JPH04261521A - Liquid crystal display device and method for repairing display defect thereof - Google Patents

Abstract

PURPOSE:To obtain the matrix type liquid crystal display device which can repair the display defects occurring in the defects of thin-film transistors (TFTs). CONSTITUTION:A conductive film is deposited on an insulating substrate 1 and a gate inorg. insulating film 3, a gate wiring 10 and a floating electrode 11 are formed. Two picture element electrodes 8 are formed so as to overlap on the floating electrode 11 via an insulating layer 4. The display defect point of the liquid crystal display device having such structure is detected and the defective TFT 2 is electrically disconnected from the picture element electrode 8 of the display defective part. The part where this picture element electrode 8 and the floating electrode 11 are overlapped is irradiated with a laser beam to connect the picture element electrode 8 and the floating electrode 11 indicating the display defect. The other end of the floating electrode 11 is similarly connected to the corresponding picture element electrode 8. Since the normal TFT is connected to the picture element electrode 8, the display defect is repaired.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matrix type liquid crystal display device using thin film transistors and a method for repairing display defects thereof.

0002

2. Description of the Related Art Matrix type liquid crystal display devices are described in, for example, a magazine published by Nikkei McGraw-Hill, Nikkei Electronics, December 15, 1986 issue, p. 193 ~200
As described in , a TFT has a pixel electrode made of a transparent conductive film arranged in a matrix and a thin film transistor (TFT) electrically connected to the pixel electrode on its surface.
Voltage is selectively applied to the liquid crystal display material filled between the array substrate and the counter substrate stacked opposite it, and the transmission of light is controlled by aligning the liquid crystal molecules in the direction of the electric field. The display is performed based on the following information.

FIG. 3 is a plan view showing the pixel structure of a TFT array substrate of a conventional matrix type liquid crystal display device, FIG. 4 is a plan view showing the vicinity of the TFT, and FIG. 5 is a plan view taken along line V-V in FIG. FIG. In the figure, reference numeral 1 denotes an insulating substrate made of glass or the like, and on the insulating substrate 1, a gate electrode 3, an insulating layer 4, a semiconductor layer 5, a source electrode 6, and a drain electrode 7, which constitute a TFT 2, are formed in layers. A pixel electrode 8 is formed on the insulating substrate 1 and is electrically connected to the drain electrode 7. 9 is a source wiring electrically connected to the source electrode 6, and 10 is a gate wiring electrically connected to the gate electrode 3.

Next, the occurrence of display defects in a matrix type liquid crystal display device formed using such a TFT array substrate and a counter substrate having a counter electrode made of a transparent conductive film will be explained. First, the liquid crystal display device is turned on. If there is a disconnection defect in any of the TFTs 2, no voltage is applied between the pixel electrode 8 to which that TFT is connected and its opposite electrode, so the liquid crystal molecules do not align and the area always becomes a dark display defect. . Additionally, if there is a short-circuit failure in any of the TFTs 2, a voltage is always applied to that pixel part, and the liquid crystal molecules are aligned in the direction of the electric field and transmit light, making it impossible to control the amount of light in that part. .

The following two types of matrix type liquid crystal display devices are conventionally known as matrix type liquid crystal display devices that prevent the occurrence of display defects caused by TFT defects as described above.

FIG. 6 shows an example of a conventional matrix type liquid crystal display device that prevents display defects from occurring. In the figure,
Two TFTs 2 are connected to the pixel electrode 8 in parallel. The other components are the same as the corresponding parts of the conventional device of FIG. In this case, even if a disconnection failure occurs in one of the TFTs 2, the pixel portion operates normally. However, T.F.
If T2 is short-circuited, the pixel portion will have a display defect, and it is not possible to identify which TFT 2 is defective, making it impossible to repair the display defect. Furthermore, since the number of TFTs 2 per pixel is twice that of the conventional device shown in FIG. 3, there is a problem that the incidence of short-circuit failures is also doubled.

For example, as a matrix type liquid crystal display device that can identify defective TFTs,
9921 is shown in FIG. In the figure,
The pixel electrode in the area surrounded by the source wiring 9 and gate wiring 10 which intersect with each other is divided into two, and one TFT 2 is connected to each pixel electrode 8 . The other components are the same as the corresponding parts of the conventional device of FIG. In this case, by observing the pixel portion in the energized state, the TFT 2 causing the display defect can be identified. However, although the display defect portion is smaller than the conventional devices shown in FIGS. 3 and 6, the display defect cannot be repaired.

[0008]

[Problems to be Solved by the Invention] Since the conventional matrix type liquid crystal display device is constructed as described above, there is a problem in that it is difficult to repair display defects caused by defects in thin film transistors (TFTs). Ta.

The present invention was made to solve the above-mentioned problems, and provides a matrix type liquid crystal display device capable of repairing display defects caused by defects in thin film transistors, and a method for repairing the display defects. The purpose is to obtain.

0010

[Means for Solving the Problems] A liquid crystal display device according to the present invention includes a plurality of pixel electrodes provided on one of two substrates sandwiching a liquid crystal for applying a voltage to the liquid crystal, and a plurality of pixel electrodes that are provided on one of two substrates sandwiching a liquid crystal. The device includes thin film transistors that are electrically connected to each other to control the application of the voltage, and floating electrodes that are respectively provided so as to overlap with at least two pixel electrodes that receive the same drive signal via an insulating layer.

[0011] Furthermore, the method for repairing display defects in a liquid crystal display device according to the present invention includes a step of separating a switching element causing a display defect from a pixel electrode in the liquid crystal display device; This method includes a step of electrically connecting an electrode and a normal pixel electrode via a floating electrode.

0012

[Operation] The floating electrode of the liquid crystal display device in this invention is
At least a portion of the insulating layer that insulates between the pixel electrode and the pixel electrode is removed to electrically connect the pixel electrode.

[0013]

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view showing the pixel structure of a TFT array substrate of a matrix type liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line II--II in FIG. 1. In FIGS. 1 and 2, 11 is a floating electrode. A conductive film of Cr is deposited at predetermined positions on an insulating substrate 1 made of glass by photolithography using a mask having a predetermined pattern, thereby forming a gate electrode 3, a gate wiring 10, and a floating electrode 11. . Next, using a mask with a predetermined pattern, a silicon nitride film (SiNX
), an insulating layer 4 consisting of amorphous silicon (ia
-Si) film and an adjacent doped amorphous silicon (n+-a-Si) film are sequentially deposited to form a semiconductor layer 5 at a predetermined position. Furthermore, using a mask with a predetermined pattern, indium/tin oxide (ITO)
) is deposited to form a pixel electrode 8 at a predetermined position. The pixel electrode 8 is divided into two parts, and one TFT 2 is connected to each pixel electrode 8. floating electrode 11
are provided at positions overlapping the two pixel electrodes 8 with the insulating layer 4 in between. Next, using a mask with a predetermined pattern, an Al film is deposited to form a source electrode 6, a source wiring 9, and a drain electrode 7 at predetermined positions.
The n+-a-Si film between the layers is removed. Si on top
A protective film 12 made of Nx is formed to obtain a TFT array substrate.

Next, the operation will be explained. A matrix type liquid crystal display device formed by sandwiching a liquid crystal between a TFT array substrate and a counter substrate is turned on and bright and dark states are observed to detect display defects. The defective TF is removed from the pixel electrode 8 by irradiating the drain electrode 7 in the display defect area with laser light.
Electrically disconnect T2. Next, a portion where the pixel electrode 8 and the floating electrode 11 overlap is irradiated with laser light from the insulating substrate 1 side or the opposing substrate side. Due to the energy of the laser beam, a part of the insulating layer 4 evaporates and disappears, and the floating electrode 11 or the pixel electrode 8, or both, melts, and the pixel electrode 8 and the floating electrode 11 exhibiting a display defect are electrically disconnected. Connect to. The other end of the floating electrode 11 is also electrically connected to the corresponding pixel electrode 8 in the same manner as described above. In this way, display defects are repaired, and the display quality and manufacturing yield of the device can be improved.

In the above embodiment, two pixel electrodes are provided in the area surrounded by the source wiring and gate wiring that intersect with each other, but there is no restriction on the number of pixel electrodes, and two pixel electrodes are provided through an insulating layer. By providing floating electrodes so as to overlap with each other, the same effect as in the above embodiment can be obtained. Also,
Even if the pixel electrode is in a region other than the region surrounded by the source wiring and the gate wiring, a floating electrode may be provided as long as it is between the pixel electrode that receives the same drive signal as that in the region, similar to the above embodiment. The effect of this can be obtained.

[0016]

Effects of the Invention The liquid crystal display device according to the present invention has a plurality of pixel electrodes provided on one of two substrates sandwiching a liquid crystal and for applying a voltage to the liquid crystal, and each electrically connected to the pixel electrode. A thin film transistor that controls the application of the voltage described above, and a floating electrode that overlaps at least two pixel electrodes that receive the same drive signal with an insulating layer in between. It is easy to identify the thin film transistor causing the display defect, and by separating the pixel electrode from the transistor and electrically connecting the separated pixel electrode and the normal pixel electrode via a floating electrode, it is possible to eliminate display defects. Effects that can be easily repaired can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a pixel structure of a TFT array substrate of a matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the TFT array substrate of FIG. 1 taken along line II-II.

FIG. 3 is a plan view showing the pixel structure of a TFT array substrate of a conventional matrix type liquid crystal display device.

FIG. 4 is a plan view showing the vicinity of the TFT of the device shown in FIG. 3;

FIG. 5 is a cross-sectional view of the device of FIG. 4 along line V-V.

FIG. 6 is a plan view showing the structure of a pixel portion of a TFT array substrate of a conventional matrix type liquid crystal display device that prevents the occurrence of display defects.

FIG. 7 is a plan view showing a structure of a pixel portion of a TFT array substrate of a matrix type liquid crystal display device in which a conventional defective TFT can be identified.

[Explanation of symbols]

2 Thin film transistor (TFT) 4 Insulating layer 8 Pixel electrode 11 Floating electrode

Claims (2)

[Claims] 1. A plurality of pixel electrodes provided on one of two substrates sandwiching a liquid crystal for applying a voltage to the liquid crystal, and a plurality of pixel electrodes each electrically connected to the pixel electrode to control the application of the voltage. What is claimed is: 1. A liquid crystal display device comprising: a thin film transistor that receives the same drive signal; and floating electrodes that are respectively provided so as to overlap with at least two pixel electrodes with an insulating layer interposed therebetween, which receive the same drive signal. 2. The liquid crystal display device according to claim 1, including the step of separating the thin film transistor causing the display defect from the pixel electrode, and connecting the thin film transistor between the separated pixel electrode and the normal pixel electrode via a floating electrode. 1. A method for repairing a display defect in a liquid crystal display device, comprising a step of electrically connecting the liquid crystal display device.