JP2001226326A - Ferridielectric liquid crystal compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new ferridielectric liquid crystal compound which exhibits a ferridielectric phase in a wide temperature range. SOLUTION: This ferridielectric liquid crystal compound represented by the general formula (1) (R is a 6 to 12C linear alkyl; X is H or F; C* is an asymmetric carbon atom).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrielectric liquid crystal compound which can be suitably used for an active matrix type liquid crystal display device driven for each pixel.

[0002]

2. Description of the Related Art Liquid crystal display devices (LCDs) are already becoming popular mainly in portable devices as flat panel displays replacing conventional CRT displays. With the recent expansion of the functions of personal computers and word processors and the increase in the amount of processing information, LC
D is also required to have higher functions, that is, higher display capacity, full color display, wide viewing angle, high-speed response, high contrast, and the like.

As a liquid crystal display system (liquid crystal driving system) that meets such a demand, a thin film transistor (TFT) or a diode (MIM) is formed for each pixel of a screen, and a liquid crystal is independently driven for each pixel. Has been proposed and implemented. Although this display method has problems such as low cost and difficulty in increasing the screen size due to low production yield, the display quality surpasses the conventional mainstream STN display method due to its high display quality. The momentum is approaching.

[0004]

In such an AM display element, the following problem occurs because a TN (twisted nematic) liquid crystal is used as a liquid crystal material. (1) The TN liquid crystal is a nematic liquid crystal, and its response speed is generally slow (several tens of ms), and good image quality cannot be obtained when displaying a moving image. (2) The viewing angle is narrow because the display is performed using the twisted state (twist alignment) of the liquid crystal molecules. Especially when performing gradation display,
The viewing angle sharply narrows. That is, the contrast ratio, color, and the like change depending on the viewing angle of the display.

In order to solve these problems, an AM using a ferroelectric liquid crystal or an antiferroelectric liquid crystal instead of a TN liquid crystal has been proposed.
Panel proposals have also been made in recent years (Japanese Unexamined Patent Publication No.
5-150257, 6-95080, etc.) These liquid crystals also have the following problems, and the wall for practical use is currently thick. (1) The ferroelectric liquid crystal has spontaneous polarization, but since spontaneous polarization always exists, image burn-in easily occurs and driving is difficult. Further, since a ferroelectric liquid crystal can display only black and white in principle, gradation display is extremely difficult. Special considerations are required for gradation display in ferroelectric liquid crystal (for example, ferroelectric liquid crystal element using monostable; Keiichi NITO et.al, SID'94, Prep
rint, p48), the development of advanced practical technology is required.

(2) Since the antiferroelectric liquid crystal does not have spontaneous polarization, the burning problem described in (1) above is avoided. In the AM driving, a liquid crystal material which is driven at least at 10 V or less is required. However, antiferroelectric liquid crystals generally have a large threshold voltage, and it is difficult to drive at a low voltage. In addition, there is a problem that gradation display is difficult due to a history (hysteresis) in optical response.

A ferrielectric liquid crystal has been proposed as a new material suitable for AM driving which can solve the above problems. This liquid crystal material can be driven at a voltage of 10 V or less, and has an optical response to applied voltage that is symmetrical in the positive voltage region and the negative voltage region and has a small hysteresis. However, the number of ferrielectric liquid crystal compounds synthesized to date is extremely small, and the conventionally known ferrielectric liquid crystal is not always satisfactory when applied to an AM driving element. In this regard, it would be beneficial to find new ferrielectric liquid crystal compounds.

[0008]

That is, the present invention is a ferrielectric liquid crystal compound represented by the following general formula (1). In the present invention, in the general formula (1), R has 9 carbon atoms.
Are preferred. Further, it is preferable that the transition temperature on the high temperature side of the ferrielectric phase be 60 ° C. or more, and that the temperature difference between the transition temperature on the high temperature side and the transition temperature on the low temperature side be 50 ° C. or more.
The liquid crystal composition using the ferrielectric liquid crystal compound of the present invention can be used as an active matrix liquid crystal display device by being sandwiched between substrates on which nonlinear active elements such as thin film transistors or diodes are installed for each pixel. it can.

[0009]

Embedded image (In the formula, R is a straight-chain alkyl group having 6 to 12 carbon atoms, X is a hydrogen atom or a fluorine atom, and C * is an asymmetric carbon atom.)

The outline of the method for producing the optically active alcohol used in the present invention is as follows. (B) CH ₃ CO (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅ + NaBH ₄ → CH ₃ CH (OH) (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅ (b) CH ₃ CH (OH) (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅ + CH ₃ CH ₂ COOCH = CH ₂ + (lipase) → CH ₃ C * H (OCOC ₂ H ₅ ) (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅ + CH ₃ C * H (OH) (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅ (C) CH ₃ C * H (OCOC ₂ H ₅ ) (CH ₂ ) ₂ CH ( CH ₃ ) C ₂ H ₅ + KOH → (R-(-))-CH ₃ C * H (OH) (CH ₂ ) ₂ CH (CH ₃ ) C ₂ H ₅

The method for producing the above optically active alcohol will be briefly described as follows. (A) Reduction of 4-ethyl-2-hexanone to alcohol. (B) Asymmetric transesterification of alcohol (a) with vinyl propionate. (C) Hydrolysis reaction of ester (b).

[0012]

The novel ferrielectric liquid crystal compound provided by the present invention exhibits a ferrielectric phase in a wide temperature range. Therefore, it is extremely useful as a practical material.

[0013]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Example 1 (Equation (1): R = C ₉ H ₁₉ , X = F (E1))
Production of (-)-3-fluoro-4- (1,4-dimethylhexyloxycarbonyl) phenyl-4'-nonyloxy-4-biphenylcarboxylic acid ester.

(1) Production of 4- (4'-n-nonylyloxy) biphenylcarboxylic acid. 10.0 g of 4- (4'-hydroxy) biphenylcarboxylic acid,
n-Nonyl bromide 17.5 g, triethylamine 16 ml (milliliter), dimethylaminopyridine 1 g
It was dissolved in 50 ml and stirred at room temperature for 24 hours. After the reaction, 1
50 ml of 0% hydrochloric acid was added, and the mixture was extracted three times with 100 ml of ether. The organic phase was washed three times with 100 ml of brine and dried over anhydrous sodium sulfate. After evaporating the solvent, the residue was washed with 400 ml of hexane to obtain the desired product.

(2) Production of 4-acetoxy-2-fluorobenzoic acid. 4.3 g of 2-fluoro-4-hydroxybenzoic acid and acetic anhydride
8.4 g was mixed in a two-neck flask and mixed. Under water cooling, 5 drops of sulfuric acid were added. After the exotherm subsided, the mixture was heated at 80 ° C. for 30 minutes. Thereafter, the reaction mixture was poured into cold water, and the precipitated crystals were separated by filtration. The crystals were dried in a vacuum and then used in the next step.

(3) R-(-)-4-acetoxy-2-fluoro-1-
Production of (1,4-dimethylhexyloxycarbonyl) benzene. 1.0 g of 4-acetoxy-2-fluorobenzoic acid was added to 7 ml of thionyl chloride and reacted under reflux for 5 hours. Next, after distilling off excess thionyl chloride, 1 ml of pyridine, 4 ml of dry ether, 0.6 g of R-(-)-5-methylheptane-2-ol
Was added dropwise. After the addition, the mixture was stirred at room temperature for one day and night.
The mixture was diluted with 200 ml of ether, and 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 was distilled off, and the crude product was purified by silica gel column chromatography using hexane / ethyl acetate as a solvent to obtain the desired product.

(4) R-(-)-4-hydroxy-2-fluoro-1-
(1,4-Dimethylhexyloxycarbonyl) production of benzene 1.0 g of the compound obtained in the above (3) was dissolved in 30 ml of ethanol, and 3 g of benzylamine was added dropwise. After stirring at room temperature for one day, the mixture was diluted with 300 ml of ether, washed with diluted hydrochloric acid and water in that order, and dried over magnesium sulfate. After evaporating the solvent, the residue was isolated and purified by silica gel column chromatography to obtain the desired product.

(5) R-(-)-3-fluoro-4- (1,4-dimethylhexyloxycarbonyl) phenyl-4'-nonyloxy-
Production of 4-biphenylcarboxylic acid ester. To 1.0 g of the compound obtained in the above (1), 10 ml of thionyl chloride was added, and the mixture was heated under reflux for 10 hours. After distilling off excess thionyl chloride, 10 ml of pyridine and 25 ml of toluene were added.
25 ml of a benzene solution of 0.8 g of the compound obtained in the above (4) was added dropwise, and reacted at room temperature for 10 hours. After completion of the reaction, ether
The mixture was diluted with 300 ml, washed with diluted hydrochloric acid, a 1N aqueous solution of sodium carbonate and water in that 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. Then, the product was recrystallized from ethanol to obtain the desired product.

The formula of the obtained liquid crystal compound is shown in Chemical formula 3, and the NMR data is shown in Table 1. The phases were identified by texture observation, observation of a conoscopic image, and measurement by DSC (differential scanning calorimeter). Observation of a conoscopic image is a powerful tool for identifying a ferrielectric phase. Observation of the conoscopic image was performed according to the literature (J. Appl. Phys. 31, 793, (1992)). The cell gap was 150 μm, and the observed liquid crystal phase was in a bulk state. The results are shown in Table 2.

Table 1 Hydrogen atom number 1 2 3 4 5 6 7 8 Example 1 δ (ppm) 7.0 7.6 7.8 8.1 7.1 7.1 8.0 5.1

[0021]

Embedded image

[0022] In the phase series, the numbers in parentheses indicate the phase transition temperature (° C.), I is an isotropic phase, SA is a smectic A phase, SCγ * is a ferrielectric phase, SX is an unidentified phase, and Cr is a crystalline phase. Show.

Claims (4)

[Claims] 1. A ferrielectric liquid crystal compound represented by the following general formula (1). Embedded image (In the formula, R is a straight-chain alkyl group having 6 to 12 carbon atoms, X is a hydrogen atom or a fluorine atom, and C * represents an asymmetric carbon atom.) 2. In the general formula (1), R has 9 carbon atoms.
The ferrielectric liquid crystal compound according to claim 1, which is: 3. The transition temperature on the high-temperature side of the ferrielectric phase is 60 ° C.
2. The ferrielectric liquid crystal compound according to claim 1, wherein the temperature difference between the transition temperature on the high temperature side and the transition temperature on the low temperature side is 50 ° C. or more. 4. An active matrix liquid crystal comprising a liquid crystal composition containing a ferrielectric liquid crystal compound according to claim 1 sandwiched between substrates on which a non-linear active element such as a thin film transistor or a diode is provided for each pixel. Display element.