JPH04298721A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent a display MIM element at a divisional part of a wiring electrode from being destroyed by static electricity during a manufacture process by arranging a nonlinear resistance element for protection at least one divisional part of the wiring electrode. CONSTITUTION:The MIM(Metal-Insulator-Metal) element 18 which is connected to respective picture element electrodes is formed on at least one of two opposite substrates, the wiring electrode 12 is divided at the center position, and the nonlinear resistance element 19 for protection is arranged at at least one of the divisional parts of the wiring electrode 12. At the center part, the element 19 for protection which does not contribute to display operation is arranged at a place where discharge and breakage are easily caused. Consequently, even if static electricity is generated to generate a potential difference between the divisional parts, the element 19 for protection is broken first to reduce the potential difference, so the elements at picture element display electrode parts can be protected.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device incorporating an MIM element as a switching element in each pixel.

0002

[Prior Art] In recent years, liquid crystal display devices have been used in everything from relatively simple devices such as watches and calculators to personal computers, word processors, office automation terminal equipment, TV image displays, etc. It is used for displaying large amounts of information. Conventionally, in liquid crystal display devices, it has been common to use a multiplex driving method for matrix display, a so-called simple matrix method. However, this method has the disadvantage that it is not suitable for large-scale matrix display because the contrast ratio between the display area and the non-display area deteriorates as the number of scanning lines increases.

[0003] As a means of solving this drawback, a so-called active matrix method, which is a method in which each pixel is driven by a switching element, has been developed. Here, a thin film transistor or a nonlinear resistance element is used as the switching element, and among these, the nonlinear resistance element is advantageous in terms of manufacturing cost because it basically has two terminals and a simple structure.

Various methods have been developed for nonlinear resistance elements, among which metal-insulator-metal (MIM)
) structure is currently the only one in practical use. When this MIM element is used as a switching element, the deterioration of contrast ratio due to increase in display capacity is clearly smaller than in the case of a simple matrix method. However, M.I.
Even if M elements are used, when performing a large-scale matrix display with more than 500 scanning lines, the same deterioration in contrast ratio as in the case of a simple matrix method occurs. Therefore, a method is sometimes taken in which the wiring electrodes are divided in the center and driven independently to halve the apparent number of scanning lines.

FIG. 4 is a plan view showing the manufacturing process for two pixels adjacent to the divided portion in this type of MIM element array. First, a first metal layer made of Ta is formed as a thin film on a glass substrate by sputtering, and then a first photolithography process is used to form the lower metal layer 1 of the MIM element, as shown in FIG. 4(a). And pattern on wiring electrode 2
ning. Next, an oxide film (not shown) that will become an insulating film of the MIM element is formed on the surface of the first metal layer using an anodic oxidation method or the like. Subsequently, after forming a thin film of the second metal layer on the glass substrate by sputtering, a second photolithography process is used to pattern the upper metal layer 3 of the MIM element, as shown in FIG. 4(b). - to ning. Next, after forming a thin ITO film on the glass substrate, a third photolithography process is used to pattern the pixel display electrode 4 as shown in FIG. 4(c), and the process is completed. do.

[0006]

Problems to be Solved by the Invention When an MIM element is used as a switching element, a characteristic defect of the element becomes a display defect in pixel units, or a so-called point defect. Various factors can be considered for defective device characteristics, but regarding MIM devices,
Since the insulating film is as thin as about 500 to 700 angstroms, it has a low breakdown voltage and is susceptible to dielectric breakdown due to static electricity generated during the process. In liquid crystal display devices, after forming an alignment film on a substrate, there is a rubbing process in which it is rubbed with a cloth.
At this time, static electricity is particularly likely to be generated and it is difficult to completely suppress this generation. Generally, charges are concentrated at the ends, so if the wiring electrode is divided in the center as described above,
Electric charge is concentrated in the divided portion. Therefore, a potential difference is created across the dividing portion, and a discharge occurs between the end of the wiring electrode and the pixel display electrode adjacent thereto, which may cause dielectric breakdown of the element. As a result, a defect occurs in which point defects are concentrated in the divided portion.

FIG. 5 is a plan view showing an example of how a defect occurs in a pixel adjacent to the divided portion of the wiring electrode 2 in the MIM element array, and parts corresponding to those in FIG. 4 are given the same reference numerals. be. In FIG. 5, arrows indicate the flow of generated static electricity, ◯ indicates a normal pixel, and × indicates a defective pixel. As can be seen from FIG. 5, half of all pixels in the divided portion of the wiring electrode 2 are defective pixels.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is an object of the present invention to provide a liquid crystal display device having a structure that suppresses the occurrence of display defects in divided portions due to static electricity. [Structure of the invention]

[0009]

[Means for Solving the Problems] This invention forms a plurality of pixel electrodes and an MIM element electrically connected to each of the pixel electrodes on at least one of two opposing substrates, and connects them to wiring electrodes. This relates to a liquid crystal display device in which MIM elements are connected row by row and wiring electrodes are divided at the center, and a protective nonlinear resistance element is arranged in at least one of the divided parts of the wiring electrodes.

0010

[Function] In this invention, the protective element that does not contribute to display is placed in the center divided part in a position where it is easily discharged and destroyed, so even if static electricity is generated during the process and a potential difference occurs in the divided part. Since the protective element is destroyed first and the potential difference is alleviated, it is possible to protect the element in the pixel display electrode portion.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be explained below with reference to the drawings.

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIGS. 1(a) to 1(c) show the manufacturing process for two pixels adjacent to the divided portion of the MIM element array in this embodiment. 1(d) is a plan view showing AA' in FIG. 1(c).
Figure 3 represents a cross-sectional view of this embodiment corresponding to a plane.

To explain the manufacturing process in FIG. 1, a first metal layer made of, for example, Ta is formed as a thin film by sputtering on a substrate 10 made of, for example, glass, and then a first photolithography process is used to form a thin film of a first metal layer made of, for example, Ta. As shown in FIG. 1A, the lower metal 11 of the display MIM element, the wiring electrode 12, and the lower metal 13 of the protective nonlinear resistance element are patterned. Next, using an anodic oxidation method or the like, an oxide film 14 that will serve as an insulating film for a display MIM element and an oxide film 15 that will serve as an insulating film for a protective nonlinear resistance element are formed on the surface of the first metal layer. Form. Subsequently, the substrate 10
After forming a second metal layer thereon by sputtering, a second photolithography process is used to form the upper metal 16 of the display MIM element and the protective layer, as shown in FIG. 1(b). The upper metal 17 of the nonlinear resistance element is patterned. In this way, the lower metal 11-oxide film 14
- MIM element 18 with upper metal 16 structure and lower metal 13
A nonlinear resistance element 19 for protecting the -oxide film 15-upper metal 17 structure is completed. Next, after forming a thin ITO film on the substrate 10, a third photolithography process is used to pattern the pixel display electrode 20 as shown in FIG. 1(c), and the process is completed. do.

Separately, as shown in FIG. 1D, scanning electrodes 22 made of, for example, ITO are formed on a substrate 21 made of, for example, glass in a direction perpendicular to the wiring electrodes 12. Then, the substrates 10 and 21 are held with a gap of 5 to 20 μm maintained, and liquid crystal 23 is injected into this gap. In this way, a desired liquid crystal display device is completed.

FIG. 2 is a diagram showing how static electricity is generated in this embodiment, and parts corresponding to those in FIG. 1 are given the same reference numerals. In FIG. 2, similarly to FIG. 5, arrows indicate the flow of generated static electricity, ◯ indicates a normal pixel, and × indicates a defective pixel. In this embodiment, since the nonlinear resistance element 19 that does not contribute to display is arranged to face the divided portion of the wiring electrode 12, when a potential difference occurs in the divided portion of the wiring electrode 12 and discharge occurs, the nonlinear resistance element 19 Resistance element 19 is damaged by electrostatic discharge, and MIM element 18 is protected. As a result, as can be seen from FIG. 2, there are no defective pixels in this example compared to the conventional example shown in FIG.

In FIG. 1, the gap d1 between the opposing upper metals 17 is made narrower than the gap d2 between the opposing pixel display electrodes 20 in order to facilitate the occurrence of discharge between the opposing nonlinear resistance elements 19. This is desirable.

FIG. 3 shows MI in another embodiment of the present invention.
FIG. 2 is a plan view showing two pixels adjacent to a divided portion of the M-element array, in which portions corresponding to those in FIG. 1 are given the same reference numerals. In the example of FIG. 3(a), the protective nonlinear resistance element 1
9 is provided only on one of the divided portions of the wiring electrode 12, but even in this case, the same effect as the embodiment shown in FIG. 1 is obtained. In the example shown in FIG. 3(b), the tip of the upper metal 17 of the protective nonlinear resistance element 19 is sharpened to facilitate discharge between the opposing nonlinear resistance elements 19, which is different from the embodiment shown in FIG. than in the case of MIM element 18
The effect of protecting can be strengthened.

[0018]

Effects of the Invention In this invention, since a protective nonlinear resistance element is disposed on at least one of the divided portions of the wiring electrode, the MIM element for displaying the divided portion of the wiring electrode is free from static electricity generated during the manufacturing process. This can prevent it from being destroyed.

[Brief explanation of the drawing]

FIG. 1 is a plan view and a sectional view for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing a situation when static electricity is generated in the embodiment shown in FIG. 1;

FIG. 3 is a plan view showing an MIM element array in another embodiment of the invention.

FIG. 4 is a plan view showing an example of the manufacturing process of a conventional MIM element array.

FIG. 5 is a plan view showing an example of how pixel defects occur in a conventional MIM element array.

[Explanation of symbols]

10, 21...Substrate 12... Wiring electrode 18...MIM element 19...Nonlinear resistance element

Claims (1)

[Claims] 1. At least one of two opposing substrates is provided with a plurality of pixel electrodes and a metal-insulator-metal structure electrically connected to each pixel electrode.
1-Insulator-Metal) element is formed, the MIM elements are connected row by row by wiring electrodes, and the wiring electrode is divided at a central portion, in which at least one of the divided portions of the wiring electrode is A liquid crystal display device characterized by arranging a protective nonlinear resistance element.