JP2001019665A - A phenyl ester compound and a liquid crystal composition containing the same. - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To obtain a liquid crystal composition having improved alignment properties. SOLUTION: A phenyl ester compound having a trifluoromethoxy group and a cyclohexane ring represented by the following general formula (1), and the phenyl ester compound,
A liquid crystal composition comprising a ferrielectric liquid crystal compound represented by the following general formulas (2) and (3) and a compound represented by the following general formula (4). Embedded image (Wherein, R ² , R ³ and R ⁴ are linear alkyl groups having 6 to 10 carbon atoms, X ¹ , X ² and X ³ are a hydrogen atom or a fluorine atom, m,
n, p and q are integers from 1 to 4, and C * is an asymmetric carbon atom. [Effect] The liquid crystal composition of the present invention has excellent alignment properties and exhibits nonlinear optical response to applied voltage. Therefore, an active matrix liquid crystal display device having excellent display quality and high reliability can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel liquid crystal composition. The novel liquid crystal composition of the present invention exhibits a non-linear optical response to an applied voltage and has excellent alignment. Therefore, an active matrix liquid crystal display device with high display quality can be realized.

[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 cathode ray tube displays (CRTs). With the recent expansion of the functions of personal computers and word processors and the increase in the capacity of processing information, LCDs also have higher functions, namely, large display capacity, full color display, wide viewing angle, high-speed response, and high contrast. Has been requested.

As a liquid crystal display system (liquid crystal driving system) that meets such demands, a thin film transistor (TFT) or a diode (M1M) is formed for each pixel of a screen, and a liquid crystal is independently driven for each pixel. Has been proposed and implemented. This display method had problems such as low manufacturing yield, which made it difficult to reduce costs and large screens.However, those problems were gradually solved, and the high display quality required Surpassing the mainstream STN display system, CRT
It is approaching momentum.

[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 milliseconds), and good image quality cannot be obtained when displaying moving images. (2) The viewing angle is narrow because display is performed 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) The ferroelectric liquid crystal has spontaneous polarization, but since spontaneous polarization always exists, seizure of both surfaces is liable to occur and driving becomes 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.
l., SID '94, Preprint, p48), and the development of advanced practical technology is required.

(B) Since the antiferroelectric liquid crystal does not have a permanent spontaneous polarization, the problem of burning described in the above (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 low-voltage driving is difficult. Further, there is a problem that gradation display is difficult due to a history (hysteresis) in optical response.

In recent years, the inventors have discovered a liquid crystal material which solves such a problem (Japanese Patent Laid-Open No. 8-337555).
This material is a liquid crystal material that can be driven at 10 V or less, has no history in optical response, and exhibits a nonlinear optical response that is symmetrical in the positive voltage region and the negative voltage region and has no hysteresis in the optical response to the applied voltage, Ideal for active matrix driving. Generally, the orientation of such a liquid crystal material is better than that of another smectic liquid crystal, which is an antiferroelectric liquid crystal. However, the orientation is inferior to that of the nematic liquid crystal, and it has been difficult to obtain the same level of contrast as a display using a nematic liquid crystal. This is due to light leakage in the state of no applied voltage due to defects on fine streaks or twist orientation. The present invention provides a compound for improving such an alignment defect and a liquid crystal material containing the compound and having excellent alignment properties.

[0009]

That is, the present invention provides a phenylester compound having a trifluoromethoxy group and a cyclohexane ring represented by the following general formula (1):
And the phenyl ester compound, the following general formula (2):
A liquid crystal composition comprising a ferrielectric liquid crystal compound represented by (3) and a compound represented by the following general formula (4).

[0010]

Embedded image (Wherein, R ² , R ³ and R ⁴ are linear alkyl groups having 6 to 10 carbon atoms, X ¹ , X ² and X ³ are a hydrogen atom or a fluorine atom, m,
n, p and q are integers from 1 to 4, and C * is an asymmetric carbon atom. )

In the liquid crystal composition of the present invention, the general formula
The phenyl ester compound represented by (1) is a property improving agent effective in eliminating alignment defects. The general formula (2)
Is a ferrielectric liquid crystal, which determines the basic electro-optical properties of the composition, wherein R ² has 8 to 10 carbon atoms, m is 2, n is 1 or 2, X It is particularly effective when ² is a fluorine atom. Compound represented by the general formula (3) are likewise ferrielectric liquid crystal compound represented by the general formula (2), but determines the basic electro-optical properties of the composition, the number of carbon atoms of R ³ is 8-10, p is 2, q is 1, X ³
Is particularly effective when is a fluorine atom. The general formula
The compound (4) is particularly effective in lowering the viscosity of the composition, and is effective when R ⁴ has 8 to 10 carbon atoms.

In the present liquid crystal composition, the amount of the phenyl ester compound represented by the general formula (1) is from 5 to 5% of the composition.
20 mol% is preferable, and particularly preferably 10 to 20 mol%. The addition amount of the ferrielectric liquid crystal compound represented by the general formula (2) is desirably 10 to 50 mol% of the composition. The addition amount of the ferrielectric liquid crystal compound represented by the general formula (3) is desirably 5 to 20 mol% of the composition. The addition amount of the compound represented by the general formula (4) is desirably 10 to 25 mol% of the composition.
In the optical response to the applied voltage of the composition, it is particularly desirable to exhibit a non-linear optical response that is symmetrical in the positive voltage region and the negative voltage region and has no hysteresis, and for each pixel, such as a thin film transistor or a diode. An active matrix liquid crystal display device is obtained by sandwiching the liquid crystal composition of the present invention between substrates on which non-linear active devices are provided.

The ferrielectric liquid crystals of the present invention represented by the general formulas (2) and (3) are disclosed in, for example, Japanese Patent Application No. 10-22476 of the present inventors.
No. 8 can be easily manufactured. The general formula (3)
In R ³ = C ₉ H ₁₉ , p = 2, q = 1, X ³ = F, it is as follows. (1) C ₉ H ₁₉ Br + HOPhPhCOOH → C ₉ H ₁₉ OPhPhCOOH (2) (1) + SOCl ₂ → C ₉ H ₁₉ OPhPhCOCl (3) CH ₃ COOPh (F) COOH + SOCl ₂ → CH ₃ COOPh (F ) COCl (4) (3) + CH ₃ C * H (OH) (CH ₂ ) ₂ CH (CH ₃ ) ₂ → CH ₃ COOPh (F) COOC * H (CH ₃ ) (CH ₂ ) ₂ CH (CH ₃ ) ₂ (5) (4) + PhCH ₂ NH ₂ → HOPh (F) COOC * H (CH ₃ ) (CH ₂ ) ₂ CH (CH ₃ ) ₂ (6) (2) + (5) → Target

The above-mentioned manufacturing method is briefly described as follows. (1) Reaction of n-nonyl bromide with 4- (4'-hydroxy) biphenylcarboxylic acid. (2) is 4- (4'-nonyloxy)
Chlorination reaction of biphenylcarboxylic acid (1). (3) Chlorination reaction of 4-acetoxy-2-fluorobenzoic acid. (4) Reaction of chloride (3) with optically active 5-methyl-2-hexanol. (5) is a deacetylation reaction of the acetyl group of the ester compound (4). (6) is chlorinated compound (2) and phenol compound (5)
Production of the desired product by reaction with

The compound of the present invention represented by the general formula (4) is
It can be easily manufactured according to Japanese Patent Application No. 8-278013 of the present inventors. The outline of the production method is represented by the general formula (4) where R ⁴ = C ₉ H
_{At 19} , it is as follows. (1) C ₉ H ₁₉ COCl + HOPhCOOH → C ₉ H ₁₉ COOPhCOOH (2) (1) + SOCl ₂ → C ₉ H ₁₉ COOPhCOCl (3) (2) + CF ₃ CH ₂ OH → C ₉ H ₁₉ COOPhCOOCH ₂ CF ₃

The above-mentioned manufacturing method will be briefly described as follows. (1) Reaction of decanoic acid chloride with p-hydroxybenzoic acid. (2) is p-decanoyloxybenzoic acid (1)
Chlorination reaction. (3) Production of the target product by the reaction of chlorinated product (2) with trifluoroethanol. In the above equation, Ph
Is a 1,4-phenylene group, and Ph (F) is 1,4-substituted at the 3-position.
A phenylene group and C * represent an asymmetric carbon.

[0017]

The present invention provides a novel compound for improving the alignment and a novel liquid crystal composition containing the same. In addition, the novel liquid crystal composition provided by the present invention has excellent alignment and exhibits nonlinear optical response to applied voltage. Therefore, an active matrix liquid crystal display device having excellent display quality and high reliability can be realized.

[0018]

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 (Equation (1): X = H (1A)) 4- (1-
Cyclohexylmethyleneoxycarbonyl) phenyl-
Preparation of 1-trifluoromethoxyphenyl-4-carboxylate.

(1) Production of p-acetoxy- (1-cyclohexylmethyleneoxycarbonyl) benzoic acid. 0.011 mol of p-acetoxybenzoic acid chloride, 0.01 mol of cyclohexanemethanol, 0.013 mol of pyridine and 10 ml (milliliter) of toluene were reacted with stirring at room temperature for 5 hours. After the reaction, the resultant was washed with an aqueous solution of hydrochloric acid, an aqueous solution of caustic soda and water in that order. After liquid separation of the toluene phase, toluene was distilled off to obtain the desired product.

(2) Production of p-hydroxy- (1-cyclohexylmethyleneoxycarbonyl) benzoic acid. A 40% methylamine methanol solution (0.02 mol as methylamine) and 10 ml of toluene were added to the p-acetoxy- (1-cyclohexylmethyleneoxycarbonyl) benzoic acid produced in (1), and the mixture was stirred at room temperature for 1 hour. The mixture was washed with an aqueous hydrochloric acid solution, a sodium hydroxide solution and water in this order, and the toluene phase was separated. The toluene was distilled off to obtain the desired product in a total yield of 55% from (1).

(3) Production of 4- (1-cyclohexylmethyleneoxycarbonyl) phenyl-1-trifluoromethoxyphenyl-4-carboxylate. 0.006 mol of p-hydroxy- (1-cyclohexylmethyleneoxycarbonyl) benzoic acid obtained in (2), 0.0058 mol of p-trifluoromethoxybenzoic acid chloride,
0.016 mol of pyridine and 10 ml of toluene were reacted at room temperature for 5 hours. The mixture was washed with an aqueous hydrochloric acid solution, a sodium hydroxide solution and water in this order, and the toluene phase was separated. The toluene was distilled off to obtain a crude product. Then, the residue was purified by a silica gel column using ethyl acetate / hexane = 5/95 as a solvent to obtain the desired product in a yield of 75%.
I got it. The NMR data is shown in Table 1.

Table 1 Hydrogen atom number 1 2 3 4 5 6 Example 1 δ (ppm) 7.8 8.1 7.5 8.1 4.0 1.7

[0023]

Embedded image

Example 2 A liquid crystal composition was prepared by mixing the following compounds corresponding to the general formulas (1), (2), (3) and (4) of the present invention at the following molar ratios. 1A: CF ₃ O-Ph-COO-Ph-COO-CH ₂ -Cyclo 15 mol% 2A: C ₉ H ₁₉ O-PhPh-COO-Ph (F) -COO-C * H (CF ₃ ) (CH ₂ ) ₂ CH (C ₂ H ₅ ) ₂ 37.5 〃 2B: C ₉ H ₁₉ O-PhPh-COO-Ph (F) -COO-C * H (CF ₃ ) (CH ₂ ) ₂ CH (CH ₃ ) ₂ 12.5 〃 3A: C ₉ H ₁₉ O-PhPh-COO-Ph (F) -COO-C * H (CH ₃ ) (CH ₂ ) ₂ CH (CH ₃ ) ₂ 20 〃 4A: C ₉ H ₁₉ COO-Ph- COO-CH ₂ CF ₃ 15 中 In the formula, Ph represents a 1,4-phenylene group, Cyclo represents a cyclohexyl group, and C * represents an asymmetric carbon atom.

Table 1 shows the results of measurement of the liquid crystal compounds (2A, 2B, 3A) used above and the liquid crystal phase phase sequence and phase transition voltage of the obtained liquid crystal composition. The liquid crystal phase was identified by texture observation, observation of a conoscopic image, measurement by DSC (differential scanning calorimeter), and optical response behavior.
Observation of a conoscopic image is a powerful means for identifying a liquid crystal phase. Observation of conoscopic images is described in the literature (J. Appl. Phys. 31,
793, (1992)), but with a cell gap of 100μ.
m, the liquid crystal phase is in a bulk state.

The electro-optical characteristics were examined. The cell was produced according to the following procedure. Polyimide coating on glass substrate with insulating film (SiO ₂ , film thickness 50 nm) and ITO electrode (film thickness about 80 nm)
Thereafter, only one of the pair of glass substrates was rubbed.
A pair of glass substrates were bonded together via a spacer having a particle size of 1.6 μm to form a test cell. The cell thickness was 1.7 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 the 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.

The light transmittance was defined as 0% light transmittance at the lowest transmitted light intensity and 100% light transmittance at the highest intensity. The phase transition voltage was a voltage at a light transmittance of 90%. At 25 ° C., a ± 10 V, 50 mHz triangular wave voltage was applied to the test cell, and a voltage (phase transition voltage) at the time of transition from the ferrielectric phase to the ferroelectric phase was determined. Further, the quality of the orientation was determined by measuring the light transmittance in a state where no voltage was applied. The smaller the value of the light transmittance, the better the orientation. The results are shown in Table 2.

Comparative Example 1 A liquid crystal composition was obtained in the same manner as in Example 3 except that 1A was not used and 4A was used at 30 mol%. Table 2 shows the results.

Table 2 Phase series Column Phase transition voltage Light transmittance at applied voltage 0 (V) Example 1 I (90) SA (63) SCγ * (<-30) Cr 3.20 Comparative Example 1 I (85) ) SA (64) SCγ * (<-30) Cr 4.2 0.7 In the phase series, parentheses indicate phase transition temperature (° C.), I is isotropic phase, SA is smectic A phase, SCγ * is ferrielectric phase,
Cr indicates a crystal phase. In addition, as is apparent from the above results, the cyclohexane compound of the present invention was very effective in improving the orientation.

Continued on front page F term (reference) 4H006 AA01 AA03 AB64 BJ20 BJ50 BM10 BM30 BM71 BP30 BT32 BT36 FC22 FC54 FE71 FE73 FE74 4H027 BA06 BA16 BC04 BD12 BE05 CA03 CF08 CN03 CN05

Claims (12)

[Claims] 1. A phenyl ester compound having a trifluoromethoxy group and a cyclohexane ring represented by the following general formula (1). Embedded image (In the formula, X represents a hydrogen atom or a fluorine atom.) 2. A liquid crystal comprising a phenyl ester compound represented by the following general formula (1), a ferrielectric liquid crystal compound represented by the following general formulas (2) and (3), and a compound represented by the following general formula (4): Composition. Embedded image (Wherein, R ² , R ³ and R ⁴ are linear alkyl groups having 6 to 10 carbon atoms, X ¹ , X ² and X ³ are a hydrogen atom or a fluorine atom, m,
n, p and q are integers from 1 to 4, and C * is an asymmetric carbon atom. ) 3. In the general formula (2), R ² has 8 carbon atoms.
To 10, m is 2, n is 1 or 2, X ² is a liquid crystal composition according to claim 2, wherein a fluorine atom. 4. In the general formula (3), R ³ has 8 carbon atoms.
10, claim p is is 2, q is 1, X ³ is a fluorine atom 2
The liquid crystal composition according to the above. 5. In the general formula (4), R ⁴ has 8 carbon atoms.
3. The liquid crystal composition according to claim 2, wherein 6. The liquid crystal composition according to claim 2, wherein the amount of the phenyl ester compound represented by the general formula (1) is 5 to 20 mol% of the composition. 7. The liquid crystal composition according to claim 2, wherein the amount of the phenyl ester compound represented by the general formula (1) is 10 to 20 mol% of the composition. 8. The liquid crystal composition according to claim 2, wherein the amount of the ferrielectric liquid crystal compound represented by the general formula (2) is 10 to 50 mol% of the composition. 9. The liquid crystal composition according to claim 2, wherein the amount of the ferrielectric liquid crystal compound represented by the general formula (3) is 5 to 20 mol% of the composition. 10. The liquid crystal composition according to claim 2, wherein the amount of the compound represented by the general formula (4) is 10 to 25 mol% of the composition. 11. The liquid crystal composition according to claim 2, wherein the composition has a non-linear optical response having no symmetry and no hysteresis in a positive voltage region and a negative voltage region in an optical response to an applied voltage. 12. An active matrix liquid crystal display device comprising the liquid crystal composition according to claim 1 sandwiched between substrates on each of which a nonlinear active device such as a thin film transistor or a diode is provided for each pixel.