JPS62167389A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:A liquid crystal composition, especially guest-host type liquid crystal composition, having high solubility in liquid crystal, capable of providing high display contrast, containing a specific, novel optically active thioindigo dyestuff. CONSTITUTION:A liquid crystal composition containing one or more optically active thioindigo dyestuffs shown by formula (R<1> is asymmetric carbon- containing substituent group; R<2> is asymmetric carbon-containing substituent group, alkyl, alkoxy, aryl or aryloxy; R<3> and R<4> are 1-3C alkyl, alkoxy, halogen, nitro, amino or 1-3C monoaminodialkylamino; m and n are 0-3 integer). In order to synthesize the dyestuff, thioindoxyl is oxidized with potassium ferricyanate to give a dyestuff having a symetric structure based on a central double bond.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal composition containing a novel thioindigo dye, particularly a guest-host type liquid crystal composition.

BACKGROUND ART A guest-host type (hereinafter referred to as GH type) liquid crystal display system is a display system using a GH type liquid crystal composition in which a pleochroic dye is added as a guest dye to a host liquid crystal serving as a matrix.

As guest dyes, not only pleochroic dyes but also isotropic dyes mixed with pleochroic dyes are used.

(, Phase change type display using chiral nematic liquid crystal as the host liquid crystal proposed by White and Taylor as one of the H-type liquid crystal display systems (Journal of Applied Physics)
J, ppl, Phys,, Vol, 45°4
718 (1974)). This phase transition method, compared to using nematic liquid crystal as the host liquid crystal,
A useful display can be obtained without the need for an auxiliary polarizer.

A chiral nematic host liquid crystal used in a phase change type GH display is generally a nematic liquid crystal to which an optically active substance is added, and a pleochroic dye is further added to this.

However, JP-A No. 69-133282 and JP-A No. 6
As disclosed in Publication No. 9-136376, a phase transition using an optically active pleochroic dye having both an optically active moiety and a chromophore moiety in its molecule instead of an optically active substance and a pleochroic dye. A display method is known. When such an optically active pleochroic dye is used in a liquid crystal display device, it acts as a circularly polarizing dichroic dye, and if a sufficient amount is used so that the incident light propagates as circularly polarized light, the total amount of the incident light is Can absorb polarized light. Such optically active pleochroic dyes include azo,
Anthraquinones are known.

Problems to be Solved by the Invention However, with respect to thioindigo dyes, no examples of optically active pleochroic dyes that do not display phase transition type GH9 crystals have been known. The object of the present invention is to obtain a thioindigo-based optically active dye that has high solubility in liquid crystals and can provide high display contrast.

Means for Solving the Problem In order to improve solubility in liquid crystal and obtain high display contrast, a thioindigo dye having a structure represented by the following general formula ([) is used.

CI) (wherein, R1 represents a substituent having an asymmetric carbon, R2 represents a substituent having an asymmetric carbon, an alkyl group, an alkoxy group,
Represents an aryl group or an aryloxy group, R5, R4
represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen, a nitro group, an amide group, a monoalkylamino group having 1 to 3 carbon atoms, or a dialkylamino group, m.

n is an integer from 0 to 3. ) Function The thioindigo dye used in the present invention has an optically active substituent having an asymmetric carbon at the 6-position of the thioindigo skeleton, and a hair alkyl group, an alkoxy group, or an aryl group at the 5'-position, as shown in the general formula [I]. group, an aryloxy group, or an optically active substituent having an asymmetric carbon. 6th place and 5th place
By introducing such a substituent into the ′ position, the thioindigo dye used in the present invention exhibits large circular dichroism,
High display contrast can be obtained. However, the thioindigo dye used in the present invention also has high solubility in liquid crystals.

EXAMPLES In addition to nematic liquid crystals, the thioindigo dyes of the present invention can be added to smectic liquid crystals, which can be used for phase change type GHM crystal displays, and can also be used for thermal writing type liquid crystal displays. In addition, display systems that use dyes or optically active substances added to liquid crystals include the TN system, SBE, and C and H systems that use ferroelectric liquid crystals. It is also possible to apply it to these display systems by taking advantage of its properties as a dichroic dye.

The thioindigo dye of the present invention generally has a high solubility in the host liquid crystal of 0.1% by weight or more and has high dichroism, so that high contrast display is possible.

The method for synthesizing the thioindigo dye of the present invention and its physical properties in liquid crystal will be explained below.

The optically active thioindigo dye represented by the general formula (1) can be synthesized from an optically active benzene derivative by the reaction route shown below.

[■]

(In the reaction formula, R1 represents a substituent having an asymmetric carbon, and R
2 represents a substituent having an asymmetric carbon, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group, R5,
R4 is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a halogen, a nitro group, an amino group, 1 to 3 carbon atoms;
represents a monoalkylamino or dialkylamino group having 5 carbon atoms, and m and n are integers of 0 to 3. ) As shown in the reaction formula representing the synthetic route, general formula (II
By oxidizing thioindoxyl shown in I) with potassium ferricyanide (K, Fe(CN)6), an optically active thioindigo dye having a symmetrical structure with respect to the central double bond can be synthesized. Still, CI) can be replaced by the general formula (I
By reacting with the imino derivatives shown in V), thioindigo dyes having an asymmetric structure with respect to the central double bond can also be synthesized.

The same dye can also be obtained from

The imino derivative shown in the general formula [■] is composed of thioindoxyl (III) and N,N-dimethyl-4 as shown below.
- Obtained by coupling nitrosoaniline.

QI[) (IV) An optically active substituted benzene having a substituent having an asymmetric carbon represented by the general formula ([1)] can be produced by combining an optically active alcohol and p-toluenesulfonyl chloride, for example, as shown in the reaction formula below. can get.

R50H-)G(,DSo2Ce-R5030+CH.

[■] [■] (In the formula, R5 has an asymmetric carbon and represents an optically active substituent, and R3 and m have the above meanings.) In the optically active thioindigo dye CI), the substituent R' and R' may be introduced from the raw material stage. If R' and R' are halogen or nitro groups, after synthesizing the thioindigo dye [1], halogenation and nitration may be carried out. It can also be introduced by doing. In addition, amine groups and alkylamino groups are
It can also be obtained by reducing the nitro group, or by further reacting with an alkylating agent after reducing the nitro group.

Example 1 6.6'-bis(S-2-methylbutyl)thioindigo was synthesized as follows.

S (→-2-methylbutanol 88y to pyridine 900
-, and 381 g of P-toluenesulfonyl chloride was added thereto over about 30 minutes at 10'C or less while cooling with water and stirring.

After further stirring for 1 hour, the mixture was left at 0°C for 16 hours. 16
While stirring while cooling to prevent the temperature from rising above ℃,
Water was added, and the mixture was further stirred for 2 hours while cooling with water. benzene 2
Extracted with 50-4 times, collected the benzene layer and extracted with N-HC.
After washing with water to remove pyridine and water until neutral, it was dried over anhydrous sodium sulfate. Benzene was distilled off under reduced pressure to obtain 238L of tosylate! I got it.

Bromobenzene e4. rsq, magnesium powder 9.9
f, Toshiley 200 (J) was added dropwise to the Grignard reagent prepared from anhydrous diethyl ether 600 at room temperature over about 1 hour, stirred at room temperature for 2 hours, further stirred under heating under reflux for 2 hours, and left at room temperature for 12 hours. .1Q%-H
,,So4 was added at below 20°C until the solution became transparent, the organic layer was separated, the aqueous layer was extracted with 2100 ml, the organic layer was collected and washed with NaHCO, an aqueous solution, and after further washing with water, Na
Dry with 2So4. After distilling off the ether, 5-2-methylbutylbenzene (boiling point 97-
100° C., 732 mmHg) 289 was obtained.

5-2-Methylbutylbenzene 20 Da to chloroform 1
00. Chlorosulfonic acid 10
0d was added dropwise while stirring. After stirring at room temperature for 1 hour, the mixture was poured into water to hydrolyze excess chlorosulfonic acid, and the chloroform layer was separated and dried over Na2804 to obtain 27 g of chlorosulfonyl chloride.

Concentrated sulfuric acid43. A mixture of 236 rnl of water and 236 rnl of water was cooled to 0° C. and the sulfonyl chloride 27i9 was added.

Lead powder 39Fj was added little by little while stirring to prevent the temperature from rising above 5°C. After everything was added, the mixture was stirred at room temperature for 2 hours, and the temperature was further raised to reflux for 6 hours. Purification by steam distillation yielded 17 g of thiophenol.

In an aqueous solution of potassium hydroxide 4y dissolved in water 200-,
Dissolve 7.4 g of the above thiophenol and add 79 g of chloroacetic acid.
．． An aqueous solution of 4y of potassium hydroxide dissolved in 50- of water was added, and the mixture was heated under reflux for 1 hour. While hot, the mixture was neutralized with hydrochloric acid, and after cooling, the resulting crystals were separated into three portions, washed with water, and dried. Recrystallized from n-hexane to give 6.2p thioglycolic acid (melting point 72
．． 2-73.0'C) was obtained.

6.2 p of the thioglycolic acid was added to 40 p of chlorobenzene.
-, add 3.0 - of phosphorus trichloride and heat at 76°C to 1.
Stir for hours. After cooling to about 60°C, aluminum chloride powder was added little by little so that the temperature did not exceed 65°C. After everything was added, the reaction was carried out at 80'C for 1 hour, and after cooling, the mixture was poured into ice for hydrolysis.

3. Extracted with benzene and purified by silica gel-benzene column chromatography to obtain thioindoxyl represented by general formula (III) having a 3-2-methylbutyl group at the 5-position.
I got 8 ji.

1.1 g of thioindoxyl obtained in this way was dissolved in a solution of potassium hydroxide 6y dissolved in 50,000 ml of water and 26° of ethanol, and a solution of potassium ferricyanide 6,0 dissolved in 6° of water was added to the solution at room temperature. The mixture was stirred for 1 hour. After making it acidic by adding hydrochloric acid, the formed precipitate was divided into three parts,
Washed with water and dried. Recrystallized from n-hexane-benzene mixed solvent to obtain 6゜5'-bis(S-2-methylbutyl).
0.44 g of thioindigo was obtained. The melting point of this dye is 21
2.8-213.6°C1 When dissolved in phenylcyclohexane-based nematic mixed liquid crystal ZLI-2444 manufactured by Merck and measured the maximum absorption wavelength, the maximum absorption wavelength was 566
It was nm.

Example 2 s-(S-2-methylbutyl)-5'-(trans-4
-propylcyclohexyl)thioindigo was synthesized as follows.

2.7 g of thioindoxyl shown in general formula 1 [) having an 8-2-methylbutyl group at the 6-position obtained in Example 1 was dissolved in a water-ethanol mixed solution in which 2.5 g of sodium hydroxide was dissolved. , N-dimethyl-4-nitrosoaniline 3. An ethanol solution of e9 was added and stirred at 50°C for 1 hour. After cooling, the product precipitate was washed in three portions with water and dried. ts-(S-2-methylbutyl)-2-(4-dimethylaminophenyl), which is an imino derivative represented by the general formula [IV] having a 5-2-methylbutyl group at the 5-position by recrystallization from n-hexane. imino)-2,3-dihydrobenzo(b)thiophen-3-one2. I got sg.

5-(trans-4-propylcyclohexyl)2,3-dihydro of thioindoxyl represented by the general formula ([1)] obtained from trans-4-propyl-4'-phenylcyclohexane in the same manner as in Example 1. 0.559 of benzo(b)thiophen-3-one and the imino derivative Q represented by the general formula [■], 71 were heated in 1 ml of chlorobenzene together with 0.1 ml of piperidine at 120°C for 2 hours. The chlorobenzene was evaporated, the remaining solid was extracted with chloroform, purified by silica gel column chromatography, and recrystallized from a mixed solvent of n-hexane-chloroform to give 5-(S-2-methylbutyl)-
s'-(trans-4-propylcyclohexyl)thioindigo o, 4s g was obtained. The melting point of this dye is 221
．． 3-221.9℃, ZI, f17 in l-2444) Maximum absorption wavelength is 561n! It was 11.

Example 3 es-(S-2-methylbutyl)-s'-(4-pentylphenyl)thioindigo was synthesized as follows.

The imino derivative 5-(S-
General formula obtained from thiophen-3-one o6γ1fi and 4-pentylbiphenyl in the same manner as in Example 1 5-(4-pentylphenyl)- of thioindoxyl shown in (IV)
2,3-dihydrobenzothiophen-3-one o,s
Heated at 120° C. for 2 hours with 0.1 − piperidine in 10 rnl of s/l total chlorobenzene. The chlorobenzene was evaporated, the remaining solid was extracted with chloroform, and tli was purified by silica gel column chromatography.
fm and recrystallized from n-hex/-chloroform mixed solvent to give 5-(S-2-methylbutyl)-s'-(4-
0.45 g of pentylphenyl)thioindigo was obtained. The melting point of this dye is 228.4-229.4°C, and ZL
The maximum absorption wavelength in I-2444 was 6 onm.

Example 4 5,5'-bis(S-2-methylbutyl)thioi/digo 1.6 cm obtained in Example 1 was converted into phenylcyclohexane-based nematic mixed liquid crystal ZLI-24441,5 manufactured by Merck & Co.
A liquid crystal composition dissolved in alj was prepared.

This liquid crystal composition was colored red, and when it was sealed in a wedge-shaped cell that had undergone homogeneous alignment treatment and left for 12 hours, discontinuous lines were observed, indicating that the molecular arrangement of the liquid crystal had a helical structure. The pitch of the helix was measured from the distance between the discontinuous lines and the inclination angle of the wedge-shaped cells using the Grandjean-Cowedge method, and was found to be 120 μm.

By mixing and adding Merck's CB-15, which is known to form a right-handed helix when added to liquid crystal, and the thioindigo dye of this example, when the same amount of each is added alone. Since the helical pitch was reduced compared to that of the thioindigo dye of this example, it was found that when added to liquid crystal, a chiral nematic having a clockwise helical structure could be formed.

Similarly, for the dyes obtained in Example 2 and Example 3, ZLI
-2444 and measured, it was found that when these dyes were added to the liquid crystal, they formed a chiral nematic phase with a clockwise helical structure, similar to the dye of Example 10. The helical pitch is as shown in Example 2.
When the dye of Example 3 was dissolved at 0.16 weight percent in ZLI-2444, it was 190, c+f11, and when the dye of Example 3 was dissolved at 0.17 weight percent in ZLI-2444, it was 230 μm.

Effects of the Invention The optically active thioindigo dye of the present invention has high solubility in liquid crystals and strong dichroism, so by using a liquid crystal composition containing this dye, high-quality guest-host type liquid crystal displays can be produced. It can be carried out.

Claims (1)

[Claims] The following general formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] (In the formula, R^1 represents a substituent having an asymmetric carbon, and R^
2 represents a substituent having an asymmetric carbon, an alkyl group, an alkoxy group, an aryl group, or an aryloxy group, and R^3
, R^4 is an alkyl group having 1 to 3 carbon atoms, and R^4 is an alkyl group having 1 to 3 carbon atoms.
alkoxy group, halogen, nitro group, amino group, 1
It represents a monoalkylamino or dialkylamino group having ~3 carbon atoms, and m and n are integers of 0 to 3. ) A liquid crystal composition comprising at least one optically active thioindigo dye represented by: