JP2857231B2 - Ester compound and liquid crystal composition containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention can take 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 ester compound which can be used as a liquid crystal material useful as a material for an optoelectronics device utilizing liquid crystal or electrochemiomics, and a liquid crystal composition containing this compound.

(Prior Art) At present, liquid crystal compounds are applied to various devices as display materials, and have been put to practical use in watches, calculators, small televisions, and the like.
These use cells having a nematic liquid crystal material as a main component, and adopt a display type called a TN type or STN type. 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 of several tens of msec and slow cited as disadvantages ing. Therefore, when used in a television, an active matrix system in which switching elements are 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, a ferroelectric liquid crystal represented by 4- (4-n-decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) synthesized by RBMeyer et al. In 1975 was used and used. New display method proposed by NAClark et al. (Applied Phys. Lett. 1980, 3
Thus, a liquid crystal cell having a high-speed response on the order of μ sec and a characteristic (memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is cut off has been made possible. Using display elements made of these materials enables a simple matrix type liquid crystal display to be driven by multiplexing without using switching elements. It will be much more advantageous in such aspects.

For this reason, many ferroelectric liquid crystal materials have been synthesized and proposed to date. In order for these ferroelectric liquid crystal materials to be used as display materials, several physical properties are required. Among them, the basic one is that a chiral smectic C phase is formed in a wide temperature range near room temperature. Show,
It has a large spontaneous polarization and is chemically stable. However, the initial ferroelectric liquid crystal was chemically unstable because the spontaneous polarization was as small as 10 nC / cm ₂ or less and many of them had a Schiff base in the molecule.

By the way, recently, a large spontaneous polarization caused by a chemically stable ester compound has been reported. For example, Is a liquid crystal of a chiral smectic C phase in a temperature range of 78.7 to 103.3 ° C. and a cholesteric phase in a temperature range of 103.3 to 120.8 ° C., and the spontaneous polarization of this liquid crystal at 83 ° C. is 89 nC / cm ² . (JP-A-61-43).

On the other hand, bicyclic compounds have been synthesized to lower the temperature at which the chiral smectic C phase is exhibited. For example, The biphenyl compound exhibits a chiral smectic C phase from 44 ° C. when the temperature is lowered (JP-A-59-118744).

In addition, a phenylpyrimidine-based compound stably showing a chiral smectic C phase at around room temperature has been reported. For example, Is a liquid crystal having a chiral smectic C phase and a smectic A phase having a temperature of 82.8 to 89.1 ° C. in a temperature range of 40.7 to 82.8 ° 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. The biphenyl compound is unstable because the chiral smectic C phase is monotropic. Furthermore, the pyrimidine-based compound has a response time as slow as 150 μsec at 43 ° C., and it is estimated that spontaneous polarization is considerably small.

In recent years, many compounds having a fluorine or trifluoromethyl group introduced on an asymmetric carbon have been reported. For example,
Heppke et al. Introduced the following formula in which fluorine was introduced on an asymmetric carbon, Is a chiral smectic C phase with a spontaneous polarization of 400 nC /
cm ² or more (Report of the 12th International Liquid Crystal Conference).

In addition, the following formula in which a trifluoromethyl group is introduced on an asymmetric carbon Is a chiral smectic C at 115.5-93.1 ° C.
Phase and spontaneous polarization are also reported to be 166 nC / cm ² (JP-A-64-3154).

That is, a liquid crystal material such as a display device that requires a high-speed response has a large spontaneous polarization, a low viscosity, or a chiral smectic C phase in a wide temperature range including near room temperature. Physical properties are required,
To date, there is no material that sufficiently satisfies these properties.

The present invention has been made based on such a situation, and an object of the present invention is to provide an ester compound containing a trifluoromethyl group useful as a liquid crystal compound and a liquid crystal composition containing the same.

(Means for Solving the Problems) The present invention provides the following general formula (I): (Wherein, R ¹ and R ² are alkyl groups which may contain a double bond and may be the same or different;
And B represent either a single bond or —COO—), and a liquid crystal composition containing the same.

The alkyl groups represented by R ¹ and R ² in the above formula (I) are preferably each having 1 to 18 carbon atoms from the viewpoint of practical structure.

In particular, in the above formula, the carbon to which R ² is bonded is an asymmetric carbon, and when optical activity is imparted around this carbon, the ferroelectric liquid crystal may be used alone or by mixing with another compound. This is preferable.

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

4'-octyloxybiphenyl-4-carboxylic acid-4
- (2-trifluoromethyl-hexanoyl) phenyl ^{IR (KBr, cm -1):} 2920,2850,1760,1740,1600,1500,1260,1160,1110 1 H-NMR (δ value ppm, in CDCl, TMS standard): 7.0 to 8.4 (m, 12H), 4.1 (t, 2H), 3.4 (m, 1H) 0.7 to 2.
3 (m, 24H) The length of the carbon chain of the alkyl group of R ¹ and R ^{2 in} the compound represented by the general formula (I) is determined in a temperature range where the compound can take a liquid crystal state or a spontaneous reaction of the compound. It affects physical properties such as polarization, and can be appropriately selected depending on the purpose. Needless to say, this compound can be used alone or in combination with another liquid crystal material.

The compounds of the present invention of the above general formula (I) are generally obtained by the following method.

(A) When A in the above formula (I) is a single bond and B is -COO-: The compound of the formula (1) used in the above reaction formula can be derived from the compound of the formula (2) as follows.

That is, compound (1) can be obtained by hydrolyzing ethyl 2-trifluoromethylalkanoate or ethyl 2-trifluoromethylalkenoate (2) using lipase P or PS.

(B) When A in the above formula (1) is a single bond of —COO— and B: (C) When A and B in the above formula (1) are -COO-: (D) When both A and B in the above formula (1) are single bonds: (Examples) Next, the present invention will be specifically described with reference to examples.

Example 1 4'-octyloxybiphenyl-4-carboxylic acid-4
-(2-trifluoromethylhexanoyloxy) phenyl 4'-octyloxybiphenyl-4-carboxylic acid-4
Synthesis of-(2-trifluoromethylhexanoyloxy) phenyl 4'-octyloxybiphenyl-4-carboxylic acid-
230 mg of (4-hydroxyphenyl) ester (0.53mo
l), (-)-2-trifluoromethylhexanoic acid 100mg
(0.54 mmol), N, N-dicyclohexylcarbodiimide 1
20 mg (0.54 mmol) and 4-dimethylaminopyridine 7 m
g (0.054 mmol) was dissolved in dry dichloromethane 22 ml and stirred at room temperature overnight. After completion of the reaction, the precipitated solid was separated by filtration, and the filtrate was washed with a 1N aqueous hydrochloric acid solution and water, and dried over anhydrous magnesium sulfate.

The magnesium sulfate was filtered off and concentrated, and the residue was purified by silica gel chromatography using a developing solvent (toluene: hexane = 3: 1 (v / v)), and recrystallized from ethanol to obtain 110 mg of a white solid. This compound had the above-mentioned physicochemical properties.

Evaluation of Liquid Crystallinity The above compound was injected into a 3 μm thick cell made of glass with a transparent electrode coated with polyimide and subjected to rubbing treatment, and observed with a polarizing microscope while controlling the temperature with a hot stage. The temperature was changed at a rate of 2 ° C. per minute.

In the temperature decreasing process, the phase changed from an isotropic liquid to a smectic A phase at 154.3 ° C., to a chiral smectic C phase at 109.8 ° C., and to an unidentifiable higher-order smectic phase at 79.5 ° C. During the heating process, the crystal changed to a chiral smectic C phase at 91.4 ° C.

In addition, when a triangular wave of 100 V and 20 Vpp was applied to the cell and the polarization reversal current was measured, it showed a value of 103.9 nC / cm ² at 84.8 ° C.

Example 2 Preparation of a liquid crystal composition As a liquid crystal composition, a phenylpyrimidine-based liquid crystal composition exhibiting a smectic C phase but having no ferroelectricity was used.

 The physical properties of this composition are as shown below.

The following formula of Example 1 is applied to the above composition, When the compound represented by the formula (1) was added at 6 wt%, the following phase transition behavior was exhibited. Here, the Sc ^* phase indicates a chiral smectic C phase.

The response speed of this composition was 192 μsec (10 Vpp / μm,
25 ° C).

(Effects of the Invention) The compound of the present invention exhibits an extremely excellent effect as a material for optoelectronics-related devices, such as being able to take a stable thermotropic liquid crystal state.

Therefore, the present invention can be said to be a liquid crystal material useful as a material for an optoelectronics-related element utilizing liquid crystal or electrochemism, such as for a display such as a liquid crystal television, a printer head, an optical Fourier transform element, and a light valve.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07M 7:00 (72) Inventor Toshihiro Hirai 3-17-35 Niisonanami, Toda City, Saitama Prefecture Inside Nihon Mining Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 69/84-69/94 C07C 69/63 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. The following general formula: (Wherein, R ¹ and R ² are alkyl groups which may contain a double bond and may be the same or different;
And B represent any of a single bond and -COO-). 2. The novel ester compound according to claim 1, wherein the compound represented by the general formula (I) has optical activity. 3. A liquid crystal composition comprising the ester compound according to claim 1 or 2.