Abstract:
An exemplary liquid crystal display includes a first substrate; a second substrate opposite the first substrate; a liquid crystal layer interposed between the first and second substrates; a plurality of pixel electrodes disposed at the second substrate; a plurality of parallel first data lines alternately disposed at the second substrate; a plurality of parallel second data lines alternately disposed at the second substrate. Each of the first data lines is disposed upon and insulative to a corresponding second data line, and each of the first and second data lines provides signals to a corresponding pixel electrode.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to liquid crystal display (LCD), and more particularly to a multi-domain vertical alignment (MVA) LCD having two different sub-pixel regions in each pixel region thereof. 
       BACKGROUND OF THE INVENTION 
       [0002]    Since liquid crystal displays are thin and light, consume relatively little electrical power, and do not cause flickering like in cathode ray tube (CRT) displays, they have helped spawn product markets such as laptop personal computers. In recent years, there has also been great demand for liquid crystal displays to be used as computer monitors and even televisions, both of which are larger than the liquid crystal displays of laptop personal computers. Such large-sized liquid crystal displays in particular require that an even brightness and contrast ratio prevail over the entire display surface, regardless of observation angle. 
         [0003]    Because the conventional twisted nematic (TN) mode liquid crystal display cannot easily satisfy these demands, a variety of improved liquid crystal displays have recently been developed. They include in-plane switching (IPS) mode liquid crystal displays, optical compensation TN mode liquid crystal displays, and multi-domain vertical alignment (MVA) mode liquid crystal displays. In multi-domain vertical alignment mode liquid crystal displays, each pixel is divided into multiple regions. Liquid crystal molecules of the pixel are vertically aligned when no voltage is applied, and are inclined in different directions when a voltage is applied. 
         [0004]    Referring to  FIG. 9 , a typical multi-domain vertical alignment liquid crystal display (LCD)  100  includes a first substrate  110 , a second substrate  120  parallel to the first substrate  110 , and a liquid crystal layer  130  sandwiched therebetween. The liquid crystal layer  130  includes a number of liquid crystal molecules  130  having negative dielectric anisotropy. 
         [0005]    The first substrate  110  assembly includes an upper polarizer  112 , a first transparent substrate  111 , a color filter  113 , a common electrode  115 , and a first alignment film  114  arranged in that order from top to bottom. The first substrate  110  further includes a number of first protrusions  141 . Referring also to  FIG. 5 , the first protrusions  141  are arranged at an inner surface of the first alignment film  114  along generally V-shaped paths. The color filter  113  includes a number a red filters (not shown), a number of blue filters (not shown), and a number of green filters (not shown) sequentially arranged in that order. 
         [0006]    The second substrate  120  assembly includes a lower polarizer  122 , a second transparent substrate  121 , a number of pixel electrodes  127 , and a second alignment film  124  arranged in that order from bottom to top. The second substrate  120  further includes a number of second protrusions  142 . The second protrusions  142  are arranged at an inner surface of the second alignment film  124  along generally V-shaped paths. The first protrusions  141  and the second protrusions  142  are arranged alternately. 
         [0007]    Referring to  FIG. 10 , when the LCD  6  is in an off state, the liquid crystal molecules  131  are oriented perpendicular to the first substrate  110 . In operation during the off state, incident light beams become linearly-polarized light beams after passing through the lower polarizer  122 . Because the light beams transmit along the long axes of the liquid crystal molecules  131 , after the linearly-polarized light beams pass through the liquid crystal layer  130 , the polarizing directions of the linearly-polarized light beams remain unchanged. Thus the linearly-polarized light beams cannot pass though the upper polarizer  112 , which has a polarizing axis perpendicular to that of the lower polarizer  122 . As a result, the LCD  100  displays a black image. 
         [0008]    Referring to  FIG. 11 , when the LCD  100  is in an on state, voltages are applied thereto, and voltage differences between the common electrode  115  and pixel electrodes  127  generate electric fields perpendicular to the first and second substrates  110 ,  120 . Because the liquid crystal molecules  131  have negative dielectric anisotropy, they are inclined to become oriented parallel to the first substrate  110 . Further, the protrusions  141 ,  142  affect the orientations of the liquid crystal molecules  131 , such that the liquid crystal molecules  131  form inclined alignments perpendicular to the slopes of the protrusions  141 ,  142 . Referring also to  FIG. 12 , the liquid crystal molecules  131  orient in four directions A, B, C and D. 
         [0009]    In operation during the on state, incident light beams become linearly-polarized light beams after passing through the lower polarizer  122 . Because of birefringence of the liquid crystal molecules  131  and the electric fields, the polarizing directions of the linearly-polarized light beams change to align with the polarizing axis of the upper polarizer  112  after passing through the liquid crystal layer  130 . Accordingly, part of the light beams pass through the upper polarizer  112 . Therefore, the LCD  100  displays an image with desired brightness. 
         [0010]    Because the liquid crystal molecules  131  are oriented in four directions A, B, C and D, color shift that would otherwise be manifest in images displayed by the LCD  100  is compensated. In particular, the LCD  100  has a more even display performance along four different viewing directions corresponding to the directions A, B, C and D. That is, the LCD  100  attains a display having four domains. 
         [0011]    However, the four-domain configuration can only compensate visual performance in four directions. 
         [0012]    What is needed, therefore, is a multi-domain vertical alignment LCD having more domains that can provide a uniform display in more viewing directions. 
       SUMMARY 
       [0013]    An exemplary liquid crystal display includes a first substrate; a second substrate opposite the first substrate; a liquid crystal layer interposed between the first and second substrates; a plurality of pixel electrodes disposed at the second substrate; a plurality of parallel first data lines alternately disposed at the second substrate; a plurality of parallel second data lines alternately disposed at the second substrate. Each of the first data lines is disposed upon and insulative to a corresponding second data line, and each of the first and second data lines provides signals to a corresponding pixel electrode. 
         [0014]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is an exploded, isometric view of an LCD device according to a first embodiment of the present invention, the LCD device including a plurality of first protrusions, a plurality of second protrusions, and a plurality of pixel regions. 
           [0016]      FIG. 2  is a top plan view of pixel regions of the LCD device of  FIG. 1 . 
           [0017]      FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 . 
           [0018]      FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 2 . 
           [0019]      FIG. 5  is a top-down view of orientations of four of the liquid crystal molecules of  FIG. 2 , according to the corresponding first protrusions and second protrusions at the pixel regions 
           [0020]      FIG. 6  is a schematic, side view of orientations of two of the liquid crystal molecules of  FIG. 2 , the liquid crystal molecules having different tilt angles. 
           [0021]      FIG. 7  is a top plan view of pixel regions of the LCD device according to a second embodiment. 
           [0022]      FIG. 8  is a top plan view of pixel regions of the LCD device according to a third embodiment. 
           [0023]      FIG. 9  is a side isometric view of a conventional LCD device. 
           [0024]      FIG. 10  is an exploded, isometric view of the LCD device in an off state of  FIG. 9 . 
           [0025]      FIG. 11  is an exploded, isometric view of the LCD device in an on state of  FIG. 9 . 
           [0026]      FIG. 12  is a top-down view of orientations of the liquid crystal molecules of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0027]    Reference will now be made to the drawings to describe preferred and exemplary embodiments of the present invention in detail. 
         [0028]    Referring to  FIG. 1  and  FIG. 2 , an MVA-type LCD device  200  according to a first embodiment of the present invention includes a first substrate assembly  210 , a second substrate assembly  220  parallel to the first substrate assembly  210 , and a liquid crystal layer  230  sandwiched between the two substrate assemblies  210 ,  220 . The liquid crystal layer  230  includes a plurality of liquid crystal molecules  231 . 
         [0029]    The first substrate assembly  210  includes a color filter  213 , a common electrode  215 , and a plurality of first protrusions  219  arranged in that order from top to bottom. The color filter  213  includes a plurality of red filter units (not shown), a plurality of green filter units (not shown), and a plurality of blue filter units (not shown). The first protrusions  219  each have a triangular section configuration, and are arranged along a plurality of V-shaped paths. 
         [0030]    The second substrate assembly  120  includes a plurality of parallel common lines  221 , a plurality of parallel scan lines  222 , a plurality of first data lines  223 , a plurality of second data lines  224  parallel to the first data lines  223 , a plurality of first thin film transistors  225 , a plurality of second thin film transistors  226 , a plurality of first pixel electrodes  227 , a plurality of second pixel electrodes  228 , and a plurality of protrusions  229 . 
         [0031]    The common lines  221  and the scan lines  222  are alternately disposed and that are parallel to each other and that each extend parallel to a first direction. The first data lines  223  that are parallel to each other and that each extend parallel to a second direction that is orthogonal to the first direction. The second lines  224  are disposed upon and insulative to the first data lines  223 . 
         [0032]    Every two adjacent first data lines  223  together with every two adjacent common lines  221  form a rectangular area defined as a pixel region  20 . Each pixel region  20  corresponds to a filter unit, and is divided into a first sub-pixel unit  201  and a second sub-pixel unit  202 . 
         [0033]    The first pixel electrodes  227  are disposed in the first sub-pixel units  201 . The second pixel electrodes  228  are disposed in the second sub-pixel units  202 . The first TFTs  225  are located in the vicinity of intersections of the scan lines  222  and the first data lines  223 , respectively. Each first TFT  225  includes a source electrode (not labeled) connected to the corresponding first data line  223 , a gate electrode (not labeled) connected to the corresponding gate line  222 , and a drain electrode (not labeled) connected to the corresponding first pixel electrode  227 . Each second TFT  226  is located in the vicinity of intersections of the scan lines  222  and the second data lines  224 . Each second TFT  226  includes a gate electrode (not labeled) connected to the same scan line  222  that the corresponding first TFT  225  is connected to, and a drain electrode (not labeled) connected to the second pixel electrode  228 . 
         [0034]    The first data line  223  includes a bent portion  290  corresponding to the second TFT  226 . The second data line  224  is coupled to the source electrode of the second TFT  226  via a through hole (not labeled) corresponding to the bent portion  290 . Each of the second protrusions  229  has a triangular section configuration, and is arranged along a plurality of V-shaped paths. The first and second protrusions  219 ,  229  are alternately disposed. 
         [0035]    Also referring to  FIGS. 3-4 , the LCD device  200  further includes a gate insulating layer  252 , a semiconductor layer  250 , a passivation layer  255 . Gate electrodes  251 ,  261  of the first and second TFTs  225 ,  226  and the scan lines  222  are disposed on the second substrate  220 , and the semiconductor layer  250  covers the gate electrodes  251 ,  261  and the scan lines  222 . The drain electrodes  253 ,  263  and the source electrodes  254 ,  264  are disposed on the semiconductor layer  250  and gate insulating layer  252 . The first data line  223  is disposed on the gate insulating layer  252 , the passivation layer  255  covers the first data lines  223 , the gate insulating layer  252 , drain electrodes  253 ,  263  and source electrodes  254 ,  264 . The second data lines  224 , the pixel electrodes  227 ,  228  are disposed on the passivation layer  255 . The passivation layer  255  includes a through hole  291  corresponding to the bent portion  290  of the first data line  223 . 
         [0036]    With theses configurations, a first gray scale voltage may be provided to the first pixel electrode  227  via the first data line  223  and the first TFT  225 . A second gray scale voltage may be provided to the second pixel electrode  228  via the second data line  224  and the second TFT  226 . Also referring to  FIGS. 5-6 , when corresponding voltages are applied to the first pixel electrode  227  and the common electrode  215 , an electric field is generated therebetween. The liquid crystal molecules  131  twist according to the electric field. The liquid crystal molecules  231  are guided by the protrusions  219 ,  229  and thereby become aligned in four different directions A, B, C, D. Thus four domains are defined according to the protrusions  219 ,  229 . When corresponding voltages are applied to the second pixel electrode  228  and the common electrode  215 , another electric field is generated therebetween. Because the voltages of the first pixel electrodes  227  are different from the voltages of the second pixel electrodes  228  in each frame, tilt angles θ 1  of the liquid crystal molecules  231  in the first sub-pixel units  201  are different from tilt angles θ 2  of the liquid crystal molecules  231  in the second sub-pixel units  202 . Thus, a total of eight domains are defined in each pixel unit  20 . That is, the LCD device  200  achieves 8-domain vertical alignment. 
         [0037]    Unlike with conventional MVA-type LCD devices, the LCD device  200  includes the first data lines  223  and the second data lines  224 . The second data lines  224  also function to make the voltages of the first pixel electrodes  227  different from the voltages of the second pixel electrodes  228 . Each pixel unit  20  may achieve 8-domain vertical alignment. 
         [0038]    Referring to  FIG. 7 , an LCD device  300  according to a second embodiment of the present invention is similar to the LCD device  200 . However, the second data lines  324  includes a bent portion  390  corresponding to the second TFT  326 , and the bent portion  390  is coupled to a source electrode of the second TFT  326  via a through hole. 
         [0039]    Referring to  FIG. 8 , an LCD device  400  according to a third embodiment of the present invention is similar to the LCD device  200 . However, two adjacent data lines  324  cooperatives with two adjacent scan lines to form a pixel region  40 . The pixel region  40  is divided into a first sub-pixel region  401  and a second sub-pixel region  402 . A source electrode of the first TFT  425  is coupled to the first electrode  423 , and a source electrode of the second TFT  426  is coupled to the second electrode  424 . 
         [0040]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit or scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.