JPH0451022A - Liquid crystal alignment method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved method for aligning liquid crystal in a liquid crystal display element using a liquid crystal having a chiral smectic phase or a liquid crystal composition thereof.

[Conventional technology]

Surface-stabilized ferroelectric liquid crystal (SSFLC) devices that utilize liquid crystals with a chiral smectic C phase (hereinafter referred to as ferroelectric liquid crystals) are characterized by high-speed response, memory properties, and pulse voltage. Because it has a clear threshold value, it has attracted attention as a new display element to replace liquid crystal elements using nematic liquid crystals, and is being actively researched.

Separately, research is being conducted on liquid crystal display elements that utilize liquid crystals having an antiferroelectric chiral smectic C phase (hereinafter referred to as antiferroelectric liquid crystals), which has been recently discovered as a new smectic phase. (Jspnn
ese Journal of Applied Phys.
sics, Vol, 27. pp, L729.

1988). Characteristics of this device include switching between fixed states, clear threshold characteristics, good memory properties, and layered structure that is switched by an electric field.

FIG. 1 shows the relationship between applied voltage and tilt angle in an antiferroelectric liquid crystal element. From this figure, it can be seen that there are three stable states in the antiferroelectric liquid crystal element. In other words, two uniform states (t
), Ul) and the third state. Chanda shows that this third state is an antiferroelectric chiral smectic C phase.
Ni et al. reported (Japanese Joan
al of Applied Phys-1cs, V
ol, 28. ppJL1261.1989. Japan
ese Jour-nal of Applied
Physics, Vol. 28. pp, L 1
265 #1989). In this way, with antiferroelectric liquid crystal elements, HaJI! Switching between three stable states occurs. In addition, in Figure 1, if a positive voltage is gradually applied, the tilt angle changes from A - B - C - D, but the tilt angle changes from 0 (■) to Vl (V), there is almost no change, and when the applied voltage exceeds Vl (V), there is a large change. Next, if you gradually lower the voltage,
The tilt angle changes as D -E -F-A, but in this case too, the tilt angle hardly changes until the applied voltage reaches V2 (V), and changes significantly when the applied voltage becomes smaller than ■2. . The same thing happens when a negative voltage is applied. In this way, the antiferroelectric liquid crystal element has a clear threshold value with respect to the applied voltage. Furthermore, the threshold value Vl (V) in the process of increasing the voltage and the threshold value V in the process of decreasing the voltage
2 (V), it can be seen that the antiferroelectric liquid crystal element has memory properties.

For information on the layer structure of antiferroelectric liquid crystals, see JapaneseJ.
Internal of Applied Physics
, Vol., 2g.

pp, L119e 1989. Japanese
Journal of Applied Physics
, Vol., 29. pp, Lllll, 1990. That is, 1 antiferroelectric liquid crystal is gradually cooled from the isotropic phase to the antiferroelectric chiral smectic C phase (S
CA), the layer structure has a chevron structure in the shape of a "<" with respect to the substrate, similar to the conventional chiral smectic C phase (Fig. 2-1). When a large voltage is applied to the device, the layer deforms into a bookshelf structure that is generally perpendicular to the substrate (Figure 2-b). When the voltage is removed, the layer returns to the chevron structure again, but the tilt angle β of the layer with respect to the substrate is smaller than at the beginning (Figure 2-C). After this, by turning the voltage on and off, il! ! Reversible switching can be performed between the layers of FIG. 2-b and FIG. 2-c. The voltage required to switch this layer may be less than the voltage originally required to change the layer structure from a chevron (Figure 2-1) to a bookshelf (Figure 2-b). Specifically, in the uniform state, the layers have a bookshelf structure, and in the third state, they have a chevron structure, and switching between layers occurs due to the hysteresis curve of the tilt angle shown in Figure 1, which is necessary for switching of liquid crystal molecules. A suitable voltage is sufficient (V/ or more). In addition, such a change in layer structure can lead to polarization! ! It is known that it can also be observed as a change in texture (tissue) under the bulge (Japanese J
our own of Applied Physics
, Vol., 29. pp, Lllllsl 99
0). The texture change in a relatively thick cell (5 μm) is shown in FIG. The original chevron structure (no.
The texture of Fig. 3) is characterized by elliptic-hyperbolic focal conics (Fig. 3-a). On the other hand, the textures of the bookshelf structure (Figure 2-b) and the chevron structure with a small slope (Figure 2-C) are composed of linear focal conics-like defects (Figure 3-b) and parabolic focal conics-like defects. (Figure 3-C). By switching the layers, the texture alternates between Figures 3-b and 3-c.

4-(1-Methylheptyloxycarponyl)phenyl 4'-oftyromutyrosibiphenyl-4-carboxylate (hereinafter abbreviated as MHPOBC) is known as a liquid crystal having an antiferroelectric chiral smectic C phase (SC2). , its structural formula and phase transition temperature are as follows.

4I jar ◆. 4. ,．． 5 x, 5 c, S C, S I A
are respectively ^ smectic physiognomy, chiral smectic C phase, and antiti
Represents electric chiral smectic C phase and antiferroelectric chiral smectic I phase. MHPOBC (Proceeding ofThe 9th
International display Re5
searchConference, pp-22e Q
ct, 16-18, 1989. Kyot.

Based on the results of X-ray diffraction, it has been reported that the above-mentioned calendar switching occurs.

Layer structure analysis of liquid crystals using y4 diffraction has recently become a subject of active research. As a result, it has been revealed that the X-ray diffraction pattern obtained using the X-ray diffraction measurement system shown in FIG. 5 and the layer structure have the following relationship. That is, the X-ray diffraction pattern of a liquid crystal element having a chevron structure usually has two peaks, as shown in FIG. 6-0V(1). In contrast, the X-ray diffraction pattern of a liquid crystal element with a bookshelf structure is
It usually has a sharp single peak as shown at 0V(I).

In the case of ferroelectric liquid crystals, it has already been reported that the layer structure undergoes some deformation due to electric fields (Jipat et al.
+ege Journal of AppliedP
bysi ase Vol, 28. pp, L4B
3.1989), layer switching (reversible deformation) as described above has not yet been reported.

One of the major problems with liquid crystal devices that utilize a chiral smectic phase that has a layered structure is that when the alignment is disturbed by mechanical shock, etc., it cannot be easily aligned like a conventional nematic liquid crystal that does not have a layered structure. is not repaired. For this reason, liquid crystal devices that utilize a chiral smectic phase have the disadvantage that if the alignment is disturbed, the device must be heated until the liquid crystal becomes a single phase, and then slowly cooled to reorient it. Was.

As a countermeasure to this problem, many studies have been conducted on methods of manufacturing display panels that are resistant to concessionary shocks, but this has not solved the essential problem.

In addition, it is possible to heat the device until the liquid crystal becomes approximately square and then slowly cool it to reorient it. It is being carried out (Japanese Patent Application Laid-Open No. 62-265622)
. However, its effectiveness is limited to contrast ratios of 1 to 3.
It was not possible to use it practically.

[Problem that the invention seeks to solve]

As mentioned above, in a liquid crystal display element using a chiral smectic phase, if the alignment is once disturbed by mechanical shock, etc., the element is heated until the liquid crystal becomes a uniform phase, and then slowly cooled to reorient it. It had the disadvantage that it had to be carried out.

The present invention is intended to solve these problems, and its purpose is to easily maintain the alignment even if the alignment is disturbed by mechanical blockage or the like in a liquid crystal display element using a liquid crystal having a chiral smectic phase. The object of the present invention is to provide an alignment method that can restore the alignment.

[Means for solving problems]

The shearing method (Appl.
1 ed Physta as, Vol-36mp
p-899* 1980 eCrysil Res,
Technol, Vol. 23. A7, pp.
.

949.1988) is known, which is a method of aligning the liquid crystal by moving one of the substrates of the liquid crystal element with an amplitude of about several tens of micrometers. The orientation principle is to eliminate strain existing in the liquid crystal by moving the substrate, and to orient the liquid crystal molecules according to the orientation force of the substrate.

The present invention is an orientation method characterized in that this shearing method is performed electrically. Specifically, this alignment method is characterized by applying a voltage to a liquid crystal element that has a chiral smectic phase and vibrating the layers. By vibrating one layer, the strain existing in the liquid crystal is eliminated, and the substrate is The liquid crystal molecules are aligned according to the alignment force.

It is known that the above-mentioned switching of the dielectric layer occurs in antiferroelectric liquid crystal devices, but electrical sharing in this device is achieved by repeatedly switching the layers by applying voltage to the wires. achieved. It was not previously known that layer switching occurs in ferroelectric liquid crystal devices, but as a result of extensive research, we newly discovered that layer switching also occurs in ferroelectric liquid crystal devices. That is, as shown in FIG. 12-0V(I), the initial layer structure of the ferroelectric liquid crystal element 1 is a chevron structure. As a voltage is applied to this element, the layers undergo deformation and eventually assume a bookshelf structure as shown in FIG. 12-50V(I).

Further, when the voltage is gradually lowered from this state, the structure returns to the tilted structure (FIG. 2-d) which is tilted with respect to the substrate, as shown in FIG. 12-oV (D). After this, reversible switching between the bookshelf structure and the tilt structure occurs when the voltage is turned on and off. In Figure 12, the layer structure after voltage application (Figure 12-0V (D)) is a tilted structure, but in general, the layer structure after voltage application depends on the type of alignment film, alignment conditions, and liquid crystal used. etc., and the chevron structure may return to a layered structure that cannot be specified.

The major difference from antiferroelectric liquid crystal devices is that the switching of this layer does not have a clear threshold for applied voltage. In this way, layer switching similar to that in antiferroelectric liquid crystal elements occurs in ferroelectric liquid crystal elements, so electrical sharing can be performed using the same method as in antiferroelectric liquid crystal elements. .

The orientation effect of electrical shearing explained above is
As specifically shown in the examples, this is much larger than when a DC voltage is simply applied to the cords.

In the present invention, vibration of a layer refers to the vibration of a layer by applying a voltage to the element, and applying a voltage to the element to create a bookshelf structure shown in FIG. 2-b and a layer structure other than the bookshelf (for example, a chevron structure shown in FIG. This means that the two states (tilt structure shown in the figure) are alternately realized. In the case of antiferroelectric chiral smectic C phase, as mentioned above, layer switching occurs according to the tilt angle hysteresis curve.
Switching the gylefter between the third state and the uniform state (or Ur) is defined as vibrating the layer.

In addition, in the case of the chiral smectic C phase, unlike the antiferroelectric chiral smectic C phase, there is no clear threshold for changes in the layer structure, so the bookshelf structure, chevron structure, and tilt structure are defined as follows. Layer switching between a bookshelf structure and a layer structure other than a bookshelf according to this definition is defined as layer vibration.

(1) The X-ray diffraction pattern of the liquid crystal element is shown in Figure 6-50V.
(I) In the case of a single peak as shown in gζ, or in the case of two or more peaks that cannot be clearly separated as shown in Figure 6-OV (D), (1-1) The apex of the peak Position is (90+θB)+5°
and when the half-width of the peak is less than 5 degrees, the layered structure is defined as bookshelf.

(1-b) The position of the apex of the peak is (90+σB) ±5°
In other words, when the half width of the curve is 5 degrees or more, the layered structure is defined as a chevron.

(1-C) The position of the apex of the peak is (90+θB) ±56
If it is not within the range, the layer structure is defined as tilted.

However, here, 2θB represents the Bragg angle of the liquid crystal.

(2) The X-ray diffraction pattern of the liquid crystal element is shown in Figure 6-0V (
The layered structure is defined as a chevron when it has two or more clearly separated peaks as shown in I).

The magnitude and waveform of the voltage applied in the present invention may be any voltage that can vibrate the layer.

Furthermore, it is possible to alternately apply a sufficiently high voltage necessary to realize the bookshelf structure shown in Figure 2-b and a sufficiently low voltage necessary to realize a layer structure other than the bookshelf structure. That's fine. For example, it is possible to vibrate the layers by alternately applying a DC voltage that is high enough to create a bookshelf structure and a DC voltage that is low enough to create a layer structure other than a bookshelf. However, in practical terms, it is more efficient to apply an alternating current voltage that can realize layer switching to the element and cause it to vibrate continuously.

The waveform of the AC voltage applied in the present invention is preferably a triangular wave, a sine wave, or the like. The frequency of the applied alternating current voltage is preferably 0.001 Hz to 10.7 Hz. The frequency of the AC voltage is more preferably L<(tO,0IHz ~ IkHz
, particularly preferably Q, lHg to 100ai.

It is preferable that glass or plastic be used as the material for the pair of parallel substrates used in the present invention, and that transparent electrodes be disposed thereon. Further, it is preferable that an organic polymer film subjected to a rubbing treatment is formed on both sides or one side of the pair of parallel substrates as an alignment film. As the organic polymer film, it is desirable to use a polyimide film, a polyamide film, a polyvinyl film, a nylon film, or the like. In addition, yttrium, silicon oxide (sto, 5ioz) is used instead of the organic polymer film.
It is also possible to form an inorganic thin film such as on one or both sides of a pair of parallel substrates. Furthermore, it is also possible to initially align the liquid crystal by sandwiching the liquid crystal between a pair of parallel substrates and using a temperature gradient method when manufacturing the device; in this case, it is possible to perform the initial alignment without performing an alignment process on the parallel substrates. It is.

The transparent electrode used in the present invention is an ITO film, NESAI
lK etc. are preferred.

In the present invention, the gap between the parallel substrates, that is, the cell gap, is preferably 0.5 to 300 μm. The cell gap is more preferably 1.0 to 10 μm.

Particularly preferably 1.5 to 5 gm.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.
The invention is not limited to this example.

Example 1 After coating polyimide on a glass substrate with ITO having a diameter of 1 tm, only one of the pair of substrates was subjected to a rubbing treatment, and a compound known as an antiferroelectric liquid crystal, 4-(1) was coated with polyimide.
-trifluoromethylnonyloxycarponyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (hereinafter, this compound will be abbreviated as TFMNPOBC).

was sandwiched between the pair of substrates via a spacer to produce a liquid crystal element with a cell spacing of 2.5 μm.

The #, formula and phase transition temperature of TFMNPOBC are as follows.

The liquid crystal element was heated until the Fs liquid crystal became a uniform phase, and then slowly cooled until it became an antiferroelectric chiral smect C phase, thereby homogeneously aligning the liquid crystal. At this time, when the orientation state was observed under a polarized light microscope, it was found that many diamond-shaped (diamond-shaped) defects had occurred.

A triangular wave voltage with a frequency of 1Hx was applied to the element in Part B for 5 minutes at a temperature of 101°C (tilt angle of 22°) to vibrate the layer continuously and perform electrical sharing. The relationship between the applied voltage (Vpp/2, where Vpp is the voltage between peaks) and the contrast ratio at this time is shown in FIG. The contrast ratio was determined by applying a DC voltage to the element after performing electrical sharing, and from the ratio of the amount of transmitted light in both uniforms (Ur and Ul). That is, after electrical sharing, a DC voltage of +20 cm was applied to the element, and the liquid crystal element was rotated so that the amount of transmitted light under crossed Nicols was minimized. The amount of transmitted light at this time is defined as T min. On the right, this element switches from the third state to the uniform state.

The threshold voltage required for switching was 17V.

Next, with the liquid crystal element fixed at the previous position lI, -20V
A direct current voltage of 200 nm was applied to the element, and the amount of transmitted light at this time was measured. Let the amount of transmitted light at this time be Trrgax. Tmax
/rmin was taken as the contrast ratio.

Note that the amount of transmitted light was detected by a photomultiplier tube, and the output voltage of the photomultiplier tube was used as a substitute for the amount of transmitted light.

For comparison, the results of similar measurements were also shown in which a DC voltage that did not cause electrical sharing was applied to the element. A greater orientation effect was observed when a triangular wave voltage was applied than when a DC voltage was applied. That is, it can be seen that alignment of the liquid crystal occurs more easily at a low voltage when electrical sharing is performed than when electrical sharing is not performed.

Example 2 MHPO was also used in TFMNPOBC used in Example 1.
N indicates that layer switching is occurring as in BC.
In order to obtain H, the Fii structure was analyzed by X-ray diffraction method. After coating a 150 gm thick glass substrate with ITO with polyimide, only one of the pair of substrates was rubbed, TFMNPOBG was sandwiched between the pair of substrates via a spacer, and a liquid crystal element with a cell spacing of 5 was formed. Created. The liquid crystal element is heated until the liquid crystal becomes a homogeneous one phase, and then the liquid crystal element is slowly cooled to bring the liquid crystal into homogeneous alignment (
The liquid crystal molecules were aligned parallel to the substrate. Using this liquid crystal element, at a temperature of 100°C (Se2 voice),
Changes in the layer structure due to voltage application were investigated using line diffraction.

The threshold voltage required for switching this device from the third state to the uniform state was 40 volts. XI!
Diffraction was performed using Ru-200 (manufactured by Rigaku H). The temperature of the liquid crystal element was controlled using a temperature control unit with an accuracy of ±0° to 1°C. The measurement system is shown in Figure 5. The measurement procedure for X-ray diffraction is as follows:
urnal of Applied Physics,
Vol, 27. p9. L725, 1988 and J
apanese Journal of Applie
d Phy-5ics e Vol, 27of
JP, L1993.1988 +). That is, first, using a capillary cell filled with liquid crystal, the Bragg angle C26B> of the liquid crystal was measured. Next, I set the counter to the Bragg corner. Using the cell prepared according to the above procedure, when α was rotated, an X-ray diffraction pattern was obtained from k. Here, α is the angle between the glass surface and the incident beam. The size of the X-ray beam was 1-. The measurement conditions for X-ray diffraction are as follows.

X-ray diffraction device: Ru-200 (Rigaku Corporation), 60kV,
200mA target: Copper filter Nickel voltage: 5QkV Current: 20 QmA Scan speed: 4deg/min Sampling: Q, ldeg, continuous scan slit: DS O, 5°, RS Q, 3 cranes, ss o, s' detector: The proposal seal counter results are shown in Figure 6. Before applying the electric field, two peaks (OV(I)) representing the chevron structure shown in FIG. 2-a were observed in the layer structure. DC voltage 50
When V is applied, the layer structure shows one sharp peak (50V (I)) representing the bookshelf structure shown in Figure 2-b.
') became. Further, when the voltage is returned to QV, the second -
The broad peak representing the chevron structure shown in Figure C (
OV (D)). After that, it was confirmed that reversible layer switching between the bookshelf structure and the chevron structure occurs by turning the voltage on and off, similar to MHPOBC.

Using the liquid crystal element used for X-ray diffraction, under a polarizing microscope, 1
Texture (group a) was observed at 00°C. When the chevron structure was formed before voltage was applied, many elliptic-hyperbolic g-type Four force luconics as shown in FIG. 3-a were observed. When a DC voltage of 50 μm is applied to the device and the layer is made into a bookshelf structure, the elliptic-hyperbolic focal conics disappears and the linear focal conics-like defects become f, as shown in Figure 3-b. Ta. Then turn off the voltage and
If the ii structure is a chevron structure with a small slope, the third
As shown in Figure 1-c, the linear focal coex-like defects disappeared and parabolic focal coex-like defects were formed. Then, by turning the voltage on and off, the texture is changed to Figure 3-b and Figure 3-CI! i!
II. Next, +50■ to the element,
Apply triangular wave and sine wave voltages of Q, lHz, 10
Texture observation was performed at 0°C. In either waveform, when the applied voltage is large (+50V or -50V
0■), the same texture as in Figure 3-b (linear focal coex-like defect) is observed, and when the applied voltage is small (OV), the same texture as in Figure 3-c (parabolic focal conics) is observed. was recognized. From the above results, it was confirmed that calendar switching definitely occurred when AC voltage was applied.

Example 3 The same liquid crystal element as in Example 1 was used, and the frequency I was applied to this element.
The contrast ratio was measured in the same manner as in Example 1 except that triangular wave voltages of Hz, 2QHz, and 1QOHz were applied. The results are shown in FIG. It is clear that the lower the frequency of the applied triangular wave voltage, the more remarkable the effect on improving the contrast ratio.

Example 4 The same liquid crystal element as in Example 1 was used, and the frequency I
The contrast ratio was measured in the same manner as in Example 1 except that a sine wave voltage and a rectangular wave voltage of Hz were applied. The results are shown in FIG. In the case of applying a sinusoidal voltage, a remarkable effect almost equivalent to that in the case of applying a triangular wave voltage (Example 3) was observed. On the other hand, when a rectangular wave voltage is applied, the effect is almost the same as that of a DC voltage application (Example 1), and it is clear that electrical sharing is less likely to occur with a rectangular wave voltage.

Example 5 A TFMNPOBC liquid crystal element was produced in the same manner as in Example 1 by coating a glass substrate with ITO with a thickness of 1 inch with polyimide. Using this element, liquid crystal was aligned in the same manner as in Example 1, and as shown in FIG. 9-a, there were many diamond-shaped defects and some domains with different alignment directions. +80 at a temperature of 100℃ for this element
When the DC voltage of (3) was applied for 5 minutes.

As shown in FIGS. g-b, the diamond-shaped defects disappeared, but almost no repair effect was observed for domains with different orientation directions. In addition to this element, +80■, ]Hz
When electrical shearing was performed by applying a triangular wave voltage for 5 minutes, domains with different orientation directions were completely repaired, and an element with a good orientation state was obtained, as shown in FIG. 9-c.

Example 6 Using the same liquid crystal element as in Example 5, this element was cooled to room temperature, the liquid crystal was crystallized, and then heated to a temperature of 100°C. As shown in Figure 10-a, the orientation was changed. The state was partially disturbed and became homeotropically aligned (liquid crystal molecules aligned perpendicularly to the substrate). ±8ov to this element
When electrical shearing was performed by applying a triangular wave voltage of 1Hz for 5 minutes, the orientation state completely recovered to homogeneous orientation as shown in Figure 10-b, and an element with a good orientation state was obtained. Ta.

Example 7 The same procedure as Example 1 was carried out except that 4-(1-methylhebutyloxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), a compound known as an antiferroelectric liquid crystal, was used. A liquid crystal device was manufactured using the following steps. MHPOBC is a compound already known to perform layer switching. The structural formula and phase transition temperature of this compound are as follows.

This liquid crystal was oriented in the same manner as in Example 1.

Observation of the orientation state using a polarizing microscope revealed the presence of many diamond-shaped defects. This element has a temperature of 100°C (tilt angle of 2
Figure 11 shows the relationship between the applied voltage (Vpp/2, where vpp is the peak-to-peak voltage) and the contrast ratio when electrical sharing is performed by applying a triangular wave voltage with a frequency of IHz (2 degrees). Ta. For comparison, the results of similar measurements were also shown in which a DC voltage that did not cause electrical sharing was applied to the element. The Fundasure Ratio was measured by applying DC voltages of +15V and -15V to the device. Note that the threshold voltage required for switching this element from the third state to the uniform state was 12V. It is clear that when a triangular wave voltage is applied compared to when a DC voltage is applied, the voltage required to obtain the same contrast ratio is lower and the alignment effect is greater.

That is, it can be seen that alignment of liquid crystal occurs more easily at low voltage when electrical sharing is performed than when electrical sharing is not performed.

Example 8 The layer structure of ferroelectric liquid crystal, which has not been known to cause layer switching, was developed using Xli? It was analyzed by diffraction method. As a ferroelectric liquid crystal, a known compound, 4-(3-
Trifluoromethyl-3-oxycarbonylpropionate (ethyl)phenyl 4'-octyloxybiphenyl-
A liquid crystal element was produced in the same manner as in Example 2 except that 4-carboxylate was used. The structural formula and phase transition temperature of this compound are as follows.

It was confirmed that layer switching between the bookshelf structure and the tilted structure occurs reversibly by turning the Fm field on and off. From this, it was found that electrical sharing can be performed in ferroelectric liquid crystals as well as in antiferroelectric liquid crystals by applying a voltage to the element.

x Here, SX represents an unidentified smectic phase. Using this liquid crystal element, the temperature was 115°C (Sc" phase).
Then, changes in the layer structure due to the application of an electric field were investigated using an X-ray diffraction method. The results are shown in FIG. Before applying an electric field, two peaks representing the chevron structure shown in Figure 2-a were observed in the layer structure, and when a DC voltage of 50 μm was applied, the layer structure was as shown in Figure 2-b. There was a single sharp peak representing the bookshelf structure.

Furthermore, when the voltage is returned to Ov, it becomes 1! ! It changed to a peak representing the tilted structure shown in 2-dlsV. Then electric example
9 Compound of Example 8 as ferroelectric liquid crystal, 4-(3-trifluoromethyl-3-oxycarbonylpropionate ethyl)phenyl 4'-octyloxybiale-4-
A liquid crystal element was produced in the same manner as in Example 1 except that carboxylate was used. This device was slowly cooled from a single phase to align the liquid crystal. This element has a temperature of 115℃ (tilt angle of 22℃)
Figure 13 shows the relationship between the applied voltage (Vpp/2, where vpp is the voltage between peaks) and the contrast ratio when electrical sharing is performed by applying a triangular wave voltage with a frequency of IHz at Ta. For comparison, the results of similar measurements were also shown in which a DC voltage that did not cause electrical sharing was applied to the element. It is clear that when a triangular wave voltage is applied compared to a DC voltage, the contrast ratio is significantly improved by applying a smaller voltage. That is, it can be seen that alignment of the liquid crystal occurs more easily at a low voltage when electrical sharing is performed than when electrical sharing is not performed.

〔Effect of the invention〕

As described above, according to the present invention, in a liquid crystal display device using a liquid crystal having a chiral smectic phase or a liquid crystal paste thereof, the liquid crystal can be maintained evenly even if the alignment is disturbed due to mechanical stress or the like. Orientation can be easily recovered by electrical shearing without using a reorientation means of heating until one phase is formed and then slowly cooling.

FIG. 3 is a diagram showing the relationship between tilt angle and applied voltage in a phase.

FIG. 2 is a cross-sectional view of a liquid crystal display element having a chiral smectic phase. 1 represents the substrate, and 2 represents the layer structure of the liquid crystal.

Figure 2-c shows the layered structure (chevron structure) in the chiral smectic phase after slow cooling from the homo-1 phase.

Here, β represents the inclination angle of the layer.

FIG. 2-b shows a layered structure (bookshelf structure) when a large electric field is applied to an element having a chevron structure.

FIG. 2-c shows the layer structure (chevron) of an element having a bookshelf structure when the electric field is turned off.

FIG. 2-d shows a tilted structure in which the layers are tilted with respect to the substrate.

[Brief explanation of the drawing]

FIG. 1 shows the structure of an antiferroelectric liquid crystal device. FIG. 3-b shows an image having a bookshelf structure. FIG. 3-c shows the orientation state of a chevron structure with a small inclination after application of an angular wave voltage. FIG. 4 is a diagram showing the relationship between applied voltage and contrast ratio in Example 1 of the present invention. Figure 5 shows the diffraction system of a one-ray diffraction device used for layer structure analysis of a liquid crystal element, where α is the rotation angle of the cell, θ is the diffraction angle, and Ki
represents the incident XIQ, and Ks represents the diffracted X-ray. FIG. 6 is a diagram of X-ray diffraction results showing changes in the layer structure with respect to applied voltage in Example 2 of the present invention. 7 and 8 are diagrams showing the relationship between applied voltage and contrast ratio in Examples 3 and 4 of the present invention. Fig. 10-b shows the orientation state after application of a triangular wave voltage. FIG. 11 is a diagram showing the relationship between applied voltage and contrast ratio in Example 7 of the present invention. FIG. 12 is a diagram of X-ray diffraction results showing changes in the layer structure with respect to applied voltage in Example 8 of the present invention. FIG. 13 is a diagram showing the relationship between applied voltage and contrast ratio in Example 9 of the present invention. Patent Applicant Mitsubishi Gas Chemical Co., Ltd. Kashima Oil Co., Ltd. Agent Patent Attorney Sadafumi Kobori Figures g-b are after DC voltage is applied, Figure 9-c is the image after application of DC voltage, Figure 9-c is the image shown in Figure 3-a, Figure 3-c is Figure ＼ ＼ 1st concave concave Y lath and ratio con) Last Ku π

Claims (4)

[Claims] (1) A liquid crystal element comprising a liquid crystal or a liquid crystal composition thereof having a chiral smectic phase and a pair of substrates having electrodes and sandwiching the liquid crystal or the liquid crystal composition, in which the liquid crystal or the liquid crystal composition is chiral. A method for aligning a liquid crystal having a chiral smectic phase or a liquid crystal composition thereof, which comprises applying a voltage to an element at a temperature exhibiting a smectic phase to vibrate a layer of the liquid crystal or the liquid crystal composition. (2) The liquid crystal alignment method according to claim 1, wherein the chiral smectic phase is an antiferroelectric chiral smectic C phase (Sc_A^*). (3) The liquid crystal alignment method according to claim 1, wherein the chiral smectic phase is a chiral smectic C phase (Sc^*). (4) The liquid crystal alignment method according to claim 1, wherein the voltage is an alternating current voltage.