JP7631465B2 - Light-absorbing composition, light-absorbing film, method for producing light-absorbing film, and optical filter - Google Patents

Description

The present invention relates to a light-absorbing composition, a light-absorbing film, and an optical filter.

In imaging devices using solid-state imaging elements such as CCDs (Charge Coupled Devices) or CMOSs (Complementary Metal Oxide Semiconductors), various optical filters are placed in front of the solid-state imaging elements to obtain images with good color reproducibility. Generally, solid-state imaging elements have spectral sensitivity over a wide wavelength range from the ultraviolet to infrared regions. Meanwhile, human visual sensitivity exists only in the visible light region. For this reason, a technique is known in which an optical filter that blocks part of the infrared or ultraviolet light is placed in front of the solid-state imaging element in order to bring the spectral sensitivity of the solid-state imaging element in the imaging device closer to the human visual sensitivity.

Conventionally, such optical filters have generally used a dielectric multilayer film to block infrared or ultraviolet rays. However, in recent years, optical filters with a film containing a light absorbent have been attracting attention. The transmittance characteristics of optical filters with a film containing a light absorbent are not easily affected by the angle of incidence, so good images with little change in color can be obtained even when light is incident on the optical filter at an angle in an imaging device. In addition, 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 with a film containing a light absorbent are also advantageous in terms of making imaging devices smaller and thinner.

As such a light absorbing agent, a light absorbing agent 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 absorbing agent formed from a phosphonic acid having a phenyl group or a halogenated phenyl group (phenyl-based phosphonic acid) and copper ions.

Patent Document 2 also describes an optical filter having a UV-IR absorbing layer capable of absorbing infrared and ultraviolet rays. The UV-IR absorbing layer contains a UV-IR absorbent formed of phosphonic acid and copper ions. In order for the optical filter to have predetermined optical properties, the UV-IR absorbing composition contains, for example, a phenyl-based phosphonic acid and a phosphonic acid having an alkyl group or a halogenated alkyl group (alkyl-based phosphonic acid).

Patent Document 3 also describes an infrared cut filter that includes an organic dye-containing layer that contains a specific organic dye and a copper phosphonate-containing layer.

International Publication No. 2018/088561 Patent No. 6232161 International Publication No. 2017/006571

In a light-absorbing composition and a light-absorbing film containing a light-absorbing compound including a phosphonic acid and a copper component, and an ultraviolet-absorbing compound, it is considered important that the ultraviolet-absorbing compound is unlikely to adversely affect the properties of the light-absorbing composition.

In view of the above circumstances, the present invention provides a light-absorbing composition and a light-absorbing film in which an ultraviolet absorbing compound is unlikely to adversely affect the properties of a light-absorbing compound containing a phosphonic acid and a copper component .

The present invention relates to
a light absorbing compound comprising a phosphonic acid and a copper component;
an ultraviolet absorbing compound,
The ratio of the content of the phosphonic acid to the content of the ultraviolet absorbing compound is 10 to 300 by mass.
A light absorbing composition is provided.

The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of:
a light absorbing compound comprising a phosphonic acid and a copper component;
an ultraviolet absorbing compound,
The ratio of the content of the phosphonic acid to the content of the ultraviolet absorbing compound is 10 to 300 on a mass basis.
A light absorbing film is provided.

The present invention also provides an optical filter having the above-mentioned light absorbing film.

According to the light absorbing composition and light absorbing film described above, the ultraviolet absorbing compound is unlikely to adversely affect the properties of the light absorbing compound containing phosphonic acid and a copper component.

FIG. 1 is a cross-sectional view showing an example of a light absorbing film according to the present invention. FIG. 2 is a cross-sectional view showing an example of an optical filter according to the present invention. FIG. 3 shows the transmission spectrum of the optical filter according to the first embodiment. FIG. 4 shows the transmission spectrum of the optical filter according to the second embodiment. FIG. 5 shows the transmission spectrum of the optical filter according to the third embodiment. FIG. 6 shows the transmission spectrum of the optical filter according to the fourth embodiment. FIG. 7 shows the transmission spectrum of the optical filter according to the fifth embodiment. FIG. 8 shows the transmission spectrum of the optical filter according to the first comparative example. FIG. 9 shows the transmission spectrum of the optical filter according to Comparative Example 2. FIG. 10 shows the transmission spectrum of the optical filter according to Comparative Example 3. FIG. 11 shows the transmission spectrum of the ultraviolet absorbing compound.

The following describes an embodiment of the present invention. Note that the following description is merely an example of the present invention, and the present invention is not limited to the following embodiment.

The light-absorbing composition according to the present invention contains a compound containing phosphonic acid and a copper component, and an ultraviolet absorbing compound. The compound containing phosphonic acid and a copper component typically has a predetermined light absorption characteristic. The compound containing phosphonic acid and a copper component is also called a phosphonic acid-containing compound. The light-absorbing composition can be cured to obtain a light-absorbing film. In the transmission spectrum of this light-absorbing film at an incident angle of 0 degrees, the transmittance T ₄₀₀ at a wavelength of 400 nm, the transmittance T ₅₅₀ at a wavelength of 550 nm, and the transmittance T ₈₀₀ at a wavelength of 800 nm satisfy the conditions of 16≦T ₅₅₀ /T ₄₀₀ and 16≦T ₅₅₀ /T _800. In order to satisfy these conditions, the light-absorbing composition contains a phosphonic acid-containing compound and an ultraviolet absorbing compound. This makes it easy for the light-absorbing film and optical filter provided using the light-absorbing composition to sufficiently absorb and shield light at a wavelength of around 400 nm. In addition, the light-absorbing film and optical filter provided by using the light-absorbing composition are likely to shield light belonging to the ultraviolet region and light belonging to the infrared region. Furthermore, the light-absorbing film and optical filter provided by using the light-absorbing composition are likely to have high transmittance of light belonging to the visible light region. As a result, the light-absorbing film and optical filter provided by using the light-absorbing composition are likely to have spectral characteristics close to the transmission spectrum corresponding to the visual sensitivity of humans.

The transmittance _T400 and the transmittance _T550 preferably satisfy the condition of 32≦ _T550 / _T400 , more preferably the condition of 80≦ _T550 / _T400 , and even more preferably the condition of 90≦ _T550 / _T400 . This makes it easy for the light-absorbing film and the optical filter provided using the light-absorbing composition to sufficiently absorb and block light having a wavelength of about 400 nm. In addition, the light-absorbing film and the optical filter provided using the light-absorbing composition are easy to block light belonging to the ultraviolet range. Furthermore, the light-absorbing film and the optical filter provided using the light-absorbing composition are easy to have a high transmittance of light belonging to the visible light range.

The transmittance _T550 and the transmittance _T800 preferably satisfy the condition of 32≦ _T550 / _T800 , more preferably satisfy the condition of 80≦ _T550 / _T800 , further preferably satisfy the condition of 200≦ _T550 / _T800 , and particularly preferably satisfy the condition of 300≦ _T550 / _T800 . This makes it easier for the light-absorbing film and optical filter provided using the light-absorbing composition to more reliably shield light belonging to the infrared region. In addition, the transmittance of light belonging to the visible light region is more reliably increased in the light-absorbing film and optical filter provided using the light-absorbing composition.

In the above transmission spectrum, for example, the following conditions (I), (II), (III), and (IV) are satisfied. This makes it easier for the light-absorbing film and optical filter provided using the light-absorbing composition to more reliably absorb and shield light at wavelengths around 400 nm, and more reliably shield light belonging to the ultraviolet range and light belonging to the infrared range. In addition, the light-absorbing film and optical filter provided using the light-absorbing composition are more reliably likely to have a high transmittance of light belonging to the visible light range. As a result, the light-absorbing film and optical filter provided using the light-absorbing composition are more likely to have spectral characteristics close to a transmission spectrum corresponding to human visual sensitivity. (I) The maximum transmittance T ^M _300-380 in the wavelength range of 300 nm to 380 nm is 1% or less.
(II) The transmittance T ₄₀₀ at a wavelength of 400 nm is 5% or less.
(III) The average transmittance T ^A _480-580 in the wavelength range of 480 nm to 580 nm is 78% or more.
(IV) The average transmittance T ^A _700-750 in the wavelength range of 700 nm to 750 nm is 10% or less.

Regarding condition (I), in the above transmission spectrum, preferably the maximum transmittance T ^M _300-385 in the wavelength range of 300 nm to 385 nm is 1% or less, and more preferably the maximum transmittance T ^M _300-390 in the wavelength range of 300 nm to 390 nm is 1% or less. This makes it easier for light-absorbing films and optical filters provided using the light-absorbing composition to more reliably shield light belonging to the ultraviolet range.

Regarding condition (II), in the above transmission spectrum, the transmittance _T400 is desirably 3% or less, more desirably 1% or less, so that a light-absorbing film and an optical filter provided using the light-absorbing composition can more reliably absorb and shield light having a wavelength of about 400 nm.

Regarding condition (III), in the above transmission spectrum, the average value T ^A _480-580 is desirably 80% or more, more desirably 82% or more, which tends to more reliably increase the transmittance of light belonging to the visible light range in a light-absorbing film and an optical filter provided using the light-absorbing composition.

Regarding condition (IV), in the above transmission spectrum, the average value ^T _700-750 is desirably 5% or less, more desirably 3% or less, which makes it easier for a light-absorbing film and an optical filter provided using the light-absorbing composition to more reliably shield light belonging to the infrared region.

In the above transmission spectrum, for example, the following condition (V) is satisfied. This makes it easier for a light-absorbing film and an optical filter provided using the light-absorbing composition to more reliably block light belonging to the infrared region.
(V) The maximum transmittance T ^M _700-1000 in the wavelength range of 700 nm to 1000 nm is 10% or less.

Regarding condition (V), the maximum value T ^M _700-1000 is desirably 7% or less, and more desirably 5% or less.

The transmission spectrum has, for example, a first cutoff wavelength λ ^50% _F of 405 nm or more and 480 nm or less. The first cutoff wavelength λ ^50% _F is a wavelength that shows a transmittance of 50% in the wavelength range of 300 nm to 450 nm in the transmission spectrum. This makes it easier for a light-absorbing film and an optical filter provided using the light-absorbing composition to more reliably sufficiently absorb and block light with a wavelength of around 400 nm.

The first cutoff wavelength λ ^50% _F is preferably 405 nm or more and 465 nm or less, and more preferably 405 nm or more and 450 nm or less.

The transmission spectrum has, for example, a second cutoff wavelength λ ^50% _S of 580 nm or more and 720 nm or less. The second cutoff wavelength λ ^50% _S is a wavelength that shows a transmittance of 50% in the wavelength range of 550 nm to 750 nm in the transmission spectrum. This makes it easier for light-absorbing films and optical filters provided using the light-absorbing composition to more reliably block light belonging to the infrared range.

The second cutoff wavelength λ ^50% _S is preferably 590 nm or more and 700 nm or less, and more preferably 600 nm or more and 680 nm or less.

The above transmission spectrum satisfies, for example, at least one of the following conditions (VI), (VII), and (VIII), which makes it easier for a light-absorbing film and an optical filter provided using the light-absorbing composition to more reliably block light belonging to the infrared region.
(VI) The maximum transmittance T ^M _800-950 in the wavelength range of 800 nm to 950 nm is 3% or less.
(VII) The maximum transmittance T ^M _700-1100 in the wavelength range of 700 nm to 1100 nm is 15% or less.
(VIII) The maximum transmittance T ^M _700-1200 in the wavelength range of 700 nm to 1200 nm is 20% or less.

Regarding condition (VI), the maximum value T ^M _800-950 is preferably 1.5% or less, and more preferably 1% or less.

Regarding condition (VII), the maximum value T ^M _700-1100 is desirably 10% or less, and more desirably 5% or less.

Regarding condition (VIII), the maximum value T ^M _700-1200 is desirably 15% or less, and more desirably 10% or less.

The phosphonic acid contained in the phosphonic acid-containing compound is not limited to a specific phosphonic acid. The phosphonic acid is, for example, represented by the following formula (a).

In formula (a), R ₁ is an alkyl group, a halogenated alkyl group in which at least one hydrogen atom in the alkyl group is substituted with a halogen atom, an aryl group, a nitroaryl group, a hydroxyaryl group, or a halogenated aryl group in which at least one hydrogen atom in the aryl group is substituted with a halogen atom. The aryl group is, for example, a phenyl group, a benzyl group, or a toluyl group.

The phosphonic acid contained in the phosphonic acid-containing compound may be an aryl-based phosphonic acid having an aryl group, a nitroaryl group, a hydroxyaryl group, or an aryl halide group. The aryl-based phosphonic acid is not limited to a specific phosphonic acid. The aryl-based phosphonic acid is, for example, phenylphosphonic acid, nitrophenylphosphonic acid, hydroxyphenylphosphonic acid, bromophenylphosphonic acid, or iodophenylphosphonic acid.

The phosphonic acid contained in the phosphonic acid-containing compound may be an alkyl phosphonic acid having an alkyl group or a halogenated alkyl group. The alkyl phosphonic acid is not limited to a specific phosphonic acid. The alkyl phosphonic acid is, for example, methyl phosphonic acid, ethyl phosphonic acid, normal (n-) propyl phosphonic acid, isopropyl phosphonic acid, normal (n-) butyl phosphonic acid, isobutyl phosphonic acid, sec-butyl phosphonic acid, tert-butyl phosphonic acid, or bromomethyl phosphonic acid.

When the phosphonic acid contained in the phosphonic acid-containing compound is an aryl phosphonic acid, the phosphonic acid-containing compound is formed by the aryl phosphonic acid and the copper component, and light having a relatively short wavelength in the wavelength range of light belonging to the infrared region is easily absorbed effectively. On the other hand, when the phosphonic acid contained in the phosphonic acid-containing compound is an alkyl phosphonic acid, the phosphonic acid-containing compound is formed by the alkyl phosphonic acid and the copper component, and light having a relatively long wavelength in the wavelength range of light belonging to the infrared region is easily absorbed effectively. For this reason, the light-absorbing composition desirably contains both aryl phosphonic acid and alkyl phosphonic acid as the phosphonic acid.

When the light-absorbing composition contains an aryl phosphonic acid and an alkyl phosphonic acid, the relationship between the content of the aryl phosphonic acid and the content of the alkyl phosphonic acid is not limited to a specific relationship. In the light-absorbing composition, the ratio R _AA of the content of the aryl phosphonic acid to the content of the alkyl phosphonic acid is, for example, 1.0 to 3.0 on a substance amount basis. This makes the transmission spectrum of the light-absorbing film and optical filter provided using the light-absorbing composition more suitable for use with an imaging element. In the light-absorbing composition, the ratio R _AA is preferably 1.3 to 2.7.

The phosphonic acid contained in the phosphonic acid-containing compound may be a phosphonic acid that does not have a group containing a halogen atom as a substituent. In this case, the light-absorbing film and optical filter provided using the light-absorbing composition tend to have good environmental resistance or are less likely to discolor.

In the light-absorbing composition, at least a portion of the copper component reacts with phosphonic acid to form a compound such as a complex containing phosphonic acid and a copper component. Compounds containing phosphonic acid and a copper component tend to effectively absorb a portion of light in the infrared range, and further exhibit high transmittance for light in the visible range.

The manner of supplying the copper component in the preparation of the light-absorbing composition is not limited to a specific embodiment. In the preparation of the light-absorbing composition, the copper component is supplied, for example, as a copper salt. The copper salt may be an anhydride or hydrate of copper chloride, copper formate, copper stearate, copper benzoate, copper pyrophosphate, copper naphthenate, and copper citrate. For example, copper acetate monohydrate is represented as Cu(CH ₃ COO) _{2.H 2} O, and one mole of copper ions is supplied by one mole of copper acetate monohydrate.

The ultraviolet absorbing compound contained in the light absorbing composition is not limited to a specific compound as long as the above conditions of 16≦T ₅₅₀ /T ₄₀₀ and 16≦T ₅₅₀ /T ₈₀₀ are satisfied in the transmission spectrum. The ultraviolet absorbing compound has, for example, an absorption maximum wavelength λ ^M _UV-C of 330 nm or more and 430 nm or less. As a result, according to the light absorbing film and optical filter provided using the light absorbing composition, when used in combination with the above compound containing phosphonic acid and a copper component, the transmission characteristics at wavelengths of 400 nm to 450 nm tend to have spectral characteristics close to the transmission spectrum corresponding to human visual sensitivity. The optical characteristics such as the transmission spectrum and absorption spectrum of the ultraviolet absorbing compound can be determined by measurement using a dispersion liquid in which the ultraviolet absorbing compound is dispersed in a specified solvent as a sample. Unless otherwise explained, the transmission spectrum and absorption spectrum of the ultraviolet absorbing compound mean those determined by such measurements.

The maximum absorption wavelength λ ^M _UV-C of the ultraviolet absorbing compound is desirably 350 nm or more and 400 nm or less.

The maximum wavelength λ ^50%-L _UV-C and the minimum wavelength λ ^50%-S _UV-C showing a 50% transmittance in the transmission spectrum of the ultraviolet absorbing compound in the wavelength range of 300 nm to 450 nm are not limited to specific values. The wavelength λ ^50% -L _UV-C is, for example, 400 nm or more and 470 nm or less. As a result, according to the light absorbing film and optical filter provided by using the light absorbing composition, when used in combination with the compound containing the above phosphonic acid and copper component, in addition to the above effect obtained by satisfying the condition of the absorption maximum wavelength λ ^M _UV-C , it is easy to control the transmittance at a wavelength of around 400 nm to be small, and the transmittance of light belonging to the visible light range is likely to be more reliably increased. As a result, the light absorbing film and optical filter provided by using the light absorbing composition are likely to have spectral characteristics close to the transmission spectrum corresponding to the visual sensitivity of humans. The concentration of the ultraviolet absorbing compound in the sample used in measuring the transmission spectrum of the ultraviolet absorbing compound to determine the wavelengths λ ^50%-L _UV-C and λ ^50%-S _UV-C is adjusted so that the transmittance at the maximum absorption wavelength λ ^M _UV-C is 8 to 12%.

The wavelength λ ^50%-L _UV-C is desirably not less than 415 nm and not more than 450 nm.

The wavelengths λ ^50%-S _UV-C and λ ^50%-L _UV-C satisfy, for example, the condition 75 nm≦λ ^50%-L _UV-C −λ ^50%-S _UV-C ≦105 nm. The wavelength λ 50% ^-S _IR at which the transmittance of the transmission spectrum of the compound containing the light-absorbing phosphonic acid and a copper component is 50% at wavelengths of 300 nm to 450 nm is likely to be included between λ ^50%-L _UV-C and λ ^50%-S _UV-C , and when used in combination with a compound containing phosphonic acid and a copper component, there is an additional advantage that the transmission characteristics at wavelengths of 400 nm to 450 nm tend to have spectral characteristics close to the transmission spectrum corresponding to human visual sensitivity. The wavelengths λ ^50%-S _UV-C and λ ^50%-L _UV-C desirably satisfy the condition 80 nm≦λ ^50%-L _UV-C −λ ^50%-S _UV-C ≦100 nm.

In the transmission spectrum of an ultraviolet absorbing compound, the wavelength λ ^80% _UV -C, which is longer than the maximum absorption wavelength λ ^M _UV -C and exhibits 80% transmittance, satisfies, for example, the condition 1.8 [%/nm]≦30/(λ ^80% _UV-C − λ ^50%-L _UV-C )≦2.6 [%/nm]. The value 30/(λ ^80% _UV-C − λ ^{50 %-L} _UV-C ) represents the average slope of the transmission spectrum of the ultraviolet absorbing compound in the range between the wavelengths λ ^50% -L _{UV -C} and λ 80% UV-C, and this value is also represented as Δλ ^80/50 _UV-C [%/nm]. By having Δλ ^80/50 _UV-C fall within these ranges, the consistency with the similar slope value in the transmission spectrum of the compound containing the above-mentioned phosphonic acid and copper component, which has light absorption properties, is improved, and when used in combination with a compound containing phosphonic acid and a copper component, the transmission characteristics at wavelengths of 400 nm to 450 nm are more likely to have spectral characteristics close to the transmission spectrum corresponding to human visual sensitivity. Desirably, the condition 1.9 [%/nm] ≦ Δλ ^80/50 _UV-C ≦ 2.4 [%/nm] is satisfied, and more desirably, 1.9 [%/nm] ≦ Δλ ^80/50 _UV-C ≦ 2.3 [%/nm] is satisfied.

The minimum value T ^m _500-700 of the transmittance in the transmission spectrum of the ultraviolet absorbing compound in the wavelength range of 500 nm to 700 nm is not limited to a specific value. The minimum value T ^m _500-700 is, for example, 80% or more. This makes it easier to reliably increase the transmittance of light in the visible light range in the light absorbing film and optical filter provided using the light absorbing composition. The minimum value T ^m _500-700 is preferably 85% or more, and more preferably 90% or more.

As described above, the ultraviolet absorbing compound is not limited to a specific compound as long as the conditions of 16≦ _T550 / _T400 and 16≦ _T550 / _T800 are satisfied in the transmission spectrum of the light absorbing film obtained by curing the light absorbing composition. On the other hand, the ultraviolet absorbing compound is preferably a compound that is compatible with other components such as a phosphonic acid-containing compound contained in the light absorbing composition and whose performance is not significantly reduced by the other components. In addition, the ultraviolet absorbing compound is preferably a compound that does not have significantly poor moisture resistance or light resistance.

The ultraviolet absorbing compound is, for example, a benzophenone-based compound, a benzotriazole-based compound, a benzoate-based compound, a cyanoacrylate-based compound, or a triazine-based compound.

Examples of the benzotriazole-based compound include the following compounds.
2-(2'-hydroxy-5'-methylphenyl)benzotriazole 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole 2-(2'-hydroxy-5-t-octylphenyl)benzotriazole 2-(2'-hydroxy-5-t-butylphenyl)benzotriazole 2-[2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl]benzotriazole 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole 2-[2'-hydroxy-3',5'-bis(α,α-dimethoxybenzoyl)phenyl]benzotriazole 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2N-benzotriazol-2-yl)phenol]
2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benzotriazole 2-(2'-hydroxy-3'-dodecyl-5'-methylphenyl)benzotriazole

Examples of triazine compounds include the following compounds:
2,4-Bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-(4-methoxynaphthyl)-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-[2-(5-methylfuran-2-yl)ethenyl]-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine 2,4-Bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol

The content of the ultraviolet absorbing compound in the light absorbing composition is not limited to a specific value. The ratio R _PU of the content of the phosphonic acid to the content of the ultraviolet absorbing compound in the light absorbing composition is, for example, 10 to 300 on a mass basis. This makes it difficult for the ultraviolet absorbing compound to adversely affect the properties of the light absorbing composition, and makes it easier for the light absorbing film and optical filter provided using the light absorbing composition to more reliably sufficiently absorb and block light with a wavelength of around 400 nm. The ratio R _PU is preferably 30 to 100.

The ratio R _UR of the content of the aryl phosphonic acid to the content of the ultraviolet absorbing compound in the light absorbing composition is not limited to a specific value. The ratio R _UR is, for example, 7 to 180 on a mass basis, and preferably 20 to 60. The ratio R _UL of the content of the alkyl phosphonic acid to the content of the ultraviolet absorbing compound in the light absorbing composition is not limited to a specific value. The ratio R _UL is, for example, 3 to 120 on a mass basis, and preferably 10 to 40. As a result, the light absorbing film and optical filter provided using the light absorbing composition are more likely to have spectral characteristics close to a transmission spectrum corresponding to the visual sensitivity of humans.

The light-absorbing composition further contains, for example, a matrix. The phosphonic acid-containing compound and the ultraviolet absorbing compound are typically dispersed in the matrix. The matrix is not limited to a specific material as long as the conditions of 16≦T ₅₅₀ /T ₄₀₀ and 16≦T ₅₅₀ /T ₈₀₀ are satisfied in the transmission spectrum of the light-absorbing film obtained by curing the light-absorbing composition. The matrix contained in the light-absorbing composition is typically a material having high transmittance at wavelengths of 400 nm to 600 nm. For example, when a layer having a thickness of 0.1 mm is formed using only that material, the transmittance of that layer at wavelengths of 400 nm to 600 nm is, for example, 70% or more, preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more.

The material of the matrix contained in the light absorbing composition is, for example, a resin. The type of resin contained in the light absorbing composition is not limited to a specific type. The resin is, for example, a cyclic polyolefin resin, an epoxy resin, a polyimide resin, a modified acrylic resin, a silicone resin, or a polyvinyl resin such as PVB. The resin may be a curable resin that can be cured by energy irradiation such as heat or light. The matrix contained in the light absorbing composition may be an organic-inorganic hybrid material or an inorganic material formed by hydrolyzing and condensing an alkoxide containing a metal component according to a sol-gel method.

The light-absorbing composition may contain a phosphate ester as necessary. The phosphate ester facilitates proper dispersion of the phosphonic acid-containing compound in the light-absorbing composition and in the light-absorbing film obtained by curing the light-absorbing composition. The phosphate ester may function as a dispersant for the phosphonic acid-containing compound, and a portion of the phosphate ester may react with a metal component to form a compound. For example, the phosphate ester may be coordinated to a phosphonic acid-containing compound containing a copper component and phosphonic acid, or may react with the compound. The phosphonic acid-containing compound may contain these compounds or their copper salt components.

The phosphate ester is not limited to a specific phosphate ester. The phosphate ester has, for example, a polyoxyalkyl group. Examples of such phosphate esters include Plysurf A208N: polyoxyethylene alkyl (C12, C13) ether phosphate ester, Plysurf A208F: polyoxyethylene alkyl (C8) ether phosphate ester, Plysurf A208B: polyoxyethylene lauryl ether phosphate ester, Plysurf A219B: polyoxyethylene lauryl ether phosphate ester, Plysurf AL: polyoxyethylene styrenated phenyl ether phosphate ester, Plysurf A212C: polyoxyethylene tridecyl ether phosphate ester, or Plysurf A215C: polyoxyethylene tridecyl ether phosphate ester. All of these are products manufactured by Daiichi Kogyo Seiyaku Co., Ltd. In addition, examples of phosphate esters include NIKKOL DDP-2: polyoxyethylene alkyl ether phosphate ester, NIKKOL DDP-4: polyoxyethylene alkyl ether phosphate ester, and NIKKOL DDP-6: polyoxyethylene alkyl ether phosphate ester. All of these are products manufactured by Nikko Chemicals Co., Ltd.

The content of the phosphoric acid ester in the light-absorbing composition is not limited to a specific value. The ratio R _PE of the content of the phosphonic acid to the content of the phosphoric acid ester in the light-absorbing composition is, for example, 1.0 or more on a mass basis. This makes it possible to suppress hydrolysis of the phosphoric acid ester even when the light-absorbing film and optical filter provided using the light-absorbing composition come into contact with water vapor, and the light-absorbing film and optical filter tend to have good weather resistance. The ratio R _PE is preferably 1.5 or more. The ratio R _PE may be 1.0 to 3.0. By making the ratio R _PE 3.0 or less, aggregation of the phosphonic acid-containing compound can be prevented, and the transmittance of light belonging to the visible light range in the light-absorbing film and optical filter provided using the light-absorbing composition tends to be more reliably high. From the viewpoint of good weather resistance and good optical properties, the ratio R _PE is preferably 1.5 to 2.0.

The light-absorbing composition may further contain at least one selected from the group consisting of metal alkoxides, hydrolysis condensates of metal alkoxides, silicon alkoxides, and hydrolysis condensates of silicon alkoxides, as necessary. This makes it easier for the phosphonic acid-containing compound to be uniformly dispersed in the light-absorbing composition, or in the light-absorbing film and optical filter provided using the light-absorbing composition. In the light-absorbing composition, at least two selected from this group may be contained in a mixed state. For example, the phosphate ester, metal alkoxide, or silicon alkoxide is mixed with a copper component and a component such as phosphonic acid in the preparation of the light-absorbing composition. In this case, a part of the metal alkoxide and silicon alkoxide may be contained in the fine particles containing the phosphonic acid-containing compound by interaction with the copper component or the component such as phosphonic acid or a compound containing these in the preparation of the light-absorbing composition.

The metal alkoxide that forms the metal alkoxide or the hydrolysis condensate of the metal alkoxide is, for example, an alkoxide of at least one metal selected from the group consisting of Li, Na, Mg, Ca, Sr, Ba, Ge, Sn, Pb, Al, Ga, In, Tl, Zn, Cd, Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Mn, Cr, Mo, W, V, Nb, Ta, Ti, and Zr.

The light-absorbing composition can be used to provide, for example, the light-absorbing film 10 shown in FIG. 1. The light-absorbing film 10 can be obtained, for example, by curing a coating of the light-absorbing composition. Therefore, the light-absorbing film 10 contains a compound containing phosphonic acid and a copper component, and an ultraviolet absorbing compound.

The thickness of the light-absorbing film 10 is not limited to a specific value. For example, in order to reduce the thickness of the light-absorbing film while the light-absorbing film exhibits the desired light absorption, it is possible to increase the concentration of the phosphonic acid-containing compound and the ultraviolet absorbing compound contained in the light-absorbing composition. In this case, the dispersibility of each compound may not be maintained in the desired state. On the other hand, in order to meet the demand for a low profile of a device equipped with a light-absorbing film, such as an imaging device, it is advantageous for the thickness of the light-absorbing film to be small. From this perspective, the thickness of the light-absorbing film 10 is, for example, 25 μm to 500 μm, preferably 50 μm to 300 μm, and more preferably 75 μm to 250 μm.

As shown in FIG. 1, the optical filter 1a is provided with a light absorbing film 10. This allows the optical filter 1a to adequately absorb and easily block light with a wavelength of about 400 nm, and to easily block light in the ultraviolet range. Furthermore, the optical filter 1a tends to have a high transmittance for light in the visible light range.

The optical filter 1a is, for example, composed of a single light absorbing film 10. When the optical filter 1a is composed of a single light absorbing film 10, it may be called a light absorbing film or a light absorbing sheet in consideration of its form. The optical filter 1a may be used, for example, separately from an imaging element or an optical component. In this case, the optical filter 1a can be produced according to a known method related to optical filters. For example, a light absorbing composition is applied to a substrate to form a coating film, and the coating film is cured to form the light absorbing film 10. Thereafter, the light absorbing film 10 is peeled off from the substrate to form a film or sheet. In this way, the film or sheet-shaped optical filter 1a can be produced. 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 using a fluorine-containing compound. The light absorbing film 10 can be produced by such a solution casting method. For example, an imaging device equipped with the optical filter 1a can be provided.

The optical filter 1a may be formed in contact with the imaging element and the optical component. On the other hand, the light absorbing film 10 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. In this way, an imaging element with a light absorbing film or an optical component with a light absorbing film can be produced. The optical component is, for example, a lens or a cover glass. For example, an imaging device equipped with an imaging element with a light absorbing film or an optical component with a light absorbing film can be provided.

Optical filter 1a may be modified, for example, to optical filter 1b shown in FIG. 2. Optical filter 1b is configured in the same manner as optical filter 1a, except for the parts that will be specifically described. The same reference numerals are used to designate components of optical filter 1b that are the same as or correspond to those of optical filter 1a, and detailed descriptions are omitted. The description of optical filter 1a also applies to optical filter 1b, so long as there is no technical contradiction.

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 of the main surfaces of the transparent dielectric substrate 20. The light absorbing film 10 may be in contact with one of the main surfaces of the transparent dielectric substrate 20, for example. In this case, the light absorbing film 10 can be formed, for example, by applying the above-mentioned light absorbing composition to one of the main surfaces of the transparent dielectric substrate 20 and curing the light absorbing composition.

The type of the transparent dielectric substrate 20 is not limited to a specific type. The transparent dielectric substrate 20 may have an absorption ability in the infrared region. The transparent dielectric substrate 20 may have an average spectral transmittance of 90% or more at wavelengths of, for example, 350 nm to 900 nm. The material of the transparent dielectric substrate 20 is not limited to a specific material, but 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 may be, for example, transparent glass made of silicate glass such as soda-lime glass and borosilicate glass, or phosphate glass and fluorophosphate glass containing coloring components such as Cu and Co. Phosphate glass and fluorophosphate glass containing coloring components are, for example, infrared absorbing glass, and are themselves light absorbing. When the light absorbing film 10 is used together with the transparent dielectric substrate 20 of infrared absorbing glass, the light absorption and transmission spectrum of both can be adjusted to produce an optical filter having desired optical characteristics, and the degree of freedom in designing the optical filter is high.

When the material of the transparent dielectric substrate 20 is a resin, the resin is, for example, a cycloolefin 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.

Each of the optical filters 1a and 1b may be modified to further include other functional films, such as an infrared reflection film and an anti-reflection film. Such functional films may be formed on the light absorbing film ₁₀ or the transparent dielectric substrate 20. For example, the optical filter may include an anti-reflection film to increase the transmittance in a predetermined wavelength range (for example, the visible light range). The anti-reflection film may be configured as a layer of a low refractive index material such as MgF2 and _SiO2 , or may be configured as a laminate of such a layer of a low refractive index material and a layer of a high refractive index material such as _TiO2 , or may be configured as a dielectric multilayer film. Such an anti-reflection film may be formed by a method involving a physical reaction, such as vacuum deposition and sputtering, or by a method involving a chemical reaction, such as CVD and sol-gel.

The optical filter may be constructed, for example, with the light absorbing film 10 disposed between two sheets of glass. This improves the rigidity and mechanical strength of the optical filter. In addition, the main surface of the optical filter becomes hard, which is advantageous from the standpoint of preventing scratches, etc. This advantage is particularly important when a relatively flexible resin is used as the binder or matrix in the light absorbing film 10.

The present invention will be described in more detail with reference to examples. Note that the present invention is not limited to the following examples. First, the evaluation method of the optical filters according to each example and each comparative example will be described.

(Transmission spectrum measurement)
The transmission spectrum of the optical filters according to each of the examples and comparative examples at an incident angle of 0° was measured using a UV-Vis-NIR spectrophotometer V-670 manufactured by JASCO Corporation.

(Thickness measurement)
The thickness of the optical filters according to each of the examples and comparative examples was measured using a micrometer. The results are shown in Table 4.

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, 1.444 g of Plysurf A208N (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which is a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain a 1-A solution. 40 g of THF was added to 3.576 g of phenylphosphonic acid and stirred for 30 minutes to obtain a 1-B solution. Next, 8.664 g of methyltriethoxysilane (MTES) (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBE-13) and 2.840 g of tetraethoxysilane (TEOS) (manufactured by Kishida Chemical Co., Ltd., special grade) were added to the 1-B solution and stirred for another 1 minute to obtain a 1-C solution. While stirring the 1-A solution, the 1-C solution was added to the 1-A solution, and stirred at room temperature for 1 minute. Next, 140 g of toluene was added to this solution, and the mixture was stirred at room temperature for 1 minute to obtain solution 1-D. Solution 1-D was placed in a flask and heated in an oil bath (manufactured by Tokyo Rika Kikai Co., Ltd., model: OSB-2100) while undergoing a solvent removal treatment using a rotary evaporator (manufactured by Tokyo Rika Kikai Co., Ltd., model: N-1110SF). The set temperature of the oil bath was adjusted to 105°C. Thereafter, the solution after solvent removal treatment was taken out of the flask to obtain solution 1-E. Solution 1-E was a dispersion of a compound containing an aryl phosphonic acid and a copper component.

3.600 g of copper acetate monohydrate was mixed with 200 g of THF and stirred for 3 hours to obtain a copper acetate solution. Next, 2.058 g of Plysurf A208N, a phosphate ester compound, was added to the obtained copper acetate solution and stirred for 30 minutes to obtain 1-F solution. 40 g of THF was added to 2.309 g of n-butylphosphonic acid and stirred for 30 minutes to obtain 1-G solution. 1-G solution was added to 1-F solution while stirring, and stirred at room temperature for 1 minute. Next, 80 g of toluene was added to this solution, and stirred at room temperature for 1 minute to obtain 1-H solution. This 1-H solution was placed in a flask and heated in an oil bath, and a solvent removal treatment was performed using a rotary evaporator. The temperature of the oil bath was adjusted to 105°C. After that, the liquid after the solvent removal treatment was taken out of the flask to obtain 1-I solution. 1-I solution was a dispersion of a compound containing butylphosphonic acid and a copper component.

0.3 g of a triazine-based ultraviolet absorbing compound and 99.7 g of toluene were mixed to obtain 1-J solution, which is a dispersion of the ultraviolet absorbing compound. The 1-J solution was put into a quartz cell (model number J/20/C/CD) manufactured by JASCO Corporation having an optical path length of 0.1 mm to prepare a sample, and the transmission spectrum of the triazine-based ultraviolet absorbing compound was measured using this sample. The measured transmission spectrum is shown in FIG. 11. According to this transmission spectrum, the absorption maximum wavelength λ ^M _UV-C of the triazine-based ultraviolet absorbing compound was 378 nm, and the transmittance at the absorption maximum wavelength λ ^M _UV-C was 9.90%. In addition, λ ^50%-S _UV-C = 329 nm, λ ^50%-L _UV-C = 419 nm, and λ ^50%-L _UV-C - λ ^50%-S _UV-C = 90 nm. Furthermore, λ ^80% _UV-C = 433 nm and Δλ ^80/50 _UV-C = 2.14.

Liquid 1-E, liquid 1-I, 20.00 g of liquid 1-J, 8.80 g of silicone resin KR-300 manufactured by Shin-Etsu Chemical Co., Ltd., and 0.09 g of aluminum alkoxide compound CAT-AC manufactured by Shin-Etsu Chemical Co., Ltd. were mixed and stirred for 30 minutes to obtain the light absorbing composition according to Example 1.

0.1 g of a surface antifouling coating agent (manufactured by Daikin Industries, product name: Optool DSX, concentration of active ingredient: 20% by mass) was mixed with 19.9 g of a hydrofluoroether-containing liquid (manufactured by 3M, product name: Novec 7100) and stirred for 5 minutes to prepare a fluorine treatment agent (concentration of active ingredient: 0.1% by mass). This fluorine treatment agent was poured onto a borosilicate glass substrate (manufactured by SCHOTT, product name: D263 T eco) having dimensions of 76 mm x 76 mm x 0.21 m. The glass substrate was then left at room temperature for 24 hours to dry the coating of the fluorine treatment agent, and the surface of the glass substrate was then lightly wiped with a dust-free cloth containing Novec 7100 to remove excess fluorine treatment agent. In this way, a fluorine-treated substrate was produced. The light absorbing composition according to Example 1 was applied to a 40 mm x 40 mm area in the center of one of the main surfaces of the fluorine-treated substrate using a dispenser 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 6 hours to volatilize the solvent and harden it. The coating film was then peeled off from the fluorine-treated substrate to obtain the optical filter according to Example 1. In this way, the optical filter according to Example 1 was obtained by the solution casting method. The transmission spectrum of the optical filter according to Example 1 is shown in Figure 3, and the characteristic values that can be seen from this transmission spectrum are shown in Tables 3 and 4.

<Examples 2 to 5>
A light absorbing composition according to Example 2, a light absorbing composition according to Example 3, a light absorbing composition according to Example 4, and a light absorbing composition according to Example 5 were each prepared in the same manner as in Example 1, except that the amounts of added raw materials were adjusted as shown in Table 1. An optical filter according to Example 2, an optical filter according to Example 3, an optical filter according to Example 4, and an optical filter according to Example 5 were each produced in the same manner as in Example 1, except that the light absorbing composition according to Example 2, the light absorbing composition according to Example 3, the light absorbing composition according to Example 4, or the light absorbing composition according to Example 5 was used instead of the light absorbing composition according to Example 1.

The transmission spectra of the optical filter according to Example 2, the optical filter according to Example 3, the optical filter according to Example 4, and the optical filter according to Example 5 are shown in Figures 4, 5, 6, and 7, respectively. In addition, the characteristic values of the optical filters according to each Example that can be seen from these transmission spectra are shown in Tables 3 and 4.

<Comparative Example 1>
A light-absorbing composition according to Comparative Example 1 was prepared in the same manner as in Example 1, except that no 1-J solution was used and the amounts of other raw materials added were adjusted as shown in Table 1. An optical filter according to Comparative Example 1 was produced in the same manner as in Example 1, except that the light-absorbing composition according to Comparative Example 1 was used instead of the light-absorbing composition according to Example 1. The transmission spectrum of the optical filter according to Comparative Example 1 is shown in FIG. 8. Furthermore, characteristic values of the optical filter according to Comparative Example 1 that can be seen from this transmission spectrum are shown in Tables 3 and 4.

<Comparative Example 2>
A light-absorbing composition according to Comparative Example 2 was prepared in the same manner as in Example 1, except that 4-bromophenylphosphonic acid was used in addition to phenylphosphonic acid, 1-J solution was not used, and the amounts of other raw materials added were adjusted as shown in Table 1. An optical filter according to Comparative Example 2 was produced in the same manner as in Example 1, except that the light-absorbing composition according to Comparative Example 2 was used instead of the light-absorbing composition according to Example 1. The transmission spectrum of the optical filter according to Comparative Example 2 is shown in FIG. 9. Furthermore, characteristic values of the optical filter according to Comparative Example 2 that can be seen from this transmission spectrum are shown in Tables 3 and 4.

<Comparative Example 3>
Except for adjusting the manufacturing conditions of the optical filter so that the thickness of the optical filter exceeds 500 μm, an optical filter according to Comparative Example 3 was manufactured in the same manner as in Comparative Example 2. The transmission spectrum of the optical filter according to Comparative Example 3 is shown in Fig. 10. In addition, the characteristic values of the optical filter according to Comparative Example 3 that can be seen from this transmission spectrum are shown in Tables 3 and 4.

As shown in Table 3, the optical filters according to the respective Examples satisfied the conditions of 16≦T ₅₅₀ /T ₄₀₀ and 16≦T ₅₅₀ /T ₈₀₀ in the transmission spectrum, suggesting that the optical filters according to the respective Examples sufficiently absorb and block light with a wavelength of about 400 nm. On the other hand, the optical filters according to the respective Comparative Examples satisfied the condition of 16≦T ₅₅₀ /T ₈₀₀ in the transmission spectrum, but did not satisfy the condition of 16≦T ₅₅₀ /T ₄₀₀ , and it was difficult to say that the optical filters according to the respective Comparative Examples sufficiently absorb and block light with a wavelength of about 400 nm. As shown in Table 4, the optical filters according to the respective Examples satisfied the above conditions (I), (II), (III), (IV), (V), (VI), (VII), and (VIII). In addition, the first cutoff wavelength λ ^50% _F and the second cutoff wavelength λ ^50% _S of the optical filters according to each comparative example were in the range of 405 nm or more and 480 nm or less and the range of 580 nm or more and 720 nm or less, respectively. On the other hand, the optical filters according to comparative examples 1 and 2 did not satisfy condition (I), and the optical filters according to each comparative example did not satisfy condition (II). In addition, the first cutoff wavelength λ ^50% _F of the optical filter according to comparative example 1 was less than 405 nm.

1a, 1b Optical filter 10 Light absorbing film 20 Transparent dielectric substrate

Claims (13)

a light absorbing compound comprising a phosphonic acid and a copper component;
an ultraviolet absorbing compound,
the ratio of the content of the phosphonic acid to the content of the ultraviolet absorbing compound is 10 to 300 by mass,
The phosphonic acid includes an aryl-based phosphonic acid and an alkyl-based phosphonic acid,
the ratio of the content of the aryl phosphonic acid to the content of the ultraviolet absorbing compound is 7 to 180 by mass,
a ratio of the content of the alkyl phosphonic acid to the content of the ultraviolet absorbing compound is 3 to 120 by mass,
The ultraviolet absorbing compound is a benzophenone-based compound, a benzotriazole-based compound, a benzoate-based compound, a cyanoacrylate-based compound, or a triazine-based compound;
Light absorbing composition. a light-absorbing film formed by curing the light-absorbing composition has a maximum transmittance of 10% or less in a transmission spectrum at an incident angle of 0 degrees in a wavelength range of 700 nm to 1000 nm;
The light absorbing composition of claim 1 . The transmission spectrum satisfies at least one of the following requirements (a), (b) and (c):
The light absorbing composition of claim 2.
(a) the maximum transmittance in the wavelength range of 800 nm to 950 nm is 3% or less;
(b) the maximum transmittance in the wavelength range of 700 nm to 1100 nm is 15% or less;
(c) The maximum transmittance in the wavelength range of 700 nm to 1200 nm is 20% or less. The transmission spectrum has a cutoff wavelength at which the transmittance is 50% within a wavelength range of 580 nm or more and 720 nm or less.
The light absorbing composition of claim 2. a light absorbing compound comprising a phosphonic acid and a copper component;
an ultraviolet absorbing compound,
a ratio of the content of the phosphonic acid to the content of the ultraviolet absorbing compound is 10 to 300 by mass,
The phosphonic acid includes an aryl-based phosphonic acid and an alkyl-based phosphonic acid,
the ratio of the content of the aryl phosphonic acid to the content of the ultraviolet absorbing compound is 7 to 180 by mass,
a ratio of the content of the alkyl phosphonic acid to the content of the ultraviolet absorbing compound is 3 to 120 by mass,
The ultraviolet absorbing compound is a benzophenone-based compound, a benzotriazole-based compound, a benzoate-based compound, a cyanoacrylate-based compound, or a triazine-based compound;
Light absorbing film. In the transmission spectrum at an incident angle of 0 degrees, the maximum transmittance in the wavelength range of 700 nm to 1000 nm is 10% or less.
The light absorbing film according to claim 5 . The transmission spectrum satisfies at least one of the following requirements (a), (b) and (c):
The light absorbing film according to claim 6 .
(a) the maximum transmittance in the wavelength range of 800 nm to 950 nm is 3% or less;
(b) the maximum transmittance in the wavelength range of 700 nm to 1100 nm is 15% or less;
(c) The maximum transmittance in the wavelength range of 700 nm to 1200 nm is 20% or less. The transmission spectrum has a cutoff wavelength at which the transmittance is 50% within a wavelength range of 580 nm or more and 720 nm or less.
The light absorbing film according to claim 6 . applying a light absorbing composition to a surface of a substrate;
curing the applied light absorbing composition to obtain a cured product ;
and peeling the cured product from the substrate.
The light absorbing composition includes a light absorbing compound including a phosphonic acid and a copper component, and an ultraviolet absorbing compound;
a ratio of the content of the phosphonic acid to the content of the ultraviolet absorbing compound is 10 to 300 by mass,
The phosphonic acid includes an aryl-based phosphonic acid and an alkyl-based phosphonic acid,
the ratio of the content of the aryl phosphonic acid to the content of the ultraviolet absorbing compound is 7 to 180 by mass,
a ratio of the content of the alkyl phosphonic acid to the content of the ultraviolet absorbing compound is 3 to 120 by mass,
The ultraviolet absorbing compound is a benzophenone-based compound, a benzotriazole-based compound, a benzoate-based compound, a cyanoacrylate-based compound, or a triazine-based compound;
A method for producing a light absorbing film. In the transmission spectrum of the light absorbing film at an incident angle of 0 degrees, the maximum transmittance in the wavelength range of 700 nm to 1000 nm is 10% or less.
The method for producing the light absorbing film according to claim 9 . The transmission spectrum satisfies at least one of the following (a), (b), and (c):
The method for producing the light absorbing film according to claim 10 .
(a) the maximum transmittance in the wavelength range of 800 nm to 950 nm is 3% or less;
(b) the maximum transmittance in the wavelength range of 700 nm to 1100 nm is 15% or less;
(c) The maximum transmittance in the wavelength range of 700 nm to 1200 nm is 20% or less. The transmission spectrum has a cutoff wavelength at which the transmittance is 50% within a wavelength range of 580 nm or more and 720 nm or less.
The method for producing the light absorbing film according to claim 10 . An optical filter comprising the light absorbing film according to any one of claims 5 to 8 .

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