JPH0566415A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain the active matrix type liquid crystal display device which enables picture element defect repair using a laser and hardly sacrifices display electrode area. CONSTITUTION:This liquid crystal display device is equipped with an array substrate where a thin film transistor(TFT) formed on an insulating substrate, a display electrode connected to the source electrode of the TFT, and an auxiliary capacity electrode connected to the display electrode are arranged in matrix nearby the intersection of a row selection line and a column selection line, and a conductor 47 which overlaps with the respective electrodes and are not connected electrically is formed between a 1st display electrode 38 among display electrodes and a 2nd display electrode 45 which is arranged nearby the intersection of the row selection line and column selection line adjacently to the 1st display electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device using a thin film transistor (hereinafter abbreviated as TFT) as a switch element.

[0002]

2. Description of the Related Art Generally, an active matrix type liquid crystal display device has a high definition by applying image signals selectively to a display element array by a switch element provided for each pixel and driving the liquid crystal quasi-statically.・ It aims to obtain a clear image with high contrast and high response speed and no crosstalk.

By the way, FIG. 5 shows a TF as a switching element.
FIG. 3 is an equivalent circuit diagram for explaining a driving principle of an active matrix type liquid crystal display device using T, in which a liquid crystal 4 and a pixel capacitance 5 are provided via a TFT 3 at each intersection of a scanning line 1 and a signal line 2. It is connected. Then, the scanning circuit 6 sequentially applies the gate pulse to the scanning line 1, and the signal holding circuit 7 outputs the image signal for one line of the scanning line 1 to the signal line 2 in synchronization with the gate pulse. The TFT 3 becomes conductive while the gate pulse is applied to the predetermined scanning line 1, and charges are accumulated in the pixel capacitor 5 in accordance with the image signal output to the predetermined signal line 2 at that time, and the liquid crystal 4 is driven. Furthermore,
When the gate pulse is transferred to the next scanning line 1, the TFT 3 becomes non-conductive, and the accumulated charges are held until the next scanning, so that the display state of the liquid crystal 4 is maintained.

In recent years, with the development of flat displays, miniaturization of display-equipped devices has been rapidly progressing. However, the demand for active matrix type liquid crystal display devices is increasing due to the demand for colorization and higher definition.
Further, as a home television receiver and a video monitor, a projection type using the same liquid crystal display device is expected from the demand for a large screen.

However, since the active matrix type liquid crystal display device requires growth of a thin film and fine processing by photolithography in its manufacturing process, it is difficult to manufacture it without defects over a large area. Therefore, this has occurred for mass production of an active matrix type liquid crystal display device which is large in size corresponding to a direct view type of an active matrix type liquid crystal display device and has high definition, or miniaturization corresponding to a projection type and ultra high definition. It is essential to develop a technology for repairing defects in a later process, and various proposals have been made. A typical example is a pixel repair method using a laser.

6 and 7 are schematic views showing an example of one pixel of an active matrix type liquid crystal display device in consideration of laser repair. FIG. 6 is a plan view of an array substrate of the liquid crystal display device, and FIG. 6 is a cross-sectional view of the liquid crystal display device taken along line CC ′ of FIG. 6 and viewed in the direction of the arrow.

As shown in the figure, each constituent element of the pixel is formed on a glass substrate 10. The display electrode 11, a part of which also serves as the auxiliary capacitance electrode, is divided along the longitudinal direction of the signal line 2, and the TFT 3 is provided for each of the divided portions. The TFT 3 includes a gate electrode 12 integrated with the scanning line 1, a gate insulating film 13, a drain electrode 14 integrated with the signal line 2,
It comprises a source electrode 15 adhered to the display electrode 11 and a semiconductor layer 16. Then, a conductor 17 is formed between the two display electrodes 11 via the gate insulating film 13 so as to overlap both display electrodes 11.
Further, an auxiliary capacitance line 18 is formed in a direction substantially parallel to the scanning line 1 so as to partially face the display electrode 11 with the gate insulating film 13 interposed therebetween. A load-like auxiliary capacity can be obtained at the overlapping portion.

This auxiliary capacitance corresponds to the pixel capacitance 5 in FIG.
Has an important function of alleviating the leakage current of the TFT 3 during the holding period and the fluctuation of the display electrode potential due to the coupling capacitance between the display electrode 11 and other electrodes.

On the other hand, as is apparent from FIG. 7, a common electrode 20 is formed on the glass substrate 19 and faces the glass substrate 10 with the liquid crystal 4 interposed therebetween. Then, a predetermined display is performed by the electric field between the display electrode 11 and the common electrode 20.

The pixel shown in FIG. 6 is mainly composed of the display electrode 11
It is formed in consideration of repairing a short circuit between the auxiliary capacitance lines 18. In general, the storage capacitor portion has a very large area, so the above-mentioned short circuit is likely to occur and accounts for most of the pixel defects.

The pixel repairing method shown in FIG. 6 will be described. When a short circuit occurs at the X portion on the auxiliary capacitance line 18, laser cutting is first performed along the broken line-(1) to remove the shorted auxiliary capacitance electrode portion. Separated from the display electrode 11.

Next, the overlapping portion between the conductor 17 and the display electrode 11 is laser-bonded to electrically connect both display electrodes 11 so that the remaining auxiliary capacitance is shared between both display electrodes 11. The purpose is to suppress the influence of the decrease in auxiliary capacity to a small level.

[0013]

By the way, the liquid crystal display elements including the active matrix type are not self-luminous types, and their functions are merely optical shutters. Therefore, in order to obtain brightness, which is an important performance as a display element, the liquid crystal display element needs to have a high light transmittance. Therefore, in the array substrate, the display electrode area needs to be as large as possible.

Under such requirements, in the example of the pixel defect repairing method shown in FIG. 6, the display electrode 11 is divided in order to suppress the fluctuation of the display electrode potential, and the TFT 3 is further provided in each display element. Has been formed. Although there is an effect of repairing the pixel defect, the area of the display electrode of the array substrate is reduced, and the transmittance required for the liquid crystal display element is sacrificed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an active matrix type liquid crystal display device capable of repairing pixel defects by a laser and hardly sacrificing a display electrode area.

[0016]

According to the present invention, there is provided a thin film transistor comprising a gate electrode, a gate insulating film, a semiconductor film, a source electrode and a drain electrode on a first insulating substrate, and a display connected to the source electrode. An array substrate in which electrodes and auxiliary capacitors connected to the display electrodes are arranged in a matrix near intersections of the row selection lines integrated with the gate electrodes and the column selection lines integrated with the drain electrodes;
An active substrate including an opposing substrate which is disposed with a predetermined gap from the array substrate and has a common electrode formed on a second insulating substrate, and a liquid crystal sandwiched between the array substrate and the opposing substrate. In a matrix type liquid crystal display device,

Of the above-mentioned display electrodes, a first display electrode and a second display electrode adjacent to the first display electrode near the intersection of the row selection line and the column selection line are respectively provided. An active matrix type liquid crystal display device, characterized in that a conductor having an overlapping portion with an electrode and not electrically connected is formed.

[0018]

According to the present invention, by devising the shape and arrangement of the constituent elements of the pixel, the pixel defect is repaired, and the active matrix type liquid crystal display device having the high display quality with almost no pixel defect and the bright display performance. Is obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

The active matrix type liquid crystal display device of the present invention is constructed as shown in FIGS. 1 and 2, FIG. 1 is a plan view showing two pixels on the array substrate, and FIG. 2 is A of FIG.
FIG. 6 is a cross-sectional view of the TFT section taken along line -A ′ and seen from the direction of the arrow.

[0021] That is, TFT 30 as apparent from FIG. 1
Is a gate electrode 32 integrated with a row selection line 31, a gate insulating film 33, a semiconductor layer 34, a drain electrode 36 integrated with a column selection line 35, an auxiliary capacitance electrode 37 formed on an insulating substrate 49 (see FIG. 2). And a source electrode 39 adhered to the display electrode 38 formed together.

Similarly, the TFT 40 has an insulating substrate 49 (see FIG. 2).
The gate electrode 41, the gate insulating film 33, the semiconductor layer 34, and the column selection line 42 which are integrated with the row selection line 31 formed above.
A drain electrode 43, an auxiliary capacitance electrode 44, and a source electrode 46 adhered to a display electrode 45 formed together.

Between the display electrode 38 and the display electrode 45, a conductor 47 electrically floating from each of the electrodes 38, 45 and the column selection line 42 is provided.
Are formed so as to overlap. Further, an auxiliary capacitance line 48 is formed across the auxiliary capacitance electrodes 37 and 44 in a direction substantially parallel to the row selection line 31. Such an array substrate will be described according to the manufacturing process with reference to FIG.

First, an insulating substrate 49 made of glass, for example.
A gate electrode 32, an auxiliary capacitance line 48 and a conductor 47 are formed by coating a Cr (chrome) film, which is a light-shielding material, on the one main surface by a sputtering method and then photoetching it into a predetermined shape. Further, a gate insulating film 33 made of, for example, silicon oxide (SiOx) is formed by plasma CVD so as to cover it. The gate insulating film 33 includes the gate electrode 32 and the source electrode 3
9 is an insulating film interposed between the two.

At a portion of the gate insulating film 33 facing the gate electrode 32, a semiconductor layer 34 made of, for example, i-type hydrogenated amorphous silicon (a-Si: H) is provided as a plasma C.
It is formed using the VD method. Further, the semiconductor layer 34
A drain region 5 made of n-type hydrogenated amorphous silicon (a-Si: H) electrically isolated from each other is provided above the drain region 5.
0 and the source region 51 are also provided by using the plasma CVD method. Then, on the gate insulating film 33 adjacent to the source region 51 side of the semiconductor layer 34, for example, I
After a TO (indium tin oxide) film is coated by the sputtering method, the display electrode 38 and the auxiliary capacitance electrode 37 are collectively formed by photoetching into a predetermined shape. Further, one end of the source electrode 39 is connected to the source region 51, and the other end of the source electrode 39 extends and is connected to the display electrode 38.

Further, one end of the drain electrode 36 is connected to the drain region 50. Here, the drain electrode 36 and the source electrode 39 are formed in the same process in which, for example, a Mo (molybdenum) film and an Al (aluminum) film are sequentially coated by a sputtering method and then photoetched into a predetermined shape. The row selection line 31 in FIG. 1 is also formed in the same process as the drain electrode 36 and the source electrode 39. Thus, the desired array substrate 52 is obtained.

On the other hand, the insulating substrate 53 made of glass, for example.
A counter electrode 55 is formed by forming a common electrode 54 made of, for example, ITO on one main surface. An alignment film 56 made of, for example, polyimide (PI) is formed on the entire main surface of the array substrate 52, and also on the entire main surface of the counter substrate 55, for example, polyimide. An alignment film 57 made of (PI) is formed. Then, the array substrate 52 and the counter substrate 5
By rubbing each of the alignment films 56 and 57 on the one main surface 5 with a cloth or the like in a predetermined direction, the alignment treatment by rubbing is performed. Further, the array substrate 52 and the counter substrate 55 are combined such that their main surfaces are opposed to each other and their alignment films 56 and 57 form an angle of about 90 °, and the liquid crystal 60 is held in a gap obtained from the alignment films 56 and 57. Has been done.

Polarizing plates 58 and 59 are attached to the other main surface side of the array substrate 52 and the counter substrate 55, respectively. From the other main surface side of either the array substrate 52 or the counter substrate 55. It is designed to illuminate.

In this embodiment, when a short circuit occurs between the auxiliary capacitance electrodes 37 and 44 at the cross mark of the auxiliary capacitance portion, the broken line is first drawn.
Laser cutting is performed along (2) to separate the defective auxiliary capacitance electrode 37 from the display electrode 38. At this point, the display electrode 38 does not become a pixel defect, but the potential difference of the pixel electrode from the surrounding normal pixels becomes so large that it cannot be ignored, and the display quality is degraded.

Therefore, next, the display electrode 38 and the display electrode 45
A conductor 47 formed between and electrically suspended
Laser bonding with the respective electrodes to electrically connect the display electrode 38 and the display electrode 45, and share the auxiliary capacitance formed by the auxiliary capacitance electrode 44 and the auxiliary capacitance line 48 with the display electrodes 38 and 45. .. By doing so, it is not necessary to divide the pixel for repairing the pixel defect, that is, there is no decrease in the display electrode area due to the pixel division, it is bright as a display element, and the pixel defect can be repaired and the display quality is good. An active matrix type liquid crystal display device can be obtained. (Other embodiments)

FIGS. 3 and 4 show another embodiment of the present invention. FIG. 3 is a plan view showing two pixels on the array substrate, and FIG. 4 is a view taken along the line BB 'in FIG. FIG. 6 is a cross-sectional view of the TFT portion cut by cutting and viewed in the direction of the arrow, and the same effect as that of the above-described embodiment can be obtained.

In this other embodiment, as compared with the case of the above embodiment, the electrically floating conductor 47 is overlapped with the display electrodes 38 and 45 of the vertically adjacent pixels in FIG. It is different in that it is formed in the place. The repairing method in the other embodiments is the same as that in the above embodiment.

[0033]

According to the present invention, by devising the shape and arrangement of the constituent elements of the pixel, the pixel defect is repaired, and the active matrix type liquid crystal having a high display quality with almost no pixel defect and a bright display performance. A display device can be realized.

[Brief description of drawings]

FIG. 1 is a plan view showing two pixels on an array substrate in an active matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the TFT section taken along the line AA ′ of FIG. 1 and viewed in the direction of the arrow.

FIG. 3 is a plan view showing two pixels on an array substrate in an active matrix type liquid crystal display device according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of the TFT section taken along line BB ′ of FIG. 3 and viewed in the direction of the arrow.

FIG. 5 is an equivalent circuit diagram of a conventional active matrix liquid crystal display device.

FIG. 6 is a plan view showing two pixels on an array substrate in a conventional active matrix type liquid crystal display device.

7 is a cross-sectional view of the TFT section taken along the line CC ′ of FIG. 6 and viewed in the direction of the arrow.

[Explanation of reference numerals] 30 , 40 ... TFT, 31 ... Row selection line, 32, 41 ... Gate electrode, 33 ... Gate insulating film, 34 ... Semiconductor film, 3
5, 42 ... Column selection lines, 36, 43 ... Drain electrodes, 3
7, 44 ... Auxiliary capacitance electrode, 38, 45 ... Display electrode, 3
9, 46 ... Source electrode, 47 ... Conductor, 48 ... Auxiliary capacitance line, 49, 53 ... Insulating substrate, 52 ... Array substrate, 54 ...
Common electrode, 55 ... Counter substrate, 60 ... Liquid crystal.

Claims (1)

[Claims] 1. A thin film transistor comprising a gate electrode, a gate insulating film, a semiconductor film, a source electrode and a drain electrode on a first insulating substrate, a display electrode connected to the source electrode, and a display electrode connected to the display electrode. An array substrate in which the formed auxiliary capacitance electrodes are arranged in a matrix in the vicinity of an intersection of a row selection line integrated with the gate electrode and a column selection line integrated with the drain electrode, and a predetermined gap with the array substrate. An active matrix type liquid crystal display device comprising: a counter substrate having a common electrode formed on a second insulating substrate; and a liquid crystal sandwiched between the array substrate and the counter substrate. Between the first display electrode of the electrodes and the second display electrode arranged near the intersection of the row selection line and the column selection line adjacent to the first display electrode, the respective electrodes are provided. An active matrix type liquid crystal display device, characterized in that a conductor having an overlapping portion with and not electrically connected is formed.