JPS61215686A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide the titled composition which exhibits an excellent contrast, by using a thioindigo coloring matter having a specific structure as a guest coloring matter to be dissolved in a host liquid crystal to enhance the solubility in the host liquid crystal and the order parameter. CONSTITUTION:A thioindigo coloring matter of the formula I [wherein R2 is a branched alkyl group; R'2 is H, an aryl, aryloxy or branched alkyl group; R1, R3, R4, R'1, R'3 and R'4 are each independently H, a halogen, an alkyl, alkoxy, aryloxy, alkylthio, arylthio, a nitro, amino, or a group of the formula II; R5 is an alkyl or aryl group; and R6 is H or an alkyl group] is used as a guest coloring matter.

Description

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

BACKGROUND ART A guest-host type (hereinafter referred to as GH type) liquid crystal display element uses a liquid crystal composition in which a pleochroic dye is added as a guest substance to a host liquid crystal. The display contrast is 5=(A, -A±)/(
It is controlled by the order parameter S of the pleochroic dye in the host liquid crystal, which is determined experimentally by A/ 2 A±). Here, A7. , represents the absorbance of a dye when vertically linearly polarized light is incident.In a GH type liquid crystal display element using a dye with parallel dichroism (P-type dye), the closer the order parameter S is to 1, the higher the contrast. Display becomes possible.

In addition to the order parameter S, the properties required of the pleochroic dye used in GH type liquid crystal displays include high solubility in the host liquid crystal, and excellent durability when used as a display element. can be mentioned.

Conventionally, most of the pleochroic dyes for GH type liquid crystal displays are azo-based and anthraquinone-based dyes, and those having various structures have been published.

However, although thioindigo dyes generally have excellent durability, there are no known pleochroic dyes that can be used in actual GH type liquid crystal displays.

Problems to be Solved by the Invention The biggest problem that prevented thioindigo dyes from being used as pleochroic dyes for GH type liquid crystal displays was that they had very low solubility in host liquid crystals.

In other words, due to the low solubility in the host liquid crystal, a liquid crystal composition in which a thioindigo dye is dissolved cannot obtain a sufficiently colored state and cannot be used for display purposes. Due to this low solubility, few examples of thioindigo dyes whose order parameter S has been measured in liquid crystals have yet been known.

The object of the present invention is to improve the solubility of a thioindigo dye in a host liquid crystal and to increase the order parameter S, thereby obtaining a GH type liquid crystal composition with excellent coloring properties and durability.

Means for Solving the Problems A thioindigo dye having a structure represented by the following general formula [1] is used as a guest dye to be dissolved in a host liquid crystal.

(In the formula, R2 represents a branched alkyl group, R2' represents an aryl group, aryloxy group, or a branched alkyl group, R1, R3, R4, R1', R', n41 are hydrogen, halogen , alkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group.

5o3R5, -N=N-R6, -C=C-R6 (R6 represents an alkyl group or an aryl group, R6 represents hydrogen or an alkyl group), or a combination of two or more thereof. . ) Function The thioindigo dye used in the present invention has a structure in which a branched alkyl group is introduced into the 6-position of the thioindigo skeleton, as shown in general formula [1].

This bulky substituent at the 6-position prevents the thioindigo molecules from approaching each other and weakens the intermolecular force, which is thought to improve the solubility in the host liquid crystal. That is, by using a thioindigo dye having a branched alkyl group at the 5-position, a GH type liquid crystal composition with excellent coloring properties can be obtained.

Examples The thioindigo dye represented by the general formula [1] used in the present invention can be obtained by, for example, the following method A or B.

Method A〉 Method B〉 [2] (In the formula, R1-R4, and R, / ~ R4' represent the above-mentioned meanings.) If thioindoxyl is 1 in the general formula [2], it corresponds to It can be obtained from thiol by a known method, for example, by the route shown below.

In addition, the imino derivative represented by the general formula [3] can be formed by thioindoxyl and P-nitroso-N, as shown in the following reaction formula.
Obtained by reaction with N-dimethylaniline.

The thioindigo dye [1:] obtained by method A is a dye with a symmetrical structure, R1=R1', R2:R2/
.

R3=R3', R4=R4'. On the other hand, according to method B, a thioindigo dye with an asymmetric structure can also be obtained. That is, by using [2] and [3] which have different substituents, a dye in which the left and right benzene ring substituents of the thioindigo skeleton are different can be obtained. The same dye can also be obtained using Method B.

Table 1 shows the order parameter S of the thioindigo dye used in the present invention. For the measurement of S, as a host liquid crystal,
ZLI-2444, commercially available from Merck & Co., was used. A dye was dissolved in this host liquid crystal to prepare a liquid crystal composition.

Table 1 The liquid crystal composition thus prepared was sealed in a homogeneous alignment cell with an inter-substrate gap of 10 μm to 50 μm depending on the concentration of the dye, and the absorption spectrum for linearly polarized light parallel and perpendicular to the liquid crystal alignment direction was measured. Then, the above-mentioned relational expression % expression % parameter was calculated.

The synthesis of the thioindigo dye used in the present invention and the measurement of the order parameter S and solubility will be explained below using specific examples.

Example 1 (Synthesis of dye shown in Table 1 A3) 5-(1-chloro-1-methylethyl)-2゜3-dihydropene/(b) Thiophen-3-one゜32 was dissolved in potassium hydroxide 12f. It was dissolved in an aqueous solution, and potassium ferricyanide 152 was dissolved in 150-water and added. After stirring at room temperature for 2 hours, the mixture was extracted with chloroform, and the chloroform layer was washed with water several times and dried over anhydrous sodium sulfate. After the crude product was purified by column chromatography, it was recrystallized from benzene-petroleum benzene to give the results shown in Table 1 A3.
The dye was obtained. Structural confirmation was performed using IR and NMR.

Example 2 (Synthesis of dyes of Table 1 AS) s-(1,1-dimethylethyl)-2,3-dihydropene/(b) Thiophen-3-one 2.1F and 6-(4
-butylphenyl)-2-(4-dimethylaminophenylimino)2,3-dihydrobenzo(b)thiophene-
3-one 4.2f was heated with piperidine o, 2f and 1200 ml in chlorobenzene 1ooR1 for 2 hours. Chlorobenzene was distilled off under reduced pressure, and the remaining solid was separated and purified by column chromatography, and then recrystallized from hexane-chloroform to obtain the dye shown in Table 1 A6. The structure was determined in Example 1.
I did the same thing.

Example 3 (Synthesis of dye of Table 1 A19) s-(1,1-
dimethylpropyl)-2,3-dihydrobenzo(b)thiophen-3-one 2.22 and 5-(phenol)-2
-(a-dimethylaminophenylimino)-2,3-dihydrobenzothiophen-3-one 3.8f to chlorobenzene 1o.

After reacting with piperidine at 120 DEG C. for 2 hours in 220 DEG C., the dye of Table 1 A19 was obtained by treatment in the same manner as in Example 2. Structure confirmation was performed in the same manner as in Example 1.

Other dyes listed in Table 1 can also be synthesized according to Examples 1-3.

Example 4 The dye of Table 1 A9 was dissolved in 1z amount percent in ZL l-2444, and the order parameter S was calculated by the method described above. The figure shows the absorption spectrum when the cell was sealed in a homogeneously aligned cell with a cell thickness of about 10 μm and linearly polarized light parallel or perpendicular to the alignment direction was incident. Curve 1 in the figure is an absorption spectrum when parallel linearly polarized light is incident, and curve 2 is an absorption spectrum when perpendicular linearly polarized light is incident.

This dye has a λma of 569 nm in ZLI-2444.
The AI at this wavelength is 1.043. A soil is 0.
It was 098. Therefore, the pigments in Table 1 & 9 are:
S=0.76. Further, when the dye &9 was similarly dissolved in ZL I-1565 manufactured by Merck & Co., and the order parameter S was measured in the same manner, it was found to be 5==0.76.

The thioindigo dyes of the present invention shown in Table 1 all have a high S value of 0.6 or more, but especially have a 4-substituted phenyl group as ~' in the general formula [1]. The dye has a very high order parameter of S>0.75, and a high contrast GM type liquid crystal display is possible.

Thioindigo dyes that do not have a branched alkyl group as R2 are very poorly soluble; for example, unsubstituted thioindigo has a solubility (0.1% by weight). However, it is difficult to obtain a colored state.

However, the dye having a branched alkyl group as R2 used in the present invention has a solubility in the host liquid crystal of at least 0.1% by weight, and a colored state capable of GH type liquid crystal display can be obtained. A saturated solution was prepared by dissolving the dyes in Table A2 in ZLI-2444, this saturated solution was diluted with benzene, and the solubility was calculated from the absorbance.The solubility was 2.64% by weight. Compared to 100
This shows that the solubility has improved by about twice as much.

Effects of the Invention As described above, the thioindigo dye used in the present invention has high solubility in the host liquid crystal and large order parameters, so it can be used as a pleochroic dye that can be used in guest-host type liquid crystal displays with good contrast. Very useful.

[Brief explanation of the drawing]

The figure is a graph showing the absorption spectrum of a homogeneous alignment cell filled with a liquid crystal composition containing a thioindigo dye in an example of the present invention. Name of agent Patent attorney Toshio Nakao and one other person Liquid crystal composition (727F+) Procedural amendment August 7, 1985 q a 1 Indication of case 1985 Patent application No. 58675 2 Name of invention Liquid crystal composition 3 Relationship with the case of the person making the amendment Patent application Colonel Address 1006 Oaza Kadoma, Kadoma City, Osaka Name (582) Representative of Matsushita Electric Industrial Co., Ltd.
Toshihiko Yamashita 4 Agent 571 Address 6, Matsushita Electric Industrial Co., Ltd., 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Contents of amendment (1) Change the scope of claims column of the specification to t. To do. (,?) Insert the following sentence at the end of page 17, line 19 of the statement. "In order to improve the solubility in the host liquid crystal, it is effective to introduce a branched alkyl group, especially a tertiary alkyl group." 2. Claims (1) Guest dyes containing the following general formula (formula where R2 represents a branched alkyl group, R2' represents hydrogen, an aryl group, an aryloxy group, or a branched alkyl group, R1+ R3t R4y R1' l R3
' + R4' is hydrogen, halogen, alkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio-8o3R6, -N=N-R6, -CH=CH-R
5 (R5 represents an alkyl group or an aryl group, R6 represents hydrogen or an alkyl group), or a combination of two or more thereof. ) A liquid crystal composition comprising at least one thioindigo dye represented by: 2) The liquid crystal composition according to claim 1, wherein R2 in the general formula is a tertiary alkyl group.

Claims (2)

[Claims] (1) As a guest dye, there are the following general formulas ▲ mathematical formulas, chemical formulas, tables, etc. represents R_1, R_3, R_4, R_1', R
_3', R_4' are hydrogen, halogen, alkyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, nitro group, amino group, ▲numerical formula, chemical formula, table, etc.▼, -NHCOR_5, -COOR_5, -
COR_5, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -S
O_2R_5, -SO_3R_5, -N=N-R_5,
-CH=CH-R_5 (R_5 represents an alkyl group or an aryl group, R_6 represents hydrogen or an alkyl group)
or a combination of two or more thereof. ) A liquid crystal composition comprising at least one type of thioindigo dye represented by: (2) In the general formula of the thioindigo dye, R_2' is 4-
The liquid crystal composition according to claim 1, wherein the liquid crystal composition is a substituted phenyl group.