Optical filter, optical filter for imaging device, imaging device, and method for manufacturing optical filter for imaging device

Abstract

An optical filter 1 comprises a frame 10 and a light absorption film 20. The frame 10 has a through-hole 12. The light absorption film 20 is disposed so as to close the through-hole 12, and contains a light absorbing compound. The mean value of the Young's modulus of the light absorption film 20 measured under continuous stiffness measurement is 2.5 GPa or less.

Description

[Technical field]

[0001] The present invention relates to an optical filter, an imaging device, and a method for manufacturing an optical filter. [Background technology]

[0002] In an imaging device using a solid-state imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), various optical filters are arranged in front of the solid-state imaging element in order to obtain an image with good color reproducibility. In general, a solid-state imaging element has a spectral sensitivity in a wide wavelength range from the ultraviolet region to the infrared region. Meanwhile, human visual sensitivity exists only in the visible light region. For this reason, a technique is known in which an optical filter that blocks part of infrared or ultraviolet light is arranged in front of the solid-state imaging element in order to bring the spectral sensitivity of the solid-state imaging element in the imaging device closer to the human visual sensitivity.

[0003] Conventionally, such optical filters generally use light reflection by a dielectric multilayer film to block infrared or ultraviolet rays. Meanwhile, in recent years, optical filters with a film containing a light-absorbing compound have been attracting attention. Since the transmittance characteristics of an optical filter with a film containing a light-absorbing compound are not easily affected by the angle of incidence, good images with little change in color can be obtained even when light is obliquely incident on the optical filter in an imaging device. In addition, a light-absorbing optical filter that does not use a light-reflecting film can suppress the occurrence of ghosts and flares caused by multiple reflections by the light-reflecting film, so that good images can be easily obtained in backlit conditions or when photographing night scenes. In addition, an optical filter with a film containing a light-absorbing agent is also advantageous in terms of miniaturization and thinning of imaging devices.

[0004] As such a light absorbing compound, a light absorbing compound formed by phosphonic acid and copper ions is known. For example, Patent Document 1 describes an optical filter having a UV-IR absorbing layer capable of absorbing infrared and ultraviolet rays. The UV-IR absorbing layer contains a UV-IR absorbent formed by phosphonic acid and copper ions. Patent Document 2 describes a method for manufacturing an optical filter having a light absorbing layer containing a light absorbing compound formed by phosphonic acid and copper ions. According to this manufacturing method, a coating film is formed on a substrate having a surface containing an organic fluorine compound, and the coating film is cured to form a light absorbing layer. The light absorbing layer is then peeled off from the substrate to obtain an optical filter. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6232161 [Patent Document 2] Patent No. 6543746 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 and 2 do not discuss any article in which a light absorbing film is attached to a frame. Therefore, the present disclosure provides an optical filter that includes a frame and a light absorbing film and can exhibit good resistance to changes in environmental conditions such as temperature changes. [Means for solving the problem]

[0007] The present invention relates to A frame having a through hole; a light absorbing film that is disposed so as to cover the through hole and contains a light absorbing compound; The average Young's modulus of the light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; An optical filter is provided.

[0008] The present invention also provides a method for producing a semiconductor device comprising the steps of: An imaging element; a lens that transmits light from a subject and collects the light on the image sensor; The optical filter is provided. An imaging device is provided.

[0009] The present invention also provides a method for producing a semiconductor device comprising the steps of: supplying a resin composition containing a light absorbing compound so as to fill a through hole of a frame having a through hole; and curing the resin composition to form a light absorbing film. The average Young's modulus of the light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; A method for manufacturing an optical filter is provided. Effect of the Invention

[0010] The optical filter described above exhibits good resistance to changes in environmental conditions such as temperature changes. [Brief description of the drawings]

[0011] [Figure 1A] FIG. 1A is a plan view showing an example of an optical filter according to the present invention. [Figure 1B] FIG. 1B is a cross-sectional view of the optical filter taken along line IB-IB shown in FIG. 1A. [Figure 2A] FIG. 2A is a plan view showing another example of a frame of an optical filter according to the present invention. [Figure 2B] FIG. 2B is a cross-sectional view of the frame taken along line IIB-IIB shown in FIG. 2A. [Figure 3A] FIG. 3A is a cross-sectional view showing yet another example of a frame of an optical filter according to the present invention. [Figure 3B] FIG. 3B is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3C] FIG. 3C is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3D] FIG. 3D is a cross-sectional view showing yet another example of a frame of an optical filter according to the present invention. [Figure 3E] FIG. 3E is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3F] FIG. 3F is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3G] FIG. 3G is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3H] FIG. 3H is a cross-sectional view showing still another example of the frame of the optical filter according to the present invention. [Figure 3I] FIG. 3I is a cross-sectional view showing yet another example of the frame of the optical filter according to the present invention. [Figure 3J] FIG. 3J is a cross-sectional view showing another example of the optical filter according to the present invention. [Figure 3K] FIG. 3K is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 3L] FIG. 3L is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 3M] FIG. 3M is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 3N] FIG. 3N is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 3O] FIG. 3O is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 3P] FIG. 3P is a cross-sectional view showing still another example of the optical filter according to the present invention. [Figure 4] FIG. 4 is a diagram showing an example of a method for producing an optical filter according to the present invention. [Diagram 5] FIG. 5 is a diagram showing a schematic diagram of an imaging device according to the present invention. [Figure 6] FIG. 6 shows the transmission spectrum of the optical filter according to the first embodiment. [Figure 7]FIG. 7 shows the transmission spectrum of the optical filter according to the second embodiment. [Figure 8] FIG. 8 shows the transmission spectrum of the optical filter according to the third embodiment. [Figure 9] FIG. 9 shows the transmission spectrum of the optical filter according to the fourth embodiment. [Figure 10] FIG. 10 shows the transmission spectrum of the optical filter according to the fifth embodiment. [Figure 11] FIG. 11 shows the transmission spectrum of the optical filter according to the sixth embodiment. [Figure 12] FIG. 12 shows the transmission spectrum of the optical filter according to Comparative Example 1. As shown in FIG. [Figure 13] FIG. 13 is a graph showing the relationship between the storage modulus E′ and the loss modulus E″ and the temperature, and the relationship between the loss tangent tan δ and the temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Since the optical filters described in Patent Documents 1 and 2 are plate-shaped or film-shaped, it is understood that when these optical filters are mounted on a camera module, for example, it is necessary to first cut the optical filter to a desired size. In this case, it is conceivable to prepare a framed filter by adhering the cut optical filter to a predetermined frame, and then to incorporate the framed filter by adhering it to the camera module. Cutting or adhering such an optical filter requires large-scale equipment or complex and precise work. In addition, the process of preparing such a framed filter is difficult to increase the yield and is prone to problems in productivity. In particular, due to the difference between the material of the frame and the material of the optical filter, when the environment of the framed filter changes, such as a temperature change, a difference is likely to occur between the amount of expansion and contraction of the optical filter and the amount of expansion and contraction of the frame. As a result, the optical filter may crack or come off the frame.

[0013] Therefore, the inventors of the present invention have been working day and night to find a structure that can exhibit good resistance to changes in environmental conditions such as temperature changes while having a frame and a light absorbing film. After much trial and error, the inventors of the present invention have finally devised the optical filter according to the present invention.

[0014] Hereinafter, embodiments of the present invention will be described. Note that the following description is merely an example of the present invention, and the present invention is not limited to these.

[0015] FIG. 1A is a plan view of an example of an optical filter according to the present invention, and FIG. 1B is a cross-sectional view of the optical filter taken along a plane that passes through line IB-IB in FIG. 1A and is perpendicular to the paper surface.

[0016] As shown in FIG. 1A and FIG. 1B, the optical filter 1 includes a frame 10 and a light absorbing film 20. The frame 10 has a through hole 12. The light absorbing film 20 is arranged to block the through hole 12 and contains a light absorbing compound. The average Young's modulus of the light absorbing film 20 measured according to the continuous stiffness measurement method is 2.5 GPa or less. This allows the optical filter 1 to exhibit good resistance to environmental changes such as temperature changes. Therefore, in the optical filter 1, even if the temperature of the environment of the optical filter 1 changes, the light absorbing film 20 is not easily cracked and the light absorbing film 20 is not easily removed from the frame 10. The average Young's modulus of the light absorbing film 20 can be determined, for example, according to the method described in the Examples. For details of the nanoindentation method (continuous stiffness measurement method), reference can be made to International Publication No. 2019 / 044758 and JP-A-2015-174270.

[0017] The average value of Young's modulus of the light absorbing film 20 is desirably 2.4 GPa or less, and more desirably 2.2 GPa or less. The Young's modulus of the light absorbing film 20 is, for example, 0.1 GPa or more, and may be 0.4 GPa or more.

[0018] The average value of the hardness of the light absorbing film 20 measured according to the continuous stiffness measurement method is not limited to a specific value. The average value of the hardness of the light absorbing film 20 is, for example, 0.06 GPa or less. The average value of the hardness may be 0.005 GPa to 0.06 GPa.

[0019] The material of the frame 10 is not limited to a specific material. The material of the frame 10 may be a metal material such as stainless steel, iron, or aluminum, a resin, a composite material, or ceramics. The metal material may be an alloy such as an aluminum alloy. Examples of the resin include nylon, polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polyvinyl chloride resin (PVC), acrylic resin, acrylonitrile-butadiene-styrene resin (ABS), polyethylene, polyester, polypropylene, polyolefin, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyimide, and epoxy resin. The composite material is, for example, a material in which a filler or fiber is dispersed in a matrix resin. The ceramic includes, for example, alumina or zirconia.

[0020] The average linear expansion coefficient of the material constituting the frame 10 at 0° C. to 60° C. is not limited to a specific range. The average linear expansion coefficient is, for example, 0.2×10 -5 [ / ℃]~25×10 -5 [ / °C]. This allows the optical filter 1 to more reliably exhibit good resistance to environmental changes such as temperature changes. The average linear expansion coefficient of the material constituting the frame 10 in the range of 0°C to 60°C is preferably 1.0×10 -5 [ / ℃]~25×10 -5 [ / ℃], and more preferably 4.0×10 -5 [ / ℃]~16×10 -5 [ / ℃].

[0021] When the material of the frame 10 is a metal material, the average linear expansion coefficient of any metal material in the temperature range of 0° C. to 60° C. is, for example, 1.0×10 -5 [ / ℃]~3.0×10 -5The average linear expansion coefficient of metal materials in the temperature range of 0°C to 60°C is 2.3×10 for aluminum and aluminum alloys such as duralumin. -5 [ / ℃]~2.8×10 -5 [ / ℃], and for iron and steel, it is 1.0×10 -5 [ / ℃]~1.3×10 -5 [ / ℃], and when the metal material is stainless steel, it is 1.0×10 -5 [ / ℃]~1.8×10 -5 The average linear expansion coefficient of the metal frame within a given temperature range can be measured in accordance with the Japanese Industrial Standard JIS R3251-1995.

[0022] When the material of the frame 10 is a resin, the average linear expansion coefficient in the temperature range of 0° C. to 60° C. is, for example, 1.0×10 -5 [ / ℃]~25×10 -5 The average linear expansion coefficient of the resin in the temperature range of 0°C to 60°C is 10×10 -5 [ / ℃]~22×10 -5 [ / ℃], and when the resin is polypropylene (PP), it is 5 × 10 -5 [ / ℃]~11×10 -5 [ / ℃] and the resin is acrylonitrile butadiene styrene (ABS), it is 6 × 10 -5 [ / ℃]~13×10 -5 [ / ℃], and when the resin is polymethyl methacrylate (PMMA), it is 5 × 10 -5 [ / ℃]~10×10 -5 [ / ℃], and when the resin is polyamide (PA), it is 5×10 -5 [ / ℃]~15×10 -5 [ / ℃], and when the resin is epoxy resin (EP), it is 4×10 -5 [ / ℃]~7×10 -5 [ / ℃], and when the resin is polyetheretherketone (PEEK), it is 3.6 × 10 -5 [ / ℃]~5×10 -5[ / ℃], and when the resin is polyetherimide (PEI), it is 4.2 × 10 -5 [ / ℃]~5.9×10 -5 [ / ℃], and when the resin is polyethylene terephthalate (PET), it is 5 × 10 -5 [ / ℃]~7×10 -5 [ / ℃], and when the resin is polyphenylene sulfide (PPS), it is 4 × 10 -5 [ / ℃]~6×10 -5 [ / °C]. The frame 10 may be made of engineering plastic. The average thermal expansion coefficient of the frame in the temperature range of 0°C to 60°C is 3.5×10 -5 [ / ℃]~15×10 -5 The average linear expansion coefficient of the resin frame within a predetermined temperature range can be measured in accordance with JIS R3251-1995.

[0023] The material of the frame 10 may be ceramics, if desired. The average linear expansion coefficient of ceramics in the temperature range of 0°C to 60°C is 0.55×10 -5 [ / ℃]~0.7×10 -5 [ / ℃], and when the ceramic is ZrO2 (zirconia), it is 0.7×10 -5 [ / ℃]~0.8×10 -5 [ / ℃], and when the ceramic is SiC (silicon carbide), it is 0.28×10 -5 [ / ℃]~0.3×10 -5 The average linear expansion coefficient of the ceramic frame within a given temperature range can be measured in accordance with JIS R3251-1995.

[0024] The method of measuring the average linear expansion coefficient of the frame 10 is not limited to a specific method. The method of measuring the average linear expansion coefficient of the frame 10 can be, for example, measured in accordance with JIS R3251-1995 using a laser thermal dilatometer LIX-2L manufactured by Advance Riko Co., Ltd. In this case, a measurement sample can be prepared by clamping the frame from both ends with a pair of quartz chips. The average thermal expansion coefficient of the frame at 0°C to 60°C can be obtained by filling the environment of the measurement sample with low-pressure high-purity He gas, and measuring the change in the length of the sample by a Michelson-type laser light interference method while changing the temperature of the environment. In this case, the heating rate is set to, for example, 2°C / min. The diameter of the measurement sample clamped by the quartz chips is, for example, 3 mm to 6 mm, and the length of the sample is, for example, 10 mm to 15 mm.

[0025] The dimension of the frame 10 in the thickness direction of the light absorbing film 20 is not limited to a specific value. The dimension is, for example, 0.2 mm to 2 mm.

[0026] The number of through holes 12 in the frame 10 is not limited to a specific value, and may be one, or may be two or more.

[0027] The size and shape of the through hole 12 in the plan view of the optical filter 1 are not limited to a specific embodiment. For example, when the optical filter 1 is used together with an imaging element, the size of the through hole 12 in the plan view of the optical filter 1 can be determined according to the size of the imaging element or the size of the image circle.

[0028] Examples of the shape of the through hole 12 in the plan view of the optical filter 1 may be a circle, a nearly circle, an ellipse, a nearly ellipse, a triangle, a square, a rectangle, a quadrangle such as a rhombus, or another polygon such as a pentagon, a hexagon, etc. For example, when the optical filter 1 is used together with an imaging element, the shape of the through hole 12 in the plan view of the optical filter 1 can be adjusted to a shape corresponding to the shape of the imaging element.

[0029] 1B, the frame 10 has a first surface 14. The first surface 14 is in contact with the through-hole 12 and is formed along a plane parallel to the main surface of the light absorbing film 20. The first surface 14 is formed, for example, in an annular shape.

[0030] The frame 10 has, for example, at least one of a convex portion and a concave portion in contact with the through hole 12. As shown in FIG. 1B, the frame 10 has, for example, a convex portion 16 in contact with the through hole 12. The convex portion 16 protrudes toward the center of the through hole 12 in a direction parallel to the main surface of the light absorbing film 20. For example, the first surface 14 is formed by an end face of the convex portion 16 in the thickness direction of the light absorbing film 20. For example, one end of the convex portion 16 in the thickness direction of the light absorbing film 20 and one end of the frame 10 in the thickness direction of the light absorbing film 20 are located on the same plane.

[0031] In addition, when the object having the main surface is a plate-like body, the main surface means the "principal surface" that is the surface having a larger area than the other surfaces, and this surface will be referred to as the main surface.

[0032] In the frame 10, the through hole 12 is formed so that a prismatic space with a volume of A×B×(t1-t2) and a prismatic space with a volume of a×b×t2 are connected to each other. When the shape of the through hole 12 in a plan view is a square, A=B and a=b. t1 is the dimension of the frame 10 in the thickness direction of the light absorbing film 20, and t2 is the distance between one end of the frame 10 in the thickness direction of the light absorbing film 20 and the first surface 14. Each of A and B is, for example, 5 to 30 mm, and each of a and b is, for example, 3 to 25 mm. t1 is, for example, 0.2 to 2 mm, may be 0.2 to 1.5 mm, or may be 0.3 to 0.9 mm. t2 is, for example, 0.1 to 0.5 mm, or may be 0.1 to 0.25 mm.

[0033] The ratio of the thickness of the light absorbing film 20 to t1 (the value obtained by dividing the thickness of the light absorbing film 20 by t1) is not limited to a specific value. The ratio may be 0.6 or more, or may be 1 or more. The ratio of the thickness of the light absorbing film 20 to t1 may be 2 or less, or may be 1.5 or less. Furthermore, the ratio of the thickness of the light absorbing film 20 to t1 may be 0.3 to 0.6, or may be 0.39 to 0.44.

[0034] The ratio of the thickness of the light absorbing film 20 to t2 (the value obtained by dividing the thickness of the light absorbing film 20 by t2) may be greater than 1 and equal to or less than 2, may be 1.2 to 1.6, or may even be 1.3 to 1.46. When the thickness of the light absorbing film 20 and t2 have such a relationship, the contact area of ​​the light absorbing film 20 with the inner surface of the through-hole 12 can be increased, and the adhesion of the light absorbing film 20 to the frame 10 can be improved.

[0035] It should be noted that FIG. 1B is a (sectional) view showing one embodiment of the optical filter 1 according to the present application. The embodiment of the optical filter 1 according to the present application will be described more specifically with reference to FIG. 1B. In FIG. 1B, the frame 10 is flat having a first end face 25 and a second end face 26 in the thickness direction. The first end face 25 is an upper end face, and the second end face 26 is a lower end face. The first end face 25 and the second end face 26 are each flat surfaces. The through hole 12 is drilled in the thickness direction of the frame 10. The frame 10 has a thickness of t1. The through hole 12 includes a protrusion 16 protruding toward the inside of the through hole 12. The protrusion 16 includes a first surface 14 and a surface 17. The first surface 14 is a surface substantially parallel to the second end face 26. The surface 17 is a surface perpendicular to the second end face 26 and the first surface 14. The length of the frame 10 in the thickness direction of the frame 10 between the second end surface 26 and the first surface 14 is t2. The light absorbing film 20 is formed inside the through hole 12. The light absorbing film 20 is flat, having a first main surface 22 and a second main surface 24 that are parallel to each other and spaced apart from each other in the thickness direction. The first main surface 22 is the upper main surface, and the second main surface 24 is the lower main surface. Each of the first main surface 22 and the second main surface 24 is a flat surface. The second main surface 24 of the light absorbing film 20 is approximately flush with the second end surface 26 of the frame 10. Flush means that two or more surfaces are connected flatly without any steps. The thickness of the light absorbing film 20 is the length of the light absorbing film 20 between the first main surface 22 and the second main surface 24 in the thickness direction of the light absorbing film 20. The first main surface 22 of the light absorbing film 20 is formed at a position closer to the first end surface 25 than the first surface 14 of the frame 10, and the thickness of the light absorbing film 20 is greater than the length t2. The light absorbing film 20 is in contact with two surfaces, the surface 17 and the first surface 14 that constitute the protrusion 16.

[0036] Regardless of the specific configuration of the above-mentioned embodiment, when a through hole in which a light absorbing film is disposed has a convex portion or a concave portion, the light absorbing film may be in contact with a part or the whole of the convex portion or the concave portion, or the light absorbing film may be in contact with at least two of the surfaces constituting the convex portion or the concave portion.

[0037] The color of the surface of the frame 10 is not limited to a specific color. The portion of the frame 10 in contact with the through-hole 12 may be black, for example, and the color of the entire surface of the frame 10 may be black. In this case, for example, when the optical filter 1 is used in an imaging device, re-reflection of light in the frame 10 can be suppressed. The frame 10 may be colored in a color that can suppress re-reflection of light.

[0038] The surface of the frame 10 may be a matte surface with reduced gloss, or may have minute irregularities formed on the surface of the frame 10 so that light is diffusely reflected. This makes it possible to diffuse the light that is re-reflected on the surface of the frame 10. As a result, when the optical filter 1 is used in an imaging device, ghosts or flares formed by direct reflection of light can be easily suppressed.

[0039] The frame 10 may be modified to a frame 10x shown in FIG. 2A and FIG. 2B. The frame 10x is configured similarly to the frame 10, except for the parts that are particularly described. The same reference numerals are used for the components of the frame 10x that are the same as or correspond to the components of the frame 10. The shape of the through hole 12 in the frame 10x in plan view is an ellipse. In the frame 10x, the through hole 12 is formed so that an elliptical cylindrical space with a volume of π(S1 / 2)×(S2 / 2)×(t3-t4) and an elliptical cylindrical space with a volume of π(s1 / 2)×(s2 / 2)×t4 are connected to each other. S1 and s1 are the lengths of the major axis of the ellipse, and S2 and s2 are the lengths of the minor axis of the ellipse. When the shape of the through hole 12 in plan view is a circle, S1=S2 and s1=s2. t3 is the dimension of the frame 10x in the thickness direction of the light absorbing film 20, and t4 is the distance between one end of the frame 10x in the thickness direction of the light absorbing film 20 and the first surface 14. Each of S1 and S2 is, for example, 5 to 30 mm, and each of s1 and s2 is, for example, 3 to 25 mm. t3 is, for example, 0.2 to 2 mm, may be 0.2 to 1.5 mm, or may be 0.3 to 0.9 mm. t4 is, for example, 0.1 to 0.5 mm, or may be 0.1 to 0.25 mm.

[0040] The ratio of the thickness of the light absorbing film 20 to t3 (the value obtained by dividing the thickness of the light absorbing film 20 by t3) is not limited to a specific value. The ratio may be 0.6 or more, or may be 1 or more. The ratio of the thickness of the light absorbing film 20 to t3 may be 2 or less, or may be 1.5 or less. The ratio of the thickness of the light absorbing film 20 to t3 may be 0.3 to 0.6, or may be 0.39 to 0.44.

[0041] The ratio of the thickness of the light absorbing film 20 to t4 (the value obtained by dividing the thickness of the light absorbing film 20 by t4) is greater than 1. The ratio may be 2 or less, may be 1.2 to 1.6, or may be 1.3 to 1.46. When the thickness of the light absorbing film 20 and t4 have such a relationship, the contact area of ​​the light absorbing film 20 with the inner surface of the through-hole 12 can be increased, and the adhesion of the light absorbing film 20 to the frame 10x can be improved.

[0042] The frame 10 is not limited to a specific embodiment as long as it has the through hole 12. The frame 10 may be modified, for example, as frames 10a to 10i shown in Figs. 3A to 3I. The frames 10a to 10i are configured similarly to the frame 10 except for parts that will be particularly described. The same reference numerals are used to designate components of the frames 10a to 10i that are the same as or correspond to those of the frame 10. Figs. 3A to 3I each show a cross section of the frames 10a to 10i formed along a plane that includes the axis of the through hole 12 and is parallel to the axis.

[0043] In the frame 10a shown in FIG. 3A, the through hole 12 is formed by an inner surface extending in a direction perpendicular to the main surface of the light absorbing film 20 (not shown). In the frame 10b shown in FIG. 3B, the through hole 12 is formed as a tapered hole. In the frame 10c shown in FIG. 3C, the through hole 12 has a portion formed as a tapered hole and a portion formed by an inner surface extending in a direction perpendicular to the main surface of the light absorbing film 20. Each of the frame 10d shown in FIG. 3D and the frame 10e shown in FIG. 3E includes a protrusion 16 in contact with the through hole 12. The protrusion 16 is formed in a ring shape around the through hole 12. The protrusion 16 in the frame 10d has, for example, a pair of side surfaces parallel to the main surface of the light absorbing film 20 and an end surface connecting the side surfaces. For example, one of the pair of side surfaces of the protrusion 16 forms the first surface 14. The protrusion 16 in the frame 10e has a tapered shape.

[0044] Each of the frame 10f shown in FIG. 3F and the frame 10g shown in FIG. 3G includes a recess 18 in contact with the through hole 12. The recess 18 is formed in an annular shape and is included in a part of the through hole 12. The recess 18 in the frame 10f has, for example, a pair of side surfaces that are parallel to the main surface of the light absorbing film 20 and face each other. One of the pair of side surfaces may be the first surface 14. The recess 18 in the frame 10g forms a wedge-shaped groove.

[0045] In the frame 10h shown in FIG. 3H, a pair of inner surfaces extending in mutually orthogonal directions in contact with the through hole 12 may be connected by a surface inclined with respect to the inner surfaces. For example, in a cross section of the frame 10h formed along a plane including the axis of the through hole 12 and parallel to the axis, the contours of the pair of inner surfaces extending in mutually orthogonal directions are connected by a contour inclined at an angle of 45° with respect to both contours. A pair of inner surfaces extending in mutually orthogonal directions in contact with the through hole 12 may be connected by a rounded curved surface. The above shape of the frame 10h can be said to be a shape in which an appropriate amount of C-face or R-chamfering is performed on some corners of the inner surfaces forming the through hole having the protrusion 16 in the frame of the optical filter shown in FIG. 1B. The size of the C-face may be C0.01 to C0.25, or may be C0.025 to C0.1. The size of the R-face may be R0.01 to R0.25, or may be R0.025 to R0.1. Incidentally, such chamfering may be performed on a part of the inner surface forming the through hole of the frame in the above-mentioned FIGS. 3A to 3G.

[0046] The frame 10i shown in Fig. 3I has a protrusion 16 in contact with the through-hole 12. The protrusion 16 has a surface formed in a tapered shape from both end faces of the frame 10i in a direction perpendicular to the main surface of the light absorbing film 20 (not shown).

[0047] 1B, the light-absorbing film 20 has a thickness that is smaller than the dimension of the frame 10 in the thickness direction of the light-absorbing film 20. In this case, even if the thickness of the light-absorbing film 20 is small, the light-absorbing film 20 is integrated with the frame 10, so that the optical filter 1 is easy to handle.

[0048] The thickness of the light absorbing film 20 is not limited to a specific thickness. The light absorbing film 20 has a thickness of, for example, 1 μm to 1000 μm.

[0049] The thickness of the light absorbing film 20 may be 10 μm to 500 μm, or may be 50 μm to 300 μm.

[0050] 1B, the light absorbing film 20 has, for example, a first main surface 22. The first main surface 22 is formed between one end and the other end of the frame 10 in the thickness direction of the light absorbing film 20. In this case, it is possible to move the optical filter 1 without touching the first main surface 22, and the yield of products including the optical filter 1 is likely to be increased. The first main surface 22 is formed, for example, in the thickness direction of the light absorbing film 20 so as to cover the first surface 14. The first main surface 22 may be formed so as to be flush with the first surface 14.

[0051] As shown in FIG. 1B, the light absorbing film 20 has, for example, a second main surface 24. The second main surface 24 is formed, for example, so as to be flush with one end of the frame 10 in the thickness direction of the light absorbing film 20. In this case, the second main surface 24 of the light absorbing film 20 does not cause a step in the optical filter 1, and the light absorbing film 20 can be prevented from contacting and being damaged by other members when the optical filter 1 is carried. As a result, the yield of products including the optical filter 1 is likely to be increased. In addition, since the light absorbing film 20 is present at one end of the through hole 12 in the thickness direction of the light absorbing film 20, it is possible to prevent light from being directly irradiated onto the inner surface of the frame 10 in contact with the through hole 12. The second main surface 24 may be formed between one end and the other end of the frame 10 in the thickness direction of the light absorbing film 20.

[0052] 1B, the light absorbing film 20 overlaps with the convex portions 16 in the thickness direction of the light absorbing film 20. As shown in FIGS. 3J to 3P, for example, the light absorbing film 20 may overlap with at least a part of a convex portion or at least a part of a concave portion formed inside the through-hole of the frame in the thickness direction of the light absorbing film 20.

[0053] 3J and 3K each show an optical filter obtained by forming a light absorbing film 20 inside the through-hole 12 of the frame 10d shown in Fig. 3D. In the optical filter shown in Fig. 3J, the light absorbing film 20 overlaps with the entire convex portion 16 in the thickness direction of the light absorbing film 20. In the optical filter shown in Fig. 3K, the light absorbing film 20 overlaps with a part of the convex portion 16 in the thickness direction of the light absorbing film 20.

[0054] In the optical filter shown in Fig. 3J, the light absorbing film 20 is in contact with three faces (two faces parallel to the end face of the frame 10d and a face perpendicular to those faces) constituting the protrusion 16 inside the through hole of the frame 10d. In the optical filter shown in Fig. 3K, the light absorbing film 20 is in contact with two faces (one face parallel to the end face of the frame 10d and a face perpendicular to that face) constituting the protrusion 16 inside the through hole of the frame 10d.

[0055] Fig. 3L shows an optical filter obtained by forming a light absorbing film 20 inside the through-hole 12 of the frame 10e shown in Fig. 3E. In the optical filter shown in Fig. 3L, the light absorbing film 20 overlaps with the entire convex portion 16 in the thickness direction of the light absorbing film 20. In the optical filter shown in Fig. 3L, the light absorbing film 20 may overlap with a part of the convex portion 16 in the thickness direction of the light absorbing film 20.

[0056] In the optical filter shown in Fig. 3L, the light absorbing film 20 is in contact with two faces constituting a triangular convex portion protruding toward the center of the through hole inside the through hole of the frame 10e. In addition, the frame 10e included in the optical filter shown in Fig. 3L has a convex portion inside the through hole, but does not have a convex portion on a surface parallel to one end face of the frame, unlike the frame included in the optical filter in Fig. 1B, etc. Such a configuration is also included in the present invention.

[0057] 3M and 3N each show an optical filter obtained by forming a light absorbing film 20 inside the through-hole 12 of the frame 10f shown in Fig. 3F. In the optical filter shown in Fig. 3M, the light absorbing film 20 overlaps with the entire recess 18 in the thickness direction of the light absorbing film 20. In the optical filter shown in Fig. 3N, the light absorbing film 20 overlaps with a part of the recess 18 in the thickness direction of the light absorbing film 20.

[0058] In the optical filter shown in Fig. 3M, the light absorbing film 20 is in contact with three faces (two faces parallel to the end face of the frame 10f and a face perpendicular to those faces) constituting the recess 18 inside the through hole of the frame 10f. In the optical filter shown in Fig. 3N, the light absorbing film 20 is in contact with two faces (one face parallel to the end face of the frame 10d and a face perpendicular to that face) constituting the recess 18 inside the through hole of the frame 10f.

[0059] Fig. 3O shows an optical filter obtained by forming a light absorbing film 20 inside the through hole 12 of the frame 10g shown in Fig. 3G. In the optical filter shown in Fig. 3O, the light absorbing film 20 overlaps with the entire recess 18 in the thickness direction of the light absorbing film 20. In the optical filter shown in Fig. 3O, the light absorbing film 20 may overlap with a part of the recess 18 in the thickness direction of the light absorbing film 20.

[0060] In the optical filter shown in Fig. 3O, the light absorbing film 20 is in contact with two faces constituting a triangular recess inside the through hole of the frame 10g that is recessed toward the outside of the through hole. In addition, the frame 10g included in the optical filter shown in Fig. 3O has a recess inside the through hole, but does not have a surface parallel to one end face of the frame, unlike the frame included in the optical filter in Fig. 1B, etc. Such a configuration is also included in the present invention.

[0061] Fig. 3P shows an optical filter obtained by forming a light absorbing film 20 inside the through-hole 12 of the frame 10i shown in Fig. 3I. In the optical filter shown in Fig. 3P, the light absorbing film 20 overlaps with a part of the protrusion 16 in the thickness direction of the light absorbing film 20. In the optical filter shown in Fig. 3P, the light absorbing film 20 may overlap with the entirety of the protrusion 16 in the thickness direction of the light absorbing film 20.

[0062] In the optical filter shown in Fig. 3P, the light absorbing film 20 is in contact with three faces constituting a trapezoidal convex portion protruding toward the center of the through hole inside the through hole of the frame 10i. Also, the frame 10i included in the optical filter shown in Fig. 3P has a convex portion inside the through hole, but does not have a surface parallel to one end face of the frame, unlike the frame included in the optical filter in Fig. 1B. Such a configuration is also included in the present invention.

[0063] As described above, in the optical filters according to FIG. 1B and FIGS. 3J to 3P, at least two of the faces constituting the convex or concave portion inside the through-hole of the frame included in the optical filter are in contact with the light absorbing film.

[0064] The light absorbing film 20 is not limited to a specific film as long as it can absorb light of a predetermined wavelength. The light absorbing film 20 has a transmission spectrum that satisfies the following requirements (I), (II), (III), (IV), (V), (VI), and (VII), for example. (I) A first cutoff wavelength exhibiting a transmittance of 50% exists in the wavelength range of 380 nm to 440 nm. (II) There is a second cutoff wavelength exhibiting a transmittance of 50% in the wavelength range of 600 nm to 720 nm. (III) The maximum transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (IV) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (V) The maximum transmittance in the wavelength range of 750 nm to 1000 nm is 5% or less. (VI) The maximum transmittance in the wavelength range of 800 nm to 950 nm is 4% or less. (VII) The transmittance at a wavelength of 1100 nm is 20% or less.

[0065] In this specification, "the maximum transmittance in the wavelength range of X nm to Y nm is A % or less" is synonymous with the transmittance being A % or less over the entire wavelength range of X nm to Y nm.

[0066] Regarding the above requirement (I), the first cutoff wavelength is preferably in the wavelength range of 385 nm to 435 nm, and more preferably in the wavelength range of 390 nm to 430 nm.

[0067] Regarding the above requirement (II), the second cutoff wavelength is preferably in the wavelength range of 610 nm to 700 nm, and more preferably in the wavelength range of 620 nm to 680 nm.

[0068] Regarding the above requirement (IV), the average transmittance in the wavelength range of 450 nm to 600 nm is desirably 78% or more, and more desirably 80% or more.

[0069] Regarding the above requirement (V), the maximum transmittance in the wavelength range of 750 nm to 1000 nm is desirably 3% or less, and more desirably 1% or less.

[0070] Regarding the above requirement (VI), the maximum transmittance in the wavelength range of 800 nm to 950 nm is desirably 2% or less, and more desirably 0.5% or less.

[0071] Regarding the above requirement (VII), the transmittance at a wavelength of 1100 nm is desirably 15% or less, and more desirably 10% or less.

[0072] The light absorbing film 20 is fixed to the frame 10, for example, by directly contacting the inner surface of the frame 10. In other words, there is no adhesive layer between the light absorbing film 20 and the frame 10. The light absorbing film 20 may be fixed to the frame 10 by an adhesive.

[0073] The light absorbing compound in the light absorbing film 20 is not limited to a specific compound as long as it can absorb light of a predetermined wavelength. The light absorbing compound may contain, for example, a phosphonic acid represented by the following formula (a) and a copper component.

[0074] [ka] [In the formula, R 11 is an alkyl group, an aryl group, a nitroaryl group, a hydroxyaryl group, or a halogenated aryl group in which at least one hydrogen atom in the aryl group is substituted with a halogen atom.

[0075] In the light absorbing film 20, for example, a phosphonic acid represented by formula (a) is coordinated to a copper component to form a light absorbing compound. For example, fine particles containing at least a light absorbing compound are formed in the light absorbing film 20. In this case, the fine particles are dispersed in the light absorbing film 20 without agglomeration. The average particle diameter of the fine particles is, for example, 5 nm to 200 nm. If the average particle diameter of the fine particles is 5 nm or more, no special process is required for finely fining the fine particles, and the structure of the fine particles containing at least a light absorbing compound is less likely to be broken. In addition, the fine particles are well dispersed in the light absorbing film 20. In addition, if the average particle diameter of the fine particles is 200 nm or less, the effect of Mie scattering can be reduced, the transmittance of visible light in the light absorbing film 20 can be improved, and the deterioration of characteristics such as contrast and haze of an image captured by an imaging device can be suppressed. The average particle diameter of the fine particles is preferably 100 nm or less. In this case, the effect of Rayleigh scattering is reduced, so that the transparency of the light absorbing film 20 to visible light is increased. In addition, the average particle diameter of the fine particles is more preferably 75 nm or less. In this case, the transparency to visible light of the light absorbing film 20 is particularly high. The average particle size of the fine particles can be measured by applying a dynamic light scattering method to the composition for the light absorbing film 20.

[0076] The light absorbing film 20 contains, for example, a hydrolysis condensate of alkoxysilane. In this case, the light absorbing film 20 has a strong skeleton having a siloxane bond (-Si-O-Si-).

[0077] The hydrolysis condensate of alkoxysilane contained in the light absorbing film 20 includes, for example, a hydrolysis condensate of dialkoxysilane. As a result, a strong skeleton having siloxane bonds is formed in the light absorbing film 20, and the light absorbing film 20 is likely to have the desired flexibility due to the organic functional group derived from the dialkoxysilane. Therefore, cracks and chipping are unlikely to occur when the light absorbing film 20 is cut. In addition, when an external force is applied so that the light absorbing film 20 bends, the light absorbing film 20 is unlikely to crack. In addition, even if the difference between the thermal expansion coefficient of the frame 10 and the thermal expansion coefficient of the light absorbing film 20 is large, the light absorbing film 20 can flexibly deform in response to the expansion and contraction of the frame 10. Therefore, the light absorbing film 20 is not easily affected by thermal stress, and problems such as cracks and peeling of the light absorbing film 20 from the frame 10 are unlikely to occur in a heat cycle test.

[0078] The hydrolysis condensate of dialkoxysilane is not limited to a specific dialkoxysilane hydrolysis condensate. This hydrolysis condensate is derived from, for example, a dialkoxysilane having a hydrocarbon group having 1 to 6 carbon atoms bonded to a silicon atom. The dialkoxysilane may have a halogenated hydrocarbon group. In the halogenated hydrocarbon group, at least one hydrogen atom in the hydrocarbon group having 1 to 6 carbon atoms bonded to a silicon atom is substituted with a halogen atom.

[0079] The hydrolysis condensate of dialkoxysilane may be derived from an alkoxysilane represented by the following formula (b), for example: In this case, the desired flexibility is more reliably imparted to the light absorbing film 20. (R2)2-Si-(OR3)2(b) [In the formula, each R2 is independently an alkyl group having 1 to 6 carbon atoms, and each R3 is independently an alkyl group having 1 to 8 carbon atoms.]

[0080] The hydrolysis condensation product of a dialkoxysilane may be, for example, a hydrolysis condensation product of dimethyldiethoxysilane, dimethyldimethoxysilane, diethyldiethoxysilane, diethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, or 3-glycidoxypropylmethyldiethoxysilane.

[0081] The hydrolysis condensation product of alkoxysilane may further contain at least one hydrolysis condensation product of tetraalkoxysilane and trialkoxysilane, which makes it easier for a dense structure to be formed in the light absorbing film 20 by siloxane bonds.

[0082] The hydrolysis condensation product of alkoxysilane may further include a hydrolysis condensation product of tetraalkoxysilane and a hydrolysis condensation product of trialkoxysilane, which makes it easier to form a dense structure by siloxane bonds in the light absorbing film 20 with more certainty.

[0083] The tetraalkoxysilane or trialkoxysilane for the hydrolysis condensation product of alkoxysilane contained in the light absorbing film 20 is not limited to a specific alkoxysilane. For example, the tetraalkoxysilane or trialkoxysilane for the hydrolysis condensate of alkoxysilane contained in the light absorbing film 20 is at least one selected from the group consisting of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, hexyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, and 3-isocyanatepropyltrimethoxysilane.

[0084] The amount of dialkoxysilane and hydrolysis condensate of dialkoxysilane in the hydrolysis condensate of alkoxysilane and hydrolysis condensate of alkoxysilane contained in the light absorbing film 20 is not limited to a specific value. The content ratio of dialkoxysilane and hydrolysis condensate of dialkoxysilane contained in the light absorbing film 20 to the total amount of alkoxysilane and hydrolysis condensate of alkoxysilane contained in the light absorbing film 20 is, for example, 6 to 48% based on the mass of the dialkoxysilane and hydrolysis condensate of dialkoxysilane converted into a complete hydrolysis condensate. This makes it easier to adjust the average value of Young's modulus of the light absorbing film 20 measured according to the continuous stiffness measurement method to a desired range more reliably. The ratio is preferably 8 to 35%, more preferably 10 to 30%. In this case, the light absorbing film 20 is likely to have high moisture resistance. This is because a dense structure is formed by siloxane bonds, and the light absorbing compound is less likely to aggregate in a high humidity environment.

[0085] The light absorbing film 20 further contains, for example, a phosphoric acid ester. The action of the phosphoric acid ester makes it easy for the light absorbing compound to be well dispersed in the light absorbing film 20. In the light absorbing film 20, the compound derived from alkoxysilane can appropriately disperse the light absorbing compound while imparting higher moisture resistance to the light absorbing film 20 compared to phosphoric acid ester. Therefore, the inclusion of alkoxysilane in the light absorbing film 20 can reduce the amount of phosphoric acid ester used. In the formation of the light absorbing film 20, the alkoxysilane present around the light absorbing compound reacts with the dialkoxysilane, so that the light absorbing film 20 is likely to be homogeneous and highly dense. The light absorbing film 20 does not need to contain phosphoric acid ester.

[0086] The phosphate ester is, for example, a phosphate ester having a polyoxyalkyl group. The phosphate ester having a polyoxyalkyl group is not limited to a specific phosphate ester. The phosphate ester having a polyoxyalkyl group is, for example, Plysurf A208N: polyoxyethylene alkyl (C12, C13) ether phosphate ester, Plysurf A208F: polyoxyethylene alkyl (C8) ether phosphate ester, Plysurf A208B: polyoxyethylene lauryl ether phosphate ester, Plysurf A219B: polyoxyethylene lauryl ether phosphate ester, Plysurf AL: polyoxyethylene styrenated phenyl ether phosphate ester, Plysurf A212C: polyoxyethylene tridecyl ether phosphate ester, or Plysurf A215C: polyoxyethylene tridecyl ether phosphate ester. All of these are products manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The phosphate ester may also be, for example, NIKKOL DDP-2: polyoxyethylene alkyl ether phosphate ester, NIKKOL DDP-4: polyoxyethylene alkyl ether phosphate ester, or NIKKOL DDP-6: polyoxyethylene alkyl ether phosphate ester. All of these are products manufactured by Nikko Chemicals Co., Ltd.

[0087] The light absorbing film 20 further contains, for example, a resin. The resin is not limited to a specific resin. The resin is, for example, a silicone resin. The silicone resin is a compound having a siloxane bond in its structure. In this case, since the hydrolysis polycondensate of the alkoxysilane also has a siloxane bond, the compatibility between the hydrolysis polycondensate of the alkoxysilane and the resin in the light absorbing film 20 is good.

[0088] The resin is preferably a silicone resin containing an aryl group such as a phenyl group. If the resin contained in the light absorbing film 20 is hard (rigid), cracks are likely to occur due to hardening shrinkage during the manufacturing process of the light absorbing film 20 as the thickness of the light absorbing film 20 increases. If the resin is a silicone resin containing an aryl group, the light absorbing film 20 is likely to have good crack resistance. In addition, silicone resins containing an aryl group have high compatibility with the phosphonic acid represented by formula (a) and are unlikely to aggregate the light absorbing compound. Specific examples of silicone resins used as the resin include KR-255, KR-300, KR-2621-1, KR-211, KR-311, KR-216, KR-212, KR-251, and KR-5230. All of these are silicone resins manufactured by Shin-Etsu Chemical Co., Ltd.

[0089] The following describes an example of a method for manufacturing the optical filter 1. The method for manufacturing the optical filter 1 includes, for example, the following steps (i) and (ii). (i) A resin composition containing a light absorbing compound is supplied so as to fill the through-hole 12 of the frame 10 . (ii) The resin composition supplied in (i) is cured to form a light absorbing film 20 .

[0090] Fig. 4 is a flow chart for explaining an example of manufacturing the optical filter 1 according to this embodiment, and as an example, a method for manufacturing the optical filter 1 according to Fig. 1A and Fig. 1B will be explained. Note that Fig. 4 used for this explanation and explanation explains the main part of the manufacturing method of the optical filter according to the present invention, and does not reflect a specific and definitive configuration.

[0091] The optical filter 1 may be manufactured by the method shown in FIG. 4. In this method, first, a substrate 30 is provided. The substrate 30 is not limited to a specific substrate. The substrate 30 may be a glass substrate, a metal substrate such as stainless steel or aluminum, a ceramic substrate such as alumina or zirconia, or a resin substrate. The substrate 30 is preferably a glass substrate. In this case, a smooth surface can be easily and inexpensively obtained.

[0092] As can be seen from FIG. 4, the substrate 30 has at least one flat major surface.

[0093] Next, a coating 32 is formed on the main surface of the substrate 30. The coating 32 is formed so as to facilitate peeling of the light absorbing film 20 in a later step. The coating 32 has, for example, hydrophobicity or water repellency. The coating 32 contains, for example, a fluorine compound. The substrate 30 may be subjected to a surface treatment by a method other than the formation of the coating 32 so as to facilitate peeling of the light absorbing film 20 in a later step. When the main surface of the substrate 30 has a property that facilitates peeling of the light absorbing film 20, the formation of the coating 32 and other surface treatments may be omitted. For example, when the substrate 30 is a substrate made of a fluororesin, the formation of the coating 32 and other surface treatments can be omitted.

[0094] Next, the frame 10 is placed on the coating 32. In this case, the frame 10 may be fixed to the substrate 30 by a jig (not shown). A plurality of frames 10 may be placed on one substrate 30. Desirably, the frame 10 is placed in a state where a portion of the surface of the frame 10 and the surface of the coating 32 are in close contact with each other so that no gap is generated between them.

[0095] As can be seen from the cross-sectional view of the frame 10 in Fig. 4 (particularly the third from the top), the frame 10 has a flat plate shape having two parallel flat main surfaces, and has a through hole 12 drilled in the thickness direction. One of the main surfaces of the frame 10 is grounded to the flat main surface of the substrate 30, or to the surface of the coating 32 formed on the main surface of the substrate 30. The frame 10 includes a protrusion 16 inside the through hole 12. The protrusion 16 also includes a first surface 14 parallel to the main surfaces of the frame 10.

[0096] Next, a predetermined amount of light-absorbing composition 20a is supplied to fill through-hole 12 of frame 10. The amount of light-absorbing composition 20a supplied is adjusted so that light-absorbing film 20 obtained by curing light-absorbing composition 20a has a thickness that allows it to exhibit desired optical properties, such as a desired transmission spectrum.

[0097] 4 (particularly the fourth or fifth diagram from the top), one end face in the thickness direction of the light absorbing film 20 is in close contact with the flat main surface of the substrate 30 or the surface of the coating 32 formed on the main surface of the substrate 30. As a result, one main surface in the thickness direction of the light absorbing film 20 is expected to be substantially flush with one main surface of the frame 10.

[0098] Also, as can be seen from Figure 4 (particularly the fourth or fifth from the top), the end face of the light-absorbing film 20 opposite the substrate 30 is formed by supplying the light-absorbing composition 20a so that it exceeds the height of the first surface 14.

[0099] Next, the light-absorbing composition 20a is cured to form the light-absorbing film 20. For example, the light-absorbing composition 20a can be cured by heating the light-absorbing composition 20a in a heating furnace or oven. The curing conditions of the light-absorbing composition 20a can be adjusted according to the curing conditions of the curable resin contained in the light-absorbing composition 20a, for example. The curing conditions can include conditions related to the temperature of the atmosphere of the light-absorbing composition 20a and conditions related to time.

[0100] 4, the ratio of the thickness of the light absorbing film 20 to the length t2 is greater than 1. The length t2 corresponds to the distance between one end face of the frame 10 and the first face 14 in the thickness direction of the light absorbing film 20.

[0101] Next, the light absorbing film 20 is peeled off from the substrate 30 together with the frame 10. This makes it possible to obtain the optical filter 1. When the light absorbing film 20 contains alkoxysilane or a hydrolyzate thereof, the light absorbing film 20 may be exposed to an atmosphere having a temperature of about 60°C to 90°C and a predetermined relative humidity of 90% or less to promote the formation of siloxane bonds in the light absorbing film 20. This makes the matrix of the light absorbing film 20 more robust.

[0102] Light-absorbing composition 20a is not limited to a specific composition as long as it can form light-absorbing film 20. Light-absorbing composition 20a contains, for example, a component contained in light-absorbing film 20 or a precursor of a component contained in light-absorbing film 20. An example of a method for preparing light-absorbing composition 20a will be described below, taking as an example a case where the light-absorbing compound contains the above-mentioned phosphonic acid and a copper component.

[0103] For example, light absorbing composition 20a may have the formula (a) R 11In the case where the phosphonic acid (aryl phosphonic acid) is an aryl group, a nitroaryl group, a hydroxyaryl group, or an aryl halide group, the solution D is prepared as follows. A copper salt such as copper acetate monohydrate is added to a predetermined solvent such as tetrahydrofuran (THF) and stirred to prepare a solution A, which is a solution of the copper salt. Next, an aryl phosphonic acid is added to a predetermined solvent such as THF and stirred to prepare a solution B. When multiple types of aryl phosphonic acid are used as the phosphonic acid represented by formula (a), each aryl phosphonic acid may be added to a predetermined solvent such as THF and stirred to prepare multiple spare solutions prepared for each type of aryl phosphonic acid, to prepare the solution B. For example, an alkoxysilane is added in the preparation of the solution B. While stirring the solution A, the solution B is added to the solution A and stirred for a predetermined time. Next, a predetermined solvent such as toluene is added to this solution and stirred to obtain the solution C. Next, the solution C is heated and subjected to a desolvation treatment for a predetermined time to obtain the solution D. As a result, the solvent such as THF and the components generated by dissociation of the copper salt such as acetic acid (boiling point: about 118°C) are removed, and the light absorbing compound is generated by the reaction of the phosphonic acid represented by formula (a) with the copper component. The temperature at which the C liquid is heated is determined based on the boiling point of the component to be removed that has dissociated from the copper salt. In the solvent removal process, the solvent such as toluene (boiling point: about 110°C) used to obtain the C liquid also volatilizes. Since it is desirable that this solvent remains to some extent in the light absorbing composition 20a, it is preferable that the amount of the solvent added and the time of the solvent removal process are determined from this perspective. In addition, o-xylene (boiling point: about 144°C) can also be used instead of toluene to obtain the C liquid. In this case, since the boiling point of o-xylene is higher than that of toluene, the amount added can be reduced to about one-fourth of the amount added of toluene.

[0104] Light-absorbing composition 20a is represented by the formula (a) R 11When the alkyl group of phosphonic acid (alkyl phosphonic acid) is contained, for example, the H solution is further prepared as follows. First, a copper salt such as copper acetate monohydrate is added to a predetermined solvent such as tetrahydrofuran (THF) and stirred to obtain a solution E of the copper salt. In addition, an alkyl phosphonic acid is added to a predetermined solvent such as THF and stirred to prepare the F solution. When multiple types of phosphonic acid are used as the alkyl phosphonic acid, each alkyl phosphonic acid may be added to a predetermined solvent such as THF and stirred to prepare the F solution by mixing multiple preliminary solutions prepared for each type of alkyl phosphonic acid. For example, an alkoxysilane is further added in the preparation of the F solution. While stirring the E solution, the F solution is added to the E solution and stirred for a predetermined time. Next, a predetermined solvent such as toluene is added to this solution and stirred to obtain the G solution. Next, the G solution is subjected to a desolvation treatment for a predetermined time while heating it to obtain the H solution. This removes the solvent such as THF and the components generated by the dissociation of the copper salt such as acetic acid. The temperature to which solution G is heated is determined in the same manner as solution C, and the solvent for obtaining solution G is also determined in the same manner as solution C.

[0105] For example, the light absorbing composition 20a can be prepared by adding an alkoxysilane while mixing the D liquid and the H liquid at a predetermined ratio, and adding a curable resin such as a silicone resin as necessary. In this case, the dialkoxysilane may be added after mixing the D liquid and the H liquid. In the light absorbing composition 20a, the aryl phosphonic acid and the alkyl phosphonic acid may react with a copper component to form a complex. In addition, a part of the added phosphoric acid ester may react with the copper component to similarly form a complex, or a part of the phosphoric acid ester may react with the phosphonic acid or the copper component to form a complex. The light absorbing film 20 formed by curing the light absorbing composition 20a can exhibit the desired light absorbing performance due to the action of each material, especially the copper component such as copper ions.

[0106] The optical filter 1 may have another functional film on one or both of the main surfaces of the light absorbing film 20. The functional film is, for example, an anti-reflection film having an anti-reflection or reflection reducing function. The anti-reflection film may be designed or manufactured to reduce the reflection of light in the visible light range that is expected to be transmitted through the light absorbing film 20. This improves the transmittance of light in the visible light range, and when the optical filter 1 is used in an imaging device, a bright image is easily obtained. The anti-reflection film is obtained by forming a dielectric film with an appropriate thickness on the main surface of the light absorbing film 20. Examples of the dielectric material are SiO2, TiO2, Ti3N4, Al2O3, and MgO. The anti-reflection film may be a single layer film of a dielectric material, or a multilayer film of different types of dielectric material. For example, when the anti-reflection film is formed using a material with a low refractive index, the anti-reflection film can exhibit a good anti-reflection function with a smaller number of layers. For example, when hollow particles or a material containing a sol thereof is encapsulated in a matrix of resin or other material, a film or layer with a low refractive index can be formed as a whole, since the apparent refractive index of the hollow particles is low. Hollow particles made of SiO2 or TiO2 are commercially available. In addition, curable resins or silane compounds that can be cured by the sol-gel method and have a low refractive index are suitable as matrices for anti-reflective coatings.

[0107] The functional film may be a reflective film capable of reflecting a part of light. The reflective film, like the light absorbing film 20, has the function of blocking a part of light. The light absorbing film 20 and the reflective film cooperate to block light of a predetermined wavelength. The reflective film may be formed, for example, as a multilayer film of dielectrics. In this case, the degree of freedom in designing the wavelength characteristics of the reflective film is high, so that the blocking of light can be adjusted more finely. In addition, since a part of the light that should be blocked by the optical filter 1 can be blocked by the reflection function, the absorbance required for the light absorbing film 20 can be reduced. As a result, the thickness of the light absorbing film 20 or the concentration of the light absorbing compound contained in the light absorbing film 20 can be reduced. The reflective film can be formed by forming a dielectric film with an appropriate thickness on the main surface of the light absorbing film 20. Examples of the dielectric material are SiO2, TiO2, Ti3N4, Al2O3, and MgO. The reflective film may be a single layer of dielectrics or a multilayer film of dielectrics.

[0108] The functional film may be formed so as to cover a part of the surface of the frame 10 in addition to the surface of the light absorbing film 20 .

[0109] It is possible to provide an imaging device equipped with the optical filter 1. As shown in Fig. 5, the imaging device 5 includes an imaging element 2, a lens 3, and the optical filter 1. The lens 3 transmits light from a subject and collects the light on the imaging element 2.

[0110] The optical filter 1 is disposed, for example, between the lens 3 and the image sensor 2 in the optical path of light from a subject. The image sensor 2 is disposed, for example, on a circuit board 50. In the image sensor 5, for example, the main surface of the light absorbing film 20 in the optical filter 1 and the light receiving surface of the image sensor 2 are separated from each other and are not in direct contact with each other. This tends to reduce the difficulty of the manufacturing process of the image sensor 5, and it is possible to reduce the number of steps or improve the manufacturing yield of the image sensor 5. EXAMPLES

[0111] The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0112] <Example 1> 4.500g of copper acetate monohydrate was mixed with 240g of tetrahydrofuran (THF) and stirred for 3 hours to obtain a copper acetate solution. Next, 1.646g of Plysurf A208N (Daiichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain A1 solution. 40g of THF was added to 0.706g of phenylphosphonic acid and stirred for 30 minutes to obtain B1α solution. 4.230g of 4-bromophenylphosphonic acid was added to 40g of THF and stirred for 30 minutes to obtain B1β solution. Next, the B1α liquid and the B1β liquid were mixed and stirred for 1 minute, and 8.664 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) and 2.840 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade) were added to this mixture and stirred for another 1 minute to obtain B1 liquid. While stirring the A1 liquid, the B1 liquid was added to the A1 liquid and stirred for 1 minute at room temperature. Next, 100 g of toluene was added to this solution, and the solution was stirred for 1 minute at room temperature to obtain C1 liquid. This C1 liquid was placed in a flask and heated in an oil bath (manufactured by Tokyo Rika Kikai Co., Ltd., model: OSB-2100) while performing a desolvation treatment using a rotary evaporator (manufactured by Tokyo Rika Kikai Co., Ltd., model: N-1110SF). The set temperature of the oil bath was adjusted to 105°C. After that, the D1 liquid after the desolvation treatment was taken out of the flask. In this manner, liquid D1 was obtained, which was a liquid composition containing an aryl phosphonic acid and a copper component.

[0113] 1.800g of copper acetate monohydrate and 100g of THF were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 1.029g of Plysurf A208N, a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain E1 solution. Also, 40g of THF was added to 1.154g of n-butylphosphonic acid and stirred for 30 minutes to obtain F1 solution. While stirring E1 solution, F1 solution was added to E1 solution and stirred at room temperature for 1 minute. Next, 30g of toluene was added to this solution, and stirred at room temperature for 1 minute to obtain G1 solution. This G1 solution was placed in a flask and heated in an oil bath, and a solvent removal treatment was performed using a rotary evaporator. The set temperature of the oil bath was adjusted to 105°C. After that, the H1 solution after the solvent removal treatment was taken out of the flask. In this way, H1 solution, a liquid composition containing n-butylphosphonic acid and a copper component, was obtained.

[0114] Liquid compositions D1 and H1, 8.800 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.090 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 10.840 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 5.660 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 4.896 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain a light absorbing composition J1.

[0115] 0.1 g of a surface antifouling coating agent (manufactured by Daikin Industries, Ltd., product name: Optool DSX, active ingredient concentration: 20% by mass) and 19.9 g of a hydrofluoroether-containing liquid (manufactured by 3M, product name: Novec 7100) were mixed and stirred for 5 minutes to prepare a fluorine treatment agent (active ingredient concentration: 0.1% by mass).

[0116] A borosilicate glass substrate (manufactured by SCHOTT, product name: D263 T eco) with dimensions of 136 mm x 108 mm x 0.70 mm was prepared. The above-mentioned fluorine treatment agent was poured onto one of the main surfaces of the glass substrate. The glass substrate was then left at room temperature for 24 hours to dry the coating of the fluorine treatment agent, and the glass surface was then lightly wiped with a dust-free cloth containing Novec 7100 to remove excess fluorine treatment agent. In this way, a fluorine-treated substrate coated with a fluorine compound was produced.

[0117] Nine types of frames having the dimensions shown in Table 5 were prepared. In Table 5, A, B, a, b, t1, and t2 correspond to the dimensions shown in Figs. 1A and 1B. Frames α-1, α-2, and α-3 were made of MC nylon. The average linear expansion coefficient of MC nylon at 0°C to 60°C is 10.1 x 10 -5 [ / ℃]. MC nylon is a registered trademark. Frames β-1, β-2, and β-3 are made of high-strength nylon. The average linear expansion coefficient of high-strength nylon at 0℃ to 60℃ is 12.5×10 -5 [ / ℃]. Frames γ-1, γ-2, and γ-3 are frames made of PPS. The average linear expansion coefficient of PPS at 0℃ to 60℃ is 4.7×10 -5 Each frame was placed on a fluorine-treated substrate. At this time, a part of the main surface of the fluorine-treated substrate was exposed through the through-hole of the frame.

[0118] The light-absorbing composition J1 liquid was injected into the through-holes of each frame using a dispenser. After that, it was dried in an environment of 45°C for 3 hours, and the temperature of the environment was gradually increased to 85°C for 10 hours to volatilize the solvent contained in the J1 liquid, promoting the reaction of the components contained in the J1 liquid, and the light-absorbing composition was cured. Then, the light-absorbing composition being cured was placed in an environment of 85°C and 85% relative humidity for 8 hours to complete the curing reaction. As a result, the light-absorbing film according to Example 1 was formed so as to block the through-holes of the frame. The thickness of the light-absorbing film was determined in advance so that the optical characteristics such as the transmission spectrum of the light-absorbing film in which the light-absorbing composition was completely cured would be predetermined characteristics, and the injection amount of the light-absorbing composition was controlled so that the light-absorbing film had that thickness. Next, the frame in which the light-absorbing film was formed in the through-hole and the light-absorbing film were slowly peeled off from the fluorine-treated substrate. In this way, an optical filter according to Example 1 was obtained.

[0119] In the optical filter of Example 1, the thickness of the light absorbing film was 207 μm, and t1 and t2 of the frame were 0.5 mm (500 μm) and 0.15 mm (150 μm), respectively, so that the ratios of the thickness of the light absorbing film to t1 and t2 were 0.414 and 1.38, respectively.

[0120] <Example 2> An optical filter according to Example 2 was produced in the same manner as in Example 1, except that, as the light absorbing composition, J2 liquid prepared under the following conditions was used instead of J1 liquid.

[0121] In the optical filter according to Example 2, the thickness of the light absorbing film was 204 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.408 and 1.36, respectively.

[0122] D1 liquid, H1 liquid, 8.800 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.090 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 5.420 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 2.830 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 2.448 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain J2 liquid, which is a light absorbing composition.

[0123] <Example 3> An optical filter according to Example 3 was produced in the same manner as in Example 1, except that, as the light absorbing composition, J3 liquid prepared under the following conditions was used instead of J1 liquid.

[0124] In the optical filter according to Example 3, the thickness of the light absorbing film was 195 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.390 and 1.30, respectively.

[0125] D1 liquid, H1 liquid, 8.800 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.090 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 2.710 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 1.415 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 1.224 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain J3 liquid, which is a light absorbing composition.

[0126] <Example 4> An optical filter according to Example 4 was produced in the same manner as in Example 1, except that, as the light absorbing composition, J4 liquid prepared under the following conditions was used instead of J1 liquid.

[0127] In the optical filter according to Example 4, the thickness of the light absorbing film was 220 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.440 and 1.47, respectively.

[0128] D1 liquid, H1 liquid, 8.800 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.090 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 9.756 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 5.732 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 5.957 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain J4 liquid, which is a light absorbing composition.

[0129] <Example 5> An optical filter according to Example 5 was produced in the same manner as in Example 1, except that, as the light absorbing composition, J5 liquid prepared under the following conditions was used instead of J1 liquid.

[0130] In the optical filter according to Example 5, the thickness of the light absorbing film was 218 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.436 and 1.45, respectively.

[0131] 4.500g of copper acetate monohydrate was mixed with 240g of tetrahydrofuran (THF) and stirred for 3 hours to obtain a copper acetate solution. Next, 6.000g of Plysurf A219B (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain A5 solution. 40g of THF was added to 0.710g of phenylphosphonic acid and stirred for 30 minutes to obtain B5α solution. 4.290g of 4-bromophenylphosphonic acid was added to 40g of THF and stirred for 30 minutes to obtain B5β solution. Next, the B5α liquid and the B5β liquid were mixed and stirred for 1 minute, and 8.664 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) and 2.840 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade) were added to this mixture and stirred for another 1 minute to obtain B5 liquid. While stirring the A5 liquid, the B5 liquid was added to the A5 liquid and stirred for 1 minute at room temperature. Next, 60 g of cyclopentanone was added to this solution, and the solution was stirred for 1 minute at room temperature to obtain C5 liquid. This C5 liquid was placed in a flask and heated in an oil bath (manufactured by Tokyo Rika Kikai Co., Ltd., model: OSB-2100) while performing a desolvation treatment using a rotary evaporator (manufactured by Tokyo Rika Kikai Co., Ltd., model: N-1110SF). The set temperature of the oil bath was adjusted to 105°C. After that, the D5 liquid after the desolvation treatment was taken out of the flask. In this manner, liquid D5, which is a liquid composition containing an aryl phosphonic acid and a copper component, was obtained.

[0132] D5 liquid, 7.040 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.070 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 5.420 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 2.830 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 2.448 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain J5 liquid, which is a light absorbing composition.

[0133] <Example 6> An optical filter according to Example 6 was produced in the same manner as in Example 1, except that, as the light absorbing composition, J6 liquid prepared under the following conditions was used instead of J1 liquid.

[0134] In the optical filter according to Example 6, the thickness of the light absorbing film was 220 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.440 and 1.47, respectively.

[0135] 4.500g of copper acetate monohydrate was mixed with 240g of tetrahydrofuran (THF) and stirred for 3 hours to obtain a copper acetate solution. Next, 3.000g of Plysurf A212C (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain A6 solution. 40g of THF was added to 0.750g of phenylphosphonic acid and stirred for 30 minutes to obtain B6α solution. 4.490g of 4-bromophenylphosphonic acid was added to 40g of THF and stirred for 30 minutes to obtain B6β solution. Next, B6α liquid and B6β liquid were mixed and stirred for 1 minute, and 8.664 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) and 2.840 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade) were added to this mixture and stirred for another 1 minute to obtain B6 liquid. While stirring A6 liquid, B6 liquid was added to A6 liquid and stirred for 1 minute at room temperature. Next, 60 g of cyclopentanone was added to this solution, and stirred for 1 minute at room temperature to obtain C6 liquid. This C6 liquid was placed in a flask and heated in an oil bath (manufactured by Tokyo Rikakikai Co., Ltd., model: OSB-2100) while performing a desolvation treatment using a rotary evaporator (manufactured by Tokyo Rikakikai Co., Ltd., model: N-1110SF). The set temperature of the oil bath was adjusted to 105°C. Then, D6 liquid after the desolvation treatment was taken out of the flask. In this manner, liquid D6, which is a liquid composition containing an aryl phosphonic acid and a copper component, was obtained.

[0136] D6 liquid, 7.040 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), 0.070 g of aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC), 5.420 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 2.830 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade), and 2.448 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were mixed and stirred for 30 minutes to obtain J6 liquid, which is a light absorbing composition.

[0137] <Comparative Example 1> An optical filter according to Comparative Example 1 was produced in the same manner as in Example 1, except that J7 liquid prepared under the following conditions was used as the light absorbing composition instead of J1 liquid.

[0138] In the optical filter according to Comparative Example 1, the thickness of the light absorbing film was 201 μm, and the ratios of the thickness of the light absorbing film to t1 and t2 were 0.402 and 1.34, respectively.

[0139] D1 liquid, H1 liquid, 8,800 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300), and 0.090 g of an aluminum alkoxide compound (manufactured by Shin-Etsu Chemical Co., Ltd., product name: CAT-AC) were added and stirred for 30 minutes to obtain J7 liquid, which is a light absorbing composition.

[0140] Tables 1 and 2 show the compounds and their amounts added when preparing the light-absorbing compositions according to Examples 1 to 6 and Comparative Example 1. As shown in these tables, toluene was used as the solvent in Examples 1 to 4. On the other hand, cyclopentanone was used as the solvent in Examples 5 and 6. When the solvent was changed, it was necessary to prevent the coating liquid from coagulating, so it was necessary to change the type of phosphoric acid ester used as a dispersant depending on the type of solvent. For this reason, in Examples 5 and 6, a phosphoric acid ester different from the phosphoric acid ester used in Examples 1 to 4 was used. It is understood that it is desirable to select a solvent and a phosphoric acid ester corresponding to that solvent depending on the chemical resistance of the frame used in the optical filter.

[0141] Table 3 shows the alkoxysilanes used in preparing the light-absorbing compositions according to Examples 1 to 6 and Comparative Example 1, their total amounts added, the solid contents assumed to be completely hydrolyzed and polycondensed by the alkoxysilanes, and their ratios.

[0142] <Measurement of transmission spectrum and thickness of light absorbing film> The transmission spectrum of the light absorbing film in the optical filters according to Examples 1 to 6 and Comparative Example 1 was measured at an incident angle of 0° using a UV-Visible Near-Infrared Spectrophotometer V-670 manufactured by JASCO Corporation. The thickness of the light absorbing film in each optical filter was measured using a laser displacement meter LK-H008 manufactured by Keyence Corporation. Of the optical filters according to each Example and Comparative Example 1, the thickness of the light absorbing film in the optical filter equipped with the frame α-1 was measured as a representative. The transmission spectra of the optical filters according to Examples 1 to 6 and Comparative Example 1 are shown in FIGS. 6 to 12, respectively. In addition, the transmission characteristics observed from these transmission spectra are shown in Table 4. In addition, the thickness of the light absorbing film in each optical filter is shown in Table 4.

[0143] <Heat cycle test> Five samples were selected for each type of frame for the optical filters according to Examples 1 to 6 and Comparative Example 1. A heat cycle test of 144 cycles was performed on the selected five samples. Each cycle included a period of 30 minutes at 85°C and 30 minutes at -40°C, and the time required for heating and cooling in each cycle was 5 minutes. A thermal shock tester TSA-103ES manufactured by ESPEC was used for the heat cycle test. If only one of the five samples had cracks or peeling, it was evaluated as "B", and if two or more samples had cracks or peeling, it was evaluated as "C". If none of the five samples had cracks or peeling, it was evaluated as "A". The results are shown in Table 6.

[0144] <Young's modulus and hardness> Using Nano Indenter XP manufactured by MTS Systems, the surface of the light absorbing film of each optical filter was measured according to the nanoindentation method (continuous stiffness measurement method). A triangular pyramidal indenter made of diamond was used as the indenter, and the measurement was performed at room temperature of about 23°C and in the atmosphere. The hardness values ​​in the indentation depth range of 5 to 10 μm in the hardness-indentation depth diagram obtained by this measurement were averaged to determine the average hardness of the surface of each optical filter. In addition, the Young's modulus values ​​in the indentation depth range of 5 to 10 μm in the Young's modulus-indentation depth diagram obtained by this measurement method were averaged to determine the average Young's modulus of each light absorbing film. In addition, considering that the main component of the light absorbing film is silicone resin, the Poisson's ratio of the light absorbing film was set to 0.4. The results are shown in Table 4.

[0145] <Glass transition temperature> Dynamic viscoelasticity measurement (DMA) by a forced vibration tensile method was carried out on the light absorbing film according to Example 1. This measurement was carried out using a Rheovibron DDV-01FP manufactured by Orientec Co., Ltd. under the following conditions. Test method: Forced vibration tension method (temperature sweep) Measurement temperature: -40℃~95℃ Heating rate: 2℃ / min Excitation frequency: 1Hz Chuck distance: 30mm Excitation amplitude: 10μm Preload: 4.9mN

[0146] From the results of DMA, the temperature dependence of the storage modulus E' and the loss modulus E" of the light absorbing film according to Example 1 was obtained. The results are shown in FIG. 13. The temperature at which the storage modulus E' decreased was 50.8°C, which indicates the temperature at which the hardness began to decrease. The loss modulus E" indicates the energy loss caused by the micro-Brownian motion accompanying the transition, and its peak temperature was 55.4°C. From these results, it was found that the glass transition point of the light absorbing film according to Example 1 was in the range of 50 to 60°C. It is understood that the presence of the glass transition point in such a temperature range is effective because it can prevent film cracking due to thermal expansion or thermal contraction when the optical filter is exposed to high temperatures or subjected to thermal cycles due to the increased flexibility accompanying the state change of the light absorbing film. The glass transition point of the light absorbing film is preferably in the range of room temperature to 80°C, more preferably in the range of 35°C to 70°C, and further preferably in the range of 40°C to 60°C.

[0147] As shown in Table 4, the average Young's modulus of the light-absorbing film in the optical filters according to Examples 1 to 6 was 0.56 GPa to 2.0 GPa. On the other hand, the average Young's modulus of the light-absorbing film in the optical filter according to Comparative Example 1 was 2.6 GPa. These results suggest that the light-absorbing films of the optical filters according to Examples 1 to 6 have the desired flexibility, but the flexibility of the light-absorbing film of the optical filter according to Comparative Example 1 is inferior. Comparing Examples 1 to 6 with Comparative Example 1, it is understood that the desired flexibility is easily imparted by adding a specific alkoxysilane to the light-absorbing composition. For example, the flexibility of the light-absorbing film is likely to increase with an increase in the amount of DMDES added. The amount of DMDES added is preferably 10% or more of the total solid content of the alkoxysilane on a mass basis, converted into solid content, and it is understood that the flexibility of the light-absorbing film can be improved by increasing the ratio in the range of 10 to 24%. On the other hand, in the light-absorbing film in each optical filter, the amount of TEOS added is about 20% of the total solid content of the alkoxysilane on a mass basis, converted into solid content. TEOS gives strength to the light absorbing film, but an increase in the ratio of TEOS in the light absorbing film may cause breakage or cracking during or after the light absorbing film is produced. For this reason, the amount of TEOS added is desirably 50% or less, and more desirably 35% or less, of the total solid content of the alkoxysilane, calculated as solid content, by mass. It is also possible to improve flexibility by increasing the amount of phosphoric acid ester added, which is a component other than the silane monomer. The content of phosphoric acid ester in the light absorbing film of the optical filters according to Examples 5 and 6 is higher than the content of phosphoric acid ester in the light absorbing film of the optical filters according to Examples 1 to 4. It is understood that this is one of the reasons for the decrease in the Young's modulus of the light absorbing film.

[0148] table 6As shown in the figure, peeling or cracking of the light absorbing film was confirmed in some samples. The optical filters according to Examples 1 to 6 showed good results in the heat cycle test. On the other hand, problems such as peeling or cracking of the light absorbing film occurred in the heat cycle test of the optical filter according to Comparative Example 1. Since the light absorbing composition for the light absorbing film of the optical filter according to Examples 1 to 6 contained DMDES in which two organic functional groups are bonded to one silicon atom, it is presumed that the thermal expansion coefficient of the light absorbing film is relatively large. However, since it has flexibility that exhibits durability against distortion based on the difference between the thermal expansion coefficient of the frame and the thermal expansion coefficient of the light absorbing film, it is considered that good results were shown in the heat cycle test. On the other hand, although Comparative Example 1 is presumed to have a higher Young's modulus and greater rigidity, it is considered that its durability against distortion caused by temperature changes was insufficient.

[0149] It is believed that cracking and peeling of the light-absorbing film can be prevented by bringing the thermal expansion coefficient of the frame and the thermal expansion coefficient of the light-absorbing film closer together. However, when the periphery of the light-absorbing film is completely fixed to the frame, it was found that it is necessary to adjust the properties of the light-absorbing film, rather than adjusting the difference between the thermal expansion coefficients of the frame and the light-absorbing film. This is suggested by the fact that in a heat cycle test of an optical filter using three types of frames with different expansion coefficients, the effect of the type of frame on the test results was hardly apparent.

[0150] According to the results of the optical filter according to the embodiment, it is understood that controlling the average Young's modulus of the light absorbing film to 0.56 GPa to 2.0 GPa is particularly effective in terms of realizing high resistance to temperature changes. In addition, the average linear expansion coefficient at 0°C to 60°C is 4.7×10 -5 ~12.5×10 -5 It will be understood that using a frame made of a material having a high thermal conductivity (Tc) is particularly important in obtaining an optical filter having high resistance to temperature changes.

[0151] [Table 1]

[0152]

Table 2

[0153]

Table 3

[0154]

Table 4

[0155]

Table 5

[0156]

Table 6

Claims

1. A frame having a through hole; a light absorbing film that is disposed so as to cover the through hole and contains a light absorbing compound; an average value of Young's modulus of said light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; The light absorbing film has a second main surface formed to be substantially flush with one end of the frame in a thickness direction of the light absorbing film. Optical filters.

2. The average linear expansion coefficient of the material constituting the frame at 0°C to 60°C is 0.2 x 10 -5 [ / ℃] ~ 25 x 10 -5 2. The optical filter according to claim 1, wherein the temperature is 100° C. or more.

3. The optical filter according to claim 1 , wherein the frame is in contact with the through hole and has a first surface formed along a plane parallel to a main surface of the light absorbing film.

4. 4. The optical filter according to claim 1, wherein the light absorbing film has a thickness smaller than a dimension of the frame in a thickness direction of the light absorbing film.

5. 5. The optical filter according to claim 1, wherein the light absorbing film has a first main surface formed between one end and the other end of the frame in a thickness direction of the light absorbing film.

6. 6. The optical filter according to claim 1, wherein the frame includes at least one of a convex portion and a concave portion therein.

7. The optical filter according to claim 6 , wherein the light absorbing film is in contact with at least a part of the convex portion or at least a part of the concave portion in a thickness direction of the light absorbing film.

8. The light absorbing film is formed on at least one of the surfaces constituting the protrusion or the recess inside the through hole.

8. The optical filter according to claim 6, wherein the first surface is in contact with at least two surfaces.

9. A frame having a through hole; a light absorbing film that is disposed so as to cover the through hole and contains a light absorbing compound; an average value of Young's modulus of said light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; the frame is a flat plate having a first end surface and a second end surface as main surfaces, and has a through hole drilled in a thickness direction of the frame; the frame includes a protrusion protruding toward an inside of the through hole, the protrusion includes a first surface that is substantially parallel to one of the first end surface and the second end surface, the light absorbing film has a first major surface and a second major surface; the second main surface is flatly connected to one of the first end surface and the second end surface, When a length in a thickness direction of the frame between the first surface and any one of the first end surface and the second end surface that is flatly connected to the second main surface of the light absorbing film is t2, a ratio of the thickness of the light absorbing film to the t2 is greater than 1 and less than or equal to 2. Optical filters.

10. An optical filter for an imaging device, comprising: the imaging device includes an imaging element, a lens that transmits light from a subject and focuses the light on the imaging element, and an optical filter for the imaging device that absorbs light of a certain wavelength directed toward the imaging element; The optical filter for the imaging device is A frame having a through hole; a light absorbing film that is disposed so as to cover the through hole and contains a light absorbing compound; The average Young's modulus of the light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; Optical filters for imaging devices.

11. The optical filter according to any one of claims 1 to 10, wherein the light absorbing film has a transmission spectrum that satisfies the following requirements (I), (II), (III), (IV), (V), (VI), and (VII): (I) There is a first cutoff wavelength showing a transmittance of 50% in the wavelength range of 380 nm to 440 nm. (II) There is a second cutoff wavelength showing a transmittance of 50% in the wavelength range of 600 nm to 720 nm. (III) The maximum transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (IV) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (V) The maximum transmittance in the wavelength range of 750 nm to 1000 nm is 5% or less. (VI) The maximum transmittance in the wavelength range of 800 nm to 950 nm is 4% or less. (VII) The transmittance at a wavelength of 1,100 nm is 20% or less.

12. The optical filter according to any one of claims 1 to 11, wherein the light absorbing film has a thickness of 1 µm to 1000 µm.

13. An imaging element; a lens that transmits light from a subject and collects the light on the image sensor; an optical filter including a frame having a through hole and a light absorbing film that is disposed so as to cover the through hole and contains a light absorbing compound; The average Young's modulus of the light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; Imaging device.

14. A method for producing an optical filter for an imaging device, comprising the steps of: the imaging device includes an imaging element, a lens that transmits light from a subject and focuses the light on the imaging element, and an optical filter for the imaging device that absorbs light of a certain wavelength directed toward the imaging element; supplying a light absorbing composition containing a light absorbing compound to fill a through hole of a frame having a through hole; and curing the light absorbing composition to form a light absorbing film. The average Young's modulus of the light-absorbing film measured according to a continuous stiffness measurement method is 2.5 GPa or less; A method for manufacturing an optical filter for an imaging device.

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