JPH0588698B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field This invention relates to novel alkoxybiphenylcarboxylic acid derivatives and liquid crystal compositions containing them. (b) Prior art At present, most liquid crystal display devices utilize the nematic phase of liquid crystal, but in recent years, in addition to this, research has been actively conducted on various display modes that utilize the smectic phase. There is. In particular, a liquid crystal display using a ferroelectric liquid crystal composition using a chiral smectic C phase is considered to be promising because it can display a large capacity and has a wide visual field. (c) Problems to be Solved by the Invention The above-mentioned ferroelectric liquid crystal composition is first required to exhibit a smectic C phase in a wide temperature range centered around room temperature. Furthermore, high-speed response is required as a device characteristic in order to perform large-capacity display, and from this viewpoint, such liquid crystal compositions are required to have high spontaneous polarization and low viscosity. Furthermore, in order to obtain good alignment and bistability when applied to liquid crystal cells,
INAC (Isotropic-Nematic-Smectic A-
Smectic C) or IAC (Isotropic-Smectic A-
It is necessary to exhibit a phase series called Smectic C), and it is necessary that the helical pitch in the nematic phase and the smectic C phase be sufficiently long. Currently, there is no single liquid crystal compound that satisfies all of these conditions, and multiple compounds are usually mixed together to provide a liquid crystal composition for practical use. In order to produce a liquid crystal composition with good properties, it is necessary to blend compounds other than liquid crystal compounds, such as optically active compounds. However, although the above-mentioned conditions except for high-speed response can be achieved using conventional blending techniques, the current state of the art is insufficient in terms of high-speed response. In particular, ferroelectric liquid crystal compositions are usually prepared by adding an optically active compound to a low-viscosity base liquid crystal composition, but currently no liquid crystal composition is known that satisfies the above-mentioned high-speed response. . Therefore, as a means of achieving high-speed response, there is a strong desire to develop new optically active compounds that induce large spontaneous polarization. The present invention was made under such circumstances, and aims to provide a novel compound capable of significantly improving the liquid crystal responsiveness of a ferroelectric liquid crystal composition, and a smectic liquid crystal composition containing the same. . (d) Means for solving the problem According to this invention, the following general formula ():

An alkoxybiphenyl carboxylic _acid derivative represented _by provided. The compound of the above formula () is a compound that has not been described in any literature. The term "linear or branched alkyl group having 1 to 12 carbon atoms" in the definition of the above formula () means methyl, ethyl, propyl, i-propyl, butyl,
i-butyl, t-butyl, pentyl, 2-methylbutyl, 2,2-dimethylpropyl, hexyl,
2 or 3-methylpentyl, 2,2-dimethylbutyl, 4-methylhexyl, 2 or 3-methylbutyl, 6-methyloctyl, n-heptyl, 2,
Included are 2-dimethylpentyl, 3,3-trimethylpentyl, 2,4-dimethylpentyl, n-octyl, 2,2,3,3-tetramethylbutyl, nonyl, decyl, undecyl, dodecyl, and the like. The carbon chain of these alkyl groups may contain a non-binding carbon. Among these, preferred compounds include 4-
(4'-n-pentyloxy-biphenyl)-carboxylic acid α-(4-methylphenyl)ethyl ester, 4-(4'-n-pentyloxy-biphenyl)
-Carboxylic acid α-(4-n-octylphenyl)
Ethyl ester, 4-(4'-n-octyloxy-biphenyl)-carboxylic acid α-(4-methylphenyl)ethyl ester, 4-(4'-n-octyloxy-biphenyl)-carboxylic acid α-(4-
n-octylphenyl)ethyl ester, 4-
(4'-n-octyloxy-biphenyl)-carboxylic acid α-(4-dodecylphenyl)ethyl ester, 4-[4'(2-methylheptyl)oxy-biphenyl]-carboxylic acid α-(4-methylphenyl) ) Ethyl ester, 4-[4'-(2-methylheptyl)oxy-biphenyl]-carboxylic acid α-
(4-n-octylphenyl)ethyl ester,
Examples include 4-(4'-n-octyloxy-biphenyl)-carboxylic acid α-[4-(2-methylheptyl)phenyl]ethyl ester. Compounds of the formula () of this invention are, for example, general formula ():

4-(4'-alkoxy-biphenyl) represented by
Carboxylic acid and general formula ():

It can be produced by reacting with α-(4-alkylphenyl)ethyl alcohol represented by the formula: In the above reaction, it is usually preferable to convert the carboxylic acid of formula () into the form of a reactive derivative, such as an acid halide such as chloride or bromide. Further, the reaction is usually carried out in an inert organic solvent such as toluene or xylene under heating. When used as the acid halide of the carboxylic acid of formula (), the reaction can be carried out in the presence of a dehalogenating agent such as pyridine. The carboxylic acid of the above formula () can be synthesized from p-oxybiphenyl according to the method described in, for example, Ichiro Nakata and Bunichi Hori, "Liquid Crystal Manufacturing Method and Application", Saiwai Shobo (1974), p. 70. , the alcohol of formula () can be synthesized, for example, by reduction of p-alkylacetonephenone. Since the alcohol of formula () above has an inhospitable carbon at the α-position, if an optically active substance (d- or l-form) is used as this alcohol, it is possible to obtain a compound of formula () having the corresponding optical activity. can. However, if a racemate is used, a corresponding optically inactive compound of formula () can also be obtained. The alkoxybiphenylcarboxylic acid derivatives of this invention include all such d-forms, l-forms, racemic forms, etc. Among such compounds of the present invention, those in optically active form are useful as additives to liquid crystal compositions. That is, the compound of formula () has a structure in which an inactive carbon atom is adjacent to an ester group, and sterically large phenyl rings are present on both sides of the inactive carbon atom. Therefore, when used as an optically active substance, the free rotation around the ester group and non-satile carbon atoms is regulated, and a large spontaneous polarization can be expected. Useful for use as a component. In particular, we discovered that this compound exhibits a strong spontaneous polarization-inducing effect when added to a liquid crystal compound exhibiting a smectic C phase, providing a highly responsive ferroelectric liquid crystal composition that has been difficult to prepare in the past. It is. However, according to this invention,
A liquid crystal composition is provided in which at least one alkoxybiphenylcarboxylic acid derivative of formula () is added to a liquid crystal compound exhibiting a smectic C phase. As the liquid crystal compound exhibiting the smectic C phase to be added here, various smectic liquid crystals known in the art can be used. Specific examples thereof include compounds represented by the following formulas (), (), and ().

[ka]

[ka]

[Formula, A and B are each a single bond or -COO-, -OCO-, -CH=CH-COO, -OCO
-CH=CH-, -O-, -S-, -OCOO- or -CO-. D and E are respectively
Single bond or -COO-, -OCO-, -CH=N-, -
N=CH-, -CH=CH-, -C≡C-, -CH=
CH−COO−, −OCO−CH=CH−, −CH ₂ CH ₂
−, −OCH ₂ −, −CH ₂ O−, −COS− or −
Indicates the SOC- group.

【formula】

[expression] and

[Formula] each independently represents a benzene ring, a pyridine ring, a pyrimidine ring, a pyrazine ring, a pyridazine ring, a piperazine ring, a cyclohexane ring, a pyran ring, a dioxacyclohexane ring, a thiapyran ring, a dithian ring, a thiadiazine ring, and a bicyclo[ 2.2.2] Indicates a six-membered ring such as an octane ring or a tetrazine ring, and the hydrogen atom in these six-membered rings is a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a nitro group, a lower alkyl group, or a lower alkoxy group. It may be substituted with a group or deuterium (D). R ₃ and R ₄ are each independently linear or branched and have 1 to 1 carbon atoms.
12 alkyl or alkoxy groups. p represents an integer of 1 or 2. ) Of course, two or more of these can be used in combination. In practice, these smectic liquid crystal compounds are
It exhibits a smectic C phase near room temperature and has IAC and
It is suitable to mix them as appropriate so that they have a phase series such as INAC. Further, the amount of the compound of formula () mixed in the liquid crystal composition is usually suitably 0.5 to 20% by weight, preferably 1 to 10% by weight. If it is less than 0.5% by weight, the effect of improving the response of the smectic liquid crystal compound will be insufficient, and if it exceeds 20% by weight, the thermal stability of the smectic C phase will be insufficient, which is not suitable. (e) Examples Example 1 4-(4'-n-octyloxy-biphenyl)-
Carboxylic acid α-(4-octylphenyl)ethyl ester 4-(4'-n-octyloxy-biphenyl)-
0.65 phosphorus pentachloride in 0.8 g (0.0026 mol) of carboxylic acid
g (0.0031 mol) and heated at about 80°C to react. POCl ₃ and excess phosphorus pentachloride were completely removed by vacuum distillation to obtain 4-(4'-n-octyloxo-biphenyl)-carboxylic acid chloride. Dissolve this in 10 ml of toluene and s-(-)-α
Add 0.5 g (0.0021 mol) of -(4-n-octylphenyl)ethyl alcohol and 1 ml of pyridine (dehydrochlorination agent). After leaving it at room temperature for 10 hours,
Heat to 60℃, keep for 3 hours, then cool. Then add to hydrochloric acid and extract with ether. The ether layer was washed with aqueous _NaHCO3 solution and then with water;
Dry _{with Na2SO4} . The ether was distilled off, the residue was purified by column chromatography (solvent: chloroform), and recrystallized from ethanol to obtain the desired 4-(4'-n-octyloxy-biphenyl).
-Carboxylic acid α-(4-octylphenyl)ethyl ester was obtained. The infrared spectrum of this compound is shown in FIG. This compound did not exhibit a liquid crystal phase and exhibited the following transition temperature (melting point). or
The light intensity [α] ^25/D was 98.7° (solvent chloroform). Crystal 51℃ ---→ Liquid Example 2 4-(4'-n-octyloxy-biphenyl)-carboxylic acid α-(4-n-octylphenyl)ethyl ester prepared in Example 1 was used to strengthen A dielectric liquid crystal composition was created. Table 1 shows the composition of the prepared liquid crystal composition.

【table】

[Table] The phase transition temperature of this composition is as follows. Since this liquid crystal composition has an IAC phase series, good alignment can be easily obtained when applied to a liquid crystal cell, and it exhibits a ferroelectric smectic C liquid crystal phase at room temperature. Smectic C50 −−→ ℃Smectic A66℃ −−→ Isotropic liquid In addition, nematic (N) phase, smectic A (S _A )
Identification of liquid crystal phases such as smectic C (S _C ) phase and smectic C (S Ivy. Example 3 A liquid crystal display device was manufactured using the liquid crystal composition prepared in Example 2. An ITO film is formed on two glass substrates, and a nylon film is applied and rubbed. Next, these two glass substrates are bonded together so that the rubbing direction is the same and the cell thickness is 2 μm. The liquid crystal composition prepared in Example 2 was injected into this cell. After injection, the cell was heated to 75°C, at which point the liquid crystal composition changes to an isotropic liquid, and then cooled to room temperature at a rate of 1°C/min to obtain good alignment. This liquid crystal element is installed between two orthogonal polarizers,
An electric field was applied and changes in transmitted light intensity were observed.
When the response speed was determined from the change in transmitted light intensity when an electric field of V _PP =20V was applied at 25°C, a high-speed response of 181 μsec was obtained. Therefore, it can be seen that the compound of formula () is extremely effective in improving the responsiveness of ferroelectric liquid crystal compositions even when added in small amounts. Example 4 Instead of 4-(4'-n-octyloxy-biphenyl)carboxylic acid in Example 1, 4-
(4'-(1-methylheptyloxy-biphenyl)
Using carboxylic acid, (R,
S) 4-(4'-(1-Methylheptyloxy-biphenyl)carboxylic acid α-(4-octylphenyl)ethyl ester was synthesized. The phase transition temperature (melting point) from crystal to isotropic liquid was 47
℃, and the light intensity [α] ^25/D was +67.5°. Example 5 A non-chiral smect C liquid crystal composition (B) shown in Table 3 was prepared. The phase transition of this liquid crystal composition (B) was as follows. S _C 50℃ −−→ S _A 68℃ −−→ N71℃ −−→ I To this liquid crystal composition (B), the compounds of Example 1 and Example 4, and (R)4-(4 ′−
n-octyloxy-biphenyl)carboxylic acid
α-Phenylethyl ester ([α] ^25/D = −77.5°,
A chiral smectic C liquid crystal composition was prepared by adding the phase transition concentration from crystal to isotropic liquid = 72°C, and a liquid crystal display device was prepared in the same manner as in Example 3. was measured. The measurement results are shown in Table 4.

【table】

【table】

[Table] As is clear from the above table, the compound of the present invention is
It exhibits faster response characteristics than the comparative compound, and in particular, the addition of 4% of the compound of Example 1 achieves a high-speed response of 80 μsec. (f) Effects of the Invention The alkoxybiphenylcarboxylic acid derivative of the present invention induces high spontaneous polarization, and by utilizing this property, it is useful for various uses, and in particular, it can improve the responsiveness of liquid crystal compositions. Useful for improvement. A smectic liquid crystal composition mixed with this compound has improved responsiveness compared to one without additives or one using other optically active compounds, and by selecting an appropriate smectic liquid crystal compound, It becomes possible to obtain an ideal ferroelectric liquid crystal composition.

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum diagram of an alkoxybiphenylcarboxylic acid derivative according to an example of the present invention.

Claims (1)

[Claims] 1 The following general formula (1): [Chemical formula] (In the formula, R ₁ and R ₂ are each the same or different and represent a linear or branched alkyl group having 1 to 12 carbon atoms. an alkoxybiphenylcarboxylic acid derivative represented by 2. A liquid crystal composition obtained by adding at least one kind of the alkoxybiphenylcarboxylic acid derivative according to claim 1 to a liquid crystal compound exhibiting a smectic C phase.