CN2237857Y - A storage capacitor structure of a thin film transistor liquid crystal display - Google Patents

Abstract

The utility model discloses a grid-shaped storage capacitor structure of a thin film transistor liquid crystal display. On the one hand, the aperture ratio can be increased; The adjacent part of the line is reduced, which can effectively reduce the short circuit phenomenon and reduce the delay capacitance effect.

Description

A storage capacitor structure of a thin film transistor liquid crystal display

The utility model relates to a storage capacitor structure of a thin film transistor liquid crystal display, in particular to designing the first electrode of the storage capacitor of the thin film transistor liquid crystal display into a grid shape, and is located at the central part of the pixel electrode, respectively separated from the pixel electrode About 1/4 of the upper and lower places, the vertical part of the grid-shaped storage capacitor is located in the upper plate light-shielding matrix, which can effectively reduce the short circuit phenomenon and reduce the delay capacitance effect.

Thin film transistors (hereinafter referred to as TFTs) have been widely used in liquid crystal displays. The signal is transmitted through the TFT and stored in the liquid crystal capacitor at each scan time (about 63.5 μs), and the signal is updated at the next scan (about 16.7 ms). But generally, the capacitance value of current liquid crystal is not large (about 0.3pf), and the signal charge that can be stored is limited. The loss of charge in each scanning interval causes the equivalent voltage to drop, causing the screen to flicker; in addition, the thin film transistor inevitably has a gate. The coupling capacitance Cgs formed by the overlapping area with the source electrode will cause a voltage drop ΔVgs on the pixel electrode (as shown in Figure 1) $\mathrm{\ΔVgs}=\frac{\mathrm{Cgs}}{\mathrm{Cls}+\mathrm{Cgs}}\&Center\; Dot;\mathrm{Vg}$

In order to reduce the above-mentioned effects, various manufacturers have designed a structure in which the storage capacitor Cs is connected in parallel with the liquid crystal capacitor to solve the above-mentioned problems. downgraded to $\mathrm{\ΔVgs}=\frac{\mathrm{Cgs}}{\mathrm{Cls}+\mathrm{Cs}+\mathrm{Cgs}}\&Center\; Dot;\mathrm{Vg}$

There are three kinds of storage capacitor manufacturing methods known in the prior art, which are described as follows: Fig. 2 (a) shows the storage capacitor of the first known thin film transistor liquid crystal display, and the storage capacitor 14 is composed of an AND gate The electrode 11 is composed of a metal electrode, a gate insulating layer 12, and an ITO electrode 13 formed at the same time. Figure 2(b) is its top view, and the oblique line part is the metal electrode of the storage capacitor. It can be seen from the figure that the metal electrode of the storage capacitor crosses the pixel electrode, which reduces the aperture ratio of the thin film transistor liquid crystal display.

Fig. 3 (a) shows the storage capacitor of the second known thin film transistor liquid crystal display, its storage capacitor 14 utilizes the extended part of the gate 11 to form together with the gate insulating layer 12, ITO electrode 13, although its storage The capacitor is located in the upper layer shading matrix 21, which increases the aperture ratio, but if there is an alignment deviation in the production, the storage capacitor value of each exposure area will change, and this design method makes the storage capacitor unable to be connected to the common electrode. When driving this Thin film transistors are prone to leakage or collapse. Figure 3(b) is its top view.

Fig. 4 (a) shows the storage capacitor of the third known thin film transistor liquid crystal display, and it is made up identical with the storage capacitor of the first kind of known mode, for avoiding affecting aperture ratio, storage capacitor 14 is arranged in the image Around the plain electrode, try to make the storage capacitor position in the upper layer light-shielding matrix 21, but this structure will make the storage capacitor very close to the scanning line, which will easily cause a short circuit between the two, and the storage capacitor is too close to the scanning line and the signal line. The delay capacitance effect is derived, and Figure 4(b) is its top view.

The storage capacitor of the thin film transistor liquid crystal display of the present utility model is as shown in Figure 5 (a), and its storage capacitor 14 is formed on the substrate simultaneously with the gate electrode 11 metal and is used as the first electrode of the storage capacitor, and the gate deposited subsequently Pole dielectric layer 12 and ITO electrode 13 are jointly formed, and the first electrode of storage capacitor is designed as grid shape, and its scope of coverage is the central part of pixel electrode, each 1/4 place apart from the upper and lower edge of pixel electrode, see Fig. 5 ( b) and Figure 5(c), the longitudinal part of the storage capacitor is located within the range of the upper shading matrix. Compared with the first known structure, this structure can obtain a larger aperture ratio under the same storage capacitor area. Compared with the second known method, the storage capacitor can be connected to the common electrode, so there is no need to worry about leakage or collapse. Compared with the third known method, the storage capacitor reduces the chance of short circuit and reduces the delay capacitance effect; according to The product made by the utility model is more novel and progressive than the known technology.

Figure 1 shows the actual waveform of the display element;

Fig. 2 (a) is the sectional view of the storage capacitor of the first known thin film transistor liquid crystal display;

Fig. 2 (b) is the top view of Fig. 2 (a);

Fig. 3 (a) is the sectional view of the storage capacitor of the second known thin film transistor liquid crystal display, which involves using the gate electrode as a part of the first electrode of the storage capacitor;

Fig. 3 (b) is the top view of Fig. 3 (a);

Fig. 4 (a) is the sectional view of the storage capacitor of the third known thin film transistor liquid crystal display, and its storage capacitor is designed as a ring and is located around the pixel electrode;

Fig. 5 (a) is the sectional view of the storage capacitor of the present utility model;

Fig. 5 (b) is the top view of Fig. 5 (a);

Fig. 5(c) is a top view of another example of the utility model.

The structure and manufacturing process of the storage capacitor of the thin film transistor liquid crystal display of the present invention will be described in detail below, and a comparison with various known methods will be made.

First, a layer of metal is sputtered on the glass substrate, and the gate electrode 11 and the first electrode 14 of the storage capacitor are etched, and then, an inverted stacked thin film transistor is grown according to a conventional method, and the first electrode of the storage capacitor is designed as a gate electrode. shape, which covers the central part of the pixel electrode to 1/4 of the upper and lower edges of the pixel electrode, and the longitudinal part of the storage capacitor is located within the range of the upper layer shading matrix; Figure 5 (b) is its top view.

Compared with the storage capacitor of the first known form in Fig. 2(b), the longitudinal parts of the storage capacitor of the utility model are respectively located in the upper layer light-shielding matrix, so the area occupied by this part of the storage capacitor does not affect the aperture ratio. The storage capacitor electrode of the known technology has a width of 30 μm, and the overlapping part of the pixel electrode deducting the upper layer light-shielding matrix is 160 μm long and 120 μm wide, and the storage capacitor longitudinal part of the utility model is 5 μm wide. The opening ratio of the storage capacitor is about 45% and can reach 48% according to the design of the utility model.

Compared with the storage capacitor of the second known technology in Fig. 3(b), because the storage capacitor shares an electrode with the gate electrode, it cannot be connected with the common electrode, and there is a possibility of leakage or collapse. On the other hand, this If there is a deviation in the alignment of the photomask in the design, the storage capacitor values in each exposure area will be different, causing deviations in the image of the liquid crystal display; and the storage capacitor designed in the utility model is not connected to the gate electrode, so the storage capacitor can be It is connected to the common electrode to avoid the above-mentioned dangers. In addition, even if there is a deviation in the alignment of the photomask in the grid-shaped storage capacitor, the total storage capacitance value will not be affected.

Compared with the storage capacitor of the third known technology in Fig. 4(b), the storage capacitor is surrounded by the pixel electrode, and because it is very close to the horizontal scanning line and the vertical signal line, it is easy to have a short circuit with each other. , In addition, it is easy to make the delay capacitance effect more obvious; and according to the utility model design, the storage capacitor is only close to the signal line in the longitudinal part, which greatly reduces the chance of short circuit, and the delay capacitance effect is also not obvious.

The number of storage capacitor electrode grids of the utility model, when considering that the line width resolution of the yellow light process is 3 μm, the number of grid-shaped grids of the storage capacitor is no more than ten; FIG. 5(C) is another top view of the utility model.

In summary, the utility model discloses a storage capacitor structure of a thin film transistor liquid crystal display. Since the storage capacitor of a thin film transistor liquid crystal display is designed in a grid shape, on the one hand, the aperture ratio can be increased; The grid-shaped storage capacitance of the crystalline liquid crystal display and the adjacent parts of the scanning and signal lines are partially reduced, which can significantly and effectively reduce the short circuit phenomenon and the delay capacitance effect.

Claims (4)

1. A storage capacitor structure of a thin film transistor liquid crystal display, characterized in that the first electrode of the storage capacitor is designed to be grid-shaped and positioned at the central part of the pixel electrode, about 1/4 above and below the pixel electrode, and the thin film The longitudinal part of the grid-shaped storage capacitor of the transistor liquid crystal display is located in the upper layer light-shielding matrix, and the number of grid-shaped bars is 2 to 10. 2. The storage capacitor structure of the thin film transistor liquid crystal display according to claim 1, characterized in that: the grid-shaped storage capacitor is composed of (a) the first electrode of the storage capacitor deposited and etched together with the gate; (b) a gate dielectric layer; and (c) pixel electrode ITO; Three layers of structure. 3. The storage capacitor structure of a thin film transistor liquid crystal display according to claim 2, wherein the first electrode is a dielectric layer not deposited together with the gate electrode. 4. The storage capacitor structure of a thin film transistor liquid crystal display according to claim 2, wherein the dielectric layer of the storage capacitor is a dielectric layer that is not deposited together with the gate dielectric layer.

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