JPH04229832A - Manufacture of liquid crystal display panel - Google Patents

Abstract

PURPOSE:To regenerate a thin-film transistor that is defective in conduction of a liquid crystal element panel used for a liquid crystal projector. CONSTITUTION:Energy of a laser beam is formed into such a size as required to pierce through each thickness of a source electrode 7 and a gate electrode 2, and these electrodes 7 and 2 are melted and conducted to a display panel, where a thin-film transistor 11 is formed, without substantially damaging a shade film 22 installed in the area of an insulating substrate 24 at the side of a counter electrode being superposed on the transistor 11.

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 liquid crystal display panel, and more particularly to a method for manufacturing a liquid crystal display panel used for a liquid crystal projector.

0002

2. Description of the Related Art In recent years, with the trend toward larger screen displays, liquid crystal projectors have come into existence. In such a projector, white light generated from a light source enters a dichroic prism through a condenser lens and is divided into red, green, and blue, and a portion of each color component, for example, red and blue, is reflected by a total reflection mirror. are then modulated by the liquid crystal display panel as transmittance changes, and the further modulated red and
The green and blue components are combined by a dichroic mirror and projected onto a screen by a projection lens.

[0003] A liquid crystal projector using a liquid crystal display panel is disclosed in Japanese Patent Application Laid-open No. 150487/1987, and its explanation will be omitted here. Now, in the above-mentioned liquid crystal projector, in order to achieve high image quality, it is necessary to increase the number of pixels in each liquid crystal display panel.For example, if a panel with dimensions of 480 pixels in height x 720 pixels in width is used, NTSC full-line display can be performed. . However, as the number of pixels increases, T
The number of FTs (thin film transistors) has also increased, and a decline in the yield of display panels has become a problem.

In order to solve this problem, a method is generally adopted in which, for example, two TFT elements are formed in one pixel electrode, and the TFT elements are operated even if one of them becomes defective.

[0005]

[Problems to be Solved by the Invention] However, even if two TFT elements are provided in one pixel electrode as described above, pinholes may be formed due to dust or the like during the process of forming a gate insulating film, for example. In some cases, two TFT elements may fail at the same time due to a display failure due to a short circuit between the auxiliary capacitor metal and the pixel electrode, or a failure of the TFT element itself due to poor contact between the semiconductor layer and the source and drain electrodes.

In this case, since the liquid crystal display panel for the projector displays in a normally white mode, a pixel electrode with a defective TFT element is displayed as a white dot on the screen. There was a problem in that the display quality was significantly degraded. Furthermore, if these TFT element defects occur in multiple locations, there is a problem that the device cannot be used as a liquid crystal display panel for a projector.

Furthermore, this problem may occur more frequently as the number of pixels increases, and has been a major obstacle in realizing larger display panels.

[0008]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to irradiate the source electrode and gate electrode of a defective TFT element with laser energy that does not damage the light shielding film. The above-mentioned problem is solved by connecting the electrode and the source electrode on the overlapping region.

[0009]

[Operation] As described above, according to the present invention, the defective TFT
Although it is not possible to completely regenerate a defective TFT element by connecting the source electrode and gate electrode of the element, it is possible to drive the defective TFT element to a black spot based on the signal applied to the gate line. can. As a result, even if a defective TFT element occurs in a liquid crystal display panel for a projector used in normally white mode, it can be reproduced.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on the embodiments shown in FIGS. 1 and 2. FIG. 1 is an enlarged view of essential parts showing one pixel of the display panel of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA in FIG. is a gate electrode made of Cr, Cr+Au, Mo, etc.; (3) is an insulating protective film made of, for example, nitride; (4) is a semiconductor layer made of amorphous silicon, Te, polysilicon, Cdse, etc.; )
is passivation that protects the surface of the semiconductor layer (4), (
6) and (7) are drain electrodes and source electrodes formed of Al, Mo, and ITO, and (8) is for making ohmic contact between the drain electrode (6), the source electrode (7), and the semiconductor layer (4). N+a-Si, (9) is a transparent display electrode made of ITO or the like, and (10) is an auxiliary capacitor electrode.

Each display electrode (9) is arranged corresponding to a color filter (not shown), and a gate electrode (2) is provided between the rows of display electrodes (9), and a drain electrode (6) is provided between each column of the display electrodes (9). is formed in such a manner as to partition between each display electrode (9), and in one corner of the intersection between the two, the gate electrode (2), the insulating protective film (3), the semiconductor layer (4), the drain electrode (6),
A plurality of thin film transistors (11) constituted by source electrodes (7) and the like are formed in such a manner that they are connected to display electrodes (9). In this embodiment, two thin film transistors (11) are formed adjacent to each other, which drives the display electrode (9) even if one of the thin film transistors (11) becomes defective. This is a spare for use.

However, if a plurality of thin film transistors (
11), each thin film transistor (
11) If the display electrode (9) itself or the display electrode (9) becomes defective, the display electrode (9) will not operate even if a plurality of thin film transistors (11) are arranged. The process where the most defects occur during the manufacturing process is to place the gate electrode (
2) Immediately after forming the auxiliary capacitance electrode (10), dust and the like adhere to the gate electrode (2) and the auxiliary capacitance electrode (10), and after the insulation protective film is formed, the dust and the like are removed and pinholes are formed. A short-circuit between the gate electrode (2) and the semiconductor layer or a short circuit between the display electrode (9) and the auxiliary capacitance electrode (10) is formed.
) may cause a short circuit. Moreover, when a contact failure occurs between the semiconductor layer, the drain electrode (6), and the source electrode (7), each of the thin film transistors (11) may become defective at the same time. In this case, the pixel becomes completely defective.

The present invention makes it possible to regenerate a thin film transistor (11) that has become defective due to the above problem to a certain extent, although it cannot be completely regenerated. The substrate (1) on which the thin film transistor (11) described above is formed includes a color filter (21), a light shielding film (22) and a counter electrode (23).
) is integrated with the substrate (24) formed thereon by a well-known method, and liquid crystal is injected into the space between them to complete a display panel for a projector. Light shielding film (22) As is well known,
It is arranged so as to overlap with the thin film transistor (11).

[0014] The display panel is subjected to a predetermined inspection to check whether or not the plurality of thin film transistors (11) are malfunctioning. For example, when various video signals are input to the thin film transistor (11) using a device such as a pattern generator, if the thin film transistor (11) malfunctions, the display electrode (9) becomes a white dot (or black dot). inform the observer.

Therefore, in the present invention, the source electrode (7) and the gate electrode (2) are short-circuited using a laser beam.
The defective display electrode (9) is turned ON and OFF to balance the surrounding contrast and regenerate it. That is, polarizing plates are placed above and below a display panel, and a black (or white) level signal is input to the panel from a pattern generator. Then, the defective thin film transistor (11
) displays a white (or black) point. Next, place the display panel on the stage of a microscope equipped with a YAG laser, etc.
Transmitted light is irradiated from the counter electrode substrate (24) side to bring a white (or black) point into the field of view of the microscope. Furthermore, the display electrode (9
) is white (or black), a region where the source electrode (7) and gate electrode (2) of the thin film transistor (11) overlap is irradiated with laser light from the substrate (1) side for a predetermined period of time. Then, the source electrode (7) is melted and a hole is formed in the insulating protective film (3), and some of the melted metal flows into the wall of the hole and is connected to the gate electrode (2). At this time, the laser energy is transferred to the source electrode (7
) and the thickness of the gate electrode (2), so that the source electrode (7) and the gate electrode (2) are melted and electrically connected. This is because even if the source electrode (7) and gate electrode (2) are melted and connected using laser light, if the light shielding film (22) on the opposing substrate (24) is melted by the laser light, the light shielding film (22) will melt as shown in FIG. A pinhole (31) is formed in the thin film transistor (11) to prevent malfunction of the thin film transistor (11) due to light leaking from the pinhole (31). For example, when the thickness of the light-shielding film is 1400 to 1500 Å, if the laser beam energy is about 20 J, the source electrode and gate electrode will be melted and the light-shielding film will not be damaged.

[0016] Also, the source electrode (7) and the gate electrode (2)
) It is effective to irradiate multiple locations with laser light to make the connection more reliable. In this embodiment, the thin film transistors are repaired using laser light after the display panel is completed, but the same modification can be performed even in an unfinished state. That is, by irradiating a laser beam onto the source electrode of the substrate on which the thin film transistor is formed, the source electrode and the gate electrode can be connected in the same way. However, in the inspection process in this case, although it is possible to inspect for disconnection defects in the drain line and gate line, it is difficult to determine whether each thin film transistor is good or bad, and in reality, inspection is performed on finished products.

[0017]

[Effects of the Invention] As detailed above, according to the present invention,
By connecting the source electrode and gate electrode of the defective TFT element using laser light, the defective TFT element can be removed.
Although the FT element cannot be completely regenerated, a defective TFT element can be driven to a black spot based on the signal applied to the gate line.

As a result, even if a defective TFT element occurs in a liquid crystal display panel for a projector used in normally white mode, it can be reproduced. Furthermore, in the present invention, in order to fuse and connect the source electrode and the gate electrode, a laser beam of energy that does not damage the light shielding film is irradiated, so that the light shielding film is not substantially damaged by the laser light and light leakage occurs. do not.

[Brief explanation of the drawing]

FIG. 1 is an enlarged plan view of essential parts of a liquid crystal display panel according to the present invention.

FIG. 2 is a sectional view taken along line AA in FIG. 1;

FIG. 3 is a cross-sectional view taken along the line AA in FIG. 1 when the light shielding film is damaged.

[Explanation of symbols]

(1) Insulating substrate (2) Gate electrode (3) Insulating protective film (4) Semiconductor layer (5) Passivation (6) Drain electrode (7) Source electrode (8) N+a-Si (9) Display electrode (10) Auxiliary capacitor electrode (21) Color filter (22) Light shielding film (23) Counter electrode (24) Substrate (31) Pinhole

Claims (2)

[Claims] 1. At least one thin film transistor having a semiconductor layer is arranged in rows and columns in correspondence with each pixel electrode made of a plurality of transparent conductive oxide films arranged in rows and columns on an insulating substrate, In a method of manufacturing an active matrix liquid crystal display panel in which a source electrode of a thin film transistor is connected to the pixel electrode corresponding to the transistor and is integrated with an insulating substrate on which a counter electrode is formed, energy of laser light is used. The source electrode and the gate electrode have a necessary size that penetrates the thickness of the source electrode and the gate electrode, and the light shielding film provided on the insulating substrate region on the opposite electrode side that overlaps with the thin film transistor is substantially damaged. A method for manufacturing a liquid crystal display panel, characterized by melting and conducting the liquid crystal display panel. 2. The method of manufacturing a liquid crystal display panel according to claim 1, wherein the source electrode is made of aluminum and the gate electrode is made of chromium.