JPH0794408B2 - Liquid crystal compounds with extremely large spontaneous polarization - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a liquid crystal compound and a liquid crystal composition, and particularly to provide a liquid crystal material having a ferroelectric property, as compared with a conventional liquid crystal material. In particular, the present invention provides a liquid crystal material which has excellent responsiveness and memory properties and is applicable to a liquid crystal display device.

<Prior Art> Liquid crystal display elements have many excellent features such as low voltage operability, low power consumption, thin display capability, and light receiving type that can be used in bright places without eye strain. Therefore, it is widely used as various display elements at present. Currently, the display method is Twis
The most common type is the ted Nematic (TN) type. This TN type display system uses a nematic liquid crystal, but it has all of the above-mentioned excellent features, but its response is very slow compared to other light emitting type display systems such as CRT. There was a drawback.
In addition, even when the applied electric field was turned off, the display could not be memorized (memory effect) because it returned to its original state. For these reasons, it cannot be said to be suitable for application to moving screens such as optical shutters, printer heads, televisions, etc., which require high-speed response and time-division operation, due to various restrictions.

In addition to the TN type as a liquid crystal display element, a guest-host (G
H) type, birefringence control (ECB) type, phase transition (PC) type, thermal effect type, etc. have been researched and developed, and each has its own characteristics, but in terms of its responsiveness, both are TN type. Compared to this, no particular improvement was made. For these,
A so-called dual frequency drive type has been developed as a liquid crystal display system that can provide a high-speed response, and its response has been considerably improved, but it is still not sufficiently satisfactory and its operation It had a defect that the circuit became too complicated. For this reason, attempts have been made to develop a new liquid crystal display system that is even more responsive.

Ferroelectric liquid crystals have recently been announced to meet this purpose. (R. Mayer et al; J. Physique 36 L69 (197
5)) It is pointed out that the display device using this ferroelectric liquid crystal has a high speed response of 100 to 1000 times compared with the 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 display devices on the other side such as moving screens of televisions, high-speed optical shutters, printer heads, computer terminals, etc.

Ferroelectric liquid crystals belong to the tilt-type chiral smectic phase as the liquid crystal phase, but among them, the practically desirable one is the 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 alone have the following conditions for use as a ferroelectric liquid crystal display device: (a) exhibit ferroelectricity in a wide temperature range including room temperature; and (b) a long helical pitch. (C) a proper tilt angle, (d) a large value of spontaneous polarization, (e) a small viscosity, (f) a high speed as a result of (d) and (e) above. It is not known that it exhibits responsiveness, and it is necessary to mix a plurality of compounds and use it as an SC ^* liquid crystal composition.

There are two methods to obtain SC ^* liquid crystal composition, one is
This is a method of mixing a plurality of compounds exhibiting an SC ^* phase, and the other method is a method of adding a chiral liquid crystal compound to a liquid crystal compound or a liquid crystal composition exhibiting a non-chiral SC phase.

With 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 branching group (mainly a methyl group). The closer this branching group is to the central nucleus (core) part of the liquid crystal molecule and the permanent dipole such as the carbonyl group, the greater the spontaneous polarization of the liquid crystal,
At the same time, the viscosity of the liquid crystal tends to be increased. Therefore, even if the spontaneous polarization of the liquid crystal is increased, the viscosity is large especially in the low temperature range, and it is not easy to obtain a high-speed response of 200 μsec or less near room temperature.

In the latter method, although it depends on the amount of the chiral liquid crystal compound to be added, it is difficult to obtain a composition having a very large spontaneous polarization as the matrix SC liquid crystal does not have spontaneous polarization. However, since the liquid crystal compound in the matrix SC composition does not require the presence of a branching group, its viscosity is extremely small. 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.

The chiral liquid crystalline compound added to the SC liquid crystal composition does not necessarily need to exhibit the SC ^* phase by itself and does not necessarily need to exhibit the liquid crystal phase, but it does not narrow the temperature range of the composition. Is preferably a liquid crystal phase, particularly a chiral smectic 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 liquid crystal central skeleton (core), and It should be as close as possible to a permanent dipole. However, since the compound having such a structure also has a strong twisting force with respect to the liquid crystal phase, the pitch becomes too short in the liquid crystal phase (SC ^* phase, etc.) in which a spiral appears, which adversely affects the orientation. Problems such as difficulty in increasing the cell thickness occurred. Therefore, either limit the amount of addition or add a chiral compound with the opposite twist direction.
SC ^{* It} was necessary to adjust the pitch of the liquid crystal composition. In this case, if the direction of the spontaneous polarization of the chiral compound opposite to the twist direction is also the opposite direction, the spontaneous polarization of the composition is canceled and becomes small, and there are many troublesome problems in adjusting the pitch. Therefore, there has been a demand for a liquid crystal compound having a large spontaneous polarization, a large pitch, and a chiral smectic phase alone when possible.

<Problems to be Solved by the Invention> An object of the present invention is to have a large spontaneous polarization, a sufficiently large pitch, and a chiral smectic phase per se, and a wide temperature range including room temperature by mixing. in SC ^* phase indicates, to provide a novel chiral liquid crystal compounds such as which enables high-speed response, and possible SC of the chiral liquid crystal compound shows a liquid crystal compound and SC phase or high-speed response liquid crystal composition ^* It is to prepare a liquid crystal composition, to provide such a composition, and to provide an optical display device having a fast response using these SC ^* liquid crystal compounds and compositions.

<Means for Solving the Problem> The chiral liquid crystal compound in the present invention is characterized by being an ester compound having two asymmetric carbon atoms in the molecule as represented by the following general formula (I). .

In the above formula, R ₁ represents an alkyl group having 2 to 10 oxygen atoms, more preferably an alkyl group having 2 to 6 carbon atoms, and an optically active secondary alcohol as a raw material. N- is the most preferable in terms of availability and price.
It is a hexyl group. m and n represent an integer of 1 or 2, which may be equal to or different from each other, more preferably m = 1 and n = 2, or m = 2 and n = 1. R ₂ represents an alkyl group having 1 to 10 carbon atoms, more preferably an alkyl group having 3 to 8 carbon atoms.

Represents that the carbon is an asymmetric carbon atom in the (R) or (S) configuration, Indicates that the carbon is an asymmetric carbon having the (S) configuration.

The liquid crystal composition in the invention is a mixture of at least one compound represented by the general formula (I) (hereinafter abbreviated as compound (I)), and preferably has a chiral smectic phase. It is the liquid crystal composition shown. More preferably, it is a chiral smectic liquid crystal composition prepared by mixing at least one compound (I) with a liquid crystal compound or composition exhibiting a smectic C phase, and in particular, a composition exhibiting a smectic C phase has a side chain in its side chain. It is preferable that the main component is a compound showing an SC phase without the presence of a branching group.

Compound (I) can be synthesized as follows. That is, the general formula (II) (In the formula, R ₁ , m, Is the same as compound (I). ) As a salt of a carboxylic acid represented by the formula (III) (In the formula, n, R ₂ , Is the same as compound (I). It can be easily obtained by reacting the lactic acid derivative represented by (4) with a basic substance such as pyridine. Alternatively, the carboxylic acid (I
It can also be obtained by directly esterifying I) and the lactic acid derivative (III) in the presence of a condensing agent such as dicyclohexylcarbodiimide.

Carboxylic acid (II) is 4-hydroxybenzoic acid (when m = 1) or 4'-hydroxybiphenyl-4-carboxylic acid (when m = 2) or its lower alkyl ester and an optically active alcohol. It can be obtained by reacting with O-tosylate of (1) under basic conditions, and when an ester is used, it is hydrolyzed and then treated with an acid.

The lactic acid derivative can be synthesized as follows.

The present inventors have already reacted (S) -ethyl lactate with silver oxide and alkyl iodide (R ₂ -I) to give (S)-, as shown in JP-A-63-115848. Ethyl 2-alkoxypropionate is obtained, and (S) -2-alkoxypropionic acid obtained by hydrolysis of this is used in the presence of a dehydrating agent such as dicyclohexylcarbodiimide to prepare hydroquinone (when n = 1) or biphenol (n = 2). Case) can be obtained by reacting with. Alternatively, (S)
It can be obtained by converting 2-alkoxypropionic acid into an acid chloride by using a chlorinating agent such as thionyl chloride and then reacting it with hydroquinone or biphenol. The latter method has excellent purity and yield of the product. In many cases.

The above synthesis method is shown below in a process diagram for easy understanding.

The structurally greatest feature of compound (I) is that it has two asymmetric carbons in the molecule. One (S)
-2-alkoxypropanoyloxy group is natural (S)
-Derived from lactic acid and its ester, the configuration of which is always (S) and the other chiral group is an optically active alcohol And the configuration is (S) or (R).

As shown in the synthetic method, optically active alcohol Is converted to O-tosylate and then reacted with hydroxycarboxylic acid or its ester to introduce a chiral group, but it is considered that the configuration is retained in the first step (tosylation). The second step is the reaction at the optically active center, but it is generally said that the reaction between the alcoholate and the tosylate under basic conditions has a reversed configuration. However, since the configuration after the reaction could not be determined directly, the optically active alcohol used as a raw material will be described below. By showing the configuration of The absolute placement of That is, for example, (S) -2
-When derived from octanol (S)),
It is referred to as (R)) derived from (R) -2-octanol, and is distinguished from (S)-in the case of a 2-alkoxypropanoyloxy group. It is considered that ((S)) actually represents (R) and ((R)) represents (S).

The most significant characteristic of compound (I) in terms of physical properties is that it has a very large spontaneous polarization, but its pitch is quite large. Already, among liquid crystal compounds in which an asymmetric carbon is directly linked to a benzene ring by an ether bond, those having large spontaneous polarization are known. A value of 89 nC / cm ² has been reported for the compound represented by.

Also derived from lactic acid According to the study by the present inventors, it has been confirmed that even a compound having: exhibits a large spontaneous polarization of 100 nC / cm ² or more.

However, in these compounds having large spontaneous polarization, since they have a strong torsional force,
The pitch in the SC ^* phase was very small, and even when 10 to 30% was added as a composition, it was necessary to adjust the pitch to be large by adding a considerable amount of the compound having the opposite twist direction.

We have Direction of twist and the direction of spontaneous polarization ((S) -2
-Methylbutyl p-decyloxybenzylidene aminocinnamate (in the direction of spontaneous polarization) is the ((S)) form In fact, it is considered to be the (R) form) on the left side and the ((R)) form on the right side. Paying attention to the fact that the direction of the twist derived from and the direction of the spontaneous polarization are on the right, In compounds containing both, especially in the ((S)) form In such a case, the present invention has been accomplished on the assumption that the twisting force may be canceled and the twisting force may be reduced to obtain a large pitch while maintaining a large spontaneous polarization.

In the case of the present compound (I), not only those which show the SC ^* phase are necessarily present, so 10 to 40% of the compound (I) is added to the pyrimidine-based host liquid crystal showing the SC phase and the spontaneous polarization thereof is measured. By extrapolating from the values, the spontaneous polarization of the compound (I) itself was determined. As a result, the ((S)) form of 4-((S) -2-propyloxypropanoyloxy) phenyl 4 ′-(1
-Methylheptyloxy) biphenyl-4-carboxylate (compound of Example 1) at 180 nC / Tc-T = 10 ° C.
^{cm 2, Tc-T = 20} ℃ at ^{260nC / cm 2, Tc-T} = 30 ℃ in 290NC /
It showed a very large value of cm ² . This is the largest compound known so far and is the first example showing that the spontaneous polarization derived from the chiral groups at both ends of the same liquid crystal molecule has additivity.

On the other hand, the compound (I) is a 4-((S) -2 in the ((R))-form.
-Propyloxypropanoyloxy) phenyl-4 '
In the case of-(1-methylheptyloxy) biphenyl-4-carboxylate (compound of Example 2), its spontaneous polarization value was only about 1/5 of that of the ((S)) form, and both spontaneous polarizations were If the directions are opposite, it indicates that they are offset as a whole.

The helical pitch of the compound (I) in the SC ^* phase was added as an extrapolated value to the parent SC liquid crystal of the pyrimidine system, as in the case of spontaneous polarization.
It became a large value of 5 μm or more at Tc−T = 5 ° C. This has, for example, 4-having only a chiral group derived from lactic acid.
((S))-2-Propyloxypropanoyloxy)
The pitch of phenyl 3'-fluoro-4'-decyloxybiphenyl-4-carboxylate is 1.3 μm (Tc-T
= 5 ° C), the effect of having two optically active groups is clearly shown.

On the other hand, in the compound of Example 2, the content of the compound (I) is 20%.
The pitch was 4 μm or less. As described above, when the absolute configuration of the optically active 1-methylalkyl group is ((S)), the compound (I) can exhibit the ideal property of large pitch and extremely large spontaneous polarization. To obtain the compound.

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.
Since compound (I) has a branched methyl group on both side chains, its phase transition temperature is considerably lower than that of compounds having a similar skeletal structure, and the compound having the general formula (I ) Is a compound having m + n = 3 or more, that is, a compound having three or more rings.

Compound (I) is prepared by mixing an SC liquid crystal compound or composition having no branched chain with a chiral compound to prepare an SC ^* liquid crystal composition, and when the chiral compound has no chiral smectic property. , There is a tendency to narrow the temperature range of the SC ^* phase in the composition. Although the compound (I) has a relatively low phase transition temperature, it exhibits a chiral smectic phase when it has three or more rings, and its temperature range is hardly narrowed even during mixing.

Now, the helical pitch of the SC ^* liquid crystal composition obtained by adding about 10 to 30% of the compound (I) to the SC liquid crystal composition is sufficiently large when the twists are offset, but further adjustment is required. When the need arises, the compound (I) should have the opposite direction of twist and the same direction of spontaneous polarization, or even the opposite direction should be a small compound of several nC / cm ² or less. For example, it can be used for pitch adjustment. A small amount of the compound (I) is sufficient in the ((S)) form in which the twist is offset, and a considerable amount is required in the ((R)) form.

Now, the compound (I) is used alone or as a mixture with a plurality of compounds.
Examples of the SC liquid crystal compound or composition include a phenylbenzoate compound (A), a pyrimidine compound (B) or a mixture thereof as shown below in the bicyclic type. Further, in order to extend the temperature range of the SC phase to a high temperature range, tricyclic compounds (C) and (D) can be used.

(R ₁ and R ₂ 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 represent a linear alkyl group or an alkoxy group,
It may be the same or different. ) (R ₃ and R ₄ have the same meaning as in compound B, and m + n
= 3. ) (R ₃ and R ₄ have the same meanings as in compound B, and Y ₁ and Y ₂
Are COO- or Represents Although these can be used alone, it is convenient to use them as a composition of two or more components because a wider temperature range can be obtained. Further, other than A to D, those having a straight chain alkyl side chain and exhibiting an SC phase can be similarly used. In addition, compounds other than A to D, which are themselves
Even if it does not show the SC phase, if it is a liquid crystalline compound having a low viscosity, adding a small amount for decreasing the viscosity of the composition is an effective method for obtaining a high response speed.

The liquid crystal compound or composition thus obtained 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 liquid crystal molecules need to be monodomains whose long axes are parallel to the electrode surface, that is, so-called homogeneous and uniformly oriented. To this end, the surface of the electrode plate is subjected to an orientation treatment by rubbing, vapor deposition, etc., an electric field or a magnetic field is applied, a temperature gradient is given, or a combination of these means isotropic. A method of gradually cooling the organic liquid phase to the liquid crystal phase for alignment is generally adopted. Even with the compound or composition of the present invention, a uniformly oriented monodomain cell can be obtained by such a method.

<Effects of the Invention> Although the effects of the present invention are as described above, the compound (I) of the present invention is a conventionally known ester-based ferroelectric liquid crystal when mixed into an SC ^* liquid crystal composition. It has a larger spontaneous polarization than that of the compound, and also has a sufficiently large helical pitch, and when it is used as an SC ^* liquid crystal composition by adding it to an SC liquid crystal compound or composition, does it require pitch adjustment? Or very easy.

In addition, the compound (I) can be easily produced industrially, is colorless in itself, and has excellent chemical stability against light, moisture, heat, etc., as shown in Examples described later. , Very practical.

Further, the ferroelectric liquid crystal compound and composition in the present invention have extremely high response speed of 100 times or more that of the conventional nematic liquid crystal, and are very promising as an optical switching element for display.

<Examples> 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.

The liquid crystal phase and the phase transition temperature were measured by using a deflection microscope equipped with a temperature adjusting stage and a differential scanning calorimeter (DSC), but the transition temperature slightly varies depending on the purity of the sample or the measurement conditions. It is a thing. The temperature is ° C
Means

The chemical structure of the product is the nuclear magnetic resonance spectrum (NM
R), infrared absorption spectrum (IR), mass spectrum (M
S) confirmed.

In the NMR data, s is a singlet (singlet), d is a doublet (doublet), t is a triplet (triplet), q is a quartet (quartet), m is a multiplet (multiplet), dd represents a double double line (double doublet). In addition, P ⁺ in MS represents a parent peak.

Example 1 Synthesis of 4-((S) -2-propyloxypropanoyloxy) phenyl 4 ′-(1-methylheptyloxy) biphenyl-4-carboxylate (((S)) form 1-a) 4 Synthesis of ′-(1-methylheptyloxy) biphenyl-4-carboxylic acid (((S)) form) p-toluenesulfonyl chloride 190.5 g (1.0 mol)
Was dissolved in 750 ml of methylene chloride and cooled to 5-10 ° C.
After adding 130.0 g (1.0 mol) of (S) -2-octanol, pyridine, being careful not to let the internal temperature exceed 10 ° C.
80 g was added dropwise. After completion of dropping, the mixture was left at 10 ° C. or lower for about 8 hours, hexane 21 was added, and the mixture was washed with 1% hydrochloric acid, water and then saturated saline. After dehydration with anhydrous sodium sulfate, the solvent was distilled off to obtain 267.0 g of (S) -2-octyl p-toluenesulfonate. (Yield 94.0%) Next, 4'-hydroxybiphenyl-4-carboxylic acid was synthesized from 4'-hydroxybiphenyl-4-carboxylic acid and ethanol.
4-Carboxylic acid ethyl ester 31.2 g (0.129 mol) 300 m
It was dissolved in 1 dimethyl sulfoxide, and 14.5 g (0.129 mol) of potassium t-butoxide was dissolved in 150 ml of dimethyl sulfoxide and added dropwise. Here, 36.9 g of (S) -2-octyl p-toluenesulfonate prepared above
(0.13 mol) was added dropwise at about 40 ° C, and then 40 to 50 ° C for 4 hours.
It was made to react with. After adding 10% hydrochloric acid to make the mixture acidic, the mixture was extracted with a hexane-ether mixed solvent, washed with water and saturated saline, and then dehydrated with anhydrous sodium sulfate. 45 g of the crude product obtained by distilling off the solvent was added with 15 g of sodium hydroxide and ethanol.
It was dissolved in 1 liter and heated under reflux for 3 hours. After cooling, hydrochloric acid was added to acidify the mixture, and the mixture was heated to dissolve it, and then cooled. The precipitated crystals were separated by filtration, recrystallized from ethanol again,
24.0 g of 4 '-(1-methylheptyloxy) biphenyl-4-carboxylic acid in the form of ((S)) was obtained. (Yield 57
%) 1-b) Synthesis of 4-hydroxyphenyl (S) -2-propyloxypropinate 20.0 g of (S) -ethyl lactate, 45.0 g of propyl iodide and 30.0 g of silver oxide were stirred in 100 ml of dimethylformamide for 40 hours. The insoluble material was filtered off, water was added to the filtrate, and the mixture was extracted 3 times with hexane. The hexane layer was dehydrated and distilled under reduced pressure to give (S) -2-propyloxypropionate ethyl 20.0 g.
Got (78 ° C./50 mmHg) This 18.0 g was stirred in 100 ml of a 5N sodium hydroxide aqueous solution for 6 hours and then adjusted to pH 3 to 4 with dilute sulfuric acid under ice cooling. After several extractions with ether, dehydration and evaporation of the solvent, 10.2 g of (S)
2-Propyloxypropionic acid was obtained. To this whole amount
20 ml of thionyl chloride and 0.5 ml of pyridine were added, and the mixture was heated under reflux for 2 hours. Excess thionyl chloride was distilled off under reduced pressure, benzene was added, the insoluble matter was filtered off, and then benzene was distilled off to obtain 10.5 g of oily (S) -2-propyloxypropionyl chloride.

9.0g of hydroquinone dissolved in 50ml of pyridine
Was added and the mixture was stirred at 30 to 40 ° C. for 20 hours. Add ethyl acetate
The organic layer was washed with 10% aqueous hydrochloric acid, water and saturated saline in this order and then dehydrated with anhydrous sodium sulfate.

After concentration, the target product was separated by silica gel column chromatography (developing solvent: hexane-ethyl acetate) to obtain 4.9 g of oily 4-hydroxyphenyl (S) -2-propyloxypropionate.

1-c) Synthesis of title compound To 4 (-S-)-form 4 '-(1-methylheptyloxy) biphenyl-4-carboxylic acid (3.57 g) obtained in 1-a) was added thionyl chloride (20 ml) and pyridine (1.0 ml). In addition, the mixture was heated and stirred for 3 hours. Excess pyridine was distilled off, toluene was added, and the insoluble matter was filtered off. Distill off the toluene,
3.54 g of 4 '-(1-methylheptyloxy) biphenyl-4-carboxylic acid chloride in the form of ((S)) was obtained.

To this, 3.78 g of 4-hydroxyphenyl (S) -2-propyloxypropionate obtained in 1-b) was dissolved in 20 ml of methylene chloride and added. 2.0 ml of pyridine was added, and the mixture was reacted under reflux for 2 hours. After allowing to cool, ethyl acetate was added, and 10% aqueous hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution, water,
It was washed successively with saturated saline. After dehydration with anhydrous sodium sulfate, the solvent was distilled off to obtain a crude product, which was purified by silica gel column chromatography (developing solvent: chloroform-hexane) and recrystallized from ethanol.
White crystals of ((S))-form 4-((S) -2-propyloxypropanoyloxy) phenyl 4 '-(1-methylheptyloxy) biphenyl-4-carboxylate
4.16 g was obtained.

This compound exhibited a chiral smectic phase. The phase transition temperature is collectively shown in Table 1 and the spectrum data is collectively shown in Table 2.

Examples 2 to 4 In Example 1, by using (R) -2-octanol instead of (S) -2-octanol,
The ((R)) form of 4-((S) -2-propyloxypropanoyloxy) phenyl 4 ′-(1-methylheptyloxy) biphenyl-4-carboxylate (Example 2) and Example 1 In 4 the 4'-hydroxybiphenyl-4-carboxylic acid was replaced with 4-hydroxybenzoic acid and the hydroquinone was replaced with 4,4'-biphenol to give 4 '-((S))-2. -Propyloxypropanoyloxy) biphenyl-4-yl 4-
(1-S-) form of (1-methylheptyloxy) benzoate (Example 3), ((R)) form (Example 4)
Got The phase transition temperature and the spectrum data are collectively shown in Tables 1 and 2.

Example 5 Preparation of Optical Switching Device Using SC ^* Liquid Crystal Composition Containing Compound (I) 2- (4-nonyloxy) phenyl-5-octylpyrimidine 40w%, 2- (4-nonyloxy) phenyl-5
When SC liquid crystal composition was prepared from 40w% of heptylpyrimidine and 20w% of 4-octyloxyphenyl 4-decyloxybenzoate, the phase transition points were as follows. (W% represents weight percent) 85% by weight of this SC composition and 4-obtained in Example 1
An SC ^* liquid crystal composition was prepared from ((S) -2-propyloxypropanoyloxy) phenyl 4 '-(1-methylheptyloxy) biphenyl-4-carboxylate 15w%.

When this composition is heated to the isotropic liquid phase and then cooled
The N ^* phase was transferred to 68 ° C, the SA phase was transferred to 57 ° C, the SC ^* phase was transferred to 48 ° C, and the SC ^* phase was maintained as it was until 0 ° C. Also, when left at a low temperature for a long time, it was crystallized and its mp was 24 ° C.

The composition is heated to an isotropic liquid phase, which has a thickness of 2.
A thin film cell was prepared by filling the space between two glass transparent electrodes (one of which was subjected to a polyimide-rubbing orientation treatment) bonded together via a 1 μm spacer.

This is gradually cooled at a rate of 5 ° C. for 1 minute, and N ^* phase, SA
The phases were oriented and a uniform SC ^* phase monodomain was obtained at 48 ° C or below.

A 21 V _pp , 50 Hz square wave was applied to this cell, and the transmitted light intensity was measured. For example, it was 68 μs at 40 ° C. and 25 ° C.
A quick response of 99 μs was confirmed. As a result, a high-speed responsive optical switching display element was obtained. The spontaneous polarization of this composition is 3.80 nC / cm ² (40 ° C), 4.92
nC / cm ² (25 ° C), and its tilt angle is 16.8 ° (40 ° C),
It was 22.1 ° (25 ° C).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Ogawa 246-4 Ikari, Kawaguchi City, Saitama Prefecture

Claims (8)

[Claims] 1. A general formula (I) (In the formula, R ₁ represents an alkyl group having 2 to 10 carbon atoms, m
And n each represent 1 or 2, which may be different from each other, and R ₂ represents an alkyl group having 1 to 10 carbon atoms. Also Represents an asymmetric carbon having an absolute configuration of (R) or (S), Is a liquid crystal compound represented by (S) representing an asymmetric carbon in the configuration. 2. The compound according to claim 1, wherein m + n = 3 in the general formula (I). 3. The compound according to claim 2, wherein in the general formula (I), R ₁ is an n-hexyl group. 4. In the general formula (I), Claims 1 and 2 wherein the absolute configuration of is (R)
Item 3. A liquid crystal compound according to item 3. 5. General formula (I) (In the formula, R ₁ represents an alkyl group having 2 to 10 carbon atoms, m
And n each represent 1 or 2, and may be different from each other, and R ₂ represents an alkyl group having 1 to 10 carbon atoms. Also Represents an asymmetric carbon having an absolute configuration of (R) or (S), Is a liquid crystal composition containing at least one liquid crystal compound represented by (S) representing an asymmetric carbon atom. 6. The liquid crystal composition according to claim 5, which exhibits a chiral smectic phase. 7. The liquid crystal composition according to claim 6, which contains a liquid crystal compound or composition exhibiting a smectic C phase. 8. In general formula (I) 8. A liquid crystal composition according to claim 7, which contains a liquid crystal compound whose absolute configuration is (R).