JPH0228631B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel liquid crystal compound and a liquid crystal composition containing the liquid crystal compound and suitable for use in liquid crystal display elements, liquid crystal light shutters, and the like. [Prior Art] Compounds containing optically active groups are attracting attention as liquid crystal compounds. The functions of compounds characterized by containing optically active groups include those that utilize the White-Taylor guest-host type electro-optical effect that utilizes a chiral nematic phase in the liquid crystal state, and those that utilize a chiral nematic phase to a nematic phase. Some of the known methods are those that utilize the phase transition phenomenon caused by an electric field, those that utilize the phase transition phenomenon that occurs due to heat between the chiral nematic phase and the smectic phase, and those that utilize the ferroelectric phenomenon of the smectic phase. Further, by forming a monomolecular cumulative film, it can be used as a nonlinear optical element, and by immobilizing it in a matrix, it can be used as an optical element such as a circularly polarized beam splitter or a filter. Therefore, research has been carried out to synthesize compounds containing optically active groups, examine their functions, and apply them to the various uses mentioned above. On the other hand, conventionally, liquid crystal display elements are well known in which a scanning electrode group and a signal electrode group are configured in a matrix, and a liquid crystal compound is filled between the electrodes to form a large number of pixels to display images or information. ing. The driving method for this display element is time-division driving, in which an address signal is selectively and periodically applied to a group of scanning electrodes, and a predetermined information signal is selectively applied in parallel to a group of signal electrodes in synchronization with the address signal. However, this display element and its driving method have major and fatal drawbacks as described below. That is, it is difficult to increase the pixel density or enlarge the screen. Among conventional liquid crystals, most of them have relatively high response speed and low power consumption, so most of them are in practical use as display elements.
Physics Letters” Vo.18, No.4 (1971, 2.15),
“Voltage―Dependent Optical” on P.127-128
Activity of a Twisted Nematic Liqid
This type of liquid crystal uses the TN (twisted nematic) type liquid crystal shown in ``Crystal'', in which the molecules of nematic liquid crystal, which has positive dielectric anisotropy, are twisted in the thickness direction of the liquid crystal layer in the absence of an electric field. On the other hand, when an electric field is applied, the nematic liquid crystal with positive dielectric anisotropy moves in the direction of the electric field. As a result, optical modulation can occur.When a display element is constructed with a matrix electrode structure using this type of liquid crystal, the region where both the scanning electrode and the signal electrode are selected (selection point)
, a voltage higher than the threshold required to align the liquid crystal molecules perpendicular to the electrode surface is applied, and no voltage is applied to areas where both the scanning electrode and the signal electrode are not selected (non-selected points), and therefore the liquid crystal The molecules maintain a stable alignment parallel to the electrode plane. By arranging linear polarizers above and below a liquid crystal cell in a cross-Nicol relationship with each other, light does not pass through selected points, but light passes through non-selected points, making it possible to use it as an image element. do. However, when a matrix electrode structure is configured, there is a possibility that the scan electrodes are selected and the signal electrodes are not selected, or the scan electrodes are not selected and the signal electrodes are selected (so-called "half-selected points"). The electric field becomes finite. If the difference between the voltage applied to the selected point and the voltage applied to the half-selected point is sufficiently large, and the voltage threshold required to align the liquid crystal molecules perpendicular to the electric field is set to an intermediate voltage value, the display element will It works normally, but if you increase the number of scanning lines (N), the time that an effective electric field is applied to one selected point while scanning the entire screen (1 frame) (duty ratio) decreases at a rate of 1/N. For this reason, when repeated scanning is performed, the effective voltage difference between selected points and non-selected points becomes smaller as the number of scanning lines increases, resulting in a decrease in image contrast and crosstalk. It has become an unavoidable drawback. This phenomenon is caused by liquid crystals that do not have bistability (the stable state is when the liquid crystal molecules are aligned horizontally with respect to the electrode surface, and they are aligned vertically only while an electric field is effectively applied). ) is essentially an unavoidable problem that arises when driving using the temporal accumulation effect (that is, repeatedly scanning). In order to improve this point, voltage averaging method, dual-frequency driving method, multiple matrix method, etc. have already been proposed, but all of these methods are insufficient, and it is necessary to increase the screen size and density of display elements. Currently, the number of scanning lines has reached a plateau due to the inability to increase the number of scanning lines sufficiently. On the other hand, looking at the field of printers, laser beam printers provide electrical image signals in the form of light to electrophotographic photoreceptors in terms of both pixel density and speed, as a means of obtaining hard copies using electrical signals as input. (LBP) is currently the best.
However, LBP has the following drawbacks: 1. The printer is large; 2. It has a high-speed moving part like a polygon scanner, which generates noise, and requires strict mechanical precision. In order to overcome these drawbacks, a liquid crystal shutter array has been proposed as an element that converts electrical signals into optical signals. However, when providing pixel signals using a liquid crystal shutter array, for example, in order to write pixel signals at a rate of 16 dots/mm within a length of 210 mm, it is necessary to have more than 3000 signal generating sections. In order to provide independent signals to each, it was originally necessary to wire lead wires to send signals to all of the signal generating parts, which was difficult to manufacture. For this reason, attempts have been made to provide pixel signals for one line in a time-division manner using a signal generating section divided into several lines. This is because the electrode for applying a signal can be shared by a plurality of signal generating sections, and the amount of wiring can be substantially reduced. However, if the number of lines (N) is increased by using a liquid crystal that does not have bistability, as is usually done in this case, the signal ON time becomes essentially 1/N, and the amount of time that can be obtained on the photoconductor is reduced. There are disadvantages in that the amount of light emitted is reduced and crosstalk problems occur. To improve the drawbacks of conventional liquid crystal devices, the use of bistable liquid crystal devices has been proposed by Clark and Lagerwall (Japanese Unexamined Patent Publication No. 107216/1983, U.S. Patent No.
4367924 specification, etc.). Bistable liquid crystals are generally chiral smectic C phase (SmC*).
H phase (SAH*), F phase (SmF*), I phase (SmI
*), a ferroelectric liquid crystal having a chiral smectate phase such as G phase (SmG*) is used. This liquid crystal has a bistable state consisting of a first optically stable state and a second optically stable state with respect to an electric field, and therefore, unlike the optical modulation element used in the above-mentioned TN type liquid crystal, for example, The liquid crystal is aligned in a first optically stable state with respect to one electric field vector, and the liquid crystal is aligned in a second optically stable state with respect to the other electric field vector. Furthermore, this type of liquid crystal has the property of very quickly taking one of the above two stable states in response to an applied electric field, and maintaining that state when no electric field is applied. By utilizing these properties, the detailed conventional TN
Significant substantial improvements can be made to many of the problems of type devices. Next, the operation of the ferroelectric liquid crystal will be explained using FIGS. 1 and 2. 1 and 1a in Figure 1
is In ₂ O ₃ , SnO ₂ or ITO (Indium-
A substrate (glass plate) coated with a transparent electrode made of a thin film such as TinOxide, etc., between which a liquid crystal molecular layer 2 is oriented perpendicular to the glass surface.
*Phase or SmH* liquid crystal is enclosed. A thick line 3 represents a liquid crystal molecule, and this liquid crystal molecule 3 has a dipole moment (P⊥) 4 in a direction perpendicular to the molecule. When a voltage above a certain threshold is applied between the electrodes on substrates 1 and 1a,
The orientation direction of the liquid crystal molecules 3 can be changed so that the helical structure of the liquid crystal molecules 3 is unraveled and all of the dipole moments (P⊥) 4 are directed in the direction of the electric field. The liquid crystal molecules 3 have an elongated shape and exhibit refractive index anisotropy in the long axis direction and the short axis direction. Therefore, for example, if crossed Nicol polarizers are placed above and below the glass surface, voltage can be applied. It is easily understood that this results in a liquid crystal optical modulation element whose optical properties change depending on the polarity. The liquid crystal cell preferably used therein can have a sufficiently thin thickness (for example, 10 μm or less). As the liquid crystal layer becomes thinner, the helical structure of the liquid crystal molecules unwinds and becomes a non-helical structure even when no electric field is applied, as shown in Figure 2, and its dipole moment P or Pa
takes either an upward direction 5 or a downward direction 5a. When an electric field E or Ea of different polarity above a certain threshold value is applied to such a cell by the voltage applying means 6 and 6a as shown in FIG. 2, the dipole moment corresponds to the electric field vector of the electric field E or Ea. The liquid crystal molecules are oriented either in the first stable state 7 or in the second stable state 7a accordingly. As mentioned earlier, there are two advantages to using such ferroelectricity as an optical modulation element. The first is that the response speed is extremely fast, and the second is that the response speed is extremely fast.
is that the orientation of liquid crystal molecules has bistability. To further explain the second point, for example, with reference to FIG. 2, when an electric field E is applied, the liquid crystal molecules are oriented in a first stable state 7, and this state remains stable even when the electric field is turned off. Furthermore, when an electric field Ea in the opposite direction is applied, the liquid crystal molecules are oriented to the second stable state 7a and change their orientation, but they remain in this state even after the electric field is turned off. Further, as long as the applied electric field E does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such fast response speed and bistability, it is preferable that the cell be as thin as possible. Specific examples of the above-mentioned liquid crystal compounds exhibiting ferroelectricity include p-decyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC) and p-hexyloxybenzylidene-p'-amino-2-chloro. Examples include propyl cinnamate (HOBACPC), 4-D-(2-methyl)-butylresolcylidene-4'-octylaniline (MBRA 8), and the like. However, when this compound is repeatedly energized as a liquid crystal element, it tends to deteriorate, and care must be taken in terms of cell airtightness, sealing conditions, operating conditions, etc., and this is a major difficulty in the development of liquid crystal elements. On the other hand, although searches have been made for stable liquid crystal compounds, no one that satisfies high-speed response and stability and has been put to practical use has yet to be found. [Problems to be Solved by the Invention] The present invention provides a novel liquid crystal compound containing an optically active group that is effective for the various uses listed above, and a method for incorporating the new compound into a ferroelectric liquid crystal. This invention was developed in order to provide a liquid crystal composition that has excellent operating life characteristics, fast response speed, and excellent bistability, and is suitable for use in liquid crystal display elements, liquid crystal shutters, etc. . [Means and effects for solving the problems] According to the present invention, (1) General formula (): (In the formula, R represents an alkyl group having 6 to 12 carbon atoms,
* indicates an asymmetric carbon atom) A ferroelectric liquid crystal composition containing at least one compound represented by the following as a compounding component. If the chain length of the alkyl group R in the general formula () is too short, there is a drawback that it lacks stability when mixed into a ferroelectric liquid crystal, resulting in a high phase transition temperature.On the other hand, if the chain length is too long, There are drawbacks of increased melting point and increased viscosity, and in view of the balance, the number of carbon atoms in the alkyl group R is preferably 4 to 20, more preferably 6 to 16, particularly preferably 6.
~12. Preferred specific examples of 4-(β-methylbutyloxy)-4′-alkylazobenzene represented by the above general formula () include S-(+)-4-(β
-Methylbutyloxy)-4'-pentyl azobenzene, S-(+)-4-(β-methylbutyloxy)-4'-octyl azobenzene, S-(+)-
4-(β-methylbutyloxy)-4′-nonylazobenzene, S-(+)-4(β-methylbutyloxy)-4′-decylazobenzene, S-(+)
Examples thereof include -4-(β-methylbutyloxy)-4'-undecylazobenzene and S-(+)-4-(β-methylbutyloxy)-4'-dodecylazobenzene. Next, a method for producing the novel liquid crystal compound of the present invention will be described. First, p-alkylaniline is added dropwise to an aqueous solution of hydrochloric acid under cooling to form a hydrochloride. Next, a sodium nitrite aqueous solution is added dropwise to form a diazonium salt. This diazonium salt aqueous solution is added dropwise to phenol under alkaline conditions to synthesize 4'-alkyl-4-hydroxyazobenzene. After purifying 4'-alkyl-4-hydroxyazobenzene, it is reacted with excess potassium hydroxide and then with optically active 2'-methylbutyl bromide to obtain the desired compound. The chemical formula for the above is as follows. 4-(β-methylbutyloxy)- of the present invention
4'-Alkylazoxybenzene is an optically active substance and mainly exhibits a cholesteric phase. A small amount of the compound of the present invention can be added to a nematic liquid crystal to obtain a liquid crystal composition for use in a White-Taylor type display element or a phase transition type display element from a chiral nematic phase to a nematic phase.
It can be added to liquid crystal compositions used in TN display elements to prevent the occurrence of reverse domains. Further, as the liquid crystal compound used in the liquid crystal composition containing the compound represented by the general formula () of the present invention and having ferroelectric properties, Smectic C
A liquid crystal compound having a phase, preferably SmC* or a ferroelectric liquid crystal compound having a chiral smectoid phase is used. Next, the liquid crystal composition of the present invention will be explained. Specific examples of ferroelectric liquid crystal compounds used in the liquid crystal composition of the present invention are listed below. Schiff base type ferroelectric liquid crystal compound: (1) DOBAMBC (p-decyloxybenzylidene p'-amino-2-methylbutyl cinnate) (Compounds in this family having an alkoxy group with the number of carbon atoms ranging from p-hexyloxy to p-decyloxy have ferroelectric properties and can be used in the composition of the present invention.) (2) DOBAMBCC (p-decyloxybenzylidene p '-amino-2-methylbutyl α1-cyanocinnamate) (Compounds in this series in which p-decyloxy group is replaced with p-tetradecyloxy group are also ferroelectric.) (3) OOBAMBCC (p-octyloxybenzylidene p'-amino-2-aminomethylbutyl- α
-chlorocinnamate) (4) HOBACPC (p-hexyloxybenzylidene p'-amino-2-chloro-α-propylcinnamate) (Compounds in this series that have an alkyl group with the number of carbon atoms from p-hexyloxy to p-dodecyloxy are ferroelectric.) (5) OOBAMBMC (p-octyloxybenzylidene p'-amino-2-methylbutyl- α-methyl cinnamate) (6) DOBMBA [p-decyloxybenzylidene
p′-(2-methylbutyloxycarbonyl)aniline] (In this system, compounds having an alkoxy group with the number of carbon atoms of p-heptyloxy to p-tetradecyloxy are ferroelectric.) Ester-type ferroelectric liquid crystal compounds: (1) 4-n-hexyloxyph Enil 4-(2″-
Methylbutyl)biphenyl-4'-carboxylate (2) 4-(2'-methylbutyl)phenyl 4'-octylbiphenyl-4-carboxylate (3) 4-(2'-methylbutyloxy)phenyl
4'-dodecyloxyphenyl-4-carboxylate (Compounds in which the above 2'-methylbutyloxy group is replaced with a 4'-nonyloxy group also exhibit ferroelectricity.) Azoxy-type ferroelectric liquid crystal compounds: (1) PACMB (p-azoxycinnamate methyl 2-butanol) In the composition of the present invention, two or more of the ferroelectric liquid crystal compound and the compound represented by the general formula () may be used as a mixture. In the composition of the present invention, 4 parts represented by the general formula () is added to 100 parts by weight of the ferroelectric liquid crystal compound.
0.01 to 100 parts by weight of -(β-methylbutyloxy)-4'-alkylazobenzene is blended. 0.01
If the amount is less than 100 parts by weight, the effect of extending the operating life will not be exhibited, and if it exceeds 100 parts by weight, the ferroelectric liquid crystal will be diluted and its properties as a ferroelectric liquid crystal will deteriorate. [Example] Next, the present invention will be explained with reference to Examples. In addition, in the following examples, the phase transition temperature is
Measurement was performed using DSC (Seiko Electronics SSC 580 DS), and confirmation was made by inserting a liquid crystal sealed in a glass plate in a temperature-controlled copper block and observing it with a polarizing microscope. Example 1 [Production of S-(+)-4-(β-methylbutyloxy)4'-heptyl azobenzene] 32.9 g (0.17 M) of 4-heptylaniline was heated to 0°C.
After cooling, 85 g of a 10% aqueous hydrochloric acid solution was added, and then 12.1 g of sodium nitrite dissolved in 70 ml of water was added. During the dropping, the solution was cooled so that the temperature did not exceed 0°C. After the dropwise addition was completed, the mixture was allowed to react for 30 minutes and then transferred to a dropping funnel.8% containing 16g of phenol was added.
It was added dropwise to 300 ml of NaOH aqueous solution. The temperature was kept below 5°C during the dropping. After the dropwise addition was completed, stirring was continued for 1 hour, and then 10% aqueous hydrochloric acid solution was added until the pH reached 5 to 6 to precipitate the reaction product. The precipitate was separated, washed with water, and then dried under reduced pressure overnight. Petroleum ether 500 after drying
ml and further dried under reduced pressure to give 34.7g.
(1.12M) of 4-hydroxy 4'-heptyl azobenzene was obtained. The yield was 71%. 4-Hydroxy 4'-heptyl azobenzene 10g
(0.013M) with 4.4g potassium hydroxide 20
It was dissolved in 1 ml of ethanol and heated under reflux for 6 hours. Next, 10 g of S-(+)-2-methylbutyl bromide was added and the mixture was heated under reflux for 12 hours. After the reaction was completed, the mixture was filtered and the solvent was distilled off. The residue was dissolved in benzene and subjected to column chromatography on silica gel. Benzene was distilled off and dried under reduced pressure to obtain 5.0g (0.14M) of S-(+).
4-(β-methylbutyloxy)4'-heptyl azobenzene was obtained. The yield was 41%. The IR, NMR data, and phase transition temperature of this compound are shown below. IR:-N=N-1600cm ^-1 ;Ar-O-CH ₂ 1240
cm ^-1 NMR (δppm): Ar-C H ₂ -2.6 (t) 0.8-2.0 Methyl, methylene Ar-O-C H ₂ -3.7 (q) Ar 6.7 - 7.9 Phase transition temperature: Cryst27℃ 8℃Ch35℃ 33°C Iso Each abbreviation has the following meaning (the same applies to subsequent examples). Cryst: Crystal Ch: Cholesteric phase Iso: Isotropic liquid Example 2 [Production of S-(+)-4-(β-methylbutyloxy)4'-hexylazobenzene] 4-hexylaniline 30.1g (0.17M) 0℃
After cooling, 85 g of a 10% aqueous hydrochloric acid solution was added, and then 11.6 g of sodium nitrite dissolved in 68 g of water was added. During the dropping, the solution was cooled so that the temperature did not exceed 0°C. After the dropwise addition was completed, the mixture was allowed to react for 30 minutes and then transferred to a dropping funnel.8% containing 16g of phenol was added.
It was added dropwise to 170 g of NaOH aqueous solution. The temperature was kept below 5°C during the dropping. After the dropwise addition was completed, stirring was continued for 0.5 hour, and then 10% aqueous hydrochloric acid solution was added until the pH reached 5 to 6 to precipitate the reaction product. The precipitate was separated, washed with water, and then dried under reduced pressure overnight. Petroleum ether after drying
Washed with 500ml and dried under reduced pressure to yield 29.6g.
(0.10M) of 4-hydroxy4'-hexylazobenzene was obtained. The yield was 59%. 4-Hydroxy-4'-hexylazobenzene 8.6g
(0.030M) with 3.3g of potassium hydroxide
It was dissolved in 1 ml of ethanol and heated under reflux for 9 hours. Next, 9.0 g of S-(+)-2-methylbutyl bromide was added and the mixture was heated under reflux for 12 hours. After the reaction was completed, the mixture was filtered and the solvent was distilled off. The residue was dissolved in benzene and subjected to column chromatography on silica gel. Benzene was distilled off and dried under reduced pressure to obtain 5.9g (0.017M) of S-
(+)4-(β-methylbutyloxy)4'hexylazobenzene was obtained. The yield was 57%. The IR, NMR data and phase transition temperature of this compound are shown below. IR:-N=N-1605cm ^-1 ;Ar-O-CH ₂ 1250
cm ^-1 NMR (δppm): Ar-C H ₂ -2.7 (t) 0.8-2.0 Methyl, methylene Ar-O-C H ₂ - 3.9 (q) Ar 7-8 Phase transition temperature:

[Formula] Example 3 [Production of S-(+)-4-(β-methylbutyloxy)4'-octyl azobenzene] 35 g (0.17 M) of 4-octyl aniline was cooled to below 0°C and added to a 10% aqueous hydrochloric acid solution. 85 g was added followed by 12.0 g of sodium nitrite dissolved in 68 ml of water. During the dropping, the solution was cooled so that the temperature did not exceed 0°C. After the dropwise addition was completed, the reaction mixture was allowed to react for 30 minutes, then transferred to a dropping funnel and added with 8% NaOH containing 16g of phenol.
It was added dropwise to 170 g of the aqueous solution. The temperature was kept below 5°C during the dropping. Continue stirring for 1 hour after completion of the dropwise addition, then adjust the pH to 5.
A 10% aqueous hydrochloric acid solution was added until the concentration reached ~6 to precipitate the reaction product. The precipitate was separated, washed with water, and then dried under reduced pressure overnight. After drying, wash with 500ml of petroleum ether and dry under reduced pressure to obtain 30.8g (0.10M) of 4-
Hydroxy-4'-heptyl azobenzene was obtained. The yield was 59%. 4-Hydroxy-
4′-octyl azobenzene 10g (0.032M) at 3.6
The mixture was dissolved in 20 ml of ethanol together with 1 g of potassium hydroxide, and heated under reflux for 6 hours. Next, 9g of S-
Add (+)-2-methylbutyl bromide and add 12
The mixture was heated to reflux for an hour. After the reaction was completed, the mixture was filtered and the solvent was distilled off. The residue was dissolved in benzene and subjected to column chromatography on silica gel. Benzene was distilled off and dried under reduced pressure to obtain 5.7g (0.15M) of S-(+)4-(β
-methylbutyloxy)4'-octyl azobenzene was obtained. The yield was 47%. The IR, NMR data and phase transition temperature of this compound are shown below. IR:-N=N-1610cm ^-1 ;Ar-O-CH ₂ 1255
cm ^-1 NMR (δppm): Ar-C H ₂ -2.5 (t) 0.8-2.0 Methyl, methylene Ar-O-C H ₂ -3.7 (q) Ar 6.8 - 7.9 Phase transition temperature:

[Formula] Example 4 S-(+)- for 100 parts by weight of DOBAMBC
A liquid crystal composition was prepared by adding 6 parts by weight of 4-(β-methylbutyloxy)-4-heptyl azobenzene. Next, a square glass substrate on which a striped ITO film with a pitch of 100 μm and a width of 62.5 μm was provided as an electrode was prepared, and the substrate was placed in an oblique evaporation apparatus with the side on which the ITO film serving as the electrode was placed facing downward. Next, a blood color of SiO ₂ was set in a molybdenum crucible. After that, inside the vapor deposition equipment
After creating a vacuum state of about 10 ^-5 Torr, SiO ₂ was obliquely vapor-deposited on the glass substrate by a predetermined method to form an obliquely-deposited film of 800 Å (electrode plate A). On the other hand, a polyimide forming solution ("PIQ" manufactured by Hitachi Chemical Co., Ltd.; non-volatile content concentration 14.5 wt%) was applied using a spinner coater onto a glass substrate on which a similar striped ITO film was formed, and the temperature was increased to 120°C. at 200℃ for 30 minutes
800Å by heating for 60 minutes and 30 minutes at 350°C.
(B electrode plate). Next, a thermosetting epoxy adhesive was applied to the periphery of the A electrode plate except for the area that would become the injection hole by screen printing, and then the striped pattern electrodes of the A electrode plate and the B electrode plate were made to intersect at right angles. The two electrode plates were stacked one on top of the other and held with a polyimide spacer so that the distance between the two electrode plates was 2 μ. The liquid crystal composition in an isotropic phase was injected into the cell thus created through the injection port, and the injection port was sealed. The temperature of this cell is lowered by slow cooling.
A pair of polarizers was placed in a crossed nicol state while the temperature was maintained at 65°C, and observation under a microscope confirmed the formation of SmC* with a monodomain helix. Next, a 40V (peak-to-peak), 100Hz square wave was repeatedly applied to this liquid crystal cell under the same sonic intensity. Deterioration was determined by comparing the initial current value and the current value after 500 hours of continuous operation. As a result, while the initial current value was 0.6 μA, it was 0.7 μA after continuous operation. Example 5 In place of the liquid crystal composition used when preparing the liquid crystal cell of Example 4, 100 parts by weight of DOBAMBC and S
-(+)-4-(β-methylbutyloxy)-
4 parts by weight of 4'-octyl azobenzene and S-
(+)-4-(β-methylbutyloxy)-4'-
A liquid crystal cell was prepared in exactly the same manner as in Example 4, except that a liquid crystal composition containing 4 parts by weight of decyl azobenzene was used. In the same manner as in Example 4, deterioration due to continuous operation was investigated from the current value. Initial current value
Compared to 0.5μA, it was 0.6μA after continuous operation. Comparative Example 1 Same as Example 4 except that S-(+)-4-(β-methylbutyloxy)-4'-heptyl azobenzene was removed from the liquid crystal composition used when preparing the liquid crystal cell of Example 4. A liquid crystal cell was prepared in exactly the same manner. The current value was measured in exactly the same manner as in Example 4. While the initial current value was 0.6 μA, it was 1.1 μA after continuous operation. Comparative Example 2 In the liquid crystal composition used when preparing the liquid crystal cell of Example 4, S-(+)-4-(β-methylbutyloxy)-4'-heptyl azobenzene was replaced with P-β-methylbutyl- A liquid crystal cell was prepared in exactly the same manner as in Example 4 except that P'-β-methylbutyloxyazobenzene was used. Example 4
The current value was measured in exactly the same manner. While the initial current value was 0.6 μA, it was 1.0 μA after continuous operation. As is clear from the above Examples and Comparative Examples, by adding 4-(β-methylbutyloxy)-4'-alkylazobenzene represented by the general formula into the liquid crystal compound, the life of the liquid crystal element can be significantly extended. It can be extended. [Effects of the Invention] The novel compound 4-(β-methylbutyloxy)4'-alkylazobenzene according to the present invention exhibits liquid crystallinity, and also has 4-(β-
The liquid crystal composition of the present invention containing 4'-alkylazobenzene (methylbutyloxy) has an extended operating life without impairing the properties of a ferroelectric liquid crystal compound, contributing to extending the life of a liquid crystal display element, It is suitable for use in liquid crystal display elements, liquid crystal light shutters, etc., and has great industrial significance.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing the operation of a ferroelectric liquid crystal. DESCRIPTION OF SYMBOLS 1, 1a...Substrate, 2...Liquid crystal molecule layer, 3...Liquid crystal molecules, 4...Dipole moment in the direction orthogonal to the molecules, 5...Upward, 5a...Downward, 6...Voltage application means, 7...First stable state , 7a...second stable state.

Claims (1)

[Claims] 1 General formula (): (In the formula, R represents an alkyl group having 6 to 12 carbon atoms,
* indicates an asymmetric carbon atom) A ferroelectric liquid crystal composition containing at least one compound represented by the following as a compounding component.