JPH0470820A - Active matrix type flat plate display device - Google Patents

Abstract

PURPOSE:To prevent a picture element defect by connecting plural thin film transistors to one picture element in series and in parallel and constituting a switching element. CONSTITUTION:An intermediate electrode 6 is connected between the drain D1 of a thin film transistor (TFT) 311 and the source S2 of a TFT 312 which are connected in common, and the drain D3 of a TFT 321 and the source S4 of a TFT 322 which are connected in common. In this constitution, the TR 311 and TR 321 are connected in parallel and the TR 312 and TR 322 are also connected in parallel. A 1st switching element 310 and a 2nd switching element 320 are connected in series. If an open-circuit defect is caused by plural switching transistors in this constitution, the individual switching transistors are connected in parallel by connecting the intermediate electrode, so a driving voltage can be applied from a nondefective switching element group to a display element.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to flat panel display devices such as liquid crystal display devices, and in particular to active display devices in which each display element has an active element.
The present invention relates to a matrix type flat panel display device.

2. Description of the Related Art Conventional active matrix type flat panel display devices have been put to practical use mainly as image display devices for televisions. FIG. 4 shows a device equivalent circuit diagram of a conventional active matrix type flat panel display device. As shown in Figure 4, a conventional active matrix display device! is a signal electrode l that supplies a voltage corresponding to a display data signal, a scan electrode 2 that supplies a scan signal for line sequential scanning, and an active element that is controlled by control voltages from the signal electrode 1 and the scan electrode 2. It is composed of a thin film transistor 3 and a display element 4. Note that one pixel is composed of a portion 5 surrounded by a broken line and consisting of one thin film transistor 3 and one display element 4.

The signal electrode 1 and the scanning electrode 2 are arranged in a matrix, and the thin film transistor 3 has its source connected to the signal electrode 1 and its gate connected to the scanning electrode 2. For image display, a voltage corresponding to a display data signal is supplied to the source of each thin film transistor 3 via each signal electrode 1, and a selected scanning voltage is supplied to the gate of each thin film transistor 3 via a selected scanning electrode 1. . As a result, each thin film transistor 3 on the selected scan electrode is turned on all at once.
Image information is displayed by charging each liquid crystal display element 4 with a voltage corresponding to a display data signal, and even after the thin film transistor 3 is turned off, the information is retained for one frame period when the next information comes. Therefore, an image with good contrast and excellent display quality can be displayed. By the way, since one pixel is composed of one thin film transistor 3 for one liquid crystal display element 4, if a defect such as a short or open in the thin film transistor 3 occurs, the liquid crystal display element 4 will not be able to display normal information. This results in fatal pixel defects.

On the other hand, as a method of suppressing pixel defects as much as possible, there is a redundant configuration in which a plurality of switching elements are used for one pixel, as disclosed in, for example, Japanese Patent Laid-Open No. 62-91993. This is a redundant configuration in which two switching elements connected in series are operated in parallel for one pixel as shown in FIG. 5. In FIG. 5, it is composed of a first switching element 310 in which thin film transistors 311,312 are connected in series, and a second switching element 320 in which thin film transistors 321, 322 are connected in series. Fifth
In the figure, S indicates a source, G indicates a gate, and D indicates a drain. Further, each source St, 33 of the first switching element 310 and the second switching element 320 is connected to the signal electrode 1, and each gate GIG2 . G3. G4 is commonly connected to the scanning electrode 2, and drains D2 and D4 are commonly connected to the pixel electrode 9 of the display element 4. The basic operation regarding image display is the same as the conventional example shown in FIG. The first switching element 310 and the second
Since the switching elements 320 are connected in parallel to drive the display element 4, redundant operations include (1) an open defect in one of the thin film transistors 311, 312, 321,322, and (2) thin film transistor 31.
1,312 and two thin film transistor oven defects in either one of thin film transistors 321 and 322, (
3) It was effective against short-circuit defects in one thin film transistor in each of the first switching element 310 and the second switching element 320.

FIG. 6 shows a device equivalent circuit of another conventional active matrix type flat panel display device. The difference from the conventional example shown in FIG. 5 is that the first switching element 310 connects the display element 41 via the pixel electrode 91, and the second switching element 320
is a point where the display element 42 is driven via the pixel electrode 92.

Problems to be Solved by the Invention In such a conventional configuration, the first switching element 31
If an oven defect occurs in the thin film transistor 0 and the second switching element 320 at the same time, the display element 4 becomes completely open, resulting in a pixel defect.

In view of these points, the present invention provides an active transistor that prevents pixel defects by configuring a switching element by connecting a plurality of thin film transistors in series and parallel to one pixel.
An object of the present invention is to provide a matrix type flat panel display device.

Means for Solving the Problem In order to achieve this object, the present invention is an active matrix type flat panel display! consists of signal electrodes and scanning electrodes arranged in a matrix, and electrodes arranged within each matrix! The switching element is composed of a plurality of switching transistors, and the plurality of switching transistors are composed of a plurality of switching element groups consisting of an integrally formed series-connected switching element group, The input and output terminal portions of each switching transistor are connected by an intermediate electrode between the plurality of switching element groups to perform parallel connection.

Effect: With this configuration, if an oven defect occurs in multiple switching transistors, since the individual switching transistors are connected in parallel by connecting the intermediate electrodes, drive voltage can be applied to the display element from the group of switching elements without defects. I can do it.

On the other hand, if a short-circuit defect occurs in a plurality of switching transistors, normal display can be performed by cutting off the intermediate electrode connected to the switching transistor having the defect.

Embodiment FIG. 1 shows a device equivalent circuit diagram of an active matrix type flat panel display device according to a first embodiment of the present invention. The feature of the present invention is that in a redundant configuration with series-connected parallel operation similar to that shown in FIG.
The intermediate electrode 6 is connected between the source S2 and the commonly connected drain D3 of the thin film transistor 321 and source S4 of the thin film transistor 322. With this configuration, the thin film transistor 3]1 and the thin film transistor 321 are connected in parallel, and the thin film transistor 312
and the thin film transistor 322 are also connected in parallel, and the first switching element 310 and the second switching element 320 are connected in series and parallel. In addition, as will be described later, depending on the defect mode of the thin film transistor, the intermediate electrode 6 may be melted with a laser beam or the like to repair the pixel defect.
Switching element 310 and second switching element 32
0 can also be separated.

The operation of the active matrix type flat panel display device of this embodiment constructed as described above will be explained below. Table 1 shows the results of comparing the display state when the number of defective thin film transistors is one or two with the conventional example shown in FIG. In addition, each yl thin film transistor 11.3
12.321°322 is Tri, Tr2. Tr3. Tr
4, OP indicates an oven defect, and SH indicates a short defect. And each status is ○ (normal), × (bad)
, △ (normal in the oven of the intermediate electrode 6 due to repair).

(Left below) Table 1 Comparison of redundant configurations (1 pixel - 1 display element) As is clear from the results in Table 1, in this example, the number of defects in one thin film transistor is the same as in the conventional case, and the number of defects in one thin film transistor is the same as in the conventional case. Regarding defects in thin film transistors, it is advantageous over open defects,
In addition, repair defects can be made the same as in the conventional method by blowing the intermediate electrode 6 open with a laser beam or the like to repair it. From this point of view, it is comprehensively superior to conventional redundant configurations.

FIG. 2 shows the redundant device configuration in the first embodiment.
An example of a pattern diagram is shown.

The intersection of the signal electrode 1 and the scanning electrode 2 is insulated by the insulating layer 7, the thin film transistors 311 and 312 of the first switching element 310 are formed of the channel layer 81, and the thin film transistors 321 and 322 of the second switching element 320 are formed of the channel layer 81. It is formed by a channel layer 82.

The sub-scan electrodes 210 and 220 are arranged in a comb shape with respect to the scan electrode 2, and the sub-scan electrode 210 is connected to the thin film transistor 31.
1.321, and the sub-scanning electrode 220 becomes the gate electrode of the thin film transistors 312 and 322.

First switching element 310 and second switching element 3
20 are connected by an intermediate electrode 6 at a certain distance. When there is a need for repair due to the defect mode of the thin film transistor, the center portion of the patching mark that does not affect the thin film transistor etc. in an oven due to melting of the intermediate electrode 6 is set as the repair portion 60.

FIG. 3 shows a device equivalent circuit diagram of an active matrix type flat panel display device according to a second embodiment of the present invention. 1st
The difference from the embodiment is the first switch.

The switching element 310 connects to the display element 41 via the pixel electrode 91.
, the second switching element 320 drives the display element 42 via the pixel electrode 92.

The operation of the active matrix type flat panel display device of the second embodiment configured as described above will be explained below. Table 2 compares the conventional example shown in FIG. 6 with the second embodiment in the case where one pixel is composed of two display elements 41° and 42.

Table 2 Comparison of redundant configurations (1 pixel = 2 display elements) (However, The frame indicates that only 1/2 pixel can be displayed.

As is clear from the results in Table 2, in the second example, 1
No display defects occur for defects in thin film transistors. Also, regarding defects in two thin film transistors, 2
It has advantages over conventional methods, such as reducing pixel defects. 1
Assuming that up to /2 pixel defects can be tolerated, it can be said that the example is superior in terms of redundancy and display quality.

Note that in this embodiment, the switching elements 310.
320 is shown as having a configuration in which two series-connected thin film transistors are connected in parallel through the intermediate electrode 6, but basically a plurality of integrated switching elements each consisting of a plurality of series-connected thin film transistors are arranged side by side. , a configuration may be adopted in which a plurality of intermediate electrodes are arranged between each switching element.

First switching element 310 and second switching element 3
20 sources Sl, S3 are signal electrodes l, gates Gl, G
2. G3. G4 is connected to the same electrode such as the scanning electrode 2, but the source S1 and the gate 1 of the first switching element 310 are connected to adjacent electrodes arranged in a matrix (for example, left and right signal electrodes and upper and lower scanning electrodes). -G
1. G2 and the source S of the second switching element 320
3 and gate G3. G4 may be separated and connected. In addition, the configuration of a 1 pixel-2 display element is shown in FIG.
Although the configuration is taken within a region surrounded by the scanning electrodes 2, a configuration in which the signal electrodes 1 are symmetrically divided into upper and lower portions or a configuration in which the scanning electrodes 2 are symmetrically divided into upper and lower portions may be used. In addition, the configuration is not limited to a configuration of 1 pixel-2 display elements, but a configuration of 1 pixel=N display elements is also possible. In this embodiment, a liquid crystal display element is used as an example of the display element, but the display element is not limited to this.
It goes without saying that the present invention is effective for any display device that can be constructed of an active matrix type, including electroluminescent display devices (ELD), plasma display devices (FDP), and the like.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, defects in thin film transistors can be reduced by connecting a switching element group consisting of a plurality of series-connected thin film transistors in parallel via an intermediate electrode. Since defects in pixel display caused by this can be prevented, high-quality display images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a device equivalent circuit diagram of an actif matrix type flat panel display device according to a first embodiment of the present invention, FIG. 2 is a device pattern diagram of the same redundant configuration, and FIG.
FIG. 4 is a device equivalent circuit diagram of an active matrix flat panel display device according to an embodiment of the present invention; FIG. 4 is a device equivalent circuit diagram of a conventional active matrix flat panel display device;
The figure is a device equivalent circuit diagram of a conventional active matrix type flat panel display device with a redundant configuration, and FIG. 6 is a device equivalent circuit diagram of a conventional active matrix type flat panel display device. ■... Signal electrode, 2, 21.22... Scanning electrode, 210.220... Sub-scanning electrode, 3
11312.321.322... Thin film transistor, 4.41.42... Display element, 6...
...Intermediate electrode, 60...Repair part, 81.82
...Chanful layer, 9.91.92...
Pixel electrode. @ 2 Diagram 1 - 3 Roasted beef - Display index g - 4 Interruption 9 - 1 tttvM

Claims (4)

[Claims] (1) An active matrix type flat panel display device consisting of signal electrodes and scanning electrodes arranged in a matrix, and switching elements and display pixels arranged in each matrix, wherein the switching elements include a plurality of switching elements. The plurality of switching transistors are composed of a plurality of switching element groups consisting of integrally formed series-connected switching element groups, and the input and output terminal portions of each switching transistor are connected between the plurality of switching element groups. An active matrix type flat panel display device that is connected in parallel using intermediate electrodes. (2) The active matrix type flat panel display device according to claim 1, wherein the repair is performed by cutting the intermediate electrode. (3) The active matrix flat panel display device according to claim 1, wherein the final outputs of a plurality of switching element groups are commonly connected to one display element. (4) The active matrix type flat panel display device according to claim 1, wherein the final outputs of the plurality of switching element groups are commonly or independently connected to the plurality of blocks for the plurality of divided display elements.