JP2020057009A - Optical filter and information terminal with camera - Google Patents

Abstract

To provide an optical filter capable of exhibiting desired optical performance with a simple configuration.SOLUTION: An optical filter (1a) disclosed herein includes a light absorption layer (10) and satisfies the following conditions (i)-(iii) when 300nm-1200 nm light enters the optical filter at an incident angle of 0°: (i) an average transmittance is 78% or greater in a wavelength range of 450-600 nm; (ii) a spectral transmittance is 1% or less in a wavelength range of 750nm-1080nm; and (iii) the spectral transmittance decreases with increasing wavelength in a wavelength range of 600nm-750 nm, and a first IR cutoff wavelength exists in a wavelength range of 620nm-680 nm. The conditions (i), (ii), and (iii) are satisfied by the light absorption layer (10).SELECTED DRAWING: Figure 1A

Description

  The present invention relates to an optical filter and an information terminal with a camera.

  In an image pickup apparatus using an image pickup device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), various optical filters are arranged in front of the image pickup device in order to obtain an image having good color reproducibility. I have. Generally, an image sensor has spectral sensitivity in a wide wavelength range from an ultraviolet region to an infrared region. On the other hand, human visibility is present only in the visible light region. For this reason, there is known a technique in which an optical filter for shielding infrared rays is arranged on the front surface of the imaging device in order to make the spectral sensitivity of the imaging device in the imaging device close to human visibility.

  Examples of the optical filter include an optical filter using light reflection like an optical filter having a dielectric multilayer film, and an optical filter having a film containing a light absorber capable of absorbing light of a predetermined wavelength. There is an optical filter that utilizes light absorption. The latter is desirable because it has a spectral characteristic that does not easily change with respect to the incident angle of the incident light.

For example, Patent Document 1 discloses a near-infrared absorbing filter formed of a near-infrared absorbing agent and a resin. The near-infrared absorber is obtained from a predetermined phosphonic acid compound, a predetermined phosphate compound, and a copper salt. The predetermined phosphonic acid compound has a monovalent group R ¹ represented by —CH ₂ CH ₂ —R ¹¹ bonded to a phosphorus atom P. R ¹¹ is a hydrogen atom, having 1 to 20 carbon atoms
Or a fluorinated alkyl group having 1 to 20 carbon atoms.

JP 2011-203467 A

  Although the near-infrared absorption filter described in Patent Document 1 can effectively absorb light at a wavelength of 800 nm to 1200 nm, it cannot be said that it has desirable light absorption characteristics at a wavelength of 650 nm to 800 nm. Therefore, the present invention provides an optical filter that can exhibit desired optical performance with a simple configuration, which is difficult to realize only with the near-infrared absorption filter described in Patent Document 1.

The present invention
With a light absorbing layer,
When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °,
(I) having an average transmittance of 78% or more at a wavelength of 450 nm to 600 nm,
(Ii) having a spectral transmittance of 1% or less at a wavelength of 750 nm to 1080 nm,
(Iii) The first IR cutoff wavelength having a spectral transmittance that decreases with an increase in the wavelength at a wavelength of 600 nm to 750 nm and having a spectral transmittance of 50% at a wavelength of 600 nm to 750 nm is within a range of 620 nm to 680 nm. Exists,
The condition (i), the condition (ii), and the condition (iii) are satisfied by the light absorbing layer.
An optical filter is provided.

  The above optical filter can exhibit desired optical performance with a simple configuration.

FIG. 1A is a sectional view showing an example of the optical filter of the present invention. FIG. 1B is a cross-sectional view illustrating another example of the optical filter of the present invention. FIG. 1C is a sectional view showing still another example of the optical filter of the present invention. FIG. 1D is a sectional view showing still another example of the optical filter of the present invention. FIG. 1E is a sectional view showing still another example of the optical filter of the present invention. FIG. 2 is a sectional view showing an example of a camera module including the optical filter of the present invention. FIG. 3 is a transmittance spectrum of the optical filter according to the first embodiment. FIG. 4 is a transmittance spectrum of the optical filter according to the second embodiment. FIG. 5 is a transmittance spectrum of the optical filter according to Example 16. FIG. 6 is a transmittance spectrum of the optical filter according to Example 17. FIG. 7 is a transmittance spectrum of the optical filter according to Example 20. FIG. 8 is a transmittance spectrum of the optical filter according to Example 21. FIG. 9 is a transmittance spectrum of the optical filter according to Example 22. FIG. 10 is a transmittance spectrum of the optical filter according to Example 36.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description relates to an example of the present invention, and the present invention is not limited thereto.

  In some cases, it is desirable that the optical filter has characteristics of transmitting light having a wavelength of 450 nm to 600 nm and cutting light having a wavelength of 650 nm to 1100 nm. However, for example, the optical filter described in Patent Literature 1 does not have sufficient light absorption characteristics at a wavelength of 650 nm to 800 nm, and has another light absorption layer or another light absorption layer to cut light at a wavelength of 650 nm to 800 nm. Requires a reflective film. Alternatively, it is necessary to use a substrate such as an infrared absorbing glass suitable for cutting light having a wavelength of 650 nm to 800 nm. As described above, it is not easy to realize an optical filter having the above desirable characteristics with a simple configuration (for example, one light absorbing layer). In fact, the inventor has repeatedly performed trial and error in order to realize an optical filter having the above-described desirable characteristics with a simple configuration. As a result, the inventor has finally devised an optical filter according to the present invention.

As shown in FIG. 1A, the optical filter 1a includes a light absorbing layer 10. The optical filter 1a 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 °. In the optical filter 1a, the condition (i), the condition (ii), and the condition (iii) below are satisfied by the light absorbing layer 10.
(I) an average transmittance of 78% or more at a wavelength of 450 nm to 600 nm; (ii) a spectral transmittance of 1% or less at a wavelength of 750 nm to 1080 nm; and (iii) a spectral transmittance and a wavelength which decrease with increasing wavelength at a wavelength of 600 nm to 750 nm. First IR cutoff wavelength existing in the range of 620 nm to 680 nm

  In the present specification, “spectral transmittance” is a transmittance when incident light of a specific wavelength is incident on an object such as a sample, and “average transmittance” is a spectral transmittance within a predetermined wavelength range. The “maximum transmittance” is the maximum value of the spectral transmittance within a predetermined wavelength range. Further, in this specification, the “transmittance spectrum” is obtained by arranging spectral transmittances at respective wavelengths within a predetermined wavelength range in order of wavelength.

  In this specification, the “IR cutoff wavelength” indicates a 50% spectral transmittance in a wavelength range of 600 nm or more when light having a wavelength of 300 nm to 1200 nm is incident on an optical filter at a predetermined incident angle. Means wavelength. The “first IR cutoff wavelength” is an IR cutoff wavelength when light is incident on the optical filter at an incident angle of 0 °. The “UV cutoff wavelength” refers to a wavelength that exhibits 50% spectral transmittance in a wavelength range of 450 nm or less when light having a wavelength of 300 nm to 1200 nm is incident on an optical filter at a predetermined incident angle. means. The “first UV cutoff wavelength” is a UV cutoff wavelength when light is incident on the optical filter at an incident angle of 0 °.

When the optical filter 1a satisfies the above conditions (i) to (iii), the optical filter 1a has a large transmission amount of light having a wavelength of 450 nm to 600 nm and effectively cuts light having a wavelength of 650 nm to 1100 nm. it can. For this reason, the transmittance spectrum of the optical filter 1a is more suitable for human luminosity than the transmittance spectrum of the near-infrared absorption filter described in Patent Document 1. Moreover, the optical filter 1a satisfies the conditions (i) to (iii) by the light absorbing layer 10.

  Regarding (i) above, the optical filter 1a preferably has an average transmittance of 80% or more, and more preferably 82% or more, at a wavelength of 450 nm to 600 nm.

Regarding (iii) above, the first IR cutoff wavelength is desirably from 630 nm to 65 nm.
Exists in the range of 0 nm. As a result, the transmittance spectrum of the optical filter 1a is more suitable for human visibility.

The optical filter 1a desirably satisfies the following condition (iv) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. Accordingly, the optical filter 1a can effectively cut light in the ultraviolet region, and the transmittance spectrum of the optical filter 1a is more suitable for human luminosity.
(Iv) Spectral transmittance of 1% or less at wavelengths of 300 nm to 350 nm

  Regarding the above (iv), the condition (iv) is desirably satisfied by the light absorbing layer 10 in the optical filter 1a.

  Regarding (iv), desirably, the optical filter 1a has a spectral transmittance of 1% or less at a wavelength of 300 nm to 360 nm when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °.

The optical filter 1a desirably satisfies the following condition (v) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. As a result, the transmittance spectrum of the optical filter 1a is more suitable for human visibility.
(V) The first UV cutoff wavelength is in the range of 380 nm to 430 nm while having a spectral transmittance that increases with an increase in the wavelength in the range of 350 nm to 450 nm.

  Regarding the above (v), preferably, the condition (v) is satisfied by the light absorbing layer 10 in the optical filter 1a.

Regarding (v) above, the first UV cutoff wavelength desirably lies within the wavelength range of 390 nm to 420 nm. As a result, the transmittance spectrum of the optical filter 1a is more suitable for human visibility.

The optical filter 1a desirably satisfies the following condition (vi) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. This makes it possible to shield infrared rays having a relatively long wavelength (1000 to 1100 nm). Conventionally, in order to cut off light of this wavelength, a light reflection film composed of a dielectric multilayer film is often used. However, according to the optical filter 1a, light of this wavelength can be effectively cut without using such a dielectric multilayer film. Even if a light reflection film composed of a dielectric multilayer film is required, the level of reflection performance required for the light reflection film can be lowered, so that the number of stacked dielectrics in the light reflection film can be reduced, and the light reflection film Cost required for formation can be reduced. In the optical filter 1a, the condition (vi) is desirably satisfied by the light absorbing layer 10.
(Vi) Spectral transmittance of 3% or less at wavelengths of 1000 to 1100 nm

The optical filter 1a desirably satisfies the following condition (vii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. In this case, the longer wavelength (110
(0 to 1200 nm). Thus, the optical filter 1a can effectively cut off light of this wavelength without using a dielectric multilayer film or with a small number of dielectric layers in the dielectric multilayer film. In the optical filter 1a, the condition (vii) is preferably satisfied by the light absorbing layer 10.
(Vii) Spectral transmittance of 15% or less at wavelengths of 1100 to 1200 nm

  For example, in the optical filter 1a, the absolute value of the difference between the second IR cutoff wavelength and the first IR cutoff wavelength is 10 nm or less (condition (viii)). The second IR cutoff wavelength is an IR cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 40 °. In this case, the transmittance characteristic of the optical filter 1a near the first IR cutoff wavelength does not easily change with respect to the incident angle of light incident on the optical filter 1a. As a result, it is possible to suppress the occurrence of different colors at the center and the periphery of the image obtained by the imaging device in which the optical filter 1a is disposed in front of the imaging device.

  In the optical filter 1a, the absolute value of the difference between the second IR cutoff wavelength and the first IR cutoff wavelength is desirably 5 nm or less.

  For example, in the optical filter 1a, the absolute value of the difference between the third IR cutoff wavelength and the first IR cutoff wavelength is 15 nm or less (condition (ix)). The third IR cutoff wavelength is an IR cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 50 °. In this case, even if the incident angle of the light incident on the optical filter 1a changes greatly, it is possible to suppress a change in the transmittance characteristic of the optical filter 1a near the first IR cutoff wavelength. As a result, even if the optical filter 1a is arranged in front of the imaging device of the imaging device capable of imaging with a wide angle of view, a high-quality image is easily obtained.

  For example, in the optical filter 1a, the absolute value of the difference between the fourth IR cutoff wavelength and the first IR cutoff wavelength is 20 nm or less. The fourth IR cutoff wavelength is an IR cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 60 °. In this case, even if the optical filter 1a is arranged in front of the image pickup device of the image pickup device capable of picking up an image with a wide angle of view, a high quality image is easily obtained.

For example, in the optical filter 1a, the absolute value of the difference between the second UV cutoff wavelength and the first UV cutoff wavelength is 10 nm or less (condition (x)). The second UV cutoff wavelength is a UV cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 40 °. In this case, the transmittance characteristic of the optical filter 1a near the first UV cutoff wavelength does not easily change with respect to the incident angle of light incident on the optical filter 1a. As a result, it is possible to suppress the occurrence of different colors at the center and the periphery of the image obtained by the imaging device in which the optical filter 1a is disposed in front of the imaging device.

  In the optical filter 1a, the absolute value of the difference between the second UV cutoff wavelength and the first UV cutoff wavelength is desirably 5 nm or less.

  For example, in the optical filter 1a, the absolute value of the difference between the third UV cutoff wavelength and the first UV cutoff wavelength is 15 nm or less (condition (xi)). The third UV cutoff wavelength is a UV cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 50 °. In this case, even if the incident angle of light incident on the optical filter 1a changes greatly, it is possible to suppress a change in the transmittance characteristic of the optical filter 1a near the first UV cutoff wavelength. As a result, even if the optical filter 1a is arranged in front of the imaging device of the imaging device capable of imaging with a wide angle of view, a high-quality image is easily obtained.

  For example, in the optical filter 1a, the absolute value of the difference between the fourth UV cutoff wavelength and the first UV cutoff wavelength is 20 nm or less. The fourth UV cutoff wavelength is a UV cutoff wavelength when light having a wavelength of 300 nm to 1200 nm is incident on the optical filter 1a at an incident angle of 60 °. In this case, even if the optical filter 1a is arranged in front of the image pickup device of the image pickup device capable of picking up an image with a wide angle of view, a high quality image is easily obtained.

The optical filter 1a desirably satisfies the following condition (xii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. In the optical filter 1a, the condition (xii) is desirably satisfied by the light absorbing layer 10.
(Xii) at a wavelength of 800 to 950 nm, a spectral transmittance of 0.5% or less, more preferably 0.1% or less.

The optical filter 1a desirably further satisfies the following condition (xiii) when light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °. In the optical filter 1a, the condition (xiii) is desirably satisfied by the light absorbing layer 10.
(Xiii) at a wavelength of 800 to 1000 nm, a spectral transmittance of 0.5% or less, more preferably 0.1% or less.

  Each color filter corresponding to RGB used in the imaging apparatus may transmit not only light in a wavelength range corresponding to each RGB but also light having a wavelength of 800 nm or more. For this reason, unless the spectral transmittance of the infrared cut filter used in the imaging device in the above wavelength range is low to some extent, light in the above wavelength range is incident on a pixel of the image sensor, and a signal is output from the pixel. . When a digital image is acquired using such an imaging device and the amount of light in the visible light region is sufficiently strong, the image can be obtained even when a low amount of infrared light passes through the color filter and the pixels of the imaging device receive light. There is no significant effect on the digital image. However, when the amount of light in the visible light region is small or in a dark portion of an image, the image is easily affected by such infrared rays, and sometimes a color such as blue or red is mixed in the image.

As described above, a color filter used together with an imaging device such as a CMOS and a CCD may transmit light in a wavelength range of 800 to 950 nm or 800 to 1000 nm. When the optical filter 1a satisfies the above conditions (xii) and (xiii), such a problem of an image can be prevented.

The light absorbing layer 10 is not particularly limited as long as it absorbs light in a predetermined wavelength range so that the optical filter 1a satisfies the above conditions (i) to (iii). For example, the light absorbing layer 10 is formed of phosphonic acid and copper ions. Containing light absorber.

  When the light absorbing layer 10 includes a light absorbing agent formed by phosphonic acid and copper ions, the phosphonic acid includes, for example, a first phosphonic acid having an aryl group. In the primary phosphonic acid, the aryl group is bonded to the phosphorus atom. This makes it easy for the optical filter 1a to satisfy the above conditions (i) to (iii).

The aryl group of the first phosphonic acid is, for example, a phenyl group, a benzyl group, a toluyl group, a nitrophenyl group, a hydroxyphenyl group, a halogenated phenyl group in which at least one hydrogen atom in the phenyl group is substituted with a halogen atom, Or a halogenated benzyl group in which at least one hydrogen atom in the benzene ring of the benzyl group is substituted with a halogen atom. Desirably, the primary phosphonic acid has, in part, a halogenated phenyl group. In this case, the optical filter 1a is more likely to satisfy the above conditions (i) to (iii).

  When the light absorbing layer 10 includes a light absorbing agent formed by phosphonic acid and copper ions, the phosphonic acid preferably further includes a second phosphonic acid having an alkyl group. In the second phosphonic acid, the alkyl group is attached to the phosphorus atom.

  The alkyl group of the second phosphonic acid is, for example, an alkyl group having 6 or less carbon atoms. This alkyl group may have any of a straight chain and a branched chain.

  When the light absorbing layer 10 includes a light absorbing agent formed by phosphonic acid and copper ions, the light absorbing layer 10 preferably further includes a phosphate ester for dispersing the light absorbing agent and a matrix resin.

The phosphoric acid ester contained in the light absorbing layer 10 is not particularly limited as long as the light absorbing agent can be appropriately dispersed. For example, the phosphoric acid diester represented by the following formula (c1) and the phosphoric acid ester represented by the following formula (c2) At least one of the phosphoric acid monoesters. In the following formulas (c1) and (c2), R ₂₁ , R ₂₂ , and R ₃ are each a monovalent functional group represented by — (CH ₂ CH ₂ O) _n R ₄ , and n Is an integer of 1 to 25, and R ₄ represents an alkyl group having 6 to 25 carbon atoms. R ₂₁ , R ₂₂ , and R ₃ are the same or different types of functional groups.

The phosphate ester is not particularly limited. For example, Plysurf A208N: polyoxyethylene alkyl (C12, C13) ether phosphate, Plysurf A208F: polyoxyethylene alkyl (C8) ether phosphate, Plysurf A208B: Polyoxyethylene lauryl ether phosphate, Plysurf A219B:
Polyoxyethylene lauryl ether phosphate, Plysurf AL: Polyoxyethylene styrenated phenyl ether phosphate, Plysurf A212C: Polyoxyethylene tridecyl ether phosphate, or Plysurf A215C: Polyoxyethylene tridecyl ether phosphorus It can be an acid ester. These are all products manufactured by Daiichi Kogyo Seiyaku. The phosphoric acid ester is NIKKOL DDP-2: polyoxyethylene alkyl ether phosphate, NIKKOL DDP-4: polyoxyethylene alkyl ether phosphate, or NIKKOL DDP-6: polyoxyethylene alkyl ether phosphate. possible. These are all products made by Nikko Chemicals.

  The matrix resin contained in the light absorbing layer 10 is, for example, a resin in which a light absorbing agent can be dispersed and which can be cured by heat or ultraviolet. Further, when a resin layer having a thickness of 0.1 mm is formed from the resin as the matrix resin, the transmittance of the resin layer with respect to light having a wavelength of 350 nm to 900 nm is, for example, 70% or more, preferably 75% or more, More desirably, a resin of 80% or more can be used. The content of the phosphonic acid is, for example, 3 to 180 parts by mass with respect to 100 parts by mass of the matrix resin.

  The matrix resin contained in the light absorbing layer 10 is not particularly limited as long as the above properties are satisfied. For example, (poly) olefin resin, polyimide resin, polyvinyl butyral resin, polycarbonate resin, polyamide resin, polysulfone resin, polyethersulfone Resin, polyamide-imide resin, (modified) acrylic resin, epoxy resin, or silicone resin. The matrix resin may contain an aryl group such as a phenyl group, and is preferably a silicone resin containing an aryl group such as a phenyl group. If the light absorbing layer 10 is hard (it is rigid), cracks tend to occur due to curing shrinkage during the manufacturing process of the optical filter 1a as the thickness of the light absorbing layer 10 increases. When the matrix resin is a silicone resin containing an aryl group, the light absorbing layer 10 tends to have good crack resistance. In addition, when a silicone resin containing an aryl group is used, when the light absorbing agent formed by the above phosphonic acid and copper ions is contained, the light absorbing agent is less likely to aggregate. Furthermore, when the matrix resin of the light absorption layer 10 is a silicone resin containing an aryl group, the phosphate ester contained in the light absorption layer 10 is similar to the phosphate ester represented by the formula (c1) or (c2). It is desirable to have a flexible linear organic functional group such as an oxyalkyl group. Because, the phosphonic acid, the silicone resin containing an aryl group, and the interaction based on the combination of the phosphoric acid ester having a linear organic functional group such as an oxyalkyl group, the light absorber hardly aggregates, and This is because good rigidity and good flexibility can be provided to the light absorbing layer. Specific examples of the silicone resin used as the matrix resin include KR-255, KR-300, KR-2621-1, KR-211, KR-311, KR-216, KR-212, and KR-251. be able to. These are all silicone resins manufactured by Shin-Etsu Chemical Co., Ltd.

  As shown in FIG. 1A, the optical filter 1a further includes, for example, a transparent dielectric substrate 20. The transparent dielectric substrate 20 is covered with the light absorbing layer 10. The transparent dielectric substrate 20 is not particularly limited as long as it is a dielectric substrate having a high average transmittance (e.g., 80% or more) at 450 nm to 600 nm.

The transparent dielectric substrate 20 is made of, for example, glass or resin. When the transparent dielectric substrate 20 is made of glass, the glass contains, for example, borosilicate glass such as D263, soda-lime glass (blue plate), white plate glass such as B270, alkali-free glass, or copper. Infrared absorbing glass such as phosphate glass or fluorophosphate glass containing copper. When the transparent dielectric substrate 20 is an infrared-absorbing glass such as a phosphate glass containing copper or a fluorophosphate glass containing copper, the infrared absorption performance and light A desired infrared absorption performance can be provided to the optical filter 1a by a combination with the infrared absorption performance of the absorption layer 10. Such an infrared-absorbing glass is, for example, BG-60, BG-61, BG-62, BG-63, or BG-67 manufactured by Schott, 500EXL manufactured by NEC Corporation, or HOYA. CM5000, CM500, C5000 or C500S manufactured by the company. Further, the infrared absorbing glass may have an ultraviolet absorbing property.

  The transparent dielectric substrate 20 may be a transparent crystalline substrate such as magnesium oxide, sapphire, or quartz. For example, sapphire has a high hardness and is therefore not easily scratched. For this reason, the plate-shaped sapphire may be disposed as a scratch-resistant protective material (protection filter) on the front surface of a camera module or a lens provided in a mobile terminal such as a smartphone and a mobile phone. By forming the light absorbing layer 10 on such a plate-like sapphire, it is possible to protect the camera module and the lens and effectively cut off light having a wavelength of 650 nm to 1100 nm. It is not necessary to dispose an optical filter having a shielding property of infrared rays having a wavelength of 650 nm to 1100 nm around an image sensor such as a CCD or a CMOS or inside a camera module. Therefore, if the light absorbing layer 10 is formed on the plate-shaped sapphire, it is possible to contribute to a reduction in the height of the camera module.

  When the transparent dielectric substrate 20 is made of a resin, the resin may be, for example, a (poly) olefin resin, a polyimide resin, a polyvinyl butyral resin, a polycarbonate resin, a polyamide resin, a polysulfone resin, a polyethersulfone resin, a polyamideimide resin, (Modified) An acrylic resin, an epoxy resin, or a silicone resin.

  The optical filter 1a forms a coating film by applying, for example, a composition (light absorbing composition) for forming the light absorbing layer 10 to one main surface of the transparent dielectric substrate 20. It can be manufactured by drying. The method for preparing the light-absorbing composition and the method for manufacturing the optical filter 1a will be described, taking as an example the case where the light-absorbing layer 10 contains a light-absorbing agent formed by phosphonic acid and copper ions.

  First, an example of a method for preparing the light absorbing composition will be described. A copper salt such as copper acetate monohydrate is added to a predetermined solvent such as tetrahydrofuran (THF) and stirred to obtain a copper salt solution. Next, a phosphoric acid ester compound such as a phosphoric acid diester represented by the formula (c1) or a phosphoric acid monoester represented by the formula (c2) is added to the copper salt solution and stirred to prepare a solution A. I do. Further, the first phosphonic acid is added to a predetermined solvent such as THF and stirred to prepare a liquid B. When a plurality of types of phosphonic acids are used as the first phosphonic acid, the phosphonic acid is added to a predetermined solvent such as THF and stirred, and a plurality of preliminary liquids prepared for each type of phosphonic acid are mixed to obtain solution B. May be prepared. Desirably, an alkoxysilane monomer is added in the preparation of Liquid B.

  When the alkoxysilane monomer is added to the light-absorbing composition, it is possible to prevent the light-absorbing agent particles from aggregating with each other. Are well dispersed. When the optical filter 1a is manufactured using the light-absorbing composition, the siloxane bond (—Si—O—Si) is treated by treating the hydrolysis and condensation polymerization of the alkoxysilane monomer sufficiently to occur. −) Is formed, and the optical filter 1a has good moisture resistance. In addition, the optical filter 1a has good heat resistance. This is because a siloxane bond has a higher binding energy than a bond such as a -CC- bond or a -CO- bond, is chemically stable, and has excellent heat resistance and moisture resistance.

Next, while stirring the liquid A, the liquid B is added to the liquid A and stirred for a predetermined time. Next, a predetermined solvent such as toluene is added to this solution and stirred to obtain a liquid C. Next, a desolvation treatment is performed for a predetermined time while heating the liquid C to obtain a liquid D. As a result, components generated by dissociation of a solvent such as THF and a copper salt such as acetic acid (boiling point: about 118 ° C.) are removed, and a light absorber is generated by the first phosphonic acid and copper ions. The temperature at which the liquid C is heated is determined based on the boiling point of the component to be removed dissociated from the copper salt. In the desolvation treatment, a solvent such as toluene (boiling point: about 110 ° C.) used to obtain the liquid C also volatilizes. Since this solvent desirably remains to some extent in the light-absorbing composition, from this viewpoint, the amount of the solvent to be added and the time for the desolvation treatment may be determined. In order to obtain the liquid C, o-xylene (boiling point: about 144 ° C.) can be used instead of toluene. In this case, since the boiling point of o-xylene is higher than the boiling point of toluene, the amount added can be reduced to about one-fourth of the amount added of toluene.

  When the light-absorbing composition further contains a second phosphonic acid, for example, the H solution is further prepared as follows. First, a copper salt such as copper acetate monohydrate is added to a predetermined solvent such as tetrahydrofuran (THF) and stirred to obtain a copper salt solution. Next, to this copper salt solution, a phosphate ester compound such as a phosphate diester represented by the formula (c1) or a phosphate monoester represented by the formula (c2) is added and stirred to prepare a solution E. I do. Further, the second phosphonic acid is added to a predetermined solvent such as THF and stirred to prepare a solution F. When a plurality of types of phosphonic acids are used as the second phosphonic acid, the second phosphonic acid is added to a predetermined solvent such as THF, and then stirred to mix a plurality of preliminary liquids prepared for each type of the second phosphonic acid. To prepare the solution F. While stirring the solution E, the solution F is added to the solution E and stirred for a predetermined time. Next, a predetermined solvent such as toluene is added to this solution and stirred to obtain a solution G. Next, a solution H is obtained by performing a desolvation treatment for a predetermined time while heating the solution G. As a result, components generated by dissociation of a solvent such as THF and a copper salt such as acetic acid are removed, and another light absorber is generated by the second phosphonic acid and copper ions. The temperature at which solution G is heated is determined in the same manner as solution C, and the solvent for obtaining solution G is also determined in the same manner as solution C.

  A light absorbing composition can be prepared by adding a matrix resin such as a silicone resin to the solution D and stirring the solution. When the light-absorbing composition contains a light-absorbing agent formed by a second phosphonic acid and copper ions, a liquid I obtained by adding a matrix resin such as a silicone resin to the liquid D and stirring the liquid. , A light absorbing composition can be prepared by further adding a liquid H and stirring.

The light absorbing composition is applied to one main surface of the transparent dielectric substrate 20 to form a coating film. For example, a liquid light-absorbing composition is applied to one main surface of the transparent dielectric substrate 20 by spin coating or application by a dispenser to form a coating film. Next, the coating film is subjected to a predetermined heat treatment to cure the coating film. For example, this coating film is exposed to an environment at a temperature of 50C to 200C. If necessary, the coating film is subjected to a humidifying treatment in order to sufficiently hydrolyze the alkoxysilane monomer contained in the light absorbing composition. For example, the cured coating is exposed to an environment at a temperature of 40C to 100C and a relative humidity of 40% to 100%. As a result, a repeating structure of siloxane bonds (Si—O) _n is formed. Thus, the optical filter 1a can be manufactured. In general, in the hydrolysis and polycondensation reaction of an alkoxysilane containing a monomer, the alkoxysilane and water may be allowed to coexist in a liquid composition to carry out these reactions. However, if water is added to the light-absorbing composition in advance when producing an optical filter, the phosphate ester or the light-absorbing agent is deteriorated in the process of forming the light-absorbing layer, and the light-absorbing performance is reduced. Or the durability of the optical filter may be impaired. For this reason, it is desirable to perform a humidification treatment after the coating film is cured by a predetermined heat treatment.

  When the transparent dielectric substrate 20 is a glass substrate, in order to improve the adhesion between the transparent dielectric substrate 20 and the light absorbing layer 10, a resin layer containing a silane coupling agent is added to the transparent dielectric substrate 20 and the light absorbing layer. 10 may be formed.

<Modification>
The optical filter 1a can be changed from various viewpoints. For example, the optical filter 1a may be changed to the optical filters 1b to 1e shown in FIGS. 1B to 1E, respectively. The optical filters 1b to 1e have the same configuration as that of the optical filter 1a, unless otherwise specified. The components of the optical filters 1b to 1e that are the same as or correspond to the components of the optical filter 1a are denoted by the same reference numerals, and detailed description thereof will be omitted. The description about the optical filter 1a also applies to the optical filters 1b to 1e unless technically contradictory.

As shown in FIG. 1B, an optical filter 1 b according to another example of the present invention has a light absorption layer 10 formed on both main surfaces of a transparent dielectric substrate 20. Thus, the optical filter 1b is not formed by one light absorbing layer 10 but by two light absorbing layers 10 as described above.
) Optical performance. The thickness of the light absorbing layer 10 on both main surfaces of the transparent dielectric substrate 20 may be the same or different. That is, the light absorbing layer 10 is provided on both main surfaces of the transparent dielectric substrate 20 so that the thickness of the light absorbing layer 10 necessary for the optical filter 1b to obtain desired optical characteristics is evenly or unevenly distributed. 10 are formed. Thereby, the thickness of each light absorbing layer 10 formed on one main surface of the transparent dielectric substrate 20 of the optical filter 1b is smaller than that of the optical filter 1a. Thereby, the internal pressure of the coating film is low, and the occurrence of cracks can be prevented. Further, the time for applying the liquid light-absorbing composition can be reduced, and the time for curing the coating film of the light-absorbing composition can be reduced. Since the light absorption layers 10 are formed on both main surfaces of the transparent dielectric substrate 20, warpage of the optical filter 1b is suppressed even when the transparent dielectric substrate 20 is thin. Also in this case, a resin layer containing a silane coupling agent is formed between the transparent dielectric substrate 20 and the light absorbing layer 10 in order to improve the adhesion between the transparent dielectric substrate 20 and the light absorbing layer 10. Is also good.

As shown in FIG. 1C, an optical filter 1c according to another example of the present invention includes an antireflection film 30. The anti-reflection film 30 is a film formed so as to form an interface between the optical filter 1c and air and for reducing reflection of light in a visible light region. The antireflection film 30 is a film formed of a dielectric such as a resin, an oxide, and a fluoride, for example. The antireflection film 30 may be a multilayer film formed by laminating two or more types of dielectrics having different refractive indexes. In particular, the antireflection film 30 may be a dielectric multilayer film made of a low refractive index material such as SiO ₂ and a high refractive index material such as TiO ₂ or Ta ₂ O ₅ . In this case, Fresnel reflection at the interface between the optical filter 1c and air is reduced, and the amount of light in the visible light region of the optical filter 1c can be increased. Also in this case, a resin layer containing a silane coupling agent is formed between the transparent dielectric substrate 20 and the light absorbing layer 10 in order to improve the adhesion between the transparent dielectric substrate 20 and the light absorbing layer 10. Is also good. In some cases, a resin layer containing a silane coupling agent may be formed between the light absorbing layer 10 and the antireflection film 30 in order to improve the adhesion of the antireflection film 30. The antireflection film 30 may be disposed on both main surfaces of the optical filter 1c, or may be disposed on only one main surface.

  As shown in FIG. 1D, an optical filter 1d according to another example of the present invention includes only the light absorbing layer 10. The optical filter 1d forms a coating film by applying a light-absorbing composition to a predetermined substrate such as a glass substrate, a resin substrate, or a metal substrate (for example, a steel substrate or a stainless steel substrate), and cures the coating film. It can be manufactured by peeling off from the substrate after having been made. The optical filter 1d may be manufactured by a melt molding method. The optical filter 1d is thin because it does not include the transparent dielectric substrate 20. Therefore, the optical filter 1d can contribute to lowering the height of the image sensor and the optical system.

As shown in FIG. 1E, an optical filter 1e according to another example of the present invention includes a light absorbing layer 10 and a pair of antireflection films 30 disposed on both surfaces thereof. In this case, the optical filter 1e can contribute to lowering the height of the imaging device and the optical system, and can increase the amount of light in the visible light region as compared with the optical filter 1d.

  Each of the optical filters 1a to 1e may be modified to include an infrared absorbing film or an ultraviolet absorbing film separately from the light absorbing layer 10 in order to enhance its functionality. The infrared absorbing film contains, for example, an organic infrared absorbing agent such as a cyanine-based, phthalocyanine-based, squarylium-based, diimmonium-based, or azo-based infrared absorbing agent or an infrared absorbing agent formed of a metal complex. The infrared absorbing film contains, for example, one or more infrared absorbing agents selected from these infrared absorbing agents. This organic infrared absorbent has a small wavelength range (absorption band) of light that can be absorbed and is suitable for absorbing light in a specific range of wavelength.

  The ultraviolet absorbing film contains, for example, a benzophenone-based, triazine-based, indole-based, merocyanine-based, or oxazole-based ultraviolet absorber. The ultraviolet absorbing film contains, for example, one or more ultraviolet absorbing agents selected from these ultraviolet absorbing agents. These ultraviolet absorbers may include, for example, those that absorb ultraviolet light in the vicinity of 300 nm to 340 nm, emit light (fluorescence) having a longer wavelength than the absorbed wavelength, and function as a fluorescent agent or a fluorescent whitening agent. The ultraviolet absorbing film can reduce the incidence of ultraviolet light that causes deterioration of a material used for an optical filter such as a resin.

  The above-mentioned infrared absorber or ultraviolet absorber may be previously contained in the transparent dielectric substrate 20 made of resin. The infrared absorbing film or the ultraviolet absorbing film can be formed, for example, by forming a resin containing an infrared absorbing agent or an ultraviolet absorbing agent. In this case, the resin needs to be capable of appropriately dissolving or dispersing the infrared absorber or the ultraviolet absorber and to be transparent. Such resins include (poly) olefin resins, polyimide resins, polyvinyl butyral resins, polycarbonate resins, polyamide resins, polysulfone resins, polyethersulfone resins, polyamideimide resins, (modified) acrylic resins, epoxy resins, and silicone resins. Can be exemplified.

  The optical filters 1a to 1e are arranged on the front side (closer to the subject) of an image pickup device such as a CCD or CMOS inside the image pickup device, for example, in order to make the spectral sensitivity of the image pickup device in the image pickup device close to human visibility. You.

  The optical filter 1a is used, for example, for manufacturing an information terminal with a camera. In this case, the camera-equipped information terminal includes, for example, a lens system, an image sensor, and an optical filter 1a. The imaging element receives light that has passed through the lens system. The optical filter 1a is disposed in front of the lens system and protects the lens system. In this case, the optical filter 1a functions as a lens system cover.

  1 shows an example of a camera module 100 provided in an information terminal with a camera. As shown in FIG. 2, the camera module 100 includes, for example, a lens system 2, a low-pass filter 3, an image sensor 4, a circuit board 5, an optical filter support housing 7, and an optical system housing 8 in addition to the optical filter 1a. ing. The peripheral edge of the optical filter 1a is fitted into, for example, an annular concave portion that is in contact with an opening formed in the center of the optical filter support housing 7. The optical filter support case 7 is fixed to the optical system case 8. Inside the optical system housing 8, the lens system 2, the low-pass filter 3, and the image sensor 4 are arranged in this order along the optical axis. The image sensor 4 is, for example, a CCD or a CMOS. The light from the subject is collected by the lens system 2 after the ultraviolet and infrared rays are cut off by the optical filter 1a, passes through the low-pass filter 3, and enters the image sensor 4. The electric signal generated by the image sensor 4 is sent to the outside of the camera module 100 by the circuit board 5.

In the camera module 100, the optical filter 1a has a cover (for protecting the lens system 2).
It also functions as a protection filter. In this case, desirably, a sapphire substrate is used as the transparent dielectric substrate 20 in the optical filter 1a. Since the sapphire substrate has high scratch resistance, for example, it is desirable that the sapphire substrate be disposed outside (the side opposite to the imaging element 4 side). Thereby, the optical filter 1a has high scratch resistance against external contact and the like, and has the above-described optical performances (i) to (iii) (more preferably, the optical performances (iv) to (xiii)). Have. Accordingly, it is not necessary to dispose an optical filter for cutting off infrared rays or ultraviolet rays near the imaging element 4, and the camera module 100 can be easily lowered. Note that the camera module 100 shown in FIG. 2 is a schematic diagram illustrating the arrangement of each component and the like, and illustrates an aspect in which the optical filter 1a is used as a protection filter. As long as the optical filter 1a functions as a protection filter, the camera module using the optical filter 1a is not limited to the one shown in FIG. 2, and if necessary, the low-pass filter 3 may be omitted, Other filters may be provided. Further, an antireflection film may be formed in contact with the light absorbing layer 10 of the optical filter 1a.

  The examples illustrate the invention in more detail. Note that the present invention is not limited to the following embodiments. First, an evaluation method of an optical filter according to an example and a comparative example will be described.

<Measurement of transmittance spectrum of optical filter>
The transmittance spectrum when light having a wavelength of 300 nm to 1200 nm was incident on the optical filters according to the examples and comparative examples was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name: V-670). . The transmittance spectrum at each angle was measured by changing the incident angle of the incident light on the optical filter from 0 ° to 65 ° in steps of 5 °.

<Measurement of thickness of light absorbing layer>
The thicknesses of the optical filters according to Examples and Comparative Examples were measured with a digital micrometer. Of the optical filters according to the examples and the comparative examples, the optical filter having a transparent dielectric substrate such as glass, the optical absorption layer of the optical filter by subtracting the thickness of the glass substrate from the thickness of the optical filter measured by a digital micrometer. The thickness was determined.

<Example 1>
1.125 g of copper acetate monohydrate ((CH ₃ COO) ₂ Cu.H ₂ O) and 60 g of tetrahydrofuran (THF) were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 0.412 g of Plysurf A208N (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), which is a phosphoric ester compound, was added to the obtained copper acetate solution, followed by stirring for 30 minutes to obtain a solution A. Phenylphosphonic acid _{(C 6 H 5 PO (OH} ) 2) and stirred with THF10g to (manufactured by Nissan Chemical Industries, Ltd.) 0.441 g 30 minutes, B-
One solution was obtained. 10 g of THF was added to 0.661 g of 4-bromophenylphosphonic acid (C ₆ H ₄ BrPO (OH) ₂ ) (manufactured by Tokyo Chemical Industry Co., Ltd.), and the mixture was stirred for 30 minutes to obtain a B-2 solution. Next, the B-1 solution and the B-2 solution were mixed and stirred for 1 minute, and 1.934 g of methyltriethoxysilane (MTES: CH ₃ Si (OC ₂ H ₅ ) ₃ ) (manufactured by Shin-Etsu Chemical Co., Ltd.) was added. 0.634 g of tetraethoxysilane (TEOS: Si (OC ₂ H ₅ ) ₄ ) (special grade, manufactured by Kishida Chemical Co., Ltd.) was added, and further 1
After stirring for 2 minutes, solution B was obtained. Solution B was added to Solution A while stirring Solution A, and the mixture was stirred at room temperature for 1 minute. Next, 25 g of toluene was added to this solution, followed by stirring at room temperature for 1 minute to obtain a solution C. The solution C was placed in a flask and heated with an oil bath (manufactured by Tokyo Rika Kikai Co., Ltd., model: OSB-2100). went. The set temperature of the oil bath was adjusted to 105 ° C. Thereafter, the solution D after the solvent removal treatment was taken out of the flask. Solution D, which is a dispersion of fine particles of copper phenyl phosphonate (absorbent) containing copper phenylphosphonate and copper 4-bromophenylphosphonate, was transparent and the fine particles were well dispersed.

0.225 g of copper acetate monohydrate and 36 g of THF were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 0.129 g of Plysurf A208N, which is a phosphoric ester compound, was added to the obtained copper acetate solution, followed by stirring for 30 minutes to obtain a solution E. Also, n-butylphosphonic acid (C _{4
H 9 PO (OH) 2)} ( stirred with THF10g to Nippon Chemical Industrial Co., Ltd.) 0.144 g 30 minutes to obtain F solution. The solution F was added to the solution E while stirring the solution E, and the mixture was stirred at room temperature for 1 minute. Next, 25 g of toluene was added to this solution, followed by stirring at room temperature for 1 minute to obtain a solution G. The solution G was placed in a flask, and the mixture was desolvated by a rotary evaporator while being heated in an oil bath. The set temperature of the oil bath was adjusted to 105 ° C. Thereafter, the H solution after the solvent removal treatment was taken out of the flask. The H liquid, which is a dispersion of copper butylphosphonate fine particles, was transparent, and the fine particles were well dispersed.

  2.200 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to Solution D, followed by stirring for 30 minutes to obtain Solution I. The liquid H was added to the liquid I and stirred for 30 minutes to obtain a light-absorbing composition (liquid J) according to Example 1. For the light-absorbing composition (solution J) according to Example 1, the content-based content of each component is shown in Table 1, and the content-based content of each component and the content-based content of each phosphonic acid are shown. Are shown in Table 2. Since the content of each phosphonic acid is determined by rounding off the second decimal place, the total may not be 100 mol%.

  A transparent glass substrate (manufactured by SCHOTT, product name: D263) made of borosilicate glass having a size of 76 mm x 76 mm x 0.21 mm was implemented using a dispenser in a range of 30 mm x 30 mm at the center of one main surface. The light absorbing composition according to Example 1 was applied to form a coating film. The thickness of the coating film was determined by trial and error so that the average transmittance of the optical filter at a wavelength of 700 to 730 nm was about 1%. When the light-absorbing composition was applied to the transparent glass substrate, a frame having an opening corresponding to the application range of the coating solution was placed on the transparent glass substrate to prevent the coating solution from flowing out, and the coating solution was dammed. By adjusting the amount of the coating solution, a coating film having a target thickness was obtained. Next, the transparent glass substrate having the undried coating film was placed in an oven and subjected to a heat treatment at 85 ° C. for 6 hours to cure the coating film. Then, the transparent glass substrate on which the above-mentioned coating film is formed is placed in a constant temperature and humidity chamber set at a temperature of 85 ° C. and a relative humidity of 85% for 20 hours to perform humidification, and a light absorbing layer is formed on the transparent glass substrate. The optical filter according to Example 1 in which was formed was obtained. The humidification treatment was performed to promote the hydrolysis and condensation polymerization of the alkoxysilane contained in the light absorbing composition applied on the transparent glass substrate, and to form a hard and dense matrix in the light absorbing layer. The thickness of the light absorption layer of the optical filter according to Example 1 was 170 μm. The transmittance spectrum of the optical filter according to Example 1 at an incident angle of 0 ° to 65 ° was measured. FIG. 3 shows transmittance spectra at incident angles of 0 °, 40 °, 50 °, and 60 °. Tables 7 and 8 show the results obtained from the transmittance spectrum of the optical filter according to Example 1 when the incident angle was 0 °. The “wavelength range with a transmittance of 78% or more” in Table 8 is a wavelength range that exhibits a spectral transmittance of 78% or more at a wavelength of 400 nm to 600 nm. The “wavelength range of transmittance 1% or less” regarding the infrared region characteristics in Table 8 is a wavelength range showing a spectral transmittance of 1% or less at a wavelength of 700 nm to 1200 nm. The "wavelength range of transmittance 0.1% or less" relating to infrared region characteristics in Table 8 is a wavelength range showing a spectral transmittance of 0.1% or less at a wavelength of 700 nm to 1200 nm. The “wavelength range of transmittance 1% or less” regarding the ultraviolet region characteristics in Table 8 is a wavelength range showing a spectral transmittance of 1% or less at a wavelength of 300 nm to 400 nm. The “wavelength range of transmittance 0.1% or less” regarding the ultraviolet region characteristics in Table 8 is a wavelength range showing a spectral transmittance of 0.1% or less at a wavelength of 300 nm to 400 nm. This is also true for Tables 10, 12, 14, 16, 16, and 20. Table 11 shows the results (incident angle: 0 ° to 65 °) of the optical filter according to Example 1, which were observed from the transmittance spectrum at an incident angle of 0 ° and 30 ° to 65 ° (in increments of 5 °). It is shown in Table 12.

<Examples 2 to 15>
Light-absorbing compositions according to Examples 2 to 15 were prepared in the same manner as in Example 1 except that the addition amount of each compound was adjusted as shown in Table 1. Example 1 was repeated except that the thickness of the light absorbing layer was adjusted as shown in Table 1 using the light absorbing composition according to Examples 2 to 15 instead of the light absorbing composition according to Example 1. In the same manner as in, optical filters according to Examples 2 to 15, respectively, were produced. Table 2 shows the content and content based on the substance amount of each phosphonic acid. Since the content of each phosphonic acid is determined by rounding off the second decimal place, the total may not be 100 mol%. The transmittance spectrum of the optical filter according to Example 2 at an incident angle of 0 ° to 65 ° was measured. FIG. 4 shows transmittance spectra at incident angles of 0 °, 40 °, 50 ° and 60 °. Tables 7 and 8 show the results obtained from the transmittance spectrum of the optical filter according to Example 2 when the incident angle was 0 °. Further, Tables 13 and 14 show the results obtained by observing the transmittance spectrum of the optical filter according to Example 2 at an incident angle of 0 ° and 30 ° to 65 ° (in increments of 5 °). Tables 7 and 8 show the results obtained from the transmittance spectra of the optical filters according to Examples 3 to 15 when the incident angle was 0 °.

<Example 16>
A transparent glass substrate (manufactured by SCHOTT, product name: D263) made of borosilicate glass having a size of 76 mm x 76 mm x 0.21 mm was implemented using a dispenser in a range of 30 mm x 30 mm at the center of one main surface. The light-absorbing composition according to Example 2 was applied to form a coating film having a predetermined thickness. When the light-absorbing composition was applied to the transparent glass substrate, a frame having an opening corresponding to the application range of the coating solution was placed on the transparent glass substrate to prevent the coating solution from flowing out, and the coating solution was dammed. Next, the transparent glass substrate having the undried coating film was placed in an oven and subjected to a heat treatment at 85 ° C. for 6 hours to cure the coating film. Thereafter, the coating film was peeled from the transparent glass substrate. An optical filter according to Example 16 including only the light absorbing layer was subjected to humidification by placing the peeled coating film in a constant temperature / humidity chamber set at a temperature of 85 ° C. and a relative humidity of 85% for 20 hours. Obtained. The measurement with a digital micrometer measured the thickness of only the light absorbing layer. As a result, the thickness of the optical filter according to Example 16 was 132 μm. The transmittance spectrum of the optical filter according to Example 16 at an incident angle of 0 ° to 65 ° was measured. FIG. 5 shows transmittance spectra at incident angles of 0 °, 40 °, 50 °, and 60 °. Tables 7 and 8 show the results obtained from the transmittance spectrum of the optical filter according to Example 16 when the incident angle was 0 °. Further, Tables 15 and 16 show the results obtained by observing the transmittance spectrum of the optical filter according to Example 16 at an incident angle of 0 ° and 30 ° to 65 ° (in increments of 5 °).

<Example 17>
A transparent glass substrate (manufactured by SCHOTT, product name: D263) made of borosilicate glass having a size of 76 mm x 76 mm x 0.21 mm was implemented using a dispenser in a range of 30 mm x 30 mm at the center of one main surface. The light-absorbing composition according to Example 2 was applied to form a coating having a thickness smaller than the thickness of the coating in Example 2. When the light-absorbing composition was applied to the transparent glass substrate, a frame having an opening corresponding to the application range of the coating solution was placed on the transparent glass substrate to prevent the coating solution from flowing out, and the coating solution was dammed. Next, the transparent glass substrate having the undried coating film was placed in an oven and subjected to a heat treatment at 85 ° C. for 6 hours to cure the coating film. Next, the light absorbing composition according to Example 2 was applied to a 30 mm × 30 mm area in the center of the other main surface of the transparent glass substrate using a dispenser, and the thickness was smaller than the thickness of the coating film in Example 2. Was formed. When the light-absorbing composition was applied to the transparent glass substrate, a frame having an opening corresponding to the application range of the coating solution was placed on the transparent glass substrate to prevent the coating solution from flowing out, and the coating solution was dammed. Next, the transparent glass substrate having the undried coating film was placed in an oven and subjected to a heat treatment at 85 ° C. for 6 hours to cure the coating film. Next, the transparent glass substrate having the above-mentioned coating film formed on both main surfaces is placed in a constant temperature / humidity chamber set at a temperature of 85 ° C. and a relative humidity of 85% for 20 hours to perform a humidification process. Thus, an optical filter according to Example 17 in which light absorbing layers were formed on both surfaces was obtained. The total thickness of the light absorbing layers formed on both surfaces of the transparent glass substrate was 193 μm. The transmittance spectrum of the optical filter according to Example 17 at an incident angle of 0 ° to 65 ° was measured. FIG. 6 shows transmittance spectra at incident angles of 0 °, 40 °, 50 ° and 60 °. Tables 7 and 8 show the results obtained from the transmittance spectrum of the optical filter according to Example 17 when the incident angle was 0 °. Tables 17 and 18 show the results obtained by observing the transmittance spectrum of the optical filter according to Example 17 at an incident angle of 0 ° and 30 ° to 65 ° (in increments of 5 °).

<Example 18>
The same procedure as in Example 1 was carried out except that Plysurf A208F (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the phosphate ester compound instead of Plysurf A208N, and the addition amount of each compound was adjusted as shown in Table 1. Thus, a light absorbing composition according to Example 18 was prepared. Instead of the light absorbing composition according to Example 1, the light absorbing composition according to Example 18 was used, and the thickness of the light absorbing layer was adjusted to 198 μm. An optical filter according to No. 18 was produced. Tables 7 and 8 show the results obtained by measuring the transmittance spectrum of the optical filter according to Example 18 at an incident angle of 0 ° to 65 ° and observing the transmittance spectrum at an incident angle of 0 °. Tables 19 and 20 show the results obtained by observing the transmittance spectrum of the optical filter according to Example 18 at an incident angle of 0 ° and 30 ° to 65 ° (in increments of 5 °).

<Example 19>
Instead of 4-bromophenylphosphonic acid, 4-fluorophenylphosphonic acid (C ₆ H ₄ FPO (OH) ₂ ) (manufactured by Tokyo Chemical Industry Co., Ltd.) was used, and the addition amount of each compound was adjusted as shown in Table 1. A light absorbing composition according to Example 19 was prepared in the same manner as Example 1 except for the above. Instead of the light absorbing composition according to Example 1, the light absorbing composition according to Example 19 was used, and the thickness of the light absorbing layer was adjusted to 168 μm. An optical filter according to No. 19 was produced. Tables 7 and 8 show results obtained by measuring the transmittance spectrum of the optical filter according to Example 19 and observing the transmittance spectrum when the incident angle was 0 °.

<Examples 20 to 35>
Examples 20 to 35 were performed in the same manner as in Example 2 except that the conditions of the humidification treatment of the dried coating film were changed as shown in Table 3 and the thickness of the light absorbing layer was adjusted as shown in Table 3. Were produced, respectively. The transmittance spectra of the optical filters according to Examples 20 to 35 were measured. FIGS. 7 to 9 show transmittance spectra of the optical filters according to Examples 20 to 22 when the incident angle is 0 °. Tables 7 and 8 show the results obtained by observing the transmittance spectra of the optical filters according to Examples 20 to 35 when the incident angle was 0 °.

<Example 36>
A sapphire substrate having a thickness of 0.3 mm was used in place of the transparent glass substrate used in Example 2, and the thickness of the light absorbing layer was adjusted to 168 μm according to Example 36 in the same manner as in Example 2. An optical filter was manufactured. A transmittance spectrum of the optical filter according to Example 36 was measured. FIG. 10 shows a transmittance spectrum of the optical filter according to Example 36 when the incident angle was 0 °. Tables 7 and 8 show the results observed from the transmittance spectrum when the incident angle was 0 °.

<Comparative Example 1>
Liquid D according to Comparative Example 1 (dispersion of fine particles of copper phenyl phosphonate) was prepared in the same manner as in Example 1, except that the addition amount of each compound was adjusted as shown in Tables 4 and 5. . 2.200 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to the liquid D according to Comparative Example 1, and the mixture was stirred for 30 minutes to obtain a light absorbing composition according to Comparative Example 1. Instead of the light absorbing composition according to Example 1, the light absorbing layer according to Comparative Example 1 was used, and the thickness of the light absorbing layer was 1
An optical filter according to Comparative Example 1 was manufactured in the same manner as in Example 1 except that the thickness was adjusted to 26 μm. The transmittance spectrum of the optical filter according to Comparative Example 1 was measured. Tables 9 and 10 show results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 1 when the incident angle is 0 °. In addition, based on the result of the transmittance spectrum measurement when the incident angle of the optical filter according to Comparative Example 1 was 0 °, the thickness of the light absorption layer of the optical filter according to Comparative Example 1 was changed to 200 μm. The transmittance spectrum was calculated, and the results observable from the transmittance spectrum are shown in Tables 9 and 10 as Comparative Calculation Example 1.

<Comparative Example 2>
Solution D according to Comparative Example 2 (dispersion of fine particles of copper phenyl phosphonate) was prepared in the same manner as in Example 1 except that the addition amount of each compound was adjusted as shown in Tables 4 and 5. did. 4.400 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to the liquid D according to Comparative Example 2, and the mixture was stirred for 30 minutes to obtain a light-absorbing composition according to Comparative Example 2. Using the light absorbing composition according to Comparative Example 2 in place of the light absorbing composition according to Example 1, adjusting the thickness of the light absorbing layer to 217 μm, and performing heat treatment and humidification for curing the coating film. An optical filter according to Comparative Example 2 was produced in the same manner as in Example 1, except that the processing conditions were changed as shown in Table 6. The transmittance spectrum of the optical filter according to Comparative Example 2 was measured. Tables 9 and 10 show results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 2 when the incident angle is 0 °. In addition, based on the result of transmittance spectrum measurement when the incident angle of the optical filter according to Comparative Example 2 was 0 °, the thickness of the light absorption layer of the optical filter according to Comparative Example 2 was changed to 347 μm. The transmittance spectrum was calculated, and the results observable from this transmittance spectrum are shown in Tables 9 and 10 as Comparative Calculation Example 2.

<Comparative Example 3>
1.125 g of copper acetate monohydrate and 60 g of THF were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 0.624 g of Plysurf A208F (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added to the obtained copper acetate solution, followed by stirring for 30 minutes to obtain a solution A. 10 g of THF was added to 0.832 g of phenylphosphonic acid (manufactured by Nissan Chemical Industries, Ltd.), and the mixture was stirred for 30 minutes to obtain a B-1 solution. 1.274 g of MTES (manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.012 g of TEOS (special grade manufactured by Kishida Chemical Co., Ltd.) were added to the B-1 solution, and the mixture was further stirred for 1 minute to obtain a B solution. Solution B was added to Solution A while stirring Solution A, and the mixture was stirred at room temperature for 1 minute. Next, 25 g of toluene was added to this solution, followed by stirring at room temperature for 1 minute to obtain a solution C. The solution C was put in a flask and heated with an oil bath (manufactured by Tokyo Rika Kikai Co., Ltd., model: OSB-2100), and the solvent was removed by a rotary evaporator (manufactured by Tokyo Rika Kiki Co., model: N-1110SF). went. The set temperature of the oil bath was adjusted to 105 ° C. Thereafter, the solution D according to Comparative Example 3 after the solvent removal treatment was taken out of the flask. Liquid D (dispersion of copper phenylphosphonate fine particles) according to Comparative Example 3 was transparent, and the fine particles were well dispersed.

  4.400 g of a silicone resin (product name: KR-300, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the solution D according to Comparative Example 3, and the mixture was stirred for 30 minutes to obtain a light-absorbing composition according to Comparative Example 3. Using the light-absorbing composition according to Comparative Example 3 in place of the light-absorbing composition according to Example 1, adjusting the thickness of the light-absorbing layer to 198 μm, and performing heat treatment for curing the coating film. Was adjusted as shown in Table 6, and an optical filter according to Comparative Example 3 was produced in the same manner as in Example 1. The transmittance spectrum of the optical filter according to Comparative Example 3 was measured. Tables 9 and 10 show results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 3 when the incident angle is 0 °. Further, based on the result of transmittance spectrum measurement when the incident angle of the optical filter according to Comparative Example 3 was 0 °, the transmission when the thickness of the light absorption layer of the optical filter according to Comparative Example 3 was changed to 303 μm. The transmittance spectrum was calculated, and the results observable from the transmittance spectrum are shown in Tables 9 and 10 as Comparative Calculation Example 3.

<Comparative Example 4>
An optical filter according to Comparative Example 4 was produced in the same manner as in Example 2, except that the thickness of the light absorbing layer was adjusted to 191 μm, and the humidification treatment of the coating film was not performed. The transmittance spectrum of the optical filter according to Comparative Example 4 was measured. Tables 9 and 10 show results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 4 when the incident angle is 0 °. Further, based on the transmittance spectrum when the incident angle of the optical filter according to Comparative Example 4 was 0 °, the transmittance spectrum when the thickness of the light absorption layer of the optical filter according to Comparative Example 4 was changed to 148 μm was The results calculated and can be seen from the transmittance spectrum are shown in Tables 9 and 10 as Comparative Calculation Example 4.

<Comparative Examples 5 and 6>
Optical filters according to Comparative Examples 5 and 6 were produced in the same manner as in Example 2 except that the thickness of the light absorbing layer was adjusted as shown in Table 9 and the humidification treatment of the coating film was adjusted as shown in Table 6. . The transmittance spectra of the optical filters according to Comparative Examples 5 and 6 were measured. Tables 9 and 10 show the results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 5 when the incident angle is 0 °. Further, based on the transmittance spectrum when the incident angle of the optical filter according to Comparative Example 5 is 0 °, the transmittance spectrum when the thickness of the light absorption layer of the optical filter according to Comparative Example 5 is changed to 155 μm is shown. The results calculated and can be seen from the transmittance spectrum are shown in Tables 9 and 10 as Comparative Calculation Example 5. Tables 9 and 10 show the results that can be observed from the transmittance spectrum of the optical filter according to Comparative Example 6 when the incident angle is 0 °. Also, based on the transmittance spectrum when the incident angle of the optical filter according to Comparative Example 6 is 0 °, the transmittance spectrum when the thickness of the light absorption layer of the optical filter according to Comparative Example 6 is changed to 161 μm is shown. Table 9 and Table 10 show the calculated values and the results observable from the transmittance spectrum as Comparative Calculation Example 6.

<Comparative Example 7>
In the same manner as in Comparative Example 1, Liquid D (dispersion liquid of fine particles of phenyl copper phosphonate) according to Comparative Example 7 was prepared. 0.225 g of copper acetate monohydrate and 36 g of THF were mixed and stirred for 3 hours to obtain a copper acetate solution. Next, 0.178 g of Plysurf A208F (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a phosphate compound was added to the obtained copper acetate solution, and the mixture was stirred for 30 minutes to obtain solution E. Further, 10 g of THF was added to 0.134 g of n-butylphosphonic acid (manufactured by Nippon Chemical Industry Co., Ltd.), and the mixture was stirred for 30 minutes to obtain a liquid F. The solution F was added to the solution E while stirring the solution E, and the mixture was stirred at room temperature for 1 minute. Next, 25 g of toluene was added to this solution, followed by stirring at room temperature for 1 minute to obtain a solution G. The solution G was placed in a flask, and the mixture was desolvated by a rotary evaporator while being heated in an oil bath. The set temperature of the oil bath was adjusted to 105 ° C. Thereafter, the H solution according to Comparative Example 7 after the desolvation treatment was taken out of the flask. 2.200 g of a silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KR-300) was added to the solution D according to Comparative Example 7, and the mixture was stirred for 30 minutes to obtain a solution I according to Comparative Example 7. The solution H according to Comparative Example 7 was added to the solution I according to Comparative Example 7 and stirred, but copper phosphonate particles were aggregated, and a light-absorbing composition having high transparency could not be obtained.

<Comparative Example 8>
An attempt was made to prepare a light-absorbing composition containing only n-butylphosphonic acid as a phosphonic acid and no alkoxysilane monomer in the amounts shown in Table 4, but copper phosphonate particles were aggregated and high transparency was obtained. Was not able to be obtained.

According to Table 7, the optical filters according to Examples 1 to 36 satisfied the above conditions (i) to (vii). From Tables 11, 13, 13, 17, and 19, (viii) the difference between the absolute value of the second IR cutoff wavelength and the first IR cutoff wavelength is 3 nm (Example 1), 4 nm (Example 2), 4 nm (Example 16), 3 nm (Example 17), 4 nm (Example 18), and (ix) the absolute value of the third IR cutoff wavelength and the first IR cutoff wavelength. The difference between
6 nm (Example 1), 7 nm (Example 2), 7 nm (Example 16), 6 nm (Example 17), 7 nm (Example 18), and (x) the second UV cutoff wavelength and the first UV. The difference between the absolute value and the cutoff wavelength is 2 nm (Example 1), 3 nm (Example 2), 3 nm (Example 16), 3 nm (Example 17), 3 nm (Example 18), and (xi) ) The difference between the absolute value of the third UV cutoff wavelength and the absolute value of the first UV cutoff wavelength is 3 nm (Example 1), 5 nm (Example 2), 5 nm (Example 16), 5 nm (Example 17), 4 nm (Example 18), and the optical filters according to Examples 1, 2, 16, 17, and 18 further satisfied the above conditions (viii) to (xi). Also, according to the transmittance spectra (not shown) of the optical filters according to Examples 3 to 15 and 19 to 36 at an incident angle of 0 ° to 65 °, the optical filters according to these examples are also described above ( viii) The conditions of (xi) were further satisfied.

According to Table 9, the optical filter according to Comparative Example 1 did not satisfy the conditions (ii), (vi), and (vii), and did not have desired characteristics in the infrared region. According to Comparative Calculation Example 1, although the characteristics in the infrared region can be improved by increasing the thickness of the light absorbing layer, the first IR cutoff wavelength is shortened and the optical performance of (iii) is improved. It was suggested that it could not be achieved. Thus, it was suggested that even when the light-absorbing composition according to Comparative Example 1 was used, an optical filter satisfying all the conditions (i) to (iii) could not be produced. Similarly, according to the results of Comparative Example 2 and Comparative Calculation Example 2 and Comparative Example 3 and Comparative Calculation Example 3 in Table 9, even when the light-absorbing compositions according to Comparative Examples 2 and 3 are used, the above (i) It was suggested that an optical filter satisfying all the conditions of (iii) could not be produced.

According to Table 9, the optical filter according to Comparative Example 4 did not satisfy the conditions (i) and (iii). According to Comparative Calculation Example 4, although the average transmittance at a wavelength of 450 to 600 nm increases by reducing the thickness of the light absorption layer, the IR cutoff wavelength hardly changes, and the maximum transmittance at a wavelength of 750 to 1080 nm also increases. It was suggested that it increased. For this reason, it was suggested that the optical filter manufacturing method according to Comparative Example 4 cannot manufacture an optical filter satisfying all the above conditions (i) to (iii). The hydrolysis and condensation polymerization of the alkoxysilane monomer contained in the light-absorbing composition is promoted by the humidifying treatment, and the curing of the light-absorbing layer proceeds, and the humidifying treatment also affects the transmittance spectrum of the optical filter. It has been suggested.

According to Table 9, the optical filter according to Comparative Example 5 did not satisfy the above condition (iii). Comparative Calculation Example 5 suggests that by reducing the thickness of the light absorbing layer, the IR cutoff wavelength increases, but the maximum transmittance at wavelengths of 750 to 1080 nm also increases. For this reason, it was suggested that the optical filter manufacturing method according to Comparative Example 5 could not manufacture an optical filter satisfying all of the above conditions (i) to (iii). In particular, it was suggested that the conditions of the humidification treatment in Comparative Example 5 were not sufficient.

According to Table 9, the optical filter according to Comparative Example 6 did not satisfy the conditions (i) and (iii). Comparative Calculation Example 6 suggests that by reducing the thickness of the light absorbing layer, the IR cutoff wavelength increases, but the maximum transmittance at wavelengths of 750 to 1080 nm also increases. For this reason, it was suggested that the optical filter manufacturing method according to Comparative Example 6 could not manufacture an optical filter having all the optical performances of the above (i) to (iii). In particular, it was suggested that the conditions of the humidification treatment in Comparative Example 6 were not sufficient.

As shown in Table 2, in the light-absorbing compositions according to Examples 3 to 5, the light-absorbing composition according to Example 3 had the highest content of n-butylphosphonic acid, and the light absorption according to Example 5 Content of n-butylphosphonic acid in the water-soluble composition is the lowest. According to this and Table 8, when the content of the alkyl phosphonic acid in the light-absorbing composition increases, the wavelength range in which the spectral transmittance is 1% or less and the spectral transmittance at a wavelength of 700 to 1200 nm is 0.1% or less. It has been suggested that the wavelength range of 1% or less expands toward the longer wavelength side. The same can be said for Examples 6 to 8, Examples 9 and 10, and Examples 11 to 15.

  As shown in Table 2, in the light absorbing compositions according to Examples 11 to 15, the light absorbing composition according to Example 11 had the highest content of n-butylphosphonic acid, and the light absorbing composition according to Example 12 The content of n-butylphosphonic acid in the water-soluble composition was the second highest, and the content of n-butylphosphonic acid in the light-absorbing composition according to Example 13 was the third highest. Content of n-butylphosphonic acid in the water-soluble composition is the lowest. According to the results of Examples 11 to 15 in Table 7, the maximum transmittance of the optical filter at wavelengths of 1000 to 1100 nm and the maximum transmittance of the optical filter at wavelengths of 1100 to 1200 nm are the lowest in Example 11 and the lowest in Example 12. The second lowest, the third lowest in Example 13, and the highest in Example 15. This suggests that increasing the content of the alkyl sulfonic acid within a predetermined range in the light-absorbing composition improves the shielding property of wavelengths in the infrared region.

  As shown in Table 2, among the light-absorbing compositions according to Examples 7, 10, and 13, the content of 4-bromophenylphosphonic acid in the light-absorbing composition according to Example 7 was the highest, and Example 13 Has the lowest content of 4-bromophenylphosphonic acid. According to the results of Examples 7, 10, and 13 in Table 7, the higher the content of 4-bromophenylphosphonic acid in the light absorbing composition, the larger the UV cutoff wavelength. This suggests that by adjusting the content of 4-bromophenylphosphonic acid in the light-absorbing composition, it is possible to optimize optical performance such as the UV cutoff wavelength of the optical filter.

  The light-absorbing compositions for producing the optical filters according to Examples 20 to 35 and Comparative Examples 4 to 6 were prepared in the same manner as the light-absorbing composition according to Example 2; As shown in FIG. 10, the optical filters according to the examples and the comparative examples had optical performances different from those of the optical filter according to the example 2. As described above, the humidification treatment is performed for the purpose of promoting hydrolysis and polycondensation of the alkoxysilane contained in the light-absorbing composition. In the optical filter according to the example, there was a difference in the average transmittance and the IR cutoff wavelength at a wavelength of 450 to 600 nm.

According to the results of Comparative Calculation Examples 4 to 6 in Table 9, although the UV cutoff wavelength can be adjusted by changing the thickness of the light absorption layer, according to the method of manufacturing the optical filters according to Comparative Examples 4 to 6, ( It is difficult to keep the IR cutoff wavelength in a desired range while satisfying other optical performances of i) to (xi). Therefore, the amount of water vapor (the amount of exposed water vapor) in the environment where the article to be treated is exposed in the humidification treatment of each of the examples and some of the comparative examples was determined as follows. The results are shown in Tables 3 and 6. The saturated water vapor pressure e [hPa] at the temperature t [° C.] was obtained by the approximate expression of Tetens: e = 6.11 × 10 (7.5 t / (t + 237.3)). From the saturated water vapor pressure e [hPa] and the relative humidity φ [%], the water vapor density ρv [g / m ³ ] was obtained from the equation ρv = 217 × e × φ / (t + 273.15). Water vapor amount × time [mol / m ³ · hour] was defined as the amount of exposed water vapor. As shown in Tables 3 and 6, it was suggested that in the humidification treatment, when the temperature was 60 ° C. or more, good optical performance was obtained when the relative humidity was 70% or more and the treatment time was 1 hour or more. This treatment condition corresponds to a condition of an exposed steam amount of 5.0 [mol / m 3 · h] or more, but when the temperature in the humidification treatment is as low as 40 ° C. and the relative humidity is 70%, and when the humidification treatment is performed. It was suggested that even when the temperature at 60 ° C. and the relative humidity were as low as 40%, good optical performance could be obtained by extending the treatment time to the same amount of exposed water vapor. These results suggested that it is desirable to perform humidification for a short time in an environment at a temperature of 60 ° C. or higher and a relative humidity of 70% or higher from the viewpoint of efficiently providing the optical filter with good optical performance.

1a to 1e Optical filter 2 Lens system 3 Low-pass filter 4 Image sensor 5 Circuit board 7 Optical filter support case 8 Optical system case 10 Light absorbing layer 20 Transparent dielectric substrate 30 Anti-reflection film 100 Camera module

Claims (11)

With a light absorbing layer,
When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °,
(I) having an average transmittance of 78% or more at a wavelength of 450 nm to 600 nm,
(Ii) having a spectral transmittance of 1% or less at a wavelength of 750 nm to 1080 nm,
(Iii) The first IR cutoff wavelength having a spectral transmittance that decreases with an increase in the wavelength at a wavelength of 600 nm to 750 nm and having a spectral transmittance of 50% at a wavelength of 600 nm to 750 nm is within a range of 620 nm to 680 nm. Exists,
The condition (i), the condition (ii), and the condition (iii) are satisfied by the light absorbing layer.
Optical filter. When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °,
(Iv) having a spectral transmittance of 1% or less at a wavelength of 300 nm to 350 nm;
The optical filter according to claim 1.   The optical filter according to claim 2, wherein the condition (iv) is satisfied by the light absorbing layer. When light having a wavelength of 300 nm to 1200 nm is incident at an incident angle of 0 °,
(V) The first UV cut-off wavelength having a spectral transmittance of 350% at a wavelength of 350 nm to 450 nm and having a spectral transmittance of 50% at a wavelength of 350 nm to 450 nm is 380 nm to 430 nm. Exists in the range of
The optical filter according to claim 1.   The optical filter according to claim 4, wherein the condition (v) is satisfied by the light absorbing layer.   The optical filter according to claim 1, wherein the light absorbing layer includes a light absorbing agent formed by phosphonic acid and copper ions.   The optical filter according to claim 6, wherein the phosphonic acid includes a first phosphonic acid having an aryl group.   The optical filter according to claim 7, wherein the first phosphonic acid has a halogenated phenyl group in which at least one hydrogen atom in the phenyl group is substituted with a halogen atom in a part thereof.   The optical filter according to claim 7, wherein the phosphonic acid further includes a second phosphonic acid having an alkyl group.   The optical filter according to claim 1, further comprising a transparent dielectric substrate covered with the light absorbing layer. Lens system,
An image sensor that receives light passing through the lens system;
The optical filter according to any one of claims 1 to 10, which is disposed in front of the lens system and protects the lens system.
Information terminal with camera.

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