JPH05196970A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which suppresses the generation of display defects in the outer peripheral part of a display picture element region by static electricity. CONSTITUTION:Switching elements 18 consisting of a metal-insulator-metal structure are connected by each column by the tantalum pattern 13 to the region B on the outer side of the display picture element region A. A dummy picture element formed by connecting two pieces of the adjacent switching elements 18 with a single ITO pattern 21b is provided. An electric discharge and breakdown are liable to arise in the part of the region B on the outer side at the end of the display picture element region A where charges are liable to concentrate. The region B around the display picture element region A is broken to release a potential difference even if the static electricity is generated during the process and the potential difference arises in the part of the region B on the outer side of the display picture element region A and, therefore, ITO patterns 21a constituting the picture element electrodes in the part of the display picture element region B are protected.

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 which a metal-insulator-metal (Metal-Insulator-Metal) element is provided as a switching element on a substrate.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices using a liquid crystal display have been used for personal computers, word processors, terminal equipment for office automation, large-capacity information display applications such as image display for televisions. , Higher image quality is required.

There are various types of this switching array, but the two-terminal non-linear resistance element is simple in structure and easy to manufacture, and among them, MIM (Metal-Insulator-Metal) has been put into practical use at present. There is an element.

FIG. 8 is a sectional view showing an example of one pixel portion of a conventional array substrate having MIM elements. This liquid crystal display device will be described according to manufacturing steps. First, a tantalum (Ta) film 2 is formed on a glass substrate 1 by a thin film forming method such as a sputtering method or a vacuum evaporation method, and is patterned by a photolithography method. Electrode and non-linear resistance element M
One electrode of the IM element is formed.

Next, the tantalum film 2 is formed by, for example, anodic oxidation in an aqueous solution of citric acid to form an oxide film 3. Further, a chromium (Cr) film 4 is formed as the other electrode of the non-linear resistance element MIM element by a thin film forming / processing method, whereby the non-linear resistance element MIM element is completed.

After that, the transparent electrode 5 for displaying an image is formed on the glass substrate 1.

[0007]

However, as described above, when a non-linear resistance element is used as a switching element, the characteristic failure of the non-linear resistance element becomes a display defect in a pixel unit, a so-called point defect.

Various factors may be considered for the defective characteristic of the non-linear resistance element, but in the non-linear resistance element of the MIM element, the oxide film 3 serving as an insulating layer is 500 to 800.
Since it is as thin as angstrom, it has low withstand voltage, and dielectric breakdown is likely to occur due to ultra-high voltage discharge due to static electricity generated during the process.

Further, in manufacturing a liquid crystal display device,
In order to control the alignment of the liquid crystal layer, there is a step of forming an alignment film such as a polyimide film on the glass substrate 1 and then rubbing with a cloth.
Static electricity is easily generated, and it is difficult to completely prevent the static electricity from causing electrostatic discharge breakdown of the non-linear resistance element, which often reduces the yield of the manufacturing process.

Since charges are generally concentrated on the edges, defects are often concentrated near the outermost periphery of the transparent electrode 5, which is the display pixel area. This is because static electricity generated in the region of the glass substrate 1 outside the display pixel region is collected in the outermost display pixel column and the transparent electrode 5, so that the neighboring display pixel electrodes in the outermost periphery, the wiring electrodes, and the like. Is a phenomenon in which electric discharge occurs between the display pixel electrodes close to each other and the element causes dielectric breakdown.

The present invention has been made in view of 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 outer peripheral portion of the display pixel area due to static electricity is suppressed.

[0012]

According to the present invention, one of a pair of substrates facing each other has non-linear resistance elements having a metal-insulator-metal structure arranged in an array, and each of the non-linear resistance elements has a pixel. In a liquid crystal display device in which electrodes are arranged and the pixel electrodes are connected to each other by wiring electrodes in each row direction, a metal-insulator-exists in a region outside the display pixel region of the pixel electrodes of the matrix array substrate.
A non-linear resistance element having a metal structure is connected to each column by a wiring electrode, and a plurality of adjacent non-linear resistance elements are connected by a single pixel electrode to provide a dummy pixel.

[0013]

According to the present invention, a non-linear resistance element having a metal-insulator-metal structure is connected to each column by a wiring electrode outside a display pixel area, and a plurality of adjacent non-linear resistance elements are connected to a single pixel. By providing dummy pixels connected by electrodes, it is easy to discharge and destroy the edge part of the display pixel area where electric charges are likely to concentrate. Even if a potential difference occurs,
Since the area around the display pixel area is destroyed and the potential difference is relieved, the element in the pixel display electrode portion can be protected. If dummy pixels around the display pixel area are formed to be the same as the display pixel area, the dummy pixels are lit and enter the field of view even when isolated from the external power source, which is unsightly and not preferable. On the contrary, if only the wiring is arranged, sufficient discharge and destruction effects cannot be obtained.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal display device of the present invention will be described below with reference to the drawings.

First, as shown in FIG. 2, reference numeral 10 is a glass substrate, and this glass substrate 10 has, for example, a 1000 mm thick dip-coated alkali protective coating of silicon oxide (SiO ₂ ) of 1.1 mm. Made of thick soda lime. And 3000 on this glass substrate 10.
A tantalum thin film 11 made of angstrom tantalum (Ta) is formed by a sputtering method. Next, a resist of a photosensitive resin is applied on the entire surface of the tantalum thin film 11, exposed using a photomask, and developed to form a resist pattern 12.

At this time, as shown in FIGS. 6A and 6B, a similar pattern is formed in a region B outside the display pixel region A that contributes to display.

Subsequently, as shown in FIG. 3, the tantalum thin film 11 is etched by the chemical dry etching method. Here, etching is performed in plasma in which tetrafluoromethane (CF ₄ ) and oxygen (O ₂ ) gas are mixed in equal amounts to form a tapered shape in the edge portion around the pattern. Subsequently, with the resist pattern 12 removed, a tantalum pattern 13 serving as a wiring electrode and a lower electrode is formed from the tantalum thin film 11, the tantalum pattern 13 serves as an anode, and a platinum plate (not shown) serves as a cathode.
Chemical formation is performed in an electrolytic solution containing a 01 wt% citric acid aqueous solution, and the voltage at this time is controlled to form an insulator layer 14 on the surface of the tantalum pattern 13 to a desired thickness.

In this embodiment, a voltage of 42 V is applied to obtain a 700 angstrom insulator layer. Further, in the tantalum pattern 13 exposed to the electrolytic solution, a metal having a film thickness of 280 angstroms has a film thickness of 700
Change to angstrom tantalum oxide (Ta ₂ O ₅ ). At the time of this anodic oxidation, the covering member is used to isolate the pad portion from the electrolytic solution.

Next, as shown in FIG. 4, titanium (Ti) having a thickness of 1500 Å is formed on the entire surface of the glass substrate 10.
A titanium thin film 15 made of is formed. A resist, which is a photosensitive resin, is coated on the titanium thin film 15 over the entire surface, exposed by using a photomask, and developed to form a resist pattern 16.

Also at this time, as shown in FIGS. 7A and 7B, a region B outside the display pixel region A contributing to the display is displayed.
Also, a similar pattern is formed.

Subsequently, as shown in FIG. 5, ethylenediamine tetra-acetic acid (EDTA) 9
g, 400 cc of water, 216 cc of hydrogen peroxide and 30 ml of ammonia water, and mixed at a room temperature to etch the resist pattern 16 on the titanium thin film 15 and remove the resist to form a titanium pattern 17 to be an upper electrode. It As a result, the tantalum pattern 13, the insulating layer
The switching element 18 is a non-linear resistance element of a metal-insulator-metal (Metal-Insulator-Metal) element composed of 14 and the titanium pattern 17.

In this embodiment, titanium (T
i) was used, but chromium (Cr), aluminum (A
l), and even if tantalum (Ta) is laminated again as the upper electrode, the same result as in the case of using titanium can be obtained.

Next, 100 over the entire surface of the glass substrate 10.
A transparent conductive film 19 made of ITO (Indium Tin Oxide) having a thickness of 0 angstrom is formed by a sputtering method, and then a resist which is a photosensitive resin is applied over the entire surface of the transparent conductive film 19 and then exposed using a photomask, A resist pattern 20 is formed by development.

The resist pattern 20 is shown in FIG.
As shown in (b) and (c), two pixels are integrally formed in a region B outside the display pixel region A that contributes to display. This corresponds to the case where one-line polarity inversion is performed.

Subsequently, water, hydrochloric acid and nitric acid are mixed in a volume ratio of 1: 1:
By the etching solution mixed at a ratio of 0.1 and heated to 30 ° C., IT which becomes the pixel electrode of each switching element 18 in the same shape as the resist pattern 20 in the display pixel area A is formed.
An O pattern 21a is formed, an ITO pattern 21b serving as a dummy pixel for each of the two switching elements 18 is formed in a region B outside the display pixel region A, and the resist pattern 20 is removed.

In this way, the switching element 18 of the non-linear resistance element having the lower metal-insulator-upper metal structure is connected to the region B outside the display pixel region A for each column by the tantalum pattern 13 which is a wiring electrode. And
The matrix array substrate 22 in which the plurality of adjacent two switching elements 18 are provided with the ITO pattern 21b as a single dummy pixel is completed.

The matrix array substrate 22 is formed in a liquid crystal display device as follows, for example.

First, an alignment film made of polyimide resin is applied to the surface on which the matrix array substrate 22 is formed, baked and rubbed to regulate the liquid crystal alignment direction. The same process is performed on the counter substrate corresponding to the matrix array substrate 22 (not shown), and rubbing is performed in a direction twisted by about 90 ° from the matrix array substrate 22. Then, the two types of matrix array substrate 22 and the counter substrate are prepared, and the molecular long axis direction of the liquid crystal is twisted by about 90 ° between the matrix array substrate 22 and the counter substrate 5 to 20.
A liquid crystal cell is constructed by injecting a liquid crystal while holding it at a distance of μm. Then, the polarization axis is about 9 outside the liquid crystal cell.
The polarizing plates may be arranged in a twisted form of 0 °.

In the above-mentioned embodiment, the ITO pattern 21b as a dummy pixel is formed integrally with two pixels in order to correspond to the case where the driving is performed by reversing the polarity of one line.
According to experiments, in the case of N-line polarity inversion drive, I pixels as dummy pixels can be obtained by connecting dummy pixels in multiples of 2N.
Since the TO pattern 21b is not lit up, it is sufficient to form 2N coefficients each.

Further, an experiment was conducted prior to the above-mentioned embodiment. As a result, the dummy pixels in the area B outside the display pixel area A were formed with the same size and pitch as the display pixel area A. However, even though the dummy pixel portion was isolated from the external power source and floated, the lighting display was performed. It was found that this is unsatisfactory and unfavorable because the outer region B located around the display pixel region A is inevitably in sight when looking at the display pixel region A which is the display portion. Further, in order to cover up the portion where the dummy pixel is formed, a black matrix or the like must be formed on the counter substrate, which is expensive in cost.

On the contrary, arranging only the wiring without forming the dummy pixel cannot exert a sufficient effect, and it is best to integrally form a plurality of dummy pixels as in the above embodiment.

[0032]

According to the liquid crystal display device of the present invention, a non-linear resistance element having a metal-insulator-metal structure is connected to each column by a wiring electrode outside the display pixel area, and a plurality of adjacent non-linear resistance elements are connected. By providing a dummy pixel in which a nonlinear resistance element is connected with a single pixel electrode, it is easy to discharge and destroy the edge part of the display pixel area where electric charges are likely to concentrate, so static electricity is generated during the process. Even if a potential difference occurs in the outer portion of the display pixel region, the region around the display pixel region is destroyed and the potential difference is alleviated, so that the element in the pixel display electrode portion can be protected. If the dummy pixels around the display pixel area are formed to be the same as the display pixel area, the dummy pixels light up even if they are isolated from the external power supply and enter the field of view, which is unsightly.
Not preferable. On the contrary, if only the wiring is arranged, sufficient discharge and destruction effects cannot be obtained. Therefore, a high-quality, large-scale, high-definition liquid crystal display device with few display defects can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a liquid crystal display device according to an embodiment of the present invention. (A) A front view showing a matrix array substrate of a liquid crystal display device (b) An enlarged view showing a display pixel region of the same as above (c) An enlarged view showing a region outside the display pixel region of the same as above

FIG. 2 is a cross-sectional view showing one manufacturing process of the above matrix array substrate.

FIG. 3 is a cross-sectional view showing a manufacturing step subsequent to the manufacturing step shown in FIG. 2 of the same matrix array substrate.

FIG. 4 is a cross-sectional view showing a manufacturing step subsequent to the manufacturing step shown in FIG. 3 of the same matrix array substrate.

5 is a cross-sectional view showing the next manufacturing step of the above-mentioned manufacturing step of the matrix array substrate shown in FIG. 4;

FIG. 6 is a diagram showing the liquid crystal display device in the state shown in FIG. 2 above. (A) Front view showing a matrix array substrate of a liquid crystal display device (b) Same as above Enlarged view showing display pixel region and other regions

FIG. 7 is a diagram showing the liquid crystal display device in the state shown in FIG. 4 above. (A) Front view showing a matrix array substrate of a liquid crystal display device (b) Same as above Enlarged view showing display pixel region and other regions

FIG. 8 is a cross-sectional view showing a matrix array substrate of a conventional liquid crystal display device.

[Explanation of symbols]

 13 Tantalum pattern as metal 14 Insulator layer as insulator 21a ITO pattern as pixel electrode 21b ITO pattern as dummy electrode 22 Matrix array substrate A Display pixel area B Outside area

Claims (1)

[Claims] 1. One of a pair of substrates facing each other is made of metal-
A liquid crystal display which is a matrix array substrate in which non-linear resistance elements having an insulator-metal structure are arranged in an array, pixel electrodes are arranged in each non-linear resistance element, and the pixel electrodes are connected to each row direction by wiring electrodes. In the device, a non-linear resistance element having a metal-insulator-metal structure is connected to each column by a wiring electrode in a region outside the display pixel region of the pixel electrode of the matrix array substrate, and a plurality of adjacent non-linear resistors are connected. A liquid crystal display device comprising a dummy pixel in which elements are connected by a single pixel electrode.