Colloidal crystal structures and articles with colloidal crystal structures

Abstract

This invention provides a colloidal crystal structure in which diffraction patterns originating from the two-dimensional crystal composed of colloidal particles are easily detected. [Solution] A colloidal crystal structure 1 comprising a base material 10, a particle immobilization layer 20 provided on one main surface side of the base material 10, and a plurality of colloidal particles 30 provided inside the particle immobilization layer 20, wherein the plurality of colloidal particles 30 are embedded in the particle immobilization layer 20 and are arranged apart from each other along a planar direction perpendicular to the thickness direction of the particle immobilization layer 20, forming at least one type of two-dimensional crystal, and the arithmetic mean roughness Ra of the surface of the particle immobilization layer 20 opposite to the base material 10 is 0.5 μm or less.

Description

Technical Field

[0001] The present invention relates to a colloidal crystal structure and an article with a colloidal crystal structure.

Background Art

[0002] Patent Document 1 discloses an immobilized two-dimensional colloidal crystal in which a single-layer colloidal crystal is immobilized by a resin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The immobilized two-dimensional colloidal crystal described in Patent Document 1 is said to be used in the optical field such as a substitute for a two-dimensional diffraction grating. And when the immobilized two-dimensional colloidal crystal described in Patent Document 1 is irradiated with light (laser light), a diffraction pattern derived from the colloidal crystal appears.

[0005] However, when the immobilized two-dimensional colloidal crystal described in Patent Document 1 is irradiated with light, due to the influence of refraction of light by the surface unevenness of the resin that fixes the colloidal crystal, the incident angle of the incident light incident on the colloidal particles of the colloidal crystal provided inside the resin may vary. And when the incident angle of the incident light on the colloidal particles varies, the diffraction angle of the diffracted light generated by the diffraction of the incident light by the colloidal particles may vary. Furthermore, when the diffraction angle of the diffracted light by the colloidal particles varies, the intensity of the diffraction pattern derived from the colloidal crystal, which is generated by the interference of the diffracted lights, may decrease (become darker), or the shape of the diffraction pattern may deteriorate (become blurred), making it difficult to detect the diffraction pattern.

[0006] As described above, in the immobilized two-dimensional colloidal crystal described in Patent Document 1, the diffraction pattern originating from the colloidal crystal may be difficult to detect due to the influence of surface irregularities in the resin. For this reason, it can be said that there is room for improvement in the immobilized two-dimensional colloidal crystal described in Patent Document 1 in terms of making the diffraction pattern originating from the colloidal crystal easier to detect.

[0007] The present invention was made to solve the above problems and aims to provide a colloidal crystal structure in which the diffraction pattern originating from the two-dimensional crystal composed of colloidal particles is easily detected. Furthermore, the present invention aims to provide an article with a colloidal crystal structure in which the above colloidal crystal structure is attached to an article. [Means for solving the problem]

[0008] The colloidal crystal structure of the present invention comprises a substrate, a particle-fixing layer provided on one main surface side of the substrate, and a plurality of colloidal particles provided inside the particle-fixing layer, wherein the plurality of colloidal particles are embedded in the particle-fixing layer and are arranged apart from each other along a planar direction perpendicular to the thickness direction of the particle-fixing layer, forming at least one type of two-dimensional crystal, and the arithmetic mean roughness Ra of the surface of the particle-fixing layer opposite to the substrate is 0.5 μm or less.

[0009] The article with a colloidal crystal structure of the present invention is characterized by comprising a target article and a colloidal crystal structure of the present invention attached to the target article. [Effects of the Invention]

[0010] According to the present invention, a colloidal crystal structure can be provided in which the diffraction pattern originating from the two-dimensional crystal composed of colloidal particles is easily detected. Furthermore, according to the present invention, an article with a colloidal crystal structure can be provided in which the above-mentioned colloidal crystal structure is attached to an article. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic plan view showing an example of a colloidal crystal structure according to Embodiment 1 of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing a first example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view illustrating an example of the behavior of light when light is irradiated onto the colloidal crystal structure shown in Figures 1 and 2. [Figure 4] Figure 4 is a schematic plan view showing an example of a diffraction pattern originating from a two-dimensional crystal when light is irradiated onto the colloidal crystal structure shown in Figures 1 and 2. [Figure 5] Figure 5 is a schematic cross-sectional view showing a second example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 6] Figure 6 is a schematic cross-sectional view showing a third example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 7] Figure 7 is a schematic cross-sectional view showing a fourth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 8] Figure 8 is a schematic cross-sectional view showing a fifth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 9] Figure 9 is a schematic cross-sectional view showing a sixth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 10] Figure 10 is a schematic cross-sectional view showing the seventh example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 11] Figure 11 is a schematic cross-sectional view showing the eighth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 12] Figure 12 is a schematic cross-sectional view showing the ninth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 13] Figure 13 is a schematic cross-sectional view showing the tenth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1. [Figure 14]FIG. 14 is a cross-sectional view schematically showing a 11th example of a cross-section along the thickness direction of the colloidal crystal structure shown in FIG. 1. [Figure 15] FIG. 15 is a plan view schematically showing an example of the colloidal crystal structure of Embodiment 2 of the present invention. [Figure 16] FIG. 16 is a plan view schematically showing an example of a diffraction pattern derived from a two-dimensional crystal when the colloidal crystal structure shown in FIG. 15 is irradiated with light. [Figure 17] FIG. 17 is a plan view schematically showing an example of the colloidal crystal structure of Embodiment 3 of the present invention. [Figure 18] FIG. 18 is a cross-sectional view schematically showing an example of an article with a colloidal crystal structure according to Embodiment 4 of the present invention. [Figure 19] FIG. 19 is a cross-sectional view schematically showing an example of an article with a colloidal crystal structure according to Embodiment 5 of the present invention. [Figure 20] FIG. 20 is a cross-sectional view schematically showing an example of an article with a colloidal crystal structure according to Embodiment 6 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, the colloidal crystal structure of the present invention and an article with the colloidal crystal structure of the present invention will be described. Note that the present invention is not limited to the following configurations, and may be appropriately changed without departing from the gist of the present invention. Also, a combination of a plurality of the individual preferred configurations described below is also the present invention.

[0013] 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 mean only a strictly literal aspect, but also a substantially equivalent range, for example, a range including a difference of about several percent.

[0014] [Colloidal Crystal Structure] The colloidal crystal structure of the present invention comprises a substrate, a particle-fixing layer provided on one main surface side of the substrate, and a plurality of colloidal particles provided inside the particle-fixing layer, wherein the plurality of colloidal particles are embedded in the particle-fixing layer and are arranged apart from each other along a planar direction perpendicular to the thickness direction of the particle-fixing layer, forming at least one type of two-dimensional crystal, and the arithmetic mean roughness Ra of the surface of the particle-fixing layer opposite to the substrate is 0.5 μm or less.

[0015] In the colloidal crystal structure of the present invention, multiple colloidal particles are embedded in a particle-fixed layer and arranged apart from each other along a planar direction perpendicular to the thickness direction of the particle-fixed layer, thereby forming at least one type of two-dimensional crystal. As a result, when light is irradiated onto the colloidal crystal structure of the present invention, a diffraction pattern originating from at least one type of two-dimensional crystal formed by the colloidal particles appears.

[0016] Furthermore, in the colloidal crystal structure of the present invention, the arithmetic mean roughness Ra of the surface of the particle-fixed layer opposite to the substrate is 0.5 μm or less. Thus, in the colloidal crystal structure of the present invention, because the surface of the particle-fixed layer opposite to the substrate is smooth, when light is irradiated onto the colloidal crystal structure of the present invention, the light is less likely to be refracted at that surface of the particle-fixed layer. For example, when light is irradiated onto the colloidal crystal structure of the present invention from the particle-fixed layer side, the irradiated light is less likely to be refracted as it passes through that surface of the particle-fixed layer, so the incident angle of the incident light incident on the colloidal particles provided inside the particle-fixed layer is less likely to vary. And, in the colloidal crystal structure of the present invention, because the incident angle of the incident light incident on the colloidal particles is less likely to vary, the diffraction angle of the diffracted light produced when the incident light is diffracted by the colloidal particles is less likely to vary. Thus, in the colloidal crystal structure of the present invention, because the diffraction angle of the diffracted light at the colloidal particles is less likely to vary, the intensity of the diffraction pattern produced by the interference of the diffracted light is increased (it becomes brighter), and the shape of the diffraction pattern is improved (it becomes clearer). As a result, in the colloidal crystal structure of the present invention, diffraction patterns originating from the two-dimensional crystal composed of colloidal particles are more easily detected.

[0017] Furthermore, when light is irradiated onto the colloidal crystal structure of the present invention from the substrate side, the effect obtained may be slightly smaller compared to when light is irradiated from the particle stationary layer side. However, because light is less likely to refract at the surface of the particle stationary layer, the diffraction pattern originating from the two-dimensional crystal composed of colloidal particles becomes easier to detect than when the arithmetic mean roughness Ra of the surface of the particle stationary layer opposite the substrate is greater than 0.5 μm.

[0018] From the above, when light is irradiated onto the colloidal crystal structure of the present invention, not only does a diffraction pattern originating from the two-dimensional crystal composed of colloidal particles appear, but the resulting diffraction pattern becomes easier to detect. In other words, the colloidal crystal structure of the present invention makes it possible to realize a colloidal crystal structure in which the diffraction pattern originating from the two-dimensional crystal composed of colloidal particles is easily detectable.

[0019] The following describes embodiments of the colloidal crystal structure of the present invention.

[0020] The embodiments described below are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Except for Embodiment 1, descriptions of matters common to Embodiment 1 are omitted, and the differences are mainly described. In particular, similar effects and benefits due to similar configurations are not mentioned sequentially for each embodiment.

[0021] The drawings shown below are schematic representations, and their dimensions, aspect ratios, and scales may differ from those of the actual product.

[0022] <Embodiment 1> In the colloidal crystal structure of Embodiment 1 of the present invention, at least one type of two-dimensional crystal is included, which has a six-fold symmetry when viewed from the thickness direction.

[0023] Figure 1 is a schematic plan view showing an example of a colloidal crystal structure according to Embodiment 1 of the present invention. Figure 2 is a schematic cross-sectional view showing a first example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0024] The colloidal crystal structure 1 shown in Figures 1 and 2 comprises a substrate 10, a particle immobilization layer 20, and a plurality of colloidal particles 30.

[0025] The base material 10 has a first main surface 10a and a second main surface 10b that are opposite to each other in the thickness direction. The first main surface 10a of the base material 10 is the main surface of the base material 10 on the side facing the particle immobilization layer 20. The second main surface 10b of the base material 10 is the main surface of the base material 10 on the side opposite to the particle immobilization layer 20.

[0026] The particle-fixing layer 20 has a first surface 20a and a second surface 20b that are opposite to each other in the thickness direction. The first surface 20a of the particle-fixing layer 20 is the surface of the particle-fixing layer 20 that is opposite to the substrate 10. The second surface 20b of the particle-fixing layer 20 is the surface of the particle-fixing layer 20 that is on the substrate 10 side.

[0027] The particle immobilization layer 20 is provided on one main surface side of the substrate 10. In the example shown in Figure 2, the particle immobilization layer 20 is provided on the first main surface 10a side, which is one main surface of the substrate 10.

[0028] Embodiments in which the particle-fixing layer 20 is provided on the first main surface 10a side of the substrate 10 include an embodiment in which the entire second surface 20b of the particle-fixing layer 20 is in contact with the first main surface 10a of the substrate 10 (i.e., no other layer is provided between the substrate 10 and the particle-fixing layer 20), an embodiment in which a part of the second surface 20b of the particle-fixing layer 20 is in contact with the first main surface 10a of the substrate 10 (i.e., another layer is provided in part between the substrate 10 and the particle-fixing layer 20), and an embodiment in which the particle-fixing layer 20 is present on the first main surface 10a side of the substrate 10, but the second surface 20b of the particle-fixing layer 20 is not in contact with the first main surface 10a of the substrate 10 (i.e., another layer is provided over the entire area between the substrate 10 and the particle-fixing layer 20).

[0029] Multiple colloidal particles 30 are arranged inside the particle immobilization layer 20.

[0030] Multiple colloidal particles 30 are embedded in the particle immobilization layer 20. This fixes the multiple colloidal particles 30 to the particle immobilization layer 20.

[0031] The statement that the colloidal particles 30 are embedded in the particle immobilization layer 20 means that, in the thickness direction of the particle immobilization layer 20 (the direction perpendicular to the plane of the paper in Figure 1, and the vertical direction in Figure 2), 90% or more of the height of the colloidal particles 30 is embedded in the particle immobilization layer 20.

[0032] In the example shown in Figure 2, the multiple colloidal particles 30 are completely embedded in the particle immobilization layer 20. As a result, the multiple colloidal particles 30 are protected by the particle immobilization layer 20.

[0033] Embodiments in which the colloidal particles 30 are completely embedded in the particle immobilization layer 20 include embodiments in which the colloidal particles 30 are in contact with the surface of the particle immobilization layer 20 from the inside, and embodiments in which the colloidal particles 30 are located inside the surface of the particle immobilization layer 20.

[0034] Multiple colloidal particles 30 are arranged spaced apart from each other along a planar direction perpendicular to the thickness direction of the particle-fixed layer 20. The multiple colloidal particles 30 are not arranged in a way that they are stacked in the thickness direction. In other words, the multiple colloidal particles 30 are arranged two-dimensionally, not three-dimensionally. Because the multiple colloidal particles 30 are arranged two-dimensionally in this way, they are less visible compared to when they are arranged three-dimensionally.

[0035] To be visible means that it can be visually confirmed in the visible light spectrum.

[0036] The visible light region refers to the wavelength range between 360 nm and 830 nm.

[0037] Multiple colloidal particles 30 constitute at least one type of two-dimensional crystal. In the example shown in Figure 1, the multiple colloidal particles 30 constitute a two-dimensional crystal R1 that has six-fold symmetry when viewed from the thickness direction.

[0038] The rotational symmetry of a two-dimensional crystal when viewed from the thickness direction can be confirmed by the diffraction pattern described later.

[0039] As described above, in the colloidal crystal structure 1, multiple colloidal particles 30 are embedded in the particle-fixed layer 20 and are arranged apart from each other along a plane direction perpendicular to the thickness direction of the particle-fixed layer 20, forming at least one type of two-dimensional crystal, the two-dimensional crystal R1 in the example shown in Figure 1. As a result, when light is shone on the colloidal crystal structure 1, a diffraction pattern originating from the two-dimensional crystal R1 formed by the colloidal particles 30 appears, specifically a diffraction pattern with six-fold symmetry.

[0040] Furthermore, in the colloidal crystal structure 1, the arithmetic mean roughness Ra of the first surface 20a, which is the surface of the particle-fixed layer 20 opposite to the substrate 10, is 0.5 μm or less. Thus, in the colloidal crystal structure 1, because the first surface 20a of the particle-fixed layer 20 is smooth, when light is irradiated onto the colloidal crystal structure 1, the light is less likely to be refracted by the first surface 20a of the particle-fixed layer 20.

[0041] The arithmetic mean roughness Ra of various target surfaces, such as the first surface 20a of the particle-fixed layer 20, refers to the arithmetic mean roughness Ra specified in "JIS B 0601:2013". Specifically, the arithmetic mean roughness Ra refers to the average area of ​​the convex portion above the center line and the concave portion below the center line when viewing the contour curve of various target surfaces, by adding the sum of the areas and dividing by the reference length. The arithmetic mean roughness Ra of various target surfaces is measured by a contact method (scanning method using a stylus). If it is difficult to measure the arithmetic mean roughness Ra of various target surfaces by a contact method, the arithmetic mean roughness Ra may be calculated from the cross-sectional shape of the target surface using analysis software, etc. When measuring or calculating the arithmetic mean roughness Ra of the interface between adjacent members (layers), it is sufficient to measure or calculate the arithmetic mean roughness Ra of the surface of one member (layer) on the other member (layer) side of the adjacent members (layers).

[0042] Figure 3 is a schematic cross-sectional view illustrating an example of the behavior of light when light is irradiated onto the colloidal crystal structure shown in Figures 1 and 2. Figure 4 is a schematic plan view illustrating an example of a diffraction pattern originating from a two-dimensional crystal when light is irradiated onto the colloidal crystal structure shown in Figures 1 and 2.

[0043] As shown in Figure 3, when light is shone onto the colloidal crystal structure 1 from the particle stationary layer 20 side, the shone light does not refract easily as it passes through the first surface 20a of the particle stationary layer 20. Therefore, the incident angle of the incident light AL that strikes the colloidal particles 30 located inside the particle stationary layer 20 becomes less variable. In the colloidal crystal structure 1, because the incident angle of the incident light AL that strikes the colloidal particles 30 does not refract easily, the diffraction angle of the diffracted light BL produced when the incident light AL diffracts at the colloidal particles 30 also becomes less variable. The diffracted light BL that is diffracted at the colloidal particles 30 includes diffracted light (reflected) BL1 that is reflected at the colloidal particles 30 and diffracted light (transmitted) BL2 that is transmitted through the colloidal particles 30. In particular, the diffracted light (reflected) BL1 that is reflected at the colloidal particles 30 passes through the first surface 20a of the particle stationary layer 20 again, but it does not refract easily at this time either, so the diffraction angle of the diffracted light (reflected) BL1 becomes less variable. Furthermore, regarding the diffracted light (transmitted) BL2 transmitted through the colloidal particles 30, the diffraction angle also becomes less variable to some extent because the incident angle of the incident light AL to the colloidal particles 30 does not vary much. Thus, in the colloidal crystal structure 1, because the diffraction angle of the diffracted light BL diffracted by the colloidal particles 30 does not vary much, the intensity of the diffraction pattern generated by the interference of the diffracted light BLs increases (it becomes brighter), and the shape of the diffraction pattern improves (it becomes clearer). For example, a bright and clear 6-fold symmetric diffraction pattern appears, as shown in Figure 4. As a result of the above, in the colloidal crystal structure 1, the diffraction pattern originating from the 2D crystal R1 composed of the colloidal particles 30 becomes easier to detect.

[0044] When light is irradiated onto the colloidal crystal structure 1 from the substrate 10 side, the effect obtained may be slightly smaller compared to when light is irradiated from the particle stationary layer 20 side (see Figure 3) because the incident light AL on the colloidal particles 30 does not pass through the first surface 20a of the particle stationary layer 20. However, because the diffracted light (transmitted) BL2 that has passed through the colloidal particles 30 is less likely to be refracted when it passes through the first surface 20a of the particle stationary layer 20, the diffraction pattern originating from the two-dimensional crystal R1 that constitutes the colloidal particles 30 is easier to detect than when the arithmetic mean roughness Ra of the first surface 20a of the particle stationary layer 20 is greater than 0.5 μm.

[0045] From the above, when light is irradiated onto the colloidal crystal structure 1, not only does a diffraction pattern originating from the two-dimensional crystal R1 composed of the colloidal particles 30 appear, but the resulting diffraction pattern becomes easier to detect. In other words, the colloidal crystal structure 1 makes it possible to realize a colloidal crystal structure in which the diffraction pattern originating from the two-dimensional crystal R1 composed of the colloidal particles 30 is easily detected.

[0046] Unlike colloidal crystal structure 1, in colloidal crystal structures where the arithmetic mean roughness Ra of the first surface 20a, which is the surface of the particle-fixed layer 20 opposite to the substrate 10, is greater than 0.5 μm, the diffraction pattern originating from the two-dimensional crystal R1 composed of the colloidal particles 30 becomes difficult to detect when irradiated with light. In fact, when light was irradiated onto a colloidal crystal structure where the arithmetic mean roughness Ra of the first surface 20a of the particle-fixed layer 20 was 0.7 μm, the diffraction pattern originating from the two-dimensional crystal R1 composed of the colloidal particles 30 became difficult to detect.

[0047] The two-dimensional crystal R1 composed of the colloidal particles 30 is unique and irreproducible. Therefore, the diffraction pattern derived from the two-dimensional crystal R1 is also unique and irreproducible. This will be explained below, along with an example of a method for manufacturing the colloidal crystal structure 1.

[0048] First, a colloidal dispersion is prepared in which multiple colloidal particles 30 are dispersed in a dispersion medium.

[0049] The type of dispersion medium is not particularly limited. The dispersion medium may be, for example, an inorganic solvent such as water, or an organic solvent such as an alcohol.

[0050] Next, the colloidal dispersion is applied to one main surface of the substrate 10.

[0051] The method of applying the colloidal dispersion is not particularly limited. For example, the colloidal dispersion may be dropped onto one main surface of the substrate 10, or the substrate 10 may be immersed in the colloidal dispersion.

[0052] Next, the dispersion medium in the colloidal dispersion applied to one main surface of the substrate 10 is dried, leaving multiple colloidal particles 30 on that main surface of the substrate 10. Then, of the remaining multiple colloidal particles 30, all but the layer closest to the substrate 10 are washed away with a washing solution such as water. As a result, the one layer of colloidal particles 30 that is not washed away will be arranged two-dimensionally on the main surface of the substrate 10, separating from each other due to electrostatic repulsion.

[0053] Finally, a particle-fixing layer 20 is formed on one main surface of the substrate 10 so that multiple colloidal particles 30 arranged in two dimensions are embedded. At this time, the arithmetic mean roughness Ra of the first surface 20a, which is the surface of the particle-fixing layer 20 opposite to the substrate 10, is set to 0.5 μm or less.

[0054] The method for forming the particle immobilization layer 20 is not particularly limited.

[0055] The method for achieving an arithmetic mean roughness Ra of the first surface 20a of the particle immobilization layer 20 of 0.5 μm or less is not particularly limited. For example, the first surface 20a may be polished after the particle immobilization layer 20 is formed, or the first surface 20a may be pressed against a smooth surface with an arithmetic mean roughness Ra of 0.5 μm or less.

[0056] As a result, colloidal crystal structure 1 is manufactured.

[0057] In the colloidal crystal structure 1 manufactured by the above method, multiple colloidal particles 30 are embedded in the particle-fixed layer 20 and arranged at a distance from each other along a plane direction perpendicular to the thickness direction of the particle-fixed layer 20, thereby forming a two-dimensional crystal R1. In this case, the two-dimensional crystal R1 is formed by utilizing the electrostatic repulsion force between the multiple colloidal particles 30, making it unique and irreproducible. Therefore, the diffraction pattern originating from the two-dimensional crystal R1 is also unique and irreproducible. In other words, the colloidal crystal structure 1 exhibits a unique diffraction pattern determined by the arrangement and particle size of the colloidal particles 30 constituting the two-dimensional crystal R1.

[0058] Colloidal crystal structure 1 can be used in a variety of applications because its diffraction pattern, derived from its two-dimensional crystal R1, is unique.

[0059] For example, if multiple colloidal crystal structures, including colloidal crystal structure 1, exist, the diffraction pattern of colloidal crystal structure 1 can be used as an indicator for individual identification to distinguish colloidal crystal structure 1 from the other multiple colloidal crystal structures. Therefore, if colloidal crystal structure 1 is attached to an object, the object can be identified by detecting and confirming the diffraction pattern of colloidal crystal structure 1. In this way, it is possible to impart an individual identification function to colloidal crystal structure 1.

[0060] The individual identification function of the colloidal crystal structure 1 makes it possible to use the colloidal crystal structure 1 for security purposes such as determining the authenticity of goods. For example, if a manufacturer, distributor, etc., attaches the colloidal crystal structure 1 to a genuine item beforehand, the authenticity of the item can be determined by checking whether or not the colloidal crystal structure 1 is attached to the item to be determined using the diffraction pattern.

[0061] If the colloidal crystal structure 1 is attached to a genuine article, the authenticity of the article can be determined, for example, by following the procedure below.

[0062] First, when light is shone on the item to be judged, it is checked whether a diffraction pattern originating from a two-dimensional crystal is detected, thereby confirming whether a colloidal crystal structure of the same type as colloidal crystal structure 1 is attached to the item to be judged. If it is determined that a colloidal crystal structure is attached to the item to be judged, it is then checked whether the diffraction pattern detected from the item to be judged is identical to the unique diffraction pattern of colloidal crystal structure 1 attached to the genuine item, thereby confirming whether the colloidal crystal structure attached to the item to be judged is identical to the colloidal crystal structure 1 attached to the genuine item. In this case, if information such as the shape, size, position, direction (angle) of the axis of symmetry along the plane direction, and what kind of diffraction pattern appears when light is shone at a certain angle of incidence is prepared in advance regarding the diffraction pattern originating from the two-dimensional crystal R1 present in the colloidal crystal structure 1, then the authenticity of the item to be judged can be determined more efficiently by checking the diffraction pattern detected from the item to be judged based on that information.

[0063] When colloidal crystal structure 1 is used for the security purposes described above, it is expected to be attached to relatively expensive items such as paintings, watches, eyewear, jewelry, and perfumes. In this case, a third party attempting to counterfeit these items would need to counterfeit not only the item itself but also the colloidal crystal structure 1 attached to it. However, as described above, the two-dimensional crystal R1 of colloidal crystal structure 1 is unique and irreproducible, and the diffraction pattern derived from the two-dimensional crystal R1 is also unique and irreproducible, so a third party cannot counterfeit colloidal crystal structure 1. Thus, colloidal crystal structure 1 provides a high level of anti-counterfeiting effect.

[0064] Furthermore, in the colloidal crystal structure 1, as described above, multiple colloidal particles 30 are arranged two-dimensionally, making them less visible compared to when they are arranged three-dimensionally. Therefore, especially when the substrate 10 and particle fixing layer 20 are transparent, as will be described later, the entire colloidal crystal structure 1 becomes difficult to see. When the colloidal crystal structure 1 is difficult to see, a third party attempting to counterfeit the above-mentioned article will have difficulty noticing the presence of the colloidal crystal structure 1 attached to the article. Therefore, a third party will not attempt to manufacture a counterfeit product that includes the colloidal crystal structure 1, and thus a complete counterfeit product including the colloidal crystal structure 1 will not be manufactured. In this respect as well, the colloidal crystal structure 1 exhibits a high level of anti-counterfeiting effect.

[0065] Furthermore, when the colloidal crystal structure 1 becomes less visible, it also has the effect of preventing the appearance (design) of the item to which the colloidal crystal structure 1 is attached from being compromised.

[0066] The following describes each component of the colloidal crystal structure 1.

[0067] (base material) The arithmetic mean roughness Ra of the second main surface 10b, which is the main surface of the substrate 10 opposite to the particle immobilization layer 20, is preferably 0.5 μm or less. When the second main surface 10b of the substrate 10 is smooth in this way, the light is less likely to be refracted by the second main surface 10b of the substrate 10 when light is irradiated onto the colloidal crystal structure 1.

[0068] As described above, in a colloidal crystal structure 1 where the arithmetic mean roughness Ra of the first surface 20a of the particle stationary layer 20 is 0.5 μm or less, the diffraction pattern originating from the two-dimensional crystal R1 composed of the colloidal particles 30 is easily detectable, and a relatively large effect is obtained when light is irradiated from the particle stationary layer 20 side. However, if the arithmetic mean roughness Ra of the second main surface 10b of the substrate 10 is 0.5 μm or less, a large effect can be obtained even when light is irradiated from the substrate 10 side onto the colloidal crystal structure 1.

[0069] The substrate 10 is preferably transparent. For example, the substrate 10 is preferably 80% or more in the visible light region. In this case, the substrate 10 becomes less visible, which enhances the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above.

[0070] The base material 10 preferably has flexibility. In this case, the colloidal crystal structure 1 can be easily attached to a bent object.

[0071] The constituent materials of the base material 10 are not particularly limited and may be inorganic materials, organic materials, or hybrid materials of inorganic and organic materials.

[0072] The base material 10 may be, for example, a glass plate, a plastic plate, or the like.

[0073] (particle fixed layer) The particle immobilization layer 20 may be in contact with the substrate 10. The particle immobilization layer 20 may be in contact with the entire first main surface 10a, which is one main surface of the substrate 10, or it may be in contact with a part of the first main surface 10a, which is one main surface of the substrate 10.

[0074] When the particle-fixed layer 20 is in contact with the substrate 10, the arithmetic mean roughness Ra of the interface between the substrate 10 and the particle-fixed layer 20 is preferably 0.5 μm or less. When the interface between the substrate 10 and the particle-fixed layer 20 is smooth in this way, when light is irradiated onto the colloidal crystal structure 1, the light is less likely to be refracted at the interface between the substrate 10 and the particle-fixed layer 20. As a result, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 is further increased, and the shape of the diffraction pattern is further improved, making the diffraction pattern easier to detect.

[0075] The particle immobilization layer 20 is preferably transparent. For example, the particle immobilization layer 20 is preferably 80% or more in light transmittance in the visible light region. In this case, the particle immobilization layer 20 becomes difficult to see, and consequently, the colloidal crystal structure 1 becomes difficult to see, thereby increasing the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above.

[0076] Preferably, the particle immobilization layer 20 has surface conformability that can follow the surface irregularities of the object to which it is attached. In this case, even if the colloidal crystal structure 1 is attached to the object from the particle immobilization layer 20 side, bubbles (air bubbles) are less likely to form at the interface between the particle immobilization layer 20 and the object. Therefore, when light is irradiated onto the colloidal crystal structure 1, the diffracted light diffracted by the colloidal particles 30 is less likely to scatter at the interface between the particle immobilization layer 20 and the object. As a result, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 is further increased, and the shape of the diffraction pattern is further improved, making the diffraction pattern even easier to detect.

[0077] The particle immobilization layer 20 may have a single-layer structure or a multi-layer structure.

[0078] The particle immobilization layer 20 preferably contains a resin layer. In this case, the particle immobilization layer 20 may contain only a resin layer, or it may contain other layers in addition to the resin layer.

[0079] The resin layer is preferably composed of an ultraviolet-curable resin.

[0080] The constituent materials of the resin layer are not particularly limited and may include polymer resins such as acrylic resins, epoxy resins, polyurethane resins, and polystyrene resins, as well as silicone resins, biopolymers, and the like. Among these resins, acrylic resins are preferred.

[0081] (Colloidal particles) It is preferable that the colloidal particles 30 are located on the second surface 20b of the particle immobilization layer 20, rather than on the first surface 20a. In other words, it is preferable that the distance between the colloidal particles 30 and the second surface 20b of the particle immobilization layer 20 is smaller than the distance between the colloidal particles 30 and the first surface 20a of the particle immobilization layer 20.

[0082] In the example shown in Figure 2, the colloidal particles 30 are located on the second surface 20b of the particle immobilization layer 20, rather than on the first surface 20a. Specifically, the colloidal particles 30 are in contact with the second surface 20b of the particle immobilization layer 20 from the inside. Also, in the example shown in Figure 2, the substrate 10 is in contact with the second surface 20b of the particle immobilization layer 20. Therefore, in the example shown in Figure 2, the colloidal particles 30 are in contact with the substrate 10.

[0083] Furthermore, the colloidal particles 30 may be located on the first surface 20a side of the particle immobilization layer 20, rather than on the second surface 20b. In other words, the distance between the colloidal particles 30 and the first surface 20a of the particle immobilization layer 20 may be smaller than the distance between the colloidal particles 30 and the second surface 20b of the particle immobilization layer 20.

[0084] Furthermore, the colloidal particles 30 may be located between the first surface 20a and the second surface 20b of the particle immobilization layer 20. In other words, the distance between the colloidal particles 30 and the first surface 20a of the particle immobilization layer 20 and the distance between the colloidal particles 30 and the second surface 20b of the particle immobilization layer 20 may be the same as each other.

[0085] When viewed from the thickness direction, the multiple colloidal particles 30 may be provided throughout the entire particle immobilization layer 20.

[0086] Furthermore, when viewed from the thickness direction, the multiple colloidal particles 30 may be provided in a part of the particle immobilization layer 20. In other words, when viewed from the thickness direction, the multiple colloidal particles 30 do not have to be provided in a part of the particle immobilization layer 20.

[0087] When viewed from the thickness direction, it is preferable that the multiple colloidal particles 30 are evenly distributed such that the distance (pitch) between the centers of adjacent colloidal particles 30 in the planar direction is constant. In this case, when viewed from the thickness direction, the multiple colloidal particles 30 may be evenly distributed throughout the entire particle-fixed layer 20, or they may be evenly distributed in a part of the particle-fixed layer 20.

[0088] The average particle size of the multiple colloidal particles 30 is preferably 100 nm or more and 1000 nm or less. In this case, the colloidal particles 30 become less visible. Furthermore, when light is irradiated onto the colloidal crystal structure 1, both the intensity of the diffracted light diffracted by the colloidal particles 30 and the intensity of the scattered light scattered by the colloidal particles 30 become low, making the structural color derived from the colloidal particles 30 less visible. As a result, the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above, is enhanced.

[0089] The average particle size of multiple colloidal particles 30 is measured using a scanning electron microscope (SEM) for 100 to 200 colloidal particles 30 out of all the colloidal particles 30 contained in the colloidal crystal structure 1.

[0090] The coefficient of variation (CV value) of the particle sizes of the multiple colloidal particles 30 is preferably 20% or less. In this case, the particle sizes of the multiple colloidal particles 30 tend to be more uniform (monodispersibility increases), making it easier for the multiple colloidal particles 30 to arrange themselves to form a two-dimensional crystal R1. As a result, when light is irradiated onto the colloidal crystal structure 1, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 increases further, and the shape of the diffraction pattern improves further, making the diffraction pattern easier to detect.

[0091] The coefficient of variation (CV value) of the particle sizes of multiple colloidal particles 30 can be calculated by measuring 100 to 200 colloidal particles 30 out of all the colloidal particles 30 contained in the colloidal crystal structure 1 using a scanning electron microscope (SEM). The coefficient of variation (CV value) is calculated as follows: D = 100 × (σ / D), where D is the average particle size and σ is the standard deviation.

[0092] The colloidal particles 30 may be inorganic particles or organic particles.

[0093] When the colloidal particles 30 are inorganic particles, their constituent materials are not particularly limited and may include, for example, silica, titanium oxide, alumina, gold, silver, etc. Among these, silica and titanium oxide are preferred.

[0094] When the colloidal particles 30 are organic particles, their constituent material is not particularly limited and may be polymers such as polystyrene, polyacrylic acid ester, polymethacrylic acid ester, or polyacrylonitrile. Among these, polystyrene is preferred.

[0095] The following describes the relationship between the refractive indices of each component of the colloidal crystal structure 1.

[0096] In the visible light region, the refractive indices of at least two components selected from the group consisting of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be the same. Specifically, as follows: In the visible light region, the refractive indices of the substrate 10 and the particle immobilization layer 20 may be the same. Alternatively, in the visible light region, the refractive indices of the substrate 10 and the colloidal particles 30 may be the same. Alternatively, in the visible light region, the refractive indices of the particle immobilization layer 20 and the colloidal particles 30 may be the same. Alternatively, in the visible light region, the refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be the same. In these cases, the colloidal crystal structure 1 becomes less visible, thus increasing the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above.

[0097] In the visible light region, the refractive indices of at least two components selected from the group consisting of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be different from each other. Specifically, as follows: In the visible light region, the refractive indices of the substrate 10 and the particle immobilization layer 20 may be different from each other. Alternatively, in the visible light region, the refractive indices of the substrate 10 and the colloidal particles 30 may be different from each other. Alternatively, in the visible light region, the refractive indices of the particle immobilization layer 20 and the colloidal particles 30 may be different from each other. Alternatively, in the visible light region, the refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be different from each other.

[0098] In the visible light region, it is preferable that the refractive index of the colloidal particles 30 is 0.001 or more and 0.15 or less compared to the refractive index of at least one of the substrate 10 and the particle immobilization layer 20. Specifically, this is as follows: In the visible light region, it is preferable that the refractive index of the colloidal particles 30 is 0.001 or more and 0.15 or less compared to the refractive index of the substrate 10. Alternatively, in the visible light region, it is preferable that the refractive index of the colloidal particles 30 is 0.001 or more and 0.15 or less compared to the refractive index of the particle immobilization layer 20. Alternatively, in the visible light region, it is preferable that the refractive index of the colloidal particles 30 is 0.001 or more and 0.15 or less compared to the refractive index of the substrate 10, and that the refractive index of the particle immobilization layer 20 is 0.001 or more and 0.15 or less. In these cases, the colloidal particles 30 become difficult to see. Furthermore, when light is shone on the colloidal crystal structure 1, both the intensity of the diffracted light diffracted by the colloidal particles 30 and the intensity of the scattered light scattered by the colloidal particles 30 become low, making it difficult to see the structural color originating from the colloidal particles 30. As a result, the anti-counterfeiting effect of the colloidal crystal structure 1 when used for security purposes, as described above, is enhanced.

[0099] In the visible light region, the refractive index of the colloidal particles 30 may be less than 0.001 or greater than 0.15 compared to the refractive index of at least one of the substrate 10 and the particle-fixed layer 20.

[0100] The refractive index of the substrate 10 in the visible light region is preferably 1.3 or higher and 2.3 or lower.

[0101] The refractive index of the particle immobilization layer 20 in the visible light region is preferably 1.3 or higher and 2.3 or lower.

[0102] Furthermore, if the particle stationary layer 20 has a multilayer structure, the refractive index of the particle stationary layer 20 in the visible light region is determined as the average value of the refractive indices of the multiple layers constituting the particle stationary layer 20 in the visible light region.

[0103] The refractive index of the colloidal particles 30 in the visible light region is preferably 1.3 or higher and 2.3 or lower.

[0104] The refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 in the visible light region are measured by the V-block method.

[0105] In the infrared region, the refractive indices of at least two components selected from the group consisting of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be the same. Specifically, as follows: In the infrared region, the refractive indices of the substrate 10 and the particle immobilization layer 20 may be the same. Alternatively, in the infrared region, the refractive indices of the substrate 10 and the colloidal particles 30 may be the same. Alternatively, in the infrared region, the refractive indices of the particle immobilization layer 20 and the colloidal particles 30 may be the same. Alternatively, in the infrared region, the refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be the same.

[0106] In the infrared region, the refractive indices of at least two components selected from the group consisting of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be different from each other. Specifically, the following may apply: In the infrared region, the refractive indices of the substrate 10 and the particle immobilization layer 20 may be different from each other. Alternatively, in the infrared region, the refractive indices of the substrate 10 and the colloidal particles 30 may be different from each other. Alternatively, in the infrared region, the refractive indices of the particle immobilization layer 20 and the colloidal particles 30 may be different from each other. Alternatively, in the infrared region, the refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 may be different from each other. In these cases, the colloidal crystal structure 1 becomes detectable in the infrared region.

[0107] The infrared region refers to the wavelength range from 830 nm upwards to 1 mm downwards.

[0108] The refractive index of the substrate 10 in the infrared region is preferably 0.4 or higher and 5.7 or lower.

[0109] The refractive index of the particle immobilization layer 20 in the infrared region is preferably 0.4 or higher and 5.7 or lower.

[0110] Furthermore, if the particle stationary layer 20 has a multilayer structure, the refractive index of the particle stationary layer 20 in the infrared region is determined as the average value of the refractive indices in the infrared region of the multiple layers constituting the particle stationary layer 20.

[0111] The refractive index of the colloidal particles 30 in the infrared region is preferably 0.4 or higher and 5.7 or lower.

[0112] The refractive indices of the substrate 10, the particle immobilization layer 20, and the colloidal particles 30 in the infrared region are measured by the V-block method.

[0113] In colloidal crystal structure 1, for example, if the refractive indices of the substrate 10, particle immobilization layer 20, and colloidal particles 30 are the same in the visible light region, and different in the infrared light region, then colloidal crystal structure 1 becomes undetectable (invisible) in the visible light region, but detectable in the infrared light region. In this case, a third party attempting to manufacture counterfeit goods would not only be unable to notice the existence of colloidal crystal structure 1, but even if they did notice its existence, they would be unable to counterfeit colloidal crystal structure 1, which has a unique and irreproducible two-dimensional crystal R1 and different refractive indices of the substrate 10, particle immobilization layer 20, and colloidal particles 30 in the infrared light region.

[0114] If the colloidal crystal structure 1 is detectable in the infrared region, then, for example, if the colloidal crystal structure 1 is attached to the back of a painting or the back of a watch dial, the colloidal crystal structure 1 will not be visible from the front of the painting, watch, etc., but will be detectable in the infrared region.

[0115] The colloidal crystal structure 1 may or may not further have members other than the substrate 10, the particle immobilization layer 20, and the plurality of colloidal particles 30.

[0116] (Middle class) Figure 5 is a schematic cross-sectional view showing a second example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0117] As shown in Figure 5, the colloidal crystal structure 1 may further have an intermediate layer 40 that is in contact with the substrate 10 and the colloidal particles 30 between the substrate 10 and the colloidal particles 30.

[0118] Because the intermediate layer 40 is in contact with the colloidal particles 30, the colloidal particles 30 are protected not only by the substrate 10 and the particle immobilization layer 20, but also by the intermediate layer 40.

[0119] Because the intermediate layer 40 is in contact with the substrate 10 and the colloidal particles 30, the colloidal particles 30 are fixed to the substrate 10 via the intermediate layer 40. When the colloidal particles 30 are fixed to the substrate 10, for example, even if an external force is applied to the colloidal crystal structure 1, the crystal structure of the two-dimensional crystal R1 composed of the colloidal particles 30 is more easily maintained. As a result, when light is irradiated onto the colloidal crystal structure 1, the diffraction pattern originating from the two-dimensional crystal R1 becomes even easier to detect.

[0120] One way to obtain a configuration in which the intermediate layer 40 is in contact with the substrate 10 and the colloidal particles 30 between the substrate 10 and the colloidal particles 30 is, for example, to use a substrate 10 to which the intermediate layer 40 is pre-provided on one main surface when manufacturing the colloidal crystal structure 1 by the method described above, to which the colloidal dispersion containing the colloidal particles 30 is applied. When the colloidal dispersion is applied to one main surface of the substrate 10 to which the intermediate layer 40 is pre-provided, the colloidal particles 30 will be arranged two-dimensionally while adsorbed on the intermediate layer 40.

[0121] The arithmetic mean roughness Ra of the interface between the substrate 10 and the intermediate layer 40 is preferably 0.5 μm or less. When the interface between the substrate 10 and the intermediate layer 40 is smooth in this way, when light is irradiated onto the colloidal crystal structure 1, the light is less likely to be refracted at the interface between the substrate 10 and the intermediate layer 40. As a result, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 is further increased, and the shape of the diffraction pattern is further improved, making the diffraction pattern easier to detect.

[0122] The thickness of the intermediate layer 40 is, for example, between 1 nm and 100 nm.

[0123] The intermediate layer 40 is preferably composed of a metal oxide. In this case, titanium oxide is preferred as the metal oxide.

[0124] 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.

[0125] Figure 6 is a schematic cross-sectional view showing a third example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0126] As shown in Figure 6, the intermediate layer 40 may further extend in the planar direction between the substrate 10 and the particle-fixing layer 20 so as to be in contact with the substrate 10 and the particle-fixing layer 20.

[0127] The arithmetic mean roughness Ra of the interface between the particle-fixed layer 20 and the intermediate layer 40 is preferably 0.5 μm or less. When the interface between the particle-fixed layer 20 and the intermediate layer 40 is smooth in this way, when light is irradiated onto the colloidal crystal structure 1, the light is less likely to be refracted at the interface between the particle-fixed layer 20 and the intermediate layer 40. As a result, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 is further increased, and the shape of the diffraction pattern is further improved, making the diffraction pattern easier to detect.

[0128] Figure 7 is a schematic cross-sectional view showing a fourth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0129] As shown in Figure 7, the particle immobilization layer 20 may include an adhesive layer 21 that constitutes the first surface 20a, which is the surface of the particle immobilization layer 20 opposite to the substrate 10. In this case, when attaching the colloidal crystal structure 1 to the target article from the particle immobilization layer 20 side, specifically from the first surface 20a side of the particle immobilization layer 20, the adhesive action of the adhesive layer 21 that constitutes the first surface 20a of the particle immobilization layer 20 makes it easier to firmly attach the colloidal crystal structure 1 to the target article.

[0130] Figure 8 is a schematic cross-sectional view showing a fifth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0131] The configuration shown in Figure 8 is the same as the configuration shown in Figure 5, except that the particle immobilization layer 20 includes the adhesive layer 21.

[0132] Figure 9 is a schematic cross-sectional view showing a sixth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0133] The configuration shown in Figure 9 is the same as the configuration shown in Figure 6, except that the particle immobilization layer 20 includes an adhesive layer 21.

[0134] In the examples shown in Figures 7, 8, and 9, the particle immobilization layer 20 is entirely composed of an adhesive layer 21. On the other hand, the particle immobilization layer 20 may also be composed of only a portion of the adhesive layer 21.

[0135] Figure 10 is a schematic cross-sectional view showing the seventh example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0136] As shown in Figure 10, the particle immobilization layer 20 may include, in addition to the adhesive layer 21, a layer other than the adhesive layer 21, for example, a non-adhesive layer 22. In this case, the particle immobilization layer 20 may include, in addition to the adhesive layer 21 that constitutes the first surface 20a, a non-adhesive layer 22 that constitutes the second surface 20b.

[0137] As shown in Figure 10, the colloidal particles 30 may be provided across the interface between the adhesive layer 21 and the non-adhesive layer 22.

[0138] The non-adhesive layer 22 may be, for example, the resin layer described above, which is preferably included in the particle-fixing layer 20.

[0139] The configuration shown in Figure 10 is the same as the configuration shown in Figure 8, except for the points mentioned above.

[0140] Figure 11 is a schematic cross-sectional view showing the eighth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0141] As shown in Figure 11, the colloidal particles 30 are not provided across the interface between the adhesive layer 21 and the non-adhesive layer 22, but may be embedded in the non-adhesive layer 22.

[0142] The configuration shown in Figure 11 is the same as the configuration shown in Figure 10, except for the points mentioned above.

[0143] Figure 12 is a schematic cross-sectional view showing the ninth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0144] The configuration shown in Figure 12 is the same as the configuration shown in Figure 9, except that the particle immobilization layer 20 includes an adhesive layer 21 and a non-adhesive layer 22, and the colloidal particles 30 are provided across the interface between the adhesive layer 21 and the non-adhesive layer 22.

[0145] Figure 13 is a schematic cross-sectional view showing the tenth example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0146] The configuration shown in Figure 13 is the same as the configuration shown in Figure 12, except that the colloidal particles 30 are embedded in the non-adhesive layer 22.

[0147] The arithmetic mean roughness Ra of the interface between the adhesive layer 21 and the non-adhesive layer 22 is preferably 0.5 μm or less. When the interface between the adhesive layer 21 and the non-adhesive layer 22 is smooth in this way, when light is irradiated onto the colloidal crystal structure 1, the light is less likely to be refracted at the interface between the adhesive layer 21 and the non-adhesive layer 22. As a result, the intensity of the diffraction pattern originating from the two-dimensional crystal R1 is further increased, and the shape of the diffraction pattern is further improved, making the diffraction pattern easier to detect.

[0148] In the examples shown in Figures 10, 11, 12, and 13, the particle immobilization layer 20 has a two-layer structure consisting of an adhesive layer 21 and a non-adhesive layer 22, but it may also have a structure of three or more layers. In this case, in order to further enhance the effect of making the diffraction pattern easier to detect, it is preferable that the arithmetic mean roughness Ra of the interface of each layer constituting the particle immobilization layer 20 is 0.5 μm or less.

[0149] (Functional layer) Figure 14 is a schematic cross-sectional view showing the 11th example of a cross-section along the thickness direction of the colloidal crystal structure shown in Figure 1.

[0150] As shown in Figure 14, the colloidal crystal structure 1 may further have a functional layer 50 provided on at least one surface selected from the group consisting of a first surface 20a, which is the surface of the particle-fixed layer 20 opposite to the substrate 10, a second main surface 10b, which is the main surface of the substrate 10 opposite to the particle-fixed layer 20, and the interface between the substrate 10 and the particle-fixed layer 20. In the example shown in Figure 14, the functional layer 50 is provided on the second main surface 10b of the substrate 10.

[0151] The functional layer 50 may be, for example, a hard coat layer, an antifouling coat layer, or an anti-reflective coat layer. In this case, the various properties of the colloidal crystal structure 1 can be improved by the hard coat layer, the durability, abrasion resistance, and weather resistance; by the antifouling coat layer, the antifouling resistance; and by the anti-reflective coat layer, the light transmittance.

[0152] In addition, Figure 14 illustrates the case where the functional layer 50 is provided in the configuration shown in Figure 2, but the functional layer 50 may also be provided in configurations other than those shown in Figure 2, for example, in any of the configurations shown in Figures 5 to 13.

[0153] The colloidal crystal structure 1 may be provided with at least one of a cutting notch and an incision. For example, the particle immobilization layer 20 may be provided with at least one of a cutting notch and an incision. Also, the substrate 10 may be provided with at least one of a cutting notch and an incision.

[0154] If the colloidal crystal structure 1 has at least one of a notch and an incision, the colloidal crystal structure 1 becomes brittle, making it prone to damage when removed after being attached to an object. Therefore, as described above, when the colloidal crystal structure 1 is used for security purposes, it becomes difficult for a third party to remove the colloidal crystal structure 1 from a genuine object and attach it to another object (for example, a counterfeit item).

[0155] <Embodiment 2> In the colloidal crystal structure of Embodiment 2 of the present invention, at least one type of two-dimensional crystal is included, which has four-fold symmetry when viewed from the thickness direction.

[0156] Figure 15 is a schematic plan view showing an example of a colloidal crystal structure according to Embodiment 2 of the present invention. Figure 16 is a schematic plan view showing an example of a diffraction pattern originating from a two-dimensional crystal when light is irradiated onto the colloidal crystal structure shown in Figure 15.

[0157] In the colloidal crystal structure 2 shown in Figure 15, the multiple colloidal particles 30 constitute a two-dimensional crystal R2 that has four-fold symmetry when viewed from the thickness direction, as at least one type of two-dimensional crystal.

[0158] When light is shone on colloidal crystal structure 2, the intensity of the diffraction pattern originating from the two-dimensional crystal R2 composed of colloidal particles 30 increases (it becomes brighter), and the shape of the diffraction pattern improves (it becomes clearer), similar to when light is shone on colloidal crystal structure 1. Specifically, a bright and clear four-fold symmetric diffraction pattern appears, as shown in Figure 16. As a result, the diffraction pattern originating from the two-dimensional crystal R2 composed of colloidal particles 30 becomes easier to detect in colloidal crystal structure 2.

[0159] A two-dimensional crystal R2 with four-fold symmetry is more difficult to realize than a two-dimensional crystal R1 with six-fold symmetry. Therefore, when used for security purposes as described above, colloidal crystal structure 2 containing a two-dimensional crystal R2 with four-fold symmetry can exhibit a higher level of anti-counterfeiting effect compared to colloidal crystal structure 1 containing a two-dimensional crystal R1 with six-fold symmetry.

[0160] A two-dimensional crystal R2 with four-fold symmetry can be realized, for example, by adjusting the thickness of the colloidal dispersion applied to one main surface of the substrate 10 when manufacturing colloidal crystal structure 2 in the same manner as colloidal crystal structure 1. For example, after applying the colloidal dispersion to one main surface of the substrate 10, the thickness of the colloidal dispersion can be changed by placing another component, such as a glass plate, on the surface of the colloidal dispersion. In this case, by changing the thickness of the other component placed on the surface of the colloidal dispersion, the weight of this component can be changed, and as a result, the thickness of the colloidal dispersion can be adjusted. When the thickness of the colloidal dispersion is within a specific range, a two-dimensional crystal R2 with four-fold symmetry can be realized.

[0161] <Embodiment 3> In the colloidal crystal structure of Embodiment 3 of the present invention, multiple colloidal particles constitute multiple types of two-dimensional crystals. Furthermore, in the colloidal crystal structure of Embodiment 3 of the present invention, when viewed from the thickness direction, the directions of the symmetry axes along the plane directions of the multiple types of two-dimensional crystals are different from each other.

[0162] Figure 17 is a schematic plan view showing an example of a colloidal crystal structure according to Embodiment 3 of the present invention.

[0163] In the colloidal crystal structure 3 shown in Figure 17, the multiple colloidal particles 30 constitute five types of two-dimensional crystals: two-dimensional crystal R3a, two-dimensional crystal R3b, two-dimensional crystal R3c, two-dimensional crystal R3d, and two-dimensional crystal R3e.

[0164] The two-dimensional crystals R3a, R3b, R3c, R3d, and R3e each possess a six-fold symmetry when viewed from the thickness direction.

[0165] Each of the two-dimensional crystals R3a, R3b, R3c, R3d, and R3e may have a symmetry other than six-fold symmetry, such as four-fold symmetry, when viewed from the thickness direction.

[0166] The two-dimensional crystals R3a, R3b, R3c, R3d, and R3e each have symmetry axes X3a, X3b, X3c, X3d, and X3e, respectively, along the plane direction.

[0167] The directions of the axes of symmetry X3a, X3b, X3c, X3d, and X3e are different from each other.

[0168] The axis of symmetry along the plane refers to the axis of symmetry along the plane when a two-dimensional crystal is symmetrical with respect to its thickness.

[0169] From the above, when classifying the types of two-dimensional crystals in colloidal crystal structure 3 by the direction of the symmetry axis along the plane direction, there are five types of two-dimensional crystals: two-dimensional crystal R3a, two-dimensional crystal R3b, two-dimensional crystal R3c, two-dimensional crystal R3d, and two-dimensional crystal R3e, each with a different direction of the symmetry axis along the plane direction.

[0170] In the colloidal crystal structure 3, the two-dimensional crystals R3a, R3b, R3c, R3d, and R3e are unique and irreproducible, and the diffraction patterns derived from them are also unique and irreproducible. Regarding the diffraction patterns of the colloidal crystal structure 3, the combination of the directions of the symmetry axes along the plane direction of the two-dimensional crystals R3a, R3b, R3c, R3d, and R3e is unique and irreproducible. Therefore, the colloidal crystal structure 3 containing the two-dimensional crystals R3a, R3b, R3c, R3d, and R3e can exhibit a higher anti-counterfeiting effect when used for security purposes as described above.

[0171] The colloidal crystal structure of the present invention is not limited to the above-described form, and various applications and modifications can be made within the scope of the present invention regarding the composition, manufacturing conditions, etc., of the colloidal crystal structure.

[0172] In the colloidal crystal structure of the present invention, embodiments 1 to 3 illustrate embodiments in which at least one type of two-dimensional crystal present in the colloidal crystal structure of the present invention includes only two-dimensional crystals having six-fold symmetry when viewed from the thickness direction in terms of the symmetry of the two-dimensional crystal (embodiments 1 and 3), or embodiments in which at least one type of two-dimensional crystal present in the colloidal crystal structure of the present invention includes only two-dimensional crystals having six-fold symmetry when viewed from the thickness direction (embodiment 2). The at least one type of two-dimensional crystal present in the colloidal crystal structure of the present invention may include both two-dimensional crystals having six-fold symmetry when viewed from the thickness direction and two-dimensional crystals having four-fold symmetry when viewed from the thickness direction. Furthermore, the at least one type of two-dimensional crystal present in the colloidal crystal structure of the present invention may include two-dimensional crystals having symmetries other than six-fold and four-fold symmetry when viewed from the thickness direction.

[0173] The number of types of two-dimensional crystals present in the colloidal crystal structure of the present invention is not limited to the five types shown in Embodiment 1, but may be multiple types other than the five.

[0174] In the colloidal crystal structure of the present invention, Embodiment 3 exemplifies a configuration in which a plurality of colloidal particles constitute a plurality of two-dimensional crystals, and the types of two-dimensional crystals are classified according to the direction of the symmetry axis along the plane direction. In the colloidal crystal structure of the present invention, the types of two-dimensional crystals may be classified according to the symmetry when viewed from the thickness direction, or according to other characteristics. For example, in the colloidal crystal structure of the present invention, as a configuration in which the types of two-dimensional crystals are classified according to the symmetry when viewed from the thickness direction, a plurality of two-dimensional crystals with different symmetries when viewed from the thickness direction may be mixed together. In this case, the colloidal crystal structure of the present invention may contain, for example, a mixture of two-dimensional crystals having six-fold symmetry when viewed from the thickness direction and two-dimensional crystals having four-fold symmetry when viewed from the thickness direction.

[0175] The form of the colloidal crystal structure of the present invention is not particularly limited and may be, for example, a tag, film, card, seal, etc.

[0176] [Articles with colloidal crystal structures] The article with a colloidal crystal structure of the present invention is characterized by comprising a target article and a colloidal crystal structure of the present invention attached to the target article.

[0177] Even in configurations where the colloidal crystal structure of the present invention is attached to an article, such as an article with the colloidal crystal structure of the present invention, the diffraction pattern originating from the two-dimensional crystal composed of the colloidal particles of the colloidal crystal structure of the present invention is easily detectable.

[0178] The following describes embodiments of the article with a colloidal crystal structure according to the present invention.

[0179] <Embodiment 4> In the colloidal crystal structure article of Embodiment 4 of the present invention, the colloidal crystal structure is attached to the article from the particle stationary layer side.

[0180] Figure 18 is a schematic cross-sectional view showing an example of an article with a colloidal crystal structure according to Embodiment 4 of the present invention.

[0181] The article 101 with a colloidal crystal structure shown in Figure 18 comprises the target article 110 and the colloidal crystal structure 1 (see Figures 1 and 2).

[0182] The colloidal crystal structure 1 is attached to the target article 110. In the example shown in Figure 18, the colloidal crystal structure 1 is attached to the target article 110 from the particle immobilization layer 20 side, specifically from the first surface 20a side of the particle immobilization layer 20. In this case, as described above, if the particle immobilization layer 20 includes an adhesive layer 21 that constitutes the first surface 20a (see Figures 7-13), the adhesive action of the adhesive layer 21 that constitutes the first surface 20a of the particle immobilization layer 20 makes it easier to firmly attach the colloidal crystal structure 1 to the target article 110.

[0183] The type of item 110 is not particularly limited. When the colloidal crystal structure 1 is used for the security purposes described above, the item 110 may be, for example, a painting, a watch, eyewear, jewelry, perfume, or the like.

[0184] Even in configurations where the colloidal crystal structure 1 is attached to the target article 110, such as article 101 with a colloidal crystal structure, the diffraction pattern (see Figures 3 and 4) originating from the two-dimensional crystal R1 composed of the colloidal particles 30 of the colloidal crystal structure 1 is easily detected.

[0185] If the colloidal crystal structure 1 and the target article 110 are transparent, for example, if the light transmittance in the visible light region of each component of the colloidal crystal structure 1 and the target article 110 is 80% or more, then when detecting the diffraction pattern of the colloidal crystal structure 1, the article 101 with the colloidal crystal structure may be irradiated with light from the colloidal crystal structure 1 side or from the target article 110 side.

[0186] In article 101 with a colloidal crystal structure, the colloidal crystal structure 1 is attached to a portion of the surface of the target article 110 on the side of the colloidal crystal structure 1 (the top surface in Figure 18). As a result, the area where the colloidal crystal structure 1 is attached to the target article 110 is convex compared to the area where the colloidal crystal structure 1 is not attached. Therefore, in article 101 with a colloidal crystal structure, a sharp step is created on the outer circumference of the colloidal crystal structure 1 between the surface of the colloidal crystal structure 1 opposite to the target article 110 (the second main surface 10b of the base material 10 in Figure 18) and the surface of the target article 110 on the side of the colloidal crystal structure 1 (the top surface in Figure 18). Consequently, in article 101 with a colloidal crystal structure, this step becomes more noticeable, which may make the colloidal crystal structure 1 more visible.

[0187] In contrast, the following embodiments can be considered as configurations that make the colloidal crystal structure 1 even less visible.

[0188] <Embodiment 5> The colloidal crystal structure article of Embodiment 5 of the present invention further comprises a step-reducing portion provided on the surface of the article facing the colloidal crystal structure, at a position on the outer periphery of the colloidal crystal structure. In the colloidal crystal structure article of Embodiment 5 of the present invention, the first thickness, which is the thickness of the end of the step-reducing portion on the colloidal crystal structure side in the planar direction, is less than or equal to the thickness of the peripheral edge of the colloidal crystal structure. In the colloidal crystal structure article of Embodiment 5 of the present invention, the second thickness, which is the thickness of the end of the step-reducing portion opposite to the colloidal crystal structure in the planar direction, is smaller than the first thickness of the step-reducing portion.

[0189] Figure 19 is a schematic cross-sectional view showing an example of an article with a colloidal crystal structure according to Embodiment 5 of the present invention.

[0190] The colloidal crystal structure article 102 shown in Figure 19 further has a step-reducing portion 120 provided on the outer periphery of the colloidal crystal structure 1 on the surface of the target article 110 on the colloidal crystal structure 1 side (the top surface in Figure 19).

[0191] The step-reducing portion 120 only needs to be provided on at least a portion of the outer periphery of the colloidal crystal structure 1 on the surface of the target article 110 that is on the colloidal crystal structure 1 side. In other words, the step-reducing portion 120 may be provided on a portion of the outer periphery of the colloidal crystal structure 1 on the surface of the target article 110 that is on the colloidal crystal structure 1 side, or it may be provided on the entire outer periphery of the colloidal crystal structure 1.

[0192] The first thickness of the step-reducing portion 120, which is the thickness of the end on the colloidal crystal structure 1 side in the planar direction, is less than or equal to the thickness of the peripheral edge of the colloidal crystal structure 1. In the example shown in Figure 19, the first thickness of the step-reducing portion 120 is the same as the thickness of the peripheral edge of the colloidal crystal structure 1. However, the first thickness of the step-reducing portion 120 may be less than the thickness of the peripheral edge of the colloidal crystal structure 1.

[0193] The second thickness of the step-reducing section 120, which is the thickness of the end opposite to the colloidal crystal structure 1 in the planar direction, is smaller than the first thickness of the step-reducing section 120. In the example shown in Figure 19, the second thickness of the step-reducing section 120 is zero. Note that the second thickness of the step-reducing section 120 may be greater than zero, as long as it is smaller than the first thickness of the step-reducing section 120.

[0194] In the colloidal crystal structure-attached article 102, the step-eliminating section 120 eliminates the step between the surface of the colloidal crystal structure 1 opposite to the target article 110 (the second main surface 10b of the base material 10 in Figure 19) and the surface of the target article 110 on the colloidal crystal structure 1 side (the top surface in Figure 19). Specifically, when the colloidal crystal structure 1 and the step-eliminating section 120 are viewed as a single unit, the step located on the outer circumference does not change abruptly, but rather changes smoothly. As a result, in the colloidal crystal structure-attached article 102, the step becomes less noticeable, making the colloidal crystal structure 1 less visible. In the colloidal crystal structure-attached article 102, the colloidal crystal structure 1 is less visible, thus increasing the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above.

[0195] As shown in Figure 19, it is preferable that the step-reducing portion 120 has an inclined surface 120a that moves away from the colloidal crystal structure 1 in the planar direction as it approaches the target article 110 in the thickness direction. In other words, it is preferable that the step-reducing portion 120 has an inclined surface 120a that decreases in height as it moves away from the colloidal crystal structure 1 in the planar direction. In this case, as the thickness of the step-reducing portion 120 decreases as it moves away from the colloidal crystal structure 1 in the planar direction, the step located on the outer circumference becomes even smoother when the colloidal crystal structure 1 and the step-reducing portion 120 are viewed as a single unit. As a result, in the article 102 with the colloidal crystal structure, the step becomes even less noticeable, making the colloidal crystal structure 1 even less visible, and thus further enhancing the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above.

[0196] Although this is a different form from Embodiment 5, in order to obtain the same effect as Embodiment 5, the colloidal crystal structure 1 may be machined so that the surface of the colloidal crystal structure 1 (the second main surface 10b of the base material 10 in Figure 18) changes smoothly from the inside to the outside (outer circumference) of the colloidal crystal structure 1 in the planar direction. For example, the colloidal crystal structure 1 may be machined so that the colloidal crystal structure 1 has an inclined surface in which the height position decreases from the inside to the outside (outer circumference) of the colloidal crystal structure 1 in the planar direction.

[0197] <Embodiment 6> In the colloidal crystal structure article of Embodiment 6 of the present invention, the periphery of the colloidal crystal structure is aligned with the periphery of the article.

[0198] Figure 20 is a schematic cross-sectional view showing an example of an article with a colloidal crystal structure according to Embodiment 6 of the present invention.

[0199] In the colloidal crystal structure-attached article 103 shown in Figure 20, the periphery of the colloidal crystal structure 1 follows the periphery of the target article 110. As a result, in the colloidal crystal structure-attached article 103, a step is less likely to occur between the surface of the colloidal crystal structure 1 opposite to the target article 110 (the second main surface 10b of the base material 10 in Figure 20) and the surface of the target article 110 on the side of the colloidal crystal structure 1 (the top surface in Figure 20). Consequently, the colloidal crystal structure 1 becomes less visible in the colloidal crystal structure-attached article 103. Because the colloidal crystal structure 1 is less visible in the colloidal crystal structure-attached article 103, the anti-counterfeiting effect when the colloidal crystal structure 1 is used for security purposes, as described above, is more likely to be enhanced.

[0200] In article 103 with a colloidal crystal structure, the periphery of the colloidal crystal structure 1 does not need to strictly follow (overlap) the periphery of the target article 110, but only needs to substantially follow the periphery of the target article 110. For example, the periphery of the colloidal crystal structure 1 may be located inside the periphery of the target article 110, or it may be located outside the periphery of the target article 110.

[0201] In the article 103 with a colloidal crystal structure, the multiple colloidal particles 30 may be provided in a part of the particle-fixed layer 20 in the planar direction, as shown in Figure 20, or they may be provided throughout the entire particle-fixed layer 20.

[0202] The colloidal crystal structure article of the present invention is not limited to the above-described form, and various applications and modifications can be made within the scope of the present invention regarding the composition, manufacturing conditions, etc., of the colloidal crystal structure article.

[0203] In the articles with the colloidal crystal structure of the present invention, embodiments 4 to 6 illustrate an embodiment in which the colloidal crystal structure of the present invention is attached to the target article from the particle stationary layer side. In the articles with the colloidal crystal structure of the present invention, the colloidal crystal structure of the present invention may also be attached to the target article from the substrate side. [Explanation of Symbols]

[0204] 1, 2, 3 Colloidal Crystal Structures 10 Base material 10a First main surface of the substrate 10b Second main surface of the substrate 20 Particle fixed layer 20a First surface of the particle immobilization layer 20b Second surface of the particle immobilization layer 21 Adhesive layer 22 Non-adhesive layer 30 colloidal particles 40 Middle Class 50 Functional Layers 101, 102, 103 Articles with colloidal crystal structures 110 Target items 120 Step-leveling section 120a Slope AL incident light BL diffracted light BL1 Diffractive light (reflection) BL2 Diffractive light (transmitted) R1, R2, R3a, R3b, R3c, R3d, R3e 2D crystal X3a, X3b, X3c, X3d, X3e axis of symmetry

Claims

1. Substrate and A particle-fixing layer provided on one main surface side of the substrate, The particle immobilization layer comprises a plurality of colloidal particles provided inside the particle immobilization layer, Multiple colloidal particles, while embedded in the particle-fixed layer, are arranged apart from each other along a planar direction perpendicular to the thickness direction of the particle-fixed layer, forming at least one type of two-dimensional crystal. A colloidal crystal structure characterized in that the arithmetic mean roughness Ra of the surface of the particle-fixed layer opposite to the substrate is 0.5 μm or less.

2. The colloidal crystal structure according to claim 1, wherein the arithmetic mean roughness Ra of the main surface on the side opposite to the particle immobilization layer in the substrate is 0.5 μm or less.

3. The colloidal crystal structure according to claim 1 or 2, wherein the particle immobilization layer is in contact with the substrate.

4. The colloidal crystal structure according to claim 3, wherein the arithmetic mean roughness Ra of the interface between the substrate and the particle immobilization layer is 0.5 μm or less.

5. The colloidal crystal structure according to claim 1 or 2, further comprising an intermediate layer in contact with the substrate and the colloidal particles between the substrate and the colloidal particles.

6. The colloidal crystal structure according to claim 5, wherein the arithmetic mean roughness Ra of the interface between the substrate and the intermediate layer is 0.5 μm or less.

7. The colloidal crystal structure according to claim 5 or 6, wherein the intermediate layer further extends in the planar direction between the substrate and the particle immobilization layer so as to be in contact with the substrate and the particle immobilization layer.

8. The colloidal crystal structure according to claim 7, wherein the arithmetic mean roughness Ra of the interface between the particle-fixed layer and the intermediate layer is 0.5 μm or less.

9. The colloidal crystal structure according to any one of claims 1 to 8, wherein the particle immobilization layer includes an adhesive layer that constitutes the surface of the particle immobilization layer opposite to the substrate.

10. The colloidal crystal structure according to any one of claims 1 to 9, wherein at least one of the two-dimensional crystals includes a two-dimensional crystal having six-fold symmetry when viewed from the thickness direction.

11. The colloidal crystal structure according to any one of claims 1 to 10, wherein at least one of the two-dimensional crystals includes a two-dimensional crystal having four-fold symmetry when viewed from the thickness direction.

12. Multiple colloidal particles constitute multiple types of two-dimensional crystals, The colloidal crystal structure according to any one of claims 1 to 11, wherein, when viewed from the thickness direction, the directions of the axes of symmetry along the plane direction of the multiple types of two-dimensional crystals are different from each other.

13. The items in question, An article with a colloidal crystal structure, characterized by comprising a colloidal crystal structure according to any one of claims 1 to 12 attached to the aforementioned article.

14. The colloidal crystal structure is attached to the target article from the particle stationary layer side, as described in claim 13.

15. The object further comprises a step-eliminating portion provided on the outer periphery of the colloidal crystal structure on the surface of the colloidal crystal structure, The first thickness, which is the thickness of the end portion on the colloidal crystal structure side in the surface direction of the step-eliminating portion, is less than or equal to the thickness of the peripheral edge of the colloidal crystal structure. The article with a colloidal crystal structure according to claim 13 or 14, wherein the second thickness, which is the thickness of the end of the step-reducing portion opposite to the colloidal crystal structure in the surface direction, is smaller than the first thickness of the step-reducing portion.

16. The colloidal crystal structure article according to claim 15, wherein the step-reducing portion has an inclined surface that moves away from the colloidal crystal structure in the surface direction as it approaches the target article in the thickness direction.

17. The colloidal crystal structure article according to claim 13 or 14, wherein the periphery of the colloidal crystal structure is along the periphery of the target article.

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