JPH10109958A - Optically active compound, and antiferroelectric liquid crystal composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new optically active compound useful for an antiferroelectric liquid crystal display element, capable of maintaining an antiferroelectric phase in a wide temperature range and simultaneously developing a smectic A phase when mixed with a antiferroelectric liquid crystal. SOLUTION: This optically active compound is shown by formula I (X and Y are each H or F; (m) is 3-8; (n) is 4-8) such as R-(-)-4-(1- methylheptyloxycrbonyl)phenyl=2-fluoro-4-(3-mehoxypropylcarbonyloxy) benzoate. The example compound is obtained by reac ting 4-(3 methoxypropylcarbonyloxy)-2-fluorobenozic acid with R-(-)-4-hydroxy-1-(1- methylheptyloxycarbonyl)benzene. When the compound of formula I is added, for example, to an antiferroelectric liquid crystal which is shown by formula II (Z is X; R is a 6-12C straight chain alkyl; (r) is 5-8; (s) is an even number of >=2) and has no smectic phase A, the obtained composition develops a smectic phase A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel phenyl ester compound, a novel antiferroelectric liquid crystal composition containing the same, and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art Liquid crystal display devices have been used in various small display devices to date because of their low voltage operation, low power consumption, and thin display. However, with the recent information, the application of liquid crystal display elements to the OA related equipment field, or the television field, and the expansion of applications, the CR
The demand for a high-performance large-sized liquid crystal display device having a display capacity and display quality higher than that of a T display device has been rapidly increasing.

However, as long as the current nematic liquid crystal is used, even an active matrix drive liquid crystal display element used for a liquid crystal television has a large size and a low cost due to the complexity of the manufacturing process and low yield. Is not easy. Even with a simple matrix driven STN type liquid crystal display element, large capacity driving is not always easy, and the response time is limited, making it difficult to display moving images. Further, a narrow viewing angle of a display element using a nematic liquid crystal has become a serious problem.
Therefore, the nematic liquid crystal display element cannot satisfy the demand for the above-mentioned high performance large liquid crystal display element.

In such a situation, a liquid crystal display element using a ferroelectric liquid crystal has attracted attention as a high-speed liquid crystal display element. The surface-stabilized ferroelectric liquid crystal (SSFLC) device, announced by Clark and Lagavar, is noted for its unprecedented fast response speed and wide viewing angle, and its switching characteristics are detailed. In order to optimize various physical constants, many ferroelectric liquid crystals have been synthesized. However, the threshold characteristics are insufficient, the layer structure has a chevron structure, the contrast is poor, the high-speed response is not realized, the alignment control is difficult, and one of the biggest features of SSFLC is
However, there are problems such as difficulty in realizing bistability, which is difficult, and difficulty in recovering the orientation due to mechanical shock, and it is necessary to overcome these problems for practical use.

[0005] Apart from this, the development of elements having a switching mechanism different from that of SSFLC is also proceeding at the same time. Switching between the three stable states of a liquid crystal material having an antiferroelectric phase (hereinafter referred to as an antiferroelectric liquid crystal material) is one of these new switching mechanisms (Japanese Journal of A).
pplied Physics, Vol. 27, pp. L729, (1988)). The antiferroelectric liquid crystal device has three stable states. That is,
Two uniform states seen in ferroelectric liquid crystal devices
(Ur, Ul) and the third state. Chandani et al. Report that this third state is an antiferroelectric phase (Japanese Jo
urnal of Applied Physics, Vol. 28, pp. L1261, (198
9), Japanese Journal of Applied Physics, Vol. 28, p.
p.L1265, (1989)).

[0006] Such switching between the three stable states is the first feature of the antiferroelectric liquid crystal device. A second feature of the antiferroelectric liquid crystal element is that there is a clear threshold value for an applied voltage. Further, it has a memory property, which is the third feature of the antiferroelectric liquid crystal element. By utilizing these excellent features, a liquid crystal display device having a high response speed and good contrast can be realized. Another major feature is that the layer structure is easily switched by an electric field (Japan
ese Journal of Applied Physics, Vol.28, pp.L119, (1
989), Japanese Journal of Applied Physics, Vol. 29,
pp.L111, (1990)). This makes it possible to manufacture a liquid crystal display element having a very small number of defects and a self-healing ability for alignment, and to realize a liquid crystal element having excellent contrast. Furthermore, it has been demonstrated that voltage gradation that is almost impossible with ferroelectric liquid crystal is possible with antiferroelectric liquid crystal, opening the way to full color, and the importance of antiferroelectric liquid crystal is further increasing. (Proceedings of the 4th International Conference on Ferroelectric Liquid Crystals, p. 77, (1993)).

As described above, the superiority of the antiferroelectric liquid crystal is becoming certain, but the driving temperature range is expanded, the response speed is further improved, and further, the antiferroelectric liquid crystal has a smectic A phase. The development of ferroelectric liquid crystals is desired. Regarding the response speed, there is a problem particularly on the low temperature side below room temperature. At present, the response speed at a low temperature side, for example, at 10 ° C., is 10 to 20 times slower than that at room temperature.
Therefore, in order to facilitate the driving on the low temperature side, a method of changing the frequency or the driving voltage, a method of installing a heater, and the like have been considered. However, there is a limit in changing the frequency and the voltage, and the change in the frequency and the voltage does not sufficiently cover the low characteristic of the liquid crystal.
When a heater is provided, the light transmittance of the element is reduced, resulting in a decrease in contrast and an element having a high display quality cannot be obtained.

In the case of an antiferroelectric liquid crystal, there are two switching operations from an antiferroelectric state to a ferroelectric state and from a ferroelectric state to an antiferroelectric state. The two switching speeds by this voltage, ie, the response speed, are important factors that determine the display quality of the display element. Since the response speed from the antiferroelectric state to the ferroelectric state (; response speed I) is, for example, a writing speed per scanning line in a simple matrix drive for line-sequential scanning, one screen is constituted. It is important to determine the number of scanning lines. As the response speed I increases, the number of scanning lines can be increased, and a high-definition element can be realized.

The required response speed from the ferroelectric state to the antiferroelectric state (; response speed II) varies depending on the design of the element driving method. For example, it changes depending on the set voltage of the offset voltage. However, if the response speed II is too fast, the ferroelectric state cannot be maintained (maintaining the bright or dark state). Conversely, if the response speed II is too slow, the ferroelectric state changes to the antiferroelectric state (bright or dark). Is not rewritten from the dark state to the dark or bright state), which is inconvenient. The response speed II is set to an optimum value after the drive method is determined. As described above, in order to realize a high-definition element, it is important that the response speed I is fast, and it is also desirable that the dependence of the response speed on the temperature be small.

[0010]

In practice, the antiferroelectric liquid crystal is capable of improving the response speed at a low temperature, expanding the temperature range of the antiferroelectric phase, and improving the smectic A phase as described above. Requires existence. Response speed was determined by M. Nakagaw
According to a, it is shown that antiferroelectric liquid crystals depend on the rotational viscosity of liquid crystal molecules (Masahiro Nakagawa, Jap.
anese Journal of Applied Physics, 30, 1759 (199
1)). That is, the lower the viscosity, the faster the response speed.
Looking at the change of the response speed with respect to the temperature, the response speed decreases exponentially at a temperature lower than the room temperature and below. The antiferroelectric liquid crystal is considered to have a high viscosity because the liquid crystal phase is a smectic phase, so that the viscosity increases rapidly at the low temperature side and the response speed decreases rapidly due to the viscous resistance. ing.

As a specific measure for solving this problem, a compound having a relatively low viscosity is added to a liquid crystal composition to lower the viscosity of the whole composition and thereby to improve the response speed. Attempts are possible. Although this method seems to be the most realistic solution at present, this method tends to lower the maximum temperature of the antiferroelectric phase, and although the response speed is improved, the antiferroelectric phase is improved. A problem arises in terms of the temperature range.

Generally, when considering an antiferroelectric liquid crystal device as a display, it is considered that the temperature of the device is at least about 40 ° C. due to the backlight. Therefore,
For normal device operation, the upper limit temperature of the antiferroelectric phase is
The temperature must be at least 40 ° C. or higher, preferably 50 ° C. or higher. It is necessary for a practical element that a smectic A phase be present on the higher temperature side than the upper limit temperature in order to obtain good orientation. On the low temperature side, it is necessary that the element can be driven at least at 10 ° C. Therefore, the minimum temperature of the antiferroelectric phase needs to be at least 0 ° C.

The present invention has been made in view of the above, and when the novel optically active compound of the present invention is mixed with an antiferroelectric liquid crystal, an antiferroelectric phase can be ensured in a wide temperature range. At the same time, by mixing this novel optically active compound with an antiferroelectric liquid crystal having no smectic A phase, a smectic A phase can be developed, and an antiferroelectric liquid crystal composition having a very high speed at a low temperature can be obtained. It has been found that the present invention can be obtained, and the present invention has been completed.

[0014]

That is, the present invention provides an optically active compound represented by the following general formula (1) and an antiferroelectric liquid crystal represented by the following general formula (2). Is an antiferroelectric liquid crystal composition.

[0015]

Embedded image (Where m is an integer of 3 to 8, n is an integer of 4 to 8, X, Y,
Z is independently an H atom or an F atom, and R is a carbon atom having 6 carbon atoms.
1212 straight-chain alkyl groups, r is an integer of 5-8, and S is an even number of 2 or more. )

As the optically active compound represented by the general formula (1), a compound in which n is 6 and a compound having no liquid crystal phase are preferable. Further, among the antiferroelectric liquid crystals represented by the general formula (2), those in which r is 5 and n is 2 are preferable. Also,
The optically active compound represented by the general formula (1) is 1 to 3 in the composition.
60 moles are preferred. The antiferroelectric liquid crystal composition of the present invention,
For practical purposes, it is necessary to have a smectic A phase. When there is no smectic A phase, the orientation is remarkably poor and it is difficult to obtain a high contrast. In the present invention, the composition obtained by adding the optically active compound represented by the general formula (1) to an antiferroelectric liquid crystal represented by the general formula (2) and having no smectic A phase is And a smectic A phase can be developed.

It is desirable that the temperature range of the antiferroelectricity of the composition be as wide as possible. Practically, the lower limit temperature of the antiferroelectric phase is 0 ° C. or lower and the upper limit temperature is 40 ° C. or higher, and it is desirable to have at least the smectic A phase on the higher temperature side than the antiferroelectric phase. Then, the antiferroelectric liquid crystal composition obtained by the present invention can be disposed between a pair of electrode substrates to provide an antiferroelectric liquid crystal display element that can be suitably driven in a wide temperature range.

The antiferroelectric liquid crystal represented by the general formula (2) used in the present invention can be easily produced by the method shown by the present inventors (Japanese Patent Laid-Open No. 4-198155).
issue). The following shows the case where r = 5 and s = 2 in the general formula (2). (B) AcO-Ph (Z) -COOH + SOCl ₂ → AcO-Ph (Z) -COCl (b) (b) + HOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ → AcO-Ph (Z) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (c) (b) + Ph-CH ₂ NH ₂ → HO-Ph (Z) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅ (d) RO-Ph-Ph-COOH + SOCl ₂ → RO-Ph-Ph-COCl (e) (b) + (d) → antiferroelectric liquid crystal

The above manufacturing method will be briefly described below. (A) is a chlorination reaction of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride. (B) is esterification by the reaction between the chlorinated product (a) and the optically active alcohol. (C) is the deacetylation of the ester of (b). (D) is a chlorination reaction of alkyloxybiphenylcarboxylic acid. (E) is chlorinated (d) and phenol (c)
And the formation of liquid crystal by the reaction with

[0020]

According to the present invention, a novel optically active compound and an antiferroelectric liquid crystal composition can be provided. The novel antiferroelectric liquid crystal composition provided by the present invention has an antiferroelectric phase over a wide temperature range and exhibits a high-speed response, thereby realizing an antiferroelectric liquid crystal display device with high display quality. it can.

[0021]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is of course not limited thereto. Example 1 (Equation (1): m = 3, X = F, Y = H, n = 6 (E
1)) Production of R-(-)-4- (1-methyl-heptyloxycarbonyl) phenyl = 2-fluoro-4- (3-methoxypropylcarbonyloxy) benzoate.

(1) Production of 4- (3-methoxypropylcarbonyloxy) -2-fluorobenzoic acid. 15.6 g (0.1 mol) of 4-hydroxy-2-fluorobenzoic acid
Was dissolved in 140 ml (milliliter) of dichloromethane. there,
Triethylamine 16ml, 4-methoxybutyric acid chloride 1
5.0 g (0.11 mol) and 0.97 g (0.
0079 mol), and the mixture was stirred at room temperature for 24 hours. 50 ml of 10% hydrochloric acid was added thereto, and the mixture was extracted three times with 100 ml of ether. The organic layer was washed three times with 100 ml of a saline solution and dried over anhydrous sodium sulfate. After evaporating the solvent, 400 ml of hexane
Then, 21.8 g (yield 80%) of the desired product was obtained.

(2) Production of R-(-)-4-acetoxy-1- (1-methylheptyloxycarbonyl) benzene. To 10.8 g (0.06 mol) of 4-acetoxybenzoic acid, 60 ml of thionyl chloride was added and reacted under reflux for 7 hours. Next, excess thionyl chloride was distilled off, and then 100 ml of pyridine and R-
5.24 g (0.0402 mol) of (-)-2-octanol was added dropwise.
After the dropwise addition, the mixture was stirred at room temperature for one day and night.
The organic layer was washed with diluted hydrochloric acid, a 1N aqueous solution of sodium hydroxide and water in that order, and dried over magnesium sulfate. The solvent is distilled off, and the crude target product is purified by silica gel column chromatography using hexane / ethyl acetate as a solvent to obtain the target product 1
0.6 g (90% yield) was obtained.

(3) Production of R-(-)-4-hydroxy-1- (1-methylheptyloxycarbonyl) benzene 10.6 g (0.0361 mol) of the compound obtained in the above (2) was dissolved in 250 ml of ethanol, and 7.74 g (0.07 mol) of benzylamine was dissolved.
72 mol) was added dropwise. Furthermore, after stirring at room temperature for 24 hours,
Dilute with 300 ml of ether, wash with diluted hydrochloric acid and water in that order,
Dried over magnesium sulfate. After evaporating the solvent, the residue was isolated and purified by silica gel column chromatography to obtain 8.9 g (0.0356 mol, 98% yield) of the desired product.

(4) Preparation of R-(-)-4- (1-methyl-heptyloxycarbonyl) phenyl = 2-fluoro-4- (3-methoxypropylcarbonyloxy) benzoate 3.1 mmol of the compound obtained in the above (1) was added to thionyl chloride 1
5 ml was added, and the mixture was heated under reflux for 5 hours. After distilling off excess thionyl chloride, 2 ml of pyridine was added to the compound obtained in (3) above.
2.12 mmol was added and reacted at room temperature for 10 hours. After completion of the reaction, the mixture was diluted with 300 ml of ether, washed with diluted hydrochloric acid, a 1N aqueous solution of sodium carbonate and water in this order, and the organic layer was dried over magnesium sulfate. Next, the solvent was distilled off, and the residue was isolated by silica gel chromatography.
Mmol, yield 75%). The 1H-NMR data of the obtained target product is shown in Table 1 and the formula is shown in the chemical formula.

Embodiment 2 (Equation (1): m = 6, X = F, Y =
H, n = 6 (E2)) Production of R-(-)-4- (1-methyl-heptyloxycarbonyl) phenyl = 2-fluoro-4- (6-methoxyhexylcarbonyloxy) benzoate. The desired product was obtained in exactly the same manner as in Example 1 except that 7-methoxyheptanoic acid was used instead of 4-methoxybutyric acid chloride. 1H-NMR of the target compound obtained
The data is shown in Table 1 and the formula is shown in Chemical Formula 4.

Examples 3 and 4 In the following antiferroelectric liquid crystal (2A), 20 mol% of the optically active compound (E1) obtained in Example 1 and the optically active compound (E2) obtained in Example 2 were added. ) Was added at 30 mol% to prepare an antiferroelectric liquid crystal composition. 2A: C ₉ H ₁₉ O-Ph-Ph-COO-Ph (3F) -COO-C * H (CF ₃ ) (CH ₂ ) ₅
In the OC ₂ H ₅ formula, Ph is a 1,4-phenylene group, Ph (3F) is a 1,4-phenylene group substituted with fluorine at the 3-position, and C * is an asymmetric carbon.

Table 2 shows the results of measurement of the phase series, response speed, and the like of the obtained composition. The phase sequence was determined by texture observation and DSC measurements. The response speed was measured as follows. Liquid crystal cell with ITO electrode with rubbed polyimide thin film (cell thickness 1.8μm)
Was filled with the composition in an isotropic phase. The cell was gradually cooled at 1 ° C. per minute to align the liquid crystal in the smectic A phase. The cell was placed between orthogonal polarizing plates so that the layer direction of the liquid crystal was parallel to the analyzer or the polarizer. A step voltage of 10 V and a frequency of 50 V was applied to the liquid crystal cell, and the time required for the change in transmitted light to change from 10 to 90% was defined as the response time, and the response speed was measured.

[0029]

Embedded image

[0030]

[Table 1] Chemical shift (ppm) hydrogen atom number 1 2 3 4 5 6 7 8 Example 1 (E1) 3.4 2.6 7.1 7.1 8.2 7.3 8.2 5.2 Example 2 (E2) 3.4 2.6 7.1 7.1 8.2 7.3 8.2 5.2

[0031]

[Table 2] Phase sequence Response time (μsec) Component Molar ratio Example 3 Cr (<− 20) SCA * (48) SA (64) I 69 E1 / 2A = 20/80 Example 4 Cr (<− 20) SCA * (60) SA (67) I 67 E2 / 2A = 30/70 Liquid crystal 2A Cr (<-50) SCA * (77) SC * (83) I 79 E1 Cr (<-50) I E2 Cr (8) I In the above phase series, the numbers in parentheses indicate the transition temperature (° C), Cr is a crystalline phase, SCA * is an antiferroelectric phase, SA is a smectic A phase, and SC * is a chiral smectic C phase. (Ferroelectric phase),
I represents an isotropic phase.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Matsumoto 22nd Wadai, Tsukuba, Ibaraki Pref. Mitsubishi Gas Chemical Company, Ltd.

Claims (8)

[Claims] 1. An optically active compound represented by the following general formula (1). Embedded image (In the formula, m is an integer of 3 to 8, n is an integer of 4 to 8, and X and Y are H or F atoms.) 2. The optically active compound according to claim 1, wherein n is 6 in the general formula (1). 3. The optically active compound according to claim 1, which is represented by the general formula (1) and has no liquid crystal phase. 4. An antiferroelectric liquid crystal composition obtained by adding an optically active compound represented by the following general formula (1) to an antiferroelectric liquid crystal represented by the following general formula (2). Embedded image (Where m is an integer of 3 to 8, n is an integer of 4 to 8, X, Y,
Z is independently an H or F atom, and R is a carbon atom having 6 to 12 carbon atoms.
, R is an integer of 5 to 8, and S is an even number of 2 or more. ) 5. In the general formula (2), r is 5 and s is 2
5. The antiferroelectric liquid crystal composition according to claim 4, wherein 6. The antiferroelectric liquid crystal composition according to claim 4, wherein the optically active compound represented by the general formula (1) is 1 to 60 mol% of the composition. 7. The antiferroelectric phase according to claim 4, wherein the lower limit temperature of the antiferroelectric phase is 0 ° C. or lower and the upper limit temperature is 40 ° C. or higher, and the antiferroelectric phase has at least a smectic A phase on a higher temperature side. Liquid crystal composition. 8. An antiferroelectric liquid crystal display device comprising the antiferroelectric liquid crystal composition according to claim 1 disposed between a pair of electrode substrates.