JPH0819048B2 - Novel lactic acid derivative, liquid crystal composition containing the same, and optical switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention can be in a stable thermotropic liquid crystal state, for example, for a display such as a liquid crystal television, an optical printer head, an optical Fourier transform element, a light valve, etc. The present invention relates to a novel lactic acid derivative that can be used as a liquid crystal material useful as a material for optoelectronics-related devices that utilize liquid crystals and electrochemichromism, a liquid crystal composition containing this compound, and an optical switching device.

(Prior Art) At present, liquid crystal compounds are applied as display materials in various devices and put to practical use in watches, calculators, small televisions and the like.
For these, cells using a nematic liquid crystal material as a main component are used, and a display method called TN type or STN type is adopted. Cell in this case is actuated based on a weak interaction between the dielectric anisotropy Δε and the electric field E of the liquid crystal compound (ΔεE ^2/2), the response speed to the electric field is low and the number m sec can be mentioned as a disadvantage ing. Therefore, when it is used in a television, an active matrix system in which a switching element is arranged and added for each pixel is mainly used as a driving system, which is one of the obstacles in achieving a large screen. However, with the advent of ferroelectric liquid crystals represented by 4- (4-n-decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) synthesized by RB Meyer in 1975, and using it. I had NA Clark
Proposed a new display method (AppliedPhys.lett.1980,
36,899) has made possible a liquid crystal cell having a high-speed response on the order of μsec and a characteristic (or memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is cut off. The use of display elements made of these materials enables LCD TVs with a simple matrix method that uses multiplex drive without switching elements, etc., and offers higher productivity, cost, reliability, and a larger screen than those with active matrix display. It will be much more advantageous in terms of.

Therefore, many ferroelectric liquid crystal materials have been synthesized and proposed so far. In order to use these ferroelectric liquid crystal materials as a display material, some physical properties are required. Among them, the basic one is that it exhibits a smectic C phase in a wide temperature range near room temperature, It has a spontaneous polarization and is chemically stable. However, the initial ferroelectric liquid crystal has a spontaneous polarization of 10 nC.
It was as small as / cm ² or less, and many of them had a Schiff base in the molecule, so they were chemically unstable.

By the way, recently, the expression of large spontaneous polarization by a chemically stable ester compound has been reported. For example, The compound becomes a liquid crystal of a chiral smectic C phase in the temperature range of 78.7 to 103.3 ° C and a cholesteric phase in the temperature range of 103.3 to 120.8 ° C, and the spontaneous polarization of this liquid crystal at 83 ° C is 89nC / cm ² . (Japanese Patent Laid-Open No. 61-43).

On the other hand, a bicyclic compound has been synthesized in order to lower the temperature at which the chiral smectic C phase is exhibited. For example, The biphenyl compound (1) shows a chiral smectic C phase from 44 ° C. when the temperature is lowered (Japanese Patent Laid-Open No. 59-118744).

Furthermore, a phenylpyrimidine compound that stably exhibits a chiral smectic phase near room temperature has been reported. For example, The compound (1) becomes a liquid crystal having a chiral smectic C phase at a temperature range of 40.7 to 82.8 ° C and a smectic A phase at a temperature of 82.8 to 89.1 ° C (JP-A-61-200973).

(Problems to be Solved by the Invention) However, the above ester compound has a drawback that the temperature range of the chiral smectic C phase is high.
In addition, the above biphenyl compound is a chiral smectic C
The phase is monotropic and unstable. Furthermore, the phenylpyrimidine compound has a response rate of 1500 at 43 ° C.
It is as slow as μs, and it is estimated that the spontaneous polarization is considerably small.

That is, liquid crystal materials such as display devices that require high-speed response have properties such as having a large spontaneous polarization, low viscosity, or exhibiting a chiral smectic C phase in a wide temperature range including near room temperature. However, there is no material which sufficiently satisfies these properties so far.

On the other hand, the present inventors have already found that a compound having a non-resilient carbon in the α-position and having a ketone group directly bonded to a benzene ring in the molecule is stable to light and the like and is in an enantiotropic liquid crystal state. It has been found that the liquid crystal exhibits a chiral smectic C phase and has a large spontaneous polarization and a high response speed when the temperature range is wide and, in particular, optical activity is imparted to the non-carbon. International application number JP88 / 0
0334).

As a result of intensive investigations by the present inventors to further improve the liquid crystal physical properties of such compounds, some of the compounds have the characteristics of the ferroelectric liquid crystal due to the use of lactic acid as a carbon source. It has been found that the temperature range of the chiral smectic C phase can be brought closer to room temperature without impairing a certain large spontaneous polarization.

The present invention has been made based on such findings,
An object of the present invention is to provide a novel lactic acid derivative useful as a liquid crystal composition, a liquid crystal composition containing the same, and an optical switching device,
And to provide intermediates for this compound.

(Means for Solving the Problems) The present invention provides the following general formula (I): (In the formula, R and R ¹ are alkyl groups, which may be the same or different, A is a single bond, —O—, —COO—,
A new lactic acid derivative represented by -OCO-, -OCOO- or -CO-, wherein l and m are 1 or 2, respectively, and 1 + m = 3, and a liquid crystal composition containing this compound,
The optical switching element comprises at least one of these compounds as a constituent element.

The alkyl groups represented by R and R ¹ in the above formula (I) are preferably those having 1 to 18 carbon atoms in view of practical production such as availability of raw materials.

In addition, in particular, when optical activity is imparted to the compound with the carbon to which OR ¹ is bonded in the above formula (I) as a non-center, the liquid crystal exhibits a chiral smectic C phase, large spontaneous polarization, and a response speed It will soon be preferable as a ferroelectric liquid crystal.

Examples of typical compounds of the above formula (I) and their physicochemical properties are as follows.

4'-octyloxybiphenyl-4-carboxylic acid-4
-(2-Pentyloxypropanoyl) phenyl ¹ H-NMR (in CDCl ₃ , TMS standard, δ value ppm): 8.24 (d, 2H),
8.20 (d, 2H), 7.71 (d, 2H), 7.60 (d, 2H), 7.36 (d, 2
H), 7.02 (d, 2H), 4.62 (q, 1H), 4.04 (t, 2H), 3.48
(M, 2H), 1.84 (m, 4H), 1.52 (d, 3H), 1.75 to 1.2 (m, 14
H), 0.87 (m, 6H) IR (KBr, cm ^-1 ): 2910,2840,1730,1690,1600,1265,121
0,1195,1075,820 4'-nonylbiphenyl-4-carboxylic acid-4- (2-
Pentyloxypropanoyl) phenyl ¹ H-NMR (CDCl ₃ , TMS standard, δ value ppm): 8.25 (d, 2H), 8.
22 (d, 2H), 7.73 (d, 2H), 7.60 (d, 2H), 7.36 (d, 2H),
7.31 (d, 2H), 4.62 (q, 1H), 3.46 (m, 2H), 2.68 (t, 2
H), 1.62 (m, 4H), 1.52 (d, 3H), 1.5 ~ 1.2 (m, 16H), 0.
88 (m, 6H) IR (KBr, cm ^-1 ): 2910,2840,1730,1690,1595,1267,121
0,1065 4-octyloxybenzoic acid-4 '-(2-pentyloxypropanoyl) biphenyl ¹ H-NMR (CDCl ₃ , TMS standard, δ value ppm): 8.20 (d, 2H), 8.
16 (d, 2H), 7.70 (d, 4H), 7.37 (d, 2H), 7.00 (d, 2H),
4.68 (m, 1H), 4.01 (t, 2H), 3.49 (m, 2H), 1.62 (m, 4
H), 1.54 (d, 3H), 1.32 (m, 14H), 0.88 (m, 6H) IR (KBr, cm ^-1 ): 2910,2840,1735,1690,1600,1270,123
0,116 5,1060 4-octylbenzoic acid-4 '-(2-pentyloxypropanoyl) biphenyl ¹ H-NMR (in CDCl ₃ , TMS standard, δ value ppm): 8.16 (d, 2H),
8.12 (d, 2H), 7.66 (d, 4H), 7.34 (d, 2H), 7.32 (d, 2
H), 4.65 (q, 1H), 3.45 (m, 2H), 2.72 (t, 2H), 1.61
(M, 4H), 1.50 (d, 3H), 1.30 (m, 1H), 0.88 (m, 6H) IR (KBr, cm ^-1 ): 2910,2840,1735,1690,1600,1270,123
The length of the carbon chain of the alkyl group of R and R ¹ in the compound represented by the general formula (I) depends on the temperature range in which the compound can be in a liquid crystal state or the spontaneous polarization of the compound. It has an influence on the physical properties and can be appropriately selected depending on the purpose. It goes without saying that this compound can be used alone or as a mixture with another liquid crystal material.

The compound of the above general formula (I) can be obtained by the following method.

In the above formula (1), l = 1 is obtained by the following reaction route.

The formula (1) with l = 2 can be obtained by the following reaction route.

The compound of the above formula (II) can be obtained by the following reaction route.

In the reaction route of the compound of the above formula (II), first, alkylation of a commercially available lactate ester is performed. This alkylation is
A method of reacting alkyl iodide in the presence of Ag ₂ O is preferable.

Then, the obtained compound is converted into the compound of the above formula (2). When Y in the formula (2) is OC ₂ H ₅ , the compound obtained above may be used as it is. In other cases, the ester is first hydrolyzed, and the obtained acid is converted to a Li salt to form a compound in which Y in formula (2) is OLi, and the acid is mixed with an inorganic halide such as thionyl chloride or phosphorus pentachloride. An acid halide (Y = halogen) can be formed by reacting with phosphorus trichloride or phosphoryl chloride, and an acid amide compound (Y = amide) can be obtained by reacting the acid halide with dimethylamine or the like. it can.

Next, the compound of the above formula (2) thus obtained is coupled with the organometallic compound of the above formula (3) and the protecting group is eliminated to obtain the compound of the above formula (II). You can In addition, from the easiness of the coupling reaction of the compounds of the above formulas (2) and (3) or the good yield,
It is preferable to use an acid amide compound as the compound of the above formula (2).

The compound of the formula (3) is a commercially available 4-bromophenol or 4- (4-bromophenyl) phenol having a protective group such as a 1-ethoxyethyl group, a tetrahydropyranyl group, a benzyl group or a trimethylsilyl group. After protection, it is obtained by reacting with a metal such as magnesium.

(Examples) Next, the present invention will be specifically described with reference to Examples.

Example 1 4'-octyloxybiphenyl-4-carboxylic acid-4
Synthesis of-(2-pentyloxypropanoyl) phenyl (-)-2-pentyloxypropionic acid ethyl ester 8.3 g (70 mmol) ethyl (-)-lactate, 25 g (126 mmol) 1-iodopentane and 13.6 g silver oxide ( (58 mmol) was placed in a flask, and the mixture was left at room temperature after stirring.

After filtering off the solid using ether, the filtrate was washed with 5% aqueous potassium hydroxide solution and water, and dried over anhydrous magnesium sulfate. The anhydrous magnesium sulfate was then filtered,
After distilling off the ether, it is distilled under reduced pressure, boiling point 117-121 ° C / 31-3
Collect the fractions of 4 mmHg, and have the following physicochemical properties (-)-2-pentyloxypropionic acid ethyl ester (colorless transparent liquid) 5.47 g (29.1 mmol, purity 9
0.7 wt%, yield 41%) was obtained.

α (l = 1, neat) = − 5.32 (assuming that the density is 0.85, [α] _D ²⁵ = −63) IR (cm ⁻¹ ): 2900,1740,1120 ¹ H-NMR (CDCl ₃ , TMS standard, ppm): 4.2 (q, 2H), 3.95 (m,
1H), 3.4 to 3.6 (m, 2H), 1.6 (m, 2H), 1.4 (d, 3H), 1.4
~ 1.2 (m, 4H), 1.3 (t, 3H), 0.9 (t, 3H) (-)-2-Pentyloxypropionic acid synthesis In flask, (-)-2-pentyloxypropionic acid obtained above 5.24 g (27.8 mmol) of ethyl ester, 26 ml of ethanol, 26 ml of water and 2.30 g of sodium hydroxide were added, and the mixture was heated under reflux for 2 hours. At this time, the cloudy mixture became a slightly yellow homogeneous solution. After distilling off ethanol, the mixture was cooled in an ice water bath. This was added to 10 g of ice + 30 ml of 6N hydrochloric acid using 50 ml of ether. After separating the two layers, the mixture was extracted with ether. Then, the organic layers were combined, washed with water, and dried over anhydrous magnesium sulfate. Anhydrous magnesium sulfate was filtered off, the filtrate was concentrated, and then distilled under reduced pressure to obtain 3.40 g (21.2 mmol, purity 99 wt% of a colorless transparent liquid having the following physicochemical properties.
(By GLC), yield 76%).

Boiling point: 127-128 ℃ / 4.0mmHg α (l = 1, neat) ＝ － 5.97 (assuming the density is 0.91 [α] ²⁵ (neat) ＝ － 66) IR (cm ^-1 ): 2900,1720,1120 ¹ H-NMR (CDCl ₃ , TMS standard, ppm): 10.8 (s, 1H), 4.1 (m,
1H), 3.7 to 3.5 (m, 2H), 1.7 (m, 2H), 1.5 (d, 3H), 1.4
(M, 4H), 1.0 (t, 3H) (−)-2-Pentyloxypropionic acid chloride synthesis In a flask, 3.22 g (20.2 mmol) of (−)-2-pentyloxypropionic acid obtained above and chloride Thionyl 3.11g
(26.1 mmol) was added and stirred at room temperature for 0.2 hours, then heated in an oil bath for 0.7 hours at 40 ° C, 0.7 hours at 50-55 ° C, 70-75
The mixture was heated and stirred at ℃ for 3 hours. After cooling to room temperature, the pressure was reduced with an aspirator to distill off excess thionyl chloride, and 3.54 g of a brown liquid [19.9 mmol, yield 99%, α (l = 1, neat) =-
6.38] was obtained.

Synthesis of 2-pentyloxypropionic acid dimethylamide In a 100 ml round-bottomed flask equipped with a magnetic stirrer, 7.85 g of (−)-2-pentyloxypropionic acid chloride obtained above and 30 ml of toluene are charged, and stirring is started. did. Then, cool to 0 ° C., add 10 ml of 40% dimethylamine aqueous solution, stir for 15 minutes, and bring to room temperature.
Stir for 45 minutes. Then, it was washed twice with 1N hydrochloric acid, twice with a 5% aqueous sodium hydroxide solution, and twice with water. After drying this over anhydrous magnesium sulfate, the solvent was distilled off to give a transparent liquid (-) having the following physicochemical properties.
-2-pentyloxypropionic acid dimethylamide 6.71
g (yield 82%) was obtained.

α (l = 1, neat) = − 2.363 ° ¹ H-NMR (in CDCl ₃ , TMS standard, δ value ppm): 4.20 (q, 1H),
3.37 (m, 2H), 3.08 (s, 3H), 2.92 (s, 3H), 1.58 (m, 2
H), 1.36 (d, 3H), 1.5 to 1.2 (m, 4H), 0.84 (m, 3H) IR (neat, cm ^-1 ): 2910,2840,1640,1400,1105 4- (2-pentyloxy) Synthesis of propanoyl) phenol In a flask, 2.03 g of 4-bromophenol (11.73 mmo
l), ethyl vinyl ether 3 ml (31.37 mmol), pyridinium-4-toluenesulfonate 0.05 g (0.20 mmo
l) and 20 ml of dry dichloromethane were taken and stirred at room temperature for 2 hours. Then, it was washed with a saturated aqueous solution of sodium hydrogen carbonate, dried over anhydrous magnesium sulfate, and the solvent was distilled off to give 4-bromophenyl-1-ethoxyethyl ether.
2.87 g was obtained.

Next, add 0.30 g (12.35 mmo) of magnesium metal to the flask.
l) was taken and dissolved in 12 ml of dry tetrahydrofuran while heating at 50 ° C. in an oil bath, 2.87 g (11.71 mm) of 4-bromophenyl-1-ethoxyethyl ether obtained above.
ol) was added dropwise over 30 minutes. Then, the mixture was heated under reflux for 30 minutes, cooled to 0 ° C., and 2.19 g (11.71 mmol) of (−)-2-pentyloxypropionic acid dimethylamide obtained above dissolved in 12 ml of dry tetrahydrofuran was added dropwise over 5 minutes. 2 hours at 0 ℃, 1 hour at room temperature, 60 ℃
After stirring for 30 minutes at 0 ° C., 20 ml of 1N hydrochloric acid was added, and the mixture was stirred for 1 hour. Then, it was extracted with ether and washed with water. After drying over anhydrous magnesium sulfate, the solvent was distilled off and the obtained oily substance was purified by silica gel column chromatography to give 4- (2-pentyloxypropanoyl) as a colorless oily substance having the following physicochemical properties.
1.47 g (53% yield) of phenol was obtained. ¹ H-NMR (in CDCl ₃ , TMS standard, δ value ppm): 8.15 (br.s, 1
H), 8.05 (d, 2H), 7.00 (d, 2H), 4.72 (q, 1H), 3.43
(M, 2H), 1.58 (m, 2H), 1.50 (d, 3H), 1.27 (m, 4H), 0.
86 (m, 3H) IR (neat, cm ^-1 ): 3250,2910,2840,1660,1595,1220 4'-octyloxybiphenyl-4-carboxylic acid-4
Synthesis of-(2-pentyloxypropanoyl) phenyl 4'-octyloxybiphenyl-4-
Carboxylic acid 300.3 mg (0.92 mmol), 4- (2-pentyloxypropanoyl) phenol 215.6 mg (0.91 mmo
l), dicyclohexylcarbodiimide 213.5 mg (1.04 mm
ol), 4-dimethylaminopyridine 13.4 mg (0.11 mmol)
And 10 ml of dry dichloromethane were taken and heated under reflux for 9 hours. The produced solid was removed by filtration, the solvent was distilled off, and the obtained oily substance was purified by silica gel column chromatography and recrystallized from ethanol to give 4'-octyloxybiphenyl-4-carboxylic acid-4 as white crystals. -(2-Pentyloxypropanoyl) phenyl 61.2 mg (yield 12%)
I got This compound had the physicochemical properties described above.

Evaluation of liquid crystallinity The above compound was injected into a cell having a thickness of 3 μm made of glass with a transparent electrode, which was coated with polyimide and subjected to rubbing treatment, and was observed with a polarizing microscope while controlling the temperature on a hot stage. The temperature change was performed at a rate of 2 ° C. for 1 minute. During the temperature decreasing process, the liquid changed from a liquid to a smectic A phase at 124.9 ° C and changed to a chiral smectic C phase at 106.4 ° C.
During the temperature rising process, the crystal changed to a chiral smectic C phase at 57.6 ° C.

A 100Hz, 40Vpp triangular wave was applied to the cell, and the spontaneous polarization value was measured from the polarization reversal current value.
It showed a large value of 7 nC / cm ² .

Example 2 4'-Nonylbiphenyl-4-carboxylic acid-4- (2-
Pentyloxypropanoyl) phenyl synthesis 4'-nonylbiphenyl-4-carboxylic acid in a flask
306.4 mg (0.95 mmol), 4-obtained by the method described in Example 1
(2-Pentyloxypropanoyl) phenol 200.9m
g (0.85 mmol), dicyclohexylcarbodiimide 196.0
mg (0.95 mmol), 4-dimethylaminopyridine 11.2 mg
(0.09 mmol) and 8 ml of dry dichloromethane were taken and stirred at room temperature for 2 hours. The resulting immobilization was removed by filtration, the solvent was distilled off, and the resulting crude crystals were purified by silica gel column chromatography and recrystallized from ethanol to give white crystals of 4'-nonylbiphenyl-4-carboxylic acid-4-. (2-
Pentyloxypropanoyl) phenyl 284.5 mg (yield 6
2%). This compound had the physicochemical properties described above.

Evaluation of liquid crystallinity When the liquid crystallinity was evaluated by the method described in Example 1, the liquid changed from a liquid to a smectic A phase at 84.7 ° C, a chiral smectic C phase at 68.0 ° C, and crystallized at 34.7 ° C. Turned into During the temperature rising process, the crystal changed to a chiral smectic C phase at 60.8 ° C. The spontaneous polarization value was 118 nC / cm ² at 38 ° C.

Example 3 Synthesis of 4-octyloxybenzoic acid-4 '-(2-pentyloxypropanoyl) biphenyl 4-hydroxy-4'-(2-pentyloxypropanoyl) biphenyl 4- (4-bromophenyl) was added to a flask. ) Phenol
250g (10.04mmol), 3ml ethyl vinyl ether (31.37m
mol) pyridinium-4-toluenesulfonate 0.05 g
(0.20 mmol) and 30 ml of dry dichloromethane were taken and stirred at room temperature for 3 hours. Then, it was washed with a saturated aqueous solution of sodium hydrogen carbonate and dried over anhydrous magnesium sulfate, and then the solvent was distilled off to obtain 3.22 g of 4- (4-bromophenyl) phenyl-1-ethoxyethyl ether.

0.30 g (12.35 mmol) of magnesium metal was placed in a flask, and 4- (4-bromophenyl) phenyl-1-ethoxyethyl ether obtained above was dissolved in 12 ml of dry tetrahydrofuran while heating to 50 ° C. in an oil bath. 3.22g
(10.03 mmol) was added dropwise over 30 minutes. After heating under reflux for 30 minutes, cool to 0 ° C and dry tetrahydrofuran 10ml.
1.49 g (7.97 mmo) of (-)-2-pentyloxypropionic acid dimethylamide obtained by the method described in Example 1
l) was added dropwise over 5 minutes. 1 hour at 0 ℃, 60 ℃
After stirring for 30 minutes at 0 ° C., 20 ml of 1N hydrochloric acid was added, and the mixture was stirred for 1 hour. Then, the mixture was extracted 3 times with ether and washed with a saturated sodium hydrogen carbonate aqueous solution and a saturated sodium chloride aqueous solution. After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the resulting oily product was purified by silica gel column chromatography to give 4-oildoxy-4'-anhydrous oil having the following physicochemical properties.
(2-pentyloxypropanoyl) biphenyl 1.57g
(Yield 63%) was obtained. ¹ H-NMR (TMS standard in CDCl ₃ , δ value ppm): 8.12 (d, 2H),
7.64 (d, 2H), 7.54 (d, 2H), 6.98 (d, 2H), 6.46 (s, 1
H), 4.70 (q, 1H), 3.50 (m, 2H), 1.62 (m, 2H), 1.50
(D, 3H), 1.28 (m, 4H), 0.87 (m, 3H) IR (neat, cm ^-1 ): 3300,2910,2840,1660,1590,1210) 4-octyloxybenzoic acid-4′- Synthesis of (2-pentyloxypropanoyl) biphenyl (4) 4-Octyloxybenzoic acid 254.7 mg (1.0
2mmol), 313.3 mg (1.00 m of 4-hydroxy-4 '-(2-pentyloxypropanoyl) biphenyl obtained above.
mol), dicyclohexylcarbodiimide 234.5 mg (1.04
mmol), 4-dimethylaminopyridine 18.0 mg (0.15 mmo
l) and 8 ml of dry dichloromethane were taken and stirred at room temperature for 1 hour. The resulting solid was removed by filtration, the solvent was distilled off, and the obtained crude crystal was purified by silica gel column chromatography and recrystallized from ethanol to give white crystal of 4-octyloxybenzoic acid-4- (2-pentyl). 250.0 mg (yield 46%) of oxypropanoyl) biphenyl (4) was obtained.
This compound had the physicochemical properties described above.

Evaluation of liquid crystallinity When the liquid crystallinity was evaluated by the method described in Example 1, the liquid changed from a liquid to a smectic A phase at 78.7 ° C in the temperature decreasing process. The crystals melted at 47 ° C during the heating process. When a 10 Hz triangular wave was applied, electric field induced tilt (electroclinic effect) was observed even in the smectic A phase.

Example 4-4 '-(2-Pentyloxypropanoyl) biphenyl 4-octylbenzoate (4) 175.1 mg (0.75 mmo) 4-octylbenzoic acid in a flask.
l), 4-hydroxy-4 obtained by the method described in Example 3
-(2-Pentyloxypropanoyl) biphenyl 211.
3 mg (0.68 mmol), dicyclohexylcarbodiimide 17
4.3 mg (0.85 mmol), 4-dimethylaminopyridine 11.2 m
g (0.09 mmol) and 8 ml of dry dichloromethane were taken and stirred at room temperature for 1 hour. The resulting solid was removed by filtration, the solvent was distilled off, and the resulting crude crystal was purified by silica gel column chromatography and recrystallized from ethanol to give white crystal of 4-octylbenzoic acid-4 '-(2-pentyl). 198.3 mg (yield 55%) of oxypropanoyl) biphenyl (4) was obtained. This compound had the physicochemical properties described above.

Evaluation of liquid crystallinity When the liquid crystallinity was evaluated by the method described in Example 1, the liquid changed from a liquid to a smectic A phase at 82.4 ° C in the temperature decreasing process,
Crystallized at 31.5 ° C. During the temperature rising process, the crystal changed to a smectic A phase at 61.3 ° C.

In the smectic A phase, electric field induced tilt (electroclinic effect) was observed.

Example 5 Preparation of Liquid Crystal Composition Compound 4′-nonylbiphenyl-4 described in Example 2
4- (2-pentyloxypropanoyl) phenyl carboxylic acid and 4- (2-
A liquid crystal composition was prepared by mixing methyloctanoyl) phenyl-4-octyloxybenzoic acid ester (International Application No. JP88 / 00334) in a molar ratio of 1: 1.

The liquid crystallinity of this liquid crystal composition was evaluated by the method described in Example 1. As a result, the temperature changed from liquid to smectic A phase at 58.1 ° C., to chiral smectic C phase at 34.7 ° C., and −20 ° C. No crystallization occurred until. That is, when the temperature is lowered, the chiral smectic C is obtained even at room temperature.
A preferable liquid crystal composition having a phase was obtained.

Example 6 Fabrication of Switching Element Thickness of the liquid crystal composition described in Example 5 made of glass with a transparent electrode coated with polyimide and subjected to rubbing treatment 4.
When injected into a 2 μm cell and applying an electric field at 25 ° C., a clear switching operation was observed. Moreover, when a rectangular wave of 42 Vpp was applied at 25 ° C., the amount of light transmission under a crossed Nicols polarization microscope at that time was detected by a photodiode, and the response speed was measured to be as fast as 146 μsec.

Comparative Example To clarify the effect of lactic acid in the present invention, the phase transition temperature and spontaneous polarization of a lactic acid derivative and a compound having a similar structure were compared. The results of this comparison are shown in Table 1 below. In the table, is the compound described in Example 1, is the compound described in Example 2, is the compound described in Example 3, and is the compound described in Example 4. ,,, are the compounds previously invented by the present inventors (International Number JP88 / 0
0334).

Comparison with the table shows that the lactic acid derivative has no smectic X phase and the temperature range of the chiral smectic C phase is lowered. The absence of the smectic X phase is preferable when the liquid crystal composition is prepared by mixing. Further, it is preferable that the temperature range of the chiral smectic C phase is lowered for the operation at room temperature. Similarly, it is found that the temperature range of the chiral smectic C phase is lower in the lactic acid derivative. On the other hand, in the comparative examples of (1) and (2), the temperature range of the smectic A phase is lower in the lactic acid derivative, which means that the temperature range is lowered when the chiral smectic C phase is to be developed by mixing or the like. Therefore, it is preferable.

The values of spontaneous polarization of lactic acid derivatives are as large as 100 nC / cm ² or more. Therefore, in the present invention, an excellent liquid crystal material having a large spontaneous polarization and a low temperature range of the chiral smectic C phase can be obtained. Will be obtained.

(Effect of the invention) The compound of the present invention can be in a liquid crystal state in a wide temperature range by using lactic acid as a non-carbon source, and has a large spontaneous polarization, and thus becomes a ferroelectric liquid crystal material having a fast response speed. It is extremely effective as a material for optoelectronic-related elements.

Therefore, the present invention can be said to be a liquid crystal material useful as a material for optoelectronics-related devices utilizing liquid crystal or electrochemiomics, for example, for displays such as liquid crystal televisions, optical printer heads, optical Fourier transform elements, light valves, and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location G02F 1/13 500 (72) Inventor Mitsuru Fukumasa 3-1735, Shinsōnan, Toda City, Saitama Prefecture No. Japan Mining Co., Ltd. (72) Inventor Akihisa Yokoyama 3-17-35, Shinzonan, Toda City, Saitama Prefecture Japan Mining Co., Ltd.

Claims (3)

[Claims] (1) The following general formula (I): (In the formula, R and R ¹ are alkyl groups, which may be the same or different, A is a single bond, —O—, —COO—,
A novel lactic acid derivative represented by -OCO-, -OCOO- or -CO-, wherein 1 and m are 1 or 2, respectively, and 1 + m = 3). 2. A liquid crystal composition comprising the lactic acid derivative represented by the general formula (I) according to claim 1. 3. An optical switching element comprising at least one lactic acid derivative represented by the general formula (I) according to claim 1 as a constituent element.