JP7625975B2 - Dichroic dye composition, liquid crystal element, retardation plate and polarizer - Google Patents

Description

The present invention relates to a dichroic dye composition, a liquid crystal element, a retardation plate, a polarizer, etc.

In liquid crystal display devices, polarizers are used to control the optical rotation and birefringence in the display, and in recent years, organic dyes have been considered as dichroic substances to be used in polarizers. For example, polarizers that use guest-host liquid crystal compositions containing a host liquid crystal material and a guest dichroic dye have been proposed (Patent Document 1, Patent Document 2).

Patent No. 5923941 Patent No. 6343866

However, the above-mentioned Patent Documents 1 and 2 do not disclose the use of a squarylium dye as a dichroic dye.
An object of the present invention is to provide a novel dichroic dye composition useful for various optical elements such as polarizers, and a liquid crystal element, a retardation plate, a polarizer, etc., which utilizes the same.

The present invention relates to the following dichroic dye composition.
[1] A dichroic dye composition comprising a squarylium dye containing a heteroatom and a liquid crystal compound that transmits visible light.

The present invention provides a novel dichroic dye composition that is useful for various optical elements such as liquid crystal elements, retardation plates, and polarizers, and liquid crystal elements, retardation plates, polarizers, etc. that utilize the same.

Hereinafter, an embodiment of the present invention will be described.
In this specification, the compound represented by formula (A1) is referred to as compound (A1). The same applies to compounds represented by other formulas. The NIR dye made of compound (A1) is also referred to as NIR dye (A1), and the same applies to other dyes. In addition, for example, the 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, any numerical range expressed by "to" includes the upper and lower limits.

In this specification, unless otherwise specified, the alkyl group may be linear, branched, or cyclic, or may be 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., and a heteroaryl group refers to a group that bonds via a carbon atom or a hetero atom constituting an aromatic ring of an aromatic compound having a hetero atom, such as a furan ring, a thiophene ring, a pyrrole ring, etc.

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).

<Dichroic dye composition>
The dichroic dye composition of the present invention (hereinafter also referred to as "the composition of the present invention") contains a squarylium dye containing a heteroatom and a liquid crystal compound that transmits visible light.
In the present invention, the squarylium dye functions as a dichroic dye. The dichroic dye means a dye having a property that the absorbance in the long axis direction of the molecule is different from the absorbance in the short axis direction. By including a dichroic dye in the article, the resulting optical element can function as a polarizer.
The squarylium dye is also a near-infrared absorbing dye that transmits visible light and has a maximum absorption wavelength in the wavelength region of 700 nm or more. Thus, an optical element capable of absorbing polarized light of

<Squarylium dyes>
The squarylium dye contained in the composition of the present invention contains a heteroatom. This increases the absorption coefficient and the visible light transmittance. The heteroatom is distinguished from the oxygen atom in the squarylium skeleton. That is, the squarylium dye of the present invention contains a heteroatom in the structure other than the squarylium skeleton.
Examples of the heteroatom include a nitrogen atom, a sulfur atom, and an oxygen atom.

The squarylium dye is preferably a compound represented by the following formula (X):

The symbols in formula (X) are as follows.
Ar is a monocyclic, condensed or linked ring having aromaticity and having 5 to 14 carbon atoms.
R ¹ and R ² , or at least one of R ¹ and R ² and the carbon atoms constituting Ar may be bonded to each other to form a heterocycle having 3 to 10 members together with the nitrogen atom.

When R ¹ and R ² do not form a heterocycle, R ¹ and R ² each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between the carbon atoms, a heteroatom or a ring structure.
The monovalent hydrocarbon group may be branched, straight-chain, or cyclic, but is preferably straight-chain from the viewpoint that the squarylium dye is likely to have a straight-chain structure, i.e., is likely to exhibit dichroism.
The monovalent hydrocarbon group more preferably has 1 to 8 carbon atoms.

When R ¹ and R ² form a heterocycle, R ¹ and R ² each independently represent a divalent hydrocarbon group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, or a ring structure.

Examples of the substituent in ^R1 and ^R2 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 19 carbon atoms.
When R ¹ and R ² have a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ¹ and R ² .

Further examples of the substituents in R ¹ and R ² include cyclic alkyl groups or 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. Examples of the substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, 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 substituents include a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, and the like.

The heteroatom in R ¹ and R ² is preferably an oxygen atom or a nitrogen atom.

When ^R1 and ^R2 each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

From the viewpoint of improving the reliability of the optical element, the substituents in R ¹ and R ² are preferably polymerizable groups.

When R ¹ and R ² are linked to each other to form a heterocycle together with the nitrogen atom, the number of members of the heterocycle is preferably 4 to 6, from the viewpoint that the squarylium dye is likely to have a linear shape, i.e., is likely to exhibit dichroism.
In such a heterocycle, one of the hydrogen atoms bonded to the carbon atom farthest from the nitrogen atom may be substituted with an alkyl group having 1 to 12, preferably 1 to 8, and more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms.
In addition, in such a heterocycle, the carbon atom farthest from the nitrogen atom may be replaced with a nitrogen atom, and the hydrogen atom bonded to the nitrogen atom may be substituted with an alkyl group having 1 to 12, preferably 1 to 8, and more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms.
The alkyl group may be branched, linear, or cyclic, but is preferably linear from the viewpoint that the squarylium dye is likely to exhibit dichroism. In addition, some or all of the hydrogen atoms in the heterocycle may be substituted with halogen atoms, and in this case, it is preferred that some or all of the hydrogen atoms bonded to the carbon atom not adjacent to the nitrogen atom are substituted with halogen atoms.

When at least one of R ¹ and R ² and the carbon atom constituting Ar are linked to each other to form a heterocycle together with the nitrogen atom, the number of members of such a heterocycle is preferably 5 to 7. In such a heterocycle, one of the hydrogen atoms bonded to the carbon atom adjacent to the nitrogen atom may be substituted with an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8, more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms, and some or all of the remaining hydrogen atoms may be substituted with an alkyl group having 1 to 4 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms. The alkyl group may be branched, straight-chained, or cyclic, but is preferably straight-chained from the viewpoint that the squarylium dye is likely to exhibit dichroism. In addition, some or all of the hydrogen atoms in such a heterocycle may be substituted with halogen atoms, and in that case, it is preferable that some or all of the hydrogen atoms bonded to the carbon atom not adjacent to the nitrogen atom are substituted with halogen atoms.

The two ^R1 's 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 they are the same on the left and right sides. The same applies to ^R2 and Ar. The same applies to the subsequent symbols. 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 they are the same on the left and right sides.

Ar may have one or more substituents. From the viewpoint that the greater the ratio (aspect ratio) of the molecular length in the minor axis direction to the molecular length in the major axis direction of the squarylium dye, the easier it is to exhibit dichroism, the substituent is preferably selected from a halogen atom, a hydroxyl group, or a monovalent organic group R ^Ar having 1 to 9 carbon atoms which may have a substituent. Note that the carbon number of R ^Ar and the carbon number of the substituent of R ^Ar are not included in the carbon number of Ar.
Examples of the halogen atom include a chlorine atom, a fluorine atom, an iodine atom, and a bromine atom.
Examples of the monovalent organic group R ^Ar include an alkyl group, an alkoxy group, an acyloxy group, an araryl group, an amino group, an alkenyl group, an alkynyl group, an imino group, a cyano group, a carbonyl group, an aryl group, and a heteroaryl group.
R ^Ar may have a substituent. The number of carbon atoms of the substituent is included in the number of carbon atoms of R ^Ar .

The squarylium dye is preferably a compound represented by any one of the following formulas (I) to (VI). The squarylium dye may contain one or more compounds.

<Squarylium dye (I)>

However, the symbols in the above formula are as follows:

R ¹¹ and R ²¹ each independently represent a hydrogen atom, an alkyl group or alkoxy group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond or a heteroatom between the carbon atoms, an acyloxy group having 1 to 19 carbon atoms, an aryl group having 6 to 11 carbon atoms, or an araryl group having 7 to 18 carbon atoms which may have a substituent and which may have an oxygen atom between the carbon atoms. The alkyl group is preferably linear from the viewpoint that the squarylium dye is likely to exhibit dichroism.

R ³¹ and R ⁵¹ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group or an alkoxy group having 1 to 8 carbon atoms, an acyloxy group having 1 to 8 carbon atoms, an aryl group having 6 to 9 carbon atoms, an araryl group having 7 to 9 carbon atoms which may have a substituent and which may have an oxygen atom between the carbon atoms, -NR ^31a R ^31b (R ^31a and R ^31b each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, -C(═O)-R ^31c (R ^31c represents a hydrogen atom, a halogen atom, a hydroxyl group, a hydrocarbon group having 1 to 8 carbon atoms which may have a substituent and which may contain an unsaturated bond, an oxygen atom, or a saturated or unsaturated ring structure between the carbon atoms), -NHR ^31d , or -SO ₂ -R ^31d (R and ^{R 31d} represents a hydrocarbon group having 1 to 8 carbon atoms, in which one or more hydrogen atoms may be substituted with a halogen atom, a hydroxyl group, a carboxy group, a sulfo group, or a cyano group, and which may contain an unsaturated bond, an oxygen atom, or a saturated or unsaturated ring structure between carbon atoms.), or a group represented by the following formula (S) (R ^31e and R ^31f independently represent a hydrogen atom, a halogen atom, or an alkyl group or alkoxy group having 1 to 3 carbon atoms; k is 2 or 3).

R ⁴¹ and R ⁶¹ each independently represent a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group or an alkoxy group having 1 to 8 carbon atoms, an acyloxy group having 1 to 8 carbon atoms, an aryl group having 6 to 9 carbon atoms, or an araryl group having 7 to 9 carbon atoms which may have a substituent and which may have an oxygen atom between the carbon atoms.

R ¹¹ and R ²¹ , R ¹¹ and R ⁴¹ , and R ²¹ and R ⁶¹ may be linked to each other and together with the nitrogen atom to form a 4- to 6-membered heterocycle A1, a 5- to 7-membered heterocycle B1, and a 5- to 7-membered heterocycle C1, respectively.

When heterocycle A1 is formed, R ¹¹ and R ²¹ are bonded to a divalent group -Q ¹ -, which represents an alkylene group having 3 to 5 carbon atoms or an alkyleneoxy group having 2 to 4 carbon atoms. Here, in the heterocycle composed of a nitrogen atom and Q ¹ , one of the hydrogen atoms bonded to the carbon atom furthest from the nitrogen atom may be substituted with an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms. The alkyl group is preferably linear from the viewpoint that the squarylium dye is likely to exhibit dichroism. In addition, some or all of the hydrogen atoms in such a heterocycle may be substituted with halogen atoms, and in that case, it is preferable that some or all of the hydrogen atoms bonded to the carbon atom not adjacent to the nitrogen atom are substituted with halogen atoms.

R ¹¹ and R ⁴¹ when heterocycle B1 is formed, and R ²¹ and R ⁶¹ when heterocycle C1 is formed are bonded to divalent groups -X ¹ -Y ¹ - and -X ² -Y ² - (X ¹ and X ² are the sides bonded to the nitrogen), where X ¹ and X ² are each a group represented by the following formula (1x) or (2x), and Y ¹ and Y ² are each a group selected from the following formulas (1y) to (5y). When X ¹ and X ² are each a group represented by the following formula (2x), Y ¹ and Y ² may each be a single bond, in which case there may be an oxygen atom between the carbon atoms.

In formula (1x), four Z's each independently represent a hydrogen atom, ^{a hydroxyl group, an alkyl group or an alkoxy group having 1 to 6 carbon atoms, or -Nx38x39 (x38 and x39 each independently represent} a hydrogen atom or an alkyl group having 1 to 8 carbon atoms). ^x31 to ^x36 each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and ^x37 represents an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 10 carbon atoms.
R ^31a , R ^31b , R ^31c , x ³¹ to x ³⁷ , and R ¹¹ , R ²¹ , R ⁴¹ and R ⁶¹ when not forming a heterocycle may be bonded to any other of them to form a 5- or 6-membered ring. x ³¹ and x ³⁶ , and x ³¹ and x ³⁷ may be directly bonded to each other.

Examples of the substituent in R ¹¹ and R ²¹ 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 19 carbon atoms.

Further examples of the substituents in R ¹¹ and R ²¹ include cyclic alkyl groups or 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. Examples of the substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, an alkoxy group, or an alkylamino group (the number of carbon atoms in the alkyl group is 1 to 12). The phenyl group and naphthyl group are preferably unsubstituted or substituted with 1 to 3 hydrogen atoms, and examples of the substituents include a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, and the like.

When R ¹¹ and R ²¹ each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

The substituents in R ¹¹ and R ²¹ are preferably polymerizable groups from the viewpoint of improving the reliability of the optical element.

Examples of compound (I) include compounds represented by any of formulas (I-1) to (I-4).

The symbols in formulas (I-1) to (I-4) are the same as those in formula (I), and unless otherwise specified, the preferred embodiments are also the same.

In the compound (I-1), X ¹ is preferably a group (2x), and Y ¹ is preferably a single bond or a group (1y). That is, -Y ¹ -X ¹ - is preferably -C(x ³¹ )(x ³² )-C(x ³³ )(x ³⁴ )- or -C(x ³⁵ )(x ³⁶ )-C(x ³¹ )(x ³² )-C(x ³³ )(x ³⁴ )-. In this case, x ³¹ , x ³² , x ³⁵ and x ³⁶ are each independently preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom or a methyl group. ^{x 33} and x ³⁴ are each independently preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8, and more preferably 3 to 8 carbon atoms. Since dichroism is easily exhibited when one linear alkyl group is bonded to the carbon atom adjacent to the nitrogen atom, it is particularly preferable that one of x ³³ and x ³⁴ is a hydrogen atom and the other is a linear alkyl group having 3 to 8 carbon atoms.

Specific examples of --Y ¹ --X ¹ -- include divalent organic groups represented by the following formulas (11-1) to (11-4) and (12-1) to (12-3).
-C(CH ₃ ) ₂ -CH(CH ₃ )-...(11-1)
-C( _CH3 ) ₂ - _CH2 -...(11-2)
-C( _CH3 ) ₂ -CH( _{nCkH2k +1} )-...(11-3)(k=2 to 6)
-C(CH ₃ ) ₂ -C(CH ₃ )(nC _k H _2k+1 )-...(11-4) (k=3 to 6)
-C( _CH3 ) ₂ - _CH2 - _CH2 -...(12-1)
-C(CH ₃ ) ₂ -CH ₂ -CH(CH ₃ )-...(12-2)
-C( _CH3 ) ₂ -CH( _CH3 )-CH2 _-... (12-3)

In addition, in the compound (I-1), from the viewpoint of improving the dichroic ratio, R ¹¹ is more preferably independently a methyl group.

In compound (I-4), R ⁵¹ is preferably a hydrogen atom or a hydroxyl group.

<Squarylium dye (II)>

Here, the symbols in the above formula are as follows:
Each ring Z2 is independently a 5- or 6-membered ring having 0 to 3 heteroatoms in the ring, and the hydrogen atom in ring Z2 may be substituted.
R ¹² and R ²² each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain an unsaturated bond between carbon atoms, a heteroatom, or a saturated or unsaturated ring structure and which may have a substituent.
R ³² and R ⁴² each independently represent a hydrogen atom, a halogen atom, or an alkyl or alkoxy group having 1 to 8 carbon atoms which may contain a heteroatom between the carbon atoms and which may have a substituent.
R ¹² and R ²² , R ¹² and R ⁴² , and R ²² and the carbon atoms or heteroatoms constituting ring Z2 may be bonded to each other to form, together with the nitrogen atom, a 4- to 6-membered heterocycle A2, a 5- to 7-membered heterocycle B2, and a 5- to 7-membered heterocycle C2, respectively, in which case the hydrogen atoms in heterocycle A2, heterocycle B2, and heterocycle C2 may be substituted.

Examples of the substituent in R ¹² and R ²² 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 19 carbon atoms.

Further examples of the substituents in R ¹² and R ²² include cyclic alkyl groups or 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. Examples of the substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, 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 substituents include a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, and the like.

When R ¹² and R ²² each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

The substituents in R ¹² and R ²² are preferably polymerizable groups from the viewpoint of improving the reliability of the optical element.

Examples of compound (II) include compounds represented by any of formulas (II-1) to (II-3). From the viewpoint of durability, compounds represented by formulas (II-1) and (II-3) are particularly preferred.

In formula (II-1) and formula (II-2), R ¹² and R ²² each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may have an unsaturated bond or a heteroatom between the carbon atoms. R ³² , R ⁴² , R ⁵² , and R ⁶² each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 8 carbon atoms which may have a substituent. An example of the substituent in the alkyl group is a halogen atom.

In formula (II-3), R ¹² represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent and may have an unsaturated bond or a heteroatom between the carbon atoms. R ^92a to R ^92d each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 or more carbon atoms which may have a substituent and may have an unsaturated bond or a heteroatom between the carbon atoms, and the total number of carbon atoms in -CR ^92a R ^92b -CR ^92c R ^92d - is 20 or less. R ³² , R ⁷² , and R ⁸² each independently represent a hydrogen atom, a halogen atom, or an alkyl group having 1 to 8 carbon atoms which may have a substituent. An example of the substituent in the alkyl group is a halogen atom.

From the viewpoint of the degree of orientation, R ¹² and R ²² in compound (II-1) and compound (II-2) are each independently a linear alkyl group having 1 to 20 carbon atoms, which may have a substituent and may have an unsaturated bond or a heteroatom between the carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms. In addition, it is preferable that the carbon atoms constituting R ¹² and R ²² are bonded to each other to form a heterocycle, and it is particularly preferable that the heterocycle is a 4- to 6-membered ring.

In terms of the degree of orientation, R ¹² in compound (II-3) is preferably a linear alkyl group having 1 to 8 carbon atoms, more preferably a linear alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group or an ethyl group.

R ³² and R ⁴² are each preferably a hydrogen atom or a halogen atom, particularly preferably a hydrogen atom, from the viewpoint of the degree of orientation.

R ⁷² and R ⁸² are each preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom, and more preferably a hydrogen atom, a halogen atom, or a methyl group.

R ^92a is more preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 18 carbon atoms which may be substituted with a halogen atom and which may have an unsaturated bond or a hetero atom between the carbon atoms. Since dichroism is easily exhibited when one linear alkyl group is bonded to the carbon atom adjacent to the nitrogen atom, R ^92a is particularly preferably a linear alkyl group having 1 to 18 carbon atoms which may be substituted with a halogen atom.
It is preferable that R ^92b to R ^92d are each independently a hydrogen atom, a halogen atom, or an alkyl group having 1 to 5 carbon atoms which may be substituted with a halogen atom.
Examples of --CR ^92a R ^92b --CR ^92c R ^92d -- include divalent organic groups represented by the following groups (13-1) to (13-9).
-CH( _CH3 )-C( _CH3 ) ₂ -...(13-1)
-C(CH ₃ ) ₂ -CH(CH ₃ )-...(13-2)
-C( _CH3 ) ₂ - _CH2 -...(13-3)
-C( _CH3 ) ₂ -CH( _C2H5 )-... ₍ 13-4)
-CH( _CH3 )-C( _CH3 )( _CH2 -CH( _CH3 ) ₂ )-...(13-5)
-CH( _CH2CH ( _CH3 ) ₂ )-C( _CH3 ) ₂ -...(13-6)
-CH(C _n H _2n+1 ) -C(CH ₃ ) ₂ -...(13-7) (n=1 to 12)
-CH (C _n H _2n+1 ) -CH ₂ - ... (13-8) (n = 1 to 12)
-C( _CH3 )( _{CnH2n +1} )-C( _CH3 ) ₂ -...(13-9)(n=1 to 12)

More specifically, examples of compound (II-1) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

More specifically, examples of compound (II-3) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

Compounds (I) to (II) can each be produced by a known method. Compound (I) can be produced by the method described in U.S. Pat. No. 5,543,086, U.S. Patent Application Publication No. 2014/0061505, and WO 2014/088063. Compound (II) can be produced by the method described in WO 2017/135359.

<Squarylium dye (III)>

Here, the symbols in the above formula are as follows:
R ¹³ and R ²³ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, an alicyclic ring or an aromatic ring.

R ¹³ may be linked with R ²³ , R ³³ , X ³¹ , X ³² , or X ³³ to form a ring.
R ²³ may be linked with R ¹³ , R ³³ , X ³¹ , X ³² , or X ³³ to form a ring.
The ring is preferably an alicyclic or aromatic ring having 3 to 6 members. The ring may have a substituent.

Examples of the substituent in R ¹³ and R ²³ 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 19 carbon atoms.

Further examples of the substituents in R ¹³ and R ²³ include cyclic alkyl groups or 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 substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, an alkoxy group, or an alkylamino group (the number of carbon atoms in the alkyl group is 1 to 12). The phenyl group and naphthyl group are preferably unsubstituted or substituted with 1 to 3 hydrogen atoms, and the substituents are preferably a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, etc.

When R ¹³ and R ²³ each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

The substituents in R ¹³ and R ²³ are preferably polymerizable groups from the viewpoint of improving the reliability of the optical element.

The number of carbon atoms in R ¹³ and R ²³ can be 1 to 20. When R ¹³ and R ²³ are linear, the number of carbon atoms is preferably 2 to 20, more preferably 3 to 16, and even more preferably 4 to 12. When R ¹³ and R ²³ are branched, the number of carbon atoms is preferably 3 to 20, more preferably 4 to 16, and even more preferably 8 to 10.
When R ¹³ and R ²³ have a substituent, or when the main chain or side chain contains an alicyclic ring or aromatic ring, the above number of carbon atoms includes the number of carbon atoms of the substituent, alicyclic ring, and aromatic ring.

R ¹³ and R ²³ may be the same or different, but are preferably the same from the viewpoint of ease of production.

From the viewpoint of the degree of orientation, R ¹³ and R ²³ are preferably linear.

R ¹³ and R ²³ are more preferably, for example, a group selected from groups (1b) to (5b) and groups (1c) to (2c).
-CH(C _n H _2n+1 ) ₂ ...(1b)
-C(C _n H _2n+1 ) ₃ ...(1c)
_-CH2 -CH( _{CnH2n +1} ) ₂ ...(2b)
_-CH2 -C( _{CnH2n +1} ) ₃ ...(2c)
-(CH ₂ ) ₂ -CH(C _n H _2n+1 ) ₂ ...(3b)
-(CH ₂ ) ₃ -CH(C _n H _2n+1 ) ₂ ...(4b)
-(CH ₂ ) _m -CH ₃ ...(5b)

However, in formulas (1b) to (4b) and formulas (1c) to (2c), n is an integer of 1 to 10, preferably 2 to 8, and more preferably 2 to 4. However, the number of carbon atoms in groups (1b) to (4b) and groups (1c) to (2c) is within the range of 1 to 20. The two C _n H _2n+1 in formulas (1b) to (4b) and the three C _n H _2n+1 in formulas (1c) to (2c) 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) and groups (1c) to (2c) may have an oxygen atom between the carbon-carbon atom.

In addition, when R ¹³ and R ²³ are linked to each other to form a heterocycle together with the nitrogen atom, the divalent group -Q ³ - to which R ¹³ and R ²³ are bonded represents an alkylene group having 3 to 5 carbon atoms or an alkyleneoxy group having 2 to 4 carbon atoms. Here, in the heterocycle composed of a nitrogen atom and Q ³ , one of the hydrogen atoms bonded to the carbon atom farthest from the nitrogen atom may be substituted with an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms. The alkyl group is preferably linear from the viewpoint that the squarylium dye is likely to exhibit dichroism. In addition, some or all of the hydrogen atoms in such a heterocycle may be substituted with halogen atoms, and in that case, it is preferable that some or all of the hydrogen atoms bonded to the carbon atom not adjacent to the nitrogen atom are substituted with halogen atoms.

R ³³ is an organic group R ^33A which does not necessarily have an unsaturated bond, or an organic group R ^33B which necessarily has an unsaturated bond.
The organic group R ^33A , which does not necessarily have an unsaturated bond, is a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, or an araryl group, which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon atoms.
The organic group R ^33B essentially containing an unsaturated bond 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 which contains a carbonyl structure and has 1 or more carbon atoms which may have a substituent, an aryl group having 6 to 9 carbon atoms which may have a substituent, or a heteroaryl group having 3 to 9 carbon atoms which may have a substituent.
R ³³ may be linked with X ³¹ , X ³² or X ³³ to form a ring. The ring is preferably a ring having 5 to 7 members. The ring may have a substituent.

Examples of the substituent in R ^33A 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 8 carbon atoms. When ^{R 33A} is an aryl group or an araryl group, the substituent is a hydrogen atom bonded to an aromatic ring or a group substituting a hydrogen atom of an alkyl group contained therein, and further includes an aryl group in addition to the above-mentioned substituents.

When R ^33A is an alkyl group or an alkoxy group, the carbon number is preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 3. When R ^33A is an aryl group, the carbon number is preferably 6 to 9. When ^{R 33A} is an araryl group, the carbon number is preferably 7 to 9.
When R ^33A has a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ^33A .

From the viewpoint of photostability, R ^33A is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

Examples of the substituent in the organic group R ^33B which essentially contains an unsaturated bond 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 imido group, a thiol group, a sulfide group, an alkoxy group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, a silyl group, and a halogenated alkyl group having 1 to 8 carbon atoms.
When R ^33B has a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ^33B .

When R ^33B is an alkenyl group, it has 2 or more carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms.
The alkenyl group is preferably a group represented by the following formula (3-1).

R ^3a , R ^3b , and R ^3c each independently represent 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 7 carbon atoms, an alkyl group having 1 to 7 carbon atoms, an aralkyl group having 6 to 7 carbon atoms, an aryl group having 6 to 7 carbon atoms which may have a substituent, a heteroaryl group having 3 to 7 carbon atoms which may have a substituent, an alkenyl group having 2 to 7 carbon atoms which may have a substituent, an alkynyl group having 2 to 7 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 7 carbon atoms (such as a trimethylsilyl group, a triphenylsilyl group, or a t-butyldiphenylsilyl group), a trialkoxysilyl group having 3 to 7 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 7 carbon atoms. R ^3b may be linked with R ^3a or R ^3c to form a 3-6 membered ring which may contain a heteroatom, and in that case, the ring may have a substituent.

Examples of the substituent in the ring formed by R ^3b linking with R ^3a or R ^3c 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 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a triorganosilyl group having 3 to 6 carbon atoms (e.g., a trimethylsilyl group), a trialkoxysilyl group having 3 to 6 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 6 carbon atoms.

The group (3-1) preferably has the following structure:

When R ^33B is an alkynyl group, it has 2 or more carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms.
The alkynyl group is preferably a group represented by the following formula (3-2).

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 7 carbon atoms, an alkyl group having 1 to 7 carbon atoms, an aralkyl group having 6 to 7 carbon atoms, an aryl group having 6 to 7 carbon atoms which may have a substituent, a heteroaryl group having 3 to 7 carbon atoms which may have a substituent, an alkenyl group having 2 to 7 carbon atoms which may have a substituent, an alkynyl group having 2 to 7 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 7 carbon atoms (e.g., a trimethylsilyl group), a trialkoxysilyl group having 3 to 7 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 7 carbon atoms.

Substituents in the aryl group, heteroaryl group, alkenyl group, and alkynyl group include halogen atoms, formyl groups, carboxy groups, sulfo groups, amino groups, N-substituted amino groups, nitro groups, alkoxycarbonyl groups, carbamoyl groups, N-substituted carbamoyl groups, imido groups, sulfide groups, alkoxy groups having 1 to 5 carbon atoms, triorganosilyl groups having 3 to 5 carbon atoms (trimethylsilyl group, etc.), trialkoxysilyl groups having 3 to 5 carbon atoms (trimethoxysilyl group, dimethoxyethoxysilyl group, etc.), and halogenated alkyl groups having 1 to 5 carbon atoms.

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

When R ^33B is an imino group, it has 1 or more carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.
The imino group is preferably a group represented by the following formula (3-3).

R ^3e and R ^3f each independently represent 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 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms, an aralkyl group having 6 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms which may have a substituent, a heteroaryl group having 3 to 10 carbon atoms which may have a substituent, an alkenyl group having 2 to 8 carbon atoms which may have a substituent, an alkynyl group having 2 to 8 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 8 carbon atoms (trimethylsilyl group, etc.), a trialkoxysilyl group having 3 to 8 carbon atoms (trimethoxysilyl group, dimethoxyethoxysilyl group, etc.), or a halogenated alkyl group having 1 to 8 carbon atoms. R ^3e and R ^3f 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.

Examples of the substituent in the aryl group, heteroaryl group, alkenyl group, alkynyl group, and the ring formed by combining R ^3e and R ^3f 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 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a triorganosilyl group having 3 to 6 carbon atoms (e.g., a trimethylsilyl group), a trialkoxysilyl group having 3 to 6 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 6 carbon atoms.

The group (3-3) preferably has the following structure:

When R ^33B is a cyano group, it is a group represented by the following formula (3-4).

When R ^33B is an organic group having 1 or more carbon atoms which contains a carbonyl structure and may have a substituent, the number of carbon atoms is 1 or more, preferably 1 to 8, more preferably 1 to 6, and further preferably 1 to 4.
Such an organic group is preferably a group represented by the following formula (3-5).

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 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms, an aralkyl group having 6 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms which may have a substituent, a heteroaryl group having 3 to 8 carbon atoms which may have a substituent, an alkenyl group having 2 to 8 carbon atoms which may have a substituent, an alkynyl group having 2 to 8 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 8 carbon atoms (e.g., a trimethylsilyl group), a trialkoxysilyl group having 3 to 8 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 8 carbon atoms.

Substituents in the aryl group, heteroaryl group, alkenyl group, and alkynyl group include halogen atoms, formyl groups, carboxy groups, sulfo groups, amino groups, N-substituted amino groups, nitro groups, alkoxycarbonyl groups, carbamoyl groups, N-substituted carbamoyl groups, imido groups, sulfide groups, alkoxy groups having 1 to 6 carbon atoms, alkyl groups having 1 to 6 carbon atoms, triorganosilyl groups having 3 to 6 carbon atoms (trimethylsilyl groups, etc.), trialkoxysilyl groups having 3 to 6 carbon atoms (trimethoxysilyl groups, dimethoxyethoxysilyl groups, etc.), and halogenated alkyl groups having 1 to 6 carbon atoms.

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

When R ^33B is an aryl group, it has 6 to 9 carbon atoms.

The aryl group is preferably a group represented by the following formula (3-6).

R ^3h , R ³ⁱ , R ^3j , R ^3k , and R ^3l are 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 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms which may have a substituent, an alkynyl group having 2 to 3 carbon atoms which may have a substituent, a trimethylsilyl group, a trimethoxysilyl group, or a halogenated alkyl group having 1 to 3 carbon atoms.
R ^3h and R ³ⁱ , R ³ⁱ and R ^3j , R ^3j and R ^3k , and R ^3k and R ^3l may be linked together to form a 3-6 membered ring which may contain a heteroatom.

Examples of substituents in the alkenyl and alkynyl groups include halogen atoms, formyl groups, carboxy groups, sulfo groups, amino groups, N-substituted amino groups, nitro groups, alkoxycarbonyl groups, carbamoyl groups, N-substituted carbamoyl groups, imido groups, sulfide groups, methoxy groups, methyl groups, and halogenated methyl groups.

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

When R ^33B is a heteroaryl group, it has 3 to 9 carbon atoms.

The heteroaryl group is preferably a group represented by any one of the following formulas (3-7) to (3-9).

X ^3a , X ^3b , X ^3c , X ^3d , and X ^3e are each independently N or CR ^3m , at least one of which is N. R ^3m is 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 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a heteroaryl group having 3 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, an alkynyl group having 2 to 6 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 6 carbon atoms (such as a trimethylsilyl group), a trialkoxysilyl group having 3 to 6 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 6 carbon atoms.
When X ^3a , X ^3b , X ^3c , X ^3d and X ^3e are CR ^3m , adjacent X ^3a to X ^3e may be bonded to each other to form a 3-6 membered ring Ar ³⁰ , Ar ³¹ , Ar ³² or Ar ³³ which may contain a heteroatom, and in this case, the ring may have a substituent.
Examples of the substituents in the heteroaryl group, the alkenyl group, the alkynyl group, and the rings Ar ³⁰ , Ar ³¹ , Ar ³² and Ar ³³ 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, a trimethylsilyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms.

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

X ^3f , X ^3g and X ^3h are each independently N or CR ³ⁿ . Y ^3a is S, O or NR ^3o .
R ³ⁿ and R ^3o each independently represent 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 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a heteroaryl group having 3 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, an alkynyl group having 2 to 6 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 6 carbon atoms (e.g., a trimethylsilyl group), a trialkoxysilyl group having 3 to 6 carbon atoms (e.g., a trimethoxysilyl group, a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 6 carbon atoms.
When X ^3f , X ^3g , and X ^3h are CR ³ⁿ and Y ^3a is NR ^3o , adjacent X ^3f , X ^3g , X ^3h , and Y ^3a may be linked to each other to form a 3-6 membered ring Ar ³⁴ , Ar ³⁵ , or Ar ³⁶ which may contain a heteroatom, and in that case, the ring may have a substituent.
Examples of the substituents in the heteroaryl group, the alkenyl group, the alkynyl group, and the rings Ar ³⁴ , Ar ³⁵ , and Ar ³⁶ 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, a trimethylsilyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms.

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

X ³ⁱ , X ^3j and X ^3k are each independently N or CR ^3p . Y ^3b is S, O or NR ^3q . R ^3p and R ^3q are 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 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a heteroaryl group having 3 to 6 carbon atoms which may have a substituent, an alkenyl group having 2 to 6 carbon atoms which may have a substituent, an alkynyl group having 2 to 6 carbon atoms which may have a substituent, a triorganosilyl group having 3 to 6 carbon atoms (such as a trimethylsilyl group), a trialkoxysilyl group having 3 to 6 carbon atoms (such as a trimethoxysilyl group or a dimethoxyethoxysilyl group), or a halogenated alkyl group having 1 to 6 carbon atoms.
When X ³ⁱ , X ^3j , and X ^3k are CR ^3p and Y ^3b is NR ^3q , adjacent X ³ⁱ , X ^3j , X ^3k , and Y ^3b may be linked to each other to form a 3-6 membered ring Ar ³⁷ , Ar ³⁸ , or Ar ³⁹ which may contain a heteroatom, and in that case, the ring may have a substituent.
Examples of the substituents in the aryl group, heteroaryl group, alkenyl group, alkynyl group, and rings Ar ³⁷ , Ar ³⁸ , and Ar ³⁹ 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, a trimethylsilyl group, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms.

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

In formula (III), X ³¹ is CR ⁴³ or N. X ³² is S, NR ⁵³ or O. X ³³ is S, NR ⁶³ or O.

R ⁴³ 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 9 carbon atoms which may have a substituent, an alkenyl group having 2 to 9 carbon atoms which may have a substituent, an alkynyl group having 2 to 9 carbon atoms which may have a substituent, an aryl group having 6 to 9 carbon atoms which may have a substituent, a heteroaryl group having 3 to 9 carbon atoms which may have a substituent, an alkoxy group having 1 to 9 carbon atoms which may have a substituent, an acyloxy group having 2 to 9 carbon atoms which may have a substituent, or -N(R ^43g ) ₂ (R ^43g is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent).

When R ⁴³ is an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an alkoxy group, an acyloxy group, or -N(R ^43g ) ₂ , R ⁴³ may be linked to any of R ¹³ to R ³³ to form a ring having 3 to 6 members. In addition, the ring may have a substituent.

Examples of the substituent in R ⁴³ 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 imido group, a thiol group, a sulfide group, an alkoxy group having 1 to 8 carbon atoms, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, a heteroaryl group having 3 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkynyl group having 2 to 8 carbon atoms, a silyl group, and a halogenated alkyl group having 1 to 8 carbon atoms.
When R ⁴³ has a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ⁴³ .

The halogen atom in R ⁴³ is preferably a fluorine atom.

The carbonyl structure-containing monovalent organic group in R ⁴³ is preferably -C(=O)-R ^43a . R ^43a is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may have a substituent, or an alkoxy group having 1 to 8 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.

The silyl group in R ⁴³ is preferably -Si(R ^43b ) _3. R ^43b is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, or an isopropyl group. The three R ^43b may be the same or different.

The sulfide group in R ⁴³ is preferably —SR ^43c . R ^43c is a hydrogen atom or an alkyl group having 1 to 9 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.

The amide structure-containing monovalent organic group in R ⁴³ is preferably -C(=O)-NH-R ^43d . R ^43d is a hydrogen atom or an alkyl group having 1 to 8 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.

The sulfonamide group in R ⁴³ is preferably —SO ₂ —N(R ^43e ) _2. R ^43e is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent, and is preferably a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, or a t-butyl group. The two R ^43e may be the same or different.

The urethane structure-containing monovalent organic group in R ⁴³ is preferably —NH—C(═O)O—R ^43f . R ^43f is a hydrogen atom or an alkyl group having 1 to 8 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.

As the alkyl group having 1 to 9 carbon atoms for R ⁴³ , 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 is preferable.

The alkenyl group having 2 to 9 carbon atoms for R ⁴³ 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.

The alkynyl group having 2 to 9 carbon atoms for R ⁴³ is preferably an acetylenyl group, a 1-propynyl group, a trimethylsilylethynyl group, a triethylsilylethynyl group, a triisopropylsilylethynyl group, or a t-butyldimethylsilylethynyl group.

The aryl group having 6 to 9 carbon atoms for R ⁴³ is preferably a phenyl group, a 4-methoxyphenyl group, a 3,4,5-trifluorophenyl group, a 4-trifluoromethylphenyl group, a 2,5-dimethylphenyl group, or a 3-nitrophenyl group.

The heteroaryl group having 3 to 9 carbon atoms for R ⁴³ 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.

The alkoxy group having 1 to 9 carbon atoms for R ⁴³ 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.

As the acyloxy group having 2 to 9 carbon atoms for R ⁴³ , an acetoxy group, a propionyloxy group, a butyryloxy group, an isobutyryloxy group, or a benzoyloxy group is preferable.

In -N(R ^43g ) ₂ in R ⁴³ , two R ^43g may be the same or different. In addition, two R ^43g may be linked to each other to form a ring. -N(R ^43g ) ₂ is preferably a dimethylamino group, a diethylamino group, an ethylisopropylamino group, or a morpholino group.

X ³² is S, NR ⁵³ or O.
R ⁵³ is a hydrogen atom, a carbonyl structure-containing monovalent organic group, a sulfo group, or an alkyl group having 1 to 9 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.
Examples of the substituent include the same substituents as those in ^R43 .

When R ⁵³ is an alkyl group having 1 to 9 carbon atoms which may have a substituent, R ⁵³ may be linked to any of R ¹³ to R ³³ to form a ring having 3 to 6 members.

X ³³ is S, NR ⁶³ or O.
R ⁶³ is a hydrogen atom, a carbonyl structure-containing monovalent organic group, a sulfo group, or an alkyl group having 1 to 9 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.
Examples of the substituent include the same substituents as those in ^R43 .

When R ⁶³ is an alkyl group, R ⁶³ may be linked with R ⁴³ to form a 3-6 membered ring.

In formula (III), X ³¹ , X ³² and X ³³ may have the following combinations.

From the viewpoint of ease of synthesis, preferred combinations are ( ^X31 , ^X32 , ^X33 ) = ( ^CR43 , S, S), ( ^CR43 , S, O), ( ^CR43 , O, S), ( ^CR43 , O, O), ( ^CR43 , ^NR53 , S), ( ^CR43 , ^NR53 , O), and more preferred combinations are ( ^X31 , ^X32 , ^X33 ) = ( ^CR43 , S, S), ( ^CR43 , S, O), ( ^CR43 , ^NR53 , S), ( ^CR43 , ^NR53 , O).

As the squarylium compound represented by formula (III), from the viewpoint of ease of synthesis and increased molecular linearity, the squarylium compound represented by the following formula (III-1) and the squarylium compound represented by the following formula (III-2) are preferred.

R ¹³ , R ²³ , R ^33A , R ^33B and R ⁴³ are the same as R ¹³ , R ²³ , R ^33A , R ^33B and R ⁴³ in formula (III), including preferred embodiments thereof.

More specifically, examples of compound (III-1) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

More specifically, examples of compound (III-2) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

Squarylium compound (III) can be synthesized by a known production method or the production method described below.

The squarylium compound (III-1) can be produced, for example, by the method described in WO 2019/230570.

A method for obtaining a squarylium compound (III-B) in which R ³³ in the squarylium compound (III) is R ^33B is shown in scheme (FB).

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. Furthermore, azide is preferably diphenylphosphoryl azide. N alkylation is preferably an S _N 2 reaction using an alkyl halide and a base, or a reductive amination reaction using an aldehyde and a reducing agent.

Step B is a reaction for converting halogens to various substituents, and may utilize, but is not limited to, cross-coupling reactions, Heck reactions, formylation, Wittig reactions of aldehydes obtained by formylation, Knevenagel reactions, Henry reactions, and nucleophilic addition reactions of alkyl metal reactants.

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

A method for synthesizing a compound in which X ³¹ , X ³² and R in the starting material (a2-1) are as follows:
Compound (a2-1-1): (X ³¹ , X ³² , R)=(-CH, S, -CH ₂ CH ₃ )
Compound (a2-1-2): (X ³¹ , X ³² , R)=(-CH, S, H)
Compound (a2-1-3): (X ³¹ , X ³² , R)=(-CH, O, -CH ₂ CH ₃ )
Compound (a2-1-4): (X ³¹ , X ³² , R)=(-CH, O, H)

A method for synthesizing a compound in which X ³¹ , X ³² , (X ³³ ) and R in the starting material (a2-1) are as follows:
Compound (a2-1-5): (X ³¹ , X ³² , R)=(-CH, -NH, -CH ₂ CH ₃ )
Compound (a2-1-6): (X ³¹ , X ³² , R)=(-CH, -NH, H)
Compound (a2-1-7): (X ³¹ , X ³² , X ³³ , R)=(-CH, -NH, -NH, -CH ₂ CH ₃ )
Compound (a2-1-8): (X ³¹ , X ³² , X ³³ , R)=(-CH, -NH, -NH, H)

A method for synthesizing a compound in which X ³¹ , X ³² and R in the starting material (a2-1) are as follows:
Compound (a2-1-9): (X ³¹ , X ³² , R)=(N, O, -CH ₂ CH ₃ )
Compound (a2-1-10): (X ³¹ , X ³² , R)=(N, O, H)

A method for synthesizing a compound in which X ³¹ , X ³² and R in the starting material (a2-1) are as follows:
Compound (a2-1-11): (X ³¹ , X ³² , R)=(N, -NH, -CH ₂ CH ₃ )
Compound (a2-1-12): (X ³¹ , X ³² , R) = (N, -NH, H)

A method for synthesizing a compound in which X ³¹ , X ³² and R in the starting material (a2-1) are as follows:
Compound (a2-1-13): (X ³¹ , X ³² , R)=(N, S, -CH ₂ CH ₃ )
Compound (a2-1-14): (X ³¹ , X ³² , R)=(N, S, H)

<Squarylium dye (IV)>

Here, the symbols in the above formula are as follows:
R ¹⁴ and R ²⁴ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, an alicyclic ring or an aromatic ring.

R ¹⁴ may be linked with R ²⁴ , R ⁵⁴ or R ⁷⁴ to form a ring.
R ²⁴ may be linked with R ¹⁴ , R ⁵⁴ or R ⁷⁴ to form a ring.
The ring is preferably an alicyclic or aromatic ring having 3 to 6 members. The ring may have a substituent.

The number of carbon atoms in R ¹⁴ and R ²⁴ can be 1 to 20. When R ¹⁴ and R ²⁴ are linear, the number of carbon atoms is preferably 2 to 12, more preferably 3 to 10, and still more preferably 4 to 8. When R ¹⁴ and R ²⁴ are branched, the number of carbon atoms is preferably 3 to 12, and more preferably 4 to 8.

The substituents in R ¹⁴ and R ²⁴ include the same groups as the substituents in R ¹³ and R ²³ in the squarylium dye (III).

When R ¹⁴ and R ²⁴ each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

When R ¹⁴ and R ²⁴ have a substituent, or when the main chain or side chain contains an alicyclic ring or aromatic ring, the above number of carbon atoms includes the number of carbon atoms of the substituent, alicyclic ring, and aromatic ring.

R ¹⁴ and R ²⁴ may be the same or different, but are preferably the same from the viewpoint of ease of production.

From the viewpoint of the degree of orientation, R ¹⁴ and R ²⁴ are preferably linear.

R ¹⁴ and R ²⁴ are more preferably, for example, a group selected from groups (1b) to (5b) and groups (1c) to (2c) in R ¹³ and R ²³ in the above squarylium dye (III).

In addition, when R ¹⁴ and R ²⁴ are linked to each other to form a heterocycle together with the nitrogen atom, the divalent group -Q ⁴ - to which R ¹⁴ and R ²⁴ are bonded is preferably the same as the divalent group -Q ³ - in the above-mentioned squarylium dye (III).

R ³⁴ is an organic group R ^34A which does not necessarily have an unsaturated bond, or an organic group R ^34B which necessarily has an unsaturated bond.
The organic group R ^34A , which does not necessarily have an unsaturated bond, is a hydrogen atom, a halogen atom, a hydroxyl group, or an alkyl group, an alkoxy group, an aryl group, or an araryl group, which may have a substituent and may contain an unsaturated bond or an oxygen atom between carbon atoms.
The organic group R ^34B essentially containing an unsaturated bond 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 which contains a carbonyl structure and has 1 or more carbon atoms which may have a substituent, an aryl group having 6 to 9 carbon atoms which may have a substituent, or a heteroaryl group having 3 to 9 carbon atoms which may have a substituent.

Examples of the substituent in R ^34A include the same groups as the substituent in R ^33A in the above squarylium dye (III).

When R ^34A is an alkyl group or an alkoxy group, the carbon number is preferably 1 to 8, more preferably 1 to 6, and even more preferably 1 to 3. When R ^34A is an aryl group, the carbon number is preferably 6 to 9. When ^{R 34A} is an araryl group, the carbon number is preferably 7 to 9.
When R ^34A has a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ^34A .

From the viewpoint of photostability, R ^34A is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and particularly preferably a hydrogen atom.

Examples of the substituent in the organic group R ^34B which necessarily has an unsaturated bond include the same groups as the substituent in R ^33B in the above squarylium dye (III).
When R ^34B has a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ^34B .

When R ^34B is an alkenyl group, it has 2 or more carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms.
As the alkenyl group, a group represented by the above formula (3-1) is preferred, similar to R ^33B in the above squarylium dye (III).

When R ^34B is an alkynyl group, it has 2 or more carbon atoms, preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 2 to 4 carbon atoms.
As the alkynyl group, a group represented by the above formula (3-2) is preferable, similar to R ^33B in the above squarylium dye (III).

When R ^34B is an imino group, it has 1 or more carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 4 carbon atoms.
The imino group is preferably a group represented by the above formula (3-3), similar to R ^33B in the above squarylium dye (III).

When R ^34B is a cyano group, it is a group represented by the above formula (3-4), similar to R ^33B in the above squarylium dye (III).

When R ^34B is an organic group having 1 or more carbon atoms which contains a carbonyl structure and may have a substituent, the number of carbon atoms is 1 or more, preferably 1 to 8, more preferably 1 to 6, and further preferably 1 to 4.
As such an organic group, a group represented by the above formula (3-5) is preferred, similar to R ^33B in the above squarylium dye (III).

When R ^34B is an aryl group, it has 6 to 9 carbon atoms.
As the aryl group, a group represented by the above formula (3-6) is preferred, similar to R ^33B in the above squarylium dye (III).

When R ^34B is a heteroaryl group, it has 3 to 9 carbon atoms.
As the heteroaryl group, a group represented by any one of the above formulas (3-7) to (3-9) is preferable, similar to R ^33B in the above squarylium dye (III).

R ⁴⁴ , R ⁵⁴ , R ⁶⁴ and R ⁷⁴ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or a monovalent organic group having 1 to 9 carbon atoms.

Examples of the halogen atom include a chlorine atom, a fluorine atom, an iodine atom, and a bromine atom.
Examples of the monovalent organic group include an alkyl group, an alkoxy group, an acyloxy group, an araryl group, an amino group, an alkenyl group, an alkynyl group, an imino group, a cyano group, a carbonyl group, an aryl group, and a heteroaryl group.

In formula (IV), ^X41 is ^CR43 or N. ^X42 is S, ^NR53 , or O. ^X43 is S, ^NR63 , or O. ^R43 , ^R53 , and ^R63 are the same as ^R43 , ^R53 , and ^R63 in the squarylium dye (III) described above, including definitions and preferred embodiments.

More specifically, examples of compound (IV) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

Compound (IV) can be produced by linking, by a coupling reaction, 4-aminobenzeneboronic acid in which R ¹⁴ and R ²⁴ are bonded to an amino group and a fused heterocyclic compound in which a halogen atom is bonded to the carbon atom between X ⁴¹ and X ⁴² , and then reacting the resulting compound with squaric acid.

<Squarylium dye (V)>

Here, the symbols in the above formula are as follows:
R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group having 1 to 9 carbon atoms which may have a substituent, an aryl group having 4 to 9 carbon atoms which may have a substituent, or an araryl group having 5 to 9 carbon atoms which may have a substituent.

In R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ , the alkyl group, aryl group or araryl group may have a substituent.
In addition, the alkyl group, aryl group, or araryl group may contain an unsaturated bond, an oxygen atom, an ester bond, an amide bond, or a thioamide bond between carbon atoms.
Furthermore, the alkyl group, aryl group, or araryl group may have an oxygen atom, an ester bond, an amide bond, or a thioamide bond at the end bonding to the thiophene ring.

Examples of the substituents in R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ 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 8 carbon atoms. When R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are an aryl group or an araryl group, the substituent is a hydrogen atom bonded to an aromatic ring or a group substituting a hydrogen atom of an alkyl group contained therein, and further includes an aryl group in addition to the above-mentioned substituents.

When R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are alkyl groups, they have 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, and more preferably 1 or 2 carbon atoms.
When R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are aryl groups, they have 4 to 9 carbon atoms, and preferably 4 to 6 carbon atoms.
When R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are an araryl group, they have 5 to 9 carbon atoms, and preferably 5 to 7 carbon atoms.

When R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ have a substituent, the above carbon number includes the carbon number of the substituent.

R ³⁵ and R ⁴⁵ , R ⁴⁵ and R ⁵⁵ , and R ⁵⁵ and R ⁶⁵ may be linked to each other to form a monocycle or a polycycle having 2 to 4 condensed rings, in which case a hydrogen atom bonded to the ring may be substituted with a substituent.

The ring formed by combining ^R35 and ^R45 , and ^R55 and ^R65 may be an alicyclic ring or an aromatic ring, a hydrocarbon ring or a heterocyclic ring. An aromatic ring is preferable. An example of the monocyclic ring is a benzene ring, and an example of the polycyclic ring is a naphthalene ring, an anthracene ring, a phenanthrene ring, a tetracene ring, a chrysene ring, etc.

When R ⁴⁵ and R ⁵⁵ are linked together, the dye (V) contains a structure in which a ring is formed between two thiophene rings to form at least three condensed rings.

The hydrogen atom bonded to the ring formed by combining R ³⁵ and R ⁴⁵ , R ⁴⁵ and R ⁵⁵ , and R ⁵⁵ and R ⁶⁵ may be substituted with a substituent.
Examples of the substituents on these connecting rings include the same groups as the substituents on R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ , and phenyl groups which may have a substituent.

R ¹⁵ and R ²⁵ are each independently an alkyl group having 1 to 20 carbon atoms or an araryl group having 4 to 20 carbon atoms.

R ¹⁵ and R ²⁵ may have a substituent and may contain an unsaturated bond or a heteroatom between the carbon atoms.
Examples of the substituent in R ¹⁵ and R ²⁵ 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 19 carbon atoms.
When R ¹ and R ² have a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of R ¹ and R ² .

Further examples of the substituents in R ¹⁵ and R ²⁵ include cyclic alkyl groups or 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 substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 12 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, 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 the substituents are preferably a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, etc.

When R ¹⁵ and R ²⁵ each contain an alicyclic ring or an aromatic ring in the main chain or side chain, 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.

The substituents in R ¹⁵ and R ²⁵ are preferably polymerizable groups from the viewpoint of improving the reliability of the optical element.

When R ¹⁵ and R ²⁵ are alkyl groups, the number of carbon atoms is 1 to 20, preferably 1 to 12, and more preferably 1 to 10. From the viewpoint of improving visible light transmittance and dichroic ratio, R ¹⁵ and R ²⁵ are preferably linear, branched, or cyclic alkyl groups having 3 to 20 carbon atoms and which may contain a heteroatom between the carbon-carbon atom. The number of carbon atoms of the alkyl group is more preferably 3 to 12 in the case of linear alkyl groups, more preferably 3 to 10 in the case of branched alkyl groups, and more preferably 5 to 10 in the case of cyclic alkyl groups. When R ¹⁵ and R ²⁵ have a substituent, the number of carbon atoms of the substituent is included in the number of carbon atoms of the substituent.

R ¹⁵ and R ²⁵ are, for example, more preferably a group selected from groups (1a) to (15a), particularly preferably group (3a).

R ¹⁵ and R ²⁵ may be linked together to form a heterocycle having 4 to 10 members together with the nitrogen atom, and from the viewpoint that the squarylium dye is likely to be linear, i.e., from the viewpoint that it is likely to exhibit dichroism, the number of members is particularly preferably 4 to 6. In such a heterocycle, one of the hydrogen atoms bonded to the carbon atom farthest from the nitrogen atom may be substituted with an alkyl group having 1 to 12 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 3 to 8 carbon atoms, which may have an unsaturated bond or a heteroatom between the carbon atoms. The alkyl group may be branched, linear, or cyclic, but from the viewpoint that the squarylium dye is likely to exhibit dichroism, a linear alkyl group is preferred. In addition, some or all of the hydrogen atoms in such a heterocycle may be substituted with halogen atoms, and in that case, it is preferred that some or all of the hydrogen atoms bonded to the carbon atom not adjacent to the nitrogen atom are substituted with halogen atoms.

When the divalent group to which R ¹⁵ and R ²⁵ are bonded is represented by -Q ⁵ -, specific examples of -Q ⁵ - include the following groups (11) to (15).

-(CH ₂ ) ₄ - (11)
-(CH ₂ ) ₅ - (12)
-C(CH ₃ ) ₂ (CH ₂ ) ₂ C(CH ₃ ) ₂ - (13)
-C( _CH3 ) ₂ ( _CH2 ) _3C ( _CH3 ) _2- (14)
-CH ₂ -CH(nC ₈ H ₁₇ )-(CH ₂ ) ₂ - (15)

As the squarylium compound (V), for example, a compound represented by the following formula (V-1) or a compound represented by the following formula (V-2) is preferable. The squarylium compound (V-1) is a squarylium compound (V) in which R ⁴⁵ and R ⁵⁵ are linked to form a cyclopentadithiophene ring. The squarylium compound (V-2) is a squarylium compound (V) in which R ⁴⁵ and R ⁵⁵ are not linked to each other and which includes a structure in which two thiophene rings are bonded.

The definitions of R ¹⁵ , R ²⁵ , R ³⁵ and R ⁶⁵ , including preferred embodiments thereof, are the same as those of R ¹⁵ , R ²⁵ , R ³⁵ and R ⁶⁵ in formula (V).
The definitions of R ^45b and R ^55b are the same as those of R ⁴⁵ and R ⁵⁵ in formula (V), including preferred embodiments thereof, except that R 45b and R 55b do not combine with each other to form a ring.

From the viewpoint of improving visible light transmittance, light resistance, and dichroic ratio, R ^45a and R ^55a are preferably linear, branched, or cyclic alkyl groups having 1 to 9 carbon atoms, which may contain an unsaturated bond or an oxygen atom between carbon atoms. The number of carbon atoms in the alkyl group is 1 to 9 in the case of linear alkyl groups, preferably 3 to 9 in the case of branched alkyl groups, and more preferably 5 to 9 in the case of cyclic alkyl groups. R ^45a and R ^55a are more preferably, for example, a methyl group or a group selected from groups (1a) to (13a) shown as specific examples of R ¹⁵ and R ²⁵ above, and are particularly preferably a methyl group, group (1a), group (3a), or group (9a).

From the viewpoint of heat resistance, light resistance, and control of NIR absorption wavelength, R ^45a and R ^55a are preferably a phenyl group which may have a substituent or a cyclic alkyl group having 5 to 9 carbon atoms. Examples of the substituent of the phenyl group include an alkyl group having 1 to 3 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, an alkoxy group, or an alkylamino group (wherein the alkyl group has 1 to 3 carbon atoms), and in particular, a methyl group, a dimethylamino group, a methoxy group, etc. are preferred. The phenyl group is preferably unsubstituted or substituted with 1 to 3 hydrogen atoms.

Specific examples of phenyl groups which may have a substituent include groups (P1) to (P6).

Specific examples of compound (V-1) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

Among these, compound (V-1-59) and the like are preferred as compound (V-1) from the viewpoint of improving the dichroic ratio.

More specifically, examples of compound (V-2) include the compounds shown in the table below. In addition, in the compounds shown in the table below, the meanings of the symbols on the left and right of the squarylium skeleton are the same.

Among these, compound (V-2-36) and the like are preferred as compound (V-2) from the viewpoint of improving the dichroic ratio.

Compound (V) can be produced by known methods, for example, the method described in WO 2019/230660.

<Squarylium dye (VI)>

However, the symbols in the above formula are as follows:

R ¹⁶ and R ²⁶ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, an alicyclic ring or an aromatic ring.

Examples of the substituent in R ¹⁶ and R ²⁶ 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 19 carbon atoms.

Further examples of the substituents in R ¹⁶ and R ²⁶ include cyclic alkyl groups or aryl groups. The aryl group is preferably a phenyl group which may have a substituent or a naphthyl group which may have a substituent. Examples of the substituents which may substitute hydrogen atoms in the phenyl group and naphthyl group include an alkyl group having 1 to 9 carbon atoms, which may contain an unsaturated bond or an oxygen atom between the carbon-carbon atom, an alkoxy group, or an alkylamino group (the alkyl group has 1 to 9 carbon atoms). The phenyl group and naphthyl group are preferably unsubstituted or substituted with 1 to 3 hydrogen atoms, and examples of the substituents include a methyl group, a t-butyl group, a dimethylamino group, a methoxy group, and the like.

The substituents in R ¹⁶ and R ²⁶ are preferably polymerizable groups from the viewpoint of improving the reliability of the optical element.

When R ¹⁶ and R ²⁶ contain an alicyclic ring or an aromatic ring in the main chain or side chain, this is preferred in terms of heat resistance and control of NIR absorption wavelength. When R ¹⁶ and R ²⁶ do not have an alicyclic ring or an aromatic ring in the main chain or side chain, this is preferred in terms of light resistance, ease of production, and improvement of the dichroic ratio. 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.

The number of carbon atoms in R ¹⁶ and R ²⁶ can be 1 to 20. When R ¹⁶ and R ²⁶ are linear, the number of carbon atoms is preferably 2 to 20, more preferably 3 to 16, and even more preferably 4 to 12. When R ¹⁶ and R ²⁶ are branched, the number of carbon atoms is preferably 3 to 20, more preferably 4 to 16, and even more preferably 4 to 8.

When R ¹⁶ and R ²⁶ have a substituent, or when the main chain or side chain contains an alicyclic ring or aromatic ring, the above number of carbon atoms includes the number of carbon atoms of the substituent, alicyclic ring, and aromatic ring.

R ¹⁶ and R ²⁶ may be the same or different, but are preferably the same from the viewpoint of ease of production. From the viewpoint of the degree of orientation, R ¹⁶ and R ²⁶ are preferably linear rather than branched, and more preferably have 1 to 8 carbon atoms, and even more preferably have 1 to 2 carbon atoms.

When R ¹⁶ and R ²⁶ are 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 liquid crystal and solvent and ease of production, the position of the branch is preferably the β position. In addition, one carbon atom may be branched into two or three.

R ¹⁶ and R ²⁶ are more preferably groups selected from groups (1b) to (5b), (1c), and (2c) described as more preferred embodiments of R ¹³ and R ²³ in the squarylium dye (III).
-CH(C _n H _2n+1 ) ₂ ...(1b)
-C(C _n H _2n+1 ) ₃ ...(1c)
_-CH2 -CH( _{CnH2n +1} ) ₂ ...(2b)
_-CH2 -C( _{CnH2n +1} ) ₃ ...(2c)
-(CH ₂ ) ₂ -CH(C _n H _2n+1 ) ₂ ...(3b)
-(CH ₂ ) ₃ -CH(C _n H _2n+1 ) ₂ ...(4b)
-(CH ₂ ) _m -CH ₃ ...(5b)

However, in formulas (1b) to (4b), (1c), and (2c), n is an integer of 1 to 10, preferably 2 to 8, and more preferably 2 to 4. However, the number of carbon atoms in groups (1b) to (4b) and groups (1c) to (2c) is within the range of 1 to 20. The two C _n H _2n+1 in formulas (1b) to (4b), (1c), and (2c), and the three C _n H _2n+1 in formulas (1c) to (2c), 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), (1c), and (2c) may have a heteroatom between the carbon-carbon atom.

R ³⁶ is a monovalent organic group having 9 or less carbon atoms and containing an atom having an unshared electron pair. By bonding a group having an unshared electron pair to the carbon atom closest to the squarylium skeleton, the electron density of the unsaturated carbocyclic ring increases, and an atom having an unshared electron pair is required for the production of the dye (reaction with squaric acid). From this viewpoint, it is preferable that the atom having an unshared electron pair in R ³⁶ is directly bonded to the carbon atom of the unsaturated carbocyclic ring to which R ³⁶ is bonded.
The atom having an unshared electron pair is preferably N, S or O.

R ³⁶ is preferably NH-Y ^36a -R ^36a , SH or OH.
In NH-Y ^36a -R ^36a , Y ^36a is a single bond or a divalent organic group having 0 to 3 carbon atoms, and is preferably -CO-, -COO-, -CONH- or -SO ₂ -.
R ³⁶ is preferably NH—R ^36a , NH—CO—R ^36a , NH—COO—R ^36a , NH—CONH—R ^36a , NH—SO ₂ —R ^36a , SH or OH.

In NH-Y ^36a -R ^36a , R ^36a is an alkyl group having 1 to 9 carbon atoms which may have a substituent and which may contain an unsaturated bond between the carbon atoms, an oxygen atom, an alicyclic ring or an aromatic ring. The upper limit of the total carbon number of Y ^36a and R ^36a is 9.

The carbon number of R ^36a is preferably 1 to 9, more preferably 1 to 4, and particularly preferably 1 or 2, when it is linear; and is preferably 3 to 9, and particularly preferably 3 or 4, when it is branched.

Examples of the substituent in R ^36a include the same groups as the substituents in R ¹⁶ and R ²⁶ .
When R ^36a has a substituent, or when it contains an alicyclic ring or aromatic ring in the main chain or side chain, the number of carbon atoms in the above includes the number of carbon atoms in the substituent, alicyclic ring, or aromatic ring.

From the viewpoint of improving the dichroic ratio, R ^36a is preferably linear.

R ^36a is more preferably a group selected from the groups (11b) to (15b), (11c) and (12c).
-CH(C _n H _2n+1 ) ₂ ...(11b)
-C(C _l H _2l+1 ) ₃ ...(11c)
_-CH2 -CH( _{CnH2n +1} ) ₂ ...(12b)
_-CH2 -C( _{ClH2l +1} ) ₃ ...(12c)
-( _CH2 ) ₂ -CH( _{CnH2n +1} ) ₂ ...(13b)
-(CH ₂ ) ₃ -CH(C _n H _2n+1 ) ₂ ...(14b)
-(CH ₂ ) _m -CH ₃ ...(15b)

However, in formulas (11b) to (14b), n is an integer of 1 to 3, preferably 2 to 3. In formulas (11c) and (12c), l is an integer of 1 to 2. In formulas (11b) to (14b), (11c), and (12c), two C _n H _2n+1 or three C _l H _2l+1 may be linear or branched, and may be the same or different. In formula (15b), m is an integer of 0 to 8, preferably 0 to 8, more preferably 0 to 3, and even more preferably 0 to 1. Furthermore, groups (11b) to (15b), (11c), and (12c) may have an oxygen atom between carbon and carbon atoms.

R ⁴⁶ is a hydrogen atom or an alkyl group having 1 to 9 carbon atoms.

The alkyl group preferably has 1 to 8 carbon atoms, and more preferably has 1 to 4 carbon atoms.
The alkyl group may be linear or branched, but is preferably linear from the viewpoint of improving the dichroic ratio.

When R ⁴⁶ is an alkyl group having 1 to 9 carbon atoms, it is more preferably a group selected from the groups (11b) to (15b), (11c), and (12c) described as preferred embodiments for R ^36a .

From the viewpoint of steric hindrance, R ⁴⁶ is preferably a hydrogen atom.

R ⁵⁶ is a hydrogen atom or an alkyl group having 1 to 9 carbon atoms.
From the viewpoint of steric hindrance, R ⁵⁶ is preferably a hydrogen atom.

R ¹⁶ and R ²⁶ , R ¹⁶ and R ⁴⁶ , and R ³⁶ and R ⁴⁶ may be linked to each other to form a ring.
As the ring, ^R16 and ^R26 , and ^R16 and ^R46 are preferably alicyclic rings having 3 to 6 members, and ^R36 and ^R46 are preferably alicyclic rings or aromatic rings having 3 to 6 members. The rings may have a substituent. Examples of the substituent include the same groups as the substituents in ^R16 and ^R26 .

^X61 is C=O, C=S, or _SO2 .

The squarylium compound (VI) is preferably a squarylium compound represented by the following formula (VI-1):

R ¹⁶ to R ⁴⁶ are the same as R ¹⁶ to R ⁴⁶ in formula (VI), including preferred embodiments thereof.

As the squarylium compound (VI), the following squarylium compound (VI-11) in which R ³⁶ is NH—CO—R ^36a , the following squarylium compound (VI-12) in which R ³⁶ is NH—SO ₂ —R ^36a , the following squarylium compound (VI-13) in which R ³⁶ is NH—CONH—R ^36a , the following squarylium compound (VI-14) in which R ³⁶ is NH—COO—R ^36a , and the following squarylium compound (VI-15) in which R ³⁶ is OH are preferable.

More specifically, squarylium compounds (VI-11) to (VI-15) include compounds in which R ¹⁶ , R ²⁶ , R ^36a and R ⁴⁶ are shown in the following table (the table also shows the abbreviations for the squarylium compounds (VI-11) to (VI-15)). In the table, when R ¹⁶ , R ²⁶ , R ^36a and R ⁴⁶ are groups with a shown formula, they show the symbol of the formula. In all compounds shown in the table, R ¹⁶ , R ²⁶ , R ^36a and R ⁴⁶ are all the same on the left and right sides of the formula.

<Method for producing compound (VI)>
The production method of the squarylium compound (VI) will be explained using the production method of the squarylium compound (VI-11), but the production method of the squarylium compound (VI) is not limited thereto.
A method for obtaining the squarylium compound (VI-11) is shown in scheme (F-A11).

(1) A starting material (pA11-1), which is a known compound, is reacted with diisopropylethylamine (CH ₃ CH ₂ N(CH(CH ₃ ) ₂ ) ₂ ) and acetic anhydride to obtain a compound (pA11-2) in which the amino group is protected.
(2) The compound (pA11-3) is obtained by a nitration reaction.
(3) The amino group is deprotected to obtain compound (pA11-4).
(4) Compound (pA11-5) is obtained by N alkylation (S _N 2 reaction using an alkyl halide and a base, or reductive amination reaction using an aldehyde and a reducing agent).
(5) The nitro group is reduced to obtain compound (pA11-6).
(6) The compound (pA11-6) is reacted with alkanoyl chloride (R ^36a --C(═O)--Cl) to obtain the compound (pA11-7).
(7) The methoxy group is deprotected to obtain compound (pA11-8).
(8) Compound (pA11-8) is reacted with squaric acid to obtain compound (VI-11).

The squarylium compound (VI-12) can be produced by changing the alkanoyl chloride (R ^36a -C(═O)-Cl) in the above step (6) to R ^36a SO ₂ Cl.
The squarylium compound (VI-13) can be produced by reacting with carbonyldiimidazole in the above step (6) and then reacting with R ^36a NH ₂ .
The squarylium compound (VI-14) can be produced by changing the alkanoyl chloride (R ^36a -C(=O)-Cl) in the above step (6) to R ^36a O-C(=O)-Cl.

In the dichroic dye composition of the present invention, the content of the squarylium dye is preferably 0.1 mmol or more, more preferably 0.3 mmol or more, per 100 parts by mass of the liquid crystal compound in order to obtain sufficient absorbance, and is preferably 10 mmol or less, more preferably 5 mmol or less, per 100 parts by mass of the liquid crystal compound in order to obtain a stable liquid crystal phase over a wide temperature range. Two or more types of dyes may be used in combination, in which case the total content is within the above range.

<Liquid Crystal Compound>
The dichroic dye composition of the present invention contains, in addition to the dye, a liquid crystal compound that transmits visible light.

Types of liquid crystal compounds include non-polymerizable liquid crystal compounds exhibiting a nematic phase, polymerizable liquid crystal compounds exhibiting a nematic phase, and polymerizable liquid crystal compounds exhibiting a smectic phase. Liquid crystal compounds may be synthesized by known methods, or commercially available products may be used.

The content of the liquid crystal compound in the dichroic dye composition of the present invention is preferably 50% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more, from the viewpoint of expressing a stable liquid crystal phase over a wide temperature range, and is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and particularly preferably 99% by mass or less, from the viewpoint of achieving sufficient absorbance.

<Other ingredients>
A compound that does not exhibit liquid crystallinity may be added to the dichroic dye composition of the present invention for the purpose of changing the physical properties of the host liquid crystal to a desired range (for example, to set the temperature range of the liquid crystal phase to a desired range). In addition, a compound such as a chiral compound, an ultraviolet absorber, an antioxidant, or a polymerization initiator may be contained. Examples of such additives include the chiral agents for TN and STN described on pages 199 to 202 of "Liquid Crystal Device Handbook" (edited by the 142nd Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, 1989).
The dichroic dye composition of the present invention may contain an optically active compound, such as cholesteryl nonanoate, which may or may not exhibit a liquid crystal phase, and may also contain various additives, such as an ultraviolet absorber and an antioxidant.

In addition, when the liquid crystal compound is a non-polymerizable liquid crystal compound exhibiting a nematic phase, a liquid crystal curable compound having a polymerizable functional group or a non-liquid crystal curable compound having a polymerizable functional group may be added to the dichroic dye composition of the present invention. From the viewpoint of producing a polymer-dispersed liquid crystal element (PDLC) having a high-quality transmission-scattering type operation mode, it is preferable that the content of the non-liquid crystal curable compound in the dichroic dye composition is greater than the content of the liquid crystal curable compound, and the total amount of the liquid crystal curable compound and the non-liquid crystal curable compound is 8% by mass or more and less than 20% by mass of the total.

In addition, PDLC exhibits a scattering state when no voltage is applied, but also includes elements that exhibit a transparent state when no voltage is applied. An element that exhibits a transparent state when no voltage is applied includes a structure made of a curable compound that has an orientation similar to that of liquid crystal molecules in the composition, and transparency is ensured by aligning the liquid crystal molecules to have the same orientation axis as the structure. In the present invention, the curable compound includes both those that have liquid crystallinity and those that do not, and it is preferable that the content of the curable compound is 5% by mass or more and less than 20% by mass of the entire composition.

<Refractive index anisotropic film, optical absorption anisotropic film>
In the present invention, the squarylium dye, which is a dichroic dye, transmits visible light and absorbs near-infrared light, so that the film formed from the dichroic dye composition of the present invention has both properties of refractive index anisotropy and light absorption anisotropy. Therefore, it functions as a retardation film in the visible light region and functions as a polarizing film in the near-infrared light region. The retardation film is used to convert linearly polarized light into circularly polarized light or elliptically polarized light, or conversely, to convert circularly polarized light or elliptically polarized light into linearly polarized light.
Polarizing films are used to split unpolarized incident light into two orthogonal polarized components, transmit one polarized component, and absorb the other. The axial direction of the transmitted polarized component is called the transmission axis, and the axial direction of the absorbed polarized component is called the absorption axis.

<Optical elements>
The dichroic dye composition of the present invention, which has both liquid crystallinity and dichroism, is useful as a material for various optical elements such as retardation plates, polarizers, liquid crystal elements, etc. Since the dichroic dye of the present invention has a property of absorbing near-infrared light, it is possible to prepare a retardation film for visible light that absorbs near-infrared light, or a near-infrared-absorbing polarizing film that transmits visible light.
Each optical element will be described below.

<Retardation plate, polarizer>
The present invention also relates to a retardation plate having a substrate and the refractive index anisotropic film of the present invention on the substrate or between a pair of substrates.
The present invention also relates to a polarizer having a substrate and the optically absorptive anisotropic film of the present invention on the substrate or between a pair of substrates.
The substrate may be generally made of glass or plastic. Examples of plastic substrates include acrylic resin, polycarbonate resin, and epoxy resin. For the substrate, see, for example, "Liquid Crystal Device Handbook" (Japan Society for the Promotion of Science). The 142nd Committee of the Japanese Society of Chemical Substances and Chemical Substances, Nikkan Kogyo Shimbun, 1989, pp. 218-231 can be used.

It is preferable to form an alignment layer (alignment film) on the surface of the substrate that contacts the refractive index anisotropic film or the light absorption anisotropic film. Examples of the alignment process include a method of applying a quaternary ammonium salt to align the layer, a method of applying a polyimide and aligning the layer by rubbing, a method of evaporating SiOx from an oblique direction to align the layer, and an alignment method using light irradiation that utilizes photoisomerization. For example, the alignment film is described on pages 240 to 256 of "Liquid Crystal Device Handbook" (edited by the 142nd Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, 1989).

When a refractive index anisotropic film or a light absorption anisotropic film is formed between a pair of substrates, for example, the pair of substrates are placed facing each other with a spacer or the like interposed therebetween at a distance of 1 to 50 μm, the dichroic dye composition of the present invention is injected into the space formed between the substrates, and photopolymerization is performed by irradiating the substrate with light of a predetermined wavelength as necessary. As the spacer, for example, the one described on pages 257 to 262 of "Liquid Crystal Device Handbook" (edited by the 142nd Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, 1989) can be used.

<Liquid crystal element>
The present invention also relates to a liquid crystal element comprising a pair of electrode substrates and a liquid crystal layer formed between the electrode substrates. The liquid crystal layer is formed from the dichroic dye composition of the present invention. The electrode layer formed on the substrate is preferably a transparent electrode layer, and can be formed from, for example, indium oxide, indium tin oxide (ITO), tin oxide, or the like. As for the transparent electrode, for example, one described on pages 232-239 of "Liquid Crystal Device Handbook" (edited by the 142nd Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, Ltd., 1989) is used.
The liquid crystal element of the present invention also functions as a retardation plate in the visible light region, and also functions as a polarizer in the near infrared light region.

The optical element of the present invention can be mounted in various devices as described below.

<Imaging device>
The imaging device of the present invention includes, for example, a solid-state imaging element, an imaging lens, and the optical element of the present invention, and can provide a good image with high color reproducibility.

<Light-wave distance measuring device>
The optical distance measuring device of the present invention includes, for example, a laser diode, a scanning unit such as a beam splitter or a MEMS mirror, a photodiode, and the optical element of the present invention. This suppresses return light noise to the laser diode and stray light within the optical distance measuring device, improves detection accuracy, and reduces false detections.

<Solar radiation control components>
The solar radiation control member of the present invention includes, for example, the optical element of the present invention, which can switch between transmitting and absorbing near-infrared light without impairing the transmittance of visible light.

<Virtual reality device>
The virtual reality device of the present invention includes a display unit such as an LCD, OLED, or μLED, a lens unit, an optical element of the present invention between the display unit and the lens unit, and a camera equipped with near-infrared lighting capable of photographing the user's eyes.
The lens unit can include a retardation plate and a reflective polarizer, and the retardation plate can be the retardation plate of the present invention.
As an optical element between the display unit and the lens unit, the retardation plate or polarizer of the present invention can be used.
The above configuration suppresses stray near-infrared light within the virtual reality device, improves gaze tracking accuracy, and reduces false detections.

Next, the present invention will be explained in more detail with reference to examples.

The dyes used in each example are as follows:
Compounds 1 to 4: Synthesized based on WO 2017/135359.
Compound 5: Pyrrolidone was reacted with TMS-Cl to obtain N-TMS pyrrolidone, which was then reacted with LDA and n-octane iodide, and water was added to obtain 5-octylpyrrolidone, which was then reduced with LiAlH ₄ to obtain the corresponding amine (3-octylpyrrolidine). The rest were synthesized based on WO 2017/135359.
Compounds 6-7: Synthesized based on WO 2017/135359.
Compound 8: Synthesized based on WO 2019/230570.

Compound 9: Synthesized according to the reaction pathway shown below.

<Step 1>
Lithium diisopropylamide (THF/hexane solution, 1.08M, 200mL, 216mmol) was placed in a nitrogen-purged 1L four-neck flask and cooled to -78°C. 3,4-dibromothiophene (50.11g, 207mmol) diluted with THF (200mL) was added over 10 minutes using a dropping funnel and stirred for 30 minutes. The temperature was raised to 0°C and stirred for 10 minutes, after which DMF (19.2mL, 248mmol) was added and stirred at 30°C for 2.5 hours. After the reaction was completed, the mixture was cooled to 0°C and saturated aqueous ammonium chloride (200mL) was added. The mixture was extracted with ethyl acetate, washed with saturated saline, dried over magnesium sulfate, and concentrated under reduced pressure to obtain a crude product (60.8g) of intermediate a1-1. The crude product was used in the next reaction as it was.
¹ H NMR (CDCl ₃ , 300 MHz) δ9.95 (1 H, s), 7.76 (1 H, s).

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

<Step 3>
Intermediate a1-2 (29.31 g, 100.6 mmol), potassium vinyl trifluoroborate (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-substituted eggplant flask (500 mL) and heated and stirred at 85° C. for 3 days. After the reaction was completed, water was added, and the mixture was extracted with dichloromethane, washed with saturated saline, dried over magnesium sulfate, and concentrated under reduced pressure to obtain a crude product of intermediate a1-3 (27.09 g). The crude product was used in the next reaction as it was.
^1H NMR ( _CDCl3 , 300MHz) δ8.00 (1H, s), 7.47 (1H, s), 6.83 (1H, dd, J=17.7, 11.0Hz), 5.73 (1H, 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).

<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-substituted recovery flask (300 mL), and the mixture was heated and stirred 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 6N 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 over two steps).
^1H 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).

<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 recovery flask (300 mL) and heated under 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 and then concentrated under reduced pressure, followed by silica gel column chromatography (hexane:ethyl acetate=95:5) to obtain intermediate a1-5 (6.938 g, 94% yield).
^1H 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).

<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 the mixture was heated and stirred at 150° C. for 5 minutes under microwave irradiation. This was repeated 7 batches, and a total of 4.926 g of intermediate a1-5 was used for the reaction. After the reaction was completed, the 7 batches were combined, extracted with ethyl acetate, concentrated, and then subjected to silica gel column chromatography (hexane:ethyl acetate=80:20) to obtain intermediate a1-6 (2.223 g, 52% yield).
^1H 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).

<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. Saturated sodium bicarbonate water was added, followed by extraction with dichloromethane, drying with magnesium sulfate, concentration, and purification by silica gel column chromatography (hexane 100%) to obtain intermediate a2-7 (369.1 mg, 6% yield).
^1H 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 (1 H, 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).

<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-substituted recovery flask (100 mL), and the mixture was heated under reflux at 80° C. for 2 hours. After completion of the reaction, the solvent was removed, and compound (9) (39.7 mg, 14% yield) was obtained by silica gel chromatography (hexane:ethyl acetate=80:20).
^1H 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).

Compound 10: Synthesized according to the reaction pathway shown below.

<Steps 1 and 2>
Intermediate a1-2 was obtained by steps similar to steps 1 and 2 of the production method of compound (9).

<Step 3>
Intermediate a1-2 (83.66 g, 272.9 mmol), THF (175 mL), ethanol (175 mL), and aqueous sodium hydroxide solution (1.0 M, 430 mL, 430 mmol) were added to a nitrogen-substituted recovery flask (2 L), and the mixture was heated and stirred at 40° C. for 1 hour. After the reaction was completed, hydrochloric acid (1.0 M, 450 mL) was added at 0° C. to acidify the mixture, and the organic solvent was removed under reduced pressure, followed by filtration using a hydrophilic membrane filter. The residue was washed with water, then with a mixed solvent of water:methanol (=1:1), and the solvent was removed by azeotropic distillation with toluene, followed by vacuum drying to obtain intermediate a4-3 (79.4 g, >99% yield).
¹ H NMR (DMSO-d ₆ , 300 MHz) δ13.51 (1H, brs), 8.23 (1H, s), 8.08 (1H, s).

<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-substituted recovery flask (300 mL), and the mixture was heated and stirred for 30 minutes at 60° C. After completion of the reaction, saturated aqueous sodium bicarbonate and ethyl acetate were added at 0° C. and separated, and the resulting organic layer was washed with saturated aqueous sodium bicarbonate, water, and saturated saline, 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 (CDCl ₃ , 400 MHz) δ8.05 (1 H, s), 7.55 (1 H, s).

<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-substituted recovery flask (500 mL), and the mixture was heated and stirred at 80° C. for 15 hours. After the reaction was completed, the mixture was concentrated, dissolved in dichloromethane, filtered with silica gel, the solvent was distilled off, and the mixture was dried in vacuum to obtain intermediate a4-5 (12.21 g, 79% yield).
¹ H NMR (DMSO-d ₆ , 300 MHz) δ10.80 (1H, s), 7.50 (1H, s), 6.92 (1H, s), 1.49 (9H, s).

<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-substituted 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 sodium bicarbonate water and ethyl acetate were added at room temperature and the mixture was separated, and the organic layer was washed with saturated sodium bicarbonate water, water, and saturated saline. 2-Ethylhexanal (7.021 g, 54.76 mmol) and sodium sulfate were added to the obtained organic layer, and the mixture was allowed to stand for 15 minutes, filtered, and the solvent was distilled off. The obtained product was transferred to a four-neck flask (1 L), methanol (270 mL), acetic acid (37 mL), and 2-ethylhexanal (14.05 g, 109.6 mmol) were added, and the mixture was stirred at −10° C. under a nitrogen atmosphere, 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 sodium bicarbonate water, hexane, and ethyl acetate were added and separated, and the obtained organic layer was washed with saturated sodium bicarbonate water, water, and saturated saline, dried over sodium sulfate, and concentrated to obtain a crude product. The raw aldehyde was removed by NH ₂ silica gel filtration, and intermediate a4-7 (12.01 g, 72% yield) was obtained by silica gel column chromatography (hexane 100%).
^1H 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).

<Step 8>
In a nitrogen-substituted two-neck flask (50 mL), 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), tri-orthotolylphosphine (132.8 mg, 0.4363 mmol), and DMF (25.0 mL) were added, and the mixture was heated and stirred at 85 ° C. for 3 hours. After the reaction was completed, a saturated aqueous ammonium chloride solution was added at 0 ° C., extracted with hexane / ethyl acetate, washed with water and saturated saline, dried over magnesium sulfate, concentrated, and subjected to silica gel column chromatography (hexane: ethyl acetate = 20: 1) to obtain intermediate a9-8 (461.9 mg, 23% yield).
^1H NMR ( _CDCl3 , 300MHz) δ7.71 (1H, d, J = 16.1Hz), 7.24 (1H, s), 6.23 (1H, d, J = 15.8Hz), 6.04 (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).

<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-substituted recovery flask (100 mL), and the mixture was heated and stirred at 80° C. for 1.5 hours. After the reaction was completed, the mixture was concentrated to about half its volume, and hexane, ethyl acetate, and saturated aqueous sodium bicarbonate were added to separate the mixture. 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 compound (10) (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).

Compound 11: Synthesized based on WO 2019/230660.

Compound 12: Synthesized based on the reaction pathway shown below.

(Step 1): Compound (1x) (3-amino-2-methoxypyridine, manufactured by Tokyo Chemical Industry Co., Ltd.) (2.5 g) was dissolved in dichloromethane (60 ml), and diisopropylethylamine (2.8 g) and acetic anhydride (2.25 g) were added thereto and stirred at room temperature for 3 hours. The product was purified by silica gel column chromatography to obtain compound (2x) (yield 94%).
(Step 2): To compound (2x) (2.5 g) was added trifluoroacetic anhydride (7.5 ml) at 0° C. and the mixture was stirred for 30 minutes, and then a mixed solution of 1.1 equivalents of nitric acid (1.1 g) and trifluoroacetic anhydride (12 g) was added dropwise at 0° C. After stirring at room temperature for 12 hours, the mixture was neutralized with an aqueous sodium hydroxide solution, and 2.4 g of the resulting solid compound (3x) was collected (yield 76%).
(Step 3): Compound (3x) (1.9 g) was dissolved in methanol (50 ml), and 1 M hydrochloric acid (18 ml) was added thereto and stirred for 12 hours at 60° C. After removing the methanol, the mixture was neutralized and 1.47 g of a solid compound (4x) was filtered off (yield 96%).
(Step 4): Compound (4x) (5.1 g) was dissolved in dichloromethane (80 ml), 2-ethylhexylaldehyde (42 ml) (20 equivalents), triacetoxyborohydride (25 g) (4 equivalents), and acetic acid (0.2 ml) were added, and the mixture was stirred at room temperature for 4 hours. After adding an alkali until the pH reached 7, the mixture was separated into dichloromethane and water, and the concentrated organic layer was purified by silica gel chromatography to obtain compound (5x) (5.9 g) (yield 78%).
(Step 5): Compound (5x) (5.9 g) was dissolved in methanol, palladium on carbon (3 g) was added, and the mixture was stirred under a hydrogen atmosphere for 5 hours. Water was added, and the palladium was removed by filtration through Celite. After removing the methanol, the mixture was separated with ethyl acetate/water to obtain the desired compound (6) (3.7 g) (yield 71%).
(Step 6): Compound (6x) (3.7 g) was dissolved in dichloromethane (50 ml) and diisopropylethylamine (2.36 g) was added. The solution was cooled to 0° C., isobutyl chloroformate (2.7 g) was added, and the mixture was stirred at room temperature for 12 hours. After the reaction was completed, the mixture was separated into dichloromethane and water, and the organic layer was concentrated and then purified by column chromatography to obtain the target compound (7x) (yield 88%).
(Step 7): Compound (7x) (5.8 g) was dissolved in 150 ml of acetonitrile, and 3 equivalents each of TMS-Cl (5.4 g) and sodium iodide (7.5 g) were added. After reacting at 80° C. for 3 hours, the mixture was concentrated and purified by column chromatography to obtain the desired compound (8x) (2 g) (yield 35%).
(Step 8): Compound (8x) and 0.6 equivalents of 3,4-dihydroxy-3-cyclobutene-1,2-dione were added and reacted in 1-butanol at 110° C. for 16 hours. After the reaction was completed, the solvent was completely removed, and the product was purified using a column and extracted with an acetic acid/methanol solution to obtain squarylium compound (12) in a yield of 35%.

Compounds 13 to 15: Synthesized based on WO 2017/135359.
In compounds 13 to 15, indoline was synthesized according to the following method.
In compound 13, 2,3,3-trimethylindolenine was reacted with an excess amount of sodium borohydride in an acetic acid solvent, and then reacted with isobutyraldehyde to synthesize N-isobutyl-2,3,3-trimethylindoline.
In the case of compound 14, isobutyronitrile was reacted with isobutylmagnesium, and then with phenylhydrazine to synthesize indolenine. In an acetic acid solvent, this indolenine was reacted with an excess of sodium borohydride, and then with propionaldehyde to synthesize N-propyl-2-isobutyl-3,3-dimethylindoline.
In the case of compound 15, indolenine was synthesized by reacting 2,3-dimethylindole with ethylmagnesium bromide and further with methallyl chloride. In acetic acid solvent, this indolenine was reacted with an excess amount of sodium borohydride and further with acetaldehyde to synthesize N-ethyl-3-isobutyl-2,3-dimethylindoline.

Compound 16: Synthesized based on the method described in Dyes and Pigments 73 (2007) 344-352.

The liquid crystal compound used was the following non-polymerizable nematic liquid crystal compound (ZLI-1132, manufactured by LCC Corporation).

<Production and Evaluation of Dichroic Dye Composition>
(Example 1)
The squarylium dye of Compound 1 below and the above liquid crystal compound were mixed to obtain a dichroic dye composition of Example 1 having a squarylium dye content of 0.19% by mass (0.34 mmol relative to 100 parts by mass of the liquid crystal compound).
The obtained dichroic dye composition was injected into a horizontal alignment cell manufactured by EHC with a gap of 5 μm maintained, and polarized light parallel to the rubbing direction and polarized light perpendicular to the rubbing direction were irradiated, respectively, and the respective absorption spectra (A|| and A⊥) were measured using a visible absorption spectrometer (manufactured by Shimadzu Corporation) to determine the dichroic ratio.

(Example 2)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 2 below was used as the squarylium dye and the squarylium dye content was 0.24% by mass (0.30 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 3)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 3 below was used as the squarylium dye and the squarylium dye content was 0.21% by mass (0.34 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 4)
The dichroic ratio was measured in the same manner as in Example 1, except that Compound 4 below was used as the squarylium dye and the squarylium dye content was 0.10% by mass (0.22 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 5)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 5 below was used as the squarylium dye and the squarylium dye content was 0.18% by mass (0.27 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 6)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 6 below was used as the squarylium dye and the squarylium dye content was 0.16% by mass (0.33 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 7)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 7 below was used as the squarylium dye and the squarylium dye content was 0.16% by mass (0.33 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 8)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 8 below was used as the squarylium dye and the squarylium dye content was 0.25% by mass (0.30 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 9)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 9 below was used as the squarylium dye and the squarylium dye content was 0.20% by mass (0.22 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 10)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 10 below was used as the squarylium dye and the squarylium dye content was 0.50% by mass (0.50 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 11)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 11 below was used as the squarylium dye and the squarylium dye content was 0.31% by mass (0.33 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 12)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 12 below was used as the squarylium dye and the squarylium dye content was 0.20% by mass (0.20 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 13)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 13 below was used as the squarylium dye and the squarylium dye content was 0.16% by mass (0.27 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 14)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 14 below was used as the squarylium dye and the squarylium dye content was 0.17% by mass (0.26 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 15)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 15 below was used as the squarylium dye and the squarylium dye content was 0.19% by mass (0.30 mmol relative to 100 parts by mass of the liquid crystal compound).

(Example 16)
A dichroic dye composition was prepared and the dichroic ratio was measured in the same manner as in Example 1, except that Compound 16 below was used as the cyanine dye instead of the squarylium dye and the cyanine dye content was 0.25% by mass (0.32 mmol relative to 100 parts by mass of the liquid crystal compound).

The dichroic ratios of the above dichroic dye compositions are shown in the table below.
Examples 1 to 15 are working examples, and Example 16 is a comparative example.

The above results show that all of the dichroic dye compositions in the examples exhibited excellent dichroism.

The dichroic dye composition of the present invention is useful as a material for optical elements such as liquid crystal elements, polarizers, and retardation plates. In addition, since the dichroic dye composition of the present invention has near-infrared absorption ability, it is particularly useful for near-infrared and infrared light sensors, etc.

Claims (10)

The present invention includes a squarylium dye containing a heteroatom and a liquid crystal compound that transmits visible light,
The dichroic dye composition , wherein the squarylium dye has a maximum absorption wavelength in a wavelength region of 700 nm or more and is a compound represented by any one of the following formulas (II), (III), (V), and (VI) :

[The symbols in the above formula are as follows:
Each ring Z2 is independently a 5- or 6-membered ring having 0 to 3 heteroatoms in the ring, and the hydrogen atoms in ring Z2 may be substituted.
R ¹² and R ²² each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may contain an unsaturated bond between carbon atoms, a heteroatom, or a saturated or unsaturated ring structure and which may have a substituent.
R ³² and R ⁴² each independently represent a hydrogen atom, a halogen atom, or an alkyl or alkoxy group having 1 to 8 carbon atoms which may contain a heteroatom between the carbon atoms and which may have a substituent.
R ¹² and R ²² , R ¹² and R ⁴² , and R ²² and the carbon atoms or heteroatoms constituting ring Z2 may be bonded to each other to form, together with the nitrogen atom, a 4- to 6-membered heterocycle A2, a 5- to 7-membered heterocycle B2, and a 5- to 7-membered heterocycle C2, respectively.

[The symbols in the above formula are as follows:
R ¹³ and R ²³ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, an alicyclic ring, or an aromatic ring.
R ³³ is an organic group R ^33A which does not necessarily have an unsaturated bond, or an organic group R ^33B which necessarily has an unsaturated bond .
X31 is ^{CR43 or} N.
X ³² is S, NR ⁵³ or O.
X ³³ is S, NR ⁶³ or O.
R ⁴³ 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 9 carbon atoms which may have a substituent, an alkenyl group having 2 to 9 carbon atoms which may have a substituent, an alkynyl group having 2 to 9 carbon atoms which may have a substituent, an aryl group having 6 to 9 carbon atoms which may have a substituent, a heteroaryl group having 3 to 9 carbon atoms which may have a substituent, an alkoxy group having 1 to 9 carbon atoms which may have a substituent, an acyloxy group having 2 to 9 carbon atoms which may have a substituent, or -N(R ^43g ) ₂ (R ^43g is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may have a substituent).
R ⁵³ and R ⁶³ each independently represent a hydrogen atom, a carbonyl structure-containing monovalent organic group, a sulfo group, or an alkyl group having 1 to 9 carbon atoms which may have a substituent.
R ¹³ may be linked with R ²³ , R ³³ , X ³¹ , X ³² or X ³³ to form a 3-6 membered ring.
R ²³ may be linked with R ¹³ , R ³³ , X ³¹ , X ³² or X ³³ to form a 3-6 membered ring.
R ³³ may be linked with X ³¹ , X ³² , or X ³³ to form a 5- to 7-membered ring.]

[The symbols in the above formula are as follows:
R ¹⁵ and R ²⁵ each independently represent an alkyl group having 1 to 20 carbon atoms, which may have a substituent, and which may contain an unsaturated bond or a heteroatom between carbon atoms, or an araryl group having 4 to 20 carbon atoms.
R ³⁵ , R ⁴⁵ , R ⁵⁵ and R ⁶⁵ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group having 1 to 9 carbon atoms which may have a substituent, an aryl group having 4 to 9 carbon atoms which may have a substituent, or an araryl group having 5 to 9 carbon atoms which may have a substituent.
R ³⁵ and R ⁴⁵ , R ⁴⁵ and R ⁵⁵ , and R ⁵⁵ and R ⁶⁵ may be linked to each other to form a monocycle or a polycycle having 2 to 4 condensed rings.
R ¹⁵ and R ²⁵ may be linked to each other to form a 4-10 membered heterocycle together with the nitrogen atom.

[The symbols in the above formula are as follows:
R ¹⁶ and R ²⁶ each independently represent an alkyl group having 1 to 20 carbon atoms which may have a substituent and which may contain an unsaturated bond between carbon atoms, a heteroatom, an alicyclic ring or an aromatic ring.
R ³⁶ is a monovalent organic group having 9 or less carbon atoms which contains an atom having an unshared electron pair.
R ⁴⁶ is a hydrogen atom or an alkyl group having 1 to 9 carbon atoms.
R ⁵⁶ is a hydrogen atom or an alkyl group having 1 to 9 carbon atoms.
X61 is C=O, C=S, or ^SO2 _.
R ¹⁶ and R ²⁶ , R ¹⁶ and R ⁴⁶ , and R ³⁶ and R ⁴⁶ may be linked together to form a ring having 3 to 6 members.] The dichroic dye composition according to claim 1 , wherein the squarylium dye is a compound represented by formula (II). The dichroic dye composition according to claim 1 , wherein the squarylium dye is a compound represented by formula (III). The dichroic dye composition according to claim 1 , wherein the squarylium dye is a compound represented by formula (V). The dichroic dye composition according to claim 1 , wherein the squarylium dye is a compound represented by formula (VI). 6. The dichroic dye composition according to claim 1, wherein the content of the liquid crystal compound is 50% by mass or more. A liquid crystal element comprising a pair of electrode substrates and a liquid crystalline layer formed between the pair of electrode substrates,
A liquid crystal device, wherein the liquid crystal layer is formed from the dichroic dye composition according to any one of claims 1 to 6 . A retardation plate comprising a substrate and a refractive index anisotropic film formed on at least one of the main surfaces of the substrate, or a retardation plate comprising a pair of substrates and a refractive index anisotropic film formed between the pair of substrates,
A retardation plate, wherein the refractive index anisotropic film is formed from the dichroic dye composition according to any one of claims 1 to 6 . A polarizer comprising a substrate and an optically absorptive anisotropic film formed on at least one main surface side of the substrate, or a polarizer comprising a pair of substrates and an optically absorptive anisotropic film formed between the pair of substrates,
A polarizer, wherein the optically absorptive anisotropic film is formed from the dichroic dye composition according to any one of claims 1 to 6 . 7. An imaging device, an optical distance measuring device, a virtual reality device, or a solar radiation control member comprising an optical element formed from the dichroic dye composition according to claim 1.