JPH07116109B2 - Optically active compound, liquid crystal composition, and liquid crystal device containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optically active compound and its use. More specifically, a ferroelectric liquid crystal composition containing at least one of the optically active compounds is used. Liquid crystal device.

(B) Conventional Technology The most widely used liquid crystal display element at present is one using a nematic phase, but it has a drawback that it is difficult to display a large capacity such as 1000 × 1000 lines. In a normal twisted nematic (TN) type liquid crystal display device, the contrast decreases as the number of lines increases.
It is virtually impossible to make a large-capacity display element such as a good-looking 1000 x 1000 line. To improve the drawbacks of this TN type liquid crystal display element, super twisted nematic (STN) type liquid crystal display element and double super twisted nematic (DSTN) type liquid crystal display element have been developed. However, at present, the limit level is to achieve a display capacity of about 1000 × 800 lines by the vertical split drive method with 1/100 duty. On the other hand, an active matrix type liquid crystal display device in which thin film transistors (TFT) are arranged on a substrate has also been developed, and it is technically possible to display large capacity such as 1000 × 1000 lines, but the manufacturing process is long and the yield is poor. Therefore, it has a drawback that the manufacturing cost becomes very high.

Promising as a means to improve the above-mentioned problems is a ferroelectric liquid crystal display device (NAClar) proposed as a liquid crystal display based on a principle different from that of the TN type display device.
k et al., Appl. Phys. Lett., ₃₆ , 899 (1980)). This display method utilizes a ferroelectric liquid crystal such as a chiral smectic C phase or a chiral smectic I phase. Since the system uses the memory property, the display capacity can be increased with the improvement of the response speed, and the manufacturing cost does not increase because the active element such as the thin film transistor is not required. Ferroelectric liquid crystal devices also have the advantage of wide vision, and they are regarded as a promising device for large-capacity displays capable of 1000 × 1000 lines or more.

(C) Problems to be Solved by the Invention It goes without saying that the liquid crystal material used for the ferroelectric liquid crystal display utilizing the smectic C phase needs to exhibit the smectic C phase in a wide temperature range around room temperature. Besides, it is necessary to satisfy various conditions.

First, high-speed response is required as a device characteristic for displaying a large capacity, and from this viewpoint, a liquid crystal material is required to have high spontaneous polarization and low viscosity. In addition, in order to obtain good orientation and bistability when applied to a liquid crystal cell, IA
C ( I sotropic-Smectic A ‐Smectic C ) or INAC ( I so
-tropic- N ematic-Smectic A -Smectic C ) the phase series that is necessary to show the liquid crystal material, and the helical pitch of nematic phase and smectic C phase is necessary that sufficiently longer than the cell thickness. Furthermore, a large value is desired for the tilt angle related to the contrast and brightness of the liquid crystal display.

However, at present, it is impossible to satisfy all the desired conditions with a single compound, and usually, a plurality of compounds are mixed and practically used as a liquid crystal composition. In order to prepare a liquid crystal composition satisfying practical requirements, a large number of single liquid crystal compounds having various properties are necessary, and sometimes a compound which does not exhibit liquid crystallinity itself is useful as a component of the liquid crystal composition. There is a possibility.

The present invention has been made under such circumstances, and a novel optically active compound capable of improving the response characteristics of a ferroelectric liquid crystal composition and a wide operating temperature range containing the same,
An object of the present invention is to provide a ferroelectric liquid crystal composition and a ferroelectric liquid crystal device that can obtain good orientation and exhibit a high-speed response at room temperature.

(D) Means and Actions for Solving the Problems Thus, according to the present invention, the following general formula (I): (In the formula, R represents an alkyl group having 1 to 15 carbon atoms, and * represents that the carbon atom is an asymmetric carbon.).

The compound of the above formula (I) (hereinafter referred to as compound (I)) is
It is a compound not described in the literature.

The compound (I) has a cis form and a trans form,
Both are included in the compound of the present invention.

In the present invention, "alkyl group having 1 to 15 carbon atoms" in the definition of the above compound (I) is methyl, ethyl, propyl, i-propyl, butyl, 1- or 2-methylpropyl, t-butyl, pentyl. , 1- or 2-methylbutyl, hexyl, 1- or 3-methylpentyl, heptyl, 1- or 4-methylhexyl, octyl, 1-methylheptyl, nonyl, 1- or 6-methyloctyl, decyl, 1-methylnonyl , Undecyl, 1-methyldecyl, dodecyl, 1-methylundecyl, and the like. In these alkyl groups, the carbon chain may contain an asymmetric carbon.

The following compounds may be mentioned as preferred examples of the compound (I).

Etc.

Compound (I) can be prepared, for example, as follows. The optically active 1-trifluoromethyl-3-phenyl-2-propenyl alcohol was changed to sodium alkoxide by reaction with sodium hydride (reaction formula (a)), while the alkoxybiphenylcarboxylic acid was changed to phosphorus pentachloride. It can be obtained by converting the carboxylic acid chloride by the reaction (reaction formula (b)), and then reacting the sodium alkoxide with the carboxylic acid chloride.

The above-mentioned optically active alcohol can be synthesized according to, for example, “Dr. Proceedings of the 13th Fluorochemical Symposium Lecture Proceedings” (1988) 4D112, Takashi Tsukamoto, Mitsunori Takeda, Masazo Hayashi, Takashi Yamazaki, Tomoya Kitazume.

The compound (I) does not necessarily exhibit a liquid crystal phase, but can be used as a ferroelectric liquid crystal composition by adding an appropriate amount to a non-chiral smectic or chiral smectic liquid crystal compound or a mixture thereof.

Generally, in order to improve the response speed of a ferroelectric liquid crystal, a group having a strong dipole moment is required near the asymmetric carbon. Free rotation of the molecule should be bound (JSPatel an
d JWGoodby, Optical Engineering, 26 , 373 (1987)).

The compounds of this invention have a strong dipole moment of CF ₃
Since the group is bonded to the asymmetric carbon and the group having a double bond is bonded to the asymmetric carbon, it is considered that the free rotation of the molecule is restricted. Moreover, the compound (I) has a structure in which it bends at the asymmetric carbon portion and in the vicinity thereof, and it can be expected to limit the rotation between molecules. Therefore, the compound (I) can be expected to have a potentially large spontaneous polarization, and it is considered that the response characteristics can be improved by adding an appropriate amount to the liquid crystal compound showing the smectic C phase or a mixture thereof.

Accordingly, the present invention also provides a ferroelectric liquid crystal composition characterized in that the smectic liquid crystal compound or a mixture thereof contains at least one optically active compound represented by the chemical formula (I).

The smectic liquid crystal compound includes various compounds known in the art, and specific examples thereof include the following general formula (I
Examples thereof include compounds represented by I), (III) and (IV).

(In the above formula, A and B are each a single bond, or -COO-,
-OCO-, -CH = CH-COO-, -OCO-CH = CH-, -O
A-, -S-, -OCOO- or -CO- group is shown. D and E are each a single bond, or -COO-, -OCO-, -CH =
N-, -N = CH-, -CH = CH-, -C≡C-, -CH = CH
-COO -, - OCO-CH = CH -, - CH 2 CH 2 -, - OCH 2 -, -
A CH ₂ —, —COS— or —SCO— group is shown.

Are independently 6-membered rings such as benzene ring, cyclohexane ring, bicyclo [2,2,2] octane ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, piperazine ring, pyran ring, and dioxacyclohexane ring. A hydrogen atom in these 6-membered ring groups may be substituted with a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a nitro group, a lower alkyl group, a lower alkoxy group or deuterium. R ₃ and R ₄ each independently represent a linear or branched alkyl group having 1 to 15 carbon atoms, and the alkyl group may contain an asymmetric carbon atom. p represents an integer of 1 or 2. ) Two or more of the above smectic liquid crystal compounds can be mixed and used. In particular, the above-mentioned smectic liquid crystal compound exhibits a smectic C phase at around room temperature, and IAC and I
It is preferable to use a suitable mixture so as to have a phase series such as NAC.

The content of the compound (I) in the ferroelectric liquid crystal composition of the present invention containing the smectic liquid crystal compound or a mixture thereof and the compound (I) is usually 0.1 to 30% by weight. It is preferably 1 to 20% by weight. If it is less than 0.1% by weight, the improvement of responsiveness is insufficient, and 3
If it exceeds 0% by weight, the thermal stability of the smectic C phase becomes insufficient, which is not suitable.

Furthermore, the present invention can provide a liquid crystal element using the above ferroelectric liquid crystal composition between a pair of electrodes.
This liquid crystal element can be made to have a known structure by using the material known in the art as it is, except that the ferroelectric liquid crystal composition of the present invention is used for the liquid crystal composition. Such a liquid crystal element is particularly preferable as a liquid crystal shutter in addition to the liquid crystal display.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(E) Example Example 1 (S) -4'-n-octyloxy-biphenyl-4-
Carboxylic acid-1-trifluoromethyl-3-phenyl-
(Trans) -2-propenyl ester [general formula (I)
Compounds of] 4'-n-octyloxy - - R = C ₈ H ₁₇ in the biphenyl-4-carboxylic acid 0.5 g (1.5 mmol), added phosphorus pentachloride 0.4 g (1.9 mmol), reacted by heating . Phosphoryl chloride and excess phosphorus pentachloride were completely removed by distillation under reduced pressure to obtain 4'-n-octyloxy-biphenyl-carboxylic acid chloride.

Next, 0.3 g of (S) -1-trifluoromethyl-3-phenyl- (trans) -2-propenyl alcohol (1.5 m
mol) in 10 ml of toluene, and add sodium hydride to 0.0
Add 5 g (2 mmol) and react. Unreacted sodium hydride was removed by filtration to obtain sodium (S) -1-trifluoromethyl-3-phenyl- (trans) -2-propenylalkoxide.

The above acid chloride dissolved in 10 ml of toluene was added, and the mixture was allowed to stand at room temperature for 12 hours, then heated to 80 ° C, kept for 3 hours and cooled. Then add to distilled water and extract with ether. The ether layer is washed with water and dried over sodium sulfate. The ether was distilled off, and the residue was purified by liquid chromatography (column: C18-silica, mobile phase solvent: methanol) to obtain the desired (S) -4'-n-octyloxy-biphenyl-4-carboxylic acid- 1-Trifluoromethyl-3-phenyl- (trans) -2-propenyl ester was obtained.

The infrared absorption spectrum of the above-obtained ester is shown in FIG. This ester has a melting point of 79 ° C and a specific rotation of 108.0 °.
Met. This ester does not exhibit a liquid crystal phase but can be used as a component of a liquid crystal composition.

Example 2 (R) -4'-n-octyloxy-biphenyl-4-
Carboxylic acid-1-trifluoromethyl-3-phenyl-
(Cis) -2-propenyl ester [general formula _{(I) R = C 8 H} 17 - compound] In Example 1, (S)-1-trifluoromethyl -
Instead of using 0.3 g (1.5 mmol) of 3-phenyl- (trans) -2-propenyl alcohol, 0.3 g (1.5 mmol of (R) -1-trifluoromethyl-3-phenyl- (cis) -2-propenyl alcohol (R) -4′-n-octyloxy-biphenyl-4-carboxylic acid-1-trifluoromethyl-3-phenyl- (cis) -2-propenyl ester in the same manner as in Example 1 except that Got

The ester obtained above had a melting point of 70 ° C and a specific optical rotation of -185.
It was 0 °. This ester did not exhibit a liquid crystal phase but could be used as a liquid crystal composition. The infrared absorption spectrum of this ester is shown in FIG.

Example 3 Preparation of Liquid Crystal Composition Liquid crystal composition (A) was prepared by adding 2 parts by weight of the compound synthesized in Example 1 to 98 parts by weight of the nonchiral pyrimidine liquid crystal composition shown in [Table 1] below. did.

This liquid crystal composition (A) exhibits a smectic C phase at room temperature, and its transition (Here, S _C , S _A , N, and I represent a smectic C phase, a smectic A phase, a nematic phase, and an isotropic liquid, respectively).

An ITO film was formed on two glass substrates, a SiO ₂ film was further formed, a polyvinyl alcohol film was applied, and rubbing was performed.

Next, the two glass substrates were bonded together with a cell thickness of 2 μm, and the liquid crystal composition (A) was injected. After injection, the cell is heated to 75 ℃, where the liquid crystal composition changes to an isotropic liquid, and then 1 ℃.
Good orientation was obtained by cooling to room temperature at / min.

This liquid crystal cell is installed between two orthogonal polarizers, and V
_When a square wave of _pp = 20 V was applied, a change in transmitted light intensity was observed. The response speed obtained by changing the transmitted light intensity was 190 μsec at 25 ° C., and the tilt angle was 10.5 °.

Example 4 A liquid crystal composition (B) was prepared in the same manner as in Example 3, except that the compound synthesized in Example 2 was used instead of the compound synthesized in Example 1.

This liquid crystal composition (B) exhibits a smectic C phase at room temperature and its transition point is (Here, S _C , S _A , N, and I represent a smectic C phase, a smectic A phase, a nematic phase, and an isotropic liquid, respectively).

Further, using this liquid crystal composition (B), a liquid crystal element was produced in the same manner as in Example 3, and the response speed was measured. As a result, it was 330 μsec at 25 ° C. and the tilt angle was 10.5 °.

From the above examples, by adding the optically active compound represented by the general formula (I) to a non-chiral liquid crystal composition, a smectic C phase is exhibited in a wide temperature range around room temperature and a high speed response is exhibited. A liquid crystal composition can be obtained.

(F) Effect of the Invention The optically active compound of the present invention has high spontaneous polarization and low viscosity, and is useful in various applications by utilizing this property, especially in a ferroelectric liquid crystal composition. It is useful for improving response speed and operating temperature range.

The smectic liquid crystal composition containing the above optically active compound has a good orientation and can provide a large-capacity ferroelectric liquid crystal device which has a high contrast, is bright, and has a wide operating temperature range.

[Brief description of drawings]

1 and 2 are infrared absorption spectrum diagrams of the optically active compound of one example of the present invention.

Claims (3)

[Claims] 1. The following general formula (I): (In the formula, R represents an alkyl group having 1 to 15 carbon atoms, and * indicates that the carbon atom is an asymmetric carbon.) 2. A ferroelectric liquid crystal composition comprising a smectic liquid crystal compound or a mixture thereof and at least one kind of the optically active compound according to claim 1. 3. A liquid crystal device comprising the liquid crystal composition according to claim 2 between a pair of electrodes.