Abstract:
A liquid crystal display (LCD) capable of preventing spots from being generated by difference in brightness caused by variation in a gap between substrates is provided. The LCD includes a first pad unit positioned on an upper corner of a lower substrate, a second pad unit positioned on a lower corner of the lower substrate diagonally across from the first pad unit, an integrated circuit electrically connected to the first pad unit and the second pad unit, and dummy pads positioned on the other upper corner of the lower substrate. The dummy pads are substantially symmetrical with second pads included in the second pad unit thus helping maintain the gap between the substrates uniform.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0119867, filed on Dec. 08, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.  
       BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a liquid crystal display, and more particularly to, a liquid crystal display capable of preventing spots from being generated by difference in brightness of various regions of the display.  
         [0004]     2. Discussion of Related Art  
         [0005]     Recently, various flat panel displays (FPDs) having a lower weight and volume than cathode ray tubes (CRTs) have been developed. The FPDs include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), and organic light emitting displays (OLEDs).  
         [0006]     Among the FPDs, the LCDs are small and light and have low power consumption. Therefore, the LCDs have been in the spotlight as substitutes that can overcome the disadvantages of the conventional CRTs. Currently, the LCDs are used in large monitors and TVs as well as in portable devices such as mobile telephones and personal digital assistants (PDA). Passive matrix LCDs having low power consumption are often used for portable display devices.  
         [0007]      FIG. 1  illustrates a conventional passive matrix LCD.  
         [0008]     Referring to  FIG. 1 , the conventional passive matrix LCD includes a liquid crystal panel  2 , a data driver  8  for driving data lines D 1  to Dm of the liquid crystal panel  2 , and a scan driver  6  for driving scan lines S 1  to Sn of the liquid crystal panel  2 .  
         [0009]     The liquid crystal panel  2  includes pixels  4  positioned where the scan lines Si to Sn and the data lines D 1  to Dm cross over one another. The pixels  4  are selected when scan signals are supplied to the scan lines S 1  to Sn to emit light components corresponding to data signals supplied to the data lines D 1  to Dm.  
         [0010]     The scan driver  6  sequentially supplies the scan signals to the scan lines S 1  to Sn in accordance with control signals from a timing controller that is not shown.  
         [0011]     The data driver  8  generates the data signals in accordance with the control signals from the timing controller and supplies the generated data signals to the data lines D 1  to Dm in synchronization with the scan signals.  
         [0012]     The conventional LCD is obtained by attaching an upper substrate and a lower substrate to each other. As illustrated in  FIG. 2 , an integrated circuit  10  is mounted on a lower substrate  12  of the LCD used for a portable device (for example, a mobile telephone). The circuits of the scan driver  6  and the data driver  8  are included in the integrated circuit  10 . Therefore, the integrated circuit  10  is commonly connected to the data lines D 1  to Dm and the scan lines S 1  to Sn.  
         [0013]     Pixels (not shown) are arranged in a matrix in an effective display region  20  of the lower substrate  12 . The data lines D 1  to Dm formed in the effective display region  20  are electrically connected to the integrated circuit  10  to receive the data signals from the integrated circuit  10 . On the other hand, first pads  14  are formed on a first side of the effective display region  20  and second pads  16  are formed on a second side of the effective display region  20  opposite the first side. The first pads  14  are positioned near an upper side of the effective display region  20  and are electrically connected to the integrated circuit  10 , and the second pads  16  are positioned near a lower side of the effective display region  20  and are electrically connected to the integrated circuit  10 . When an upper substrate that is not shown and the lower substrate  12  are attached to each other or coupled together, the first pads  14  are electrically connected to the scan lines S 1  to Sn/2 positioned in the upper part of the effective display region  20  of the upper substrate and the second pads  16  are electrically connected to the scan lines Sn/2+1 to Sn positioned in the lower part of the effective display region  20  of the upper substrate.  
         [0014]     In the conventional LCD, the scan lines S 1  to Sn and the data lines D 1  to Dm are connected to the integrated circuit  10  and the effective display region  20  displays a predetermined image in response to the scan signals and the data signals supplied from the integrated circuit  10 .  
         [0015]     Dummy pads  18  are formed adjacent to the second pads  16 . The dummy pads  18  are used for maintaining a gap when the upper substrate and the lower substrate  12  are attached to each other. This gap corresponds to a cell gap created by formation of liquid crystal cells between the two substrates. However, in the conventional LCD, spots are generated by difference in brightness in the parts where the dummy pads  18  are formed and/or on the boundaries between the dummy pads  18  and the second pads  16 . The spots are generated by non-uniformity in the heights of the dummy pads  18  and the second pads  16  when the upper substrate and the lower substrate  12  are attached to each other.  
       SUMMARY OF THE INVENTION  
       [0016]     Accordingly, it is an aspect of the present invention to provide a liquid crystal display (LCD) capable of preventing spots from being generated by difference in brightness.  
         [0017]     According to a first aspect of the present invention, there is provided an LCD obtained by attaching or coupling an upper substrate and a lower substrate together. The LCD includes a first pad unit positioned on a first upper side, or a first upper corner, of the lower substrate, a second pad unit positioned on a second lower side, or a second lower corner, of the lower substrate, the first upper corner and the second lower corner located diagonally opposite each other, an integrated circuit electrically connected to the first pad unit and the second pad unit, and dummy pads positioned on a second upper side, or on the other upper corner, of the lower substrate. The dummy pads are substantially symmetrical to the second pads with respect to a line of symmetry dividing the lower substrate into an upper portion and a lower portion.  
         [0018]     In one embodiment, the dummy pads are not electrically connected to the integrated circuit. The LCD further includes data lines formed in an effective display region of the lower substrate to be electrically connected to the integrated circuit. The effective display region may also be called the display region. The first pad unit and the second pad unit are positioned outside the effective display region. The LCD further includes a third pad unit positioned on the upper substrate to be electrically connected to the first pad unit, a fourth pad unit positioned on the upper substrate to be electrically connected to the second pad unit, and scan lines formed in the effective display region of the upper-substrate to be electrically connected to the third pad unit and the fourth pad unit. The LCD further includes pixels positioned in the areas where the scan lines and the data lines cross over one another to display images corresponding to data signals supplied from the data lines.  
         [0019]     One embodiment includes a liquid crystal display having a first substrate and a second substrate coupled to and facing the first substrate. The first substrate includes a first display region, first pads, second pads, dummy pads and an integrated circuit. The second substrate includes a second display region facing the first display region, third pads electrically connected to the first pads and the fourth pads electrically connected to the second pads. The dummy pads are adapted to maintain a cell gap substantially uniform.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     These and/or other aspects and features of the invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which:  
         [0021]      FIG. 1  illustrates a conventional passive matrix liquid crystal display (LCD);  
         [0022]      FIG. 2  illustrates a lower substrate of the conventional LCD;  
         [0023]      FIG. 3  illustrates a lower substrate of an LCD according to an embodiment of the present invention;  
         [0024]      FIG. 4  illustrates an upper substrate of the LCD according to the embodiment of the present invention; and  
         [0025]      FIG. 5  illustrates a dummy unit of the lower substrate illustrated in  FIG. 3 .  
         [0026]      FIG. 6  illustrates a passive matrix LCD according to the embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0027]     Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.  
         [0028]      FIGS. 3 and 4  schematically illustrate the lower substrate and the upper substrate of a passive matrix liquid crystal display (LCD) according to an embodiment of the present invention. The lower substrate and the upper substrate shown in  FIGS. 3 and 4  may be used in the LCD of  FIG. 6 .  
         [0029]     Referring to  FIGS. 3 and 4 , the lower substrate  112  of the LCD according to one embodiment of the present invention includes an effective display region  120 , an integrated circuit  110 , first pads  114 , second pads  116 , and dummy pads  118 . The effective display region  120  may also be referred to as the display region. The first pads  114 , the second pads  116 , and the dummy pads  118  may be respectively located in a first pad unit, a second pad unit, and a dummy pad unit.  
         [0030]     Pixels  40  (shown in  FIG. 6 ) are located in the effective display region  120  where the data lines D 1  to Dm cross over scan lines S 1  to Sn. The pixels are selected when scan signals are supplied to the scan lines S 1  to Sn to display images corresponding to data signals supplied from the data lines D 1  to Dm.  
         [0031]     The data lines D 1  to Dm are formed in the effective display region  1 ? 0  and are electrically connected to the integrated circuit  110  positioned under the effective display region  120 . The data lines D 1  to Dm receive the data signals from the integrated circuit  110 .  
         [0032]     The first pads  114  are formed outside the effective display region  120 . In one embodiment, the first pads  114  are formed near or adjacent to a first upper side, or corner of the lower substrate  112 . The first pads  114  are electrically connected to the integrated circuit  110  to receive the scan signals from the integrated circuit  110 . The first pads  114  are electrically connected to third pads  132  formed on an upper substrate  130  when the lower substrate  112  is coupled to the upper substrate  130 . In the embodiment shown, since the third pads  132  are electrically connected to the scan lines S 1  to Sn/2 formed near the upper end, or the upper half, of the effective display region  120 , the scan signals supplied from the integrated circuit  110  are sequentially supplied to the scan lines S 1  to Sn/2.  
         [0033]     The second pads  116  are formed outside the effective display region  120 . In one embodiment, the second pads  116  may be formed on a second lower side, or corner, of the lower substrate  112 . This second lower corner is located diagonally opposite the first upper corner where the first pads  114  are formed. The second pads  116  are electrically connected to the integrated circuit  110  to receive the scan signals from the integrated circuit  110 . The second pads  116  are electrically connected to fourth pads  134  formed on the upper substrate  130  when the lower substrate  112  is coupled to the upper substrate  130 . In the embodiment shown, since the fourth pads  134  are electrically connected to the scan lines Sn/2+1 to Sn formed near the lower end, or lower half, of the effective display region  120 , the scan signals supplied from the integrated circuit  110  are sequentially supplied to the scan lines Sn/2+1 to Sn.  
         [0034]     The third pads  132  and the fourth pads  134  are formed on the upper substrate  130 . The third pads  132  are electrically connected to the scan lines S 1  to Sn/2 formed in the upper end, or upper half, of the effective display region  120  of the upper substrate  130 . The third pads  132  are electrically connected to the first pads  114  when the upper substrate  130  and the lower substrate  112  are attached to each other or coupled together. Therefore, the third pads  132  supply the scan signals supplied from the integrated circuit  110  to the scan lines S 1  to Sn/2.  
         [0035]     The fourth pads  134  are electrically connected to the scan lines Sn/2+1 to Sn formed near the lower end, or lower half, of the effective display region  120  of the upper substrate  130 . The fourth pads  134  are electrically connected to the second pads  116  when the upper substrate  130  and the lower substrate  112  are attached to each other. Therefore, the fourth pads  134  supply the scan signals supplied from the integrated circuit  110  to the scan lines Sn/2+1 to Sn.  
         [0036]     In the LCD according to the embodiments of the present invention, the dummy pads  118  are formed in a region adjacent to the second pads  116 . The dummy pads  118  are used for maintaining a substantially uniform gap (e.g., cell gap) when the upper substrate  130  and the lower substrate  112  are attached to each other. Therefore, the dummy pads  118  are formed to be substantially symmetrical to the second pads  116 . For example, in the embodiment shown in  FIG. 5 , the dummy pads  118  are positioned near or adjacent to the second upper side of the lower substrate  112  (e.g., near the upper right corner of the lower substrate  112  in the orientation shown in  FIG. 5 ) to be substantially symmetrical with the second pads  116  positioned on the second lower side. As such, the dummy pads  118  formed on an upper corner of the lower substrate  112  on the same side. where the second pads  116  are located. Further, the dummy pads  116  are symmetrical with the second pads  118  with respect to a line of symmetry between the two pads  116  and  118  that substantially divides the lower substrate  112  into an upper portion and a lower portion. When the dummy pads  118  are symmetrical with the second pads  116 , it is possible to maintain the gap substantially uniform when the upper substrate  130  and the lower substrate  112  are attached to each other. Therefore, it is possible to prevent spots from being generated by difference in brightness. On the other hand, since the dummy pads  118  are used for maintaining the gap uniform, electrical signals need not be supplied from the outside to these dummy pads.  
         [0037]     As described above, in the LCD according to the embodiments of the present invention, the dummy pads positioned near or adjacent to an upper end of the effective display region are symmetrical with the pads positioned near or adjacent to a lower end of the effective display region so that it is possible to maintain the cell gap substantially uniform between the upper substrate and the lower substrate and to thus prevent spots from being generated by difference in brightness.  
         [0038]      FIG. 6  illustrates a passive matrix LCD  200  of an embodiment of the present invention. The passive matrix LCD  200  includes a liquid crystal panel  50 , a data driver  80  for driving data lines D 1  to Dm of the liquid crystal panel  50 , and a scan driver  60  for driving scan lines S 1  to Sn of the liquid crystal panel  50 . The liquid crystal panel  50  includes the pixels  40  positioned where the scan lines S 1  to Sn and the data lines D 1  to Dm cross over one another. The passive matrix LCD  200  is obtained by coupling the upper substrate  130  to the lower substrate  112 .  
         [0039]     Although certain exemplary embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes might be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.