Sheet member

Abstract

A sheet member 1 comprises: a top surface 111 including a first region 130 and a second region 140; a reverse surface 122; and a through hole 15 formed between the top surface and the reverse surface. The first region 130 is formed as at least a portion of a riblet structure RB and is the top surface of a protruding structure 13 protruding from the second region, and an opening 151 of the through hole 15 formed in the second region 140.

Description

Sheet material

[0001] The present invention relates to the technical field of, for example, sheet members having a riblet structure.

[0002] Patent Document 1 describes an aircraft having a fuselage or the like with a riblet structure formed on the surface. In this case, it is required to easily form the riblet structure on the surface of an object such as an aircraft.

[0003] US Patent Application Publication No. 2011 / 0186685

[0004] According to a first aspect, a sheet member having a riblet structure is provided, comprising a surface including a first region and a second region, a back surface, and a through hole formed between the surface and the back surface, wherein the first region is the surface of a convex structure protruding from the second region and formed as at least part of the riblet structure, and the second region has an opening for the through hole formed therein.

[0005] According to a second aspect, there is provided a sheet member having a riblet structure, the sheet member comprising a through hole formed between a front surface and a back surface.

[0006] According to a third aspect, there is provided a sheet member having a riblet structure, wherein the front surface has a first surface on which the riblet structure is formed and a second surface different from the first surface, and the back surface has a third surface opposite the first surface and a fourth surface opposite the second surface, wherein an adhesive surface is formed on the third surface for attaching the sheet member to an object, and no adhesive surface is formed on the fourth surface.

[0007] According to a fourth aspect, there is provided a sheet member having a riblet structure on its surface, the back surface of which has an adhesive surface of an adhesive layer, the adhesive layer including a first adhesive layer portion having a first thickness and a second adhesive layer portion having a second thickness different from the first thickness.

[0008] According to a fifth aspect, there is provided a sheet member having a riblet structure on its surface and an adhesive layer on its back surface, the adhesive layer including a first adhesive portion having a first adhesive performance and a second adhesive portion having a second adhesive performance different from the first adhesive performance.

[0009] According to a sixth aspect, there is provided a sheet member having a riblet structure, the sheet member having, on its surface, a first surface on which the riblet structure is formed and a second surface different from the first surface on which the riblet structure is not formed.

[0010] FIG. 1(a) is a perspective view showing the appearance of the libretto sheet of this embodiment, and FIG. 1(b) is a cross-sectional view (II' cross-sectional view of FIG. 1(a)) showing the structure of the libretto sheet of this embodiment. FIG. 2(a) is a perspective view showing the libretto structure, FIG. 2(b) is a cross-sectional view (II-II' cross-sectional view of FIG. 2(a)) showing the libretto structure, and FIG. 2(c) is a top view showing the libretto structure. FIG. 3(a) is a front view showing an aircraft, which is an example of an object to which a libretto sheet can be attached, and FIG. 3(b) is a side view showing an aircraft, which is an example of an object to which a libretto sheet can be attached. FIGS. 4(a) and 4(b) are each cross-sectional views showing an object to which a libretto sheet has been attached. FIG. 5 shows a first specific example of the position at which a through-hole opening is formed. FIG. 6 shows a second specific example of the position at which a through-hole opening is formed. FIGS. 7(a) to 7(b) each show an example of a through-hole formed in a libretto sheet. Each of Figures 8(a) to 8(b) shows an example of a through hole formed in a riblet sheet. Each of Figures 9(a) to 9(d) is a plan view showing the shape of a through hole. Figure 10(a) is a plan view showing a riblet sheet in which a single opening (a single through hole) is formed, and each of Figures 10(b) to 10(d) is a plan view showing a riblet sheet in which multiple openings (multiple through holes) are formed. Each of Figures 11(a) to 11(e) is a plan view showing a riblet sheet in which multiple openings distributed at equal intervals are formed. Figure 12 is a plan view showing a riblet sheet in which multiple openings distributed periodically are formed. Each of Figures 13(a) and 13(b) is a plan view showing a riblet sheet in which multiple openings distributed unevenly are formed. Each of Figures 14(a) to 14(d) is a cross-sectional view showing the cross-sectional shape of a through hole. Each of Figures 15(a) to 15(d) is a cross-sectional view showing the cross-sectional shape of a through hole. Figures 16(a) to 16(c) are cross-sectional views showing steps for manufacturing a libretto sheet by imprint molding using a mold. Figure 17 shows a libretto sheet according to a second modified example. Figures 18(a) and 18(b) show a libretto sheet according to the second modified example. Figure 19 shows a libretto sheet according to a third modified example.Fig. 20 is a cross-sectional view showing a libretto sheet in a fourth modified example. Fig. 21 is a perspective view showing a libretto sheet in a fifth modified example. Fig. 22 is a cross-sectional view showing a libretto sheet in a sixth modified example. Fig. 23 is a cross-sectional view showing a libretto sheet in a seventh modified example. Figs. 24(a) to 24(c) are each cross-sectional views showing a method of attaching a libretto sheet to an object in an eighth modified example. Fig. 25 is a cross-sectional view showing a libretto sheet in a ninth modified example. Figs. 26(a) to 26(b) are each cross-sectional views showing the process of manufacturing a libretto sheet in a ninth modified example.

[0011] Next, an embodiment of the sheet member will be described with reference to the drawings.

[0012] (1) Structure of Libretto Sheet 1 First, the structure of the libretto sheet 1, which is an example of an embodiment of a seat member, will be described with reference to Figures 1(a) and 1(b). Figure 1(a) is a perspective view showing the appearance of the libretto sheet 1 of this embodiment, and Figure 1(b) is a cross-sectional view (cross-sectional view taken along II' in Figure 1(a)) showing the structure of the libretto sheet 1 of this embodiment.

[0013] As shown in Figures 1(a) and 1(b), libretto sheet 1 is a film-like (in other words, a sheet-like, layer-like, foil-like, tape-like, or band-like sheet member. The sheet member may also be referred to as a film member. In the example shown in Figures 1(a) and 1(b), the Y-axis direction is the width direction of libretto sheet 1, and the Z-axis direction is the thickness direction of libretto sheet 1. Libretto sheet 1 is a film-like sheet member whose thickness is much smaller than its width. As an example, the width of libretto sheet 1 may be several centimeters or more, 10-odd centimeters or more, several tens of centimeters or more, or one meter or more. On the other hand, the thickness of libretto sheet 1 may be one millimeter or less, one centimeter or less, or a few centimeters or less.

[0014] The libretto sheet 1 may have a longitudinal shape extending along a length direction intersecting the width direction and the thickness direction. In other words, the libretto sheet 1 may have a longitudinal shape in which the direction intersecting the width direction and the thickness direction is the longitudinal direction. In the example shown in Figures 1(a) and 1(b), the X-axis direction is the length direction (longitudinal direction) of the libretto sheet 1. As an example, the length of the libretto sheet 1 may be several centimeters or more, a dozen centimeters or more, several tens of centimeters or more, one meter or more, a dozen meters or more, or several tens of meters or more.

[0015] However, the riblet sheet 1 does not have to have a longitudinal shape extending along a length direction intersecting the width direction and thickness direction. For example, the riblet sheet 1 may have a rectangular shape in a plan view. As an example, the riblet sheet 1 extending along the length direction may be divided along the length direction into multiple sheet members, each having a rectangular shape.

[0016] As shown in FIG. 1( b), the libretto sheet 1 includes an adhesive layer 11 and a structural layer 12. Specifically, the libretto sheet 1 has a laminated structure in which the adhesive layer 11 and the structural layer 12 are laminated. The adhesive layer 11 and the structural layer 12 are laminated so that the surface 111 of the adhesive layer 11 (the surface facing the +Z side in the example shown in FIG. 1( b)) faces the back surface 122 of the structural layer 12 (the surface facing the -Z side in the example shown in FIG. 1( b)). In other words, the adhesive layer 11 and the structural layer 12 are laminated so that the adhesive layer 11 is formed on the back surface 122 of the structural layer 12. In other words, the adhesive layer 11 and the structural layer 12 are laminated so that the structural layer 12 is formed on the surface 111 of the adhesive layer 11. In this case, the surface 121 of the structural layer 12 (the surface facing the +Z side in the example shown in FIG. 1( b)) may be considered to be the surface of the libretto sheet 1. On the other hand, the back surface 112 of the adhesive layer 11 (in the example shown in Figure 1 (b) , the surface facing the -Z side) may be considered to be the back surface of the libretto sheet 1.

[0017] The adhesive layer 11 is a layer containing an adhesive for attaching the libretto sheet 1 to an object OBJ (e.g., a moving object described later). In other words, the adhesive layer 11 is a layer containing an adhesive for attaching the structural layer 12 to an object OBJ (e.g., a moving object described later). For this reason, the libretto sheet 1 (particularly the structural layer 12) may be attached to the object OBJ via the adhesive layer 11. In other words, the libretto sheet 1 (particularly the structural layer 12) may be attached to the object OBJ using the adhesive layer 11. Note that the libretto sheet 1 does not have to include the adhesive layer 11. In this case, when attaching the libretto sheet 1 to the object, an operator may apply adhesive between the object and the libretto sheet 1.

[0018] Specifically, at least a portion of the back surface 112 of the adhesive layer 11 (the surface facing the -Z side in the example shown in Figure 1(b)) is an adhesive surface for attaching the libretto sheet 1 (particularly, the structural layer 12) to the object OBJ. In other words, the back surface 112 of the adhesive layer 11 has an adhesive surface for attaching the libretto sheet 1 (particularly, the structural layer 12) to the object OBJ. In this case, the libretto sheet 1 (particularly, the structural layer 12) may be attached to the object OBJ by the back surface 112 (adhesive surface) of the adhesive layer 11 coming into contact with the object OBJ.

[0019] The structural layer 12 is a layer in which the riblet structure RB is formed. In other words, the structural layer 12 is a layer having the riblet structure RB. Therefore, the riblet sheet 1 is a sheet member in which the riblet structure RB is formed. In other words, the riblet sheet 1 is a sheet member having the riblet structure RB. However, in Figures 1(a) and 1(b), the riblet structure RB formed in the structural layer 12 is omitted to simplify the drawings.

[0020] Specifically, the riblet structure RB is formed on at least a portion of the surface 121 of the structure layer 12. Therefore, the structure layer 12 is a layer in which the riblet structure RB is formed on at least a portion of its surface 121. In other words, the structure layer 12 is a layer in which the riblet structure RB is formed on at least a portion of its surface 121. Therefore, the riblet sheet 1 is a sheet member in which the riblet structure RB is formed on at least a portion of its surface 121. In other words, the riblet sheet 1 is a sheet member in which the riblet structure RB is formed on at least a portion of its surface 121.

[0021] An example of the riblet structure RB is shown in Figures 2(a) to 2(c), where Figure 2(a) is a perspective view showing the riblet structure RB, Figure 2(b) is a cross-sectional view (cross-sectional view taken along II-II' in Figure 2(a)) showing the riblet structure RB, and Figure 2(c) is a top view showing the riblet structure RB.

[0022] As shown in Figures 2(a) to 2(c), the riblet structure RB may include a convex structure 13. That is, the convex structure 13 may be formed on the surface 121 of the structure layer 12 as at least a part of the riblet structure RB. In particular, as shown in Figures 2(a) to 2(c), the riblet structure RB may include a plurality of convex structures 13. That is, the surface 121 of the structure layer 12 may have a plurality of convex structures 13 formed as at least a part of the riblet structure RB.

[0023] Each of the multiple convex structures 13 may extend along a predetermined extension direction. In this case, the riblet structure RB may include multiple convex structures 13 extending along the predetermined extension direction. Each of the multiple convex structures 13 may be arranged along a predetermined arrangement direction. In this case, the riblet structure RB may include multiple convex structures 13 arranged along the predetermined arrangement direction.

[0024] As an example, the riblet structure RB may include a structure in which a plurality of convex structures 13 extending along a predetermined extension direction are arranged along a predetermined arrangement direction that intersects the predetermined extension direction. In other words, the riblet structure RB may include a structure in which a plurality of convex structures 13 formed to extend along the predetermined extension direction are arranged along the predetermined arrangement direction. Each of the extension direction and the arrangement direction may be a direction along the surface 121. Each of the extension direction and the arrangement direction may be a direction that intersects the height direction (described below) in which the convex structures 13 protrude. Furthermore, one of the extension direction and the arrangement direction may be the longitudinal direction of the riblet sheet 1, and the other of the extension direction and the arrangement direction may be the lateral direction of the riblet sheet 1. In the example shown in Figures 2(a) to 2(c), the riblet structure RB includes a structure in which a plurality of convex structures 13 extending along the X-axis direction are arranged along the Y-axis direction. That is, Figures 2(a) to 2(c) show an example in which the predetermined extension direction is the X-axis direction and the predetermined arrangement direction is the Y-axis direction that intersects (typically, is perpendicular to) the X-axis direction.

[0025] The convex structures 13 are structures that protrude from the surroundings along a predetermined height direction. The convex structures 13 are structures that protrude from the surroundings along a predetermined height direction that intersects both the predetermined extension direction in which the convex structures 13 extend and the predetermined arrangement direction in which the convex structures 13 are arranged. The height direction may be the thickness direction of the riblet sheet 1. In the example shown in Figures 2(a) to 2(c), the convex structures 13 are structures that protrude from the surroundings along the Z-axis direction, which is the thickness direction of the riblet sheet 1. In other words, Figures 2(a) to 2(c) show an example in which the predetermined height direction is the Z-axis direction that intersects (typically perpendicular to) the X-axis direction and the Y-axis direction.

[0026] The convex structure 13 has, for example, a pair of side surfaces 191 and 192 facing opposite to each other. Note that in this embodiment, "a state in which one surface and the other surface face opposite to each other" may mean, for example, a state in which one surface faces one side of an axis intersecting the one surface and the other surface, while the other surface faces the other side along the same axis (i.e., the opposite side from the one side). In the example shown in Figures 2(a) to 2(c), the convex structure 13 has a side surface 191 facing the -Y side and a side surface 192 facing the +Y side. Each of the pair of side surfaces 191 and 192 is a flat surface. However, at least one of the pair of side surfaces 191 and 192 may include a curved surface.

[0027] The pair of side surfaces 191 and 192 may be non-parallel to each other. In this case, the pair of side surfaces 191 and 192 of the convex structure 13 may be connected via one end thereof (in the examples shown in Figures 2(a) to 2(c) , the upper end on the +Z side). The portion where the pair of side surfaces 191 and 192 of the convex structure 13 are connected constitutes a corner 193 of the convex structure 13. The corner 193 of the convex structure 13 may constitute the vertex of the convex structure 13. The corner 193 of the convex structure 13 may constitute the ridge line of the convex structure 13. The corner 193 of the convex structure 13 may constitute the boundary between the pair of side surfaces 191 and 192 of the convex structure 13. In this case, the pair of side surfaces 191 and 192 may be considered to be connected via the corner 193 of the convex structure 13. In the example shown in FIGS. 2( a ) to 2 ( c ), a pair of side surfaces 191 and 192 are connected so that the upper end of the side surface 191 and the upper end of the side surface 192 are in contact with each other.

[0028] The convex structure 13 may be a structure formed by a pair of side surfaces 191 and 192. The convex structure 13 may be a structure including the pair of side surfaces 191 and 192 on its surface. In this case, the shape of a cross section of the convex structure 13 including the Z axis may be a triangular shape. In this case, the shape of a cross section of the convex structure 13 including the Z axis may be a symmetrical triangular shape, or may be an asymmetrical triangular shape. However, the shape of a cross section of the convex structure 13 including the Z axis may have any shape other than a triangular shape.

[0029] The side surfaces 191 and 192 may be referred to as inclined surfaces 191 and 192, respectively. The surface 121 of the structure layer 12 may be considered to include the side surfaces 191 and 192. Furthermore, if the corner portion 193 (vertex or ridge) of the convex structure 13 is not a corner but a curved surface (convex surface), the surface 121 of the structure layer 12 may be considered to include the corner portion 193.

[0030] A groove structure 14 that is recessed compared to the surrounding area is formed between adjacent convex structures 13. For this reason, the riblet structure RB may include a structure in which a plurality of groove structures 14 extending along a predetermined extension direction are arranged along a predetermined arrangement direction. In other words, the riblet structure RB may include a structure in which groove structures 14 formed to extend along a predetermined extension direction are lined up along a predetermined arrangement direction. Note that the groove structure 14 may be considered to be a structure recessed with respect to the vertex or ridge line (for example, the above-mentioned corner portion 193) of the convex structure 13.

[0031] The groove structure 14 may be considered to be a structure located between a side surface 191 of one convex structure 13 and a side surface 192 of another convex structure 13 adjacent to the one convex structure 13 along the arrangement direction in which the convex structures 13 are arranged. Specifically, the side surface 191 of one convex structure 13 and the side surface 192 of another convex structure 13 adjacent to the one convex structure 13 along the first arrangement direction in which the convex structures 13 are arranged may be connected via a boundary portion 194 connecting their other end portions (in the example shown in FIGS. 2( a ) to 2 ( c ), the lower end portions on the −Z side). In other words, the side surfaces 191 and 192 that are provided on two adjacent convex structures 13 and face each other may be connected via the boundary portion 194 that forms the boundary between the two adjacent convex structures 13. In the example shown in FIGS. 2( a ) to 2 ( c ), the boundary portion 194 includes a surface that intersects with each of the side surfaces 191 and 192 to which the boundary portion 194 connects. In this case, the groove structure 14 may be a structure formed by the boundary portion 194. The groove structure 14 may be a structure including a groove that the boundary portion 194 faces. The boundary portion 194 may be considered to be the bottom surface of the groove structure 14. In this case, the boundaries between each of the side surfaces 191 and 192 and the boundary portion 194 may be used as the boundary between the convex structure 13 and the groove structure 14. The groove structure 14 may also be referred to as a groove-shaped structure or a concave structure.

[0032] However, in some cases, the groove structure 14 may be considered to be a structure formed by the boundary portion 194 and the side surfaces 191 and 192 connected by the boundary portion 194. The groove structure 14 may be considered to be a structure including a groove facing the boundary portion 194 and the side surfaces 191 and 192 connected by the boundary portion 194. In other words, the side surfaces 191 and 192 may be considered to be side surfaces of the groove structure 14.

[0033] It should be noted that the surface 121 of the structure layer 12 may be considered to include a boundary portion 194 (for example, the bottom surface of the groove structure 14 ) in addition to or instead of the side surfaces 191 and 192 .

[0034] In this way, the surface 121 of the structure layer 12 has convex structures 13 (particularly, a plurality of convex structures 13) and groove structures 14 (particularly, a plurality of groove structures 14) formed as at least a part of the riblet structure RB. In other words, the surface 121 of the structure layer 12 includes a convex region 130 in which the convex structures 13 (particularly, a plurality of convex structures 13) are formed, and a groove region 140 in which the groove structures 14 (particularly, a plurality of groove structures 14) are formed. In this case, the convex region 130, which is part of the surface 121 of the structure layer 12, may be considered to be equivalent to the surface of the convex structures 13. Furthermore, the convex structures 13 may be considered to be a structure protruding from the groove region 140, which is part of the surface 121 of the structure layer 12.

[0035] Although the convex structures 13 are not formed in the groove region 140, depending on the flatness of the surface of the groove region 140, it may be considered that a minute uneven structure is formed in the groove region 140. Even in this case, the height of the convex structures of the minute uneven structure formed in the groove region 140 is lower than the height H_rb of the convex structures 13 formed in the convex region 130. Conversely, the groove region 140 may be formed with a minute uneven structure including convex structures that are lower than the height H_rb of the convex structures 13 formed in the convex region 130. Furthermore, the pitch (i.e., arrangement period) of the convex structures included in the minute uneven structure formed in the groove region 140 is shorter than the pitch P_rb of the convex structures 13 formed in the convex region 130. Conversely, the groove region 140 may be formed with a minute uneven structure including convex structures that are arranged at a pitch shorter than the pitch P_rb of the convex structures 13 formed in the convex region 130.

[0036] In any case, the flatness of the groove region 140 remains lower than the flatness of the convex region 130. Therefore, as long as the flatness of the groove region 140 is lower than the flatness of the convex region 130, a minute uneven structure may be formed in the groove region 140.

[0037] When a plurality of convex structures 13 are formed in the convex region 130, the convex region 130 may be considered to include a plurality of partial convex regions 131, each having a plurality of convex structures 13 formed therein. Each partial convex region 131 may be a region extending along the direction in which the convex structures 13 formed in each partial convex region 131 extend (in the example shown in FIGS. 2( a ) to 2 ( c ), the X-axis direction). In other words, each partial convex region 131 may be a region whose longitudinal direction is the direction in which the convex structures 13 formed in each partial convex region 131 extend (in the example shown in FIGS. 2( a ) to 2 ( c )), similarly, when a plurality of groove structures 14 are formed in the convex region 130, the groove region 140 may be considered to include a plurality of partial groove regions 141, each having a plurality of groove structures 14 formed therein. Each partial groove region 141 may be a region that extends along the direction in which the groove structure 14 formed in each partial groove region 141 extends (the X-axis direction in the example shown in FIGS. 2(a) to 2(c)). In other words, each partial groove region 141 may be a region whose longitudinal direction is the direction in which the groove structure 14 formed in each partial groove region 141 extends (the X-axis direction in the example shown in FIGS. 2(a) to 2(c)). In this case, each partial convex region 131 is located between two adjacent partial groove regions 141. Similarly, each partial groove region 141 is located between two adjacent partial convex regions 131.

[0038] The plurality of convex structures 13 may be formed so that the plurality of convex structures 13 are arranged regularly. For example, the plurality of convex structures 13 may be formed so that the plurality of convex structures 13 are arranged at an equal pitch along a predetermined arrangement direction. For example, the plurality of convex structures 13 may be formed so that a structure group including at least two convex structures 13 is arranged at an equal pitch along a predetermined arrangement direction. The plurality of convex structures 13 may be formed so that at least two convex structures 13 are arranged regularly according to a first rule in a first portion of the surface 121 of the structure layer 12, and at least two convex structures 13 are arranged regularly according to the same first rule in a second portion of the surface 121 of the structure layer 12. The plurality of convex structures 13 may be formed so that at least two convex structures 13 are arranged regularly according to the first rule in the first portion of the surface 121 of the structure layer 12, and at least two convex structures 13 are arranged regularly according to a second rule different from the first rule in the second portion of the surface 121 of the structure layer 12. Furthermore, since the convex structures 13 and the groove structures 14 are formed alternately, a state in which multiple convex structures 13 are arranged in a regular pattern may be considered equivalent to a state in which multiple groove structures 14 are arranged in a regular pattern.

[0039] The height H_rb of at least one of the multiple convex structures 13 may be set to a height determined according to the pitch P_rb of the convex structures 13. For example, the height H_rb of at least one of the multiple convex structures 13 may be less than or equal to the pitch P_rb of the convex structures 13. For example, the height H_rb of at least one of the multiple convex structures 13 may be less than half the pitch P_rb of the convex structures 13. Furthermore, the height H_rb of at least one of the multiple convex structures 13 may be within a range of 1 / 2 ±10% of the pitch P_rb of the convex structures 13. The height H_rb may be the height from the bottom surface of the groove structure 14 (i.e., the boundary 194). Furthermore, the height H_rb may be referred to as the depth from the vertex or ridge (i.e., the corner 193) of the convex structure 13.

[0040] The riblet structure RB may be used as a structure capable of reducing the resistance to fluid (particularly, at least one of frictional resistance and turbulent frictional resistance) of the surface of the riblet sheet 1 (i.e., the surface 121 of the structural layer 12). In this case, the surface 121 of the structural layer 12 on which the riblet structure RB is formed may be considered to be a surface capable of reducing the resistance to fluid of the surface of the riblet sheet 1 (typically, the surface 121 of the structural layer 12).

[0041] As described above, the riblet sheet 1 on which the riblet structure RB is formed may be attached to an object OBJ via an adhesive layer 11. In this case, the riblet structure RB may be used as a structure that can reduce the resistance (particularly, at least one of frictional resistance and turbulent frictional resistance) of the surface of the object OBJ to which the riblet sheet 1 is attached to a fluid. For this reason, the riblet sheet 1 may be attached to an object OBJ that has a component that is installed (in other words, located) in a fluid. Note that the term "fluid" here refers to a medium (e.g., at least one of gas and liquid) that flows relative to the surface of the object OBJ. For example, if the surface of the object OBJ moves relative to the medium while the medium itself is stationary, this medium may also be referred to as a fluid. Note that the state in which the medium is stationary may also refer to a state in which the medium is not moving relative to a predetermined reference object (e.g., the ground surface).

[0042] Attaching the libretto sheet 1 to the object OBJ may be considered equivalent to forming a libretto structure RB on the surface of the object OBJ. In this case, when the libretto structure RB is formed on the surface of the object OBJ by attaching the libretto sheet 1 to the object OBJ, the libretto structure RB can be formed more easily on the surface of the object OBJ than when the libretto structure RB is formed directly on the surface of the object OBJ without using the libretto sheet 1. This is because, in order to form the libretto structure RB on the surface of the object OBJ, it is sufficient to attach the libretto sheet 1 to the object OBJ.

[0043] A moving body is an example of an object OBJ to which the riblet sheet 1 can be attached. In particular, a moving body that can move through a fluid is an example of an object OBJ to which the riblet sheet 1 can be attached. Examples of the moving body include at least one of a railway vehicle, an automobile, an aircraft, a ship, a windmill, and a turbine.

[0044] For example, Figures 3(a) and 3(b) show an aircraft PL having a riblet sheet 1 attached to at least a portion of its surface. As shown in Figures 3(a) and 3(b), the riblet sheet 1 may be attached to at least a portion of the fuselage PL1 of the aircraft PL. The riblet sheet 1 may be attached to at least a portion of the main wing PL2 of the aircraft PL. The riblet sheet 1 may be attached to at least a portion of the vertical tail PL3 of the aircraft PL. The riblet sheet 1 may be attached to at least a portion of the horizontal tail PL4 of the aircraft PL.

[0045] When such a riblet sheet 1 is attached to at least a portion of the surface of a moving body (or any object OBJ, the same applies hereinafter), the moving body becomes more easily movable relative to the fluid. This reduces the resistance that hinders the movement of the moving body relative to the fluid, leading to energy savings. In other words, it becomes possible to manufacture an environmentally friendly moving body. For example, when the riblet sheet 1 is attached to at least a portion of the surface of an aircraft, the resistance that hinders the movement of the aircraft is reduced, leading to fuel savings for the aircraft. For example, when the riblet sheet 1 is attached to at least a portion of the surface of a wind turbine (e.g., a blade member provided on the wind turbine), the resistance that hinders the movement (typically, rotation) of the wind turbine is reduced, leading to higher efficiency of the wind turbine. For example, when the riblet sheet 1 is attached to at least a portion of the surface of an engine turbine (particularly, a turbine blade), the resistance that hinders the movement (typically, rotation) of the engine turbine is reduced, leading to higher efficiency and energy savings for the engine turbine. For example, when the riblet sheet 1 is attached to at least a portion of the surface of a power-generating turbine (particularly, a turbine blade), resistance that impedes the movement (typically, rotation) of the power-generating turbine is reduced, leading to higher efficiency of the power-generating turbine (i.e., improved power generation efficiency). As a result, the riblet sheet 1 has the potential to contribute to "13.2.2 Reduce total greenhouse gas emissions per year," one of the goals set out in Goal 13 of the United Nations-led Sustainable Development Goals (SDGs) "Take urgent action to combat climate change and its impact."

[0046] The libretto sheet 1 may be attached to the object OBJ by an application device for attaching the libretto sheet 1 to the object OBJ. The application device may automatically attach the libretto sheet 1 to the object OBJ without the need for worker intervention. The application device may semi-automatically attach the libretto sheet 1 to the object OBJ with the intervention of a worker. The application device may assist the worker in attaching the libretto sheet 1 to the object OBJ.

[0047] (2) Technical Issues Arising When Attaching Libretto Sheet 1 to Object OBJ As described above, the libretto sheet 1 is attached to the object OBJ via the adhesive layer 11. In this case, depending on how the libretto sheet 1 is attached, a technical issue of air bubbles remaining between the libretto sheet 1 and the object OBJ may arise. For example, as shown in Figure 4(a), which is a cross-sectional view showing the object OBJ to which the libretto sheet 1 is attached, a technical issue of air bubbles remaining between the adhesive layer 11 of the libretto sheet 1 and the surface of the object OBJ may arise.

[0048] Incidentally, even if the libretto sheet 1 does not have an adhesive layer 11, an adhesive is usually applied between the libretto sheet 1 and the object OBJ in order to attach the libretto sheet 1 to the object OBJ. For this reason, even if the libretto sheet 1 does not have an adhesive layer 11, a technical problem of air bubbles remaining between the libretto sheet 1 and the object OBJ may arise depending on the method of attaching the libretto sheet 1 to the object OBJ and / or the method of applying the adhesive.

[0049] If air bubbles remain in this manner, as shown in FIG. 4( a), the air bubbles may unintentionally deform the structure layer 12. In particular, the air bubbles may unintentionally deform the surface 121 of the structure layer 12. As a result, the deformation of the surface 121 of the structure layer 12 may deteriorate the resistance reduction effect of the riblet structure RB (i.e., the effect of reducing the resistance of the surface of the moving body to which the riblet sheet 1 is attached to the fluid). Furthermore, the deformation of the surface 121 of the structure layer 12 may impair the aesthetic appearance of the riblet sheet 1. Furthermore, if air bubbles remain, the adhesion between the riblet sheet 1 and the object OBJ may deteriorate. As a result, the riblet sheet 1 may unintentionally peel off from the object OBJ.

[0050] To solve these technical problems, contractors who attach the libretto sheet 1 to the object OBJ are expected to attach the libretto sheet 1 to the object OBJ so that no air bubbles remain. In other words, contractors are expected to attach the libretto sheet 1 to the object OBJ little by little so that no air bubbles remain. In some cases, if air bubbles remain during the process of attaching the libretto sheet 1 to the object OBJ, contractors are expected to partially peel off the libretto sheet 1 attached to the object OBJ, remove the air bubbles, and then reattach the libretto sheet 1 to the object OBJ. Alternatively, the same applies not only to cases where a contractor manually attaches the libretto sheet 1 to the object OBJ, but also to cases where a device is used to automatically attach the libretto sheet 1 to the object OBJ. However, gradually attaching the libretto sheet 1 to the object OBJ so that no air bubbles remain is time-consuming and labor-intensive.

[0051] Therefore, in this embodiment, to solve the technical problem of residual air bubbles, through holes 15 are formed in the libretto sheet 1, as shown in FIG. 4( a), a cross-sectional view showing an object OBJ to which the libretto sheet 1 is attached. The through holes 15 penetrate the libretto sheet 1 along the thickness direction of the libretto sheet 1. Therefore, the through holes 15 are formed between the surface of the libretto sheet 1 (i.e., the surface 121 of the structural layer 12) and the back surface of the libretto sheet 1 (i.e., the back surface 112 of the adhesive layer 11). In other words, the through holes 15 are through holes that connect the surface of the libretto sheet 1 (i.e., the surface 121 of the structural layer 12) to the back surface of the libretto sheet 1 (i.e., the back surface 112 of the adhesive layer 11). The through holes 15 are through holes formed between the surface of the libretto sheet 1 (i.e., the surface 121 of the structural layer 12) and the back surface of the libretto sheet 1 (i.e., the back surface 112 of the adhesive layer 11).

[0052] When the through holes 15 penetrate the riblet sheet 1, openings 151 of the through holes 15 are formed on the front surface of the riblet sheet 1. Similarly, openings 152 of the through holes 15 are formed on the back surface of the riblet sheet 1.

[0053] In this case, even if air bubbles remain between the libretto sheet 1 and the object OBJ, the air contained in the bubbles (or any fluid including any gas or liquid, the same applies below) is removed from the space between the libretto sheet 1 and the object OBJ via the through holes 15. Specifically, the air contained in the bubbles enters the through holes 15 from the openings 152 and is then released into the space outside the libretto sheet 1 via the openings 151. In other words, the through holes 15 function as a gas release path for removing the air contained in the bubbles. In other words, the through holes 15 function as air holes for releasing the air contained in the bubbles. As a result, the possibility of air bubbles remaining between the libretto sheet 1 and the object OBJ is reduced. This reduces the effort required to attach the libretto sheet 1 to the object OBJ so that no air bubbles remain. As a result, in this embodiment, the riblet structure RB can be easily formed on the surface of the object OBJ. Furthermore, because the possibility of air bubbles remaining is low, the possibility of the structure layer 12 being unintentionally deformed by air bubbles is also reduced. As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB and maintain the aesthetic appearance of the riblet sheet 1. Furthermore, because there is little possibility of air bubbles remaining, there is also less possibility of the adhesion between the riblet sheet 1 and the object OBJ deteriorating. As a result, there is less possibility that the riblet sheet 1 will unintentionally peel off from the object OBJ.

[0054] The through holes 15 may have any characteristics as long as the through holes 15 can be used as a gas release path for removing air contained in bubbles remaining between the riblet sheet 1 and the object OBJ. Examples of the characteristics of the through holes 15 include at least one of the following: the formation position of the through holes 15, the formation position of at least one of the openings 151 and 152 of the through holes 15, the size of the through holes 15, the size of at least one of the openings 151 and 152 of the through holes 15, the number of the through holes 15, the number of at least one of the openings 151 and 152 of the through holes 15, the shape of the through holes 15, and the shape of at least one of the openings 151 and 152 of the through holes 15. An example of the characteristics of the through holes 15 will be further explained below.

[0055] (3) Characteristics of the Through Hole 15 (3-1) Formation Position of the Opening 151 of the Through Hole 15 First, the formation position of the opening 151 of the through hole 15, which is an example of the characteristics of the through hole 15, will be described.

[0056] (3-1-1) First Specific Example of the Formation Position of the Opening 151 of the Through Hole 15 As shown in Figure 5, in a first specific example, the opening 151 of the through hole 15 may be formed in a groove region 140 in which no convex structure 13 is formed. Specifically, the opening 151 of the through hole 15 may be formed in at least one of a plurality of partial groove regions 141 included in the groove region 140. On the other hand, in the first specific example, the opening 151 of the through hole 15 does not have to be formed in a convex region 130 in which a convex structure 13 is formed. In other words, the opening 151 of the through hole 15 does not have to be formed in any of a plurality of partial convex regions 131 included in the convex region 130.

[0057] In this first specific example, the through holes 15 do not affect the shape of the convex structures 13. In other words, even when the through holes 15 are formed, the riblet sheet 1 forms convex structures 13 having the same shape as the convex structures 13 that would be formed if the through holes 15 were not formed. Therefore, there is little possibility that the drag reduction effect of the riblet structure RB will deteriorate due to a change in the shape of the convex structures 13. As a result, the drag reduction effect of the riblet structure RB is appropriately maintained. Furthermore, there is little possibility that the strength of the convex structures 13 will decrease due to a change in the shape of the convex structures 13. As a result, the strength of the convex structures 13 is appropriately maintained.

[0058] When the opening 151 of the through hole 15 is formed in the partial groove region 141, the size (i.e., width) S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be less than the pitch P_rb of the convex structures 13. For example, when the pitch P_rb of the convex structures 13 is 100 μm, the size S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be less than 100 μm. In this case, it is possible to appropriately form the through hole 15 that satisfies the condition that the opening 151 is not formed in the convex region 130 but the opening 151 is formed in the groove region 140.

[0059] Furthermore, it is not necessary for any openings 151 of the through holes 15 to be formed in the entire convex region 130 of the riblet sheet 1. In this case, the drag reduction effect of the riblet structure RB and the strength of the convex structure 13 are more appropriately maintained. However, the openings 151 of the through holes 15 may be formed in at least a part of the convex region 130 of the riblet sheet 1. For example, the openings 151 of the through holes 15 may be formed in the side surface 191 of the convex structure 13. For example, the openings 151 of the through holes 15 may be formed in the side surface 192 of the convex structure 13. For example, the openings 151 of the through holes 15 may be formed so as to straddle at least one of the side surfaces 191 and 192 of the convex structure 13 and the corner portion 193.

[0060] Alternatively, openings 151 of the through holes 15 may be formed in a first region portion of the convex region 130 of the riblet sheet 1, while no openings 151 of the through holes 15 may be formed in a second region portion different from the first region portion of the convex region 130 of the riblet sheet 1. As an example, openings 151 of the through holes 15 may be formed in a first partial convex region 131 included in the convex region 130 of the riblet sheet 1, while no openings 151 of the through holes 15 may be formed in a second partial convex region 131 included in the convex region 130 of the riblet sheet 1. In other words, openings 151 of the through holes 15 may be formed in the convex region 130. In this case, the drag reduction effect of the riblet structure RB and the strength of the convex structure 13 are appropriately maintained in the second region portion of the convex region 130 of the riblet sheet 1.

[0061] (3-1-2) Second Specific Example of the Formation Position of Opening 151 of Through Hole 15 The second specific example differs from the above-described first specific example in which opening 151 of through hole 15 is formed in a single partial groove region 141 in that opening 151 of through hole 15 is formed across multiple partial groove regions 141, as shown in Fig. 6. Fig. 6 shows an example in which opening 151 is formed across three partial groove regions 141 (specifically, partial groove regions 141#1, 141#2, and 141#3).

[0062] When the opening 151 of the through hole 15 is formed across multiple partial groove regions 141, the size (i.e., width) S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be larger than the pitch P_rb of the convex structures 13. For example, the size S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be twice the pitch P_rb of the convex structures 13, or may be larger than twice the pitch P_rb of the convex structures 13. For example, the size S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be three times the pitch P_rb of the convex structures 13, or may be larger than three times the pitch P_rb of the convex structures 13. For example, the size S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be four times the pitch P_rb of the convex structures 13, or may be larger than four times the pitch P_rb of the convex structures 13. For example, when the pitch P_rb of the convex structures 13 is 100 μm, the size S151 of the opening 151 along at least one of the X-axis direction and the Y-axis direction may be greater than 100 μm, 200 μm, 300 μm, 400 μm, or greater than 400 μm. Thus, in the second specific example, the size of the opening 151 is larger than in the first specific example. As a result, the difficulty of forming the through holes 15 is reduced, and therefore the through holes 15 are easier to form.

[0063] The opening 151 may be formed between two partial convex regions 131 that sandwich a plurality of partial groove regions 141 across which the opening 151 is formed. In other words, the opening 151 may be formed between two convex structures 13 that are respectively formed in two partial convex regions 131 that sandwich a plurality of partial groove regions 141 across which the opening 151 is formed. For example, in the example shown in FIG. 6 , the three partial groove regions 141#1, 141#2, and 141#3 across which the opening 151 is formed are sandwiched between the partial convex region 131#1 and the partial convex region 131#4. In this case, the opening 151 may be formed between the partial convex region 131#1 and the partial convex region 131#4. In other words, the opening 151 may be formed between the convex structures 13 that are formed in the partial convex region 131#1 and the partial convex region 131#4. A part of the convex structure 13 may be configured to surround the opening 151. A part of the convex structure 13 may be curved along the periphery of the opening 151.

[0064] When an opening 151 is formed between two partial convex regions 131 (i.e., between two convex structures 13), the end of the opening 151 may be spaced apart from the two convex structures 13 that sandwich the opening 151. Specifically, the end of the opening 151 may be spaced apart from the two convex structures 13 that sandwich the opening 151 by a predetermined first distance DM1 or more. In other words, the distance between the end of the opening 151 and the two convex structures 13 that sandwich the opening 151 may be the predetermined first distance DM1 or more. Here, the distance between the end of the opening 151 and the two convex structures 13 that sandwich the opening 151 may mean the distance from the boundary between at least one of the side surfaces 191 and 192 of the convex structure 13 and the groove structure 14 (i.e., the boundary between at least one of the side surfaces 191 and 192 and the boundary portion 194) to the end of the opening 151. In this case, the predetermined first distance DM1 may be equal to the length of at least one of the short sides of the side surfaces 191 and 192 of the convex structure 13 (the distance in the Y-axis direction in FIG. 6 ). Also, in this case, the predetermined first distance DM1 may be longer than at least one of the short sides of the side surfaces 191 and 192 of the convex structure 13. Also, the predetermined first distance DM1 may be from the corner 193 (i.e., the ridge) of the convex structure 13 to the end of the opening 151. That is, the end of the opening 151 may be located in the partial groove region 141. Note that the end of the opening 151 in this paragraph refers to the end of the opening 151 in a predetermined arrangement direction in which the multiple convex structures 13 are arranged (in the example shown in FIG. 6 , the Y-axis direction). In the example shown in FIG. 6 , the end of the opening 151 in this paragraph includes an end 1511 of the opening 151 on the +Y side and an end 1512 of the opening 151 on the -Y side.

[0065] In this way, when the ends of the opening 151 are separated from the two convex structures 13 that sandwich the opening 151, the shapes of the two convex structures 13 that sandwich the opening 151 are not affected by the opening 151. Therefore, the number of convex structures 13 whose shapes change due to the opening 151 does not increase more than necessary. As a result, the drag reduction effect of the riblet structure RB is not deteriorated more than necessary due to changes in the shape of the convex structures 13. As a result, the drag reduction effect of the riblet structure RB is maintained appropriately. Furthermore, the strength of the convex structures 13 is not reduced more than necessary due to changes in the shape of the convex structures 13. As a result, the strength of the convex structures 13 is maintained appropriately.

[0066] At least one of the plurality of partial groove regions 141 formed across the opening 151 does not have to be continuous along the extension direction of the convex structure 13. In other words, at least one of the plurality of partial groove regions 141 formed across the opening 151 may be divided by the opening 151 (i.e., the through hole 15). For example, in the example shown in FIG. 6 , of the three partial groove regions 141#1, 141#2, and 141#3 formed across the opening 151, the partial groove region 141#2 may be divided into two regions that sandwich the opening 151 along the extension direction of the convex structure 13 (the X-axis direction in the example shown in FIG. 6 ). In other words, the partial groove region 141#2 may be divided by the opening 151 (i.e., the through hole 15) into a first region located on the +X side of the opening 151 and a second region located on the −X side of the opening 151.

[0067] Since the groove structure 14 is formed in the partial groove region 141, the division of the partial groove region 141 may be considered equivalent to the division of the groove structure 14. In other words, the groove structure 14 formed in at least one of the plurality of partial groove regions 141 across which the opening 151 is formed does not have to be continuous along the extension direction of the convex structure 13. In other words, the groove structure 14 formed in at least one of the plurality of partial groove regions 141 across which the opening 151 is formed may be divided by the opening 151 (i.e., the through hole 15). For example, in the example shown in FIG. 6 , the groove structure 14 formed in the partial groove region 141#2 may be divided into first and second groove structures that sandwich the opening 151 along the extension direction of the convex structure 13 (the X-axis direction in the example shown in FIG. 6 ). In other words, the groove structure 14 formed in the partial groove region 141#2 may be divided by the opening 151 (i.e., the through hole 15) into a first groove structure located on the +X side of the opening 151 and a second groove structure located on the -X side of the opening 151.

[0068] The partial convex regions 131 located between the plurality of partial groove regions 141 across which the openings 151 are formed do not have to be continuous along the extension direction of the convex structure 13. In other words, the partial convex regions 131 located between the plurality of partial groove regions 141 across which the openings 151 are formed may be divided by the openings 151 (i.e., by the through holes 15). For example, in the example shown in FIG. 6 , the partial convex regions 131#2 and 131#3 are located between the three partial groove regions 141#1, 141#2, and 141#3 across which the openings 151 are formed. In this case, each of the partial convex regions 131#2 and 131#3 may be divided into two regions sandwiching the opening 151 along the extension direction of the convex structure 13 (the X-axis direction in the example shown in FIG. 6 ). In other words, each of the partial convex regions 131#2 and 131#3 may be divided by the opening 151 (i.e., the through hole 15) into a first region located on the +X side of the opening 151 and a second region located on the -X side of the opening 151.

[0069] Since the convex structures 13 are formed in the partial convex regions 131, the division of the partial convex regions 131 may be considered equivalent to the division of the convex structures 13. In other words, the convex structures 13 formed in the partial convex regions 131 located between the plurality of partial groove regions 141 across which the openings 151 are formed do not have to be continuous along the extension direction of the convex structures 13. In other words, the convex structures 13 formed in the partial convex regions 131 located between the plurality of partial groove regions 141 across which the openings 151 are formed may be divided by the openings 151 (i.e., the through holes 15). For example, in the example shown in FIG. 6 , the convex structures 13 formed in each of the partial convex regions 131#2 and 131#3 may be divided into first and second convex structures that sandwich the opening 151 along the extension direction of the convex structures 13 (the X-axis direction in the example shown in FIG. 6 ). In other words, the convex structures 13 formed in each of the partial convex regions 131#2 and 131#3 may be separated by the opening 151 (i.e., the through hole 15) into a first convex structure located on the +X side of the opening 151 and a second convex structure located on the -X side of the opening 151.

[0070] However, the more the number of convex structures 13 divided by the openings 151 increases, the more likely it is that the drag reduction effect of the riblet structure RB will deteriorate. For this reason, the number of convex structures 13 divided by the openings 151 may be smaller than the number of convex structures 13 that are not divided by the openings 151. The area of ​​the region within the convex region 130 where the convex structures 13 are divided by the openings 151 may be smaller than the area of ​​the region within the convex region 130 where the convex structures 13 are not divided by the openings 151. As a result, excessive deterioration of the drag reduction effect of the riblet structure RB is prevented.

[0071] Typically, the number of convex structures 13 divided by the openings 151 may be equal to or less than the number that satisfies the condition that the deterioration of the drag reduction effect due to the division of the convex structures 13 is negligibly small. The area of ​​the region in the convex region 130 where the convex structures 13 are divided by the openings 151 may be equal to or less than the area that satisfies the condition that the deterioration of the drag reduction effect due to the division of the convex structures 13 is negligibly small. As a result, excessive deterioration of the drag reduction effect due to the riblet structure RB is more appropriately prevented.

[0072] The convex structure 13 divided by the opening 151 may be spaced apart from the opening 151. Specifically, as shown in FIGS. 7( a) and 7(b), the end of the convex structure 13 divided by the opening 151 may be spaced apart from the end of the opening 151 by a predetermined second distance DM2 or more along the extension direction of the convex structure 13. For example, in the example shown in FIGS. 7( a) and 7(b), the +X side end 132 of the convex structure 13 divided by the opening 151 may be spaced apart from the −X side end 1513 of the opening 151 by the second distance DM2 or more along the X axis direction, which is the extension direction of the convex structure 13. For example, in the example shown in FIGS. 7( a) and 7(b), the −X side end 133 of the convex structure 13 divided by the opening 151 may be spaced apart from the +X side end 1514 of the opening 151 by the second distance DM2 or more along the X axis direction, which is the extension direction of the convex structure 13.

[0073] It should be noted that the convex structure 13 may be considered not to be formed in the region between the end of the convex structure 13 and the end of the opening 151. For example, the convex structure 13 may be considered not to be formed in the region between the end 132 on the +X side of the convex structure 13 and the end 1513 on the −X side of the opening 151. For example, the convex structure 13 may be considered not to be formed in the region between the end 133 on the −X side of the convex structure 13 and the end 1514 on the +X side of the opening 151. In this case, the region between the end of the convex structure 13 and the end of the opening 151 is a region where the convex structure 13 is not formed, and therefore may be considered to be included in the groove region 140. Alternatively, the region between the end of the convex structure 13 and the end of the opening 151 is a region where the convex structure 13 would have been formed originally, and therefore may be considered to be included in the convex region 130.

[0074] The height of an edge structure portion, which is a part of the convex structure 13 divided by the opening 151 and includes an end portion in the extension direction of the convex structure 13, may gradually decrease as the edge structure portion approaches the opening 151 along the extension direction of the convex structure 13. Specifically, as shown in FIGS. 8( a) and 8(b), the convex structure 13 divided by the opening 151 may include an edge structure portion 134 including the end portion 132 and an edge structure portion 135 including the end portion 133. In this case, the height of the edge structure portion 134 may gradually decrease as the edge structure portion 134 approaches the opening 151 (particularly, the end 1513 of the opening 151) along the X-axis direction, which is the extension direction of the convex structure 13. Similarly, the height of the edge structure portion 135 may gradually decrease as the edge structure portion 135 approaches the opening 151 (particularly, the end 1514 of the opening 151) along the X-axis direction, which is the extension direction of the convex structure 13. Note that Figure 8(a) shows an example in which the convex structure 13 divided by the opening 151 is not further away from the opening 151 than a predetermined second distance DM2, and Figure 8(b) shows an example in which the convex structure 13 divided by the opening 151 is further away from the opening 151 than a predetermined second distance DM2.

[0075] (3-2) Respective Shapes of Openings 151 and 152 of Through Hole 15 Next, the respective shapes of openings 151 and 152 of through hole 15, which are an example of the characteristics of through hole 15, will be described. Specifically, the respective shapes of openings 151 and 152 of through hole 15 on the surface of riblet sheet 1 (i.e., on the surface along the XY plane) will be described. In the following explanation, for the sake of convenience, the shape of opening 151 will be described. However, the following explanation can be used as an explanation of the shape of opening 152 by replacing the term "opening 151" with the term "opening 152."

[0076] As shown in Fig. 9(a), the shape of the opening 151 may be circular. As shown in Fig. 9(b), the shape of the opening 151 may be elliptical. As shown in Fig. 9(c), the shape of the opening 151 may be polygonal. As shown in Fig. 9(d), the shape of the opening 151 may be a shape surrounded by a closed curve, such as a polygon with rounded vertices. The shape of the opening 151 may also be any other shape.

[0077] (3-3) Number of Through Holes 15 Next, the number of through holes 15, which is an example of the characteristics of the through holes 15, will be described.

[0078] As shown in Figure 10(a), a single through hole 15 may be formed in the riblet sheet 1. In this case, as shown in Figure 10(a), a single opening 151 corresponding to the single through hole 15 may be formed in the surface of the riblet sheet 1 (i.e., the surface 121 of the structural layer 12). Furthermore, although not shown, a single opening 152 corresponding to the single through hole 15 may be formed in the back surface of the riblet sheet 1 (i.e., the back surface 112 of the adhesive layer 11).

[0079] As shown in Figure 10(b), a plurality of through holes 15 may be formed in the riblet sheet 1. In this case, as shown in Figure 10(b), a plurality of openings 151 corresponding to the plurality of through holes 15 may be formed in the surface of the riblet sheet 1 (i.e., the surface 121 of the structural layer 12). Furthermore, although not shown, a plurality of openings 152 corresponding to the plurality of through holes 15 may be formed in the back surface of the riblet sheet 1 (i.e., the back surface 112 of the adhesive layer 11).

[0080] 10C, when a plurality of through holes 15 are formed (i.e., a plurality of openings 151 are formed), the plurality of openings 151 corresponding to the plurality of through holes 15 may include at least two openings 151 (i.e., a plurality of openings 151) formed in a single partial groove region 141. In other words, at least two through holes 15 (i.e., a plurality of through holes 15) may be formed in a single partial groove region 141.

[0081] 10D , when a plurality of through holes 15 are formed (i.e., a plurality of openings 151 are formed), the plurality of openings 151 corresponding to the plurality of through holes 15 may include at least two openings 151 (i.e., a plurality of openings 151) formed in at least two partial groove regions 141 (i.e., a plurality of partial groove regions 141). In other words, at least two through holes 15 (i.e., a plurality of through holes 15) may be formed in each of the at least two partial groove regions 141 (i.e., a plurality of partial groove regions 141).

[0082] When multiple through holes 15 are formed (i.e., multiple openings 151 are formed), the multiple openings 151 may be distributed at equal intervals on the surface of the riblet sheet 1. The multiple openings 151 may include multiple openings 151 distributed at equal intervals on the surface of the riblet sheet 1. For example, as shown in FIG. 11( a), the multiple openings 151 may include multiple first openings 151 distributed at equal intervals along the X-axis direction. For example, as shown in FIG. 11( b), the multiple openings 151 may include multiple second openings 151 distributed at equal intervals along the Y-axis direction. For example, as shown in FIG. 11( c), the multiple openings 151 may include multiple third openings 151 distributed at equal intervals along any direction along the XY plane. For example, as shown in FIG. 11( d), the multiple openings 151 may include multiple fourth openings 151 distributed at equal intervals along the X-axis direction and multiple fifth openings 151 distributed at equal intervals along the Y-axis direction. 11( e), the plurality of openings 151 may include a plurality of sixth openings 151 distributed at equal intervals along an arbitrary first direction along the XY plane, and a plurality of seventh openings 151 distributed at equal intervals along an arbitrary second direction along the XY plane and different from the first direction. Although detailed description will be omitted to avoid duplication, the plurality of openings 152 may also be distributed at equal intervals on the back surface of the riblet sheet 1.

[0083] When multiple through holes 15 are formed (i.e., multiple openings 151 are formed), the multiple openings 151 may be periodically distributed on the surface of the libretto sheet 1. The multiple openings 151 may include multiple openings 151 that are periodically distributed on the surface of the libretto sheet 1. In other words, the distribution pattern of the multiple openings 151 on the surface of the libretto sheet 1 may be a periodic distribution pattern. For example, as shown in FIG. 12 , the multiple openings 151 may be formed so that unit opening groups 153, each including at least one opening 151, appear repeatedly on the surface of the libretto sheet 1. Although detailed description will be omitted to avoid duplication, the multiple openings 152 may also be periodically distributed on the back surface of the libretto sheet 1.

[0084] When multiple through holes 15 are formed (i.e., multiple openings 151 are formed), the multiple openings 151 may be distributed non-uniformly on the surface of the libretto sheet 1. In this case, the multiple openings 151 may be considered to be distributed non-periodically on the surface of the libretto sheet 1. As an example, the multiple openings 151 may be formed so that the distribution pattern of the multiple openings 151 formed in a first partial region 1211 of the surface of the libretto sheet 1 differs from the distribution pattern of the multiple openings 151 formed in a second partial region 1212 different from the first partial region 1211 of the surface of the libretto sheet 1. Although detailed description will be omitted to avoid redundant explanation, the multiple openings 152 may also be formed so that the distribution pattern of the multiple openings 152 formed in a first partial region of the back surface of the libretto sheet 1 differs from the distribution pattern of the multiple openings 152 formed in a second partial region of the back surface of the libretto sheet 1 different from the first partial region.

[0085] The first partial region 1211 and the second partial region 1212 may be regions determined depending on the direction in which the riblet sheet 1 is attached to the object OBJ.

[0086] As an example, when attaching a libretto sheet 1 to an object OBJ, the libretto sheet 1 is usually attached to the object OBJ starting from its edge (in other words, its outer edge). In this case, as shown in FIG. 13( a), the first partial region 1211 may be closer to the edge (outer edge) of the libretto sheet 1 than the second partial region 1212. Here, the possibility of air bubbles forming at the edge (outer edge) of the libretto sheet 1 that is attached to the object OBJ first is higher than the possibility of air bubbles forming in portions other than the edge (outer edge) of the libretto sheet 1 that is attached to the object OBJ after the edge (outer edge) of the libretto sheet 1. Therefore, as shown in FIG. 13( a), in order to efficiently remove air bubbles that form at the edge (outer edge) of the libretto sheet 1, the number of openings 151 formed per unit area in the first partial region 1211 may be greater than the number of openings 151 formed per unit area in the second partial region 1212.

[0087] It is to be noted that the opening 151 may not be formed in the first partial region 1211 or the second partial region 1212. The opening 151 may be formed only in one further divided partial region of the first partial region 1211 or the second partial region 1212. While the opening 151 is formed in one further divided partial region of the first partial region 1211 or the second partial region 1212, the opening 151 may not be formed in another further divided partial region of the first partial region 1211 or the second partial region 1212.

[0088] As another example, when attaching a libretto sheet 1 to an object OBJ, typically, one end 1E of the libretto sheet 1 is first attached to the object OBJ, and then the libretto sheets 1 are sequentially attached to the object OBJ along a predetermined attachment direction. In this case, as shown in FIG. 13( b), the first partial region 1211 may include the one end 1E of the libretto sheet 1 that is attached to the object OBJ first or may include an area near the one end 1E, and the second partial region 1212 may include an area away from the one end 1E along the attachment direction. Here, the likelihood of air bubbles forming near the one end 1E of the libretto sheet 1 that is attached to the object OBJ first is higher than the likelihood of air bubbles forming in portions of the libretto sheet 1 other than the one end 1E that are attached to the object OBJ following the one end 1E of the libretto sheet 1. Therefore, as shown in Figure 13 (b), in order to efficiently remove air bubbles that occur at the ends of the riblet sheet 1, the number of openings 151 formed per unit area in the first partial region 1211 may be greater than the number of openings 151 formed per unit area in the second partial region 1212.

[0089] However, the number of openings 151 formed per unit area in the first partial region 1211 may be fewer than the number of openings 151 formed per unit area in the second partial region 1212. In other words, the number of openings 151 formed per unit area in the second partial region 1212 may be greater than the number of openings 151 formed per unit area in the first partial region 1211. In this case, air bubbles that occur in portions other than one end 1E of the libretto sheet 1, which is attached to the object OBJ immediately after one end 1E of the libretto sheet 1, can be efficiently removed. Furthermore, since the first partial region 1211 has fewer openings 151, it may be possible to prevent the libretto sheet 1 from warping or deforming when attached to the object OBJ. The number of openings 151 formed per unit area in the first partial region 1211 may be the same as the number of openings 151 formed per unit area in the second partial region 1212. In this case, air bubbles that occur in various locations on the libretto sheet 1 can be efficiently removed.

[0090] (3-4) Shape of Through Hole 15 Next, a description will be given of the shape of the through hole 15, which is an example of the characteristics of the through hole 15. In particular, the following describes the shape of the cross section of the through hole 15 along the direction in which the through hole 15 penetrates the riblet sheet 1 (the Z-axis direction).

[0091] 5 and 6 described above, the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that the inner wall surface 16 of the through hole 15 is a surface that is along (typically parallel to) a predetermined intersecting direction that intersects with the surface of the riblet sheet 1. The predetermined intersecting direction may be the thickness direction of the riblet sheet 1, or the Z-axis direction. In this case, the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that the inner wall surface 16 of the through hole 15 is a surface that is along (typically parallel to) the Z-axis direction. Note that, in this embodiment, the "inner wall surface 16 of the through hole 15" means "the inner wall surface of the riblet sheet 1 facing the through hole 15." In other words, in this embodiment, the "inner wall surface 16 of the through hole 15" means "the inner wall surface of at least one of the adhesive layer 11 and the structural layer 12 facing the through hole 15."

[0092] Alternatively, as shown in Figures 14(a) to 14(d), the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that at least a portion of the inner wall surface 16 of the through hole 15 is inclined with respect to a predetermined intersecting direction that intersects with the surface of the riblet sheet 1. In other words, the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that at least a portion of the inner wall surface 16 of the through hole 15 is inclined with respect to the predetermined intersecting direction from the surface of the riblet sheet 1 (i.e., the surface 121 of the structural layer 12) to the back surface of the riblet sheet 1 (i.e., the back surface 112 of the adhesive layer 11). In particular, the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that at least a portion of the inner wall surface 16 of the through hole 15 is gradually inclined with respect to the predetermined intersecting direction from the surface of the riblet sheet 1 to the back surface of the riblet sheet 1. For example, the cross-sectional shape of the through hole 15 may be a shape that satisfies the condition that at least a portion of the inner wall surface 16 of the through hole 15 is inclined with respect to the Z-axis direction. In other words, the cross-sectional shape of the through-hole 15 may be tapered.

[0093] As a first example, as shown in FIG. 14( a), a pair of inner wall surface portions 16X of the inner wall surface 16 of the through hole 15 may be inclined with respect to a predetermined intersecting direction (Z-axis direction). The pair of inner wall surface portions 16X are surfaces that face each other along the X-axis direction, which is the extension direction of the convex structure 13. Note that when the fluid reduction effect of the riblet structure RB is exerted, the fluid normally flows along the convex structure 13 (i.e., flows along the extension direction of the convex structure 13), and therefore the pair of inner wall surface portions 16X may be considered to face each other along the direction of the fluid flow (the so-called streamline direction) on the surface of the riblet sheet 1. In particular, as shown in FIG. 14( a), the pair of inner wall surface portions 16X may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the through hole 15 decreases continuously (or in steps) from the surface of the riblet sheet 1 toward the back surface of the riblet sheet 1. Specifically, the pair of inner wall surface portions 16X may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 along the extension direction of the convex structure 13 decreases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. In other words, as shown in Figure 14 (a), the pair of inner wall surface portions 16X may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 formed on the front surface of the libretto sheet 1 is larger than the size of the openings 152 formed on the back surface of the libretto sheet 1. Specifically, the pair of inner wall surface portions 16X may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 along the extension direction of the convex structure 13 is larger than the size of the openings 152 along the extension direction of the convex structure 13.

[0094] 5 and 6, in this first example, as shown in FIG. 14(a), the inner wall surface portion 16X of the through hole 15 (particularly the inner wall surface portion 16Xa located downstream of the fluid flow) is less likely to function as a wall that blocks the fluid flow along the convex structure 13. Therefore, the fluid flow along the convex structure 13 is less likely to be blocked. As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB.

[0095] As a second example, as shown in Figure 14(b), a pair of inner wall surface portions 16X may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 increases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. Specifically, the pair of inner wall surface portions 16X may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 along the extension direction of the convex structures 13 increases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. In other words, as shown in Figure 14(b), the pair of inner wall surface portions 16X may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 formed on the front surface of the libretto sheet 1 is smaller than the size of the openings 152 formed on the back surface of the libretto sheet 1. Specifically, a pair of inner wall surface portions 16X may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of opening 151 along the extension direction of convex structure 13 is smaller than the size of opening 152 along the extension direction of convex structure 13.

[0096] In this second example, as shown in FIG. 14( b), compared to the examples shown in FIGS. 5 and 6, the fluid flowing along the convex structure 13 is less likely to flow into the through hole 15. This is because the size of the opening 151 that functions as the fluid inlet into the through hole 15 is relatively small. Therefore, the flow of fluid along the convex structure 13 is less likely to be blocked by the through hole 15 (particularly by the inner wall surface portion 16X). As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB. Furthermore, because the size of the opening 152 facing the air bubble is relatively large, it becomes easier to remove the air contained in the air bubble.

[0097] As a third example, as shown in FIG. 14( c), a pair of inner wall surface portions 16Y of the inner wall surface 16 of the through hole 15 may be inclined with respect to a predetermined intersecting direction (Z-axis direction). The pair of inner wall surface portions 16Y are surfaces that face each other along the Y-axis direction, which is the arrangement direction of the convex structures 13. Note that when the fluid reduction effect of the riblet structure RB is exerted, the fluid normally flows along the convex structures 13 (i.e., flows along the extension direction of the convex structures 13), and therefore the pair of inner wall surface portions 16Y may be considered to face each other along a direction that intersects the direction of the fluid flow (the so-called streamline direction) on the surface of the riblet sheet 1. In particular, as shown in FIG. 14( c), the pair of inner wall surface portions 16Y may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the through hole 15 decreases continuously (or in steps) from the surface of the riblet sheet 1 toward the back surface of the riblet sheet 1. Specifically, the pair of inner wall surface portions 16Y may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 along the arrangement direction of the convex structures 13 decreases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. In other words, as shown in Figure 14 (c), the pair of inner wall surface portions 16Y may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 formed on the front surface of the libretto sheet 1 is larger than the size of the openings 152 formed on the back surface of the libretto sheet 1. Specifically, the pair of inner wall surface portions 16Y may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 along the arrangement direction of the convex structures 13 is larger than the size of the openings 152 along the arrangement direction of the convex structures 13.

[0098] 5 and 6, in this third example, as shown in Fig. 14(c), the inner wall surface portion 16Y of the through hole 15 is less likely to function as a wall that blocks the flow of fluid along the convex structure 13. Therefore, the possibility of blocking the flow of fluid along the convex structure 13 is reduced. As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB.

[0099] As a fourth example, as shown in Figure 14(d), a pair of inner wall surface portions 16Y may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 increases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. Specifically, the pair of inner wall surface portions 16Y may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the through holes 15 along the arrangement direction of the convex structures 13 increases continuously (or in steps) from the front surface of the libretto sheet 1 toward the back surface of the libretto sheet 1. In other words, as shown in Figure 14(d), the pair of inner wall surface portions 16Y may be inclined with respect to the predetermined intersecting direction (Z-axis direction) so that the size of the openings 151 formed on the front surface of the libretto sheet 1 is smaller than the size of the openings 152 formed on the back surface of the libretto sheet 1. Specifically, a pair of inner wall surface portions 16Y may be inclined with respect to a predetermined intersecting direction (Z-axis direction) so that the size of opening 151 along the arrangement direction of convex structures 13 is smaller than the size of opening 152 along the arrangement direction of convex structures 13.

[0100] In the fourth example, as shown in FIG. 14( c), compared to the examples shown in FIGS. 5 and 6, the fluid flowing along the convex structure 13 is less likely to flow into the through hole 15. This is because the size of the opening 151 that functions as the fluid inlet into the through hole 15 is relatively small. Therefore, the flow of the fluid along the convex structure 13 is less likely to be blocked by the through hole 15 (particularly by the inner wall surface portion 16X). As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB. Furthermore, because the size of the opening 152 facing the air bubble is relatively large, it is easier to remove the air contained in the air bubble.

[0101] 14(b) and the fourth example shown in Fig. 14(d), the size of the opening 151 may be smaller than the width (i.e., the size in the X-axis direction) of a single convex structure 13, and the size of the opening 152 may be larger than the width (i.e., the size in the X-axis direction) of a single convex structure 13. However, in the second example shown in Fig. 14(b) and the fourth example shown in Fig. 14(d), the size of the opening 151 may be larger than the width (i.e., the size in the X-axis direction) of a single convex structure 13, and the size of the opening 152 may be smaller than the width (i.e., the size in the X-axis direction) of a single convex structure 13.

[0102] 14(a) and the third example shown in Fig. 14(c), the size of the opening 151 may be larger than the width (i.e., the size in the X-axis direction) of a single convex structure 13, and the size of the opening 152 may be smaller than the width (i.e., the size in the X-axis direction) of a single convex structure 13. However, in the first example shown in Fig. 14(a) and the third example shown in Fig. 14(c), the size of the opening 151 may be smaller than the width (i.e., the size in the X-axis direction) of a single convex structure 13, and the size of the opening 152 may be larger than the width (i.e., the size in the X-axis direction) of a single convex structure 13.

[0103] 14(a) and 14(b), the inclination directions of the pair of inner wall surface portions 16X relative to the axis along the Z axis are different. Specifically, in the first example shown in FIG. 14(a), the inner wall surface portion 16Xa of the pair of inner wall surface portions 16X located downstream in the fluid flow is inclined toward the −X side with respect to the axis along the Z axis, while the inner wall surface portion 16Xb of the pair of inner wall surface portions 16X located upstream in the fluid flow is inclined toward the +X side with respect to the axis along the Z axis. In the second example shown in FIG. 14(b), the inner wall surface portion 16Xa of the pair of inner wall surface portions 16X located downstream in the fluid flow is inclined toward the +X side with respect to the axis along the Z axis, while the inner wall surface portion 16Xb of the pair of inner wall surface portions 16X located upstream in the fluid flow is inclined toward the −X side with respect to the axis along the Z axis. However, the inclination directions of the pair of inner wall surface portions 16X relative to the axis along the Z axis may be the same. 15(a) to 15(c), a pair of inner wall surface portions 16X (i.e., inner wall surface portions 16Xa and 16Xb) may be inclined toward the downstream side of the fluid flow (the −X side in the example shown in FIG. 15(a)) with respect to an axis along the Z axis. Note that FIG. 15(a) shows an example in which the amount of inclination of the inner wall surface portion 16Xa with respect to the axis along the Z axis is the same as the amount of inclination of the inner wall surface portion 16Xb with respect to the axis along the Z axis. FIG. 15(b) shows an example in which the amount of inclination of the inner wall surface portion 16Xa with respect to the axis along the Z axis is greater than the amount of inclination of the inner wall surface portion 16Xb with respect to the axis along the Z axis. FIG. 15(c) shows an example in which the amount of inclination of the inner wall surface portion 16Xa with respect to the axis along the Z axis is smaller than the amount of inclination of the inner wall surface portion 16Xb with respect to the axis along the Z axis. Even in this case, the inner wall surface portion 16X of the through hole 15 (particularly the inner wall surface portion 16Xa located downstream of the fluid flow) is less likely to function as a wall that blocks the fluid flow along the convex structure 13. This reduces the possibility that the fluid flow along the convex structure 13 will be blocked. As a result, it is possible to prevent a deterioration in the drag reduction effect of the riblet structure RB.

[0104] Even when the inclination directions of the pair of inner wall surface portions 16X with respect to the Z-axis are different, the inclination amounts of the inner wall surface portions 16Xa and 16Xb with respect to the Z-axis may be the same or different. When the inclination amounts of the inner wall surface portions 16Xa and 16Xb are different, the inclination amounts of the inner wall surface portions 16Xa and 16Xb may be set so that the opening 152 is smaller than the opening 151 (i.e., the opening 152 is extremely small). As a result, the opening 152 formed in the adhesive layer 11 can be made as small as possible, while reducing the likelihood that the inner wall surface portion 16X of the through hole 15 (particularly the inner wall surface portion 16Xa located downstream of the fluid flow) will function as a wall blocking the fluid flow along the convex structure 13. Alternatively, when the inclination amount of the inner wall surface portion 16Xa and the inclination amount of the inner wall surface portion 16Xb are different, the inclination amounts of the inner wall surface portion 16Xa and the inner wall surface portion 16Xb may be set so that the opening 151 is smaller than the opening 152 (i.e., the opening 151 is extremely small). As a result, the possibility that the fluid flowing along the convex structure 13 will flow into the inside of the through hole 15 can be reduced.

[0105] Alternatively, one of the pair of inner wall surface portions 16X may be inclined with respect to an axis along the Z axis, while the other of the pair of inner wall surface portions 16X may not be inclined with respect to the axis along the Z axis. For example, as shown in FIG. 15( d ), the inner wall surface portion 16Xa located downstream of the fluid flow may be inclined toward the downstream side of the fluid flow (the −X side in the example shown in FIG. 15( a )), and the inner wall surface portion 16Xb located upstream of the fluid flow may not be inclined (i.e., may have a surface along the Z axis). Even in this case, the inner wall surface portion 16X of the through hole 15 (particularly the inner wall surface portion 16Xa located downstream of the fluid flow) is less likely to function as a wall that blocks the fluid flow along the convex structure 13. This reduces the possibility that the fluid flow along the convex structure 13 will be blocked. As a result, it is possible to prevent a deterioration in the resistance reduction effect of the riblet structure RB.

[0106] Similarly, in the examples shown in Figures 14(c) and 14(d), the inclination directions of the pair of inner wall surface portions 16Y relative to the axis along the Z axis are different. Specifically, in the third example shown in Figure 14(c), the inner wall surface portion 16Ya located on the +Y side of the pair of inner wall surface portions 16X is inclined toward the +Y side with respect to the axis along the Z axis, and the inner wall surface portion 16Yb located on the -Y side of the pair of inner wall surface portions 16X is inclined toward the -Y side with respect to the axis along the Z axis. In the fourth example shown in Figure 14(d), the inner wall surface portion 16Ya located on the +Y side of the pair of inner wall surface portions 16X is inclined toward the -Y side with respect to the axis along the Z axis, and the inner wall surface portion 16Yb located on the -Y side of the pair of inner wall surface portions 16X is inclined toward the +Y side with respect to the axis along the Z axis. However, the inclination directions of the pair of inner wall surface portions 16Y relative to the axis along the Z axis may be the same. For example, the pair of inner wall surface portions 16Y (i.e., inner wall surface portions 16Ya and 16Yb) may be inclined in the same direction relative to the axis along the Z axis. In this case, the amount of inclination of the inner wall surface portion 16Ya relative to the axis along the Z axis may be the same as the amount of inclination of the inner wall surface portion 16Yb relative to the axis along the Z axis. The amount of inclination of the inner wall surface portion 16Ya relative to the axis along the Z axis may be greater than the amount of inclination of the inner wall surface portion 16Yb relative to the axis along the Z axis. The amount of inclination of the inner wall surface portion 16Ya relative to the axis along the Z axis may be less than the amount of inclination of the inner wall surface portion 16Yb relative to the axis along the Z axis.

[0107] Furthermore, even when the inclination directions of the pair of inner wall surface portions 16Y with respect to the axis along the Z axis are different, the inclination amount of the inner wall surface portion 16Ya with respect to the axis along the Z axis and the inclination amount of the inner wall surface portion 16Yb with respect to the axis along the Z axis may be the same or different. When the inclination amounts of the inner wall surface portions 16Ya and 16Yb are different, the inclination amounts of the inner wall surface portions 16Ya and 16Yb may be set so that the opening 152 is smaller than the opening 151 (i.e., the opening 152 is extremely small). As a result, the opening 152 formed in the adhesive layer 11 can be made as small as possible, while reducing the possibility that the inner wall surface portion 16Y of the through hole 15 functions as a wall that blocks the flow of fluid along the convex structure 13. Alternatively, when the inclination amount of the inner wall surface portion 16Ya and the inclination amount of the inner wall surface portion 16Yb are different, the inclination amounts of the inner wall surface portion 16Ya and the inner wall surface portion 16Yb may be set so that the opening 151 is smaller than the opening 152 (i.e., the opening 151 is extremely small). As a result, the possibility that the fluid flowing along the convex structure 13 will flow into the through hole 15 can be reduced.

[0108] Alternatively, one of the pair of inner wall surface portions 16Y may be inclined relative to an axis along the Z axis, while the other of the pair of inner wall surface portions 16Y may not be inclined relative to an axis along the Z axis.

[0109] 14( a) and the third example shown in Fig. 14(c), when a plurality of through holes 15 are formed, all of the plurality of through holes 15 may satisfy the condition that the size of the opening 151 is larger than the size of the opening 152. Alternatively, while at least one of the plurality of through holes 15 satisfies the condition that the size of the opening 151 is larger than the size of the opening 152, at least another of the plurality of through holes 15 may not satisfy the condition that the size of the opening 151 is larger than the size of the opening 152.

[0110] 14(b) and the fourth example shown in Fig. 14(d), when a plurality of through holes 15 are formed, all of the plurality of through holes 15 may satisfy the condition that the size of the opening 151 is smaller than the size of the opening 152. Alternatively, while at least one of the plurality of through holes 15 satisfies the condition that the size of the opening 151 is smaller than the size of the opening 152, at least another of the plurality of through holes 15 may not satisfy the condition that the size of the opening 151 is smaller than the size of the opening 152.

[0111] In addition, when multiple through holes 15 are formed in one riblet sheet 1, the multiple openings 15 may include at least two through holes 15 having different shapes. For example, the multiple through holes 15 may include at least two of the through holes 15 shown in Figure 5, the through holes 15 shown in Figure 6, the through holes 15 shown in Figure 14(a), the through holes 15 shown in Figure 14(b), the through holes 15 shown in Figure 14(c), the through holes 15 shown in Figure 14(d), the through holes 15 shown in Figure 15(a), the through holes 15 shown in Figure 15(b), the through holes 15 shown in Figure 15(c), and the through holes 15 shown in Figure 15(d).

[0112] (4) Manufacturing Method of Riblet Sheet 1 The libretto sheet 1 may be manufactured using a processing device capable of performing removal processing. For example, the processing device may perform removal processing to remove a portion of the libretto sheet 1 (specifically, a portion of the structural layer 12) by irradiating processing light onto the libretto sheet 1 on which the riblet structure RB has not yet been formed. In this case, the processing device may perform removal processing to remove a portion of the libretto sheet 1 (typically, a portion of the structural layer 12) so that the riblet structure RB is formed on the surface of the libretto sheet 1 (specifically, the surface 121 of the structural layer 12). In this case, the processing device may be considered to function as a manufacturing device that manufactures the libretto sheet 1.

[0113] Alternatively, the libretto sheet 1 may be manufactured by imprint molding using a mold. That is, the libretto sheet 1 may be manufactured by an in-house imprint molding apparatus that performs imprint molding using a mold. The mold used to generate the imprint has a mold structure formed therein that has a shape complementary to the libretto structure RB. In this case, the mold structure formed in the mold may be pressed against the libretto sheet 1 (specifically, the structure layer 12) on which the libretto structure RB is not formed, thereby transferring the libretto structure RB corresponding to the mold structure to the libretto sheet 1. As a result, the libretto structure RB may be formed on the surface of the libretto sheet 1. In this case, the imprint molding apparatus may be considered to function as a manufacturing apparatus that manufactures the libretto sheet 1. Alternatively, the libretto structure RB may be formed by applying a photocurable resin to the material sheet 100, and irradiating the photocurable resin layer with curing light while pressing the mold 3a against the applied photocurable resin. Note that at least one of a rotating roller and a spindle may be used as the mold. In this case, the rotating body including at least one of a roller and a spindle may have groove shapes for transferring the riblet structure RB, as well as protrusion shapes for processing the through holes 15, formed at a predetermined interval.

[0114] Alternatively, the riblet sheet 1 may be manufactured by any other method.

[0115] When through holes 15 are formed in the riblet sheet 1, the through holes 15 may be formed after the riblet structure RB is formed. For example, in cases where a step of providing the riblet structure RB in the sheet using riblet processing means capable of processing riblets (such as a mold, optical processing, or mechanical processing) is performed, and then a step of providing the through holes 15 in the sheet using a means capable of processing holes, such as a mold, optical processing, or mechanical processing, which is the same as or different from the riblet processing means, is performed, it can be said that the through holes 15 are formed after the riblet structure RB is formed. When through holes 15 dividing the convex structures 13 are formed as described above, the through holes 15 dividing the convex structures 13 may be formed after the riblet structure RB including a series of convex structures 13 not divided by the through holes 15 is formed. In other words, the convex structures 13 may be divided after the riblet structure RB including a series of convex structures 13 not divided by the through holes 15 is formed. Furthermore, according to this manufacturing method, when the convex structure 13 is formed at a position away from the opening 151 as described above, there is an advantage that the through hole 15 can be formed without affecting the shape of the already formed convex structure 13. In other words, there is an advantage that the through hole 15 can be formed without damaging (or breaking) the already formed convex structure 13. Furthermore, when the riblet structure RB is formed using a photocurable resin as described above, by forming the through hole 15 after forming the riblet structure RB, there is less risk that the through hole 15 will be filled with the photocurable resin.

[0116] Alternatively, when through holes 15 are formed in the riblet sheet 1, the riblet structure RB and the through holes 15 may be formed simultaneously. For example, when a process is performed in which a mold having a structure corresponding to the riblet structure RB and the through holes 15 is pressed against a sheet to provide the riblet structure RB and the through holes 15 in the sheet at one time, it can be said that the riblet structure RB and the through holes 15 are formed simultaneously. When through holes 15 that divide the convex structures 13 are formed as described above, the riblet structure RB including the convex structures 13 divided by the through holes 15 may be formed simultaneously with the through holes 15 that divide the convex structures 13.

[0117] Alternatively, when through holes 15 are formed in the riblet sheet 1, the riblet structure RB may be formed after the through holes 15 are formed. For example, when a process of forming the through holes 15 in the sheet using a means capable of processing holes, such as a mold, optical processing, or mechanical processing, is performed, and then a process of forming the riblet structure RB in the sheet using a riblet processing means (such as a mold, optical processing, or mechanical processing) that can process riblets, which is the same as or different from the hole processing means, is performed, it can be said that the riblet structure RB is formed after the through holes 15 are formed. In this case, the riblet structure RB can be formed after the sheet has already been formed with the through holes 15. Furthermore, when through holes 15 that divide the convex structures 13 are formed as described above, a riblet structure RB including the convex structures 13 that are substantially divided by the already formed through holes 15 may be formed after the through holes 15 are formed.

[0118] The sheet portions of the riblet sheet 1 corresponding to the groove regions 140 may be formed from a material that is permeable to air but impermeable to water. In this case, air contained in bubbles remaining between the riblet sheet 1 and the object OBJ may be released to the space outside the riblet sheet 1 through the sheet portions that are formed from a material that is permeable to air but impermeable to water. In this case, the sheet portions that are formed from a material that is permeable to air but impermeable to water may be considered to function as through holes 15. The sheet portions that are formed from a material that is permeable to air but impermeable to water may be considered to function as through holes 15.

[0119] (5) Modifications Next, modifications of the riblet sheet 1 will be described.

[0120] (5-1) First Modification In the first modification, the riblet sheet 1 may be manufactured by simultaneously forming the riblet structure RB and the through holes 15 by imprint molding using two molds.

[0121] Specifically, in the first modified example, as shown in Fig. 16(a), a first mold 21a may be used in which a mold structure having a shape complementary to the riblet structure RB is formed, and a second mold 22a may be used in which a mold structure having a shape complementary to the through hole 15 is formed. Each of the first mold 21a and the second mold 22a may be a mold made of paper, a mold made of resin, a mold made of metal, or a mold made of some other material.

[0122] Then, as shown in FIG. 16( a), a material sheet 100, which is the material for the riblet sheet 1, is sandwiched between a first mold 21a and a second mold 22a. The material sheet 100 may include an adhesive layer 11 without through holes 15 and a structure layer 12 without riblet structures RB and through holes 15. As a result, as shown in FIG. 16( b), the mold structure formed in the first mold 21a transfers (i.e., forms) the riblet structures RB to the material sheet 100. Furthermore, the mold structure formed in the second mold 22a transfers (i.e., forms) the through holes 15 to the material sheet 100. At this time, at least one of the material sheet 100, the first mold 21a, and the second mold 22a may be heated to facilitate the transfer of the riblet structures RB and through holes 15 to the material sheet 100. Then, the first mold 21a and the second mold 22a are removed from the material sheet 100. As a result, a riblet sheet 1 having a riblet structure RB and through holes 15 formed therein is manufactured as shown in FIG. 16(c).

[0123] Furthermore, after the riblet structure RB and the through holes 15 are formed in the material sheet 100, at least one of the first mold 21a and the second mold 22a may not be removed from the material sheet 100. In this case, at least one of the first mold 21a and the second mold 22a that has not been removed from the material sheet 100 may be used as a protective member for protecting the libretto sheet 1. For example, the first mold 21a that has not been removed from the material sheet 100 may be used as a protective member for protecting the surface of the libretto sheet 1 (i.e., the structural layer 12). The second mold 22a that has not been removed from the material sheet 100 may be used as a protective member for protecting the back surface of the libretto sheet 1 (i.e., the adhesive layer 11). Alternatively, the second mold 22a that has not been removed from the material sheet 100 may be used as a peeling member for avoiding unintended adhesion of the adhesive surface included in the back surface of the libretto sheet 1 (i.e., the back surface 112 of the adhesive layer 11).

[0124] (5-2) Second Modification Next, the libretto sheet 1 in the second modification will be described. In the following description, the libretto sheet 1 in the second modification will be referred to as libretto sheet 1b. The following description will mainly focus on the differences between the above-described libretto sheet 1 and libretto sheet 1b. Therefore, unless otherwise specified, the features of libretto sheet 1b may be the same as the features of libretto sheet 1b. The same applies to the third and subsequent modifications.

[0125] In a second modified example, as shown in FIG. 17 which shows a riblet sheet 1b in the second modified example, the surface of the riblet sheet 1b (i.e., the surface 121 of the structure layer 12) may include a riblet surface 123b and a non-riblet surface 124b different from the riblet surface 123b. The riblet surface 123b is the surface on which the riblet structure RB is formed. As described above, the riblet surface 123b includes a convex region 130 on which the convex structures 13 are formed, and a groove region 140 on which the convex structures 13 are not formed (a groove structure 14 is formed). On the other hand, the non-riblet surface 124b is the surface on which the riblet structure RB is not formed. The non-riblet surface 124b does not have to include the convex region 130 and the groove region 140.

[0126] In this case, as shown in Figure 17, an adhesive layer 11 may be formed on the back surface of the riblet surface 123b of the back surface 122 of the structural layer 12 (i.e., the surface portion located on the back side of the riblet surface 123b). On the other hand, an adhesive layer 11 may not be formed on the back surface of the non-riblet surface 124b of the back surface 122 of the structural layer 12 (i.e., the surface portion located on the back side of the non-riblet surface 124b). In other words, the riblet sheet 1b may include a first sheet portion 103b in which the adhesive layer 11 and the structural layer 12 are laminated, and a second sheet portion 104b that includes the structural layer 12 but does not have the adhesive layer 11 formed thereon. In this case, the back surface of the riblet sheet 1 may include a first surface portion 113b (i.e., the back surface of the first sheet portion 103b) corresponding to the back surface of the adhesive layer 11, and a second surface portion 114b (i.e., the back surface of the second sheet portion 104b) corresponding to the back surface of the structural layer 12. In other words, the back surface of the libretto sheet 1b includes a first surface portion 113b which is an adhesive surface and a second surface portion 114b which is a non-adhesive surface (i.e., not an adhesive surface).

[0127] In particular, as shown in FIG. 17 , the surface of the riblet sheet 1b may include two riblet surfaces 123b and a non-riblet surface 124b located between the two riblet surfaces 123b. That is, the riblet sheet 1b may include two first sheet portions 103b and a second sheet portion 104b located between the two first sheet portions 103b. Alternatively, the surface of the riblet sheet 1b may include a plurality of riblet surfaces 123b and a plurality of non-riblet surfaces 124b such that the riblet surfaces 123b and the non-riblet surfaces 124b are alternately arranged in the direction along the surface of the riblet sheet 1b. That is, the riblet sheet 1b may include a plurality of first sheet portions 103b and a plurality of second sheet portions 104b such that the first sheet portions 103b and the second sheet portions 104b are alternately arranged in the direction along the surface of the riblet sheet 1b.

[0128] When the libretto sheet 1b in this second modified example is attached to the object OBJ, the first sheet portion 103b is attached to the object OBJ, while the second sheet portion 104b is not attached to the object OBJ. Here, if the coefficients of linear thermal expansion of the libretto sheet 1b and the object OBJ differ, the amount of heat-induced deformation of the libretto sheet 1b may differ from the amount of heat-induced deformation of the object OBJ. As a result, a force due to the difference in deformation acts on the libretto sheet 1b from the object OBJ, and the libretto sheet 1b may peel off from the object OBJ. However, in the second modified example, because the second sheet portion 104b is not attached to the object OBJ, the force due to the difference in deformation is absorbed by the second sheet portion 104b. As a result, the possibility of the libretto sheet 1b peeling off from the object OBJ is reduced or eliminated.

[0129] In addition, in the second modified example, through holes 15 may also be formed in the riblet sheet 1b.

[0130] 18(a), the through hole 15 may be formed in the first sheet portion 103b where the adhesive layer 11 and the structural layer 12 are laminated. In other words, the through hole 15 may be formed so that an opening 151 is formed in the riblet surface 123b which is the front surface of the first sheet portion 103b, and an opening 152 is formed in the first surface portion 113b which is the back surface of the first sheet portion 103b.

[0131] 18(b), in addition to or instead of the first sheet portion 103b, a through hole 15 may be formed in a second sheet portion 104b that includes the structural layer 12 but does not have the adhesive layer 11 formed therein. In other words, the through hole 15 may be formed so that an opening 151 is formed in a non-riblet surface 124b that is the front surface of the second sheet portion 104b, and an opening 152 is formed in a second surface portion 114b that is the back surface of the second sheet portion 104b.

[0132] (5-3) Third Modification Next, the libretto sheet 1 in the third modification will be described. In the following description, the libretto sheet 1 in the third modification will be referred to as the libretto sheet 1c.

[0133] In a third modified example, as shown in Fig. 19 showing a riblet sheet 1c in the third modified example, grooves 115c may be formed on the back surface 112 of the adhesive layer 11. The grooves 115c are a series of grooves that extend to the end of the back surface 112. Specifically, the grooves 115c are a series of grooves that extend to the end of the back surface 112 in the direction along the back surface 112.

[0134] Even if air bubbles remain between the riblet sheet 1c and the object OBJ as a result of attaching the riblet sheet 1c of this third modified example to the object OBJ, the air contained in the bubbles (or any fluid including any gas or liquid, the same applies below) is removed from the space between the riblet sheet 1c and the object OBJ via the grooves 115c. In other words, the grooves 115c function as gas release paths for removing the air contained in the bubbles. In other words, the grooves 115c function as air holes for releasing the air contained in the bubbles. As a result, the third modified example also provides the same effects as those obtained by forming the through holes 15 that function as the gas release paths described above.

[0135] The riblet sheet 1c in which the grooves 115c are formed may also have the through holes 15. Alternatively, the riblet sheet 1c in which the grooves 115c are formed may not have the through holes 15 formed.

[0136] 19 , a plurality of grooves 115c may be formed on the back surface 112 of the adhesive layer 11. However, a single groove 115c may be formed on the back surface 112 of the adhesive layer 11.

[0137] When multiple grooves 115c are formed, the multiple grooves 115c may be formed in the same manner as the multiple through holes 15 described above with reference to Figures 11 to 13.

[0138] For example, the multiple grooves 115c may be distributed at equal intervals on the back surface 112 of the adhesive layer 11. The multiple grooves 115c may include multiple grooves 115c distributed at equal intervals on the back surface 112 of the adhesive layer 11. For example, the multiple grooves 115c may include multiple first grooves 115c distributed at equal intervals along the X-axis direction. For example, the multiple grooves 115c may include multiple second grooves 115c distributed at equal intervals along the Y-axis direction. For example, the multiple grooves 115c may include multiple third grooves 115c distributed at equal intervals along any direction along the XY plane. For example, the multiple grooves 115c may include multiple fourth grooves 115c distributed at equal intervals along the X-axis direction and multiple fifth grooves 115c distributed at equal intervals along the Y-axis direction. For example, the plurality of grooves 115c may include a plurality of sixth grooves 115c distributed at equal intervals along any first direction along the XY plane, and a plurality of seventh grooves 115c distributed at equal intervals along any second direction along the XY plane and different from the first direction.

[0139] For example, the plurality of grooves 115c may be periodically distributed on the back surface 112 of the adhesive layer 11. The plurality of grooves 115c may include a plurality of grooves 115c that are periodically distributed on the back surface 112 of the adhesive layer 11. In other words, the distribution pattern of the plurality of grooves 115c on the back surface 112 of the adhesive layer 11 may be a periodic distribution pattern. For example, the plurality of grooves 115c may be formed such that unit groove groups each including at least one groove 115c appear repeatedly on the back surface 112 of the adhesive layer 11.

[0140] For example, the plurality of grooves 115c may be distributed unevenly on the back surface 112 of the adhesive layer 11. As an example, the plurality of grooves 115c may be formed such that the distribution pattern of the plurality of grooves 115c formed in a first surface region of the back surface 112 of the adhesive layer 11 is different from the distribution pattern of the plurality of grooves 115c formed in a second surface region of the back surface 112 of the adhesive layer 11 that is different from the first surface region.

[0141] The first surface area and the second surface area may be areas determined depending on the direction in which the riblet sheet 1 is attached to the object OBJ.

[0142] As an example, as explained with reference to FIG. 13( a), when attaching a libretto sheet 1 to an object OBJ, the libretto sheet 1 is usually attached to the object OBJ starting from its edge (in other words, its outer edge). In this case, the first surface region may be closer to the edge (outer edge) of the libretto sheet 1 than the second surface region. Here, the possibility of air bubbles forming at the edge (outer edge) of the libretto sheet 1 that is attached to the object OBJ first is higher than the possibility of air bubbles forming in portions other than the edge (outer edge) of the libretto sheet 1 that is attached to the object OBJ after the edge (outer edge) of the libretto sheet 1. Therefore, to efficiently remove air bubbles that form at the edge (outer edge) of the libretto sheet 1, the number of grooves 115c formed per unit area in the first surface region may be greater than the number of grooves 115c formed per unit area in the second surface region.

[0143] 13(b), when attaching a libretto sheet 1 to an object OBJ, typically, one end 1E of the libretto sheet 1 is attached to the object OBJ first, and then the libretto sheets 1 are sequentially attached to the object OBJ along a predetermined attachment direction. In this case, the first surface region may include the one end 1E of the libretto sheet 1 that is attached to the object OBJ first or may include an area near the one end 1E, and the second surface region may include an area away from the one end 1E along the attachment direction. Here, the possibility of air bubbles forming near the one end 1E of the libretto sheet 1 that is attached to the object OBJ first is higher than the possibility of air bubbles forming in portions other than the one end 1E of the libretto sheet 1 that are attached to the object OBJ after the one end 1E of the libretto sheet 1. Therefore, in order to efficiently remove air bubbles that occur at the ends of the riblet sheet 1, the number of grooves 115c formed per unit area in the first surface region may be greater than the number of grooves 115c formed per unit area in the second surface region.

[0144] However, the number of grooves 115c formed per unit area in the first surface region may be smaller than the number of grooves 115c formed per unit area in the second surface region, and the number of grooves 115c formed per unit area in the first surface region may be the same as the number of grooves 115c formed per unit area in the second surface region.

[0145] Furthermore, one or more grooves 115c formed on the back surface 112 of the adhesive layer 11 may be connected to openings 152 on the adhesive layer 11 side of the through holes 15 in the riblet sheet 1. In this case, it is possible to efficiently release air from the space between the riblet sheet 1 and the object OBJ through the grooves 115c. Furthermore, one or more grooves 115c formed on the back surface 112 of the adhesive layer 11 may be connected to the back surface of the non-riblet surface 124b in the second modified example, on which the adhesive layer 11 is not provided. In this case as well, it is possible to efficiently release air from bubbles.

[0146] (5-4) Fourth Modification Next, the libretto sheet 1 in the fourth modification will be described. In the following description, the libretto sheet 1 in the fourth modification will be referred to as the libretto sheet 1d.

[0147] In a fourth modified example, as shown in Figure 20 showing a libretto sheet 1d in the fourth modified example, the adhesive layer 11 may include a first adhesive layer portion 116d and a second adhesive layer portion 117d. The first adhesive layer portion 116d has a first adhesive property. On the other hand, the second adhesive layer portion 117d has a second adhesive property different from the first adhesive property. As described above, because the back surface 112 of the adhesive layer 11 functions as an adhesive surface, the back surface 112 of the adhesive layer 11 may be considered to include the back surface of the first adhesive layer portion 116d (i.e., the first surface portion having the first adhesive property) and the back surface of the second adhesive layer portion 117d (i.e., the second surface portion having the second adhesive property).

[0148] The adhesive performance of the adhesive layer 11 depends on the thickness of the adhesive layer 11. Therefore, the thickness of the first adhesive layer portion 116d and the thickness of the second adhesive layer portion 117d may be different. Specifically, the first adhesive layer portion 116d may have a first thickness. On the other hand, the second adhesive layer portion 117d may have a second thickness that is different from the first thickness.

[0149] As shown in FIG. 20 , the first adhesive layer portion 116d may include a portion of the adhesive layer 11 that faces the groove region 140 where the convex structures 13 are not formed. The first adhesive layer portion 116d may include a portion of the adhesive layer 11 that overlaps the groove region 140 along the thickness direction of the riblet sheet 1d. In other words, the first adhesive layer portion 116d may include a portion of the adhesive layer 11 on which the groove region 140 is formed. On the other hand, the second adhesive layer portion 117d may include another portion of the adhesive layer 11 that faces the convex region 130 on which the convex structures 13 are formed. The second adhesive layer portion 117d may include a portion of the adhesive layer 11 that overlaps the convex region 130 along the thickness direction of the riblet sheet 1d. In other words, the second adhesive layer portion 117d may include a portion of the adhesive layer 11 on which the convex region 130 is formed.

[0150] In this case, the thickness of the second adhesive layer portion 117d overlapping the convex region 130 may be thicker than the thickness of the first adhesive layer portion 116d overlapping the groove region 140. That is, the adhesive layer 11 may include a first adhesive layer portion 116d having a first thickness and a second adhesive layer portion 117d having a second thickness thicker than the first thickness. Typically, the thickness of the first adhesive layer portion 116d facing the groove region 140 is set to the standard value of the thickness of the adhesive layer 11, and the thickness of the second adhesive layer portion 117d facing the convex region 130 may be thicker than the standard value of the thickness of the adhesive layer 11. This is because, since the convex structure 13 is formed in the convex region 130, even if the thickness of the second adhesive layer portion 117d overlapping the convex region 130 is increased, the thickness of the structure layer 12 does not become excessively thin.

[0151] Generally, the thicker the adhesive layer 11, the higher the adhesive performance of the adhesive layer 11. Therefore, the second adhesive performance of the second adhesive layer portion 117d, which is thicker than the first adhesive layer portion 116d, is higher than the first adhesive performance of the first adhesive layer portion 116d, which is thinner than the second adhesive layer portion 117d. Therefore, the adhesive layer 11 may include a first adhesive layer portion 116d having a first adhesive performance and a second adhesive layer portion 117d having a second adhesive performance higher than the first adhesive performance. Typically, the adhesive layer 11 may include a first adhesive layer portion 116d having standard adhesive performance that the adhesive layer 11 is normally expected to have, and a second adhesive layer portion 117d having adhesive performance higher than the standard adhesive performance.

[0152] The libretto sheet 1d of the fourth modified example improves the adhesive performance of the adhesive layer 11 compared to when the thickness of the adhesive layer 11 is constant (for example, set to a standard value). As a result, the libretto sheet 1d is less likely to be unintentionally peeled off from the object OBJ. In other words, the libretto sheet 1d can be firmly attached to the object OBJ.

[0153] The riblet sheet 1d of the fourth modified example may also have the through holes 15 formed therein. Alternatively, the riblet sheet 1d of the fourth modified example may not have the through holes 15 formed therein.

[0154] In the fourth modified example, the shape of the back surface portion of the riblet sheet 1 where the second adhesive layer portion 117d is located is not limited to a triangular cross section, and may be a rectangular, semicircular, or polygonal cross section. The second adhesive layer portion 117d may also be located in a portion of the adhesive layer 11 facing the groove region 140 where the convex structures 13 are not formed.

[0155] (5-5) Fifth Modification Next, the libretto sheet 1 in the fifth modification will be described. In the following description, the libretto sheet 1 in the fifth modification will be referred to as the libretto sheet 1e.

[0156] In the above description, the riblet structure RB includes a convex structure 13 extending along a predetermined extension direction. On the other hand, in the fifth modified example, as shown in FIG. 21 which shows a riblet sheet 1e in the fifth modified example, the riblet structure RB may include a convex structure 13e in addition to or instead of the convex structure 13. The convex structure 13e may differ from the convex structure 13 extending along a predetermined extension direction in that it does not have to extend along the predetermined extension direction. Other features of the convex structure 13e may be the same as other features of the convex structure 13.

[0157] A plurality of convex structures 13e may be formed on the riblet sheet 1e. The plurality of convex structures 13e may include at least two convex structures 13e arranged along the X-axis direction. The plurality of convex structures 13e may include at least two convex structures 13e arranged along the Y-axis direction. The plurality of convex structures 13e may include at least two convex structures 13e arranged along any direction along the XY plane.

[0158] In particular, the plurality of convex structures 13e may include at least two convex structures 13e arranged along an arbitrary first direction along the XY plane, and at least two convex structures 13e arranged along an arbitrary second direction along the XY plane and different from the first direction. For example, the plurality of convex structures 13e may include at least two convex structures 13e arranged along the X-axis direction, and at least two convex structures 13e arranged along the Y-axis direction.

[0159] When the multiple convex structures 13e include both at least two convex structures 13e arranged along the first direction and at least two convex structures 13e arranged along the second direction, the resistance reduction effect of the riblet structure RB can be adequately achieved even when the fluid flow direction changes on the surface of the riblet sheet 1e. Alternatively, the resistance reduction effect of the riblet structure RB can be adequately achieved even when the orientation of the riblet sheet 1e changes with respect to the fluid flow direction. For example, in any of the following situations: a first situation in which the fluid flows along the X-axis direction on the surface of the riblet sheet 1e; a second situation in which the fluid flows along the Y-axis direction on the surface of the riblet sheet 1e; and a third situation in which the fluid flows along a direction intersecting both the X-axis and Y-axis directions on the surface of the riblet sheet 1e, the fluid can flow through the spaces between the multiple convex structures 13e (i.e., within the groove structure). As a result, the resistance reduction effect of the riblet structure RB can be adequately achieved in any of the first to third situations. For example, even a moving body that may be exposed to crosswinds while traveling can enjoy the effect of reducing resistance.

[0160] The riblet sheet 1e of the fifth modified example may also have the through holes 15. Alternatively, the riblet sheet 1e of the fifth modified example may not have the through holes 15 formed therein.

[0161] (5-6) Sixth Modification In the sixth modification, as shown in FIG. 22 which shows a libretto sheet 1 in the sixth modification, the surface 121 of the structural layer 12 may be covered with a protective sheet 31f. The protective sheet 31f may be a member for protecting the structural layer 12. In particular, the surface 121 of the structural layer 12 may be covered with the protective sheet 31f before the libretto sheet 1 is attached to the object OBJ. In this case, the protective sheet 31f may be removed from the structural layer 12 after the libretto sheet 1 is attached to the object OBJ. Note that the first mold 21a described in the first modification may be used as the protective sheet 31f, or a member different from the first mold 21a may be used.

[0162] Furthermore, in the sixth modified example, as shown in FIG. 22 , the back surface 112 of the adhesive layer 11 may be covered with a protective sheet 32f. The protective sheet 32f may be a member for protecting the adhesive layer 11. The protective sheet 32f may be a member for preventing unintended adhesion of the adhesive layer 11. In particular, the back surface 112 of the adhesive layer 11 may be covered with the protective sheet 32f before the libretto sheet 1 is attached to the object OBJ. In this case, the protective sheet 32f may be removed from the adhesive layer 11 after the libretto sheet 1 is attached to the object OBJ. This has the advantage that pressure can be easily applied when attaching the libretto sheet 1 to the object OBJ. Note that the second mold 22a described in the first modified example may be used as the protective sheet 32f, or a member different from the second mold 22a may be used.

[0163] The protective sheet 31f for protecting the structure layer 12 may have a shape complementary to the riblet structure RB formed in the structure layer 12. As an example, a resin protective sheet may be used as the protective sheet 31f, and the resin protective sheet 31f may be formed on the structure layer 12, thereby transferring the riblet structure RB formed in the structure layer 12 to the protective sheet 31f. In this case, the protective sheet 31f removed from the structure layer 12 shows the initial shape of the riblet structure RB formed in the structure layer 12. Therefore, the protective sheet 31f removed from the structure layer 12 may be used as a replica showing the initial shape of the riblet structure RB formed in the structure layer 12. Specifically, the protective sheet 31f may be used as a replica to guarantee the quality of the riblet structure RB by showing the initial shape of the riblet structure RB. In other words, the protective sheet 31f may be used to ensure the traceability of the quality of the riblet structure RB.

[0164] The riblet sheet 1 f of the sixth modified example may also have the through holes 15. Alternatively, the riblet sheet 1 f of the sixth modified example may not have the through holes 15 formed therein.

[0165] (5-7) Seventh Modification Next, the libretto sheet 1 in the seventh modification will be described. In the following description, the libretto sheet 1 in the seventh modification will be referred to as the libretto sheet 1g.

[0166] In the seventh modified example, as shown in Figure 23 which shows a riblet sheet 1g in the seventh modified example, part of the adhesive used to form the adhesive layer 11 may protrude to the sides of the adhesive layer 11 and the structural layer 12. In this case, the adhesive protruding to the sides of the adhesive layer 11 and the structural layer 12 may function as an edge sealer 17g. The edge sealer 17g may function to prevent air and the like from entering between the object OBJ and the riblet sheet 1e.

[0167] The edge sealer 17g may be formed so that the height of the edge sealer 17g decreases with increasing distance from the adhesive layer 11 and the structural layer 12. In other words, the edge sealer 17g may be formed so that the surface of the edge sealer 17g has a gentle slope.

[0168] In addition, the surface of the edge sealer 17g may be configured to have a slope from the surface of the object OBJ to the riblet sheet 1g.

[0169] The riblet sheet 1g of the seventh modified example may also have the through holes 15 formed therein. Alternatively, the riblet sheet 1g of the seventh modified example may not have the through holes 15 formed therein.

[0170] (5-8) Eighth Modification In the above description, the libretto sheet 1, in which the adhesive layer 11 and the structural layer 12 are laminated, is attached to the object OBJ. On the other hand, in the eighth modification, a libretto sheet 1h that includes the structural layer 12 but does not include the adhesive layer 11 may be attached to the object OBJ.

[0171] 24A, an adhesive 41h may be disposed between the object OBJ and the rear surface 122 of the structure layer 12. In particular, the adhesive 41h may be disposed at or near the center of the rear surface 122 of the structure layer 12 in a plan view.

[0172] 24(b), a force may be applied to the structural layer 12 to press the structural layer 12 against the object OBJ. In this case, the structural layer 12 may be protected by a protective sheet 31f (see FIG. 22) to prevent the riblet structure RB formed on the surface 121 of the structural layer 12 from being damaged by the force applied to the structural layer 12. Alternatively, a force may be applied to the object OBJ to press the structural layer 12 against the object OBJ.

[0173] As a result, as shown in Figure 24(b), the adhesive 41h disposed between the back surface 122 of the structural layer 12 and the object OBJ is gradually spread between the back surface 122 of the structural layer 12 and the object OBJ. Thereafter, the adhesive 41h is gradually spread (i.e., crushed) and ultimately becomes the adhesive layer 11 that bonds the back surface 122 of the structural layer 12 and the object OBJ, as shown in Figure 24(c). Note that in the state shown in Figure 24(c), the libretto sheet 1h including the adhesive layer 11 and the structural layer 12 formed by spreading the adhesive 41h may be considered equivalent to the libretto sheet 1 described above.

[0174] According to the eighth modified example, the adhesive 41h is gradually spread (i.e., crushed), so that there is little possibility of air bubbles remaining between the riblet sheet 1h and the object OBJ. As a result, the eighth modified example can also achieve the same effect as that obtained by forming the through holes 15 that function as the gas release paths described above.

[0175] When combining the eighth modified example with the sixth modified example, when the riblet sheet 1h is attached to the object OBJ, the adhesive 41h may be applied to the portion where the protective sheet 32f is present. In other words, the protective sheet 32f may be located at the location where the adhesive 41h is applied.

[0176] The through holes 15 may also be formed in the riblet sheet 1h of the eighth modified example. In this case, the through holes 15 may be processed and provided in the riblet sheet 1 after the adhesive layer 11 is formed by spreading the adhesive 41h. This configuration can prevent or reduce adhesion of the adhesive 41h to the inside of the through holes 15. Alternatively, the riblet sheet 1h of the eighth modified example may not have the through holes 15 formed therein.

[0177] (5-9) Ninth Modification Next, the libretto sheet 1 in the ninth modification will be described. In the following description, the libretto sheet 1 in the ninth modification will be referred to as the libretto sheet 1i.

[0178] In the ninth modified example, as shown in Figure 25 which shows a riblet sheet 1i in the ninth modified example, the riblet sheet 1i may include an additional functional layer 18i in addition to the adhesive layer 11 and the structural layer 12. The additional functional layer 18i may be formed on the surface 121 of the structural layer 12. In particular, the additional functional layer 18i may be formed on the surface 121 of the structural layer 12 on which the riblet structure RB is formed. In other words, the riblet sheet 1i may have a laminated structure in which the adhesive layer 11, the structural layer 12, and the additional functional layer 18i are laminated.

[0179] The libretto sheet 1i may include a single additional functional layer 18i. Alternatively, the libretto sheet 1i may include multiple additional functional layers 18i. For example, multiple stacked additional functional layers 18i may be formed on the surface 121 of the structural layer 12.

[0180] The additional functional layer 18i may be a layer for adding an additional function to the libretto sheet 1i. For example, the additional functional layer 18i may include a paint layer containing paint of a predetermined color. In this case, the additional functional layer 18i may be considered to add the additional function of design to the libretto sheet 1i. For example, the additional functional layer 18i may include a high-hardness layer for preventing damage to the libretto structure RB. In this case, the additional functional layer 18i may be considered to add the additional function of durability to the libretto sheet 1i. For example, the additional functional layer 18i may include an electrical insulating layer for preventing static buildup in the libretto sheet 1i. In this case, the additional functional layer 18i may be considered to add the additional function of antistatic properties to the libretto sheet 1i. For example, the additional functional layer 18i may include an anti-reflection layer for preventing light reflection on the surface of the libretto sheet 1i. In this case, the additional functional layer 18i may be considered to add the additional function of anti-reflection properties to the libretto sheet 1i. For example, the additional functional layer 18i may include an anti-glare layer for reducing the glossiness of the surface of the libretto sheet 1i. In this case, the additional functional layer 18i may be considered to add an additional function of gloss prevention to the libretto sheet 1i.

[0181] A libretto sheet 1i including an additional functional layer 18i may also be manufactured using the same manufacturing method as a libretto sheet 1 not including an additional functional layer 18i. For example, as shown in FIG. 26(a), the libretto sheet 1i may be manufactured by pressing a mold 21i against a material sheet 100i, which is the material of the libretto sheet 1i. The material sheet 100i may include an adhesive layer 11, a structural layer 12, and an additional functional layer 18i, in which no libretto structure RB is formed. The mold 21i may be a mold in which a mold structure having a shape complementary to the libretto structure RB is formed. As a result, the libretto structure RB may be transferred (formed) to the structural layer 12 and the additional functional layer 18i, as shown in FIG. 26(b).

[0182] The riblet sheet 1i of the ninth modified example may also have the through holes 15 formed therein. Alternatively, the riblet sheet 1i of the ninth modified example may not have the through holes 15 formed therein.

[0183] (5-10) Other Modifications In the above description, the libretto sheet 1 includes the adhesive layer 11 and the structural layer 12. However, the libretto sheet 1 does not have to include the adhesive layer 11. That is, the libretto sheet 1 may include the structural layer 12 but not the adhesive layer 11. In other words, a libretto sheet 1 may be manufactured that includes the structural layer 12 but does not include the adhesive layer 11. Even in this case, the structural layer 12 may be attached to the object OBJ (e.g., a moving object) using any attachment method. For example, the structural layer 12 may be attached to the object OBJ (e.g., a moving object) using the method described in the eighth modification. Alternatively, a new adhesive layer 11 may be formed on a libretto sheet 1 that includes the structural layer 12 but does not include the adhesive layer 11, and then the structural layer 12 may be attached to the object OBJ (e.g., a moving object) via the newly formed adhesive layer 11.

[0184] Furthermore, the openings 151 of the through holes 15 formed in the riblet sheet 1 may reach the convex structure 13. In other words, at least one of the side surfaces 191 and 192 of the convex structure 13 may be hollowed out by the openings 151. In this case, when the through holes 15 are formed after the riblet structure RB is formed to manufacture the riblet sheet 1, it is possible to simplify the control of the processing of the through holes 15. When multiple openings 151 are formed in the riblet sheet 1, the openings 151 at predetermined positions may be openings that hollow out at least one of the side surfaces 191 and 192 of the convex structure 13.

[0185] (6) Supplements The following supplementary notes are added to the above-described embodiments. [Supplementary Note A1] A sheet member having a riblet structure, the sheet member having a laminated structure including a structural layer having the riblet structure formed on its surface and an adhesive layer formed on the back surface of the structural layer so that its surface faces the back surface of the structural layer and for attaching the structural layer to an object, wherein grooves are formed on the back surface of the adhesive layer. [Supplementary Note A2] The sheet member described in Supplementary Note A1, wherein the grooves extend to an end of the back surface of the adhesive layer in a direction along the back surface of the adhesive layer. [Supplementary Note A3] The sheet member described in Supplementary Note A1 or A2, wherein a plurality of the grooves are formed on the back surface of the adhesive layer. [Supplementary Note A4] The sheet member described in Supplementary Note A3, wherein the plurality of grooves include at least one first groove formed on a first surface portion of the back surface of the adhesive layer and at least one second groove formed on a second surface portion of the back surface of the adhesive layer that is different from the first surface portion, wherein the distribution pattern of the at least one first groove differs from the distribution pattern of the at least one second groove. [Appendix A5] The sheet member according to Appendix A4, wherein the first surface portion is closer to an end of the adhesive layer than the second surface portion, and the number of the first grooves per unit area is greater than the number of the second grooves per unit area. [Appendix B1] A sheet member having a riblet structure, comprising: a front surface including a first region and a second region; a back surface; and through holes formed between the front surface and the back surface, wherein the first region is a surface of a convex structure protruding from the second region formed as at least a part of the riblet structure, and openings of the through holes are formed in the second region. [Appendix B2] The sheet member according to Appendix B1, wherein the first region comprises a plurality of partial regions, and the second region includes at least one region between two adjacent partial regions of the plurality of partial regions. [Appendix B3] The sheet member according to Appendix B1 or B2, wherein the second region is a region where the convex structures are not formed. [Appendix B4] The sheet member according to any one of Appendices B1 to B3, wherein the opening is not formed in the first region.[Appendix B5] The sheet member according to any one of Appendices B1 to 4, wherein the width of the opening in a direction intersecting the extension direction of the convex structures is less than 100 μm. [Appendix B6] The sheet member according to any one of Appendices B1 to 5, wherein a plurality of the openings are formed in the second region. [Appendix B7] The sheet member according to Appendices B6, wherein the plurality of openings are distributed at equal intervals on the surface of the sheet member. [Appendix B8] The sheet member according to Appendices B6 or 7, wherein the second region comprises a plurality of partial regions in a direction intersecting the extension direction of the convex structures, and the plurality of openings are distributed at equal intervals in the direction intersecting the extension direction of the convex structures. [Appendix B9] The sheet member according to Appendix B6 or 7, wherein the plurality of openings include a plurality of first openings formed in a first partial region of the second region and a plurality of second openings formed in a second partial region of the second region that is different from the first partial region, and wherein a distribution pattern of the plurality of first openings differs from a distribution pattern of the plurality of second openings. [Appendix B10] The sheet member according to Appendix B9, wherein the first partial region is closer to an edge of the sheet member than the second partial region, and wherein the number of the first openings per unit area is greater than the number of the second openings per unit area. [Appendix B11] A sheet member having a riblet structure, comprising through holes formed between a front surface and a back surface. [Appendix B12] The sheet member according to Appendix B11, wherein the surface includes a first region and a second region, the first region is a surface of a convex structure formed as at least a part of the riblet structure and protruding from the second region, the second region includes a plurality of partial regions, and the opening of the through hole is formed across the plurality of partial regions of the second region. [Appendix B13] The sheet member according to Appendix B12, wherein the convex structures include a plurality of convex structures extending in the extension direction in a direction intersecting the extension direction of the convex structures, and the opening is located between two of the plurality of convex structures.[Appendix B14] The sheet member according to any one of Appendices B11 to 13, wherein the surface is arranged, in a direction intersecting the extension direction of the convex structures, with a plurality of partial regions of the first region extending in the extension direction and a plurality of partial regions of the second region extending in the extension direction alternately, and at least one of the plurality of partial regions of the first region is separated by the through hole. [Appendix B15] The sheet member according to any one of Appendices B11 to 14, wherein the surface is arranged, in a direction intersecting the extension direction of the convex structures, with a plurality of partial regions of the first region extending in the extension direction and a plurality of partial regions of the second region extending in the extension direction alternately, and at least one of the plurality of partial regions of the first region is not connected in the extension direction. [Appendix B16] The sheet member according to any one of Appendices B11 to 15, wherein the sheet member has a plurality of partial regions in the first region, and the second region includes at least one region between two adjacent partial regions of the plurality of partial regions. [Appendix B17] The sheet member according to any one of Appendices B11 to 16, wherein the second region is a region in which the convex structures are not formed. [Appendix B18] The sheet member according to any one of Appendices B11 to 17, wherein the openings and the convex structures are separated by a predetermined distance or more in a direction along the surface of the sheet member. [Appendix B19] The sheet member according to any one of Appendices B11 to 18, wherein the convex structures extend along a predetermined extension direction that is a direction along the surface of the sheet member, and wherein a height of an end structure portion that is at least a part of the convex structures and includes an end of the convex structures along the extension direction gradually decreases as the end structure portion approaches the opening along the extension direction. [Appendix B20] The sheet member according to any one of Appendices B11 to B19, wherein an end of the opening is located in the second region. [Appendix B21] The sheet member according to any one of Appendices B11 to B20, wherein an end of the opening is spaced apart from the convex structure.[Appendix B22] The sheet member according to Appendix B20 or B21, wherein the convex structures extend on the surface of the sheet member along a predetermined extension direction, and the ends of the openings are ends of the openings in a direction intersecting the extension direction. [Appendix B23] The sheet member according to any one of Appendix B1 to B22, wherein the through holes have openings on the surface and the back surface, and at least a part of the inner wall surface of the through holes is inclined with respect to an intersecting direction intersecting the surface of the sheet member from the opening on the surface toward the opening on the back surface. [Appendix B24] The sheet member according to Appendix B23, wherein the opening on the back surface is smaller than the opening on the surface. [Appendix B25] The sheet member according to Appendix B23, wherein the opening on the back surface is larger than the opening on the surface. [Appendix B26] The sheet member according to any one of Appendix B23 to B25, wherein a pair of inner wall surface portions facing each other along the extension direction of the convex structures are inclined with respect to the intersecting direction. [Appendix B27] The sheet member according to any one of Appendices B21 to B24, wherein at least a portion of the inner wall surface gradually slopes from the opening on the front surface toward the opening on the back surface. [Appendix B28] The front surface has a first surface on which the riblet structure is formed and a second surface different from the first surface on which the riblet structure is not formed, the back surface has a third surface that is the back surface of the first surface and a fourth surface that is the back surface of the second surface, the third surface is an adhesive surface, and at least a portion of the fourth surface is a non-adhesive surface, and the sheet member can be attached to an object using the adhesive surface. [Appendix B29] The sheet member according to Appendices B28, wherein the sheet member has a plurality of partial surfaces on the first surface, and the second surface includes at least one surface between two adjacent partial surfaces of the plurality of partial surfaces. [Appendix B30] The sheet member according to any one of Appendices B1 to 29, wherein the back surface has an adhesive surface, and a groove is formed on the back surface of the adhesive layer. [Appendix B31] The sheet member according to Appendices B30, wherein the groove is connected to an end of the back surface of the adhesive layer in a direction along the back surface of the adhesive layer.[Appendix B32] The sheet member according to any one of Appendices B1 to 31, wherein the back surface has an adhesive surface of an adhesive layer, and the adhesive layer includes a first adhesive portion having a first thickness and a second adhesive portion having a second thickness different from the first thickness. [Appendix B33] The sheet member according to any one of Appendices B1 to 21, wherein the back surface has an adhesive surface, and the adhesive surface includes a first adhesive portion having first adhesive performance and a second adhesive portion having second adhesive performance different from the first adhesive performance. [Appendix B34] A sheet member having a riblet structure, wherein the front surface has a first surface on which the riblet structure is formed and a second surface different from the first surface, the back surface has a third surface opposite the first surface and a fourth surface opposite the second surface, an adhesive surface for attaching the sheet member to an object is formed on the third surface, and no adhesive surface is formed on the fourth surface. [Appendix B35] The sheet member according to Appendix B34, wherein the first surface includes a plurality of partial surfaces, and the second surface includes at least one surface between two adjacent partial surfaces of the plurality of partial surfaces. [Appendix B36] The sheet member according to Appendix B34 or B35, wherein the first surface has through-hole openings extending from the front surface to the back surface. [Appendix B37] A sheet member having a riblet structure on its front surface, wherein the back surface has an adhesive surface of an adhesive layer, and the adhesive layer includes a first adhesive layer portion having a first thickness and a second adhesive layer portion having a second thickness different from the first thickness. [Appendix B38] The sheet member according to Appendix B37, wherein the thickness of the second adhesive portion is thicker than the thickness of the first adhesive portion. [Appendix B39] The sheet member according to Appendix B37 or B38, wherein the second adhesive performance of the second adhesive portion is higher than the first adhesive performance of the first adhesive portion. [Appendix B40] A sheet member described in any one of Appendices B37 to 39, wherein the surface has a first region and a second region, the first region is a surface of a convex structure protruding from the second region and formed as at least part of the riblet structure, the second adhesive portion faces the first region, and the first adhesive portion faces the second region.[Appendix B41] The sheet member according to Appendix B40, wherein the convex structures are not formed in the second region. [Appendix B42] A sheet member having a riblet structure on its surface, and an adhesive layer on its back surface, wherein the adhesive layer includes a first adhesive portion having a first adhesive property and a second adhesive portion having a second adhesive property different from the first adhesive property. [Appendix B43] The sheet member according to Appendix B42, wherein the thickness of the second adhesive portion is different from the thickness of the first adhesive portion. [Appendix B44] The sheet member according to Appendix B42, wherein the thickness of the second adhesive portion is thicker than the thickness of the first adhesive portion. [Appendix B45] The sheet member according to any one of Appendices B42 to B44, wherein the second adhesive property of the second adhesive portion is higher than the first adhesive property of the first adhesive portion. [Appendix B46] A sheet member having a riblet structure, the sheet member having, on its surface, a first surface on which the riblet structure is formed and a second surface different from the first surface on which the riblet structure is not formed. [Appendix C1] A moving body comprising the sheet member described in any one of Appendices A1 to A5 and B1 to B46. [Appendix C2] A moving body having the sheet member described in any one of Appendices A1 to A5 and B1 to B46 attached to its surface. [Appendix C3] The moving body described in Appendix C1 or C2, the moving body including at least one of a railway vehicle, an automobile, an aircraft, a ship, a windmill, and a turbine. [Appendix C4] A blade member comprising the sheet member described in any one of Appendices A1 to A5 and B1 to B46. [Appendix C5] A blade member having the sheet member described in any one of Appendices A1 to A5 and B1 to B46 attached to its surface. [Appendix C6] A windmill comprising the blade member described in Appendix C5 or C6. [Appendix C7] An application device that applies the sheet member according to any one of Appendices A1 to A5 and B1 to B46 to an object. [Appendix C8] An application device that attaches the sheet member according to any one of Appendices A1 to A5 and B1 to B46 to an object. [Appendix C8] A manufacturing device for manufacturing the sheet member according to any one of Appendices A1 to A5 and B1 to B46.[Appendix C9] A manufacturing method for manufacturing the sheet member according to any one of Appendices A1 to A5 and B1 to B46.

[0186] The requirements of the above-described embodiments may be combined as appropriate. Some of the requirements of the above-described embodiments may not be used. The requirements of the above-described embodiments may be replaced with requirements of other embodiments as appropriate. Furthermore, to the extent permitted by law, the disclosures of all publications and U.S. patents relating to the devices, etc. cited in the above-described embodiments are incorporated herein by reference.

[0187] Furthermore, the present invention can be modified as appropriate within the scope of the claims and the entire specification without going against the gist or idea of ​​the invention, and sheet members with such modifications are also included in the technical idea of ​​the present invention.

[0188] REFERENCE SIGNS LIST 1 riblet sheet 11 adhesive layer 111 surface 112 back surface 12 structure layer 121 surface 122 back surface 13 convex structure 130 convex region 131 partial convex region 14 groove structure 140 groove region 141 partial groove region 15 through-hole 151, 152 opening RB riblet structure OBJ object

Claims

1. A sheet member having a riblet structure, comprising: a surface including a first region and a second region; a back surface; and a through hole formed between the surface and the back surface, wherein the first region is a surface of a convex structure protruding from the second region and formed as at least a part of the riblet structure, and the second region has an opening for the through hole formed therein.

2. The sheet member according to claim 1, wherein the first region comprises a plurality of partial regions, and the second region includes at least one region between two adjacent partial regions among the plurality of partial regions.

3. A sheet member according to claim 1 or 2, wherein the second region is a region in which the convex structures are not formed.

4. A sheet member according to any one of claims 1 to 3, wherein the opening is not formed in the first region.

5. A sheet member according to any one of claims 1 to 4, wherein the width of the opening in a direction intersecting the extension direction of the convex structures is less than 100 µm.

6. A sheet member according to any one of claims 1 to 5, wherein a plurality of the openings are formed in the second region.

7. The sheet member according to claim 6, wherein the plurality of openings are distributed at equal intervals on the surface of the sheet member.

8. A sheet member as described in claim 6 or 7, wherein the second region has a plurality of partial regions in a direction intersecting the extension direction of the convex structure, and the plurality of openings are distributed at equal intervals in the direction intersecting the extension direction of the convex structure.

9. A sheet member as described in claim 6 or 7, wherein the plurality of openings include a plurality of first openings formed in a first partial region of the second region and a plurality of second openings formed in a second partial region of the second region different from the first partial region, and a distribution pattern of the plurality of first openings is different from a distribution pattern of the plurality of second openings.

10. The sheet member according to claim 9, wherein the first partial region is closer to an end of the sheet member than the second partial region, and the number of the first openings per unit area is greater than the number of the second openings per unit area.

11. A sheet member having a riblet structure, the sheet member comprising a through hole formed between the front surface and the back surface.

12. A sheet member as described in claim 11, wherein the surface includes a first region and a second region, the first region is a surface of a convex structure protruding from the second region formed as at least a part of the riblet structure, the second region includes a plurality of partial regions, and the opening of the through hole is formed across the plurality of partial regions of the second region.

13. A sheet member as described in claim 12, wherein the convex structures include a plurality of convex structures extending in a direction intersecting the extension direction of the convex structures, and the opening is located between two of the plurality of convex structures.

14. A sheet member as described in any one of claims 11 to 13, wherein the surface is arranged in a direction intersecting the extension direction of the convex structure with a plurality of partial regions of the first region extending in the extension direction and a plurality of partial regions of the second region extending in the extension direction, alternately arranged, and at least one of the plurality of partial regions of the first region is separated by the through hole.

15. A sheet member according to any one of claims 11 to 14, wherein the surface is arranged in a direction intersecting the extension direction of the convex structure with a plurality of partial regions of the first region extending in the extension direction and a plurality of partial regions of the second region extending in the extension direction alternately arranged, and at least one of the plurality of partial regions of the first region is not connected in the extension direction.

16. A sheet member according to any one of claims 11 to 15, wherein the sheet member has a plurality of partial regions in the first region, and the second region includes at least one region between two adjacent partial regions among the plurality of partial regions.

17. A sheet member according to any one of claims 11 to 16, wherein the second region is a region in which the convex structures are not formed.

18. A sheet member according to any one of claims 11 to 17, wherein the opening and the convex structure are spaced apart by a predetermined distance or more in a direction along the surface of the sheet member.

19. A sheet member as described in any one of claims 11 to 18, wherein the convex structure extends along a predetermined extension direction which is a direction along the surface of the sheet member, and the height of an end structure portion which is at least a part of the convex structure and includes an end portion of the convex structure along the extension direction gradually decreases as the end structure portion approaches the opening along the extension direction.

20. A sheet member according to any one of claims 11 to 19, wherein an end of the opening is located in the second region.

21. A sheet member according to any one of claims 11 to 20, wherein an end of the opening is spaced apart from the convex structure.

22. A sheet member as described in claim 20 or 21, wherein the convex structures extend along a predetermined stretching direction on the surface of the sheet member, and the ends of the openings are ends of the openings in a direction intersecting the stretching direction.

23. A sheet member as described in any one of claims 1 to 22, wherein the through hole has openings on the front surface and the back surface, and at least a portion of the inner wall surface of the through hole is inclined from the opening on the front surface toward the opening on the back surface with respect to a cross direction intersecting the front surface of the sheet member.

24. The sheet member according to claim 23, wherein the opening on the rear surface is smaller than the opening on the front surface.

25. The sheet member according to claim 23, wherein the opening on the rear surface is larger than the opening on the front surface.

26. A sheet member according to any one of claims 23 to 25, wherein a pair of inner wall surface portions facing each other along the extension direction of the convex structure are inclined with respect to the intersecting direction.

27. A sheet member according to any one of claims 21 to 24, wherein at least a portion of the inner wall surface is gradually inclined from the opening on the front surface to the opening on the back surface.

28. A sheet member as described in any one of claims 1 to 27, wherein the front surface has a first surface on which the riblet structure is formed and a second surface different from the first surface on which the riblet structure is not formed, the back surface has a third surface which is the back surface of the first surface and a fourth surface which is the back surface of the second surface, the third surface is an adhesive surface, and at least a portion of the fourth surface is a non-adhesive surface, and the sheet member is attached to an object using the adhesive surface.

29. The sheet member according to claim 28, wherein the first surface of the sheet member has a plurality of partial surfaces, and the second surface of the sheet member includes at least one surface between two adjacent partial surfaces of the plurality of partial surfaces.

30. A sheet member according to any one of claims 1 to 29, wherein the back surface has an adhesive surface, and a groove is formed on the back surface of the adhesive layer.

31. The sheet member according to claim 30, wherein the groove extends to an end of the rear surface of the adhesive layer in a direction along the rear surface of the adhesive layer.

32. A sheet member according to any one of claims 1 to 31, wherein the back surface has an adhesive surface of an adhesive layer, and the adhesive layer includes a first adhesive portion having a first thickness and a second adhesive portion having a second thickness different from the first thickness.

33. A sheet member according to any one of claims 1 to 21, wherein the back surface has an adhesive surface, and the adhesive surface includes a first adhesive portion having a first adhesive performance and a second adhesive portion having a second adhesive performance different from the first adhesive performance.

34. A sheet member having a riblet structure, wherein the front surface has a first surface on which the riblet structure is formed and a second surface different from the first surface, the back surface has a third surface opposite the first surface and a fourth surface opposite the second surface, an adhesive surface is formed on the third surface for attaching the sheet member to an object, and no adhesive surface is formed on the fourth surface.

35. The sheet member according to claim 34, wherein the first surface includes a plurality of partial surfaces, and the second surface includes at least one surface between two adjacent partial surfaces of the plurality of partial surfaces.

36. A sheet member according to claim 34 or 35, wherein the first surface has a through hole opening extending from the front surface to the back surface.

37. A sheet member having a riblet structure on a surface thereof, the back surface thereof having an adhesive surface of an adhesive layer, the adhesive layer including a first adhesive layer portion having a first thickness and a second adhesive layer portion having a second thickness different from the first thickness.

38. The sheet member according to claim 37, wherein the second adhesive portion has a thickness greater than the thickness of the first adhesive portion.

39. A sheet member according to claim 37 or 38, wherein the second adhesive performance of the second adhesive portion is higher than the first adhesive performance of the first adhesive portion.

40. A sheet member as described in any one of claims 37 to 39, wherein the surface has a first region and a second region, the first region is a surface of a convex structure protruding from the second region formed as at least part of the riblet structure, the second adhesive portion faces the first region, and the first adhesive portion faces the second region.

41. The sheet member according to claim 40, wherein the convex structures are not formed in the second region.

42. A sheet member having a riblet structure on its surface and an adhesive layer on its back surface, the adhesive layer including a first adhesive portion having a first adhesive performance and a second adhesive portion having a second adhesive performance different from the first adhesive performance.

43. The sheet member according to claim 42, wherein the thickness of the second adhesive portion is different from the thickness of the first adhesive portion.

44. The sheet member according to claim 42, wherein the second adhesive portion has a thickness greater than the thickness of the first adhesive portion.

45. A sheet member according to any one of claims 42 to 44, wherein the second adhesive performance of the second adhesive portion is higher than the first adhesive performance of the first adhesive portion.

46. ​​A sheet member having a riblet structure, the sheet member having, on its surface, a first surface on which the riblet structure is formed, and a second surface different from the first surface on which the riblet structure is not formed.

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