JPH09176647A - New ferroelectric liquid crystal compound, liquid crystal composition containing the same and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an arntiferroelectric liquid crystal composition which has a high speed of response as well as a widened range of temperature at which the composition is in an antiferroelectric liquid crystal phase by using a liquid crystal compound having a thiol carboxylic acid ester group vicinal to an optically active group. SOLUTION: This liquid crystal composition comprises a ferroelectric liquid crystal compound represented by the formula (wherein Y is a single bond, -O- or -COO-; (m) is 6-14; and (n) is 2-10). By adding 0.1-50.0wt.%, desirably 1.0-20.0wt.% liquid crystal compound represented by the formula to another antiferroelectric liquid crystal compound or composition, the temperature at which an antiferroelectric liquid crystal phase appears can be raised, and the response speed τ can be retained or slightly improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel liquid crystal compound having a thiolcarboxylic acid ester group adjacent to an optically active group, a liquid crystal composition containing the same, and a liquid crystal display device.

[0002]

2. Description of the Related Art Liquid crystal display devices are 1) low-voltage operable 2).
Since it has excellent features such as low power consumption, 3) thin display, and 4) light receiving type, TN method, STN method,
A guest-host method has been developed and put to practical use.

However, those using nematic liquid crystals which are widely used at present have a response speed of several msec to several tens m.
There is a drawback of as slow as sec, and there are various restrictions in application.

In order to solve these problems, an STN method and an active matrix method using thin-layer transistors have been developed. However, STN-type display elements have excellent display quality such as display contrast and viewing angle. However, there is a problem that high accuracy is required for controlling the cell gap and the tilt angle, and that the response is slightly slow.

For this reason, there is a demand for the development of a new liquid crystal display system having excellent responsiveness, and the optical response time is μs
Attempts have been made to develop ferroelectric liquid crystals capable of realizing ultra-high-speed devices as short as c-orders.

Ferroelectric liquid crystals were first described in 1975 by Meyor.
DOBMMBC (p-decyloxybenzylidene-p-amino-2-methylbutylcinnamate) was synthesized for the first time (Le Journal de Phys).
sque, 36, 1975, L-69).

Further, in 1980, Clark and Lag
Ferroelectric liquid crystals have attracted a great deal of attention since the reporting of characteristics on display devices such as the fast response time of DOBAMBC in sub-microseconds and memory characteristics by AWall [N. A. Clark, et al. , Appl.
Phys. Lett. 36.899 (1980)].

However, their methods have many technical problems for practical use. In particular, there is no material showing a ferroelectric liquid crystal at room temperature, and it is effective for controlling the alignment of liquid crystal molecules indispensable for a display. No practical method has been established.

Since this report, various attempts have been made from both sides of the liquid crystal material / device, and a display device utilizing switching between two twisted states has been prototyped. A high-speed electro-optical device using the same has also been disclosed in, for example, No. 107216, but high contrast and proper threshold characteristics have not been obtained.

[0010] From such a viewpoint, other switching methods have been searched, and a transient scattering method has been proposed.
Then, in 1988, the present inventors reported a three-state switching method of a liquid crystal having a tristable state [A.
D. L. Chandani, T .; Hagiwara,
Y. Suzuki et al. , Japan. J. of
Appl. Phys. , 27, (5), L729-L7
32 (1988)].

The above-mentioned "having three states" means a liquid crystal electro-optical device in which a ferroelectric liquid crystal is sandwiched between a first electrode substrate and a second electrode substrate which is arranged with a predetermined gap. 1 is configured so that a voltage for forming an electric field is applied to the first and second electrode substrates, and when a voltage is applied as a triangular wave shown in FIG. In addition, the ferroelectric liquid crystal has a first stable state [1 in FIG. 1 (D)] when there is no electric field, and when the electric field is applied, the molecular orientation has the first stable state. It has a second stable state [2 in FIG. 1 (D)] different from the stable state, and further has a third molecular orientation stable state [different from the first and second stable states with respect to the other electric field direction]. Figure 1 (D)
3] is included. Regarding the liquid crystal electro-optical device utilizing the tri-stable state, that is, the tri-state, the applicant of the present application filed as Japanese Patent Application No. 63-70212 and is disclosed in Japanese Patent Laid-Open No. 2-153322.

The characteristics of the antiferroelectric liquid crystal exhibiting a tristable state will be described in more detail. Clark / Ragawell (Cla
In the surface-stabilized ferroelectric liquid crystal device proposed by rk-Lagawall, two stable liquid crystal molecules in which the ferroelectric liquid crystal molecules are uniformly aligned in one direction in the S ^* C phase as shown in FIGS. 2 (a) and 2 (b). A state is shown, which is stabilized in one of the states depending on the direction of the applied electric field, and the state is maintained even when the electric field is cut off.

However, in practice, the orientation state of the ferroelectric liquid crystal molecules shows a twisted two state in which the director of the liquid crystal molecules is twisted, or shows a Chevron structure in which the layer is bent in a square shape. With the Sieblon layer structure, the switching angle becomes small, which causes low contrast, which is a major obstacle to practical use.

On the other hand, in the S ^* (3) phase in which the "anti" ferroelectric liquid crystal exhibits a tristable state, in the above-mentioned liquid crystal electro-optical device, when there is no electric field, as shown in FIG. The molecules are tilted in opposite directions and arranged antiparallel, and the dipoles of the liquid crystal molecules cancel each other. Therefore, the spontaneous polarization is canceled in the entire liquid crystal layer. The liquid crystal phase showing this molecular arrangement corresponds to 1 in FIG.

Further, when a voltage sufficiently higher than the threshold value of (+) or (-) is applied, FIGS.
Are tilted in the same direction and arranged in parallel. In this state, the dipoles of the molecules are also aligned in the same direction, so that spontaneous polarization occurs and a ferroelectric phase is formed. That is, in the S ^* (3) phase of the “anti” ferroelectric liquid crystal, the “anti” ferroelectric phase when there is no electric field and the two ferroelectric phases depending on the polarity of the applied electric field are stable, and the “anti” ferroelectric liquid crystal is stable. Switching between the three stable states is performed with a DC threshold value between the phase and the two ferroelectric phases. Due to the change in the liquid crystal molecule arrangement accompanying the switching, the light transmittance changes in a double hysteresis shown in FIG.

A memory effect can be realized by applying a bias voltage to the double hysteresis as shown in FIG. 4A and further superimposing a pulse voltage.

Further, by applying an electric field, the layer of the ferroelectric phase is stretched to form a book Schierf structure. On the other hand, the "anti" ferroelectric phase in the third stable state has a similar bookshelf structure. Since the layer structure switching by the application of the electric field gives a dynamic shear to the liquid crystal layer, alignment defects are improved during driving, and good molecular alignment can be realized.

In the "anti" ferroelectric liquid crystal, since the image display is performed by alternately using the hysteresis on both the positive side and the negative side, it is possible to prevent the afterimage phenomenon of the image due to the accumulation of the internal electric field due to the spontaneous polarization. You can

As described above, the "anti" ferroelectric liquid crystal is
It can be said that this is a very useful liquid crystal compound capable of 1) high-speed response, 2) high contrast and a wide viewing angle, and 3) excellent alignment characteristics and a memory effect.

Regarding the liquid crystal phase showing the tristable state of the "anti" ferroelectric liquid crystal, 1) A. D. L. Chandani
et al., Japan J. et al. Appl. Phys., 2
8 , L-1265 (1989), 2) H.E. Orihar
a et al., JapanJ. Appl. Phys.,
29 , L-333 (1990),
Due to its "anti" ferroelectric properties, the S ^* CA phase (Antive
rroelectricStic C ^* phase). The present inventors have defined this liquid crystal phase as the S ^* (3) phase because it switches between the three stable states.

Liquid crystal compounds having a "stable" antiferroelectric phase S ^* (3) showing a tristable state in the phase series are disclosed in Japanese Patent Application Laid-Open Nos. 1-331667, 1-316372 and 1-316372. There are JP-A-1-316339, JP-A-2-28128, and JP-A-1-213390 of Ichihashi et al. As a liquid crystal electro-optical device utilizing a tristable state, the present applicant has JP-A-2-40625, Kaihei 2-153322
And Japanese Patent Application Laid-Open No. 2-173724.

When the "anti" ferroelectric liquid crystal is applied to a liquid crystal display, 1) operating temperature range, 2) response speed, 3)
It is difficult to satisfy all the spontaneous polarization, 4) hysteresis characteristics, etc. with a single liquid crystal, and it is usually prepared as a mixed liquid crystal of ten or more kinds.

For applications of antiferroelectric liquid crystal displays,
There are OA, vehicle-mounted, projector, etc., and it is important to have a high-speed response in a low temperature range and to take an antiferroelectric phase even at a high temperature. That is, it is required to take an antiferroelectric liquid crystal phase in a temperature range as wide as possible. Therefore, in order to perform blending so that the antiferroelectric phase appears at a high temperature, it is necessary to add a liquid crystal compound in which a smectic phase appears at a high temperature. However, when such a compound is added, there is a problem that the response speed becomes slower than before addition.

[0024]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a novel liquid crystal compound exhibiting liquid crystallinity and a high response speed (or decrease in response speed) while expanding the temperature range of the antiferroelectric liquid crystal phase. To provide an antiferroelectric liquid crystal composition.

[0025]

One of the aspects of the present invention is to provide the following general formula (1):

Embedded image (In the formula, Y is a single bond, a group selected from the group consisting of —O— and —COO—, m is an integer of 6 to 14, and n is 2
Is an integer of 10 to 10. ) Relates to a ferroelectric liquid crystal compound.

Another aspect of the present invention relates to a liquid crystal composition containing at least one ferroelectric liquid crystal compound according to claim 1.

Yet another aspect of the present invention relates to a liquid crystal display device using the liquid crystal composition according to claim 2.

In particular, the following general formula (1) of the present invention:

Embedded image (In the formula, Y is a single bond, a group selected from the group consisting of —O— and —COO—, m is an integer of 6 to 14, and n is 2
Is an integer of 10 to 10. ) 0.1 wt% to 50.0 wt%, preferably 1.0 wt% to 20.0 wt% of the total amount of the liquid crystal compound represented by (4) in other antiferroelectric liquid crystal compounds or other antiferroelectric liquid crystal compositions. %, The appearance temperature of the antiferroelectric liquid crystal phase can be raised and the response speed τ can be maintained (or slightly improved).

Examples of the liquid crystal compound and the liquid crystal composition include Japanese Patent Application Nos. 7-248636 and 7-48636, which are filed by the present applicant.
179520, 7-179519, 7-16
No. 2859, No. 7-1641412, No. 7-16141
No. 0, No. 7-161409, No. 7-146866,
No. 7-146862, No. 7-146861, No. 7-
140001, 7-126025, 7-115.
No. 208, No. 7-94293, No. 7-93115,
7-77349, 7-74480, 6-28.
No. 7399, No. 6-277114, No. 6-27711
No. 3, No. 6-277111, No. 6-277110,
6-277109, 6-243320, 6-
248649, 6-234220, 5-215.
No. 060, No. 5-140088, and the like, and known antiferroelectric liquid crystal compounds and compositions can be given.

The method of measuring the response speed in the present invention is as follows. That is, the thickness is 2 μm, which is made of glass with a transparent electrode on which polyimide is applied and subjected to rubbing treatment
The measuring compound or composition was injected into the cell of No. 2, and the liquid crystal measuring cell thus prepared was set on the hot stage, and the cell was placed in a deflection microscope with a photomultiplier tube with two deflection plates orthogonal to each other without an electric field. It was arranged so as to have a dark field. When the liquid crystal in the cell is in the antiferroelectric phase, the cell shown in FIG.
The response speed τ can be obtained from the change in the relative transmittance of light when a ± 50 V rectangular wave as shown in FIG. τ
Is from the state of the ferroelectric phase (at the end of the rectangular wave voltage on the negative side) to the state of the next ferroelectric phase via the state of the antiferroelectric phase (the relative transmittance becomes 90% by applying the rectangular wave voltage on the positive side) Time), the unit is μsec
It is.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION The novel liquid crystal compound of the present invention is
It can be produced by the following synthetic route.

The first step,

Embedded image

Second step,

Embedded image

Third step,

[Chemical 6]

[0035]

The present invention will be described below with reference to examples.
The present invention is not limited to this.

Example 1 The following formula

Embedded image 4- (1-methylheptylthiocarbonyl) represented by
Process for producing phenyl 4-n-nonyloxyphenyl benzoate

1. Synthesis of 2-octathiol (corresponding to the first step) 52 g of S-form 2-octanol was dissolved in 520 ml of pyridine, and tosyl chloride (TsCl) was added thereto while cooling with ice.
1 g divided charge is added and the reaction is carried out for 5 hours while maintaining the temperature. The reaction solution was dispersed in dilute hydrochloric acid, extracted with ether, washed with saturated aqueous sodium hydrogen carbonate and saturated brine, and the solvent was evaporated to give a crude product 2-
Obtained octyl syl ester. This was purified by silica gel chromatography to obtain a purified product with a yield of 75%. 56.
8 g of 2-octyl siltyl ester and 48 g of potassium xanthate were heated and stirred in 600 ml of acetone for 18 hours, the solid matter was filtered off, the acetone was distilled off with an evaporator, and the residual oily substance was purified by silica gel chromatography to obtain 22.5 g. To obtain R-form 2-octanol xanthate. 30 ml of ethylenediamine was added to 22.5 g of 2-octanol xanthate and the mixture was reacted at room temperature for 5 hours under a nitrogen atmosphere. The reaction solution was dispersed in diluted hydrochloric acid, extracted with benzene, washed with diluted sulfuric acid, dried over anhydrous sodium sulfate, and benzene was distilled off to obtain 6.8 g of 2-octathiol.

2. Synthesis of 4-nonyloxybiphenylcarboxybenzoic acid (corresponding to the second step) 37 g of 4-nonyloxybiphenylcarboxybenzoic acid chloride and 13.8 g of parahydroxybenzoic acid were put in 200 ml of a dichloromethane solvent, and 2 g of dimethylaminopyridine (DMAP) was added. Is added and the mixture is stirred under a dry nitrogen atmosphere at room temperature for about 20 hours. Disperse the reaction solution in water,
The aqueous phase is made neutral and extracted with dichloromethane. After drying this over magnesium sulfate, the solvent was distilled off to obtain 30 g of a target crude product.

3. Final reaction Synthesis of 4- (1-methylheptylthiocarbonyl) phenyl 4-n-nonyloxybiphenylbenzoic acid ester (corresponding to the third step) 1. 16 g of 4-nonyloxybiphenylcarboxybenzoic acid obtained in the reaction of 1., 3.4 g of 2-octathiol and a catalytic amount of DMAP were put in 100 ml of dichloromethane, and EDC.HCl [1- (3-dimethylaminopropyl) was added.
-3-ethylcarbodiimide hydrochloride] as a dehydrating agent at room temperature for 8 to 12 hours. The reaction solution was extracted with water and dichloromethane, dried over magnesium sulfate, and then the solvent was distilled off to obtain 13 g of a crude product. Purification using silica gel chromatography gave 8.5 g of a purified product.

The following formula of Example 1 thus obtained was obtained.

Embedded image The following phase transition temperature was obtained by observing the liquid crystal compound represented by the above with a polarization microscope with a hot stage.

[Table 1]

The compound of Example 1 was added to 10 parts by weight of 100 parts by weight of the following basic antiferroelectric liquid crystal composition to obtain a novel antiferroelectric liquid crystal composition (I) of the present invention.

[0042]

Embedded image The following phase transition temperatures were obtained by observing this basic antiferroelectric liquid crystal composition with a polarization microscope equipped with a hot stage.

[Table 2]

The response speed τ of the antiferroelectric liquid crystal composition of Example 1 is as follows.

[Table 3]

Comparative Example 1 As a comparative example, the following phase transition temperatures were obtained by observing the basic antiferroelectric liquid crystal composition with a polarizing microscope equipped with a hot stage.

[Table 4]

The response speed τ of the antiferroelectric liquid crystal composition of Comparative Example 1 is as follows.

[Table 5]

Example 2 In the same manner as in Example 1 except that equimolar 4-nonylbiphenylcarboxybenzoic acid chloride was used in place of 4-nonyloxybiphenylcarboxybenzoic acid chloride of Example 1, -(1-Methylheptylthiocarbonyl) phenyl 4-n-nonylbiphenylbenzoic acid ester was obtained.

Embedded image

The following phase transition temperatures were obtained by observing the liquid crystal compound with a polarizing microscope equipped with a hot stage.

[Table 6]

4- (1-Methylheptylthiocarbonyl) phenyl 4-n-nonylbiphenyl benzoate 1 was added to 100 parts by weight of the basic antiferroelectric liquid crystal composition.
0 part by weight was added to obtain a novel antiferroelectric liquid crystal composition (II) of the present invention.

The following phase transition temperatures were obtained by observing the antiferroelectric liquid crystal composition (II) with a polarizing microscope equipped with a hot stage.

[Table 7]

The response speed τ of the antiferroelectric liquid crystal composition (II) is as follows.

[0051]

[Table 8]

[0052]

【effect】

(1) A novel liquid crystal compound can be provided by the present invention. (2) The composition of the present invention to which the novel liquid crystal compound of the present invention is added has a temperature at which an antiferroelectric liquid crystal phase can appear as compared with the antiferroelectric liquid crystal composition of the present invention to which the novel liquid crystal compound is not added. The range was expanded, and the response speed at room temperature (around 30 ° C.) was slightly improved, showing extremely favorable results, which is different from the tendency that was conventionally considered to be an antinomy.

[Brief description of the drawings]

1 (A) shows an applied triangular wave, (B) shows a commercially available nematic liquid crystal, (C) shows a two-state liquid crystal, and (D) shows a tristable state liquid crystal. .

FIG. 2 shows two stable alignment states of a ferroelectric liquid crystal molecule proposed by Clark / Ragawell.

FIG. 3A shows three stable alignment states of the “anti” ferroelectric liquid crystal molecule of the present invention, and FIG. 3B shows each of (a), (b), and (c) of (A). ) Shows the three-state switching and the change in the liquid crystal molecular alignment.

FIG. 4 is an applied voltage-light transmittance characteristic diagram showing that the “anti” ferroelectric liquid crystal molecules change their light transmittance by drawing a double hysteresis with respect to an applied voltage.

FIG. 5A shows a relationship between applied voltage and time, and FIG.
Is a graph showing a response state of liquid crystal molecules when the applied voltage is applied.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeharu Hashimoto 3-5 Kasumigaseki, Chiyoda-ku, Tokyo Showa Shell Sekiyu Co., Ltd.

Claims (3)

[Claims] 1. The following general formula (1): (In the formula, Y is a single bond, a group selected from the group consisting of —O— and —COO—, m is an integer of 6 to 14, and n is 2
Is an integer of 10 to 10. ) A ferroelectric liquid crystal compound represented by. 2. A liquid crystal composition containing at least one kind of the ferroelectric liquid crystal compound according to claim 1. 3. A liquid crystal display device using the liquid crystal composition according to claim 2.