JPH0629224B2 - Liquid crystal compound and liquid crystal composition - Google Patents

Description

The present invention relates to a liquid crystal compound and a liquid crystal composition, and particularly to a liquid crystal material having ferroelectricity, which is compared with a conventional liquid crystal material. Then, the present invention provides a liquid crystal material which is particularly applicable to a liquid crystal display device having excellent responsiveness and memory property.

<Prior Art> Liquid crystal display elements have excellent characteristics such as low-voltage operation, low power consumption, thin display capability, and light-receiving type that do not cause eye strain. It is used.

At present, as a display method, Twisted Nematic
A nematic liquid crystal called (TN) type is generally used as a material. However, this TN type display element has a drawback that its response is very slow as compared with other light receiving type display elements (CRT and the like), and has been restricted in various applications. As a liquid crystal display system, TN
Type, guest-host (GH) type, dynamic scattering (D
S) type, birefringence control (ECB) type, phase transition (PC) type,
Although the thermal effect type and the like have been researched and developed, and each has its own characteristics, it was hard to say that the responsiveness was greatly improved compared to the TN type. Therefore, development of a new liquid crystal display system having excellent responsiveness has been attempted.

Ferroelectric liquid crystals have recently been published to meet this purpose (RBMayer et al., JP
hysique 36 L69 (1975) and NAClark et al., Appl.Phy
s.Lett., 36 P899 (1980)) A display device using this is
A high-speed response of about 100 times that of a conventional liquid crystal is obtained, and it can be expected to be applied to display devices in various fields such as moving images of televisions and high-speed optical shutters.

Ferroelectric liquid crystals belong to the tilt type chiral smectic phase as the liquid crystal phase, and in particular, the chiral smectic C (SC ^* ) phase is practically desirable.

Liquid crystal compounds exhibiting a chiral smectic C phase have been studied so far, and some of them are already known.

(S) -2-methylbutyl-p-decyloxybenzylidene aminocinnamate (DOBAMBC), which is known as a ferroelectric liquid crystal synthesized for the first time as a typical example.
There is a series of Schiff base type liquid crystals such as, but these are all not suitable for practical use due to their difficulty in chemical stability against water and light.
(1) P.Kelleretal J.de Physique 37 C3 (1976); 2) idem Acad Sc.Paris 282 C639 (1976); 3) BIOstrouskiietal Ferroelectrics 24 309 (1980); 4) K.Yoshino et al Japanese J.of Appl.Physics23 L17
5 (1984); 5) Isogai et al. JP-A-59-98051) As a chemically stable chiral smectic liquid crystal, an ester type has already been reported by Goodby et al. (1) JW-Goodby et al Liquid Crystal & Ordered Fl
uids Vo14.P1〜; 2) JW-Goodby TMLeslie, Mol.Cryst.Liq.Cryst.110 17
5 1984) However, the appearance of the chiral smectic phase is high temperature or monotropic even at low temperature, the process of introducing the chiral group is complicated, and spontaneous polarization is not observed. It wasn't big enough, and I couldn't say it was satisfactory anyway.

<Problems to be Solved by the Invention> The present inventors have focused on an ester compound as a liquid crystal compound excellent in light and chemical stability, and a novel compound capable of taking a chiral smectic C phase near room temperature by itself or in combination. The inventors of the present invention have made earnest studies as to whether or not the liquid crystal compound (1) can be obtained.

That is, the present invention intends to provide a novel ferroelectric liquid crystal compound which is excellent in light and chemical stability and is colorless and capable of operating at room temperature, and a liquid crystal composition containing the same.

<Means for Solving Problems> In order to solve the above problems, the present invention provides a compound represented by formula (I) (hereinafter, referred to as a compound of the present invention or compound I). (In the formula, R represents an alkyl group or an alkoxy group having 1 to 20 carbon atoms, preferably a linear alkoxy group having 8 to 14 carbon atoms, n represents an integer of 0 or 1, and a ring X represents a 1,4-phenylene group substituted by a fluorine atom or a chlorine atom, and ring Y represents a 1,4-phenylene group or a 1,4-phenylene group substituted by a fluorine atom, and when n = 1, Ring Y is preferably a 1,4-phenylene group, R ^* represents an optically active alkyl group, preferably a 2 or 3-methylbutyl group or a 1-methylalkyl group, and particularly a 2-methylbutyl group. , A group selected from the group consisting of a 3-methylbutyl group, a 1-methylpropyl group and a 1-methylheptyl group.) And a liquid crystal group containing this compound. To provide things.

Ferroelectricity of liquid crystal is the chiral smectic phase (SC ^* , SF ^* , SG ^* , SH ^* , SI ^*) of the liquid crystal tilt system.
It appears when SJ ^* , SK ^* ) is taken, but in compound I, among the chiral smectic phases, most of the most practical SC ^* phases can take a relatively wide temperature range.

Further, among the compound I, there are some which take only the SA phase and do not take the chiral smectic phase, and some which do not have the liquid crystal property by themselves, but these are compounded by a plurality of compounds I or other compounds. By blending with a chiral smectic liquid crystal compound or the like, it can be used as a liquid crystal composition capable of exhibiting ferroelectricity. In that case, the temperature range of the chiral smectic phase that was in the high temperature range can be lowered.

In order for a liquid crystal to have a chiral smectic phase, the molecule needs to be asymmetric and optically active. Therefore, generally, an optically active group is introduced into a liquid crystal molecule as a substituent. . In Compound I, an optically active alcohol is used, and the condition is satisfied by connecting it to the molecular end by an ester bond, and its introduction is easy.

In order for the chiral smectic liquid crystal to have a high-speed response as a ferroelectric liquid crystal, it is necessary to have a large spontaneous polarization (Ps). Compound I has a carbonyl group which is a permanent dipole in the vicinity of its asymmetric carbon in the molecule, and C may be C depending on the optically active alcohol used.
It also has a —O bond and a C-halogen bond adjacent to the asymmetric carbon and can have a large spontaneous polarization.

Compound I has no chemical bond unstable to heat, light, moisture, etc. in its molecular skeleton, is chemically sufficiently stable, and is practically usable in that respect.

As described above, the compound I is used alone or as a liquid crystal composition, but the liquid crystal composition in the present invention is composed of a plurality of compounds I or contains at least one compound I as a compounding component thereof. Therefore, it has liquid crystallinity.

The compound of compound I can be produced, for example, as follows.

Compound I has the general formula II (In the formula, R and ring X have the same meanings as in general formula (I).) An acid chloride represented by the following formula (hereinafter referred to as acid chloride II).
And the general formula III (Wherein n and ring Y have the same meanings as in formula (I)) and an optically active phenol derivative (hereinafter referred to as phenol derivative III) in the presence of a basic substance such as pyridine. It can be easily obtained by reacting with.

The acid chloride II has the general formula IV (In the formula, R and ring X have the same meanings as in formula II.) Easily by reacting a benzoic acid derivative (hereinafter referred to as carboxylic acid IV) with a chlorinating agent such as thionyl chloride. Can be obtained. At this time, it may be carried out in the presence of a solvent or a basic substance (pyridine, DMF, etc.).

This acid chloride II can be stored by purification by distillation or the like, but it is easily hydrolyzed, and it is difficult to say that it is very suitable for long-term storage. Therefore, after converting the carboxylic acid IV to the acid chloride II using thionyl chloride or the like, without isolation and purification, the excess thionyl chloride was distilled off under reduced pressure, and the phenol derivative III was directly dissolved in a solvent such as pyridine. In addition, it is often convenient to react.

The compound I is a carboxylic acid IV and a phenol derivative II.
In a solvent such as I and methylene chloride in the presence of a catalyst such as N, N-dimethylaminopyridine and 4-pyrrolidinopyridine,
It can be directly obtained by using a dehydration condensing agent such as dicyclohexylcarbodiimide.

The carboxylic acid IV has various production methods depending on the kind of the ring X and whether R is an alkyl group or an alkoxy group. To give a few examples, 3-chloro-4-alkoxybenzoic acid is commercially available
2-chloro-4-hydroxybenzoic acid can be obtained by reacting it with an alkyl halide under basic conditions, or by directly chlorinating 4-alkoxybenzoic acid with a chlorinating agent such as N-chlorosuccinimide. Fluoro-4-alkoxybenzoic acid is 2-fluoro-4 obtained by alkaline hydrolysis of 3-fluoro-4-cyanophenol.
It can be obtained by alkylation of hydroxybenzoic acid. 3-Chloro-4-alkylbenzoic acid is obtained by directly chlorinating 4-alkylbenzoic acid or nitrating 4-alkyl-4-benzoic acid.
It can be obtained by alkyl-4-nitrobenzoic acid, 4-alkyl-3-aminobenzoic acid by reduction, and chlorination by Sandmeyer reaction. Similarly,
3-Fluoro-4-alkylbenzoic acid can also be obtained. 2-Fluoro-4-alkylbenzoic acid is obtained by converting m-fluorobromobenzene into a Grignard compound and then alkylating it to give 3-fluoroalkylbenzene.
This can be reacted with acetyl chloride in the presence of aluminum chloride to give 2-fluoro-4-alkylacetophenone, which can be obtained by replacing the acetyl group with carboxylic acid with sodium hypochlorite or the like. Other carboxylic acids IV can be easily obtained by almost the same method.

The phenol derivative III is an optically active alcohol ester of 4-hydroxybenzoic acid and a halogen-substituted product when n = 0, and an optically active alcohol ester of 4′-hydroxyphenyl-4-carboxylic acid when n = 1. Is.

These are the corresponding hydroxycarboxylic acids, ie the general formula V (Wherein n and ring Y have the same meanings as in formula III), and easily obtained by dehydration condensation of hydroxycarboxylic acid V represented by the formula and optically active alcohol (R ^* -OH) in the presence of a catalyst. When the optically active alcohol is a secondary alcohol such as (S) -2-butanol or (S) -2-octanol and the hydroxyl group is directly bonded to the asymmetric carbon, It can be obtained by protecting the hydroxy group of hydroxycarboxylic acid V, converting it into an acid chloride, and then reacting it with an optically active alcohol. However, in order to obtain the compound I using such a secondary alcohol, the acid chloride II and the general formula VI are rather used. (In the formula, n and ring Y have the same meanings as in general formula III.)
I (In the formula, R, ring X, n and ring Y have the same meanings as in formula (I).) After obtaining an aldehyde derivative, it is oxidized to a carboxylic acid and further chlorinated. It is preferable to use a method in which the acid chloride is converted to an acid chloride, and this is reacted with an optically active alcohol.

This method can of course be used in the case of a primary optically active alcohol, but in that case, the process is long and complicated as compared with the above-mentioned method.

The obtained liquid crystal compound or liquid crystal composition can be used as a liquid crystal display cell by forming a thin film having a uniform thickness (1 μm to 20 μm) between two transparent electrode plates. In the cell, the liquid crystal molecules need to have a so-called homogeneous and uniform orientation parallel to the electrode surface.

For this purpose, the cell surface is subjected to an alignment treatment, an electric field or a magnetic field is applied, or a temperature gradient is applied, and the isotropic liquid phase to the liquid crystal phase is gradually cooled to achieve uniform alignment. The method of obtaining the mono domain is taken. Further, as seen in a part of the compound I, a compound having a chiral nematic phase between a smectic phase and an isotropic liquid phase, or in a liquid crystal composition, in the temperature range showing the chiral nematic phase,
Alignment is performed by the same alignment means as in ordinary nematic liquid crystals (eg, surface treatment such as rubbing, application of electric field or magnetic field), and this is cooled to the chiral smectic phase, so that the monodomain is also uniformly aligned. Can be obtained.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples, but the gist and the scope of application of the present invention are not limited to these Examples.

(Example 1) Synthesis (in the above, 2MB represents a 2-methylbutyl group) 3-fluoro-4-tetradecyloxybenzoic acid 2.4 g
(6.8 mmol) with thionyl chloride 10 ml and pyridine 0.5 g
Was heated and stirred, and refluxed for 1 hour. Excess thionyl chloride was distilled off under reduced pressure, and 2.1 g (6.8 mmol) of 4'-hydroxybiphenyl-4-carboxylic acid- (S) -2-methylbutyl ester dissolved in 10 ml of pyridine was added thereto. This was heated to 40-50 ° C and stirring was continued for 1 hour.
After cooling, 200 ml of ethyl acetate and 100 ml of 10% hydrochloric acid water were added, and the mixture was stirred, the organic layer was separated, and washed with water and saturated brine. Glauber's salt was added and dried, and then the solvent was distilled off to obtain 4.6 g of crude crystals. Purification by silica gel column chromatography (developing solvent; n-hexane-ethyl acetate mixed system), (S) -2-methylbutyl-
3.15 g of 4 '-(3-fluoro-4-tetradecyloxybenzoyloxy) biphenyl-4-carboxylate
(Yield 75%) was obtained.

The structure was confirmed by nuclear magnetic resonance spectrum (NMR), infrared absorption spectrum (IR), mass spectrum (MS) and the like. The transition point was measured by using a polarization microscope and a differential scanning calorimeter (DSC) together.

NMR: δ6.8~8.1 (multiplet, 11H, aromatic) δ3.9~4.2 _{(multiplet, 4H, -O-CH 2 -} ) δ1.6~2.1 ( multiplet, 3H) δ1.2~1.5 ( multiplet, 24H) δ0.8~1.1 _{(multiplet, 9H, -CH 3) IR:} 1730,1720,1620,1240,1200,1120,935,86
0,770,755 (cm ^-1 ) MS: 618 (P ⁺ ) In addition, the phase transition temperature from the isotropic liquid (abbreviated as I) to the SA phase is 145.5 ° C, and from the SA phase to the SC ^* phase. Transition temperature
The temperature was 107.3 ° C, the transition temperature from the SC ^* phase to another smectic phase (abbreviated as Sm) was 48 ° C (monotropic), and the melting point was 52 ° C.

Then, 3-fluoro-4-tetradecyloxybenzoic acid is replaced with 3-fluoro-4-alkoxybenzoic acid having 1 to 20 carbon atoms in the alkyl side chain, 3-fluoro-4-alkylbenzoic acid, 2 -Fluoro-4-alkoxybenzoic acid, 2-fluoro-4-alkylbenzoic acid, 3
-Chloro-4-alkoxybenzoic acid, 3-chloro-4-
Alkylbenzoic acid, 2-chloro-4-alkoxybenzoic acid, 2-chloro-4-alkylbenzoic acid, etc. are used, and 4'-hydroxybiphenyl-4-carboxylic acid-
Instead of (S) -2-methylbutyl ester, 4-hydroxybenzoic acid- (S) -2-methylbutyl ester,
3-chloro-4-hydroxybenzoic acid- (S) -2-methylbutyl ester, 2-chloro-4-hydroxybenzoic acid- (S) -2-methylbutyl ester, 3-fluoro-4-hydroxybenzoic acid- (S) -2-Methylbutyl ester, 2-fluoro-4-hydroxybenzoic acid-
The same reaction was carried out using (S) -2-methylbutyl ester and the like to obtain the corresponding compound I. The phase transition points of typical ones are shown in Table 1 on the next page.

In the table, 2MB is (S) -2-methylbutyl group, 3MP is (S) -3-methylpentyl group, 1MP is optically active 1
-Methylpropyl group, 1MH represents an optically active 1-methylheptyl group, and A to E in ring X and ring Y are A
Is B is C is D is E is Where C is a crystalline phase, I is an isotropic liquid phase, N ^* is a chiral nematic phase, SA is a smectic A phase, SC ^* is a chiral smectic C phase, and Sm is a higher order smectic phase. Further, * indicates that the melting point is unknown because it does not crystallize. Also, -indicates that the phase exists, -indicates that it does not exist, and the number on the right side of-indicates the transition temperature from that phase to the next high-temperature phase. () Indicates that the phase is monotropic. The value to the right of phase C is also the melting point of compound I.

(Example 2) To 80 parts of 4 '-(3-fluoro-4-tetradecyloxybenzoyloxy) biphenyl-4-carboxylate obtained in Example 1 was added 3-fluoro-4-((S) -2.
20 parts of (methylbutyloxycarbonyl) phenyl-4-dodecyloxybenzoate were mixed to prepare a liquid crystal composition.

The SA-SC ^* transition layer dropped to 61 ° C., and when cooled, showed a stable SC ^* phase up to around room temperature.

(Example 3) Production of liquid crystal display element The (S) -2-methylbutyl-obtained in Example 1 was sandwiched between two glass transparent electrodes via a spacer having a thickness of 7 µm.
4 '-(3-Fluoro-4-tetradecyloxybenzoyloxy) biphenyl-4-carboxylate was added to 148
It was heated to ℃ and filled as an isotropic liquid to prepare a thin film cell.

Slow cooling with a gentle temperature gradient (0.2 to 0.3 per minute)
(° C.) to orient the SA phase to obtain a uniform monodomain.

This cell is cooled to SC ^* phase, and electric field (5Vp-p,
When a rectangular wave of 0.1 KHz) was applied, a clear switching operation was confirmed.

Furthermore, when a rectangular wave of 120 Vp-p, 800 KHz is applied and the optical switching operation is detected by Photo Multiplayer,
The response speed was 100 μsec or less.

<Effects of the Invention> Compared with DOBAMBC, which is conventionally known as a ferroelectric liquid crystal compound, the compound of the general formula (I) of the present invention is industrially used as shown in the above-mentioned Examples. It can be easily produced, is colorless in itself, is excellent in chemical stability to light, water, etc., and also exhibits a chiral smectic C phase in a lower temperature range.

Moreover, in the liquid crystal composition of the present invention, as in the case of a general liquid crystal composition, the liquid crystal temperature range is lower than that of a single compound, and it is expected that the liquid crystal composition can be used at room temperature.

Further, the liquid crystal compound and the liquid crystal composition of the present invention have an extremely large response speed of about 100 times that of the nematic liquid crystal, as in the conventional ferroelectric liquid crystal.

Therefore, it is extremely useful as a constituent material of a display optical switching element.

Claims (7)

[Claims] 1. A general formula (I) (In the formula, R represents an alkyl group or an alkoxyl group having 1 to 20 carbon atoms, n represents an integer of 0 or 1, and the ring X is 1,4 substituted with a fluorine atom or a chlorine atom.
Represents a phenylene group, ring Y represents a 1,4-phenylene group or a fluorine-substituted 1,4-phenylene group,
R ^* represents an optically active alkyl group. ) A liquid crystal compound represented by: 2. The compound according to claim 1, wherein n = 1 and the ring Y is a 1,4-phenylene group. 3. The compound according to claim 1, wherein n = 0. 4. The compound according to claim 2 or 3, wherein R ^* is an optically active 1-methylalkyl group. 5. The compound according to claim 2 or 3, wherein R ^* is a group selected from the group consisting of a 2-methylbutyl group, a 3-methylbutyl group, a 1-methylpropyl group and a 1-methylheptyl group. The described compound. 6. General formula (I) (In the formula, R represents an alkyl group or an alkoxyl group having 1 to 20 carbon atoms, n represents an integer of 0 or 1, and the ring X is 1,4 substituted with a fluorine atom or a chlorine atom.
Represents a phenylene group, ring Y represents a 1,4-phenylene group or a fluorine-substituted 1,4-phenylene group,
R ^* represents an optically active alkyl group. ) A liquid crystal composition containing a compound represented by: 7. The liquid crystal composition according to claim 6, which exhibits a chiral smectic C phase.