Optical element, roll master disk, and method for manufacturing optical element

Abstract

This optical element comprises: a base material 11; and a plurality of convex structures 3 arranged on at least one surface of the base material 11 at a pitch equal to or less than a wavelength band of visible light. The structure 3 has a composite structure comprising a first tapered part 31 formed on a surface of the base material 11 and a second tapered part 32 formed on the first tapered part 31. The taper ratio C2 of the second tapered part 32 is smaller than the taper ratio C1 of the first tapered part 31. The second tapered part 32 has a needle-like tapered shape thinner than the first tapered part 31, and the height h of the structure 3 is 400 nm or more.

Description

Optical element, roll master, and method for manufacturing optical element

[0001] The present invention relates to an optical element, a roll master, and a method for manufacturing an optical element. This application claims the benefit of priority from Japanese Patent Application No. 2024-097557, filed on June 17, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, the applications of film-like optical elements (anti-reflection films) having anti-reflection properties have been expanding. Anti-reflection films are applied to various devices, such as display devices installed in smartphones or personal computers, in-vehicle cameras for autonomous driving technology, and cameras in devices using virtual reality (VR) or augmented reality (AR).

[0003] Furthermore, as one of the microfabrication technologies, imprinting technology has been developed, in which a roll master having a microrelief structure formed on its outer peripheral surface is pressed against a film substrate, and the microrelief structure of the roll master is transferred to a resin layer of the film substrate. Using this imprinting technology, for example, a microrelief structure (so-called moth-eye structure) arranged at a period (pitch) equal to or less than the wavelength of visible light can be transferred to a resin layer of a transparent film substrate. This imparts anti-reflection properties to the film substrate, enabling efficient mass production of anti-reflection films.

[0004] The micro-relief structure on the surface of such an anti-reflection film makes the change in refractive index relative to incident light gradual, making it difficult for abrupt changes in refractive index that cause reflection to occur. Therefore, by providing an anti-reflection film in necessary locations on the various devices described above, it is possible to suppress reflection of incident light.

[0005] As such an antireflection film, for example, Patent Document 1 discloses an optical element including a plurality of structures each having an elliptical cone or frustum of an elliptical cone shape. Also, Patent Document 2 discloses an optical element including a plurality of structures each having a cone shape, in which the effective refractive index of the structures in the depth direction gradually increases toward the substrate of the optical element and forms an S-shaped curve.

[0006] Patent No. 4404161 Patent No. 5257066

[0007] As the applications of devices to which anti-reflection films are applied expand, the ability to detect light in a wide wavelength band (e.g., 380 to 950 nm) from the visible light range to the near-infrared range is required depending on the application of the device. For example, a camera mounted on the windshield of a vehicle needs to be able to properly detect and capture images of the surrounding environment in dark places, such as when driving at night. Furthermore, in wearable devices such as VR or AR, an eye-tracking camera is installed in a dark place within the housing of the device where no light enters. For this reason, the eye-tracking camera needs to be able to detect human eye movements and facial expressions in dark places within the housing. Therefore, when an anti-reflection film is installed on an anti-reflection-treated portion of the windshield where the above-mentioned vehicle-mounted camera is installed, or on the cover glass of the eye-tracking camera, the anti-reflection film is required to exhibit anti-reflection properties for light in a wide wavelength band from the visible light range to the near-infrared range.

[0008] On the other hand, due to the structure of automobiles, windshields are positioned at an extreme incline, and an on-board camera is installed behind this inclined windshield. Therefore, when an anti-reflection film is attached to an inclined windshield to perform anti-reflection treatment, the angle of incidence of light on the anti-reflection film can be very high, for example, approximately 45° to 70°. Therefore, in this case, the anti-reflection film is required to exhibit anti-reflection properties against light obliquely incident at such a high angle. Furthermore, since lightweight and compactness are essential for wearable devices such as VR, the camera must be installed close to the face and be able to detect a wide range of the face. Therefore, even in this case, the anti-reflection film used in the camera is required to exhibit anti-reflection properties against light obliquely incident at a high angle, for example, approximately 45° to 70°.

[0009] However, the conventional antireflection films described in Patent Documents 1 and 2 above have a problem in that they are unable to adequately handle light in a wide wavelength range from the visible light region to the near-infrared region, and that the antireflection properties deteriorate in some wavelength ranges. Furthermore, the conventional antireflection films also have a problem in that the antireflection properties deteriorate for light that is obliquely incident at a high angle of about 45° to 70°.

[0010] For example, in the anti-reflection film described in Patent Document 1, the multiple structures constituting the micro-relief structure have a monotonous structure of an elliptical cone or elliptical truncated cone shape. Therefore, there is a problem in that only incident light in a specific wavelength band is prevented from reflecting, while incident light in other wavelength bands exhibits a sub-reflection peak, resulting in increased reflection. Furthermore, the anti-reflection film described in Patent Document 2 suppresses the sub-reflection peak and broadens the anti-reflection range in the visible light range compared to the monotonous elliptical cone shape of Patent Document 1, but it is difficult to prevent reflection of incident light in the near-infrared range. Furthermore, it is also difficult to accommodate oblique incident light at high angles, for example, about 45° to 70°.

[0011] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide an optical element, a roll master, and a method for manufacturing an optical element that can ensure anti-reflection properties for incident light in a wide wavelength band from the visible light region to the near-infrared region, as well as for oblique incident light at high angles.

[0012] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a method for manufacturing a light-emitting device comprising: a substrate; and a plurality of convex structures arranged on at least one surface of the substrate at a pitch equal to or less than the wavelength band of visible light, wherein the structures have a composite structure consisting of a first tapered portion formed on the surface of the substrate and a second tapered portion formed on the first tapered portion, and a taper ratio C of the second tapered portion is ２ is the taper ratio C of the first tapered portion １ the second tapered portion has a needle-like tapered shape that is thinner than the first tapered portion, and the height h of the structure is 400 nm or more.

[0013] The structure may have a change point where the taper ratio of the side surface of the structure changes at a joining position between the top of the first tapered section and the bottom of the second tapered section.

[0014] The first tapered portion and the second tapered portion may have a shape that approximates a linear taper, and the vertical cross-sectional shapes of the tapered surfaces of the first tapered portion and the second tapered portion may be substantially straight lines.

[0015] The height h of the structure may be 490 nm or more.

[0016] The height h of the second tapered portion ２ is 160 to 300 nm, and the height h of the first tapered portion １ may be set to 150 to 500 nm.

[0017] In addition, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a roll master for manufacturing the optical element, comprising: a cylindrical or columnar master substrate; and a first fine uneven structure formed on the outer peripheral surface of the master substrate, wherein the first fine uneven structure includes a plurality of recesses having an inverted shape of the structures of the optical element, and the recesses have a composite structure consisting of a first tapered recess having an inverted shape of the first tapered portion, and a second tapered recess formed inside the first tapered recess and having an inverted shape of the second tapered portion.

[0018] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for manufacturing the optical element, comprising the steps of: manufacturing a roll master on which a first fine uneven structure is formed; applying a resin layer made of a curable resin to the surface of the substrate of the optical element; and forming a second fine uneven structure including the structures of the optical element in the resin layer by transferring the first fine uneven structure of the roll master to the resin layer, wherein the first fine uneven structure includes a plurality of recesses having an inverted shape of the structures of the optical element, and the recesses have a composite structure consisting of a first tapered recess having an inverted shape of the first tapered portion, and a second tapered recess formed inside the first tapered recess and having an inverted shape of the second tapered portion.

[0019] The process for manufacturing the roll master includes: a film formation process for forming a resist layer on the outer peripheral surface of the master substrate of the roll master; an exposure process for forming a latent image by irradiating the resist layer with laser light; a development process for developing the resist layer on which the latent image has been formed and forming a pattern in the resist layer; and an etching process for etching the master substrate using the resist layer on which the pattern has been formed as a mask to form a concavo-convex pattern of the first fine concavo-convex structure on the outer peripheral surface of the master substrate, wherein in the etching process, etching conditions may be changed during etching of the master substrate to form the concavo-convex pattern having the composite structure consisting of the first tapered concavo-convex structure.

[0020] According to the present invention, an optical element can be provided that can ensure anti-reflection properties for incident light in a wide wavelength band from the visible light region to the near-infrared region, as well as for obliquely incident light at a high angle.

[0021] FIG. 1 is a partially enlarged cross-sectional view showing an optical film according to one embodiment of the present invention. FIG. 2 is a partially enlarged cross-sectional view showing a structure according to the same embodiment. FIG. 3 is a plan view showing a fine concavo-convex structure of the optical film according to the same embodiment. FIG. 4 is a perspective view schematically showing a roll master according to the same embodiment. FIG. 5 is a block diagram showing the configuration of an exposure device used in manufacturing the roll master according to the same embodiment. FIG. 6 is a schematic diagram showing an exposure method for the roll master according to the same embodiment. FIG. 7 is an explanatory diagram showing the correspondence between an exposure signal and an exposure pattern according to the same embodiment. FIG. 8 is a process diagram showing a method for manufacturing a roll master according to the same embodiment. FIG. 9 is a process diagram showing a method for manufacturing a roll master according to the same embodiment. FIG. 10 is a process diagram showing a method for manufacturing an optical film according to the same embodiment. FIG. 11 is a process diagram showing a method for manufacturing an optical film according to the same embodiment. FIG. 12 is a schematic diagram showing the configuration of a transfer device according to the same embodiment. FIG. 13 is a schematic diagram showing convex structures according to a comparative example. FIG. 14 is a schematic diagram showing convex structures according to an example. FIG. 15 is a graph showing the relationship between the height h of the convex structures according to the example and the average reflectance Re in the wavelength band of 400 to 950 nm. θ＝７０° Fig. 16 is a graph showing the relationship between the wavelength λ of incident light and the reflectance Re when the light is obliquely incident at a low angle of about 10°. Fig. 17 is a graph showing the relationship between the wavelength λ of incident light and the reflectance Re when the light is obliquely incident at a high angle of about 70°.

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Dimensions, materials, and other specific numerical values ​​shown in the embodiments are merely examples for facilitating understanding of the invention and, unless otherwise specified, do not limit the present invention. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0023] [1. Configuration of Optical Film] [1.1. Schematic Configuration of Optical Film] First, the schematic configuration of an optical film 1, which is an optical element according to one embodiment of the present invention, will be described with reference to Fig. 1. Fig. 1 is a partially enlarged cross-sectional view showing the optical film 1 according to this embodiment.

[0024] As shown in FIG. 1 , an optical film 1 according to this embodiment is an example of an optical element and is a film-like optical element. The optical film 1 is a transparent optical film (anti-reflection film) having an anti-reflection function and is transparent to visible light. For example, the optical film 1 is a moth-eye film having a microrelief structure 2 with anti-reflection properties formed on its surface. Note that, although this embodiment will mainly describe an example of an optical film 1 having a microrelief structure 2 formed on one surface of the optical film 1, the microrelief structure 2 may be formed on both surfaces (front and back) of the optical film 1.

[0025] Generally, when a periodic uneven structure is provided on the surface of a transparent film, diffraction occurs when light passes through the uneven structure, and the linear component of the transmitted light is significantly reduced. However, if the pitch of the uneven structure is shorter than the wavelength of the incident light (e.g., visible light or near-infrared light) that is transmitted, diffraction does not occur, and effective anti-reflection properties can be obtained for incident light with a wavelength corresponding to the pitch and depth of the uneven structure. Thus, among uneven structures, a fine uneven structure 2 having a pitch equal to or shorter than the wavelength of visible light is also called a moth-eye structure.

[0026] Forming the microrelief structure 2 on the surface of the optical film 1 can effectively suppress reflection at the interface between the optical film 1 and air. For example, when the optical film 1 is used in the windshield of the aforementioned automobile or an eye-tracking camera of a wearable device such as a VR, it is necessary to appropriately suppress the reflection of visible light or near-infrared light incident at a high incident angle θ to maintain a good field of view for the camera. From this perspective, the refractive index n of the optical film 1 is preferably 1.40 or more and 2.00 or less, and more preferably 1.43 or more and 2.00 or less. Furthermore, the transmittance of the optical film 1 at a wavelength of 550 nm is preferably 94.0% or more, more preferably 98.0% or more, particularly preferably 98.5% or more.

[0027] The surface region of the optical film 1 includes a concave-convex pattern region in which a fine concave-convex structure 2 is formed. The concave-convex pattern region is a transparent region (anti-reflection region) to which anti-reflection properties are imparted by the fine concave-convex structure 2. The fine concave-convex structure 2 is composed of a plurality of convex structures 3 (convex portions) and concave portions 4 arranged at a pitch P equal to or less than the wavelength of visible light (e.g., 350 nm or less). Due to this fine concave-convex structure 2, the concave-convex pattern region of the optical film 1 has an extremely low reflectance of incident light and a high light transmittance.

[0028] The optical film 1 according to this embodiment can be used as an anti-reflection film provided in the various devices described above. The wavelength λ of light incident on the optical film 1 (incident light) is in a wide wavelength band from the visible light region to the near-infrared region. The wavelength λ of the incident light is, for example, 380 nm to 780 nm, preferably 380 nm to 950 nm, and more preferably 380 nm to 2000 nm.

[0029] Furthermore, the optical film 1 according to this embodiment is applicable not only to incident light (normal incidence light: incident angle θ=0°) incident from a direction perpendicular (Z direction) to the surface (XY plane) of the optical film 1, but also to oblique incident light (incident angle θ>0°) incident from a direction inclined with respect to the perpendicular direction. In particular, the optical film 1 according to this embodiment is applicable not only to oblique incident light incident at a high incident angle θ of, for example, 45° or more, but also to oblique incident light incident at an ultra-high incident angle θ of, for example, about 70°.

[0030] As described above, the optical film 1 according to this embodiment exhibits anti-reflection properties against incident light in a wide wavelength range from the visible light region to the near-infrared region, and also ensures anti-reflection properties against obliquely incident light at a high angle. The configuration for realizing the excellent anti-reflection properties of the optical film 1 will be described in detail below.

[0031] [1.2. Layer Structure of Optical Film] Next, the layer structure of the optical film 1 according to this embodiment will be described in more detail with reference to FIG.

[0032] As shown in FIG. 1 , the optical film 1 includes, for example, a flexible, transparent substrate 11 and a transparent resin layer 12 laminated on at least one surface of the substrate 11. Thus, the optical film 1 according to this embodiment has, for example, a two-layer structure including the substrate 11 and the resin layer 12. However, the present invention is not limited to this example. A laminated structure of three or more layers may be formed by providing another intermediate layer, such as an adhesion layer (not shown) for enhancing adhesion, between the substrate 11 and the resin layer 12. Alternatively, a laminated structure of three or more layers may be formed by providing resin layers 12, 12 on both the front and back surfaces of the substrate 11. Furthermore, a coating layer or the like may be added on the surface of the resin layer 12. Alternatively, instead of separating the substrate 11 and the resin layer 12, the optical film may be integrally formed from the same material (e.g., glass material or resin material) to form a single-layer optical film.

[0033] The substrate 11 is a flexible, transparent film substrate. The substrate 11 may be composed of a single sheet-like transparent member, or may be composed of a plurality of sheet-like transparent members laminated together. The thickness of the substrate 11 is appropriately selected depending on the application of the optical film 1, and it is preferable to impart flexibility, rigidity, thickness, etc., according to the application.

[0034] Examples of materials for the substrate 11 include transparent plastic materials and glass materials. Specifically, examples of plastic materials for the substrate 11 include polyethylene terephthalate (PET), methyl methacrylate (co)polymers, polycarbonate, styrene (co)polymers, methyl methacrylate-styrene copolymers, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, polyester, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, and polyurethane. Examples of glass materials for the substrate 11 include soda-lime glass, lead glass, hard glass, quartz glass, and liquid crystal glass. However, the material for the substrate 11 is not particularly limited to the materials exemplified above.

[0035] When a plastic material is used as the substrate 11, a primer layer (not shown) may be further provided by surface treatment to further improve the surface energy, coatability, slipperiness, flatness, etc. of the surface of the plastic material. Examples of this primer layer include organoalkoxymetal compounds, polyester, acrylic-modified polyester, polyurethane, etc. Furthermore, to obtain the same effect as providing a primer layer, the surface of the substrate 11 may be subjected to corona discharge treatment, UV irradiation treatment, etc.

[0036] The substrate 11 can be formed, for example, by stretching the resin described above or diluting it in a solvent, forming it into a film, and then drying it. The thickness of the substrate 11 is preferably selected appropriately depending on the application of the optical film 1. The thickness of the substrate 11 is, for example, approximately 10 μm or more and 500 μm or less, preferably 50 μm or more and 500 μm or less, and more preferably 50 μm or more and 300 μm or less. When the thickness of the substrate 11 is 10 μm or more, the protective performance and durability of the optical film 1 are improved. On the other hand, when the thickness of the substrate 11 is 500 μm or less, the optical film 1 can be made lighter. Furthermore, the flexibility of the substrate 11 allows it to be curved and deformed. Therefore, the optical film 1 can be suitably attached to a curved surface, and the durability of the optical film 1 can also be improved.

[0037] The resin layer 12 is a transparent resin layer, and is laminated on the surface of the substrate 11. In order to suppress reflection inside the optical film 1 and improve contrast, the refractive index of the resin layer 12 is preferably the same as the refractive index of the substrate 11. Furthermore, the resin layer 12 preferably has the same transparency as the substrate 11. A concavo-convex pattern such as the fine concavo-convex structure 2 is formed on the resin layer 12. In this embodiment, the fine concavo-convex structure 2 is formed, for example, by transfer processing using a roll master, which will be described later.

[0038] The resin layer 12 is a layer formed of a curable resin. The resin layer 12 is formed, for example, of a cured product of a curable resin composition (transfer material) such as an energy ray-curable resin composition. In the process of forming the resin layer 12, first, an uncured energy ray-curable resin composition is applied as a transfer material onto the surface of the substrate 11, and the concavo-convex pattern of the microrelief structure 2 is transferred to the energy ray-curable resin composition. Thereafter, the curable resin composition is cured by irradiation with energy rays. As a result, a resin layer 12 to which the concavo-convex pattern of the microrelief structure 2 has been transferred is formed on the surface of the substrate 11.

[0039] The energy ray-curable resin composition is a resin that has the property of being cured by irradiation with energy rays. Here, the energy rays may be, for example, ultraviolet rays, electron beams, infrared rays, laser beams, visible light, ionizing radiation (X-rays, α-rays, β-rays, γ-rays, etc.), microwaves, or high frequency waves. From the viewpoint of ease of handling, for example, it is preferable to use an ultraviolet-curable resin composition as the energy ray-curable resin composition. The ultraviolet-curable resin composition is a resin that has the property of being cured by irradiation with ultraviolet rays.

[0040] Furthermore, the energy ray-curable resin composition may contain, as necessary, a filler or a functional additive, etc. For example, the ultraviolet ray-curable resin composition may contain an acrylate or an initiator, and may also contain a monofunctional monomer, a bifunctional monomer, a polyfunctional monomer, etc.

[0041] Furthermore, the cured product of the energy ray-curable resin composition may have hydrophilic properties. For this reason, the energy ray-curable resin composition preferably contains one or more functional groups having hydrophilic properties. Examples of such functional groups having hydrophilic properties include a hydroxyl group, a carboxyl group, and a carbonyl group.

[0042] [1.3. Features of the Microrelief Structure] Next, the features of the microrelief structure 2 of the optical film 1 according to this embodiment will be described in more detail with reference to FIGS. 1 to 3. FIG. 2 is a partially enlarged cross-sectional view showing the microrelief structure 2 of the optical film 1 according to this embodiment. FIG. 3 is a plan view showing the microrelief structure 2 of the optical film 1 according to this embodiment. For ease of explanation, in the thickness direction (Z direction) of the optical film 1, the direction toward the substrate 11 (-Z direction) will be referred to as the downward direction or lower side, and the direction opposite the substrate 11 (+Z direction) will be referred to as the upward direction or upper side.

[0043] 1 to 3, the fine concave-convex structure 2 (moth-eye structure) according to this embodiment is composed of a plurality of convex structures 3 (convex portions) and a plurality of concave portions 4. The plurality of convex structures 3 and the plurality of concave portions 4 are formed in a resin layer 12 laminated on the surface of a substrate 11 of an optical film 1. By providing the fine concave-convex structure 2 in the resin layer 12 in the concave-convex pattern region of the entire surface of the optical film 1, the surface (XY plane) of the concave-convex pattern region becomes the concave-convex surface of the moth-eye structure.

[0044] The convex structures 3 (convex portions) protrude in a direction (Z direction) perpendicular to the surface (XY plane) of the optical film 1. The multiple structures 3 are arranged on the surface (XY plane) of the substrate 11 at a pitch P that is equal to or less than the wavelength of visible light (for example, 350 nm or less).

[0045] The recesses 4 are recessed portions formed between adjacent structures 3, 3. The recesses 4 are also arranged on the surface (XY plane) of the substrate 11 at a pitch P that is equal to or less than the wavelength of visible light (for example, 350 nm or less).

[0046] The microrelief structure 2 according to this embodiment is characterized by the shape of the convex structures 3. The structures 3 according to this embodiment have a composite structure in which at least two tapered portions (a first tapered portion 31 and a second tapered portion 32) are stacked in the thickness direction (Z direction) of the optical film 1.

[0047] In detail, the structure 3 has a composite structure consisting of a first tapered portion 31 (lower tapered portion) and a second tapered portion 32 (upper tapered portion). The first tapered portion 31 and the second tapered portion 32 are structures having a tapered shape that becomes thinner with increasing distance from the substrate 11. The first tapered portion 31 is formed on the surface of the substrate 11 and is a portion that serves as a base on the bottom side of the structure 3. The second tapered portion 32 is formed on the first tapered portion 31 and is a portion that serves as the apex on the tip side of the structure 3.

[0048] The first tapered portion 31 has a tapered shape, for example, a truncated cone shape, that narrows toward the upper side in the Z direction (the side opposite to the substrate 11). The shape of the first tapered portion 31 in the example shown in FIGS. 1 and 2 is a truncated cone shape, but other truncated cone shapes are also acceptable. For example, the first tapered portion 31 may be an elliptical truncated cone shape, or any other truncated cone shape, such as a triangular truncated cone, a square truncated cone, a hexagonal truncated cone, or an octagonal truncated cone. Furthermore, the first tapered portion 31 preferably has a truncated cone shape that is symmetrical with respect to a central axis in the Z direction, but may also have a truncated cone shape that is asymmetrical with respect to the central axis.

[0049] The second tapered portion 32 has a tapered shape, such as a cone shape or a frustum shape, that narrows toward the upper side in the Z direction (the side opposite the substrate 11). The shape of the second tapered portion 32 in the example shown in FIGS. 1 and 2 is a truncated cone shape, but other truncated cone shapes are also acceptable. For example, the second tapered portion 32 may be an elliptical truncated cone shape, or any other truncated cone shape, such as a triangular truncated cone, a square truncated cone, a hexagonal truncated cone, or an octagonal truncated cone. Examples of truncated cone shapes include a flat-topped truncated cone shape and a truncated cone shape with a convex or concave curved top. The shape of the second tapered portion 32 may also be a pyramid shape with a pointed apex, such as a cone shape or an elliptical cone shape, or any other pyramid shape, such as a triangular pyramid, a square pyramid, a hexagonal pyramid, or an octagonal pyramid. Furthermore, the second tapered portion 32 is preferably a truncated cone shape or a pyramid shape that is symmetrical with respect to the central axis in the Z direction, but may also be a truncated cone shape or a pyramid shape that is asymmetrical with respect to the central axis.

[0050] A single structure 3 is formed by stacking the first tapered portion 31 and the second tapered portion 32 one above the other. The bottom of the lower first tapered portion 31 is disposed on the surface of the substrate 11 or adjacent to the surface. The top of the lower first tapered portion 31 and the bottom of the upper second tapered portion 32 are joined together.

[0051] Therefore, as shown in FIG. 2, the diameter φ of the bottom of the first tapered portion 31 １ and the diameter φ of the top of the first tapered portion 31 ２ and the diameter φ of the top of the second tapered portion 32 ３ Compared with φ １ >φ２ >φ ３ The diameter φ of the top of the first tapered portion 31 is ２ is equal to the diameter of the bottom of the second tapered portion 32, and both are φ ２ is.

[0052] In this embodiment, since the second tapered portion 32 has a frustum shape, the top of the second tapered portion 32 is a substantially flat surface, and the diameter φ of the top (substantially flat top surface) of the second tapered portion 32 is ３ is greater than 0 (φ ３ >0). However, the present invention is not limited to this example, and the top (curve surface) of the second tapered portion 32 may be a convex or concave curved surface instead of a flat surface. In addition, when the second tapered portion 32 has a cone shape, the tip of the second tapered portion 32 has a pointed shape, so the diameter φ of the top of the second tapered portion 32 ３ may be substantially zero (φ ３ ≒0).

[0053] 1 to 3, in this embodiment, for example, a plurality of structures 3 are arranged without gaps on the surface (XY plane) of the substrate 11, and the bottoms of the first tapered portions 31 of adjacent structures 3 are in contact with each other. In this case, the arrangement pitch P of the structures 3 is set to a value obtained by multiplying the diameter φ of the bottom of the first tapered portion 31 by the distance φ. １ (P≒φ １ ). In this way, by arranging the plurality of structures 3 without any gaps, the packing rate of the structures 3 on the surface (XY plane) of the optical film 1 can be increased, and the area of ​​the flat surface where the structures 3 are not present can be reduced, thereby improving the anti-reflection properties. However, without being limited to such an example, the plurality of structures 3 may be arranged on the surface (XY plane) of the substrate 11 with some gaps between them. In this case, the arrangement pitch P of the structures 3 is set to be equal to or smaller than the diameter φ of the bottom of the first tapered portion 31. １ is larger than (P>φ １ The filling rate is the ratio of the area occupied by the structures 3 on the surface of the optical film 1 when the surface (XY plane) is viewed in plan view.

[0054] [1.4. Characteristics of Tapered Shape and Taper Ratio] Next, the tapered shapes and taper ratios of the first tapered section 31 and the second tapered section 32 according to this embodiment will be described in more detail.

[0055] 1 and 2, the tapered shape of the first tapered section 31 is preferably an approximately linear tapered shape, and the vertical cross-sectional shape of the tapered surface (side surface) of the first tapered section 31 is preferably a substantially straight line. Similarly, the tapered shape of the second tapered section 32 is preferably an approximately linear tapered shape, and the vertical cross-sectional shape of the tapered surface (side surface) of the second tapered section 32 is preferably a substantially straight line.

[0056] Here, the term "approximate linear taper shape" includes a linear taper shape and a shape that is substantially considered to be a linear taper shape. A linear taper shape is a taper shape in which the diameter of the tapered portion changes linearly. In a linear taper shape, the vertical cross-sectional shape of the tapered surface consists of straight lines and does not include curves. A shape that is substantially considered to be a linear taper shape is a shape that can be considered to be a linear taper shape if the error range is allowed, even though there is a slight deviation within the error range from a perfect linear taper shape due to molding errors when molding the tapered portion.

[0057] The tapered shapes of the first tapered portion 31 and the second tapered portion 32 according to this embodiment are preferably linear tapered shapes, but may be shapes that approximate a linear tapered shape and do not have to be completely linear tapered shapes. In other words, as long as the vertical cross-sectional shape of the tapered surfaces of the first tapered portion 31 and the second tapered portion 32 is a tapered shape consisting essentially of straight lines, the vertical cross-sectional shape may be a tapered shape that includes partially curved lines or minute irregularities.

[0058] In this way, the first tapered portion 31 and the second tapered portion 32 according to this embodiment have a taper ratio C １ , C ２ The two different linear tapered approximation shapes are combined to have an effect of improving the anti-reflection properties for incident light in different wavelength bands, such as the visible light region and the near-infrared region.

[0059] Next, the taper ratios of the first tapered portion 31 and the second tapered portion 32 will be described. As shown in FIGS. 1 and 2, the taper ratio C ２ is the taper ratio C of the side surface of the first tapered portion 31 １ is smaller than (C ２ <C １ ). In other words, the second tapered portion 32 has a tapered shape that is thinner than the first tapered portion 31 and has a tapered, needle-like shape that narrows. From this perspective, the second tapered portion 32 can be said to be a long, thin, needle-like structure. On the other hand, the first tapered portion 31 has a tapered shape that is thicker than the second tapered portion 32 and has a stable tapered shape that becomes thicker toward the substrate 11 side. From this perspective, the first tapered portion 31 can be said to be a relatively thick, base-like structure.

[0060] Here, the taper ratio C of the first tapered portion 31 １ is calculated by the following formula (1), and the taper ratio C of the second tapered portion 32 is ２ is calculated by the following formula (2). １ is the height of the first tapered portion 31 in the Z direction, and h ２ is the height of the second tapered portion 32 in the Z direction. １ = (φ １ -φ ２ ) / h １ ... (1) C ２ = (φ ２ -φ ３ ) / h ２ ...(2)

[0061] Taper ratio C of the first tapered portion 31 １ is preferably 0.30 to 0.75, and more preferably 0.30 to 0.65. This has the effect of improving the anti-reflection characteristics against obliquely incident light at a high angle. In addition, the taper ratio C of the second tapered portion 32 is ２ is preferably, for example, 0.10 to 0.18, and more preferably 0.12 to 0.18, which has the effect of improving the anti-reflection properties against obliquely incident light at a high angle.

[0062] The taper ratio C of the first tapered portion 31 １The taper ratio C of the second tapered portion 32 to ２ The ratio (C ２ / C １ ) is preferably 0.2 to 0.5, and more preferably about 0.5, which has the effect of improving the anti-reflection properties against obliquely incident light at a high angle.

[0063] As described above, the taper ratio C of the first tapered portion 31 １ is the taper ratio C of the second tapered portion 32 ２ Unlike C ２ is C １ is smaller than (C ２ <C １ ). In other words, the taper angle of the first tapered portion 31 is larger than the taper angle of the second tapered portion 32. Therefore, the inclination angle of the side surface (tapered surface) of the second tapered portion 32 with respect to the XY plane is larger than the inclination angle of the side surface (tapered surface) of the first tapered portion 31 with respect to the XY plane. As a result, the side surface (tapered surface) of the entire structure 3, which is the combination of the first tapered portion 31 and the second tapered portion 32, has a shape that is recessed near the center in the Z direction (the position of the change point 33).

[0064] The structure 3 has a change point 33 at which the taper ratio of the side surface (tapered surface) of the entire structure 3 changes discontinuously at the junction between the top of the first tapered portion 31 and the bottom of the second tapered portion 32. Below the change point 33 (junction position), the side surface of the structure 3 is the side surface of the first tapered portion 31 having a linearly tapered approximation shape, and has a constant taper ratio C １ On the other hand, above the change point 33 (bonding position), the side surface of the structure 3 is a side surface of the second tapered portion 32 having a linearly tapered approximation shape, and has the above taper ratio C １ A constant taper ratio C smaller than ２ It has.

[0065] In this way, the structure 3 according to this embodiment has different taper ratios C １ , C ２ The structure 3 has a composite structure consisting of a first tapered portion 31 and a second tapered portion 32 having a taper ratio C １ , C ２There is provided a change point 33 where the two types of tapered structures, the first tapered section 31 and the second tapered section 32, work to exhibit anti-reflection properties against incident light in a wide wavelength band including the visible light region and the near-infrared region, and against obliquely incident light at a wide range of incident angles.

[0066] [1.5. Characteristics of the Height of the Structure] Next, the height h of the structure 3 according to this embodiment and the height h of the first tapered portion 31 will be described. １ , and the height h of the second tapered portion 32 ２ will be explained in more detail.

[0067] As shown in FIG. 2 , the height h of the structures 3 is the height of the structures 3 in the Z direction (thickness direction of the optical film 1). The height h of the structures 3 is the height h of the first tapered portion 31. １ and the height h of the second tapered portion 32 ２ and the sum of (h = h １ +h ２ It is preferable that the height h of the plurality of structures 3 constituting the fine concave-convex structure 2 is approximately the same, but some error in the height h between the plurality of structures 3 is acceptable.

[0068] The height h of the structures 3 is preferably 400 nm or more. As a result, the plurality of structures 3 constituting the fine uneven structure 2 have a height h suitable for antireflection, and therefore, antireflection properties can be ensured not only for incident light in the short-wavelength visible light range, but also for incident light in the long-wavelength near-infrared range and for oblique incident light at a wide range of incident angles.

[0069] Furthermore, the height h of the structures 3 is more preferably 490 nm or more, and even more preferably 560 nm or more, which makes it possible to ensure antireflection properties against incident light in an even wider wavelength band from the visible light region to the near-infrared region.

[0070] The height h of the structures 3 is preferably 1500 nm or less, and more preferably 1000 nm or less, in the visible range, for example, which has the effect of suppressing transfer defects.

[0071] The height h of the second tapered portion２ is preferably 160 to 300 nm, and more preferably 190 to 230 nm, which has the effect of improving the anti-reflection properties at wide angles of incidence.

[0072] Height h of the first tapered portion １ is preferably 150 to 500 nm, more preferably 220 to 340 nm, which has the effect of improving anti-reflection properties while improving transfer defects.

[0073] The height h of the structures 3 may be the arithmetic mean value (average height) of the heights of the structures 3 constituting the fine concave-convex structure 2. For example, the heights of the structures 3 constituting the fine concave-convex structure 2 are measured, and the arithmetic mean value (average height) of these measured values ​​can be calculated as the height h. Similarly, the height h of the first tapered portion 31 １ and the height h of the second tapered portion 32 ２ can also be calculated using the arithmetic mean value.

[0074] [1.6. Characteristics of Arrangement of Structural Elements] Next, the arrangement of the plurality of structural elements 3 on the surface of the optical film 1 according to this embodiment will be described in more detail.

[0075] As shown in FIG. 3 , the planar shape (dot shape) of the structures 3 when projected onto the surface (XY plane) of the optical film 1 is, for example, circular; however, this is not limited to this example and may be any shape, such as an ellipse, an oval, or a polygon.

[0076] 1 to 3, the multiple structures 3 of the microrelief structure 2 have the same size, shape, and height h. However, the configuration of the structures 3 is not limited to this, and two or more types of structures 3 having different sizes, shapes, and heights may be formed on the surface of the resin layer 12.

[0077] The structures 3 and recesses 4 of the microrelief structure 2 (hereinafter sometimes referred to as "the recesses and protrusions of the microrelief structure 2") are periodically arranged on the surface (XY plane) of the substrate 11 at a predetermined pitch P. In this way, the microrelief structure 2 has a periodic structure in which a plurality of structures 3 and recesses 4 are periodically arranged on the XY plane. Here, the pitch P is the center-to-center distance (vertex-to-vertex distance) between adjacent structures 3, 3, as shown in Figures 2 and 3. In this way, the pitch P of the recesses and protrusions of the microrelief structure 2 means the period of the periodic structure of the microrelief structure 2.

[0078] The pitch P of the concave-convex structure 2 may be the arithmetic mean value (average pitch, average period) of the center-to-center distance between adjacent structures 3, 3 in the fine concave-convex structure 2. For example, a plurality of combinations of adjacent structures 3, 3 in the fine concave-convex structure 2 can be picked up, the center-to-center distance between the structures 3, 3 in each combination can be measured, and the arithmetic mean value (average pitch, average period) of these measured values ​​can be calculated as the pitch P. The concave-convex pattern of the fine concave-convex structure 2 can be observed using, for example, a scanning electron microscope (SEM) or a cross-sectional transmission electron microscope (cross-sectional TEM).

[0079] In this embodiment, in order to impart anti-reflection properties to visible light, the pitch P of the concave-convex structure 2 is equal to or less than the wavelength of visible light. Here, the wavelength band of visible light is 360 nm to 830 nm, and the concave-convex structure 2 according to this embodiment has a regular arrangement with a pitch P less than the wavelength band of visible light. From this viewpoint, the pitch P of the concave-convex structure 2 may be, for example, 350 nm or less, preferably 250 nm or less, for example, about 200 nm. Furthermore, the pitch P of the concave-convex structure 2 may be, for example, 100 nm or more, preferably 120 nm or more, and more preferably 130 nm or more. A pitch P of less than 100 nm is undesirable because it may be difficult to form the concave-convex structure 2. On the other hand, a pitch P of more than 350 nm is undesirable because the intensity of diffracted light may increase, which may cause external light to be diffracted on the surface on which the concave-convex structure 2 is formed, thereby reducing the anti-reflection effect. If the pitch P is 350 nm or less, the anti-reflection properties of the fine concave-convex structure 2 can be improved, and a desired anti-reflection effect can be obtained.

[0080] The aspect ratio (height h / pitch P) of the structures 3 of the microrelief structure 2 is preferably 0.66 or more and 1.96 or less, more preferably 0.76 or more and 1.96 or less. When the aspect ratio is 0.66 or more, low reflection characteristics can be improved. On the other hand, when the aspect ratio is 1.96 or less, releasability when peeling the microrelief structure 2 from the roll master can be improved.

[0081] 3, the size D of the structures 3 of the microrelief structure 2 is the size (dot size) of the planar shape of the structures 3 when the structures 3 of the microrelief structure 2 are projected onto the surface (XY plane) of the optical film 1. The size D of the structures 3 according to this embodiment is the diameter φ of the bottom of the first tapered portion 31 described above. １ (D=φ １ For example, when the planar shape of the structure 3 is a circle, the size D of the structure 3 is the diameter of the circle, and when the planar shape of the structure 3 is an ellipse, the size D of the irregularities is the major axis of the ellipse.

[0082] The size D of the structures 3 is determined depending on the exposure resolution when exposing the concave-convex pattern of the fine concave-convex structure to the outer peripheral surface of the roll master in the roll master manufacturing method described later. The size D of the structures 3 is equal to or smaller than the pitch P (for example, equal to or smaller than 350 nm) (D≦P), and is preferably equal to the pitch P (D≈φ １ ≒P), for example, about 200 nm. For example, as shown in FIG. 3 , if the size D of the structures 3 is set to be equal to the pitch P, multiple structures 3 can be densely arranged on the XY plane, thereby reducing the area of ​​the gap between adjacent structures 3. The size D of the structures 3 may be the arithmetic mean value (average size) of the sizes of the planar shapes of the multiple structures 3 that make up the fine concave-convex structure 2. For example, the sizes of the planar shapes of the multiple structures 3 that make up the fine concave-convex structure 2 can be measured, and the arithmetic mean value (average size) of these measured values ​​can be calculated as the size D.

[0083] Here, the arrangement of the concavo-convex pattern of the micro concavo-convex structure 2 on the surface (XY plane) of the optical film 1 according to this embodiment will be described in more detail with reference to Fig. 3. In Fig. 3, the X direction corresponds to the longitudinal direction of the optical film 1, the Y direction corresponds to the width direction of the optical film 1, and the Z direction corresponds to the thickness direction of the optical film 1.

[0084] As shown in Fig. 3, a plurality of structures 3 of the microrelief structure 2 are arranged in a hexagonal lattice pattern on the surface of the optical film 1 according to this embodiment. In the hexagonal lattice pattern, the plurality of structures 3 are arranged at the vertices of the hexagonal lattice on the XY plane. In the example of Fig. 3, the planar shape of the structures 3 is circular, but it may be other shapes such as elliptical or polygonal.

[0085] Here, the plurality of structures 3 are arranged along a plurality of tracks T that are parallel to one another. In other words, the plurality of structures 3 are arranged along a plurality of rows of tracks T on the surface of the optical film 1.

[0086] The tracks T are virtual straight lines extending in a predetermined first direction (X direction) on the XY plane of the optical film 1, and indicate the arrangement direction of the concavo-convex pattern of the fine concavo-convex structure 2. A plurality of tracks T are arranged at predetermined intervals (track pitch P) in a second direction (Y direction) perpendicular to the first direction (X direction). Ｔ ) are spaced apart. Here, the first direction is the direction in which the tracks T extend (hereinafter referred to as the "track extension direction"). The second direction is the direction in which the tracks T are arranged (hereinafter referred to as the "track pitch direction"), and is a direction perpendicular to the first direction. For example, as shown in FIG. 3 , the first direction (track extension direction) may be the longitudinal direction (X direction) of the optical film 1, and the second direction (track pitch direction) may be, for example, the width direction (Y direction) of the optical film 1. However, the present invention is not limited to this example, and the track extension direction may be any direction other than the longitudinal direction (X direction) of the optical film 1.

[0087] Here, as shown in FIG. 3, the dot pitch P Ｄ is the pitch P (period) of the plurality of structures 3 arranged along the track T in the track extension direction (X direction). Ｔ is the mutual interval between a plurality of tracks T, T adjacent to each other in the track pitch direction (Y direction).

[0088] Dot pitch P Ｄ and track pitch P Ｔ Similarly to the pitch P described above, P is equal to or less than the wavelength of visible light, for example, 350 nm or less, preferably 250 nm or less, and may be, for example, about 200 nm. Ｄ , P Ｔ is, for example, 100 nm or more, preferably 120 nm or more, and more preferably 130 nm or more. This allows the fine uneven structure 2 to function as a so-called moth-eye structure that suppresses reflection of incident light in a wide wavelength band.

[0089] Dot pitch P Ｄ and track pitch P ＴThe dot pitches P may be the same or different as long as they are within the above range. Ｄ is the track pitch P Ｔ (P Ｄ >P Ｔ ). For example, P Ｄ = 230 nm, P Ｔ = 150 nm.

[0090] In addition, in the hexagonal lattice arrangement of the fine concave-convex structure 2 shown in FIG. 3, the structures 3 are spaced apart at half a pitch (½P) in the X direction between the tracks T, T adjacent to each other in the Y direction. Ｄ ). That is, between tracks T, T adjacent in the Y direction, the phases of the structures 3 arranged in the X direction are shifted by half a period (180°). Specifically, between two adjacent tracks T, T, the structures 3 arranged in one track T are arranged at the middle position in the X direction (a position shifted by half a pitch) of the structures 3 arranged in the other track T. As a result, as shown in FIG. 3 , a plurality of structures 3 are arranged in a hexagonal lattice pattern in three adjacent rows of tracks T.

[0091] In this way, the arrangement of the structures 3 is set to a half pitch (½P) for each track T. Ｄ ) the plurality of structures 3 can be arranged in a close-packed hexagonal lattice pattern on the XY plane. Therefore, the proportion of the area occupied by the plurality of structures 3 on the XY plane (the packing rate of the structures 3) can be maximized, thereby improving the antireflection function per unit area.

[0092] The arrangement of the projections and recesses of the microrelief structure 2 is not limited to the above-mentioned hexagonal lattice example, and may be other arrangements. For example, the arrangement of the projections and recesses of the microrelief structure 2 may be a square lattice arrangement in which the structures 3 are arranged at the vertices of a square lattice, a rectangular lattice arrangement, or another lattice arrangement. However, in order to pack the structures 3 most densely on the XY plane, a hexagonal lattice arrangement is preferable.

[0093] Furthermore, the shape of the tracks T is not limited to the linear track T example described above, but may be, for example, tracks of curved shapes such as arcs arranged concentrically. Furthermore, the tracks T of these shapes may be made to wobble (meander). By making the tracks T wobble in this way, it is possible to suppress the occurrence of unevenness in appearance.

[0094] 1.7. Principle of Antireflection Properties Next, the principle of how the optical film 1 according to this embodiment has excellent antireflection properties against incident light in a wide wavelength range and obliquely incident light at a high angle will be described.

[0095] As described above, the optical film 1 according to this embodiment exhibits anti-reflection properties against incident light in a wide wavelength range from the visible light region to the near-infrared region, while also ensuring anti-reflection properties against obliquely incident light at a high angle, for example, about 45 to 70°. In order to achieve such excellent anti-reflection properties, each structure 3 of the fine concave-convex structure 2 of the optical film 1 according to this embodiment has a composite structure (two-stage tapered structure) consisting of the above-mentioned first tapered portion 31 and second tapered portion 32. The second tapered portion 32 is needle-shaped and thinner than the first tapered portion 31, and the taper ratio C ２ is the taper ratio C of the first tapered portion 31 １ In addition, the height h of the structures 3 is 400 nm or more, and preferably 490 nm or more.

[0096] Here, to enhance the anti-reflection properties for incident light in the short wavelength range, such as the visible light range, thin, needle-like convex structures (corresponding to the second tapered portion 32) having a height of approximately 200 nm may be employed, and the convex structures may be arranged at a pitch equal to or less than the wavelength of visible light (e.g., 380 nm). A fine uneven structure formed from such convex structures reduces the effective spatial refractive index on the surface of the optical film. Therefore, the interference effect of light waves in the visible light range weakens reflected light, thereby enhancing the anti-reflection properties. However, when a fine uneven structure formed from convex structures having a height of approximately 200 nm is used, the anti-reflection properties for incident light in the near-infrared range (e.g., 800 nm to 950 nm) are adversely affected.

[0097] Therefore, in order to realize an anti-reflection structure that utilizes an interference effect according to each wavelength band of incident light, it is necessary to set the height of the convex structures in proportion to the wavelength λ of the incident light. Therefore, when the total height of the convex structures is around 200 nm, anti-reflection properties can only be obtained for incident light in the visible light range, and anti-reflection properties cannot be obtained for incident light in the near-infrared range.

[0098] Furthermore, with regard to the property of the antireflection characteristics that change depending on the angle of incidence θ of obliquely incident light (incident angle dependency), when light is obliquely incident at an extremely high angle of about 70°, the wavelength band in which the antireflection characteristics are effective shifts to the short wavelength side. Therefore, in order to accommodate both oblique incidence and long wavelength bands, it is necessary to ensure that the total height of the convex structures is sufficiently high.

[0099] Therefore, to prevent reflection of incident light of long wavelengths such as the near-infrared region, the total height of the convex structures should be set to 400 nm or more. This makes it possible to prevent reflection of light of a long wavelength band of about 950 nm due to the interference effect between the waves of the incident light when the light is obliquely incident at an ultra-high angle of about 70°. However, when the convex shape of the convex structures is a simple elliptical cone shape as described in Patent Document 1, the wave interference effect can prevent reflection only of incident light of long wavelengths, and the wave interference effect is weakened for incident light of a short wavelength band such as the visible light region, resulting in a problem of deterioration of anti-reflection properties.

[0100] Therefore, in the optical film 1 according to this embodiment, the height h of the convex structures 3 is set to 400 nm or more as described above, and a thin, needle-like second tapered portion 32 (needle-like structure) is provided on the tip side of the structures 3, and a composite structure consisting of the second tapered portion 32 and the first tapered portion 31 is adopted. In this case, a taper ratio C １ , C ２A change point 33 is formed where the wavelengths of the incident light components clearly change. Such a composite structure 3 produces two interference effects of light waves of different wavelength bands, making it possible to prevent reflection of incident light in the visible light range while also preventing reflection of incident light in the near-infrared range. Therefore, excellent anti-reflection properties can be exhibited against incident light in a wide wavelength range from the visible light range to the near-infrared range.

[0101] In contrast, in the conventional technology described in Patent Document 2, the side shape of the structure changes gently to form an S-shaped curve, and there is no clear change point 33 like in the side of the structure 3 according to this embodiment. In the conventional technology of Patent Document 2, the change point of the wave interference effect is not clear, which causes a problem in that the anti-reflection properties due to the interference effect of waves in two different wavelength bands are weakened.

[0102] In this regard, the structure 3 according to this embodiment has a taper ratio C １ , C ２ The tapered portion 31 has a composite structure of two tapered portions 31 and 32 with different taper ratios C １ , C ２ Therefore, according to the structure 3 of this embodiment, it is possible to prevent reflection of incident light in a wide wavelength band from the visible light region to the near-infrared region, and also to prevent reflection of obliquely incident light at an ultra-high angle of about 70°.

[0103] [1.8. Uses of Optical Film] The optical film 1 according to this embodiment can be applied to various devices, such as the above-mentioned on-board camera for the autonomous driving technology of automobiles, a highly inclined windshield arranged adjacent to the on-board camera, an eye-tracking camera for a wearable device that uses VR or AR, a display device provided in a smartphone or personal computer, or the like, a cover glass thereof, or an optical component. However, without being limited to such examples, the optical film 1 may also be used as, for example, a shielding member such as a face shield or an eye shield, or an anti-reflection film for other uses. The optical film 1 may also be used as, for example, a surface plasmon filter, a light-emitting device, or any other optical component.

[0104] By applying the optical film 1 including the structure 3 according to this embodiment as an anti-reflection film to the various devices described above, the sensitivity of the image sensor of the camera provided in the device can be improved, thereby improving the accuracy of autonomous driving using the camera and the operating accuracy of VR devices, etc., and reducing the size and weight of the various devices.

[0105] [2. Configuration of Roll Master] [2.1. Overall Configuration of Roll Master] Next, the configuration of the roll master 100 used to produce the optical film 1 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a perspective view schematically showing the roll master 100 according to this embodiment.

[0106] As shown in FIG. 4 , the roll master 100 according to this embodiment includes a cylindrical or columnar master substrate 110 and a fine concave-convex structure 120 (convex-convex pattern) formed on the outer peripheral surface of the master substrate 110.

[0107] The roll master 100 according to this embodiment is a master used in, for example, a roll-to-roll imprinting technique. In the roll-to-roll imprinting technique, the outer peripheral surface of the roll master 100 is pressed against a band-shaped optical film while the roll master 100 is rotating, thereby transferring the concave-convex pattern formed on the outer peripheral surface of the roll master 100 to the surface of the optical film. By using such an imprinting technique, it is possible to efficiently manufacture a large-area optical film 1 to which the concave-convex pattern formed on the outer peripheral surface of the roll master 100 has been transferred.

[0108] The roll master 100 according to this embodiment is a roll-shaped master having a cylindrical or columnar shape. The outer peripheral surface of the roll master 100 serves as a molding surface for molding a concave-convex structure on the surface of the optical film 1. A concave-convex pattern to be a transfer pattern is arranged two-dimensionally on the outer peripheral surface of this roll master 100. The concave-convex pattern (first fine concave-convex structure) arranged on the outer peripheral surface of the roll master 100 and the concave-convex pattern (second fine concave-convex structure) arranged on the surface of the optical film 1 have an inverted concave-convex relationship. That is, the shape, arrangement, arrangement pitch, etc. of the concave-convex pattern of the roll master 100 are the same as those of the concave-convex pattern of the optical film 1.

[0109] The master substrate 110 is, for example, a cylindrical or columnar member as shown in Fig. 4. The concave-convex pattern to be transferred (fine concave-convex structure 120) is formed on the outer peripheral surface of the master substrate 110. The master substrate 110 may be made of a glass material such as fused silica glass or synthetic silica glass, or may be made of a metal such as stainless steel, or a metal having an outer peripheral surface coated with SiO ２ It may be configured as a material coated with, for example.

[0110] However, it is preferable that at least the outer peripheral surface of the master substrate 110 is made of a glass material such as quartz glass. Furthermore, it is more preferable that the entire master substrate 110 is made of a glass material such as quartz glass. The reason for this is that SiO ２ This is because, by forming the master substrate 110 from a glass material containing fluorine as a main component, a fine concave-convex pattern can be easily formed on the outer peripheral surface of the master substrate 110 by etching using a fluorine compound. Specifically, a concave-convex pattern is formed on a resist layer provided on the outer peripheral surface of the master substrate 110 using laser light lithography. Thereafter, the outer peripheral surface of the master substrate 110 is dry-etched using the concave-convex pattern of the resist layer as a mask, thereby easily forming a concave-convex pattern on the outer peripheral surface of the master substrate 110. The master substrate 110 formed from a glass material is, for example, a transparent roll type.

[0111] The size of the master substrate 110 is not particularly limited, but the axial length (roll width) of the master substrate 110 may be, for example, 100 mm or more, and the outer diameter of the master substrate 110 may be, for example, 50 mm or more and 300 mm or less. Furthermore, when the master substrate 110 has a cylindrical shape, the thickness of the cylinder may be, for example, 2 mm or more and 50 mm or less.

[0112] As shown in Fig. 4, a concave-convex pattern region 102 is provided on the outer peripheral surface of the master substrate 110 according to this embodiment. The concave-convex pattern region 102 is a cylindrical curved surface region provided around the entire circumference of the roll master 100 in the circumferential direction (hereinafter also referred to as the "roll circumferential direction"), and occupies most of the outer peripheral surface of the master substrate 110. For example, the width of the concave-convex pattern region 102 in the roll width direction may be several hundred mm (e.g., 500 mm). The concave-convex pattern region 102 of such a roll master 100 corresponds to the concave-convex pattern region of the optical film 1 described above (the region where the fine concave-convex structure 2 is formed).

[0113] 2.2. Configuration of the Fine Relief Structure in the Relief Pattern Region Next, with reference to FIG. 4, the fine relief structure 120 formed in the relief pattern region 102 on the outer peripheral surface of the roll master 100 according to this embodiment will be described in detail.

[0114] A fine concave-convex structure 120 (first fine concave-convex structure) is formed as a transfer pattern in the concave-convex pattern region 102 of the roll master 100. This fine concave-convex structure 120 (first fine concave-convex structure) of the roll master 100 has an inverted shape of the fine concave-convex structure 2 (second fine concave-convex structure) of the optical film 1. In other words, the recesses 130 of the fine concave-convex structure 120 of the roll master 100 have an inverted shape corresponding to the convex structures 3 (convex portions) of the fine concave-convex structure 2 of the optical film 1. Furthermore, the convex portions 140 of the fine concave-convex structure 120 of the roll master 100 have an inverted shape corresponding to the recesses 4 of the fine concave-convex structure 2 of the optical film 1.

[0115] In the example of the fine concave-convex structure 120 shown in Fig. 4, a plurality of recesses 130 having a circular planar shape are formed in the concave-convex pattern region 102 of the roll master 100. These recesses 130 are arranged in a hexagonal lattice pattern on the outer peripheral surface of the master substrate 110. The convex portions 140 are protruding portions provided between the plurality of adjacent recesses 130, 130.

[0116] Each recess 130 has a composite structure consisting of an outer first tapered recess 131 and an inner second tapered recess 132. The second tapered recess 132 is formed at the center inside the first tapered recess 131. The inner diameter of the second tapered recess 132 is smaller than the inner diameter of the first tapered recess 131. The second tapered recess 132 is positioned deeper than the first tapered recess 131.

[0117] The first tapered recess 131 is a relatively thick tapered recess, and has an inverted shape of the first tapered portion 31 of the structure 3 of the optical film 1 described above (see FIGS. 9 and 10). The second tapered recess 132 is a relatively elongated tapered recess, and has an inverted shape of the second tapered portion 32 of the structure 3 of the optical film 1 described above (see FIGS. 9 and 10). The taper ratio and depth of the first tapered recess 131 are respectively the taper ratio C of the first tapered portion 31 １ and height h １ Similarly, the taper ratio and depth of the second tapered recess 132 are substantially the same as the taper ratio C of the second tapered portion 32, respectively. ２ and height h ２ is substantially identical to

[0118] As described above, the recesses 130 of the microrelief structure 120 of the roll master 100 have a composite structure consisting of the first tapered recesses 131 and the second tapered recesses 132, and have a shape corresponding to the composite structure of the structures 3 of the optical film 1. Therefore, by transferring the microrelief structure 120 consisting of the plurality of recesses 130 to the optical film 1, it is possible to appropriately form the microrelief structure 2 consisting of the plurality of structures 3 shown in Fig. 1 on the surface of the optical film 1. Details of the transfer of such a microrelief structure 120 will be described later.

[0119] Next, the arrangement of the plurality of recesses 130 that constitute the microrelief structure 120 will be described in detail. On the outer peripheral surface of the roll master 100 according to this embodiment, the plurality of recesses 130 of the microrelief structure 120 are arranged in a hexagonal lattice pattern at a pitch P' that is equal to or less than the wavelength of visible light. The pitch P' of the recesses 130 of the microrelief structure 120 is the same as the pitch P of the structures 3 of the microrelief structure 2 of the optical film 1 described above. The pitch P' is equal to or less than the wavelength of visible light, and may be, for example, 350 nm or less, preferably 250 nm or less, and may be, for example, about 200 nm.

[0120] Here, similar to the hexagonal lattice arrangement of the structures 3 of the fine concave-convex structure 2 described above (see FIG. 3), the recesses 130 of the fine concave-convex structure 120 of the roll master 100 are also arranged along a plurality of tracks T' that are parallel to one another, as shown in the enlarged view of FIG. 4. The plurality of tracks T' are arranged at predetermined intervals (track pitch P) in a second direction (track pitch direction) perpendicular to the first direction (track extension direction). Ｔ For example, as shown in FIG. 4, the first direction (track extension direction) may be the roll circumferential direction, and the second direction may be the roll width direction.

[0121] Here, the dot pitch P Ｄ The track pitch P′ is the pitch (period) of the plurality of recesses 130 arranged in the first direction (for example, the roll circumferential direction) along the track T′. Ｔ The dot pitch P′ of the recesses 130 of the micro concave-convex structure 120 is the distance between the tracks T′ arranged adjacent to each other in the second direction (for example, the roll width direction). Ｄ ', Track Pitch P Ｔ ' are the dot pitches P of the structures 3 of the fine relief structure 2 of the optical film 1 described above. Ｄ , track pitch P Ｔ For example, the dot pitch P Ｄ ' may be 230 nm, and the track pitch P Ｔ ' may be 150 nm.

[0122] In the hexagonal lattice arrangement of the fine concave-convex structure 120 shown in FIG. 4, the recesses 130 are arranged at half a pitch (½P) in the circumferential direction of the roll between the tracks T′, T′ adjacent in the width direction of the roll. Ｄ That is, between the tracks T, T adjacent to each other in the roll width direction, the phases of the recesses 130 arranged in the roll circumferential direction are shifted by half a period (180°).

[0123] In this way, the arrangement of the recesses 130 is set to a half pitch (½P) for each track T′ (i.e., for each rotation of the roll). Ｄ By shifting the recesses 130 from the center of the roll master 100, the recesses 130 can be arranged in a close-packed hexagonal lattice pattern on the outer peripheral surface of the roll master 100. This makes it possible to maximize the proportion of the area occupied by the recesses 130 of the fine concave-convex structure 120 on the outer peripheral surface (the filling rate of the recesses 130). This makes it possible to improve the anti-reflection function per unit area of ​​the optical film 1 to which the fine concave-convex structure 120 has been transferred.

[0124] Note that various dimensions such as the depth H', size D' (dot size), and aspect ratio (depth H' / arrangement pitch P') of the recesses 130 of the microrelief structure 120 are the same as the height h, size D (dot size), and aspect ratio (height h / arrangement pitch P) of the structures 3 of the microrelief structure 2 of the optical film 1 described above. Therefore, detailed description of these dimensions will be omitted.

[0125] The above has described the fine concave-convex structure 120 formed in the concave-convex pattern region 102 of the roll master 100. By transferring the fine concave-convex structure 120 of the roll master 100 to the optical film 1, the above-mentioned fine concave-convex structure 2 (see FIGS. 1 to 3 ) can be suitably formed in the concave-convex pattern region of the optical film 1.

[0126] 3. Configuration of Exposure Apparatus Next, the configuration of the exposure apparatus 200 used in manufacturing the roll master 100 according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a block diagram showing the configuration of the exposure apparatus 200 used in manufacturing the roll master 100 according to this embodiment.

[0127] As shown in FIG. 5 , the exposure apparatus 200 includes a laser light source 201, a first mirror 203, a photodiode (PD) 205, a condenser lens 207, an electro-optic deflector (EOD) 209, a collimator lens 211, a second mirror 213, a movable optical table 220, a spindle motor 225, a turntable 227, and a control device 230.

[0128] The laser light source 201 is a light source that emits laser light 202 for exposing the roll master 100. The laser light source 201 may be, for example, a semiconductor laser light source that emits laser light with a wavelength in the blue light band of 400 nm to 500 nm. The laser light source 201 is controlled by a control device 230.

[0129] The laser light 202 emitted from the laser light source 201 travels straight as a parallel beam and is reflected by the first mirror 203. The first mirror 203 is composed of a polarizing beam splitter and has the function of reflecting one polarized component and transmitting the other polarized component. The polarized component that has transmitted through the first mirror 203 is photoelectrically converted by the photodiode 205. The photoelectrically converted light reception signal is input to the laser light source 201. This allows the laser light source 201 to adjust the output of the laser light 202 based on feedback from the input light reception signal.

[0130] The laser beam 202 reflected by the first mirror 203 is guided to the deflection optical system, which includes a condenser lens 207, an electro-optical deflector element 209, and a collimator lens 211.

[0131] In the deflection optical system, the laser beam 202 is focused onto an electro-optical deflection element 209 by a condenser lens 207. The electro-optical deflection element 209 is an element that can control the irradiation position of the laser beam 202 at a distance of about nanometers. The electro-optical deflection element 209 makes it possible to finely adjust the irradiation position of the laser beam 202 on the master substrate 110 of the roll master 100. After the irradiation position of the laser beam 202 is adjusted by the electro-optical deflection element 209, the laser beam 202 is collimated again by a collimator lens 211. The collimated laser beam 202 is reflected by a second mirror 213 and directed horizontally onto a movable optical table 220.

[0132] The moving optical table 220 includes a beam expander (BEX) 221 and an objective lens 223. The roll master 100 is placed on a turntable 227. The turntable 227 is a table that supports the roll master 100 and can be rotated by a spindle motor 225.

[0133] The beam expander 221 shapes the laser beam 202 guided by the second mirror 213 into a desired beam shape. The shaped laser beam 202 passes through an objective lens 223 and is irradiated onto a resist layer formed on the outer peripheral surface of the master substrate 110 of the roll master 100.

[0134] When the master substrate 110 of the roll master 100 is irradiated with the laser beam 202, the spindle motor 225 rotates the turntable 227 and the master substrate 110 about the roll axis 110a, while the movable optical table 220 moves the irradiation position of the laser beam 202 in the axial direction (roll width direction) of the roll master 100. For example, with each rotation of the master substrate 110, the movable optical table 220 moves the irradiation position of the laser beam 202 by one feed pitch (track pitch) in the direction of arrow R (feed pitch direction). This allows the laser beam 202 to be spirally irradiated onto the outer peripheral surface of the master substrate 110, thereby exposing the resist layer on the outer peripheral surface of the master substrate 110 along a spiral scanning trajectory. The irradiation position of the laser beam 202 may be moved by moving either the laser head including the laser light source 201 or the turntable 227 supporting the roll master 100 along a slider.

[0135] The control device 230 also controls the emission of the laser beam 202 from the laser light source 201, thereby controlling the irradiation time and irradiation position of the laser beam 202. The control device 230 generates an exposure signal that controls the emission of the laser beam 202. The control device 230 may have, for example, a function generator including a signal generation circuit that can generate a signal of an arbitrary waveform. The control device 230 includes a formatter 231 and a driver 233.

[0136] The formatter 231 generates an exposure signal for controlling the emission of the laser beam 202 from the reference clock signal. The exposure signal is a signal representing the concave-convex pattern to be formed on the outer peripheral surface of the roll master 100. The driver 233 controls the emission of the laser beam 202 from the laser beam source 201 based on the exposure signal generated by the formatter 231. For example, the driver 233 may control the laser beam source 201 so that the laser beam 202 is emitted when the exposure signal consisting of a rectangular pulse wave is at a high level. The spindle motor 225 also rotates the turntable 227 based on a rotation control signal generated from the reference clock signal. For example, the spindle motor 225 may control the rotation of the turntable 227 so that the turntable 227 rotates once during a period in which a predetermined number of pulses of the rotation control signal are input.

[0137] As described above, the laser light source 201 is controlled by an exposure signal generated by the control device 230, and the laser light 202 emitted from the laser light source 201 is irradiated onto the roll master 100 placed on the turntable 227. Furthermore, the spindle motor 225 rotates the turntable 227 on which the roll master 100 is placed, based on the rotation control signal. Here, the exposure signal and the rotation control signal may be generated from a common reference clock signal and may be synchronized with each other.

[0138] The above describes an example of the configuration of the exposure device 200 according to this embodiment. The exposure device 200 according to this embodiment can expose the outer peripheral surface of the master substrate 110 of the roll master 100 to light, thereby precisely forming an exposure pattern (concave-convex pattern) of a desired shape.

[0139] 6, an exposure method for exposing the outer peripheral surface of the master substrate 110 of the roll master 100 using the exposure device 200 will be described. Fig. 6 is a schematic diagram illustrating the exposure method for the roll master 100 according to this embodiment.

[0140] 6 , in the exposure method for the roll master 100 according to this embodiment, an exposure pattern is formed by irradiating the outer peripheral surface of the master substrate 110 with laser light 202 using the exposure device 200 described above. As described above, the exposure device 200 includes a laser light source 201 that emits the laser light 202 and a control device 230 that controls the emission of the laser light 202.

[0141] In the exposure step, while the master substrate 110 of the roll master 100 is rotated around the roll axis 110a and while the laser light source 201 of the exposure device 200 is moved in the roll width direction (the direction of arrow R in FIG. 6 ), the outer peripheral surface of the master substrate 110 is irradiated with laser light 202. As a result, the outer peripheral surface of the master substrate 110 is irradiated with the laser light 202 in a spiral pattern, and an exposure pattern of a desired shape can be formed in a desired region of the outer peripheral surface of the master substrate 110.

[0142] An exposure pattern corresponding to the fine uneven structure 120 is formed in the uneven pattern region 102 on the outer peripheral surface of the master substrate 110. The example in Fig. 6 shows a state in which the exposure pattern corresponding to the fine uneven structure 120 is formed by irradiating the uneven pattern region 102 with laser light 202 along a spiral irradiation locus.

[0143] 7, a specific description will be given of the correspondence between the exposure signal used by the exposure apparatus 200 according to this embodiment and the exposure pattern formed on the outer peripheral surface of the master substrate 110. Fig. 7 is an explanatory diagram showing the correspondence between the exposure signal and the exposure pattern according to this embodiment.

[0144] As shown in Fig. 7, in this embodiment, an exposure pattern in which circular dot patterns are arranged in a hexagonal lattice pattern is formed on the outer peripheral surface of the master substrate 110 by irradiating the laser beam 202 along a spiral irradiation locus. In this exposure pattern, circular dot patterns corresponding to the recesses 130 of the fine concave-convex structure 120 are arranged in a hexagonal lattice pattern. These circular dot patterns are arranged at a predetermined track pitch P ＴThe dots are arranged along a plurality of rows of tracks T' arranged in a line. The planar shape of the dot pattern is not limited to the circular example shown in Fig. 7, but may be, for example, an elliptical or oblong shape having a major axis in the extension direction of the tracks T'.

[0145] The exposure device 200 according to this embodiment uses, as the exposure signal, for example, a pulse wave signal that alternates between high and low levels at a predetermined period in order to form an exposure pattern consisting of a plurality of dot patterns arranged along the track T'. The period of the pulse wave signal is t. The exposure device 200 controls the irradiation of the laser light 202 so that a circular dot pattern is formed on the outer peripheral surface of the master substrate 110 when the exposure signal is at a high level.

[0146] Furthermore, in order to form an exposure pattern in which the dot pattern is arranged in a hexagonal lattice as shown in Fig. 7, the frequency of the exposure signal is set so that the exposure signal is shifted by 1 / 2 pulse (t / 2) between tracks T', T' adjacent to each other in the roll width direction of the master substrate 110. In other words, while maintaining the continuity of the exposure signal, the phase of the exposure signal is inverted by 180° for each revolution of the spiral laser irradiation locus (i.e., for each track T'). As a result, the position of the dot pattern is shifted by 0.5 pitches (=(1 / 2) x P Ｄ’ ) in the circumferential direction of the roll. In this way, an exposure pattern in which dot patterns are precisely arranged in a hexagonal lattice pattern can be formed on the outer circumferential surface of the master substrate 110 using a spiral laser irradiation locus.

[0147] Incidentally, when the laser beam 202 is irradiated along a spiral irradiation locus as described above, the length of one circumference of the master substrate 110 can vary from circumference to circumference due to processing errors in the master substrate 110. Therefore, if the exposure signal and the rotation control signal are not synchronized, the arrangement of the exposure pattern will be disrupted as the exposure progresses. Furthermore, the spindle motor 225 of the turntable 227 that rotates the master substrate 110 has fluctuations in rotation speed, and the fluctuations in rotation speed will also disrupt the arrangement of the exposure pattern.

[0148] Therefore, in this embodiment, the exposure signal and the rotation control signal are synchronized by sharing a reference clock on which they are based. This allows the frequency of the exposure signal to be set to any value without being limited by dividing or multiplying the rotation control signal. Therefore, it is possible to continuously form a desired exposure pattern on the outer peripheral surface of the master substrate 110 while maintaining the continuity of the exposure signal. Therefore, in the exposure pattern of the fine uneven structure 120 in which multiple dot patterns are arranged in a hexagonal lattice pattern, interruptions in the exposure pattern and disruptions in the arrangement can be prevented, and the exposure pattern can be continuously formed with high precision.

[0149] 7 has been described above, with reference to Fig. 7, an example has been described in which a hexagonal lattice-shaped exposure pattern corresponding to the fine uneven structure 120 is formed in the uneven pattern region 102 on the outer peripheral surface of the master substrate 110. As described above, according to this embodiment, an exposure pattern corresponding to the fine uneven structure 120 of the uneven pattern region 102 can be formed on the outer peripheral surface of the roll master 100 using the exposure device 200. Therefore, the exposure pattern can be formed easily and quickly, and the manufacturing cost and manufacturing time of the roll master 100 can be reduced.

[0150] 5. Method for Manufacturing Roll Master Next, a method for manufacturing the roll master 100 according to this embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 and Fig. 9 are process diagrams showing the method for manufacturing the roll master 100 according to this embodiment.

[0151] In this embodiment, lithography using laser light, which can control the irradiation position with high precision, is used to form a concave-convex pattern of the fine concave-convex structure 120 on the outer peripheral surface of the master substrate 110, thereby manufacturing the roll master 100 according to this embodiment. By using such laser light lithography, it is possible to precisely control the arrangement of the concave-convex pattern of the fine concave-convex structure 120.

[0152] The method for manufacturing the roll master 100 according to this embodiment includes a film-forming step (S10), an exposure step (S12), a development step (S14), and an etching step (S16). First, in the film-forming step (S10), a resist layer 111 is formed on the outer peripheral surface of the master substrate 110. Next, in the exposure step (S12), a latent image 112 is formed by irradiating the resist layer 111 with laser light. Furthermore, in the development step (S14), the resist layer 111 on which the latent image 112 has been formed is developed to form a pattern in the resist layer 111. Thereafter, in the etching step (S16), the master substrate 110 is etched using the resist layer 111 on which the pattern has been formed as a mask, thereby forming a concavo-convex pattern of the fine concavo-convex structure 120 on the outer peripheral surface of the master substrate 110. Each step in the method for manufacturing the roll master 100 according to this embodiment will be described below.

[0153] (S10) Film Forming Process In the film forming process, first, as shown in A of FIG. 8, a master substrate 110 of the roll master 100 is prepared. The master substrate 110 is, for example, a cylindrical or columnar glass master. Next, as shown in B of FIG. 8, a resist layer 111 is formed on the outer peripheral surface of the master substrate 110. The resist layer 111 contains an inorganic or organic material capable of forming a latent image 112 by laser light. As the inorganic material, for example, a metal oxide containing one or more transition metals such as tungsten or molybdenum can be used. Furthermore, a resist layer containing an inorganic material can be formed by, for example, a sputtering method. On the other hand, as the organic material, for example, a novolac resist or a chemically amplified resist can be used. Furthermore, a resist layer containing an organic material can be formed by, for example, a spin coating method.

[0154] (S12) Exposure Step Next, in the exposure step, as shown in C of Fig. 8 , a laser beam 202 is irradiated onto the resist layer 111 formed on the outer peripheral surface of the master substrate 110. Specifically, the roll master 100 is placed on the turntable 227 of the exposure device 200 shown in Fig. 5 , and the roll master 100 is rotated while the laser beam 202 (exposure beam) is irradiated onto the resist layer 111. At this time, the laser beam 202 is irradiated onto the resist layer 111 while moving in the axial direction (roll width direction) of the roll master 100, thereby exposing the resist layer 111 along a spiral irradiation locus. As a result, a latent image 112 corresponding to the irradiation spot of the laser beam 202 is formed on the resist layer 111.

[0155] In this embodiment, the concave-convex pattern region 102 in the center in the roll width direction of the outer circumferential surface of the roll master 100 is intermittently irradiated with laser light 202 along a spiral irradiation locus. As a result, the resist layer 111 in the concave-convex pattern region 102 is exposed over the entire surface with an exposure pattern corresponding to the fine concave-convex structure 120 (for example, a pattern in which the circular dot pattern shown in FIG. 7 is arranged in a hexagonal lattice shape). As a result, a latent image 112 of the exposure pattern corresponding to the fine concave-convex structure 120 is formed in the resist layer 111 in the concave-convex pattern region 102.

[0156] (S14) Development Step Next, in the development step, as shown in A of FIG. 9 , the resist layer 111 on which the latent image 112 is formed is developed using a developer. As a result, a pattern of openings 113 corresponding to the latent image 112 is formed in the resist layer 111. For example, if the resist layer 111 contains the inorganic material described above, an alkaline solution such as a TMAH (Tetramethylammonium Hydroxide) aqueous solution can be used to develop the resist layer 111. Furthermore, if the resist layer 111 contains the organic material described above, various organic solvents such as esters or alcohols can be used to develop the resist layer 111.

[0157] In the developing step, for example, a developer is dropped onto the resist layer 111 while rotating the roll master 100, and the resist layer 111 is developed. As a result, a plurality of openings 113 are formed in the resist layer 111, as shown in A of Fig. 9. When the resist layer 111 is formed using a positive resist, the latent image 112 (exposed portion) exposed to the laser light 202 dissolves faster in the developer than the non-exposed portion, and therefore a pattern of openings 113 corresponding to the latent image 112 (exposed portion) is formed in the resist layer 111.

[0158] In this embodiment, openings 113 are formed in the uneven pattern region 102 in an opening pattern corresponding to the fine uneven structure 120 (for example, a pattern in which the circular dot pattern shown in Figure 7 is arranged in a hexagonal lattice pattern).

[0159] (S16) Etching Step Next, in the etching step, the outer peripheral surface of the master substrate 110 is etched using the pattern of the resist layer 111 in which the openings 113 are formed as a mask. As a result, as shown in B of FIG. 9, a concavo-convex pattern (fine concavo-convex structure 120) corresponding to the exposure pattern and the pattern of the openings 113 is formed on the outer peripheral surface of the master substrate 110. Etching of the master substrate 110 may be performed by either dry etching or wet etching. When the master substrate 110 is made of SiO ２ When the master substrate 110 is made of a glass material mainly containing fluorine (for example, quartz glass), the etching of the master substrate 110 may be dry etching using a carbon fluoride gas or wet etching using hydrofluoric acid or the like.

[0160] According to the etching process of this embodiment, a fine concave-convex structure 120 corresponding to the openings 113 is formed as a concave-convex pattern in the concave-convex pattern region 102 of the outer peripheral surface of the master substrate 110. The fine concave-convex structure 120 is, for example, a moth-eye structure in which a plurality of recesses 130 and protrusions 140 are arranged in a hexagonal lattice pattern at a pitch P' on the nano-order (e.g., 350 nm or less) that is equal to or less than the wavelength of visible light.

[0161] As described above, the recess 130 has a composite structure consisting of a first tapered recess 131 and a second tapered recess 132. The first tapered recess 131 is a tapered recess formed on the outer periphery of the master substrate 110. The first tapered recess 131 is a tapered hole in the shape of a truncated cone that is thicker than the second tapered recess 132. The second tapered recess 132 is a needle-like tapered hole that is thinner than the first tapered recess 131. The second tapered recess 132 is a tapered recess formed at the bottom of the first tapered recess 131. The taper ratio C of the second tapered recess 132 ２ is the taper ratio C of the first tapered recess 131 １ is smaller than.

[0162] The microrelief structure 120 of the roll master 100 (see B in FIG. 9 ) has an inverted shape of the microrelief structure 2 of the optical film 1 described above (see FIG. 1 ). Therefore, the recesses 130 of the microrelief structure 120 have an inverted shape of the convex structures 3 (convex portions) of the microrelief structure 2, and the convex portions 140 of the microrelief structure 120 have an inverted shape of the recesses 4 of the microrelief structure 2. Of the recesses 130 of the microrelief structure 120 of the roll master 100, the first tapered recesses 131 have an inverted shape of the first tapered portions 31 of the structures 3 of the microrelief structure 2 of the optical film 1, and the second tapered recesses 132 have an inverted shape of the second tapered portions 32 of the structures 3.

[0163] In order to form the recess 130 having a composite structure consisting of the first tapered recess 131 and the second tapered recess 132 in the master substrate 110, in the etching step (S16) according to this embodiment, when etching the outer peripheral surface of the master substrate 110 using an etching gas, the etching conditions are changed during the etching. For example, the etching rate in the depth direction of the recess 130 can be changed by switching the etching gas during the etching, for example, by switching to CF4 gas, which has strong isotropic etching properties, or by changing the input power output or pressure. It is also effective to reform the resist during the etching and etch again. This allows the first tapered recess 131 and the second tapered recess 132, which have different taper ratios, to be formed stepwise in the master substrate 110 in a single etching step.

[0164] As described above, in the etching process according to this embodiment, the resist layer 111, on which an opening pattern consisting of a plurality of openings 113 is formed, is used as a mask to simultaneously etch the entire outer peripheral surface of the master substrate 110. This makes it possible to process the fine concave-convex structure 120 (anti-reflection concave-convex pattern) including a plurality of concave portions 130 having a composite structure on the outer peripheral surface of the master substrate 110.

[0165] 6. Method for Producing Optical Film Next, a method for producing the optical film 1 according to this embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 and Fig. 11 are process diagrams showing the method for producing the optical film 1 according to this embodiment.

[0166] The method for producing the optical film 1 according to this embodiment includes a step (S20) of preparing a roll master 100, a coating step (S22) of coating a resin layer 12A made of a curable resin on the surface of the substrate 11 of the optical film 1, a first transfer step (S24) of transferring a transfer pattern formed on the outer peripheral surface of the roll master 100 to the resin layer 12A of the optical film 1, and a molding step (S28) of molding the optical film 1 into a predetermined shape. Furthermore, when a concave-convex pattern is provided on both sides of the optical film 1 (see FIG. 11 ), the method for producing the optical film 1 according to this embodiment may include a second coating and transfer step (S26) in addition to the above steps.

[0167] (S20) Roll Master Preparation Step The roll master 100 preparation step (S20) may be, for example, each step (film formation step (S10), exposure step (S12), development step (S14), and etching step (S16)) of the method for manufacturing the roll master 100 according to this embodiment described with reference to Figures 8 and 9. By the method for manufacturing the roll master 100, a roll master 100 having a fine relief structure 120 formed on its outer peripheral surface is suitably prepared.

[0168] (S22) Coating Step In the coating step (S22), an uncured resin layer 12A made of a curable resin (transfer material) is coated on the surface of the substrate 11 of the optical film 1. The curable resin (transfer material) is a resin material that has fluidity before curing, and is, for example, an energy ray-curable resin such as an ultraviolet-curable resin or a photocurable resin. In this embodiment, the transfer pattern of the roll master 100 is continuously transferred to the resin layer 12A of the optical film 1 by a roll-to-roll system, so the coating step (S22) and the subsequent transfer step (S24) are performed simultaneously in parallel.

[0169] (S24) Transfer Step In the transfer step (S24), the transfer pattern on the outer peripheral surface of the roll master 100 is transferred to one surface of the optical film 1. In detail, as shown in A of FIG. 10 , an uncured resin layer 12A (transfer material) applied to the substrate 11 of the optical film 1 is brought into close contact with the outer peripheral surface of the roll master 100. Thereafter, energy rays such as ultraviolet rays are irradiated onto the resin layer 12A from the light source 58 to cure the resin layer 12A. Thereafter, the substrate 11 integrated with the cured resin layer 12A (corresponding to the resin layer 12) is peeled off from the roll master 100.

[0170] This results in the optical film 1 shown in B of Fig. 10. In the optical film 1, a resin layer 12 is laminated on the surface of a substrate 11, and a microrelief structure 2 is formed on the surface of the resin layer 12. If necessary, an intermediate layer (not shown), such as an adhesion layer, adhesive layer, or base layer, may be further provided between the resin layer 12 and the substrate 11 of the optical film 1.

[0171] According to the transfer process of this embodiment, the transfer pattern (fine concave-convex structure 120) on the outer peripheral surface of the roll master 100 is transferred to the resin layer 12 of the optical film 1, and the fine concave-convex structure 2 is formed on the surface of the resin layer 12. In detail, the fine concave-convex structure 120 of the concave-convex pattern region 102 of the roll master 100 is transferred to the resin layer 12 of the optical film 1, and thereby the fine concave-convex structure 2 having an anti-reflection function is formed on the surface of the optical film 1.

[0172] The microrelief structure 120 of the roll master 100 and the microrelief structure 2 of the optical film 1 have mutually inverted recessed and projected shapes. In the transfer step, the recessed portions 130 of the microrelief structure 120 of the roll master 100 form the convex structures 3 (protruding portions) of the microrelief structure 2 of the optical film 1, and the protruding portions 140 of the microrelief structure 120 of the roll master 100 form the recessed portions 4 of the microrelief structure 2 of the optical film 1.

[0173] Here, as shown in A of Fig. 10 , the recesses 130 of the fine concave-convex structure 120 of the roll master 100 according to this embodiment have a composite structure (two-step tapered recess structure) consisting of first tapered recesses 131 and second tapered recesses 132. By transferring the recesses 130 to such a two-step tapered recess structure, as shown in B of Fig. 10 , the structures 3 of the fine concave-convex structure 2 of the optical film 1 have a composite structure (two-step tapered convex structure) consisting of first tapered portions 31 and second tapered portions 32.

[0174] By the above coating step (S22) and transfer step (S24), a fine concave-convex structure 2 is formed in the resin layer 12 on one surface of the optical film 1, as shown in B of Fig. 10. The resin layer 12 having the fine concave-convex structure 2 may be provided on only one surface (one side) of the optical film 1, as shown in B of Fig. 10, or may be provided on both surfaces (both front and back) of the optical film 1, as shown in B of Fig. 11. In the latter case, a second coating and transfer step (S26) described below may be carried out.

[0175] 11A, after the first transfer step (S24), a resin layer 12A made of a curable resin is also applied to the other surface (rear surface) of the substrate 11 of the optical film 1. Next, the transfer pattern (fine relief structure 120) formed on the outer peripheral surface of the roll master 100 is transferred to the resin layer 12A on the other surface (rear surface) of the optical film 1.

[0176] 11A, an uncured resin layer 12A coated on the other surface of the film substrate 11 is brought into close contact with the outer peripheral surface of the roll master 100. Next, the resin layer 12A is irradiated with energy rays such as ultraviolet rays from a light source 58 to cure the resin layer 12A. Thereafter, the substrate 11 integrated with the cured resin layer 12A (corresponding to the resin layer 12) is peeled from the roll master 100. As a result, an optical film 1 is obtained in which the resin layers 12 are laminated on both the front and back surfaces of the substrate 11 and a microrelief structure 2 is formed on the surface of the resin layer 12, as shown in FIG. 11B.

[0177] (S28) Molding Step Next, in the molding step (S28), the optical film 1 obtained in the transfer step (S24 or S26) is molded into a predetermined size and shape. For example, the optical film 1 is cut to a predetermined size, cut out into a desired shape, or punched into a desired shape using a mold. This allows the optical film 1 to be molded into a product (sheet product) suitable for the intended use. A cutting machine, a laser processing device, a punching press, or the like can be used for this molding process.

[0178] Next, a method for continuously transferring a transfer pattern from a roll master 100 to the optical film 1 by a roll-to-roll system in the method for producing the optical film 1 according to this embodiment will be described with reference to Fig. 12. Fig. 12 is a schematic diagram showing the configuration of a transfer device 5 according to this embodiment.

[0179] 12, the transfer device 5 includes a roll master 100, a substrate supply roll 51, a take-up roll 52, guide rolls 53 and 54, a nip roll 55, a peeling roll 56, a coating device 57, and a light source 58. In other words, the transfer device 5 shown in Fig. 12 is a roll-to-roll type imprint transfer device.

[0180] The substrate supply roll 51 is, for example, a roll on which the substrate 11 of the optical film 1 is wound into a roll shape. The take-up roll 52 is a roll for winding up the optical film 1 having the microrelief structure 2 formed on the resin layer 12. The guide rolls 53 and 54 are rolls for transporting the substrate 11 before and after transfer. The nip roll 55 is a roll for pressing the substrate 11 coated with the uncured resin layer 12A against the outer peripheral surface of the roll master 100. The peeling roll 56 is a roll for peeling off the substrate 11, on which the resin layer 12 to which the microrelief structure 120 has been transferred, from the roll master 100.

[0181] The coating device 57 coats the substrate 11 with a transfer material made of, for example, an uncured curable resin composition, to form an uncured resin layer 12A on the substrate 11. The coating device 57 may be, for example, a gravure coater, a wire bar coater, or a die coater. The light source 58 is a light source that emits light of a wavelength capable of curing the photocurable resin composition, and is, for example, an ultraviolet lamp.

[0182] The curable resin composition may be, for example, a photocurable resin that is cured by irradiation with light of a predetermined wavelength. Specifically, the photocurable resin composition may be an ultraviolet-curable resin such as an acrylic resin acrylate or an epoxy acrylate. The photocurable resin composition may also contain an initiator, a filler, a functional additive, a solvent, an inorganic material, a pigment, a charge inhibitor, or a sensitizing dye, as necessary.

[0183] The uncured resin layer 12A may be formed of a thermosetting resin composition. In this case, the transfer device 5 may be provided with a heat source (e.g., a heater) instead of the light source 58, and the resin layer 12A may be cured by heating it with the heat source. The thermosetting resin composition may be, for example, a phenolic resin, an epoxy resin, a melamine resin, or a urea resin.

[0184] Next, a roll-to-roll transfer method using the transfer device 5 having the above configuration will be described.

[0185] First, the strip-shaped substrate 11 wound around the substrate supply roll 51 is unwound from the substrate supply roll 51 and continuously fed out via the guide roll 53. Next, a photocurable resin composition (transfer material) is continuously applied onto the surface of the substrate 11 by the coating device 57, and an uncured resin layer 12A is laminated on the substrate 11. Furthermore, the resin layer 12A laminated on the substrate 11 is pressed against the outer peripheral surface of the roll master 100 by the nip roll 55. As a result, the fine concavo-convex structure 120 formed on the outer peripheral surface of the roll master 100 is continuously transferred to the resin layer 12A.

[0186] Next, the resin layer 12A to which the microrelief structure 120 has been transferred is cured by irradiation with light from the light source 58. As a result, an inverted structure of the microrelief structure 120 (for example, the above-described microrelief structure 2) is formed in the resin layer 12. Thereafter, the optical film 1 composed of the resin layer 12 on which the microrelief structure 2 has been formed and the substrate 11 is peeled from the roll master 100 by a peeling roll 56. Thereafter, the optical film 1 is sent out to a take-up roll 52 via a guide roll 54 and taken up into a roll by the take-up roll 52.

[0187] As described above, the transfer device 5 according to this embodiment can continuously transfer the microrelief structure 120 formed on the outer peripheral surface of the roll master 100 by a roll-to-roll method to manufacture the optical film 1. Therefore, the optical film 1 can be mass-produced efficiently.

[0188] Next, an optical element according to an embodiment of the present invention will be described. Note that the following embodiment is merely an example for illustrating the effects and feasibility of the optical element according to the present invention, and the present invention is not limited to the following embodiment.

[0189] [1. Design and Manufacturing Conditions] Optical films according to examples of the present invention and optical films according to comparative examples were designed and manufactured under the conditions described below while changing the shape and dimensions of the convex structures of the fine concave-convex structure formed on the surface of the optical film.

[0190] Table 1 and Figures 13 to 14 show the design conditions for the convex structures of the microrelief structure (corresponding to the convex structures 3 in the optical film 1 according to the above embodiment) in the optical films according to Examples 1 to 3, Comparative Examples 1 to 4, and the Reference Example. Table 1 also shows the results of measuring the average reflectance of the optical films according to Examples 1 to 3, Comparative Examples 1 to 4, and the Reference Example when incident light in the visible light to near-infrared light region is obliquely incident. Furthermore, Figures 13 to 14 also show images of the cross section of the actually produced microrelief structure observed with a scanning electron microscope (SEM).

[0191]

[0192] (1) Conditions common to Examples and Comparative Examples As shown in Table 1 and Figures 13 to 14, in all of Examples 1 to 3 and Comparative Examples 1 to 4, a fine uneven structure (moth-eye structure) was formed by regularly arranging a plurality of convex structures on the surface (XY plane) of the substrate of the optical film at a predetermined pitch P. However, in Examples 1 to 3 and Comparative Examples 1 to 4, the shapes and dimensions of the plurality of convex structures constituting the fine uneven structure were different from one another.

[0193] In order to manufacture the optical films according to Examples 1 to 3 and Comparative Examples 1 to 4, first, roll masters 100 (see FIG. 4) according to Examples 1 to 3 and Comparative Examples 1 to 4 were manufactured, respectively.

[0194] Specifically, as shown in Fig. 8 above, first, in the film-forming step (S10), a resist layer 111 was formed on the outer peripheral surface of the master substrate 110. Next, in the exposure step (S12), a latent image 112 was formed by irradiating the resist layer 111 with laser light. Furthermore, in the development step (S14), the resist layer 111 on which the latent image 112 was formed was developed to form a pattern in the resist layer 111. Thereafter, in the etching step (S16), the master substrate 110 was etched using the resist layer 111 on which the pattern was formed as a mask, and a concavo-convex pattern of the fine concavo-convex structure 120 was formed on the outer peripheral surface of the master substrate 110.

[0195] By changing the etching conditions in this etching step (S16), a fine concave-convex structure 120 corresponding to various convex structures as shown in Figures 13 and 14 was formed on the outer peripheral surface of the master substrate 110. In this way, roll masters 100 corresponding to the optical films according to Examples 1 to 3 and Comparative Examples 1 to 4 were manufactured, respectively.

[0196] Next, using the various roll masters 100 according to Examples 1 to 3 and Comparative Examples 1 to 4, roll-to-roll nanoimprinting was performed to transfer the fine concave-convex structure onto the surface of the optical film.

[0197] 9 above, first, in the coating step (S22), a resin layer 12A made of a curable resin was coated on the surface of the substrate 11 of the optical film 1. Next, in the transfer step (S24), the resin layer 12A was cured by irradiation with ultraviolet light while the microrelief structure 120 formed on the outer peripheral surface of the roll master 100 was transferred to the resin layer 12A of the optical film 1. Thereafter, the optical film 1 was peeled from the roll master 100 to obtain an optical film 1 having a microrelief structure 2 formed on the resin layer 12.

[0198] Here, a 125 μm thick PET film (manufactured by Toyobo Co., Ltd., product name "A4360") was used as the substrate 11 of the optical film 1. A UV resin (manufactured by Dexerials Corporation, product name "SK1120"), which is an ultraviolet-curable acrylic resin composition, was used as the transfer material for forming the resin layer 12A of the optical film 1. A UV-LED device that irradiates ultraviolet light with a wavelength of 365 nm was used to cure the resin layer 12A.

[0199] In this manner, optical films according to Examples 1 to 3 and Comparative Examples 1 to 4 were produced. As shown in Table 1 and Figures 13 and 14, the shapes and dimensions of the convex structures differed from one another in Examples 1 to 3 and Comparative Examples 1 to 4, but the arrangement pitch P of the convex structures was the same for all of them, 200 μm, and the size of the bottom of the convex structure (for example, the diameter φ of the bottom of the first tapered portion 31 of the structure 3 according to Examples 1 to 3) was the same. １ ) was set to 200 μm, the same as the pitch P.

[0200] In the reference examples shown in Table 1, an optical film consisting of only a substrate was used, and no convex structures were formed on the surface of the optical film. A 125 μm thick PET film (manufactured by Toyobo Co., Ltd., product name "A4360") was used as the substrate in the reference examples.

[0201] (2) Conditions of Comparative Examples <Comparative Example 1> In Comparative Example 1, the convex structures of the microrelief structure of the optical film have a simple structure consisting of bell-shaped elliptical cones, as shown in Fig. 13. The convex structures according to Comparative Example 1 correspond to the convex structures described in the above-mentioned Patent Document 1 (Japanese Patent No. 4404161). The overall height h of the convex structures according to Comparative Example 1 is approximately 310 nm.

[0202] <Comparative Example 2> In Comparative Example 2, the convex structures of the microrelief structure of the optical film are non-tapered composite structures, as shown in Fig. 13, and the side surfaces of the convex structures have inflection points at the midpoints of the slopes. The convex structures according to Comparative Example 2 are convex structures in which bell-shaped structures are stacked in two tiers, one above the other. The overall height h of the convex structures according to Comparative Example 2 is approximately 620 nm.

[0203] A roll master according to Comparative Example 2 was manufactured in order to manufacture an optical film having convex structures with a two-tiered bell-shaped structure according to Comparative Example 2. In the etching step (S16) for manufacturing the roll master of Comparative Example 2, the etching conditions were changed during etching of the master substrate 110, and concave structures with a two-tiered bell-shaped structure having the inflection point were formed on the outer peripheral surface of the master substrate 110.

[0204] Specifically, in the etching step (S16) of Comparative Example 2, CHF gas was used as the etching gas to perform anisotropic etching. Then, during the etching, the gas was switched, and etching was performed with CF gas. Then, etching was performed by switching to CHF gas. By switching the gas during etching, a concave structure having a composite structure in which two bell-shaped concave structures with different curved shapes and thicknesses were stacked one on top of the other was formed on the outer circumferential surface of the roll master. Then, the concave structure with a two-tiered bell structure having an inflection point of the roll master was transferred to the resin layer of the optical film, thereby forming a convex structure with a two-tiered bell structure having an inflection point according to Comparative Example 2.

[0205] Comparative Example 3 In Comparative Example 3, the convex structure of the microrelief structure of the optical film has a composite structure in which two tapered structures (first tapered portion, second tapered portion) are stacked one above the other, as shown in Fig. 13. As such, the convex structure according to Comparative Example 3 has a composite structure (two-stage tapered structure) in which two tapered portions with different taper ratios are stacked one above the other, similar to the convex structure 3 according to the present embodiment (see Fig. 1, etc.) and the convex structures according to Examples 1 to 3 (see Fig. 14). However, the overall height h of the convex structure according to Comparative Example 3 is approximately 300 nm, which is shorter than the height h (400 nm or more) of the convex structures according to Examples 1 to 3.

[0206] A roll master according to Comparative Example 3 was manufactured in order to manufacture an optical film having convex structures according to Comparative Example 3. In the etching step (S16) for manufacturing the roll master of Comparative Example 3, the etching conditions were changed during etching of the master substrate 110, and concave structures having the above-mentioned two-step tapered structure were formed on the outer peripheral surface of the master substrate 110.

[0207] Specifically, in the etching step (S16) of Comparative Example 3, CHF gas was used as the etching gas to perform anisotropic etching in the first step. Then, in the second step, the gas was switched during the etching process to CF gas for etching. By switching the gas during the etching process, a two-stage tapered concave structure having a composite structure in which two tapered sections with different taper ratios and thicknesses were stacked one above the other was formed on the outer circumferential surface of the roll master. The two-stage tapered concave structure of the roll master had a transition point on its side where the taper ratio changed. The second tapered section of the two-stage tapered structure was formed in the first step, and the first tapered section was formed in the second step. The two-stage tapered concave structure of the roll master was then transferred to the resin layer of the optical film to form a two-stage tapered convex structure having a transition point according to Comparative Example 3.

[0208] Comparative Example 4 In Comparative Example 4, similarly to Comparative Example 3, the convex structures of the microrelief structure of the optical film have a composite structure in which two tapered structures (tapered portions) are stacked one above the other, as shown in Fig. 13. In this way, the convex structure according to Comparative Example 4 also has a composite structure (two-stage tapered structure) in which two tapered portions with different taper ratios are stacked one above the other. However, the overall height h of the convex structures according to Comparative Example 4 is approximately 353 nm, which is shorter than the height h (400 nm or more) of the convex structures according to Examples 1 to 3.

[0209] In Comparative Example 4, as in Comparative Example 3, in the etching process (S16) for manufacturing the roll master of Comparative Example 4, the etching conditions were changed during the etching of the master substrate 110, and a recessed structure having the above-mentioned two-stage tapered structure was formed on the outer peripheral surface of the master substrate 110.

[0210] Specifically, in the etching step (S16) of Comparative Example 4, CHF gas was used as the etching gas to perform anisotropic etching as the first step. Then, as the second step, the gas was switched during the etching process to perform etching with CF gas. By switching the gas during the etching process, a concave structure with a two-step tapered structure having a composite structure in which two tapered sections with different taper ratios and thicknesses were stacked one above the other was formed on the outer circumferential surface of the roll master. The concave structure with a two-step tapered structure having a change point on the roll master was then transferred to the resin layer of the optical film, thereby forming a convex structure with a two-step tapered structure having a change point according to Comparative Example 4. The second tapered section of the two-step tapered structure was formed in the first step, and the first tapered section was formed in the second step. The concave structure of the roll master was then transferred to the resin layer of the optical film, thereby forming a convex structure with a two-step tapered structure according to Comparative Example 4.

[0211] (3) Conditions of the Examples Example 1 In Example 1, the convex structures of the fine concave-convex structure of the optical film have a composite structure in which two tapered structures (first tapered portion 31 and second tapered portion 32 shown in FIG. 2) are stacked one above the other, as shown in FIG. 14. In this way, the convex structure according to Example 1 has a composite structure (two-stage tapered structure) in which two tapered portions with different taper ratios are stacked one above the other. The overall height h of the convex structure according to Example 1 is approximately 413 nm.

[0212] A roll master according to Example 1 was manufactured in order to manufacture an optical film having convex structures according to Example 1. In the etching step (S16) for manufacturing the roll master of Example 1, the etching conditions were changed during etching of the master substrate 110, and concave structures having the above-mentioned two-step tapered structure were formed on the outer peripheral surface of the master substrate 110.

[0213] Specifically, in the etching step (S16) of Example 1, a mixture of CHF3 gas and CF4 gas was used as the etching gas to perform slightly isotropic anisotropic etching in the first step. Then, in the second step, the gas was switched during the etching process to perform etching with CF4 gas. By switching the gas during the etching process, a two-stage tapered concave structure having a composite structure in which two tapered sections with different taper ratios and thicknesses are stacked one on top of the other was formed on the outer circumferential surface of the roll master. The two-stage tapered concave structure of the roll master had a transition point on its side where the taper ratio changed. The second tapered section of the two-stage tapered structure was formed in the first step, and the first tapered section was formed in the second step. The two-stage tapered concave structure of the roll master was then transferred to the resin layer of the optical film to form the two-stage tapered convex structure having a transition point according to Example 1.

[0214] <Example 2> In Example 2, as in Example 1, the convex structures of the microrelief structure of the optical film are a composite structure in which two tapered structures (first tapered portion 31 and second tapered portion 32 shown in FIG. 2) are stacked one above the other, as shown in Figure 14. In this way, the convex structure according to Example 2 has a composite structure (two-stage tapered structure) in which two tapered portions with different taper ratios are stacked one above the other. The overall height h of the convex structure according to Example 2 is approximately 493 nm.

[0215] In Example 2, as in Example 1, in the etching process (S16) for manufacturing the roll master of Example 2, the etching conditions were changed during the etching of the master substrate 110, and a recessed structure having the above-mentioned two-stage tapered structure was formed on the outer peripheral surface of the master substrate 110.

[0216] Specifically, in the etching step (S16) of Example 2, a mixture of CHF3 gas and CF4 gas was used as the etching gas to perform slightly isotropic anisotropic etching in the first step. Then, in the second step, the gas was switched during the etching process to perform etching with CF4 gas. By switching the gas during the etching process, a two-stage tapered recessed structure having a composite structure in which two tapered sections with different taper ratios and thicknesses were stacked one above the other was formed on the outer circumferential surface of the roll master. The two-stage tapered recessed structure of the roll master had a transition point on its side where the taper ratio changed. The second tapered section with the two-stage tapered structure was formed in the first step, and the first tapered section was formed in the second step. In Example 2, the etching time in the second step was 30% longer than in Example 1, thereby increasing the height of the first tapered section. Thereafter, the concave structures with a two-step tapered structure of the roll master were transferred to the resin layer of the optical film, thereby forming the convex structures with a two-step tapered structure having a change point according to Example 2.

[0217] 14, the height of the convex structure produced in Example 2 is approximately 493 nm. It can be seen that the lower portion of the convex structure according to Example 2 is a thick truncated cone-shaped tapered structure (first tapered portion 31), and above that, a thin, elongated cone-shaped tapered structure (second tapered portion 32) has grown in a needle shape.

[0218] <Example 3> In Example 3, as in Example 1, the convex structures of the fine concave-convex structure of the optical film are a composite structure in which two tapered structures (first tapered portion 31 and second tapered portion 32 shown in FIG. 2) are stacked one above the other, as shown in Figure 14. In this way, the convex structure according to Example 3 has a composite structure (two-stage tapered structure) in which two tapered portions with different taper ratios are stacked one above the other. The overall height h of the convex structure according to Example 3 is approximately 567 nm.

[0219] In Example 3, as in Example 1, in the etching process (S16) for manufacturing the roll master of Example 3, the etching conditions were changed during the etching of the master substrate 110, and a recessed structure having the above-mentioned two-stage tapered structure was formed on the outer peripheral surface of the master substrate 110.

[0220] Specifically, in the etching step (S16) of Example 3, a mixture of CHF3 gas and CF4 gas was used as the etching gas to perform slightly isotropic anisotropic etching in the first step. Then, in the second step, the gas was switched during the etching process to perform etching with CF4 gas. By switching the gas during the etching process, a two-stage tapered recessed structure having a composite structure in which two tapered sections with different taper ratios and thicknesses were stacked one above the other was formed on the outer circumferential surface of the roll master. The two-stage tapered recessed structure of the roll master had a transition point on its side where the taper ratio changed. The second tapered section with the two-stage tapered structure was formed in the first step, and the first tapered section was formed in the second step. In Example 3, the etching time in the second step was 50% longer than in Example 1, thereby increasing the height of the first tapered section. Thereafter, the concave structures with a two-step tapered structure of the roll master were transferred to the resin layer of the optical film, thereby forming the convex structures with a two-step tapered structure having a change point according to Example 3.

[0221] 14, the height of the convex structure produced in Example 3 is approximately 567 nm. It can be seen that the lower portion of the convex structure according to Example 3 is a thick truncated cone-shaped tapered structure (first tapered portion 31), and above that, a thin, elongated cone-shaped tapered structure (second tapered portion 32) grows in a needle shape.

[0222] 2. Evaluation of Antireflection Properties The optical film samples according to Examples 1 to 3 and Comparative Examples 1 to 4 produced as described above were subjected to a test to evaluate the antireflection properties.

[0223] In this evaluation test, the wavelength λ of incident light was changed in 1 nm increments within a range of 400 to 950 nm, and the incident light of each wavelength λ was made incident on the surface of each optical film sample (the finely uneven surface on which the fine uneven structure was formed) at an incident angle θ of 10° or 70°. The reflectance Re [%] of the incident light on the surface of the optical film at this time was measured using a spectroscopic reflectometer (manufactured by JASCO Corporation, product name "V770"). At this time, black tape was attached to the back surface of each optical film sample, and only the reflectance on the surface (finely uneven surface) of each sample was measured.

[0224] The reflectance was determined as the average reflectance Re [%] of incident light having a wavelength λ of 400 to 950 nm. That is, the wavelength λ of the incident light was changed in 1 nm increments within the range of 400 to 950 nm, and the reflectance Re [%] for each wavelength λ was measured. The average value of these 550 reflectances Re was calculated and used as the average reflectance Re. In addition, the incident angle θ of the incident light with respect to the surface of the optical film was set to 10° or 70°, and the average reflectance Re when θ = 10° was calculated as follows: θ＝１０° [%] and the average reflectance Re when θ = 70° θ＝７０° Furthermore, Re [%] was calculated. θ＝１０° and Re θ＝７０° The average value Re_ave [%] of the above values ​​was also calculated.

[0225] The Re thus obtained θ＝１０° , Re θ＝７０° and Re_ave are shown in Table 1. Also, FIG. 15 shows the relationship between the height h of the convex structure and the average reflectance Re in the wavelength band of 400 to 950 nm. θ＝７０° 10 is a graph showing the relationship between

[0226] As shown in Table 1, the average reflectance Re when θ = 10° θ＝１０° Regarding the Re in all of Comparative Examples 1 to 4 and Examples 1 to 3, θ＝１０° Therefore, in the case of oblique incidence at a low angle of incidence θ of about 10°, there is no significant difference in antireflection properties between Comparative Examples 1 to 4 and Examples 1 to 3.

[0227] On the other hand, the average reflectance Re when θ=70° θ＝７０° Regarding the Re, as shown in Table 1 and FIG. 15, the Re of Comparative Examples 1 to 4 θ＝７０° In contrast, the Re of Examples 1 to 3 is around 10%, which is worse. θ＝７０° is 6.5% or less, which is a significant improvement compared to Comparative Examples 1 to 4. In particular, the Re of Examples 2 and 3 θ＝７０° is 5% or less, which is a significant improvement compared to Comparative Examples 1 to 4. θ＝７０° If Re is 6.5% or less, there is an effect that the prevention of reflection from extremely oblique angles is superior to that of the prior art. θ＝７０° If the ratio is 5% or less, the anti-reflection properties are even better than those of a general moth-eye.

[0228] As described above, in Examples 1 to 3, excellent anti-reflection properties were ensured for obliquely incident light in a wide wavelength range of 400 to 950 nm, even in the case of oblique incidence at a high angle of about 70°. The reason for this is believed to be as follows.

[0229] That is, in Examples 1 to 3, the height h of the convex structures having a two-step tapered structure is high, at 400 nm or more, and particularly in Examples 2 and 3, the height h is even higher, at 490 nm or more. On the other hand, in Comparative Examples 3 and 4, although the convex structures have a two-step tapered structure similar to Examples 1 to 3, the height h of the convex structures is low, at approximately 350 nm or less. Therefore, in Comparative Examples 3 and 4, the antireflection properties against incident light in the long-wavelength near-infrared region are deteriorated at high angles of oblique incidence of about 70°. In contrast, Examples 1 to 3 are provided with convex structures having a high two-step tapered structure, and are therefore compatible with both long-wavelength near-infrared light and short-wavelength visible light. Therefore, it is considered that, compared to Comparative Examples 3 and 4, they have superior antireflection properties against high-angle oblique incidence of about 70° over a wide wavelength band.

[0230] Furthermore, in Comparative Example 2, the height h of the convex structures is 620 nm, which is higher than the height h of the convex structures in Examples 1 to 3, and therefore it is possible to accommodate light in the long-wavelength near-infrared region. However, the shape of the convex structures in Comparative Example 2 is not a two-step tapered structure. Therefore, in Comparative Example 2, at high angles of oblique incidence, it was not possible to accommodate both the long-wavelength near-infrared region and the short-wavelength visible light region, and the antireflection properties were reduced. Furthermore, in Comparative Example 1, the height h of the convex structures is low and the shape of the convex structures is not a two-step tapered structure, and therefore it is thought that the antireflection properties against high-angle oblique incidence light are poor.

[0231] Next, the relationship between the wavelength band of incident light (350 to 1000 nm) and the anti-reflection properties will be evaluated with reference to Figures 16 and 17. Figure 16 is a graph showing the relationship between the wavelength λ of incident light and the reflectance Re when the light is obliquely incident at a low angle of about 10°. Figure 17 is a graph showing the relationship between the wavelength λ of incident light and the reflectance Re when the light is obliquely incident at a high angle of about 70°.

[0232] As shown in Figure 16, at low-angle oblique incidence where the incident angle θ is about 10°, the reflectance Re of Comparative Examples 1 to 3 and Examples 2 and 3 is about 0 to 3%, which is lower than the reflectance Re of the Reference Example (about 5 to 6%) in a wide wavelength band (350 to 1000 nm) from the visible light region to the near-infrared region. This shows that by providing a fine concave-convex structure having convex structures of various shapes as shown in Figures 13 and 14, as in Comparative Examples 1 to 3 and Examples 2 and 3, it is possible to improve the anti-reflection properties at low-angle oblique incidence. Note that the reflectance Re of Comparative Example 4 is about 0 to 4%, which is lower than the reflectance Re of the Reference Example (about 5 to 6%), but is higher than Examples 2 and 3.

[0233] On the other hand, as shown in FIG. 17, when light was obliquely incident at a high angle, where the incident angle θ was about 70°, there was a difference in the antireflection properties between Comparative Examples 1 to 4 and Examples 2 and 3 in a wide wavelength band (350 to 1000 nm) from the visible light region to the near-infrared region.

[0234] Specifically, in the short-wavelength visible light region of 550 nm or less, the reflectance Re of Examples 2 and 3 is very low at around 2%, whereas the reflectance Re of Comparative Examples 1 to 4 is high at around 4 to 12%. Therefore, it can be seen that when incident light in the short-wavelength visible light region (350 to 550 nm) is obliquely incident at a high angle of about 70°, Examples 2 and 3 can exhibit better anti-reflection properties than Comparative Examples 1 to 3.

[0235] Furthermore, even in the near-infrared region of about 950 nm, the reflectance Re of Examples 2 and 3 is suppressed to 10% or less, which is less than half the reflectance Re (about 18%) of the Reference Example. In contrast, the reflectance Re of Comparative Examples 1 to 4 is high, at about 12 to 15%. Therefore, it can be seen that Examples 2 and 3 can exhibit very good anti-reflection properties compared to Comparative Examples 1 to 4, even when incident light in the near-infrared region of about 950 nm is obliquely incident at a high angle of about 70°.

[0236] From the above results, it was confirmed that Examples 1 to 3 can exhibit excellent anti-reflection properties against incident light in a wide wavelength band from the visible light region (380 to 750 nm) to the near-infrared region (approximately 950 nm), and can ensure anti-reflection properties even when the incident light is obliquely incident at a high angle of approximately 70°. The convex structures according to Examples 1 to 3 have a composite structure (two-stage tapered structure) in which the two tapered portions described above are stacked, and the height h of the convex structure is 400 nm or more, preferably 490 nm or more. Therefore, it is believed that anti-reflection properties can be ensured against incident light in a wide wavelength band from the visible light region to the near-infrared region, and also against obliquely incident light at a high angle of approximately 70°.

[0237] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention.

[0238] REFERENCE SIGNS LIST 1 Optical film 2 Fine concave-convex structure 3 Structure 4 Recess 5 Transfer device 11 Substrate 12 Resin layer 12A Uncured resin layer 31 First tapered portion 32 Second tapered portion 33 Change point 100 Roll master 102 Concave-convex pattern area 110 Master substrate 111 Resist layer 112 Latent image 113 Opening 120 Fine concave-convex structure 130 Recess 131 First tapered recess 132 Second tapered recess 140 Convex portion 200 Exposure device 201 Laser light source 202 Laser light

Claims

1. A method for manufacturing a light-emitting device comprising: a substrate; and a plurality of convex structures arranged on at least one surface of the substrate at a pitch equal to or less than the wavelength band of visible light, wherein the structures have a composite structure consisting of a first tapered portion formed on the surface of the substrate and a second tapered portion formed on the first tapered portion, and a taper ratio C of the second tapered portion ２ is the taper ratio C of the first tapered portion １ the second tapered portion has a needle-like tapered shape that is thinner than the first tapered portion, and a height h of the structure is 400 nm or more.

2. The optical element according to claim 1, wherein the structure has a change point where the taper ratio of the side surface of the structure changes at the joint position between the top of the first tapered section and the bottom of the second tapered section.

3. An optical element according to claim 1 or 2, wherein the first tapered portion and the second tapered portion have a shape that approximates a linear taper, and the vertical cross-sectional shapes of the tapered surfaces of the first tapered portion and the second tapered portion are substantially straight lines.

4. The optical element according to claim 1 or 2, wherein the height h of the structure is 490 nm or more.

5. Height h of the second tapered portion ２ is 160 to 300 nm, and the height h of the first tapered portion １ The optical element according to claim 1 or 2, wherein the wavelength is 150 to 500 nm.

6. A roll master for manufacturing the optical element according to claim 1 or 2, comprising: a cylindrical or columnar master substrate; and a first fine uneven structure formed on the outer peripheral surface of the master substrate, wherein the first fine uneven structure includes a plurality of recesses having an inverted shape of the structures of the optical element, and the recesses have a composite structure consisting of a first tapered recess having an inverted shape of the first tapered portion, and a second tapered recess formed inside the first tapered recess and having an inverted shape of the second tapered portion.

7. A method for manufacturing an optical element according to claim 1 or 2, comprising: a step of manufacturing a roll master on which a first fine uneven structure is formed; a step of applying a resin layer made of a curable resin to the surface of the substrate of the optical element; and a step of forming a second fine uneven structure including the structures of the optical element in the resin layer by transferring the first fine uneven structure of the roll master to the resin layer, wherein the first fine uneven structure includes a plurality of recesses having the inverted shapes of the structures of the optical element, and the recesses have a composite structure consisting of a first tapered recess having the inverted shape of the first tapered portion, and a second tapered recess formed inside the first tapered recess and having the inverted shape of the second tapered portion.

8. The method for manufacturing an optical element according to claim 7, wherein the process for manufacturing the roll master includes: a film formation process for forming a resist layer on the outer peripheral surface of a master substrate of the roll master; an exposure process for forming a latent image by irradiating the resist layer with laser light; a development process for developing the resist layer on which the latent image has been formed and forming a pattern in the resist layer; and an etching process for etching the master substrate using the resist layer on which the pattern has been formed as a mask to form a concavo-convex pattern of the first fine concavo-convex structure on the outer peripheral surface of the master substrate, wherein in the etching process, etching conditions are changed during etching of the master substrate to form the concavo-convex pattern having the composite structure consisting of the first tapered concavo-convex ...

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