Abstract:
A liquid crystal display device includes a pixel electrode at a pixel area between a gate line and a data line, a switching device at an intersection between the gate line and the data line, the switching device comprising a light-shielding member overlapping the switching device and extending from an end at the pixel electrode side of a metal thin film provided within the switching device into the pixel area, for blocking light incident on the metal thin film.

Description:
This application claims the benefit of Korean Patent Application No. P00-26876 filed May 19, 2000, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a liquid crystal display, and more particularly to a liquid crystal display device and method of fabricating the same that reduces a reflectivity of an LCD display screen. 
     2. Description of the Related Art 
     Generally, a liquid crystal display (LCD) of an active matrix driving system uses thin film transistors (TFT&#39;s) as switching devices to display images. Since such LCD&#39;s can be made smaller than cathode ray tubes, they have been widely used as monitors for personal computers or notebook computers, as well as in office automation equipment, such as copy machines, etc. . . and in portable equipment, such as a cellular phones and pagers, etc. 
     Referring to  FIGS. 1 and 2 , in the conventional LCD device, a gate line  14  and a data line  13  is formed on a rear substrate  1  crossing each other, and a pixel electrode  10  is formed at the interior thereof. A TFT  12  is formed at an intersection between the gate line  14  and the data line  13 . 
     The TFT  12  includes a gate electrode  3 , a source electrode  6  and a drain electrode  7  to apply a data signal at the data line  13  to the pixel electrode  10  during an application of a scanning pulse to the gate electrode  3 . The gate electrode  3  is connected to the gate line  14 , while the source electrode  6  is connected to the data line  13 . The drain electrode  7  is connected, via a contact hole  9 , to the pixel electrode  10 , which is deposited with a transparent conductive material such as indium-tin-oxide (ITO). A gate insulating film  4 , deposited using an inorganic insulating material, is formed on the gate electrode  3  and the gate line  14 , and an active layer  20  and an ohmic contact layer  5  are deposited thereon. A passivation layer  8  made from either an inorganic insulating material or an organic insulating material is formed on the TFT  12 . 
     In the conventional LCD device, a storage capacitor  19  is provided on the gate line  14 . The storage capacitor  19  accumulates a driving voltage (charge) of the next scanning line during the previous scanning period, to thereby lower the driving voltage. An upper electrode  15  of the storage capacitor  19  is made from a metal alloy upon formation of the source electrode  6  and the drain electrode  7 , as shown in  FIG. 3 . The gate line  14  that overlaps the upper electrode  15  serves as a lower electrode of the storage capacitor  19 . The upper electrode  15  of the storage capacitor  19  is connected, via a contact hole  16  passing through a passivation layer  8 , to the pixel electrode  10 . 
     A black matrix  11  is provided on a front substrate  2 , which is opposed to the rear substrate  1 , with a liquid crystal therebetween. The black matrix  11  is positioned at a portion other than an effective display area of a pixel to absorb all wavelengths of light incident thereon. Further, on the front substrate  2  there are provided a common electrode, a color filter and an alignment film (not shown) in addition to the black matrix  11 . 
     Such an LCD device has a problem in that a large amount of reflective light is generated at the display screen due to a structure of the black matrix  11 . More specifically, the black matrix  11  does not overlap with a pixel electrode side portion  17  of the drain electrode  7  and a pixel electrode side portion  18  of the upper electrode  15  of the storage capacitor, as shown in  FIG. 1 , due to its pattern structure. As a result, as shown in  FIGS. 2 and 3 , when external light is incident on areas O 1  and O 2  of the black matrix  11 , the upper electrode  15  of the storage capacitor and on the drain electrode  7 , it is reflected from the upper electrode  15  and the drain electrode  7 , which are made of metal. Such a reflected light is incident on a user&#39;s eye, and reduces the contrast, thereby reducing quality of a displayed image. For instance, since an aircraft cockpit is exposed to direct sunlight, various LCD panels installed in the cockpit of the aircraft generate a large amount of reflected light. Therefore, the LCD panel in an aircraft may have a deterioration of picture clarity due to the reflected light, sometimes causing pilot error. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a liquid crystal display and a fabricating method thereof that reduce a reflectivity of the display screen. 
     In order to achieve these and other objects of the invention, a liquid crystal display device according to one aspect of the invention includes a pixel electrode at a pixel area between a gate line and a data line, a switching device at an intersection between the gate line and the data line, the switching device comprising a light-shielding member overlapping the switching device and extending from an end at the pixel electrode side of a metal thin film provided within the switching device into the pixel area, for blocking light incident on the metal thin film. 
     A liquid crystal display device according to another aspect of the present invention includes a pixel electrode at a pixel area between a gate line and a data line, a charging device on the gate line, the charging device including a metal thin film, a light-shielding member overlapping the charging device and extending from an end at the pixel electrode side of a metal thin film into the pixel area, for blocking light incident on the metal thin film. 
     A liquid crystal display device according to still another aspect of the present invention includes a pixel electrode at a pixel area between a gate line and a data line, a thin film transistor at an intersection between the gate line and the data line and including a first metal thin film a storage capacitor on the gate line and including a second metal thin film, a black matrix at a boundary portion between pixel areas, first dummy black matrix connected to the black matrix and extending from an end at the pixel electrode side of the metal thin film into the pixel area, and a second dummy black matrix connected to the black matrix and extending from an end at the pixel electrode side of the second metal thin film into the pixel area. 
     A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the steps of forming a pixel electrode at a pixel area between a gate line and a data line, forming a switching device including a metal thin film at an intersection between the gate line and the data line, and forming a light-shielding member for blocking light incident on the metal thin film to overlap with the switching device, the light-shielding member extending from an end at the pixel electrode side of a metal thin film of the switching device into the pixel area. 
     A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the steps of forming a pixel electrode at a pixel area between a gate line and a data line, forming a charging device including a first metal thin film on the gate line, and forming a light-shielding member for blocking light incident on the metal thin film to overlap the metal thin film, the light-shielding member extending from an end at the pixel electrode side of the first metal thin film into the pixel area. 
     A method of fabricating a liquid crystal display device according to still another aspect of the present invention includes the the steps of forming a pixel electrode at a pixel area between a gate line and a data line on a rear substrate, forming a thin film transistor including a first metal thin film at an intersection between the gate line and the data line on the rear substrate, forming a storage capacitor including a second metal thin film on the rear substrate and overlapping the gate line, forming a black matrix on a front substrate opposed to the rear substrate at a boundary portion between pixel areas, forming a first dummy black matrix extending from an end at the pixel electrode side of the first metal thin film into the pixel area on the front substrate, and forming a second dummy black matrix extending from an end at the pixel electrode side of the second metal thin film into the pixel area on the front substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects of the invention will be apparent from the following detailed description of the embodiment of the present invention with reference to the accompanying drawings. 
       In the drawings: 
         FIG. 1  is a plan view showing a structure of one pixel at a rear substrate of a conventional liquid crystal display device; 
         FIG. 2  is a section view of a thin film transistor taken along the line A-A′ of  FIG. 1 ; 
         FIG. 3  is a section view of a thin film transistor taken along the line B-B′ of  FIG. 1 ; 
         FIG. 4  is a plan view showing a structure of one pixel at a rear substrate of a liquid crystal display device according to an embodiment of the present invention; 
         FIG. 5  is a section view of a thin film transistor taken along the line C-C′ of  FIG. 4 ; and 
         FIG. 6  is a section view of a thin film transistor taken along the line D-D′ of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in  FIGS. 4 and 5 , an LCD device according to an embodiment of the present invention includes a gate line  34  and a data line  33  formed on a rear substrate  21  crossing each other. A pixel electrode  30  is formed at the interior thereof. A TFT  32  is formed at an intersection between the gate line  34  and the data line  33 . 
     The TFT  32  includes a gate electrode  23 , a source electrode  26  and a drain electrode  27  to apply a data signal at the data line  33  to the pixel electrode  30  during an “on” period of a scanning pulse to the gate electrode  23 . The gate electrode  23  is connected to the gate line  34  while the source electrode  26  is connected to the data line  33 . The drain electrode  27  is connected to the pixel electrode  30 . 
     A process of fabricating such a TFT will be described below. First, a metal thin film is formed by depositing aluminum (Al) or copper (Cu) on the rear substrate  1  using, for example, a sputtering technique. The metal thin film is selectively patterned, to remain only at a desired portion of the rear substrate  21  using photolithography. A wet etching method may be used for the photolithography. The patterned metal thin film is formed into the gate electrode  23  and the gate line  34 . 
     Subsequently, an insulating material, such as silicon oxide or silicon nitride, is deposited onto the entire substrate by chemical vapor deposition (CVD) to form a gate insulating film  24 . The gate insulating film  24  covers the gate electrode  23  and the gate line  14 . An active layer  40  and an ohmic contact layer  25  are sequentially deposited onto the gate insulating film  4  by, for example, CVD. The active layer  40  is made of an amorphous silicon or polycrystalline silicon, and is not doped with impurities. The ohmic contact layer  25  is made of amorphous silicon or polycrystalline silicon, and is doped with n-type or p-type impurities at a high concentration. The active layer  40  and the ohmic contact layer  25  are patterned by photolithography, including isotropic etching, to remain only at a portion corresponding to the gate electrode  23 . The source electrode  26  and the drain electrode  27  are formed on the ohmic contact layer  25 . The source electrode  26  and the drain electrode  27  are formed by depositing a metal such as molybdenum (Mo), titanium (Ti) or tantalum (Ta), etc., or a molybdenum alloy, such as MoW, MoTa or MoNb, etc. on the ohmic contact layer  25  using CVD or sputtering, and then patterning it. Upon patterning of the source electrode  26  and the drain electrode  27 , the ohmic contact layer  25  on the gate electrode  23  is patterned due to an over-etching, to expose the active layer  40 . 
     On the TFT  32  that has the structure as described above, an inorganic insulating material such as silicon oxide or silicon nitride, or an organic insulating material such as an acrylic compound, BCB (β-stagged-divinyl-siloxane-benzocyclobutene) or PFCB (perfluorocyclobutane), is deposited. The insulating material deposited on the TFT  32  in this manner becomes a passivation layer  28 . A portion of the passivation layer  28  covering the drain electrode  27  is patterned. A contact hole  29  exposing the drain electrode  27  is defined in the patterned passivation layer  28 . Subsequently, a transparent conductive material, such as ITO or IZO (indium-zinc-oxide), is deposited on the passivation layer  28  and the contact hole  29 . The transparent conductive film contacts the drain electrode  27  through the contact hole  29 . The transparent conductive film is patterned to remain only at a pixel area between the gate line  34  and the data line  33 , thereby forming the pixel electrode  30 . 
     The LCD device further includes a storage capacitor  39  formed on the gate line  14 . The storage capacitor  39  accumulates a driving voltage (charge) for the next scanning line during the previous scanning period, to thereby lower the required driving voltage. An upper electrode  35  of the storage capacitor  39  is formed by patterning a metal or a metal alloy to overlap the gate line  34  upon formation of the source electrode  26  and the drain electrode  27 , as shown in  FIG. 6 . The gate line  34  overlaps the upper electrode  35  and serves as a lower electrode of the storage capacitor  39 . The upper electrode  35  of the storage capacitor  39  is connected, via a contact hole  36  formed by patterning of the passivation layer  30 , to the pixel electrode  30 . 
     A black matrix  31  is provided on a front substrate  22 , which is opposed to the rear substrate  21 , with a liquid crystal therebetween. The black matrix  31  is positioned at a portion other than an effective display area of a pixel, that is, at a boundary portion between pixels where the TFT  32 , the data line  33 , the gate line  34  and the storage capacitor  39  are positioned, so as to prevent a color signal interference between pixels and to shut off a reflected light inputted from the display screen. To this end, the black matrix  31  includes a first shield  31   a  overlapping the TFT  32 , and a second shield  31   b  overlapping the storage capacitor  39 . The first shield  31   a  extends, by a desired distance C 1 , from an end at the pixel electrode side of the drain electrode  27  as shown in  FIG. 5 , to thereby absorb light incident to the metal thin film of the TFT  32 , including the drain electrode  27 . The second shield  31   b  extends, by a desired distance C 2 , from an end at the pixel electrode side of the upper electrode  35 , as shown in  FIG. 6  to absorb light incident to the metal thin film of the storage capacitor  39 , including the upper electrode  35 . The black matrix  31  is formed on the front substrate  22  by coating an organic material, such as polyimide, to which a black pigment is added. Furthermore, on the front substrate  22  there is a common electrode, a color filter and an alignment film (not shown), in addition to the black matrix  31 . 
     As described above, the black matrix formed at a boundary portion between pixels extends into the drain electrode of the TFT and the upper electrode of the storage capacitor. Accordingly, a deterioration of contrast caused by a reflected light incident on the metal thin film can be minimized. Such an LCD device is suitable, for example, for a display panel for aircraft cockpits exposed to direct sunlight. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood by the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.