JPH08893U - Liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a liquid crystal display device having no display defect by providing an appropriate auxiliary capacitance in accordance with insufficient charging of a display electrode. [Configuration] Auxiliary capacitance electrode (20) has a plurality of electrodes (21)
(22), and the overlapping area of those electrodes and the display electrode (7) is different between the electrode (21) and the electrode (22). Liquid crystal display device that can be cut with a high-energy beam.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

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

[0002]

[Prior art]

 In an active matrix type liquid crystal display device, a thin film transistor charges a pixel capacitance composed of a liquid crystal and a pair of electrodes sandwiching the liquid crystal, and the display is performed by changing the alignment state of the liquid crystal. However, since the parasitic capacitance formed between the gate electrode and the source electrode is formed in series with the pixel capacitance, the voltage applied to the liquid crystal is reduced by ΔV as shown in FIG. This decrease in voltage (ΔV) increases as the ratio of parasitic capacitance to pixel capacitance increases.

Therefore, there is an attempt to reduce the voltage drop by forming the auxiliary capacitance in parallel with the pixel capacitance. As a thin film transistor having a structure having the auxiliary capacitance, for example, in JP-A-60-110165, the auxiliary capacitance is formed on the entire surface of the display electrode.

[0004]

[Problems to be solved by the device]

 As described above, the active matrix liquid crystal display device having the structure having the auxiliary capacitance needs a large current for charging as compared with the one having only the pixel capacitance. For this reason, when the current is insufficient due to poor characteristics, charging is more likely to be insufficient. In this case, the voltage applied to the liquid crystal becomes small and the alignment becomes insufficient, which causes a problem of display failure.

[0005]

[Means for Solving the Problems]

 The liquid crystal display device of the present invention is an active matrix type liquid crystal display device in which a large number of pixel-corresponding display electrodes are arranged in a matrix, and the display electrodes are associated with auxiliary capacitance electrodes. At least one electrode of the plurality of electrodes has an area overlapping with the display electrode different from that of the other electrodes, and the connecting portion has a plurality of electrodes and a connecting portion connecting the electrodes. It can be cut by irradiation with high energy rays.

[0006]

[Action]

 According to the liquid crystal display device of the present invention, since the auxiliary capacitance electrodes having different areas are provided, it is possible to select the auxiliary capacitance electrode according to the insufficient charging of the display electrode, and by using the high energy beam or the like. The auxiliary capacitance electrode can be easily separated only by cutting the connecting portion of the auxiliary capacitance electrode. Therefore, the auxiliary capacitance can be reduced to a desired value, and thus the current value required for charging the display electrode is reduced, and the shortage of charging is eliminated.

[0007]

【Example】

1A and 1B respectively show a sectional structure and a planar structure for one pixel of a display electrode substrate of a liquid crystal display device of the present invention. The configuration of FIG. 1 will be described below in the order of the structural process. A gate electrode (2) and an auxiliary capacitance electrode (20) are formed on a glass substrate (1). Next, a gate insulating film (3), an amorphous silicon film (4) and a passivation insulating film (5) are successively formed by plasma CVD, and then a predetermined pattern is formed. Further, a phosphorus-doped n ⁺ amorphous silicon film (6) is formed by a plasma CVD method, and then a predetermined pattern is formed. Thereafter, the display electrode (7) and the drain / source electrode (8) are formed, and the n ⁺ amorphous silicon film between the drain and source electrodes is removed by etching.

As shown in FIG. 1B, the auxiliary capacitance featured by the present invention is an auxiliary capacitance electrode 20 extending from a gate electrode line 2'adjacent to a display electrode 7 and a dual capacitance. It is composed of a gate insulating film (3) sandwiched between the poles.

Thus, the auxiliary capacitance electrode (20) is, specifically, a first auxiliary capacitance electrode (21) connected to the gate electrode line (2 ′) and the first electrode (21). It comprises a second auxiliary capacitance electrode (22) connected by narrow connecting portions A and B at both ends.

At this time, the first auxiliary capacitance electrode (21) and the second auxiliary capacitance electrode (22) have an overlapping area of both electrodes (21) (22) and the display electrode (7), That is, the effective area is different.

In the case of this embodiment, the display electrode (7) is cut out on the positions of the two connecting portions A and B between the first and second auxiliary capacitance electrodes (21) and (22). Since the concave portion is located, the display electrode (7) is not irradiated with the high-energy beam to the connecting portions A and B, for example, the laser beam, and only the connecting portions A and B can be irradiated. it can.

Therefore, when the charging current is insufficient due to the characteristic defect of the thin film transistor, a desired auxiliary capacitance among the first auxiliary capacitance electrode (21) and the second auxiliary capacitance electrode (22) having different areas is obtained. The second auxiliary capacitance having a large effective area is obtained by cutting the connecting portions A and B of the first and second auxiliary capacitance electrodes (21) and (22) with a laser beam, leaving the auxiliary capacitance electrode that can be made small. Separate the electrodes (22). As a result, only the auxiliary capacitance of the first auxiliary capacitance electrode (21) becomes effective, which is about 1/2 of the total auxiliary capacitance before the laser beam cutting.

In this embodiment, as shown in FIG. 1B, the auxiliary capacitance electrode 22 is made larger than the auxiliary capacitance electrode 21.

Although the case where the number of auxiliary capacitance electrodes is two has been described in this embodiment, the number of storage capacitance electrodes is not necessarily limited to two. Even in the case of a plurality of three or more, they may be arranged continuously under the auxiliary capacitance electrode 22 of FIG.

Embodiment 2 FIGS. 2A and 2B show a sectional structure and a planar structure of another embodiment of the present invention, respectively. Also in the case of the same figure, after forming the auxiliary capacitance electrode (20) on the glass substrate (1) by a predetermined pattern, the auxiliary capacitance insulating film (9) is formed by the plasma CVD method. Next, the gate electrode (2) and the display electrode (7) are formed. Further, after a gate insulating film (3), an amorphous silicon film (4) and a passivation insulating film (5) are continuously formed, a predetermined pattern is formed. Further, a phosphorus-doped n ⁺ amorphous silicon film (6) is formed by a plasma CVD method, and then a predetermined pattern is formed. Then, a contact hole with the display electrode is opened, a drain / source electrode (8) is formed, and the n ⁺ amorphous silicon film between the drain and source electrodes is removed by etching. As shown in FIG. 2B, the auxiliary capacitance of this embodiment also has a display electrode (7), an auxiliary capacitance electrode (20) (having a first electrode (21) and a second electrode (22)), and It is composed of a storage capacitor insulating film (9) sandwiched between both electrodes.

The present embodiment is different from that of FIG. 1 in that the auxiliary capacitance line (2) is connected to the connecting portions A and B between the first auxiliary capacitance electrode (21) and the second auxiliary capacitance electrode. Any of the electrodes (21) and (22) can be separated. Therefore, by making the areas of both electrodes (21) (22) different, the set capacitance value can be selected depending on which electrode (21) (22) is cut off.

The difference of this embodiment from that of FIG. 1 is that two thin film transistors TFT1 and TFT2 are arranged in parallel, and when one transistor TFT1 is defective and the current required for charging is insufficient, In addition to the connecting portions A and B, the periphery C of the TFT 1 is cut by a high-energy beam or the like to cut off the thin film transistor TFT1 having poor characteristics, so that the parasitic capacitance can be reduced.

Although the case where the number of auxiliary capacitance electrodes is two has been described in the present embodiment, the number of storage capacitance electrodes is not necessarily limited to two. Even in the case of three or more electrodes, they may be arranged in series above or below the auxiliary capacitance electrode 21 in FIG. However, the connecting portion of the auxiliary capacitance electrode is provided in the notch in the display electrode.

[0019]

[Effect of device]

 As described above, the auxiliary capacitance electrode is composed of a plurality of electrodes, and at least one of the electrodes has a different area. Therefore, one of the electrodes that can obtain a desired auxiliary capacitance is selected and the other auxiliary capacitance is selected. Since the capacitive electrode is separated by the high energy beam, it is possible to select the set capacitance value very easily.

[Brief description of drawings]

FIG. 1 is a cross-sectional view and a plan view of a display electrode substrate of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view and a plan view of another embodiment of the device of the present invention.

FIG. 3 is a voltage waveform diagram.

[Explanation of symbols]

 20 auxiliary capacitance electrode 21 first auxiliary capacitance electrode 22 second auxiliary capacitance electrode

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[Procedure amendment]

[Submission date] December 20, 1995

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 3]

Claims (2)

[Scope of utility model registration request] 1. In an active matrix liquid crystal display device in which a large number of pixel-corresponding display electrodes are arranged in a matrix, and the display electrodes are associated with auxiliary capacitance electrodes, the pixel-corresponding auxiliary capacitance electrodes are a plurality of electrodes. And at least one electrode of the plurality of electrodes has an area overlapping with the display electrode different from that of the other electrodes, and the connection portion is irradiated with high energy rays. A liquid crystal display device characterized in that it can be cut with. 2. The liquid crystal display device according to claim 1, wherein the auxiliary capacitance electrode comprises two electrodes.