Liquid Crystal Display (LCD) is one of the most widely used flat panel displays. There are various modes to realize image display, such as TN (twisted nematic liquid crystal) mode, IPS (In Plane Switching liquid crystal) mode crystal, and VA (Vertical Alignment liquid crystal) mode.
As a branch mode of the VA mode, there is a HVA mode which uses a powered light-alignment method to realize a liquid crystal layer with a certain pre-tilt angle in the PI surface, so as to omit traditional friction alignment.
To achieve a wide viewing angle of a liquid crystal display, the pixel electrode in the HVA mode adopts a Multi-Domain structure. FIG. 1 is a schematic diagram of a pixel structure in a prior art HVA mode. As shown in FIG. 1 and FIG. 2, the pixel structure includes a scan line 110 and a data line 120. The scan line 110 and the data line 120 cross each other to define a pixel unit. The pixel unit includes a pixel electrode 200 and a common electrode 140. The pixel electrode 200 includes a main body portion 210 and peripheral portion 220. The main body portion includes a first trunk electrode 211, a second trunk electrode 212, and branch electrodes 213. The first trunk electrode 211 is disposed laterally and the second trunk electrode 212 is longitudinally disposed. The centers of the first trunk electrode 211 and the second trunk electrode 212 perpendicularly intersect to form four display regions. A plurality of branch electrodes 213 are disposed in each display region, and a slit is formed between adjacent branch electrodes 213. The peripheral portion 220 has a shape of a mouth, and the peripheral portion 220 is connected to the distal end of the branch electrode 213. The common electrode 140 is located under the pixel electrode 200. The common electrode 140 forms a storage capacitor with the pixel electrode 200. The storage capacitor serves to hold the voltage in the pixel capacitor and reduce a voltage drop of the pixel capacitance caused by current leakage.
However, in the pixel structure described above, the storage capacitor has a relatively small overlapping area between the pixel electrode and the common electrode, so that the storage capacitor has a limited effect of holding the voltage in the pixel capacitor. In order to improve the technical problem, the prior art proposed a way that the pixel electrodes in FIG. 1 are expanded outward. The peripheral portion is thus closer to the scan line and the data line, and the lengths of the branch electrodes are outwardly increased. In this way, the overlapping area between the pixel electrode and the common electrode is increased, thereby increasing the storage capacitance. However, as the pixel electrode expands toward the scan line and the data line, parasitic capacitance between the pixel electrode and the scan line and the data line increases, thereby resulting in a poor display effect. Furthermore, since the pixel electrode expands toward the scan line and the data line, the pixel electrode is closer to a black matrix, on which a common electrode being provided, on the color filter substrate. The liquid crystal between the pixel electrode and the color filter substrate is influenced by the topography of the branch electrodes and the topography (slope) of the black matrix, which results in a disorder of a liquid crystal pre-deflection, and is easy to form dark veins.