JPH0339499B2 - - 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. In this specification, the term "liquid crystal compound" includes substances that are useful as a compounding component of liquid crystal even if a liquid crystal phase is not observed by itself. [Background of the Invention] Currently, liquid crystal image display devices are widely used in practical use, and a TN (Twisted Nematic) type display system is mainly adopted. This TN display method has advantages such as low power consumption and less eye fatigue because it receives light without emitting light itself, 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 Lagarwall, Applied Physics Letters, 36899 (1980). This ferroelectric liquid crystal was discovered by RB Meyer et al. [RB Meyer et al., J. de Physique, 36, L-69]
(1975)], and is said to belong to the chiral smectic C (hereinafter abbreviated as Sc ^* ) phase or the chiral smectic H (hereinafter abbreviated as S _H *) phase based on the molecular arrangement. As such ferroelectric liquid crystal compounds, those shown in Table 1 are known so far (Ph. Martino Laga).
Laguard), J.Physique (J.Physique),
37, C3-129 (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 around room temperature, and a liquid crystal composition containing this liquid crystal compound. [Structure of the Invention] That is, the first invention of the present invention is an invention of a liquid crystal compound, which has the general formula () (In the formula, R is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, R ^* is an alkyl group containing an asymmetric carbon atom, m is 1 or 2, and n is 1) It is a liquid crystal compound characterized by having a chemical structure. 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 (). [Operations and Effects of the Invention] Many of the liquid crystal compounds represented by the general formula () exhibit a ferroelectric liquid crystal phase as shown below, and this ferroelectric liquid crystal phase is a Sc ^* phase or a ferroelectric liquid crystal phase.
Belongs to the 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, Mol.Cryst.Liq.
Cryst), 40, 30 (1977)]. And the spontaneous polarization is
It faces in a direction perpendicular to this spiral 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. In other words, it is necessary to have an optically active group at the end of the molecule to induce a helical structure, and to have 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 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 formula () of the present invention exhibits ferroelectricity over a wide temperature range (MR) even when it is alone, but it can be mixed with other ferroelectric liquid crystalline compounds at around room temperature. It is possible to exhibit a wide MR. The ferroelectric liquid crystal compound to be mixed may be an existing ferroelectric liquid crystal compound or the formula () of the present invention.
There are compounds such as 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. [Method for producing chemical substance] The method for producing the substance represented by the general formula () will be described in detail below, and optically active alcohols are used as one of the raw materials for production. In the general formula (), R ^* may be an optically active group, but from the viewpoint of industrial use of the substance of the formula (), there is an additional restriction that it must be an optically active alcohol that is inexpensive and easily available. Currently, optically active alcohols that are easily available industrially include S(-)-2-methyl-butyl alcohol as a primary alcohol, and S(+)-2-octanol and R(-)-2-octanol as secondary alcohols. Although other secondary alcohols such as optically active 2-pentanol, 2-hexanol, 2-heptanol, etc. are available, they are extremely expensive. For this reason, it is clear that 2-methyl-butyl and 2-octyl groups are currently most suitable as R ^* in general formula (), but other optically active groups can also be used in principle. . These other optically active alcohols are described, for example, in the literature (RHPickard et al.
J.Chem.Sec., 99, 45 (1911)) by optically resolving racemic 2-alkanols. The substance of general formula () is suitably produced according to the following reaction route. In formula (), m = 1 and n = 1, specifically, P-alkylphenyl P'-(2-methylbutoxycarbonyl)benzoate, P-alkyloxyphenyl P'- (2-methylbutoxycarbonyl)benzoic acid ester, P-alkyloxyphenyl P'-(1-methyl-propoxycarbonyl)benzoic acid ester, P-alkyloxyphenyl P'-(1-methyl-butoxycarbonyl)benzoic acid acid ester, P-alkyloxyphenyl P'-(1-methyl-hexyloxycarbonyl)benzoic acid ester, P-alkylphenyl P'-(1-methyl-heptyloxycarbonyl)benzoic acid ester, P-alkyloxy Examples include phenyl P'-(1-methyl-heptyloxycarbonyl)benzoate, P-alkyloxyphenyl P'-(1-methyl-nonyloxycarbonyl)benzoate, and the like. In addition, in formula (), when m = 2 and n = 1, 4'-n-alkyl-4-biphenylyl P-
(2-methylbutoxycarbonyl)benzoic acid ester, 4'-n-alkyloxy-4-biphenylyl
P-(2-methylbutoxycarbonyl)benzoic acid ester 4'-n-alkyloxy-4-biphenylyl
P-(2-methylpentoxycarbonyl)benzoic acid ester, 4'-n-alkyloxy-4-biphenylyl
P-(2-methylhexoxycarbonyl)benzoic acid ester, 4'-n-alkyl-4-biphenyl P-(1
-methyl-pentoxycarbonyl)benzoic acid ester, 4'-n-alkyloxy-4-biphenylyl
P-(1-methyl-hexoxycarbonyl)benzoic acid ester, 4'-n-alkyl-4-biphenyl P-(1
-methyl-heptoxycarbonyl)benzoic acid ester, 4'-n-alkyl-4-biphenyl P-(1
-methyl-undecyloxycarbonyl)benzoic acid ester, etc. In the general formula () of the present invention, R ^* is a 2-methyl-butyl group The optically active center (*) represented by -COO
-The second carbon from the group is generally a number
Shows spontaneous polarization of nC/ ^cm2 . On the other hand, R* is a 1-methylheptyl group

〔Example〕

The present invention will be explained in more detail below based on Examples, but the present invention is not limited to the Examples described. Example 1 [4'-n-decyloxy-4-biphenylyl S-
p-(2-methyl-butoxycarbonyl)-benzoic acid ester (in the formula (), R=n-C ₁₀ H ₂₁ O-,
R ^* =− _CH2 −C _* H( _CH3 ) _−C2H5 , m= ₂ , n=
Production of 4'-n-decyloxy-4-hydroxybiphenyl is obtained by monoalkylating commercially available 4,4'-dihydroxybiphenyl in the presence of an equivalent amount of p-toluenesulfonic acid n-decyl ester and an alkali. Manufactured by. It is a crystal with a melting point of 149℃. Terephthalaldehyde acid chloride (boiling point 133−135
℃/15mmHg) dissolved in 400ml of toluene,
200g S(-)-2-methylbutanol, pyridine
The mixture was added dropwise to 230 g of ice-cooled solution with stirring, heated under reflux for 2 hours, cooled with ice, acidified with 6N hydrochloric acid, and separated into an organic layer, which was washed with water, 2N NaOH, and then water. After distilling off toluene, the reaction product was distilled under reduced pressure to obtain S-p-(2-methylbutoxycarbonyl)benzaldehyde (boiling point 118-124℃/
3.5mmHg) 297g was obtained. 113 g of this benzaldehyde was dissolved in 250 ml of acetic acid, heated to 20°C, and 70 g of chromic anhydride,
A solution consisting of 150 ml of acetic acid and 20 ml of water was added dropwise with stirring over a period of 3 hours, followed by stirring at 30°C for 1 hour. 250ml
of water was added to collect the precipitated crystals, which were recrystallized twice from ethanol to obtain 78 g of S-p-(2-
Methylbutoxycarbonyl)benzoic acid (mp.158
-160℃). 12g of this benzoic acid, 15ml of oxalate chloride,
(COCl) ₂ and 25 ml of toluene for 3 hours, and then excess oxalate chloride and toluene were distilled off under reduced pressure to obtain Sp-(2-methylbutoxycarbonyl)benzoate. This was used in the next step without purification. Dissolve the above 15 g of 4'-n-decyloxy-4-hydroxybiphenylyl in 80 ml of anhydrous pyridine, cool on ice, and add the entire benzoate chloride to this solution.
Add the solution dissolved in 50 ml of toluene dropwise with stirring, and make 80
The reaction was carried out at ℃ for 2 hours. The reaction solution was treated in a conventional manner to collect the product, which was recrystallized twice from ethyl acetate as colorless crystals to give the title compound 4'-n-decyloxy-4-biphenylyl S-p-(2-methyl Butoxycarbonyl)-benzoic acid ester was obtained. (Sample No. 9 in Table 2). Moreover, the elemental analysis values are in good agreement with the theoretical values as shown below. Theoretical value (as C ₃₅ H ₄₄ O ₅ ) Analytical value C 77.17% 77.4% H 8.14% 8.0% O 14.69% - Physical properties of other compounds of formula () produced according to the above method are shown in Example 1 It is shown in Table 2 along with that of .

【table】

[Table] Example 2 (Use Example 1) Using 4-(1-methyl-heptyloxycarbonyl)benzoic acid 4'-dodecyloxy-4-biphenylyl ester of No. 10 in Table 2, A liquid crystal composition having the following composition was prepared. The method for preparing the composition is to weigh the five types of liquid crystal compounds mentioned above to a predetermined weight, and mix the five types of compounds while heating and melting them in a sample bottle. An experimental liquid crystal device was produced using the obtained composition. A polyimide polymer film is placed on a glass substrate on which an indium oxide transparent electrode has already been provided, and rubbed with gauze in a certain direction, and a glass fiber ( A liquid crystal cell was assembled using a spacer (diameter: 6 μm), and the above liquid crystal composition was vacuum-sealed into the cell. When this liquid crystal element was installed between two orthogonal polarizers and an electric field was applied, the result was 20V.
Changes in transmitted light intensity were observed as a result of the application of . When the response time was determined from the change in transmitted light intensity at this time, it was found to be approximately 0.7 msec at 25°C, and the contrast was also 1:20. Regarding the above liquid crystal composition, when the temperature change of the texture was investigated using a polarizing microscope, it was found that from 0°C
It was found that it becomes a ferroelectric liquid crystal in the temperature range of 50℃, and its spontaneous polarization is 21nC/cm ² at 25℃.
It was confirmed that the spontaneous polarization was significantly larger than the spontaneous polarization (4 to 6 nC/cm ² ) of the compound No. 1 in Table 1 mentioned above. Example 3 (Use Example 2) and Comparative Example A liquid crystal composition was prepared using the compound of sample No. 3 in Table 2 in place of the compound of sample No. 10 in the composition of Example 2, and the experiment was carried out. As a result of measuring its characteristics in the same manner as in Example 2, the response time was 0.55 msec, and the spontaneous polarization value at 25°C was 17 nC/cm ² . For comparison, sample No. 10 from the composition of Example 2 was prepared.
A similar measurement was performed on a liquid crystal composition excluding the compound, and the response time was 1.8 msec, and the spontaneous polarization value was 4 nC/cm ² . From the above results, it can be seen that the compound of the present invention has excellent properties as a component of a ferroelectric liquid crystal composition.

Claims (1)

[Claims] 1. General formula (In the above formula, R is an alkyl group or an alkoxy group having 1 to 20 carbon atoms, R ^* is an alkyl group containing an asymmetric carbon atom, m is 1 or 2, and n is 1) A liquid crystal compound characterized by having a chemical structure. 2. A liquid crystalline compound, wherein R ^* in formula () according to claim 1 is an optically active 2-methylbutyl group [formula]. 3. A liquid crystalline compound, wherein R ^* in formula () according to claim 1 is an optically active 2-octyl group [formula].