Mold, sheet member, moving body, and manufacturing method

Abstract

This mold for molding a sheet member comprises a molding surface with which a material of the sheet member comes into contact. A plurality of recessed structural bodies extending in a first direction are formed on the molding surface so as to be aligned along a second direction intersecting the first direction. At least one of a corner section of a first recessed structural body from among the plurality of recessed structural bodies and a boundary section of the first structural body and a second recessed structural body from among the plurality of recessed structural bodies that is adjacent thereto in the second direction includes a curved surface. If the curvature radius of the curved surface is denoted as R, the pitch of the plurality of recessed structural bodies is denoted as P, and the depth of the plurality of recessed structural bodies from the molding surface is denoted as H, the mold satisfies a first condition of "1 µm < R < 7 µm", and satisfies at least one of a second condition of "5 µm < P < 200 µm" and a third condition of "2.5µm < H < 100 µm".

Description

Mold, sheet member, moving body, and manufacturing method

[0001] The present invention relates to the technical fields of, for example, a mold used for imprint molding a sheet member, a sheet member having a riblet structure formed on its surface, a moving body to which a sheet member is attached, and a manufacturing method for manufacturing a sheet member using a mold.

[0002] Patent Document 1 describes an aircraft having a fuselage with a riblet structure formed on its surface. In this case, it is required to effectively utilize the characteristics of the riblet structure.

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

[0004] According to a first aspect, there is provided a mold used for molding a film-like sheet member, the mold having a molding surface with which a material of the sheet member comes into contact, the molding surface having a first surface, on which a plurality of concave structures extending in a first direction are formed so as to be aligned along a second direction intersecting the first direction, at least one of a corner of a first concave structure among the plurality of concave structures and a boundary between a first concave structure and a second concave structure among the plurality of concave structures adjacent to each other along the second direction includes a curved surface, the radius of curvature of the curved surface is R, the pitch of the plurality of concave structures is P, and the depth of the plurality of concave structures from the molding surface is H. In this case, the mold satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers".

[0005] According to a second aspect, there is provided a film-like sheet member having a riblet structure formed on its surface, wherein a first surface of the sheet member has, as at least a part of the riblet structure, a plurality of convex structures extending in a first direction formed so as to be aligned along a second direction intersecting the first direction, and at least one of a corner of a first convex structure among the plurality of convex structures and a boundary portion between the first convex structure and a second convex structure among the plurality of convex structures adjacent along the second direction includes a curved surface, the radius of curvature of the curved surface is R, the pitch of the plurality of convex structures is P, and the height of the plurality of convex structures from the boundary portion is H. In this case, the sheet member satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers".

[0006] According to a third aspect, there is provided a moving body that is movable through a fluid, and has the sheet member provided by the second aspect attached to at least a portion of the surface of the moving body.

[0007] According to a fourth aspect, there is provided a mold used for molding a film-like sheet member, the mold having a molding surface with which the material of the sheet member comes into contact, the molding surface having a first surface, and the first surface having a plurality of recessed structures extending in a first direction formed thereon so as to be aligned along a second direction intersecting the first direction.

[0008] According to a fifth aspect, there is provided a film-like sheet member having a riblet structure formed on its surface, wherein a first surface of the sheet member has a plurality of convex structures extending in a first direction, as at least part of the riblet structure, arranged along a second direction intersecting the first direction.

[0009] According to a sixth aspect, there is provided a moving body that is movable through a fluid, the moving body having the sheet member provided by the fifth aspect attached to at least a portion of the surface of the moving body.

[0010] According to a seventh aspect, there is provided a film-like sheet member having a longitudinal direction in a first direction, the sheet member having a surface on which a riblet structure is formed, and a plurality of convex portions formed within the surface and extending in a direction intersecting the first direction, the plurality of convex portions including a first convex portion and a second convex portion, and on the surface between the first convex portion and the second convex portion, a plurality of convex structures extending in the first direction and protruding relative to the surface are formed in the first intersecting direction as at least a part of the riblet structure, the radius of curvature of the curved surface is R, the pitch of the plurality of convex structures is P, and the height of the plurality of convex structures from the boundary portion is H. In this case, the sheet member satisfies the first condition of "1 micrometer < R < 7 micrometers" and at least one of the second condition of "5 micrometers < P < 200 micrometers" and the third condition of "2.5 micrometers < H < 100 micrometers".

[0011] According to an eighth aspect, there is provided a moving body that is movable through a fluid, the moving body having the sheet member provided by the seventh aspect attached to at least a portion of the surface of the moving body.

[0012] According to a ninth aspect, there is provided a manufacturing method for manufacturing a sheet member using the mold provided by the first aspect or the fourth aspect.

[0013] According to a tenth aspect, there is provided a manufacturing apparatus for manufacturing a sheet member using the mold provided by the first or fourth aspect.

[0014] 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. FIG. 4 is a perspective view schematically showing the structure of a first manufacturing apparatus. FIG. 5 is a perspective view schematically showing the structure of a second manufacturing apparatus. FIG. 6(a) is a perspective view showing a mold structure, FIG. 6(b) is a cross-sectional view (VI-VI' cross-sectional view of FIG. 6(a)) showing the mold structure, and FIG. 6(c) is a top view showing the mold structure. Fig. 7 is a perspective view schematically showing the structure of a second manufacturing apparatus. Fig. 8 is a cross-sectional view schematically showing the structure of a processing system. Fig. 9 is a system configuration diagram showing the system configuration of a processing system. Fig. 10(a) is a perspective view showing a riblet portion and a non-riblet portion, and Fig. 10(b) is a cross-sectional view showing a riblet portion and a non-riblet portion. Fig. 11(a) is a perspective view showing a riblet structure in a modified example, and Fig. 11(b) is a cross-sectional view showing a riblet structure in a modified example. Fig. 12(a) is a perspective view showing a mold structure in a modified example, and Fig. 12(b) is a cross-sectional view showing a mold structure in a modified example.

[0015] Next, embodiments of a mold, a sheet member, a moving body, and a manufacturing method will be described with reference to the drawings.

[0016] (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.

[0017] As shown in FIGS. 1( a) and 1(b), the libretto sheet 1 is a film-like (in other words, sheet-like, layer-like, foil-like, tape-like, or band-like) sheet member. In the example shown in FIGS. 1(a) and 1(b), the Y-axis direction is the width direction of the libretto sheet 1, and the Z-axis direction is the thickness direction of the libretto sheet 1. The libretto sheet 1 is a film-like sheet member whose thickness is much smaller than its width. As an example, the width of the libretto sheet 1 may be several centimeters or more, a dozen centimeters or more, several tens of centimeters or more, or one meter or more. On the other hand, the thickness of the libretto sheet 1 may be one millimeter or less, one centimeter or less, or a few centimeters or less.

[0018] The libretto sheet 1 has a longitudinal shape extending along a length direction intersecting the width direction and the thickness direction. In other words, the libretto sheet 1 has 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.

[0019] 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.

[0020] As shown in FIG. 1( b), the libretto sheet 1 may include an adhesive layer 11 and a coating layer 12. The adhesive layer 11 is a layer containing an adhesive for attaching the coating layer 12 to an object (e.g., a moving object, as described below). Therefore, the libretto sheet 1 may be attached to the object via the adhesive layer 11. The libretto sheet 1 may not 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. The coating layer 12 is a layer having a predetermined function. In the example shown in FIG. 1( b), the coating layer 12 includes a paint layer 121 and a coating layer 122. The paint layer 121 is a layer containing paint of a predetermined color. The coating layer 122 is a layer that protects the surface of the paint layer 121. The coating layer 122 may include a clear layer that is transparent in the visible light range. However, the coating layer 12 may not include at least one of the paint layer 121 and the coating layer 122. The coating layer 12 may include a layer different from at least one of the paint layer 121 and the coating layer 122. For example, the coating layer 12 may include an anti-reflection layer that prevents light from being reflected on the surface of the coating layer 12. The coating layer 12 may include an anti-glare layer that reduces the glossiness of the surface of the coating layer 12. Alternatively, the coating layer 122 may function as at least one of the anti-reflection layer and the anti-glare layer.

[0021] A riblet structure RB is formed on the surface of the libretto sheet 1. However, in Figures 1(a) and 1(b), the riblet structure RB formed on the surface of the libretto sheet 1 is omitted for simplicity of the drawings. The riblet structure RB formed on the surface of the libretto sheet 1 will be described in detail later with reference to Figures 2(a) to 2(c). In the following description, the surface of the libretto sheet 1 on which the riblet structure RB is formed will be referred to as the "riblet structure surface 130." Figures 1(a) and 1(b) show an example in which the surface of the coating layer 12 is the riblet structure surface 130. In other words, Figures 1(a) and 1(b) show an example in which the riblet structure RB is formed on the surface of the coating layer 12.

[0022] 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.

[0023] As shown in Figures 2(a) to 2(c), the riblet structure RB may include a plurality of convex structures 81. Each of the plurality of convex structures 81 may extend along a predetermined first extension direction. In this case, the riblet structure RB may include a plurality of convex structures 81 extending along the predetermined first extension direction. Each of the plurality of convex structures 81 may be arranged along a predetermined first arrangement direction. In this case, the riblet structure RB may include a plurality of convex structures 81 arranged along the predetermined first arrangement direction.

[0024] As an example, the riblet structure RB may include a structure in which a plurality of convex structures 81 extending along a predetermined first stretching direction are arranged along a predetermined first array direction that intersects the predetermined first stretching direction. In other words, the riblet structure RB may include a structure in which the convex structures 81 formed to extend along the predetermined first stretching direction are lined up along the predetermined first array direction. Each of the first stretching direction and the first array direction may be a direction that intersects the first height direction, described below, in which the convex structures 81 protrude. Furthermore, one of the first stretching direction and the first array direction may be the longitudinal direction of the liblet sheet 1, and the other of the first stretching direction and the first array direction may be the lateral direction of the liblet 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 81 extending along the X-axis direction, which is the longitudinal direction (length direction) of the liblet sheet 1, are arranged along the Y-axis direction, which is the width direction of the liblet sheet 1. That is, Figures 2(a) to 2(c) show an example in which the predetermined first extension direction is the X-axis direction and the predetermined first arrangement direction is the Y-axis direction that intersects (typically, is perpendicular to) the X-axis direction.

[0025] The convex structures 81 are structures that protrude from the surroundings along a predetermined first height direction. The convex structures 81 are structures that protrude from the riblet structure surface 130 along a predetermined first height direction that intersects both the predetermined first extension direction in which the convex structures 81 extend and the predetermined first arrangement direction in which the convex structures 81 are arranged. The first height direction may be the thickness direction of the libretto sheet 1. In the example shown in Figures 2(a) to 2(c), the convex structures 81 are structures that protrude from the surroundings along the Z-axis direction, which is the thickness direction of the libretto sheet 1. In other words, Figures 2(a) to 2(c) show an example in which the predetermined first height direction is the Z-axis direction that intersects (typically, is perpendicular to) the X-axis direction and the Y-axis direction. The convex structures 81 may include a protruding structure that protrudes from the surroundings. The convex structures 81 may include a convex structure that protrudes from the surroundings. The convex structures 81 may include a mountain-shaped structure that protrudes from the surroundings.

[0026] The convex structure 81 has, for example, a pair of side surfaces 811 and 812 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 FIGS. 2( a) to 2(c), the convex structure 81 has a side surface 811 facing the -Y side and a side surface 812 facing the +Y side. Each of the pair of side surfaces 811 and 812 is a flat surface. However, at least one of the pair of side surfaces 811 and 812 may include a curved surface.

[0027] The pair of side surfaces 811 and 812 may be non-parallel to each other. The side surfaces 811 and 812 may be referred to as inclined surfaces 811 and 812, respectively. In this case, the pair of side surfaces 811 and 812 of the convex structure 81 may be connected via one end thereof (in the example shown in Figures 2(a) to 2(c) , the upper end on the +Z side). The portion where the pair of side surfaces 811 and 812 of the convex structure 81 are connected constitutes a corner 813 of the convex structure 81. The corner 813 of the convex structure 81 may constitute the vertex of the convex structure 81. The corner 813 of the convex structure 81 may constitute the ridge line of the convex structure 81. The corner 813 of the convex structure 81 may constitute the boundary between the pair of side surfaces 811 and 812 of the convex structure 81. In this case, the pair of side surfaces 811 and 812 may be considered to be connected via the corner 813 of the convex structure 81. In the example shown in FIGS. 2A to 2C, a pair of side surfaces 811 and 812 are connected so that the upper end of the side surface 811 and the upper end of the side surface 812 are in contact with each other.

[0028] The convex structure 81 may be a structure formed by a pair of side surfaces 811 and 812 and a corner portion 813. The convex structure 81 may be a structure including the pair of side surfaces 811 and 812 and the corner portion 813 on its surface. In this case, the shape of a cross section of the convex structure 81 including the Z axis may be a triangular shape. In this case, the shape of a cross section of the convex structure 81 including the Z axis may be a symmetrical triangular shape or an asymmetrical triangular shape. However, the shape of a cross section of the convex structure 81 including the Z axis may have any shape other than a triangular shape.

[0029] The side surfaces 811 and 812 may be referred to as inclined surfaces 811 and 812, respectively. The riblet structure surface 130 may be considered to include the side surfaces 811 and 812. Furthermore, if the corner portion 813 (vertex or ridge line) of the convex structure 81 is not a corner but a curved surface (convex surface), the riblet structure surface 130 may be considered to include the corner portion 813.

[0030] Between adjacent convex structures 81, groove structures 82 that are recessed compared to the surrounding area are formed. For this reason, the riblet structure RB may include a structure in which a plurality of groove structures 82 extending along a predetermined first extension direction are arranged along a predetermined first arrangement direction. In other words, the riblet structure RB may include a structure in which groove structures 82 formed to extend along the predetermined first extension direction are lined up along the predetermined first arrangement direction. Note that the groove structures 82 may be considered to be recessed structures with respect to the vertices or ridgelines (for example, the above-mentioned corner portions 813) of the convex structures 81.

[0031] The groove structure 82 may be considered to be a structure located between a side surface 811 of one convex structure 81 and a side surface 812 of another convex structure 81 adjacent to the one convex structure 81 along the first arrangement direction in which the convex structures 81 are arranged. Specifically, the side surface 811 of one convex structure 81 and the side surface 812 of another convex structure 81 adjacent to the one convex structure 81 along the first arrangement direction in which the convex structures 81 are arranged may be connected via a boundary portion 814 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 811 and 812 that are provided on two adjacent convex structures 81 and face each other may be connected via the boundary portion 814 that forms the boundary between the two adjacent convex structures 81. In the example shown in FIGS. 2( a ) to 2 ( c ), the boundary portion 814 includes a surface that intersects with each of the side surfaces 811 and 812 to which the boundary portion 814 connects. In this case, the groove structure 82 may be a structure formed by the boundary portion 814. The groove structure 82 may be a structure including a groove that is faced by the boundary portion 814. The boundary portion 814 may be considered to be the bottom surface of the groove structure 82. In this case, the boundaries between each of the side surfaces 811 and 812 and the boundary portion 814 may be used as the boundary between the convex structure 81 and the groove structure 82. The groove structure 82 may also be referred to as a groove-shaped structure or a concave structure.

[0032] However, in some cases, the groove structure 82 may be considered to be a structure formed by the boundary portion 814 and the side surfaces 811 and 812 connected by the boundary portion 814. The groove structure 82 may be considered to be a structure including a groove facing the boundary portion 814 and the side surfaces 811 and 812 connected by the boundary portion 814.

[0033] It should be noted that the riblet structure surface 130 may be considered to include the boundary portion 814 (e.g., the bottom surface of the groove structure 82) in addition to or instead of the side surfaces 811 and 812.

[0034] The multiple convex structures 81 may be formed so that the multiple convex structures 81 are arranged regularly. For example, the multiple convex structures 81 may be formed so that the multiple convex structures 81 are arranged at an equal pitch along a predetermined first arrangement direction. For example, the multiple convex structures 81 may be formed so that a structural group including at least two convex structures 81 is arranged at an equal pitch along a predetermined first arrangement direction. The multiple convex structures 81 may be formed so that at least two convex structures 81 are arranged regularly according to a first rule in a first portion of the surface of the libretto sheet 1, and at least two convex structures 81 are arranged regularly according to the same first rule in a second portion of the surface of the libretto sheet 1. The multiple convex structures 81 may be formed so that at least two convex structures 81 are arranged regularly according to a first rule in the first portion of the surface of the libretto sheet 1, while at least two convex structures 81 are arranged regularly according to a second rule that is different from the first rule in the second portion of the surface of the libretto sheet 1. Furthermore, since the convex structures 81 and the groove structures 82 are formed alternately, a state in which multiple convex structures 81 are arranged in a regular pattern may be considered equivalent to a state in which multiple groove structures 82 are arranged in a regular pattern.

[0035] The riblet structure RB may be used as a structure capable of reducing the resistance to a fluid (particularly, at least one of frictional resistance and turbulent frictional resistance) of the surface (typically, the riblet structure surface 130) of the riblet sheet 1. In this case, the riblet structure surface 130 on which the riblet structure RB is formed may be considered to be a surface capable of reducing the resistance to a fluid of the surface (typically, the riblet structure surface 130) of the riblet sheet 1.

[0036] The riblet sheet 1 on which the riblet structure RB is formed may be attached to an object via the adhesive layer 11. In this case, the riblet structure RB may be used as a structure that can reduce the resistance of the surface of the object to which the riblet sheet 1 is attached to a fluid (particularly, at least one of frictional resistance and turbulent frictional resistance). For this reason, the riblet sheet 1 may be attached to an object having 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. For example, if the surface of an object 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).

[0037] An example of an object to which the riblet sheet 1 can be attached is a moving body. In particular, an example of an object to which the riblet sheet 1 can be attached is a moving body that can move through a fluid. Examples of moving bodies include at least one of a railway vehicle, an automobile, an aircraft, a ship, a windmill, and a turbine.

[0038] 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.

[0039] When such a riblet sheet 1 is attached to at least a portion of the surface of a moving body (or any object, 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, 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."

[0040] (2) Details of the Shape of the Riblet Structure RB Next, with reference again to Figures 2(a) to 2(c), the details of the shape of the riblet structure RB will be further described.

[0041] As described above, the convex structure 81 includes, for example, a pair of side surfaces 811 and 812 facing opposite to each other and connected via a corner 813 .

[0042] In this embodiment, the corner 813 may include a curved surface. That is, the corner 813 may have a shape that has been subjected to chamfering (particularly, R-chamfering, or rounding). FIGS. 2( a) to 2(c) show an example in which the corner 813 includes a curved surface 8131 that connects the pair of side surfaces 811 and 812 that the convex structure 81 has. That is, FIGS. 2(a) to 2(c) show an example in which the entire corner 813 is a curved surface. However, a part of the corner 813 may be a curved surface, and another part of the corner 813 may be a flat surface.

[0043] As described above, the corner 813 connects a pair of side surfaces 811 and 812 facing opposite each other. Typically, the corner 813 includes a curved surface. Therefore, the corner 813 and the side surfaces 811 and 812 may be distinguished based on whether or not they include a curved surface. However, if the corner 813 includes a curved surface (e.g., a curved surface 8131) connected to the side surface 811 or 812, the side surface 811 or 812 may be considered to include a curved surface instead of the corner 813.

[0044] When the corners 813 include a curved surface, a riblet structure RB with higher shape accuracy can be formed by imprint molding using the mold 3 described below, compared to when the corners 813 do not include a curved surface (for example, when the corners 813 are flat). In other words, when the corners 813 include a curved surface, a riblet structure RB with a shape closer to the target shape can be formed, compared to when the corners 813 do not include a curved surface (for example, when the corners 813 are flat). The reason for this will be described later when explaining the manufacturing method for manufacturing the riblet sheet 1 using the mold 3. However, the corners 813 do not have to include a curved surface. In other words, the corners 813 may be flat.

[0045] Note that the pair of side surfaces 811 and 812 being non-parallel to each other may include a virtual surface (typically a plane) including the side surface 811 intersecting with a virtual surface (typically a plane) including the side surface 812. In this case, the virtual surface including the side surface 811 and the virtual surface including the side surface 812 may be an approximate plane of the side surface 811 and an approximate plane of the side surface 812, respectively.

[0046] When the pair of side surfaces 811 and 812 are not parallel to each other, the side surface 811 may be considered to be inclined with respect to the side surface 812, and the side surface 812 may be considered to be inclined with respect to the side surface 811. Typically, when the pair of side surfaces 811 and 812 are not parallel to each other, each of the pair of side surfaces 811 and 812 may be inclined with respect to the direction in which the convex structure 81 protrudes (the Z-axis direction in the example shown in FIGS. 2( a ) to 2 ( c )). In this case, each of the side surfaces 811 and 811 may be referred to as an inclined portion. However, the pair of side surfaces 811 and 812 may be parallel to each other.

[0047] Furthermore, as mentioned above, the side surface 811 of one convex structure 81 and the side surface 812 of another convex structure 81 adjacent to the one convex structure 81 along the first arrangement direction in which the convex structures 81 are arranged may be connected via a boundary portion 814 connecting their other end portions (in the examples shown in Figures 2(a) to 2(c), the lower end portions on the -Z side).

[0048] In this embodiment, the boundary portion 814 includes a curved surface. That is, the boundary portion 814 may have a shape that has been subjected to chamfering (particularly, R-chamfering, or rounding). FIGS. 2( a ) to 2 ( c ) show an example in which the boundary portion 814 includes a flat surface 8141, a curved surface 8142 connecting the flat surface 8141 and the side surface 811, and a curved surface 8143 connecting the flat surface 8141 and the side surface 812. That is, FIGS. 2( a ) to 2 ( c ) show an example in which a portion of the boundary portion 814 is a curved surface. However, the entire boundary portion 814 may be a curved surface. For example, when the boundary portion 713 includes a curved surface connecting the pair of side surfaces 711 and 712 as described above, the boundary portion 814 may include a curved surface connecting the side surfaces 811 and 812 of two adjacent convex structures 81, similar to the corner portion 813 described above.

[0049] As described above, the boundary portion 814 connects the side surfaces 811 and 812 of two adjacent convex structures 81. Typically, this boundary portion 814 includes a curved surface. Therefore, the boundary portion 814 and the side surfaces 811 and 812 may be distinguished based on whether or not they include a curved surface. However, if the boundary portion 814 includes a curved surface (for example, at least one of the curved surfaces 8142 and 8143) connected to the side surface 811 or 812, the side surface 811 or 812 may be considered to include a curved surface instead of the boundary portion 814.

[0050] When the boundary 814 includes a curved surface, a riblet structure RB with higher shape accuracy can be formed by imprint molding using the mold 3 described below, compared to when the boundary 814 does not include a curved surface (for example, when the boundary 814 is flat). In other words, when the boundary 814 includes a curved surface, a riblet structure RB with a shape closer to the target shape can be formed, compared to when the boundary 814 does not include a curved surface (for example, when the boundary 814 is flat). The reason for this will be described later when explaining the manufacturing method for manufacturing the riblet sheet 1 using the mold 3. However, the boundary 814 does not have to include a curved surface. In other words, the boundary 814 may be flat.

[0051] However, the side surface 811 of one convex structure 81 and the side surface 812 of another convex structure 81 may be connected without a boundary portion 814 including a surface. For example, the side surface 811 of one convex structure 81 and the side surface 812 of another convex structure 81 may be connected so that their other end portions (in the example shown in Figures 2(a) to 2(c) , the lower end portions on the -Z side) are in contact. In this case, the portion where the other end portion of the side surface 811 of one convex structure 81 and the other end portion of the side surface 812 of the other convex structure 81 are connected may be referred to as the boundary portion 814.

[0052] The height H_rb of at least one of the multiple convex structures 81 may be set to a height determined according to the pitch P_rb of the convex structures 81. For example, the height H_rb of at least one of the multiple convex structures 81 may be less than or equal to the pitch P_rb of the convex structures 81. For example, the height H_rb of at least one of the multiple convex structures 81 may be less than half the pitch P_rb of the convex structures 81. Furthermore, the height H_rb of at least one of the multiple convex structures 81 may be within a range of 1 / 2 ±10% of the pitch P_rb of the convex structures 81. Note that the height H_rb may be the height from the bottom surface of the groove structure 82 (i.e., the boundary portion 814). Furthermore, the height H_rb may be referred to as the depth from the vertex or ridge line (i.e., the corner portion 813) of the convex structure 81.

[0053] As an example, the pitch P_rb of the convex structures 81 may be greater than 5 micrometers and less than 200 micrometers. That is, the pitch P_rb of the convex structures 81 may satisfy a first pitch condition of "5 micrometers < P_rb < 200 micrometers." In this case, the height H_rb of at least one of the multiple convex structures 81 may be greater than 2.5 micrometers and less than 100 micrometers. That is, the height H_rb of at least one of the multiple convex structures 81 may satisfy a first height condition of "2.5 micrometers < H_rb < 100 micrometers." That is, the riblet structure RB may satisfy at least one of the first pitch condition and the first height condition. However, due to constraints on the processing accuracy of the riblet structure RB, 2.0 micrometers may be used instead of 2.5 micrometers as the lower limit value of the height H_rb of at least one of the multiple convex structures 81 (for example, the lower limit value of the height H_rb under circumstances where the pitch P_rb is the lower limit value of 5 micrometers).

[0054] A riblet structure RB that satisfies this first pitch condition can more appropriately reduce the resistance to fluid on the surface of the riblet sheet 1, compared to a riblet structure RB that does not satisfy the first pitch condition. In other words, a riblet structure RB that satisfies the first pitch condition can more appropriately reduce the resistance to fluid on the surface of an object (e.g., a moving body) to which the riblet sheet 1 is attached, compared to a riblet structure RB that does not satisfy the first pitch condition. However, even a riblet structure RB that does not satisfy the first pitch condition can reduce the resistance to fluid on the surface of the riblet sheet 1 (and further, the resistance to the surface of the object to which the riblet sheet 1 is attached) compared to a case in which the riblet structure RB is not formed in the first place.

[0055] Similarly, a riblet structure RB that satisfies this first height condition can more appropriately reduce the resistance to fluid on the surface of the riblet sheet 1, compared to a riblet structure RB that does not satisfy the first height condition. In other words, a riblet structure RB that satisfies the first height condition can more appropriately reduce the resistance to fluid on the surface of an object (e.g., a moving body) to which the riblet sheet 1 is attached, compared to a riblet structure RB that does not satisfy the first height condition. However, even a riblet structure RB that does not satisfy the first height condition can reduce the resistance to fluid on the surface of the riblet sheet 1 (and further, the resistance to the surface of the object to which the riblet sheet 1 is attached) compared to a case in which the riblet structure RB is not formed in the first place.

[0056] In addition, the height H_rb of the convex structure 81 in this embodiment may mean the size of the convex structure 81 in the direction in which the convex structure 81 protrudes (the Z-axis direction in the examples shown in Figures 2(a) to 2(c)). The height H_rb of the convex structure 81 may mean the distance from the lower end of the convex structure 81 to the upper end of the convex structure 81 in the direction in which the convex structure 81 protrudes. The height H_rb of the convex structure 81 may mean the distance from the boundary 814 connecting to the lower end of the convex structure 81 to the corner 813 corresponding to the vertex of the convex structure 81 in the direction in which the convex structure 81 protrudes. In addition, the height H_rb of the convex structure 81 may be considered to be substantially equivalent to the depth of the groove structure 82.

[0057] Furthermore, the pitch P_rb of the convex structures 81 in this embodiment may refer to the distance between the corresponding identical portions (e.g., vertices) of two adjacent convex structures 81 in the first arrangement direction. In the example shown in FIGS. 2( a) to 2(c), the pitch P_rb of the convex structures 81 may refer to the distance between the vertices of two adjacent convex structures 81 in the Y-axis direction. Note that, because the convex structures 81 and the groove structures 82 are alternately formed in the first arrangement direction, the pitch P_rb of the convex structures 81 may be considered equivalent to the pitch of the groove structures 82. The pitch of the groove structures 82 may refer to the distance between the corresponding identical portions of two adjacent groove structures 82 in the first arrangement direction. In the example shown in FIGS. 2( a) to 2(c), the pitch of the groove structures 82 may refer to the distance between the corresponding identical portions of two adjacent groove structures 82 in the Y-axis direction.

[0058] (3) Manufacturing Method of Libretto Sheet 1 Next, a manufacturing method for manufacturing the libretto sheet 1 will be described. In this embodiment, a manufacturing method for manufacturing the libretto sheet 1 using a mold 3 will be described. Typically, in this embodiment, a manufacturing method for manufacturing the libretto sheet 1 by imprint molding using the mold 3 will be described. In this case, the mold structure MB formed in the mold 3 is pressed against the material sheet 100, which is the material of the libretto sheet 1 (specifically, the coating layer 12 on which the libretto structure RB is not formed). The material sheet 100 includes at least the coating layer 12 on which the libretto structure RB is not formed. The material sheet 100 may include an adhesive layer 11 in addition to the coating layer 12. As a result, the libretto structure RB corresponding to the mold structure MB is transferred to the material sheet 100 (typically the coating layer 12). In other words, the libretto structure RB is formed on the surface of the material sheet 100. As a result, the material sheet 100 on which the libretto structure RB is formed on its surface is manufactured as the libretto sheet 1.

[0059] The mold 3 may be made of any material as long as the riblet sheet 1 can be manufactured using the mold 3. As an example, at least one of a mold made of zirconia (zirconia ceramics), a mold made of pre-hardened steel, a mold made of as-rolled steel, and a mold made of stainless steel may be used as the mold 3. However, a mold made of any metal may also be used as the mold 3. Alternatively, a mold made of any material other than metal may be used as the mold 3.

[0060] However, the riblet sheet 1 may be manufactured by a manufacturing method different from the manufacturing method using the mold 3. For example, the riblet sheet 1 may be manufactured using a processing device capable of performing removal processing. As an example, the processing device may perform removal processing to remove a portion of the material sheet 100 (e.g., a portion of the coating layer 12) by irradiating processing light onto the material sheet 100. In this case, the processing device may perform removal processing to remove a portion of the material sheet 100 (typically, a portion of the coating layer 12) so that a riblet structure RB is formed on the surface of the material sheet 100.

[0061] (3-1) Manufacturing Apparatus 2 for Libretto Sheet 1 First, to explain the manufacturing method for manufacturing the libretto sheet 1 by imprint molding using a mold 3, we will explain the manufacturing apparatus 2 for manufacturing the libretto sheet 1 by imprint molding using a mold 3. Below, as examples of the manufacturing apparatus 2, a first manufacturing apparatus 2a and a second manufacturing apparatus 2b will be explained in order.

[0062] (3-1-1) First Manufacturing Apparatus 2a First, the first manufacturing apparatus 2a will be described with reference to Fig. 4. Fig. 4 is a perspective view that schematically shows the structure of the first manufacturing apparatus 2a.

[0063] As shown in FIG. 4, the first manufacturing apparatus 2a includes a flat mold 3a, which is an example of the mold 3, a feed roller 21a, a table 22a, a heater 23a, and a recovery roller (winding roller) 24a.

[0064] The flat mold 3a is a flat mold 3. Specifically, the flat mold 3a is a flat member having a molding surface 30 that is a flat surface. The molding surface 30 is a surface on which the mold structure MB is formed. The mold structure MB is a structure for transferring the riblet structure RB to the material sheet 100. In this case, the first manufacturing apparatus 2a may transfer (i.e., form) the riblet structure RB on the surface of the material sheet 100 by pressing the molding surface 30 against the material sheet 100.

[0065] The feed roller 21a is a cylindrical member around which the material sheet 100 is wrapped. Like the riblet sheet 1, the material sheet 100 is a sheet-like member extending in the longitudinal direction. The feed roller 21a rotates around its central axis to sequentially supply the material sheet 100 onto the table 22a. Then, the mold structure MB formed on the molding surface 30 of the mold 3a is pressed against the material sheet 100 supplied onto the table 22a. As a result, the riblet structure RB corresponding to the mold structure MB is transferred to the material sheet 100. The table 22a may heat the material sheet 100 to make it easier to transfer the riblet structure RB to the material sheet 100. In other words, the table 22a may soften the material sheet 100 by heating it. Each time the riblet structure RB is transferred to the material sheet 100, the recovery roller 24a rotates around its central axis to recover (in other words, wind up) the material sheet 100 to which the riblet structure RB has been transferred. As a result, the material sheet 100 to which the riblet structure RB has been transferred is wound around the recovery roller 24a. Furthermore, at the same time that the recovery roller 24a recovers the material sheet 100, the feed roller 21a supplies a new material sheet 100 to the table 22a.

[0066] The first manufacturing apparatus 2a alternately repeats the pressing of the mold 3a against the material sheet 100 and the supply and recovery of the material sheet 100. For example, the first manufacturing apparatus 2a may use the feed roller 21a to supply a first portion of the material sheet 100 onto the table 22a. The first manufacturing apparatus 2a may then press the mold structure MB formed on the molding surface 30 of the mold 3a against the first portion of the material sheet 100 supplied onto the table 22a. As a result, the riblet structure RB corresponding to the mold structure MB is transferred to the first portion of the material sheet 100. The first manufacturing apparatus 2a may then use the recovery roller 24a to recover the first portion of the material sheet 100 to which the riblet structure RB has been transferred, and may use the feed roller 21a to supply a second portion of the material sheet 100 adjacent to the first portion along the longitudinal direction onto the table 22a. Thereafter, the first manufacturing apparatus 2a may press the mold structure MB formed on the molding surface 30 of the mold 3a against a second portion of the material sheet 100 supplied onto the table 22a. As a result, a riblet structure RB corresponding to the mold structure MB is transferred to the second portion of the material sheet 100. Thereafter, the first manufacturing apparatus 2a may repeat the same operation. As a result, a riblet structure RB is formed in the material sheet 100 extending along the longitudinal direction (the X-axis direction in the example shown in FIG. 4). In other words, a riblet sheet 1 extending along the longitudinal direction (the X-axis direction in the example shown in FIG. 4) is manufactured.

[0067] In the above example, the mold 3a was pressed against the material sheet 100 to deform the material sheet 100 and transfer the riblet structure RB, but the riblet structure RB may also be formed by applying a photocurable resin to the material sheet 100 and then pressing the mold 3a against the applied photocurable resin while irradiating the photocurable resin with curing light.

[0068] (3-1-2) Second Manufacturing Apparatus 2b Next, the second manufacturing apparatus 2b will be described with reference to Fig. 5. Fig. 5 is a perspective view that schematically shows the structure of the second manufacturing apparatus 2b.

[0069] As shown in FIG. 5, the second manufacturing apparatus 2b includes a roller mold 3b, which is an example of the mold 3, a feed roller 21b, an auxiliary roller 22b, an auxiliary roller 23b, and a recovery roller (winding roller) 24b.

[0070] The roller die 3b is a cylindrical die 3. Specifically, the roller die 3b is a cylindrical member that can function as a roller that can rotate around a central axis. In this case, the curved outer peripheral surface (i.e., side surface) of the cylindrical member is used as the molding surface 30 of the roller die 3b. Therefore, a mold structure MB is formed on the curved outer peripheral surface of the cylindrical member used as the roller die 3b. is used.

[0071] The feed roller 21b is a cylindrical member around which the material sheet 100 is wound. The feed roller 21b rotates around its central axis to sequentially supply the material sheet 100. The material sheet 100 supplied by the feed roller 21b is sent to the recovery roller 24b by auxiliary rollers 22b and 23b, each of which can rotate around its central axis. Here, the roller die 3b is pressed against the surface of the material sheet 100 sent out by the auxiliary rollers 22b and 23b. More specifically, the material sheet 100 sent out by the auxiliary rollers 22b and 23b is sandwiched between the roller die 3b and the auxiliary rollers 22b and 23b, respectively, and at this time, the mold structure MB formed on the molding surface 30 of the roller die 3b is pressed against the surface of the material sheet 100. As a result, the riblet structure RB corresponding to the mold structure MB is transferred to the material sheet 100. In addition, at least one of the auxiliary rollers 22b and 23b may heat the material sheet 100 so that the riblet structure RB is easily transferred to the material sheet 100. In other words, at least one of the auxiliary rollers 22b and 23b may soften the material sheet 100 by heating it. The material sheet 100 to which the riblet structure RB has been transferred is collected (i.e., wound up) by the collection roller 24b, which can rotate around its central axis. In other words, the material sheet 100 to which the riblet structure RB has been transferred is wound around the collection roller 24b.

[0072] In the above example, the roller mold 3b was pressed against the material sheet 100 to deform the material sheet 100 and transfer the riblet structure RB, but the riblet structure RB may also be formed by applying a photocurable resin to the material sheet 100, and then pressing the roller mold 3b against the applied photocurable resin while irradiating the photocurable resin with curing light.

[0073] (3-2) Details of the Shape of the Mold Structure MB Next, an example of the mold structure MB formed on the molding surface 30 of the mold 3 (for example, at least one of the molds 3a and 3b) will be described with reference to Figures 6(a) to 6(c). Figure 6(a) is a perspective view showing the mold structure MB, Figure 6(b) is a cross-sectional view showing the mold structure MB (cross-sectional view taken along line VI-VI' in Figure 6(a)), and Figure 6(c) is a top view showing the mold structure MB.

[0074] As shown in Figures 6(a) to 6(c), the mold structure MB is a structure that is complementary to the riblet structure RB. For example, as shown in Figures 6(a) to 6(c), the mold structure MB may include a structure in which a plurality of groove structures 72 extending along a predetermined second extension direction along the molding surface 30 are arranged along a predetermined second arrangement direction that is along the molding surface 30 and intersects the second extension direction. In the example shown in Figures 6(a) to 6(c), the mold structure MB includes a structure in which a plurality of groove structures 72 extending along the X-axis direction are arranged along the Y-axis direction. Note that the groove structure 72 may also be referred to as a groove-shaped structure or a recessed structure.

[0075] A convex structure 71 that protrudes compared to the surrounding area is formed between adjacent groove structures 72. Therefore, the mold structure MB may include a structure in which a plurality of convex structures 71 extending in the second extension direction along the molding surface 30 are arranged in a second arrangement direction that is along the molding surface 30 and intersects the second extension direction. In the example shown in Figures 6(a) to 6(c), the mold structure MB includes a structure in which a plurality of convex structures 71 extending in the X-axis direction are arranged in the Y-axis direction.

[0076] When the roller die 3b (see FIG. 5) described above is used as the die 3, the mold structure MB may be formed on the molding surface 30 (i.e., the outer peripheral surface) of the roller die 3b so that the second extension direction in which the groove structure 72 extends is a direction that includes a directional component along the rotation direction of the roller die 3b (i.e., the rotation direction about the central axis of the roller die 3b). In the example shown in FIG. 5, the rotation direction of the roller die 3b (i.e., the rotation direction about the central axis of the roller die 3b) is the rotation direction about the Y axis. In this case, the mold structure MB may be formed on the molding surface 30 (i.e., the outer peripheral surface) of the roller die 3b so that the second extension direction in which the groove structure 72 extends is a direction that includes a directional component along the rotation direction about the Y axis. In this case, the rotation of the roller die 3b can form a series of convex structures 81 in the material sheet 100 that are longer and continuously connected along the second extension direction, compared to when the second extension direction in which the groove structure 72 extends does not include a directional component along the rotation direction in which the roller die 3b rotates.

[0077] Typically, the mold structure MB may be formed on the molding surface 30 (i.e., the outer peripheral surface) of the roller die 3b so that the second extension direction in which the groove structure 72 extends coincides with the direction along the rotation direction in which the roller die 3b rotates. In the example shown in Figure 5, the rotation direction in which the roller die 3b rotates (i.e., the rotation direction around the central axis of the roller die 3b) is the rotation direction around the Y axis. In this case, the mold structure MB may be formed on the molding surface 30 (i.e., the outer peripheral surface) of the roller die 3b so that the second extension direction in which the groove structure 72 extends includes a directional component along the rotation direction around the Y axis. In this case, by rotating the roller die 3b, a series of convex structures 81 that are continuously connected and longer along the second extension direction can be formed in the material sheet 100.

[0078] 7, when the second stretching direction in which the groove structure 72 extends is the Y-axis direction, the second manufacturing apparatus 2b cannot form, by rotating the roller die 3b, a convex structure 71 that is continuously connected over a distance longer than the width (length in the Y-axis direction) of the material sheet 100. On the other hand, when the second stretching direction in which the groove structure 72 extends is the rotation direction about the Y-axis (or a direction that includes a directional component along the rotation direction about the Y-axis), as shown in FIG. 5, the second manufacturing apparatus 2b can form, by rotating the roller die 3b, a convex structure 71 that is continuously connected over a distance longer than the width (length in the Y-axis direction) of the material sheet 100.

[0079] It should be noted that the state in which "the second extension direction in which the groove structure 72 extends is a direction that includes a directional component along the rotation direction in which the roller die 3b rotates" may be considered equivalent to the state in which "the second extension direction in which the groove structure 72 extends is a direction that includes a directional component along an intersecting direction that intersects the central axis of the roller die 3b." The state in which "the second extension direction in which the groove structure 72 extends coincides with the direction along the rotation direction in which the roller die 3b rotates" may be considered equivalent to the state in which "the second extension direction in which the groove structure 72 extends intersects the central axis of the roller die 3b."

[0080] Referring again to FIGS. 6( a) to 6(c), the plurality of groove structures 72 may be formed so that the plurality of groove structures 72 are arranged regularly. The plurality of groove structures 72 may be formed so that the plurality of groove structures 72 are arranged at an equal pitch along a predetermined second arrangement direction. For example, the plurality of groove structures 72 may be formed so that structures each including at least two groove structures 72 are arranged at an equal pitch along the predetermined second arrangement direction. The plurality of groove structures 72 may be formed so that at least two groove structures 72 are arranged regularly according to a third rule in a first portion of the molding surface 30, and at least two groove structures 72 are arranged regularly according to the same third rule in a second portion of the molding surface 30. The plurality of groove structures 72 may be formed so that at least two groove structures 72 are arranged regularly according to the third rule in the first portion of the molding surface 30, while at least two groove structures 72 are arranged regularly according to a fourth rule different from the third rule in the second portion of the molding surface 30. Furthermore, since the groove structures 72 and the convex structures 71 are formed alternately, a state in which multiple groove structures 72 are arranged regularly may be considered equivalent to a state in which multiple convex structures 71 are arranged regularly.

[0081] The material that has entered the groove structure 72 (i.e., the material sheet 100) forms the convex structures 81 that make up the riblet structure RB. In other words, the material that has entered the multiple groove structures 72 each forms multiple convex structures 81 that make up the riblet structure RB. For this reason, the groove structure 72 that makes up the mold structure MB is a structure for molding the convex structures 81 that make up the riblet structure RB. For this reason, the shape (e.g., cross-sectional shape) of the groove structure 72 is complementary to the shape (e.g., cross-sectional shape) of the convex structures 81. On the other hand, the convex structures 71 that make up the mold structure MB are structures for molding the groove structures 82 that make up the riblet structure RB. For this reason, the shape (e.g., cross-sectional shape) of the convex structures 71 is complementary to the shape (e.g., cross-sectional shape) of the groove structures 82.

[0082] The convex structure 71 has, for example, a pair of side surfaces 711 and 712 facing opposite each other. In the example shown in Figures 6(a) to 6(c), the convex structure 71 has a side surface 711 facing the -Y side and a side surface 712 facing the +Y side. Each of the pair of side surfaces 711 and 712 is a flat surface. However, at least one of the pair of side surfaces 711 and 712 may include a curved surface.

[0083] The pair of side surfaces 711 and 712 may be non-parallel to each other. In this case, the pair of side surfaces 711 and 712 of the convex structure 71 may be connected via one end thereof (the upper end on the +Z side in the examples shown in FIGS. 6( a ) to 6( c )). The portion where the pair of side surfaces 711 and 712 of the convex structure 71 are connected constitutes a boundary portion 713 corresponding to the boundary between the two groove structures 72 located on both sides of the convex structure 71 along the second arrangement direction. Note that the boundary portion 713 where the pair of side surfaces 711 and 712 of the convex structure 71 are connected may be considered to constitute a corner of the convex structure 71. The boundary portion 713 where the pair of side surfaces 711 and 712 of the convex structure 71 are connected may be considered to constitute the boundary portion between the pair of side surfaces 711 and 712 of the convex structure 71. In this case, the pair of side surfaces 711 and 712 may be considered to be connected via the boundary portion 713.

[0084] The boundary portion 713 is a structure for forming the boundary portion 814 of the riblet structure RB (i.e., the boundary portion 814 connecting two adjacent convex structures 81). Here, since the boundary portion 814 includes a curved surface as described above, the boundary portion 713 also includes a curved surface. In other words, the boundary portion 713 has a shape that has been subjected to chamfering (particularly, R-chamfering, or round processing). However, if the boundary portion 814 does not include a curved surface, the boundary portion 713 does not have to include a curved surface. In other words, the boundary portion 713 may be a flat surface.

[0085] 6( a) to 6(c) show an example in which the boundary portion 713 includes a flat surface 7131, a curved surface 7132 connecting the flat surface 7131 and the side surface 711, and a curved surface 7133 connecting the flat surface 7131 and the side surface 712. In other words, Fig. 6(a) to 6(c) show an example in which a part of the boundary portion 713 is a curved surface. However, the entire boundary portion 713 may be a curved surface.

[0086] As described above, the boundary portion 713 connects a pair of side surfaces 711 and 712 facing opposite each other. Typically, the boundary portion 713 includes a curved surface. Therefore, the boundary portion 713 and the side surfaces 711 and 712 may be distinguished based on whether or not they include a curved surface. However, if the boundary portion 713 includes a curved surface (e.g., at least one of the curved surfaces 7132 and 7133) connected to the side surface 711 or 712, the side surface 711 or 712 may be considered to include a curved surface instead of the boundary portion 713.

[0087] Note that the pair of side surfaces 711 and 712 being non-parallel to each other may include a virtual surface (typically a plane) including the side surface 711 intersecting with a virtual surface (typically a plane) including the side surface 712. In this case, the virtual surface including the side surface 711 and the virtual surface including the side surface 712 may be an approximate plane of the side surface 711 and an approximate plane of the side surface 712, respectively.

[0088] When the pair of side surfaces 711 and 712 are not parallel to each other, the side surface 711 may be considered to be inclined with respect to the side surface 712, and the side surface 712 may be considered to be inclined with respect to the side surface 711. Typically, when the pair of side surfaces 711 and 712 are not parallel to each other, each of the pair of side surfaces 711 and 712 may be inclined with respect to the direction in which the convex structure 71 protrudes (the Z-axis direction in the example shown in Figures 6(a) and 6(b)). In this case, each of the side surfaces 711 and 712 may be referred to as an inclined portion. However, the pair of side surfaces 711 and 712 may be parallel to each other.

[0089] The side surface 711 of one convex structure 71 and the side surface 712 of another convex structure 71 adjacent to the one convex structure 71 along the second arrangement direction may be connected via their other end portions (the lower end portions on the -Z side in the examples shown in Figures 6(a) to 6(c)). In other words, the side surfaces 711 and 712 that are respectively provided on two adjacent convex structures 71 and that face each other may be connected via a corner portion 714 of a groove structure 72 located between the two adjacent convex structures 71. The corner portion 714 of the groove structure 72 may be considered to constitute a boundary portion that corresponds to the boundary between the two convex structures 71 located on both sides of the groove structure 72 along the second arrangement direction.

[0090] The corner portion 714 is a structure for forming the corner portion 813 of the riblet structure RB (i.e., the vertex of the convex structure 81). Here, since the corner portion 813 includes a curved surface as described above, the corner portion 714 also includes a curved surface. In other words, the corner portion 714 has a shape that has been subjected to chamfering (particularly, R-chamfering, or round processing). However, if the corner portion 813 does not include a curved surface, the corner portion 714 does not have to include a curved surface. In other words, the corner portion 714 may be a flat surface.

[0091] 6( a) to 6(c) show an example in which the corner 714 includes a curved surface 7141 that connects the side surfaces 711 and 712 of two adjacent convex structures 71. In other words, Fig. 6(a) to 6(c) show an example in which the entire corner 714 is a curved surface. However, only a part of the corner 714 may be a curved surface.

[0092] As described above, the corner 714 connects the side surfaces 711 and 712 of two adjacent convex structures 71. Typically, this corner 714 includes a curved surface. Therefore, the corner 714 and the side surfaces 711 and 712 may be distinguished based on whether or not they include a curved surface. However, if the corner 714 includes a curved surface (e.g., a curved surface 7141) connected to the side surface 711 or 712, the side surface 711 or 712 may be considered to include a curved surface instead of the corner 714.

[0093] The groove structure 72 may be considered to be a structure formed by a pair of side surfaces 711 and 712 and a corner portion 714. The groove structure 72 may be considered to be a structure including a groove facing the corner portion 714 and the pair of side surfaces 711 and 712 connected by the corner portion 714. On the other hand, the convex structure 71 may be considered to be a structure formed by a boundary portion 713. The convex structure 71 may be considered to be a structure including the boundary portion 713 on its surface. In this case, the boundaries between each of the side surfaces 711 and 712 and the boundary portion 713 may be used as the boundaries between the convex structure 71 and the groove structure 72.

[0094] However, in some cases, the convex structure 71 may be considered to be a structure formed by a boundary portion 713 and side surfaces 711 and 712 connected by the boundary portion 713. The convex structure 71 may be considered to be a structure including the boundary portion 713 and the side surfaces 711 and 712 connected by the boundary portion 713 on its surface.

[0095] In this manner, in this embodiment, at least one of the boundary portion 713 and the corner portion 714 may include a curved surface. When at least one of the boundary portion 713 and the corner portion 714 includes a curved surface, a riblet structure RB with higher shape accuracy can be formed compared to when neither the boundary portion 713 nor the corner portion 714 includes a curved surface. The reason for this will be explained below.

[0096] As an example, when at least one of the boundary 713 and the corner 714 includes a curved surface, the heated and softened material sheet 100 is more likely to penetrate up to the tip of the groove structure 72 (i.e., up to the corner 714) compared to when neither the boundary 713 nor the corner 714 includes a curved surface. As a result, there is a lower possibility of defects in the shape of the tip (i.e., the corner 813) of the convex structure 81 of the riblet structure RB formed by the groove structure 72. In other words, there is a lower possibility of part of the riblet structure RB being chipped off. Therefore, it is possible to form a riblet structure RB with relatively high shape accuracy.

[0097] As another example, when at least one of the boundary portion 713 and the corner portion 714 includes a curved surface, the material sheet 100 pressed against the mold 3 is more easily separated from the mold 3 than when neither the boundary portion 713 nor the corner portion 714 includes a curved surface. As a result, there is a lower possibility that part of the material sheet 100 will remain in the mold 3. This reduces the possibility that part of the riblet structure RB will be chipped. Therefore, it is possible to form a riblet structure RB with relatively high shape accuracy.

[0098] As described above, a mold made of zirconia (zirconia ceramics) may be used as the mold 3. When a mold made of zirconia (zirconia ceramics) is used as the mold 3, the material sheet 100 pressed against the mold 3 is more easily separated from the mold 3 than when a mold made of a material other than zirconia is used as the mold 3. However, zirconia is a relatively expensive material. Therefore, the cost of the mold 3 can be reduced by using a mold made of a material cheaper than zirconia (e.g., at least one of pre-hardened steel, as-rolled steel, and stainless steel) as the mold 3. In this case, the mold 3 made of a material other than zirconia may have a mold structure MB in which at least one of the boundary portion 713 and the corner portion 714 includes a curved surface. As a result, even when a mold made of a material other than zirconia is used as the mold 3, the material sheet 100 pressed against the mold 3 is more easily separated from the mold 3, similar to when a mold made of zirconia is used as the mold. This effect of making it easier to separate the material sheet 100 pressed against the mold 3 from the mold 3 is particularly advantageous when a mold made of a material other than zirconia is used as the mold 3. It goes without saying that a mold structure MB in which at least one of the boundary portions 713 and the corner portions 714 includes a curved surface may be formed in the mold 3 made of zirconia.

[0099] The radius of curvature R_mb of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 may be set to an appropriate value. For example, if the height H_rb of the convex structure 81 satisfies the first height condition of "2.5 micrometers < H_rb < 100 micrometers" as described above, when the riblet sheet 1 is formed using a mold structure MB with a radius of curvature R_mb greater than 7 micrometers, the effect of the riblet structure RB in reducing the resistance of the surface of the riblet sheet 1 to the fluid (and further, the resistance of the surface of the object to which the riblet sheet 1 is attached) may be weakened. For this reason, the radius of curvature R_mb may be set to a value smaller than 7 micrometers. Furthermore, when the radius of curvature R_mb is less than 1 micrometer, forming the curved boundary portion 713 and the corner portion 714 may become difficult from the perspective of the manufacturing accuracy of the mold 3 (i.e., the forming accuracy of the mold structure MB). In other words, the shape accuracy of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 may deteriorate. For this reason, the radius of curvature R_mb may be set to a value greater than 1 micrometer. In other words, the radius of curvature R_mb may satisfy the first curvature condition of "1 micrometer < R_mb < 7 micrometers." As a result, a mold structure MB for forming a riblet structure RB that can appropriately exhibit the effect of reducing resistance to a fluid can be formed with high precision. Therefore, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exhibit the effect of reducing resistance to a fluid is formed with high precision. Note that a riblet sheet 1 manufactured using a mold 3 that satisfies the first curvature condition typically satisfies the curvature condition that "the radius of curvature R_rb of the curved surface included in at least one of the corner portion 813 and the boundary portion 814 is greater than 1 micrometer and less than 7 micrometers."

[0100] Preferably, taking into account a margin, the radius of curvature R_mb may be set to a value greater than 1 micrometer and greater than 4 micrometers. In other words, the radius of curvature R_mb may satisfy the second curvature condition of "1 micrometer < R_mb < 4 micrometers." As a result, a mold structure MB for forming a riblet structure RB that can more appropriately exhibit the effect of reducing resistance to a fluid can be formed with greater precision. Therefore, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can more appropriately exhibit the effect of reducing resistance to a fluid is formed with greater precision. Note that a riblet sheet 1 manufactured using a mold 3 that satisfies the second curvature condition typically satisfies the curvature condition that "the radius of curvature R_rb of the curved surface included in at least one of the corner portion 813 and the boundary portion 814 is greater than 1 micrometer and less than 4 micrometers."

[0101] More preferably, taking into consideration an additional margin, the radius of curvature R_mb may be set to a value greater than 2 micrometers and greater than 3 micrometers. In other words, the radius of curvature R_mb may satisfy the second curvature condition of "2 micrometers < R_mb < 3 micrometers." As a result, a mold structure MB for forming a riblet structure RB that can more appropriately exhibit the effect of reducing resistance to a fluid can be formed with greater precision. Therefore, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can more appropriately exhibit the effect of reducing resistance to a fluid is formed with greater precision. Note that a riblet sheet 1 manufactured using a mold 3 that satisfies the third curvature condition typically satisfies the curvature condition that "the radius of curvature R_rb of the curved surface included in at least one of the corner portion 813 and the boundary portion 814 is greater than 2 micrometers and less than 3 micrometers."

[0102] Furthermore, the radius of curvature R_mb of the curved surface included by a certain boundary portion 713 may be constant regardless of the position on the curved surface. In this case, the radius of curvature R_rb of the curved surface included by the boundary portion 814 of the riblet structure RB formed by the boundary portion 713 of the mold structure MB may be constant regardless of the position on the curved surface. Alternatively, the radius of curvature R_mb of the curved surface included by a certain boundary portion 713 may vary depending on the position on the curved surface. For example, the radius of curvature R_mb of a first portion of the curved surface included by a certain boundary portion 713 may be different from the radius of curvature R_mb of a second portion of the same curved surface included by the same boundary portion 713. In this case, the radius of curvature R_rb of the curved surface included by the boundary portion 814 of the riblet structure RB formed by the boundary portion 713 of the mold structure MB may vary depending on the position on the curved surface. For example, the radius of curvature R_rb of a first portion of a curved surface included in a given boundary 814 may be different from the radius of curvature R_rb of a second portion of the same curved surface included in the same boundary 814 .

[0103] Similarly, the radius of curvature R_mb of the curved surface included by a certain corner 714 may be constant regardless of the position on the curved surface. In this case, the radius of curvature R_rb of the curved surface included by a corner 813 of a riblet structure RB formed by the corner 714 of the mold structure MB may be constant regardless of the position on the curved surface. Alternatively, the radius of curvature R_mb of the curved surface included by a certain corner 714 may vary depending on the position on the curved surface. For example, the radius of curvature R_mb of a first portion of the curved surface included by a certain corner 714 may be different from the radius of curvature R_mb of a second portion of the same curved surface included by the same corner 714. In this case, the radius of curvature R_rb of the curved surface included by a corner 813 of a riblet structure RB formed by the corner 714 of the mold structure MB may vary depending on the position on the curved surface. For example, the radius of curvature R_rb of a first portion of the curved surface included in a certain corner 813 may be different from the radius of curvature R_rb of a second portion of the same curved surface included in the same corner 813.

[0104] The radius of curvature R_mb of the curved surface of at least one of the boundary 713 and the corner 714 formed in the first portion of the molding surface 30 may be different from the radius of curvature R_mb of the curved surface of at least one of the boundary 713 and the corner 714 formed in a second portion different from the first portion of the molding surface 30. In other words, the radius of curvature R_mb of the curved surface of at least one of the boundary 713 and the corner 714 may vary depending on the position at which at least one of the boundary 713 and the corner 714 is formed. As a result, the radius of curvature R_rb of the curved surface of at least one of the corner 813 and the boundary 814 constituting the riblet structure RB may also vary depending on the position at which at least one of the corner 813 and the boundary 814 is formed. In this case, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB is formed with high precision, which can appropriately exhibit the effect of reducing resistance to fluid, compared to a case in which the radius of curvature R_rb is fixed regardless of position.

[0105] As an example, the radius of curvature R_mb of the curved surface of at least one of the boundary portion 713 and the corner portion 714 may vary depending on the formation density of the convex structures 71 at the position where at least one of the boundary portion 713 and the corner portion 714 is formed. In other words, the radius of curvature R_mb at a certain position on the molding surface 30 may be set to a value depending on the formation density of the convex structures 71 at that position. The formation density of the convex structures 71 may be the number of convex structures 71 that intersect with the axis of a unit length extending in the direction in which the multiple convex structures 71 are arranged (i.e., the pitch direction). The formation density of the convex structures 71 may be the number of convex structures 71 present in an area of ​​a unit length along the direction in which the multiple convex structures 71 are arranged. The formation density of the convex structures 71 may be the number of convex structures 71 arranged in an area of ​​a unit area. The formation density of the convex structures 71 may be the volume of the convex structures 71 located in an area of ​​a unit volume.

[0106] For example, at positions where the formation density of the convex structures 71 is relatively high, the formation density of the groove structures 72 substantially formed by the convex structures 71 is also high. As a result, at positions where the formation density of the groove structures 72 is relatively high, it is more likely that the heated and softened material sheet 100 will have difficulty entering the multiple groove structures 72, compared to positions where the formation density of the groove structures 72 is relatively low. Therefore, the radius of curvature R_mb may be relatively large at positions where the formation density of the convex structures 71 is relatively high, so that the heated and softened material sheet 100 will easily enter the multiple groove structures 72. On the other hand, at positions where the formation density of the convex structures 71 is relatively low, the formation density of the groove structures 72 substantially formed by the convex structures 71 is also low. As a result, at positions where the formation density of the groove structures 72 is relatively low, it is less likely that the heated and softened material sheet 100 will have difficulty entering the multiple groove structures 72, compared to positions where the formation density of the groove structures 72 is relatively high. For this reason, at positions where the formation density of the convex structures 71 is relatively low, there is relatively little need to make the radius of curvature R_mb relatively large so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72. Therefore, at positions where the formation density of the convex structures 71 is relatively high, the radius of curvature R_mb may be relatively small. In summary, when the formation density of the convex structures 71 in the first portion of the molding surface 30 is higher than the formation density of the convex structures 71 in the second portion of the molding surface 30, the radius of curvature R_mb in the first portion of the molding surface 30 may be larger than the radius of curvature R_mb in the second portion of the molding surface 30. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exhibit the effect of reducing resistance to a fluid is formed with high precision.

[0107] As another example, the radius of curvature R_mb of the curved surface of at least one of the boundary 713 and the corner 714 may vary depending on the temperature of the mold 3 at the position where at least one of the boundary 713 and the corner 714 is formed or the temperature of the material sheet 100 in contact with the mold 3 at that position (hereinafter referred to as the "forming temperature"). In other words, the radius of curvature R_mb at a certain position on the forming surface 30 may be set to a value depending on the forming temperature at that position. For example, at a position where the forming temperature is relatively low, the fluidity of the material sheet 100 that has been heated and softened is relatively low. As a result, at a position where the forming temperature is relatively low, the material sheet 100 that has been heated and softened is more likely to have difficulty penetrating the multiple groove structures 72 compared to a position where the forming temperature is relatively high. Therefore, the radius of curvature R_mb may be relatively large at a position where the forming temperature is relatively low so that the molten material can more easily enter the multiple groove structures 72. On the other hand, at positions where the forming temperature is relatively high, the fluidity of the heated and softened material sheet 100 is relatively high. As a result, at positions where the forming temperature is relatively high, the heated and softened material sheet 100 is less likely to have difficulty entering the multiple groove structures 72 compared to positions where the forming temperature is relatively low. For this reason, at positions where the forming temperature is relatively high, there is relatively little need to relatively increase the radius of curvature R_mb so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72. For this reason, at positions where the forming temperature is relatively high, the radius of curvature R_mb may be relatively small. In summary, when the forming temperature of the first portion of the forming surface 30 is lower than the forming temperature of the second portion of the forming surface 30, the radius of curvature R_mb of the first portion of the forming surface 30 may be larger than the radius of curvature R_mb of the second portion of the forming surface 30. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exhibit the effect of reducing resistance to fluid is accurately formed.

[0108] As another example, the radius of curvature R_mb of the curved surface of at least one of the boundary 713 and the corner 714 may vary depending on the depth H_mb of the groove structure 72 at the position where at least one of the boundary 713 and the corner 714 is formed. That is, the radius of curvature R_mb at a certain position on the molding surface 30 may be set to a value depending on the depth H_mb of the groove structure 72 at that position. For example, at a position where a relatively deep groove structure 72 is formed, it is more likely that the heated and softened material sheet 100 will have difficulty entering the multiple groove structures 72 compared to a position where a relatively shallow groove structure 72 is formed. Therefore, the radius of curvature R_mb may be relatively larger at a position where a relatively deep groove structure 72 is formed so that the heated and softened material sheet 100 will more easily enter the multiple groove structures 72. On the other hand, at positions where relatively shallow groove structures 72 are formed, it is less likely that the heated and softened material sheet 100 will have difficulty entering the multiple groove structures 72, compared to positions where relatively deep groove structures 72 are formed. Therefore, at positions where relatively shallow groove structures 72 are formed, there is less need to relatively increase the radius of curvature R_mb so that the heated and softened material sheet 100 will easily enter the multiple groove structures 72. Therefore, at positions where relatively shallow groove structures 72 are formed, the radius of curvature R_mb may be relatively small. In summary, when the depth H_mb of the groove structure 72 formed in the first portion of the forming surface 30 is deeper than the depth H_mb of the groove structure 72 formed in the second portion of the forming surface 30, the radius of curvature R_mb in the first portion of the forming surface 30 may be larger than the radius of curvature R_mb in the second portion of the forming surface 30. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exhibit the effect of reducing resistance to fluid is accurately formed.

[0109] Alternatively, the radius of curvature R_mb of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 may vary depending on the angle of the side surfaces 711 and 712 at the position where at least one of the boundary portion 713 and the corner portion 714 is formed (e.g., the angle relative to an axis along the Z axis).

[0110] The radius of curvature R_mb of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 may be set based on the measurement results of riblet structures RB formed using multiple molds 3 with different radii of curvature R_mb. For example, an operator who manufactures the mold 3 (e.g., an operator of the processing system 4) may manually set the radius of curvature R_mb based on the measurement results of the riblet structure RB. Alternatively, a device that manufactures the mold 3 (e.g., the processing system 4 described below) may automatically set the radius of curvature R_mb based on the measurement results of the riblet structure RB.

[0111] As described above, one purpose of changing the radius of curvature R_mb of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 is to create a situation in which the heated and softened material sheet 100 can easily enter the multiple groove structures 72. Here, as the fluidity of the heated and softened material sheet 100 increases, the heated and softened material sheet 100 can easily enter the multiple groove structures 72. The fluidity of the heated and softened material sheet 100 increases as the temperature of the heated and softened material sheet 100 increases. The temperature of the heated and softened material sheet 100 increases as the molding temperature increases. Therefore, in addition to or instead of changing the radius of curvature R_mb, the molding temperature when molding the riblet sheet 1 may be adjusted. In other words, the molding temperature at each position on the molding surface 30 may be adjusted so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72 at each position on the molding surface 30. In other words, the molding temperatures at each position on the molding surface 30 may be different from each other. Even in this case, as in the case where the radius of curvature R_mb is changed, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exert the effect of reducing resistance to fluid is precisely formed.

[0112] As an example, the molding temperature at a certain position on the molding surface 30 may be adjusted according to the formation density of the convex structures 71 at that position. For example, as described above, at positions where the formation density of the convex structures 71 is relatively high, it is more likely that the heated and softened material sheet 100 will have difficulty penetrating into the multiple groove structures 72, compared to positions where the formation density of the groove structures 72 is relatively low. Therefore, the molding temperature may be relatively high at positions where the formation density of the convex structures 71 is relatively high so that the heated and softened material sheet 100 will more easily penetrate into the multiple groove structures 72. On the other hand, the molding temperature may be relatively low at positions where the formation density of the convex structures 71 is relatively low. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exert the effect of reducing resistance to fluid is formed with high precision.

[0113] As another example, the molding temperature at a certain position on the molding surface 30 may be adjusted depending on the depth H_mb of the groove structure 72 at that position. For example, as described above, at positions where relatively deep groove structures 72 are formed, it is more likely that the heated and softened material sheet 100 will have difficulty penetrating the multiple groove structures 72 compared to positions where relatively shallow groove structures 72 are formed. Therefore, the molding temperature may be relatively high at positions where relatively deep groove structures 72 are formed so that the heated and softened material sheet 100 will more easily penetrate the multiple groove structures 72. On the other hand, the molding temperature may be relatively low at positions where relatively shallow groove structures 72 are formed. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exert the effect of reducing resistance to fluid is formed with high precision.

[0114] As another example, the molding temperature at a certain position on the molding surface 30 may be adjusted according to the radius of curvature R_mb of the curved surface included in at least one of the boundary portion 713 and the corner portion 714 at that position. For example, as described above, at a position where the radius of curvature R_mb is relatively small, the heated and softened material sheet 100 is more likely to have difficulty entering the multiple groove structures 72 compared to a position where the radius of curvature R_mb is relatively large. Therefore, the molding temperature may be relatively high at a position where the radius of curvature R_mb is relatively small so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72. On the other hand, the molding temperature may be relatively low at a position where the radius of curvature R_mb is relatively large. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB capable of appropriately exhibiting the effect of reducing resistance to a fluid is formed with high precision.

[0115] As another example, the molding temperature at a certain position on the molding surface 30 may be adjusted depending on the presence or absence of a mold structure MB (e.g., groove structure 72) at that position. In other words, the molding temperature at a position on the molding surface 30 where the mold structure MB is formed may be different from the molding temperature at a position on the molding surface 30 where the mold structure MB is not formed. For example, at a position where the groove structure 72 is formed, the molding temperature may be relatively high so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72. On the other hand, at a position where the groove structure 72 is not formed, there is less need to adjust the molding temperature so that the heated and softened material sheet 100 can easily enter the multiple groove structures 72. Therefore, at a position where the groove structure 72 is not formed, the molding temperature may be relatively low. As a result, it is possible to manufacture a riblet sheet 1 in which a riblet structure RB that can appropriately exert the effect of reducing resistance to fluid is accurately formed.

[0116] Because the groove structure 72 is a structure for forming the above-described convex structures 81, the depth H_mb of at least one of the multiple groove structures 72 may be the same as the height H_rb of at least one of the multiple convex structures 81. Furthermore, the pitch P_mb of the groove structure 72 may be the same as the pitch P_rb of the convex structures 81. Therefore, in the mold structure MB as well, similar to the riblet structure RB, the depth H_mb of at least one of the multiple groove structures 72 may be set to a depth determined according to the pitch P_mb of the groove structures 72. For example, the depth H_mb of at least one of the multiple groove structures 72 may be equal to or less than the pitch P_mb of the groove structures 72. For example, the depth H_mb of at least one of the multiple groove structures 72 may be equal to or less than half the pitch P_mb of the groove structures 72. Furthermore, the depth H_mb of at least one of the multiple groove structures 72 may be within a range of 1 / 2 ± 10% of the pitch P_mb of the groove structures 72. The depth H_mb may be the depth from the vertex, ridge, or upper surface (for example, the boundary portion 713) of the convex structure 81.

[0117] As an example, the pitch P_mb of the groove structures 72 may be greater than 5 micrometers and less than 200 micrometers. That is, the pitch P_mb of the groove structures 72 may satisfy a second pitch condition of "5 micrometers < P_mb < 200 micrometers." In this case, the depth H_mb of at least one of the plurality of groove structures 72 may be greater than 2.5 micrometers and less than 100 micrometers. The depth H_mb of at least one of the plurality of groove structures 72 may satisfy a second height condition of "2.5 micrometers < H_mb < 100 micrometers." That is, the mold structure MB may satisfy at least one of the second pitch condition and the second height condition.

[0118] Here, when the pitch P_mb of the groove structure 72 satisfies the second pitch condition of "5 micrometers < P_mb < 200 micrometers," the pitch of the convex structures 81 formed by the mold structure MB will be in the range of 5 micrometers to 200 micrometers. In other words, the pitch P_rb of the convex structures 81 will satisfy the above-mentioned first pitch condition of "5 micrometers < P_rb < 200 micrometers." As a result, as described above, the riblet structure RB can reduce the resistance of the surface of the riblet sheet 1 to the fluid (and further, the resistance of the surface of the object to which the riblet sheet 1 is attached).

[0119] Furthermore, when the depth H_mb of at least one of the multiple groove structures 72 satisfies the second height condition of "2.5 micrometers < H_mb < 100 micrometers," the height H_rb of the convex structure 81 formed by the mold structure MB falls within the range of 2.5 micrometers to 100 micrometers. In other words, the height H_rb of the convex structure 81 satisfies the above-mentioned first height condition of "2.5 micrometers < H_rb < 100 micrometers." As a result, as described above, the riblet structure RB can reduce the resistance of the surface of the riblet sheet 1 to a fluid (and further, the resistance of the surface of an object to which the riblet sheet 1 is attached).

[0120] In this embodiment, the depth H_mb of the groove structure 72 may refer to the size of the groove structure 72 in the direction in which the groove structure 72 is recessed (the Z-axis direction in the examples shown in Figures 6(a) to 6(c)). The depth H_mb of the groove structure 72 may refer to the distance from the lower end of the groove structure 72 to the upper end of the groove structure 72 in the direction in which the groove structure 72 is recessed. The depth H_mb of the groove structure 72 may refer to the distance from a corner 714 connecting to the lower end of the groove structure 72 to a boundary 713 that forms the upper end of the groove structure 72 in the direction in which the groove structure 72 is recessed. The depth H_mb of the groove structure 72 may be considered to be substantially equivalent to the height of the convex structure 71.

[0121] Furthermore, the pitch P_mb of the groove structures 72 in this embodiment may refer to the distance between the corresponding identical portions of two adjacent groove structures 72 in the second arrangement direction. In the example shown in FIGS. 6( a) to 6(c), the pitch P_mb of the groove structures 72 may refer to the distance between the corners 714 of two adjacent groove structures 72 in the Y-axis direction. Note that, because the groove structures 72 and the convex structures 71 are alternately formed in the second arrangement direction, the pitch P_mb of the groove structures 72 may be considered equivalent to the pitch of the convex structures 71. The pitch of the convex structures 71 may refer to the distance between the corresponding identical portions of two adjacent convex structures 71 in the second arrangement direction. In the example shown in FIGS. 6( a) to 6(c), the pitch of the convex structures 71 may refer to the distance between the corresponding identical portions of two adjacent convex structures 71 in the Y-axis direction.

[0122] (3-3) Manufacturing Method of Mold 3 Next, a manufacturing method for manufacturing the mold 3 will be described. In this embodiment, a manufacturing method for manufacturing the mold 3 using a processing system 4 that performs removal processing will be described. In this case, the processing system 4 may perform removal processing to remove a portion of the mold 3 by irradiating the molding surface 30 of the mold 3 with processing light EL. In particular, the processing system 4 may perform removal processing to remove a portion of the mold 3 so as to form a mold structure MB on the molding surface 30 of the mold 3. As a result, a mold 3 having a mold structure MB formed on the molding surface 30 is manufactured. However, the manufacturing method of the mold 3 is not limited to a manufacturing method that uses the processing system 4.

[0123] The structure of the processing system 4 will be described below with reference to Fig. 8 and Fig. 9. Fig. 8 is a cross-sectional view schematically showing the structure of the processing system 4. Fig. 9 is a system configuration diagram showing the system configuration of the processing system 4.

[0124] 8 and 9 , the processing system 4 includes a processing device 41, a processing light source 42, and a control device 43. At least a portion of the processing device 41 is housed in the internal space of a housing 44. The internal space of the housing 44 may or may not be purged with a purge gas such as nitrogen gas. The internal space of the housing 44 may or may not be evacuated. However, the processing device 41 does not have to be housed in the internal space of the housing 44. In other words, the processing system 4 does not have to include a housing 44 that houses the processing device 41.

[0125] The processing device 41 is capable of processing the workpiece W, which is the material of the mold 3, under the control of the control device 43. The processing device 41 performs removal processing to remove a portion of the workpiece W. By performing removal processing, the processing device 41 forms a mold structure MB in the workpiece W. As a result, the workpiece W on which the mold structure MB is formed is manufactured as the mold 3. In other words, the workpiece W on which the mold structure MB is formed is manufactured as the mold 3, in which the surface on which the mold structure MB is formed becomes the molding surface 30.

[0126] The processing device 41 irradiates the workpiece W with processing light EL in order to process the workpiece W. The processing light EL may be any type of light as long as it can process the workpiece W when irradiated onto the workpiece W. The processing light EL may include pulsed light (e.g., pulsed light having an emission time of picoseconds or less). Alternatively, the processing light EL may not include pulsed light. In other words, the processing light EL may be continuous light. The processing light EL is supplied to the processing device 41 from a processing light source 42 that generates the processing light EL via a light propagation member (e.g., at least one of an optical fiber and a mirror) not shown. The processing device 41 irradiates the workpiece W with the processing light EL supplied from the processing light source 42.

[0127] In order to process the workpiece W, the processing device 41 includes a processing head 411 , a head drive system 412 , a stage 413 , and a stage drive system 414 .

[0128] The machining head 411 irradiates the workpiece W with the machining light EL from the machining light source 42. The machining head 411 is equipped with a machining optical system 4111 in order to irradiate the workpiece W with the machining light EL. The machining head 411 irradiates the workpiece W with the machining light EL via the machining optical system 4111. The machining optical system 4111 may, for example, focus the machining light EL on the surface of the workpiece W. The machining optical system 4111 may, for example, control the optical characteristics of the machining light EL. Examples of the optical characteristics of the machining light EL include at least one of the intensity of the machining light EL, changes in the intensity of the machining light EL over time, the focusing position of the machining light EL, the angle of incidence of the machining light EL with respect to the workpiece W, the shape of the machining light EL in an optical plane intersecting the optical axis of the machining optical system 111, the intensity distribution of the machining light EL in the optical plane, and the pulse number of the machining light EL (when the machining light EL is pulsed light).

[0129] The head drive system 412 moves the machining head 411 along at least one of the X-axis, Y-axis, and Z-axis directions under the control of the control device 43. The head drive system 412 may move the machining head 411 along at least one of the θX-axis, θY-axis, and θZ-axis directions in addition to or instead of at least one of the X-axis, Y-axis, and Z-axis directions. When the machining head 411 moves, the positional relationship between the stage 413 (and further, the workpiece W placed on the stage 413) and the machining head 411 changes. Furthermore, when the positional relationship between the stage 413, the workpiece W, and the machining head 411 changes, the irradiation position of the machining light EL on the workpiece W changes.

[0130] A workpiece W is placed on the stage 413. The stage 413 does not have to hold the workpiece W placed on it. In other words, the stage 413 does not have to apply a holding force to the workpiece W placed on it to hold the workpiece W. Alternatively, the stage 413 may hold the workpiece W placed on it. In other words, the stage 413 may apply a holding force to the workpiece W placed on it to hold the workpiece W. For example, the stage 413 may hold the workpiece W by vacuum suction and / or electrostatic suction. Alternatively, a jig for holding the workpiece W may hold the workpiece W, and the stage 413 may hold the jig that holds the workpiece W.

[0131] The stage drive system 414 moves the stage 413 under the control of the control device 43. Specifically, the stage drive system 414 moves the stage 413 relative to the machining head 411. For example, under the control of the control device 43, the stage drive system 414 may move the stage 413 along at least one of the X-axis direction, the Y-axis direction, the Z-axis direction, the θX direction, the θY direction, and the θZ direction. Note that moving the stage 413 along at least one of the θX direction, the θY direction, and the θZ direction may be considered equivalent to changing the orientation of the stage 413 (and further the workpiece W placed on the stage 413) around at least one of the X-axis, the Y-axis, and the Z-axis. Alternatively, moving the stage 413 along at least one of the θX direction, the θY direction, and the θZ direction may be considered equivalent to rotating (or rotationally moving) the stage 413 around at least one of the X-axis, the Y-axis, and the Z-axis.

[0132] When the stage 413 moves, the positional relationship between the stage 413 (and further the workpiece W placed on the stage 413) and the processing head 411 changes. Furthermore, when the positional relationship between the stage 413, the workpiece W, and the processing head 411 changes, the irradiation position of the processing light EL on the workpiece W changes.

[0133] The control device 43 controls the operation of the machining system 4. For example, the control device 43 may generate machining control information for machining the workpiece W, and may also control the machining device 41 based on the machining control information so that the workpiece W is machined in accordance with the generated machining control information. In other words, the control device 43 may control the machining of the workpiece W.

[0134] The control device 43 may include, for example, an arithmetic device and a storage device. The arithmetic device may include, for example, at least one of a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The control device 43 functions as a device that controls the operation of the machining system 4 by the arithmetic device executing a computer program. This computer program is a computer program for causing the control device 43 (e.g., the arithmetic device) to perform (i.e., execute) the operations to be performed by the control device 43, which will be described later. In other words, this computer program is a computer program for causing the control device 43 to function so as to cause the machining system 4 to perform the operations to be performed later. The computer program executed by the arithmetic device may be recorded in a storage device (i.e., a recording medium) included in the control device 43, or may be recorded in any storage medium (e.g., a hard disk or semiconductor memory) built into or externally attachable to the control device 43. Alternatively, the arithmetic device may download the computer program to be executed from a device external to the control device 43 via a network interface.

[0135] (4) Modified Examples As described above, the first manufacturing apparatus 2a, which is an example of the manufacturing apparatus 2 for producing the riblet sheet 1, alternately presses the mold 3a against the material sheet 100 and supplies and recovers the material sheet 100, in order to produce the riblet sheet 1. Therefore, depending on the supply amount (recovery amount) of the material sheet 100, the material sheet 100 may include, as shown in Figure 4 described above, riblet portions 101 in which the riblet structure RB is formed by pressing the mold 3a against the material sheet 100, and non-riblet portions 102 in which the riblet structure RB is not formed because the mold 3a is not pressed against the material sheet 100. In other words, as shown in Figure 4, riblet portions 101 and non-riblet portions 102 may appear alternately along the longitudinal direction of the riblet sheet 1.

[0136] In this case, there is a possibility that the multiple convex structures 81 that make up the riblet structure RB will be divided by the non-riblet portions 102. Specifically, as shown in Figure 10(a), which is a perspective view showing the riblet portions 101 and the non-riblet portions 102, and Figure 10(b), which is a cross-sectional view showing the riblet portions 101 and the non-riblet portions 102, there is a possibility that a non-riblet portion 102 will be formed between two riblet portions 101 that are adjacent along the longitudinal direction of the riblet sheet 1. As a result, there is a possibility that the convex structures 81 that should be formed continuously across the two adjacent riblet portions 101 will be divided by the non-riblet portions 102 that exist in the two adjacent riblet portions 101.

[0137] In particular, because the mold 3 is not pressed against the non-riblet portion 102, the non-riblet portion 102 may have a convex shape relative to the riblet portion 101, as shown in Figures 10(a) and 10(b). In other words, the height of the non-riblet portion 102 (e.g., the height of the upper surface of the non-riblet portion 102) may be higher than the height of the riblet portion 101 (e.g., at least one of the height of the molding surface 30 in the riblet portion 101 and the height of the convex structure 81). In this case, as shown in Figures 10(a) and 10(b), the non-riblet portion 102 may act on the fluid as an obstacle that blocks the flow of the fluid that flows along the convex structure 81 between two adjacent convex structures 81. In other words, the non-riblet portion 102 may act on the fluid as an obstacle that blocks the flow of the fluid that flows within the groove structure 82 along the groove structure 82. As a result, when the non-riblet portions 102 are present, the resistance of the surface of the riblet sheet 1 to the fluid (and further the resistance to the surface of the object to which the riblet sheet 1 is attached) may be higher than when the non-riblet portions 102 are not present. In other words, the resistance reduction effect of the riblet structure RB may be deteriorated. As a result, a moving body to which the riblet sheet 1 is attached may not be able to fully enjoy the resistance reduction effect of the riblet structure RB (that is, the effect of reducing the resistance of the surface of the moving body to which the riblet sheet 1 is attached to the fluid). In particular, the higher the height of the non-riblet portions 102 that separate the convex structures 81 and the groove structures 82, the more likely it is that a moving body to which the riblet sheet 1 is attached will not be able to fully enjoy the resistance reduction effect.

[0138] 10( a) and 10(b), a riblet portion 101 may be formed between two adjacent non-riblet portions 102 along the longitudinal direction. As a result, the fluid flowing along the surface of the riblet sheet 1 flows from the outside of the groove structure 72 into the inside of the groove structure 72, and then flows from the inside of the groove structure 72 to the outside of the groove structure 72. In this case, too, the non-riblet portion 102 may act on the fluid as an obstacle that blocks the flow of the fluid flowing along the groove structure 82 within the groove structure 82. In other words, the drag reduction effect of the riblet structure RB may be deteriorated.

[0139] 11( a) and 11(b), the first manufacturing apparatus 2a may form the riblet structure RB in the vicinity of the boundary 103 between the riblet portion 101 and the non-riblet portion 102 such that the depth of the groove structure 82 becomes shallower as the groove structure 82 approaches the boundary 103 along the first stretching direction in which the groove structure 82 extends. Specifically, as shown in FIG. 11(b), in a case in which the riblet portion 101 is divided into a first riblet portion 1011 located in the vicinity of the boundary 103 and a second riblet portion 1012 other than the first riblet portion 1011, the first manufacturing apparatus 2a may form the riblet structure RB in such a way that the depth of the groove structure 82 formed in the first riblet portion 1011 becomes shallower as it approaches the boundary 103 along the first stretching direction.

[0140] In this case, as shown in Figure 11 (b), the resistance of the non-riblet portions 102 to the fluid flowing within and along the groove structure 82 is reduced. This reduces the degree of deterioration in the resistance reduction effect. As a result, a moving body to which the riblet sheet 1 is attached can enjoy an appropriate resistance reduction effect.

[0141] To form the riblet structure RB shown in Figures 11(a) and 11(b), the first manufacturing apparatus 2a may use a flat mold 3a having a mold structure MB shown in Figures 12(a) and 12(b). Specifically, as shown in Figures 12(a) and 12(b), the flat mold 3a may have a mold structure MB formed thereon such that, in the vicinity of an end 39 of the molding surface 30 in the second extension direction in which the groove structure 72 formed in the flat mold 3a extends, the depth H_mb of the groove structure 72 becomes shallower as the groove structure 72 approaches the end 39 along the second extension direction in which the groove structure 72 extends. In other words, the mold structure MB may be formed such that, in the vicinity of the end 39, the height of the convex structure 71 becomes lower as the convex structure 71 approaches the end 39 along the second extension direction in which the convex structure 71 extends. 12(b), when the molding surface 30 is divided into a first surface portion 31 located near the end portion 39 and a second surface portion 32 other than the first surface portion 31, the mold structure MB may be formed in the flat plate mold 3a such that the depth H_mb of the groove structure 72 formed in the first surface portion 31 becomes shallower as the groove structure 72 approaches the end portion 39 along the second stretching direction. The mold structure MB may be formed in the flat plate mold 3a such that the height of the convex structure 71 formed in the first surface portion 31 becomes lower as the convex structure 71 approaches the end portion 39 along the second stretching direction.

[0142] 11( a) and 11(b), when the depth H_mb of the groove structure 72 gradually becomes shallower, a part of the molding surface 30 (for example, at least a part of the second surface portion 32) may be curved. In this case, similar to the case where the convex structure 71 and part of the groove structure 72 include curved surfaces as described above, it is also possible to obtain the effect that the material sheet 100 pressed against the mold 3a can be more easily separated from the mold 3a.

[0143] Furthermore, not only the first manufacturing apparatus 2a that manufactures the riblet sheet 1 using a flat mold 3a, but also any manufacturing apparatus may manufacture the riblet sheet 1 shown in Figures 11(a) and 11(b).

[0144] Alternatively, the first manufacturing apparatus 2a may adjust the supply amount (recovery amount) of the material sheet 100 so that non-riblet portions 102 are not formed in the material sheet 100 when alternately repeating the pressing of the mold 3a against the material sheet 100 and the supply and recovery of the material sheet 100. In other words, the first manufacturing apparatus 2a may adjust the supply amount (recovery amount) of the material sheet 100 so that no gap is formed between a first portion of the material sheet 100 against which the mold 3a is pressed at a first timing and a second portion of the material sheet 100 against which the mold 3a is pressed at a second timing following the first timing when alternately repeating the pressing of the mold 3a against the material sheet 100 and the supply and recovery of the material sheet 100.

[0145] (5) Supplementary Notes The following supplementary notes are provided regarding the above-described embodiment. [Supplementary Note 1] A mold used for molding a film-like sheet member, the mold having a molding surface with which a material of the sheet member comes into contact, the molding surface having a first surface, a plurality of concave structures extending in a first direction being formed on the first surface so as to be aligned along a second direction intersecting the first direction, at least one of a corner of a first concave structure of the plurality of concave structures and a boundary between a first concave structure and a second concave structure of the plurality of concave structures adjacent to each other along the second direction includes a curved surface, when a radius of curvature of the curved surface is R, a pitch of the plurality of concave structures is P, and a depth of the plurality of concave structures from the molding surface is H, the mold satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers". [Supplementary Note 2] The mold according to Supplementary Note 1, wherein the mold includes a cylindrical member rotatable around a central axis, and the molding surface is at least a part of the curved outer peripheral surface of the cylindrical member. [Supplementary Note 3] The mold according to Supplementary Note 2, wherein the first direction is a direction including a directional component along a rotational direction in which the cylindrical member rotates. [Supplementary Note 4] The mold according to Supplementary Note 2 or 3, wherein the first direction is a direction including a directional component along an intersecting direction intersecting the central axis of the cylindrical member. [Supplementary Note 5] The mold according to any one of Supplements 1 to 4, wherein the mold includes a flat-plate member having a flat shape, the molding surface of which is a flat surface. [Appendix 6] The mold described in Appendix 5, wherein the molding surface further has a second surface, wherein a plurality of third concave structures that are part of the plurality of concave structures are formed on the first surface, wherein the second surface is located between the first surface and an end of the molding surface and wherein a plurality of fourth concave structures that are part of the plurality of concave structures are formed on the second surface, and wherein a depth of at least one of the plurality of fourth concave structures becomes shallower as the at least one of the plurality of fourth concave structures approaches the end.[Appendix 7] The mold according to any one of Appendices 1 to 6, wherein the sheet member includes a riblet structure surface formed by the plurality of recessed structures, and the riblet structure surface is capable of reducing the resistance of the sheet member to the fluid. [Appendix 8] The mold according to any one of Appendices 1 to 7, wherein the mold further satisfies a fourth condition of "1 micrometer < R < 4 micrometers". [Appendix 9] The mold according to any one of Appendices 1 to 8, wherein the mold further satisfies a fifth condition of "2 micrometers < R < 3 micrometers". [Appendix 10] The mold according to any one of Appendices 1 to 9, wherein the sheet member is a member that is attached to the surface of a movable body that can move through a fluid. [Appendix 11] The mold according to any one of Appendices 1 to 10, wherein the radius of curvature of the curved surface in a first portion of the molding surface is different from the radius of curvature of the curved surface in a second portion that is different from the first portion of the molding surface. [Supplementary Note 12] The mold according to Supplementary Note 11, wherein when the formation density of the recessed structures in the first portion is higher than the formation density of the recessed structures in the second portion, the radius of curvature of the curved surface in the first portion is larger than the radius of curvature of the curved surface in the second portion. [Supplementary Note 13] The mold according to any one of Supplements 1 to 12, wherein the height of at least one of the plurality of recessed structures is equal to or less than the pitch of the plurality of recessed structures. [Supplementary Note 14] The mold according to any one of Supplements 1 to 13, wherein the height of at least one of the plurality of recessed structures is equal to or less than half the pitch of the plurality of recessed structures. [Supplementary Note 15] The mold according to any one of Supplements 1 to 14, wherein the mold is used to manufacture the sheet member by imprint molding.[Appendix 16] A film-like sheet member having a riblet structure formed on its surface, wherein a first surface of the sheet member has a plurality of convex structures extending in a first direction formed as at least a part of the riblet structure so as to be aligned along a second direction intersecting the first direction, and at least one of a corner of a first convex structure of the plurality of convex structures and a boundary between the first convex structure and a second convex structure of the plurality of convex structures adjacent along the second direction includes a curved surface, and when a radius of curvature of the curved surface is R, a pitch of the plurality of convex structures is P, and a height of the plurality of convex structures from the boundary portion is H, the sheet member satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers". [Supplementary Note 17] A movable body movable in a fluid, wherein the sheet member described in Supplementary Note 16 is attached to at least a portion of the surface of the movable body. [Supplementary Note 18] A mold used for molding a film-like sheet member, wherein the mold has a molding surface with which the material of the sheet member comes into contact, the molding surface having a first surface, and a plurality of concave structures extending in a first direction are formed on the first surface so as to be aligned along a second direction intersecting the first direction. [Supplementary Note 19] A film-like sheet member having a riblet structure formed on its surface, wherein a plurality of convex structures extending in the first direction are formed on the first surface of the sheet member as at least a portion of the riblet structure so as to be aligned along a second direction intersecting the first direction. [Supplementary Note 20] A movable body movable in a fluid, wherein the sheet member described in Supplementary Note 19 is attached to at least a portion of the surface of the movable body.[Appendix 21] A film-like sheet member having a longitudinal direction in a first direction, the sheet member having: a surface on which a riblet structure is formed; and a plurality of convex portions formed within the surface and extending in a direction intersecting the first direction, the plurality of convex portions including a first convex portion and a second convex portion, and a plurality of convex structures extending in the first direction and protruding from the surface are formed on the surface between the first convex portions and the second convex portions in the first intersecting direction as at least a part of the riblet structure, when the radius of curvature of the curved surface is R, the pitch of the plurality of convex structures is P, and the height of the plurality of convex structures from the boundary portion is H, the sheet member satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers". [Supplementary Note 22] A moving body capable of moving in a fluid, wherein the sheet member according to Supplementary Note 21 is attached to at least a portion of the surface of the moving body. [Supplementary Note 23] A manufacturing method for manufacturing a sheet member using the mold according to any one of Supplements 1 to 15 and 18. [Supplementary Note 24] A manufacturing apparatus for manufacturing a sheet member using the mold according to any one of Supplements 1 to 15 and 18. [Supplementary Note 25] A manufacturing method for manufacturing the mold according to any one of Supplements 1 to 15 and 18. [Supplementary Note 26] A manufacturing apparatus for manufacturing the mold according to any one of Supplements 1 to 15 and 18.

[0146] 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.

[0147] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or idea of ​​the invention that can be read from the claims and the entire specification, and molds, sheet members, movable bodies and manufacturing methods that involve such modifications are also included in the technical idea of ​​the present invention.

[0148] REFERENCE SIGNS LIST 1 riblet sheet 11 adhesive layer 12 coating layer 121 paint layer 122 coating layer 130 riblet structure surface 3 mold 30 molding surface 71, 81 convex structure 72, 82 groove structure RB riblet structure MB mold structure

Claims

1. A mold used to form a film-like sheet member, the mold includes a flat plate member having a flat molding surface that comes into contact with the material of the sheet member, the molding surface has a first surface and a second surface; a plurality of first concave structures extending in a first direction are formed on the first surface so as to be aligned along a second direction intersecting the first direction; the second surface is located between the first surface and an end of the molding surface, and a plurality of second concave structures are formed; The depth of at least one of the plurality of second concave structures becomes shallower as the at least one of the plurality of second concave structures approaches the end portion. Type.

2. The sheet member includes a riblet structure surface formed by the plurality of first concave structures, The riblet structure surface can reduce the resistance of the seat member to the fluid. The mold of claim 1 .

3. The sheet member is a member that is attached to the surface of a moving body that can move through a fluid.

3. The mold of claim 2.

4. The height of at least one of the plurality of first concave structures is equal to or less than the pitch of the plurality of first concave structures. The mold of claim 1 .

5. The height of at least one of the plurality of first concave structures is equal to or less than half the pitch of the plurality of concave structures. The mold of claim 1 .

6. at least one of a corner of one of the plurality of first concave structures and a boundary between the one concave structure and another concave structure adjacent to the one of the plurality of first concave structures along the second direction includes a curved surface, When the radius of curvature of the curved surface is R, the pitch of the plurality of first concave structures is P, and the depth of the plurality of first concave structures from the molding surface is H, the mold satisfies a first condition of "1 micrometer < R < 7 micrometers" and at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers." The mold of claim 1 .

7. The mold further satisfies the fourth condition of "1 micrometer < R < 4 micrometers." 7. The mold of claim 6.

8. The mold further satisfies the fifth condition: "2 micrometers < R < 3 micrometers." 8. The mold of claim 7.

9. The radius of curvature of the curved surface at a first portion of the forming surface is different from the radius of curvature of the curved surface at a second portion of the forming surface that is different from the first portion.

7. The mold of claim 6.

10. When the formation density of the first concave structures in the first portion is higher than the formation density of the first concave structures in the second portion, the radius of curvature of the curved surface in the first portion is larger than the radius of curvature of the curved surface in the second portion.

10. The mold of claim 9.

11. The mold is used to manufacture the sheet member by imprint molding. The mold of claim 1 .

12. A film-like sheet member having a riblet structure formed on its surface, On the first surface of the sheet member, as at least a part of the riblet structure, a plurality of convex structures extending in a first direction are formed so as to be aligned along a second direction intersecting the first direction, at least one of a corner of a first convex structure among the plurality of convex structures and a boundary between the first convex structure and a second convex structure among the plurality of convex structures adjacent to each other along the second direction includes a curved surface, When the radius of curvature of the curved surface is R, the pitch of the plurality of convex structures is P, and the height of the plurality of convex structures from the boundary portion is H, the sheet member satisfies a first condition of "1 micrometer < R < 7 micrometers" and also satisfies at least one of a second condition of "5 micrometers < P < 200 micrometers" and a third condition of "2.5 micrometers < H < 100 micrometers", the sheet member has a second surface located between the first surface and an end of the sheet member and having a plurality of recessed structures formed thereon; The depth of at least one of the plurality of recessed structures becomes shallower as the at least one of the plurality of recessed structures approaches the end portion. Sheet member.

13. A plurality of recesses between a plurality of convex structures formed on the first surface are connected to the concave structures formed on the second surface. The sheet member according to claim 12.

14. A moving body that can move through a fluid, The sheet member according to claim 12 or 13 is attached to at least a part of the surface of the moving body. Mobile object.

15. A film-like sheet member having a riblet structure formed on its surface, On the first surface of the sheet member, as at least a part of the riblet structure, a plurality of convex structures extending in a first direction are formed so as to be aligned along a second direction intersecting the first direction, the sheet member has a second surface located between the first surface and an end of the sheet member and having a plurality of recessed structures formed thereon; The depth of at least one of the plurality of recessed structures formed on the second surface becomes shallower as the at least one of the plurality of recessed structures approaches the end portion. Sheet member.

16. A moving body that can move through a fluid, The sheet member according to claim 15 is attached to at least a part of the surface of the moving body. Mobile object.

17. A manufacturing method for manufacturing a sheet member using the mold according to any one of claims 1 to 11.

18. A manufacturing apparatus for manufacturing a sheet member using the mold according to any one of claims 1 to 11.