Structure for absorbing light, member, optical device, and method for manufacturing structure

Abstract

A structure for absorbing light, a member, an optical device, and a method of manufacturing a structure are disclosed. A technique for facilitating implementation of a structure capable of sufficiently absorbing light provides a structure for absorbing light incident on the structure and having a wavelength [lambda], the structure including a substrate having a plurality of concave surfaces on a light incident surface. Light is incident on an inner region of each of the plurality of concave surfaces. The light satisfies 400 nm < = lambda < = 40 [mu] m. Each of the plurality of concave surfaces satisfies Dd > = Daft; d < bgt >; lambda, Wagt; [lambda] and Wb < = [lambda] / 2, where Dd represents a depth of a bottom portion of each of the plurality of concave surfaces, Wa represents a width of the inner region at a position of a distance Da from the bottom portion of each of the plurality of concave surfaces, and Wb represents a width of the inner region at a position of a distance Db from the bottom portion.

Description

Technical Field

[0001] The present disclosure relates to a structure, a component, an optical device, and a method for manufacturing a structure. Background Art

[0002] To date, many techniques for enhancing antireflection performance have been used in components of devices affected by reflected light and scattered light. For example, stray light such as unnecessary reflected light or scattered light around the optical path of an optical device such as a telescope, a microscope, or a camera may interfere with the acquisition of a clear image. Therefore, in these optical devices, it is required to enhance the antireflection performance around the optical path. As related art, for example, a method of using a black material around the optical path and a method of roughening the surface are known. However, sometimes it is not sufficient to sufficiently suppress reflected light or scattered light only by using the above-mentioned methods.

[0003] As described in Japanese Patent Application Laid-Open No. 2007-304466, a method of forming an uneven structure (a structure of a so-called subwavelength structure (SWS)) having a pitch equal to or less than the wavelength of incident light on the surface of a component is sometimes used. This technique utilizes the principle that the reflectance decreases when the refractive index of incident light changes slowly at the air layer and the surface layer portion of the component surface.

[0004] In addition, a technique using the following structure is also known: as described in International Publication No. WO2016 / 159045, an uneven structure having a pitch greater than the wavelength of incident light is formed and the uneven structure suppresses the reflection of incident light (so-called antireflection).

[0005] Using only the structure having a pitch equal to or less than the wavelength of incident light described in Japanese Patent Application Laid-Open No. 2007-304466 or the uneven structure having a pitch greater than the wavelength of incident light described in International Publication No. WO2016 / 159045, the absorption of light is not sufficient, and thus there is still room for improvement. Summary of the Invention

[0006] One aspect of the present disclosure is to provide a technique that facilitates the realization of a structure capable of sufficiently absorbing light.

[0007] A structure that is configured to absorb light having a wavelength λ incident thereon, the structure including a substrate having a plurality of concave surfaces on an incident surface of the light. The light is incident on an inner region of each of the plurality of concave surfaces. The light satisfies 400 nm ≤ λ ≤ 40 μm. Each of the plurality of concave surfaces satisfies Dd ≥ Da > Db > λ, Wa > λ, and Wb ≤ λ / 2, where Dd represents a depth of a bottom of each of the plurality of concave surfaces, Wa represents a width of the inner region at a position at a distance Da from the bottom of each of the plurality of concave surfaces, and Wb represents a width of the inner region at a position at a distance Db from the bottom.

[0008] More features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A is a view for illustrating an example of the structure of the first embodiment.

[0010] Figure 1B is a view for illustrating an example in the structure of the first embodiment where Db > λ is satisfied.

[0011] Figure 2 is a view for illustrating an example of the structure of the first embodiment.

[0012] Figure 3 is a view for illustrating an example of the structure of the first embodiment.

[0013] Figure 4A is a top view for illustrating an example of the structure of the first embodiment (an example of lines and spaces).

[0014] Figure 4B is a cross-sectional view for illustrating an example of the structure of the first embodiment (an example of lines and spaces).

[0015] Figure 4C is a top view for illustrating an example of the structure of the first embodiment (a first example of two-dimensionally arranging a plurality of concave surfaces).

[0016] Figure 4D is a cross-sectional view for illustrating an example of the structure of the first embodiment (a first example of two-dimensionally arranging a plurality of concave surfaces).

[0017] Figure 4E is a top view for illustrating an example of the structure of the first embodiment (a second example of two-dimensionally arranging a plurality of concave surfaces).

[0018] Figure 4FIt is a cross-sectional view for illustrating an example of the structure of the first embodiment (a second example of arranging a plurality of concave surfaces two-dimensionally).

[0019] Figure 5 It is an explanatory diagram for illustrating the cone angle.

[0020] Figure 6A It is a view for illustrating an example of the structure of the first embodiment.

[0021] Figure 6B It is a view for illustrating an example of the structure of the first embodiment.

[0022] Figure 7 It is a diagram for schematically illustrating the configuration of a laser processing machine to be used in the manufacturing method of the second embodiment.

[0023] Figure 8 It is a flowchart of the laser processing in the manufacturing method of the second embodiment.

[0024] Figure 9A It is an explanatory diagram for illustrating an example of laser processing.

[0025] Figure 9B It is an explanatory diagram for illustrating an example of laser processing.

[0026] Figure 9C It is an explanatory diagram for illustrating an example of laser processing.

[0027] Figure 9D It is an explanatory diagram for illustrating an example of laser processing.

[0028] Figure 9E It is an explanatory diagram for illustrating an example of laser processing.

[0029] Figure 10A It is a view for illustrating an injection molding apparatus for producing a resin component according to an embodiment of the present disclosure.

[0030] Figure 10B It is a view for illustrating the step of forming a cavity in the injection molding apparatus.

[0031] Figure 10C It is a view for illustrating the step of injecting resin into the cavity of the injection molding apparatus.

[0032] Figure 10D It is a view for illustrating the step of cooling the resin while maintaining pressure after injecting the resin into the cavity.

[0033] Figure 10E It is a view for illustrating the step of performing mold opening to take out the resin component.

[0034] Figure 11 It is a view showing an example of an optical device and components for illustrating another embodiment.

[0035] Figure 12 It is a table showing the conditions of Examples 1 to 3 and Comparative Example 1.

[0036] Figure 13 It is a view showing the spatial definition of the simulation of Example 1.

[0037] Figure 14 It is a graph showing the results of Example 1 and Comparative Example 1.

[0038] Figure 15 It is a graph showing the results of Examples 1 to 3.

[0039] Figure 16 It is a diagram showing the electric field distribution diagram of Example 1.

[0040] Figure 17 It is a diagram showing the electric field distribution diagram of Example 3.

[0041] Figure 18 It is a diagram showing the electric field distribution diagram of Example 2.

[0042] Figure 19 It is a table showing the details of Examples 4 to 6.

[0043] Figure 20 It is a table showing the details of Examples 7 to 9.

[0044] Figure 21 It is a schematic representation of die transfer on the die surface.

[0045] Figure 22 It is a microscopic image of the structure of Example 6.

[0046] Figure 23 It is a view showing an example of the structure of the first embodiment.

[0047] Figure 24 It is a view showing an example of the structure of the first embodiment.

[0048] Figure 25 It is a graph showing the measurement results of the reflectivity of the structure. Detailed Description

[0049] <First Embodiment>

[0050] As a first embodiment, the present disclosure provides a structure 1 for absorbing light L having a wavelength λ incident on the structure 1. The structure 1 includes a substrate 3 having a plurality of concave surfaces 2 on an incident surface 6 of the light L. The light L is incident on an inner region 4 of each of the plurality of concave surfaces 2. The light L satisfies 400 nm ≤ λ ≤ 40 μm. Each of the plurality of concave surfaces 2 satisfies Dd ≥ Da > Db > λ, Wa > λ, and Wb ≤ λ / 2, where Dd represents the depth of the bottom 5 of the concave surface 2, Wa represents the width of the inner region 4 at a position at a distance Da from the bottom 5 of the concave surface 2, and Wb represents the width of the inner region 4 at a position at a distance Db from the bottom 5.

[0051] Reference Figure 1A and Figure 1B describe the structure 1 of this embodiment. Figure 1A 、 Figure 1B 、 Figure 2 、 Figure 3 、 Figure 5 、 Figure 6A and Figure 6B are all views obtained by magnifying a part of a cross-section taken along a direction perpendicular to the reference plane 8 of the structure 1.

[0052] The structure 1 of this embodiment absorbs light L having a wavelength of λ (400 nm ≤ λ ≤ 40 μm). As Figure 1A shown, the structure 1 includes a substrate 3 having a plurality of concave surfaces 2 on an incident surface 6 of the light L. The light L is incident on an inner region 4 of each of the plurality of concave surfaces 2. Each of the plurality of concave surfaces 2 is a three-dimensional region at least a part of which is defined by the concave surface 2, and may be a region defined between the concave surfaces 2 or a region surrounded by the concave surfaces 2. The inner region 4 only requires translucency and is usually a vacuum space or a gas space, but may be a solid region in which a translucent material is arranged. The structure 1 includes a convex portion 7, and a part of the surface of the convex portion 7 forms the concave surface 2 or a part of the concave surface 2. The inner region 4 is positioned between the plurality of convex portions 7 in the XY direction. In Figure 1AIn the structure 1, the reference plane 8 is an imaginary 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 generally contacts the vertices of the plurality of convex portions 7. 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 from the reference plane 8 toward the bottom 5 of the concave surface 2. The convex portions 7 protrude from the bottom 5 of the concave surface 2 toward the reference plane 8. Therefore, the concave surface 2 can be referred to as a recessed surface, and the convex portions 7 can be referred to as protruding portions. The concave surface 2 is recessed in the direction from the reference plane 8 toward the bottom 5. The convex portions 7 protrude from the bottom 5 in the direction toward the reference plane 8. That is, the concave surface 2 can be referred to as a "recessed surface", and the convex portions 7 can be referred to as "protruding portions".

[0053] As Figure 1A shown, the depth from the reference plane 8 to the bottom 5 of the concave surface 2 is represented by Dd. In other words, the distance between the reference plane 8 and the bottom 5 is the depth Dd. The width of the internal region 4 at the position of the distance Da from the bottom 5 in the Z direction perpendicular to the reference plane 8 is represented by Wa. In addition, the width of the internal region 4 at the position of the distance Db from the bottom 5 in the Z direction perpendicular to the reference plane 8 is represented by Wb. The depth of the concave surface 2 refers to the depth from the reference plane 8 in the Z direction perpendicular to the reference plane 8. In each figure, X and Y indicate directions perpendicular to each other and perpendicular to Z.

[0054] The structure 1 satisfies the following Expressions 1 to 3.

[0055] Dd≥Da>Db>λ (Expression 1), Wa>λ (Expression 2), and Wb≤λ / 2 (Expression 3).

[0056] Figure 1B It is shown that the structure 1 satisfies Db>λ in Expression 1.

[0057] The depth Dd of the concave surface 2 and the widths Wa and Wb of the internal region 4 can each be determined in a certain cut surface of the structure 1 parallel to the direction Z, where the direction Z is perpendicular to the reference plane 8. Preferably, the depth Dd of the concave surface 2 and the widths Wa and Wb of the internal region 4 are determined in a surface perpendicular to the structure 1, in which surface, for each concave surface 2, its depth becomes maximum and the width of the internal region 4 at the outermost surface of the structure 1 becomes minimum.

[0058] The light L to be absorbed by the structure 1 is an electromagnetic wave including at least one of visible light or infrared light, and the light L has a wavelength λ of 400 nm ≤ λ ≤ 40 μm. However, in addition to at least one of visible light or infrared light, the structure 1 can also be configured to absorb ultraviolet light. The wavelength λ is preferably λ ≤ 4 μm, more preferably λ ≤ 3 μm, and further preferably λ ≤ 2.5 μm. A wavelength of 40 μm can be regarded as the boundary between mid-infrared light and far-infrared light. A wavelength of 4 μm can be regarded as the boundary between mid-infrared light and far-infrared light. A wavelength of 3 μm can be regarded as the boundary between near-infrared light and mid-infrared light. A wavelength of 2.5 μm can be regarded as the boundary between near-infrared light and mid-infrared light. The wavelength λ can satisfy λ > 1 μm or λ > 800 nm, or can satisfy λ ≤ 1 μm or λ ≤ 800 nm. A wavelength of 800 nm can be regarded as the boundary between visible light and infrared light, and a wavelength of 400 nm can be regarded as the boundary between visible light and ultraviolet light. Which wavelength λ to use at the absorption target of the structure 1 can be determined according to the application of the structure 1. Preferably, even for a plurality of wavelengths λa and λb in visible light and infrared light, when the wavelength λ satisfies λ = λa or λ = λb, the above expressions 1 to 3 are also satisfied. Both the wavelength λa and the wavelength λb can be within the wavelength range of visible light, and both the wavelength λa and the wavelength λb can be within the wavelength range of infrared light. In addition, the wavelength λa can be within the wavelength range of visible light, and the wavelength λb can be within the wavelength range of infrared light.

[0059] Hereinafter, in some cases, the portion from the distance Db to the distance Dd in the inner region 4 is referred to as the "first portion 41", and the portion from the bottom of the concave surface (i.e., the distance 0 from the bottom 5) to the distance Db is referred to as the "second portion 42".

[0060] The structure 1 of this embodiment can efficiently absorb the light L and can prevent or reduce reflection. The inventor believes the reasons are as follows. That is, when Wa, which is the opening width of the first portion 41, is greater than λ, the light L with a wavelength of λ can be guided to the concave surface 2 by diffraction and propagation. In addition, since Db > λ and Wb ≤ λ / 2 are satisfied, the influence of the diffraction and propagation of the light L on the light L directly incident on the second portion 42 without hitting the concave surface 2 forming the first portion 41 is reduced. Therefore, the light L can be absorbed and the intensity of the light L can be reduced.

[0061] Da and Db are selected to satisfy Expressions 1 to 3. It is possible to satisfy Da≈Dd, that is, the position of the distance Da from the bottom 5 of the concave surface 2 can be the reference plane 8. However, in this case, for Da, the minute unevenness caused by the undulating substrate surface is ignored, so Da and Dd do not require to exactly match each other. In this case, Wd as the opening width in the reference plane 8 satisfies Wa≈Wd. The following examples all satisfy Da≈Dd and Wa≈Wd.

[0062] Figure 2 Examples satisfying Dd≈Da and Wa≈Wd are shown. In addition, Figure 3 Examples are shown in which the concave surface 2 forming the first part 41 and the concave surface 2 forming the second part 42 have different inclinations, and the concave surface 2 forming the second part 42 has a steeper inclination.

[0063] The concave surface 2 used herein refers to the concave surface 2 that satisfies Expressions 1 to 3, and the structure 1 of this embodiment may include another concave surface 27. Another concave surface 27 is a concave surface that does not satisfy at least one of Expressions 1 to 3. In addition, each of the plurality of concave surfaces 2 only requires to satisfy Expressions 1 to 3, and the plurality of concave surfaces 2 may have different shapes and Da, Db, Dd, Wa, and Wb may vary as long as Expressions 1 to 3 are satisfied. As will be described later, in the case of the description of Dc, De, Df, Ge, Go, and the cone angle, the plurality of concave surfaces 2 may also have different values.

[0064] In the plan view with respect to the incident surface 6, that is, when the structure 1 is observed from the Z direction in the top view, the number of the plurality of concave surfaces 2 or the number of the convex portions 7 forming the plurality of concave surfaces 2 is preferably 3 surfaces / mm 2 or more or 3 portions / mm 2 or more, more preferably 5 surfaces / mm 2 or more or 5 portions / mm 2 or more, further preferably 10 surfaces / mm 2 or more or 10 portions / mm 2 or more, still further preferably 100 surfaces / mm 2 or more or 100 portions / mm 2 or more, even further preferably 1000 surfaces / mm 2 or more or 1000 portions / mm 2 or more. In the plan view with respect to the incident surface 6, the number of the plurality of concave surfaces 2 or the number of the convex portions 7 forming the plurality of concave surfaces 2 is preferably 1000000 surfaces / mm 2 or less or 1000000 portions / mm 2Hereinafter, more preferably, it is 100,000 surfaces / mm 2 or less, or 100,000 portions / mm 2 Hereinafter, further preferably, it is 10,000 surfaces / mm 2 or less, or 10,000 portions / mm 2 Hereinafter.

[0065] Wa is Wa > λ, and preferably Wa ≥ 2λ, more preferably Wa ≥ 4λ. Additionally, preferably Wa ≤ 100λ, more preferably Wa ≤ 40λ.

[0066] In addition, preferably Wa > 1μm, more preferably Wa ≥ 10μm.

[0067] Preferably Wa ≤ 300μm, more preferably Wa ≤ 200μm, further preferably Wa ≤ 100μm, more preferably Wa ≤ 70μm.

[0068] When Wa > λ is satisfied, the opening width of the first portion 41 is large enough, and the light L is efficiently trapped in the concave surface 2 to cause light trapping. In addition, when Wa is large and the opening width of the first portion 41 is large enough, the structure 1 can be easily manufactured.

[0069] Wb is Wb ≤ λ / 2, and preferably Wb ≥ λ / 4, but it can be Wb < λ / 4. Additionally, preferably Wb ≤ 400nm, but Wb can be Wb ≤ 200nm and preferably Wb ≥ 100nm.

[0070] When Db > λ and Wb ≤ λ / 2 are satisfied, in the second portion 42, the depth is deep relative to the opening width. Therefore, the diffraction and propagation of the light L can be weakened, so that the light L is absorbed, thereby reducing the intensity of the light L, making it possible to prevent reflection.

[0071] Visual inspection of the effect of absorption with respect to visible light. That is, when the structure 1 absorbs the light L in a wide wavelength range of visible light, the incident surface 6 may appear black. Moreover, based on the electromagnetic field simulation using the FDTD method shown in Example 1, when the electromagnetic field distribution at a specific wavelength is 0.85 or less, it can be determined that there is no reflection.

[0072] Dd is Dd > λ, and preferably Dd > 2λ, more preferably Dd ≥ 4λ, further more preferably Dd ≥ 5λ, still more preferably Dd ≥ 10λ, even more preferably Dd ≥ 100λ.

[0073] In addition, preferably Dd > 10μm, more preferably Dd ≥ 100μm. Furthermore, preferably Dd ≤ 1000μm.

[0074] When Dd is large enough, the concave surface 2 is wide enough. When the concave surface 2 is wide enough, the number of reflections from when the light L is incident on the structure 1 until the light L returns to the reference surface 8 is large. Therefore, even when the light L returns from the second part 42 to the reference surface 8, sufficient light trapping occurs even for the light L that is not sufficiently absorbed in the second part 42. Therefore, the light L is absorbed and reflection is suppressed. In addition, when the concave surface 2 is wide enough, the light L is reflected from various directions to cause diffraction, so that the waves of the light L can be effectively canceled out with each other.

[0075] Therefore, in particular, Dd - Da is preferably Dd - Da > λ, more preferably Dd - Da > 2λ, further more preferably Dd - Da ≥ 4λ, more preferably Dd - Da ≥ 5λ, further preferably Dd - Da ≥ 10λ, even more preferably Dd - Da ≥ 100λ.

[0076] In the internal region 4, Dd ≥ Da > Db > λ is satisfied, but it is preferable to satisfy Da > Dd / 2, and it is preferable to satisfy Db < Dd / 2. When Da > Dd / 2 is satisfied, the light L is easily trapped in the upper half (the incident side of the light L) of the internal region 4. When Db < Dd / 2 is satisfied, the light incident on the lower half of the internal region 4 from the upper half is easily absorbed.

[0077] In addition, as Figure 1B shown, in the structure 1 of this embodiment, it is preferable that the width Wc of each region at the position of the distance Dc from the bottom 5 of each of the plurality of concave surfaces 2 satisfies Dc ≤ λ and Wc ≤ λ / 4. When a portion with a narrow width is provided at a position close to the bottom 5, during repeated large numbers of reflections, the diffraction and propagation of the light L are weakened, so that the light L is absorbed, and thus the intensity of the light L decreases.

[0078] In addition, in the structure 1 of this embodiment, it is preferable that the plurality of concave surfaces 2 include a first concave surface 2 and a second concave surface 2, and the distance Ge between the first concave surface 2 and the second concave surface 2 at the position of the distance De (assuming Dd ≥ De ≥ Db) from the bottom 5 of the first concave surface 2 satisfies Ge ≤ 100 μm. The first concave surface 2 and the second concave surface 2 are generally concave surfaces 2 formed by a common convex portion 7. Ge is more preferably Ge ≤ 10 μm, further preferably Ge ≤ 1 μm. In addition, Ge preferably satisfies Ge < Wa. It can satisfy Da ≥ De ≥ Db, and Figure 1AExamples where Da > De > Db are shown. As another example, Dd ≥ De ≥ Da can be satisfied, and the position at a distance De from the bottom 5 of the concave surface 2 can be the position where the reference plane 8 is located (i.e., De can be equal to Dd). However, also in this case, for De, the minute unevenness caused by the undulating substrate surface is ignored, so De and Dd do not require to exactly match each other. Figure 2 Examples where De ≈ Dd are shown. In this case, Ge is the interval between the concave surfaces 2 when observing the structure 1 in a top view.

[0079] In addition, it is preferable that the distance Go between the bottom 5 of the first concave surface 2 and the bottom 5 of the second concave surface 2 satisfies Go > 1 μm. Go more preferably satisfies Go ≥ 5 μm, and further preferably satisfies Go ≥ 10 μm. Go preferably satisfies Go ≤ 100 μm.

[0080] It is preferable that Go satisfies Go > 1 μm. In addition, Go preferably satisfies Go ≤ 100λ, and more preferably satisfies Go ≤ 40λ.

[0081] Go preferably satisfies Go ≤ 300 μm, more preferably satisfies Go ≤ 200 μm, further preferably satisfies Go ≤ 100 μm, and even more preferably satisfies Go ≤ 70 μm.

[0082] In addition, it is preferably satisfied that Go ≥ Wa.

[0083] In addition, in the structure 1 of this embodiment, it is preferable that the width Wg of the internal region 4 at a distance Dg from the bottom 5 satisfies Db < Dg < Da and Wg = λ. That is, it is preferable that "width Wa" > λ is satisfied at a distance Da, "width Wg" = λ is satisfied at a distance Dg, and "width Wb" ≤ λ / 2 is satisfied at a distance Db. Figure 1A Examples where "distance Dg" > De are shown, but "distance Dg" ≤ De or Dg = De can also be satisfied.

[0084] When Go > 1 μm is satisfied, diffraction of the light L can be prevented, and the structure 1 can also be easily manufactured. In addition, when Go ≤ 300 μm is satisfied, a sufficient number of concave portions can be obtained for absorbing incident light and obtaining an antireflection effect.

[0085] The period of the internal region 4 is sometimes referred to as "pitch". The pitch corresponds to the average value of Go, or, as shown in Figure 2 when De ≈ Dd, the pitch corresponds to the average value of (Wa + Ge).

[0086] Further, in the structure 1 of this embodiment, it is preferable that the extinction coefficient of the substrate 3 with respect to the light L is greater than 1.0. The extinction coefficient of the material for forming the substrate 3 with respect to the light L is more preferably 2.0 or greater, and further preferably 4.0 or greater.

[0087] A large extinction coefficient of the substrate 3 is advantageous for sufficiently reducing the intensity of the light L through the structure 1. When the extinction coefficient of the substrate 3 is small, the light L is likely to be incident on the substrate 3, and the absorption effect of the concavo-convex shape cannot be sufficiently obtained.

[0088] Further, in the structure 1 of this embodiment, the substrate 3 is opaque with respect to the light L having the wavelength λ, that is, the light L having the wavelength λ is reflected or absorbed. Specifically, it is preferable that the transmittance of the light L with respect to the substrate 3 is less than 1%. The transmittance is obtained in consideration of the thickness of the substrate 3.

[0089] When the transmittance of the light L of the substrate 3 is sufficiently small, the structure 1 can sufficiently absorb the light L, thereby reducing the intensity of the light L.

[0090] In the structure 1 of this embodiment, in a plan view with respect to the incident surface 6, that is, when the structure 1 is observed from the Z direction in a top view, the shape of the concave surface 2 or the XY cross-sectional shape is not limited. Examples of the shape include a circle, an ellipse, a rectangle, a polygon, a line, any other shape, and combinations thereof. In addition, the three-dimensional shape of the concave surface 2 is not particularly limited. The XZ cross-sectional shape may be a triangle, a polygon, a shape with a curved surface, a parabola, a catenary, or other shapes. In addition, the three-dimensional shape may be a shape obtained by rotating those shapes, a bullet shape, or a so-called line and space in which the same cross-sectional shape is continuous in the Y direction. In a plan view with respect to the incident surface 6, it is preferable that a plurality of concave surfaces 2 are two-dimensionally arranged.

[0091] In an example of the line and space, as Figure 4A and for showing Figure 4A the a-a' cross section of Figure 4B illustrated in, each of the plurality of concave surfaces 2 is a groove having a longitudinal direction along the Y direction and a lateral direction along the X direction in a plan view with respect to the incident surface 6, and the grooves are arranged side by side along the X direction (lateral direction).

[0092] In a first example of two-dimensionally arranging a plurality of concave surfaces 2, as Figure 4C and for showing Figure 4C the b-b' cross section of Figure 4D illustrated in, the plurality of concave surfaces 2 are arranged side by side along the X direction and the Y direction. Each of the concave surfaces 2 is surrounded by a continuous convex portion 7. In this example, it is easier to evaluate the number of concave surfaces than the number of convex portions.

[0093] In a second example of arranging a plurality of concave surfaces 2 in a two-dimensional manner, as Figure 4E and for showing Figure 4E the c-c' cross section of Figure 4F as illustrated in, the plurality of concave surfaces 2 are arranged side by side in the X direction and the Y direction. Each of the concave surfaces 2 is located between the convex portions 7 arranged discretely. In addition to the concave surfaces 2, Figure 4E another concave surface 27 located between the concave surfaces 2 and between the convex portions 7 in the X direction and the Y direction is also shown. The other concave surface 27 is shallower than the concave surface 2. In this example, it is easier to evaluate the number of convex portions than the number of concave surfaces.

[0094] In addition, in the structure 1 of this embodiment, each of the concave surfaces 2 preferably has a taper angle θ of 60 degrees or more in a portion where the distance from the bottom 5 is more than 2Dd / 3 and less than 9Dd / 10. The taper angle θ is more preferably 75 degrees or more. Refer to Figure 5 for the description of the taper angle θ. The straight line 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 represented by T. The angle formed between the straight line T and the plane parallel to the upper surface of the structure is the taper angle θ.

[0095] When the taper angle θ is 60 degrees or more, the inclination of the concave surface 2 near the reference plane 8 is sufficient, and the light L is absorbed while being reflected by the concave surface 2 multiple times, so that the reflection is reduced. In addition, when the inclination of the concave surface 2 near the reference plane 8 is sufficient, the light L is efficiently guided to the deep part of the concave portion, thereby efficiently reducing the intensity of the light L.

[0096] In addition, in the structure 1 of this embodiment, the width of the internal region 4 gradually decreases from the position at the distance Da from the bottom 5 toward the position at the distance Db from the bottom 5.

[0097] That is, in the internal region 4, the width at the deeper position is the same as or smaller than the width at the shallower position. The term "deep" means closer to the bottom 5, and the term "shallow" means having a closer distance to the reference plane 8. The internal region 4 may have a portion with a constant width.

[0098] When the width of the internal region 4 gradually decreases, the light L is efficiently guided to the deep part of the concave surface 2, thereby efficiently reducing the intensity of the light L. In addition, when the concave surface 2 is formed such that the width of the internal region 4 gradually decreases, the structure 1 can be easily manufactured.

[0099] In addition, in the structure 1 of this embodiment, the plurality of concave surfaces 2 may include the following concave surfaces 2: from a distance Db from the bottom 5 of the concave surface 2 to a distance Df (assuming Da ≥ Df > Db), the width of the internal region 4 is not less than Wb and not more than λ / 2. This example is shown in Figure 6A and Figure 6B . In Figure 6A and Figure 6B , the concave surface 2 has an intermediate portion "m" from Db to Df, where the width of the internal region 4 at any position is not less than Wb and not more than λ / 2. In the example of Figure 6A , Dd > Da is satisfied, and in the concave surface 2, the inclination from the bottom 5 to Db, the inclination from Db to Df, and the inclination from Df to Da are different from each other, and from Db to Df, the width is substantially constant and not less than Wb and not more than λ / 2. The internal region 4 formed by the intermediate portion "m" is sometimes referred to as the "intermediate portion 412". The intermediate portion 412 is a part of the first portion 41. Figure 6A and Figure 6B show a portion 411 obtained by excluding the intermediate portion 412 from the first portion 41.

[0100] In Figure 6B , Dd > Da is satisfied, and in the concave surface 2, the inclination from the bottom 5 to Db, the inclination from Db to Df, and the inclination from Df to Da gradually decrease along the distance from the bottom 5.

[0101] By providing the intermediate portion 412, the number of times of reflection of the light L from when it is incident on the structure 1 to when it returns to the reference surface 8 increases. Therefore, the light L is sufficiently absorbed, so its intensity decreases, preventing reflection.

[0102] In addition, in the structure 1 of this embodiment, the substrate 3 may be made of metal.

[0103] The metal includes alloys, and examples thereof include aluminum, titanium, tungsten, copper, iron, nickel, and stainless steel. Among them, aluminum is preferred.

[0104] In addition, in the structure 1 of this embodiment, the substrate 3 may be made of resin.

[0105] The substrate 3 may have any shape according to the purpose, and may have, for example, the shape of a flat surface, a curved surface, an inclined surface, and a shape including a plurality of these surfaces.

[0106] Refer to Figure 23 for an example of the structure 1 of this embodiment. Figure 23is a view obtained by magnifying a part of a cross-section taken along a direction perpendicular to the reference surface 8 of the structure 1. Each of the plurality of concave surfaces 2 includes a first inclined surface S1 and a second inclined surface S2. The second inclined surface S2 is positioned on a side closer to the bottom 5 than the first inclined surface S1. The angle d1 formed between the first inclined surface S1 and the reference plane 8 and the angle d2 formed between the second inclined surface S2 and the reference plane 8 may satisfy d1 > d2. The reference plane 8 is an imaginary plane that contacts the plurality of convex portions 7 forming the concave surface 2.

[0107] The first inclined surface S1 may be an inclined surface positioned at a distance of more than 2Dd / 3 from the bottom 5. The second inclined surface S2 may be an inclined surface connected to the first inclined surface S1. Additionally, the concave surface 2 may include a third inclined surface S3. The third inclined surface S3 is an inclined surface that extends from the second inclined surface S2 and connects to the bottom 5. Each inclined surface corresponds to the following part of the concave surface 2: the part that defines an inner region 4 whose width gradually decreases at a substantially constant rate toward the bottom 5 (however, as described later, the shape of each inclined surface may have a specific waviness or roughness).

[0108] The concave surface 2 includes a first inclined surface S1, a second inclined surface S2, and a third inclined surface S3. The first inclined surface S1 is formed near the vertex of the convex portion 7. The second inclined surface S2 is positioned on a side closer to the bottom 5 of the concave surface 2 than the first inclined surface S1 and extends from the first inclined surface S1 in the direction toward the bottom 5. The third inclined surface S3 extends from the second inclined surface S2 in the direction toward the bottom 5 and connects to the bottom 5. When the plane that contacts the plurality of convex portions forming the concave surface is defined as the reference plane 8, the angle d1 formed between the first inclined surface S1 and the reference plane 8 is greater than the angle d2 formed between the second inclined surface S2 that extends from the first inclined surface S1 toward the bottom 5 of the concave surface 2 and the reference plane 8.

[0109] In addition to the light L incident on the structure 1 at an angle α equal to or approximately 90 degrees with respect to the reference plane 8, the light L2 can also be incident on the structure 1 from a direction almost parallel to the reference plane 8. The angle formed between the light L2 and the reference plane 8 is referred to as the "angle β". The angle α formed between the light L and the reference plane 8 is generally greater than the angle β and is generally 90 degrees. For simplicity, now consider the case where the light L2 is specularly reflected by the first inclined surface S1. When the light L2 is incident on the first inclined surface S1 at an angle β and the angle d1 of the first inclined surface S1 is equal to 90 - β degrees, 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 less than 90 - β degrees, the light L2 incident on the first inclined surface S1 at an angle β is reflected to the side opposite to the bottom 5 (the reference plane 8 side). When such reflection occurs, the reflected light cannot be absorbed by the structure 1, so the absorption performance of the structure 1 is reduced. When the angle d1 of the first inclined surface S1 is greater than 90 - β degrees, the light L2 incident at an angle β is reflected by the first inclined surface S1 towards the bottom 5. Therefore, the reflected light can be absorbed by the concave surface 2. The angle β can be set to various angles according to the use purpose of the structure 1. Generally, the angle β is less than 20 degrees and can be equal to or less than 10 degrees. The region between the two normal lines Lu and Ld of the first inclined surface S1 extending parallel to the incident direction of the light L2 is represented by "a". Then, the light L2 passing through the region "a" is reflected by the first inclined surface S1, so the light absorption efficiency is reduced. The length of the region "a" decreases as d1 increases. Therefore, in order to suppress the reflection of the light L2, it is only necessary to maximize d1. At the same time, the condition for the width of the internal region capable of efficiently absorbing the light L is Wd > λ and Wb ≤ λ / 2. When aiming to satisfy Wb ≤ λ / 2 while maximizing d1, the depth Dd of the concave surface 2 becomes extremely large. Therefore, when using the laser processing manufacturing method described later, the processing time is significantly increased. Therefore, it is not practical to maximize d1 while satisfying the above conditions.

[0110] Therefore, a second inclined surface S2 is formed between the first inclined surface S1 and the third inclined surface S3, and the angle d2 formed between the second inclined surface S2 and the reference plane 8 is set to satisfy d2 < d1. In this way, d1 can be maximized without changing Dd.

[0111] Preferably, the angle d1 formed between the first inclined surface S1 and the reference plane 8 is 80 degrees or greater, more preferably 85 degrees or greater, further preferably 86 degrees or greater, and even more preferably 88 degrees or greater. The maximum value of the angle d1 is 90 degrees. In this case, preferably, the angle d2 formed between the second inclined surface S2 and the reference plane 8 is 55 degrees or less, more preferably 50 degrees or less, further preferably 45 degrees or less, and even more preferably 42 degrees or less. Preferably, the angle d2 is half or less of the angle d1. The above configuration achieves minimization of the reflection of the light L2 and efficient absorption of the light L.

[0112] The number of inclined surfaces forming each concave surface in the concave surface 2 is not limited to three. It is desirable that the angle d1 formed between the first inclined surface S1 and the reference plane 8 be the maximum value. However, when the light L2 has a low intensity and does not cause any problems in actual use, the angle d1 can be appropriately adjusted according to the allowable range of the reflected light. Additionally, for each of the plurality of concave surfaces 2, it is only required that the angle d1 formed between the first inclined surface S1 and the reference plane 8 be greater than the angle d2 formed between the second inclined surface S2 extending from the first inclined surface S1 toward the bottom 5 of the concave surface 2 and the reference plane 8. As long as this relationship between the angles is satisfied, the shapes and angles of each of the plurality of concave surfaces 2 can be different, and the lengths of the first inclined surface S1, the second inclined surface S2, and the third inclined surface S3, the angles d1 and d2, and the length of the region "a" can be different.

[0113] In addition, when using the laser processing manufacturing method described later, the processed surface has a specific roughness. Each of the first inclined surface S1, the second inclined surface S2, and the third inclined surface S3 can have a specific waviness or roughness, and each boundary between the inclined surfaces may not be distinct. In this case, the angle d1 is the average value of the first inclined surface S1 that can have the above shape. When the average value of the angle d1 in the entire structure 1 is large, the length of the region "a" in the entire structure 1 becomes correspondingly small. Therefore, the reflection of the light L2 can be minimized.

[0114] Each of the plurality of concave surfaces may include a first curved surface and a second curved surface closer to the bottom of the concave surface than the first curved surface, and the center of the first curved surface may be located inside the concave surface, and the center of the second curved surface may be located outside the concave surface.

[0115] Reference Figure 24 This example describing the embodiment. Figure 24 is obtained by magnifying a part of a cross-section taken along a direction perpendicular to the reference plane 8 of the structure 1.

[0116] The center O of the first curved surface R1 1 ("The center of the curved surface" means the center of a circle whose circumference includes a part approximating the curved surface) is located inside the concave surface 2. In other words, the curved surface R1 has an outwardly convex shape with respect to the concave surface 2. The center O of the second curved surface R2 that extends from the first curved surface R1 towards the bottom 5 of the concave surface 2 and is connected to the bottom 5 2 is located outside the concave surface 2. In other words, the second curved surface R2 has an inwardly convex shape with respect to the curved surface 2.

[0117] In addition to the light L, the light L2 is incident on the structure 1 from a direction substantially parallel to the incident surface 6.

[0118] The region between the two normal lines Lu and Ld of the first curved surface R1 that extends parallel to the incident direction of the light L2 is denoted by "a". Then, the light L2 passing through the region "a" is reflected by the first curved surface R1, so the light absorption efficiency is reduced. The length of the region "a" decreases as the angle d1 formed between the first curved surface R1 and the reference plane 8 increases. Therefore, in order to suppress the reflection of the light L2, it is only required to maximize d1. Specifically, it is only required that the center O of the curved surface R1 that allows the maximization of d1 1 is provided inside the curved surface R1 of the concave surface 2. At the same time, the conditions for achieving efficient absorption of the light L are Wd > λ and Wb ≤ λ / 2. When aiming to satisfy Wb ≤ λ / 2 while maximizing d1, the depth of the concave surface 2 becomes extremely large. Therefore, when using the laser processing manufacturing method described later, the processing time increases significantly. Therefore, it is not practical to maximize d1 while satisfying the above conditions.

[0119] Therefore, the second curved surface R2 that extends from the first curved surface R1 towards the bottom 5 of the concave surface 2 is formed such that the second curved surface R2 has its center O 2 with a shape located outside the concave surface 2. In this way, d1 can be maximized without changing Dd.

[0120] Preferably, the angle d1 formed between the first curved surface R1 and the reference plane 8 is 80 degrees or more, more preferably 85 degrees or more, further preferably 86 degrees or more, and even more preferably 88 degrees or more. The maximum value of the angle d1 is 90 degrees. The above configuration achieves the minimization of the reflection of the light L2 and the efficient absorption of the light L.

[0121] The number of curved surfaces for forming each concave surface in the concave surface 2 is not required to be limited to two. It is desirable that the angle d1 formed between the first curved surface R1 and the reference plane 8 has a maximum value. However, when the light L2 has a low intensity and does not cause any problems in actual use, the angle d1 can be appropriately adjusted according to the allowable range of the reflected light.

[0122] In addition, it is only required that the center O of the first curved surface R1 of each concave surface among the plurality of concave surfaces 2 1 is located inside the concave surface 2, and the center O of the second curved surface R2 that extends from the first curved surface R1 towards the bottom 5 of the concave surface 2 and is connected to the bottom 5 2 is located outside the concave surface 2. As long as the above-mentioned conditions are met, the shape or angle of each concave surface among the plurality of concave surfaces 2 can be different, and the center position, length, angle d1, and length of the region "a" of each of the curved surfaces of the first curved surface R1 and the second curved surface R2 can be different.

[0123] In addition, when using the laser processing manufacturing method described later, the processed surface has a specific roughness. Each of the first curved surface R1 and the second curved surface R2 can have a specific waviness or roughness, and each boundary between the curved surfaces may not be obvious. In this case, the angle d1 is the average value of the first curved surface R1 that can have the above shape. When the average value of the angle d1 in the entire structure 1 is large, the length of the region "a" in the entire structure 1 becomes correspondingly small. Therefore, the reflection of the light L2 can be minimized.

[0124] <Second Embodiment>

[0125] As a second embodiment, the present disclosure provides a method for manufacturing the structure 1 of the first embodiment, including forming a substrate by subjecting a base material to laser processing. Moreover, as a first example of laser processing, the laser processing may include: a first step of applying pulsed laser light having an irradiation width Pa to the first column of the base material in the main scanning direction; a second step of further applying pulsed laser light having an irradiation width Pa to the first column (N - 1) times in the main scanning direction while shifting the irradiation position by Pb in the main scanning direction from the first step; a third step of performing scanning such 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. In addition, the irradiation diameter of the pulsed laser light is represented by φ, and Pa, Pb, and Pc satisfy φ / 2 < Pa < φ, Pb = φ / N, and Pc < φ. In addition, Pb is not required to be strict and can be zero.

[0126] In addition, as a second example of laser processing, the laser processing may include: a first step of applying pulsed laser light having an irradiation width Pa to a first column of a substrate in a main scanning direction; a second step of performing scanning such that the irradiation position is shifted by Pc in a 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 repeating the fourth step such that the pulsed laser light having the irradiation width Pa is applied to the first column only further (N - 1) times in the main scanning direction while shifting the irradiation position by Pb in the main scanning direction from the first step. In addition, the irradiation diameter of the pulsed laser light is represented by φ, and Pa, Pb, and Pc satisfy φ / 2 < Pa < φ, Pb = φ / N, and Pc < φ. In addition, Pb is not required to be strict and may be zero.

[0127] Reference Figure 7 FIG. shows a schematic configuration diagram of the laser processing machine 70 in the present disclosure described in the second embodiment of the present disclosure. In Figure 7 FIG., the laser processing machine 70 is arranged on a frame 21. A fiber laser for oscillating femtosecond pulses can be used as the laser oscillator 11. The beam diameter of the laser emitted from the laser oscillator 11 is enlarged by a beam expander 12. Then, the laser is incident on an Fθ lens 14 through a galvanometer mirror 13 and is focused on a substrate 15. The substrate 15 is fixed to a fixing table 16 and can be freely moved by a moving stage 17. The galvanometer control unit 18 of the laser processing machine controls the laser oscillator 11 and the galvanometer mirror 13. Figure 7 One galvanometer mirror is shown, but when controlling the laser in two axial directions, two mirrors are required, so 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 vertically moving the stage 17 is performed based on a signal from a displacement meter (not shown) so that the distance between the laser focusing position and the substrate becomes constant. The host computer 20 includes a user interface and a processing data storage unit, and can control the control units for the galvanometer mirror 13 and the moving stage 17 in association with each other at a predetermined timing.

[0128] Next, with reference to the Figure 8 flowchart of the laser processing in the second embodiment, the laser processing in this embodiment is described, in which the galvanometer mirror drive and the stage movement are combined with each other so that an area exceeding the area that can be processed by the galvanometer mirror drive is processed after the stage movement is performed.

[0129] After the base material 15 is fixed to the fixing table 16, reading of alignment marks, correction of laser processing positions, etc. are performed so that the position information required for processing is acquired and corrected to prepare for processing. In step 31, an instruction to move to a desired position is given to the stage control unit. In step 32, the processing position data is transmitted to the galvanometer control unit and an instruction for laser processing conditions is given. In step 33, the completion of the stage movement is checked, and in step 34, processing is started. In step 35, the laser is paused and the galvanometer mirror is moved to a desired position. After checking the end of the movement of the galvanometer mirror in step 36, the laser is oscillated while moving the galvanometer mirror under desired conditions so that processing is performed. In step 37, the completion of the processing is checked and the laser oscillation is paused. In step 38, it is determined whether the processing of the galvanometer area has ended, and when the processing has not ended, the process returns to step 35. When the processing in the galvanometer area has ended, it is determined that the processing in the galvanometer area has ended, and when processing in other areas is required, the process returns to step 31.

[0130] In the above-mentioned processing, steps 35 to 37 are repeated.

[0131] During the repetition, the following operations can be repeated. Scanning is performed so that laser is applied linearly in the main scanning direction, the irradiation is stopped, scanning is performed at a sub-scanning pitch in the direction perpendicular to the main scanning direction, and again scanning is performed linearly in the main scanning direction.

[0132] As another example, during the repetition, the first example mentioned above can be performed. That is, irradiation in the main scanning direction can be performed multiple times on the same line, and multiple irradiations can be performed with the beam points slightly offset from each other. Then, the operation of performing scanning in the sub-scanning direction after irradiations in the main scanning direction are repeated multiple times (N times) can be repeated. Refer to Figure 9A and Figure 9B for the description of this method.

[0133] Figure 9A An example is shown in which irradiation in the main scanning direction is repeated for the first column to satisfy N = 4. For convenience, the first irradiation to the fourth irradiation are shown in parallel, but these views show the irradiations for the same first column. In the first irradiation, main scanning is performed so that a beam with a beam diameter φ is applied at a pitch Pa. At this time, it is preferable that φ / 2 < Pa < φ. In the second irradiation and subsequent irradiations, irradiation is performed so that the beam center at the time of irradiation is offset by Pb in the main scanning direction from the beam center of the previous irradiation. It is preferable that Pb satisfies Pb = φ / N. In Figure 9A the example, Pb = φ / 4 is satisfied. When this operation is repeated N times, the N irradiations accumulate in the main scanning direction. Figure 9AThe lower part shows the accumulation of four irradiations.

[0134] Figure 9B An example is shown in which, for the second and subsequent columns, the irradiation position is scanned in the sub-scanning direction while repeating the main scan four times. The irradiation for the second column is performed by performing the scan with the beam center shifted by Pc in the sub-scanning direction from the beam center at the time of irradiation for the first column, and the irradiation for the third column is performed by performing the scan with the beam center further shifted by Pc in the sub-scanning direction. It is preferable that Pc satisfies Pc < φ, and also satisfies P ≤ φ / 2.

[0135] As another example, during the repetition, the second example mentioned above can be performed. That is, the following operations are repeated. Irradiation is performed in the main scanning direction on the same line, the irradiation position is scanned in the sub-scanning direction, and irradiation is performed on the next line. Then, these operations can be repeated for the same line. By this repetition, the substrate 3 is processed by approximately 1 mm 2 to approximately 10 mm 2 and this operation is further repeated to perform the processing. Refer to Figure 9C and Figure 9D for the description of this method.

[0136] Figure 9C An example is shown in which irradiation is performed in the main scanning direction starting from the first column, the irradiation position is scanned in the sub-scanning direction, and irradiation is performed on the next line, and these operations are repeated until the fourth column.

[0137] Figure 9D An example is shown in which the irradiation position further returns to the first column in the sub-scanning direction, and similarly, the irradiation from the first column to the fourth column is repeated four times while performing the scan. At this time, the irradiation is performed such that the beam center is shifted by Pb in the main scanning direction from the beam center of the previous irradiation. It is preferable that Pb satisfies Pb = φ / N. Figure 9E The accumulation of four irradiations is shown.

[0138] As described above, by the method of accumulating the irradiation in the main scanning direction and the sub-scanning direction while slightly offsetting the beam center in the main scanning direction and the sub-scanning direction, the beam spot hits the same position multiple times within a short period of time, and the applied beams interact with each other, thereby generating a randomized fine structure. The order of passage, the number of repetitions, Pb, Pc, the frequency of the laser, etc. are adjusted so that operations such as thermal effects, optical effects of light, interference, interference between the applied beams, interference between the light reflected from the fine structure and the laser, and reflection from the fine structure can be controlled. Therefore, for example, fine processing such as the pitch of the concave surface 2 can be controlled. For example, the accumulation of heat on the processing surface can be reduced by lowering the frequency of the applied laser, and control such as reducing the removal amount of the substrate 3 by laser irradiation can be performed.

[0139] In addition, when the optical component is regarded as the substrate 3 and the structure 1 is produced by forming the concave surface 2 on the surface of the optical component, it is also effective to adopt a method of performing the processing while suppressing the oxygen concentration in the atmosphere during the processing. As a method of reducing the oxygen concentration, the entire processing apparatus can be placed in a nitrogen atmosphere, or the processing can be performed in the case where the heat dissipation component is installed in a cleaning box including a laser transmission window. In addition to this, the processing can be performed while blowing high-purity nitrogen onto the heat dissipation component, or any other measures can be used.

[0140] According to the manufacturing method of this embodiment, by using a simple manufacturing process, the structure 1 of the first embodiment in which the optical component is regarded as the substrate 3 can be obtained without generating exhaust gas even in a vacuum environment.

[0141] In addition, when the processing is performed not only by the processing method of slightly offsetting the beam center as described above, but also by adjusting the intensity of the applied laser, for example, the fine processing of the shape of the concave surface 2 can be controlled. For example, when the concave surface 2 illustrated in Figure 6B is to be formed by processing, it is preferable to increase the intensity of the laser used in the processing for the intermediate portion 411, the intermediate portion 412, and the second portion 42 of the internal region 4.

[0142] In addition, when the concave surface 2 illustrated in Figure 23 is to be formed by processing, it is desirable that the intensity of the laser for processing the second inclined surface S2 of the concave surface 2 be set lower than the intensity of the laser for processing the first inclined surface S1, and the intensity of the laser for processing the third inclined surface S3 be set higher than the intensity of the laser for processing the second inclined surface S2.

[0143] In addition, when the concave surface 2 illustrated in Figure 24When forming the concave surface 2 as exemplified, it is desirable that after forming the first curved surface R1 of the concave surface 2 by machining while slowly decreasing the intensity of the laser for forming the first curved surface R1 of the concave surface 2 as machining progresses to a greater depth, machining continues to start forming the second curved surface R2 and proceeds to a greater depth while increasing the intensity of the laser again.

[0144] To adjust the intensity of the laser, there are methods for adjusting the laser oscillation energy of the laser oscillator 11 shown in Figure 7 and a method for adjusting by inserting an optical element (not shown) capable of changing the transmittance of the laser between the laser oscillator 11 and the beam expander 12. The adjustment command value is stored in the host computer 20 synchronously with the storage of the processing data. The intensity of the laser is adjusted by controlling the laser oscillator 11 and the optical element (not shown) through the intermediation of the galvanometer control unit 18.

[0145] In addition, as a method for controlling the fine machining of the shape of, for example, the concave surface 2, in addition to the adjustment of the intensity of the laser mentioned above, the machining pitch Pa, Pb, Pc of the pulsed laser can be adjusted as machining progresses to a greater depth, or the passing order, the number of repetitions, the frequency of the laser, etc. can be adjusted. In addition, a combination thereof can also be used. When the laser oscillator 11 has a function of changing the pulse oscillation time of the pulsed laser, the pulse oscillation time can be adjusted, or the adjustment of the pulse oscillation time can be used in combination with the above adjustments.

[0146] In Figure 25 the actual measurement results of the reflectance of the structure 1 obtained by actually changing the shape of the concave surface 2 are shown. Figure 25 The results indicated by the dashed line in Figure 6B correspond to the results of the structure 1 having the shape exemplified in Figure 25 The results indicated by the solid line in Figure 24 correspond to the results of the structure 1 having the shape exemplified in Figure 6B In the structure 1 having the shape exemplified in Figure 24 the angle d1 is 65 degrees and the angle d2 is 78 degrees. In the structure 1 having the shape exemplified in Figure 25 the actual measurement results of the reflectance are shown, where the horizontal axis represents the scattering angle and the vertical axis represents the reflectance. Figure 25 The scattering angle in Figure 6B is the angle at which light with a wavelength of λ = 800 nm incident at an angle of 80 degrees (corresponding to β = 10 degrees) with respect to the reference plane 8 of the structure 1 is scattered by the structure 1 and then travels. The structure 1 having the shape exemplified in Figure 24The structure 1 having the shape exemplified in has a reflectance of less than 1%, so the reflectance is successfully reduced efficiently. Having Figure 24 The reflectance of the structure 1 having the shape exemplified in is further lower than that of the structure 1 having the shape exemplified in Figure 6B The reflectance of the structure 1 having the shape exemplified in . As described above, Figure 24 The shape shown in has a first curved surface R1 that allows the length of the allowable region "a" to be reduced, thus minimizing the reflection of the light L2 and efficiently absorbing the light L.

[0147] <Third Embodiment>

[0148] As a third embodiment, the present disclosure provides a method of manufacturing the structure 1 of the first embodiment, in which the structure 1 is obtained by transferring the concave-convex structure of a molding die having a concave-convex structure to a resin. This method may include a step of forming the molding die by subjecting a molding die material to laser processing, and a step of injection molding the resin using the molding die.

[0149] Refer to Figures 10A to 10E the schematic processing diagram of to describe the third embodiment.

[0150] Figures 10A to 10E Shows the respective stages of the process of manufacturing the structure 1 by injection molding. The first molding die 91 forming the molding die 900 includes the structure 1 produced in the second embodiment and has a concave-convex structure on its surface. Figures 10A to 10E The injection molding machine shown in includes a pressure device 911 communicating with a cylinder 99 and a hopper 910 for loading a resin material.

[0151] A screw (not shown) is provided inside the cylinder 99 and is driven to rotate by a drive source such as a motor (not shown), so that the resin material inside the hopper 910 is sent to the distal end of the cylinder 99. In addition, a heater (not shown) is provided in the cylinder 99, and the resin material loaded by the hopper 910 is heated to a glass transition temperature or higher while being conveyed toward the distal end inside the cylinder 99. Therefore, the resin material is melted into a liquid. Then, the resin material is accumulated in the space at the distal end portion of the cylinder 99.

[0152] As described above, the first molding die 91 has a concave-convex structure on its surface. When forming the cavity 920, the second molding die 98 and the first molding die 91 are closed.

[0153] The resin material is loaded into the hopper 910. First, as a molding die preparation step, as shown in , the molding die (900) is installed in the injection molding machine. Then, by using a drive mechanism (not shown), as shown in , Figure 10A in , the molding die (900) is installed in the injection molding machine. Then, by using a drive mechanism (not shown), as shown in , Figure 10BAs shown in the figure, the first molding die 91 and the second molding die 98 are subjected to mold closing. Before or during mold closing, the first molding die 91 and the second molding die 98 are heated by a heater (not shown). The heating temperature of the mold in this step is referred to as the "mold temperature".

[0154] Subsequently, the Figure 10C injection step and Figure 10D the pressure holding step and the cooling step are performed. In the Figure 10C injection step, the molten resin 912 is injected from the cylinder 99 into the cavity 920 formed by the first molding die 91 and the second molding die 98 through the pressure device 911. The pressure device 911 includes a hydraulic cylinder and the like. Moreover, in the Figure 10D pressure holding step and the cooling (solidification) step, for example, the pressure device 911 applies pressure to the molten resin 912 in the cavity 920 at a set pressure that can transfer the molten resin to the molding die to form a fine shape, and holds this pressure for a predetermined period of time (pressure holding). In this way, the pressure of the molten resin 912 in the cavity is maintained at the pressure holding pressure.

[0155] Subsequently, the first molding die 91 and the second molding die 98 are cooled so that the molten resin 912 is cooled to a temperature equal to or lower than the glass transition temperature, thereby allowing the molten resin 912 to change from a liquid to a solid. The first molding die 91 and the second molding die 98 are cooled by, for example, a mechanism (not shown) for circulating a coolant for cooling around the molding die 900. Thereafter, the Figure 10E mold opening step and the demolding step are performed. Demolding is performed by, for example, protruding the ejector pin passing through the molding die into the cavity. By repeating the steps mentioned above, a large number of structures 1 can be manufactured.

[0156] According to the manufacturing method of this embodiment, through a simple manufacturing process, the structure 1 of the first embodiment can be manufactured by a method that does not generate exhaust gas even in a vacuum environment. In addition, according to the manufacturing method of this embodiment, the structure 1 of the first embodiment can be mass-produced in a short period of time and at low cost.

[0157] <Other Embodiments>

[0158] In addition, the present disclosure provides a member including the structure 1 of the first embodiment as another embodiment. The member may be formed of the structure 1 or may include a support member for supporting the structure 1.

[0159] In addition, the present disclosure provides an optical device including the structure 1 of the first embodiment. In recent years, in optical devices and the like, it has been necessary to further reduce reflected light and scattered light in order to improve their performance. In addition, the shapes of components have become increasingly complex year by year and their sizes have become smaller year by year. In addition, the types of environments that can be adapted to are also increasing. The first embodiment is relatively easy to manufacture, and the three-dimensional substrate 3 can have such a structure. Since the substrate itself has a concave-convex shape, the concern about film peeling caused by oil, vibration, heat, etc. is reduced compared to the case where a concave-convex shape is formed by film deposition. In particular, there is a concern about the presence of exhaust gas in a vacuum environment. In addition, since the substrate itself has a concave-convex shape, high strength can be obtained regardless of how fine the concave-convex shape is, and thus it has the advantage that the concave-convex shape itself is difficult to break.

[0160] Examples of members including the structure 1 of the first embodiment include optical members and lenses formed by the structure 1 of the first embodiment, and lens barrels and housings including the structure 1 of the first embodiment on their inner walls. In addition, examples of optical devices including the structure 1 of the first embodiment include binoculars, microscopes, semiconductor exposure devices, camera systems (such as digital still cameras, digital video cameras), and imaging devices (such as mobile phones) including an imaging element for receiving light that has passed through the optical member of the present disclosure.

[0161] Figure 11 The configuration of a digital single-lens reflex camera 1100, which is an example of the optical device of this embodiment, is shown.

[0162] In Figure 11 the digital camera 1100 shown, the camera body 1102 and the lens barrel 1101 are coupled to each other, but the lens barrel 1101 is a so-called interchangeable lens that can be removably mounted on the camera body 1102.

[0163] Light from an object passes through an optical system including a plurality of lenses 1103 and 1105 arranged on the optical axis of the photographing optical system in a housing 1120 including, for example, the lens barrel 1101, and is received by the imaging element 1110.

[0164] In this configuration, the members of this embodiment are, for example, the housing 1121, the inner lens barrel 1104, or the lens barrel 1101. The housing 1121 and the lens barrel 1101 each include the structure 1 of the first embodiment and a support member.

[0165] During an observation period before shooting, light from an object is reflected by a main mirror 1107 in a housing 1121 of a camera body 1102, passes through a prism 1111, and then passes through a viewfinder lens 1112, thereby showing an image to be shot to a photographer. The main mirror 1107 is, for example, a semi-reflective mirror, and the light that has passed through the main mirror 1107 is reflected by a sub-mirror 1108 in the direction of an autofocus (AF) unit 1113. For example, this reflected light is used for distance measurement. In addition, the main mirror 1107 is mounted to and supported by a main mirror holder 1140 by adhesion or the like. At the time of shooting, the main mirror 1107 and the sub-mirror 1108 are moved out of the optical path via a drive mechanism (not shown), and a shutter 1109 is opened, so that a photographed light image incident on an image pickup element 1110 from a lens barrel 1101 is imaged. In addition, an aperture 1106 is configured to change the brightness and depth of focus at the time of shooting by changing its aperture area.

[0166] [Example]

[0167] <Simulation of the structure of the first embodiment>

[0168] Simulations were performed on the structures 1 of Examples 1 to 3 and on Comparative Example 1 that does not include the concave surface 2. Figure 12 The dimensions in each of Examples 1 to 3 and Comparative Example 1 are shown. The structures of Examples 1 to 3 and Comparative Example 1 all have the same dimensions. The wavelength λ of the light L is set to be from 350 nm to 850 nm. When the shortest wavelength in the range of the light L as the target is represented by λmin and the longest wavelength therein is represented by λmax, λmin is 350 nm, and λmax is 850 nm.

[0169] By using the shapes of Examples 1 to 3 and Comparative Example 1 as models, an electromagnetic field simulation using the FDTD method was performed. The space of the electromagnetic field simulation is a three-dimensional space. As Figure 13As shown, the x-axis is defined as the horizontal direction of the structure, the y-axis is defined as the depth direction of the structure, and the z-axis is defined as the thickness direction of the structure. Additionally, periodic boundary conditions are applied in the x-axis and y-axis directions such that the case where the concave surface 2 is infinitely expanded is simulated. The range of the unit space is set to 2 μm in the x-axis direction, 12 μm in the z-axis direction, and 0.2 μm in the y-axis direction. A structure including an internal region exists in this unit space, and its dimensions are set to 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 substrate 3 is set to pure aluminum. The space within the unit space other than the structure is all vacuum. Hereinafter, the vacuum region is referred to as "air". The incident direction of the light L (electromagnetic wave) is set to be from top to bottom in the z-axis direction, that is, from the air towards the structure. At this time, the wave of the light L is polarized light having an electric field vibrating in a direction perpendicular to the traveling direction.

[0170] In Figure 14 and Figure 15 the graph of Figures 16 to 18 and the results are shown in the distribution map of

[0171] The shape of Example 1 is as follows. The width at a height of 0.224 μm from the bottom is 0.175 μm, the width at a height of 0.350 μm from the bottom is 0.228 μm, the width at a height of 0.400 μm from the bottom is 0.250 μm, and the width at a height of 0.527 μm from the bottom is 0.303 μm. As Figure 12 shown, the dimension corresponding to Wb is 0.154 μm, and the dimension corresponding to Db is 0.175 μm. The dimension corresponding to Wa is 2 μm, and the dimension corresponding to Da - Db is 4.35 μm. Figure 14 is a graph for showing the simulation results obtained by comparing and examining Example 1 and Comparative Example 1. The horizontal axis represents the wavelength of the light L, and the vertical axis represents the average value of the electric field in the air. This average value of the electric field excludes the value of the incident wave and represents only the reflected wave. Compared with the electric field of Comparative Example 1, the electric field of Example 1 is smaller. That is, the intensity of the reflected light returning to the air in Example 1 is smaller.

[0172] Additionally, Figure 16The electric field distribution of the incident wave of Example 1 when light L with a wavelength of 527 nm is excluded is shown. The electric field is maximum at a position approximately 1 / 2 wavelength in the z direction, and the electric field attenuates at a position 1 / 2 wavelength deeper than this position. In a deeper region, the electric field is the same as that of the structure and becomes constant, and no amplitude is observed. This result is obtained by the light trapping effect obtained by the second part 42. In addition, by forming the concave surface 2 of the first part 41, the electric field gradually attenuates due to diffraction and interference caused complexly from the deep part to the surface, and the electric field in the air decreases. Therefore, an antireflection effect can be obtained.

[0173] The shape of Example 2 is as follows. The width at a height of 0.0179 μm from the bottom is 0.175 μm, and the width at a height of 0.35 μm from the bottom is 0.486 μm. As Figure 12 shown, the dimension corresponding to Wb is 0.436 μm, and the dimension corresponding to Db is 0.175 μm. The dimension corresponding to Wa is 2 μm, and the dimension corresponding to Da - Db is 5.42 μm.

[0174] The shape of Example 3 is as follows. The width at a height of 0.350 μm from the bottom is 0.137 μm, the width at a height of 0.400 μm from the bottom is 0.150 μm, the width at a height of 0.442 μm from the bottom is 0.155 μm, the width at a height of 0.457 μm from the bottom is 0.175 μm, and the width at a height of 0.527 μm from the bottom is 0.199 μm. As Figure 12 shown, the dimension corresponding to Wb is 0.155 μm, and the dimension corresponding to Db is 0.442 μm. The dimension corresponding to Wa is 2 μm, and the dimension corresponding to Da - Db is 5.22 μm.

[0175] The shape of Example 3 satisfies Expressions 1 to 3 when λ ≥ 350 nm.

[0176] Figure 15 is a graph for showing the simulation results obtained by comparing and examining Examples 1 to 3. Similar to Figure 14 that, the horizontal axis represents the wavelength of light L, and the vertical axis represents the average value of the electric field in the air excluding the incident wave.

[0177] Compared with Examples 1 and 2, Example 3 has a smaller electric field in a wide wavelength range. It is considered that the reason is that in Example 3, when Da - Db is large, the concave surface 2 is wide enough, and the number of reflections from when light L is incident on the structure 1 to when light L returns to the reference plane 8 is large, so that light L is sufficiently absorbed and its intensity thus decreases.

[0178] Example 3 has a larger shape of Db compared with Examples 1 and 2. It is considered that the reason is that in Example 3, the light L can be sufficiently captured in the first part 41.

[0179] Compared with Examples 1 and 3, Example 2 has a higher electric field in a wide wavelength range.

[0180] Figure 17 The electric field distribution of the incident wave of Example 3 excluding the wavelength of 527 nm is shown. Figure 18 The electric field distribution of the incident wave of Example 2 excluding the wavelength of 527 nm is shown. Compared with Figure 17 the electric field distribution of Example 3, in the Figure 18 electric field distribution of Example 2, a state can be observed in which the light L is incident on the structure without being captured near the bottom 5 of the concave surface 2. Therefore, it is important to understand the shape of the second part 42, especially Wb.

[0181] This simulation was performed on the structure 1 with the same concave surface shape two-dimensionally arranged at a pitch of 2 μm, but the shape of the concave surface 2 is not limited thereto. In addition, the average period of the pitch is preferably greater than 1 μm, but either a regular periodic arrangement or a random arrangement can be adopted.

[0182] <Manufacturing the structure by the manufacturing method of the second embodiment>

[0183] As described above, the structures 1 of Examples 4, 5, and 6 are obtained by mounting the optical component regarded as the substrate 3 on the Figure 7 laser processing apparatus shown in and performing laser processing. The material of the optical component is an Invar alloy material as a low thermal expansion material. When the Invar alloy material is used for the substrate 3 of the optical component, deformation caused by temperature influence can be reduced, and the influence on optical performance can be lowered.

[0184] Figure 19 The laser oscillator wavelength, laser processing conditions, average pitch of the concave portions as the processing result, average values of Dd, Wa, Wb, Db, wavelength of the absorbed light L, and warpage influence of the optical component are shown for each of Examples 4 to 6 in the production of the structure 1.

[0185] Describe the relationship between the laser processing trajectory and the Figure 19 items of the processing conditions shown in. While performing irradiation at the set output and oscillation frequency, laser processing is performed by the processing method described in the second example of the second embodiment.

[0186] The pitch and depth of the structure 1 can be changed according to the laser wavelength selected when using laser processing. As the Dd of the structure 1 becomes smaller, the removal amount removed by processing can be reduced, so that the overall warpage of the optical component after processing can be reduced. That is, the laser wavelength can be selected according to the thickness of the substrate 3 and the desired dimensional tolerance.

[0187] In all of Examples 4 to 6, each value can be satisfied regardless of the laser wavelength or output. The oscillation frequency is sufficiently large compared to the main scanning speed, so the same position is irradiated with multiple pulses in a superimposed manner. By the initial pulse, a groove is formed as the concave surface 2, and the pulses emitted subsequently are reflected, for example, on the side surface of the groove to deeply excavate the center of the groove. Therefore, a fine concave surface 2 is formed.

[0188] By laser processing, all of the structures 1 of Examples 4 to 6 can be produced as shown in Figure 19 . That is, a structure 1 including concave portions is obtained, where the Wa of each concave portion is 3 μm, 10 μm, or 20 μm, the Wb is 0.15 μm, the Db is 0.40 μm, and the shape of the concave surface is randomized in a top view. In addition, an optical component that absorbs incident light with a wavelength of 0.35 μm or more and has an antireflection function is also obtained. Figure 22 An image of the structure 1 of Example 6 is shown. This image was obtained by observing the structure 1 at a magnification of 50 times using a laser microscope (VK-X3000: manufactured by KEYENCE CORPORATION). A large number of concave surfaces 2 with a randomly arranged concave-convex shape can be observed.

[0189] An invar alloy material is used as the material of the optical component, but steel, nickel and its alloys, copper and its alloys, aluminum and its alloys, molybdenum, niobium, tantalum, rhenium, hafnium, zirconium, and yttrium are also applicable.

[0190] The optical component can be processed in a nitrogen atmosphere. Processing in a nitrogen atmosphere is particularly effective for materials that are prone to oxidation in the material of the optical component. In laser processing, debris is generated from the material that is melted and solidified by heat. In materials that are prone to oxidation, the debris combines with oxygen, and its physical properties change, which has an adverse effect on the stability of laser processing. Therefore, when performing processing in a nitrogen atmosphere, the processing stability can be improved.

[0191] <Manufacturing the structure by the manufacturing method of the third embodiment>

[0192] Next, an example in which injection molding is used to transfer the antireflection surface to the resin component is shown.

[0193] The structures 1 of Examples 7 to 9 are formed by Figures 10A to 10EInjection molding manufacturing as shown. In this case, an injection molding machine J180EL III (product name) manufactured by JSW Corporation is used as the injection molding machine. Further, die steel material is used as the material for the molding die. As the resin material loaded from the hopper 910, for example, a resin material obtained by coloring a glass filler-containing polycarbonate G3430H produced by TEIJIN LIMITED black with a colorant is used.

[0194] Figure 20 Shows the laser oscillator wavelength, laser processing conditions, average pitch of the concave-convex structure, average value and depth of Dd of the structure 1, Wa, Wb, Db, wavelength of the absorbed light L, and demolding resistance when producing the molding die for each of Examples 7 to 9.

[0195] Figure 21 Is a schematic representation of die transfer on the surface of the molding die. Figure 21 The processing conditions of the die surface are the same as those of the second example. As Figure 21 Shown, the concave surface 2 of the structure 1 in each of Examples 7 to 9 is formed as a resin assembly having the shape of the convex portion 7 of the molding die 91 transferred thereto.

[0196] The average value of Dd affects the demolding resistance in injection molding. As Dd becomes smaller, the demolding resistance becomes smaller, and warpage deformation of the entire resin assembly and the like can be suppressed.

[0197] Can be produced as Figure 20 Shown all the structures 1 of Examples 7 to 9. That is, a structure 1 including a concave surface is obtained, where Wa of each concave surface is 3 μm, 10 μm, or 20 μm, Wb is 0.8 μm, Db is 2.5 μm, and the shape of the concave surface in the top view is randomized. Further, a resin assembly that absorbs incident light with a wavelength of 2.1 μm or more and has an antireflection function can be mass-produced in a short period of time and at low cost.

[0198] In the example, die steel material is used as the material for the molding die, but nickel alloy or copper alloy can also be used. Further, although polycarbonate containing glass filler is used as the resin, polycarbonate without glass filler, acrylonitrile-butadiene-styrene, polyoxymethylene, polyphthalamide, polypropylene, polybutylene terephthalate, fluororesin, or polyamide can also be used as the resin.

[0199] In addition, the molding die can be produced in a nitrogen atmosphere. Producing in a nitrogen atmosphere is particularly effective in cases where the material of the molding die is prone to oxidation. In laser processing, debris is generated from the material that is melted and solidified by heat. In materials that are prone to oxidation, the debris combines with oxygen and its physical properties change, thus having an adverse effect on the stability of laser processing. Therefore, when production is carried out in a nitrogen atmosphere, the processing stability can be improved.

[0200] In the example, injection molding is used as the transfer technique, but roll forming or press forming can also be carried out alternatively.

[0201] According to the present disclosure, a technique is provided that facilitates the realization of a structure capable of sufficiently absorbing light.

[0202] Although the present disclosure has been described with reference to exemplary embodiments, it should be understood that the present invention is not limited to the disclosed exemplary embodiments. The following claims should be given the broadest interpretation to cover all such modifications as well as equivalent structures and functions.

Claims

1. A structure for absorbing light having a wavelength λ incident on the structure, the structure including a substrate having a plurality of concave surfaces on an incident surface of the light, in, The light is incident on an inner region of each of the plurality of concave surfaces, wherein the light satisfies 400 nm ≤ λ ≤ 40 μm, and wherein each of the plurality of concave surfaces satisfies Dd ≥ Da > Db > λ, Wa > λ, and Wb ≤ λ / 2, where Dd represents the depth of the bottom of each of the plurality of concave surfaces, Wa represents the width of the inner region at a position at a distance Da from the bottom of each of the plurality of concave surfaces, and Wb represents the width of the inner region at a position at a distance Db from the bottom.

2. The structure according to claim 1, wherein Wa ≥ 2λ is satisfied.

3. The structure according to claim 1, wherein Each of the plurality of concave surfaces satisfies λ ≥ Dc and Wc ≤ λ / 4, where Wc represents the width of the inner region at a position at a distance Dc from the bottom of each of the plurality of concave surfaces.

4. The structure according to claim 1, in, The plurality of concave surfaces include a first concave surface and a second concave surface, and wherein Ge ≤ 100 μm is satisfied, where Ge represents the distance 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.

5. The structure according to claim 1, in, The plurality of concave surfaces include a first concave surface and a second concave surface, and wherein Ge < Wa is satisfied, where Ge represents the distance 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.

6. The structure according to claim 1, in, The plurality of concave surfaces include a first concave surface and a second concave surface, and wherein Go ≥ Wa is satisfied, where Go represents the distance between the bottom of the first concave surface and the bottom of the second concave surface.

7. The structure according to claim 1, in, The plurality of concave surfaces include a first concave surface and a second concave surface, and wherein Go ≥ 1 μm is satisfied, where Go represents the distance between the bottom of the first concave surface and the bottom of the second concave surface.

8. The structure according to claim 1, wherein: The extinction coefficient of the substrate with respect to light is greater than 1.

0.

9. The structure according to claim 1, wherein: In a plan view relative to the incident surface, the number of the plurality of concave surfaces or one of the number of convex portions forming the plurality of concave surfaces is 100 surfaces / mm 2 Above or 100 parts / mm 2 above.

10. The structure according to claim 1, wherein: In a plan view with respect to the incident surface, the plurality of concave surfaces are two-dimensionally arranged.

11. The structure according to claim 1, wherein: Each of the plurality of concave surfaces has a cone angle θ of 60 degrees or more in a portion where the distance from the bottom is more than 2Dd / 3 and less than 9Dd / 10.

12. The structure according to claim 1, wherein: The inner region has a width that gradually decreases from the position at a distance Da from the bottom toward the position at a distance Db from the bottom.

13. The structure according to claim 1, wherein: The plurality of concave surfaces include concave surfaces as follows: from a distance Db to a distance Df from the bottom of the concave surface, the width of the inner region is not less than Wb and not more than λ / 2, provided that Da ≥ Df > Db.

14. The structure according to claim 1, wherein: The substrate is made of one of metal or resin.

15. The structure according to claim 1, in, Each of the plurality of concave surfaces includes a first inclined surface and a second inclined surface, the second inclined surface being positioned on a side closer to a bottom of the concave surface than the first inclined surface, and Wherein, when a plane in contact with the plurality of convex portions forming the concave surface is set as a reference plane, an angle d1 formed between the first inclined surface and the reference plane and an angle d2 formed between the second inclined surface and the reference plane satisfy: d1>d2.

16. The structure according to claim 15, wherein: d1 ≥ 80 degrees is satisfied.

17. The structure according to claim 15, wherein: d1 ≥ 85 degrees is satisfied.

18. The structure according to claim 1, in, Each of the plurality of concave surfaces includes a first curved surface and a second curved surface, the second curved surface being positioned on a side closer to a bottom of the concave surface than the first curved surface, and The center of the first curved surface is located inside the concave surface, and the center of the second curved surface is located outside the concave surface.

19. An optical device comprising the structure according to any one of claims 1 to 18.

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