Concave-convex structure, optical member and electronic device

Abstract

To provide a concavo-convex structure having a more complex concavo-convex pattern, and to provide an optical member and electronic device.SOLUTION: A concavo-convex structure comprises a plurality of collective structures, each consisting of a plurality of recesses and protrusions, formed on a surface of a substrate. An average width of areas occupied by the recesses or protrusions on the surface of the substrate is equal to or less than a wavelength belonging to the visible light band.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a concave-convex structure, an optical member, and an electronic device. [Background technology]

[0002] In recent years, optical members using concave-convex structures having an average period equal to or less than the wavelength of incident light have been widely developed. Such concave-convex structures exhibit fundamentally different properties from those of concave-convex structures having an average period greater than the wavelength of incident light, and it is expected that optical members having even better properties may be realized.

[0003] For example, the following Patent Document 1 discloses a diffractive optical element having a columnar structure with an average period equal to or less than the wavelength of incident light as such a concave-convex structure. The following Patent Document 1 also discloses that the diffractive optical element is formed by performing spatially selective exposure using a laser interference exposure method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-57622 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the optical diffraction element disclosed in the above Patent Document 1 is not capable of forming any concave-convex structure other than the concave-convex structure corresponding to the interference pattern of the laser light, since the concave-convex structure is formed by the laser interference exposure method. In particular, the optical diffraction element disclosed in the above Patent Document 1 is not capable of forming a complex concave-convex structure in which a plurality of concave-convex aggregates each composed of a plurality of concaves or convexities are arranged.

[0006] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a concave-convex structure having a more complex concave-convex structure, an optical element provided with the concave-convex structure, and an electronic device provided with the concave-convex structure. [Means for solving the problem]

[0007] In order to solve the above problems, according to one aspect of the present invention, there is provided a concave-convex structure comprising a plurality of aggregate structures each composed of a plurality of concave or convex portions provided on the surface of a substrate, wherein the average width of the area occupied by the concave or convex portions on the surface of the substrate is equal to or less than a wavelength belonging to the visible light band.

[0008] When the average width of the area occupied by the recess or protrusion on the surface of the substrate is a, the average width of the bottom or apex surface of the recess or protrusion facing the surface of the substrate is b, and the length of the recess or protrusion in a direction perpendicular to the surface of the substrate is h, the average width of the cross section of the recess or protrusion at a position h / 2 away from the surface of the substrate in the perpendicular direction may be (a+b) / 2 or more.

[0009] The average distance between the centers of gravity of adjacent recesses or protrusions in the aggregate structure may be 0.65(x1 / 2+x2 / 2) or more and 2.0(x1 / 2+x2 / 2) or less, where x1 and x2 are the average widths of the areas that the recesses or protrusions occupy on the surface of the substrate, respectively.

[0010] The aggregate structure may have an average width of 0.2 μm or more.

[0011] The shape of the area occupied by the recessed or protruding portions on the surface of the base material may be substantially circular.

[0012] In the collective structure, each of the lengths of the recesses or protrusions in a direction perpendicular to the surface of the substrate may belong to any of at least two or more groups having different center values.

[0013] In the aggregate structure, each of the average widths of the regions occupied by the recesses or protrusions on the surface of the base material may belong to any of at least two or more groups having different center values.

[0014] The length of the recessed or protruding portions in a direction perpendicular to the surface of the substrate may vary stepwise within the assembly structure.

[0015] The average width of the region occupied by the recessed or protruding portions on the surface of the substrate may vary stepwise within the aggregate structure.

[0016] The length of the recessed or protruding portions in a direction perpendicular to the surface of the substrate may vary irregularly within the aggregate structure.

[0017] The average width of the area occupied by the depressions or protrusions on the surface of the substrate may vary randomly within the aggregate structure.

[0018] Each of the collective structures may be regularly arranged.

[0019] Each of the collection structures may be randomly arranged.

[0020] Within the aggregate structure, each of the recesses or protrusions may be provided in a close-packed arrangement.

[0021] In order to solve the above problems, according to another aspect of the present invention, there is provided an optical member using the above concave-convex structure or using a transfer product to which the concave-convex structure has been transferred.

[0022] In order to solve the above problems, according to another aspect of the present invention, there is provided an electronic device that uses the above concave-convex structure or a transferred product to which the concave-convex structure has been transferred.

[0023] According to the above configuration, the arrangement and vertical length of the concave and convex portions can be controlled with high accuracy and high reproducibility. Effect of the Invention

[0024] As described above, according to the present invention, it is possible to provide a concave-convex structure having a more complicated concave-convex structure, an optical member provided with the concave-convex structure, and an electronic device provided with the concave-convex structure. [Brief description of the drawings]

[0025] [Figure 1A] FIG. 2 is a cross-sectional view of a substrate on which a concave-convex structure is formed, cut in the thickness direction. [Figure 1B] FIG. 2 is a plan view of one main surface of a substrate on which a concave-convex structure is formed, viewed from a perpendicular direction. [Figure 2A] FIG. 4 is a cross-sectional view showing a specific configuration of a protrusion, which is an example of a concave-convex portion. [Figure 2B] 10 is a cross-sectional view showing a specific configuration of a recess, which is another example of the uneven portion. FIG. [Diagram 3] FIG. 13 is a plan view illustrating the arrangement intervals of each of the concave and convex portions. [Figure 4] 1A to 1C are schematic diagrams showing examples of arrangements of concave-convex portions when the concave-convex portions have the same size or when the concave-convex portions have different sizes. [Diagram 5] 1A and 1B are a cross-sectional view and a plan view showing a schematic example of a protrusion-recess structure. [Figure 6] 11A and 11B are a cross-sectional view and a plan view showing a schematic diagram of another example of a concave-convex structure. [Figure 7] 11A and 11B are a cross-sectional view and a plan view showing a schematic diagram of another example of a concave-convex structure. [Figure 8] 11A and 11B are a cross-sectional view and a plan view showing a schematic diagram of another example of a concave-convex structure. [Figure 9] 11A and 11B are a cross-sectional view and a plan view showing a schematic diagram of another example of a concave-convex structure. [Figure 10A] FIG. 2 is a schematic perspective view of an assembly structure in the concavo-convex structure according to Examples 1 to 9. [Figure 10B] FIG. 2 is a schematic plan view of the concave-convex structures according to Examples 1 to 9. [Figure 11A] 1 is a schematic perspective view of an assembly structure in a concavo-convex structure according to Comparative Example 1. FIG. [Figure 11B]2 is a schematic plan view of a concave-convex structure according to Comparative Example 1. FIG. [Figure 12A] 3 is an explanatory diagram showing a schematic cross-sectional shape of a protrusion in Example 1. FIG. [Figure 12B] 10 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 2. FIG. [Figure 12C] 13 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 3. FIG. [Figure 12D] 13 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 4. FIG. [Figure 12E] FIG. 13 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 5. [Figure 12F] FIG. 13 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 8. [Figure 12G] 13 is an explanatory view showing a schematic cross-sectional shape of a protrusion in Example 9. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and duplicated explanations will be omitted.

[0027] <1. Configuration of concave-convex structure> First, the configuration of a concave-convex structure according to one embodiment of the present invention will be described with reference to Fig. 1A and Fig. 1B. Fig. 1A is a cross-sectional view showing an example of a vertical structure of a concave-convex structure according to this embodiment, and Fig. 1B is a plan view showing an example of a planar structure of a concave-convex structure according to this embodiment. Fig. 1A shows a cross-sectional view of a substrate on which a concave-convex structure is formed cut in the thickness direction, and Fig. 1B shows a plan view of one main surface of the substrate on which a concave-convex structure is formed viewed from a perpendicular direction.

[0028] As shown in FIGS. 1A and 1B, the concave-convex structure 20 is configured by arranging a plurality of assembly structures 210, each of which is an assembly of a plurality of concave-convex portions 200, on one main surface of a sheet-like substrate .

[0029] The concave-convex structure 20 is used, for example, as an optical member. The concave-convex structure 20 may be used, for example, as an optical member such as a light guide plate, a light diffusion plate, a microlens array, a Fresnel lens array, a diffraction grating, or an anti-reflection film. When the concave-convex structure 20 is used as an optical member, the concave-convex structure 20 may be used in electronic devices such as personal computers, laptops, television devices, wearable devices, smartphones, or tablet terminals.

[0030] The substrate 10 is made of, for example, a transparent material. The substrate 10 may be made of, for example, an organic resin such as polycarbonate, polyethylene terephthalate, polymethyl methacrylate, triacetyl cellulose (TAC), cyclic olefin polymer (COP) or cyclic olefin copolymer (COC), or a transparent glass material such as quartz glass, soda lime glass or lead glass. Note that "transparent" means that the transmittance of light having a wavelength belonging to the visible light band (approximately 360 nm to 830 nm) is high (for example, the transmittance of light is 70% or more).

[0031] The concave-convex portion 200 is a concave structure recessed in the thickness direction of the substrate 10, or a convex structure protruding in the thickness direction of the substrate 10. Although only a convex structure is illustrated as the concave-convex portion 200 in figures other than FIG. 2B, it goes without saying that the concave-convex portion 200 may also be a concave structure. A structure having an inverted concave-convex shape of the concave-convex structure 20 can be easily formed by, for example, transferring the concave-convex shape to an organic resin or the like using an imprint technique using the concave-convex structure 20 as a master (or a replica master).

[0032] The length of the uneven portion 200 in the direction perpendicular to the surface of the base material 10 (i.e., the depth of the recess or the height of the protrusion, hereinafter also referred to as the perpendicular length) is provided so as to belong to at least one of two or more groups having different center values. For example, as shown in FIG. 1A, the uneven portion 200 may include a first protrusion 222 having the longest perpendicular length, a third protrusion 226 having the shortest perpendicular length, and a second protrusion 224 having a perpendicular length intermediate between the first protrusion 222 and the third protrusion 226. The first protrusion 222, the second protrusion 224, and the third protrusion 226 are provided so as to have a difference in perpendicular length equal to or greater than the formation variation, and the aggregate structure 210 is provided so as to include a plurality of types of uneven portions 200 provided with different perpendicular lengths. That is, each of the uneven portions 200 is not formed to have a random perpendicular length, but can be formed by controlling so as to have a desired perpendicular length. Needless to say, the uneven portion 200 may be provided with four or more different vertical lengths.

[0033] Here, the size of the area occupied by the uneven portion 200 on the surface of the base material 10 may be set to be larger as the vertical length of the uneven portion 200 is longer. For example, the first convex portion 222 may be formed so that the area occupied by the first convex portion 222 on the surface of the base material 10 is the largest, the third convex portion 226 may be formed so that the area occupied by the second convex portion 224 on the surface of the base material 10 is the intermediate size between the first convex portion 222 and the third convex portion 226. That is, the uneven portion 200 may be set so that the area occupied by the uneven portion 200 on the surface of the base material 10 is larger as the vertical length is larger. Therefore, the size of the area occupied by the uneven portion 200 on the surface of the base material 10 is set to belong to at least one of two or more groups having different center values.

[0034] In addition, each of the multiple types of unevenness 200 (the first convex portion 222, the second convex portion 224, and the third convex portion 226 in FIG. 1A) formed with different vertical lengths may be provided in one aggregate structure 210 with at least one type. For example, one aggregate structure 210 may be configured to include all of the first convex portion 222, the second convex portion 224, and the third convex portion 226. Alternatively, one aggregate structure 210 may be configured with any of the first convex portion 222, the second convex portion 224, and the third convex portion 226. The number and arrangement of the first convex portion 222, the second convex portion 224, and the third convex portion 226 provided in the aggregate structure 210 can be appropriately controlled based on the function realized by the aggregate structure 210 or the concave-convex structure 20.

[0035] For example, the aggregate structure 210 may be configured so that the vertical length of the uneven portion 200 changes stepwise within the aggregate structure 210. That is, the aggregate structure 210 may be provided so that the vertical length of the uneven portion 200 changes gradually along a predetermined direction. Specifically, the vertical length of the uneven portion 200 may change so as to draw an arc or become a straight line along a predetermined direction throughout the aggregate structure 210. Similarly, the aggregate structure 210 may be configured so that the size or average width of the area that the uneven portion 200 occupies on the surface of the substrate 10 also changes stepwise.

[0036] Alternatively, for example, the aggregate structure 210 may be configured such that the vertical length of the uneven portion 200 varies irregularly. That is, the aggregate structure 210 may be provided such that the vertical length of the uneven portion 200 varies randomly. Specifically, the vertical length of the uneven portion 200 may vary such that no regularity is observed throughout the aggregate structure 210. Similarly, the aggregate structure 210 may be configured such that the size or average width of the area that the uneven portion 200 occupies on the surface of the substrate 10 also varies randomly.

[0037] The aggregate structure 210 is formed by assembling a plurality of uneven portions 200. For example, as shown in FIG. 1B, the aggregate structure 210 may be formed by arranging a plurality of uneven portions 200, each of which has a substantially circular planar shape on the surface of the substrate 10, in a close-packed arrangement. In such a case, the overall average width of the aggregate structure 210 may be formed to be, for example, at least 0.2 μm or more, and preferably larger than a wavelength belonging to the visible light band. Each of the aggregate structures 210 may be spaced apart from each other at a distance wider than the distance between each of the uneven portions 200, for example, may be spaced apart from each other at a distance larger than a wavelength belonging to the visible light band.

[0038] The planar shape of the region occupied by the uneven portion 200 on the surface of the substrate 10 may be substantially circular as described above, but may also be, for example, elliptical or polygonal. The arrangement of the uneven portion 200 in the aggregate structure 210 may be close-packed as described above, but may also be a square lattice arrangement, a hexagonal lattice arrangement, a staggered lattice arrangement, or the like. The planar shape of the uneven portion 200 on the surface of the substrate 10 and the arrangement of the uneven portion 200 in the aggregate structure 210 can be appropriately controlled based on the function realized by the aggregate structure 210 or the uneven structure 20.

[0039] Each of the concave-convex portions 200 may be provided so that the average width of the region on the surface of the base material 10 is equal to or less than the wavelength belonging to the visible light band. Similarly, the interval between each of the concave-convex portions 200 in the aggregate structure 210 may be equal to or less than the wavelength belonging to the visible light band. Specifically, the average width and interval of the regions of the concave-convex portion 200 may be 100 nm or more and 350 nm or less. When the average width and interval of the regions of the concave-convex portion 200 are within the above ranges, the aggregate structure 210 and the concave-convex structure 20 can function as a so-called moth-eye structure that suppresses reflection of incident light belonging to the visible light band.

[0040] Each of the aggregate structures 210 may be arranged regularly. For example, as shown in FIG. 1B, each of the aggregate structures 210 may be arranged regularly with a predetermined interval between the aggregate structures 210 having the same configuration and arrangement of the concave-convex portion 200. Alternatively, each of the aggregate structures 210 may be arranged irregularly. For example, each of the aggregate structures 210 may be arranged irregularly with a random size interval between each other. The arrangement of each of the aggregate structures 210 can be appropriately controlled based on the function realized by the concave-convex structure 20.

[0041] <2. Configuration of the concave or convex portion> Next, the configuration of the concave-convex portion 200 in the assembly structure 210 will be described in more detail with reference to FIGS. 2A to 4. FIG.

[0042] First, a specific configuration of the uneven portion 200 will be described with reference to Fig. 2A and Fig. 2B. Fig. 2A is a cross-sectional view showing a specific configuration of a convex portion 2001, which is an example of the uneven portion 200, and Fig. 2B is a cross-sectional view showing a specific configuration of a concave portion 2002, which is another example of the uneven portion 200. Note that in Fig. 2A and Fig. 2B, the convex portion 2001 and the concave portion 2002 are assumed to have an isotropic three-dimensional shape in the in-plane direction of the substrate 10.

[0043] 2A, the protrusion 2001 may be provided in a three-dimensional shape obtained by cutting a prolate spheroid along a plane perpendicular to the axis of rotation near the poles and near the equator. In other words, the protrusion 2001 may be provided in a three-dimensional bullet-shaped shape.

[0044] 2A, the width of the convex portion 2001 on the surface of the substrate 10 is a, the width of the flat surface at the top of the convex portion 2001 is b, and the distance from the surface of the substrate 10 to the flat surface at the top of the convex portion 2001 (i.e., the height of the convex portion 2001) is h. In this case, the width w of the convex portion 2001 at a height of h / 2 from the surface of the substrate 10 is preferably (a+b) / 2 or more. Furthermore, the width w of the convex portion 2001 at a height of h / 2 from the surface of the substrate 10 is more preferably 1.2 times or more of (a+b) / 2.

[0045] When the shape of the convex portion 2001 satisfies the above-mentioned conditions, the convex portion 2001 is provided in a three-dimensional shape with an outline extending from the surface of the substrate 10 toward the apex portion bulging outward. The convex portion 2001 having such a shape can further improve the anti-reflection properties of the assembly structure 210 and the concave-convex structure 20. The upper limit of w is not particularly limited, but taking into consideration the shape of the convex portion 2001, the upper limit of w is, for example, a. However, taking into consideration the anti-reflection properties of the concave-convex structure 20, it is preferable that w is, for example, 1.41 times or less of (a+b) / 2. However, the upper limit of w can be appropriately selected depending on the application of the concave-convex structure 20.

[0046] On the other hand, as shown in Fig. 2B, the recess 2002 may be provided in a shape obtained by inverting the protrusion 2001 shown in Fig. 2A upside down with respect to the surface of the substrate 10 as a plane of symmetry. For example, the recess 2002 may be provided in a bowl-shaped depression shape with a flat bottom.

[0047] 2B, the width of the recess 2002 on the surface of the substrate 10 is a, the width of the flat surface at the bottom of the recess 2002 is b, and the distance from the surface of the substrate 10 to the flat surface at the bottom of the recess 2002 (i.e., the depth of the recess 2002) is h. In this case, the width w of the recess 2002 at a depth of h / 2 from the surface of the substrate 10 is preferably (a+b) / 2 or more, as in the case of the protrusion 2001. Moreover, the width w of the recess 2002 at a depth of h / 2 from the surface of the substrate 10 is more preferably 1.2 times or more of (a+b) / 2, as in the case of the protrusion 2001.

[0048] When the shape of the recess 2002 satisfies the above-mentioned conditions, the recess 2002 is provided in a three-dimensional shape with an outline from the surface to the bottom of the substrate 10 bulging outward. The aggregate structure 210 and the concave-convex structure 20 having the recess 2002 of such a shape can further improve the anti-reflection properties of a transfer product with an inverted concave-convex shape. The upper limit of w is not particularly limited, but considering the shape of the recess 2002, the upper limit of w is, for example, a. However, considering the anti-reflection properties of the concave-convex structure 20, it is preferable that w is, for example, 1.41 times or less of (a+b) / 2. However, the upper limit of w can be appropriately selected depending on the application of the concave-convex structure 20.

[0049] Next, a specific configuration of the arrangement of the concave-convex portions 200 in the assembly structure 210 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a plan view illustrating the arrangement intervals of the concave-convex portions 200. Fig. 4 is a schematic diagram showing an example of the arrangement of the concave-convex portions 200 when the sizes of the concave-convex portions 200 are the same or when the sizes of the concave-convex portions 200 are different.

[0050] The arrangement interval of adjacent concave-convex portions 200 will be described with reference to Fig. 3. As shown in Fig. 3, the width of one concave-convex portion 200-1 on the surface of the substrate 10 is x1, and the width of one concave-convex portion 200-2 adjacent to the concave-convex portion 200-1 on the surface of the substrate 10 is x2. In this case, the average distance i between the center of gravity of the concave-convex portion 200-1 and the center of gravity of the concave-convex portion 200-2 is preferably 0.65 (x1 / 2+x2 / 2) or more and 2.0 (x1 / 2+x2 / 2) or less. Moreover, the average distance i between the center of gravity of the concave-convex portion 200-1 and the center of gravity of the concave-convex portion 200-2 is more preferably 0.8 (x1 / 2+x2 / 2) or more and 1.2 (x1 / 2+x2 / 2) or less.

[0051] When the average distance i between the centers of gravity of the adjacent concave-convex portions 200 satisfies the above-mentioned condition, the adjacent concave-convex portions 200 are provided with appropriate overlap or spacing, and therefore the anti-reflection properties of the aggregate structure 210 and the concave-convex structure 20 can be further improved. For example, when the average distance i between the centers of gravity is less than 0.65 (x1 / 2+x2 / 2), the adjacent concave-convex portions 200 overlap each other too much, which reduces the substantial vertical length of the concave-convex portions 200, and the anti-reflection properties of the aggregate structure 210 and the concave-convex structure 20 are degraded, which is not preferable. In addition, when the average distance i between the centers of gravity is more than 2.0 (x1 / 2+x2 / 2), the adjacent concave-convex portions 200 are spaced too far from each other, which increases the flat surfaces between the concave-convex portions 200, and therefore the anti-reflection properties of the aggregate structure 210 and the concave-convex structure 20 are degraded, which is not preferable.

[0052] In addition, when the planar shape of the uneven portion 200 on the surface of the base material 10 is a circle or an ellipse, the above x1 and x2 may be the diameter or major axis of the circle or ellipse of the planar shape of the uneven portion 200. In addition, in such a case, the center of gravity of the uneven portion 200 may be the center of the circle or ellipse of the planar shape of the uneven portion 200. On the other hand, when the planar shape of the uneven portion 200 on the surface of the base material 10 is a polygon, the above x1 and x2 may be the diameter of the circumscribing circle of the polygon of the planar shape of the uneven portion 200. In addition, in such a case, the center of gravity of the uneven portion 200 may be the center of the circumscribing circle of the planar shape of the uneven portion 200.

[0053] The intervals between each of the multiple concave-convex portions 200 will be described with reference to Fig. 4. As shown in Fig. 4, for example, when the size of the area occupied by the concave-convex portion 200 on the surface of the base material 10 is substantially constant (in the case of the concave-convex portion 200A), the concave-convex portion 200A may be provided at intervals equal to the size of the area occupied by the concave-convex portion 200 on the surface of the base material 10 so as to be arranged in a close-packed arrangement.

[0054] For example, when the size of the area that the uneven portion 200 occupies on the surface of the base material 10 varies (in the case of the uneven portion 200B), the uneven portion 200B may be provided at regular intervals. In such a case, although the uneven portion 200B is not arranged in a close-packed manner, the uneven portion 200B is easily formed.

[0055] For example, when the size of the area occupied by the uneven portion 200 on the surface of the substrate 10 varies (in the case of the uneven portion 200C), the uneven portion 200C may be provided at intervals controlled according to the size of the area occupied by each of the uneven portions 200 on the surface of the substrate 10. In such a case, the uneven portion 200C can realize a close-packed arrangement even when the size of the area occupied by the uneven portion 200 on the surface of the substrate 10 varies. According to this embodiment, the arrangement of each of the uneven portions 200 and the size on the surface of the substrate 10 can be controlled with high accuracy. Therefore, even when the size of the area occupied by the uneven portion 200 on the surface of the substrate 10 varies (in the case of the uneven portion 200C), the uneven portion 200 can be formed in a close-packed arrangement.

[0056] As described above, the concave-convex portions 200 of the concave-convex structure 20 are formed with a plurality of different vertical lengths. That is, the vertical length of the concave-convex portions 200 is set so as to belong to one of a plurality of groups having different center values. Therefore, in the concave-convex structure 20, the vertical length of each of the concave-convex portions 200 is controlled with high precision so that each of the concave-convex portions 200 has a predetermined vertical length. In addition, the concave-convex structure 20 is provided so that the collective structures 210 composed of the plurality of concave-convex portions 200 are spaced apart from each other. Therefore, the formation positions of the concave-convex portions 200 are controlled with high precision so that they are provided at different intervals within the collective structures 210 and between the collective structures 210. Therefore, the concave-convex structure 20 according to this embodiment can have a more complicated concave-convex shape.

[0057] <3. Specific examples of concave-convex structures> Next, a specific example of the concave-convex structure 20 according to this embodiment will be described with reference to Fig. 5 to Fig. 9. Fig. 5 to Fig. 9 are cross-sectional views and plan views that typically show one example of the concave-convex structure 20 according to this embodiment. Note that in the plan views of Fig. 5 to Fig. 9, circles with darker dot hatching correspond to higher convex portions.

[0058] (First concrete example) As shown in FIG. 5, the concave-convex structure 21 may be a structure in which collective structures 211 in which convex portions 201 are arranged in a square lattice pattern are provided at predetermined intervals. In the concave-convex structure 21, the height of the convex portions 201 in the collective structure 211 is provided so as to increase or decrease stepwise in a first direction, and the height of the convex portions 201 is provided so as to be approximately the same in a second direction perpendicular to the first direction. Therefore, in the concave-convex structure 21 shown in FIG. 5, the collective structure 211 can be formed as a structure that shows a triangular wave-like (sawtooth-like) shape as a whole in the first direction. Such a concave-convex structure 21 can be used, for example, as a diffraction element having anti-reflection properties due to a moth-eye structure.

[0059] (Second concrete example) As shown in Fig. 6, the concave-convex structure 22 may be a structure in which collective structures 212 in which convex portions 202 are arranged in a square lattice pattern are provided at predetermined intervals. In the concave-convex structure 22, the height of the convex portions 202 in the collective structure 212 is provided to increase stepwise toward the center of the collective structure 212. Therefore, in the concave-convex structure 22 shown in Fig. 6, the collective structure 212 can be formed as a structure that exhibits a convex lens-like shape as a whole. Such a concave-convex structure 22 can be used, for example, as a microlens array having anti-reflection properties due to a moth-eye structure.

[0060] (Third concrete example) As shown in Fig. 7, the concave-convex structure 23 may be a structure in which collective structures 213 in which convex portions 203 are arranged in a square lattice pattern are provided at predetermined intervals. In the concave-convex structure 23, the height of the convex portions 203 in the collective structure 213 is provided so as to increase stepwise toward the center of the collective structure 213, and the height of the convex portions 203 is provided in a shape in which the height decreases concentrically so that the height falls within a predetermined range. Therefore, in the concave-convex structure 23 shown in Fig. 7, the collective structure 213 can be formed as a structure that shows a Fresnel lens-like shape as a whole. Such a concave-convex structure 23 can be used, for example, as a Fresnel lens array having anti-reflection properties due to a moth-eye structure.

[0061] (Fourth Specific Example) As shown in FIG. 8, the concave-convex structure 24 may be a structure in which collective structures 214 in which convex portions 204 are arranged in a square lattice pattern are provided at predetermined intervals. In the concave-convex structure 24, the heights of the convex portions 204 in the collective structure 214 are arranged to be irregular (random). However, since the heights of the convex portions 204 are arranged to belong to one of a plurality of groups having different center values, more strictly, the arrangement of the convex portions 204 having different heights is arranged to be irregular (random) in the collective structure 214. Therefore, in the concave-convex structure 24 shown in FIG. 8, the collective structure 214 may be formed as a moth-eye structure in which the heights of the convex portions 204 are irregular as a whole. Such a concave-convex structure 24 can be used, for example, as an anti-reflection film or a light diffusion plate with less interference light and diffracted light.

[0062] (Fifth Specific Example) As shown in FIG. 9, the concave-convex structure 25 may be a structure in which an aggregate structure 215 in which convex portions 205 are arranged in an irregular (random) arrangement is provided at a predetermined interval. In the concave-convex structure 25, similar to the concave-convex structure 24 shown in FIG. 8, the convex portions 205 having different heights are arranged in an irregular (random) manner within the aggregate structure 215. Therefore, in the concave-convex structure 25 shown in FIG. 9, the aggregate structure 215 may be formed as a moth-eye structure in which the height and arrangement of the convex portions 205 are irregular as a whole. The concave-convex structure 25 can be used, for example, as an anti-reflection film or a light diffusion plate that generates less interference light and diffracted light. Note that the concave-convex structure 25 shown in FIG. 8 has a lower regularity than the concave-convex structure 24 shown in FIG. 8, and therefore can further suppress the occurrence of unintended diffracted light or interference light.

[0063] <4. Method for manufacturing concave-convex structure> Next, a manufacturing method for the concave-convex structure 20 according to this embodiment will be briefly described.

[0064] The concave-convex structure 20 of this embodiment can be manufactured by forming a resist pattern corresponding to the concave-convex structure on the outer peripheral surface of the substrate 10 using thermal lithography with laser light, and then etching the substrate 10 using the resist pattern as a mask.

[0065] Alternatively, the concave-convex structure 20 of this embodiment may be manufactured using known micro-processing techniques such as electron beam lithography using an electron beam lithography apparatus, multi-patterning using photolithography, or ultra-fine cutting using a diamond bit.

[0066] Furthermore, the concave-convex structure 20 according to this embodiment may be manufactured by an imprint technique using the concave-convex structure 20 formed by the manufacturing method described above as a master. Specifically, the concave-convex structure 20 (i.e., the master) may be pressed against a sheet-like resin or the like to transfer the concave-convex shape of the surface, thereby manufacturing a transfer product having an inverted concave-convex shape of the master. EXAMPLES

[0067] The concave-convex structure according to this embodiment will be described in more detail below with reference to examples and comparative examples. Note that the examples shown below are examples of conditions for showing the feasibility and effects of the concave-convex structure and the manufacturing method thereof according to this embodiment, and the concave-convex structure and the manufacturing method thereof according to this embodiment are not limited to the following examples.

[0068] (Examples 1 to 9) By the following steps, masters corresponding to the concave-convex structures of Examples 1 to 9 were produced, and transfers of the produced masters (convex-convex structures of Examples 1 to 9) were produced using an imprinting technique.

[0069] Specifically, first, a tungsten oxide film was formed to a thickness of 55 nm on the outer peripheral surface of a cylindrical quartz glass substrate (axial length 100 mm, outer peripheral thickness 4.5 mm) by sputtering to form a resist layer. Next, using an exposure device, thermal lithography was performed with a laser beam from a semiconductor laser light source with a wavelength of 405 nm to form latent images corresponding to each of Examples 1 to 9 on the resist layer.

[0070] Subsequently, the exposed substrate was developed at 27°C for 900 seconds using a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) (manufactured by Tokyo Ohka Kogyo Co., Ltd.) to dissolve the resist layer in the latent image portion, and form a concave-convex structure corresponding to each of Examples 1 to 9 in the resist layer. Next, using the developed resist layer as a mask, reactive ion etching (RIE) was performed using CHF3 gas (30 sccm) at a gas pressure of 0.5 Pa and input power of 150 W, and the substrate was etched for 30 minutes. After that, the remaining resist layer was removed.

[0071] By the above steps, a master having a concave-convex structure formed on its outer peripheral surface was produced, and a transfer product was produced using the produced master. Specifically, the concave-convex structure formed on the outer peripheral surface of the master was transferred to an ultraviolet curing resin using a transfer device, to produce the transfer products according to Examples 1 to 9. Note that a polyethylene terephthalate (PET) film was used as the sheet-like substrate for the transfer product, and the ultraviolet curing resin was cured at 1000 mJ / cm 2 by a metal halide lamp. 2 The resin was cured by exposure to ultraviolet light for 1 minute.

[0072] Comparative Example 1 A transfer product (convexoconcave structure according to Comparative Example 1) was produced in the same manner as in Examples 1 to 9, except that a latent image corresponding to Comparative Example 1 was formed in a resist layer by photolithography using exposure with a mask.

[0073] 10A and 10B show schematic shapes of the concave-convex structure formed in the concave-convex structure according to Examples 1 to 9, and Fig. 11A and 11B show schematic shapes of the concave-convex structure formed in the concave-convex structure according to Comparative Example 1. Fig. 10A is a schematic perspective view of an assembly structure in the concave-convex structures according to Examples 1 to 9, and Fig. 10B is a schematic plan view of the concave-convex structures according to Examples 1 to 9. Fig. 11A is a schematic perspective view of an assembly structure in the concave-convex structure according to Comparative Example 1, and Fig. 11B is a schematic plan view of the concave-convex structure according to Comparative Example 1.

[0074] 10A and 10B, the concave-convex structure according to Examples 1 to 9 is provided by arranging a plurality of assembly structures each of which is an assembly of a plurality of convex portions. Specifically, the concave-convex structure is provided by arranging the assembly structures, each of which is spaced apart from each other, such that the convex portions protruding vertically from the surface of the substrate are arranged in a close-packed manner on a plane. The assembly structures are provided such that the convex portion located in the center is gradually higher, so that the overall structure has a convex lens-like shape.

[0075] Here, the concave-convex structures according to Examples 1 to 9 differ from one another in the three-dimensional shape of the convex portions and the average distance between the centers of gravity of adjacent convex portions, as shown in the following Table 1. However, the concave-convex structures according to Examples 1 to 9 are provided so as to have the same convex lens-like shape as a whole.

[0076] 11A and 11B, the concave-convex structure according to Comparative Example 1 is provided by arranging a plurality of single convex portions that protrude vertically from the surface of a substrate. Specifically, the concave-convex structure is provided by cutting a cone with a plane parallel to the bottom surface, and arranging the truncated cone shapes, excluding the small cone portion, at a distance from each other. Therefore, the concave-convex structure according to Comparative Example 1 and the concave-convex structures according to Examples 1 to 9 differ from each other in that the convex lens-like structure is composed of a single convex portion or multiple convex portions.

[0077] (Evaluation Results) The concave-convex structures produced as described above were evaluated according to Examples 1 to 9 and Comparative Example 1. Specifically, the shapes of the microstructures of the concave-convex structures of Examples 1 to 9 and Comparative Example 1 were observed with an atomic force microscope (AFM) and a scanning electron microscope (SEM).

[0078] In addition, for the concave-convex structures according to Examples 1 to 9, the shapes of the convex portions were measured by AFM, and the average width b of the flat surface at the top of the convex portions, the average width a of the convex portion region on the substrate surface, and the average width w of the convex portions at h / 2, where h is the height of the convex portions, were calculated. Furthermore, for the concave-convex structures according to Examples 1 to 9, the average distance between the centers of gravity of adjacent convex portions was calculated by SEM. Note that a, b, w, and the average distance between the centers of gravity were calculated as the average values ​​of the convex portions within one aggregate structure.

[0079] Furthermore, a spectrophotometer (V500 manufactured by JASCO Corporation) was used to measure the surface reflection spectra of the concave-convex structures according to Examples 1 to 9 and Comparative Example 1. Table 1 below shows the minimum reflectance values ​​within the wavelength range of 380 nm to 780 nm. It is more preferable that the minimum reflectance value within the wavelength range of 380 nm to 780 nm be 1% or less.

[0080] Table 1 below shows the measurement results of the shape and center-of-gravity distance of the convex portions of the concave-convex structures according to Examples 1 to 9, and the measurement results of the reflectance of the concave-convex structures according to Examples 1 to 9 and Comparative Example 1. Also, Figs. 12A to 12G show schematic cross-sectional shapes of the concave portions (corresponding to the convex portions in the transfer product) in the masters according to Examples 1 to 5 and Examples 8 to 9, determined from the AFM measurement results. Figs. 12A to 12G are explanatory diagrams showing schematic cross-sectional shapes of the concave portions (corresponding to the convex portions in the transfer product) in the masters according to Examples 1 to 5 and Examples 8 to 9, respectively. Note that the shapes shown in Figs. 12A to 12G are schematic, and may not completely match the shapes of the concave-convex structures of the actual masters or transfer products.

[0081] [Table 1]

[0082] Referring to the results in Table 1, it can be seen that the concave-convex structures according to Examples 1 to 9 have a convex lens-like structure formed as an aggregate structure of a plurality of convex portions, and therefore have a lower reflectance than the concave-convex structure according to Comparative Example 1. In other words, it can be seen that the concave-convex structures according to Examples 1 to 9 have a higher anti-reflection effect than the concave-convex structure according to Comparative Example 1.

[0083] Furthermore, when comparing the concave-convex structures of Examples 1, 4, and 5, it can be seen that the width w of the convex portion at h / 2 becomes smaller than (a+b) / 2, and the thinner the convex portion becomes, the higher the reflectivity becomes and the lower the anti-reflection effect becomes.

[0084] Furthermore, when comparing the concave-convex structures of Examples 1 and 6 to 8, it is found that when the average distance between the centers of gravity is narrower than the above-mentioned preferred range, the overlap between the convex portions increases and the effective height of the convex portions decreases, resulting in an increase in reflectance and a decrease in anti-reflection effect. On the other hand, when comparing the concave-convex structures of Examples 1 and 9, it is found that when the average distance between the centers of gravity is wider than the above-mentioned preferred range, the flat portions between the convex portions increase, resulting in an increase in reflectance and a decrease in anti-reflection effect.

[0085] Although the preferred embodiment of the present invention has been described in detail above with reference to the accompanying drawings, the present invention is not limited to such an example. It is clear that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present invention.

[0086] For example, the concave-convex structure 20 according to this embodiment can be used as an optical member, and electronic devices incorporating the concave-convex structure 20 according to this embodiment are also included in the scope of the present invention. [Explanation of symbols]

[0087] 10 Base material 20, 21, 22, 23, 24, 25 uneven structure 200 Uneven part 201, 202, 203, 204, 205 Convex 210, 211, 212, 213, 214, 215 set structure

Claims

1. A plurality of aggregate structures each composed of a plurality of recesses provided on a surface of a substrate are provided, an average width of an area occupied by the recesses on the surface of the base material is equal to or less than a wavelength in the visible light band; The recesses are provided in the aggregate structure such that the depth of the recesses increases stepwise toward the center of the aggregate structure, and the aggregate structure is formed as a concave lens-like structure as a whole; each of the individual aggregate structures functions as a single microlens, the plurality of recesses constituting each of the aggregate structures functions as a moth-eye structure having an anti-reflection function, and the entire concave-convex structure consisting of the plurality of aggregate structures functions as a microlens array also having an anti-reflection function due to the moth-eye structure, the plurality of aggregate structures are arranged spaced apart from one another on a surface of the substrate; A concave-convex structure, wherein the intervals between adjacent ones of the plurality of aggregate structures are wider than the intervals between adjacent ones of the plurality of recesses within each aggregate structure.

2. The concave-convex structure according to claim 1 , wherein a flat surface is formed between the adjacent aggregate structures.

3. When the average width of the area occupied by the recess on the surface of the substrate is a, the average width of the apex surface of the recess facing the surface of the substrate is b, and the length of the recess in the direction perpendicular to the surface of the substrate is h, The concave-convex structure according to claim 1 , wherein an average width of the cross section of the recess at a position h / 2 away from the surface of the base in the perpendicular direction is (a+b) / 2 or more.

4. The average distance between the centers of gravity of adjacent recesses in the aggregate structure is expressed as the average width of the area occupied by the recesses on the surface of the substrate x １ and x ２ In this case, 0.65 (x １ / 2+x ２ / 2) or more 2.0(x １ / 2+x ２ 4. The concave-convex structure according to claim 1, wherein the concave-convex structure is equal to or smaller than 1 / 2.

5. The concave-convex structure according to any one of claims 1 to 4, wherein an average width of the entire assembly structure is 0.2 µm or more.

6. The concave-convex structure according to any one of claims 1 to 5, wherein the shape of the region occupied by the concave portion on the surface of the base material is substantially circular.

7. The concave-convex structure according to claim 1 , wherein the depth of the recesses changes stepwise within the assembly structure.

8. The concave-convex structure according to any one of claims 1 to 6, wherein an average width of an area occupied by the concaves on the surface of the substrate changes stepwise within the aggregate structure.

9. The concave-convex structure according to any one of claims 1 to 6, wherein an average width of the region occupied by the recesses on the surface of the substrate varies irregularly within the aggregate structure.

10. The concave-convex structure according to any one of claims 1 to 9, wherein each of the aggregate structures is regularly arranged.

11. The concave-convex structure according to any one of claims 1 to 9, wherein each of the collective structures is irregularly arranged.

12. The concave-convex structure according to any one of claims 1 to 11, wherein in the collective structure, each of the recesses is provided in a close-packed arrangement.

13. An optical member comprising the concave-convex structure according to any one of claims 1 to 12.

14. An electronic device comprising the concave-convex structure according to any one of claims 1 to 12.

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