Abstract:
A liquid crystal display device (LCD) is provided. The LCD includes first and second substrates; a plurality of gate lines on the first substrate; a plurality of data lines crossing the gate lines to define a plurality of pixel regions; a thin film transistor at a crossing intersection of the gate line and the data line; a pixel electrode in the pixel region, the pixel electrode having a zigzag slit pattern formed therein, the slit pattern dividing the pixel electrode into at least two domains; a dielectric protrusion on the second substrate; and a liquid crystal layer between the first and second substrates.

Description:
This application claims the benefit of Korean Patent Application No. 2004-118378, filed on Dec. 31, 2004, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a liquid crystal display device (LCD), and more particularly, to a vertical alignment mode multi-domain LCD capable of providing a high image quality and a manufacturing method thereof. 
     DESCRIPTION OF THE RELATED ART 
     A liquid crystal display device (LCD) includes two substrates, a liquid crystal layer interposed between the two substrates, electrodes formed on inner surfaces of the two substrates, and polarizers attached on outer surfaces of the two substrates. When a voltage is applied to the electrodes, the LCD transmits or blocks light by adjusting an alignment of liquid crystal molecules according to the relationship between the liquid crystal and the polarizer, thereby displaying an image. 
     Recently, an active matrix type (AM) thin film transistor (TFT) LCD has been developed. The AM TFT LCD adjusts each pixel electrode using a transistor. 
     A vertical alignment mode LCD uses a negative-type liquid crystal with a negative dielectric anisotropy. The negative-type liquid crystal has a property where a major axis of its molecules are arranged perpendicular to an alignment layer when no voltage is applied thereto and are arranged at a slight angle to the alignment layer when a voltage is applied thereto. By using such a property of the negative-type liquid crystal, the vertical alignment mode LCD adjusts the light transmittance of the liquid crystal to thereby display an image. 
     Meanwhile, in order to obtain a wide viewing angle, the vertical alignment mode LCD uses an alignment technique such as a patterned vertical alignment (PVA) or a multi-domain vertical alignment (MVA) that aligns liquid crystal molecules in a desired direction by distorting an electric field applied to a liquid crystal layer through an auxiliary electrode, a rib or a slit formed on a substrate. 
       FIG. 1A  is a plan view of a unit pixel of a related art LCD, and  FIG. 1B  is a sectional view taken along line A-A′ in  FIG. 1A . 
     In  FIGS. 1A and 1B , the related art LCD includes first and second substrates  1  and  2  facing each other, and gate and data lines  7  and  9  formed substantially perpendicular to each other on the first substrate  1  to thereby define a pixel region. 
     On the first substrate  1 , a pixel electrode  13  with an electric field induction window  14  is formed in the defined pixel region and a common auxiliary electrode  11  is formed on the same layer as the gate line  7  so as to overlap with the periphery of the pixel electrode  13 . 
     A gate insulating layer  3  is formed on the gate line  7 , and a passivation layer  5  is formed on the data line  9 . 
     A black matrix layer  4  is formed on the second substrate  2 , and a color filter layer  6  is formed on the black matrix layer  4 . A common electrode  8  is formed on the color filter layer  6  and a dielectric structure  10  is formed on the common electrode  8 . 
     A liquid crystal layer (not shown) is formed between the first and second substrates  1  and  2 . 
     The electric field induction window  14 , the common auxiliary electrode  11  and the dielectric structure  10  in the related art LCD distorts an electric field applied to the liquid crystal layer. 
     The distorted electric field causes the liquid crystal to be arranged in a desired direction, thereby driving liquid crystal molecules in a unit pixel and resulting in a multi-domain effect. 
     However, because a domain of the related art LCD has a rectangular shape, the distances between the edges of the domain and the dielectric structure vary from one another. 
     This structure causes an asymmetric electric field to occur, thereby making it difficult to obtain a stable picture texture. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a multi-domain liquid crystal display device and manufacturing method thereof that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An advantage of the present invention is to provide a vertical alignment mode multi-domain LCD and a manufacturing method thereof, which can provide a stable picture texture, a wide viewing angle and a high aperture ratio through an effective distortion of an electric field by changing the structure of the data line, a pixel electrode, and a dielectric structure of the related art. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device (LCD) including: first and second substrates; a plurality of gate lines on the first substrate; a plurality of data lines crossing the gate lines to define a plurality of pixel regions; a thin film transistor at a crossing intersection of the gate line and the data line; a pixel electrode in the pixel region, the pixel electrode having a zigzag slit pattern formed therein, the slit pattern dividing the pixel electrode into at least two domains; a dielectric protrusion on the second substrate; and a liquid crystal layer between the first and second substrates. 
     In another aspect of the present invention, an LCD (liquid crystal display device) including: first and second substrates; a plurality of gate lines on the first substrate; a plurality of zigzag data lines crossing the gate lines to define a plurality of pixel regions; a thin film transistor at a crossing of the gate line and the data line; a pixel electrode in the pixel region, the pixel electrode having a zigzag edge and a zigzag slit pattern formed therein, the slit pattern dividing the pixel electrode into at least two domains; a zigzag dielectric protrusion on the second substrate; and a liquid crystal layer between the first and second substrates. 
     In another aspect of the present invention, a method for manufacturing a liquid crystal display device (LCD), the method comprising: providing first and second substrates; forming a gate line on the first substrate; forming a data line crossing the gate line with an insulating layer therebetween to define a pixel region; forming a pixel electrode in the pixel region with a slit having a zigzag pattern, the pixel electrode being divided by the slit into a plurality of domains; forming a dielectric protrusion on the second substrate corresponding to the domains, the dielectric protrusion being parallel to the zigzag slit pattern; and forming a liquid crystal layer between the first and second substrates. 
     In another aspect of the present invention, a method for manufacturing a liquid crystal display device (LCD), the method comprising: providing first and second substrates; forming a gate line on the first substrate; forming a data line crossing the gate line with an insulating layer therebetween to define a pixel region; forming a pixel electrode in the pixel region with a slit having a zigzag pattern, the pixel electrode being divided by the slit into a plurality of domains; forming a dielectric protrusion on the second substrate corresponding to the domains, the dielectric protrusion being parallel to the zigzag slit pattern; and forming a liquid crystal layer between the first and second substrates. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1A  is a plan view of a pixel unit of a related art LCD; 
         FIG. 1B  is a sectional view taken along line A-A′ in  FIG. 1A ; 
         FIG. 2  is a plan view of a multi-domain LCD according to an embodiment of the present invention; 
         FIG. 3  is a sectional view taken along line B-B′ in  FIG. 2 ; and 
         FIG. 4  is a plan view of a multi-domain LCD according to another embodiment of the present invention; and 
         FIG. 5  is a plan view of a multi-domain LCD according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to an embodiment of the present invention, example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 2  is a plan view of a multi-domain LCD according to an embodiment of the present invention, and  FIG. 3  is a sectional view taken along line B-B′ in  FIG. 2 . 
     Referring to  FIGS. 2 and 3 , the multi-domain LCD includes first and second substrates  101  and  102  facing each other, and gate and data lines  107  and  109  intersecting substantially perpendicular to each other on the first substrate  101  to thereby define a pixel region. 
     A thin film transistor (TFT) is formed at an intersection between the gate line  107  and the data line  109 . The TFT includes a gate electrode extended from the gate line  107 , a semiconductor layer formed on the gate electrode with a gate insulating layer  103  therebetween, a source electrode extended from the data line  109  to the semiconductor layer, and a drain electrode formed spaced apart from the source electrode by a predetermined distance on the semiconductor layer. 
     A pixel electrode  113  is formed in the pixel region connected to the drain electrode. A slit pattern  114  is formed in the pixel electrode  113  in the pixel region in such a way to divide the pixel electrode  113  into at least one or more domains, for example, {circle around (1)} {circle around (2)}, {circle around (3)} and {circle around (4)}. 
     Here, although the pixel electrode  113  is divided into the domains {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} by the slit pattern  114 , the divided domains {circle around (1)}, {circle around (2)}, {circle around (3)} and {circle around (4)} are electrically connected to one another to constitute one pixel electrode. 
     The vertical alignment mode multi-domain LCD may be manufactured using the following method. An isolating layer  103  is formed on the substrate  101 , and then the data line  109  is formed on the insulating layer  103 . At this time, a passivation layer  105  is formed on the data line  109 , and the pixel electrode  113  is formed on the passivation layer  105 . 
     The gate insulating layer  103  and the passivation layer  105  may be made of benzocyclobutene (BCB), acrylic resin, polyamide complex compounds, SiNx, SiOx, or the like. 
     The pixel electrode  13  may be made of indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), or the like. 
     A black matrix layer  104  is formed on the second substrate  102 , and a color filter layer  106  is formed on the black matrix layer  104 . A common electrode  108  is formed on the color filter layer  106 , and dielectric protrusions  110  are formed on the common electrode  108 . 
     The dielectric protrusions  110  are formed corresponding to the domains □, □, □ and □ and preferably have a dielectric constant identical to or smaller than that of liquid crystal injected into a gap between the first and second substrates  101  and  102 . 
     A liquid crystal layer is formed between the first and second substrates  101  and  102 . The liquid crystal is preferably a vertical alignment type liquid crystal containing chiral dopants, and the liquid crystal layer preferably has a negative dielectric anisotropy. 
     The dielectric protrusion  110  is formed in a zigzag pattern, and the slit pattern  114  is formed in the pixel electrode  113  in a zigzag pattern in parallel to the zigzag dielectric protrusion  110 . 
     Also, an auxiliary pattern  111  is formed extending from the dielectric protrusion  110  near an edge of the domain in the pixel electrode  113 . The auxiliary pattern  111  is formed so as to minimize the electric field distortion generated between the pixel electrode  113  and the dielectric protrusion  110 . 
     Although not shown in the drawings, an alignment layer may be formed on the first and/or second substrate(s). 
     In the resulting multi-domain vertical alignment (MVA) mode LCD, because the distance between the dielectric protrusion  110  and an edge portion of the domain of the pixel electrode  113  becomes relatively uniform in the pixel region, the electric field is uniformly formed, and thus a stable picture texture may be obtained. 
       FIG. 4  is a plan view of a multi-domain LCD according to another embodiment of the present invention, and  FIG. 5  is a plan view of a multi-domain LCD according to a third embodiment of the present invention. 
     A detailed description of the same elements in  FIGS. 4 and 5  as found in  FIGS. 2 and 3  will be omitted for simplicity. 
       FIGS. 4 and 5  show a pixel electrode  213  or  313  formed in a pixel region on a first substrate, which is defined by a gate line  207  or  307  and a data line  209  or  309 . A slit pattern  214  or  314  is formed in the pixel electrode  213  or  313  in the pixel region in such a way as to divide the pixel electrode  213  or  313  into at least one or more domains. 
     Although the pixel electrode  213  or  313  is divided into the domains by the slit pattern  214  or  314 , the divided domains are electrically connected to one another to thereby constitute one pixel electrode. 
     The data line  209  or  309  is formed in a zigzag pattern, and the pixel electrode  213  or  313  is also formed in a zigzag pattern. 
     A passivation layer (not shown) is formed on the data line  209  or  309 , and the pixel electrode  213  or  313  is formed on the passivation layer. 
     Although not shown in  FIGS. 4 and 5 , but as shown in  FIG. 3 , a black matrix layer  104  is formed on a second substrate  102  facing the first substrate, and a color filter layer  106  is formed on the black matrix layer  104 . A common electrode  108  is formed on the color filter layer  106 , and dielectric protrusions  210  or  310  are formed on the common electrode  108 . 
     The dielectric protrusions  210  or  310  are formed corresponding to the respective domains divided by the slit pattern  214  or  314  and preferably has a dielectric constant identical to or smaller than that of liquid crystal injected into a gap between the first and second substrates. 
     The dielectric protrusion  210  or  310  is formed in a zigzag pattern, and the slit pattern  214  or  314  is formed in the pixel electrode  213  or  313  in a zigzag pattern in parallel to the zigzag dielectric protrusion  210  or  310 . 
     Also, the data line  209  or  309  is formed in a zigzag pattern and an edge of the pixel electrode  213  or  313  is also formed in a zigzag pattern as the zigzag data line  209  or  309 . 
     A liquid crystal layer is formed between the first and second substrates. The liquid crystal is initially aligned vertically when no voltage is applied thereto. The liquid crystal is preferably a vertical alignment type liquid crystal containing chiral dopants, and the liquid crystal layer preferably has a negative dielectric anisotropy. 
     When a voltage is applied to the liquid crystal, an electric field forms between the pixel electrode  213  or  313  on the first substrate and the common electrode  108  on the second substrate. The electric field is distributed symmetrically with respect to the dielectric protrusion  210  or  310 . 
     When the data line  209  or  309  and the pixel electrode  213  or  313  are formed in a zigzag pattern as described above, a disclination region where an electric field distortion occurs in the electric field distributed between the dielectric protrusion  210  or  310  and the pixel electrode  213  and  313  can be minimized, thereby resulting in a stable alignment of the liquid crystal. 
     Also, because the distance between the dielectric protrusion  210  or  310  and an edge portion of the domain of the pixel electrode  213  or  313  becomes relatively uniform in the pixel region, an electric field is uniformly formed and thus a stable picture texture can be obtained. 
     Meanwhile, the slit pattern  314  may have the same zigzag angle as the edge portion of the pixel electrode  313  as illustrated in  FIG. 5 . Also, the slit pattern  214  may have a different zigzag angle from the edge portion of the pixel electrode  213  as illustrated in  FIG. 4 . 
     An auxiliary pattern  211  or  311  is formed at an edge of the domain in the pixel electrode  213  or  313  in such a way to extend from the dielectric protrusion  210  or  310 . 
     The auxiliary pattern  211  or  311  is formed so as to minimize an electric field distortion generated between the pixel electrode  213  or  313  and the dielectric protrusion  210  or  310 . 
     As described above, the present invention can provide an LCD with a wide viewing angle by using a multi-domain structure and forming a slit in the pixel electrode and a dielectric protrusion with a zigzag pattern. 
     Also, the data line and the pixel electrode are formed in a zigzag pattern to thereby minimize the electric field distortion generated in the electric field distribution between the dielectric protrusion and the pixel electrode. Consequently, the liquid crystal is stably aligned and the picture texture is stable because of effective control of the electric field distortion. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.