WO2019198760A1

WO2019198760A1 - Light-absorbing element, light-absorbing body, and method for manufacturing light-absorbing element

Info

Publication number: WO2019198760A1
Application number: PCT/JP2019/015644
Authority: WO
Inventors: 拓男田中; レニルクマールムダチャティ
Original assignee: 国立研究開発法人理化学研究所
Priority date: 2018-04-12
Filing date: 2019-04-10
Publication date: 2019-10-17
Also published as: JPWO2019198760A1; JP7325122B2

Abstract

This light-absorbing element 10 for absorbing light is provided with a spiral structure 3 formed of a metallic material. The spiral structure 3 includes a base part 3a and a linear part 3b extending from the base part 3a. An axis passing through the base part 3a is defined as a reference axis C, and a direction extending radially from the reference axis C is defined as a radial direction. The linear part 3b extends spirally from the base part 3a while turning around the reference axis C and moving gradually from the base part 3a to the outside in the radial direction.

Description

Light absorbing element, light absorbing body, and method of manufacturing light absorbing element

The present invention relates to a light absorbing element that absorbs light in a wide wavelength range. More specifically, the present invention relates to a light absorbing element having an ultrafine metal structure that absorbs light in a wide wavelength range (for example, a visible wavelength range and a near infrared wavelength range).

Black coating that absorbs light in a wide wavelength range is indispensable for optical technology for the purpose of suppressing light reflection and stray light, for example. However, it is extremely difficult to actually make a truly black one. In particular, it was almost impossible to achieve black color on a flat surface. Actually, a black and white structure is realized by forming a concavo-convex structure or a fuzzy structure on the surface and capturing light inside the structure. Therefore, the thickness of the layer necessary for obtaining black is increased.

In recent years, technology has been developed to suppress light reflection and absorb light by utilizing the resonance interaction between light and a nanometer-scale ultrafine metal structure. Such a technique is disclosed in Patent Document 1 below, for example.

International Publication No. WO2016 / 132979

However, Patent Document 1 does not disclose an ultrafine metal structure that absorbs light in a wide wavelength range. Therefore, an ultrafine metal structure that absorbs light in a wide wavelength range is desired. For example, it is desired to realize a black surface of an optical device using such an ultrafine metal structure.

Therefore, an object of the present invention is to provide a technique for an ultrafine metal structure capable of absorbing light in a wide wavelength range.

In order to achieve the above-mentioned object, the light absorption element according to the present invention comprises a spiral structure formed of a metal material,
The spiral structure includes a base portion and a linear portion extending from the base portion,
An axis passing through the base point is a reference axis, and a direction extending radially from the reference axis is a radial direction,
The linear portion extends spirally from the base point while rotating around the reference axis and moving from the base point to the outside in the radial direction.

Further, a light absorber according to the present invention has the above-described light absorption element and an element support surface that supports the light absorption element, and a large number of the light absorption elements are arranged on the element support surface.

The manufacturing method according to the present invention is a manufacturing method of a light absorbing element, wherein the light absorbing element includes a spiral structure formed of a metal material,
The spiral structure includes a base portion and a linear portion extending from the base portion,
An axis passing through the base point is a reference axis, and a direction extending radially from the reference axis is a radial direction,
The linear part extends spirally from the base point part while turning around the reference axis and moving from the base part to the outside in the radial direction,
A spiral metal layer formed of a metal material and having a spiral pattern is formed on the surface of the object to be processed. The spiral metal layer includes a base point layer portion corresponding to the base point portion and a line corresponding to the linear portion. Including a layered portion.

According to the present invention, a very fine metal structure capable of absorbing light in a wide wavelength range can be realized.

The structure of the light absorption element by 1st Embodiment of this invention is shown. It is a 1B-1B arrow line view of FIG. 1A. It is a flowchart which shows the manufacturing method by 1st Embodiment. It is explanatory drawing of the manufacturing method by 1st Embodiment. The SEM image of the light absorption element manufactured with the manufacturing method by 1st Embodiment is shown. 3 shows a structure of a light absorption element according to a second embodiment of the present invention. It is a 5B-5B arrow line view of FIG. 5A. It is a flowchart which shows the manufacturing method by 2nd Embodiment. It is explanatory drawing of the manufacturing method by 2nd Embodiment. The SEM image of the light absorption element manufactured with the manufacturing method by 2nd Embodiment is shown. The structure of the light absorber by embodiment of this invention is shown. It is a 9B-9B arrow line view of FIG. 9A. It is an experimental result regarding the optical characteristic of the light absorber manufactured according to the manufacturing method of 1st Embodiment. It is an experimental result regarding the optical characteristic of the light absorber manufactured according to the manufacturing method of 2nd Embodiment. It is a schematic diagram which shows the other form of a spiral structure. It is a schematic diagram which shows the other form of a light absorber. It is an experimental result regarding the optical characteristic of the light absorber which has the structure where the spiral structure is not separated from the surface of the support.

Embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted. Further, the following description does not limit the invention described in the claims. For example, the present invention is not limited to one provided with all of the components described below.

[First Embodiment]
(Configuration of light absorbing element)
FIG. 1A shows a structure of a light absorption element 10 according to the first embodiment of the present invention. 1B is a view taken in the direction of arrows 1B-1B in FIG. 1A. The light absorbing element 10 absorbs light in a wide wavelength range. The wide wavelength range may include all or a part or some part of the range from visible light (approximately 380 nm wavelength) to far infrared light (approximately 1 mm wavelength). For example, the wide wavelength range may include a part or all of the visible wavelength range (ie, 380 nm to 810 nm). Further, the wide wavelength range includes an infrared wavelength range (810 nm to 1 mm) in addition to a part or all of the visible wavelength range or instead of part or all of the visible wavelength range. A part may be further included. Here, a part of the infrared wavelength range may include a near-infrared wavelength range (a wavelength range of 0.76 μm to 2.5 μm).

The light absorbing element 10 includes a spiral structure 3 that is an extremely fine metal structure having an overall size of, for example, several thousand micrometers or less. The spiral structure 3 is made of a metal material. The spiral structure 3 includes a base portion 3a and a linear portion 3b extending from the base portion 3a in a spiral shape. Hereinafter, an axis passing through the base point portion 3a is defined as a reference axis C, a direction parallel to the reference axis C is defined as an axial direction, and a direction perpendicular to the reference axis C and radially extending from the reference axis C is defined as a radial direction. In the present embodiment, as shown in FIGS. 1A and 1B, the linear portion 3b spirals from the base point portion 3a while rotating around the reference axis C and moving from the base point portion 3a to the outside in the radial direction and the axial direction. It extends in a shape. However, according to the present invention, the entire linear portion 3b may be located on a plane including the base point portion 3a. That is, the linear portion 3b extends spirally from the base point portion 3a while turning around the reference axis C and moving from the base point portion 3a to the outside in the radial direction while being positioned on the plane including the base point portion 3a. Also good.

The metal material forming the spiral structure 3 is, for example, Au, Ag, or Cu, but may be other materials (Ni or the like). In addition, although each metal material or each metal mentioned below is also Au, Ag, or Cu, for example, another material may be sufficient.

In the present embodiment, the radial dimension of the base portion 3a is larger than the radial thickness of the linear portion 3b. For example, for each radial direction, the radial dimension of the base point portion 3a may be larger than the radial thickness of the linear portion 3b. Here, the radial thickness of the linear portion 3b means the radial dimension of each portion of the linear portion 3b that is spaced apart from each other in the radial direction. The diameter of the linear portion 3b in the radial direction is, for example, 50 nm or more and 150 nm or less (for example, about 100 nm).

In the present embodiment, the radial interval (gap) between the portions adjacent to each other in the radial direction in the linear portion 3b may be the same as the radial thickness of the linear portion 3b. That is, in one example, the radial interval is 50 nm or more and 150 nm or less (for example, about 100 nm).

The radial dimension of the spiral structure 3 may be, for example, 500 nm or more and 2000 nm or less, but is not limited to this range.

In one example, the linear portion 3b extends from the base point portion 3a and goes around the reference axis C at least twice. However, the present invention is not limited to this, and the linear portion 3b may, for example, rotate around the reference axis C for less than two turns, or may turn around the reference axis C for more than three turns. In one example, the linear portion 3b extends in a curved shape as shown in FIG. 1B when viewed from the axial direction. In one example, the reference axis C is oriented in a direction perpendicular to a surface 5a of the support 5 described later, as shown in FIG. 1A. In one example, the linear portion 3b formed of a metal material continuously extends from the coupling position with the base point portion 3a to the tip.

Further, the light absorbing element 10 includes a support 5 that supports the spiral structure 3. The support 5 has a surface 5a that is axially spaced from the linear portion 3b, and a protruding portion 5b that protrudes from the surface 5a and is coupled to the base point portion 3a. The protrusion 5b may be formed of a non-metallic material (for example, a transparent material such as glass). In FIG. 1A, the support 5 includes a substrate 5A having a surface 5a.

In the first embodiment, the entire surface 5a of the support 5 is formed of a non-metallic material (for example, a transparent material such as glass), and a metal layer 7 is formed on a part of the surface 5a. Yes. In FIG. 1A, only the metal layer 7 is illustrated as a cross section by a plane parallel to the reference axis C, and the plane is a surface in the vicinity of the reference axis C. The metal layer 7 includes a spiral metal layer portion 7a and a peripheral metal surface portion 7b. In FIG. 1B, a broken line indicates a virtual boundary line between the spiral metal layer portion 7a and the peripheral metal surface portion 7b. When viewed from a direction perpendicular to the surface 5a, the spiral metal layer portion 7a is located between the portions adjacent to each other in the radial direction in the linear portion 3b, and extends spirally along the linear portion 3b. Yes. Light absorption due to the interaction between the metal layer 7 and the spiral structure 3 is expected. The metal layer 7 may be omitted.

Further, the light absorbing element 10 includes a protective layer 8 formed so that the spiral structure 3 is embedded therein. The protective layer 8 is bonded to the surface 5a (via the metal layer 7 in FIG. 1A). The protective layer 8 is formed of a transparent material (for example, a polymer). The protective layer 8 protects the spiral structure 3 and prevents its damage.

(Method for manufacturing light absorbing element)
FIG. 2 is a flowchart showing a method for manufacturing the light absorbing element 10 according to the first embodiment of the present invention. 3A to 3J are explanatory views of the manufacturing method according to the first embodiment.

In step S1, an object 5A is prepared as shown in FIG. 3A. In the example of FIG. 3A, the entire surface 5a of the object to be processed 5A is formed of a nonmetallic material. In the embodiment, the target object 5A is a substrate formed of silicon as a non-metallic material. Note that the target object 5A may be formed of a non-metallic material other than silicon.

In step S2, a spiral metal layer 15 having a spiral pattern (hereinafter also simply referred to as a spiral pattern) is formed on the surface 5a of the object 5A as shown in FIGS. 3E and 3F described later. The spiral metal layer 15 is made of a metal material. In the embodiment, step S2 includes steps S21 to S25.

In step S21, the resist layer 11 is formed on the surface 5a of the workpiece 5A. The resist layer 11 is formed of a material that is sensitive to electron beams. The material is, for example, polymethyl methacrylate (PMMA). In this case, a resist layer 11 made of PMMA is formed on the surface 5a by applying a PMMA film to the surface 5a.

In step S22, as shown in FIG. 3B, the surface of the resist layer 11 is irradiated with an electron beam in a spiral pattern.

In step S23, the portion of the spiral pattern irradiated with the electron beam in the resist layer 11 is dissolved by immersing the object to be processed 5A in the developer. As a result, as shown in FIG. 3C, the spiral groove 13 is formed by removing the spiral pattern portion in the resist layer 11. The bottom surface of the spiral groove 13 becomes the exposed surface 5a of the workpiece 5A.

The spiral groove 13 has a central groove portion 13a corresponding to the base point portion 3a and a linear groove portion 13b corresponding to the linear portion 3b. When viewed from a direction orthogonal to the surface 5a of the workpiece 5A, the linear groove 13b extends spirally from the central groove 13a. In each direction parallel to the surface 5a, the size of the central groove 13a is larger than the thickness of the linear groove 13b. Here, the thickness of the linear groove part 13b means the dimension of each part spaced apart from each other in the direction away from the central groove part 13 in the linear groove part 13b. Due to the dimensional relationship between the central groove portion 13a and the linear groove portion 13b, a linear layer among a later-described base layer portion 15a corresponding to the central groove portion 13 and a later-described linear layer portion 15b corresponding to the linear groove portion 13b. The portion 15b is separated from the object to be processed 5A (surface 5a) by the etching process described later, but the base layer 15a remains bonded to the object to be processed 5A even after the etching process described later.

In step S24, a metal material is deposited on the bottom surface 5a of the spiral groove 13 and the surface of the remaining resist layer 11 by a vacuum deposition method or a sputtering method, thereby forming a metal layer on the surface of the resist layer 11 as shown in FIG. 3D. 16 and the spiral metal layer 15 is formed on the bottom surface of the spiral groove 13.

In step S25, lift-off processing is performed. In the lift-off process, the resist layer 11 remaining on the object to be processed 5A is completely dissolved in an appropriate solvent (organic solvent), whereby the metal layer 16 is removed from the object to be processed 5A and the surface 5a of the object to be processed 5A is removed. The directly formed spiral metal layer 15 is left. Thereby, as shown in FIGS. 3E and 3F, the spiral metal layer 15 is formed on the surface 5a of the workpiece 5A. FIG. 3F is a view taken in the direction of the arrow 3F-3F in FIG. 3E. The spiral metal layer 15 includes a base point layer portion 15a corresponding to the base point portion 3a, and a linear layer portion 15b corresponding to the linear portion 3b and extending spirally from the base point layer portion 15a. In FIG. 3F, a broken line is a virtual boundary line between the base layer portion 15a and the linear layer portion 15b.

In step S3, an etching process for isotropically removing the exposed surface of the surface 5a of the object 5A is performed. This etching process may be, for example, a process by inductively coupled plasma reactive ion etching (ICP-RIE: Inductively Coupled Plasma Reactive Ion Etching). In this ICP-RIE, an etching gas is turned into plasma by applying a high frequency to the etching gas in a vacuum reaction chamber, and the exposed surface of the surface 5 of the object to be processed 5A is exposed by a chemical reaction caused by the plasmatized gas. Etching isotropically. In order to etch the exposed surface 5a isotropically, a bias voltage may not be applied to the object to be processed 5A.

By the etching process in step S3, in the object 5A, as shown in FIG. 3G, a new surface 5a that is axially spaced from the linear layer portion 15b and a base portion 3a that protrudes from the surface 5a and is coupled to the base portion 3a. The protruding portion 5b is formed. At this point, the etching process is finished. In addition, 5 A of to-be-processed objects after an etching process comprise the above-mentioned support body 5. FIG.

In step S4, a metal layer 7 is further formed on the target object 5A and the spiral metal layer 15 as shown in FIG. 3H by vacuum deposition or sputtering. In this case, the metal layer 7 on the workpiece 5A has the above-described spiral metal layer portion 7a and the peripheral metal surface portion 7b. Further, the base layer 15a and the metal layer 7 on the base layer 15a constitute the above-described base 3a, and the linear layer 15b and the metal layer 7 on the linear layer 15b are linear. The shape portion 3b is formed.

In step S4, at the position corresponding to the back of the spiral metal layer 15, the spiral metal layer 15 becomes an obstacle to the deposited metal material, so that the above-described spiral metal layer portion 7a is formed. Moreover, since the metal layer 7 is further formed in the spiral metal layer 15 by step S4, the thickness of the spiral structure 3 can be increased correspondingly.

Further, as shown in FIG. 3I, the linear portion 3b extends spirally while moving downward in the axial direction (downward in this figure) due to gravity or stress. As a result, the light absorption element 10 described above is formed. 3E, FIG. 3G, and FIG. 3H are cross-sectional views taken along a plane that includes the base layer 15a and is parallel to the paper surface of the drawing. FIG. 3I and FIG. The cross section in the position away from the spiral structure 3 is shown.

In step S5, a protective layer 8 made of a transparent material is formed so as to embed the spiral structure 3 therein. For example, a film of a transparent material solution is formed on the surface 5a of the workpiece 5A (in FIG. 3J, via the metal layer 7 on the surface 5a), and the protective layer 8 is formed by drying the solution. In one example, the transparent material is a polymer and the protective layer 8 is a polymer layer. By step S5, the spiral structure 3 is embedded in the protective layer 8.

When the stress is adjusted by heating or cooling the object to be processed (substrate) 5A when forming the metal layers 15, 7 and the like by vapor deposition, contrary to the case of FIG. 3I, as shown in FIG. 3K, It is also possible to obtain a spiral structure that spirally extends from the base portion 3a on the side away from the surface 5a. In this case, the other points of the manufacturing method of the light absorption element 10 may be the same as described above.

Note that step S4 described above may be omitted. In this case, step S5 is performed after step S3. Further, step S4 and step S5 may be omitted.

FIG. 4 is an SEM (Scanning Electron Microscope) image of the light absorbing element 10 manufactured in the example of the manufacturing method according to the first embodiment. In FIG. 4, the dimension in the range indicated by the double arrow is 500 nm.

According to the first embodiment, the light absorption element 10 can absorb light in a wide wavelength region by having the spiral structure 3 that is the above-described three-dimensional ultrafine metal structure. For example, the light absorbing element 10 described above can absorb infrared light having a wide wavelength range. In this case, the light absorbing element 10 can absorb both light having a wide wavelength range in the visible light range and light having a wide wavelength range of infrared rays (for example, a wide wavelength range of near infrared rays). Such an effect was confirmed by experiments as shown in FIG.

[Second Embodiment]
(Configuration of light absorbing element)
FIG. 5A shows the structure of the light absorption element 10 according to the first embodiment of the present invention. FIG. 5B is a view taken along arrow 5B-5B in FIG. 1A. The light absorbing element 10 according to the second embodiment is the same as the light absorbing element 10 according to the first embodiment in the points not described below.

In the light absorbing element 10 of the second embodiment, the configuration of the support 5 is different from that of the first embodiment. In 2nd Embodiment, the whole surface 5a of the support body 5 is formed with the metal material, and the above-mentioned metal layer 7 is formed in this surface 5a. In the example of the second embodiment, the support 5 has a non-metal layer (substrate) 19 formed of a non-metal material and a metal layer 21 formed on the non-metal layer 19. In FIG. 5A, only the metal layer 7 is shown as a cross section by a plane parallel to the reference axis C, and the plane is a plane in the vicinity of the reference axis C.

(Method for manufacturing light absorbing element)
FIG. 6 is a flowchart showing a method for manufacturing the light absorbing element 10 according to the second embodiment of the present invention. 7A to 7K are explanatory views of the manufacturing method according to the second embodiment.

In step S100, the object 5B is prepared. In the embodiment, step S100 includes steps S111 to S113. In step S111, a substrate 19 is prepared as shown in FIG. 7A. Here, the material of the substrate 19 may be a metal or a non-metal, and may be transparent or opaque. In step S112, as shown in FIG. 7B, the metal layer 21 is formed on the entire surface of the substrate 19 by vacuum deposition or sputtering. In step S113, the sacrificial tank 23 is formed on the metal layer 21 as shown in FIG. 7C by an appropriate method such as a CVD (Chemical Vapor Deposition) method. The sacrificial tank 23 may be a layer formed of, for example, silicon nitride. The object 5B is obtained by sequentially stacking the metal layer 21 and the sacrificial layer 23 on the substrate 19 in this manner, and the sacrificial layer 23 forms the surface 5a of the object 5B.

In step S200, the spiral metal layer 15 having a spiral pattern as shown in FIG. 7G described later is formed on the surface 5a of the workpiece 5B. The spiral metal layer 15 is made of a metal material. In the embodiment, step S200 includes, for example, steps S211 to S215.

In step S211, the resist layer 11 is formed on the surface of the sacrificial tank 23 as shown in FIG. 7D. The resist layer 11 is formed of a material that is sensitive to electron beams. The material is, for example, polymethyl methacrylate (PMMA).

In step S212, the surface of the resist layer 11 is irradiated with an electron beam in a spiral pattern.

In step S213, the object 5B is immersed in the developer to dissolve the spiral pattern portion irradiated with the electron beam in the resist layer 11. As a result, as shown in FIG. 7E, the spiral groove 13 is formed in the resist layer 11 by removing the spiral pattern portion. The bottom surface of the spiral groove 13 becomes the exposed surface 5 a of the sacrificial layer 23. The structure of the spiral groove 13 is the same as that in the first embodiment.

In step S214, a metal material is deposited on the bottom surface 5a of the spiral groove 13 and the surface of the remaining resist layer 11 by a vacuum deposition method or a sputtering method, so that a metal layer is formed on the surface of the resist layer 11 as shown in FIG. 7F. 16 and the spiral metal layer 15 is formed on the bottom surface of the spiral groove 13.

In step S215, lift-off processing is performed. In the lift-off process, the metal layer 16 is removed from the target object 5B by dissolving the resist layer 11 remaining on the substrate with an appropriate solvent, and the spiral metal layer 15 formed directly on the surface 5a of the sacrificial layer 23. Leave. Thereby, as shown in FIG. 7G, the spiral metal layer 15 is formed on the surface 5a of the object to be processed 5B (sacrificial layer 23). The structure of the spiral metal layer 15 is the same as that in the first embodiment.

In step S300, an etching process for isotropically removing the exposed surface of the surface of the sacrificial layer 23 as the surface 5a of the object 5B is performed. This etching process is the same as that in the first embodiment.

As a result of the etching process in step S300, in the object to be processed 5B, as shown in FIG. 7H, a new surface 5a that is axially spaced from the linear layer portion 15b and a base portion 3a that protrudes from the surface 5a and is coupled to the base point portion 3a. The protruding portion 5b is formed. Here, the surface 5a is the surface of the metal layer 21 in FIG. 7H, but may be the surface of the remaining portion of the sacrificial layer 23, unlike FIG. 7H. The protruding portion 5 b is a remaining portion of the sacrificial layer 23. In addition, the to-be-processed object 5B after an etching process comprises the above-mentioned support body 5. FIG.

In step S400, the metal layer 7 is further formed on the target object 5B and the spiral metal layer 15 as shown in FIG. 7I by vacuum deposition or sputtering. In this case, the metal layer 7 on the workpiece 5A has the above-described spiral metal layer portion 7a and the peripheral metal surface portion 7b. Further, the base layer 15a and the metal layer 7 on the base layer 15a form the above-described base 3a, and the linear layer 15b and the metal layer 7 on the linear layer 15b are described above. The linear portion 3b is formed.

Further, as shown in FIG. 7J, the linear portion 3b may extend spirally while moving downward in the axial direction (downward in this figure) due to gravity or stress. As a result, the light absorption element 10 described above is formed. 7G to 7I are cross-sectional views taken along a plane including the base layer 15a and parallel to the paper surface of the drawing. FIG. 7J and FIG. 7K to be described later show the spiral structure 3 in a direction perpendicular to the paper surface of the drawing. The cross section in the position away from is shown.

In step S500, as shown in FIG. 7K, a transparent material protective layer 8 is formed so as to embed the spiral structure 3 in the same manner as in the first embodiment.

Note that step S400 described above may be omitted. In this case, step S500 is performed after step S300. Further, step S400 and step S500 may be omitted.

FIG. 8 is an SEM image of the light absorbing element 10 manufactured in the example of the manufacturing method based on the second embodiment. In FIG. 8, the dimension in the range indicated by the double arrow is 500 nm.

The light absorbing element 10 according to the second embodiment can obtain the same effects as the light absorbing element 10 according to the first embodiment.

[Light absorber]
FIG. 9A shows a configuration of the light absorber 20 according to the embodiment of the present invention. FIG. 9B is a view taken along arrow 9B-9B in FIG. 9A. The light absorber 20 has a large number of light absorption elements 10 and an element support surface 5 a that supports these light absorption elements 10.

The element support surface 5 a is the surface of the support 5 of each light absorbing element 10. That is, the surface 5a of the support body 5 in many light absorption elements 10 constitutes one element support surface 5a. Therefore, the support 5 is shared by many light absorption elements 10. Such a support 5 includes an element support surface 5a, a number of protrusions 5b protruding from the element support surface 5a, and a base portion 5c having the element support surface 5a.

Also, the protective layer 8 is shared by many light absorbing elements 10. That is, one protective layer 8 is formed on the element support surface 5a (for example, through the metal layer 7 which is not shown), and a large number of light absorbing elements 10 are embedded in the protective layer 8. .

A large number of light absorbing elements 10 are arranged on the element support surface 5a. For example, as shown in FIG. 9B, a large number of light absorbing elements 10 may be regularly arranged densely on the element support surface 5a. Alternatively, the multiple light absorbing elements 10 may be densely arranged on the element support surface 5a at random. The light absorption rate by the light absorber 20 increases as the density of the many light absorption elements 10 increases.

As shown in FIG. 9B (in this example, in the horizontal direction of the figure), the interval between adjacent light absorption elements 10 on the element support surface 5a (that is, the dimension of the gap between the light absorption elements 10) is P, When the radial dimension of the spiral structure 3 of the light absorbing element 10 is Q, P may be smaller than Q (for example, P is less than half of Q). The relationship between P and Q is a relationship in the first direction (the left-right direction in FIG. 9B) along the element support surface 5a, but is perpendicular to the first direction and in the second direction along the element support surface 5a ( The same applies to the vertical direction in FIG. 9B. That is, in the second direction, when the distance between the adjacent light absorption elements 10 on the element support surface 5a is R and the radial dimension of the spiral structure 3 of the light absorption element 10 is S, R is smaller than S. Good (for example, R is less than half of S). For example, Q and S may be 500 nm or more and 1500 nm or less, and P and R may be 500 nm or less (for example, 500 nm).

The light absorber 20 according to the present embodiment absorbs light in a continuous wide wavelength range (for example, with an absorption rate of 80% or more). In this case, it is assumed that the width of the wide wavelength region is A or more and B or less. In this case, in one example, A is 100 nm, 200 nm, 500 nm, 1000 nm, 1500 nm, 2000 nm, or 2500 nm, and for each value of A, B may be 6000 nm, 5000 nm, 4000 nm, or 3000 nm. In another example, A can be 100 nm, 200 nm, or 500 nm, and for each value of A, B can be 2000 nm or 1000 nm. According to the present invention, the width of the wide wavelength range is not limited to the above examples.

In the light absorber 20, a large number of light absorbing elements 10 absorb light in a wide wavelength range. Since each light absorption element 10 has an ultrafine structure, the light absorption elements 10 can be arranged densely. Therefore, the element support surface 5a of the light absorber 20 can be made black that is close to true black.

Such a light absorber 20 may form a black surface for suppressing reflection of light or stray light in an optical apparatus. In the example of FIG. 9A, the light absorber 20 is provided on the target surface 30 a for suppressing reflection or stray light in the optical device 30. The optical apparatus is, for example, a camera, an astronomical telescope, or an optical measurement device (for example, a spectrophotometer), but is not limited thereto. The target surface 30a is, for example, the inner surface of a camera barrel and the back surface of a reflection surface (for example, the back surface of the reflection mirror) in the optical apparatus, but is not limited thereto.

In one example, the base portion 5c is formed in a sheet shape. In this case, the light absorber 20 is also formed in a sheet shape as a whole. Therefore, after manufacturing the sheet-like light absorber 20, the light absorber 20 can be attached to the target surface 30 a of the optical device 30.

The light absorber 20 can be manufactured as follows. A large number of spiral structures 3 are simultaneously formed on the common base portion 5c by the manufacturing method according to the first embodiment or the second embodiment described above. When the light absorber 20 is manufactured by the manufacturing method of the first embodiment, the base portion 5c is prepared as the object to be processed 5A, and the above-described steps for each of the multiple spiral structures 3 with respect to the object to be processed 5A. S2 to S5 are performed. Similarly, when the light absorber 20 is manufactured by the manufacturing method according to the second embodiment, the base portion 5c is prepared as the target object 5B, and a large number of spiral structures 3 are formed on the target object 5B. The above-described steps S200 to S500 are performed for each.

FIG. 10A shows the experimental results regarding the optical characteristics of the light absorber 20 manufactured according to the manufacturing method of the first embodiment. FIG. 10B is an experimental result regarding the optical characteristics of the light absorber 20 manufactured according to the manufacturing method of the second embodiment. 10A and 10B, the horizontal axis indicates the wavelength (μm), and the vertical axis indicates the reflectance of the light incident on the light absorber 20. A wavelength range where the reflectance is low indicates that the light absorptance is high. FIG. 10A and FIG. 10B show the case where a large number of spiral structures 3 are arranged at equal intervals with the interval between adjacent spiral structures 3 (intervals P and R in FIG. 9B) being 500 nm.

In the case of FIG. 10A, a light absorption rate of about 80% or more is obtained in the wavelength range of 1.5 μm to 4 μm. In the case of FIG. 10B, an optical absorptance of about 80% or more is obtained in the wavelength range of 1.5 μm to 2 μm and the wavelength range of 3.2 μm to 4.3 μm.

The present invention is not limited to the above-described embodiments, and various changes can be made within the scope of the technical idea of the present invention. For example, the effects described above do not necessarily limit the present invention. In addition, the present invention may exhibit any of the effects shown in the present specification or other effects that can be grasped from the present specification.
Further, any one of the following modification examples 1 to 9 may be adopted alone, or two or more of the modification examples 1 to 9 may be arbitrarily combined and employed. In this case, the points not described below are the same as described above.

[Modification 1]
11A and 11B are schematic views showing other forms of the spiral structure 3. 11A and 11B are views of the light absorbing element 10 as viewed from the direction of the reference axis C.

As shown in FIG. 11A, when viewed from the direction of the reference axis C, the linear portion 3b may extend from the base point portion 3a so as to form a substantially N-gonal shape every time the reference axis C is rotated once. Good. Here, N is an integer of 3 or more, 3 in the case of FIG. 11A and 4 in the case of FIG. 11B, but may be 5 or more. In other words, in the process of extending from the base point portion 3a, the linear portion 3b may be bent so as to be bent N times each time the reference axis C is rotated once, and may extend linearly except at the bent portion. In this case, the first turn may be bent (N + 1) as shown in FIG. 11B.

Each time the linear portion 3b makes one round of the reference axis C in the course of extending from the base point portion 3a so as to form a substantially N-gonal shape once every round of the reference axis C as described above. The number of times of bending may change.

[Modification 2]
FIG. 11C is a schematic diagram showing another form of the spiral structure 3. FIG. 11C is a diagram of the light absorption element 10 as viewed from the direction of the reference axis C.

The linear portion 3b may not be continuous from the coupling position with the base point portion 3a to the tip, and as shown in FIG. 11C, the linear portion 3b is discontinuously from the coupling position with the base point portion 3a to the tip. It may extend. That is, the discontinuous part 41 may exist in the linear part 3b.

In this case, the discontinuous linear portion 3b may be formed as follows in accordance with the manufacturing method of the first embodiment. Instead of the spiral metal layer 15, a spiral transparent layer made of a transparent material having the same shape and dimensions as the spiral metal layer 15 is formed on the surface of the object 5A. Thereafter, a resist layer is formed on the surface of the object to be processed 5A and the spiral transparent layer, and only the resist layer on the spiral transparent layer is irradiated with an electron beam in a discontinuous spiral pattern. A resist layer having a spiral pattern is melted and removed. Thereafter, similarly to the above-described Steps S24 and S25, a metal layer is formed and a lift-off process is performed, so that a spiral metal layer extending discontinuously on the spiral transparent layer is formed. Thereafter, by performing step S3 described above, the spiral transparent layer and the spiral metal layer thereon are separated from the new surface 5a of the workpiece 5A. Thereafter, step S4 described above is not performed, but step S5 described above may be performed.

Similarly, the discontinuous linear portion 3b can be formed following the manufacturing method of the second embodiment.

[Modification 3]
For the light absorber 20 according to the embodiment of the present invention, the incident angle of the linearly polarized light on the element support surface 5a (the surface 5a of the support 5) is changed, and the light absorber 20 is changed while changing the polarization direction of the linearly polarized light. The light absorption rate of was measured. According to the measurement results, the light absorptance was constant at each wavelength of the incident light regardless of the incident angle and polarization direction of the light.

Therefore, the direction of the protrusion 5b (reference axis C) of each light absorbing element 10 of the light absorber 20 does not affect the light absorption characteristics. Therefore, the protrusion 5b of each light absorbing element 10 may extend from the surface 5a of the support 5 in a direction perpendicular to the surface 5a, or in an oblique direction with respect to the perpendicular direction. Also good. In other words, in the above description, the reference axis C of the spiral structure 3 is oriented in a direction perpendicular to the surface 5a of the support 5, but may be oriented in a direction inclined from the direction perpendicular to the surface 5a.

[Modification 4]
In FIG. 1A and FIG. 5A, the spiral structure 3 and the metal layer 7 or the metal layer 21 as the ground are separated from each other, but a part of the linear part 3b of the spiral structure 3 (for example, the base part 3a side and The tip portion on the opposite side) may be in contact with the metal layer 7.

[Modification 5]
FIG. 12 is a diagram showing another form of the light absorber 20. In FIG. 9A described above, the support body 5 and a large number of light absorption elements 10 arranged on the element support surface 5a of the support body 5 have a set of light absorption configurations. In this case, the light absorber 20 may be formed by stacking a plurality of sets of light absorption structures as shown in FIG. In FIG. 12, the base portion 5c may be made of a transparent material. Thus, the light absorption rate of the light absorber 20 can be further increased by laminating a plurality of sets (for example, many sets).

Such a light absorber 20 can be manufactured as follows, for example. A base portion 5c having a second light absorption structure is formed on the protective layer 8 having the first light absorption structure, and the second light absorption structure is laminated on the first light absorption structure. The third and subsequent sets of light absorption structures may be laminated in the same manner.
[Modification 6]
5A and 9A, the peripheral metal layer portion 7a may not extend over the entire surface 5a, and may exist only in the vicinity of the spiral structure 3.
In FIG. 7H, the metal layer 21 may not extend over the entire surface of the substrate 19, and may exist only in the vicinity of the spiral structure 3.

[Modification 7]
In FIG. 1A and FIG. 5A, the linear portion 3b gradually approaches the surface 5a of the support 5 while rotating around the reference axis C in the process of extending from the base point portion 3a. However, the present invention is not limited to this. . For example, the linear portion 3b may gradually move away from the surface 5a of the support 5 while rotating around the reference axis C in the process of extending from the base point portion 3a. For example, by performing step S3 or S300 in a state where the surface 5a of the

object

5A or 5B is directed vertically downward, the linear portion 3b is moved in the process of extending from the base point portion 3a due to gravity. While turning, it gradually moves away from the surface 5a.

[Modification 8]
In the light absorber 20 described above, the spiral structure 3 of each light absorbing element 10 has the same radial dimension. However, there may be a plurality of types of radial dimensions of the multiple spiral structures 3 arranged on the element support surface 5a. With this configuration, it is expected that light in a wider wavelength range can be absorbed.

[Modification 9]
In the first embodiment, the base point portion 3a and the linear portion 3b of the light absorbing element 10 may be in a state of being coupled to the object to be processed 5A (support 5). For example, in the manufacturing method of the first embodiment described above, steps S3 to S5 may be omitted, and the structure shown in FIGS. 3E and 3F may be the light absorbing element according to the present invention. In this case, in FIGS. 3E and 3F, the spiral metal layer 15 forms a spiral structure of the light absorption element according to the present invention. That is, the base layer portion 15a of the spiral metal layer 15 forms a base portion of the spiral structure, and the linear layer portion 15b of the spiral metal layer 15 forms a linear portion of the spiral structure.

In this case, the light absorber of the present invention may be formed by forming a large number of the spiral metal layers 15 of FIGS. 3E and 3F on the surface 5a of the single support 5. The light absorption rate of this light absorber was measured. The measurement results are shown in the graph of FIG. In FIG. 13, the horizontal axis indicates the wavelength (μm) of incident light to the light absorber, and the vertical axis indicates the light absorption rate of the light absorber. The solid line in FIG. 13 shows the case of the light absorber using the spiral metal layer 15 in FIGS. 3E and 3F obtained by omitting steps S3 to S5. The broken line in FIG. 13 indicates the case of the above-described light absorber 20 obtained by performing the above-described steps S1 to S5. In any of the light absorber formed by the spiral metal layer 15 (spiral structure) and the light absorber 20 obtained in steps S1 to S5, the interval between adjacent spiral structures (intervals corresponding to the intervals P and R in FIG. 9B). Was set to about several hundred nanometers.

As can be seen from FIG. 13, the light absorptivity of the light absorber by the spiral metal layer 15 (solid line in FIG. 13) is the light absorptivity of the light absorber 20 obtained by performing steps S1 to S5 (FIG. 13). Is about 60% or more in the wavelength range of 1.5 μm to 4 μm.

Similarly, in the manufacturing method of the second embodiment described above, the processes of steps S300 to S500 may be omitted. In this case, the structure shown in FIG. 7G may be a light absorption element according to the present invention. In this case, in FIG. 7G, the spiral metal layer 15 forms a spiral structure of the light absorption element according to the present invention. That is, the base layer portion 15a of the spiral metal layer 15 forms a base portion of the spiral structure, and the linear layer portion 15b of the spiral metal layer 15 forms a linear portion of the spiral structure. In this case, step S113 for forming the sacrificial layer 23 may be omitted, and the spiral metal layer 15 may be formed on the metal layer 21 in step S200.

The light absorber of the present invention may be formed by forming a large number of spiral metal layers 15 shown in FIG. 7G on the surface 5a of one support 5. Also in this case, the sacrificial layer 23 may be omitted as described above.

3 Spiral structure

3a Base part

3b Linear part 5 Support body 5a Surface (element support surface)
5b Protruding part 5c Base part 7 Metal layer 7a Spiral metal layer part 7b Peripheral metal layer part 8 Protective layers 5A, 5B Object to be processed (substrate)
10 light absorption element 11 resist layer 13 spiral groove 15 spiral metal layer (second metal layer)
15a Base point layer portion 15b Linear layer portion 16 Metal layer (second metal layer)
17 Protective layer 19 Substrate (non-metal layer)
20 light absorber 21 metal layer (first metal layer)
23 Sacrificial tank 30 Optical device 30a Target surface 41 Discontinuous portion C Reference axis

Claims

A light absorbing element for absorbing light,
It has a spiral structure made of metal material,
The spiral structure includes a base portion and a linear portion extending from the base portion,
An axis passing through the base point is a reference axis, and a direction extending radially from the reference axis is a radial direction,
The light absorption element, wherein the linear portion extends in a spiral shape from the base point while turning around the reference axis and moving from the base point to the outside in the radial direction.
A direction parallel to the reference axis as an axial direction,
2. The linear portion according to claim 1, wherein the linear portion extends spirally from the base point portion while rotating around the reference axis and moving from the base point portion to the outside in the radial direction and the axial direction. Light absorbing element.
The light absorption element according to claim 1, wherein a radial dimension of the base portion is larger than a thickness of the linear portion in the radial direction.
The light absorbing element includes a support that supports the spiral structure;
4. The light absorption according to claim 2, wherein the support has a surface that is spaced apart from the linear portion in the axial direction, and a protrusion that protrudes from the surface and is coupled to the base portion. element.
The light absorption element according to claim 4, wherein the entire surface of the support is formed of a metal material.
A light absorbing element according to any one of claims 1 to 5;
An element support surface for supporting the light absorbing element,
A light absorber in which a large number of the light absorption elements are arranged on the element support surface.
The light absorber according to claim 6, wherein the light absorber forms a black surface for suppressing reflection of light or stray light in an optical device.
A method of manufacturing a light absorbing element for absorbing light,
The light absorbing element includes a spiral structure formed of a metal material,
The spiral structure includes a base portion and a linear portion extending from the base portion,
An axis passing through the base point is a reference axis, and a direction extending radially from the reference axis is a radial direction,
The linear part extends spirally from the base point part while turning around the reference axis and moving from the base part to the outside in the radial direction,
(A) A spiral metal layer formed of a metal material and having a spiral pattern is formed on the surface of the object to be processed. The spiral metal layer includes a base layer corresponding to the base and a linear portion. The manufacturing method of the light absorption element containing the corresponding linear layer part.
(B) After (A), by performing an etching process that isotropically removes the exposed surface of the surface of the object to be processed, the object to be processed has the linear layer portion to The manufacturing method of the light absorption element of Claim 8 which forms the new surface which is spaced apart in the axial direction, and the protrusion part which protrudes from this surface and was couple | bonded with the said base point layer part.
In (A) above,
(A1) forming a resist layer on the surface of the object to be processed;
(A2) Irradiate the surface of the resist layer with an electron beam in a spiral pattern;
(A3) With the developer, the portion of the spiral pattern irradiated with the electron beam in the resist layer is dissolved, thereby forming a groove of the spiral pattern,
(A4) forming a metal layer on the bottom surface of the groove and the surface of the remaining resist layer;
(A5) The manufacturing method of the light absorption element according to claim 8 or 9, wherein the metal layer of the spiral pattern is formed as the spiral metal layer by melting the remaining resist layer.
The object to be processed has a first metal layer and a sacrificial tank formed on the metal layer,
In (A) above,
(A1) forming a resist layer on the surface of the sacrificial tank;
(A2) Irradiating the surface of the resist layer with an electron beam in a spiral pattern;
(A3) The portion of the spiral pattern irradiated with the electron beam in the resist layer is dissolved by the developer, thereby forming a groove of the spiral pattern,
(A4) forming a second metal layer on the bottom surface of the groove and the surface of the remaining resist layer;
(A5) By dissolving the remaining resist layer, the second metal layer of the spiral pattern is formed as the spiral metal layer,
The method for manufacturing a light-absorbing element according to claim 9, wherein the new surface in (B) is a surface of the first metal layer.
The method for manufacturing a light-absorbing element according to claim 10, wherein the object to be processed is a substrate formed of a nonmetallic material.