Light-absorbing components, light-absorbing films, filters, and methods for manufacturing filters.

Abstract

The light-absorbing composition of this invention contains a light absorber, a curable resin, and an alkoxysilane. The alkoxysilane includes a dialkoxysilane. Because the alkoxysilane in the light-absorbing composition includes a dialkoxysilane, a robust framework with siloxane bonds is formed in the light-absorbing layer, and the organic functional groups of the dialkoxysilane readily impart the desired flexibility to the light-absorbing layer.

Description

[Technical Field]

[0001] This invention relates to a light-absorbing composition and a filter. [Previous Technology]

[0002] In imaging devices using solid-state imaging elements such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), various filters are disposed on the surface in front of the solid-state imaging element in order to obtain images with good color reproduction. Generally, solid-state imaging elements have spectral sensitivity over a wide wavelength range from the ultraviolet region to the infrared region. On the other hand, human visual sensitivity exists only in the visible light region. Therefore, a technique is known to be used to dispose of a filter that blocks a portion of infrared or ultraviolet light on the surface in front of the solid-state imaging element so that the spectral sensitivity of the solid-state imaging element in the imaging device is close to that of human visual sensitivity.

[0003] Previously, such filters generally used light reflection caused by dielectric multilayer films to block infrared or ultraviolet rays. On the other hand, in recent years, filters with films containing light-absorbing agents have attracted attention. The transmittance characteristics of filters with films containing light-absorbing agents are not easily affected by the angle of incidence, so even when light is obliquely incident on the filter in the imaging device, a good image with less tonal variation can be obtained. In addition, light-absorbing filters that do not use light-reflecting films can suppress ghosting or glare caused by multiple reflections caused by light-reflecting films, so it is easy to obtain good images in backlit conditions or night scene photography. Furthermore, filters with films containing light-absorbing agents are also advantageous for miniaturization and thinning of imaging devices.

[0004] For example, Patent Document 1 describes a filter having a UV-IR absorption layer capable of absorbing infrared and ultraviolet light. The UV-IR absorption layer comprises a UV-IR absorber formed from phosphonic acid and copper ions. Patent Document 2 describes an infrared cutoff filter having a layer containing an organic pigment and a layer containing copper phosphonate. Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Patent No. 6232161; Patent Document 2: Japanese Patent No. 6281023 [Summary of the Invention]

[0006] [Problem to be Solved by the Invention] The technology described in Patent Documents 1 and 2 has room for further study from the viewpoint of imparting the desired flexibility to the light-absorbing layer in a filter. Therefore, the present invention provides a light-absorbing composition that is advantageous from the viewpoint of imparting the desired flexibility to the light-absorbing layer in a filter. Furthermore, the present invention provides a filter having a light-absorbing layer with desired flexibility. [Technical Means for Solving the Problem]

[0007] The present invention provides a light-absorbing composition comprising a light absorber, a curable resin, and an alkoxysilane, wherein the alkoxysilane comprises a dialkoxysilane.

[0008] Furthermore, the present invention provides a filter having a light-absorbing layer formed from a hardened form of the aforementioned light-absorbing composition.

[0009] Furthermore, the present invention provides a filter comprising a light-absorbing layer containing a light-absorbing agent and a hydrolyzed condensate of an alkoxysilane, wherein when one principal surface of the light-absorbing layer is measured using a nanoindenter and according to the nanoindentation method (continuous stiffness measurement method), the average Young's modulus is 2.00 GPa or less, and the average hardness is 0.06 GPa or less. [Effects of the Invention]

[0010] The above-mentioned light-absorbing composition is advantageous from the viewpoint of imparting the desired flexibility to the light-absorbing layer in the filter. Furthermore, the light-absorbing layer of the above-mentioned filter has the desired flexibility.

Implementation Method

[0012] As for filters with a light-absorbing layer, we consider filters of the type consisting of a single light-absorbing layer and filters of the type where the light-absorbing layer is formed on a substrate such as glass or resin. In the case of the former type of filter, if the light-absorbing layer is rigid or has a high hardness like glass, the flexibility of the light-absorbing layer is easily reduced. For example, if the filter is bent or mechanically deformed, the light-absorbing layer may crack or wrinkle. In the case of the latter type of filter where the light-absorbing layer is formed on a flexible substrate such as resin, there is also a risk that the light-absorbing layer may crack or wrinkle when the filter is deformed. Therefore, careful attention is required when operating such filters.

[0013] When fabricating wafers by cutting large-area filters during the manufacturing process, large glass cutting equipment such as slicing machines is required. Furthermore, when cutting filters, it is sometimes necessary to study problems associated with the properties of the glass material, such as cracks or fragments. Also, when mounting and attaching filters to sensors such as solid-state imaging elements, if the filter is rigid, its inherent warpage (uneven flatness) can sometimes make mounting and attaching difficult. To facilitate this process, it is advantageous to increase the flexibility of the light-absorbing layer.

[0014] Therefore, the inventors have been studying the technology that is advantageous from the point of view of imparting the desired flexibility to the light-absorbing layer day and night, and have developed the light-absorbing composition and filter of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described. Furthermore, the following description is only one example of the present invention, and the present invention is not limited thereto.

[0016] The light-absorbing composition of the present invention contains a light absorber, a curable resin, and an alkoxysilane. Furthermore, the alkoxysilane includes dialkoxysilane.

[0017] When forming a light-absorbing layer using a light-absorbing composition, silanol groups are generated by the hydrolysis of alkoxysilanes. The compound from the alkoxysilane containing the generated silanol groups further reacts and condenses, thereby forming a robust framework with siloxane bonds (-Si-O-Si-). If the material containing this framework has fewer organic components (organic functional groups), the formed light-absorbing layer is less likely to possess the desired flexibility. In this case, the framework with siloxane bonds is prone to breakage when subjected to strong local pressure in the light-absorbing layer. However, since the alkoxysilane in the light-absorbing composition includes dialkoxysilanes, a robust framework with siloxane bonds is formed in the light-absorbing layer, and the organic functional groups of the dialkoxysilanes easily impart the desired flexibility to the light-absorbing layer. Therefore, for example, when cutting a light-absorbing layer formed using a light-absorbing composition, cracks and fragments are less likely to occur. Furthermore, even when the light-absorbing layer is bent using light-absorbing components, the light-absorbing layer is not easily broken.

[0018] For example, consider providing a filter that is integral with a solid-state imaging element or optical component, such as a CCD or CMOS, by coating a light-absorbing composition onto the image element or optical component. If the filter integral with the image element or optical component is placed in a specified thermal cycling environment, thermal expansion and contraction may occur. The light-absorbing layer formed using the light-absorbing composition tends to have the desired flexibility and easily deforms in accordance with thermal expansion and contraction. Therefore, damage and breakage of the light-absorbing layer can be easily suppressed.

[0019] Furthermore, after a highly flexible filter is manufactured into a filter with a flat surface, it can be bent along the curved configuration surface to form a curved surface when assembled into an optical system. By making the main surface of the filter curved, it is also possible to cope with the design of special imaging devices that are based on the complex configuration of sensors.

[0020] Dialkoxysilanes are not limited to specific dialkoxysilanes. Dialkoxysilanes have, for example, a hydrocarbon group having 1 to 6 carbon atoms bonded to a silicon atom. Alkoxysilanes may also have a haloalkyl group having at least one hydrogen atom of a hydrocarbon group having 1 to 6 carbon atoms bonded to a silicon atom, wherein a halogen atom is substituted by a halogen atom. In this case, the light-absorbing layer formed using the light-absorbing composition is further endowed with the desired flexibility.

[0021] The diekoxysilane may also be, for example, an alkoxysilane represented by formula (b) below. In this case, it is more readily possible to impart the desired flexibility to the light-absorbing layer formed using the light-absorbing composition. (R2)2-Si-(OR3)2 (b) [wherein, R2 is independently an alkyl group having 1 to 6 carbon atoms, and R3 is independently an alkyl group having 1 to 8 carbon atoms]

[0022] Dialkoxysilane may also be, for example, dimethyldiethoxysilane, dimethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, or 3-glycidoxypropylmethyldiethoxysilane.

[0023] In the light-absorbing composition, the alkoxysilane may further include at least one of tetraalkoxysilane and trialkoxysilane. Thereby, the light-absorbing layer formed using the light-absorbing composition can easily form a dense structure through siloxane bonds.

[0024] In the light-absorbing composition, the alkoxysilane may further include tetraalkoxysilane and trialkoxysilane. In this way, the light-absorbing layer formed using the light-absorbing composition can more reliably form a dense structure through siloxane bonds.

[0025] In the light-absorbing composition, at least one of the tetraalkoxysilane and trialkoxysilane is not limited to a specific alkoxysilane. For example, in the light-absorbing composition, the alkoxysilane is selected from tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, hexyltriethoxysilane, hexyltrimethoxysilane, and hexyltrimethoxysilane. At least one of the group consisting of silane, trifluoropropyltriethoxysilane, trifluoropropyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-isocyanopropyltriethoxysilane, and 3-isocyanopropyltrimethoxysilane.

[0026] The content of dialkoxysilane in the alkoxysilane is not limited to a specific value. The content of dialkoxysilane in the alkoxysilane is, for example, 15-48% by mass, after converting the alkoxysilane to a fully hydrolyzed condensate. This makes it easier and more reliable to impart the desired flexibility to the light-absorbing layer formed using the light-absorbing composition.

[0027] The ideal content of dialkoxysilane in alkoxysilanes is 15-20% by mass, based on the conversion of alkoxysilanes to fully hydrolyzed condensates. This allows the light-absorbing layer formed using light-absorbing components to exhibit higher moisture resistance. This is because the dense structure formed by siloxane bonds prevents the light absorber from coalescing in high-humidity environments.

[0028] A light absorber is not limited to a specific light absorber as long as it can absorb light of a specified wavelength. A light absorber can be formed from, for example, a phosphonic acid represented by formula (a) below and copper ions. [In the formula, R11 is a haloaryl group consisting of an alkyl, aryl, nitroaryl, hydroxyaryl, or an aryl group in which at least one hydrogen atom is replaced by a halogen atom.]

[0029] In the light-absorbing composition, for example, a light absorber is formed by coordinating the phosphonic acid represented by formula (a) with copper ions. Also, for example, microparticles containing at least the light absorber are formed in the light-absorbing composition. In this case, the microparticles are dispersed in the light-absorbing composition without agglomeration due to the action of the alkoxysilane. The average particle size of these microparticles is, for example, 5 nm to 200 nm. If the average particle size is 5 nm or more, no special steps for miniaturizing the microparticles are needed, and the possibility of damage to the structure of the microparticles containing at least the light absorber is small. Furthermore, the microparticles are well dispersed in the light-absorbing composition. Also, if the average particle size is 200 nm or less, the effect caused by Mie scattering can be reduced, the transmittance of visible light in the filter can be improved, and the reduction in contrast and haze characteristics of images captured by the imaging device can be suppressed. Ideally, the average particle size is 100 nm or less. In this case, the transparency to visible light is improved in filters made using light-absorbing components because the effects of Rayleigh scattering are reduced. Furthermore, the average particle size is ideally below 75 nm. In this case, filters made using light-absorbing components exhibit particularly high transparency to visible light. Moreover, the average particle size can be determined using dynamic light scattering.

[0030] Phosphate esters can be used as dispersants for light absorbers. Therefore, light-absorbing compositions can also contain phosphate esters. On the other hand, in light-absorbing layers formed using light-absorbing compositions, compounds from alkoxysilanes, compared to phosphate esters, can impart higher moisture resistance to the light-absorbing layer and appropriately disperse the light absorber. Therefore, by including alkoxysilanes in the light-absorbing composition, the amount of phosphate ester used can be reduced. In the formation of the light-absorbing layer, by reacting alkoxysilanes present around the light absorber with dialkoxysilanes, the light-absorbing layer is homogeneous and easily possesses high density. Furthermore, light-absorbing compositions may also not contain phosphate esters.

[0031] Phosphate esters include, for example, phosphate esters containing polyoxyalkyl groups. Phosphate esters containing polyoxyalkyl groups are not limited to specific phosphate esters. Examples of phosphate esters containing polyoxyalkyl groups include Plysurf A208N: polyoxyethylene alkyl (C12, C13) ether phosphate; Plysurf A208F: polyoxyethylene alkyl (C8) ether phosphate; Plysurf A208B: polyoxyethylene lauryl ether phosphate; Plysurf A219B: polyoxyethylene lauryl ether phosphate; Plysurf AL: polyoxyethylene styrene phenyl ether phosphate; Plysurf A212C: polyoxyethylene tridecyl ether phosphate; or Plysurf A215C: polyoxyethylene tridecyl ether phosphate. These are all products manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd. Furthermore, the phosphate ester can also be, for example, NIKKOL DDP-2: polyoxyethylene alkyl ether phosphate; NIKKOL DDP-4: polyoxyethylene alkyl ether phosphate; or NIKKOL DDP-6: polyoxyethylene alkyl ether phosphate. These are all products manufactured by Nikko Chemicals.

[0032] In the light-absorbing composition, the curing resin is not limited to a specific resin. The curing resin is, for example, a polysiloxane resin. Polysiloxane resin is a compound having siloxane bonds in its structure. In this case, the hydrolytic condensate of alkoxysilanes also has siloxane bonds; therefore, in the light-absorbing layer formed using the light-absorbing composition, the hydrolytic condensate of alkoxysilanes has good affinity with the curing resin.

[0033] Ideally, the resin should be a polysiloxane resin containing aryl groups such as phenyl groups. If the resin contained in the filter is hard (i.e., rigid), cracks are easily generated during the filter manufacturing process due to hardening shrinkage as the thickness of the layer containing the resin increases. If the resin is a polysiloxane resin containing aryl groups, the layer formed by the light-absorbing components tends to have good crack resistance. Furthermore, polysiloxane resins containing aryl groups have high compatibility with the phosphonic acid represented by formula (a), making it less likely for the light absorber to aggregate. Specific examples of polysiloxane resins used as matrix resins include KR-255, KR-300, KR-2621-1, KR-211, KR-311, KR-216, KR-212, KR-251, and KR-5230. These are all polysiloxane resins manufactured by Shin-Etsu Chemical Co., Ltd.

[0034] Taking the case where the light absorber is formed by the above-mentioned phosphonic acid and copper ions as an example, one example of a method for preparing a light-absorbing composition will be described.

[0035] For example, when the light-absorbing composition contains a phosphonic acid (aryl phosphonic acid) in which R11 in formula (a) is aryl, nitroaryl, hydroxyaryl, or haloaryl, solution D is prepared as follows: A solution A, which is a copper salt, is prepared by adding a copper salt such as copper acetate monohydrate to a specified solvent such as tetrahydrofuran (THF) and stirring. Next, an aryl phosphonic acid is prepared by adding a specified solvent such as THF and stirring. When multiple aryl phosphonic acids are used as the phosphonic acid represented by formula (a), each aryl phosphonic acid can be added to a specified solvent such as THF, and then stirred and mixed with multiple preparative solutions prepared according to the type of each aryl phosphonic acid to prepare solution B. For example, alkoxysilane is added to the preparation of solution B. Solution B is added to solution A while stirring and stirred for a specified time. Next, a specified solvent such as toluene is added to the solution and stirred to obtain solution C. Next, solution C is heated and subjected to a solvent removal process for a specified time to obtain solution D. This removes components arising from the dissociation of copper salts such as THF and acetic acid (boiling point: approximately 118°C), and generates a light absorber by reacting phosphonic acid (represented by formula (a)) with copper ions. The heating temperature of solution C is determined based on the boiling point of the components to be removed from the copper salt dissociation. Furthermore, during the solvent removal process, solvents such as toluene (boiling point: approximately 110°C) used to obtain solution C also evaporate. Ideally, this solvent should remain to a certain extent in the light-absorbing components; therefore, the amount of solvent added and the duration of the solvent removal process can be determined from this perspective. Alternatively, o-xylene (boiling point: approximately 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 amount added can be reduced to about one-quarter of the amount of toluene added.

[0036] When the light-absorbing composition contains an alkyl phosphonic acid (alkyl phosphonic acid) in formula (a), solution H is prepared, for example, 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 solution E, which is a solution of the copper salt. Then, an alkyl phosphonic acid is added to a specified solvent such as THF and stirred to prepare solution F. When multiple phosphonic acids are used as alkyl phosphonic acids, each alkyl phosphonic acid can be added to a specified solvent such as THF, and then stirred and mixed with multiple preparative solutions prepared according to the type of each alkyl phosphonic acid to prepare solution F. For example, in the preparation of solution F, an alkoxysilane is added. While stirring solution E, solution F is added to solution E and stirred for a specified time. Next, a specified solvent such as toluene is added to the solution and stirred to obtain solution G. Next, solution G is heated and subjected to a solvent removal process for a specified time to obtain solution H. This removes components generated by the dissociation of solvents such as THF and copper salts such as acetic acid. The heating temperature for solution G is determined in the same way as for solution C, and the solvent used to obtain solution G is also determined in the same way as for solution C.

[0037] For example, while mixing liquid D and liquid H in a specified ratio, alkoxysilane is added, and curable resins such as polysiloxane are added as needed, thereby preparing a light-absorbing composition. In this case, dialkoxysilane can also be added after mixing liquid D and liquid H.

[0038] As shown in FIG. 1, the filter 1a includes a light-absorbing layer 10. The light-absorbing layer 10 contains a light absorber and a hydrolysis condensate of alkoxysilanes. The light-absorbing layer 10 is characterized by its softness; for example, when the average Young's modulus of one of the main surfaces 10a of the light-absorbing layer 10 is measured using a nanoindenter and according to the nanoindentation method (continuous stiffness measurement method), the average value is 2.00 GPa or less. The average value of the Young's modulus may also be, for example, 0.10 to 2.00 GPa. Furthermore, the average value of the hardness is 0.06 GPa or less. The average value of the hardness may also be 0.005 to 0.06 GPa. Thus, the light-absorbing layer 10 contains a framework of siloxane bonds formed by the hydrolysis condensate of alkoxysilanes and has the desired softness. For details on the nanoindentation method (continuous stiffness determination method), please refer to International Publication No. 2019 / 044758 and Japanese Patent Application Publication No. 2015-174270.

[0039] The alkoxysilane hydrolysis condensate contained in the light-absorbing layer 10 includes, for example, a dialkoxysilane hydrolysis condensate. This gives the light-absorbing layer 10 the desired flexibility.

[0040] From another perspective, the light-absorbing layer 10 may also be formed from a hardened form of, for example, the light-absorbing composition described above. In this case, the light-absorbing layer 10 readily possesses the desired flexibility.

[0041] When filter 1a is subjected to a moisture resistance test at a temperature of 85°C and a relative humidity of 85% for 1000 hours, filter 1a meets the following conditions, for example. Under these conditions, filter 1a exhibits good moisture resistance. Furthermore, regarding each parameter, the term "change amount" refers to the absolute value of the difference between the parameter values ​​before and after the moisture resistance test. The term "change amount of average transmittance" represents the absolute value of the difference between the average transmittance before the moisture resistance test and the average transmittance after the moisture resistance test within the specified wavelength range. The term "change amount of maximum transmittance" represents the absolute value of the difference between the maximum transmittance before the moisture resistance test and the maximum transmittance after the moisture resistance test within the specified wavelength range. Also, the unit of change amount of parameters related to transmittance expressed as a percentage is expressed as "point". (i) The change amount of average transmittance ΔT450-600 in the wavelength range of 450-600 nm is 3 points or less. (ii) The change in UV cutoff wavelength Δλuvc is less than 5 nm, and the change in IR cutoff wavelength Δλirc is less than 5 nm. Furthermore, the UV cutoff wavelength is the wavelength with 50% transmittance in the wavelength range of 350 nm to 450 nm. The IR cutoff wavelength is the wavelength with 50% transmittance in the wavelength range of 600 nm to 800 nm. (iii) The change in the value obtained by subtracting the UV cutoff wavelength from the IR cutoff wavelength Δλirc-uvc is less than 10 nm. (iv) The change in maximum transmittance ΔTmax300-350 in the wavelength range of 300 to 350 nm is less than 1 point. ΔTmax300-350 is ideally less than 0.5 points. (v) The change in maximum transmittance ΔTmaX300-360 in the wavelength range of 300 to 360 nm is less than 1 point. (vi) Ideally, the variation in average transmittance ΔTAVE at wavelengths of 700–750 nm should be less than 3 points. Ideally, ΔTAVE at 700–750 nm should be less than 1 point. (vii) Ideally, the variation in maximum transmittance ΔTmax at wavelengths of 750–1080 nm should be less than 3 points. Ideally, ΔTmax at 750–1080 nm should be less than 1 point.(viii) The changes in maximum transmittance ΔTmax800-950 at wavelengths of 800-950 nm, ΔTmax800-1000 at wavelengths of 800-1000 nm, ΔTmax800-1050 at wavelengths of 800-1050 nm, ΔTmax800-1100 at wavelengths of 800-1100 nm, ΔTmax800-1150 at wavelengths of 800-1150 nm, and ΔTmax800-1200 at wavelengths of 800-1200 nm are each 3 points or less. The ideal values ​​for ΔTmax800-950, ΔTmax800-1000, ΔTmax800-1050, ΔTmax800-1100, ΔTmax800-1150, and ΔTmax800-1200 are all below 1 point.

[0042] As shown in FIG. 1, the filter 1a is composed of, for example, a light-absorbing layer 10 as a single entity. In this case, the filter 1a is used separately from, for example, an imaging element or optical component. The filter 1a can also be bonded to an imaging element and an optical component. On the other hand, the filter 1a can also be formed by coating the above-mentioned light-absorbing composition onto an imaging element or optical component and then curing the light-absorbing composition.

[0043] The filter 1a can be manufactured by, for example, peeling the light-absorbing layer 10 formed on the substrate from the substrate. In this case, the substrate material can be glass, resin, or metal. Surface treatments such as coating with a fluorine-containing compound can also be applied to the surface of the substrate.

[0044] Filter 1a can be replaced with, for example, filter 1b as shown in FIG. 2. Unless otherwise specified, filter 1b is constructed in the same manner as filter 1a. Components of filter 1b that are identical or corresponding to those of filter 1a are marked with the same symbols, and detailed descriptions are omitted. The description of filter 1a also applies to filter 1b as long as there is no technical contradiction.

[0045] As shown in FIG. 2, the filter 1b includes a light-absorbing layer 10 and a transparent dielectric substrate 20. The light-absorbing layer 10 is formed parallel to one of the main surfaces of the transparent dielectric substrate 20. The light-absorbing layer 10 may also, for example, be in contact with one of the main surfaces of the transparent dielectric substrate 20. In this case, for example, the light-absorbing layer 10 is formed by coating one of the main surfaces of the transparent dielectric substrate 20 with the aforementioned light-absorbing composition and then hardening the light-absorbing composition.

[0046] The type of transparent dielectric substrate 20 is not limited to a specific type. The transparent dielectric substrate 20 may have absorption energy in the infrared region. The transparent dielectric substrate 20 may have an average spectral transmittance of 90% or more within, for example, wavelengths of 350 nm to 900 nm. The material of the transparent dielectric substrate 20 is not limited to a specific material, such as a specified 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 cutoff glass made of silicate glass such as soda-lime glass or borosilicate glass. The infrared cutoff glass is, for example, a phosphate glass containing CuO or a fluorophosphate glass.

[0047] When the material of the transparent dielectric substrate 20 is resin, the resin is, for example, cycloalkene resin such as norbornene resin, polyarylate resin, acrylic resin, modified acrylic resin, polyimide resin, polyetherimide resin, polyurethane resin, polyetherurethane resin, polycarbonate resin, or polysiloxane resin.

[0048] Filters 1a and 1b can be modified to have other functional films such as infrared reflective films. Example

[0049] The present invention will be described in more detail through embodiments. Furthermore, the present invention is not limited to the following embodiments.

[0050] <Example 1> (Preparation of aryl phosphonate copper) 4.500 g of copper acetate monohydrate and 240 g of tetrahydrofuran (THF) were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 1.646 g of Plysurf A208N (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.), a phosphate ester compound, was added to the obtained copper 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. Next, solutions B-1 and B-2 were mixed and stirred for 1 minute. 8.664 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) and 2.830 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., premium grade) were added to the mixture, and the mixture was stirred for another minute to obtain solution B. While stirring solution A, solution B was added to solution A, and the mixture was stirred at room temperature for 1 minute. Next, 140 g of toluene was added to the solution, and the mixture was stirred at room temperature for 1 minute to obtain solution C. Solution C was placed in a flask and heated using an oil bath (manufactured by Tokyo Rikagi Co., Ltd., model: OSB-2100), and desolventized using a rotary evaporator (manufactured by Tokyo Rikagi Co., Ltd., model: N-1110SF). The oil bath temperature was set to 105°C. Then, the desolventized solution D of Example 1 was removed from the flask. The solvent is not completely removed during the desolventizing process; instead, the desolventizing process is carried out in a manner that reduces the viscosity to a certain extent. Liquid D, which serves as a dispersion of aryl phosphonate copper (UV-IR absorber), is obtained in this way.

[0051] (Preparation of Alkyl Phosphonate Copper) 4.500 g of copper acetate monohydrate and 240 g of THF were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 2.572 g of Plysurf A208N (a phosphate ester compound) was added to the obtained copper acetate solution and stirred for 30 minutes to obtain solution E. Then, 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. Next, 100 g of toluene was added to this solution and stirred at room temperature for 1 minute to obtain solution G. Solution G was placed in a flask and heated in an oil bath, and then desolventized using a rotary evaporator. The oil bath temperature was set to 105°C. Subsequently, solution H of Example 1 after desolventization was removed from the flask. The solvent is not completely removed during the desolventizing process; instead, the desolventizing process is carried out in a manner that reduces the viscosity of the H liquid to a certain extent. In this way, the H liquid, which serves as a dispersion of copper butylphosphonate (IR absorber), is obtained.

[0052] (Preparation of the light-absorbing composition) 12.57 g of polysiloxane resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to solution D and 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 then 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., premium grade), and 4.896 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-22) were added to it as alkoxysilanes and stirred for 30 minutes to obtain the light-absorbing composition of Example 1. Regarding alkoxysilanes, assuming that when obtaining their fully hydrolyzed condensate, the content of MTES silane compounds, by mass, is 60.0%, TEOS silane compounds, and DMDES silane compounds, the light-absorbing composition of Example 1 is prepared in this manner. Furthermore, calculations were performed based on the following premise: the amount of silane compound (solid component) from MTES present in the complete hydrolysis condensate of alkoxysilanes relative to the amount of MTES added was 37.64% by mass; the amount of silane compound (solid component) from TEOS present in the complete hydrolysis condensate of alkoxysilanes relative to the amount of TEOS added was 28.84% by mass; and the amount of silane compound (solid component) from DMDES present in the complete hydrolysis condensate of alkoxysilanes relative to the amount of DMDES added was 50.01% by mass. Calculations were also performed using the same premise for Examples 2 and 3 and Comparative Example 1. The relationship between the amount of alkoxysilane added in the preparation of liquid D and the preparation of the light-absorbing component is shown in Table 2.

[0053] (Fabrication of the filter) A fluorinated substrate (active ingredient concentration: 0.1% by mass) was prepared by mixing 0.1 g of a surface antifouling coating agent (manufactured by Daikin Industries, Ltd., product name: OPTOOL DSX, active ingredient concentration: 20% by mass) with 19.9 g of a hydrofluoric ether solution (manufactured by 3M Corporation, product name: NOVEC 7100) and stirring for 5 minutes. This fluorinated substrate was then coated onto a circular borosilicate glass substrate (manufactured by SCHOTT Corporation, product name: D263 Teco) with a diameter of 200 mm and a thickness of 0.7 mm. The glass substrate was then left at room temperature for 24 hours to allow the fluorinated substrate coating to dry. Afterward, the glass surface was gently wiped dry with a lint-free cloth containing NOVEC 7100 to remove excess fluorinated substrate. This method was used to fabricate the fluorinated substrate.

[0054] The light-absorbing composition of Example 1 was coated onto a fluorinated substrate using a dispenser. A stainless steel mold frame (internal dimensions: approximately 100 mm square) was used to ensure sufficient coating thickness. The substrate coated with the light-absorbing composition was left to stand for a specified time to allow the components of the light-absorbing composition to react sufficiently. Then, the substrate was slowly heated from room temperature to allow the solvent to evaporate slowly and the light-absorbing composition to harden. The maximum temperature reached during this heating was adjusted to 85°C. The substrate was then placed at 85°C and 85% relative humidity for approximately 2 hours to promote the hydrolysis reaction of alkoxysilanes, thereby obtaining a light-absorbing film. The light-absorbing film obtained in this manner was peeled off from the substrate by pulling up its ends, resulting in the filter of Example 1 with a top view dimension of approximately 100 mm square.

[0055] (Cut of the filter) The filter of Example 1 was cut into short strips using a rotary cutter (manufactured by OLFA) with a circular blade of 28 mm in diameter. Specifically, the filter was cut along four straight lines parallel to one side of the filter and spaced 20 mm apart, with a load of approximately 30 N applied. The obtained short strip samples were observed at 50x magnification using a metal microscope. As a result, no cracks or breaks occurred around the cut surface of the sample, confirming that the filter of Example 1 was cut well.

[0056] <Example 2> Similar to Example 1, liquid D, as a dispersion of aryl copper phosphonate (UV-IR absorber), and liquid H, as a dispersion of butyl copper phosphonate (IR absorber), were obtained. Next, 12.57 g of polysiloxane resin (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KR-300) was added to liquid D and stirred for 30 minutes to obtain liquid I. A mass fraction equivalent to 40% of the total volume of liquid H was added to liquid I. Then, 5.420 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13), 2.830 g of tetraethoxysilane (TEOS) (premium 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), all alkoxysilanes, were added and the mixture was stirred for 30 minutes to obtain the light-absorbing composition of Example 2. Regarding the alkoxysilanes, assuming that a completely hydrolyzed condensate was obtained, the content of silane compounds from MTES, TEOS, and DMDES, by mass, was 65.0%, 20.0%, and 15.0%, respectively. The light-absorbing composition of Example 2 was prepared in this manner.

[0057] The filter of Example 2 was prepared in the same manner as that of Example 1, except that the light-absorbing composition of Example 2 was used instead of the light-absorbing composition of Example 1. Furthermore, the filter of Example 2 was cut into short strips in the same way as the filter of Example 1. The obtained short strip samples were observed at 50x magnification using a metal microscope. As a result, no damage such as splitting or breaking occurred around the cut surface of the sample, confirming that the filter of Example 2 was well cut.

[0058] <Example 3> Similar to Example 1, solution D as a dispersion of aryl copper phosphonate (UV-IR absorber) and solution H as a dispersion of butyl copper phosphonate (IR absorber) were obtained. Next, 12.57 g of polysiloxane resin (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KR-300) was added to solution D and stirred for 30 minutes to obtain solution I. An amount equivalent to 40% by mass of the total volume of solution H was added to solution I, and then 7.344 g of dimethyldiethoxysilane (DMDES) (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KBE-22), an alkoxysilane, was added and 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 mixture of solution I and solution H. Regarding alkoxysilanes, assuming that when their complete hydrolysis condensate is obtained, the content of silane compounds from MTES is 42.1% by mass, the content of silane compounds from TEOS is 10.5% by mass, and the content of silane compounds from DMDES is 47.4% by mass, the light-absorbing composition of Example 3 is prepared in this manner.

[0059] The filter of Example 3 was prepared in the same manner as that of Example 1, except that the light-absorbing composition of Example 3 was used instead of the light-absorbing composition of Example 1. Furthermore, the filter of Example 3 was cut into short strips in the same way as the filter of Example 1. The obtained short strip samples were observed at 50x magnification using a metal microscope. As a result, no damage such as splitting or breaking occurred around the cut surface of the sample, confirming that the filter of Example 3 was well cut.

[0060] <Comparative Example 1> Liquid D, as a dispersion of aryl copper phosphonate (UV-IR absorber), and liquid H, as a dispersion of butyl copper phosphonate (IR absorber), were obtained in the same manner as in Example 1. Next, 12.57 g of polysiloxane resin (manufactured by Shin-Etsu Chemical Industry Co., Ltd., product name: KR-300) was added to liquid D and stirred for 30 minutes to obtain liquid I. An amount equivalent to 40% by mass of the total volume of liquid H was added to liquid I, and the mixture was stirred for another 30 minutes to obtain the light-absorbing composition of Comparative Example 1. In the preparation of the light-absorbing composition of Comparative Example 1, no alkoxysilane was added to the mixture of liquid I and liquid H.

[0061] The filter of Comparative Example 1 was prepared in the same manner as that of Example 1, except that the light-absorbing composition of Comparative Example 1 was used instead of the light-absorbing composition of Example 1. Furthermore, an attempt was made to cut the filter of Comparative Example 1 into short strips in the same way as the filter of Example 1. However, multiple cracks appeared around the four straight lines parallel to one side of the filter and spaced 20 mm apart, making it impossible to cut the filter of Comparative Example 1 properly, and a short strip sample could not be obtained.

[0062] <Transmittance Spectrum Measurement> The transmittance spectrum of each filter at an incident angle of 0° was measured using a UV-Vis-NIR spectrophotometer (manufactured by Nippon Spectrophotometer Co., Ltd., product name: V-670). The transmittance spectra of the filters of Example 1, Example 2, Example 3, and Comparative Example 1 are shown in Figures 3, 4, 5, and 6, respectively. Furthermore, the transmittance characteristics read from Figures 3 to 6 are shown in Table 1.

[0063] <Thickness Measurement> The thickness of the filter was measured by measuring the distance from the surface of the filter using a laser displacement meter (manufactured by Keyence, product name: LK-H008). The results are shown in Table 1.

[0064] <Young's Modulus and Hardness> The surface of the filter was measured using a nano indenter (manufactured by MTS Systems, product name: Nano Indenter XP) according to the nano indentation method (continuous stiffness measurement method). A diamond triangular pyramidal indenter was used as the indenter, and the measurement was conducted at room temperature (approximately 23°C) and in atmospheric conditions. The average hardness values ​​within the indentation depth range of 5–10 μm in the hardness-indentation depth graph obtained by this measurement were averaged to determine the average surface hardness of each filter. Furthermore, the average Young's modulus values ​​within the indentation depth range of 5–10 μm in the Young's modulus-indentation depth graph obtained by this measurement were averaged to determine the average Young's modulus of each filter. Moreover, based on the fact that the main component of the filter is polysiloxane, the Poisson's ratio of the filter was specified as 0.4. The results are shown in Table 3. In the examples, the average Young's modulus was 0.87–1.6 GPa, and the average hardness was 0.020–0.048 GPa. On the other hand, in the comparative example, the average Young's modulus was 2.6 GPa, and the hardness was 0.11 GPa, indicating poor softness.

[0065] <Determination of Haze> The haze of filters of Examples 1 to 3 and filters of Comparative Example 1 was measured using a HAZE METER (manufactured by Murakami Color Technology Research Institute Co., Ltd., product name: HM-65L2) in accordance with Japanese Industrial Standard JIS K 7136. The results are shown in Table 3.

[0066] <Moisture Resistance Test> The filters of Examples 1 to 3 were placed inside a constant temperature and humidity chamber (manufactured by Tokyo Rikagi K. Co., Ltd., KCL-2000A) set at 85°C and 85% relative humidity for 1000 hours to conduct a moisture resistance test. The transmittance spectra of the filters of Examples 1 and 2 at a 0° incident angle were measured using a UV-Vis-NIR spectrophotometer (manufactured by Nippon Spectrophotometer Co., Ltd., product name: V-670) after the moisture resistance test. The results are shown in Figures 7 and 8. In Figures 7 and 8, the solid lines represent the transmittance spectra of the filters before the moisture resistance test, and the dashed lines represent the transmittance spectra of the filters after the moisture resistance test. The parameter values ​​read from these transmittance spectra are shown in Table 4. Furthermore, the filter of Example 3 after the moisture resistance test was cloudy and did not allow light to pass through at all.

[0067] As shown in Table 3, the filters of Examples 1 to 3 are shown to have higher flexibility compared to the filter of Comparative Example 1. Furthermore, as shown in Table 4, the filters of Examples 1 and 2 are shown to meet the conditions (i) to (viii) above and have good moisture resistance.

[0068] The light-absorbing film of the filter in the embodiment of the present invention has a small Young's modulus and high flexibility. Therefore, after the light-absorbing film is fabricated on a flat substrate, the light-absorbing film peeled off from the substrate is laminated along the surface of other substrates such as lenses, flexible filters, resin-based filters with high flexibility, or other optical elements that have arbitrary curved surfaces or highly flexible flat surfaces. In this way, a light-absorbing film with uniform thickness can be laminated on the curved surface to form an optical element or filter with light absorption function.

[0069] Furthermore, in recent years, smartphones and other portable communication devices have increasingly used highly flexible substrates, such as displays using organic EL. The light-absorbing film of the embodiment of the present invention, as a substrate, is also compatible with such flexible displays or panels, and therefore can be easily applied to these fields.

[0070] In conventional spin coating or dip coating methods, forming a film of uniform thickness on a curved surface requires very precise control, which is quite difficult. On the other hand, the above method is very effective because it can form a light-absorbing film of uniform thickness on a curved surface relatively easily.

[0071] An adhesive can be used to bond the light-absorbing film to the curved surface. The calcined film can be laminated along the curved surface of the substrate, followed by heat treatment or heat and humidification treatment. In the latter case, the calcination temperature is preferably below 60°C, and the final heat and humidification temperature is preferably above 80°C.

[0072] Furthermore, as a substrate for fabricating a light-absorbing film, a substrate on which wires made of materials such as glass fiber, carbon fiber, or cellulose nanofiber are formed on the surface (e.g., in a lattice pattern) can be used. In this case, after the light-absorbing film is formed on the substrate, a light-absorbing film with wires formed inside or on the surface can be obtained by peeling it off together with the wires. Since such wires give the light-absorbing film appropriate mechanical rigidity, a light-absorbing film with both flexibility and rigidity can be fabricated.

[0073] Furthermore, after forming a coating on a flat substrate, by deforming the substrate and performing heating or heating and humidification treatment, a light-absorbing film with a special surface state (e.g., lens-shaped) corresponding to the final substrate shape can be formed. By deforming or hardening the light-absorbing film according to the required substrate shape, light-absorbing filters with various surface states (planar or curved) can be manufactured.

[0074] The light-absorbing film of the embodiment of the present invention also has excellent impact resistance. Therefore, it has the advantage of not being easily limited by the usage environment. The light-absorbing film of the embodiment of the present invention can be effectively used in wearable devices, such as those subjected to long-term vibration and strong impact, especially in camera modules, optical sensors, or parts of various optical systems built into wearable cameras or action cameras.

[0075] [Table 1] Optical properties Thickness [μm] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Maximum transmittance at 300–350 nm [%) Maximum transmittance in the 300–360 nm range [%] UV cutoff wavelength [nm] Average transmittance in the 450–600 nm range [%) IR cutoff wavelength [nm] Average transmittance at 700–750 nm [%) Maximum transmittance in the 750–1080 nm range [%] Maximum transmittance in the 800–950 nm range [%] Maximum transmittance in the 800–1000 nm range [%) Maximum transmittance in the 800–1050 nm range [%] Maximum transmittance in the 800–1100 nm range [%] Maximum transmittance in the 800–1150 nm range [%] Maximum transmittance in the 800–1200 nm range [%] The difference between the IR cutoff wavelength and the UV cutoff wavelength [nm] Example 1 0.05 0.05 405 86.32 631 0.70 0.27 0.27 0.27 0.27 0.27 0.58 2.41 225 236 Example 2 0.04 0.04 404 86.93 638 1.64 0.33 0.13 0.13 0.25 0.48 1.59 4.90 235 197 Example 3 0.04 0.04 401 88.03 643 2.63 0.61 0.36 0.36 0.36 0.81 2.30 6.44 242 146 Comparative Example 1 0.07 0.07 407 85.76 630 0.68 0.22 0.22 0.22 0.22 0.22 0.62 2.65 223 201

[0076] [Table 2] Amount added [g] Solid content [g] Solid content ratio Four Alkoxy silane three Alkoxy silane two Alkoxy silane All silane monomers Four Alkoxy silane three Alkoxy silane two Alkoxy silane All silane monomers Four Alkoxy silane three Alkoxy silane two Alkoxy silane All silane monomers TEOS MTES DMDES TEOS MTES DMDES TEOS MTES DMDES Example 1 Preparation of aryl copper phosphonates 2.830 8.664 0.000 11.494 0.816 3.261 0.000 4.077 6.7% 26.6% 0.0% 33.3% The final preparation of light-absorbing components 5.660 10.840 4.896 21.396 1.632 4.080 2.448 8.161 13.3% 33.3% 20.0% 66.7% total 8.490 19.504 4.896 32.890 2.449 7.341 2.448 12.238 20.0% 60.0% 20.0% 100.0% Example 2 Preparation of aryl copper phosphonates 2.830 8.664 0.000 11.494 0.816 3.261 0.000 4.077 10.0% 40.0% 0.0% 50.0% The final preparation of light-absorbing components 2.830 5.420 2.448 10.698 0.816 2.040 1.224 4.081 10.0% 25.0% 15.0% 50.0% total 5.660 14.084 2.448 22.192 1.632 5.301 1.224 8.158 20.0% 65.0% 15.0% 100.0% Example 3 Preparation of aryl copper phosphonates 2.830 8.664 0.000 11.494 0.816 3.261 0.000 4.077 10.5% 42.1% 0.0% 52.6% The final preparation of light-absorbing components 0.000 0.000 7.344 7.344 0.000 0.000 3.673 3.673 0.0% 0.0% 47.4% 47.4% total 2.830 8.664 7.344 18.838 0.816 3.261 3.673 7.750 10.5% 42.1% 47.4% 100.0% Comparative Example 1 Preparation of aryl copper phosphonates 2.830 8.664 0.000 11.494 0.816 3.261 0.000 4.077 20.0% 80.0% 0.0% 100.0%

[0077] [Table 3] Average hardness [GPa] Average value of Young's modulus [GPa] Haze Example 1 0.020 0.87 0.34 Example 2 0.048 1.6 0.31 Example 3 0.028 1.1 0.13 Comparative Example 1 0.11 2.6 0.7

[0078] [Table 4] Optical properties 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Maximum transmittance at 300–350 nm [%) Maximum transmittance in the 300–360 nm range [%] UV cutoff wavelength [nm] Average transmittance in the 450–600 nm range [%) IR cutoff wavelength [nm] Average transmittance at 700–750 nm [%) Maximum penetration at 750–1080 nm Rate[%] Maximum transmittance in the 800–950 nm range [%] Maximum transmittance in the 800–1000 nm range [%) Maximum transmittance in the 800–1050 nm range [%] Maximum transmittance in the 800–1100 nm range [%] Maximum transmittance in the 800–1150 nm range [%] Maximum transmittance in the 800–1200 nm range [%] The difference between the IR cutoff wavelength and the UV cutoff wavelength [nm] Example 1 initial value 0.05 0.05 405 86.32 631 0.70 0.27 0.27 0.27 0.27 0.27 0.58 2.41 225 After the test 0.01 0.01 410 86.02 632 0.62 0.15 0.15 0.15 0.15 0.15 0.42 1.81 222 Change 0.04 0.04 5 0.30 1 0.08 0.12 0.12 0.12 0.12 0.12 0.16 0.60 3 Example 2 initial value 0.04 0.04 404 86.93 638 1.64 0.33 0.13 0.13 0.25 0.48 1.59 4.90 235 After the test 0.05 0.05 409 86.84 638 1.43 0.27 0.25 0.25 0.25 0.37 1.24 4.14 230 Change 0.01 0.01 5 0.08 0 0.21 0.06 0.12 0.12 0.00 0.11 0.35 0.77 5 [Simplified Explanation of the Diagram]

[0011] [Figure 1] is a cross-sectional view showing one example of the filter of the present invention. [Figure 2] is a cross-sectional view showing another example of the filter of the present invention. [Figure 3] is the transmittance spectrum of the filter of Example 1. [Figure 4] is the transmittance spectrum of the filter of Example 2. [Figure 5] is the transmittance spectrum of the filter of Example 3. [Figure 6] is the transmittance spectrum of the filter of Comparative Example 1. [Figure 7] is the transmittance spectrum of the filter of Example 1 before and after the moisture resistance test. [Figure 8] is the transmittance spectrum of the filter of Example 2 before and after the moisture resistance test.

Claims

1. A light-absorbing composition comprising a light absorber, a resin, and an alkoxysilane, wherein the light absorber comprises a phosphonic acid and a copper ion represented by formula (a), [wherein R11 is a halogenated aryl group in which at least one hydrogen atom of an alkyl, aryl, nitroaryl, hydroxyaryl, or aryl group is replaced by a halogen atom], and the alkoxysilane comprises a dialkoxysilane represented by formula (b), (R2)2-Si-(OR3)2 (b) [wherein R2 is an alkyl group having 1 to 6 carbon atoms, and R3 is an alkyl group having 1 to 8 carbon atoms], and the ratio of the dialkoxysilane content to the total content of the alkoxysilane is 15 to 48% by mass, after converting all the alkoxysilanes into hydrolyzed condensates.

2. The light-absorbing component as claimed in claim 1, wherein, The aforementioned alkoxysilanes further include either tetraalkoxysilanes or trialkoxysilanes.

3. A light-absorbing film formed from the light-absorbing composition of claim 1 or 2.

4. The light-absorbing film of claim 3 has a Young's modulus of less than 2.00 GPa and a hardness of less than 0.06 GPa.

5. A filter having the light-absorbing film of claim 3.

6. A filter having the light-absorbing film of claim 4.

7. A method for manufacturing a filter, comprising: coating a light-absorbing composition of claim 1 or 2 onto a substrate; and forming a light-absorbing film on the substrate by means of the light-absorbing composition.

8. The method of manufacturing the filter as claimed in claim 7 further includes: peeling the light-absorbing film from the substrate.

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