Abstract:
The present invention discloses an IPS-LCD device. The IPS-LCD device according to the present invention implements a multi-domain for a liquid crystal layer. The liquid crystal molecules are aligned in various directions with respect to each different domain. Therefore, the different domains compensate for one another such that a color shift is prevented in spite of wide viewing angles. To form the multi-domain, the present invention provides a plurality of dielectric protrusions.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 09/836,351 filed Apr. 18, 2001, now U.S. Pat. No. 6,803,979; which claims priority to Korean Patent Application No.: 2000-20723, filed Apr. 19, 2000, and Korean Patent Application No. 2000-53614, filed Sep. 8, 2000, each of which is incorporated by reference for all purposes as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device implementing in-plane switching (IPS) where an electric field to be applied to liquid crystal is generated in a plane parallel to a substrate. 
     2. Discussion of the Related Art 
     A typical liquid crystal display (LCD) device uses optical anisotropy and polarization properties of liquid crystal molecules. The liquid crystal molecules have a definite orientational order in alignment resulting from their thin and long shapes. The alignment orientation of the liquid crystal molecules can be controlled by supplying an electric field to the liquid crystal molecules. In other words, as the alignment direction of the electric field is changed, the alignment of the liquid crystal molecules also changes. Because incident light is refracted to the orientation of the liquid crystal molecules due to the optical anisotropy of the aligned liquid crystal molecules, image data is displayed. 
     A liquid crystal is classified into a positive liquid crystal and a negative liquid crystal, in view of electrical property. The positive liquid crystal has a positive dielectric anisotropy such that long axes of liquid crystal molecules are aligned parallel to an electric field. Whereas, the negative liquid crystal has a negative dielectric anisotropy such that long axes of liquid crystal molecules are aligned perpendicular to an electric field. 
     By now, an active matrix LCD that the thin film transistors and the pixel electrodes are arranged in the form of a matrix is most attention-getting due to its high resolution and superiority in displaying moving video data. 
       FIG. 1  is a cross-sectional view illustrating a typical twisted nematic (TN) LCD panel. As shown in  FIG. 1 , the TN-LCD panel has lower and upper substrates  2  and  4  and an interposed liquid crystal layer  10 . The lower substrate  2  includes a first transparent substrate  1   a  and a thin film transistor (“TFT”) “S”. The TFT “S” is used as a switching element to change orientation of the liquid crystal molecules. The lower substrate  2  further includes a pixel electrode  15  that applies an electric field to the liquid crystal layer  10  in accordance with signals applied by the TFT “S”. The upper substrate  4  has a second transparent substrate  1   b , a color filter  8  on the second transparent substrate  4 , and a common electrode  14  on the color filter  8 . The color filter  8  implements color for the LCD panel. The common electrode  14  serves as another electrode for applying a voltage to the liquid crystal layer  10 . The pixel electrode  15  is arranged over a pixel portion “P,” i.e., a display area. Further, to prevent leakage of the liquid crystal layer  10  between the lower and upper substrates  2  and  4 , those substrates are sealed by a sealant  6 . 
     As described above, because the pixel and common electrodes  15  and  14  of the conventional TN-LCD panel are positioned on the lower and upper substrates  2  and  4 , respectively, the electric field induced therebetween is perpendicular to the lower and upper substrates  1   a  and  1   b . The above-mentioned liquid crystal display device has advantages of high transmittance and aperture ratio, and further, since the common electrode on the upper substrate serves as an electrical ground, the liquid crystal is protected from a static electricity. 
       FIGS. 2A and 2B  show different alignments of the positive TN liquid crystal molecules  10 , respectively, without and with an electric field (off and on states). In  FIG. 2A , various arrows show the gradual rotating of the liquid crystal molecules  10  with polar angles 0 to 90 degrees, which are measured on a plane parallel to the lower and upper substrate  2  and  4 . At the same time, the liquid crystal molecules  10  are gradually rotated to 90 degrees from the lower substrate  2  to the upper substrate  4 . That is to say, the long axes of the liquid crystal molecules  10  gradually rotate along a helical axis (not shown) that is perpendicular to the lower and upper substrates  2  and  4 . First and second polarizers  18  and  30  are positioned on the exterior surfaces of the lower and upper substrate  2  and  4 , respectively. At this point, the broken lines on the first and second polarizers  18  and  30  correspond to first and second transmittance axis of the first and second polarizers  18  and  30 , respectively. After rays of light travel through a TN liquid crystal panel in the off state, as discussed above, they are linearly polarized and rotated 90 degrees. 
     As shown in  FIG. 2B , when there is an electric field “E” applied to the positive TN liquid crystal molecules  10 , the liquid crystal molecules are aligned perpendicular to the upper and lower substrates  4  and  2 . That is to say, with the electric field E applied across the liquid crystal molecules  10 , the liquid crystal molecules  10  rotate to be parallel to the electric field “E”. In this case, the rotation of the linearly polarized light does not take place. Therefore, light is blocked by the second polarizers  30  after it travels through the first polarizer  18 . 
     However, the above-mentioned operation mode of the TN-LCD panel has a disadvantage of a narrow viewing angle. That is to say, the TN liquid crystal molecules rotate with polar angles 0 to 90 degrees, which are too wide. Because of the large rotating angle, contrast ratio and brightness of the TN-LCD panel fluctuate rapidly with respect to the viewing angles. 
     To overcome the above-mentioned problem, an in-plane switching (IPS) LCD panel was developed. The IPS-LCD panel implements a parallel electric field that is parallel to the substrates, which is different from the TN or STN (super twisted nematic) LCD panel. A detailed explanation about operation modes of a typical IPS-LCD panel will be provided with reference to  FIGS. 3 ,  4 A, and  4 B. 
     As shown in  FIG. 3 , first and second substrates  1   a  and  1   b  are spaced apart from each other, and a liquid crystal “LC” is interposed therebetween. The first and second substrates  1   a  and  1   b  are called an array substrate and a color filter substrate, respectively. Pixel and common electrodes  15  and  14  are disposed on the first substrate  1   a . The pixel and common electrodes  15  and  14  are parallel with and spaced apart from each other. On a surface of the second substrate  1   b , a color filter  25  is disposed opposing the first substrate  1   a . The pixel and common electrodes  15  and  14  apply an electric field “E” to the liquid crystal “LC”. The liquid crystal “LC” has a negative dielectric anisotropy, and thus it is aligned parallel to the electric field “E”. 
       FIGS. 4A and 4B  conceptually illustrate operation modes for a typical IPS-LCD device. In an off state, the long axes of the LC molecules “LC” maintain a definite angle with respect to a line that is perpendicular to the pixel and common electrodes  15  and  14 . The pixel and common electrode  15  and  14  are parallel with each other. Herein, the angle difference is 45 degrees, for example. 
     In an on state, an in-plane electric field “E”, which is parallel with the surface of the first substrate  1   a , is generated between the pixel and common electrodes  15  and  14 . The reason is that the pixel electrode  15  and common electrode  14  are formed together on the first substrate  1   a . Then, the LC molecules “LC” are twisted such that the long axes thereof coincide with the electric field direction. Thereby, the LC molecules “LC” are aligned such that the long axes thereof are perpendicular to the pixel and common electrodes  15  and  14 . 
     In the above-mentioned IPS-LCD panel, there is no transparent electrode on the color filter, and the liquid crystal used in the IPS-LCD panel includes a negative dielectric anisotropy. 
       FIGS. 5A and 5B  are conceptual plane views illustrating alignment of the liquid crystal molecules of the above-mentioned IPS-LCD panel, respectively, in off and on states. As shown in  FIG. 5A , each liquid crystal molecule  10  is aligned in a proper direction by a pair of alignment layers (not shown), which are formed on opposing surfaces of the first and second substrate  1   a  and  1   b . As shown in  FIG. 5B , the electric field “E” is applied between the pixel and common electrodes  15  and  14  such that each molecule  10  is aligned in accordance with the electric field “E”. That is to say, each liquid crystal molecule  10  rotates to a definite angle in accordance with the electric field “E”. 
     Compared with the TN-LCD device of  FIG. 1 , the IPS-LCD device has a wider viewing angle owing to a smaller rotating angle of the liquid crystal molecules. 
     The IPS-LCD device has the advantage of a wide viewing angle. Namely, when a user looks at the IPS-LCD device in a top view, the wide viewing angle of about 70 degrees is achieved in up, down, right and left directions. 
     By the above-mentioned operation modes and with additional elements such as polarizers and alignment layers, the IPS-LCD device displays images. The IPS-LCD device has a wide viewing angle, low color dispersion qualities, and the fabricating processes thereof are simpler among those of various LCD devices. 
     However, because the pixel and common electrodes are disposed on the same plane on the lower substrate, the transmittance and aperture ratio are low. In addition, a response time according to a driving voltage should be improved, and a color&#39;s dependence on the viewing angle should be decreased. 
       FIG. 6  is a graph of the CIE (Commission Internationale de l&#39;Eclairage) color coordinates and shows the color dispersion property of the conventional IPS-LCD device. The horseshoe-shaped area is the distribution range of the wavelength of visible light. The results are measured using point (0.313, 0.329) in CIE coordinate as a standard white light source and with various viewing angles of right, left, up and down, and 45 and 135 degrees. Obviously, the range of the color dispersion is so long, which means that the white light emitted from the conventional IPS-LCD device is dispersed largely according to the viewing angle. This results from the fact that the operation mode of the IPS-LCD device is controlled by birefringence. S. Endow et al. indicated the above-mentioned problem in their paper “Advanced 18.1-inch Diagonal Super-TFT-LCDs with Mega Wide Viewing Angle and Fast Response Speed of 20 ms: IDW 99′ 187 page”. 
       FIG. 7  is a graph illustrating transmittance with respect to viewing angles for first to eighth gray levels (gray scale) of a conventional IPS-LCD device. Except for the first gray level, “level  1 ,” each gray level has the highest transmittance at a viewing angle of 0 degree. The first gray level, “level  1 ,” has gray inversion regions. When the viewing angle is beyond 60 degrees, the first gray level, “level  1 ,” has the higher transmittance than the fourth gray level, “level  4 .” The first gray level, “level  1 ,” should implement a black state of the LCD panel. However, gray inversion occurs at viewing angles larger than 60 degrees, such that a white state, but not a black state, is produced at the larger viewing angles. The above-mentioned gray inversion results from a birefringence dependence of the IPS-LCD device and causes a poor display quality of the IPS-LCD device. 
       FIG. 8  shows an example of the IPS-LCD device according to the related art. As shown in  FIG. 8 , zigzag-shaped pixel electrodes  35  and zigzag-shaped common electrodes  34  are alternately arranged such that first and second electric fields  46   a  and  46   b  are alternately induced along the zigzag-shaped electrodes. The first and second electric fields  46   a  and  46   b  have different directions. Therefore, a multi-domain is achieved owing to the first and second electric fields  46   a  and  46   b.  An alignment layer (not shown) is also used for a first state alignment of liquid crystal molecules (reference  10  of  FIG. 3 ). The alignment layer (not shown) beneficially has one rubbing direction  44 . 
     The above-mentioned zigzag-shaped common and pixel electrodes  34  and  35  minimize the color shift. However, between bending portions “D” of the common and pixel electrodes  34  and  35 , an electric field is induced perpendicular to the rubbing direction  44 . That is to say, long axes of the liquid crystal molecules are perpendicular to the electric field induced between the bending portions “D.” Then, the liquid crystal molecules cannot rotate, but keep the first state alignment such that an abnormal alignment is present at each boundary portion “C” between the different domains. 
     The abnormal alignment at the boundary portion “C” causes a light leak such that white lines are shown on a display area, the pixel region “P” shown in  FIG. 1 , of the LCD device. The above-mentioned white lines are called a disclination. A black matrix may be expanded to the pixel regions to cover the disclination. However, the expanded black matrix causes a low aperture ratio. 
     Now, with reference to  FIGS. 9A and 9B , effect of the multi-domain is explained in detail. A liquid crystal layer generally has a birefringence, because each liquid crystal molecule has a long and thin shape. The birefringence changes with respect to a viewing angle.  FIG. 9A  is a cross-sectional view illustrating a single-domain for a liquid crystal molecule  10  between upper and lower polarizers  30  and  18 . At this point, the birefringence of the liquid crystal molecule  10  involves different values for the first, second, and third position “a”, “b”, and “c”, which involve different viewing angles. Therefore, the birefringence of the liquid crystal molecule  10  cannot be zero with respect to viewing angles. If the birefringence of the liquid crystal layer is not zero, the perfect black state cannot be achieved between the upper and lower polarizers  30  and  18 . 
     To overcome the above-mentioned problem, the multi-domain shown in  FIG. 9B  is adopted for a LCD device. As shown, there are first and second liquid crystal molecules  10   a  and  10   b  arranged opposite to each other. The birefringence of the first liquid crystal molecule  10   a  involves different values for the first, second, and third position “a 1 ”, “b 1 ”, and “c 1 .” Whereas, the birefringence of the second liquid crystal molecule  10   b  involves different values for the fourth, fifth, and sixth position “a 2 ”, “b 2 ”, and “c 2 .” The first and fourth positions “a 1 ” and “a 2 ” involve the same viewing angle. Because the first and second liquid crystal molecules  10   a  and  10   b  are symmetrically opposed with each other, birefringence of the first liquid crystal molecule  10   a  at the first position “a 1 ” is compensated by that of the second liquid crystal molecule  10   b  at the fourth position “a 2 .” That is to say, each birefringence of the first liquid crystal molecule  10   a  is compensated by corresponding birefringence of the second liquid crystal molecule  10   b . In other words, sum of the birefringence between the first and second liquid crystal molecules  10   a  and  10   b  is about zero. Accordingly, the multi-domain shown in  FIG. 9B  improves the display quality of the LCD device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an IPS-LCD device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an IPS-LCD device having low color dispersion and low white inversion with respect to viewing angles. 
     Another object of the present invention is to provide an IPS-LCD device having optimized common and pixel electrodes such that high aperture ratio, low color shift, and fast response time are achieved. 
     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. 
     In order to achieve the above object, the present invention provides an IPS-LCD device, which includes: first and second substrates opposing each other; a gate line on the first substrate; a data line perpendicular to the gate line; a thin film transistor at a crossing portion between the gate and data lines; a common line parallel to the gate line; a plurality of common electrodes electrically connected to the common line, wherein the common electrodes are spaced apart from each other; a plurality of pixel electrodes alternately arranged with the plurality of common electrodes, wherein each pixel electrode is spaced apart from an adjacent common electrode; a plurality of dielectric protrusions between the first and second substrates; and a liquid crystal layer between the first and second substrates, wherein the liquid crystal layer and the dielectric protrusion have different dielectric constants. 
     The dielectric protrusion has a smaller or larger dielectric constant than the liquid crystal layer. 
     The dielectric protrusion is an organic material, which is preferably selected from a group consisting of photoresist, benzocyclobutene (BCB), and acryl resin. 
     A plurality of first dielectric protrusions are disposed over a plurality of pixel electrodes. A plurality of second dielectric protrusions are disposed over a plurality of common electrodes. The plurality of first and second protrusions are formed on the first substrate having the pixel electrodes, or the plurality of first and second protrusions are formed on the second substrate. 
     The dielectric protrusion is a chevron-shaped dielectric protrusion, and the chevron-shaped dielectric protrusion has a zigzag shape extending along a line perpendicular to the common and pixel electrodes. 
     The pixel electrode is selected from a group consisting of indium tin oxide (ITO) and indium zinc oxide (IZO). The common electrode is selected from a group consisting of chromium (Cr), aluminum (Al), aluminum alloy (Al alloy), molybdenum (Mo), tantalum (Ta), tungsten (W), antimony (Sb), and an alloy thereof. The common electrode is further selected from a group consisting of indium tin oxide (ITO) and indium zinc oxide (IZO). 
     The liquid crystal layer is a positive liquid crystal having a positive dielectric anisotropy, and long axes of liquid crystal molecules are aligned parallel to the common and pixel electrodes in off state. In another aspect, the liquid crystal layer is a negative liquid crystal having a negative dielectric anisotropy, and long axes of liquid crystal molecules are aligned perpendicular to the common and pixel electrodes in an off state. 
     In another aspect, the present invention provides an in-plane-switching liquid crystal display panel, which includes: first and second substrates opposing each other; a gate line on the substrate; a data line perpendicular to the gate line; a thin film transistor at a crossing portion between the gate and data lines; a main common line parallel to the gate line; first and second auxiliary common lines perpendicular to the main common line, the first and second auxiliary common lines being parallel to and spaced apart from each other; a plurality of common electrodes electrically connected to the common line, wherein the common electrodes are spaced apart from each other; a plurality of pixel electrodes alternately arranged with the plurality of common electrodes, wherein each pixel electrode is spaced apart from an adjacent common electrode; a plurality of dielectric protrusions between the first and second substrates; and a liquid crystal layer between the first and second substrates. 
     The dielectric protrusion has a smaller or larger dielectric constant than the liquid crystal layer. 
     The dielectric protrusion is an organic material, which is preferably selected from a group consisting of photoresist, benzocyclobutene (BCB), and acryl resin. 
     A plurality of first dielectric protrusions are disposed over a plurality of pixel electrodes. A plurality of second dielectric protrusions are disposed over a plurality of common electrodes. The plurality of first and second protrusions are formed on the first substrate having the pixel electrodes, or the plurality of first and second protrusions are formed on the second substrate. 
     The dielectric protrusion is a chevron-shaped dielectric protrusion, and the chevron-shaped dielectric protrusion has a zigzag shape extending along a line perpendicular to the common and pixel electrodes. 
     The pixel electrode is selected from a group consisting of indium tin oxide (ITO) and indium zinc oxide (IZO). The common electrode is selected from a group consisting of chromium (Cr), aluminum (Al), aluminum alloy (Al alloy), molybdenum (Mo), tantalum (Ta), tungsten (W), antimony (Sb), and an alloy thereof. The common electrode is further selected from a group consisting of indium tin oxide (ITO) and indium zinc oxide (IZO). 
     The liquid crystal layer is a positive liquid crystal having a positive dielectric anisotropy, and long axes of liquid crystal molecules are aligned parallel to the common and pixel electrodes in off state. In another aspect, the liquid crystal layer is a negative liquid crystal having a negative dielectric anisotropy, and long axes of liquid crystal molecules are aligned perpendicular to the common and pixel electrodes in an off state. 
     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 DRAWING 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a cross-sectional view illustrating a typical liquid crystal display device; 
         FIGS. 2A and 2B  illustrate operation modes of a typical TN-LCD panel; 
         FIG. 3  is a cross-sectional view illustrating a typical IPS-LCD device; 
         FIGS. 4A and 4B  are perspective views illustrating operation modes of the typical IPS-LCD device of  FIG. 3 ; 
         FIG. 5A and 5B  are plan views illustrating, respectively, off state alignment and on state alignment of liquid crystal molecules of the IPS-LCD device shown in  FIG. 3 ; 
         FIG. 6  is a CIE graph illustrating a color coordinate property with respect to various viewing angles of the typical IPS-LCD device; 
         FIG. 7  is a graph illustrating transmittance with respect to viewing angles for first to eighth gray levels of the typical IPS-LCD device; 
         FIG. 8  is a plan view illustrating an example for an IPS-LCD device according to the related art; 
         FIGS. 9A and 9B  are cross-sectional views illustrating, respectively, single-domain and multi-domain for liquid crystal molecules; 
         FIG. 10  is a plan view illustrating an IPS-LCD device according to the first preferred embodiment of the present invention; 
         FIG. 11  is an expanded plan view of a portion “Z” of  FIG. 12 ; 
         FIG. 12  is a plan view illustrating a degree of freedom for a liquid crystal molecule according to the preferred embodiment; 
         FIG. 13  is a partial cross-sectional view illustrating a dielectric protrusion of the first preferred embodiment; 
         FIG. 14  is a plan view illustrating an IPS-LCD device according to the second preferred embodiment of the present invention; 
         FIG. 15  is a plan view illustrating an IPS-LCD device according to the third preferred embodiment of the present invention; 
         FIGS. 16A to 16C  are partial cross-sectional views illustrating various structures for a dielectric protrusion of the third preferred embodiment; 
         FIGS. 17A and 17B  are plan views illustrating alignment characteristics of, respectively, a positive liquid crystal and a negative liquid crystal for the third preferred embodiment; 
         FIG. 18  is a plan view illustrating an IPS-LCD device according to the fourth preferred embodiment of the present invention; 
         FIGS. 19A and 19B  are plan views illustrating alignment characteristics of, respectively, a positive liquid crystal and a negative liquid crystal for the fourth preferred embodiment; and 
         FIG. 20  is a plan view illustrating an IPS-LCD device according to the fifth preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     First Preferred Embodiment 
       FIG. 10  is a plan view illustrating an IPS-LCD device according to the first preferred embodiment. As shown, a gate line  50  and a common line  60  are transversely arranged, and a data line  70  is formed perpendicular to the gate and common lines. A plurality of pixel electrodes  76  are formed perpendicular to the gate and common lines  50  and  60 . At a crossing point between the gate and data lines  50  and  70 , a gate electrode  52  and a source electrode  72  are integrally formed with the gate and data lines  50  and  70 , respectively. In addition, a drain electrode  74  is spaced apart from the source electrode  72 . The gate, source, and drain electrodes  52 ,  72 , and  74  are included in a thin film transistor (“TFT”) “S”. The pixel electrodes  76  are electrically connected with the drain electrode  74 . The common line  60  includes a plurality of common electrodes  62 . The plurality of common electrodes  62  are parallel to the pixel electrodes  76  and are alternately arranged with the plurality of pixel electrodes  76 . 
     On the plurality of the pixel and common electrodes  76  and  62 , a plurality of dielectric protrusions  90  are alternately-disposed. First to fourth reference lines “X 1 ” to “X 4 ” are drawn to specify a position of the dielectric protrusion  90 . The first to fourth reference lines “X 1 ” to “X 4 ” are perpendicular to the common and pixel electrodes  62  and  76 . The first to fourth reference lines “X 1 ” to “X 4 ” have the same interval between the adjacent ones. The dielectric protrusions  90  on the plurality of pixel electrodes  76  are disposed along the first and third reference lines “X 1 ” and “X 3 ”. Meanwhile, the dielectric protrusions  90  on the plurality of common electrodes  62  are disposed along the second and fourth reference lines “X 2 ” and “X 4 ”. The above-mentioned sequence of the dielectric protrusions  90  on the pixel and common electrodes  76  and  62  can be reversed without deterioration in operation property. That is to say, if the dielectric protrusions  90  on the plurality of pixel electrodes  76  are disposed along the second and fourth reference lines “X 2 ” and “X 4 ”, the dielectric protrusions  90  on the plurality of common electrodes  62  are disposed along the first and third reference lines “X 1 ” and “X 3 ”, and vice versa. 
     The dielectric protrusion  90  is made of a dielectric substance. Each dielectric protrusion  90  has a smaller dielectric constant than the liquid crystal (reference  80  of  FIG. 11 ) has. The dielectric constant of the dielectric protrusion  90  is preferably below or equal to 5. Because of the smaller dielectric constant of the dielectric protrusion  90 , an electric field applied between the pixel and common electrodes  76  and  62  has a relatively smaller intensity at the peripheries of the dielectric protrusions  90 . In other words, each dielectric protrusion  90  serves to distort an electric field induced between the pixel and common electrodes  76  and  62 . 
       FIG. 11  shows an alignment of liquid crystal molecules  80  in detail. In an off state, long axes of the liquid crystal molecules  80  are uniformly aligned parallel to the common and pixel electrodes  62  and  76 . However, when an electric field “E” is applied between the pixel and common electrodes  76  and  62 , the liquid crystal molecules  80  are aligned in various directions such that a multi-domain is achieved. That is to say, the electric field “E” is distorted by the dielectric protrusions  90  such that various angles are present between the first-aligned liquid crystal molecules  80  and the electric field. The liquid crystal molecules  80  rotate right or left depending on the directions of the distortion of the electric field “E” such that the multi-domain is formed. 
     In other words, the liquid crystal molecules  80  are at first aligned parallel to the common and pixel electrodes  62  and  76 . When the electric field “E” is applied and distorted to be at various angles with the liquid crystal molecules  80 , each liquid crystal molecule  80  rotates to a smaller angled direction between the long axes of the liquid crystal molecules and the electric field “E”. The smaller angled direction is clockwise or counterclockwise depending on a relative position of a liquid crystal molecule  80  with respect to the dielectric protrusion  90 . That is to say, a first portion of the liquid crystal molecules  80  rotates right and a second portion thereof rotates left such that the multi-domain is symmetrically formed. 
     Preferably, the liquid crystal molecules  80  are a positive liquid crystal having positive dielectric anisotropy. In addition, in the off state, the long axes of the liquid crystal molecules  80  are preferably aligned parallel to the common and pixel electrodes  62  and  76 . That is to say, a rubbing direction of an alignment layer (not shown) for the liquid crystal molecules  80  is preferably parallel to the common and pixel electrodes  62  and  76 . 
       FIG. 12  shows the degree of freedom for liquid crystal molecule  80  with respect to a rubbing direction  100 . In a first state alignment (off state), the liquid crystal molecule  80  is aligned corresponding to the rubbing direction  100 , which is preferably parallel to the common and pixel electrodes  62  and  76  of  FIG. 11 . As shown in  FIG. 12 , the liquid crystal molecule  80  can rotate right or left, which means that the degree of freedom of the liquid crystal molecule  80  is two. The liquid crystal molecules  80  may be a negative liquid crystal instead of the positive liquid crystal. In that case, the rubbing direction  100  is preferably perpendicular to the common electrodes  62  and pixel electrodes  76 . 
     The above-mentioned multi-domain decreases a color&#39;s dependence on viewing angles such that a gray inversion shown in  FIG. 7  is prevented. 
     Now, with reference to  FIG. 13 , a preferable structure of the above-mentioned dielectric protrusion  90  is provided.  FIG. 13  is a cross-sectional view taken along a line “XIII—XIII” of  FIG. 11 . As shown in  FIG. 13 , the dielectric protrusion  90  is disposed over the pixel electrode  76  or common electrode  62  and directly faces or abuts the liquid crystal molecules  80 . The dielectric protrusion  90  is preferably made of an organic substance, usually photoresist, benzocyclobutene (BCB), and acryl resin. The common electrodes  62  is covered by a gate-insulating layer  160 , whereas the pixel electrode  76  is covered by a passivation layer  168 . The dielectric protrusion  90  further may serve as a spacer to maintain a cell gap between first and second substrates  110  and  120 . 
     The pixel electrode  76  is preferably made from a transparent conductive material, usually indium tin oxide (ITO) and indium zinc oxide (IZO), which have a high transmittance. Meanwhile, the common electrode  62  is usually made of the same material as the gate line  50 , and the transparent conductive material is also preferably used for the common electrode  62  to achieve a higher aperture ratio. The gate and data lines  50  and  70  are preferably selected from a group consisting of chromium (Cr), aluminum (Al), aluminum alloy (Al alloy), molybdenum (Mo), tantalum (Ta), tungsten (W), antimony (Sb), and an alloy thereof. 
     For the first preferred embodiment, the plurality of dielectric protrusions  90  are alternately disposed over the common and pixel electrodes  62  and  76 . However, the dielectric protrusions  90  may be disposed on any position in the pixel region, which is defined by the gate and data lines  50  and  70  of  FIG. 11 . For example, the dielectric protrusions  90  may be disposed between the common and pixel electrodes  62  and  76  to form the multi-domain. 
     Second Preferred Embodiment 
       FIG. 14  is a plan view illustrating an IPS-LCD device according to the second preferred embodiment. As shown in  FIG. 14 , a gate line  50  and a common line  60  are transversely arranged, and a data line  70  is formed perpendicular to the gate and common lines. A plurality of pixel electrodes  86  are formed parallel to the gate and common lines  50  and  60 . At a crossing point between the gate and data lines  50  and  70 , a thin film transistor (“TFT”) “S” is disposed. 
     The common line  60  has first and second auxiliary common lines  88   a  and  88   b , which are spaced apart from each other and perpendicular to the common line  60 . In addition, a plurality of common electrodes  82  are formed perpendicular to the first and second auxiliary common lines  88   a  and  88   b . The common electrodes  82  and pixel electrodes  86  are alternately arranged. 
     On the plurality of the pixel and common electrodes  86  and  82 , a plurality of dielectric protrusions  90  are alternately disposed. The dielectric protrusion  90  is made of a dielectric substance. A positive liquid crystal (reference  80  of  FIG. 12 ) is preferably used with a rubbing direction that is parallel to the common and pixel electrodes  82  and  86 . If a negative liquid crystal is used for the second preferred embodiment, a rubbing direction that is perpendicular to the common and pixel electrodes  82  and  86  is employed for the second preferred embodiment. The dielectric protrusion  90  of the second preferred embodiment has the same structure and material as that of the first preferred embodiment. 
     The pixel electrode  86  is preferably made from a transparent conductive material, usually indium tin oxide (ITO) and indium zinc oxide (IZO), which have a high transmittance. Meanwhile, the common electrode  82  is usually made of the same material as the gate line  50 , and the transparent conductive material is also preferably used for the common electrode  82  to achieve a higher aperture ratio. 
     For the second preferred embodiment, the plurality of dielectric protrusions  90  are alternately disposed over the common and pixel electrodes  82  and  86 . However, the dielectric protrusions  90  may be disposed on any position in the pixel region defined by the gate and data lines  50  and  70  of  FIG. 14 . For example, the dielectric protrusions  90  may be disposed between the common and pixel electrodes  82  and  86  to form the multi-domain, or may be disposed only over the plurality of pixel electrodes  86  or common electrodes  82 . 
     In addition, the dielectric protrusions  90  of the first and second preferred embodiment preferably have the smaller dielectric constant than the liquid crystal  80  (see  FIG. 13 ). However, the dielectric protrusions  90  may have a larger dielectric constant than the liquid crystal  80 . In that case, though an alignment of the liquid crystal molecules  80  is opposite to that of  FIG. 11 , a multi-domain is surely formed. 
     Third Preferred Embodiment 
       FIG. 15  is a plan view illustrating an IPS-LCD device according to the third preferred embodiment. As shown, a gate line  50  and a common line  60  are transversely arranged, and a data line  70  is formed perpendicular to the gate and common lines on a pixel region “P.” A plurality of pixel electrodes  76  are formed perpendicular to the gate and common lines  50  and  60 . At a crossing point between the gate and data lines  50  and  70 , a gate electrode  52  and a source electrode  72  are integrally formed with the gate and data lines  50  and  70 , respectively. In addition, a drain electrode  74  is spaced apart from the source electrode  72 , and an active layer  54  is disposed between the drain and source electrodes  74  and  72 . The gate, source, and drain electrodes  52 ,  72 , and  74 , and the active layer  54  are included in a thin film transistor (“TFT”) “S”. The pixel electrodes  76  are electrically connected with the drain electrode  74 . The common line  60  includes a plurality of common electrodes  62 . The plurality of common electrodes  62  are parallel to the pixel electrodes  76  and are alternately arranged with the plurality of pixel electrodes  76 . 
     Across the plurality of common and pixel electrodes  62  and  76 , a plurality of chevron-shaped dielectric protrusions  190  are disposed. The plurality of chevron-shaped dielectric protrusions  190  are parallel to and spaced apart from each other. Each chevron-shaped dielectric protrusion  190  is alternately bent at each crossing point with the pixel electrode  76  or common electrode  62  to have a zigzag shape. The chevron-shaped dielectric protrusion  190  has a smaller dielectric constant than a liquid crystal  80  has. The dielectric constant of the dielectric protrusion  190  is preferably below or equal to 5. Because of the smaller dielectric constant of the chevron-shaped dielectric protrusions  90 , an electric field applied between the pixel and common electrodes  76  and  62  has a relatively smaller intensity in periphery of the chevron-shaped dielectric protrusions  190 . 
     In other words, each chevron-shaped dielectric protrusion  190  serves to distort an electric field induced between the pixel and common electrodes  76  and  62  such that a multi-domain for the liquid crystal molecules  80  is formed. That is to say, first and second liquid crystal portions  80   a  and  80   b  are symmetrically aligned with respect to the pixel electrode  76  or common electrode  62 , which is centered therebetween. 
     Now, with reference to  FIGS. 16A to 16C , various structures for the chevron-shaped dielectric protrusion  190  are provided. As shown in  FIG. 16A , the chevron-shaped dielectric protrusion  190  is preferably disposed over the common electrode  62  or pixel electrode  76  and directly faces the liquid crystal molecules  80  interposed between first and second substrates  110  and  120 . The chevron-shaped dielectric protrusion  190  is preferably made of an organic substance, usually photoresist, benzocyclobutene (BCB), and acryl resin. The common electrodes  62  is covered by a gate-insulating layer  160 , whereas the pixel electrode  76  is covered by a passivation layer  168 . 
       FIG. 16B  shows a first modification for the chevron-shaped dielectric protrusion. As shown, a chevron-shaped dielectric protrusion  192  is formed on an inner surface of the second substrate  120  instead of the first substrate  110  having the common and pixel electrodes  62  and  76 . 
       FIG. 16C  shows a second modification for the chevron-shaped dielectric protrusion. As shown, a chevron-shaped dielectric protrusion  194  is thick enough that a cell gap “G” is maintained between the first and second substrates  110  and  120 . In this case, the chevron-shaped dielectric protrusion  194  may substitute for a spacer, which is used to maintain the cell gap “G”. 
       FIG. 17A  shows a degree of freedom for liquid crystal molecule  80  with respect to a first rubbing direction  100 . In a first state alignment (off state), the liquid crystal molecule  80  is aligned corresponding to the first rubbing direction  100 , which is preferably parallel to the common and pixel electrodes  62  and  76  of  FIG. 15 . As shown, the liquid crystal molecule  80  can rotate right or left, which means that the degree of freedom of the liquid crystal molecule  80  is two. 
     The liquid crystal molecules  80  may be a negative liquid crystal instead of the positive liquid crystal. In this case as shown in  FIG. 17B , a second rubbing direction  102 , which is perpendicular to the common electrodes  62  and pixel electrodes  76 , is used instead of the first rubbing direction  100  of  FIG. 17A . The right and left rotating liquid crystal molecules, respectively, are included in first and second domains of the multi-domain. 
     Fourth Preferred Embodiment 
       FIG. 18  is a plan view illustrating an IPS-LCD device according to the fourth preferred embodiment. As shown, a gate line  50  and a common line  60  are transversely arranged, and a data line  70  is formed perpendicular to the gate and common lines on a pixel region “P.” A plurality of pixel electrodes  86  are formed parallel to the gate and common lines  50  and  60 . At a crossing point between the gate and data lines  50  and  70 , a thin film transistor (“TFT”) “S” is disposed. 
     The common line  60  has first and second auxiliary common lines  88   a  and  88   b , which are perpendicular to the common line  60  and spaced apart from each other. In addition, a plurality of common electrodes  82  are formed perpendicular to the first and second auxiliary common lines  88   a  and  88   b.  The common electrodes  82  and pixel electrodes  86  are alternately arranged. 
     Across the plurality of common and pixel electrodes  82  and  86 , a plurality of chevron-shaped dielectric protrusions  196  are disposed. The plurality of chevron-shaped dielectric protrusions  196  are parallel to and spaced apart from each other. Each chevron-shaped dielectric protrusion  196  is alternately bent at each crossing point with the pixel electrode  86  or common electrode  82  to have a zigzag shape. The chevron-shaped dielectric protrusion  196  serves to distort an electric field induced between the pixel and common electrodes  86  and  82  such that a multi-domain for the liquid crystal molecules  80  is formed. That is to say, first and second liquid crystal portions  80   a  and  80   b  are symmetrically aligned with respect to the pixel electrode  86  or common electrode  82 , which is centered on therebetween. 
       FIG. 19A  shows a degree of freedom for liquid crystal molecule  80  with respect to a second rubbing direction  102 . In a first state alignment (off state), the liquid crystal molecule  80  is aligned corresponding to the second rubbing direction  102 , which is preferably perpendicular to the common and pixel electrodes  82  and  86  of  FIG. 18 . As shown, the liquid crystal molecule  80  can rotate right or left, which means that the degree of freedom of the liquid crystal molecule  80  is two. On the contrary, the liquid crystal molecules  80  may be a negative liquid crystal instead of the positive liquid crystal. In this case as shown in  FIG. 19B , a first rubbing direction  100 , which is parallel to the common electrodes  82  and pixel electrodes  86 , is used instead of the second rubbing direction  102  of  FIG. 19A . The right and left rotating liquid crystal molecules, respectively, are included in first and second domains of the multi-domain. 
     Fifth Preferred Embodiment 
     The fifth preferred embodiment of  FIG. 20  is different from the third preferred embodiment of  FIG. 15  in that a chevron-shaped dielectric protrusion  198  is alternately bent only at crossing points with a plurality of common electrodes  62 . Therefore, in an on state, liquid crystal molecules  80  are divided into first and second liquid crystal portions  80   a  and  80   b  with each common electrode  62  centered therebetween. The first and second liquid crystal portions  80   a  and  80   b  are rotated, respectively, right and left such that a symmetrical multi-domain is achieved. 
     At this point, a positive liquid crystal or negative liquid crystal is preferably used as shown in  FIGS. 17A and 17B . A detailed description about the positive or negative liquid crystal is omitted. 
     As previously explained, the first to fifth preferred embodiments adopt a multi-domain, where different domains compensate for each other. To achieve the multi-domain, the first to fifth preferred embodiments use distorted electric fields such that liquid crystal molecules are symmetrically aligned in the various domains. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the method of manufacturing a thin film transistor of 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.