Anti-reflective coating material, optical member with Anti-reflective film, optical device, and image capturing device

Abstract

To provide an optical member equipped with an anti-reflective film, which offers both a reduced reflectance and high strength.SOLUTION: An optical member 10 comprises an anti-reflective film 12 formed on a base material 11, where the anti-reflective film 12 includes a resin layer 4 and deformed fibers 1 bound in the resin layer 4, each fiber having a core portion and a plurality of projections 3 extending from the core portion. Tips of the plurality of projections 3 of the deformed fibers 1 protrude from a surface of the resin layer 4.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a paint having an antireflection function, an optical member provided with an antireflection film formed by the paint, an optical device, and an imaging device.

Background Art

[0002] An optical device such as a lens barrel has a housing and an optical system including a plurality of lenses 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 a subject 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. Light rays that do not contribute to the formation of the subject image are incident from disordered directions, so they are incident not only on optical members such as lenses but also on other parts, and become factors 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.

[0003]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the optical component disclosed in Patent Document 1 has a glossiness of 0.3 at an incident angle of 60° on the inner wall surface, and when the incident angle increases, the effect of reducing the reflectance is insufficient.

[0006] In addition, the optical component disclosed in Patent Document 2 has a glossiness of 0.1 at an incident angle of 85° on the inner wall surface, and the reflectance is reduced. However, since the fine particles are spherical in shape, the contact area with the resin is small, and there is a risk that the fine particles are likely to be removed inside the optical component (lens barrel).

[0007] Therefore, in an optical member provided with an antireflection film, it has been difficult to achieve both reduction of reflectance and suppression of peeling of fine particles.

Means for Solving the Problems

[0008] The optical member for solving the above problems is an optical member having an antireflection film provided on a substrate, wherein the antireflection film has a resin layer and a modified fiber having a core portion and a plurality of convex portions extending from the core portion and binding to the resin layer, and the tips of the plurality of convex portions of the modified fiber protrude from the surface of the resin layer.

Effects of the Invention

[0009] The optical member of the present invention contains a modified fiber having a core portion and a plurality of convex portions extending from the core portion in the antireflection film, and since the tips of the convex portions protrude from the surface of the resin layer, it is possible to prevent the light incident between the convex portions from reaching the imaging element by diffusing between the convex portions. In addition, the binding force between the modified fiber and the resin is also sufficient. Therefore, it is possible to provide an optical member having a reflectance of less than 0.2% at an incident angle of 85° and being difficult to peel off the modified fiber.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Preferred embodiments of the present invention will be described below.

[0012] <Antireflection Paint> The antireflection paint used to form an antireflection film on the optical member of the present invention contains profiled fibers having a core portion and a plurality of convex portions extending from the core portion, a resin, and an organic solvent.

[0013] (Profiled Fiber) FIG. 1 and FIG. 2 are diagrams showing an embodiment of the profiled fiber contained in the antireflection paint of the present invention. FIG. 1(a) is a side view in the length direction, and FIGS. 1(b) and (c) are cross-sectional views in a direction perpendicular to the length direction. The profiled fiber refers to a fiber whose cross-sectional shape in a direction perpendicular to the length direction is other than a circle, an ellipse, and a convex polygon in which all interior angles are smaller than 180°. The profiled fiber 1 has a core portion 2 and a plurality of convex portions 3 extending from the core portion.

[0014] The length L of the profiled fiber 1 is preferably 0.2 mm or more and 1.0 mm or less. The length of the profiled fiber can be cut to a desired length with a cutting machine. If the length L of the profiled fiber is shorter than 0.2 mm, the ratio of the cut surface that does not have an antireflection function in the profiled fiber increases, and the antireflection function may become insufficient. On the other hand, if the length L of the profiled fiber is longer than 1.0 mm, it may be difficult to make the convex portion of the profiled fiber protrude from the surface of the resin when forming the antireflection film. Also, when applying the paint with a spray gun, the tip of the spray nozzle may be easily clogged.

[0015] The thickness T of the profiled fiber 1 is preferably 10 μm or more and 50 μm or less. Here, the thickness T of the profiled fiber refers to the length of the cross-section in a direction perpendicular to the length direction of the profiled fiber. In other words, it is the length of the cross-section orthogonal to the fiber axis. Further, the thickness T is the maximum value of the sum of the lengths of the core part 2 and the convex part 3 in the cross-section direction. Therefore, in Fig. 1(b), the length indicated by the arrow is the thickness T of the profiled fiber.

[0016] Here, the aspect ratio, which is the ratio (L / T) of the length L to the thickness T of the profiled fiber 1, is preferably 4 or more and 100 or less. When the aspect ratio is within this range, it becomes easier for the tip of the convex part 3 of the profiled fiber to protrude from the surface of the resin layer when forming the antireflection film. However, when the aspect ratio is less than 4 and approaches an isotropic shape, there is a high possibility that the cut surface of the profiled fiber will protrude from the surface of the resin layer, and the antireflection function may become insufficient. On the other hand, when the aspect ratio is greater than 100, it becomes difficult to control the orientation of the profiled fiber 1, and there is a possibility that the tip of the convex part 3 will hardly protrude from the surface of the resin layer.

[0017] The core part 2 is the part drawn by the dotted line in Fig. 1(b) and is circular in shape. However, the core part 2 does not necessarily have to be circular in shape and may be square. The length of the core part (the length of the cross-section in a direction perpendicular to the length direction of the profiled fiber) represents the diameter of the circle when the core part is circular, the diameter of the inscribed circle of the polygon when the core part is polygonal, and the diameter on the long radius side in the case of an elliptical shape. Note that the core part 2 may have a hole part 21 as shown in Fig. 1(c).

[0018] The convex portion 3 extends from the core portion 2 and is made of the same material as the core portion 2. Here, in FIG. 1(b), there are eight convex portions 3, but two or more convex portions are sufficient. If there are two or more convex portions, it is possible to diffuse the light incident between the two convex portions, prevent it from returning to the optical path, and prevent it from reaching the imaging element. In order to more efficiently diffuse light in the profiled fiber, it is preferable that the number of convex portions is three or more and eight or less. Therefore, a Y-shaped shape having three convex portions as shown in FIG. 2(a) also exhibits the effects of the present invention. Examples of commercially available profiled fibers having eight convex portions include Octa (registered trademark) manufactured by Teijin Frontier Co., Ltd. It is difficult to manufacture those having nine or more convex portions.

[0019] The length C of the convex portion 3 L is preferably 5 μm or more and 20 μm or less. More preferably, it is 5 μm or more and 12.5 μm or less. The length C of the convex portion 3 L If it is less than 5 μm, the length of the convex portion 3 protruding from the surface of the resin layer becomes short, and sufficient light reflection between the plurality of convex portions may not occur, and the effect of reducing the reflectance may be insufficient. On the other hand, the length C of the convex portion 3 L If it is greater than 20 μm, the convex portion may tilt or fall, and light may not sufficiently enter between the plurality of convex portions. As a result, the effect of reducing the reflectance may be insufficient.

[0020] The thickness C of the convex portion 3 T is preferably 2 μm or more and 6 μm or less. The thickness C of the convex portion 3 T If it is thinner than 2 μm, the convex portion may tilt or fall, and light may not sufficiently enter between the plurality of convex portions. As a result, the effect of reducing the reflectance may be insufficient. On the other hand, the thickness C of the convex portion 3 T If it is thicker than 6 μm, the distance between the plurality of convex portions becomes small, and sufficient light reflection between the plurality of convex portions may not occur, and the effect of reducing the reflectance may be insufficient.

[0021] Further, the shape of the convex portion 3 does not need to have a rounded tip as shown in FIG. 1(b), and a shape with a pointed tip as shown in FIG. 2(b) may be used.

[0022] Further, the convex portions 3 do not necessarily need to be formed radially from the core portion 2 at substantially equal intervals as shown in FIG. 1(b), and may have a shape in which the intervals between the convex portions are not constant as shown in FIG. 2(c).

[0023] Further, the convex portions 3 do not necessarily need to be formed in a constant size as shown in FIG. 1(b), and may have a shape having different sizes as shown in FIG. 2(d).

[0024] Further, the cross-sections of the profiled fibers 1 in the direction perpendicular to the length direction do not all need to be the same, and the profiled fibers having a shape as shown in FIG. 2(d) may have a shape as shown in FIG. 2(e) in another cross-section. Examples of fibers having such a shape include crimped fibers in which each individual fiber in the fiber is shrunk and wound. Commercially available crimped fibers include Calcuro (registered trademark) manufactured by Teijin Frontier Co., Ltd.

[0025] Note that the material of the profiled fiber is not particularly limited, and can be selected from, for example, polyester, nylon, acrylic, polypropylene, rayon, polyethylene, polyurethane, cotton linen, knitted wool, and combinations thereof. Further, in order to improve the performance of the antireflection film, the profiled fiber may be subjected to processing, light resistance treatment, softening treatment, fade resistance treatment, etc.

[0026] The content of the profiled fiber contained in the antireflection paint of the present invention is preferably 50 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the paint solid content before mixing the profiled fiber. Here, the paint solid content refers to all the solid components contained in the antireflection paint including not only the resin constituting the resin layer described later but also additives and the like. If the content of the profiled fiber is less than 50 parts by mass, there is a risk that the antireflection function cannot be sufficiently obtained. On the other hand, if it is more than 200 parts by mass, when the paint is applied with a spray gun, the tip of the spray nozzle is likely to be clogged. Further, even if an antireflection film can be formed, since the amount of the paint solid content such as resin is small, the binding between the resin layer and the profiled fiber becomes insufficient, and there is a risk that the profiled fiber is likely to fall out.

[0027] Incidentally, the content of the profiled fiber can be expressed as 33 parts by mass or more and 67 parts by mass or less with respect to 100 parts by mass of the paint solid content, assuming that the profiled fiber is also regarded as part of the solid content.

[0028] (Resin) The resin contained in the antireflection paint of the present invention constitutes a resin layer after the antireflection paint dries. The type of resin is not particularly limited, and for example, it can be selected from acrylic resins, urethane resins, epoxy resins, and combinations thereof. Also, either a solvent-soluble resin or a reaction-curing resin may be used.

[0029] Moreover, it is preferable that the resin contained in the antireflection paint of the present invention is 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the antireflection paint. If the content of the resin is less than 5 parts by mass, the adhesion to the substrate may deteriorate. On the other hand, if the content of the resin exceeds 50 parts by mass, it may be difficult to make the antireflection film into a thin layer.

[0030] (Organic solvent) The type of the organic solvent contained in the antireflection paint of the present invention is not particularly limited, and examples thereof include water, thinner, ethanol, isopropyl alcohol, n-butyl alcohol, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate. Also, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, toluene, xylene, acetone, cellosolves, glycol ethers, ethers, etc. may be mentioned. These solvents may be used alone or in combination of a plurality of types.

[0031] Moreover, the organic solvent contained in the antireflection paint of the present invention is preferably 5 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the antireflection paint. When the content of the organic solvent is less than 5 parts by mass, it may be difficult to form a thin layer of the antireflection film. In addition, when applying with a spray gun, there is a risk that the discharge part of the spray gun may be clogged. On the other hand, when the content of the organic solvent exceeds 80 parts by mass, the adhesion to the base material may deteriorate. Also, when applying with a spray gun, there is a risk of dripping.

[0032] The preferred viscosity of the antireflection paint is preferably 10 mPa·s or more and 200 mPa·s or less. When the viscosity of the antireflection paint is less than 10 mPa·s, the adhesion between the base material and the antireflection film may deteriorate. On the other hand, when it is greater than 200 mPa·s, it may be difficult to form a thin layer of the antireflection film.

[0033] (Additive) The antireflection paint of the present invention may further contain an additive. For example, a dispersant, a curing agent, a curing catalyst, a plasticizer, a thixotropy-imparting agent, a leveling agent, an infrared-transmitting organic colorant, an infrared-transmitting inorganic colorant, a preservative, an ultraviolet absorber, an antioxidant, a coupling agent, etc. can be mentioned. Moreover, a filler for the purpose of coloring and matting may be mixed.

[0034] (Surface treatment of profiled fibers) In the antireflection paint of the present invention, for the purpose of improving the dispersibility of profiled fibers, it is possible to perform a coating treatment on the surface of the profiled fibers. For the coating treatment, a surfactant, an inorganic salt, various resins can be used.

[0035] To give an example, the surface of the profiled fibers cut to a desired length is treated with a tannin compound, tartar emetic, etc. to form a tannin compound, etc. on the fiber surface. Thereby, by utilizing the water retention property of the tannin compound, etc., the electrical conductivity of the flock surface is kept good. Or, inorganic salts, inorganic silicon compounds, surfactants and mixtures thereof are attached to the surface of the profiled fibers.

[0036] Examples of the tannin compound include natural tannin and synthetic tannin. Examples of the inorganic salt include sodium chloride (NaCl), barium chloride (BaCl2), and magnesium chloride (MgCl2). Further, magnesium sulfate (MgSO4), sodium silicate (Na2SiO3), sodium carbonate (Na2CO3), and sodium sulfate (Na2SO4) are included. Examples of the inorganic silicon compound include colloidal silica and the like. Furthermore, examples of the surfactant include anionic surfactants, nonionic surfactants, amphoteric surfactants, and cationic surfactants.

[0037] (Method for producing an antireflection coating) The method for producing the antireflection coating of the present invention is not particularly limited as long as the irregular fibers can be dispersed in the antireflection coating. For example, a bead mill, a ball mill, a jet mill, a three-roll mill, a planetary rotating device, a mixer, an ultrasonic disperser, etc. are included.

[0038] (Optical member) FIG. 3 is a diagram showing an example of an embodiment of the optical member of the present invention.

[0039] The optical member 10 has an antireflection film 12 provided on a base material 11, and the antireflection film 12 is formed from the antireflection coating of the present invention. The antireflection film 12 has a resin layer 4 and irregular fibers 1 that are bound to the resin layer 4. Here, the irregular fibers 1 are the irregular fibers described in FIGS. 1 and 2, and have a core portion and a plurality of convex portions extending from the core portion.

[0040] Since the tips of the convex portions of the irregular fibers 1 protrude from the surface of the resin of the resin layer 4, the antireflection film 12 can diffuse light incident between two convex portions. Further, as shown in FIG. 3, the irregular fibers 1 are bound to the resin layer 4 via a plurality of convex portions. Therefore, compared with the case where spherical particles are bound to the resin layer, the area of contact between the irregular fibers 1 and the resin layer 4 is large, so the irregular fibers 1 are less likely to peel off from the resin layer 4.

[0041] The material of the base material 11 is not particularly limited. For example, as metals, aluminum, titanium, stainless steel, magnesium alloys, etc. can be mentioned. Also, as plastics, polycarbonate resin, acrylic resin, ABS resin, fluororesin, etc. can be mentioned.

[0042] The content of the profiled fibers contained in the antireflection film 12 is preferably 33 parts by mass or more and 67 parts by mass or less with respect to 100 parts by mass of the antireflection film. If the content of the profiled fibers is less than 33 parts by mass, there is a possibility that the antireflection function cannot be sufficiently obtained. On the other hand, if it is more than 67 parts by mass, since the amount of solid components such as resin is small, the binding between the resin layer and the profiled fibers becomes insufficient, and there is a possibility that the profiled fibers are likely to fall out.

[0043] The thickness of the antireflection film 12 is not particularly limited, but it is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 200 μm or less. If the thickness of the antireflection film becomes thinner than 10 μm, there is a possibility that the concealment as an antireflection film cannot be sufficiently obtained. Also, if the thickness of the antireflection film exceeds 500 μm, the film thickness unevenness of the antireflection film becomes large, which causes peeling. In addition, in order to increase the film thickness, it is also possible to apply the coating in multiple times instead of applying it once.

[0044] In addition, in order to improve the adhesion between the base material 11 and the antireflection film 12, a primer layer may be provided between the base material 11 and the antireflection film 12. Any material can be used for the primer layer. As an example, epoxy resin, urethane resin, acrylic resin, silicone resin, fluororesin, etc. can be mentioned.

[0045] Also, the thickness of the primer layer is preferably 2 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less. If the film thickness is less than 2 μm, there is a possibility that the adhesion is insufficient, and if it exceeds 30 μm, it may have an adverse effect on the accuracy of the thickness of the antireflection film 12.

[0046] (Manufacturing method of the antireflection film) The method for manufacturing the antireflection film is not particularly limited, and examples thereof include brush coating, spray coating, dip coating, transfer, and the like. Among these, spray coating is preferable from the viewpoint of excellent followability to the substrate shape.

[0047] Further, the method for curing the antireflection film is not particularly limited, and it may be dried at room temperature, or curing may be promoted by heat or ultraviolet rays may be applied.

[0048] <Optical device> FIG. 4 shows the configuration of a single-lens reflex digital camera, which is an example of a preferred embodiment of the imaging device of the present invention. In FIG. 4, a camera body 602 and a lens barrel 601, which is an optical device, are coupled. The lens barrel 601 is a so-called interchangeable lens that is detachable from the camera body 602.

[0049] Light from the subject passes through an optical system composed of a plurality of lenses 603, 605, etc. arranged on the optical axis of the imaging optical system within the housing 620 of the lens barrel 601 and is received by the imaging element 610. Here, the lens 605 is supported by an inner cylinder 604 and is movably supported with respect to the outer cylinder of the lens barrel 601 for focusing and zooming. The inner cylinder 604 is a support for supporting the lens 605.

[0050] During the observation period before shooting, light from the subject is reflected by the main mirror 607 within the housing 621 of the camera body, passes through the prism 611, and an image of the shooting image is projected onto the photographer through the viewfinder lens 612. The main mirror 607 is, for example, a half mirror, and the light transmitted through the main mirror is reflected by the sub-mirror 608 in the direction of the AF (autofocus) unit 613. For example, this reflected light is used for distance measurement. Further, the main mirror 607 is attached and supported to the main mirror holder 640 by adhesion or the like. During shooting, the main mirror 607 and the sub-mirror 608 are moved out of the optical path via a drive mechanism (not shown), the shutter 609 is opened, and a shooting optical image incident from the lens barrel 601 is formed on the imaging element 610. Further, the aperture 606 is configured to be able to change the brightness and depth of focus during shooting by changing the aperture area.

[0051] The optical member of the present invention can be used in an imaging device and an optical instrument by forming an antireflection film 630 on a base material such as a housing 620 and an inner cylinder 604.

[0052] The material of the housing 620 is not particularly limited. For example, as metals, aluminum, titanium, stainless steel, magnesium alloy, etc. can be mentioned. Also, as plastics, polycarbonate resin, acrylic resin, ABS resin, fluororesin, etc. can be mentioned.

[0053] The optical instrument of the present invention has an antireflection film having a low reflectance even for a large incident angle inside the housing. Therefore, the probability of occurrence of flare and ghost in an image taken using the optical instrument of the present invention and an imaging device having an imaging element can be made sufficiently small.

[0054] <Evaluation method> (Reflectance measurement) The reflectance was measured using an optical member provided with an antireflection film on a surface of 150 mm × 70 mm in size of ABS resin.

[0055] The above optical member was measured every 1 nm for the reflectance at an incident angle of 85° in the wavelength range of 500 nm to 600 nm using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-770), and the average value was taken as the reflectance. The measurement was performed after correcting the background.

[0056] (Strength of the antireflection film) The strength of the antireflection film was tested in accordance with JIS Z 1522. The reflectance of the antireflection film before and after the tape test was measured respectively, and those with the difference in reflectance before and after the test within 0.03% were rated as A, and those greater than 0.03% were rated as B.

Example

[0057] (Example 1) (Preparation of the antireflection paint) First, a profiled fiber A-1 (manufactured by Teijin Frontier Co., Ltd., trade name: Octa) having a cross-sectional shape as shown in Fig. 1(c) was prepared. The profiled fiber A-1 is made of polyester, with a thickness T of 25 μm, a core diameter of 12.5 μm, 8 convex portions, and the length C of the convex portion L being 6.25 μm and the thickness C T being 3 μm.

[0058] Next, the profiled fiber A-1 was cut into 1 mm lengths using a cutting machine. That is, the aspect ratio, which is the ratio of the length to the thickness of the profiled fiber A-1, is 40. After cutting, the profiled fiber A-1 was dyed with a black dye.

[0059] The profiled fiber A-1 and an acrylic resin were mixed in a beaker with thinner, which is an organic solvent, so that the cut profiled fiber A-1 was 50 parts by mass with respect to 100 parts by mass of the paint solid content. In addition, in order to adjust the color tone, a colorant such as a matting agent or carbon black may be added separately. A stirrer was used for mixing, and the mixture was stirred at a speed of 200 rpm for 60 minutes at room temperature (23°C) to obtain an antireflection paint for Example 1.

[0060] <Fabrication of optical member> Subsequently, the antireflection paint of Example 1 was applied to the surface of an ABS resin with a size of 150 mm × 70 mm using a spray gun (manufactured by Anest Iwata, trade name: W-200).

[0061] Thereafter, the ABS resin coated with the antireflection paint was put into a constant temperature drying oven at a temperature of 100°C and dried for 120 minutes to form an antireflection film with a thickness of 70 μm, and an optical member of Example 1 as shown in Fig. 3 was obtained. When the obtained optical member was observed with a scanning electron microscope, it was confirmed that the tips of the convex portions of the profiled fibers protruded from the surface of the resin layer of the antireflection film.

[0062] <Evaluation of optical member> When the reflectance of the optical member of Example 1 was evaluated, it was 0.12%. Also, when the strength of the optical member of Example 1 was evaluated, since there was no difference in reflectance before and after the tape test, the evaluation was A.

[0063] (Examples 2 to 44) In Examples 2 to 44, the type, length, aspect ratio, and content with respect to the resin of the profiled fiber were changed as shown in Tables 1 and 2, and an antireflection coating and an optical member were obtained in the same manner as in Example 1. When the obtained optical member was observed with a scanning electron microscope, it was confirmed that the tips of the convex portions of the profiled fiber protruded from the surface of the resin layer of the antireflection film in all the optical members. The evaluation results of each example are summarized in Table 3.

[0064] Also, the types of the profiled fibers are as follows. (A-1) Hollow 8-fin fiber Cross-sectional shape: Fig. 1(c), Material: polyester, Thickness T: 25 μm, Diameter of the core part: 12.5 μm, Convex parts: 8, Length C of the convex part L : 6.25 μm, Thickness C of the convex part T : 3 μm (A-2) Hollow 8-fin fiber Cross-sectional shape: Fig. 1(c), Material: polyester, Thickness T: 50 μm, Diameter of the core part: 25 μm, Convex parts: 8, Length C of the convex part L : 12.5 μm, Thickness C of the convex part T : 6 μm (A-3) Y-shaped nylon fiber Cross-sectional shape: Fig. 2(a), Material: rayon, Thickness T: 20 μm, Diameter of the core part: 3 μm, Convex parts: 3, Length C of the convex part L : 9.9 μm, Thickness C of the convex part T : 2.5 μm (A-4) Crimped fiber Cross-sectional shape: Figs. 2(d)(e), Material: polyester, Thickness T: 10 μm, Diameter of the core part: 5 μm, Convex parts: 4, Length C of the convex part L : 2.5 μm, Thickness C of the convex part T : 2 μm (A-5) Spherical nylon fiber Cross-sectional shape: perfect circle, Material: nylon, Thickness T: 10 μm, Convex parts: none

[0065]

Table 1

[0066]

Table 2

[0067]

Table 3

[0068] (Comparative Example 1) <Preparation of Antireflection Coating> First, spherical fibers A-5 having a true circular cross-sectional shape were prepared. The spherical fibers A-5 are made of nylon and have a thickness T of 10 μm. That is, the diameter of the cross-section is 10 μm.

[0069] Next, after the spherical fibers A-5 were dyed with a black dye, they were cut into lengths of 1 mm using a cutting machine. That is, the aspect ratio, which is the ratio of the length to the thickness of the spherical fibers A-5, is 100.

[0070] The spherical fibers A-5 and an acrylic resin were mixed in a beaker with thinner, which is an organic solvent, so that the cut spherical fibers A-5 would be 50 parts by mass with respect to 100 parts by mass of the solid content of the coating. In addition, in order to adjust the color tone, colorants such as a matting agent and carbon black may be added separately. A stirrer was used for mixing, and it was stirred at a speed of 200 rpm for 60 minutes at room temperature (23°C) to obtain the antireflection coating of Comparative Example 1.

[0071] <Preparation of Optical Member> Subsequently, the antireflection coating of Comparative Example 1 was applied to the surface of an ABS resin with a size of 150 mm × 70 mm using a spray gun (manufactured by Anest Iwata Corporation, product name: W-200).

[0072] Thereafter, the ABS resin coated with the antireflection coating was put into a constant temperature drying oven with the temperature set at 100°C and dried for 120 minutes to form an antireflection film with a thickness of 70 μm, and an optical member of Comparative Example 1 as shown in Figure 3 was obtained.

[0073] <Evaluation of Optical Member> When the reflectance of the optical member of Comparative Example 1 was evaluated, it was 0.35%.

[0074] In addition, when the strength of the optical member of Comparative Example 1 was evaluated, since there was no difference in reflectance before and after the tape test, the evaluation was rated as A.

[0075] (Comparative Examples 2 to 12) In Comparative Examples 2 to 12, the type, length, aspect ratio, and content with respect to the resin of the profiled fibers were changed as shown in Table 4, and an antireflection coating and an optical member were obtained in the same manner as in Comparative Example 1. The evaluation results of each comparative example are summarized in Table 5.

[0076]

Table 4

[0077]

Table 5

[0078] According to the results of the examples and comparative examples, the reflectances of Examples 1 to 44 using profiled fibers were less than 0.20%, which was good. On the other hand, the reflectances of Comparative Examples 1 to 12 using spherical particles were higher than 0.2%.

[0079] Among the examples, Examples 1 to 16 and Examples 21 to 44 in which the content of the profiled fibers was 50 parts by mass or more had a lower reflectance than Examples 17 to 20 in which the content of the profiled fibers was 43 parts by mass.

[0080] Among the examples, Examples 1 to 36 in which the length of the convex portion of the profiled fibers was 6.25 μm or more had a lower reflectance than Examples 37 to 44 in which the length of the convex portion was 2.5 μm.

[0081] In addition, although the reflectance of Comparative Example 12 was lower than that of Comparative Examples 1 to 11, peeling of the spherical particles was visually confirmed by the tape test, and the change in reflectance before and after the tape test was also as large as 0.04%. This is considered to be due to the fact that the content of the spherical particles was as large as 69 parts by mass.

Explanation of Signs

[0082] 1 Irregular fiber 2 Core part 3 Convex part 4 Resin layer 11 Base material 12 Antireflection film 21 Hole part 600 Imaging device 601 Optical instrument 604 Support 620 Housing 630 Antireflection film

Claims

1. An optical member having an antireflection film provided on a substrate, wherein the antireflection film has a resin layer and a modified fiber having a core portion and a plurality of convex portions extending from the core portion, which is bonded to the resin layer, and an optical member characterized in that tips of the plurality of convex portions protrude from a surface of the resin layer.

2. The optical member according to claim 1, wherein a length of the modified fiber is 0.2 mm or more and 1.0 mm or less.

3. The optical member according to claim 1 or 2, wherein a length of the convex portion is 5 μm or more and 20 μm.

4. The optical member according to any one of claims 1 to 3, wherein a thickness of a cross section in a direction perpendicular to a length direction of the modified fiber is 10 μm or more and 50 μm or less.

5. The optical member according to claim 4, wherein an aspect ratio of the modified fiber, which is a ratio of the length to the thickness, is 4 or more and 100 or less.

6. The optical member according to any one of claims 1 to 5, wherein the number of the convex portions is 3 or more and 8 or less.

7. The optical member according to any one of claims 1 to 6, wherein a content of the modified fiber with respect to 100 parts by mass of the antireflection film is 33 parts by mass or more and 67 parts by mass or less.

8. The optical member according to any one of claims 1 to 7, wherein a thickness of the resin layer of the antireflection film is 10 μm or more and 500 μm or less.

9. An optical device having a housing and an optical system including a plurality of lenses in the housing, wherein an antireflection film is formed on a support for supporting the plurality of lenses and / or an inner wall surface of the housing, the antireflection film has a resin layer and a modified fiber having a core portion and a plurality of convex portions extending from the core portion, which is bonded to the resin layer, and an optical device characterized in that tips of the plurality of convex portions protrude from a surface of the resin layer.

10. An imaging device including a housing, an optical system including a plurality of lenses in the housing, and an imaging element that receives light that has passed through the optical system, wherein an antireflection film is formed on a support for supporting the plurality of lenses and / or an inner wall surface of the housing, the antireflection film has a resin layer and a modified fiber having a core portion and a plurality of convex portions extending from the core portion, which is bonded to the resin layer, and an imaging device characterized in that tips of the plurality of convex portions protrude from a surface of the resin layer.

11. The imaging device according to claim 10, wherein the imaging device is a camera.

12. An antireflection coating characterized by containing a deformed fiber having a core part and a plurality of convex parts extending from the core part, a resin, and an organic solvent.

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