WO2019230570A1

WO2019230570A1 - Near-infrared absorbing dye, optical filter and imaging device

Info

Publication number: WO2019230570A1
Application number: PCT/JP2019/020536
Authority: WO
Inventors: 繁樹服部
Original assignee: Ａｇｃ株式会社
Priority date: 2018-05-29
Filing date: 2019-05-23
Publication date: 2019-12-05
Also published as: JP7310806B2; JPWO2019230570A1

Abstract

The present invention relates to: a near-infrared absorbing dye which is composed of a compound represented by formula (A1); and a near-infrared absorbing dye which is composed of a compound represented by formula (A2). In formula (A1) and formula (A2), each of R¹, R², R⁵ and R⁶ independently represents a hydrogen atom, a halogen atom, a hydroxyl group, or an optionally substituted alkyl group, alkoxy group, aryl group or alaryl group which may contain an unsaturated bond or an oxygen atom between carbon atoms; and each of R³, R⁴, R⁷ and R⁸ independently represents an optionally substituted linear or branched chain alkyl group which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon atoms.

Description

Near-infrared absorbing dye, optical filter, and imaging device

The present invention relates to a near-infrared absorbing dye that transmits light in the visible wavelength region and shields light in the near-infrared wavelength region, an optical filter, and an imaging device including the optical filter.

An imaging apparatus using a solid-state imaging device transmits near-infrared light (hereinafter referred to as “near red”) to transmit visible light (hereinafter also referred to as “visible light”) in order to obtain a clear image with good color tone reproduction. A near-infrared cut filter that also shields the outside light) is used. In a near-infrared cut filter, near-infrared light is shielded by an absorption layer in which a near-infrared absorbing dye is dispersed in a resin or a reflective layer made of a dielectric multilayer film that reflects near-infrared light.

As a near-infrared absorbing dye used for such a near-infrared cut filter, a dye having a squarylium skeleton and a heteroaromatic ring structure on both sides thereof is known. For example, Patent Document 1 describes a near-infrared absorbing dye having a structure in which a heteroaryl ring containing a chalcogen atom is present on both sides of a squarylium skeleton and an amino group is bonded to the heteroaryl ring.

International Publication No. 2017/104283

Here, in the near-infrared absorbing dye used for the near-infrared cut filter, in the absorbing layer containing the same, an absorbing layer is used in order to sufficiently exhibit the optical characteristics of transmitting visible light and shielding near-infrared light. The solubility with respect to the resin which comprises is calculated | required. However, a near-infrared absorbing dye having both optical properties that transmit visible light and shield near-infrared light and sufficient solubility in a resin has not been obtained.

The present invention relates to a near-infrared-absorbing dye having both optical properties that transmit visible light and shield near-infrared light and high solubility in a resin, an optical filter, and an imaging device that excels in color reproducibility using the optical filter. For the purpose of provision.

The present invention relates to a near-infrared absorbing dye comprising a compound represented by the formula (A1) (hereinafter also referred to as a near-infrared absorbing dye (A1)) and a near-infrared absorbing dye comprising a compound represented by the formula (A2) (hereinafter referred to as “infrared absorbing dye”). A near-infrared absorbing dye (also referred to as A2).

In formula (A1),
R ¹ and R ² are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon-carbon atoms, An alkoxy group, an aryl group or an araryl group; R ¹ and R ² may be connected to each other to form a 3 to 6-membered alicyclic or aromatic ring that may contain a hetero atom, in which case the hydrogen atom bonded to the ring is substituted with a substituent. May be.
R ³ and R ⁴ may each independently have a substituent, and may be a linear or branched chain which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon-carbon atoms. It is an alkyl group.

In formula (A2),
R ⁵ and R ⁶ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon-carbon atoms, An alkoxy group, an aryl group or an araryl group,
R ⁷ and R ⁸ may each independently have a substituent, and may have a linear or branched chain which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon-carbon atoms. It is an alkyl group.

Moreover, the optical filter according to the present invention is characterized by comprising an absorption layer containing the near-infrared absorbing dye (A1) or the near-infrared absorbing dye (A2) and a resin.
In addition, an imaging apparatus according to the present invention includes a solid-state imaging device, an imaging lens, and the optical filter.

According to the present invention, it is possible to provide a near-infrared absorbing dye having an optical characteristic of transmitting visible light and shielding near-infrared light and having high solubility in a resin. Furthermore, according to the present invention, it is possible to provide an optical filter using the dye and an imaging device excellent in color reproducibility using the optical filter.

FIG. 1 is a cross-sectional view schematically showing an example of the optical filter of the embodiment. FIG. 2 is a cross-sectional view schematically showing another example of the optical filter of the embodiment. FIG. 3 is a cross-sectional view schematically showing another example of the optical filter of the embodiment. FIG. 4 is a cross-sectional view schematically showing another example of the optical filter of the embodiment. FIG. 5 is a cross-sectional view schematically showing another example of the optical filter of the embodiment. FIG. 6 is a cross-sectional view schematically showing another example of the optical filter of the embodiment. FIG. 7 is a cross-sectional view schematically showing another example of the optical filter of the embodiment.

Embodiments of the present invention will be described below.
In this specification, the near-infrared absorbing dye may be abbreviated as “NIR dye”, and the ultraviolet absorbing dye may be abbreviated as “UV dye”.
In this specification, a compound represented by the formula (A1) is referred to as a compound (A1). The same applies to compounds represented by other formulas. The NIR dye composed of the compound (A1) is also called NIR dye (A1), and the same applies to other dyes. For example, a group represented by the formula (1a) is also referred to as a group (1a), and the same applies to groups represented by other formulas.
In this specification, “to” representing a numerical range includes upper and lower limits.

<NIR dye>
The present invention provides an NIR dye (A1) represented by the formula (A1) and an NIR dye (A2) represented by the formula (A2).

The NIR dye (A1) of the present invention has a squarylium skeleton at the center of the molecular structure, and one thiophene ring is bonded to each of the left and right sides of the squarylium skeleton, and the thiophene ring is in the α position opposite to the squarylium skeleton. , An amino group having two linear or branched alkyl groups which may have a substituent and may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon and carbon atoms (hereinafter referred to as an amino group) , “Amino group (X)”). The amino group (X) does not have a configuration in which an aromatic ring is directly bonded to a nitrogen atom.

The NIR dye (A2) of the present invention has a squarylium skeleton at the center of the molecular structure, and one thienothiophene ring is bonded to each side of the squarylium skeleton, and the thienothiophene ring is an α on the opposite side of the squarylium skeleton. In this structure, an amino group (X) is bonded to the position.

NIR dye (A1) and NIR dye (A2) are common in that they have a squarylium skeleton and an amino group (X). The NIR dye (A1) and the NIR dye (A2) are common in that the group connecting the squarylium skeleton and the amino group (X) contains a thiophene ring. Since the NIR dye (A1) and the NIR dye (A2) of the present invention have such a structure, they have excellent optical properties that transmit visible light and shield near-infrared light, and have high solubility in resins.

In the NIR dye (A1) and the NIR dye (A2), the greater the number of rings including the thiophene ring that connects the squarylium skeleton and the amino group (X), that is, the NIR dye (A2) has a larger number than the NIR dye (A1). The maximum absorption wavelength is larger. Therefore, the NIR dye can be properly used according to the desired wavelength region.

Hereinafter, the NIR dye (A1) and the NIR dye (A2) will be described in detail. The NIR dye (A1) is represented by the following formula (A1).

In formula (A1), R ¹ and R ² may each independently have a hydrogen atom, a halogen atom, a hydroxyl group, or a substituent, and an unsaturated bond or an oxygen atom is present between carbon-carbon atoms. An alkyl group, alkoxy group, aryl group or araryl group which may be contained. R ¹ and R ² may be connected to each other to form a 3 to 6-membered alicyclic or aromatic ring that may contain a hetero atom, in which case the hydrogen atom bonded to the ring is substituted with a substituent. May be. Two R ^{1 s} in the formula (A1) may be different on the left and right sides of the squarylium skeleton, but are preferably the same on the left and right sides from the viewpoint of ease of production. The same applies to R ² and R ³ and R ⁴ described later.

Here, unless otherwise specified, in this specification, the alkyl group may be linear, branched, cyclic, or a combination of these structures. The alkyl group has an unsaturated bond between carbon and carbon atoms when it is linear or branched, or when it is cyclic and does not form an aromatic ring. An example where the alkyl group is cyclic and has an unsaturated bond between carbon and carbon atoms but does not form an aromatic ring is cycloalkene. The alkyl group having an oxygen atom between carbon-carbon atoms may be any of linear, branched, and cyclic. The same applies to the alkyl group that the alkoxy group has. Further, the same applies to the alkyl group in the case where the following aryl group has an alkyl group and the alkyl group of the araryl group.
As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned, A fluorine atom and a chlorine atom are preferable.

In this specification, unless otherwise specified, an aryl group is bonded through an aromatic ring of an aromatic compound, for example, a carbon atom constituting a benzene ring, naphthalene ring, biphenyl, furan ring, thiophene ring, pyrrole ring, etc. Group. The aryl group includes a structure in which a hydrogen atom bonded to a ring constituent atom other than a carbon atom contributing to the bond is substituted with an alkyl group, for example, a tolyl group or a xylyl group.

In this specification, unless otherwise specified, an araryl group refers to a group in which an alkyl group is bonded to an aromatic ring and bonded via a carbon atom constituting the alkyl group. The araryl group includes a structure in which a hydrogen atom bonded to a ring atom other than an atom to which an alkyl group contributing to the bond is bonded is substituted with an alkyl group.

Examples of the substituent in R ¹ and R ² include a halogen atom, a hydroxyl group, a carboxy group, a sulfo group, a cyano group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, Examples thereof include an imide group and an alkoxy group having 1 to 20 carbon atoms. When R ¹ and R ² are an aryl group or an araryl group, the substituent is a group that replaces the hydrogen atom bonded to the aromatic ring or the hydrogen atom of the alkyl group that these have, and in addition to the above substituent, an aryl group including.

When R ¹ and R ² are an alkyl group or an alkoxy group, the carbon number is preferably 1-20, more preferably 1-15, and still more preferably 1-12. When R ¹ and R ² are aryl groups, the carbon number is preferably 6-20, more preferably 6-15, and still more preferably 6-12. When R ¹ and R ² are araryl groups, the carbon number is preferably 7 to 20, more preferably 7 to 16, and even more preferably 7 to 13.
When R ¹ and R ² have a substituent, the carbon number includes the carbon number of the substituent.

R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, particularly preferably a hydrogen atom, from the viewpoint of light stability.

R ² is a linear or branched alkyl group having 3 to 20 carbon atoms which may contain an oxygen atom between carbon-carbon atoms from the viewpoint of visible light permeability and solubility in a resin and a solvent. Is preferred. The number of carbon atoms in the alkyl group is more preferably 3 to 12 when it is linear, and more preferably 4 to 10 when it is branched. R ² is more preferably, for example, a group selected from groups (1a) to (5a), particularly preferably group (1a). In particular, when one or both of R ³ and R ⁴ is a linear alkyl group, R ² is preferably a branched alkyl group having 4 to 10 carbon atoms.

R ² is preferably a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, particularly preferably a hydrogen atom, from the viewpoint of ease of production.

R ¹ and R ² may be linked to each other to form an alicyclic ring or aromatic ring, and in that case, the number of members is 3-6. The number of members is the number of atoms including two carbon atoms of the thiophene ring to which R ¹ and R ² are bonded. The alicyclic or aromatic ring may contain a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, and a sulfur atom. Moreover, the hydrogen atom couple | bonded with the said alicyclic ring or an aromatic ring may be substituted by the substituent, and the substituent illustrated as the substituent in R < ¹ > and R < ² > is mentioned as a substituent.

R ³ and R ⁴ may each independently have a substituent, and may be a linear or branched chain which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon-carbon atoms. It is an alkyl group.

As the substituents for R ³ and R ^4, the same substituents as those for R ¹ and R ² , that is, a halogen atom, a hydroxyl group, a carboxy group, a sulfo group, a cyano group, an amino group, an N-substituted amino group, Examples thereof include a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imide group, and an alkoxy group having 1 to 20 carbon atoms.

Examples of the substituent in R ³ and R ⁴ further include a cyclic alkyl group or an aryl group. As the aryl group, a phenyl group which may have 1 to 5 substituents or a naphthyl group which may have 1 to 7 substituents is preferable. Examples of the substituent which may substitute the hydrogen atom of the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms which may contain an unsaturated bond or an oxygen atom between carbon-carbon atoms, an alkoxy group, or an alkyl group. And an amino group (the alkyl group has 1 to 12 carbon atoms). The phenyl group and naphthyl group are preferably unsubstituted or substituted with 1 to 3 hydrogen atoms. The substituent is preferably a methyl group, a tertiary butyl group, a dimethylamino group, a methoxy group, or the like.

When R ³ and R ⁴ contain an alicyclic ring or an aromatic ring in the main chain or side chain, it is preferable in terms of heat resistance and lengthening of the NIR absorption wavelength. When R ³ and R ⁴ do not have an alicyclic ring or an aromatic ring in the main chain or side chain, it is preferable in terms of light resistance, ease of production, and solubility in resins and solvents. The number of carbon atoms in the alicyclic ring is preferably 3 to 10. The aromatic ring preferably has 4 to 14 carbon atoms.

Examples of the carbon number of R ³ and R ⁴ include 1-20. The number of carbon atoms of R ³ and R ⁴ is preferably 2 to 20, more preferably 3 to 16, and still more preferably 4 to 12 when it is linear. The number of carbon atoms of R ³ and R ⁴ is preferably 3 to 20, more preferably 4 to 16, and still more preferably 8 to 10 when branched.
When R ³ and R ⁴ have a substituent, and when the main chain or side chain contains an alicyclic ring or an aromatic ring, the above carbon number includes the carbon number of the substituent, the alicyclic ring, or the aromatic ring.

R ³ and R ⁴ may be the same or different, but are preferably the same from the viewpoint of ease of production. One of R ³ and R ⁴ is preferably branched from the viewpoint of solubility in the resin and the solvent, and more preferably both are branched.

When R ³ and R ⁴ are branched, the number of branches is not particularly limited. The number of branches is preferably 1 to 5, and more preferably 1 to 3. From the viewpoint of solubility in a resin and a solvent, the position of branching is preferably α-position, and from the viewpoint of ease of production, β-position is preferable. One carbon atom may be branched into two or may be branched into three.

R ³ and R ⁴ are more preferably, for example, a group selected from the groups (1b) to (5b).
—CH (C _n H _{2n + 1} ) ₂ (1b)
-C (C _n H _{2n + 1} ) ₃ (1c)
—CH ₂ —CH (C _n H _{2n + 1} ) ₂ (2b)
—CH ₂ —C (C _n H _{2n + 1} ) ₃ (2c)
— (CH ₂ ) ₂ —CH (C _n H _{2n + 1} ) ₂ (3b)
— (CH ₂ ) ₃ —CH (C _n H _{2n + 1} ) ₂ (4b)
— (CH ₂ ) _m —CH ₃ (5b)

However, in the formulas (1b) to (4b), n is an integer of 1 to 10, preferably 2 to 8, and more preferably 4 to 6. Two or three C _n H _{2n + 1} in the formulas (1b) to (4b) may be linear or branched, and may be the same or different. In the formula (5b), m is an integer of 0 to 19, preferably 1 to 19, more preferably 2 to 15, and further preferably 3 to 11. Further, the groups (1b) to (5b) may have an oxygen atom between carbon-carbon atoms.

Among these, the group (1b) and the group (1c) are preferable in terms of solubility because the branching position is in the α-position. The group (2b) and the group (2c) are preferable in terms of ease of production since the branching position is in the β-position, and the group (2b) is particularly preferable. The group (2b), for example, two _(C _{n H 2n + 1)} is the base are both CH ₃ (3a), two of _(C _{n H 2n + 1)} one is _C 2 _{H 5,} and the other is C The group (1a) which is ₄ H ₉ is preferred.

More specifically, as NIR dye (A1), R ¹ to R ⁴ are compounds shown in the following Table 1 (Table 1 also shows abbreviations as NIR dye (A1)). Is mentioned. In Table 1, R ¹ to R ⁴ represent formula symbols when the formula is a group shown. In all the compounds shown in Table 1, R ¹ to R ⁴ are all the same on the left and right sides of the formula.

NIR dye (A2) is represented by the following formula (A2).

In the formula (A2), R ⁵ can be the same as R ¹ in the formula (A1), including preferred embodiments. R ⁶ is the same as R ² in formula (A1), including preferred embodiments. Furthermore, R ⁷ and R ⁸ in formula (A2) are the same as R ³ and R ⁴ in formula (A1), including preferred embodiments.

More specifically, as NIR dye (A2), R ⁵ to R ⁸ are compounds shown in the following Table 2 (Table 2 also shows abbreviations as NIR dye (A2)). Is mentioned. In Table 2, R ⁵ to R ⁸ represent formula symbols when the formula is a group shown. In all the compounds shown in Table 2, R ⁵ to R ⁸ are all the same on the left and right sides of the formula.

The NIR dye (A1) has a maximum absorption wavelength λ _max (A1) in a dichloromethane solution of approximately 600 to 750 nm. The NIR dye (A1) has a light transmittance at a wavelength of 418 nm and a light at a wavelength of 482 nm when the concentration is adjusted so that the transmittance of light having a maximum absorption wavelength λ _{max (A1)} is 10% in a dichloromethane solution. The transmittance is preferably 85% or more, more preferably 90% or more, still more preferably 92% or more, and particularly preferably 94% or more.

The NIR dye (A1) preferably has a steep slope of the spectral transmittance curve on the short wavelength side of the absorption peak having the maximum absorption wavelength λ _{max (A1)} in the dichloromethane solution. Thereby, for example, in an optical filter including an absorption layer containing an NIR dye (A1) and a dielectric multilayer film, the influence of the angle dependency that the absorption wavelength is shifted by the incident angle of light inherently possessed by the dielectric multilayer film is affected. Without receiving, the light absorption characteristics of the dielectric multilayer film can be fully utilized, and as a result, an optical filter having particularly excellent near-infrared shielding characteristics can be obtained.

Among NIR dyes (A1) shown in Table 1, NIR dye (A1-1) and the like are preferable from the viewpoint of solubility.

The NIR dye (A2) has a maximum absorption wavelength λ _max (A2) in a dichloromethane solution of approximately 700 to 850 nm. The NIR dye (A2) has a light transmittance at a wavelength of 418 nm and a light at a wavelength of 482 nm when the concentration is adjusted so that the transmittance of light having a maximum absorption wavelength λ _{max (A2)} is 10% in a dichloromethane solution. The transmittance is preferably 85% or more, more preferably 90% or more, still more preferably 92% or more, and particularly preferably 94% or more.

The NIR dye (A2) has an absorption layer containing a NIR dye (A2) and a dielectric multilayer film, for example, because the maximum absorption wavelength λ _{max (A2)} in the dichloromethane solution is in the above range. In the dielectric multilayer film, it is possible to effectively suppress the light omission that a part of the near-infrared light to obtain a high reflectivity according to the incident angle increases, and as a result, an optical filter having particularly excellent near-infrared shielding characteristics is obtained. be able to.

Among the NIR dyes (A2) shown in Table 2, NIR dyes (A2-1) and the like are preferable from the viewpoint of solubility.

NIR dye (A1) and NIR dye (A2) have good solubility in organic solvents and good compatibility with transparent resins. As a result, even if the absorption layer is thinned, it has excellent spectral transmittance characteristics and the optical filter can be thinned, so that thermal expansion of the absorption layer due to heating can be suppressed. Therefore, for example, during the heat treatment when forming a functional layer such as a reflection layer or an antireflection layer laminated on the absorption layer, occurrence of cracks or the like of these layers can be suppressed.

The NIR dye (A1) and the NIR dye (A2) are, for example, 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid) and squalic acid bonded to formula (A1) or formula (A2). And a thiophene derivative capable of forming the structure shown in FIG. For example, when the NIR dye (A1) and the NIR dye (A2) have a bilaterally symmetric structure, 2 equivalents of a thiophene derivative having a desired structure may be reacted with 1 equivalent of squaric acid within the above range.

Hereinafter, as a specific example, a reaction route for obtaining the NIR dye (A1) is shown. In the following scheme (F1), squaric acid is represented by (s). In scheme ^{^{(F1), R 1 ~ R}} 4 are the same meaning as ^R 1 ~ ^{R 4} in the formula (A1).

According to Scheme (F1), a thiophene derivative having a bromine atom at the amino group introduction position and a desired substituent (R ¹ , R ² ) at the β-position is used as a starting material.

A thiophene derivative as a starting material is reacted with a tertiary amine having a desired substituent (R ³ , R ⁴ ), and the intermediate A1-1 has the desired substituent (R ¹ , R ² , NR ³ R ⁴ ). A thiophene derivative is obtained. By reacting 2 equivalents of Intermediate A1-1 with 1 equivalent of squaric acid (s), NIR dye (A1) is obtained.

The NIR dye (A2) can be produced by the following scheme (F2). In the following scheme (F2), squaric acid is represented by (s). In scheme ^{^{(F2), R 5 ~ R}} 8 are the same meaning as ^R 5 ~ ^{R 8} in Formula (A2).

In Scheme (F2), intermediate A2 in which a bromine atom was introduced by reacting N-bromosuccinimide (NBS) at the amino group introduction position of a thienothiophene derivative having a desired substituent (R ⁵ , R ⁶ ) at the β-position Get -1.

Intermediate A2-1 is reacted with a tertiary amine having the desired substituent (R ⁷ , R ⁸ ), and intermediate A2-2 has the desired substituent (R ⁵ , R ⁶ , NR ⁷ R ⁸ ). A thienothiophene derivative is obtained. One equivalent of squaric acid (s) is reacted with two equivalents of intermediate A2-2 to give NIR dye (A2).

The use of the NIR dye (A1) and NIR dye (A2) of the present invention is not particularly limited. For example, the present invention can be applied to an optical filter that blocks near infrared light.

<Optical filter>
An optical filter according to an embodiment of the present invention (hereinafter also referred to as “the present filter”) includes an absorption layer containing the NIR dye (A1) or NIR dye (A2) of the present invention and a resin. In this filter, the absorption layer may contain two or more selected from NIR dye (A1) and NIR dye (A2). In the following description, an NIR dye composed of one or more selected from NIR dye (A1) and NIR dye (A2) is referred to as NIR dye (A).

The filter may further include a reflective layer made of a dielectric multilayer film in addition to the absorbing layer. In the following description, “reflection layer” refers to a reflection layer made of a dielectric multilayer film.

This filter may further have a transparent substrate. In this case, the absorption layer is provided on the main surface of the transparent substrate. When this filter has a transparent substrate, an absorption layer, and a reflection layer, an absorption layer and a reflection layer are provided on the main surface of a transparent substrate. This filter may have an absorption layer and a reflective layer on the same main surface of a transparent substrate, and may have on a different main surface. When the absorption layer and the reflection layer are provided on the same main surface, the stacking order is not particularly limited.

本 This filter may also have other functional layers. Examples of the other functional layer include an antireflection layer that suppresses visible light transmittance loss. In particular, when the absorption layer has an outermost surface configuration, a visible light transmittance loss due to reflection occurs at the interface between the absorption layer and air. Therefore, an antireflection layer may be provided on the absorption layer.

Next, a configuration example of this filter will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an optical filter 10 </ b> A composed of an absorption layer 11. The absorption layer 11 can be comprised by the layer containing NIR pigment | dye (A) and resin. In the optical filter 10A, the absorption layer 11 can take the form of a film or a substrate.

FIG. 2 is a configuration example of an optical filter 10B provided with a reflective layer 12 on one main surface of the absorbing layer 11. In the optical filter 10B, the absorption layer 11 can be composed of a layer containing a NIR dye (A) and a resin. The phrase “including the reflective layer 12 on one main surface (upper side) of the absorbing layer 11 is not limited to the case where the reflecting layer 12 is provided in contact with the absorbing layer 11, and the absorbing layer 11, the reflecting layer 12, The following configuration is also the same, including the case where another functional layer is provided in between.

FIG. 3 is a cross-sectional view schematically showing an example of the optical filter of the embodiment having a transparent substrate and an absorption layer. FIG. 4 is a cross-sectional view schematically showing an example of an optical filter according to an embodiment having a transparent substrate, an absorption layer, and a reflection layer. The optical filter 10 </ b> C includes the transparent substrate 13 and the absorption layer 11 disposed on one main surface of the transparent substrate 13. The optical filter 10 </ b> D includes a transparent substrate 13, an absorption layer 11 disposed on one main surface of the transparent substrate 13, and a reflective layer 12 provided on the other main surface of the transparent substrate 13. In the

optical filters

10C and 10D, the absorption layer 11 can be composed of a layer containing the NIR dye (A) and a resin.

FIG. 5 shows an optical filter 10E having an absorption layer 11 on one main surface of the transparent substrate 13, and

reflection layers

12a and 12b on the other main surface of the transparent substrate 13 and on the main surface of the absorption layer 11. It is a structural example. FIG. 6 is a configuration example of an optical filter 10F that includes

absorption layers

11a and 11b on both main surfaces of the transparent substrate 13, and further includes reflection layers 12a and 12b on the main surfaces of the absorption layers 11a and 11b.

5 and 6, the two reflecting

layers

12a and 12b to be combined may be the same or different. For example, the

reflective layers

12a and 12b have a property of reflecting ultraviolet light and near infrared light and transmitting visible light, and the reflective layer 12a reflects ultraviolet light and light in the first near infrared region, The reflection layer 12b may be configured to reflect ultraviolet light and second near-infrared light.

In FIG. 6, the two

absorption layers

11a and 11b may be the same or different. When the absorption layers 11a and 11b are different, for example, the absorption layers 11a and 11b may be a combination of a near infrared absorption layer and an ultraviolet absorption layer, or may be a combination of an ultraviolet absorption layer and a near infrared absorption layer. The near-infrared absorbing layer can be composed of a layer containing a NIR dye (A) and a resin.

FIG. 7 is a configuration example of an optical filter 10G including an antireflection layer 14 on the main surface of the absorption layer 11 of the optical filter 10D shown in FIG. The antireflection layer 14 may cover not only the outermost surface of the absorption layer 11 but also the entire side surface of the absorption layer 11. In that case, the moisture-proof effect of the absorption layer 11 can be enhanced.

Hereinafter, the absorption layer, the reflective layer, the transparent substrate, and the antireflection layer will be described.
(Absorption layer)
The absorption layer contains the NIR dye (A). The absorbing layer may further contain an NIR dye other than the NIR dye (A) (hereinafter referred to as other NIR dye) as long as the effect of the present invention is not impaired.

The content of the NIR dye (A) in the absorbing layer is preferably 0.1 to 30 parts by mass with respect to 100 parts by mass of the resin as the total amount of the NIR dye (A) and other NIR dyes. Desirable near infrared absorptivity is obtained at 0.1 parts by mass or more, and decrease in near infrared absorptivity and increase in haze value are suppressed at 30 parts by mass or less. The total content of the NIR dye (A) and other NIR dyes is more preferably 0.5 to 25 parts by mass, and further preferably 1 to 20 parts by mass.

Other NIR dyes have a maximum absorption wavelength in the range of 660 to 1100 nm, and there is a predetermined difference between the maximum absorption wavelength and the maximum absorption wavelength λ _{max (A)} of the NIR dye (A). preferable. The difference between the maximum absorption wavelengths of both is preferably 30 nm or more, more preferably 50 nm or more, further preferably 80 nm or more, and particularly preferably 100 nm or more.

Other NIR dyes include cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, dithiol metal complex compounds, diimonium compounds, polymethine compounds, phthalide compounds, naphthoquinone compounds, anthraquinone compounds, indophenol compounds, And squarylium compounds other than the NIR dye (A). Other NIR dyes may be used alone or in combination of two or more.

The absorption layer contains a NIR dye (A) and a resin, and is typically a layer or (resin) substrate in which the NIR dye (A) is uniformly dissolved or dispersed in the resin. The resin is usually a transparent resin, and the absorption layer may contain other NIR dyes in addition to the NIR dye (A). Further, the absorption layer may contain a dye other than the NIR dye, particularly a UV dye.

Specific examples of UV dyes include oxazole, merocyanine, cyanine, naphthalimide, oxadiazole, oxazine, oxazolidine, naphthalic acid, styryl, anthracene, cyclic carbonyl, and triazole. Pigments. Among these, oxazole-based and merocyanine-based dyes are preferable. Moreover, UV dye may be used individually by 1 type for an absorption layer, and may use 2 or more types together.

Transparent resins include acrylic resin, epoxy resin, ene / thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyimide Examples thereof include resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, and polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins. These resins may be used alone or in combination of two or more.

The transparent resin is preferably a resin having a high glass transition point (Tg) from the viewpoints of transparency, solubility of the NIR dye (A), and heat resistance. Specifically, at least one selected from polyester resins, polycarbonate resins, polyethersulfone resins, polyarylate resins, polyimide resins, and epoxy resins is preferable, and at least one selected from polyester resins and polyimide resins is more preferable. .

The absorbing layer is further in the range not impairing the effect of the present invention, adhesion imparting agent, color tone correction dye, leveling agent, antistatic agent, thermal stabilizer, light stabilizer, antioxidant, dispersant, flame retardant, You may have arbitrary components, such as a lubricant and a plasticizer.

The absorption layer is prepared by, for example, dissolving or dispersing a dye containing the NIR dye (A), a resin or a raw material component of the resin, and each component blended as necessary, in a solvent, It can be formed by applying it to a substrate, drying it, and curing it as necessary. The base material may be a transparent substrate optionally included in the filter, or may be a peelable base material used only when forming the absorption layer. The solvent may be a dispersion medium that can be stably dispersed or a solvent that can be dissolved.

In addition, the coating liquid may contain a surfactant to improve voids due to fine bubbles, dents due to adhesion of foreign matters, and repelling in the drying process. Furthermore, for example, a dip coating method, a cast coating method, or a spin coating method can be used for coating the coating liquid. An absorption layer is formed by applying the coating liquid onto a substrate and then drying it. Further, when the coating liquid contains a resin raw material component, a curing treatment such as thermosetting or photocuring is further performed.

Further, the absorption layer can be manufactured in a film form by extrusion molding, and this film may be laminated on another member and integrated by thermocompression bonding or the like. For example, when this filter contains a transparent substrate, you may stick this film on a transparent substrate.

This filter may have two or more absorption layers. When the absorption layer is composed of two or more layers, each layer may be the same or different. In the case where the absorption layer is composed of two or more layers, an example in which one layer is a near infrared absorption layer made of a resin containing a NIR dye and the other layer is an ultraviolet absorption layer made of a resin containing a UV dye is given. . Further, the absorption layer itself may be a substrate (resin substrate).

In this filter, the thickness of the absorption layer is preferably 0.1 to 100 μm. When the absorption layer is composed of a plurality of layers, the total thickness of each layer is preferably 0.1 to 100 μm. If the thickness is less than 0.1 μm, the desired optical characteristics may not be sufficiently exhibited. If the thickness exceeds 100 μm, the flatness of the layer may be reduced, and the in-plane variation of the absorptance may occur. The thickness of the absorption layer is more preferably 0.3 to 50 μm. Moreover, when other functional layers, such as a reflection layer and an antireflection layer, are provided, depending on the material, if the absorption layer is too thick, cracking or the like may occur. Therefore, the thickness of the absorption layer is more preferably 0.3 to 10 μm.

(Transparent substrate)
In this filter, the transparent substrate is an optional component. When the filter includes a transparent substrate, the thickness of the transparent substrate is preferably 0.03 to 5 mm, and more preferably 0.05 to 1 mm from the viewpoint of thinning. As a material of the transparent substrate, glass, (birefringent) crystal, or resin can be used as long as it transmits visible light.

As glass for transparent substrates, absorption glass (near-infrared absorbing glass substrate) obtained by adding CuO or the like to fluorophosphate glass or phosphate glass, soda lime glass, borosilicate glass, alkali-free glass And quartz glass. The “phosphate glass” includes silicic acid phosphate glass in which a part of the glass skeleton is composed of SiO ₂ .

When the transparent substrate is a fluorophosphate glass, specifically, in terms of cation%, P ⁵⁺ : 20 to 45%, Al ³⁺ : 1 to 25%, R ⁺ : 1 to 30% (provided that R ⁺ is Li ⁺ , Na ⁺ , K ⁺ , and the value on the left is the sum of the respective contents), Cu ²⁺ : 1 to 20%, R ²⁺ : 1 to 50% (however, , R ²⁺ is at least one of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ , and the value on the left is the sum of the respective content ratios) and an anion In terms of%, it is preferable to contain F ⁻ : 10 to 65% and O ²⁻ : 35 to 90%.

When the transparent substrate is phosphate glass, P ₂ O ₅ : 30 to 80%, Al ₂ O ₃ : 1 to 20%, R ₂ O: 0.5 to 30% in terms of mass% ( However, R ₂ O is at least one of Li ₂ O, Na ₂ O, and K ₂ O, and the value on the left is the sum of the respective content ratios.), CuO: 1 to 12%, RO: 0.5 to 40% (provided that RO is at least one of MgO, CaO, SrO, BaO, ZnO, and the value on the left is the sum of the respective content ratios. It is preferable to contain a certain).

Examples of commercially available products include NF-50E, NF-50EX, NF-50T, NF-50TX, NF-50GX (manufactured by AGC Co., Ltd., trade name), BG-60, BG-61 (above, manufactured by SCHOTT Co., Ltd.) CD5000 (manufactured by HOYA, trade name) and the like.

The above-described CuO-containing glass may further contain a metal oxide. When the metal oxide contains, for example, one or more of Fe ₂ O ₃ , MoO ₃ , WO ₃ , CeO ₂ , Sb ₂ O ₃ , V ₂ O _5, etc., the CuO-containing glass exhibits ultraviolet absorption characteristics. Have. The content of these metal oxides, relative to the CuO-containing glass 100 parts by _weight, the _{_{Fe 2 O 3, MoO 3,}} WO 3 and at least one selected from the group consisting of CeO _2, _Fe 2 _{O 3} : 0.6 to 5 parts by mass, MoO ₃ : 0.5 to 5 parts by mass, WO ₃ : 1 to 6 parts by mass, CeO ₂ : 2.5 to 6 parts by mass, or Fe ₂ O ₃ and Sb ₂ O ₃ two _Fe 2 _O 3 of 0.6 to 5 parts ₊ Sb ₂ O 3: 0.1 to 5 parts by weight, or _V 2 _{O 5} and the two _{_{_{CeO 2 V 2 O 5: 0.01}}} ~ 0.5 parts by mass + CeO ₂ : 1 to 6 parts by mass is preferable.

Transparent resins for transparent substrates include acrylic resin, epoxy resin, ene thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine Examples thereof include oxide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, and polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins. These resins may be used alone or in combination of two or more.

(Reflective layer)
In this filter, the reflective layer is an optional component. The reflective layer is made of a dielectric multilayer film and has a function of shielding light in a specific wavelength range. Examples of the reflective layer include those having wavelength selectivity that transmit visible light and mainly reflect light having a wavelength other than the light shielding area of the absorption layer. In this case, the reflection region of the reflection layer may include a light shielding region in the near infrared region of the absorption layer. The reflective layer is not limited to the above characteristics, and may be appropriately designed according to specifications for shielding light in a predetermined wavelength range.

In the case where the filter includes a reflective layer, the NIR dye (A) preferably has a reflection characteristic in which the transmittance of light having the maximum absorption wavelength λ _{max (A)} is 1% or less. Thereby, this filter synergistically obtains a high light shielding property (high OD value) at the maximum absorption wavelength λ _{max (A)} of the NIR dye (A).

The filter may have one reflective layer or two or more layers. When the reflective layer is composed of two or more layers, each layer may be the same or different. When the reflective layer has two or more layers, one layer shields at least near-infrared light, in particular, a near-infrared shielding layer having the above-described reflection characteristics, and the other layer shields at least ultraviolet light. A combination to form an ultraviolet shielding layer may be used.

The reflective layer is composed of a dielectric multilayer film in which a low refractive index dielectric film (low refractive index film) and a high refractive index dielectric film (high refractive index film) are alternately stacked. Examples of the material for the high refractive index film include Ta ₂ O ₅ , TiO ₂ , and Nb ₂ O ₅ . Of these, TiO ₂ is preferable from the viewpoint of film formability, reproducibility in refractive index, and stability. Examples of the material for the low refractive index film include SiO ₂ and SiO _x N _y . From the viewpoint of reproducibility, stability, economical efficiency, etc. in film formability, SiO ₂ is preferable. The thickness of the reflective layer is preferably 2 to 10 μm.

(Antireflection layer)
Examples of the antireflection layer include a dielectric multilayer film, an intermediate refractive index medium, and a moth-eye structure in which the refractive index gradually changes. Among these, the use of a dielectric multilayer film is preferable from the viewpoint of high light utilization efficiency and productivity.

This filter has an absorption layer containing the NIR dye (A), so that it can realize excellent light shielding properties against near-infrared light and high visible light transmittance. This filter can be used for, for example, an imaging device such as a digital still camera, an ambient light sensor, and the like.

An imaging apparatus using the present filter includes a solid-state imaging device, an imaging lens, and the present filter. This filter can be used, for example, disposed between an imaging lens and a solid-state imaging device, or directly attached to a solid-state imaging device, an imaging lens, or the like of an imaging apparatus via an adhesive layer.

Next, the present invention will be described more specifically with reference to examples. First, in Examples 1 and 2, NIR dyes (A1-1) and NIR dyes (A2-1) shown in Tables 1 and 2, respectively, were produced. Further, in Examples 3 and 4, comparative NIR dyes (Acf1) and NIR dyes (Acf2) having different structures from the NIR dye (A) were produced. The optical properties of the obtained NIR dye were measured and evaluated.

Also, examples (Example 5) of the obtained optical filter having an absorption layer containing the NIR dye will be described.

In each of the following examples, the structure of the produced NIR dye was confirmed by 1H NMR. In addition, an ultraviolet-visible spectrophotometer (manufactured by Hitachi High-Technologies Corporation, model U-4150) was used for evaluating the optical properties of the NIR dye and the absorption layer containing the NIR dye.

[Example 1]
The NIR dye (A1-1) was synthesized according to the reaction route shown below.

<Step A1-1-1>
2-Bromothiophene (2.00 g, 12.3 mmol) and shaved magnesium (0.597 g, 24.6 mmol) were placed in the flask and dissolved in anhydrous tetrahydrofuran (18 ml) under a nitrogen atmosphere. The solution was refluxed for 3 hours and cooled to -40 ° C. In a separate flask, N-chlorosuccinimide (1.64 g, 12.3 mmol) was dissolved in anhydrous toluene (31 ml) under a nitrogen atmosphere, and bis- (2-ethylhexyl) amine (2.96 g, 12.3 mmol) was added. For 20 minutes. Tetraisopropyl orthotitanate (3.49 g, 12.3 mmol) was added dropwise to the mixed solution cooled to −40 ° C., stirred for 5 minutes, and then mixed with N-chlorosuccinimide and bis- (2-ethylhexyl) amine. The solution was added dropwise. The mixture was stirred at room temperature for 3 hours, and after completion of the reaction, a saturated aqueous potassium carbonate solution (25 ml) was added. Subsequently, the mixture was diluted with ethyl acetate and filtered, and the resulting solution was extracted with ethyl acetate. The obtained organic layer was washed with saturated brine, the solvent was removed, and intermediate A1-1-1 (1.00 g, yield 25%) was obtained by silica gel column chromatography (hexane: triethylamine = 100: 3). Obtained.

<Step A1-1-2>
Into the flask was added intermediate A1-1-1 obtained in step A1-1-1 (1.00 g, 3.09 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.176 g, 1 .55 mmol) was added and dissolved in a mixed solution of normal butanol (8 ml) and toluene (8 ml) under a nitrogen atmosphere. The mixture was stirred at reflux for 3 hours. After completion of the reaction, the solvent was removed and NIR dye (A1-1) (0.570 g, yield 51%) was obtained by silica gel chromatography (dichloromethane: methanol = 20: 1). .

[Example 2]
The NIR dye (A2-1) was synthesized according to the reaction route shown below.

<Step A2-1-1>
Thieno [3,2-b] thiophene (4.00 g, 28.5 mmol) was placed in the flask and dissolved in anhydrous dimethylformamide (28.5 ml) under a nitrogen atmosphere. The solution was cooled to −15 ° C., and an anhydrous dimethylformamide solution (28.5 ml) in which N-bromosuccinimide (5.08 g, 28.5 mmol) was dissolved was added dropwise. The mixture was stirred at room temperature for 30 minutes and then stirred at 60 ° C. for 5 hours. After completion of the reaction, the mixture was poured into ice water and extracted with diisopropyl ether. The obtained organic layer was washed with saturated brine, the solvent was removed, and intermediate A2-1-1 (5.09 g, yield 81%) was obtained by silica gel column chromatography (hexane).

<Step A2-1-2>
A flask was charged with intermediate A2-1-1 (2.00 g, 9.13 mmol) obtained in step A2-1-1 and shaved magnesium (0.440 g, 18.3 mmol), and anhydrous tetrahydrofuran was added under a nitrogen atmosphere. (13 ml). The solution was refluxed for 3 hours and cooled to -40 ° C. In a separate flask, N-chlorosuccinimide (0.490 g, 3.65 mmol) was dissolved in anhydrous toluene (18 ml) under a nitrogen atmosphere, and bis- (2-ethylhexyl) amine (0.880 g, 3.65 mmol) was added. For 20 minutes.

Tetraisopropyl orthotitanate (2.59 g, 9.13 mmol) was added dropwise to the mixed solution cooled to −40 ° C. and stirred for 5 minutes, followed by mixing of N-chlorosuccinimide and bis- (2-ethylhexyl) amine. The solution was added dropwise. The mixture was stirred at room temperature for 3 hours, and after completion of the reaction, a saturated aqueous potassium carbonate solution (18 ml) was added. Subsequently, the mixture was diluted with ethyl acetate and filtered, and the resulting solution was extracted with ethyl acetate. The obtained organic layer was washed with saturated brine, the solvent was removed, and intermediate A2-1-2 (0.987 g, yield 28%) was obtained by silica gel column chromatography (hexane: triethylamine = 100: 3). Obtained.

<Step A2-1-3>
Into the flask was added intermediate A2-1-2 (0.411 g, 1.08 mmol) obtained in step A2-1-2, 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.0617 g, 0 .541 mmol) was added and dissolved in a mixed solution of normal butanol (3 ml) and toluene (3 ml) under a nitrogen atmosphere. The mixture was stirred at reflux for 3 hours. After completion of the reaction, the solvent was removed and NIR dye (A2-1) (0.100 g, yield 22%) was obtained by silica gel chromatography (dichloromethane: methanol = 50: 1). .

[Example 3]
An NIR dye (Acf1) was synthesized according to the reaction route shown below.

<Step Acf1-1>
Dithieno [3,2-b: 2 ′, 3′-d] thiophene (2.00 g, 10.2 mmol) was placed in the flask and dissolved in anhydrous dimethylformamide (10 ml) under a nitrogen atmosphere. The above solution was cooled to −15 ° C., and an anhydrous dimethylformamide solution (10 ml) in which N-bromosuccinimide (1.81 g, 10.2 mmol) was dissolved was added dropwise. The mixture was stirred at room temperature for 30 minutes and then stirred at 60 ° C. for 5 hours. After completion of the reaction, the mixture was poured into ice water and extracted with diisopropyl ether. The obtained organic layer was washed with saturated brine and the solvent was removed, and then intermediate Acf1-1 (2.58 g, yield 92%) was obtained by silica gel column chromatography (dichloromethane).

<Step Acf1-2>
The intermediate Acf1-1 (2.57 g, 9.34 mmol) obtained in Step Acf1-1 and ground magnesium (0.450 g, 18.7 mmol) were placed in a flask, and anhydrous tetrahydrofuran (13 ml) was added under a nitrogen atmosphere. Dissolved. The solution was refluxed for 3 hours and cooled to -40 ° C. In a separate flask, N-chlorosuccinimide (1.25 g, 9.34 mmol) was dissolved in anhydrous toluene (23 ml) under a nitrogen atmosphere, and bis- (2-ethylhexyl) amine (2.26 g, 9.34 mmol) was added. For 20 minutes.

Tetraisopropyl orthotitanate (2.65 g, 9.34 mmol) was added dropwise to the mixed solution cooled to −40 ° C., stirred for 5 minutes, and then mixed with N-chlorosuccinimide and bis- (2-ethylhexyl) amine. The solution was added dropwise. The mixture was stirred at room temperature for 3 hours, and after completion of the reaction, a saturated aqueous potassium carbonate solution (18 ml) was added. Subsequently, the mixture was diluted with ethyl acetate and filtered, and the resulting solution was extracted with ethyl acetate. The obtained organic layer was washed with saturated brine, the solvent was removed, and intermediate Acf1-2 (1.02 g, yield 25%) was obtained by silica gel column chromatography (hexane: triethylamine = 100: 3). .

<Step Acf1-2>
Into the flask was added intermediate Acf1-2 (1.02 g, 2.35 mmol) obtained in Step Acf1-2, 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.134 g, 1.17 mmol). And dissolved in a mixed solution of normal butanol (6 ml) and toluene (6 ml) under a nitrogen atmosphere. The mixture was stirred at reflux for 3 hours. After completion of the reaction, the solvent was removed, and the dye (Acf1) (0.569 g, yield 51%) was obtained by silica gel chromatography (hexane: ethyl acetate: triethylamine = 100: 1: 3). Obtained.

[Example 4]
An NIR dye (Acf2) was synthesized according to the reaction route shown below.

<Step Acf2-1>
To the flask was added 3-bromothieno [3,2-b] thiophene (3 g, 13.7 mmol), [1,1′-bis (diphenylphosphino) ferrocene] palladium (II) dichloride dichloromethane adduct (0.0447 g, .0. 0548 mmol) was added, dissolved in a 0.5 M solution of isobutylzinc bromide in tetrahydrofuron (41 ml, 20.6 mmol) under a nitrogen atmosphere and stirred at reflux for one day. After completion of the reaction, a saturated aqueous ammonium chloride solution was added and extracted with diisopropyl ether to obtain an organic layer. The organic layer was washed with a 5% aqueous hydrochloric acid solution and then with a saturated saline solution, the solvent was removed, and an intermediate Acf2-1 (2.32 g, 58%) was obtained by silica gel column chromatography (hexane). .

<Step Acf2-2>
The intermediate Acf2-1 (2.32 g, 11.8 mmol) obtained in Step Acf2-1 was placed in a flask and dissolved in anhydrous dimethylformamide (12 ml) under a nitrogen atmosphere. The solution was cooled to −15 ° C., and an anhydrous dimethylformamide solution (12 ml) in which N-bromosuccinimide (4.63 g, 26.0 mmol) was dissolved was added dropwise. The mixture was stirred at room temperature for 30 minutes and then stirred at 60 ° C. for 5 hours. After completion of the reaction, the mixture was poured into ice water and extracted with diisopropyl ether. The obtained organic layer was washed with saturated brine and the solvent was removed, and then intermediate Acf2-2 (3.55 g, yield 85%) was obtained by silica gel column chromatography (hexane).

<Step Acf2-3>
The flask was charged with palladium (II) acetate (0.111 g, 0.0.494 mmol), sodium tertiary butoxide (1.92 g, 20.0 mmol), tritertiary butylphosphine (0.200 g, 0.991 mmol), Dissolved in anhydrous toluene (15 ml) under nitrogen atmosphere. The above mixed solution was stirred at 60 ° C. for 10 minutes and returned to room temperature, and 4,4′-dinormaloctyldiphenylamine (3.94 g, 10.0 mmol) and the intermediate Acf2-2 obtained in Step Acf2-2 ( A mixed solution in which 3.55 g (10.0 mmol) was dissolved in anhydrous toluene (4 ml) was added dropwise and stirred at reflux for 3 hours. After completion of the reaction, the solvent was removed from the filtrate obtained by filtration, and intermediate Acf2-3 (1.56 g, 23%) was obtained by silica gel column chromatography (hexane).

<Step Acf2-4>
In a flask, intermediate Acf2-3 (1.56 g, 2.35 mmol) obtained in step Acf2-3, palladium (II) acetate (0.0269 g, 0.120 mmol), xanthophos (0.102 g, 0.176 mmol) , Triethylsilane (3.58 g, 30.8 mmol) was added and dissolved in anhydrous toluene (23 ml) under a nitrogen atmosphere. The mixed solution was stirred at reflux for 7 hours. After completion of the reaction, the solvent was removed and intermediate Acf2-4 (1.16 g, 84%) was obtained by silica gel column chromatography (hexane).

<Step Acf2-5>
Into the flask was added intermediate Acf2-4 (1.16 g, 1.98 mmol) obtained in step Acf2-4, 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.113 g, 0.988 mmol). And dissolved in a mixed solution of normal butanol (5 ml) and toluene (5 ml) under a nitrogen atmosphere. The mixture was stirred at reflux for 3 hours. After completion of the reaction, the solvent was removed, and NIR dye (Acf2) (0.464 g, 37% yield) was obtained by silica gel chromatography (dichloromethane: hexane = 2: 1).

[Evaluation]
(Measurement of transmittance in dichloromethane)
The NIR dyes (A1-1), (A2-1), and NIR dyes (Acf1), (Acf2) obtained above were dissolved in dichloromethane, and a light absorption spectrum at a wavelength of 400 to 1000 nm was measured to obtain an absorbance curve. From this, the maximum absorption wavelength λ _{max (A) DCM} was determined. Furthermore, from the absorbance curve in which the dye concentration in dichloromethane was adjusted so that the light transmittance at the maximum absorption wavelength λ _{max (A) DCM} was 10%, the transmittance T _{418 (A) DCM} and the wavelength at a wavelength of ₄₁₈ nm were obtained. The transmittance T _{482 (A) DCM} at ₄₈₂ nm was determined. The results are shown in Table 3. For the wavelengths 418 nm and 482 nm, absorption wavelengths that were next larger than the maximum absorption wavelength of the NIR dye (A1-1) and NIR dye (A2-1) in the measurement wavelength region were selected and compared.

(Solubility in resin coating solution)
The solubility of the NIR dyes (A1-1) and (A2-1) obtained above and the NIR dyes (Acf1) and (Acf2) in the coating solution of the transparent resin was evaluated.

That is, a transparent resin (Neoprim (registered trademark) C3G30 (trade name, polyimide resin, manufactured by Mitsubishi Gas Chemical Co., Ltd.)) was dissolved in a mixed solution (1: 1) of γ-butyrolactone and cyclohexanone at a concentration of 10% by mass. The NIR dye was dissolved in the solution, and the solubility (mass%) in the resin was evaluated. The results are shown in Table 3.

As is clear from the above evaluation results, the NIR dyes (A1-1) and (A2-1) and the NIR dyes (Acf1) and (Acf2) all have a high light shielding property against near-infrared light. In addition, from the above evaluation results, the NIR dye (Acf1) of Example 3 which is a comparative example and the NIR dye (Acf2) of Example 4 were compared to the case where either the visible light transmittance or the solubility in the coating solution was low. It can be seen that the example NIR dye (A1-1) of Example 1 and the NIR dye (A2-1) of Example 2 have high visible light transmittance and high solubility in the coating solution. Further, for NIR dye (A1-1) and NIR dye (A2-1), the coating solution obtained in the above test was applied on a glass plate (D263; manufactured by SCHOTT, trade name) and dried to form a film. An absorption layer having a thickness of 1 μm could be obtained.

[Example 5]
The optical filter having the configuration shown in FIG. 7 is manufactured by the following method.
As a transparent substrate, a glass substrate having a thickness of 0.21 mm made of CuO-containing fluorophosphate glass (manufactured by AGC Co., Ltd., trade name: NF-50GX) or a glass substrate having a thickness of 0.2 mm (D263; manufactured by SCHOTT, product) Name).

As the reflective layer, a dielectric multilayer film formed as follows is used. The dielectric multilayer film is formed by laminating, for example, a total of 42 layers of TiO ₂ films and SiO ₂ films alternately on one main surface of the glass substrate by vapor deposition. The configuration of the reflection layer is simulated by using the number of dielectric multilayer films, the thickness of the TiO ₂ film, and the thickness of the SiO ₂ film as parameters. Is designed to have an average transmittance of 0.03%.

In addition, an absorption layer having a thickness of about 1.0 μm is formed on the main surface on the opposite side of the reflective layer of the glass substrate by combining one or more of transparent resin and NIR dye (A). Form. Thereafter, seven layers of TiO ₂ films and SiO ₂ films are alternately laminated on the surface of the absorption layer by vapor deposition to form an antireflection layer, thereby obtaining an optical filter (NIR filter).

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on May 29, 2018 (Japanese Patent Application No. 2018-102387), the contents of which are incorporated herein by reference.

The near-infrared absorbing dye of the present invention can realize excellent light-shielding properties for near-infrared light, and can form a homogeneous absorption layer because it has high solubility in solvents and resins. It is applicable to an optical filter that shields light. The optical filter of the present invention can be applied to an imaging apparatus.

10A, 10B, 10C, 10D, 10E, 10F, 10G ... optical filter, 11, 11a, 11b ... absorbing layer, 12, 12a, 12b ... reflecting layer, 13 ... transparent substrate, 14 ... antireflection layer.

Claims

A near-infrared absorbing dye comprising a compound represented by the formula (A1).

In formula (A1),
R 1 and R 2 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon-carbon atoms, An alkoxy group, an aryl group or an araryl group; R 1 and R 2 may be connected to each other to form a 3 to 6-membered alicyclic or aromatic ring that may contain a hetero atom, in which case the hydrogen atom bonded to the ring is substituted with a substituent. May be.
R 3 and R 4 may each independently have a substituent, and may be a linear or branched chain which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon-carbon atoms. It is an alkyl group.
The near-infrared absorbing dye according to claim 1, wherein R 1 is a hydrogen atom.
A near-infrared absorbing dye comprising a compound represented by the formula (A2).

In formula (A2),
R 5 and R 6 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon-carbon atoms, An alkoxy group, an aryl group or an araryl group;
R 7 and R 8 may each independently have a substituent, and may have a linear or branched chain which may contain an unsaturated bond, an oxygen atom, an alicyclic ring or an aromatic ring between carbon-carbon atoms. It is an alkyl group.
The near-infrared absorbing dye according to claim 3, wherein R 5 is a hydrogen atom.
An optical filter comprising an absorption layer containing the near-infrared absorbing dye according to any one of claims 1 to 4 and a resin.
The optical filter according to claim 5, further comprising a reflective layer including a dielectric multilayer film.
The optical filter according to claim 5, further comprising a transparent substrate, wherein the absorption layer is provided on the transparent substrate.
The optical filter according to claim 7, wherein the transparent substrate is made of glass.
The optical filter according to claim 8, wherein the glass is near-infrared absorbing glass.
The optical filter according to claim 7, wherein the transparent substrate is made of a resin.
An imaging apparatus comprising: a solid-state imaging device; an imaging lens; and the optical filter according to any one of claims 5 to 10.