JP2980962B2 - 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
6,899) has made possible a liquid crystal cell having a high-speed response on the order of μsec and a characteristic (memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is cut off. 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 ones show a chiral smectic C phase in a wide temperature range near room temperature, It has a large spontaneous polarization and is chemically stable. However, the initial ferroelectric liquid crystal has a spontaneous polarization.
Since it was as small as 10 nC / cm ² or less and had many Schiff bases in the molecule, it was chemically unstable.

However, recently, the occurrence of large spontaneous polarization 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 in a temperature range of 40.7 to 82.8 ° C. and a smectic A phase at 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. The biphenyl compound is unstable because the chiral smectic C phase is monotropic. Furthermore, the pyrimidine-based compound has a slow response time of 1500 μsec at 43 ° C.,
It is estimated that the spontaneous polarization is quite 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).

Further, a compound of 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 be the same or different, and a liquid crystal composition containing the same.

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

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, it becomes a ferroelectric liquid crystal 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.

5- (2-fluoro-2-methylheptanoyloxy)
-2- (4-hexyloxybiphenyl) pyrimidine IR (KBr, cm ^-1 ): 2920,2850,1770,1600,1420,1220,1120 ¹ H-NMR (δ value ppm, in CDCl ₃ , based on TMS): 8.60 to 8.80 (d, 2H), 8.38 to 8.60 (d, 2H), 7.70 to 7.83 (d, 2H), 7.53 to 7.70 (d, 2H), 6.93 to 7.10 (d, 2H), 4.06 (t, 2H 0.73 to 2.43 (m, 22H) 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, It affects physical properties such as spontaneous polarization of the compound, and can be appropriately selected depending on the purpose. This compound can be used alone, of course.
It goes without saying that it can be used 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.

Here, the compound (A) used in the above reaction formula can be synthesized according to the following formula.

The compound of the formula (1) used in the above reaction formula can be derived from the compound of the formula (3) as follows.

That is, an amine-hydrogen fluoride complex or silicon tetrafluoride is allowed to act on 2-methyl-1,2-epoxyalkane of the optically active formula (3), and the optically active 2-fluoro- (2) of the formula (2) is reacted.
2-methyl-1-alkanol is obtained (JP-A-64-0560).
No. 58). An oxidizing agent such as potassium permanganate is allowed to act on this to obtain the compound of the formula (1).

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

Example 1 5- (2-fluoro-2-methylheptanoyloxy) -2- (4-hexyloxybiphenyl) pyrimidine 5- (2-fluoro-2-methylheptanoyloxy)
Synthesis of 2- (4-hexyloxybiphenyl) pyrimidine 600 mg (1.7 mmol) of 5-hydroxy-2- (4-hexyloxybiphenyl) pyrimidine, 280 mg (1.7 mmol) of (−)-2-fluoro-2-methylheptanoic acid ), N, N-
350 mg (1.7 mmol) of dicyclohexylcarbodiimide and 20 mg (0.17 mmol) of 4-dimethylaminopyridine were dissolved in 20 ml of dry dichloromethane 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 toluene as a developing solvent, and recrystallized from ethanol to obtain 180 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.

During the cooling process, the liquid became a non-identifiable higher smectic phase from an isotropic liquid at 126.7 ° C, and became a crystal at 83.7 ° C.
During the heating process, a high-order smectic phase that could not be identified from the crystal was formed at 86.2 ° 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.

The response speed of this composition was 100 μsec (10 Vpp / μ
m, 25 ° C).

Comparative Example Preparation of Composition Using Comparative Compound 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.

In the above composition, the following formula of a comparative compound, When 6 wt% of a compound represented by the following formula was added, the following phase transition behavior was exhibited.

The response speed of this composition was 61 μsec (10 Vpp / μ
m, 25 ° C).

Thus, a compound in which the skeleton is changed to biphenyl,
It can be seen that the composition does not show a cholesteric phase and is not preferable due to problems such as orientation.

(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.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshihiro Hirai 3-17-35 Nishinaminami, Toda City, Saitama Japan Inside Mining Co., Ltd. (56) References JP-A-61-200973 (JP, A) JP-A Hei 3-151368 (JP, A) Natruforsch. , B: Chem. Sci. (58) Fields investigated (Int. Cl. ⁶ , DB name) C07D 239/34 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. The following general formula: (Wherein, R ¹ and R ² are alkyl groups, which may be the same or different). 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.