JPH02197818A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the heat resistance of orientation control films and the adhesiveness to glass substrates by applying an org. solvent or silicon as underlying films on the glass substrates and calcining the coating to form silicon oxide films, then forming org. high-polymer films thereon and rubbing these films, thereby forming the orientation control films. CONSTITUTION:The underlying films 10, 10' consisting of the metal oxide are formed between the glass substrates 1, 1' and transparent electrodes 5, 5' and the orientation control films 7, 7' consisting of the org. high polymer are formed thereon. The heat resistance of the orientation control films 7, 7' and the adhesiveness to the glass substrates 1, 1' are improved by forming the underlying films 10, 10' in such a manner. The above-mentioned underlying films 10, 10' are formed by a vapor deposition method, sputtering method, CVD method, dipping method for calcining the films after dipping in a soln., and a spin coating method for executing calcination after spin coating.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a field effect liquid crystal display element.

[Conventional technology]

Figure 2 shows an example of a twisted nematic type (TN type) liquid crystal display element, which is one of the field effect type liquid crystal display elements. The substrate 1 shown in FIG. 1 and the substrate 1' shown in FIG. , a nematic phase liquid crystal 3 is sealed in the internal space formed by these. The predetermined spacing is obtained by spacers 4, such as fiberglass, glass powder, etc. Note that the sealing member 2 may also be used as a spacer without using the spacer 4 in particular.

The first and second substrates 1.1' each have a predetermined pattern of electrodes 5.5' formed on their opposing inner surfaces, and further have liquid crystal molecules near the surface in contact with the liquid crystal in a desired manner. Liquid crystal alignment control surfaces [7, 7'] formed with liquid crystal alignment control surfaces 6, 6' for aligning in a certain direction are coated. Such alignment control surfaces 6 and 6' are formed by coating the substrate surfaces with electrodes with alignment control films 7 and 7' made of, for example, an organic polymer material, and rubbing the surface with cotton, cloth, etc. in a fixed direction. It is made by applying processing.

Regarding the liquid crystal alignment direction, a first fixed direction is selected for the liquid crystal alignment control surface 6 of the first substrate 1, and a second fixed direction is selected for the liquid crystal alignment control surface 6' of the second substrate 1'. By changing the directions, the molecules of the nematic phase liquid crystal 3 sandwiched between the substrates 1.1' are twisted and oriented from the first direction to the second direction. The angle formed between the first direction and the second direction, that is, the twist angle of the liquid crystal molecules is arbitrarily selected, but generally approximately 90 degrees is selected.

A first polarizing plate 8 and a second polarizing plate 8' are arranged on the outside of the substrates 1 and 1', respectively. In this case, the angle formed by the polarization axes of the two polarizing plates 8.8' is usually the same as the twist angle of the liquid crystal molecules (the angle formed between the first direction and the second direction) or zero degrees (that is, the angle between each (the polarization axes are parallel) are selected. Usually, the alignment direction of the liquid crystal alignment surface and the polarization axis of the polarizing plate are arranged to be parallel or orthogonal to each other. When such a display element performs a normal display when viewed from the first substrate side, it is a reflective display element in which a reflector 9 is arranged on the back surface of the second polarizing plate 8', or a second polarizing display element is used. A light guide such as an acrylic resin plate or a glass plate of a desired thickness is inserted between the plate and the reflector 9, and a light source (not shown) is placed at an appropriate location on the side of the light guide, which is widely used as a nighttime display element. There is.

Here, the twist angle of the liquid crystal molecules is 90 degrees, and the two polarizing plates 8
．． The principle of display operation of a liquid crystal display element in the case of a reflective type with a polarization axis crossing angle of 90 degrees as shown in FIG. 8' will be explained. Now, when there is no electric field in the liquid crystal layer, external light (ambient light incident on the first polarizing plate 8 of this liquid crystal display element) first passes through the first polarizing plate 8 and is directed along its polarization axis. The light becomes linearly polarized and enters the liquid crystal layer 3, but the liquid crystal molecules are separated by 9 between the layers.
Since the polarized light is twisted by 0 degrees, when it passes through the liquid crystal layer, the plane of polarization of the polarized light is rotated by 90 degrees, and the polarization plane of the polarized light is rotated by 90 degrees.
Transparent. This light is reflected by the reflecting plate 9, passes through the second polarizing plate 8', the liquid crystal layer 3°, and the first polarizing plate 8 in the reverse order to the above, and is emitted to the outside of the liquid crystal display element. Therefore, the observer can observe the polarized light that is incident on the liquid crystal display element, reflected by the reflector, and then comes out of the liquid crystal display element again.

In such a display element, certain selected electrodes 5.
When a predetermined voltage is applied to 5' and an electric field is applied to a predetermined region of the liquid crystal layer, the liquid crystal molecules in that region are aligned along the direction of the electric field. As a result, the optical rotation power of the liquid crystal molecules is lost in that region, so the plane of polarization does not rotate in that region.

The light polarized by the first polarizing plate 8 is blocked by the second polarizing plate 8'. Therefore, the area appears dark to the observer.

In a liquid crystal display device in which the polarization axes of the two polarizing plates 8, 8' are parallel, areas in the liquid crystal layer where no electric field is present appear dark, and areas to which an electric field is applied appear bright.

Therefore, desired display can be performed by applying voltage to desired selected electrodes.

As described above, in the twisted structure liquid crystal display element, the liquid crystal molecules sealed between both glass substrates are oriented substantially parallel to the glass substrate surface.

In the liquid crystal layer, liquid crystal molecules need to be oriented at a predetermined angle, generally with a twist of about 90 degrees. This liquid crystal alignment characteristic is determined by the alignment control films 7 and 7' having alignment control surfaces 6 and 6' formed on the glass substrate surface facing the liquid crystal.
carried out by

Organic polymers are generally used as the material for the alignment control films 7, 7'. Furthermore, various organic polymers have been proposed, but those using an organic polymer containing at least one of an imide ring and a quinazoline ring are:
This is an excellent product because it provides an alignment control film that has good alignment control ability and does not lose its ability even when treated at high temperatures.

[Problem to be solved by the invention]

As the sealing material 2, frit glass or organic adhesive is generally used. Therefore, when frit glass is used as the sealing material 2, high-temperature heat treatment at about 400° C. is required to melt the frit glass even if a low melting point frit glass is used. Therefore, when an alignment control film 7.7' made of an organic polymer containing at least one of the imide ring and quinazoline ring having heat resistance is used as the alignment control film 7.7', the organic polymer film Even if it has a heat resistance of 400°C or higher, the portion in contact with the glass substrates 1 and 1' will deteriorate at a lower temperature, and the wear grooves formed in a certain direction by the 400°C heat treatment may be damaged. There is a drawback that the polymer film itself evaporates and the property of the alignment control film 7, 7' for aligning the liquid crystal is lost.

For example, when a polyimide isoindoquinazoline dione film (hereinafter referred to as PIIQ film) is used as an organic polymer film, PIIQ itself is analyzed by thermobalance.

It is known through infrared analysis that it has a heat resistance of about 450°C. However, as shown in Figure 2, the soda glass substrate 1
, 1', and a transparent electrode 5.5' is formed on the transparent electrode 5.5'.
When a PIIQ film of 0 is formed and abrasion grooves are created by rubbing with cloth etc. to form an orientation control film 7.7', it is approximately 350
The ability to orient liquid crystal molecules was lost by heat treatment at ℃.

This thermally degraded portion is the portion where the glass substrate 1.1' and the alignment side W film 7.7' are in direct contact.

On the other hand, when an organic polymeric sealing material is used as the sealing material 2, heat resistance is not a big problem because the heat treatment temperature is relatively low. However, since organic polymer sealants allow water to pass through them, when used in liquid crystal display elements, moisture resistance life becomes a problem. When an organic polymer is used as an alignment control film,
In Figure 2, orientation control [7, 7' and glass substrate 1.1]
Due to poor adhesion during humidification of ', moisture infiltrates from the outside through the sealing material 2 between the alignment control films 7, 7' and the glass substrate 1.1', lowering the creeping resistance of the glass substrate 1.1'. . For this reason, when a voltage is applied to the liquid crystal display element to turn on the electrode portion, a defective phenomenon (hereinafter referred to as a bleeding defect) occurs in which areas around the electrode that should not be lit are also lit.

For example, as shown in Figure 2, a transparent electrode 5.5' is formed on a soda glass substrate 1.1', and about 1000 PIs are placed on it.
Form an IQ film, rub with cloth to create abrasion grooves to control orientation 11197.7', seal with epoxy adhesive, and create an ester liquid crystal with positive dielectric anisotropy based on azoxy liquid crystal. When a device was constructed by injecting liquid crystal 3 containing 100% of the total amount of liquid crystal 3 and subjected to a humidification test at 70° C. and 95% humidity, a bleeding defect occurred in about 50 hours. This is a practical problem since it has a lifespan of 6 months to 1 year when converted to normal environmental conditions.

The present invention has been made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a method for manufacturing a liquid crystal display element that can improve the heat resistance of an alignment control film and the adhesion to a glass substrate.

[Means to solve the problem]

In order to achieve the above object, in the present invention, in a method for manufacturing a liquid crystal display element, an organic solution of silicon is applied to a glass substrate as a base film and then baked to form a silicon oxide film, and an organic polymer film is formed on this. The alignment control film is formed by forming and rubbing this.

(Function) By doing the above, each film thickness can be easily adjusted and a uniform thickness can be obtained, so that the heat resistance of the alignment control film and the adhesion to the glass substrate can be improved depending on the size of the substrate. However, it can be mass-produced at low cost.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a cross section V showing an embodiment of the present invention.

Note that the same or equivalent members as in FIG. 2 are given the same reference numerals and their explanations will be omitted. Also, the polarizing plate and reflector are omitted.

As shown in FIG. 1, a glass substrate 1.1' and a transparent electrode 5,
Metal oxide base fiI between 5'! ! 10.10' is formed, and alignment control films 7, 7 made of organic polymer are formed thereon.
′ is formed. By forming the underlayer [10, 10' in this manner, the heat resistance of the alignment control film 7.7' and the adhesion to the glass substrate 1.1' are improved. The base film 1
O and 10' can be formed by well-known methods such as vapor deposition, sputtering, CVD, a dipping method in which the solution is immersed and then baked, and a spin coating method in which the solution is immersed and then baked.

First, the results of experiments using two to three metal oxides as materials for the base film 10 and 10' for a frit-sealed liquid crystal display element will be described.

Example 1 A soda glass substrate was immersed in a solution of diluted silicon hydroxide in an alcohol-based solvent, and after being pulled up,
After baking at 00℃ to form a silicon oxide film of approximately 1,500 layers, a transparent electrode was formed, and on top of that a silicon oxide film of approximately 1,000 layers was formed.
A Q orientation control film was formed.

Example 2 A soda glass substrate was heated to about 300°C, 1x1, 0-
After forming a silicon oxide film of about 1,500 layers by electron beam evaporation using silicon dioxide as a deposition source at a pressure of less than 'torr, a transparent electrode is formed on it, and then a PIIQ alignment control film of about 1,000 layers is formed on top of it. was formed.

Example 3 A soda glass substrate was immersed in a solution in which silicon hydroxide and aluminum hydroxide were diluted in an alcohol-based solvent so that the solid content concentration ratio was 5=1, and after being pulled out, the substrate was heated at 500°C. After firing to form a film made of a mixture of about 1000 silicon oxide and aluminum oxide, a transparent electrode was formed, and about 1000 PIIQ self-regulating control film was formed thereon.

Example 4 A soda glass substrate was immersed in a solution of diluted titanium chloride in an alcohol-based solvent, and after being pulled up,
After baking at 0° C. to form a titanium oxide film of approximately 800 μm, a transparent electrode was formed, and a PIIQ alignment control film of approximately 100 μm was formed thereon.

Example 5 A soda glass substrate was immersed in a solution of diluted silicon hydroxide in an alcohol-based solvent, pulled up and fired at 500°C to form a silicon oxide film of about 1000 layers, and then a transparent electrode was formed. , and about 1500 people I)
An I I Q orientation control film was formed.

PII thus formed according to Examples 1 to 5
Regarding the heat resistance of Q, it did not lose its ability to align liquid crystal molecules up to about 450°C.

Therefore, a low melting point frit glass is used as the sealing material 6, and the composition of the frit glass is, for example, 3;
s: 28moQ%, PbO: 61moQ%, Zno
:5mon%, CuO:5moR%, BizOa:1
rao Q% as the basic composition, 5iOz: 1.5 parts by weight, AΩ208: 2.
When using a mixture of 0 parts by weight, the
It is necessary to bake for 0 minutes to seal the glass substrate 1.2. As mentioned above, in the conventional example, the alignment of liquid crystal molecules was disturbed by heating to about 350°C, whereas in the case of using the alignment control film of this embodiment, the alignment was not impaired even by heating to 450°C.

When frit glass was used in this way, a liquid crystal display element with good display quality could not be obtained in the conventional example, but in this example, good display quality could be achieved.

Next, a case of a liquid crystal display element sealed with an organic polymer adhesive will be described.

Example 6 A soda glass substrate was immersed in a solution of diluted silicon hydroxide in an alcohol-based solvent, pulled up, and fired at 500°C to form a silicon oxide film of about 1,500 layers, after which a transparent electrode was formed. Then, a PIIQ orientation control film is formed thereon. Thereafter, it was sealed with an epoxy adhesive, and a liquid crystal material containing an azoxy liquid crystal as a matrix and an ester liquid crystal having positive dielectric anisotropy added thereto was injected to form a liquid crystal display element.

Example 7 A soda glass substrate is heated to about 300°C and IXI, 0″″
Electron beam evaporation is performed using silicon dioxide as a deposition source at a pressure of 100% or less to form an oxygen-silicon film of about 500%, then a transparent electrode is formed, and a PI IQ alignment control film is formed thereon. Thereafter, it was sealed with an epoxy adhesive, and a liquid crystal material containing an azoxy liquid crystal as a matrix and an ester liquid crystal having positive dielectric anisotropy added thereto was injected to form a liquid crystal display element.

When the liquid crystal display cord obtained in Example 6.7 was subjected to a humidification test at 70°C and 95%, the result was 300%.
No bleeding defects occurred even after hours, which corresponds to a lifespan of more than 5 years under normal environmental conditions. As mentioned above, the lifespan of the conventional example is less than one year, but the lifespan of this embodiment has been greatly improved, and there are no practical problems when applying the liquid crystal display element to electronic desk calculators, electronic watches, etc. The life time will not be .

In the above embodiment, a case was described in which PXXQ was used as the alignment control film, but next, an embodiment in which polyimide was used as the alignment control film will be described.

Example 8 A soda glass substrate was immersed in a solution of silicon hydroxide diluted in an alcohol-based solvent, and after being pulled up, 5
After baking at 00° C. to form a silicon oxide film of about 1,500 layers, a transparent electrode was formed, and a polyimide alignment control film of about 1,000 layers was formed thereon.

Example 9 A soda glass substrate was heated to about 300°C and heated to 1×10-f.
Silicon dioxide is used as an evaporation source at a pressure below itorr (electron beam evaporation is performed to form a silicon oxide film of about 1,000 layers, a transparent electrode is formed on it, and a polyimide film of about 1,000 layers is further formed on it. As described above, the heat resistance of the polyimide formed in Examples 8 and 9 did not lose its ability to orient liquid crystal molecules up to around 450°C. Heat resistance was about 350°C.

Example 10 A soda glass substrate was immersed in a solution of silicon hydroxide diluted in an alcohol-based solvent, and after being pulled up, 5
After baking at 00° C. to form a silicon oxide film of about 800 layers, a transparent electrode is formed, and a polyimide alignment control film of about 800 layers is formed thereon. Thereafter, it was sealed with an epoxy adhesive, and a liquid crystal material containing an azoxy liquid crystal as a matrix and an ester liquid crystal having positive dielectric anisotropy added thereto was injected to form a liquid crystal display element.

Example 11 A soda glass substrate is heated to about 300°C and lXl0-'t
Electron beam evaporation is performed using silicon dioxide as a deposition source at a pressure of less than orr, to form a silicon oxide film of approximately 1,300 layers, a transparent electrode is formed, and a polyimide alignment control film of approximately 400 layers is formed thereon. Thereafter, it was sealed with an epoxy adhesive, and a liquid crystal material containing an azoxy liquid crystal as a matrix and an ester liquid crystal having positive dielectric anisotropy in °C was injected to form a liquid crystal display element.

When the liquid crystal display device obtained in Example 10.11 was subjected to a humidification test under conditions of 70''c and 95%, no bleeding defects occurred even after 300 hours or more.

In addition, when there is no silicon oxide base film shown in the example, about 50
Bleeding defects occurred over time.

Note that the above-described embodiments are merely examples, and the effect can be obtained by using silicon oxide, aluminum oxide, or titanium oxide alone or in a mixture thereof as the metal oxide for the base film 7. In addition, as orientation control [5], the above embodiment is P
Although we have explained IIQ and polyimide,
It is sufficient that the ring contains at least one of an imide ring and a quinazoline ring. Further, as a result of experiments, it was found that the thickness of the alignment control film 5 in the range of 100 to 5,000 microns and the thickness of the base film 7 in the range of 10 to 100 microns were sufficient for the device.

〔Effect of the invention〕

As is clear from the above description, the method for manufacturing a liquid crystal display element according to the present invention involves forming a base film made of silicon oxide on a glass substrate, and forming a transparent electrode and an alignment control film made of an organic polymer thereon. Therefore, the heat resistance of the alignment control film and the adhesion to the glass substrate are improved. In addition, as mentioned above, since the base film is formed between the glass substrate and the transparent electrode, there is no voltage drop and the rise and response of the voltage-luminance characteristics are not affected. Because the direction of the electric field is not perpendicular in a part of the etched area, a phenomenon in which the liquid crystal molecules stand up in the opposite direction to the initial tilt angle occurs at the electrode edge.This causes parts with different viewing angles in the etched area of the electrode, resulting in 4 displays. The so-called edge domain, which causes quality deterioration, does not become particularly large.

[Brief explanation of the drawing]

The drawings show a liquid crystal display element; FIG. 1 is a sectional view of a conventional example, and FIG. 2 is a sectional view of a liquid crystal display element according to an embodiment of the manufacturing method of the present invention. 1.1'...Glass substrate, 5.5'...Transparent electrode,
7.7'...Orientation control film, 2...Sealing material, 10.
10'... Base film. M1 figure

Claims (1)

[Claims] 1. In the method for manufacturing a liquid crystal display element, as a base film,
A liquid crystal display element characterized in that an organic solution of silicon is applied to a glass substrate and then baked to form a silicon oxide film, an organic polymer film is formed on this, and an alignment control film is formed by rubbing this. manufacturing method.