JPH06289407A - Production of bistable liquid crystal display device - Google Patents

Abstract

PURPOSE:To make it possible to obtain the uniform and stable orientation of nematic liquid crystal molecules without being affected by the flow at the time of liquid crystal injection and to cause bistable switching of the two stable orientation states of the nematic liquid crystal molecules. CONSTITUTION:This process for production of the bistable liquid crystal display device consists in forming electrodes 2a, 2b on a pair of substrates 1a, 1b, forming oriented films 4a, 4b on these electrodes 2a, 2b, arranging the substrates 1a, 1b nearly parallel and opposite with and to each other in such a manner that the vapor deposition directions of the respective oriented films on both substrates vary from each other and interposing a nematic liquid crystal added with a chiral element between these substrates to form a liquid crystal cell and forming a means for switching which switches the optical axis of the liquid crystal by selectively applying voltages to the electrodes 2a, 2b. The nematic liquid crystal is injected into the liquid crystal in the direction perpendicular to the vapor deposition direction of the oriented film of either of the upper or lower substrate 1a or 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bistable liquid crystal display device, and more particularly to a method for manufacturing a bistable liquid crystal display device capable of bistable switching of a nematic liquid crystal. .

[0002]

2. Description of the Related Art Up to now, a display system using a liquid crystal has been known as a DS (dynasty) method by converting an electric signal applied to the liquid crystal into optical information.
mic scattering) method, TN (twisted nematic) method,
ECB (electrically controlled birefringence) system, PC (phase change) system, memory system, GH (gu
est-host) method, SSF (surfacestabirized felo-ele)
ctric) method is considered.

Among them, the systems currently used as display devices in products such as watches, calculators, word processors, personal computers, and televisions are mainly the TN system using nematic liquid crystal and its improved STN system. However, since the operating principle of the TN method and the STN method is a field effect type utilizing the induced anisotropy of liquid crystal molecules, the response speed is only on the order of msec, and a higher response speed is required.
For use as a D terminal or the like, the response speed is insufficient when combined with the current nematic liquid crystal. In addition, the electro-optical effect is generated in a twisted and homogeneous alignment state of liquid crystal molecules and in a state where the electro-optical effect occurs on the substrate surface of the liquid crystal molecules.
In principle, the viewing angle dependence on the twist direction of the liquid crystal molecules cannot be avoided because of the switching between the two states.

In response to these, as a liquid crystal element having a high response speed, Clark (NAClark) and Lagabal (L)
a surface-stabilized ferroelectric liquid crystal device (Surface Stabilized Felo-electric Liquid)
Crystal Display, SSFLCD) (Appl. Phy. Lett.,
36, 899 (1980); JP-A-56-107216; US Patent No.
4366924).

The SSFLCD is an element that performs switching on a cone in which liquid crystal molecules can move by utilizing an electrical interaction between the polarity of spontaneous polarization and the polarity of an electric field that the smectic liquid crystal has, and therefore, is different from the nematic liquid crystal. It has the advantages that extremely high-speed switching is possible and that it does not depend on the viewing angle. However, on the other hand, since smectic liquid crystals have a layered structure, it is difficult to control the alignment, and it is difficult to recover the alignment once broken due to impact or the like.

In addition to the above method, Georges. Duran proposes a bistable liquid crystal optical element (International Publication No. WO 92/00546) which is composed of two transparent substrates on which electrodes are formed and nematic liquid crystals are injected between the substrates. Georges. Duran has proposed two types of bistable liquid crystal display devices using nematic liquid crystals.

One is to use a chiral ion for driving torque (International Publication No. WO 91/11747), in which both right-handed and left-handed chiral ions are mixed in a liquid crystal and a bias is applied to the ion distribution by a voltage. This is used as the driving torque. In this system, liquid crystal molecules can be switched in parallel to the substrate surface by applying a pulsed electric field, as in the SSFLCD. However, since this method uses impurities as ions for the driving torque, there is an inherently large problem in terms of reliability.

The other one uses flexo-polarization for torque, in which a nematic liquid crystal shows a stable orientation in two directions by using a SiO oblique deposition film as an orientation film and selecting film conditions. This is what you use. In this method, flexo-polarization due to orientation distortion is used as a driving torque, and therefore problems such as impurities do not occur and high reliability is expected. Also in this method, like SSFLCD, liquid crystal molecules can be switched in parallel to the substrate surface by applying a pulsed electric field, and the response speed is about 100 μsec, and liquid crystal molecules switch in parallel to the substrate surface. There is no visual angle dependency. Further, since the nematic liquid crystal is used, there is no problem of alignment control, which is a problem in SSFLCD, and the operating temperature range can be made sufficiently wide.

Georges. Reported by Duran (1991, SID Proceedings PP606-607, Appl. Phys.
Lett. 60 (9), 2 March 1992 pp1085-1086) The structure of the nematic bistable liquid crystal display device is as shown in FIG. In FIG. 1, 1 is a substrate (glass substrate), 2 is a nematic liquid crystal layer, 3 is an electrode (transparent electrode), 4 is an alignment film (SiO alignment film), and 5 is a spacer.

Further, in 1991, the following was reported as a detail of the nematic bistable liquid crystal display device in the SID Proceedings. First, the vapor deposition angle of the SiO alignment film is 74 ° from the substrate radiation, the film thickness of the SiO alignment film is 30 Å, and the diameter of the spacer is about 1 to 3 μm.
Georges. According to Duran's report, under such conditions, the alignment direction of liquid crystal molecules becomes as shown in FIG.
The orientation in the direction C perpendicular to the O vapor deposition direction and parallel to the substrate surface becomes stable. However, since the anchoring energy of the interface is weak, when twist power is applied by adding a chiral agent, it tilts by θ ° from the substrate surface, and the direction projected on the substrate surface is α ° and −α from the SiO vapor deposition direction. Orientations in the tilted directions A and B are developed.

Next, Georges. The content reported by Duran will be explained based on FIG. 6, a and b
Indicates the direction in which the SiO vapor deposition direction and the orientation of liquid crystal molecules can be stabilized. In FIGS. 6, a and b, the broken line arrow indicates Si.
The directions of O vapor deposition, ~ and '~' indicate directions in which the alignment of liquid crystal molecules on the surfaces of the upper and lower substrates can be stabilized. Figure 6, a
And b are SiO oblique vapor deposition films as alignment films, and the SiO vapor deposition directions on the upper and lower substrates are 45 ° from parallel (antiparallel) or antiparallel (antiparallel) to the substrate cross-sectional direction.
It is the direction of rotation (twist). In addition, the liquid crystal material used is 22.5 between the upper and lower substrates with a single liquid crystal.
° Use a chiral agent added to twist.
The twist direction due to the effect of the chiral agent is opposite to the twist direction of the SiO vapor deposition direction between the upper and lower substrates. Under such conditions, the liquid crystal molecule orientation that can stably exist due to the effect of the chiral agent is limited, and in FIG.
Two combinations of'and-'are stable. 7, c and d show the alignment of the liquid crystal molecules in the cross section of the liquid crystal cell, and FIGS. 7 and 7c show-', FIG.
Corresponds to the -'orientation in FIG.

However, when the nematic liquid crystal is injected into the SiO oblique vapor deposition substrate of FIG. 6A, if the nematic liquid crystal flows in a direction other than the arrows e and e'or the arrows f and f'of FIG. Does not take molecular orientation. For example,
As shown in FIG. 6A, a nematic liquid crystal is applied to a liquid crystal cell composed of upper and lower substrates that are surface-aligned so as to have the orientation shown in FIG.
When the liquid crystal is injected from the upper side or the lower side (thick line arrow in FIG. 9) of the substrate of FIG. 6, a and ′ of FIGS. 6A and 6B are oriented as shown in FIG. 9 due to the influence of the flow on the inflow direction of the liquid crystal.

As a result, it is impossible to obtain the splay orientations of − ′ and − ′ in FIG. 6A, and stable bistable switching cannot be performed. FIG. 6, b
The same is true for. Georges. According to Duran's report, the nematic bistable liquid crystal display element reported is only partially switched in the pixel, and uniform stable switching is not obtained. The reason for this may be the effect of the flow during injection.

Conventionally, as a method for injecting liquid crystal into a liquid crystal cell, for example, a method in which an injection hole is provided below the substrate by a vacuum injection method and the liquid crystal is injected from one position is generally used. The method of injecting liquid crystal in consideration of the alignment direction of liquid crystal molecules is not used. Therefore, the liquid crystal molecules are affected by the flow at the time of liquid crystal injection, and there is a problem that they are not uniformly and stably aligned. There is also a method of injecting liquid crystal while applying a magnetic field for the purpose of providing a pretilt angle, but a method of applying a magnetic field to make the alignment direction of liquid crystal molecules uniform is not used.

Further, according to a general liquid crystal injection method,
Since there is only one injection hole for the liquid crystal, the injected liquid crystal molecules are aligned concentrically around the injection hole, and the alignment direction is not uniform.

[0016]

[Means for Solving the Problems]
In view of the above problems, the present invention has been completed as a result of intensive research focusing on the fact that bistability switching is possible if the alignment control of the liquid crystal molecule of FIG. Came to do. According to this invention,
Electrodes are formed on a pair of substrates, an alignment film is formed on the electrodes, and the substrates are arranged so as to be substantially parallel so that the vapor deposition directions of the alignment films of both substrates are different from each other. A liquid crystal cell is formed by interposing a nematic liquid crystal to which a chiral agent is added between these substrates, and a switching means for switching the optical axis of the liquid crystal by selectively applying a voltage to the electrode is formed. A method of manufacturing a bistable liquid crystal display device, which comprises injecting a nematic liquid crystal in a direction perpendicular to a vapor deposition direction of an alignment film on one of an upper substrate and a lower substrate. It

Further, according to the present invention, in the method for manufacturing the bistable liquid crystal display device, the nematic liquid crystal is injected in a direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate. As a method, 1. After the nematic liquid crystal is injected, the photosensitive resin pattern is provided on the alignment film on the upper or lower substrate in a direction perpendicular to the vapor deposition direction of the alignment film, and then the alignment film on either the upper or lower substrate is formed. 1. The process is performed from the vicinity of the direction perpendicular to the vapor deposition direction of 1. The nematic liquid crystal is injected from near the vertical direction to the vapor deposition direction of either the upper or lower substrate while applying a magnetic field in the direction perpendicular to the vapor deposition direction of the alignment film on the upper or lower substrate. , Or 3. After the nematic liquid crystal is injected into the isotropic phase by heating the substrate and the nematic liquid crystal, the nematic liquid crystal is kept in the isotropic phase. A method for manufacturing a bistable liquid crystal display device is provided.
These methods can also be used in combination.

As the substrate used in the present invention, a substrate generally used in liquid crystal display devices can be applied.
Examples thereof include a glass substrate and an insulating inorganic substrate such as quartz, and a glass substrate is preferable. An electrode is formed on the substrate, and as the electrode to be used, an electrode generally used in a liquid crystal display device can be applied. For example, InO ₂ ,
SnO ₂ , ITO (Indium Tin Oxide), etc.
ITO is preferred. This electrode is formed in a desired pattern on the substrate, and as a method therefor, a known method can be applied, and examples thereof include an anodic oxidation method and a sputtering method, and the sputtering method is preferable. The thickness of the electrode is 300
~ 5000 angstrom is suitable, 1000 ~
3000 Angstroms is preferred.

An electrode protective film may be formed on the above electrode. As the electrode protective film, an electrode protective film generally used in a liquid crystal display device can be applied.
Examples thereof include O ₂ , Ta, Nb, and silicon nitride, and examples of commercially available products include OCD (OCDP-59310) manufactured by Tokyo Ohka.
The film thickness of the electrode protective film is suitably 300 to 5000 angstroms, preferably 500 to 2000 angstroms. As a method for forming the electrode protective film, a known method can be applied, for example, a solid reaction method, a melt epitaxy method, a sol-gel method, a precipitation reaction method, a chemical plating method, an anodic oxidation method, a vacuum deposition method, The sputtering method, the plasma method, the CVD method, the PVD method, and the like are listed, and are appropriately selected depending on the electrode protective film to be used. For example, in the case of SiO ₂ , it can be formed by a sputtering method, and OCD manufactured by Tokyo Ohka
In the case of (OCD P-59310), after applying with a spinner,
It can be formed by firing.

An alignment film is formed on the above-mentioned electrode or electrode protection film, and the alignment film to be used is, for example, SiO ₂ or S.
iNx, SiO, MgO, MgF ₂ , Au, CeO ₂ , C
Orientation films of eF ₃ , Al ₂ O _{3 and the} like are mentioned, and SiO orientation film is preferable. As a method for forming the alignment film, an oblique vapor deposition method can be applied. When it is formed by the oblique vapor deposition method, the vapor deposition angle is appropriately 70 ° to 76 ° from the substrate normal, and 73 ° to 75 ° is preferable. 20-300 angstrom is suitable as the film thickness of the alignment film,
100-200 Angstroms is preferred.

Next, a liquid crystal cell is prepared by arranging the upper and lower substrates so as to face each other in a substantially parallel manner so that the vapor deposition directions of the alignment films of the upper and lower substrates are twisted with each other, and providing spacers to bond them. This twist angle is 30 °
˜160 °, preferably about 45 °. As the spacer, a spacer generally used in a liquid crystal display device can be applied, and examples thereof include silica beads. When silica beads are used, the diameter of silica beads is appropriately 1 to 3 μm, and 1.0 to 1.5
μm is preferred. As the seal member to which the spacers are attached, a seal member generally used in liquid crystal display devices can be applied, and examples thereof include epoxy resin-based and acrylic-based seal members.

Nematic liquid crystal is injected between the substrates thus formed. As a method for injecting the nematic liquid crystal into the liquid crystal cell, a known method can be applied, and examples thereof include a vacuum injection method. When injecting the nematic liquid crystal into the liquid crystal cell, it is essential to inject the nematic liquid crystal in the direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate.

By injecting the nematic liquid crystal in this way, it is possible to suppress the influence of the flow of the liquid crystal at the time of injection, to obtain a uniformly stable liquid crystal molecular orientation, and to perform bistable switching. A bistable liquid crystal display device can be obtained. As a specific method of injecting nematic liquid crystal, (1) after forming a photosensitive resin pattern on the alignment film of the upper or lower substrate in a direction perpendicular to the vapor deposition direction of the alignment film, A method of injecting nematic liquid crystal from the vicinity of a direction perpendicular to the vapor deposition direction of one of the alignment films on the substrate, (2) above or below while applying a magnetic field in a direction perpendicular to the vapor deposition direction of the alignment film on the substrate. Alternatively, a method of injecting a nematic liquid crystal from the vicinity of a direction perpendicular to the vapor deposition direction of one of the alignment films on the lower substrate, (3) heating the substrate and the nematic liquid crystal to keep the phase of the nematic liquid crystal in an isotropic phase After that, there is a method of injecting a nematic liquid crystal from the vicinity of a direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate.

Method of injecting the nematic liquid crystal (1)
In the method of forming the photosensitive resin (photoresist) and the photosensitive resin to be used, known forming methods and photosensitive resins can be applied. The layer thickness of the photoresist is preferably 0.5 to 2.5 μm and 1.0 to
1.5 μm is preferable. The resist pitch is 0.1-5.
0 μm is suitable, and 1.0 to 2.0 μm is preferable.

In the method (2) for injecting the nematic liquid crystal, the strength of the magnetic field needs to be at least such that the long axes of the nematic liquid crystal molecules are perfectly aligned in the direction of the magnetic field, and the nematic liquid crystal to be used. It is appropriately selected depending on the liquid crystal. As a method for applying a magnetic field, for example, the magnetic pole N and the magnetic pole S are placed so as to sandwich the liquid crystal cell so that the magnetic field is applied in a direction perpendicular to the vapor deposition direction of the alignment film on the upper or lower substrate. There is a method of applying a magnetic field uniformly in the same direction. A turntable may be provided below the liquid crystal cell in order to control the direction of the magnetic field so that the magnetic field is applied in a direction perpendicular to the deposition direction of the alignment film on the upper or lower substrate.

Further, in the method (3) of injecting the nematic liquid crystal, a known method can be applied to the method of heating the nematic liquid crystal. Nematic liquid crystal,
It is necessary to heat to the transition temperature at which the phase of the nematic liquid crystal used changes to the isotropic phase, and it is selected according to the nematic liquid crystal used. For example, when using 5CB manufactured by Merck, the temperature is about 50 ° C. The heating time is the time until the nematic liquid crystal completely enters the liquid crystal cell.

As the method of heating the substrate, a known method can be applied. The heating temperature of the substrate is the same as the heating temperature of the nematic liquid crystal, and the heating time is the same as the heating time of the nematic liquid crystal. In this way, by changing the phase of the nematic liquid crystal to the isotropic phase, the nematic liquid crystal easily returns to the stable molecular alignment of the liquid crystal.

Method for injecting the above nematic liquid crystal (1)
By using (3) to (3), nematic liquid crystal is injected in a direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate, and the molecular alignment of the liquid crystal becomes uniform and stable. Further, the effect is enhanced by using these methods in combination. As the nematic liquid crystal used in the present invention, known nematic liquid crystals can be applied, for example, Schiff base type, azo type, azoxy type, biphenyl type, benzoic acid ester type, terphenyl type, cyclohexylcarboxylic acid type, Examples include phenylcyclohexane-based, pyrimidine-based, dioxane-based liquid crystal compounds, and a mixture thereof can also be used. Examples of commercially available products include Z series manufactured by Merck, E series manufactured by BDH, R series manufactured by Roche, L series manufactured by Chisso, D series manufactured by Dainippon Ink and Co., and 5CB manufactured by Merck. It is also possible to use mixtures of these.

In the present invention, a chiral agent (optically active compound) is added to the nematic liquid crystal for use. The chiral agent is added to adjust the helical pitch of the liquid crystal phase, and a known chiral agent can be applied. Examples of types of chiral agents include cholesteryl bromide,
Examples thereof include cholesteryl-n-hexyl ether, cholesteryl benzoate, cholesteryl-n-hexyl heptanoate and the like. Examples of commercially available products include S-811 manufactured by Merck & Co., Inc.

The addition amount of the chiral agent is appropriately selected depending on the types of the nematic liquid crystal and the chiral agent, but it is appropriate to add 0.01 to 5% of the chiral agent to the nematic liquid crystal, and 0.01 to 5%. It is preferable to add 1%. Further, in the present invention, compounds other than the nematic liquid crystal and the chiral agent may be appropriately mixed and used. This compound does not necessarily have to exhibit a liquid crystal phase, and for example, a compound for adjusting the temperature range of a liquid crystal layer of a liquid crystal composition or an optically active compound that exhibits a large spontaneous polarization or induces a spontaneous polarization in a ferroelectric liquid crystal layer. Examples include compounds.

After injecting the nematic liquid crystal as described above, the injection port is sealed and a voltage is selectively applied to the electrodes to form a switching means for switching the optical axis of the liquid crystal. Manufacture a stable liquid crystal display device. Known methods and materials can be applied as methods and materials for sealing the inlet. In the liquid crystal display device manufactured in this manner, the substrate cross-section direction and the liquid crystal molecule long axis have a constant tilt angle in the upper substrate, and the substrate cross-section direction and the liquid crystal molecule long axis are substantially parallel in the lower substrate, and the upper and lower sides are parallel to each other. In the state 1 in which the molecular long axes of the liquid crystal molecules projected on the respective substrate surfaces are substantially in the same direction, in the lower substrate, the substrate cross-sectional direction and the liquid crystal molecule long axes have a constant tilt angle, and in the upper substrate, The two stable nematic liquid crystal molecules in the state 2 in which the cross-sectional direction of the substrate and the long axis of the liquid crystal molecule are substantially parallel to each other and the long axes of the liquid crystal molecules projected on the upper and lower substrate surfaces are in substantially the same direction as each other There is an orientation state.

[0032]

According to the manufacturing method of the present invention, the influence of the flow at the time of injecting the liquid crystal is eliminated, and uniformly stable molecular alignment of the nematic liquid crystal can be obtained. Therefore, in the upper substrate, the cross-sectional direction of the substrate and the long axis of the liquid crystal molecules have a constant tilt angle, and in the lower substrate, the cross-sectional direction of the substrate and the long axis of the liquid crystal molecules are substantially parallel to each other, and projected on the upper and lower substrate surfaces. In the state 1 in which the major axes of the liquid crystal molecules are substantially in the same direction, the substrate cross-section direction and the liquid crystal molecule major axis have a constant tilt angle in the lower substrate, and the substrate cross-section direction and the liquid crystal molecule length in the upper substrate. Bistability of state 2 (alignment state of two stable nematic liquid crystal molecules) in which the axes are almost parallel and the long axes of the liquid crystal molecules projected on the upper and lower substrate surfaces are substantially in the same direction. Switching is realized.

[0033]

The present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto. Example 1 A bistable liquid crystal display device of the present invention was manufactured by a method of injecting a nematic liquid crystal after providing a pattern of a photosensitive resin.

A method of manufacturing the bistable liquid crystal display device of the present invention will be described with reference to FIGS. FIG. 2 is a cross-sectional view of a liquid crystal display portion of the bistable liquid crystal display device of the present invention which is driven by multiplex. FIG. 4 is an explanatory view showing a resist pattern when manufacturing the bistable liquid crystal display device of the present invention.

First, a plurality of ITO electrodes (transparent electrodes) 2a and 2b having a thickness of 1000 angstroms are formed in stripes on each of the glass substrates (substrates) 1a and 1b by sputtering so that they are parallel to each other. Was formed by arranging the patterns. After forming the ITO electrodes 2a and 2b, a SiO ₂ film (electrode protective film) 3 is formed on the electrodes.
A and 3b were formed with a film thickness of 1000 angstrom by the sputtering method. After forming the electrode protection films 3a and 3b, SiO alignment films (alignment films) 4a and 4b were formed on the electrode protection film by the oblique vapor deposition method. The film thickness was 150 Å, and the vapor deposition angle was 74 ° from the substrate normal.

After forming the SiO alignment films 4a and 4b,
A photoresist was applied to either one of the SiO alignment films 4a and 4b by a spinner, exposed by an exposure machine so as to form a pattern as shown in FIG. 4, and then developed. In this embodiment, the photoresist made by Tokyo Ohka (OFPR-80
0) was used, the exposure time was 30 seconds, and the development time was 90 seconds. The thickness of the resist layer was 1.2 μm and the resist pitch was 1.5 μm.

Next, Si of the upper and lower glass substrates 1a and 1b
The upper and lower glass substrates 1a and 1b are arranged so as to face each other so that the vapor deposition direction of the O orientation film is twisted by 45 ° from the same direction.
In between, silica beads 5 having a diameter of 1.0 μm were dispersed as a spacer and bonded with a sealing member made of epoxy resin to form a liquid crystal cell.

Nematic liquid crystal was injected into the liquid crystal cell manufactured through the above steps from the vicinity of the direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate by a vacuum injection method. Host liquid crystal 5CB as nematic liquid crystal
Chiral agent S-811 (Merck)
Was used in a mixture of 0.36 w%. The nematic liquid crystal was injected from the left side of the substrate in FIG. After the injection, the injection port was sealed with an acrylic UV curable resin.

After that, the bistable liquid crystal display device of the present invention was manufactured by forming switching means for switching the optical axis of the liquid crystal by selectively applying a voltage to the ITO electrodes 2a and 2b. FIG. 8 shows the response characteristic when a pulsed electric field is applied to the bistable liquid crystal display device produced by the above procedure. As is clear from FIG. 8, the bistable liquid crystal display device manufactured in this manner was capable of responding in the order of 200 μsec.

The bistable liquid crystal display device manufactured as described above exhibited stable bistable properties in the area of 1 cm 2. This is done by placing the polarizing plate in a crossed Nicol state, applying positive and negative pulse electrolysis, and examining the switching angle in the dark state and the bright state, which alternates by applying electrolysis, by moving the polarizing plate. Confirmed by Further, the contrast of the bistable liquid crystal display device manufactured in this way was 15: 1.

Example 2 A bistable liquid crystal display device of the present invention was manufactured by a method of injecting a nematic liquid crystal while applying a magnetic field. A method for manufacturing the bistable liquid crystal display device of the present invention will be described with reference to FIGS.

FIG. 3 is a diagram showing an ideal inflow direction or a direction in which a magnetic field is applied when the nematic liquid crystal of the present invention is injected. First, in the same manner as in Example 1, a plurality of ITO electrodes 2a and 2b having a thickness of 1000 angstroms were arranged in stripes on each of the glass substrates 1a and 1b so as to be parallel to each other. Formed on the ITO electrode by SiO ₂ film (electrode protection film) 3a
And 3b were formed with a film thickness of 1000 angstrom.

After forming the electrode protection films 3a and 3b, SiO (orientation films) 4a and 4b were formed on the electrode protection film by the oblique evaporation method. The film thickness was 50 Å, and the vapor deposition angle was 74 ° from the substrate normal. After forming the SiO alignment films 4a and 4b, S of the upper and lower glass substrates 1a and 1b is formed.
The vapor deposition direction of the iO orientation film is set to be twisted by 45 ° from the same direction, and the upper and lower glass substrates 1a and 1b are arranged to face each other so as to be substantially parallel to each other.
A liquid crystal cell was prepared by dispersing silica beads 5 having a diameter of 1.5 μm as a spacer between b and pasting them together with a sealing member made of epoxy resin.

A magnetic pole N and a magnetic pole S are placed on the liquid crystal cell produced through the above steps so as to sandwich the liquid crystal cell, and a magnetic field is uniformly applied to both the upper and lower substrates in the direction of arrow e or f of FIG. Nematic liquid crystal was injected by a vacuum injection method from the vicinity of the direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate. As a nematic liquid crystal, 0.36w of chiral agent S-811 was added to host liquid crystal 5CB.
% Mixture was used. The strength of the magnetic field is such that the long axes of the molecules of the nematic liquid crystal are perfectly aligned in the direction of the magnetic field, and is 10,000 Gauss in this embodiment. After the nematic liquid crystal was injected, the injection port was sealed with an acrylic UV curable resin.

After that, a switching means for switching the optical axis of the liquid crystal by selectively applying a voltage to the ITO electrodes 2a and 2b was formed to manufacture the bistable liquid crystal display device of the present invention. FIG. 8 shows the response characteristic when a pulsed electric field is applied to the bistable liquid crystal display device produced by the above procedure. As is apparent from FIG. 8, the bistable liquid crystal display device manufactured as described above was capable of responding in the order of 100 μsec.

The bistable liquid crystal display device manufactured as described above exhibited stable bistable properties in the area of 1 cm 2. This was confirmed by the same method as in Example 1. Further, the contrast of the bistable liquid crystal display device manufactured in this way was 20: 1.

Example 3 A bistable liquid crystal display device of the present invention was manufactured by a method of heating a nematic liquid crystal to bring it into an isotropic phase and then injecting the nematic liquid crystal. A method of manufacturing the bistable liquid crystal display device of the present invention will be described with reference to FIG. First, a liquid crystal cell was prepared in the same manner as in Example 2. After a liquid crystal cell was prepared, a host liquid crystal 5CB mixed with a chiral agent S-811 at 0.36 w% was used as a nematic liquid crystal, which was heated to 50 ° C.
In a liquid crystal cell heated to 0 ° C., from the vicinity of the direction vertical to the vapor deposition direction of the alignment film on either the upper or lower substrate,
It was injected by the vacuum injection method. After the nematic liquid crystal was injected, the injection port was sealed with an acrylic UV curable resin.

After that, the bistable liquid crystal display device of the present invention was manufactured by forming switching means for switching the optical axis of the liquid crystal by selectively applying a voltage to the ITO electrodes 2a and 2b. FIG. 8 shows the response characteristic when a pulsed electric field is applied to the bistable liquid crystal display device produced by the above procedure. As is apparent from FIG. 8, the bistable liquid crystal display device manufactured as described above was capable of responding in the order of 100 μsec.

The bistable liquid crystal display device manufactured in this manner exhibited stable bistable properties in the area of 1 cm 2. This was confirmed by the same method as in Example 1. Further, the contrast of the bistable liquid crystal display device manufactured in this way was 20: 1.

Comparative Example A description will be given with reference to FIGS. 2 and 9. First, a liquid crystal cell was prepared in the same manner as in Example 2. After forming the liquid crystal cell, nematic liquid crystal was injected into the liquid crystal cell from above or below the substrate in FIG. 9 by a vacuum injection method. As a nematic liquid crystal, a chiral agent S-8 is added to a host liquid crystal 5CB.
A mixture of 11 and 0.36 w% was used. Then I
A liquid crystal display device was manufactured by forming switching means for switching the optical axis of the liquid crystal by selectively applying a voltage to the TO electrodes 2a and 2b.

The liquid crystal display device manufactured as described above was unable to attain a uniformly stable alignment state of nematic liquid crystal molecules, and bistable switching was not realized. This was confirmed by the same method as in Example 1.

[0052]

According to the manufacturing method of the present invention, it is possible to obtain uniformly stable nematic liquid crystal molecule alignment without being affected by the flow at the time of liquid crystal injection. Therefore, the bistable liquid crystal display device obtained by the manufacturing method of the present invention can bistable switch the alignment state of two stable nematic liquid crystal molecules.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal display portion of a bistable liquid crystal display device of the present invention.

FIG. 2 is a cross-sectional view of a liquid crystal display portion of a bistable liquid crystal display device of the present invention which is driven by multiplex.

FIG. 3 is an explanatory diagram showing an ideal inflow direction or a direction in which a magnetic field is applied when injecting a nematic liquid crystal according to the present invention.

FIG. 4 is an explanatory view showing a resist pattern when manufacturing the bistable liquid crystal display device of the present invention.

FIG. 5 is an explanatory diagram showing a stable alignment direction of liquid crystal molecules.

FIG. 6 is an explanatory diagram showing a relationship between a vapor deposition direction of an alignment film and liquid crystal molecule alignment.

FIG. 7 is an explanatory diagram showing alignment of liquid crystal molecules in a cross section of a liquid crystal cell.

FIG. 8 is a diagram showing response characteristics when a pulsed electric field is applied to the bistable liquid crystal display device of the present invention.

FIG. 9 is an explanatory diagram showing the influence of the flow on the alignment of liquid crystal molecules when nematic liquid crystal is injected from above or below the substrate.

[Explanation of symbols]

1 substrate (glass substrate) 2 nematic liquid crystal layer 3 electrode (transparent electrode) 4 alignment film (SiO alignment film) 5 spacer (silica beads) A direction of long axis of liquid crystal molecule showing bistability (tilt by θ ° , Direction inclined by α ° or −α ° from the SiO vapor deposition direction) B direction of long axis of liquid crystal molecule exhibiting bistability (tilt by θ °, or direction inclined by α ° or −α ° from the SiO vapor deposition direction) C Direction of long axis of liquid crystal molecules exhibiting bistability (direction perpendicular to SiO vapor deposition direction and parallel to substrate surface) Direction where liquid crystal molecule alignment can be stabilized on the upper substrate surface Stabilization of liquid crystal molecule alignment on the upper substrate surface Direction of stable orientation of liquid crystal molecules on the upper substrate surface 'Direction of stable orientation of liquid crystal molecules on the lower substrate surface' Direction of stable orientation of liquid crystal molecules on the lower substrate surface 'Liquid crystal on the lower substrate surface One with stable molecular orientation e Direction of ideal inflow direction or magnetic field applied during nematic liquid crystal injection e'Direction of ideal inflow direction or magnetic field applied during nematic liquid crystal injection f Ideal direction of inflow direction or magnetic field applied during nematic liquid crystal injection f 'Ideal inflow direction or direction to apply magnetic field during nematic liquid crystal injection 1a glass substrate (substrate) 1b glass substrate (substrate) 2a ITO electrode (transparent electrode) 2b ITO electrode (transparent electrode) 3a SiO ₂ film (electrode protection film) ) 3b SiO ₂ film (electrode protective film) 4a SiO alignment film (alignment film) 4b SiO alignment film (alignment film)

Claims (4)

[Claims] 1. An electrode is formed on a pair of substrates, an alignment film is formed on the electrodes, and the alignment films of both substrates are opposed to each other so that the deposition directions of the alignment films are different from each other and the substrates are substantially parallel to each other. Liquid crystal cells are formed by interposing a nematic liquid crystal added with a chiral agent between these substrates, and a switching means for selectively applying a voltage to the electrodes to switch the optical axis of the liquid crystal is formed. In the method for manufacturing a bistable liquid crystal display device described above, a nematic liquid crystal is injected in a direction perpendicular to the vapor deposition direction of the alignment film on either the upper or lower substrate. Production method. 2. A nematic liquid crystal is injected onto an alignment film of an upper or lower substrate to form a pattern of a photosensitive resin in a direction perpendicular to a vapor deposition direction of the alignment film, and then, either of the upper or lower substrate. 2. The method for manufacturing a bistable liquid crystal display device according to claim 1, wherein the bistable liquid crystal display device is manufactured in the vicinity of a direction perpendicular to the vapor deposition direction of one of the alignment films. 3. The nematic liquid crystal is injected perpendicularly to the vapor deposition direction of either the upper or lower substrate while applying a magnetic field in the direction perpendicular to the vapor deposition direction of the upper or lower substrate. The method for manufacturing a bistable liquid crystal display device according to claim 1, wherein the method is performed from the vicinity of the direction. 4. The injection of the nematic liquid crystal is carried out by heating the substrate and the nematic liquid crystal to hold the phase of the nematic liquid crystal in the isotropic phase, and then, with respect to the vapor deposition direction of the alignment film on either the upper or lower substrate. 2. The method for manufacturing a bistable liquid crystal display device according to claim 1, wherein the method is performed from near the vertical direction.