Infrared sensor cover and infrared sensor

Abstract

An infrared sensor cover (7) covers an infrared sensor that uses infrared light to measure the distance to a measured object. It comprises: a substrate (10); and a micro-protrusion structure (11) disposed on at least one surface of the substrate (10) and having a plurality of protrusions (12) arranged at a spacing (P) less than the wavelength λ of the infrared light. The infrared sensor cover (7) is disposed on the infrared sensor such that infrared light can be incident on the infrared sensor cover (7) from a direction inclined relative to the surface of the infrared sensor cover (7), and the ratio (H / λ) of the height (H) of the protrusions (12) to the wavelength λ is 0.5 or more.

Description

Technical Field

[0001] This invention relates to an infrared sensor cover and an infrared sensor.

[0002] This application claims a priority interest based on Japanese Patent Application No. 2024-019704, filed on February 13, 2024, the contents of which are incorporated herein by reference. Background Technology

[0003] In recent years, technologies such as those used in the automotive industry have become widespread. These technologies involve illuminating the area around a vehicle with infrared light (especially near-infrared light) from an infrared sensor and detecting the infrared light reflected off obstacles (the objects being measured), including other vehicles and pedestrians. This allows for the determination of the distance and relative speed between the vehicle and these obstacles. For example, optical ranging devices utilizing infrared remote sensing technologies such as LiDAR (Light Detection and Ranging) are employed.

[0004] Typically, in infrared sensors, a cover is placed around the sensor body to protect it. Infrared sensor covers are often made of glass or resin. However, when only glass or resin is used, infrared light is reflected from the cover surface, resulting in insufficient infrared transmittance and potentially degrading the performance of the infrared sensor. Therefore, for example, Patent Document 1 proposes an infrared sensor cover with an anti-reflective layer on its surface to prevent infrared light reflection.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2018-124279 Summary of the Invention

[0006] The technical problem that the invention aims to solve However, even with the conventional infrared sensor cover described in Patent Document 1, there is a problem that when infrared light is incident from a direction obliquely to the cover surface (hereinafter referred to as "oblique incidence"), the reflection of the obliquely incident infrared light cannot be sufficiently suppressed, resulting in a decrease in infrared transmittance. Especially in systems that use infrared sensors to scan and detect infrared light at a wide angle (e.g., 60°), the transmittance of infrared light incident obliquely to the cover surface deteriorates significantly, becoming a factor in the decrease in the detection accuracy of the infrared sensor. Therefore, a technology has been desired in the past to provide excellent anti-reflection performance for infrared light (especially near-infrared light) incident obliquely within a wide incident angle range (e.g., -60° to +60°), thereby improving the detection accuracy of the infrared sensor.

[0007] Therefore, the present invention was made in view of the above-mentioned problems, and the object of the present invention is to provide an infrared sensor cover and an infrared sensor that can improve the anti-reflection performance of obliquely incident infrared light in a wide incident angle range including wide-angle incident light.

[0008] Technical solutions used to solve technical problems To solve the above problems, according to one aspect of the present invention, an infrared sensor cover is provided for covering an infrared sensor that uses infrared light to measure the distance to a measured object, comprising: Substrate; and A micro-protrusion structure is disposed on at least one surface of the substrate and has a plurality of protrusions arranged at a spacing (P) below the wavelength λ of the infrared light. The infrared sensor cover is disposed on the infrared sensor, such that the infrared light can be incident on the infrared sensor cover from a direction inclined relative to the surface of the infrared sensor cover. Furthermore, the ratio (H / λ) of the height (H) of the protrusion to the wavelength λ is 0.5 or more.

[0009] The ratio (P / λ) of the spacing (P) of the protrusion to the wavelength λ can be less than 0.5.

[0010] The ratio (H / P) of the height (H) of the protrusion to the spacing (P) can be 3 or less.

[0011] The infrared radiation can be near-infrared radiation with a wavelength λ of 800nm ​​or more and 2500nm or less.

[0012] The shape of the protrusion can be substantially elliptical cone, elliptical frustum, or elliptical bell or dome shape in planar shape.

[0013] When the infrared light is incident on the surface of the infrared sensor cover at an angle of incidence greater than 0° and less than 60°, the reflectivity of the infrared light can be less than 3%.

[0014] Furthermore, to solve the above problems, according to another aspect of the present invention, an infrared sensor is provided, which comprises: The aforementioned infrared sensor cover; A light irradiation device that irradiates an infrared laser onto the object being tested through the infrared sensor cover; and A light detection device that detects reflected light of infrared radiation from the object being tested through the infrared sensor cover.

[0015] Invention Effects According to the present invention, it is possible to improve the anti-reflection performance against obliquely incident infrared radiation within a wide incident angle range, including wide-angle incident radiation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the overall structure of the optical ranging device according to the first embodiment of the present invention.

[0017] Figure 2 This is a cross-sectional view showing the infrared sensor cover of this embodiment.

[0018] Figure 3 This is a cross-sectional view of an infrared sensor cover, representing a modified example of this embodiment.

[0019] Figure 4 This is a top view showing the arrangement of multiple protrusions in the micro-convex structure of this embodiment.

[0020] Figure 5 This is a top view showing the arrangement of multiple protrusions in a micro-convex-concave structure of a modified example of this embodiment.

[0021] Figure 6 This is a perspective view showing an example of the protrusion of the micro-convex structure of this embodiment.

[0022] Figure 7 This is a perspective view showing an example of the protrusion of the micro-convex structure of this embodiment.

[0023] Figure 8 This is a perspective view showing an example of the protrusion of the micro-convex structure of this embodiment.

[0024] Figure 9 This is a partially enlarged cross-sectional view showing the micro-convex and concave structure of this embodiment.

[0025] Figure 10 It is a graph showing the results of simulating the relationship between the height of the protrusion of the micro-concave-convex structure of this embodiment and the incident angle and reflectivity.

[0026] Figure 11 This is a perspective view schematically representing the master disk of this embodiment.

[0027] Figure 12 This is a schematic diagram showing the structure of a transfer apparatus for manufacturing transfer materials using the master disc in this embodiment.

[0028] Figure 13 This is an explanatory diagram showing the general structure of the exposure apparatus in this embodiment.

[0029] Figure 14 This is a schematic diagram illustrating the method for measuring reflectance and diffracted light in an embodiment. Detailed Implementation

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The specific dimensions, materials, and values ​​shown in these embodiments are merely examples to facilitate understanding of the invention and, unless otherwise specified, do not limit the scope of the invention. Furthermore, in this specification and the accompanying drawings, elements with substantially the same function or structure are labeled with the same symbols, redundant descriptions are omitted, and illustrations of elements not directly related to the present invention are omitted.

[0031] 【1. Overall Structure of the Optical Rangefinder】 First, refer to Figure 1 The overall structure of the optical ranging device 1 using an infrared sensor according to the first embodiment of the present invention is described. Figure 1 This is a schematic diagram showing the overall structure of the optical ranging device 1 of this embodiment.

[0032] like Figure 1 As shown, the optical ranging device 1 equipped with an infrared sensor in this embodiment is a device that illuminates a target area 5 with light and detects the light reflected by the object 6, thereby measuring the distance, direction, size, shape, relative speed, etc. of the object 6. The optical ranging device 1 may include, for example, a ranging sensor (infrared sensor) utilizing remote sensing technology such as LiDAR. The preferred ranging method for the optical ranging device 1 is, for example, the TOF method, which calculates the distance to the object 6 by measuring the time of flight (TOF). However, various ranging methods, such as triangulation, may also be used. The time of flight (TOF) is the round-trip time from the emission of the illuminating light to the reception of the reflected light from the optical ranging device 1.

[0033] The optical ranging device 1 of this embodiment can be applied to various technical fields utilizing remote sensing. For example, the optical ranging device 1 can be applied to autonomous driving technology in the automotive field, ADAS (Advanced Driver-Assistance Systems) or traffic control radar devices, surveying in the construction field, surveying using aircraft / satellites, cleaning robots, 3D mapping surveying in various terminal devices (smartphones, smart glasses, smartwatches, personal computers, tablet PCs, etc.) utilizing AR (Augmented Reality) / MR (Mixed Reality) / VR (Virtual Reality) technologies, various surveying in fields such as geology / seismology / atmospheric physics / oceanography, or military applications, etc.

[0034] The optical ranging device 1 of this embodiment is mounted on vehicles such as automobiles, buses, trucks, and motorcycles, and is suitable for autonomous driving technology or ADAS. In this case, the optical ranging device 1 can measure the distance and orientation of the object 6 present around the vehicle, especially in the space in front of the vehicle, or create a 3D map. However, it is not limited to this example; the optical ranging device 1 can be mounted on various products in the aforementioned technical fields.

[0035] like Figure 1 As shown, the optical ranging device 1 of this embodiment includes a light illumination device 2 (emitter), a light detection device 3 (receiver), and a controller 4. This optical ranging device 1 is an example of an infrared sensor that uses infrared light to measure the distance to the object being measured, and functions as a ranging sensor such as LiDAR.

[0036] The light irradiation device 2 is a device (emitter) for irradiating light (infrared rays) onto the ranging target area 5. The light irradiation device 2 irradiates the ranging target area 5 with infrared rays emitted from a light source. The infrared rays irradiated by the light irradiation device 2 are lasers with an infrared wavelength (wavelength: approximately 700 nm to 1000 μm). As the infrared laser, lasers with wavelengths such as near-infrared (wavelength: approximately 700 nm to 2500 nm), mid-infrared (wavelength: approximately 2.5 μm to 4 μm), and far-infrared (wavelength: approximately 4 μm to 1000 μm) can be used. This infrared laser is preferably a laser with a near-infrared wavelength (e.g., 800 nm to 2500 nm, preferably 850 nm to 1550 nm) that is invisible to the human eye. The light source provided by the light irradiation device 2 is preferably a semiconductor laser or other laser source that emits infrared laser rays of the aforementioned wavelengths.

[0037] The light irradiation device 2 includes, for example, a light source with a light-emitting element that emits infrared laser light, an optical element that diffuses the laser light, and a housing (none of which are shown). The light irradiation device 2 emits pulsed laser light from the light source, diffuses the laser light through the optical element, and irradiates the ranging target area 5 with the diffused light (irradiation light). Alternatively, the light irradiation device 2 can also irradiate the ranging target area 5 by changing the irradiation direction of the pulsed laser light emitted from the light source in a wide-angle scanning manner.

[0038] The light detection device 3 is a device (receiver) for detecting infrared light (reflected light) irradiated from the light irradiation device 2 and reflected by the object under test 6. The light detection device 3 includes, for example, an optical filter and a light-receiving section with a light-receiving element (neither shown). The optical filter filters out light other than the reflected light reflected by the object under test 6 (e.g., sunlight or illumination light) as noise, allowing only light corresponding to the wavelength of the infrared laser emitted from the light irradiation device 2 to pass through. This improves the detection sensitivity of the light-receiving element to the reflected light. The light-receiving element is composed of a photoelectric conversion element that receives incident reflected light and generates a voltage. The light-receiving element is, for example, an image sensor such as a CMOS (Complementary Metal Oxide Semiconductor) sensor or a CCD (Charge Coupled Device) sensor. The light-receiving section, for example, receives the reflected light from the object under test 6 by multiple light-receiving elements arranged in two dimensions on the light-receiving surface, converts the light intensity at each pixel position on the light-receiving surface into an electrical signal, and outputs it to the controller 4.

[0039] The controller 4 is an example of a control unit that controls the operation of the light illumination device 2, the light detection device 3, and other various devices included in the optical rangefinder 1. The controller 4 may include, for example, a processor, a memory, an input device, an output device, a communication device, etc. (none of which are shown).

[0040] The processor is, for example, a CPU (Central Processing Unit) or other microprocessor. The processor executes a program stored in memory or other storage medium. Thus, it performs various processes in the optical ranging device 1, enabling it to perform various functions specified by the program.

[0041] Memory is a storage medium for storing programs and other various types of data. Examples of memory types include RAM (Random Access Memory) and ROM (Read Only Memory). ROM is a non-volatile memory that stores the program used by the processor, as well as the data used to run the program. RAM is a volatile memory that temporarily stores variables, calculation parameters, and calculation results used by the processor. Programs stored in ROM are read into RAM and executed by processors such as the CPU.

[0042] Controller 4 controls the light irradiation device 2 and the light detection device 3 to perform the ranging action of the optical ranging device 1. For example, controller 4 repeatedly performs laser irradiation by the light irradiation device 2 and reflected light detection by the light detection device 3, while simultaneously scanning the target area 5 in three dimensions and creating a three-dimensional map. At this time, controller 4 calculates the distance, direction, relative speed, etc. from the optical ranging device 1 to the object 6 based on the time difference between the laser emission timing of the light irradiation device 2 and the reflected light detection timing of the light detection device 3 (i.e., the time of flight of light: TOF).

[0043] Thus, the optical ranging device 1 scans the target area 5 with a laser to create a three-dimensional map representing the distance and direction of the object 6 within the target area 5. For this purpose, the optical ranging device 1 must illuminate the laser within the widest possible angular range (i.e., the field of view (FOV)). Since the laser emitted from the light source of the illumination device 2 has a narrow diffusion range, the field of view of the ranging sensor would be narrowed if used directly. Therefore, it is preferable to use a diffuser or similar device to diffuse the laser, illuminating the target area 5 with a wide field of view, thereby expanding the illumination area.

[0044] The diffuser plate used to diffuse the laser has a microlens array. By changing the shape of the microlenses, the desired diffusion angle (i.e., field of view) can be obtained. However, in ranging sensors such as the TOF sensor described above, the width of the laser irradiation area (the horizontal and vertical range of the ranging target area 5) and the laser irradiation distance (the measurable distance) are inversely related. Therefore, it is preferable to balance the two and determine the width of the irradiation area.

[0045] Thus, the optical ranging device 1 of this embodiment uses infrared laser to scan a wide range of ranging target area 5, irradiating infrared laser not only in the front direction of the optical ranging device 1, but also in the tilt direction, and also receiving the laser reflected light reflected by the object being measured 6 from the tilt direction.

[0046] 【2. Overview of the Infrared Sensor Cover】 In addition, such as Figure 1 As shown, the optical ranging device 1 (infrared sensor) of this embodiment includes an infrared sensor cover 7. The infrared sensor cover 7 (hereinafter sometimes simply referred to as "cover 7") is a cover for protecting the sensor body of the infrared sensor, and is configured to cover the sensor body. Here, the sensor body of the infrared sensor is, for example, a device assembly including the light irradiation device 2 (emitter), the light detection device 3 (receiver), and the controller 4 described above.

[0047] Cover 7 is configured to cover both or one of the light-emitting and light-receiving surfaces of the infrared sensor body. For example, Figure 1The cover 7 shown is a flat plate component, which is provided on the opening formed on one side of the housing of the optical ranging device 1 (infrared sensor), and is configured to cover both the light-emitting surface of the light irradiation device 2 and the light-receiving surface of the light detection device 3.

[0048] Furthermore, Gai 7 is not limited to Figure 1 Example shape and configuration. For example, the cover 7 may not be flat, but may be made of a curved plate-shaped cover. In addition, multiple covers 7 may be provided on an infrared sensor, and each of the multiple covers 7 may individually cover the light-emitting surface of the light irradiation device 2 and the light-receiving surface of the light detection device 3.

[0049] The cover 7 is made of a material that allows infrared light to pass through the infrared sensor, and preferably a material that allows good transmission of near-infrared light. Therefore, infrared laser light irradiated by the light irradiation device 2 of the infrared sensor can pass through the cover 7 from the inside to the outside. Furthermore, laser light reflected by the object being measured 6 can also pass through the cover 7 from the outside to the inside.

[0050] Thus, in the optical ranging device 1 (infrared sensor) of this embodiment, the light irradiation device 2 and the light detection device 3, which are the main body of the sensor, are covered by the cover 7. Furthermore, the light irradiation device 2 irradiates infrared laser light into the optical ranging device 1 in both the frontal and tilted directions through the cover 7, thereby scanning the entire ranging target area 5 including the object 6. On the other hand, when the irradiated infrared laser light is reflected by the object 6 and returns from the frontal and tilted directions of the optical ranging device 1, the light detection device 3 receives and detects the reflected light through the cover 7.

[0051] As described above, the cover 7 of the infrared sensor in this embodiment receives infrared laser light and its reflected light from both the inside and outside. Furthermore, in the optical ranging device 1 (infrared sensor) of this embodiment, the cover 7 is configured to receive infrared laser light and its reflected light not only from a direction perpendicular to the surface of the cover 7 (normal direction) but also from a direction inclined relative to the surface (inclination direction) at a wide angle of incidence θ. Here, the range of the angle of incidence θ of the infrared laser light and its reflected light incident obliquely relative to the cover 7 varies depending on the specifications and application of the optical ranging device 1 (infrared sensor), and may be, for example, -45° to +45°, -60° to +60°, -75° to +75°, etc., and sometimes is an extremely wide angle and a wide range. In addition, in this specification, when the angle of incidence θ is a positive value (e.g., +45°), it means that the obliquely incident light is incident from a direction inclined to one side (negative X-axis direction) relative to the normal direction (Z direction) of the surface of the cover 7. On the other hand, when the incident angle θ is negative (e.g., -45°), it means that the obliquely incident light is incident from the direction of the normal to the surface of the cover 7 (Z direction) to the other side (positive X-axis direction).

[0052] Thus, when an infrared laser with a wavelength longer than visible light is incident obliquely at a wide angle (e.g., about 60°) θ onto the cover of an infrared sensor, a conventional cover cannot adequately suppress the reflection of the obliquely incident infrared light. Therefore, in a conventional cover, the reflectivity of this obliquely incident infrared light can reach, for example, more than 3%, and the transmittance of the obliquely incident infrared light can drop to, for example, below 97%, leading to a decrease in the detection accuracy of the infrared sensor.

[0053] Therefore, the infrared sensor and cover 7 of this embodiment aim to significantly improve the anti-reflective performance of the cover 7 for obliquely incident infrared light (especially near-infrared light) within a wide incident angle range (e.g., -60° to +60°) including normal incident light and wide-angle incident light, thereby improving the detection accuracy of the infrared sensor passing through the cover 7. To this end, the surface of the cover 7 of this embodiment has a micro-uneven structure as an anti-reflective layer corresponding to wide-angle obliquely incident infrared light. The features of the micro-uneven structure of the cover 7 of this embodiment are described in detail below.

[0054] 【3. Structure of the Infrared Sensor Cover】 Next, refer to Figures 2-3 The structure of the infrared sensor cover 7 in this embodiment will be explained. Figure 2 This is a cross-sectional view showing the infrared sensor cover 7 of this embodiment. Figure 3 This is a cross-sectional view showing the infrared sensor cover 7 according to a modified embodiment of this invention.

[0055] like Figure 2 As shown, the infrared sensor cover 7 has a substrate 10 and a micro-protrusion structure 11.

[0056] The substrate 10 is the substrate that constitutes the main body of the cover 7. The substrate 10 is a plate-shaped or sheet-shaped substrate. The substrate 10 is, for example, a flat plate, but it can also be a curved plate, as long as it is a plate shape suitable for mounting the cover 7 on the infrared sensor. The thickness of the substrate 10 is not particularly limited and can be appropriately adjusted according to the wavelength λ of the infrared light used by the infrared sensor, the purpose of the cover 7, etc.

[0057] The substrate 10 is formed, for example, from an inorganic material such as glass or an organic material such as resin. The material of the substrate 10 is preferably a resin (e.g., thermoplastic resin, photocurable resin, etc.) with excellent infrared transmittance for use in infrared sensors, and particularly preferably a resin with excellent near-infrared transmittance. Examples of such resins include polymethyl methacrylate, polycarbonate, A-PET, cyclic olefin copolymers, and cyclic olefin polymers. Alternatively, the substrate 10 may also be formed from an inorganic material with excellent infrared transmittance. Examples of such inorganic materials include silicon-based materials, and more specifically, glass. The infrared transmittance of the substrate 10 is preferably 97% or higher.

[0058] The micro-protrusion structure 11 is a micro-protrusion structure (moth-eye structure) formed on the surface of the substrate 10. The micro-protrusion structure 11 has the function of preventing infrared reflection from the surface of the cover 7 (anti-reflection function).

[0059] like Figure 2 and Figure 3 As shown, the micro-protrusion structure 11 is disposed on at least one surface of the substrate 10. Figure 2 In the example, micro-protrusion structures 11 are provided on both surfaces of the substrate 10 (i.e., surface 10A and back surface 10B). On the other hand, Figure 3 In the example, the micro-protrusion structure 11 is provided only on one surface (i.e., surface 10A) of the substrate 10.

[0060] The micro-protrusion structure 11 has multiple protrusions 12 and multiple recesses 13. A protrusion 12 is a protruding structure that extends vertically from the surface of the substrate 10. A recess 13 is a recessed portion between adjacent protrusions 12. The size and spacing P of the protrusions 12 are, for example, about tens of nm to tens of μm, preferably about hundreds of nm to several μm (nanometer scale), which is extremely fine.

[0061] To utilize the infrared anti-reflection function of the micro-protrusion structure 11, the protrusions 12 of the micro-protrusion structure 11 are disposed on the surface of the substrate 10 at a spacing P that is less than or equal to the wavelength λ of the infrared light used by the infrared sensor. In other words, the spacing P of the protrusions 12 of the micro-protrusion structure 11 is less than or equal to the wavelength λ of the infrared light used by the infrared sensor. For example, when the infrared light used by the infrared sensor is near-infrared light, and the wavelength λ of the near-infrared light is in the range of 800 nm to 2500 nm, the spacing P of the protrusions 12 is preferably less than or equal to the wavelength λ of the near-infrared light. Furthermore, the spacing P is the distance between the vertices of two adjacent protrusions 12 (i.e., the distance between the center points of the planar shapes of the two protrusions 12) (see reference). Figure 4 ).

[0062] In this embodiment, by providing a micro-protrusion structure 11 on the surface of the cover 7, consisting of a plurality of protrusions 12 arranged at such a small pitch P, a moth-eye structure with excellent anti-reflective properties against infrared light can be formed on the surface of the cover 7. As a result, an effective refractive index gradient is formed between the air and the material of the cover 7, so light (infrared light) incident on the surface of the cover 7 and transmitted through the micro-protrusion structure 11 is slowly refracted, suppressing surface reflection.

[0063] like Figure 2 As shown, if micro-uneven structures 11 are formed on both surfaces (surface 10A and back surface 10B) of the substrate 10, infrared reflection from both surfaces 10A and 10B of the substrate 10 can be suppressed. Therefore, as Figure 1As shown, in the case where infrared light (illumination light and reflected light) is incident on the cover 7 from both the surface side and the back side of the cover 7 in the infrared sensor, as... Figure 2 As shown, it is preferable to provide micro-protrusion structures 11 on the two surfaces (surface 10A and back surface 10B) of the substrate 10 of the cover 7 to suppress the reflection of infrared rays incident on the two surfaces of the cover 7.

[0064] In addition, such as Figure 3 As shown, the micro-protrusion structure 11 can also be formed only on one surface (surface 10A) of the substrate 10, while not forming the micro-protrusion structure 11 on the other surface (back surface 10B). This can also suppress infrared reflection from the surface 10A of the substrate 10 and suppress infrared reflection from one surface of the cover 7. Furthermore, although not shown, the micro-protrusion structure 11 can be provided on one surface of the substrate 10, and a multilayer anti-reflective film can be provided on the other surface.

[0065] 【4. The structure of the micro-convex and concave structure】 Next, refer to Figures 4-8 The structure of the micro-protrusion structure 11 in this embodiment will be described in more detail. Figure 4 This is a top view showing the arrangement of the plurality of protrusions 12 of the micro-convex-concave structure 11 in this embodiment. Figure 5 This is a top view showing the arrangement of a plurality of protrusions 12 in the micro-convex-concave structure 11 of this embodiment. Figures 6-8 This is a perspective view showing an example of the protrusion 12 of the micro-concave-convex structure 11 of this embodiment.

[0066] The multiple protrusions 12 of the micro-concave-convex structure 11 can be arranged regularly on the surface of the substrate 10 or arranged irregularly. Figure 4 This represents an example of a regular configuration of multiple protrusions 12 having an elliptical planar shape. Figure 5 This represents an example of a regular arrangement of multiple protrusions 12 having a circular planar shape.

[0067] like Figure 4 and Figure 5 As shown, in the micro-protrusion structure 11 of this embodiment, a plurality of protrusions 12 are arranged regularly in a hexagonal lattice on the surface of the substrate 10 (on the XY plane). The plurality of protrusions 12 are spaced at predetermined intervals (dot spacing P) along multiple tracks T extending in the X direction. D Configuration. Track T is an imaginary line representing the arrangement direction of the protrusions 12. Multiple tracks T are parallel to each other and spaced at specified intervals (track spacing P) along the Y direction. T Configuration.

[0068] Here, the point spacing P D It refers to the spacing of the protrusions 12 along the track direction (X direction), i.e., the length direction of track T. That is, the point spacing P. DIt is the distance between the vertices of two adjacent protrusions 12 along the track direction (X direction). Point spacing P D Equal to the above spacing P (P D =P). On the other hand, the track spacing P T It refers to the spacing of the protrusions 12 along the direction perpendicular to the track direction (X direction), i.e., the direction perpendicular to the track (Y direction). Track spacing P T It is equal to the interval between two adjacent tracks T and T' along the perpendicular direction (Y direction) of the track. For example... Figure 4 As shown, when the protrusions 12 are arranged in a hexagonal lattice, the orbital spacing P T For values ​​smaller than the above spacing P (P T <P). Furthermore, although not illustrated, when the protrusions 12 are arranged in a square lattice, the dot spacing P D and track spacing P T The value equal to the above spacing P (P) D =P T =P).

[0069] like Figure 4 and Figure 5 As shown, the multiple protrusions 12 are arranged regularly in a hexagonal lattice shape along the aforementioned multiple orbitals T. Therefore, the point spacing P between any two randomly selected protrusions 12 is... D The track spacing P is approximately a fixed value. T It is also a roughly fixed value. Furthermore, when comparing two columns of protrusions 12 arranged on two adjacent tracks T and T along the Y direction, the offset point P of the arrangement of one column of protrusions 12 in the X direction relative to the other column of protrusions 12 is... D One-half (P) D / 2). Thus, by shifting the convex portion 12 in the X direction by P along each track T. D In the / 2 configuration, multiple protrusions 12 are arranged regularly in a hexagonal lattice within the overall micro-protrusion structure 11. This allows for the densest filling of the protrusions 12 on the surface of the substrate 10, increasing the filling rate of the protrusions 12. Therefore, the anti-reflective performance of the micro-protrusion structure 11 per unit area on the surface of the substrate 10 can be improved.

[0070] Furthermore, the fill rate is the proportion of the area occupied by the plurality of protrusions 12 on the surface (XY plane) of the substrate 10. When the surface (flat surface) of the substrate 10 is filled with the plurality of protrusions 12, and there are no flat surfaces between the protrusions 12, the fill rate is 100%. On the other hand, as... Figure 4 As shown, when multiple protrusions 12 are arranged with a certain gap on the surface (flat surface) of the substrate 10, and the recesses 13 between the multiple protrusions 12 have flat surfaces, the filling rate is less than 100%. Figure 4As shown, even if the multiple protrusions 12 are arranged with gaps between them, it is preferable to minimize the gaps as much as possible and increase the fill rate to, for example, 80% or more, preferably 90% or more. This improves the anti-reflective performance of the micro-protrusion structure 11.

[0071] Furthermore, the micro-protrusion structure 11 is preferably as follows: Figure 4 and Figure 5 As shown, the plurality of protrusions 12 on the surface of the substrate 10 are arranged in a hexagonal lattice pattern at the vertices and center of the hexagons. This allows a large number of protrusions 12 to be arranged in a densest possible configuration on the surface of the substrate 10 (in the XY plane), improving the anti-reflective performance of the moth-eye structure. However, the plurality of protrusions 12 in the micro-convex-concave structure 11 are not limited to the hexagonal lattice pattern described above; for example, they can also be arranged regularly in other ways, such as a square lattice, a rectangular lattice, or a triangular lattice. Alternatively, the plurality of protrusions 12 can also be irregularly arranged on the surface of the substrate 10. For example, the plurality of protrusions 12 can also be irregularly arranged at positions randomly offset from a reference position within a specified range of variation, while based on the various lattice patterns described above.

[0072] 【4.1. Preferred range of the distance P between the protrusions】 The spacing P of the protrusions 12 can be, for example, multiple sets of spacing (point spacing P) between adjacent protrusions 12, 12. D Or track spacing P T The arithmetic mean of ). For example, select multiple groups of two adjacent protrusions 12, 12 along the track direction (X direction), and calculate or measure the point spacing P of these multiple groups of protrusions 12, 12. D Then, the distance P between multiple points can be calculated or measured. D The arithmetic mean of the interval is used as the interval P.

[0073] The spacing P is smaller than or equal to the wavelength λ of the infrared light used by the infrared sensor, and preferably smaller than the minimum value of that infrared band. For example, the spacing P can be less than 1000 nm, and preferably more than 100 nm and less than 900 nm. Thus, the micro-protrusion structure 11 can function well as a moth-eye structure to suppress the reflection of broadband infrared incident light.

[0074] However, when the spacing P is less than 100 nm, it becomes difficult to form the micro-protrusion structure 11 through nanoimprinting or the like, which is therefore not preferred. Therefore, the lower limit of the spacing P is not particularly limited, but from the viewpoint of stably forming the micro-protrusion structure 11, it is preferred to be 100 nm or more. Furthermore, when the spacing P exceeds the wavelength λ of the infrared light used by the infrared sensor, infrared diffraction occurs, leading to a decrease in the anti-reflective performance of the moth-eye structure, which is also not preferred. Furthermore, the dot spacing P... D and track spacing P TThe sizes of the elements can be the same or different, as long as they are within the preferred range of the aforementioned spacing P.

[0075] 【4.2. Preferred shape of protrusion 12】 like Figures 6-8 As shown, the three-dimensional shape of the protrusion 12 of the micro-convex-concave structure 11 can be any shape that protrudes in a direction perpendicular to the surface of the substrate 10 (Z direction). For example, it can be a cone shape (conical shape, elliptical cone shape, pyramidal shape), a frustum shape (frustum shape, elliptical frustum shape, frustum pyramidal shape), a bell shape, a dome shape, or any shape such as a protrusion or needle shape. The planar shape of the protrusion 12 is preferably circular, for example (see reference). Figure 5 ), oval (refer to) Figure 4 However, it can also be any shape such as a polygon. In addition, the planar shape of the protrusion 12 is the planar shape that represents the shape of the protrusion 12 when the protrusion 12 is projected onto the surface of the substrate 10 (XY plane).

[0076] From the viewpoint of ease of forming the protrusion 12, the three-dimensional shape of the protrusion 12 is preferably substantially elliptical in planar shape (see reference). Figure 4 The three-dimensional shape of the protrusion 12 is preferably substantially an elliptical cone shape (see reference). Figure 6 ), an elliptical frustum shape with a flat top (see reference) Figure 7 ), or a bell-shaped or dome-shaped planar shape (see reference). Figure 8 )wait.

[0077] Thus, the three-dimensional shape of the protrusion 12 is preferably an elliptical cone or the like, in which the cone shape extends or contracts along the track direction (X direction). Thus, if the shape of the protrusion 12 is an elliptical planar shape (refer to...), Figure 4 The three-dimensional shape of the protrusion 12 facilitates efficient manufacturing of a micro-convex-concave structure 11 with a large number of protrusions 12. For example, according to the master disk 100 manufacturing method using laser exposure described later (see...). Figure 13 The recess 122 of the micro-uneven structure 120 formed on the outer peripheral surface of the roller-shaped mother disk 100 (refer to) Figure 11 The planar shape of the micro-convex structure 120 of the master disc 100 is easily elliptical, making it difficult to form a complete circle. The recess 122 of the micro-convex structure 120 of the master disc 100 has a shape that is the reverse of the shape of the protrusion 12 of the micro-convex structure 11 of the cover 7. Therefore, it is preferable to allow the shape of the protrusion 12 of the micro-convex structure 11 formed by the roller master disc 100 to be a three-dimensional shape with an elliptical planar shape. As a result, the micro-convex structure 11 with the elliptical protrusion 12 can be easily and with high precision manufactured using the master disc manufacturing method using this laser exposure method.

[0078] Furthermore, in this specification, "substantially elliptical" means not limited to a geometrically strictly elliptical shape, but includes shapes such as oblong and oval that can be substantially considered elliptical. Similarly, "substantially elliptical cone" or "elliptical frustum" means not limited to a geometrically strictly elliptical cone or frustum shape, but includes shapes that can be substantially considered elliptical cones or frustums (e.g., shapes deformed by extending or contracting a cone or frustum shape along the orbital direction (X direction)).

[0079] 【4.3. Materials with Micro-uneven Structures】 Although described in detail later, the micro-protrusion structure 11 is formed, for example, by roll-to-roll embossing using a roller master. The protrusion shape formed on the outer peripheral surface of the roller master has the reverse shape of the micro-protrusion structure 11. The protrusion shape on the outer peripheral surface of the roller master is transferred to an uncured resin layer laminated on the surface of the substrate 10, and then the uncured resin layer is cured to form the micro-protrusion structure 11. In this way, by transferring the micro-protrusion structure 11 to the surface of the substrate 10 of the cover 7 using a roller master, the cover 7 with anti-reflective function can be easily manufactured. To manufacture the cover 7 using this embossing technique, the micro-protrusion structure 11 can be formed, for example, on a resin layer laminated on the surface of the substrate 10, or it can be formed on a resin layer constituting the substrate 10 itself. The resin layer on which the micro-protrusion structure 11 is formed is, for example, a cured product of a curable resin.

[0080] The cured product of a curable resin is preferably transparent. A curable resin comprises a polymerizable compound and a curing initiator. The polymerizable compound is a resin cured by a curing initiator. Examples of polymerizable compounds include epoxy polymerizable compounds and acrylic polymerizable compounds. Epoxy polymerizable compounds are monomers, oligomers, or prepolymers having one or more epoxy groups within their molecules. Examples of epoxy polymerizable compounds include various bisphenol type epoxy resins (bisphenol A, F, etc.), phenolic varnish type epoxy resins, various modified epoxy resins such as rubber and polyurethane, naphthalene type epoxy resins, biphenyl type epoxy resins, phenolic varnish type epoxy resins, stilbene type epoxy resins, triphenol methane type epoxy resins, dicyclopentadiene type epoxy resins, triphenylmethane type epoxy resins, and prepolymers of these substances.

[0081] Acrylic acid polymerizable compounds are monomers, oligomers, or prepolymers having one or more acryloyl groups within their molecules. Monomers are further classified into monofunctional monomers having one acryloyl group, difunctional monomers having two acryloyl groups, and polyfunctional monomers having three or more acryloyl groups.

[0082] Examples of "monofunctional monomers" include carboxylic acids (acrylic acid), hydroxyl groups (2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate), alkyl or alicyclic monomers (isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate), and other functional monomers (2-methoxyethyl acrylate, methoxyethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, N,N-dimethylaminoethyl acrylate, N... N-Dimethylaminopropylacrylamide, N,N-Dimethylacrylamide, Acryloylmorpholine, N-Isopropylacrylamide, N,N-Diethylacrylamide, N-Vinylpyrrolidone, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate, 2,4,6-tribromophenyl acrylate, 2,4,6-tribromophenyl methacrylate, 2-(2,4,6-tribromophenoxy)ethyl acrylate, 2-ethylhexyl acrylate, etc.

[0083] Examples of "difunctional monomers" include tripropylene glycol diacrylate, trimethylolpropane-diallyl ether, and polyurethane acrylate.

[0084] Examples of "multifunctional monomers" include trimethylolpropane triacrylate, pentaerythritol pentaacrylate and hexaacrylate, and di(trimethylolpropane)tetraacrylate.

[0085] Examples of polymerizable acrylic compounds other than those listed above include morpholine acrylate, glyceryl acrylate, polyether acrylate, N-vinylformamide, N-vinylcaprolactam, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, polyethylene glycol acrylate, EO-modified trimethylolpropane triacrylate, EO-modified bisphenol A diacrylate, aliphatic polyurethane oligomers, and polyester oligomers. From the viewpoint of the transparency of the cap 7, polymerizable compounds are preferably acrylic polymerizable compounds.

[0086] A curing initiator is a material that causes a curable resin to cure. Examples of curing initiators include thermosetting initiators and photosetting initiators. Curing initiators can also be cured by a certain energy line other than heat or light (such as an electron beam). When the curing initiator is a thermosetting initiator, the curable resin is a thermosetting resin; when the curing initiator is a photosetting initiator, the curable resin is a photosetting resin.

[0087] From the viewpoint of the transparency of the cap 7, the curing initiator is preferably a UV-curing initiator. Therefore, the curable resin is preferably a UV-curable acrylic resin. A UV-curing initiator is a type of photocuring initiator. Examples of UV-curing initiators include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexylphenyl one, and 2-hydroxy-2-methyl-1-phenylpropane-1-one.

[0088] In addition, the resin that forms the micro-uneven structure 11 can also be a resin that imparts functions such as hydrophilicity, hydrophobicity, and anti-fogging.

[0089] Furthermore, additives may be added to the resin forming the micro-textured structure 11, depending on the intended use of the cap 7. Examples of such additives include inorganic fillers, organic fillers, leveling agents, surface conditioners, and defoamers. Furthermore, examples of inorganic fillers include metal oxide particles such as SiO2, TiO2, ZrO2, SnO2, and Al2O3.

[0090] Furthermore, the micro-protrusion structure 11 can also be formed directly on the surface of the substrate 10 as described above by imprinting with a roller disc. However, it is not limited to this example; for example, a resin film (e.g., a thermoplastic resin film) with the micro-protrusion structure 11 formed can also be adhered to the surface of the substrate 10.

[0091] 【5. Characteristics of the height H and spacing P of the protrusions in a micro-convex-concave structure】 Next, refer to Figure 9 This section describes the characteristics of the height H of the protrusion 12 of the micro-convex-concave structure 11 in this embodiment, which is related to the spacing P. Figure 9 This is a partially enlarged cross-sectional view showing the micro-convex-concave structure 11 of this embodiment.

[0092] like Figure 9 As shown, the infrared sensor cover 7 of this embodiment has a micro-protrusion structure 11 for suppressing the reflection of incident light 31 (hereinafter sometimes referred to as "oblique incident light 31") incident from an oblique direction relative to the surface (XY plane) of the substrate 10. The micro-protrusion structure 11 has a plurality of protrusions 12 regularly arranged on the surface of the substrate 10 at a predetermined spacing P. Each protrusion 12 protrudes in a direction perpendicular to the surface of the substrate 10 (Z direction: normal direction). The height H of the protrusion 12 is the normal direction (Z direction) length from the root of the protrusion 12 to its apex. The spacing P of the protrusions 12 is the distance between the apexes of adjacent protrusions 12, 12 on the XY plane.

[0093] From the perspective of the infrared uniformity and light distribution of the cover 7, such as Figure 9As shown in the example, it is preferable that the height H of the plurality of protrusions 12 is the same as that of each other, and that the spacing P of the protrusions 12 is equal. However, it is not limited to this example, and the height H of the plurality of protrusions 12 may be unequal within a specified error range. The spacing P of the protrusions 12 may also be unequal within a specified error range.

[0094] The spacing P of the protrusions 12 is preferably less than or equal to the wavelength λ of the infrared incident light 31 incident on the cover 7 (P≦λ). Thus, the micro-protrusion structure 11 functions as a moth-eye structure to suppress the reflection of infrared light of wavelength λ, thereby suppressing the reflection of infrared light of wavelength λ on the surface of the cover 7.

[0095] 【5.1. Ratio of convex height H to wavelength λ (First condition)】 Here, we will explain the first condition for the micro-convex-concave structure 11 of this embodiment, namely the height H of the protrusion 12.

[0096] The ratio (=H / λ) of the height H of the protrusion 12 to the wavelength λ of the infrared incident light 31 is preferably 0.5 or more. That is, the height H of the protrusion 12 is preferably 0.5 times or more of the wavelength λ, satisfying the following formula (1).

[0097] H / λ≧0.5 ・・・(1) By satisfying equation (1), the anti-reflection performance against obliquely incident light 31 can be improved. Therefore, the anti-reflection characteristics of the micro-convex-concave structure 11 can be improved against obliquely incident light 31 in a wide incident angle θ range (e.g., θ = -60° to +60°), including wide-angle incident light (e.g., 45° or more). The reasons are explained below.

[0098] In this embodiment, a micro-protrusion structure 11 (moth-eye structure) with multiple micro-protrusions 12 arranged at intervals P below the wavelength λ of the infrared incident light 31 is formed on the surface of the substrate 10 of the cover 7. This allows for continuous variation of the refractive index n at the air-cover 7 interface, suppressing the reflection of incident light 31 from the surface of the cover 7. To improve the anti-reflection effect of the micro-protrusion structure 11 on obliquely incident light, it is preferable to minimize the change in refractive index n. Therefore, it is preferable to set the height H of the protrusions 12 of the micro-protrusion structure 11 to a predetermined height or higher.

[0099] Therefore, the inventors conducted simulations using the RCWA (Rigorous Coupled-Wave Analysis) method to thoroughly investigate the relationship between the anti-reflection effect on obliquely incident light, especially wide-angle obliquely incident light 31, and the height H of the protrusion 12. The results showed that if the height H of the protrusion 12 is more than 0.5 times the wavelength λ of the obliquely incident infrared light (i.e., satisfying the above equation (1)), the anti-reflection effect on the obliquely incident light 31 can be improved. In particular, the larger the incident angle θ of the obliquely incident light 31, the more significant the improvement in the anti-reflection effect. Therefore, based on this discovery, the inventors recognized that the condition (first condition) of the ratio (H / λ) of the height H of the protrusion 12 to the wavelength λ of the obliquely incident light 31 being more than 0.5 is crucial, and thus conceived of a micro-convex-concave structure 11 that satisfies this first condition.

[0100] The micro-convex-concave structure 11 satisfies the first condition (H / λ≧0.5), such as... Figure 9 As shown, even if the infrared obliquely incident light 31 is incident on the surface of the cover 7 at a wide angle, the reflected light 32 reflected on the surface of the cover 7 can be reduced, and the transmitted light 33 transmitted through the cover 7 can be increased. Therefore, the reflectivity of the obliquely incident light 31 on the surface of the cover 7 can be suppressed to, for example, 3% or less, preferably 2.5% or less, and the transmittance of the obliquely incident light 31 transmitted through the cover 7 can be increased to, for example, 97% or more, preferably 97.5% or more. Therefore, compared with the prior art, the cover 7 with the micro-uneven structure 11 according to this embodiment can significantly improve the anti-reflection performance against infrared light (especially near-infrared light) obliquely incident within a wide incident angle θ range (e.g., -60° to +60°), reducing the reflectivity of the wide-angle obliquely incident light 31 to 3% or less. Therefore, the detection accuracy of the infrared sensor covered by the cover 7 of this embodiment can be significantly improved.

[0101] 【5.2. Ratio of spacing P to wavelength λ (Second condition)】 Next, as a second condition for the micro-convex-concave structure 11 of this embodiment, the condition for the spacing P of the protrusions 12 will be explained.

[0102] The ratio (=P / λ) of the spacing P of the protrusions 12 to the wavelength λ of the infrared incident light 31 is preferably 0.5 or less. That is, the spacing P of the protrusions 12 is 0.5 times or less of the wavelength λ, and preferably satisfies the following formula (2).

[0103] P / λ≦0.5 ・・・(2) By satisfying equation (2), the amount of infrared incident light 31 transmitted through the cover 7 can be increased. Therefore, the amount of light received by the infrared sensor covered by the cover 7 and the amount of light emitted from the infrared sensor can be increased, thereby improving the detection accuracy of the infrared sensor. The reason is explained below.

[0104] Typically, when periodic micro-undulation structures are formed on the surface of optical elements, high-order diffraction light is generated when light passes through these structures, resulting in a significant reduction in the linear component of the transmitted light (see reference). Figure 14 However, when the spacing P between the protrusions of the micro-structure is shorter than the wavelength λ of the transmitted light, the diffracted light will decrease.

[0105] At this point, if the spacing P is too wide compared to the wavelength λ of the obliquely incident light 31, the obliquely incident light 31 will bend due to diffraction on the surface of the cover 7. Therefore, the amount of light received and emitted by the infrared sensor will decrease, resulting in a decrease in the detection accuracy of the infrared sensor.

[0106] In contrast, according to the micro-uneven structure 11 of this embodiment, the ratio of the spacing P to the wavelength λ is 0.5 times or less (second condition), and the spacing P is set to an appropriate size corresponding to the wavelength λ. This suppresses the generation of high-order diffracted light on the surface of the cover 7, thereby improving the straightness of the obliquely incident light 31 and increasing the amount of transmitted light 33 passing through the cover 7. Therefore, it increases the amount of transmitted light 33 passing through the cover 7 towards the infrared sensor and the amount of irradiated light emanating from the infrared sensor and passing through the cover 7. Thus, it increases the amount of light received and emitted by the infrared sensor, thereby further improving the detection accuracy of the infrared sensor.

[0107] Furthermore, by simultaneously satisfying both the first condition (H / λ≧0.5) and the second condition (P / λ≦0.5), a micro-concave-convex structure 11 with excellent anti-reflection effect and diffraction suppression effect on wide-angle oblique incident light 31 can be achieved.

[0108] 【5.3. Aspect Ratio (H / P) of the Convex Part (Third Condition)】 Next, as the third condition for the micro-convex-concave structure 11 of this embodiment, the condition for the aspect ratio of the convex portion 12 will be explained.

[0109] The aspect ratio is the ratio of the height H of the protrusion 12 to the distance P (=H / P). This aspect ratio (H / P) is preferably 3 or less. That is, the height H of the protrusion 12 is preferably 3 times or less than the distance P, satisfying the following formula (3).

[0110] H / P≦3 ・・・(3) By satisfying equation (3), when the micro-unraveling structure 11 is formed on the surface of the cover 7 by imprinting the master disc, the demolding performance when peeling the master disc from the cover 7 with the micro-unraveling structure 11 can be improved. Therefore, the micro-unraveling structure 11 can be formed easily and with high precision by imprinting the master disc.

[0111] That is, when the spacing P of the protrusions 12 constituting the micro-convex structure 11 is too narrow, or the height H of the protrusions 12 is too high, the aspect ratio (H / P) will become too large. Therefore, the release properties during the above-mentioned embossing process decrease, making it difficult to manufacture the micro-convex structure 11.

[0112] In contrast, according to the micro-convex structure 11 of this embodiment, the aspect ratio (H / P) is 3 or less (third condition), and the height H is set to an appropriate size corresponding to the spacing P. As a result, the demolding performance during the above-mentioned embossing can be improved, and thus the micro-convex structure 11 of the desired shape can be easily and with high precision without producing defects.

[0113] 【5.4. Simulation Results】 Next, refer to Figure 10 The results illustrate the relationship between the height H of the protrusion 12 of the micro-convex structure 11 and the incident light reflectance R of the micro-convex structure 11 surface at each incident angle θ [°] to verify the anti-reflection effect based on the first condition (H / λ≧0.5) of the height H of the protrusion 12. Figure 10 It is a graph representing the simulation results.

[0114] The simulation conditions are as follows.

[0115] Incident light wavelength λ: 900nm Incident angle θ: 10°, 40°, 60°, 70° The height H of the protrusion 12: 200nm, 300nm, 500nm, 650nm The longitudinal cross-sectional shape of the protrusion 12 is approximately parabolic. The planar shape of the protrusion 12 is circular. Planar configuration of convex portion 12: hexagonal lattice (see reference) Figure 5 ) The spacing P of the protrusion 12 is 300 nm. The refractive index of the material of protrusion 12 is 1.5. Air refractive index: 1.0 Table 1 shows the relationship between the height H [nm] of the convex part 12, the incident angle θ [°], and the incident light reflectivity R [%] obtained through this simulation. Furthermore, this relationship is also shown in... Figure 10 The curve in the graph.

[0116] [Table 1] As shown in Table 1 and Figure 10As shown, regardless of the height H of the protrusion 12, the larger the incident angle θ of the obliquely incident light, the greater the reflectivity R. However, it is known that when H = 500nm and 650nm, compared with H = 200nm and 300nm, the absolute value and rate of increase of the reflectivity R can be suppressed to a lower value. For example, when θ = 60° wide-angle incident light, the reflectivity R at H = 200nm and 300nm are 6.14% and 3.52% respectively, which significantly exceed the reference reflectivity (e.g., 3%, preferably 2.5%). Therefore, when the height H is low, the anti-reflection effect of the micro-protrusion structure 11 decreases. In contrast, the reflectivity R at H = 500nm and 650nm are 1.14% and 1.41% respectively, which are significantly lower than the reference reflectivity (e.g., 3%, preferably 2.5%). Therefore, when the height H is high, it can be said that the anti-reflection effect for obliquely incident light at a wide angle of about 60° is excellent. In addition, the reference reflectance is the upper limit of the reflectance required for infrared sensor covers used in vehicles such as LiDAR (e.g., 3%, preferably 2.5%).

[0117] Therefore, based on the simulation results above, if the height H of the protrusion 12 is a specified height (e.g., 500 nm) or more and H / λ is 0.5 or more, relative to the wavelength λ of the obliquely incident light, the reflectivity R of the obliquely incident light, including a wide range (10° to 60°) of approximately 60° wide-angle incident light, can be suppressed to less than 3%, preferably less than 1.5%. Therefore, it can be said that the anti-reflection effect on the obliquely incident light is extremely excellent.

[0118] 6. Structure of the master disk Next, refer to Figure 11 This describes the master disk 100 used to mold the micro-convex structure 11 of the infrared sensor cover 7 of this embodiment. Figure 11 This is a perspective view schematically representing the master disk 100 of this embodiment.

[0119] The master disc 100 is a mold that transfers the micro-protrusion structure 120 onto the surface of a transfer material (such as the infrared sensor cover 7 of this embodiment) by roll-to-roll printing. From the viewpoint of efficient production of transfer materials, the master disc 100 is preferably a cylindrical or cylindrical roller-shaped master disc, but it can also be a flat master disc. If the master disc 100 is a roller-shaped master disc, the micro-protrusion structure 120 of the master disc 100 can be seamlessly transferred onto the substrate of the transfer material by roll-to-roll printing. As a result, transfer materials with the micro-protrusion structure 120 of the master disc 100 can be manufactured with high production efficiency.

[0120] like Figure 11 As shown, the mother disk 100 has a roller-shaped substrate 110 and a micro-protrusion structure 120 formed on the outer peripheral surface of the substrate 110.

[0121] The substrate 110 is, for example, a roller-shaped component that serves as a roller mother disc substrate. The shape of the substrate 110 is as follows: Figure 11 The substrate 110 can be a hollow cylinder or a solid cylinder without internal cavities. Furthermore, the material of the substrate 110 is not particularly limited; it can be fused silica glass or synthetic quartz glass, or a metal such as stainless steel. The dimensions of the substrate 110 are not particularly limited; for example, the length of the substrate 110 along its central axis 110a (hereinafter sometimes referred to as the axial direction) can be 100 mm or more, and the outer diameter of the substrate 110 can be 50 mm or more and 300 mm or less. Additionally, the radial thickness of the cylindrical substrate 110 can be 2 mm or more and 50 mm or less.

[0122] The micro-convex-concave structure 120 is a micro-convex-concave pattern formed on the outer peripheral surface of the master disk 100. The micro-convex-concave structure 120 includes a plurality of micro-concave portions 122 arranged at a predetermined interval P, and a plurality of micro-convex portions 123 disposed between adjacent two concave portions 122. The micro-convex-concave structure 120 of the master disk 100 has an inverted shape of the micro-convex-concave structure of the transfer material (e.g., the micro-convex-concave structure 11 of the cover 7 described above). For example, the shape of the concave portion 122 of the micro-convex-concave structure 120 of the master disk 100 is the shape of the convex portion 12 of the micro-convex-concave structure 11 of the cover 7 (see reference). Figures 2-9 The reverse shape of the micro-convex-concave structure 120 of the mother disk 100 is the same as the concave shape of the micro-convex-concave structure 11 of the cover 7 (see reference). Figures 2-9 The reverse shape of the micro-convex and concave structure 120 of the mother disk 100. In addition, the spacing (circumferential point spacing) of the recesses 122 of the micro-convex and concave structure 120 of the cover 7 is the same as the spacing P of the protrusions 12 of the micro-convex and concave structure 11 of the cover 7.

[0123] The master disc 100 with this structure is disposed in a roll-to-roll type printing transfer device, for example... Figure 12 The transfer apparatus 300 is shown. The master disk 100 is capable of manufacturing a transfer object (such as the infrared sensor cover 7 of this embodiment) with the micro-protrusion structure 120 formed on its outer peripheral surface. For example, the micro-protrusion structure 120 on the outer peripheral surface of the master disk 100 can be continuously transferred to the resin layer on the surface of the cover 7, and the micro-protrusion structure 11 can be formed on the surface of the cover 7 with high precision and efficiency.

[0124] 7. Method for manufacturing transfer materials Next, refer to Figure 12 This describes a method for efficiently manufacturing transfer materials such as the infrared sensor cover 7 of this embodiment using a transfer apparatus 300 equipped with a master disk 100. Figure 12 This is a schematic diagram showing the structure of the transfer apparatus 300 for manufacturing transfer materials using the master disk 100 of this embodiment.

[0125] like Figure 12As shown, the transfer apparatus 300 is a roll-to-roll pressure transfer apparatus. The transfer apparatus 300 transfers the micro-protrusion structure 120 of the master disk 100 to the resin layer of the workpiece in a roll-to-roll manner. As a result, it is possible to continuously manufacture transfer works with the micro-protrusion structure 120 formed on the outer peripheral surface of the master disk 100.

[0126] like Figure 12 As shown, the transfer device 300 includes a master plate 100, a substrate supply roller 301, a take-up roller 302, guide rollers 303 and 304, a pressing roller 305, a peeling roller 306, a coating device 307, and a light source 309.

[0127] The substrate supply roller 301 is, for example, a roller that winds the film-like substrate 311 into a roll shape. The take-up roller 302 is a roller for taking up the film-like substrate 331 having a resin layer 312 with a micro-protrusion structure 120 transferred on it. In addition, guide rollers 303 and 304 are rollers for conveying the film-like substrate 311 before and after transfer. The pressing roller 305 is a roller that presses the film-like substrate 311 with the resin layer 312 laminated on it onto the master disc 100. The peeling roller 306 is a roller that peels the film-like substrate 311 with the micro-protrusion structure 120 transferred on the resin layer 312 from the master disc 100.

[0128] Furthermore, the film-like substrate 311 can be the same as the substrate 10 of the infrared sensor cover 7 of this embodiment described above (see reference). Figure 2 The substrate can be the same as (etc.), or it can be a different substrate than substrate 10. In the latter case, it can also be... Figure 12 The substrate 311, which has a resin layer 312 with a micro-protrusion structure 120 formed in the transfer apparatus 300, is adhered to the substrate 10 of the cover 7 (see reference). Figure 2 , Figure 3 The cover 7 is manufactured on the surface of the substrate 311 (see reference 120) having a resin layer 312 with the micro-unravel structure 120 transferred thereon. Figure 12 ) is pasted onto the substrate 10 of cover 7 (refer to) Figure 2 , Figure 3 The surface of the cover 7 is formed with a micro-uneven structure 11.

[0129] The coating apparatus 307 includes a coating unit such as a coating machine, which coats the photocurable resin composition onto a film substrate 311 to form a resin layer 312. The coating apparatus 307 can be, for example, a gravure coating machine, a wire rod coating machine, or a die coating machine. Furthermore, the light source 309 is a light source that emits light with a wavelength capable of curing the photocurable resin composition, such as an ultraviolet lamp.

[0130] Furthermore, the photocurable resin composition is a resin that is cured by irradiation with light of a specified wavelength. Specifically, the photocurable resin composition can be, for example, an acrylic resin, acrylate, epoxy acrylate, or other ultraviolet-curable resin. In addition, the photocurable resin composition may, as needed, include initiators, fillers, functional additives, solvents, inorganic materials, pigments, antistatic agents, or sensitizing pigments.

[0131] Alternatively, the resin layer 312 may also be formed from a thermosetting resin composition. In this case, a heater is provided in the transfer apparatus 300 instead of the light source 309, and the resin layer 312 is heated by the heater to cure the resin layer 312, thereby transferring the micro-unraveling structure 120. The thermosetting resin composition may be, for example, phenolic resin, epoxy resin, melamine resin, or urea resin.

[0132] Next, the method for manufacturing transfer material using the above-described transfer apparatus 300 will be explained.

[0133] First, a film-like substrate 311 is continuously fed out from the substrate supply roller 301 and conveyed by the guide roller 303. Next, a photocurable resin composition is coated onto the surface of the fed substrate 311 by the coating apparatus 307, and an uncured resin layer 312 is stacked on the surface of the substrate 311.

[0134] Then, the uncured resin layer 312, laminated on the surface of the substrate 311, is pressed onto the outer peripheral surface of the mother disk 100 by the pressing roller 305. As a result, the micro-protrusion structure 120 formed on the outer peripheral surface of the mother disk 100 is transferred to the uncured resin layer 312. Afterwards, light, such as ultraviolet light, is irradiated onto the resin layer 312 with the transferred micro-protrusion structure 120 from the light source 309. As a result, the uncured resin layer 312 cures, and the shape of the transferred protrusion pattern on the cured resin layer 312 stabilizes.

[0135] Next, the substrate 311, to which the cured resin layer 312 is laminated, is peeled off from the outer peripheral surface of the master disc 100 by the peeling roller 306. This forms a micro-protrusion structure 11 in reverse shape with the micro-protrusion structure 120 of the master disc 100 on the resin layer 312. Afterward, the substrate 311 peeled off from the master disc 100 is conveyed via the guide roller 304 and wound up by the take-up roller 302.

[0136] In this way, by using the roll-to-roll transfer apparatus 300, transfer objects (such as the infrared sensor cover 7 of this embodiment) with the micro-protrusion structure 120 formed on the master disk 100 can be continuously manufactured. As a result, transfer objects with high precision transfer of the micro-protrusion structure 120 can be mass-produced efficiently and at low cost.

[0137] 8. Method for manufacturing the master disc [8.1. Overview of Master Disc Manufacturing Method] Next, the method for manufacturing the master disk 100 using the manufacturing apparatus of the master disk 100 of this embodiment (steps S10 to S50) will be described. The manufacturing apparatus for the master disk 100 of this embodiment includes, for example, a film forming apparatus, an exposure control apparatus, an exposure apparatus, a developing apparatus, an etching apparatus, an exposure control apparatus, and various other control devices.

[0138] (S10: Resist film formation process) According to the method for manufacturing the master disk 100 in this embodiment, a resist layer is first formed on the outer peripheral surface of the substrate 110 of the master disk 100 using a film forming apparatus.

[0139] More specifically, the substrate 110 of the master disk 100 is preferably made of a substrate such as quartz glass. The substrate 110 is a cylindrical or cylindrical roll-shaped substrate. A resist layer is formed on the outer peripheral surface of the substrate 110 by forming a film using a resist material.

[0140] The resist layer is formed from an inorganic or organic material capable of forming a latent image using a laser. As an inorganic material, a metal compound containing a transition metal can be used, preferably a metal oxide containing one or more transition metals such as tungsten (W) or molybdenum (Mo). Such inorganic materials can be formed into a resist layer, for example, using a sputtering method. On the other hand, as an organic material, phenolic varnish-based resists or chemically amplified resists can be used, for example. Such organic materials can be formed into a resist layer, for example, using a spin coating method.

[0141] (S20: Exposure control signal generation process) Next, an exposure control signal corresponding to the embossed pattern (exposure pattern) of the micro-embossed structure 120 of the master disk 100 is generated by the exposure control device.

[0142] (S30: Exposure process) Then, a laser is irradiated onto the resist layer using an exposure device based on the exposure control signal generated in S20 above. This exposes the resist layer with a predetermined exposure pattern, forming a latent image corresponding to the micro-uneven structure 120.

[0143] More specifically, a laser is irradiated onto the resist layer using an exposure device, causing denaturation in the irradiated areas of the resist layer. This exposes the resist layer, forming multiple latent images. During exposure, the laser light used as the exposure beam can be continuously or intermittently irradiated onto the resist layer.

[0144] (S40: Development process) Next, the resist layer on which the latent image is formed is developed using a developing apparatus. Thus, a resist pattern corresponding to the micro-unraveling structure 120 is formed on the resist layer.

[0145] More specifically, the developing apparatus adds developing solution to the resist layer in S30 where a latent image has been formed, thereby developing the resist layer. This forms a resist pattern with a three-dimensional uneven structure in the resist layer. This resist pattern is composed of multiple recesses with three-dimensional shapes. The three-dimensional shapes of the multiple recesses correspond to the three-dimensional shapes of each recess 122 of the micro-uneven structure 120.

[0146] Furthermore, when the resist layer is a positive resist, the exposed areas, compared to the unexposed areas, dissolve faster in the developer, and are thus removed during development. This results in a resist pattern formed in the resist layer with the latent image removed. Conversely, when the resist layer is a negative resist, the exposed areas, compared to the unexposed areas, dissolve slower in the developer, and are thus removed during development. This results in a resist pattern formed in the resist layer with residual latent image.

[0147] (S50: Etching process) Subsequently, the outer peripheral surface of the substrate 110 of the master disk 100 is etched using an etching apparatus with the resist layer having the resist pattern formed as a mask. As a result, a raised and recessed pattern corresponding to the micro-raised and recessed structure 120 is formed on the outer peripheral surface of the substrate 110.

[0148] More specifically, using the resist layer with the resist pattern corresponding to the micro-protrusion structure 120 formed in S40 as a mask, the outer peripheral surface of the substrate 110 is etched. This forms a micro-protrusion structure 120 (protrusion pattern) composed of multiple recesses 122 on the outer peripheral surface of the substrate 110. The protrusion shape of the micro-protrusion structure 120 of the master disk 100 corresponds to the protrusion shape of the resist pattern and is equivalent to a reversed shape of the three-dimensional shape of the micro-protrusion structure 11 of the transfer material.

[0149] Furthermore, the etching of the substrate 110 can be performed using either dry etching or wet etching. For example, when the substrate 110 is made of quartz glass (SiO2), the substrate 110 can be etched using dry etching with a fluorocarbon gas (e.g., CHF3) or wet etching with a gas such as hydrofluoric acid.

[0150] 【8.2. Exposure Apparatus and Exposure Method】 Next, refer to Figure 13 The exposure apparatus 200 and exposure method used in the manufacturing method of the master disk 100 of this embodiment will be described in more detail. Figure 13 This is an explanatory diagram showing the schematic structure of the exposure apparatus 200 in this embodiment.

[0151] like Figure 13As shown, the exposure apparatus 200 includes a laser light source 201, a first reflector 203, a photodiode 205, a deflection optical system, a control mechanism 230, a second reflector 213, a moving optical stage 220, a spindle motor 225, and a turntable 227. Furthermore, the substrate 110 is placed on the turntable 227 and is capable of rotating about a central axis 110a.

[0152] Laser source 201 is the light source that emits laser 200A, such as a solid-state laser or a semiconductor laser. The wavelength of the laser 200A emitted by laser source 201 is not particularly limited; for example, it can be a wavelength in the blue light band of 400nm to 500nm. Furthermore, the spot diameter of laser 200A (the spot diameter irradiating the resist layer) only needs to be smaller than the diameter of the opening surface of the recess 122 of the micro-uneven structure 120, for example, approximately 200nm. The laser 200A emitted from laser source 201 is controlled by control mechanism 230.

[0153] The laser 200A emitted from the laser source 201 travels in a straight line as a parallel beam, is reflected by the first reflecting mirror 203, and is guided to the deflection optical system.

[0154] The first reflector 203 is composed of a polarization beam splitter, which has the function of reflecting one polarization component and transmitting the other polarization component. The polarization component transmitted through the first reflector 203 is received by the photodiode 205 and photoelectric conversion is performed. In addition, the light signal photoelectrically converted by the photodiode 205 is input to the laser source 201, and the laser source 201 performs phase modulation of the laser 200A based on the input light signal.

[0155] In addition, the deflection optical system includes a condenser lens 207, an electro-optic deflector (EOD) 209, and a collimating lens 211.

[0156] In the deflection optical system, laser 200A is focused by condenser lens 207 onto electro-optic deflection element 209. Electro-optic deflection element 209 is a component capable of controlling the irradiation position of laser 200A. Exposure apparatus 200 can also change the irradiation position of laser 200A on the guiding moving optical stage 220 via electro-optic deflection element 209 (i.e., the so-called Wobble mechanism). After the irradiation position of laser 200A is adjusted by electro-optic deflection element 209, it is again transformed into a parallel beam by collimating lens 211. Laser 200A emitted from the deflection optical system is reflected by second mirror 213 and guided horizontally and parallel onto moving optical stage 220.

[0157] The moving optical stage 220 includes a beam expander 221 and an objective lens 223. The laser 200A, which guides the moving optical stage 220, is shaped into the desired beam shape by the beam expander 221 and then irradiates the resist layer formed on the substrate 110 of the master disk 100 via the objective lens 223.

[0158] Furthermore, the movable optical stage 220 moves one feed pitch (track pitch) in the direction of arrow 224 (feed pitch direction) along the axial direction of the substrate 110 for each revolution of the substrate 110. The substrate 110 is mounted on a turntable 227. The spindle motor 225 rotates the turntable 227, thereby causing the substrate 110 to rotate about the central axis 110a of the cylindrical mother disk 100. In this way, while the substrate 110 rotates, the movable optical stage 220 moves in the R direction, thereby irradiating the resist layer on the outer peripheral surface of the substrate 110 with laser 200A along a spiral trajectory. As a result, a latent image is formed on the resist layer along the spiral irradiation trajectory of laser 200A.

[0159] In addition, the control mechanism 230 includes a formatter 231 and a driver 233 to control the irradiation of the laser 200A.

[0160] The driver 233 controls the emission of the laser source 201 based on the exposure signal generated by the formatter 231. Specifically, the driver 233 can control the laser source 201 so that the larger the amplitude of the exposure signal waveform, the greater the output intensity of the laser 200A. Furthermore, the driver 233 can control the emission timing of the laser 200A based on the shape of the exposure signal waveform, thereby controlling the irradiation position of the laser 200A. The greater the output intensity of the laser 200A, the larger the size and depth of the latent image formed in the resist layer can be, thus ultimately enabling a larger opening size and depth of the recess 122 formed in the substrate 110.

[0161] By controlling the exposure via the control mechanism 230, the resist layer on the outer peripheral surface of the substrate 110 of the master disk 100 is exposed, forming a latent image of any pattern on the resist layer. Then, the resist layer is developed, and the outer peripheral surface of the substrate 110 is etched using the developed resist layer as a mask. As a result, a micro-bump structure 120 with a raised pattern corresponding to the drawing pattern of the input image can be formed on the outer peripheral surface of the substrate 110 of the master disk 100. Therefore, if a raised pattern with the reverse shape of the micro-bump structure 11 of the infrared sensor cover 7 as a transfer material is prepared as the drawing pattern, the micro-bump structure 120 with the reverse shape of the micro-bump structure 11 of the cover 7 can be well formed on the outer peripheral surface of the master disk 100.

[0162] 【9. Summary】 The infrared sensor cover 7 and the optical ranging device 1 having an infrared sensor covered by the infrared sensor cover 7 have been described in detail above.

[0163] According to this embodiment, an infrared sensor cover 7 is provided to cover an infrared sensor that measures the distance to a measured object using infrared light. In this embodiment, the cover 7 is disposed on the infrared sensor such that infrared light can be incident on the cover 7 from a direction inclined relative to the surface of the cover 7. The cover 7 includes a substrate 10 and a micro-protrusion structure 11 disposed on at least one surface of the substrate 10. The micro-protrusion structure 11 has a plurality of protrusions 12 arranged at a spacing P less than or equal to the wavelength λ of the infrared light used by the infrared sensor. In the micro-protrusion structure 11, the ratio (H / λ) of the height H of the protrusion 12 to the wavelength λ of the infrared light is 0.5 or more (first condition: H / λ ≥ 0.5).

[0164] Thus, the surface of the cover 7 in this embodiment is provided with a micro-unraveling structure 11 serving as an anti-reflective layer. The height H of the plurality of protrusions 12 of this micro-unraveling structure 11 is at least 0.5 times the infrared wavelength λ (H / λ≧0.5), and is adjusted to provide excellent anti-reflective performance against infrared light incident at a wide angle of, for example, about 60°. As a result, the anti-reflective performance of the cover 7 against infrared light (especially near-infrared light) incident at an oblique angle within a wide range of incident angles, including normal incident (θ=0°) and wide-angle incident (e.g., θ=-60° or more +60° or less), can be significantly improved. Therefore, the reflectivity of obliquely incident infrared light on the surface of the cover 7 can be significantly reduced to, for example, 3% or less, and the transmittance of infrared light passing through the cover 7 can be significantly increased to, for example, 97% or more. As a result, the infrared light irradiated from the infrared sensor at a wide angle via the cover 7, and the reflected infrared light incident from the infrared sensor at a wide angle via the cover 7, can pass through the cover 7 with sufficient transmittance. Therefore, it can significantly improve the detection accuracy of infrared sensors that illuminate and receive obliquely incident infrared light.

[0165] Furthermore, the ratio of the spacing P of the protrusions 12 to the wavelength λ of the infrared light (P / λ) is preferably 0.5 or less (second condition: P / λ≤0.5).

[0166] Therefore, the spacing P of the protrusions 12 can be adjusted to a suitable size corresponding to the wavelength λ of the obliquely incident infrared light. This suppresses the generation of high-order diffracted light on the surface of the cover 7, thereby improving the straightness of the obliquely incident infrared light onto the cover 7. Consequently, the amount of transmitted light passing through the cover 7 towards the infrared sensor, as well as the amount of irradiated light emanating from the infrared sensor and passing through the cover 7, can be increased. Therefore, the amount of light received and emitted by the infrared sensor can be increased, further improving the detection accuracy of the infrared sensor.

[0167] Furthermore, the ratio (H / P) of the height H of the protrusion 12 to the spacing P is preferably 3 or less (third condition: H / P≤3). That is, the aspect ratio of the protrusion 12 is preferably 3 or less.

[0168] Therefore, the ratio (H / P, i.e., aspect ratio) of the height H of the protrusion 12 of the micro-convex structure 11 to the spacing P can be adjusted to fit the size of the imprint using the roller-shaped master disc 100. Thus, during the imprinting process, the micro-convex structure 11 of the cover 7 can be smoothly peeled from the micro-convex structure 120 on the outer peripheral surface of the master disc 100, improving demolding performance. Consequently, the desired shape of the micro-convex structure 11 can be easily and precisely formed on the micro-convex structure 11 without defects.

[0169] Furthermore, the infrared light used in the infrared sensor is preferably near-infrared light with a wavelength λ between 800 nm and 2500 nm.

[0170] Therefore, the cover 7 of this embodiment can be suitably applied to optical ranging devices 1 such as LiDAR that are equipped with near-infrared sensors that use near-infrared light.

[0171] Furthermore, the shape of the protrusion 12 of the preferred micro-concave-convex structure 11 is substantially elliptical cone, elliptical frustum, or elliptical bell or dome shape in planar shape.

[0172] Thus, if the shape of the protrusion 12 is an elliptical planar shape (refer to...) Figure 4 ) three-dimensional shape (refer to) Figures 6-8 This allows for the efficient manufacture of micro-convex-concave structures 11 with a large number of protrusions 12. For example, according to the master disc manufacturing method using laser exposure described above (see...). Figure 13 The recess 122 of the micro-unravel structure 120 formed on the outer peripheral surface of the roller-shaped mother disk 100 (see reference) Figure 11 The planar shape of the cover 7 is prone to being elliptical, making it difficult to manufacture a complete circle. Therefore, it is preferable to allow the shape of the protrusion 12 of the micro-convex structure 11 of the cover 7 formed by the roller master 100 to be a three-dimensional shape with an elliptical planar shape. As a result, the micro-convex structure 11 having the elliptical protrusion 12 can be easily and with high precision manufactured using the master disc manufacturing method of this laser exposure method.

[0173] When the infrared light used in the infrared sensor is incident on the surface of the infrared sensor cover 7 at an incident angle θ greater than 0° and less than 60°, the reflectivity of the infrared light is less than 3%.

[0174] Therefore, even if the infrared light is incident obliquely onto the cover 7 at a wide angle θ as described above, the infrared light can still pass through the cover 7 with a high transmittance of over 97%, thereby further improving the detection accuracy of the infrared sensor.

[0175] Example The following describes in detail an embodiment of the infrared sensor cover 7 described above. It should be noted that the following embodiments are examples illustrating the feasibility and effects of the infrared sensor cover 7 of this embodiment, and the present invention is not limited to these embodiments.

[0176] In the following embodiments, multiple samples of the infrared sensor cover 7 described in the above embodiments were fabricated, and tests were conducted to evaluate the anti-reflection performance, etc., of these samples. The test conditions, evaluation methods, and evaluation results are described below.

[0177] 【1. Experimental Conditions】 (1) Manufacturing method of infrared sensor cover In this embodiment, an infrared sensor cover 7 with a micro-protrusion structure 11 formed on its surface was fabricated through the following steps.

[0178] First, it was made Figure 11 The substrate 110 of the cylindrical mother disc 100 shown (refer to) Figure 11 Next, a micro-protrusion structure 120 with an inverted shape of the micro-protrusion pattern of the micro-protrusion structure 11 of the cover 7 of the embodiment is formed on the outer peripheral surface of the substrate 110 of the master disk 100. Specifically, this is achieved by the laser exposure method described above (see...). Figure 13 The resist layer on the outer peripheral surface of the substrate 110 of the master disk 100 is exposed. Then, using the developed resist layer as a mask, the substrate 110 is etched to form a micro-protrusion structure 120 with multiple recesses 122. In this way, a roller-shaped master disk 100 with the micro-protrusion structure 120 formed on its outer peripheral surface is manufactured.

[0179] Next, using the master disc 100, the micro-convex structure 11 of the cover 7 is formed by roll-to-roll. Specifically, using... Figure 12 The transfer apparatus 300 shown deposits an uncured resin layer 312 made of UV-curable resin on the surface of a film substrate 311, transferring the micro-uneven structure 120 of the outer peripheral surface of the master disk 100 to the uncured resin layer 312. Furthermore, a 60 μm thick polyethylene terephthalate (PET) film is used as the film substrate 311. Next, the film is irradiated with a metal halide lamp at 1000 mJ / cm². 2 The resin layer 312, composed of UV-curable resin, is cured by exposing it to ultraviolet light for 1 minute. Afterward, the cured resin layer 312 is peeled off from the master disk 100. In this manner, a transfer image of the micro-unraveling structure 120 of the master disk 100 is created and transferred to the resin layer 312.

[0180] Next, the transfer material consisting of the resin layer 312 and the film substrate 311 was adhered to the surface of the substrate 10 of the cover 7 using an adhesive film, thus fabricating the cover 7 of the embodiment. As the substrate 10 of the cover 7, a polycarbonate substrate with a thickness of 2 mm was used.

[0181] As described above, the following are formed by embossing: Figure 4 The micro-protrusion structure 11, which is arranged in a hexagonal lattice and has multiple protrusions 12, is used to fabricate a cover 7 on the surface of the substrate 10.

[0182] In the embodiments detailed below, the height H and spacing P of the protrusions 12 of the micro-convex-concave structure 11 as described above were changed. Furthermore, in the comparative example, a cover 7 having the micro-convex-concave structure 11 was also fabricated in the same manner as in the above embodiments, but the height H and spacing P of the protrusions 12 of the micro-convex-concave structure 11 were changed to different values ​​than in the embodiments.

[0183] (2) Conditions for the height H and spacing P of the protrusions 12 of the micro-concave-convex structure 11 Tables 2 and 3 show the conditions for the height H and spacing P of the protrusions 12 of the micro-convex-concave structure 11 of the cover 7 in each embodiment and comparative example. As shown in Tables 2 and 3, the micro-convex-concave structure 11 was formed by changing the height H and spacing P of the protrusions 12 to different values ​​in each embodiment and comparative example. In any case, the arrangement of the protrusions 12 is as follows: Figure 4 The hexagonal lattice arrangement shown has an elliptical planar shape for the protrusions, and the micro-convex-concave structure 11 is formed only on one surface of the cover 7.

[0184] Furthermore, Table 2 shows Examples 1-8 and Comparative Example 1 when near-infrared light with a wavelength λ of 905 nm is used as the incident light (infrared light used by the infrared sensor) on the cover 7. On the other hand, Table 3 shows Examples 10-13 and Comparative Examples 10-13 when near-infrared light with a wavelength λ of 1550 nm is used as the incident light (infrared light used by the infrared sensor) on the cover 7.

[0185] [Table 2] [Table 3] 【2. Evaluation Methods】 In addition, Tables 2 and 3 also show the results of evaluating the (1) anti-reflection effect (reflectivity R), (2) diffraction light suppression effect (transmitted light increase effect), and (3) demolding properties of the cover 7 of each embodiment and comparative example during transfer. These evaluation methods are as follows.

[0186] (1) Measurement method of reflectivity R and evaluation criteria for anti-reflection effect Figure 14 This is a schematic diagram illustrating the method for measuring reflectance R and diffracted light according to an embodiment. Figure 14 As shown, near-infrared light was incident at an angle θi from a direction inclined relative to the normal direction (Z direction) of the surface of cover 7, and the amount of light Qr of the positively reflected light (m=0) was measured. A semiconductor laser with a wavelength of λ=905nm or 1550nm was used as the incident light source. A laser power meter (S122C manufactured by Thorlabs) was used as the light intensity measuring instrument.

[0187] The reflectivity measurement steps are as follows: First, without the cover 7 of the micro-uneven structure 11 involved in each embodiment and each comparative example, the amount of incident light Qi is measured. Next, light is incident on the micro-uneven structure 11 involved in each embodiment and each comparative example at an incident angle θi (relative to the normal direction +10°, +40°, +60°), and the amount of reflected light Qr (θ = θi = θr) is measured by a laser power meter set at a position with the same reflection angle θr as the incident angle θi.

[0188] Then, the reflectivity R (%) is calculated from the measured incident light intensity Qi and reflected light intensity Qr using the following formula.

[0189] R (%) = (Qr / Qi) × 100 Reflectivity R is an indicator of the anti-reflective performance of the micro-unfold structure 11 on the surface of the cover 7. The lower the reflectivity R of obliquely incident light, the higher the anti-reflective performance of the micro-unfold structure 11 against obliquely incident light. The following benchmarks were used as the evaluation criteria for reflectivity R (anti-reflective performance).

[0190] Grade A rating: Reflectivity R is below 1.0% (especially effective against reflections from obliquely incident light). Grade B rating: Reflectivity R greater than 1.0% and less than 2.5% (excellent anti-reflection effect for oblique incident light). Grade C rating: Reflectivity R greater than 2.5% (poor anti-reflection effect for oblique incident light) (2) Measurement methods for diffracted light and evaluation criteria for diffraction suppression effect In addition, such as Figure 14 As shown, near-infrared light (wavelength λ = 905 nm or 1550 nm) is incident from a direction oblique to the normal direction (Z direction) relative to the surface of the cover 7, and the presence or absence of diffracted light is measured. Specifically, the diffracted light measurement steps are as follows: the incident light is obliquely incident at an incident angle θi (relative to the normal direction +60°, +70°, +80°) onto the micro-uneven structure 11 involved in each embodiment and each comparative example, and the power meter is scanned within an angle range of -89° to +89° relative to the normal direction to measure whether higher-order reflected diffracted light (m = ±1, ±2, ...) other than positively reflected light (m = 0) is generated.

[0191] The following criteria were used as the evaluation standard for the diffraction suppression effect (increased transmitted light).

[0192] Grade A rating: No diffracted light was produced (excellent diffraction suppression effect). Grade C: Diffracted light is produced (poor diffraction suppression effect). (3) Demolding test and evaluation criteria As described above, by using a roll-to-roll method with a cylindrical master disc 100, the micro-concave-convex structure 11 involved in each embodiment and each comparative example is transferred to a resin layer 312 (UV-curable resin) on a substrate 311 (PET film), the resin layer 312 is cured, and then a test is conducted to peel the cured resin layer 312 from the outer peripheral surface of the master disc 100 (transfer and demolding test).

[0193] As a result, the appearance of the micro-protrusion structure 11 transferred to the resin layer 312 was observed with the naked eye, and the following were evaluated: (a) whether there were defects in the micro-protrusion structure 11, (b) the stability of the resin layer 312 in the demolding process from the master disc 100, and (c) the film tension stability in the roll-to-roll manner. The following criteria were used as the evaluation criteria for demolding performance.

[0194] Grade A rating: No defects were observed, and demolding performance was stable (particularly excellent demolding properties). Grade B rating: No defects were observed, but demolding was unstable and film tension was unstable (excellent demolding performance). Grade C rating: Defects occur, demolding is unstable, and film tension is unstable (poor demolding performance). 【3. Evaluation Results】 (1) Evaluation of the first condition (H / λ≥0.5) As shown in Table 2, when the wavelength λ of the obliquely incident light is 905 nm, in order to satisfy the first condition (H / λ≥0.5), the height H of the protrusion 12 of the micro-concave-convex structure 11 needs to be at least half the wavelength λ, i.e., 452.5 nm. In this respect, in Examples 1 to 8, the height H of the protrusion 12 is at least 487 nm, which is at least 0.5 times the wavelength λ, thus satisfying the first condition (H / λ≥0.5). In contrast, in Comparative Example 1, the height H of the protrusion 12 is 250 nm, which is less than 0.5 times the wavelength λ, and therefore does not satisfy the first condition (H / λ≥0.5).

[0195] As a result, in Comparative Example 1, the larger the incident angle θi of the obliquely incident light, the higher the reflectivity R, and the lower the evaluation of anti-reflection performance. For example, when θ = +40°, the reflectivity R of Comparative Example 1 was 1.89%, and the anti-reflection performance was rated as B. Furthermore, when the incident angle was wide-angle θ = +60°, the reflectivity R of Comparative Example 1 reached as high as 4.89%, and the anti-reflection performance was rated as C.

[0196] In contrast, in Examples 1-8, even with an increase in the incident angle θi of the obliquely incident light, the reflectivity R hardly increases, and the anti-reflection performance evaluation remains approximately Grade A. For example, in Examples 1-7, regardless of whether θ = +10°, +40°, or +60°, the reflectivity R is below 1.0%, ensuring a Grade A evaluation. Furthermore, in Example 8, only when θ = +60° is a Grade B evaluation, but even in this case, the reflectivity R = 1.68% (Grade B evaluation) of Example 8 is significantly lower than the reflectivity R = 4.89% (Grade C evaluation) of Comparative Example 1. Therefore, it can be seen that even in Example 8, the anti-reflection performance for wide-angle (θ = +60°) obliquely incident light is significantly improved. As described above, in Examples 1-8, the reflectivity R for the aforementioned wide-angle obliquely incident light can be suppressed to a value sufficiently lower than the aforementioned reference reflectivity (e.g., 3%, preferably 2.5%).

[0197] Furthermore, as shown in Table 3, when the wavelength λ of the obliquely incident light is 1550 nm, in order to satisfy the first condition (H / λ≥0.5), the height H of the protrusion 12 needs to be half the wavelength λ, i.e., 775 nm or more. In this respect, in Examples 10-13, the height H of the protrusion 12 is 810 nm or more, which is more than 0.5 times the wavelength λ, thus satisfying the first condition (H / λ≥0.5). In contrast, in Comparative Examples 10-13, the height H of the protrusion 12 is 520 nm or less, which is less than 0.5 times the wavelength λ, and therefore does not satisfy the first condition (H / λ≥0.5).

[0198] As a result, in Comparative Examples 10-13, the larger the incident angle θi of the obliquely incident light, the higher the reflectivity R, and the lower the evaluation of anti-reflection performance. For example, when the incident light was incident at a wide angle of θ = +60°, the reflectivity R of Comparative Examples 10-13 was 2.51% to 6.8%, and the anti-reflection performance was rated as C. In particular, in Comparative Example 13, due to the extremely small H / λ = 0.16, even when θ = +40°, the reflectivity R was as high as 3.2% (rated as C), and further, when the incident light was incident at a wide angle of θ = +60°, the reflectivity R was significantly higher than 6.8% (rated as C), and the anti-reflection performance was significantly reduced.

[0199] In contrast, in Examples 10-13, although the reflectivity R slightly increased as the incident angle θi of the obliquely incident light increased, the anti-reflection performance was rated as Grade A or Grade B. For example, even when θ = +60°, the reflectivity R of Examples 10-13 was 2.11% or less (Grade B), which is significantly lower than the reflectivity R of Comparative Examples 10-14, which was 2.51-6.8% (Grade C). As described above, even in Examples 10-13, the reflectivity R of the wide-angle obliquely incident light can be suppressed to a value sufficiently lower than the reference reflectivity (e.g., 3%, preferably 2.5%).

[0200] The above comparison results confirm that by ensuring the height H of the protrusion 12 and the wavelength λ satisfy the first condition (H / λ≥0.5), the anti-reflection effect on near-infrared obliquely incident light can be improved over a wide incident angle θ range. In particular, it can be confirmed that the anti-reflection effect on wide-angle obliquely incident light, such as around 60°, can be significantly improved. Therefore, it can be said that satisfying the above first condition (H / λ≥0.5) increases the transmittance of near-infrared obliquely incident light passing through the cover 7, thereby improving the detection accuracy of the infrared sensor.

[0201] (2) Evaluation of the second condition (P / λ≤0.5) As shown in Table 2, when the wavelength λ of the obliquely incident light is 905 nm, in order to satisfy the second condition (P / λ≤0.5), the spacing P of the protrusions 12 of the micro-concave-convex structure 11 needs to be half the wavelength λ, i.e., 452.5 nm or less. In this respect, in Examples 1 to 7, the spacing P of the protrusions 12 is 450 nm or less, which is less than 0.5 times the wavelength λ, thus satisfying the second condition (P / λ≤0.5). In contrast, in Example 8, the spacing P of the protrusions 12 is 500 nm, which is more than 0.5 times the wavelength λ, and therefore does not satisfy the second condition (P / λ≤0.5).

[0202] As a result, in Example 8, as Figure 14 As shown, reflected diffracted light (m = ±1, ±2) is generated on the surface of the protrusion 12 of the micro-uneven structure 11. Therefore, in Example 8, the obliquely incident light incident on the micro-uneven structure 11 is bent, the straightness of the obliquely incident light decreases, and the transmittance of the obliquely incident light passing through the cover 7 decreases. As a result, the diffraction light suppression effect in Example 8 is rated as C.

[0203] In contrast, in Examples 1-7, no reflected diffracted light was generated on the surface of the protrusion 12 of the micro-uneven structure 11 (m = ±1, ±2). In Examples 1-7, the straightness of obliquely incident light incident on the micro-uneven structure 11 did not decrease, and the transmittance of obliquely incident light passing through the cover 7 did not decrease. As a result, the diffraction suppression effect of Examples 1-7 is excellent, and it is rated as Grade A.

[0204] The above comparison results confirm that by ensuring the spacing P of the protrusions 12 satisfies the second condition (P / λ≤0.5) with the wavelength λ, the diffraction suppression effect on near-infrared obliquely incident light can be improved over a wide incident angle θ range. Therefore, it can be said that satisfying the above second condition (P / λ≤0.5) can further improve the transmittance of near-infrared obliquely incident light passing through the cover 7, thereby further improving the detection accuracy of the infrared sensor.

[0205] (3) Evaluation of the third condition (H / P≤3) As shown in Tables 2 and 3, in Examples 1 to 6, 8, and Examples 10 to 12, the ratio of the height H of the protrusion 12 to the spacing P (i.e., the aspect ratio = H / P) is 2.8 or less, satisfying the third condition (H / P ≤ 3). In contrast, in Examples 7 and 13, the aspect ratio is 3.52, which does not satisfy the third condition (H / P ≤ 3).

[0206] As a result, in Examples 7 and 13, when the micro-convex structure 11 was transferred using the roller master disk 100 in a roll-to-roll manner, the protrusions 12 of the micro-convex structure 11 developed defects, resulting in unstable demolding and unstable film tension. Therefore, the demolding performance was rated as Grade C.

[0207] In contrast, in Examples 1-3, 5, 6, 8 and Examples 11 and 12, no defects were generated in the protrusions 12 of the micro-convex structure 11 during the above-described imprinting process, and both demolding and film tension were stable; therefore, the demolding performance was rated as Grade A. Furthermore, in Examples 4 and 10, no defects were generated in the protrusions 12 of the micro-convex structure 11 during the above-described imprinting process, but demolding and film tension were slightly unstable; therefore, the demolding performance was rated as Grade B.

[0208] The above comparison results confirm that by ensuring the ratio of the height H of the protrusion 12 to the spacing P (i.e., aspect ratio = H / P) satisfies the third condition (H / P ≤ 3), the demolding performance during the embossing process can be improved, preventing defects in the protrusion 12 of the micro-convex-concave structure 11. Furthermore, it can be confirmed that, as in Examples 1-3, 5, 6, 8 and Examples 11, 12, by satisfying the condition of an aspect ratio of 2.8 or less (H / P ≤ 2.8), in addition to preventing defects in the protrusion 12 during the embossing process, it can also stabilize demolding and film tension during the embossing process, further improving demolding performance.

[0209] While embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such embodiments. Those skilled in the art will readily conceive of various modifications and alterations within the scope of the claims, and these are naturally understood to fall within the technical scope of the present invention.

[0210] Explanation of reference numerals in the attached figures 1. Optical ranging device (infrared sensor) 2. Light irradiation device 3. Optical Detection Device 4 Controller 5. Target area for ranging 6. Test object 7. Infrared sensor cover 10 Substrate 11. Micro-convex and concave structure 12 convex part 13 recess 100 master disks 110 Substrate 120 micro-convex-concave structure 122 recess 123 convex part 300 transfer device 311 substrate 312 Resin Layer

Claims

1. An infrared sensor cover that covers an infrared sensor that uses infrared light to measure the distance to a measured object, characterized in that, have: Substrate; as well as A micro-protrusion structure is disposed on at least one surface of the substrate and has a plurality of protrusions arranged at a spacing (P) below the wavelength λ of the infrared light. The infrared sensor cover is disposed on the infrared sensor, such that the infrared light can be incident on the infrared sensor cover from a direction inclined relative to the surface of the infrared sensor cover. Furthermore, the ratio (H / λ) of the height (H) of the protrusion to the wavelength λ is 0.5 or more.

2. The infrared sensor cover according to claim 1, characterized in that, The ratio (P / λ) of the spacing (P) of the protrusion to the wavelength λ is 0.5 or less.

3. The infrared sensor cover according to claim 1, characterized in that, The ratio (H / P) of the height (H) of the protrusion to the spacing (P) is 3 or less.

4. The infrared sensor cover according to claim 1, characterized in that, The infrared radiation is near-infrared radiation with a wavelength λ between 800nm ​​and 2500nm.

5. The infrared sensor cover according to claim 1, characterized in that, The shape of the protrusion is essentially an elliptical cone, an elliptical frustum, or a bell or dome shape with an elliptical planar shape.

6. The infrared sensor cover according to claim 1, characterized in that, When the infrared light is incident on the surface of the infrared sensor cover at an angle of incidence greater than 0° and less than 60°, the reflectivity of the infrared light is less than 3%.

7. An infrared sensor, characterized in that, have: Infrared sensor cover according to any one of claims 1 to 6; A light irradiation device that irradiates an infrared laser onto the object being tested through the infrared sensor cover; and A light detection device that detects reflected light of infrared radiation from the object being tested through the infrared sensor cover.

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