JPH0678280B2 - Ferroelectric 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. In addition, the present invention relates to a liquid crystal material having applicability 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 operability, low power consumption, thin display capability, and light receiving type that prevent eye strain, so they are widely used as various display elements. Is used for.

At present, the most common display method is a twisted nematic (TN) type, which uses a nematic liquid crystal as a material. However, this TN type display element has a drawback that the response is very slow compared to other light emitting type display elements (CRT etc.),
It was subject to various application restrictions. In addition to the TN type, R & D on liquid crystal display types includes guest-host (GH) type, dynamic scattering (DS) type, birefringence control (ECB) type, phase transition (PC) type and thermal effect type. Although each of them has its own characteristics, it was hard to say that all of them were significantly improved in responsiveness as compared with 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 goal (RBMayer et al., J. Phy.
sique 36 L-69 (1975)), a display device using this has a high-speed response that is about 100 times or more that of conventional liquid crystals, and can be used for moving images such as televisions and high-speed optical shutters. It can be expected to be applied to display devices in various fields.

The ferroelectric liquid crystal belongs to the tilt type chiral smectic phase as the liquid crystal phase, and 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.

As a typical example, a series of Schiff base-based compounds such as (S) -2-methylbutyl p-decyloxybenzylidene aminocinnamate (abbreviated as DOBAMBC), which is known as the first synthesized ferroelectric liquid crystal, is used. Liquid crystals can be mentioned, but all of them are not suitable for practical use because they have drawbacks in chemical stability against water and light.

(1) P. Keller et al., J. de Physique 37 C3 (1976);
2) idem.Acad.Sc.Paris 282 C639 (1976); 3) BIOstr
ouskii et al., Ferroelectrics 24 309 (1980); 4) K.
Yoshino et al., Japanese J. of Appl. Physics 23 L175
(1984); 5) Isogai et al. JP-A-59-98051) Some chemically stable chiral smectic liquid crystals have already been reported by Goodby et al. (1) JWGoodby et al., Liquid Crystals & Ord
ered Fluids Vol.4P1〜; 2) JWGoodby, TMLeslie, Mo
l.Cryst.Liq.Cryst.110 175 1984) <Problems to be solved by the invention> However, in these cases, the appearance of the chiral smectic phase is in the high temperature region, or is monotropic even in the low temperature region. However, the process of introducing the chiral group is complicated, and the spontaneous polarization is not sufficiently large, so that it cannot be said to be satisfactory in any case.

The problem to be solved by the present invention focuses on an ester compound as a liquid crystal compound excellent in light and chemical stability, and a liquid crystal phase having strong induction at around room temperature, particularly a chiral smectic C, by itself or in combination. The present invention provides a novel liquid crystal compound capable of taking a phase, and further provides a particularly ferroelectric liquid crystal composition containing such a compound and capable of operating at room temperature.

<Means for Solving Problems> In order to solve the above-mentioned problems, the present invention provides general formula (I)
(Hereinafter, referred to as compound of the present invention or compound I) (In the formula, R represents an alkyl group or an alkoxyl group having 1 to 20 carbon atoms, preferably a linear alkyl group having 8 to 16 carbon atoms, X represents a fluorine atom or a chlorine atom, and n Represents 0 or 1, and when X is a fluorine atom, the ring Y is And when X is a chlorine atom, the ring Y is And R ^* represents an optically active group, but (S) -2-
Methylbutyl group, optically active 1-methylpropyl, 31-
It is preferably a group selected from the group consisting of a methylheptyl group and a 2-chloropropyl group, and in particular, when n is 1, it is preferably a (S) -2-methylbutyl group. ) A ferroelectric compound represented by

Ferroelectricity of liquid crystal is the chiral smectic phase (SC ^* , SF ^* , SG ^* , SH ^* , SI ^* , SJ ^* , etc.) in which the liquid crystal is tilted.
It appears when taking SK ^* ), but in compound I,
Of the chiral smectic phases, many are capable of taking the most practical SC ^* phase in a relatively wide temperature range,
In addition, some of the compounds I have only the SA phase and do not have the chiral smectic phase, or some have no liquid crystal phase by themselves, but these are compounded between the compounds I or other chiral smectic phases. It can be used as a liquid crystal composition capable of exhibiting ferroelectricity by blending with a liquid crystal compound. 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, which is linked to the molecular end by an ester bond to satisfy the condition, so that introduction thereof is easy.

In order for a chiral smectic liquid crystal to have a high-speed response as a ferroelectric liquid crystal, it must have a large spontaneous polarization (Ps). Compound I has a carbonyl group which is a large permanent dipole in the vicinity of its asymmetric carbon in the molecule, and further, depending on the optically active alcohol used,
It also has a C—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 of the present invention comprises a plurality of compounds I, or contains at least one compound I as a compounding component thereof. , Has liquid crystallinity.

Next, a method for producing compound I will be described. Compound I has the general formula (II) (In the formula, R and X have the same meanings as in the general formula (1).) An acid chloride represented by the following (hereinafter referred to as acid chloride II)
And the general formula (III) (In the formula, n, ring Y and R ^* have the same meanings as in the general formula (I).) An optically active phenol derivative represented by the formula (hereinafter referred to as phenol derivative III) and a base substance such as pyridine are present. It can be easily obtained by reacting below.

The acid chloride II has the general formula (IV) (Wherein R and X have the same meanings as in the general 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 is easily hydrolyzed and is not very suitable for long-term storage. Therefore, the carboxylic acid IV was converted to the acid chloride II using thionyl chloride, the excess thionyl chloride was distilled off under reduced pressure, and the phenol derivative III was directly dissolved in a solvent such as pyridine without isolation and purification. In addition, it is often practical to react.

Carboxylic acid IV is 4'-alkylbiphenyl-4-carboxylic acid which is not substituted with halogen, or 4'-alkoxybiphenyl-4-carboxylic acid, and N-chlorosuccinimide (NCS), bromine, periodic acid- After direct halogenation with iodine or the like, or nitration, 3'-amino-4'-alkylbiphenyl-4 is obtained by reduction.
-Carboxylic acid or 3'-amino-4'-alkoxybiphenyl-4-carboxylic acid, which can be obtained by the Sandmeyer reaction. Especially when a fluorine atom is introduced, it is introduced by the latter reaction.

In addition to this, when introducing a fluorine atom, 1
-Alkyl-4-bromo-2-fluorobenzene or 1-alkoxy-4-bromo-2-fluorobenzene was used as a Grignard compound and reacted with iodobenzene in the presence of a catalyst such as palladium (II) chloride to give 3- It can also be obtained by preparing fluoro-4-alkylbiphenyl or 3-fluoro-4-alkoxybiphenyl, acetylating it by a conventional method, and oxidizing it with sodium hypochlorite.

On the other hand, the phenol derivative III is an optically active alcohol when n = 0 and an optically active phenol derivative when n = 1.

The optically active phenol derivative has the general formula (V) (Wherein ring Y has the same meaning as in general formula (I)), the corresponding 4-hydroxybenzoic acid or its derivative V and an optically active alcohol are dehydrated and condensed in the presence of an acid catalyst. , Can be easily obtained. Further, when the optically active alcohol to be reacted at this time is a secondary alcohol such as (S) -2-butanol or (S) -2-octanol, and the hydroxyl group is directly bonded to the asymmetric carbon. Is hydroxybenzoic acid V
It can be obtained by protecting the hydroxyl group of 1, then converting to an acid chloride and reacting with an optically active alcohol. However, when the optically active alcohol is such a secondary alcohol, the following method is preferable in order to obtain the compound I (n = 1) of the present invention.

That is, acid chloride II and general formula (VI) (In the formula, ring Y has the same meaning as in formula I)
4-hydroxybenzaldehyde derivative VI
To react with the general formula (VII) (Wherein R, X and ring Y have the same meanings as in the general formula I), a benzaldehyde derivative is obtained, which is then oxidized to a carboxylic acid and further chlorinated to give an acid chloride. , Compound I (n = 1) can be obtained by reacting with an optically active alcohol.

This method can be similarly used in the case of an optically active primary alcohol. However, since the process is long and complicated, the above method is preferable.

Now, the obtained ferroelectric compound or liquid crystal composition is
Uniform thickness (1μm to 20μ) between two transparent electrode plates
By using the thin film of m), it can be used as a liquid crystal display cell. 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 liquid crystal composition is gradually cooled from the isotropic liquid phase to the liquid crystal phase by subjecting the cell surface to an alignment treatment, applying an electric field or magnetic field, or placing a temperature gradient. Then, a uniformly oriented monodomain is obtained. 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 a liquid crystal composition, is To obtain a monodomain that is also uniformly oriented by aligning by the same alignment means as in nematic liquid crystal (eg surface treatment such as rubbing, application of electric field or magnetic field), and then cooling to a chiral smectic phase. You can

Even in the case of compound I or a liquid crystal composition containing compound I, a uniformly aligned monodomain cell can be obtained in exactly the same manner.

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

(Example 1) (2MB represents a (S) -2-methylbutyl group) 3'-chloro-4'-octyloxybiphenyl-4-
2.50 g (6.9 mmol) of carboxylic acid, 15 ml of thionyl chloride and 1.0 ml of pyridine were heated and stirred, and refluxed for 2 hours. Excess thionyl chloride was distilled off under reduced pressure, to which 3-
Fluoro-4-hydroxybenzoic acid (S) -2-methylbutyl ester (1.60 g, 7.0 mmol) was dissolved in 12 ml of pyridine and added. After stirring at 40 ° C to 50 ° C for 1 hour, the mixture was allowed to cool and 200 ml of ethyl acetate and 100 ml of 10% hydrochloric acid water were added.

The organic layer was separated, and this was washed with saturated aqueous sodium hydrogen carbonate solution,
The extract was washed with water and saturated saline, added with Glauber's salt, and dried. The solvent was distilled off to obtain 4.0 g of crude crystals. Purification by silica gel column chromatography (developing solvent: n-hexane-ethyl acetate mixed system), 2-fluoro-4-[(S)-
3.6 g of white crystals of 2-methylbutoxycarbonyl] phenyl-3'-chloro-4'-octyloxybiphenyl-4-carboxylate were obtained. (Yield 92%) The structure was confirmed by nuclear magnetic resonance spectrum (NMR) and mass spectrum (MS). The transition point was measured by using a polarization microscope and a differential scanning calorimeter (DSC) together.

NMR: δ6.9 to 8.3 (multiline, 10H, aromatic) δ4.06 (triplet, δ 4.18 (double double line, -COO-CH _2- ) δ 1.7 ~ 2.0 (multiple line, 3H) δ 1.2 ~ 1.6 (multiple line, 12H) δ 0.8 ~ 1.1 (multiple line, 9H , -CH ₃ ) MS: 586, 588 (strength ratio 3: 1P ⁺ ) Phase transition temperature is 114 ° C from isotropic liquid to chiral nematic phase (N ^* phase), SA phase from N ^* phase Of the SA phase to SC ^* phase was 71 ° C, and the melting point was 42.5 ° C.

Then, in place of the 3'-chloro-4'-octyloxybiphenyl-4-carboxylic acid, 3'-chloro-4-alkoxybiphenyl-4 having 1 to 20 carbon atoms in the side chain.
-Carboxylic acid, 3'-chloro-4'-alkylbiphenyl-4-carboxylic acid, 3'-fluoro-4-alkoxybiphenyl-4-carboxylic acid, 3'-fluoro-4'-
Alkyl biphenyl-4-carboxylic acid is used, and 3-
Instead of fluoro-4-hydroxybenzoic acid (S) -2-methylbutyl ester, optically active (S) -2-methylbutanol, (S) -3-methylpentanol,
(S) -4-methylhexanol, (S) -5-methylheptanol, (S) -2-butanol, (S) -2-
Pentanol, (S) -2-hexanol, (S) -2
-Heptanol, (S) -2-octanol, (S)-
2-nonanol, (S) -2-decanol, (R) -2
-Optically active alcohol such as chloropropanol and 4-
The optically active alcohol ester of hydroxybenzoic acid, the optically active alcohol ester of 3-fluoro-4-hydroxybenzoic acid, the optically active alcohol ester of 2-fluoro-4-hydroxybenzoic acid, and 2-chloro-4-hydroxybenzoic acid. The same reaction was carried out using the above-mentioned optically active alcoholic ester of an acid and the corresponding compound I was obtained.

The phase transition points of typical ones are shown in the following table.

(Example 2) Preparation of liquid crystal composition 2-fluoro-4-[(S) -2- obtained in Example 1
Methylbutoxycarbonyl] phenyl-3′-chloro-
A liquid crystal composition was prepared by mixing 6 parts of 4′-octyloxybiphenyl-4-carboxylate with 1 part of 3-fluoro-4-[(S) -2-methylbutoxycarbonyl] benzoyl-4-dodecyloxybenzoate. did. The N ^* phase-I phase transition point and the SA phase-N ^* phase transition point of this liquid crystal composition were 109.5 ° C. and 102 ° C., respectively, which did not decrease so much.
The SA phase-SC ^* phase transition point decreased to 59.5 ° C, and the SC ^* phase-crystal phase transition point was below room temperature. As a result, the SC
^* Liquid crystal composition showing a phase is obtained.

(Example 3) Production of liquid crystal display device Example in which an isotropic liquid phase was obtained by heating to 120 ° C between two glass transparent electrode plates which had been surface-treated by rubbing through a spacer having a thickness of 4 µm. 2-Fluoro-4-[(S) -2-methylbutoxycarbonyl] phenyl-3'-chloro-4'-octyloxybiphenyl-4-carboxylate obtained in 1 was filled to prepare a thin film cell.

The chiral nematic phase was oriented by slowly cooling to 110 ° C while applying an electric field.

When further slowly cooled to 100 ° C., a uniformly oriented smectic A phase monodomain was obtained. When this cell was cooled to 60 ℃, it became SC ^* phase. When a rectangular wave of 5V, 0.1KHz was applied to this cell, and the optical switching operation was detected by the photomultiplier, the response speed was 100 µsec or less.

As a result, a liquid crystal display device having a fast response speed was obtained.

<Effects of the Invention> The compound I of the present invention can be easily produced industrially, as shown in the examples, as compared with DOBAMBC conventionally known as a ferroelectric liquid crystal compound. It can be produced, is colorless in itself, is excellent in chemical stability against light, water and the like, and at the lower temperature region, exhibits a chiral smectic C phase.

Moreover, in the liquid crystal composition of the present invention, a decrease in the liquid crystal temperature range is recognized as in a general liquid crystal composition as compared with a single compound, and the liquid crystal composition can be used at room temperature.

Furthermore, the response speed of the liquid crystal composition of the present invention is 100 times or more that of a nematic liquid crystal, which is extremely high.

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

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Claims (9)

[Claims] 1. A general formula (I) (In the formula, R represents an alkyl group or an alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom or a chlorine atom, n represents 0 or 1, and when X is a fluorine atom, the ring Y is And when X is a chlorine atom, the ring Y is And R ^* represents an optically active group. ) A ferroelectric compound represented by. 2. The ferroelectric compound according to claim 1, wherein R is a linear alkoxyl group having 8 to 16 carbon atoms. 3. The ferroelectric compound according to claim 2, wherein n is 0. 4. The ferroelectric compound according to claim 2, wherein n is 1 and X is a fluorine atom. 5. The ferroelectric compound according to claim 2, wherein n is 1 and X is a chlorine atom. 6. The ferroelectric compound according to claim 3, 4 or 5, wherein R ^* is (S) -2-methylbutyl group. 7. An optically active 1-methylpropyl group, wherein R ^* is
The ferroelectric compound according to claim 3, which is a group selected from the group consisting of a 1-methylpropyl group and a 2-chloropropyl group. 8. General formula (I) (In the formula, R represents an alkyl group or an alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom or a chlorine atom, n represents 0 or 1, and when X is a fluorine atom, the ring Y is And when X is a chlorine atom, the ring Y is And R ^* represents an optically active group. ) A liquid crystal composition containing a ferroelectric compound represented by: 9. The liquid crystal composition according to claim 8, which exhibits a chiral smectic phase.