JP6007470B2 - Dichroic dye, liquid crystal composition, and liquid crystal element - Google Patents

Description

  The present invention relates to a novel dichroic dye used for liquid crystal display and the like, a liquid crystal composition containing the dye, and a liquid crystal element.

  Many types of liquid crystal display elements have been proposed. For example, a guest-host type liquid crystal element is a cell in which a liquid crystal composition in which a dichroic dye is dissolved in a liquid crystal is sealed in a cell, and an electric field is applied to the cell. This is a liquid crystal element that displays by changing the orientation of the light and changing the light absorption state of the cell. This guest-host system is expected as a reflective liquid crystal element that uses a backlight and consumes less power.

Here, the dichroic dye constituting the liquid crystal composition together with the liquid crystal has properties such as an appropriate light absorption characteristic, a high dichroic order parameter value (S value), a high solubility in the host liquid crystal, and durability. Required.
Anthraquinone dyes and azo dyes are known as dichroic dyes used in liquid crystal elements. In general, anthraquinone-based dyes are capable of obtaining various colors from yellow to cyan depending on their molecular structure, and are said to have excellent light resistance, but have the disadvantage of a small extinction coefficient and sharp absorption spectrum. There is. In contrast, azo dyes generally have a high dichroic ratio and a large extinction coefficient. Furthermore, since the absorption spectrum is broad, the number of dyes to be mixed can be reduced compared to anthraquinone dyes in applications where a desired black liquid crystal composition is formed by mixing with other dichroic dyes, In addition, there is an advantage that high contrast can be achieved even if the addition amount is small.

Patent Document 1 discloses a specific disazo dichroic dye having a thienothiazole ring.
Patent Document 2 discloses a specific heterocyclic azo dichroic dye, a blue dichroic dye having an order parameter (S value) of 0.80 or more, a liquid crystal composition containing the dye, and a contrast. Are described.

  Patent Documents 3 and 4 disclose azo dichroic dyes having a specific structure, and describe that they exhibit a high order parameter (S value).

Japanese Patent Laid-Open No. 1-146960 JP 2000-239664 A JP 2009-7486 A JP 2010-155924 A

The dichroic dye described in Patent Document 1 has a problem that the dichroism and solubility for obtaining a good display contrast are not sufficient, as listed as a comparative example in Patent Document 2.
In addition, the dichroic dye described in Patent Document 2 is a dichroic dye having absorption in the long wavelength region because the absorption peak wavelength (λmax) is on the short wavelength side as shown as a comparative example in the present specification. It was insufficient to meet the needs, for example, the needs of uses requiring an achromatic liquid crystal composition.

In Patent Documents 3 and 4, since the absorption peak wavelength (λmax) is on the short wavelength side, there is a need for a dichroic dye having absorption in a long wavelength region, for example, an application requiring an achromatic liquid crystal composition. It was insufficient to meet the needs.
An object of the present invention is to provide a novel azo dichroic dye having an absorption maximum wavelength in a long wavelength region while maintaining a high order parameter (S value). Another object of the present invention is to provide a guest-host liquid crystal composition and a liquid crystal element including the same, which can realize a high-contrast display up to a long wavelength region by using a novel azo dichroic dye. With the goal.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a specific substituent at the position A on the naphthalene ring of the azo dichroic dye represented by the following structural formula (II) or (III). Surprisingly, it has been found that the introduction of an azo dichroic dye can achieve a longer wavelength while maintaining a high order parameter (S value). The present invention has been accomplished based on these findings.
That is, the gist of the present invention is as follows .

( 1 ) An azo dichroic dye represented by the following structural formula (II) or (III):

(In the formula, each of R ^{21 and} R ³¹ independently represents an alkyl group or an alkoxy group and an arbitrary number of phenylene group, cyclohexane-diyl group, or —COO— group as a divalent linking group; R represents a monovalent group bonded in combination or order, R ²² and R ³² each independently represent a hydrogen atom, a methyl group or an ethyl group, and R ²³ and R ³³ each independently represent an alkyl group Alternatively, an alkoxy group and any number of phenylene groups and cyclohexane-diyl groups may be bonded through any of —O—CO—, —CO—O—, —CH ₂ O—, and —O—CH ₂ —. A cycloalkyl group which is a monovalent group often bonded in any combination and order, or R ²² and R ²³ , R ³² and R ³³ form a 5-membered or 6-membered ring, A ² , A ³ Germany, respectively In the general formula (II), a naphthylene group having a diazo bond at the 1,4-position is a halogen atom, an alkoxy group having 1 to 3 carbon atoms, or a hydroxyl group, a thiol group, or a carboamide group. You may have a C1-C3 alkyl group, a C1-C3 alkylsulfonyl group, a C1-C3 lower fluoroalkyl group, and a C1-C3 alkoxycarbonyl group as a substituent. )
(2) The azo dichroic dye according to (1), wherein A ² in the structural formula (II) or A ^{3 in} (III) is a hydroxy group or a thiol group .

(3) The absorption maximum wavelength (λmax) is 630 nm or more, (1) or
The azo dichroic dye described in (2) .
(4) A liquid crystal composition comprising the dichroic dye according to any one of (1) to (3 ) above.
(5) A liquid crystal element comprising a liquid crystal layer containing the liquid crystal composition according to (4) .

  The azo dichroic dye of the present invention has a maximum absorption wavelength in the long wavelength region while maintaining a high order parameter (S value), so that it is necessary for realizing a high contrast display up to the long wavelength region. A host-type liquid crystal composition and a liquid crystal element including the same can be provided.

It is a schematic sectional drawing in the voltage application state of the phase transition mode guest host type | mold liquid crystal display element which shows an example of the liquid crystal element produced using the azo type dichroic dye of this invention. FIG. 2 is a schematic cross-sectional view of a phase transition mode guest-host type liquid crystal display element showing an example of a liquid crystal element produced using the azo-based dichroic dye of the present invention in a state where no voltage is applied.

  The dichroic dye of the present invention is represented by the following structural formula (I).

In the formula, R ¹ , R ² and R ³ each independently represent any monovalent group, and A can form a hydrogen bond with a hydrogen bonding substituent (for example, nitrogen, oxygen, sulfur, halogen, etc.). A substituent having at least one hydrogen), the ring Ar may have a thienothiazole group which may have a substituent, 1,4-phenylene which may have a substituent or a substituent A 1,4-naphthylene ring is shown, and n is an integer of 2 or more. The plurality of rings Ar may be the same or different.

1. Regarding R ¹ , R ² and R ^{3 In the} structural formula (I), R ¹ , R ² and R ³ each independently represent any monovalent group.
R ¹ represents an arbitrary monovalent group. R ¹ is preferably a structure having a low polarity and extending the molecular length or a partial structure of liquid crystal molecules, since it may be easily dissolved in the liquid crystal. R ¹ is preferably a group in which an alkyl group or an alkoxy group and an arbitrary number of phenylene groups, cyclohexane-diyl groups or divalent linking groups are bonded in any combination and order.

Although it does not specifically limit as a bivalent coupling group, For example, a methylene group, ethylene group, trimethylene group, tetramethylene group, octamethylene group, decamethylene group, pentamethylene group, hexamethylene group, heptamethylene group A linear, branched or cyclic alkylene group having 1 to 10 carbon atoms such as a cyclohexylene group; a linear chain having 2 to 10 carbon atoms such as a vinylene group, a propenylene group or an isopropenylene group, A branched or cyclic alkenylene group; a linear, branched or cyclic alkynylene group having 2 to 10 carbon atoms such as an ethynylene group, a propynylene group, and an isopropynylene group; a methoxycarbonyl group, an ethoxycarbonyl group, etc. Examples thereof include ester groups having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms; ether groups; carbonyl groups;

Examples of the alkyl group of R ¹ described above include 1 to 1 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a hexyl group, and an octyl group. 10 linear or branched ones are preferable, among which linear ones are more preferable, and linear alkyl groups having 3 to 8 carbon atoms are particularly preferable.
Examples of the alkoxy group that R ¹ has include methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, hexyl group, octyl group A linear or branched group having 1 to 10 carbon atoms, such as a straight chain group, is more preferable, and a linear alkoxy group having 3 to 8 carbon atoms is particularly preferable.

In addition, when R ¹ has a structure in which a phenylene group and / or a cyclohexane-diyl group are connected in any combination and in any order, the phenylene group and / or cyclohexane-diyl group can be directly or cyclic structure and azo bond It is linked via a divalent linking group that does not contain.
Although it does not specifically limit as a bivalent coupling group which does not contain a cyclic structure and an azo bond, For example, a methylene group, ethylene group, propylene group, isopropylene group, butylene group, isobutylene group, sec-butylene group , A tert-butylene group, a hexylene group, an octylene group, a hexamethylene group, a heptamethylene group and the like, a linear or branched alkylene group having 1 to 10 carbon atoms; a vinylene group, a propenylene group, an isopropenylene group, Linear or branched alkenylene group having 2 to 10 carbon atoms such as butenylene group, isobutenylene group, sec-butenylene group, tert-butenylene group, hexenylene group, octenylene group; ethynylene group, propynylene group, isopropynylene group, butynylene Group, isobutynylene group, sec-butynylene group, tert-butyl Straight chain or branched alkynylene groups having 2 to 10 carbon atoms such as len, hexynylene and octynylene; methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, tert-butoxycarbonyl, acetyl Examples thereof include an ester group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms such as an oxy group and a benzoyloxy group; an ether group; a carbonyl group; a group obtained by combining them.

Among them, the number of bonded atoms is preferably a 2, -O-CO -, - CO -O -, - CH 2 O -, - O-CH 2 - and the like are more preferable, -CH ₂ O-is Particularly preferred.
By setting R ¹ to the structure as described above, a high order parameter can be achieved. In the above structure, the bonding position of alkyl group and phenylene group, alkyl group and cyclohexane-diyl group, or phenylene group and cyclohexane-diyl group, alkoxy group and phenylene group, alkoxy group and cyclohexane-diyl group is not particularly limited, but high In order to achieve the order parameter, it is particularly preferable to bond at the 4-position.

R ¹ is, for example, a linear alkyl group having 3 to 10 carbon atoms, preferably 3 to 8 carbon atoms, such as propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group; 4-propylcyclohexyl group 4-alkylcyclohexyl group having 9 to 16 carbon atoms, preferably 9 to 14 carbon atoms such as 4-butylcyclohexyl group, 4-pentylcyclohexyl group, 4-hexylcyclohexyl group and 4-peptylcyclohexyl group; A 4-alkylphenyl group having 9 to 16 carbon atoms, preferably 9 to 14 carbon atoms, such as a phenyl group, a 4-pentylphenyl group, and 4-hexylphenyl; 4- (4-propylcyclohexyl) phenyl group, 4- ( 4-butylcyclohexyl) phenyl group, 4- (4-pentylcyclohexyl) phenyl group, 4- (4-heptylcyclohexyl) 4- (4-alkylcyclohexyl) phenyl group having 15 to 22 carbon atoms, preferably 15 to 20 carbon atoms such as an phenyl group; 4-propoxycyclohexyl group, 4-butyloxycyclohexyl group, 4-pentyloxycyclohexyl group, 4 A 4-alkoxycyclohexyl group having 9 to 16 carbon atoms, preferably 9 to 14 carbon atoms such as -hexyloxycyclohexyl group and 4-peptyloxycyclohexyl group; 4-butyloxyphenyl group, 4-pentyloxyphenyl group, 4 -4-alkyloxyphenyl group having 9 to 16 carbon atoms, preferably 9 to 14 carbon atoms such as hexyloxyphenyl; 4- (4-propoxyoxycyclohexyl) phenyl group, 4- (4-butyloxycyclohexyl) phenyl Group, 4- (4-pentyloxycyclohexyl) phenyl group, 4- (4- Heptyl carbon atoms such as oxy) phenyl group 15-22, with preference given to 4- (4-alkyloxy) phenyl group such as 15 to 20 carbon atoms.

R ² represents an arbitrary monovalent group. R ² may be any group as long as it does not impair the performance of the present invention. Specifically, hydrogen atom, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert- Examples thereof include linear or branched alkyl groups having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, such as a butyl group, a hexyl group, and an octyl group. Of these, a hydrogen atom, a methyl group and an ethyl group are preferable, and a hydrogen atom is particularly preferable.

R ³ represents an arbitrary monovalent group. R ³ is preferably a structure having a low polarity and extending the molecular length, or a partial structure of liquid crystal molecules because it may be easily dissolved in the liquid crystal. R ³ is preferably a group in which an alkyl group or an alkoxy group and an arbitrary number of phenylene groups, cyclohexane-diyl groups or divalent linking groups are bonded in any combination and order. It is particularly preferable to adopt a structure in which is bonded to a nitrogen atom via an alkylene group. The divalent linking group has the same meaning as the divalent linking group exemplified for R ¹ .

Examples of the alkyl group possessed by R ³ include the methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, and hexyl group exemplified as the alkyl group possessed by R ^1. And a linear or branched group having 1 to 10 carbon atoms such as an octyl group is preferable, among which a linear group is more preferable, and a linear alkyl group having 3 to 8 carbon atoms is particularly preferable.

Examples of the alkoxy group possessed by R ³ include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, and a tert- group exemplified as the alkoxy group possessed by R ^1. A linear or branched group having 1 to 10 carbon atoms such as a butoxy group, a hexyl group or an octyl group is preferable. Among them, a linear group is more preferable, and a linear alkoxy having 3 to 8 carbon atoms is preferable. The group is particularly preferred.

Further, when R ³ has a structure in which a phenylene group and / or a cyclohexane-diyl group are connected in any combination and in any order, the phenylene group and / or cyclohexane-diyl group can be directly or cyclic structure and azo bond It is linked via a divalent linking group that does not contain.
Examples of the divalent linking group containing no ring structure and an azo bond include, but are not particularly limited, for example, carbon atoms described above as the divalent linking group containing no ring structure and an azo bond R ¹ has 1 10 to 10 linear or branched alkylene groups;
A linear or branched alkenylene group of the above-mentioned linear or branched alkynylene group having 2 to 10 carbon atoms; an ester group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms; A carbonyl group; a group combining them; and the like.

Among them, the number of bonded atoms is preferably a 2, -O-CO -, - CO -O -, - CH 2 O -, - O-CH 2 - and the like are more preferable, -CH ₂ O-is Particularly preferred.
By setting R ³ to the structure as described above, a high order parameter can be achieved. In the above structure, the bonding position of alkyl group and phenylene group, alkyl group and cyclohexane-diyl group, or phenylene group and cyclohexane-diyl group, alkoxy group and phenylene group, alkoxy group and cyclohexane-diyl group is not particularly limited, but high In order to achieve the order parameter, it is particularly preferable to bond at the 4-position.

As the alkylene group bonded to the nitrogen atom and a divalent linear or branched alkylene group having 1 to 10 carbon atoms, are employed as the linking group does not contain a ring structure and an azo bond R ¹ has .
R ³ includes, for example, a (4-butylphenyl) methyl group, a (4-pentylphenyl) methyl group, a (4-hexylphenyl) methyl group and the like having 10 to 17 carbon atoms (4-alkylphenyl) methyl group; (4-alkoxyphenyl) methyl group having 10 to 17 carbon atoms such as 4-butoxyphenyl) methyl group, (4-pentyloxyphenyl) methyl group, (4-hexyloxyphenyl) methyl group; (4-propylcyclohexyl) (4-alkyl having 10 to 17 carbon atoms such as methyl group, (4-butylcyclohexyl) methyl group, (4-pentylcyclohexyl) methyl group, (4-hexylcyclohexyl) methyl group, (4-heptylcyclohexyl) methyl group, etc. (Cyclohexyl) methyl group; (4- (4-propylcyclohexyl) phenyl) methyl group, (4- ( 4-butylcyclohexyl) phenyl) methyl group, (4- (4-pentylcyclohexyl) phenyl) methyl group, (4- (4-hexylcyclohexyl) phenyl) methyl group, (4- (4-heptylcyclohexyl) phenyl) methyl (4- (4-alkylcyclohexyl) phenyl) methyl group having 16 to 23 carbon atoms such as a group; (4- (4-propylcyclohexyl) cyclohexyl) methyl group, (4- (4-butylcyclohexyl) cyclohexyl) methyl group , (4- (4-pentylcyclohexyl) cyclohexyl) methyl group, (4- (4-hexylcyclohexyl) cyclohexyl) methyl group, (4- (4-heptylcyclohexyl) cyclohexyl) methyl group and the like, 4- (4-alkylcyclohexyl) cyclohexyl C10-17 (4-alkyloxyphenyl) methyl groups such as methyl group, (4-butyloxyphenyl) methyl group, (4-pentyloxyphenyl) methyl group, (4-hexyloxyphenyl) methyl group; (4-butoxyphenyl) methyl group, (4-pentyloxyphenyl) methyl group, (4-hexyloxyphenyl) methyl group and the like having 10 to 17 carbon atoms (4-alkoxyphenyl) methyl group; (4-propyloxycyclohexyl) ) Methyl group, (4-butyloxycyclohexyl) methyl group, (4-pentyloxycyclohexyl) methyl group, (4-hexyloxycyclohexyl) methyl group, (4-heptyloxycyclohexyl) methyl group and the like. (4-alkyloxycyclohexyl) methyl group; Pyroxycyclohexyl) phenyl) methyl group, (4- (4-butyloxycyclohexyl) phenyl) methyl group, (4- (4-pentyloxycyclohexyl) phenyl) methyl group, (4- (4-hexyloxycyclohexyl) phenyl C4-C23- (4- (4-alkyloxycyclohexyl) phenyl) methyl groups such as methyl group and (4- (4-heptyloxycyclohexyl) phenyl) methyl group; (4- (4-propyloxycyclohexyl) ) Cyclohexyl) methyl group, (4- (4-butyloxycyclohexyl) cyclohexyl) methyl group, (4- (4-pentyloxycyclohexyl) cyclohexyl) methyl group, (4- (4-hexyloxycyclohexyl) cyclohexyl) methyl group , (4- (4-Heptylo C16-23 (4- (4-alkyloxycyclohexyl) cyclohexyl) methyl groups such as xylcyclohexyl) cyclohexyl) methyl group and the like can be mentioned.

R ² and R ³ may combine to form a ring structure. Specifically, R ² and R ³ are linked to form an alkylene group, more preferably a —CH ₂ CH ₂ CH ₂ CH ₂ — group, a —CH (CH ₃ ) CH ₂ CH ₂ CH ₂ — group, or the like. You may do it.
R ³ is preferably the following structural formula (IV) in order to obtain a high order parameter and ease of synthesis.

-CH ₂ -XR ⁴ (IV)
R ⁴ represents an arbitrary monovalent group. In R ⁴ , a hydrogen atom, an alkyl group, an alkoxyalkyl group, an alkoxy group, and a divalent linking group shown below may be bonded in any combination and order. The divalent linking group has the same meaning as the divalent linking group exemplified for R ¹ .
Specific examples of the group that R ⁴ has include a hydrogen atom; methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group, cyclopropyl A linear, branched or cyclic alkyl group having 1 to 10 carbon atoms such as a group, a cyclobutyl group, a cyclopentyl group or a cyclohexyl group; a carbon number such as an ethoxymethyl group, a butoxymethyl group, an ethoxymethyl group or a butoxyethyl group 2-10 alkoxyalkyl groups; C1-C10 linear or branched alkoxy groups, such as a methoxy group, butoxy group, hexyloxy group, nonyloxy group, etc. are mentioned.

In particular, C3-C7 linear, branched or cyclic alkyl groups and C3-C7 linear or branched alkoxy groups realize high order parameters and high solubility in host liquid crystals. It is possible and preferable.
X represents a phenylene group or a cyclohexylene group, and specific examples thereof include a 1,4-phenylene group and a 1,4-cyclohexylene group.

It is preferable that at least one of X and R ⁴ contains a cyclohexylene group because a high order parameter and high solubility in a host liquid crystal may be realized.
2. About A In Structural Formula (I), A represents a hydrogen bonding substituent. The hydrogen bonding substituent is not particularly limited as long as it is a substituent capable of forming a hydrogen bond between molecules or within a molecule. For example, —NH ₂ , —SH, —OH, —NH—C (═R) NH ₂ (R represents an oxygen atom or an imino group), a substituent selected from —NH—COCF ₃ and the like.

Examples of A in the structural formula (I) include a substituent having at least one hydrogen capable of forming a hydrogen bond with nitrogen, oxygen, sulfur, halogen, or the like. The hydrogen in the substituent of A is not particularly limited as long as it has an electron density lower than that of a hydrogen atom bonded to a normal aliphatic carbon. A can be a hydroxy group, a thiol group, an amino group, an alkyl group. Amino group, carboamide group, sulfonamide group and the like can be mentioned. Of these, a hydroxy group (—OH group) is particularly preferable.

  The technical characteristics of the azo dichroic dye of the present invention, and the liquid crystal composition and liquid crystal element containing the dye, which are both a long absorption maximum wavelength and a high order parameter (S value), By introducing the specific substituent at position A on the naphthalene ring of formula (I), hydrogen on the substituent forms a hydrogen bond or a state close to a hydrogen bond with a nearby azo group. This is considered to be realized with unexpected effects.

3. Regarding Ring Ar Ring Ar may have a thienothiazole group which may have a substituent, and may have a substituent 1
, 4-phenylene or 1,4-naphthylene ring. Two or more rings Ar may be the same or different. When ring Ar has a substituent, examples of the substituent include an electron-donating substituent such as an alkoxy group and an alkyl group; or a cyano group, a nitro group, an alkylsulfonyl group, a halogenated alkyl group, a halogen atom, and alkoxycarbonyl. And electron withdrawing groups such as groups.

Examples of the alkoxy group that is a substituent of the ring Ar include, for example, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, and the like, preferably Includes an alkoxy group having 1 to 4 carbon atoms, especially 1 to 3 carbon atoms.
Examples of the alkyl group that is a substituent of the ring Ar include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Preferably, an alkyl group having 1 to 4 carbon atoms, especially 1 to 3 carbon atoms is used.

Among these, a methyl group or a methoxy group is particularly preferable as the electron donating group. Examples of the alkylsulfonyl group that is a substituent of the ring Ar include carbon such as a methylsulfonyl group, an ethylsulfonyl group, an isopropylsulfonyl group, an n-butylsulfonyl group, an isobutylsulfonyl group, a sec-butylsulfonyl group, and a tert-butylsulfonyl group. Examples thereof include alkylsulfonyl groups having 1 to 10, preferably 1 to 4, and especially 1 to 3 carbon atoms.

  Examples of the halogenated alkyl group as a substituent for the ring Ar include 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms such as a trifluoromethyl group, a pentaaloroethyl group, a heptafluoropropyl group, and a nonafluorobutyl group. Of these, a lower fluoroalkyl group having 1 to 3 carbon atoms is mentioned. Examples of the halogen atom of the ring Ar include fluorine, chlorine, bromine and iodine, preferably fluorine, chlorine and bromine.

Examples of the alkoxycarbonyl group as a substituent for the ring Ar include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, an isopropoxycarbonyl group, an n-butoxycarbonyl group, an isobutoxycarbonyl group, a sec-butoxycarbonyl group, and a tert-butoxy group. Examples thereof include an alkoxycarbonyl group having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, particularly 1 to 3 carbon atoms, such as a carbonyl group.

Among these, as the electron-withdrawing group, a trifluoromethyl group, a fluorine atom, a chlorine atom, a methoxycarbonyl group, an ethoxycarbonyl group, and a propoxycarbonyl group are particularly preferable.
4). About n n represents an integer of 2 or more. A molecule having n of 5 or more is advantageous for increasing the wavelength, but is difficult to produce and has low solubility in the host liquid crystal.
Among the dichroic dyes represented by the structural formula (I) of the present invention, azo dichroic dyes represented by the following structural formula (II) or (III) are preferable.

(Wherein R ^{21 to} R ²³ and R ^{31 to} R ³³ each independently represent any monovalent group, A ² ,
A ³ represents a hydrogen bonding substituent. )
5. R ^{21 to} R ²³ and R ^{31 to} R ^{33 In the} structural formulas (II) and (III), R ^{21 to} R ²³ and R ^{31 to} R ³³ each independently represent an arbitrary monovalent group.

R ^{21 in} Structural Formula (II) and R ^{31 in} (III) are synonymous with R ^{1 in} Structural Formula (I) described above, and R ^{22 in} Structural Formula (II) and R ^{32 in} (III) are the structures described above. It is synonymous with R ^{2 in} formula (I).
Further, examples of the radicals R ³³ are indicated by R ³ of the above-described structural formula (I) in R ²³ and (III) of structural formula ^(II), and has the same meaning, R ²³ and R ^33, the following structural formula (IV) is preferred in order to obtain high order parameters and ease of synthesis.

-CH ₂ -XR ⁴ (IV)
R ⁴ represents an arbitrary monovalent group. In R ⁴ , a hydrogen atom, an alkyl group, an alkoxyalkyl group, an alkoxy group, and a divalent linking group shown below may be bonded in any combination and order. The divalent linking group has the same meaning as the divalent linking group exemplified for R ¹ .
Specific examples of the group that R ⁴ has include a hydrogen atom; methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, hexyl group, octyl group, cyclopropyl A linear, branched or cyclic alkyl group having 1 to 10 carbon atoms such as a group, cyclobutyl group, cyclopentyl group and cyclohexyl group; total carbon number such as ethoxymethyl group, butoxymethyl group, ethoxymethyl group and butoxyethyl group 2-10 alkoxyalkyl groups; C1-C10 linear or branched alkoxy groups, such as a methoxy group, a butoxy group, a hexyloxy group, a nonyloxy group, are mentioned.

In particular, a linear or branched alkyl group having 3 to 7 carbon atoms or a linear or branched alkoxy group having 3 to 7 carbon atoms may realize high order parameters and high solubility in a host liquid crystal. preferable.
X represents a phenylene group or a cyclohexylene group, and specific examples thereof include a 1,4-phenylene group and a 1,4-cyclohexylene group.
It is preferable that at least one of X and R ⁴ contains a cyclohexylene group because a high order parameter and high solubility in a host liquid crystal may be realized.

6). A ² and A ^{3 In the} structural formulas (II) and (III), A ² and A ³ represent a hydrogen bonding substituent and have the same meaning as A in the structural formula (I) described above.
Among the dichroic dyes represented by the structural formula (I), (II) or (III) of the present invention, an azo dichroic dye represented by the following structural formula (V) or (VI) is preferable.

In the above formula, R ⁵¹ , R ⁵² , R ⁶¹ , R ⁶² and R ⁴ each represent an independent monovalent group, and X represents a phenylene group or a cyclohexylene group.
R ^{51 in the} structural formula (V) and R ^{61 in the} (VI) are synonymous with R ¹ in the structural formula (I), and R ^{52 in the} structural formula (V) and R ^{62 in} (VI) are the structures described above. It is synonymous with R ^{2 in} formula (I).
Furthermore, X and R ⁴ are, above structural formula (IV), the same meaning as X and R ^4.

7). Molecular Weight The dichroic dye of the present invention represented by the structural formula (I) described above usually has a molecular weight of 3000 or less, preferably 1500 or less, from the viewpoint of solubility in the host liquid crystal and response speed.
8). Specific Examples Specific examples of the dichroic dye represented by the structural formula (I) are illustrated below, but the present invention is not limited to these unless it exceeds the gist.

9. Synthesis Method The above-described dichroic dye of the present invention can be synthesized by performing an azo coupling reaction between the intermediate (VII) and the intermediate (VIII). Intermediate (VII) can be synthesized by a known method, for example, by the method described in JP-A-58-38756 or the method of Examples. Intermediate (VIII) can be synthesized, for example, by the method described in the examples when A is a hydroxy group.

10. Liquid Crystal Composition One or two or more of the dichroic dyes of the present invention are added to pages 154 to 192 of the “Liquid Crystal Device Handbook” (Nikkan Kogyo Shimbun, published in 1989) edited by the Japan Society for the Promotion of Science 142nd Committee, Known methods for various host liquid crystal compounds such as biphenyl, phenylcyclohexane, phenylpyrimidine, cyclohexylcyclohexane and the like which show nematic or smectic phases described in pages 715 to 722, or host liquid crystal compositions containing these compounds The liquid crystal composition can be easily prepared by mixing in step (b).

Examples of such a liquid crystal compound include compounds described in JP-A-3-14892. The type of the preferred host liquid crystal varies depending on the driving method. For example, in the case of an active matrix system, a fluorine liquid crystal is preferable.
The content ratio of the dichroic dye of the present invention in the liquid crystal composition is not particularly limited, but is usually 0.05 to 15% by weight including the case where two or more kinds are contained. It is preferably 1 to 5% by weight.

  Examples of the host liquid crystal compound at that time include Np-type liquid crystal compounds and Nn-type liquid crystal compounds represented by the following structural formulas (IX) to (XIII).

In formulas (IX) to (XIII), ring E represents a cyclohexane ring, a benzene ring, a dioxane ring, or a pyrimidine ring, and q represents an integer of 1 to 3. Z represents a single bond, —CO—O—, —CH ₂ CH ₂ —, —CH═CH—, or —C≡C—. D ¹ and D ³ each independently represent a hydrogen atom or a halogen atom such as a fluorine atom or a chlorine atom; D ² represents a halogen atom such as a fluorine atom or a chlorine atom; a halogen atom such as a fluorine atom or a chlorine atom; A C1-C7 alkyl group as a substituent, also an alkenyl group, an alkoxy group, a substituted alkyl group, a substituted alkenyl group, a cyclohexyl group having a substituted alkoxy group as a substituent, or a substituted alkyl group thereof, substituted The phenyl group which has an alkenyl group and a substituted alkoxy group as a substituent is shown. D ⁷ and D ⁸ each independently represent a cyano group or a halogen atom such as a fluorine atom or a chlorine atom. D ¹¹ and D ^{13 each} represent a cyano group. D ⁴ , D ⁵ , D ⁶ , D ⁹ , D ¹⁰ , D ¹² , and D ¹⁴ are each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or 1 to 10 carbon atoms. Or an alkoxyalkyl group having 2 to 10 carbon atoms.

The liquid crystal composition of the present invention includes dichroic dyes other than the dichroic dye of the present invention, and optically active substances that may or may not exhibit a liquid crystal phase, such as cholesteryl nonanoate, Various additives such as ultraviolet absorbers and antioxidants may be contained.
The dichroic dye of the present invention or a liquid crystal composition containing the same preferably has an absorption maximum wavelength in a long wavelength region of 630 nm or more, more preferably 650 nm or more, further preferably 680 nm or more, and most preferably 690 nm or more. Further, the dichroic dye of the present invention or the liquid crystal composition containing the same preferably has a high order parameter of 0.78 or more, more preferably 0.80 or more, and most preferably 0.81 or more. The liquid crystal composition of the present invention can be suitably used as various electro-optical devices such as display elements for computers, watches, calculators, etc., electro-optical shutters, electro-optical apertures, optical communication optical path switching switches, optical modulators and the like. it can.

The order parameter (S value) of the dye can be obtained from the following formula described in “Liquid Crystal Device Handbook” edited by the 142th Committee of the Japan Society for the Promotion of Science based on spectroscopic measurement.
S = (A // − A⊥) / (2A⊥ + A //)
Here, “A //” and “A⊥” are the absorbance of the dye with respect to light polarized parallel and perpendicular to the alignment direction of the liquid crystal, respectively, and the S value is theoretically in the range of 0 to 1. The closer the value is to 1, the more the contrast as a guest-host type liquid crystal element is improved.

11 Liquid Crystal Element By sandwiching a liquid crystal layer containing the liquid crystal composition containing the dichroic dye of the present invention between two substrates with electrodes, at least one of which is transparent, Shoichi Matsumoto and Ryo Tsunoda “ Latest Technology of Liquid Crystals ”(Industry Research Committee, published in 1983), p. L. Heilmeier-type guest hosts described in Fergason, SID85Digest, 68 (1985), “Liquid Crystal Device Handbook” (Nikkan Kogyo Shimbun, 1989) pages 315-329, etc. A guest host effect such as a transfer guest host was used. As described above, various modes of the liquid crystal element can be used in the present invention. However, in the phase transition mode obtained by adding an optically active substance to the nematic liquid crystal composition, a polarizing plate is not used. Since the contrast is high and the display is bright, it is particularly preferable as a reflective liquid crystal display element.

  As an example of the liquid crystal element of the present invention, FIGS. 1 and 2 are schematic cross-sectional views of an active drive type phase change mode guest-host type liquid crystal display element. FIG. 1 shows a voltage application state of the liquid crystal display element, and FIG. 2 shows a voltage non-application state. In the figure, 1 is incident light, 3 is a transparent glass plate, 4 is a transparent electrode, 5 is an alignment film, 6 is a liquid crystal compound molecule, 7 is a dichroic dye molecule, 9 is a reflective layer, and 10 is reflected light.

  When no voltage is applied (FIG. 2), the liquid crystal compound molecule 6 exhibits a cholesteric phase, and the dichroic dye molecule 7 also exhibits a cholesteric structure together with the liquid crystal compound molecule 6. Therefore, even if the incident light 1 is natural light, the polarizing plate Is absorbed by the dichroic dye molecule 7 without using. When a voltage is applied (FIG. 1), the liquid crystal compound molecules 6 and the dichroic dye molecules 7 are aligned in the direction of the electric field, so that light is transmitted and reflected by the reflective layer 9. Thus, in a liquid crystal element, light transmission and absorption can be controlled by the presence or absence of an electric field.

<Synthesis of Intermediate M03>

Intermediate M01 (TCI, .96 g, 50 mmol) and intermediate M02 (TCI, 8.91 g, 50 mmol) in methanol
(100 ml) of the mixture was heated to reflux for 30 minutes. Add acetic acid (25 ml), stir at 70 ° C for 30 minutes, cool with ice, add Na (CN) BH ₃ (2.51 g, 40 mmol) in small portions (internal temperature 35 ° C or less), and allow to react at room temperature overnight. It was. The mixture was concentrated under reduced pressure, water was added, toluene and ethyl acetate were added, insolubles were removed by Celite filtration, and the organic layer and the aqueous layer were separated. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate. The organic phase was concentrated under reduced pressure, and the resulting oily residue was generated by column chromatography (Merck7734, 500 g, hexane / ethyl acetate 4 / 1-3 / 1), and M03 (9.87 g, 61% yield). )Obtained.
<Synthesis of Intermediate M006>

Intermediate M04 (2.57 g, 15.1 mmol) was diluted in methylene chloride (30 ml, 11.7 VRm), triethylamine (2.1 ml, 15.1 mmol) was added, cooled in an ice bath, and then ethyl chloroformate (2.1 ml, 15.1). mmol) was added dropwise. After stirring for 30 minutes, Intermediate M01 (2.40 g, 15.1 mmol) and 4-dimethylaminopyridine (10 mg) were added, and the mixture was warmed to room temperature and stirred for 12 hours. The precipitated crystals were filtered and dried to obtain Intermediate M05 (3.81 g, yield 81%) as a white solid.

Sodium tetrahydroborate (990 mg, 26.2 mmol) was diluted in tetrahydrofuran (THF) (22 ml, 6VR), cooled in an ice bath, and iodine (3.17 g, 12.5 mmol) diluted in THF (5.6 ml) was added for 30 minutes. The solution was slowly added dropwise. After stirring for another 30 minutes, Intermediate M05 (3.70 g, 11.9 mmol) was added, and the mixture was stirred for 40 minutes under reflux with heating. After cooling the reaction solution, the reaction solution was added to 3N hydrochloric acid (60 ml), and the precipitated solid was filtered and dried to obtain Intermediate M06 (3.13 g, yield 73%) as a white solid.
<Synthesis of Intermediate M09>

Intermediate M07 (11.9 g, 60.2 mmol) was diluted in methylene chloride (120 ml, 10VR), triethylamine (8.34 ml, 60.2 mmol) was added, and after cooling in an ice bath, ethyl chloroformate (5.94 ml, 60.2 mmol) ) Was added dropwise. After stirring for 30 minutes, Intermediate M01 (9.60 g, 60.2 mmol) and 4-dimethylaminopyridine (10 mg) were added, and the mixture was warmed to room temperature and stirred for 2 days. The precipitated crystals were filtered and dried to obtain 8.4 g (yield 90%) of intermediate M08 as a white solid.

Sodium tetrahydroborate (4.90 g, 130 mmol) is diluted in THF (120 ml, 6VR), cooled in an ice bath, and iodine (15.7 g, 61.9 mmol) diluted in THF (30 ml) is slowly added dropwise over 30 minutes. did. After stirring for another 30 minutes, Intermediate M08 (20.0 g, 58.9 mmol) was added, and the mixture was stirred for 4 hours under reflux with heating. After cooling the reaction solution, the reaction solution was added to 1N hydrochloric acid (100 ml), extracted with ethyl acetate, dried over magnesium sulfate, and the filtered filtrate was concentrated to obtain 23.7 g of a crude product. The crude product was purified by silica gel column (SiO2: 300 ml, hexane: ethyl acetate = 1: 20-1: 10) to obtain Intermediate M09 (9.7 g, yield 50%).
<Synthesis of Intermediate M15>

Intermediate M14 was synthesized by the method described in International Publication No. 2005/49023 pamphlet.
Intermediate M14 (6.10 g, 35.2 mmol) was dissolved in tetrahydrofuran (13 ml), calcium carbonate (14.8 g, 140 mmol) and 1,4-dibromobutane (7.98 g, 37.0 mmol) were added, and the mixture was heated under reflux for 10 hours. And stirred. The reaction mixture was cooled to room temperature, water (50 ml) was added, and the mixture was extracted with ethyl acetate (100 ml). The organic layer was dried over anhydrous magnesium sulfate, the filtrate after filtration was concentrated, and the resulting residue was purified by silica gel column chromatography (60N Kanto Kagaku, hexane / ethyl acetate 20 / 1-15 / 1) Intermediate M15 (4.03 g, 50% yield) was obtained as a brown oil.
<Synthesis of Intermediate M17>

Intermediate M15 (5.0 g, 22.0 mmol) was diluted in acetic acid (20 ml), 48% bromic acid (20 ml) was added, and the mixture was heated to reflux at 120 ° C. for 19 hours. The reaction solution was returned to room temperature, added dropwise to a 10% aqueous sodium hydroxide solution (100 ml) under ice cooling, and extracted twice with chloroform (60 ml). The organic layer is dried over magnesium sulfate, the solution obtained by filtration is concentrated, and the resulting residue is purified by silica gel column chromatography (60N Kanto Science 150 ml, hexane / ethyl acetate 10 / 1-3 / 1). Intermediate M17
(3.90 g, yield 83%) was obtained.

Example 1
<Synthesis of Compound 1>

Intermediate M10 was synthesized by the method described in JP 2010-155924 A.
Intermediate M10 (1.89 g, 3.0 mmol) was added with N-methyl-2-pyrrolidone (100 ml), ice-cooled, concentrated hydrochloric acid (0.875 ml, 10.5 mmol) and sodium nitrite (0.217 g, 3.15 mmol) in water. (1 ml)
The solution was added and stirred for 1 hour to obtain a diazo solution. A solution of intermediate M03 (0.964 g, 3.0 mmol) in N-methyl-2-pyrrolidone (10 ml) was ice-cooled and a diazo solution was added dropwise. Sodium acetate (2 g, 24 mmol) was added, and after stirring at room temperature for 1 hour, methanol (50 ml) was added and suction filtered. The cake obtained was washed with methanol and water, and the resulting powder was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Kagaku, hexane / chloroform 1 / 2-1 / 3-0 / 1), The obtained powder was washed with about 100 ml of THF / ethanol 5/2, and then washed by spraying with ethanol. Further powder was taken and washed with ethanol to give compound 1 (0.67 g, yield 23%)
Got.

[Example 2]
<Synthesis of Compound 2>

Intermediate M11 was synthesized by the method described in JP 2010-155924 A.
Intermediate M11 (1.69 g, 3.0 mmol) was added with N-methyl-2-pyrrolidone (30 ml) and 35% aqueous hydrochloric acid (845 mg), ice-cooled, sodium nitrite (217 mg, 3.15 mmol) was added, and 30 minutes The mixture was stirred to obtain a diazo solution. In a separate container, a solution of intermediate M06 (892 mg, 3.0 mmol) in THF (20 ml) was ice-cooled, and the diazo solution was added dropwise. Sodium acetate (3.0 g, 36 mmol) was added, and the mixture was stirred for 30 minutes and then warmed to room temperature. Water (100 ml) was added, and the precipitated solid was subjected to suction filtration, and further washed with a solution of n-hexane / chloroform = 3/1. The resulting cake was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Science 500 ml: n-hexane / chloroform 2/1 to 1/2), and the resulting powder was extracted with chloroform / ethyl acetate 1/1. Washing was carried out to obtain Compound 2 (160 mg, yield 3%).

Example 3
<Synthesis of Compound 3>

Intermediate M12 was synthesized by the method described in JP-A-1-146960.
Acetic acid: propionic acid = 17: 8 (29 ml) was added to intermediate M12 (948 mg, 3.0 mmol), ice-cooled, 40% ditrosylsulfuric acid (1.05 g, 3.15 mmol) was added dropwise, and the mixture was stirred for 30 min. Obtained. In a separate container, a solution of intermediate M06 (892 mg, 3.0 mmol) in THF (20 ml) was ice-cooled, and the diazo solution was added dropwise. Sodium acetate (2.0 g, 24 mmol) was added, and the mixture was stirred for 30 minutes and then warmed to room temperature. Water (100 ml) was added and the precipitated solid was filtered off with suction. The obtained cake was washed with methanol and water, and the obtained powder was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Science 300 ml: n-hexane / chloroform 1 / 1-1 / 2) The obtained powder was washed with ethyl acetate (10 ml), filtered and dried to obtain Compound 3 (88 mg, yield 4.7%).

Example 4
<Synthesis of Compound 4>

Acetic acid: propionic acid = 17: 8 (30 ml) was added to intermediate M12 (948 mg, 3.0 mmol), ice-cooled, 40% ditrosylsulfuric acid (1.05 g, 3.3 mmol) was added dropwise, and the mixture was stirred for 30 min. Obtained. In a separate container, a solution of intermediate M09 (976 mg, 3.0 mmol) in THF (30 ml) was ice-cooled, and the diazo solution was added dropwise. Sodium acetate (2.0 g, 24 mmol) was added, and the mixture was stirred for 30 minutes and then warmed to room temperature. Water (100 ml) was added and the precipitated solid was filtered off with suction. The obtained cake was washed with methanol and water, and the obtained powder was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Science 350ml: n-hexane / chloroform 1 / 1-1 / 2) The obtained powder was washed with ethyl acetate (20 ml), filtered and dried to obtain Compound 4 (82 mg, yield 4.2%).

Example 5
<Synthesis of Compound 5>

Intermediate M18 was synthesized by the method described in JP-A-62-555.
Intermediate M18 (2.37 g, 4 mmol) was converted to N-methyl-2-pyrrolidone: dimethylformamide = 3: 1 (71 ml
And 35% aqueous hydrochloric acid (1.0 ml) and sodium nitrite (290 mg, 4.2 mmol) were slowly added dropwise while maintaining the temperature at 5 ° C. or lower and stirred for 30 minutes to obtain a diazo solution. In a separate container, a solution of intermediate M17 (853 mg, 4.0 mmol) in THF (40 ml) was ice-cooled, and the diazo solution was added dropwise thereto. After stirring for 30 minutes, the temperature was raised to room temperature, water (60 ml) and methanol (60 ml) were added, and the precipitated solid was suction filtered. The obtained cake was washed with methanol and water, and the obtained powder was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Science 300 ml: n-hexane / chloroform 3 / 1-0 / 1), The obtained solid was treated with ethyl acetate (20 ml), chloroform (10 ml
) Was added and washed. The solid obtained by filtration was dried to obtain Compound 5 (100 mg, yield 0.3%).

[Comparative Example 1]
<Synthesis of Comparative Compound 1>

Comparative compound 1 was synthesized by the method described in JP-A-1-146960.
[Comparative Example 2]
<Comparative compound 2>

Intermediate M16 was synthesized according to the method described in JP-A-10-231437.
Intermediate M16 (2.06 g, 4.5 mmol) was added with N-methyl-2-pyrrolidone (48 ml) and dimethylformamide (12 ml), ice-cooled, concentrated hydrochloric acid (1.27 ml, 12.1 mmol) and sodium nitrite (326 mg, 4.71 mmol) in water (1 ml) was added and stirred for 1 hour to obtain a diazo solution. A solution of intermediate M15 (1.02 g, 4.5 mmol) in methanol (10 ml) and THF (10 ml) was ice-cooled and a diazo solution was added dropwise. Sodium acetate (5 g, 60 mmol) was added, and after stirring at room temperature for 1 hour, water (100 ml) was added,
Suction filtered. The obtained cake was washed with methanol and water, and the obtained powder was purified by silica gel column chromatography (adsorption method, silica gel 60N Kanto Kagaku, hexane / ethyl acetate 3/1 to 1/1). The powder was washed with about 50 ml of THF / ethyl acetate 1/3 to obtain Comparative Compound 2 (0.27 g, yield 9%).

[Evaluation of λmax and order parameter (S value) of dichroic dye]
The obtained dichroic dyes “compounds 1 to 5” and “comparative compounds 1 to 2” were each 0.1% by weight in a fluorine-based liquid crystal mixture marketed under the trade name MCL-2039 (product of Merck). To prepare a guest-host liquid crystal composition. The glass substrate with a transparent electrode coated, cured, and rubbed with a polyimide resin was opposed to this, and sealed in a cell with a gap of 50 μm configured so that the liquid crystal was aligned in parallel. The absorbance (A //) for linearly polarized light parallel to the orientation direction of the colored cell and the absorbance (A⊥) for polarized light perpendicular to the orientation direction were measured, and the order parameter (S value) at the absorption peak (λmax) was determined. It calculated | required from the following formula.

S = (A // − A⊥) / (2A⊥ + A //)
The results are shown in Table 1.

  From Table 1, all of the azo dye compounds 1 to 5 (Examples 1 to 5) represented by the structural formula (I) of the present invention have an absorption maximum wavelength (λmax) of 630 nm or more. As can be seen from FIG. And the azo dye compounds 1 to 5 (Examples 1 to 5) represented by the structural formula (I) of the present invention all show a high order parameter (S value) while realizing a longer wavelength. Thus, it can be seen that both a longer wavelength and a higher contrast can be realized.

1; incident light 3; transparent glass substrate
4; Transparent electrode
5; Alignment film 6; Liquid crystal compound molecule
7; Dichroic dye molecule
9; reflective layer 10; reflected light

Claims (5)

An azo dichroic dye represented by the following structural formula (II) or (III):

(In the formula, each of R ²¹ and R ³¹ independently represents an alkyl group or an alkoxy group, and an arbitrary number of phenylene group, cyclohexane-diyl group, or —COO— group as a divalent linking group; R represents a monovalent group bonded in combination or order, R ²² and R ³² each independently represent a hydrogen atom, a methyl group or an ethyl group, and R ²³ and R ³³ each independently represent an alkyl group Alternatively, an alkoxy group and any number of phenylene groups and cyclohexane-diyl groups may be bonded through any of —O—CO—, —CO—O—, —CH ₂ O—, and —O—CH ₂ —. A cycloalkyl group which is a monovalent group often bonded in any combination and order, or R ²² and R ²³ , R ³² and R ³³ form a 5-membered or 6-membered ring, A ² , A ³ each In the general formula (II), a naphthylene group having a diazo bond at positions 1 and 4 is a halogen atom or an alkoxy group having 1 to 3 carbon atoms. , An alkyl group having 1 to 3 carbon atoms, an alkylsulfonyl group having 1 to 3 carbon atoms, a lower fluoroalkyl group having 1 to 3 carbon atoms, and an alkoxycarbonyl group having 1 to 3 carbon atoms as a substituent. .) The azo dichroic dye according to claim 1, wherein A ² in the structural formula (II) or A ^{3 in} (III) is a hydroxy group or a thiol group. The azo dichroic dye according to claim 1 or 2 , wherein the absorption maximum wavelength (λmax) is 630 nm or more. A liquid crystal composition comprising the dichroic dye according to any one of claims 1 to 3 . A liquid crystal element comprising a liquid crystal layer containing the liquid crystal composition according to claim 4 .

Images