JP3186825B2 - Liquid crystal compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal material suitable for use in an electro-optical device utilizing the response of a chiral smectic liquid crystal to an electric field, in particular, a ferroelectric liquid crystal material containing a pyrimidine ring and an optical tristable state. And a liquid crystal material having a high light leakage rate.

[0002]

2. Description of the Related Art Liquid crystal display devices are 1) low-voltage operable 2).
Since it has excellent features such as low power consumption, 3) thin display, and 4) light receiving type, TN method, STN method,
A guest-host method has been developed and put into practical use. However, those using a nematic liquid crystal which is widely used at present have a response speed of several milliseconds.
It has a drawback as slow as c to several tens of msec, and is subject to various restrictions in application. In order to solve these problems, an STN method and an active matrix method using a thin-layer transistor and the like have been developed. However, the display quality of the STN display element such as display contrast and viewing angle has been excellent. However, there are problems in that high precision is required for controlling the cell gap and the tilt angle, and that the response is slightly slow. For this reason, the development of a new liquid crystal display system having excellent responsiveness has been demanded, and the development of a ferroelectric liquid crystal capable of realizing an ultrahigh-speed device having an extremely short optical response time on the order of μsec has been attempted. Ferroelectric liquid crystal is 1
In 975, DOBAMBC (p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate) was first synthesized by Meyor et al. (Le Jour)
nal de Physique, 36, 1975, L
-69). Further, in 1980, Clark and Laga
Since the report on the characteristics of the display device such as the sub-microsecond high-speed response and memory characteristics of DOBAMBC by Wall has been reported, ferroelectric liquid crystals have attracted much attention [N. A. Clark, et al. , Appl.
Phys. Lett. 36.899 (1980)]. However, their method has many technical issues for practical use, and there is no material showing ferroelectric liquid crystal especially at room temperature.
An effective and practical method for controlling the alignment of liquid crystal molecules indispensable for display displays has not been established. Since this report, various attempts have been made from both the liquid crystal material and device sides, and a display device utilizing switching between two twisted states has been prototyped, and a high-speed electro-optical device using the same has also been disclosed in, for example, JP-A-56-107216. However, high contrast and proper threshold characteristics have not been obtained. From such a viewpoint, other switching schemes have been searched, and a transient scattering scheme has been proposed. Then, in 1988, the present inventors reported a three-state switching method of a liquid crystal having a tristable state [A. D.
L. Chandani, T .; Hagiwara, Y .; S
uzuki et al. , Japan. J. ofApp
l. Phys. , 27, (5), L729-L732
(1988)]. The above-mentioned "having three states" refers to a liquid crystal electro-optical device in which a ferroelectric liquid crystal is sandwiched between a first electrode substrate and a second electrode substrate disposed at a predetermined gap. A voltage for forming an electric field is applied to the first and second electrode substrates, and when a voltage is applied as a triangular wave shown in FIG. 1A, the ferroelectric liquid crystal is applied with no electric field as shown in FIG. 1D. Sometimes, the molecular orientation has a first stable state (2 in FIG. 1D), and when an electric field is applied, the molecular orientation is different from the first stable state in one electric field direction (FIG. 1D). 1) and a third molecular orientation stable state (3 in FIG. 1D) different from the first and second stable states with respect to the other electric field direction. A liquid crystal compound having a liquid crystal phase S * (3) exhibiting a tristable state in a phase series is disclosed in Japanese Unexamined Patent Publication No. Hei.
No. 316,367, JP-A-1-316372, JP-A-1
JP-A-316339, JP-A-2-28128, and JP-A-1-213390 such as Ichihashi. As a liquid crystal electro-optical device utilizing a tristable state, the present applicant has disclosed JP-A-2-40625 and JP-A-2-40625. New proposals are made in JP-A-2-153322 and JP-A-2-173724, but the liquid crystal compound of the present invention is unknown. Further, there is no disclosure of a liquid crystal exhibiting a tristable state with a good memory effect. The three-state switching method applies a clear threshold characteristic and a hysteresis characteristic to a driving voltage indicated by a liquid crystal phase S * (3) exhibiting a tristable state that is basically different from a conventional bistable state in liquid crystal molecular alignment. This is considered to be an epoch-making driving method that can realize large-screen moving image display by a simple matrix method. Further, the performance of a display element using a liquid crystal exhibiting a tristable state greatly depends on a hysteresis shape which is a physical property inherent to the tristable liquid crystal. In the hysteresis of the shape shown in FIG. 2, an ideal dark state can be realized at 0 V. However, when the voltage is increased from 0 V to V ₁ or when the voltage is decreased from 0 V to −V ₁ , light leakage occurs. It can be said that a liquid crystal exhibiting a tristable state having such a hysteresis has a poor memory effect in a dark state. This phenomenon causes a decrease in the contrast of the display element. In contrast, an ideal dark state voltage V ₃ or the voltage -V ₃ was realized with 0V in hysteresis as shown in FIG. 3
It can be said that the memory effect in the dark state is good. Then, the contrast of the display element becomes good. However, in reality, it is not easy to obtain a liquid crystal compound having an ideal hysteresis curve as shown in FIG. 3, but a hysteresis curve as shown in FIG. 4 and a bias voltage Vb ₀ = (V ₂ + V ₃ ). When (C) ÷ (D) × 100 at the time of ÷ 2 is expressed as a light leakage rate (%), most liquid crystal compounds have a light leakage rate in a range of 5 to 10%, and a light leakage rate of 0 to 5%. It was very difficult to find a liquid crystal compound having a light leakage rate.

[0003]

[Object] The object of the present invention is to provide a liquid crystal phase S * exhibiting a tristable state.
An object of the present invention is to provide a novel pyrimidine ring-containing liquid crystal compound which can be expected to be applied to a new electro-optical element or a liquid crystal display utilizing (3), and has an excellent light leakage rate.

[0004]

The present invention has a general formula

Embedded image (Wherein, R ₁ is a straight-chain alkyl group or alkoxy group having 8 to 12 carbon atoms, R ₂ is a straight-chain alkyl group having 6 to 8 carbon atoms,
t represents hydrogen or fluorine, and * represents an asymmetric carbon). One specific example of a method for synthesizing the compound of the present invention will be described below. (A) Commercially available 5-alkyl-2- (2'-fluoro-
After refluxing 4'-cyanophenyl) -pyrimidine with potassium hydroxide in diethylene glycol, the reaction solution is stirred into a mixed solvent of methanol: concentrated hydrochloric acid = 2: 1. The generated crystals were collected and recrystallized with ethanol,
-Fluoro-4- (n-alkyl-2-pyrimidinyl)
Obtain benzoic acid (5). Next, the compound (5) is refluxed in excess thionyl chloride to obtain a chloride (6). (B) Reflux 2-fluoro-4-benzyloxybenzoic acid in excess thionyl chloride to obtain its chloride (7). The optically active 1,1,1-trifluoro-2-
The alkanol is added to give the corresponding 2-fluoro-4-benzyloxybenzoate (8) in the presence of triethylamine in methylene chloride. Next, catalytic reduction
Fluoro-4-hydroxybenzoic acid ester (9) is obtained. (C) The compound of the above (6) and (9) is reacted in methylene chloride in the presence of triethylamine to give 3-fluoro-4- (5-alkyl-
2-pyrimidinyl) benzoic acid 3-fluoro-4-
(1,1,1-trifluoro-2-alkyloxycarbonyl) phenyl ester (10) can be obtained. (Below)

Embedded image

Embedded image

Example 1 3-Fluoro-4- (1,1,1-trifluoro-2-
Octyloxycarbonyl) phenyl 4- (5-n-
Synthesis of undecyloxy-2-pyrimidinyl) benzoate

Embedded image 1.1 g of 4- (5-n-undecyloxy-2-pyrimidinyl) benzoic acid and optically active 2-fluoro-4-hydroxybenzoic acid 1,1,1 in a 100 ml round bottom flask
-Trifluoro-2-octyl ester 1.0 g, 4-
0.03 g of dimethylaminopyridine and 20.5 ml of methylene chloride were added and stirred. N, N'-
0.68 g of dicyclohexylcarbodiimide was added and reacted at room temperature for 24 hours. After completion of the reaction, white insolubles were removed by filtration. The methylene chloride layer was thoroughly washed with dilute hydrochloric acid and water, dried, and then the organic solvent was removed under reduced pressure. The obtained crude product was purified by column chromatography and recrystallization,
0.8 g of the desired product was obtained. Specific rotation [α] D ²⁰ + 28.20 ° (C: 2.01 C
HCl ₃ ) Infrared absorption spectrum (KBr method) (cm ^-1 ) 2928,2855,1746,1615,1576,1438,1283,1241,1184,1152,
1069, 1055, 1013, 750 The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 1] However, S * (3) indicates an optically tristable state phase.

Example 2 3-Fluoro-4- (1,1,1-trifluoro-2-
Synthesis of decyloxycarbonyl) phenyl 4- (5-n-undecyloxy-2-pyrimidinyl) benzoate

Embedded image 1.05 g of 4- (5-n-undecyloxy-2-pyrimidinyl) benzoic acid and 1,1,1 optically active 2-fluoro-4-hydroxybenzoic acid in a 100 ml round bottom flask
-Trifluoro-2-decyl ester 1.05 g, 4-
0.03 g of dimethylaminopyridine and 20 ml of methylene chloride were added and stirred. 0.66 g of N, N'-dicyclohexylcarbodiimide was added to this mixture and reacted at room temperature for 24 hours. After completion of the reaction, white insolubles were removed by filtration.
The methylene chloride layer was thoroughly washed with dilute hydrochloric acid and water, dried, and then the organic solvent was removed under reduced pressure. The resulting crude product is
Purification by column chromatography and recrystallization afforded 0.9 g of the desired product. Specific rotation [α] D ²⁰ + 26.84 ° (C: 2.015
(In CHCl ₃ ) Infrared absorption spectrum (KBr method) (cm ⁻¹ ) 2924,2853,1737,1618,1581,1438,1326,1286,1241,1183,
1158, 1129, 1015, 872, 754 The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 2] However, S * (3) indicates an optically tristable state phase.

Example 3 3-Fluoro-4- (1,1,1-trifluoro-2-
Synthesis of octyloxycarbonyl) phenyl [3-fluoro-4- (5-n-octylpyrimidin-2-yl)] benzoate

Embedded image 3-fluoro-4- (5-n-octylpyrimidine-2
-Yl) 0.92 g of benzoic acid was heated under reflux with excess thionyl chloride for 5 hours, and unreacted thionyl chloride was distilled off to give 3-fluoro-4- (5-n-octylpyrimidin-2-yl). Benzoic acid chloride was obtained. Subsequently, optically active 2-fluoro-4-hydroxybenzoic acid 1,1,1-
0.88 g of trifluoro-2-octyl ester and 0.84 g of triethylamine were dissolved in 10 ml of chloroform, and the previously synthesized 3-fluoro-4- (5-n-
Octylpyrimidin-2-yl) benzoic acid chloride to 12
The solution dissolved in ml of chloroform was added dropwise little by little,
Stirred overnight at room temperature. After the reaction mixture was put in water to make the solution neutral, only the chloroform layer was extracted. After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the residue was purified by silica gel column chromatography and recrystallization to obtain 0.5 g of the desired product. Specific rotation [α] D ²⁰ + 26.66 ° (C: 2.025
In CHCl ₃ ) Infrared absorption spectrum (KBr method) (cm ⁻¹ ) 2932,2887,1750,1736,1618,1579,1429,1284,1250,1191,
1121, 1076, 1064, 748 The phase transition temperatures (° C.) observed by polarizing microscope with a hot stage are as follows.

[Table 3] However, S * (3) indicates an optically tristable state phase.

Example 4 3-Fluoro-4- (1,1,1-trifluoro-2-
Synthesis of octyloxycarbonyl) phenyl [3-fluoro-4- (5-n-octyloxypyrimidin-2-yl)] benzoate

Embedded image 0.94 g of 3-fluoro-4- (5-n-octyloxypyrimidin-2-yl) benzoic acid was heated under reflux with excess thionyl chloride for 5 hours, and unreacted thionyl chloride was distilled off to give 3- Fluoro-4- (5-n-octyloxypyrimidin-2-yl) benzoic acid chloride was obtained. Then, optically active 2-fluoro-4-hydroxybenzoic acid
1,1,1-trifluoro-2-octyl ester
86 g of triethylamine and 0.82 g of triethylamine were dissolved in 10 ml of chloroform, and the previously synthesized 3-fluoro-4 was synthesized.
A solution of-(5-n-octyloxypyrimidin-2-yl) benzoic acid chloride dissolved in 12 ml of chloroform was added dropwise little by little, and the mixture was stirred at room temperature for 24 hours. After the reaction mixture was put in water to make the solution neutral, only the chloroform layer was extracted. After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the residue was purified by silica gel column chromatography and recrystallization to obtain 1.4 g of the desired product. Specific rotation [α] D ²⁰ + 26.36 ° (C: 2.040
CHCl ₃ ) Infrared absorption spectrum (KBr method) (cm ^-1 ) 2927,2855,1745,1617,1576,1441,1290,1251,1183,1126,
1070,753 The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 4] However, S * (3) indicates an optically tristable state phase.

Comparative example

Embedded image

[Table 5]

Example 5 A rubbed polyimide alignment film was formed on an ITO electrode substrate.
The liquid crystal cell having a cell thickness of 1.6 μm provided in
Liquid crystal compounds in the Isotropic phase
And filled to form a liquid crystal thin film cell. The created LCD
Multiplier with two polarizing plates orthogonal to each other
Length when a DC voltage of -40 V is applied to a polarized light microscope
The polarizer was arranged so as to overlap the axial direction. This liquid crystal cell
To the SA phase with a temperature gradient of 0.1 to 1.0 ° C. for 1 minute
Cooled slowly. Further cooling, temperature to take S * (3) phase
± 40V, 1Hz triangular wave voltage applied in the degree range
did. From the resulting hysteresis curve,
Threshold voltage was determined. V₁: Relative light transmittance of 10 when the voltage was reduced from the bright state
% Voltage V_Two: Relative light transmittance of 90 when the voltage is reduced from the bright state
% Voltage V_Three: Relative light transmittance 10 when voltage is increased from dark state
% Voltage V_Four: Relative light transmittance 90 when voltage is increased from dark state
And the parameters of the threshold characteristics and the width of the hysteresis.
Then, a drive margin M represented by the following equation was obtained. When the drive margin M ≧ 2 or more, an appropriate threshold
The width of the steresis is obtained, and the contrast is improved. Ma
In the hysteresis curve shown in FIG. 3, the bias voltage Vb₀= (V_Two+ V_Three4) The relative light transmittance in the dark state at (÷ 2) [(C) in FIG.
Ratio of relative light transmittance [(D) in FIG. 4] (C) / (D) × 1
00 was determined as the light leakage rate. In addition, TCA is SA or
Is the transition temperature from the S * (2) phase to the S * (3) phase
And T is the measured temperature. The results are shown in the following table.
You. (Below)

[Table 6]

[0011]

[Consideration] As for the light leakage rate, the compound of Example 1 is about 3.35 times, that of Example 3 is about 1.5 times, and that of Example 4 is It is improved by about 3.35 times, and that of the second embodiment is a form that achieves the ideal. The driving margin of the first embodiment is also 4.
The improvement is twice as much, that of the second embodiment is 4.7 times, that of the third embodiment is 2.1 times, and that of the fourth embodiment is 6.8 times.
Except for the working voltage of the fourth embodiment, the operating voltage is extremely low, which is an excellent effect.

[0012]

The novel liquid crystals of the present invention all exhibit stable three states and an excellent light leakage rate, so that a display device having excellent contrast can be provided.

[Brief description of the drawings]

FIG. 1 shows the optical response characteristics of a triangular wave to which A is applied, B of a commercially available nematic liquid crystal, C of a two-state liquid crystal, and D of a three-state liquid crystal.

FIG. 2 shows the poor hysteresis of the memory effect of the dark part for the three-state liquid crystal.

FIG. 3 shows ideal hysteresis for a three-state liquid crystal with a good memory effect in a dark part.

FIG. 4 shows hysteresis for explaining a light leakage rate.

Continued on the front page (72) Inventor Nobuhiro Okabe 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Inside Showa Shell Sekiyu K.K. Inside the Itami Plant (72) Inventor Yasuhiro Hasegawa 5-41 Senmon, Itami-shi, Hyogo Prefecture Inside the Itami Plant of Teikoku Chemical Industry Co., Ltd. (JP, A) European Patent Application Publication 445037 (EP, A2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 239/26 C09K 19/34 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] 1. A compound of the general formula (Wherein, R ₁ is a linear alkyl group having 8 to 12 carbon atoms , R ₂
Is a linear alkyl group having 6 to 8 carbon atoms, * represents an asymmetric carbon. ) An optically active liquid crystal compound exhibiting a tristable state represented by 2. A compound represented by the following formula : An optically active liquid crystal compound showing a tristable state represented by