JPH0675242A - Production of nonlinear element substrate - Google Patents

Abstract

(57) [Summary] [Objective] To obtain a non-linear device substrate having a ferroelectric layer having a large remanent polarization and a low coercive electric field. [Structure] By applying shear stress to a ferroelectric layer formed on a substrate, the orientation direction of molecules in the ferroelectric substance is controlled, and the ratio of the crystal structure capable of exhibiting ferroelectricity is increased. In order to apply shear stress to the ferroelectric layer, the surface of the ferroelectric layer is rubbed with cloth, paper, resin or the like. When the substrate has flexibility, it is possible to give a shear stress by stretching or bending the ferroelectric layer.

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 non-linear element substrate used for a display device such as a liquid crystal display device or an optical modulator.

[0002]

2. Description of the Related Art Conventionally, a non-linear element substrate has been used as an active substrate of a liquid crystal display device. FIG. 5 (a),
An example of such an active substrate is shown in (b) and (c). In FIG. 5A, the first electrode 12 is formed on the substrate 11, and the ferroelectric layer 1 is formed so as to cover the first electrode 12.
3 is formed, and the second electrode 14 is formed thereon. In FIG. 2B, the ferroelectric layer 3 is formed on the substrate 11.
Is formed, and the first electrode 12 is formed on the first electrode 12 in a separated state.
And the second electrode 14 is formed. In addition, FIG.
In the above, the first electrode 12 and the second electrode 14 are formed on the substrate 11 at a distance from each other, and the ferroelectric layer 13 is formed so as to cover the first electrode 12 and the second electrode 14. Further, a liquid crystal is sealed between these non-linear element substrate and counter substrate 15 to form a liquid crystal display device.

In such a non-linear element substrate, the ferroelectric layer is a polyvinylidene fluoride-trifluoroethylene copolymer (polyvinylidene fluoride) which can exhibit ferroelectricity only by a coating process such as spin coating or dipping. It is known that the content is about 50 to 80 mol%. This material has excellent properties such as a relatively large remanent polarization, a stable coercive electric field, and good heat resistance, and is widely used.

[0004]

The above-mentioned polyvinylidene fluoride-trifluoroethylene copolymer has the following structure.
Although it has excellent properties, it has the following drawbacks when used as a non-linear element substrate used as an active substrate of a liquid crystal display device, for example. For example, when the film thickness is 2000 angstrom, the coercive electric field is 20
Since the voltage is about V, a driving voltage of 30 to 40 V or more is required, and the characteristic of low power consumption, which is one of the greatest merits of the liquid crystal display device, cannot be fully utilized. Further, since the value of the remanent polarization is insufficient, sufficient contrast cannot be obtained, and good display cannot be obtained. When polyvinylidene fluoride-trifluoroethylene copolymer is used instead of polyvinylidene fluoride-trifluoroethylene copolymer, the heat resistance can be further improved. Property is not expressed, and it is necessary to perform stretching treatment or poling treatment. It is difficult to perform the above-mentioned treatment on the layer formed on the substrate, and sufficient ferroelectricity is not obtained.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a method of manufacturing a non-linear element substrate having a ferroelectric layer having a large remanent polarization and a low coercive electric field.

[0006]

According to the method of manufacturing a non-linear substrate of the present invention, a first electrode and a second electrode sandwich a ferroelectric layer on a substrate, or the same wide surface of the ferroelectric layer. First on top
Forming a first electrode, a second electrode and a ferroelectric layer on the substrate in a predetermined arrangement in the nonlinear element substrate formed by separating the electrode of the first electrode and the second electrode from each other; Applying a shear stress to the ferroelectric layer, whereby the above object is achieved.

By rubbing the shear stress,
It may be applied to the ferroelectric layer.

The shear stress may be applied by stretching or bending of the ferroelectric layer.

[0009]

[Function] By giving shear stress to the ferroelectric layer formed on the substrate, the orientation direction of the molecules in the ferroelectric layer is controlled, whereby the proportion of the crystal structure capable of exhibiting the ferroelectricity. Will increase.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following materials and process conditions.

FIG. 1 shows an example of a non-linear element substrate manufactured by using the manufacturing method of the present invention.

In this non-linear element substrate, the first electrode 2 is formed on the substrate 1 so as to cover it,
A ferroelectric layer 3 is formed on the substrate 1. Further, the second electrode 4 is formed on the ferroelectric layer 3 so as to partially overlap the first electrode 2.

The ferroelectric layer 3 is made of a material whose molecular orientation is controlled by applying shear stress. Examples of such materials include polyvinylidene fluoride-trifluoroethylene copolymer, polyvinylidene fluoride-tetrafluoroethylene copolymer, polyvinylidene fluoride homopolymer, vinylidene cyanide-vinyl acetate copolymer, and the like. .

As a method of applying a shear stress to the ferroelectric layer 3, for example, (1) the surface of the ferroelectric layer 3 is rubbed with cloth, paper or resin.

(2) When the substrate has flexibility, the ferroelectric layer 3 is stretched or bent.

And the like.

The element structure is not limited to the one shown here, and for example, the first electrode may be above and the second electrode may be below the ferroelectric layer. Good. Further, the first and second electrodes may be arranged in parallel above or below the ferroelectric layer.

This non-linear element substrate can be manufactured as follows.

(Embodiment 1) In this embodiment, FIG.
Was formed using a polyvinylidene fluoride-trifluoroethylene (content ratio 78:22) copolymer. As a method of applying shear stress to the ferroelectric layer 3, a method of rubbing the surface of the ferroelectric layer 3 was used. Specifically, it is as follows.

First, a first electrode was formed on a glass substrate using a conductor such as aluminum, titanium, tantalum, niobium, copper or ITO. Next, the polyvinylidene fluoride-trifluoroethylene copolymer was dissolved in methyl ethyl ketone, and this was applied to a thickness of 2000 angstrom by a spin coating method so as to cover the first electrode. After that, bake at 145 ° C for 30 minutes, 50 ° C / h
A ferroelectric layer was formed by lowering the temperature at a rate of r.

Next, the surface of the ferroelectric layer was rubbed with a nylon cloth, YO-10 (manufactured by Yoshikawa Kako Co., Ltd.). After that, ultrasonic cleaning was performed using isopropyl alcohol to remove the fibers and the like adhering to the surface of the ferroelectric layer. On top of that, a conductor such as aluminum, titanium, tantalum, niobium, copper, or ITO is used.
The electrode 4 of was formed to be a non-linear element substrate.

In the nonlinear element obtained as described above,
Connect a capacitor with a capacity of 100 nF in series to obtain ± 40
The measurement result of the electric field-electrical displacement hysteresis curve when a triangular wave of V and 30 Hz is applied is shown in FIG. here,
E indicates an electric field and D indicates an electric displacement. Also here
As a comparative example, an element substrate formed in the same manner as in Example 1 except that the rubbing step was not performed is also shown.

As can be seen from FIG. 2, in the nonlinear element substrate of this embodiment, the remanent polarization indicated by the symbol Pr in FIG. 2 becomes large and the coercive electric field indicated by the symbol Ec in FIG. 2 decreases. is doing.

(Embodiment 2) In this embodiment, FIG.
The ferroelectric layer 3 of 1. was formed using a polyvinylidene fluoride-tetrafluoroethylene (content ratio 20:80) copolymer. This non-linear element substrate was manufactured in the same manner as in Example 1.

With respect to the non-linear element substrate obtained as described above, the result of measuring the electric field-electrical displacement hysteresis curve in the same manner as in Example 1 is shown in FIG.

As can be seen from FIG. 3, in the nonlinear element substrate of this embodiment, the remanent polarization is large and the coercive electric field is small.

Usually, the polyvinylidene fluoride-tetrafluoroethylene copolymer does not exhibit ferroelectricity unless it is subjected to poling treatment or stretching treatment, but it is exhibited by rubbing treatment.

(Embodiment 3) In this embodiment, FIG.
The ferroelectric layer 3 of was formed using polyvinylidene fluoride. This non-linear element substrate was manufactured in the same manner as in Example 1.

FIG. 4 shows the result of measuring the electric field-electrical displacement hysteresis curve of the non-linear element substrate obtained as described above in the same manner as in Example 1.

As can be seen from FIG. 4, in the nonlinear element substrate of this embodiment, the remanent polarization is large and the coercive electric field is small.

Usually, the polyvinylidene fluoride homopolymer does not exhibit ferroelectricity unless it is subjected to poling treatment or stretching treatment, but it is exhibited by rubbing treatment.

(Embodiment 4) In this embodiment, FIG.
Was formed using a polyvinylidene fluoride-trifluoroethylene (content ratio 78:22) copolymer. A polystyrene substrate was used as the substrate 1, and an insulating film was formed thereon. In addition, shear stress was applied to the ferroelectric layer 3 by bending the substrate 1. Specifically, it is as follows.

First, an insulating film made of silicon oxide or the like is formed on a polystyrene substrate by sputtering.
On top of this, aluminum, titanium, tantalum, niobium,
The first electrode was formed of a conductor such as copper or ITO. Next, a polyvinylidene fluoride-trifluoroethylene (content ratio 78:22) copolymer was dissolved in methyl ethyl ketone, and this was applied by a spin coating method to a thickness of 2000 angstroms. After that, by baking at 145 ° C. for 30 minutes and lowering the temperature at a rate of 50 ° C./hr,
A ferroelectric layer was formed.

The polystyrene substrate in that state is bent so that the ferroelectric layer side becomes convex, and then returned to the original state. afterwards,
Aluminum, titanium, tantalum, niobium, copper, ITO
The second electrode was formed of a conductor such as to obtain a non-linear element.

With respect to the non-linear element substrate obtained as described above, the electric field-electrical displacement hysteresis curve was measured in the same manner as in Example 1. The result was not as great as in Example 1, but similar results were obtained. Was given.

In this example, the same effect was obtained when the ferroelectric layer was formed using polyvinylidene fluoride-tetrafluoroethylene copolymer or polyvinylidene fluoride.

[0037]

As is apparent from the above description, according to the present invention, a nonlinear element substrate having ferroelectricity can be obtained by applying shear stress to the ferroelectric layer formed on the substrate. it can. By applying this nonlinear element substrate to a liquid crystal display device or the like, it is possible to obtain a liquid crystal display device having a high contrast and a low driving voltage and excellent display quality. The present invention can also be used for display elements such as electroluminescence and electrochromism, and for non-linear optical elements.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a non-linear element substrate manufactured using a manufacturing method of the present invention.

2 is an electric field-electrical displacement hysteresis curve of the nonlinear element substrate of Example 1. FIG.

3 is an electric field-electrical displacement hysteresis curve of the nonlinear element substrate of Example 2. FIG.

FIG. 4 is an electric field-electrical displacement hysteresis curve of a nonlinear element substrate of Example 3.

FIG. 5 is a diagram showing an example of a non-linear element substrate used as an active matrix substrate.

[Explanation of symbols]

 1 substrate 2 first electrode 3 ferroelectric layer 4 second electrode

Claims (3)

[Claims] 1. A first electrode and a second electrode sandwiching a ferroelectric layer on a substrate, or a first electrode and a second electrode separated from each other on the same wide surface of the ferroelectric layer. Then, in the formed nonlinear element substrate, the step of forming the first electrode, the second electrode, and the ferroelectric layer in a predetermined arrangement on the substrate, and the step of applying shear stress to the ferroelectric layer. And a method for manufacturing a non-linear element substrate, including: 2. The method of manufacturing a nonlinear element substrate according to claim 1, wherein the shear stress is applied to the ferroelectric layer by rubbing treatment. 3. The method for manufacturing a non-linear element according to claim 1, wherein the shear stress is applied by stretching or bending of the ferroelectric layer.