JPH0730051B2 - Liquid crystal compound and liquid crystal composition - Google Patents

Description

The present invention relates to a novel liquid crystal compound and a liquid crystal composition containing at least one kind of the liquid crystal compound.

[Conventional technology]

At present, liquid crystals are widely used as display materials, but most of such display elements are TN (Twisted Nematic) type display systems, which use liquid crystal materials belonging to the nematic phase. This TN type display system has excellent features such as eyestrain and extremely low power consumption because it is a light receiving type, but it has a slow response speed, can not obtain contrast depending on the viewing angle, and has a large screen. However, there are drawbacks such as the need to add active elements such as TFT (Thin film Transistor) in order to make a high-definition display element.
Recently, high-speed response is required for display devices, and improvement of liquid crystal materials has been attempted to meet such demand. However, other emissive displays (CRT, E
L, plasma display, etc.), the response speed was not sufficient and high-definition display was not possible. Light receiving type,
A new liquid crystal display method that replaces the TN type display method that uses a nematic phase is necessary in order to take advantage of the characteristics of liquid crystal such as low power consumption, and to secure the response speed and high definition comparable to those of a light emitting display. Among the new liquid crystal display systems, one that is expected to have the above excellent characteristics is a display system utilizing the optical switching phenomenon of a ferroelectric liquid crystal (NAClark, STLagerwall; Appl.Phys.Lett.,
36, 899 (1980)) there is. Ferroelectric liquid crystal RB in 1975
Its existence was announced by Meyer et al. (RBMey
er et al., J. Phys. (Paris) 36 , L-69 (1975)), and belongs to a chiral smectic C phase (SmC ^* phase) or a chiral smectic H phase (SmH ^* phase) due to the structure of liquid crystal.
After that, further chiral smectic I phase (SmI ^* phase), chiral smectic F phase (SmF ^* phase), chiral smectic G phase (SmG ^* phase), chiral smectic J phase (SmJ ^* phase)
Phase) and a chiral smectic K phase (SmK ^* phase) have been revealed as liquid crystal phases exhibiting ferroelectricity. As the ferroelectric liquid crystal compounds, those shown in Table 1 below are known (P
h.Martinot-Lagarde, J.Phys. (Paris) 37 , C3-129 (197
6) etc.).

This ferroelectric liquid crystal has a very fast response speed because it has spontaneous polarization, and can express a bistable state with a memory property. Furthermore, since it has excellent viewing angle characteristics, it has a large capacity and a large capacity. Suitable as a screen display.

[Problems to be solved by the invention]

However, these ferroelectric liquid crystal compounds have drawbacks such as a high temperature range of the chiral mechanic phase, a small spontaneous polarization, and poor threshold characteristics, and are not necessarily satisfactory.

The present inventors have arrived at the present invention as a result of studying various compounds for the main purpose of developing a liquid crystal material suitable for use in a display system utilizing the optical switching phenomenon of a ferroelectric liquid crystal.

[Outline of Invention]

The present invention has the general formula (I) (In the above general formula, R ₁ is an alkyl group or an alkoxy group having 1 to 18 carbon atoms, and R ^* is an optically active carbon atom having 7 carbon atoms.
The present invention provides a liquid crystal compound represented by a 4-methylhexyl group, a 6-methyloctyl group or a 1-methylheptyl group within the range of 9 to 9).

The present invention also provides a liquid crystal composition containing at least one kind of the optically active liquid crystalline compound as a blending component.

[Detailed Description of the Invention]

The liquid crystalline compound represented by the general formula (I) is, for example, the compound represented by the general formula (II) (Wherein R is an alkyl group or an alkoxy group having 1 to 18 carbon atoms), the 2,3-dicyanopyrazine derivative represented by the formula is hydrolyzed and then decarboxylated to give a compound represented by the general formula (III): A 2-carboxypyrazine derivative represented by the formula (1) is halogenated to form an acid halide, and the compound is represented by the general formula (IV): HO-R ^* (IV) (wherein R ^* is an optically active 4-methylhexyl group). Group, which represents a 6-methyloctyl group or a 1-methylheptyl group), and reacts to esterify the compound.

The 2,3-dicyanopyrazine derivative represented by the general formula (II) can be obtained by using a production method known per se [Tadataka Tsuda et al., Journal of Japan Agricultural Chemistry Vol. 52, p. 213 (1978)]. It is what is done.

The liquid crystal compounds represented by the general formula (I) of the present invention thus obtained include the following compounds.

5- (pn-pentyloxyphenyl) pyrazine-2
-Carboxylic acid-4'-methylhexyl ester, 5-
(Pn-hexyloxyphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- (p-
n-octyloxyphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- (pn-decyloxyphenyl) pyrazine-2-carboxylic acid-4 '
-Methylhexyl ester, 5- (pn-dodecyloxyphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- (pn-tridecyloxyphenyl) pyrazine-2-carboxylic acid-4 ′ -Methylhexyl ester, 5- (pn-tetradecyloxyphenyl) pyrazine-2-carboxylic acid-4′-methylhexyl ester, 5- (pn-hexadenoxyphenyl) pyrazine-2-carboxylic acid Acid-4'-methylhexyl ester, 5- (pn-octadecyloxyphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- (pn-octylphenyl) pyrazine-2-carboxylic acid -4'-methylhexyl ester, 5
-(Pn-decylphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- (pn-dodecylphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester, 5- ( p-n-hexyloxyphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (pn-octyloxyphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (Pn-nonyloxyphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (pn-decyloxyphenyl) pyrazine-
2-carboxylic acid-6'-methyloctyl ester, 5-
(Pn-undecyloxyphenyl) pyrazine-2-
Carboxylic acid-6'-methyloctyl ester, 5- (p
-N-dodecyloxyphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (pn-)
Tridecyloxyphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (pn-tetradecyloxyphenyl) pyrazine-2-carboxylic acid-
6'-methyloctyl ester, 5- (pn-hexadecyloxyphenyl) pyrazine-2-carboxylic acid-
6'-methyloctyl ester, 5- (pn-decylphenyl) pyrazine-2-carboxylic acid-6'-methyloctyl ester, 5- (pn-dodecylphenyl) pyrazine-2-carboxylic acid-6 ' -Methyloctyl ester, 5- (pn-decyloxyphenyl) pyrazine-
2-carboxylic acid-1'-methylheptyl ester, 5-
(Pn-dodecyloxyphenyl) pyrazine-2-carboxylic acid-1'-methylheptyl ester, 5- (p-
n-dodecylphenyl) pyrazine-2-carboxylic acid,
1'-methylheptyl ester.

In the present invention, the compound represented by the general formula (I) having a ferroelectric chiral smectic phase is used as a display device as shown by N, A, Clark, et al. In addition, since it has an excellent threshold characteristic with respect to electric field response, it is possible to prevent crosstalk and to provide good contrast, especially when a ferroelectric chiral smectic liquid crystal is used in a display driven by a simple matrix electrode. . Such characteristics are the same for a liquid crystal composition containing at least one liquid crystalline compound represented by the general formula (I) in the present invention, which contains a compound having no chiral smectic phase by itself. It is also excellent when the liquid crystal is used as a high-definition large-screen display device.

Further, the novel liquid crystalline compound of the present invention can improve the threshold characteristics when used as a TN type liquid crystal device by mixing and using it with a normal nematic liquid crystal.

As described above, the liquid crystalline compound of the present invention can be used alone as a ferroelectric liquid crystal device material, and for example, the following Table 1
By combining with a ferroelectric liquid crystal as shown in
It becomes possible to extend the temperature range of the chiral smectic phase. In such a case, at least one kind of the liquid crystal compounds of the present invention represented by the general formula (I) is
1 to 99% by weight, especially 5 to 95% by weight of the obtained liquid crystal composition
It is preferable to use it in a ratio such that

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 5- (p-octyloxyphenyl) pyrazine-2-carboxylic acid-4'-methylhexyl ester.

(1) 5- (p-octyloxyphenyl) pyrazine-
Synthesis of 2,3-dicarbonitrile.

Selenium dioxide 11.4g (0.1mol), dioxane 100ml, water 2m
l were mixed and stirred at 70 to 75 ° C. for 2 hours, and then a solution of p-octyloxyacetophenone 24.8 g (0.1 mol) -dioxane (60 ml) was added. After refluxing for 2 hours, the mixture was cooled and the precipitated metal selenium was passed through. 10.8g of DAMN (0.1mo
l) and 3.0 ml of acetic acid were added, and the mixture was refluxed at 90 to 93 ° C for 2 hours. After cooling after the reaction, the liquid was concentrated to obtain a crude product.
After recrystallization from hexane, 27.2 g (82% yield) of product was obtained. Melting point 79 ° C. IR (ν cm ^-1 ): 2245 (C≡N).

Elemental analysis C ₂₀ H ₂₂ N ₄ O Calculated: C 71.83 H 6.63 N 16.75 Found: C 72.02 H 6.75 N 16.55.

(2) 5- (p-octyloxyphenyl) pyrazine-
Synthesis of 2,3-dicarboxylic acid.

5- (p-octyloxyphenyl) pyrazine-2,3-
Dicarbonitrile (8.7g, 0.026mol) was placed in a solution of sodium hydroxide (15g, 0.375mol) -water (600ml), 95
The mixture was stirred at 0 ° C for 3 hours. After the reaction, concentrated hydrochloric acid was added to acidify the reaction solution, and the precipitate was passed through. After washing 5 times with 60 ml of water and vacuum drying, 8.1 g (84% yield) of product was obtained. After recrystallization from ethanol-water, melting point 163 ° C. IR (νcm ^-1 : 3400
~ 2550 (OH), 1730, 1695 (C = 0).

Elemental analysis calculated for C ₂₀ H ₂₄ N ₂ O ₅ : C 64.50 H 6.50 N 7.52 Found: C 64.52 H 6.70 N 7.36.

(3) 5- (p-octyloxyphenyl) pyrazine-
Synthesis of 2-carboxylic acids.

5- (p-octyloxyphenyl) pyrazine-2,3-
Dicarboxylic acid (8.1 g, 0.0218 mol) was placed in dichlorobenzene (100 ml), and the oil bath was set to 160 ° C. and stirred for 3.5 hours. After standing overnight, the precipitate was filtered off and washed twice with 60 ml of hexane to give 4.1 g of product. After recrystallization from ethanol-water, melting point 165 ° C, decomposition point 190 ° C. IR (νcm ^-1 ): 3400-2
500 (OH), 1680 (C = 0).

Elemental analysis Calcd for C ₁₉ H ₂₄ N ₂ O ₃ : C 69.49 H 7.37 N 8.53 Found: C 69.65 H 7.35 N 8.38 (4) Esterification.

5- (p-octyloxyphenyl) pyrazine-2-carboxylic acid (1.64 g, 5 mmol) was placed in 20 ml of thionyl chloride and refluxed for 2 hours. After the reaction, excess thionyl chloride was distilled off under reduced pressure, and the residue was dissolved in 50 ml of toluene. The toluene solution was washed with 70 ml of water four times, dried over magnesium sulfate and then passed through. 0.5 g of active 4-(-) methyl-1-hexanol was added to the liquid, and a mixed solution of 0.4 g of pyridine and 10 ml of toluene was added dropwise with stirring under cooling to 0 ° C.
Then, the mixture was stirred at 5 ° C or lower for 30 minutes and then at 25 ° C for 1 hour. After passing the reaction solution, the solution was washed twice with 100 ml of water. Next, the toluene solution was dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by column chromatography using silica gel (60 g) eluting with toluene, and the obtained crystals were recrystallized from hexane to obtain 0.8 g (yield 36%) of the product.

IR (νcm ^-1 ): 1730 (C = 0).

Calculated: C 62.70 H 12.50 N 9.14 as elemental analysis C ₁₆ H ₃₈ N ₂ O ₃ .

Found: C 62.51 H 12.30 N 9.20.

Examples 2 to 10 In the same manner as in Example 1, the compounds of Examples 2 to 10 shown in Table 2 below were obtained.

The phase transition temperatures thereof are also shown in Table 2. In the table, Cryst represents a crystalline state, SmC ^* represents a chiral smectic phase, SmA represents a smectic A phase, and Iso represents an isotropic liquid.

Example 11 A liquid crystal cell having a cell thickness of about 2 μm provided with an ITO (Indium Tin Oxide) film as an electrode was provided with 4′-methylhexyl-5- (n.
-Tetradecyloxyphenyl) pyrazine-2-carbonate was encapsulated to obtain a uniform monodomain chiral smectic phase. When the electric field response was measured at 55 ° C, a response speed of 1 msec or less was obtained at a driving voltage of 45V.
Moreover, it was found that it has an excellent threshold characteristic because it does not reverse even if a DC electric field of 30 V is applied for 5 msec.

Example 12 Two kinds of liquid crystal compounds of the present invention were mixed to obtain a liquid crystal composition shown in Table 3 below. This liquid crystal composition has SmC ^{* at} 39 to 62 ° C.
Showed a phase. Further, when this liquid crystal composition was enclosed in a liquid crystal cell having an ITO film and having a cell thickness of about 2 μm to form a chiral smectic phase, a uniform monodomain was obtained. When the electric field response was examined at 45 ° C, a response speed of 1 msec or less was obtained at 25 V, and good contrast was obtained.

[Effects of the Invention] The liquid crystal compound and the liquid crystal composition of the present invention are effective as a ferroelectric chiral smectic liquid crystal or a liquid crystal composition having excellent threshold characteristics against electric field response, and are used for a display driven by a simple matrix electrode. In this case, crosstalk can be prevented and good contrast can be provided, which is particularly excellent when used as a high-definition / large-screen display device.

Further, among the liquid crystal compounds of the present invention, even those not having a liquid crystal phase capable of exhibiting ferroelectricity represented by the SmC ^* phase can be prepared by mixing them with a normal nematic liquid crystal to prepare a liquid crystal composition. , It is possible to improve the threshold characteristic when used as a TN type liquid crystal element.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hirozo Segawa 4-7 Kyowa-cho, Nakajo-machi, Kita-gun, Niigata Prefecture Nakajo Plant, Kyowa Gas Chemicals Co., Ltd. (72) Ichiharu Katagiri Ota-ku, Tokyo Shimomaruko 3-30-2 Canon Inc. (72) Inventor Kenji Shinjo 3-30-2 Shimomaruko Ota-ku, Tokyo Incorporated Canon Inc. (72) Kazuo Yoshinaga 3-30 Shimomaruko, Ota-ku, Tokyo No. 2 in Canon Inc. (56) References JP-A-62-89669 (JP, A)

Claims (4)

[Claims] 1. A general formula (I) (In the above general formula, R ₁ represents an alkyl group or an alkoxy group having 1 to 18 carbon atoms; R ^* represents an optically active 4-methylhexyl group, 6-methyloctyl group or 1-methylheptyl group) A compound represented by. 2. The compound according to claim 1, wherein R ₁ is a linear alkyl group or alkoxy group having 6 to 16 carbon atoms. 3. General formula (I) (In the above general formula, R ₁ represents an alkyl group or an alkoxy group having 1 to 18 carbon atoms; R ^* represents an optically active 4-methylhexyl group, 6-methyloctyl group or 1-methylheptyl group) At least one compound represented by
A liquid crystal composition containing a seed. 4. The liquid crystal composition according to claim 3, wherein R ₁ is a linear alkyl group or alkoxy group having 6 to 16 carbon atoms.