JPH02124538A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent a display defect which spreading to peripheral picture elements from being caused by making a picture element electrode and a write bus overlap with each other by a connection part which is led out of one side and interposing an insulating film at the overlap part. CONSTITUTION:The picture element electrode E and write bus WB are made to overlap with each other by the connection part 8 which is led out of one side, and the insulating film 9 is interposed at the overlap part. Then, when the corresponding position of this connection part 8 is irradiated with, for example, a laser beam, the connection part 8 is fused together with the insulating film 9 to change upper and lower conductive layers, i.e., the picture element electrode E and write bus WB into an electrically conductive state. Therefore, when an ever-off point defective picture element is detected, the potential of the picture element electrode E of the ever-off point detect picture element is made symmetrical between the positive and negative sides by connecting the picture element electrode E and write bus WB of the picture element electrically. Consequently, the expansion of a display defect at the periphery of the picture element can be prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding an active matrix type liquid crystal display device, the purpose of this invention is to prevent the expansion of display defects caused by ever-off point defects, and to prevent the expansion of display defects caused by ever-off point defects. A pixel electrode, a thin film transistor arranged in correspondence with the pixel electrode, a scan bus for applying a selection signal to the thin film transistor, and a write bus for supplying display data to the pixel electrode via the thin film transistor. , the pixel electrode and the write bus are partially overlapped by a connection portion led out from at least one side;
In addition, an insulating film is interposed in this overlap portion.

[Industrial application field]

The present invention relates to an active matrix liquid crystal display device.

[Conventional technology]

FIGS. 3(a) and 3(b) schematically show the structure of a conventional thin-film transistor-driven liquid crystal display device. As shown in Figure (a), the control electrode of the thin film transistor (hereinafter abbreviated as TPT) 3 is connected to the scanning bus SB, one of the controlled electrodes is connected to the write bus WB, also called a data bus, and the other is connected to the pixel electrode. is connected to 已. 2'rFT3 is turned on upon receiving a selection signal from the scan path SB, and the display data on the write bus WB at this time is sent to the pixel electrodes to perform display.

-F The cross-sectional structure of the liquid crystal display device is as shown in (b), which is a cross-sectional view taken along the arrow AA in Fig. W
B. Alignment film 4. and scan bus S, not shown.
B, between a TFT substrate P in which TPT3 etc. are formed on a glass substrate 1, a counter electrode E' made of an ITO film etc. and a counter substrate P° in which an alignment film 4' is formed on a glass substrate 1'- , has a configuration in which the liquid crystal 5 is sandwiched between the two.

In this configuration, the potential of the pixel electrode E of a pixel (hereinafter referred to as an ever-off point defect) that is always kept insulated from the write bus WB due to a disconnection defect in the TFT 3, etc. It is determined by the potential of WB.

[Problem to be solved by the invention]

When such an ever-off point defect exists, the optical state around the ever-off point defect changes as driving time passes, causing a phenomenon in which the display defect expands, significantly impairing display quality.

As a result of various studies on the causes of the display defects, the present inventors found that
In the display defect area, a potential difference exists between the pixel electrode E and the counter electrode E° even when no voltage is applied from the outside.
Therefore, even if a voltage waveform with positive and negative symmetry is applied from the outside, the voltage applied to the liquid crystal 5 becomes asymmetrical, and it has been found that the pixel exhibits a different optical state compared to a normal pixel. That is, it is considered that the electric charge in the ever-off point defect portion flows around to the surrounding pixels, and as a result, the potential in the peripheral portion changes.

Here, the reason why the ever-off point defect portion has a charge can be understood as follows. The potential of the ever-off point defective portion is determined by the shadows of the surrounding scan bus SB and write lotus WB. Of these, voltages with positive and negative symmetry are applied to the write bus WB, while the potential of the scan bus SB is 0 even on time average.
It has a DC component that does not Therefore, it is understood that the potential of the ever-off point defect also has a certain DC component, and as a result, the charges in the liquid crystal 5 gather at the ever-off point defect.

An object of the present invention is to prevent the expansion of display defects caused by ever-off point defects.

[Means to solve the problem]

The present invention partially overlaps the pixel electrode and the write bus by a connection portion led out from at least one side,
Moreover, an insulating film is interposed in this overlap portion.

[For production]

When a corresponding part of the connection part led out from the pixel electrode or the write bus is irradiated with a laser beam, for example, the connection part melts together with the insulating film, thereby connecting the conductive layer under L, that is, the pixel electrode and the write bus, with electricity. can be converted into a conductive state.

Therefore, when an ever-off point defective pixel is detected, the pixel electrode of that pixel is electrically connected to the write bus as described above, so that the potential of the pixel electrode of the ever-off point defective pixel becomes symmetrical in positive and negative. This makes it possible to prevent the display defects from expanding.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1(a) is a plan view of a main part showing one pixel of the above-described embodiment, and FIG. 1(b) is a sectional view taken along the line B-B in FIG. 1(a).

In this embodiment, as shown in FIG. 5A, the TFT 3 is turned on in response to a selection signal from the scanning bus SB, and the display data on the write bus WB is sent to the pixel electrode E, which is no different from the conventional method. A part of the lotus WB including the lotus WB is led out in a direction perpendicular to its extension direction, and this led out extension part 11 is covered with an insulating film 9, and the pixel electrode E
The difference is that they are formed in layers with this insulating film 9 interposed therebetween. A portion of the extension portion 11 that overlaps the pixel electrode E is defined as a connection portion 8 .

FIG. 1(b) shows a cross-sectional structure of the connection portion 8, in which an insulating film 9 (for example, approximately 110 mm
A pixel electrode E is laminated via a SiN film (SiN film with a thickness of 0 nm). The size of this connecting portion 8 is approximately 20 mm in this embodiment.
The size was μm×20 um. Note that 4 in the drawing is an alignment film.

The write bus WB, that is, the extension part 11, as shown in the figure,
A laminated film of a Cr (chromium) film 12 and an Affi film 13 was used.

TFT3 mentioned above. The pixel electrode E, the scanning lotus SB, the writing lotus WB, the connecting portion 8, and the like are formed on the glass substrate 1-1-, and constitute a TPT substrate P.

Although the structure of the TFT 3 is not particularly shown in the figure, a 960-diameter layer is formed on the glass substrate 1 corresponding to the pixel electrode E using an a-3i (amorphous silicon) layer as an active semiconductor layer and a SiN film as a gate insulating film. x240 pixels were formed.

The thus formed TPT substrate P and the above-mentioned counter substrate P
'A liquid crystal display device was constructed by filling the space between the two and the liquid crystal.

In this example, there were a total of six ever-off point defects in the liquid crystal display device, and for any three of these,
The connecting portion 8 between the pixel electrode E and the writing lotus WB is irradiated with a laser beam (beam diameter of about 10 μm) to destroy the insulating film 9.
The upper and lower pixel electrodes E and the write bus WB were electrically connected. When this panel was subjected to a running test, it was found that there were 10
While the above display defects appeared within 200 hours, no display defects were observed at the three points where the pixel electrode E and write bus WB were electrically connected by laser irradiation even after 200 hours had passed. .

FIG. 2 is a diagram showing a modification of the present invention, in which a part of the pixel electrode E is extended, and this extension part 11 is arranged as a connection part 8 facing the write bus WB with the connection line in between. It is.

The effect of this modification is exactly the same as that of the above-mentioned embodiment.

In addition, in the connection part 8 of the above-mentioned embodiment and modification,
As the insulating film 9 interposed between the pixel electrode E and the write bus WB, it is practically desirable to use an insulating film made of the same material as the insulating films from Day 1 to 1, or an insulating film made of the same material as the alignment film. This is because these materials have been conventionally used in actual products, so there is no risk of any problems occurring in the manufacturing process or in terms of properties.

Further, the insulating film 9 is made of the same material 1 as the gate insulating film, for example, a SiN film, and the film thickness is set to be the same as that of the gate insulating film.
Assuming that there are approximately 3,000 people in the department and approximately 500 people in the insulation film 9,
In the ever-off point defective pixel, the write bus WB is written to the insulating film 9.
A voltage of about 30V is applied between the pixel electrode E and the pixel electrode E. However, in a normal pixel, when the TFT 3 is on, the pixel electrode E has the same potential as the writing lot WB, so this voltage difference is used to connect the pixel electrode E. E and write bus WB can be electrically connected.

In other words, the dielectric strength voltage of the SiN film is approximately 20
Since V1 is about 3,000 people, it is about 100cm, so - [As mentioned above, the thickness of the insulating film in the TFT section including the gate insulating film is about 3,000 people, and the thickness of the insulating film 9 in the connection part 8 is about 100cm. 50
0, apply voltage to all gate electrodes to turn on all TFTs 3, and apply an AC voltage of approximately 30 V to all write buses WB, the voltage applied to the insulating film 9 at the connection part 8 will be normal. As mentioned above, since the pixel is OV, no change occurs, but since a voltage of about 30V is applied to the ever-off point defective pixel, the insulation of the insulating film 9 is broken, and the pixel electrode E and write bus WB are electrically connected. connected.

By selecting the material and thickness of the insulating film 9 in this way, the pixel electrode E and the write bus WB at the connection part 8 can be
In addition to being connected by laser beam irradiation, they can also be electrically connected.

〔Effect of the invention〕

As described above, according to the present invention, even if an ever-off point defect exists in a thin film transistor-driven liquid crystal display device, it is possible to prevent the display defect from spreading to peripheral pixels.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams explaining the configuration of one embodiment of the present invention, Figure 2 is a detailed diagram explaining the present invention, and Figures 3 (a) and (b) are diagrams explaining the problems of the conventional technology. It is. In the figure, ■, 1° is a glass substrate, 3 is TPT (Fi
Film transistor L4, 4'' is an alignment film, 5 is a liquid crystal, 8 is a connecting portion, 9 is an insulating film, SB is a scanning bus, WB is a write bus, and E is a pixel electrode.

Claims (3)

[Claims] (1) A plurality of pixel electrodes (E) arranged in a matrix on an insulating substrate (1), thin film transistors (3) arranged in correspondence with the pixel electrodes, and a selection signal applied to the thin film transistors. In the configuration, the pixel electrode (E) and the write bus (WB) are connected to the pixel electrode (E), and the write bus (WB) supplies display data to the pixel electrode (E) via the thin film transistor. The connection part (8) led out from at least one side overlaps the part, and the insulating film (9) is formed in this overlap part.
) is used as an active matrix liquid crystal display device. (2) The insulating film (9) is connected to the thin film transistor (3).
2. The active matrix liquid crystal display device according to claim 1, wherein the insulating film is made of the same material as the gate insulating film (2) of the active matrix type liquid crystal display device. (3) The active matrix liquid crystal display device according to claim 1, wherein the insulating film (9) is an insulating film made of the same material as the alignment film (4).