Patent Publication Number: US-7916257-B2

Title: TFT substrate and liquid crystal display device having the same comprising patterns disposed at different heights

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relies for priority upon U.S. patent application Ser. No. 12/124,941, filed May 21, 2008 and U.S. patent application Ser. No. 11/210,132, filed Aug. 22, 2005, now U.S. Pat. No. 7,388,638, which claims priority of Korean Patent Application Number 2004-66468, filed Aug. 23, 2004, the contents of which are herein incorporated by reference in their entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a TFT substrate and a display device having the TFT substrate. More particularly, the present invention relates to a TFT substrate and a liquid crystal display device having the TFT substrate. 
     2. Description of the Related Art 
     A liquid crystal display (LCD) device includes a color filter substrate, a thin film transistor (TFT) substrate and a liquid crystal layer. The color filter substrate includes a color filter layer and a common electrode. The TFT substrate includes a TFT and a pixel electrode that is electrically connected to the TFT. The liquid crystal layer is disposed between the TFT substrate and the color filter substrate. When a data voltage is applied to the pixel electrode, an electric field is generated between the pixel electrode and the common electrode to alter an arrangement of liquid crystal molecules of the liquid crystal layer. As a result, an optical transmissivity is altered to display an image. 
     When a contrast ratio of the LCD device is high, the LCD device displays a clear image. Therefore, it would be desirable to improve the contrast ratio for LCD devices. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a TFT substrate capable of enhancing a contrast ratio by reducing contrast ratio deterioration due to a stepped portion is provided. 
     In accordance with the present invention, a liquid crystal display device having the above TFT substrate is also provided. 
     In an exemplary TFT substrate according to the present invention, the TFT substrate includes a substrate, a plurality of gate lines, a plurality of data lines, a plurality of pixel electrodes, a protection layer and a pattern. The gate lines are formed on the substrate and extend in a first direction. The data lines are formed on the substrate and extend in a second direction that is substantially perpendicular to the first direction. Each of the pixel electrodes is electrically connected to a TFT that is also electrically connected to a selected gate line and a selected data line. The protection layer is formed on the substrate such that the protection layer covers the gate lines and the data lines. The pattern is disposed in a pixel region of the substrate to induce a stepped portion of the protection layer. The pixel region is defined by adjacent gate lines and adjacent data lines. A longitudinal direction of the pattern forms an angle of about 30 degrees to about 60 degrees with respect to one of the first and second directions. A side of the pattern forms an inclination angle of no more than about 45 degrees when a thickness of the pattern is more than about 3000 angstroms. The side of the pattern forms an inclination angle of no more than about 50 degrees when a thickness of the pattern is in a range of about 2000 angstroms to about 3000 angstroms. The side of the pattern forms an inclination angle of no more than about 90 degrees when a thickness of the pattern is less than about 2000 angstroms. 
     In an exemplary LCD device according to the present invention, the LCD device includes an upper substrate, a polarization layer, a lower substrate and a liquid crystal layer. The polarization plate has a transmission axis. The lower substrate faces the upper substrate, and is disposed on the polarization plate. The lower substrate includes a plurality of gate lines, a plurality of data lines, a plurality of pixel electrodes, a protection layer and a pattern. The gate lines are formed on the substrate and extend in a first direction. The data lines are formed on the substrate and extend in a second direction that is substantially perpendicular to the first direction. Each of the pixel electrodes is electrically connected to a TFT that is also electrically connected to a selected gate line and a selected data line. The protection layer is formed on the substrate such that the protection layer covers the gate lines and the data lines. The pattern is disposed in a pixel region of the substrate to induce a stepped portion of the protection layer. The pixel region is defined by adjacent gate lines and adjacent data lines. A longitudinal direction of the pattern forms an angle of about 30 degrees to about 60 degrees with respect to one of the first and second directions. A side of the pattern forms an inclination angle of no more than about 45 degrees when a thickness of the pattern is more than about 3000 angstroms. The side of the pattern forms an inclination angle of no more than about 50 degrees when a thickness of the pattern is in a range of about 2000 angstroms to about 3000 angstroms. The side of the pattern forms an inclination angle of no more than about 90 degrees when a thickness of the pattern is less than about 2000 angstroms. The liquid crystal layer is disposed between the upper and lower substrates. 
     In another exemplary LCD device according to the present invention, the LCD device includes a first substrate, a second substrate, a liquid crystal layer and a voltage applying part. The first substrate has a first base substrate, a plurality of patterns disposed at different height with respect to the first base substrate, and an insulation layer formed on the first base substrate. The insulation layer has a plurality of raised portions by covering the patterns. The second substrate faces the first substrate. The liquid crystal layer is disposed between the first and second substrates. The voltage applying part generates electric fields passing through the liquid crystal layer. A side of the raised portions forms an inclination angle of no more than about 45 degrees when a height of the raised portions is more than about 3000 angstroms, the side of the raised portions forms an inclination angle of no more than about 50 degrees when a height of the raised portions is in a range of about 2000 angstroms to about 3000 angstroms, and the side of the raised portions forms an inclination angle of no more than about 90 degrees when a height of the raised portions is less than about 2000 angstroms. 
     When a pattern (for example, a protruding portion) disposed in the pixel region induces a stepped portion of an alignment film, a longitudinal direction of the patterns forms an angle of about 30 degrees to about 60 degrees with respect to the transmission axis of the polarizing plate. The pattern satisfies the above-mentioned relation between thickness and inclination angle, and as a result, a light leakage is minimized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a layout illustrating a TFT substrate of an LCD according to a first exemplary embodiment of the present invention; 
         FIG. 2  is a cross-sectional view taken along a line II-II′ in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along a line III-III′ in  FIG. 1 ; 
         FIG. 4  is a layout illustrating a TFT substrate according to a second exemplary embodiment of the present invention; 
         FIG. 5  is a cross-sectional view taken along a line V-V′ in  FIG. 4 ; and 
         FIG. 6  is a circuit diagram of the LCD device in  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     When patterns being disposed in a pixel region and inducing a stepped portion forms an angle of about 30 degrees to about 60 degrees, liquid crystal molecules that makes contact with the stepped portion are not vertically erected, so that light is leaked through the stepped portion to lower a contrast ratio. According to the present invention, a condition of the patterns for reducing the patterns. 
     It should be understood that the exemplary embodiments of the present invention described below may be varied and modified in many different ways without departing from the inventive principles disclosed herein, and the scope of the present invention is therefore not limited to these particular embodiments. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art by way of example and not of limitation. 
     Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanied drawings. It is noted that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by embodiments that will be described below. The embodiments are only examples for showing the spirit of the present invention to a person skilled in the art. In the figures, a thickness of layers is exaggerated in order to improve clarity. The term “disposed on” means “disposed over”. In other words, another structure may be disposed therebetween. The term “disposed directly on” means that no other structures are disposed therebetween. 
       FIG. 1  is a layout illustrating a TFT substrate of an LCD according to a first exemplary embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along a line II-II′ in  FIG. 1 , and  FIG. 3  is a cross-sectional view taken along a line III-III′ in  FIG. 1 . 
     Referring to  FIGS. 1 ,  2  and  3 , a liquid crystal display (LCD) device according to the present embodiment includes a thin film transistor (TFT) substrate  100 , a color filter substrate  200  facing the TFT substrate  100 , and a liquid crystal layer  300  disposed between the TFT substrate  100  and the color filter substrate  200 . Liquid crystal molecules  310  of the liquid crystal layer  300  are arranged such that a longitudinal direction of the liquid crystal molecules is substantially perpendicular to the TFT substrate  100  and the color filter substrate  200 . 
     The TFT substrate  100  and the color filter substrate  200  include a first alignment layer  11  and optionally a second alignment layer (not shown) in order to arrange the liquid crystal molecules  310  in the longitudinal direction. 
     A plurality of gate lines  121  and a plurality of storage electrode lines  131  are formed on a first insulation substrate  110 . 
     The gate line  121  transfers a gate signal, and a portion of the gate line  121  corresponds to a gate electrode. An end portion  129  of the gate line  121  is enlarged to form the gate electrode, and the gate line  121  is electrically connected to an external device through the end portion  129 . When a gate driving circuit is mounted directly on the first insulation substrate  110 , the end portion  129  of the gate line  121  is connected to an output terminal of the gate driving circuit. 
     The storage electrode lines  131  are formed such that the storage electrode lines  131  are substantially parallel with the gate line  121 . Alternatively, the storage electrode lines  131  are formed substantially parallel with data lines  171  (as shown in  FIG. 1 ). The storage electrode line  131  includes a storage electrode  135 . The storage electrode  135  includes a protruding portion  133 . A longitudinal direction of the protruding portion  133  forms an angle of about 45 degrees with respect to a longitudinal direction of the storage electrode lines  131 . A voltage applied to the storage electrode  135  is substantially the same as a reference voltage applied to a common electrode  270  of the color filter substrate  200 . 
     The gate line  121  and the storage electrode line  131  have a single layered structure as shown in  FIGS. 2 and 3 . Alternatively, the gate line  121  and the storage electrode line  131  may have a multi-layered structure. For example, the gate line  121  and the storage electrode line  131  may include a lower layer (not shown) and an upper layer (not shown). The lower and upper layers may have different physical characteristics. The upper layers of the gate line  121  and the storage electrode line  131  may comprise a metal having a relatively low electric resistivity, such as aluminum, aluminum alloy, etc. The lower layer may comprise a material having a relatively high adhesive force to indium tin oxide (ITO), such as molybdenum (Mo), molybdenum alloy, chromium (Cr), etc. For example, the lower layer may comprise chromium (Cr) and the upper layer may comprise aluminum neodymium alloy (AlNd). 
     A first polarizing layer  21  is disposed under the first insulation substrate  110 . The first polarizing layer  21  has a transmission axis  21 ′ that is disposed substantially parallel with the gate line  121 . The storage electrode  135  includes the protruding portion  133  protruded such that a longitudinal direction of the protruding portion  133  forms an angle of about 45 degrees with respect to a longitudinal direction of the transmission axis  21 ′. 
     The protruding portion  133  induces a stepped portion at a pixel region for displaying an image when the layers are formed on the protruding portion  133 . In other words, due to the formation of the protruding portion  133  on the substrate  110 , a surface of the pixel region is not planar. Therefore, the liquid crystal molecules  310  that are disposed at the stepped portion are inclined. In other words, the liquid crystal molecules  310  disposed on a flat region are vertically arranged, but the liquid crystal molecules  310  disposed at the stepped portion are not vertically arranged, so that light leaks through the liquid crystal layers  310  disposed at the stepped portion. Therefore, the resulting a contrast ratio of the display device is lowered. 
     Hereinafter, a stepped portion condition for reducing light leakage will be explained. In an experiment, amount of light leakage was measured by varying a thickness and an inclination of the protruding portion  133 . In order to reduce light leakage, a thickness of the protruding portion and an inclination of the protruding portion were adjusted. According to results of the experiment, an inclination of the protruding portion  133  was adjusted according to a thickness of the protruding portion  133 . The inclination of the protruding portions  133  were set in cases when the thickness of the protruding portion  133  was no thicker than about 2000 angstroms, when the thickness of the protruding portion  133  was in a range from about 2000 angstroms to about 3000 angstroms, and when the thickness of the protruding portion was thicker than about 3000 angstroms, respectively. 
     Table 1 below shows a portion of results of the experiment. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Thickness 
                 Inclination θ 
                   
                   
               
               
                 (Angstrom) 
                 (Degrees) 
                 Light leakage 
                 Contrast ratio acceptable? 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 3000 
                 90 
                 0.056 
                 No 
               
               
                 2000 
                 90 
                 0.0279 
                 Yes 
               
               
                 1000 
                 90 
                 0.0012 
                 Yes 
               
               
                 3000 
                 45 
                 0.0154 
                 Yes 
               
               
                 2000 
                 45 
                 0.0066 
                 Yes 
               
               
                 1000 
                 45 
                 0.0018 
                 Yes 
               
               
                 3000 
                 22.5 
                 0.0024 
                 Yes 
               
               
                   
               
            
           
         
       
     
     In an embodiment in which the protruding portion has a thickness greater than about 3000 angstroms and has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , the inclination angle of the protruding portion is substantially equal to or less than about 45 degrees. In an embodiment in which the protruding portion has a thickness in the range of about 2000 angstroms to about 3000 angstroms and has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , the inclination angle of the protruding portion is substantially equal to or less than about 50 degrees. In an embodiment in which the protruding portion has a thickness less than about 2000 angstroms and has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , the inclination angle of the protruding portion is substantially equal to or less than about 90 degrees. 
     That is, when a protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and has an inclination angle substantially equal to or less than about 90 degrees, an allowable thickness of the protruding portion is substantially equal to or less than about 2000 angstroms. When the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and has an inclination angle substantially equal to or less than about 50 degrees, an allowable thickness of the protruding portion is substantially equal to or less than about 3000 angstroms. When the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and has an inclination angle substantially equal to or less than about 45 degrees, a thickness more than about 3000 angstroms is allowable. 
     The protruding portion  133  induces stepped portions of the alignment film  11  that make contact with liquid crystal molecules of the liquid crystal layer  300 . Therefore, the same logic is applied when the ‘protruding portion’ is replaced by the ‘stepped portions of the alignment film’ in the above explanation. 
     Electrical resistivity decreases as a thickness of the storage electrode increases. However, when the inclination of the protruding portion  133  that protrudes from the storage electrode satisfies the inclination condition described above, the light leakage is minimized. 
     In  FIG. 1 , an opening portion of a pixel electrode  190  is disposed over the protruding portion  133 , so that the pixel electrode  190  does not overlap with the protruding portion  133 . Alternatively, even when the protruding portion  133  overlaps with the pixel electrode  190  to generate a storage capacitance, the above-mentioned condition is not changed. 
     The protruding portion  133  and the gate electrode  190  are formed from the same metal layer during the same manufacturing process, so that the protruding portion  133  is optically opaque like the gate electrode  190 . The protruding portion  133  is disposed in the pixel region (or display region), so that reducing a width of the protruding portion  133  is preferable. A width of the protruding portion  133  is, preferably, no wider than about 10 μm. According to the present embodiment, the protruding portion  133  has a width of about 7 μm. 
     Inclination of the gate line  121  and the storage electrode line  131  are substantially the same as that of the protruding portion  133 . 
     A gate insulation layer  140  is formed on the first insulation substrate  110  having the gate line  131 , the storage electrode line  131  and the protruding portion  133  formed thereon. The gate insulation layer  140  comprises silicon nitride (SiNx) as an exemplary embodiment. 
     A semiconductor layer  151  comprising, for example, amorphous silicon (a-Si), is formed on the gate insulation layer  140 . The semiconductor layer  151  extends substantially parallel with the data line  171 , and overlaps with the data line  171 . A portion  154  of the semiconductor layer  151  extends toward the gate electrode  124 . A width of the semiconductor layer  151  is increased at a region where the gate line  121  and the storage electrode line  131  are merged. 
     Ohmic contact layers  161  are formed on the semiconductor layer  151 . The ohmic contact layers  161  comprise n-type dopant in amorphous silicon (n+a-Si). The ohmic contact layers  161  are disposed over the portion  154  of the semiconductor layer  151 . 
     The sides of the semiconductor layer  151  and the ohmic contact layers  161  are inclined to have an inclination angle of about 30 degrees to about 80 degrees with respect to the substrate  110 . 
     A plurality of data lines  171  and a plurality of drain electrodes  175  are formed on the gate insulation layer  140  and the ohmic contact layers  161 , respectively. 
     The data lines  171  extend such that a longitudinal direction of the data lines  171  is substantially perpendicular to a longitudinal direction of the gate line  121  and the data lines  171  are substantially parallel with the storage electrode line  131 . The data lines  171  transmit data voltages. The data lines  171  extend in a straight line. Alternatively, when one pixel has a chevron shape having a bent portion, the data line  171  may be bent along an edge portion of the pixel. 
     The drain electrode  175  extends toward the storage electrode  135  such that the drain electrode  175  overlaps with the storage electrode  135 . A source electrode  173  protrudes from the data line  171 . The gate electrode  124 , the source electrode  173  and the drain electrode  175  form a thin film transistor TFT. A channel layer is formed at the portion  154  between the source electrode  173  and the drain electrode  175 . An end portion  179  of the data line  171  has a wider width than other portions of the data line  171  in order to be easily connected to an external circuit. 
     The data line  171  has a single layered structure. Alternatively, the data line  171  may have a multi-layered structure. For example, the data line  171  may include a lower layer (not shown) and an upper layer (not shown). The lower and upper layers may have different physical characteristics. The upper layer of the data line  171  may comprise a metal having a relatively low electric resistivity, such as aluminum, aluminum alloy, etc. The lower layer may comprise a material having a relatively high adhesive force to indium tin oxide (ITO), such as molybdenum (Mo), molybdenum alloy such as molybdenum tungsten (MoW), chromium (Cr), etc. For example, the lower layer may comprise chromium (Cr) and the upper layer may comprise aluminum neodymium alloy (AlNd). Alternatively, the data line  171  may have a triple-layered structure of molybdenum or molybdenum alloy/aluminum or aluminum alloy/molybdenum or molybdenum alloy. Molybdenum nitride, molybdenum neodymium, etc. may be used for the molybdenum alloy. 
     The ohmic contact layers  161  disposed between the semiconductor layer  151 , and the source and drain electrodes  173  and  175  lower a contact resistivity. The semiconductor layer  151  has a portion that is not covered by the data line  171  and the drain electrode  175 , but a majority of the semiconductor layer  151  has substantially the same as or wider width than a width of the data line  171 . 
     A protection layer  180  is formed on the first insulation substrate  110  such that the protection layer  180  covers the semiconductor layer  151  exposed between the source and drain electrodes  173  and  175 , and the data line  171 . The protection layer  180  comprises, for example, silicon nitride. 
     The protection layer  180  includes a contact hole  185   b  exposing a portion of the drain electrode  175 , a contact hole  182   b  exposing an end portion  179  of the data line  171 , and a contact hole  181   b . A portion of the gate insulation layer  140 , which corresponds to the contact hole  181   b , is removed, so that an end portion  129  of the gate line  121  is exposed through the contact hole  181   b.    
     A side face of the contact holes  181   b ,  182   b  and  185   b  has, for example, an inclination of about 30 degrees to about 85 degrees with respect to the substrate  110 . 
     The contact holes  181   b ,  182   b  and  185   b  may comprise various cross-sectional shapes such as a polygon, a circle, etc. when viewed from a plan view perspective. The contact holes  181   b ,  182   b  and  185   b  may have, e.g., a cross-sectional area of about 0.5 μm×15 μm to about 2 μm×60 μm. 
     The upper layer of the end portion  129  of the gate line  121 , the end portion  179  of the data line  171 , and the drain electrode  175 , exposed by the contact holes  181   b ,  182   b , and  185   b , respectively, are removed. In detail, the upper layer including aluminum or aluminum alloy is removed in order to enhance the connection to a conductor layer, as will be described in greater detail below. 
     The pixel electrode  190  comprising an optically transparent and electrically conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), etc., contact supporting members  81  and  82 , and a subsidiary electrode  197  are formed on the protection layer  180 . 
     The pixel electrode  190  is disposed in the pixel region surrounded by the gate lines  121  and the data lines  171 . The pixel electrode  190  is electrically connected to the drain electrode  175  through the contact hole  185   b.    
     The contact supporting members  81  and  82  are electrically connected to the end portion  129  of the gate line  129 , and the end portion  179  of the data line  171  through the contact holes  182   b  and  181   b , respectively. The contact supporting members  81  and  82  enhance an electrical contact stability, and protect the end portions  129  and  179  of the gate and data lines  121  and  171 , respectively. Here, the contact supporting members  81  and  82  are optional. When the gate line  121  and the data line  171  are electrically connected to output terminals of a gate driving circuit and a data driving circuit formed on the first insulation substrate  110 , the contact supporting members  81  and  82  are not required. 
     The pixel electrode  190  includes the opening portions  191   a  and  191   b . A first virtual line extending along the opening portion  191   a  meets a second virtual line extending along the opening portion  191   b  to form an angle of about 90 degrees. A width of the opening portions  191   a  and  191   b  is no wider than about 10 μm. The pixel electrode  190  overlaps a portion of the storage electrode  135 . In other words, a portion of the storage electrode  135  is not covered by the pixel electrode  190 , so that the storage electrode  135  blocks light leakage between the pixel electrodes  190  adjacent to each other. 
     The pixel electrode  190  comprises an optically transparent and electrically conductive material such as ITO, IZO, etc. Alternatively, the pixel electrode  190  may comprise a metal that is opaque, when the LCD device corresponds to a reflective type LCD device. The contact supporting members  81  and  82  may comprise the same material as that of the pixel electrode  190 . Alternatively, the contact supporting members  81  and  82  may comprise a different material from that of the pixel electrode  190 . 
     The color filter substrate  200  comprises a second insulating substrate  210 , a light blocking layer  220  and a color filter layer  230 . The light blocking layer  220  includes an opening portion disposed over the pixel electrode  190 . The color filter layer  230  includes a plurality of red color filters, a plurality of green color filters and a plurality of blue color filters. Each of the red, green and blue color filters are formed on the second insulation layer  210  exposed though the opening portions of the light blocking layer  220 . 
     The color filter substrate  200  further comprises an over-coating layer  250  formed on the color filter layer  230  and the light blocking layer  220 . The over-coating layer  250  comprises, for example, an organic material. 
     The color filter substrate  200  further comprises a common electrode  270  formed on the over-coating layer  250 . The common electrode  270  comprises an optically transparent and electrically conductive material such as ITO, IZO, etc. The common electrode  270  includes an opening portion  271  that is positioned to be substantially parallel and aligned with the opening portion  191   a  of the pixel electrode  190 . 
     The opening portion  271  controls a direction of the liquid crystal molecules  310 . The opening portion  271  has a width of, e.g., about 9 μm to about 12 μm. Instead of the opening portions  271  of the common electrode  270 , an upper protrusion may be formed on the common electrode  270 . Instead of the opening portion  191   a  of the pixel electrode  190 , a lower protrusion may be formed on pixel electrode  190 . When the upper protruding portion is formed on the common electrode  270 , the common electrode  270  may be directly formed on the color filter layer  230 . The upper and lower protrusions may be formed at substantially the same position of the opening portions  271  or the opening portion  191   a.    
     The first and second polarizing layers  21  and  22  are formed on outer surfaces of the first and second insulation substrates  110  and  210 , respectively. One of the first and second polarizing layers  21  and  22  has a light transmission axis that is substantially in parallel with the gate line  121 . 
     The LCD device optionally includes a retardation film for compensating a retardation value of the liquid crystal layer  300 . 
     The liquid crystal layer  300  includes liquid crystal molecules forming a substantially perpendicular angle with respect to the first and second insulation substrates  110  and  210  in a default state. The liquid crystal layer  300  has a negative permittivity anisotropy. 
     When a reference voltage is applied to the common electrode  270  and a data voltage is applied to the pixel electrode  190 , a primary electric field is formed between the common electrode  270  and the pixel electrode  190 . The primary electric fields are generated substantially perpendicular to the planar surfaces of the common electrode  270  and the pixel electrode  190 . Then, liquid crystal molecules  310  are rearranged such that a direction of the liquid crystal molecules  310  is substantially perpendicular to the primary electric fields. In other words, the liquid crystal molecules  310  are inclined. 
     The opening portion  271  of the common electrode  270  and the opening portion  191   a  of the pixel electrode  190  alter the electric fields to form a horizontal component. Therefore, four domains are generated in the pixel region. Two of the domains adjacent to each other have a different inclination angle. Each domain has a width of about 10 μm to about 30 μm. 
     When the pixel region has a size of smaller than about 100 μm×300 μm, the pixel region includes four domains. When the pixel region has a size of substantially equal to or larger than about 100 μm×300 μm, the pixel region may include four domains or eight domains. 
     When an inclination angle of the liquid crystal molecules  310  forms an angle of 45 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , a maximum luminance may be obtained. According to the present invention, all liquid crystal molecules  310  of each domain are inclined at an angle of about 45 degrees with respect to the gate line  121 , and the gate line  121  is substantially perpendicular to or parallel with edges of the first and second insulation substrates  110  and  210 . Therefore, when the first polarizing layer  21  is attached on the outer surface of the first insulation substrate  110  such that the transmission axis  21 ′ of the first polarizing layer  21  is substantially perpendicular to or parallel with edges of the first insulation substrate  110 , a maximum luminance may be obtained. 
       FIG. 4  is a layout illustrating a TFT substrate according to a second exemplary embodiment of the present invention.  FIG. 5  is a cross-sectional view taken along a line V-V′ in  FIG. 4 , and  FIG. 6  is a circuit diagram of the LCD device in  FIG. 4 . 
     Referring to  FIGS. 4 ,  5  and  6 , a TFT  101  is formed in a pixel region. The TFT  101  is electrically connected to the gate line  121  and the data line  171 . A first liquid crystal capacitor C LC1  is formed, the first liquid crystal capacitor C LC1  being defined by the pixel electrode  190 - 1  that is electrically connected to the drain electrode  175  of the TFT  101 , a common electrode  270 , and liquid crystal layer  300  disposed between the pixel electrode  190 - 1  and the common electrode  270 . A second liquid crystal capacitor C LC2  is formed, the second liquid crystal capacitor C LC2  defined by the pixel electrode  190 - 2  that is electrically connected to the drain electrode  175  of the TFT  101 , a common electrode  270  and liquid crystal layer  300  disposed between the pixel electrode  190 - 1  and the common electrode  270 . 
     When a voltage of about 7V is applied to the pixel electrode  190 - 1  and a voltage of about 5V is applied to the common electrode  270 , a voltage difference of about 2V is applied between the pixel electrode  190 - 1  and the common electrode  270 . However, a voltage difference less than about 2V is applied between the floating pixel electrode  190 - 2  and the common electrode  270 , because the storage capacitor C FI0  is electrically connected in series with the second liquid crystal capacitor C LC2 . That is, by applying a voltage of about 7V, two different voltages may be applied to the first and second liquid crystal capacitors C LC1  and C LC2 , respectively. Therefore, a first light that passes through the first liquid crystal capacitors C LC1  and a second light that passes through the second liquid crystal capacitors C LC2  interfere with each other. This interface enhances the display quality. 
     Additionally, a storage capacitor C st1  for reducing voltage drop caused by a leakage current flowing between the storage electrode line  131  and the pixel electrode  190 - 1 , and a storage capacitor C st2  that is electrically connected to the storage electrode line  131  and the floating pixel electrode  190 - 2  are formed. The pixel electrode  190 - 1  and the floating pixel electrode  190 - 2  cover a portion of the data line  171 . In detail, when a side of the data line  171  is spaced apart from a side of the storage electrode line  131  by at least about 1 μm, the storage electrode line  131  having a uniform voltage applied thereto blocks light. 
     The edges of the pixel electrode  190 - 1  and the floating pixel electrode  190 - 2  are aligned at an angle of about 90 degrees, and the protruding portions extending along the edges form an angle of 45 degrees with respect to the transmission axis  21 ′. 
     In embodiments in which the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 45 degrees, the thickness of the protruding portion is thicker than about 3000 angstroms. In embodiments in which the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 50 degrees, the thickness of the protruding portion is in a range of about 2000 angstroms to about 3000 angstroms. In embodiments in which the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 90 degrees, the thickness of the protruding portion is thicker than about 3000 angstroms. 
     In other words, when the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 90 degrees, an allowable thickness of the protruding portion is substantially equal to or less than about 2000 angstroms. When the protruding portion has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 50 degrees, an allowable thickness of the protruding portion is substantially equal to or less than about 3000 angstroms. When the protruding portion that has a longitudinal direction forming an angle of about 30 degrees to about 60 degrees with respect to the transmission axis  21 ′ of the first polarizing layer  21 , and an inclination angle substantially equal to or less than about 45 degrees, a thickness more than about 3000 angstroms is allowable. 
     As described above, a pattern (for example, a protruding portion) disposed in the pixel region induces a stepped portion of an alignment film and a longitudinal direction of the pattern forms an angle of about 30 degrees to about 60 degrees with respect to the transmission axis of the polarizing plate. If the pattern satisfies the above-mentioned relationship between the thickness and inclination angle, the light leakage may be minimized. 
     Hereinbefore, the present invention was explained with reference to a VA mode LCD device. Alternatively, the present invention may be applied to a TN mode LCD device, or other mode LCD devices. 
     Having described the exemplary embodiments of the present invention, it is noted that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by appended claims.