JPH04119327A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To easily obtain a ferroelectric liquid crystal display element showing a uniform oriented state by forming an oriented film, sealing ferroelectric liquid crystal and adding an ultrasonic wave. CONSTITUTION:Transparent electrode substrates 5 and 6 are constituted by laminating transparent electrodes 2a and 2b and the oriented films 3a and 3b on transparent substrates 1a and 1b in this order, and they are respectively arranged so that the oriented films 3a and 3b may face each other and the ferroelectric liquid crystal 4 is sealed between the substrates 5 and 6. Then, the ultrasonic wave is added to the surface of either of two transparent electrode substrates 1a and 1b with which an ultrasonic oscillator is brought into contact. Thus, the ferroelectric liquid crystal 4 obtained by sealing the liquid crystal display element is uniformly oriented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for manufacturing a liquid crystal display element in which a ferroelectric liquid crystal is encapsulated.

[Technical Background of the Invention and Prior Art] Liquid crystal display elements conventionally used in watches, computers, word processors, etc. have a basic structure of two transparent electrode substrates with an alignment film provided on a transparent electrode. The structure is such that the alignment film is placed on the inside and the liquid crystal is sealed between them. Generally, in a liquid crystal display element, it is necessary to align the liquid crystals in a certain direction, that is, to align them, so in the above liquid crystal display element, an alignment film is provided to align the liquid crystal molecules.

The mainstream of such liquid crystal display elements is a display using a leistytone nematic (TN) mode in which a nematic liquid crystal has a twisted structure. However, this TN type liquid crystal display element has the disadvantage of slow response speed, currently limited to 20 milliseconds, which is a major problem when used in television panels, etc., which require high-speed response. It becomes.

In contrast, recently, ferroelectric liquid crystals with high-speed response are expected to open up the field of new displays.
being researched.

Ferroelectric liquid crystals not only respond quickly to changes in electric field, but also adopt either the first optically stable state or the second optically stable state in response to the applied electric field, and also respond to changes in the voltage. It also has the property of maintaining its state when no voltage is applied, that is, it has bistability (also called memory property). Therefore, liquid crystal display elements using ferroelectric liquid crystals only require the application of a pulsed voltage when switching between two states, and the power supply and electronic circuits required to maintain the optical state are required. is not required, and power consumption is also reduced compared to conventional liquid crystal display elements.

In other words, a liquid crystal display element using ferroelectric liquid crystal can be said to be a liquid crystal display element that has a simple structure and achieves high-speed response.

This kind of ferroelectric liquid crystal has an extremely high viscosity compared to the above-mentioned nematic liquid crystal, etc., so it is difficult to align it uniformly after filling the liquid crystal between two transparent electrode substrates (inside the cell). there were. Therefore, in order to obtain a uniform alignment state, the liquid crystal is generally cooled gradually over a long period of time after being injected. However, slow cooling for a long period of time has the problem that productivity is low and that a sufficiently uniform orientation cannot be obtained by slow cooling alone.

In order to solve this problem, a method of slowly cooling the liquid crystal while applying a high frequency electric field after injecting the liquid crystal into the cell (Japanese Patent Laid-Open No. 62-265
622, JP-A-2-84619), or a method of applying a DC voltage after liquid crystal injection (JP-A-62-2
65622) has been proposed. By applying such a high frequency electric field or DC voltage, uniform alignment of liquid crystals can be easily obtained, but since the above application generally requires a high voltage, the electrode substrate may be short-circuited, and the transparent electrode may There are differences in the applied effects depending on the alignment film provided.

Japanese Patent Laid-Open No. 63-286817 discloses that a cell (liquid crystal display element) in which a forced electric field liquid crystal is injected is fixed and submerged in a tank of an ultrasonic oscillator containing a medium, and a cell (liquid crystal display element) in which a forced electric field liquid crystal is injected is fixed and submerged, and the layer surface of the liquid crystal is A method of irradiating ultrasound in parallel directions is disclosed. By using this method, it is not only easy to obtain a uniform alignment of the liquid crystal, but also it is difficult to cause short-circuits of the electrode substrate during the above-mentioned application and fluctuations in the application effect due to differences in the alignment film.
The above problems are solved.

However, in the above method, the liquid crystal display element is suspended in the medium of the ultrasonic oscillator, so the medium must be dried. Additionally, cleaning may be required, which increases the number of steps, which is disadvantageous in terms of manufacturing. Furthermore, there is a problem in that the medium may enter from the seal portion of the liquid crystal display element or the like and enter the liquid crystal.

[Object of the Invention] An object of the present invention is to provide a method for manufacturing a liquid crystal display element that can easily manufacture a ferroelectric liquid crystal display element exhibiting a uniform alignment state.

[Summary of the Invention] The present invention provides the following steps (1) to (3): (1) forming an alignment film on a transparent electrode provided on a substrate; (2) forming an alignment film on a transparent electrode provided on a substrate; A process of arranging two sheets with the alignment film inside and sealing a ferroelectric liquid crystal between them. (3) Applying ultrasonic waves while bringing an ultrasonic vibrator into contact with one surface of the two transparent electrode substrates. A method of manufacturing a liquid crystal display element comprises the step of applying.

Preferred embodiments of the method for manufacturing a liquid crystal display element of the present invention are as follows.

1) The method for manufacturing a liquid crystal display element as described above, characterized in that the contact of the ultrasonic vibrator with the surface of the transparent electrode substrate is carried out by contacting the tip surface of the ultrasonic vibrator with the surface of the substrate.

2) The method for manufacturing a liquid crystal display element as described above, wherein the ultrasonic vibrator is brought into contact with the surface of the transparent electrode substrate by scanning.

3) The method for manufacturing a liquid crystal display element as described above, wherein the frequency of the ultrasonic waves is in the range of 16 to 60 kHz.

4) The output of the ultrasonic oscillator to the ultrasonic vibrator is 5 to 60
The method for manufacturing a liquid crystal display element as described above, characterized in that the voltage is within the range of 0W.

[Effects of the Invention] A feature of the method for manufacturing a liquid crystal display element of the present invention is that in order to uniformly orient the ferroelectric liquid crystal, ultrasonic waves are applied to the cell surface by direct contact with an ultrasonic vibrator. . Therefore, there is no need for post-processing, that is, drying or cleaning of the medium, which is required when ultrasonic waves are applied to a liquid crystal display element in a medium, which has the advantage of simplifying manufacturing. Furthermore, since no medium is used, there is no possibility that the medium will enter the liquid crystal of the liquid crystal display element. Furthermore, since no high voltage is used, there is no possibility of short circuits between the substrates, making it a safe manufacturing method.

Therefore, the present invention can be said to be a method of manufacturing a liquid crystal display element that is simpler and safer than the conventional method of uniformly aligning liquid crystal.

Further, since it is easy to obtain uniform alignment of the liquid crystal, there is also the advantage that the slow cooling of the liquid crystal can be shortened.

[Detailed Description of the Invention] A method of manufacturing a liquid crystal display element according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an example of a liquid crystal display element manufactured according to the present invention.

Transparent electrodes 2a, 2b and alignment films 3a, 3b are laminated in this order on transparent substrates 1a, 1b to constitute a transparent electrode substrate 5.6.

The transparent electrode substrates 5.6 are arranged so that the alignment films 3a and 3b face each other, and the ferroelectric liquid crystal 4 is sealed between them. The method for manufacturing a liquid crystal display element of the present invention includes applying ultrasonic waves to one surface of the two transparent electrode substrates while bringing an ultrasonic vibrator into contact with the liquid crystal display element. It is characterized by uniformly oriented.

The liquid crystal display element obtained by the manufacturing method of the present invention is
In addition to what is shown in the figure, it is possible to use other configurations that are used for ordinary liquid crystal display elements, such as providing an electrical insulating layer, using a spacer, and providing a polarizing plate. In particular, it is preferable to use a spacer to ensure a gap between both alignment films (ie, the thickness of the liquid crystal layer). As spacers, glass fibers, glass beads, plastic beads, and metal oxide particles such as alumina and perilla are used.

The particle size of the spacer varies depending on the liquid crystal used, the alignment film material, the setting of the cell gap, the particles used as the spacer, etc., but is generally 1.2 μm to 66 μm.

The transparent substrate, transparent electrode, and ferroelectric liquid crystal used in the method for manufacturing a liquid crystal display element of the present invention may be any of the known ones that have been conventionally used in ferroelectric liquid crystal display elements.

For example, as a transparent substrate, in addition to glass such as float glass with good smoothness, polyester such as polyethylene terephthalate and polybutylene terephthalate, epoxy resin, phenol resin, polyimide, polycarbonate, polysulfone, polyether sulfone, polyetherimide, acetyl cellulose, polyamino acid ester,
It is formed from heat-resistant resins such as aromatic polyamides, vinyl polymers such as polystyrene, polyacrylic esters, polymethacrylic esters, polyacrylamide, polyethylene, polypropylene, fluorine-containing resins such as polyvinylidene fluoride, and modified products thereof. Examples include plastic films.

Transparent electrodes include indium oxide (In203), tin oxide (SnO2), and ITO (indium tin
oxide), etc.

Examples of the alignment film include polymer films such as polyimide, polyvinyl alcohol, and polyamide (nylon), films formed from organic silane compounds, and thin films such as 5in2.5iO1Ti02 formed by vacuum deposition.

The thickness of the alignment film varies depending on the liquid crystal used and the material of the alignment film, but is preferably in the range of 200 to 2000λ.

Further, the ferroelectric liquid crystal used in the present invention may be any conventionally known ferroelectric liquid crystal.

Specifically, liquid crystals having ferroelectricity include chiral smectic C phase (mC" H phase (Srl H" I phase (Sm I" J phase (SmJ") K phase (SmK' G phase (SmG" or F It is a liquid crystal with a 2000mA (SmF).

less than, Extortion that can be used in the present invention 1 The following is an example of a liquid crystal.

(R is monoalkyl group or monoalkoxy (R is n-alkyl group or n-alkoxy (R is n-alkyl group or n-alkoxy (R is one alkyl group or n -alkoxy basis, m=5-10. 12. moreover, In addition to the above, For example, something like the following (here, R=CI+3 C2H5) IL CH3 N CH3 N CH3 CH3-CH-CH.

~ In addition to the above, all known ferroelectric liquid crystals, such as those described in ``High Speed Liquid Crystal Technology 1'' (published by CMC), p. 127-161, can be used in the present invention.

In addition, as a specific liquid crystal composition, C3 manufactured by Chisso ■
-1018, C5-1023, C3-1025, C5-
1026, Robwick ■ glue.

F0004, DOF0006, DOFOOO8, ZLI-4237-000, ZLI-4237- manufactured by Merck & Co.
Examples include, but are not limited to, Zoo, ZLI-4654-100. There is no problem in adding dichroic dyes, viscosity reducers, etc. which are soluble in the liquid crystal to these liquid crystals.

Next, the method for manufacturing a liquid crystal display element of the present invention will be explained step by step.

First, transparent electrodes in a display pattern such as stripes or grids are provided on a transparent substrate by a conventional method. Alternatively, a substrate with transparent electrodes is prepared.

A coating solution for forming an alignment film containing a polymer such as polyimide is applied onto the transparent electrode (and the exposed substrate) and dried to form an alignment film. In addition, an insulating layer is provided on the transparent electrode,
The above coating liquid may be applied thereon and dried. or,
The alignment film may be formed by vacuum deposition of 5i02 or the like described above. When the alignment film is made of polymer, it is generally 10
Heat treatment is performed in the range of 0 to 350°C.

The alignment film provided on the transparent mold 8i (and the substrate) is coated with synthetic fibers such as nylon, polyester, and polyacrylonitrile, and natural fibers such as cotton and wool.

Two transparent electrode substrates each made of a transparent substrate, a transparent electrode, and an alignment film manufactured as described above are placed facing each other with a gap between them, with the alignment film on the inside, to form a cell.

The size of this gap, that is, the cell gap, is 1.2μ
It is numerically about m to 6 μm.

Next, ferroelectric liquid crystal is injected into this cell, sealed, and then slowly cooled.

Ultrasonic waves are applied to one surface of the two transparent electrode substrates of the thus obtained cell while bringing an ultrasonic transducer into contact with the surface.

The application of the ultrasonic waves is performed, for example, as follows.

This will be explained with reference to the attached FIGS. 2, 3, and 4.

FIG. 2 is a schematic diagram showing an example of a state in which an ultrasonic wave is applied to a liquid crystal display element with a force of 1 t.

In FIG. 2, a device for applying ultrasonic waves consists of an ultrasonic oscillator 11, an ultrasonic vibrator 15, and a power source, which are connected by wires. The ultrasonic transducer 15 consists of a transducer 12 and a tip 13 (the tip of the ultrasonic transducer) attached to the transducer. The tip of this tip 13 is in contact with the substrate surface of the liquid crystal display element 14.

Ultrasonic waves of arbitrary high frequency are emitted from the ultrasonic oscillator 11, and converted into vibrations by the transducer 12 of the ultrasonic vibrator 15.
The vibrations are transmitted to the tip 13 (the tip of the ultrasonic transducer) attached to the transducer. Then, the tip of this tip 13 moves while contacting the fixed substrate surface of the liquid crystal display element 14, and contacts the entire substrate surface. Thereby, it is possible to uniformly align the liquid crystal by applying ultrasonic waves to the liquid crystal within the liquid crystal display element. At this time, ultrasonic waves may be applied by fixing the distal tip 13 and moving the liquid crystal display element 14. The movement may be performed once in one direction using a chip having the same length as the vertical or horizontal direction of the surface of the liquid crystal display element, or may be performed by scanning using a small chip. Alternatively, a single contact may be made using a chip having a surface area larger than that of the liquid crystal display element. For actual manufacturing, it is preferable to fix the cell and automate scanning of the chip.

The chip may have any shape; for example, the shapes shown in the attached FIGS. 3 and 4 can be used.

FIG. 3 shows a distal tip in the form of two overlapping cylinders with different diameters. The surface in contact with the cell is circular.

In FIG. 4, a simple cylindrical distal tip is shown. The surface in contact with the cell is circular.

As the ultrasonic oscillator used, for example, ■Nippon Tokki Seisakusho's ultrasonic homogenizer = (US50, US-150)
T, US-300T, US600T).

The frequency of the ultrasonic waves is preferably in the range of 16 to 100 kHz, more preferably in the range of 16 to 60 kHz. Furthermore, the energy of the contact surface of the ultrasonic transducer with the surface of the transparent electrode substrate depends on the output, contact area, and movement speed described below. Therefore, in the present invention, the output of the oscillator is generally in the range of 5 to 600 W, and 10 to 3
A range of 00W is preferred. The surface area of the tip tip generally has a diameter in the range of 3 to 50 mm, preferably 5 to 30 mm. If the surface shape is not circular, it is preferable that the shape has a surface area corresponding to this shape. The scanning speed is generally in the range of 1 to 30 m/min, preferably in the range of 3 to 20 m/min. Furthermore, the application of the above-mentioned ultrasonic waves may be performed in a state where the cell is heated to raise the temperature of the liquid crystal. It may be effective depending on the type of liquid crystal.

By the above manufacturing method of the present invention, it is possible to easily obtain a high dielectric liquid crystal display element exhibiting a uniform alignment state.

Of course, the liquid crystal display element of the present invention can be provided with structures provided in conventional liquid crystal display elements, such as a reflecting plate, a polarizing plate, and a retardation plate, depending on the purpose of use.

Next, examples of the present invention and comparative examples will be described. However, the present invention is not limited to this embodiment.

[Example 1] Indium on two glass plates with a thickness of 1.1 mm
A transparent electrode made of tin oxide (ITO) was formed in a stripe shape (electrode width: 100 μm, gap between electrodes: 15 μm).

A polyimide alignment film coating solution (LX-5400, manufactured by Hitachi Chemical) was applied using a spinner to the electrode-containing surfaces of the two glass plates with ITO electrodes.

The spinner conditions were: rotation speed 2500 r, p, m, and time 30 seconds. After coating, a heat treatment was performed at 350° C. for 160 minutes to form an alignment film.

Both sides of this coating film were rubbed with a nylon napkin, and with each rubbed side facing inside, the two glass plates were placed with a 2 μm spacer ( A cell with a cell gap of 2 μm was prepared by overlapping the fibers with a true thread ball (manufactured by Catalysts & Chemicals Industry Co., Ltd.). Ferroelectric liquid crystal DOF0004 manufactured by Robic was injected into this cell at 100°C, and slowly cooled to room temperature at a rate of about 1°C/min.

Next, ■Nippon Tokki Seisakusho's ultrasonic homogenizer (U
S-150T), the tip of the tip (diameter 20 mm), which is the tip of the ultrasonic transducer, was placed on the surface of one substrate of the cell.
, under the conditions of an output of 150 W and a tip moving speed of 6 m/min.
Ultrasonic waves were applied by moving while making contact.

In this way, a liquid crystal display element was manufactured.

[Comparative Example 1] A liquid crystal display element was manufactured in the same manner as in Example 1 except that ultrasonic waves were not applied to the surface of the cell substrate.

' Indication, Part 6 When the liquid crystal display elements obtained in Example 1 and Comparative Example 1 manufactured as described above were observed for the orientation state of the liquid crystal using a polarizing microscope, the liquid crystal display obtained in Example 1 was observed. Although the liquid crystal of the device was uniformly oriented, the liquid crystal of the liquid crystal display device obtained in Comparative Example 1 had several domains with different orientations and could not be said to be uniform.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration example of a liquid crystal display element obtained by the manufacturing method of the present invention. FIG. 2 is a schematic diagram showing an example of a state in which ultrasonic waves are applied to a liquid crystal display element. FIG. 3 is a schematic diagram showing an example of the shape of the chip. FIG. 4 is a schematic diagram showing an example of the shape of the chip. 1a, 1b: Transparent substrate 2a, 2b = Transparent electrode 3a, 3b: Alignment film 4: Liquid crystal 11: Ultrasonic oscillator 12: Converter: Tip chip: Liquid crystal display element: Ultrasonic vibrator

Claims (1)

[Claims] 1. Steps (1) to (3) below: (1) Forming an alignment film on the transparent electrode provided on the substrate; (2) Arranging two of the above transparent electrode substrates with the alignment film inside. (3) applying ultrasonic waves to one surface of the two transparent electrode substrates while bringing an ultrasonic vibrator into contact with the surface of the two transparent electrode substrates; Production method.