JPH08211352A - Optically active compound and liquid crystal composition containing same - Google Patents

Abstract

PURPOSE: To provide a ferroelectric liquid crystal material having fast response characteristics and excellent memory property by mixing a liquid crystal compd. with an optically active compd. in which asymmetric carbon atoms in a lactone ring form S- or R-coordination. CONSTITUTION: A ferroelectric chiral smectic liquid crystal compsn. is obtd. by adding a chiral dopant containing an optically active compd. expressed by formula to a liquid crystal compd. showing a smectic C phase. In formula, R is a propyl group or butyl group, (n) is 1 or 2, and two asterisks (*) are asymmetric carbon atoms. Since the compd. expressed by formula has two asymmetric carbon atoms in the lactone ring, two kinds of diastereomers exist and each has a function to suppress the free rotation in the permanent dipole part. The cis-isomer (both of the two asymmetric carbon atoms are in the S- or R-coordination has higher spontaneous polarization, low viscosity and fast responsiveness than the trans-isomer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a novel optically active compound and a liquid crystal composition containing the same.
The optically active compound provided by the present invention is a compound exhibiting ferroelectricity (chiral smectic C phase) excellent in responsiveness and memory property when mixed with another liquid crystal compound, and is an electro-optical switching element. Is used as.

[0002]

2. Description of the Related Art The response speed (τ) of a ferroelectric liquid crystal is expressed as τ = η / (Ps x E) (Ps: spontaneous polarization, η: viscosity, E: applied electric field), and spontaneous polarization (Ps) Is larger, the smaller is τ,
That is, the response speed becomes faster. Therefore, in order to obtain a ferroelectric liquid crystal having a high response speed, it is necessary to develop a material having a large spontaneous polarization. Actually, in order to increase spontaneous polarization, a connector (spacer portion) between a core skeleton containing a cyclic molecule (benzene ring, pyrimidine ring, cyclohexane ring, etc.) and a chiral skeleton has been actively studied (Japanese Patent Laid-Open No. HEI-1). -23855
No. 7). However, although they exhibit large spontaneous polarization, on the contrary, in many cases, the viscosity is increased and the response speed is slowed, and the temperature range of the liquid crystal phase or the Sc ^* phase is narrowed. It wasn't a design guide. Therefore, it has been desired to develop a ferroelectric liquid crystal having a wider temperature range of Sc ^* phase and a larger spontaneous polarization than the known ferroelectric liquid crystal.

Therefore, in Japanese Patent Application Laid-Open No. 3-58981, γ-
A liquid crystal compound having a butyrolactone ring has a carbonyl group having a permanent dipole moment fixed to the inside of a 5-membered ring in order to exhibit ferroelectricity, and by having two asymmetric carbon atoms in this ring, It is described that suppressing the free rotation of this part and making the direction of the permanent dipole constant as a whole increases the spontaneous polarization, and thus speeds up the response speed. However, this Japanese Patent Laid-Open No. 3-589
Γ having a phenipimirimidine ring described in 81.
When blended with the base liquid crystal, the butyrolactone derivative has a slow response speed and is clearly far from practical use. Moreover, it is considered that the spontaneous polarization is not increased probably because the tilt angle is small. Further, regarding the phase transition temperature, it is not possible to show a phase sequence of chiral smectic C phase-chiral smectic A phase-cholesteric phase-isotropic phase.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an optically active substance used in a ferroelectric liquid crystal material as follows. A structurally physically and chemically stable compound 1. 2. A compound that exhibits ferroelectricity by mixing with another liquid crystal compound and exhibits a Sc ^* phase in a wide temperature range. 3. A compound having a large induced spontaneous polarization derived from a permanent dipole moment. 4. A compound showing a fast response to an applied voltage. We have found a compound satisfying the following conditions: it is desirable that the helical pitches of the cholesteric phase and the chiral smectic C phase be sufficiently long and that the tilt angle is large, either alone or in a composition containing at least one of these. An object of the present invention is to provide a compound that can be actually used as a liquid crystal of a display device.

[0005]

The present invention is based on the formula (1) (I)

Embedded image (In the formula, R represents a propyl group or a butyl group, and n is 1
Or 2 and the two symbols * indicate asymmetric carbon atoms. And (2) the two asymmetric carbons of the lactone ring each have (S) coordination.
(3) The optically active compound described in (1) above, wherein the two asymmetric carbons of the lactone ring are each (R) coordinated. (4) The above (1) to (3) At least one optically active compound described above, and (5) a liquid crystal compound or composition exhibiting a smectic C phase, at least the optically active compound described in (1) to (3) above. The present invention relates to a ferroelectric chiral smectic liquid crystal composition, which is obtained by adding one type of chiral dopant.

The optically active compound of the present invention is disclosed in JP-A 3-5.
8981 is a novel compound, which has a carbonyl group having a permanent dipole moment fixed to the inside of a 5- or 6-membered ring in order to exhibit ferroelectricity, and two compounds in this ring. By having an asymmetric carbon of, the free rotation of this part is suppressed, and the direction of the permanent dipole is kept constant as a whole, so it exhibits a large unprecedented induced spontaneous polarization, and hence the response speed. It turns out that speeding up can be obtained. Further, the tilt angle is set to 22.
Since the value is 5 °, which is close to the ideal angle, it was found that the spontaneous polarization was increased. Further, in formula (I), there are two types of diastereomers because they have two asymmetric carbon atoms in the lactone ring, and as a result, they meet the purpose of suppressing the free rotation of the permanent dipole. Although,
In terms of spontaneous polarization, viscosity, and response speed, the cis-form (two asymmetric carbons each having (S) or (R) coordination) has higher spontaneous polarization, lower viscosity, and higher speed than the trans-form. It is a response. Further, in the present invention, the above-mentioned optically active compound is not a substance in which a liquid crystal state is observed alone, but is a compound which exhibits induced spontaneous polarization when mixed with a liquid crystal composition even if it does not exhibit a liquid crystal phase itself.

The optically active compound of the present invention can be produced by the following method. That is, the formula (I)
The compound represented by (n = 1) is an optically active glycidyl ether represented by the formula (II) and a dicarboxylic acid diester derivative represented by the formula (III) (wherein R ′ represents a lower alkyl group, R Can be synthesized by reacting with (as described above) in the presence of a base in an organic solvent.

[0008]

Embedded image R'O-C (O) -CHR-C (O) -OR '(III) The reaction conditions are the compound of formula (II) and 1 to 5 equivalents of formula (III) in an organic solvent in 1 to 5 equivalents. It can be obtained by refluxing for 2 to 30 hours in the presence of the base. As the base used at this time, potassium-t-butoxide, sodium methoxide, sodium ethoxide, sodium hydride, calcium hydride, potassium hydride, lithium hydride, n-butyl lithium or lithium diisopropylamide is preferable, As the organic solvent, alcohols such as t-butanol, ethers such as tetrahydrofuran and diethyl ether, aprotic organic solvents such as dimethylformamide, and mixed solvents of the above organic solvents are preferable.

The above-mentioned starting compound, the compound of formula (II), is
It can be produced by a conventional method from a 2- (4-hydroxyphenyl) -5-octyl-pyrimidine derivative and commercially available optically active epichlorohydrin. The formula (I) (n
The compound represented by the formula (2) is the same as the compound represented by the formula (IV) instead of the dicarboxylic acid diester derivative represented by the formula (III) (wherein R and R ′ are as described above). Can be manufactured using. _{R'O-C (O) -CH 2} -CHR-C (O) -OR '(IV)

The optically active compound of the present invention, which does not exhibit a liquid crystal phase by itself, has a smectic C phase-nematic phase-isotropic phase or a smectic C phase-smectic A phase-nematic phase-isotropic phase. Addition of about 0.1 to 6% to a non-chiral liquid crystal or liquid crystal composition exhibiting a phase sequence shows a ferroelectric (chiral) exhibiting a phase sequence of chiral smectic C phase-chiral smectic A phase-cholesteric phase-isotropic phase. Smectic C phase) is induced. Therefore,
The optically active substance of the present invention showing no liquid crystal phase is useful as an additive for inducing ferroelectricity.

The liquid crystal composition in the present invention can be obtained by mixing at least one compound of the formula (I) and at least one other liquid crystal compound in an appropriate ratio. Compounds that can be mixed with this may include compounds or compositions exhibiting ferroelectricity, or non-chiral liquid crystals or liquid crystal compositions, and preferable compounds can be exemplified below. The liquid crystal composition according to the present invention is preferably a ferroelectric liquid crystal composition, particularly a ferroelectric Sc ^* liquid crystal composition.

[0012]

[Chemical 4] In the above formula (V), R ₁ and R ₂ each have 1 to 1 carbon atoms.
5 represents a straight chain or branched alkyl group or alkoxy group, and may contain an asymmetric carbon atom.

[0013]

[Examples] The compounds of the present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples. Hereinafter, symbols K, Sc ^* , N ^* ,
I represents a crystal, a chiral smectic C phase, a cholesteric phase, and an isotropic phase, respectively. The compound was purified by silica gel column chromatography and recrystallization.

Example 1 350 mg of an optically active glycidyl ether represented by the formula (II) obtained by a conventional method, 862 mg of diethyl n-butylmalonate, 209 mg of potassium t-butoxide, and 10 ml of t-butanol were mixed to obtain 12 The mixture was stirred under reflux for an hour. The reaction solution is returned to room temperature, neutralized with 4N-hydrochloric acid, and then the product is extracted with dichloromethane. The extract was purified by silica gel column chromatography to obtain 120 mg of trans form (2S, 4R) of γ-lactone body represented by the following structural formula.
And 170 mg of cis isomer (2S, 4S) were obtained. (2S, 4R) body

[0015]

Embedded image Phase transition temperature NMR δ ppm (CDCl ₃ ) δ: 0.7 to 3.0 (27H, m) 4.1 to 4.3 (2H, m) 4.85 (1H, m) 6.93 (2H, d, J = 9Hz) ) 8.38 (2H, d, J = 9 Hz) 8.60 (2H, s) IR (KBr): 1779 cm ^-1

(2S, 4S) body

[Chemical 6] Phase transition temperature NMR δppm (CDCl ₃ ) δ: 0.7 to 3.00 (27H, m) 4.1 to 4.3 (2H, m) 4.75 (1H, m) 7.00 (2H, d, J = 9Hz) ) 8.38 (2H, d, J = 9Hz) 8.58 (2H, s) IR (KBr): 1779 cm ^-1

Example 2 Preparation of Ferroelectric Liquid Crystal Composition Compound (2%) represented by formula (VII) synthesized in Example 1
To the non-optically active pyrimidine-based liquid crystal (A) having the Sc phase shown below.

[Chemical 7]

By blending, a liquid crystal composition was prepared. At this time, the phase transition temperature of the liquid crystal composition is And shows a chiral smectic C phase at room temperature.

(Measurement of Spontaneous Polarization, Viscosity, Response Speed, and Inclination Angle) The obtained liquid crystal composition containing the lactone derivative was heated to form an isotropic liquid, and then polyimide was applied thereto and subjected to rubbing treatment. It was injected into a thin cell with a transparent electrode (2.4 microns). After that, the cell is slowly cooled to obtain a uniform Sc ^* monodomain in which the helical structure has disappeared.
In C, a spontaneous polarization was measured by applying a triangular wave voltage of 48 Vpp and 50 Hz to this cell. Similarly, a rectangular wave voltage of 24 Vpp and 50 Hz is applied to the cell at 25 ° C.
The response speed and viscosity were measured. 48Vp to the same cell
A rectangular wave voltage of p, 0.1 Hz was applied and the angular difference between the extinction positions corresponding to the two switching states was measured.
The tilt angle was / 2. Table 1 shows the measurement results of spontaneous polarization, viscosity, response speed and tilt angle when the lactone derivative represented by the formula (VII) was added to the 2% liquid crystal composition.

Comparative Example The measurement results of known lactone derivatives are shown in Tables 2 and 3.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

INDUSTRIAL APPLICABILITY As described above, the compound of the present invention is a liquid crystal composition which is mixed with a known liquid crystal compound to improve the temperature range exhibiting ferroelectricity, spontaneous polarization, viscosity and response. An effective optically active substance for mixing could be provided. Further, the compound of the present invention was able to provide a ferroelectric liquid crystal material having a very high response speed as compared with known lactone derivatives as shown in the examples and further having a very excellent memory property. .

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Claims (5)

[Claims] 1. Formula (I): (In the formula, R represents a propyl group or a butyl group, and n is 1
Or 2 and the two symbols * indicate asymmetric carbon atoms. ) An optically active compound represented by: 2. The optically active compound according to claim 1, wherein the two asymmetric carbon atoms of the lactone ring each have (S) coordination. 3. The optically active compound according to claim 1, wherein the two asymmetric carbon atoms of the lactone ring each have (R) coordination. 4. A liquid crystal composition comprising at least one optically active compound according to any one of claims 1 to 3. 5. A ferroelectric chiral smectic characterized in that a chiral dopant containing at least one optically active compound according to any one of claims 1 to 3 is added to a liquid crystal compound or composition exhibiting a smectic C phase. Liquid crystal composition.