1. Field of the Invention
This invention relates to a display apparatus, and particularly to a display apparatus wherein liquid crystal molecules are driven in an in-plane switching mode.
2. Description of the Related Art
A liquid crystal display apparatus of an in-plane switching mode attracts attention as a liquid crystal mode which implements a wide viewing angle and a high contrast. FIG. 13 illustrates operation of a liquid crystal display apparatus of a fringe field switching (FFS) mode which is one of in-plane switching modes. In FIG. 13, an optical axis is indicated by a double-sided arrow mark.
Referring to FIG. 13, the liquid crystal display apparatus of the FFS mode shown includes a common electrode 201 provided on a driving substrate not shown. Electrode portions 202a of a pixel electrode 202 are formed by patterning on the common electrode 201 with an insulating film interposed therebetween, and an orientation film 203 is provided in such a manner as to cover the pixel electrode 202. A liquid crystal layer 205 is sandwiched between the orientation film 203 on the driving substrate side and a face of an opposing substrate (not shown) on which an orientation film 204 is formed. Further, two polarizing plates 206 and 207 are disposed under crossed Nicols with the substrates sandwiched therebetween. Here, the rubbing direction of the two orientation films 203 and 204 coincides with the direction of one of transmission axes of the two polarizing plates 206 and 207. Further, the rubbing direction of the two orientation films 203 and 204 and the transmission axis of one of the polarizing plates 206 and 207 here, the polarizing plate 207 are set so as to be substantially in parallel to the extension direction of the electrode portions 202a of the pixel electrode within a range within which the direction in which liquid crystal molecules m rotates is defined.
In the liquid crystal display apparatus of the FFS mode, when no voltage is applied between the common electrode 201 and the electrode portions 202, the axis of liquid crystal molecules m which form the liquid crystal layer 205 is directed perpendicularly to the transmission axis of the polarizing plate 206 on the incidence side but parallelly to the transmission axis of the polarizing plate 207 on the emergence side. Thus, light incident from the polarizing plate 206 comes to the polarizing plate 207 on the emergence side without any phase difference provided thereto by the liquid crystal layer 205 and is absorbed by the polarizing plate 207 thereby to display the black. On the other hand, if a voltage is applied between the common electrode 201 and the pixel electrode 202, then the orientation direction of the liquid crystal molecules m is rotated to an oblique direction with respect to the extension direction of the pixel electrode 202 by an in-plane electric field generated between the common electrode 201 and the pixel electrode 202. Thereupon, the field strength upon white display is optimized so that the axis of the liquid crystal molecules m at a central location in the thicknesswise direction of the liquid crystal layer 205 may exhibit rotation by 45°. Consequently, when the light h incident from the polarizing plate 206 of the incidence side passes through the liquid crystal layer 205, it is converted into linearly polarized light rotated by 90° and passes through the polarizing plate 207 on the emergence side thereby to display the white.
In such a liquid crystal display apparatus of the FFS mode as described above, a plurality of scanning lines 213 and a plurality of signal lines 215 are wired in a matrix along outer peripheral sides of a rectangular display screen of a driving substrate 211, and a pixel electrode 202 is provided at each of intersecting locations of the scanning lines 213 and the signal lines 215. Each pixel electrode 202 is provided in a substantially rectangular outer shape within a pixel region a of a substantially rectangular shape defined by scanning lines 213 and signal lines. The pixel electrodes 202 are patterned in a comb-like shape such that they have a plurality of electrode portions 202a extending in parallel to the major sides of the outer shape as disclosed in Japanese Patent No. 3,742,837.
Another example of a configuration of a pixel electrode is shown in FIG. 15. Referring to FIG. 15, a pixel electrode 202 having a substantially rectangular outer shape is provided in a pixel region a of a substantially rectangular shape defined by scanning lines 213 and signal lines 215 wired along outer peripheral sides of a display screen. A plurality of electrode portions 202a extend obliquely with respect to the outer shape of the pixel region a. The configuration of the pixel electrode just described is disclosed, for example, in U.S. Pat. No. 7,145,621.
Both of the configurations described above with reference to FIGS. 14 and 15 have an optical configuration similar to that described hereinabove with reference to FIG. 13. In short, the rubbing direction of the two orientation films 203 and 204 and the direction of the transmission axis of one of the polarizing plates 206 and 207, in FIG. 13, of the polarizing plate 207, are set substantially in parallel to the pixel electrode 202, that is, the comb-shaped electrode portions 202a.