JPH05331107A - Antiferroelectric liquid crystal compound - Google Patents

Abstract

PURPOSE:To obtain a new compound, capable of stably exhibiting an antiferroelectric S*(3) phase showing the tristable state in a low-temperature region including ambient temperature, providing expectable high-speed response and further extremely effectively useful as a component liquid crystal constituting an antiferroelectric mixed liquid crystal. CONSTITUTION:The objective compound of formulas I to III (R<1> and R<2> are 4-18C alkyl; Rf is CF3 or C2F5; X is O, COO, CO or single bond; * indicates optically active carbon), e.g. 4-n-octyloxy-2',3'-difluoro-4''-(1,1,1-trifluoro-2- octyloxycarbonyl)-p-terphenyl. The compound of formula II in which X is O is obtained by subjecting a boronic acid of formula IV derived from a 4- alkoxy-1-bromobenzene and 2,3-difluorophenylboronic acid and 4- bromobenzonitrile to coupling reaction, converting the nitrile group in the resultant compound of formula V into carboxyl group by hydrolysis, further converting the carboxyl group into an acid chloride, providing a compound of formula VI and then reacting the prepared compound with an optically active alcohol of formula VII.

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 into practical use. However, a nematic liquid crystal that is widely used at present has a response speed of several mse.
It has a drawback that it is as slow as c to several tens of msec, and is subject to various restrictions in application. In order to solve these problems, an STN method and an active matrix method using a thin layer transistor have 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. Therefore, 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 as short as μsec. Ferroelectric liquid crystal has 1
In 975, DOBAMBC (p-decyloxybenzylidene-p-amino-2-methylbutyl cinnamate) was first synthesized by Meyor et al. (Le Jour).
nal de Physique, vol. 36, 1975, L
-69). In addition, 1980, Clark and Laga
Since the characteristics of display devices such as sub-microsecond high-speed response of DOBAMBC and memory characteristics have been reported by WALL, ferroelectric liquid crystals have attracted great attention [N. A. Clark, et al. , Appl. P
hys. Lett. 36.899 (1980)]. However, their method has many technical problems for practical use, and in particular, there is no material that exhibits ferroelectric liquid crystal at room temperature, and it is effective and practical for the alignment control of liquid crystal molecules, which is indispensable for display display. The method was not established either. Since this report, various attempts have been made from both sides of liquid crystal materials / devices, and a display device utilizing switching between twisted two states has been prototyped. 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 .; Hagiwara, Y. S
uzuki et al. , Japan. J. ofApp
l. Phys. , 27, (5), L729-L732
(1988)]. The above-mentioned “having three states” means a liquid crystal electro-optical device in which a ferroelectric liquid crystal is sandwiched between a first electrode substrate and a second electrode substrate which is arranged with a predetermined gap. A voltage for forming an electric field is applied to the first and second electrode substrates, and when a voltage is applied as the triangular wave shown in FIG. 1A, the ferroelectric liquid crystal is not present as shown in FIG. 1D. The molecular orientation has a first stable state (in FIG. 1D) when an electric field is applied, and the second stable state (FIG. 1D) in which the molecular orientation is different from the first stable state in one electric field direction when an electric field is applied. , And further has a third molecular orientation stable state (in FIG. 1D) different from the first and second stable states with respect to the other electric field direction. Regarding the liquid crystal electro-optical device utilizing the tri-stable state, that is, the tri-state, the applicant of the present application filed as Japanese Patent Application No. 63-70212 and disclosed in Japanese Patent Laid-Open No. 2-153.
It is published as No. 322. The characteristics of the antiferroelectric liquid crystal exhibiting the tristable state will be described in more detail. Clerk/
In the surface-stabilized ferroelectric liquid crystal device proposed by Clark-Lagawall, the ferroelectric liquid crystal molecules are uniformly aligned in one direction as shown in FIGS. 2 (a) and 2 (b) in the S * C phase. It shows one of two stable states, and is stabilized in either one of the states depending on the direction of the applied electric field, 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. In 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, "anti" ferroelectric liquid crystal shows tri-stable state S *
In the phase (3), in the liquid crystal electro-optical device, when there is no electric field, the molecules in each adjacent layer are tilted in opposite directions and antiparallel to each other as shown in FIG. They 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 shown in FIGS. 3B and 3C are tilted in the same direction and arranged in parallel. 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.
That is, in the S * (3) phase of the “anti” ferroelectric liquid crystal, the “anti” ferroelectric phase when there is no electric field and the two ferroelectric phases depending on the polarity of the applied electric field are stable, and the “anti” ferroelectric liquid crystal is stable. Switching between the three stable states is performed with a DC threshold value between the phase and the two ferroelectric phases. Due to the change in the liquid crystal molecule alignment accompanying this switching, the light transmittance changes with the double hysteresis shown in FIG. A memory effect can be realized by applying a bias voltage to the double hysteresis as shown in FIG. 4A and further superimposing a pulse voltage. Further, by applying an electric field, the layer of the ferroelectric phase is stretched to form a Bookshelf structure. On the other hand, in the "anti" ferroelectric phase in the third stable state, a similar Bookshelf structure occurs. 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. In the "anti" ferroelectric liquid crystal, since the image display is performed by alternately using the hysteresis on both the plus side and the minus side, it is possible to prevent the afterimage phenomenon of the image due to the accumulation of the internal electric field due to the spontaneous polarization. As mentioned above,
“Anti” ferroelectric liquid crystal is a very useful liquid crystal compound that can achieve 1) fast response, 2) high contrast and wide viewing angle, and 3) good alignment characteristics and memory effect. Regarding the liquid crystal phase showing the tristable state of the "anti" ferroelectric liquid crystal, 1) A. D. L. Chandani e
tal., Japan J. Appl. Phys., 2
8 , L-1265 (1989), 2) H.M. Orihar
a et al., Japan J. Appl. Phys.,
29 , L-333 (1990),
S * CA phase (Antifer)
roelectricSticic C * phase). The present inventors defined this liquid crystal phase as the S * (3) phase because it switches between tristable states. A liquid crystal compound having an "anti" ferroelectric phase S * (3) showing a tristable state in a phase series is disclosed in Japanese Patent Application Laid-Open No. 1-3163 of the present application.
67, JP-A-1-316372, and JP-A-1-316.
No. 339, No. 2-28128, and No. 1-213390 of Ichihashi et al., And the applicant of the present invention discloses a liquid crystal electro-optical device utilizing a tristable state.
No. 0625, JP-A-2-153322, and JP-A2-1.
A new proposal is made in No. 73724. "Anti"
When applying ferroelectric liquid crystals to liquid crystal displays, 1)
It is difficult to satisfy all of the operating temperature range, 2) response speed, 3) spontaneous polarization, 4) hysteresis characteristics, etc. with a single liquid crystal, and it is usually prepared as a dozen or more kinds of mixed liquid crystals. In particular, in the operating temperature range of 1), it is desired to develop an "anti" ferroelectric liquid crystal that exhibits stable display operating characteristics in a lower temperature range including room temperature. However, in the low temperature region including room temperature, the "anti" ferroelectric S * (3) phase is stably developed,
Moreover, "anti" ferroelectric liquid crystal which shows high-speed response has not been found yet.

[0003]

The object of the present invention is to provide an antiferroelectric S * (3) which exhibits a tristable state in a low temperature region including room temperature.
The point is to provide a compound that exhibits a stable phase and is expected to have a high-speed response, and is very effective as a component liquid crystal that constitutes an antiferroelectric mixed liquid crystal.

[0004]

The first aspect of the present invention is to provide a general formula

[Chemical 7] (In the formula, R ¹ and R ² are independently selected from the group consisting of alkyl groups having 4 to 18 carbon atoms, Rf is —CF ₃ or —C ₂ F ₅ , X is O, COO, CO or a single bond. * Represents an optically active carbon.) With respect to an antiferroelectric liquid crystal compound. The second of the present invention is the general formula

[Chemical 8] (Wherein R ¹ , R ² , Rf, X and * are the same as above), and relates to the antiferroelectric liquid crystal compound. The third of the present invention is the general formula

[Chemical 9] (Wherein R ¹ , R ² , Rf, X and * are the same as above), and relates to the antiferroelectric liquid crystal compound.

The first preferred group of compounds of the present invention is represented by the general formula

[Chemical 10] An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above) can be mentioned. A second preferred compound group of the present invention is represented by the general formula:

[Chemical 11] An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above) can be mentioned. As a third preferred compound group of the present invention, a compound represented by the general formula

[Chemical formula 12] An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above) can be mentioned.

The compounds of the present invention are commercially available from N.I. Miyaura et al. [Synth. Commun., 11, 513 (198
It can be produced by combining the known synthesis means of 1)]. That is, the compound-1 in the following reaction formula was synthesized by a coupling reaction between 4-alkyl or 4-alkoxy-1-bromobenzene and 2,3-difluorophenylboronic acid to synthesize compound-1 and further lithiated [ Compound-1], boronic acid [Compound-
1] is subjected to a coupling reaction with 4-bromobenzonitrile to synthesize compound-1 and then converted to a carboxyl group by hydrolysis of the nitrile group, and then acid chloride [compound- 1],
It can be synthesized by performing an ester reaction with an optically active alcohol such as 1,1,1-trifluoromethyl-2-alkanol. In addition, the compound-2 shown in Synthesis Method Example 2 described below is prepared by synthesizing the compound-2 using lithium difluorobenzene as a starting material by addition reaction to an alkyl aldehyde, dehydration reaction and reduction reaction.
It can be synthesized by the same operation as the following compound by deriving boronic acid [-2], performing a coupling reaction with 4-bromo-4'-cyanobiphenyl, and then converting a cyano group into a carboxyl group. .. Further, Compound-3 shown in Synthesis Method Example 3 to be described later was prepared by using o-fluoroanisole as a starting material to induce boronic acid, a coupling reaction, a hydrolysis reaction, and an optically active 1,1,1- It can be synthesized by an esterification reaction with trifluoro-2-alkanol. (Below margin)

[0007]

[Chemical 13]

[0008]

[Chemical 14]

[0009]

[Chemical 15]

[0010]

Example 1

[Chemical 16] 4-n-octyloxy-2,3-difluoro-4 ″-
Synthesis of (1,1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl

[Chemical 17] 7.5 g of o-difluorobenzene was dissolved in 80 ml of dry tetrahydrofuran (THF), and then -7 in a nitrogen stream.
After cooling to 0 ° C, 42 ml of butyllithium (1.6 mol / l hexane solution) was added dropwise at -55 ° C or lower. After continuing stirring at the same temperature for 1.5 hours, a THF solution containing 24.8 g of triisopropyl borate was -65 to -60.
Dropwise at ° C. After completion of dropping, stirring was continued for 12 hours at room temperature, 60 ml of 10% hydrochloric acid aqueous solution was further added, and stirring was continued for 1 hour. The reaction mixture was extracted with ether, washed with water and dried, and then the solvent was distilled off under reduced pressure to obtain 9.0 g of 2,3-difluorophenylboronic acid. This 9.0 g was dissolved in 60 ml of ether, and 60 ml of 10% hydrogen peroxide solution was added dropwise with heating under reflux. After completion of dropping, heating and refluxing were continued for another 2 hours. The ether layer is separated, washed with water and dried, and the solvent is distilled off under reduced pressure.
7.1 g of 3-difluorophenol was obtained. 2,3-difluoro-phenol 8.1g was dissolved in acetone 100ml, K ₂ CO ₃ 17g and n- octyl bromide 1
After adding 2.0 g and heating and refluxing for 8 hours, acetone was distilled off under reduced pressure. 100 ml of ether was added to the residue for extraction, the insoluble matter was filtered off, washed with 10% aqueous NaOH solution and water, and the solvent was distilled off under reduced pressure to obtain 15 g of a crude product. This is purified by silica gel column chromatography,
12.1 g of 2,3-difluoro-1-n-octyloxybenzene was obtained.

[Chemical 18] 12.1 g of the compound synthesized in [1] was dried with 60 m of THF.
It was dissolved in 1 l, cooled to -70 ° C under a nitrogen stream, 32 ml of butyllithium was added dropwise, and stirring was continued for 2 hours at the same temperature. Next, triisopropyl borate 1 at -60 ° C or lower
8.8 g of THF solution was added dropwise, and stirring was continued at room temperature for 12 hours. Further, 60 ml of 10% hydrochloric acid aqueous solution was added, and stirring was continued for 1 hour. The reaction mixture was extracted with ether, washed with water, dried and the solvent was distilled off under reduced pressure to obtain 13.2 g of 4-n-octyloxy-2,3-difluorophenylboronic acid.

[Chemical 19] 4-Bromo-4'-cyanobiphenyl 2.58 g, tetrakistriphenylphosphine palladium (O) 400
mg, benzene 36 ml, and Na ₂ CO ₃ aqueous solution ( ₂ mo
(1/1) 3.69 g of 4-n-octyloxy-2,3-difluorophenylboronic acid dissolved in 36 ml of the mixture was dissolved in 15 ml of ethanol and added. After heating and stirring for 12 hours, the mixture was cooled to 5 ° C. and the precipitated crystals were collected by filtration. The obtained crystal was purified by silica gel column chromatography and then recrystallized from methylene chloride hexane to obtain 2.95 g of 4-n-octyloxy-2,3-difluoro-4 ″ -cyano-p-terphenyl. It was

[Chemical 20] 2.46 g of the compound obtained in [3], 250 ml of ethanol
After heating and stirring KOH and 9 g for 72 hours, 10 g of acetic acid was further added and heating and stirring was continued for 2 hours. After cooling, the precipitated crystals were collected by filtration, washed with water and dried to give 2.38 g of 4-n-.
Octyloxy-2,3-difluoro-4 ″ -carboxyl-p-terphenyl was obtained.

[Chemical 21] 2.35 g of the compound obtained in [4], methylene chloride 2
0 ml, 3 ml SOCl ₂ and a few drops of dimethylformamide (DMF) were heated at 40 ° C. for 2 hours. After distilling off the solvent, it was dissolved in 30 ml of methylene chloride, and (R)-
1,1,1-Trifluoro-2-octanol 1.04
g, dimethylaminopyridine (DMAP) 0.69 g,
Triethylamine 0.58 g methylene chloride 30
It was dripped into the ml solution. After the dropping was completed, stirring was continued at room temperature for 4 hours. The obtained reaction solution is washed successively with diluted hydrochloric acid and water,
After the solvent was distilled off, the residue was purified by silica gel column chromatography and recrystallization to give 4-n-octyloxy-2,3.
-Difluoro-4 "-(1,1,1-trifluoro-2
-Octyloxycarbonyl) -p-terphenyl 1.
70 g was obtained.

[Table 1]

Example 2

[Chemical formula 22] 4-n-nonyloxy-2,3-difluoro-4 ″-
(1,1,1-Trifluoro-2-octyloxycarbonyl) -p-terphenyl Instead of the n-octyl bromide of [1] of Example 1,
Synthesis was carried out in exactly the same manner using n-nonyl bromide.

[Table 2]

Embodiment 3

[Chemical formula 23] 4-n-decyloxy-2,3-difluoro-4 ″-
(1,1,1-Trifluoro-2-octyloxycarbonyl) -p-terphenyl Instead of the n-octyl bromide of [1] of Example 1,
Synthesis was carried out in exactly the same manner using n-decyl bromide.

[Table 3]

Embodiment 4

[Chemical formula 24] 4-n-octyloxy-2 ', 3'-difluoro-
Synthesis of 4 "-(1,1,1-trifluoro-2-octyloxy) -p-terphenyl

[Chemical 25] 4-bromophenol 8.0 g, a n- octyl bromide and K ₂ CO ₃ 13 g was heated to reflux for 12 hours in acetone 100 ml. The solvent was evaporated under reduced pressure, isopropyl ether was added to the obtained residue for extraction, and the extract was washed with 5% NaOH aqueous solution and water successively. The solvent was distilled off under reduced pressure, the residue was purified by column chromatography, and then distilled to obtain 8.4 g of 4-.
Bromo-1-n-octyloxybenzene was obtained. This 4-bromo-1-n-octyloxybenzene 4.2
g, tetrakistriphenylphosphine palladium (O) 0.56 g, benzene 53 ml and Na ₂ CO ₃ aqueous solution (2 mol / l) 53 ml into a mixture.
A solution of 2,3-difluorophenylboronic acid (3.0 g) synthesized in the same manner as in [1] above in 26 ml of ethanol was added dropwise, and the mixture was heated under reflux for 5 hours. 200 ml of ether after cooling
Was added to extract the product, which was washed with water and dried, and then the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography to give 4-n-octyloxy-2 ', 3'.
2.8 g of difluorobiphenyl were obtained.

[Chemical formula 26] 4-n-octyloxy-2 ′, 3 ′ obtained in [1]
-2.72 g of difluorobiphenyl in 20 m of dry THF
It was dissolved in 1 l, cooled to -70 ° C under a nitrogen stream, and 5.5 ml of butyllithium (1.6 mol / l hexane solution) was added dropwise. Stirring was continued for 2 hours at the same temperature, and then a THF solution of 3.21 g of triisopropyl borate was added dropwise. After stirring for 12 hours at room temperature, 7.7 ml of 10% hydrochloric acid aqueous solution
Was added and the mixture was further stirred for 1 hour. [1] of Example 1 below
The same post-treatment was carried out to obtain 2.27 g of 4- (pn-octyloxy) phenyl-2,3-difluorobenzeneboronic acid.

[Chemical 27] 4-n-octyloxy-2 ′, 3′- was treated with 2.26 g of the compound obtained in [2] and 1.09 g of 4-bromobenzonitrile in the same manner as in [3] of Example 1. Difluoro-4 ″ -cyano-p-terphenyl 2.15 g
Got

[Chemical 28] The compound 2.15 g obtained in [3] was used as a starting material and treated in the same manner as in [5] of Example 1 to give 4-n-octyloxy-2 ′, 3′-difluoro-4 ″ -carboxyl- 1.88 g of p-terphenyl was obtained.

[Chemical 29] 4-n-octyloxy-2 ′, 3 ′ obtained in [4]
4-difluoro-4 ″ -carboxyl-p-terphenyl was treated as a starting material in the same manner as in [5] of Example 1 to give 4-n-octyloxy-2 ′,
1.64 g of 3′-difluoro-4 ″-(1,1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl was obtained. The phase transition point was measured by re-drying the compound with absolute ethanol. The crystals were used.

[Table 4]

Example 5

[Chemical 30] 4-n-nonyloxy-2 ', 3'-difluoro-4 "
-(1,1,1-Trifluoro-2-octyloxycarbonyl) -p-terphenyl Using n-nonyl bromide instead of n-octyl bromide of Example 1 [1], a completely similar method was performed. Was synthesized.

[Table 5]

Example 6

[Chemical 31] 4-n-decyloxy-2 ', 3'-difluoro-4 "
-(1,1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl Substituting the n-octyl bromide of [1] of Example 4,
It was synthesized in exactly the same manner using n-decyl bromide.

[Table 6]

Example 7

[Chemical 32] 4-n-octyloxy-3-fluoro-4 ″-(1,
1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl

[Chemical 33] To a solution of 50 g of o-fluoroanisole dissolved in 50 ml of carbon disulfide, a solution of 27 g of carbon disulfide and 63.8 g of bromine was gradually added dropwise at -5 ° C to 5 ° C with stirring for 1 hour. After completion of dropping, the mixture was further stirred at 5 ° C. for 30 minutes, 125 ml of water was added, and the mixture was extracted with chloroform. The chloroform layer was washed successively with Na ₂ S ₂ O ₃ and NaHCO ₃ aqueous solution, and then the solvent was distilled off under reduced pressure with an evaporator to give 4-bromo-2-fluoroanisole 70.
9 g was obtained. Next, 9.6 g of Mg was added to 230 ml of tetrahydrofuran, and 70.9 g of 4-bromo-2-fluoroanisole was gradually added dropwise to prepare a Grignard reagent. This is triisopropyl borate 12
To a mixture of 3.8 g and 391 ml of THF, -60
The solution was added dropwise with stirring at ℃ to -50 ℃. After dripping, after reacting for 2 hours at room temperature, 242 ml of 1N-HCl was added,
After reacting for an additional 1 hour, extract with ether, wash with water,
After concentration under reduced pressure, 46.2 g of 4-methoxy-3-fluorobenzeneboronic acid was obtained.

[Chemical 34] 4-bromo-4′-cyanobiphenyl 2.4 g, tetrakistriphenylphosphine Pd (O) 0.37 g, 2
A mixture of 15.2 ml of an aqueous solution of N sodium carbonate and 19.4 ml of benzene was added to 4-synthesized in (1).
A solution of 1.9 g of methoxy-3-fluoro-benzeneboronic acid dissolved in 14.4 ml of ethanol was gradually added dropwise with stirring, and the mixture was refluxed for 8 hours. After refluxing, the mixture was cooled and the precipitated crystals were filtered off, washed with water and methanol in this order, and dried to give 4-methoxy-3-fluoro-4 ″ -cyano-p-.
2.5 g of terphenyl was obtained.

[Chemical 35] 4-Methoxy-3-fluoro-4 ″ -obtained in [2]
2.5 g of cyano-p-terphenyl and 20 methylene chloride
0 ml was added, 8 g of BBr ₃ dissolved in 50 ml of methylene chloride was gradually added dropwise with stirring, and the mixture was stirred at room temperature for 1 hour.
Allowed to react overnight. Disperse this in 200 ml of water and add THF.
It was extracted with. After the solvent was distilled off under reduced pressure, it was recrystallized with a tetrahydrofuran-methanol mixed solvent to give 4-hydroxy-3-fluoro-4 ″ -cyano-p-terphenyl.2.
2 g was obtained. Then 4-hydroxy-3-fluoro-
A mixture of 1 g of 4 ″ -cyano-p-terphenyl, 0.77 g of n-octyl bromide, 0.55 g of K ₂ CO ₃ and 10 ml of dimethylformamide was mixed at 100 ° C. for 1 hour.
The reaction was carried out with stirring for an hour. After the reaction, the mixture was dispersed in 50 ml of water, extracted with ethyl acetate, washed with water, and then the solvent was distilled off under reduced pressure to obtain a solid product. This was recrystallized from methanol to synthesize 1.23 g of the desired compound.

[Chemical 36] 1.23 g of 4-n-octyloxy-3-fluoro-4 ″ -cyano-p-terphenyl, 4.5 g of KOH powder,
While stirring 123 ml of ethanol, mix 7
The mixture was refluxed for 2 hours, 4.7 g of acetic acid was added thereto, and the mixture was further refluxed for 2 hours. After refluxing, cooling and precipitating crystals were collected by filtration, washed with water and dried to give 4-n-octyloxy-3-fluoro-4 ″ -hydroxyl-p-terphenyl 1.2.
g was obtained.

[Chemical 37] 4-n-octyloxy-3-fluoro-obtained in [4]
A mixture of 1.2 g of 4 ″ -hydroxyl-p-terphenyl, 0.8 g of thionyl chloride, 20 ml of methylene chloride and a catalytic amount of dimethylformamide was refluxed at 40 ° C. for 2 hours, concentrated under reduced pressure after refluxing, and further concentrated in toluene. Then, unreacted thionyl chloride was distilled off azeotropically several times to obtain an acid chloride compound. (R)-(+)-1,1,1-trifluoro-2-
Octanol [α] D ²⁰ = + 25.6 (C = 0.9960, CHCl
₃ ) 0.45 g, dimethylaminopyridine (DMA
P) in a mixed solution of 0.3 g, triethylamine 0.26 g, and methylene chloride 20 ml, 20 m of the acid chloride form
The 1 methylene chloride solution was gradually added dropwise with stirring while cooling with ice water. Further, the reaction was carried out at room temperature overnight. The reaction solution was washed with dilute hydrochloric acid and water in this order, and the solvent was distilled off, followed by purification by silica gel chromatography and ethanol recrystallization.
-N-octyloxy-3-fluoro-4 "-(1,
1.7 g of 1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl was obtained. To measure the phase transition point, the compound was recrystallized from absolute ethanol and further purified before use.

[Table 7]

Example 8 4-n-nonyloxy-3-fluoro-4 "-(1,
1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl

[Chemical 38] N-Nonyl bromide was used in place of the n-octyl bromide of [3] of Example 7 for synthesis.

[Table 8]

Example 9 4-n-decyloxy-3-fluoro-4 "-(1,
1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl

[Chemical Formula 39] N-decyl bromide was used in place of the n-octyl bromide of [3] of Example 7 for synthesis in exactly the same manner.

[Table 9]

Comparative example

[Chemical 40] Synthesis of 4-n-octyloxy-4 ″-(1,1,1-trifluoro-2-octyloxycarbonyl) -p-terphenyl 4 ″ -n-octyloxyterphenyl-4-carboxylic acid 1.6 g Was heated under reflux with excess thionyl chloride for 6 hours, and then unreacted thionyl chloride was distilled off to give 4 ″ -n.
-Octyloxyterphenyl-4-carboxylic acid chloride was obtained. To a solution prepared by dissolving the acid chloride in 50 ml of methylene chloride, 0.7 g of 1,1,1-trifluoro-2-octanol, 0.4 g of triethylamine and 0.1 g of dimethylaminopyridine were dissolved in 50 ml of methylene chloride. The mixture was gradually added under ice cooling and reacted at room temperature all day and night. Then, the reaction solution was poured into ice water and extracted with methylene chloride. The methylene chloride phase was washed with dilute hydrochloric acid, water, an aqueous solution of sodium carbonate, and water in this order, dried over anhydrous sodium sulfate, and then the solvent was distilled off. The crude product was obtained. This was purified by silica gel chromatography to obtain 1.1 g of the optically active target compound. To measure the phase transition point, the compound was recrystallized from absolute ethanol and further purified before use. The phase transition temperature (° C.) of the target compound by observation with a polarizing microscope equipped with a hot stage is as follows.

[Table 10]

Example 10 A liquid crystal cell having a 1.9 μm cell thickness having a rubbing-treated polyimide alignment film on an ITO electrode substrate was filled with the liquid crystal compound obtained in Example 4 in an Isotropic phase to prepare a liquid crystal thin film cell. did. The prepared liquid crystal cell was placed in a polarizing microscope with a photomultiplier in which two polarizing plates are orthogonal to each other so as to have a dark field at a voltage of 0V. This liquid crystal cell is gradually cooled to the SA phase with a temperature gradient of 0.1 to 1.0 ° C./1 minute. Cool down further, 2
A pulse voltage of ± 30 V shown in FIG. 5 (A) is applied at 5 ° C. The response speeds obtained from the change in transmittance shown in FIG. 5B are τr, τd, and τ. The data of the compound of Example 4 is shown in FIG. 6, and the data of the compound of the comparative example is shown in FIG. 7.

[0021]

[Effect] The antiferroelectric liquid crystal compound of the present invention, in which at least one fluorine atom is substituted in the terphenyl skeleton, has an antiferroelectric S * (3) phase at a significantly lower temperature than the unsubstituted one. It became clear that it showed a high response speed.

[Brief description of drawings]

FIG. 1A shows optical response characteristics of an applied triangular wave, B is a commercially available nematic liquid crystal, C is a two-state liquid crystal, and D is a three-state liquid crystal.

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

FIG. 3 shows three stable alignment states of the “anti” ferroelectric liquid crystal molecule of the present invention.

FIG. 4 is an applied voltage-light transmittance characteristic diagram showing that “anti” ferroelectric liquid crystal molecules draw a double hysteresis corresponding to an applied voltage to change the light transmittance.

5A is a graph showing a relationship between an applied voltage and time, and FIG. 5B is a graph showing a response state of liquid crystal molecules when the applied voltage is applied.

FIG. 6 is a graph showing the relationship between the temperature and the response speed of the compound of Example 4.

FIG. 7 is a graph showing the relationship between temperature and response speed of the compound of Comparative Example.

Claims (6)

[Claims] 1. A general formula: (In the formula, R ¹ and R ² are independently selected from the group consisting of alkyl groups having 4 to 18 carbon atoms, Rf is —CF ₃ or —C ₂ F ₅ , X is O, An antiferroelectric liquid crystal compound represented by COO, CO or a single bond. * Represents optically active carbon. 2. A general formula: An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² , Rf, X and * are the same as above). 3. A general formula: An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² , Rf, X and * are the same as above). 4. A general formula: An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above). 5. A general formula: An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above). 6. A general formula: An antiferroelectric liquid crystal compound represented by the formula (wherein R ¹ , R ² and * are the same as above).