JPH0452258B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel liquid crystal substance and a liquid crystal composition containing the liquid crystal substance, and more particularly to a chiral liquid crystal substance having an optically active group and a chiral liquid crystal composition containing the same. Currently, TN (Twisted
Nematic type display devices are the most widely used, but they are inferior to light emitting type display devices (electroluminescent displays, plasma displays, etc.) in terms of response speed, and improvements in this point are not possible. Despite various attempts, there does not seem to be much potential for significant improvement. Therefore
Various attempts have been made to develop liquid crystal display devices based on different principles to replace TN display elements, one of which is a display method that uses ferroelectric liquid crystals (NAClark
et al; Applied Phys.lett., 36899 (1980)). This method utilizes the chiral smectic C phase (hereinafter abbreviated as SC ^* phase) or chiral smectic H phase (hereinafter abbreviated as SH ^* phase) of ferroelectric liquid crystal, which is It is desirable to have one in Some compounds used for this purpose are already known, but they have problems in practical use in terms of stability and the like. The present inventors aimed to develop a liquid crystal material suitable for use in this display method.
The present invention was achieved by searching for various liquid crystal substances containing optically active groups. That is, the present invention is based on the general formula (In the above formula, R ₁ ^* represents an optically active alkyl group having 4 to 8 carbon atoms; R ₂ represents a linear or branched alkyl group or alkoxy group having 6 to 10 carbon atoms; l,
(m is 1 or 2, respectively, and (l+m) is 3) A carbonate ester derivative and a liquid crystal composition containing the same. Among the compounds of formula (), most of the compounds (a ₂ ) where l=l, m=2 and the compound (b ₁ ) where l=2, m=1 are suitable for liquid crystal display systems that utilize ferroelectricity. The SC ^* phase is exhibited over a wide temperature range. Also other SC ^*
It has excellent compatibility with compounds that exhibit phase and SH ^* phase, and compounds that exhibit cholesteric phase.
Can be used to mix with them and expand their SC ^* phase temperature range. Table 1 shows the phase transition points of the main compounds of formula () of the present invention.

【table】

[Table] In the above table, C represents the crystalline phase, SA represents the smectic A phase, SB represents the smectic B phase, I represents the isotropic liquid phase, Ch represents the cholesteric phase, and N represents the nematic phase. The numbers on the right side of the column indicate the phase transition temperature from that phase to the phase on the right, and - indicates that the phase is not indicated. When a chiral smectic liquid crystal composition is constructed using a compound of formula (), it is also possible to construct it from only a plurality of compounds of formula (), or a compound of formula () and other smectic liquid crystals may be used. It is also possible to produce a liquid crystal composition exhibiting an SC ^* phase by mixing. When applying the optical switching effect of the SC ^* phase to a display element, there are three superior features compared to the TN display system. The first feature is that it responds very quickly, and its response time is less than 1/100 of that of a normal TN display type element. The second feature is that it has a memory effect, which, combined with the above-mentioned high-speed response, facilitates time-division driving. The third feature is that in the TN display method, gray scale is achieved by adjusting the applied voltage, but there are difficult problems such as the temperature dependence of the threshold voltage and the voltage dependence of the response speed. However, when applying the optical switching effect of the SC ^* phase, gradation can be easily obtained by adjusting the polarity reversal time, making it very suitable for graphical display. There are two possible display methods: 1.
One method is a birefringent type that uses two polarizers, and the other is a guest-host type that uses a dichroic dye. Since the SC ^* phase has spontaneous polarization, by reversing the polarity of the applied voltage, the molecule is reversed with the helical axis as the rotation axis. A liquid crystal composition having an SC ^* phase was injected into a liquid crystal display cell that had been subjected to alignment treatment so that the liquid crystal molecules were aligned parallel to the electrode surface, and the director of the liquid crystal molecules was arranged so that one plane of polarization was parallel to the other. By sandwiching the liquid crystal cell between two polarizers and applying a voltage to reverse the polarity, a bright field and a dark field (determined by the facing angle of the polarizers) can be obtained. On the other hand, when operating in a guest-host mode, a bright field and a colored field (determined by the arrangement of polarizing plates) can be obtained by reversing the polarity of the applied voltage. Generally, it is difficult to align liquid crystal molecules parallel to the glass wall surface in a smectic state, but it is difficult to align liquid crystal molecules parallel to the glass wall surface in a smectic state. ,
Liquid crystal molecules are aligned, but in liquid crystal materials with cholesteric phase, 50V~
By cooling at a cooling rate of 1° C./min while applying a DC voltage of 100 V, a uniformly oriented monodomain state can be easily obtained. Since the compound of formula () also has an optically active carbon atom, it has the ability to induce a twisted structure by adding it to a nematic liquid crystal.
A nematic liquid crystal with a twisted structure, that is, a chiral nematic liquid crystal, has a so-called reverse domain (striped pattern) of a TN display element.
Therefore, the compound of formula () can be used as an inhibitor of reverse domain formation. The racemic form corresponding to the optically active form of formula () can be produced in the same manner by using the racemic form instead of the S-alkyl chloroformate as a raw material in the method for producing the optically active form described below. It has been manufactured and shows almost the same phase transition temperature as (). The racemic form shows an SC phase instead of the SC ^* phase, and the optically active form ()
It can be used to adjust the pitch of chiral smectick by adding it to. The compound of formula () of the present invention in which l=1, m=1 or 2 (hereinafter abbreviated as a) can be produced by the following steps. That is, the known substance p-hydroxybenzaldehyde () is reacted with S-alkyl chloroformate in the presence of pyridine to obtain the compound (). Compound () is treated with an oxidizing agent such as chromic anhydride in an acetic acid solvent to obtain compound (). Compound () is reacted with thionyl chloride to obtain compound (), and () is converted into phenols of formula () (p-alkylphenol, p-alkoxyphenol, p-
hydroxy-p'-alkylbiphenyl, p-hydroxy-p'-alkoxybiphenyl, etc.) to obtain the desired compound (a). Next, in the compound of formula (), l = 2, m = 1 or 2
The substance (hereinafter abbreviated as b) can be produced by the following steps. Previously, p-hydroxy-p'-cyanobiphenyl () is reacted with formic acid and a catalyst such as Raney-nickel to obtain the compound (). Compound () is reacted with S-alkyl chloroformate in the presence of pyridine to obtain compound (). Compound () is treated with an oxidizing agent such as chromic anhydride in an acetic acid solvent to obtain compound (). Compound () is reacted with thionyl chloride to form compound (), and () is converted to the final target compound () in the presence of pyridine.
) phenols (p-alkylphenol, p-alkoxyphenol, p-hydroxy-p'-alkylbiphenyl, p-hydroxy-
p'-alkyloxybiphniel, etc.) to obtain the target compound (b). The liquid crystal compounds and liquid crystal compositions of the present invention will be explained in more detail below with reference to Examples. Example 1 [S-(p-2-methylbutyloxycarbonyloxy)benzoic acid-p-nonyloxy-p'-biphenylyl ester (l = 1 in the formula (),
m = 2, R ₁ ^* = 2 = methylbutyl, R ₂ = C ₉ H ₁₉ O
Production of p-hydroxybenzaldehyde 16g (0.131
mole) dissolved in 100 ml of dry pyridine,
S-2-methylbutyl chloroformate 17.9g
(0.119 mol) was added and reacted. After stirring well and standing overnight, 100 ml of toluene and 100 ml of water were added, and the mixture was washed with 6N hydrochloric acid, then with a 2N aqueous sodium hydroxide solution, and further washed with water until neutral. Toluene was distilled off to obtain a residue of 27.5 g (0.109 mol) of compound ().
Compound () was dissolved and stirred in 77 ml of acetic acid, and 21.8 g (0.218 mol) of chromic anhydride was added to 17 ml of water.
A solution dissolved in 27 ml of acetic acid was added dropwise while keeping the temperature of the system below 30°C. After the dropwise addition was completed, the inner temperature was kept at 40°C on a water bath for 4 hours, and then cooled. water
300 ml was added and the precipitated crystals were filtered and washed with water. The crystals were recrystallized from ethanol to obtain 14.7 g of compound (). The melting point of this substance is 176℃ ~
It was 179℃. 13 g (0.108 mol) of thionyl chloride was added to 14.7 g (0.058 mol) of compound (), heated under reflux for 1 hour, and then excess thionyl chloride was distilled off to obtain 15.0 g of compound (). p-hydroxy-p'-nonyloxybiphenyl
1.5 g (0.005 mol) was dissolved in 5 ml of pyridine, and 0.9 g (0.003 mol) of compound () was added to react. Stir well and leave overnight, then add 50 ml of toluene and 50 ml of water, stir and extract, then transfer to a separatory funnel and remove the organic layer.
It was washed with 6N hydrochloric acid, then with a 2N aqueous sodium hydroxide solution, and further washed with water until the washing solution became neutral. Toluene was distilled off and the residue was recrystallized from ethanol to obtain 0.8 g of the desired S-(p-2-methylbutyloxycarbonyloxy)benzoic acid-p-nonyloxy-p'-biphenylyl ester. This is a smectic and cholesteric liquid crystal.
SC ^* was 102.8°C, SC ^* -Ch point was 139.8°C, and Ch-I point was 170.4°C. Moreover, the elemental analysis values of this compound were in good agreement with the calculated values as shown below. Actual value Calculated value (as C ₃₄ H ₄₂ O ₆ ) C 74.3% 74.69% H 7.4% 7.75% Examples 2 to 5 Various p- Hydroxy-p′-
Example 1 except that alkylbiphenyl or p-hydroxy-p'-alkyloxybiphenyl is used.
The compound of the formula () shown in Table 1 was synthesized by performing the operation according to the procedure described in . Their phase transition points are shown in Table 1. Example 6 [S-(p-2-methylbutyloxycarbonyloxy)-p'-biphenylcarboxylic acid-p-nonyloxyphenyl ester (in the formula (), l=2, m=1, R ₁ ^* = 2-methylbutyl, R ₂ =
Production of p _- hydroxy-p'-cyanobiphenyl compound () 83.4 g (0.427 mol), Raney _- nickel 79 g,
Add 825 ml of formic acid and 275 ml of water, and heat and stir under reflux for 4 hours. After cooling and separating the crystals, 1.5
Dissolve in ethanol and heat. Distill the ethanol and mix the residue with 500ml of toluene and 50ml of ethanol.
Recrystallize from ml. The separated crystals were dried to obtain 40.8 g of compound (). The melting point of this thing is 177.8
The temperature was between 178.9°C and 178.9°C. 13.6 g (0.090 mol) of S-2-methylbutyl chloroformate was added to a solution of 19.8 g (0.100 mol) of compound () in 100 ml of dry pyridine and reacted. After stirring well and leaving it overnight, add toluene.
100 ml and 100 ml of water were added, and the mixture was washed with 6N hydrochloric acid, then with 2N aqueous sodium hydroxide solution, and further washed with water until neutral. Toluene was distilled off to obtain a residue of 20.3 g of compound (2). 20g (0.064 mol) of compound () was dissolved and stirred in 60ml of acetic acid, and then 12.8g of chromic anhydride was added.
(0.128 mol) dissolved in 10 ml of water and 16 ml of acetic acid was added dropwise while keeping the temperature of the system below 30°C. After the dropwise addition was completed, the inner temperature was kept at 40°C on a water bath for 4 hours, and then cooled. 300 ml of water was added, and the precipitated crystals were filtered and washed with water. Crystals in ethanol 400
Recrystallization from ml gave 12.5 g of compound (). The melting point of this product is C-Ch point 230.6℃, Ch-I point 250.8
It was warm at ℃. 9 g (0.075 mol) of thionyl chloride was added to 10 g (0.030 mol) of compound (), and after refluxing for 1 hour, excess thionyl chloride was distilled off to obtain compound ().
9.2g was obtained. Dissolve 1.2 g (0.005 mol) of p-nonyloxyphenol in 5 ml of pyridine, and dissolve the above compound (
) 1.5g (0.004mol) was added and reacted. After stirring well and leaving overnight, 50 ml of toluene and 50 ml of water were added and extracted with stirring, then transferred to a separatory funnel, and the organic layer was washed with 6N hydrochloric acid, then with 2N aqueous sodium hydroxide solution, and further washed with water until the washings became neutral. . Toluene is distilled off and the residue is recrystallized from ethanol to obtain the desired S.
-(p-2-methylbutyloxycarbonyloxy)-p'-biphenylcarboxylic acid. 0.9 g of p-nonyloxyphenyl ester was obtained. This is a smectic and cholesteric liquid crystal, and its C-SC ^* point is 82.1℃, and its SC ^* -Ch point is
The temperature was 149.4°C, and the Ch-I point was 175.0°C. Moreover, the elemental analysis values of this compound were in good agreement with the calculated values as shown below. Actual value Calculated value (as C ₃₄ H ₄₂ O ₆ ) C 74.2% 74.69% H 7.5% 7.75% Examples 7 to 11 Various p-alkylphenols or p-alkoxy instead of p-nonyloxyphenol in Example 6 A compound of the formula () shown in Table 1 was synthesized by carrying out the operation according to Example 6 except that phenol was used. Their phase transition points are shown in Table 1. Examples 12 and 13 S-2-methylbutyl chloroformate in Example 6 was replaced with optically active 2-octyl chloroformate, and p-nonyloxyphenol was replaced with p-octylphenol or p-octyloxyphenol. The compound of formula () was synthesized by carrying out the same operation as in Example 6 except that each of these compounds was used. Their phase transition points are shown in Table 1. Example 14 (Use example 1) 4-ethyl-4'-cyanobiphenyl 20% by weight 4-pentyl-4'-cyanobiphenyl 40% by weight 4-octyloxy-4'-cyanobiphenyl
25% by weight 4-pentyl-4'-cyanoterphenyl
A nematic liquid crystal composition consisting of 15% by weight was injected into a cell (electrode spacing of 10 μm) consisting of transparent electrodes coated with polyvinyl alcohol (PVA) as an alignment agent and subjected to parallel alignment treatment by rubbing the surface.
When a TN-type display cell was used and observed under a polarizing microscope, it was observed that a reverse domain was generated. In the above nematic liquid crystal composition, l = 1, m = 2, R ₁ ^* = 2-methylbutyl and R ₂ in the formula () of the present application.
When 0.1% by weight of the compound =C ₇ H ₁₅ (Example 2) was added and a TN cell was observed in the same manner, the reverse domain was eliminated and a uniform nematic phase was observed. Example 15 (Usage example 2) Chemical formula (However, * indicates optically active carbon.) In the formula () and 60% by weight of the compound, l=1, m=2, R ₁ ^* =2-methylbutyl.
A mixture consisting of 20% by weight of each of the compounds R ₂ = C ₉ H ₁₉ O (Example 1) and R ₂ = C ₁₀ H ₂₁ O (Example 5) is as follows:
It exhibits SC ^* phase up to 65℃, Ch phase at higher temperatures, and becomes an isotropic liquid at 100℃. PVA is applied to this mixture as an orientation treatment,
When the cell was injected into a cell equipped with a transparent electrode whose surface had been rubbed and subjected to parallel alignment treatment, and a DC voltage of 50V was applied, the cell was gradually cooled from an isotropic liquid region to an SC ^* phase, resulting in a uniform monodomain cell. was gotten. This liquid crystal cell is arranged in a crossed Nicol state.
When a low-frequency alternating current of 0.5 Hz and 15 V was applied between two polarizers, a clear switching action was observed, and a liquid crystal display element with very good contrast and fast response speed (2 m _sec ) was obtained. It was done. Furthermore, the value of spontaneous polarization (Ps) of this liquid crystal composition is
It was 2nC/ ^cm2 . Example 15 (Usage example 3) Chemical formula (However, * indicates optically active carbon.) In the formula (), l=2, m=1, R ₁ ^* = 2-methylbutyl,
R ₂ = C ₆ H ₁₃ (Example 7), R ₂ = C ₉ H ₁₉ O (Example 6)
A mixture consisting of 20% by weight of each compound exhibits an SC ^* phase up to 70℃, a Ch phase at higher temperatures,
It becomes an isotropic liquid at 103℃. Add the anthraquinone dye D-16 to this mixture.
(BDH product) was added in a so-called guest-host type by adding 3% by weight and injected into the same cell as in Example 13, and one polarizer was placed so that the plane of polarization was parallel to the molecular axis. However, when a low frequency alternating current of 0.5 Hz and 15 V was applied, a clear switching operation was observed, and a color liquid crystal display element with very good contrast and a fast response speed (2 m _sec ) was obtained. The spontaneous polarization value of this liquid crystal composition is 3nC/cm ²
It was hot.

Claims (1)

[Claims] 1. General formula (In the above formula, R ₁ ^* represents an optically active alkyl group having 4 to 8 carbon atoms, R ₂ represents a straight or branched alkyl group or alkoxy group having 6 to 10 carbon atoms, and l
and m are each 1 or 2, and (l+m) is 3). 2 General formula where l=1 and m=2 in formula () (In the above formula, R ₁ ^* and R ₂ are the same as ()) The carbonate ester derivative according to claim 1. 3 General formula where l=2 and m=1 in formula () (In the above formula, R ₁ ^* and R ₂ are the same as ()) The carbonate ester derivative according to claim 1. 4 General formula (In the above formula, R ₁ ^* represents an optically active alkyl group having 4 to 8 carbon atoms, R ₂ represents a straight or branched alkyl group or alkoxy group having 6 to 10 carbon atoms, and l
and m are each 1 or 2, and (l+m) is 3. 5. The chiral smectic liquid crystal composition according to claim 4, which comprises only a plurality of compounds of formula ().