JPS62247327A - Production of ferroelectric liquid crystal element - Google Patents

Abstract

PURPOSE:To improve bistability of the titled element by providing an inlet on a vertical axis perpendicular to the direction of the uniaxial orientation treatment of an orientation controlling film, and by providing the inlet so as to intersect at a vertical or almost vertical position of between the direction of advancing the liquid crystal and the direction of the uniaxial orientation treatment of the orientation controlling film. CONSTITUTION:The stripe like transparent electrodes 5 are formed on a glass substrate 1. A spacer is inserted between a pair of parallel substrates formed orientation controlling films which are given the uniaxial orientation treatment on the transparent electrodes 5 respectively, and are composed of a high polymer. And, the ferroelectric liquid crystal is poured in a liquid crystal cell 3 from the plural inlets 2 provided on an one side of the glass substrates 1. The liquid crystal cell 3 is formed by combining the pair of transparent electrodes 5 with each other with a matrix like, and sticking the electrodes with a adhesive 4 formed on the glass substrate. By providing the inlet 2 on the vertical axis 8 in the direction 7 of the uniaxial orientation treatment of the orientation controlling film, the liquid crystal is poured into the cell 3 maintaining the direction 6 of advancing the liquid crystal and the prescribed direction 7 in the vertical or the almost vertical, thereby obtaining the liquid crystal element having the bistability.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ferroelectric liquid crystal element that is applied to a liquid crystal display element, a liquid crystal-optical shutter array, etc., and specifically relates to a method for manufacturing a ferroelectric liquid crystal element that is applied to a liquid crystal display element, a liquid crystal-optical shutter array, etc. The present invention relates to a method of manufacturing a ferroelectric liquid crystal element with improved display and driving characteristics.

[Prior Art] Conventional liquid crystal elements include two types of liquid crystal elements, such as M, Shut (silk,
5cbadt) and Duburi 21, Helfri Nhi (L
Applied Physics
Letters” (“Applied Physics L
etLers”) Volume 18, No. 4 (February 1971)
“Voltage Dependent Optical Activity”, pp. 127-128)
Of a Twisted Nematic Liquid Crystal (“Voltage Dependent
0Ptical Activity ofa T
twisted Nematic Liquid (:r
A device using a twisted nematic liquid crystal as shown in "Ystal" is known. This TN type liquid crystal has a high pixel density and a matrix electrode structure. Due to the problem of generating talk, the number of pixels was limited.

In addition, is there a known display device that connects a switching element using a transistor to each pixel and switches each pixel?However, the process of forming thin film transistors on a substrate is extremely complicated, and the display device has a large area. There are some difficult issues to be solved.

Clark (C1
ark) and Lagerwall (Japanese Unexamined Patent Publication No. 107216/1983, US Pat. No. 4,367.924, etc.). As a liquid crystal having bistability, a ferroelectric liquid crystal having a chiral smectic C phase (Ss (:'') or H phase (S)) is generally used.The film thickness of this liquid crystal is The helical structure of is kept small enough that it is released and thus has a bistable state with respect to the electric field consisting of a first optically stable state and a second optically stable state.

For this reason, unlike the optical modulation element used in the TN type liquid crystal described above, for example, the first
For the other electric field vector, the liquid crystal is aligned in a second optically stable state.

[Problem to be solved by the invention] In order to exhibit the predetermined driving characteristics of an optical modulation element using a liquid crystal having bistable properties as described above, it is necessary to use a liquid crystal disposed between a pair of y-row plates. , it is necessary that the molecules be in such a state that conversion between two stable orientation states can effectively occur.

However, the chiral smectic liquid crystal element, which has the helical structure released and is given bistability, as described above,
Extremely difficult problems exist in creating such devices. In other words, according to research conducted by the present inventors, it is extremely difficult to achieve the above-mentioned bistability in ferroelectric liquid crystals. Further research by the present inventors revealed that the direction of movement of the liquid crystal and the uniaxial alignment treatment (
(rubbing treatment, oblique evaporation, etc.)
It has been found that there is a close relationship with the bistability of liquid crystals, and that a liquid crystal element with the most bistability can be realized when these are perpendicular to each other.

Therefore, in view of the above-mentioned advantages, the object of the present invention is to provide an optical system using a strong, high-quality liquid crystal as a display element having high-speed response, high-density pixels, and a large area, or an optical shutter having a high shutter speed. In the modulation element,
The object of the present invention is to provide a liquid crystal element that can fully exhibit its characteristics by improving bistability, which has been a problem in the past.

[Means for Solving the Problems] That is, the present invention provides a method in which a ferroelectric liquid crystal is sandwiched between a pair of substrates each having an alignment control film formed with a transparent electrode and uniaxially aligned on at least one of the substrates. In the liquid crystal device having a cell structure, when ferroelectric liquid crystal is injected into the liquid crystal cell, the injection hole is provided on the vertical axis or substantially perpendicular axis of the uniaxial alignment treatment direction of the alignment control aS. This is a method for manufacturing a ferroelectric liquid crystal device.

The present invention will be explained in detail below.

FIG. 1 is an explanatory diagram showing an example of a ferroelectric liquid crystal manufactured by the method of the present invention. In FIG. 1, the method for producing a ferroelectric liquid crystal of the present invention involves forming a striped transparent electrode 5 on a glass substrate l, and applying a uniaxial alignment treatment to the transparent electrode by coating it with a polymeric substance. A spacer is interposed between a pair of parallel substrates on which an alignment control film is formed, and the pair of transparent electrodes are combined to form a matrix, and an adhesive layer 4 is provided to fix the liquid crystal cell 3. In the step of injecting ferroelectric liquid crystal through a plurality of injection holes 2 provided on one side of the glass substrate l, by providing the injection holes 2 on the vertical axis 8 of the uniaxial alignment treatment direction 7 of the alignment control film, In this method, injection is performed while maintaining a state in which the traveling direction 6 of the liquid crystal and the uniaxial alignment treatment direction 7 of the alignment control film 31 are perpendicular or substantially perpendicular, thereby obtaining a bistable liquid crystal element.

In the present invention, in order to inject a ferroelectric liquid crystal into a liquid crystal cell, the liquid crystal cell is housed in a vacuum container, and the liquid crystal is brought into contact with an injection hole of the liquid crystal cell while being heated under vacuum. Heating is performed to reduce the viscosity of the liquid crystal and increase the injection speed. Next, the liquid crystal cell is returned to atmospheric pressure and pressurized to perform injection due to the pressure difference inside and outside the cell.

In the present invention, the ferroelectric liquid crystal is heated to the isokyoshi phase (liquid), then injected into the cell, and after injection, the temperature is lowered to the 5aIC11 phase.

In the present invention, the ferroelectric liquid crystal 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 polymeric substance coated on the substrate, such as a terene cloth, or by performing a uniaxial alignment process by oblique vapor deposition or the like.

In the present invention, the direction of the uniaxial alignment treatment of the alignment control film and the direction of liquid crystal injection are required to be perpendicular or substantially perpendicular. still,
Vertical or substantially perpendicular means that the direction of the uniaxial alignment axis formed by the uniaxial alignment treatment of the alignment control film and the direction in which the liquid crystal is injected into the liquid crystal cell are perpendicular or substantially perpendicular.

[Function] As mentioned above, the present invention was made in consideration of the relationship between the injection direction of the liquid crystal and the direction of the axial alignment process, and is related to bistability. Control 1 model -・
It is presumed that bistability can be improved by setting the liquid crystal injection direction and the uniaxial alignment treatment direction of the alignment control film perpendicular or nearly perpendicular to the axial alignment treatment direction. be done.

[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.

1' 34° 75°Cry
st == Sac” ;== SmA 4++
++ 15□-3° 34°
66° Example 1 An experiment was 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/glass substrate. The transparent electrode was made of indium tin oxide with a layer thickness of 100 OA, and striped spacers with a width of 80 gm were formed at a pitch of 1004 m by photoetching. On the upper and lower substrates, the striped spacers were orthogonally crossed to create a matrix structure consisting of matrix electrode groups.

Polyimide alignment film is polyimide forming liquid (Hitachi Chemical ■
A layer of 70 OA (manufactured by PIQ) was formed, and after firing, it was rubbed with a terene cloth. The rubbing process is perpendicular to the longitudinal direction of the substrate shown in FIG. 1, and perpendicular to the liquid crystal injection direction.

The liquid crystal layer thickness is kept almost uniform at 2.0μ layer.
2.0 gm alumina spacers were sprinkled on the substrates, the two substrates were glued together, and six injection holes were provided at the edge of one substrate.

To inject the liquid crystal, place the liquid crystal cell in a vacuum container and raise the temperature to a temperature (approximately 75° C.) at which the two-component liquid crystal becomes an equilactic phase.
In addition, in order to degas the inside of the liquid crystal cell, the atmosphere of the cell is brought to a vacuum by evacuating the cell. In this state, the liquid crystal is brought into contact with the injection hole of the liquid crystal cell. Thereafter, the atmosphere in the liquid crystal cell is returned to atmospheric pressure, and the pressure difference generated inside and outside the cell promotes injection. At this time, the injection was performed so that the injection direction of the liquid crystal and the direction of the uniaxial alignment treatment by rubbing treatment were parallel to each other.

After the injection of the liquid crystal was completed and the injection hole was sealed, it was confirmed by observation using a WJ microscope under crossed Nicols that a high-quality monodomain with no defects had been obtained. Also, by applying a pulsed electric field to the electrode, a transition between stable states was performed, or 1 m5ec
Switching was performed at a voltage of 5 V, and the contrast ratio was 1:10. As described above, good bistability could be achieved.

Comparative Example 1 A comparative experiment was conducted using the same cell configuration and manufacturing process as in Example 1, except that the rubbing direction was set at 45° with respect to the end surface of the substrate.

This cell under a crossed Nicol microscope! When inspected by Bl, no monodomain was obtained, and a texture in which bright and dark areas continuously changed was observed here and there.

This is because the layer structure of smectic liquid crystal is not formed uniformly.
It reflects the direction of the molecular axis of the liquid crystal, which is formed in a wavy shape.

Next, when a pulsed electric field of 1 m5ec and 5 V was applied to the electrodes of the cell, there was a region around 40% of the entire cell area that did not switch despite the application of the electric field. This result shows that good bistability was not achieved in the comparative example.

[Effects of the Invention] As explained above, the method for manufacturing a ferroelectric liquid crystal element of the present invention allows liquid crystal to be injected into a liquid crystal cell by controlling the direction of movement of the liquid crystal and controlling the orientation. Since this is carried out in a substantially vertical state, a liquid crystal element with improved bistability can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of a ferroelectric liquid crystal manufactured by the method of the present invention. l...Substrate, 2...Injection hole 3...
Liquid crystal cell 4... Adhesive layer 5... Transparent electrode 6... Liquid crystal injection direction 7... Uniaxial alignment treatment direction

Claims (3)

[Claims] (1) In a liquid crystal element having a cell structure in which a ferroelectric liquid crystal is sandwiched between a pair of substrates on which transparent electrodes are formed and at least one substrate has an alignment control film subjected to a uniaxial alignment treatment, When injecting liquid crystal into a liquid crystal cell,
1. A method for manufacturing a ferroelectric liquid crystal device, characterized in that an injection hole is provided on an axis perpendicular or substantially perpendicular to a direction of uniaxial alignment treatment of an alignment control film. (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 element according to claim 1, wherein the uniaxially aligned film is formed by oblique vapor deposition.