Squarylium compounds, optical filters, and imaging devices

Abstract

The purpose of the present invention is to provide: a near-infrared absorbent dye that is superior in terms of blocking near-infrared light, in particular, blocking light with wavelengths of 600-1100 nm; an optical filter; and an image acquisition device that employs the optical filter and that is superior in terms of color reproducibility. The present invention relates to a squarylium compound represented by formula (A1).　In formula (A1), each of R1, R2, R3, and Ar1 is as defined in the specification.

Description

[Technical Field]

[0001] The present invention relates to a novel squarylium compound, an optical filter containing the compound as a near-infrared absorbing dye, and an imaging device equipped with the optical filter. [Background technology]

[0002] In order to reproduce color tones well and obtain clear images, imaging devices using solid-state imaging elements use near-infrared cut filters that transmit light in the visible range (hereinafter also referred to as "visible light") and block light in the near-infrared range (hereinafter also referred to as "near-infrared light"). Near-infrared cut filters block near-infrared light by an absorption layer in which a near-infrared absorbing dye is dispersed in a resin, or a reflection layer made of a dielectric multilayer film that reflects near-infrared light.

[0003] Known near-infrared absorbing dyes for use in such near-infrared cut filters include squarylium compounds having a squarylium skeleton and heteroaromatic ring structures on both sides thereof. For example, Patent Document 1 describes a near-infrared absorbing dye having a structure in which heteroaryl rings containing chalcogen atoms are on both sides of a squarylium skeleton and an amino group is bonded to the heteroaryl rings. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 104283 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, with the widespread use of near-infrared light, near-infrared absorbing dyes used in near-infrared cut filters are required to have the ability to block long wavelengths of near-infrared light, particularly light with wavelengths of 600 to 1100 nm, from the viewpoint of highly accurate luminosity correction in imaging devices.

[0006] The present invention aims to provide a novel squarylium compound that is excellent in blocking near-infrared light, particularly light with a wavelength of 600 to 1100 nm, an optical filter, and an imaging device that uses the optical filter and has excellent color reproducibility. [Means for solving the problem]

[0007] The present invention relates to the following squarylium compounds, etc. [1] A squarylium compound represented by the following formula (A1):

[0008] [ka]

[0009] [The meanings of the symbols in the above formula are as follows: R 1 and R 2 R are each independently an alkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an unsaturated bond between carbon atoms, an oxygen atom, an alicyclic ring, or an aromatic ring. 1 is R 2 or Ar 1 may be linked to form a ring. 2 is R 1 or Ar 1 may be linked to form a ring. R 3 R is an alkenyl group having 2 or more carbon atoms which may have a substituent, an alkynyl group having 2 or more carbon atoms which may have a substituent, an imino group having 1 or more carbon atoms which may have a substituent, a cyano group, an organic group having a carbonyl structure and having 1 or more carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 3 to 13 carbon atoms which may have a substituent. 3 Ar 1 may be linked to form a ring. Ar 1 is a divalent group containing an aromatic ring having 3 to 14 carbon atoms, which may contain a heteroatom. [Effects of the Invention]

[0010] In the squarylium compound according to the present invention, a substituent having an unsaturated bond, such as an aryl group, an alkenyl group, or an alkynyl group, is bonded to a specific position on the aromatic ring, thereby introducing a conjugated system into the side chain as well, thereby shifting the wavelength of the near-infrared absorption region to a longer wavelength. The squarylium compound can provide a near-infrared absorbing dye that has excellent blocking properties for long-wavelength near-infrared light. Furthermore, the present invention can provide an optical filter using the dye and an imaging device that uses the optical filter and has excellent color reproducibility. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another example of the optical filter according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically showing another example of the optical filter according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view schematically showing another example of the optical filter according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described. 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 formula (A1) is referred to as compound (A1). The same applies to compounds represented by other formulas. An NIR dye consisting of compound (A1) is also referred to as NIR dye (A1), and the same applies to other dyes. Furthermore, for example, a group represented by formula (1a) is also referred to as group (1a), and the same applies to groups represented by other formulas. In this specification, the use of "to" to indicate a range of values ​​includes the upper and lower limits.

[0013] In this specification, unless otherwise specified, the alkyl group may be linear, branched, cyclic, or a combination of these structures. Unless otherwise specified, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc., with a fluorine atom being preferred. In this specification, unless otherwise specified, an aryl group refers to a group that bonds via a carbon atom constituting an aromatic ring of an aromatic compound, such as a benzene ring, a naphthalene ring, a biphenyl ring, etc. Furthermore, a heteroaryl group refers to a group that bonds via a carbon atom or a heteroatom constituting an aromatic ring of an aromatic compound having a heteroatom, such as a furan ring, a thiophene ring, a pyrrole ring, etc.

[0014] In this specification, a squarylium compound refers to a compound having a squarylium skeleton represented by the following formula (S1) that can have a resonance structure represented by the following formula (S2) in its structural formula. In this specification, the squarylium skeleton is represented by either formula (S1) or formula (S2).

[0015] [ka]

[0016] <Squarylium compounds> The present invention provides a squarylium compound (A1) represented by formula (A1). The squarylium compound (A1) of the present invention has a squarylium skeleton at the center of its molecular structure, with one aromatic ring bonded to each side of the squarylium skeleton. This provides the squarylium compound (A1) with excellent optical properties for blocking near-infrared light. A substituent having an unsaturated bond is bonded to the aromatic ring at the position closest to the squarylium skeleton. This expands the conjugated system, shifting the near-infrared absorption region to longer wavelengths. Specifically, the inclusion of a substituent having an unsaturated bond enables a longer wavelength of approximately 40 to 300 nm. Furthermore, an amino group having two alkyl groups is bonded to the aromatic ring on the side opposite the squarylium skeleton. This provides the squarylium compound (A1) with excellent visible light transmittance.

[0017] The squarylium compound (A1) will be described in detail below. The squarylium compound (A1) is represented by the following formula (A1).

[0018] [ka]

[0019] R 1 and R 2 are each independently an alkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an unsaturated bond between carbon atoms, an oxygen atom, an alicyclic ring, or an aromatic ring. The two R in formula (A1) 1 may be different on the left and right sides of the squarylium skeleton, but from the viewpoint of ease of production, 1 It is preferable that R 2 , R 3 , Ar 1 The same applies to the symbols that follow. That is, the two symbols in the chemical formula may be different on the left and right sides of the squarylium skeleton, but from the viewpoint of ease of production, it is preferable that the symbols on the left and right sides are the same.

[0020] R 1 is R 2 or Ar 1may be linked to form a ring. 2 is R 1 or Ar 1 may be linked to form a ring. The ring is preferably an alicyclic or aromatic ring having 3 to 6 members. The ring may have a substituent.

[0021] R 1 and R 2 Examples of the substituent in 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, an imido group, and an alkoxy group having 1 to 20 carbon atoms.

[0022] R 1 and R 2 Further examples of the substituent in the formula (I) include cyclic alkyl groups and aryl groups. The aryl group is preferably a phenyl group which may have 1 to 5 substituents or a naphthyl group which may have 1 to 7 substituents. The substituent which may substitute a hydrogen atom of the phenyl group or naphthyl group includes an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon atoms, an alkoxy group, or an alkylamino 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, and examples of the substituent include a methyl group, a t-butyl group, a dimethylamino group, and a methoxy group.

[0023] R 1 and R 2 However, when the main chain or side chain contains an alicyclic or aromatic ring, this is preferable in terms of heat resistance and shifting the NIR absorption wavelength to a longer wavelength. 1 and R 2 However, when the main chain or side chain does not have an alicyclic or aromatic ring, 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 number of carbon atoms in the aromatic ring is preferably 4 to 14.

[0024] R 1 and R 2The carbon number of R may be 1 to 20. 1 and R 2 In the case of a linear structure, the number of carbon atoms in R is preferably 2 to 20, more preferably 3 to 16, and even more preferably 4 to 12. 1 and R 2 In the case of a branched chain, the number of carbon atoms is preferably 3 to 20, more preferably 4 to 16, and even more preferably 8 to 10. R 1 and R 2 has a substituent, or contains an alicyclic or aromatic ring in the main chain or side chain, the number of carbon atoms does not include the number of carbon atoms in the substituent, alicyclic or aromatic ring.

[0025] R 1 and R 2 R may be the same or different, but it is preferable that they are the same from the viewpoint of ease of production. 1 and R 2 From the viewpoint of solubility in a resin and a solvent, it is preferable that either one of the two is branched, and it is more preferable that both are branched.

[0026] R 1 and R 2 When the alkylene group is branched, the number of branches is not particularly limited. The number of branches is preferably 1 to 5, more preferably 1 to 3. From the viewpoints of both solubility in resins and solvents and ease of production, the branching position is preferably the β-position. Furthermore, one carbon atom may be branched into two or three branches.

[0027] R 1 and R 2 is more preferably, for example, a group selected from groups (1b) to (5b). -CH(C n H 2n+1 )2…(1b) -C(C n H 2n+1 )3…(1c) -CH2-CH(C n H 2n+1 )2…(2b) -CH2-C(C n H 2n+1 )3…(2c) -(CH2)2-CH(C n H 2n+1 )2…(3b) -(CH2)3-CH(C n H 2n+1 )2…(4b) -(CH2) m -CH3…(5b)

[0028] In the formulas (1b) to (4b), n is an integer of 1 to 10, preferably 2 to 8, and more preferably 2 to 4. In the formulas (1b) to (4b), two or three C n H 2n+1 may be linear or branched, and may be the same or different. In formula (5b), m is an integer of 0 to 19, preferably 1 to 19, more preferably 2 to 15, and even more preferably 3 to 11. Furthermore, groups (1b) to (5b) may have an oxygen atom between carbon atoms.

[0029] R 3 is an alkenyl group having 2 or more carbon atoms which may have a substituent, an alkynyl group having 2 or more carbon atoms which may have a substituent, an imino group having 1 or more carbon atoms which may have a substituent, a cyano group, an organic group having a carbonyl structure and having 1 or more carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 3 to 13 carbon atoms which may have a substituent.

[0030] R 3 Ar 1 may be linked to form a ring. The ring is preferably a ring having 5 to 7 members. The ring may have a substituent.

[0031] As mentioned above, R 3 is a substituent having an unsaturated bond. 3 By bonding to the heteroaryl ring, the conjugated system of the squarylium compound is expanded, shifting the near-infrared absorption range to longer wavelengths. The Two R's 3 may be different on the left and right sides of the squarylium skeleton, but from the viewpoint of ease of production, 3are preferably the same.

[0032] R 3 Examples of the substituent in include a halogen atom, a hydroxyl group, a carbonyl structure-containing monovalent organic group, a phosphate 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, an imide group, a thiol group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, a silyl group, and a halogenated alkyl group having 1 to 20 carbon atoms. R 3 When R has a substituent, 3 The number of carbon atoms in the group does not include the number of carbon atoms in the substituents.

[0033] The alkenyl group has 2 or more carbon atoms, preferably 2 to 30 carbon atoms, more preferably 2 to 22 carbon atoms, and even more preferably 2 to 14 carbon atoms. The alkenyl group is preferably a group represented by the following formula (3-1).

[0034] [ka]

[0035] R 3a , R 3b , R 3care each independently a hydrogen atom, a halogen atom, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms. 3b is R 3a or R 3c may be linked to form a 3- to 6-membered ring which may contain a heteroatom, and in that case, the ring may have a substituent.

[0036] Aryl group, heteroaryl group, alkenyl group, alkynyl group, R 3b R 3a or R 3c Examples of the substituent in the ring formed by linking with the above include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, a triisopropylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0037] Preferred examples of the group (3-1) include the following structures:

[0038] [ka]

[0039] The alkynyl group has 2 or more carbon atoms, preferably 2 to 30 carbon atoms, more preferably 2 to 22 carbon atoms, and even more preferably 2 to 14 carbon atoms. The alkynyl group is preferably a group represented by the following formula (3-2).

[0040] [ka]

[0041] R 3d is a hydrogen atom, a halogen atom, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, a triisopropylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0042] Examples of the substituent in the aryl group, heteroaryl group, alkenyl group, and alkynyl group include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0043] Preferred examples of the group (3-2) include the following structures:

[0044] [ka]

[0045] The imino group has 1 or more carbon atoms, preferably 1 to 30 carbon atoms, more preferably 1 to 22 carbon atoms, and even more preferably 1 to 14 carbon atoms. The imino group is preferably a group represented by the following formula (3-3). [ka]

[0046] R 3e , R 3fare each independently a hydrogen atom, a halogen atom, a hydroxyl group, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms. 3e and R 3f may be linked to form a 3- to 6-membered ring which may contain a hetero atom, and in that case, the ring may have a substituent.

[0047] Aryl group, heteroaryl group, alkenyl group, alkynyl group, R 3e and R 3f Examples of the substituent in the ring formed by linking the groups include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (e.g., a trimethylsilyl group, a triphenylsilyl group, a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0048] Preferred examples of the group (3-3) include the following structures:

[0049] [ka]

[0050] The cyano group is a group represented by the following formula (3-4).

[0051] [ka]

[0052] The organic group having one or more carbon atoms and containing a carbonyl structure and optionally having a substituent has one or more carbon atoms, preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and even more preferably 1 to 10 carbon atoms. Such an organic group is preferably a group represented by the following formula (3-5).

[0053] [ka]

[0054] R 3g is a hydrogen atom, a hydroxyl group, a cyano group, an amino group, an N-substituted amino group, an alkoxycarbonyl group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0055] Examples of the substituent in the aryl group, heteroaryl group, alkenyl group, and alkynyl group include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0056] Preferred examples of the group (3-5) include the following structures:

[0057] [ka]

[0058] The aryl group has 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, and more preferably 6 to 10 carbon atoms. The aryl group is preferably a group represented by the following formula (3-6).

[0059] [ka]

[0060] R 3h , R 3i , R 3j , R 3k , R 3lare each independently a hydrogen atom, a halogen atom, a hydroxyl group, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0061] R 3h and R 3i , R 3i and R 3j , R 3j and R 3k , R 3k and R 3l may be linked to each other to form a 3- to 6-membered ring which may contain a heteroatom, and in that case, the ring may have a substituent.

[0062] Aryl group, heteroaryl group, alkenyl group, alkynyl group, R 3h and R 3i , R 3i and R 3j , R 3j and R 3k , R 3k and R 3lExamples of the substituent in the ring formed by linking the groups include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (e.g., a trimethylsilyl group, a triphenylsilyl group, a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0063] Preferred examples of the group (3-6) include the following structures:

[0064] [ka]

[0065] The heteroaryl group has 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, and more preferably 3 to 10 carbon atoms. The heteroaryl group is preferably a group represented by any one of the following formulas (3-7) to (3-9).

[0066] [ka]

[0067] X 3a , X 3b , X 3c , X 3d , X 3e are each independently N or CR 3m and at least one is N. R 3mis a hydrogen atom, a halogen atom, a hydroxyl group, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0068] X 3a , X 3b , X 3c , X 3d , X 3e is CR 3m If so, the adjacent X 3a ~X 3e are linked together to form a 3-6-membered ring Ar which may contain a heteroatom 30 , Ar 31 , Ar 32 , Ar 33 In this case, the ring may have a substituent.

[0069] Aryl group, heteroaryl group, alkenyl group, alkynyl group, ring Ar 30 , Ar 31 , Ar 32 , Ar 33Examples of the substituent in include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0070] Preferred examples of the group (3-7) include the following structures:

[0071] [ka]

[0072] [ka]

[0073] X 3f , X 3g , X 3h are each independently N or CR 3n Y 3a is S, O or NR 3o is.

[0074] R 3n and R 3oare each independently a hydrogen atom, a halogen atom, a hydroxyl group, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0075] X 3f , X 3g , X 3h is CR 3n and Y 3a NR 3o If so, the adjacent X 3f , X 3g , X 3h , Y 3a are linked together to form a 3-6-membered ring Ar which may contain a heteroatom 34 , Ar 35 , Ar 36 In this case, the ring may have a substituent.

[0076] Aryl group, heteroaryl group, alkenyl group, alkynyl group, ring Ar 34 , Ar 35 , Ar 36Examples of the substituent in include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0077] Preferred examples of the group (3-8) include the following structures:

[0078] [ka]

[0079] [ka]

[0080] X 3i , X 3j , X 3k are each independently N or CR 3p Y 3b is S, O or NR 3q R 3p and R 3qare each independently a hydrogen atom, a halogen atom, a hydroxyl group, a formyl 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, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aralkyl group having 6 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 20 carbon atoms which may have a substituent, an alkenyl group having 2 to 20 carbon atoms which may have a substituent, an alkynyl group having 2 to 20 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0081] X 3i , X 3j , X 3k is CR 3p and Y 3b NR 3q If so, the adjacent X 3i , X 3j , X 3k , Y 3b are linked together to form a 3-6-membered ring Ar which may contain a heteroatom 37 , Ar 38 , Ar 39 In this case, the ring may have a substituent.

[0082] Aryl group, heteroaryl group, alkenyl group, alkynyl group, ring Ar 37 , Ar 38 , Ar 39Examples of the substituent in include a halogen atom, a formyl group, a carboxy group, a sulfo group, an amino group, an N-substituted amino group, a nitro group, an alkoxycarbonyl group, a carbamoyl group, an N-substituted carbamoyl group, an imido group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, a triorganosilyl group having 3 to 20 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 20 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 20 carbon atoms.

[0083] Preferred examples of the group (3-9) include the following structures:

[0084] [ka]

[0085] Ar 1 is a divalent group containing an aromatic ring having 3 to 14 carbon atoms, which may contain a heteroatom. 1 is preferably a divalent group containing an aromatic hydrocarbon ring having 6 to 14 carbon atoms, or a divalent group containing a heteroaryl ring having 3 to 13 carbon atoms.

[0086] The aromatic hydrocarbon ring may be a monocyclic ring, a polycyclic ring, or a condensed ring, and is preferably a monocyclic ring, i.e., a benzene ring.

[0087] The heteroaryl ring may be a monocyclic ring, a polycyclic ring, or a fused ring, and examples thereof include a 5- or 6-membered monocyclic ring and a fused ring formed by condensing two or three 5- or 6-membered rings. Preferred fused rings include a fused ring of two 5-membered rings, a fused ring of a 5-membered ring and a 6-membered ring, and a fused ring of three 5-membered rings.

[0088] The heteroatom in the heteroaryl ring is preferably a nitrogen atom, a sulfur atom, or an oxygen atom. 1 Preferably, the heteroatom has 1 to 3 heteroatoms. When the heteroatom has two or more heteroatoms, the heteroatoms may be the same or different. As the heteroaryl ring, from the viewpoint of ease of production, a pyrrole ring, a thiophene ring, a furan ring, an imidazole ring, an oxazole ring, a thiazole ring, and a thienothiophene ring are particularly preferred.

[0089] Ar 1 is the above R 3 In addition to the above, the alkyl group may have one or more substituents. Examples of such substituents include a hydrogen atom, a halogen atom, a sulfo group, a hydroxyl group, a cyano group, a nitro group, a carbonyl structure-containing monovalent organic group, a phosphate group, a silyl group, a thiol group, a sulfide group, an amide structure-containing monovalent organic group, a sulfonamide group, a urea group, a urethane structure-containing monovalent organic group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkenyl group having 2 to 14 carbon atoms which may have a substituent, an alkynyl group having 2 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 13 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an acyloxy group having 2 to 13 carbon atoms which may have a substituent, or —N(R 47 )2(R 47 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent.

[0090] The squarylium compound (A1) is preferably a squarylium compound represented by the following formula (A2) having a heteroaryl ring in which two five-membered rings are fused, or a squarylium compound represented by the following formula (A3) having a five-membered heteroaryl ring.

[0091] [ka]

[0092] R 1 ~R 3 is R in formula (A1) 1 ~R 3 The same applies to the above, including preferred embodiments.

[0093] X 1 is CR 4 Or N.

[0094] R 4 is a hydrogen atom, a halogen atom, a sulfo group, a hydroxyl group, a cyano group, a nitro group, a carbonyl structure-containing monovalent organic group, a phosphate group, a silyl group, a thiol group, a sulfide group, an amide structure-containing monovalent organic group, a sulfonamide group, a urea group, a urethane structure-containing monovalent organic group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkenyl group having 2 to 14 carbon atoms which may have a substituent, an alkynyl group having 2 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 13 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an acyloxy group having 2 to 13 carbon atoms which may have a substituent, or —N(R 47 )2(R 47 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent.

[0095] R 4 is an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkenyl group having 2 to 14 carbon atoms which may have a substituent, an alkynyl group having 2 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 13 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an acyloxy group having 2 to 13 carbon atoms which may have a substituent, or —N(R 47 )2, then R 4 is R 1 ~R 3 may be linked to any one of the above to form a ring having 3 to 6 members. In addition, the ring may have a substituent.

[0096] R 4Examples of the substituent in include a halogen atom, a hydroxyl group, a carbonyl structure-containing monovalent organic group, a phosphate 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, an imide group, a thiol group, a sulfide group, an alkoxy group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heteroaryl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, a silyl group, and a halogenated alkyl group having 1 to 20 carbon atoms. R 4 When R has a substituent, 4 The number of carbon atoms in the group does not include the number of carbon atoms in the substituents.

[0097] R 4 The halogen atom in is preferably a fluorine atom.

[0098] R 4 The carbonyl structure-containing monovalent organic group in the formula (I) is -C(=O)-R 41 is preferred. 41 represents a hydrogen atom, an alkyl group having 1 to 15 carbon atoms which may have a substituent, or an alkoxy group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, an octyloxy group, an isopropoxy group, an isobutoxy group, or a 2-ethylhexyloxy group.

[0099] R 4 The silyl group in 42 )3 is preferred. 42 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, a t-butyl group, or a 2-ethylhexyl group. 42 may be the same or different.

[0100] R4 The sulfide group in 43 is preferred. 43 represents a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, a t-butyl group, or a 2-ethylhexyl group.

[0101] R 4 The amide structure-containing monovalent organic group in the formula (I) is -C(=O)-NH-R 44 is preferred. 44 represents a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, a t-butyl group, or a 2-ethylhexyl group.

[0102] R 4 The sulfonamide group in the formula (R) is -SO2-N(R 45 )2 is preferred. 45 is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, a t-butyl group, or a 2-ethylhexyl group. 45 may be the same or different.

[0103] R 4 The urethane structure-containing monovalent organic group in 46 is preferred. 46 represents a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, a t-butyl group, or a 2-ethylhexyl group.

[0104] R 4 In the above, the alkyl group having 1 to 14 carbon atoms is preferably a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, an isopropyl group, an isobutyl group, a t-butyl group, or a 2-ethylhexyl group.

[0105] R 4 In the above formula, the alkenyl group having 2 to 14 carbon atoms is preferably a vinyl group, a 1-propenyl group, an isobutenyl group, a styryl group, a 2-fluorovinyl group, a 2,2-difluorovinyl group, or a 3,3,3-trifluoropropenyl group.

[0106] R 4 The alkynyl group having 2 to 12 carbon atoms in the formula (I) is preferably an acetylenyl group, a 1-propynyl group, a trimethylsilylethynyl group, a triethylsilylethynyl group, a triisopropylsilylethynyl group, or a t-butyldimethylsilylethynyl group.

[0107] R 4 In the above, the aryl group having 6 to 20 carbon atoms is preferably a phenyl group, a 4-methoxyphenyl group, a 3,4,5-trifluorophenyl group, a 4-trifluoromethylphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2,5-dimethylphenyl group, or a 3-nitrophenyl group.

[0108] R 4 In the above formula, the heteroaryl group having 3 to 13 carbon atoms is preferably a pyridyl group, a pyrimidyl group, a quinolyl group, a furyl group, a thienyl group, an oxazolyl group, an imidazolyl group, a thiazolyl group, a benzoxazolyl group, a benzimidazolyl group or a benzthiazolyl group.

[0109] R 4 In the above formula, the alkoxy group having 1 to 15 carbon atoms is preferably a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a hexyloxy group, an octyloxy group, an isopropoxy group, an isobutoxy group, or a 2-ethylhexyloxy group.

[0110] R 4 In the above formula, the acyloxy group having 2 to 13 carbon atoms is preferably an acetoxy group, a propionyloxy group, a butyryloxy group, an isobutyryloxy group, or a benzoyloxy group.

[0111] R 4 In -N(R47 )2 in two R 47 may be the same or different. 47 They may be linked together to form a ring. 47 )2 is preferably a dimethylamino group, a diethylamino group, a diphenylamino group, an ethylisopropylamino group, or a morpholino group.

[0112] X 2 is S, NR 5 , or O. R 5 represents a hydrogen atom, a carbonyl structure-containing monovalent organic group, a sulfo group, or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a hydrogen atom, a methyl group, an ethyl group, an isobutyl group, a 2-ethylhexyl group, a benzyl group, a t-butoxycarbonyl group, a benzyloxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group, an allyloxycarbonyl group, a 2,2,2-triethoxycarbonyl group, or a 2-nitrobenzenesulfonyl group.

[0113] R 5 is an alkyl group having 1 to 15 carbon atoms which may have a substituent, R 5 is R 1 ~R 3 may be linked to any one of the above to form a 3- to 6-membered ring.

[0114] X 3 is S, NR 6 , or O. R 6 represents a hydrogen atom, a carbonyl structure-containing monovalent organic group, a sulfo group, or an alkyl group having 1 to 15 carbon atoms which may have a substituent, and is preferably a hydrogen atom, a methyl group, an ethyl group, an isobutyl group, a 2-ethylhexyl group, a benzyl group, a t-butoxycarbonyl group, a benzyloxycarbonyl group, a 9-fluorenylmethyloxycarbonyl group, an allyloxycarbonyl group, a 2,2,2-triethoxycarbonyl group, or a 2-nitrobenzenesulfonyl group.

[0115] R 6 is an alkyl group having 1 to 15 carbon atoms which may have a substituent, R 6 is R4 may be linked to form a 3- to 6-membered ring.

[0116] In formula (A2), X 1 ,X 2 ,X 3 The following combinations are included: (X 1 ,X 2 ,X 3 )=(CR 4 ,S,S), (CR 4 ,S,O), (CR 4 ,S,NR 6 ), (CR 4 ,O,S), (CR 4 ,O,O), (CR 4 ,O,NR 6 ), (CR 4 ,NR 5 ,S), (CR 4 ,NR 5 ,O), (CR 4 ,NR 5 ,NR 6 ), (N,S,S), (N,S,O), (N,S,NR 6 ), (N,O,S), (N,O,O), (N,O,NR 6 ), (N,NR 5 ,S), (N,NR 5 ,O), (N,NR 5 ,NR 6 ).

[0117] From the viewpoint of increasing the wavelength, it is preferable to use (X 1 ,X 2 ,X 3 )=(CR 4 ,S,S), (CR 4 ,S,O), (CR 4 ,O,S), (CR 4 ,O,O), (CR 4 ,NR 5 ,S), (CR 4 ,NR 5 , O), and more preferably (X 1 ,X 2 ,X 3 )=(CR 4 ,S,S), (CR 4,S,O), (CR 4 ,NR 5 ,S), (CR 4 ,NR 5 ,O).

[0118] In formula (A3), X 1 ,X 2 The following combinations are included: (X 1 ,X 2 )=(CR 4 ,S), (CR 4 ,NR 5 ), (CR 4 ,O), (N,S), (N,NR 5 ), (N,O). From the viewpoint of increasing the wavelength, it is preferable to use (X 1 ,X 2 )=(CR 4 ,S), (CR 4 ,NR 5 ), (CR 4 , O), more preferably (CR 4 ,S), (CR 4 ,O).

[0119] As the squarylium compound represented by formula (A2), a squarylium compound represented by the following formula (A4) is preferred, in view of ease of synthesis and the fact that it is expected to be able to absorb light in a longer wavelength region among fused ring skeletons of five-membered rings.

[0120] [ka]

[0121] R 1 ~R 3 is R in formula (A1) 1 ~R 3 The same applies to the above, including preferred embodiments. R 4 is R in formula (A2) 4 The same applies to the above, including preferred embodiments.

[0122] As the squarylium compound represented by formula (A3), a squarylium compound represented by the following formula (A5) is preferred, in view of ease of synthesis and the fact that it is expected to be able to absorb light in a longer wavelength region among five-membered ring skeletons.

[0123] [ka]

[0124] R 1 ~R 3 is R in formula (A1) 1 ~R 3 The same applies to the above, including preferred embodiments. R 4 is R in formula (A3) 4 The same applies to the above, including preferred embodiments.

[0125] More specifically, the squarylium compound (A4) is 1 ~R 4 However, the compounds shown in Table 1 below (Table 1 also shows the abbreviations for the squarylium compounds (A4)) are included. In Table 1, R 1 ~R 4 In all compounds shown in Table 1, R 1 ~R 4 are all identical on both sides of the equation.

[0126] [Table 1]

[0127] More specifically, the squarylium compound (A5) is R 1 ~R 4 However, the compounds shown in Table 2 below (Table 2 also shows the abbreviations for the squarylium compounds (A5)) are included. In Table 2, R 1 ~R 4 In all compounds shown in Table 2, R 1 ~R4 are all identical on both sides of the equation.

[0128] [Table 2]

[0129] The squarylium compound (A1) has a maximum absorption wavelength λ max(A1) However, it is generally in the range of 600 to 1100 nm. Maximum absorption wavelength λ max(A1) When the wavelength is in this range, the compound has absorption in the long wavelength region of the near infrared region, and can absorb near infrared light of 600 to 1100 nm. Furthermore, the squarylium compound (A2) has a maximum absorption wavelength λ max(A2) However, it is generally in the range of 700 to 1100 nm. The squarylium compound (A3) has a maximum absorption wavelength λ max(A3) However, it is generally in the range of 800 to 1100 nm. The squarylium compound (A4) has a maximum absorption wavelength λ max(A4) However, it is generally in the range of 650 to 950 nm. The squarylium compound (A5) has a maximum absorption wavelength λ max(A5) However, it is generally in the range of 700 to 950 nm.

[0130] The method for producing the squarylium compound (A1) will be explained using the methods for producing the squarylium compound (A2) and the squarylium compound (A3), but the method for producing the squarylium compound (A1) is not limited to these. A method for obtaining the squarylium compound (A2) is shown in Scheme (F-A2).

[0131] [ka]

[0132] A method for obtaining the squarylium compound (A3) is shown in Scheme (F-A3).

[0133] [ka]

[0134] In the schemes (F-A2) and (F-A3), step (A) is a reaction for converting a carboxylic acid into a dialkylamine, and the details are shown in the following scheme. In the following scheme, HetAr means heteroaryl. Azide is preferably diphenylphosphoryl azide. N alkylation is S-alkylation using alkyl halide and base. N 2 reaction or a reductive amination reaction using an aldehyde and a reducing agent is preferred.

[0135] [ka]

[0136] In schemes (F-A2) and (F-A3), step B (step (B)) is a reaction for converting a halogen into various substituents, and a cross-coupling reaction, a Heck reaction, formylation, a Wittig reaction of an aldehyde obtained by formylation, a Knevenagel reaction, a Henry reaction, a nucleophilic addition reaction of an alkyl metal reactant, or the like can be utilized, but is not limited to these.

[0137] The starting material (a2-1) in the scheme (F-A2) can be obtained, for example, from a known compound by the following synthesis method.

[0138] In the starting material (a2-1), X 1 , X 2 and R is: Compound (a2-1-1):(X 1 , X 2 , R)=(-CH, S, -CH2CH3) Compound (a2-1-2):(X1 , X 2 , R)=(-CH, S, H)

[0139] [ka]

[0140] In the starting material (a2-1), X 1 , X 2 and R is: Compound (a2-1-3):(X 1 , X 2 , R)=(-CH, O, -CH2CH3) Compound (a2-1-4):(X 1 , X 2 , R)=(-CH, O, H)

[0141] [ka]

[0142] In the starting material (a2-1), X 1 , X 2 , (X 3 ), and R is the following compound: Compound (a2-1-5): (X 1 , X 2 , R)=(-CH, -NH, -CH2CH3) compound (a2-1-6):(X 1 , X 2 , R)=(-CH, -NH,H) compound (a2-1-7):(X 1 , X 2 , X 3 , R)=(-CH, -NH, -NH, -CH2CH3) compound (a2-1-8):(X 1 , X 2 , X 3 , R)=(-CH, -NH, -NH, H)

[0143] [ka]

[0144] In the starting material (a2-1), X 1 , X 2 and R is: Compound (a2-1-9):(X 1 , X 2 , R)=(N, O, -CH2CH3) Compound (a2-1-10):(X 1 , X 2 , R)=(N, O, H)

[0145] [ka]

[0146] In the starting material (a2-1), X 1 , X 2 and R is: Compound (a2-1-11):(X 1 , X 2 , R)=(N, -NH, -CH2CH3) Compound (a2-1-12):(X 1 , X 2 , R)=(N, -NH, H)

[0147] [ka]

[0148] In the starting material (a2-1), X 1 , X 2 and R is: Compound (a2-1-13):(X 1 , X 2 , R)=(N, S, -CH2CH3) Compound (a2-1-14):(X 1 , X 2 , R)=(N, S, H)

[0149] [ka]

[0150] The starting material (a3-1) in the scheme (F-A3) can be obtained, for example, by the following synthesis method.

[0151] [ka]

[0152] The squarylium compound (A1) of the present invention is useful as a near-infrared absorbing dye.

[0153] <Optical filters> An optical filter according to one embodiment of the present invention (hereinafter also referred to as "the filter") comprises an absorption layer containing a near-infrared absorbing dye and a resin, and contains the squarylium compound (A1) of the present invention as the near-infrared absorbing dye. Hereinafter, the near-infrared absorbing dye formed from the squarylium compound (A1) will also be referred to as "NIR dye (A1)."

[0154] In addition to the absorption layer, the present filter may further include a reflective layer made of a dielectric multilayer film. In the following description, the term "reflective layer" refers to a reflective layer made of a dielectric multilayer film.

[0155] The present filter may further include a transparent substrate. In this case, the absorbing layer is provided on the main surface of the transparent substrate. When the present filter includes a transparent substrate, an absorbing layer, and a reflective layer, the absorbing layer and the reflective layer are provided on the main surface of the transparent substrate. The present filter may include the absorbing layer and the reflective layer on the same main surface of the transparent substrate, or may include the absorbing layer and the reflective layer on different main surfaces. When the absorbing layer and the reflective layer are provided on the same main surface, the stacking order thereof is not particularly limited.

[0156] The filter may also have other functional layers. Examples of such layers include an anti-reflection layer that suppresses loss of visible light transmittance. In particular, when the absorbing layer is configured as the outermost surface, a loss of visible light transmittance occurs due to reflection at the interface between the absorbing layer and air, so it is recommended to provide an anti-reflection layer on the absorbing layer.

[0157] Next, an example of the configuration of this filter will be described with reference to the drawings. 1 is a cross-sectional view showing an optical filter 10A including an absorbing layer 11. The absorbing layer 11 may be a layer containing an NIR dye (A1) and a resin. In the optical filter 10A, the absorbing layer 11 may be in the form of a film or a substrate.

[0158] 2 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment having a transparent substrate, an absorption layer, and a reflection layer. The optical filter 10D has a transparent substrate 13, an absorption layer 11 disposed on one main surface of the transparent substrate 13, and a reflection layer 12 disposed on the other main surface of the transparent substrate 13. Note that the phrase "having the absorption layer 11 on one main surface (above) of the transparent substrate 13" does not necessarily mean that the absorption layer 11 is provided in contact with the transparent substrate 13, but also includes a case where another functional layer is provided between the transparent substrate 13 and the absorption layer 11, and the same applies to the following configurations.

[0159] FIG. 3 shows an example of the configuration of an optical filter 10F that includes absorbing layers 11a and 11b on both main surfaces of a transparent substrate 13, and further includes reflective layers 12a and 12b on the main surfaces of the absorbing layers 11a and 11b.

[0160] Fig. 4 shows an example of the configuration of an optical filter 10G in which an antireflection layer 14 is provided on the main surface of the absorption layer 11 of the optical filter 10D shown in Fig. 2. The antireflection layer 14 may be configured to cover not only the outermost surface of the absorption layer 11 but also the entire side surface of the absorption layer 11. In this case, the moisture-proof effect of the absorption layer 11 can be improved.

[0161] The absorbing layer, the reflective layer, the transparent substrate and the anti-reflection layer will be described below.

[0162] (Absorption layer) The absorbing layer contains an NIR dye (A1). The absorbing layer may further contain an NIR dye other than the NIR dye (A1) (hereinafter referred to as an other NIR dye) as long as the effects of the present invention are not impaired.

[0163] The content of the NIR dye (A1) in the absorbing layer, as a total amount of the NIR dye (A1) and other NIR dyes, is preferably 0.1 to 30 parts by mass per 100 parts by mass of the resin. When the content is 0.1 part by mass or more, the desired near-infrared absorption ability is obtained, and when the content is 30 parts by mass or less, a decrease in near-infrared absorption ability and an increase in haze value are suppressed. Furthermore, the total content of the NIR dye (A1) and other NIR dyes is more preferably 0.5 to 25 parts by mass, and even more preferably 1 to 20 parts by mass.

[0164] The other NIR dyes have a maximum absorption wavelength in the range of 660 to 1100 nm, and the maximum absorption wavelength λ of the NIR dye (A1) is max(A1)) The difference in maximum absorption wavelength between the two is preferably 30 nm or more, more preferably 50 nm or more, even more preferably 80 nm or more, and particularly preferably 100 nm or more.

[0165] Examples of 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). One of the other NIR dyes may be used alone, or two or more may be used in combination.

[0166] The absorbing layer contains the NIR dye (A1) and a resin, and is typically a layer or (resin) substrate in which the NIR dye (A1) is uniformly dissolved or dispersed in the resin. The resin is usually a transparent resin, and the absorbing layer may contain other NIR dyes in addition to the NIR dye (A1). Furthermore, the absorbing layer may contain dyes other than the NIR dye, particularly UV dyes.

[0167] Specific examples of UV dyes include oxazole-based, merocyanine-based, cyanine-based, naphthalimide-based, oxadiazole-based, oxazine-based, oxazolidine-based, naphthalic acid-based, styryl-based, anthracene-based, cyclic carbonyl-based, and triazole-based dyes. Among these, oxazole-based and merocyanine-based dyes are preferred. The UV dyes may be used alone or in combination in the absorption layer.

[0168] Examples of transparent resins include acrylic resins, epoxy resins, enethiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine 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.

[0169] From the viewpoints of transparency, solubility of the NIR dye (A1), and heat resistance, the transparent resin is preferably a resin with a high glass transition point (Tg), specifically, at least one selected from polyester resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, polyimide resin, and epoxy resin is preferred, and at least one selected from polyester resin and polyimide resin is more preferred.

[0170] The absorbing layer may further contain optional components such as an adhesion imparting agent, a color tone correcting dye, a leveling agent, an antistatic agent, a heat stabilizer, a light stabilizer, an antioxidant, a dispersing agent, a flame retardant, a lubricant, and a plasticizer, within a range that does not impair the effects of the present invention.

[0171] The absorbing layer can be formed, for example, by dissolving or dispersing a dye containing the NIR dye (A1), a resin or raw materials for the resin, and other components, if necessary, in a solvent to prepare a coating solution, which is then applied to a substrate, dried, and optionally cured. The substrate may be a transparent substrate optionally included in the filter, or a peelable substrate used only when forming the absorbing layer. The solvent may be a dispersion medium in which the dye can be stably dispersed or a solvent in which the dye can be dissolved.

[0172] The coating liquid may also contain a surfactant to prevent voids caused by microbubbles, depressions caused by the adhesion of foreign matter, and repellency during the drying process. For example, dip coating, cast coating, or spin coating can be used to apply the coating liquid. The coating liquid is applied to a substrate and then dried to form an absorbing layer. When the coating liquid contains resin raw materials, it is further subjected to a curing treatment such as heat curing or photocuring.

[0173] The absorbing layer can also be produced in the form of a film by extrusion molding, and this film may be laminated to another member and integrated by thermocompression bonding, etc. For example, when the present filter includes a transparent substrate, this film may be attached to the transparent substrate.

[0174] The present filter may have two or more absorbing layers. When the absorbing layer is composed of two or more layers, each layer may be the same or different. When the absorbing layer is composed of two or more layers, for example, one layer may be a near-infrared absorbing layer made of a resin containing an NIR dye, and the other layer may be an ultraviolet absorbing layer made of a resin containing a UV dye. Furthermore, the absorbing layer itself may be a substrate (resin substrate).

[0175] In the present filter, the thickness of the absorbing layer is preferably 0.1 to 100 μm. When the absorbing layer is composed of multiple layers, the total thickness of the layers is preferably 0.1 to 100 μm. If the thickness is less than 0.1 μm, the desired optical properties may not be fully exhibited, and if the thickness exceeds 100 μm, the flatness of the layer may decrease, causing in-plane variations in absorptance. The thickness of the absorbing layer is more preferably 0.3 to 50 μm. Furthermore, when other functional layers such as a reflective layer or an anti-reflection layer are provided, if the absorbing layer is too thick, cracks may occur depending on the material of the layer. Therefore, the thickness of the absorbing layer is more preferably 0.3 to 10 μm.

[0176] (Transparent substrate) In the present filter, the transparent substrate is an optional component. When the present filter includes a transparent substrate, the thickness of the transparent substrate is preferably 0.03 to 5 mm, and from the viewpoint of thinning, more preferably 0.05 to 1 mm. As the material of the transparent substrate, glass, (birefringent) crystal, or resin can be used as long as it transmits visible light.

[0177] Examples of glass for transparent substrates include absorption-type glass (near-infrared absorbing glass substrate) made by adding CuO or the like to fluorophosphate glass or phosphate glass, soda-lime glass, borosilicate glass, alkali-free glass, quartz glass, etc. Note that "phosphate glass" also includes silicophosphate glass, in which part of the glass skeleton is composed of SiO2.

[0178] If the transparent substrate is fluorophosphate glass, the specific cationic percentage is P 5+ : 20~45%, Al 3+ :1~25%, R + :1~30% (However, R + Li + , Na + , K. + At least one of the following is present, and the value on the left is the total of the respective content ratios), Cu 2+ :1~20%, R 2+ :1~50% (However, R 2+ is Mg 2+ , Ca 2+ , Sr2+ , Ba 2+ , Zn 2+ At least one of the above is contained, and the value on the left is the total of the content ratio of each), and in anion % expression, F - : 10-65%, O 2- It is preferable that the content is 35 to 90%.

[0179] Furthermore, when the transparent substrate is a phosphate-based glass, it preferably contains, in mass %, 30 to 80% P2O5, 1 to 20% Al2O3, 0.5 to 30% R2O (where R2O is at least one of Li2O, Na2O, and K2O, and the value on the left is the total of the respective contents), 1 to 12% CuO, and 0.5 to 40% RO (where RO is at least one of MgO, CaO, SrO, BaO, and ZnO, and the value on the left is the total of the respective contents).

[0180] The CuO-containing glass may further contain one or more metal oxides, such as Fe2O3, MoO3, WO3, CeO2, Sb2O3, and V2O5, which impart ultraviolet absorption properties to the CuO-containing glass. The content of these metal oxides is preferably at least one selected from the group consisting of Fe2O3, MoO3, WO3, and CeO2 in the following amounts relative to 100 parts by mass of the CuO-containing glass: Fe2O3: 0.6 to 5 parts by mass, MoO3: 0.5 to 5 parts by mass, WO3: 1 to 6 parts by mass, and CeO2: 2.5 to 6 parts by mass; or two of Fe2O3 and Sb2O3 in the following amounts: Fe2O3: 0.6 to 5 parts by mass + Sb2O3: 0.1 to 5 parts by mass; or two of V2O5 and CeO2 in the following amounts: V2O5: 0.01 to 0.5 part by mass + CeO2: 1 to 6 parts by mass, relative to 100 parts by mass of the CuO-containing glass.

[0181] Examples of transparent resins for transparent substrates include acrylic resins, epoxy resins, enethiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine 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.

[0182] (reflective layer) In this filter, the reflective layer is an optional component. The reflective layer is made of a dielectric multilayer film and has the function of blocking light in a specific wavelength range. For example, the reflective layer may have wavelength selectivity such that it transmits visible light and mainly reflects light of wavelengths other than the light blocking range of the absorbing layer. In this case, the reflective region of the reflective layer may include the light blocking region of the absorbing layer in the near-infrared range. The reflective layer is not limited to the above characteristics and may be designed appropriately according to the specifications for blocking light in a specific wavelength range.

[0183] When the filter has a reflective layer, the maximum absorption wavelength λ of the NIR dye (A1) max(A1) It is preferable that the filter has a reflection characteristic in which the transmittance of light having a wavelength λ of the maximum absorption of the NIR dye (A1) is 1% or less. max(A1) In this way, high light blocking properties (high OD value) can be obtained synergistically.

[0184] The present filter may have one reflective layer or two or more reflective layers. When the reflective layer is composed of two or more layers, the layers may be the same or different. When the reflective layer is composed of two or more layers, one layer may be a near-infrared shielding layer that shields at least near-infrared light, particularly having the above-mentioned reflective properties, and the other layer may be an ultraviolet shielding layer that shields at least ultraviolet light.

[0185] The reflective layer is composed of a dielectric multilayer film in which dielectric films with low refractive index (low refractive index film) and dielectric films with high refractive index (high refractive index film) are alternately laminated. Materials for the high refractive index film include Ta2O5, TiO2, and Nb2O5. Of these, TiO2 is preferred in terms of film formation, reproducibility in refractive index, stability, etc. Materials for the low refractive index film include SiO2, SiO x N y In terms of reproducibility, stability, economy, etc. in film formation, SiO2 is preferred. The thickness of the reflective layer is preferably 2 to 10 μm.

[0186] (Anti-reflection layer) Examples of the antireflection layer include a dielectric multilayer film, an intermediate refractive index medium, a moth-eye structure in which the refractive index changes gradually, etc. Among these, the use of a dielectric multilayer film is preferred from the viewpoint of high light utilization efficiency and productivity.

[0187] The filter has an absorption layer containing the NIR dye (A1), which allows it to achieve excellent near-infrared light blocking properties and high visible light transmittance. The filter can be used in imaging devices such as digital still cameras and ambient light sensors.

[0188] An imaging device using this filter includes a solid-state imaging element, an imaging lens, and this filter. The filter can be used, for example, by being placed between the imaging lens and the solid-state imaging element, or by being directly attached to the solid-state imaging element, imaging lens, etc. of the imaging device via an adhesive layer. [Example]

[0189] Next, the present invention will be described in more detail. First, NIR dyes (A1-1) to (A1-11) and NIR dyes (B1) to (B3) were produced as dyes used in the examples. Furthermore, NIR dyes (Acf1) to (Acf4) and (Bcf1) to (Bcf3) were produced as dyes used in the comparative examples. The optical properties of the obtained NIR dyes were measured and evaluated.

[0190] An example of an optical filter having an absorption layer containing the obtained NIR dye will also be described.

[0191] In the following examples, the structure of the NIR dye produced is 1 The optical properties of the NIR dye and the absorption layer containing the dye were evaluated using an ultraviolet-visible spectrophotometer (Shimadzu Corporation, UV-3600Plus model).

[0192] [Example 1] Preparation of NIR dye (A1-1) The NIR dye (A1-1) was synthesized according to the reaction pathway shown below.

[0193] [ka]

[0194] <Step 1> Lithium diisopropylamide (THF / hexane solution, 1.08 M, 200 mL, 216 mmol) was placed in a nitrogen-purged 1 L four-neck flask and cooled to -78 °C. 3,4-Dibromothiophene (50.11 g, 207 mmol) diluted with THF (200 mL) was added via a dropping funnel over 10 minutes, followed by stirring for 30 minutes. The mixture was warmed to 0 °C and stirred for 10 minutes. DMF (19.2 mL, 248 mmol) was added, and the mixture was stirred at 30 °C for 2.5 hours. After completion of the reaction, the mixture was cooled to 0 °C and saturated aqueous ammonium chloride (200 mL) was added. The mixture was extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to obtain the crude product intermediate a1-1 (60.8 g). This crude product was used directly in the next reaction. 1 H NMR (CDCl3, 300MHz) δ9.95(1H,s),7.76(1H,s).

[0195] <Step 2> Potassium carbonate (42.86 g, 310 mmol), the crude product of intermediate a1-1 (60.82 g), DMF (200 mL), ethyl mercaptoacetate (25 mL, 229 mmol), and 18-crown-6-ether (2.742 g, 10.4 mmol) were placed in a nitrogen-purged 500 mL four-neck flask and heated with stirring overnight at 60° C. After cooling to room temperature, the solid was filtered off, water was added, and the mixture was extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated under reduced pressure, and then washed with hexane to give intermediate a1-2 (42.6 g, 71% yield for two steps). 1 H NMR (CDCl3, 300MHz) δ8.01(1H,s),7.47(1H,s),4.39(2H,q,J=7.1Hz),1.40(3H,t,J=7.2Hz).

[0196] <Step 3> Intermediate a1-2 (29.31 g, 100.6 mmol), potassium vinyltrifluoroborate (15.52 g, 110.1 mmol), palladium(II) chloride (374.6 mg, 2.007 mmol), triphenylphosphine (1.571 g, 5.990 mmol), cesium carbonate (97.72 g, 299.9 mmol), and THF / water (9 / 1) (200 mL) were added to a nitrogen-purged recovery flask (500 mL) and heated with stirring at 85 °C for 3 days. After the reaction was completed, water was added, and the mixture was extracted with dichloromethane, washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to obtain crude intermediate a1-3 (27.09 g). This crude product was used in the next reaction. 1 H NMR (CDCl3, 300MHz) δ8.00(1H,s),7.47(1H,s),6.83(1H,dd,J=17.7,11.0Hz),5.73(1 H,d,J=17.6Hz),5.48(1H,d,J=10.9Hz),4.40(2H,q,J=7.1Hz),1.41(3H,t,J=7.1Hz).

[0197] <Step 4> The crude product, lithium hydroxide monohydrate (4.617 g, 110.0 mmol), tetrabutylammonium iodide (1.848 g, 5.003 mmol), water (33 mL), methanol (20 mL), and THF (67 mL) were added to a nitrogen-purged recovery flask (300 mL) and heated with stirring at 80°C for 3 hours. After the reaction was completed, hexane was added, and the mixture was extracted with water and then acidified with 6 N hydrochloric acid. The mixture was extracted with ethyl acetate, dried over magnesium sulfate, concentrated under reduced pressure, and washed with dichloromethane to obtain intermediate a1-4 (18.69 g, 88% yield for two steps). 1 H NMR(DMSO-d6,300MHz)δ8.04(1H,s),7.72(1H,s),6.91(1H,dd,J=17.6,11.1Hz),5.69(1H,d,J=17.8Hz),5.47(1H,d,J=11.1Hz).

[0198] <Step 5> Intermediate a1-4 (7.489 g, 35.61 mmol), diphenylphosphoryl azide (11.3 mL, 52.0 mmol), triethylamine (7.3 mL, 52 mmol), and THF (140 mL) were placed in a nitrogen-purged two-necked flask (300 mL), and the mixture was heated to reflux at 80°C for 2.5 hours. After cooling to room temperature, silica gel (500 cm 3 ) was added, and the mixture was filtered, concentrated under reduced pressure, and purified by silica gel column chromatography (hexane:ethyl acetate=95:5) to obtain intermediate a1-5 (6.938 g, 94% yield). 1 H NMR(CDCl3,300MHz)δ8.04(1H,s),7.55(1H,s),6.83(1H,dd,J=17.8,11.1Hz),5.73(1H,d,J=17.6Hz),5.51(1H,d,J=11.1Hz).

[0199] <Step 6> Intermediate a1-5 (724.4 mg, 3.495 mmol), THF (8.0 mL), and water (8.0 mL) were added to a nitrogen-substituted microwave test tube and heated and stirred at 150 °C for 5 minutes under microwave irradiation. This was repeated seven times, and a total of 4.926 g of intermediate a1-5 was used for the reaction. After the reaction was completed, the seven batches were combined, extracted with ethyl acetate, concentrated, and then purified by silica gel column chromatography (hexane:ethyl acetate = 80:20) to obtain intermediate a1-6 (2.223 g, 52% yield). 1 H NMR(CDCl3,300MHz)δ7.02(1H,s),6.76(1H,dd,J=17.7,11.0Hz),6.43(1H,s),5.53(1H,d,J=17.6Hz),5.35(1H,d,J=10.9Hz),3.91(2H,brs).

[0200] <Step 7> Intermediate a1-6 (89.4 mg, 0.493 mmol), isobutyraldehyde (0.20 mL, 2.2 mmol), sodium triacetoxyborohydride (469.6 mg, 2.216 mmol), and 1,2-dichloroethane (2.5 mL) were added to a nitrogen-purged screw-cap test tube and stirred at room temperature for 9.5 hours. After adding saturated aqueous sodium bicarbonate, the mixture was extracted with dichloromethane, filtered through Florisil, and concentrated. Intermediate a1-7 (65.3 mg, 45% yield) was obtained by silica gel column chromatography (100% hexane). 1 H NMR(CDCl3,300MHz)δ6.90(1H,s),6.76(1H,dd,J=17.6,10.9Hz),6.04(1H,s),5.57(1H,d,J=17 .6Hz),5.33(1H,d,J=10.9Hz),3.09(4H,d,J=7.3Hz),2.22-2.08(2H,m),0.93(12H,d,J=6.6Hz).

[0201] <Step 8> Intermediate a1-7 (276.8 mg, 0.9431 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (64.7 mg, 0.567 mmol), n-butanol (23.5 mL), and toluene (23.5 mL) were added to a nitrogen-purged two-neck flask (100 mL) and heated to reflux at 130°C for 1.5 hours. After completion of the reaction, the solvent was removed, and NIR dye (A1-1) (63.6 mg, 20% yield) was obtained by silica gel column chromatography (dichloromethane:ethyl acetate = 99:1). 1 H NMR(CDCl3,300MHz)δ8.58(2H,dd,J=17.6,11.1Hz),6.10(2H,s),5.74(2H,d,J=17.6Hz), 5.72(2H,d,J=11.4Hz),3.28(8H,d,J=7.3Hz),2.30-2.20(4H,m),0.98(24H,d,J=6.6Hz).

[0202] [Example 2] Preparation of NIR dye (A1-2) The NIR dye (A1-2) was synthesized according to the reaction pathway shown below.

[0203] [ka]

[0204] <Steps 1-6> Intermediate a1-6 was obtained by steps similar to steps 1 to 6 of the production method for NIR dye (A1-1).

[0205] <Step 7> Intermediate a1-6 (3.008 g, 16.59 mmol), 2-ethylhexanal (9.297 g, 72.51 mmol), sodium triacetoxyborohydride (15.38 g, 72.58 mmol), and 1,2-dichloroethane (82.5 mL) were added to a nitrogen-purged two-neck flask (200 mL) and stirred at room temperature for 7.5 hours. After adding saturated aqueous sodium bicarbonate, the mixture was extracted with dichloromethane, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane 100%) to obtain intermediate a2-7 (369.1 mg, 6% yield).1 H NMR(CDCl3,400MHz)δ6.91(1H,s),6.76(1H,dd,J=17.6,11.0Hz),6.05(1H,s),5.57(1H,d,J=17.6Hz),5 .33(1H,d,J=11.0Hz),3.14(4H,d,J=9.8Hz),1.88-1.77(2H,m),1.44-1.21(16H,m),0.93-0.85(12H,m).

[0206] <Step 8> Intermediate a2-7 (249.9 mg, 0.6160 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (37.8 mg, 0.331 mmol), trimethyl orthoformate (0.33 mL, 3.0 mmol), and 1-propanol (30 mL) were added to a nitrogen-purged recovery flask (100 mL) and heated to reflux at 80°C for 2 hours. After the reaction was completed, the solvent was removed and purified by silica gel chromatography (hexane:ethyl acetate = 80:20) to obtain NIR dye (A1-2) (39.7 mg, 14% yield). 1 H NMR(CDCl3,300MHz)δ8.59(2H,dd,J=17.6,11.1Hz),6.09(2H,s),5.73(2H,d,J=17.3Hz),5.72(2H ,d,J=11.4Hz),3.33(8H,d,J=7.3Hz),2.00-1.87(4H,m),1.45-1.21(32H,m),0.99-0.85(24H,m).

[0207] [Example 3] Preparation of NIR dye (A1-3) The NIR dye (A1-3) was synthesized according to the reaction pathway shown below.

[0208] [ka]

[0209] <Steps 1-2> Intermediate a1-2 was obtained by steps similar to steps 1 and 2 of the production method for NIR dye (A1-1).

[0210] <Step 3> Intermediate a1-2 (100.61 g, 328.2 mmol) and THF (500 mL) were placed in a nitrogen-purged four-neck flask (2 L), and isopropyl magnesium chloride-lithium chloride complex (THF solution, 1.3 M, 500 mL, 650 mmol) was added dropwise over 1 hour at -78 °C. After stirring for 1.5 hours, DMF (64 mL, 827 mmol) was added, and the mixture was stirred at 0 °C for 1 hour. After the reaction was completed, saturated aqueous ammonium chloride was added, extracted with ethyl acetate, washed with saturated aqueous ammonium chloride and then with saturated brine, dried over sodium sulfate, and concentrated to obtain a crude product. This was dissolved in dichloromethane, filtered through silica gel, concentrated to approximately half its volume, and reprecipitated by adding hexane. The precipitated solid was filtered by suction, washed with hexane, and dried to obtain intermediate a3-3 (65.24 g, 83% yield). 1 H NMR(CDCl3,300MHz)δ10.02(1H,s),8.39(1H,s),8.03(1H,s),4.40(2H,q,J=7.1Hz),1.41(3H,t,J=7.2Hz).

[0211] <Step 4> Intermediate a3-3 (20.00 g, 83.2 mmol) and toluene (300 mL) were added to a nitrogen-purged recovery flask (1 L) and stirred at 50 °C to dissolve. Separately, sodium hydride (55%, dispersed in liquid paraffin, 4.370 g, 100.2 mmol) and toluene (150 mL) were added to a nitrogen-purged four-neck flask (1 L). Diethyl cyanomethylphosphonate (16.0 mL, 17.7 g, 15.7 mmol) was added dropwise at 0 °C and stirred at room temperature for 10 minutes. The intermediate a3-3 / toluene solution was added dropwise at 0 °C over 15 minutes and stirred for 1 hour. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with water and saturated brine, dried over sodium sulfate, and concentrated to obtain crude intermediate a3-4 (31.34 g, E / Z = 84 / 16). This crude product was used directly in the next reaction. E-isomer: 1H NMR(CDCl3,300MHz)δ8.03(1H,s),7.82(1H,s),7.47(1H,d,J=16.7Hz),5.81(1H,d,J=16.7Hz),4.42(2H,q,J=7.1Hz),1.42(3H,t,J=7.1Hz).Z body: 1 H NMR(CDCl3,300MHz)δ8.58(1H,s),8.00(1H,s),7.14(1H,d,J=11.8Hz),5.54(1H,d,J=11.8Hz),4.40(2H,q,J=7.1Hz),1.41(3H,t,J=7.2Hz).

[0212] <Step 5> The crude product of intermediate a3-4 (31.34 g), THF (150 mL), ethanol (150 mL), and aqueous sodium hydroxide (1.0 M, 125 mL, 125 mmol) were added to a nitrogen-purged recovery flask (1 L), and the mixture was heated and stirred at 40°C for 30 minutes. After completion of the reaction, hydrochloric acid (1 M, 135 mL, 135 mmol) was added at 0°C to terminate the reaction. The organic solvent was distilled off, and the mixture was filtered through a hydrophilic membrane filter. The residue was washed with water, water / methanol (1 / 1), and hexane, and then water was removed by azeotropy with toluene to obtain intermediate a3-5 (19.32 g, 99% yield, E / Z=86 / 14). E-isomer: 1 H NMR(DMSO-d6,300MHz)δ13.46(1H,brs),8.39(1H,s),8.20(1H,s),7.84(1H,d,J=16.7Hz),6.05(1H,d,J=16.7).Z body: 1 H NMR(DMSO-d6,300MHz)δ13.46(1H,brs),8.58(1H,s),8.17(1H,s),7.50(1H,d,J=11.8Hz),5.97(1H,d,J=11.8).

[0213] <Step 6> Intermediate a3-5 (25.03 g, 106.4 mmol), toluene (500 mL), triethylamine (30.0 mL, 215 mmol), and diphenylphosphoryl azide (32.17 g, 116.9 mmol) were added to a nitrogen-purged recovery flask (1 L) and heated with stirring at 60°C for 30 minutes. After the reaction was completed, the reaction solution was transferred to a separatory funnel, washed with saturated aqueous sodium bicarbonate, extracted with ethyl acetate, washed with saturated aqueous sodium bicarbonate and water, and then the organic layer was concentrated. The resulting solid was washed with hexane and dried in vacuo to obtain intermediate a3-6 (26.47 g, >99% yield, E / Z=88 / 12). E isomer: 1 H NMR(DMSO-d6,400MHz)δ8.51(1H,s),8.40(1H,s),7.86(1H,d,J=16.9Hz),6.10(1H,d,J=16.9Hz).Z body: 1 H NMR(DMSO-d6,400MHz)δ8.70(1H,s),8.36(1H,s),7.54(1H,d,J=12.0Hz),6.01(1H,d,J=11.7Hz).

[0214] <Step 7> Intermediate a3-6 (6.614 g, 28.47 mmol), dioxane (1.00 L), and water (500 mL) were added to a nitrogen-purged recovery flask (2 L) and heated to reflux at 120°C for 2 hours. After the reaction was completed, the solvent was distilled off, the residue was dissolved in THF, and the mixture was filtered through base-treated silica gel. The solvent was distilled off and the residue was dried in vacuo to obtain intermediate a3-7 (4.12 g, 70% yield, 91% purity, E / Z=94 / 6). E-isomer: 1 H NMR(DMSO-d6,300MHz)δ7.67(1H,d,J=16.6Hz),7.66(1H,s),6.23(1H,s),6.07(2H,s),5.71(1H,d,J=16.9Hz).Z body: 1 H NMR(DMSO-d6,300MHz)δ7.82(1H,s),7.26(1H,d,J=11.7Hz),6.19(1H,s),6.02(2H,s),5.80(1H,d,J=11.7Hz).

[0215] <Step 8> Intermediate a3-7 (2.504 g, 12.14 mmol), 2-ethylhexanal (7.697 g, 60.03 mmol), methanol (120 mL), and acetic acid (60 mL) were added to a nitrogen-purged recovery flask (500 mL). 2-Picoline borane (2.603 g, 24.10 mmol) was added at 0 ° C. and stirred for 30 minutes, then stirred at room temperature for an additional 3 hours. After the reaction was completed, the solvent was removed under reduced pressure, extracted with ethyl acetate, washed with saturated sodium bicarbonate water, dried over magnesium sulfate, concentrated, and then purified by silica gel column chromatography (hexane:dichloromethane = 80:20) to obtain intermediate a3-8 (3.50 g, 67% yield). 1 H NMR(CDCl3,300MHz)δ:7.39(1H,d,J=16.5Hz),7.23(1H,s),6.03(1H,s),5.64(1H,d,J=16 .5Hz),3.16(4H,d,J=7.5Hz),1.93-1.73(2H,m),1.47-1.22(16H,m),1.02-0.83(12H,m).

[0216] <Step 9> Intermediate a3-8 (13.20 g, 30.64 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (5.327 g, 46.70 mmol), trimethyl orthoformate (33.2 g, 313 mmol), and 1-propanol (1.50 L) were added to a nitrogen-purged recovery flask (2 L) and heated to reflux at 80 °C for 1.5 hours. After the reaction was completed, the solvent was concentrated to approximately half its original volume, and hexane was added to cause reprecipitation. NIR dye (A1-3) (10.93 g, 76% yield) was obtained by silica gel chromatography (dichloromethane:ethyl acetate = 50:1). 1 H NMR(CDCl3,300MHz)δ9.33(2H,d,J=16.5Hz),6.17(2H,s),5.75(2H,d,J=16.5Hz), 3.37(8H,d,J=7.1Hz),2.01-1.88(4H,m),1.47-1.23(32H,m),1.01-0.87(24H,m).

[0217] [Example 4] Preparation of NIR dye (A1-4) The NIR dye (A1-4) was synthesized according to the reaction pathway shown below.

[0218] [ka]

[0219] <Steps 1-2> Intermediate a1-2 was obtained by steps similar to steps 1 and 2 of the production method for NIR dye (A1-1).

[0220] <Step 3> Intermediate a1-2 (83.66 g, 272.9 mmol), THF (175 mL), ethanol (175 mL), and aqueous sodium hydroxide (1.0 M, 430 mL, 430 mmol) were added to a nitrogen-purged recovery flask (2 L) and stirred at 40°C for 1 hour. After the reaction was completed, the mixture was acidified by adding hydrochloric acid (1.0 M, 450 mL) at 0°C. The organic solvent was removed under reduced pressure, and the mixture was filtered using a hydrophilic membrane filter. The residue was washed with water and then with a water:methanol (1:1) mixed solvent. The solvent was removed by azeotropic distillation with toluene, and the mixture was dried under vacuum to obtain intermediate a4-3 (79.4 g, >99% yield). 1 H NMR (DMSO-d6, 300MHz) δ13.51(1H,brs),8.23(1H,s),8.08(1H,s).

[0221] <Step 4> Intermediate a4-3 (26.53 g, 100.8 mmol), toluene (200 mL), triethylamine (21.0 mL, 151 mmol), and diphenylphosphoryl azide (30.62 g, 111.3 mmol) were added to a nitrogen-purged recovery flask (300 mL), and the mixture was heated and stirred at 60° C. for 30 minutes. After the reaction was completed, saturated aqueous sodium bicarbonate and ethyl acetate were added at 0° C. and the layers were separated. The resulting organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated brine, dried over sodium sulfate, concentrated, washed with hexane, and then vacuum-dried to obtain intermediate a4-4 (25.24 g, 96% yield). 1 H NMR(CDCl3,400MHz)δ8.05(1H,s),7.55(1H,s).

[0222] <Step 5> Intermediate a4-4 (12.01 g, 46.19 mmol), t-butyl alcohol (100 mL), and toluene (100 mL) were added to a nitrogen-purged recovery flask (500 mL) and heated with stirring for 15 hours at 80° C. After the reaction was completed, the mixture was concentrated, dissolved in dichloromethane, filtered through silica gel, the solvent was distilled off, and the mixture was dried in vacuo to obtain intermediate a4-5 (12.21 g, 79% yield). 1 H NMR (DMSO-d6, 300MHz) δ10.80(1H,s),7.50(1H,s),6.92(1H,s),1.49(9H,s).

[0223] <Steps 6-7> Intermediate a4-5 (12.20 g, 36.49 mmol), sodium iodide (11.00 g, 73.40 mmol), and acetonitrile (370 mL) were added to a nitrogen-purged recovery flask (1 L), and chlorotrimethylsilane (7.776 g, 71.58 mmol) was added at 40 °C. After heating and stirring for 16.5 hours, saturated aqueous sodium bicarbonate and ethyl acetate were added at room temperature and the layers were separated. The organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated brine. 2-Ethylhexanal (7.021 g, 54.76 mmol) and sodium sulfate were added to the resulting organic layer, and the mixture was allowed to stand for 15 minutes. The mixture was then filtered and the solvent was evaporated. The resulting mixture was transferred to a four-neck flask (1 L), and methanol (270 mL), acetic acid (37 mL), and 2-ethylhexanal (14.05 g, 109.6 mmol) were added. The mixture was stirred under a nitrogen atmosphere at -10 °C, and a solution of 2-picoline borane (7.900 g, 71.65 mmol) in methanol (100 mL) was added dropwise over 10 minutes. After stirring for 19 hours, saturated aqueous sodium bicarbonate, hexane, and ethyl acetate were added and the mixture was separated. The resulting organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated brine, dried over sodium sulfate, and concentrated to obtain the crude product. The starting aldehyde was removed by NH2 silica gel filtration, and intermediate a4-7 (12.01 g, 72% yield) was obtained by silica gel column chromatography (100% hexane). 1 H NMR(CDCl3,300MHz)δ6.98(1H,s),6.14(1H,s),3.13(4H,d,J=7.5Hz),1.91-1.75(2H,m),1.45-1.21(16H,m),1.00-0.82(12H,m).

[0224] <Step 8> Intermediate a4-7 (458.6 mg, 1.000 mmol), diethylamine (1.0 mL, 7.1 mmol), copper iodide (4.2 mg, 0.022 mmol), bis(triphenylphosphine)palladium(II) dichloride (7.4 mg, 0.011 mmol), triisopropylsilylacetylene (0.24 mL, 1.1 mmol), and THF (1.0 mL) were added to a nitrogen-purged microwave test tube and stirred at 120 °C for 1 hour under microwave irradiation. After completion of the reaction, the mixture was extracted with ethyl acetate, concentrated, and then purified by silica gel column chromatography (hexane 100%) to obtain intermediate a4-8 (540 mg, 89% purity, 86% yield) as a mixture with the starting triisopropylsilylacetylene. 1 H NMR(CDCl3,300MHz)δ7.11(1H,s),5.98(1H,s),3.17-3.06(4H,m),1.90-1.74(2H,m),1.37-1.23(16H,m),1.20-1.04(21H,m),0.93-0.84(12H,m).

[0225] <Step 9> Intermediate a4-8 (62.3 mg, 98.7 μmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (17.1 mg, 0.150 mmol), trimethyl orthoformate (0.11 mL, 1.0 mmol), and 1-propanol (67 mL) were added to a nitrogen-purged screw-cap test tube and heated to reflux at 80°C for 1 hour. After the reaction was completed, saturated aqueous sodium bicarbonate was added at 0°C, followed by extraction with ethyl acetate, washing with saturated brine, drying over magnesium sulfate, concentration, and silica gel chromatography (hexane:ethyl acetate = 80:20) to obtain NIR dye (A1-4) (0.5 mg, yield 0.8%). 1 H NMR(CDCl3,300MHz)δ5.99(2H,s),3.35-3.25(8H,m),1.97-1.86(4H,m),1.39-1.15(62H,m),0.97-0.78(24H,m).

[0226] [Example 5] Preparation of NIR dye (A1-5) The NIR dye (A1-5) was synthesized according to the reaction pathway shown below.

[0227] [ka]

[0228] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0229] <Step 8> Intermediate a4-7 (2.282 g, 4.976 mmol), N,N-dimethylacrylamide (0.780 mL, 7.60 mmol), triethylamine (2.09 mL, 15.0 mmol), palladium(II) acetate (58.1 mg, 0.259 mmol), triorthotolylphosphine (154.8 mg, 0.5086 mmol), and DMF (25.0 mL) were added to a nitrogen-purged three-neck flask (100 mL) and stirred at 100 °C for 1 hour. After completion of the reaction, saturated aqueous ammonium chloride solution was added at 0 °C, extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 50:50) to give intermediate a5-8 (917.2 mg, 39% yield). 1 H NMR(CDCl3,300MHz)δ7.69(1H,d,J=15.2Hz),7.21(1H,s),6.70(1H,d,J=15.2Hz),6.07(1H,s),3.21 (3H,s),3.19-3.12(4H,m),3.09(3H,s),1.91-1.77(2H,m),1.46-1.21(16H,m),0.95-0.83(12H,m).

[0230] <Step 9> Intermediate a5-8 (559.9 mg, 1.205 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (200.1 mg, 1.754 mmol), trimethyl orthoformate (1.267 g, 11.94 mmol), and 1-propanol (60 mL) were added to a nitrogen-purged recovery flask (100 mL) and heated to reflux at 80 °C for 2.5 hours. After the reaction was completed, hexane was added at 0 °C and the crude product was reprecipitated. This was then purified by silica gel column chromatography (dichloromethane:methanol:triethylamine = 30:2:1) to obtain NIR dye (A1-5) (390.0 mg, 63% yield). 1 H NMR(CDCl3,300MHz)δ9.12(2H,d,J=16.1Hz),6.68(2H,d,J=16.1Hz),6.11(2H,s),3.34(8H,d,J =6.6Hz),3.25(6H,s),3.11(6H,s),1.97-1.87(4H,m),1.41-1.24(32H,m),0.97-0.85(24H,m).

[0231] [Example 6] Preparation of NIR dye (A1-6) The NIR dye (A1-6) was synthesized according to the reaction pathway shown below.

[0232] [ka]

[0233] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0234] <Step 8> Intermediate a4-7 (2.281 g, 4.974 mmol), t-butyl acrylate (1.10 mL, 7.48 mmol), triethylamine (2.09 mL, 15.0 mmol), palladium(II) acetate (57.9 mg, 0.258 mmol), triorthotolylphosphine (153.3 mg, 0.5037 mmol), and DMF (25.0 mL) were added to a nitrogen-purged three-neck flask (100 mL) and stirred at 100 °C for 1 hour. After completion of the reaction, saturated aqueous ammonium chloride solution was added at 0 °C, extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 80:20) to obtain intermediate a6-8 (1.035 g, 41% yield). 1 H NMR(CDCl3,400MHz)δ7.60(1H,d,J=15.9Hz),7.20(1H,s),6.14(1H,d,J=15.7Hz),6.04(1H,s ),3.21-3.09(4H,m),1.89-1.78(2H,m),1.54(9H,s),1.44-1.22(16H,m),0.94-0.84(12H,m).

[0235] <Step 9> Intermediate a6-8 (1.090 g, 2.155 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (372.3 mg, 3.264 mmol), trimethyl orthoformate (2.306 g, 21.73 mmol), and 1-propanol (110 mL) were added to a nitrogen-purged recovery flask (200 mL) and heated to reflux at 80 °C for 3 hours. After completion of the reaction, the solvent was distilled off, and NIR dye (A1-6) (360.0 mg, 31% yield) was obtained by silica gel column chromatography (hexane:ethyl acetate = 5:1). 1 H NMR(CDCl3,400MHz)δ9.52(2H,d,J=15.9Hz),6.23(2H,d,J=15.9Hz),6.12(2H,s),3.42 -3.27(8H,m),1.99-1.88(4H,m),1.63(18H,s),1.44-1.24(32H,m),0.95-0.87(24H,m).

[0236] [Example 7] Preparation of NIR dye (A1-7) The NIR dye (A1-7) was synthesized according to the reaction pathway shown below.

[0237] [ka]

[0238] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0239] <Step 8> Intermediate a4-7 (2.005 g, 4.372 mmol), isobutyl acrylate (859.6 mg, 6.707 mmol), triethylamine (1.365 g, 13.49 mmol), palladium(II) acetate (49.3 mg, 0.220 mmol), triorthotolylphosphine (131.9 mg, 0.4334 mmol), and DMF (25.0 mL) were added to a nitrogen-purged two-neck flask (50 mL), and the mixture was heated and stirred at 80°C for 2 hours, followed by heating and stirring at 115°C for 4 hours. The same amounts of the reagents as above except for intermediate a4-7 were added, and the mixture was heated and stirred at 100°C for 1.5 hours. After the reaction was completed, saturated aqueous ammonium chloride solution was added at 0°C, and the mixture was extracted with ethyl acetate. The resulting organic layer was washed with water and saturated brine, dried over sodium sulfate, and concentrated. Intermediate a7-8 (713.1 mg, 32% yield) was obtained by silica gel column chromatography (hexane:ethyl acetate=30:1). 1 H NMR(CDCl3,300MHz)δ7.70(1H,d,J=15.8Hz),7.24(1H,s),6.23(1H,d,J=15.8Hz),6.04(1H,s),4.00(2H,d,J=6.6Hz),3 .24-3.08(4H,m),2.08-1.99(1H,m),1.91-1.78(2H,m),1.45-1.23(16H,m),1.00(6H,d,J=6.6Hz),0.94-0.85(12H,m).

[0240] <Step 9> Intermediate a7-8 (713.0 mg, 1.410 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (242.6 mg, 2.127 mmol), trimethyl orthoformate (1.880 g, 17.70 mmol), and 1-propanol (70 mL) were added to a nitrogen-purged recovery flask (100 mL) and refluxed at 80 °C for 2 hours. After the reaction was completed, saturated aqueous sodium bicarbonate was added and the mixture was extracted with ethyl acetate. The resulting organic layer was washed with water and saturated brine, dried over sodium sulfate, and concentrated. Hexane was added and the resulting solid was filtered off. The resulting solid was purified by silica gel column chromatography (dichloromethane:ethyl acetate = 40:1) to obtain NIR dye (A1-7) (420.0 mg, 55% yield). 1 H NMR(CDCl3,300MHz)δ9.56(2H,d,J=16.1Hz),6.32(2H,d,J=15.8Hz),6.13(2H,s),4.08(4H,d,J=6.6Hz),3.40-3. 31(8H,m),2.28-2.06(2H,m),2.01-1.86(4H,m),1.45-1.25(32H,m),1.08(12H,d,J=6.6Hz),0.99-0.87(24H,m).

[0241] [Example 8] Preparation of NIR dye (A1-8) The NIR dye (A1-8) was synthesized according to the reaction pathway shown below.

[0242] [ka]

[0243] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0244] <Step 8> Intermediate a4-7 (2.576 g, 4.999 mmol) and THF (10 mL) were placed in a nitrogen-purged two-neck flask (100 mL), and n-butyllithium (hexane solution, 1.55 M, 6.45 mL, 10.0 mmol) was added at -78 °C. After stirring for 5 minutes, DMF (1.55 mL, 20.0 mmol) was added and stirred for 30 minutes, followed by further stirring at 0 °C for 30 minutes. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated, and then purified by silica gel column chromatography (hexane:ethyl acetate = 98:2) to obtain intermediate a8-8 (1.52 g, 75% yield). 1 H NMR(CDCl3,400MHz)δ9.88(1H,s),7.77(1H,s),5.97(1H,s),3.18(4H,d,J=7.3Hz),1.92-1.81(2H,m),1.43-1.28(16H,m),0.90-0.87(12H,m).

[0245] <Step 9> Sodium hydride (60%, dispersed in liquid paraffin, 147.8 mg, 3.695 mmol) and THF (20 mL) were added to a nitrogen-purged three-neck flask (300 mL). Triethyl phosphonoacetate (0.830 mL, 4.20 mmol) was added at 0 °C and stirred at room temperature for 10 minutes. After that, a solution of intermediate a8-8 (1.227 g, 3.009 mmol) in THF (10 mL) was added at 0 °C and stirred for 30 minutes. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 95:5) to obtain intermediate a8-9 (1.44 g, >99% yield). 1 H NMR(CDCl3,300MHz)δ7.70(1H,d,J=15.8Hz),7.24(1H,s),6.22(1H,d,J=16.1Hz),6.04(1H,s),4. 28(2H,q,J=7.1Hz),3.23-3.07(4H,m),1.91-1.75(2H,m),1.45-1.21(19H,m),0.94-0.84(12H,m).

[0246] <Step 10> Intermediate a8-9 (474.4 mg, 0.9929 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (172.0 mg, 1.508 mmol), trimethyl orthoformate (1.10 mL, 10.0 mmol), and 1-propanol (50 mL) were added to a nitrogen-purged three-neck flask (200 mL) and stirred at 80 °C for 1 hour. After the reaction was completed, saturated aqueous sodium bicarbonate was added at 0 °C, extracted with ethyl acetate, washed with saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 60:40) to obtain NIR dye (A1-8) (308.1 mg, 60% yield). 1 H NMR(CDCl3,300MHz)δ9.58(2H,d,J=15.8Hz),6.31(2H,d,J=15.8Hz),6.13(2H,s),4.37(4H,q ,J=6.6Hz),3.35(8H,d,J=6.0Hz),1.99-1.87(4H,m),1.53-1.19(38H,m),1.03-0.80(24H,m).

[0247] [Example 9] Preparation of NIR dye (A1-9) The NIR dye (A1-9) was synthesized according to the reaction pathway shown below.

[0248] [ka]

[0249] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0250] <Step 8> Intermediate a4-7 (1.994 g, 4.349 mmol), methyl acrylate (560.4 mg, 6.509 mmol), triethylamine (1.300 g, 12.84 mmol), palladium(II) acetate (49.9 mg, 0.222 mmol), triorthotolylphosphine (132.8 mg, 0.4363 mmol), and DMF (25.0 mL) were added to a nitrogen-purged two-neck flask (50 mL) and stirred at 85 °C for 3 hours. After the reaction was completed, saturated aqueous ammonium chloride solution was added at 0 °C, extracted with hexane / ethyl acetate, washed with water and saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 20:1) to obtain intermediate a9-8 (461.9 mg, 23% yield). 1 H NMR(CDCl3,300MHz)δ7.71(1H,d,J=16.1Hz),7.24(1H,s),6.23(1H,d,J=15.8Hz),6.0 4(1H,s),3.82(3H,s),3.15(4H,d,J=7.3Hz),1.47-1.21(16H,m),0.96-0.83(12H,m).

[0251] <Step 9> Intermediate a9-8 (461.9 mg, 0.996 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (172.2 mg, 1.509 mmol), trimethyl orthoformate (1.279 g, 12.05 mmol), and 1-propanol (50 mL) were added to a nitrogen-purged recovery flask (100 mL) and stirred at 80 °C for 1.5 hours. After the reaction was completed, the mixture was concentrated to approximately half its volume, and hexane, ethyl acetate, and saturated aqueous sodium bicarbonate were added to separate the layers. The resulting organic layer was washed with water, dried over sodium sulfate, concentrated, and washed with hexane. The resulting solid was purified by silica gel column chromatography (dichloromethane:ethyl acetate = 30:1) to obtain NIR dye (A1-9) (345.5 mg, 69% yield). 1H NMR(CDCl3,300MHz)δ9.57(2H,d,J=14.3Hz),6.32(2H,d,J=16.1Hz),6.13(2H,s),3.94( 6H,s),3.35(8H,d,J=7.1Hz),2.00-1.87(4H,m),1.48-1.23(32H,m),1.01-0.85(24H,m).

[0252] [Example 10] Preparation of NIR dye (A1-10) The NIR dye (A1-10) was synthesized according to the reaction pathway shown below.

[0253] [ka]

[0254] <Steps 1-8> Intermediate a8-8 was obtained by steps similar to steps 1 to 8 of the NIR dye (A1-8) production method.

[0255] <Step 9> Intermediate a8-8 (206.2 mg, 0.5058 mmol), ethyl cyanoacetate (66.1 mg, 0.584 mmol), piperidine (0.010 mL, 0.10 mmol), and ethanol (5.0 mL) were added to a nitrogen-purged screw-cap test tube and stirred for 3 hours at 60° C. After the reaction was completed, the mixture was concentrated and purified by silica gel chromatography (hexane:ethyl acetate=98:2) to give intermediate 10-9 (203.2 mg, 80% yield). 1 H NMR(CDCl3,300MHz)δ8.32(1H,s),8.13(1H,s),6.00(1H,s),4.38(2H,q,J=7.1Hz),3.15(4H,d ,J=7.3Hz),1.93-1.78(2H,m),1.44-1.23(16H,m),1.40(3H,t,J=7.1Hz),0.98-0.86(12H,m).

[0256] <Step 10> Intermediate a10-9 (192.8 mg, 0.3835 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (132.6 mg, 1.163 mmol), trimethyl orthoformate (0.88 mL, 8.0 mmol), and 1-propanol (20 mL) were added to a nitrogen-purged recovery flask (100 mL) and heated to reflux at 80 °C for 4 hours. After the reaction was completed, saturated aqueous sodium bicarbonate was added at 0 °C, followed by extraction with ethyl acetate, washing with saturated brine, drying over magnesium sulfate, and concentration. NIR dye (A1-10) (4.8 mg, 3% yield) was obtained by silica gel chromatography (hexane:ethyl acetate = 80:20). 1 H NMR(CDCl3,300MHz)δ9.84(2H,s),6.16(2H,s),4.45(4H,q,J=7.1Hz),3.37(8H,d,J=7. 1Hz),1.98-1.87(4H,m),1.45(6H,t,J=7.1Hz),1.42-1.19(32H,m),0.98-0.82(24H,m).

[0257] [Example 11] Preparation of NIR dye (A1-11) The NIR dye (A1-11) was synthesized according to the reaction pathway shown below.

[0258] [ka]

[0259] <Steps 1-8> Intermediate a8-8 was obtained by steps similar to steps 1 to 8 of the NIR dye (A1-8) production method.

[0260] <Step 9> Intermediate a8-8 (203.5 mg, 0.4991 mmol), malononitrile (33.7 mg, 0.510 mmol), piperidine (0.010 mL, 0.10 mmol), and ethanol (5.0 mL) were added to a nitrogen-purged screw-cap test tube and stirred at 60° C. for 1 hour. After the reaction was completed, the mixture was concentrated and purified by silica gel chromatography (hexane:ethyl acetate=98:2) to give intermediate a11-9 (155.3 mg, 68% yield). 1H NMR(CDCl3,300MHz)δ8.24(1H,s),7.64(1H,s),5.98(1H,s),3.16(4H,d,J=7.3Hz),1.92-1.77(2H,m),1.44-1.21(16H,m),0.97-0.83(12H,m).

[0261] <Step 10> Intermediate a11-9 (146.9 mg, 0.3224 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (84.5 mg, 0.741 mmol), trimethyl orthoformate (0.55 mL, 5.0 mmol), and 1-propanol (25 mL) were added to a nitrogen-purged screw-cap test tube and heated to reflux at 80 °C for 1 hour. After the reaction was completed, saturated aqueous sodium bicarbonate was added at 0 °C, followed by extraction with ethyl acetate, washing with saturated brine, drying over magnesium sulfate, concentration, and silica gel chromatography (hexane:ethyl acetate = 80:20) to obtain NIR dye (A1-11) (4.8 mg, 3% yield). 1 H NMR(CDCl3,300MHz)δ9.61(2H,s),6.21(2H,s),3.40(8H,d,J=7.3Hz),1.99-1.87(4H,m),1.38-1.24(32H,m),0.96-0.86(24H,m).

[0262] [Example 12] Preparation of NIR dye (B1) The NIR dye (B1) was synthesized according to the reaction pathway shown below.

[0263] [ka]

[0264] <Step 1> 4-Bromo-2-thiophenecarboxylic acid (25.21 g, 121.8 mmol), toluene (300 mL), triethylamine (25 mL, 179 mmol), and diphenylphosphoryl azide (36.54 g, 132.8 mmol) were added to a nitrogen-purged recovery flask (1 L) and stirred at 65°C for 1.5 hours. After the reaction was completed, saturated aqueous sodium bicarbonate and toluene were added at 0°C and the mixture was separated. The resulting organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated brine, dried over sodium sulfate, filtered through silica gel, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 10:1) to obtain intermediate b1-1 (25.8 g, >99% yield). 1 H NMR(CDCl3,400MHz)δ7.73(1H,d,J=1.2Hz),7.55(1H,d,J=1.5Hz).

[0265] <Step 2> Intermediate b1-1 (13.75 g, 67.39 mmol) and t-butyl alcohol (300 mL) were placed in a nitrogen-purged recovery flask (1 L) and heated with stirring at 95° C. for 16.5 hours. The reaction solution was concentrated, then dissolved in dichloromethane and filtered. The filtrate was concentrated and dried in vacuo to obtain intermediate b1-2 (15.6 g, 83% yield). 1 H NMR(DMSO-d6,300MHz)δ10.65(1H,s),6.99(1H,d,J=1.7Hz),6.43(1H,d,J=1.7Hz),1.47(9H,s).

[0266] <Step 3> Intermediate b1-2 (14.99 g, 57.19 mmol), sodium iodide (16.28 g, 108.6 mmol), and acetonitrile (500 mL) were added to a nitrogen-purged recovery flask (1 L), and chlorotrimethylsilane (11.61 g, 106.9 mmol) was added at 50 °C. After heating and stirring for 4.5 hours, saturated aqueous sodium bicarbonate and toluene were added at room temperature and the mixture was separated. The organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated brine, and dried over sodium sulfate. Hydrochloric acid (1.0 M, 80 mL, 80 mmol) was added to the mixture and stirred at room temperature for 30 minutes. The precipitated solid was collected by suction filtration and dried in vacuo to obtain intermediate b1-3 (11.6 g, >99% yield).1 H NMR(DMSO-d6,300MHz)δ6.96(1H,s),6.31(1H,s),5.90(3H,brs).

[0267] <Step 4> A nitrogen-purged recovery flask (500 mL) was charged with intermediate b1-3 (5.984 g, 27.89 mmol), sodium acetate (3.511 g, 42.80 mmol), methanol (140 mL), acetic acid (30 mL), and 2-ethylhexanal (10.80 g, 99.78 mmol). A solution of 2-picoline borane (6.009 g, 56.18 mmol) in methanol (140 mL) was added at 0 °C, and the mixture was stirred for 30 minutes and then at room temperature for an additional 19 hours. After the reaction was complete, water and hexane were added, and the organic layer was separated. The organic layer was washed with water, saturated sodium bicarbonate water, and saturated brine, dried over sodium sulfate, concentrated, and purified by silica gel column chromatography (100% hexane) to obtain intermediate b1-4 (8.18 g, 73% yield). 1 H NMR(CDCl3,300MHz)δ6.44(1H,d,J=1.5Hz),5.73(1H,d,J=1.3Hz),3.07(4H,d,J=7.2Hz),1.85-1.71(2H,m),1.40-1.18(16H,m),0.94-0.82(12H,m).

[0268] <Step 5> Intermediate b1-4 (501.3 mg, 1.24 mmol), N,N-dimethylacrylamide (198.3 mg, 2.00 mmol), N,N-diisopropylethylamine (0.650 mL, 3.73 mmol), palladium(II) acetate (15.3 mg, 68.2 μmol), triorthotolylphosphine (38.9 mg, 0.128 mmol), and DMF (10.0 mL) were added to a nitrogen-purged two-neck flask (50 mL) and stirred at 60 °C for 64 h. After completion of the reaction, saturated aqueous ammonium chloride solution was added at 0 °C, and the mixture was extracted with hexane / ethyl acetate. The resulting organic layer was washed with water and saturated brine, dried over sodium sulfate, concentrated, and purified by alumina column chromatography (hexane:ethyl acetate:triethylamine = 8:2:1 to 6:2:1) to obtain intermediate b1-5 (112.8 mg, 22% yield).1 H NMR (CDCl3,300MHz) δ7.46(1H,d,J=15.2Hz), 6.61(1H,d,J=1.5Hz), 6.52(1H,d,J=15.2Hz), 5.95(1H,d,J=1.5 Hz), 3.17-3.02(4H,m), 3.14(3H,s), 3.05(3H,s), 1.88-1.72(2H,m), 1.42-1.18(16H,m), 0.95-0.81(12H,m).

[0269] <Step 6> Intermediate b1-5 (112.8 mg, 0.268 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (46.2 mg, 0.405 mmol), trimethyl orthoformate (301.6 mg, 2.84 mmol), and 1-propanol (15 mL) were added to a nitrogen-purged recovery flask (30 mL) and heated to reflux at 80°C for 2 hours. After the reaction was completed, saturated aqueous sodium bicarbonate was added at room temperature, followed by extraction with hexane / ethyl acetate, washing with water and saturated brine, drying over sodium sulfate, concentration, and washing with hexane to obtain NIR dye (B1) (70.0 mg, 56% yield). 1 H NMR(CDCl3,300MHz)δ8.69(2H,d,J=16.3Hz),6.58(2H,d,J=16.1Hz),6.42(2H,s),3.36(8H,d,J =7.5Hz),3.24(6H,s),3.08(6H,s),1.98-1.85(4H,m),1.43-1.21(32H,m),0.98-0.83(24H,m).

[0270] [Example 13] Preparation of NIR dye (B2) The NIR dye (B2) was synthesized according to the reaction pathway shown below.

[0271] [ka]

[0272] <Steps 1-4> Intermediate b1-4 was obtained by steps similar to steps 1 to 4 of the NIR dye (B1) production method.

[0273] <Step 5> Intermediate b1-4 (6.09 g, 15.1 mmol) and THF (30 mL) were added to a nitrogen-purged two-neck flask (500 mL), and n-butyllithium (hexane solution, 1.55 M, 20.0 mL, 31.0 mmol) was added at -78 ° C. After stirring for 10 minutes, DMF (4.80 mL, 62.0 mmol) was added and stirred for 50 minutes, and then stirred at 0 ° C. for an additional 2.5 hours. After the reaction was completed, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with saturated brine, dried over sodium sulfate, concentrated, and then purified by silica gel column chromatography (hexane: ethyl acetate = 15:1) to obtain intermediate b2-5 (3.97 g, 75% yield). 1 H NMR(CDCl3,300MHz)δ9.64(1H,s),7.23(1H,d,J=1.5Hz),6.16(1H,d,J=1.5Hz),3 .12(4H,d,J=7.3Hz),1.88-1.73(2H,m),1.49-1.17(16H,m),1.02-0.78(12H,m).

[0274] <Step 6> Sodium hydride (60%, dispersed in liquid paraffin, 0.545 g, 13.6 mmol) and THF (50 mL) were added to a nitrogen-purged three-neck flask (300 mL). Triethyl phosphonoacetate (3.047 g, 13.6 mmol) was added at 0 ° C. and stirred at room temperature for 15 minutes. After that, a solution of intermediate b2-5 (3.97 g, 11.3 mmol) in THF (60 mL) was added at -40 ° C. and stirred for 2 hours. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with saturated brine, dried over sodium sulfate, concentrated, and then purified by silica gel column chromatography (hexane: ethyl acetate = 15:1) to obtain intermediate b2-6 (3.73 g, 81% yield). 1H NMR(CDCl3,300MHz)δ7.46(1H,d,J=15.8Hz),6.64(1H,d,J=1.1Hz),6.07(1H,d,J=15.8Hz),5.95(1H,d,J=1.3 Hz),4.24(2H,q,J=7.1Hz),3.10(4H,d,J=7.3Hz),1.90-1.70(2H,m),1.44-1.20(19H,m),0.98-0.83(12H,m).

[0275] <Step 7> Intermediate b2-6 (3.73 g, 9.19 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (1.57 g, 13460.8 mmol), trimethyl orthoformate (9.85 g, 92.8 mmol), and 1-propanol (50 mL) were added to a nitrogen-purged recovery flask (1 L) and heated with stirring at 80 °C for 1.5 hours. After the reaction was completed, the solvent was concentrated to approximately one-third of its original volume, and hexane was added to cause reprecipitation. The NIR dye (B2) was purified by silica gel column chromatography (dichloromethane: ethyl acetate = 15:1) to obtain 2.98 g (71% yield). 1 H NMR(CDCl3,300MHz)δ9.23(2H,d,J=15.8Hz),6.43(2H,s),6.28(2H,d,J=15.8Hz),4.32(4H,q,J=7.0 Hz),3.36(8H,d,J=7.1Hz),2.05-1.81(4H,m),1.51-1.17(38H,m),1.02-0.80(24H,m).

[0276] [Example 14] Preparation of NIR dye (B3) The NIR dye (B3) was synthesized according to the reaction pathway shown below.

[0277] [ka]

[0278] <Steps 1-5> Intermediate b1-4 was obtained by steps similar to steps 1 to 5 of the NIR dye (B2) production method.

[0279] <Step 6> Sodium hydride (60%, dispersed in liquid paraffin, 78.2 mg, 1.96 mmol) and THF (5 mL) were added to a nitrogen-purged two-neck flask (50 mL). Diethyl cyanomethylphosphonate (297.9 mg, 1.68 mmol) was added at 0 ° C. and stirred at room temperature for 10 minutes. After that, a solution of intermediate b2-5 (562.1 mg, 1.60 mmol) in THF (10 mL) was added at -40 ° C. and stirred for 30 minutes. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with ethyl acetate, washed with saturated brine, dried over sodium sulfate, concentrated, and then purified by silica gel column chromatography (hexane: toluene = 1:1) to obtain intermediate b3-6 (362.5 mg, 61% yield). 1 H NMR(CDCl3,300MHz)δ6.61(1H,d,J=1.3Hz),5.81(1H,d,J=1.5Hz),5.47(1H,d,J=16. 3Hz), 3.21-3.01 (4H, m), 1.88-1.69 (2H, m), 1.44-1.18 (16H, m), 1.00-0.82 (12H, m).

[0280] <Step 7> Intermediate b3-6 (362.5 mg, 0.968 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (162.0 mg, 1.42 mmol), trimethyl orthoformate (1.038 g, 9.78 mmol), and 1-propanol (50 mL) were added to a nitrogen-purged recovery flask (100 mL) and heated with stirring at 80 °C for 1.5 hours. After the reaction was completed, the mixture was returned to room temperature, hexane (50 mL) was added, and the mixture was allowed to stand overnight. The precipitated solid was filtered and purified by silica gel column chromatography (dichloromethane: ethyl acetate = 10:1) to obtain NIR dye (B3) (302.0 mg, 76% yield). 1 H NMR(CDCl3,400MHz)δ9.03(2H,d,J=16.1Hz),6.36(2H,s),5.73(2H,d,J=16.4Hz), 3.38(8H,d,J=7.3Hz),1.96-1.83(4H,m),1.42-1.20(32H,m),0.99-0.84(24H,m).

[0281] [Example 15] Preparation of NIR dye (Acf1) The NIR dye (Acf1) was synthesized according to the reaction pathway shown below.

[0282] [ka]

[0283] <Step 1> Thieno[3,2-b]thiophene (4.00 g, 28.5 mmol) was placed in a flask and dissolved in anhydrous dimethylformamide (28.5 mL) under a nitrogen atmosphere. The solution was cooled to -15 °C, and a solution of N-bromosuccinimide (5.08 g, 28.5 mmol) in anhydrous dimethylformamide (28.5 mL) was added dropwise. The mixture was stirred at room temperature for 30 minutes and then at 60 °C for 5 hours. After the reaction was complete, it was poured into ice water and extracted with diisopropyl ether. The resulting organic layer was washed with saturated brine, and the solvent was removed. The intermediate acf1-1 (5.09 g, 81% yield) was obtained by silica gel column chromatography (hexane).

[0284] <Step 2> A flask was charged with intermediate acf1-1 (2.00 g, 9.13 mmol) and magnesium turnings (0.440 g, 18.3 mmol) and dissolved in anhydrous tetrahydrofuran (13 mL) under a nitrogen atmosphere. 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 and stirred for 20 minutes.

[0285] Tetraisopropyl orthotitanate (2.59 g, 9.13 mmol) was added dropwise to the mixed solution cooled to -40°C and stirred for 5 minutes. A mixed solution of N-chlorosuccinimide and bis-(2-ethylhexyl)amine was then added dropwise. The mixture was stirred at room temperature for 3 hours, and upon completion of the reaction, saturated aqueous potassium carbonate (18 mL) was added. The mixture was then diluted with ethyl acetate and filtered. The resulting solution was extracted with ethyl acetate. The resulting organic layer was washed with saturated brine, the solvent was removed, and intermediate ACF1-2 (0.987 g, 28% yield) was obtained by silica gel column chromatography (hexane:triethylamine = 100:3).

[0286] <Step 3> The intermediate acf1-2 (0.411 g, 1.08 mmol) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.0617 g, 0.541 mmol) were placed in a flask and dissolved in a mixture of n-butanol (3 mL) and toluene (3 mL) under a nitrogen atmosphere. The mixture was refluxed and stirred for 3 hours. After the reaction was complete, the solvent was removed and the NIR dye (Acf1) (0.100 g, 22% yield) was obtained by silica gel chromatography (dichloromethane:methanol = 50:1).

[0287] [Example 16] Preparation of NIR dye (Acf2) The NIR dye (Acf2) was synthesized according to the reaction pathway shown below.

[0288] [ka]

[0289] <Step 1> Zinc bromide (9.00 g, 40.0 mmol) was placed in a flask, and isobutylmagnesium bromide (1.0 M THF solution, 40 mL, 40 mmol) was added at −78° C. under a nitrogen atmosphere, followed by stirring at room temperature for 2 hours.

[0290] A microwave-safe test tube was charged with [1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II) (29.8 mg, 53.8 μmol) and 3-bromothieno[3,2-b]thiophene (2.00 g, 9.13 mmol). Under a nitrogen atmosphere, the above-prepared isobutylzinc bromide (1.0 M THF solution, 13.7 mL, 13.7 mmol) was added and stirred at 150 °C for 30 min under microwave irradiation. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with diethyl ether, washed with 5% hydrochloric acid and saturated brine, dried over magnesium sulfate, and the solvent was removed. The product was purified by silica gel column chromatography (hexane / dichloromethane) to obtain intermediate ACF2-1 (680.8 mg, 38% yield).

[0291] <Step 2> Intermediate ACF2-1 (0.600 g, 3.06 mmol) was placed in a flask and dissolved in anhydrous diethyl ether (6.5 mL) under a nitrogen atmosphere. t-Butyllithium (pentane solution, 1.6 M, 2.00 mL, 3.21 mmol) was added at 0 °C and stirred at room temperature for 1 hour. A solution of iodine (0.81 g, 3.21 mmol) in diethyl ether (11 mL) was added at 0 °C and stirred at room temperature for 1 hour. After the reaction was completed, the mixture was poured into ice water, extracted with diethyl ether, washed with saturated aqueous sodium bicarbonate and saturated brine, dried over magnesium sulfate, and the solvent was removed. The mixture was purified by silica gel column chromatography (100% hexane) to obtain intermediate ACF2-2 (631.2 mg, 64% yield).

[0292] <Step 3> A flask was charged with intermediate acf2-2 (0.630 g, 1.96 mmol), pyrrolidine (0.242 mL, 2.93 mmol), copper powder (12.5 mg, 0.196 mmol), potassium phosphate (0.830 g, 3.92 mmol), and N,N-dimethylaminoethanol (1.96 mL), and the mixture was heated and stirred at 60 °C for 22 hours under a nitrogen atmosphere. After the reaction was completed, water (1.96 mL) was added at room temperature, extracted with diisopropyl ether, dried over magnesium sulfate, and the solvent was removed. The mixture was then purified by silica gel column chromatography to obtain intermediate acf2-3 (0.443 g, 85% yield).

[0293] <Step 4> The intermediate acf2-3 (0.443 g, 1.67 mmol) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (94.7 mg, 0.830 mmol) were placed in a flask, dissolved in a mixture of n-butanol (2.23 mL) and toluene (6.70 mL) under a nitrogen atmosphere, and refluxed for 3 hours. After the reaction was complete, the solvent was removed and purified by silica gel chromatography (dichloromethane:methanol = 95:5) to obtain the NIR dye (Acf2) (0.127 g, 25% yield).

[0294] [Example 17] Preparation of NIR dye (Acf3) The NIR dye (Acf3) was synthesized according to the reaction pathway shown below.

[0295] [ka]

[0296] <Step 1> Zinc bromide (9.00 g, 40.0 mmol) was placed in a flask, and isobutylmagnesium bromide (1.0 M THF solution, 40 mL, 40 mmol) was added at −78° C. under a nitrogen atmosphere, followed by stirring at room temperature for 2 hours.

[0297] A microwave-safe test tube was charged with [1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II) (44.7 mg, 0.055 mmol) and 3-bromothieno[3,2-b]thiophene (3.00 g, 13.7 mmol). Under a nitrogen atmosphere, the above-prepared isobutylzinc bromide (THF solution, 0.50 M, 41.1 mL, 20.6 mmol) was added and stirred at 150 °C for 30 min under microwave irradiation. After completion of the reaction, saturated aqueous ammonium chloride solution was added, extracted with diethyl ether, washed with 5% hydrochloric acid and saturated brine, dried over magnesium sulfate, and the solvent was removed. The resulting mixture was purified by silica gel column chromatography (100% hexane) to give intermediate ACF3-1 (2.66 g, 84% yield).

[0298] <Step 2> Intermediate ACF3-1 (2.65 g, 11.5 mmol) was placed in a flask and dissolved in anhydrous diethyl ether (23.8 mL) under a nitrogen atmosphere. t-Butyllithium (pentane solution, 1.6 M, 7.55 mL, 12.1 mmol) was added at 0 °C and stirred at room temperature for 1 hour. A solution of iodine (3.07 g, 12.1 mmol) in diethyl ether (40.8 mL) was added at 0 °C and stirred at room temperature for 1 hour. After the reaction was completed, the mixture was poured into ice water, extracted with diethyl ether, washed with saturated aqueous sodium bicarbonate and saturated brine, dried over magnesium sulfate, and the solvent was removed. The mixture was purified by silica gel column chromatography (100% hexane) to obtain intermediate ACF3-2 (3.67 g, 90% yield).

[0299] <Step 3> A flask was charged with intermediate acf3-2 (2.00 g, 5.61 mmol), pyrrolidine (0.689 mL, 8.39 mmol), copper powder (35.7 mg, 0.561 mmol), potassium phosphate (2.38 g, 11.2 mmol), and N,N-dimethylaminoethanol (5.61 mL), and the mixture was heated and stirred at 60 °C for 22 hours under a nitrogen atmosphere. After the reaction was completed, water (5.61 mL) was added at room temperature, extracted with diisopropyl ether, dried over magnesium sulfate, and the solvent was removed. The mixture was then purified by silica gel column chromatography to obtain intermediate acf3-3 (1.46 g, 87% yield).

[0300] <Step 4> The intermediate acf3-3 (0.921 g, 3.08 mmol) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (0.175 g, 1.54 mmol) were placed in a flask, dissolved in a mixture of n-butanol (7.5 mL) and toluene (7.5 mL) under a nitrogen atmosphere, and refluxed for 2 hours. After the reaction was complete, the solvent was removed and the NIR dye (Acf3) (48.4 mg, 23% yield) was obtained by silica gel chromatography (dichloromethane:methanol = 95:5).

[0301] [Example 18] Preparation of NIR dye (Acf4) The NIR dye (Acf4) was synthesized according to the reaction pathway shown below.

[0302] [ka]

[0303] <Steps 1-7> Intermediate a4-7 was obtained by steps similar to steps 1 to 7 of the production method for NIR dye (A1-4).

[0304] <Step 8> Intermediate a4-7 (455.7 mg, 0.9937 mmol) and THF (5.0 mL) were placed in a nitrogen-purged, two-necked eggplant flask (50 mL). At -78 °C, n-butyllithium (hexane solution, 1.55 M, 1.00 mL, 1.55 mmol) was added. After 15 min of stirring, allyl bromide (0.26 mL, 3.0 mmol) was added and the mixture was stirred for 1 h. The mixture was then further stirred at 0 °C for 1 h. Saturated aqueous ammonium chloride was added, followed by extraction with ethyl acetate, washing with saturated brine, drying over magnesium sulfate, and removal of the solvent. The mixture was then purified by silica gel column chromatography (100% hexane). Further purification was performed by recycled preparative GPC (solvent: chloroform) to obtain intermediate acf4-8 (59.0 mg, 13% yield). 1H NMR(CDCl3,300MHz)δ6.64(1H,s), 6.06-5.91(1H,m), 6.05(1H,s), 5.21(1H,ddt,J=16.9,1.6,1.5Hz), 5.14(1H,ddt,J=9.9,1. 4,1.3Hz), 3.39(1H,ddd,J=6.6,1.3,1.1Hz), 3.09(4H,d,J=7.3Hz), 1.88-1.72(2H,m), 1.42-1.19(16H,m), 0.97-0.80(12H,m).

[0305] <Step 9> A nitrogen-purged screw-cap test tube was charged with intermediate acf4-8 (59.0 mg, 0.141 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (23.8 mg, 0.209 mmol), trimethyl orthoformate (0.15 mL, 1.4 mmol), and 1-propanol (7 mL) and heated with stirring at 80 °C for 1 hour. After completion of the reaction, saturated aqueous sodium bicarbonate was added at 0 °C, and the mixture was extracted with hexane / ethyl acetate. The resulting organic layer was washed with water and saturated brine, dried over magnesium sulfate, concentrated, and purified by silica gel column chromatography (hexane:ethyl acetate = 80:20) to give the NIR dye (Acf4) (7.5 mg, 12% yield). 1 H NMR (CDCl3, 400MHz) δ6.08-5.98(2H,m), 6.04(2H,s), 5.25(2H,ddd,J=17.0,5.6,1.6Hz), 5.15(2H,ddd,J=9.8,4 .2,1.5Hz), 4.30(H,d,J=6.4Hz), 3.36-3.20(8H,m), 1.96-1.84(4H,m), 1.42-1.20(32H,m), 0.95-0.83(24H,m).

[0306] [Example 19] Production of NIR dye (Bcf1) The NIR dye (Bcf1) was synthesized according to the reaction pathway shown below.

[0307] [ka]

[0308] <Step 1> Tetrahydrofuran-2,5-dione (10.03 g, 100.2 mmol), bis(2-ethylhexyl)amine (33.0 mL, 109.9 mmol), and 1,4-dioxane (100 mL) were placed in a nitrogen-purged recovery flask (300 mL) and heated with stirring at 80°C for 3 hours. After the reaction was completed, the mixture was concentrated and separated into hydrochloric acid and dichloromethane. The resulting organic layer was dried over sodium sulfate and then concentrated to quantitatively obtain intermediate bcf1-1.

[0309] <Step 2> Intermediate bcf1-1 (3.000 g, 8.785 mmol), Lawesson's reagent (4.264 g, 10.54 mmol), and toluene (50 mL) were placed in a nitrogen-purged recovery flask (200 mL) and heated under reflux for 2 hours. After the reaction was completed, the mixture was concentrated and purified by silica gel column chromatography (hexane:ethyl acetate = 6:1) to obtain intermediate bcf1-2 (852 mg, 63% yield).

[0310] <Step 3> Intermediate bcf1-2 (100.0 mg, 0.3090 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (19.4 mg, 0.170 mmol), 1-butanol (0.6 mL), and toluene (0.6 mL) were added to a nitrogen-purged screw-cap test tube and heated under reflux for 1 hour. After the reaction was completed, the mixture was concentrated and purified by silica gel chromatography (hexane:ethyl acetate = 90:10) to obtain the NIR dye (Bcf1) (17.2 mg, 15% yield).

[0311] [Example 20] Preparation of NIR dye (Bcf2) The NIR dye (Bcf2) was synthesized according to the reaction pathway shown below.

[0312] [ka]

[0313] <Step 1> A nitrogen-purged recovery flask (300 mL) was charged with cyclopentane-1,2-dicarboxylic acid (6.00 g, 37.9 mmol), triethylamine (27 mL, 194 mmol), DMF (3 drops), and dichloromethane (150 mL). Oxalyl chloride (3.30 mL, 38.0 mmol) was slowly added at 0 °C, and the mixture was heated to reflux for 1 hour. Subsequently, bis(2-ethylhexyl)amine (11.4 mL, 37.94 mmol) was added, and the mixture was heated to reflux for 1 hour. After the reaction was complete, the mixture was concentrated, and the solids were removed by suction filtration. The resulting organic layer was washed with hydrochloric acid, dried over sodium sulfate, concentrated, and purified by silica gel column chromatography (dichloromethane / methanol = 96 / 4) to obtain intermediate bcf2-1 (12.0 g, 83% yield).

[0314] <Step 2> Intermediate bcf2-1 (10.0 g, 26.2 mmol), diphosphorus pentasulfide (6.00 g, 27.0 mmol), and toluene (600 mL) were placed in a nitrogen-purged recovery flask (2000 mL) and heated under reflux for 2 hours. After the reaction was completed, the mixture was concentrated and purified by activated alumina column chromatography (hexane 100%) to obtain intermediate bcf2-2 (700 mg, 7% yield).

[0315] <Step 3> Intermediate bcf2-2 (790 mg, 2.17 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (376 mg, 3.30 mmol), trimethyl orthoformate (3.6 mL, 33 mmol), and 1-propanol (100 mL) were placed in a nitrogen-purged recovery flask (300 mL) and heated under reflux for 1 hour. After the reaction was complete, the mixture was concentrated and purified by silica gel chromatography (hexane:dichloromethane = 10:0-3:2, hexane:ethyl acetate = 10:0-5:1) to obtain the NIR dye (Bcf2) (123 mg, 14% yield).

[0316] [Example 21] Preparation of NIR dye (Bcf3) The NIR dye (Bcf3) was synthesized according to the reaction pathway shown below.

[0317] [ka]

[0318] <Step 1> Cis-1,2-cyclohexanedicarboxylic anhydride (10.0 g, 64.9 mmol), bis(2-ethylhexyl)amine (22 mL, 73.3 mmol), and 1,4-dioxane (100 mL) were placed in a nitrogen-purged recovery flask (300 mL) and heated with stirring at 80°C for 3 hours. After the reaction was completed, the mixture was concentrated and separated into hydrochloric acid and dichloromethane. The resulting organic layer was dried over sodium sulfate and then concentrated to obtain a crude intermediate bcf3-1. This crude product was used in the next reaction.

[0319] <Step 2> Intermediate bcf3-1 (3.25 g, 8.22 mmol), Lawesson's reagent (5.46 g, 13.5 mmol), and toluene (60 mL) were placed in a nitrogen-purged recovery flask (200 mL) and heated under reflux for 2 hours. After the reaction was completed, the mixture was concentrated and purified by activated alumina column chromatography (hexane 100%) to obtain intermediate bcf3-2 (808 mg, 26% yield).

[0320] <Step 3> Intermediate bcf3-2 (300 mg, 0.794 mmol), 3,4-dihydroxy-3-cyclobutene-1,2-dione (52.4 mg, 0.459 mmol), 1-butanol (2 mL), and toluene (2 mL) were added to a nitrogen-purged screw-cap test tube and heated under reflux for 1 hour. After the reaction was completed, the mixture was concentrated and purified by silica gel chromatography (hexane:ethyl acetate = 9:1-4:1) to obtain the NIR dye (Bcf3) (190 mg, 57% yield).

[0321] [Example 22] Transmittance measurement in dichloromethane The NIR dyes (A1-1) to (A1-11), (B1) to (B3), and NIR dyes (Acf1) to (Acf4), (Bcf1) to (Bcf3) obtained above were dissolved in dichloromethane, and the optical absorption spectrum was measured at wavelengths of 300 to 1300 nm. The maximum absorption wavelength λ was determined from the absorbance curve. max(A)DCMasked for.

[0322] [Table 3]

[0323] As is clear from the above evaluation results, the NIR dyes (A1-1) to (A1-11) of the examples all have higher light-shielding properties against near-infrared light than the NIR dyes (Acf1) to (Acf4) of the comparative examples. Furthermore, the above evaluation results show that the NIR dyes (A1-2) to (A1-11) exhibit wavelengths longer than the NIR dye (Acf1) by 50 nm or more, up to 264 nm, indicating that direct bonding of an unsaturated bond group to the 3-position of the thienothiophene ring significantly increases the maximum absorption wavelength in the near-infrared region. On the other hand, the NIR dye (Acf4), which incorporates an allyl group to which no unsaturated bond is directly bonded, exhibits a wavelength longer than the NIR dye (Acf1) by only about 10 nm.

[0324] Similarly, the NIR dyes (B1) to (B3) of the examples have higher light-shielding properties against near-infrared light than the NIR dyes (Bcf1) to (Bcf3) of the comparative examples. Furthermore, the NIR dyes (B1) to (B3) exhibit wavelengths longer than the NIR dye (Bcf1) by 100 nm or more, up to 138 nm, indicating that the maximum absorption wavelength in the near-infrared region can be significantly longer by directly bonding an unsaturated bond group to the 3-position of the thiophene ring. On the other hand, the NIR dyes (Bcf2) to (Bcf3), which have an alkyl group introduced at the 3-position of the thiophene ring, exhibit wavelengths longer than the NIR dye (Bcf1) by only about 30 nm.

[0325] [Example 23] For the NIR dyes (A1-1) to (A1-11) and (B1) to (B3), the coating solutions obtained in the above tests were applied to a glass plate (D263; product name, manufactured by SCHOTT) and dried to obtain an absorbing layer with a thickness of 1 μm.

[0326] The optical filter having the configuration shown in FIG. 2 is manufactured by the following method. As the transparent substrate, a glass substrate made of CuO-containing fluorophosphate glass (manufactured by AGC, trade name: NF-50GX) having a thickness of 0.21 mm or a glass substrate (D263; manufactured by SCHOTT, trade name) having a thickness of 0.2 mm is used.

[0327] The reflective layer uses a dielectric multilayer film formed as follows. The dielectric multilayer film is formed on one main surface of a glass substrate by vapor deposition, for example, by laminating a total of 42 layers of alternating TiO2 and SiO2 films. The configuration of the reflective layer is simulated using the number of layers in the dielectric multilayer film, the thickness of the TiO2 film, and the thickness of the SiO2 film as parameters, and is designed so that the average transmittance of light with wavelengths from 850 to 1100 nm is 0.03% on the spectral transmittance curve at an incident angle of 0 degrees.

[0328] On the main surface of the glass substrate opposite the reflective layer, an absorption layer approximately 1.0 μm thick is formed by combining a transparent resin and one or more NIR dyes (A1). After this, an anti-reflection layer is formed on the surface of the absorption layer by alternately laminating seven TiO2 and SiO2 films by vapor deposition, thereby obtaining an optical filter (NIR filter).

[0329] 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 present invention. This application is based on Japanese patent applications filed on December 4, 2019 (Patent Application No. 2019-219968) and May 29, 2020 (Patent Application No. 2020-094783), the contents of which are incorporated herein by reference. [Industrial Applicability]

[0330] The squarylium compound of the present invention is useful as a near-infrared absorbing dye because it can achieve excellent light-blocking properties, especially for light in the long wavelength region of near-infrared light, and can be applied to optical filters that block near-infrared light. The optical filter of the present invention can be applied to an imaging device. [Explanation of symbols]

[0331] 10A, 10D, 10F, 10G...optical filters, 11, 11a, 11b...absorption layers, 12, 12a, 12b...reflective layers, 13...transparent substrate, 14...anti-reflection layer.

Claims

1. A squarylium compound represented by the following formula (A4): 【Chemical 1】 [The meanings of the symbols in the above formula are as follows: R １ and R ２ R are each independently an alkyl group having 1 to 20 carbon atoms, which may have a substituent and which may contain an unsaturated bond between carbon atoms, an oxygen atom, an alicyclic ring, or an aromatic ring. １ is R ２ or R ４ may be linked to form a ring. ２ is R １ or R ４ may be linked to form a ring. R ３ is an alkenyl group having 2 or more carbon atoms which may have a substituent, an alkynyl group having 2 or more carbon atoms which may have a substituent, an imino group having 1 or more carbon atoms which may have a substituent, a cyano group, an organic group having 1 or more carbon atoms which contains a carbonyl structure and which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, or a heteroaryl group having 3 to 13 carbon atoms which may have a substituent. R ４ is a hydrogen atom, a halogen atom, a sulfo group, a hydroxyl group, a cyano group, a nitro group, a carbonyl structure-containing monovalent organic group, a phosphate group, a silyl group, a thiol group, a sulfide group, an amide structure-containing monovalent organic group, a sulfonamide group, a urea group, a urethane structure-containing monovalent organic group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkenyl group having 2 to 14 carbon atoms which may have a substituent, an alkynyl group having 2 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 20 carbon atoms which may have a substituent, a heteroaryl group having 3 to 13 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an acyloxy group having 2 to 13 carbon atoms which may have a substituent, or —N(R ４７ ) ２ (R ４７ is a hydrogen atom or an alkyl group having 1 to 15 carbon atoms which may have a substituent.

2. An optical filter including an absorption layer containing a near-infrared absorbing dye and a resin, An optical filter comprising the squarylium compound of claim 1 as the near-infrared absorbing dye.

3. 3. The optical filter according to claim 2, further comprising a reflective layer including a dielectric multilayer film.

4. 4. The optical filter according to claim 2, further comprising a transparent substrate, and the absorbing layer is provided on the transparent substrate.

5. 5. The optical filter according to claim 4, wherein the transparent substrate is made of glass.

6. 6. The optical filter according to claim 5, wherein the glass is a near-infrared absorbing glass.

7. 5. The optical filter according to claim 4, wherein the transparent substrate is made of a resin.

8. An imaging device comprising a solid-state imaging element, an imaging lens, and the optical filter according to any one of claims 2 to 7.

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