JP2010155924A - Dichroic dye - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dichroic azo dye having an absorption peak wavelength in a long wavelength range of ≥600 nm and an order parameter of as high as ≥0.81. <P>SOLUTION: The dichroic azo dye is expressed by structural formula (I). In the formula, R<SP>1</SP>, R<SP>2</SP>and R<SP>3</SP>are each independently an arbitrary monovalent group; X is an electron donating substituent; the ring Ar is 1,4-phenylene which may have a substituent or 1,4-naphthylene ring which may have a substituent; n is an integer of ≥2; and the multiple rings Ar may be the same or different. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a novel dichroic dye used for liquid crystal display and the like and a liquid crystal element including the same.

  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 method of displaying by changing the orientation of the cell 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.

  The dichroic dye used in the liquid crystal element is required to have properties such as appropriate absorption characteristics, high order parameter (S value), high solubility in the host liquid crystal, and durability. On the other hand, as a blue azo dichroic dye necessary for constituting a black liquid crystal composition having a large market need, a dye having a nitro group, a cyano group and a heterocyclic ring has been known. A dye having a nitro group, a cyano group or a heterocyclic ring has a great difficulty in durability and solubility in a host liquid crystal. In addition, it is difficult to manufacture, and the order parameter in the short wavelength region is likely to be low because of the secondary absorption in the short wavelength region.

  Further, Patent Document 1 has a description of a dye represented by the following structural formula similar to the present invention, but the absorption maximum wavelength in chloroform is 593 nm, which is a short wavelength, and a high order parameter in a wavelength region of 600 nm or more. It was not enough for the purpose to get.

JP-A 62-555

  An object of the present invention is to provide an azo dichroic dye having an absorption maximum wavelength in a long wavelength region of 600 nm or more and a high order parameter of 0.81 or more.

As a result of intensive studies, the inventor has found that an azo dichroic dye represented by the following structural formula (I) having an electron donating group on the naphthalene ring has an absorption maximum wavelength in a long wavelength region of 600 nm or more, and 0. It has been found that it has a high order parameter of 81 or more, and has found that the above-mentioned problems can be solved. That is, the gist of the present invention is as follows.
[1] An azo dichroic dye represented by the following structural formula (I)

(Wherein R ¹ , R ² and R ³ each independently represents any monovalent group, X represents an electron-donating monovalent group, and ring Ar may have a substituent. 1,4-phenylene or a 1,4-naphthylene ring which may have a substituent is represented, and n represents an integer of 2 or more, and a plurality of rings Ar may be the same or different.
However, the case where “the ring Ar bonded to R ¹ is a 1,4-phenylene group and R ¹ is represented by the following structural formula (II)” is excluded.

(In formula (II), R ⁴ represents an alkyl group, and ring A ¹ and ring A ² are each independently 1,
A 4-phenylene group or a (trans) -cyclohexane-1,4-diyl group,
L ¹ represents a divalent linking group containing no cyclic structure and no azo bond. ))
[2] The azo dichroic dye according to [1], wherein X is an alkoxy group or an alkyl group.

  The liquid crystal material element using a liquid crystal composition containing a dichroic dye having an absorption maximum wavelength in the long wavelength region and having a high order parameter can display a high contrast up to the long wavelength region.

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

(Wherein R ¹ , R ² and R ³ each independently represents any monovalent group, X represents an electron-donating monovalent group, and ring Ar may have a substituent. 1,4-phenylene or a 1,4-naphthylene ring which may have a substituent is represented, and n represents an integer of 2 or more, and a plurality of rings Ar may be the same or different.
However, the case where “the ring Ar bonded to R ¹ is a 1,4-phenylene group and R ¹ is represented by the following structural formula (II)” is excluded.

(In formula (II), R ⁴ represents an alkyl group, and ring A ¹ and ring A ² are each independently 1,
A 4-phenylene group or a (trans) -cyclohexane-1,4-diyl group,
L ¹ represents a divalent linking group containing no cyclic structure and no azo bond. ))
Hereinafter, the azo dichroic dye represented by the structural formula (I) of the present invention will be described in detail.
In addition, the dichroic dye represented by the above general formula (I) is “the Ar bonded to R ¹ is a 1,4-phenylene group, and R ¹ is represented by the following structural formula (II)” Case "is not included.

(In formula (II), R ³ represents an alkyl group, and ring A ¹ and ring A ² are each independently 1,
A 4-phenylene group or a (trans) -cyclohexane-1,4-diyl group,
L ¹ represents a divalent linking group containing no cyclic structure and no azo bond. )
Since the compound having the above structure is included in the compound described in the general formula (I) described in Japanese Patent Application No. 2007-170700, which is a prior application, this is excluded from the scope of the present invention.

1. About 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.
In the structural formula (I), R ¹ represents an arbitrary monovalent group. R ¹ may be any group as long as it does not impair the performance of the present invention, but is preferably a structure having a low polarity and extending a polar molecular length, a partial structure of liquid crystal molecules, etc., as generally found in azo dichroic dyes, The alkyl group is preferably a single bond, or a group bonded through a phenylene group, a cyclohexane-diyl group, and a group in which these are connected in any combination and in any order, 2-4.

Examples of the alkyl group of R ¹ include ¹ to 10 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. Of these, a linear or branched 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.
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 is a single bond or a cyclic structure and an azo group. They are linked via a divalent linking group that does not contain a bond.

  The divalent linking group not containing a cyclic structure and an azo bond is not particularly limited. For example, 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, etc., a linear or branched alkylene group having 1 to 10 carbon atoms; vinylene group, propenylene group, isopropenylene group, butenylene group, isobutenylene group, sec-butenylene group , Tert-butenylene group, hexenylene group, octenylene group, etc., linear or branched alkenylene group having 2 to 10 carbon atoms; ethynylene group, propynylene group, isopropynylene group, butynylene group, isobutynylene group, sec-butynylene group, tert-butynylene group, hexynylene group, octynyl A linear or branched alkynylene group having 2 to 10 carbon atoms, such as a group; methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, isopropoxycarbonyl group, tert-butoxycarbonyl group, acetyloxy group, benzoyloxy group, etc. And an ester group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, an ether group, a carbonyl group, a group in which they are combined, and the like.

Among these, those having 2 bonding atoms are preferable, —O—CO—, —CO—O—, —CH 2 O—, —O—CH 2 — and the like are more preferable, and —CH 2 O— is particularly preferable.
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 the alkyl group and the phenylene group, the alkyl group and the cyclohexane-diyl group, or the phenylene group and the cyclohexane-diyl group is not particularly limited, but in order to achieve a high order parameter, it must be bonded at the 4-position. Is particularly preferred.

Specifically, for example, a linear alkyl group having 3 to 10 carbon atoms, preferably 3 to 8 carbon atoms such as a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an 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) fur Carbon atoms such as a cycloalkenyl group 15 to 22, preferably and the like 4- (4-alkyl) phenyl group 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.

Among 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 may be any substituent as long as it does not impair the performance of the present invention, but is preferably a structure having a low polarity and extending the length of a polar molecule, a partial structure of a liquid crystal molecule, or the like, which is commonly found in azo dichroic dyes. Among them, the alkyl group described above as the group for R ¹ is a single bond, or a group bonded via a phenylene group, a cyclohexane-diyl group, and a group in which these are connected in any combination and in any order in 2 to 4 groups. In addition, a structure in which an alkylene group is bonded to an N atom is preferable.

The alkyl group possessed by R ³ is preferably a linear or branched group having ¹ to 10 carbon atoms exemplified as the alkyl group possessed by R ^1. 3-8 linear alkyl groups are particularly preferred.
In addition, 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 is a single bond or a cyclic structure and an azo group. They are linked via a divalent linking group that does not contain a bond.

  Although it does not specifically limit as a bivalent coupling group which does not contain a cyclic structure and an azo bond, For example, C1-C1 mentioned above as a bivalent coupling group which does not contain the cyclic structure and azo bond which R1 has. 10 linear or branched alkylene groups; the above-described linear or branched alkenylene groups having 2 to 10 carbon atoms; the above-described linear or branched alkynylene groups having 2 to 10 carbon atoms; Similarly, the above-mentioned ester group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms; ether group; carbonyl group;

Among these, those having 2 bonding atoms are preferable, —O—CO—, —CO—O—, —CH 2 O—, —O—CH 2 — and the like are more preferable, and —CH 2 O— is particularly preferable.
In addition, as an alkylene group couple | bonded with N atom, the C1-C10 linear or branched alkylene group mentioned above as a bivalent coupling group which does not contain the cyclic structure and azo bond which R1 has is mentioned.

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 the alkyl group and the phenylene group, the alkyl group and the cyclohexane-diyl group, or the phenylene group and the cyclohexane-diyl group is not particularly limited, but may be bonded at the 4-position from the viewpoint of obtaining a high order parameter. Particularly preferred.

Specifically, a carbon number of 10 to 17 (4-alkylphenyl) methyl group such as (4-butylphenyl) methyl group, (4-pentylphenyl) methyl group, (4-hexylphenyl) methyl group; (4-propylcyclohexyl) methyl group having 10 to 17 carbon atoms such as butoxyphenyl) methyl group, (4-pentyloxyphenyl) methyl group, (4-hexyloxyphenyl) methyl group; (4-alkylcyclohexyl) having 10 to 17 carbon atoms such as, (4-butylcyclohexyl) methyl group, (4-pentylcyclohexyl) methyl group, (4-hexylcyclohexyl) methyl group, (4-heptylcyclohexyl) methyl group, etc. Methyl group; (4- (4-propylcyclohexyl) phenyl) methyl group, (4- (4-butyl Chloro) phenyl) methyl group, (4- (4-pentylcyclohexyl) phenyl) methyl group, (4- (4-hexylcyclohexyl) phenyl) methyl group, (4- (4-heptylcyclohexyl) phenyl) methyl group, etc. (4- (4-alkylcyclohexyl) phenyl) methyl group having 16 to 23 carbon atoms; (4- (4-propylcyclohexyl) cyclohexyl) methyl group, (4- (4-butylcyclohexyl) cyclohexyl) methyl group, (4 A carbon number of 16 to 23 (4- (4- (4-pentylcyclohexyl) cyclohexyl) methyl group, (4- (4-hexylcyclohexyl) cyclohexyl) methyl group, (4- (4-heptylcyclohexyl) cyclohexyl) methyl group, etc.); 4-alkylcyclohexyl) cyclohexyl) methyl group And the like.
R2 and R3 may combine to form a ring structure. Specifically, by connecting R2 and R3, an alkylene group, more preferably _CH 2 _CH 2 _CH 2 CH ₂ group and _{CH (CH 3) CH 2 CH} 2 CH 2 group or the like may be formed.

2. About X In Structural Formula (I), X represents an electron-donating substituent such as an alkoxy group or an alkyl group.
Examples of the alkoxy group of X 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. 4, Among them, an alkoxy group having 1 to 3 carbon atoms is mentioned.

As the alkyl group for X, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, etc. Especially, a C1-C3 alkyl group is mentioned. By selecting the above group, the wavelength of the dye can be increased.
In order to maintain a high order parameter, X is preferably a smaller substituent, and more preferably a methyl group or a methoxy group.

3. Regarding Ring Ar Ring Ar represents a 1,4-phenylene or 1,4-naphthylene ring which may have a substituent. Two or more rings Ar may be the same or different. When the ring Ar has a substituent, examples of the substituent include those described above as the substituent for X, preferably an alkyl group having 1 to 4 carbon atoms, particularly an alkyl group having 1 to 3 carbon atoms, or 1 to 1 carbon atoms. 4, Among them, an alkoxy group having 1 to 3 carbon atoms is mentioned. Among these, a methyl group or a methoxy group is particularly preferable.

4). n represents an integer of 2 or more. A molecule having n of 5 or more is usually 4 or less, more preferably 3 or less, because it is difficult to produce and has low solubility in the host liquid crystal. Further, when n is 2, sufficient wavelength may not be achieved, so 3 is most preferable as n.
5). Molecular Weight The dichroic dye of the present invention represented by the general 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.

6). Specific Examples Specific examples of the dichroic dyes represented by the general formula (I) are illustrated below, but the present invention is not limited to these unless it exceeds the gist.

7). Synthesis Method The above-described dichroic dye of the present invention can be synthesized by performing an azo coupling reaction between the intermediate (III) and the intermediate (IV). Intermediate (III) can be prepared by known methods such as A.I. V. Iva
Shchenko's “Dichroic Dye for Liquid Crystal Display” (CMC, published in 1994), Hiroshi Horiguchi's “Review Synthetic Dyes” (Sankyo Publishing, published in 1968), and the methods described in the literature cited therein, etc. It can synthesize | combine by making it react. Intermediate (IV) can be synthesized, for example, by the method described in the examples when X is a methoxy group. That is, a cross-coupling reaction using a palladium catalyst is performed with 1-bromo-3-methoxynaphthalene synthesized by the method described in J. Am. Chem. Soc. 1976, 98, 3237 and amine R ² R ³ NH. Can be synthesized.

8). 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. Methods known to host liquid crystal compounds such as biphenyl-based, phenylcyclohexane-based, phenylpyrimidine-based, cyclohexylcyclohexane-based host liquid crystal compounds having nematic or smectic phases described in pages 715-722, or host liquid crystal compositions containing these compounds The liquid crystal composition can be easily prepared by mixing in step (b).

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 general formulas (IV) to (VIII).

[In formulas (IV) to (VIII), ring B 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—. Y ¹ and Y ³ each independently represent a hydrogen atom, a halogen atom such as a fluorine atom or a chlorine atom, and Y ² represents a halogen atom such as a fluorine atom or a chlorine atom, or 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. Y ⁷ and Y ⁸ each independently represent a cyano group or a halogen atom such as a fluorine atom or a chlorine atom. Y ¹¹ and Y ^{13 each} represent a cyano group. Y ⁴ , Y ⁵ , Y ⁶ , Y ⁹ , Y ¹⁰ , Y ¹² , and Y 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. ]

As the liquid crystal composition of the present invention, an optically active substance that may or may not exhibit a liquid crystal phase, such as a dichroic dye other than the dichroic dye of the present invention, and cholesteryl nonanoate, You may contain various additives, such as a ultraviolet absorber and antioxidant.

  The dichroic dye of the present invention has an absorption maximum wavelength in a long wavelength region of 600 nm to 650 nm and usually has a high order parameter of 0.81 or more, and as a liquid crystal composition containing the same, a computer, It can be suitably used as various electro-optical devices such as display elements for watches, calculators, etc., electro-optical shutters, electro-optical apertures, optical communication optical path switching switches, optical modulators, and the like.

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.

9. Liquid crystal device By sandwiching 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, Ryo Tsunoda, “Latest Liquid Crystal Technology (Industrial Research Committee, published in 1983), page 34, J.A. L. Heilmeier-type guest hosts described in Fergason, SID85Digest, 68 (1985), “Liquid Crystal Device Handbook” (published by Nikkan Kogyo Shimbun, 1989), pages 315 to 329, etc. Various liquid crystal elements using a guest host effect such as a transition type guest host can be formed. 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.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[Synthesis of dichroic dye]

<Synthesis of Intermediate M04>
A mixture of M01 (26.1 g, 106 mmol), triethylamine (22.2 ml, 159 mmol) and 1,4-dioxane (50 ml) was cooled in an ice bath, diphenylphosphoryl azide (22.8 ml, 106 mmol) and tert-butyl alcohol. (30.4 ml, 318 ml) was sequentially added dropwise. After heating under reflux for 2 hours, water (200 ml) was added under cooling in an ice bath, and the precipitate was collected by filtration and washed with water. To the obtained powder was added ethanol (300 ml) and concentrated hydrochloric acid (17 ml, 204 mmol) diluted with water (51 ml), and the mixture was heated to reflux for 3 hours. After cooling to room temperature, water (500 ml) was added, the precipitate was collected by filtration, washed with water, and further washed with methanol (100 ml) to obtain M02 (14.7 g, yield 55%).

  A mixture of M02 (12.6 g, 50 mmol) and N, N-dimethylformamide (200 ml) was cooled in an ice bath and concentrated hydrochloric acid (10.4 ml) and sodium nitrite (3.62 g, 52.5 mmol) in water ( 10 ml) solution was added dropwise. After stirring for 2 hours under cooling in an ice bath, a solution of amidosulfuric acid (0.97 g, 10 mmol) in water (10 ml) was added to obtain a diazo solution. In a separate container, a mixture of 1-aminonaphthalene (7.16 g, 50 mmol), acetic acid (100 ml) and water (50 ml) was taken, and the diazo solution was added dropwise with cooling in an ice bath. The mixture was stirred for 1 hour under cooling in an ice bath, and sodium acetate (20 g, 240 mmol) was added. Water (200 ml) was added, the precipitate was collected by filtration and purified by silica gel column chromatography, and the resulting powder was washed with methanol to obtain Compound M03 (15.64 g, yield 84%).

  A mixture of M03 (15.64 g, 42.1 mmol) and N-methyl-2-pyrrolidone (300 ml) was cooled in an ice bath and concentrated hydrochloric acid (12.3 ml) and sodium nitrite (3.05 g, 44.2 mmol). Of water (10 ml) was added dropwise. After stirring in an ice bath for 1.5 hours, amidosulfuric acid (1 g, 10 mmol) was added to obtain a diazo solution. In a separate container, a mixture of 1-aminonaphthalene (6.03 g, 42.1 mmol), acetic acid (100 ml) and water (50 ml) was taken, and the diazo solution was added dropwise with cooling in an ice bath. After stirring for 15 minutes under cooling in an ice bath, sodium acetate (16 g, 200 mmol) was added. After stirring for 1 hour under cooling in an ice bath, water (200 ml) was added, and the precipitate was collected by filtration and subjected to silica gel column chromatography. The resulting powder was washed with methanol to obtain M04 (13.0 g, yield 59%).

  <Synthesis of Intermediate M09>

To a mixture of M05 (26.2 g, 85 mmol), 4-nitrophenylboronic acid (14.5 g, 87 mmol), potassium carbonate (46.8 g, 338 mmol), water (10 ml) and toluene (250 ml) was added tetrakis under nitrogen atmosphere. (Triphenylphosphine) palladium (0) (8.86 g, 7.7 mmol) was added, and the mixture was heated to reflux overnight. After cooling to room temperature, chloroform and water were added and the mixture was stirred, insoluble material was removed by celite filtration, and the organic layer was separated. The organic layer was washed with water and saturated brine, and dried over anhydrous sodium sulfate. Concentration under reduced pressure and recrystallization from methanol gave M06 (21 g, 60% yield).
M06 (16.4 g, 46.6 mmol) was dissolved in tetrahydrofuran (250 ml), 5% palladium on carbon (3.0 g) was added, and the mixture was purged with hydrogen and stirred overnight at room temperature at 5 atm. The palladium carbon was removed by filtration, and the filtrate was concentrated under reduced pressure to obtain M07 (14.5 g, yield 97%).

Thereafter, M09 was obtained in the same manner as the synthesis of M04.
<Synthesis of Intermediate M21>

M20 was synthesized by the method described in J. Am. Chem. Soc. 1976, 98, 3237.
M12 (4.77 g, 20 mmol), phthalimide (2.94 g, 20 mmol), triphenylphosphine
(5.77 g, 22 mmol) and tetrahydrofuran (100 ml) were added diethyl azodicarboxylate (2.2 mol / L toluene solution, 10 ml, 22 mmol) at room temperature, stirred at room temperature for 2 hours, and then silica gel column chromatography. Purification by chromatography (silica gel 500 g, hexane / ethyl acetate 10 / 1-5 / 1) gave M18 (6.83 g, 93% yield).

M18 (6.83 g, 18.6 mmol), ethanol (100 ml) and hydrazine monohydrate (2 ml, 41
mmol) was added and heated to reflux for 1.5 hours. After cooling to room temperature, the precipitate was filtered off, washed with tetrahydrofuran, the filtrate was concentrated, 1N aqueous sodium hydroxide solution was added, and the mixture was extracted with a mixed solvent of tetrahydrofuran and ether. The organic layer was washed with water and saturated brine, and dried over anhydrous sodium sulfate. After concentration under reduced pressure, the resulting amorphous material was suspended in methanol and 1N hydrochloric acid (30 ml) was added. Methanol was distilled off, the precipitate was collected by filtration, and washed with water to give M19 (2.13 g, yield 42%).

M20 (1.84 g, 7.76 mmol), M19 (2.13 g, 7.78 mmol), toluene (20 ml), sodium-tert-butoxide (1.86 g, 19.4 mmol), Pd ₂ (dba) ₃ (0.18 g, 0.20 mmol) , Rac-BINAP (0.36 g, 0.58 mmol) was stirred at 85 ° C. for 2 hours, 95 ° C. for 2 hours, 105 ° C. for 2 hours, and 115 ° C. for 0.5 hour, cooled to room temperature, and water and ethyl acetate were added. In addition, the mixture was filtered through Celite and washed with ethyl acetate. The filtrate was separated, and the organic layer was washed with water and saturated brine, and dried over anhydrous sodium sulfate. Concentration under reduced pressure and purification by silica gel column chromatography (silica gel 100 g, hexane / ethyl acetate 100 / 1-20 / 1-10 / 1-4 / 1), the powder was washed with methanol / water, and M21 (2.56 g, yield 84%).

[Example 1]
<Synthesis of Compound 1>
A mixture of intermediate “M04” (0.45 g, 0.86 mmol) obtained above and N, N-dimethylformamide (40 ml) was cooled in an ice bath, concentrated hydrochloric acid (0.35 ml) and sodium nitrite ( 0.071 g, 1.0 mmol) aqueous solution was added. After stirring for 2 hours under cooling in an ice bath, an aqueous solution of amidosulfuric acid (0.03 g, 0.3 mmol) was added to obtain a diazo solution. In a separate container, a solution of the intermediate “M21” (0.34 g, 0.86 mmol) obtained above in tetrahydrofuran (10 ml) was taken, and the diazo solution was added while cooling in an ice bath. After stirring for 15 minutes, sodium acetate (1 g, 12 mmol) was added, and after stirring for 30 minutes, methanol (40 ml) was added. The precipitate was collected by filtration and purified by silica gel column chromatography and recrystallization to give compound 1 (0.49 g). Yield 61%).

<Evaluation of λmax and order parameter (S value)>
The obtained dichroic dye “Compound 1” was dissolved at a concentration of 0.1% by weight in a fluorine-based liquid crystal mixture marketed under the trade name MCL-2039 (product of Merck) to obtain a guest-host liquid crystal composition. It was adjusted. 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 (λ _max ). Was determined from the following equation.

S = (A // − A⊥) / (2A⊥ + A //)
The results are shown in Table 1.
[Examples 2 to 7 and Comparative Example 1]
<Synthesis of Compound 2>
Using the intermediate “M041” as (III) and the intermediate “M211” as (IV) in the following reaction formula, the dichroic dye “Compound 2” was synthesized according to the following reaction formula. Intermediate 041 can be synthesized based on the same method as Intermediate M04, and Intermediate M211 can be synthesized based on the same method as Intermediate M21.

<Synthesis of Compound 3>
Using the intermediate “M04” as (III) and the intermediate “M211” as (IV) in the above reaction scheme, a dichroic dye “compound 3” was synthesized according to the above reaction scheme.
<Synthesis of Compound 4>
Using the intermediate “M041” as (III) and the intermediate “M21” as (IV) in the above reaction scheme, a dichroic dye “compound 4” was synthesized according to the above reaction scheme.

<Synthesis of Compound 5>
Using the intermediate “M04” as (III) and the intermediate “M212” as (IV) in the above reaction scheme, a dichroic dye “compound 5” was synthesized according to the above reaction scheme. Intermediate M212 can be synthesized based on a method similar to that for intermediate M21.

<Synthesis of Compound 6>
In the above reaction formula, intermediate (M09) is used as (III) and intermediate (M2) is used as (IV).
The dichroic dye “Compound 6” was synthesized according to the above reaction formula.
<Synthesis of Compound 7>
Using the intermediate “M09” as (III) and the intermediate “M211” as (IV) in the above reaction scheme, a dichroic dye “compound 7” was synthesized according to the above reaction scheme.

  For the obtained dichroic dyes “compounds 2 to 7”, the order parameter (S value) was calculated from the absorbance at the absorption peak (λmax) in the same manner as in Example 1, and the results were shown together with “Comparative Compound 1”. It is shown in Table 1.

  As described above, all of the dye compounds 1 to 7 (Examples 1 to 7) represented by the general formula (I) of the present invention have a λmax of 600 nm or more and an S value of 0.81 or more. Example Compound 1 (Comparative Example 1) had a low value of λmax of less than 600 nm and an S value of 0.79.

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.

Explanation of symbols

1; Incident light
3; Transparent glass substrate
4; Transparent electrode
5: Alignment film
6; Liquid crystal compound molecules
7; Dichroic dye molecule
9; reflective layer
10; Reflected light

Claims (2)

An azo dichroic dye represented by the following structural formula (I)

(Wherein R ¹ , R ² and R ³ each independently represents any monovalent group, X represents an electron-donating monovalent group, and ring Ar may have a substituent. 1,4-phenylene or a 1,4-naphthylene ring which may have a substituent is represented, and n represents an integer of 2 or more, and a plurality of rings Ar may be the same or different.
However, the case where “the ring Ar bonded to R ¹ is a 1,4-phenylene group and R ¹ is represented by the following structural formula (II)” is excluded.

(In formula (II), R ⁴ represents an alkyl group, and ring A ¹ and ring A ² are each independently 1,
A 4-phenylene group or a (trans) -cyclohexane-1,4-diyl group,
L ¹ represents a divalent linking group containing no cyclic structure and no azo bond. ))   The azo dichroic dye according to claim 1, wherein X is an alkoxy group or an alkyl group.

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