JPH03125117A - Manufacture of ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To remove a linear orientation flaw from an effective display area and to improve picture quality by forming a liquid crystal injection hole at or nearby a substrate corner part and setting the uniaxial orientation processing direction of an orientation control film within a range of + or -15 deg. to the bisector of the corner angle. CONSTITUTION:The linear orientation flaw is generated from the end part of the injection hole with extremely high probability, so the linear orientation flaw generated from the injection hole end perpendicularly to the uniaxial orientation direction is removed from the effective display area by limiting the orientation processing direction and the position and size of the injection hole. Namely, the direction 6 of the uniaxial orientation processing of an orienting film is set to a linear direction at + or -15 deg. to the bisector of the angle of the corner 10 of the substrate and the injection hole 2 is formed at or nearby the corner part 10 of the substrate at such a position and to such size that the straight line which passes the injection hole 2 and is perpendicular to the uniaxial orientation processing direction does not pass the effective display area of the liquid crystal element. Then, ferroelectric liquid crystal is injected through the injection hole 2. Consequently, the liquid crystal element with superior picture quality is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ferroelectric liquid crystal element applied to display devices, optical printer heads of copying machines, etc.
More specifically, the present invention relates to a method for manufacturing a ferroelectric liquid crystal element with improved display and driving characteristics by improving the initial alignment state of liquid crystal molecules.

[Prior Art] A type of display element that uses the refractive index anisotropy of liquid crystal molecules to control transmitted light in combination with a polarizing element is disclosed by C1ark and Lagerwal.
l) proposed by Il (U.S. Pat. No. 4,367,924).
specification, US Pat. No. 4,639,089, etc.). This liquid crystal generally has a chiral smectic C phase (Sm*C) or H phase (Sm*H) in a specific temperature range,
In this state, the property of taking either the first optically stable state or the second optically stable state in response to an applied electric field and maintaining that state when no electric field is applied, that is, bistable. It also has a quick response to changes in electric field, and is expected to be widely used as a high-speed and memory-type display element. Ferroelectric liquid crystals are generally used as such liquid crystals. A ferroelectric liquid crystal element using ferroelectric liquid crystal incorporates a matrix electrode composed of a scanning electrode and a signal electrode, and a scanning signal is sequentially applied to the scanning electrode, and is synchronized with the scanning signal. An information signal is applied to the signal electrode. That is, the ferroelectric liquid crystal element is driven by multiplexing. As a method for aligning ferroelectric liquid crystal molecules in such a ferroelectric liquid crystal element, an alignment film is formed on the surface of an electrode substrate provided with a transparent electrode (matrix electrode), and then rubbing, oblique evaporation, etc. A method of performing uniaxial alignment treatment has been adopted.

FIG. 2 is a schematic diagram showing the direction of conventional uniaxial alignment processing and the position of the liquid crystal injection port. As shown in the figure, it is said that a monodomain with the fewest defects can be realized by arranging the liquid crystal injection port so that the liquid crystal injection direction is parallel or substantially parallel to the axial alignment processing direction.

[Problems to be Solved by the Invention] However, when the uniaxial alignment treatment direction is parallel to the end surface of the substrate, the following drawbacks exist.

(2) When a liquid crystal element is subjected to multiplexing driving as described above, a domain whose area changes in synchronization with the applied pulse is generated.

■In the matrix-structured liquid crystal cell, the above-mentioned liquid crystal molecules in the first optically stable state and liquid crystal molecules in the second optically stable state coexist in the area (between pixels) where there is no electrode on either the upper or lower substrate, resulting in a decrease in image quality. .

■The image quality is improved by the above-mentioned liquid crystal molecules in the first optically stable state changing to the second optically stable state, and liquid crystal molecules in the second optically stable state changing to the first optically stable state. descend.

Therefore, in order to improve these drawbacks, it has been found that the uniaxial alignment process can be performed so that the angle thereof forms a constant angle with respect to the end surface of the substrate.

However, at this time, if the liquid crystal is injected parallel or substantially parallel to the uniaxial alignment treatment direction as described above, a new problem occurs in the ferroelectric liquid crystal element. That is, since a ferroelectric liquid crystal having a chiral smectic C layer forms a layer in a direction perpendicular to the uniaxial alignment treatment direction, linear alignment defects occur in parallel to the layer.

Therefore, in view of the above-mentioned circumstances, it is an object of the present invention to improve the method of manufacturing a highly dielectric liquid crystal element so that the above-mentioned linear alignment defects do not occur, and to manufacture a liquid crystal element that can fully exhibit its characteristics. The goal is to make it possible.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a pair of substrates each having a transparent electrode and an alignment film formed on at least one of them are placed facing each other, their peripheries are bonded, and a ferroelectric layer is formed inside the pair of substrates. In the method of manufacturing a ferroelectric liquid crystal device in which a ferroelectric liquid crystal is injected, the direction of the uniaxial alignment treatment of the alignment film is a straight line that makes an angle of ±15 with respect to the bisector of the angle formed by the corner of the substrate. In the direction of
In addition, the injection hole is provided at or near a corner of the substrate at a position and size such that a straight line passing through the injection hole perpendicular to the uniaxial alignment treatment direction does not pass through the effective display area of the liquid crystal element, and the injection hole is It is injected with dielectric liquid crystal.

The present invention was made based on the research results of the present inventors that the probability that linear orientation defects occur from the end of the injection hole is extremely high.

The present invention will be explained in detail below.

FIG. 1 is an explanatory diagram illustrating a method for manufacturing a ferroelectric liquid crystal element according to the present invention. As shown in the figure, in the method of manufacturing a ferroelectric liquid crystal device of the present invention, a striped transparent electrode 5 is formed, and furthermore, a stripe-like transparent electrode 5 is formed on the transparent electrode 5, and a width of ± A pair of glass substrates 1 each having an alignment (control) film formed thereon that has been subjected to a uniaxial alignment process in the direction indicated by the arrow 6 within a range 15'' of 15'', with a spacer interposed therebetween, and a pair of transparent electrodes 5. The substrate 1
A liquid crystal cell 3 is constructed by fixing the peripheral portion through an adhesive layer 4. In the step of injecting the ferroelectric liquid crystal into the liquid crystal cell 3, the injection hole 2 is placed at or near the substrate corner 10, which is the starting point of the bisector 7, and the injection hole 2 is passed through the injection hole in the uniaxial alignment treatment direction 6. It is provided at a position and with a size such that the vertical straight line 8 does not pass inside the effective display area boundary line 9.

For example, the liquid crystal cell 3 is housed in a vacuum container, the liquid crystal is brought into contact with the injection hole of the liquid crystal cell while being evacuated and heated under a vacuum, and then the liquid crystal cell is returned to atmospheric pressure and pressurized, so that the inner and outer parts of the cell are Liquid crystal is injected using a pressure difference. Here, heating is performed to lower the viscosity of the liquid crystal and increase the injection speed.

Further, the ferroelectric liquid crystal is heated to an isotropic phase (liquid) and then injected into the cell, and after injection, the temperature is lowered to change it to the Sm*C phase.

The ferroelectric liquid crystal used is not particularly limited, and a wide variety of commonly used ferroelectric liquid crystals can be used.

Further, the alignment control film can be formed by rubbing a polymer film coated on a substrate with a terene cloth or the like, or by subjecting it to a uniaxial alignment process by oblique vapor deposition or the like.

[Function] As described above, in the present invention, when the uniaxial alignment process is performed in a direction with a certain angle to the end surface of the substrate, linear alignment defects that occur in a direction perpendicular to the uniaxial alignment process direction are injected. This was done by focusing on the fact that the injection hole is generated from the end of the hole, and in the present invention, since the orientation treatment direction and the position and size of the injection hole are limited as described above, the injection hole Linear alignment defects that occur perpendicularly to the uniaxial alignment processing direction from the edge are excluded from the effective display area.

The electroconductive liquid crystal device manufactured in this way can be suitably used as a display device having high-speed response, high density pixels and a large area, or an optical modulation device such as an optical shutter having a high shutter speed. .

(1) (2) liquid'd(u Cheer up LL sex L [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

In this example, the following two-component liquid crystal was used as the ferroelectric liquid crystal material.

Experiments were conducted using a liquid crystal cell having the configuration shown in FIG.

A liquid crystal cell has a layered structure when viewed in a cross-sectional view, and consists of a glass substrate/transparent electrode/polyimide film/liquid crystal/polyimide film/transparent electrode fi/glass substrate. The transparent electrodes were made of indium tin oxide with a thickness of 1000 layers, and striped transparent electrodes having a width of 80 μm and a pitch of 100 μm were formed by photo-etching. On the upper and lower substrates, the striped transparent electrodes were crossed at right angles to form a matrix structure consisting of matrix electrode groups.

Polyimide alignment film is made from polyimide forming liquid (Hitachi Chemical Co., Ltd.
Co., Ltd., PIQ) with a thickness of 700 layers, and after firing,
It was rubbed with a terrane cloth. The rubbing direction is the first
The direction was parallel to the bisector of the corner angle of the substrate shown in the figure.

The liquid crystal layer thickness was kept almost uniform at 2.0 μm.
Spread 2.0μm alumina spacers on the substrate,
Two substrates are bonded together with adhesive, one substrate is
Two injection holes were provided at the corner of the substrate, which is the starting point of the bisector of the corner angle of the substrate that determined the rubbing direction. however,
The injection hole was moved sufficiently away from the effective display area so that a straight line perpendicular to the rubbing direction passing through the end of the injection hole closest to the effective display area did not pass through the effective display area.

In order to inject the liquid crystal, the liquid crystal cell is placed in a vacuum container, the temperature is raised to the temperature (approximately 75°C) at which the two-component liquid crystal reaches the isokinetic phase, and the inside of the liquid crystal cell is evacuated to remove the atmosphere. The test was carried out by placing the cell under vacuum and, in this state, bringing the liquid crystal into contact with the injection hole of the liquid crystal cell. Thereafter, the atmosphere in the liquid crystal cell was returned to atmospheric pressure, and the pressure difference created inside and outside the cell facilitated injection.

When the injection of liquid crystal was completed, the injection hole was sealed and then visually observed under crossed Nicols. As a result, it was observed that linear alignment defects were generated from the end of the injection hole in a direction perpendicular to the rubbing direction. However, it was found that the monodomains did not occur within the effective display area, and that high-quality monodomains were obtained only within the effective display area. Further, a pulsed electric field was applied to the electrode as appropriate to perform translocation between stable states, and the switching was performed well at a voltage of 18 V at 1 m5 ec, and the contrast ratio was 1:8.

A liquid crystal device was manufactured using the same cell configuration and manufacturing process except that the injection hole in Example 1 was placed at the short end of one substrate.

When this cell was visually observed under crossed nicols, it was found that, as in Example 1, a linear alignment defect occurred from the injection hole end in a direction perpendicular to the rubbing direction, and moreover, it largely passed through the effective area. It was observed that

Also, when this cell is observed under a crossed Nicols microscope,
No monodomain was obtained, and a texture with continuously changing bright and dark areas was observed everywhere.

The cell configuration and production process were the same as in Example 1, except that the injection hole position in Example 1 was set closer to the effective display area, and the straight line perpendicular to the rubbing direction was set to pass through the effective display area. A liquid crystal device was manufactured.

When this cell was visually observed under crossed nicols, it was found that, as in Example 1, a linear alignment defect occurred from the end of the injection hole in a direction perpendicular to the rubbing direction, and moreover, it passed through the effective area, albeit slightly. was observed doing so.

[Effects of the Invention] As explained above, according to the method for manufacturing a ferroelectric liquid crystal element of the present invention, the liquid crystal injection hole is provided at or near the corner of the substrate, and the direction of the uniaxial alignment treatment of the alignment control film is set at the corner. A position where the treatment is performed in a direction that forms an angle within the range of ±15'' with respect to the bisector of the corner, and where a straight line passing through the injection hole and perpendicular to the uniaxial alignment treatment direction does not pass within the effective display area of the liquid crystal element. Since the injection hole is formed with a size of , linear alignment defects are excluded from the effective display area, and a liquid crystal element with high quality monodomains within the effective display area and improved image quality can be manufactured. can.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one example of a ferroelectric liquid crystal device manufactured by the method of the present invention, and FIG. 2 is an explanatory diagram showing an example of a uniaxial alignment treatment direction and a liquid crystal injection port in a ferroelectric liquid crystal device according to a conventional example. It is a schematic diagram which shows a position typically. :Substrate, :Injection hole, :Liquid crystal cell, :Adhesive layer, :Transparent electrode, Knee-axis alignment processing direction, Bisector of the substrate corner angle, :A straight line passing through the injection hole and perpendicular to the uniaxial alignment processing direction 6, : Effective display area boundary line, corner of two boards.

Claims (2)

[Claims] (1) In a method for manufacturing a ferroelectric liquid crystal element, in which a pair of substrates each having a transparent electrode and an alignment film formed on at least one of them are placed facing each other, their peripheries are bonded, and ferroelectric liquid crystal is injected into the substrate, the alignment The direction of the uniaxial orientation treatment of the film is a straight line that makes an angle within the range of ±15° with respect to the bisector of the angle formed by the corner of the substrate, and the direction of the uniaxial orientation treatment is a straight line that passes through the injection hole. An injection hole is provided at or near a corner of the substrate at a position and size such that a vertical straight line does not pass through the effective display area of the liquid crystal element, and the ferroelectric liquid crystal is injected through this injection hole. A method for manufacturing a ferroelectric liquid crystal element. (2) The method for manufacturing a ferroelectric liquid crystal element according to claim 1, wherein the uniaxial alignment treatment is a rubbing treatment. (3) The method for manufacturing a ferroelectric liquid crystal device according to claim 1, wherein the uniaxially aligned film is formed by oblique evaporation.