JPH05333340A - Ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain bistability at the time of orientation and the threshold value characteristic suitable for matrix driving by subjecting liquid crystal molecules to a rubbing treatment in the average molecule major axis direction of the liquid crystal molecules in an ideal bistable state in addition to the normal direction of a liquid crystal layer. CONSTITUTION:A first rubbing axis direction R1 is the direction coinciding with the normal direction L1 of the liquid crystal layer. The liquid crystal molecules 10 are controlled in orientation uniformly over the entire surface of the element by the rubbing treatment. A second rubbing axis direction R2 is the direction coinciding with the average molecule major axis direction M1 of the liquid crystal molecules 10 or intersecting therewith at an angle within 5 deg. when the liquid crystal molecules 10 are oriented in the direction shown by solid lines in Fig by impressing the electric field having one direction between the substrate 2. A third rubbing axis direction R3 is the direction coinciding with the average molecule major axis direction M2 of the liquid crystal molecules 10 or intersecting therewith at an angle within 5 when the liquid crystal molecules 10 are oriented in the direction shown by alternate long and short dash lines in Fig by impressing the electric field having an opposite direction between the substrate 2.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of displaying moving images using a ferroelectric liquid crystal material used for TV screens, general OA equipment, display panels for automobiles, etc., or displays for in-vehicle navigation. The present invention relates to a ferroelectric liquid crystal element.

[0002]

2. Description of the Related Art As a display element used in each of the above-mentioned applications, a liquid crystal material is filled between a pair of base materials in which scanning electrodes and signal electrodes are arranged in a matrix, so that pixels are formed in the overlapping portions of both electrodes. The configured liquid crystal element is widespread.
However, this simple matrix type liquid crystal element has a problem that the response speed is slow and so-called crosstalk occurs when the number of pixels increases, which makes it difficult to display a clear and high-definition screen.

Therefore, a non-linear element such as a thin film transistor (TFT) is formed in a portion corresponding to each pixel on the base material, and each pixel is operated independently to prevent crosstalk, resulting in a clear and high-definition image. An active matrix type liquid crystal element capable of screen display has been developed and has already been put to practical use. However, in the above active matrix type liquid crystal element, it is difficult to form a non-linear element without any defect for all pixels on the screen, which leads to high cost due to low yield or large screen. Difficulties are a problem.

In order to solve the above problems of the conventional liquid crystal element,
As a surface-stabilized ferroelectric material using a ferroelectric liquid crystal material.
Electronic Liquid Crystal Device (SSFLCD) is based on Clark and Lag
proposed by erwall (JP-A-56-107)
216, U.S. Pat. No. 4,367,924). the above
Ferroelectric liquid crystal elements, such as SSFLCD, are
At least a distance that can suppress the formation of cancer structures.
Also, a pair of base materials 2 and 2 whose one surface is subjected to orientation treatment,
Chiral smectic sandwiched between the base materials 2 and 2.
Phase C (S_C ^*Phase), and the orientation of liquid crystal molecules is
Ferroelectric liquid crystal material controlled by surface alignment treatment 1
And a pair of polarizers 3, 3 arranged outside the substrates 2, 2.
And (see FIG. 2).

In the above ferroelectric liquid crystal element, the liquid crystal molecules 10 whose orientation is controlled by the orientation treatment of the surface of the base material 2
When the cell spacing between the substrates 2 and 2 is sufficiently wide as shown in FIG. 3, has a helical structure with the liquid crystal layer normal L1 as an axis, and the dipole 11 of each liquid crystal molecule 10 is Turn to different directions. However, when the cell spacing is smaller than one pitch of the spiral structure (dimension α in FIG. 3), the liquid crystal molecule 10 suppresses the formation of the spiral structure, and the spiral structure is unraveled.
As shown by the solid line or the one-dot chain line in FIG. 4, the dipole 11 in the molecule can take only one of the two states of upward and downward.

In this state, the pair of base materials 2, 2
When a voltage in either forward or reverse direction is applied between them, the dipoles 11 of all the liquid crystal molecules 10 are aligned in one of the upper and lower directions according to the direction of the electric field, and accordingly, all the liquid crystal molecules 10 are aligned. Will be switched between two states depending on the direction of the electric field. These two states continue to exist stably even after the voltage application is stopped, and the device exhibits bistability (memory property).

On the other hand, in the polarizers 3 and 3, as shown in FIG. 5, the polarization axes 30 and 30 are orthogonal to each other, and the polarization axis 30 of either one of the polarizers 3 has two states which the liquid crystal molecule 10 can take. The liquid crystal molecules 10 in any one of them are laminated so as to coincide with the average long axis direction of the molecules. Therefore, FIG.
In the ferroelectric liquid crystal device having the layer structure of No. 2, when the direction of the voltage applied between the pair of base materials 2 and 2 is switched to either the forward or reverse direction, the liquid crystal molecule 10 is switched between the two states accordingly. As a result, a state in which the polarization axis 30 of one of the polarizers 3 is matched and a state in which the polarization axis 30 is not matched are generated, and display in two states of bright (ON) and dark (OFF) is possible.

As described above, in the ferroelectric liquid crystal device, the liquid crystal molecules have bistability and, unlike the conventional liquid crystal, switching between the bright and dark states is performed by the dipole, so that the response speed is extremely several tens of μs. fast. Therefore, according to the ferroelectric liquid crystal element, it is possible to display a clear and highly vivid image without crosstalk at high speed by simple matrix driving.

The ferroelectric liquid crystal element is manufactured as follows. First, a ferroelectric liquid crystal material 1 exhibiting an isotropic phase is sandwiched between a pair of base materials 2 and 2, and the base materials 2 and 2 are
Are arranged at a distance where the formation of a helical structure of liquid crystal molecules is suppressed. Next, the whole is heated to a temperature above the isotropic phase transition temperature of the ferroelectric liquid crystal material 1 and gradually cooled. Then, the ferroelectric liquid crystal material 1 undergoes a phase transition from the isotropic phase to the chiral smectic C phase (S _C ^* phase) through the smectic A phase (S _A phase), and the liquid crystal molecules are at the surface of the substrates 2 and 2. By the orientation treatment performed on the substrate, the orientation is uniformly controlled over the entire surface of the base material.

After that, a pair of polarizers are provided outside the substrates 2 and 2.
By stacking layers 3 and 3, the ferroelectric liquid crystal having the layer structure shown in FIG.
The device is obtained. In the above ferroelectric liquid crystal element, the liquid
Control of crystal molecule orientation greatly affects performance such as response characteristics
Therefore, the orientation treatment of the substrate surface is important. Orientation of substrate
As a logical method, as shown in FIG.
The base material 2 is an organic polymer film having a thickness of about 0.1 μm or less.
On the surface of the rabbi and rub the surface in one direction with a suitable cloth.
The general method is When this process is applied,
Smectic of ferroelectric liquid crystal material by heating and slow cooling
Phase A (S_APhase) to chiral smectic C phase (S _C ^*
When the liquid crystal molecules undergo a phase transition to
So that it matches the rubbing direction,
The orientation is controlled uniformly.

[0011]

However, in the method of aligning a base material by rubbing the surface of a liquid crystal alignment film, if the rubbing strength is too high, as shown in FIG. The liquid crystal molecules 10 are forcibly oriented in a direction in which the average long axis of the liquid crystal molecules coincides with the rubbing axial direction r, and the liquid crystal molecules 10 are in a monostable state that does not show bistability. Bistability (memory property), which is a feature of, may be lost.

Even if the liquid crystal molecules are not forcibly aligned in the rubbing direction as described above, if the rubbing strength is too strong, the liquid crystal molecules are strongly affected by the rubbing. The force that strongly pulls back in the axial direction of rubbing may act on the liquid crystal molecules, and the bistability of the device may be reduced or lost. That is, when a voltage is applied, as shown by the broken line in FIG. 7, the liquid crystal molecules 10 whose molecular long axes are oriented in a predetermined direction by the action of the dipoles described above move in the rubbing axial direction r when the applied voltage is stopped. As the solid line is pulled back, the angle formed by the long axis of the molecule and the liquid crystal layer normal L1 becomes smaller, and the bistability of the device is reduced or lost.

On the other hand, if the rubbing strength on the surface of the liquid crystal alignment film is too weak, there arises a problem that the liquid crystal molecules cannot be uniformly aligned on the entire surface of the device. Further, in the conventional ferroelectric liquid crystal element, there is also a problem that a sufficient display contrast cannot be obtained by simple matrix driving because the switching threshold voltage value of liquid crystal molecules due to the action of the dipole is low. That is, in the simple matrix drive, a voltage that is about ⅓ of that of a pixel that performs writing is always applied to a pixel that does not perform writing. Therefore, when the threshold voltage value is low,
Even unnecessary pixels are responded, and the display contrast is lowered, resulting in display failure.

The present invention has been made in view of the above circumstances, and has a bistability at the time of orientation and a threshold characteristic suitable for matrix driving, and is capable of high-definition and high-pixel-number display. The object is to provide a possible ferroelectric liquid crystal device.

[0015]

In order to solve the above problems, a ferroelectric liquid crystal device of the present invention is a liquid crystal in which the surface of a liquid crystal alignment film is formed by liquid crystal molecules sandwiched between base materials. When the liquid crystal molecules are aligned by applying a unidirectional electric field between the first direction that coincides with the normal direction of the layer and the pair of base materials,
When the liquid crystal molecules are aligned by applying an electric field in a direction opposite to the second direction that intersects with the average molecular major axis direction of the liquid crystal molecules or intersects at an angle of 5 ° or less, the liquid crystal molecules are aligned. It is characterized in that the rubbing treatment is performed in three directions of a third direction that coincides with the average molecular long axis direction of the molecule or intersects at an angle within 5 °.

According to the ferroelectric liquid crystal element of the present invention having the above structure, not only in the first direction which is the normal direction of the liquid crystal layer, but also in the average long axis direction of the liquid crystal molecules in the ideal bistable state. Since the surface of the liquid crystal alignment film is also rubbed in the second and third directions which coincide with the average molecular long axis direction when voltage is applied or intersect at an angle of 5 ° or less, the above-mentioned heating and slow cooling treatments are performed. Therefore, when the ferroelectric liquid crystal material undergoes a phase transition, the liquid crystal molecules are in a monostable state, and there is no fear of losing the bistability characteristic of the ferroelectric liquid crystal element.

Further, since the liquid crystal molecules are subjected to the alignment force from the above three directions, the pullback action due to the rubbing in the normal direction of the liquid crystal layer is alleviated, and the device can have good bistability. Furthermore, according to the present invention, even if the rubbing strength in the first direction is sufficiently strong, the bistability of the device can be improved as described above by appropriately adjusting the ratio with the rubbing strength in the other two directions. Since it is not lost, liquid crystal molecules can be uniformly and favorably aligned on the entire surface of the device.

Furthermore, according to the present invention, the liquid crystal molecules are subjected to alignment force from the second and third directions which coincide with the average molecular long axis direction in the ideal bistable state or intersect at an angle within 5 °. Therefore, when switching from one of the above-mentioned bistable states to the other, it requires extra energy by the amount of this forcing, and as a result,
The applied voltage required for switching is high, that is, the threshold value is high, and it is possible to obtain a sufficient display contrast by simple matrix driving.

The present invention will be described below. In the ferroelectric liquid crystal device of the present invention, as shown in FIG. 2, a ferroelectric liquid crystal material 1 is sandwiched between a pair of base materials 2 and 2, and a pair of polarizers 3 and 3 are provided outside the ferroelectric liquid crystal material 1 as in the prior art. It is configured by overlapping. The base materials 2 and 2 are arranged at a distance at which the formation of a helical structure of liquid crystal molecules is suppressed, and a liquid crystal alignment film 21 is formed on each of the surfaces thereof. As shown in FIG. 1, rubbing processing is performed in three rubbing axis directions R1 to R3.

The rubbing method is the same as the conventional one. That is, a suitable cloth (rubbing cloth) is set on the surface of a cylindrical rubbing roll whose axis is arranged parallel to the surface of the liquid crystal alignment film 21, and the liquid crystal alignment film 21 is rotated while the rubbing roll is rotated in the circumferential direction. When the liquid crystal alignment film 21 is pressed against the surface of the rubbing roll, the liquid crystal alignment film 21 is rubbed in a direction orthogonal to the axis of the rubbing roll. This process may be performed for the first to third rubbing axis directions R1 to R3.

The first rubbing axis direction R1 coincides with the normal direction L1 of the liquid crystal layer, and the rubbing treatment uniformly controls the alignment of the liquid crystal molecules 10 over the entire surface of the device. The second rubbing axis direction R2 is an average molecular long axis of the liquid crystal molecules 10 when a liquid crystal molecule 10 is aligned in the direction indicated by the solid line in the figure by applying an electric field in one direction between the substrates 2 and 2. The third rubbing axis direction R3 is a direction that coincides with or intersects with the direction M1 at an angle of 5 ° or less, and in the third rubbing axis direction R3, an electric field in the opposite direction is applied between the base materials 2 and 2 to show the liquid crystal molecules 10 by a chain line. It is a direction that is aligned with or intersects with the average molecular major axis direction M2 of the liquid crystal molecules 10 at an angle of 5 ° or less. By the rubbing treatment in the above two directions, the bistability at the time of alignment and the threshold characteristic suitable for matrix driving are secured, and the ferroelectric liquid crystal element of the present invention is capable of high definition and high pixel number display. It will be

The second and third rubbing axis directions R
2, R3 and the average molecular major axis directions M1, M of the liquid crystal molecule 10
The angle intersecting with 2 is limited to within 5 °, in the case where the angle exceeds 5 °, when the application of the electric field is stopped, the direction of the average molecular long axis of the liquid crystal molecule 10 is ideal. This is because the state deviates greatly from the stable state and the bistability characteristic of the ferroelectric liquid crystal element is lost.

The rubbing treatment directions of the liquid crystal alignment films 21 and 21 formed on the surfaces of the pair of base materials 2 and 2 may or may not coincide with each other. In order to uniformly control the alignment of the liquid crystal molecules 10 over the entire surface of the device and to develop an ideal bistable state, as described above, the rubbing strength in the first rubbing axis direction R1 and other Two rubbing axis directions R2, R3
It is desirable to adjust the ratio of the rubbing strength to the rubbing strength within a suitable range. The second and third rubbing axis directions R2, R
It is preferable that the rubbing strengths of 3 are exactly the same in order to realize ideal bistability, but there may be a slight difference.

The range of the ratio of the rubbing strength is not particularly limited in the present invention, but the ratio X of the rubbing strength X in the first rubbing axis direction R1 and the rubbing strength Y in the other two rubbing axis directions R2, R3. : Y, X: Y = 50: 1
It is preferably about 1:50. When the ratio X: Y of the rubbing strength is out of the range where Y is larger than the above range, the rubbing strength in the first rubbing axis direction R1 is too weak, and the liquid crystal molecules 10 are removed during the heating and slow cooling treatments. The orientation may not be uniformly controlled over the entire surface of the device. Conversely, the ratio X: Y
When X is outside the above range, the rubbing strength in the second and third rubbing axis directions R2 and R3 is too weak, and the liquid crystal molecules 10 are pulled back in the first rubbing axis direction R1. Therefore, the ideal bistable state may not be exhibited.

The rubbing strength referred to here is the number of times of rubbing N, the pushing amount M (mm) of the tip of the rubbing cloth, the radius r (mm) of the rubbing roll, the rotation speed n (rpm) of the rubbing roll and the stage movement. Speed V (mm / min)
Is the rubbing density L (mm) calculated by the following formula (Tatsuo Uchida et al., Proceedings of the 13th Liquid Crystal Symposium 3Z2
2, 1987).

[0026]

[Equation 1]

Therefore, each rubbing axis direction R1 to R3
In order to adjust the rubbing strength as described above, the pressure for pressing the rubbing roll on which the rubbing cloth is set against the liquid crystal alignment film 21, the rotation speed of the rubbing roll, the stage moving speed, the number of times of rubbing, and the like may be controlled. As the liquid crystal alignment film 21 that is subjected to the rubbing treatment, a polyimide-based polymer, a derivative thereof, or a copolymer thereof is suitable in view of heat resistance, stability, and use results in other liquid crystal display device systems. Although used, other polymers such as polyvinyl alcohol may be used in consideration of compatibility with the ferroelectric liquid crystal material 1. Further, in consideration of the characteristics of the device, it is desirable that the polymer material forming the liquid crystal alignment film 21 has less coloring and is excellent in transparency and has a high dielectric constant in order to reduce a voltage drop.

The liquid crystal alignment film 21 is formed by coating or printing a coating solution in which a polymer material is dissolved or dispersed in an appropriate solvent to remove the solvent by drying, or by curing the polymer material with a curable prepolymer ( It is formed by applying or printing a coating liquid in which an oligomer or a monomer) is dissolved or dispersed in an appropriate solvent, drying and removing the solvent, and curing the prepolymer.

For coating the coating liquid, a usual coating method such as a bar coating method, a spin coating method or a spray coating method can be adopted, and various printing methods such as the above-mentioned screen printing method and offset printing method can be adopted. You can also The thickness of the liquid crystal alignment film 21 is not particularly limited, but is 30Å to 0.
About 5 μm is preferable.

As the ferroelectric liquid crystal material 1, a commercially available single component or a plurality of components are preferably used, but various polymer liquid crystals of side chain type, main chain type, etc., and ferroelectric polymer liquid crystals are assisted. The performance may be adjusted by blending another liquid crystal component such as mixing as a component. Further, a mixture of a dichroic dye, various additives, a non-liquid crystal compound, a non-liquid crystal polymer and the like may be used for adjusting the characteristics.

Granular spacers are mixed in the ferroelectric liquid crystal material 1 in order to keep the distance between the base materials 2 and 2 constant. The spacer may be made of silica, glass fiber or resin, and the particle size thereof can be selected according to the desired electrode gap. The mixing ratio may be about 10 to 200 per 1 mm ^{2 of} liquid crystal area. The ferroelectric liquid crystal material 1 is a creamy S with relatively high viscosity.
_{Since the C} ^* phase is shown and the distribution of the spacers is not localized by the flow of the liquid crystal, if the spacers are uniformly dispersed in the liquid crystal, the distance between the base materials 2 and 2 can be kept constant.

As the base material 2, various base materials 2 such as a glass plate which have been conventionally used as the base material 2 of a ferroelectric liquid crystal element can be used, but the drawback of the glass plate is that it is heavy and easily broken. A plastic film or a plastic plate is preferably used to eliminate the above problem and form a lightweight and durable element. As a plastic film, polyethylene terephthalate (PET) film, polyether sulfone (PES) film, etc., which has excellent heat resistance, practical strength, optical uniformity, etc., and does not cause coloring due to birefringence when combined with a polarizing plate. The amorphous plastic film of is preferably used. The thickness of the plastic film is preferably about 50 to 500 μm.

As the plastic plate, plastic plates having excellent optical properties such as various acrylic resin plates, polycarbonate plates, polystyrene plates and the like are used. Especially, when combined with a polarizing plate, coloring due to birefringence occurs. A non-crystalline plastic plate is preferred. The thickness of the inflexible plastic plate is preferably about 0.5 to 3 mm.

On the surface of the base material 2, as in the conventional case, ITO is used.
A transparent conductive layer such as (indium tin oxide) is formed. In the case of an element for simple matrix driving or the like, a predetermined pattern is formed on the transparent conductive layer by etching or the like. As the polarizer 3, a commercially available product having a film shape, a plate shape, or the like may be used. The ferroelectric liquid crystal device of the present invention is not particularly limited in configuration other than rubbing the surface of the liquid crystal alignment film 21 in three directions. For example, the liquid crystal alignment film 21 may be formed only on the surface of the one base material 2. Further, a reflective film may be provided on the back surface of one of the base materials 2 to form a reflective display element. Besides, various design changes similar to those of the conventional ferroelectric liquid crystal element can be made without changing the gist of the present invention.

[0035]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. Example 1 A transparent conductive film having an ITO film formed on the surface of a PES film (product number FST-134 manufactured by Sumitomo Bakelite Co., Ltd.
On the conductive surface of 3), a 1% aqueous solution of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., NH-20) was applied by a spin coating method, and the solvent was dried off to form a polymer film.
Rubbing cloth (product number YA25 manufactured by Yoshikawa Kako Co., Ltd.)
C), the first to third rubbing axis directions R1 to R1 shown in FIG.
A liquid crystal alignment film was formed by rubbing in three directions of R3. In the rubbing process, the rubbing strength X in the first rubbing axis direction R1 and the rubbing strength Y in the other two rubbing axis directions R2 and R3 are X: Y = 10: 3 (X
= 1250 mm, Y = 375 mm), and the rubbing conditions were set.

Next, a ferroelectric liquid crystal material (product number ZLI3654 manufactured by Merck Japan Co., Ltd.) and a particle size are provided between two transparent conductive films whose orientations are adjusted so that the rubbing directions of the liquid crystal alignment film are antiparallel. A mixture with a silica spacer of 2 μm is sandwiched, heated to the isotropic phase transition temperature of the liquid crystal or higher, and then slowly cooled at a rate of 1 ° C. for 1 minute to align the liquid crystal,
A ferroelectric liquid crystal device was manufactured.

Example 2 In order that the rubbing directions of the liquid crystal alignment film are parallel to each other,
Other than adjusting the orientation of the two transparent conductive films,
A ferroelectric liquid crystal device was manufactured in the same manner as in Example 1 above. Example 3 For rubbing in the first rubbing axial direction R1, a rubbing cloth of product number YA18R manufactured by Yoshikawa Kako Co., Ltd., and for rubbing in the other two rubbing axial directions R2 and R3, product number YA15 manufactured by Yoshikawa Kako.
While using the rubbing cloth of N, the rubbing strength X in the first rubbing axis direction R1 and the rubbing strength Y in the other two rubbing axis directions R2 and R3 are X: Y = 2: 1.
A ferroelectric liquid crystal element was manufactured in the same manner as in Example 2 except that the rubbing conditions were set so that (X = 500 mm, Y = 250 mm).

Comparative Example 1 Using a rubbing cloth of the product number YA25C manufactured by Yoshikawa Kako Co., Ltd.,
Rubbing strength X = 12 only in the first rubbing axis direction R1
A ferroelectric liquid crystal device was manufactured in the same manner as in Example 2 except that the rubbing treatment of 50 mm was performed. Comparative Example 2 Using a rubbing cloth of product number YA18R manufactured by Yoshikawa Kako Co., Ltd.
Rubbing strength X = 12 only in the first rubbing axis direction R1
A ferroelectric liquid crystal device was manufactured in the same manner as in Example 2 except that the rubbing treatment of 50 mm was performed.

Comparative Example 3 Using a rubbing cloth of the product number YA15N manufactured by Yoshikawa Kako Co., Ltd.,
Rubbing strength X = 12 only in the first rubbing axis direction R1
A ferroelectric liquid crystal device was manufactured in the same manner as in Example 2 except that the rubbing treatment of 50 mm was performed. The following tests were carried out on the ferroelectric liquid crystal devices of the above Examples and Comparative Examples to evaluate the characteristics.

Measurement of Threshold Voltage The ferroelectric liquid crystal elements of each of the examples and comparative examples were sandwiched between a pair of polarizing films by adjusting the angle, as shown in FIG. 8 between two transparent conductive films. Immediately after applying a reset pulse of ± 20 V and 100 μs, a driving pulse of ± aV and 100 μs is applied to the He-Ne laser light (wavelength 633).
(nm) transmitted light intensity was measured. The measurement was repeated by gradually increasing the voltage a of the drive pulse from 0 V, and the maximum voltage at which the transmitted light intensity did not change before and after the application of the drive pulse was used as the threshold voltage.

[0041]Responsiveness and contrast evaluation Ferroelectric liquid crystal elements of each Example and Comparative Example are provided with a pair of polarizing films.
Two transparent conductive films sandwiched by adjusting the angle between them
In the meantime, the reset of ± 20V and 100μs shown in Fig. 9 (a)
After applying pulse, ± 20V, 100 shown in Fig. 9 (b)
Apply a drive pulse of μs and start applying this drive pulse
From the point in time, transmission of He-Ne laser light (wavelength 633 nm)
Time t until the over-light intensity reaches 90% of the maximum transmitted light intensity
_ONI asked. In addition, between the two transparent conductive films
After applying the motion pulse, apply the reset pulse and
He-Ne laser from the start of reset pulse application
-The transmitted light intensity of light (wavelength 633 nm) is the maximum transmitted light intensity.
Time t to reach 10% _OFFI asked.

Further, the ratio T between the maximum value T _MAX and the minimum value T _MIN of the transmitted light intensity measured in the above response speed measurement.
_MAX / T _MIN was obtained and the contrast was evaluated. The above results are shown in Table 1.

[0043]

[Table 1]

From the results in Table 1 above, it was found that the threshold values of the devices of Comparative Examples 1 to 3 in which the liquid crystal alignment film was rubbed in only one direction were extremely low at 1 V or less, and the response and contrast were poor. .. On the other hand, Examples 1 to 3
It was found that all of the above devices had a high threshold value, good contrast and excellent responsiveness. Furthermore, when a driving pulse or a reset pulse was applied to the ferroelectric liquid crystal elements of the above-mentioned respective Examples and Comparative Examples, and the orientation of the liquid crystal molecules was observed with a polarizing microscope, Comparative Examples 1 to 3 were obtained.
It was found that in each of the above devices, only a part of the liquid crystal molecules was bistable aligned according to the applied voltage. On the other hand, in all of the devices of Examples 1 to 3, it was confirmed that the liquid crystal molecules were bistable aligned according to the applied voltage over the entire surface of the device.

[0045]

As described in detail above, the ferroelectric liquid crystal element of the present invention is subjected to rubbing treatment in the direction of the average long axis of liquid crystal molecules in the ideal bistable state in addition to the direction of the normal to the liquid crystal layer. Since the liquid crystal alignment film is provided, the liquid crystal molecules can be favorably aligned, and the memory stability during alignment and
It has a threshold characteristic suitable for matrix driving. Therefore, according to the ferroelectric liquid crystal element of the present invention,
High-definition, high-pixel-number display is possible by simple matrix driving.

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a relationship between a rubbing direction of a liquid crystal alignment film and liquid crystal molecules in a ferroelectric liquid crystal device of the present invention.

FIG. 2 is a perspective view showing an example of a layer structure of a ferroelectric liquid crystal device manufactured by the present invention.

FIG. 3 is a diagram schematically illustrating a state of liquid crystal molecules when the cell spacing is sufficiently wide.

FIG. 4 is a diagram schematically illustrating an alignment state of liquid crystal molecules when the cell spacing is narrow.

5 is a diagram schematically illustrating a relationship between an average molecular long axis of liquid crystal molecules and a polarization axis of a polarizer in the alignment state of FIG.

FIG. 6 is a diagram schematically illustrating monostable orientation of liquid crystal molecules.

FIG. 7 is a diagram schematically illustrating a state where liquid crystal molecules are pulled back in the rubbing axis direction.

FIG. 8 is a waveform diagram showing a reset pulse and a drive pulse applied between transparent conductive films of devices for measuring the threshold voltage of the ferroelectric liquid crystal devices of Examples and Comparative Examples.

9 (a) and 9 (b) are reset pulses and drive pulses applied between transparent conductive films of devices for evaluating the response and contrast of the ferroelectric liquid crystal devices of Examples and Comparative Examples. It is a waveform diagram showing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferroelectric liquid crystal material 10 Liquid crystal molecules 2 Base material 21 Liquid crystal alignment film R1 First rubbing axis direction R2 Second rubbing axis direction R3 Third rubbing axis direction L1 Liquid crystal layer normal direction M1 Average molecular long axis direction M2 Average molecular long axis direction

Claims (1)

[Claims] 1. A ferroelectric comprising a ferroelectric liquid crystal material sandwiched between a pair of base materials having a liquid crystal alignment film formed on at least one surface, the ferroelectric liquid crystal material being arranged at a distance that suppresses the formation of a helical structure of liquid crystal molecules. In the liquid crystal liquid crystal element, the surface of the liquid crystal alignment film is formed in a first direction that coincides with the normal direction of the liquid crystal layer formed by the liquid crystal molecules sandwiched between the base materials and in one direction between the pair of base materials. When the liquid crystal molecules are aligned by applying an electric field, an electric field in the opposite direction between the second direction, which coincides with the average long-axis direction of the liquid crystal molecules or intersects at an angle of 5 ° or less, is applied between the pair of base materials. Ferroelectricity, characterized in that, when the liquid crystal molecules are aligned by application, rubbing treatment is performed in three directions of a third direction that coincides with the average molecular long axis direction of the liquid crystal molecules or intersects at an angle of 5 ° or less. Liquid crystal element.