JPH03212620A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To allow nearly the complete repair of the spot defects occurring in the shorting between electrodes by providing conductors which overlap on respective display electrodes respectively via insulating films and are not electrically connected to other picture element constituting elements between the respective display electrodes which are dividedly disposed to plural pieces per picture element. CONSTITUTION:The display electrodes 26 are dividedly disposed by two pieces per picture element and TFTs 13 are respectively provided on the respective display electrodes 26. The conductor 31 insulated by the gate insulating film 22 is provided on the two display electrode 26 so as to partly overlap thereon. The broken line a1 part of an auxiliary capacity line 17 is first cut by a laser when a shorting arises at the point x1 between the display electrode 26 and the auxiliary capacity line 17. The overlap part between the conductor 31 and the two display electrode 26 is then punched by a laser to short the conductor 31 and the two display electrode 26 through the gate insulating film 22 so that the two display electrode 26 are electrically conducted by the conductor 31. Eventually half the initial auxiliary capacity remains in this way and the high display grade is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an active matrix liquid crystal display device using thin film transistors and the like as switching elements for driving pixels.

(Prior Art) Liquid crystal display devices have characteristics such as being thin, lightweight, and low power consumption, and are widely used as display devices for portable devices. Among these, the active matrix type is particularly often used for personal computer display devices that require high definition, television screens, and the like. This active matrix liquid crystal display device uses a thin film transistor (hereinafter referred to as a thin film transistor) provided for each pixel.
Image signals are selectively applied to the display element array using a switching element such as TPT, which makes it possible to obtain a clear image with high contrast and no crosstalk.

The operating principle of the active matrix liquid crystal display device will be explained below with reference to FIG. In FIG. 4, at each intersection of a plurality of scanning lines 11, which are row selection lines, and a plurality of signal lines 12, which are column selection lines, a switching element is provided.
A F T 13 is provided, and the liquid crystal layer 14 and the pixel capacitor 15 are connected via this TFT 13 . Then, the scanning circuit 16 sequentially applies gate pulses to the plurality of scanning lines 11. Further, the signal hold circuit 17 outputs the image signal for one line of the scanning line 11 to which the gate pulse is added to the plurality of signal lines 12 in synchronization with the gate pulse.

T P T 13 is in a conductive state while a gate pulse is applied to the corresponding scanning line 11, and accumulates charge in the pixel capacitor 15 according to the image signal output to the signal line 12 at that time. to drive the liquid crystal layer 14. When the gate pulse moves to the next scanning line 11, the T F T 13 for one line becomes non-conductive, and the accumulated charges are held until the next scanning.

As a result, the display state of the liquid crystal layer 14 is maintained.

5 and 6 show an example of the configuration of one pixel of this type of active matrix liquid crystal display device.
The figure is a plan view on the array substrate, and Figure 6 is Figure 5 VI-V.
It is a sectional view of a part.

The T F T 13 is formed on a glass substrate 20 shown in the lower part of the figure, and includes a gate electrode 21 . It consists of a gate insulating film 22, a semiconductor layer 23, a drain electrode 24 integral with the signal line 12, and a source electrode 25, and a display electrode 26 is connected to this source electrode 25. Further, an auxiliary capacitance line 27 is formed substantially parallel to the scanning line 11. This auxiliary capacitance line 27 is provided so as to partially face the display electrode 26 with the gate insulating film 22 in between, and provides additional auxiliary capacitance at the overlapped portion with the display electrode 26. This auxiliary capacitance increases the pixel capacitance 15 in FIG. 4 and alleviates leakage current of the TFT 13 during the holding period and fluctuations in display electrode potential due to capacitive coupling between the display electrode 26 and other electrodes.

On the other hand, a common electrode 29 is formed on the glass substrate 28 in the upper part of the figure, and faces the glass substrate 20 in the lower part of the figure with the liquid crystal layer 14 interposed therebetween. The electric field between this common electrode 29 and the display electrode 26 drives the liquid crystal layer 14 located between them to perform a predetermined display.

(Problems to be Solved by the Invention) The active matrix liquid crystal display device having the structure described above has a complicated electrode arrangement and uses multilayer wiring, so short circuits between the electrodes are likely to occur. Most of these short circuits occur between the gate electrode 21 and the source electrode 25, which are arranged with the gate insulating film 22 in between, and between the display electrode 26 and the auxiliary capacitor line 27. When such a short circuit occurs, the potential of the display electrode 26 does not reach a predetermined value, causing point defects on the display screen. In particular, bright spot defects greatly impair image quality and are a major factor in reducing yield.

If such a point defect occurs, repair is required to remove the short portion. Various repair methods have been proposed in the past, and a typical example is a repair method using a laser.

In this repair method, for example, when a short circuit occurs between the display electrode 26 and the auxiliary capacitance line 27, the auxiliary capacitance line 27 is cut at the broken line part a with a laser to remove the short part, as shown in FIG. It is being removed.

However, according to the above repair method, the repaired pixel loses its auxiliary capacitance, so it becomes more susceptible to leakage current of the TFT 13 and capacitive coupling between the display electrode 26 and other electrodes. For this reason, the potential of the display electrode 26 deviates from a predetermined potential, and it is difficult to make point defects completely inconspicuous. Further, such a repair method cannot be applied to cases where the auxiliary capacitance line 27 is supplied with power only from one side or to a short circuit between the gate electrode 21 and the source electrode 25.

An object of the present invention is to provide an active matrix liquid crystal display device that can almost completely repair point defects caused by short circuits between electrodes, etc., by a laser repair method, and has high display quality with almost no point defects. Our goal is to provide the following.

[Structure of the invention]

(Means for Solving the Problems) An active matrix liquid crystal display device according to the present invention has a plurality of row selection lines and column selection lines arranged so as to intersect each other with an insulating film interposed therebetween, and each of these lines forming one pixel. A switching element and a display electrode are provided through the switching element at each intersection, and an auxiliary capacitor is formed in a part of the display electrode,
In a structure in which a liquid crystal layer is sandwiched between the display electrode and a common electrode facing the display electrode, the display electrode is divided into a plurality of parts per pixel, and each display electrode is provided with the switching element. , a conductor is provided between each of the display electrodes and overlaps with each display electrode via an insulating film and is not electrically connected to other pixel constituent elements.

(Function) In the present invention, when a short circuit occurs between electrodes, the short section is removed by laser cutting, etc., and then the conductor is shorted at the overlapped portion with each display electrode, and each display electrode is connected to the conductor. Connect electrically.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. Note that parts corresponding to those of the apparatus shown in FIGS. 4, 5, and 6 will be described with the same reference numerals.

FIG. 1 is a plan view showing one pixel portion on the array substrate. In FIG. 1, a plurality of scanning lines 11 are row selection lines.
and a plurality of signal lines 12, which are column selection lines, are arranged so as to cross each other, and a TFT 13, which is a switching element, is provided at each intersection. This TP
T+3 is a gate electrode 21 integrated with the scanning line 11
, a semiconductor layer 23, a drain electrode 24 integrated with the signal line 12, and a source electrode 25.
A display electrode 26 is connected to 5. Further, an auxiliary capacitance line 27 is formed substantially parallel to the scanning line 11.

Two TPTIs 3 and display electrodes 26 as the switching elements are provided for each pixel, and these are arranged in parallel along the length direction of the scanning line 11 as a row selection line in the horizontal direction in the figure. . That is, the display electrode 26 is divided into two parts per pixel, and each of the divided display electrodes 26 is provided with a TFT 13. Furthermore, conductors 31 are provided for the two display electrodes 26 per pixel so as to partially overlap with each of them. However, as shown in FIG. 2, this conductor 31 is insulated from the two display electrodes 26 by a gate insulating film 22.

Furthermore, the scanning line 11 crosses these two display electrodes 26.
The auxiliary capacitance line 27 is formed substantially parallel to the auxiliary capacitance line 27.

FIG. 2 is a sectional view taken along the line n-yn in FIG. 1 of the one pixel portion.

The configuration of this part will be explained below according to the manufacturing process. First, the array substrate A side shown in the lower part of the figure will be explained. First, a chromium (Cr) film, which is a light-shielding material, is coated on the entire surface (upper surface in the figure) of an insulating substrate 20 made of, for example, glass by sputtering, and then photo-etched into a predetermined shape. A gate electrode 21, an auxiliary capacitance line 27, and a conductor 31 are respectively formed. At this time, the scanning line 11 as the row selection line in FIG. 1 is also formed integrally with the gate electrode 21 in the same process. Next, a gate insulating film 22 made of silicon oxide (S i Ox), for example, is formed by plasma CVD so as to cover these.

This gate insulating film 22 is the gate electrode 2 in FIG.
This is an insulating film interposed between the drain electrode 24 and the source electrode 25. Further, in a portion of the gate insulating film 22 facing the gate electrode 21, a semiconductor layer 23 made of, for example, i-type hydrogenated amorphous silicon (a-3i: H) is formed using a plasma CVD method. . On this semiconductor layer 23, a drain region 24a and a source region 251 made of n-type a-3i:H and electrically isolated from each other are provided using the same plasma CVD method.

Further, a display electrode 26 is provided on a portion of the gate insulating film 22 adjacent to the source region 2Sa side. The display electrode 26 is formed, for example, by coating an ITO (indium tin oxide) film by sputtering and then photoetching it into a predetermined shape. Also, source area 2
5! One end of a source electrode 25 is connected to the display electrode 26 , and the other end of the source electrode 25 extends over and is connected to the display electrode 26 .

On the other hand, one end of the drain electrode 24 is connected to the drain region 241 . Here, the drain electrode 24 and the source electrode 25 are formed in the same process, for example, by sequentially forming a molybdenum (MO) film and an aluminum (A1) film by sputtering and then photoetching them into a predetermined shape. Further, the signal line 12 as a column selection line in FIG. 1 is also formed integrally with the drain electrode 24 in the same process.

As a result, a predetermined array substrate A is obtained.

Next, on the opposing substrate B side shown in the upper part of the figure, first, a common electrode 29 made of, for example, ITO is formed on one main surface (lower surface in the figure) of an insulating substrate 28 made of, for example, glass.

Here, on the entire surface of one main surface of the array substrate A, an alignment film 3 made of, for example, low-temperature cure type polyimide (PI) is formed.
2 is formed, but an alignment film 33 made of, for example, low-temperature cure type polyimide is also formed on the entire main surface of the counter substrate B.

Then, by rubbing the alignment films 32 and 33 formed on one main surface of the array substrate A and the counter substrate B in a predetermined direction with a cloth or the like, an alignment treatment by rubbing is performed, respectively. Further, as described above, the array substrate A and the counter substrate B have their main surfaces facing each other, and their orientation axes are approximately 9
Combine to form G'. Then, the liquid crystal layer 14 is sandwiched within the interval obtained by these.

Note that polarizing plates 34 and 35 are attached to each of the other surfaces of the array substrate A and the counter substrate B, and illumination is applied from the other main surface side of either the array substrate A or the counter substrate B. will be held.

In the above configuration, if a short circuit occurs between the display electrode 26 and the auxiliary capacitance line 27, for example at the point x1 marked with an X in FIG. The shorted portion is removed by cutting portions corresponding to both sides of the display electrode 26 on the left side in the figure. Next, the overlapping portions of the conductor 31 and the two display electrodes 26 are punched out using a laser, and the gate insulating film 22 is penetrated to short-circuit between the conductor 31 and the two display electrodes 26, thereby making the two display electrodes 26 conductive. It is electrically connected by the body 31.

In this way, for the entire pixel, the initial auxiliary capacitance is 1
/2 remains, compared to the conventional case shown in Figure 5.
It is possible to suppress leakage current of the TFT 13 and deviation in display electrode potential due to capacitive coupling between the display electrode 26 and surrounding electrodes, and it is possible to make the repaired pixel almost invisible.

Furthermore, if the gate electrode 21 and the source electrode 25 are short-circuited, for example at point x2 marked with an X in FIG. By separating the
Remove the short part. In this case, do the same as above,
By electrically connecting the two display electrodes 26 with the conductor 31, charge can also be supplied to the display electrode 26 separated from the TFT 13.

We actually observed the display state of an LCD panel with the above point defect repaired in white raster, black raster, and video display, but in all cases, the difference in brightness between the repaired pixel and its surrounding pixels was very large. We were able to keep it small and to a level that poses no practical problems.

FIG. 3 shows one on the array substrate in another embodiment of the present invention.
FIG. 3 is a plan view showing a pixel portion. This embodiment differs from the embodiment shown in FIG. 1 in the position of the auxiliary capacitance line 27 and the shape of the two display electrodes 26.

That is, the auxiliary capacitor line 27 is arranged at the upper end of the two display electrodes 26, and each display electrode 26 is provided with the auxiliary capacitor line 27.
A constricted portion 36 along the line 7 is provided.

In the above configuration, if a short circuit occurs between the display electrode 26 and the auxiliary capacitance line 27, that is, at point x3 marked with an X in FIG. , remove the short part. Thereafter, the overlapping portions of the conductor 31 and the two display electrodes 26 are punched out using a laser, and the two display electrodes 26 are electrically connected via the conductor 31.

In the embodiment shown in FIG. 1, the auxiliary capacitor line 4G is supplied with power from both sides in order to disconnect the auxiliary capacitor line 27 in the event of a short circuit between the auxiliary capacitor line 27 and one of the display electrodes 26. Even if only one spot can be repaired on one line, on the other hand, if power is supplied from one side, repair cannot be done. On the other hand, in the embodiment shown in FIG.
6, it can be applied even when the auxiliary capacitance line 27 is supplied with power only from one side. The effect of laser repair is exactly the same as the embodiment shown in FIG.

In each of the above embodiments, two display electrodes 26 are provided for each pixel, but the display electrodes 26 may be divided into three or more and arranged in parallel. By dividing the display electrode 26 into a plurality of parts for each pixel in this manner, it becomes easier to identify a failed part. Further, the auxiliary capacitance line 27 does not need to be particularly provided if it is not necessary.

〔Effect of the invention〕

As described above, according to the present invention, point defects caused by short circuits between electrodes, etc. can be almost completely repaired by laser repair methods, etc., and therefore, there are almost no point defects and high An active matrix liquid crystal display device with high display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view of one pixel portion on an array substrate showing an embodiment of an active matrix liquid crystal display device according to the present invention, FIG. 2 is a sectional view taken along the line ■-■ in FIG. 1, and FIG. A plan view of one pixel portion on an array substrate showing another embodiment of the present invention, FIG. 4 is an explanatory diagram of the operating principle of an active matrix type liquid crystal display device, and FIG. FIG. 6 is a plan view of one pixel portion on the array substrate shown, and FIG. 6 is a sectional view taken along the line Vl-VI in FIG. 11.. Row selection line, 12.. Column selection line, 13.. Switching element, 14.. Liquid crystal layer, 22.. Insulating film, 26.
-Display electrode, 29... common electrode, 31... conductor.

Claims (1)

[Claims] (1) A plurality of row selection lines and a plurality of column selection lines are arranged so as to intersect with each other via an insulating film, and a switching element is displayed at each intersection of these lines, each forming one pixel, via the switching element. In an active matrix liquid crystal display device in which an electrode is provided, an auxiliary capacitance is formed in a part of the display electrode, and a liquid crystal layer is sandwiched between the display electrode and a common electrode opposite thereto, the display electrode is Each pixel is divided into a plurality of parts and arranged, and each display electrode is provided with the switching element, and each display electrode overlaps with each display electrode via an insulating film and is electrically connected to other pixel constituent elements. An active matrix liquid crystal display device characterized by having a conductor that is not electrically connected.