JPH0527268A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which can protect the display elements of the divided parts of wiring electrodes against an electrostatic breakdown. CONSTITUTION:At least one of a pair of substrates facing each other of this liquid crystal display device consists of a matrix array substrate formed by disposing plural nonlinear resistance elements each having a three-layered structure consisting of a metallic layer 13-insulator layer 15-metallic layer 17 in an array form, disposing picture element electrodes 18 respectively in series to the respective nonlinear resistance elements and further connecting the respective line or row directions by the wiring electrodes 14. In addition, the wiring electrodes are divided at a center. The radius of curvature at the corners of the picture element electrodes facing the divided side thereof is set not smaller than the radius of curvature of the picture element electrodes in other parts and larger than the radius of curvature at the corners of the divided parts of the wiring electrodes, by which the above-mentioned purposes are achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a liquid crystal display device in which a switching element including a non-linear resistance element having a three-layer structure of a metal layer-insulator layer-metal layer is incorporated in each pixel.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have changed from relatively simple devices such as watches and calculators to personal computers, word processors, OA terminal devices, TV image displays and the like. It has been used for large capacity display applications.

In this type of liquid crystal display device, conventionally,
It has been common to use a multiplex drive system for matrix display, that is, a so-called simple matrix system. However, this method is disadvantageous in that it is not suitable for large-scale matrix display because the contrast ratio between the display portion and the non-display portion deteriorates as the number of scanning lines increases.

Therefore, as one means for solving this drawback, a method of driving each pixel by a switching element, that is, an active matrix method has been developed. In this case, a thin film transistor or a non-linear resistance element is used as the switching element, but a non-linear resistance element which basically has two terminals and has a simple structure is advantageous in terms of manufacturing cost.

Various methods have been developed as a non-linear resistance element. Among them, metal layer-insulator layer-metal layer (M
An element having a three-layer structure (IM) has been put into practical use at present. When the non-linear resistance element of this MIM is used as a switching element, the deterioration of the contrast ratio accompanying the increase of the display capacity is obviously smaller than that of the simple matrix method. However, when performing a large-scale matrix display in which the number of scanning lines exceeds 500, the same problem still occurs. Therefore, a method of dividing the wiring electrodes at the center and driving them independently to halve the number of apparent scanning lines may be used. An example is shown below.

5 and 6 are a cross-sectional view showing a manufacturing process of a matrix array substrate in a conventional liquid crystal display device and a plan view of two pixels adjacent to each other in a divided portion. First, as shown in FIG. 5A, a Ta film 2 is formed on a glass substrate 1 by a sputtering method, and then patterning is performed using a first photolithography process.
Then, as shown in FIG. 6A, the first metal layer (lower electrode) 3 of the non-linear resistance element and the wiring electrode 4 integral with this are formed.

Next, as shown in FIG. 5C, an oxide film is formed on the surfaces of the first metal layer 3 and the wiring electrode 4 by using an anodic oxidation method or the like, and the insulator layer 5 of the nonlinear resistance element is formed. To get
Further, after forming, for example, a Ti film 6 on the entire surface by a sputtering method, as shown in FIGS. 5D and 6B, patterning is performed by using a second photolithography process to obtain a nonlinear resistance element. The second metal layer (upper electrode) 7 of is formed.

Finally, as shown in FIGS. 5 (e) and 6 (c), a thin film of ITO (indium-tin-oxide) is formed on the entire surface, and then the pixel electrode 8 is formed by the third photolithography process. All the steps are completed by performing the patterning of.

[0009]

When the non-linear resistance element is used as a switching element as described above, the defective characteristic of the element becomes a display defect in a pixel unit, that is, a so-called point defect.
There are various possible causes for defective characteristics of the device.
Since the insulator layer of the M element is as thin as 500 to 800 angstroms, the breakdown voltage is low and the dielectric breakdown is likely to occur due to the ultrahigh voltage discharge due to the static electricity generated during the process.

In the manufacture of a liquid crystal display device, there is a process of rubbing with a cloth after forming an alignment film such as a polymide film on a substrate for controlling the alignment of a liquid crystal layer, and static electricity is easily generated. Therefore, it is difficult to completely suppress the occurrence of electrostatic discharge near the wiring electrode divisions, and the manufacturing process yield is often reduced.

In general, the electric charge is concentrated on the end portion, so that when the wiring electrode is divided at the center as described above, it is concentrated on the divided portion. For this reason, a potential difference is generated at the dividing portion, and discharge may occur between adjacent display pixel electrodes or between a wiring electrode end and a display pixel electrode adjacent thereto, which may cause dielectric breakdown of the element. As a result, defects such as point defects concentrated on the divided portions occurred.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device in which the occurrence of display defects in the divided portions due to static electricity is suppressed.

[0013]

According to the present invention, at least one of a pair of substrates facing each other has a non-linear resistance element having a three-layer structure of a metal layer-insulator layer-metal layer arranged in an array, and In a liquid crystal display device composed of a matrix array substrate in which pixel electrodes are arranged in series with a non-linear resistance element, and each row or each column direction is connected by wiring electrodes, the wiring electrodes are divided at the center and face each other on the divided side. The radius of curvature of the corner of the above-mentioned pixel electrode is not smaller than that of the pixel electrodes of other portions, and the corner of the divided portion of the wiring electrode is
It is a large liquid crystal display device compared to.

[0014]

According to the present invention, since the wiring end portion of the central divided portion is arranged in a structure and a distance relationship that is more likely to cause discharge and destruction than the neighboring pixel electrodes, electrostatic discharge may occur at the divided portion during the process. Even if occurs, this portion is destroyed first and the potential difference is relieved, so that the element in the pixel display electrode portion can be protected. If the division gap length of the central division is short,
A discharge is generated here, the end of the wiring electrode is damaged, and
Display pixels can be prevented from being destroyed simply by opening the cursor. Furthermore,
If at least one insulating layer at the end of the wiring electrode is removed, the discharge will occur more easily. However, since the voltage difference during operation is not so large as to cause discharge, it does not affect display performance or reliability.

Further, according to the experiments prior to the invention, the radius of curvature of the corner of the wiring electrode division portion was set in the range of 1 to 2 μm, and the radius of curvature of the corner of the pixel electrode was set in the range of 1 to 10 μm. When the occurrence of defects due to electric discharge was examined instead, it was found that the occurrence of defects was remarkably reduced when the corner radius of the pixel electrode was 4 μm or more. That is, the corner of the pixel electrode
It is more preferable that the radius of curvature of is 4 μm or more.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. The matrix array substrate of the liquid crystal display device according to the present invention is constructed as shown in FIGS. 1 to 4, and the manufacturing method will be described.

First, as shown in FIG. 1A, a Ta film 12 is formed on a glass substrate 11 by a sputtering method, and then a pattern is formed by using a first photolithography process.
Then, as shown in FIGS. 1B and 2A, the first metal layer (lower electrode) 13 of the non-linear resistance element and the wiring electrode 14 integral therewith are formed.

Next, as shown in FIGS. 1 (c) and 2 (b), an oxide film is formed on the surfaces of the first metal layer 13 and the wiring electrode 14 by using an anodic oxidation method or the like, and a nonlinear resistance is formed. The insulator layer 15 of the device is obtained. Further, for example, a Ti film 16 is formed on the entire surface.
After being formed by a sputtering method, as shown in FIG. 1D and FIG. 2B, patterning is performed using a second photolithography process to form a second metal layer (upper part) of the nonlinear resistance element. The electrode) 17 is formed.

Finally, as shown in FIG. 1 (e), FIG. 3 and FIG. 4, a thin film of ITO (indium tin oxide) is formed on the entire surface, and then the third photolithography process is used to form the pixel electrode 18 Perform patterning. At this time, the radius of curvature r ₁ of the corner A of the pixel electrode 18 facing (close to) the division line side is the radius of curvature r _{2 of the} corner B of the pixel electrode in the other part. Is equal to or larger than the above, and is set larger than the radius of curvature r _{3 of the} corner C of the wiring electrode 14. That is, there is a relation of r ₁ r ₂ and r ₃ . Specifically, in this embodiment, r ₁ = 4 μm and r ₂ = 2
μm and r ₃ = 1 μm. In FIGS. 3 and 4, the glass substrate 11 and the insulator layer 15 are omitted for convenience. With the above, all steps are completed.

In the above embodiment, the pixel electrode counters (proximity) to the division line side of the wiring electrodes.
Focusing on the corners, we rounded them so that there would be no discharge due to the concentration of the electric field, but for the sake of safety, the pixel corners that entered the inside from the dividing line and all the pixel corners. −
Even if the same roundness is added to, the same effect can be obtained. That is, similar effects were obtained even when r ₁ = r ₂ = 4 μm and r ₃ = 1 μm. A liquid crystal display device is formed using the matrix array substrate as described above, for example, as follows.

First, an alignment film made of a polyimide resin is applied to the surface of the matrix array substrate on which the nonlinear resistance element is formed.
The liquid crystal alignment direction is regulated by firing and rubbing. Similar processing is performed on the counter substrate, and rubbing is performed in a direction twisted by about 90 ° from one liquid crystal display substrate. The above-mentioned two types of substrates are prepared, and liquid crystals are injected to form a liquid crystal cell by holding the substrates at a distance of 5 to 20 μm so that the major axis direction of the liquid crystal is twisted by about 90 ° between the substrates. Then, the polarizing plate may be arranged outside the liquid crystal cell with the polarization axis twisted by about 90 °.

[0022]

According to the present invention, it is possible to protect the display element in the divided portion of the wiring electrode from electrostatic breakdown.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a matrix array substrate in a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a plan view of the same.

FIG. 4 is an enlarged plan view showing a main part of FIG.

FIG. 5 is a cross-sectional view showing a manufacturing process of a matrix array substrate in a conventional liquid crystal display device.

FIG. 6 is a plan view of the same.

[Explanation of symbols]

11 ... Glass substrate, 12 ... Ta film, 13 ... First metal layer, 14 ... Wiring electrode, 15 ... Insulator layer, 16 ... Ti film,
17 ... 2nd metal layer, 18 ... Pixel electrode.

Claims (2)

[Claims] 1. A plurality of non-linear resistance elements having a three-layer structure of a metal layer-insulator layer-metal layer are arranged in an array on at least one of a pair of substrates facing each other, and each non-linear resistance element has a pixel. In a liquid crystal display device comprising a matrix array substrate in which electrodes are arranged in series, and each row or each column direction is connected by wiring electrodes, the wiring electrodes are divided at the center, and the pixel electrodes of the pixel electrodes facing each other are divided. A liquid crystal display device, characterized in that the radius of curvature of the corner is not smaller than that of the pixel electrode in other portions and is larger than that of the corner of the divided portion of the wiring electrode. 2. The liquid crystal display device according to claim 1, wherein the corner radius of the pixel electrode facing the division side of the central division of the wiring electrode is 4 μm or more.