JP4992381B2 - Diffraction grating pattern and its verification method - Google Patents

Description

The present invention forgery prevention effect is high, easily directed to the diffraction grating pattern capable of authenticity determination the verification how.

  In recent years, for the purpose of preventing counterfeiting of securities such as gift certificates and checks, cards such as credit cards, cash cards and ID cards, and certificates such as passports and licenses, the surface of securities, cards and certificates, etc. A diffraction grating pattern is affixed to the surface.

  The diffraction grating pattern has a directional gloss that cannot be expressed by a normal printing technique. In addition, the diffraction grating pattern can change the display image according to the direction of observation by controlling the direction in which light is diffracted, the angle, the brightness, and the like. It is also possible to display a stereoscopic image. Therefore, a forgery prevention measure for the information printed matter is applied by attaching the diffraction grating pattern having such properties to the information printed matter.

To determine the properties of the diffraction grating,
(1) Spatial frequency of diffraction grating (pitch of grating line),
(2) direction of diffraction grating (direction of grating line),
(3) Drawing area of diffraction grating (arrangement of diffraction grating cell),
There are three parameters.

  Specifically, when the diffraction grating pattern is viewed from a fixed point, the color of the diffraction grating pattern changes according to the spatial frequency value of (1). Further, the direction in which the diffraction grating appears to shine changes according to the direction of the diffraction grating in (2). In addition, a display image (a pattern, a character, a symbol, or the like) is determined by the drawing area of the diffraction grating in (3).

(Type of diffraction grating)
As the diffraction grating, a rectangular diffraction grating 90 as shown in FIG. 12 and a sinusoidal diffraction grating 91 as shown in FIG. 13 are widely used. A diffraction grating having such a rectangular or sinusoidal cross-sectional shape is called a “binary grating”. A typical binary lattice has a lattice line pitch of about 0.5 to 2 μm and a lattice depth of about 0.1 to 1 μm. When incident light Li is incident on these binary gratings from vertically above, diffracted light Ld is emitted in a plurality of directions.

  As a diffraction grating other than the binary grating, a so-called “blazed grating” having a sawtooth cross-sectional shape as shown in a cross-sectional view in FIG. 14 is also known.

  In the blazed grating 92, when the diffraction angle with respect to the incident light Li from the vertical direction coincides with the reflection angle of the light from the inclined surface, diffracted light Ld having a diffraction efficiency of theoretically 100% is generated in the coincidence direction. . Also, no light is emitted in the other directions. That is, the blazed grating can obtain a very high diffraction efficiency as compared with the binary grating. Further, the traveling direction of light can be strictly controlled. Therefore, the blazed grating has high visibility and is more suitable for use in security applications (see, for example, Patent Document 1).

  As the blazed grating, there is not only a blazed grating 93 having a sawtooth cross section as shown in FIG. 14, but also a blazed grating 93 having a stepped cross section as shown in FIG. A blazed grating having a stepped cross-sectional shape has a characteristic that the amount of diffracted light increases as the number of steps increases.

(Method of constructing image with diffraction grating)
As a method of constructing an image with a diffraction grating, the surface of the substrate is divided into a plurality of regions, and each of a plurality of micro regions (cells) of about several μm to several hundreds of μm arranged in the region is described above. A general method is to form a diffraction grating in which three parameters relating to the diffraction grating are varied. Thereby, an image having directional gloss is obtained.

  As the shape of the cell, a rectangular or circular shape is often used. When a plurality of rectangular cells are arranged in an orderly manner, there is an advantage that an area where a diffraction grating can be formed can be increased and a bright display image can be obtained. A circular cell is formed when a photosensitive material surface is spot-exposed by a two-beam interference of a laser to form a diffraction grating pattern. For the purpose of improving security, there is also a diffraction grating pattern composed of cells having a shape other than a rectangle or a circle.

(Diffraction grating pattern master production method)
As a method for producing a master plate of a diffraction grating pattern, for example, there are methods disclosed in Patent Document 2 and Patent Document 3. In these methods, an XY stage on which a planar substrate coated with a photosensitive resist is placed is moved by computer control, and a diffraction grating pattern is formed on the substrate surface using an electron beam exposure apparatus.

  In the production of an original blazed grating, there is a method of obtaining the shape of the blazed grating by adjusting the electron beam irradiation time and intensity in accordance with the electron beam irradiation position and changing the depth of the groove to be processed. (For example, refer to Patent Document 4). The blazed grating is more difficult to manufacture than the binary grating, and is suitable for use in security applications in terms of manufacturing technology.

  As another method for producing a master plate of a diffraction grating pattern, a method for exposing an interference fringe (synonymous with a diffraction grating) to a photosensitive material by two-beam interference of a laser is known (for example, see Non-Patent Document 1). .

(Diffraction grating pattern replication method)
When the master of the diffraction grating pattern is created, the diffraction grating pattern is duplicated as follows. First, a metal stamper is produced from a master plate of a diffraction grating pattern having an uneven shape by a method such as electroforming. Next, a thermoplastic resin or a photocurable resin is applied onto a film such as PET, and a metal stamper is adhered. Then, the resin is cured by applying heat or light. Thereby, the diffraction grating pattern is duplicated.

  The replicated diffraction grating pattern is attached to a substrate such as paper or plastic plate via an adhesive layer after a light reflecting layer is provided by a method such as vapor deposition of a metal or dielectric thin film layer such as aluminum. The

In addition, when a diffraction grating pattern is affixed on securities or cards, a protective layer is further provided as necessary to prevent stains and scratches on the printed layer and the diffraction grating pattern layer.
JP 2006-11513 A Japanese Patent Laid-Open No. 2-72315 US Pat. No. 5,058,992 JP 2000-39508 A Junpei Takiuchi, "Holography", 1st edition, Maruzen Co., 1993

  As described above, the diffraction grating pattern is used in many information printed materials that require security.

  However, as the diffraction grating pattern technology is widely recognized, the occurrence of counterfeit products tends to increase. Therefore, there is a situation in which a sufficient anti-counterfeit effect cannot be exhibited only by pasting the diffraction grating pattern having the above configuration on the surface of securities or the like.

  Further, even if the diffraction grating pattern exhibits a forgery prevention effect, it takes time to find a counterfeit product if the authenticity determination cannot be easily performed. In this case, there is a risk that the outflow of counterfeit products may increase.

The present invention has been made in view of the above circumstances, and an object thereof is forgery preventing effect is high, easily provide the authenticity determination and may diffraction grating pattern and validates how.

  The present invention takes the following means in order to solve the above problems.

In the invention corresponding to claim 1, the first cell in which a blazed grating for diffracting incident light in a specific direction is formed on the surface of the substrate, and the blazed grating of the first cell has a lattice line direction of approximately 180 degrees. A diffraction grating pattern comprising a second cell in which different blazed gratings are formed, wherein the first cell and the second cell are alternately arranged adjacent to the surface of the substrate; Forming a first cell group and a second cell group composed of a plurality of second cells, and displaying a first image occupying the top of the concealed image by diffracted light from the blazed grating of the first cell group, A second image occupying the lower part of the concealed image is displayed by the diffracted light from the blazed grating of the two-cell group, and the first image is inverted in advance so that the image is inverted upside down when displayed with a mirror. diffraction grating pattern is an image A.

  The invention corresponding to claim 2 is the diffraction grating pattern according to claim 1, wherein the first cell and the second cell are formed in a rectangular region having a side length of 300 μm or less. is there.

  The invention corresponding to claim 3 is the diffraction grating pattern corresponding to claim 1 or claim 2, wherein the first cell group and the second cell group are alternately adjacent to each other in the form of stripes. It is a diffraction grating pattern.

  The invention corresponding to claim 4 is the diffraction grating pattern corresponding to any one of claims 1 to 3, wherein the blazed grating formed in the first cell and the blazed grating formed in the second cell. Is a diffraction grating pattern having substantially the same grating depth.

The invention corresponding to claim 5 is a method for verifying a diffraction grating pattern corresponding to any one of claims 1 to 4, wherein light is reflected at a predetermined position on the surface of the diffraction grating pattern. A step of installing a functional article, and an image displayed by diffracted light from the first cell group reflected by the light-reflective article and an image displayed by diffracted light from the second cell group are connected. And a step of verifying the diffraction grating pattern based on the obtained image.

<Terminology>
In the present invention, the “grating line direction” refers to the azimuth angle of the diffraction grating on the substrate surface. That is, it refers to the angle of the lattice line when viewed in a plan view.

<Action>
Therefore, the present invention has the following effects by taking the above-described means.

In the invention corresponding to claim 1, the first cell in which the blazed grating that diffracts incident light in a specific direction is formed on the surface of the substrate and the blazed grating of the first cell are different in the lattice line direction by about 180 degrees. A diffraction grating pattern comprising a second cell on which a blazed grating is formed, wherein the first cell and the second cell are alternately arranged adjacent to the surface of the substrate, and the first cell comprises a plurality of first cells. A first image occupying the upper part of the concealed image by the diffracted light from the blazed grating of the first cell group is formed, and the blazed grating of the second cell group is formed Since the second image occupying the lower part of the concealed image is displayed by the diffracted light from the first image, the first image is an image that has been vertically inverted so that the image is vertically inverted when displayed with a mirror. Image displayed by group and second cell group Only when a combination of the image to be more displayed, it is possible to provide a diffraction grating pattern capable of observing a predetermined image (hidden image).

  Thereby, for example, only when a mirror is installed at a predetermined position on the diffraction grating pattern, a concealed image obtained by connecting an image displayed on the mirror and an image not displayed on the mirror can be displayed. As described above, since a predetermined image (a concealed image) is displayed only by using a mirror, it is possible to provide a diffraction grating pattern that has a high anti-counterfeit effect and can easily determine authenticity.

  The invention corresponding to claim 2 is the diffraction grating pattern corresponding to claim 1, wherein the first cell and the second cell are formed in a rectangular region having a side length of 300 μm or less. The jaggy of the image to be displayed can be made inconspicuous.

  The invention corresponding to claim 3 is that in the diffraction grating pattern corresponding to claim 1 or claim 2, since the first cell group and the second cell group are alternately adjacent to each other in the form of stripes, When a hidden image is displayed using a mirror, a clear and high-quality display image can be obtained.

  The invention corresponding to claim 4 is the diffraction grating pattern corresponding to any one of claims 1 to 3, wherein the blazed grating formed in the first cell and the blazed grating formed in the second cell are gratings Since the depth is substantially the same, the amount of diffracted light can be made substantially the same. That is, since the luminance distribution of the image by the first cell group and the luminance distribution of the image by the second cell group are the same, the image displayed by the first cell group and the image displayed by the second cell group When connected, the brightness distribution of the connected images can be made uniform.

The invention corresponding to claim 5 is the method for verifying a diffraction grating pattern according to any one of claims 1 to 4, wherein the light reflective article is placed at a predetermined position on the surface of the diffraction grating pattern. Based on the image obtained by connecting the step of installing, the image displayed by reflecting the diffracted light from the first cell group by the light-reflective article, and the image displayed by the diffracted light from the second cell group. And a step of verifying the diffraction grating pattern, and the authenticity of the diffraction grating pattern can be easily determined.

  ADVANTAGE OF THE INVENTION According to this invention, the anti-counterfeit effect is high and can provide the diffraction grating pattern which can authenticate easily, its verification method, and information printed matter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
(1-1. Configuration)
FIG. 1 is a schematic diagram showing the configuration of a diffraction grating pattern 5 according to the first embodiment of the present invention.

  In the diffraction grating pattern 5, the surface of the substrate 6 is divided into a plurality of regions (hereinafter also referred to as “cells”), and a blazed grating is formed in each cell.

  Here, when all the lattice line directions of the blazed grating formed in each cell are the same, the diffracted light is emitted in a specific direction. For example, in the diffraction grating pattern of FIG. 2, the area of the cell in which the blazed grating is formed is changed, and the letter “T” is displayed by controlling the amount of diffracted light. When the lattice line directions are the same as shown in FIG. 2, since the direction in which the diffracted light is emitted is limited, the observable position is limited, but a display image with very high luminance can be observed. In addition, as shown in FIG. 3, the cell is formed with a blazed lattice having the same lattice line direction, and when observed at an observation point, three colors of R (red), G (green), and B (blue) By arranging three types of cells whose spatial frequencies are set adjacent to each other, a full color image can be expressed by the same principle as that of a CRT display or a liquid crystal display.

  As described above, the blazed grating formed in the diffraction grating pattern 5 changes the color of the diffracted light observed at the observation point according to the spatial frequency, and the emission direction of the diffracted light changes according to the grating line direction. Therefore, it is possible to display an image such as a pattern, a character, a symbol, or the like by using such a property of the diffraction grating. Furthermore, the effect of shining in rainbow colors can be expressed by changes in observation points and illumination conditions.

  In the diffraction grating pattern 5 according to the present embodiment, the first cell 10 and the second cell 20 are formed on a part or all of the surface of the substrate 6, and emits diffracted light in different directions.

  In the first cell 10, a blazed grating 11 that diffracts incident light in a specific direction is formed on the surface of the substrate 6. A first cell group is formed from the plurality of first cells 10. A part of the concealed image is displayed by the “first diffracted light L1” from the blazed grating 11 of the first cell group. Note that an image displayed by the first cell group is referred to as a “first image P1” for convenience.

  In the second cell 20, a blazed grating 21 having a lattice line direction that is approximately 180 degrees different from the lattice line direction of the blazed grating 11 of the first cell 10 is formed on the surface of the substrate 6 different from the first cell 10. It is a thing. A second cell group is formed from the plurality of second cells 20. The other part of the concealed image is displayed by the “second diffracted light L2” from the blazed grating 21 of the second cell group. Note that an image displayed by the second cell group is referred to as a “second image P2” for convenience.

  The first cells 10 and the second cells 20 are alternately arranged adjacent to each other in a stripe shape, and are based on a first cell group composed of a plurality of first cells and a second cell group composed of a plurality of second cells. Form on the surface of the material. Therefore, a cross-sectional view of the diffraction grating pattern 5 is shown, for example, in FIG. 4 is a cross-sectional view taken along line X-X ′ in FIG.

  In FIG. 4, when incident light Li is incident from vertically above the diffraction grating pattern 5, first diffracted light L <b> 1 (left side of the paper) is emitted from the blazed grating 11 formed in the first cell 10. Therefore, the first image P1 displayed by the first cell group can be seen at the first observation point E1. Further, the second diffracted light L2 (on the right side of the drawing) is emitted from the blazed grating 21 formed in the second cell 20. Therefore, the second image P2 can be seen at the second observation point E2. Here, the second diffracted light L2 is diffracted in a direction in which the first diffracted light L1 is mirror-inverted with the normal direction of the substrate surface as an axis.

  Thus, the first diffracted light L1 from the first cell 10 and the second diffracted light L2 from the second cell 20 are diffracted in different directions.

  Therefore, in the diffraction grating pattern 5 according to the present embodiment, the blazed grating of the first cell 10 is not obtained so that a predetermined image (hidden image) cannot be obtained unless images displayed when viewed from different directions are combined. And the blazed grating of the second cell 20 are formed. For example, as described later, the diffraction grating pattern 5 is formed such that the upper image of the character “SECURITY” is displayed by the first cell group and the lower image is displayed by the second cell group.

(1-2. Action)
Next, the operation of the diffraction grating pattern 5 according to this embodiment will be described.

  As shown in FIG. 4, when the incident light Li from the normal direction of the diffraction grating pattern 5 is incident, the first cell is observed at the first observation point E1 by the first diffracted light L1 from the first cell 10. Only the first image P1 by the group is observed. At this time, the second image P2 by the second cell group is not observed. On the other hand, at the second observation point E2, only the second image P2 by the second cell group is observed, and the first image P1 by the first cell group is not observed.

  That is, the display image can be changed depending on the position where the diffraction grating pattern 5 is observed, the illumination conditions, and the like by arranging the cells composed of the blazed gratings 11 and 21 having different grating line directions.

  By using such a property, the concealed image is displayed in the diffraction grating pattern 5 according to the present embodiment. This will be described with reference to FIGS.

  FIG. 5A shows an example of a concealment image displayed by the diffraction grating pattern 5. Here, the character “SECURITY” is displayed as a hidden image.

  Specifically, the upper part of the character “SECURITY” is displayed as the first image P1 by the first cell group (FIG. 5B), and the lower part of the character “SECURITY” is displayed as the second image P2 in the second cell. It is made to display by a group (FIG.5 (C)). At this time, the first image P1 is an image that is inverted in advance so that the image is inverted upside down when displayed with a mirror.

  Specifically, as shown in FIG. 6, the first cell group is formed so as to correspond to the pixels of the first image P1 and the pixels of the second image P2 while alternately arranging two types of blazed gratings 11 and 21 adjacent to each other. And a second cell group is formed. Thereby, the diffraction grating pattern 5 displaying the upper image and the lower image of the character “SECURITY” is formed in the same region (FIG. 7).

  If the mirror M is installed at a predetermined portion of the diffraction grating pattern 5 as described above, the characters “SECURITY” can be observed as shown in FIG.

  When the mirror M is not used, the upper image or the lower image of the characters “SECURITY” is recognized at different observation points, and the concealed image is not observed. Needless to say, the concealment image may be not only a character such as “SECURITY” but also a pattern, a symbol, or the like.

(1-3. Effect)
As described above, the diffraction grating pattern 5 according to this embodiment includes the first cell 10 in which the blazed grating 11 that diffracts the incident light Li in a specific direction is formed on the surface of the substrate 1, and the first cell 10. The blazed grating 11 includes second cells 20 formed with blazed gratings 21 whose lattice line directions are different by approximately 180 degrees, and the first cells 10 and the second cells 20 are alternately adjacent to the substrate surface. A first cell group consisting of a plurality of first cells 10 and a second cell group consisting of a plurality of second cells 20 are formed and concealed by the first diffracted light L1 from the blazed grating 11 of the first cell group. appears first image P1 occupying the top of the image, the second image P2, which accounts for the lower portion of the concealed image by the second diffraction light L2 from the second cell group of blazed grating 21 is displayed, the first image P1 is a mirror When displayed with To invert, since an image obtained by pre upside down, only when a combination of the second image P2 to be displayed with the first image P1 to be displayed by the first cell group with a second cell group, predetermined A diffraction grating pattern capable of observing an image (hidden image) can be provided.

  Thereby, for example, only when the mirror M is installed at a predetermined position on the diffraction grating pattern 5, a concealed image obtained by connecting an image displayed on the mirror M and an image not displayed on the mirror M can be displayed. it can. As described above, since the predetermined image (the concealed image) is displayed only by using the mirror M, it is possible to provide a diffraction grating pattern that has a high anti-counterfeit effect and can be easily determined as authentic.

  Further, the diffraction grating pattern 5 according to the present embodiment displays a concealed image by a blazed grating. Since the blazed grating has a higher luminance than the binary grating and is difficult to manufacture, high security can be realized. If a binary grating is used as the diffraction grating formed in the first cell 10 and the second cell 20, a plurality of diffracted lights are emitted in various directions. Therefore, a hidden image cannot be displayed using a binary lattice.

  Further, in order to display the concealed image, a special device or the like is not necessary, and a generally available mirror or a planar article having a light reflecting layer on the surface may be used, and authenticity determination of the diffraction grating pattern 5 is performed. It can be done easily.

  In addition, as the 1st cell 10 and the 2nd cell 20, the rectangular thing whose length of one side is 300 micrometers or less is desirable. By setting the thickness to 300 μm or less, it is possible to make the resolution smaller than that of the human eye, thereby making it possible to make the image jaggy (stepped jaggedness generated due to insufficient resolution) inconspicuous. Needless to say, other than a rectangular cell, other shapes such as a circle, an ellipse, and a triangle may be used. In the case of a shape other than a rectangle, jaggies can be made inconspicuous by setting the size so that the length of one side fits inside a rectangular region of 300 μm.

  Further, it is desirable that the first cells 10 and the second cells 20 are alternately arranged adjacent to each other in a stripe shape. This is because the alternate arrangement in stripes is the simplest configuration for displaying a concealed image using the mirror M. Furthermore, since the first image P1 and the second image P2 are simply arranged alternately alternately, the manufacturing is easy. In addition, it is expected that noise light other than diffracted light is less likely to be generated by arranging cells in which blazed gratings in the same grating line direction are arranged in a line. As a result, when the concealed image is displayed using the mirror M, a clear and high quality image can be obtained.

  Moreover, it is desirable that the blazed grating 11 formed in the first cell 10 and the blazed grating 21 formed in the second cell 20 have substantially the same grating depth. Since the amount of diffracted light emitted from the diffraction grating changes according to the grating depth, even if the spatial frequency and the grating line direction are the same, the brightness varies depending on the grating depth. Therefore, by making the grating depth the same and making the amount of diffracted light almost the same, fluctuations in the brightness of the display image can be avoided. For example, it is possible to prevent deterioration in image quality due to the difference between the brightness of the first image P1 by the first cell group and the brightness of the second image P2 by the second cell group. In addition, it is possible to prevent deterioration in image quality due to partial unevenness in luminance. That is, since the luminance distribution of the image by the first cell group and the luminance distribution of the image by the second cell group are the same, the image displayed by the first cell group and the image displayed by the second cell group When connected, the brightness distribution of the connected images can be made uniform.

  The diffraction grating pattern 5 according to the present embodiment can be used by being attached to an arbitrary region on the surface of a sheet-like or flat information printed matter such as paper, a plastic plate, a plastic film, or the like. FIG. 9 is a schematic diagram showing the concept of the information printed matter 50 to which the diffraction grating pattern 5 is attached. Further, the cross-sectional configuration of the information printed matter 50 to which the diffraction grating pattern 5 is affixed is shown in FIG. 10 (corresponding to the sectional view taken along line YY ′ in FIG. 9). In general, the diffraction grating pattern 5 is disposed after the light reflection layer 54 is provided via the adhesive layer 53. Furthermore, a protective layer 55 may be provided as necessary to protect the layer of the diffraction grating pattern 5. In addition, when the information printed matter 50 is a credit card, an ID card, or the like, a layer for preventing warpage of the printed matter base 51 or a layer for improving the adhesion of printing ink may be provided. Further, a magnetic film layer or the like may be separately provided on the printed material base 51. Even when the printed material base 51 is paper, layers having various functions are provided as necessary.

  In this way, by attaching the diffraction grating pattern 5 on the sheet-like or flat-plate-like printed material base 51 via the adhesive layer 53, the information printed matter 50 can be prevented from being imitated by a copying machine or the like. As a result, it is possible to provide the information printed matter 50 such as gift certificates, bills and other securities, cards, and various certificates that are extremely difficult to imitate.

  In addition, the information printed matter 50 to which the diffraction grating pattern 5 is attached is generally flat and often has a structure that can withstand scratches and wear by providing a protective layer on the surface. Therefore, it is possible to easily and reliably display the hidden image using the mirror M as a verifier.

  Further, the diffraction grating pattern 5 is not limited to a rectangular shape as shown in FIG. 9, but a circular or elliptical shape, a belt-like shape that traverses / cuts vertically on the information printed matter 50, or the entire surface of the information printed matter 50. Needless to say, it may be in various shapes, such as covering everything.

<Second Embodiment>
In the present embodiment, a method for verifying the diffraction grating pattern 5 according to the first embodiment will be described.

  First, the mirror M which is a light reflective article is installed at a predetermined position on the surface of the diffraction grating pattern 5. That is, as shown in FIG. 11, when light is incident on the diffraction grating pattern 5, the first cell 10 and the second cell 20 emit diffracted light in directions opposite to each other. Therefore, as shown in FIG. 11, the mirror M is installed perpendicularly to the diffraction grating pattern 5 in the direction of emission of the first diffracted light L1 by the first cell 10, so that the first diffracted light L1 is reflected on the surface of the mirror M. Make a mirror reflection.

  Subsequently, a first image P1 displayed by reflecting the first diffracted light L1 from the first cell group by the mirror M, and a second image P2 displayed by the second diffracted light L2 from the second cell group The diffraction grating pattern 5 is verified based on the images connected to each other.

  That is, the first diffracted light L1 described above is specularly reflected by the surface of the mirror M and reaches the observation point E2, so that the observer can see the first image P1 displayed by the first cell group. Further, since the mirror M is installed perpendicular to the diffraction grating pattern 5, the emission directions of the first diffracted light L1 and the second diffracted light L2 coincide.

  Therefore, an image obtained by combining the first image P1 from the first cell group and the second image P2 from the second cell group is set to be a part or all of a predetermined continuous image in advance. Then, at the observation point E2, the first image P1 displayed by the first cell group is perceived on the surface of the mirror M as an image displaying the upper part of the predetermined image, and the second image P2 displayed by the second cell group. Is perceived on the diffraction grating pattern 5 as an image displaying the lower part of the predetermined image.

  In this way, when the first image P1 and the second image P2 reflected in the mirror are connected, if a predetermined image (hidden image) is completed, it is determined that the diffraction grating pattern 5 is genuine. On the other hand, if the predetermined image is not completed, the diffraction grating pattern 5 is determined to be fake.

  The authenticity determination of the diffraction grating pattern 5 is verified based on the image obtained by connecting the first image P1 and the second image P2 by installing the mirror M at a predetermined position by the method described above. can do.

  If the diffraction grating pattern 5 is attached to the information printed matter 50 and the concealed image is displayed only by a predetermined verification method, the authenticity of the information printed matter 50 can be easily determined.

  In the present embodiment, the mirror M is installed vertically with respect to the diffraction grating pattern 5, but is not limited to being vertical. That is, the installation angle of the mirror M can be changed by adjusting the blaze angle of the blazed grating.

<Others>
Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

It is a schematic diagram which shows the structure of the diffraction grating pattern which concerns on the 1st Embodiment of this invention. It is a schematic diagram for demonstrating the structure of the cell which concerns on the same embodiment. It is a schematic diagram for demonstrating the structure of the cell which concerns on the same embodiment. It is a schematic diagram which shows the cross section of the diffraction grating pattern which concerns on the same embodiment. It is a figure which shows the example of the concealment image which concerns on the same embodiment. It is a schematic diagram which shows the example of the diffraction grating pattern which concerns on the same embodiment. It is a schematic diagram which shows the example of the diffraction grating pattern which concerns on the same embodiment. It is a schematic diagram which shows the display to the mirror of the concealment image which concerns on the same embodiment. It is a schematic diagram which shows the concept of the information printed matter with which the diffraction grating pattern which concerns on the embodiment was affixed. It is a schematic diagram which shows the cross-sectional structure of the information printed matter with which the diffraction grating pattern which concerns on the embodiment was affixed. It is a schematic diagram for demonstrating the verification method of the diffraction grating pattern which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the concept of a general rectangular diffraction grating. It is a schematic diagram which shows the concept of a general sinusoidal diffraction grating. It is a schematic diagram which shows the concept of a general blazed grating. It is a schematic diagram which shows the concept of a general step-like blazed grating.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 5 ... Diffraction grating pattern, 6 ... Base material, 10 ... 1st cell, 11 ... Blaze grating, 20 ... 2nd cell, 21 ... Blaze grating, 51 ... Printed matter Substrate, 52 ... printing layer, 53 ... adhesive layer, 54 ... light reflecting layer, 55 ... protective layer, 90 ... rectangular diffraction grating, 91 ... sinusoidal diffraction grating, 92.93 ... blazed grating, Li ... incident light, Ld ... diffracted light, L1 ... first diffracted light, L2 ... second diffracted light, P1 ... first image, P2 ... second image, E1 ... first observation point, E2 ... second observation point, M ... mirror.

Claims (5)

A first cell in which a blazed grating that diffracts incident light in a specific direction is formed on a substrate surface;
The blazed grating of the first cell is a diffraction grating pattern including a second cell on which a blazed grating having a lattice line direction different by about 180 degrees is formed,
The first cells and the second cells are alternately arranged adjacent to the substrate surface to form a first cell group composed of a plurality of first cells and a second cell group composed of a plurality of second cells. ,
A first image occupying the top of the concealed image by the diffracted light from the blazed grating of the first cell group is displayed;
A second image occupying the lower part of the concealed image is displayed by diffracted light from the blazed grating of the second cell group;
The diffraction grating pattern according to claim 1, wherein the first image is an image that has been vertically inverted so that the image is vertically inverted when displayed by a mirror . The diffraction grating pattern according to claim 1,
The diffraction grating pattern, wherein the first cell and the second cell are formed in a rectangular region having a side length of 300 μm or less. The diffraction grating pattern according to claim 1 or 2,
The diffraction grating pattern, wherein the first cell group and the second cell group are alternately adjacent to each other in a striped configuration. The diffraction grating pattern according to any one of claims 1 to 3,
A diffraction grating pattern, wherein the blazed grating formed in the first cell and the blazed grating formed in the second cell have substantially the same grating depth. A method for verifying a diffraction grating pattern according to any one of claims 1 to 4, comprising:
Installing a light reflective article at a predetermined position on the surface of the diffraction grating pattern;
Based on an image obtained by connecting an image displayed by diffracted light from the first cell group reflected by the light-reflective article and an image displayed by the diffracted light from the second cell group, A method for verifying a diffraction grating pattern, comprising: verifying the diffraction grating pattern.

Images