Coating material, film, and method for producing member having film

Abstract

A coating material has fibers 31, a resin, and a solvent. The length L of the fibers 31 is in the range of 1-1,000 μm. The fibers 31 are characterized by each having an inner wall 313 surrounding a void 314 formed in the fiber, and at least one end of an end section in the longitudinal direction covers the void 314.

Description

Method for manufacturing a paint, a film, and a member having the film

[0001] The present disclosure relates to a paint and a film containing hollow fibers and a resin, and a method for manufacturing a member having the film. The present disclosure also relates to an optical member, an optical device, an imaging device, etc. using the film for optical applications.

[0002] A paint containing hollow fibers and a resin is known. By using this paint as a film, improvement in the functions of an article to which it is applied, such as the optical performance and the design property of an optical member, can be expected. Patent Document 1 discloses using the film as an antireflection film.

[0003] An optical device such as a lens barrel has a housing and an optical system including a plurality of lenses or mirrors provided in the housing. Light rays incident on the optical device are mainly incident on the lenses, and the light rays are imaged to form an image. On the other hand, there are also light rays that are not imaged and do not contribute to the formation of the subject image. Since the light rays that do not contribute to the formation of the subject image are incident from disordered directions, they are also incident on optical members other than lenses, etc., and become a factor for generating unnecessary reflected light and scattered light inside the housing. These lights are called stray light. When the stray light reaches the imaging element, flare and ghost occur, and the antireflection film is known as a means for suppressing this stray light.

[0004] Japanese Unexamined Patent Application Publication No. 2009 - 108155, Japanese Unexamined Patent Application Publication No. 2020 - 008843<00000​​​​​​​A second embodiment for solving the above problems is a film comprising a resin layer made of resin and fibers protruding from the resin layer, wherein the length of the fibers is in the range of 1 μm to 1000 μm, the fibers have an inner wall surrounding a void formed within the fibers, and at least one end of the longitudinal end covers the void.

[0008] A third embodiment for solving the above problems is a method for manufacturing paint, characterized by comprising the steps of: impregnating fibers having an inner wall surrounding a void formed inside with water; cutting the fibers; drying the fibers; and mixing the dried fibers with a resin and a solvent.

[0009] This disclosure provides a coating and film having hollow fibers of a predetermined size, and a method for manufacturing the film. Furthermore, this disclosure provides optical components, optical instruments, and imaging devices using the film for optical applications.

[0010] Schematic diagram of the component of this disclosure. Side perspective view of the fiber. Side perspective view of the fiber. Front cross-sectional view of the fiber. Front cross-sectional view of the fiber. Front cross-sectional view of the fiber. Front cross-sectional view of the fiber. Front cross-sectional view of the fiber. Front cross-sectional view of the fiber. Schematic diagram of the spray can of this disclosure. Schematic diagram of the imaging device of this disclosure. Schematic diagram of the display device of this disclosure. Schematic diagram of the building material of this disclosure. Schematic diagram of the clothing of this disclosure. Schematic diagram of the camera mounting device of this disclosure. SEM image of the cross-section of the hollow short fiber 1 according to Example 1. Front cross-sectional view of the fiber used in the comparative example.

[0011] Patent Document 2 discloses a method of applying a black paint containing irregularly shaped fibers having protrusions, thereby forming a structure in which the tips of the protrusions of the irregularly shaped fibers protrude into the air, and suppressing the reflection of obliquely incident light, which is prone to reflection and scattering. However, these irregularly shaped fibers tend to settle in the paint, requiring recovery work such as thorough stirring before use, resulting in insufficient storage stability.

[0012] On the other hand, Patent Document 1 discloses an anti-reflective coating using fibrous hollow silica microparticles with an average particle size in the range of 5 to 500 nm. The aim is to obtain a smooth coating by using microparticles. However, smooth coatings are structurally prone to reflection, resulting in insufficient anti-reflective function. Furthermore, smooth coatings also have insufficient aesthetic appeal. On the other hand, hollow microparticles do not easily settle in the coating, resulting in excellent storage stability. However, it is difficult to form the structure disclosed in Patent Document 1 using these microparticles, and increasing the thickness was particularly difficult. Therefore, it was not possible to suppress the reflection of light incident at an oblique angle.

[0013] The inventors investigated paints and films that can suppress the reflection of obliquely incident light. As a result, they found that a film having a resin layer and a fiber layer protruding from the resin layer, as described in Patent Document 1, can be obtained with high anti-reflective performance. The reason for this is that, in the film obtained when the paint dries, the fiber structure in the fiber layer protruding from the resin layer traps the obliquely incident light inside the structure.

[0014] Further investigation into the thickness of the fiber layer revealed that a thicker layer yielded higher anti-reflective performance. It was also found that to obtain a thick fiber layer, fibers with sufficient length and low specific gravity are preferable. This is thought to be because the overturning moment of a fiber depends on its specific gravity; lighter fibers are less likely to tilt, making it easier to create a thicker fiber layer.

[0015] It is known that paints containing fibers longer than a certain length tend to settle in the paint because the weight of each fiber is large. For this reason, it is known that it is preferable to use fibers that have voids. However, even if fibers have voids, if these voids extend to the outer surface, paint components such as solvents and resin components penetrate into the inside of the fibers, making settling in the paint unavoidable. Furthermore, even during painting, because the fibers contain paint components, it is thought that the overturning moment is large even after application to the substrate, and the fiber layer tends to become thin.

[0016] The inventors then conducted further research and found that by using hollow fibers with at least one end sealed and the inner wall inside the fiber surrounding the void, the penetration of paint components into the hollow fibers can be suppressed. As a result, they found that an anti-reflective coating can be obtained that reduces the sedimentation of fibers in the coating and makes it easier to form a thick fiber layer. Furthermore, they found that because the fibers are hollow, the incident light is further refracted and scattered in the hollow portion, which reduces the transmittance and improves the anti-reflective effect.

[0017] Therefore, the coating and film of this disclosure employ a fiber-containing structure having a length in the range of 1 μm to 1000 μm, having an inner wall surrounding a void formed inside, and at least one end of the longitudinal edge covering the void.

[0018] [Embodiment 1] <Optical Member> The member using the film of this disclosure is a member having at least one of the following functions: optical properties, antifouling properties, antibacterial properties, antiviral properties, abrasion resistance, and design properties. First, the optical member will be described.

[0019] Figure 1 is a schematic cross-sectional view of an optical member according to Embodiment 1, cut from the stacking direction. The member 100 of this disclosure comprises a film 10 including a resin layer 2 and a fiber layer 3. In Figure 1, the film 10 is provided on a substrate 1, and the resin layer 2 of the film 10 is provided on the surface 1A of the substrate 1. Fibers 31 protrude from the surface 2A of the resin layer 2. Multiple fibers 31 are bound to each other using a resin 22, which has the same components as the resin constituting the resin layer 2, as a binder, and the gaps formed by the binding of the multiple fibers 31 are voids 24.

[0020] To explain Figure 1 from a different perspective, it can be said that the multiple fibers 3 are bonded to each other to form a fiber structure 30. The fiber structure 30 has a portion that is included in the resin layer 2 and a portion that is not included in the resin layer 2. The fiber layer 3 includes the portion of the fiber structure 30 that is not included in the resin layer 2 and protrudes, forming a void 24. The fiber structure 30 does not necessarily need to be bound with a binder; it may also be formed by intertwining, wrapping, etc., with each other. Furthermore, the film of this disclosure does not necessarily need to be formed over the entire surface 1A of the member 100; for example, it may be formed in a minute area of ​​1 mm square that is a part of the surface 1A.

[0021] (Substrate) The substrate 1 has a surface 1A of the substrate and a surface 1B which is the back surface of the substrate, opposite to the surface 1A of the substrate. A film 10, which is an anti-reflective film, is provided on the surface 1A of the substrate, in close contact with the surface 1A of the substrate. To increase the adhesion between the surface 1A of the substrate and the film 10, a primer layer may be provided on the surface 1A of the substrate. Examples of components constituting the primer layer include epoxy resin, urethane resin, acrylic resin, silicone resin, and fluororesin. The thickness of the primer layer is preferably in the range of 2 μm to 30 μm. If it is too thin, the adhesion may be insufficient, and if it is too thick, assembly may become difficult. In addition, the surface roughness of the surface 1A of the substrate may be increased to improve adhesion with the film 10.

[0022] The material of the base material 1 is not particularly limited, and metals or resins can be used. Examples of metals include aluminum, aluminum alloys, titanium, titanium alloys, stainless steel, magnesium, and magnesium alloys. From the viewpoint of cost and durability, aluminum alloys or magnesium alloys are preferred. Examples of resins include strong ones such as polycarbonate resin, acrylic resin, ABS resin, fluororesin, and PBT resin. Other resins include synthetic rubbers such as silicone rubber, butadiene rubber, and acrylonitrile rubber, as well as flexible ones such as natural rubber. Because the fiber structure 30 contains voids 24, it is easy to obtain strength and flexibility, and it can be suitably used as a high-strength or highly flexible component when combined with the above base material.

[0023] (Anti-reflective coating) The anti-reflective coating, film 10, includes a resin layer 2 made of resin and fibers 3 protruding from the resin layer 2. The anti-reflective performance is particularly suitable for visible light with wavelengths of 300 nm to 780 nm, but is not limited to that range, and functions similarly for near-infrared light with wavelengths of 780 nm to 2500 nm. The thickness (T2 + T3) of the film 10 is preferably in the range of 30 μm to 400 μm. Higher anti-reflective performance is achieved within this range. If it is less than 30 μm, the light confinement effect for obliquely incident light may be insufficient depending on the usage environment. If it exceeds 400 μm, depending on the manufacturing conditions, assembly of the coated article may become difficult. The anti-reflective coating may be subjected to post-processing. Further materials may be coated, for example, a low refractive index material such as resin or silica may be coated to slow down the change in refractive index of the medium incident on the fibers 3 from the air, thereby adding a function to prevent surface reflection. Furthermore, surface modification processing may be applied. Roughening the surface makes it easier to trap incident light. Examples include blasting, UV ozone irradiation, flame treatment, plasma etching, and plasma surface treatment. Blasting can provide an even greater anti-reflective effect by physically roughening the surface, regardless of the material of the fiber 3. Plasma surface treatment can further enhance the light trapping effect by creating a nano-sized uneven structure on the surface of the polymer material fiber 3. The effect depends on the material of the fiber 3, but polyester is particularly preferable.

[0024] [Resin layer] The resin layer 2 supports the fiber structure 30 and also plays a role in ensuring close contact between the base material 1 and the fiber structure 30.

[0025] The resin constituting the resin layer 2 is the cured product of the resin composition. The type of resin is not particularly limited and may be a single resin or a mixture. Examples of usable resins include acrylic resins, polyester resins, alkyd resins, fluororesins, epoxy resins, polyurethane resins, and polyether resins. Copolymers of each resin may also be used, but acrylic urethane resin is preferred due to its high adhesion to resin substrates and metal substrates.

[0026] The resin layer 2 may contain the fibers 31 included in the fiber layer 3. The fibers 31 included in the resin layer 2 will be explained in the section on the fiber layer.

[0027] The thickness T2 of the resin layer 2 is preferably in the range of 1 μm to 100 μm, and more preferably in the range of 20 μm to 80 μm. If T2 is too thin, the fibers 31 may detach from the film 10 depending on the usage environment. On the other hand, if it is too thick, the film thickness of the film 10 will be large, which may make it difficult to assemble the painted article depending on the manufacturing conditions.

[0028] [Fiber layer] The fiber layer 3 has a three-dimensional and complex uneven shape and is responsible for trapping incident light and scattering and absorbing it in the recesses 311 of the fiber 31.

[0029] The fiber layer 3 includes portions of the fiber 31 that are not included in the resin layer 2 of the fiber structure 30 and protrude from the surface 2A of the resin layer 2. In addition, voids 24, which are gaps between multiple fibers 31, are formed. Figures 2A and 2B are side perspective views of the fiber 31, and Figures 3A to 3F are front cross-sectional views of the fiber 31 cut by a plane perpendicular to the stretching direction, which is the fiber axis direction.

[0030] The thickness T3 of the fiber layer 3 is preferably in the range of 30 μm to 300 μm. Higher anti-reflective performance is achieved within this range. If it is less than 30 μm, the light confinement effect against obliquely incident light may be insufficient depending on the usage environment. If it exceeds 300 μm, depending on the manufacturing conditions, the fibers 31 may become prone to bending or assembly of painted articles may become difficult. The thickness T3 of the fiber layer 3 is the length of the fibers 31 protruding from the resin layer 2, and is the longest distance from the resin layer 2 to the tip of the fiber 31 in the +Z direction in Figure 1. It can be measured using a three-dimensional shape measuring machine (product name VR-3200, manufactured by Keyence), a laser microscope, a confocal microscope, or other known height measuring devices.

[0031] {Fibers} The fiber 31 has a length L in the range of 1 μm to 1000 μm. The fiber is preferably a short fiber. The fiber length L is preferably in the range of 10 μm to 1000 μm, and more preferably 400 μm or less. If it is too long, it may easily cause clogging depending on the performance of the painting equipment such as spray paint. In other words, if spray painting is used, it is more preferable that it be 400 μm or less. On the other hand, if it is too short, the thickness of the fiber structure 30 that traps light when the film 10 is formed may be small, so the anti-reflective function due to the light trapping effect may be insufficient. Methods of crushing or cutting the long fibers can be used to adjust the length, but the cutting method is preferred. For example, disc cutters, rotary cutters, guillotine cutters, etc. can be used for cutting. Cutting the long fibers with a cutter while feeding them on a conveyor is preferred from the viewpoint of mass production, and a method of continuously cutting using a guillotine cutter and a belt conveyor is more preferred. When using hollow fibers, the frictional heat from the guillotine cutter is transferred to the cut surface, causing the fiber cross-section to plasticize and making it easier to close the ends, which is particularly preferable. The preferred lower limit is 50 μm or more, and more preferably 100 μm or more. Hereafter, unless otherwise specified, "cross-section" refers to a cross-section perpendicular to the axial direction of the fiber.

[0032] The fiber 31 has an inner wall 313 surrounding a void 314 formed within the fiber, and an outer wall 310. At least one end of the fiber 31 in the longitudinal direction, which is the fiber axis direction, covers the void 314. In other words, it is preferable that the fiber 31 is a hollow short fiber. Hollow means that the fiber has a void 314 inside the cross-sectional shape of the fiber in which there is no material that constitutes the fiber. The void 314 may be scattered like bubbles or may be a continuous cavity in the fiber length direction, but it is preferable that it be a cavity because it has a high effect in reducing specific gravity.

[0033] At least one end of the hollow short fiber in the direction of the fiber axis, which is the longitudinal direction, must be a continuous surface, and the void 314 is not exposed at the end. In other words, the end is closed, and when a cross section perpendicular to the fiber length direction is cut out at any position, the void 314 is visible as shown in Figure 3A, but the end has a general shape as shown in Figure 3F. When the fiber 31 comes into contact with the substrate 1 during painting, it tilts according to the overturning moment which is correlated with the specific gravity, but when the end is closed, the void (cavity) inside the fiber 31 is less likely to be filled with paint components. As a result, the overturning moment of the fiber 31 on the substrate 1 becomes smaller, and it becomes less likely to tilt. For this reason, even with a low concentration (low content) of fiber 31, it is easier to make the fiber structure 30 thicker, and thus the anti-reflective performance is improved. Continuous means that there are no voids in the same cross section, as shown in Figure 3E, and the surface shape may be curved. The end may have irregularities, but the size of the irregularities at the end is preferably 10 μm or less, and more preferably 1 μm or less.

[0034] It is preferable that both ends of the fiber 31 in the longitudinal direction, which is the fiber axis direction, cover the void 314. Even if only one end face covers the void 314, the internal pressure within the void 314 is maintained, making it difficult for paint components to penetrate into the fiber 31. However, if both ends of the fiber are covered, the penetration of paint components can be reduced even further. Furthermore, from the viewpoint of preventing sedimentation in the paint, which will be described later, it is preferable that the fiber is filled with a gas such as air and has a low effective specific gravity.

[0035] The void diameter R of the hollow portion of the hollow fiber 31 is the diameter of the void or its equivalent diameter. The equivalent diameter d is defined as d = 4A / p, where A is the cross-sectional area of ​​the void and p is the circumference of the void. The void diameter R is preferably in the range of 5% to 90% of the fiber thickness T, and more preferably in the range of 15% to 60%. If it is larger than this, depending on the manufacturing conditions, the strength of the fiber 31 may become insufficient, the fiber 31 of the fiber structure 30 may bend, and the thickness T3 of the fiber layer may become thinner. On the other hand, if it is smaller than this, it may be difficult to obtain the effect of preventing paint settling, and the effect of reducing transmittance due to refraction and scattering of incident light in the hollow portion may not be obtained.

[0036] The porosity, which indicates the proportion of voids in the fiber 31, is the ratio of the void cross-sectional area to the fiber cross-sectional area including the hollow portion. A porosity of 5% to 70% is preferable, and a range of 15% to 60% is more preferable. A high porosity has a greater effect in reducing the effective specific gravity, but if it is too high, the shape cannot be maintained, and the fiber layer 3 may not be able to be made thick enough. In that case, the strength and adhesion may be impaired, and light incident on the fiber structure 30 may be transmitted through.

[0037] Preferably, the fiber 31 has a protrusion 312 and a recess 311 that is recessed toward the axial center from the protrusion 312 on the outer wall 310 which is the periphery. The periphery is the outermost part when a cross section perpendicular to the stretching direction of the fiber is cut out. The axial center is the centroid of that perpendicular cross section, and when the periphery is inscribed in a figure selected from a circle, ellipse, or polygon (inscribed by the dashed lines in Figures 3B to 3D), it is the center of that figure.

[0038] To absorb the light diffused within the recesses 311 and prevent reflected light from escaping, the material of the fiber 31 and the material of the recesses 311 are preferably light absorbers, and more preferably black. The number of recesses per fiber cross-section may be one or more, and the number may vary depending on the cutting position relative to the axial direction of the fiber, but to more efficiently confine light and prevent reflection, three or more are preferable, and five or more are preferable. Also, to ensure the strength of the fiber, 16 or fewer are preferable, and 12 or fewer are preferable. The recesses 311 may be continuous in the length direction of the fiber, or they may be scattered in a hole-like manner. However, from the viewpoint of preventing paint from penetrating, it is preferable that they do not communicate with internal voids. The method of forming the recesses is not particularly limited, and for example, a molten resin solution can be extruded and spun using a fiber mold or die having an uneven shape. In this case, a fiber with continuous recesses formed as shown in Figure 2A will be formed. Alternatively, for example, soluble particles can be kneaded and spun, and then the particles can be removed by a dissolution treatment to form the recesses 311. Furthermore, recesses 311 can also be formed by applying an alkaline weight reduction treatment to fibers that do not have an uneven surface. In these cases, the recesses 311 tend to be formed in a scattered manner, resulting in a side view as shown in Figure 2B and a cross-section as shown in Figure 3C. The shape of the fiber 31 can be observed using an optical microscope or a transmission electron microscope. The cross-sectional shape can be observed by the above means after exposing the cross-section using a cutter, microtome, or cross polisher.

[0039] It is preferable that the fibers 31 are bound to each other using resin 22, which has the same components as the resin that constitutes the resin layer 2, as a binder. This is because it increases the mechanical strength of the fiber structure 30. That is, it is preferable that at least a portion of the fibers 31 are covered with resin 22. The content of resin components attached to the fibers 31 in the fiber layer 3 is preferably 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the fiber layer 3. If particles are attached to the fibers 31, the resin is more likely to flow off when the coating film dries, and the amount of resin in the fiber layer 3 can be reduced. Since the resin in the fiber layer easily reflects incident light, reducing the amount of resin is advantageous for the anti-reflective function. As the fiber density of the fiber structure increases, the resin components cling to the fibers in a way that crosslinks the fibers, so the ratio of resin components tends to increase. A method for measuring the resin content is, for example, the TG-DTA method. The fiber layer 3 is scraped off from the film 10, and the heat weight loss of the scraped fiber layer 3 is measured. At a temperature where fiber decomposition has not yet begun and the resin is not thermally decomposed or burned, the resin content in the fiber layer 3 can be determined by dividing the weight loss of the scraped fiber layer 3 by the weight of the fiber layer 3 before measurement and multiplying by 100. Alternatively, the resin content can be measured using a surface analysis device such as TOF-SIMS.

[0040] The fiber content 31 is preferably 5 parts by mass or more and less than 60 parts by mass, and more preferably 5 parts by mass or more and less than 33 parts by mass, per 100 parts by mass of the film. If the content is too low, the density of the fiber 31 decreases, and depending on the usage environment, the anti-reflective function may not be sufficient. On the other hand, if the content is too high, depending on the manufacturing method, the area ratio of the fiber cross-section in the fiber structure may increase, and the reflectivity on the surface of the fiber structure may increase. Also, because the film thickness (T2 + T3) of the film 10 increases, depending on the manufacturing method, it may become difficult to assemble the painted article. In addition, because the ratio of fiber to resin component is high, the fiber may easily fall off the film 10. The fiber may include not only fiber 31 which has a convex portion 312 at the periphery and a concave portion 311 which is recessed toward the axial center from the convex portion 312, but also other fibers. The fiber content 31 per 100 parts by mass of the total amount of fiber is preferably 20 parts by mass or more, more preferably 50 parts by mass or more. Even more preferably 80 parts by mass or more, and most preferably 100 parts by mass.

[0041] The width S of the fiber recess is preferably in the range of 0.5 μm to 30 μm. In the case of the fiber 31 in Figure 2A, the width S can be rephrased as the distance between adjacent protrusions 312. The width S is more preferably in the range of 5 μm to 15 μm. If the width S is less than 0.5 μm, depending on the usage environment, less light may enter the recess 311, and the anti-reflective function due to light confinement may be insufficient. On the other hand, if the width S is greater than 30 μm, depending on the usage environment, light may be reflected in the same way as on a flat surface, and the anti-reflective function may be insufficient.

[0042] The fiber thickness T is preferably in the range of 0.1 μm to 100 μm, and more preferably in the range of 1 μm to 50 μm. Fiber thickness refers to the maximum length when cut by a plane perpendicular to the fiber axis. If the fiber is thicker than this, the density of the fiber structure on the coating film increases, and depending on the usage environment, light may not be able to enter the fiber structure, potentially increasing surface reflection. On the other hand, if the fiber is thinner, depending on the usage environment, incident light may pass through, potentially resulting in insufficient anti-reflective function, and the fiber strength may decrease, causing the fiber structure 30 to become thinner.

[0043] The aspect ratio (L / T) of the fiber is the ratio of the length L to the thickness T, and it is preferably in the range of 5 or more and 500 or less. The larger the aspect ratio, the easier the fibers are to entangle and the easier it is to form a fiber structure. If it is too high, depending on the use environment, there is a risk of bending due to the specific gravity of the fiber itself.

[0044] The material of the fiber is not particularly limited, and polyamide, polyester, acrylic, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polycarbonate, aramid, rayon, cotton, wool, etc. are used. Among them, organic polymers such as polyamide, polyester, acrylic, and aramid are preferable because of the ease of forming concave-convex shapes and hollow shapes. Among them, polyesters such as polyethylene terephthalate are more preferable, and a antireflection film with high strength and difficult to shed short fibers from the film can be formed. Also, when using hollow fibers, using a thermoplastic resin makes it easier to close the ends. Examples of thermoplastic resins include polyamide, polyester, acrylic, aramid, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, polycarbonate, etc. Among them, polyesters such as polyethylene terephthalate are more preferable from the viewpoint of strength. Also, it is preferably black in order to enhance the antireflection effect of visible light. It may be a raw-attached short fiber kneaded with a black pigment such as carbon black inside the yarn before spinning, or a short fiber dyed using a dye, but from the viewpoint of antireflection, raw-attached short fibers are preferable, and it is preferable that all surfaces including the cross-section, the outer wall 310, the concave portions 311, the convex portions 312, and the inner wall 313 forming the void 314 that constitute the outer wall 310 are black. That is, the fiber 31 is preferably a black raw-attached yarn.

[0045] {Particles attached to the fibers} The fibers 31 may have particles attached to the protrusions 312 and recesses 311. The particles may include first particles 32 and second particles 33. Preferably, the number of particles attached to the recesses 311 is greater than the number of particles attached to the protrusions 312. In this case, the capillary force acting on the recesses 311 is weakened by the attachment of the particles, and after application to the substrate, the resin containing the resin component or solvent flows out more easily to the protrusions 312 or the resin layer 2 side. Therefore, the surface reflection of the fiber structure 30 (fiber layer 3) is suppressed in the dried film 10. As a result, the film 10 can obtain high anti-reflective performance not only for obliquely incident light but also for perpendicularly incident light. The relationship between the amount of particles attached to the recesses 311 and the amount of particles attached to the protrusions 312 can be determined, for example, from images acquired with an optical microscope or a transmission electron microscope. The coverage rate can be calculated and compared from the area of ​​particles attached to the recess 311 and the area of ​​particles attached to the convex portion 312. Alternatively, for example, after identifying the composition of the particles, the amount of elements present per unit surface area of ​​the recess and convex portion can be determined and identified by energy-dispersive X-ray spectroscopy (SEM-EDX). The latter method allows for identification even when the apparent coverage rate is the same but the elemental ratios differ. Furthermore, since the step of identifying the constituent elements of the particles is taken, the relative sizes of particles can be determined even if there are multiple types of particles. While particles are effective even if they only cover the surface to some extent, it is preferable that the coverage rate in the recess 311 is 20% or more, and more preferably 35% or more. The coverage rate in the convex portion 312 should be lower than the coverage rate in the recess 311.

[0046] While known methods may be used to attach the particles to the fiber 31, it is preferable to mix a fiber having a convex portion on its periphery and a concave portion that is recessed toward the axial center from the convex portion, particles and / or particle precursors, and a solvent, and then dry the mixture. When the mixture is dried, the solvent gradually evaporates, but the rate of evaporation differs between the fiber concave portion and the fiber convex portion. The convex portion has a large volatilization space, so the vapor pressure is low and evaporation is fast. On the other hand, the concave portion has a narrow volatilization space, so the vapor pressure is high and evaporation is slow. Also, because the solvent has surface tension, it flows into the concave portion. Due to this difference in evaporation rate and the surface tension of the solvent, as the drying process progresses, the solvent accumulates in the concave portion while increasing the concentration of particles, so that when drying is complete, a fiber with particles concentrated in the concave portion is obtained. For the above reasons, a solvent with high surface tension is preferable. Preferably it is 40 mN / m or more, and more preferably 60 mN / m or more. As the solvent to be used, a mixed solvent containing water or an aqueous solvent is preferred, and most preferably pure water.

[0047] The particles may be organic particles or inorganic particles. Examples of the organic particles include coloring materials such as disperse dyes and pigments, and functional polymers such as light absorbers and conductive polymers. Among the inorganic particles, functional particles preferably include conductive aids, insulating materials, or matting agents. Since the conductive aids and insulating materials control the charge property of the antireflection film and are used for preventing adhesion of dust and the like, it is preferable that the particles contain inorganic particles. For example, examples of the conductive aid which is an example of the first particle 32 include aluminum, zirconium, zinc, magnesium, their hydroxides, carbon nanotubes, graphene, conductive carbon black, and tin-doped indium oxide (ITO). Among them, hydroxyaluminum colloids such as metaaluminum acid and aluminum hydroxide, and magnesium hydroxide are more preferable. When performing the adhesion treatment of the particles in an aqueous solvent, an acidic colloid of a metal oxide having an OH group on the surface is also effective from the viewpoint of water dispersibility, and alumina sol is particularly preferable. Examples of the insulating material include oxides of aluminum, zirconium, zinc, magnesium, and the like. The matting agent which is an example of the second particle 33 can improve the antireflection effect, and examples thereof include silica (silicon oxide), porous silica (silicon oxide), titania, porous titania, calcium carbonate, talc, mica, zinc oxide, cerium oxide, and the like. Among them, a matting agent made of a porous material is particularly suitable for antireflection. When performing an aqueous treatment, acidic colloidal silica is suitable from the viewpoint of water dispersibility. Further, the above particles can also function as a dispersant for preventing adhesion between fibers and preventing aggregation in a paint. Therefore, from the viewpoint of the storage stability of the paint, it is preferable that they are adhered, it is more preferable that more surfaces are covered, and it is even more preferable that the entire surface is covered.

[0048] When the fiber 31 has an uneven shape, the particle diameter of the particles is preferably smaller than the width S of the concave portion 311. Further, it is preferably 3 μm or less, and more preferably 1 μm or less. When it is 3 μm or less, the reflected light can be diffused into the concave portion by Mie scattering. When it is 1 μm or less, Rayleigh scattering occurs and the scattering becomes stronger, improving the antireflection performance.

[0049] As described above, in the first embodiment, the fibers contained in the film provided on the member have a length in the range of 1 μm to 1000 μm, and at least one end of the longitudinal end covers the void. Therefore, the sedimentation of fibers in the paint is reduced, the overturning moment is reduced even after application to the substrate, and it is easy to form a thick fiber layer. As a result, the dried film has higher anti-reflective performance than conventional films because light incident on the fiber structure (fiber layer) is scattered inside the structure.

[0050] [Embodiment 2] <Anti-reflective coating> The coating of the present disclosure is a coating comprising fibers, a resin, and a solvent, and is the raw material (precursor) of the film 10 described above. The film 10 of the first embodiment is obtained by drying the coating.

[0051] (Fiber) The fiber is the same as the fiber described in the {Fiber} section of Embodiment 1, and the fiber 31 has a convex portion 312 on its periphery and a concave portion 311 that is recessed toward the axial center from the convex portion 312.

[0052] The fiber content 31 is preferably 5 parts by mass or more and less than 60 parts by mass, and more preferably 5 parts by mass or more and less than 33 parts by mass, per 100 parts by mass of paint solids. If the content is too low, the density of the fiber 31 decreases, and depending on the usage environment, the anti-reflective function of the film 10 may not be sufficient. On the other hand, if the content is too high, depending on the manufacturing method, the volume ratio of fibers in the fiber structure increases, and the volume of the voids that trap light decreases, which may increase the reflectivity on the surface of the fiber structure. In addition, the film thickness (T2 + T3) of the film 10 increases, which may make it difficult to assemble the painted articles depending on the manufacturing method. Furthermore, because the ratio of fibers to resin components is high, the fibers may easily detach from the film 10.

[0053] Furthermore, from the viewpoint of paint stability, the content is preferably less than 60 parts by mass, and more preferably less than 33 parts by mass, per 100 parts by mass of paint solids. If it exceeds this amount, the fiber density in the paint will increase too much, potentially causing the fibers to intertwine, form aggregates, and settle. The fibers may include not only fibers 31 having convex portions 312 on their periphery and concave portions 311 that are recessed toward the axial center from the convex portions 312, but also other fibers. The content of fibers 31 per 100 parts by mass of the total amount of fibers is preferably 20 parts by mass or more, more preferably 50 parts by mass or more. Even more preferably 80 parts by mass or more, and most preferably 100 parts by mass.

[0054] (Particles) The particles are the same as those described in the section {Particles attached to the fibers} of Embodiment 1. The particles may include first particles 32 and second particles 33. There are more particles attached to the recesses 311 than to the protrusions 312. As a result, the capillary force acting on the recesses 311 is weakened by the attachment of the particles, and after application to the substrate, the resin component or the resin containing the solvent flows out more easily to the protrusions 312 or the resin layer 2 side. Therefore, the surface reflection of the fiber structure 30 (fiber layer 3) is suppressed in the dried film 10. As a result, the film 10 can be made to have high anti-reflective performance not only for obliquely incident light but also for perpendicularly incident light. The adhesion of particles in the paint can be observed, for example, by washing the paint with water or a solvent, separating the fibers from the paint by filtration or centrifugation, and then observing it using an optical microscope or a transmission electron microscope.

[0055] (Resin) The resin contained in the paint refers to the uncured resin composition. The resin may be dissolved in the paint or may be an uncrosslinked prepolymer. The type of resin is not particularly limited and may be a single resin or a mixture. Examples of usable resins include acrylic resins, polyester resins, alkyd resins, fluororesins, epoxy resins, polyurethane resins, and polyether resins. Copolymers of each resin may also be used, with acrylic urethane resin being preferred. In addition to the resin, a resin composition containing additives and solvents may also be used. Resin compositions can be one-component curing type or two-component curing type, and either may be used. Among these, the two-component curing type is preferred from the viewpoint of adhesion and strength to resin substrates and metal substrates.

[0056] (Solvent) The solvent may be water or an organic solvent, and can be used depending on the application of the paint. Paints with water as the main component have the advantage of having a low environmental impact. When an organic solvent is included, the adhesion and quick drying properties of the paint film are improved, and the types of resin components that can be used differ from those when water is included. The organic solvents that can be used may be those commonly used in paints, for example, alcohols (methanol, ethanol, isopropanol, n-butyl alcohol, ethylene glycol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (ethyl acetate, butyl acetate, etc.), halides (chloroform, methylene chloride, etc.), olefins (butane, hexane, etc.), ethers (tetrohydrofuran (THF), butyl ether, dioxane, etc.), aromatics (benzene, xylene, toluene, etc.), and amides (N,N-dimethylformamide, dimethylacetamide). Mixed solvents of these are also acceptable. When attaching particles to the fibers 31, it is preferable to select a solvent that balances the solubility of the resin with its affinity for the particles. It is preferable that the solvent dissolves the resin well and does not have too high an affinity for the particles. Affinity can be defined by known methods such as surface energy, HSP value, or SP value. If the affinity for the particles is too high, depending on the manufacturing method, the solvent containing the dissolved resin may tend to accumulate in the depressions of the fibers 31. Conversely, if the affinity for the particles is too low, depending on the manufacturing method, the particle dispersibility may be poor, and the storage stability of the coating may be impaired. For this reason, for particles suitable for the aforementioned aqueous treatment, an organic solvent system is more preferable, and for particles suitable for solvent-based treatment, an aqueous solvent is more preferable.

[0057] <Method for Manufacturing Anti-Reflective Coating> The method for manufacturing the coating of the present disclosure is not particularly limited, but preferred manufacturing methods are described below.

[0058] First, fibers having an inner wall surrounding a void formed inside are impregnated with water, and then the fibers are cut (S01). This ensures that at least one end of the fiber's longitudinal edge covers the void. The means of cutting are not particularly limited, but it is preferable to use a cutter or a guillotine cutter. A guillotine cutter may or may not have a heating mechanism, and is particularly preferable because continuous cutting can heat the fiber cross-section due to frictional heat between the fiber and the guillotine. When cutting, it is preferable to cut without stopping midway after starting the cutting process. Furthermore, when the fibers are made of thermoplastic resin, it is preferable to heat the fibers while cutting them. Heating makes the fibers more easily deformable, and pressure cutting makes the cut surface plasticized, making it easier to seal the void. That is, the end of the fiber, which is the cut surface, is terminated, making it easier to cover the void with the end. It is also preferable that the amount of water impregnated into the fibers is sufficiently large. When fibers are sufficiently saturated with water, the inside of the fibers swells easily, and heat is transferred more readily. Plasticization is promoted, making it easier to fill voids, but also easier for them to become blocked. Cutting is preferably done continuously. Continuous cutting means cutting the fibers continuously while feeding them on a belt conveyor or the like. Continuity can be controlled, for example, by the rotation speed; the faster the rotation speed and the slower the feed speed, the shorter the fibers become, and the easier they are to heat. Hollow fibers made of thermoplastic resin only need to have 50% or more of the resin component constituting the hollow fiber be thermoplastic resin, and may also be 100% thermoplastic resin.

[0059] Next, the fibers are dried (S02). This completes the termination of the ends, which are the cut surfaces of the fibers, and the voids are covered by the ends. The atmosphere and temperature for drying are not particularly limited, but if the fibers were heated during cutting, it is preferable to dry them at a temperature lower than the heating temperature.

[0060] Then, the dried fibers, resin, and solvent are mixed (S03). The means of mixing are not particularly limited, as long as the fibers can be dispersed in the paint. Examples include jet mills, mixers, magnetic stirrers, dissolvers, paint shakers, and rotators. The paint of this disclosure can be obtained by following the above procedure.

[0061] <Method for Manufacturing Optical Components> The method for manufacturing an optical component, which is an example of a component of this disclosure, is not particularly limited, but preferred manufacturing methods are described below.

[0062] First, the above-mentioned paint and solvent are mixed to obtain a mixed solution (S11). A curing agent may also be included during mixing. In particular, when using a two-component curing type resin, it is preferable to mix the curing agent in addition to the solvent.

[0063] Next, the resulting mixture is spray-coated onto the substrate (S12). Spray coating has the advantage that, as soon as the paint droplets land on the substrate, drying begins, which prevents the fibers from collapsing and makes it easier to form a thick fibrous structure.

[0064] Then, the spray-coated substrate is dried (S13). Drying may be done by heating or by drying at room temperature. The component of this disclosure can be obtained by following the above procedure.

[0065] As described above, in the second embodiment, the fibers contained in the paint, which is the raw material for the film, have a length in the range of 1 μm to 1000 μm, and at least one end of the longitudinal edge covers the void. Therefore, the sedimentation of fibers in the paint is reduced, the overturning moment is reduced even after application to the substrate, and it is easier to form a thick fiber layer. Thus, in the film obtained by drying the paint of this disclosure, the light incident on the fiber structure (fiber layer) is trapped inside the structure and scattered internally, so a higher anti-reflective performance than conventional films can be obtained.

[0066] [Embodiment 3] <Aerosol Can Containing Paint> Figure 4 is a schematic diagram of an aerosol can according to the present disclosure. The aerosol can 60 comprises a liquid container 62 containing the paint of Embodiment 2, a gas container 61 containing a propellant, and a connecting member 63 connecting the liquid container 62 and the gas container 61. The method of use is not limited, but it can be used, for example, as exterior wall paint for buildings, automotive paint, or toy paint.

[0067] The liquid container 62 is a container for storing anti-reflective paint. The liquid container 62 may have, for example, a cylindrical container body, and the inside of the container may be divided into liquid spaces. The paint is filled into the liquid container 62 and connected to the gas container 61.

[0068] The gas container 61 comprises, for example, a metal cylinder filled with a propellant and a holder attached to the cylinder. The propellant stored in the cylinder is not particularly limited, and various known propellants used in aerosol products can be used. For example, liquefied gas, compressed gas, etc. can be used as the propellant. Examples of the liquefied gas include various liquefied petroleum gases, dimethyl ether, and liquefied gases mixed therewith. Examples of the compressed gas include compressed air, nitrogen gas, carbon dioxide, and other compressed gases. For example, the container may have a cylindrical body, and the gas space and liquid space inside the container may be connected. By pressing a button installed on the container body, the propellant and paint may be mixed within the connecting member and ejected to the outside of the container. The above is an example of a spray can for a one-component paint, but when using a two-component curing type paint, a system that makes it difficult for the curing reaction to occur when not in use is more preferable. For example, a design in which the liquid chambers for the paint and the hardener are separated is preferred, and specifically, known spray can designs such as those described in Japanese Patent Publication No. 2018-177244 and Japanese Patent Publication No. 2009-23684 can be used.

[0069] [Embodiment 4] <Device Application> (Optical Instrument, Imaging Device) Figure 5 is a schematic diagram showing one embodiment of the configuration of a single-lens reflex digital camera 600, which is an example of an imaging device, and is equipped with a lens barrel, which is an example of a preferred embodiment of the imaging device of the present disclosure. In Figure 5, the camera body 602 and the lens barrel 601, which is an optical instrument, are coupled together, and the lens barrel 601 is a so-called interchangeable lens that can be attached to and detached from the camera body 602.

[0070] Light from the subject is received by the image sensor and captured when it passes through an optical system consisting of multiple lenses 603, 605, etc., which are an example of components arranged on the optical axis of the imaging optical system inside the housing of the lens barrel 601. Here, lens 605 is supported by an inner barrel 604 and is movably supported relative to the outer barrel of the lens barrel 601 for focusing and zooming. The inner barrel 604 is a support that supports lens 605.

[0071] During the observation period before shooting, light from the subject is reflected by the main mirror 607, which is an example of a component inside the camera body housing 621, passes through the prism 611, and the image is projected onto the photographer through the viewfinder lens 612. The main mirror 607 is, for example, a half-mirror, and the light that passes through the main mirror is reflected by the sub-mirror 608 towards the AF (autofocus) unit 613, and this reflected light is used, for example, for distance measurement. The main mirror 607 is also attached and supported to the main mirror holder 640 by adhesive or the like. During shooting, the main mirror 607 and sub-mirror 608 are moved out of the optical path via a drive mechanism (not shown), the shutter 609 is opened, and the image of the photographic light incident from the lens barrel 601 is projected onto the image sensor 610. The aperture 606 is configured to change the brightness and depth of field during shooting by changing the aperture area.

[0072] To apply the component 100 of this disclosure to a lens barrel, the housing 620 has the same configuration as the base material 1, and an anti-reflective film 630 with the same configuration as the film 10 is provided on the inner wall surface 620A of the housing. Alternatively, the inner cylinder 604 has the same configuration as the base material 1, and an anti-reflective film 630 with the same configuration as the film 10 is provided on the first surface 604A of the support, which is the surface of the inner cylinder that supports the lens. By adopting such a configuration, light rays that do not form an image and do not contribute to the formation of an image of the subject among the light rays incident on the optical instrument are less likely to return to the optical path by hitting the fiber structure. As a result, the amount of stray light reaching the image sensor 610 is reduced. According to the imaging device of this disclosure, since the amount of stray light reaching the image sensor is reduced, it is possible to provide an imaging device that is less prone to flare and ghosting and has excellent image quality.

[0073] Although a single-lens reflex digital camera was used as an example to describe the imaging device, this disclosure is not limited to this and may also include smartphones or compact digital cameras. Furthermore, it may also include automotive modules such as automotive cameras, ADAS (Advanced Driver-Assistance Systems) cameras, and LiDAR (Optical Detection and Distance Measurement) modules, which have lenses or mirrors and image sensors or light-receiving elements.

[0074] (Display Device) Figure 6 is a schematic diagram showing one embodiment of the configuration of a head-up display 300, which is an example of a preferred embodiment of the display device of the present disclosure.

[0075] The head-up display 300 is installed in a vehicle such as an automobile and projects image light onto the windshield 8, which is an example of a display unit, to display a virtual image IM that can be seen by a viewer, such as a driver, who has eyes 9. The head-up display 300 has a housing 13, an image generation unit 4, and reflectors 51 and 52. The head-up display 300 is installed, for example, in the dashboard in front of the steering wheel H.

[0076] The image generation unit 4 is located inside the housing 13. The image generation unit 4 includes a light source 42 and a display panel 41. The light source 42 is a device that emits light, such as a plurality of LEDs. The display panel 41 is a device that modulates the light emitted from the light source 42 to generate image light, such as a self-emissive display like a transmissive liquid crystal display or an organic EL display.

[0077] The reflectors 51 and 52 are installed inside the housing 13. Each reflector 51 and 52 has a reflective surface 51A and 52A, respectively, and reflects the image light generated by the image generation unit 4 at each reflective surface. Before being reflected by the reflective surface 51A, the generated image light may, if necessary, pass through an optical path via a focusing lens 53 or the like. The reflector 52 has a drive mechanism 521 including a motor and gears, and the drive mechanism 521 is driven by a control device (not shown), allowing adjustment of the angle of the reflective surface 52A. Each reflector 51 and 52 is a concave mirror. Each reflector 51 and 52 has a free-form surface made of resin on which a metal film such as aluminum is formed. The metal film can be formed, for example, by vapor deposition. The image light reflected by the reflector 52 is magnified and projected toward the front glass 8 located on the outside of the housing 13 via the transmissive plate 7. The transmissive plate 7 is, for example, an acrylic plate.

[0078] To apply the component 100 of this disclosure to a display device, the housing 13 has the same configuration as the base material 1, and an anti-reflective film 210 having the same configuration as the film 10 is provided on the inner wall surface 13A of the housing. By adopting this configuration, light rays generated when the backlight of the head-up display is turned on or when ambient light is incident, and light rays that do not contribute to the formation of reflected image light within the housing, are less likely to return to the optical path by hitting the fiber structure. As a result, the amount of stray light reaching the display area 81 of the windshield 8 is reduced. With the display device of this disclosure, since the amount of stray light reaching the windshield 8 is reduced, it is possible to provide a display device with excellent image (virtual image) quality generated from image light.

[0079] In the embodiments of the display device described herein, the case in which a head-up display is installed in an automobile was described as an example, but it is also applicable to other vehicles such as trains and airplanes. It is also applicable to uses other than vehicles. Furthermore, it is also applicable to display devices such as projectors used indoors or outdoors. In Figure 6, the anti-reflective coating 210 is provided at three locations on the inner wall surface 13A of the housing 13, but the number and position of the anti-reflective coating provided inside the housing 13 are not limited to this form. Also, although two reflectors are provided inside the housing 13, depending on the design of the optical system, there may be only one reflector.

[0080] (Building Material) Figure 7 is a schematic diagram of a building which is an example of a building material of the present disclosure. The building material is an example of a member comprising a base material and a film provided on the base material. The building 70 includes an exterior wall 73, windows 71 and doors 72. To apply the member 100 of the present disclosure to the building 70, the exterior wall 73 is made to have the same configuration as the base material 1, and the film 10 is provided on it. The film 10 exhibits attractive reflective properties to visible light, making it highly aesthetically pleasing. Furthermore, because it absorbs a lot of light, it can be used as a heat-absorbing material, making it highly valuable as a building material. In addition to the exterior walls of buildings, it can also be suitably used for the exterior of automobiles, etc.

[0081] (Clothing and Blackout Curtains) Figure 8 is a schematic diagram of a poncho, which is an example of clothing according to the present disclosure. Clothing is an example of a component comprising a base material and a membrane provided on the base material. The poncho 500 includes sleeves 501 and a body 502. To apply the component 100 of the present disclosure to the poncho 500, the sleeves 501 and body 502 are made to have the same configuration as the base material 1, and the membrane 10 is provided on them. The membrane 10 exhibits aesthetically pleasing reflective properties to visible light, making it highly suitable for use in clothing. Furthermore, because it has low reflectivity in the near-infrared region, it can block infrared rays, resulting in clothing that is black but has a heat-shielding effect. On the other hand, due to its properties, it is difficult to see with imaging devices that utilize lasers, such as night vision cameras and LiDAR, making it suitable for use as a blackout curtain to emphasize traffic signs.

[0082] (Camera Mounting Device) Figure 9 is a schematic diagram of an in-vehicle camera bracket, which is an example of a camera mounting device of the present disclosure. The bracket 700 is an example of an optical member comprising a base material and a film provided on the base material. The bracket is for mounting an in-vehicle camera on the windshield of an automobile and includes a bracket body portion 701 having a main body adhesive portion that adheres to the windshield, a camera mounting portion 702 connected to the bracket body portion 701 to which an imaging means, which is the in-vehicle camera, is attached, and a camera front portion 703 which is an embodiment of a camera hood positioned in front of the camera front portion 703. To apply the member 100 of the present disclosure to the bracket 700, it is preferable to have the same configuration as the base material 1 for the camera front portion 703 and to provide the film 10 on it. By adopting such a configuration as an in-vehicle camera module with an in-vehicle camera mounted on the bracket 700, light rays that do not contribute to the formation of the subject image among the light rays incident on the in-vehicle camera are less likely to return to the optical path because they hit the fiber structure. As a result, the amount of stray light reaching the in-vehicle camera, its optical system, and at least one of the image sensor is reduced. Furthermore, by positioning the front of the camera facing the mounting surface, stray light originating from light perpendicularly incident from the mounting surface, such as sunlight, can be prevented. According to the camera mounting device of this disclosure, the amount of stray light reaching the camera, its optical system, and at least one of the image sensor is reduced. Therefore, images with excellent quality that are less prone to flare and ghosting can be obtained, making it suitable for use in ADAS (Advanced Driver-Assistance Systems) and the like. The bracket may also have a heating mechanism to prevent glass fogging and a textured structure to prevent reflection. Although a mounting device for an in-vehicle camera with the mounting location on the windshield has been described as an example, this disclosure is not limited to this, and the mounting location may be, for example, the windshield glass, sunroof glass, or rear glass. Also, there may be one camera or multiple cameras to be mounted.

[0083] <Method for Evaluating Anti-Reflection Function> The anti-reflection function of the film in this embodiment can be evaluated by its reflectance. For example, a component can be prepared by applying a coating film to the surface of a 50 mm x 50 mm substrate made of polycarbonate, and the reflectance at incident angles of 5° and 80° can be measured using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-770).

[0084] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited in any way by the following examples unless it exceeds the gist of the disclosure. Unless otherwise specified, amounts of components expressed in "parts" and "%" are based on mass.

[0085] <Preparation of Short Fibers> (Preparation of Short Fibers 1-15 and Comparative Short Fiber 1) First, as shown in Figure 3B, a hollow fiber A (manufactured by Teijin Frontier Co., Ltd., product name: Octa) was prepared, having a square cross-section and recesses inscribed in the periphery of the square. Fiber A is made of polyester, has a thickness T of 25 μm, and has eight protrusions and eight recesses with a width S of 10 μm. It is a hollow 8-fin fiber in which the voids on a square with a side length of 9 μm form a continuous hollow section in the length direction (X direction). The fibers wound on a bobbin were bundled into a tow shape using a skein lifting machine and immersed in water. The tow-shaped fibers were removed from the water and the moisture content was measured to be 50% of the total weight. Next, the tow-shaped fibers were fed on a belt conveyor and continuously cut with a guillotine cutter to produce 60 kg of pile with a length of 200 μm. The obtained pile was washed, pressure-dyed with a black disperse dye, dried, and collected.

[0086] Next, the mixture was added to 300 L of water heated to 60°C, and 0.9 kg of colloidal silica with a particle size of 0.03 μm (manufactured by Nissan Chemical Corporation, trade name Snowtex ST-O) and 2.1 kg of alumina sol with a particle size of 0.01 μm (manufactured by Nissan Chemical Corporation, trade name AS-520-A) were added and stirred for 30 minutes. The resulting aqueous dispersion was filtered and dehydrated. Then, it was dried at 80°C using a dryer to obtain short fibers 1.

[0087] Figure 10 is an SEM image of the cross-section of short fiber 1. When the obtained short fiber 1 was observed with a transmission electron microscope (Hitachi High-Tech, product name SU-70), it was found that a first particle with an average particle diameter of approximately 0.01 μm and a second particle with an average particle diameter of approximately 0.03 μm were attached to it. An image was obtained in which 80% of the area of ​​the recess was covered with the first and second particles, and 20% of the area of ​​the convex part was covered with the first and second particles. Elemental analysis of the first and second particles revealed that the first particle was mainly composed of Al, and the second particle was mainly composed of Si. Based on these results and the components added, it is assumed that they were alumina sol and colloidal silica, respectively.

[0088] Table 1 summarizes the conditions and characteristics of short fiber 1. Short fibers 2 to 15 were obtained using the same process as for short fiber 1, except for the fiber type and length shown in the left side of Table 1. Note that for fiber G, since it was a fiber dope-dyed with carbon black, pressure dyeing was not performed. Furthermore, comparative short fiber 1 was obtained using the same process as for short fiber 1, except for the use of fiber H.

[0089] Furthermore, the fibers A to H used are as follows:

[0090] (Fiber A) Hollow 8-fin fiber cross-sectional shape: Figure 3B, Material: Polyester, Thickness T: 25 μm, Hollow void diameter R: 9 μm, Number of depressions: 8, Dyed with black dye (Fiber B) Hollow 8-fin fiber cross-sectional shape: Figure 3B, Material: Polyester, Thickness T: 50 μm, Hollow void diameter R: 18 μm, Number of depressions: 8, Dyed with black dye (Fiber C) Triangular prism nylon hollow fiber cross-sectional shape: Figure 3E, Material: Nylon, Thickness T: 20 μm, Hollow void diameter R: 6 μm, Irregularities: None, Dyed with black dye (Fiber D) Spherical hollow fiber cross-sectional shape: Figure 3A, Material: Polyester, Thickness T: 25 μm, Hollow void diameter R: 15 μm, Irregularities: None, Dyed with black dye (Fiber E) Irregular spherical hollow fiber cross-sectional shape: Figure 3C, Material: Polyester, Thickness T: 25 μm, Hollow void diameter R: 15 μm, Irregularities: Scattered on the side, Dyed with black dye (Fiber F) Spherical hollow large-diameter fiber cross-sectional shape: Figure 3C, Material: Polyester, Thickness T: 80 μm, Hollow diameter R: 30 μm, Irregularities: None, Dyed with black dye (Fiber G) 8-fin hollow dope-dyed fiber cross-sectional shape: Figure 3B, Material: Polyester, Thickness T: 25 μm, Hollow diameter R: 9 μm, Irregularities: 8 recesses on the periphery, Dyed with black dye (Fiber H) Spherical fiber cross-sectional shape: Figure 11, Material: Polyester, Thickness T: 25 μm, Hollow diameter R: None, Irregularities: None, Dyed with black dye

[0091] (Preparation of comparative short fiber 2) 1.4 kg of glass fiber (manufactured by Asahi Fiber Glass Co., Ltd., product name: MFJH-20) with an average length of 300 μm and a number average diameter of 10 μm was added to water to a concentration of 10% by mass and thoroughly dispersed, and heated to 70°C while stirring. After adjusting the pH to 2.5 using sulfuric acid, 3 kg of 20% by mass titanium sulfate aqueous solution was slowly added as titanium dioxide over 30 hours. The pH during addition was maintained at 2.5 using sodium hydroxide aqueous solution. After the addition was complete, sodium hydroxide aqueous solution was added to neutralize the pH to 7, then cooled, filtered, washed with water, and dried at 110°C. 0.5 kg of this was weighed out and added to 49.5 kg of 30% by mass sodium hydroxide aqueous solution, heated while stirring, and held at 95°C for 2 days. After cooling, it was filtered, washed, dried at 110°C, and then calcined at 550°C to obtain fibrous hollow titanium dioxide particles. Scanning electron microscopy revealed that the fibrous hollow titanium oxide particles had a number-average length of 200 μm, a number-average diameter of approximately 11 μm, an aspect ratio of 18.2, numerous hollow pores, and a number-average outer diameter of approximately 7 μm. The obtained particles were pressure-stained with a black disperse dye and dried, and comparative short fibers 2 were recovered.

[0092] (Preparation of comparative short fibers (3)) 1.7 kg of acidic alumina fine particle dispersion (manufactured by Catalytic Chemical Industries, Ltd., product name: Cataloid AS-3) and 0.5 kg of pure alumina were stirred at room temperature, and 60 g of 1% by mass sodium hydroxide aqueous solution was added. Then, 600 mL of strongly basic anion exchange resin (manufactured by Mitsubishi Chemical Corporation, product name: DAIAION SA-20A) was gradually added, and stirring was continued for 20 hours. After stirring, the ion exchange resin was removed, and 2.1 kg of stable alkaline alumina fine particle dispersion (pH 10.0) was prepared.

[0093] Next, 60 g of aqueous sodium silicate solution (silica concentration: 5% by mass) was added to 2.1 kg of the prepared alkaline alumina microparticle dispersion. The mixture was then heated to 150°C, and 1.2 kg of 1% by mass silicate solution was added over 5 hours. While maintaining the temperature at 150°C, stirring was continued for another hour, after which the solution was cooled to room temperature. Subsequently, the solution was washed with pure water using an ultrafiltration membrane (manufactured by Asahi Kasei Corporation, product name: SIP-1013). After washing, the solution was concentrated to obtain 2.4 kg of silica-coated alumina microparticle dispersion with a solid content of 5% by mass. The average particle size of the silica-coated alumina microparticles, which were the dispersed phase of this dispersion, was 201 nm. Dealuminization treatment was performed on the 2.4 kg of silica-coated alumina microparticle dispersion by adding 0.1 kg of concentrated hydrochloric acid solution (concentration 35.5% by mass) dropwise to adjust the pH to 1.0. Next, 10 L of concentrated hydrochloric acid aqueous solution (35.5% by mass) and 5 L of pure water were added, and ultrafiltration was performed until the pH reached 3, separating the dissolved aluminum salt. 0.8 kg of the silica fine particle dispersion after alumina removal was concentrated to a solid content of 5% by mass. Then, 0.03 kg of ammonia aqueous solution (15% by mass) and 0.05 kg of methanol were added to 0.08 kg of the dispersion to dilute it to a solid content of 2.5% by mass. Next, the mixture was heated to 80°C in a heated tank with a stirrer, and 0.006 kg of tetraethyl orthosilicate solution (methanol solvent) with a silica equivalent concentration of 5% by mass was added over 16 hours. After removing the solvent with a rotary evaporator, ammonia was added to adjust the pH to 10. Finally, the mixture was heated at 150°C for 1 hour to obtain 0.02 kg of fibrous hollow silica fine particle dispersion. The silica microparticles, which constitute the dispersed phase in the obtained fibrous hollow silica microparticle dispersion, had a refractive index of 1.34, lower than that of solid silica, indicating that they possessed a hollow structure. The obtained fibrous hollow silica microparticles had an average particle diameter of 0.2 μm and an aspect ratio of 5. Using the effective medium approximation with a refractive index of 1.55 for silica, the ratio of air to silica was calculated to be 38%, and the pore size was estimated to be 0.12 μm. The obtained particles were pressure-stained with a black disperse dye and dried, and a comparative short fiber 3 was recovered.

[0094] <Preparation of Paint> (Example 1) First, the obtained short fibers 1 were mixed with a two-component acrylic urethane black paint (manufactured by Musashi Paint Holdings Co., Ltd., product name: Neo Lavasan N7812-00) with butyl acetate as the main solvent, so that the weight of the short fibers was 32% of the total solids weight, and the mixture was stirred for 2 hours using a paint shaker to obtain anti-reflective paint 1.

[0095] (Examples 2-15, Comparative Examples 1-3) Anti-reflective coatings 2-15 and comparative anti-reflective coatings 1-3 were obtained in the same manner as in Example 1, except that the short fibers and weight concentration were changed to the values ​​shown in Table 2.

[0096] (Example 16) An anti-reflective coating 16 was obtained in the same manner as in Example 1, except that the black paint mixed with short fibers was changed to an acrylic emulsion-based water-based paint (manufactured by Nichia Paint Co., Ltd., product name: Aqua Black III) with water as the main solvent.

[0097] (Example 17) An anti-reflective coating 17 was obtained in the same manner as in Example 1, except that the black coating used to mix the short fibers was changed to an alkyd coating (manufactured by Natco, trade name: Futacoat Black) with ethylbenzene as the main solvent.

[0098] <Evaluation of Paints> 10 kg of each paint was prepared and sealed in 18-liter cans to evaluate the paint's stability. The cans were stored in a room at 25°C for 365 days. The cans were stirred at 200 rpm for 2 minutes using a propeller stirring rod of a stirrer (manufactured by Shinto Kagaku Co., Ltd., product name Three One Motor BL3000). 10 g was taken from a depth of 3 cm from the paint surface, and the solid content weight concentration was measured. A decrease of 3% or more from the solid content concentration immediately after sealing was classified as stability C, indicating that short fibers had settled at the bottom of the container and irreversibly aggregated. A decrease of less than 3% was classified as stability B, and a decrease of less than 1.5% was classified as stability A. The stability evaluation results for anti-reflective paints 1-17 and comparative paints 1-3 are shown in the right side of Table 2.

[0099] <Preparation of anti-reflective coating and film for spraying> (Example 18) Anti-reflective coating 1, isocyanate curing agent (manufactured by Musashi Paint Holdings Co., Ltd., product name: curing agent H-760), and methyl ethyl ketone (MEK, manufactured by Kishida Chemical Co., Ltd.) as thinner were mixed in a ratio of anti-reflective coating:curing agent:thinner of 100:10:40, and stirred with a spatula for 3 minutes to obtain anti-reflective coating 1 for spraying. The obtained anti-reflective coating 1 for spraying was applied to a substrate at a pressure of 0.4 MPa using a spray gun with a nozzle diameter of 1.8 mm (manufactured by Anest Iwata, product name: WIDER-2-18K2G), and heated and dried in an oven at 120°C for 2 hours to obtain coating film 1. A black polycarbonate sheet (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name: Yupiron) was used as the substrate.

[0100] (Examples 19-32, Comparative Examples 4-6) Spray anti-reflective coatings 2-15 and comparative spray anti-reflective coatings 1-3 were obtained in the same manner as in Example 18, except that the anti-reflective coating used was changed to those listed in Table 3. Coating films 2-15 and comparative coating films 1-3 were obtained by coating and drying in the same manner as in Example 18. In Table 3, MEK is methyl ethyl ketone and PC is polycarbonate.

[0101] (Examples 33-36) Spray paints 16-19 were obtained in the same manner as in Example 18, except that the anti-reflective paint used and the ratio of anti-reflective paint:hardener:thinner were changed to those shown in Table 3. The paint films 16-19 were then applied and dried in the same manner as in Example 18. In Table 3, the white spirit used was manufactured by Kishida Chemical Co., Ltd.

[0102] (Examples 37-40) Coating films 20-23 were obtained in the same manner as in Example 18, except that the base materials used were cut aluminum die-cast ADC12 (manufactured by Standard Test Piece Co., Ltd.), SUS301 SUS plate (manufactured by Test Piece Co., Ltd.), butadiene-acrylonitrile rubber (manufactured by Naigai Rubber Co., Ltd., product name: Hanenite GP60LE), and polyester nonwoven fabric (manufactured by Shimojima Co., Ltd., product name: Flower Wrap). It was confirmed that coating films 22 and 23 followed the fibrous structure without peeling or creasing even when folded in half.

[0103] <Evaluation of Coating Film> (Evaluation of Film Thickness) The cross-sections of the coating films for the examples and comparison were broken, and the thickness of the resin layer and fiber layer was measured by observation using a transmission electron microscope (Hitachi High-Tech Science, product name: SU-70). The measurement results and the total thickness are shown in Table 4.

[0104] (Evaluation of Reflectance) The reflectance of the coating film at incident angles of 5° and 80° was measured using the absolute reflectance measurement unit (ARMN-920) of a UV-Vis-Near-Infrared Spectrophotometer (manufactured by JASCO Corporation, product name: V-770) at incident angles of 5° and 80°. The wavelength of the incident light was measured every 2 nm in the range of 550 nm to 650 nm, and baseline correction was performed. The measurement results and evaluation ranks, with the average value of the obtained data used as the reflectance at 600 nm, are shown in Table 4. The evaluation ranks were set as follows: 5° Incidence: A: Reflectance less than 0.05, showing good anti-reflective performance. B: Reflectance between 0.05 and 0.15, within the acceptable range for an anti-reflective coating. C: Reflectance of 0.15 or more, within the unacceptable range for an anti-reflective coating. 80° Incidence: A: Reflectance less than 0.30, showing good anti-reflective performance. B: The reflectivity was between 0.3 and 1, which was within the acceptable range for an anti-reflective coating. C: The reflectivity was 1 or higher, which was outside the acceptable range for an anti-reflective coating.

[0105] Furthermore, when the reflectance of coating film 1 was measured using the same method except that the wavelength of the incident light was set to 1450 nm to 1550 nm, the reflectance was 0.03% for 5° incident light and 0.49% for 80° incident light, confirming that it functions as a near-infrared anti-reflective coating.

[0106] (Evaluation of Adhesion) The adhesion of the coating film was evaluated using a tape cross-cut test in accordance with JIS-K5600-6. The evaluation rank was set as follows, according to the evaluation result classification of the JIS standard. The evaluation results are shown in Table 4. A: Classification 0... No peeling at all, showing good adhesion. B: Classification 1-3... Somewhat prone to peeling, but within a range acceptable for practical use. C: Classification 4-5... Prone to peeling, and within an unacceptable range for a coating film.

[0107] <Preparation of spray can> (Example 41) A spray paint 7 was filled into a refillable sprayer (manufactured by FIRSTINFO), and air was added at a pressure of 0.4 MPa to produce a spray can as Example 41. It was confirmed that spray painting was possible by pressing the button on the top of the container and that there were no blockages.

[0108] <Manufacturing of optical instruments, imaging devices, display devices, buildings, and clothing> (Example 42) A square tube was made by bonding coating films 1 together, and one end of the tube was sealed with an illuminometer to create an optical instrument as a simple example 42 with an optical path. When 100 lx of light was shone through the hole in the optical instrument, it showed an illuminance of 100 lx, confirming that stray light was suppressed.

[0109] (Example 43) An imaging device (manufactured by lomography, product name: Konstruktor F camera) was fabricated as Example 43 by applying a coating to the inner wall surface of the lens barrel in the same manner as in Example 18. When a subject placed 1m in front of a high-intensity lightbox (manufactured by TRIOPTICS, product name LG3) with an illuminance set to 150,000 lx was photographed from a distance of 3m, it was confirmed that flare and ghosting were suppressed.

[0110] (Example 44) A projection device was fabricated in the same manner as in Example 42, except that an illuminance meter was used as the projector, and a display device was fabricated as Example 44, which projects an image onto a glass screen. It was confirmed that the display device had minimal reflection on the glass.

[0111] (Example 45) Coating film 1 was applied to the exterior wall of a building to create a building material as Example 45. It was confirmed that the exterior wall was matte and aesthetically pleasing.

[0112] (Example 46) The coating 23 of the polyester nonwoven fabric base material prepared in Example 40 was cut to conform to the wearer, and the two pieces of fabric, the front and back, were sewn together to create a poncho, which is an example of clothing that covers the wearer's body, as Example 46. It was confirmed that the garment was non-glossy and aesthetically pleasing.

[0113] (Example 47) The bracket shown in Figure 9 was molded using PBT resin, and a cut piece of coating 23 was attached to the front part 703 of the camera. Double-sided tape for glass (manufactured by 3M Corporation, product name: Scotch Tape for Glass) was attached to the upper surface of the bracket body to create a simple camera mounting device as Example 47. An imaging device (manufactured by lomography, product name: Konstruktor F camera) was attached to the camera mounting part, and the device was attached to the windshield of a car to check its function as an in-vehicle camera. It was confirmed that flare and ghosting were suppressed.

[0114]

[0115]

[0116]

[0117]

[0118] As shown in Table 4, coatings 1 to 23 all received good reflectance evaluations of A or B. In contrast, comparative coatings 1 to 3 all received reflectance evaluations of C.

[0119] Furthermore, the short fibers in Example 9 were longer than those in the other examples, at 800 μm in length, which required time to determine the optimal spray coating conditions. Therefore, the experiment confirmed that it is preferable for the short fibers to be 400 μm or less in length.

[0120] <Preparation of short fibers 2> Using the same method as in the preparation of short fibers 1, fiber A was cut to a length of 500 μm, and 15 kg of the resulting pile was placed in 300 L of water heated to 60°C. 1.2 kg of alum and 0.018 cm³ of formic acid (purity 77% by mass) were added, and the mixture was stirred for 10 minutes. Next, 0.3 kg of tannic acid was added, and the mixture was stirred for 20 minutes. Subsequently, another 0.3 kg of alum was added, and the mixture was stirred for 10 minutes. After that, the mixture was filtered without washing and dehydrated. The resulting pile was placed in 150 L of water containing 0.1 kg of surfactant and 0.1 kg of zirconium carbonate, and the mixture was stirred at 45°C for 10 minutes. The resulting aqueous dispersion was filtered and dehydrated. The mixture was then dried in a dryer at 80°C to obtain short fibers 16. Zirconium carbonate is the first particle.

[0121] When the obtained short fibers 16 were observed using a transmission electron microscope (Hitachi High-Tech, product name SU-70), it was found that particles with an average particle diameter of approximately 0.01 μm were attached and densely packed within them. Images were obtained showing that 70% of the area of ​​the concave parts was covered by the first particles, and 35% of the area of ​​the convex parts was covered by the first particles. Elemental analysis of the particles revealed that they were mainly composed of zirconium.

[0122] Next, using the fibers shown in the left side of Table 5, short fibers 17 to 26 were obtained in the same manner as the process for obtaining short fiber 16, except that the fiber length was changed. Note that for fiber G, since it was a fiber dope-dyed with carbon black, pressure dyeing was not performed. Table 5 summarizes the production conditions and characteristics of short fibers 16 to 26.

[0123] (Examples 48-58) Anti-reflective coatings 18-28 were prepared in the same manner as in Example 1, except that short fibers 16-26 were used, so that the weight of the short fibers was 32% of the total solids weight, and the coating stability was evaluated. The correspondence between the short fibers used and the prepared coatings, as well as the evaluation results, are summarized in Table 5.

[0124]

[0125] (Examples 59-69) Spray anti-reflective coatings 20-30 were obtained in the same manner as in Example 18, except that anti-reflective coatings 18-28 were used. The correspondence of the prepared spray coatings is summarized in Table 6. The obtained spray anti-reflective coatings were applied to a substrate at a pressure of 0.2 MPa using a spray gun with a 1.8 mm pore size (manufactured by Anest Iwata, product name: WIDER-2-18K2G), and heated and dried in an oven at 120°C for 2 hours to obtain coating films 24-34. The film thickness and reflectivity of the obtained coating films 24-34 were evaluated. The results are shown in Table 6. In addition, the discharge performance of the obtained spray anti-reflective coatings was evaluated at a standard pressure of 0.2 MPa using spray guns with different pore sizes (manufactured by Anest Iwata). The film thickness and reflectivity of the coating films 24-34 prepared during the first discharge test were also evaluated.

[0126]

[0127] (Evaluation of discharge performance) Ten A4-sized black polycarbonate sheets (manufactured by Mitsubishi Gas Chemical, product name: Yupiron) were painted using spray guns of each nozzle size, and the presence or absence of clogging after painting all ten sheets was checked. The experiment was conducted three times, and the evaluation ranks were set as follows: A: Clogging occurred 0 times out of 3. Shows good discharge stability under standard conditions. B: Clogging occurred 1 time out of 3. Conditions need to be refined. C: Clogging occurred 2 times out of 3. Conditions need to be refined. D: Clogging occurred 3 times out of 3. Stable discharge is difficult.

[0128] Table 7 shows the results of the discharge performance evaluation of the 20 to 30 spray paints that were prepared.

[0129]

[0130] The results showed that the shorter the short fiber length, the higher the discharge stability. It was also found that if the fiber length is 400 μm or less, it is highly likely that it can be used in spray guns with a 1.0 mm pore size, which are readily available commercially.

[0131] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are attached to make the scope of the invention public.

[0132] This application claims priority based on Japanese Patent Application No. 2024-228806, filed on 25 December 2024, and Japanese Patent Application No. 2025-024001, filed on 18 February 2025, and all of the contents of those applications are incorporated herein by reference.

Claims

1. A paint comprising fibers, a resin, and a solvent, wherein the length of the fibers is in the range of 1 μm to 1000 μm, and the fibers have an inner wall surrounding a void formed within the fibers, and at least one end of the longitudinal end covers the void.

2. The paint according to claim 1, wherein the length of the fibers is in the range of 10 μm or more and 400 μm or less.

3. The paint according to claim 1 or 2, wherein both ends of the longitudinal end of the fiber cover the void.

4. The paint according to any one of claims 1 to 3, wherein the porosity, which indicates the proportion of voids in the fibers, is in the range of 10% or more and 60% or less.

5. The paint according to any one of claims 1 to 4, wherein the fiber content is in the range of 5 parts by mass or more and less than 33 parts by mass per 100 parts by mass of paint solids.

6. The paint according to any one of claims 1 to 5, wherein the fiber has a convex portion on its periphery and a concave portion that is recessed toward the axial center from the convex portion.

7. The paint according to any one of claims 1 to 6, wherein the fibers are made of a thermoplastic resin.

8. The paint according to any one of claims 1 to 6, wherein the fiber is made of polyester.

9. The paint according to any one of claims 1 to 8, wherein the thickness of the fibers is in the range of 0.1 μm or more and 100 μm or less.

10. The paint according to claim 9, wherein the aspect ratio of the fibers is in the range of 5 to 500.

11. The paint according to any one of claims 1 to 10, wherein the fiber is a hollow fiber.

12. The paint according to any one of claims 1 to 11, wherein the fiber is a black dope-dyed yarn.

13. A spray can comprising a liquid container storing the paint described in any one of claims 1 to 12, a gas container storing a propellant, and a connecting member connecting the liquid container and the gas container.

14. A film comprising a resin layer made of resin and fibers protruding from the resin layer, wherein the length of the fibers is in the range of 1 μm or more and 1000 μm or less, and the fibers have an inner wall surrounding a void formed within the fibers, and at least one end of the longitudinal end covers the void.

15. The film according to claim 14, wherein the length of the fibers protruding from the resin layer is in the range of 30 μm or more and 300 μm or less.

16. The film according to claim 14 or 15, wherein at least a portion of the fibers is covered with the resin constituting the resin layer.

17. The film according to any one of claims 14 to 16, wherein the length of the fibers is in the range of 10 μm or more and 1000 μm or less.

18. The membrane according to any one of claims 14 to 17, wherein both ends of the longitudinal end of the fiber cover the void.

19. The membrane according to any one of claims 14 to 18, wherein the porosity, which indicates the proportion of voids in the fibers, is in the range of 10% or more and 60% or less.

20. The film according to any one of claims 14 to 19, wherein the fiber content is in the range of 5 parts by mass or more and less than 33 parts by mass per 100 parts by mass of paint solids.

21. The film according to any one of claims 14 to 20, wherein the fiber has a convex portion at its periphery and a concave portion that is recessed toward the axial center from the convex portion.

22. The film according to any one of claims 14 to 21, wherein the fibers are made of a thermoplastic resin.

23. The membrane according to any one of claims 14 to 21, wherein the fiber is made of polyester.

24. The film according to any one of claims 14 to 23, wherein the thickness of the fibers is in the range of 0.1 μm or more and 100 μm or less.

25. The membrane according to claim 24, wherein the aspect ratio of the fibers is in the range of 5 to 500.

26. The membrane according to any one of claims 14 to 25, wherein the fiber is a hollow fiber.

27. The membrane according to any one of claims 14 to 26, wherein the fiber is a black dope-dyed yarn.

28. A member comprising a base material and a film provided on the base material, wherein the film is the film described in any one of claims 14 to 27.

29. An optical member comprising the film described in any one of claims 14 to 27.

30. An optical instrument having a housing and an optical system consisting of a plurality of lenses or mirrors within the housing, wherein the film described in any one of claims 14 to 27 is formed on a support that supports the plurality of lenses or mirrors and / or on the inner wall surface of the housing.

31. An imaging device comprising, in addition to the optical instrument according to claim 30, an image sensor that receives light that has passed through the optical system.

32. A display device having an image generation unit that generates image light within the housing of an optical device according to claim 30.

33. A camera mounting device comprising: a bracket for supporting a camera unit having a light-receiving section and for mounting to a surface to be mounted; and a hood having a surface that widens in a direction away from the light-receiving section in front of the camera unit, and which is attached to the bracket such that the surface faces the surface to be mounted, wherein the surface is formed of the film according to any one of claims 14 to 27.

34. A method for manufacturing a paint, comprising the steps of: impregnating fibers having an inner wall surrounding a void formed inside with water, cutting the fibers; drying the fibers; and mixing the dried fibers, a resin, and a solvent.

35. The method for manufacturing paint according to claim 34, wherein the fibers are made of a thermoplastic resin, and in the step of cutting the fibers, the fibers are heated and pressed while being cut.

36. A method for manufacturing a component, comprising the steps of: mixing the paint described in claim 1 with a solvent to obtain a mixed liquid; spray-applying the mixed liquid onto a substrate; and drying the spray-applied substrate.

37. The method for manufacturing a member according to claim 36, wherein a curing agent is further mixed in the step of obtaining the mixed liquid.

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