JPH0792573B2 - Display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a display device that performs display by applying a drive signal to a display pixel electrode via a switching element, and in particular, the pixel electrodes are arranged in a matrix. The present invention relates to an active matrix drive type display device which is arranged in a matrix to perform high density display.

<Prior Art> Conventionally, in a liquid crystal display device, an EL display device, a plasma display device, and the like, a display pattern is formed in a pixel shape by selecting display picture elements arranged in a matrix. As a display pixel selection method, the active matrix drive method, in which individual picture elements are arranged with independent electrodes and a switching element is connected to each of the picture element electrodes to drive display, is capable of high-contrast display. It has been put to practical use in televisions, word processors, and computer terminal displays. As a switching element for selectively driving the pixel electrode, a TFT (thin film transistor) element, MI
M (metal-insulating layer-metal) element, MOS transistor element,
Diodes, varistors, etc. are generally used, and by switching the voltage applied between the pixel electrode and the counter electrode facing it, the liquid crystal, EL light-emitting layer or plasma light-emitter, etc., which is interposed therebetween, The optical modulation is visually recognized as a display pattern.

<Problems to be Solved by the Invention> When a switching element is connected to a pixel electrode for high-density display, it is necessary to arrange a large number of pixel electrodes and switching elements. However, the switching element may be formed as a malfunctioning element when it is manufactured on the substrate, and a pixel electrode connected to such a malfunctioning element becomes a defect that does not contribute to display. It is extremely difficult to detect this defect at the manufacturing stage of the picture element electrode substrate, and it is almost impossible for a large display panel having 100,000 to 500,000 picture elements or more.

As a technique for repairing a pixel defect, as shown in JP-A-61-153619, a plurality of transistors are provided for each pixel electrode, and only one transistor is connected to the pixel electrode. If the transistor connected to the electrode is defective, a technique has been proposed in which the transistor and the pixel electrode are cut by a laser trimmer or an ultrasonic cutter and the other transistor is connected to the pixel electrode. Further, in this case, as a connecting means between the transistor and the pixel electrode, a method of attaching a minute conductor with a dispenser,
A method of arranging Au, Al or the like on a substrate and irradiating a laser beam to coat Au, Al or the like on a predetermined portion is exemplified. Further, JP-A-61-56382 and JP-A-59-101693 disclose a technique of electrically connecting metal layers by irradiating a laser beam to dissolve a metal.

However, the above-mentioned conventional defect repairing technique is a method in which after detecting a defect, metal is evaporated and redeposited or locally melted by laser irradiation to electrically connect, and a transistor substrate manufacturing process before assembling a display panel is performed. Is used in. The reason is that after the display panel is completed, a part of the metal evaporated or melted by the laser light irradiation is mixed in the display medium such as liquid crystal interposed between the pixel electrode and the counter electrode or the laser light is emitted. It has been considered that the light energy reduces the alignment ability of the liquid crystal, resulting in a marked deterioration of the optical characteristics of the display medium. Therefore, any of the conventional pixel defect repairing methods described above is applied in the transistor substrate manufacturing process before the display panel is assembled, that is, before the display medium is inserted. However, as described above, it is very difficult to detect transistor defects in the transistor substrate manufacturing stage, and it is necessary to electrically inspect the operating characteristics of all the transistors arrayed according to the number of pixel electrodes. Requires a great deal of time and labor, and requires the use of extremely high-precision measuring machines and the like. As a result, the inspection process becomes complicated, mass productivity is hindered, and the cost is increased, and it cannot be used for a large-sized display panel having a large number of picture elements.

<Means for Solving Problems> In view of the above problems, the present invention has a structure capable of easily detecting a malfunction of a switching element and easily repairing a pixel defect caused thereby. And a display device having the above. That is, in the display device of the present invention, a display medium whose optical characteristics are modulated in response to an applied voltage is inserted between a pair of upper and lower substrates at least one of which is transparent, and the inner surface of the one substrate is A plurality of picture element electrodes arranged in a matrix for applying a voltage to the display medium to generate a display pattern for each picture element, a switching element electrically connected to an extended end portion of the picture element electrode, and a connecting portion are provided. Preliminary switching elements arranged in non-conduction with the extended ends of the picture element electrodes via an insulating layer are arrayed, and the opposite inner surface of the other substrate applies a voltage to the display medium in cooperation with the picture element electrodes. A display device in which electrodes are formed, and the display medium displays normal picture elements different from each other in a normal picture element and a defective picture element in response to a voltage applied to the picture element electrode when a picture element defect is detected. Pattern and defective pixel display pattern The connecting portion and the extended end portion of the picture element electrode, which are opposed to each other via the insulating layer, constitute a picture element correcting section for correcting the defective picture element, and the picture element correcting section is the transparent element. The insulating layer and the connecting portion or the extended end portion of the pixel electrode are mutually melted by the energy ray irradiated through the substrate having a light property, and at the time of solidification, the connecting portion and the extended end portion of the pixel electrode become It is characterized in that it is made of a member that is electrically connected and is isolated from the display medium through an insulating protective film. Further, in the display device of the present invention, the display medium is inserted between the pair of upper and lower substrates, and the pixel electrode and the counter electrode for applying a voltage to the display medium are internally provided. A defective picture element can be easily optically detected from a large number of picture elements, and at least one of a pair of upper and lower substrates constituting a display panel is a translucent substrate for the defective picture element. Light energy is externally radiated through the light-transmitting substrate to the picture element modifying section formed between the electrode of the pre-switching element side and the picture element electrode portion, and the insulating layer between them is melt-fractured, and the pre-switching element. And the pixel electrodes can be electrically connected.

<Operation> The display device having the above structure is driven in full, that is, by applying a drive voltage simultaneously between all the pixel electrodes and the counter electrodes formed on the inner surface of the other display panel substrate facing the pixel electrodes. A defect of the switching element connected to the element electrode can be optically easily detected. If all pixel electrodes are driven simultaneously, the corresponding display medium will cause optical modulation according to the drive voltage, but if the switching element is defective, normal optical modulation will not occur and it will be observed as a pixel defect. Will be done. Even if the number of picture element electrodes is hundreds of thousands or more, the picture element defects can be easily and instantly identified with the naked eye by using a magnifying lens or the like.

When the pixel defective portion is specified, light energy is applied to the pixel correction portion between the pre-switching element side electrode and the pixel electrode portion from the outside through the translucent display panel substrate to dissolve the electrode metal. The insulating layer that has been kept in the non-conducting state is electrically broken down to electrically connect the preliminary switching element and the pixel electrode. If necessary, the defective switching element connected to the pixel electrode may be disconnected by light energy to separate it from the pixel electrode. At this time, if the display medium in the picture element correction portion irradiated with light between the pre-switching element side electrode and the picture element electrode portion is a liquid crystal, the liquid crystal layer in this portion is temporarily disturbed in orientation during light irradiation and becomes clouded. It was confirmed that the alignment ability was restored and a normal display operation was performed after a short time after the light irradiation. Therefore, the characteristics of the display medium do not deteriorate. Even when a display medium other than liquid crystal is used, the area of the picture element correction portion can be set to be extremely small, so that the picture element defect can be repaired without substantially degrading the display quality.

<Embodiment> FIG. 1 is a configuration diagram of a liquid crystal display device showing one embodiment of the present invention. FIG. 1 (A) is a plan view of a TFT substrate and FIG. 1 (B) is FIG. A) is a cross-sectional view of the liquid crystal display device corresponding to the P-P cross section of FIG. 1A, and FIG. 1C is QQ of FIG.
It is a sectional view of a liquid crystal display device corresponding to a section.

Although the present embodiment exemplifies a transmissive liquid crystal display device in which a pixel electrode is selected by controlling opening / closing of a TFT by an active matrix driving method, the same applies to a reflective liquid crystal display device.

The surface of the glass substrate 1 is covered with a base coat film 2 made of Ta ₂ O ₅ , Al ₂ O ₃ or Si ₃ N ₄ to a thickness of 3000 Å to 9000 Å, and a gate bus line 3 for supplying a scanning signal and a data signal are provided on the base coat film 2. The source bus lines 4 for supplying the electric power are arranged in a grid pattern. The gate bus wiring 3 is generally formed of a single-layer or multi-layer metal such as Ta, Al, Ti, Ni, Mo, etc., but Ta is used in this embodiment. The source bus line 4 is also made of the same metal, but Ti is used in this embodiment. A base insulating film, which will be described later, is interposed at the intersection of the gate bus wiring 3 and the source bus wiring 4. In a rectangular area surrounded by the gate bus wiring 3 and the source bus wiring 4, picture element electrodes 5 made of a transparent conductive film (ITO) are arranged to form a picture element pattern in a matrix. 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.
Further, a spare TFT 7 is arranged near another corner of the picture element electrode 5, and the spare TFT 7 and the picture element electrode 5 are opposed to each other in a non-conductive state. The TFT 6 and the spare TFT 7 are arranged side by side on the gate bus line 3 and connected to the source bus line 4 by a branch line 8.

As shown in FIG. 1 (B), the structure near the TFT 6 is composed of a Ta gate electrode 9 formed on a part of the gate bus line 3 and Ta ₂ O ₅ obtained by anodizing the surface of the gate electrode 9. the gate insulating film 10, extends substantially the entire base coat layer 2 overlying this, SiN _X serving as a gate insulating film (e.g., Si ₃ N
₄ ) a base insulating film 11 made of amorphous silicon (a-Si), an intrinsic semiconductor layer 12 made of amorphous silicon (a-Si), a semiconductor protective film 13 made of SiN _X for protecting the upper surface of the intrinsic semiconductor layer 12, a source,
A for obtaining ohmic contact with the drain electrode
An n-type semiconductor layer 14 made of -Si is sequentially stacked, and a source electrode 15 made of Ti, Ni, Al, etc. connected to the branch wiring 8 and a drain connected to the pixel electrode 5 are formed on the n-type semiconductor layer 14. Electrode 16
It consists of a structure that is installed in parallel. The pixel electrode 5 connected to the end of the drain electrode 16 is patterned on the base insulating film 11. The thickness of the base insulating film 11 is appropriately 1500Å to 6000Å, but in this embodiment, it is set to 2000Å to 3500Å. A protective film 17 made of SiN _X is coated on almost the entire surface of the TFT 6 and the pixel electrode 5 to cover the upper surface thereof.
An alignment layer 19 that regulates the alignment of the liquid crystal molecules 18, such as SiO _{2 or} a polyimide resin, is deposited on top. The thickness of the protective film 17 is 20
About 00Å to 10000Å is suitable, but in this embodiment, it is 5000
Å It is set before and after. The base insulating film 11 and the protective film
Other than SiN _X , SiO _X , Ta ₂ O ₅ , Al ₂ O _{3 and} other oxides and nitrides can be used as 17. Further, the protective film 17 may have a windowed structure removed at the central portion of the pixel electrode 5 instead of covering the entire surface.

A color filter layer 21, a counter electrode 22 facing the pixel electrode 5 and an alignment layer 23 are formed on the inner surface of the other glass substrate 20 facing the glass substrate 1 on which the pixel electrode 5 is formed,
A black matrix (not shown) is provided around the color filter layer 21 as needed.

Twisted nematic liquid crystal molecules 18, which are twisted and oriented as a display medium, are enclosed between the pair of glass substrates 1 and 20, and orientation is changed in response to voltage application between the picture element electrode 5 and the counter electrode 22. The optical modulation is performed by.

Next, the configuration around the spare TFT 7 will be described with reference to FIG. The structure of the transistor element portion of the spare TFT 7 is the same as that of the above TFT 6. The same Ta, Ni, Al as the gate electrode 9 is formed on the base coat film 2 separated from the gate electrode 9 by a predetermined distance.
Alternatively, the joint metal layer 24 made of Ti or the like is formed in an island shape. This joint metal layer 24 can be patterned simultaneously with the formation of the gate electrode 9. The above-described base insulating film 11 is deposited on the joint metal layer 24, and the extended end 16a of the drain electrode 16 of the spare TFT 7 is placed thereon. The end of the pixel electrode 5 is on the base insulating film 11 on the joint metal layer 24.
Laminated with a metal piece 25 made of Ti, Al, Ni or Ta,
It is separated from the extended end 16a of the drain electrode 16 and both are kept in a non-conductive state. The extended end of the drain electrode 16
The end portions of the pixel electrodes on 16a and the metal piece 25 are completely covered with the protective film 17. The base insulating film 11 located between the joint metal layer 24, the drain electrode extension end 16a and the metal piece 25 acts as an interlayer insulator between the upper and lower metals, and its thickness is 1000Å to 70.
A suitable value is about 00Å, but in this embodiment, since the base insulating film 11 that also serves as the gate insulating film of the TFT is used, 2000Å ~
Set to 3500Å. Further, the protective film 17 on the drain electrode extension end 16a and the metal piece 25 isolates the liquid crystal molecule 18 which is the display medium from the drain electrode extension end 16a and the metal piece 25, and when connecting them electrically, It is intended to have a function as a buffer layer that reduces the scattering of deposited metal in light irradiation and reduces damage to the liquid crystal molecules 18, and 1500 Å-15000 Å is suitable, but in the present embodiment, protection of the TFT 6 is provided. Since it uses the membrane 17, it is set to around 5000Å.

A driving voltage is applied to all the picture element electrodes 5 from all the lines of the gate bus wiring 3 and the source bus wiring 4 of the liquid crystal display device having the above structure through the TFT 6 to drive the entire liquid crystal. When the TFT 6 is defective, the liquid crystal molecules 18 have an incomplete alignment conversion operation, whereby the display pattern of this pixel becomes a defective display pattern, and all of them are easily and instantly visually recognized.
As shown in FIG. 2, the detected pixel defect portion uses laser light, infrared rays, electron beams, and other heat rays as light energy through the glass substrate 1 below or the glass substrate 20 above from the outside as joint energy on the spare TFT7 side. Irradiate towards layer 24. In this embodiment, YAG laser light is used. When irradiated with laser light, the joint metal layer 24, the base insulating film 11, the drain electrode extension end
16a melt | dissolve mutually and an interlayer insulation layer is dielectrically destroyed and the drain electrode 16 and the joint metal layer 24 will be in a conduction state. Similarly, when the metal piece 25 on the pixel electrode 5 side and the joint metal layer 24 are irradiated with the laser beam, the respective metals melt and come into contact with each other to be in a conductive state. Therefore, the drain electrode 16 of the spare TFT 7 and the pixel electrode 5 are electrically connected. At this time, the electrical connection between the defective TFT 6 and the pixel electrode 5 can be cut by laser light irradiation if necessary. Joint metal layer 24, base insulating film 1
In the present embodiment, the mutual dissolution of the drain electrode extension end 16a and the metal piece 25 by laser irradiation is controlled by setting the laser irradiation conditions, and the film thickness is thicker than the base insulating film 11 and sufficient thickness of about 5000 Å and denseness are required. Since it is covered with the protective film 17 that it has, it will be isolated from the liquid crystal and proceed, and therefore the liquid crystal will not be contaminated by the dissolved metal. Since the protective film 17 is a transparent insulator and allows the laser light to pass therethrough, the laser light is absorbed by the metal material and acts to instantly heat and melt it. Therefore, at the time of laser light irradiation, the metal material and the interlayer insulating layer sandwiched by the metal material are dissolved and mixed with each other, but the protective film 17 is not destroyed. It was experimentally confirmed that the irradiated part of the liquid crystal layer irradiated with the laser light became cloudy, but this cloudiness disappeared and the liquid crystal was restored to its original alignment state. As described above, the defect of the pixel electrode connected to the defective TFT is repaired by the spare TFT.

The arrangement structure of the spare TFT 7 and the pixel electrode 5 may be the structure shown in FIG. 3 or 4 other than the above. FIG. 3 shows that a through hole is formed in the base insulating film 11 in advance and the joint metal layer is formed.
24 and the metal piece 25 are connected so that when the TFT 6 is defective, only the drain electrode extension end 16a of the spare TFT 7 and the joint metal layer 24 are electrically connected by light energy. Further, in FIG. 4, the joint metal layer 24 is abolished, and the drain electrode extension end 16a of the spare TFT 7 is arranged directly below the metal piece 25 via the base insulating film 11, and both are directly melt-connected by light energy irradiation. Is. In FIGS. 3 and 4, it is apparent that the extended end 16a of the drain electrode and the metal piece 25 may be formed in the opposite relationship. Further, as the display panel substrate, at least one of the substrates needs to use a translucent member (glass, plastic, etc.) in order to enable laser irradiation, but the base coat film 2 is not always necessary and may be omitted.

Although the above embodiments have described the active matrix type liquid crystal display device, the present invention is not limited to this, and a wide range of liquid crystal displays for obtaining a display pattern by using various switching elements such as MIM elements, diodes and varistors. It can be applied to a device and can also be used as 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> As described in detail above, according to the present invention, a malfunction of a switching element can be optically detected very easily, and a detected pixel defect can be easily repaired by irradiation with light energy after manufacturing a display panel. can do. Further, since the inspection process and the repair process are easy and the mass productivity is secured, the cost of the display device can be reduced.

[Brief description of drawings]

1 (A), (B) and (C) are a plan view, a P-P sectional view and a Q-Q sectional view of a liquid crystal display device showing an embodiment of the present invention, respectively. FIG. 2 is a schematic configuration diagram for explaining a connection state of the preliminary TFT and the pixel electrode by laser irradiation. FIG. 3 and FIG. 4 are configuration diagrams of the vicinity of the spare TFT used for explaining another embodiment of the present invention. 1,20 …… Glass substrate, 6 …… TFT, 7 …… Spare TFT, 9 ・ ・ ・
… Gate electrode, 11 …… Base insulating film, 15 …… Source electrode, 16 …… Drain electrode, 17 …… Protective film, 18 …… Liquid crystal molecule, 19,23 …… Alignment layer, 21 …… Color filter, 22 ......
Counter electrode

Front page continued (72) Inventor Kiyoshi Nakazawa 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka (72) Inventor Ken Kanamori 22-22 Nagaike-cho, Nagano-cho, Abeno-ku, Osaka-shi, SHAP Co., Ltd. ) References JP 61-235816 (JP, A) JP 63-276032 (JP, A) JP 59-101693 (JP, A)

Claims (2)

[Claims] 1. A display medium, of which optical characteristics are modulated in response to an applied voltage, is inserted between a pair of upper and lower substrates, at least one of which has a translucency, and the display medium is provided on the inner surface of the one substrate. A plurality of picture element electrodes arranged in a matrix to generate a display pattern for each picture element by applying a voltage, a switching element electrically connected to the extended end of the picture element electrode, and a connecting portion are the picture element electrodes. Preliminary switching elements are arranged opposite to each other in an electrically non-conducting state via the extended end portion and an insulating layer, and a counter electrode that applies a voltage to the display medium in cooperation with the pixel electrode is arranged on the inner surface of the other substrate. In the display device formed, the display medium displays normal picture elements which are different from each other in the normal picture element and the defective picture element in response to the voltage applied to the picture element electrode when the defect of the picture element is detected. Pattern and defective pixel display pattern The connecting portion and the extended end portion of the picture element electrode, which are opposed to each other through the insulating layer, constitute a picture element correcting section for correcting the defective picture element, and the picture element correcting section is , The insulating layer and the connecting portion or the extended end portion of the pixel electrode are mutually melted by an energy ray irradiated through the substrate having the light-transmitting property, and when the connecting portion and the pixel electrode are solidified. A display device comprising a member electrically connected to the extended end portion and being separated from the display medium via an insulating protective film. 2. The display device according to claim 1, wherein the switching element is formed of a thin film transistor, an insulating protective film is formed below the alignment layer, and has a film thickness equal to or larger than a gate insulating film which is a constituent film of the thin film transistor.