JP3133405B2 - 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 device using a liquid crystal material containing a pyrazine ring and exhibiting an optically tristable state.

[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. In addition, the active matrix type display element has a problem in that the yield in production technology is low and the cost is high. 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.

[0003] Ferroelectric liquid crystals were introduced in 1975 by Meyer.
DOBMMBC (p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate) was synthesized for the first time (Le Journal de Phys).
sque, 36, 1975, L-69). further,
In 1980, Clark and Lagwall made the DO
Ferroelectric liquid crystals have attracted much attention since the characteristics of display devices such as the fast response of sub-microsecond of BAMBC and the memory characteristics were reported [N. A. C
lark, et al. , Appl. Phys. Let
t. 36.899 (1980)]. However, their method has many technical issues for practical use, and there is no material showing ferroelectric liquid crystal at room temperature, and it is effective and practical for controlling the alignment of liquid crystal molecules indispensable for display displays. There was no established method. Since this report, liquid crystal materials /
Various attempts have been made from both sides of the device, and a display device utilizing switching between two twisted states has been trial-produced.
Although it is proposed in, for example, -107216, high contrast and proper threshold characteristics have not been obtained.

[0004] From such a viewpoint, other switching schemes have been searched, and a transient scattering scheme has been proposed.
Thereafter, in 1988, a three-state switching method for a liquid crystal having a tristable state was reported [A. D. L. Chan
dani, T .; Hagiwara, Y .; Suzukie
tal. , Japan. J. of Appl. Phys
s. , 27, (5), L729-L732 (198
8)]. 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. Sometimes the molecular orientation is in the first stable state (Fig. 1
D), and has a second stable state (1 in FIG. 1D) in which the molecular orientation in one electric field direction differs from the first stable state when an electric field is applied, and the other electric field It means having a third molecular orientation stable state (3 in FIG. 1D) different from the first and second stable states in the direction.
The three-state switching method applies a clear threshold characteristic and a hysteresis characteristic to a driving voltage shown in a liquid crystal phase S ^* (3) showing a tristable state that is basically different from a conventional bistable state in liquid crystal molecular alignment. And
This is considered to be an epoch-making driving method capable of realizing a large-screen moving image display by the 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. With 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 ₂ or voltage achieved at 0V in hysteresis as shown in Figure 3 -
V ₂ is maintained until it can be said that the memory effect of the dark state is good. Then, the contrast of the display element becomes good.

[0005] A liquid crystal compound having a liquid crystal phase S ^* (3) exhibiting a tristable state in a phase series is disclosed in Japanese Patent Application Laid-Open No. HEI 1 (1994) -1972 filed by the present inventor.
JP-316163, JP-A-1-316372, JP-A-1-316339, JP-A-2-28128 and JP-A-1-213390 such as Ichihashi, and as a liquid crystal electro-optical device utilizing a tristable state. Has made new proposals in JP-A-2-40625, JP-A-2-153322 and JP-A-2-173724, but the liquid crystal compound of the present invention is unknown.

[0006]

The present invention has been made in view of the above problems, and as a result of intensive studies on liquid crystal compounds containing a heterocyclic ring, it has been found that a liquid crystal compound containing a pyrazine ring as a heterocyclic ring is chemically and photochemically stable and has a large dielectric anisotropy. Liquid crystal phase S exhibiting tristable state, which is not obtained with the conventional ferroelectric liquid crystal
^* It was found to have (3). In addition, it has been found that a liquid crystal compound containing a pyrazine ring has a low threshold voltage. An object of the present invention is to provide a new electro-optical element and a liquid crystal display using a liquid crystal phase S ^* (3) exhibiting a tristable state of a liquid crystal compound containing a novel pyrazine ring.

[0007]

The present invention has the following general formula:

Embedded image [Wherein R ₁ ′ and R ₂ ′ are alkyl groups having 4 to 18 carbon atoms, R ₃ ′ is CH ₃ , CF ₃ or C ₂ F ₅ , X ′ is O, COO, CO or a single bond, and t is Indicates that at least one halogen atom is substituted. ^{* Indicates} optically active carbon. ] The present invention relates to an antiferroelectric liquid crystal device characterized in that a liquid crystal compound selected from the group consisting of: In particular, in the present invention, the liquid crystal compound represented by the following general formula

Embedded image [Wherein R ₁ ′ and R ₂ ′ are alkyl groups having 4 to 18 carbon atoms, R ₃ ′ is CH ₃ , CF ₃ or C ₂ F ₅ , and t is that at least one halogen atom is substituted. Is shown. ^{* Indicates} optically active carbon. ] Is preferably selected from the group consisting of:

The above-mentioned t is most preferably F,
Next, Cl and Br are in that order. Specific examples of the target compound of the present invention include: 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) phenyl 4- (2-alkylpyrazin-5-yl) benzoate 4- (1,1 , 1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 4- (2-alkylpyrazin-5-yl) benzoate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) phenyl 4- (2 -Alkoxypyrazin-5-yl) benzoate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 4- (2-alkoxypyrazin-5-yl) benzoate 4- (1,1,1 -Trifluoro-2-alkyloxycarbonyl) phenyl 4- (2-alkylcarbonyloxypyrazin-5-yl ) Benzoate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 4- (2-alkylcarbonyloxypyrazin-5-yl) benzoate 4- (1,1,1-trifluoro-2 -Alkyloxycarbonyl) phenyl 2- (4-alkylphenyl) pyrazin-5-yl-carboxylate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 2- (4-alkylphenyl) Pyrazin-5-yl-carboxylate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) phenyl 2- (4-alkoxyphenyl) pyrazin-5-yl-
Carboxylate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 2- (4-alkoxyphenyl) pyrazin-5-yl-carboxylate 4- (1,1,1-trifluoro- 2- (alkyloxycarbonyl) phenyl 2- (4-alkylcarbonyloxyphenyl) pyrazin-5-yl-carboxylate 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) fluorophenyl 2- (4- Alkylcarbonyloxyphenyl) pyrazin-5-yl-carboxylate Further, in place of the CF ₃ group in the above compound, a CH ₃ group and C ₂ F ₅ group, and in place of the F atom in the above compound, C
Compounds substituted with an l atom or a Br atom are also exemplified.

An example of a method for synthesizing the compound according to the present invention is as follows. (A) Alkyloxybenzene is dissolved in methylene chloride, AlCl ₃ and acetyl chloride are added,
(Alkyloxy) acetophenone (1) is obtained. Next, selenium dioxide, dioxane, and water are added, and the mixture is heated and stirred to obtain 4- (alkyloxy) phenylglyoxal monohydrate (2). Next, diaminomaleonitrile is added to obtain 2,3-dinitrile 5- (4-alkyloxyphenyl) pyrazine (3). This is hydrolyzed (4) and then decarboxylated to give 2- (4-alkyloxyphenyl) pyrazin-5-yl-carboxylic acid (5)
Get. Next, 2- (4-alkyloxyphenyl) pyrazin-5-yl-carboxylic acid chloride (6) is obtained with thionyl chloride. (B) benzyloxyhalogen-substituted benzoic acid is refluxed in excess thionyl chloride to obtain its chloride (7). To this is added an optically active 1,1,1-trifluoro-alkanol to give the corresponding 4-benzyloxy-halogen-substituted benzoate (8) in methylene chloride in the presence of triethylamine. Next, catalytic reduction is performed to give 4-hydroxy-
A halogen-substituted benzoate (9) is obtained. (C) Compounding the above compounds (6) and (9) in methylene chloride
The reaction is carried out in the presence of triethylamine to give 4- (1,1,1-trifluoro-2-alkyloxycarbonyl) halogen-substituted phenyl 2-
(4-alkyloxyphenyl) pyrazin-5-yl-
Obtain the carboxylate.

Embedded image

Embedded image

[0010]

EXAMPLES Example 1 4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 2- (4-n-octyloxyphenyl) pyrazine-5
-Yl-carboxylate

Embedded image 1) Synthesis of 1,1,1-trifluoro-2-octyl ester of 4-benzyloxybenzoic acid

Embedded image 4.3 g of 4-benzyloxybenzoic acid chloride are dissolved in 50 ml of methylene chloride and then the optically active 1,1,1 is dissolved.
2.9 g of 1-trifluoro-2-octanol, 0.6 g of dimethylaminopyridine and 1.7 g of triethylamine
Was dissolved in 50 ml of methylene chloride, and the solution was added little by little under ice-cooling. The reaction mixture was returned to room temperature and reacted overnight, and the reaction solution was poured into ice water, extracted with methylene chloride, and the methylene chloride phase was washed successively with dilute hydrochloric acid, water, a 1N aqueous sodium carbonate solution and water, and then dried over anhydrous magnesium sulfate. After drying, the solvent was distilled off to obtain a crude product. This is toluene-
The residue was treated by silica gel column chromatography and recrystallized from ethanol to obtain 3.8 g of the desired compound. 2) Synthesis of 4-hydroxybenzoic acid 1,1,1-trifluoro-2-octyl ester

Embedded image The compound obtained in 1) was dissolved in 100 ml of methanol, 0.4 g of 10% supported Pb-carbon was added, and a hydrogenolysis reaction was carried out under a hydrogen atmosphere to obtain 2.8 g of the target compound. 3) Synthesis of 4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 2- (4-n-octyloxyphenyl) pyrazin-5-yl-carboxylate

Embedded image 2- (4-n-octyloxyphenyl) pyrazine-5
After 1.5 g of -yl-carboxylic acid was heated under reflux with excess thionyl chloride for 4 hours, unreacted thionyl chloride was distilled off to give 2- (4-n-octyloxyphenyl) pyrazin-5-yl. -A carboxylic acid chloride is obtained. Then
Optically active 4-hydroxybenzoic acid 1, synthesized in 2)
1.3 g of 1,1-trifluoro-2-octyl ester
And 0.5 g of triethylamine were dissolved in 10 ml of methylene chloride, and a solution of the previously synthesized 2- (4-n-octyloxyphenyl) pyrazin-5-yl-carboxylic acid chloride in 20 ml of methylene chloride was obtained. Add dropwise little by little. Further, a solution prepared by dissolving 0.2 g of dimethylaminopyridine in 5 ml of methylene chloride is added. Stirred overnight at room temperature. After the reaction mixture was put in water to make the solution neutral, only the methylene chloride layer was extracted. After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the residue was purified by silica gel chromatography and recrystallization.
8 g were obtained. Optical rotation [α] 20 / D = + 33.10 ° The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 1] FIG. 4 shows the infrared absorption spectrum of the target compound. Example 2 4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 2- (4-n-nonyloxyphenyl) pyrazine-5
Il-carboxylate

Embedded image 2- (4-n-nonyloxyphenyl) pyrazine-5
After heating 1.6 g of yl-carboxylic acid together with excess thionyl chloride under reflux for 4 hours, unreacted thionyl chloride is distilled off to give 2- (4-n-nonyloxyphenyl) pyrazin-5-yl-carboxylic acid. An acid chloride was obtained. Next, Example 1
Optically active 4-hydroxybenzoic acid synthesized in 2)
1,1,1-trifluoro-2-octyl ester
3 g and 0.5 g of triethylamine are dissolved in 10 ml of methylene chloride, and the previously synthesized 2- (4-n-nonyloxyphenyl) pyrazin-5-yl-carboxylic acid chloride is dissolved in 20 ml of methylene chloride. Is added dropwise little by little. Furthermore, 5 ml of 0.2 g of dimethylaminopyridine
The solution dissolved in methylene chloride is added. Stirred overnight at room temperature. After the reaction mixture was put in water to make the solution neutral, only the methylene chloride 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 1.6 g of the desired product. Optical rotation [α] 20 / D = + 32.41 ° The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 2] FIG. 5 shows the infrared absorption spectrum of the target compound. Example 3 4- (1,1,1-trifluoro-2-octyloxycarbonyl) phenyl 2- (4-n-decyloxyphenyl) pyrazine-5
Il-carboxylate

Embedded image 2- (4-n-decyloxyphenyl) pyrazine-5
After heating 1.6 g of yl-carboxylic acid together with excess thionyl chloride under reflux for 4 hours, unreacted thionyl chloride was distilled off to give 2- (4-n-decyloxyphenyl) pyrazin-5-yl-carboxylic acid. An acid chloride was obtained. Next, Example 1
Optically active 4-hydroxybenzoic acid synthesized in 2)
1,1,1-trifluoro-2-octyl ester
3 g and 0.5 g of triethylamine were dissolved in 10 ml of methylene chloride, and a solution of the previously synthesized 2- (4-n-decyloxyphenyl) pyrazin-5-yl-carboxylic acid chloride in 20 ml of methylene chloride. Is added dropwise little by little. Furthermore, 5 ml of 0.2 g of dimethylaminopyridine
Was dissolved in methylene chloride, 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 methylene chloride layer was extracted. After drying over anhydrous magnesium sulfate, methylene chloride was distilled off, and the residue was purified by silica gel column chromatography and recrystallization to obtain 1.7 g of the desired product. Optical rotation [α] 20 / D = + 31.51 ° The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 3] FIG. 6 shows the infrared absorption spectrum of the target compound. Example 4 4- (2-octyloxycarbonyl) phenyl 2-
(4-n-octyloxyphenyl) pyrazin-5-yl-carboxylate

Embedded image Using the optically active 2-octanol in place of the optically active 1,1,1-trifluoro-2-octanol of Example 1, the target compound was synthesized in exactly the same manner as in Example 1. Optical rotation [α] 20 / D = −20.91 ° The phase transition temperature (° C.) observed by a polarizing microscope equipped with a hot stage is as follows.

[Table 4] FIG. 7 shows the infrared absorption spectrum of the target compound. Example 5 The liquid crystal compound 4- (1,1,1-trifluoro-2) obtained in Example 1 was added to a liquid crystal cell having a cell thickness of 1.6 μm having a rubbed polyimide alignment film on an ITO electrode substrate.
-Octyloxycarbonyl) phenyl 2- (4-n
-Octyloxyphenyl) pyrazin-5-yl-carboxylate in the Isotropic phase,
A liquid crystal thin film cell was created. The prepared liquid crystal cell was placed in a polarizing microscope equipped with a photomultiplier in which two polarizing plates were orthogonal to each other so that the polarizer and the molecular long axis direction when a DC voltage of -15 V was applied overlapped. This liquid crystal cell
The mixture was gradually cooled to a S ^* c phase with a temperature gradient of 1.0 ° C. for 1 minute. FIG. 8 shows a case where the cooling was further performed and a triangular wave voltage of ± 15 V and 10 Hz was applied in a temperature range of 95 ° C. to 82 ° C. Dark state when the applied voltage is in the negative range,
By observing that the intermediate state in the 0 volt range, the bright state in the plus range, and the light transmittance changed into three states, it was confirmed that there were three stable alignment states of the liquid crystal molecules. The same effect was confirmed for the compounds of the other examples in the same S ^* (3) phase. Example 6 The liquid crystal thin film cell prepared and used in Example 5 is arranged in a polarizing microscope equipped with a photomultiplier in which two polarizing plates are orthogonal to each other so that a dark field is obtained at a voltage of 0 V. The liquid crystal cell is gradually cooled to the SA phase at a temperature gradient of 0.1 to 1.0 ° C./1 minute. Continue to cool down, 95-
In the temperature range of 82 ° C., ± 30 shown in FIG.
V, 10 Hz triangular wave voltage is applied. The hysteresis as shown in FIG. 9B was obtained from the relationship between the applied voltage at 85 ° C. and the transmittance. 0V to ₊ V 3, is extremely small changes of the brightness of the transmittance up to 0V _{to-V 3.} This indicates that the memory effect in the dark area is extremely good. Also,
The fact that the threshold voltage is around ± 15 V indicates that the threshold voltage is low.

[0011]

According to the present invention, a novel liquid crystal device driven in a tristable state using a liquid crystal compound represented by a specific general formula 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 a good hysteresis of a memory effect in a dark part for a three-state liquid crystal.

FIG. 4 shows an infrared absorption spectrum of the target compound of Example 1. In each of the following infrared absorption spectrum diagrams, the vertical axis indicates transmittance (%), and the horizontal axis indicates wave number (cm ^-1 ).

FIG. 5 shows an infrared absorption spectrum of the target compound of Example 2.

FIG. 6 shows an infrared absorption spectrum of the target compound of Example 3.

FIG. 7 shows an infrared absorption spectrum of the target compound of Example 4.

FIG. 8 is a graph showing good hysteresis of a memory effect in a dark part exhibited by the three-state liquid crystal compound of the present invention;
The graph shows the change of the light transmittance with respect to the applied triangular wave voltage.

FIG. 9 shows a good hysteresis of the memory effect in the dark part of the three-state liquid crystal compound of Example 6 of the present invention in Example 6, wherein (a) shows the applied triangular wave voltage;
(B) shows the hysteresis of the change in light transmittance of the compound of Example 1 with respect to the applied triangular wave voltage.

Continuation of front page (72) Inventor Hiroyuki Mogamiya 3-5-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Showa Shell Sekiyu KK (56) References JP-A-2-223563 (JP, A) JP-A-2-2 149568 (JP, A) JP-A-2-69440 (JP, A) JP-A-3-223390 (JP, A) Journal of the Chemical Society of Japan; 1992, 10, 1203-1212 Journal of the Chemical Society of Japan; 1992, 10, 1213-1219 (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13 C07D 241/24 C09K 19/34 C09K 19/42 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] [Claim 1] The following general formula: [Wherein R ₁ ′ and R ₂ ′ are alkyl groups having 4 to 18 carbon atoms, R ₃ ′ is CH ₃ , CF ₃ or C ₂ F ₅ , X ′ is O, COO, CO or a single bond, and t is Indicates that at least one halogen atom is substituted. ^{* Indicates} optically active carbon. ] An anti-ferroelectric liquid crystal device characterized by utilizing a liquid crystal compound selected from the group consisting of: 2. The following general formula: [Wherein R ₁ ′ and R ₂ ′ are alkyl groups having 4 to 18 carbon atoms, R ₃ ′ is CH ₃ , CF ₃ or C ₂ F ₅ , and t is that at least one halogen atom is substituted. Is shown. ^{* Indicates} optically active carbon. ] An anti-ferroelectric liquid crystal device characterized by utilizing a liquid crystal compound selected from the group consisting of: