JPH1067715A - Ferridielectric liquid crystal compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject new compound suitably usable for an active matrix-type liquid crystal display element in which each pixel is driven. SOLUTION: This ferridielectric liquid crystal compound is shown by the formula (R is a 8-10C chain alkyl; (m) is an integer of 2-4; (n) is an integer of >=2; C* is an asymmetric carbon atom), e.g. R-(+)-3-trifluoromethyl-4-(1- trifluoromethyl-3-ethoxy-propyloxycarbonyl)phenyl-4'-n-nonyloxybipheny l-4- carboxylate. This liquid crystal compound of the formula is obtained by the following process: p-acetoxybenzoic acid is chlorinated by thionyl chloride followed by reaction with an optically active alcohol, and the reaction product is deacetylated and then reacted with a 4-alkyloxybiphenyl-4-carboxylic acid chloride. This ferridielectric liquid crystal compound is extremely low in threshold voltage and high in display grade.

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. An active matrix (AM) display element is 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]

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. (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. A special device is required for gradation display (for example, a ferroelectric liquid crystal element using monostable; Ke
iichi NITO et.al, SID'94, Preprint, p48), requires the development of advanced practical technology.

(2) Since the antiferroelectric liquid crystal does not have permanent spontaneous polarization, the burning problem described in the above (1) is avoided. In AM drive, at least 10
Although a liquid crystal material that is driven at a voltage of V or less is required, 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. An object of the present invention is to provide a new material suitable for AM driving which can solve the above-mentioned problems, and a ferrielectric liquid crystal can be considered as this new material.

A ferrielectric liquid crystal having a ferrielectric phase (SCγ * phase) was obtained in 1989 by 4- (1-methylheptyloxycarbonyl) phenyl = 4- (4′-octyloxybiphenyl).
First discovered in carboxylate (abbreviated MHPOBC) (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 apparent from the molecular arrangement state. However, in the coexistence state, the spontaneous polarizations cancel each other out, and 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 above-described intermediate state 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 substance.

Furthermore, 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
(-). FIG. 1 shows that in this ferroelectric state FO (+) or FO (-), a spontaneous polarization larger than that in the ferrielectric state FI (+) or FI (-) appears. As described 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.

The conventional ferroelectric liquid crystal switches between FO (+) and FO (-), whereas the ferrielectric liquid crystal displays 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, a ferrielectric liquid crystal generally has a small difference between a voltage changing from a ferrielectric state to a ferroelectric state and a voltage changing from a ferroelectric state to a ferrielectric state. That is, the width of the hysteresis tends to be very narrow, and is characterized by a V-shaped optical response.
It has properties suitable for gradation display in M drive and AM drive. 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.

However, the number of ferrielectric liquid crystals synthesized so far is extremely small, and the conventionally known ferrielectric liquid crystal has a problem in terms of hysteresis and threshold voltage when applied to an AM driving element. Nothing has been found satisfactory. The present invention relates to a new ferrielectric liquid crystal that can be suitably used for AM driving.

[0016]

That is, the present invention provides a liquid crystal compound represented by the following general formula (1).

Embedded image (Wherein, R represents a straight-chain alkyl group having 8 to 10 carbon atoms, and m represents 2 to
An integer of 4 n is an integer of 2 or more, and C * is an asymmetric carbon)

In the present invention, R has 9 carbon atoms and n
Is preferably 2 from the threshold voltage and the temperature range of the ferrielectric phase. For practical use, the transition temperature on the high-temperature side of the ferrielectric phase is preferably 30 ° C. or higher, and the temperature range of the ferrielectric phase is preferably 10 ° C. or higher.

The threshold voltage at the time of transition from the ferrielectric state to the ferroelectric state needs to be 5 V / μm or less, preferably 2 V / μm or less. The ferrielectric liquid crystal obtained according to the present invention has 2
Switching between one ferrielectric state and two ferroelectric states, and desirably there is no difference between the voltage changing from the ferrielectric state to the ferroelectric state and the voltage changing from the ferroelectric state to the ferrielectric state. Further, the ferrielectric liquid crystal obtained by the present invention can form an active matrix liquid crystal display element by being sandwiched between substrates on which a non-linear active element such as a thin film transistor or a diode is provided for each pixel.

The optically active alcohol used in the present invention can be prepared by the method disclosed by the present inventors (JP-A-4-983).
No. etc.). The outline of the manufacturing method is as follows. (B) Br (CH ₂ ) _m OC _n H _{2n + 1} + Mg → MgBr (CH ₂ ) _m OC _n H _{2n + 1} (b) (b) + CF ₃ COOH → CF ₃ CO (CH ₂ ) _m OC _n H _{2n + 1} (c) (b) + (LiAlH ₄ ) → CF ₃ CH (OH) (CH ₂ ) _m OC _n H _{2n + 1} (d) (c) + CH ₃ COCl → CF ₃ CH (OCOCH ₃ ) (CH ₂ ) _m OC _n H _{2n + 1} (e) (d) + (lipase) → R-(+) CF ₃ CH (OH) (CH ₂ ) _m OC _n H _{2n + 1} + S- ( -) CF ₃ CH (OCOCH ₃ ) (CH ₂ ) _m OC _n H _{2n + 1}

The method for producing the optically active alcohol will be briefly described as follows. (A) is a Grignard reagent preparation of an alkyloxybromide. (B) shows the production of a ketone by the reaction of a Grignard reagent and trifluoroacetic acid.
(C) Production of racemic alcohol by reduction of ketone. (D) Acetylation of racemic alcohol. (E)
Is an asymmetric hydrolysis reaction of acetate by lipase. By this reaction, the target optically active alcohol in R-form and the acetate in S-form are obtained.

The ferrielectric liquid crystal of the present invention will be described in detail in Examples, but can be easily produced by the method already disclosed by the present inventors (JP-A-3-292388). The outline of the manufacturing method is as follows. (1) AcO-Ph (CF ₃ ) -COOH + SOCl ₂ → AcO-Ph (CF ₃ ) -COCl (2) (1) + CF ₃ C * H (OH) (CH ₂ ) _m OC _n H _{2n + 1} → AcO-Ph (CF ₃ ) -COO-C * H (CF ₃ ) (CH ₂ ) _m OC _n H _{2n + 1} (3) (2) + (Ph-CH ₂ NH ₂ ) → HO-Ph ( CF ₃ ) -COO-C * H (CF ₃ ) (CH ₂ ) _m OC _n H _{2n + 1} (4) RO-Ph-Ph-COOH + SOCl ₂ → RO-Ph-Ph-COCl (5) (3 ) + (4) → target liquid crystal compound where AcO is an acetyl group, Ph is a 1,4-phenylene group, and Ph (C
F ₃ ) represents a —CF ₃ substituent at the 3-position of the 1,4-phenylene group.

The above-mentioned manufacturing method is briefly described as follows. (1) is a chlorination reaction of 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. (Five)
Is the production of liquid crystals by the reaction of phenol (3) with chloride (4).

[0023]

According to the present invention, a novel ferrielectric liquid crystal can be provided. Since the ferrielectric liquid crystal of the present invention has an extremely low threshold voltage, an active matrix driven liquid crystal display device having a high display quality can be realized.

[0024]

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): R = C ₉ H ₁₉ , m = 2, n = 2 (E1)) R-(+)-3-trifluoromethyl-4- (1-trifluoromethyl-3 -Ethoxy-propyloxycarbonyl) phenyl =
Production of 4'-n-nonyloxybiphenyl-4-carboxylate.

(1) Production of 4- (4'-n-nonyloxy) biphenylcarboxylic acid. 4- (4'-hydroxy) biphenylcarboxylic acid 10 g, n-nonyl bromide 14.0 g, ethanol 1,500 ml (milliliter),
The mixture was added to a mixture of 200 ml of water and reacted under reflux for 10 hours.
Further, 500 ml of water was added and the mixture was stirred for 3 hours. After completion of the reaction, the mixture was acidified by adding concentrated hydrochloric acid, and then 500 ml of the solvent was distilled off. This was sufficiently washed with water and recrystallized from chloroform to obtain 11.0 g of the desired product (1) as white crystals.

(2) Production of 4-acetoxy-2-trifluoromethylbenzoic acid. 4.3 g of 4-hydroxy-2-trifluoromethylbenzoic acid and 8.4 g of acetic anhydride were placed in a two-neck flask and mixed. Under water cooling, 5 drops of sulfuric acid were added. 80 ℃ after fever subsides
For 30 minutes. Then the reaction mixture is poured into cold water,
The precipitated crystals were filtered. The crystals were dried in a vacuum and then used in the next step. The yield was 4.7 g.

(3) Production of R-(+)-4-acetoxy-2-trifluoromethyl-1- (1-trifluoromethyl-3-ethoxy-propyloxycarbonyl) benzene. 1 g of 4-acetoxy-2-trifluoromethylbenzoic acid was added to 7 ml of thionyl chloride and reacted under reflux for 5 hours. Next, excess thionyl chloride was distilled off, and a mixture of 1 ml of pyridine, 4 ml of dry ether, and 1.0 g of R-(+)-1,1,1-trifluoro-4-ethoxy-2-butanol was added dropwise. After dripping,
The mixture was stirred overnight at room temperature, 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 target product was purified by silica gel column chromatography using hexane / ethyl acetate as a solvent to obtain 1.2 g of the target product.

(4) Production of R-(+)-4-hydroxy-2-trifluoromethyl-1- (1-trifluoromethyl-3-ethoxy-propyloxycarbonyl) benzene 1.2 g of the above compound (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 0.96 g of the desired product.

(5) R-(+)-3-trifluoromethyl-4- (1-trifluoromethyl-3-ethoxy-propyloxycarbonyl) phenyl = 4'-n-nonyloxybiphenyl-4-carboxylate Manufacturing of. A large excess of thionyl chloride was added to 1.0 g of 4- (4'-n-nonyloxy) biphenylcarboxylic acid prepared in (1), and the mixture was refluxed for 5 hours. After distilling off excess thionyl chloride, pyridine 1
After adding 0 ml and 25 ml of toluene, 25 ml of a benzene solution containing 0.84 g of the phenol derivative obtained in (4) was added dropwise, 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 hydroxide 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. Then, recrystallize with ethanol
1.3 g were obtained.

Examples 2 and 3 (General formula (1): R = C ₉ H ₁₉ , m = 3, n = 2 (E2)) R-(+)-3-trifluoromethyl-4- (1- Trifluoromethyl-4-ethoxy-butyloxycarbonyl) phenyl = 4 '
Preparation of -n-nonyloxybiphenyl-4-carboxylate, and (general formula (1): R = C ₉ H ₁₉ , m = 4, n = 2 (E3)) R-(+)-3-trifluoro Methyl-4- (1-trifluoromethyl-5-ethoxy-pentyloxycarbonyl) phenyl =
Production of 4'-n-nonyloxybiphenyl-4-carboxylate.

Instead of R-(+)-1,1,1-trifluoro-4-ethoxy-2-butanol in Example 1, R-(+)-1,1,1-
Trifluoro-5-ethoxy-2-pentanol, R-(+)-1,
The desired product was obtained in exactly the same manner as in Example 1, except that 1,1-trifluoro-6-ethoxy-2-hexanol was used.

The formula and 1H-NMR spectrum data of the target compound obtained in Examples 1 to 3 are shown in Chemical Formula 3 and Table 1, respectively. Phase identification can be performed by texture observation, conoscopic image observation and
The measurement was performed by DSC (differential scanning calorimetry). Observation of a conoscopic image is a powerful tool for identifying a ferrielectric phase. Observation of conoscopic images is described in the literature (J. Appl. Phys. 31,
793, (1992)). In addition, the optical response was examined. The cell was created by the following procedure. After a glass substrate with an ITO electrode was coated with polyimide (film thickness: 80 nm), only one of the pair of glass substrates was rubbed. Particle size 1.6μ
A pair of glass substrates were bonded to each other via a spacer m to form a test cell.

A test cell was filled with the above compound in an isotropic phase. The cell was gradually cooled at 1.0 ° C./min to align the liquid crystal. Next, a triangular wave voltage of ± 10 V, 5 Hz was applied to the test cell, and a change in the amount of transmitted light was measured by a photomultiplier. The threshold voltage was defined as a value at which the transmitted light intensity was 90%. These results are summarized in Table 2.

[0034]

Table 1 1H-NMR spectrum data of Examples 1 to 3 (E1-E3)-hydrogen atom number 1 2 3 4 5 6 7 8 E1 δ (ppm) 4.0 7.0 7.6 7.8 8.2 7.8 8.0 5.8 E2 4.0 7.0 7.6 7.8 8.2 7.8 8.0 5.6 E3 4.0 7.0 7.6 7.8 8.2 7.8 8.0 5.6

[0035]

[Table 2] Numerical values in parentheses in the above phase series indicate the transition temperature (° C.), Cr indicates a crystal phase, SCγ * indicates a chiral smectic Cγ phase (ferrielectric phase), and I indicates an isotropic phase.

[0036]

Embedded image

[Brief description of the drawings]

FIG. 1 shows a molecular arrangement state in a ferrielectric phase.

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

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

Claims (10)

[Claims] 1. A ferrielectric liquid crystal compound represented by the following general formula (1). Embedded image (Wherein, R represents a straight-chain alkyl group having 8 to 10 carbon atoms, and m represents 2 to
An integer of 4 n is an integer of 2 or more, and C * is an asymmetric carbon) 2. In the general formula (1), R has 9 carbon atoms.
The ferrielectric liquid crystal compound according to claim 1, which is: 3. The ferrielectric liquid crystal compound according to claim 1, wherein n is 2 in the general formula (1). 4. The transition temperature on the high-temperature side of the ferrielectric phase is 30.
2. The ferrielectric liquid crystal compound according to claim 1, wherein the temperature is higher than or equal to ° C. 5. The ferrielectric liquid crystal compound according to claim 1, wherein the temperature range of the ferrielectric phase is 10 ° C. or higher. 6. The ferrielectric liquid crystal compound according to claim 1, wherein the threshold voltage at the time of transition from the ferrielectric state to the ferroelectric state is 5 V / μm or less. 7. The ferrielectric liquid crystal compound according to claim 1, wherein a threshold voltage at the time of transition from the ferrielectric state to the ferroelectric state is 2 V / μm or less. 8. The ferrielectric liquid crystal according to claim 1, wherein switching is performed between two ferrielectric states and two ferroelectric states by a voltage. 9. The ferrielectric liquid crystal according to claim 1, wherein there is no difference between a voltage changing from the ferrielectric state to the ferroelectric state and a voltage changing from the ferroelectric state to the ferrielectric state. 10. An active matrix liquid crystal display device comprising the ferrielectric liquid crystal according to claim 1 sandwiched between substrates on which a non-linear active device such as a thin film transistor or a diode is provided for each pixel.