JPH0211578B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel ferroelectric liquid crystal material useful for electro-optical devices that utilize the response of ferroelectric smectic liquid crystals to electric fields. [Prior Art] Liquid crystals have been applied as various electro-optical elements. Because they are particularly compact and energy efficient, they are used as voltage-driven light bulbs to display clocks and calculators. The liquid crystal elements currently in practical use are mainly nematic liquid crystal,
It is based on the dielectric alignment effect of cholesteric liquid crystals, where the dielectric anisotropy causes the long axis direction of the average molecule to be oriented in a specific direction by an applied electric field. Since the coupling force-dielectric coupling force with the applied electric field by this mechanism is rather weak, the electro-optical response time of these devices is very slow for many potential applications. Liquid crystal elements are low voltage and low power consumption, so
Although it has excellent characteristics such as good compatibility with other devices and compactness, its responsiveness and nonlinearity are still insufficient, especially when applied to display elements with a large number of pixels, which is expected. Therefore, MOS panels that form switching elements for each pixel and
On the other hand, research and development on TFT panels is becoming more active. Under these circumstances, Clark et al. (US Pat.4367924)
devised a liquid crystal element based on a new display principle using a smectic phase that eliminates the drawbacks of such liquid crystal elements. This will be briefly explained below. FIG. 1 is a schematic diagram of the smectic C ^* or H phase. A liquid crystal consists of each molecular layer 1, in which the average direction of the long molecular axes is tilted by an angle Ψ ₀ with respect to the direction perpendicular to the layer. Meyer et al. Le Journal de Physique Vol. 36 (March 1975
PPL-69to-L-71), in a paper entitled "Ferroelectric liquid crystals", states that smectic C or H liquid crystals consisting of optically active molecules generally have an electric dipole density P→ and are ferroelectric. It is shown that. This dipole density P→ is in the direction of molecular inclination.
perpendicular to n^ and parallel to the plane of the smekchitsk layer.
What they showed is also applicable to the smectic H phase, but the H phase has a greater viscosity for rotation about an axis perpendicular to the layer. The presence of electric dipoles in these chiral smectics provides a stronger binding force to the electric field than in dielectric anisotropy. Furthermore, this bonding force is polar in the sense that the preferred direction of P is parallel to E→, so reversing the direction of the applied electric field will reverse the direction of P→. . In other words, by reversing the electric field, the direction of molecules can be controlled by moving them along the cone, as shown in Figure 2. By detecting the change in the average long axis direction of the molecules using two polarizing plates, it can be used as an electro-optical element. Electro-optical elements that utilize the response of this smectic C ^* phase or H phase to an electric field are TN type because the coupling force between the spontaneous polarization and the electric field is 3 to 4 orders of magnitude larger than the coupling force due to dielectric anisotropy. Compared to liquid crystal elements, it has excellent high-speed response, and by selecting appropriate orientation control, it can provide memory properties, making it suitable for use as high-speed optical shutters and displays with a large amount of displayed information. is expected to be applied. By the way, various types of chiral smectic liquid crystal materials having ferroelectricity have been synthesized and studied. The first ferroelectric liquid crystal synthesized is generally referred to as POBAMBC. P-decyloxybenzilident-P'-amino-2-
methyl-cynnamate, and this series of liquid crystals is
Various types of ferroelectric liquid crystals have been synthesized as research objects in the form of the following structural formulas. ₍ Here _: system, and there are problems such as poor stability. As an extension of this system, the general formula A type of chiral smectic liquid crystal compound in which a hydroxyl group is introduced into one benzene ring and has an intramolecular hydrogen bond, represented by BIOstrovskii et al. Cryst Letter 82 (1982) 61], and in a wide temperature range including room temperature,
It is attracting attention as a compound exhibiting the Sc ^* phase. Because it has intramolecular hydrogen bonds, it is superior in terms of stability compared to Schizophrenic liquid crystals, but there are problems with stability with organic seals, which are still common, and it cannot be put to practical use immediately. . In addition, azoxy-based liquid crystal materials are available from P.Keller
[Amn Phys. 3 (1978) 139], but the temperature range is not sufficient and the compound is dark yellow, which poses practical problems. Under these circumstances, ester-based liquid crystals, which have a proven track record of stability as TN-type liquid crystal materials, are worthy of attention. In the known literature, by BIOstrovskii3 has been reported as a material exhibiting chiral smectic liquid crystals in a temperature range relatively close to room temperature.
Also, GW Gray et al. [Mol Cryst Liq Cryst37
(1976) 189, 48 (1978) 37] reported a biphenyl ester material that exhibits a chiral smectic liquid crystal phase in a high temperature range. [Object of the Invention] As described above, the object of the present invention is to develop a useful chiral smectant that can be used in electro-optical elements using ferroelectric liquid crystals, although there is currently no liquid crystal material that can be put to practical use. An object of the present invention is to provide a liquid crystalline compound. [Structure of the Invention] That is, the present invention provides an optically active 3-chloro, 4-alkoxyphenyl, 4'-
It relates to (6-methylbutyl)biphenylcarboxylic acid ester. (Here, n is 1 to 12, * indicates an asymmetric carbon atom.) Known biphenyl ester compounds include:
GW Gray et al., the general formula [Mol.Cryst
Liq Cryst48 (1978) 37]. The phase transition temperatures of these compounds are as follows.

【table】

〔Example〕

Next, a method for producing the compound of the present invention will be described. Commercially available optically active 4'-(2-methylbutyl)-4
-Cyanobiphenyl was hydrolyzed to form 4'-(2-(methylbutyl)biphenyl-4-carboxylic acid), converted to chloride with thionyl chloride, and 3-chloro-4-
The compound of the present invention was synthesized by esterification with n-alkoxyphenol. Hereinafter, specific methods for synthesizing the compounds and their properties will be shown in Examples. Example 1 Optically active 3-chloro-4-n-octyloxyphenyl 4'-(2-methylbutyl)biphenyl-4''-carboxylic acid ester 1st stage 4'-(2-methylbutyl)biphenyl-4-carvone Production of acid In a 500ml 4-necked flask, add sodium hydroxide.
Add and dissolve 48 g, 120 ml of water, and 120 ml of ethanol, and then add commercially available optically active 4'(2-methyl-butyl).
10 g of -4-cyanobiphenyl was added and reacted for 18 hours under heating and reflux. After the reaction was completed, the mixture was poured into 1.5 ml of ice water, and then acidified with hydrochloric acid to precipitate the carboxylic acid. After separating, drying and recrystallizing, 4'(2-methyl-butyl)biphenyl-4-
8.9 g (82%) of carboxylic acid was obtained. ν ^nujol _nax(cn-1) 2750〜2380, 1680 δ ^(CD3)2C=0 _TMS (ppm); 8.22, (d, J=9Hz, 2H)
,
7.84, (d, J=9Hz, 2H), 7.75, (d, J=
9Hz, 2H), 7.37, (d, J=9Hz, 2H) 2.25
~2.88, m, 2H Second stage production of 3-chloro-4-octyloxyphenol In a 200 ml four-necked flask, put 20 g of chlorohydroquinone, 24 g of n-octyl bromide, 17.3 g of anhydrous potassium carbonate, and 100 ml of dimethyl formaldehyde. The mixture was reacted for 8 hours at 70 to 80°C under a nitrogen stream. After post-treatment by a conventional method, the obtained oil was separated and purified by silica gel chromatography to obtain 15 g of 3-chloro-4-octyloxyphenol. ν ^film _nax(cn-1) 3380, 1510 δ ^CDCl3 _TMS (ppm) 6.52-6.93, m, 3H 5.53, brs, 1H
3.42, t, J=6Hz, 2H 3rd stage 3-chloro-4-n-octyloxyphenyl
Production of 4'-(2-methylbutyl)biphenylcarboxylic acid ester 50ml of thionyl chloride was added to 5g of optically active 4'-(2-methylbutyl)biphenyl-4-carboxylic acid, and after reacting under reflux for 6 hours, excess Thionyl chloride was distilled off under reduced pressure to obtain an oily acid chloride. (ν ^film _nax 1765, 1735 cm ^-1 ) 4.78 g of 3-chloro-4-n-octyloxyphenol was added to the obtained 4'-(2-methylbutyl)biphenyl-4-carboxylic acid chloride under water cooling.
15 ml of dry pyridine was added, and the mixture was allowed to react overnight while slowly returning to room temperature. After the reaction was completed, the precipitate was separated and extracted with ether. The organic layer is
After washing sequentially with water, 2NHCl, and 5% NaOH, water,
Washed with saturated saline until neutral. This organic layer was dried and the ether was distilled off under reduced pressure to obtain a crude product. This was repeatedly purified to obtain 5 g (50%) of the desired product. δ ^CDCl3 _TMS (ppm) 7.06~8.39, m, 11H Aromatic ring hydrogen 2.59, t, J=6Hz, 2H, - CH ₂ -O-2.23~
2.84, m, 2H

[Formula] The transition temperature of this compound is as follows. Cryst47℃ *Sc ^* Phase 60℃ 62Chlestric115℃ 116℃Iso (* indicates supercooling) This compound is closer to room temperature than the compound with n=8 in Table 1 to which Cl is not added. in the temperature range
It exhibits an SmC ^* phase, and its temperature range is slightly wider. This compound was heated and melted and injected into a cell assembled with two substrates having transparent electrodes whose surfaces were rubbed so that the rubbing direction was at an angle of 180° and a gap of 4 μm. This liquid crystal cell was gradually cooled from 120°C at a rate of 0.1°C/min or less. This cell is sandwiched between two polarizing plates.
When 10V, 1Hz alternating current was applied, it was confirmed that the display state changed in response to the switching of the 1Hz electric field. When an electric field of ±10 V was applied at 50°C, the response was 6 ms and a contrast value of 14 was obtained. In addition, the measured values of each physical property are at 50℃ and the pitch is 2.00μ.
m-cone angle 41° and spontaneous polarization 1.3×10 ^-8 C/cm ²
The value of was obtained. The cone angle is close to the value of 45°, which provides maximum contrast, and the spontaneous polarization is also relatively large, making it a chiral smectic liquid crystal material suitable for electro-optical devices. Example 2 Optically active 3-chloro-4-n-decyloxyphenyl, 4'-(2-methylbutyl)biphenyl-4''-carboxylic acid ester Optically active 4'-(2''-methylbutyl)biphenyl-4 - 5 ml of thionyl chloride was added to 1 g of carboxylic acid and reacted under reflux for 6 hours, and then excess thionyl chloride was distilled off under reduced pressure to obtain an oily acid chloride. To this acid chloride, 1.06 g of 3-chloro-4-n-decyloxyphenol synthesized in the same manner as in Example 1 and 4 ml of dry pyridine were added under ice cooling.
The reaction took place all day and night while slowly returning to room temperature.
After the reaction was completed, the precipitate was separated and extracted with ether. The organic layer was washed successively with water, 2NHCl, and 5% NaoH, washed with water and saturated brine until neutral, and then dried, and the ether was distilled off under reduced pressure. By repeatedly purifying the obtained crude product, 1.48 g (74%) of the desired ester was obtained. ν ^film _nax (cm ^-1 ) 1734, 1605, 1580 1260 δ ^CDCl3 _TMS (ppm) 6.87~8.35, m, 11H, aromatic ring hydrogen 4.02, t, J=6Hz, 2H, -CH ₂ -O-2.28~
2.80, m, 2H,

[Formula] The transition temperature of this compound is as follows. Cryst38.2 *SnC ^* phase 51.5℃ 52℃Chlecteric102℃ 102℃Iso (* indicates supercooling) As mentioned above, it exhibits a chiral smectic phase in the temperature range close to room temperature and has ferroelectricity. However, it was confirmed that it can be used as a liquid crystal for electro-optical devices. Example 3 Optically active 3-chloro-4-n-hexyloxyphenyl, 4'-(2-methylbutyl)biphenyl-4''-carboxylic acid ester To 1 g of optically active 4-16-methyloctyloxy)benzoic acid After adding 10 ml of thionyl chloride and reacting under reflux for 6 hours, excess thionyl chloride was distilled off under reduced pressure to obtain an oily acid chloride.The obtained acid chloride was treated in the same manner as in Example 1. 0.95 g of 3-chloro-4-n-hexyloxyphenol synthesized in step 1 and 3 ml of dry pyridine were added under ice-cooling, and the reaction was allowed to proceed overnight while slowly returning to room temperature. After the reaction, the precipitate was separated and extracted with ether. The organic layer was mixed with water, 2NHCl, 5%
After successively washing with NaOH, further washing with water and saturated brine until neutral, drying, and ether was distilled off under reduced pressure. The obtained crude product was purified repeatedly,
1.16 g (61%) of ester was obtained. δ ^CDCl3 _TMS (ppm) 7.02-8.35, m, 11H, 4.02, t, J
=6Hz, 2H, _-CH2 -O-2.22~2.80, m,
2H,

〔Effect of the invention〕

As shown in the Examples above, the compound of the present invention exhibits an Sc ^* phase near room temperature and is a useful liquid crystal material having ferroelectricity, and has a chiral smectic liquid crystal composition over a wide temperature range including room temperature. It can be an effective ingredient in obtaining things.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a smectic C ^* phase or H phase, and FIG. 2 is a schematic diagram showing the movement of liquid crystal molecules in a chiral smectic phase along a cone due to an electric field.

Claims (1)

[Claims] 1. General formula (In the above formula, n is 1 to 12, * indicates an asymmetric carbon atom.) Optically active 3-chloro-4-n
-alkoxyphenyl, 4'-(2-methylbutyl)
A liquid crystal compound with the structure of biphenyl-4″-carboxylic acid ester.