JPH02294623A - Active matrix display device - Google Patents

Abstract

PURPOSE:To correct picture element defect by connecting a stand-by switching element and a signal line between a protection film which is isolated from a display medium and a substrate. CONSTITUTION:A connection part 25 were the extended end part 8a of the signal input terminal of the stand-by switching element 7 and branch line 8 branching from the signal line face each other closely across at least an insulating film 11 in a nonconductive state is formed and then coated with the protection film 17. When a picture element defect place is specified, the connection part 25 is irradiated with the light energy of laser light, etc., from outside through transparent substrates 1 and 20 and at the connection part 25, the extended end 8a of the signal input terminal of the stand-by switching element 7 and the branch wiring 8 branching from the signal line are connected electrically to each other by the laser irradiation. Further, the defective element 7 connected to a picture element electrode 5 can be cut by light energy irradiation and disconnected from the picture element electrode 5 when necessary. Consequently, the picture element defect caused by the switching element defect can be corrected.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a display device that performs display by applying a drive signal to display picture element electrodes via a switching element, and particularly relates to a display device that performs display by applying a drive signal to a display picture element electrode through a switching element. The present invention relates to an active matrix drive type display device that performs high-density display by arranging the display device.

(Prior Art) Conventionally, in liquid crystal display devices, EL display devices, plasma display devices, etc., display patterns are formed on the screen by selectively driving pixel electrodes arranged in a matrix. There is. A voltage is applied between a selected picture element electrode and a counter electrode facing the selected picture element electrode, and the display medium interposed therebetween is optically modulated. This optical modulation is visually recognized as a display pattern. As a method for driving picture element electrodes, an active matrix driving method is known in which individual independent picture element electrodes are arranged and a switching element is connected to each of the picture element electrodes and driven. The switching elements that selectively drive the picture element electrodes include TPT (thin film transistor) elements, MIM (metal-insulating layer-metal) elements, and M
OS transistor elements, diodes, varistors, etc. are generally known.

The active matrix drive method is capable of displaying images with a high level of image resistance, and has been put to practical use in liquid crystal televisions, word processors, terminal display devices for combination coaters, and the like.

(Problem to be solved by the invention) When performing high-density display using such a display device,
It is necessary to arrange a very large number of picture element electrodes and switching elements. However, the switching element may be formed as a malfunctioning element at the time of fabrication on the substrate. A picture element electrode connected to such a defective element will cause a picture element defect that does not contribute to display.

For example, a configuration for correcting pixel defects is disclosed in Japanese Patent Application Laid-Open No. 61-1
It is disclosed in Japanese Patent No. 53619. In this configuration, a plurality of switching elements are provided for each picture element electrode. One of the plurality of switch notching elements is connected to the picture element electrode, and the others are not connected to the picture element electrode. If a switching element connected to a picture element electrode is defective, the switching element is separated from the picture element electrode by a laser trimmer, an ultrasonic power cutter, or the like, and another switching element is connected to the picture element electrode. The switching element and the picture element electrode are connected by attaching a minute conductor using a dispenser or the like, or by coating a predetermined portion of the substrate with A us A 1 or the like.

Furthermore, JP-A-61-56382 and JP-A-59-
Japanese Patent No. 101693 discloses a configuration in which metal layers are electrically connected to each other by irradiating laser light to melt the metal.

The above defect correction must be performed on the active matrix substrate before the display device is assembled. The reason for this is that after the display device is completed, some of the metal evaporated or melted by laser beam irradiation gets mixed into the display medium, such as liquid crystal, interposed between the picture element electrode and the counter electrode.
This is because the optical characteristics of the display medium are significantly deteriorated.

Therefore, all of the conventional pixel defect correction methods described above are applied in the active matrix substrate manufacturing process before assembly of a display device, that is, before encapsulation of a display medium.

However, it is extremely difficult to detect pixel defects at the stage of manufacturing an active matrix substrate.

Especially in large display devices with 100,000 to 500,000 picture elements or more, extremely high-precision measuring equipment is required to detect the electrical characteristics of all picture element electrodes and discover defective switching elements. Must. Therefore, the inspection process becomes complicated and mass productivity is hindered. Therefore, this results in higher costs. For these reasons, the reality is that in large display devices with a large number of picture elements, it is not possible to correct pixel defects in the substrate using the above-mentioned laser beam.

The present invention has been made to solve these problems. That is, an object of the present invention is to provide an active matrix display device in which a pixel defect caused by a defective switching element can be corrected while the display device is in a state where the position of the pixel defect can be easily identified.

(Means for Solving the Problems) An active matrix display device of the present invention includes a pair of substrates, at least one of which is translucent, and is inserted between the substrates and has optical characteristics modulated in response to an applied voltage. A display medium, picture element electrodes arranged in a matrix on the inner surface of one of the pair of substrates, a switching element and a preliminary switching element each electrically connected to the picture element electrodes, and the switching element. and a scanning line connected to the auxiliary switching element, and a signal line connected to the switching element, and an extended end of the signal input terminal of the auxiliary switching element and a branch wiring branched from the signal line. However, the above-mentioned object is achieved by forming connection portions that are disposed close to each other in a non-conducting state with at least an insulating film interposed therebetween, and the connection portions are covered with a protective film.

(Function) By driving the active matrix display device having the above-mentioned configuration over the entire surface, it is possible to easily confirm the position where a pixel defect occurs. By driving all picture element electrodes, the corresponding display medium produces optical modulation in accordance with the driving voltage. However, if the switching element is defective, even if this optical modulation is incomplete, it can be easily identified using a magnifying lens or the like.

When a pixel defective site is identified, light energy such as a laser beam is irradiated from the outside to the connecting portion through the light-transmitting substrate. At the connection part, the extension end of the signal input terminal of the preliminary switching element and the branch wiring branched from the signal line are electrically connected to each other by laser beam irradiation. In this way, the spare TFT 7 and the signal line are electrically connected via the connecting portion.

Furthermore, if necessary, a defective switching element connected to a picture element electrode can be cut off by irradiation with light energy and separated from the picture element electrode.

Since the connecting portion is covered with a protective film, molten metal and the like will not be mixed into the display medium, and the characteristics of the display medium will not deteriorate. That is, since the connection between the preliminary switching element and the signal line described above is performed between the protective film and the substrate that are separated from the display medium, pixel defects can be corrected without adversely affecting the display medium. .

(Example) The present invention will be described below with reference to an example. FIG. IA shows an active matrix substrate used in an embodiment of the display device of the present invention. The structure of each cross section taken along lines B-BIN and C-C in FIG. IA is shown in FIG. IB and FIG. IC. Ta205, Al20, Sl3N on glass substrate 1
The base coat film 2 consisting of A, etc. has a thickness of 3000 to 90 mm.
Gate bus wiring 3 which supplies scanning signals and second bus wiring 4 which supplies data signals are formed by 00 people.
are arranged in a grid. The gate bus wiring 3 is generally formed of a single layer of metal such as Ta, AI, TI, Nl, Mo, or a multilayer of these metals, but Ta is used in this embodiment. The source bus wiring 4 is also made of gold ash, but
In this embodiment, T1 is used. A base insulating film 11, which will be described later, is interposed at the intersection of the gate bus line 3 and the source bus line 4. A transparent conductive film (■T
A pixel electrode 5 consisting of pixel electrode 5 is provided, forming a matrix pixel pattern. A TFT 6 is arranged near the corner of the picture element electrode 5, and the TFT 6 and the picture element electrode 5 are electrically connected by a drain electrode l6. Picture element electrode 5
A spare TFT 7 is placed near the other corner of the
7 and the picture element electrode 5 are electrically connected by a drain electrode 16a. The TFT 6 and the spare TFT 7 are arranged in parallel on the gate bus wiring 3, and the source electrode 15 of the TFT 6 and the source bus wiring 4 are connected by a branch wiring 8. The source electrode 15a of the preliminary TFT 7 is guided to the connection portion 25 by the source electrode extension end 8a. In the connecting portion 25, the source electrode extension end 8a is opposed to the branch wiring 8 in a non-conducting state. Therefore, among the two TFTs 6 and 7, TFT
Only the FT8 is electrically connected to the source bus wiring 4, and the spare TFT7 is not connected to the source bus wiring 4.

Details of the cross-sectional configuration of the connecting portion 25 will be described later.

The cross-sectional configuration near the TFT 6 will be explained with reference to FIG. IB.

Note that the configuration of the preliminary TFT7 is also the same as that of the TFT6. A T film obtained by anodizing the surface of the gate electrode 9 is placed on the Ta gate electrode 9 formed as a part of the gate bus wiring 3.
A gate insulating film 10 made of a203 is formed.

From above, SiN, which also functions as a gate insulating film, is shown.
, (for example, Si3N4) is deposited over the entire surface of the base. On the base insulating film 11, an intrinsic half i12 of amorphous silicon (a-SI) and a semiconductor layer protection film 13 made of SiNy, bz for protecting the upper surface of the intrinsic semiconductor layer 12 are sequentially deposited.

Furthermore, from above, a-81 is formed to obtain ohmic contact with the source electrode and drain electrode that will be formed later.
An n-type semiconductor layer 14 consisting of is laminated. A source electrode l5 and a drain electrode 16 are provided on the n-type semiconductor layer 14.
is formed. Source electrode 15 and drain electrode 1
6 consists of Ti%N1, A1, etc.

Is the picture element electrode 5 a pattern on the base insulating film 11? will be accomplished. The appropriate thickness of the base insulating film 11 is about 1500A to 6000A, but in this embodiment, the thickness is about 2000A to 350A.
It is set to 0 people. A protective film 7 made of SiN (SiN) is formed on the entire surface of the substrate, covering the upper surfaces of the TFT 6 and the picture element electrode 5, and an alignment layer 19 for regulating the orientation of liquid crystal molecules 18 is deposited on the protective film 17. The thickness of the membrane 17 is 20
Approximately 00 to 1000 people is appropriate, but in this embodiment, it is set to around 5000 people. Base insulating film 1
1 and protective film l7 are SIO8, "ra" in addition to SINX.
2o, A120, or other oxides or nitrides. The protective film 17 is not formed on the entire surface of the substrate,
A window-opening structure may be used in which only the portions not directly involved in display, such as the TFT 6, spare TFT 7, and bus wiring, are covered and the central portion of the picture element electrode 5 is removed.

On the inner surface of the other glass substrate 20 facing the glass substrate 1 on which the picture element electrodes 5 are formed, a color filter 21, a counter electrode 22, and a distribution layer 23 are formed in an overlapping manner. A black matrix (not shown) is provided around the color filter 2l as necessary.

Twisted nematic liquid crystal molecules 18 are sealed between the pair of glass substrates 1 and 20 as a display medium. The orientation of the liquid crystal molecules 18 is changed in response to the voltage applied between the picture element electrode 5 and the counter electrode 22, and optical modulation is performed. This optical modulation is visually recognized as a display pattern.

The cross-sectional configuration of the connecting portion 25 will be explained using FIG. 1C. A joint metal layer 24 is formed on the base coat film 2.

The shape of the joint metal layer 24 is rectangular in plan view, as shown in FIG. IA. The joint metal 11i24 is made of Ta, AI, TI, Nl, Mo, etc., like the gate bus wiring 3, and can be patterned at the same time as the gate bus wiring 3 is formed. The base insulating film 11 described above is deposited on the joint metal layer 24. On the base insulating film II, there is a pre-NTFT
Source electrode extension end 8a connected to source electrode 15 of No. 7
and a technical wiring 8 connected to the source bus wiring 4 are placed. The source electrode extension end 8a and the branch wiring 8 are separated from each other and maintain a non-conducting state. Therefore, reservation @T
FT7 is not electrically connected to source bus wiring 4. The source electrode extension end 8a and the branch wiring 8 are protected by a protective film l7.
completely covered by.

Joint metal layer 24, source electrode extension end 8a and branch wiring 8
The base insulating film 11 located between these metal layers and wiring functions as an interlayer insulating film between these metal layers and wiring. A thickness of 1,000 to 7,000 is suitable for the thickness of the interlayer insulating film, but in this example, the base insulating film 11, which also functions as the gate insulating film of TFTs 6 and 7, is used, so as mentioned above, The number is set at 2,000 to 3,500 people.

The protective film 17 is used to electrically connect the technical wiring 8 and the source electrode extension end 8a in a state where they are separated from the liquid crystal molecules 18 which are the display medium. Therefore, the appropriate thickness of the protective film 17 is about 1,500 to 15,000. In this embodiment, since a protective film for TFTs 6 and 7 is used, the thickness thereof is set to about 5,000 layers.

A driving voltage is applied from all of the gate bus wiring 3 and ground bus wiring 4 of the liquid crystal display device having the above configuration to all the pixel electrodes 5 via the TFT 6, thereby driving the entire display device. When the display device is driven in this manner, pixel defects are easily visible.

If a pixel defect occurs due to a defect in the TFT 6, it can be easily corrected using the connecting portion 25. FIG. 2 shows a cross-sectional view of the connecting portion 25 used to correct pixel defects. As shown by the arrow 26 in FIG. 2, the joint metal scrap layer 24 is irradiated with laser light, infrared rays, electron beams, or other energy from the outside through the lower glass substrate 1.

In this example, YAG laser light was used. When the branch wiring 8, the base insulation film 1l, and the joint metal layer 24 overlap, when the laser beam is irradiated, dielectric breakdown of the base insulation film 11 occurs, and the branch wiring R8 and the joint metal layer 24 are melted and connected to each other. It becomes conductive. Similarly, dielectric breakdown of the base insulating film 11 also occurs in the overlapping portion of the source electrode extending end 8a, the base insulating film l1, and the joint metal ash layer 24, and the source electrode extending end 8a and the joint metal layer 24 overlap each other. They are fused and connected to become electrically conductive. In this way, the branch wiring 8 and the source electrode extension end 8a are electrically connected via the joint metal layer 24, and the preliminary TFT 7 is driven by the source bus wiring 4. In this example, the laser light was irradiated from the glass substrate l side, but
The laser beam may be irradiated from any side of the substrate as long as it is a substrate that transmits the laser beam.

Even if pixel defects are repaired using laser light in this way, since the protective film 17 is formed above the connection portion 25, molten metal will not get mixed into the liquid crystal display medium. do not have. Furthermore, since the protective film l7 is a transparent insulator, the laser light passes through it. Therefore, the protective film l7 is not destroyed by the laser beam. Although the liquid crystal layer near the portion irradiated with the laser beam becomes cloudy, this cloudiness disappears and the original state is restored, so that there is no deterioration in image quality.

If it is necessary to separate the TFT 6 from the picture element electrode 5 due to poor insulation of the TFT 6, the drain electrode l6 portion of the TFT 6 is irradiated with a laser beam and the portion is cut. By separating the TFT 6 and the picture element electrode 5, the picture element electrode 5 is normally driven by the preliminary TFT 7.

FIG. 3 shows a plan view of an active matrix IJ substrate used in another embodiment of the present invention. In this example, TFT6
The positions of the auxiliary TFT 7 and the spare TFT 7 are reversed from those in the embodiment shown in FIG. IA. The connecting portion 25 is provided between the gate bus wiring 3 and the branch wiring 8. Similar to the embodiment shown in FIG.
In a rectangular area surrounded by the gate bus wiring 3 and the source bus wiring 4, a picture element electrode 5 made of a transparent electrode (IT◯) is provided. A TFT 6 and a spare TFT 7 are arranged near two corners of the picture element electrode 5, respectively, and the TFTs 6 and 7 and the picture element electrode 5 are electrically connected by drain electrodes 16 and 16a, respectively.

The configuration of TFTs 6 and 7 is similar to that shown in FIG. IB. The TFT 6 and the preliminary TFT 7 are arranged in parallel on the gate bus wiring 113, and the TFT 8 is connected to the source bus wiring 4 by the technical wiring 8. Pre@TFT7 source electrode 1
5a is guided to the connection portion 25 by the source electrode extension end 8a. In the connecting portion 25, the source electrode extension end 8a is opposed to the branch wiring 8 in a non-conducting state. Therefore, TFT
Among the TFTs 6 and 7, only the TFT 6 is electrically connected to the source bus wiring 4, and the pre-TFT 7 is not connected to the source bus wiring 4.

A cross-sectional view of the connecting portion 25 along line c'-c' in FIG.
It is similar to Figure IC.

In the case of this embodiment as well, as in the embodiment of FIG.
By irradiating the TFT 5 with laser light or the like, pixel defects caused by defects in the TFT 6 can be corrected.

The configuration of the connecting portion 25 may be the configuration shown in FIG. 4 or 5 in addition to the configuration shown in FIG.

In the configuration shown in FIG. 4, a through hole 27 is provided in the base insulating film 11, and the joint metal contact 24 and the source electrode extension end 8a are electrically connected in advance. If a defect occurs in the TFT 6, only the overlapping portion of the branch wiring 8 and the joint metal layer 24 is connected using optical energy. In the configuration shown in FIG. 5, the joint metal layer 24 is not provided, and the source electrode extension end 8a is placed directly above the branch wiring 8 with the base insulating film 11 in between. If a defect occurs in the TFT 6, the source electrode extension end 8a may be damaged by light energy irradiation.
and the branch wiring 8 are directly fused and connected.

In FIG. 4, the through hole 27 may be provided on the side of the branch wiring 8, and the branch wiring 8 and the joint metal scrap layer 24 may be connected in advance. In this configuration, only the overlapping portion of the source electrode extension end 8a and the joint metal layer 24 is connected by laser beam radiation. Further, in FIG. 5, a configuration may be adopted in which the technical wiring 8 is formed on the source electrode extension end 8a via the base insulating film 11. Furthermore, in any of the embodiments, the base coat film 2 does not necessarily have to be provided and can be omitted.

Although each of the above embodiments shows a transmissive liquid crystal display device,
The present invention can be similarly applied to reflective display devices. Furthermore, in the above embodiments, an active matrix liquid crystal display device using TPT has been described, but the present invention is not limited thereto. The present invention is also applicable to a wide range of display devices using various switching elements such as MIM elements, diodes, and varistors. Furthermore, the present invention can also be applied to various display devices using a thin film light emitting layer, a dispersed EL light emitting layer, a plasma light emitter, etc. as a display medium.

(Effects of the Invention) The active matrix display device of the present invention is capable of correcting pixel defects caused by defective switching elements while the display device is in a state where the location of the pixel defect can be easily identified. It becomes easy and mass production is ensured. Therefore, it contributes to cost reduction as a display device.

4. Figure IA is a plan view of an active matrix substrate used in an embodiment of the display device of the present invention, Figure IB and IC
The figure is a cross-sectional view of a display device using the active matrix substrate of Figure IA taken along the lines B-B and C-C in Figure IA, respectively. FIG. 3 is a cross-sectional view of the connecting portion used, and FIG. 4 is a plan view of an active matrix substrate used in another embodiment of the present invention.
5 and 5 are cross-sectional views showing other embodiments of the connecting portion.

1, 20... Glass substrate, 3... Gate bus wiring, 4... Source bus wiring, 5... Picture element electrode, 6...
・T F T, 7... Spare TPT, 8... Branch wiring,
8a source electrode extension end, 9... gate electrode, 11...
・Base insulating film, 15, 15a...source electrode, !
6, 16a... Drain electrode, 17... Protective film,
18...Liquid crystal molecules, 19,23...Alignment layer, 2
DESCRIPTION OF SYMBOLS 1... Color filter, 22... Counter electrode, 24...
...Joint metal layer, 25...Connection part.

that's all

Claims (1)

[Claims] 1. A pair of substrates, at least one of which is translucent;
a display medium inserted between the substrates and whose optical characteristics are modulated in response to an applied voltage; pixel electrodes arranged in a matrix on the inner surface of one of the pair of substrates; and the pixel electrodes. a switching element and a backup switching element electrically connected to each other; a scanning line connected to the switching element and the backup switching element; and a signal line connected to the switching element; A connecting portion is formed in which the extending end of the signal input terminal of the element and a branch wiring branched from the signal line are placed close to each other in a non-conducting state with at least an insulating film interposed therebetween, and the connecting portion is covered with a protective film. active matrix display device.