JPS62231936A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain the titled element having an improved transmittance at the time of opening a picture element shutter by mounting a coating film composed of a high polymer having a specific structural unit which orientates preferentially plural layers in one direction on at least one substrate of a pair of substrates. CONSTITUTION:The titled element comprises the pair of the upper substrate 11a and the lower substrate 11b which are disposed in parallel and transparent electrodes 12a, 12b which are wired to each substrates. The orientation controlling films 14a, 14b composed of the film of the high polymer shown by formula I are disposed on the substrates 11a and 11b respectively. In formula I, R is a bivalent group shown by formula II. In order to mount the polyimido type high polymer film having the structural unit on the substrate 1, polyamic acid is dissolved in N-methylpyrrolidone (NMP), dimethylformamide (DMF) and dimethylacetoamide (DMAC), etc., and the obtd. solution is coated on the substrate, and subsequently, the substrate is thermally treated, thereby dehydrating and ring closuring it to form an imido binding.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a liquid crystal element used in a liquid crystal display element, a liquid crystal-optical shutter, etc., particularly a liquid crystal element using ferroelectric liquid crystal,
More specifically, the present invention relates to a liquid crystal element with improved display characteristics by improving the initial alignment state of liquid crystal molecules.

[Conventional technology]

A type of display element that uses the refractive index anisotropy of ferroelectric liquid crystal molecules to control transmitted light in combination with a polarizing element has been developed by Clark and Lager.
vall) (Japanese Unexamined Patent Publication No. 58-107
No. 216, U.S. Patent No. 4,387,924, etc.)
, this ferroelectric liquid crystal generally exhibits
Chiral smectic C phase (5raC”) or H phase (
Sa+H°), and in this state, it assumes either the first optically stable state or the second optically stable state in response to an applied electric field, and maintains that state when no electric field is applied. It has the property of maintaining its stability, that is, bistability, and also has a quick response to changes in electric field, and is expected to be widely used as a high-speed and memory-type display element.

In order for an optical modulation element using this bistable liquid crystal to exhibit predetermined driving characteristics, the liquid crystal disposed between a pair of parallel substrates must be
It is necessary that the molecules be in such a state that conversion between two stable states can occur effectively. For example, for ferroelectric liquid crystals having Sac'' or SmH' phases, Sac
-or S+s) It is necessary to form a region (monodomain) in which the liquid crystal molecular phase having the l'' phase is perpendicular to the substrate surface, and the liquid crystal molecular axes are arranged substantially parallel to the substrate surface.

By the way, as a method for aligning ferroelectric liquid crystals, a method using an alignment control film that has been subjected to a uniaxial alignment treatment such as a rubbing treatment or an oblique evaporation treatment is generally known.

Most of these conventional alignment methods have been applied to ferroelectric liquid crystals having a helical structure that does not exhibit bistability. For example, the alignment method disclosed in Japanese Patent Application Laid-Open No. 60-230 [1:15] involves controlling the alignment of a ferroelectric liquid crystal using a polyimide compound rubbed with a ferroelectric liquid crystal in a state of a helical structure that does not exhibit bistability. Met.

However, when the conventional alignment control film as described above is applied to control the alignment of a ferroelectric liquid crystal with a non-helical structure that exhibits bistability as announced by Clark and Lagauer, it has the following problems. was.

However, according to experiments conducted by the present inventors, the conventional orientation amount u
The tilt angle of a ferroelectric liquid crystal with a non-helical structure obtained by aligning by It was found that the angle is smaller than the angle (■) which is 1/2 of the apex angle of the pentagonal pyramid shown. In particular, the tilt angle θ of a ferroelectric liquid crystal with a non-helical structure obtained by alignment using a conventional alignment control film is generally about 10°, and the transmittance at that time is about 3 to 5% at most.

In this way, according to Clark and Lagauer, the tilt angle of a ferroelectric liquid crystal C with a non-helical structure that achieves bistability should be the same as the tilt angle of a ferroelectric liquid crystal with a helical structure. In fact, the tilt angle θ of the non-helical structure is smaller than the tilt angle O of the helical structure. Furthermore, it has been found that the reason why the tilt angle becomes smaller than 0 in the helical structure from 0 in the non-helical structure is due to the twisted arrangement of the liquid crystal molecules in the non-helical structure. In other words, in a ferroelectric liquid crystal with a non-helical structure, as shown in FIG. They are arranged in a continuous twisted manner toward the axis 43 (direction of twisted arrangement 44), and this may be the reason why the tilt angle f60 for a non-helical structure becomes smaller than the tilt angle ■ for a helical structure. ing.

Note that 41 in the IA represents a uniaxial alignment axis obtained by the Ravinck process or the oblique evaporation process formed on the upper and lower substrates.

By the way, in the case of a liquid crystal element that utilizes the birefringence of liquid crystal, the transmittance under crossed Nicols is expressed as follows. The zero tilt in the non-helical structure described above appears as an angle between the average molecular axes of the twisted liquid crystal molecules in the first and second alignment states. According to the above equation, the maximum transmittance occurs when the tilt θ is 22.5°, but the tilt angle O in a non-helical structure that achieves bistable properties is large, at an angle of about 10°. Therefore, when considering application as a display device, there is a problem that the transmittance is about 3 to 5%, which is not sufficient.

It is therefore an object of the present invention to solve the aforementioned problems, namely to increase the tilt angle in a ferroelectric liquid crystal with a non-helical structure that achieves at least two stable states, in particular bistability, and thereby An object of the present invention is to provide a liquid crystal element with improved transmittance when the shutter is opened.

Another object of the present invention is to provide a liquid crystal element using an alignment control film suitable for forming monodomains of ferroelectric liquid crystal.

[Means for Solving the Problem] and [Operation] That is, the present invention comprises a pair of parallel substrates and an arrangement of molecules forming a plurality of layers perpendicular to the planes of the pair of parallel substrates. In a liquid crystal element having a ferroelectric liquid crystal, at least one of the pair of parallel substrates has a structural unit represented by the following general formula (I) that preferentially orients the plurality of groups in one direction. This is a liquid crystal element characterized by having a coating made of a polymeric substance.

General formula (1) %formula%() A code representing a divalent group shown in The present invention will be explained in detail below.

7tS1 is a sectional view showing one embodiment of the liquid crystal element of the present invention. The liquid crystal element shown in No. 16 has a pair of upper and lower substrates 11a and 11b arranged in parallel, and transparent electrodes 12a and tzb'? that are wired to each substrate. :&1 is counted. A ferroelectric liquid crystal, preferably a non-helical ferroelectric liquid crystal 13 exhibiting at least two stable states, is arranged between the upper substrate 11a and the lower substrate 11b.

The transparent electrodes 12a and 12b described above are 1 ferroelectric liquid crystal 13.
In order to perform multiplexing drive, it is preferable that the wiring be arranged in a stripe shape, and that the stripe shapes be arranged so as to intersect with each other.

In the liquid crystal element of the present invention, alignment controls n214a and 14b formed of a polymeric substance lQ represented by the general formula (1) are arranged on the substrates 11a and Ilb, respectively.

Specific examples of the polymeric substance having the structural unit represented by the general formula (I) are as follows.

(1).

Day υ (2).

(5).

In order to provide a film of a polyimide polymer having a structural unit represented by the above general formula (I) on a substrate, polyamic acid is mixed with N-methylpyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DM).
AC), dimethyl sulfoxide (DMSO), dimethyl sulfate, sulfolane, butyrolavone, cresol, phenol, halogenated phenol, cyclohexanone, dioxane, etc., and coated on a substrate, followed by heat treatment for dehydration and ring closure. It is formed by adding an imide bond.

Polyamic acid, which is a polyimide precursor, is synthesized by condensation of tetracarboxylic acid anhydride and diamine. The anhydride of tetracarboxylic acid used is 2,2-bis[4
-(2,:l-dicarboxyphenoxy)phenyl]propanedioic anhydride is useful.

The diamine is p-phenylenediamine.

m-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, benzidine, 4,4'-diaminoterphenyl.

4.4'-diaminodiphenylsulfyl', 4.
4'-diaminodiphenylsulfone, 1.5-diaminonaphthalene, 5(8)amino-1(4'-aminophenyl)1.3.3-trimethylindane, 3.3'-
Benzophenone diamine and the like are used.

The polyamic acid obtained in this way has an intrinsic viscosity ([
[eta]) The obtained polyamic acid, preferably 0.1 to 5.0, is diluted with a solvent and then applied to a substrate to form an FJ film. After coating, a polyimide polymer thin film can be provided by dehydration and ring closure at 100 to 400°C.

The film of these polymeric substances can function as an insulating film, and is usually formed to have a thickness in the range of about 100 Å to 1 μm, preferably 500 Å to 200 OA.

In addition, as a method for forming the 11λ layer of these polymeric substances, a solution of the polymeric substance or its precursor solution is coated with a spinner coating method, a dip coating method, a screen printing method, a spray coating method, a roll coating method, or the like. After coating, a method of curing under predetermined curing conditions (for example, heating) can be used.

Next, a ferroelectric liquid crystal having molecular alignment forming a plurality of layers perpendicular to the planes of a pair of parallel substrates used in the liquid crystal element of the present invention will be described.

FIG. 2 schematically depicts an example of a ferroelectric liquid crystal cell using a helical structure. 21a and 21b are I!
1203, 5nOz and ITO (Indium Tin
It is a substrate (glass plate) coated with a transparent electrode such as SmC0(
Chiral smectic C phase) liquid crystal is sealed.

A thick line 23 represents a liquid crystal molecule, and this liquid crystal molecule 23 has a dipole moment (ρ, ) 24 in a direction perpendicular to the molecule. At this time, the angle forming the apex angle of the pentagonal pyramid represents the tilt angle of 0 in the chiral smectic phase of the helical structure. Substrates 21a and 21b
When a voltage higher than a certain threshold is applied between the upper electrodes, the helical structure of the liquid crystal molecules 23 is unraveled, and the dipole moment (P
(4) The alignment direction of the liquid crystal molecules 23 can be changed so that all of the liquid crystal molecules 24 are oriented in the direction of the electric field.

However, a ferroelectric liquid crystal using this helical structure returns to its original helical structure when no electric field is applied, and does not show any decline in bistability.

In a preferred embodiment of the invention, a ferroelectric liquid crystal element as shown in FIG. 3 can be used which has at least two stable states, especially a bistable state. In other words, when the thickness of the liquid crystal cell is made sufficiently thin (for example, jf 1), the helical structure of the liquid crystal molecules unravels even when no electric field is applied, and becomes a non-helical structure, as shown in Figure 3. The dipole moment Pa or pb takes either an upward (34a) or downward (34b) state fE, and a bistable state is formed. When such a cell is given an electric field Ea or Eb of different polarity above a certain threshold as shown in FIG. 3, the dipole moment electric field Ea or Eb will be directed upward 34a or downward 34b in accordance with the electric field vector. and accordingly the liquid crystal molecules are in the first stable state 5m 33 a
or the second stable state 33b. 1/2 of the angle formed by the first and second stable states at this time
corresponds to a tilt angle of 0.

There are two advantages to using such a ferroelectric liquid crystal as an optical modulation element. Firstly, the response speed is extremely fast, and secondly, the alignment of liquid crystal molecules has bistability. To explain the second point with reference to FIG. 3, for example, when the electric field Ea is applied, the liquid crystal molecules are oriented in a first stable state 333a, and this state remains stable even when the electric field is turned off. Furthermore, when an electric field Eb in the opposite direction is applied, the liquid crystal molecules are oriented to the second stable state 33b and the orientation of the molecules is changed.
It remains in this state even if the electric field is turned off. or.

As long as the electric field Ea that decreases does not exceed a certain level of rice planting, each orientation state is maintained. In order to effectively realize the fast response speed and the memory effect due to bistability, it is preferable for the cell to be as thin as possible, and it is generally 0.5 to 20 μm, especially 1 μ to 5 μm. is suitable. A liquid crystal-electro-optical device having a matrix electrode structure using a highly conductive liquid crystal of this type has been proposed, for example, by Clark and Ragaval in US Pat. No. 43G7924.

Examples of the ferroelectric liquid crystal that can be used in the liquid crystal element of the present invention include p-decyloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBG
), P-hexyloxybenzylidene-p'-amino-2-chloropropylcinnamate ()IOBACP
C), p-decyloxybenzylidene-p'-amino-2
-Methylbutyl-α-cyanosinname) (DOBA
MBCC), P-tetradecyloxybenzylidene-
p'-Amino-2-methylbutyl-α-cyanocinnamate (TDOBAMBCG), P-amino-2-methylbutyl-α-cyanocinnamate-P’-amino/-2-methylbutyl-α
(OOBAMBCC), p-octyloxybenzylidene-p'-amino-2-methylbutyl-α-methylcinnamate, 4,4'-azoxycinnamic acid-bis(2-methylbutyl) ester, 4-o -(2-methyl)butylresocylidene-4
'-Octylaniline, 4-(2'-methylbutyl)phenyl-4'-octyloxybiphenyl-4-carboxylate, 4-hexyloxyphenyl-4-(2''
-Methylbutyl)biphenyl-4'-rupoxylate, 4-octyloxyphenyl-4-(2'-methylbutyl)biphenyl-4'-rupoxylate, 4-hebutylphenyl-4-(4''-methylhexyl)biphenyl- Examples include 4'-rupoxylate, 4-(2'-methylbutyl)phenyl-4-(4"-methylhexyl)biphenyl-4'-rupoxylate, and these may be used alone or in combination of two or more. It is also possible to contain other cholesteric liquid crystals or smectic liquid crystals as long as they exhibit ferroelectricity.

Furthermore, in the present invention, a chiral smectic phase can be used as the ferroelectric liquid crystal, and specifically, a chiral smectic C phase (Sa + C, H phase (Sd), one phase (Sm
l◆), K phase (SIIIK gloss G phase (S+++G◆)) can be used.

Next, in the liquid crystal element of the present invention, the aforementioned alignment control IEs 214a and 14b can be obtained by subjecting the surface of the coating of the aforementioned polymeric substance to a uniaxial alignment treatment such as a rubbing treatment. In this case, in one aspect of the present invention, uniaxial alignment axes such as rubbing axes can be parallel to or intersect with each other.

In particular, in the present invention, it is preferable that the uniaxial orientation axes intersect as shown in FIG. 5. In other words, as shown in FIG. During the electric field, the respective uniaxial orientation axes 51 and 52 intersect at an angle 55 in the opposite direction to the direction 44 of the twisted arrangement shown in FIG. When the chiral smectic phase is aligned in the presence of such a uniaxially aligned surface by lowering the temperature of the phase on the higher temperature side, the axis 53 of the liquid crystal molecules adjacent to the lower substrate 1
are parallel to each other. In this chiral smectic phase, the liquid crystal molecules are oriented at a tilt angle θ (or -〇) from the axis 54 of the liquid crystal molecules in the smectic A phase (SmA), which is oriented at an angle between uniaxial orientation 4+l+ 51 and 52 as the temperature decreases. , first and second stable states (first stable state when the tilt angle is 0, second stable state when the tilt angle is -0) can be formed.

In this liquid crystal element, when one polarization axis 56 of crossed Nicols is set parallel to the axis 53 of the liquid crystal molecules corresponding to the molecular axis direction in the first stable state, and the other polarization axis 57 is made orthogonal to the polarization axis 56, the maximum You can get contrast.

In a preferred embodiment of the present invention, the above-mentioned tilt 0 is made equal to the tilt 0 in the helical structure by pre-treatment of applying an alternating current.
Alternatively, the angle can be increased to the same degree. Let the tilt angle at this time be θ'. The alternating current used in this case has a voltage of 20 to 500 volts, preferably 30 to +5 volts.
Same wave number lO~500Hz at 0 volts, preferably ■0
~200 Hz can be used, and the AC application pretreatment can be performed with the application time being about several seconds to about 10 minutes.

Further, such AC application pre-processing is performed at a stage before writing is performed on the liquid crystal element according to, for example, a video signal or an information signal, and preferably, such a liquid crystal element is incorporated into a device and the weight when operating such a device is reduced. The above-mentioned AC application pre-treatment can be performed at a time, or alternatively, the AC application pre-treatment can be performed at the time of manufacturing such a liquid crystal element.

Such alternating current application pretreatment is based on one experiment conducted by the present inventors.
That is, when an alternating current electric field is applied to a ferroelectric liquid crystal element having a bistable state as shown in FIG. 4 or FIG. 5, the tilt angle 0 before application increases to the same degree as the tilt O in the helical structure. .theta.', and in the state shown in FIG. 5, the increased tilt angle .theta.' can be maintained even after the alternating current application is removed.

In addition, such AC application pretreatment is performed on a ferroelectric liquid crystal with large spontaneous polarization (for example, 5 ne/ca+2 or more at 25°C, preferably IO+IC/C!12 to 300 nc/cm2).
; nc is a unit indicating nanocoulombs). This spontaneous polarization can be determined by Δ111 using the triangular wave application method in a 100-tile cell.

・Japanese Journal of Applied Physics
Applied Physics) 22 (10),
1361-ET83 (1983), co-authored by K. Myasato et al.・Ferroelectric Liquid Crystalpa (“Direct Method wi
th Triangular Wavesfar Me
aSuring 5pontaneous Po1ar
ization 1nFerroelectric L
iquid Crystal”).

In the present invention, it is possible to omit the use of one film that controls one of the orientation controls N14a and 1, 4b described above. In another specific example of the present invention, the above-mentioned orientation control! 1
It is also possible to use a separate alignment control film for one of the pas 14a and 14b. Examples of other coatings forming the orientation control film include coatings of polyvinyl alcohol, polyamide, polyester, polyimide, polyamideimide, polyesterimide, and the like. In addition, as other orientation control films, SiO and 5i0
It is also possible to use an amorphous material such as No. 2 formed by oblique evaporation.

[Example] The present invention will be described below by showing Examples and Comparative Examples, and further by giving specific examples.

Example 1 Two 0.7 am thick glass plates were prepared, and 100 OA of ITOy was formed on each glass plate.

2.2-bis [
4-(2,3-dicarboxyphenoxy)phenyl]brovanic acid anhydride and P-phenylenediamine were condensed at a molar ratio of 1=1, and the synthesized polyamic acid was diluted with NMP.
The solution diluted to % by weight was applied for 40 seconds using a spinner with a rotation speed of 3500 r, p, m. After application, heat treatment was performed for about 1 hour ml. The thickness of the coating film at this time was about 850A.

The first pattern was subjected to a rubbing treatment with a cloth, and two sheets of glass (plates were placed in a cell Ml) so that the rubbing axes of the respective alignment control films were parallel to each other.

The cell thickness (distance between the upper and lower substrates) was maintained by photoresist spacers previously formed on the lower substrate.

By vacuum injecting the above-mentioned mixed liquid crystal into this liquid crystal cell (this is called a 1.8#L Otori cell) under an isotropic phase, and then slowly cooling it from the tokichi phase to 30°C at 0.5°C. I was able to orient it. Subsequent experiments were conducted at 30°C.

Mixed liquid crystal (ffi amount ratio) H3 Ca1170ite OCO) (pregnancy C) Iz5H-C2)
! s 1H3 C)+3 (Temperature range of "Smc"; 3 to 35°C) Observation of the lever cell under crossed nicols reveals monodomains that form a chiral smectic C phase with a uniform, defect-free, non-helical structure. Ta.

A pulse electric field (20V, 5OOILs) is applied to this liquid crystal cell.
By applying ec), the direction of the liquid crystal molecules is aligned in one stable state, and while rotating the liquid crystal cell under crossed Nicols, the darkest state fEj where the amount of transmitted light is the lowest is found. A pulsed electric field of opposite polarity to the previous pulse (
-20V, SOD end sec) was applied to transition to the other stable molecular alignment state, and the liquid crystal cell was rotated to find the angle at which the darkest state was found.The positions of the two darkest states of 0 or more are as follows. Corresponding to the detection of the stable average molecular axes of the liquid crystal, the angle between them corresponds to a tilt angle of 20.

When we measured the tilt angle of the liquid crystal cell mentioned above, we found that
It was 13°. That is, the liquid crystal cell of this example has a memory-like yE realized by a bistable chiral smectic phase;
Below, you can see that it has a large tilt angle that is not found in conventional models. Further, when the amount of transmitted light in the brightest state of this liquid crystal cell was added to 5111, it was 11%. The amount of transmitted light at this time was measured using Photomul.

Next, the present inventors measured the twist alignment angle and direction of the liquid crystal molecules with respect to the normal direction of the substrate in the liquid crystal cell described above. For this measurement, instead of the 1.8 g+s photoresist spacer used in the liquid crystal cell described above, 3.
A liquid crystal cell (referred to as an IOH cell) was prepared in exactly the same manner except that 0 μl of alumina beads were used as a spacer.

To measure the twist alignment angle of liquid crystal molecules, rotate one analyzer from the intersection angle in the darkest state under crossed Nicols.
By changing the intersection angle, we found the position that would make the light even darker, and measured the angle at which one analyzer was rotated from the orthogonal position. This angle corresponds to the twist angle δ mentioned above.

Therefore, the above 3. Regarding the Ol cell, from the observer's perspective, clockwise rotation is positive (+) and counterclockwise rotation is negative (-).
In this case, the analyzer was rotated 5 to 7 degrees in the negative direction from crossed nicols, and then the liquid crystal cell was rotated to search for a dark state. Also, move the polarizer 5 to 7 degrees in the positive direction from crossed Nicols.
Even with rotation, a dark state was similarly obtained. Therefore, the liquid crystal molecules in this device form a twisted arrangement in the positive direction,
The long sleeves of liquid crystal molecules on the adjacent surfaces of the upper and lower substrates are lO″-14
It was found that it was twisted with a twist angle δ of °.

Example 2 The same procedure as Example 1 was used, except that rubbing axes intersecting at angles of 45° and 20° in the negative direction (-) were used in place of the parallel wrapping axes used in the 1.8 μm cell of Example 1. A liquid crystal cell was created in exactly the same manner.

When the tilt angle of this liquid crystal cell was measured, it was 14
''. Both of these two liquid crystal cells were 5III
S+sA exists on the high temperature side of C., but S+++A
It was found that the optical axis of is located on the bisector of the angle formed by the crossed rubbing axes.

Next, a high electric field alternating current with a voltage of 70 volts and a frequency of 70 Hz was applied to each of the above-mentioned 2 g liquid crystal cells for about 5 minutes (AC application pretreatment), and the tilt angle θ' at this time was set to δI11
Established. The results are shown in Table 1 below.

Table 1 For these two types of liquid crystal cells, the torsion angle δ shown in Figure 4 was measured using the same method used to measure the torsion angle δ of the liquid crystal element of the 3gm cell described above. 4
In a liquid crystal device using crossed Rahing axes of 5° and -20°, the twist angle δ of the liquid crystal molecules with respect to the normal to the upper and lower substrates is not observed, and the liquid crystal molecular axes adjacent to the upper and lower substrates are parallel to each other. I found it to be powerful. Moreover, the intersection angle is -45° and -20°.
In the liquid crystal device using the crossed rubbing axes, the tilt angle θ' shown in Table 1 could be maintained even if the driving rectangular pulses of +20 volts and -204 volts (1 m5ec) were applied alternately. Actually, depending on the video signal or information signal, this liquid crystal element is
This corresponds to the point that even when a time division driving method such as that described in Japanese Patent No. 6 or Japanese Unexamined Patent Publication No. 59-19347 is applied, the maximum tilt f110' can be maintained. Also, the transmittance at this time was measured.

Both were about 17%.

The direction of the twisted state with twist angle δ is determined by the interaction between the substrate and the liquid crystal near the interface. In other words, whether the polarization direction of the liquid crystal molecules near the interface is inward with respect to the substrate,
The outward orientation is determined by the properties of the substrates, and when the same alignment control film is used for both the upper and lower substrates, the liquid crystal between the substrates is forcibly oriented in a twisted alignment.

If the direction of twisted alignment along the normal line of the substrate and the uniaxial alignment axis are shifted or in the same direction, the molecules near the interface of the substrates are aligned in the direction of the alignment axis of each substrate, making the twisted alignment state more stable. In the state where the tilt angle is O' after the above-mentioned alternating current application pretreatment, a metastable orientation state is obtained.

The state of the tilt angle θ' after the above-mentioned alternating current application pretreatment is due to the polarization of molecules near the interface, or it is necessary that one substrate faces inward and the other substrate faces outward.

When the uniaxial alignment axis is shifted in the opposite direction to the twisted alignment direction of the liquid crystal, that is, when the uniaxial alignment axis is crossed at an angle opposite to the twisted alignment direction, the stabilization energy due to the interaction between molecular polarization and the interface The stabilization energy due to forced anchoring by the -axis orientation axis is larger than that of the -axis orientation axis.

Therefore, a state with a stable tilt angle θ' can be realized.

Therefore, in order to realize an enhanced electroconductive liquid crystal element with high transmittance, it is necessary to eliminate the twisted alignment state and to align the uniaxial alignment axis in a direction that stabilizes the ideal aligned IE added by the AC application pre-treatment. It is necessary to shift them from each other. This direction is opposite to the direction in which the liquid crystal is twisted and arranged at a twist angle δ determined by the interface between the liquid crystal and the substrate.

Comparative Example 1 As the alignment control film used when creating the 1.81 cell of Example 1, 3.3',4.4'-diphenyltetracarboxylic acid anhydride and p-phenylenediamine were mixed in a molar ratio of 1:1. 3.5 of polyamic acid obtained by dehydration condensation reaction.
A liquid crystal cell was prepared in exactly the same manner except that polyimide 11, which was formed by dehydrating and ring-closing a coating film of 1% by weight N-methyl-2-pyrroli solution, was subjected to a rubbing treatment.

When the tilt angle O and transmittance of this liquid crystal cell were measured in the same manner as in Example 1, the tilt angle θ was 6° to 81°.
The transmittance at that time was about 3 to 5%. That is, the comparative cell has a small tilt angle under a memory state realized by a stable chiral smectic phase, and its transmittance is completely insufficient for application to a display device.

Comparative Example 2 The alignment control films used when creating the 1.8μI cell of Example 1 were 3.3', 4. C-diphenyltetracarboxylic anhydride and 4,4'-diaminodiphenyl in 1:
Coating I with a 3.5% by weight N-methyl-2-pyrrolidone solution of polyamic acid obtained by dehydration condensation reaction at a molar ratio of 1
A liquid crystal cell was prepared in exactly the same manner except that a polyimide film formed by dehydrating and ring-closing the II film was used instead of a rubbed polyimide film.

When the tilt angle θ and transmittance of this liquid crystal cell were determined as ΔIII in the same manner as in Example 1, the tilt angle 0 was 6°.
~7°, and the transmittance at that time was about 3 to 4%.

Comparative Example 3 3.3',4.4'-diphenyltetracarboxylic acid anhydride and 4.4'-diaminoterphenyl were used as the orientation control m11Q used when creating the 1.8μ■ cell in Example 1. Instead of a polyimide film formed by dehydrating and ring-closing a coating film of a 3.5% by weight N-methyl-2-pyrrolidone solution of polyamic acid obtained by dehydration and synthesis reaction at a molar ratio of 1:1, rubbing treatment was performed. A liquid crystal cell was created in exactly the same manner except for using the same method.

When the tilt angle θ and transmittance of this liquid crystal cell were measured in the same manner as in Example 1, the tilt angle 0 was 5° to 7°.
The transmittance at that time was about 3 to 4%.

Examples 3 to 12 Instead of the orientation control 21 film used in the 1.8μ layer cell of Example 1, polyimide obtained from polyamic acid synthesized by condensing the starting materials shown in Table 2 below was used. A liquid crystal cell was prepared in exactly the same manner as in Example 1, except that the coating mentioned in 3 was formed and the coating was rubbed.
The transmittance at that time was measured. The results are shown in Table 3.

[Effects of the Invention] By controlling the orientation using the liquid crystal element of the present invention, it is possible to obtain a monodomain of a ferroelectric liquid crystal, particularly a ferroelectric liquid crystal having at least two stable states obtained by a non-helical structure. The first effect is to increase the tilt angle θ under at least two stable states, particularly under a bistable state (i.e., under a memory state) developed by the non-helical structure of the ferroelectric liquid crystal. The second excellent effect is that it can be used in a variety of ways.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing one embodiment of the liquid crystal element of the present invention, Fig. fjS2 is a perspective view schematically showing a liquid crystal element using a ferroelectric liquid crystal with a helical structure, and Fig. 3 is a diagram showing a liquid crystal element with a non-helical structure. FIG. 4 is a perspective view schematically showing a liquid crystal element using ferroelectric liquid crystal, and FIG. FIG. 2 is an explanatory diagram showing the relationship between the uniaxial alignment axis and the axis of liquid crystal molecules used in the liquid crystal element of the present invention. lea...upper board 11b...lower board 12
a, 12b...Transparent electrode 13...Ferroelectric liquid crystal 14a, +4b...Orientation control film 21...Substrate 22
...Liquid crystal molecule layer 23...Liquid crystal molecule 24...
・Dipole moment 'l'la...First stable state 3 pieces b...Second stable state 34a...L direction dipole moment 34b...Downward dipole moment ◎...Helical structure Tilt angle θ at...Tilt angle Ea, Eb at non-helical structure...Electric field

Claims (5)

[Claims] (1) In a liquid crystal element comprising a pair of parallel substrates and a ferroelectric liquid crystal having a molecular arrangement forming a plurality of layers perpendicular to the planes of the pair of parallel substrates, the pair of parallel substrates A liquid crystal element, wherein at least one of the substrates has a coating of a polymeric substance having a structural unit represented by the following general formula that preferentially orients the plurality of layers in one direction. General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R is the following formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲
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There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲There are mathematical formulas, chemical formulas, tables, etc.▼,▲Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Represents a divalent group shown by (2) The liquid crystal element according to claim 1, wherein the ferroelectric liquid crystal is a liquid crystal having at least two stable states. (3) The liquid crystal element according to claim 1, wherein the ferroelectric liquid crystal is a bistable liquid crystal. (4) The liquid crystal element according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal. (5) The liquid crystal device according to claim 1, wherein the ferroelectric liquid crystal is a chiral smectic liquid crystal with a non-helical structure.