A thin film transistor liquid crystal display (TFT-LCD) has the characteristics of being light, thin and small. Besides, it has the advantages of low power consumption, radiative-free and relatively lower cost of manufacture. These characteristics and advantages make the TFT-LCD play a leading role in the flat panel display field. The TFT-LCD is highly adapted to be applied to a desktop computer, a palmtop computer, a personal digital assistant (PDA), a portable phone, a TV set and various office automation devices and audio-visual devices.
A liquid crystal display panel is a main component of a liquid crystal display. With the appearance of large-sized liquid crystal display, in order to solve the problem with wide viewing angle (i.e., when a user views the image right in front of the screen and obliquely in front of the screen, the brightness of the images are different. In general, the brightness of the image seen right in front of the screen is bigger than that seen obliquely in front of the screen), a multi-domain vertical alignment (MVA) type liquid crystal display panel has been developed, which employs a negative polarity liquid crystal material having a negative dielectric anisotropy, that is, when the liquid crystal display panel is not powered, the liquid crystal molecule is arrayed in perpendicular to the liquid crystal display panel.
With reference to FIGS. 1 and 2, FIG. 1 is a schematic view of a pixel structure of a conventional MVA type LCD panel, in which color filter substrate is omitted for purpose of clarity; and FIG. 2 is a sectional view along A-A line in FIG. 1. As shown in FIG. 2, the LCD panel comprises a lower layer of thin film transistor array substrate (also referred to as TFT array substrate) 1, an upper layer of color filter substrate (also referred to as CF substrate) 2, and a liquid crystal layer 3 which is sandwiched between the TFT array substrate 1 and the CF substrate 2 and is composed of a plurality of liquid crystal molecules. As shown in FIG. 1, the TFT array substrate 1 comprises a plurality of scanning lines 10, a plurality of data lines 11 and a plurality of pixel regions 12 defined by the plurality of scanning lines 10 and the plurality of data lines 11 that are intersected with and perpendicular to each other. FIG. 1 shows only one of the pixel regions 12. The pixel region 12 is formed with a pixel electrode 14 which is divided into two subpixel electrodes 141, 142 with a slit 18 formed therebetween. A first and a second thin film transistors 15, 16 are formed near the position where the scanning lines 10 intersect with the data lines 11 for controlling the two subpixel electrodes 141, 142 respectively. The first and the second thin film transistor 15, 16 each comprises a gate electrode G, a source electrode S and a drain electrode D. The gate electrodes G of the first and the second thin film transistors 15, 16 are electrically connected to different scanning lines 10 respectively, the source electrodes S are electrically connected to the same data line 11, and the drain electrodes D are electrically connected to the two subpixel electrodes 141, 142 respectively. As shown in FIG. 2, a black matrix (BM) 22, a color filter layer 23 and a common electrode 24 that covers the black matrix 22 and the color filter layer 23 are sequentially formed on the CF substrate 2. Besides, the CF substrate 2 further comprises a bump 28 provided on the common electrode at a location corresponding to the two subpixel electrodes 141, 142. Due to the existence of the bump 28, liquid crystal molecules tend to tilt perpendicular to the surface on which the bump 28 is located when a voltage is not applied, i.e., the liquid crystal molecules have a pretilt angle that inclines towards different directions. Therefore, the inclination direction of liquid crystal molecules after the liquid crystal display panel is powered can be controlled effectively and rapidly, thereby improving responding speed of liquid crystal molecules, and when the liquid crystal display panel is in normal operation, the liquid crystal layer 3 can be divided into a plurality of tiny areas having different inclination directions so as to improve a wide viewing angle characteristic of the liquid crystal display panel.
However, such the liquid crystal display panel requires that liquid crystal molecules have a pretilt angle when not powered so as to improve the responding speed of liquid crystal molecules. In order to form the pretilt angle, a masking process is additionally needed to form the bump 28 on the CF substrate 2. Besides, the bump 28 is typically made from a transparent material in order not to improve aperture ratio of the liquid crystal display panel. However, the existence of the bump 28 will generally result in light leakage when the liquid crystal display panel is in a dark state, thereby decreasing contrast ratio of the liquid crystal display panel.