JPH0766125B2 - Chiral smectic liquid crystal element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal display device, a liquid crystal device used in a liquid crystal-optical shutter, and the like, and more particularly to a liquid crystal device using a chiral smectic liquid crystal, and more specifically to an initial liquid crystal molecule. A liquid crystal device having improved display characteristics by improving the alignment state, and 2.
The present invention relates to a liquid crystal device that can display black and white with a small amount of transmitted light after extinction in two bistable states and can be applied to a color display device.

[Conventional technology]

Display devices of the type in which transmitted light rays are controlled by combining with a polarizing element by utilizing the refractive index anisotropy of ferroelectric liquid crystal molecules have been proposed by Clack and Lagerwall. 56-107216, U.S. Pat. No. 4367924, etc.). This ferroelectric liquid crystal generally has a chiral smectic C phase (Sm
C ^* ) or H phase (SmH ^* ), and in this state, in response to an applied electric field, takes one of a first optical stable state and a second optical stable state, and applies an electric field When it does not exist, it has the property of maintaining that state, that is, bistability, and has a quick response to changes in the electric field, and is expected to be widely used as a high-speed and memory type display element.

In order for the optical modulation element using the liquid crystal having the bistability to exhibit a predetermined driving characteristic, the liquid crystal disposed between the pair of parallel substrates has the two stable states regardless of the electric field application state. It is necessary that exchanges between the two take place effectively. For example SmC ^* or SmH ^* For the ferroelectric liquid crystal having a phase perpendicular to the substrate plane liquid crystal molecules phase having SmC ^* or SmH ^* phase, thus a region where the liquid crystal molecular axes are aligned substantially parallel to the substrate surface ( Mono domain) needs to be formed.

In order to use it as a black and white character display element or a color display element, a polarizing plate is arranged in crossed Nicols, and a liquid crystal element is sandwiched between them so that the first stable state becomes dark and the orientation is black, and the transmitted light amount. Needs to be small.

In order to satisfy these functions, it is necessary to create a special alignment state suitable for it.

By the way, as a method of aligning a ferroelectric liquid crystal, a method of using an alignment control film subjected to a uniaxial alignment treatment such as a rubbing treatment or an oblique vapor deposition 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 European Patent Publication No. 91661 and Japanese Patent Laid-Open No. 60-230635 discloses a wholly aromatic polyimide obtained by rubbing a ferroelectric liquid crystal under a helical structure that does not exhibit bistability. The orientation was controlled by a polyamide or polyvinyl alcohol film.

However, when the conventional alignment control film as described above is applied to the alignment control film for the ferroelectric liquid crystal of the non-helical structure exhibiting the bistability announced by Clark and Lagauol, the following problems will occur. Had.

[Problems to be solved by the invention]

That is, according to the experiments by the present inventors, the tilt angle θ (angle θ shown in FIG. 3 to be described later) in the ferroelectric liquid crystal having the non-helical structure obtained by aligning with the conventional alignment control film is spiral. A ferroelectric liquid crystal having a structure and a tilt angle (second
It was found that the angle was smaller than the angle which is half the apex angle of the triangular pyramid shown in the figure). In particular, the tilt angle θ of a ferroelectric liquid crystal having a non-helical structure obtained by aligning with a conventional alignment control film is generally about several degrees, and the transmittance at that time is about 3 to 5% at most.

Thus, according to Clarke and Lagauall, the tilt angle should be the same as the tilt angle in a ferroelectric liquid crystal having a helical structure, which is the non-helical ferroelectric liquid crystal that realizes bistability. Actually, the tilt angle θ in the non-spiral structure is smaller than the tilt angle in the spiral structure. That is, in order for the tilt angle θ to color the maximum tilt angle, the alignment state of the liquid crystal molecules needs to be the uniform alignment shown in FIG. 4, but in reality, as shown in FIG. There is a problem that a sufficiently large tilt angle θ cannot be formed because the liquid crystal molecules are in the splay alignment state due to the twisted alignment at the twist angle α. Further, the liquid crystal element in the splay alignment state exhibits an optical response characteristic with respect to a pulse signal as shown in FIG. 7, and this optical response characteristic causes flickering on the display screen when multiplexing driving is performed. There was a problem.

Therefore, an object of the present invention is to solve the above problems,
That is, to provide a liquid crystal element in which the tilt angle of a ferroelectric liquid crystal having a non-helical structure that realizes at least two stable states, particularly bistability, is increased, thereby improving the transmittance when the pixel shutter is opened. is there.

Another object of the present invention is to provide a liquid crystal element that does not cause a flicker on the screen during multiplexing driving.

Further, according to the experiments conducted by the present inventors, in a conventional alignment state using polyvinyl alcohol as an alignment control film, the color tone after extinction of the alignment is black, the amount of transmitted light after extinction is small, and the performance of the liquid crystal shutter is good. However, since there are many defects such as zigzag defects and the bistability during switching is not good, clear image quality cannot be obtained when actually matrix-driven.

In addition, when the wholly aromatic polyimide was used, the uniform orientation was good, there were few defects, and the bistability at the time of switching was good, but the orientation after extinction was blue, so clear images could not be obtained in this case either. .

Therefore, the present invention can realize the ferroelectric liquid crystal device in the uniform alignment state shown in FIG. 4 by using the specific alignment control film, and accordingly, the pulse signal as shown in FIG. 6 is obtained. It is an object of the present invention to realize a liquid crystal element that exhibits optical response and does not cause flicker on the screen during multiplexing driving.

Another object of the present invention is to provide a liquid crystal display which is black after extinction and which can correspond to a black and white display or a color display as a liquid crystal shutter and has a good liquid crystal switching performance.

[Means for solving problems]

That is, the present invention is a liquid crystal device characterized by using an alicyclic polyimide for an alignment control film in controlling the alignment of a ferroelectric liquid crystal device.

Preferably, the aliphatic polyimide is a polyimide resin film having a structural unit represented by the following general formula [I] or a polyimide film having each structural unit represented by the following general formulas [Ia] and [II] to [XII]. Is.

(R ₁ is a tetravalent aliphatic organic residue, n is 0 or 1) R ₂ : aliphatic group, R ₃ : aromatic group R ₄ : an aromatic group, R ₅ : an aliphatic group R ₆ : aromatic group, R ₇ : cycloaliphatic group R ₈ : cycloaliphatic group, R ₉ : aromatic group R ₁₀ and R ₁₁ are aliphatic groups R ₁₂ and R ₁₃ are aliphatic groups, and either one of them is a cycloaliphatic group.

The aliphatic group described in the present specification refers to an aliphatic group having no aromatic group.

〔Example〕

 Hereinafter, the present invention will be described in detail.

1 (a) and 1 (b) are cross-sectional views showing embodiments of the liquid crystal element of the present invention. The liquid crystal element shown in FIG. 1 (a) has a pair of upper and lower substrates 11a and 11b arranged in parallel.
And transparent electrodes 12a and 12b wired on the respective substrates. A ferroelectric liquid crystal, preferably a non-helical ferroelectric liquid crystal 13 having at least two stable states, is arranged between the plate 11a and the lower substrate 11b.

It is preferable that the transparent electrodes 12a and 12b described above are wired in a stripe shape, and the stripe shapes intersect each other in order to drive the ferroelectric liquid crystal 13 by multiplexing.

In the liquid crystal element shown in FIG. 1 (a), alignment control films 14a and 14b made of the above-mentioned aliphatic polyimide resin are arranged on the substrates 11a and 11b, respectively.

Further, the alignment control film 14 used in the liquid crystal element shown in FIG.
Either one of a and 14b is an aliphatic polyimide resin,
It is also possible to use the other one as an orientation control film other than the aliphatic polyimide resin. The orientation control film used at this time may be a film formed of polyimide, polyamide, or polyvinyl alcohol. Further, as shown in FIG. 1 (b), in the present invention, the use of the alignment control film 14b used in the liquid crystal element of FIG. 1 (a) can be omitted.

In the present invention, a uniaxial alignment axis can be imparted to the alignment control films 14a and 14b described above. This uniaxial orientation axis can be preferably imparted by a rubbing treatment.
At this time, the above-mentioned uniaxial orientation axes can be parallel to each other, but they can also intersect with each other.

The aliphatic polyimide used for the orientation control films 14a and 14b of the present invention can be synthesized by polycondensing tetracarboxylic dianhydride and diamine to form so-called polyamic acid, and then dehydrating and ring-closing.

However, the polymerization method is not particularly limited,
Any of solution polymerization, interfacial polymerization, bulk polymerization, phase polymerization and the like can be adopted. The above-mentioned polymerization reaction may be carried out by a one-step method in which the polyamic acid produced is not isolated but is converted into a polyimide.
Alternatively, it may be carried out by a two-step method in which a polyimide is produced or polyamic acid is isolated, then dehydrated and ring-closed to obtain a polyimide.

The solution method is usually suitable as the polymerization method in the present invention. The solvent used in the solution method is not particularly limited as long as it can dissolve the polyamic acid produced. As a typical example, N, N-dimethylformamide,
N, N-dimethylacetamide, N-methylpyrrolidone,
Examples thereof include N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfolane, hexamethylphosphoramide, and ptyrolactone. These may be used alone or as a mixture. Further, even a solvent which does not dissolve polyamic acid can be added to the above solvent within a range in which polyamic acid can be dissolved.

The reaction temperature of the polycondensation reaction for producing polyamic acid is −
You can select any temperature from 20 ℃ to 150 ℃, but especially -5 ℃
The range of -100 ° C is preferred.

In the present invention, in order to convert polyamic acid to polyimide, a method of dehydration and ring closure by heating is usually adopted. The temperature for the heat dehydration ring closure can be selected from 150 ° C to 400 ° C, preferably 170 ° C to 350 ° C. The time required for this dehydration ring closure depends on the above reaction temperature, but is 30 seconds to
It is suitable to spend 10 hours, preferably 5 minutes to 5 hours. Further, as another method of converting polyamic acid into polyimide, a method of chemically ring-closing using a dehydration ring-closing catalyst may be adopted. For these methods, known methods used in ordinary polyimide synthesis can be adopted as they are, and conditions are not particularly limited.

Further, vapor deposition polymerization in which a film of tetracarboxylic dianhydride and diamine is directly formed on a substrate in a vapor phase is also possible.

Specific examples of the aliphatic tetracarboxylic acid dianhydride and the diami compound are shown below.

(1) Aliphatic tetracarboxylic dianhydride When the alicyclic tetracarboxylic dianhydride is used as the tetracarboxylic dianhydride in the present invention, the diamine used in the present invention is not particularly limited as long as the object of the present invention is not impaired. Typical examples thereof include p-phenylenediamine, n-phenylenediamine, diaminodiphenylmethane, diaminodiphenylether, 2,2-diaminophenylpropane, diaminodiphenylsulfone, diaminobenzophenone. , Diaminonaphthalene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-di (4-aminophenoxy) diphenylsulfone, 2,2-bis (4 -(4-aminophenoxy) phenyl) propane and the like.

(2) Aliphatic diamine compound (O) in _{NH 2 -CH 2 CH 2 -O-} CH 2 CH 2 -NH 2 present invention, when using an aliphatic diamine as the diamine, tetracarboxylic dianhydride used in the present invention, the present invention There is no particular limitation as long as the purpose is not impaired. Typical examples thereof include pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, 2,2-bis (dicarboxyphenic acid). Examples thereof include phenyl) propane dianhydride, bis (dicarboxyphenyl) sulfone dianhydride, and bis (dicarboxyphenyl) ether dianhydride.

Further, instead of the above-mentioned aromatic tetracarboxylic dianhydride, a combination of all aliphatic polyimides by combining the above-mentioned aliphatic tetracarboxylic dianhydride and aliphatic diamine may be used.

The polyimide used in the present invention, olefins represented by vinyl alcohol or other polymerizable monomers (for example, propylene, α-olefins such as isobutylene, methyl vinyl ether, alkyl vinyl ethers represented by methyl vinyl ether, One or more kinds such as vinyl chloride) and copolymers with aliphatic polyimide are also included.

The orientation control films 14a and 14b are formed by a film of an aliphatic polyimide resin, but it is possible to have a function as an insulating film, and is usually about 30Å to 1μ, preferably 50Å to 2000Å, more preferably 70Å to 1000Å Is formed with a film thickness of.

Further, as a method for forming a coating film of these aliphatic polyimides, the precursor polyamic acid resin is dissolved in a suitable solvent in an amount of 0.1% by weight to 20% by weight, preferably 0.2% by weight to 10% by weight. Solution or its precursor solution is applied by a spinner coating method, a dip coating method, a screen printing method, a spray coating method, a roll coating method or the like, and then cured under predetermined curing conditions (for example, heating). Can be used.

Polyimide soluble in N-methylpyrrolidone (NMP), gamma-butyrolactone, etc. is not polyamic acid,
It is also possible to apply after forming the polyimide ring.

Next, a ferroelectric liquid crystal having an array of molecules forming a plurality of layers perpendicular to the surfaces of a pair of substrates used in the liquid crystal element of the present invention will be described.

FIG. 2 is a schematic drawing of an example of a ferroelectric liquid crystal cell using a spiral structure. 21a and 21b are In ₂ O ₃ and SnO ₂
A substrate (glass plate) coated with a transparent electrode such as ITO or Indium Tin Oxide (ITO), and multiple liquid crystal molecular layers between them.
22 was oriented so that it was a layer perpendicular to the glass substrate surface.
Liquid crystal of SmC ^* (C phase of chiral smectic) is enclosed. A thick line 23 represents a liquid crystal molecule,
The liquid crystal molecule 23 has a dipole moment (P⊥) 24 in a direction orthogonal to the molecule. At this time, it represents the tilt angle in the chiral smectic phase of the helical structure, which takes the angle forming the apex angle of the triangular pyramid. When a voltage above a certain threshold is applied between the electrodes on the substrates 21a and 21b, liquid crystal molecules
23 unwound spiral structure, dipole moment (P ⊥) 24
The orientation direction of the liquid crystal molecules 23 can be changed so that all are oriented in the direction of the electric field.

However, the ferroelectric liquid crystal using this helical structure returns to the original helical structure when no electric field is applied, and does not exhibit the bistability described below.

In a preferred embodiment of the present invention, at least 2 when no electric field is applied.
It is possible to use the ferroelectric liquid crystal element shown in FIG. 3 which has two stable states, especially a bistable state. That is, when the thickness of the liquid crystal cell is made sufficiently thin (for example, 1 μ), the helical structure of the liquid crystal molecules is unwound and becomes a non-helical structure even when no electric field is applied, as shown in FIG. Child moment Pa or Pb is upward (34a) or downward (3
A bistable state is formed by taking either of the states of 4b). When electric fields Ea or Eb with different polarities above a certain threshold value are applied to such a cell, the dipole moment electric field Ea or Eb rises corresponding to the electric field vector.
The liquid crystal molecules are oriented to either the first stable state 33a or the second stable state 33b in accordance with the change in the direction of 34a or downward 34b. Half of the angle formed by the first and second stable states at this time corresponds to the tilt angle θ.

There are two advantages of 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. Explaining the second point with reference to FIG. 3, for example, when an electric field Ea is applied, the liquid crystal molecules are aligned in the first stable state 33a, but this state is stable even when the electric field is cut off. Moreover, when the electric field Eb in the opposite direction is applied, the liquid crystal molecules are in the second stable state.
It is oriented to 33b and changes its molecular orientation, but it remains in this state even when the electric field is turned off. Also, the applied electric field
As long as Ea does not exceed a certain threshold, they are also maintained in their respective orientations. With such a fast response speed,
To effectively realize the memory effect of bistability,
It is preferable that the cell is as thin as possible, and generally 0.5 μ to 20 μ, particularly 1 μ to 5 μ is suitable. A liquid crystal-electro-optical device having a matrix electrode structure using a ferroelectric liquid crystal of this kind has been proposed by Clark and Lagabal in US Pat. No. 4,367,924.

Ferroelectric liquid crystals that can be used in the liquid crystal element of the present invention include, for example, p-dekioxybenzylidene-p'-amino-2-methylbutyl cinnamate (DOBAMBC), p
-Hexyloxybenzylidene-p'-amino-2-chloropropyl cinnamate (HOBACPC), p-decyloxybenzylidene-p'-amino-2-methylbutyl-α-
Cyanocinnamate (DOBAMBCC), p-tetradexylobenzylidene-p'-amino-2-methylbutyl-α-
Cyanocinnamate (TDOBAMBCC), p-octyloxybenzylidene-p'-amino-2-methylbutyl-α
-Chlorocinnamate (OOBAMBCC), p-octyloxybenzylidene-p'-amino-2-methylbutyl-α
-Methylcinnamate, 4,4'-azoxycinnamate bis- (2-methylbutyl) ester, 4-o
-(2-Methyl) butyl resorcylidene-4'-octylaniline, 4- (2'-methylbutyl) phenyl-
4'-octyloxybiphenyl-4-carboxylate, 4-hexyloxyphenyl-4- (2 "-methylbutyl) biphenyl-4'-carboxylate, 4-octyloxyphenyl-4- (2" -methylbutyl) ) Biphenyl-4'-carboxylate, 4-heptylphenyl-4- (4 "-methylhexyl) biphenyl-4 '
-Carboxylate, 4- (2 "-methylbutyl) phenyl-4- (4" -methylhexyl) biphenyl-4 '
-Carboxylate and the like can be used, and these can be used alone or in combination of two or more kinds, and can also contain other collectable liquid crystals or smectic liquid crystals within a range showing ferroelectricity.

In the present invention, a chiral smectic phase can be used as the ferroelectric liquid crystal. Specifically, the chiral smectic C phase (SmC ^* ), H phase (SmH ^* ), I phase (Sm
I ^* ), K phase (SmK ^* ) and G phase (SmG ^* ) can be used.

FIG. 4 is a cross-sectional view schematically showing a uniform alignment state of the ferroelectric liquid crystal element when no voltage is applied.
The figure shows the optical response characteristics to the pulse signal at that time. That is, FIG. 4 is a cross-sectional view of the vertical layer 32 formed by a plurality of chiral smectic liquid crystal molecules shown in FIG. 3 as seen from the normal direction, and 41 in FIG. 4 is a liquid crystal molecule shown in FIG. 33a or 33b represents a mapping (C-delector) onto the vertical layer 32, and 42 represents liquid crystal molecules for the vertical layer 32.
It represents the tip of 33a or 33b. Therefore, according to FIG. 4, the liquid crystal molecules in the vertical layer 32 are oriented substantially parallel to each other, and the tilt angle θ can be brought close to the maximum tilt angle. This state is called a uniform orientation state.

On the other hand, FIG. 5 shows the arrangement state in the vertical layer 32 in the same manner as in FIG. As can be seen from FIG. 5, the tips 42 of the liquid crystal molecules 41 in the vertical layer 32 rotate along the circumference in the layer thickness direction of the vertical layer. Therefore, the liquid crystal molecules adjacent to the substrates 21a and 21b are not parallel to each other, and the liquid crystal molecules in the vertical layer 32 are oriented in a continuously twisted state from the substrates 21a to 21b. Become. Such an alignment state is called a splay alignment state.

This splay alignment state adopts the uniform alignment state shown in FIG. 4 under the condition that a predetermined voltage is applied, but once the applied voltage is cut off and the memory state is restored, it returns to the splay alignment state shown in FIG. It has been found. Therefore, in the splay alignment state, as shown in FIG. 7, under the voltage application state, the optical characteristics of high transmittance based on the uniform alignment state are shown, but when the voltage is not applied, the tilt angle θ is small, and the original splay alignment state is obtained. Since it returns to the state, the optical characteristics have low transmittance based on this.

On the other hand, in the uniform alignment state shown in FIG.
Since the splay alignment state described above is not adopted, it is possible to maintain the high transmittance characteristic when a voltage is applied as it is, even under the memory state when the applied voltage is cut off, as shown in FIG.

That is, although FIG. 6 shows the transmittance curve 61 when a pulse 62 having a voltage of 10 V and a pulse width of 500 μsec is applied,
It can be seen that the transmittance at the time of pulse application is maintained even under the memory condition of 0 V. FIG. 7 shows a transmittance curve 71 when a pulse 72 having a similar voltage of 10 V and a pulse width of 500 μsec is applied. According to the transmittance curve 71, the transmittance is high when a pulse is applied, which causes the flicker during driving. Further, the transmittance is drastically lowered under the memory condition of 0 volt, which causes the darkness on the display screen. Therefore, in order to eliminate the flicker and to increase the tilt angle, the uniform alignment state is preferable.

Furthermore, in a preferred embodiment of the present invention, the AC application pretreatment is effective for the ferroelectric liquid crystal to adopt the uniform alignment state shown in FIG. By this AC application pretreatment, it is possible to increase the above-described tilt angle θ to an angle equal to or about the same as the tilt angle in the spiral structure. As the alternating current used at this time, a voltage of 20 to 500 V, preferably 30 to 150 V and a frequency of 10 to 500 Hz, preferably 10 to 200
Hz can be used, and AC application pretreatment can be performed with the application time of several seconds to 10 minutes. Further, the AC application pretreatment is performed before the liquid crystal element is written according to, for example, a video signal or an information signal, and preferably, the wait time when the liquid crystal element is written in the device and the device is operated. Or perform the above-mentioned AC application pretreatment,
Alternatively, a pretreatment for AC application can be performed even when manufacturing such a liquid crystal element.

Such AC application pretreatment can be performed by increasing the tilt angle θ before application to the same degree as the tilt angle in the spiral structure, and even after removing the AC application, the tilt angle θ is increased. The tilt angle can be maintained.

Further, such a pre-treatment for applying an alternating current is performed by a ferroelectric liquid crystal having a large spontaneous polarization (for example, 5 nc / cm ² or more at 25 ° C., preferably 10 nc / cm 2
^{2 to} 300 nc / cm ² ; nc is a unit indicating nanocoulomb). This spontaneous polarization can be measured by the triangular wave printing method * with a 100μ cell.

* Japanese Journal of Applicd Physisc 2
2 (10), pp. 661-663 (1983)
Co-authored by K. Miyasato and others, "Directive Mesoud Dry Angler Waves Foe Mediaring Spontaneous Polarization Fueroelectric Liquid Crystal"("Direct
Method with Triangular Waves for Measuring Sponta
neous Polarization in Fcrroelectric Liquid Crysta
l ").

〔Example〕

Hereinafter, the present invention will be described with reference to specific examples and comparative examples.

Hereinafter, the liquid crystal cells used in the examples are In ₂ O ₃ and ITO (Indium
A layer for preventing shorting between the upper and lower electrodes is provided on a transparent electrode such as Tin Oxide), and an orientation control layer is further laminated thereon.

Example 1 2,2-Bis (4- (4-aminophenoxywaenyl) propane (12,3 g) was added to N, N-dimethylformamide (189 ml) and stirred to give a uniform solution, and then 3,5,6- 7.5 g of tolcarboxy-2-carboxymethylnorbornane-2: 3,5: 6-dianhydride was added, and stirring was continued at room temperature for 6 hours.
It became a light brownish viscous liquid. When this viscous liquid was precipitated in a large amount of toluene, a white solid 17.6
g polyamic acid was obtained.

The obtained polyamitic acid was dissolved in dimethylformamide at a ratio of 2% by weight, and 180% was dissolved in a spinner at a rotation speed of 3000 rpm.
It was applied for 2 seconds. After forming the film, the film was heated and baked at 250 ° C. for 1 hour to form a coating film of a polyimide resin represented by the following formula [1] repeatedly. The film thickness of the coating film at this time is about 200
It was Å.

The coating after the baking is rubbed with an acetate flocked cloth, then washed with an isopropyl alcohol solution and sprayed with alumina beads having an average particle diameter of about 1 μm on one glass plate, and then each rubbing treatment axis A cell was prepared by stacking two glass plates so that the cells were parallel to each other.

When the cell thickness of this cell was measured with a Beret phase plate (measurement by phase difference), it was about 1 μm. "CS-1011" (trade name) manufactured by Chitsso Co., Ltd. was vacuum-injected into the cell under the isotropic phase, and then 60 ° C at 0.5 ° C / h from the isotropic phase.
Orientation could be achieved by slow cooling to ℃. The subsequent experiments were conducted at 60 ° C.

The phase change of "CS-1011" described above was as follows.

(SmA: smectic phase A, Ch: cholesteric phase, Iso;
Observation of this cell under orthogonal Nicols revealed that monodomains constituting a uniform, defect-free, non-helical chiral smectic C phase were obtained.

Next, a high electric field alternating current with a voltage of 70 V and a frequency of 70 Hz was applied to the above-mentioned liquid crystal cell for about 1 minute (AC application pretreatment). The tilt angle θ at this time was measured and found to be 18 °.

This tilt angle θ is due to the pulse electric field (10V, 500μ
sec) is applied to align the liquid crystal molecule direction to one stable state, and while the liquid crystal cell is rotated under orthogonal Nicols, find the position in the darkest state where the transmitted light amount becomes the lowest, and then the previous pulse. And pulsed electric field of opposite polarity (-10V, 5
(00 μsec) is applied to transfer to the other stable molecular alignment state to make it a bright state, and then the liquid crystal cell is rotated again to find the angle at which it becomes the darkest state. The positions of these two darkest states correspond to detecting the stable average molecular axis of the liquid crystal, and the angle between these two states corresponds to the tilt angle θ.

It was found that the liquid crystal cell of this example maintained a tilt angle of 18 ° for a period of one week or longer.

Further, when the liquid crystal element of the present example was subjected to multiplexer driving under the following driving conditions, a display screen without flicker was formed.

Driving conditions (1) First step: A signal with a pulse width of 500 μsec and a voltage of 10 V and a signal with a pulse width of 500 μsec and a voltage of −5 V are applied to all the scanning lines at one time.

(2) Second step: Using a pulse width of 500 μsec and a voltage of 10 V as a scanning selection signal, sequentially applying this signal to scanning lines, and synchronizing with this scanning selection signal, a signal with a pulse width of 500 μsec and a voltage of 5 V and a pulse A signal with a width of 500 μsec and a voltage of -5 V is selectively applied to the signal line.

Further, when this liquid crystal element was adjusted to the extinction position under a crossed Nicols polarizer, the color tone of the alignment was black.

When this device was driven with a driving voltage of 10 V and a pulse width of 500 msec, the image quality was clear and the display was very poor.

Example 2 Diaminodiphenyl ether (DDE), 20.48 g (0.102 mol) was dissolved in N, N-dimethylformamide (DMF) 247.5 g, and then TCA.AH 23.15 g (0.103 mol) was added as a powder. The reaction was carried out at 25 ° C with stirring. After 24 hours, a small amount of this reaction solution was sampled and 0.5 g / 100 polyamic acid was added.
Intrinsic viscosity (30 ° C) was measured by adding dimethylformamide to a concentration of ml. The obtained polyamitic acid had an ηinh of 0.99 dl / g.

Next, dimethylformamide was further added to the reaction solution to adjust the polyamic acid concentration to 6.1% by weight and 30 g of the solution was added to 100 m.
The mixture was transferred to a 1-liter flask, 1.32 g of acetic anhydride and 1.02 g of pyridine were sequentially added to this solution, mixed and stirred, and then reacted at 135 ° C. for 2 hours.

Then, the reaction product was poured into a large amount of methanol to solidify and recover the soluble polyimide resin, followed by drying at 80 ° C. overnight,
A polyimide resin represented by repeating formula [2] below was obtained.

The obtained polyimide was dissolved in dimethylamide at a ratio of 2% by weight and applied for 180 seconds by a spinner having a rotation speed of 3000 rpm. A liquid crystal element was produced using the substrate which was formed at 170 ° C. for 1 hour after the film formation.

A voltage of 70 V was applied to the produced liquid crystal cell at a frequency of 7 V as in Example 1.
A high electric field alternating current of 0 Hz was applied for about 1 minute (pretreatment for alternating current application). The tilt angle θ at this time was measured and found to be 18.5 °. Further, it was found that the liquid crystal cell of this example maintained a tilt angle of 18 ° or more for one week or more, and there was no flicker during writing.

This liquid crystal element was also subjected to the same experiment as in Example 1, and as a result, the color tone of the alignment observed under a microscope was black, the image quality as a display was good, and the image quality was clear.

Examples 3 to 7 Using the substrate on which the polyimide resin shown by repeating the structural unit shown in Table 1 is formed, the same cell as in Example 1 was prepared and the same experiment as in Example 1 was conducted. . The tilt angle θ at that time and the tilt angle θ after standing for 1 week were measured. The results are shown in Table 1. Also shown are the results regarding the orientation color tone and the image quality.

Comparative Example 1 The polyimide resin used in Example 1 and the liquid crystal cell was prepared from (3,3 ′, 4,4′-diphenyltetracarboxylic anhydride and p-phenylenediamine in a molar ratio of 1: 1). In the same manner as in Example 1, except that the coating film of the polyamic acid obtained by the dehydration condensation reaction in 3.5% by weight of N-methyl-2-pyrrolidone solution was replaced with polyimide produced by dehydration ring closure. A cell was prepared and subjected to the same AC application pretreatment as in Example 1.

The tilt angle θ of the liquid crystal cell at this time was measured and found to be 8 °. A display screen was formed by using the liquid crystal cell in the same multiplexing driving as in Example 1, but flicker occurred during writing.

Further, the color tone of this liquid crystal element after being extinguished was blue, and the image quality was unclear.

Comparative Example 2 A liquid crystal cell was prepared in the same manner as in Example 1 except that the polyimide resin used when preparing the liquid crystal cell of Example 1 was replaced by polyvinyl alcohol, and the same pre-treatment for AC application as in Example 1 was carried out. went.

The tilt angle θ of the liquid crystal cell at this time was measured and found to be 17.5. Furthermore, this liquid crystal cell has a tilt angle θ of 18 °.
When the maintenance time of was measured, the tilt angle was 15.5 on the second day.
It was found that the tilt angle decreased to about 10 ° after one week. A display screen was formed on the liquid crystal cell after left for one week by the same multiplexing driving as in Example 1, but flicker occurred during writing.

The extinction position of this liquid crystal element was black, but there were many defects.
The image quality was unclear because it tended to be monostable.

〔The invention's effect〕

According to the present invention, it is possible to realize a ferroelectric liquid crystal in a uniform alignment state in which an increased tilt angle can be obtained, and moreover, this uniform alignment state can be stably maintained for a long time.

Furthermore, a black color at the extinction position and a clear image quality can be obtained.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional views showing an embodiment of a ferroelectric liquid crystal device of the present invention, and FIG. 2 schematically shows a liquid crystal device using a ferroelectric liquid crystal having a helical structure. FIG. 3 is a perspective view, FIG. 3 is a perspective view schematically showing a liquid crystal device using a ferroelectric liquid crystal having a non-helical structure, FIG. 4 is a sectional view schematically showing a uniform alignment state, and FIG. 5 is a splay alignment state. FIG. 6 is a cross-sectional view schematically showing the above, FIG. 6 is a characteristic diagram showing optical response characteristics in a uniform alignment state, and FIG. 7 is a characteristic diagram showing optical response characteristics in a splay alignment state. 11a …… upper substrate 11b …… lower substrate 12a, 12b …… transparent electrode 13 …… ferroelectric liquid crystal 14a, 14b …… light distribution control film, 21a, 21b …… substrate 22 …… liquid crystal molecular layer 23 …… liquid crystal Molecule 24 …… Dipole moment 32 …… Vertical layer 33a …… First stable state 33b …… Second stable state 34a …… Upward dipole moment 34b …… Upward dipole moment …… Tilt angle in helical structure Ea, Eb …… Electrolysis θ …… Tilt angle in non-helical structure 41 …… Projection of liquid crystal molecules to the vertical layer (C-director 42 …… Tip of liquid crystal molecule to vertical layer 61 …… Uniform alignment state) Transmittance curve 62,72 …… Pulse 71 …… Transmittance curve in splay orientation state

Claims (21)

[Claims] 1. A chiral smectic liquid crystal device having an alignment control film and a chiral smectic liquid crystal between a pair of substrates, wherein the alignment control film comprises a. A polyimide having a structural unit represented by the following general formula [I], a general formula: [I] (R ₁ is a tetravalent aliphatic organic residue, n is 0 or 1.) b. A polyimide having a structural unit represented by the following general formula [VIII], or a general formula [VIII] (R ₄ is an aromatic group and R ₅ is an aliphatic group.) C. Polyimide having a structural unit represented by the following general formula [IX], general formula [IX] (R ₆ is an aromatic group and R ₇ is a cycloaliphatic group.) A chiral smectic liquid crystal device characterized by being formed of an aliphatic polyimide. 2. The aliphatic polyimide according to claim 1, which is an aliphatic polyimide having a cyclic saturated hydrocarbon group.
A chiral smectic liquid crystal device according to item. 3. The aliphatic polyimide is represented by the following general formula [I
The chiral smectic liquid crystal device according to claim 1, which is a polyimide having a structural unit represented by a]. General formula [I a] (R ₂ is an aliphatic group and R ₃ is an aromatic group.) 4. The chiral smectic liquid crystal device according to claim 1, wherein the aliphatic polyimide is a polyimide having a structural unit represented by the following formula [II]. Formula [II] 5. The aliphatic polyimide according to claim 1, which is a polyimide having a structural unit represented by the following formula [III].
A chiral smectic liquid crystal device according to item. Formula [III] 6. The chiral smectic liquid crystal device according to claim 1, wherein the aliphatic polyimide is a polyimide having a structural unit represented by the following formula [IV]. Formula [IV] 7. The chiral smectic liquid crystal device according to claim 1, wherein the aliphatic polyimide is a polyimide having a structural unit represented by the following formula [V]. Formula [V] 8. The chiral smectic liquid crystal device according to claim 1, wherein the aliphatic polyimide is a polyimide having a structural unit represented by the following formula [VI]. Expression [VI] 9. The aliphatic polyimide according to claim 1, which is a polyimide having a structural unit represented by the following formula [VII]:
A chiral smectic liquid crystal device according to item. Formula [VII] 10. The chiral smectic liquid crystal device according to claim 1, wherein the aliphatic polyimide is a polyimide having a structural unit represented by the following general formula [X]. General formula [X] (R ₈ is a cycloaliphatic group, and R ₉ is an aromatic group.) 11. The aliphatic polyimide is represented by the following general formula [X
The chiral smectic liquid crystal device according to claim 1, which is a polyimide having a structural unit represented by [I]. General formula [XI] (R ₁₀ and R ₁₁ are aliphatic groups.) 12. The aliphatic polyimide represented by the following general formula [XI
The chiral smectic liquid crystal device according to claim 1, which is a polyimide having a structural unit represented by [I]. General formula [XII] (R ₁₂ and R ₁₃ are aliphatic groups, and one of them is a cycloaliphatic group.) 13. The chiral smectic liquid crystal device according to claim 1, wherein the degree of polymerization of the polymer is 100 to 200,000. 14. The chiral smectic liquid crystal device according to claim 1, wherein the degree of polymerization of the polymer is 500 to 5,000. 15. The chiral smectic liquid crystal device according to claim 1, wherein the alignment control film has a uniaxial alignment axis. 16. The chiral smectic liquid crystal device according to claim 15, wherein the uniaxial alignment axis is an alignment axis provided by a rubbing treatment. 17. The chiral smectic liquid crystal device according to claim 1, wherein the chiral smectic liquid crystal is a liquid crystal exhibiting at least two stable alignment states in the absence of an electric field. 18. The chiral smectic liquid crystal element according to claim 1, wherein the tilt angle of the chiral smectic liquid crystal is 18 ° or more. 19. The film thickness of the aliphatic polyimide coating is 30Å
The chiral smectic liquid crystal element according to claim 1, which is ˜1 μm. 20. The film thickness of the aliphatic polyimide coating is 50Å
The chiral smectic liquid crystal device according to claim 1, which is ˜2000Å. 21. The film thickness of the aliphatic polyimide coating is 70Å
The chiral smectic liquid crystal device according to claim 1, wherein the chiral smectic liquid crystal device has a thickness of about 1000Å.