JPH075519B2 - Liquid crystalline compound and composition thereof, optical switching element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound and a liquid crystal composition, particularly to provide a liquid crystal material having ferroelectricity, and further to a liquid crystal display device. The present invention provides a material having the following availability.

[Conventional technology]

Liquid crystal display devices are widely used as various display devices because they have excellent characteristics such as low voltage operation, low power consumption, thin display capability, and light receiving type that do not cause eye strain. .

At present, as a liquid crystal display system, a nematic liquid crystal called Twisted Nematic type (TN type) is used most as a material. However, this TN type liquid crystal has a drawback that its response speed is slower than that of a light emitting diode, an electroluminescence, etc., and thus there is a limitation in application. However, as described above, a new display method has been developed which utilizes the characteristics of light receiving type and low power consumption and has a high-speed response.

In recent years, ferroelectric liquid crystals have been attracting attention as one that meets this purpose. The display element that uses this ferroelectric liquid crystal has a high-speed response of about several hundred times compared to the conventional TN type liquid crystal, and since it also has bistability, it can be used for moving images such as television It can be expected to be applied to display devices in various fields such as high-speed optical shutters.

Ferroelectric liquid crystals were found by RB Meyer et al. (Jiurnal de Huisique, 36 (1975),
L-69), it is possible to make a display element with a memory effect with a response speed of the order of microseconds.
Since it was announced by A. Clark et al. (Applied Physics Letters, 36 (1980) 899), it has become a very noticeable entity.

Ferroelectric liquid crystal is a kind of smectic liquid crystal, and belongs to the chiral smectic phase among them, and among chiral smectic phases, chiral smectic C phase, chiral smectic H phase, etc. are currently used. Have the possibility of Among them, the chiral smectic C phase (hereinafter referred to as SC
^* Abbreviated as phase) is desirable from the viewpoint of handling.

A liquid crystal compound exhibiting an SC ^* phase has been announced so far, and as a representative one, (s) -2-methylbutyl-p, which is known as the first synthesized ferroelectric liquid crystal, is known.
-Decyloxybenzylidene aminocinnamate (DOBA
MBC) is a series of Schiff chlorine-based liquid crystals, but Schiff bases are not practical because they are unstable to moisture, light and the like.

(Pey Keller et al., Giulnar de Fijique, 37 C3
-129; K. Yoshino et al., Japanese Journal of Applied Physics, 23 L175 (1984); JP Sho 59
-98051) The characteristic of the liquid crystal compound having the SC ^* phase is the smectic C
It is necessary that an asymmetric carbon atom is present in a part of the molecular structure of the liquid crystal compound having a phase (not racemized).
In order to introduce this asymmetric carbon atom into a compound, a method of incorporating easily available optically active 2-methylbutanol into the compound by a method such as an ester bond is a general method. It may be possible to use it.

[Problems to be solved by the invention]

The present inventors intend to provide a liquid crystal compound having excellent stability against moisture, light and the like and a liquid crystal composition containing the liquid crystal compound.

[Means for solving problems]

The first point of the present invention is to provide a liquid crystal compound represented by the following general formula I.

(In the formula, R is an alkyl group having 20 or less carbon atoms,
m and n represent 1 or 2. And, the second point is to provide a liquid crystal composition comprising at least two kinds of liquid crystal components and containing a compound represented by the general formula I.

When the liquid crystal has a layered structure and its constituent molecules are tilted with respect to the layer normal, and the constituent molecules have asymmetric carbon atoms (not racemized), the layers are twisted little by little. , Will show a helical structure. The liquid crystal exhibits ferroelectricity when the spontaneous polarization is in the direction perpendicular to the helical axis. From such a viewpoint, the present inventors have found that the SC is stable at light and moisture and at a temperature higher than the melting point.
^{* A} compound capable of obtaining a phase was earnestly studied, and a compound represented by the general formula I was obtained. SC above melting point
^* Obtaining a phase means SC only under supercooling (below melting point)
^* Considering that the compound that obtains the phase is greatly restricted in terms of practicality, this is a great advantage.

The compound represented by the general formula I of the present invention, of course, exhibits ferroelectricity by itself, but when mixed with another ferroelectric liquid crystal, SC ^*
It is possible to use it so as to widen the temperature range of the phase, and in practice, a method of blending it with various ferroelectric liquid crystals and using it as a liquid crystal composition is generally used. These ferroelectric liquid crystal compositions can be used as a display device utilizing the optical switching phenomenon of ferroelectric liquid crystals.

Next, a method for producing the compound represented by formula I will be described. Among the compounds represented by the general formula I, the following general formula II The compounds represented by the formulas (the meanings of the symbols in the formula are the same as those in the general formula I) include an ester obtained by esterification of 4'-hydroxybiphenyl-4-acetic acid and an optically active alcohol, and 4-alkoxybenzoic acid. Can be obtained by an esterification reaction by reacting the acid halide with an acid halide. Other production methods can also be obtained by an esterification reaction product of an acid halide of 4-alkoxybenzoic acid and 4'-hydroxybiphenyl-4-acetic acid and an optically active alcohol.

Also, the following general formula III (The meanings of the symbols in the formula are the same as those in the general formula I) The compound represented by the formula is 4'-alkoxybiphenyl-4
It can be obtained by a condensation reaction between an acid halide of a carboxylic acid and an ester of an optically active alcohol of 4-hydroxyphenylacetic acid.

Also in this case, similarly to the above-mentioned case, it can be obtained also by the esterification reaction of the acid halide of 4'-alkoxybiphenyl-4-carboxylic acid and the optically active alcohol after the esterification of 4-hydroxyphenylacetic acid. it can.

Now, the obtained liquid crystal compound or the composition using the same has a uniform thickness (1 μm) between two transparent electrode plates.
It can be used as a liquid crystal cell by forming a thin film having a thickness of up to 20 μm). In the display cell, the liquid crystal molecules are
It is necessary to be a so-called monodomain, which is so-called homogeneous and has a uniform orientation parallel to the electrode plate. Therefore, the cell surface is subjected to orientation treatment such as rubbing or vapor deposition, or an electric field or magnetic field is applied. It is possible to obtain a uniformly aligned monodomain cell by applying a voltage, or by providing a temperature gradient, or by a method of gradually cooling from an isotropic liquid phase to a liquid crystal phase in the state where these means are used in combination and aligning. .

At this time, in order to exhibit a good orientation, the liquid crystal material is I (isotropic liquid) phase-N when cooled from a high temperature state.
^* (Chiral nematic) or Ch (cholesteric) phase-
It shows a phase sequence of SA (smectic A) phase-SC ^* (chiral smectic C) phase, and it is said that it is necessary to increase the helical pitch in N ^* or Ch phase and SC ^* phase.

JP-A-60-32748 describes the following compounds having a structure similar to the compound of the general formula (I) of the present invention.

Phase transition temperature (℃) Cr80 SC ^* 121 SA165 Ch171 I Phase transition temperature (℃) Cr64 SC ^* 139 SA189 I Phase transition temperature (℃) Cr55 SC ^* 126 SA171 I These compounds have very narrow temperature range of Ch phase, or do not show N ^* or Ch phase, and have a wide range of SA phase. When such a compound is added to the liquid crystal composition, the temperature range of the N ^* phase of the obtained liquid crystal composition is narrowed,
It can be understood that there is a tendency to expand the SA phase.

In contrast, the compound of the general formula (I) of the present invention has a wider temperature range of the Ch phase and a higher temperature range of the SA phase when compared with the compounds having the same corresponding terminal groups described in the above publication. Is clearly narrowed. Therefore, when the compound of the general formula (I) of the present invention is added to the liquid crystal composition, the SA phase of the obtained liquid crystal composition can be narrowed and the N ^* or Ch phase can be expanded. It can be understood that it is suitable for preparing a liquid crystal composition having a phase series and exhibiting a good alignment property.

〔The invention's effect〕

The present invention is as described above, but the compound represented by the general formula I of the present invention is, compared with DOBAMBC conventionally known as a ferroelectric liquid crystal compound, as shown in Examples described later, It can be easily produced industrially, is colorless in itself, has superior chemical stability to light, water, etc. due to its molecular structure, and exhibits a ferroelectric liquid crystal phase above its melting point. . Moreover, in the composition of the present invention, the liquid crystal temperature range is expanded or decreased as compared with a single compound, as in a general liquid crystal composition. Further, the ferroelectric compound and the liquid crystal composition of the present invention have a response speed of 1000% or less of the nematic liquid crystal like the conventional ferroelectric liquid crystal.
It is about twice as large.

Therefore, it is extremely promising as a light switching element for display.

〔Example〕

The present invention will be specifically described below with reference to examples, but of course the gist and scope of the present invention are not limited to these examples. In the following description, the value of the phase transition temperature is slightly different depending on the measuring method and the purity.

Example 1 Synthesis (general formula corresponding to R = n-C ₈ H ₁₇ in III) p-hydroxyphenyl acetic acid 136 g, (s)-2-methyl butanol 100 g, 400 ml toluene, Dean-Stark type paratoluenesulfonic acid 1.0g The reaction container equipped with a reflux condenser was heated under reflux for 15 hours to separate the generated water. About 16 g of water was separated.

The reaction solution was cooled, further diluted with 200 ml of toluene, washed with sodium bicarbonate water, further washed with water, and then toluene was distilled off under reduced pressure to obtain 210 g of a crude product. With this bigle tube
And distilled to obtain 175 g of p-hydroxyphenylacetic acid (s) -2-methylbutyl ester as an intermediate.
Boiling point 180 ℃ / 5mmHg.

Next, 20 g of thionyl chloride was added to 7.50 g of 4'-n-octyloxybiphenyl-4-carboxylic acid, and the mixture was heated under reflux for 2 hours, and then excess thionyl chloride was distilled off under reduced pressure to remove 4'-n-octyloxybiphenyl. An enyl-4-carboxylic acid chloride was obtained. Here, 4.8 g of p-hydroxyphenylacetic acid (s) -2-methylbutyl ester prepared above was dried with pyridine.
The solution dissolved in 30 g was added to the above carboxylic acid chloride and stirred overnight at room temperature. The next day, the reaction mixture was diluted with ethyl acetate 30
The solution was added to 0 ml and washed several times with diluted hydrochloric acid to remove the pyridine content, and then repeatedly washed with water to remove the hydrochloric acid content. The ethyl acetate layer was dehydrated and then concentrated under reduced pressure to obtain 11.0 g of a crude product. Recrystallization from ethanol was repeated 3 times to obtain 9.00 g of the desired product. Yield 74.0% The structure of the obtained target substance was confirmed by a nuclear magnetic resonance spectrum, an infrared absorption spectrum and a mass spectrum.

Nuclear magnetic resonance spectrum (CDCl ₃₎ δ8.30~6.85 (multiplet, 12H, aromatic), δ4.10~3.83 _{(multiplet, 4H, -OCH 2 -, -} COOCH 2 -), δ 2.10 to 1.10 (multiple lines, 15H), δ 0.75 to 1.0 (multiple lines,
9H, methyl group) Infrared absorption spectrum (KBr) (main absorption) (cm ^-1 ) 300
0 to 2850, 1733, 1520, 1290, 1165, 1080 Mass spectrum 530 (M ⁺ ) Example 2 n-octyloxybiphenyl-4-in Example 1
The following compounds were used instead of the carboxylic acid.
(1) n-decanoxybiphenyl-4-carboxylic acid, (2) n
-Tetradecanoxybiphenyl-4-carboxylic acid. Also the reaction was carried out and worked up as in Example 1 In these cases, the corresponding target compound (formula II in the _{R = n-C 10 H 21} , R = n-
Corresponds to C ₁₄ H ₂₉ . Was obtained in the same yield as in Example 1.

The nuclear magnetic resonance spectra of these compounds showed a pattern quite similar to that of the compound of Example 1, and only the difference in methylene chain length was recognized as a difference. The infrared absorption spectrum also showed the same pattern except that the absorption intensities were different, and the mass spectrum gave the respective parent peaks.

Table 1 shows the phase transition temperatures of the compounds of Examples 1 and 2.

In Table 1, I is an isotropic liquid phase, S _A is a smectic A phase, and SC
^{* Indicates} a chiral smectic C phase, and C indicates a crystalline phase.

In addition, ● indicates that the phase exists. The number on the right of ● represents the transition temperature from that phase to the higher temperature phase. The transition temperature is ° C.

Example 3 Manufacturing (formula corresponding to R = n-C ₈ H ₁₇ in II) 4'-hydroxy Biff enyl-4-acetate 22.8 g, (s)
15 g of 2-methylbutanol, 100 ml of toluene, and 0.2 g of paratoluenesulfonic acid were heated under reflux for 15 hours in a reaction vessel equipped with a Dean-Stark type reflux device, and the generated water was separated. After the reaction, cool the reaction mixture and add 100 ml of toluene,
It was washed with sodium bicarbonate water, and the washing with water was repeated. The toluene layer was distilled off under reduced pressure to obtain 31.0 g of a crude product. This product was purified by silica gel column chromatography with ethyl acetate-hexane solvent to obtain 4'as an intermediate.
24.5 g of -hydroxybiphenyl-4-acetic acid (s) -2-methylbutyl ester was obtained. Next, a solution prepared by dissolving 3.0 g of 4'-hydroxybiphenyl-4-acetic acid (s) -2-methylbutyl ester in 2.7 g of 4-n-octyloxybenzoic acid chloride was dissolved in 10 g of dry pyridine. The mixture was stirred overnight at room temperature. Next day, add 150 ml of ethyl acetate to the reaction mixture.
Was added and washed several times with dilute hydrochloric acid to remove the pyridine content, and then repeatedly washed with water to remove the hydrochloric acid content. The ethyl acetate layer was dehydrated and then concentrated under reduced pressure to obtain 5.3 g of a crude product. The product was purified by silica gel column chromatography (ethyl acetate-hexane system) and then recrystallized from ethanol to obtain 4.0 g of the desired product. yield
76% The structure of the obtained target substance was confirmed by a nuclear magnetic resonance spectrum, an infrared absorption spectrum and a mass spectrum.

Nuclear magnetic resonance spectrum (CDCl ₃₎ δ8.3~6.85 (multiplet, 12H, aromatic protons), δ4.15~3.85 _{(multiplet, 4H, -OCH 2 -, -} COOCH 2 -), δ2.10 to 1.10 (multiple line, 15H), δ1.0 to 0.75 (multiple line, 9H, methyl group) Infrared absorption spectrum (KBr) (cm ^-1 ) (main absorption position) 3000 to 2900, 1730, 1610 , 1505, 1285, 1170, 108
0, mass spectrum 530 (M ⁺ ) Example 4 Reaction and post-treatment were performed in the same manner as in Example 3 except that the following compounds were used separately in place of 4-n-octyloxybenzoic acid chloride in Example 3. And so on. (1)
4-n-decanooxybenzoic acid chloride, (2) 4-n-
Dodecanoxybenzoic acid chloride, (3) 4-n-tetradecanooxybenzoic acid chloride These products have the following general formula II:
a _{n-C 10 H 21, R} = n-C 12 H 25, R = n-C 14 H 29 is a corresponding compound. Then, the target product was obtained with a yield substantially similar to that in Example 3. The nuclear magnetic resonance spectra of these compounds showed a pattern quite similar to that of the compound of Example 3, and only the difference in methylene chain length was recognized as a difference. The infrared absorption spectrum also showed the same pattern with only different absorption intensities, and the mass spectrum gave each parent peak.

Table 2 shows the phase transition temperatures of the compounds of Examples 3 and 4.

In Table 2, I is an isotropic liquid phase, Ch is a cholesteric phase, Sc
^{* Indicates} a chiral smectic C phase, and C indicates a crystalline phase. In addition, ● indicates that the phase exists, and ●
The number to the right of indicates the transition temperature from that phase to the higher temperature phase. The transition temperature is ° C.

The compound of Example 5 Example 1 (compound of Table 1 R = C ₈ H ₁₇₎ and known compound p-n-octyl oxybenzoate 4 '- (2
4.2-Methylbutoxycarbonyl) -4-biphenylyl ester (see JP-A-60-32748, phase transition from crystal to Sc ^* phase at 80 ° C and at 121 ° C from Sc ^* phase to smectic A phase) 3.2 parts by weight of the mixture is from the crystals at 55 ° C.
Sc ^* smectic from Sc ^* phase by phase to phase transfer to 103 ℃ A
Phase transferred to the phase. Thus, the liquid crystalline compound of the present invention is
By blending with a known ferroelectric liquid crystal compound, the temperature range exhibiting the ferroelectricity could be made wider than that when used alone.

Example 6 The liquid crystalline compound obtained in Example 1 was filled in an isotropic liquid state between two glass transparent electrodes with a spacer having a thickness of 2 μm, and after slowly cooling, the Sc ^* phase at 90 ° C. Got 5V to this,
When a rectangular wave of 0.1 Hz was applied, a clear switching operation was confirmed, and when a 15 V, 20 KHz rectangular wave was applied and the optical switching operation was detected by a photomultiplier, a clear switching operation was observed. As a result, a liquid crystal display element having a high response speed was obtained.

Example 7 When the glass transparent electrode was filled with the liquid crystal composition obtained in Example 5 as in Example 6 and the same rectangular wave as in Example 6 was applied, a clear switching operation could be observed. It was

Front Page Continuation (72) Inventor Masashi Osawa 5-12-23 Akatsuka, Itabashi-ku, Tokyo (72) Inventor Yoshiyoshi Arai 5-8-6-402 Higashi, Hasuda, Saitama Prefecture (72) In fact, Mio Kurokawa, Omiya, Saitama Prefecture 2-39 Yoshino-cho

Claims (5)

[Claims] 1. A general formula (I) (In the formula, R is an alkyl group having 20 or less carbon atoms,
m and n represent 1 or 2. ) An optically active liquid crystalline compound represented by: 2. A compound represented by the following general formula (II) (The meaning of the symbols in the formula is the same as in the general formula (I)) The liquid crystal compound according to claim 1. 3. A compound represented by the following general formula (III): (The meaning of the symbols in the formula is the same as in the general formula (I)) The liquid crystal compound according to claim 1. 4. A liquid crystal composition comprising at least two kinds of liquid crystal components, which is represented by the general formula (I): (In the formula, R is an alkyl group having 20 or less carbon atoms,
m and n represent 1 or 2. ) A liquid crystal composition containing an optically active compound represented by: 5. General formula (I) (In the formula, R is an alkyl group having 20 or less carbon atoms,
m and n represent 1 or 2. ) An optical switching element having at least one kind of an optically active liquid crystalline compound represented by