direction (ordinary ray or ordinary light). By providing an isotropic reflective layer having a refractive index equal to the refractive index for extraordinary rays, the brightness of the image due to the light diffraction structure is usually low and cannot be visually recognized, but when viewed through a linear polarizing plate, the light diffraction The brightness of the image is improved by the structure, and the image can be visually recognized.
[0006]
In this case, it is desirable to use a film having a refractive index anisotropy having a difference between the refractive index for ordinary light and the refractive index for extraordinary light of 0.1 or more, preferably 0.3 or more.
[0007]
The light diffractive structure according to the present invention that achieves the above second object is obtained by embossing a light diffractive structure on a film having a refractive index anisotropy, and then refracting the film in a specific direction (ordinary ray or ordinary light). An isotropic first reflective layer having a refractive index equal to the refractive index for extraordinary rays) is provided. Further, the first reflection layer is embossed with another light diffraction structure to provide a second reflection layer. The second reflection layer is made of TiO, in addition to a metal reflection layer of Al or the like. ₂ A transparent layer having a different refractive index from the first reflective layer may be used.
[0008]
Also in this case, it is desirable to use a film having a refractive index anisotropy having a difference between the refractive index for ordinary light and the refractive index for extraordinary light of 0.1 or more, preferably 0.3 or more.
[0009]
That is, the light diffraction structure of the present invention, in a light diffraction structure having a light diffraction structure consisting of a relief pattern uneven,
The light diffraction structure is formed on a surface of a layer of a transparent medium having a refractive index anisotropy, and a layer of an isotropic transparent medium having a refractive index substantially equal to a refractive index in a specific direction of the transparent medium is formed by the light diffraction structure. It is characterized by being provided above.
[0010]
In this case, it is desirable that the difference between the refractive index of the transparent medium having the refractive index anisotropy for ordinary rays and the refractive index for extraordinary rays is 0.1 or more.
[0011]
Another light diffraction structure of the present invention is a light diffraction structure having a light diffraction structure composed of a relief pattern,
The light diffraction structure includes a first light diffraction structure and a second light diffraction structure, wherein the first light diffraction structure is formed on a layer surface of a first transparent medium having a refractive index anisotropy, and A layer of an isotropic second transparent medium having a refractive index substantially equal to a refractive index in a specific direction of the medium is provided on the light diffraction structure, and the second light diffraction structure is provided with an isotropic third transparent medium. It is formed on a layer surface of a medium, and a reflection layer is provided on the second light diffraction structure.
[0012]
In this case, the difference between the refractive index of the first transparent medium having the refractive index anisotropy with respect to the ordinary ray and the refractive index with respect to the extraordinary ray is desirably 0.1 or more.
[0013]
Further, it is preferable that the reflection layer is formed of a layer of a fourth transparent medium having a refractive index different from that of the third transparent medium, or is formed of a metal reflection layer.
[0014]
Further, the layer of the second transparent medium and the layer of the third transparent medium may be the same layer.
[0015]
Still another light diffraction structure of the present invention is a light diffraction structure having a light diffraction structure composed of an uneven relief pattern,
A transparent medium having a plurality of light diffraction structures as the light diffraction structure, wherein at least two of the light diffraction structures are formed on a layer surface of a transparent medium having a refractive index anisotropy, and each of the light diffraction structures has a refractive index anisotropy. A layer of an isotropic transparent medium having a refractive index substantially equal to the refractive index of a specific direction is provided on each light diffraction structure, and the specific directions of the transparent medium having each refractive index anisotropy are mutually different. It is characterized by being laminated in different directions.
[0016]
In this case, it is desirable that the difference between the refractive index of the transparent medium having each refractive index anisotropy with respect to the ordinary ray and the refractive index with respect to the extraordinary ray is 0.1 or more.
[0017]
In the present invention, an optically diffractive structure is formed on the surface of a layer of a transparent medium having refractive index anisotropy, and a layer of an isotropic transparent medium having a refractive index substantially equal to the refractive index of the transparent medium in a specific direction is formed. Because it is provided on the light diffraction structure, the image due to the light diffraction structure cannot be clearly seen under normal natural light, and the image due to the light diffraction structure must be clearly seen when viewed through a linear polarizer. Thus, an anti-counterfeiting effect can be improved, and a light diffraction structure excellent in design can be obtained.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, some embodiments of the light diffraction structure according to the present invention will be described.
[0019]
In general, a transparent light diffractive structure composed of a conventional relief hologram or diffraction grating has a light diffractive structure forming layer 1 (refractive index n) as shown in a sectional view of FIG. _p ) Is embossed to form an uneven relief pattern 3 on the surface thereof, and has a refractive index (n) different from that of the light diffraction structure forming layer 1. _r ) Is formed along the uneven relief pattern 3, Fresnel reflection occurs at the interface between the light diffraction structure forming layer 1 and the reflection layer 2, and the light is diffracted by the diffracted light from the relief pattern 3. An image by the structure is visually recognized.
[0020]
On the other hand, in the first light diffraction structure according to the present invention, as shown in the sectional view of FIG. 1A, the light diffraction structure forming layer 1 has a refractive index anisotropy (ordinary refractive index n). ₁ , Extraordinary ray refractive index n ₂ (N ₁ ≠ n ₂ The light diffraction structure forming layer 1 is embossed to form an uneven relief pattern 3 on its surface. As a result, the light diffraction structure forming layer 1 has a different refractive index depending on the polarization direction of the incident light. Therefore, the refractive index n of the light diffraction structure forming layer 1 with respect to ordinary rays ₁ When the reflective layer 2 having the same refractive index as that of FIG. 1 is formed along the relief pattern 3 having irregularities, the incident light 4 of the linearly polarized light component in the direction of the ordinary ray has no refractive index difference at the interface with the reflective layer 2. As shown in (b), no reflected light is generated, and the light is transmitted as the transmitted light 5, so that the image by the light diffraction structure cannot be visually recognized.
[0021]
However, the incident light 6 of the linearly polarized component in the direction of the extraordinary ray has a refractive index difference at the interface with the reflective layer 2, so that reflected light 7 is generated as shown in FIG. The image by the light diffraction structure can be visually recognized by the diffracted light by the reflected light 7.
[0022]
Normal natural light contains light of an arbitrary polarization component, and even if the first light diffraction structure of the present invention is viewed under natural light, the reflected light of the extraordinary ray is reflected by another reflected light (transmitted through the reflective layer 2). Light 5 reflected by the substrate or the like) and cannot be clearly seen.
[0023]
However, by arranging the linear polarizing plate on the observation side in the same polarization direction as the extraordinary ray, and seeing the reflected light 7 transmitted through the polarizing plate, the image by the light diffraction structure can be clearly recognized. As compared with the conventional reflection type hologram or reflection type diffraction grating as shown in FIG. 3, an anti-counterfeiting effect can be improved and an optical diffraction structure excellent in design can be provided.
[0024]
Further, in the second optical diffraction structure according to the present invention, as shown in the sectional view of FIG. 2A, the reflection layer 2 of the optical diffraction structure having the configuration of FIG. Is formed, and the second reflective layer 12 is provided thereunder. That is, in this case, as the first light diffraction structure forming layer 1, the refractive index anisotropy (ordinary refractive index n ₁ , Extraordinary ray refractive index n ₂ (N ₁ ≠ n ₂ The first light diffraction structure forming layer 1 is embossed to form a first concave-convex relief pattern 3 on the surface thereof. As a result, the first light diffraction structure forming layer 1 has a different refractive index depending on the polarization direction of the incident light. Then, the refractive index n of the first light diffraction structure forming layer 1 with respect to ordinary light. ₁ The first reflective layer 2 having the same refractive index as that of the first concave and convex portions is formed along the first uneven relief pattern 3. Next, the first reflection layer 2 is used as a second light diffraction structure forming layer 2, and the second light diffraction structure forming layer 2 is embossed to form a second relief pattern 13 having irregularities on its surface. The second reflection layer 12 is provided below. The second reflection layer 12 is a metal reflection layer of Al or the like, or TiO. ₂ Transparent layer (n) having a different refractive index from the first reflective layer 2 such as ₃ ).
[0025]
In the second light diffractive structure according to the present invention, the incident light 4 of the linearly polarized light component in the direction of the ordinary ray has no refractive index difference at the interface with the first reflection layer 2, and is shown in FIG. As described above, no reflected light is generated from the first uneven relief pattern 3, the transmitted light is reflected by the second uneven relief pattern 13, and the second light diffraction structure forming layer 2 is diffracted by the reflected light 8. The image of the second concave-convex relief pattern 13 can be visually recognized.
[0026]
In addition, since the incident light 6 of the linearly polarized component in the direction of the extraordinary ray has a refractive index difference at the interface between the first light diffraction structure forming layer 1 and the first reflection layer 2, as shown in FIG. Reflected light 7 is generated, and the first concave-convex relief pattern 3 can be visually recognized by being superimposed on the image of the second concave-convex relief pattern 13 by the diffracted light of the reflected light 7 from the first concave-convex relief pattern 3.
[0027]
Normal natural light contains light having an arbitrary polarization component. Even when the second light diffraction structure of the present invention is viewed under natural light, reflected light 7 from the first reflective layer 2 due to extraordinary light is different from other light. (Reflected light 8 from the second reflective layer 12, or reflected light from the base material, etc.) and cannot be clearly seen.
[0028]
However, by arranging the linear polarizing plate on the observation side in the same polarization direction as the extraordinary ray, and seeing the reflected light 7 transmitted through the polarizing plate, the reflected light from the first reflective layer 2, namely, At the same time, the image of the first uneven pattern of the relief pattern 3 can be visually recognized, and at the same time, the light transmitted through the first reflective layer 2 and reflected from the second reflective layer 12 can be visually recognized. As a result, an image based on the relief pattern 3 having the first unevenness is newly added to the image based on the relief pattern 13 having the second unevenness which was viewed under natural light, and can be visually recognized. With respect to the reflection type hologram or the reflection type diffraction grating described above, an anti-counterfeiting effect can be improved and an optical diffraction structure excellent in design can be provided.
[0029]
Next, as a typical example of the material having the refractive index anisotropy used for the light diffraction structure forming layer (first light diffraction structure forming layer) 1, a stretched film such as a uniaxially stretched film or a biaxially stretched film is used. Is raised. Materials include polyethylene resin, polypropylene resin, polymethylpentene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, vinyl chloride-vinyl acetate copolymer resin, ethylene-vinyl acetate copolymer resin, ethylene-vinyl alcohol Representative examples include copolymer resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polyethylene naphthalate-isophthalate copolymer resins, polymethyl methacrylate resins, polyethyl methacrylate resins, polybutyl acrylate resins, nylon 6 or nylon 66, and the like. Polyamide resin, cellulose triacetate resin, cellophane, polystyrene resin, polycarbonate resin, polyarylate resin, polyimide resin, polysulfone resin, etc. can be used. The liquid crystal film made from can also be used.
[0030]
Various types of light diffraction structures such as holograms and diffraction grating patterns can be used as the light-diffraction structure as the uneven relief pattern (the first uneven relief pattern 3 and the first uneven relief pattern 13). , Patterns similar to those used in this field, and any patterns. The pattern itself can be obtained by calculating a hologram diffraction grating, or by using a holographic stereogram technique or the like, from a two-dimensional or three-dimensional image data obtained from a digital image captured by a digital camera or computer graphics, in addition to capturing the actual object. It can be created by appropriate means.
[0031]
In addition, as the embossing of such a light diffraction structure, a flat press method using a lithographic uneven shape obtained by copying unevenness of the light diffraction structure by plating or a roll press method using an uneven shape on a roll is used. Accordingly, the light diffraction structure forming layers (the first light diffraction structure forming layer 1 and the second light diffraction structure forming layer 2) can be heated and pressed while being brought into contact with the concavo-convex mold.
[0032]
The reflective layer (first reflective layer) 2 has the same refractive index as that of the above-mentioned light diffraction structure forming layer (first light diffraction structure forming layer) 1 for ordinary rays or extraordinary rays, Any material having no refractive index anisotropy may be used. The specific material to be used is selected according to the optical characteristics of the light diffractive structure forming layer 1, and as a usable material, for example, polyethylene (polyethylene (PE), ethylene-vinyl acetate copolymer (EVA) ), Vinyl chloride-vinyl acetate copolymer], polypropylene (PP), vinyl (polyvinyl chloride (PVC), polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinylidene chloride (PVdC), polyvinyl acetate ( PVAc), polyvinyl formal (PVF)], polystyrene [polystyrene (PS), styrene-acrylonitrile copolymer (AS), acrylonitrile-butadiene-styrene copolymer (ABS)], acrylic [polymethyl methacrylate (PMMA) , MMA-styrene copolymer], polycarbonate (PC), cellulose [ethylcellulose (EC), cellulose acetate (CA), propylcellulose (CP), acetic acid / cellulose acetate (CAB), cellulose nitrate (CN)], fluorine-based [polychlorofluoroethylene (PCTFE) ), Polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), polyvinylidene fluoride (PVdF)], urethane type (PU), nylon type [type 6, type 66, type 610, type 11], and thermoplastic resins such as polyester (alkyd) type [polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT)], and novolak type phenol resin.
[0033]
In addition, thermosetting resins such as resol-type phenolic resins, urea resins, melamine resins, polyurethane resins, epoxies, unsaturated polyesters, and natural resins such as proteins, rubber, shellac, copal, starch, and rosin may also be used. it can.
[0034]
Further, these resins can be emulsions for waterborne coatings. Examples of emulsions for aqueous coatings include vinyl acetate (homo) emulsion, vinyl acetate-acrylate copolymer emulsion, vinyl acetate-ethylene copolymer resin emulsion (EVA emulsion), and vinyl acetate-vinyl versatate copolymer resin emulsion. , Vinyl acetate-polyvinyl alcohol copolymer resin emulsion, vinyl acetate-vinyl chloride copolymer resin emulsion, acrylic emulsion, acrylic silicone emulsion, styrene-acryl copolymer resin emulsion, polystyrene emulsion, urethane emulsion, chlorinated polyolefin emulsion, epoxy-acrylic dispersion John, SBR latex or the like can be used.
[0035]
The second reflective layer 12 can be classified into the following two types according to its appearance.
[0036]
a) Silver type
The reflective layer has a mirror surface. As a material of the light reflecting layer, aluminum (Al), zinc (Zn), indium (In), gold (Au), silver (Ag), cobalt (Co), tin (Sn), selenium (Se), titanium ( Simple metals such as Ti), iron (Fe), tellurium (Te), copper (Cu), lead (Pb), nickel (Ni), and palladium (Pd), or alloys thereof.
[0037]
Examples of the method for forming the thin film of the light reflecting layer include a thin film forming method such as a vacuum evaporation method, a sputtering method, and an ion plating method. Appropriate conditions may be set for the thin film depending on the color tone, design, application, etc., but the thickness is preferably in the range of 50 ° to 1 μm, and more preferably 100 to 1000 °. When it is desired to provide a colored light reflecting layer having transparency, the film thickness is preferably 200 ° or less. When it is desired to provide a colored light reflecting layer having a concealing property, the film thickness is desirably 200 mm or more. As described above, the thin film can be set as necessary in consideration of the application of the light diffraction structure and the total design, as required, such as color tone, concealing property, and transparency.
[0038]
b) Transparent type
An image by the light diffraction structure appears to emerge on the transparent layer. Materials for forming the transparent vapor-deposited layer are conventionally known materials, for example, ZnS, TiO. ₂ , SiO ₂ , Cr ₂ O ₃ And the like, and are not particularly limited. In addition, it can be formed by a method similar to a conventional method such as a vacuum evaporation method and a sputtering method. The thickness is preferably in the range of 50 to 500 °, particularly preferably in the range of 100 to 400 °.
[0039]
In addition, the following forms can be considered as modifications of the light diffraction structure of the present invention, particularly, the light diffraction structure of FIG.
[0040]
a) The second light diffraction structure (the second relief pattern 13 having irregularities) is not provided on the first reflection layer 2, but another second light diffraction structure formation layer is newly provided, and the second light diffraction structure formation layer is provided. Then, a second light diffraction structure (second relief pattern 13 with irregularities) is formed. By using an isotropic material for the second light diffraction structure forming layer, the same function and effect as described above can be obtained. In this case, as a processing step, the first reflection layer 2 is formed in the same manner as in FIG. 1, and the second light diffraction structure (second relief pattern 13 of the second unevenness) is formed on the separately prepared second light diffraction structure forming layer. After the second reflection layer 12 is provided along the second light diffraction structure, the second reflection layer 12 may be bonded to the first reflection layer 2.
[0041]
b) When the above-mentioned transparent type is used as the second reflection layer 12, the second light diffraction structure forming layer provided with the second reflection layer 12 is provided on the first light diffraction structure formation layer 1. The same operation and effect can be obtained.
[0042]
c) The second light diffraction structure forming layer and the second reflection layer 12 (the second diffraction structure) are different in refractive index similarly to the first light diffraction structure formation layer 1 and the first reflection layer 2 (the first diffraction structure). It is formed by using a material having anisotropy, and is arranged in a direction in which an image of each light diffraction structure can be visually recognized by linearly polarized light in different directions (preferably orthogonal directions). With this configuration, when the linear polarizing plate is rotated (preferably rotated in an orthogonal angle range) when viewed through the linear polarizing plate, the images of the first diffraction structure and the second diffraction structure alternate. Recognized, it is possible to provide higher designability and forgery prevention effect. Furthermore, it is also possible to laminate three or more layers by changing the direction of linearly polarized light.
[0043]
Hereinafter, specific examples of the light diffraction structure of the present invention will be described.
(Specific example 1)
50 μm thick 2,6-polyethylene naphthalate (PEN) film (ordinary refractive index n ₁ = 1.64, extraordinary ray refractive index n ₂ = 1.88) as a material, and a hologram-type uneven surface having fine unevenness of a relief hologram on its surface was applied to the above-mentioned film and heated and pressed to give an uneven shape of the hologram. After the formation of the irregularities, PEN and a copolyester of naphthalate 70 / terephthalate 30 (coPEN) (refractive index n = 1.64) were formed on the surface of the formed irregularities so as to have a thickness of 1 μm.
[0044]
In this state, the hologram image could not be seen in the thus obtained light diffraction structure, but the hologram image could be visualized and viewed by looking through the linear polarizing plate.
(Specific example 2)
50 μm thick 2,6-polyethylene naphthalate (PEN) film (ordinary refractive index n ₁ = 1.64, extraordinary ray refractive index n ₂ = 1.88) as a material, and a hologram-type uneven surface having fine unevenness of a relief hologram on its surface was applied to the above-mentioned film and heated and pressed to give an uneven shape of the hologram. After the formation of the irregularities, PEN and a copolyester (coPEN) of naphthalate 70 / terephthalate 30 (refractive index n = 1.64) were formed on the surface of the formed irregularities so as to have a thickness of 2 μm.
[0045]
Further, the concave / convex shape of the second hologram was formed on the coPEN surface by the same method, and aluminum was formed on the concave / convex surface to have a thickness of 30 nm.
[0046]
In this state, only the second hologram image can be seen in the light diffraction structure thus obtained, and the first hologram image is visualized by viewing through the linear polarizing plate, and both hologram images are visualized. The image could be seen at the same time.
[0047]
By the way, the adherend to which the light diffraction structure of the present invention is applied includes an ID (identification) card, for example, a savings card at a bank, a credit card, an identification card (student ID or employee ID), Although it is not in a card format, there are an examination card for ID, a passport, and the like. If a savings card or a credit card of a bank or the like is used improperly, it damages a legitimate holder (or contractor) and a financial institution, a store, a credit company, and the like.
[0048]
The light diffraction structure of the present invention can be applied to bills, gift certificates, stock certificates, securities, and the like. These can result in losses based on par value, and sometimes speculative value, when used fraudulently. The optical diffraction structure of the present invention is also applicable to a driver's license, a card-type certificate, for example, a certificate indicating fire protection, disinfection, fire protection or the like, or a qualification or grade for hygiene. Although these are intended to prevent unauthorized persons from being involved, unauthorized use may lead to danger or a crime. For winning lottery tickets, horse races, bicycle races, etc., even after winning the competition, the winning ticket has a monetary value, and forgery or falsification leads to fraud. The application of the structure is valid.
[0049]
Since the light diffraction structure of the present invention having the configuration of FIG. 1 is transparent, the light diffraction structure of the present invention is applied to a portion where information such as a face photograph, an ID number, etc., which is particularly lossy when altered, is provided. By sticking the body, the effectiveness can be further improved. In addition, by providing a relationship between the pattern, characters, and the like shown on the adherend and the pattern formed on the light diffraction structure of the present invention, it is possible to improve the determination accuracy, add value such as improving the design. Can also be added.
[0050]
In the case of the light diffraction structure of the present invention having the configuration shown in FIG. 2, if the second reflective layer 12 is of a transparent type, the pattern of the adherend can always be visually recognized. By sticking the optical diffraction structure of the present invention to a portion to which information having a large loss when altered is provided, the effectiveness can be further improved. In addition, by providing a relationship between the pattern, characters, and the like shown on the adherend and the pattern formed on the light diffraction structure of the present invention, it is possible to improve the determination accuracy, add value such as improving the design. Can also be added.
[0051]
In addition to these, the light diffractive structure of the present invention can be used in boxes, cases, bags, and the like of luxury watches, jewelry, precious metals, antiques, and the like. It can be applied by affixing or the like utilizing the fact that it is high. In addition, copies of software such as music software, video software, computer software, or game software recorded on magnetic or optical recording media may also be illegally copied without obtaining proper copyright permission. If this is the case, the financial loss of the copyright holder or publisher will be large, and the optical diffraction structure of the present invention can be applied to such a recording medium or its box or case.
[0052]
As described above, the light diffraction structure of the present invention can be applied to various uses, and the shape and material of the adherend are various. In order to be applicable to various uses, it is preferable that it is in the form of a sticking label having an adhesive layer or a transfer sheet for transfer. The adherend is not limited to an opaque one, and may be a transparent one.
[0053]
When the authenticity identification body (light diffraction structure) of the present invention is formed in a label shape, one of the layers constituting the label is set as a layer having a low tensile strength, and if the layer is to be peeled off, the layer is broken from the layer. A brittle label may be used. Alternatively, when the adhesive strength between the label body and the adhesive layer is partially changed, and the label once applied is to be peeled off, a part of the adhesive layer remains on the adherend and the peeling is also performed. If you try to attach the other label to another adherent (often unauthentic intentions), not only is it not possible to apply smoothly because part of the adhesive layer is missing, An arrangement may be made in which unevenness is caused by the presence or absence of the agent layer, or non-uniformity of the adhesive layer when viewed from above the label.
[0054]
The light diffractive structure of the present invention has been described based on its principle and embodiments, but the present invention is not limited to these embodiments, and various modifications are possible.
[0055]
【The invention's effect】
As is clear from the above description, according to the light diffraction structure of the present invention, the light diffraction structure is formed on the layer surface of the transparent medium having the refractive index anisotropy, and the refractive index of the transparent medium is substantially equal to the refractive index in a specific direction. Since an isotropic transparent medium layer having an equal refractive index is provided on the light diffraction structure, an image by the light diffraction structure cannot be clearly recognized under normal natural light, and the light is transmitted through a linear polarizing plate. When viewed, the image obtained by the light diffraction structure can be clearly recognized, and the light diffraction structure having improved anti-counterfeiting effect and excellent design can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining the configuration and operation of a first optical diffraction structure according to the present invention.
FIG. 2 is a diagram for explaining the configuration and operation of a second light diffraction structure according to the present invention.
FIG. 3 is a diagram for explaining the configuration and operation of a second conventional light diffraction structure.
[Explanation of symbols]
1. Light diffraction structure forming layer (first light diffraction structure forming layer)
2. Reflective layer (first reflective layer, second light diffraction structure forming layer)
3. Relief pattern of unevenness (relief pattern of first unevenness)
4: Incident light of linear polarization component in the direction of ordinary light
5: transmitted light
6: Incident light of the linearly polarized light component in the direction of the extraordinary ray
7 ... Reflected light
8 ... reflected light
12: second reflective layer
13: relief pattern of second irregularities

Claims (9)

In a light diffraction structure having a light diffraction structure consisting of an uneven relief pattern,
The light diffraction structure is formed on the surface of a transparent medium layer having a refractive index anisotropy, and the isotropic transparent medium layer having a refractive index substantially equal to the refractive index in a specific direction of the transparent medium is formed on the light diffraction structure. An optical diffraction structure provided on the light diffraction structure. The optical diffraction structure according to claim 1, wherein a difference between a refractive index of the transparent medium having the refractive index anisotropy with respect to an ordinary ray and a refractive index with respect to an extraordinary ray is 0.1 or more. In a light diffraction structure having a light diffraction structure composed of an uneven relief pattern,
The light diffraction structure includes a first light diffraction structure and a second light diffraction structure, wherein the first light diffraction structure is formed on a layer surface of a first transparent medium having a refractive index anisotropy, and A layer of an isotropic second transparent medium having a refractive index substantially equal to the refractive index in a specific direction of the medium is provided on the light diffraction structure, and the second light diffraction structure is an isotropic third transparent medium. An optical diffraction structure formed on a layer surface of a medium, wherein a reflection layer is provided on the second optical diffraction structure. 4. The optical diffraction structure according to claim 3, wherein the difference between the refractive index of the first transparent medium having the refractive index anisotropy for ordinary rays and the refractive index for extraordinary rays is 0.1 or more. The light diffraction structure according to claim 3, wherein the reflection layer comprises a layer of a fourth transparent medium having a refractive index different from that of the third transparent medium. The light diffraction structure according to claim 3, wherein the reflection layer comprises a metal reflection layer. The light diffraction structure according to any one of claims 3 to 6, wherein the layer of the second transparent medium and the layer of the third transparent medium are formed of the same layer. In a light diffraction structure having a light diffraction structure consisting of an uneven relief pattern,
A transparent medium having a plurality of light diffraction structures as the light diffraction structure, wherein at least two of the light diffraction structures are formed on a layer surface of a transparent medium having a refractive index anisotropy, and each having a refractive index anisotropy. A layer of an isotropic transparent medium having a refractive index substantially equal to the refractive index of a specific direction is provided on each light diffraction structure, and the specific directions of the transparent medium having each refractive index anisotropy are mutually different. An optical diffraction structure characterized by being stacked in different directions. 9. The optical diffraction structure according to claim 8, wherein a difference between a refractive index of the transparent medium having each refractive index anisotropy for an ordinary ray and a refractive index for an extraordinary ray is 0.1 or more.

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