JPH03239230A - Active matrix substrate - Google Patents

Abstract

PURPOSE:To lessen the lowering of an opening rate by setting the area that a spare switching element occupies on a substrate smaller than the area that a switching element occupies. CONSTITUTION:The area that the spare switching element 4 occupies on the substrate is set smaller than the area that the switching element 3 occupies. The length in the extending direction of a gate bus stay 8 of a spare TFT 4 formed on a gate bus stay 8 is set at 1/2 that of a TFT 3. The widths of the TFT 3 and the spare TFT 4 are equal and, therefore, the area that the spare TFT 4 occupies on this substrate is half the area that the TFT 3 occupies on the substrate. The picture element defect by the defect of the switching element is corrected in this way and the lowering of the opening rate is lessened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an active matrix substrate for configuring a display device in combination with a display medium such as a liquid crystal. The present invention relates to an active matrix substrate.

(Prior Art) Active matrix display devices have been rapidly developed in recent years because they provide higher image quality than conventional simple matrix display devices.

On an active matrix substrate used in an active matrix display device, picture element electrodes are arranged in a matrix, and a switching element is connected to each picture element electrode. Examples of switching elements include thin film transistors (hereinafter referred to as "TFTJ"), MOS transistors, MIM (metal-insulating layer-metal) elements, diodes,
Varistors and the like are commonly used.

The TPT provided on each picture element electrode on the active matrix substrate is formed by repeating a thin film forming process and a patterning process. It is difficult to form all TPTs formed through such a large number of steps without defects. Defects in TPT cause pixel defects, leading to a decrease in the yield of active matrix substrates.

Extra TPT on each pixel electrode to correct pixel defects
Active matrix substrates equipped with 1-2- are used. In addition to the TPT electrically connected to the picture element electrode, a spare TPT is formed on this substrate. The spare TPT is not electrically connected to the picture element electrode, but is provided close to the picture element electrode so that it can be connected to the picture element electrode later.

FIG. 2 shows an example of such a conventional active matrix substrate. A large number of parallel gate bus lines 1 are formed on an insulating substrate, and a large number of source bus lines 2 are formed to cross the gate bus lines 1. Gate bus wiring 1
In the area surrounded by the source bus wiring 2 and the source bus wiring 2, there is a picture element electrode 5.
is formed. A gate bus branch line 8 branches along the source bus line 2 from near the intersection of the gate bus line 1 and the source bus line 2. There is a T on gate bus branch line 8.
A PT3 and a spare TFT4 are formed.

The lengths of the TPT 3 and the spare TFT 4 in the extending direction of the gate bus branch line 8 are made equal. Also, since the widths of TPT3 and spare TFT4 are equal, TPT3 and spare TFT4
occupy the same area on this substrate.

3- The source electrodes of TPT3 and spare TFT4 are connected to source bus wiring 2. A drain electrode of the TPT 3 is electrically connected to the picture element electrode 5.

The drain electrode of the spare TFT 4 is provided with a spare pad 6 having the same width as the width of the drain electrode in the extending direction of the gate bus branch line 8.
are electrically connected. A connection pad 7 having a width smaller than that of the spare pad 6 is electrically connected to the spare pad 6 . A picture element electrode 5 is superimposed on the connection pad 7 with an insulating film interposed therebetween. Therefore, the preliminary TFT 4 and the picture element electrode 5
is not electrically connected. With this configuration, the picture element electrode 5 is driven only by the TPT 3.

In this active matrix substrate, picture element defects caused by defects in the TPT 3 are corrected as follows. If the pixel defect is caused by an ON failure of the TPT 3, that is, a defect in which the video signal is not sufficiently applied to the pixel electrode 5, laser light is irradiated to the overlapped portion of the connection bar, door, and pixel electrode 5. This destroys the insulating film located between them. When the insulating film is destroyed, the connection pad 7 is electrically connected to the picture element electrode 5, and therefore the spare TFT 4 is electrically connected to the picture element electrode 5. With such a connection, the picture element electrode 5 having a picture element defect is driven by the spare TFT 4. If the pixel defect is caused by an OFF defect in the TPT3, that is, a defect in which the video signal applied to the pixel electrode 5 is not sufficiently retained, the spare TFT 4 is used as a pixel as in the case of the ON defect described above. connected to the electrode 5;
Further, the TPT 3 and the picture element electrode 5 are disconnected. This cutting is performed, for example, by irradiating a laser beam along line BB' in FIG. As described above, the picture element electrode 5 is driven only by the preliminary TFT 4.

(Problems to be Solved by the Invention) Correcting pixel defects as described above improves the yield of active matrix substrates, but it also has the following drawbacks. The spare TFT4 is used in place of the TPT3 when the TPT3 is defective. Therefore, spare TFT4 is designed to have the same performance as TPT3. That is, the area occupied by the spare TFT 4 on the substrate is designed to be the same as that of the TPT 3. In a substrate having such a spare TPT, the area of the picture element electrode is smaller than that of a substrate not having a spare TPT, and the aperture ratio is lowered. A decrease in the aperture ratio is undesirable because it causes a decrease in image quality.

Such drawbacks become more noticeable as the number of picture element electrodes increases. That is, as the number of picture element electrodes increases, the number of bus lines also increases, and the time during which an ON signal is applied to one bus line becomes shorter.

If the application time of the ON signal becomes shorter, it becomes impossible to apply a sufficient video signal to the picture element electrode, so it is necessary to increase the width of the channel layer of the TPT. Therefore,
The area occupied by the TPT on the substrate increases. In active matrix substrates with a huge number of pixel electrodes, TP
By providing a spare TPT in addition to the T, the aperture ratio will be significantly reduced.

The present invention solves the above-mentioned problems, and an object of the present invention is to provide an active matrix substrate in which the reduction in aperture ratio is reduced even when a preliminary switching element is provided. It is.

(Means for Solving the Problems) The active matrix substrate of the present invention includes picture element electrodes formed in a matrix on an insulating substrate, a switching element electrically connected to the picture element electrodes, and a switching element electrically connected to the picture element electrodes. an active matrix substrate having a preliminary switching element insulated proximity to an elementary electrode, the area occupied by the preliminary switching element on the substrate being smaller than the area occupied by the switching element on the substrate; The above objective is achieved.

Further, the switching element and the preliminary switching element may be thin film transistors (Embodiments) The present invention will be described below with reference to embodiments.

FIG. 1 shows a plan view of an embodiment of an active matrix substrate of the present invention. A large number of parallel gate bus lines 1 are formed on an insulating substrate, and a large number of source bus lines 2 are formed to cross the gate bus lines 1. A picture element electrode 5 is formed in a region surrounded by the gate bus wiring 1 and the source bus wiring 2. A gate lot branch line 8 branches along the source bus line 2 from near the intersection of the gate bus line 1 and the source bus line 2. A TFT 3 and a spare TFT 4 are formed on the gate bus branch line 8 . Spare T
The length of the gate bus branch line 8 of FT4 in the extension direction is TFT
It is set to one half of that of 3. Also, TFT3
Since the widths of the spare TFT 4 and the spare TFT 4 are equal, the area occupied by the spare TFT 4 on this substrate is one half of the area occupied by the TFT 3 on this substrate.

The source electrodes of the TFT 3 and the spare TFT 4 are connected to the source bus wiring 2. The drain electrode of the TFT 3 is electrically connected to the picture element electrode 5.

The drain electrode of the spare TFT 4 is provided with a spare pad 6 having the same width as the width of the drain electrode in the extending direction of the gate bus branch line 8.
are electrically connected. A connecting pad 7 having a width smaller than that of the spare pad 6 is electrically connected to the spare pad 6 . A picture element electrode 5 is superimposed on the connection pad 7 with an insulating film interposed therebetween. Therefore,
The preliminary TFT 4 and the picture element electrode 5 are not electrically connected. With such a configuration, the picture element electrode 5 is driven only by the TFT 3.

In this active matrix substrate, picture element defects caused by defects in the TFT 3 are corrected in the same manner as in the conventional example described above. If the pixel defect is caused by an ON failure of the TFT 3, a laser beam is irradiated to the overlapping portion of the connection pad 7 and the pixel electrode 5, and the insulation located between the connection pad 7 and the pixel electrode 5 is removed. Destroy the membrane. When the insulating film is broken, the connection pad 7 is electrically connected to the picture element electrode 5, and therefore the spare TFT 4 is electrically connected to the picture element electrode 5.

With such a connection, the picture element electrode 5 having a picture element defect is driven by the spare TFT 4. Pixel defect is TF
If it is caused by an OFF failure of T3, the spare TFT 4 is connected to the picture element electrode 5, and the TFT 3 and the picture element electrode 5 are further disconnected, as in the case of the above-mentioned ON failure. This cutting is performed, for example, by irradiating a laser beam along line AA' in FIG. As described above, the picture element electrode 5 is driven only by the preliminary TFT 4.

In such an active matrix substrate, there are only a few pixel defects due to defects in the TFT 3 that occur during the manufacturing process.

Moreover, they do not occur concentrated in one area, but are scattered. Therefore, it is sufficient that the pixel defects are corrected to the extent that they are unrecognizable when viewing the entire displayed image. The present invention has been made with attention to this point. normal T
The FT3 is kept in an ON state for a predetermined time by the ON signal of the gate bus wiring 1. When the TFT 3 is turned on, a video signal is applied from the source bus wiring 2 to the picture element electrode 5.

Generally, the ratio of the voltage applied to the picture element electrode 5 to the signal voltage applied to the source bus wiring 2 is called a charging rate.

In this embodiment, the TF
The area that T3 occupies on this substrate is set. That is, the length 9 =10- of the channel layer of the TFT 3 in the extending direction of the gate bus branch line 8 is set so as to achieve the above charging rate. If the charging rate is low, not only will images not be faithfully reproduced, but display irregularities will also occur.

On the other hand, the area occupied by the spare TFT 4 on this substrate is one half of the area occupied by the TFT 3 on this substrate. In this embodiment, since the widths of the TFT 3 and the spare TFT 4 in the extending direction of the gate bus line 1 are equal, the length of the channel layer in the extending direction of the gate bus branch line 8 of the spare TFT 4 is T
It is one half of that of FT3. Therefore, the pixel electrode 5 which has a pixel defect due to a defect in the TFT 3 and is driven only by the TFT 4 cannot be charged to a sufficient charging rate compared to the pixel electrode 5 which is driven by a normal TFT 3. . However, as mentioned above, the pixel electrodes 5 that have pixel defects due to defects in the TFTs 3 are scattered, so if a certain level of voltage is applied to the pixel electrodes 5, it will hardly affect the display. . The length of the gate bus branch line 8 of the spare TFT4 in the extending direction is half that of the TFT3.
If so, then 11- It was confirmed that it had almost no effect on the display.

In this embodiment, the area occupied by the preliminary TFT 4 on the substrate is T
Although the case where it is one half of that of FT3 has been described, the present invention is not limited to this. Reserve TPT
If the area occupied on the substrate is substantially smaller than that of TPT, it is within the scope of the present invention.

Furthermore, in this embodiment, an active matrix substrate using TPT was explained as a switching element.
It can also be applied to active matrix substrates using transistors (MOS), MIM elements, diodes, varistors, etc.

(Effects of the Invention) In the active matrix substrate of the present invention, pixel defects due to defective switching elements can be corrected, and the decrease in aperture ratio is reduced. Therefore, according to the invention:
The yield of active matrix substrates can be improved without degrading the image quality of the display device.

4. of. FIG. 1 is a plan view of an embodiment of the active matrix substrate of the present invention, and FIG. 2 is a plan view of a conventional active matrix substrate.

1... Gate bus wiring, 2... Source bus wiring, 3
... TFT, 4... Spare TFT, 5... Picture element electrode, 6... Spare pad, 7... Connection pad, 8...
Gate bus branch line.

that's all

Claims (1)

[Claims] 1. A picture element electrode formed in a matrix on an insulating substrate, a switching element electrically connected to the picture element electrode, and a spare that is insulated and adjacent to the picture element electrode. An active matrix substrate comprising: a switching element, wherein an area occupied by the preliminary switching element on the substrate is smaller than an area occupied by the switching element on the substrate.