JPS6167827A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To attain rapid response, formation of high density picture elements and display on a large area by sealing specific liquid crystal components between a pair of substrates and providing one surfaces of the substrates with an effect for orientating the molecular axes of liquid crystal contacted with an interference to one direction with priority. CONSTITUTION:The surfaces of substrates 11, 11' contacted with the liquid crystal at their interference are provided with an effect for arraying the molecular axes of liquid crystal with priority in one direction by using liquid crystal components containing a liquid crystal generating phase transfer from an isotropic phase to a Ch phase, an SmA phase and chiral smectic phases such as SmC*, SmH*, SmF*, SmJ*, SmK*, SmI*, and SmG* in the temperature reducing process and a liquid crystal generating phase transfer from the isotropic phase to the Ch phase and a crystal phase or from the isotropic phase to the Ch phase, the SmA phase and the crystal phase in the temperature reducing process to form a monodomain arraying liquid crystal molecules 13 in one direction. Consequently, both liquid crystal working characteristic and monodomain property of the liquid crystal layer can be obtained and long stability of orientation can be improved. Thus, the liquid crystal element can be used for a display element requiring rapid response, formation of high density picture element and a large display area or an optical shutter.

Description

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

■! It is difficult to increase the pixel density or increase the screen size. Among conventional liquid crystals, most of them are practically used as display elements because they have relatively high response speed and low power consumption.
Hadt and W. He1frich “Appliec
l Physics Letters'' Vo,
18.

No. 4 (1971, 2, 15), P, 127-128
“Vol t age-Dependent 0
ptical Activity of aTw
isted Nematic Liquid C
TN (twisted ne
matLc) type liquid crystal, which forms a structure (helical structure) in which nematic liquid crystal molecules with positive dielectric anisotropy are twisted in the thickness direction of the liquid crystal layer in an electroless state. The liquid crystal molecules form a parallel arrangement between the two electrodes. on the other hand.

When an electric field is applied, nematic liquid crystals with positive dielectric anisotropy align 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. voltage is applied,
No voltage is applied to a region where neither the scanning electrode nor the signal electrode is selected (non-selected point), and therefore the liquid crystal molecules maintain a stable alignment parallel to the electrode plane. By arranging linear polarizers in an a-Snicol relationship above and below such a liquid crystal cell, no light is transmitted at selected points.

Since light is transmitted at non-selected points, g! It becomes possible to use it as an i-image element. However, when a matrix electrode structure is configured, there may be an area where the scanning electrode is selected and the signal electrode is not selected, or an area where the scanning electrode is not selected and the signal electrode is selected (a so-called "half-selected point"). The difference between the voltage applied to the zero selection point, where a finite electric field is applied, and the voltage applied to the half selection point is sufficiently large, and the voltage threshold required to align the liquid crystal molecules perpendicular to the electric field is a voltage value in between. If set, the display element will operate normally, but if you increase the number of scanning lines (N), the entire screen (
The time during which an effective electric field is applied to one selected point (ciuty ratio) decreases at a rate of l/N during scanning of one selected point (one frame).For this reason, if repeated scanning is performed The effective voltage difference between the selected point and the non-selected point becomes smaller as the number of scanning lines increases, resulting in unavoidable drawbacks such as a reduction in image contrast and crosstalk. This phenomenon is caused by liquid crystals that do not have bistability (the stable state is when the liquid crystal molecules are aligned horizontally with respect to the electrode surface, and they are aligned vertically only while an electric field is effectively applied). This is an unavoidable problem that arises when driving using the temporal accumulation effect (that is, repeatedly scanning). In order to improve this point, the TL applanation method, two-frequency drive method, multiple matrix method, etc. have already been proposed, but all of these methods are insufficient, and it is necessary to increase the screen size of one display element and increase the density. Currently, the number of scanning lines has reached a plateau due to the inability to increase the number of scanning lines sufficiently. 'On the other hand, looking at the field of printers, laser beams provide electrical image signals in the form of light to electrophotographic photoreceptors in terms of both pixel density and speed, as a means of obtaining hard copies by inputting electrical signals. Printer (LBP)
is currently the best. However, LBP has drawbacks such as: (1) The device is large when used as a printer; (2) It has a high-speed moving part 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 the 1ttA signal into an optical signal. However, when providing pixel signals using a liquid crystal shutter array, for example, in order to write pixel signals at a rate of 16 dat/mm within a length of 210 mm, it is necessary to have 3000 or more signal generating units. First, in order to provide independent signals to each, it was necessary to wire a wire for sending 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 a plurality of signal generating sections, and the actual wiring can be significantly reduced. However, if the number of lines (N) is increased using a liquid crystal that does not have bistability, as is usually done in this case, the signal ON time becomes essentially 1/N, which reduces the amount of light that can be obtained on the photoreceptor. The disadvantage is that the amount of light emitted is reduced, leading to crosstalk problems.

To improve the drawbacks of conventional liquid crystal devices, the use of bistable liquid crystal devices has been proposed by C1ark and Lage Rwa Il (
JP-A-56-107216, U.S. Patent No. 4367
No. 924, etc.), as a bistable liquid crystal! ±, generally chiral smectic C phase (SmC') or other chiral smectic phases, specifically chiral smectic H phase (SmH''), chiral smectic F phase (SmF), chiral smectic phase A ferroelectric liquid crystal having a smectic I phase (SmH phase) and a chiral smectic G phase (SmG*) is used.

This liquid crystal has a bistable state consisting of a first optically stable state and a second optically stable state with respect to an electric field. Therefore, unlike the optical modulation element used in the TN type liquid crystal described above, 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
It has the property of very quickly taking one of the two stable states in response to an applied electric field, and maintaining that state when no electric field is applied. By utilizing such properties, many of the problems of the conventional TN type device described above can be significantly improved.

This point will be explained in more detail below in conjunction with the present invention (SO).However, in order for an optical modulation element using this bistable liquid crystal to exhibit predetermined drive characteristics, a pair of It is necessary that the liquid crystal placed between the parallel substrates be in a molecular arrangement state that effectively converts between the two stable states, regardless of the applied state of the electric field.For example, SmC For strong aA'l! liquid crystals with chiral smectic phases or other chiral smectic phases, the liquid crystal molecular layer with 3m0 quintillion or other chiral smectic phases is perpendicular to the substrate plane, so that the liquid crystal molecular axes are It is necessary to form regions (monodomains) arranged almost parallel to the substrate surface.However, in conventional optical modulation elements using bistable liquid crystals, the alignment of liquid crystals with such a monodomain structure is difficult. The reality is that sufficient characteristics could not be obtained because the state was not necessarily formed satisfactorily.

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,
How to apply a large magnetic field? However, the method of applying shear force is incompatible with the method of injecting liquid crystal after the cell is made. be.

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

As a result of further research for the above-mentioned purpose, the present inventors have found that, in particular, the orientation during the cooling process in which the liquid crystal material transitions from another phase (for example, a high-temperature state such as an isotropic phase) to a low-temperature state of a smectic phase. As a result, during the cooling process, the isotropic phase changed to the cholesteric phase, the smectic A phase (SmA), the chiral smectic C phase (S mc*), the chiral smectic H phase (SmH), and the chiral smectic G phase. (5m0 pieces) A liquid crystal that undergoes a phase transition to a chiral smectic phase, and from an isotropic phase to a cholesteric phase and a crystalline phase, or from an isotropic phase to a cholesteric phase, smectic A (SmA), and a crystalline phase. When using a liquid crystal composition containing a liquid crystal that causes a phase transition,
By giving the surface of the substrate that contacts the liquid crystal at the interface an effect that aligns the molecular axis of the liquid crystal in one direction, it is possible to form a monodomain in which the liquid crystal molecules are aligned in one direction. We have found that it is possible to obtain a liquid crystal element with a structure that is compatible with the operating characteristics of the element based on the bistability of the liquid crystal and the monodomain property of the liquid crystal layer, and also to improve the alignment stability over a long period of time.

The present invention is based on the above-mentioned knowledge. That is, the liquid crystal element of the present invention changes from an isotropic phase to a cholesteric phase to a smectoid A phase (SmA) during the cooling process between a pair of substrates.
and a liquid crystal that undergoes a phase transition to a chiral smectic phase (hereinafter referred to simply as a liquid crystal that exhibits a single chiral smectic phase).
A liquid crystal that undergoes a phase transition from an isotropic phase to a cholesteric phase and a crystalline phase, or from an isotropic phase to a cholesteric phase, a smectic A phase (SmA), and a crystalline phase (hereinafter simply referred to as the "cholesteric phase") during the temperature cooling process. It has a cell structure in which a liquid crystal composition containing at least one type of liquid crystal (hereinafter referred to as "liquid crystal") and exhibiting a chiral smectic phase at a predetermined temperature is enclosed.

The present invention is 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.

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

The liquid crystal composition used in the present invention exhibits ferroelectricity.

Table 1 shows specific examples of liquid crystals that undergo a phase transition from an isotropic phase to a cholesteric phase, a smectic A phase (SmA), and a chiral smectic phase (i.e., a liquid crystal exhibiting a chiral smectic phase) during the temperature-lowering process described above. , a liquid crystal that undergoes a phase transition from an isotropic phase to a cholesteric phase and a crystalline phase or from an isotropic phase to a cholesteric phase, SmA, and a crystalline phase during the cooling process (i.e.

Table 2 shows specific examples of liquid crystals exhibiting a cholesteric phase.

Table 1 Specific examples of liquid crystals exhibiting a chilyle smectic phase (compound name, structural formula, and phase transition point) 4-(2'-methylbutyl)phenyl-4'octyloxybiphenyl-4-carboxylate 78°C
80℃ 128.3℃ crystal ;= Sm3
= SmC wood ;= SmA171.0℃
174.2℃;= cholesteric phase;= isotropic phase 4-pentylphenyl-4-(4#-methylhexyl)biphenyl-4'-carboxylate 91.5℃ 93℃ crystal;=SmC;=SmA112℃
131”c;= cholesteric phase; isotropic phase methylbutyloxy)phenyl ester 40.5°C
42℃ 58℃ 65℃Crystal; Bi Sm
C*;= SmA ; Cholesteric phase; Isotropic phase 7.
′, /′.

5・'/' Table 2 Specific examples of liquid crystals exhibiting cholesteric phase (compound name, structural formula, and phase transition point) (A) Cholesteryl propionate 107°C
117℃ crystal = cholesteric phase ;= isotropic phase CB)
Cholesteryl nonanate 78℃ 92℃ Crystal ;= Cholesteric phase = Isotropic phase (C)
Cholesteryl palmitate 77℃
83℃ Crystal; = Cholesteric phase = Isotropic phase (D)
Cholesteryl nonanate 148℃ 176℃ Crystal; = cholesteric phase 2 Isotropic phase - -54℃ SmA4--54T, phase '-3014-(2"-methylbutyloxy)-4-cyanobiphenyl\ Cholesteric phase '9℃ Crystal; = cholesteric phase; isotropic phase 4- (2-methylbutyl)-4'-
Hexyloxyazobenzene 4-(2-methylbutyl)
Phenyl-4'-decyloxybenzoate 4-hexyloxy-4'-(2-methylbutyl)benzoate These liquid crystals exhibiting a chiral smectic phase or the liquid crystals exhibiting a nematic phase are used in combination of two or more of each. You can also.

The ratio of the liquid crystal exhibiting the chiral smectic phase and the liquid crystal exhibiting the cholesteric phase in the liquid crystal composition used in the present invention varies depending on the type of liquid crystal used;
Liquid crystals that generally exhibit the above-mentioned irradial smectic phase 1
The amount of liquid crystal exhibiting the above-mentioned Flestic phase is 0.1 to 50 parts by weight, preferably 1 to 20 parts by weight.

When constructing an element using these materials.

The liquid crystal composition is SmC wood, SmH', SmF''.

In order to maintain the temperature state such that SmI wood and SmG Kyo occur, the element can be supported by a copper block or the like in which a heater is embedded, if necessary.

Figure 1 is for explaining the operation of ferroelectric liquid crystal.

This is a schematic drawing of an example of a cell. 11 and 11' are In2O3, 5n02 or ITO (Indium
A substrate (glass plate) coated with a transparent 71 pole made of a thin film of -Tin Oxide)'5, between which the liquid crystal molecular layer 12 is oriented perpendicular to the glass surface.
mC tree.

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

The liquid crystal cell preferably used in the optical modulation element of the present invention can be made sufficiently thin (for example, less than IJt). Even when no electric field is applied, the helical structure of liquid crystal molecules unwinds and becomes a non-helical structure.

The dipole moment P or P' takes either an upward direction (24) or a downward direction (24'). When an electric field E or E' with a different polarity above a certain threshold value is applied to such a cell by the voltage applying means 21 and 21' as shown in FIG. 2, the dipole moment is The liquid crystal molecules change direction upward 24 or downward 24' in response to the electric field vector, and accordingly the liquid crystal molecules enter the first stable state 2.
3 or the second stable state 823'.

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

The first is that the response speed is extremely fast. 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 an electric field E is applied, the liquid crystal molecules are oriented in a first stable state 23, and this state remains stable even when the electric field is removed. Furthermore, when an opposite electric field E' is applied, the liquid crystal molecules enter a second stable state t62.
:Orients to r and changes the orientation of the molecule.

It remains in this state even if 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.

The biggest problem in forming devices using liquid crystals with such ferroelectricity is, as mentioned earlier, that SmC
*, SmH book, SmF*.

A layer having a chiral smectic phase such as SmI tree or SmG tree was aligned perpendicularly to the substrate surface, and liquid crystal molecules were aligned approximately parallel to the substrate surface.

It is difficult to form cells with high monodomain properties, and the main purpose of the present invention is to provide a solution to this problem.

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 i o t' provided with such a transparent electrode 102' contains 1, for example, -silicon oxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium Mide,
Inorganic insulating materials such as cerium fluoride, silicon nitride, silicon carbide, boron nitride, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparakyrine, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, Using organic insulating materials such as cellulose resin, melamine resin, urea resin or acrylic resin?
An orientation control 1iLO5 formed with an Ik film can be provided.

This oriented Wl@105 can be obtained by forming a film of an inorganic insulating material or an organic insulating material as described above, and then rubbing the surface with velvet, cloth, or paper in one direction (5 pings).

In another preferred embodiment of the present invention, the alignment control film 105 can be obtained by coating an inorganic insulating material such as S)O or 5L02 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 the Pel jar 501 is evacuated by a vacuum pump (not shown) extending from the suction port 505. Crucible 507 made of tungsten or molybdenum is Pelger 50
Lupo 507 contains several grams of crystals 5 such as S io , S io2 , MgF2, etc.
08 is aR. The crucible 507 has two lower arms 507a, 507b, each of which has a conductor &15
Connected to 09,510. Power supply 506 and switch 5
04 is the external conductor 509.51011 of Pelger 501
Connected in series to JI. The board 502 is Pelger 50
1 and directly above the crucible 507 at an angle θ with respect to the vertical axis of the Pelger 501 .

When the switch 504 is opened, the Pel jar 501 is first brought into a vacuum state of about 10-5 mmHg pressure, and then the switch 504 is closed and the electric current W506 is applied until the crucible 507 becomes incandescent at an appropriate temperature and the crystal 508 is produced. Power is supplied through node a1. The required current for a suitable temperature range (700-1000°C) is about 100100A. crystal 508
is then evaporated to form an upward molecular flow indicated by S in the figure, and the fluid S is incident on the substrate 502 at an angle of θ with respect to the substrate 502.

As a result, the substrate 502 is coated. The angle θ is the "incident angle" described in 1, and the direction of the fluid S is the "oblique deposition direction" described above.
It is. The film thickness of this film is as follows:
1 by a time-dependent thickness calibration of the device prior to insertion into the device. When an excessively thick film is formed, the power from the power source 506 is reduced, the switch 504 is opened, and the Pel Jar 501 and its interior are cooled. Next, the pressure is increased 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 t o t' made of glass or plastic or on the substrate 101', the surface of the film is etched by an oblique etching method. By etching the surface, an orientation control effect can be imparted to the surface.

It is preferable that the above-mentioned orientation control 1151105 also functions as an insulating film at the same time, and for this purpose, the film thickness of this orientation control 119105 is generally set in the range of 100 to 1μ, preferably 500 to 5000. I can do it. 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, a film similar to the aA alignment control film 105 can be provided on the other substrate 101.

The liquid crystal layer 103 in the cell structure 100 shown in FIG. 3 is made of SmC tree, SmH", and SmF tree.

It depends on whether it is a chiral smectic phase such as SmI tree or 3m0 quintillion. This chiral smectic liquid crystal layer 103 contains the aforementioned liquid crystal exhibiting a cholesteric phase.

An important point of the present invention is that a liquid crystal composition containing the above-mentioned liquid crystal exhibiting a cholesteric phase is used.

During phase transition from a high temperature phase to a smectic phase or a chiral smectic phase, the liquid crystal molecular axes undergo orientation control 111
arranged along the orientation control direction given to 19105,
As a result, uniform monodomains are formed, and no disturbance in orientation occurs even during long-term storage.

FIG. 4 shows another specific example of the liquid crystal element of the present invention. The liquid crystal element shown in FIG.
A plurality of spacer members 201 are arranged between t'. This spacer member 201 is, for example, an orientation control WII1
05 is provided Tier 1 One board 10 L' upper Ni S
to, S i 02 .

Aj1203, inorganic compounds such as TiO2, or polyvinyl alcohol, polyimide, polyamideimide,
Polyesterimide, polyvaraxylylene/, polyester J, polycarbonate.

After forming a film of resin such as polyvinyl acetal, polyvinyl acetate, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, or photoresist resin by an appropriate method, the spacer member 201 is placed at a predetermined position. It can be obtained by etching it so that it 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 lO2'.

Next, regarding the method for manufacturing the liquid crystal element of the present invention, the liquid crystal layer 103
The orientation control method 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 it becomes an isotropic phase. Thereafter, the temperature of the heating case is lowered, and the liquid crystal composition in the isotropic phase in the cell 100 is transferred to the temperature lowering process. This is thought to have the effect of aligning the liquid crystal molecular axes in the rubbing direction, and to maintain a stable alignment state even during long-term storage.

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 (
s) and the other scanning type J4i (
6(C) and (d) show the electrical signals applied to the selected signal electrode 43(s) and the unselected signal electrode 43(s), respectively. In FIGS. 7(a) to 7(d), which represent the electrical signals given to (n), the horizontal axis represents time and the vertical axis represents voltage. For example, when displaying a moving image, The scanning electrode groups 42 are selected sequentially and periodically. Now, if the threshold voltage for providing the first stable state of a liquid crystal cell having bistability is Vt hl, and the threshold voltage for providing the second stable state is -vt h2, then
As shown in FIG. 7(a), the electrical signal applied to the selected scanning electrode 42(s) alternates between V at phase (time) 11 and -V at phase (time) t2. It is voltage. Further, the other scanning electrodes 42(n) are in a grounded state as shown in FIG. 7(b), and have an electric signal O. On the other hand, 12! The selected signal electrode 43 (s
) The electricity (No. 8 is v as shown in FIG. 7(C)), and the electricity given to the unselected signal electrode 43(n) is v as shown in FIG. 7(d). <-V, and above a certain 0, the voltage V is V<Vt h 1<2V
It is set to a desired value that satisfies -V>-Vt h2>-2V. FIG. 8 shows the IL pressure waveform (applied to each pixel when such an upper air signal is applied).
a) to (d) correspond to pixels A, B, C, and D in FIG. 6, respectively. That is, as is clear from FIG. 8, a voltage of 2v exceeding the threshold value vth1 is applied to the pixel A on the selected scanning line in one phase t2. In addition, in pixel B existing on the scanning line, the phase is 1 and the threshold value '-v
A voltage of -2v exceeding th2 is applied. Therefore, depending on whether or not a signal electrode is selected on the scanning electrode line selected by 1, if 1 is selected, the liquid crystal molecules are aligned in a stable state of: 1IJl, and 11! If not selected: i
The orientation is aligned to the stable state of 42. In any case, the previous history of each pixel is not related to IA.

On the other hand, as shown in pixels C and D, on the unselected scanning line, the voltage applied to all pixels C and D is +■ or -■, and neither exceeds the threshold voltage. The liquid crystal molecules in pixels 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 read in, and that signal state can be maintained until the next selection after the end of a frame. 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.In this case, the value of voltage V and the value of phase (tl+t2)=T are ,
Although it depends on the liquid crystal material used and the H of the cell, it is usually 0.1 sec to 2 rns e at 3 ports to 70 ports.
A range of c is used. Therefore, in this case, the t signal given to the selected scan electrode is in the first stable state (
A change from either the stable state 7IJ of jS2 (supposed to be in the "bright" state when converted to an optical signal) to the stable state 7IJ (supposed to be in the "dark" state when converted to an optical signal), or vice versa. can also occur. The aforementioned SmC tree, SmH tree,
SmF end, SmI tree.

Compared to the case where a liquid crystal exhibiting a chiral smectic phase such as SmG wood is used alone, the use of a liquid crystal composition containing a liquid crystal exhibiting a cholesteric phase used in the present invention provides better alignment and fewer alignment defects. An oriented state is obtained.

Especially when the cell thickness is thin, or SmC', SmH*, and SmF* have bistability (memory property).

In the case of a chiral smectic phase such as SmI tree or SmG tree, from the viewpoint of switching characteristics (response speed), it is preferable that the restraining force (effect due to orientation treatment of the substrate) on the liquid crystal molecules on the substrate surface is weaker. When only one substrate surface is subjected to alignment treatment, a faster response speed can be obtained than when alignment treatment is performed on both substrate surfaces. At this time, in a cell with a cell thickness of 2 pm, when only one side of the substrate is subjected to alignment treatment, a response speed that is approximately twice as fast as that when both substrates are aligned can be obtained.

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

[Example L]

A striped ITOIl with a pitch of 1100p and a width of 62.5 mm! A square glass substrate provided with an ITO film serving as an electrode is prepared, and set in the oblique evaporation apparatus shown in Fig. 5 with the side on which the ITO film serving as the electrode is facing downward, and then Si02 is placed in a molybdenum crucible. I set the crystal. After that, the inside of the vapor deposition apparatus is made into a vacuum state of about to-5 Torr, and then Si is deposited on the glass substrate by a predetermined method.
O2 was obliquely evaporated to form an obliquely evaporated film of 800 people (
A electrode plate).

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 coating l#J machine onto a glass substrate on which a similar striped ITO film was formed. and 200°C for 30 minutes at 120°C.
Heating was performed at 350°C for 60 minutes and 350°C for 30 minutes to form a film of 800 people (electrode plate B).

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 overlapped so that they are perpendicular to each other. The cells were maintained using polyimide spacers so that the distance between the two electrode plates was 2 tiles.

Next, 4-(2'-methylbutyl)phenyl-4'-ctyloxybiphenyl-4-carboxy 1/ ) 1
A liquid crystal composition was prepared by adding 5 parts by weight of cholesteryl nonanate to 00 m.

This liquid crystal was heated to obtain an isotropic phase, which was prepared as described above, and injected into the cell through the injection port, and the injection port was sealed.

After lowering the temperature of this cell by slow cooling, a pair of polarizers was placed in a crossed nicol state, and microscopic observation revealed that
It was confirmed that an SmC tree with a monodomain non-helical structure was formed.

Furthermore, after maintaining this liquid crystal element in the SmC* state for 500 hours, the same jl micromirror was used again! When I conducted an investigation,
It was confirmed that the SmC tree still had a monodomain non-helical structure.

On the other hand, as a comparative experiment, we fabricated a liquid crystal element using the same method as described above, except that the cholesteryl nonanate used in the liquid crystal element described above was omitted, and then observed it with a microscope. Sm with helical structure
Although the formation of C-terminus was confirmed, after conducting a 500-hour durability test, 5m0 pieces did not form a monodomain.

[Example 2] A polyimide forming solution (R manufactured by Hitachi Chemical Co., Ltd.) was placed on a square glass substrate provided with striped ITOIIQ of @ 82.5 am with a pitch of 1100 uL as an electrode.
PIQj, non-volatile content concentration 14.5 wt%) was applied using a spinner coater.

120°C for 30 minutes, 200°C for 60 minutes, and 35
Heating was performed at 0° C. for 30 minutes to form a film of 800 people (electrode plate A).

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 distance between the two electrode plates is 21
It was held with a polyimide spacer so as to have an L shape, and was made into a cell.

1 Offi part of 4-(2-methylbutyl)phenyl-4'-decyloxybenzoate was added to 100 parts by weight of 4-(2'-methylbutyl)phenyl-4'-ctyloxybiphenyl-4-carboxylate to prepare a liquid crystal. The composition was prepared. This liquid crystal composition was heated to form an isotropic phase and injected into the cell through an injection port, and the injection port was sealed. After lowering the temperature of this cell by slow cooling, a pair of polarizers were placed in a crossed nicol state, and observation with a microscope w1 revealed that
It was confirmed that an SmC tree with a monodomain non-helical structure was formed.

Furthermore, after maintaining this liquid crystal element in the SmC main state for 700 hours, similar microscopic microscopy was performed again, and it was confirmed that it was still an SmC tree with a monodomain non-helical structure.

On the other hand, as a comparative experiment, the 4-(2
-Methylbutyl)phenyl-4'-desyloxybenzoate was omitted, but a liquid crystal device was fabricated in the same manner as described above, and then microscopically observed. Although the formation of trees was confirmed, after 700 hours of durability testing, 5m0 trees did not form monodomains.

[Examples 3 and 4] 4-pentylphenyl-4-(4'- Methylhexyl)phenyl-4'-poxylate (Example 3), P-n-octyloxybenzo-P'-(
2-methylbutyloxy) phenyl ester (Z male side 4
) was used, but a liquid crystal element was prepared in the same manner as in Example 2, and then observed using an m-microscope.

5m0 monodomain non-helical structures were formed. Furthermore, for each example, 7
When a 00 hour durability test was conducted, it was confirmed that the wood was made of the main SmC wood.

[Examples 5 to 7] 4-(2-methylbutyl)phenyl used in Example 2
Substituting 4′-denroxyhensoate, 4-(Z″-
Methylbutyl)-4゛-cyanobiphenyl C Example 5)
, cholesteryl benzonate (Example 6), 4-(2
'-Methylbutyloxy)-4'-cyanobiphenyl(
A liquid crystal element was prepared in the same manner as in Example 2 except that Example 7) was used, and then! II microscopic observation revealed that an SmC tree with a non-helical structure was formed. Furthermore, when a 700-hour durability test similar to the above-mentioned Example 2 was conducted for each example, it was confirmed that it was a monodomain S mC*.

On the other hand, in each of the above-mentioned Examples, except that the use of the liquid crystal exhibiting a cholesteric phase used in Examples 5 to 7 was omitted, liquid crystal elements were prepared in the same manner, and then a similar durability test was conducted. In the case of , the SmC tree was not a monodomain either.

[Example 8] A solution having the following composition (solution composition(
1)) was applied and dried at 120°C for 30 minutes to form a thin film.

Solution structure (1) Acetomethoxyaluminum diisopropylate Ig Polyester resin (Toyobo: Vylon 30P) 0.5g Tetrahydrofuran 100mJ 1 then 1
The rubbed plastic substrates were rubbed in one direction under the pressure of 00 g/cIrI', and the rubbed plastic substrates were twisted together so that the upper and lower rubbing directions were parallel to each other, and the periphery of the substrates except for the area that would become the injection port was sealed. The distance between the pair of plastic substrates at this time was 1=.

Next, 4jTEi parts of 4-(2-methylbutyl)-41-hexyloxyazobenzene were added to 100 parts by weight of 4-(2'-methylbutyl)phenyl-4'-ctyloxybiphenyl-4-carboxylate to form a liquid crystal composition. Adjusted things.

This liquid crystal composition was heated to form an isotropic phase, prepared as described above, and injected into the cell through the injection port under reduced pressure, and the injection port was sealed. After lowering the temperature of this cell by slow cooling, a pair of polarizers were placed in a crossed nicol state, and microscopic observation revealed that 5m0 monodomain non-helical structures were formed.

Furthermore, after maintaining this liquid crystal element in the SmC* state for 500 hours, similar microscopic observation was performed again, and it was confirmed that it still had a monodomain non-helical structure with 5m0 lines.

On the other hand, as a comparative experiment, the 4-(2
A liquid crystal device was fabricated in the same manner as described above, except that methylbutyl)-4'-hexyloxyazobenzene was omitted, and then revealed in 11'9. Although the formation of 5 m0 was confirmed, after 500 hours of durability testing, 3 quintillion had not formed a monodomain.

(Examples 9 to 11) In place of 4-(2-methylbutyl)-4'-hexyloxyazobenzene used in Example 8.

4-(do-methylbutyl)-'4'-cyanobiphenyl (Example 9), cholesteryl benzonate (Example 1')
Example 2 except that 0), 4-(2'-methylbutyloxy)-4'-cyanobiphenyl (Example 11) was used.
After creating a liquid crystal element in the same manner as above, microscopic observation revealed that 5m0 monodomain non-helical structures were formed. Further, for each example, Example 8 described above
When a similar 500-hour durability test was conducted, it was confirmed that the material was monodomain SmC*.

On the other hand, in each of the above-mentioned Examples, except that the use of the liquid crystal exhibiting the cholesteric phase used in Examples 9 to 11 was omitted, liquid crystal elements were prepared in the same manner, and then the same durability tests were conducted. However, the SmC tree was not a monodomain.

[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(B) is a sectional view taken along the line A-x. Figure 4 is. FIG. 3 is a cross-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. 7C&) to (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 lot, io1', substrate 102, 102'; electrode 103; liquid crystal layer 104, 201; spacer member 105,
Orientation control IP14 106; adhesive 107.108, polarizer 109, heating element patent applicant Canon Co., Ltd. art

Claims (18)

[Claims] (1) Between a pair of substrates, at least one type of liquid crystal that undergoes a phase transition from an isotropic phase to a cholesteric phase, a smectic A phase, and a chiral smectic phase during a cooling process; and a liquid crystal that changes from an isotropic phase to a cholesteric phase during a cooling process; At least one liquid crystal that undergoes a phase transition from an isotropic phase to a cholesteric phase, a smectic phase, and a crystalline phase during the cooling process.
It has a cell structure encapsulating a liquid crystal composition containing seeds,
A liquid crystal element characterized in that the surface of at least one of the pair of substrates has the effect of preferentially arranging the molecular axis direction of the liquid crystal that contacts at an 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 smectic phase is a C phase, H phase, F phase, I phase, or G phase. (4) The liquid crystal device according to claim 2 or 3, wherein the chiral smectic phase has 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 substance is SiO, SiO_2 or TiO_
2. The liquid crystal element according to claim 7, which is No. 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.