Security tag

Abstract

To provide a security tag capable of exhibiting a high forgery prevention effect.SOLUTION: A security tag 1 comprises: a resin layer 10; and a plurality of colloidal particles 20 (first colloidal particle 20a and second colloidal particle 20b) embedded in the resin layer 10, arranged apart from each other along a surface direction perpendicular to a thickness direction of the resin layer 10. The plurality of colloidal particles 20 contain several types of particle groups (first particle group 25a and second particle group 25b) each having a different average particle diameter. At least one aggregation region (first aggregation region Paa1 and second aggregation region Pba1), formed by an aggregation of the colloidal particles 20, exists independently per particle group in the resin layer 10. One type of two-dimensional crystal (two-dimensional crystal Raa1 and two-dimensional crystal Rba1) constituted by the colloidal particles 20 exists in each aggregation region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a security tag.

Background Art

[0002] Patent Document 1 discloses a forgery prevention structure including a particulate fixing layer having spherical fine particles and a particulate fixing resin for holding and fixing the spherical fine particles, the particulate fixing resin including one or more resins, the spherical fine particles being arranged so that half or more of the height thereof is not buried, the spherical fine particles being arranged in a single planar shape over the entire surface with an area filling rate of 30% or more or in an arbitrary shape, having an average particle diameter of 2.5 μm or less, and having 70% or more of the number of particles in the range of 0.8 times or more and 1.2 times or less of the average particle diameter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the forgery prevention structure described in Patent Document 1, authenticity determination is performed by utilizing a color change that is confirmed by moving the position of a light source or an observation point.

[0005] However, in the forgery prevention structure described in Patent Document 1, since the color change is confirmed, it cannot be made difficult to visually recognize in the visible light region. Therefore, there is room for improvement in enhancing the forgery prevention effect in the forgery prevention structure described in Patent Document 1.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a security tag capable of exhibiting a high forgery prevention effect.

Means for Solving the Problem

[0007] The security tag of the present invention includes a resin layer and a plurality of colloidal particles that are buried in the resin layer and are arranged side by side at intervals along a plane direction perpendicular to the thickness direction of the resin layer. The plurality of colloidal particles include a plurality of types of particle groups having different average particle diameters. In the resin layer, at least one aggregation region formed by the aggregation of the colloidal particles exists independently for each of the particle groups, and one type of two-dimensional crystal composed of the colloidal particles exists in each of the aggregation regions. It is characterized by this.

Advantages of the Invention

[0008] According to the present invention, a security tag capable of exhibiting a high anti-counterfeiting effect can be provided.

Brief Description of the Drawings

[0009]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, the security tag of the present invention will be described. Note that the present invention is not limited to the following configurations, and may be appropriately modified without departing from the gist of the present invention. In addition, a combination of a plurality of the individual preferred configurations described below is also within the scope of the present invention.

[0011] Each of the embodiments shown below is an exemplification, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. In the following embodiments from Embodiment 2 onwards, descriptions of matters common to Embodiment 1 will be omitted, and different points will be mainly described. In particular, the same operational effects due to the same configurations will not be sequentially mentioned for each embodiment.

[0012] In the following description, when the embodiments are not particularly distinguished, the security tag of the present invention is simply referred to as "the security tag of the present invention".

[0013] The drawings shown below are schematic diagrams, and their dimensions, scales of aspect ratios, etc. may differ from those of actual products.

[0014] In this specification, unless otherwise specified, terms indicating the relationship between elements (e.g., "parallel", "perpendicular", etc.) and terms indicating the shape of elements do not only mean the exact and strict aspects, but also mean substantially equivalent ranges, for example, ranges including differences of about several percent.

[0015] The security tag of the present invention includes a resin layer and a plurality of colloidal particles embedded in the resin layer and arranged at intervals along a plane direction perpendicular to the thickness direction of the resin layer. The plurality of colloidal particles include a plurality of types of particle groups having different average particle diameters from each other. In the resin layer, there is at least one aggregation region formed by the aggregation of the colloidal particles independently for each of the particle groups, and in each of the aggregation regions, there is one type of two-dimensional crystal composed of the colloidal particles. This is the feature.

[0016] [Embodiment 1] In the security tag of Embodiment 1 of the present invention, when viewed from the thickness direction, the two-dimensional crystal has a six-fold symmetry.

[0017] FIG. 1 is a plan view schematically showing an example of the security tag of Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a cross-section along the thickness direction of the security tag shown in FIG. 1.

[0018] The security tag 1 shown in FIGS. 1 and 2 has a resin layer 10 and a plurality of colloidal particles 20.

[0019] In the security tag 1, the plurality of colloidal particles 20 are embedded in the resin layer 10. Thereby, the plurality of colloidal particles 20 are fixed to the resin layer 10.

[0020] In this specification, when colloidal particles are embedded in a resin layer, it means that 90% or more of the height of the colloidal particles is embedded in the resin layer in the thickness direction of the resin layer (the direction perpendicular to the paper surface in FIG. 1 and the vertical direction in FIG. 2).

[0021] In the example shown in FIG. 2, the plurality of colloidal particles 20 are completely embedded in the resin layer 10. Thereby, the plurality of colloidal particles 20 are protected by the resin layer 10.

[0022] The mode in which the colloidal particles 20 are completely embedded in the resin layer 10 includes a mode in which the colloidal particles 20 are in contact with the surface of the resin layer 10 from the inside and a mode in which the colloidal particles 20 are located inside the surface of the resin layer 10.

[0023] In the security tag 1, the plurality of colloidal particles 20 are arranged side by side at intervals along a plane direction perpendicular to the thickness direction of the resin layer 10 (hereinafter, simply referred to as the thickness direction). The plurality of colloidal particles 20 are not arranged so as to be stacked in the thickness direction. That is, the plurality of colloidal particles 20 are arranged two-dimensionally, not three-dimensionally.

[0024] In the security tag 1, since the plurality of colloidal particles 20 are arranged two-dimensionally in a state of being embedded in the resin layer 10, the plurality of colloidal particles 20 are less likely to be visually recognized in the visible light region as compared with the case where the plurality of colloidal particles 20 are arranged three-dimensionally. Further, in the security tag 1, since the resin layer 10 is often transparent, the resin layer 10 is originally less likely to be visually recognized in the visible light region. Therefore, the security tag 1 having the resin layer 10 and the plurality of colloidal particles 20 in such a state is less likely to be visually recognized in the visible light region.

[0025] The security tag 1 is used, for example, for security purposes such as authenticity determination of articles. For example, when a manufacturer, a distributor, etc. attach the security tag 1 to a genuine article in advance, by checking whether the security tag 1 is attached to the target article, it is possible to perform an authenticity determination as to whether the target article is genuine or fake.

[0026] When the security tag 1 is used for the security applications described above, for example, it is assumed to be attached to expensive items such as paintings, watches, etc. In this case, the security tag 1 is assumed to be attached to, for example, the back surface of a painting, the back surface of a frame storing the painting, etc. Also, the security tag 1 is assumed to be attached to, for example, the back surface of the dial part of a watch. In any case, a third party attempting to counterfeit these expensive items needs to counterfeit the security tag 1 as well. However, since the security tag 1 is difficult to be visually recognized in the visible light region, it becomes difficult for a third party attempting to manufacture a counterfeit product to notice the existence of the security tag 1. Therefore, it is unlikely that a third party will attempt to manufacture a counterfeit product including the security tag 1, and it is difficult to manufacture a complete counterfeit product including the security tag 1.

[0027] Therefore, the security tag 1 in which a plurality of colloidal particles 20 are two-dimensionally arranged in a state of being buried in the resin layer 10 can exhibit a high anti-counterfeiting effect.

[0028] When viewed from the thickness direction, it is preferable that the plurality of colloidal particles 20 are provided throughout the security tag 1.

[0029] Note that when viewed from the thickness direction, the plurality of colloidal particles 20 may be provided in a part of the security tag 1. That is, when viewed from the thickness direction, the plurality of colloidal particles 20 do not necessarily have to be provided in a part of the security tag 1.

[0030]

[0031] ​In the security tag 1, the plurality of colloidal particles 20 include a plurality of types of particle groups having different average particle diameters from each other.

[0032] In this specification, that the average particle diameters of the plurality of types of particle groups are different from each other means that when a combination of two types of particle groups is selected from the plurality of types of particle groups, for any combination of particle groups, the ratio of the average particle diameters of the particle groups is less than 0.97 or greater than 1.03, preferably less than or equal to 0.95 or greater than or equal to 1.05, and particularly preferably less than 0.9 or greater than 1.1.

[0033] In the examples shown in FIGS. 1 and 2, the plurality of colloidal particles 20 include a first particle group 25a composed of a plurality of first colloidal particles 20a and a second particle group 25b composed of a plurality of second colloidal particles 20b.

[0034] In the examples shown in FIGS. 1 and 2, the average particle diameters of the first particle group 25a (the plurality of first colloidal particles 20a) and the second particle group 25b (the plurality of second colloidal particles 20b) are different from each other. That is, in the examples shown in FIGS. 1 and 2, the ratio of the average particle diameters of the first particle group 25a and the second particle group 25b is less than 0.97 or greater than 1.03.

[0035] In the examples shown in FIGS. 1 and 2, the average particle diameter of the first particle group 25a is smaller than the average particle diameter of the second particle group 25b. That is, in the examples shown in FIGS. 1 and 2, the ratio of the average particle diameter of the first particle group 25a to the average particle diameter of the second particle group 25b is less than 0.97.

[0036] Note that the average particle diameter of the first particle group 25a may be larger than the average particle diameter of the second particle group 25b. That is, the ratio of the average particle diameter of the first particle group 25a to the average particle diameter of the second particle group 25b may be greater than 1.03.

[0037] In the security tag 1, among the average particle sizes of multiple types of particle groups, the difference between the average particle sizes of the two types of particle groups with the closest average particle sizes is preferably 50 nm or more and 10 μm or less, and more preferably 100 nm or more and 5 μm or less.

[0038] In the examples shown in FIGS. 1 and 2, the difference between the average particle sizes of the first particle group 25a and the second particle group 25b is preferably 50 nm or more and 10 μm or less, and more preferably 100 nm or more and 5 μm or less.

[0039] The average particle size of the first particle group 25a is preferably 1 nm or more and 50 μm or less.

[0040] The average particle size of the second particle group 25b is preferably 1 nm or more and 50 μm or less.

[0041] The average particle size of the particle group is measured using a scanning electron microscope (SEM) for preferably 100 or more and 200 or less colloidal particles among all the colloidal particles constituting the particle group.

[0042] Hereinafter, when the first colloidal particle 20a and the second colloidal particle 20b are not particularly distinguished, it is simply also referred to as the colloidal particle 20.

[0043] In the security tag 1, in the resin layer 10, there is at least one aggregation region formed by the aggregation of the colloidal particles 20, independent for each particle group.

[0044] In the example shown in FIG. 1, in the resin layer 10, there is one aggregation region formed by the aggregation of the colloidal particles 20 for each particle group. Specifically, for the first particle group 25a, a first aggregation region Paa1 formed by the aggregation of the first colloidal particles 20a exists in the resin layer 10. For the second particle group 25b, a second aggregation region Pba1 formed by the aggregation of the second colloidal particles 20b exists in the resin layer 10.

[0045] In security tag 1, the first set region Paa1 and the second set region Pba1 are unique regions that cannot be reproduced because they are formed by, for example, the method described later. Therefore, it is impossible to forge another security tag that has set regions with exactly the same shape, size, etc. as the first set region Paa1 and the second set region Pba1.

[0046] Therefore, security tag 1 in which the first set region Paa1 and the second set region Pba1 exist can exhibit a high forgery prevention effect.

[0047] In security tag 1, one type of two-dimensional crystal composed of colloidal particles 20 exists in each set region.

[0048] In the example shown in FIG. 1, a two-dimensional crystal Raa1 composed of first colloidal particles 20a exists in the first set region Paa1. A two-dimensional crystal Rba1 composed of second colloidal particles 20b exists in the second set region Pba1.

[0049] When viewed from the thickness direction, the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 each have six-fold rotational symmetry.

[0050] The rotational symmetry of the two-dimensional crystal when viewed from the thickness direction is confirmed by the diffraction pattern described later.

[0051] In security tag 1, the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 are unique crystals that cannot be reproduced because they are formed by, for example, the method described later. Therefore, it is impossible to forge another security tag that has two-dimensional crystals with exactly the same shape, size, etc. as the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1.

[0052] Therefore, security tag 1 in which the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 exist can exhibit a high forgery prevention effect.

[0053] From the above, according to the security tag 1 in which a plurality of colloidal particles 20 are two-dimensionally arranged in a state of being buried in the resin layer 10, the first aggregation region Paa1 and the second aggregation region Pba1 exist, and the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 exist, a security tag capable of exhibiting a high forgery prevention effect can be realized.

[0054] In the security tag 1, when viewed from the thickness direction, it is preferable that the directions of the symmetry axes along the plane direction of the two-dimensional crystal are different from each other in at least one set of adjacent aggregation regions in the plane direction.

[0055] In the example shown in FIG. 1, the two-dimensional crystal Raa1 has a symmetry axis Xaa1 as the symmetry axis along the plane direction. The two-dimensional crystal Rba1 has a symmetry axis Xba1 as the symmetry axis along the plane direction.

[0056] In this specification, the symmetry axis along the plane direction means the symmetry axis along the plane direction when the two-dimensional crystal is line-symmetric when viewed from the thickness direction.

[0057] In the example shown in FIG. 1, when viewed from the thickness direction, in a set of adjacent first aggregation region Paa1 and second aggregation region Pba1 in the plane direction, the direction of the symmetry axis Xaa1 along the plane direction of the two-dimensional crystal Raa1 and the direction of the symmetry axis Xba1 along the plane direction of the two-dimensional crystal Rba1 are different from each other.

[0058] Note that when viewed from the thickness direction, the directions of the symmetry axis Xaa1 along the plane direction of the two-dimensional crystal Raa1 and the symmetry axis Xba1 along the plane direction of the two-dimensional crystal Rba1 may be the same as each other.

[0059] The two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 are unique crystals that cannot be reproduced, and the combination of the directions of the symmetry axes along their plane directions is also a unique combination that cannot be reproduced.

[0060] Therefore, in addition to the presence of the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1, the security tag 1 can exhibit a higher anti-counterfeiting effect by the combination of the directions of the symmetry axes along these plane directions.

[0061] In the security tag 1, the lower limit of the median value of the areas of all the aggregated regions when viewed from the thickness direction is not particularly limited, but is preferably 10 μm 2 or more. In this case, as will be described later, the diffraction patterns derived from the two-dimensional crystals are likely to be confirmed.

[0062] In the example shown in FIG. 1, the median value of the areas of the first aggregated region Paa1 and the second aggregated region Pba1 when viewed from the thickness direction is preferably 10 μm 2 or more. In this case, as will be described later, the diffraction patterns derived from the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 are likely to be confirmed.

[0063] On the other hand, in the technique described in Patent Document 1, the specific region that the spherical fine particles have in the fine particle fixing layer is very small. Therefore, in the technique described in Patent Document 1, it is difficult to confirm the diffraction pattern derived from the array structure of the spherical fine particles.

[0064] In the security tag 1, the upper limit of the median value of the areas of all the aggregated regions when viewed from the thickness direction is not particularly limited, but is preferably 2.25 mm 2 or less. In this case, each aggregated region does not become too large as a whole, and the time required to form each aggregated region is not too long, so the manufacturing efficiency of the security tag 1 is likely to increase. Furthermore, since each aggregated region does not become too large as a whole, the security tag 1 is difficult to visually recognize.

[0065] In the example shown in FIG. 1, the median value of the areas of the first aggregated region Paa1 and the second aggregated region Pba1 when viewed from the thickness direction is preferably 2.25 mm 2 or less.

[0066] The area of each aggregation region is determined as follows. First, the security tag is imaged with a microscope (e.g., a scanning electron microscope). Then, by analyzing the obtained image with image analysis software, while determining the range of each aggregation region (e.g., the first aggregation region formed by the aggregation of the first colloidal particles, the second aggregation region formed by the aggregation of the second colloidal particles, etc.) formed by the aggregation of colloidal particles, the area of each aggregation region is measured. At this time, the range of each aggregation region is defined as a region that satisfies both the condition that adjacent colloidal particles belong to the same particle group and the condition that adjacent colloidal particles are arranged symmetrically (e.g., six-fold symmetry, four-fold symmetry, etc.). As the image analysis software, for example, "ImageJ" provided by the National Institutes of Health of the United States, "WinROOF" manufactured by Mitani Corporation, "A Image-kun" manufactured by Asahi Kasei Engineering Co., Ltd., etc. can be used. When determining the area of each aggregation region in the security tag, the security tag may be divided into a plurality of regions and imaged, and then the area of each aggregation region may be measured for the image of each region by the method described above.

[0067] The median of the areas of all the aggregation regions is defined as the area whose rank is in the middle when the areas of the aggregation regions are arranged in ascending (or descending) order. When the number of aggregation regions is odd, the area when the rank of the area of the aggregation region is in the middle is the median, while when the number of aggregation regions is even, the average value of the two areas whose ranks of the areas of the aggregation regions are closest to the middle is the median.

[0068] As shown in FIG. 2, the resin layer 10 has a first surface 10a and a second surface 10b that face each other in the thickness direction. At this time, the colloidal particles 20 may be present on the first surface 10a side of the first surface 10a and the second surface 10b of the resin layer 10. That is, the distance between the colloidal particles 20 and the first surface 10a of the resin layer 10 may be smaller than the distance between the colloidal particles 20 and the second surface 10b of the resin layer 10.

[0069] Note that the colloidal particles 20 may be present on the second surface 10b side of the first surface 10a and the second surface 10b of the resin layer 10. That is, the distance between the colloidal particles 20 and the first surface 10a of the resin layer 10 may be greater than the distance between the colloidal particles 20 and the second surface 10b of the resin layer 10.

[0070] Further, the colloidal particles 20 may be present in the middle of the first surface 10a and the second surface 10b of the resin layer 10. That is, the distance between the colloidal particles 20 and the first surface 10a of the resin layer 10 may be the same as the distance between the colloidal particles 20 and the second surface 10b of the resin layer 10.

[0071] In the visible light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be the same as each other. In this case, the security tag 1 becomes completely invisible in the visible light region. Therefore, the anti-counterfeiting effect by the security tag 1 is further enhanced.

[0072] When the security tag 1 becomes completely invisible in the visible light region, a third party attempting to manufacture a counterfeit product cannot notice the presence of the security tag 1. Therefore, since the third party does not attempt to manufacture a counterfeit product including the security tag 1, a complete counterfeit product including the security tag 1 is not manufactured. Further, when the security tag 1 becomes completely invisible, it is prevented that the security tag 1 has an adverse effect on the appearance (design) of the article.

[0073] In this specification, the visible light region means a wavelength region of 360 nm or more and 830 nm or less.

[0074] In this specification, that the refractive indices in the visible light region are the same as each other means that the ratio of the refractive indices in the visible light region is 0.95 or more and 1.05 or less.

[0075] In the visible light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be different from each other.

[0076] In this specification, the refractive indices in the visible light region being different from each other means that the ratio of the refractive indices in the visible light region is less than 0.95 or greater than 1.05.

[0077] The refractive index of the resin layer 10 in the visible light region is preferably 1.3 or more and 2.3 or less.

[0078] The refractive index of the colloidal particles 20 in the visible light region is preferably 1.3 or more and 2.3 or less.

[0079] The refractive indices of the resin layer and the colloidal particles in the visible light region are measured by the V-block method.

[0080] In the infrared light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be different from each other. In this case, the security tag 1 becomes detectable in the infrared light region.

[0081] In this specification, the infrared light region means a wavelength region of 830 nm or more and 1 mm or less.

[0082] In this specification, the refractive indices in the infrared light region being different from each other means that the ratio of the refractive indices in the infrared light region is less than 0.95 or greater than 1.05.

[0083] In the infrared light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be the same as each other.

[0084] In this specification, the refractive indices in the infrared light region being the same as each other means that the ratio of the refractive indices in the infrared light region is 0.95 or more and 1.05 or less.

[0085] The refractive index of the resin layer 10 in the infrared light region is preferably 0.4 or more and 5.7 or less.

[0086] The refractive index of the colloidal particles 20 in the infrared light region is preferably 0.4 or more and 5.7 or less.

[0087] The refractive indices of the resin layer and the colloidal particles in the infrared light region are measured by the V-block method.

[0088] In the security tag 1, in the visible light region, the refractive indices of the resin layer 10 and the colloidal particles 20 are the same as each other, and in the infrared light region, since the refractive indices of the resin layer 10 and the colloidal particles 20 are different from each other, the security tag 1 becomes invisible (undetectable) in the visible light region and detectable in the infrared light region. In this case, a third party attempting to manufacture a counterfeit product cannot notice the existence of the security tag 1, and even if by any chance they notice the existence of the security tag 1, there exist the uniquely irreproducible first set region Paa1 and second set region Pba1, and furthermore, there exist the uniquely irreproducible two-dimensional crystals Raa1 and Rba1, and it is impossible to manufacture a counterfeit product of the security tag 1 in which the refractive indices of the resin layer 10 and the colloidal particles 20 are different from each other in the infrared light region.

[0089] When the security tag 1 is detectable in the infrared light region, the security tag 1 can be attached, for example, to the back of a painting or to the back of the dial part of a watch so that the security tag 1 is not visible from the front of the painting, watch, etc. Even in this case, since infrared light (infrared rays) can pass through glass, plastic, etc., the security tag 1 can be detected in the infrared light region.

[0090] In the security tag 1, when the refractive indices of the resin layer 10 and the colloidal particles 20 are the same as each other in the visible light region, in the infrared light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be the same as each other or may be different from each other.

[0091] In security tag 1, in the visible light region, when the refractive indices of the resin layer 10 and the colloidal particles 20 are different from each other, that is, when security tag 1 is detectable in the visible light region, in the infrared light region, the refractive indices of the resin layer 10 and the colloidal particles 20 may be the same as each other or may be different from each other. This is because when security tag 1 is not detected in the infrared light region, the relationship between the refractive indices of the resin layer 10 and the colloidal particles 20 in the infrared light region does not affect the detectability of security tag 1.

[0092] The resin layer 10 is preferably composed of an ultraviolet curable resin.

[0093] Examples of the constituent material of the resin layer 10 include polymer resins such as acrylic resins, epoxy resins, polyurethane resins, and polystyrene resins, silicone resins, and biopolymers. Among these resins, acrylic resins are preferred. Further, among acrylic resins, polydialkylacrylamide is preferred.

[0094] The colloidal particles 20 may be inorganic particles or organic particles.

[0095] When the colloidal particles 20 are inorganic particles, examples of the constituent material thereof include silica, titanium oxide, alumina, gold, silver, etc. Among them, silica and titanium oxide are preferred. When the colloidal particles 20 are composed of silica, if the resin layer 10 is composed of polydialkylacrylamide, the resin layer 10 is likely to adsorb to the colloidal particles 20, so the colloidal particles 20 are likely to be fixed to the resin layer 10.

[0096] When the colloidal particles 20 are organic particles, examples of the constituent material thereof include polymers such as polystyrene, polyacrylate ester, polymethacrylate ester, and polyacrylonitrile. Among them, polystyrene is preferred.

[0097] As shown in FIG. 2, the security tag 1 may further include a substrate 30 provided on the first surface 10a side of the resin layer 10. In this case, the colloidal particles 20 are protected not only by the resin layer 10 but also by the substrate 30.

[0098] In the aspect where the substrate 30 is provided on the first surface 10a side of the resin layer 10, there are an aspect where the substrate 30 is separated from the first surface 10a of the resin layer 10 and another layer (for example, the intermediate layer 40 described later) is provided between them, and an aspect where the substrate 30 is in contact with the first surface 10a of the resin layer 10.

[0099] Examples of the substrate 30 include transparent plates such as glass plates and plastic plates.

[0100] As shown in FIG. 2, the security tag 1 may further include an intermediate layer 40 provided between the resin layer 10 and the substrate 30 and in contact with the resin layer 10 and the substrate 30. In this case, the colloidal particles 20 are protected not only by the resin layer 10 and the substrate 30 but also by the intermediate layer 40.

[0101] As shown in FIG. 2, the intermediate layer 40 preferably contacts the colloidal particles 20.

[0102] In the example shown in FIG. 2, the colloidal particles 20 are present on the first surface 10a side of the first surface 10a and the second surface 10b of the resin layer 10. Specifically, the colloidal particles 20 are in contact with the first surface 10a of the resin layer 10 from the inside. Further, in the example shown in FIG. 2, the intermediate layer 40 is in contact with the first surface 10a of the resin layer 10. Therefore, in the example shown in FIG. 2, the intermediate layer 40 is in contact with the colloidal particles 20.

[0103] Since the intermediate layer 40 is in contact with the colloidal particles 20, the colloidal particles 20 are fixed to the substrate 30 via the intermediate layer 40. When the colloidal particles 20 are fixed to the substrate 30, for example, even if an external force is applied to the security tag 1, the structure of the two-dimensional crystal composed of the colloidal particles 20, here, the structures of the two-dimensional crystals Raa1 and Rba1 are likely to be maintained.

[0104] The thickness of the intermediate layer 40 is, for example, 1 nm or more and 100 nm or less.

[0105] The intermediate layer 40 is preferably composed of a metal oxide. In this case, titanium oxide is preferable as the metal oxide.

[0106] The intermediate layer 40 may be composed of a material other than a metal oxide. For example, the intermediate layer 40 may be composed of a silane coupling agent.

[0107] The security tag 1 is manufactured, for example, as follows.

[0108] <Step of forming the intermediate layer> FIG. 3 is a cross-sectional view schematically showing a step of forming an intermediate layer in an example of a method for manufacturing a security tag according to Embodiment 1 of the present invention.

[0109] First, a substrate 30 is prepared.

[0110] Next, as shown in FIG. 3, an intermediate layer 40 is formed on the surface of the substrate 30.

[0111] The method for forming the intermediate layer 40 is not particularly limited.

[0112] <Step of applying the colloidal dispersion> FIG. 4 is a cross-sectional view schematically showing a step of applying a colloidal dispersion in an example of a method for manufacturing a security tag according to Embodiment 1 of the present invention.

[0113] First, a colloidal dispersion 50 is prepared by dispersing a plurality of colloidal particles 20, here, a plurality of first colloidal particles 20a and a plurality of second colloidal particles 20b, in a dispersion medium.

[0114] Examples of the dispersion medium include inorganic solvents such as water, organic solvents such as alcohol, and the like.

[0115] It is preferable that a polymer is added to the colloidal dispersion 50. In this case, for example, a solution in which the polymer is dissolved in the dispersion medium is prepared in advance, and a plurality of colloidal particles 20, here, a plurality of first colloidal particles 20a and a plurality of second colloidal particles 20b are added to this solution and stirred to produce the colloidal dispersion 50.

[0116] According to the polymer added to the colloidal dispersion 50, for example, depletion attraction acting between the colloidal particles 20 of the same type of particle group as described later is caused.

[0117] Next, as shown in FIG. 4, the colloidal dispersion 50 is applied to the surface of the base material 30 of the intermediate layer 40 on the side opposite to the base material 30.

[0118] The method of applying the colloidal dispersion 50 is not particularly limited, and examples thereof include a method of dropping the colloidal dispersion 50 onto the surface of the base material 30 of the intermediate layer 40 on the side opposite to the base material 30, and a method of immersing the base material 30 with the intermediate layer 40 in the colloidal dispersion 50.

[0119] In this step, it is preferable that the colloidal particles 20 and the intermediate layer 40 have the same polarity of charge as each other. In this case, as shown in FIG. 4, the colloidal particles 20, here, the first colloidal particles 20a and the second colloidal particles 20b, are dispersed at positions away from the intermediate layer 40 by the electrostatic repulsive force acting between them and the intermediate layer 40 in the colloidal dispersion 50.

[0120] When the pH of the colloidal dispersion 50 is higher than the isoelectric point of the constituent materials (for example, silica) of the colloidal particles 20, here, the first colloidal particles 20a and the second colloidal particles 20b, the first colloidal particles 20a and the second colloidal particles 20b will carry a negative charge on their surfaces. On the other hand, when the pH of the colloidal dispersion 50 is lower than the isoelectric point of the constituent materials (for example, silica) of the colloidal particles 20, here, the first colloidal particles 20a and the second colloidal particles 20b, the first colloidal particles 20a and the second colloidal particles 20b will carry a positive charge on their surfaces.

[0121] When the pH of the colloidal dispersion 50 is higher than the isoelectric point of the constituent material (for example, titanium oxide) of the intermediate layer 40, the intermediate layer 40 will carry a negative charge on the surface opposite to the substrate 30. On the other hand, when the pH of the colloidal dispersion 50 is lower than the isoelectric point of the constituent material (for example, titanium oxide) of the intermediate layer 40, the intermediate layer 40 will carry a positive charge on the surface opposite to the substrate 30.

[0122] Hereinafter, at this point of the present process, the case where the first colloidal particles 20a, the second colloidal particles 20b, and the intermediate layer 40 carry charges of the same polarity (for example, negative charges) will be described.

[0123] <Three - dimensional crystal formation step> FIG. 5 is a cross - sectional view schematically showing a three - dimensional crystal formation step in an example of a method for manufacturing a security tag according to Embodiment 1 of the present invention.

[0124] In the previous step, when the colloidal dispersion 50 is applied to the surface of the intermediate layer 40 opposite to the substrate 30, as shown in FIG. 5, a plurality of colloidal particles 20, which are of the same type of particle group, attract each other by depletion attraction. Specifically, among the plurality of colloidal particles 20, the first colloidal particles 20a constituting the first particle group 25a attract each other by depletion attraction, and the second colloidal particles 20b constituting the second particle group 25b attract each other by depletion attraction.

[0125] Then, the mutually attracting first colloidal particles 20a approach each other and are arranged three - dimensionally, thereby forming a three - dimensional crystal Saa1. Also, the mutually attracting second colloidal particles 20b approach each other and are arranged three - dimensionally, thereby forming a three - dimensional crystal Sba1. As a result, a colloidal eutectic, which is an aggregate in a state where the three - dimensional crystal Saa1 and the three - dimensional crystal Sba1 are mixed, is formed.

[0126] In the example shown in FIG. 5, since the first colloidal particles 20a constituting the three-dimensional crystal Saa1 and the second colloidal particles 20b constituting the three-dimensional crystal Sba1 have charges of the same polarity (for example, negative charges) on their surfaces as the intermediate layer 40, the three-dimensional crystal Saa1 and the three-dimensional crystal Sba1 are formed at positions away from the intermediate layer 40.

[0127] <Adsorption step of three-dimensional crystal> FIG. 6 is a cross-sectional view schematically showing the adsorption step of the three-dimensional crystal in an example of the method for manufacturing the security tag according to Embodiment 1 of the present invention.

[0128] For the structure shown in FIG. 5, the pH of the colloidal dispersion 50 is adjusted. At this time, the pH of the colloidal dispersion 50 is adjusted to be higher than the isoelectric point of the constituent materials (for example, silica) of the colloidal particles 20, here the first colloidal particles 20a and the second colloidal particles 20b, and lower than the isoelectric point of the constituent materials (for example, titanium oxide) of the intermediate layer 40. As a result, the first colloidal particles 20a and the second colloidal particles 20b will carry negative charges, and the intermediate layer 40 will carry positive charges. In this way, by adjusting the pH of the colloidal dispersion 50, it is possible to make the first colloidal particles 20a and the intermediate layer 40 carry charges of different polarities from each other, and the second colloidal particles 20b and the intermediate layer 40 carry charges of different polarities from each other.

[0129] The method for adjusting the pH of the colloidal dispersion 50 is not particularly limited, and examples include a method of dissolving carbon dioxide in the colloidal dispersion.

[0130] When the pH of the colloidal dispersion 50 is adjusted so that the first colloidal particles 20a and the intermediate layer 40 carry charges of different polarities from each other, and the second colloidal particles 20b and the intermediate layer 40 carry charges of different polarities from each other, as shown in FIG. 6, the three-dimensional crystal Saa1 and the three-dimensional crystal Sba1 are adsorbed to the intermediate layer 40 by the electrostatic attraction acting between them and the intermediate layer 40. That is, the three-dimensional crystal Saa1 and the three-dimensional crystal Sba1 will come into contact with the intermediate layer 40.

[0131] <Formation process of two-dimensional crystal> FIG. 7 is a cross-sectional view schematically showing a formation process of a two-dimensional crystal in an example of a method for manufacturing a security tag according to Embodiment 1 of the present invention.

[0132] The structure shown in FIG. 6 is washed with a cleaning liquid 60. Specifically, as shown in FIG. 7, the colloidal dispersion 50 is replaced with the cleaning liquid 60.

[0133] When the structure shown in FIG. 6 is washed with the cleaning liquid 60, as shown in FIG. 7, all but one layer located closest to the intermediate layer 40 among the plurality of first colloidal particles 20a and the plurality of second colloidal particles 20b are washed away. At this time, among the plurality of first colloidal particles 20a and the plurality of second colloidal particles 20b, only one layer located closest to the intermediate layer 40 remains without being washed away because it is strongly adsorbed to the intermediate layer 40 by electrostatic attraction.

[0134] As a result, the one layer of first colloidal particles 20a will be two-dimensionally arranged while being separated from each other by electrostatic repulsive force in a state of being adsorbed to the intermediate layer 40. Thereby, a first aggregation region Paa1 (see FIG. 1) is formed by the one layer of first colloidal particles 20a, and a two-dimensional crystal Raa1 (see FIG. 1) composed of the first colloidal particles 20a is formed in the first aggregation region Paa1. When viewed from the thickness direction, the two-dimensional crystal Raa1 has six-fold symmetry.

[0135] Also, the one layer of second colloidal particles 20b will be two-dimensionally arranged while being separated from each other by electrostatic repulsive force in a state of being adsorbed to the intermediate layer 40. Thereby, a second aggregation region Pba1 (see FIG. 1) is formed by the one layer of second colloidal particles 20b, and a two-dimensional crystal Rba1 (see FIG. 1) composed of the second colloidal particles 20b is formed in the second aggregation region Pba1. When viewed from the thickness direction, the two-dimensional crystal Rba1 has six-fold symmetry.

[0136] The cleaning liquid 60 is not particularly limited, and examples thereof include water.

[0137] The cleaning method using the cleaning liquid 60 is not particularly limited, and examples thereof include a method of immersing the structure shown in FIG. 6 in the cleaning liquid 60.

[0138] <Formation step of resin layer> FIG. 8 is a cross-sectional view schematically showing a formation step of a resin layer in an example of a method for manufacturing a security tag according to Embodiment 1 of the present invention.

[0139] With respect to the structure shown in FIG. 7, as shown in FIG. 8, while removing the cleaning liquid 60 on the surface opposite to the base material 30 of the intermediate layer 40, the resin layer 10 is formed on the surface opposite to the base material 30 of the intermediate layer 40 so that the first colloidal particles 20a and the second colloidal particles 20b are buried.

[0140] The method for forming the resin layer 10 is not particularly limited, and examples thereof include the following methods.

[0141] In the structure shown in FIG. 7, when the cleaning liquid 60 is water, first, a water-soluble resin is added to the cleaning liquid 60 (here, water) to fix the first colloidal particles 20a and the second colloidal particles 20b with the water-soluble resin. Then, when the cleaning liquid 60 (here, water) is removed by drying, the water-soluble resin adheres to the first colloidal particles 20a and the second colloidal particles 20b, thereby fixing the first colloidal particles 20a and the second colloidal particles 20b more firmly. In this way, the resin layer 10 is formed on the surface opposite to the base material 30 of the intermediate layer 40 so that the first colloidal particles 20a and the second colloidal particles 20b are buried.

[0142] As a result of forming the resin layer 10 as described above, as shown in FIG. 1, the first aggregation region Paa1 and the second aggregation region Pba1 exist in the resin layer 10. The first aggregation region Paa1 and the second aggregation region Pba1 are unique regions that cannot be reproduced because they are formed by, for example, the method described above.

[0143] Furthermore, as shown in FIG. 1, a two-dimensional crystal Raa1 exists in the first set region Paa1, and a two-dimensional crystal Rba1 exists in the second set region Pba1. Since the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 are formed by, for example, the method described above, they are unique crystals that cannot be reproduced.

[0144] Thus, the security tag 1 is manufactured.

[0145] The security tag 1 is detected, for example, by using the diffraction pattern of the security tag 1 as follows.

[0146] When the security tag 1 is irradiated with light, diffraction patterns derived from the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 appear simultaneously. In the example shown in FIG. 1, since the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 have six-fold symmetry, a six-fold symmetric diffraction pattern Taa derived from the two-dimensional crystal Raa1 and a six-fold symmetric diffraction pattern Tba derived from the two-dimensional crystal Rba1, as shown in FIG. 9, appear simultaneously. FIG. 9 is a plan view schematically showing an example of the diffraction pattern derived from the two-dimensional crystal shown in FIG. 1.

[0147] Since the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 are unique crystals that cannot be reproduced, a diffraction pattern in which diffraction patterns derived from the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1, for example, the diffraction pattern Taa and the diffraction pattern Tba are combined, is also a unique diffraction pattern that cannot be reproduced. Thus, from the security tag 1 in which the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 exist, a unique diffraction pattern determined by the arrangement, particle size, etc. of the first colloidal particles 20a constituting the two-dimensional crystal Raa1 and the second colloidal particles 20b constituting the two-dimensional crystal Rba1 is detected.

[0148] Therefore, by detecting the unique diffraction pattern of the security tag 1, the security tag 1 that is difficult to be visually recognized in the visible light region can be detected.

[0149] When detecting Security Tag 1, light may be irradiated from a direction perpendicular to the main surface of Security Tag 1 (incident angle: 90°), or light may be irradiated from other directions (incident angle: other than 90°).

[0150] When detecting Security Tag 1, a diffraction pattern can be detected by the reflected light reflected from Security Tag 1 when light is irradiated on Security Tag 1.

[0151] When detecting Security Tag 1, a diffraction pattern can be detected by the transmitted light transmitted through Security Tag 1 when light is irradiated on Security Tag 1.

[0152] When detecting Security Tag 1, by irradiating light from a direction perpendicular to the main surface of Security Tag 1 (incident angle: 90°) and detecting the reflected light reflected in the perpendicular direction from Security Tag 1, a diffraction pattern can be detected. Therefore, when detecting Security Tag 1, the position of the light source that irradiates light on Security Tag 1 and the position of the detector that detects the reflected light reflected from Security Tag 1 can be combined. For example, the light source and the detector can be integrated.

[0153] On the other hand, in the technology described in Patent Document 1, a forgery prevention structure is detected by confirming a color change by moving the position of the light source or the observation point. Therefore, in the technology described in Patent Document 1, a forgery prevention structure cannot be detected without moving the positions of the light source and the observation point. For example, in a state where the positions of the light source and the observation point are combined.

[0154] From the above, when detecting Security Tag 1, unlike the case of detecting the forgery prevention structure described in Patent Document 1, conditions such as the positional relationship between the light source and the detector are not restricted.

[0155] As described above, the method for detecting a security tag using the diffraction pattern of the security tag of the present invention may also be one of the present inventions.

[0156] Since a unique diffraction pattern is detected from Security Tag 1, for example, when Security Tag 1 is attached to an authentic article, the authenticity determination of the target article can be efficiently performed by utilizing the unique diffraction pattern of Security Tag 1 as follows.

[0157] First, by checking whether a diffraction pattern derived from a two-dimensional crystal is detected when the target article is irradiated with light, it is confirmed whether a security tag of the same type as Security Tag 1 is attached to the target article. And when it is determined that a security tag is attached to the target article, by checking whether the diffraction pattern detected from the target article is the same as the unique diffraction pattern of Security Tag 1 attached to the authentic article, it is confirmed whether the security tag attached to the target article is the same as Security Tag 1 attached to the authentic article. At this time, regarding the diffraction pattern derived from the two-dimensional crystal existing in Security Tag 1, for example, information such as shape, size, position, direction of the symmetry axis along the plane direction, and further information such as what kind of diffraction pattern appears when irradiated with light at what incident angle are encoded. Then, by using the encoded information to check the diffraction pattern detected from the target article, the authenticity determination of the target article can be performed more efficiently.

[0158] In the above, in the security tag of the present invention, an embodiment in which another layer (for example, an intermediate layer) is provided between the resin layer and the base material is exemplified. However, in the security tag of the present invention, no other layer may be provided between the resin layer and the base material, and the resin layer and the base material may be in contact.

[0159] FIG. 10 is a cross-sectional view schematically showing another example of the security tag according to Embodiment 1 of the present invention.

[0160] The security tag 1' shown in FIG. 10 has a resin layer 10, a plurality of colloidal particles 20, and a base material 30, similar to the security tag 1 (see FIG. 2). However, unlike the security tag 1 (see FIG. 2), it does not have an intermediate layer 40.

[0161] As shown in FIG. 10, the base material 30 is in contact with the resin layer 10. Specifically, the base material 30 is in contact with the first surface 10a of the resin layer 10.

[0162] As shown in FIG. 10, it is preferable that the base material 30 is in contact with the colloidal particles 20.

[0163] In the example shown in FIG. 10, the colloidal particles 20 are present on the first surface 10a side among the first surface 10a and the second surface 10b of the resin layer 10. Specifically, the colloidal particles 20 are in contact with the first surface 10a of the resin layer 10 from the inside. Further, in the example shown in FIG. 10, the base material 30 is in contact with the first surface 10a of the resin layer 10. Therefore, in the example shown in FIG. 10, the base material 30 is in contact with the colloidal particles 20.

[0164] The security tag 1' can be manufactured in the same manner as the security tag 1, except that, for example, the <intermediate layer forming step> is not performed.

[0165] [Embodiment 2] In the security tag of Embodiment 2 of the present invention, when viewed from the thickness direction, the two-dimensional crystal has a four-fold symmetry.

[0166] FIG. 11 is a plan view schematically showing an example of the security tag of Embodiment 2 of the present invention.

[0167] In the security tag 2 shown in FIG. 11, in the resin layer 10, there are a first aggregation region Pab1 formed by aggregation of first colloidal particles 20a and a second aggregation region Pbb1 formed by aggregation of second colloidal particles 20b.

[0168] In the first aggregation region Pab1, there exists a two-dimensional crystal Rab1 composed of the first colloidal particles 20a. In the second aggregation region Pbb1, there exists a two-dimensional crystal Rbb1 composed of the second colloidal particles 20b.

[0169] When viewed from the thickness direction, the two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 each have a four-fold symmetry.

[0170] The security tag 2 is detected, for example, by using the diffraction pattern of the security tag 2 as follows.

[0171] When the security tag 2 is irradiated with light, diffraction patterns derived from the two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 appear simultaneously. In the example shown in FIG. 11, since the two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 have a four-fold symmetry, a four-fold symmetric diffraction pattern Tab derived from the two-dimensional crystal Rab1 and a four-fold symmetric diffraction pattern Tbb derived from the two-dimensional crystal Rbb1, as shown in FIG. 12, appear simultaneously. FIG. 12 is a plan view schematically showing an example of the diffraction pattern derived from the two-dimensional crystal shown in FIG. 11.

[0172] The two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 having a four-fold symmetry are more difficult to realize compared to the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 having a six-fold symmetry. Therefore, the security tag 2 in which the two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 having a four-fold symmetry exist can exhibit a higher forgery prevention effect compared to the security tag 1 in which the two-dimensional crystal Raa1 and the two-dimensional crystal Rba1 having a six-fold symmetry exist.

[0173] The two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 having four-fold symmetry are realized, for example, when manufacturing the security tag 2 in the same manner as the security tag 1, by adjusting the thickness of the colloidal dispersion 50 applied to the surface on the opposite side of the base material 30 of the intermediate layer 40. For example, after applying the colloidal dispersion 50 to the surface on the opposite side of the base material 30 of the intermediate layer 40, the thickness of the colloidal dispersion 50 can be changed by placing another base material such as a glass plate on the surface of the colloidal dispersion 50. At this time, by changing the thickness of the other base material placed on the surface of the colloidal dispersion 50, the weight of the other base material can be changed, and as a result, the thickness of the colloidal dispersion 50 can be adjusted. When the thickness of the colloidal dispersion 50 is within a specific range, the two-dimensional crystal Rab1 and the two-dimensional crystal Rbb1 having four-fold symmetry are realized.

[0174] [Embodiment 3] In the security tag according to Embodiment 3 of the present invention, in the resin layer, a plurality of aggregation regions formed by aggregation of colloidal particles exist independently for each group of particles.

[0175] FIG. 13 is a plan view schematically showing an example of the security tag according to Embodiment 3 of the present invention.

[0176] In the security tag 3 shown in FIG. 13, in the resin layer 10, a plurality of aggregation regions formed by aggregation of colloidal particles 20 exist for each group of particles.

[0177] In the example shown in FIG. 13, in the resin layer 10, three aggregation regions formed by aggregation of colloidal particles 20 exist for each group of particles. Specifically, for the first particle group 25a, a first aggregation region Pac1, a first aggregation region Pac2, and a first aggregation region Pac3 formed by aggregation of the first colloidal particles 20a exist in the resin layer 10. For the second particle group 25b, a second aggregation region Pbc1, a second aggregation region Pbc2, and a second aggregation region Pbc3 formed by aggregation of the second colloidal particles 20b exist in the resin layer 10.

[0178] In the first aggregation region Pac1, there exists a two-dimensional crystal Rac1 composed of first colloidal particles 20a. In the first aggregation region Pac2, there exists a two-dimensional crystal Rac2 composed of first colloidal particles 20a. In the first aggregation region Pac3, there exists a two-dimensional crystal Rac3 composed of first colloidal particles 20a.

[0179] When viewed from the thickness direction, the two-dimensional crystals Rac1, Rac2, and Rac3 each have six-fold symmetry.

[0180] Note that when viewed from the thickness direction, the two-dimensional crystals Rac1, Rac2, and Rac3 may each have a symmetry other than six-fold symmetry, for example, four-fold symmetry.

[0181] The two-dimensional crystal Rac1 has a symmetry axis Xac1 as a symmetry axis along the plane direction. The two-dimensional crystal Rac2 has a symmetry axis Xac2 as a symmetry axis along the plane direction. The two-dimensional crystal Rac3 has a symmetry axis Xac3 as a symmetry axis along the plane direction.

[0182] In the second aggregation region Pbc1, there exists a two-dimensional crystal Rbc1 composed of second colloidal particles 20b. In the second aggregation region Pbc2, there exists a two-dimensional crystal Rbc2 composed of second colloidal particles 20b. In the second aggregation region Pbc3, there exists a two-dimensional crystal Rbc3 composed of second colloidal particles 20b.

[0183] When viewed from the thickness direction, the two-dimensional crystals Rbc1, Rbc2, and Rbc3 each have six-fold symmetry.

[0184] Note that when viewed from the thickness direction, the two-dimensional crystals Rbc1, Rbc2, and Rbc3 may each have a symmetry other than six-fold symmetry, for example, four-fold symmetry.

[0185] The two-dimensional crystal Rbc1 has a symmetry axis Xbc1 as the symmetry axis along the plane direction. The two-dimensional crystal Rbc2 has a symmetry axis Xbc2 as the symmetry axis along the plane direction. The two-dimensional crystal Rbc3 has a symmetry axis Xbc3 as the symmetry axis along the plane direction.

[0186] In the example shown in FIG. 13, when viewed from the thickness direction, in the set region of all pairs adjacent in the plane direction, the directions of the symmetry axes along the plane direction of the two-dimensional crystals are different from each other. Specifically, the direction of the symmetry axis Xac1 along the plane direction of the two-dimensional crystal Rac1, the direction of the symmetry axis Xac2 along the plane direction of the two-dimensional crystal Rac2, the direction of the symmetry axis Xac3 along the plane direction of the two-dimensional crystal Rac3, the direction of the symmetry axis Xbc1 along the plane direction of the two-dimensional crystal Rbc1, the direction of the symmetry axis Xbc2 along the plane direction of the two-dimensional crystal Rbc2, and the direction of the symmetry axis Xbc3 along the plane direction of the two-dimensional crystal Rbc3 are different from each other.

[0187] Note that when viewed from the thickness direction, in the set region of all pairs adjacent in the plane direction, the directions of the symmetry axes along the plane direction of the two-dimensional crystals may be the same as each other. Specifically, the direction of the symmetry axis Xac1 along the plane direction of the two-dimensional crystal Rac1, the direction of the symmetry axis Xac2 along the plane direction of the two-dimensional crystal Rac2, the direction of the symmetry axis Xac3 along the plane direction of the two-dimensional crystal Rac3, the direction of the symmetry axis Xbc1 along the plane direction of the two-dimensional crystal Rbc1, the direction of the symmetry axis Xbc2 along the plane direction of the two-dimensional crystal Rbc2, and the direction of the symmetry axis Xbc3 along the plane direction of the two-dimensional crystal Rbc3 may be the same as each other.

[0188] Also, when viewed from the thickness direction, among all sets of regions of pairs adjacent in the plane direction, in the set regions of some pairs, the directions of the symmetry axes along the plane direction of the two-dimensional crystal may be different from each other, and in the set regions of the remaining pairs, the directions of the symmetry axes along the plane direction of the two-dimensional crystal may be the same as each other. Specifically, when viewed from the thickness direction, the direction of the symmetry axis Xac1 along the plane direction of the two-dimensional crystal Rac1, the direction of the symmetry axis Xac2 along the plane direction of the two-dimensional crystal Rac2, the direction of the symmetry axis Xac3 along the plane direction of the two-dimensional crystal Rac3, the direction of the symmetry axis Xbc1 along the plane direction of the two-dimensional crystal Rbc1, the direction of the symmetry axis Xbc2 along the plane direction of the two-dimensional crystal Rbc2, and the direction of the symmetry axis Xbc3 along the plane direction of the two-dimensional crystal Rbc3 may be different from each other in some combinations, and may be the same as each other in the remaining combinations. For example, when viewed from the thickness direction, the direction of the symmetry axis Xac1 along the plane direction of the two-dimensional crystal Rac1 and the direction of the symmetry axis Xbc1 along the plane direction of the two-dimensional crystal Rbc1 may be different from each other, and the direction of the symmetry axis Xac2 along the plane direction of the two-dimensional crystal Rac2, the direction of the symmetry axis Xac3 along the plane direction of the two-dimensional crystal Rac3, the direction of the symmetry axis Xbc2 along the plane direction of the two-dimensional crystal Rbc2, and the direction of the symmetry axis Xbc3 along the plane direction of the two-dimensional crystal Rbc3 may be the same as each other.

[0189] The two-dimensional crystals Rac1, Rac2, Rac3, Rbc1, Rbc2, and Rbc3 are irreproducible and unique crystals, and the combination of the directions of the symmetry axes along their plane directions is also an irreproducible and unique combination.

[0190] Therefore, in addition to the existence of the two-dimensional crystals Rac1, Rac2, Rac3, Rbc1, Rbc2, and Rbc3, the security tag 3 can exhibit a higher anti-counterfeiting effect due to the combination of the directions of the symmetry axes along their plane directions.

[0191] The security tag of the present invention is not limited to the above-described embodiments, and various applications and modifications can be made within the scope of the present invention regarding the configuration, manufacturing conditions, etc. of the security tag.

[0192] In the above embodiments, in the security tag of the present invention, an embodiment in which a plurality of colloidal particles include two types of particle groups having different average particle diameters has been exemplified. However, the plurality of colloidal particles may include three or more types of particle groups having different average particle diameters.

[0193] In the above embodiments, in the security tag of the present invention, an embodiment in which there is one aggregation region formed by aggregation of colloidal particles for each particle group or three aggregation regions for each particle group has been exemplified. However, two aggregation regions may exist for each particle group, or four or more aggregation regions may exist for each particle group.

[0194] In the above embodiments, in the security tag of the present invention, an embodiment in which the number of aggregation regions formed by aggregation of colloidal particles is the same for all particle groups (the same for each particle group) has been exemplified. However, the number of aggregation regions may be different for all particle groups (different for each particle group), or may be different for some particle groups. As an embodiment in which the number of aggregation regions is different for some particle groups, for example, when a plurality of colloidal particles include three types of particle groups, the number of aggregation regions in each of two types of particle groups among the three types of particle groups is the same, and the number of aggregation regions in the remaining one type of particle group is different from the number of aggregation regions in each of the above-described two types of particle groups. Thus, in the security tag of the present invention, the number of aggregation regions in each particle group is not particularly limited, and at least one aggregation region may exist independently for each particle group.

[0195] In the above embodiments, in the two-dimensional crystal present in the security tag of the present invention, an embodiment in which the two-dimensional crystal has six-fold symmetry or four-fold symmetry when viewed from the thickness direction for each aggregation region has been exemplified. However, the two-dimensional crystal may have a symmetry other than six-fold symmetry and four-fold symmetry when viewed from the thickness direction for each aggregation region.

[0196] In the security tag of the present invention, when viewed in the thickness direction, there may be a set region in which the two-dimensional crystal has a six-fold symmetry, or there may be a set region in which the two-dimensional crystal has a four-fold symmetry, or there may be a set region in which the two-dimensional crystal has a symmetry other than six-fold symmetry and four-fold symmetry.

[0197] In the above embodiments, an aspect has been exemplified in which the symmetry when the two-dimensional crystal existing in the security tag of the present invention is viewed in the thickness direction is the same for all set regions. However, the symmetry when the two-dimensional crystal is viewed in the thickness direction may be different for all set regions, or may be different for some set regions. That is, in the security tag of the present invention, two-dimensional crystals having different symmetries when viewed in the thickness direction may be mixed. For example, in the security tag of the present invention, among all the set regions, in some set regions, there may be a two-dimensional crystal having a six-fold symmetry when viewed in the thickness direction, and in the remaining set regions, there may be a two-dimensional crystal having a four-fold symmetry when viewed in the thickness direction.

[0198] In the security tag of the present invention, it is sufficient that at least one set region formed by the aggregation of colloidal particles exists independently for each particle group, and there may be a region where different particle groups are mixed, specifically, a region where a particle group having a relatively large average particle diameter and a particle group having a relatively small average particle diameter are mixed.

[0199] The form of the security tag of the present invention is not particularly limited, and examples thereof include a film, a card, a sticker, and the like.

[0200] The following content is disclosed in this specification.

[0201] <1> A resin layer, A plurality of colloidal particles buried in the resin layer and arranged side by side at intervals along a plane direction perpendicular to the thickness direction of the resin layer, The plurality of colloidal particles include a plurality of types of particle groups having different average particle diameters from each other. In the resin layer, at least one aggregation region formed by aggregation of the colloidal particles exists independently for each of the particle groups. A security tag, characterized in that one type of two-dimensional crystal composed of the colloidal particles exists in each of the aggregation regions.

[0202] <2> The security tag according to <1>, wherein when viewed from the thickness direction, the two-dimensional crystal has six-fold symmetry.

[0203] <3> The security tag according to <1>, wherein when viewed from the thickness direction, the two-dimensional crystal has four-fold symmetry.

[0204] <4> The security tag according to any one of <1> to <3>, wherein when viewed from the thickness direction, in at least one set of the aggregation regions adjacent to each other in the plane direction, the directions of the symmetry axes of the two-dimensional crystal along the plane direction are different from each other.

[0205] <5> The resin layer has a first surface and a second surface opposite to each other in the thickness direction. The security tag according to any one of <1> to <4>, wherein the colloidal particles exist on the first surface side of the resin layer among the first surface and the second surface of the resin layer.

[0206] <6> The security tag according to <5>, further comprising a base material provided on the first surface side of the resin layer.

[0207] <7> The security tag according to <6>, further comprising an intermediate layer provided between the resin layer and the base material and in contact with the resin layer and the base material.

[0208] <8> The security tag according to <7>, wherein the intermediate layer contacts the colloidal particles.

[0209] <9> The security tag according to <7> or <8>, wherein the intermediate layer is composed of a metal oxide.

[0210] <10> The security tag according to <6>, wherein the substrate contacts the resin layer.

[0211] <11> The security tag according to <10>, wherein the substrate contacts the colloidal particles.

Explanation of Reference Numerals

[0212] 1, 1', 2, 3 Security tag 10 Resin layer 10a First surface of the resin layer 10b Second surface of the resin layer 20 Colloidal particles 20a First colloidal particle 20b Second colloidal particle 25a First particle group 25b Second particle group 30 Substrate 40 Intermediate layer 50 Colloidal dispersion 60 Cleaning liquid Paa1, Pab1, Pac1, Pac2, Pac3 First aggregation region Pba1, Pbb1, Pbc1, Pbc2, Pbc3 Second aggregation region Raa1, Rab1, Rac1, Rac2, Rac3, Rba1, Rbb1, Rbc1, Rbc2, Rbc3 Two-dimensional crystal Saa1, Sba1 Three-dimensional crystal Taa, Tab, Tba, Tbb Diffraction pattern Xaa1, Xac1, Xac2, Xac3, Xba1, Xbc1, Xbc2, Xbc3 Axis of symmetry

Claims

**Claim 1** A resin layer, A plurality of colloidal particles that are buried in the resin layer and are arranged at intervals along a plane direction perpendicular to the thickness direction of the resin layer, and The plurality of colloidal particles include a plurality of types of particle groups having different average particle diameters, In the resin layer, at least one aggregation region formed by aggregation of the colloidal particles exists independently for each of the particle groups, A security tag, characterized in that one type of two-dimensional crystal composed of the colloidal particles exists in each of the aggregation regions. **Claim 2** The security tag according to claim 1, wherein when viewed from the thickness direction, the two-dimensional crystal has a six-fold symmetry. **Claim 3** The security tag according to claim 1, wherein when viewed from the thickness direction, the two-dimensional crystal has a four-fold symmetry. **Claim 4** The security tag according to any one of claims 1 to 3, wherein in at least one set of the aggregation regions adjacent to each other in the plane direction when viewed from the thickness direction, the directions of the symmetry axes of the two-dimensional crystal along the plane direction are different from each other. **Claim 5** The resin layer has a first surface and a second surface facing each other in the thickness direction, The security tag according to any one of claims 1 to 3, wherein the colloidal particles exist on the first surface side of the first surface and the second surface of the resin layer. **Claim 6** The security tag according to claim 5, further comprising a substrate provided on the first surface side of the resin layer. **Claim 7** The security tag according to claim 6, further comprising an intermediate layer provided between the resin layer and the substrate and in contact with the resin layer and the substrate. **Claim 8** The security tag according to claim 7, wherein the intermediate layer is in contact with the colloidal particles. **Claim 9** The security tag according to claim 7, wherein the intermediate layer is composed of a metal oxide. **Claim 10** The security tag according to claim 6, wherein the substrate is in contact with the resin layer. **Claim 11** The security tag according to claim 10, wherein the substrate is in contact with the colloidal particles.

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