JPH10120629A - Phenyl ester compound and ferridielectric liquid crystal composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new compound capable of actualizing a ferridielectric liquid crystal display element high in display quality, comprising a compound having a specific structure. SOLUTION: This phenyl ester compound is shown by formula I ((m) is 5-12; (n) is an integer of 1-4) such as 4-(2,2,2-trifluoroethyl)-(2,2,2-trifloroethyl)- decanoyloxy benzoate. The compound of formula I is obtained by dissolving 4-hydroxybenzoic acid in dichloromethane, successively adding triethylamine, n-decanoic acid chloride and dimethylaminopyridine, reacting them, adding an acid, extracting the reaction mixture with an ether to give 4- decanoyloxybenzoic acid, adding thionyl chloride to the benzoic acid, further adding 2,2,2-trifluoroethanol and pyridine and reacting. A ferridielectric liquid crystal composition suitable for a liquid crystal display element of an active matrix type is obtained by adding 1-50mol% of the composition a ferridielectric liquid crystal of formula II (R is a 6-12C straight-chain alkyl; X is H or F; (p) is an integer of 2-4).

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 and a ferrielectric liquid crystal containing the same, and is 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, large 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. An active matrix (AM) display element is proposed and implemented. This display method has problems such as low production yield, low cost is difficult, and large screen is difficult.
Due to the high display quality, it has surpassed the STN display method which has been mainstream in the past, and is approaching the CRT.

[0004]

However, 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 display angle is narrow because display is performed by using the twisted state (twist alignment) of 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.

(A) A ferroelectric liquid crystal has spontaneous polarization. However, since spontaneous polarization always exists, image burn-in easily occurs and driving is difficult. Further, when the ferroelectric liquid crystal is displayed in the surface stabilization mode, only binary display of black and white can be performed, so that gradation display is extremely difficult. A special device is required when performing gradation display (for example, a ferroelectric liquid crystal element using monostable; Keiichi NITO et.al, S
ID'94, Preprint, p48), requiring the development of advanced practical technology.

(B) Since the antiferroelectric liquid crystal does not have permanent spontaneous polarization, the problem of burn-in described in (A) is avoided. At least 10V for AM drive
A liquid crystal material driven below is required. However, the antiferroelectric liquid crystal generally has 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. An object of the present invention is to provide a new material suitable for AM driving that can solve the above problems,
A liquid crystal having a ferrielectric phase can be considered as this new material.

[0008] In 1989, a liquid crystal compound having a ferrielectric phase (SCγ * phase) was obtained from 4- (1-methylheptyloxycarbonyl) phenyl 4- (4'-octyloxybiphenyl) carboxylate (abbreviated as MHPOBC). First discovered (Japanese Journal of Applied Physics, Vol.29, No.
1, 1990, pp. L131-137).

Structural formula of MHPOBC and phase transition temperature (° C.)
Is shown below. Structural formula: C ₈ H ₁₇ -O-Ph-Ph-COO-Ph-COO-C * H (CH ₃ ) -C ₆ H ₁₃ where Ph is 1,4-phenylene group and C * is asymmetric carbon Represent. Phase series: I (147) SA (122) SCα * (121) SC * (119) SCγ * (11
8) SCA * (65) SIA * (30) Cr where I is isotropic, SA is smectic A phase, SCα * is chiral smectic Cα phase, SC * is chiral smectic C phase (ferroelectric phase), SCγ * Is chiral smectic C
γ phase (ferrielectric phase), SCA * is chiral smectic C
A phase (antiferroelectric phase), SIA * is chiral smectic IA
The phase, Cr, indicates a crystalline phase.

In order to explain a ferrielectric liquid crystal, FIG.
2 shows the molecular arrangement state in the ferrielectric phase, and FIG. 2 shows the optical response of the ferrielectric phase to a triangular wave. In the ferrielectric phase, FI (+) (when the applied voltage is positive) or FI
The molecular arrangement is (-) (when the applied voltage is negative). In the absence of an electric field, FI (+) and FI (-) coexist because they are equivalent. Therefore, the average optical axis is in the direction of the normal to the layer, and is in a dark state under the conditions of the polarizing plate shown in FIG. This state corresponds to a state where the transmitted light intensity is 0 at a voltage of 0 in FIG.

Further, FI (+) and FI (-) have spontaneous polarizations, respectively, as evident from the molecular arrangement state. However, in the coexistence state, the spontaneous polarizations cancel each other, so that the average spontaneous polarization is zero. Becomes For this reason, the ferrielectric liquid crystal escapes the image sticking phenomenon observed in the ferroelectric liquid crystal, like the antiferroelectric liquid crystal.

When a voltage is applied to the ferrielectric liquid crystal, a region (domain) having an extinction position appears at a lower voltage than when the ferroelectric state is reached. This region has an optical axis in a direction inclined from the normal direction, though not so much as in the ferroelectric state. This intermediate state is considered FI (+) or FI (-). In this case, in FIG. 2, the transmitted light intensity on the stairs should be observed instead of a continuous change in the transmitted light intensity between the voltages 0 V and 4 V.
However, continuous transmitted light intensity was observed in FIG. This is probably because the threshold voltage of FI (+) → FO (+) or FI (-) → FO (-) is not clear. In the present invention, a liquid crystal phase in which the intermediate state described above is always observed is referred to as a ferrielectric phase, and a liquid crystal compound in which the ferrielectric phase is the broadest in the phase series is referred to as a ferrielectric liquid crystal.

Further, when the applied voltage is increased, the ferroelectric phase FO (+) or FO (-) which is in a stable state according to the direction of the electric field is increased.
Phase transition. That is, in FIG. 2, the transmitted light intensity is in a saturated state (a flat portion on the left and right), and the intensity is FO (+) or FO
(-). In this ferroelectric state FO (+) or FO (-),
It can be seen from FIG. 1 that a spontaneous polarization larger than that of the ferrielectric state FI (+) or FI (-) appears. As mentioned above,
In the ferrielectric phase, the coexistence state of FI (+) and FI (-) can be used as dark, and the ferroelectric states FO (+) and FO (-) can be used as light.

Conventional ferroelectric liquid crystals switch between FO (+) and FO (-), while ferrielectric liquid crystals have FO (+), FI (+), FI (-) and It has the great feature of switching between the four states of FO (-). In addition, all of the display principles use birefringence of liquid crystal, and a display element with small viewing angle dependence can be manufactured.

As shown in FIG. 2, the ferrielectric phase generally has a small difference between the voltage at which the ferrielectric state changes to the ferroelectric state and the voltage at which the ferroelectric state changes to the ferrielectric state. It is characterized by a very narrow hysteresis width and a V-shaped optical response.
It has properties suitable for gradation display in driving and AM driving. In addition, the threshold voltage, which is the voltage at which the ferrielectric liquid crystal changes from a ferrielectric state to a ferroelectric state, tends to be much smaller than that of an antiferroelectric liquid crystal. It can be said that the dielectric liquid crystal is suitable for AM driving.

[0016]

However, the number of ferrielectric liquid crystals synthesized to date is extremely small,
Further, the conventionally known ferrielectric liquid crystal alone has the following problems when applied to an AM driving element. First, the ferrielectric liquid crystal has a very small hysteresis width in the optical response to voltage, but is not completely eliminated. For this reason, a problem has arisen in gradation display, and it is required to reduce the width of hysteresis as much as possible. Second, ferrielectric liquid crystals are not so excellent in orientation. Therefore, it is inferior in contrast in comparison with the current active matrix drive display device using a nematic liquid crystal. An object of the present invention is to improve these points, to reduce the hysteresis of a ferrielectric liquid crystal, and to improve an alignment property, and an additive containing the additive, which is preferably used for an AM drive and containing the same. Liquid crystal composition.

[0017]

That is, the present invention relates to a phenyl ester compound represented by the following general formula (1), wherein in the general formula (1), m is 9 and the compound does not have a liquid crystal phase. It is preferable to obtain a ferrielectric liquid crystal composition having excellent physical properties. Also,
The present invention is a ferrielectric liquid crystal composition obtained by adding a phenyl ester compound represented by the following general formula (1) to a ferrielectric liquid crystal represented by the following general formula (2).

[0018]

Embedded image (In the formula (1), m represents an integer of 5 to 12, n represents an integer of 1 to 4, and
In (2), R is a linear alkyl group having 6 to 12 carbon atoms, X is an H atom or an F atom, p is an integer of 2 to 4, and q is an integer of 2 to 4. )

The amount of the phenyl ester compound represented by the general formula (1) is preferably 1 to 50 mol% of the composition,
More preferably, it is 1 to 30 mol%. As a ferrielectric liquid crystal liquid crystal composition, the transition temperature on the high temperature side of the ferrielectric phase is 40 ° C. or more, and the transition temperature on the low temperature side is 0 ° C. or less,
It is preferable to have a smectic A phase on the higher temperature side than the ferrielectric phase. Then, the ferrielectric liquid crystal liquid crystal composition of the present invention is sandwiched between substrates on each of which a non-linear active element such as a thin film transistor or a diode is provided to form an active matrix liquid crystal display element. Driving of the used liquid crystal by voltage is performed by switching between two ferrielectric states, two ferroelectric states, and an intermediate state between them.

The ferrielectric liquid crystal of the present invention can be easily produced by the present inventors in Japanese Patent Application No. 8-91235.
The outline of the production method is as follows for a compound in which p = 3 and q = 2 in the general formula (2). (1) AcO-Ph (3X) -COOH + SOCl ₂ → AcO-Ph (3X) -COCl (2) (1) + CF ₃ C * H (OH) (CH ₂ ) ₃ OC ₂ H ₅ → AcO- Ph (3X) -COO-C * H (CF ₃ ) (CH ₂ ) ₃ OC ₂ H ₅ (3) (2) + (Ph-CH ₂ NH ₂ ) → HO-Ph (3X) -COO-C * H (CF ₃ ) (CH ₂ ) ₃ OC ₂ H ₅ (4) RO-Ph-Ph-COOH + SOCl ₂ → RO-Ph-Ph-COCl (5) (3) + (4) → Desired ferrielectricity In the formula, AcO is an acetyl group, Ph is a 1,4-phenylene group, and Ph (3
X) is a 1,4-phenylene group which may be F-substituted at the 3-position, and C * represents an asymmetric carbon.

The above-mentioned manufacturing method is briefly described as follows. (1) is a chlorination reaction of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride. (2)
Is the formation of an ester by the reaction of chloride (1) with an optically active alcohol. (3) is the deacetylation of ester (2). (4) is the chlorination of 4'-alkyloxybiphenyl-4-carboxylic acid. (5) is phenol (3) and chloride
(4) to produce a liquid crystal.

[0022]

The present invention provides a novel phenyl ester compound and a ferrielectric liquid crystal composition containing the same. And the novel ferrielectric liquid crystal composition provided by the present invention has greatly reduced hysteresis and excellent alignment. Therefore, a ferrielectric liquid crystal display element having high display quality can be realized.

[0023]

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 (general formula (1): m = 9, n = 1 (E1)) 4-
Production of (2,2,2-trifluoroethyl) -decanoyloxybenzoate.

(1) Production of 4-decanoyloxybenzoic acid. 12.2 g (0.1 mol) of 4-hydroxybenzoic acid in dichloromethane
Dissolved in 140 ml (milliliter). Triethylamine there 1
6 ml, 20.1 g (0.11 mol) of n-decanoic acid chloride and 0.97 g (0.0079 mol) of dimethylaminopyridine are added in sequence, and the mixture is added at room temperature.
The mixture was stirred day and night. To this, add 50 ml of 10% hydrochloric acid and add ether
Extracted three times with 100 ml. The organic layer was washed three times with 100 ml of a saline solution and dried over anhydrous sodium sulfate. After evaporating the solvent, the residue was washed with 400 ml of hexane to obtain 23.9 g (yield: 82%) of the target 4-decanoyloxybenzoic acid.

(2) Production of 4- (2,2,2-trifluoroethyl) -decanoyloxybenzoate. 0.5 g of 4-decanoyloxybenzoic acid obtained in the above (1) (0.00 g)
(17 mol) was added with thionyl chloride (10 ml), and the mixture was heated under reflux for 4 hours. Thionyl chloride was distilled off, and the entire amount of the obtained acid chloride was dissolved in toluene. There, 0.08 g (0.0015 mol) of 2,2,2-trifluoroethanol and 0.27 g of pyridine
(0.0034 mol), and the mixture was stirred at room temperature for 24 hours. Here, 10 ml of water was added, and the mixture was stirred for 30 minutes.
And extracted twice with 20 ml of dichloromethane. After the organic layer was washed with 20 ml of water, it was evaluated with anhydrous sodium sulfate. The solvent was distilled off to obtain 0.5 g of a crude product. This was isolated by silica gel chromatography.
76%).

Example 2 (general formula (1): m = 9, n = 3
(E2)) Production of 4- (4,4,4-trifluorobutyl) -decanoyloxybenzoate. The desired product was obtained in the same manner as in Example 1 except that 4,4,4-trifluorobutanol was used instead of 2,2,2-trifluoroethanol. Example 1,
The 1H-NMR data and melting point of the target compound (E1, E2) obtained in 2 are shown in Table 1, and its chemical formula is shown in Chemical Formula 4. The liquid crystal phase was observed by texturer observation and DSC (differential scanning calorimetry) measurement, but no liquid crystal phase was observed.

[0027]

[Table 1] Proton number 1 2 3 4 5 6 Melting point (° C) Example 1 2.6 8.1 7.2 4.7 30 Example 2 2.6 8.1 7.2 4.4 2.3 2.1 35

[0028]

Embedded image

Example 3 A ferrielectric liquid crystal (2A) represented by the following formula was used in Example 1
20 mol% of the phenyl ester compound (E1) obtained in was added to obtain a ferrielectric liquid crystal composition. Table 2 shows the measurement results of the phase series, hysteresis, and orientation. 2A: C ₉ H ₁₉ -O-Ph-Ph-COO-Ph (3F) -COO-C * H (CF ₃ ) (CH ₂ ) ₃ OC ₂ H ₅ Ph in the formula is a 1,4-phenylene group, Ph (3F) is a 1,4-phenylene group substituted by fluorine at the 3-position, and C * is an asymmetric carbon.

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 conoscopic images is described in the literature (J. Ap
pl. Phys. 31, 793, (1992)).

The hysteresis and the like were measured according to the following procedure.
After polyimide coating of a glass substrate with an insulating film (SiO ₂ , thickness of 50 nm) and ITO electrode (about 80 nm in thickness), only one of the pair of glass substrates was rubbed. Particle size 1.6μm
A pair of glass substrates were bonded to each other via the spacer described above to form a test cell. The cell thickness was 2 μm. The liquid crystal was heated to a temperature at which the liquid crystal became an isotropic phase, and the liquid crystal was injected into a test cell by capillary action. Thereafter, the liquid crystal was gradually cooled at a rate of 1 ° C./min to parallel align the liquid crystal. Next, a triangular wave voltage of ± 10 V, 50 mHz was applied to the test cell at 25 ° C., and the test cell was driven to observe the hysteresis. The result is shown in FIG.

At 25 ° C., empty cells were placed between orthogonal polarizing plates, and the amount of transmitted light was determined. The amount of transmitted light was set to 0%. Next, a test cell was placed, and the amount of transmitted light in the ferroelectric state was determined, and the amount of transmitted light was set to 100%. At 25 ° C., the applied light amount to the test cell was 0, the amount of transmitted light was determined, and the value of the light leakage was used to evaluate the degree of orientation. For comparison, Table 2 shows the results of evaluating the characteristics of the ferrielectric liquid crystal (2A) in the same manner as described above except that the measurement temperature was 40 ° C.

[0033]

[Table 2] Light leakage Measurement temperature phase sequence (%) (° C) Example 3 Cr (<-20) SCγ * (71) SA (82) I 1.0 25 liquid crystal 2A Cr (34) SCγ * (101) SA (103) I 3.0 40 The values in parentheses in the above phase series are the transition temperature (° C), Cr is the crystal phase, SCγ * is the chiral smectic Cγ phase (ferrielectric phase), SA is the smectic A phase, and I is the same. Each phase is shown.

[Brief description of the drawings]

FIG. 1 shows a molecular arrangement state in a ferrielectric phase. FI
(+) And FI (-) indicate a ferrielectric state, and FO (+) and FO (-) indicate a ferroelectric state.

FIG. 2 shows an optical response of a ferrielectric phase to a triangular wave voltage.

FIG. 3 shows the optical response of the composition of Example 3 to a triangular wave voltage.

FIG. 4 shows an optical response of the liquid crystal 2A to a triangular wave voltage.

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

Claims (10)

[Claims] 1. A phenyl ester compound represented by the following general formula (1). Embedded image (In the formula, m is an integer of 5 to 12, and n is an integer of 1 to 4.) 2. The phenyl ester type compound according to claim 1, wherein m is 9 in the general formula (1). 3. The phenyl ester compound according to claim 1, wherein the compound represented by the general formula (1) has no liquid crystal phase. 4. A ferrielectric liquid crystal composition obtained by adding a phenyl ester compound represented by the following general formula (1) to a ferrielectric liquid crystal represented by the following general formula (2). Embedded image (In the formula (1), m represents an integer of 5 to 12, n represents an integer of 1 to 4, and
In (2), R is a linear alkyl group having 6 to 12 carbon atoms, X is an H atom or an F atom, p is an integer of 2 to 4, and q is an integer of 2 to 4. ) 5. In the general formula (2), R has 9 carbon atoms.
The ferrielectric liquid crystal liquid crystal composition according to claim 4, which is: 6. The ferrielectric liquid crystal composition according to claim 4, wherein the amount of the phenyl ester compound represented by the general formula (1) is 1 to 50 mol% of the composition. 7. The ferrielectric liquid crystal liquid crystal composition according to claim 4, wherein the amount of the phenyl ester compound represented by the general formula (1) is 1 to 30 mol% of the composition. 8. The ferrielectric phase having a transition temperature on the high temperature side of 40.
The ferrielectric liquid crystal composition according to claim 4, which has a transition temperature on the low temperature side of 0 ° C or higher at 0 ° C or higher and a smectic A phase on the higher temperature side than the ferrielectric phase. 9. An active matrix liquid crystal display device, wherein the ferrielectric liquid crystal composition according to claim 4 is sandwiched between substrates on which a non-linear active element such as a thin film transistor or a diode is provided for each pixel. 10. The method of driving a liquid crystal using a voltage using a nonlinear active element by two ferrielectric states and two ferroelectric states,
8. The active matrix liquid crystal display element according to claim 7, wherein the active matrix liquid crystal display element is switched by switching to an intermediate state.