JPH08113553A - Strong antiferroelectric liquid crystal compound and liquid crystal composition containing the same - Google Patents

Abstract

PURPOSE: To obtain a new compound exhibiting a strong antiferroelectric phase near room temperature or at a temperature lower than the room temperature and capable of improving response speed of a liquid crystal composition by adding it as a liquid crystal composition component. CONSTITUTION: This compound is expressed by the formula [(m) is 4-14; (n) is 4-12; Cf is CH3 or CF3 ; * is a center of optical activity], e.g. 3-fluoro-4-(1,1,1- trifluoro-2-alkyloxycarbonyl)phenyl-4-n-alkylcarbonyloxybenzoate. The compound is obtained by reacting 2-fuoro-4-benzyloxybenzoic acid chloride with an optically active 1,1,1-trifluoro-2-alkanol, carrying out hydrocracking of the resultant compound, and further, reacting the resultant alkyl ester with 4-n- alkylcarbonyloxybenzoic acid in the presence of dicyclohexylcarbodiimide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel antiferroelectric liquid crystal compound.

[0002]

2. Description of the Related Art Liquid crystal display devices have 1) low voltage operability and 2)
It has excellent features such as low power consumption, 3) thin display, 4) light receiving type, etc., so far, TN method, STN method,
A guest-host method has been developed and put to practical use. However, a nematic liquid crystal that is widely used at present has a response speed of several mse.
It has a drawback of being slow from c to several tens of msec, and is subject to various restrictions in application. In order to solve these problems, an active matrix method using an STN method or a thin layer transistor method has been developed, but the STN type display element has excellent display quality such as display contrast and viewing angle. However, there are problems that high precision is required for controlling the cell gap and the tilt angle, and that the response is rather slow. The thin film transistor method has a complicated structure, has a low manufacturing yield, and is consequently expensive. For this reason,
There has been a demand for the development of a new liquid crystal display system having excellent responsiveness, and an attempt has been made to develop a ferroelectric liquid crystal capable of realizing an ultra-high speed device having an optical response time of the order of μsec or so. Ferroelectric liquid crystal, 1975, Meyo
DOBAMBC (p-decyloxybenzylidene-p-amino-2-methylbutyl cinnamate) was first synthesized by r et al. (Le Journal de Ph)
ysique, vol. 36, 1975, L-69). further,
1980 DO by Clark and Lagwall
Since the characteristics of BAMBC such as sub-microsecond high-speed response and memory characteristics on display devices have been reported, ferroelectric liquid crystals have attracted great attention [N. A. Cl
ark, et al. , Appl. Phys. Lett.
36.899 (1980)]. However, their method has many technical problems for practical use, and there are few ferroelectric liquid crystals that satisfy the practical characteristics required for a display, especially at room temperature. Neither effective nor practical method for sequence control has been established. Since this report, various attempts have been made from both sides of liquid crystal materials / devices, prototype display devices utilizing switching between twisted two states have been produced, and high-speed electro-optical devices using the same have been disclosed, for example, in JP-A-56-107216. However, high contrast and proper threshold characteristics have not been obtained. From this point of view, other switching methods were also searched, and a transient scattering method was proposed. Then, in 1988, the inventors of the present invention reported a three-state switching method for a liquid crystal having three stable states [A. D. L. Chandani, T .; Ha
giwara, Y .; Suzuki et al. , Jap
an. J. ofAppl. Phys. , 27, (5),
L729-L732 (1988)]. The above-mentioned “having a tristable state” means a liquid crystal electro-optical device in which an antiferroelectric liquid crystal is sandwiched between a first electrode substrate and a second electrode substrate arranged with a predetermined gap. 1 is configured so that a voltage for forming an electric field is applied to the first and second electrode substrates, and when the voltage is applied as a triangular wave shown in FIG. 1A, the antiferroelectric liquid crystal causes no electric field. Sometimes the molecular orientation becomes the first stable state [Fig. 3 (a)], the transmittance of the liquid crystal electro-optical device shows the first stable state (Fig. 1D), and in one electric field direction when the electric field is applied. The second stable state whose molecular orientation is different from the first stable state [Fig.
(B)], the transmittance of the liquid crystal electro-optical device shows the second stable state (in FIG. 1D), and the third molecule different from the first and second stable states in the other electric field direction. This means that the alignment stable state [FIG. 3 (c)] is reached and the transmittance of the liquid crystal electro-optical device shows the third stable state (FIG. 1D). Regarding the liquid crystal electro-optical device utilizing the tri-stable state, the present applicant has filed as Japanese Patent Application No. Sho 63-70212 and is disclosed as Japanese Patent Application Laid-Open No. 2-153322. The characteristics of the antiferroelectric liquid crystal exhibiting the tristable state will be described in more detail. Clark / Lagawell
In the surface-stabilized ferroelectric liquid crystal device proposed by Lagwall), two stable states in which ferroelectric liquid crystal molecules are uniformly aligned in one direction as shown in FIGS. 2 (a) and 2 (b) in the S * C phase are proposed. Depending on the direction of the applied electric field, it is stabilized in one of the states, and that state is maintained even when the electric field is cut off. However, in reality, the alignment state of the ferroelectric liquid crystal molecules shows a twisted two-state in which the director of the liquid crystal molecules is twisted, or the layer has a chevron structure in which the layers are bent. With the Sieblon layer structure, the switching angle becomes small, which causes low contrast, which is a major obstacle to practical use. On the other hand, in the SmC * A phase in which the "anti" ferroelectric liquid crystal shows a tristable state, in the liquid crystal electro-optical device, when there is no electric field, the molecules in the adjacent layers move in opposite directions as shown in FIG. The tilts are arranged antiparallel, and the dipoles of the liquid crystal molecules cancel each other out. Therefore, the spontaneous polarization is canceled in the entire liquid crystal layer. The liquid crystal phase showing this molecular arrangement corresponds to that in FIG. 1D. Further, when a voltage sufficiently higher than the threshold value of (+) or (−) is applied, the liquid crystal molecules are tilted in the same direction and arranged in parallel as shown in FIGS. 3B and 3C. In this state, the dipoles of the molecules are also aligned in the same direction, so spontaneous polarization occurs and a ferroelectric phase is formed. "Anti" In SmC * A phase of ferroelectric liquid crystal, "Anti" when no electric field is applied
The two ferroelectric phases become stable due to the polarity of the ferroelectric phase and the applied electric field, and high-speed microsecond order switching between the three stable states is achieved with a DC threshold value between the "anti" ferroelectric phase and the two ferroelectric phases. It is something to do. That is, the molecular alignment of the liquid crystal changes depending on the polarity and magnitude of the applied electric field, and the optical axis of the liquid crystal can be changed into three states. It can be used as an electro-optical display device.
When the light transmittance is plotted against the applied voltage of the AC triangular wave, the double hysteresis as shown in FIG. 4 is shown. As shown in FIG. 4A, a memory effect can be realized by applying a bias voltage to this double hysteresis and further superimposing a pulse voltage. And
In the "anti" ferroelectric liquid crystal, both positive and negative hysteresis can be alternately used to display an image, so that the afterimage phenomenon of the image due to the accumulation of the internal electric field due to spontaneous polarization can be prevented. . Further, by applying an electric field, the layer of the ferroelectric phase is stretched to form a Bookshelf structure. On the other hand, the first stable state “anti” ferroelectric phase has a similar Bookshelf structure. Since the layer structure switching by the application of the electric field gives a dynamic shear to the liquid crystal layer, alignment defects are improved during driving, and good molecular alignment can be realized. As described above, the “anti” ferroelectric liquid crystal is a very useful liquid crystal compound that can achieve 1) high-speed response, 2) high contrast and wide viewing angle, and 3) good alignment characteristics and memory effect. Can be said. Regarding the liquid crystal phase showing the tristable state of "anti" ferroelectric liquid crystal, 1) A. D. L.
Chandani et al., Japan J. Ap
pl. Phys., 28, L-1265 (1989) and 2) H. Orihara et al., Japan
J. Appl. Phys., 29, L-333 (19
90), and the S * C A phase (Antiferroelectric S) associated with the “anti” ferroelectric property was reported.
However, the present inventors defined it as the S * (3) phase (referred to as the SmC * A phase in this specification) because the liquid crystal phase switches between tristable states. did. Liquid crystal compounds having an “anti” ferroelectric phase SmC * A in a phase series exhibiting a tristable state are disclosed in Japanese Patent Application Laid-Open Nos. 1-331667, 1-316372, 1-316339, There are JP-A-2-28128 and JP-A-1-213390 of Ichihashi, etc., and regarding the liquid crystal electro-optical device utilizing the tristable state, the present applicant discloses JP-A-2-40625 and JP-A-2-153322.
And Japanese Patent Application Laid-Open No. 2-173724.

[0003]

DISCLOSURE OF THE INVENTION The present invention is to provide a novel antiferroelectric liquid crystal compound having a fluorine substituent at a specific position of a benzene nucleus constituting a skeleton structure, and a liquid crystal composition containing the same.

[0004]

The present invention has the general formula [I]

[Chemical 4] (Wherein, m = 4 to 14, n = 4 to 12, Cf = CH ₃ or CF ₃ , and * represents an optically active center). The present invention relates to an antiferroelectric liquid crystal compound exhibiting a stable state. In the skeleton of the compound having the following structure, the presence or absence of fluorine and the presence or absence of the antiferroelectric phase [S * (3)] depending on the difference in the substitution position. When the optically active part is CF ₃ , when there is no fluorine,
The antiferroelectric phase [S * (3)] appears only in the compounds substituted with fluorine at the positions of and. When the optically active moiety is CH ₃ ,
Compounds with fluorine substitution at position
* (3)] appears. From the above, the compound substituted with fluorine at the position, that is, the compound of the present invention, can exhibit the antiferroelectric phase [S * (3)].

[0005]

Embedded image

The following are synthetic examples of the compound of the present invention. 2-Fluoro-4-benzyloxybenzoic acid chloride is reacted with an optically active 1,1,1-trifluoro-2-alkanol to give 2-fluoro-4
-Benzyloxybenzoic acid 1,1,1-trifluoro-2-alkyl ester was obtained, which was hydrolyzed to give
2-Fluoro-4-hydroxybenzoic acid 1,1,1-
A trifluoro-2-alkyl ester was obtained. The resulting alkyl ester is reacted with 4-n-alkylcarbonyloxybenzoic acid in the presence of dicyclohexylcarbodiimide to give the desired compound, optically active 3-fluoro-4- (1,1,1-trifluoro-2). -Alkyloxycarbonyl) phenyl 4-n-alkylcarbonyloxybenzoate is obtained.

[0007]

[Examples] The compounds of the present invention are described below by referring to Examples, but the invention is not limited thereto.

Example 1 1) 1,1,1-trifluoro-2-decyl 2'-
Synthesis of fluoro-4'-benzyloxybenzoate

[Chemical 6] 1.30 g of 2-fluoro-4-benzyloxybenzoic acid chloride was dissolved in 10 ml of methylene chloride, and then 0.96 g of optically active 1,1,1-trifluoro-2-decanol, 0.55 g of dimethylaminopyridine and triethylamine. A solution of 0.48 g and 20 ml of methylene chloride was added little by little under ice cooling. The reaction mixture was returned to room temperature, reacted overnight, poured into ice water,
Extract with methylene chloride and dilute the methylene chloride phase with dilute hydrochloric acid, water,
It was washed successively with a 1N aqueous sodium carbonate solution and water, dried over anhydrous magnesium sulfate and the solvent was distilled off to obtain a crude product. This was treated with a toluene-silica gel column chromatograph and recrystallized with ethanol to obtain 1.80 g of the desired product. 2) 1,1,1-trifluoro-2-decyl 2'-
Synthesis of fluoro-4'-hydroxybenzoate

[Chemical 7] The compound obtained in 1) was dissolved in 15 ml of ethanol,
0.36 g of 10% supported Pd-carbon was added and hydrogenation reaction was carried out in a hydrogen atmosphere to obtain 1.40 g of the target compound. 3) Synthesis of 4-n-decanoyloxybenzoic acid

Embedded image 1.9 g of 4-hydroxybenzoic acid and 1.4 g of triethylamine are dissolved in 40 ml of dichloromethane. Decanoyl chloride (2.7 g) and dimethylaminopyridine (0.2 g) were added, and the mixture was stirred at room temperature for about 20 hours. Dilute hydrochloric acid is added, and the organic layer is separated with a separating funnel. The solvent is distilled off, the residue is washed with n-hexane and then dried to obtain about 2.7 g of the desired compound. 4) Synthesis of 3-fluoro-4- (1,1,1-trifluoro-2-decyloxycarbonyl) phenyl 4-n-decanoyloxybenzoate

[Chemical 9] 4-n-decanoyloxybenzoic acid 0.28 obtained in 3)
g and 0.32 g of 1,1,1-trifluoro-2-decyl 2'-fluoro-4'-hydroxybenzoate obtained in 2) are dissolved in about 30 ml of tetrahydrofuran. Add 0.25 g of dicyclohexylcarbodiimide and 0.02 g of dimethylaminopyridine, and stir at room temperature for about 20 hours. After distilling off the solvent, the residue is dissolved in dichloromethane and washed with water. The organic layer is dried over anhydrous magnesium sulfate and the solvent is distilled off. The residue is purified by silica gel column chromatography (developing solvent: hexane / ethyl acetate = 20/1) to obtain 0.20 g of the desired compound. The following phase transition temperature (° C.) was obtained by observing the hot stage with a polarizing microscope.

[Table 1] Here, S * (3) is a phase showing a tristable state.

Example 2 1) 1,1,1-trifluoro-2-octyl 2 '
-Fluoro-4'-hydroxybenzoate synthesis

[Chemical 10] The optically active 1,1,1-used in 1) of Example 1
Instead of 0.96 g of trifluoro-2-decanol,
A similar reaction is carried out using 0.95 g of 1,1,1-trifluoro-2-octyl alcohol. Obtained 1,
1,1-trifluoro-2-octyl 2'-fluoro-4'-benzyloxybenzoate was prepared in Example 1-2).
The product was hydrolyzed in the same manner as in (1) to give 1.38 g of the desired product. 2) 3-fluoro-4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 4-n-
Synthesis of decanoyloxybenzoate

[Chemical 11] 1,1,1-trifluoro-2 used in 4) of Example 1
Instead of 0.32 g of -decyl 2'-fluoro-4'-hydroxybenzoate 1, obtained in 1) of Example 2 1,
Using 0.35 g of 1,1-trifluoro-2-octyl 2'-fluoro-4'-hydroxybenzoate,
The same reaction and treatment are carried out to give the target compound 0.18
get g. The following phase transition temperature (° C) was obtained by observation with a polarizing microscope equipped with a hot stage.

[Table 2]

Example 3 1) 1,1,1-trifluoro-2-hexyl 2 '
-Fluoro-4'-hydroxybenzoate synthesis

[Chemical 12] The optically active 1,1,1-used in 1) of Example 1
Instead of 0.96 g of trifluoro-2-decanol,
1,1,1-trifluoro-2-hexanol 0.97
A similar reaction is carried out using g. The 1,1,1-trifluoro-2-hexyl 2′-fluoro-4′-benzyloxybenzoate thus obtained was hydrolyzed in the same manner as in 2) of Example 1 to obtain 1.40 g of the desired product. Obtained. 2) 3-fluoro-4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl 4-n-
Synthesis of decanoyloxybenzoate

[Chemical 13] 1,1,1-trifluoro-2 used in 4) of Example 1
Instead of 0.32 g of -decyl 2'-fluoro-4'-hydroxybenzoate 1, obtained in 1) of Example 3 1,
Using 0.30 g of 1,1-trifluoro-2-hexyl 2′-fluoro-4′-hydroxybenzoate,
After subjecting to the same reaction and treatment, the desired compound 0.16
get g. The following phase transition temperature (° C) was obtained by observation with a polarizing microscope equipped with a hot stage.

[Table 3]

Example 4 1) Synthesis of 2-octyl 2'-fluoro-4'-hydroxybenzoate

Embedded image The optically active 1,1,1-used in 1) of Example 1
Instead of 0.96 g of trifluoro-2-decanol,
A similar reaction is carried out using 0.65 g of optically active 2-octyl alcohol. The obtained 2-octyl 2'-fluoro-4'-benzyloxybenzoate was hydrolyzed in the same manner as in 2) of Example 1 to give 0.82 g of the desired product.
I got 2) Synthesis of 3-fluoro-4- (2-octyloxycarbonyl) phenyl 4-n-decanoyloxybenzoate

[Chemical 15] 1,1,1-trifluoro-2 used in 4) of Example 1
A similar reaction using 0.32 g of 2-decyl 2'-fluoro-4'-hydroxybenzoate instead of 0.22 g of 2-octyl 2'-fluoro-4'-hydroxybenzoate obtained in 1) of Example 4. And treated to give 0.11 g of the desired compound. The following phase transition temperature (° C) was obtained by observation with a polarizing microscope equipped with a hot stage.

[Table 4]

Example 5 1) Synthesis of 2-hexyl 2'-fluoro-4'-hydroxybenzoate

Embedded image The optically active 1,1,1-used in 1) of Example 1
Instead of 0.96 g of trifluoro-2-decanol,
A similar reaction is carried out using 0.55 g of optically active 2-hexanol. Obtained 2-hexyl 2'-fluoro-
4'-Benzyloxybenzoate was hydrolyzed in the same manner as in Example 1, 2) to obtain 0.71 g of the desired product. 2) Synthesis of 3-fluoro-4- (2-hexyloxycarbonyl) phenyl 4-n-decanoyloxybenzoate

[Chemical 17] 1,1,1-trifluoro-2 used in 4) of Example 1
A similar reaction using 0.22 g of 2-hexyl 2'-fluoro-4'-hydroxybenzoate obtained in 1) of Example 5 instead of 0.32 g of decyl 2'-fluoro-4'-hydroxybenzoate. And treated to give 0.10 g of the desired compound. The following phase transition temperature (° C) was obtained by observation with a polarizing microscope equipped with a hot stage.

[Table 5]

Example 6 1) Synthesis of 4-n-undecanoyloxybenzoic acid

Embedded image Instead of 2.7 g of decanoyl chloride used in 3) of Example 1, 2.9 g of undecanoyl chloride was used to obtain about 2.7 g of the target compound by the same procedure. 2) Synthesis of 3-fluoro-4- (1,1,1-trifluoro-2-decyloxycarbonyl) phenyl 4-undecanoyloxybenzoate

Embedded image In place of 0.28 g of 4-n-decanoyloxybenzoic acid used in 4) of Example 1, 4-n-undecanoyloxybenzoic acid obtained in 1) of Example 6 was used.
The target compound 0.21 was prepared in the same manner using 3 g.
get g. The following phase transition temperature (° C.) was obtained by observing with a polarization microscope using a hot stage.

[Table 6]

Example 7 1) Synthesis of 3-fluoro-4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 4-undecanoyloxybenzoate

Embedded image 1,1,1-trifluoro-2-decyl 2'-fluoro-4'-hydroxybenzoate used in 4) of Example 1 was replaced by 0.32 g of 1,1, obtained in 1) of Example 2. 0.30 g of 1-trifluoro-2-octyl 2'-fluoro-4'-hydroxybenzoate was used, and instead of 0.28 g of 4-n-decanoyloxybenzoic acid used in 4) of Example 1 4-n-undecanoyloxybenzoic acid obtained in 1) of Example 6
Using 30 g, the target compound 0.2
0 g are obtained. The following phase transition temperature (° C.) was obtained by observing with a polarization microscope using a hot stage.

[Table 7]

Example 8 1) Synthesis of 3-fluoro-4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl 4-undecanoyloxybenzoate

[Chemical 21] 1,1,1-trifluoro-2-decyl 2'-fluoro-4'-hydroxybenzoate used in 4) of Example 1 was replaced with 0.32 g of 1,1,1 obtained in 1) of Example 3. 0.29 g of 1-trifluoro-2-hexyl 2'-fluoro-4'-hydroxybenzoate was used, and instead of 0.28 g of 4-n-decanoyloxybenzoic acid used in 4) of Example 1 4-n-undecanoyloxybenzoic acid obtained in 1) of Example 6
Using 30 g, the target compound 0.1
8 g are obtained. The following phase transition temperature (° C.) was obtained by observing with a polarization microscope using a hot stage.

[Table 8]

Example 9 1) Synthesis of 3-fluoro-4- (2-octyloxycarbonyl) phenyl 4-undecanoyloxybenzoate

[Chemical formula 22] 2-Octyl 2 obtained in 1) of Example 4 instead of 0.32 g of 1,1,1-trifluoro-2-decyl 2'-fluoro-4'-hydroxybenzoate used in 4) of Example 1 0.22 g of'-fluoro-4'-hydroxybenzoate was used, and 0.28 of 4-n-decanoyloxybenzoic acid used in 4) of Example 1 was used.
By the same procedure, 0.31 g of 4-n-undecanoyloxybenzoic acid obtained in 1) of Example 6 was used in place of g to obtain 0.11 g of the desired compound. The following phase transition temperature (° C.) was obtained by observing with a polarization microscope using a hot stage.

[Table 9]

Example 10 Antiferroelectric liquid crystal composition 1 was prepared by mixing the compounds shown below in the ratios shown below.

[Chemical formula 23] Antiferroelectric liquid crystal compositions 1 were mixed with the compounds of Examples 2, 3 and 5 in the proportions shown below to prepare antiferroelectric liquid crystal compositions 2, 3 and 4.

[Chemical formula 24] The response speed of each composition is shown in FIG. The method of measuring the response speed will be described below.

Method for Measuring Response Speed A liquid crystal cell having a cell thickness of 2.0 μm and having a rubbing-treated polyimide alignment film on a transparent electrode substrate was filled with the liquid crystal compound or the liquid crystal composition obtained in Example in an isotropic phase. A liquid crystal thin film cell was prepared. The prepared liquid crystal cell was
1 to 1.0 ° C./min. The mixture was gradually cooled with a temperature gradient of 2 to deposit. This liquid crystal cell was placed in a polarizing microscope with a photomultiplier tube in which two polarizing plates were orthogonal to each other so as to provide a dark field at a voltage of 0V. When the liquid crystal is in the antiferroelectric phase, the relative transmittance of light when a triangular wave voltage of ± 40 V and 1 Hz is applied to the cell is plotted against the applied voltage as shown in FIG. As shown in the figure, it is characterized by having two hysteresis which are substantially symmetrical when a positive voltage is applied and when a negative voltage is applied. The response times τ, τr, τd can be obtained from the change in the relative transmittance of light when a ± 50 V rectangular wave as shown in FIG. 6 is applied to the cell. τ is from the ferroelectric phase state (specifically, at the end of the rectangular wave voltage on the negative side) to the next ferroelectric phase state (specifically when the rectangular wave voltage on the positive side is applied It is the time until the relative transmittance reaches 90%). τr is the time from the state of the antiferroelectric phase (specifically when a rectangular wave voltage is applied) to the state of the ferroelectric phase (specifically when the relative transmittance reaches 90%). Τd is the time from the state of the ferroelectric phase (specifically, when the rectangular wave voltage ends) to the state of the antiferroelectric phase (specifically, when the relative transmittance reaches 10%). .
The unit is μsec. Is. Response time τ, τr,
The short τd means that the response speed of the liquid crystal is fast.

The embodiments of the present invention are listed below. 1. General formula [I]

[Chemical 25] (Wherein, m = 4 to 14, n = 4 to 12, Cf = CH ₃ or CF ₃ , and * represents an optically active center). An antiferroelectric liquid crystal compound that exhibits a stable state. 2. General formula (II)

[Chemical formula 26] (In the formula, m = 4 to 14, n = 4 to 12, and * represents an optically active center.) An antiferroelectric property exhibiting an optical tristable state, which is characterized by comprising a compound represented by the formula: Liquid crystal compound. 3. General formula (III)

[Chemical 27] (In the formula, m = 4 to 14, n = 4 to 12, and * represents an optically active center.) An antiferroelectric property exhibiting an optical tristable state, which is characterized by comprising a compound represented by the formula: Liquid crystal compound. 4. General formula (IV)

[Chemical 28] [Wherein, m = (8, 9, 10, 11, 12), n =
(4, 6, 8), and * indicates an optically active center. ] The antiferroelectric liquid crystal compound which shows the optical tristable state characterized by consisting of the compound represented by these. 5. General formula [V]

[Chemical 29] [Wherein, m = (8, 9, 10, 11, 12), n =
(4, 6, 8), and * indicates an optically active center. ] The antiferroelectric liquid crystal compound which shows the optical tristable state characterized by consisting of the compound represented by these. 6.

Embedded image (In the formula, * represents an optically active center.) An antiferroelectric liquid crystal compound exhibiting an optically tristable state, which is characterized by comprising a compound represented by the formula. 7.

[Chemical 31] (In the formula, * represents an optically active center.) An antiferroelectric liquid crystal compound exhibiting an optically tristable state, which is characterized by comprising a compound represented by the formula. 8.

Embedded image (In the formula, * represents an optically active center.) An antiferroelectric liquid crystal compound exhibiting an optically tristable state, which is characterized by comprising a compound represented by the formula. 9.

[Chemical 33] (In the formula, * represents an optically active center.) An antiferroelectric liquid crystal compound exhibiting an optically tristable state, which is characterized by comprising a compound represented by the formula. 10.

Embedded image (In the formula, * represents an optically active center.) An antiferroelectric liquid crystal compound exhibiting an optically tristable state, which is characterized by comprising a compound represented by the formula. 11. A liquid crystal composition comprising one or more antiferroelectric liquid crystal compounds described in 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0020]

[Effect] According to the present invention, a novel antiferroelectric liquid crystal compound exhibiting an antiferroelectric phase at or near room temperature can be provided. It was possible to improve the response speed of the liquid crystal composition by adding the liquid crystal compound of the present invention as one component of the liquid crystal composition.

[Brief description of drawings]

FIG. 1A is an applied triangular wave, B is a commercially available nematic liquid crystal, C is a two-state liquid crystal, and D is a three-stable state liquid crystal.
The respective optical response characteristics are shown.

FIG. 2 shows two stable alignment states of a ferroelectric liquid crystal molecule proposed by Clark / Ragawell.

FIG. 3A shows three stable alignment states of the “anti” ferroelectric liquid crystal molecule of the present invention. B is each (a) of A,
The three-state switching corresponding to (b) and (c) and the change of the liquid crystal molecular alignment are shown.

FIG. 4 is an applied voltage-light transmittance characteristic diagram showing that the “anti” ferroelectric liquid crystal molecule draws double hysteresis with respect to the applied voltage and the light transmittance changes.

FIG. 5 shows a model of a hysteresis curve of relative transmittance with respect to a triangular wave applied voltage.

FIG. 6A shows the relationship between applied voltage and time, and FIG.
Is a graph showing the response state of liquid crystal molecules when the applied voltage is applied.

7 is a graph showing the relationship between temperature and response speed of compositions 1, 2, 3 and 4 of Example 10. FIG.

Claims (4)

[Claims] 1. A compound of the general formula [I] (Wherein, m = 4 to 14, n = 4 to 12, Cf = CH ₃ or CF ₃ , and * represents an optically active center). An antiferroelectric liquid crystal compound that exhibits a stable state. 2. A compound represented by the general formula [II]: (In the formula, m = 4 to 14, n = 4 to 12, and * represents an optically active center.) An antiferroelectric property exhibiting an optical tristable state, which is characterized by comprising a compound represented by the formula: Liquid crystal compound. 3. A compound represented by the general formula [III]: (In the formula, m = 4 to 14, n = 4 to 12, and * represents an optically active center.) An antiferroelectric property exhibiting an optical tristable state, which is characterized by comprising a compound represented by the formula: Liquid crystal compound. 4. A liquid crystal composition comprising one or more antiferroelectric liquid crystal compounds according to claim 1, 2 or 3.