JP2589867B2 - Active matrix display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention 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 particularly relates to a display device that The present invention relates to a display device of an active matrix drive system which performs high-density display by being arranged in a matrix.

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. . A voltage is applied between the selected picture element electrode and a counter electrode facing the selected picture element electrode, and optical modulation of a display medium such as a liquid crystal interposed between these electrodes is performed. This optical modulation is visually recognized as a display pattern. As a driving method of the pixel electrodes, an active matrix driving method in which individual independent pixel electrodes are arranged and a switching element is connected to each of the pixel electrodes to drive the pixel electrodes is known. TFTs are used as switching elements to selectively drive picture element electrodes.
(Thin film transistor) elements, MIM (metal-insulating layer-metal) elements, MOS transistor elements, diodes, varistors, and the like are generally known. The active matrix drive system 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 such an active matrix display device, for example, when a switching element is formed as a defective element,
Since a signal to be originally applied is not applied to the picture element electrode connected to the defective element, the picture element electrode appears on the display screen as a point-like picture element defect, that is, a point defect.

If such a defective element can be found after forming the switching element and before assembling the display device, some of the defective elements can be corrected by laser trimming or the like. However, 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 because of time and cost.

On the other hand, after the substrate on which the switching element is formed and the counter substrate are attached to each other to form a display device, a point defect can be easily detected visually by applying a predetermined electric signal to the bus wiring. However, in the state where the display device is assembled in this way, point defects cannot be corrected. Since such defective products must be discarded, the cost is greatly increased.

(Problems to be Solved by the Invention) A display device having a structure that can easily detect a pixel defect and easily correct the pixel defect has been developed. FIGS. 7 and 8 are plan views of one substrate constituting such a liquid crystal display device. In the liquid crystal display device shown in FIG. 7, a source bus line 23 is arranged orthogonally to the gate bus lines 21 arranged in parallel with each other. A pixel electrode 41 is arranged in each rectangular region surrounded by the two gate bus lines 21 and the two source bus lines 23. On the gate bus branch line 22 branched from the gate bus wiring 21, a TFT 31 functioning as a switching element is formed. The gate bus branch line 22 has a portion functioning as a gate electrode of the TFT 31 and a portion smaller in width than the portion. The drain electrode 33 of the TFT 31 is electrically connected to the pixel electrode 41, and the TFT 3
One source electrode 32 is connected to the source bus wiring 23.

The picture element defect can be visually detected by operating the display device. When a pixel defect due to a defect of the TFT 31 is found, first, the thinned portion of the gate bus branch line 22 is irradiated with laser light to separate the TFT 31 from the gate bus line 21. Next, a laser beam is applied to a portion where the source electrode 32, which is the input terminal of the TFT 31, and the gate bus branch line 22, and a portion where the drain electrode 33, which is the output terminal of the TFT 31, and the gate bus wiring 22, are overlapped. As a result, the source electrode 32 and the drain electrode 33 are electrically connected via the gate bus branch line 22. With this correction, the bad TFT31
Is directly driven by the source bus wiring 23.

The display device shown in FIG. 8 is provided with a gate bus protrusion 43 branched from the gate bus wiring 21 and a source bus protrusion 46 branched from the source bus wiring 23. II in Fig. 8
FIG. 3 shows a cross-sectional view along the line I-III. As shown in FIG. 3, a source bus projection 46 is superimposed on the gate bus projection 43 at a substantially central portion with an insulating film interposed therebetween. Also,
On the end of the gate bus protrusion 43, a conductive piece 44 electrically connected to the picture element electrode 41 is overlapped with the insulating film interposed therebetween. In this display device, the width of the portion of the gate bus branch line 22 functioning as the gate electrode is equal to the width of the other portions.

Also in this display device, the detection of a picture element defect can be visually performed by operating the display device. TFT31
When a pixel defect due to a defect is found, the overlapping portion of the gate bus projecting portion 43 and the source bus projecting portion 46 and the overlapping portion of the gate bus projecting portion 43 and the conductive piece 44 are interposed via the transparent substrate. Is irradiated with laser light. Further, the base of the gate bus projection 43 is cut by irradiation with laser light or the like, and the gate bus projection 43 and the gate bus wiring 21 are separated. Thus, the pixel electrode 41 is directly driven by the lease bus line 23.

In the normal picture element electrode 41 of the display device shown in FIGS. 7 and 8, the signal supplied from the source bus line 23 within the selection time of the gate bus line 21
Is held for one cycle until is selected. However, the pixel electrode 41 modified as described above has the gate bus wiring 21
Lease bus wiring 23 whether or not is selected
When this modified picture element electrode 41 is viewed through one cycle, a display corresponding to the effective value of the signal voltage input to the source bus wiring 23 during this cycle is performed.
Therefore, the corrected pixel electrode 41 displays the average brightness of all the pixel electrodes 41 connected to the source bus wiring 23 connected to the corrected pixel electrode 41, and it is a complete point defect. Can be avoided. That is, although the repaired picture element electrode cannot operate normally, it becomes very difficult to determine a point defect.

In the above-described correction of the pixel defect, the connection portion between the source bus wiring 23 and the correction pixel electrode 41 must be smaller than the normal resistance of the TFT 31 in the ON state. Because
Source bus wiring 23 that changes one after another for each selection period of TFT 31
Is required to be directly input to the correction picture element electrode 41 immediately.

In a display device having such a pixel defect correcting function, for example, as shown by a hatched portion 81 in FIG.
If a picture element defect is caused by a leak between the source bus wiring 23 connected to the picture element electrode 41 and the source bus wiring 23, as described in FIG. The electrode 33 is connected via the gate bus branch line 22,
It can be corrected by cutting the gate bus branch line 22. However, as shown by the shaded area 82 in FIG.
If a pixel defect occurs due to a leak between the pixel bus 41 and the source bus wiring 23 connected to the pixel electrode adjacent to the pixel electrode 41, the above-described correction will make the adjacent pixel pixel adjacent. The picture element electrode where the source bus wiring 23 and 23 are defective
It is connected via 41 and a line defect appears on the screen. Since line defects have a more serious effect than point defects, the yield of the display device is greatly reduced.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a pixel defect due to a leak between a pixel electrode and a signal line adjacent to a signal line connected to the pixel electrode. It is an object of the present invention to provide an active matrix display device which can correct the occurrence of the problem.

(Means for Solving the Problems) An active matrix display device according to the present invention includes a pair of insulating substrates, picture element electrodes arranged in a matrix on one of the pair of substrates, A scanning line and a signal line wired vertically and horizontally between the pixel electrodes, a scanning branch line branched from the scanning line, a switching element formed at the tip of the scanning branch line, and connected to the pixel electrode; A scanning line protrusion protruding from a scanning line adjacent to the scanning line connected to the pixel electrode to a corner of the pixel electrode; and a signal line adjacent to the signal line connected to the pixel electrode. A signal line protruding portion that protrudes to a corner portion and is superimposed on the scanning line protruding portion via an insulating film, and is electrically connected to the picture element electrode; and an end portion of the scanning line protruding portion via an insulating film. Superposed conductor pieces, whereby the above object is achieved. .

In addition, the scanning branch line, a portion having a large width of the tip portion,
A configuration having a small width portion other than the tip portion can be adopted.

Further, another scanning line protrusion protruding from the adjacent scanning line to another corner of the picture element electrode, and protruding from the signal line connected to the picture element electrode to the other corner, And another signal line protrusion that is superimposed on the scan line protrusion via an insulating film, and electrically connected to the pixel electrode, and overlaps with an end of the other scan line protrusion via the insulation film. Other conductor pieces that have been
May be further provided.

Further, the active matrix display device of the present invention includes a pair of insulating substrates, pixel electrodes arranged in a matrix on any one of the pair of substrates, and vertically and horizontally between the pixel electrodes. A wired scanning line and a signal line, a scanning branch line branched from the scanning line, and formed at the tip of the scanning branch line,
A switching element connected to the pixel electrode, an additional capacitance line superimposed on the pixel electrode, an additional capacitance line protrusion projecting from the additional capacitance line to a corner of the pixel electrode, A signal line protrusion protruding from the signal line adjacent to the signal line connected to the electrode to the corner portion and superimposed on the additional capacitance wire protrusion via an insulating film, and electrically connected to the pixel electrode; And a conductor piece overlapped with an end portion of the additional capacitance wiring protruding portion via an insulating film, thereby achieving the above object.

In addition, the scanning branch line, a portion having a large width of the tip portion,
A configuration having a small width portion other than the tip portion can be adopted.

In addition, another additional capacitance wiring projection that projects from the additional capacitance wiring to another corner of the picture element electrode, and another projection that projects from the signal line connected to the picture element electrode to the other corner, And another signal line protruding portion superimposed on the additional capacitance wiring protruding portion via an insulating film, and electrically connected to the picture element electrode, and an end portion of the other additional capacitance wiring protruding portion via the insulating film. And another conductor piece superimposed and superimposed.

(Operation) In the active matrix display device of the present invention, when a pixel defect occurs due to a leak between a pixel electrode and a signal connected to the pixel electrode, light from the outside of the substrate is generated. By the energy irradiation, the input terminal and the output terminal of the switching element are connected via the scanning branch line. Further, the scanning branch line is separated from the scanning line as necessary.

Further, when a pixel defect occurs due to a leak between the pixel electrode and a signal line adjacent to the signal line connected to the pixel electrode, the scanning line protrusion and the signal line protrusion are Light energy is applied to the overlapping portion and the overlapping portion of the scanning line protrusion and the conductor piece. Further, the scanning line protrusion and the scanning line are separated by light energy irradiation. This allows
The picture element electrode is directly connected to an adjacent signal line.

Further, in the active matrix display device of the present invention having the additional capacitance wiring, a pixel defect occurs due to a leak between a pixel electrode and a signal line adjacent to a signal line connected to the pixel electrode. In such a case, light energy is applied to the overlapping portion of the additional capacitance wiring projection and the signal line projection and the overlapping portion of the additional capacitance wiring projection and the conductor piece. Further, the projecting portion of the additional capacitance line and the additional capacitance line are separated by light energy irradiation. Thereby, the picture element electrode is directly connected to the adjacent signal line.

(Example) An example of the present invention will be described below.

FIG. 1 shows a plan view of an active matrix substrate used in one embodiment of the display device of the present invention. Figure 1 shows the first
FIG. 2 shows a sectional view of the display device along the line II-II in the figure. FIG. 3 is a sectional view taken along the line III-III of FIG. The active matrix display device of this embodiment will be described according to the manufacturing process. The display device according to the present embodiment includes a pair of insulating substrates 1 and 2, pixel electrodes 41 arranged in a matrix on one substrate 1, and scanning lines wired vertically and horizontally between the pixel electrodes 41. A source bus line 23 functioning as a signal line, a source bus line 23 functioning as a signal line, a gate bus branch line 22 branched from the gate bus line 21 as a scanning branch line, and a pixel formed at the tip of the gate bus branch line 22. A TFT 31 functioning as a switching element connected to the electrode 41, a gate bus protrusion 43 protruding from a gate bus line 21b adjacent to the gate bus line 21a connected to the pixel electrode 41 to a corner of the pixel electrode 41; , Source bus wiring connected to the pixel electrode 41
Projecting from the source bus wiring 23b adjacent to 23a to the corner,
The source bus protrusion 46 overlapped with the gate bus protrusion 43 via the gate insulating film 11, and is electrically connected to the pixel electrode 41, and is connected to the end of the gate bus protrusion 43 via the gate insulating film 11. And a superposed conductor piece 44. The gate bus branch line 22 has a portion having a large width at the tip portion functioning as the gate electrode 25 and a portion having a small width other than the tip portion. The gate bus line 21 is composed of the gate bus lines 21a, 21b,..., And the source bus line 23 is the source bus lines 23a, 23b.
Consists of ...

In this example, a transparent glass substrate was used as the insulating substrate 1. The gate bus wiring 21, the gate bus branch line 22, and the gate bus protrusion 43 are generally formed of a single layer such as Ta, Ti, Al, Cr or a multi-layer metal thereof.
It was used. The gate bus wiring 21, the gate bus branch line 22, and the gate bus protrusion 43 are formed by patterning a Ta metal layer formed by a sputtering method. Before forming the gate bus wiring 21 and the like, the glass substrate 1
A base coat film made of Ta ₂ O ₅ or the like may be formed thereon.

Gate bus lines 21, on the gate bus branch line 22 and the gate bus projection portion 43, to form an insulating base film 11 made of SiN _X over the entire surface. The gate insulating film 11 has a thickness of 300
It is formed to a thickness of 0 °. Before the gate insulating film 11 is formed, the anodic oxide film made of Ta ₂ O ₅ may be formed by anodic oxidation of the gate bus wiring 21, the gate bus branch line 22, and the gate bus protrusion 43.

Next, a TFT 31 functioning as a switching element was formed at the end of the gate bus branch line 22. The second about TFT31
This will be described with reference to the drawings. Gate insulating film as described above
After the formation of 11, an amorphous silicon (a-Si) layer which will later become a channel layer 12 and an etching stopper layer 13
A SiN _X layer was deposited. The thickness of the a-Si layer is 300
Å, The thickness of the SiN _X layer is 2000Å. Next, the SiN _X layer was patterned to form an etching stopper layer 13.
Further, on the entire surface of the a-Si layer and the etching stopper layer 13, an n ⁺ -type a-Si layer to which P (phosphorus) is added, which will later become the contact layers 14 and 14, is formed to a thickness of 800 Å by a plasma CVD method. Deposited. Next, the a-Si layer and the n ⁺ -type a-Si layer were simultaneously patterned to form a channel layer 12 and contact layers 14 and 14.

Next, a Ti metal layer to be a source electrode 32, a source bus wiring 23, a drain electrode 33, and a conductor piece 44 later was formed.
The source bus wiring 23 and the like are generally formed of a single layer of Ti, Al, Mo, Cr, or the like, or a multilayer metal thereof. In this embodiment, Ti is used. The Ti metal layer is formed by a sputtering method. By patterning this Ti metal layer, the source electrode 32, the source bus wiring 23, the drain electrode 3
3, and the conductor piece 44 was formed. The source bus wiring 23 crosses the gate bus wiring 21 with the gate insulating film 11 described above interposed therebetween. Also, as shown in FIGS. 1 and 3, the source bus projection 46 is formed so as to overlap the gate bus projection 43 substantially at the center with the gate insulating film 11 interposed therebetween. The conductor piece 44 is formed on the end of the gate bus protrusion 43 with the gate insulating film 11 interposed therebetween.

Next, as shown in FIG. 1, ITO (Indium) is placed in a rectangular area surrounded by the gate bus wiring 21 and the source bus wiring 23.
A pixel electrode 41 made of tin oxide) was formed. Picture element electrode 4
1 is superimposed on the end of the drain electrode 33 of the TFT 31 and is electrically connected to the drain electrode 33. As shown in FIG. 3, the picture element electrode 41 is also formed on the conductor piece 44 so as to overlap.

Further, on the entire surface of the substrate formed with the pixel electrode 41 was deposited a protective film 17 made of SiN _X. The protective film 17 may have a window shape removed at the center of the pixel electrode 41. On the protective film 17, an alignment film 19 was formed. On a glass substrate 2 facing the glass substrate 1, a counter electrode 3 and an alignment film 9 are formed. A liquid crystal layer 18 is sealed between these substrates 1 and 2,
The active matrix type display device of this embodiment is completed.

By driving the entire active matrix display device of the present embodiment, the position where a pixel defect occurs can be easily specified visually. A pixel defect due to insufficient application of the signal of the source bus line 23 to the pixel electrode 41 due to a defect of the TFT 31, or a defect between the pixel electrode 41 and the source bus line 23a connected to the pixel electrode 41. When a picture element defect occurs due to a leak, light energy such as laser light is applied from outside the substrate 1 or 2. In this embodiment, a YAG laser beam was used as the light energy. The gate insulating film 11 is destroyed by the laser light irradiation, and the source electrode 32 and the drain electrode 33 of the TFT 31 are connected via the gate electrode 25.
Further, the gate bus branch line 22 is separated from the gate bus wiring 21 as necessary. As described above, even if the same laser beam is used, cutting of the metal layer and connection between the metal layers can be performed by appropriately setting the conditions. Further, the connection between the source electrode 32 and the drain electrode 33 and the cutting of the gate bus branch line 22 may be performed in reverse order.

The pixel electrode 41 corrected in this way displays the average brightness of all the pixel electrodes 41 connected to the lease bus line 23a, and avoids a complete point defect. be able to. A protective film is formed on the entire surface of the substrate 1.
Since the layer 17 is formed, the characteristics of the liquid crystal layer 18 as a display medium do not deteriorate even when the laser beam is irradiated.

If a pixel defect occurs due to a leak between the pixel electrode 41 and the source bus line 23b adjacent to the source bus line 23a connected to the pixel electrode 41, the gate bus protrusion 43 The laser beam is applied to the overlapping portion between the gate bus projecting portion 43 and the conductor bushing portion 43 and the overlapping portion between the gate bus projecting portion 43 and the conductor piece 44. Further, the gate bus protrusion 43 and the gate bus wiring 21b are separated by laser beam irradiation. As a result, the picture element electrode 41 having a picture element defect is directly connected to the adjacent source bus wiring 23b.

The pixel electrode 41 modified in this way is
The average brightness of all the pixel electrodes 41 connected to the source bus wiring 23b adjacent to the source bus wiring 23a to which 41 is connected will be displayed, and it will be a complete point defect. Can be avoided.

FIG. 4 is a plan view of an active matrix substrate used in another embodiment of the present invention. This display device has another gate bus projection 53 projecting from the gate bus line 21b to another corner of the pixel electrode 41 in addition to the configuration of FIG.
And another source bus protrusion 56 projecting from the source bus wiring 23a to the other corner portion and overlapping the gate bus protrusion 53 via the gate insulating film 11, and being electrically connected to the pixel electrode 41. And another conductor piece 54 overlapped on the end of the gate bus projection 53 with the gate insulating film 11 interposed therebetween. The gate bus branch line 22 has the same width over the entire length, unlike the substrate of FIG.

In the active matrix display device of the present embodiment,
If a picture element defect is caused by a leak between the picture element electrode 41 and the source bus wiring 23b adjacent to the source bus wiring 23a connected to the picture element electrode 41, the embodiment shown in FIG. It can be modified in the same way as in the example. TFT3
A pixel defect due to insufficient application of the signal of the source bus wiring 23a to the pixel electrode 41 due to the defect 1 or a pixel electrode
41 and the source bus wiring 23a connected to the picture element electrode 41
If there is a pixel defect due to a leak between
The laser beam is applied to the overlapping portion of the gate bus projection 53 and the source bus projection 56 and the overlapping portion of the gate bus projection 53 and the conductor piece 54. Further, the gate bus projection 53 and the gate bus wiring 21b are separated by laser beam irradiation. As a result, the picture element electrode 41 having a picture element defect is directly connected to the source bus wiring 23a.

FIG. 5 is a plan view of an active matrix substrate used in still another embodiment of the display device of the present invention. In the display device of the present embodiment, the gate bus line 21 is superimposed on the pixel electrode 41, and an additional capacitance 42 (shaded portion) is formed at the overlapping portion of the gate bus line 21 and the pixel electrode 41. In the display device of this embodiment, compared to the embodiment of FIG.
Has the advantage that the aperture ratio is large despite having The additional capacitor 42 has a function of holding a signal from the source bus line 23 stored in the pixel electrode 41.
In this embodiment as well, the picture element defect can be corrected as in the embodiment of FIG.

FIG. 6 is a plan view of an active matrix substrate used in still another embodiment of the display device of the present invention. In the display device of the present embodiment, the additional capacitance wiring 24 is provided, and the additional capacitance 42 (shaded portion) is formed at the overlapping portion of the pixel electrode 41 and the additional capacitance wiring 24. Counter substrate 2
The same signal as that of the upper counter electrode 3 is applied. Additional capacitance wiring
24 is formed simultaneously with the gate bus wiring 21. In this embodiment, the gate bus projection 43 in the embodiment of FIG.
Instead of and 53, additional capacitance projections 45 and 55 projecting from the additional capacitance wiring 24 respectively project at the corners of the pixel electrode 41. Therefore, in the present embodiment, by irradiating a laser beam to the overlapping portion of the additional capacitance wiring protrusion 45 and the source bus protrusion 46 and the overlapping portion of the additional capacitance wiring protrusion 45 and the conductor piece 44, The picture element defect is corrected. Similarly,
By irradiating a laser beam to the overlapping portion of the additional capacitance wiring projection 55 and the source bus projection 56 and the overlapping portion of the additional capacitance wiring projection 55 and the conductor piece 54, the picture element defect is corrected. .

In the embodiment shown in FIGS. 5 and 6, the configuration in which an additional capacitor is provided in the above-described embodiment of FIG. 4 has been described. However, in the present invention, the configuration in which an additional capacitor is provided in the configuration of FIG. Can also.

(Effect of the Invention) In the active matrix type display device of the present invention, in the state of the display device in which the picture element defect can be easily detected,
The defect of the switching element or the pixel defect due to the leak between the pixel electrode and the signal line connected to the pixel electrode can be corrected so as to be inconspicuous. Further, even if a pixel defect occurs due to a leak between the pixel electrode and a signal line adjacent to the signal line connected to the pixel electrode, the defect can be corrected so as to be inconspicuous. Therefore, according to the present invention, a display device can be produced with a high yield, which can contribute to a reduction in the cost of the display device.

[Brief description of the drawings]

FIG. 1 is a plan view of an active matrix substrate used in an active matrix type display device according to one embodiment of the present invention, and FIG. 2 is a view II-II in FIG. 1 of a display device using the substrate of FIG. FIG. 3 is a sectional view taken along the line, FIG.
FIG. 4 is a cross-sectional view taken along the line III, FIG. 4 is a plan view of a substrate used in another embodiment of the display device of the present invention, FIG.
FIGS. 7A and 7B are plan views of a substrate used in an embodiment of a display device of the present invention having an additional capacitance. FIGS. 7 and 8 are plan views of an active matrix substrate used in an improved example of an active matrix display device. FIGS. FIG. 1 is a diagram showing a cause of a leak of a pixel electrode in a conventional active matrix substrate. 1,2 ... glass substrate, 3 ... counter electrode, 9, 19 ... alignment film, 11 ... gate insulating film, 12 ... channel layer, 13 ... etching stopper layer, 14 ... contact layer, 18 ... ... Liquid crystal layer, 21, 21a, 21b ... Gate bus wiring, 22 ... Gate bus branch line, 23, 23a, 23b ... Source bus wiring, 24 ... Additional capacitance wiring, 25 ... Gate electrode, 31 ... TFT , 32 ... source electrode, 33 ... drain electrode, 41 ... picture element electrode, 42 ... additional capacitance, 43, 53 ... gate bus protrusion, 44, 54 ... conductor piece, 46, 56 ... Source bus projection, 55 ... additional capacitance wiring projection.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiaki Fujiwara 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hiroshi Fujiki 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Eiji Marumoto 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) References JP-A-1-48037 (JP, A) JP-A 1-255831 (JP, A) JP-A-2-135320 (JP, A) JP-A-2-193114 (JP, A) JP-A-1-157322 (JP, U)

Claims (6)

(57) [Claims] 1. A pair of insulating substrates, a plurality of pixel electrodes arranged in a matrix on one of the pair of substrates, and a scanning line wired vertically and horizontally between the pixel electrodes. A signal line, a scanning branch line branched from the scanning line, a switching element formed at the tip of the scanning branch line, connected to the pixel electrode, and adjacent to the scanning line connected to the pixel electrode. A scanning line protrusion protruding from the scanning line to a corner of the pixel electrode; and a signal line protruding from the signal line adjacent to the signal line connected to the pixel electrode to the corner, and an insulating film formed on the scanning line protrusion. An active matrix, comprising: a signal line protrusion superimposed via the insulating film; and a conductor piece electrically connected to the picture element electrode and superposed via an insulating film at an end of the scan line protrusion. Display device. 2. The active matrix display device according to claim 1, wherein said scanning branch line has a portion having a large width at a tip portion and a portion having a small width other than the tip portion. 3. A scanning line projecting portion projecting from the adjacent scanning line to another corner of the picture element electrode, and projecting from the signal line connected to the picture element electrode to the other corner. And another signal line protrusion overlapped with the other scan line protrusion via an insulating film, and electrically connected to the picture element electrode, and an insulating film at an end of the other scan line protrusion. The active matrix display device according to claim 1, further comprising: another conductive piece superimposed on the other. 4. A pair of insulating substrates; a plurality of pixel electrodes arranged in a matrix on one of the pair of substrates; and a plurality of scanning lines wired vertically and horizontally between the pixel electrodes. A signal line, a scanning branch line branched from the scanning line, a switching element formed at the tip of the scanning branch line, connected to the pixel electrode, and an additional capacitance wiring superimposed on the pixel electrode; An additional capacitance wiring projection projecting from the additional capacitance wiring to a corner of the picture element electrode; and an additional capacitance wiring projection projecting from the signal line adjacent to the signal line connected to the picture element electrode to the corner. And a conductor piece electrically connected to the picture element electrode and superposed on an end of the additional capacitance wire projection via an insulating film. Active matrix display device. 5. The active matrix display device according to claim 4, wherein said scanning branch line has a portion having a large width at a tip portion and a portion having a small width other than the tip portion. 6. An additional capacitance line projecting portion projecting from the additional capacitance line to another corner of the picture element electrode, and projecting to the other corner from the signal line connected to the picture element electrode. And another signal line protrusion overlapped with the other additional capacitance wiring protrusion via an insulating film, and electrically connected to the picture element electrode and insulated at an end of the other additional capacitance wiring protrusion. The active matrix display device according to claim 4, further comprising: another conductive piece superimposed via a film.