Light-absorbing composition, light-absorbing membrane, and optical filter

Abstract

To provide a light-absorbing composition which is advantageous for providing a light-absorbing film having desired optical characteristics even when it does not contain a phenyl-based phosphonic acid and an alkyl-based phosphonic acid, and to provide the light-absorbing film, and an optical filter having the light-absorbing film.SOLUTION: A light-absorbing composition enables provision of a light-absorbing film which contains a light-absorbing agent formed of a phosphonic acid represented by the following formula (A) and copper ions, and a curable resin, and has desired characteristics by curing a coating film of the light-absorbing composition. In the formula (A), each of R1 to R5 independently represents a hydrogen atom, a halogen atom, a hydroxy group or a nitro group, and n represents an integer of 1 to 3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a light-absorbing composition, a light-absorbing film, and an optical filter. [Background technology]

[0002] CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) In imaging devices using solid-state imaging elements such as OLEDs, various optical filters are placed in front of the solid-state imaging elements to obtain images with good color reproducibility. Solid-state imaging elements generally have spectral sensitivity over a wide wavelength range, from the ultraviolet to the infrared regions. Meanwhile, human visual sensitivity exists only in the visible light region. Therefore, a known technique is to place an optical filter in front of the solid-state imaging element to block part of the infrared or ultraviolet light, in order to bring the spectral sensitivity of the solid-state imaging element in the imaging device closer to the human visual sensitivity.

[0003] Conventionally, such optical filters have typically utilized light reflection by a dielectric multilayer film to block infrared or ultraviolet light. However, in recent years, optical filters equipped with a film containing a light-absorbing agent have been attracting attention. Because the transmittance characteristics of optical filters equipped with a film containing a light-absorbing agent are less affected by the angle of incidence, they can produce good images with little change in color even when light is incident on the optical filter at an angle in an imaging device. Furthermore, light-absorbing optical filters that do not use a light-reflecting film can suppress the occurrence of ghosts and flares caused by multiple reflections by the light-reflecting film, making it easier to obtain good images in backlit conditions or when photographing night scenes. In addition, optical filters equipped with a film containing a light-absorbing agent are advantageous in terms of miniaturizing and thinning imaging devices.

[0004] As such a light absorber, a light absorber formed from phosphonic acid and copper ions is known. For example, Patent Document 1 describes an optical filter having a light absorbing layer containing a light absorber formed from phosphonic acid having a phenyl group or a halogenated phenyl group and copper ions.

[0005] Patent Document 2 describes an optical filter having a UV-IR absorbing layer capable of absorbing infrared and ultraviolet rays. The UV-IR absorbing layer contains a UV-IR absorber formed from phosphonic acid and copper ions. The UV-IR absorbing composition contains, for example, a phenyl-based phosphonic acid and an alkyl-based phosphonic acid so that the optical filter has predetermined optical properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6339755 [Patent Document 2] Patent No. 6232161 Summary of the Invention [Problem to be solved by the invention]

[0007] In the optical filter described in Patent Document 1, the UV cutoff wavelength is less than 400 nm. In addition, the technology described in Patent Document 1 has room for improving light absorption performance in the wavelength range exceeding 1000 nm. On the other hand, in the technology described in Patent Document 2, the UV-IR absorbing composition contains a phenyl-based phosphonic acid and an alkyl-based phosphonic acid so that the optical filter satisfies predetermined optical properties.

[0008] Therefore, the present disclosure does not contain phenyl-based phosphonic acids and alkyl-based phosphonic acids. The present invention also provides a light-absorbing composition that is advantageous for providing a light-absorbing film having desired optical properties even when the composition is a non-transitory film. The present invention also provides such a light-absorbing film and an optical filter including the light-absorbing film. [Means for solving the problem]

[0009] The present invention provides a light absorber formed by a phosphonic acid represented by the following formula (A) and a copper ion; and a curable resin, A light absorbing composition is provided. [ka] [In formula (A), R1 to R5 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, or a nitro group, and n represents an integer of 1 to 3.]

[0010] The present invention provides a light absorber formed by a phosphonic acid represented by the following formula (A) and a copper ion; and a cured product of the curable resin, A light absorbing film is provided. [ka] [In formula (A), R1 to R5 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, or a nitro group, and n represents an integer of 1 to 3.]

[0011] The present invention also provides an optical filter comprising the above-mentioned light-absorbing film. [Effects of the Invention]

[0012] The light-absorbing composition is advantageous in providing a light-absorbing film having desired optical properties. The light-absorbing film and the optical filter tend to have the desired optical properties. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a light-absorbing film according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of an optical filter according to the present invention. [Figure 3]FIG. 3 shows the transmittance spectrum of the optical filter according to the first embodiment. [Figure 4] FIG. 4 shows the transmittance spectrum of the optical filter according to the second embodiment. [Figure 5] FIG. 5 shows the transmittance spectrum of the optical filter according to the third embodiment. [Figure 6] FIG. 6 shows the transmittance spectrum of the optical filter according to Comparative Example 1. As shown in FIG. [Figure 7] FIG. 7 shows the spectrum of the optical filter according to Comparative Example 2. [Figure 8] FIG. 8 shows the transmittance spectrum of a transparent glass substrate. DETAILED DESCRIPTION OF THE INVENTION

[0014] Light absorbers formed from phenyl-based phosphonic acid and copper ions tend to have the property of absorbing light in the wavelength range corresponding to ultraviolet light and in the relatively short wavelength range of near-infrared light. On the other hand, light absorbers formed from alkyl-based phosphonic acid and copper ions tend to have the property of absorbing light in the relatively long wavelength range of near-infrared light. For this reason, for example, in order to achieve a desired spectral transmittance in an optical filter used in an imaging device, a light-absorbing composition containing phenyl-based phosphonic acid and alkyl-based phosphonic acid has been used.

[0015] Meanwhile, the present inventors have conducted extensive research into whether it is possible to realize a light-absorbing film having desired optical properties, not only by using a combination of light-absorbing compositions having different absorption properties, but also without containing such a specific phosphonic acid. As a result, the present inventors have newly discovered that a light-absorbing composition containing a light absorber formed from a specific phosphonic acid and copper ions is advantageous for realizing a light-absorbing film having desired optical properties. Based on this new finding, the present inventors have devised the light-absorbing composition according to the present invention.

[0016] Hereinafter, embodiments of the present invention will be described. Note that the following description relates to examples of the present invention, and the present invention is not limited to these.

[0017] The light-absorbing composition according to the present invention contains a light-absorbing agent and a curable resin. The light-absorbing agent is formed from a phosphonic acid represented by the following formula (A) and copper ions.

[0018] [ka] [In formula (A), R1 to R5 each independently represent a hydrogen atom, a halogen atom, a hydroxy group, or a nitro group, and n represents an integer of 1 to 3.]

[0019] The phosphonic acid represented by formula (A) is, for example, a phosphonic acid having an aralkyl group. The phosphonic acid represented by formula (A) has, in its molecular structure, a cyclic hydrocarbon group, which is a benzene ring, and a non-cyclic hydrocarbon group. Therefore, it is considered that the light absorber has the characteristics of the light absorption of each functional group. As a result, the light absorbing composition is advantageous in realizing a light absorbing film having desired optical properties. The aralkyl group (aralkyl group) means an aralkyl group. Alkyl group (-C n’ H 2n’+1 (n' represents an integer of 1 or more)) one of the hydrogen atoms is phenyl Specific examples of aralkyl groups include benzyl groups, phenylmethyl groups (-CH2-C6H5 (in formula (A), n = 1)) and phenylmethyl groups (-CH2-C6H5 (in formula (A), n = 1)). Examples include a phenylethyl group (-C2H4-C6H5 (in formula (A), n=2)).

[0020] The phosphonic acid represented by formula (A) may be, for example, a benzyl group, a halogenated benzyl group in which at least one hydrogen atom on the benzene ring of the benzyl group is substituted with a halogen atom, or a benzyl group in which at least one hydrogen atom on the benzene ring of the benzyl group is substituted with a hydroxy group. The phosphonic acid represented by formula (A) may be a phosphonic acid having a hydroxybenzyl group in which at least one hydrogen atom on the benzene ring of the benzyl group is substituted with a nitro group, or a nitrobenzyl group in which at least one hydrogen atom on the benzene ring of the benzyl group is substituted with a nitro group. Furthermore, the phosphonic acid represented by formula (A) may be a phosphonic acid having a phenethyl group, a halogenated phenethyl group in which at least one hydrogen atom on the benzene ring of the phenethyl group is substituted with a halogen atom, a hydroxyphenethyl group in which at least one hydrogen atom on the benzene ring of the phenethyl group is substituted with a hydroxy group, or a nitrophenethyl group in which at least one hydrogen atom on the benzene ring of the phenethyl group is substituted with a nitro group. These are examples of the phosphonic acid represented by formula (A).

[0021] In the phosphonic acid represented by formula (A), an aralkyl group or modified aralkyl group such as a benzyl group, a halogenated benzyl group, a hydroxybenzyl group, a nitrobenzyl group, a phenethyl group, a halogenated phenethyl group, a hydroxyphenethyl group, or a nitrophenethyl group is directly bonded to the phosphorus atom. Meanwhile, in the phosphonic acid represented by formula (A), a hydrocarbon group having 1 to 3 carbon atoms may be further present between the aralkyl group or modified aralkyl group and the phosphorus atom.

[0022] The phosphonic acid represented by formula (A) is, for example, at least one selected from the group consisting of benzylphosphonic acid, fluorobenzylphosphonic acid, difluorobenzylphosphonic acid, chlorobenzylphosphonic acid, dichlorobenzylphosphonic acid, bromobenzylphosphonic acid, dibromobenzylphosphonic acid, iodobenzylphosphonic acid, diiodobenzylphosphonic acid, hydroxybenzylphosphonic acid, nitrobenzylphosphonic acid, phenethylphosphonic acid, fluorophenethylphosphonic acid, difluorophenethylphosphonic acid, chlorophenethylphosphonic acid, dichlorophenethylphosphonic acid, bromophenethylphosphonic acid, dibromophenethylphosphonic acid, iodophenethylphosphonic acid, diiodophenethylphosphonic acid, hydroxyphenethylphosphonic acid, and nitrophenethylphosphonic acid.

[0023] In the light-absorbing composition, the ratio of the content of the phosphonic acid represented by formula (A) to the content of the copper ions is not limited to a specific value. The ratio is, for example, 0.7 to 0.9 on a substance basis. In this case, it is easier to realize a light-absorbing film having desired optical properties using the light-absorbing composition.

[0024] In the light-absorbing composition, the ratio of the content of the phosphonic acid represented by formula (A) to the content of the copper ions is desirably 0.75 to 0.85.

[0025] The light-absorbing composition may contain a light absorber formed from a phosphonic acid other than the phosphonic acid represented by formula (A) and copper ions. In this case, the phosphonic acid other than the phosphonic acid represented by formula (A) is a phosphonic acid represented by the following formula (B). The phosphonic acid represented by formula (B) may be a phosphonic acid having an alkyl group, such as methylphosphonic acid, ethylphosphonic acid, or butylphosphonic acid, or a phosphonic acid having a phenyl group (including a halogenated phenyl group in which some of the hydrogen atoms on the benzene ring are substituted with halogen atoms). Based on the characteristics exhibited by the light absorber composed of the phosphonic acid represented by formula (B) and a copper component, it is expected that the performance corresponding to those characteristics will be promoted.

[0026] [ka] [In formula (B), R 21 represents an alkyl group, a phenyl group, a halogenated alkyl group or halogenated phenyl group in which at least one hydrogen atom is substituted with a halogen atom, a nitrophenyl group, or a hydroxyphenyl group.]

[0027] When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0° onto a light-absorbing film obtained by curing a coating film of the light-absorbing composition, for example, the following conditions (i) to (iii) are satisfied: Be satisfied. (i) The UV cutoff wavelength, which exhibits a spectral transmittance of 50% at wavelengths of 350 nm to 450 nm, is within the wavelength range of 400 nm to 450 nm. (ii) The IR cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm is 700 nm or less. (iii) The difference ΔT between the IR cutoff wavelength and the UV cutoff wavelength 50% is 240 nm or more.

[0028] When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0° onto a light-absorbing film obtained by curing a coating film of the light-absorbing composition, for example, the following conditions (iv) to (vii) are satisfied: It is filled with (iv) The spectral transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (v) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (vi) The spectral transmittance in the wavelength range of 800 nm to 1100 nm is 10% or less. (vii) The spectral transmittance in the wavelength range of 800 nm to 1150 nm is 15% or less.

[0029] Typically, a light-absorbing agent is dispersed in the light-absorbing composition. For example, microparticles containing at least a light-absorbing agent are formed in the light-absorbing composition. The average particle diameter of the microparticles is, for example, 5 nm to 200 nm. When the average particle diameter of the microparticles is 5 nm or more, no special process is required for micronization of the microparticles, and the structure of the microparticles containing at least a light-absorbing agent is less likely to be destroyed. Furthermore, the microparticles are well dispersed in the light-absorbing composition. Furthermore, when the average particle diameter of the microparticles is 200 nm or less, the influence of Mie scattering can be reduced, the visible light transmittance of the light-absorbing film can be improved, and deterioration of characteristics such as contrast and haze of images captured by an imaging device can be suppressed. The average particle diameter of the microparticles is preferably 100 nm or less. In this case, the influence of Rayleigh scattering is reduced, thereby increasing the transparency to visible light of the light-absorbing film formed using the light-absorbing composition. Furthermore, the average particle diameter of the microparticles is more preferably 75 nm or less. In this case, the transparency to visible light of the light-absorbing film formed using the light-absorbing composition is particularly high. The average particle size of the fine particles can be measured by dynamic light scattering.

[0030] In the light-absorbing composition, the curable resin is not limited to a specific resin, and may be, for example, a silicone resin.

[0031] The curable resin is preferably a silicone resin containing an aryl group such as a phenyl group. If the resin contained in the light absorbing film is hard (rigid), cracks are likely to occur due to cure shrinkage during the production of the light absorbing film as the thickness of the layer containing the resin increases. When the silicone resin contains an aryl group, the light-absorbing film formed from the light-absorbing composition tends to have good crack resistance. Furthermore, the silicone resin containing an aryl group has high compatibility with the phosphonic acid represented by formula (A) and is less likely to cause the light absorber to aggregate. Specific examples of silicone resins 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. These are all silicone resins manufactured by Shin-Etsu Chemical Co., Ltd.

[0032] The light-absorbing composition may further contain, for example, a phosphate ester, which facilitates appropriate dispersion of the light absorber in the light-absorbing composition or in a light-absorbing film obtained by curing the light-absorbing composition.

[0033] The phosphate ester is, for example, a phosphate ester having a polyoxyalkyl group. The phosphate ester having a polyoxyalkyl group is not limited to a specific phosphate ester. Examples of the phosphate ester having a polyoxyalkyl 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, and Plysurf A215C: polyoxyethylene tridecyl ether phosphate ester. All of these are products manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. The phosphate ester may also be, for example, NIKKOL DDP-2: polyoxyethylene alkyl ether phosphate ester, NIKKOL DDP-4: polyoxyethylene alkyl ether phosphate ester, or NIKKOL DDP-6: polyoxyethylene alkyl ether phosphate ester. All of these are products manufactured by Nikko Chemicals Co., Ltd.

[0034] The light-absorbing composition may further contain an alkoxysilane, if necessary. In this case, a siloxane bond (-Si-O-Si-) is formed by hydrolysis and polycondensation of the alkoxysilane, and the light-absorbing film tends to have a dense structure. The alkoxysilane may be a monomer, an oligomer or polymer in which hydrolysis and polycondensation have progressed to a certain extent, or a mixture thereof.

[0035] An example of a method for preparing a light-absorbing composition is described below. A copper salt such as copper acetate monohydrate is added to a predetermined solvent such as tetrahydrofuran (THF) and stirred to prepare a solution A of the copper salt. A phosphate ester may be added during the preparation of Solution A. Next, a phosphonic acid represented by formula (A), such as benzylphosphonic acid, is added to a predetermined solvent such as THF and stirred to prepare Solution B. When using multiple types of phosphonic acids, each phosphonic acid may be added to a predetermined solvent such as THF and stirred to prepare Solution B, which is a mixture of multiple preliminary solutions prepared for each type of phosphonic acid. While stirring Solution A, Solution B is added to Solution A and stirred for a predetermined period of time. Next, a predetermined solvent such as toluene is added to this solution and stirred to obtain Solution C. Next, Solution C is subjected to a desolvation treatment for a predetermined period of time while heating it to obtain Solution D. This removes components generated by dissociation of the copper salt, such as solvents such as THF and acetic acid (boiling point: approximately 118°C), and a light absorber is produced from the phosphonic acid represented by formula (A) and copper ions. The temperature to which Liquid C is heated is determined based on the boiling point of the component to be removed that has dissociated from the copper salt. During the solvent removal process, the solvent used to obtain Liquid C, such as toluene (boiling point: approximately 110°C), also volatilizes. It is desirable for this solvent to remain to some extent in the light-absorbing composition, so the amount of solvent added and the duration of the solvent removal process should be determined from this perspective. Alternatively, o-xylene (boiling point: approximately 144°C) can be used instead of toluene to obtain Liquid 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-fourth of the amount added of toluene.

[0036] Next, the liquid D is mixed with a curable resin such as a silicone resin and stirred for a predetermined period of time to prepare a light-absorbing composition.

[0037] The light-absorbing composition can be used to provide, for example, a light-absorbing film 10 as shown in FIG. 1. The light-absorbing film 10 contains, for example, a light-absorbing agent formed from phosphonic acid represented by the above formula (A) and copper ions, and a cured product of a curable resin. Typically, the light-absorbing agent is dispersed in the cured product. The light-absorbing film 10 can be obtained, for example, by curing a coating of the light-absorbing composition.

[0038] In the light-absorbing film 10, the ratio of the content of the phosphonic acid represented by formula (A) to the content of the copper ions is 0.7 to 0.9 on a substance amount basis, and this ratio is preferably 0.75 to 0.85.

[0039] The light absorbing film 10 satisfies, for example, the above conditions (i) to (iii) when light with a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°.

[0040] When the light-absorbing film 10 satisfies condition (i), it has a high ability to block light in a wavelength range shorter than the wavelength corresponding to the limit of human visual sensitivity. In addition, with recent changes in the sensitivity of sensors in image sensors, particularly improvements in sensor sensitivity in the ultraviolet wavelength range, it is advantageous to be able to effectively block ultraviolet light near the lower limit of the visible light range (near about 400 nm). From this perspective, it is also desirable for the light-absorbing film 10 to satisfy condition (i). Regarding condition (i), the light-absorbing film 10 preferably has a UV cutoff wavelength within a wavelength range of 400 nm to 430 nm. Regarding condition (i), the light-absorbing film 10 has a spectral transmittance that increases with increasing wavelength within a wavelength range of 350 nm to 450 nm, for example.

[0041] When the light-absorbing film 10 satisfies condition (ii), it has a high ability to block light in a wavelength range longer than the wavelength corresponding to the limit of human visual sensitivity. Regarding condition (ii), it is preferable that the IR cutoff wavelength is 690 nm or less in the light-absorbing film 10. Regarding condition (ii), in the light-absorbing film 10, for example, the spectral transmittance decreases as the wavelength increases in the wavelength range of 600 nm to 750 nm.

[0042] When the light-absorbing film 10 satisfies the condition (iii), 50% or more of the light-absorbing film 10 The wavelength range in which the transmittance of the light is exhibited is likely to coincide with the wavelength range corresponding to the range of human visual sensitivity. (iii ) in the light absorbing film 10, the difference ΔT 50% is preferably 250 nm or more. More preferably, it is 260 nm or more.

[0043] The light absorbing film 10 further satisfies, for example, the above conditions (iv) to (vii) when light with a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°.

[0044] When the light-absorbing film 10 satisfies the condition (iv), it can effectively block light in the ultraviolet region outside the range of human visibility. Regarding the condition (iv), the light-absorbing film 10 desirably has a spectral transmittance of 1% or less in the wavelength range of 300 nm to 360 nm.

[0045] When the light-absorbing film 10 satisfies the condition (v), the transmittance of light in the visible light region is high. This is advantageous for forming an image using an imaging element. Regarding the condition (v), the light-absorbing film 10 preferably has an average transmittance of 78% or more in the wavelength range of 450 nm to 600 nm, and more preferably 80% or more.

[0046] When the light absorbing film 10 satisfies the conditions (vi) and (vii), it is possible to obtain a light that is not subject to the human visual sensitivity. With regard to the condition (vi), the light-absorbing film 10 has a spectral transmittance of preferably 5% or less, more preferably 3% or less, in the wavelength range of 800 nm to 1100 nm. With regard to the condition (vii), the light-absorbing film 10 has a spectral transmittance of preferably 5% or less, more preferably 3% or less, in the wavelength range of 800 nm to 1100 nm. The spectral transmittance in the wavelength range of 800 nm to 1150 nm is preferably 10% or less, and more preferably 5% or less.

[0047] As shown in FIG. 1, an optical filter 1a having a light absorbing film 10 can be provided.

[0048] The optical filter 1a satisfies, for example, the following conditions (I) to (III) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°. (I) The UV cutoff wavelength showing a spectral transmittance of 50% at wavelengths of 350 nm to 450 nm is within the wavelength range of 400 nm to 450 nm. (II) The IR cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm is 700 nm or less. (III) ΔT, the difference between the IR cutoff wavelength and the UV cutoff wavelength 50% is 240 nm or more.

[0049] Regarding condition (I), the UV cutoff wavelength of the optical filter 1a is preferably within the wavelength range of 400 nm to 430 nm. Regarding condition (I), the spectral transmittance of the optical filter 1a increases with increasing wavelength, for example, within the wavelength range of 350 nm to 450 nm.

[0050] Regarding condition (II), it is desirable that the IR cutoff wavelength of the optical filter 1a is 690 nm or less. Regarding condition (II), in the optical filter 1a, for example, the spectral transmittance decreases as the wavelength increases in the wavelength range of 600 nm to 750 nm.

[0051] Regarding the condition (III), in the optical filter 1a, the difference ΔT 50%is preferably 250 nm or more, and more preferably 260 nm or more.

[0052] The optical filter 1a further satisfies the following conditions (IV) to (VII) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°. (IV) The spectral transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (V) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (VI) The spectral transmittance in the wavelength range of 800 nm to 1100 nm is 10% or less. (VII) The spectral transmittance in the wavelength range of 800 nm to 1150 nm is 15% or less.

[0053] Regarding condition (IV), the optical filter 1a preferably has a spectral transmittance of 1% or less in the wavelength range of 300 nm to 360 nm.

[0054] Regarding condition (V), the average transmittance of the optical filter 1a in the wavelength range of 450 nm to 600 nm is preferably 78% or more, and more preferably 80% or more.

[0055] Regarding the condition (VI), the spectral transmittance of the optical filter 1a in the wavelength range of 800 nm to 1100 nm is preferably 5% or less, and more preferably 3% or less. Regarding condition (1), the spectral transmittance of the optical filter 1a in the wavelength range of 800 nm to 1150 nm is preferably 10% or less, and more preferably 5% or less.

[0056] The optical filter 1a is composed of, for example, a single light absorbing film 10. The optical filter 1a is used, for example, separately from the imaging element or optical component. The optical filter 1a may be bonded to the imaging element and the optical component. Alternatively, the optical filter 1a may be formed by applying the above-mentioned light-absorbing composition to the imaging element or the optical component and curing the light-absorbing composition.

[0057] The optical filter 1a can be produced, for example, by peeling off the light-absorbing film 10 formed on a substrate from the substrate. In this case, the material of the substrate may be glass, resin, or metal. The surface of the substrate may be subjected to a surface treatment such as coating with a fluorine-containing compound.

[0058] The optical filter 1a may be modified, for example, to the optical filter 1b shown in FIG. 2. The optical filter 1b has the same configuration as the optical filter 1a, unless otherwise specified. The same reference numerals are used to designate components of the optical filter 1b that are the same as or correspond to the components of the optical filter 1a, and detailed descriptions thereof will be omitted. The description of the optical filter 1a also applies to the optical filter 1b, provided that there is no technical contradiction.

[0059] As shown in Fig. 2, the optical filter 1b includes a light-absorbing film 10 and a transparent dielectric substrate 20. The light-absorbing film 10 is formed parallel to one main surface of the transparent dielectric substrate 20. The light-absorbing film 10 may be in contact with one main surface of the transparent dielectric substrate 20, for example. In this case, the light-absorbing film 10 is formed, for example, by applying the above-mentioned light-absorbing composition to one main surface of the transparent dielectric substrate 20 and curing the light-absorbing composition.

[0060] The type of transparent dielectric substrate 20 is not limited to a specific type. The transparent dielectric substrate 20 may have absorption ability in the infrared region. The transparent dielectric substrate 20 may have an average spectral transmittance of 90% or more in the wavelength range of 350 nm to 900 nm, for example. The material of the transparent dielectric substrate 20 is not limited to a specific material, and may be, 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, transparent glass or infrared-cutting glass made of silicate glass such as soda-lime glass and borosilicate glass. The infrared-cutting glass is, for example, phosphate glass or fluorophosphate glass containing CuO.

[0061] When the material of the transparent dielectric substrate 20 is a resin, the resin is, for example, a cyclic olefin resin such as a norbornene 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.

[0062] Each of the optical filters 1a and 1b may be modified to further include other functional films such as an infrared reflective film. [Example]

[0063] The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[0064] Example 1 (Preparation of Light-Absorbing Composition) 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, 4.333 g of a phosphate ester compound, Plysurf A208N (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), was added to the obtained copper acetate solution and stirred for 30 minutes to obtain solution A1. 120 g of THF was added to 3.144 g of benzylphosphonic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and stirred for 30 minutes to obtain solution B1. While stirring, solution A1 was added to solution A1. The solution was added with 120 g of toluene and stirred at room temperature for 1 minute to obtain solution C1. Solution C1 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., model: OSB-2100), while a solvent removal treatment was carried out using a rotary evaporator (Tokyo Rikakikai Co., Ltd., model: N-1110SF). The temperature of the oil bath was adjusted to 105°C. The liquid after the solvent removal treatment was then removed from the flask to obtain solution D1, which was a dispersion of a light absorber formed from benzylphosphonic acid and copper ions.

[0065] 8.80 g of silicone resin (product name: KR-300, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the D1 solution and stirred for 30 minutes to obtain a light-absorbing composition according to Example 1, which contains a light absorber formed from benzylphosphonic acid and copper ions. In the light-absorbing composition according to Example 1, the mass ratio of the content of benzylphosphonic acid to the content of phosphate ester compound was 0.726, and the molar ratio of the content of benzylphosphonic acid to the content of copper ions was 0.810.

[0066] (Fabrication of optical filters) The light-absorbing composition according to Example 1 was applied using a dispenser to a 40 mm x 40 mm area in the center of one main surface of a transparent glass substrate (manufactured by SCHOTT, product name: D263 T eco) made of borosilicate glass and having dimensions of 76 mm x 76 mm x 0.21 mm, forming a coating film. The resulting coating film was thoroughly dried at room temperature, and then placed in an oven and heat-treated at 45°C for 2 hours and at 85°C for 30 minutes to volatilize the solvent. The coating film was then baked for 3 hours at 125°C, 1 hour at 150°C, and 3 hours at 170°C to thoroughly harden the coating film. In this way, the light-absorbing film according to Example 1 was formed, and the optical filter according to Example 1 was obtained.

[0067] <Example 2> 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, 4.333 g of Plysurf A208N (Dai-ichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the resulting copper acetate solution and stirred for 30 minutes to obtain Solution A2. 120 g of THF was added to 3.774 g of 4-chlorobenzylphosphonic acid (Johoku Chemical Industry Co., Ltd.) and stirred for 30 minutes to obtain Solution B2. Solution B2 was added to Solution A2 while stirring and stirred at room temperature for 1 minute. Next, 120 g of toluene was added to this solution and stirred at room temperature for 1 minute to obtain Solution C2. Solution C2 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., Model: OSB-2100) while the solvent was removed using a rotary evaporator (Tokyo Rikakikai Co., Ltd., Model: N-1110SF). The temperature of the oil bath was adjusted to 105° C. Thereafter, the liquid after the solvent removal treatment was taken out of the flask to obtain liquid D2, which was a dispersion liquid of a light absorber formed by 4-chlorobenzylphosphonic acid and copper ions.

[0068] 8.80 g of silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to D2 liquid and stirred for 30 minutes to obtain a light-absorbing composition according to Example 2, which contains a light absorber formed from 4-chlorobenzylphosphonic acid and copper ions. In the light-absorbing composition according to Example 2, the mass ratio of the content of 4-chlorobenzylphosphonic acid to the content of the phosphate ester compound was 0.871, and the molar ratio of the content of 4-chlorobenzylphosphonic acid to the content of copper ions was 0.811.

[0069] The light-absorbing composition according to Example 2 was applied using a dispenser to a 40 mm x 40 mm area in the center of one main surface of a transparent glass substrate made of borosilicate glass (manufactured by SCHOTT, product name: D263 T eco) having dimensions of 76 mm x 76 mm x 0.21 mm, to form a coating film. The obtained coating film was thoroughly dried at room temperature and then placed in an oven at 45°C. The coating film was then subjected to a heat treatment at 125°C for 2 hours and then at 85°C for 30 minutes to volatilize the solvent. The coating film was then subjected to a baking treatment at 125°C for 3 hours, at 150°C for 1 hour, and at 170°C for 3 hours to sufficiently harden the coating film. In this way, the light-absorbing film according to Example 2 was formed, and the optical filter according to Example 2 was obtained.

[0070] Example 3 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, 4.333 g of Plysurf A208N (Dai-ichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the resulting copper acetate solution and stirred for 30 minutes to obtain Solution A3. 120 g of THF was added to 3.774 g of 4-chlorobenzylphosphonic acid (Johoku Chemical Industry Co., Ltd.) and stirred for 30 minutes to obtain Solution B3. Solution B3 was added to Solution A3 while stirring and stirred at room temperature for 1 minute. Next, 120 g of toluene was added to this solution and stirred at room temperature for 1 minute to obtain Solution C3. Solution C3 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., Model: OSB-2100) while the solvent was removed using a rotary evaporator (Tokyo Rikakikai Co., Ltd., Model: N-1110SF). The oil bath temperature was adjusted to 105°C. The liquid after the solvent removal treatment was then removed from the flask to obtain Solution D3, a dispersion of a light absorber formed from 4-chlorobenzylphosphonic acid and copper ions. In Solution D3, the mass ratio of the content of 4-chlorobenzylphosphonic acid to the content of the phosphate ester compound was 0.871, and the molar ratio of the content of phosphonic acid to the content of copper ions was 0.811.

[0071] 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, 2.572 g of Plysurf A208N (Dai-ichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the resulting copper acetate solution and stirred for 30 minutes to obtain solution A4. 2.886 g of n-butylphosphonic acid and 40 g of THF were added and stirred for 30 minutes to obtain solution B4. Solution B4 was added to solution A4 while stirring 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 C4. This solution C4 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., model: OSB-2100) while the solvent was removed using a rotary evaporator (Tokyo Rikakikai Co., Ltd., model: N-1110SF). The oil bath temperature was adjusted to 105°C. The liquid after the solvent removal treatment was then removed from the flask to obtain Liquid D4, a dispersion of a light absorber formed from n-butylphosphonic acid and copper ions. In Liquid D4, the mass ratio of the content of n-butylphosphonic acid to the content of the phosphate ester compound was 1.123, and the molar ratio of the content of phosphonic acid to the content of copper ions was 0.927.

[0072] D4 solution in an amount equivalent to 20 mass % of the total amount of D4 solution and 8.80 g of silicone resin (product name: KR-300, manufactured by Shin-Etsu Chemical Co., Ltd.) were added to D3 solution and stirred for 30 minutes to obtain a light-absorbing composition according to Example 3, which contains a light absorber consisting of 4-chlorobenzylphosphonic acid, n-butylphosphonic acid, and copper ions. In the light-absorbing composition according to Example 3, the mass ratio of the total content of 4-chlorobenzylphosphonic acid and n-butylphosphonic acid to the content of the phosphate ester compound was 0.898, and the molar ratio of the total content of 4-chlorobenzylphosphonic acid and n-butylphosphonic acid to the content of copper ions was 0.833.

[0073] The light-absorbing composition according to Example 3 was applied using a dispenser to a 40 mm x 40 mm area in the center of one main surface of a transparent glass substrate (manufactured by SCHOTT, product name: D263 T eco) made of borosilicate glass and having dimensions of 76 mm x 76 mm x 0.21 mm, to form a coating film. The resulting coating film was thoroughly dried at room temperature, and then placed in an oven and heat-treated at 45°C for 2 hours and at 85°C for 30 minutes to volatilize the solvent. The coating film was then baked at 125°C for 3 hours, at 150°C for 1 hour, and at 170°C for 3 hours to thoroughly harden the coating film. In this way, the light absorbing film according to Example 3 was formed, and the optical filter according to Example 3 was obtained.

[0074] <Comparative Example 1> 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, 7.172 g of Plysurf A208F (Dai-ichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the resulting copper acetate solution and stirred for 30 minutes to obtain Solution A5. 2.508 g of phenylphosphonic acid (Nissan Chemical Industries, Ltd.) was added to 40 g of THF and stirred for 30 minutes to obtain Solution B5. Solution B5 was added to Solution A5 while stirring and stirred at room temperature for 1 minute. Next, 180 g of toluene was added to this solution and stirred at room temperature for 1 minute to obtain Solution C5. Solution C5 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., Model: OSB-2100) while the solvent was removed using a rotary evaporator (Tokyo Rikakikai Co., Ltd., Model: N-1110SF). The oil bath temperature was adjusted to 120°C. Thereafter, the liquid after the solvent removal treatment was taken out of the flask, and liquid D5, which was a dispersion liquid of a light absorber formed from phenylphosphonic acid and copper ions, was obtained.

[0075] 17.60 g of silicone resin (product name: KR-300, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to D5 solution and stirred for 30 minutes to obtain a light-absorbing composition according to Comparative Example 1, which contains a light absorber formed from phenylphosphonic acid and copper ions. In the light-absorbing composition according to Comparative Example 1, the mass ratio of the content of phenylphosphonic acid to the content of phosphoric acid ester compound was 0.350, and the molar ratio of the content of phenylphosphonic acid to the content of copper ions was 0.704.

[0076] The light-absorbing composition according to Comparative Example 1 was applied using a dispenser to a 40 mm x 40 mm area in the center of one main surface of a transparent glass substrate (manufactured by SCHOTT, product name: D263 T eco) made of borosilicate glass and having dimensions of 76 mm x 76 mm x 0.21 mm, to form a coating film. The resulting coating film was thoroughly dried at room temperature, and then placed in an oven and heat-treated at 85°C for 3 hours to volatilize the solvent. The coating film was then baked for 3 hours at 125°C, 1 hour at 150°C, and 8 hours at 170°C to thoroughly harden the coating film. In this way, the light-absorbing film according to Comparative Example 1 was formed, and the optical filter according to Comparative Example 1 was obtained.

[0077] <Comparative Example 2> 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, 4.333 g of Plysurf A208F (Dai-ichi Kogyo Seiyaku Co., Ltd.), a phosphate ester compound, was added to the resulting copper acetate solution and stirred for 30 minutes to obtain Solution A6. 2.523 g of n-butylphosphonic acid (Johoku Chemical Industry Co., Ltd.) and 40 g of THF were added and stirred for 30 minutes to obtain Solution B6. Solution B6 was added to Solution A6 while stirring and stirred at room temperature for 1 minute. Next, 120 g of toluene was added to this solution and stirred at room temperature for 1 minute to obtain Solution C6. Solution C6 was placed in a flask and heated in an oil bath (Tokyo Rikakikai Co., Ltd., Model: OSB-2100) while the solvent was removed using a rotary evaporator (Tokyo Rikakikai Co., Ltd., Model: N-1110SF). The temperature of the oil bath was adjusted to 105° C. Thereafter, the liquid after the solvent removal treatment was taken out of the flask to obtain liquid D6, which was a dispersion liquid of a light absorber formed from n-butylphosphonic acid and copper ions.

[0078] 8.80 g of silicone resin (product name: KR-300, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to D6 solution and stirred for 30 minutes to obtain a light-absorbing composition according to Comparative Example 2, which contains a light absorber formed from n-butylphosphonic acid and copper ions. In the light-absorbing composition according to Comparative Example 2, the mass ratio of the content of n-butylphosphonic acid to the content of the phosphate ester compound was 0.582, and the molar ratio of the content of n-butylphosphonic acid to the content of copper ions was 0.811.

[0079] The light-absorbing composition according to Comparative Example 2 was applied using a dispenser to a 40 mm x 40 mm area in the center of one main surface of a transparent glass substrate (manufactured by SCHOTT, product name: D263 T eco) made of borosilicate glass and measuring 76 mm x 76 mm x 0.21 mm, forming a coating film. The resulting coating film was thoroughly dried at room temperature, and then placed in an oven and heat-treated at 45°C for 2 hours and at 85°C for 30 minutes to volatilize the solvent. The coating film was then thoroughly cured by baking at 125°C for 3 hours, 150°C for 1 hour, and 170°C for 3 hours. In this way, the light-absorbing film according to Comparative Example 2 was formed, and an optical filter according to Comparative Example 2 was obtained.

[0080] <Amount of ingredients added> Table 1 shows the amounts of materials added used in preparing the light-absorbing compositions according to Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2. In addition, Table 1 also shows the ratio of the phosphonic acid content to the phosphate ester content on a mass basis, and the ratio of the phosphonic acid content to the copper ion content on a substance amount basis, in each light-absorbing composition.

[0081] <Transmittance spectrum measurement> Using an ultraviolet-visible-near-infrared spectrophotometer (manufactured by JASCO Corporation, product name: V-670), the transmittance spectra of the optical filters according to each example and comparative example were measured at an incident angle of 0°. The transmittance spectra of the optical filters according to example 1, example 2, example 3, comparative example 1, and comparative example 2 are shown in Figures 3, 4, 5, 6, and 7, respectively. Table 2 shows the transmittance characteristics read from Figures 3 to 7.

[0082] <Thickness measurement> The thickness of the light-absorbing film was measured by measuring the distance from the surface of the optical filter using a laser displacement meter (Keyence Corporation, product name: LK-H008) and subtracting the thickness of the transparent glass substrate. The results are shown in Table 2.

[0083] As shown in FIGS. 3 to 5 and Table 2, the optical filters according to Examples 1 to 3 satisfied all of the above conditions (I) to (VII) regarding the transmittance spectrum. Considering the transmittance characteristics of the substrate, the light absorbing films according to Examples 1 to 3 have the above (i) to (vii) ) were satisfied. On the other hand, the optical filter according to Comparative Example 1 did not satisfy the above condition (II). Furthermore, the optical filter according to Comparative Example 2 did not satisfy the above conditions (I), (II), and (IV).

[0084] Furthermore, the optical filters according to Examples 1 to 3 can be used as optical filters consisting only of the light-absorbing film by removing the light-absorbing film from the transparent glass substrate. Figure 8 shows the transmittance spectrum of the transparent glass substrate. The transmittance spectrum of the transparent glass substrate shows almost no absorption in the wavelength range of approximately 350 nm or more (the transmittance of around 92% is due to a decrease caused by Fresnel reflection on the surface). This suggests that an optical filter consisting only of the light-absorbing film can also satisfy the above conditions (I) to (VII).

[0085] When it is intended to peel off the light-absorbing film from the transparent glass substrate, a known method can be used, such as, but not limited to, applying a release agent or mold release agent containing a fluorine compound or the like before applying the light-absorbing composition to the transparent glass substrate. By carrying out such a procedure in advance, the peeling operation becomes easier. Furthermore, when only the light-absorbing film is provided as an optical filter, for example, but not limited to, metal, resin, or even fluorine-containing resin can be used as the substrate for forming the coating film.

[0086] Furthermore, it is known to those skilled in the art that the transmittance in a predetermined wavelength range (for example, the visible light range) can be increased by forming a light absorbing film or an anti-reflection film on a transparent substrate on which the light absorbing film is formed. Anti-reflection coatings are made up of layers of low refractive index materials such as MgF2 and SiO2, or layers of low refractive index materials and high refractive index materials such as TiO2. Such an anti-reflection film may be formed by a physical method such as vacuum deposition or sputtering, or by a chemical method such as CVD or a sol-gel process.

[0087] Furthermore, the light-absorbing film according to the present invention is formed on a substrate of phosphate glass or fluorophosphate glass containing a coloring component such as Cu or Co. Examples of such substrates include infrared-absorbing glass. When infrared-absorbing glass on which a light-absorbing film is formed is used, the light absorption and spectrum of both can be adjusted to obtain a light-absorbing filter with a desired spectrum.

[0088] The light-absorbing film according to the present invention is used as an optical filter by sandwiching it between two or more glass plates, for example. The rigidity and mechanical strength of the optical filter are improved, and the hard main surface has the advantage of preventing scratches. In particular, when a relatively flexible curable resin is used as a binder or matrix, the advantages obtained from these viewpoints are great.

[0089] [Table 1]

[0090] [Table 2]

Claims

1. a light absorber formed by a phosphonic acid represented by the following formula (A) and a copper ion; and a curable resin, Light-absorbing composition. 【Chemical 1】 [In formula (A), R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, or a nitro group, and n represents an integer of 1 to 3.

2. The light-absorbing film obtained by curing a coating of the light-absorbing composition satisfies the following conditions (i) to (iii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: The light-absorbing composition according to claim 1 . (i) The UV cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 350 nm to 450 nm is within the wavelength range of 400 nm to 450 nm. (ii) The IR cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm is 700 nm or less. (iii) the difference between the IR cutoff wavelength and the UV cutoff wavelength is 240 nm m or more.

3. 3. The light-absorbing composition according to claim 2, wherein the light-absorbing film further satisfies the following conditions (iv) to (vii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: 。 (iv) The spectral transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (v) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (vi) The spectral transmittance in the wavelength range of 800 nm to 1100 nm is 10% or less. (vii) The spectral transmittance in the wavelength range of 800 nm to 1150 nm is 15% or less.

4. 4. The light-absorbing composition according to claim 1, wherein the ratio of the content of said phosphonic acid to the content of said copper ions is 0.7 to 0.9 on an amount of substance basis.

5. a light absorber formed by a phosphonic acid represented by the following formula (A) and a copper ion; and a cured product of the curable resin, Light absorbing film. 【Chemistry 2】 [In formula (A), R 1 ~R 5 each independently represents a hydrogen atom, a halogen atom, a hydroxy group, or a nitro group, and n represents an integer of 1 to 3.

6. 6. The light-absorbing film according to claim 5, which satisfies the following conditions (i) to (iii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: (i) The UV cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 350 nm to 450 nm is within the wavelength range of 400 nm to 450 nm. (ii) The IR cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm is 700 nm or less. (iii) the difference between the IR cutoff wavelength and the UV cutoff wavelength is 240 nm m or more.

7. 7. The light-absorbing film according to claim 6, further satisfying the following conditions (iv) to (vii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: (iv) The spectral transmittance in the wavelength range of 300 nm to 350 nm is 1% or less. (v) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (vi) The spectral transmittance in the wavelength range of 800 nm to 1100 nm is 10% or less. (vii) The spectral transmittance in the wavelength range of 800 nm to 1150 nm is 15% or less.

8. 8. The light-absorbing film according to claim 5, wherein the ratio of the content of said phosphonic acid to the content of said copper ions is 0.7 to 0.9 on an amount of substance basis.

9. An optical filter comprising the light-absorbing film according to any one of claims 5 to 8.

10. 10. The optical filter according to claim 9, which satisfies the following conditions (I) to (III) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: (I) The UV cutoff wavelength showing a spectral transmittance of 50% in the wavelength range of 350 nm to 450 nm is within the wavelength range of 400 nm to 450 nm. (II) The IR cutoff wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm is 700 nm or less. (III) The difference between the IR cutoff wavelength and the UV cutoff wavelength is 240 nm. m or more.

11. 11. The optical filter according to claim 10, further satisfying the following conditions (IV) to (VII) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0°: (IV) The spectral transmittance at wavelengths of 300 nm to 350 nm is 1% or less. (V) The average transmittance in the wavelength range of 450 nm to 600 nm is 75% or more. (VI) The spectral transmittance in the wavelength range of 800 nm to 1100 nm is 10% or less. (VII) The spectral transmittance in the wavelength range of 800 nm to 1150 nm is 15% or less.

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