Color-forming structure

Abstract

To provide a color-producing structure which can increase the intensity of reflected light at a wide observation angle and can enhance the adhesion between an irregular structure and a laminate film.SOLUTION: The color-producing structure includes: an irregular structure layer 30 having an irregular structure in a surface; and an optical layer as a laminate film that emits reflected light having been made more intense by interference. The width of a protruding unit 31 is in the range of 10 μm to 100 μm, both inclusive, in planer view of the irregular structure taken from a direction along the thickness direction of the irregular structure layer 30. The protruding unit 31 has trenches 32 lattice-shaped in the planer view, in a surface of the protruding unit 31, the trenches 32 being arranged at smaller intervals than the intervals at which the protruding units 31 are arranged.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a color-developing structure that exhibits structural color. [Background technology]

[0002] Structural colors, often observed in natural organisms such as Morpho butterflies, are visible due to optical phenomena caused by the microscopic structure of an object, such as light diffraction, interference, and scattering. For example, structural colors caused by multilayer interference occur when light is reflected at the interfaces of adjacent thin films and the reflected light interferes with one another. Multilayer interference is one of the principles behind the coloration of Morpho butterfly wings. In Morpho butterfly wings, in addition to multilayer interference, the scattering and diffraction of light occurs due to the minute irregularities on the wing surface, resulting in a vivid blue color that can be seen from a wide viewing angle.

[0003] As a structure for artificially reproducing structural colors like those of Morpho butterfly wings, a structure in which a multilayer film layer is stacked on a fine uneven structure has been proposed, as described in Patent Document 1. The angle of emergence of reflected light intensified by interference in the multilayer film layer depends on the angle of incident light, so in a structure in which multilayer film layers are stacked on a flat surface, the perceived color changes significantly depending on the observation angle. In contrast, in the structure of Patent Document 1, the reflected light intensified by interference is scattered by the unevenness, so the color changes more gradually depending on the observation angle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-56942 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, the more vivid the color observed from a structure, the more visible the attachment location of the structure will be when the structure is attached to an article. To improve the vividness of a specific color observed, it is desirable that the intensity of reflected light be high in the wavelength range of this specific color. In structures in which scattered reflected light is observed, such as the structure described in Patent Document 1, there is still room for improvement in a structure for increasing the intensity of reflected light over a wide observation angle.

[0006] Furthermore, in a structure having a laminated film such as a multilayer film on a concave-convex structure, one of the challenges is to prevent the laminated film from peeling off from the concave-convex structure. In particular, when the convex or concave portions that make up the concave-convex structure have curved or inclined side surfaces, it is desirable to improve the adhesion between the side surfaces and the laminated film. [Means for solving the problem]

[0007] A color-developing structure for solving the above problem comprises a concave-convex structure layer having a concave-convex structure on its surface composed of a plurality of concave-convex elements that are convex or concave portions, and an optical layer that is a laminated film positioned on the concave-convex structure, has a surface shape that follows the concave-convex structure, and emits reflected light that is intensified by interference, wherein, in a planar view of the concave-convex structure seen from a direction along the thickness direction of the concave-convex structure layer, the width of the concave-convex elements is 10 μm or more and 100 μm or less, and the concave-convex elements have concaves and convexes that have a lattice-like shape in a planar view on the surface of the concave-convex element, and the lattice-like concaves and convexes are made up of grid lines that are arranged at intervals smaller than the arrangement interval of the plurality of concave-convex elements.

[0008] According to the above configuration, reflected light in a specific wavelength range that is intensified by interference in the optical layer is scattered by the concavo-convex structure consisting of multiple concavo-convex elements and emitted in various directions. The reflected light is then further scattered by the lattice-like concavo-convex surfaces of the concavo-convex elements, increasing the intensity of the reflected light at each observation angle. As a result, the specific color corresponding to the wavelength range of the reflected light intensified by the optical layer can be observed over a wide observation angle, and the observed specific color becomes more vivid.

[0009] Furthermore, since the surface of the concave-convex elements has a lattice-like texture, the contact area between the optical layer and the concave-convex elements increases, thereby enhancing adhesion between the concave-convex elements and the optical layer, making it difficult for the optical layer to peel off from the concave-convex structure layer.

[0010] In the above configuration, the difference in height between the lattice-like irregularities may be 0.01 μm or more and 1.0 μm or less, and the interval between the lattice lines may be 0.02 μm or more and 10.0 μm or less. According to the above configuration, the scattering effect due to the grid-like unevenness can be suitably obtained.

[0011] In the above configuration, in the plan view, the plurality of concave and convex elements may be arranged in a two-dimensional lattice pattern, and at least one of the directions in which the lattice lines extend may coincide with the direction in which the lattice points in the two-dimensional lattice are arranged.

[0012] According to the above configuration, scattering caused by the unevenness elements occurs isotropically, and furthermore, scattering caused by the lattice-like unevenness also occurs isotropically. In this way, since the degree of directional dependence of scattering does not differ significantly between the unevenness elements and the lattice-like unevenness, the scattering effect of the lattice-like unevenness is suitably added to the scattering effect of the unevenness elements.

[0013] In the above configuration, the uneven elements may be protrusions, and the grid-like unevenness may be grooves formed on the surfaces of the protrusions. According to the above configuration, the concave-convex structure layer can be formed by molding using an intaglio plate, and the concave-convex structure layer can be efficiently formed using a resin.

[0014] In the above configuration, the surface of the convex portion may be a surface that increases in height from the end of the convex portion toward the center when viewed in the plane, and that follows an imaginary plane that forms a curve in a cross section along the thickness direction.

[0015] According to the above configuration, the angle of the surface of the uneven element with respect to the incident light tends to be non-uniform within the surface, so that the scattering effect of the uneven structure can be suitably obtained.

[0016] In the above configuration, the shape of the concave-convex elements in the plan view may be a square or a regular hexagon. According to the above configuration, the shape and arrangement of the uneven elements can be easily designed, and the scattering effect of the uneven structure can be suitably obtained.

[0017] In the above configuration, a ratio of a maximum value of a dimension in the thickness direction within the concave-convex element to a width of the concave-convex element may be 0.1 or more and 1.0 or less. According to the above-described configuration, reflection within the concave-convex elements is suppressed, and therefore light in a wavelength range different from the reflected light enhanced by the optical layer is prevented from emitting from the color-emitting structure, thereby improving the visibility of the color of the reflected light.

[0018] In the above configuration, the proportion of flat portions included in the surface of the concave-convex structure layer may be 10% or less per unit area of ​​the surface in the plan view. According to the above configuration, the proportion of scattered components in the reflected light from the optical layer is sufficiently ensured, thereby accurately suppressing color changes due to changes in the observation angle. Furthermore, the proportion of specular reflection components in the reflected light from the optical layer is kept low, thereby reducing the strain on the eyes of the observer of the color-producing structure.

[0019] In the above configuration, the optical layer may be a laminate of a plurality of dielectric thin films, and the refractive indexes of the dielectric thin films adjacent to each other in the optical layer may be different from each other. According to the above configuration, the intensity of the reflected light is greater than in a configuration that utilizes interference from a single thin film, and therefore the observed colors are more vivid.

[0020] In the above configuration, an absorbing layer may be provided on the optical layer on the opposite side to the concave-convex structure layer, and the absorbing layer may have light absorption properties that absorb at least a portion of light transmitted through the optical layer.

[0021] According to the above configuration, light in a wavelength range different from the reflected light enhanced by the optical layer is prevented from being visible when viewed from the side where the concave-convex structure layer is located, thereby preventing a decrease in the visibility of the color of the reflected light.

[0022] In the above configuration, an adhesive layer may be provided that is located on the opposite side of the optical layer from the concave-convex structure layer, and an outermost surface of the color-producing structure may be included in the adhesive layer. According to the above configuration, a color-developing structure suitable for a color-developing sticker or transfer sheet that is attached to an adherend so that the adherend is located on the opposite side of the optical layer from the concave-convex structure layer can be obtained.

[0023] In the above configuration, an antireflection layer may be provided on the side of the concave-convex structure layer opposite to the optical layer. According to the above configuration, the surface reflection of the color-producing structures is suppressed when viewed from the side where the concave-convex structure layer is located, and therefore, a decrease in the visibility of the color of reflected light is suppressed. [Effects of the Invention]

[0024] According to the present invention, in the color-producing structure, the intensity of reflected light can be increased over a wide observation angle, and the adhesion between the concave-convex structure and the laminated film can be improved. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 2 is a diagram showing a cross-sectional structure of a color-producing structure according to an embodiment. [Figure 2] FIG. 3 is a diagram showing a perspective structure of a concave-convex structure layer in the embodiment. [Figure 3] 3A and 3B are diagrams showing the cross-sectional structure of convex portions provided in the concave-convex structure layer in the embodiment. [Figure 4] 3A and 3B are diagrams showing the planar structure and cross-sectional structure of the concavo-convex structure layer in the embodiment. [Figure 5] 10A and 10B are diagrams showing modified examples of the planar structure of the concavo-convex structure layer in the embodiment. [Figure 6] 10A and 10B are diagrams showing modified examples of the planar structure of the concavo-convex structure layer in the embodiment. [Figure 7] FIG. 10 is a diagram showing a part of the manufacturing process of the concave-convex structure layer of the embodiment, and is a diagram showing a step of forming a mold by cutting. [Figure 8] FIG. 4 is a diagram showing a part of the manufacturing process of the concave-convex structure layer of the embodiment, showing a step of forming the concave-convex structure layer by extrusion molding. [Figure 9] 10A and 10B are diagrams showing a cross-sectional structure when the coloring structure of the embodiment is applied to a coloring sticker. [Figure 10] FIG. 4 is a diagram showing a cross-sectional structure when the color-developing structure of the embodiment is applied to a transfer sheet. DETAILED DESCRIPTION OF THE INVENTION

[0026] An embodiment of a color-emitting structure will be described with reference to the drawings. The incident light and reflected light that the color-emitting structure targets are light in the visible region. In the following description, light in the visible region refers to light in the wavelength range of 360 nm to 830 nm.

[0027] [Basic structure of color-forming structure] As shown in FIG. 1, the color-forming structure 10 includes a substrate 20, a concave-convex structure layer 30, and a multilayer film layer 40.

[0028] The substrate 20 is a flat layer and supports the concave-convex structure layer 30. The substrate 20 is made of a material that transmits light in the visible region, i.e., a material that is transparent to light in the visible region. The substrate 20 is, for example, a synthetic quartz substrate or a sheet made of a resin such as polyethylene terephthalate, polycarbonate, acrylic, or polypropylene. From the viewpoint of increasing the flexibility of the color-developing structure 10, the substrate 20 is preferably a resin sheet. The thickness of the substrate 20 is, for example, 10 μm or more and 100 μm or less.

[0029] The concave-convex structure layer 30 is located on the substrate 20. The concave-convex structure layer 30 has a concave-convex structure on the surface opposite to the surface facing the substrate 20. The concave-convex structure is composed of a plurality of protrusions 31. The protrusions 31 protrude toward the multilayer film layer 40. The protrusions 31 are an example of concave-convex elements.

[0030] The concave-convex structure layer 30 is formed from a resin that transmits light in the visible range, i.e., a resin that is transparent to light in the visible range. Examples of the resin material for the concave-convex structure layer 30 include a photocurable resin, a thermosetting resin, and a thermoplastic resin. Specific examples of the resin material for the concave-convex structure layer 30 include acrylic, polycarbonate, polystyrene, AS resin, and MS resin.

[0031] The multilayer film layer 40 covers the surface of the concave-convex structure layer 30 and has a surface shape that follows the concave-convex structure of the concave-convex structure layer 30. The multilayer film layer 40 is an example of an optical layer. The multilayer film layer 40 is a stack of multiple thin films and has a structure in which high-refractive-index layers 41 and low-refractive-index layers 42 are alternately stacked. Each of the high-refractive-index layers 41 and the low-refractive-index layers 42 is a dielectric thin film. The refractive index of the high-refractive-index layer 41 is higher than the refractive index of the low-refractive-index layer 42. For example, the layer in contact with the concave-convex structure layer 30 is the high-refractive-index layer 41, and the outermost layer on the opposite side of the concave-convex structure layer 30 is the low-refractive-index layer 42.

[0032] The high-refractive index layer 41 and the low-refractive index layer 42 are formed from a material that transmits light in the visible region, i.e., a material that is transparent to light in the visible region. As long as the refractive index of the high-refractive index layer 41 is greater than that of the low-refractive index layer 42, the materials of these layers are not limited. However, the greater the difference in refractive index between the high-refractive index layer 41 and the low-refractive index layer 42, the more intense the reflected light can be obtained with fewer layers. From this perspective, for example, when the high-refractive index layer 41 and the low-refractive index layer 42 are made of inorganic materials, it is preferable that the high-refractive index layer 41 be made of titanium dioxide (TiO2) and the low-refractive index layer 42 be made of silicon dioxide (SiO2). However, the high-refractive index layer 41 and the low-refractive index layer 42 may also be made of organic materials.

[0033] The thickness of each of the high-refractive-index layers 41 and the low-refractive-index layers 42 may be designed using a transfer matrix method or the like depending on the desired color to be emitted by the color-emitting structure 10. The thickness of each of the high-refractive-index layers 41 and the low-refractive-index layers 42 may be selected, for example, from the range of 10 nm to 500 nm. The thicknesses of the layers constituting the multilayer film 40 may be the same or may vary depending on the layer. Note that FIG. 1 illustrates an example of the multilayer film 40 consisting of eight layers, in which high-refractive-index layers 41 and low-refractive-index layers 42 are alternately stacked in this order from the position closest to the concave-convex-structure layer 30. The number of layers and the stacking order of the multilayer film layer 40 are not limited thereto, and the high-refractive-index layers 41 and low-refractive-index layers 42 may be designed to obtain reflected light in the desired wavelength range. For example, the low-refractive-index layer 42 may be in contact with the concave-convex-structure layer 30, and the high-refractive-index layers 41 and low-refractive-index layers 42 may be alternately stacked thereon. The outermost layer on the opposite side to the concave-convex structure layer 30 may also be either the high refractive index layer 41 or the low refractive index layer 42. Furthermore, as long as the high refractive index layers 41 and the low refractive index layers 42 are alternately stacked, the material of the layer in contact with the concave-convex structure layer 30 and the outermost layer on the opposite side may be the same. Furthermore, the multilayer film layer 40 may include three or more layers with different refractive indices.

[0034] In short, the multilayer film 40 is configured so that the refractive indexes of adjacent layers are different from each other, and the reflectance of light incident on the multilayer film 40 in a specific wavelength range is higher than the reflectance in other wavelength ranges.

[0035] The coloring structure 10 does not necessarily have to include the base material 20. When the coloring structure 10 does not include the base material 20, the concave-convex structure layer 30 may be formed from a material other than resin, such as synthetic quartz.

[0036] [Configuration of uneven structure] The concave-convex structure of the concave-convex structure layer 30 will be described in detail. Fig. 2 shows a perspective structure of the concave-convex structure layer 30. As shown in Fig. 2, in the concave-convex structure of the concave-convex structure layer 30, a plurality of convex portions 31 are arranged without any gaps. The convex portions 31 have grooves 32 extending in a fine lattice pattern on their surfaces. In addition, in figures other than Fig. 3, the grooves 32 are illustrated as lattice lines on the surfaces of the convex portions 31 to make the arrangement of the grooves 32 easier to understand.

[0037] FIG. 3 shows the cross-sectional structure of the protrusions 31. The width W of the protrusions 31 is 10 μm or more and 100 μm or less. It is preferable that the width W is uniform among the multiple protrusions 31. If the width W is 10 μm or more, the diffraction of light due to the regular arrangement of the protrusions 31 is suppressed. Therefore, the visibility of rainbow colors as diffracted light is suppressed, thereby improving the visibility of the color of the reflected light enhanced by the multilayer film layer 40. Furthermore, if the width W is 10 μm or more, the protrusions 31 are not too fine, facilitating the formation of a concave-convex structure and improving the production efficiency of the color-producing structure 10. On the other hand, if the width W is 100 μm or less, the protrusions 31 are prevented from being recognized by the human eye as a single structure. From the viewpoint of achieving a balance between these effects, the width W is preferably 40 μm or more and 50 μm or less.

[0038] The maximum length H of the protrusions 31 is the maximum value of the height of the protrusions 31 along the thickness direction of the concave-convex structure layer 30. The maximum length H is preferably, for example, 10 μm or less. The maximum length H of the multiple protrusions 31 is preferably constant.

[0039] The aspect ratio of the protrusions 31, i.e., the ratio of the maximum length H to the width W, is preferably 0.1 or more and 1.0 or less. If the aspect ratio is 0.1 or more, an uneven structure is formed that has sufficient undulations compared to a flat surface, and therefore the scattering effect of the uneven structure is high.

[0040] On the other hand, if the aspect ratio is 1.0 or less, reflection of light within the convex portions 31 is suppressed. If reflection within the convex portions 31 is large, it is possible that light of a wavelength range different from the wavelength range enhanced by the multilayer film layer 40, among the incident light, is reflected within the convex portions 31 and emitted toward the viewer. If such light is visible, the visibility of the color of the reflected light enhanced by the multilayer film layer 40 decreases. In contrast, as described above, if the aspect ratio is 1.0 or less, the visibility of light of a wavelength range different from the light reflected by the multilayer film layer 40 is suppressed, and therefore a decrease in the clarity of the perceived color is suppressed. Note that the convex portions 31 are preferably designed to have a shape that makes it difficult to reflect light of a wavelength range different from the wavelength range enhanced by the multilayer film layer 40.

[0041] The depth D of the grooves 32 is preferably 0.01 μm or more and 1.0 μm or less. The depth D of the grooves 32 within one convex portion 31 may or may not be constant. Furthermore, the depth D of the grooves 32 within a plurality of convex portions 31 may or may not be constant. The depth D of the grooves 32 is, in other words, the difference in height between the minute concaves and convexes that are the grooves 32.

[0042] The spacing Pg between the grooves 32 is the pitch of the grating formed by the grooves 32, in other words, the spacing between the grating lines. The spacing Pg between the grooves 32 is preferably 0.02 μm or more and 10.0 μm or less. Furthermore, the spacing Pg between the grooves 32 is preferably 1 / 50 or more and 1 / 5 or less of the width W of the protrusion 31. Within one protrusion 31, the spacing Pg between the grooves 32 may or may not be constant. For example, the spacing Pg between the grooves 32 in the two directions in which the grating lines are arranged may or may not be the same. Furthermore, within multiple protrusions 31, the spacing Pg between the grooves 32 may or may not be constant.

[0043] The width of the grooves 32 may be set to a size that allows the formation of lattice-shaped grooves 32 on the surfaces of the protrusions 31 at the intervals Pg. The shape of the grooves 32 in a cross section along the thickness direction of the concave-convex structure layer 30 is not particularly limited. As exemplified in Fig. 3, the grooves 32 may have a shape in which the width narrows toward the bottom, or the grooves 32 may have a shape in which the width is constant from the opening to the bottom.

[0044] When the imaginary curved surface where the openings of the grooves 32 are located, in other words, the imaginary curved surface along the surface of the convex portion 31, is taken as the reference surface 31S, the reference surface 31S is one continuous curved surface, and the height of the reference surface 31S gradually increases from the end portion to the center of the convex portion 31 in a plan view of the uneven structure seen from the thickness direction. The height of the reference surface 31S is greatest at the center of the convex portion 31.

[0045] In the cross section along the thickness direction, the reference surface 31S forms a curved line that protrudes toward the multilayer film layer 40. When the reference surface 31S forms a curved line, the angle of the surface of the convex portion 31 with respect to the incident light tends to be more non-uniform within the surface, which tends to enhance the scattering effect of the reflected light. The curvature of this curve may or may not be constant. For example, the curvature of the curve formed by the reference surface 31S may be different between the end portion and the center portion of the convex portion 31.

[0046] If the curvature of the curve is constant, it is easier to suppress light reflection within the convex portions 31 compared to a configuration in which the curvature is greater at the center of the convex portions 31. On the other hand, if the curvature of the curve is not constant, the convex portions 31 can be configured so that the angle of the surface of the convex portions 31 with respect to the incident light becomes more non-uniform within the surface, and therefore the shape of the convex portions 31 can also be designed to enhance the scattering effect of the reflected light of the multilayer film layer 40.

[0047] Fig. 4 shows the planar structure and cross-sectional structure of the concave-convex structure layer 30. As shown in Fig. 4, in a plan view of the concave-convex structure seen from the thickness direction of the concave-convex structure layer 30, the convex portions 31 have a square shape. The multiple convex portions 31 have the same square shape, and are arranged in a square lattice pattern along the direction in which the sides of the square extend. A square lattice is an example of a two-dimensional lattice.

[0048] In detail, the plurality of protrusions 31 are aligned along the first direction dx and the second direction dy. The first direction dx and the second direction dy are perpendicular to each other. The plurality of protrusions 31 are aligned so that the first direction dx and the second direction dy are aligned along the directions in which the sides of the squares that form the protrusions 31 in the plan view extend. In rows of protrusions 31 adjacent to each other in the second direction dy, the positions of the protrusions 31 in one row in the first direction dx coincide with the positions of the protrusions 31 in the other row in the first direction dx. In other words, the positions of the centers C of the protrusions 31 in the first direction dx coincide in adjacent rows.

[0049] The width W of the protrusions 31 is the length of one side of the square. The period Px of the arrangement of the protrusions 31 in the first direction dx and the period Py of the arrangement of the protrusions 31 in the second direction dy match, and the periods Px and Py match the width W. In this configuration, as described above, the multiple protrusions 31 are arranged without any gaps, and the surface of the concave-convex structure layer 30 does not have any flat portions.

[0050] In the plan view, the lattice formed by the grooves 32 is composed of a plurality of lattice lines extending in the first direction dx and aligned along the second direction dy, and a plurality of lattice lines extending in the second direction dy and aligned along the first direction dx. That is, the extending direction of the lattice lines coincides with the direction in which the lattice points are aligned in the two-dimensional lattice formed by the protrusions 31. In both the first direction dx and the second direction dy, the spacing between the lattice lines, i.e., the spacing Pg between the grooves 32, is smaller than the periods Px and Py that are the arrangement intervals of the protrusions 31.

[0051] In two adjacent protrusions 31 in the first direction dx, the grooves 32 may or may not be continuous. In two adjacent protrusions 31 in the second direction dy, the grooves 32 may or may not be continuous. In addition, the lattice pattern formed by the grooves 32 in the plan view may be the same for multiple protrusions 31, or may be different. If the lattice pattern is the same for multiple protrusions 31, it is easy to design the arrangement of the grooves 32 and to form the grooves 32.

[0052] When light is incident on the color-producing structure 10 of this embodiment, the light reflected at each interface between the high-refractive-index layer 41 and the low-refractive-index layer 42 in the multilayer film layer 40 interferes. Furthermore, due to the uneven structure formed by the convex portions 31 of the uneven structure layer 30, the angle of each interface relative to the incident light changes within the color-producing structure 10, causing the reflected light to be emitted in various directions. In other words, the reflected light from the multilayer film layer 40 is scattered. As a result, light in a specific wavelength range that has been intensified by interference is emitted in various directions, making a specific color visible at a wide observation angle.

[0053] Furthermore, since the convex portions 31 have grooves 32, minute irregularities exist on the surfaces of the convex portions 31, which further scatters the reflected light. As a result, the intensity of the reflected light observed is increased at each observation angle. That is, over a wide observation angle, the intensity of the reflected light in a specific wavelength range that has been intensified by interference is increased. This increases the vividness of the specific color observed over a wide observation angle.

[0054] Furthermore, reflected light in the above-mentioned specific wavelength range can be observed whether the multilayer film layer 40 is observed from the side where the uneven structure layer 30 is located or from the opposite side of the uneven structure layer 30.

[0055] Furthermore, since the multilayer film layer 40 fits into the grooves 32, the contact area between the multilayer film layer 40 and the protrusions 31 is increased compared to when the protrusions 31 do not have grooves 32 and the surface of the protrusions 31 is a single continuous curved surface. This increases the adhesion between the protrusions 31 and the multilayer film layer 40. As a result, the multilayer film layer 40 is less likely to peel off from the concave-convex structure layer 30. Therefore, even when the color-producing structure 10 is attached to a curved surface, the occurrence of cracks and the like due to peeling of the multilayer film layer 40 is suppressed, and the above-mentioned specific color can be preferably produced.

[0056] Moreover, because the protrusions 31 are arranged in a two-dimensional lattice pattern, scattering caused by the protrusions 31 occurs isotropically. Furthermore, because the grooves 32 are lattice-shaped, scattering caused by the grooves 32 also occurs isotropically. In this way, the degree of directional dependency of scattering does not differ significantly between the protrusions 31 and the grooves 32, so the scattering effect of the grooves 32 is suitably added to the scattering effect of the protrusions 31. In this configuration, the anisotropy of brightness in the color-forming structure 10, in other words, the difference in brightness depending on the observation direction, can be reduced compared to, for example, a configuration in which the grooves 32 extend in the form of multiple parallel lines.

[0057] [Variations of the arrangement of convex portions] Modified examples of the arrangement of the protrusions 31 will be described with reference to FIGS. 5 shows the planar structure of the concave-convex structure layer 30 in the first modified example. In the first modified example, the shape of the convex portions 31 in the plan view is square, and the convex portions 31 are arranged in an oblique lattice pattern. The oblique lattice is a two-dimensional lattice in which a unit cell is a parallelogram with two adjacent sides of different lengths.

[0058] More specifically, rows of multiple protrusions 31 aligned in the first direction dx are aligned in the second direction dy. In adjacent rows of protrusions 31, the positions of the protrusions 31 in one row in the first direction dx are shifted by 1 / 2 the period Px of the protrusions 31 from the positions of the protrusions 31 in the other row in the first direction dx. In other words, in adjacent rows, the positions of the centers C of the protrusions 31 in the first direction dx are shifted by 1 / 2Px.

[0059] The period Px of the arrangement of the protrusions 31 in the first direction dx is equal to the width W of the protrusions 31, and the period Py of the arrangement of the protrusions 31 in the second direction dy that are positioned in the same direction as the first direction dx is twice the width W.

[0060] In the plan view, the lattice formed by the grooves 32 is composed of a plurality of lattice lines extending in the first direction dx and aligned along the second direction dy, and a plurality of lattice lines extending in the second direction dy and aligned along the first direction dx. That is, the direction in which the lattice lines extending in the first direction dx coincides with the direction in which the lattice points are aligned in the two-dimensional lattice formed by the protrusions 31. In both the first direction dx and the second direction dy, the spacing between the lattice lines, i.e., the spacing Pg between the grooves 32, is smaller than the periods Px and Py.

[0061] The grooves 32 may or may not be continuous between two adjacent protrusions 31 in the first direction dx or the second direction dy. The lattice pattern formed by the grooves 32 in the plan view may be the same for the plurality of protrusions 31 or may be different for the plurality of protrusions 31. When the lattice pattern is the same for the plurality of protrusions 31, it is easy to design the arrangement of the grooves 32 and to form the grooves 32.

[0062] In the first variant, compared to the form in which the protrusions 31 are arranged in a square lattice pattern along the first direction dx and the second direction dy, as shown in Figure 4 above, the first variant reduces the visibility of a lattice pattern on the color-producing structure 10 even when the protrusions 31 are large.

[0063] 6 shows the planar structure of the concave-convex structure layer 30 in the second modified example. In the second modified example, the shape of the convex portions 31 in the plan view is a regular hexagon, and the convex portions 31 are arranged in a triangular lattice pattern. In other words, the convex portions 31 are arranged in a hexagonal lattice pattern. The triangular lattice and the hexagonal lattice are examples of two-dimensional lattices.

[0064] More specifically, the plurality of protrusions 31 are arranged along the first direction dx such that the sides of the regular hexagons of adjacent protrusions 31 are in contact with each other. The plurality of protrusions 31 are arranged such that the direction in which a pair of opposing sides of the regular hexagon extends is along the second direction dy. The rows of protrusions 31 extending in the first direction dx are arranged along the second direction dy.

[0065] When the widths of the short side direction and the long side direction of the protrusion 31 are different, as in the second modification, both the width W1 of the short side direction and the width W2 of the long side direction are 10 μm or more and 100 μm or less. The width W1 of the short side direction is the length of the short side of the smallest rectangle inscribed in the protrusion 31 when the short side width W1 is hypothetically arranged in the plan view. The width W2 of the long side direction is the length of the long side of the smallest rectangle. The maximum length H of the protrusion 31 may be set based on the width W1 of the short side direction; that is, it is preferable that the ratio of the maximum length H to the width W1 of the short side direction is 0.1 or more and 1.0 or less. The form in which the protrusion 31 has a square shape when viewed in the plan view is a form in which the width W1 of the short side direction and the width W2 of the long side direction are the same.

[0066] In rows of adjacent protrusions 31 along the second direction dy, the positions of the centers C of the protrusions 31 in the first direction dx are shifted by ½ of the width W1, which is the period Px of the protrusions 31. Rows of adjacent protrusions 31 along the second direction dy are in contact with each other, and in this configuration, the surface of the concave-convex structure layer 30 does not have a flat portion.

[0067] The period Px of the arrangement of the convex portions 31 in the first direction dx is equal to the width W1, and the period Py of the arrangement of the convex portions 31 in the second direction dy that are aligned in the first direction dx is 1.5 times the width W2.

[0068] In the plan view, the lattice formed by the grooves 32 is composed of a plurality of lattice lines extending in the first direction dx and aligned along the second direction dy, and a plurality of lattice lines extending in the second direction dy and aligned along the first direction dx. That is, the direction in which the lattice lines extending in the first direction dx coincides with the direction in which the lattice points are aligned in the two-dimensional lattice formed by the protrusions 31. In both the first direction dx and the second direction dy, the spacing between the lattice lines, i.e., the spacing Pg between the grooves 32, is smaller than the periods Px and Py.

[0069] The grooves 32 may or may not be continuous between two adjacent protrusions 31 in the first direction dx or the second direction dy. The lattice pattern formed by the grooves 32 in the plan view may be the same for the plurality of protrusions 31 or may be different for the plurality of protrusions 31. When the lattice pattern is the same for the plurality of protrusions 31, it is easy to design the arrangement of the grooves 32 and to form the grooves 32.

[0070] In the second modified example, compared to an embodiment in which the square protrusions 31 are arranged in a square lattice pattern in a plan view, even when the protrusions 31 are large, a lattice pattern is less likely to be visible on the color-producing structure 10. Furthermore, because the shape of the protrusions 31 in the plan view is a regular hexagon, the direction in which the scattered reflected light is emitted is more likely to be wider than when the shape of the protrusions 31 is square.

[0071] The shape of the protrusions 31 in the plan view is not limited to a square or a regular hexagon, but may be another polygon such as a triangle or a rectangle, or may be a circle. Furthermore, the shape of the protrusions 31 in the plan view does not have to be uniform among the multiple protrusions 31.

[0072] To enhance the scattering effect of reflected light and emit the reflected light over a wider angle, it is preferable that the angle of the surface of the protrusions 31 relative to the incident light be as non-uniform as possible within the surface. For example, if the shape of the protrusions 31 in the plan view is quadrangular, the change in the inclination of the reference plane 31S from the vertex of the rectangle toward the center of the rectangle is different from the change in the inclination of the reference plane 31S from the midpoint of the side of the rectangle toward the center of the rectangle. Therefore, the inclination tends to vary greatly depending on the location within the surface of the protrusions 31. Therefore, when the shape of the protrusions 31 is quadrangular, the scattering effect of reflected light is likely to be enhanced.

[0073] The height of the reference surface 31S of the protrusion 31 does not have to gradually increase from the end portion to the center portion of the protrusion 31 in the plan view, and the reference surface 31S does not have to be curved in a cross section along the thickness direction. The multiple protrusions 31 may be arranged in a two-dimensional lattice pattern different from the above-described form, or may be arranged regularly or irregularly in an arrangement different from the two-dimensional lattice.

[0074] The more irregular the shape and arrangement of the plurality of protrusions 31, the more effective the scattering of reflected light. For example, when the protrusions 31 have a quadrangular shape in the plan view, and at least one of the widths in the short side direction and the widths in the long side direction of adjacent protrusions 31 is different from each other, the more effective the scattering of reflected light is compared to a case where the shape of the plurality of protrusions 31 is uniform.

[0075] Furthermore, the multiple convex portions 31 may be arranged with gaps between adjacent convex portions 31. In other words, the surface of the concave-convex structure layer 30 may have flat portions between adjacent convex portions 31. However, in the above-mentioned plan view, the ratio of flat portions per unit area on the surface of the concave-convex structure layer 30 is preferably 10% or less. Reflected light is scattered less in the area where the multilayer film layer 40 is laminated on the flat portions. However, if the ratio of flat portions is 10% or less, the ratio of scattered components in the reflected light from the multilayer film layer 40 is sufficiently ensured, thereby effectively suppressing color changes due to changes in observation angle. Furthermore, if the ratio of flat portions is 10% or less, the ratio of specular reflection components in the reflected light from the multilayer film layer 40 is kept low, thereby reducing the strain on the observer's eyes. Note that, to enhance these effects, the smaller the ratio of flat portions, the more preferable.

[0076] [Method of manufacturing color-developing structure] A method for manufacturing the color-developing structure 10 will be described. Methods for forming the concave-convex structure of the concave-convex structure layer 30 include transfer molding using heat or light, injection molding, extrusion molding, mechanical processing such as cutting, etching, etc. The intaglio plate used for transfer molding, etc., is formed by mechanical processing or etching.

[0077] For example, when machining is used, a concave-convex structure consisting of protrusions 31 having grooves 32, or an intaglio plate for forming the concave-convex structure, can be formed by adjusting the cutting conditions and selecting an appropriate tool. Machining conditions include, for example, adjusting the machining speed and the vibration state of the cutting tool. The concave-convex structure or intaglio plate may also be formed by machining the same location multiple times or by combining different machining methods.

[0078] An example of a method for manufacturing the relief structure layer 30 using machining and extrusion molding will be described with reference to FIGS. First, as shown in Fig. 7, a roll-shaped mold 100, which is an intaglio plate for forming the concave-convex structure, is formed by cutting. Specifically, while the mold 100 attached to a processing machine is rotated, a cutting tool 110 corresponding to the shape of the desired convex portions 31 is pressed against the mold 100. By reciprocating the cutting tool 110, concave portions 101 corresponding to the convex portions 31 are formed on the surface of the mold 100. For example, by using a tool having partial chips on its surface as the cutting tool 110, it is possible to form ridges extending in a grid pattern, i.e., ridges corresponding to the grooves 32, on the inner surface of the concave portions 101.

[0079] 8, the fabricated mold 100 and a molding roll 220 are mounted in an extrusion molding machine 200, and molten resin is extruded from a T-die 210 between the mold 100 and the roll 220. The resin that has passed between the mold 100 and the roll 220 is cooled, thereby obtaining a resin sheet 60 having a surface onto which the concave-convex patterns of the mold 100 are transferred. The obtained resin sheet 60 is a sheet comprising a concave-convex structure layer 30.

[0080] Next, an example of a method for manufacturing a concave-convex structure layer 30 by transfer molding using light will be described. In this case, a photocurable resin is applied to the substrate 20, and the resin is cured by irradiating it with light such as ultraviolet light while pressing an intaglio plate having inverted concave-convex patterns of the pattern to be formed against the resin. As a result, a resin-made concave-convex structure layer 30 having a surface onto which the intaglio plate concave-convex patterns are transferred is formed on the substrate 20. Note that a thermosetting resin may be used instead of the photocurable resin, and in this case, heating may be performed instead of irradiating light.

[0081] After the concave-convex structure layer 30 is formed, the layers that make up the multilayer film layer 40 are laminated in order on the concave-convex structured surface of the concave-convex structure layer 30. When the high-refractive index layer 41 and the low-refractive index layer 42 that make up the multilayer film layer 40 are made of inorganic materials, the high-refractive index layer 41 and the low-refractive index layer 42 are each formed using a known thin film formation technique such as sputtering, vacuum evaporation, or atomic layer deposition. When the high-refractive index layer 41 and the low-refractive index layer 42 are each formed of organic materials, the high-refractive index layer 41 and the low-refractive index layer 42 may be formed using a known technique such as self-organization.

[0082] [Examples of application of color-forming structures] As application examples of the color-forming structure, the configurations of a color-forming sticker and a transfer sheet will be described. First, the structure when the color-forming structure is applied to a color-forming sticker will be described. The color-forming sticker is attached to an adherend and used for decorating the adherend, etc.

[0083] 9, the coloring structure constituting the coloring sticker 11 includes a substrate 20, a concave-convex structure layer 30, a multilayer film layer 40, an absorption layer 50, and an adhesive layer 51. The absorption layer 50 and the adhesive layer 51 are located on the opposite side of the multilayer film layer 40 from the concave-convex structure layer 30.

[0084] The absorbing layer 50 covers the irregularities on the outermost surface of the multilayer film layer 40. The absorbing layer 50 has light-absorbing properties that absorb light transmitted through the multilayer film layer 40. For example, the absorbing layer 50 contains a material that absorbs light in the visible region, such as a light absorber or a black pigment. Specifically, the absorbing layer 50 is preferably a layer in which a black inorganic pigment, such as carbon black, titanium black, black iron oxide, or black complex oxide, is mixed with a resin. The thickness of the absorbing layer 50 is, for example, 1 μm or more and 10 μm or less.

[0085] The adhesive layer 51 contacts the absorbent layer 50 on the side opposite the multilayer film layer 40 with respect to the absorbent layer 50. The surface of the adhesive layer opposite to the surface contacting the absorbent layer 50 is the outermost surface of the color-developing sticker 11. The adhesive layer 51 is a layer that has adhesive properties to an adherend, and is made of, for example, an acrylic or urethane pressure-sensitive adhesive. The thickness of the adhesive layer 51 is, for example, 10 μm or more and 100 μm or less.

[0086] The absorbing layer 50 and the adhesive layer 51 are formed by using a known coating method such as an inkjet method, a spray method, a bar coating method, a roll coating method, a slit coating method, or a gravure coating method.

[0087] The color-forming sticker 11 is attached to the adherend so that the adhesive layer 51 is in contact with the adherend, i.e., so that the adherend is located on the opposite side of the multilayer film layer 40 from the uneven structure layer 30. An observer observes the color-forming sticker 11 from the side of the multilayer film layer 40 where the uneven structure layer 30 is located. An article consisting of the adherend and the color-forming sticker 11 is a color-forming article.

[0088] Of the incident light, a portion of the light outside the specific wavelength range reflected by the multilayer film layer 40 is transmitted through the multilayer film layer 40. Because the wavelength range of this transmitted light is different from the wavelength range of the light reflected by the multilayer film layer 40, when such transmitted light is visible, the visibility of the color of the reflected light decreases. In the color-developing sticker 11, the absorption layer 50 is provided, so that the transmitted light through the multilayer film layer 40 is absorbed by the absorption layer 50, and this transmitted light is prevented from being reflected by the surface of the adherend or the like and being emitted toward the substrate 20.

[0089] Therefore, light in a wavelength range different from the reflected light from the multilayer film layer 40 is prevented from being seen by the observer, and therefore the visibility of the color of the reflected light is prevented from decreasing. As a result, the desired color can be suitably obtained in the color-developing sticker 11.

[0090] The color-forming sticker 11 may have an anti-reflection layer on the surface of the base material 20 opposite to the concave-convex structure layer 30. The anti-reflection layer has the function of suppressing surface reflection on the outermost surface of the color-forming sticker 11. The suppression of surface reflection by the anti-reflection layer further improves the visibility of the color of the reflected light intensified by the multilayer film layer 40.

[0091] Next, a structure in which the color-developing structure is applied to a transfer sheet will be described. The transfer sheet is a sheet used to attach a color-developing sheet to an adherend. In other words, the transfer sheet is used to transfer the color-developing sheet provided on the transfer sheet to an adherend.

[0092] As shown in FIG. 10, the color-developing structure constituting the transfer sheet 12 includes a substrate 20, a concave-convex structure layer 30, a multilayer film layer 40, an absorption layer 52, and an adhesive layer 53. The transfer sheet 12 is configured so that the substrate 20 can be peeled off from the concave-convex structure layer 30. Specifically, the transfer sheet 12 includes a release layer 54 between the substrate 20 and the concave-convex structure layer 30. The release layer 54 contains a component that functions as a release agent, such as silicone oil or a fluorine compound. The release layer 54 is formed on the surface of the substrate 20 by a known coating method.

[0093] The absorbing layer 52 and the adhesive layer 53 are located on the opposite side of the multilayer film layer 40 from the concave-convex structure layer 30. The absorbing layer 52 covers the concave-convex portions on the outermost surface of the multilayer film layer 40. The adhesive layer 53 is in contact with the absorbing layer 52 on the opposite side of the multilayer film layer 40 from the absorbing layer 52, and is located on the outermost side of the transfer sheet 12. The absorbing layer 52 has a structure similar to that of the absorbing layer 50 of the color-forming sticker 11 described above, and the adhesive layer 53 has a structure similar to that of the adhesive layer 51 of the color-forming sticker 11 described above.

[0094] When the transfer sheet 12 is used, it is fixed to the surface of the adherend so that the adhesive layer 53 contacts the adherend. Then, the substrate 20 is peeled off. The substrate 20 may be peeled off by peeling at the interface between the substrate 20 and the release layer 54, or by peeling at the interface between the release layer 54 and the concave-convex-structure layer 30, resulting in peeling together with the release layer 54. This transfers the color-forming sheet 13, which includes the concave-convex-structure layer 30, the multilayer film layer 40, the absorption layer 52, and the adhesive layer 53, to the adherend. When peeling occurs at the interface between the substrate 20 and the release layer 54, the release layer 54 is also included in the color-forming sheet 13. The outermost surface of the color-forming sheet 13 opposite the adhesive layer 53 is the surface of the release layer 54 or the concave-convex-structure layer 30.

[0095] As described above, the transfer sheet 12 and the color-forming sheet 13 are attached to the adherend so that the adherend is located on the opposite side of the multilayer film layer 40 from the uneven structure layer 30. An observer observes the color-forming sheet 13 from the side of the multilayer film layer 40 where the uneven structure layer 30 is located. An article consisting of the adherend and the color-forming sheet 13 is a color-forming article.

[0096] Since the color-forming sheet 13 includes the absorbing layer 52, the transmitted light through the multilayer film layer 40 is absorbed by the absorbing layer 52, and this transmitted light is prevented from being reflected by the surface of the adherend or the like and being emitted toward the concave-convex structure layer 30. This prevents light in a wavelength range different from the light reflected from the multilayer film layer 40 from being seen by an observer, thereby preventing a decrease in the visibility of the color of the reflected light. This allows the color-forming sheet 13 to preferably produce the desired color.

[0097] Furthermore, since the color-forming sheet 13 does not have the base material 20 that is the base material used during manufacturing, the flexibility of the color-forming sheet 13 is increased. Furthermore, the thickness of the color-forming sheet 13 is thinner than when the color-forming sheet 13 has the base material used during manufacturing. Therefore, the portion where the color-forming sheet 13 is attached is prevented from swelling.

[0098] The transfer sheet 12 may not include the release layer 54, and the substrate 20 may be configured to be peelable from the rugged-structure layer 30 by adjusting the materials. For example, the substrate 20 may contain a release agent, or the materials of the substrate 20 and the rugged-structure layer 30 may be selected so that the adhesion between the substrate 20 and the rugged-structure layer 30 is low.

[0099] Furthermore, when transferring the color-developing sheet 13, heating and pressure, application of water pressure, ultraviolet irradiation, etc. may be performed. Such stimuli applied during transfer may cause the releasability of the substrate 20 and the adhesiveness of the adhesive layer 53 to appear. For example, the adhesive layer 53 may be formed from a thermoplastic resin that functions as a heat-sealing agent, such as polyethylene, polyvinyl acetate, acrylic, polyamide, polyester, polypropylene, or polyurethane. In such a form, the adhesiveness of the adhesive layer 53 appears when heated.

[0100] The shape and material of the adherend to which the color-developing sticker 11 or color-developing sheet 13 is attached are not particularly limited, and the adherend may be, for example, a resin molded product such as a card or a three-dimensional object, or may be paper. In short, the adherend may have a surface to which the adhesive layers 51, 53 can adhere.

[0101] Furthermore, even if the absorbing layers 50, 52 do not absorb all light in the visible range, as long as they have light-absorbing properties that absorb at least a portion of the light that passes through the multilayer film layer 40, it is possible to suppress a decrease in color visibility due to reflected light compared to a case in which such a light-absorbing layer is not provided. For example, the absorbing layers 50, 52 may be layers containing a pigment of a color corresponding to the wavelength range of light that passes through the multilayer film layer 40. However, if the absorbing layers 50, 52 are black layers containing a black pigment, there is no need to adjust the color according to the wavelength range of the transmitted light, and the absorbing layers 50, 52 absorb light in a wide wavelength range, so that a decrease in color visibility due to reflected light can be suppressed simply and preferably.

[0102] As described above, according to the above embodiment, the following effects can be obtained. (1) Because the multilayer film layer 40 is stacked on an uneven structure consisting of multiple protrusions 31, reflected light in a specific wavelength range that is intensified by interference in the multilayer film layer 40 is scattered and emitted in various directions. Furthermore, because the protrusions 31 have minute unevenness on their surface, which is the lattice-like grooves 32, the reflected light is further scattered, increasing the intensity of the reflected light at each observation angle. Therefore, a specific color corresponding to the wavelength range of the reflected light intensified by the multilayer film layer 40 can be observed at a wide observation angle, and the observed specific color becomes more vivid.

[0103] Furthermore, since the surface of the protrusions 31 has minute irregularities, which are the grid-like grooves 32, the contact area between the protrusions 31 and the multilayer film layer 40 increases. This improves the adhesion between the protrusions 31 and the multilayer film layer 40. As a result, the multilayer film layer 40 is less likely to peel off from the uneven structure layer 30. The concave-convex structure can be formed by molding using an intaglio plate, and the concave-convex structure layer 30 can be efficiently formed using a resin.

[0104] (2) By setting the depth D of the grooves 32 to 0.01 μm or more, the undulations on the surfaces of the protrusions 31 are sufficiently ensured, and the scattering effect of the grooves 32 is suitably obtained. Furthermore, by setting the depth D of the grooves 32 to 1.0 μm or less, the undulations on the surfaces of the protrusions 31 are prevented from becoming too large, and the scattering effect is prevented from becoming excessive.

[0105] (3) By setting the interval Pg of the grooves 32 to 0.02 μm or more, the interval between the grid lines is prevented from becoming excessively small, making it easier to form the grooves 32. Also, the scattering effect is prevented from becoming excessive. By setting the interval Pg of the grooves 32 to 10.0 μm or less, the frequency of the undulations on the surface of the convex portions 31 is sufficiently ensured, so that the scattering effect of the grooves 32 can be suitably obtained.

[0106] (4) The plurality of protrusions 31 are arranged in a two-dimensional lattice pattern, and at least one of the directions in which the lattice lines of the lattice formed by the grooves 32 extend coincides with the direction in which the lattice points of the two-dimensional lattice are arranged. With this configuration, scattering caused by the protrusions 31 occurs isotropically, and further, scattering caused by the grooves 32 also occurs isotropically. In this way, the degree of directional dependence of scattering does not differ significantly between the protrusions 31 and the grooves 32, so the scattering effect of the grooves 32 is suitably added to the scattering effect of the protrusions 31.

[0107] (5) The surface of the convex portion 31 increases in height from the end portion of the convex portion 31 toward the center portion in a plan view, and is a surface along a reference plane 31S, which is a virtual surface that forms a curve in a cross section along the thickness direction of the concave-convex structure layer 30. With this configuration, the angle of the surface of the convex portion 31 with respect to the incident light tends to be non-uniform within the surface, and therefore, the scattering effect of the concave-convex structure can be suitably obtained.

[0108] (6) If the shape of the protrusions 31 in plan view is a square or a regular hexagon, the shape and arrangement of the protrusions 31 can be easily designed, and the scattering effect of the uneven structure can be suitably obtained. (7) If the ratio of the maximum length H, which is the maximum dimension in the thickness direction within the protrusions 31, to the width W of the protrusions 31 is 0.1 or more and 1.0 or less, reflection within the protrusions 31 is suppressed, thereby suppressing the emission of light in a wavelength range different from the reflected light enhanced by the multilayer film layer 40. Therefore, the visibility of the color of the reflected light is improved.

[0109] (8) If the proportion of flat portions included in the surface of the concave-convex structure layer 30 per unit area of ​​the surface in a plan view is 10% or less, the proportion of scattered components in the reflected light from the multilayer film layer 40 is sufficiently ensured, thereby accurately suppressing color changes due to changes in the observation angle. In addition, the proportion of specular reflection components in the reflected light from the multilayer film layer 40 is kept small, thereby reducing the strain on the eyes of the observer of the color-producing structure 10.

[0110] (9) If the color-producing structure includes the absorption layers 50, 52 located on the opposite side of the concave-convex structure layer 30 with respect to the multilayer film layer 40, it is possible to prevent light in a wavelength range different from the reflected light enhanced by the multilayer film layer 40 from being visible when viewed from the side where the concave-convex structure layer 30 is located. Therefore, it is possible to prevent a decrease in the visibility of the color of the reflected light.

[0111] (10) If the color-forming structure has adhesive layers 51, 53 located on the opposite side of the uneven structure layer 30 from the multilayer film layer 40, a color-forming structure suitable for a color-forming sticker or transfer sheet that can be attached to an adherend so that the adherend is located on the opposite side of the uneven structure layer 30 from the multilayer film layer 40 can be obtained.

[0112] (11) If the color-producing structure has an anti-reflection layer located on the opposite side of the multilayer film layer 40 from the uneven structure layer 30, the surface reflection of the color-producing structure is suppressed when viewed from the side where the uneven structure layer 30 is located, thereby preventing a decrease in the visibility of the color of the reflected light.

[0113] [Variations] The above embodiment can be modified as follows: The following modifications may also be combined with each other.

[0114] In the above embodiment, an example of application of the color-developing structure has been described in which the structure is observed from the side of the multilayer film layer 40 where the relief-structure layer 30 is located. Alternatively, the color-developing structure may be used so as to be observed from the side of the relief-structure layer 30 where the multilayer film layer 40 is located. In this case, an absorption layer or an adhesive layer may be provided on the side of the relief-structure layer 30 opposite the multilayer film layer 40. Furthermore, the relief-structure layer 30 or the substrate 20 may have a function of absorbing light transmitted through the multilayer film layer 40.

[0115] In the above embodiment, an example was given in which the multilayer film layer 40 was laminated as an optical layer on the concave-convex structure layer 30. Alternatively, a dielectric layer and a metal layer may be laminated on the concave-convex structure layer 30. In this case, the optical layer is composed of the dielectric layer and the metal layer. In short, the optical layer may be a laminated film that is located on the concave-convex structure, has a surface shape that follows the concave-convex structure, and emits reflected light that is enhanced by interference.

[0116] For example, when the color-producing structure is observed from the side where the concave-convex structure layer 30 is located relative to the optical layer, a dielectric layer is laminated on the concave-convex structure layer 30, and a metal layer is laminated on the dielectric layer. The dielectric layer is a single-layer thin film made of a dielectric material. When light is incident on the dielectric layer, the light reflected at the interfaces on the front and back of the dielectric layer interferes, resulting in the emission of light in an intensified wavelength range. The metal layer enhances the reflection of light in the wavelength range that is enhanced by interference at the interface between the dielectric layer and the metal layer.

[0117] In addition to the layers described in the above embodiment, the color-developing structure may include other layers, such as a layer for improving adhesion between these layers or a layer having an ultraviolet absorbing function. The concave-convex structure of the concave-convex structure layer 30 may be composed of a plurality of concave portions recessed relative to the optical layer. That is, the concave-convex structure may be composed of a plurality of concave-convex elements that are convex portions or concave portions. When the concave-convex elements are concave portions, the concave portions have lattice-like protrusions or grooves on their surfaces. The surfaces of the concave portions are the inner surfaces of the concave portions. The shape of the concave portions in plan view is configured similarly to the shape of the convex portions 31. That is, the width of the concave portions in plan view is sufficient to be 10 μm or more and 100 μm or less. The depth of the concave portions is configured similarly to the height of the convex portions 31. The height of the convex portions 31 and the depth of the concave portions are, in other words, the dimensions of the concave-convex elements along the thickness direction of the concave-convex structure layer 30. The spacing and height difference of the lattice-like concave portions are configured similarly to the spacing and height difference of the grooves 32.

[0118] [Example] The above-mentioned color-developing structure will be described using specific examples and comparative examples. Example 1 As described above with reference to Figures 9 and 10, a mold for forming the concave-convex structure layer was formed by cutting, and a concave-convex structure layer made of acrylic resin was formed by extrusion molding using this mold. The mold was formed so that the maximum length H of the convex portions in the concave-convex structure layer was approximately 10 μm, the convex portions had a square shape in plan view with a width W of approximately 50 μm, and multiple convex portions were arranged in a square lattice pattern without gaps. When forming the mold, recesses corresponding to the convex portions were cut by continuously changing the depth in an arc from the edge to the center of the square region. A cutting tool with partial chips on its surface was used, and by adjusting processing conditions such as the tool vibration state and processing speed, lattice-like protrusions were formed on the inner surface of the recesses during the formation of the recesses. Using this mold, a concave-convex structure layer was formed with convex portions having grooves corresponding to the protrusions. The spacing Pg of the formed grooves was approximately 3 μm, and the maximum depth D was 0.01 μm.

[0119] Next, five 60 nm thick TiO thin films and five 80 nm thick SiO thin films were alternately stacked on the concave-convex structure layer using a vacuum deposition method, to obtain the color-developing structure of Example 1. The TiO thin films were the high refractive index layers, and the SiO thin films were the low refractive index layers.

[0120] Example 2 The color-developing structure of Example 2 was obtained using the same materials and processes as in Example 1, except that the mold processing conditions were changed so that the maximum groove depth D was 0.10 μm. Specifically, by increasing the processing speed, it is possible to increase the groove depth D, and by decreasing the processing speed, it is possible to decrease the groove depth D.

[0121] Example 3 The color-developing structure of Example 3 was obtained using the same materials and steps as in Example 1, except that the processing conditions for the mold were changed so that the maximum groove depth D was 0.50 μm.

[0122] Example 4 The color-developing structure of Example 4 was obtained using the same materials and steps as in Example 1, except that the processing conditions for the mold were changed so that the maximum groove depth D was 1.00 μm.

[0123] Example 5 The color-developing structure of Example 5 was obtained using the same materials and steps as in Example 1, except that the processing conditions for the mold were changed so that the maximum groove depth D was 1.50 μm.

[0124] Example 6 The color-developing structure of Example 6 was obtained using the same materials and steps as in Example 1, except that the processing conditions for the mold were changed so that the maximum groove depth D was 3.00 μm.

[0125] (Comparative Example) The color-developing structure of the comparative example was obtained using the same materials and processes as in the example, except that a cutting tool without chips was used to prepare the mold, and the recesses were formed by adjusting the processing conditions so as not to form protrusions. In the color-developing structure of the comparative example, the protrusions of the concave-convex-structure layer did not have lattice-shaped grooves.

[0126] (Evaluation method) Using an optical system that can independently set the incident angle θi and the reflection angle θr of the color-producing structure, the reflection characteristics of the surface reflection of the color-producing structures of the example and comparative example were confirmed. Specifically, the incident angle θi was fixed at 30°, and the reflection spectral characteristics, i.e., the reflection intensity of each wavelength in specular reflection, was measured when the reflection angle θr was 30°.

[0127] (Evaluation results) In both the Examples and Comparative Examples, wavelength-selective reflection spectra due to multilayer interference were obtained, specifically, reflection spectra with peaks near 450 nm to 500 nm. However, in the peak wavelength range, the reflection intensity of the Examples was lower than that of the Comparative Examples. This indicates that the specular reflection intensity of the Examples was lower than that of the Comparative Examples, and the scattering effect of the reflected light was enhanced. Therefore, the intensity of the reflected light was enhanced at observation angles other than specular reflection. This suggests that the blue light enhanced by the multilayer film can be vividly observed over a wide observation angle.

[0128] Table 1 shows the evaluation results of the scattering effect based on the measurement results of the reflection characteristics for each example and comparative example. In the evaluation of the scattering effect, a case where the reflection intensity was smaller than that of the comparative example in the peak wavelength range, i.e., the wavelength range intensified by multilayer film interference, around 450 nm to 500 nm, and the reflection intensity was equivalent to that of the comparative example in the wavelength range of 600 nm or more, was marked as "◯". A case where the reflection intensity was smaller than that of the comparative example in the range of 450 nm to 500 nm and also smaller than that of the comparative example in the wavelength range of 600 nm or more was marked as "△". A case where the reflection intensity was equivalent to or greater than that of the comparative example in the range of 450 nm to 500 nm, and the reflection intensity was equivalent to that of the comparative example in the wavelength range of 600 nm or more, was marked as "X".

[0129] [Table 1]

[0130] As shown in Table 1, an increase in the scattering effect in the peak wavelength range was confirmed in all of Examples 1 to 6. For Example 6, a decrease in specular reflection intensity, i.e., an increase in the scattering effect, was confirmed even in wavelength ranges other than the peak wavelength range.

[0131] In wavelength ranges other than the peak wavelength range, the reflection intensity is small to begin with, so even if the reflected light is scattered, the effect is small, and no significant decrease in specular reflection intensity is observed in Examples 1 to 5. On the other hand, in Example 6, the groove depth D is large, i.e., the unevenness of the convex surface is large, so the scattering effect is large, and it is thought that a decrease in specular reflection intensity was observed even in wavelength ranges other than the peak wavelength range. When the appearances of the Examples and Comparative Examples were observed, Example 6 was brighter than the Comparative Examples, but had a slightly whitish blue color compared to the other Examples. [Explanation of symbols]

[0132] 10...Coloring structure 11...Coloring sticker 12...Transfer sheet 13...Coloring sheet 20...Base material 30...Uneven structure layer 31...Convex part 31S…Reference surface 32…Groove 40…Multilayer film layer 41...High refractive index layer 42...Low refractive index layer 50, 52...Absorption layer 51,53...adhesive layer 54...peeling layer 60...Resin sheet 100...Mold 101...recess 110...Cutting tools 200...Extrusion molding machine 210...T die 220...Roll

Claims

1. a concave-convex structure layer having a concave-convex structure on its surface, the concave-convex structure being composed of a plurality of concave-convex elements; an optical layer that is a laminated film positioned on the concave-convex structure, has a surface shape that follows the concave-convex structure, and emits reflected light that is intensified by interference, In a plan view of the concave-convex structure seen from a direction along the thickness direction of the concave-convex structure layer, the width of the concave-convex elements is 10 μm or more and 100 μm or less, In the plan view, the plurality of concave-convex elements are arranged in a two-dimensional lattice pattern, The concave-convex elements have grooves on the surfaces of the convex portions that are the concave-convex elements, the grooves having a grid shape in the plan view, the grid grooves being made up of grid lines arranged at intervals smaller than the arrangement intervals of the plurality of concave-convex elements, The surface of the convex portion has a height that increases from the end portion toward the center portion of the convex portion in the plan view, and is a surface along an imaginary plane that forms a curve in a cross section along the thickness direction, and the groove is recessed along the thickness direction over the entire surface of the convex portion. Chromogenic structure.

2. the depth of the grid-like grooves is 0.01 μm or more and 1.0 μm or less; The spacing between the grid lines is 0.02 μm or more and 10.0 μm or less. The color-forming structure according to claim 1 .

3. At least one of the directions in which the grid lines extend coincides with the direction in which the grid points are arranged in the two-dimensional grid formed by the plurality of concave-convex elements. The color-forming structure according to claim 1 or 2.

4. The shape of the concave-convex elements in the plan view is a square or a regular hexagon. The color-forming structure according to any one of claims 1 to 3.

5. The ratio of the maximum dimension of the uneven element along the thickness direction to the width of the uneven element is 0.1 or more and 1.0 or less. The color-forming structure according to any one of claims 1 to 4.

6. The proportion of flat portions included in the surface of the concave-convex structure layer is 10% or less per unit area of ​​the surface in a plan view. The color-developing structure according to any one of claims 1 to 5.

7. The optical layer is a laminate of a plurality of dielectric thin films, and the refractive indexes of the adjacent dielectric thin films in the optical layer are different from each other. The color-forming structure according to any one of claims 1 to 6.

8. an absorbing layer located on the opposite side of the optical layer from the concave-convex structure layer, The absorption layer has a light absorption property of absorbing at least a part of the light transmitted through the optical layer. The color-developing structure according to any one of claims 1 to 7.

9. an adhesive layer located on the opposite side of the optical layer from the concave-convex structure layer, The outermost surface of the color-developing structure is included in the adhesive layer. The color-forming structure according to any one of claims 1 to 8.

10. an antireflection layer located on the opposite side of the concave-convex structure layer from the optical layer; The color-forming structure according to any one of claims 1 to 9.

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