JP2625267B2 - Active matrix display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying a driving signal to a display pixel electrode through a switching element.
The present invention relates to a display device for performing display, and more particularly to an active matrix drive type display device in which picture element electrodes are arranged in a matrix to perform high-density display.

[0002]

2. Description of the Related Art Conventionally, in a liquid crystal display device, an EL display device, a plasma display device, and the like, a display pattern is formed on a screen by selectively driving picture element electrodes arranged in a matrix. As a display picture element selection method, there is known an active matrix driving method in which individual independent picture element electrodes are provided, and a switching element is connected to each of the picture element electrodes to perform display driving.

As switching elements for selectively driving picture element electrodes, TFT (thin film transistor) elements, MIM
A (metal-insulating layer-metal) element, a MOS transistor element, a diode, a varistor, and the like are generally used, and a voltage applied between a pixel electrode and a counter electrode facing the pixel electrode is switched by a switching element. A display medium, such as a liquid crystal, an EL light emitting layer, or a plasma light emitting body, interposed between the electrodes is optically modulated, and the optical modulation is visually recognized as a display pattern. Such an active matrix driving method is capable of high-contrast display and has been put to practical use in liquid crystal televisions, word processors, computer terminal displays, and the like.

In a display device of this type, when a switching element in a defective state is incorporated as it is, a signal to be applied is not input to a pixel electrode connected to the switching element. It will be recognized as a point defect above.

[0005] Such a point defect can be corrected by laser trimming or the like if it is found at the stage of manufacturing the substrate on which the switching element is provided. However, it is extremely difficult to find a point defect from hundreds of thousands of display picture elements, and it is almost impossible at a mass production level in consideration of time and cost. The active matrix type liquid crystal display panel is formed by bonding an active matrix substrate and a counter substrate and sealing liquid crystal between the substrates. The active matrix substrate has a plurality of picture elements arranged in a matrix by forming picture element electrodes in a region surrounded by a gate bus wiring and a source bus wiring arranged in a grid pattern. A switching element electrically connected to the pixel electrode switches an input signal to the pixel electrode. In such an active matrix type liquid crystal display panel, for example, when a switching element is formed as a defective element, a signal which should be applied is not applied to a picture element electrode connected to the defective element. Above, it appears as a dot-shaped picture element defect, that is, a point defect.

If the above-mentioned defective element can be found after forming the switching element and before assembling the display device,
Some can be corrected by laser trimming or the like. But,
It is extremely difficult to detect a defective element from hundreds of thousands of switching elements in a state of the substrate before assembling the display device. That is, it is almost impossible to perform the above detection at a mass production level in terms of time and cost.

On the other hand, after the substrate on which the switching elements are provided is bonded to the counter substrate and liquid crystal is sealed between the two substrates to produce a liquid crystal display device, a predetermined electric signal is applied to each pixel electrode. The point defect can be easily detected visually by performing the display operation. However, it is difficult to repair point defects at the stage of producing the liquid crystal display device. As a result, products having point defects must be discarded, resulting in a decrease in yield and an increase in cost.

By the way, according to the method described below, a point defect can be easily detected and easily repaired. That is,
Turn on the display device enclosing the liquid crystal to find point defects,
A method of irradiating a defective pixel having a point defect with a laser beam through a glass substrate, thereby short-circuiting a pixel electrode of the defective pixel and a source bus line closest to the pixel electrode, thereby electrically connecting the defective pixel to a source bus line. is there. According to this method, regardless of the signal from the gate bus line, the signal from the source bus line is directly input to the picture element electrode of the defective picture element.

Here, in a normal picture element having no point defect, only the source signal supplied within the selection time of the gate bus line is charged, and the charged electric charge corresponds to one cycle, that is, the next selection time comes. Will be held until. On the other hand, in a picture element in which the picture element electrode and the source bus line are short-circuited by the irradiation of the laser beam, the source signal is always input and charged regardless of whether the gate bus line is selected or not. Therefore, when viewed through one cycle, the effective value of the source voltage input during this period is applied to the liquid crystal. Therefore, the defective picture element is turned on at the average brightness of all the picture elements connected to the source bus line belonging to the defective picture element. This means that the defective picture element is not a perfect luminescent spot nor a black spot and is lit at an intermediate luminance. Therefore, the defective picture element corrected by the irradiation of the laser beam is not operating normally, but is in a state where it is extremely difficult to be recognized as a point defect. That is, the point defect is substantially repaired.

FIG. 7 shows a conventional example of a display device capable of performing a repair operation by the above-described method. Each of the redundant structures capable of short-circuiting the picture element electrode 120 and the source bus line 110 by irradiating a laser beam is illustrated in FIG. A configuration is provided for each element. This redundant structure is provided in a portion corresponding to the lower left portion of the pixel electrode 120 in FIG.
A gate bus line protrusion 150 protruding toward 20, a conductor piece 170 and a source bus line 110 that are overlapped with an end portion of the gate bus line protrusion 150 via an insulating film, and protrude from the gate bus line protrusion 150. And a source bus line projecting portion 160 superimposed on the source bus line. These are electrically insulated from each other in an initial state before being irradiated with the laser beam. In the drawing, reference numeral 130 denotes a TFT.

FIG. 8 shows this redundant structure in an enlarged manner. When a point defect is found as described above, a laser beam is first irradiated onto a region 171 shown by a broken line in FIG. As a result, the base end of the gate bus line protrusion 150 is cut. Next, a second laser light irradiation is performed on a region 172 indicated by a broken line in the overlapping portion of the gate bus line protrusion 150 and the source bus line protrusion 160, thereby melting both the protrusions 150 and 160 and electrically connecting the both. Connect to After that, a third laser light irradiation is performed on the region 173 of the conductor piece 170, thereby electrically connecting the conductor piece 170 and the gate bus line protrusion 150. Then, since the conductor piece 170 is electrically connected to the picture element electrode 120, the source bus line 110 and the picture element electrode 120 are short-circuited by the above-described three times of laser light irradiation. The defect is corrected.

By the way, in this type of display device,
An additional capacitor is formed to improve display quality. FIG. 9 shows a conventional example of a display device provided with an additional capacitor. An additional capacitor bus line for forming an additional capacitor parallel to the gate bus line 100 in a portion corresponding to the lower part of the picture element electrode 120 in the drawing. 181 is wired to form an additional capacitor 180 shown by oblique lines in the figure. More specifically, a conductive film (upper electrode) of the same material as the picture element electrode 120 is formed on the additional capacitance bus line 181 serving as a lower electrode with an insulating film interposed therebetween. An additional capacitor 180 is provided between the conductive film and the conductive film.

Note that a plurality of additional capacitance bus lines 181 wired on the glass substrate are short-circuited at the edge of the glass substrate, and are set to the same potential as the opposing substrate bonded to the glass substrate. Therefore, the additional capacity 180
Are arranged in parallel with the liquid crystal capacitance sealed between the pixel electrode 120 and the opposing substrate.

FIG. 10 shows another conventional example of a display device in which an additional capacitance is formed.
The configuration is such that an additional capacitance 180 indicated by oblique lines is formed in the gate bus line 100 adjacent to the gate bus line 100 connected to the pixel electrode 120 via T130.

[0015]

However, in the display device shown in FIGS. 9 and 10 in which the additional capacitance is formed, there is a possibility that a specific picture element defect accompanying the formation of the additional capacitance 180 may occur. That is, in each case, a defect 183 such as a pinhole occurs in the additional capacitance 180, and due to this, the additional capacitance bus line 181 and the gate bus line 100
Current leaks between the pixel electrode 120 and the pixel electrode 120 to cause a pixel defect. By the way, in the case of FIG. 9,
Due to current leakage occurring between the pixel electrode 120 and the additional capacitance bus line 181, no voltage is applied to the liquid crystal corresponding to the pixel electrode 120, thereby causing a pixel defect.

The picture element defect caused by such a defect 183 cannot be repaired by the above-described short-circuit method by laser beam irradiation. In other words, in the case of FIG. 9, even if the source bus line 110 is short-circuited, the signal from the source bus line 110 only flows to the opposite substrate, and no voltage is applied to the liquid crystal. Can not. In the case of FIG. 10, a current leak occurs between the source bus line 110 and the gate bus line 100 via the picture element electrode 120, which is recognized as a linear picture element defect. Becomes

The present invention solves the above-mentioned drawbacks of the prior art, and can easily repair a pixel defect caused by a defect such as a pinhole generated in an additional capacitance forming portion after production, thereby improving the yield and improving the yield. It is an object of the present invention to provide an active matrix display device capable of reducing costs.

[0018]

According to the active matrix display device of the present invention, a gate bus line and a source bus line are arranged in a grid pattern on one of a pair of insulating substrates, and are surrounded by both bus lines. In an active matrix liquid crystal display device in which picture element electrodes are respectively arranged in the designated areas and switching elements are connected to the picture element electrodes, the gate bus lines and the source bus lines, respectively, A conductor bus line serving as a lower electrode for forming a capacitor, a first conductor having one end overlapped with the conductor bus line via an insulating film, and an insulator below the other end of the first conductor The second superimposed on the membrane
A conductor, a source bus line protrusion protruding from the source bus line and overlapping above the other end of the second conductor with an insulating film interposed therebetween, and an insulating film interposed on the conductor bus line. And an upper electrode for forming an additional capacitor connected to the pixel electrode on the first conductor forming portion, thereby achieving the above object.

Instead of the conductor bus line, one end of the first conductor and the upper electrode may be overlapped with a gate bus line adjacent to the gate bus line via an insulating film.

[0020]

In the above structure, when it is detected that a picture element defect due to a defect such as a pinhole has occurred in the additional capacitance forming portion, first, the first conductor piece at the corresponding position is connected to the conductor bus line side. As an example of light energy, the end portion is irradiated with a laser beam, for example, and the first conductor piece is cut from the conductor bus line at the irradiation portion. As a result, the first conductor piece and the conductor bus line are in an insulated state, so that the influence of the current leak in the additional capacitance portion does not affect the pixel electrodes. Therefore,
The picture element in this state is in a state in which no voltage is applied to the liquid crystal and no defect occurs.

Next, a laser beam is applied to the overlapping portion of the projecting portion from the source bus line and the second conductor piece and the overlapping portion of the first conductor piece and the second conductor. By irradiating the former with the laser beam, the insulating film sandwiched between the source bus line projecting portion and the second conductor piece is melted and destroyed, whereby both are short-circuited at the end of the irradiated portion. Similarly, the first conductor piece and the second conductor piece are short-circuited by irradiating the latter with laser light, and the picture element electrode and the second conductor piece that are electrically connected to the first conductor piece are separated. It will be conducted. Therefore, by such a repairing operation, the source bus line and the pixel electrode are eventually electrically connected.

As a result, regardless of whether the gate bus line is selected or not, the source signal is always input to the defective picture element, and eventually the effective value of the source voltage is applied to the liquid crystal. It will light up to the average brightness of all picture elements connected to the line. Therefore,
The defective pixel due to the defect is substantially repaired.

[0023]

Embodiments of the present invention will be described below.

FIG. 1 shows an active matrix display device according to an embodiment of the present invention.
Liquid crystal is sealed between a pair of upper and lower transparent insulating substrates. On the lower glass substrate 1 (see FIGS. 2 and 3), a plurality of gate bus lines 10 and 10 functioning as scanning lines are provided.
. And a plurality of source bus lines 20 functioning as signal lines are wired in a grid pattern.
ITO (In) is placed in each of the rectangular areas surrounded by 0 and 20.
The pixel electrodes 40 made of a dium tin oxide film are arranged in a matrix. A gate electrode 11 protruding toward the picture element electrode 40 is branched from the gate bus line 10, and a TFT 30 is provided near a tip of the gate electrode 11.
Is formed. The TFT 30 functions as a switching element and is connected to the picture element electrode 40. The tip of the gate electrode 11 extends to the front of the source electrode 31 formed so as to project from the source bus line 20 toward the pixel electrode 40.

An additional capacitance bus line (lower electrode) 70 for forming an additional capacitance is provided between the gate bus line 10 adjacent to the gate bus line 10 to which the TFT 30 is connected and the pixel electrode 40. The additional capacitance electrode (upper electrode) 71 is formed on the additional capacitance bus line 70 with the gate insulating film 50 (see FIGS. 2 and 3) interposed therebetween. The additional capacity bus line 70
One end of a first conductor piece 72 having a rectangular shape long in this direction is laminated on a portion facing the TFT 30 with an insulating film 73 interposed therebetween. A second conductor piece 74 is overlapped below the other end of the first conductor piece 72 with the gate insulating film 50 interposed therebetween. The additional capacitance electrode 71 and the pixel electrode 40 are made of ITO.
The films are simultaneously formed by patterning, and both are connected above the first conductor piece 72. As a result, an additional capacitance indicated by oblique lines is formed.

In addition, the source bus line projecting portion 21 is overlapped above the second conductor piece 74 with the gate insulating film 50 interposed therebetween. The source bus line projecting portion 21 is formed to project from a corresponding position of the source bus line 20 toward the first conductor piece 72.

Next, the sectional structure of this display device will be described in the order of steps with reference to FIGS. First, a Ta film is laminated on the glass substrate 1 by a sputtering method, and then the Ta film is patterned by a photolithography method to form the gate bus lines 10 and the gate electrodes 11.
At this time, the second conductor piece 74 shown in FIG. 3 is formed at the same time. It should be noted that Ti, Al, Cr may be used instead of the Ta single layer film.
Or a conductor having a multilayer structure of Ta, Ti, Al, and Cr. Further, an insulating film 12 such as Ta ₂ O ₅ (see FIG. 3) may be formed as a base coat film between the gate bus line 10 and the glass substrate 1.

Next, a gate insulating film 50 of a 300 nm-thickness SiNx film is laminated on the gate bus line 10 by a plasma CVD method. The gate bus line 10
May be anodized to form a Ta oxide film on its surface. In this case, since two insulating films are formed, there is an advantage that the insulating property can be further improved.

Next, the film thickness is continuously formed on the gate insulating film 50.
A semiconductor layer 52 made of an a-Si (amorphous silicon) film having a thickness of 30 nm and an etching stopper layer 53 made of a SiNx film having a thickness of 200 nm are sequentially laminated by a plasma CVD method. Then, when the etching stopper layer 53 is patterned, an n ⁺ amorphous silicon film (hereinafter referred to as a-Si) to which phosphorus is added is
The layers are stacked to a thickness of 80 nm by the VD method, and are patterned to form contact layers 60a and 60b. The contact layers 60a and 60b are formed in order to improve the ohmic contact between the semiconductor layer 52 and the source electrode 31 and the drain electrode 32 to be laminated next.

After patterning the contact layers 60a and 60b, a source conductor is laminated thereon by sputtering. As the source conductor, Ti, Al, M
Although o, Cr and the like can be selected, Ti is employed in this embodiment. Next, the source conductor is patterned, so that the source bus line 20 (and its protruding portion 21),
The source electrode 31, the drain electrode 32, and the first conductor piece 72 of the TFT 30 are formed. Next, an ITO film is laminated on the glass substrate 1 by a sputtering method, and is patterned to form the pixel electrode 40 and the additional capacitance electrode 71. The picture element electrode 40 is the drain electrode 3 of the TFT 30.
2 and the first conductor piece 72, and are in conduction with these.

Next, a protective film layer 75 made of SiNx is laminated on the picture element electrode 40, and an alignment film 76 (see FIG. 2) is laminated thereon. The protective film layer 75 can be formed in a window shape in which the central portion of the pixel electrode 40 is opened. The alignment film 76 is formed for aligning liquid crystal molecules of a liquid crystal as a display medium sealed between the glass substrate 1 and an opposing substrate bonded to the glass substrate 1. An active matrix display device according to this embodiment is manufactured.

In the above display device, the additional capacitance electrode 7
A repair method in the case where a defect such as a pinhole is generated in FIG. 1 and a pixel defect is generated by the defect will be described below with reference to FIG. Note that such a picture element defect is detected by causing the display device to perform a display operation and visually recognizing it. Also, at this time, the picture element defect described in the above prior art is also found,
This repair method is the same as in the conventional example, and therefore will not be described.

When a picture element defect caused by a defect such as a pinhole is detected, firstly, the picture element defect is located in a region 90 (the base of the first conductor piece 72) of the first conductor piece 72 at a corresponding position as indicated by a broken line in the drawing. A laser beam is irradiated through the glass substrate 1 as an example of light energy. In this embodiment, a YAG laser was used as the laser irradiation device. The direction of laser light irradiation may be from the glass substrate 1 side or from the counter substrate side. However, in this embodiment, the counter substrate is covered with a light-shielding conductor and laser light cannot be directly irradiated. It is preferable to irradiate from the back side of the glass substrate 1 as shown by an outline arrow.

By irradiating the region 90 with the laser beam, the conductors (the portion of the second conductor piece 72 and the continuous portion of the picture element electrode 40 and the additional capacitance electrode 71) in the region 90 are scattered, and the boundary between the irradiated portion And both sides are cut off. As a result, the pixel electrode 40 and the additional capacitance electrode 71 are in an insulated state. Therefore, in this state, the influence of the current leak in the additional capacitance portion does not affect the pixel electrode 40. Therefore, the picture element in this state does not have a defect in which no voltage is applied to the liquid crystal.

Next, laser light is sequentially applied to regions 91 and 92 indicated by broken lines in FIG. Here, the region 91 corresponds to the overlapping portion of the projecting portion 21 from the source bus line 20 and the second conductor piece 74, while the region 92 corresponds to the overlapping portion of the first conductor piece 72 and the second conductor 74. Is equivalent to Therefore, area 9
Irradiation of the first and second source bus line projections 21 and the second
The gate insulating film 50 sandwiched between the conductor pieces 74 is melt-ruptured, whereby the source bus line protrusion 21 and the second conductor piece 74 are short-circuited at the end of the irradiated portion. Similarly, the first conductor piece 72 and the second conductor piece 74 are short-circuited by irradiating the region 92, and the first conductor piece 72
The pixel electrode 40 electrically connected to the second conductive piece 74 is electrically connected to the pixel electrode 40. Therefore, by irradiating the regions 91 and 92 with the laser light, the source bus line 20 and the pixel electrode 40 are eventually electrically connected.

As a result, regardless of whether the gate bus line is selected or not, the source signal is always input to the defective picture element, and eventually the effective value of the source voltage is applied to the liquid crystal, and the defective picture element is connected to the adjacent source bus. It will light up to the average brightness of all picture elements connected to the line. Therefore,
The defective pixel due to the defect is substantially repaired. In addition, both the conductor pieces 72 and 74 and the source bus line protrusion 21
Is formed in the protective film layer 7 as described above.
5, the conductive atoms melted by the irradiation of the laser beam do not mix into the liquid crystal. Therefore, the display characteristics of the liquid crystal are favorably maintained.

When the region 90 is irradiated, the first conductor piece 72 serving as a conductor, the additional capacitance electrode 71 and the pixel electrode 40 are irradiated.
Are cut and the source bus line projecting portion 21 and the conductor pieces 72 and 74 are melted in the irradiation of the regions 91 and 92. This can be achieved by appropriately setting the irradiation conditions of the laser beam. is there. The order of irradiation to the regions 90 to 92 is not limited to the above order.

The above redundant structure may be the structure shown in FIG. In this case, in the initial state before the laser light irradiation, the upper and lower conductors sandwiching the gate insulating film 50, that is, the second conductor piece 74, the first conductor piece 72, and the gate bus line protrusion 21 are formed. A semiconductor layer 52, an etching stopper layer 53, and a contact layer 61 are stacked between the gate insulating film 50 and the source bus line protrusion 21 and the first conductor piece 72 in order to prevent a current leak from occurring between them. It has a structure to do.

FIG. 6 shows another embodiment of the present invention.
In this embodiment, the additional capacitance electrode 71 is formed on the gate bus line 10 adjacent to the gate bus line 10 connected to the TFT 30, and
The first conductor piece 72 and the second
The conductor piece 74 is provided, and a redundant structure in which the source bus line projecting portion 21 is overlapped with the second conductor piece 74 is adopted. According to this embodiment, it is possible to perform the same repairing operation as in the above-described embodiment, and it has the following advantages.

That is, when the additional capacitance bus line 70 is provided as in the above-described embodiment, the light blocking area is increased by the provision of the additional capacitance bus line 70, and the entire display screen becomes dark. According to the structure of the embodiment, the additional capacitance bus line 70 is not provided, so that the light blocking area can be naturally reduced, and the entire display screen can be brightened.

In this embodiment, when the adjacent gate bus line 10 is in a non-selected state, the same signal as that on the opposite side is input to the gate bus line 10 and the gate bus line 10 is used as an additional capacitance bus line. I do.

[0042]

According to the present invention described above, a defective pixel due to a defect such as a pinhole in an additional capacitance forming portion, which has been difficult in the past, can be easily repaired after the formation of the active matrix display layer. . Further, it is possible to detect and repair a defective pixel caused by a defective switching element. Therefore, according to the present invention, the production yield of the active matrix display device can be improved, and the cost can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of an active matrix display device according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 4;

FIG. 4 is a partially enlarged view of FIG. 1;

FIG. 5 is a diagram showing another example of the redundant structure of the active matrix display device.

FIG. 6 is a plan view showing another embodiment of the present invention.

FIG. 7 is a plan view showing a conventional example.

FIG. 8 is a partially enlarged view of FIG. 7;

FIG. 9 is a plan view showing a conventional example of an active matrix display device having an additional capacitance.

FIG. 10 is a plan view showing another conventional example of an active matrix display device having an additional capacitance.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate 10 gate bus line 20 source bus line 21 source bus line protrusion 30 TFT 40 picture element electrode 50 gate insulating film 70 additional capacitance bus line 71 additional capacitance electrode 72 first conductor piece 74 second conductor piece

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor: Manabu Takahama 22-22 Nagaikecho, Abeno-ku, Osaka City Inside Sharpe Corporation (72) Inventor Naofumi Kondo 22-22, Nagaikecho, Abeno-ku, Osaka City Sharpe Corporation ( 72) Inventor Katsumi Irie 22-22, Nagaike-cho, Abeno-ku, Osaka-shi Inside Sharpe Co., Ltd. (56) References JP-A-2-124538 (JP, A) JP-A-4-136918 (JP, A)

Claims (2)

(57) [Claims] 1. A gate bus line and a source bus line are arranged in a grid pattern on one of a pair of insulating substrates, and picture element electrodes are respectively arranged in a region surrounded by both bus lines. An active matrix liquid crystal display device in which switching elements are respectively connected to the picture element electrode and the gate bus line and the source bus line, a conductor bus line provided to the picture element electrode and serving as a lower electrode for forming an additional capacitance; A first conductor having one end overlapped with the conductor bus line via an insulating film, and a second conductor having an insulating film interposed below the other end of the first conductor; A source bus line projecting portion projecting from the source bus line and overlapping above the other end of the second conductor with an insulating film interposed therebetween, and overlapping with the insulating film sandwiching the insulating film above the conductor bus line; The first The active matrix display device comprising an upper electrode for additional capacity formed which is connected to the picture elements electrodes on collector forming part. 2. The device according to claim 1, wherein one end of said first conductor and said upper electrode are overlapped with a gate bus line adjacent to said gate bus line via an insulating film instead of said conductor bus line. Active matrix display device.