JPH06102635B2 - Novel liquid crystal compound and liquid crystal composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound and a liquid crystal composition, and particularly to a liquid crystal material having ferroelectricity. In particular, 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) and NAClark et al., Appl.Phy
s.Lett. 36 P899 (1980)), a display device using this can obtain a high-speed response of about 100 times or more compared with conventional liquid crystal, and can be used for moving images such as televisions and high-speed optical shutters. It can be expected to be applied to display elements 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 bases such as p-decyloxybenzylideneaminocinnamic acid (S) -2-methylbutyl (abbreviated as DOBAMBC), which is known as the first synthesized ferroelectric liquid crystal, is used. LCD can be mentioned,
All of these have drawbacks in chemical stability against water, light, etc., and are not suitable for practical use.

(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) KY
oshino et al., Japanese J. of Appl. Physics 23 L175
(1984); 5) Isogai et al., JP-A-59-98051) Goodby et al. Have already reported some chemically stable chiral smectic liquid crystals. (1) JWGoodby et al., Liquid Crystals & Ord
ered Fluids Vol.4 P1 ~; 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 at a high temperature region, or is monotropic even at a 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,
Disclosed is a novel liquid crystal compound capable of exhibiting a liquid crystal phase having a ferroelectric property near room temperature, particularly a chiral smectic C phase, by itself or in combination. The present invention provides a liquid crystal composition of

<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 alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom, a chlorine atom or a nitro group, 2MB ^* represents an optically active 2-methylbutyl group, n
Represents 0 or 1, but when n = 0, X represents a fluorine atom or a chlorine atom, and when n = 1, X represents a nitro group. The present invention provides a novel ferroelectric liquid crystal 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, the optically active group is linked to the benzene ring by an ether bond and the condition is satisfied, so that introduction thereof is easy.

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 a compound represented by the general formula (I) will be described. Compound I has the general formula (II) (In the formula, R represents an alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom, a chlorine atom or a nitro group, and n represents 0 or 1.) Referred to as chloride II)
And the general formula (III) (In the formula, R ^* represents an optically active alkyl group.) An optically active phenol derivative (hereinafter, referred to as phenol derivative III) can be easily reacted by reacting in the presence of a basic substance such as pyridine. Obtainable.

The acid chloride II has the general formula (IV) (In the formula, R and X have the same meanings as in the general formula (II).) A benzoic acid derivative (hereinafter referred to as carboxylic acid IV) is reacted with a chlorinating agent such as thionyl chloride or phosphorus oxychloride. It can be easily obtained. At this time, it may be carried out in the presence of a solvent or a basic substance (such as pyridine).

This acid chloride II is easily hydrolyzed, and it is hard to say that it is very suitable for purification treatment and 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 can be easily obtained by directly nitrating or chlorinating 4'-alkoxybiphenyl-4-carboxylic acid or 4-alkoxybenzoic acid when X is a nitro group or a chlorine atom. When is a fluorine atom, it can be obtained by nitration, reductive amination, diazotization, and fluorination. Alternatively, it can also be obtained by nitrating, fluorinating, or chlorinating 4'-hydroxybiphenyl-4-carboxylic acid or 4-hydroxybenzoic acid in the same manner, and alkylating them by a conventional method. .

On the other hand, the phenol derivative III can be more easily obtained from hydroquinone and an optically active alcohol tosylate or an optically active halide.

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.

<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 3-Fluoro-4-dodecyloxybenzoic acid 4-((S) -2-
Synthesis of methylbutoxy) phenyl 3-fluoro-4-dodecyloxybenzoic acid 615 mg (2 mmol)
Was dissolved in 10 ml of dichloromethane and 3 ml of thionyl chloride was added. 0.5 ml of pyridine was added to this solution, and the mixture was heated with stirring under reflux of the solvent for 3 hours, and then excess thionyl chloride was distilled off under reduced pressure. The oily 3-fluoro-4-dodecyloxybenzoic acid chloride obtained was dissolved in 5 ml of dichloromethane, and then dissolved in 5 ml of dichloromethane and 1 ml of pyridine. 4-((S) -2-methylbutoxy) phenol 360 m
g was added, and the mixture was heated with stirring under reflux of the solvent for 3 hours. After cooling down,
Ether (50 ml) was added, the mixture was washed with 10% aqueous hydrochloric acid, water and then saturated brine, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 920 mg of a white crude product. Purified by silica gel column chromatography (chloroform / hexane = 1/1), white crystals of 4-((S) -2-methylbutoxy) phenyl 3-fluoro-4-dodecyloxybenzoate (695 mg, yield 75%) ) Got.

The structure was confirmed by infrared absorption spectrum (IR), mass spectrum (MS) and nuclear magnetic absorption spectrum (NMR).

IR: 1715,1600,1565,1500,1350,1280,1180,1120,1025,79
0,750 cm ^-1 MS: 470 (M ⁺ ) This compound showed a chiral smectic C phase under cooling from the isotropic liquid phase. The phase transition temperature is shown below.

44.5 ° C (Iso-SA), 40.3 ° C (SA-SC ^* ), 54 ° C (C →
I) Here, Iso represents an isotropic liquid phase, SA represents a smectic A phase, SC ^* represents a chiral smectic C phase, and C represents a crystalline phase.

In Example 1, instead of 3-fluoro-4-dodecyloxybenzoic acid, other 3-fluoro-4-alkoxybenzoic acid, 3-chloro-4-alkoxybenzoic acid, 3-nitro-4-alkoxybenzoic acid Using 3'-nitro-4'-alkoxybiphenyl-4-carboxylic acid and the like, the corresponding compound I was obtained in exactly the same manner. The following table shows the phase transition temperatures of typical compounds among them.

In the table, · indicates that the phase exists, − indicates that the phase does not exist, and ○ indicates that the phase exists, but it is difficult to measure the phase transition temperature due to crystallization. ,
・ The numerical value on the right of indicates the transition temperature from that phase to the higher temperature phase.

(Example 2) Preparation of liquid crystal composition Among the compounds shown in Table 1, the compound (No. 1) 18.4
%, The compound of (No.2) 18.3% by weight, the compound of (No.3) 18.3% by weight, 3-fluoro-4-dodecyloxybenzoic acid [4- [4-(( S) -2-Methylbutoxy] phenyl] phenyl 11.3% by weight, 4-fluoro-4-tetradecyloxybenzoic acid 4- [4-((S) -2-
Methylbutoxy) phenyl] phenyl 11.2% by weight and 3'-fluoro-4'-dodecyloxybiphenyl-4-
Carboxylic acid 4-((S) -2-methylbutoxy) phenyl 2
A liquid crystal composition consisting of 2.5% by weight was prepared.

This liquid crystal composition showed a smectic A phase at 81 ° C. or lower and a chiral smectic C phase at room temperature of 60 ° C. or lower when cooled from the isotropic liquid phase.

The spontaneous polarization of this liquid crystal composition was measured and found to be about 40 ° C.
It was 0.6 nC / cm ² . As a result, a liquid crystal composition exhibiting ferroelectricity near room temperature was obtained.

The liquid crystal composition was left standing below freezing for a long time to be crystallized and then its melting point was measured to be about 38 ° C.

(Example 3) Preparation of liquid crystal display element Two glass transparent electrodes coated with polyimide and subjected to an alignment treatment by rubbing were attached at an interval of 2.3 µm to prepare a thin film cell. This cell was filled with the liquid crystal composition prepared in Example 2 in an isotropic liquid phase in a heated state. The mixture was gradually cooled to room temperature, the smectic A phase and then the smectic C phase were oriented, and a uniform monodomain was obtained.

An electric field (23 V _PP , 50 Hz rectangular wave) was applied to this cell at 40 ° C., and its optical switching operation was detected by a photomultiplier. The response speed was about 900 μsec. Further, when it was similarly detected at 55 ° C., it was about 450 μsec. As a result, a liquid crystal display element having a high 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. In addition to being excellent in chemical stability against light and water, a chiral smectic C phase appears in a lower temperature range.

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.

Claims (3)

[Claims] 1. A general formula (I) (In the formula, R represents an alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom, a chlorine atom or a nitro group, 2MB ^* represents an optically active 2-methylbutyl group, n
Represents 0 or 1, but when n = 0, X represents a fluorine atom or a chlorine atom, and when n = 1, X represents a nitro group. ) A novel liquid crystalline compound represented by 2. General formula (I) (In the formula, R represents an alkoxyl group having 1 to 20 carbon atoms, X represents a fluorine atom, a chlorine atom or a nitro group, 2MB ^* represents an optically active 2-methylbutyl group,
n represents 0 or 1, but when n = 0, X represents a fluorine atom or a chlorine atom, and when n = 1, X represents a nitro group. ) A liquid crystal composition containing a novel liquid crystal compound represented by 3. The liquid crystal composition according to claim 2, which exhibits a chiral smectic phase.