Diffraction grating pattern

Abstract

To provide a diffraction grating pattern allowing a pattern composed of a diffraction grating to switch between states of a latent image and a visualized image, without requiring special devices for recognition or discrimination of the pattern, while enabling easy authenticity discrimination.SOLUTION: A diffraction grating pattern 1 includes at least two kinds of unit pixels composed of a diffraction grating combined so that one kind of unit pixels forms a prescribed shape in an alignment of the other kind of unit pixels, the unit pixels arranged in plural. The unit pixel 10 is formed by multiple kinds of diffraction gratings having different diffraction angles being aligned so that the diffraction angles gradually change in a prescribed direction. The prescribed direction is different between different kinds of unit pixels, and the diffraction angle is equivalent in at least one alignment portion in a corresponding physical relation of the alignment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diffraction grating pattern combining diffraction gratings, and more particularly to a diffraction grating pattern formed by unit pixels combining a plurality of diffraction gratings with different diffraction angles step by step.

Background Art

[0002] A display body composed of diffraction gratings has a directional gloss that cannot be expressed by ordinary printing technology, and is therefore widely used for displays and security products for the purpose of preventing forgery of credit cards, securities, vouchers, etc. There is a demand for producing more diverse and original patterns.

[0003] In response to such demands, a display body having a diffraction grating pattern composed of a collection of cell (dot)-shaped diffraction gratings is known.

[0004] As a method of manufacturing a display body using a diffraction grating as a pixel, for example, a method of successively exposing a photosensitive film by changing the pitch, direction, and light intensity of minute interference fringes (diffraction gratings) caused by two-beam interference of laser light, or using an electron beam exposure apparatus and moving an X-Y stage on which a planar substrate is placed under computer control to arrange a plurality of minute dots composed of diffraction gratings on the surface of the substrate to produce a diffraction grating pattern is known.

[0005] By forming the produced diffraction grating pattern on a security product, effects such as forgery prevention can be obtained. However, in recent years, forgery techniques have become more sophisticated, and there is a growing demand for products with a higher forgery prevention effect. Therefore, a diffraction grating pattern in which a plurality of types of diffraction gratings are combined and the appearance of the diffraction grating pattern changes, such as the hue changing or the latent image / apparent image state switching depending on the observation conditions, has also been proposed.

[0006] For example, Patent Document 1 proposes a diffraction grating pattern structure formed by minute cells made of diffraction gratings, which consists of a first pixel pattern made of diffraction gratings having different grating angles and grating pitches and a second pixel pattern made of diffraction gratings having different grating angles and grating pitches. When the pattern illumination or the angle of the device is changed, the hue changes, and a specific pattern is expressed by the hue change, so that a novel visual image can be obtained, and the diffraction grating pattern can enhance forgery prevention.

[0007] The diffraction grating pattern proposed in Patent Document 1 only changes according to the viewing angle and the like of the hue of a specific pattern part, and there is no significant difference from the appearance of the conventional diffraction grating pattern. Also, the specific pattern always appears as a visible image and cannot be switched to a latent image, and the change in appearance and the forgery prevention effect are limited.

[0008] Also, for example, Patent Document 2 discloses a diffraction grating pattern having an optical diffraction structure characterized in that the diffraction grating stripes of the latent image part and the background part form a 90-degree angle. However, this latent image cannot be discriminated in a normal viewing state and requires a discriminator, so there is a problem in terms of ease of discrimination.

[0009] Also, Patent Document 3 discloses an encrypted recording medium in which a first encrypted pattern and a second encrypted pattern generated from an original latent image from an encrypted image by a visual decryption type secret sharing method are superimposed on a substrate, and the latent image can be visually recognized only when light sources are introduced from two directions, namely, a certain specific angle and the angle orthogonal thereto. However, this medium randomly shines in a normal observation state, and the latent image part and the background part cannot be distinguished. Moreover, since light sources from two directions are required for observation, there is also a problem in terms of ease of discrimination.

[0010] As described above, although conventional diffraction grating patterns and diffraction grating recording media have a certain anti-copying effect, when observing the entire image, the visual changes are limited, and there has been a problem that it is difficult to create a pattern with a high anti-counterfeiting effect that is colorful. In addition, a special device or the like is required for visual recognition and discrimination of the pattern, and there is also a problem in terms of ease of discrimination.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0012] An object of the present invention is to provide a diffraction grating pattern that can switch between a latent image state and a visible image state of a pattern composed of a diffraction grating, does not require a special device or the like for visual recognition and discrimination of the pattern, and is easy to distinguish between genuine and fake.

Means for Solving the Problems

[0013] To solve the above problems, one aspect of the present invention is a diffraction grating pattern in which at least two types of unit pixels composed of diffraction gratings are combined so that a predetermined shape is formed by another type of unit pixel in the arrangement of one type of unit pixel, and a plurality of them are arranged, wherein the unit pixel at least one is formed by arranging a plurality of types of diffraction gratings having different diffraction angles the direction from the outer periphery to the center of the unit pixel such that the diffraction angle gradually changes along, at least one of the unit pixels is formed by arranging a plurality of types of diffraction gratings with different diffraction angles so that the diffraction angle gradually changes along the direction from the center to the outer periphery of the unit pixel, andIt is a diffraction grating pattern with the same diffraction angle at at least one array site in the corresponding positional relationship of the above array.

[0014] In the above diffraction grating pattern, The diffraction angle of the diffraction grating may be configured to change over approximately 180° within the unit pixel.

[0018] In the above diffraction grating pattern, It may include an area where no diffraction grating exists.

[0019] Another aspect of the present invention is An article formed by forming the diffraction grating pattern according to any of the above on the surface.

Advantages of the Invention

[0020] According to the diffraction grating pattern of the present invention, since the pattern of diffracted light from the unit pixel changes according to the viewing angle or the illumination angle of the diffraction grating pattern, a special determination device or the like is not required. Also, at a specific angle, the directions of diffracted light from a plurality of types of unit pixels become the same, so the pattern formed by the unit pixels becomes latent, and from another angle, the direction of the diffracted light is different and the pattern becomes visible. Therefore, the visual change is large, and a highly unique pattern can be obtained.

Brief Description of the Drawings

[0021]

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Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below. Also, in the embodiments shown below, technically preferable limitations are made to implement the invention, but this limitation is not an essential requirement of the present invention.

[0023] FIG. 1 is an explanatory diagram of a first unit pixel that forms a diffraction grating pattern of the present invention. The first unit pixel 10 has a substantially circular outer shape, and the diffraction grating that constitutes the first unit pixel 10 emits diffracted light at an angle that gradually changes according to the angle of rotation in the direction of orbiting around the center of the first unit pixel 10. Explaining with FIG. 1(a), in region a1, a diffraction grating that emits diffracted light with respect to incident light from the 0° direction is formed at the center in its circumferential direction. As it orbits counterclockwise as shown by the illustrated arrow, a diffraction grating is formed such that diffracted light is emitted with respect to incident light from a gradually larger angle. For example, at a similar center in region b1, a diffraction grating is formed such that diffracted light is emitted with respect to incident light from approximately the 45° direction. That is, the numerical values of the angles described in each region are shown as representative values of each region.

[0024] Here, and hereinafter, the angle of the incident light is based on the angle in the direction shown in FIG. 1(b). Also, for the sake of simplicity of description, the angle of the incident light from which diffracted light is emitted from the diffraction grating is simply referred to as "the angle of the diffraction grating".

[0025] As it rotates counterclockwise from region a1, the angle of the diffraction grating changes, but the manner of change is not particularly limited. For example, it could be 0° for all of region a1, 45° for all of region b1, and similarly 90° in region c1, 135° in region d1, and 180° in region a2. When the angle of the diffraction grating is 180°, the optical effect is the same as when it is 0°, so this is regarded as 0°, and thereafter it is 45° in region b2, 90° in region c2, and 135° in region d2.

[0026] The change in the angle of the diffraction grating may be in a manner other than those described above. For example, it may change in fine increments such as 1°, 5°, or 10° increments from region a1 toward region b1. It may also change in a substantially continuous and smooth manner. To avoid misunderstanding, it should be noted that the numerical values of the angles shown in Fig. 1(a) are reference numerical values indicating the mode of change. For example, if the diffraction grating has a 10° increment, the angle at the center on the region a1 side in the circumferential direction of region b1 is 40°, and on the region c1 side it is 50°. Also, the displays of regions a1, b1, etc. and the lines separating the regions are for explanatory purposes only and do not indicate the physical separation of the diffraction grating.

[0027] Fig. 2 is a conceptual diagram of the first unit pixel forming the diffraction grating pattern of the present invention. The diffraction grating constituting the first unit pixel 10a has innumerable diffraction grating patterns engraved while changing the angle of the diffraction grating according to the angle in the circumferential direction, and the diffraction gratings at each angle form a continuous pattern, and as a whole, diffraction gratings with different angles are formed so as to be arranged in concentric circles 10b.

[0028] Fig. 3 is an explanatory diagram of how it looks when light is irradiated from the 0° direction to the first unit pixel forming the diffraction grating pattern of the present invention. When light is irradiated from the 0° direction, diffracted light is strongly emitted particularly from the center of the regions a1 where the angle of the diffraction grating is 0° and a2 where it is 180° at the center, and the diffracted light weakens as it goes to the periphery. Since no diffracted light is emitted from the other regions, as a whole, the portions of regions a1 and a2 appear bright and shiny, and the other portions appear dark.

[0029] FIG. 4 is an explanatory view of a second unit pixel that forms the diffraction grating pattern of the present invention. The second unit pixel 11 has substantially the same diameter as the first unit pixel 10. Similar to the first unit pixel 10, the diffraction grating that constitutes the second unit pixel 11 has a gradually changing diffraction grating angle in the direction of going around the center of the second unit pixel 11, but the direction of going around is opposite. As it goes around clockwise as shown by the arrow in the figure, a diffraction grating is formed such that diffracted light is emitted with respect to incident light from a gradually larger angle as a whole, and is arranged in concentric circles as shown in FIG. 2.

[0030] Among the diffraction gratings that constitute the second unit pixel 11, the portions where the angles of the diffraction gratings are 0°, 90°, and 180° are in the corresponding arrangement portions of the first unit pixel 10. Therefore, for incident light from these angles, the first unit pixel 10 and the second unit pixel 11 emit diffracted light in the same manner.

[0031] FIG. 5 is an explanatory view of a first form of the diffraction grating pattern of the present invention. The diffraction grating pattern 1 is formed by combining the aforementioned first unit pixel 10 and second unit pixel 11. The mode of combination is not particularly limited, but FIG. 5 shows an example in which, with the first unit pixel 10 as a base, a pattern of the character "ロ" is formed by the second unit pixel 11. At this time, since both the first unit pixel 10 and the second unit pixel 11 are substantially circular, a gap region 10c that is not included in either is generated. Whether a diffraction grating of an arbitrary pattern is formed in this gap region 10c or not is acceptable.

[0032] FIG. 6 is an external appearance explanatory view when the first form of the diffraction grating pattern of the present invention is irradiated with light from the 0° direction. When the diffraction grating pattern 1 described above is irradiated with light from the 0° direction, since both the first unit pixel 10 and the second unit pixel 11 emit diffracted light in regions a1 and a2 as described above, as a whole, it becomes a mode of the diffraction grating pattern 1a where the same region shines, and the pattern of the character "ロ" formed by the second unit pixel 11 cannot be seen and is in a latent image state. The same appearance is obtained when irradiated from the direction where the angle of the diffraction grating is 180°.

[0033] On the other hand, FIG. 7 shows how it looks when the direction of the incident light is changed from 0°. Here, (a) irradiation from the direction of 22.5°, (b) 45°, (c) 67.5°, and (d) 90° are shown respectively.

[0034] In the diffraction grating pattern 1b when the incident light is irradiated from the direction of 22.5°, diffracted light is emitted from near the boundaries between region a1 and region b1 and between region a2 and region b2 in the portion where the first unit pixel 10 is formed, while in the "ロ"-shaped portion where the second unit pixel 11 is formed, diffracted light is emitted from near the boundaries between region a1 and region d2 and between region a2 and region d1. Therefore, since the light-emitting sites in the portion where the first unit pixel 10 is formed and the portion where the second unit pixel 11 is formed are different, a "ロ"-shaped pattern can be seen on the background.

[0035] In the diffraction grating pattern 1c when the incident light is irradiated from the direction of 45°, diffracted light is emitted from near the centers of region b1 and region b2 in the portion where the first unit pixel 10 is formed, while in the "ロ"-shaped portion where the second unit pixel 11 is formed, diffracted light is emitted from near the centers of region d2 and region d1. Therefore, a "ロ"-shaped pattern can still be seen from the background, and its light-emitting pattern is also different from that of the diffraction grating pattern 1b.

[0036] In the diffraction grating pattern 1d when the incident light is irradiated from the direction of 67.5°, diffracted light is emitted from near the boundaries between region b1 and region c1 and between region b2 and region c2 in the portion where the first unit pixel 10 is formed, while in the "ロ"-shaped portion where the second unit pixel 11 is formed, diffracted light is emitted from near the boundaries between region d2 and region c2 and between region d1 and region c1. Therefore, the "ロ"-shaped pattern can be seen as different from both the diffraction grating pattern 1b and the diffraction grating pattern 1c.

[0037] In the diffraction grating pattern 1e when incident light is irradiated from a direction of 90°, since both the first unit pixel 10 and the second unit pixel 11 emit diffracted light in regions c1 and c2, as a whole, it becomes a mode of the diffraction grating pattern 1e where the same region emits light, and the pattern of the character "ロ" formed by the second unit pixel 11 cannot be seen and is in a latent image state.

[0038] As can be seen from each of the above examples, when the incident light is incident while being rotated counterclockwise from a direction of 0°, from the state where the pattern of the character "ロ" cannot be seen in the latent image state, in the first unit pixel 10 which is the base part, the light-emitting part rotates counterclockwise, and in the second unit pixel 11 in the shape of the character "ロ", the light-emitting part seems to rotate clockwise, the part in the shape of the character "ロ" can be seen as a visible image, and it seems to change to a latent image again. Thus, in the diffraction grating pattern of the present invention, a unique visual effect can be obtained only by changing the angle of the incident light without requiring a special determination device.

[0039] All of the above unit pixels and diffraction grating patterns can be formed by known methods such as a method using "two-beam interference" and "drawing by an electron beam (EB)".

[0040] By forming such a diffraction grating pattern on the surface of an article, an article that can prevent forgery by copying can be obtained. Articles that require forgery prevention can be applied to all those that require credibility such as cards, prepaid cards, gift certificates, traveler's checks, passbooks, tickets, admission tickets, business cards, etc., regardless of the material such as paper, resin, metal materials, etc., and the surface is not limited to a flat surface, and there may be curvature, unevenness, etc. to the extent that it does not cause problems in the reading performance of the visual or diffraction grating pattern.

[0041] As a method of forming the diffraction grating pattern on the surface of an article, it is preferably formed in the form of a transfer sheet or a sticker (label). The transfer sheet can be configured, for example, by sequentially laminating a release protective layer, a diffraction grating pattern formation layer, a thin film layer, a resin layer, and an adhesive layer on a support film.

[0042] A transfer sheet having a diffraction grating pattern with such a configuration is overlaid on a substrate via an adhesive layer and transferred by heat pressing. Then, after the transfer, the support film is peeled off to obtain an article having a diffraction grating pattern.

[0043] FIG. 8 is an explanatory diagram of the third and fourth unit pixels forming the diffraction grating pattern of the present invention. In the third unit pixel 12, similar to the first and second unit pixels, in the direction of orbiting around the center, the angle at which diffracted light is emitted gradually changes according to the orbiting angle. If the angles of the diffraction gratings in each region are represented by representative values, they are 0° in region a1, 22.5° in region b1, 45° in region c1, 67.5° in region d1, 90° in region a2, 112.5° in region b2, 135° in region c2, and 157.5° in region d2. That is, as it rotates counterclockwise, the angle rotates by 22.5° per region.

[0044] Also, the fourth unit pixel 13 has substantially the same diameter as the third unit pixel 12. The diffraction grating constituting the fourth unit pixel 13, similar to the third unit pixel 12, has an angle at which diffracted light is emitted gradually changing according to the orbiting angle in the direction of orbiting around the center of the fourth unit pixel 13, but the orbiting direction is opposite. As it orbits clockwise, a diffraction grating is formed such that diffracted light is emitted with respect to incident light from a gradually larger angle.

[0045] FIG. 9 is an explanatory diagram of the appearance when light is irradiated from the 0° direction to the second form of the diffraction grating pattern of the present invention. By combining the third and fourth unit pixels, similar to the diffraction grating pattern in FIG. 5, the third unit pixel 12 is formed at the underlying part, and the fourth unit pixel 13 is formed at the part of the "ロ" - shaped pattern. When light is irradiated onto this diffraction grating pattern from the 0° direction, as described above, both the third unit pixel 12 and the fourth unit pixel 13 emit diffracted light in region a1. Therefore, as a whole, it becomes a mode of the diffraction grating pattern 2a where the same region shines, and the "ロ" - shaped pattern formed by the fourth unit pixel 13 cannot be seen and is in a latent image state.

[0046] On the other hand, FIG. 10 shows how it looks when the direction of the incident light is changed from 0 degrees. Here, the cases of irradiation from the directions of (a) 22.5°, (b) 45°, (c) 67.5°, and (d) 90° are shown respectively.

[0047] In the diffraction grating pattern 2b when the incident light is irradiated from the direction of 22.5°, diffracted light is emitted from the vicinity of the center of the region b1 in the portion where the third unit pixel 12 is formed, while diffracted light is emitted from the vicinity of the center of the region d2 in the "ロ" - shaped portion where the fourth unit pixel 13 is formed. Therefore, since the light - emitting sites in the portion where the first unit pixel 10 is formed and the portion where the second unit pixel 11 is formed are different, a "ロ" - shaped pattern can be seen from the base.

[0048] In the diffraction grating pattern 2c when the incident light is irradiated from the direction of 45°, diffracted light is emitted from the vicinity of the center of the region c1 in the portion where the third unit pixel 12 is formed, while diffracted light is emitted from the vicinity of the center of the region c2 in the "ロ" - shaped portion where the fourth unit pixel 13 is formed. Therefore, a "ロ" - shaped pattern can still be seen from the base, and its light - emitting pattern is also different from that of the diffraction grating pattern 2b.

[0049] In the diffraction grating pattern 2d when the incident light is irradiated from the direction of 67.5°, diffracted light is emitted from the vicinity of the center of the region d1 in the portion where the third unit pixel 12 is formed, while diffracted light is emitted from the vicinity of the center of the region b2 in the "ロ" - shaped portion where the fourth unit pixel 13 is formed. Therefore, the "ロ" - shaped pattern looks different from both the diffraction grating pattern 2b and the diffraction grating pattern 2c.

[0050] In the diffraction grating pattern 2e when the incident light is irradiated from the direction of 90°, both the third unit pixel 12 and the fourth unit pixel 13 emit diffracted light from the vicinity of the center of the region a². Therefore, as a whole, it becomes a state of the diffraction grating pattern 2e where the same region emits light, and the "ロ" - shaped pattern formed by the fourth unit pixel 13 cannot be seen, and it becomes a latent image state.

[0051] FIG. 11 is an explanatory view of fifth and sixth unit pixels forming the diffraction grating pattern of the present invention. The fifth unit pixel 14 shown in FIG. 11(a) has a substantially circular outer shape, and the diffraction grating constituting the fifth unit pixel 14 has an angle of the diffraction grating gradually changing according to the distance from the center in the direction from the outer periphery to the center of the fifth unit pixel 14, that is, in the radial direction. Explaining with FIG. 11(a), in the outermost peripheral region, the angle of the diffraction grating is 0°, and as approaching the center side, the angle of the diffraction grating gradually increases. The region where it becomes 180° is substantially equivalent to 0° as described above, further increases to 45° and 90°, and at the center, the angle of the diffraction grating becomes 180°. Note that the numerical values of the angles marked in each region are shown as representative values of each region.

[0052] Also, the sixth unit pixel 15 shown in FIG. 11(b) has substantially the same diameter as the fifth unit pixel 14, and the diffraction grating constituting it has a direction of change in the angle of the diffraction grating opposite to that of the fifth unit pixel 14. That is, at the center, the angle of the diffraction grating is 0°, and in the direction from the center to the outer periphery, the angle of the diffraction grating gradually increases, becomes 180°, changes to 45° and 90° again, and becomes 180° in the outermost peripheral region. Note that the numerical values of the angles marked in each region are shown as representative values of each region.

[0053] FIG. 12 is an explanatory view of the appearance when light is irradiated from the 0° direction in the third form of the diffraction grating pattern of the present invention. By combining the fifth and sixth unit pixels, similar to the first form of the diffraction grating pattern in FIG. 5, the fifth unit pixel 14 is formed at the base part, and the sixth unit pixel 15 is formed at the part of the "ロ" - shaped pattern. When light is irradiated onto this diffraction grating pattern from the 0° direction, as described above, both the fifth unit pixel 14 and the sixth unit pixel 15 emit diffracted light in the regions marked 0° and 180° in FIG. 11. Therefore, as a whole, it becomes a mode of the diffraction grating pattern 3a where the same region shines, and the "ロ" - shaped pattern formed by the sixth unit pixel 15 cannot be seen and is in a latent image state.

[0054] On the other hand, Fig. 13 shows how it looks when the direction of the incident light is changed from 0 degrees. Here, the cases of irradiation from directions of (a) 22.5°, (b) 45°, (c) 67.5°, and (d) 90° are shown respectively.

[0055] In the diffraction grating pattern 3b when the incident light is irradiated from the direction of 22.5°, diffracted light is emitted from near the boundary between the 0° region and the 45° region inside it in the portion where the fifth unit pixel 14 is formed, while in the "ロ"-shaped portion where the sixth unit pixel 15 is formed, diffracted light is emitted from near the boundary between the 0° region and the 45° region outside it. Therefore, since the light-emitting sites in the portion where the fifth unit pixel 14 is formed and the portion where the sixth unit pixel 15 is formed are different, a "ロ"-shaped pattern can be seen from the base.

[0056] In the diffraction grating pattern 3c when the incident light is irradiated from the direction of 45°, diffracted light is emitted from near the center of the 45° region in the portion where the fifth unit pixel 14 is formed and the portion where the sixth unit pixel 15 is formed. However, since their positions are different, the light-emitting sites are different. Therefore, a "ロ"-shaped pattern can be seen from the base, and its light-emitting pattern is also different from that of the diffraction grating pattern 3b.

[0057] In the diffraction grating pattern 3d when the incident light is irradiated from the direction of 67.5°, diffracted light is emitted from near the boundary between the 45° region and the 90° region inside it in the portion where the fifth unit pixel 14 is formed, while in the "ロ"-shaped portion where the sixth unit pixel 15 is formed, diffracted light is emitted from near the boundary between the 45° region and the 90° region outside it. Therefore, since the light-emitting sites in the portion where the fifth unit pixel 14 is formed and the portion where the sixth unit pixel 15 is formed are different, a "ロ"-shaped pattern can be seen, and its light-emitting pattern is different from both the diffraction grating pattern 3b and the diffraction grating pattern 3c.

[0058] In the diffraction grating pattern 3e when incident light is irradiated from a 90° direction, since both the fifth unit pixel 14 and the sixth unit pixel 15 emit diffracted light in the regions marked 0° and 180° in FIG. 11, the overall diffraction grating pattern 3e shows a state where the same region emits light, and the "ロ" - shaped pattern formed by the sixth unit pixel 15 cannot be seen and is in a latent image state.

[0059] FIG. 14 is an explanatory diagram of the seventh and eighth unit pixels forming the diffraction grating pattern of the present invention. The seventh unit pixel 16 shown in FIG. 14(a) has a form in which concentric diffraction gratings are cut into a rectangle. The diffraction grating constituting the seventh unit pixel 16 has an angle of the diffraction grating gradually changing according to the distance from the center in the direction from the outer periphery to the center of the seventh unit pixel 16. Explaining with FIG. 14(a), in the outermost region corresponding to the corner of the rectangle, the angle of the diffraction grating is 0°, and as it approaches the center side, the angle of the diffraction grating gradually increases. The region where it becomes 180° is substantially equivalent to 0° as described above, and further increases to 45° and 90°, and at the center, the angle of the diffraction grating is 180°. The numerical values of the angles marked in each region are shown as representative values of each region.

[0060] Also, the eighth unit pixel 17 shown in FIG. 14(b) has the same form as the seventh unit pixel 16, and the direction of change in the angle of the diffraction grating constituting it is opposite to that of the seventh unit pixel 16. That is, at the center, the angle of the diffraction grating is 0°, and in the direction from the center to the outer periphery, the angle of the diffraction grating gradually increases, becomes 180°, and then changes to 45° and 90° again, and becomes 180° in the region corresponding to the corner of the outermost rectangle. The numerical values of the angles marked in each region are shown as representative values of each region.

[0061] FIG. 15 is an explanatory view of the appearance when light is irradiated from the 0° direction to the fourth form of the diffraction grating pattern of the present invention. By combining the seventh and eighth unit pixels, similar to the first form of the diffraction grating pattern in FIG. 5, the seventh unit pixel 16 is formed at the base part, and the eighth unit pixel 17 is formed at the part of the "ロ" - shaped pattern. When light is irradiated onto this diffraction grating pattern from the 0° direction, as described above, both the seventh unit pixel 16 and the eighth unit pixel 17 emit diffracted light in the regions marked 0° and 180° in FIG. 14. Therefore, as a whole, it becomes the state of the diffraction grating pattern 4a where the same region shines, and the "ロ" - shaped pattern formed by the eighth unit pixel 17 cannot be seen and is in a latent image state.

[0062] On the other hand, FIG. 16 shows how it looks when the direction of the incident light is changed from 0 degrees. Here, the cases of irradiation from the directions of (a) 22.5°, (b) 45°, (c) 67.5°, and (d) 90° are shown respectively.

[0063] In the diffraction grating pattern 4b when the incident light is irradiated from the 22.5° direction, diffracted light is emitted from near the boundary between the 0° region and the 45° region inside at the part where the seventh unit pixel 16 is formed, while diffracted light is emitted from near the boundary between the 0° region and the 45° region outside at the "ロ" - shaped part where the eighth unit pixel 17 is formed. Therefore, since the light - emitting parts are different at the part where the seventh unit pixel 16 is formed and the part where the eighth unit pixel 17 is formed, the "ロ" - shaped pattern can be seen from the base.

[0064] In the diffraction grating pattern 4c when the incident light is irradiated from the 45° direction, diffracted light is emitted from near the center of the 45° region at the part where the seventh unit pixel 16 is formed and the part where the eighth unit pixel 17 is formed. However, since their positions are different, the light - emitting parts are different. Therefore, the "ロ" - shaped pattern can be seen from the base, and its light - emitting pattern is also different from that of the diffraction grating pattern 4b.

[0065] In the diffraction grating pattern 4d when incident light is irradiated from a direction of 67.5°, diffracted light is emitted from near the boundary between the 45° region and the inner 90° region in the portion where the seventh unit pixel 16 is formed, whereas diffracted light is emitted from near the boundary between the 45° region and the outer 90° region in the "ロ"-shaped portion where the eighth unit pixel 17 is formed. Therefore, since the light-emitting sites are different between the portion where the seventh unit pixel 16 is formed and the portion where the eighth unit pixel 17 is formed, the "ロ"-shaped pattern can be seen, and its light-emitting pattern is different from both the diffraction grating pattern 4b and the diffraction grating pattern 4c.

[0066] In the diffraction grating pattern 4e when incident light is irradiated from a direction of 90°, both the seventh unit pixel 16 and the eighth unit pixel 17 emit diffracted light in the regions marked 0° and 180° in FIG. 14. Therefore, as a whole, it becomes the mode of the diffraction grating pattern 4e where the same region glows, and the "ロ"-shaped pattern formed by the eighth unit pixel 17 cannot be seen, and it becomes a latent image state.

[0067] FIG. 17 is an explanatory diagram of the ninth and tenth unit pixels forming the diffraction grating pattern of the present invention. The ninth unit pixel 18 shown in FIG. 17(a) is in a form where strip-shaped diffraction gratings are combined to form a rectangle, and the diffraction gratings constituting the ninth unit pixel 18 gradually change in angle in the direction from one side of the ninth unit pixel 18 toward the opposite side. Explaining with FIG. 17(a), in the strip-shaped region corresponding to the uppermost side, the angle of the diffraction grating is 0°, and as it approaches the lower side, the angle of the diffraction grating gradually increases. The region where it becomes 180° is substantially equivalent to 0° as described above, and further increases to 22.5° and 45°. In the strip-shaped region corresponding to the lowermost side, the angle of the diffraction grating is 157.5°. The numerical values of the angles marked in each region are shown as representative values of each region.

[0068] Also, the tenth unit pixel 19 shown in FIG. 17(b) has the same form as the ninth unit pixel 18 The diffraction grating that makes up the structure has a direction of change in the angle of the diffraction grating opposite to that of the ninth unit pixel 18. That is, in the strip-shaped region at the bottom edge, the angle of the diffraction grating is 22.5°, and as it approaches the upper edge, the angle of the diffraction grating gradually increases. The region where the angle becomes 180° is substantially equivalent to 0° as described above, and further increases to 22.5° and 45°. In the strip-shaped region corresponding to the uppermost edge, the angle of the diffraction grating is 180°. The numerical values of the angles marked in each region are shown as representative values of each region.

[0069] Figure 18 is an explanatory diagram of the appearance when light is irradiated from the 0° direction onto the fifth form of the diffraction grating pattern of the present invention. By combining the ninth and tenth unit pixels, similar to the first form of the diffraction grating pattern in Figure 5, the ninth unit pixel 18 is formed at the underlying part, and the tenth unit pixel 19 is formed at the part of the "ロ" - shaped pattern. When this diffraction grating pattern is irradiated with light from the 0° direction, as described above, both the ninth unit pixel 18 and the tenth unit pixel 19 emit diffracted light in the regions marked 0° and 180° in Figure 17. Therefore, as a whole, it becomes the aspect of the diffraction grating pattern 4a where the same strip-shaped region shines, and the "ロ" - shaped pattern formed by the eighth unit pixel 17 cannot be seen and is in a latent image state.

[0070] On the other hand, Figure 19 shows how it looks when the direction of the incident light is changed from 0 degrees. Here, it shows the cases of irradiation from the directions of (a) 22.5°, (b) 45°, (c) 67.5°, and (d) 90° respectively.

[0071] In the diffraction grating pattern 5b when the incident light is irradiated from the 22.5° direction, diffracted light is emitted from near the center of the 22.5° region in both the part where the ninth unit pixel 18 is formed and the "ロ" - shaped part where the tenth unit pixel 17 is formed. However, because their positions are different, the light - emitting parts in the part where the ninth unit pixel 18 is formed and the part where the tenth unit pixel 19 is formed are different, so that the "ロ" - shaped pattern can be seen from the background.

[0072] In the diffraction grating pattern 5c when incident light is irradiated from a 45° direction, diffracted light is emitted from near the center of the 45° region in the portion where the ninth unit pixel 18 is formed and the portion where the tenth unit pixel 19 is formed. However, since their positions are different, the light-emitting sites are different, so a "ロ" (Japanese character) shaped pattern can be seen from the base, and its light-emitting pattern is also different from the diffraction grating pattern 5b.

[0073] In the diffraction grating pattern 5d when incident light is irradiated from a 67.5° direction, diffracted light is emitted from near the center of the 67.5° region in both the portion where the ninth unit pixel 18 is formed and the "ロ" shaped portion where the tenth unit pixel 17 is formed. However, since their positions are different, the light-emitting sites are different between the portion where the ninth unit pixel 18 is formed and the portion where the tenth unit pixel 19 is formed, so a "ロ" shaped pattern can be seen, and its light-emitting pattern is different from both the diffraction grating pattern 5b and the diffraction grating pattern 5c.

[0074] In the diffraction grating pattern 5e when incident light is irradiated from a 90° direction, both the ninth unit pixel 18 and the tenth unit pixel 19 emit diffracted light in the region marked as 90° in FIG. 17. Therefore, as a whole, the diffraction grating pattern 5e has a mode where the same region emits light, and the "ロ" shaped pattern formed by the tenth unit pixel 19 cannot be seen and is in a latent image state.

[0075] In the above examples, the diffraction grating patterns composed of combinations of two types of unit pixels have been described. However, the diffraction grating pattern of the present invention is not limited to this, and it can also be configured by combining three or more types of unit pixels.

[0076] As described above, in the diffraction grating pattern of the present invention, without the need for a special determination device or the like, when the angle of illumination from the light source is changed, the pattern from which diffracted light is emitted rotates accordingly. It can be switched so that it looks like [a certain state], or the part where it is issued seems to move, and any pattern can become a latent image or a visible image with respect to the base, and a diffraction grating pattern having a unique optical effect can be obtained.

Explanation of symbols

[0077] 1, 1a, 1b, 1c, 1d, 1e, 2a, 2b, 2c, 2d, 2e, 3a, 3b, 3c, 3d, 3e, 4a, 4b, 4c, 4d, 4e, 5a, 5b, 5c, 5d, 5e ··· diffraction grating pattern 10, 10a ··· first unit pixel 10b ··· concentric circles 10c ··· gap 11 ··· second unit pixel 12 ··· third unit pixel 13 ··· fourth unit pixel 14 ··· fifth unit pixel 15 ··· sixth unit pixel 16 ··· seventh unit pixel 17 ··· eighth unit pixel 18 ··· ninth unit pixel 19 ··· tenth unit pixel

Claims

1. A diffraction grating pattern in which at least two types of unit pixels each composed of a diffraction grating are combined and arranged in an array of one type of unit pixel such that a predetermined shape is formed by unit pixels of another type, and a plurality of such combinations are arranged, wherein at least one of the unit pixels is formed by arranging a plurality of types of diffraction gratings having different diffraction angles such that the diffraction angle gradually changes along a direction from the outer periphery to the center of the unit pixel, wherein at least one of the unit pixels is formed by arranging a plurality of types of diffraction gratings having different diffraction angles such that the diffraction angle gradually changes along a direction from the center to the outer periphery of the unit pixel, and in at least one array portion having a corresponding positional relationship in the array, a diffraction grating pattern in which the diffraction angles are equal.

2. The diffraction grating pattern according to Claim 1, wherein the diffraction angle of the diffraction grating changes over substantially 180° within the unit pixel.

3. The diffraction grating pattern according to Claim 1 or 2, characterized by including a region where no diffraction grating exists.

4. An article having formed on its surface the diffraction grating pattern according to any one of Claims 1 to 3.

Images