JPS60114824A - Control method of orientation of liquid crystal and element used by said method - Google Patents

Abstract

PURPOSE:To form a mono-domain of liquid crystal arrayed in one direction by changing another phase to the uniaxial anisotoropic phase of the liquid crystal arrayed in the parallel direction with the liquid crystal direction of the uniaxial anisotoropic phase under a temperature falling condition at a position close to the phase interface between the uniaxial anisotoropic phase of the liquid crystal and another phase on the high temperature side and generating the phase change continuously from the interface surface to its vertical direction. CONSTITUTION:When the temperature of a case in which a cell 100 is set up is controlled so as to be gradually fallen under a condition applying temperature gradient by regarding a part close to a heating element as a high temperature part, a temperature at a position close to the side wall 104' of a nucleus generating member 104 is falen lower than a phase transition temperature from an isotropic phase to smectic A (SmA) phase and the nucleus of the SmA phase is formed at the area. The nucleus of the formed SmA phase is a mono-domain orientated in the horizontal direction to the surface 109 of a substrate 101. When the temperature of the case is fallen further, the mono-domain area of the SmA phase expands continuously. When the temperature of the case reaches a prescribed temperature, the liquid crystal is transferred to the SmA phase almost in the whole area. When the temperature gradient is released, the whole is kept at a uniform temperature and the liquid crystal is transferred to a smectic C (SmC) phase.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal alignment control method used in producing liquid crystal elements such as liquid crystal display elements and liquid crystal-optical shutter arrays, and elements used in the method, and more specifically relates to an initial alignment control method of liquid crystal molecules. The present invention relates to a liquid crystal alignment control method that improves display and drive characteristics, and an element used in the method.

Conventionally, a liquid crystal display element displays 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 N 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. Although it has been adopted.

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 are 1, for example, M, 5ch, which are used practically as a single display element because of their relatively high response speed and low power consumption.
dt and WJ (by elfric'h ``AppliedPh
ysics Letters"Vo, 18, No, 4
(1971, 2, 15 people P, 127-128 Volt
age −, Dependent Opt+1calA
activity of a Tvisted Nema
This type of liquid crystal uses a T N (twisted nematic) type liquid crystal shown in ``Tic Liquid Crypt'al''.In this type of liquid crystal, molecules of nematic liquid crystal with positive dielectric anisotropy are The liquid crystal layer forms a twisted structure (helical structure) in the thickness direction, and the liquid crystal molecules are arranged in parallel on both electrode surfaces.On the other hand, when an electric field is applied, a positive dielectric anisotropy is formed. The nematic liquid crystals in the device 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 (selection point) has a threshold that is required to align the liquid crystal molecules perpendicular to the electrode surface. The above voltage is applied, and no voltage is applied to the region where neither the scanning electrode nor the signal electrode is selected (non-selected point).

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 form one image element. It becomes possible. However, when a matrix electrode structure is configured, there are areas where scanning electrodes are selected and signal electrodes are not selected, or areas where scanning electrodes are not selected and signal electrodes are selected (so-called "half-selected points").
) will also have a finite electric field. If 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 opening required to align the liquid crystal molecules perpendicular to the electric field is set to an intermediate voltage value, the display element works normally, but when the number of scanning lines (N) is increased, the time during which an effective electric field is applied to one selected point while scanning the entire screen (one frame) (duty ratio) increases. )
decreases at a rate of l/N. For this reason, the effective voltage difference between selected points and non-selected points when repeating scanning is performed becomes smaller as the number of scanning lines increases, resulting in a decrease in image contrast and Crosstalk is an unavoidable drawback. This phenomenon occurs because liquid crystals 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 essentially an unavoidable problem that arises when driving (i.e., repeatedly scanning) using the temporal accumulation effect.

In order to improve this point, voltage averaging method, dual frequency driving method, multiple matrix method, etc. have already been proposed, but all methods are insufficient and a) large screen size and high density of one display element are required. 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 beam printers 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 using electrical signals as input. (LBP) is also excellent at the current stage.

However, for LBP.

There are disadvantages such as 1. The device used as a printer becomes large; 2. There is a high-speed driving 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 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 dat/dat within a length of 210+o+, it is necessary to have 3000 or more signal generating units. In order to give independent signals to each,
Originally, lead wires had to be wired to send signals to each signal generating section, which was difficult to manufacture.

For this reason, attempts have been made to time-divisionally provide pixel signals for I LINE (line) to signal generating sections divided into several lines. This is because the electrode for applying a signal can be shared by a plurality of signal generating sections, and the amount of actual wiring can be significantly reduced.

However, in this case, if the number of lines (N) is increased using a liquid crystal that does not have bistability, as is usually done, then r#IJ becomes substantially Kl/N when the signal is ON. There is a comparable problem when the amount of light obtained on the body is reduced, and the problem of crosstalk occurs.

In order to improve the drawbacks of conventional liquid crystal elements, the use of bistable liquid crystal elements has been proposed by C1ark and Lagerwall (Japanese Unexamined Patent Publication No. 56-107216, U.S. Pat. No. 4,367,924).
number specification etc.). Bistable liquid crystals generally include chi2lsmectic C phase (SMC) or H phase (
SmH*) 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, and therefore the above-mentioned TN
For example, the liquid crystal is oriented in a first optically stable state for one electric field vector and in a second optically stable state for the other electric field vector. The liquid crystal is aligned in the state. In addition, this type of liquid crystal
It has the property of very quickly taking one of the above two stable states in response to an applied electric field, and maintaining that state when no electric field is applied. By utilizing such properties, substantial improvements can be obtained in many of the problems of the conventional TN type device described above. This point will be explained in 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 arranged on a pair of parallel substrates tliJI/C must be It is necessary that the molecules be in such a state that conversion between two stable states can occur effectively. For example, for a ferroelectric liquid crystal having an SmC" or SmH* phase, the liquid crystal molecular layer having an SmC* or SmH" phase is perpendicular to the substrate surface, and therefore the liquid crystal molecular axes are aligned approximately parallel to the substrate surface. A region (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, these.

None of them necessarily gave satisfactory results. For example, how to apply a magnetic field.

The problem is that it requires a large-scale device and is incompatible with thin-layer cells that have good operating characteristics.

In addition, the method of applying shear force is incompatible with the method of injecting liquid crystal after forming the cell.

By the way, in the device using the TN type liquid crystal as mentioned above,
One way to form monodomains of liquid crystal molecules parallel to the substrate surface is to rub the substrate surface with something like cloth (
A rubbing method, a method of diagonally depositing SiO, etc. are used. For example, the liquid crystal in contact with the rubbed substrate surface is given a directionality, and the liquid crystal molecules preferentially align in that direction, resulting in the lowest energy (ie, stable) state. For this type of rubbing surface,
It has the effect of preferentially arranging liquid crystal molecules in one direction. A structure having a plane to which this orientation effect is imparted is shown, for example, in Canadian Patent No. 1010136 of %W, Elfrich and MSchadt. In addition to the method of creating an orientation effect using the two-ping method, a structure with a plane formed by diagonally vapor depositing SiO or 5io2 on a substrate is used, and the uniaxial anisotropy of this SiO or stow is The plane has the effect of preferentially aligning liquid crystal molecules in one direction.

In this way, alignment control methods using the %2 pinning method and oblique evaporation method are one of the preferred methods for producing liquid crystal elements, but these methods cannot be applied to liquid crystals that have bistability. When alignment is controlled, a plane is formed that has a wall effect that preferentially orients the liquid crystal in only one direction.
It has drawbacks such as bistability to electric fields, high-speed response, and inhibiting monodomain formation.

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

As a result of further research for the above-mentioned purpose, the present inventors focused on the orientation during the temperature-falling process of transitioning to phase (2), and found that a phase transition from another phase (high temperature phase) to -axial anisotropic phase was observed. In this case, the spatial phase interface between another phase region and the above-mentioned axially anisotropic phase region (at the spatial phase interface between another phase region and the above-mentioned axially anisotropic phase region, the uniaxially anisotropic molecular axis generated by a new phase transition When the liquid crystal molecules are oriented parallel to the direction of anisotropic liquid crystal molecules, and the growing direction of the -axial anisotropic phase region is orthogonal to the direction of alignment of the liquid crystal molecules, the monodomain-axis is extremely stable. Furthermore, the present inventors used a structure having sidewall surfaces with horizontal orientation as a nucleation member (meaning a member that promotes the generation of a liquid crystal layer in a -axis anisotropic phase). It is possible to form the initial uniaxially anisotropic nucleus as a monodomain uniaxially anisotropic phase in which the liquid crystal molecules are aligned parallel to the nucleation member. As a result, it has been found that a liquid crystal element can be obtained that has a structure that is compatible with the operating characteristics of the element based on the bistability of the liquid crystal and the monodomain nature of the liquid crystal layer.

The present invention is based on the above-mentioned knowledge, and consists in forming a phase interface between the aligned uniaxially anisotropic phase of liquid crystal and another phase on the high temperature side of the phase, and is changed to a uniaxially anisotropic phase with liquid crystals aligned in a direction parallel to the liquid crystal alignment direction of the -axis anisotropic phase under decreasing temperature, and the phase change is caused to occur continuously from the phase interface in a direction perpendicular to the liquid crystal alignment direction. In particular, it is characterized by a liquid crystal orientation control method that forms liquid crystal monodomains aligned in the -° direction.

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

Particularly suitable liquid crystal materials for use in the present invention include:
It is a liquid crystal that has bistability and ferroelectricity, and specifically, it is a liquid crystal that has bistable properties and has ferroelectricity.
A liquid crystal having a phase C") or an H phase (SmH*) can be used.

For more information on ferroelectric liquid crystals, see e.g. LE JOU
RNAL DE PHYSIQUE LETTER8”
36 (L-69) 1975, r Ferroelec
tric Liquid Crystals ”App
Lied physics 1etters”36(L
-69) 1975 %r Ferroelectr
ic 1quidCrystals J ;Appl
ied Physics Letters' 36(1
1) l 980. rsubmicro 5econ
d j3istableElectrooptic S
witching in Liquid Crysta
ls J; 6 Hardwood Physics” 16 (141) 1981 r
Ferroelectric liquid crystals disclosed in these documents can be used in the present invention.

Specific examples of ferroelectric liquid crystal compounds include desyloxybenzylidene-P'-amino-2-methylbutylcinnamate (DOBAMBC), hexyloxybenzylidene-p/-amino-2-chloropropylcinnamate (H
OBACPC), 4-o-(2-methyl)-puterresol cylidene-4'-octylaniline (MBRA
8).

When forming a 4flj device using these materials, the device may be placed in a copper block with a heater embedded, etc., as necessary, in order to maintain the temperature such that the liquid crystal compound becomes the SmC* phase or SmH* phase. can be supported.

FIG. 1 schematically depicts an example of a cell for explaining the operation of a ferroelectric liquid crystal. 11 and.

1-1' is "*Os r 5n02 or ITO (
It is a substrate (glass plate) covered with a transparent electrode made of a thin film such as Indium-Tin Oxide (Indium-Tin Oxide), etc., between which a liquid crystal molecular layer 12 of SmC" phase or SmH" phase is oriented perpendicularly to the glass surface. Liquid crystal is enclosed.

A thick line 13 represents a liquid crystal molecule, and this liquid crystal molecule 13 has a dipole moment (P) 14 in a direction perpendicular to the molecule. When a voltage higher than a certain threshold is applied between the electrodes on the substrates 11 and 11', the liquid crystal molecules 1
Get rid of the helical structure of 3, dipole moment) (P) 1
The alignment direction of the liquid crystal molecules 13 can be changed so that all of the liquid crystal molecules 4 are oriented in the direction of the electric field. The liquid crystal molecules 13 have an elongated shape and exhibit refractive index anisotropy in the major and minor axis directions. Therefore, for example, if crossed Nicol polarizers are placed above and below the glass surface, voltage can be applied. It is easily understood that the liquid crystal optical modulator is a liquid crystal optical modulator whose optical characteristics change depending on the polarity.

The liquid crystal cell preferably used in the liquid crystal element of the present invention can have a sufficiently thin thickness (for example, 10 μm or less). As the liquid crystal layer becomes thinner, 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 its dipole moment P or P' becomes Upward (24) or Downward (
24'). When an electric field E or E' with a different polarity of a certain polarity or more is applied to such a cell by the voltage applying means 21 and 21' as shown in FIG. The liquid crystal molecules are oriented upward 24 or downward 24' in response to the electric field vector 24', and accordingly the liquid crystal molecules are aligned in either the first stable state 23 or the second stable state 23/.

As mentioned earlier, there are two advantages to using such ferroelectricity as a liquid crystal 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 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 turned off. Also, when applying an electric field E' in the opposite direction,
The liquid crystal molecules are oriented in a second stable state 23' and change their orientation, but they remain in this state even after cutting the stain boundary. Further, as long as the applied electric field E does not exceed a certain open chain, each orientation state is maintained. In order to effectively achieve such fast response speed and bistability, it is preferable that the button cell is as thin as possible.

As mentioned earlier, the biggest problem in forming confectionery using liquid crystals with ferroelectric properties is SmC.
It is difficult to form a highly monodomain cell in which a layer having a *phase or S mH* is aligned perpendicularly to the substrate surface and liquid crystal molecules are aligned approximately parallel to the substrate surface. It is the main objective of the present invention to provide a solution to this point.

FIG. 3(A) is a partial plan view of an example of a liquid crystal confectionery obtained by the liquid crystal alignment control method of the present invention, and FIG. 3(B) is a sectional view taken along the line AA'. be. In both cases, in order to make the cell structure easier to understand, the liquid crystal cell 1 shown in Fig. 3 is
00 is a pair of substrates l (l and 101' made of glass or plastic plates, etc.) and spacers (not shown).
The pair of substrates are held at a predetermined distance by an adhesive 10.
6 has a cell structure bonded to the substrate 103.
An electrode group consisting of a plurality of transparent electrodes 102 (for example, an electrode group for applying a scanning voltage in a matrix electrode structure)
is formed of a predetermined number of turns, such as a strip pattern. On the substrate 101', an electrode group (for example, a signal voltage application electrode group in a matrix electrode structure) consisting of a plurality of transparent electrodes 102' intersecting with the transparent electrode 102 described above is connected to a lead 107/ It is formed of a pattern of segments connected in a zigzag pattern. The transparent electrode 102 is connected to the lead 107, and the transparent electrode 102' is connected to the lead H17N, and signals from an external circuit are input to the terminals of the leads 107 and 107'', respectively.

Such substrates 101 and 1011 include, for example, silicon oxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride,
Silicon nitride, silicon carbide, boron occlusion, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride.

An insulating film (not shown) made of polyamide, polystyrene, cellulose resin, melamine resin, area resin, acrylic resin, or the like can be provided. This insulating film layer 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, thus preventing the liquid crystal compound from deteriorating even if the operation is repeated. There is no.

The cell structure in this specific example includes a liquid crystal layer 103 that exhibits ferroelectricity at a predetermined temperature as described above, a nucleation member 104, and a heating element 105 such as a heater.

The nucleation member 104 is made of, for example, polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylerin, polyester, polycarbonate,
After forming a film with resins such as polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine 1111, oil resin and acrylic resin, or inorganic compounds such as SiO%stow or Tie, It is formed into a multi-band shape using the 7 otolithography method. Further, the nucleus generating part 104 can be formed of the same material as the substrate 101 or 101'.

Further, as the first heating element 105, for example, indium oxide, tin oxide or ITO (Indium Tin Oxide) is used.
It is suitable to use a thin film resistor such as ).

A liquid crystal cell 100 such as the one shown in FIG.
Optical modulation will occur when a voltage is applied between 02 and 102'.

To give a more specific example of the liquid crystal cell 100 shown in FIG. 3, for example, the transparent electrode 1 (12 has a width of 62.5μ
A band-shaped scanning electrode group with a diameter of m, and a transparent electrode 102'
forms one pixel, and can be a signal electrode group of 62.5 μm×62.5 μm. It is also preferable that the

Such a liquid crystal cell 100 is housed in a heating case (not shown), and polarizers 108 and 108' are vertically orthogonal to each other.
can be arranged and operated as a liquid crystal shutter array for an electrophotographic printer. In this case, the third
Arrow B in Figure (A) is the rotation direction of the electrophotographic photosensitive drum.

For example, the nucleation member 104 is prepared by applying a polyimide forming solution (non-volatile content concentration: 14.5 wt % to PIQ) manufactured by Hitachi Chemical Co., Ltd. for 10 seconds on the substrate 101 using a spinner coating machine rotating at 3.00 Orpm. death.

Heating was performed at 120° C. for 30 minutes to form a 2μ thick film. Next, a positive resist solution (C5HIPLEY AZ1350") was applied with a spinner and prebaked. This resist layer was exposed using a strip mask with a mask width of 0.5 mm. Then, a developer containing tetramethylammonium hydroxide was applied. By developing with liquid "MF312", the exposed portion of the resist film and the underlying polyimide film are etched to form through holes.
After washing with water and drying, the resist film in the least exposed areas was removed using methyl ethyl ketone. After that, 200℃
A nucleation member of PIQ (polyimide) can be formed by heating at 350° C. for 30 minutes.

Hereinafter, DOBAM, a liquid crystal material exhibiting constant ferroelectric properties at a given temperature, will be described.
Taking the case of BC as an example, a method for controlling the alignment of the liquid crystal layer 103 will be specifically explained using FIG. 3.

“First, liquid crystal cell 1 in which DOBAMBC is sealed
00 is set in a heating case (not shown) such that the entire cell is heated uniformly.

Next, the temperature of the heating case is controlled so that the average temperature of the cell is, for example, 90°C. At this time, DOBAM
BC is in a SmC* phase or SmA phase state as a liquid crystal phase. Here, when a current is applied to the heating element (heater) 105 and the current value is gradually increased, first, only the very vicinity of the heating element 105 exceeds approximately 118°C, which is the transition temperature of SmA → isotropic phase, and reaches the isotropic phase. That is, a phase transition occurs to a liquid phase state. Further, as the current is increased, the constant phase region expands while the heating element 105 and t are kept in a parallel state, and eventually the entire liquid crystal layer 103 becomes in the constant phase.

In this state, the longitudinal direction of the liquid crystal cell 100 (Fig.
) is uniform in temperature in the direction C), and the heating element 10 is heated from the two-core hanging member 104 in the transverse direction (direction B in FIG. 3 (5)).
A temperature gradient is formed such that the temperature gradually increases in the direction of 5. For example, the side wall surface 104 of the nucleation member 104
For example, the vicinity of
A temperature gradient is formed by setting the temperature near the heating element 105, which is separated by m, to about 140° C., for example.

Next, with the above-mentioned temperature gradient applied to the cell 100, the temperature of the case in which the cell 100 is set is raised to 90°C, and the temperature is gradually lowered at a rate of, for example, 1 (1'c/h). 3, first, the nucleation member 104
The temperature in the vicinity of the side wall surface 104' becomes lower than the tosokoshi phase → SmA phase transition temperature (approximately 1 jli, 6° C.), and the nucleus of the SmA phase is formed in this region. At this time, the nucleation member 1
Both the side wall surface 104I of 04 and the surface 109 of the substrate 101 have the effect of aligning liquid crystal molecules in the horizontal direction, so when the SmA phase is formed near the side wall surface 104', the liquid crystal molecule axis is aligned with the substrate 101. 101 and parallel to the longitudinal direction of the sidewall surface 104', the nuclei of the S mA phase formed are thus formed between the sidewall surface 104' and the substrate 1 (11 It is a monodomain oriented in the horizontal direction with respect to the plane lO9.As the temperature of the case is further lowered, the already formed togoyoshi phase near the phase interface between SmA and the togoyoshi phase changes to S
A phase transition occurs in SmA in a direction parallel to the arrangement direction of mA, and as a result, when the temperature continues to decrease under a temperature gradient, SmA
The monodomain region of the phase expands continuously. At this time, the growth rate of the phase interface between the monodomain region and the isotonic phase region of BmA 40 is determined in the longitudinal direction of the liquid crystal cell 100 (the third
It is desirable that the speed be the same throughout the direction (direction of arrow C in Figure A). When the temperature of the case reaches, for example, about 70'C, almost the entire liquid crystal, except for the vicinity of the heating element 105, undergoes a phase transition to the SmA phase.

Next, when the current flowing through the heating element 105 is gradually lowered to release the temperature gradient, the temperature of the liquid crystal cell l (+11) becomes 70'C uniformly throughout the entire cell, and the liquid crystal undergoes a phase transition to the SmC" phase. At this time, the molecular arrangement of the liquid crystal in the vicinity of the first heating element 105 may be in a random state, but in the region where the electrodes 102 and 102/ are formed, it is a uniform monodomain. .

What are the important points in the liquid crystal alignment method described above?

It is desirable to provide as large a temperature gradient as possible in the B direction in FIG. 3(A), but it is desirable to provide a uniform temperature in the C direction. It is the same as the one on the back.

This point will be explained using FIGS. 4(A) to 4(D).

In other words, in FIG. 4(A), an element is formed by making the heating element 105 into a band shape, and SmA is applied to this element by the method described above.
The growth process of the SmA phase region during the temperature decreasing process by slow cooling when forming the phase is schematically shown.

In the figure, 201 is the SmA phase region 202 and the Tokichi phase region 203.
represents the phase interface of When the heating element 105 has a linear shape with a uniform width as shown in the figure, if the liquid crystal cell 100 is set in a case (not shown), the length of the liquid crystal cell 1.00 will be Since the temperature is lower at the end E than at the center in the direction,
The phase interface 201 grows parallel to the side wall surface 104' of the nucleation member 104 near the center, but grows at an angle at the end E as shown in the figure. Fourth
Figures 4(B) and 4(B) show the alignment states of liquid crystal molecules in the edge E region and central region shown in Figure (A), respectively.
C) Shown schematically.

As shown in Figure 4 CB), SmA in the region of end E
The phase 202 indicates the long axis direction 202/ of liquid crystal molecules.

As can be seen in the figure, the side wall surface 104/ and the phase interface 201
When the liquid crystal molecules 202' are tilted to a greater extent than parallel (the tilt angle is θ), the alignment direction of the liquid crystal molecules 202' is aligned with the side wall surface 104.
′ and is tilted by an angle θ2 (θ,
Medium θ,). This means that in the vicinity of the phase interface 201, S
When the mA phase grows, the liquid crystal molecules 202 become SmA
This is presumed to be due to the tendency to align in a direction perpendicular to the growth direction of the phase. Furthermore, in a region where the inclination angle θ of the phase interface 201 changes rapidly, the liquid crystal molecules become aligned and separate into different domains with greatly different alignment directions, 204
A defect line appears as shown in .

On the other hand, as shown in No. 41@+(C), the SmA phase 202 in the central region is aligned with the liquid crystal molecule axis direction 202/, which is approximately parallel to the side wall surface 104' and the phase interface 2017. Hayakeshi parallel and uniform monodomain Sm
A phase 202 is formed.

Fig. 4 (D) is a table heating element 1 that has been improved in view of the above points.
05. Heating element 1 as shown in the figure
By narrowing the width of the heater pattern at the end of 05, the resistance value of the heating element at that end is increased, and the amount of heat generated at that end is increased. The temperature in the longitudinal direction can be made uniform. For this reason.

Since the phase interface 201 between the SmA phase 202 and the equal diameter 203 is parallel to the side wall surface 201, a uniform monodomain is obtained as a whole.

Now, when the alignment is completed through the steps described above, and a voltage is applied in between, and the characteristics of the switch ink as a liquid crystal optical modulation element are investigated, non-uniformity may occur depending on the optical contrast or response speed region. be. This phenomenon is thought to be due to structural distortion caused by the temperature gradient set during orientation. To deal with this, a method for completing the alignment process - raising the temperature of the carrier case and converting the liquid crystal into SMC*
Phase phase transition to SmA phase, then SmA phase again
Gradually lowering the temperature of the case to the C'' state has the effect of eliminating the aforementioned distortion due to structural relaxation.

FIG. 5 shows another example of a heating element for preventing the temperature at the ends of the liquid crystal cell 100 from becoming lower than that at the center during the formation of a temperature gradient during the alignment process. heating element 10
5 is a heating element 301 that heats the edge of the liquid crystal cell 100;
．． 302 can be used to compensate for the temperature drop at the ends as described above. Like this, liquid crystal cell 1
By providing the heating elements 105, 301 and 302 around υ0, a uniform monodomain of the SmA phase is formed.

FIG. 6 shows another embodiment based on the present invention, in which a heating element 105' is separately provided on the back side of the substrate 101. The heating element 105/ is used to heat the entire liquid crystal cell 10. For example, when actually used as a liquid crystal optical change element, if the orientation of the liquid crystal is disturbed due to some trouble, the heating element 105/ By using the same method, it is possible to carry out reorientation through predetermined steps.

Of course, this heating element 105' can also be provided on the back side of the substrate 101'. That is, - the SmC* phase formed by the method described above is heated with the heating element 105' to phase-transform the entire liquid crystal cell 100 to the SmA phase;
A uniform monodomain can be formed again by slow cooling to the C* phase.

The liquid crystal cell ioo shown in FIG.
A specific example is shown in which a heating element 110 made of an alloy thin film is provided. The shape of this heating element 110 is preferably the shape shown in FIG. 4(D) or FIG. 5 described above.

Further, the liquid crystal cell 100 shown in FIG.
5) Model-shaped ITO or Ni with a gradient in thickness
A specific example is shown in which a heating element 111 made of a -Cr thin film is provided.

When a constant voltage is applied in the longitudinal direction (perpendicular to the plane of the paper) of this liquid crystal cell 100, the side wall surface 104 of the nucleation member 104
A temperature gradient is formed in the vicinity of ', where the temperature increases in the vertical direction.

At this time, between the first heating element Ill and the electrode 102, an organic insulating film such as polyimide or an inorganic insulating film 11 such as S10 is used.
It is desirable to provide 2. [9] In forming the liquid crystal element of the present invention, a spacer can be used to directly control the thickness of the liquid crystal layer to a predetermined value. Figure 9 shows
An example of the structure of a liquid crystal element of the present invention having such a spacer structure is shown. That is, the liquid crystal element shown in FIG. 9 includes a substrate 1 having an electrode 102 having a transparent conductive pattern.
01 and the substrate 1 placed opposite to this substrate 101.
A spacer member 113 is formed between the substrates 101 and 101', thereby making it possible to stabilize the uniformity of the film thickness of the liquid crystal 103 disposed between the substrates 101 and 101'. The spacer member 113 is obtained by applying an electrically insulating material to a predetermined thickness on one of the substrates, and then forming the spacer member 113 into the shape shown in the figure by photolinography.

In producing this liquid crystal element, the heating element 105 is heated in the manner described above to obtain a single phase such as DOBMB C with a temperature gradient, and then the temperature is lowered while maintaining the temperature gradient. , nucleation member 104
A monodomain with an sm human face grows from the side wall surface 104' of the spacer 113 toward the side wall surface 113' of the spacer 113, and the other side wall surface 113' of the spacer 113 grows like the aforementioned side wall surface 104'. Therefore, SmA monodomains similarly grow from this side wall surface 113''. This spacer 113 is made of the same material as the nucleation member 104 described above, and is simultaneously grown during the 7 otolithic process. It has a band-like shape and can be made in multiple pieces.

10 to 12 show examples of driving the liquid crystal element of the present invention.

Figure 1θ shows a ferroelectric liquid crystal compound sandwiched between = q
) , '+ +7 cell 41 having a square electrode structure
FIG. 42 is a scanning electrode group, and 43 is a signal electrode group. FIGS. 11(a) and 11(b) show the electrical signals given to the selected scanning electrode 42(8) and the other scanning electrodes (unselected scanning electrodes) 42(n), respectively.
FIGS. 6(c) and 6(d) represent the electrical signals applied to the selected signal electrode 43(II) and the unselected signal electrode 43(n), respectively. . In FIGS. 11(a) to 11(d), the horizontal axis represents force F time, and the vertical axis represents voltage. For example, when displaying a moving image, the scanning electrode group 42
are selected sequentially and periodically. Now, in order to give the first stable state of the liquid crystal cell with bistability, the threshold voltage is set to v t
h, and the threshold voltage for providing the second stable state is −
vth, the electrical signal given to one selected scanning electrode 42(s) is as shown in FIG. 11(a).
At phase (time) t, V, at phase (time) t, -V
It is an alternating voltage such that Also, the other scanning electrodes 42(n) are in a grounded state as shown in FIG. 11(b). The energy signal is 0. On the other hand, the electric signal given to the selected signal electrode 43(II) is v as shown in FIG. 11(c), and the electric signal given to the unselected signal electrode 43(n) is shown in FIG. As shown in (d), the voltage V is V (V th, (2V and -V) -V th,) -2V
is set to a desired value that satisfies The voltage waveform applied to each pixel when such an electrical signal is given is the first
Shown in Figure 2. Figures 12(a) to (d) are the first
0 corresponds to 9 pixels A, B, C, and D in the figure. That is, as is clear from FIG. 12, the pixels on the selected scanning line.

At phase t, a voltage of 2v exceeding the threshold +1vth is applied. Also, in pixel B existing on the same scanning line, the phase t,
A voltage of -2V exceeding the threshold lit -Vth is applied. Therefore, depending on whether a signal electrode is selected on the selected scanning electrode line, if one is selected, the liquid crystal molecules are aligned in the first stable state.

If 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, pixel C,! -On one unselected scan line as shown in D, the voltage applied to all pixels C and D is +
(2) or - (2), neither of which exceeds the threshold 1 direct 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, signals for one line are written, and until the next frame is selected,
This means that the signal state can be maintained. Therefore, even if the number of scanning electrodes increases, no reduction in contrast or crosstalk will occur, regardless of the actual duty ratio. At this time, the directness and phase of the voltage value V (t++t*) = the directivity of T depends on the liquid crystal material used and the thickness of the cell, but it is usually 0.1 μsec at 3 volts to 70 volts.
A range of ~2 rnaec is used. Therefore, in this case, the electrical signal given to the selected scanning electrode is
from a stable state (which is assumed to be a "bright" state when converted to an optical signal) to a second stable state (which is assumed to be a "dark" state when converted to an optical signal), or vice versa. It is also possible to bring about changes in

[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 of a liquid crystal element used in the present invention, and FIG. 3(B) is a cross-sectional view taken along line AA'. Figure 4 (A), Figure 4 (B) and Figure 4 (C)
1 is a plan view schematically showing the growth process of liquid crystal. Fourth
Figure (D) is a plan view showing another embodiment of the liquid crystal cell used in the present invention. FIG. 5 is a plan view showing another embodiment of the liquid crystal cell used in the present invention. Figure 6, Figure 7, Figure 8
9 and 9 are cross-sectional views showing preferred embodiments of the liquid crystal cell of the present invention. m=kine; Figure 1θ is a plan view schematically showing the electrode structure of the optical modulation element used in the present invention. 9 in Figure 10) ~ (
d) is an explanatory diagram showing signals for driving the optical modulation element of the present invention. FIGS. 12(a) to 12(d) are explanatory diagrams showing voltage waveforms applied to each pixel. 100; liquid crystal cell 101, 101'; substrate 102I102'; electrode 103; liquid crystal layer 104; nucleation member. 104': Side wall surface 105.105' of nucleation member, 301.302.110.111
; Heating element 106; Adhesive 107.107', 107'': Lead wire 108.10
8': Polarizer 109; Surface 112 of substrate 101; Insulating film 113; Spacer member patent applicant Canon Corporation (b) (d) (b) (d)

Claims (1)

[Scope of Claims] (1) A phase interface is formed between a uniaxially anisotropic phase of liquid crystal arranged in one direction between a pair of substrates and another phase on the high temperature side of the phase, and a phase interface near the phase interface is formed. , the phase is caused to undergo a phase transition to a uniaxially anisotropic phase of liquid crystals aligned in a direction parallel to the liquid crystal alignment direction of the -axis anisotropic phase under temperature reduction, and the phase transition is continuously carried out from the phase interface in a direction perpendicular to the liquid crystal alignment direction. A method for controlling the alignment of liquid crystals, characterized by forming monodomains of liquid crystals aligned in one direction by causing the formation of monodomains of liquid crystals. (2) The liquid crystal orientation control method according to claim 1, wherein the phase interface has linearity. (3) The uniaxial anisotropy that is initially formed is near the interface with a member that promotes the generation of liquid crystal nuclei (hereinafter, the "member that promotes the generation of liquid crystal nuclei" is referred to as the "nucleation member"). A method for controlling the alignment of a liquid crystal as described in item 1 of the scope above. (4) The phase transition is a phase transition caused by lowering the temperature of the phase on that side, which has a temperature gradient where the side in the vertical direction is high near the interface with the nucleation member, under such a temperature gradient. A method for controlling liquid crystal alignment according to claim 1. (5) The liquid crystal arranged in one direction is
A method for controlling the alignment of a liquid crystal according to claim 1, wherein the liquid crystal is a phase. (6) The temperature of the smectic human phase is lowered to cause a phase transition to the smectic C phase or H phase.
Liquid crystal orientation control method described in Section 1. (7) The liquid crystal orientation control method according to claim 6, wherein the smectic C phase or H phase is a chiral smectic C phase or H phase. (8) The liquid crystal orientation control method according to claim 7, wherein the chiral smectine C phase or H phase is arranged in a non-helical structure. (9) The liquid crystal orientation control method according to claim 1, wherein another phase on the high-temperature side of the -axis anisotropic phase is a caninematic phase, a cholesteric phase, or an isotropic phase. 4. The liquid crystal orientation control method according to claim 3, wherein the nucleating member and the substrate have the effect of aligning the liquid crystals in a horizontal direction. α■ The liquid crystal orientation control method according to claim 3, wherein the nucleation member is a member having a band-like shape. 12. The liquid crystal orientation control method according to claim 11, wherein a plurality of the band-shaped nucleation members are arranged. a3. The liquid crystal alignment control method according to claim 3, wherein the nucleation member is a member having a side wall surface. α→ The liquid crystal orientation control method according to claim 3, wherein the nucleation member is formed of a resin or an inorganic substance. (c) The resin is polyvinyl alcohol, polyimide,
Resins consisting of polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, and photoresist resin. 15. The liquid crystal orientation control method according to claim 14, wherein the resin is at least one selected from the group. 0Q A liquid crystal alignment control element comprising a cell structure including a nucleation member between a pair of substrates and a heating element disposed at a predetermined distance from the nucleation member. α force The liquid crystal alignment control element according to claim 16, wherein the nucleation member is a member having a band-like shape. (IF!l) The liquid crystal alignment control element according to claim 17, wherein a plurality of the band-shaped nucleation members are arranged. (g) The nucleation member is made of resin or an inorganic substance. A liquid crystal alignment control element according to claim 16.b) The resin is polyvinyl alcohol, polyimide, polyamideimide, or polyesterimide. At least one selected from the resin group consisting of polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, Yurya resin, acrylic resin, and photoresist resin. 20. The liquid crystal alignment control element according to claim 19, which is a resin. (c) The liquid crystal alignment control element according to claim 16, wherein the heating element is a resistance heating element. 17. The liquid crystal alignment control element according to claim 16, wherein the heating element is a thin film resistance heating element. (2) A liquid crystal alignment control element according to claim 22, wherein the thin film resistance heating element is a heating element having a band-like shape. 24. The liquid crystal orientation control element according to claim 23, wherein the strip-shaped thin film resistance heating element is a heating element that generates a larger amount of heat near its center than near its ends. (c) The liquid crystal alignment control element according to claim 23, wherein the thin film resistance heating element having a band-like shape is a heating element having a center portion wider than its end portions. (c) The liquid crystal alignment control element according to claim 16, wherein the -dynamic anisotropic phase is a smectic phase (c) the thin film resistance heating element is formed around the substrate. (c) A liquid crystal alignment control element according to claims 2 and 7, wherein the smectic phase is a smectic human phase. (c) A liquid crystal alignment control element according to claim 16, wherein a conductive thin film serving as a polarity is provided on opposing surfaces of the pair of substrates. (g) A liquid crystal alignment control element comprising a cell structure including a nucleation member between a pair of substrates and a planar heating element. Op. The liquid crystal alignment control element according to claim 30, wherein the nucleation member is a member having a band-like shape. 0. The liquid crystal alignment control element according to claim 30, wherein a plurality of the nucleation members each having a band-like shape are arranged. (to) The liquid crystal alignment control element according to claim 30, wherein the nucleation member is formed of a resin or an inorganic substance. (b) The resin is polyvinyl alcohol, polyimide, polyamideimide, polyesterimide, polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, yurya resin, 34. The liquid crystal alignment control element according to claim 33, which is a resin selected from at least one resin selected from the resin group consisting of acrylic resin and photoresist resin. (g) The liquid crystal alignment control element according to claim 30, wherein the planar heating element is a resistance heating element; (c) Claim 30, wherein the planar heating element is a thin film resistance heating element. The liquid crystal alignment control element described in 2. 37. The liquid crystal alignment control element according to claim 36, wherein the thin film resistance heating element is a model-shaped heating element. (to) The liquid crystal alignment control element according to claim 3, wherein the -axis anisotropic phase is a smectic phase. 39.) The liquid crystal alignment control element according to claim 38, wherein the smectic phase is a smectic phase. - The liquid crystal alignment control element according to claim 30, wherein a conductive thin film serving as an electrode is provided on opposing surfaces of the pair of substrates. αη A cell structure comprising a compound exhibiting a uniaxially anisotropic phase at a predetermined temperature and a nucleation member between a pair of substrates, and a compound exhibiting a uniaxially anisotropic phase at the predetermined temperature being transferred from the uniaxially anisotropic phase to the phase on the high temperature side. means for causing a phase transition, means for imparting a temperature gradient to the phase on the high temperature side from the nucleation member in the vertical direction thereof, and cooling for causing the phase on the high temperature side to undergo a phase transition to a dynamically anisotropic phase under the temperature gradient. 1. A liquid crystal alignment control device, comprising: means. 42. The liquid crystal alignment control device according to claim 41, wherein the coffin crystals arranged in one direction are smecti or tsuku physiognomy. (b) The temperature of the smectic human phase is lowered to cause a phase transition to the smectic C phase or H phase.
The liquid crystal alignment control device described in 2. 44. The liquid crystal alignment control device according to claim 43, wherein the smectic C phase or H phase is a chiral smectic C phase or H phase. 45. The liquid crystal alignment control device according to claim 44, wherein the smectic C phase or H phase is arranged in a non-helical structure. 42. The liquid crystal orientation control device according to claim 41, wherein the other phase on the high temperature side of the -axis anisotropic phase is a nematic phase, a cholesteric phase, or an isotropic phase. 00 The resin is polyvinyl alcohol, polyimide,
Polyamideimide, polyesterimide, polyparaxylylene, polyester 5% polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, acrylic resin, and photoresist resin. Patent claim provided with a sexual thin film:
0th 44th;