JP2632683B2 - Liquid crystalline compounds with extremely large spontaneous polarization - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel liquid crystal compound useful as an electro-optical display material, and more particularly to a liquid crystal material having ferroelectricity. Compared to the liquid crystal material of
In particular, it is an object of the present invention to provide a liquid crystal material which has excellent responsiveness and memory properties and can be used for a liquid crystal display device.

(Prior art)

The liquid crystal display element has low voltage operation, low power consumption,
It has many excellent features such as thin display, light receiving type, so it can be used even in bright places and eyes are not tired.
Widely used. At present, the display method is
The so-called Twisted Nematic (TN) type is the most common. This TN-type display system uses a nematic liquid crystal, but in this case, while having all the above-mentioned excellent features, its response is very slow as compared with other light-emitting display systems such as a CRT. There was a disadvantage. When the applied electric field was turned off, the display was not restored (memory effect) because it returned to the original state. For these reasons, it cannot be said that the method is suitable for application to a moving image plane such as an optical shutter, a printer head, and a television, which require a high-speed response and time-sharing operation, due to various restrictions.

In addition to the TN type, R & D has been conducted on guest-host (GH) type, birefringence control (ECB) type, phase transition (PC) type, and thermal effect type liquid crystal display devices. However, the responsiveness was not particularly improved compared to the TN type. On the other hand, a so-called dual frequency drive type has been developed as a liquid crystal display system capable of obtaining a high-speed response, and the responsiveness has been considerably improved, but it cannot be said that it is still satisfactory. In addition, there is a disadvantage that the operation circuit becomes too complicated. For this reason, development of a new liquid crystal display system with even better responsiveness has been attempted.

To meet this goal, ferroelectric liquid crystals have recently been announced. (R. Mayer et al; J. Physique 36 L69 (197
5)) It has been pointed out that a display device using this ferroelectric liquid crystal has a high-speed response of 100 to 1000 times as compared with a conventional liquid crystal display and a memory effect brought about by bistability (NAClark, STLagerwall). : Appl Phys.Lett; 3
6 899 (1980)), and can be expected to be applied to moving images such as televisions, high-speed optical shutter printer heads, and other display devices such as computer terminals.

The ferroelectric liquid crystal belongs to a tilt type chiral smectic phase as a liquid crystal phase. Among them, a practically desirable one is a chiral smectic C (hereinafter abbreviated as SC ^* ) phase having the lowest viscosity. It is called.

Liquid crystal compounds exhibiting the SC ^* phase have been studied so far, and many compounds have already been synthesized. However, these SC ^* compounds are required to be used alone as a ferroelectric liquid crystal display device under the following conditions: (a) exhibit ferroelectricity over a wide temperature range including room temperature; (b) exhibit a long spiral pitch. (C) having an appropriate tilt angle, (d) having a large spontaneous polarization, (e) having a low viscosity, and (f) having a high speed as a result of the above (d) and (e). There is no known material which satisfies responsiveness, and it is necessary to use it as an SC ^* liquid crystal composition.

There are two methods for obtaining the SC ^* liquid crystal composition, one is a method of mixing a plurality of compounds exhibiting the SC ^* phase, and the other is a non-chiral smectic C (hereinafter abbreviated as SC). In this method, a chiral liquid crystal compound or composition is added to a liquid crystal compound or composition exhibiting a phase.

In the former method, it is easy to obtain a wide temperature range and strong spontaneous polarization. However, the compound having the SC ^* phase has an asymmetric carbon in the molecule, particularly in the side chain, and has a branched group (mainly a methyl group). The closer the branched group is to a large permanent dipole such as a central portion (core) of a liquid crystal molecule and a carbonyl group, the greater the spontaneous polarization of the liquid crystal, but the higher the viscosity of the liquid crystal tends to be. Therefore, even if the spontaneous polarization of the liquid crystal is increased, the viscosity increases particularly in a low temperature range, and it is not easy to obtain a high-speed response of 200 μsec or less around room temperature.

In the latter method, although depending on the amount of the chiral liquid crystal compound to be added, spontaneous polarization does not exist in the base SC liquid crystal, so that it is difficult to obtain a composition having a very large spontaneous polarization as a composition. However, the liquid crystal compound in the parent SC composition does not require the presence of a branching group, and therefore has a very low viscosity. Therefore, it is easy to obtain a high-speed response by adding a chiral liquid crystal compound and giving spontaneous polarization as SC ^* liquid crystal.
At present, the latter method is becoming mainstream.

As a chiral liquid crystalline compound to be added to the SC liquid crystal composition, it is not necessary to show the SC ^* phase alone, and it is not always necessary to show the liquid crystal phase, but in order not to narrow the temperature range of the composition. Preferably represents a liquid crystal phase, particularly a chiral smectic (hereinafter abbreviated as S ^* ) phase. In order to increase the spontaneous polarization of the composition as much as possible, a molecular structure capable of exhibiting a large spontaneous polarization, that is, the asymmetric carbon of the chiral group is as close as possible to the central nucleus (core) and the permanent structure such as carbonyl group Although it is necessary to be as close as possible to the dipole, in such a structure, the twist pitch is too short in the SC ^* phase where the spiral appears due to the large torsional force on the liquid crystal phase, which adversely affects the orientation. And it is difficult to increase the cell thickness. Therefore, it was necessary to limit the amount of addition or to adjust the helical pitch of the SC ^* liquid crystal composition by adding a chiral compound having the opposite direction of twist. In this case, if the direction of the spontaneous polarization of the chiral compound having the opposite twist direction is also opposite, the spontaneous polarization of the composition is canceled out and becomes small, and there are many troublesome adjustments to the helical pitch. Therefore, a chiral liquid crystal compound which has a large spontaneous polarization, a large helical pitch, and exhibits the SC ^* phase itself as much as possible has been desired.

[Problems to be solved by the invention]

The problem to be solved by the present invention is that while having a large spontaneous polarization, the helical pitch is relatively large, and the SC ^* phase exhibits a S ^* phase itself and is mixed over a wide temperature range including room temperature by mixing. And to provide a novel and chiral liquid crystal compound capable of high-speed response.

[Means for solving the problem]

The present invention solves the above problems by using a general formula And a compound represented by the formula:

In the above formula, R ₁ represents an alkyl group having 2 to 16 carbon atoms, more preferably an alkyl group having 2 to 6 carbon atoms, and the raw chiral alcohol The most preferable in terms of availability, price, etc. is n-
It is a hexyl group.

X is a central linking group, Or a single bond.

m and n represent an integer of 1 or 2 and may be equal to or different from each other, but when m = n = 1, the general formula (I)
(Hereinafter abbreviated as compound (I)) is a bicyclic compound, and has a large decrease in liquid crystallinity.
When m = n = 2, the compound (I) becomes a four-ring compound, the viscosity increases, and the spontaneous polarization decreases. Therefore, the compound (I) is more preferably a three-ring compound in which m + n = 3.

When X is a single bond, at least one of m and n represents 2.

R ₂ represents an alkyl group having 1 to 10 carbon atoms, but has 1 carbon atom, that is, a methyl group. When the number of carbon atoms is too large, the viscosity of the compound (I) increases, and a linear alkyl group having 2 to 8 carbon atoms is more preferable.

The carbon atoms each independently represent an asymmetric carbon atom having the absolute configuration of (R) or (S). As described later, more preferred are (S) and (R) Or different combinations such as (R) and (S).

The liquid crystal composition in the present invention is one or more compounds (I) and a liquid crystal compound or a liquid crystal composition other than the compound (I), particularly a liquid crystal compound or a liquid crystal composition other than the compound (I). Has no branching in the side chain as the main component,
What consists of a compound which shows SC phase is preferable.

The compound of the formula (I) according to the present invention can be produced, for example, according to the following production method.

[R ₁ , R ₂ , m, n, in the above formulas (II) to (IV)] R ₁ , R ₂ , m, n, in the formula (I) Each has the same meaning. A lactic acid derivative represented by the formula (II) is reacted with a chlorinating agent such as thionyl chloride to produce an acid chloride represented by the formula (III). Next, after reacting the acid chloride represented by the formula (III) with the optically active phenol represented by the formula (IV) in the presence of a basic substance such as pyridine, ethyl acetate is added as an extraction solvent, and 10% Wash sequentially with aqueous hydrochloric acid, saturated aqueous sodium carbonate, water, and saturated saline. After the extract is dried, the solvent is distilled off from the extract, the crude product obtained is separated and purified by silica gel chromatography, and further recrystallized from ethanol to produce the compound of formula (V) according to the present invention. be able to.

Further, the lactic acid derivative of the formula (II) and the optically active phenol of the formula (IV) are directly esterified in the presence of a dehydrating agent such as dicyclohexylcarbodiimide to produce the compound of the formula (V) according to the present invention. Can also.

(2) When X is a single bond [R ₁ , R ₂ , m, n, in the above formulas (VI) to (VII)] R ₁ , R ₂ , m, n, in the formula (I) Has the same meaning as The 2-alkoxypropionate chloride represented by the formula (VI) is reacted with the optically active phenol represented by the formula (VII) in the same manner as in the case of (1), purified, and purified according to the formula (VIII) according to the present invention. ) Can be produced.

The lactic acid derivative represented by the formula (II) can be produced according to the following production method.

As disclosed by the present inventors in Japanese Patent Application No. 61-140157, ethyl lactate was converted to silver oxide and alkyl iodide (R ₂ -I).
To give ethyl 2-alkoxypropionate, and hydrolyze the resulting 2-alkoxypropionic acid with a chlorinating agent such as thionyl chloride to give 2-alkoxypropionic acid.
Produce an alkoxypropionate chloride. This acid chloride and 4'-hydroxybiphenyl-4-carboxylic acid (n
= 2) or 4-hydroxybenzoic acid (n =
1) in the presence of pyridine to give a compound of formula (I
The lactic acid derivative of I) can be produced.

The optically active phenol represented by the formula (IV) can be produced according to the following production method.

P-Toluenesulfonic acid ester of 4-4'-biphenol (when m = 2) or hydroquinone (when m = 1) and an optically active 2-alkanol Is reacted under basic conditions and then treated with an acid to produce the optically active phenol of the formula (IV).

The optically active phenol represented by the formula (VII) can also be produced according to the above production method.

Table 1 shows the transition temperature, the direction of the induced helix, and the direction and the value of the spontaneous polarization of typical compounds of the formula (I) thus produced.

The liquid crystal phase and the phase transition temperature were measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (DSC), but the transition temperature slightly fluctuated depending on the purity of the sample or the measurement conditions. Is what you do.

In Table 1, C represents a crystal phase, SC ^* represents a chiral smectic C phase, SA represents a smectic A phase, and I represents an isotropic liquid phase. Indicates that the phase exists;
Indicates that the phase does not exist (or cannot be confirmed), the number to the right of indicates the transition temperature from the phase to the higher temperature phase, and the parentheses indicate that the phase is monotropic. Express. Further, the “direction of helix” refers to the direction of helix induced when added to a liquid crystal exhibiting a nematic (hereinafter abbreviated as N) phase, and “magnitude of spontaneous polarization”
Represents a value at a temperature 10 ° lower than the upper limit temperature of the SC ^* phase.

The greatest structural feature of the compound (I) of the present invention is that it has two asymmetric carbon atoms in the molecule,
It exists on both sides of the core.

On the other hand, the 2-alkoxypropanoyloxy group is derived from lactic acid and its ester, and its steric configuration is (S) or (R), and the lactic acid derivative of the formula (III) or the compound (I) It is thought that it does not change even if it leads.

The other 1-methylalkoxy group is an optically active alcohol And its configuration is still (S)
Or (R). However, as shown in the synthesis method, this optically active alcohol is first converted into p-toluenesulfonic acid ester, and then hydroquinone or 4,4
The chiral group is introduced into the optically active phenol of the formula (IV) by reacting with 4'-biphenol. In this first step (tosylation), although the configuration is considered to be retained, The reaction in the second step is a reaction in the optically active center, and generally, the reaction between the alcoholate and the tosylate under basic conditions is such that the configuration is reversed. Therefore, in the compound (I) of the present invention, the (R) -1-methylalkoxy group is converted from the (S) -form 2-alkanol, and the (S) -1-methylalkoxy group is converted from the (R) -form 2-alkanol. It can be considered that a compound having an alkoxy group is obtained.

The most significant feature of the compound (I) of the present invention in physical properties is that it has a very large spontaneous polarization.
Already, among the liquid crystal compounds having a 1-methylalkoxy group, those having a large spontaneous polarization are known, for example, For the compound shown by, a value of 89 nC / cm ² was reported. In addition, according to a study by the present inventors, it has been confirmed that a compound having a 2-alkoxy-propanoyloxy group derived from lactic acid shows a large spontaneous polarization of 100 nC / cm ² or more.

However, a spontaneous polarization of this value is not always sufficient, and a compound having a larger spontaneous polarization is required to obtain a faster response. In addition, a compound having a large spontaneous polarization, such as a 2-alkoxypropanoyloxy group, itself has a strong torsional force, and therefore has a chiral nematic (hereinafter referred to as N ^*).
Is abbreviated. ) Spiral pitch in the phase and S ^* phase is very small, so when adding 10 to 30% as a composition, add a considerable amount of the reverse of the twist direction to adjust the helical pitch to be large. In that case, there are many troublesome points such as making the directions of the spontaneous polarization uniform and not canceling each other.

The present inventors have proposed a 1-methylalkoxy group When the direction of spontaneous polarization derived from is the direction of spontaneous polarization of the well-known ferroelectric liquid crystal (S) -2-methylbutyl p-decyloxybenzylideneaminocinnamate (DOBAMBC), In the body, it is an (R) body, and the direction of the twist of the helix is right-handed in the (S) body,
(R) body is left-handed, and 2-alkoxypropanoyloxy group The direction of spontaneous polarization derived from (S) is (R)
Focusing on the fact that the helix direction is right-handed in the (S) body and left-handed in the (R) body, In compounds containing both Depending on the combination of configuration Is (S) Is (R) or vice versa Is (R) Is (S), the torsional force is canceled out to be small, and the spontaneous polarization is added to obtain a very large one, and the present invention has been achieved.

Since this compound (I) does not necessarily show an SC ^* phase enantiotropically as a single compound, it is used as a pyrimidine-phenylbenzoate-based base liquid crystal showing an SC phase.
The spontaneous polarization of the composition was measured by adding 10 to 50%, and the spontaneous polarization of the composition was extrapolated from the value to obtain the spontaneous polarization alone. For example, 4-((S) -2-propoxypropanoyloxy) benzo The acid 4 '-((R) -1-methylheptyloxy) biphenyl-4-yl (the compound of Example 1)
350 nC / cm ² at -T = 5 ° (TC is the upper limit temperature of SC ^* ), TC-T
= 10 °, a very large value of 420 nC / cm ² and TC-T = 20 °, 490 nC / cm ² . This is the largest compound known so far. Moreover, the value is almost twice as large as the sum of the spontaneous polarizations derived from both chiral groups, and the spontaneous polarization derived from the chiral groups at both ends of the same liquid crystal molecule is enhanced with an effect that can be said to be synergistic. This is the first example that shows a match. This is thought to be due to the fact that the presence of a plurality of branched methyl groups further inhibits the rotation of the molecular long axis.

on the other hand, In 4-((S) -2-propoxypropanoyloxy) benzoic acid 4 '-((S) -1-methylheptyloxy) biphenyl-4-yl (compound of Example 2), both of which are (S), When measured under the same conditions, the value of spontaneous polarization is only about 1/5 of 80 nC / cm ² at TC-T = 10 °, and when the directions of both spontaneous polarizations are reversed, they are totally offset. You can see that it is.

Table 1 shows the direction of the helix, and the direction and magnitude of the spontaneous polarization along with the phase transition temperature of each compound. As can be seen from the table, the helix direction is 2-alkoxypropanoyloxy. Asymmetric carbon of the group Is an asymmetric carbon atom of a 1-methylalkoxy group Is always constant irrespective of the absolute arrangement.

From this, it is considered that the twisting force induced by the 2-alkoxypropanoyloxy group is stronger than that by the 1-methylalkoxy group. 3-fluoro-4-decyloxyphenyl 4 '-((S) -2-propyloxypropanoyloxy) which is a compound having only a 2-alkoxypropanoyloxy group as a chiral group in a liquid crystal composition exhibiting an N phase The helical pitch of the N ^* phase was measured by mixing biphenyl-4-carboxylate, and the helical pitch was measured as an extrapolated value to be 0.43 μm. On the other hand, when the helical pitch of the compound of Example 3 was measured in the same manner, the helical pitch was as large as 0.63 μm, and it was confirmed that the torsional forces of the two chiral groups were cancelled.

On the other hand, from Table 1, the direction of the spontaneous polarization of the compound (I) is determined by the asymmetric carbon atom of the 2-alkoxypropanoyloxy group. It can be seen that the absolute configuration is determined.

In general, introducing a branching group into the side chain of a liquid crystal molecule lowers the liquid crystallinity and lowers its phase transition temperature, but in compound (I), a branched methyl group is present in both side chains. Therefore, its phase transition temperature is considerably lower than that having a similar skeletal structure, and it is only from m + n = 3 rings that exhibit liquid crystallinity that it has a liquid crystal phase alone. I will not show it.

The compound (I) is effectively used as an SC liquid crystal compound having no branched chains or as an SC ^* liquid crystal when mixed with a composition. In this case, when the chiral compound has no chiral smecticity, Tends to narrow the temperature range of the SC ^* phase in the composition. Compound (I) has a relatively low phase transition temperature, but shows an S ^* phase, and does not substantially narrow the temperature range during mixing.

The SC ^* liquid crystal composition obtained by adding about 10 to 30% of the compound (I) to the SC liquid crystal composition has a sufficiently large helical pitch when the twist is canceled out. When the need arises, the direction of the twist is opposite to that of the compound (I), and the direction of the spontaneous polarization is the same, or even if the direction is reversed, a small compound of several nC / cm ² or less is used. If there is, it can be used for adjusting the helical pitch. This amount is small enough when the compound (I) is twisted off as in the compound of Example 1, and conversely, a considerable amount is required when the twist is countable as in the compound of Example 2. .

The compound (I) may be used alone or in combination with a plurality of compounds.
Examples of the SC liquid crystal compound or composition include a phenylbenzoate-based compound (A) and a pyrimidine-based compound (B) as shown below in a two-ring type.
In order to extend the temperature range of the SC phase to a high temperature range, tricyclic compounds (C) and (D) can be used.

A: (R ₃ and R ₄ represent any of a linear alkyl group, an alkoxy group, an alkylcarbonyloxy group, an alkoxycarbonyl group, and an alkoxycarbonyloxy group, and may be the same or different.) (R ₃ and R ₄ are the same as described above.) C: (R ₃ and R ₄ are the same as above, and m ′ + n ′ = 3.) D: (R ₃ and R ₄ are the same as above, and Y ₁ and Y ₂ are each —COO— or Represents These can be used alone, but it is more convenient to use them as a composition of two or more components because a wider temperature range can be obtained. In addition, other than (A) to (D), those having a side chain of linear alkyl and showing an SC phase can be used in the same manner. In addition, if the compound is a compound other than (A) to (D) and does not exhibit the SC phase itself, it may be added in a small amount to lower the viscosity of the composition if the compound is a liquid crystal compound having a small viscosity. This is an effective way to get

The obtained liquid crystal compound or composition can be used as a liquid crystal display cell by forming a thin film having a uniform thickness (about 1 μm to 20 μm) between two transparent electrode plates.

In the display cell, the molecules of the liquid crystal need to be monodomains in which the molecular major axis is parallel to the electrode surface, that is, a so-called homogeneous and uniform orientation. For this purpose, the surface of the electrode plate is subjected to an alignment treatment such as rubbing or vapor deposition, or an electric or magnetic field is applied, or a temperature gradient is provided, or a plurality of these means are used together in an isotropic manner. In general, a method of gradually cooling from the ionic liquid phase (I) to the liquid crystal phase to orient the liquid crystal phase is adopted.

In particular, recently, a cell in which a liquid crystal exhibiting a phase sequence of isotropic liquid phase (I) → chiral nematic phase (N ^* ) → smectic A phase (SA) → chiral smectic C phase (SC ^* ) has been subjected to alignment treatment. In particular, a method of aligning by increasing the helical pitch of N ^* is often used, and the same method is used for an SC ^* liquid crystal composition containing about 10 to 30% of the compound (I) of the present invention. Thereby, a mono-domain cell uniformly aligned can be easily obtained.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples.
Of course, the spirit and scope of the present invention are not limited by these examples.

Example 1 4-((S) -2-propoxypropanoyloxy)
Benzoic acid 4 '-((R) -1-methylheptyloxy)
Synthesis of biphenyl-4-yl 1-a 4 '-((R) -1-methylheptyloxy)
Synthesis of biphenyl-4-ol 190.5 g (1.0 mol) of p-toluenesulfonyl chloride was dissolved in 750 ml of methylene chloride and cooled to 5 to 10 ° C. After 130.0 g (1.0 mol) of (S) -2-octanol was added to this solution, 80 g of pyridine was added dropwise while taking care that the internal temperature did not exceed 10 ° C. After completion of the dropwise addition, the mixture was allowed to stand at 10 ° C. or lower for about 8 hours.
Washed with hydrochloric acid, water and then with saturated saline. After the extract was dehydrated with anhydrous sodium sulfate, the solvent was distilled off to obtain 267.0 g of (S) -1-methylheptyl p-toluenesulfonate.
(Yield 94.0%) 4,4'-biphenol (46.5 g, 0.25 mol) was dissolved in dimethyl sulfoxide (400 ml).
-29.4 g (0.26 mol) of potassium butoxide was dissolved in 250 ml of dimethyl sulfoxide and added dropwise. At room temperature, the reaction mixture is added to the p-toluenesulfonic acid (S) prepared above.
A solution of 71.0 g (0.25 mol) of -1-methylheptyl in 100 ml of tetrahydrofuran was added dropwise over 30 minutes. After completion of the dropwise addition, the mixture was stirred at 50 to 55 ° C for 4 hours.

After cooling, hydrochloric acid was added to the reaction mixture to make it weakly acidic, water 1 was added, and the mixture was extracted three times with ether. The combined ether layers were washed with water, and then concentrated to obtain a crude product (4,4'-biphenol as a raw material and 4,4'-di-((R) -1-methylheptyloxy) bialkyl dialkyl derivative) biphenyl Are separated by column chromatography, and further n
Recrystallized from -hexane to give white crystals of 4 '-((R) -1-methylheptyloxy) biphenyl-4-ol 3
5.8 g were obtained. Synthesis of 1-b 4-((S) -2-propoxypropanoyloxy) benzoic acid (S) -Ethyl lactate 20.0 g, propyl iodide 45.0 g, and silver oxide 30.0 g in 100 ml 40 in dimethylformamide
Stirred for hours. The insolubles were separated, water was added to the solution, and the mixture was extracted three times with hexane. After dehydrating the hexane layer, the organic solvent was distilled under reduced pressure to obtain 20.0 g of ethyl (S) -2-propoxypropionate. (Boiling point: 78 ° C./50 mmHg) 18.0 g of this was stirred in 100 ml of 5N aqueous sodium hydroxide solution for 6 hours, and then adjusted to pH 3 to 4 with dilute sulfuric acid under ice-cooling. After several extractions with ether,
After dehydration, the ether was distilled off to obtain 10.2 g of (S) -2-propoxypropionic acid. To this total amount, 20 ml of thionyl chloride and 0.5 ml of pyridine were added, and the mixture was refluxed for 2 hours. After distilling off excess thionyl chloride from the reaction mixture under reduced pressure, benzene was added to the reaction mixture to dissolve it. After separating insolubles, benzene was distilled off from the liquid to obtain oily (S) -2-propoxy. 10.5 g of propion acid chloride were obtained.

5.0 g of this was dropped into 4.9 g of 4-hydroxybenzoic acid dissolved in 30 ml of pyridine and reacted at 30 to 40 ° C. for 8 hours. After unreacted acid chloride was esterified by adding ethanol, the mixture was made weakly acidic by adding aqueous hydrochloric acid and extracted with ether. The solvent was distilled off, and the obtained crude crystals were repeatedly recrystallized from n-hexane to obtain 4.8 g of crystals of 4-((S) -1-propoxypropanoyloxy) benzoic acid.

1-c Synthesis of the title compound To 1.20 g of 4-((S) -2-propoxypropanoyloxy) benzoic acid obtained in 1-b, 5 drops of thionyl chloride and 3 drops of pyridine were added, and the mixture was stirred with heating for 3 hours. After the excess thionyl chloride was distilled off from the reaction mixture, benzene was added to the reaction mixture to dissolve it, insoluble substances were separately removed, and benzene was distilled off from the liquid to give 4-((S) -2-propoxypropanoyl). 1.15 g of oxy) benzoic acid chloride were obtained. to this,
1.27 g of 4 '-((R) -1-methylheptyloxy) biphenyl-4-ol obtained in 1-a was added to 20 ml of methylene chloride.
Was added. 2.0 ml of pyridine is added to this mixture.
Was added and reacted at reflux temperature for 2 hours. After cooling, ethyl acetate was added to the reaction mixture as an extraction solvent.
The extract was washed successively with saturated aqueous sodium hydrogen carbonate, water and saturated saline. After the extract was dehydrated with anhydrous sodium sulfate, the solvent was distilled off, and the crude product obtained was separated and purified by silica gel column chromatography (distilled solvent: chloroform-hexane), and further recrystallized from ethanol. −
1.40 g of 4 '-((R) -1-methylheptyloxy) biphenyl-4-yl ((S) -2-propoxypropanoyloxy) benzoate was obtained. This compound exhibited a chiral smectic (S ^* ) phase.

The phase transition temperature, the direction and value of the spontaneous polarization, and the direction of the induced helix are shown in Table 1. As shown in the main text, it has a very large spontaneous polarization.

Examples 2 to 4 By using (R) -2-octanol instead of (S) -2-octanol in Example 1,
4 (-((R) -1-Methylheptyloxy) biphenyl-4-yl) ((S) -2-propoxypropanoyloxy) benzoate was obtained. Example 2 In Examples 1 and 2, 4-((4-hydroxybiphenyl-4-carboxylic acid was used instead of 4,4′-biphenol and hydroquinone was used instead of 4-hydroxybenzoic acid to obtain 4-(( S) -2-Propoxypropanoyloxy) biphenyl-4-carboxylic acid 4-((R) -1
-Methylheptyloxy) phenyl (Example 3) and 4 '((S) -2-propoxypropanoyloxy) biphenyl-4-carboxylate 4-((S) -1-methylheptyloxy) phenyl (Example 4) was obtained. The physical properties of each compound are shown in Table 1.

Example 5 Preparation of SC ^* Liquid Crystal Composition Containing Compound (I) and Preparation of Optical Switching Device Using the Same Among the phenol benzoate compounds represented by A as an example of a bicyclic SC liquid crystal compound or a mixture, R ₁ And R ₂ are both alkoxy (R ₁ = C ₁₀ H ₂₁ O-, R ₂ = C ₈ H
₁₇ O-, 10 _{wt%; R 1 = C 9 H} 19 O-, R 2 = C 6 H 13 O-, 10 wt%;
R ₁ = C ₈ H ₁₇ O-, R ₂ = C ₁₀ H ₂₁ O-, 10% by weight; R ₁ = R ₂ = C ₈ H ₁₇ O
-, 10% by weight) and four pyrimidine components represented by B (R ₃ =
_{C 8 H 17 -, R 4} = C 10 H 21 -, 24 _{wt%; R 3 = C 8 H} 17 -, R 4 = C 9 H
₁₉ - 27 _{wt%; R 3 = C 8 H} 17 -, R 4 = C 6 H 13 O-, 6 wt%; R ₃
= C ₉ H _19- , R ₄ = C ₉ H ₁₉ O-, 3% by weight). This composition shows SC phase below 65 ° C, up to 67 ° C
The N phase showed up to 72 ° C. in the SA phase. The melting point was 5 ° C.

80% of this SC composition and 4 '-((S)-obtained in Example 3
2-propoxypropanoyloxy) biphenyl-4-
Carboxylic acid 4-((R) -1-methylheptyloxy)
When a liquid crystal composition comprising 20% of phenyl was prepared,
At 8.5 ° C or less, it showed SC ^* phase. SA phase up to 58.8 ° C, up to 67 ° C
It showed an N ^* phase, above which it exhibited an isotropic liquid phase.
The melting point of this composition was 0 ° C. or less.

Heating this SC ^* composition to 80 ° C. to an isotropic liquid phase,
This was filled between two glass transparent electrodes (one of which had been subjected to polyimide coating and rubbing alignment treatment) via a 2.4 μm thick spacer to form a thin film cell. This was gradually cooled at a rate of 5 ° per minute, and N ^* phase, SA
The phase was oriented, and a monodomain of SC ^* phase could be obtained below 58 ° C.

A rectangular wave of 24 V and 50 Hz was applied to this cell, and the transmitted light intensity was measured. As a result, an extremely fast response of 57 μs at 29 ° C. and 60 μs at 24 ° C. was confirmed.

The spontaneous polarization of this composition at 25 ° C. was 26 nC / cm ² , and the tilt angle was 30.5 °.

[Effects of the Invention] The compound (I) of the present invention has a spontaneous polarization with a large amount of a known ester-based ferroelectric liquid crystal compound when an SC ^* liquid crystal composition is obtained by mixing. The spiral pitch is also sufficiently large, and when added to the SC liquid crystal compound or composition and used as an SC ^* liquid crystal composition, the spiral pitch can be easily adjusted.

Further, as shown in the examples, compound (I) can be easily produced industrially, and is itself colorless,
Excellent chemical stability against moisture, heat, etc.
Very practical.

Further, the ferroelectric liquid crystal compound and the composition containing the same according to the present invention have a response speed of a conventional nematic liquid crystal.
It is extremely large, 100 times or more, and is extremely useful as an optical switching element for display.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location // G02F 1/13 500 G02F 1/13 500 C07M 7:00 (72) Inventor Masashi Osawa Chiba 76-2 Jonai-cho, Sakura City (56) References Special Table Sho-63-502507 (JP, A)

Claims (4)

(57) [Claims] 1. The compound of the general formula (I) Wherein R ₁ represents an alkyl group having 2 to 10 carbon atoms,
m and n each independently represent 1 or 2, and X is Or X represents a single bond, and when X is a single bond, at least one of m and n represents 2, and R ₂ represents an alkyl group having 1 to 10 carbon atoms. Also Each independently represents an asymmetric carbon atom of (R) or (S) in the absolute configuration.] 2. In the general formula (I) The absolute configuration of (R) is Is the absolute configuration of (S), The absolute configuration of (S) and 2. The compound according to claim 1, wherein the absolute configuration of (R) is (R). 3. The compound according to claim 1, wherein R ₁ in the general formula (I) is an n-hexyl group. 4. In the general formula (I), X is 4. The compound according to claim 1, 2 or 3, which is: