Structure that absorbs light, member, optical instrument, and method for manufacturing structure

Abstract

To provide a technique advantageous in achieving a structure that can sufficiently absorb light.SOLUTION: A structure that absorbs incident light with a wavelength λ is provided. The structure comprises a base material having a plurality of concave surfaces on an incidence surface for the light. The light is incident on an inside region of each of the plurality of concave surfaces. The light satisfies 400 nm≤λ≤40 μm. For each of the plurality of concave surfaces, the depth Dd of the bottom of the concave surface, the width Wa of the inside region at a position of a distance Da from the bottom of the concave surface, and the width Wb of the inside region at a position of a distance Db from the bottom, satisfy Dd≥Da>Db>λ, Wa>λ, and Wb≤λ / 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Relates to a structure, a member, an optical device, and a method for manufacturing a structure.

Background Art

[0002] Conventionally, many techniques for enhancing antireflection performance have been used for components of devices affected by reflected light or scattered light. For example, in the vicinity of the optical path of optical devices such as telescopes, microscopes, and cameras, if stray light such as unnecessary reflected light or scattered light occurs, a clear image may not be obtained. Therefore, in these optical devices, it is necessary to enhance the antireflection performance in the vicinity of the optical path. As conventional techniques, methods such as configuring the vicinity of the optical path with a black material or making the surface rough are known. However, simply using the above methods may not sufficiently suppress reflected light or scattered light.

[0003] As described in Patent Document 1, a method of forming an uneven structure with a period equal to or less than the wavelength of incident light (so-called SWS: SubWavelength Structure) on the component surface may be utilized. Such a technique utilizes the principle that the reflectance is reduced by the gradual change in the refractive index of incident light in the air layer and the surface layer portion of the component surface.

[0004] In addition, there is also a technique that utilizes a structure that forms an uneven structure with a period larger than the wavelength of incident light and suppresses the reflection of incident light (so-called antireflection) as described in Patent Document 2.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Structures with a period equal to or less than the wavelength of incident light as in Patent Document 1 or uneven structures with a period greater than the wavelength of incident light as in Patent Document 2 alone do not have sufficient light absorption and there is room for improvement.

[0007] An object of the present invention is to provide a technique advantageous for realizing a structure capable of sufficiently absorbing light.

Means for Solving the Problems

[0008] A structure that absorbs light with a wavelength λ of incident light, comprising a base material having a plurality of concave surfaces on the light incident surface, the light enters the inner region of each of the plurality of concave surfaces, the light satisfies 400 nm ≤ λ ≤ 40 μm, for each of the plurality of concave surfaces, the depth Dd of the bottom of the concave surface, the width Wa of the inner region at a position at a distance Da from the bottom of the concave surface, and the width Wb of the inner region at a position at a distance Db from the bottom satisfy Dd ≥ Da > Db > λ, Wa > λ, and Wb ≤ λ / 2 to provide a structure.

Effects of the Invention

[0009] According to the present invention, a technique advantageous for realizing a structure capable of sufficiently absorbing light is provided.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] <First Embodiment> In a first embodiment of the present invention, there is provided a structure 1 that absorbs light L having an incident wavelength λ, the structure 1 including a substrate 3 having a plurality of concave surfaces 2 on an incident surface 6 of the light L, the light L entering an inner region 4 of each of the plurality of concave surfaces 2, the light L satisfying 400 nm ≤ λ ≤ 40 μm, and for each of the plurality of concave surfaces 2, a depth Dd of a bottom 5 of the concave surface 2, a width Wa of the inner region 4 at a position at a distance Da from the bottom 5 of the concave surface 2, and a width Wb of the inner region 4 at a position at a distance Db from the bottom 5 satisfying Dd ≥ Da > Db > λ, Wa > λ, and Wb ≤ λ / 2.

[0012] The structure 1 of the present embodiment will be described with reference to FIG. 1. Note that FIGS. 1(a), 1(b), 2, 3, 5, 6(a), and 6(b) are all enlarged views of a part of a cross section cut in a direction perpendicular to a reference plane 8 of the structure 1.

[0013] The structure 1 of this embodiment absorbs light L with a wavelength λ (400 nm ≤ λ ≤ 40 μm). As shown in Fig. 1(a), the structure 1 includes a substrate 3 having a plurality of concave surfaces 2 on the incident surface 6 of the light L. The light L enters the inner region 4 of each of the plurality of concave surfaces 2. The inner region 4 of the plurality of concave surfaces 2 is a three-dimensional region at least partially defined by the concave surfaces 2, and can be a region sandwiched by the concave surfaces 2 or a region surrounded by the concave surfaces 2. The inner region 4 only needs to have light transmittance, and is typically a vacuum space or a gas space, but may also be a solid region in which a light-transmitting material is arranged. The structure 1 includes a convex portion 7, and a part of the surface of the convex portion 7 constitutes the concave surface 2 or a part thereof. The inner region 4 is located between the plurality of convex portions 7 in the XY direction. In the structure 1 of Fig. 1, the reference plane 8 is a virtual plane that contacts the plurality of convex portions 7 of the substrate 3 and covers the concave surface 2. The plan view with respect to the incident surface 6 is also the plan view with respect to the reference plane 8. The reference plane 8 typically contacts the vertices of the plurality of convex portions 7. Note that the substrate 3 has an opposite surface 9 on the side opposite to the incident surface 6 and the reference plane 8. The distance between the reference plane 8 and the opposite surface 9 is the thickness of the substrate 3. The concave surface 2 is recessed in the direction from the reference plane 8 to the bottom 5. The convex portion 7 protrudes in the direction from the bottom 5 to the reference plane. That is, the concave surface 2 can be referred to as a "recessed surface", and the convex portion 7 can be referred to as a "protruding portion".

[0014] As shown in Fig. 1(a), the depth from the reference plane 8 to the bottom 5 of the concave surface 2 is referred to as Dd. In other words, the distance between the reference plane 8 and the bottom 5 is the depth Dd. The width of the inner region 4 at a position with a distance Da in the direction Z perpendicular to the reference plane 8 from the bottom 5 is referred to as Wa. Also, the width of the inner region 4 at a position with a distance Db in the direction Z perpendicular to the reference plane 8 from the bottom 5 is referred to as Wb. The depth of the concave surface 2 refers to the depth with respect to the direction Z perpendicular to the reference plane 8 from the reference plane 8. In each figure, X and Y are perpendicular to each other and perpendicular to the direction Z.

[0015] The structure 1 satisfies the following formulas 1 to 3. Dd ≥ Da > Db > λ (Formula 1), Wa > λ (Formula 2), Wb ≤ λ / 2 (Formula 3). Fig. 1(b) shows that the structure 1 satisfies Db > λ in Formula 1. The depth Dd of the concave surface 2 and the widths Wa and Wb of the inner region 4 can be determined on a certain cross-section parallel to the direction Z perpendicular to the reference plane 8 of the structure 1. Preferably, for each concave surface 2, it is determined on a plane perpendicular to the structure 1 where the depth is maximum and the width of the inner region 4 on the outermost surface of the structure 1 is minimum.

[0016] The light L absorbed by the structure 1 is an electromagnetic wave including at least one of visible light and infrared light, and the wavelength λ of the light L satisfies 400 nm ≤ λ ≤ 40 μm. However, the structure 1 can also be configured to absorb ultraviolet light in addition to at least one of visible light and infrared light. λ is preferably λ ≤ 4 μm, more preferably λ ≤ 3 μm, and even more preferably λ ≤ 2.5 μm. The wavelength 40 μm can be treated as the boundary between mid-infrared and far-infrared. The wavelength 4 μm can be treated as the boundary between mid-infrared and far-infrared. The wavelength 3 μm can be treated as the boundary between near-infrared and mid-infrared. The wavelength 2.5 μm can be treated as the boundary between near-infrared and mid-infrared. λ may be λ > 1 μm, or λ > 800 nm, or λ ≤ 1 μm, or λ ≤ 800 nm. The wavelength 800 nm can be treated as the boundary between visible light and infrared light, and the wavelength 400 nm can be treated as the boundary between visible light and ultraviolet light. Which wavelength λ is to be the target of absorption by the structure 1 may be determined according to the use of the structure 1. For a plurality of wavelengths λa and λb in visible light and infrared light, it is preferable that the above formulas 1 to 3 are satisfied whether λ = λa or λ = λb. Both the wavelength λa and the wavelength λb may be in the wavelength range of visible light, or both the wavelength λa and the wavelength λb may be in the wavelength range of infrared light. Also, the wavelength λa may be in the wavelength range of visible light and the wavelength λb may be in the wavelength range of infrared light.

[0017] Hereinafter, in the inner region 4, the portion from the distance Db to the distance Dd may be referred to as the first part 41, and the portion from the concave surface bottom (i.e., the distance 0 from the bottom 5) to the distance Db may be referred to as the second part 42.

[0018] The structure 1 of this embodiment can efficiently absorb the light L and prevent and reduce reflection. The inventors consider the reasons as follows. That is, since the opening width Wa of the first part 41 is larger than λ, the light L with a wavelength of λ can be guided to the concave surface 2 by diffraction and propagation. Also, for the light L that directly enters the second part 42 without hitting the concave surface 2 forming the first part 41, by Db > λ and Wb ≤ λ / 2, the effects of diffraction and propagation of the light L can be reduced, and it is possible to absorb and reduce the intensity of the light L.

[0019] Da and Db are selected to satisfy formulas 1 to 3. Da may be approximately equal to Dd, that is, the position at a distance Da from the bottom 5 of the concave surface 2 may be the reference plane 8. However, also in this case, for Da, since the fine irregularities due to the undulations of the base material surface are ignored, Da and Dd do not have to exactly coincide. In that case, the opening width Wd at the reference plane 8 satisfies Wa ≈ Wd. In the following examples, in all cases, Da ≈ Dd and Wa ≈ Wd are used.

[0020] FIG. 2 shows an example where Dd ≈ Da and Wa ≈ Wd. Also, FIG. 3 shows an example where the inclination of the concave surface 2 forming the first part 41 and the inclination of the concave surface 2 forming the second part 42 are different, and the inclination of the concave surface 2 forming the second part 42 is steeper.

[0021] In this specification, the concave surface 2 refers to the concave surface 2 that satisfies formulas 1 to 3, and the structure 1 of this embodiment may have other concave surfaces 27. The other concave surfaces 27 are concave surfaces that do not satisfy at least any one of formulas 1 to 3. Also, for the plurality of concave surfaces 2, each only needs to satisfy formulas 1 to 3, and as long as they satisfy them, the shapes of each of the plurality of concave surfaces 2 may be different, and Da, Db, Dd, Wa, and Wb may be different. As will be described later, when describing Dc, De, Df, Ge, Go, and the taper angle, for each of the plurality of concave surfaces 2, each value may be different.

[0022] The number of the plurality of concave surfaces 2 or the number of the convex portions 7 constituting the plurality of concave surfaces 2 is preferably 3 per mm in a plan view with respect to the incident surface 6, that is, when the structure 1 is viewed from above in the Z direction.2 or more, more preferably 5 pieces / mm 2 or more, more preferably 10 pieces / mm 2 or more, more preferably 100 pieces / mm 2 or more, more preferably 1,000 pieces / mm 2 or more. The number of the plurality of concave surfaces 2 or the number of the convex portions 7 constituting the plurality of concave surfaces 2 is preferably 1,000,000 pieces / mm or less, more preferably 100,000 pieces / mm or less, still more preferably 10,000 pieces / mm or less, in a plan view with respect to the incident surface 6. 2 or less, more preferably 100,000 pieces / mm 2 or less, more preferably 10,000 pieces / mm 2 or less.

[0023] Wa>λ, preferably Wa≧2λ, more preferably Wa≧4λ. Also, preferably Wa≦100λ, more preferably Wa≦40λ. Also, preferably Wa>1μm, more preferably Wa≧10μm.

[0024] Preferably Wa≦300μm, more preferably Wa≦200μm, still more preferably Wa≦100μm, still more preferably Wa≦70μm.

[0025] By satisfying Wa>λ, the opening width of the first part 41 is sufficiently large, the light L is efficiently taken into the concave surface 2, and light trapping occurs. Also, when Wa is large and the opening width of the first part 41 is sufficiently large, the manufacturing of the structure 1 is easy.

[0026] Wb≦λ / 2, preferably Wb≧λ / 4, but Wb<λ / 4 may also be acceptable. Also, preferably Wb≦400nm, Wb≦200nm may also be acceptable, and preferably Wb≧100nm.

[0027] By having Db > λ and Wb ≤ λ / 2, in the second part 42, the depth is greater than the aperture width, weakening, absorbing the diffraction and propagation of the light L, reducing the intensity of the light L, and making it possible to prevent reflection.

[0028] The effect of absorption on visible light can be visually confirmed. That is, if the structure 1 absorbs the light L in a wide wavelength range of visible light, the incident surface 6 may appear black. Further, based on the electromagnetic field simulation by the FDTD method shown in Example 1, if the electric field distribution at a specific wavelength is 0.85 or less, it can be determined that there is no reflection.

[0029] Dd is Dd > λ. Dd is preferably Dd > 2λ, more preferably Dd ≥ 4λ, still more preferably Dd ≥ 5λ, still more preferably Dd ≥ 10λ, still more preferably Dd ≥ 100λ.

[0030] Also, Dd is preferably Dd > 10 μm, more preferably Dd ≥ 100 μm. Also, Dd is preferably Dd ≤ 1000 μm.

[0031] By Dd being large enough, the concave surface 2 becomes wide enough. When the concave surface 2 is wide enough, the number of reflections from when the light L is incident until it returns to the reference surface 8 is large. For the light L that could not be completely absorbed in the second part 42, sufficient light trapping also occurs while returning from the second part 42 to the reference surface 8, absorbing the light L and suppressing reflection. Also, when the concave surface 2 is wide enough, diffraction occurs due to the light L being reflected from various directions, and thereby the waves of the light L can be effectively canceled by each other's waves.

[0032] Therefore, particularly regarding Dd - Da, it is preferable that Dd - Da > λ, more preferably Dd - Da > 2λ, still more preferably Dd - Da ≥ 4λ, still more preferably Dd - Da ≥ 5λ, still more preferably Dd - Da ≥ 10λ, still more preferably Dd - Da ≥ 100λ.

[0033] In the inner region 4, Dd ≧ Da > Db > λ, but it is preferable to satisfy Da > Dd / 2, and it is also preferable to satisfy Db < Dd / 2. By satisfying Da > Dd / 2, it becomes easier to capture the light L in the upper half of the inner region 4 (the entrance side for the light L). By satisfying Db < Dd / 2, it becomes easier to absorb the light L that has entered the lower half of the inner region 4 from the upper half.

[0034] Also, as shown in Fig. 1(b), in the structure 1 of the present embodiment, for each of the widths Wc of the plurality of regions at the position of the distance Dc from the bottom 5 of each of the plurality of concave surfaces 2, it is preferable to satisfy Dc ≦ λ and Wc ≦ λ / 4. By providing a narrow portion at a position close to the bottom 5, while repeating multiple reflections, the diffraction and propagation of the light L are weakened and absorbed, reducing the intensity of the light L.

[0035] Also, in the structure 1 of the present embodiment, the plurality of concave surfaces 2 include a first concave surface 2 and a second concave surface 2. At the position of the distance De (where Dd ≧ De ≧ Db) from the bottom 5 of the first concave surface 2, the distance Ge between the first concave surface 2 and the second concave surface 2 preferably satisfies Ge ≦ 100 μm. The first concave surface 2 and the second concave surface 2 are typically concave surfaces 2 formed by a common convex portion 7. More preferably, Ge is Ge ≦ 10 μm, and even more preferably Ge ≦ 1 μm. Also, it is preferable that Ge satisfies Ge < Wa. It may be that Da ≧ De ≧ Db, and Fig. 1(a) shows an example of Da > De > Db. Alternatively, it may be that Dd ≧ De ≧ Da, or the position at the distance De from the bottom 5 of the concave surface 2 may be the position of the reference plane 8 (that is, De is equal to Dd). However, also in this case, regarding De, since the minute irregularities due to the undulations of the base material surface are ignored, De and Dd do not have to completely match. Fig. 2 shows an example where De ≒ Dd. In this case, Ge is the interval between the concave surfaces 2 when the structure 1 is viewed from above.

[0036] Also, the distance Go between the bottom 5 of the first concave surface 2 and the bottom 5 of the second concave surface 2 preferably satisfies Go > 1 μm. More preferably, Go satisfies Go ≧ 5 μm, and even more preferably, Go satisfies Go ≧ 10 μm. Preferably, Go satisfies Go ≦ 100 μm.

[0037] Preferably, Go satisfies Go > 1 μm. Also preferably, Go satisfies Go ≦ 100λ, and more preferably, Go satisfies Go ≦ 40λ. Preferably, Go satisfies Go ≦ 300 μm, more preferably, Go satisfies Go ≦ 200 μm, more preferably, Go satisfies Go ≦ 100 μm, and more preferably, Go satisfies Go ≦ 70 μm. Also, it is preferable that Go satisfies Go ≧ Wa.

[0038] Also, in the structure 1 of the present embodiment, it is preferable that the width Wg of the inner region 4 at a distance Dg from the bottom 5 satisfies Db < Dg < Da and Wg = λ. That is, it is preferable that the width Wa > λ is satisfied at the distance Da, the width Wg = λ is satisfied at the distance Dg, and the width Wb ≦ λ / 2 is satisfied at the distance Db. In FIG. 1(a), an example where the distance Dg > De is shown, but the distance Dg ≦ De may be satisfied, or Dg = De may be satisfied.

[0039] By having Go > 1 μm, diffraction of the light L can be prevented, and also, fabrication of the structure 1 becomes easy. Also, by having Go ≦ 300 μm, a sufficient number of recesses can be obtained to absorb incident light and obtain an antireflection effect.

[0040] The period of the inner region 4 may be referred to as the pitch. The pitch is the average value of Go, or when De ≒ Dd as shown in FIG. 2, the pitch corresponds to the average value of (Wa + Ge).

[0041] Also, in the structure 1 of the present embodiment, it is preferable that the attenuation coefficient of the base material 3 with respect to the light L is greater than 1.0. More preferably, the attenuation coefficient of the material constituting the base material 3 with respect to the light L is 2.0 or more, and even more preferably, 4.0 or more.

[0042] A large attenuation coefficient of the base material 3 is advantageous for the structure 1 to sufficiently reduce the intensity of the light L. If the attenuation coefficient of the base material 3 is small, the light L easily penetrates into the base material 3, and the absorption effect due to the uneven shape cannot be sufficiently obtained.

[0043] Also, in the structure 1 of the present embodiment, the base material 3 is opaque to the light L with wavelength λ, that is, it reflects or absorbs the light L with wavelength λ. Specifically, the transmittance of the light L with respect to the base material 3 is preferably less than 1%. The transmittance is obtained in consideration of the thickness of the base material 3.

[0044] Since the transmittance of the light L with respect to the base material 3 is sufficiently small, the structure 1 can sufficiently absorb the light L and reduce the intensity.

[0045] In the structure 1 of the present embodiment, there is no limitation to the shape of the concave surface 2 when viewed in plan with respect to the incident surface 6, that is, when the structure 1 is viewed from above in the Z direction, or the XY cross-sectional shape. Examples include a circle, an ellipse, a rectangle, a polygon, a line, any other shape, and combinations thereof. Also, there is no limitation to the three-dimensional shape of the concave surface 2. The XZ cross-sectional shape may be a triangle, a polygon, a shape with a curved surface, a parabola, a catenary curve, etc. Also, the three-dimensional shape may be a shape obtained by rotating these, a bullet shape, or a so-called line and space in which the same cross-sectional shape is continuous in the Y direction. When viewed in plan with respect to the incident surface 6, it is preferable that the plurality of concave surfaces 2 are arranged two-dimensionally.

[0046] In the example of line and space, as illustrated in FIG. 4(a) and FIG. 4(b) showing the a-a' cross-section thereof, each of the plurality of concave surfaces 2 is a groove having a longitudinal direction along the Y direction and a short-side direction along the X direction in plan view with respect to the incident surface 6, and the grooves are arranged along the X direction (short-side direction). In the first example where the plurality of concave surfaces 2 are arranged two-dimensionally, as illustrated in FIG. 4(c) and FIG. 4(d) showing the b-b' cross-section thereof, each of the plurality of concave surfaces 2 is arranged along the X direction and the Y direction. Each of the concave surfaces 2 is surrounded by continuous convex portions 7. In this example, it is easier to evaluate the number of concave surfaces than to evaluate the number of convex portions. In a second example where a plurality of concave surfaces 2 are arranged two-dimensionally, as illustrated in FIG. 4(e) and FIG. 4(f) showing the c-c' cross section thereof, each of the plurality of concave surfaces 2 is arranged side by side along the X direction and the Y direction. Each of the concave surfaces 2 is sandwiched by convex portions 7 arranged discretely. In FIG. 4(e), in addition to the concave surfaces 2, other concave surfaces 27 located between the concave surfaces 2 and between the convex portions 7 in the X direction and the Y direction are shown. The other concave surfaces 27 are shallower than the concave surfaces 2. In this example, it is easier to evaluate the number of convex portions than the number of concave surfaces.

[0047] Also, in the structure 1 of the present embodiment, for each of the concave surfaces 2, preferably in a portion where the distance from the bottom 5 is 2Dd / 3 or more and 9Dd / 10 or less, the taper angle θ is 60 degrees or more. More preferably, the taper angle θ is 75 degrees or more. The taper angle θ will be described with reference to FIG. 5. A straight line T connecting the position where the distance from the bottom 5 of the concave surface 2 is 2Dd / 3 and the position where the distance from the bottom 5 is 9Dd / 10 is shown. The angle formed by the straight line T and a plane (reference plane 8) parallel to the upper surface of the structure is the taper angle θ.

[0048] If the taper angle θ is 60 degrees or more, the inclination of the concave surface 2 in the vicinity of the reference plane 8 is sufficient, and the light L is absorbed while being reflected multiple times by the concave surface 2, and the reflection is reduced. Also, if the inclination of the concave surface 2 in the vicinity of the reference plane 8 is sufficient, the light L is efficiently guided to the deeper part of the concave portion, and the intensity of the light L is efficiently reduced.

[0049] Also, in the structure 1 of the present embodiment, the width of the inner region 4 gradually decreases from the position where the distance from the bottom 5 is Da to the position where the distance from the bottom 5 is Db.

[0050] That is, for the inner region 4, the width at a deeper position is the same as or smaller than the width at a shallower position. Deep means closer to the bottom 5, and shallow means closer to the distance from the reference plane 8. The inner region 4 may have a portion with a constant width.

[0051] By gradually reducing the width of the inner region 4, the light L is efficiently guided to the deep portion of the concave surface 2, and the intensity of the light L is efficiently reduced. Further, by forming the concave surface 2 such that the width of the inner region 4 gradually decreases, the structure 1 can be easily manufactured.

[0052] Further, in the structure 1 of the present embodiment, the plurality of concave surfaces 2 may include a concave surface 2 in which the width of the inner region 4 is equal to or greater than Wb and equal to or less than λ / 2 at a distance Df from the bottom 5 of the concave surface 2 to a distance Df (where Da ≧ Df > Db). This is illustrated in FIGS. 6(a) and 6(b). In these figures, the width of the inner region 4 at any position within the middle portion m from Db to Df of the concave surface 2 is equal to or greater than Wb and equal to or less than λ / 2. In the example illustrated in FIG. 6(a), Dd > Da, and the concave surface 2 has different slopes from the bottom 5 to Db, from Db to Df, and from Df to Da, and has a substantially constant width of equal to or greater than Wb and equal to or less than λ / 2 from Db to Df. The inner region 4 formed by the middle portion m may be referred to as a middle portion 412. The middle portion 412 is a part of the first portion 41. The portion excluding the middle portion 412 from the first portion 41 is denoted by 411 in FIGS. 6(a) and 6(b).

[0053] In the example illustrated in FIG. 6(b), Dd > Da, and the slopes of the concave surface 2 from the bottom 5 to Db, from Db to Df, and from Df to Da gradually decrease along with the distance from the bottom 5.

[0054] By providing the middle portion 412, the number of reflections of the light L from the time of incidence until it returns to the reference plane 8 increases, and the light L is sufficiently absorbed, its intensity is reduced, and reflection is prevented.

[0055] Further, in the structure 1 of the present embodiment, the base material 3 can be made of metal. The metal includes alloys, and examples thereof include aluminum, titanium, tungsten, copper, iron, nickel, stainless steel, etc. Among them, aluminum is preferable.

[0056] Further, in the structure 1 of the present embodiment, the base material 3 can be made of resin. The base material 3 may have any shape according to the purpose, for example, it can be a flat surface, a curved surface, an inclined surface, or a shape having a plurality of these.

[0057] An example of the structure 1 of this embodiment will be described with reference to FIG. 23. FIG. 23 is an enlarged view of a part of a cross-section cut in a direction perpendicular to the reference plane 8 of the structure 1. For each of the plurality of concave surfaces 2, the concave surface 2 includes a first inclined surface S1 and a second inclined surface S2 located on the side of the bottom 5 from the first inclined surface S1. The angle d1 formed by the first inclined surface S1 and the reference plane 8 and the angle d2 formed by the second inclined surface S2 and the reference plane 8 can satisfy d1>d2. The reference plane 8 is a virtual plane in contact with the plurality of convex portions 7 forming the concave surface 2.

[0058] The first inclined surface S1 can be an inclined surface located in a portion where the distance from the bottom 5 is 2Dd / 3 or more. The second inclined surface S2 can be an inclined surface connected to the first inclined surface S1. Further, it may include a third inclined surface S3, and the third inclined surface S3 is an inclined surface connected from the second inclined surface S2 to the bottom side. Each inclined surface refers to a portion of the concave surface 2 where the width of its inner region 4 gradually decreases towards the bottom in a substantially constant manner (however, as will be described later, it may have undulations and roughness of a specific shape).

[0059] The concave surface 2 is composed of a first inclined surface S1, a second inclined surface S2, and a third inclined surface S3. The first inclined surface S1 is an inclined surface provided near the top of the convex portion 7. The second inclined surface S2 is located on the side of the bottom of the concave surface from the first inclined surface and is connected from the first inclined surface S1 in the bottom direction. The third inclined surface S3 is connected from the second inclined surface S2 in the bottom direction. And taking the plane in contact with the plurality of convex portions forming the concave surface as the reference plane 8, the angle d1 formed by the first inclined surface S1 and the reference plane 8 is larger than the angle d2 formed by the second inclined surface connected from the first inclined surface towards the bottom of the concave surface 2 and the reference plane 8.

[0060] In the structure 1, in addition to the light L incident at an angle α that is close to being perpendicular to the reference plane 8, the light L2 can be incident from a direction that is close to being parallel to the reference plane 8. Let the angle formed by the light L2 and the reference plane 8 be the angle β. Note that the angle α formed by the light L and the reference plane 8 is typically larger than the angle β and is typically 90 degrees. For the sake of simplicity, consider the case where the light L2 is specularly reflected by the first inclined surface S1. When the angle d1 of the first inclined surface S1 with respect to the light L2 incident at the angle β is equal to 90 degrees - β, the light L2 is reflected by the first inclined surface S1 in the same direction as the incident direction of the light L2. When the angle d1 of the first inclined surface S1 is smaller than 90 degrees - β, the light L2 incident at the angle β is reflected by the first inclined surface S1 to the side opposite to the bottom 5 side (the reference plane 8 side). In this case, this reflected light cannot be absorbed by the structure 1, and the absorption characteristics deteriorate. When the angle d1 of the first inclined surface S1 is larger than 90 degrees - β, the light L2 incident at the angle β is reflected by the first inclined surface S1 to the bottom 5 side, and this reflected light can be absorbed by the concave surface 2. The angle β can vary depending on the use of the structure 1, but as a guideline, it is less than 20 degrees and can be 10 degrees or less. If the region sandwiched between the two normal lines Lu and Ld erected toward the light L2 from the first inclined surface S1 is a, the light L2 irradiated on a is reflected by the first inclined surface S1 and reduces the light absorption efficiency. Since the length of a decreases as d1 increases, in order to suppress the reflection by the light L2, d1 can be maximized. On the other hand, the conditions for the width of the inner region that efficiently absorbs the light L are Wd > λ and Wb ≤ λ / 2. If we try to maximize d1 and satisfy Wb ≤ λ / 2, the depth Dd of the concave surface 2 becomes extremely large, and in the laser processing method described later, the processing time increases significantly and it is not practical.

[0061] Therefore, by providing the second inclined surface S2 between the first inclined surface S1 and the third inclined surface S3 and making the angle d2 formed by the second inclined surface S2 and the reference plane 8 satisfy d2 < d1, d1 can be maximized without changing Dd.

[0062] The angle d1 formed by the first inclined surface and the reference surface 8 is preferably 80° or more, more preferably 85° or more, still more preferably 86° or more, and most preferably 88° or more, with a maximum value of 90°. In that case, the angle d2 formed by the second inclined surface S2 and the reference surface 8 is preferably 55° or less, more preferably 50° or less, still more preferably 45° or less, and most preferably 42° or less. The angle d2 is preferably not more than half of the angle d1. With the above configuration, the reflection of the light L2 can be minimized and the light L can be efficiently absorbed.

[0063] Note that the inclined surfaces constituting each of the concave surfaces 2 are not limited to three. It is desirable that the angle d1 formed by the first inclined surface S1 and the reference surface 8 is the largest, but if the intensity of the light L2 is low and there is no practical problem, it may be appropriately adjusted according to the allowable range of the reflected light. Further, for the plurality of concave surfaces 2, it is sufficient that the angle d1 formed by each first inclined surface S1 and the reference surface 8 is larger than the angle formed by the second inclined surface S2 that connects toward the bottom of the concave surface 2 from the first inclined surface S1 and the reference surface 8. As long as these are satisfied, the shapes and angles of each of the plurality of concave surfaces 2 may be different, and the lengths of the first inclined surface S1, the second inclined surface S2, the third inclined surface S3, the angles d1 and d2, and the length of the region a may be different.

[0064] Also, in the laser processing method described later, since the processed surface has a unique roughness, each of the first inclined surface S1, the second inclined surface S2, and the third inclined surface S3 may have a unique undulation and roughness of the shape, and the boundaries of each may be unclear. In that case, the angle d1 is the average value of the shapes of each of the first inclined surfaces S1, but if the average value of d1 in the entire structure is large, the length of a in the entire structure will also be small, so the reflection of the light L2 can be minimized.

[0065] For each of the plurality of concave surfaces, the concave surface may include a first curved surface and a second curved surface located on the bottom side of the concave surface from the first curved surface, the center of the first curved surface is inside the concave surface, and the center of the second curved surface is outside the concave surface.

[0066] This embodiment will be described with reference to FIG. 24. FIG. 24 is an enlarged view of a part of a cross-section taken in a direction perpendicular to the reference plane 8 of the structure 1.

[0067] The center O of the first curved surface R1 (the center of the curved surface means the center of a circle whose part of the circumference approximates the curved surface) 1 is inside the concave surface 2. In other words, the first curved surface R1 is convex with respect to the outside of the concave surface 2. The center O of the second curved surface connecting from the first curved surface R1 toward the bottom of the concave surface 2 2 is outside the concave surface 2. In other words, the second curved surface R2 is convex with respect to the inside of the concave surface 2.

[0068] In addition to the light L, the light L2 enters the structure 1 from a direction substantially parallel to the incident surface 6. Assuming that the region sandwiched between the two normal lines Lu and Ld erected from the first curved surface R1 toward the light L2 is a, the light L2 irradiated on a is reflected by the first curved surface R1, reducing the light absorption efficiency. Since the length of a decreases as the angle d1 formed by the first curved surface R1 and the reference plane 8 increases, to suppress the reflection by the light L2, d1 may be maximized. Specifically, the center of the curved surface R1 that becomes the curved surface with the maximum d1 may be provided inside the concave surface 2 from R1. On the other hand, the conditions for efficiently absorbing the light L are Wd>λ and Wb≦λ / 2. If we try to maximize d1 and satisfy Wb≦λ / 2, the depth of the concave surface 2 becomes very large, and in the laser processing method described later, the processing time increases significantly and it is not practical.

[0069] Therefore, by providing the second curved surface R2 from the first curved surface R1 toward the bottom 5 of the concave surface 2, and making the center O of the second curved surface R2 outside the concave surface 2, it is possible to maximize d1 without changing Dd. 2

[0070] The angle d1 formed by the first curved surface R1 and the reference plane 8 is preferably 80° or more, more preferably 85° or more, still more preferably 86° or more, and most preferably 88° or more, and the maximum value is 90°. With the above configuration, the reflection of the light L2 can be minimized and the light L can be efficiently absorbed. ​

[0071] The curved surfaces forming each of the concave surfaces 2 do not necessarily have to be limited to two surfaces. It is desirable that the angle d1 formed by the first curved surface R1 and the reference surface 8 be the maximum, but if the intensity of the light L2 is low and there is no practical problem, it may be adjusted as appropriate according to the allowable range of the reflected light.

[0072] Also, for the plurality of concave surfaces 2, the center O of each first curved surface R1 1 is inside the concave surface 2, and the center O of the second curved surface R2 that connects from the first curved surface R1 toward the bottom 5 of the concave surface 2 2 may be outside the concave surface 2. As long as these conditions are satisfied, the shapes and angles of each of the plurality of concave surfaces 2 may be different, and the lengths of the first curved surface R1, the second curved surface R2, the center positions of the curved surfaces, the angle of d1, and the length of the region a may be different.

[0073] Also, in the laser processing method described later, since the processed surface has a specific roughness, each of the first curved surface R1 and the second curved surface R2 may have a specific shape undulation and roughness, and the boundaries of each may be unclear. In that case, the angle of d1 is the average value of the shapes of each of the first curved surfaces R1, but if the average value of d1 in the entire structure is large, the length of a in the entire structure will also be small, so the reflection of the light L2 can be minimized.

[0074] <Second Embodiment> As a second embodiment, the present invention provides a method for manufacturing the structure 1 of the first embodiment, which is characterized by forming a base material by performing laser processing on a base material. Further, as a first example of the laser processing, in the laser processing, a first step of irradiating the first row of the base material with a pulsed laser having an irradiation width Pa in the main scanning direction, and shifting the irradiation position by Pb in the main scanning direction from the first step, and irradiating the first row with the pulsed laser having the irradiation width Pa in the main scanning direction, and repeating this N - 1 more times in the second step, a third step of scanning so that the irradiation position is shifted by Pc in the sub-scanning direction, a fourth step of performing the first step and the second step at a position shifted by Pc in the sub-scanning direction, and a fifth step of repeating the third step and the fourth step one or more times. However, letting the irradiation diameter of the pulsed laser be φ, Pa, Pb, and Pc satisfy φ / 2 < Pa < φ, Pb = φ / N, and Pc < φ. Also, Pb does not have to be exact and may be zero. Also, as a second example of the laser processing, in the laser processing, a first step of irradiating the first row of the base material with a pulsed laser having an irradiation width Pa in the main scanning direction, a second step of scanning so that the irradiation position is shifted by Pc in the sub-scanning direction, a third step of performing the first step and the second step at a position shifted by Pc in the sub-scanning direction, a fourth step of repeating the second step and the third step one or more times, and a fifth step of shifting the irradiation position by Pb in the main scanning direction from the first step and repeating the fourth step of irradiating the first row with the pulsed laser having the irradiation width Pa in the main scanning direction N - 1 more times. However, letting the irradiation diameter of the pulsed laser be φ, Pa, Pb, and Pc satisfy φ / 2 < Pa < φ, Pb = φ / N, and Pc < φ. Also, Pb does not have to be exact and may be zero.

[0075] A second embodiment of the present invention will be described with reference to the schematic configuration diagram of the laser processing machine 70 of the present invention shown in FIG. 7. In FIG. 7, the laser processing machine 70 is disposed on the gantry 21. As the laser oscillator 11, a fiber laser that oscillates femtosecond pulses can be used. The laser beam emitted from the laser oscillator 11 is expanded in beam diameter by the beam expander 12, then enters the Fθ lens 14 by the galvano mirror 13, and is focused on the base material 15. The base material 15 is fixed to the fixed table 16 and can be freely moved by the moving stage 17. The laser processing machine galvano control unit 18 controls the laser oscillator 11 and the galvano mirror 13. Although one galvano mirror is shown in FIG. 7, when controlling the laser beam in two axial directions, two mirrors are required, and the number of mirrors is appropriately selected according to the application. The stage control unit 19 controls the moving stage 17. When performing autofocus, control such as moving the moving stage 17 up and down is performed so that the distance between the laser focusing position and the substrate becomes constant based on a signal from a displacement meter (not shown). The host computer 20 includes a user interface and a processing data storage unit, and can control the control units of the galvano mirror 13 and the moving stage 17 in mutual interlock at a predetermined timing.

[0076] Next, regarding the laser processing step of this embodiment in which the galvano mirror drive and the stage movement are combined, and the area exceeding the area that can be processed by the galvano mirror drive is moved by the stage for processing, FIG. 8 is a flowchart of the laser processing step according to the second embodiment, and this will be used for explanation.

[0077] After fixing the base material 15 on the fixed table 16, operations such as reading the alignment marks and correcting the laser processing position are performed to obtain and correct the position information required for processing, and prepare for processing. In step 31, a movement instruction is sent to the stage control unit to move to a desired position. In step 32, the galvanometer control unit is sent the processing position data and the laser processing conditions are instructed. In step 33, it is confirmed that the movement of the stage is completed, and in step 34, the processing is started. In step 35, the laser is paused and the galvanometer mirror is moved to a desired position. After confirming the end of the movement of the galvanometer mirror in step 36, the laser is oscillated while moving the galvanometer mirror under desired conditions to perform the processing. In step 37, it is confirmed that the processing is completed and the laser oscillation is paused. In step 38, it is determined whether the processing in the galvanometer area has ended. If not, the process returns to step 35. When the processing in the galvanometer area is completed, the processing in the galvanometer area is considered to be completed. If processing in other areas is required, the process returns to the step 31 process.

[0078] In the above process, steps 35 to 37 are repeated. In the repetition, scanning is performed so that the laser is irradiated in a line in the main scanning direction, the irradiation is stopped, scanning is performed at the sub-scanning pitch in the direction perpendicular to the main scanning direction, and then scanning in a line in the main scanning direction again can be repeated.

[0079] Alternatively, in the repetition, the above first example can be adopted. That is, on the same line, the irradiation in the main scanning direction may be performed multiple times, and the multiple irradiations can be performed so that the beam spots are shifted little by little. Then, after repeating the irradiation in the main scanning direction a plurality of times (N times), the scanning in the sub-scanning direction may be repeated. This method will be described with reference to FIGS. 9(a) and (b).

[0080] Fig. 9(a) shows an example in which the irradiation in the main scanning direction is repeated N = 4 times for the first column. For the first to fourth irradiations, they are shown in parallel for convenience, but these represent the irradiation of the same first column. In the first scan, the main scan is performed so that a beam with a beam diameter φ is irradiated at a pitch Pa. At this time, it is preferable that φ / 2 < Pa < φ. After the second time, the beam center during irradiation is shifted by Pb in the main scanning direction from the beam center of the previous scan for irradiation. Pb is preferably Pb = φ / N. In the example of Fig. 9(a), Pb = φ / 4. When this is repeated N times, the irradiations for N times are integrated in the main scanning direction. The lower part of Fig. 9 shows the integration for 4 times.

[0081] Fig. 9(b) further shows an example in which, for the second column and subsequent columns, while scanning the irradiation position in the sub-scanning direction, the main scan is repeated 4 times. The irradiation of the second column is scanned so that the beam center is shifted by Pc in the sub-scanning direction with respect to the beam center during the irradiation of the first column, and the irradiation of the third column is scanned so that it is further shifted by Pc in the sub-scanning direction. Pc is preferably Pc < φ, and more preferably P ≦ φ / 2.

[0082] Alternatively, in the repetition, the above second example can be used. That is, on one line, irradiation is performed in the main scanning direction, then the irradiation position is scanned in the sub-scanning direction, and irradiation is performed on the next line, and this is repeated. Then, for the same line, this can be repeated. By this repetition, processing of about 1 mm 2 to 10 mm 2 of the base material 3 is performed, and by further repeating this, processing is carried out. This method will be described with reference to Figs. 9(c) and (d).

[0083] Fig. 9(c) shows an example in which irradiation is performed in the main scanning direction from the first column, the irradiation position is scanned in the sub-scanning direction, and irradiation is performed on the next line, and this is repeated up to the fourth column.

[0084] FIG. 9(d) further shows an example in which the irradiation position is returned to the first column in the sub-scanning direction, and this is repeated four times while scanning from the first column to the fourth column. At this time, irradiation is performed such that the beam center is shifted by Pb in the main scanning direction from the beam center of the previous cycle. Pb is preferably Pb = φ / N. FIG. 9(e) illustrates four integrations.

[0085] According to the method of integrating in the main scanning direction and the sub-scanning direction while slightly shifting the beam center in the main scanning direction and the sub-scanning direction in this way, the beam spot hits the same location multiple times in a short time, and the light irradiated interacts with each other, creating a randomized fine structure. By adjusting the order of the paths, the number of repetitions, Pb, Pc, the frequency of the laser, etc., effects such as the thermal effect, the optical effect of light, interference, interference between the irradiated laser lights, interference between the reflected light from the fine structure and the laser light, and reflection from the fine structure can be controlled. As a result, fine processing control such as the pitch of the concave surface 2, for example, becomes possible. For example, by lowering the frequency of the irradiated laser, heat accumulation on the processed surface can be reduced, and control such as reducing the removal amount of the base material 3 by laser irradiation can be achieved.

[0086] Also, when manufacturing the structure 1 by forming the concave surface 2 on the surface of the optical component as the base material 3, a method of suppressing the oxygen concentration in the atmosphere during processing is also effective. As a method of reducing the oxygen concentration, the entire processing apparatus may be replaced with a nitrogen atmosphere, or a heat dissipation component may be installed in a purge box equipped with a laser transmission window for processing, or processing may be performed while blowing high-purity nitrogen gas onto the heat dissipation component, and the means is not limited.

[0087] According to the manufacturing method of this embodiment, the structure 1 of the first embodiment can be obtained with a simple manufacturing process, and outgassing does not occur even in a vacuum environment, using an optical component as the base material 3.

[0088] In addition to the method of performing machining while gradually shifting the beam center as described above, by performing machining while adjusting the intensity of the laser to be irradiated, it is possible to control microfabrication such as the shape of the concave surface 2. For example, when machining the concave surface 2 illustrated in FIG. 6(b), it is preferable to sequentially increase the intensity of the laser used for machining in each of the middle part 411, middle part 412, and second part 42 of the inner region 4.

[0089] In addition, when machining the concave surface 2 illustrated in FIG. 23, it is desirable that the intensity of the laser for machining the second inclined surface S2 is lower than the intensity of the laser for machining the first inclined surface S1 of the concave surface 2, and it is desirable that the intensity of the laser for machining the third inclined surface S3 is higher than the intensity of the laser for machining the second inclined surface S2.

[0090] In addition, when machining the concave surface 2 illustrated in FIG. 24, after shifting to the machining of the second curved surface R2 while gradually decreasing the intensity of the laser for machining the first curved surface R1 of the concave surface 2 as the machining depth progresses, it is desirable to progress the machining depth while increasing the intensity of the laser again. In order to adjust the intensity of the laser, there are means for controlling and adjusting the laser oscillation energy of the laser oscillator 11 shown in FIG. 7 from the outside, and means for inserting an optical element capable of changing the laser transmittance between the laser oscillator 11 and the beam expander 12 (not shown) for adjustment. The adjustment instruction value is stored in the host computer 20 in synchronization with the machining data, and the intensity of the laser is adjusted by controlling the laser oscillator 11 and the optical element (not shown) from the galvanometer control unit 18.

[0091] In addition, as means for controlling microfabrication such as the shape of the concave surface 2, in addition to adjusting the intensity of the laser, the machining pitches Pa, Pb, Pc of the pulsed laser may be adjusted as the machining depth progresses, or the order of the passes, the number of repetitions, the frequency of the laser, etc. may be adjusted, or these may be combined. If the laser oscillator 11 has a function of changing the pulse oscillation time of the pulsed laser, the pulse oscillation time may be adjusted, or these may be combined.

[0092] Further, the measured reflectance results of the structure 1 with the actual shape of the concave surface 2 changed are shown in FIG. 25. The results indicated by the broken line in FIG. 25 correspond to the results of the structure 1 with the shape illustrated in FIG. 6(b). The results indicated by the solid line in FIG. 25 correspond to the results of the structure with the shape illustrated in FIG. 24. In the structure with the shape illustrated in FIG. 6(b), the angle d1 is 65 degrees and the angle d2 is 78 degrees. In the structure with the shape illustrated in FIG. 24, the angle d1 is 85 degrees and the angle d2 is 78 degrees. The measured reflectance results in FIG. 25 have the light with λ = 800 nm incident from an angle of 80 degrees (corresponding to β = 10 degrees) with respect to the reference plane 8 of the structure 1, and the angle at which the light travels after being scattered by the structure 1 is taken as the scattering angle on the horizontal axis. The vertical axis represents the reflectance. Both the structure with the shape illustrated in FIG. 6(b) and the structure with the shape illustrated in FIG. 24 had reflectances below 1%, and the reflectance could be efficiently reduced. The structure with the shape illustrated in FIG. 24 had a lower reflectance than the structure with the shape illustrated in FIG. 6(b). Thus, FIG. 24 has a configuration in which the length of the region a on the first curved surface R1 is reduced, thereby minimizing the reflection of the light L2 and being a shape capable of efficiently absorbing the light L.

[0093] <Third Embodiment> As a third embodiment of the present invention, there is provided a method for manufacturing the structure 1 of the first embodiment, in which the structure 1 is obtained by transferring the concavo-convex structure of a mold having a concavo-convex structure to a resin. This method can include a step of forming a mold by performing laser processing on a mold material, and a step of injection molding a resin with the mold.

[0094] The third embodiment will be described with reference to the schematic process diagrams shown in FIGS. 10(a) to (e). FIGS. 10(a) to (e) show each stage of the process of manufacturing the structure 1 by injection molding. The first mold 91 constituting the mold 900 includes the structure 1 produced in the second embodiment and has a concavo-convex structure on the surface. The injection molding machine shown in FIGS. 10(a) to (e) includes a pressurizing device 911 communicating with a cylinder 99 and a hopper 910 for introducing a resin material.

[0095] Inside the cylinder 99, a screw (not shown) is provided and is rotationally driven by a drive source such as a motor (not shown), and the resin material inside the hopper 910 is sent to the tip of the cylinder 99. Further, a heater (not shown) is provided in the cylinder 99, and the resin material introduced from the hopper 910 is heated to a temperature equal to or higher than the glass transition temperature while being conveyed toward the tip inside the cylinder 99 and melted into a liquid state. Then, it is stored in the space at the tip of the cylinder 99.

[0096] The first mold 91 has an uneven structure on its surface as described above. The second mold 98 is closed with the first mold 91 when forming the cavity 920.

[0097] Resin material is charged into the hopper 910. First, as a mold preparation step, as shown in Fig. 10(a), the mold (900) is attached to an injection molding machine. Then, by a drive mechanism (not shown), the first mold 91 and the second mold 98 are closed as shown in Fig. 10(b). Prior to closing the mold or at the time of closing the mold, the first mold 91 and the second mold 98 are heated by a heater (not shown). The heating temperature of the mold in this step is called the mold temperature.

[0098] Subsequently, the injection step shown in Fig. 10(c), the pressure holding step shown in Fig. 10(d), and the cooling step are executed. In the injection step shown in Fig. 10(c), the molten resin 912 is poured from the cylinder 99 into the cavity 920 formed by the first mold 91 and the second mold 98 by a pressurizing device 911. The pressurizing device 911 is configured using a hydraulic cylinder or the like. Further, in the pressure holding step shown in Fig. 10(d) and the cooling (solidification) step, for example, with a set pressure capable of transferring the molten resin to the mold to form a fine shape, the molten resin 912 in the cavity 920 is pressurized from the pressurizing device 911 and the pressure is maintained for a predetermined time (pressure holding). Thereby, the pressure of the molten resin 912 in the cavity is maintained at the pressure holding pressure.

[0099] Subsequently, the first mold 91 and the second mold 98 are cooled, and the molten resin 912 is cooled to a temperature below the glass transition temperature, causing it to transition from a liquid state to a solid state. The cooling of the first mold 91 and the second mold 98 is performed, for example, by a mechanism (not shown) that circulates a coolant around the mold 900. Thereafter, the mold opening process and the demolding process shown in FIG. 10(e) are carried out. This demolding is performed, for example, by protruding ejector pins penetrating the mold into the cavity. By repeating the above steps, a large number of structures 1 can be manufactured.

[0100] According to the manufacturing method of the present embodiment, the structure 1 of the first embodiment can be manufactured by a simple manufacturing process without generating outgassing even in a vacuum environment. Further, according to the manufacturing method of the present embodiment, it is possible to mass-produce the structure 1 of the first embodiment in a short time and at low cost.

[0101] <Other Embodiments> In addition, as a further embodiment of the present invention, a member including the structure 1 of the first embodiment is provided. The member may be composed of the structure 1 or may include a support that supports the structure 1. In addition, an optical device including the structure 1 of the first embodiment is provided. In recent years, in optical devices and the like, further reduction of reflected light and scattered light has been required for their high performance. Also, year by year, the components are becoming smaller in complex shapes. In addition, the environments in which they can be applied are increasing in variety. The first embodiment is relatively easy to fabricate, and this structure can also be applied to a three-dimensional substrate 3. Since the substrate itself has an uneven shape, compared with the case of fabricating by film formation, the concern about peeling of the film due to oil, vibration, heat, etc. is alleviated, and particularly in a vacuum environment, outgassing is a concern. Also, since the substrate itself has an uneven shape, despite the fine uneven shape, high strength can be obtained, and there is an advantage that the uneven shape itself is not easily damaged.

[0102] Examples of members including the structure 1 of the first embodiment include an optical member made of the structure 1 of the first embodiment, a lens, a lens barrel having the structure 1 of the first embodiment on its inner wall, and a housing. Examples of optical devices including the structure 1 of the first embodiment include binoculars, microscopes, semiconductor exposure devices, or imaging devices including an imaging element that receives light that has passed through the optical member of the present invention, such as a digital still camera or a digital video camera, or a mobile phone.

[0103] FIG. 11 shows the configuration of a single-lens reflex digital camera 1100, which is an example of the optical device of the present embodiment.

[0104] In the digital camera 1100 shown in FIG. 11, the camera body 1102 and the lens barrel 1101 are coupled, and the lens barrel 1101 is a so-called interchangeable lens that is detachable from the camera body 1102.

[0105] Light from the subject passes through an optical system including a plurality of lenses 1103, 1105, etc. disposed on the optical axis of the imaging optical system within the housing 1120 of the lens barrel 1101, and is received by the imaging element 1110.

[0106] In this configuration, the member of the present embodiment is, for example, the housing 1121, the inner cylinder 1104, or the lens barrel 1101. The housing 1121 and the lens barrel 1101 include the structure 1 of the first embodiment and a support.

[0107] During the observation period before shooting, the light from the subject is reflected by the main mirror 1107 inside the housing 1121 of the camera body 1102, passes through the prism 1111, and then the captured image is projected onto the photographer through the viewfinder lens 1112. The main mirror 1107 is, for example, a half mirror, and the light passing through the main mirror 1107 is reflected by the sub-mirror 1108 in the direction of the AF (auto focus) unit 1113. For example, this reflected light is used for distance measurement. Also, the main mirror 1107 is mounted and supported on the main mirror holder 1140 by adhesion or the like. During shooting, the main mirror 1107 and the sub-mirror 1108 are moved out of the optical path via a drive mechanism (not shown), the shutter 1109 is opened, and the captured optical image incident from the lens barrel 1101 is formed on the imaging element 1110. Also, the aperture 1106 is configured to be able to change the brightness and depth of field during shooting by changing the aperture area.

Example

[0108] <Simulation of the structure of the first embodiment> Simulations were performed on the structures 1 of Examples 1 to 3 and Comparative Example 1 having no concave surface 2. Fig. 12 shows the respective dimensions of Examples 1 to 3 and Comparative Example 1. In each case, the size of the structure was the same. The wavelength λ of the light L was set to 350 nm to 850 nm. Representing the shortest wavelength of the region of the target light L as λmin and the longest wavelength as λmax, λmin = 350 nm and λmax = 850 nm.

[0109] Electromagnetic field simulations using the FDTD method were performed with the shapes of Examples 1 to 3 and Comparative Example 1 as models. The space for the electromagnetic field simulation was a three-dimensional space of xyz. As shown in FIG. 13, the x-axis was defined as the horizontal direction of the structure, the y-axis as the depth direction of the structure, and the z-axis as the thickness direction of the structure. Also, periodic boundary conditions were applied in the x-axis and y-axis directions to simulate the situation where the concave surface 2 extends infinitely. The range of the unit space was 2 μm in the x-axis direction, 12 μm in the z-axis direction, and 0.2 μm in the y-axis direction. Inside this unit space, there was a structure including an inner region, and its size was 2 μm in the x-axis direction, 6 μm in the z-axis direction, and 0.2 μm in the y-axis direction. The material of the base material 3 was pure aluminum. All spaces other than the structure in the unit space were set to vacuum. Hereinafter, the vacuum region will be referred to as air. The incident direction of the light L (electromagnetic wave) was from top to bottom in the z-axis direction, that is, from the air into the structure. At this time, the wave of the light L was polarized such that the electric field vibrated perpendicular to the traveling direction. The results are shown in the graphs of FIGS. 14 and 15 and the distribution diagrams of FIGS. 16 to 18.

[0110] The shape of Example 1 has a width of 0.175 μm at a height of 0.224 μm from the bottom, a width of 0.228 μm at a height of 0.350 μm from the bottom, a width of 0.250 μm at a height of 0.400 μm from the bottom, and a width of 0.303 μm at a height of 0.527 μm from the bottom. As shown in FIG. 12, the size corresponding to Wb is 0.154 μm, and the size corresponding to Db is 0.175 μm. The size corresponding to Wa is 2 μm, and the size corresponding to Da - Db is 4.35 μm. FIG. 14 is a graph of the simulation results of a comparative study of Example 1 and Comparative Example 1. The horizontal axis is the wavelength of the light L, and the vertical axis is the average value of the electric field in the air. This average value of the electric field is the value excluding the incident wave and shows only the reflected wave. Compared with the electric field of Comparative Example 1, the electric field of Example 1 is smaller. That is, in Example 1, the intensity of the reflected light returning to the air is smaller.

[0111] FIG. 16 shows the electric field distribution excluding the incident wave when the light L with a wavelength of 527 nm in Example 1 is used. The electric field becomes the largest at a position about 1 / 2 of the wavelength in the z direction, decays at a position 1 / 2 of the wavelength deeper from that position, and in a region deeper than that, it becomes the same as the electric field of the structure and becomes constant without an observable amplitude. This is due to the optical trapping effect by the second part 42. Furthermore, due to the concave surface 2 forming the first part 41, diffraction and interference occur complexly from the deep part to the surface, and the electric field decays, and the electric field in the air becomes smaller. Therefore, an antireflection effect is obtained.

[0112] The shape of Example 2 has a width of 0.175 μm at a height of 0.0179 μm from the bottom and a width of 0.486 μm at a height of 0.35 μm from the bottom. As shown in FIG. 12, the size corresponding to Wb was 0.436 μm, and the size corresponding to Db was 0.175 μm. The size corresponding to Wa was 2 μm, and the size corresponding to Da - Db was 5.42 μm.

[0113] The shape of Example 3 has a width of 0.137 μm at a height of 0.350 μm from the bottom, a width of 0.150 μm at a height of 0.400 μm from the bottom. Also, it has a width of 0.155 μm at a height of 0.442 μm from the bottom, a width of 0.175 μm at a height of 0.457 μm from the bottom, and a width of 0.199 μm at a height of 0.527 μm from the bottom. As shown in FIG. 12, the size corresponding to Wb was 0.155 μm, and the size corresponding to Db was 0.442 μm. The size corresponding to Wa was 2 μm, and the size corresponding to Da - Db was 5.22 μm. The shape of Example 3 satisfies Equations 1 to 3 when λ ≧ 350 nm.

[0114] FIG. 15 is a graph of the simulation results for comparative study of Examples 1 to 3. Similar to FIG. 14, the horizontal axis is the wavelength of the light L, and the vertical axis is the average value of the electric field excluding the incident wave in the air.

[0115] Compared with Examples 1 and 2, in Example 3, the electric field was small in a wide wavelength range. This is presumably because in Example 3, when Da - Db is large, the concave surface 2 is sufficiently wide, and the number of reflections until the light L returns to the reference surface 8 after entering is large, so that the light L is sufficiently absorbed and the intensity is reduced.

[0116] Example 3 has a shape with a larger Db compared to Examples 1 and 2. This is presumably because in Example 3, the light L can be sufficiently trapped in the first part 41.

[0117] Compared with Examples 1 and 3, in Example 2, the electric field was high in a wide wavelength range. FIG. 17 shows the electric field distribution excluding the incident wave of Example 3 at a wavelength of 527 nm. FIG. 18 shows the electric field distribution excluding the incident wave of Example 2 at a wavelength of 527 nm. Comparing with the electric field distribution of Example 3 in FIG. 17, it can be seen from the electric field distribution of Example 2 in FIG. 18 that the light L enters without being trapped up to the vicinity of the bottom 5 of the concave surface 2. Therefore, it can be seen that the shape of the second part 42, particularly Wb, is important.

[0118] Note that the simulation modeled the structure 1 in which the same concave surface shape was arranged two-dimensionally with a pitch of 2 μm, but the shape of the concave surface 2 is not limited to this. Also, the pitch preferably has an average period larger than 1 μm, but it may be a periodic arrangement with regularity or a random arrangement.

[0119] <Manufacture of the structure by the manufacturing method of the second embodiment> The structures 1 of Examples 4, 5, and 6 were obtained by installing optical components on the base material 3 in the laser processing apparatus shown in FIG. 7 and performing laser processing as described above. The material of the optical component was an Invar material, which is a low thermal expansion material. By using the Invar material as the base material 3 of the optical component, deformation due to temperature influence can be reduced, and the influence on optical performance can be minimized.

[0120] FIG. 19 shows the laser oscillator wavelength, laser processing conditions, average pitch of the recesses as the processing result, average of Dd, Wa, Wb, Db, wavelength of the light L to be absorbed, and warping effect of the optical component for Examples 4 to 6.

[0121] The relationship between the laser processing trajectory and the items of the processing conditions shown in FIG. 19 will be described. The laser processing was performed by the processing method described in the second example of the second embodiment while irradiating with the set output and oscillation frequency.

[0122] When using laser processing, the pitch and depth of the structure 1 can be changed depending on the selected laser wavelength. The smaller the Dd of the structure 1, the smaller the removal amount to be removed by the processing, and the overall warping of the optical component after the processing can be reduced. That is, the laser wavelength can be selected according to the thickness of the base material 3 and the required dimensional tolerance.

[0123] In any of Examples 4 to 6, the respective numerical values could be satisfied regardless of the laser wavelength or output. Since the oscillation frequency is sufficiently large with respect to the main scanning speed, the same location is irradiated with a plurality of pulses overlapping. The concave surface 2 is formed with grooves by the initial pulses, and the subsequent pulses reflect off the side surfaces of the grooves, etc., to deeply dig the center of the grooves to form minute concave surfaces 2.

[0124] By laser processing, the structures 1 of Examples 4 to 6 can all be fabricated as shown in FIG. 19. That is, structures 1 having recesses with Wa of 3 μm, 10 μm, 20 μm, Wb of 0.15 μm, Db of 0.40 μm, and a randomly shaped concave shape in top view were obtained, and an optical component that absorbs incident light with a wavelength of 0.35 μm or more and has an antireflection function was obtained. FIG. 22 shows an image of the structure 1 of Example 6. This image is an observation of the structure 1 at a magnification of 50 times using a laser microscope (VK-X3000: manufactured by Keyence Corporation). An uneven shape with a large number of randomly arranged concave surfaces 2 can be read.

[0125] An Invar material was used as the material for the optical component, but it can also be applied to other materials such as steel, nickel and its alloys, copper and its alloys, aluminum and its alloys, molybdenum, niobium, tantalum, rhenium, hafnium, zirconium, yttrium, etc.

[0126] The optical component may be processed in a nitrogen atmosphere. Processing in a nitrogen atmosphere is particularly effective for materials that are prone to oxidation among the materials of the optical component. In laser processing, debris is generated when the material melts and solidifies due to heat. Since oxygen binds to the debris in materials that are prone to oxidation and the physical properties change, it has an adverse effect on the stability of laser processing. Therefore, the processing stability can be improved by using a nitrogen atmosphere.

[0127] <Manufacture of the structure by the manufacturing method of the third embodiment> Next, an example in which an antireflection surface is transferred to a resin component using injection molding is shown. The structures 1 of Examples 7 to 9 were manufactured by injection molding shown in FIG. 10. Here, as the injection molding machine, an injection molding machine J180EL III (trade name) manufactured by Japan Steel Works, Ltd. was used. Also, the material of the mold is steel for molds. As the resin material introduced from the hopper 910, for example, polycarbonate G3430H with glass filler manufactured by Teijin Limited, colored black with a colorant, was used.

[0128] FIG. 20 shows the laser oscillator wavelength, laser processing conditions, average pitch of the uneven structure, depth, and the average of Dd, Wa, Wb, Db of the structure 1, and the wavelength of the light L absorbed and the release resistance for Examples 7 to 9.

[0129] FIG. 21 shows an image diagram of the mold surface after forming transfer. The processing conditions of the mold surface in FIG. 21 are the same as those in the second embodiment. The concave surface 2 of the structures 1 of Examples 7 to 9 was formed as a resin component obtained by transferring the convex portion 7 of the mold 91 as shown in FIG. 21.

[0130] The average of Dd affected the release resistance in injection molding. The release resistance was smaller as Dd was smaller, and it was possible to suppress the overall warping deformation of the resin component.

[0131] The structures 1 of Examples 7 to 9 can all be produced as shown in Fig. 20. That is, with Wa being 3 μm, 10 μm, and 20 μm, Wb being 0.8 μm, and Db being 2.5 μm, a structure 1 having recesses with a randomized concave shape in top view was obtained, and a resin component that absorbs incident light with a wavelength of 2.1 μm or more and has an antireflection function could be mass-produced in a short time and at low cost.

[0132] In the examples, die steel was used as the material for the mold, but nickel alloys, copper alloys, etc. may also be used. Also, polycarbonate with glass filler was used as the resin, but the resin may be polycarbonate without glass filler, acrylonitrile-butadiene-styrene, polyoxymethylene, polyphthalamide, polypropylene, polybutylene terephthalate, fluororesin, polyamide, etc.

[0133] Also, the mold may be produced in a nitrogen atmosphere. Producing in a nitrogen atmosphere is effective especially when the material of the mold is prone to oxidation. In laser processing, debris is generated when the material melts and solidifies due to heat. Since oxygen binds to the debris in a material prone to oxidation and the physical properties change, it has an adverse effect on the stability of laser processing, so the processing stability can be improved by using a nitrogen atmosphere.

[0134] In the examples, injection molding was used as the transfer technique, but it may also be carried out by roll forming, press molding, etc.

[0135] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A structure that absorbs light with a wavelength λ of incident light, comprising a base material having a plurality of concave surfaces on the light incident surface, the light enters the inner region of each of the plurality of concave surfaces, the light satisfies 400 nm ≤ λ ≤ 40 μm, For each of the plurality of concave surfaces, the depth Dd of the bottom of the concave surface, the width Wa of the inner region at a position at a distance Da from the bottom of the concave surface, and the width Wb of the inner region at a position at a distance Db from the bottom satisfy Dd≧Da>Db>λ, Wa>λ, and Wb≦λ / 2 A structure that satisfies this. (Configuration 2) The structure according to Configuration 1, which satisfies Wa≧2λ. (Configuration 3) The structure according to Configuration 1 or 2, which satisfies Wa≧4λ. (Configuration 4) The structure according to any one of Configurations 1 to 3, which satisfies Wa>1μm. (Configuration 5) The structure according to any one of Configurations 1 to 4, which satisfies Wa≧10μm. (Configuration 6) The structure according to any one of Configurations 1 to 5, which satisfies Wa≦100μm. (Configuration 7) The structure according to any one of Configurations 1 to 6, which satisfies Wa≦70μm. (Configuration 8) The structure according to any one of Configurations 1 to 7, which satisfies Wb≧λ / 4. (Configuration 9) The structure according to any one of Configurations 1 to 8, which satisfies Wb≦400nm. (Configuration 10) The structure according to any one of Configurations 1 to 9, which satisfies λ≦4μm. (Configuration 11) The light, and the structure according to any one of Configurations 1 to 10, which satisfies λ>800nm. (Configuration 12) The light, and the structure according to any one of Configurations 1 to 11, which satisfies λ≦800nm. (Configuration 13) The structure according to any one of Configurations 1 to 12, which satisfies Da>Dd / 2. (Configuration 14) The structure according to any one of Configurations 1 to 13, which satisfies Db<Dd / 2. (Configuration 15) The structure according to any one of Configurations 1 to 14, satisfying Dd≧4λ. (Configuration 16) The structure according to any one of Configurations 1 to 15, satisfying Dd>10μm. (Configuration 17) The structure according to any one of Configurations 1 to 16, satisfying Dd≧100μm. (Configuration 18) The structure according to any one of Configurations 1 to 17, satisfying Dd≦1000μm. (Configuration 19) For each of the plurality of concave surfaces, the width Wc of the inner region at a position at a distance Dc from the bottom of the concave surface satisfies λ≧Dc and Wc≦λ / 4. The structure according to any one of Configurations 1 to 18. (Configuration 20) The plurality of concave surfaces include a first concave surface and a second concave surface. The distance Ge between the first concave surface and the second concave surface at a position at a distance De from the bottom of the first concave surface, provided that Dd≧De≧Da, satisfies Ge≦100μm. The structure according to any one of Configurations 1 to 19. (Configuration 21) The structure according to Configuration 20, satisfying Ge≦10μm. (Configuration 22) The plurality of concave surfaces include a first concave surface and a second concave surface. The distance Ge between the first concave surface and the second concave surface at a position at a distance De from the bottom of the first concave surface, provided that Dd≧De≧Da, satisfies Ge<Wa. The structure according to any one of Configurations 1 to 21. (Configuration 23) The plurality of concave surfaces include a first concave surface and a second concave surface. The distance Go between the bottom of the first concave surface and the bottom of the second concave surface satisfies Go≧Wa. The structure according to any one of Configurations 1 to 22. (Configuration 24) The plurality of concave surfaces include a first concave surface and a second concave surface. The distance Go between the bottom of the first concave surface and the bottom of the second concave surface satisfies Go>1μm. The structure according to any one of Configurations 1 to 23. (Configuration 25) The attenuation coefficient of the base material with respect to the light is greater than 1.0, the structure according to any one of Configurations 1 to 24. (Configuration 26) The transmittance of the light with respect to the base material is less than 1%, the structure according to any one of Configurations 1 to 25. (Configuration 27) In plan view with respect to the incident surface, the number of the plurality of concave surfaces or the number of convex portions constituting the plurality of concave surfaces is 100 pieces / mm 2 or more, the structure according to any one of Configurations 1 to 26. (Configuration 28) In plan view with respect to the incident surface, the number of the plurality of concave surfaces or the number of convex portions constituting the plurality of concave surfaces is 10,000 pieces / mm 2 or less, the structure according to any one of Configurations 1 to 27. (Configuration 29) In plan view with respect to the incident surface, the plurality of concave surfaces are arranged two-dimensionally, the structure according to any one of Configurations 1 to 28. (Configuration 30) For each of the plurality of concave surfaces, in a portion where the distance from the bottom is 2Dd / 3 or more and 9Dd / 10 or less, the taper angle θ is 60 degrees or more, the structure according to any one of Configurations 1 to 29. (Configuration 31) The width of the inner region gradually decreases from the position of the distance Da from the bottom toward the position of the distance Db from the bottom, the structure according to any one of Configurations 1 to 30. (Configuration 32) The plurality of concave surfaces include a concave surface in which the width of the inner region is Wb or more and λ / 2 or less at a distance Df from the bottom of the concave surface, provided that Da ≧ Df > Db, the structure according to any one of Configurations 1 to 31. (Configuration 33) For each of the plurality of concave surfaces, the concave surface includes a first inclined surface and a second inclined surface located on the bottom side of the concave surface with respect to the first inclined surface, with a plane in contact with a plurality of convex portions forming the concave surface as a reference plane, an angle d1 formed by the first inclined surface and the reference plane, and an angle d2 formed by the second inclined surface and the reference plane are d1 > d2 The structure according to any one of Configurations 1 to 32 that satisfies (Configuration 34) The structure according to Configuration 33 that satisfies d1 ≥ 80 degrees. (Configuration 35) The structure according to Configuration 33 that satisfies d1 ≥ 85 degrees. (Configuration 36) For each of the plurality of concave surfaces, the concave surface includes a first curved surface and a second curved surface located on the bottom side of the concave surface with respect to the first curved surface. The structure according to any one of Configurations 1 to 32, wherein the center of the first curved surface is inside the concave surface, and the center of the second curved surface is outside the concave surface. (Configuration 37) The structure according to any one of Claims 1 to 36, wherein the base material is made of metal. (Configuration 38) The structure according to any one of Claims 1 to 37, wherein the base material is made of aluminum. (Configuration 39) The structure according to any one of Claims 1 to 38, wherein the base material is made of resin. (Configuration 40) A member including the structure according to any one of Configurations 1 to 39. (Configuration 41) An optical device including the structure according to any one of Configurations 1 to 39. (Method 1) A method for manufacturing the structure according to any one of Configurations 1 to 39, wherein the base material is formed by performing laser processing on a material. (Method 2) A method for manufacturing the structure according to any one of Configurations 1 to 39, wherein the concavo-convex structure of a mold having a concavo-convex structure is transferred to a resin. (Method 3) The manufacturing method according to Method 2, comprising a step of forming a mold by performing laser processing on a mold material, and a step of injection molding a resin with the mold.

Explanation of Reference Numerals

[0136] 1 Structure 2 Concave surface 27 Other concave surface 3 Base material 4 Inner region 41 First part 42 Second part 412 Middle part 5 Bottom 6 Incident surface 7 Convex part 8 Reference surface 9 Opposite surface 11 Laser oscillator 12 Beam expander 13 Galvano mirror 14 Fθ 15 Base material 16 Fixing table 17 Moving stage 18 Galvano control unit 19 Stage control unit 20 Host computer 900 Molding die 99 Cylinder 911 Pressing device 910 Hopper 920 Cavity 91 First molding die 98 Second molding die 900 Molding die 912 Molten resin 920 Cavity 1100 Digital camera 1101 Lens barrel 1102 Camera body 1103 Lens 1104 Inner cylinder 1105 Lens 1106 Diaphragm 1108 Sub - mirror 1109 Shutter 1110 Image sensor 1111 Prism 1112 Finder lens 1120 Camera housing 1121 Housing 1140 Main mirror holder

Claims

1. A structure that absorbs incident light of wavelength λ, A substrate having a plurality of concave surfaces on the light incident surface, the light is incident on an inner region of each of the plurality of concave surfaces; The light satisfies 400 nm≦λ≦40 μm, For each of the plurality of concave surfaces, the depth Dd of the bottom of the concave surface, the width Wa of the inner region at a position a distance Da from the bottom of the concave surface, and the width Wb of the inner region at a position a distance Db from the bottom are Dd≧Da>Db>λ, Wa>λ, and Wb≦λ / 2 A structure that satisfies.

2. The structure according to claim 1 , wherein Wa≧2λ.

3. The structure according to claim 1 , wherein Wa≧4λ.

4. The structure according to claim 1 , wherein Wa>1 μm.

5. The structure according to claim 1 , wherein Wa≧10 μm.

6. The structure according to claim 1 , wherein Wa≦100 μm.

7. The structure according to claim 1 , wherein Wa≦70 μm.

8. The structure of claim 1 , wherein Wb≧λ / 4.

9. The structure according to claim 1 , wherein Wb≦400 nm.

10. The structure of claim 1 , wherein λ≦4 μm.

11. The structure of claim 1 , wherein the light satisfies λ>800 nm.

12. The structure of claim 1 , wherein the light satisfies λ≦800 nm.

13. The structure according to claim 1 , wherein Da>Dd / 2.

14. The structure of claim 1 , wherein Db<Dd / 2.

15. The structure of claim 1 , wherein Dd≧4λ.

16. The structure of claim 1 , wherein Dd>10 μm.

17. The structure according to claim 1 , wherein Dd≧100 μm.

18. The structure according to claim 1 , wherein Dd≦1000 μm.

19. The structure according to claim 1 , wherein for each of the plurality of concave surfaces, a width Wc of the inner region at a position a distance Dc from a bottom of the concave surface satisfies λ≧Dc and Wc≦λ / 4.

20. The structure of claim 1, wherein the plurality of concave surfaces include a first concave surface and a second concave surface, and a distance Ge between the first concave surface and the second concave surface at a position a distance De from a bottom of the first concave surface, where Dd≧De≧Da, satisfies Ge≦100 μm.

21. 21. The structure of claim 20, wherein Ge≦10 μm.

22. 2. The structure of claim 1, wherein the plurality of concave surfaces include a first concave surface and a second concave surface, and a distance Ge between the first concave surface and the second concave surface at a position a distance De from a bottom of the first concave surface, where Dd≧De≧Da, satisfies Ge<Wa.

23. The structure of claim 1 , wherein the plurality of concave surfaces includes a first concave surface and a second concave surface, and a distance Go between a bottom of the first concave surface and a bottom of the second concave surface satisfies Go≧Wa.

24. 2. The structure of claim 1, wherein the plurality of concave surfaces include a first concave surface and a second concave surface, and a distance Go between a bottom of the first concave surface and a bottom of the second concave surface satisfies Go>1 μm.

25. The structure of claim 1 , wherein the substrate has an extinction coefficient for the light greater than 1.

0.

26. 10. The structure of claim 1, wherein the light transmittance through the substrate is less than 1%.

27. In a plan view of the entrance surface, the number of the plurality of concave surfaces or the number of the convex portions constituting the plurality of concave surfaces is 100 pieces / mm ２ The structure according to claim 1 .

28. In a plan view of the incidence surface, the number of the plurality of concave surfaces or the number of convex portions constituting the plurality of concave surfaces is 10,000 pieces / mm ２ 2. The structure of claim 1 , wherein:

29. The structure according to claim 1 , wherein the plurality of concave surfaces are arranged two-dimensionally in a plan view with respect to the incidence surface.

30. The structure according to claim 1 , wherein, for each of the plurality of concave surfaces, a taper angle θ is 60 degrees or more in a portion that is at a distance from the bottom that is 2Dd / 3 or more and 9Dd / 10 or less.

31. 2. The structure of claim 1, wherein the width of the inner region tapers from a distance Da from the base to a distance Db from the base.

32. The structure according to claim 1 , wherein the plurality of concave surfaces include a concave surface having a width of the inner region of Wb or more and λ / 2 or less at a distance Db to a distance Df from a bottom of the concave surface, where Da≧Df>Db.

33. For each of the plurality of concave surfaces, the concave surface includes a first inclined surface and a second inclined surface located closer to the bottom side of the concave surface than the first inclined surface, and a plane that is in contact with a plurality of convex portions that form the concave surface is used as a reference surface, An angle d1 that the first inclined surface makes with the reference plane; The angle d2 that the second inclined surface makes with the reference plane is d1>d2 The structure of claim 1 , wherein

34. 34. The structure of claim 33, wherein d1 > 80 degrees.

35. 34. The structure of claim 33, wherein d1 > 85 degrees.

36. For each of the plurality of concave surfaces, the concave surface includes a first curved surface and a second curved surface located closer to the bottom of the concave surface than the first curved surface; 2. The structure of claim 1, wherein the center of the first curved surface is inside the concave surface and the center of the second curved surface is outside the concave surface.

37. The structure of claim 1 , wherein the substrate is made of a metal.

38. The structure of claim 1 , wherein the substrate is made of aluminum.

39. The structure according to claim 1 , wherein the substrate is made of a resin.

40. A component comprising the structure of any one of claims 1 to 39.

41. 40. An optical instrument comprising a structure according to any one of claims 1 to 39.

42. The method for manufacturing a structure according to any one of claims 1 to 39, wherein the base material is formed by performing laser processing on a base material.

43. The method for producing the structure according to claim 1 , further comprising the step of transferring the uneven structure of a mold having an uneven structure to a resin.

44. The method according to claim 43, further comprising the steps of: forming a mold by subjecting a mold material to laser processing; and injection molding a resin with the mold.

Images