JPH05232424A - Liquid crystalline compound, composition and display device - Google Patents

Abstract

PURPOSE:To obtain a high contrast by using a specific liquid crystal compsn. and oriented films having a high pretilt angle. CONSTITUTION:The novel compds. expressed by formula and the liquid crystal compsn. 7 contg. at least one kind of these compds. are formed. Transparent electrodes 2a, 2b are respectively formed on the opposite surfaces of a pair of light translucent substrates 9, 10. Insulating films covering the respective transparent electrodes 2a, 2b are formed and the org. oriented films 4a, 4b covering these films are formed. The liquid crystal 7 is packed between a pair of the light translucent substrates 9, 10. A pair of the substrates 9, 10 having the oriented films 4a, 4b subjected to an orientation treatment are so disposed to face each other that the orientation treatment directions of the oriented films 4a, 4b are approximately parallel with each other. The liquid crystal compsn. expressed by formula is incorporated between these substrates 9 and 10. The pretilt angle at the boundary between the oriented films 4a, 4b and the liquid crystal compsn. 7 is preferably 8 deg.. In the formula, R1 and R2 may be the same or different and denote an alkyl group having 1 to 15c of a straight chain or branched chain; m, n denote an integer of 0 or 1.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystal compound, a liquid crystal composition containing the same and a liquid crystal device.

[0002]

2. Description of the Related Art At present, liquid crystal display devices are used in a wide range of fields such as timepieces, calculators, office automation equipment such as word processors and personal computers, pocket televisions, etc., but generally used liquid crystal display devices utilize a nematic phase. It was done. As a liquid crystal display device using nematic liquid crystal, a twisted nematic type (Twisted Nemati
c TN type liquid crystal display device, Super twisted type (Supe
rtwistedBirefrengence Effect, SBE type) liquid crystal display device.

However, in the twisted nematic liquid crystal display element, there is a drawback that the driving margin becomes narrower as the number of scanning lines increases and a sufficient contrast cannot be obtained, so that it is difficult to make a large-capacity display element. .. In order to improve this TN type liquid crystal display element, a super twisted nematic (STN) type liquid crystal display element and a double layer super twisted nematic (DSTN) type liquid crystal display element have been developed. However, the display capacity of 800 × 1024 lines is currently the limit.

On the other hand, a thin film transistor (TF) is formed on the substrate.
An active matrix type liquid crystal display device in which T) is arranged has also been developed, and it has become possible to display a large capacity such as 1000 × 1000 lines, but the manufacturing process is long, the yield is likely to decrease, and the manufacturing cost is very high. It has the drawback that In addition, it is considered that this method is difficult to manufacture a large-capacity display element such as 2000 × 2000 lines due to restrictions such as semiconductor mobility.

However, the demand for display devices in the world is becoming higher and higher,
In particular, DTP (D esk T op P ublishi
ng), EWS (E ngineering W ork
In fields such as Station, WYIWYG ( W ha
t y ou s ee i s w hat y ou g e
The concept of t) is vigorously emphasized. This is a concept of displaying the same as the one printed out on the display device. Since the resolution of the current laser printer is about 400 DPI (400 dot / inch), in order to realize the concept of WYSIWYG, a display device having at least A4 size or more and 2000 × 2000 or more resolution is required. ..

A ferroelectric liquid crystal display element (NA Clark ST Lager) is promising as a liquid crystal element capable of displaying a large capacity of 2000 × 2000 lines or more.
wall, Appl. Phys. Lett. , 36 , 899
(1980); JP-A-56-107216; U.S. Pat. No. 4367924)
Is. This liquid crystal display element is different from the field effect type nematic liquid crystal display device that utilizes the dielectric anisotropy of liquid crystal molecules, and the molecules are arranged so that the polarities of the spontaneous polarization of the ferroelectric liquid crystal and the polarity of the electric field are matched. It is a switching liquid crystal display element.

Ferroelectric liquid crystal elements are chiral smectic C
Phase, chiral smectic F phase, chiral smectic I phase, and other ferroelectric liquid crystals are used. Although these ferroelectric liquid crystals have a helical structure, it is disclosed that when these ferroelectric liquid crystals are sandwiched between liquid crystal cells having a cell thickness smaller than the helical pitch, the helical structure is unraveled. Actually, as shown in FIG. 1, it is possible to realize a state in which a region in which liquid crystal molecules are inclined and stabilized by an angle θ with respect to the smectic layer normal and a region in which liquid crystal molecules are inclined and stabilized by θ in the opposite direction are mixed. Research has revealed. By applying an electric field in the direction perpendicular to the paper surface in FIG. 1, the directions of the liquid crystal molecules and their spontaneous polarization can be made uniform, and switching between the two states can be performed by switching the polarity of the applied electric field. It can be performed. With this switching, the birefringent light changes in the ferroelectric liquid crystal in the cell, so that the transmitted light can be controlled by sandwiching the ferroelectric liquid crystal element between two polarizers. Further, even if the voltage application is stopped, the alignment of the liquid crystal molecules is maintained in the state before the voltage application is stopped by the alignment regulating force of the interface, so that the memory effect can be obtained. In addition, since the spontaneous polarization of the liquid crystal and the electric field directly act on the time required for the switching drive, a high-speed response on the order of μsec can be obtained.

As described above, the characteristics of this ferroelectric liquid crystal device include bistability, memory property, and high-speed response. Therefore, it is possible to construct a high-resolution liquid crystal display device having a large number of scanning lines by a multiplex drive system by using this ferroelectric liquid crystal, and since an active element such as a thin film transistor is not required, the manufacturing cost is reduced. It has the advantage of not increasing. In addition, the ferroelectric liquid crystal device has the advantage that it has a wide visual field, and it is highly promising as a large-capacity display-like device that realizes the concept of WYSIWYG.

[0009]

Ferroelectric liquid crystal devices have the advantages described above, but display high-contrast display without flicker in large-capacity display devices having 1000 × 1000 or more scanning lines. The following problems will arise. That is, one method for displaying without flicker is to rewrite one screen within 16.7 msec (60 Hz). In this case, the ferroelectric liquid crystal material is required to have a very high response speed. For example, 10 scan lines
In the case of 00 display elements, as can be seen from the following equation, 8.4 μ
A high-speed response of sec is required. 16.7 (msec) ÷ 1000 ÷ 2 = 8.4 μsec (Here, dividing by 2 is for ferroelectric liquid crystal,
This is because writing requires at least 2 pulses. )

However, it is not easy at present to realize the required response speed by improving the ferroelectric liquid crystal material. In addition, considering that the response speed must be further increased when producing a display device having a larger capacity, it is quite difficult to increase the capacity by increasing the speed of the liquid crystal material. You can easily imagine.

As a powerful technique for solving such a problem, a technique called partial rewriting (Kanbe, Proc. Of the Institute of Electronics, Information and Communication Engineers Special Workshop, "Optoelectronics" -Liquid Crystal Display and Related Materials-, 1990) January, p18-2
6) is proposed. This method is a method to access only where the screen needs to be rewritten. As a result, it becomes possible to provide a display element that can follow the movement of the mouse, which requires high speed in displaying graphics.

However, in order to obtain a display without flicker by using this partial rewriting method, a bias voltage which is ⅓ of the writing voltage is applied to the pixels which are not rewritten (hereinafter, this driving method will be used). Called 1/3 bias driving method). This driving method has been proposed in, for example, Japanese Patent Laid-Open No. 64-59389, but the biggest problem in using the 1/3 bias method is 1 / n
A bias voltage of 3 is applied, and this bias voltage causes fluctuations in the molecules of pixels that are not rewritten, resulting in a decrease in contrast. For example, the ferroelectric liquid crystal display prototyped using the partial rewriting method has not been obtained with a contrast of only 5: 1 (Kanbe, IEICE Technical Seminar, "Optoelectronics" -related to liquid crystal display. Materials-1990 1
Mon, p18-26). Further, the present inventors have produced a display device by combining various ferroelectric liquid crystal compositions with liquid crystal devices having various configurations, but it was obtained when a display was performed using the 1/3 bias driving method. The contrast value is 1.
It was about 5 to 8 and was a very unsatisfactory product.

In order to solve such a problem of contrast, it is necessary to apply an appropriate liquid crystal material to a ferroelectric liquid crystal device having an appropriate constitution. From such a viewpoint, a novel liquid crystal compound useful for improving contrast, a liquid crystal composition using the same, and a liquid crystal element are required. A practical ferroelectric liquid crystal composition is usually prepared by mixing a plurality of components. At times, a compound that does not exhibit a smectic C phase or a compound that does not exhibit a liquid crystal phase at all may be used as the component. The properties required for the ferroelectric liquid crystal composition include not only the high contrast achieved by combining with an appropriate device structure, but also the following properties. That is, the response speed is required to be high, and from this point, low viscosity is required. Increasing the spontaneous polarization is also useful for increasing the response speed, but in order to obtain good bistability of the ferroelectric liquid crystal device, it is possible to obtain good alignment when applied to the ferroelectric liquid crystal device. In order to obtain the property, the phase sequence of the ferroelectric liquid crystal composition is important, and in general, INAC (Isotrop)
ic-Nematic-Smectic A- Smec
The tic C ) phase series is most preferred. A long helical pitch in the nematic phase and smectic C phase is also necessary for obtaining good orientation. It is also required to be stable around room temperature, not colored, not to have a high viscosity, and to have an appropriate tilt angle in the smectic C phase.

The present invention has been made under such circumstances, and a novel liquid crystal compound, a liquid crystal composition, and a liquid crystal display useful for producing a practical high-contrast ferroelectric liquid crystal composition. The purpose is to provide a device.

[0015]

The present invention provides the following formula (I);

[0016]

[Chemical 2] (In the formula, R ₁ and R ₂ are the same or different and each represents a linear or branched alkyl group having 1 to 15 carbon atoms, and m and n each independently represent an integer of 0 or 1.) A novel compound represented by, and a liquid crystal composition characterized by containing at least one compound thereof, and forming transparent electrodes respectively on the surfaces facing each other of the pair of translucent substrates, each transparent electrode is coated In the liquid crystal display device, an insulating film is formed, an organic alignment film that covers the insulating film is formed, and liquid crystal is filled between a pair of transparent substrates.
A pair of substrates having alignment films that have been subjected to alignment treatment are arranged to face each other so that the alignment treatment directions of the alignment films are substantially parallel, and at least one liquid crystal composition described above is contained between the substrates. Provided is a ferroelectric liquid crystal display device.

Here, the compound of formula (I)
Chi, R₁Is preferably a straight-chain 5-12 carbon atom.
A rukyl group, more preferably linear 7 to 9 carbons
Represents an alkyl group having. Specifically, -C₇H₁₅,-
C₈H₁₇, -C₉H₁₉Is. Also R₂Is preferably straight
An alkyl group having 3 to 10 carbons in the chain is shown, and
Preferably, a linear alkyl group having 4 to 6 carbon atoms is shown.
You Specifically, -C_FourH ₉, -C_FiveH₁₁, -C₆H₁₃so
is there. Where m is preferably 1 and n is preferably
Is 0.

Specific compounds obtained by combining these include 2-cyano-4-butylphenyl 4-octyloxybenzoate, 2-cyano-4-pentylphenyl 4-octyloxybenzoate and 2-cyano-4-.
Hexylphenyl 4-octyloxybenzoate,
2-Cyano-4-pentylphenyl 4-heptyloxybenzoate and 2-cyano-4-pentylphenyl
4-nonanyloxy benzoate is mentioned.

The compound represented by the formula (I) is obtained, for example, by first reacting 2-cyano-4-alkylphenol with sodium hydroxide to obtain a sodium alkoxide. Separately from this, a desired ester compound can be obtained by reacting 4-alkoxybenzoic acid with phosphorus pentachloride to form an acid chloride and then reacting with the sodium alkoxide in a toluene solvent in the presence of pyridine.

The compound represented by the formula (I) does not necessarily show a smectic C phase, but it is apt to show a smectic A phase and a nematic phase, and it is mixed with another compound to form INA.
It can be said that it is a useful material for realizing the C-phase series. Moreover, the melting points are not high, and it is easy to mix with other compounds. It is stable both chemically and to light and is free of color.

Next, conditions for using the compound of the present invention in the liquid crystal composition will be described. The compound represented by formula (I) can be applied to various liquid crystal compositions by combining with various compounds in an appropriate ratio. In particular, it is useful when making a ferroelectric liquid crystal composition. Examples of the compounds that may be combined when the ferroelectric liquid crystal composition is prepared include the compounds represented by the chemical formulas (II) and (III).

[0022]

[Chemical 3]

[0023]

[Chemical 4] The ferroelectric liquid crystal composition of the present invention comprises the compound (I)
It can be prepared by mixing with the above-mentioned ferroelectric liquid crystal or composition. In particular, it is suitable to prepare so that the phase sequence is INAC. Usually, the content of the compound (I) is preferably 10 wt% or more as a whole, and 20 wt% or less of the whole one component contained in the compound (I) group.

When the total content of the compound (I) is less than 10 wt%, the effect of improving the contrast is insufficient by the 1/3 bias driving, and the content per single component is 20 w.
If it exceeds t%, the INAC phase series is not exhibited, and thus orientation failure occurs, which is not suitable. Various additives may be added to the ferroelectric liquid crystal composition of the present invention as long as the effects intended by the present invention are not impaired. For example, from the viewpoint of improving the orientation, another liquid crystal compound having a fluoroalkyl group at the terminal or a liquid crystal compatible compound may be blended (usually 0.01 to 1 wt%).

It is needless to say that the ferroelectric liquid crystal composition needs to exhibit a chiral smectic phase and needs to include an optically active compound having an appropriate structure, and it is appropriate to use a compound other than the compounds (II) and (III). It goes without saying that various compounds may be added. Needless to say, the compound of the present invention can be applied to various liquid crystal compositions such as a nematic liquid crystal composition, a smectic A liquid crystal composition and an antiferroelectric liquid crystal composition.

The liquid crystal composition containing the compound of the present invention can be applied to various liquid crystal elements. Next, the ferroelectric liquid crystal composition containing the compound represented by the formula (I) is applied to the ferroelectric liquid crystal element. As an example of realizing a high contrast by using a pair of substrates in a liquid crystal device in which a ferroelectric liquid crystal is sandwiched between a pair of insulating precision substrates on which at least electrodes and an alignment film subjected to uniaxial alignment treatment are formed. The directions of the uniaxial alignment treatment are parallel, the driven liquid crystal phase is a chiral smectic C phase, and the smectic layer structure in the chiral smectic C phase has a chevron structure bent in a V shape. In the temperature range, it occurs inside the area surrounded by the lightning defect that occurs in the uniaxial orientation treatment direction and the hairpin defect that occurs behind the defect, or in the uniaxial orientation treatment direction. The alignment state generated outside the region surrounded by the hairpin defect and the lightning defect generated behind the defect is a uniform state, and the ferroelectric liquid crystal is represented by the formula (I). A ferroelectric liquid crystal device characterized by containing at least one compound containing

Generally, it is said that the layer structure of the chiral smectic C layer has a febron structure which is generally in the shape of a dogleg as shown in FIG. 2 (a). There are two directions in which the layers bend, as shown in Fig. 2 (a). At this time, an alignment defect called a zigzag defect occurs at a place where the bending direction of the layer changes. FIG. 2B is a schematic diagram when observing the zigzag defect with a polarization microscope. The zigzag defect can be classified into a defect called a lightning defect and a defect called a hairpin defect. As a result of previous research, the layer structure
It has been clarified that the part with <<>> corresponds to the lightning defect and the part with the layer structure >><< corresponds to the hairpin defect (N. Hiji).
et al., Jpn. Appl. Phys., 27, L1.
(1988).). The relationship between the rubbing direction and the pretilt angle θ _P is shown in Fig. 2, and the above two orientations are called the C1 orientation and the C2 orientation because of the relationship with the rubbing direction (Kanbe, IEICE Technical Seminar Lecture Proceedings "Optoelectronics" -Liquid Crystal Display and Related Materials-, 1990
January 18th, p18-26). The case where the rubbing axis and the bending direction of the layer are the same is defined as C1 orientation (chevron 1), and the opposite case is defined as C2 orientation (chevron 2).

Now, when the pretilt angle θ _P is increased,
The difference in the alignment state of the liquid crystal molecules between the C1 orientation and the C2 orientation becomes remarkable, and when an alignment film showing a large value of 8 ° or more is used, a clear extinction position is obtained in the C1 orientation on the high temperature side. And a region showing no extinction position are observed, and in the C2 orientation on the low temperature side, only a region showing a clear extinction position is observed. It is generally accepted that the uniform orientation and the twist orientation are distinguished by the presence or absence of an extinction position (Fukuda, Takezoe, “Structure and Physical Properties of Ferroelectric Liquid Crystals”, Corona Publishing Co., Ltd., 1990, p327), now here. In the above, the one exhibiting the extinction position in the C1 orientation will be called C1U (C1 uniform) orientation, and the one not exhibiting the extinction position in the C1 orientation will be called C1T (C1 twist) orientation. Since only one type of C2 orientation was obtained, only the C2 orientation will be described.

When a voltage waveform of 1/3 bias as shown in FIG. 3 (b) is applied, the obtained contrast is as follows, and only the C1U array can realize a practically high contrast. C1U> C2 >> C1T The ferroelectric liquid crystal composition containing the compound containing the compound (I) of the present invention, when combined with an alignment film having a large pretilt angle, tends to show C1U alignment, and is driven by 1/3 bias. Gives good contrast.

FIG. 4 is a sectional view showing an example of the liquid crystal element of the present invention. A plurality of transparent electrodes 2a are arranged in a stripe pattern on a glass substrate 1a so as to be parallel to each other, and an insulating film 3a and an alignment film 4a are formed on the transparent electrode 2a. The alignment film 4a is uniaxially aligned by rubbing. Processing is performed to form the substrate 9. On the other hand, on the other side of the glass substrate 1b, a plurality of transparent electrodes 2b are formed in stripes so as to be parallel to each other under the same conditions.
The insulating film 3b and the alignment film 4b are formed thereon, and the alignment film 4
The substrate 10 is formed by subjecting b to the rubbing orientation treatment.

Next, this substrate 10 is the other substrate 9
And the alignment films 4a and 4b are opposed to each other, the transparent electrodes 2a and 2b are orthogonal to each other, and the rubbing directions are substantially the same, and the seal member 6 is spaced at an interval of about 1.5 to 3 μm.
Stick together. A liquid crystal cell 11 is produced by interposing a ferroelectric liquid crystal between these substrates 9 and 10. Furthermore, polarizing plates 12a and 12b whose polarization axes are substantially orthogonal to each other are arranged above and below the cell, and one polarization axis of the polarizing plates is made to substantially coincide with one of the optical axes of the liquid crystals of the cell to form a liquid crystal display device. To do.

Of course, the liquid crystal element for which the liquid crystal composition containing at least one of the general formula (I) can be used is not limited to the above-mentioned ferroelectric liquid crystal element, but a ferroelectric liquid crystal element having another structure, or It goes without saying that the present invention can be applied to liquid crystal elements using nematic I (TN, STN, DSTN, etc.), liquid crystal elements using smectic A phase (thermal writing, electronic, etc.), and antiferroelectric liquid crystal elements.

[0033]

【Example】

Example 1 p- (p'-octyloxyphenyl) -benzoic acid-
Synthesis of (2-cyano-4-pentyl) -phenyl p- (p'-octyloxyphenyl) -benzoic acid 0.7
0.6 g (0.0029 mol) of phosphorus pentachloride was added to g (0.0024 mol), and the mixture was heated to about 80 ° C. and reacted. Generated POC
l ₃ and the excess phosphorus pentachloride was distilled off under reduced pressure, p- (p '
-Octyloctiphenyl) -benzoic acid chloride was obtained. This is dissolved in 10 ml of toluene, 4-pentyl)
-0.7 g (0.0030 mol) of phenyl and 1 ml of pyridine (dehydrochlorinating agent) were added, and the mixture was allowed to stand at room temperature for 10 hours, then 7
After keeping at 0 ° C. for 3 hours, it was cooled to room temperature. Then, ice and hydrochloric acid were added, and the mixture was extracted with ether. The ether layer is Na
It was washed with an aqueous HCO ₃ solution, then with water, and dried over Na ₂ SO ₄ . The ether was distilled off, the residue was purified by high performance liquid chromatography (Waters Multiplet 3000 liquid chromatography; C-18 silica gel column; solvent methanol + chloroform (8: 2)) and recrystallized from ethanol. The target p- (p'-octyloxyphenyl) -benzoic acid- (2-cyano-4-pentyl) -phenyl was obtained. The infrared absorption spectrum of this compound is shown in FIG. From this spectrum, functional group, unsaturated bond, etc. could be identified, and it was found that the compound had the above-mentioned structure. Further, this compound exhibited an N phase, and its transition temperature was K68 ° C to 129 ° CI.

This compound does not exhibit a smectic phase, but is useful as a component of a liquid crystal composition. The compounds used in the examples of the present invention are shown in Table 1.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

Example 2 A liquid crystal composition N having the composition shown in Table 2 was prepared using the compounds shown in Table 1.
o. 201 was created.

[0039]

[Table 4] The transition temperature of this liquid crystal composition was as follows. This liquid crystal composition showed the INAC phase series at room temperature.

Example 3 1000 Å thick ITO on each of two glass substrates
A film is formed, a 500 Å SiO ₂ insulating film is formed on the film, and the alignment film shown in Table 3 is formed on the film with a spin coater to a thickness of 400 Å, and then a rayon cloth is used for rubbing. Uniaxial orientation treatment was performed. A liquid crystal cell was produced by bonding these substrates with a thickness of 20 μm so that the rubbing directions were anti-parallel. A nematic liquid crystal E-8 manufactured by Merck & Co., Inc. was injected into this, and the pretilt angle of the liquid crystal molecules from the substrate was measured using the magnetic field capacitance method. The results are shown in Table 3.

[0041]

[Table 5]

Example 4 A ferroelectric liquid crystal device having the structure shown in FIG. 4 was produced. A plurality of ITO transparent electrodes 2 with a thickness of 1000Å on the glass substrate 1a
a are arranged in stripes so as to be parallel to each other, and 500 Å SiO is formed as the insulating film 3a in that shape, and then PSI-A-2001 (Chiso Petrochemical Co., Ltd.) is formed as the alignment film 4a. Polyimide (manufactured by the company) was formed with a spin coater to a thickness of 400 Å, and then uniaxially oriented by rubbing with a rayon cloth to form a substrate 9. On the other hand, the glass substrate 1b on the other side was also treated under the same conditions to form the substrate 10.

Next, this substrate 9 and the other substrate 10
And so that the alignment films 4a and 4b face each other, the transparent electrodes 2a and 2b are orthogonal to each other, and the rubbing directions are substantially the same, the epoxy films are made of epoxy resin at intervals of 1.5 μm. The seal members 6 were used for bonding.
Between the substrates 9 and 10, the ferroelectric liquid crystal composition No. 3 manufactured in Example 2 was injected from the injection port by a vacuum injection method. After injecting 201, the injection port was cured with an acrylic UV curable resin to prepare the liquid crystal cell 11. Further, polarizing plates 12a and 12b whose polarizing axes are substantially orthogonal to each other are arranged above and below the cell, and one polarizing axis of the polarizing plate is made to substantially coincide with either optical axis of the liquid crystal of the cell and a liquid crystal display device is provided. did.

When the state of orientation of this ferroelectric liquid crystal element was examined, in the temperature region from the smectic C-smectic A transition point to room temperature, a region having a small C2 orientation surrounded by minute zigzag defects was found. Except for, the entire surface was C1U oriented. The tilt angle in the chiral smectic C phase of these ferroelectric liquid crystal devices was measured. The tilt angle was defined as 1/2 of the angle between the two extinction positions obtained by applying a rectangular wave of ± 10 V to the liquid crystal cell. The tilt angle was plotted against temperature (Fig. 6).

The voltage (V = ± 10) of the waveform shown in FIG.
V) was applied and the memory pulse width was measured. Figure 7
Shown in. The memory pulse width is the minimum pulse width that allows bistable switching. When the pulse width was set to the memory pulse width and the waveform of FIG. 3A was applied, a contrast of 30 or more was obtained. A voltage (V = ± 10V) having a 1/3 bias waveform shown in FIG. 3B is applied,
The memory pulse width was measured. The memory pulse width is the minimum pulse width that allows bistable switching.
The results are shown in Fig. 7. When the pulse width was set to the memory pulse width and the waveform of FIG. 3B was applied, a high contrast of 10 was obtained. In this case, it can be concluded that a good black state can be maintained even when a bias is applied, and the fluctuation of molecules due to the bias voltage is suppressed.

Comparative Example 1 Liquid crystal composition No. 1 prepared in Example 2 Of the components contained in 201, compound No. No. 126 of the ferroelectric liquid crystal composition No. 126 removed for comparison. 202 was produced. This liquid crystal composition also showed a smectic C phase at room temperature. This liquid crystal composition No. The composition of 202 is shown in Table 2. The ferroelectric liquid crystal composition No. 1 in Example 4 was used. No. 201 is a ferroelectric liquid crystal composition No. for comparison. A ferroelectric liquid crystal element was produced in the same manner as in Example 4 except that the liquid crystal element was replaced with 202. When the orientation was observed, it was observed that the memory returned to the twisted state, and the memory was only in the range of 7 ° C. from the AC point. It can be seen that the memory property of the composition of Example 4 is improved by this comparative example.

Comparative Example 2 Ferroelectric liquid crystal composition No. 1 having the composition shown in Table 2 was prepared using the compounds shown in Table 1. 206 to 211 were produced. The ferroelectric liquid crystal composition No. 1 in Example 4 was used. No. 201 is a ferroelectric liquid crystal composition No. for comparison. A ferroelectric liquid crystal element was produced in the same manner as in Example 4 except that any of 206 to 211 was substituted. Further, the ferroelectric liquid crystal composition No. 1 in Example 4 was used. No. 201 is a ferroelectric liquid crystal composition No. for comparison. 206 to 211, and the alignment film PSI-A-2001 in Example 4 is replaced with PSI-S-.
A ferroelectric liquid crystal element was produced in the same manner as in Example 4 except that it was replaced with PVA or PVA.

Table 4 shows the results of investigations on these ferroelectric liquid crystal elements. Neither of the ferroelectric liquid crystal elements provided the good results as obtained in Example 4.

[0049]

[Table 6]

Example 5 Ferroelectric liquid crystal composition No. 1 having the composition shown in Table 2 was prepared using the compounds shown in Table 1. 203 was produced. The transition temperature of this liquid crystal composition was as follows.

[0051] This liquid crystal composition also showed a smectic C phase at room temperature. The ferroelectric liquid crystal composition No. 1 in Example 4 was used. 201 is a ferroelectric liquid crystal composition No. A ferroelectric liquid crystal device was produced in the same manner as in Example 4 except that the liquid crystal was replaced with 203. Observation of the orientation revealed that in the temperature range from the smectic C-smectic A transition point to room temperature, except for the area of C2 orientation surrounded by minute zigzag defects, which is small in area,
The entire surface was C1U oriented.

The tilt angle in the chiral smectic C phase of these ferroelectric liquid crystal devices was measured. The tilt angle was defined as 1/2 of the angle between the two extinction positions obtained by applying a rectangular wave of ± 10 V to the liquid crystal cell. The tilt angle was plotted against temperature (Fig. 8). A voltage (V = ± 10 V) having a waveform shown in FIG. 3A was applied and the memory pulse width was measured. The results are shown in Fig. 9. The memory pulse width is the minimum pulse width that allows bistable switching. Set the pulse width to the memory pulse width, and
When a waveform of 1 was applied, a contrast of 30 or more was obtained.

A voltage (V = ± 10 V) having a 1/3 bias waveform shown in FIG. 3B was applied and the memory pulse width was measured. The memory pulse width is the minimum pulse width that allows bistable switching. The results are shown in Fig. 9. When the pulse width was set to the memory pulse width and the waveform of FIG. 3B was applied, a high contrast ratio of 10 was obtained. In this case, it can be concluded that a good black state can be maintained even when a bias is applied, and the fluctuation of molecules due to the bias voltage is suppressed.

Example 6 Ferroelectric liquid crystal composition No. 1 having the composition shown in Table 2 was prepared using the compounds shown in Table 1. 204 was produced. The transition temperature of this liquid crystal composition was as follows. This liquid crystal composition also showed a smectic C phase at room temperature. The ferroelectric liquid crystal composition No. 1 in Example 4 was used. 201 is a ferroelectric liquid crystal composition No. A ferroelectric liquid crystal device was produced in the same manner as in Example 5 except that the liquid crystal element was replaced with 204. When the orientation was observed, it was found to be C1U orientation over the entire surface in the temperature range from the smectic C-smectic A transition point to room temperature, except for the area of C2 orientation surrounded by minute zigzag defects and having a small area.

The tilt angle in the chiral smectic C phase of these ferroelectric liquid crystal devices was measured. The tilt angle was defined as 1/2 of the angle between the two extinction positions obtained by applying a rectangular wave of ± 10 V to the liquid crystal cell. The tilt angle was plotted against temperature (Fig. 10). A voltage (V = ± 10 V) having a waveform shown in FIG. 3A was applied and the memory pulse width was measured. The results are shown in Fig. 9. The memory pulse width is the minimum pulse width that allows bistable switching. Set the pulse width to the memory pulse width.
When the waveform of (a) was applied, a contrast of 50 or more was obtained.

A memory pulse width was measured by applying a voltage (V = ± 10 V) having a 1/3 bias waveform shown in FIG. 3 (b). The memory pulse width is the minimum pulse width that allows bistable switching. The results are shown in Fig. 11. When the pulse width was set to the memory pulse width and the waveform of FIG. 3B was applied, a high contrast ratio of 20 was obtained. In this case, it can be concluded that a good black state can be maintained even when a bias is applied, and the fluctuation of molecules due to the bias voltage is suppressed.

Example 7 Ferroelectric liquid crystal composition No. 1 having the composition shown in Table 2 was prepared using the compounds shown in Table 1. 205 was produced. The transition temperature of this liquid crystal composition was as follows. This liquid crystal composition also showed a smectic C phase at room temperature. The ferroelectric liquid crystal composition No. 1 in Example 4 was used. 201 is a ferroelectric liquid crystal composition No. A ferroelectric liquid crystal element was produced in the same manner as in Example 5 except that 205 was substituted. When the orientation was observed, it was found to be C1U orientation over the entire surface in the temperature range from the smectic C-smectic A transition point to 80 ° C. except for the area of C2 orientation surrounded by minute zigzag defects and having a small area.

The tilt angle in the chiral smectic C phase of these ferroelectric liquid crystal devices was measured. The tilt angle was defined as 1/2 of the angle between the two extinction positions obtained by applying a rectangular wave of ± 10 V to the liquid crystal cell. The tilt angle was plotted against temperature (Fig. 12). A voltage (V = ± 10 V) having a waveform shown in FIG. 3A was applied and the memory pulse width was measured. The results are shown in Fig. 13. The memory pulse width is the minimum pulse width that allows bistable switching. Set the pulse width to the memory pulse width.
When the waveform of (a) was applied, a contrast of 20 or more was obtained.

A memory pulse width was measured by applying a voltage (V = ± 10 V) having a 1/3 bias waveform shown in FIG. 3 (b). The memory pulse width is the minimum pulse width that allows bistable switching. The results are shown in Fig. 13. Further, when the pulse width was set to the memory pulse width and the waveform of FIG. 3B was applied, a good memory state was shown.

[0060]

INDUSTRIAL APPLICABILITY The compound (I) of the present invention has a melting point not so high, is likely to show a smectic phase and a nematic phase, and is stable chemically and to light. Therefore, the compound (I) is useful as a component of a liquid crystal composition, and by combining it with other compounds,
Various liquid crystal compositions including various ferroelectric liquid crystal compositions can be prepared and can be applied to various liquid crystal devices.
In particular, when a ferroelectric liquid crystal display device utilizing C1U orientation is manufactured using a ferroelectric liquid crystal composition containing the compound (I) of the present invention and an orientation film having a high pretilt angle,
High contrast can be obtained even in the 3-bias drive.

[Brief description of drawings]

FIG. 1 is a diagram for explaining switching of a ferroelectric liquid crystal.

FIG. 2 is a diagram for explaining a chevron layer structure of a chiral smectic C phase, and a C1 orientation and a C2 orientation.

3A is a diagram showing an applied voltage waveform of 0 bias, FIG.
(b) is a figure which shows an example of the applied voltage waveform of 1/3 bias.

FIG. 4 is a cross-sectional view of a device for explaining a ferroelectric liquid crystal device of the present invention.

FIG. 5 is a diagram showing an infrared absorption spectrum of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 6 is a graph showing changes in tilt angle with temperature of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 7 is a graph showing a temperature change of a memory pulse width of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 8 is a graph showing a change in tilt angle with temperature of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 9 is a diagram showing a temperature change of a memory pulse width of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 10 is a graph showing a change in tilt angle with temperature of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 11 is a graph showing a temperature change of a memory pulse width of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 12 is a graph showing a change in tilt angle with temperature of a ferroelectric liquid crystal composition using the compound of the present invention.

FIG. 13 is a diagram showing a temperature change of a memory pulse width of a ferroelectric liquid crystal composition using the compound of the present invention.

[Explanation of symbols]

 1a, 1b Glass substrate 2a, 2b Transparent electrode 3a, 3b Electrode protective film 4a, 4b Alignment film 6 Sealing member 7 Liquid crystal 9,10 Substrate 11 Liquid crystal cell 12a, 12b Polarizing plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoaki Kurata 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. Inside the company

Claims (5)

[Claims] 1. The following formula (I): (In the formula, R ₁ and R ₂ are the same or different and each represents a linear or branched alkyl group having 1 to 15 carbon atoms, and m and n each independently represent an integer of 0 or 1.) A compound having: 2. A liquid crystal composition comprising at least one compound of formula (I) according to claim 1. 3. A transparent electrode is formed on each of the surfaces of the pair of translucent substrates facing each other, an insulating film is formed to cover each transparent electrode, and an alignment film is formed to cover the insulating film. In a liquid crystal display device in which liquid crystal is filled between optical substrates, a pair of substrates having an alignment film subjected to alignment treatment is used.
A ferroelectric liquid crystal display device, wherein the alignment films are arranged so as to face each other so that the alignment treatment directions of the alignment films are substantially parallel, and at least one liquid crystal composition according to claim 2 is contained between the substrates. 4. The device according to claim 3, wherein the pretilt angle at the interface between the alignment film and the liquid crystal composition is 8 ° or more. 5. The device according to claim 3, wherein the tilt angle of the liquid crystal composition is not larger than the pretilt angle by 5 ° or more in the driving temperature range.