1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a wide viewing angle characteristic and being capable of producing a high quality display.
2. Description of the Related Art
In recent years, liquid crystal displays (hereinafter, referred to as “LCDs”) have been widely used. Mainstream LCDs so far have been twisted nematic type LCDs in which nematic liquid crystal molecules having a positive dielectric anisotropy are twisted. However, this type of LCDs have a problem of excessive viewing angle dependence, which is caused by the orientation of liquid crystal molecules.
In order to alleviate the viewing angle dependence, alignment-divided vertical alignment type LCDs have been developed, and are now used increasingly widely.
For example, Japanese Patent No. 2947350 discloses an MVA (Multi-domain Vertical Alignment) type LCD, which is one kind of alignment-divided vertical alignment type LCDs. An MVA type LCD displays images in a normally black (NB) mode using a vertical alignment type liquid crystal layer which is provided between a pair of electrodes. The MVA type LCD includes domain-regulating means (slits or ribs), such that liquid crystal molecules fall (are inclined) in a plurality of different directions in each pixel when a voltage is applied.
Japanese Laid-Open Patent Publication No. 2003-43525 discloses a CPA (Continuous Pinwheel Alignment) type LCD, which is one kind of alignment-divided vertical alignment type LCDs. In a CPA type LCD, a pair of electrodes face each other with a vertical alignment type liquid crystal layer interposed therebetween. One of the pair of electrodes includes a portion having no conductive layer (openings or cut-out portions), such that liquid crystal molecules are inclined radially in each pixel when a voltage is applied.
Recently, demands for displaying moving picture information have been rapidly increasing in personal computer monitors and mobile terminal devices (for example, cellular phones and PDAs) as well as in liquid crystal TVs. In order to realize high quality display of moving pictures in an LCD, the response time of the liquid crystal layer needs to be short (i.e., the response speed of the liquid crystal layer needs to be high). More specifically, it is required to reach a predetermined gray level within one-vertical scanning period (typically, within one frame).
As a driving method for improving the response characteristic of LCDs, a method of applying a voltage which is higher than the voltage corresponding to the gray level to be displayed (the predetermined gray level) is known. (The voltage higher than the voltage corresponding to the gray level to be displayed is referred to as an “overshoot voltage”, and such a method is referred to as an “overshoot driving”.) An application of an overshoot voltage (hereinafter, referred to as an “OS voltage”) can improve the response characteristic in gray scale display. For example, Japanese Laid-Open Patent Publication No. 2000-231091 discloses an MVA type LCD which can be driven by overshoot driving (hereinafter, referred to as an “OS driving”).
However, in order to drive an LCD by OS driving as disclosed in Japanese Laid-Open Patent Publication No. 2000-231091, a frame memory for storing image information needs to be additionally provided. This increases the production cost.