JPH0542426B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a liquid crystal compound and a liquid crystal composition containing this liquid crystal compound, and in particular to a ferroelectric liquid crystal compound that has excellent image display response and a liquid crystal composition containing this liquid crystal compound. It is about things. [Background of the Invention] Currently, image display devices using liquid crystals are widely used in practical use, and are mainly TN (twisted nematic).
(Twisted Nematic)] type display method is adopted. This TN display method has advantages such as low power consumption and less eye fatigue because it is light-receiving and does not itself emit light, but has the disadvantage of slow response speed for image display. have. Recent image display devices tend to require particularly high-speed response. In order to cope with this problem, efforts are being made to improve the response characteristics of liquid crystal compounds. However, the current light-receiving display systems still have a large difference in response time compared to light-emitting display systems such as light emitting diodes, electroluminescence (EL), or plasma displays. Efforts are being made to find a new display system that takes advantage of the light-receiving, low-power consumption characteristics of liquid crystal displays and also provides high-speed response. As one of the attempts, for example, NA Clark (NAClark), ST Raghav (ST
A display device that utilizes the optical switching phenomenon of ferroelectric liquid crystals has been proposed, as shown in Lagerwall, Applied Physics Letters, 36 , 899 (1980). This ferroelectric liquid crystal was discovered by RB Meyer et al. [RB Meyer et al., J.Physique, 36, L-69]
(1975)], is said to belong to the chiral smectic C (hereinafter abbreviated as S _C ^* ) phase or the chiral smectic H (hereinafter abbreviated as S _H ^* ) phase based on the molecular arrangement. . As described above, as ferroelectric liquid crystal compounds, the compounds shown in Table 1 are known so far [Ph. Martino Laga (Ph.
J.Phy-
sique, 37 , C ₃ −129 (1976)].

[Purpose of the invention]

An object of the present invention is to provide a ferroelectric liquid crystal compound having excellent light resistance and a molecular structure such that MR is near room temperature, and a liquid crystal composition containing this liquid crystal compound. [Summary of the Invention] That is, if the present invention is summarized, the first aspect of the present invention is as follows.
The invention is an invention of a liquid crystal compound, which has the general formula: (In the formula, R is an alkoxy group having 20 or less carbon atoms, R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom, m is 1, 2, and n is 1.) It is characterized by the following. The second invention is an invention of a liquid crystal composition, which is characterized in that it contains at least one liquid crystal compound represented by the above general formula. A liquid crystal compound represented by such a general formula exhibits a ferroelectric liquid crystal phase, and this ferroelectric liquid crystal phase is S _C
Belongs to ^* phase or S _H ^* phase. The characteristics of both liquid crystal phases are that the molecules are arranged tilted in a specific direction, and the tilt direction is slightly shifted from layer to layer, maintaining a helical structure as a whole. RB Meyer, Molecular
Mol.Cryst.Liq.Cryst, 40 , 30 (1977)]. The spontaneous polarization is oriented in a direction perpendicular to this helical axis (perpendicular to the layer plane). By the way, as a result of a detailed study on the relationship between the molecular structure of liquid crystalline compounds and the development of ferroelectricity, the present inventors have found the following points regarding the molecular arrangement of such liquid crystals and the molecular structure for inducing spontaneous polarization. found that it is necessary. That is, it has an optically active group at the end of the molecule to induce a helical structure, and a substituent at the end of the molecule that has a permanent dipole in a direction almost perpendicular to the long axis of the liquid crystal molecule to induce spontaneous polarization. It is to have. Therefore,
It was found that the carbon-carbon double bond attached to the benzene ring found in existing ferroelectric liquid crystal compounds is not an essential molecular structure for the development of a ferroelectric liquid crystal phase. Now, the compound of the formula of the present invention satisfies the above two conditions, and since it does not contain a carbon-carbon double bond bonded to a benzene ring in its molecular structure, it has light resistance that is not seen in existing ferroelectric liquid crystal compounds. have.
Furthermore, as shown in the examples below, the compound of the formula of the present invention exhibits ferroelectricity over a wide temperature range (MR) even when used alone, but when mixed with other ferroelectric liquid crystal compounds, it exhibits ferroelectricity over a wide temperature range (MR) around room temperature. It is possible to show that Examples of the ferroelectric liquid crystal compound to be mixed include existing ferroelectric liquid crystal compounds and compounds having the formula of the present invention. These ferroelectric liquid crystal compositions can be used in display devices utilizing the above-mentioned optical switching phenomenon of ferroelectric liquid crystals, and can perform high-speed response optical switching. A compound of the general formula is a compound of the general formula (wherein R is an alkoxy group having 20 or less carbon atoms, and R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom.)
Examples of the liquid crystalline compound represented by the formula include the following. (1) p-(2-methylbutoxycarbonyl)-benzylidene-p'-methoxyaniline, (2) p-(2-
methylbutoxycarbonyl)-benzylidene-
p'-Ethoxyaniline, (3) p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-bropoxyaniline, (4) p-(2-methylbutoxycarbonyl)-benzylidene-p'-n- Butoxyaniline, (5)p-(2-methylbutoxycarbonyl)
-benzylidene-p'-n-pentyloxyaniline, (6)p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-hexyloxyaniline,
(7)p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-heptyloxyaniline, (8)p
-(2-methylbutoxycarbonyl)-benzylidene-p'-n-octyloxyaniline, (9)p-
(2-methylbutoxycarbonyl)-benzylidene-p'-n-nonyloxyaniline, (10)p-(2-
methylbutoxycarbonyl)-benzylidene-
p'-n-decyloxyaniline, (11)p-(2-methylbutoxycarbonyl)-benzylidene-p'-
n-undecyloxyaniline, (12)p-(2-methylbutoxycarbonyl)-benzylidene-p'-
n-Tridecyloxyaniline, (13)p-(2-methylbutoxycarbonyl)-benzylidene-p'-
n-pentadecyloxyaniline, (14)p-(2-
methylbutoxycarbonyl)-benzylidene-
p'-n-hexadecyloxyaniline, (15)p-
(2-Methylbutoxycarbonyl)-benzylidene-p'-n-heptadecyloxyaniline, (16)p-
(2-Methylbutoxycarbonyl)-benzylidene-p'-n-octadecyloxyaniline, (17)p-
(2-Methylbutoxycarbonyl)-benzylidene-p'-n-nonadecyloxyaniline, (18)p-
(2-Methylbutoxycarbonyl)-benzylidene-p'-n-eicosyloxyaniline On the other hand, a compound of the general formula (wherein,
R is an alkoxy group having 20 or less carbon atoms, and R ^*
is an optically active group and an alkyl group containing an asymmetric carbon atom. ) The following specific examples can be given as the liquid crystalline compound represented by: (1) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-methoxyphenyl)aniline, (2) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-ethoxyphenyl) enyl)aniline, (3)p-(2-methylbutoxycarbonyl)-
Benzylidene-4-(4'-n-proboxyphenyl)aniline, (4)p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-butoxyphenyl)aniline, (5)p-( 2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-pentyloxyphenyl)aniline, (6)p-(2-
methylbutoxycarbonyl)-benzylidene-4
-(4′-n-hexyloxyphenyl)aniline,
(7) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-heptyloxyphenyl)
Aniline, (8) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-nonyloxyphenyl)aniline, (9) p-(2-methylbutoxycarbonyl)-benzylidene-4-( 4'-n-decyloxyphenyl)aniline, (10)p-(2-methylbutoxycarbonyl)-benzylidene-4-
(4'-n-undecyloxyphenyl)aniline,
(11) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-dodecyloxyphenyl)
Aniline, (12) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-tridecyloxyphenyl)aniline, (13) p-(2-methylbutoxycarbonyl)-benzylidene-4- (4'-n
-tetradecyloxyphenyl)aniline, (14)p
-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-pentadecyloxyphenyl)
Aniline, (15) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-hexadecyloxyphenyl)aniline, (16) p-(2-methylbutoxycarbonyl)-benzylidene-4- (4′−
n-heptadecyloxyphenyl)aniline, (17)
p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-octadecyloxyphenylaniline, (18) p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-nona Decyloxyphenylaniline, (19)p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n
-Eicosyloxyphenylaniline The present invention will be explained in more detail based on Examples below, but the present invention is not limited to these Examples. In addition, the value of the phase transition temperature in the examples varies slightly depending on the measurement method and the purity of the compound. Example 1 p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-tetradecyloxyaniline A liquid crystal compound was synthesized by the method shown below. First, mix 358 g of commercially available terephthalaldehyde acid, 700 ml of toluene, and 2 g of pyridine.
After 300 ml of thionyl chloride was added dropwise at room temperature, the mixture was gradually heated to reflux until the reaction mixture became uniform. After cooling to room temperature, unreacted thionyl chloride and toluene as a solvent were distilled off under reduced pressure, and the remaining reaction product was distilled under reduced pressure to obtain terephthalaldehyde acid chloride (boiling point 133-135°C/
15 Torr). Next, commercially available s(-)-2-methylbutanol (optically active amyl alcohol) and pyridine
A solution of 315 g of the above terephthalaldehyde acid chloride dissolved in 400 ml of toluene was added dropwise to 230 g of the ice-cooled mixture, followed by heating under reflux for 2 hours. The reaction solution was cooled to room temperature, further cooled on ice, and acidified with 6N hydrochloric acid to remove pyridine in the organic layer.Then, the organic layer was washed in the order of water, 2N aqueous sodium hydroxide solution, and water. . The solvent toluene was distilled off under reduced pressure, and the remaining reaction product was distilled off under reduced pressure to obtain p-(2-methylbutoxycarbonyl).
-Benzaldehyde (boiling point 118-124℃/
3.5 Torr). On the other hand, p-n-tetradecyloxyaniline (melting point: 101° C.) was obtained by hydrogenating and reducing p-n-tetradecyloxynitrobenzene in ethanol using a palladium/carbon catalyst. The above p-(2-methylbutoxycarbonyl)-
44.3 g of benzaldehyde and 32 g of p-n-tetradecyloxyaniline were mixed with p-toluenesulfonic acid.
Dissolve in toluene with 0.1g. While heating this under reflux, the moisture generated by dehydration condensation is
Removed with a Stark type capacitor. After cooling the reaction solution, the organic layer was washed with water, the solvent toluene was distilled off under reduced pressure, and the remaining solid was recrystallized from ethanol to obtain yellow crystals. The calculated and measured elemental analysis values of the obtained yellow crystals were as follows. The molecular formula was calculated as C ₃₃ H ₄₉ NO ₃ .

[Table] Example 2 p-(2-methylbutoxycarbonyl)-benzylidene-4-(4'-n-octyloxyphenyl)aniline Synthesis of 4-amino-4'-n obtained by hydrogenation reduction of known 4-nitro-4'-n-octoxybiphenyl using a palladium/carbon catalyst in an ethyl acetate solution.
Synthesis was carried out in the same manner as in Example 1 by dehydration condensation of 3 g of -octoxybiphenyl and 2.2 g of p-(2-methylbutoxycarbonyl)benzaldehyde described in Example 1. The elemental analysis values of the synthesized liquid crystalline compound are as follows.

Table 2 shows the phase transition temperatures of the compounds produced in Examples 1 and 2 as described above. As is clear from the table, the compound of the present invention exhibited an S _C ^* phase.

【table】

[Table] Example 3 p-(2-methylbutoxycarbonyl)-benzylidene-p'-n- shown in No. 2 in Table 2 above
Heptoxyaniline and p- shown in No. 6 in Table 2
(2-Methylbutoxycarbonyl)-benzylidene-p'-n-octoxyaniline mixed in an equimolar ratio undergoes a phase transition from the crystalline phase (C) to the S _C ^* phase at 42.4°C, and at 44.3°C. There was a phase transition from the S _C ^* phase to the smectic A phase at 73°C, and from the smectic A phase (S _A ) to an isotropic liquid ( ) at 73°C. Example 4 p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-heptoxyaniline shown in No. 2 in Table 2 and p-(2-
methylbutoxycarbonyl)-benzylidene-
p'-n-octoxyaniline and p-(2-methylbutoxycarbonyl)-benzylidene-4-
(4′-n-heptylphenyl)-aniline in an equimolar ratio, the composition changes from the crystalline phase (C) to the S _C ^* phase.
A phase transition occurred at 43.2°C, from the S _C ^* phase to the smectic phase A phase (S _A ) at 67.8°C, and from the smectic A phase to the isotropic liquid ( ) at 96.3°C. Example 5 p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-octoxyaniline shown in Table 2 No. 3 and known p-decyloxybenzylidene-p shown in Table 1 No. 1 ’-amino-2-methylbutylcinnamate in an equimolar ratio mixture from the crystals.
Phase transition to S _H ^* phase at 17.7℃, and from S _H ^* phase to S _C at 34.0℃
^* phase, S _C ^* phase to S _A phase at 58.2℃, and phase transition from S _A phase to isotropic liquid at 93.9℃. As described above, by mixing the compound of the present invention with the compound of the present invention or an existing ferroelectric liquid crystal compound, the temperature range (MR) exhibiting ferroelectricity can be expanded to around room temperature. Example 6 Next, regarding the photostability of the liquid crystal compound according to the present invention, the following experiment was conducted in comparison with a conventional product. The product of the present invention is p-(2-methylbutoxycarbonyl)-benzylidene-p'-n-tetradecyloxyaniline of Example 1. and the known p-decyloxybenzylidene-p'-amino- shown in No. 1 in Table 1 as a comparative example.
2-methylbutyl cinnamate was used. These samples were placed in a glass capillary with a diameter of 2 mm, and the changes in the phase transition temperature from smectic A phase to isotropic liquid (T _SA -) when irradiated with light using a weather meter were investigated. The weather meter is a WE-SUN-DC model manufactured by Suga Test Instruments, and the light source is a carbon arc. Table 3 shows the relationship between the measured _TSA- and the light irradiation time.

〔Effect of the invention〕

As is clear from the above description, the liquid crystal compound and liquid crystal composition according to the present invention exhibit ferroelectric liquid crystal, have a molecular structure stable against light, and are similar to existing ferroelectric liquid crystals. It has the remarkable effect of being able to provide stability and high-speed response to light that cannot be seen in other compounds.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing response waveforms of a liquid crystal display element using a liquid crystal compound according to the present invention.

Claims (1)

[Claims] 1. General formula: (In the formula, R is an alkoxy group having 20 or less carbon atoms, R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom, m is 1, 2, and n is 1.) A liquid crystalline compound characterized by: 2 In claim 1, the general formula
A liquid crystalline compound characterized in that R ^* is an optically active 2-methylbutyl group. 3 In claim 1, the compound of the general formula has the following general formula: (In the formula, R is an alkoxy group having 20 or less carbon atoms, and R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom.) 4 In claim 3, the general formula
A liquid crystalline compound characterized in that R ^* is an optically active 2-methylbutyl group. 5 In claim 1, the compound of the general formula has the following general formula: (In the formula, R is an alkoxy group having 20 or less carbon atoms, and R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom.) 6 In claim 5, the general formula
A liquid crystalline compound characterized in that R ^* is an optically active 2-methylbutyl group. 7. In a liquid crystal composition containing a liquid crystal compound, at least one compound has the general formula: (In the formula, R is an alkoxy group having 20 or less carbon atoms, R ^* is an optically active group and an alkyl group containing an asymmetric carbon atom, m is 1, 2, and n is 1.) A liquid crystal composition comprising a liquid crystal compound represented by: 8 In claim 7, the general formula
A liquid crystal composition characterized in that R ^* is an optically active 2-methylbutyl group.