Optical filter and method for manufacturing optical filter

Abstract

The invention provides an optical filter and a method for manufacturing the optical filter. The optical filter is provided with a light-absorbing layer formed by curing a light-absorbing composition. The light-absorbing composition contains a light absorber, a curable resin, and an alkoxysilane. The alkoxy silane contains a dialkoxy silane. Since the alkoxysilane of the light-absorbing composition contains dialkoxysilane, a firm skeleton having a siloxane bond is formed in the light-absorbing layer, and desired flexibility is easily imparted to the light-absorbing layer by an organic functional group of the dialkoxysilane.

Description

[0001] This application is a divisional application, and the Chinese national application number of the application it is directed to is 202080027825.6, the filing date is April 17, 2020, and the invention title is "Light Absorbing Composition and Filter". Technical Field

[0002] The present invention relates to a light absorbing composition and a filter. Background Art

[0003] 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 filters are arranged in front of the solid-state imaging element in order to obtain an image with good color reproducibility. Generally, a solid-state imaging element has spectral sensitivity in a wide wavelength range from the ultraviolet region to the infrared region. On the other hand, the visual sensitivity of a human being exists only in the visible light region. Therefore, in order to make the spectral sensitivity of the solid-state imaging element in the imaging device close to the visual sensitivity of a human being, a technique of arranging a filter that shields a part of light in the infrared or ultraviolet region in front of the solid-state imaging element is known.

[0004] Conventionally, as such a filter, a filter that shields infrared rays or ultraviolet rays by light reflection based on a dielectric multilayer film is common. On the other hand, in recent years, a filter having a film containing a light absorber has attracted attention. The transmittance characteristics of a filter having a film containing a light absorber are not easily affected by the incident angle. Therefore, even when light is incident obliquely on the filter in an imaging device, a good image with little change in hue can be obtained. In addition, a light absorption type filter that does not use a light reflection film can suppress the occurrence of ghosts or light spots due to multiple reflections based on the light reflection film, and thus it is easy to obtain a good image in a backlight state or when shooting at night. Furthermore, a filter having a film containing a light absorber is also advantageous in terms of miniaturization and thinning of the imaging device.

[0005] For example, Patent Document 1 describes a filter having a UV-IR absorption layer capable of absorbing infrared rays and ultraviolet rays. The UV-IR absorption layer contains a UV-IR absorber formed from phosphonic acid and copper ions. In addition, Patent Document 2 describes an infrared cut-off filter having an organic dye layer and a copper phosphonate layer.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent No. 6232161 Gazette

[0009] Patent Document 2: Japanese Patent Publication No. 6281023 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] In the technologies described in Patent Documents 1 and 2, there is still room for further research in terms of imparting desired flexibility to the light absorption layer in the filter. Therefore, the present invention provides a light-absorbing composition that is advantageous in terms of imparting desired flexibility to the light absorption layer in the filter. In addition, the present invention provides a filter having a light absorption layer with desired flexibility.

[0012] Means for Solving the Problems

[0013] The present invention provides a light-absorbing composition containing:

[0014] a light absorber;

[0015] a curable resin; and

[0016] an alkoxysilane,

[0017] The above alkoxysilane includes dialkoxysilane.

[0018] In addition, the present invention provides a filter having a light absorption layer formed of a cured product of the above light-absorbing composition.

[0019] In addition, the present invention provides a filter,

[0020] which has a light absorption layer containing a hydrolysis condensate of a light absorber and an alkoxysilane,

[0021] When measuring one main surface of the above light absorption layer using a nanoindentation instrument according to the nanoindentation method (continuous stiffness measurement method), the average value of the Young's modulus is 2.00 GPa or less, and the average value of the hardness is 0.06 GPa or less.

[0022] Advantages of the Invention

[0023] The above light-absorbing composition is advantageous in terms of imparting desired flexibility to the light absorption layer in the filter. In addition, the light absorption layer of the above filter has desired flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a cross-sectional view showing an example of the filter of the present invention.

[0025] Figure 2 is a cross-sectional view showing another example of the filter of the present invention.

[0026] Figure 3 is the transmittance spectrum of the filter of Example 1.

[0027] Figure 4 is the transmittance spectrum of the filter of Example 2.

[0028] Figure 5 is the transmittance spectrum of the filter of Example 3.

[0029] Figure 6 is the transmittance spectrum of the filter of Comparative Example 1.

[0030] Figure 7 is the transmittance spectrum of the filter of Example 1 before and after the moisture resistance test.

[0031] Figure 8 is the transmittance spectrum of the filter of Example 2 before and after the moisture resistance test. Detailed Embodiments

[0032] As a filter having a light absorption layer, there are known a filter of a type composed of a light absorption layer alone, and a filter of a type in which a light absorption layer is formed on a substrate such as glass or resin. In the case of the former type of filter, if the property of the light absorption layer is hard or has a high hardness such as glass, the flexibility of the light absorption layer is likely to decrease. For example, when it is desired to bend or mechanically deform the filter, cracks or wrinkles may occur in the light absorption layer. In the case of the latter type of filter in which a light absorption layer is formed on a flexible substrate such as resin, when it is desired to similarly deform the filter, cracks or wrinkles may also occur in the light absorption layer. Therefore, it is necessary to be very careful when handling these filters.

[0033] When cutting a filter formed in a large area in the manufacturing process to produce a chip, equipment for cutting glass such as a large slicing machine is required. In addition, when cutting the filter, it is sometimes necessary to study problems associated with the properties of the glass material, namely cracks or chipping. Further, when it is desired to bond the filter to a sensor such as a solid-state imaging device, if the filter is hard, it may be difficult to dispose of and bond the filter due to the inherent warping (non-uniform flatness) of the filter. To facilitate such processing, it is advantageous to improve the flexibility of the light absorption layer.

[0034] Therefore, the present inventors repeatedly conducted day and night research on techniques advantageous in terms of imparting the desired flexibility to the light absorption layer, and developed the light-absorbing composition and filter of the present invention.

[0035] Embodiments of the present invention will be described below. It should be noted that the following description relates to an example of the present invention, and the present invention is not limited by these examples.

[0036] The light-absorbing composition of the present invention contains a light absorber, a curable resin, and an alkoxysilane. In addition, the alkoxysilane contains a dialkoxysilane.

[0037] When forming a light-absorbing layer using the light-absorbing composition, silanol groups are generated by hydrolysis of the alkoxysilane. The resulting compound derived from the alkoxysilane having silanol groups further reacts and undergoes polycondensation, thereby forming a strong skeleton having a siloxane bond (-Si-O-Si-). If the organic component (organic functional group) in the substance having this skeleton is small, it is difficult for the formed light-absorbing layer to have the desired flexibility. In this case, when a strong pressure is locally applied to the light-absorbing layer, the skeleton having a siloxane bond is likely to break. However, since the alkoxysilane of the light-absorbing composition contains a dialkoxysilane, while forming a strong skeleton having a siloxane bond in the light-absorbing layer, the desired flexibility can be easily imparted to the light-absorbing layer by the organic functional groups possessed by the dialkoxysilane. Therefore, for example, when cutting the light-absorbing layer formed using the light-absorbing composition, cracks and chipping are not easily generated. In addition, even when the light-absorbing layer formed using the light-absorbing composition is bent, the light-absorbing layer is not easily broken.

[0038] For example, it is contemplated to provide a filter in which a light-absorbing composition is coated on a solid-state imaging element such as a CCD and a CMOS or an optical component and integrated with the imaging element or the optical component. When the filter integrated with the imaging element or the optical component is placed in a specific thermal cycle environment, thermal expansion and thermal contraction may occur. The light-absorbing layer formed using the light-absorbing composition easily has the desired flexibility and easily deforms following thermal expansion and thermal contraction. Therefore, breakage and damage of the light-absorbing layer are easily suppressed.

[0039] In addition, regarding a filter having high flexibility, after being fabricated into a filter having a flat surface, when assembled into an optical system, it may be bent along a curved configuration surface to form a curved surface. By making the main surface of the filter a curved surface, it is also possible to cope with the design of a special imaging device premised on a complex configuration of a sensor.

[0040] The dialkoxysilane is not limited to a specific dialkoxysilane. The dialkoxysilane has, for example, a hydrocarbon group having 1 to 6 carbon atoms bonded to a silicon atom. The alkoxysilane may also have a halogenated hydrocarbon group in which at least one hydrogen atom of the hydrocarbon group having 1 to 6 carbon atoms bonded to the silicon atom is substituted by a halogen atom. In this case, it is easier to further impart the desired flexibility to the light-absorbing layer formed using the light-absorbing composition.

[0041] The dialkoxysilane can be, for example, an alkoxysilane represented by the following formula (b). In this case, it is easier to more reliably impart the desired flexibility to the light absorption layer formed using the light-absorbing composition.

[0042] (R2)2-Si-(OR3)2(b)

[0043] [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.]

[0044] The dialkoxysilane can be, for example, dimethyldiethoxysilane, dimethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, or 3-glycidoxypropylmethyldiethoxysilane.

[0045] In the light-absorbing composition, the alkoxysilane can further contain at least one of a tetraalkoxysilane and a trialkoxysilane. Thereby, in the light absorption layer formed using the light-absorbing composition, it is easy to form a dense structure by using siloxane bonds.

[0046] In the light-absorbing composition, the alkoxysilane can further contain a tetraalkoxysilane and a trialkoxysilane. Thereby, it is easier to more reliably form a dense structure by using siloxane bonds in the light absorption layer formed using the light-absorbing composition.

[0047] In the light-absorbing composition, at least one of the tetraalkoxysilane and the trialkoxysilane is not limited to a specific alkoxysilane. For example, in the light-absorbing composition, the alkoxysilane is selected from the group consisting of tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, hexyltriethoxysilane, hexyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-isocyanatopropyltrimethoxysilane.

[0048] The content of the dialkoxysilane in the alkoxysilane is not limited to a specific value. Regarding the content of the dialkoxysilane in the alkoxysilane, for example, when the alkoxysilane is converted into a completely hydrolyzed condensate, it is 15 to 48% by mass. Thereby, it is easier to more reliably impart the desired flexibility to the light absorption layer formed using the light-absorbing composition.

[0049] Regarding the content of dialkoxysilane in alkoxysilane, it is preferable that the alkoxysilane is converted into a completely hydrolyzed condensate and is 15 to 20% by mass. Thus, the light absorption layer formed using the light-absorbing composition is likely to exhibit high moisture resistance. The reason is that a dense structure is formed through siloxane bonds, and the light absorber is not likely to aggregate in a high-humidity environment.

[0050] The light absorber is not limited to a specific light absorber as long as it can absorb light of a specific wavelength. The light absorber can be formed, for example, from a phosphonic acid represented by the following formula (a) and copper ions.

[0051] [Chemical formula 1]

[0052]

[0053] [In the formula, R 11 is an alkyl group, an aryl group, a nitroaryl group, a hydroxyaryl group, or a haloaryl group in which at least one hydrogen atom in the aryl group is substituted by a halogen atom.]

[0054] In the light-absorbing composition, for example, the phosphonic acid represented by the formula (a) coordinates on copper ions to form a light absorber. In addition, for example, fine particles containing at least the light absorber are formed in the light-absorbing composition. In this case, due to the action of alkoxysilane, the fine particles do not aggregate but are dispersed in the light-absorbing composition. 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 for miniaturizing the fine particles is required, and the structure of the fine particles containing at least the light absorber is less likely to be damaged. In addition, in the light-absorbing composition, the fine particles are well dispersed. In addition, if the average particle diameter of the fine particles is 200 nm or less, the influence caused by Mie scattering can be reduced, the transmittance of visible light in the filter can be increased, and the reduction of characteristics such as the contrast and haze of the image captured by the imaging device can be suppressed. The average particle diameter of the fine particles is preferably 100 nm or less. In this case, the influence caused by Rayleigh scattering is reduced, and thus the transparency of the filter made of the light-absorbing composition 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 of the filter made of the light-absorbing composition to visible light is particularly high. It should be noted that the average particle diameter of the fine particles can be measured by the dynamic light scattering method.

[0055] As a dispersant for a light absorber, a phosphate ester is sometimes used. Accordingly, the light-absorbing composition may also contain a phosphate ester. On the other hand, in a light-absorbing layer formed using the light-absorbing composition, a compound derived from an alkoxysilane can appropriately disperse the light absorber while imparting high moisture resistance to the light-absorbing layer as compared with the phosphate ester. Therefore, by including an alkoxysilane in the light-absorbing composition, the amount of the phosphate ester used can be reduced. In the formation of the light-absorbing layer, the alkoxysilane present around the light absorber reacts with a dialkoxysilane, and the light-absorbing layer is easily made homogeneous and has high denseness. It should be noted that the light-absorbing composition may not contain a phosphate ester.

[0056] The phosphate ester is, for example, a phosphate ester having a polyoxyalkylene group. The phosphate ester having a polyoxyalkylene group is not limited to a specific phosphate ester. Examples of the phosphate ester having a polyoxyalkylene group include 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 them are products manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. In addition, the phosphate ester may 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 them are products manufactured by Nikkol Chemicals Co., Ltd.

[0057] In the light-absorbing composition, the curable resin is not limited to a specific resin. The curable resin is, for example, a silicone resin. A silicone resin is a compound having a siloxane bond in its structure. In this case, since the hydrolysis condensate of the alkoxysilane also has a siloxane bond, the hydrolysis condensate of the alkoxysilane has good compatibility with the curable resin in the light-absorbing layer formed using the light-absorbing composition.

[0058] The resin is preferably a silicone resin containing aryl groups such as phenyl groups. If the resin contained in the optical filter is rigid, cracks are likely to occur due to curing shrinkage during the manufacturing process of the optical filter as the thickness of the layer containing the resin increases. If the resin is a silicone resin containing aryl groups, the layer formed from the light-absorbing composition is likely to have good crack resistance. In addition, the silicone resin containing aryl groups has high compatibility with the phosphonic acid represented by formula (a), and the light absorber is not likely to agglomerate. Specific examples of the silicone resin used as the matrix resin include KR-255, KR-300, KR-2621-1, KR-211, KR-311, KR-216, KR-212, KR-251, and KR-5230. They are all silicone resins manufactured by Shin-Etsu Chemical Co., Ltd.

[0059] Taking the case where the light absorber is formed from the above-mentioned phosphonic acid and copper ions as an example, an example of the preparation method of the light-absorbing composition will be described.

[0060] For example, the light-absorbing composition contains R in formula (a) 11In the case of a phosphonic acid that is an aryl, nitroaryl, hydroxyaryl, or haloaryl (aryl-based phosphonic acid), Solution D is prepared as follows. A copper salt such as copper(II) acetate monohydrate is added to a specified solvent such as tetrahydrofuran (THF) and stirred to prepare Solution A, which is a solution of the copper salt. Next, the aryl-based phosphonic acid is added to a specified solvent such as THF and stirred to prepare Solution B. When two or more aryl-based phosphonic acids are used as the phosphonic acid represented by formula (a), each aryl-based phosphonic acid can be added to a specified solvent such as THF, followed by stirring, and two or more preliminary solutions prepared for each type of aryl-based phosphonic acid can be mixed to prepare Solution B. For example, an alkoxysilane is added during the preparation of Solution B. While stirring Solution A, Solution B is added to Solution A and stirred for a specified time. Next, a specified solvent such as toluene is added to this solution and stirred to obtain Solution C. Then, while heating Solution C, a solvent removal treatment is performed for a specified time to obtain Solution D. Thereby, solvents such as THF and components generated by the dissociation of the copper salt such as acetic acid (boiling point: about 118°C) are removed, and a light absorber is formed using the phosphonic acid represented by formula (a) and copper ions. The temperature for heating Solution C is determined based on the boiling point of the component to be removed that is dissociated from the copper salt. It should be noted that in the solvent removal treatment, solvents such as toluene (boiling point: about 110°C) used to obtain Solution C also volatilize. Since this solvent preferably remains in the light-absorbing composition to a certain extent, the addition amount of the solvent and the time of the solvent removal treatment can be specified from this aspect. It should be noted that o-xylene (boiling point: about 144°C) can be used instead of toluene to obtain Solution C. In this case, since the boiling point of o-xylene is higher than that of toluene, the addition amount can be reduced to about one-fourth of the addition amount of toluene.

[0061] The light-absorbing composition contains R in formula (a) 11In the case of phosphonic acid having an alkyl group (alkyl phosphonic acid), for example, the H solution can be further prepared as follows. First, a copper salt such as copper acetate monohydrate is added to a specified solvent such as tetrahydrofuran (THF) and stirred to obtain the E solution which is a solution of the copper salt. In addition, the alkyl phosphonic acid is added to a specified solvent such as THF and stirred to prepare the F solution. When two or more phosphonic acids are used as the alkyl phosphonic acid, each alkyl phosphonic acid can be added to a specified solvent such as THF, and then stirred, and two or more preliminary solutions prepared according to each type of alkyl phosphonic acid are mixed to prepare the F solution. For example, 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 specified time. Then, a specified solvent such as toluene is added to this solution and stirred to obtain the G solution. Then, while heating the G solution, a solvent removal treatment is performed for a specified time to obtain the H solution. Thereby, solvents such as THF and components generated by the dissociation of copper salts such as acetic acid are removed. The temperature for heating the G solution is determined in the same manner as that for the C solution, and the solvent used to obtain the G solution is also determined in the same manner as that for the C solution.

[0062] For example, the D solution and the H solution can be mixed in a specified ratio, and alkoxysilane is added, and a curable resin such as an organosilicon resin is added as needed, thereby preparing a light-absorbing composition. In this case, the dialkoxysilane can be added after the mixing of the D solution and the H solution.

[0063] As Figure 1 shown, the optical filter 1a includes a light-absorbing layer 10. The light-absorbing layer 10 contains a light absorber and a hydrolytic condensate of alkoxysilane. The light-absorbing layer 10 is characterized by its soft property. For example, when one main surface 10a of the light-absorbing layer 10 is measured by a nanoindentation instrument according to the nanoindentation method (continuous stiffness measurement method), the average value of the Young's modulus is 2.00 GPa or less. The average value of the Young's modulus can be, for example, 0.10 to 2.00 GPa. In addition, the average value of the hardness is 0.06 GPa or less. The average value of the hardness can be 0.005 to 0.06 GPa. In this way, the light-absorbing layer 10 includes a skeleton having a siloxane bond through the hydrolytic condensate of alkoxysilane and has the desired softness. For the detailed content of the nanoindentation method (continuous stiffness measurement method), reference can be made to International Publication No. 2019 / 044758 and Japanese Patent Laid-Open No. 2015-174270.

[0064] The hydrolytic condensate of alkoxysilane contained in the light-absorbing layer 10 includes, for example, a hydrolytic condensate of dialkoxysilane. Thereby, the light-absorbing layer 10 has the desired softness.

[0065] From other aspects, the light absorption layer 10 can be formed, for example, from a cured product of the above-described light-absorbing composition. In this case, the light absorption layer 10 easily has the desired flexibility.

[0066] When a humidity resistance test is performed in which the environment of the optical filter 1a is maintained at a temperature of 85°C and a relative humidity of 85% for 1000 hours, the optical filter 1a satisfies the following conditions, for example. In this case, the optical filter 1a exhibits good humidity resistance. Note that, for each parameter, the "change amount" refers to the absolute value of the difference between the parameter values before and after the humidity resistance test. The "change amount of the average transmittance" represents the absolute value of the difference between the average value of the transmittances before the humidity resistance test and the average value of the transmittances after the humidity resistance test in a specific wavelength range. The "change amount of the maximum transmittance" represents the absolute value of the difference between the maximum value of the transmittances before the humidity resistance test and the maximum value of the transmittances after the humidity resistance test in a specific wavelength range. In addition, the unit of the change amount of the transmittance-related parameter expressed as a percentage is represented as "percentage point".

[0067] (i) The change amount ΔT of the average transmittance in the wavelength range of 450 to 600 nm 450-600 is 3 percentage points or less. ΔT 450-600 is preferably 1 percentage point or less, more preferably 0.5 percentage point or less.

[0068] (ii) The change amount Δλuvc of the UV cut-off wavelength is 5 nm or less, and the change amount Δλirc of the IR cut-off wavelength is 5 nm or less. Note that the UV cut-off wavelength is the wavelength at which the transmittance reaches 50% in the wavelength range of 350 nm to 450 nm. The IR cut-off wavelength is the wavelength at which the transmittance reaches 50% in the wavelength range of 600 nm to 800 nm.

[0069] (iii) The change amount Δλirc-uvc of the value obtained by subtracting the UV cut-off wavelength from the IR cut-off wavelength is 10 nm or less.

[0070] (iv) The change amount ΔT of the maximum transmittance in the wavelength range of 300 to 350 nm max300-350 is 1 percentage point or less. ΔT max300-350 is preferably 0.5 percentage point or less.

[0071] (v) The change amount ΔT of the maximum transmittance in the wavelength range of 300 to 360 nm max300-360 is 1 percentage point or less. ΔT max300-360 is preferably 0.5 percentage point or less.

[0072] (vi) The change amount ΔT of the average transmittance in the wavelength range of 700 to 750 nm AVE700-750 is 3 percentage points or less. ΔT AVE700-750 is preferably 1 percentage point or less.

[0073] (vii) The change amount ΔT of the maximum transmittance in the wavelength range of 750 to 1080 nm max750-1080 is 3 percentage points or less. ΔT max750-1080 is preferably 1 percentage point or less.

[0074] (viii) The change amount ΔT of the maximum transmittance in the wavelength range of 800 to 950 nm max800-950 , the change amount ΔT of the maximum transmittance in the wavelength range of 800 to 1000 nm max800-1000 , the change amount ΔT of the maximum transmittance in the wavelength range of 800 to 1050 nm max800-1050 , the change amount ΔT of the maximum transmittance in the wavelength range of 800 to 1100 nm max800-1100 , the change amount ΔT of the maximum transmittance in the wavelength range of 800 to 1150 nm max800-1150 , and the change amount ΔT of the maximum transmittance in the wavelength range of 800 to 1200 nm max800-1200 are each 3 percentage points or less. ΔT max800-950 , ΔT max800-1000 , ΔT max800-1050 , ΔT max800-1100 , ΔT max800-1150 , and ΔT max800-1200 are each preferably 1 percentage point or less.

[0075] As Figure 1 shown, the filter 1a is constituted by, for example, a single light absorption layer 10. In this case, the filter 1a is used separately from the imaging element or the optical component, for example. The filter 1a can also be joined to the imaging element and the optical component. On the other hand, the above light-absorbing composition can be coated on the imaging element or the optical component and the light-absorbing composition can be cured to thereby constitute the filter 1a.

[0076] The filter 1a is produced, for example, by peeling the light absorption layer 10 formed on the substrate from the substrate. In this case, the material of the substrate can be glass, can be resin, or can be metal. Surface treatment such as coating with a fluorine-containing compound can be performed on the surface of the substrate.

[0077] The filter 1a can be changed to the filter 1b as Figure 2 shown, for example. Except in the case of special description, the filter 1b is constituted in the same manner as the filter 1a. The same reference numerals are given to the constituent elements of the filter 1b that are the same as or corresponding to the constituent elements of the filter 1a, and the detailed description thereof is omitted. As long as there is no technical contradiction, the description of the filter 1a also applies to the filter 1b.

[0078] As Figure 2As shown, the optical filter 1b includes a light absorption layer 10 and a transparent dielectric substrate 20. The light absorption layer 10 is formed parallel to one main surface of the transparent dielectric substrate 20. The light absorption layer 10 can be in contact with one main surface of the transparent dielectric substrate 20, for example. In this case, the above light-absorbing composition is coated on one main surface of the transparent dielectric substrate 20 and the light-absorbing composition is cured to form the light absorption layer 10.

[0079] The type of the transparent dielectric substrate 20 is not limited to a specific type. The transparent dielectric substrate 20 can have an absorption ability in the infrared region. The transparent dielectric substrate 20 can have an average spectral transmittance of 90% or more, for example, in a wavelength range of 350 nm to 900 nm. The material of the transparent dielectric substrate 20 is not limited to a specific material and is, for example, a specific glass or resin. When the material of the transparent dielectric substrate 20 is glass, the transparent dielectric substrate 20 is, for example, a transparent glass or an infrared cut-off glass made of a silicate glass such as soda-lime glass and borosilicate glass. The infrared cut-off glass is, for example, a phosphate glass or a fluorophosphate glass containing CuO.

[0080] When the material of the transparent dielectric substrate 20 is resin, the resin is, for example, a cyclic olefin resin such as a norbornene-based resin, a polyarylate resin, an acrylic resin, a modified acrylic resin, a polyimide resin, a polyetherimide resin, a polysulfone resin, a polyethersulfone resin, a polycarbonate resin, or a silicone resin.

[0081] The optical filters 1a and 1b can be modified respectively in such a way as to further include other functional films such as an infrared reflection film.

[0082] Examples

[0083] The present invention will be described in more detail by way of examples. It should be noted that the present invention is not limited to the following examples.

[0084] <Example 1>

[0085] (Preparation of Copper Arylphosphonate)

[0086] 4.500 g of copper(II) acetate monohydrate was mixed with 240 g of tetrahydrofuran (THF) and stirred for 3 hours to obtain a copper(II) acetate solution. Subsequently, 1.646 g of Plysurf A208N (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which is a phosphoric acid ester compound, was added to the obtained copper(II) acetate solution and stirred for 30 minutes to obtain Solution A. 40 g of THF was added to 0.706 g of phenylphosphonic acid and stirred for 30 minutes to obtain Solution B-1. 40 g of THF was added to 4.230 g of 4-bromophenylphosphonic acid and stirred for 30 minutes to obtain Solution B-2. Subsequently, Solution B-1 and Solution B-2 were mixed and stirred for 1 minute. Then, 8.664 g of methyltriethoxysilane (MTES) (product name: KBE-13, manufactured by Shin-Etsu Chemical Co., Ltd.) and 2.830 g of tetraethoxysilane (TEOS) (special grade, manufactured by Kishida Chemical Co., Ltd.) were added to the mixed solution and further stirred for 1 minute to obtain Solution B. While stirring Solution A, Solution B was added to Solution A and stirred at room temperature for 1 minute. Subsequently, 140 g of toluene was added to the solution and stirred at room temperature for 1 minute to obtain Solution C. Solution C was placed in a flask and the solvent was removed while heating with an oil bath (manufactured by Tokyo Rikakikai Co., Ltd., model: OSB-2100) and 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. Subsequently, Solution D of Example 1 after the solvent removal treatment was taken out from the flask. In the solvent removal treatment, the solvent was not completely removed and the viscosity was reduced to a certain extent. Thus, Solution D, which is a dispersion of aryl copper phosphonate (UV-IR absorber), was obtained.

[0087] (Preparation of alkyl copper phosphonate)

[0088] 4.500 g of copper(II) acetate monohydrate was mixed with 240 g of THF and stirred for 3 hours to obtain a copper(II) acetate solution. Subsequently, 2.572 g of Plysurf A208N, which is a phosphoric acid ester compound, was added to the obtained copper(II) acetate solution and stirred for 30 minutes to obtain Solution E. 40 g of THF was added to 2.886 g of n-butylphosphonic acid and stirred for 30 minutes to obtain Solution F. While stirring Solution E, Solution F was added to Solution E and stirred at room temperature for 1 minute. Subsequently, 100 g of toluene was added to the solution and stirred at room temperature for 1 minute to obtain Solution G. Solution G was placed in a flask and the solvent was removed while heating with an oil bath and using a rotary evaporator. The set temperature of the oil bath was adjusted to 105 °C. Subsequently, Solution H of Example 1 after the solvent removal treatment was taken out from the flask. In the solvent removal treatment, the solvent was not completely removed and the viscosity of Solution H was reduced to a certain extent. Thus, Solution H, which is a dispersion of butyl copper phosphonate (IR absorber), was obtained.

[0089] (Production of Light-Absorbing Composition)

[0090] 12.57 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to Solution D, and the mixture was stirred for 30 minutes to obtain Solution I. An amount equivalent to 40% by mass of the total amount of Solution H was added to Solution I, and further 10.840 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 5.660 g of tetraethoxysilane (TEOS) (special grade manufactured by Kishida Chemical Co., Ltd.), and 4.896 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22), which are alkoxysilanes, were added thereto, and the mixture was stirred for 30 minutes to obtain the light-absorbing composition of Example 1. The light-absorbing composition of Example 1 was prepared as follows: Assuming that a complete hydrolysis condensate of alkoxysilane was obtained, in the complete hydrolysis condensate of alkoxysilane, the content of the silane compound derived from MTES was 60.0% by mass, the content of the silane compound derived from TEOS was 20.0% by mass, and the content of the silane compound derived from DMDES was 20.0% by mass. It should be noted that the following premise was used for the calculation: The ratio of the amount of the silane compound (solid component) derived from MTES present in the complete hydrolysis condensate of alkoxysilane to the added amount of MTES was 37.64% by mass; the ratio of the amount of the silane compound (solid component) derived from TEOS present in the complete hydrolysis condensate of alkoxysilane to the added amount of TEOS was 28.84% by mass; the ratio of the amount of the silane compound (solid component) derived from DMDES present in the complete hydrolysis condensate of alkoxysilane to the added amount of DMDES was 50.01% by mass. In Examples 2 and 3 and Comparative Example 1, the calculation was also carried out on the same premise. The relationship between the preparation of Solution D and the added amounts of alkoxysilanes added in the preparation of the light-absorbing composition is shown in Table 2.

[0091] (Fabrication of Filter)

[0092] Mix 0.1 g of a surface anti-fouling coating agent (manufactured by Daikin Industries, Ltd., product name: OPTOOL DSX, concentration of active ingredient: 20% by mass) with 19.9 g of a solution containing hydrofluoroether (manufactured by 3M Company, product name: Novec 7100), and stir for 5 minutes to prepare a fluorine treatment agent (concentration of active ingredient: 0.1% by mass). Overflow coat this fluorine treatment agent onto a circular borosilicate glass (manufactured by SCHOTT Company, product name: D263 T eco) with a diameter of 200 mm and a thickness of 0.7 mm. Thereafter, leave this glass substrate at room temperature for 24 hours to dry the coating film of the fluorine treatment agent, and then gently wipe the glass surface with a lint-free cloth containing Novec 7100 to remove the excess fluorine treatment agent. Thus, a fluorine-treated substrate is produced.

[0093] Apply the light-absorbing composition of Example 1 onto the fluorine-treated substrate using a coater. At this time, use a template made of stainless steel (inner dimensions: approximately 100 mm square) to coat it in such a way that the coating film can maintain a sufficient thickness. Leave the substrate coated with the light-absorbing composition for a specified time, and after the components of the light-absorbing composition have fully reacted, slowly heat the substrate from room temperature to slowly evaporate the solvent and simultaneously cure the light-absorbing composition. Adjust the maximum temperature reached during this heating to 85 °C. Further, leave the substrate in an environment of a temperature of 85 °C and a relative humidity of 85% for about 2 hours to promote the hydrolysis reaction of the alkoxysilane, and obtain a light-absorbing film. For the light-absorbing film thus obtained, lift its end and peel it off from the substrate to obtain the filter of Example 1 having a size of approximately 100 mm square when viewed from above.

[0094] (Cutting of the filter)

[0095] Use a rotary cutter (manufactured by Olfa Corporation) with a circular blade having a diameter of 28 mm to cut the filter of Example 1 into strips. Specifically, apply a load of approximately 30 N to the filter along four straight lines parallel to one side of the filter and positioned at 20 mm intervals to cut the filter. Use a metallurgical microscope to observe the obtained strip-shaped sample at a magnification of 50 times. As a result, no damage such as splitting or fracture occurred at the periphery of the cross-section of the sample, and it was confirmed that the filter of Example 1 was cut well.

[0096] <Example 2>

[0097] In the same manner as in Example 1, Dispersion D as a dispersion of aryl phosphonic acid copper (UV-IR absorber) and Dispersion H as a dispersion of butyl phosphonic acid copper (IR absorber) were obtained. Subsequently, 12.57 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to Dispersion D, and the mixture was stirred for 30 minutes to obtain Solution I. An amount equivalent to 40% by mass of the total amount of Dispersion H was added to Solution I, and further, 5.420 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) as an alkoxysilane, 2.830 g of tetraethoxysilane (TEOS) (special grade manufactured by Kishida Chemical Co., Ltd.), and 2.448 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were added thereto, and the mixture was stirred for 30 minutes to obtain the light-absorbing composition of Example 2. The light-absorbing composition of Example 2 was prepared as follows: assuming that a complete hydrolysis condensate of the alkoxysilane was obtained, in the complete hydrolysis condensate of the alkoxysilane, the content of the silane compound derived from MTES was 65.0% by mass, the content of the silane compound derived from TEOS was 20.0% by mass, and the content of the silane compound derived from DMDES was 15.0% by mass.

[0098] A filter of Example 2 was produced in the same manner as in Example 1, except that the light-absorbing composition of Example 2 was used instead of the light-absorbing composition of Example 1. Further, the filter of Example 2 was cut into strips in the same manner as the filter of Example 1. The obtained strip-shaped sample was observed at a magnification of 50 times using a metal microscope. As a result, no damage such as cracking or fracture occurred at the periphery of the cross-section of the sample, and it was confirmed that the filter of Example 2 was cut well.

[0099] <Example 3>

[0100] In the same manner as in Example 1, Dispersion D, which is a dispersion of aryl phosphonic acid copper (UV-IR absorber), and Dispersion H, which is a dispersion of butyl phosphonic acid copper (IR absorber), were obtained. Next, 12.57 g of an organosilicon resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to Dispersion D, and the mixture was stirred for 30 minutes to obtain Solution I. An amount equivalent to 40% by mass of the total amount of Dispersion H was added to Solution I, and further, 7.344 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22), which is an alkoxysilane, was added thereto, and the mixture was stirred for 30 minutes to obtain the light-absorbing composition of Example 3. In the preparation of the light-absorbing composition of Example 3, methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) were not added to the mixed solution of Solution I and Dispersion H. The light-absorbing composition of Example 3 was prepared as follows: assuming that a complete hydrolysis condensate of alkoxysilane was obtained, in the complete hydrolysis condensate of alkoxysilane, the content of the silane compound derived from MTES was 42.1% by mass, the content of the silane compound derived from TEOS was 10.5% by mass, and the content of the silane compound derived from DMDES was 47.4% by mass.

[0101] Except for using the light-absorbing composition of Example 3 in place of the light-absorbing composition of Example 1, the filter of Example 3 was produced in the same manner as in Example 1. Further, the filter of Example 3 was cut into strips in the same manner as the filter of Example 1. The obtained strip-shaped sample was observed at a magnification of 50 times using a metallurgical microscope. As a result, no damage such as splitting or fracture occurred at the periphery of the cross-section of the sample, and it was confirmed that the filter of Example 3 was cut well.

[0102] <Comparative Example 1>

[0103] In the same manner as in Example 1, Dispersion D, which is a dispersion of aryl phosphonic acid copper (UV-IR absorber), and Dispersion H, which is a dispersion of butyl phosphonic acid copper (IR absorber), were obtained. Next, 12.57 g of an organosilicon resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to Dispersion D, and the mixture was stirred for 30 minutes to obtain Solution I. An amount equivalent to 40% by mass of the total amount of Dispersion H was added to Solution I, and the mixture was further stirred for 30 minutes to obtain the light-absorbing composition of Comparative Example 1. In the preparation of the light-absorbing composition of Comparative Example 1, alkoxysilane was not added to the mixed solution of Solution I and Dispersion H.

[0104] A filter of Comparative Example 1 was produced in the same manner as in Example 1, except that the light-absorbing composition of Comparative Example 1 was used instead of the light-absorbing composition of Example 1. Further attempts were made to cut the filter of Comparative Example 1 into strips in the same manner as the filter of Example 1. However, a large number of cracks were generated around four straight lines parallel to one side of the filter and positioned at 20 mm intervals, and the filter of Comparative Example 1 could not be cut well, and a strip-shaped sample could not be obtained.

[0105] <Transmittance spectrum measurement>

[0106] Using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-670), the transmittance spectra of each filter at an incident angle of 0° were measured. The transmittance spectra of the filters of Example 1, Example 2, Example 3, and Comparative Example 1 are respectively as Figure 3 , Figure 4 , Figure 5 and Figure 6 shown. In addition, the transmittance-related characteristics read from Figures 3 - 6 are shown in Table 1.

[0107] <Thickness measurement>

[0108] The distance from the surface of the filter was measured using a laser displacement meter (manufactured by KEYENCE CORPORATION, product name: LK-H008), and the thickness of the filter was thereby measured. The results are shown in Table 1.

[0109] <Young's modulus and hardness>

[0110] Using a nanoindenter (manufactured by MTS Systems Corporation, product name: Nano Indenter XP), the surface of the filter was measured according to the nanoindentation method (continuous stiffness measurement method). A diamond triangular pyramid indenter was used as the indenter, and the measurement was performed at room temperature of about 23°C and in the atmosphere. In the hardness-indentation depth graph obtained from this measurement, the hardness values in the range of indentation depths of 5 to 10 μm were averaged to determine the average value of the surface hardness of each filter. In addition, in the Young's modulus-indentation depth graph obtained from this measurement, the Young's modulus values in the range of indentation depths of 5 to 10 μm were averaged to determine the average value of the Young's modulus of each filter. In addition, considering that the main component of the filter is silicone resin, the Poisson's ratio of the filter was determined to be 0.4. The results are shown in Table 3. The average value of Young's modulus in the examples was 0.87 to 1.6 GPa, and the average value of hardness was 0.020 to 0.048 GPa. On the other hand, in the comparative examples, the average value of Young's modulus was 2.6 GPa and the hardness was 0.11 GPa, indicating poor flexibility.

[0111] <Measurement of haze>

[0112] Using a haze meter (manufactured by Murakami Color Research Institute, product name: HM-65L2), the haze of the filters of Examples 1 to 3 and the filter of Comparative Example 1 was measured in accordance with Japanese Industrial Standard JIS K 7136. The results are shown in Table 3.

[0113] <Moisture resistance test>

[0114] The filters of Examples 1 to 3 were stored inside a thermo-hygrostat (manufactured by Tokyo Rikakikai Co., Ltd., KCL-2000A) set at a temperature of 85°C and a relative humidity of 85% for 1000 hours to conduct the moisture resistance test. Using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-670), the transmittance spectra of the filters of Examples 1 and 2 after the moisture resistance test were measured at an incident angle of 0°. The results are shown in Figure 7 and Figure 8 . Figure 7 and Figure 8 . In

[0115] and

[0116] , the solid line represents the transmittance spectrum of the filter before the moisture resistance test, and the dashed line represents the transmittance spectrum of the filter after the moisture resistance test. The values of the respective parameters read from these transmittance spectra are shown in Table 4. It should be noted that the filter of Example 3 after the moisture resistance test became cloudy and did not transmit light at all.

[0117] Further, in recent years, in portable communication devices such as smartphones, substrates with high flexibility, such as displays using organic EL, are often used. The light absorption film of the embodiment of the present invention can also exhibit followability even for such flexible display screens or panels as substrates, and thus is easily applicable in these fields.

[0118] In common coating methods such as spin coating or dip coating, it is very difficult to form a film with a uniform thickness on a curved surface and requires very precise control. On the other hand, according to the above method, it is possible to relatively easily form a light absorption film with a uniform thickness on a curved surface, which is very effective.

[0119] An adhesive can be used in bonding the light absorption film to the curved surface. The pre-fired film can be laminated along the curved surface of the substrate, etc., and then heat treatment, or heat and humidity treatment can be carried out. In the latter case, the pre-firing temperature is preferably 60 °C or lower, and the final heat and humidity temperature is preferably 80 °C or higher.

[0120] In addition, as the substrate for making the light absorption film, a substrate obtained by forming wires made of materials such as glass fiber, carbon fiber, or cellulose nanofiber on the surface (e.g., in a lattice pattern) can be used. In this case, after forming the light absorption film on the substrate, it is peeled off together with the wires, whereby a light absorption film with wires formed inside or on the surface can be obtained. Such wires can impart appropriate mechanical rigidity to the light absorption film, so that a light absorption film with flexibility and rigidity can be made.

[0121] Furthermore, after forming a coating film on a flat substrate, the light absorption film can be formed into a special surface state (e.g., lens shape) corresponding to the final substrate shape by deforming the substrate and simultaneously performing heat treatment, or heat and humidity treatment. By deforming or curing the light absorption film corresponding to the required shape of the substrate, light absorption filters with various surface states (flat or curved) can be fabricated.

[0122] The impact resistance of the light absorption film according to the embodiment of the present invention is also excellent. Therefore, it has the advantage of not being easily restricted by the use environment. The light absorption film according to the embodiment of the present invention can be effectively used for, for example, a camera module, an optical sensor, or a part of various optical systems built in a wearable device exposed to long-term vibration and strong impact, particularly a wearable camera or an action camera.

[0123]

[0124]

[0125] [Table 3]

[0126]

[0127]

Claims

1. A filter having a light absorption layer, wherein the light absorption layer contains a resin and a light absorbent, the average value of the Young's modulus of the light absorption layer measured by nanoindentation, i.e., continuous stiffness measurement, is 2.00 GPa or less, and the average value of the hardness is 0.06 GPa or less.

2. The optical filter according to claim 1, wherein When the filter is subjected to a moisture resistance test of being held for 1000 hours in an environment of a temperature of 85°C and a relative humidity of 85%, the following (i), (ii), and (iii) are satisfied, (i) The change amount ΔT of the average transmittance in the wavelength range of 450 nm to 600 nm before and after the moisture resistance test 450-600 is 3 percentage points or less; (ii) When the wavelength at which the transmittance reaches 50% in the wavelength range of 350 nm to 450 nm is defined as the UV cut-off wavelength, the change amount Δλuvc of the UV cut-off wavelength before and after the moisture resistance test is 5 nm or less. When the wavelength at which the transmittance reaches 50% in the wavelength range of 600 nm to 800 nm is defined as the IR cut-off wavelength, the change amount Δλirc of the IR cut-off wavelength before and after the moisture resistance test is 5 nm or less; (iii) The change amount Δλirc-uvc of the value obtained by subtracting the UV cut-off wavelength from the IR cut-off wavelength before and after the moisture resistance test is 10 nm or less.

3. The optical filter according to claim 1, wherein When the filter is subjected to a moisture resistance test of being held for 1000 hours in an environment of a temperature of 85°C and a relative humidity of 85%, the following (iv), (v), (vi), and (vii) are satisfied, (iv) The change amount ΔT of the maximum transmittance in the wavelength range of 300 nm to 350 nm before and after the moisture resistance test max300-350 is 1 percentage point or less; (v) The change amount ΔT of the maximum transmittance in the wavelength range of 300 nm to 360 nm before and after the moisture resistance test max300-360 is 1 percentage point or less; (vi) The change amount ΔT of the average transmittance in the wavelength range of 700 nm to 750 nm before and after the moisture resistance test AVE700-750 is 3 percentage points or less; (vii) The change amount ΔT of the maximum transmittance in the wavelength range of 750 nm to 1080 nm before and after the moisture resistance test max750-1080 is 3 percentage points or less.

4. The optical filter according to claim 1, wherein, the light absorption layer contains at least one selected from the group consisting of a hydrolyzate of an alkoxysilane and a polymer of the hydrolyzate of the alkoxysilane.

5. The optical filter according to claim 4, wherein, The alkoxysilane contains at least one selected from the group consisting of a dialkoxysilane, a trialkoxysilane, and a tetraalkoxysilane.

6. The optical filter according to claim 5, wherein, In terms of the hydrolyzed polymer of the alkoxysilane, the mass ratio of the dialkoxysilane to the total mass of the dialkoxysilane, trialkoxysilane, and tetraalkoxysilane is 15% to 48%.

7. The optical filter according to any one of claims 1 to 6, wherein, The light absorbent contains a phosphonic acid and a copper component.

8. A method for manufacturing a filter, wherein, Including: Coating a light-absorbing composition containing a light absorbent and a curable resin on the surface of a substrate to form a coating film; And Curing the coating film to form a light absorption layer.

9. The manufacturing method of the optical filter according to claim 8, wherein, Further including: Peeling the light absorption layer from the substrate.

10. The manufacturing method of the optical filter according to claim 9, wherein, Further including: Laminating the light absorption layer on the surface of a substrate including a curved surface.

11. The manufacturing method of the optical filter according to claim 8, wherein, The average value of the Young's modulus of the light absorption layer measured by nanoindentation, i.e., continuous stiffness measurement, is 2.00 GPa or less, and the average value of the hardness is 0.06 GPa or less.

12. The manufacturing method of the optical filter according to claim 8, wherein, The light-absorbing composition contains at least one selected from the group consisting of an alkoxysilane and a hydrolyzate of an alkoxysilane.

13. The method for manufacturing a filter according to claim 12, wherein, The alkoxysilane contains at least one selected from the group consisting of a dialkoxysilane, a trialkoxysilane, and a tetraalkoxysilane.

14. The method for manufacturing a filter according to claim 13, wherein, In terms of the hydrolyzed polymer of the alkoxysilane, the mass ratio of the dialkoxysilane to the total mass of the dialkoxysilane, trialkoxysilane, and tetraalkoxysilane is 15% to 48%.

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