JP2002338526A - Optically active compound and liquid crystal composition comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chiral dopant having characteristics such that helical twist power(HTP) is large and the pitch of induced helices becomes short according to a temperature rise. SOLUTION: This optically active compound is represented by the following general formula (1) [wherein, n is 0 or an integer of 1-5; A is selected from a structural formula group consisting of a single bond (-), Ph and Cy (Ph denotes 1,4-phenylene group; and Cy denotes trans-1,4-cyclohexylene group) when n is 0; and A is selected from a structural formula group consisting of a single bond (-), COO, Cy, Ph, O-Ph and COO-Ph (Ph and Cy are each the same as described in A); X is hydrogen atom or fluorine atom; C* is asymmetric carbon atom]. Thereby, the chiral dopant having the characteristics such that the HTP is large and the pitch of induced helices becomes short according to the temperature rise is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel optically active compound, a liquid crystal composition containing the same, and a liquid crystal display device using the liquid crystal composition.

[0002]

2. Description of the Related Art Various display modes of a liquid crystal display element are known, and in many of the display modes, control of a helical pitch of a liquid crystal is required. The following modes are required to control the helical pitch of the liquid crystal. At present, a practically used and frequently used mode is a twisted nematic mode (T mode) using a nematic liquid crystal.
N mode) and a super twisted nematic mode (STN mode).

In the TN mode, liquid crystal molecules are oriented so as to be twisted by 90 degrees between an upper substrate and a lower substrate, and a ピ ッ チ pitch of a helix is formed in a cell. In the STN mode, the liquid crystal molecules are oriented so as to be twisted around 220 degrees between the upper substrate and the lower substrate.
/ 5 pitch is formed. The TN mode is used in a simple matrix drive liquid crystal display element and an active matrix drive liquid crystal display element, and the STN mode is used in a simple matrix drive liquid crystal display element.

As another mode, there is a selective reflection (SR) mode of a chiral nematic liquid crystal.
As shown in FIGS. 1 and 2, in the SR mode, the liquid crystal takes a planar state in which the helical axis is perpendicular to the substrate and a focal conic state in which the direction of the helical axis is random.
These two states can be switched by a voltage pulse. In the planar state, light having a wavelength corresponding to the helical pitch is reflected, but in the focal conic state, light passes through the element. Display is possible by making the reflection state bright and the transmission state dark. An optically active compound that induces a helical structure is usually called a chiral dopant. Until now, many chiral dopants have been synthesized,
A typical compound is a compound having the following structure.

[0005]

Embedded image

The most important performance required of a chiral dopant is to have a large torsional force. The torsional force (HTP) is a physical quantity defined by the following equation. HTP (μm ⁻¹ ) = 1 / ((addition amount of chiral dopant)
(wt%) / 100) × Induced spiral pitch (μm)) Chiral dopants usually do not exhibit liquid crystallinity, and
Many have a large molecular weight, and when added in a large amount to the mother liquid crystal, various performances are often deteriorated. Examples of the performance deterioration include a decrease in the phase transition temperature from the isotropic phase to the nematic phase, an increase in the liquid crystal viscosity, and liability to cause crystallization. Chiral dopan with a large torsion force,
Since a desired helical pitch can be obtained with a small amount of addition, deterioration of various performances can be suppressed.

In the SR mode, in addition to these problems, there is a problem that the helical pitch has a temperature dependency. In other words, in the SR mode, light corresponding to the helical pitch is reflected (selectively reflected) to be in a bright state, but with the chiral dopants developed so far, the helical pitch becomes longer with an increase in temperature, and the color of the reflected light changes. There was a problem of doing it. The change of the selective reflection wavelength with the temperature rise is called "wavelength shift". A case where the selective reflection wavelength becomes longer due to a temperature rise is defined as a positive wavelength shift, and a case where the wavelength becomes shorter as a negative wavelength shift.

In order to eliminate the temperature dependence of the selective reflection wavelength,
A combination of a chiral dopant exhibiting a positive wavelength shift and a chiral dopant exhibiting a negative wavelength shift was studied.However, the number of chiral dopants exhibiting a negative wavelength shift was extremely small, and the amount of the shift was too small. Was difficult.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a chiral dopant having a feature that the HTP is large and the pitch of the induced helix becomes shorter as the temperature rises.

[0010]

That is, the present invention relates to an optically active compound represented by the following general formula (1).

[0011]

Embedded image (In the formula, n is 0 or an integer of 1 to 5, and when n is 0, A is a single bond (-), -Ph- and -Cy- (-Ph- represents a 1,4-phenylene group. , -Cy- represents a trans-1,4-cyclohexylene group), when n is an integer of 1 to 5, A is a single bond (-), -O-, -COO-, -Cy-, -Ph-,-
O-Ph- and -COO-Ph- (-Ph- and -Cy- are as defined above) are each selected from the group of structural formulas, X is a hydrogen atom or a fluorine atom, and C * is an asymmetric carbon atom. It is. )

In the present invention, n in the general formula (1) is 3, X is a hydrogen atom, and A is -Cy-, -Ph-,
Compounds selected from the group consisting of -O-Ph- and -COO-Ph- are preferred. Also, the torsional force (HT
An optically active compound exhibiting the property that P) is 9 or more and that the pitch of the induced helix becomes shorter as the temperature rises is preferred. This compound is suitably used as an additive for nematic liquid crystals, and is suitably used as a nematic liquid crystal composition containing at least one or more optically active compounds represented by the general formula (1). A liquid crystal element in which an object is held between substrates having electrodes.

The optically active substance includes an R-form and an S-form, both of which can be suitably used. That is, the difference between the properties of the R-form and the S-form is due to the handiness of the helical pitch (right helix,
Left spiral) is a different point. Therefore, in use, any of them can be selected in consideration of the chirality of the chiral dopant used in combination. When a large amount of the optically active compound of the present invention is added alone to a nematic liquid crystal as a mother liquid crystal, the resulting composition may crystallize at room temperature depending on the combination. However, in this case too,
Since other chiral dopants are used in combination, or it is not essential to fix a combination that produces the same effect, it can be easily avoided in adjusting a practical composition.

[0014]

According to the present invention, there is provided a chiral dopant having a feature that the HTP is large and the pitch of the induced helix becomes shorter as the temperature rises. Therefore, TN
In the liquid crystal used in the mode and the STN mode, the helical pitch can be adjusted only by adding a small amount of the chiral dopant of the present invention, so that the performance deterioration of the mother liquid crystal can be suppressed. Further, in the SR mode liquid crystal, by using a chiral dopant that induces a positive wavelength shift in combination with the present invention, a liquid crystal having no helical pitch temperature change can be obtained.

[0015]

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is of course not limited thereto. Example 1 (Equation (1): n = 3, A = -Ph-, X = H (E
1)) Production of (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4'-n-propylbiphenyl-4-carboxylate. 1.5 g of 4'-n-propylbiphenyl-4-carboxylic acid (6.2 mmo
l), N, N-dicyclohexylcarbodiimide (DCC) 1.29 g
(6.2 mmol) and 30 mL (milliliter) of dichloromethane were charged into a reaction vessel, and (R) -1-methyl-3-ethylpentyl-
1.56 g (6.2 mmol) of 4-hydroxybenzoate, then 4-
0.15 g (1.2 mmol) of dimethylaminopyridine was added, and the mixture was stirred at room temperature for 12 hours.

After completion of the reaction, the precipitated solid was separated by filtration and washed with diethyl ether. Diethyl ether 60 in the filtrate
Add 2 ml of 2N hydrochloric acid, 1N aqueous sodium hydroxide,
Then washed with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was distilled off to obtain crude (R) -4- (1-
Methyl-3-ethylpentyloxycarbonyl) phenyl-
4'-n-propylbiphenyl-4-carboxylate 2.7 g
(91% yield). The resulting crude product is purified by high performance liquid chromatography to obtain the desired (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4′-n-propylbiphenyl-4-carboxy 2.2 g (74 yield)
%).

Embodiment 2 (Equation (1): n = 3, A = -Ph-, X
= F (E2)) Preparation of (R) -3-fluoro-4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4'-n-propylbiphenyl-4-carboxylate. In Example 1, (R) -1-methyl-3-ethylpentyl-
Instead of 4-hydroxybenzoate, (R) -1-methyl-3-
Synthesis was carried out in the same manner as in Example 1 except that ethylpentyl-2-fluoro-4-hydroxybenzoate was used.

Embodiment 3 (Equation (1): n = 0, A = -Ph-, X
= H (E3)) Preparation of (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-biphenyl-4-carboxylate. Synthesis was performed in the same manner as in Example 1 except that biphenyl-4-carboxylic acid was used instead of 4′-n-propylbiphenyl-4-carboxylic acid.

Embodiment 4 (Equation (1): n = 3, A = -Cy-, X
= H (E4)) Preparation of (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4- (trans-4-n-propylcyclohexyl) phenylcarboxylate.

(1) Synthesis of 4-acetoxybenzoic acid chloride. 40.0 g (222 mmol) of 4-acetoxybenzoic acid and 264 g (2.22 mol) of purified thionyl chloride were charged into a reaction vessel, and heated under reflux (79 ° C.) for 4 hours. Next, thionyl chloride was first distilled off under normal pressure, 150 mL of toluene was added thereto, and toluene and thionyl chloride were distilled off under reduced pressure to obtain 44 g of 4-acetoxybenzoic acid chloride (yield 99%).

(2) (R) -1-methyl-3-ethylpentyl-4-
Synthesis of acetoxybenzoate. 4-acetoxybenzoic acid chloride 10.0 g (50.4 mmol),
6.0 g (46.1 mmol) of (R) -4-ethyl-2-hexanol and 100 mL of toluene were charged into a reaction vessel, and pyridine was added thereto.
7.3 g (92.1 mmol) was added dropwise, and the mixture was stirred at room temperature for 3 hours. After adding 20 mL of water to the reaction solution and stirring at room temperature for 30 minutes, the organic layer was separated. The organic layer was washed with 2N hydrochloric acid, 1N aqueous sodium hydroxide solution, and then with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was distilled off to remove (R) -1-methyl-3-ethylpentyl-4-acetoxybenzoate.
3.5 g (92% yield) was obtained.

(3) (R) -1-methyl-3-ethylpentyl-4-
Synthesis of hydroxybenzoate. 13.5 g (46.2 mmol) of (R) -1-methyl-3-ethylpentyl-4-acetoxybenzoate and 230 mL of toluene were charged into a reaction vessel, and 7.2 g of a methanol solution of methylamine at a concentration of 40% was added thereto (7.2 g of methylamine 92.4%). mmol), and the mixture was stirred at room temperature for 3 hours. After washing the reaction solution with 2N hydrochloric acid and water, the organic layer was separated. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was distilled off to obtain 11 g of (R) -1-methyl-3-ethylpentyl-4-hydroxybenzoate (yield 95).
%).

(4) Synthesis of (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4- (trans-4-n-propylcyclohexyl) phenylcarboxylate. 4- (trans-4-n-propylcyclohexyl) benzoic acid 1.5 g
(6.1 mmol), N, N-dicyclohexylcarbodiimide (DCC)
1.26 g (6.1 mmol) and 30 mL of dichloromethane were charged into a reaction vessel, and (R) -1-methyl-3-ethylpentyl-
1.52 g (6.1 mmol) of 4-hydroxybenzoate, then 4-
0.15 g (1.2 mmol) of dimethylaminopyridine was added, and the mixture was stirred at room temperature for 12 hours.

After completion of the reaction, the precipitated solid was filtered off and washed with diethyl ether. Diethyl ether 6 in the filtrate
0 mL was added, and this was washed with 2N hydrochloric acid, 1N aqueous sodium hydroxide solution, and then with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was distilled off.
2.8 g (96% yield) of -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4- (trans-4-n-propylcyclohexyl) phenylcarboxylate was obtained. The resulting crude product is purified by high performance liquid chromatography to obtain the desired (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4- (trans-4-n-propylcyclohexyl) )
2.4 g (80% yield) of phenylcarboxylate were obtained.

Example 5 (Equation (1): n = 3, A = -Cy-, X
= F (E5)) (R) -3-fluoro-4- (1-methyl-3-
Ethylpentyloxycarbonyl) phenyl-4- (trans-4-
Production of n-propylcyclohexyl) phenylcarboxylate. In (1) of Example 4, except that 2-fluoro-4-acetoxybenzoic acid was used instead of 4-acetoxybenzoic acid,
Synthesized in the same manner as in Example 4.

Embodiment 6 (Equation (1): n = 3, A = -O-, X
= H (E6)) Production of (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4-n-propyloxybenzoate. 1.44 g (8.0 mmol) of 4-n-propyloxybenzoic acid, 1.65 g (8.0 mmol) of N, N-dicyclohexylcarbodiimide (DCC) and 30 mL of dichloromethane were charged into a reaction vessel, and the mixture was added thereto.
2.0 g (8.0 mmol) of (R) -1-methyl-3-ethylpentyl-4-hydroxybenzoate and then 0.20 g (1.6 mmol) of 4-dimethylaminopyridine were added, and the mixture was stirred at room temperature for 12 hours.

After completion of the reaction, the precipitated solid was separated by filtration and washed with diethyl ether. 60 m of diethyl ether in the filtrate
L was added, and this was washed with 2N hydrochloric acid, 1N aqueous sodium hydroxide solution, and then with water. The organic layer was dried over anhydrous sodium sulfate, filtered, and the solvent was distilled off to obtain crude (R) -4
3.2 g of-(1-methyl-3-ethylpentyloxycarbonyl) phenyl-4-n-propyloxybenzoate (yield 97
%). The obtained crude product is purified by high performance liquid chromatography to obtain 2.5 g of the desired (R) -4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4-n-propyloxybenzoate (yield 76%).

Example 7 (Formula (1): n = 3, A = -COO-,
X = F (E7)) Production of (R) -3-fluoro-4- (1-methyl-3-ethylpentyloxycarbonyl) phenyl-4-n-butanoyloxybenzoate. In Example 6, 4-n-propyloxybenzoic acid and (R)-
Instead of 1-methyl-3-ethylpentyl-4-hydroxybenzoate, 4-n-butanoyloxybenzoic acid and (R) -1-
Synthesis was carried out in the same manner as in Example 6, except that methyl-3-ethylpentyl-2-fluoro-4-hydroxybenzoate was used. Tables 1 and 2 show 1H-NMR measurement results of the optically active compounds (E1 to E7) obtained in the above Examples.
And the common part of the structural formula and the part specified by n and A are shown in Chemical formula 4, respectively.

Table 1 1H-NMR (δ, ppm) [common part of general formula] benzene ring left benzene ring right asymmetric carbon right terminal methyl number 1 2 3 4 5 6 7 8 9 10 E1 7.73 8.25 7.73 8.25 7.32 8.13 7.32 8.13 5.25 0.87 E2 7.73 8.23 7.73 8.23 7.12 − 7.12 8.02 5.27 0.87 E3 7.75 8.25 7.75 8.25 7.12 − 7.12 8.02 5.27 0.87 E4 7.35 8.11 7.35 8.11 7.27 8.11 7.27 8.11 5.24 0.89 E5 7.36 8.09 7.36 8.09 7.08 − 7.08 8.00 5.26 0.89 E6 6.98 8.13 6.98 8.13 7.28 8.13 7.28 8.13 5.25 0.87 E7 7.28 8.26 7.28 8.26 7.11 − 7.11 8.00 5.28 0.92

Table 2 1H-NMR (δ, ppm) [part defined by n and A] Left terminal methyl side chain methylene benzene ring part number: 1234456E1 0.99 2.66 7.32 7.58 7.32 7.58 E2 1.00 2.65 7.28 7.58 7.28 7.58 E3--7.50 7.66 7.50 7.66 E4 0.89 * 1----E5 0.89 * 1----E6 1.07 4.02---- E7 1.10 2.63---- Note) * 1: Peak of methylene group is 1 Appears at ~ 2 ppm, but indicates that one of the shift positions could not be identified.

[0031]

Embedded image

The phase transition temperature of each of the optically active compounds (E1 to E7) was confirmed by observation with a polarizing microscope and DSC. The results were as follows. (Here, the values in parentheses indicate the phase transition temperature (° C.), Iso is an isotropic phase, SA is a smectic A phase, SX is an unidentified smectic phase, Cr
y indicates a crystal phase. ) E1: Iso (125) SA (96) Cry E2: Iso (113) SA (75) Cry E3: Iso (48) Cry E4: Iso (77) SA (45) Cry E5: Iso (65) SA (56 ) Cry E6: Iso (51) Cry E7: Iso (35) Cry

Example 8 The optically active compounds (E1 to E7) prepared above were treated with H
TP and wavelength shift were measured. 15 wt% of the optically active compound obtained in Example 1 was added to a nematic liquid crystal (ZLI-1565) manufactured by Merck & Co., to prepare a chiral nematic (N *) liquid crystal composition. The upper limit temperature and characteristic reflection behavior of the N * phase of the prepared liquid crystal composition were examined, and finally, the torsional force (HTP) was determined from the characteristic reflection behavior. The maximum temperature of the N * phase was determined by observation with a polarizing microscope and DS
C measurement was performed.

The characteristic reflection behavior was performed according to the following procedure. A liquid crystal cell with an ITO electrode (cell thickness 10 μm) was filled with the liquid crystal composition prepared above in an isotropic phase. This cell
After applying a square wave voltage of ± 60 V for about 1 minute at 60 ° C,
It was rapidly cooled to room temperature to obtain a planar orientation. This liquid crystal cell
The characteristic reflection behavior at 25 ° C and 60 ° C was examined using a self-recording spectrophotometer. HTP at 25 ° C. and 60 ° C. were determined by the following equations, respectively. HTP (μm ⁻¹ ) = n / (λ ₂₅ × C / 100) HTP (μm ⁻¹ ) = n / (λ ₆₀ × C / 100) where n is the refractive index of the chiral nematic liquid crystal, and λ ₂₅ is
25 ° C. and λ ₆₀ represent the characteristic reflection wavelength (μm) at 60 ° C., and C represents the concentration of the chiral agent (wt%). As the refractive index n, a value 1.6 of the mother liquid crystal ZLI-1565 was adopted.

The wavelength shift was obtained from the following equation. Wavelength shift (nm) = λ ₆₀ * −λ ₂₅ * where λ ₆₀ * is the characteristic reflection wavelength (nm) at 60 ° C., λ
₂₅ * represents the characteristic reflection wavelength (nm) at 25 ° C. The optically active compound (E1) of Example 1 had a large HTP of 9 or more, and had a property that the helix became shorter as the temperature increased. In the same manner as described above, the HTP and wavelength shift of the optically active compounds (E2 to E7) obtained in Examples 2 to 7 were examined. The results are shown in Table 3.

Comparative Examples 1 to 3 HTP and wavelength shift of known compounds CB15, S811 and CN shown in the description of the prior art were measured in exactly the same manner as in Example 8. The value of HTP is CB1
5, in S811, the measurement was performed with a composition in which 15 wt% was added to the nematic liquid crystal, and in CN, the measurement was performed with a composition in which 30 wt% was added. The results are shown in Table 3.

Table 3 Compounds Iso-N * (° C.) HTP (1 / μm) Wavelength shift (nm) E1 85 10.5 -185 E2 83 9.5 -145 E3 76 11.0-75 E4 83 11.3 −74 E5 82 10.5 −78 E6 69 13.0 −32 E770 10.7 −19 CB15 747.9 +193 S811 73 10.1 +7 CN 82 5.2 +34 Note) Iso-N * Shows the phase transition temperature from the isotropic phase to the chiral nematic phase (the maximum temperature of the N * phase).

[Brief description of the drawings]

Fig. 1 Planar molecular orientation of chiral nematic liquid crystal

Fig. 2 Focal conic molecular alignment of chiral nematic liquid crystal

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09K 19/54 C09K 19/54 B G02F 1/13 500 G02F 1/13 500 F term (Reference) 4H006 AA01 AB64 BJ50 BM30 BM71 BP30 4H027 BA02 BB03 BB04 BD14 BD16 CC08 CF08 CP08

Claims (9)

[Claims] 1. An optically active compound represented by the following general formula (1). Embedded image (In the formula, n is 0 or an integer of 1 to 5, and when n is 0, A is a single bond (-), -Ph- and -Cy- (-Ph- represents a 1,4-phenylene group. , -Cy- represents a trans-1,4-cyclohexylene group), when n is an integer of 1 to 5, A is a single bond (-), -O-, -COO-, -Cy-, -Ph-,-
O-Ph- and -COO-Ph- (-Ph- and -Cy- are as defined above) are each selected from the group of structural formulas, X is a hydrogen atom or a fluorine atom, and C * is an asymmetric carbon atom. It is. ) 2. The optically active compound according to claim 1, wherein n is 3 in the general formula (1). 3. The optically active compound according to claim 1, wherein in the general formula (1), X is a hydrogen atom. 4. In the general formula (1), A is -Cy-, -Ph
The optically active compound according to claim 1, which is selected from the group consisting of structural formulas consisting of-, -O-Ph- and -COO-Ph-. 5. The optically active compound according to claim 1, which has a torsional force (HTP) of 9 or more. 6. The optically active compound according to claim 1, wherein the pitch of the induced helix decreases with increasing temperature. 7. An additive for a nematic liquid crystal represented by the general formula (1). 8. A nematic liquid crystal composition comprising at least one optically active compound represented by the general formula (1). 9. A liquid crystal device in which the nematic liquid crystal composition according to claim 8 is sandwiched between substrates having electrodes.