JPS6125128A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To allow operation characteristics of the element based upon the bistability of liquid crystal and the monodomain property of a liquid crystal layer to consist together by providing a couple of substrates across a liquid crystal compound which consists of >=2 kinds of liquid crystal showing an Sm* including at least cholesteric liquid crystal, and performing a specific orientation treatment for at least either of the substrates. CONSTITUTION:The substrates 101 and 101' are held at a specific interval across spacers 104 and adhered together with an adhesive agent 106. Plural transparent electrodes 102 are formed on the substrate 101 and pluralf transparent electrodes 102' crossing the electrodes 102 are formed on the substrate 101'. An orientation control film 105 is formed on the substrate 101' by vapor-depositing SiO, SiO2, etc., and rubbed in one direction as the orientation treatment. The liquid crystal compound 13 consisting of >=2 kinds of liquid crystal having an Sm*A phase including liquid crystal showing the cholesteric phase is charged between the substrates 101 and 101'. Consequently, the liquid crystal element 100 which his both the operation characteristics of the element 100 based upon the bistability of the liquid crystal 103 and the monodomain property of the liquid crystal layer 103 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal device used in a liquid crystal display device, a liquid crystal light shutter, etc., and more specifically, a liquid crystal device with improved display and driving characteristics by improving the initial orientation state of liquid molecules. It is related to the element.

Conventionally, liquid crystal display elements display images or information by configuring a scanning electrode group and a signal electrode group in a matrix, and filling a liquid crystal compound between the electrodes to form a large number of pixels.
well known.

The driving method for this display element is time-division driving, in which an address signal is selectively and periodically applied to a group of scanning electrodes, and a predetermined information signal is selectively applied in parallel to a group of signal electrodes in synchronization with the address signal. However, this display element and its driving method have major and fatal drawbacks as described below.

That is, it is difficult to increase the pixel density or enlarge the screen. Among conventional liquid crystals, most of them have relatively high response speed and low power consumption, so most of them are in practical use as single display elements. APpliedPhysics Letters”
Vo, 18, No. 4 (1971°2.15),
“Voltage-Depende” on P127-128
ntOptical Activity of a
TwistedNematic Liquid Cry
TN (twisted nema) shown in "stal"
This type of liquid crystal forms a structure (helical structure) in which nematic liquid crystal molecules with positive dielectric anisotropy are arranged in the thickness direction of the liquid crystal layer in the absence of an electric field. However, a structure is formed in which the liquid crystal molecules are arranged in parallel on both electrode surfaces. On the other hand, when an electric field is applied, nematic liquid crystals with positive dielectric anisotropy are aligned in the direction of the electric field, resulting in optical modulation. When a display element is constructed with a matrix electrode structure using this type of liquid crystal, the area where both the scanning electrode and the signal electrode are selected (selected point) has a threshold value greater than or equal to the threshold required to align the liquid crystal molecules perpendicular to the electrode surface. A voltage is applied to the region where neither the scanning electrode nor the signal electrode is selected (unselected point), and therefore the liquid crystal molecules maintain a stable alignment parallel to the electrode plane. By arranging linear polarizers above and below a liquid crystal cell in a cross-Nicol relationship with each other, light does not pass through selected points, but light passes through non-selected points, making it possible to use it as an image element. Become. However, when a matrix electrode structure is configured, there may be a region where the scanning electrode is selected and the signal electrode is not selected, or a region where the scanning electrode is not selected and the signal electrode is selected (a so-called "half-selected point path"). A finite electric field is applied.The difference between the voltage applied to the selected point and the voltage applied to the half-selected point is sufficiently large, and the voltage threshold required to align the liquid crystal molecules perpendicular to the electric field is set to an intermediate voltage value. If this is the case, the display element will operate normally, but if the number of scanning lines (N) is increased, an effective electric field will be generated at one selected point while scanning the entire screen (1 frame). The time taken (duty ratio) decreases at the rate of l/N.For this reason, when repeated scanning is performed, the effective voltage difference between selected points and non-selected points increases as the number of scanning lines increases. The larger the number, the smaller it becomes, and as a result, a decrease in image contrast and crosstalk become unavoidable drawbacks.Such phenomena are caused by liquid crystals that do not have bistability (electrolyte, polar surface , the stable state is when the liquid crystal molecules are aligned horizontally, and they are aligned vertically only while an electric field is effectively applied) is driven using the temporal accumulation effect (i.e., repeatedly scanned). This is an unavoidable problem in terms of wood quality.In order to improve this point,
Voltage averaging methods, dual-frequency driving methods, multiple matrix methods, etc. have already been proposed, but all of them are insufficient. The current situation is that it has reached a plateau because it cannot be increased.

On the other hand, looking at the field of printers, laser beam printers provide electrical image signals in the form of light to an electrophotographic photoreceptor, both in terms of pixel density and speed, as a means of obtaining hard copies using electrical signals as input. LBP) is also excellent in current quantity. However, for LBP.

There are disadvantages such as 1. The printer is large in size; 2. It has high-speed moving parts such as a polygon scanner, which generates noise and requires strict mechanical precision. In order to overcome these drawbacks, a liquid crystal shutter array has been proposed as an element that converts electrical signals into optical signals. However, when providing pixel signals using a liquid crystal shutter array, for example, in order to write pixel signals at a rate of 16 dots/mm within a length of 210 mm, it is necessary to have 3000 or more signal generating sections. First, in order to provide independent signals to each, it was originally necessary to wire lead wires to send signals to each signal generating section, which was difficult to manufacture.

Therefore, an attempt has been made to provide pixel signals for ILINE (line) in a time-division manner using a signal generating section divided into several lines. In this way, the electrode that gives the signal can be
“This is because it can be made common to multiple signal generators, and the actual wiring can be significantly reduced. When the number of rows (N) is increased using
The time required is essentially 17N, which reduces the amount of light that can be obtained on the photoreceptor, and there is a problem of crosstalk.

C1ark and Lagerwall proposed the use of bistable liquid crystal elements to improve the drawbacks of conventional liquid crystal elements.

It has been proposed (Japanese Unexamined Patent Publication No. 56-107216, US Pat. No. 4,367,924, etc.).

Bistable liquid crystals generally include chiral smectic C phase (SmC') or other chiral smectic phases, specifically chiral smectic Ha (SmH').
, a chiral smectic F phase (SmF), a chiral smectic ■ phase (SmI), and a chiral smectic G phase (SmG).

This liquid crystal has a bistable state consisting of a first optically stable normal state and a second optically stable state with respect to an electric field, and therefore, unlike the optical modulation element used in the above-mentioned TN type liquid crystal, for example, one The liquid crystal is aligned in a first optically stable state with respect to the electric field vector, and the liquid crystal is aligned in a second optically stable state with respect to the other electric field vector. In addition, this type of liquid crystal can respond to an applied electric field by very quickly taking one of the two stable states described above, and maintaining that state when no electric field is applied. Considerable substantial improvements are obtained over many of the problems of TN-type devices. This point will be explained in more detail below in connection with the present invention. However, in order for an optical modulation element using this bistable liquid crystal to exhibit predetermined driving characteristics, the liquid crystal placed between a pair of parallel substrates must be It is necessary that the molecules be in such a state that conversion between stable states can occur effectively. For example, for ferroelectric liquid crystals with S m C or other chiral smectic phases,
A region in which 5m0 or other liquid crystal molecular layers having a chiral smectic phase are perpendicular to the substrate surface, and therefore the liquid crystal molecular axes are arranged almost parallel to the substrate surface (monodomain)
needs to be formed. However, in conventional optical modulation elements using liquid crystals with bistability, the alignment state of the liquid crystals having such a monodomain structure was not always formed satisfactorily, and therefore sufficient characteristics could not be obtained. is the reality.

For example, methods of applying a magnetic field, methods of applying shear force, etc. have been proposed in order to provide such an orientation state. However, none of these methods necessarily gave satisfactory results. for example,
The method of applying a magnetic field requires large-scale equipment and is incompatible with thin-layer cells with good operating characteristics. The problem is that it is incompatible with the "method of injecting."

In view of the above-mentioned circumstances, the main object of the present invention is to provide a bistable device which has potential suitability as a display element with fast response, high density pixels and a large area, or an optical shutter with a high shutter speed. An object of the present invention is to provide a method for controlling the alignment of liquid crystal that can fully demonstrate its properties by improving monodomain formation or initial alignment, which has been a problem in the past in optical modulation elements using liquid crystals having .

As a result of further research for the above-mentioned purpose, the present inventors have found that, in particular, the liquid crystal material is less likely to have a smectic phase, such as SmA (smectic A phase), than another phase (for example, high-temperature S such as Tokichi phase).
A liquid crystal composition containing two or more types of liquid crystals exhibiting at least an irradial smectic phase, and at least one of them further exhibiting a cholesteric phase. When using , it is possible to form monodomains aligned in one direction with priority given to the molecular axis direction of the liquid crystal on the surface of the substrate that contacts the liquid crystal at the interface, and as a result, the operating characteristics of the device based on the bistability of the liquid crystal can be improved. It has been found that it is possible to obtain a liquid crystal element having a structure that can achieve both the monodomain property of the liquid crystal layer and the monodomain property of the liquid crystal layer.

The present invention is based on the above-mentioned knowledge, that is, the liquid crystal element of the present invention has two or more types of liquid crystals exhibiting a chiral smectic phase such as SmH, SmF, SmI, and 3m0 wood between a pair of substrates. and at least one of the two or more types of liquid crystals further includes a liquid crystal exhibiting a cholestic phase; Among the substrates, at least one surface of the substrate has the effect of preferentially aligning the molecular axis direction of the liquid crystal that contacts at the interface in one direction.

Hereinafter, the present invention will be described in further detail with reference to the drawings as necessary.

The liquid crystal composition used in the present invention contains at least two or more types of liquid crystals exhibiting a chiral smectic phase, and at least one of them further contains a liquid crystal exhibiting a cholesteric phase, and has ferroelectricity. . Specifically, SmC, SmF trees, and 5JIII trees.

A liquid crystal composition having a chiral smectic phase of 3m0 trees can be used.

Table 1 shows specific examples of liquid crystals exhibiting a chiral smectic phase used in the liquid crystal composition of the present invention.

On the other hand, Table 2 shows specific examples of liquid crystals that exhibit a chiral smectic phase and further exhibit a cholesteric phase.

Table ゛ 1 Specific examples of liquid crystals exhibiting a chilyle smectic phase (compound name, structural formula, and phase transition point) (1) ? H3 C10H210-@-CH= s-@-CH= CH=
COOCH2CHC2H5* 5rnH book 63℃ (2) 0 sentences C6H130-@-CH=Nsha CH=CH-C00CH
2CHCH3 Wood 60℃ 64℃ 78℃ Crystal → S
mH” → SmC tree → SmA → Tokichi phase 2
7℃ 3m0 pieces 38℃ -Methylbutyl-α-methylcinnamate Formula and phase transition point) 4-(2'-methylbutyl)phenyl-4'octyloxybiphenyl-4-carboxylate 78°C
80℃ 128.3℃ crystal + Sm3
−+ SmC” → SmA171.0
℃ 174.2℃ → Cholesteric phase → Tokichi phase 4-hexyloxyphenyl-4-(
2″-Methylbutyl)biphenyl-4′-rupoxylate 68.8°C 80.2°C 163.
5℃* Crystal → SmC → Cholesteric phase →
Tokichi phase 4-octyloxyphenyl-4-(2”-
Methylbutyl)biphenyl-4'-rupoxylate 76℃ 88.6℃ 155.4℃
Crystal -SmC* -Cholesteric phase -Tokiyoshi phase 4-Betylphenyl-4-(4''-methylhexyl)biphenyl-4'-rupoxylate 91.5°C 93°C Crystal -+ SmC book -+ SmA112
℃ 131℃→ Cholesteric phase → Tokichi phase (E) Biphenyl-4'-lupoxylate 83.4℃ 114℃H3 ◎-OCCH2) s Presentation I (C2H535℃
93°C 145°C Two or more liquid crystals exhibiting a chiral smectoid phase or liquid crystals exhibiting a cholesteric phase may be used in combination.

The ratio of the liquid crystal exhibiting a chiral smectic phase to the liquid crystal exhibiting a chiral smectic phase as well as the cholesteric phase in the liquid crystal composition used in the present invention varies depending on the type of liquid crystal used, but in general, the liquid crystal exhibiting a chiral smectic phase differs depending on the type of liquid crystal used. It can be contained in a proportion of 0.1 to 50 parts by weight, preferably O,l-10 parts by weight, which exhibits a cholesteric phase per 1 part by weight.

When constructing an element using these materials, the element can be supported by a copper block with a heater embedded, etc., if necessary, in order to maintain the temperature state such that the liquid crystal composition becomes a chiral smectic phase. .

FIG. 1 schematically depicts an example of a cell for explaining the operation of a ferroelectric liquid crystal. 11 and 11' are I n
203.3n02 or ITO (Indium T
A substrate (glass plate) coated with a transparent electrode made of a thin film such as
SmC* oriented so that 2 is perpendicular to the glass surface.

Chiral smectic phase liquid crystals such as SmI wood, SmF', and SmI*SmG* are sealed. A thick line 13 represents a liquid crystal molecule, and this liquid crystal molecule 1
3 has a dipole moment (P) 14 in the direction perpendicular to its molecule. When a voltage higher than a certain threshold is applied between the electrodes on the substrates 11 and 11', the helical structure of the liquid crystal molecules 13 is unraveled, and the liquid crystal molecules 13 are aligned so that all the dipole moments (P) 14 are directed in the direction of the electric field. You can change direction. The liquid crystal molecules 13 have an elongated shape and exhibit refractive index anisotropy in the long axis direction and short axis direction,
Therefore, it is easily understood that, for example, if crossed Nicol polarizers are placed above and below a glass surface, a liquid crystal optical modulation element whose optical characteristics change depending on the polarity of applied voltage can be obtained.

The liquid crystal cell preferably used in the optical modulation element of the present invention can have a sufficiently thin thickness (for example, 10 μl or less). As the liquid crystal layer becomes thinner in this way, the helical structure of the liquid crystal molecules unwinds and becomes a non-helical structure even when no electric field is applied, as shown in Figure 2, and the dipole moment P or P' is directed upward. (24) or downward (24'). When an electric field E or E' with a different polarity, which is equal to or higher than a certain threshold value, is applied to such a cell by the voltage applying means 21 and 21' as shown in FIG. The direction is changed to upward direction 24 or downward direction 24' in accordance with the vector, and accordingly, the liquid crystal molecules are aligned in either the first stable state s23 or the second stable state 23'.

As mentioned earlier, there are two advantages to using such ferroelectricity as an optical modulation element.

The first is that the response speed is extremely fast, and the second is that the alignment of liquid crystal molecules has bistability. To further explain the second point, for example, with reference to FIG. 2, when the electric field E is applied, the liquid crystal molecules are aligned in a first stable state s23, and this state remains stable even when the electric field is turned off. Furthermore, when an opposite electric field E' is applied, the liquid crystal molecules enter a second stable state 23.
', and changes the orientation of the molecule, but it remains in this state even when the electric field is turned off.

Further, as long as the applied electric field E does not exceed a certain threshold value, each orientation state is maintained. In order to effectively realize such fast response speed and bistability, it is preferable that the cell be as thin as possible.

As mentioned earlier, the biggest problem in forming devices using liquid crystals with such ferroelectricity is S m
C-tree, SmH-tree, SmF-tree.

It is difficult to form a highly monodomain cell in which a layer with a chiral smectic phase such as SmI or SmG is aligned perpendicular to the substrate surface, and liquid crystal molecules are aligned approximately parallel to the substrate surface. This is the main objective of the present invention to provide a solution to this point.

FIGS. 3(A) and 3(B) show an embodiment of the liquid crystal element of the present invention. FIG. 3(A) is a plan view of a liquid crystal element according to the present invention, and FIG. 3(B) is a sectional view taken along the line A-x.

In the cell structure 100 shown in FIG. 3, a pair of substrates 101 and 101' made of glass or plastic plates are held at a predetermined distance by a spacer 104, and an adhesive 106 is used to seal the pair of substrates. It has a bonded cell structure, and furthermore, an electrode group (for example, an electrode group for applying a scanning voltage in a matrix electrode structure) consisting of a plurality of transparent electrodes 102 is arranged on a substrate 101 in a predetermined pattern such as a strip pattern. It is formed of. Substrate 101'
An electrode group (for example, a signal voltage application electrode group in a matrix electrode structure) is formed on the transparent electrode 102 and a plurality of transparent electrodes 102' intersecting with each other.

The substrate 101' provided with such a transparent electrode 102' has a
For example - silicon oxide, silicon dioxide, aluminum oxide,
Inorganic insulating materials such as zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate,
polyvinyl acetal, polyvinyl chloride, polyamide,
The alignment control film 105 may be formed using an organic insulating material such as polystyrene, cellulose resin, melamine resin, area resin, or acrylic resin.

The orientation control film 105 is obtained by forming a film of an inorganic insulating material or an organic insulating material as described above, and then rubbing the surface of the film in one direction with velvet, cloth, or paper.

In another preferred embodiment of the present invention, the alignment control film 105 can be obtained by forming a film of an inorganic insulating material such as SiO or SiO2 on the substrate 101' by oblique vapor deposition.

In the apparatus shown in FIG. 5, a Pel jar 501 is placed on an insulating substrate 503 having a suction port 505, and a vacuum pump (not shown) extending from the suction port 505 evacuates the Pel jar 501. A crucible 507 made of tungsten or molybdenum is disposed inside and in the Pelger 501, and the crucible 507 contains crystals 508 of several grams of S io , S io2 , MgF2, etc.
is placed @. The crucible 507 has two lower arms 50
7a, 507b, and the arms have conductive wires 509, 507b, respectively.
510. A power supply 506 and switch 504 are in series between external conductors 509 and 510 of Pelger 501.

Connected. The substrate 502 is placed inside the Pelger 501 and directly above the crucible 507 at an angle of θ with respect to the vertical axis of the Pelger 501.
are arranged at an angle of

When the switch 504 is opened, the Pel jar 501 is first evacuated to approximately 10-5 mmHg pressure, and then the switch 504 is closed and the power supply 506 is turned on until the crucible 507 becomes incandescent at a suitable temperature and the crystal 508 is evaporated. Power is supplied in a regulated manner. The required current for a suitable temperature range (700-1000°C) is about 100 am ps. The crystal 508 is then evaporated to form an upward molecular stream indicated by S in the figure, and the fluid S is incident on the substrate 502 at an angle θ with respect to the substrate 502, so that the substrate 502 coated. The angle θ is the above-mentioned "incident angle", and the direction of the fluid S is the above-mentioned "oblique deposition direction". Determined by calibration. When a film of appropriate thickness is formed, the electric current 950
6 and open the switch 504 to cool the Pel jar 501 and its interior.Then, the pressure is raised to atmospheric pressure and the substrate 502 is removed from the Pel jar 501.

In another specific example, after forming a film of the above-mentioned inorganic insulating material or organic insulating material on the surface of the substrate 101' made of glass or plastic or on the substrate 101', the surface of the film is etched by an oblique etching method. By doing so, it is possible to impart an orientation control effect to the surface.

It is preferable that the above-mentioned alignment control film 105 also functions as an insulating film at the same time.
The film thickness of No. 5 is generally 100 to IJL, preferably 500
It can be set to a range of 5,000 to 5,000 people. This insulating film also has the advantage of being able to prevent the generation of current caused by trace amounts of impurities contained in the liquid crystal layer 103, and therefore does not deteriorate the liquid crystal compound even if the operation is repeated.

Further, in the liquid crystal element of the present invention, the above-mentioned alignment control is performed.

Something similar to membrane 105 can be provided on the other substrate 101.

The liquid crystal layer in the cell structure lOO shown in FIG. 3 may have a chiral smectic phase. The liquid crystal phase 103 exhibiting this chiral smectic phase undergoes a phase transition from another phase on the higher temperature side than the chiral smectic phase, such as the Toyoyoshi phase or the cholesteric phase, to the smectic A phase during the cooling process, and roughly changes to the chiral smectic phase during the cooling process. It is formed by being transferred.

An important point in the present invention is that when a liquid crystal composition containing a liquid crystal exhibiting a cholesteric phase is used to cause a phase transition from a high temperature phase to SmA, the liquid crystal molecular axis of SmA is aligned in the alignment control direction given to the alignment control film 105. As a result, a uniform monodomain is formed.

FIG. 4 shows another specific example of the liquid crystal element of the present invention. The liquid crystal element shown in FIG. 4 consists of a pair of substrates 101 and 10.
A plurality of spacer members 201 are arranged between 1'. This spacer member 201 has, for example, an orientation amount @[910
On the substrate 101' where 5 is not provided, StO, Si
O2゜A sentence 203. Inorganic compounds such as TiO2, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea After forming a film of resin such as resin, acrylic resin, or photoresist resin by an appropriate method, spacer member 2 is placed in a predetermined position.
It can be obtained by etching so that 03 is arranged.

In such a cell structure 100, polarizers 107 and 108 in a crossed nicol state or a parallel nicol state are arranged on both sides of the substrates 101 and 101', respectively, and the electrode 1
Optical modulation will occur when a voltage is applied between 02 and 102'.

Next, regarding the method for manufacturing the liquid crystal element of the present invention, the liquid crystal layer 10
The orientation control method No. 3 will be specifically explained using FIG. 3.

First, the cell structure 100 in which the liquid crystal composition is sealed is placed in a heating case (
(not shown).

Next, the liquid crystal composition in the cell 100 is heated to a temperature at which the liquid crystal composition becomes an isotonic phase. After that, the temperature of the heating case is lowered, and the liquid crystal composition in the isokyoshi phase in the cell 100 is transferred to a cooling process.
It is possible that a coarse transition occurs to SmA or from the cholesteric phase of the Grand Shuan structure to SmA.

At this time, the liquid crystal molecular axes of SmA are aligned in the rubbing direction.

Thereafter, this SmA undergoes a phase transition to a chiral smectic phase in the process of cooling down, and a chiral smectic phase such as monodomain SmC'' having a non-helical structure is obtained, for example, when the cell thickness is set to approximately 1ILm.

FIG. 6 is a schematic diagram of a cell 41 having a matrix electrode structure in which a ferroelectric liquid crystal compound is sandwiched between. 42 is a scanning electrode group, and 43 is a signal electrode group. Figure 7 (
a) and (b) respectively show the selected scanning electrode 42 (
6(C) and (d) respectively show the electrical signals given to the selected signal electrodes 42(n) and the electrical signals given to the other scanning electrodes (unselected scanning electrodes) 42(n). In FIGS. 7(a) to 7(d), which represent the electric signal applied to the signal electrode S) and the electric signal applied to the unselected signal electrode 43(n), the horizontal axis represents time and the vertical axis represents voltage, respectively. represent. For example, when displaying a moving image, the scanning electrode groups 42 are sequentially and periodically selected. Now, if the threshold voltage for providing the first stable state of the liquid crystal cell having bistable property is Vthl, and the threshold voltage for providing the second stable state is -vt h2, then the selected scan electrode 42 ( s) is the electrical signal given to the seventh
As shown in figure (a), in one phase (time) tl,
It is an alternating voltage that becomes -V at phase (time) t2. Further, the other scanning electrodes 42(n) are as shown in FIG.
As shown in b), it is in a grounded state and the electric % signal is O. On the other hand, the electric signal given to the selected signal electrode 43 (s) is V as shown in FIG. 7(C),
Further, the electric signal applied to the unselected signal type Jii43(n) is <-V as shown in FIG. 7(d). In the above, the voltage V is set to a desired value that satisfies V<Vthl<2V and -V<-Vth2<-2v. FIG. 8 shows the voltage waveform applied to each pixel when such an electric signal is applied. FIGS. 8(a) to 8(d) respectively show pixel A in the sixth
, B, C and D. That is, as is clear from FIG. 8, in pixel A on the selected scanning line,
At phase t2, a voltage of 2V exceeding the threshold value Vthl is applied. In addition, to the pixel B existing on the same scanning line, a voltage of -2V exceeding the threshold value -vth2 is applied at phase t1. Therefore, depending on whether a signal electrode is selected on one selected scanning electrode line, if a signal electrode is selected, the liquid crystal molecules are
If it is not selected, the orientation is aligned to the second stable state. In any case, it has nothing to do with the previous history of each pixel.

On the other hand, as shown in pixels C and D, on unselected scanning lines, the voltage applied to all pixels C and D is +V or -■, neither of which exceeds the threshold voltage. Therefore, the liquid crystal molecules in each pixel C and D maintain the orientation corresponding to the signal state when scanned last time without changing the orientation state. That is, when a scanning electrode is selected, a signal for one line is written, and the signal state can be maintained until the next frame is selected. Therefore, even if the number of scanning electrodes increases, the actual duty ratio does not change, and there is no reduction in contrast or crosstalk. At this time, the value of the voltage value V and the value of the phase (t 1 + t 2) = T depend on the liquid crystal material used and the thickness of the cell, but are usually 0.1 gs e c at 3 ports to 70 ports.
A range of ˜2 msec is used. Therefore, in this case, the electrical signal given to the selected scanning electrode is
from the stable state 8 (supposed to be a "bright" state when converted into an optical signal) to a second stable state (supposed to be a "dark" state when converted to an optical signal), or vice versa. Either change can occur.

Liquid crystal exhibiting chiral smectic phase (D.

BAMBC, HOBACPC, MBRA8, etc.) When used in the present invention, the use of a liquid crystal composition containing a liquid crystal exhibiting a chiral smectic phase and further exhibiting a cholesteric phase results in better alignment and fewer alignment defects than when used alone. An oriented state with less is obtained.

Especially when the cell thickness is thin or bistability (memory property)
SmC, SmH trees with .

In the case of SmF, SmI, and SmC trees, in terms of switching characteristics (response speed), it is preferable that the restraining force (effect due to substrate alignment treatment) on the liquid crystal molecules on the substrate surface be weaker. A faster response speed can be obtained when only the surface is aligned than when the substrate surfaces on both sides are aligned. At this time, in a cell having a cell thickness of 2 pm, a response speed approximately twice as fast can be obtained when only one substrate is subjected to alignment treatment as compared to a response speed when both substrates are subjected to alignment treatment.

Hereinafter, the present invention will be explained according to examples.

[Example 1] Striped ■TOII with a pitch of 100 gm @ 62.5 pLm! l! A square glass substrate provided with an ITO film serving as an electrode is prepared, and placed in the oblique evaporation apparatus shown in FIG. 5 with the side on which the ITO film serving as the electrode is facing downward. Next, SiO2 is placed in a molybdate crucible. I set the crystal. After that, the inside of the vapor deposition equipment was heated to 10-5 To
After establishing a vacuum state of about rr, Si02 was obliquely vapor-deposited on the glass substrate by a predetermined method to form an obliquely-deposited film of 800 people (electrode plate A).

On the other hand, a polyimide forming solution (rPIQ manufactured by Hitachi Chemical Co., Ltd. with a non-volatile content concentration of 14.5 wt%) was applied using a spinner coater onto a glass substrate on which a similar striped ITO film was formed. ℃ for 30 minutes, 200℃ for 60 minutes, and 350℃ for 30 minutes.
A film of 0.00 people was formed (B electrode plate).

Next, a thermosetting epoxy adhesive is applied to the periphery of the A electrode plate except for the injection hole by screen printing, and then the striped pattern electrodes of the A electrode plate and the B electrode plate are overlapped so that they are perpendicular to each other. , the distance between the two electrode plates is 2p
It was held with a polyimide spacer so as to have an L shape, and was made into a cell.

Next, P-decyloxybenzylidene-P'-amino-2-
4-hexyloxyphenyl 4-(2″
A liquid crystal composition was prepared by adding 8 parts by weight of -methylbutyl)biphenyl-4'-rupoxylate.

This liquid crystal composition was heated to form an isokyoshi phase, injected into the cell prepared above through the injection port, and the injection port was sealed. The temperature of this cell was lowered by slow cooling to about 70'C!
When a pair of polarizers were placed in a crossed nicol state and observed under a microscope, it was confirmed that a monodomain helical SmC'' was formed.

〔Example? ]

A polyimide forming solution (rPIQ manufactured by Hitachi Chemical Co., Ltd.) was placed on a square glass substrate on which a striped ITO film with a pitch of 100 #Lm and a width of 62.5 μm was provided as an electrode.
A film with a non-volatile content of 14°5 wt%) was applied using a spinner coating machine, and heated at 120°C for 30 minutes, 200°C for 60 minutes, and then heated at 350°C for 30 minutes to form a film of 800 people ( A electrode plate).

Next, the polyimide coated electrode plate obtained in the same manner as above was subjected to a rubbing treatment with a cloth. (B electrode plate) Next, after applying thermosetting epoxy adhesive to the periphery of the A electrode plate except for the injection hole, the striped pattern electrodes of the A electrode plate and the B electrode plate are perpendicular to each other. The two electrode plates were stacked one on top of the other and held with a polyimide spacer so that the distance between the two electrode plates was 2 to form a cell.

P-decyloxybenzylidene-P'-amino-2-methylbutylcinname) (DOBAMBC) 100 parts by weight, 4-hebutylphenyl-4-(4''-methylhexyl)biphenyl-4'-rupoxylate 5
A liquid crystal composition was prepared by adding parts by weight. This liquid crystal composition was injected into the cell through the injection port, and the injection port was sealed. The temperature of this cell is lowered by slow cooling,
When a pair of polarizers were placed in a crossed nicol state while the temperature was maintained at about 70° C., and microscopic observation was performed, it was confirmed that SmC' with a monodomain helix was formed.

[Brief explanation of drawings]

1 and 2 are perspective views showing a liquid crystal cell used in the present invention. FIG. 3(A) is a plan view showing the liquid crystal element of the present invention, and FIG. 3(CB) is a sectional view taken along line a-a. FIG. 4 is a sectional view showing another specific example of the liquid crystal element of the present invention. FIG. 5 is a cross-sectional view schematically showing an oblique evaporation apparatus used in producing the liquid crystal element of the present invention. FIG. 6 is a plan view schematically showing the electrode structure of a liquid crystal element used in the present invention. FIGS. 7(a) to 7(d) are explanatory diagrams showing signals for driving the liquid crystal element used in the present invention. FIGS. 8(a) to 8(d) are explanatory diagrams showing voltage waveforms applied to each pixel. 100; cell structure 101, 101': substrate 102, 102', electrode 103: liquid crystal layer-1 104, 201; spacer member 105; alignment control film 106: adhesive 107, 108; polarizer 109, heating element patent application People Canon Co., Ltd. Figure 7 (b)
Cd) (b)

Claims (18)

[Claims] (1) A cell structure in which a pair of substrates is filled with a liquid crystal composition containing two or more types of liquid crystals exhibiting a chiral smectic phase, at least one of which is a liquid crystal exhibiting a cholesteric phase. None. A liquid crystal element, characterized in that the surface of at least one of the pair of substrates has the effect of preferentially aligning the molecular axis direction of the liquid crystal that contacts at the interface in one direction. (2) The liquid crystal element according to claim 1, wherein the liquid crystal composition is a liquid crystal that sequentially undergoes a phase transition from a smectic A phase to a chiral smectic phase during a cooling process. (3) The liquid crystal element according to claim 2, wherein the chiral smetic phase is a C phase, H phase, F phase, I phase, or G phase. (4) The liquid crystal element according to claim 2 or 3, wherein the chiral smectic phase is a phase having a non-helical structure. (5) A patent claim in which the surface of one of the pair of substrates has an effect of preferentially aligning the molecular axis direction of liquid crystal in one direction, and the surface of the other substrate does not have this effect. The liquid crystal element according to range 1. (6) Claim 1 or 5, wherein the surface having the effect is a surface obtained by rubbing the surface of the substrate.
The liquid crystal element described in . (7) The liquid crystal element according to claim 6, wherein the surface is a surface formed by a coating of an organic insulating material or an inorganic insulating material. (8) The organic insulating material is polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea. 8. The liquid crystal element according to claim 7, wherein the resin is at least one selected from the resin group consisting of resin, acrylic resin, and photoresist resin. (9) The inorganic insulating material is SiO, SiO_2 or Ti
The liquid crystal element according to claim 7, which is O_2. (10) The liquid crystal element according to claim 1 or 5, wherein the surface having the effect is a surface obtained by diagonally depositing an insulating material on the surface of the substrate. (11) The liquid crystal element according to claim 10, wherein the insulating material is SiO or SiO_2. (12) The liquid crystal element according to claim 1 or 5, wherein the surface having the effect is a surface obtained by obliquely etching the surface of the substrate. (13) The liquid crystal element according to claim 12, wherein the surface is a surface formed of a film or a substrate of an organic or inorganic insulating material. (14) the organic insulating material is polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate,
Claim 13: The resin is at least one selected from the resin group consisting of polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, and photoresist resin. The liquid crystal element described in . (15) The inorganic insulating material is glass, SiO, SiO_
14. The liquid crystal element according to claim 13, which is TiO_2 or TiO_2. (16) The liquid crystal element according to claim 2, wherein the other substrate is a substrate provided with a spacer member obtained by forming a film of an insulating material and then etching except for a predetermined position. (17) The liquid crystal element according to claim 16, wherein the spacer member is a band-shaped member. (18) The liquid crystal element according to claim 17, which is an element comprising a plurality of the band-shaped spacer members.