Abstract:
A liquid crystal display includes an upper substrate, a lower substrate and a liquid crystal layer interposed between the upper substrate and the lower substrate. The lower substrate includes a pixel array divided into a plurality of columns of pixel areas and a plurality of rows of pixel areas. Each pixel area includes a upper sub-pixel electrode, a lower sub-pixel electrode insulated to the upper sub-pixel electrode and a TFT switch electrically connected to the lower sub-pixel electrode. The upper sub-pixel electrode is electrically connected to a lower sub-pixel electrode of a previous column, and the lower sub-pixel electrode is electrically connected to a upper sub-pixel electrode of a next column.

Description:
RELATED APPLICATIONS 
       [0001]    The present application is a division of U.S. application Ser. No. 11/684,762 filed Mar. 12, 2007, which claims priority to Taiwan Patent Application Serial Number 95109332, filed Mar. 17, 2006. All of these applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present invention relates to a liquid crystal display. More particularly, the present invention relates to a liquid crystal display containing sub-pixel electrodes. 
         [0004]    2. Description of Related Art 
         [0005]    Very wide viewing angles and high definition, among others, are the advantages of a multi-domain vertical alignment (MVA) liquid crystal display (LCD). Some slits and protrusions are formed on the inner surfaces of two transparent substrates in a conventional MVA LCD in which vertically aligned liquid crystal molecules are tilted symmetrically in opposite directions to compensate for viewing angles. 
         [0006]    As disclosed in U.S. Pat. No. 6,922,183 (hereinafter, the “&#39;183 patent”), the lateral electric field applied to the slits on the inner surface of the transparent electrode of an MVA LCD has to be increased, so the liquid crystal molecules in the proximity of the slit can be inclined efficiently and liquid crystal molecular response time can be reduced. A pixel electrode is divided into two sub-pixel electrodes, and thus a pixel is divided into two sub-pixels. The two equipotential sub-pixel electrodes with opposite polarities are electrically isolated to each other by the slit. Lateral electric field is created on the slits to reduce response time of liquid crystal molecules. 
         [0007]    However, the invention disclosed by the &#39;183 patent requires each of two sub-pixel electrodes to be connected with a switch as a driving device for the corresponding sub-pixel. The number of driving devices for each pixel is thus doubled. In addition, sub-pixels with opposite polarities must have their own contact holes to conduct their own electronic signals. When a pixel electrode is divided into several sub-pixel electrodes, sub-pixel electrodes with the same polarity have to be connected by additional wire in order to use one single switch as the driving device. The additional wire will increase both the complexity of electric circuit and the difficulty of manufacturing process. 
       SUMMARY 
       [0008]    An LCD is provided. The pixel electrode array of the LCD comprises plural first pixel electrode and plural pixel electrode having opposite polarities. 
         [0009]    Each of the first pixel electrode comprises a first connecting part and two first sub-pixel electrodes located in two adjacent pixel areas. Each first sub-pixel electrode has at least three corners. The two first sub-pixel electrodes are diagonally connected through the first connecting part at respective corners of the two first sub-pixel electrodes and separately located on one of the first pixel area and one of the second pixel area located adjacently. 
         [0010]    Similarly, each of the second pixel electrode comprises a second connecting part and two second sub-pixel electrodes located in two adjacent pixel areas. Each second sub-pixel electrode has at least three corners. The two second sub-pixel electrodes are diagonally connected through the second connecting part at respective corners of the two second sub-pixel electrodes and separately located on one of the first pixel area and one of the second pixel area located adjacently in such a manner that one of the two first sub-pixel electrodes and one of the two second sub-pixel electrodes are disposed side by side. Hence, each pixel area comprises at least a first sub-pixel electrode and a second sub-pixel electrode. 
         [0011]    Plural first switches are located on the first pixel areas to control the first pixel electrodes, respectively. Plural second switches are located on the second pixel areas to control the second pixel electrodes, respectively. 
         [0012]    Accordingly, pixel electrode is divided into several structurally connected sub-pixel electrodes and only one driving switch device is required for one pixel electrode. Furthermore, the first sub-pixel electrode and the second sub-pixel electrode are alternatively arranged. Same electric potential with opposite polarities can be applied to neighboring first pixel electrode and second pixel electrode. At least one first sub-pixel electrode and one second sub-pixel electrode can be formed in each pixel area without additional signal line and driving switch device. 
         [0013]    It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
           [0015]      FIG. 1  illustrates the pixel array of an LCD according to an embodiment of the present invention; 
           [0016]      FIG. 2  illustrates the pixel array of an LCD according to another embodiment of the present invention; 
           [0017]      FIG. 3  illustrates the pixel array of an LCD according to another embodiment of the present invention; and 
           [0018]      FIG. 4  illustrate a cross sectional view of a conventional LCD. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Accordingly, this invention provides an LCD, each pixel electrode of the LCD is divided into several sub-pixel electrodes. The two neighboring sub-pixel electrodes in the same pixel have opposite polarities. The number of switch devices does not need to be increased. Only conventional signal line and switch device are required to obtain two neighboring sub-pixel electrodes with opposite polarities in the same pixel. The LCD response time can thus be reduced. 
       Embodiment 1 
       [0020]      FIG. 1  illustrates the pixel array of an LCD according to an embodiment of the invention. The pixel array  100  comprises pixel electrodes  110  and  115 . The pixel electrode  110  comprises two sub-pixel electrodes  110   a  and  110   b . The sub-pixel electrodes  110   a ,  110   b  are formed in two neighboring pixel areas  120  sharing an edge and diagonally connected to each other through a connecting part  110   c . Similarly, pixel electrode  115  comprises two sub-pixel electrodes  115   a  and  115   b . The sub-pixel electrodes  115   a  and  115   b  are formed in two neighboring pixel areas  120  sharing an edge and diagonally connected to each other through a connecting part  115   c . Therefore, a repeating unit of the pattern formed by the first sub-pixel electrodes  110   a ,  110   b  and the second sub-pixel electrodes  115   a ,  115   b  is two first sub-pixel electrodes  110   a ,  110   b  in the two diagonal areas of a parallelogram and two second sub-pixel electrodes  115   a ,  115   b  in the other two diagonal areas of the parallelogram. 
         [0021]    Each of the above mentioned pixel area  120  is defined by a pair of scan lines  130  and a pair of data lines  140 . A switch device  150  is formed in one corner of the pixel area  120 . The switch device  150  of this embodiment is a thin film transistor with a gate, a source and a drain connected to the scan line  130 , the data line  140 , the sub-pixel electrode  110   b  or  115   b , respectively. 
         [0022]    The pixel electrodes  110 ,  115  shown in  FIG. 1  are formed on a switch device substrate alternatively. The two neighboring pixel electrodes  110 ,  115  can be controlled to have opposite polarities, so that one pixel area  120  comprising two sub-pixel electrodes  110   b ,  115   a  (or  110   a ,  115   b ) with opposite polarities can be obtained. The sub-pixel electrodes  110   b ,  115   a  (or  110   a ,  115   b ) in one pixel area  120  belong to two different pixel electrodes  115 ,  110 . Because, for example, the two sub-pixel electrodes ( 110   a ,  110   b ) or ( 115   a ,  115   b ) of one pixel electrode  110  or  115  are still connected to each other, only one switch device is required to drive the pixel electrodes  110 ,  115 . In addition, dot inversion method or any appropriate method can be used to allow the two neighboring pixel electrodes  110 ,  115  to have opposite polarities. 
       Embodiment 2 
       [0023]      FIG. 2  illustrates the pixel array of an LCD according to another embodiment of the invention.  FIG. 2  shows that pixel array  200  is composed of pixel electrodes  210  and  215 . The pixel electrode  210  is divided into three sub-pixel electrodes  210   a ,  210   b , and  210   c . The sub-pixel electrodes  210   a ,  210   b , and  210   c  are formed in the two neighboring pixel areas  220  sharing an edge. The sub-pixel electrode  210   b  is diagonally connected to the sub-pixel electrodes  210   a  and  210   c  through connecting parts  210   d  and  210   e . Similarly, the pixel electrode  215  is divided into three sub-pixel electrodes  215   a ,  215   b , and  215   c . The sub-pixel electrodes  215   a ,  215   b , and  215   c  are formed in the two neighboring pixel areas  22  sharing an edge. The sub-pixel electrode  215   b  is diagonally connected to sub-pixel electrodes  215   a  and  215   c  through connecting parts  215   d  and  215   e . Therefore, a repeating unit of the pattern formed by, for example, the first sub-pixel electrodes  210   a ,  110   b  and the second sub-pixel electrodes  215   a ,  215   b  is two first sub-pixel electrodes  210   a ,  210   b  in the two diagonal areas of a parallelogram and two second sub-pixel electrodes  215   a ,  215   b  in the other two diagonal areas of the parallelogram. 
         [0024]    Each of the above mentioned pixel area  220  is defined by a pair of scan lines  230  and a pair of data lines  240 . In addition, a switch device  250  is formed in one corner of each pixel area  220 . The switch device  250  in this embodiment is a thin film transistor with a gate, a source and a drain connected to the scan line  230 , the data line  240  and the sub-pixel electrode  210   c  or  215   c , respectively. 
         [0025]    As shown in  FIG. 2 , the pixel electrodes  210  and  215  are alternatively formed on a switch device substrate. The three sub-pixel electrodes  210   a ,  215   b ,  210   c  (or  215   a ,  210   b ,  215   c ) within the same pixel area  220  have opposite polarities between the sub-pixel electrodes  210   a ,  210   c  (or  215   a ,  215   c ) and the sub-pixel electrode  215   b  (or  210   b ) when the neighboring pixel electrode  210  and the pixel electrode  215  have opposite polarities. Although the sub-pixel electrodes  210   a ,  210   b    210   c  of the pixel electrode  210  are arranged in two pixel areas  220  sharing an edge, the sub-pixel electrodes  210   a ,  210   b ,  210   c  of the pixel electrode  210  are connected through the connecting parts  210   d  and  210   e . Hence, only one switch device  250  is required for the pixel electrode  210 . Similarly, the sub-pixel electrodes  215   a ,  215   b ,  215   c  of the pixel electrode  215  are also connected through the connecting parts  215   d  and  215   e ; hence only one switch device  250  is required for the pixel electrode  215 . The way to obtain two neighboring pixel electrodes  210 ,  215  with opposite polarities can be, for example, dot inversion. 
       Embodiment 3 
       [0026]      FIG. 3  illustrates the pixel array of an LCD according to another embodiment of the invention. The pixel array  300  is composed of pixel electrodes  310  and  315 . The pixel electrode  310  is divided into two sub-pixel electrodes  310   a  and  310   b  located in two pixel areas  320  sharing a corner. The sub-pixel electrodes  310   a  and  310   b  are connected to each other through a connecting part  310   c . Similarly, pixel electrode  315  comprises two sub-pixel electrodes  315   a ,  315   b  located in two pixel areas  320  sharing a corner. The sub-pixel electrodes  315   a  and  315   b  are connected to each other through a connecting part  315   c . Therefore, a repeating unit of a pattern formed by the first sub-pixel electrodes  310   a ,  310   b  and the second sub-pixel electrodes  315   a ,  315   b  is two first sub-pixel electrodes  310   a ,  310   b  located in the two opposite edges of a parallelogram and two second sub-pixel electrodes  315   a ,  315   b  located in the other two opposite edges of the parallelogram. 
         [0027]    The above mentioned pixel area  320  is defined by a pair of scan line  330  and a pair of data line  340 . A switch device  350  is formed in one corner of the pixel area  320 . The switch device  350  in this embodiment is a thin film transistor with a gate, a source and a drain connected to the scan line  330 , the data line  340 , the sub-pixel electrode  310   a  or  315   a , respectively. 
         [0028]    The pixel electrodes  310 ,  315  shown in  FIG. 3  are formed on a switch device substrate alternatively. The two neighboring pixel electrodes  310 ,  315  can be controlled to have opposite polarities, so that the same pixel area  320  comprising two sub-pixel electrodes  310   b ,  315   a  (or  315   b ,  310   a ) with opposite polarities can be obtained. Although the two sub-pixel electrodes  310   b ,  315   a  (or  315   b ,  310   a ) in one pixel area  320  belong to two different pixel electrodes  315  and  310 , the two sub-pixel electrodes  310   a ,  310   b  (or  315   a ,  315   b ) belonged the pixel electrode  310  (or  315 ) are still connected to each other through the connecting part  310   c . Hence, only one switch device is required to drive the pixel electrode  310  (or  315 ). In addition, dot inversion method or any appropriate method can be used to allow the two neighboring pixel electrodes  310 ,  315  to have opposite polarities. 
         [0029]    The above mentioned pixel array structure can be applied to any flat panel display, for example, LCD. Referring to  FIG. 4 , an LCD  400  comprises a lower substrate  410 , an upper substrate  420  and a liquid crystal layer  430  disposed therebetween. There are many possible modifications for the lower substrate  410  and the upper substrate  420  of recent LCD  400  products. For the first example, the upper substrate  420  can be a color filter if the lower substrate  410  is a control circuit board. For the second example, the control circuit board and the color filter layer can be formed on the lower substrate  410 , and there is only a common electrode layer on the upper substrate  420 . Based on the location of the control circuit and the color filter, the structure can be either COA (Color Filter on Array) or AOC (Array on Color Filter). The detailed structures of COA and AOC are not shown in  FIG. 4  because these possible modifications are apparent to those skilled in the art. 
         [0030]    Accordingly, the pixel electrode is only divided into several structurally connected sub-pixel electrodes. Only one driving switch device is required for one pixel. Furthermore, pixel electrodes with opposite polarities are alternatively arranged. At least two sub-pixel electrodes can be formed on each pixel area without additional signal line and driving switch device. 
         [0031]    It will be apparent to those skilled in the art that various modifications and variations can be made to the structures of the present invention without departing from the scope or spirit thereof. In view of the foregoing, it is intended that the present invention cover modifications and variations thereof provided they fall within the scope of the following claims.