JPH11158121A - Liquid crystal compound and antiferroelectric liquid crystal composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a new antiferroelectric liquid crystal compound which has stable antiferroelectricity and excellent temperature dependency of response speed enough to use for a display. SOLUTION: This compound shown by the formula [(m) is 4-14; (n) is 2-10; Cf is CF3 , CH3 , CCIF2 CCl2 F; * denotes optically active carbon] [e.g. 4-(1,1,1- trifluoro-2-hexyloxycarbonyl)phenyl-4'-(9-decenyloxy)-2-fluorobiphenyl-4- carboxylate] is obtained by the reaction of a compound which is obtained by the reaction of 4'-alkenyloxy-3-fluoro-4-biphenylcarboxylic acid with a chlorinating agent (e.g. thionyl chloride) with (1,1,1-trifluoro-2-alkyl)-4-hydroxybenzoate in methylene chloricle as a solvent in the presence of triethylamine and/or dimethylaminopyridine as catalyst(s) under nitrogen gas at room temperature over night or longer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiferroelectric liquid crystal compound exhibiting stable antiferroelectricity at around room temperature and having excellent temperature dependence of response speed which is an indispensable characteristic for display display.

[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 into practical use. However, those using a nematic liquid crystal which is widely used at present have a response speed of several milliseconds.
It has a drawback as slow as c to several tens of msec, and is subject to various restrictions in application.

In order to solve these problems, the STN method and the active matrix method using thin-layer transistors have been developed. However, the STN type display element has 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.

[0004] 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.

[0005] Ferroelectric liquid crystals were introduced in 1975 by Meyer.
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 method has 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.

[0008] 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 experimentally manufactured. No. 107216, but high contrast and proper threshold characteristics have not been obtained.

From such a viewpoint, other switching schemes have been searched, and a transient scattering scheme 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" refers to a liquid crystal electro-optical device in which a ferroelectric liquid crystal is sandwiched between a first electrode substrate and a second electrode substrate arranged at a predetermined gap. Wherein 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. 1A, the ferroelectric liquid crystal is applied as shown in FIG. 1D. Has a second stable state in which the molecular orientation has a first stable state (1 in FIG. 1D) when no electric field is applied, and the molecular orientation is different from the first stable state in one electric field direction when an electric field is applied. State (2 in FIG. 1D) and a third molecular orientation stable state (3 in FIG. 1D) different from the first and second stable states in the other electric field direction. The applicant of the present invention discloses a three-stable state, that is, a liquid crystal electro-optical device utilizing the three states.
No. 3-70212 and Japanese Patent Application Laid-Open No. Hei 2-15332.
Published as Issue 2.

The characteristics of the antiferroelectric liquid crystal exhibiting a tristable state will be described in more detail. Clark / Lagerval (C
In the surface-stabilized ferroelectric liquid crystal device proposed by L.Lark-Lagawall, two 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, and the state is stabilized to 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. In the case of the Chevron layer structure, the switching angle becomes small and causes a low contrast, which is a major obstacle for 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, the molecules are reversed in each adjacent layer as shown in FIG. 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 exhibiting this molecular arrangement corresponds to 1 in FIG. 1D.

Further, when a voltage sufficiently higher than the threshold value of (+) or (-) is applied, FIGS.
Are arranged in parallel in the same direction. 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 in the absence of an electric field and the two ferroelectric phases depending on the polarity of the applied electric field become stable, and the “anti” ferroelectric phase becomes stable. "Switching between three stable states with a DC threshold value between a ferroelectric phase and 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. This double
As shown in FIG. 4A, a memory effect can be realized by applying a bias voltage to the hysteresis and further superimposing a pulse voltage.

Further, the layer of the ferroelectric phase is stretched by the application of an electric field, thereby forming a bookshelf 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 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, image display is performed using both the positive and negative hysteresis alternately, so that the afterimage phenomenon of an image due to accumulation of an internal electric field based on spontaneous polarization can be prevented.

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.

For the liquid crystal phase exhibiting 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
rroelectric Sectic 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 an "anti" ferroelectric phase S ^* (3) exhibiting a tristable state in a phase series are disclosed in JP-A-1-316367, JP-A-1-316372 and JP-A-1-316372, filed by the present inventors. There are JP-A-1-316339, JP-A-2-28128 and JP-A-1-213390 such as Ichihashi. As a liquid crystal electro-optical device utilizing a tristable state, the applicant of the present invention is disclosed in JP-A-2-40625. Kaihei 2-153322
And Japanese Patent Application Laid-Open No. 2-173724.

When an "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 of spontaneous polarization and 4) hysteresis characteristics etc. with a single liquid crystal, and it is usually prepared as a dozen or more kinds of mixed liquid crystal.

At present, antiferroelectric liquid crystal compounds, which are generally known as antiferroelectric liquid crystal materials, have a large temperature dependence of response speed, and may cause defects such as display unevenness when displayed on a display. There is concern that there is.

[0021]

SUMMARY OF THE INVENTION An object of the present invention is to modify the main skeleton of a conventionally known antiferroelectric liquid crystal compound, specifically by selecting a fluorine-modified site of the main skeleton. In addition, by introducing a double bond to the terminal of the alkyl group on the achiral side of a conventionally known antiferroelectric liquid crystal compound, while exhibiting stable antiferroelectricity,
An object of the present invention is to provide a novel antiferroelectric liquid crystal compound which is sufficiently usable in a display and has excellent temperature dependence of response speed.

[0022]

Means for Solving the Problems In order to achieve the above object, the present inventors have specifically proposed an antiferroelectric liquid crystal compound in which a fluorine modification site in a main skeleton of a conventional antiferroelectric liquid crystal compound is optimized. Efforts have been made for the synthesis of crystalline liquid crystal compounds. In addition, research has been conducted on the synthesis of antiferroelectric liquid crystal compounds in which a double bond is introduced into an alkyl group terminal on the achiral side of a conventional antiferroelectric liquid crystal compound. Furthermore, when synthesizing the compound group, research has been conducted on the synthesis of a novel antiferroelectric liquid crystal compound modified with the two fluorine elements. As a result, not only the conventional antiferroelectric liquid crystal compound but also an antiferroelectric liquid crystal compound having more excellent temperature dependence of the response speed by combining the modifications, and thus completing the present invention.

The first aspect of the present invention is the general formula (1)

Embedded image (Wherein, m is an integer of 4 to 14, n is an integer of 2 to 10, C
f is a group selected from the group consisting of CF ₃ , CH ₃ , CCIF ₂ and CCIF ₂ F, and * indicates an optically active carbon. )
And an antiferroelectric liquid crystal compound represented by the formula:

A second aspect of the present invention relates to an antiferroelectric liquid crystal composition comprising at least one antiferroelectric liquid crystal compound according to claim 1.

The compounds of the present invention are listed in the following table.

Preferred compounds of the present invention are listed below.

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

[0031]

[Table 6]

[0032]

[Table 7]

[0033]

[Table 8]

A general method for synthesizing the compound of the present invention and its reaction formula are shown below. By reacting 4'-alkenyloxy-3-fluoro-4-biphenylcarboxylic acid (i) with a chlorinating agent such as thionyl chloride, 4'-alkenyloxy-3-fluoro-4-biphenylcarboxylic acid chloride ( Adjust ii). To this was added (1,1,1-trifluoro-2-alkyl) -4 prepared by a conventional method.
-Reacting hydroxybenzoate (iii) with methylene chloride as a solvent, and using triethylamine (hereinafter abbreviated as TEA) and dimethylaminopyridine (hereinafter abbreviated as DMAP) as a catalyst under a nitrogen atmosphere at room temperature overnight or more. The reaction solution is washed with a hydrochloric acid solution, dried over anhydrous magnesium sulfate, and methylene chloride is distilled to obtain a crude product. This crude product was separated and purified using a mixed solution of hexane / ethyl acetate using silica gel to obtain 4- (1,1,1-
Trifluoro-2-alkoxycarbonyl) phenyl-
4'-alkenyloxy-2-fluorobiphenyl-4
Obtaining carboxylate (iv). It can be further purified using ethanol. Further, the separation and purification of the crude product, the ester synthesis, and the recrystallization of the liquid crystal can be replaced by known methods other than the methods described above.

[0035]

Embedded image

The method for measuring the response speed in the present invention is as follows. The compound was injected into a 2 μm-thick cell made of glass with a transparent electrode that had been coated with polyimide and rubbed, and the liquid crystal physical property measurement cell was set on a hot stage. It was arranged in a polarizing microscope equipped with a multiplier so as to provide a dark field without an electric field. When the liquid crystal in the cell is in the antiferroelectric phase,
The response time τ can be determined from the change in the relative transmittance of light when a rectangular wave of ± 50 V as shown in FIG. 5 is applied to the cell. τ is the state of the ferroelectric phase (at the end of the rectangular wave voltage on the minus side), the state of the next ferroelectric phase via the state of the antiferroelectric phase (the relative transmittance is 90% by applying the rectangular wave voltage on the plus side) ), And the unit is μsec.

From the response speed (τ) obtained by the above method, the temperature dependence (τI) of the response speed is calculated using the following equation (1).

ΤI (80/60) = Log (τ60) / Log (τ80) (1) Note that τI (80/60) indicates the temperature dependence at 80 to 60 ° C., and τ60 and τ80 are 60, respectively. The response speed at 80 ° C and the response speed at 80 ° C are shown. Further, the above-mentioned τI is usually 1 or more, and a smaller value indicates that the temperature dependency is better.

[0038]

The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited thereto.

Example 1

Embedded image 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl-4 '-(9-decenyloxy)
Synthesis of -2-fluorobiphenyl-4-carboxylate By reacting 3-fluoro-4'-9-decenyloxy-4-biphenylcarboxylic acid with a chlorinating agent such as thionyl chloride, 3-fluoro-4'- Prepare (9-decenyloxy) -4-biphenylcarboxylic acid chloride. To 0.26 g (0.7 mmol) of this compound, 0.20 g of (1,1,1-trifluoro-2-hexyl) -4-hydroxybenzezoate prepared by a conventional method.
(0.7 mmol) in methylene chloride as a solvent and TEA
0.07 g (0.7 mmol), DMAP 0.02 g
(0.2 mmol) as a catalyst and react at room temperature overnight or more in a nitrogen atmosphere. The reaction solution is washed with a hydrochloric acid solution, dried over anhydrous magnesium sulfate, and methylene chloride is distilled to obtain a crude product. This crude product was separated and purified with a 20/1 (v / v) mixed solution of hexane / ethyl acetate using silica gel to give 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl-.
0.34 g (82%) of 4 '-(9-decenyloxy) -2-fluorobiphenyl-4-carboxylate is obtained. It can be further purified using ethanol.

¹ H-NMR of this compound (CDCl ₃ , T
(MS standard, δ value ppm) is 8.3 to 6.9 (m, 11H), 5.9 to 5.75.
(M, 1H), 5.7-5.5 (m, 1H), 5.1-
4.9 (dd, 2H), 4.1-3.9 (t, 2H),
2.1 to 2.0 (q, 2H) 1.95 to 0.85 (m,
23H).

The above compound was injected into a cell having a thickness of 2 μm made of glass having a transparent electrode coated with polyimide and subjected to rubbing treatment. Table 9 also shows τI (80/60) represented by 1).

Comparative Example 1

Embedded image A 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl-4 '-(decyloxy) -2-fluorobiphenyl-4-carboxylate represented by is coated with polyimide and subjected to a rubbing treatment. It is injected into a cell having a thickness of 2 μm made of glass with a transparent electrode, and observed at 80 ° C. and 60 ° C. by observation with a polarizing microscope equipped with a hot stage, and τI (80/60) represented by the formula (1).
Are also shown in Table 9.

Comparative Example 2

Embedded image 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl-4 '-(9-decenyloxy) -biphenyl-4-carboxylate represented by the formula: Table 9 shows the response speed at 80 ° C. and 60 ° C. observed by a polarizing microscope equipped with a hot stage at 80 ° C. and τI (80/60) represented by the formula (1).
Shown in

Comparative Example 3

Embedded image A 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) phenyl-4 '-(decyloxy) -2-fluorobiphenyl-4-thiocarboxylate represented by Into a 2 μm-thick cell made of glass with a transparent electrode, and observed at 80 ° C. and 60 ° C. by observation with a polarizing microscope equipped with a hot stage, and τI (80/6) represented by the formula (1).
0) is also shown in Table 9.

Comparative Example 4

Embedded image 4- (1,1,1-trifluoro-2-hexyloxycarbonyl) -3-fluorophenyl-4 ′ represented by
-(9-decenyloxy) -2-fluorobiphenyl-
4-Carboxylate was injected into a 2 μm-thick cell made of glass with a transparent electrode coated with polyimide and subjected to rubbing treatment.
Table 9 also shows the response speed at 0 ° C. and 60 ° C. and τI (80/60) represented by the formula (1).

[0046]

[Table 9]

[0047]

[Discussion] 1) From the comparison between Example 1 and Comparative Examples 1, 2, and 3,
Compared with Comparative Example 1, Comparative Example 2, and Comparative Example 3, in which the temperature dependence of the response speed was superior to the conventional antiferroelectric liquid crystal compound, the antiferroelectric liquid crystal compound of Example 1 showed that It can be seen that the temperature dependence of the response speed was further improved by about 5%, about 5%, and about 1%. 2) From a comparison between Example 1 and Comparative Example 4, it was found from Japanese Patent Application No. 9-103.
It can be seen that the temperature dependency of the response speed was further improved by about 3% even in comparison with Comparative Example 4 in which the response speed was excellent in the temperature dependency invented in 834.

[0048]

[Effect] By optimizing the location of fluorine modification of the main skeleton of the conventional antiferroelectric liquid crystal compound, a double bond has been introduced into the terminal of the achiral alkyl group of the conventional antiferroelectric liquid crystal compound. As a result, an antiferroelectric liquid crystal compound exhibiting stable antiferroelectricity near room temperature and having a characteristic that the temperature dependence of response speed, which is indispensable as a display material, is small is provided.

[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 ferroelectric liquid crystal molecules proposed by Clark / Lagerval.

FIG. 3 (A) shows three stable alignment states of the “anti” ferroelectric liquid crystal molecules of the present invention, and (B) shows each of (A), (b) and (c) of A. The corresponding three-state switching and the change of the liquid crystal molecule arrangement are shown.

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.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Noriko Yamakawa 2-3-2 Daiba, Minato-ku, Tokyo Showa Shell Sekiyu KK

Claims (2)

[Claims] 1. A compound of the general formula (1) (Wherein, m is an integer of 4 to 14, n is an integer of 2 to 10, C
f is a group selected from the group consisting of CF ₃ , CH ₃ , CCIF ₂ and CCl ₂ F, and * indicates an optically active carbon. An antiferroelectric liquid crystal compound represented by the formula: 2. An antiferroelectric liquid crystal composition comprising at least one antiferroelectric liquid crystal compound according to claim 1.