Patent Document

This is a Continuation of application Ser. No. 10/453,568 filed on Jun. 4, 2003 now U.S. Pat. No. 6,900,862. 
    
    
     The present invention claims the benefit of Korean Application No. 2002/78870 filed in Korea on Dec. 11, 2002, which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an in-plane switching mode liquid crystal display device, and more particularly, to an in-plane switching mode liquid crystal display device that is capable of preventing distortion of a horizontal electric field applied to a liquid crystal layer. 
     2. Discussion of the Related Art 
     Recently, many efforts have been made to study and develop various types of flat display panels, such as liquid crystal display devices (LCDs), plasma display panels (PDPs), field emission display devices (FEDs), and vacuum fluorescent display devices (VFDs). Some of these types of flat display panels, especially LCDs, have been applied in and incorporated into various portable electronic equipment including mobile phones, personal data assistants devices (PDAs), and notebook computers because of their high quality image, lightness, small thickness, compact size and low power consumption. 
     In general, a liquid crystal display device has various display modes depending on an alignment of liquid crystal molecules deposited therein. Currently, a twisted nematic (TN) mode is commonly employed because of its ease of white-black display, rapid response time and low driving voltage. In a TN mode, when voltage is applied to liquid crystal molecules of the liquid crystal display device, the liquid crystal molecules are aligned at right angles to a substrate of the liquid crystal display device. However, a viewing angle of the liquid crystal display device thus is reduced due to refractive anisotropy of the liquid crystal molecules aligned at right angles to the substrate. 
     In order to solve the above-mentioned viewing angle problem, various types of liquid crystal display devices having wide viewing angle characteristics, such as in plane switching (IPS) mode liquid crystal display devices, have been developed. For example, in an IPS mode liquid crystal display device, liquid crystal molecules generally are aligned in a plane by including at least a pair of electrodes arranged in parallel to each other in pixel areas and forming a horizontal electric field parallel to a substrate. 
       FIG. 1  is a plan view of an in-plane switching mode liquid crystal display device according to a related art. In  FIG. 1 , a liquid crystal display panel  1  includes a plurality of gate lines  3  arranged along one direction at a predetermined interval from each other, a plurality of data lines  4  arranged along a direction perpendicular to the gate lines  3  at a predetermined interval from each other, a plurality of pixel electrodes  7   a  and  7   b  formed within pixel areas defined by the gate and data lines  3  and  4  crossing each other, a plurality of common electrodes  5   a - 5   c  formed within the pixel areas, and a plurality of thin film transistors  10  formed within the pixel areas and switched by signals of the gate lines  3  to transfer signals of the data lines  4  to the pixel electrodes  7   a  and  7   b . The common electrodes  5   a - 5   c  and the pixel electrodes  7   a  and  7   b  are generally formed of nontransparent metal. 
     In addition, each of the thin film transistors  10  includes a gate electrode  11  in which a scan signal is applied from a corresponding one of the gate lines  3 , a semiconductor layer  12  formed on the gate electrode  11 , and source and drain electrodes  13  and  14  formed on the semiconductor layer  12  and receiving a picture signal through a corresponding one of the data lines  4 . In particular, when the scan signal is applied to the gate electrode  11 , the semiconductor layer  12  becomes a channel layer. In addition, the first, second and third common electrodes  5   a - 5   c  and the first and second pixel electrodes  7   a  and  7   b  are arranged parallel to the data lines  4 . Further, at the middle of each of the pixel areas, a common line  16  connects to the common electrodes  5   a - 5   c , and a pixel electrode line  18  connects to the pixel electrodes  7   a  and  7   b , such that the pixel electrode line  18  overlaps with the common line  16 . 
     Further, the IPS mode liquid crystal display device includes a liquid crystal layer, such that the liquid crystal molecules deposited therein are aligned parallel to the common electrodes  5   a - 5   c  and the pixel electrodes  7   a  and  7   b . Also, the IPS mode liquid crystal display device includes a black matrix (not shown) for preventing light leakage, and the black matrix is made of nonconductive material having nonconductive characteristics. Thus, when the thin film transistor  10  is operated to apply signals to the pixel electrodes  7   a  and  7   b , a horizontal electric field between the common electrodes  5   a - 5   c  and the pixel electrodes  7   a  and  7   b  is generated parallel to the liquid crystal display panel  1 . Accordingly, the liquid crystal molecules become perpendicularly aligned to the common electrodes  5   a - 5   c  and the pixel electrodes  7   a  and  7   b  due to the horizontal electric field, thereby preventing gray level inversion caused by the refractive anisotropy of the liquid crystal molecules aligned at right angles to the liquid crystal display panel  1 . 
     However, when the horizontal electric field is generated between the common electrodes  5   a - 5   c  and the pixel electrodes  7   a  and  7   b , a second electric field also could be generated between the pixel electrodes  7   a  and  7   b , and the data lines  4 , such that this second electric field distorts the horizontal electric field. In this situation, the liquid crystal molecules would not be aligned perfectly parallel to the liquid crystal display panel  1 , and cross talk in the vertical direction would be generated. Therefore, the first common electrode  5   a  is arranged between the first pixel electrode  7   a  and a corresponding one of data lines  4 . Also, the third common electrode  5   c  is arranged between the second pixel electrode  7   b  and another corresponding one of the data lines  4 , to thereby prevent an electric field from being generated between the pixel electrodes  7   a  and  7   b  and the data lines  4 . In particular, to effectively prevent an electric field from being formed between the pixel electrodes  7   a  and  7   b  and the data lines  4 , the first and third common electrodes  5   a  and  5   c  have to be arranged near to the corresponding data lines  4 . Thus, the total number of the common electrodes  5   a - 5   c  is greater than the total number of the pixel electrodes  7   a  and  7   b  by one. Accordingly, by arranging one more common electrode in each of the pixel areas, a region for blocking light is increased. However, such arrangement undesirably lowers an aperture ratio of the IPS mode liquid crystal display device. 
     Alternatively, a width of the first and third common electrodes  5   a  and  5   c  has to be increased to effectively prevent an electric field being formed between the pixel electrodes  7   a  and  7   b  and the data lines  4 . Similarly, such increase of a width of the common electrodes  5   a  and  5   b  also greatly lowers an aperture ratio of the IPS mode liquid crystal display device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an in-plane switching mode liquid crystal display device that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide an in-plane switching mode liquid crystal display device that is capable of preventing cross talk in the vertical direction by preventing distortion of a horizontal electric field applied to a liquid crystal layer by forming a black matrix of a dielectric material. 
     Another object of the present invention is to provide an in-plane switching mode liquid crystal display device that is capable of removing a common electrode arranged near a data line and is capable of preventing cross talk in the vertical direction. 
     Another object of the present invention is to provide an in-plane switching mode liquid crystal display device that is capable of improving an aperture ratio by decreasing a width of a common electrode arranged near to a data line and is capable of preventing cross talk in the vertical direction. 
     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 herein, the in-plane switching mode liquid crystal display device includes first and second substrates, a plurality of gate lines and data lines on the first substrate to define a plurality of pixel areas, a driving element in each of the pixel areas of the first substrate, at least one first and second electrodes in each of the pixel areas of the first substrate, a black matrix on the second substrate, the black matrix being made of a black resin material having resistance not greater than 10 8  Ωcm and a dielectric constant not less than 14, and a liquid crystal layer between the first and second substrates. 
     In another aspect, the in-plane switching mode liquid crystal display device includes first and second substrates, a plurality of gate lines and data lines on the first substrate to define a plurality of pixel areas, a driving element in each of the pixel areas of the first substrate, at least a pair of electrodes in each of the pixel areas of the first substrate, a black matrix on the second substrate, the black matrix being made of a black resin material having low resistance and high dielectric constant, and a liquid crystal layer between the first and second substrates. 
     In another aspect, the in-plane switching mode liquid crystal display device includes first and second substrates, a plurality of gate lines and data lines on the first substrate to define a plurality of pixel areas, a driving element in each of the pixel areas of the first substrate, at least a pair of electrodes in each of the pixel areas of the first substrate, a dielectric black matrix on the second substrate, an electric field being generated between the dielectric black matrix and the data lines that does not distort a horizontal electric field between the pair of electrodes, and 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 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 plan view of an in-plane switching mode liquid crystal display device according to a related art; 
         FIG. 2A  is a sectional view of a thin film transistor of an exemplary in-plane switching mode liquid crystal display device according to the present invention; 
         FIG. 2B  is a sectional view of a pixel of the exemplary in-plane switching mode liquid crystal display device according to the present invention; 
         FIG. 3A  is a sectional view of another exemplary in-plane switching mode liquid crystal display device according to the present invention; and 
         FIG. 3B  is a sectional view of another exemplary in-plane switching mode liquid crystal display device according to the present invention. 
     
    
    
     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. 
       FIG. 2A  is a sectional view of a thin film transistor of an exemplary in-plane switching mode liquid crystal display device according to the present invention, and  FIG. 2B  is a sectional view of a pixel of the exemplary in-plane switching mode liquid crystal display device according to the present invention. In  FIG. 2A , an exemplary IPS mode liquid crystal display device may include a first substrate  120  and a thin film transistor formed on the first substrate  120 . The thin film transistor may include a gate electrode  111 , a semiconductor layer  112 , and source and drain electrodes  113  and  114 . The gate electrode  111  may be formed on the first substrate  120 , and a gate insulating layer  122  may be laminated onto an entire surface of the first substrate  120  covering the gate electrode  111 . In addition, the semiconductor layer  112  may be formed onto the gate insulating layer  122  above the gate electrode  111 , and the source electrode  113  and the drain electrode  114  may be formed thereon. A passivation layer  124  also may be formed on the entire surface of the first substrate  120  covering the source and drain electrodes  113  and  114 . 
     The IPS mode liquid crystal display device also may include a second substrate  130  bonded to the first substrate  120  with a predetermined space therebetween, such that a liquid crystal layer  140  may be interposed between the first and second substrates  120  and  130 . Also, a black matrix  132  and a color filter layer  134  may be formed on the second substrate  130 . 
     In particular, the black matrix  132  may be formed between a thin film transistor forming region and pixels, i.e., the gate and data lines regions, to prevent light leakage to a region in which liquid crystal molecules are not operated, i.e., a non-display region in which images are not displayed. In addition, the black matrix  132  may be formed of a black resin material, which has low resistance and high dielectric characteristics. For example, the black matrix  132  may be formed by a photolithography process by laminating a black resin including one of carbon pigment and red/green/blue mixture pigments onto the second substrate  130 , forming a pattern mask, irradiating light such as ultraviolet light and activating a developer to form a desired pattern. Thus, the black matrix  132  may be a dielectric having characteristics opposite to a nonconductive material. Accordingly, an electric field may be formed between the black matrix  132  and another conductive/dielectric material. Preferably, the black matrix  132  may have a resistance not greater than about 10 8  Ω·cm and a dielectric constant not less than about 14 in a measure frequency of 1 kHz. Moreover, the black matrix  132  may be formed among R, G, B pixels (or sub-pixels). Accordingly, the black matrix  132  may be formed onto the second substrate  130  as a matrix shape, and the color filter layer  134  may be formed by laminating R, G, B color resist between the black matrix  132 . 
     Further, the color filter layer  134  may include red (R), green (G) and blue (B) color filter layers for producing colored light. Moreover, an overcoat layer (not shown) may be formed on the color filter layer  134  to improve flatness of the second substrate  130  and to protect the color filter layer  134 . 
     In  FIG. 2B , the IPS mode liquid crystal display device may include a plurality of gate lines (not shown) formed on the first substrate  120 , a plurality of common electrodes  105   a - 105   c  formed on the first substrate  120 , and a plurality of pixel electrodes  107   a  and  107   b  formed on the gate insulating layer  122 . The pixel electrodes  107   a  and  107   b  may be parallel to the common electrodes  105   a - 105   c . Also, the common electrodes  105   a - 105   c  and the pixel electrodes  107   a  and  107   b  may be made of a nontransparent metal having small resistivity or a transparent material such as indium tin oxide (ITO) or indium zinc oxide (IZO). 
     Further, a plurality of data lines  104  may be formed on the gate insulating layer  122 . Thus, when the thin film transistor is switched by signals of the gate lines (not shown) to transfer signals of the data lines  104  to the pixel electrodes  107   a  and  107   b , a first horizontal electric field E 1  may be generated between the common electrodes  105   a - 105   c  and the pixel electrodes  107   a  and  107   b . Accordingly, liquid crystal molecules in the liquid crystal layer  140 , which may be initially arranged according to an alignment direction of an alignment layer (not shown), may then be rotated according to the first horizontal electric field E 1 , to thereby display images on the liquid crystal display device. 
     In addition, because the black matrix  132  may be formed of a black resin material having dielectric characteristics, second electric fields E 2  may be generated between the data lines  104  and the black matrix  132 . In particular, an intensity of the electric fields E 2  between the data lines  104  and the black matrix  132  may be very small in comparison with an intensity of the first horizontal electric field E 1  (E 1 &gt;&gt;E 2 ). However, because the second electric fields E 2  may have a generally vertical direction, the second electric fields E 2  do not affect or distort the first horizontal electric field E 1 . The second electric fields E 2  may prevent a third electric field from being generated between the data lines  104  and the pixel electrodes  107   a  and  107   b , thereby preventing a distortion of the first horizontal electric field E 1  and preventing cross talk in the vertical direction. Further, a width of the common electrodes  105   a  and  105   c  arranged close to the data lines  104  may be reduced, thereby improving an aperture ratio of the IPS mode liquid crystal display device. 
     Additionally, the second electric fields E 2  may be coupled with an arrangement of the common electrodes  105   a  and  105   c  being close to the data lines  104  to prevent a distortion of the first horizontal electric field E 1 . When the arrangement of the common electrodes  105   a  and  105   c  being close to the data lines  104  is coupled with the second electric fields E 2 , the intensity of the second electric fields E 2  may be lower than when the second electric fields E 2  are not coupled with the arrangement of the common electrodes  105   a  and  105   c  being close to the data lines  104 . 
       FIG. 3A  is a sectional view of another exemplary in-plane switching mode liquid crystal display device according to the present invention. In  FIG. 3A , another exemplary IPS mode liquid crystal display device may include a first substrate  220 , a plurality of common electrodes  205   a - 205   c  formed on the first substrate  220 , and a plurality of pixel electrodes  207   a  and  207   b  formed on the first substrate  220 . A thin film transistor (not shown), a plurality of gate lines (not shown), and a plurality of data lines  204  also may be formed on the first substrate  220 . In particular, a gate insulating layer  222  may be formed on an entire surface of the first substrate  220 , and the data lines  204  may be formed on the gate insulating layer  222 . Also, a passivation layer  224  may be formed on the entire surface of the first substrate  220  covering the data lines  204 , and the common electrode  205   a - 205   c  and the pixel electrodes  207   a  and  207   b  may be formed on the passivation layer  224 . In addition, the common electrodes  205   a  and  205   c  may be formed close to a corresponding one of the data lines  204 . 
     The IPS mode liquid crystal display device also may include a second substrate  230  bonded to the first substrate  220  with a predetermined space therebetween, such that a liquid crystal layer  240  may be interposed between the first and second substrates  220  and  230 . Also, a black matrix  232  and a color filter  234  may be formed on the second substrate  230 . In particular, the black matrix  232  may be formed of a black resin material, which has low resistance and high dielectric characteristics. Accordingly, an electric field may be formed between the black matrix  232  and another conductive/dielectric material. Thus, when the thin film transistor (not shown) is switched by signals of the gate lines (not shown) to transfer signals of the data lines  204  to the pixel electrodes  207   a  and  207   b , a first horizontal electric field may be generated between the common electrodes  205   a - 205   c  and the pixel electrodes  207   a  and  207   b . Also, minute electric fields may be generated between the data lines  240  and the black matrix  232 , such that an intensity of the minute electric fields is much smaller than an intensity of the first horizontal electric field between the common electrodes  205   a - 205   c  and the pixel electrodes  207   a  and  207   b . Accordingly, the minute electric fields between the data lines  240  and the black matrix  232  do not distort the first horizontal electric field. Yet, the minute electric fields between the data lines  240  and the black matrix  232  may prevent an electric field from being generated between the data lines  204  and the pixel electrodes  207   a  and  207   b , thereby preventing a distortion of the first horizontal electric field between the common electrodes  205   a - 205   c  and the pixel electrodes  207   a  and  207   b  and preventing cross talk in the vertical direction. Further, a width of the common electrodes  205   a  and  205   c  arranged close to the data lines  204  may be reduced, thereby improving an aperture ratio of the IPS mode liquid crystal display device. 
     Moreover, the IPS mode liquid crystal display device also may be referred to as a 4 block IPS mode liquid crystal display device because the arrangement of the three common electrodes  205   a - 205   c  and the two pixel electrodes  207   a  and  207   b  forms four light transmittance regions. Furthermore, the arrangement of the common electrodes  205   a - 205   c  and the pixel electrode  207   a  and  207   b  may be similarly applied to form various block-types IPS mode liquid crystal display devices. For example, a 2 block IPS mode liquid crystal display device may be formed by arranging one pixel electrode between two common electrodes, or a 6 block IPS mode liquid crystal display device may be formed by arranging three pixel electrodes interposed between four common electrodes. 
       FIG. 3B  is a sectional view of another exemplary in-plane switching mode liquid crystal display device according to the present invention. In  FIG. 3B , another exemplary IPS mode liquid crystal display device may include a first substrate  320 , a plurality of common electrode  305   a - 305   c  formed on the first substrate  320 , and a plurality of pixel electrodes  307   a  and  307   b  formed on the first substrate  320 . A thin film transistor (not shown), a plurality of gate lines (not shown), a plurality of data lines  304  also may be formed on the first substrate  320 . In particular, the pixel electrodes  307   a  and  307   b  may be formed on the first substrate  320 , and a gate insulating layer  322  may be formed on an entire surface of the first substrate  320  covering the pixel electrodes  307   a  and  307   b . Also, the data lines  304  and the common electrodes  305   a - 305   c  may be formed on the gate insulating layer  322 . A passivation layer  324  may be formed on the entire surface of the first substrate  320  covering the data lines  304  and the common electrodes  305   a - 305   c . In addition, the common electrodes  305   a  and  305   c  may be formed close to a corresponding one of the data lines  304 . 
     The IPS mode liquid crystal display device also may include a second substrate  330  bonded to the first substrate  320  with a predetermined space therebetween, such that a liquid crystal layer  340  may be interposed between the first and second substrates  320  and  330 . Also, a black matrix  332  and a color filter  334  may be formed on the second substrate  330 . In particular, the black matrix  332  may be formed of a black resin material, which has low resistance and high dielectric characteristics. Accordingly, an electric field may be formed between the black matrix  332  and another conductive/dielectric material. Thus, when the thin film transistor (not shown) is switched by signals of the gate lines (not shown) to transfer signals of the data lines  304  to the pixel electrodes  307   a  and  307   b , a first horizontal electric field may be generated between the common electrodes  305   a - 305   c  and the pixel electrodes  307   a  and  307   b . Also, minute electric fields may be generated between the data lines  340  and the black matrix  332 , such that an intensity of the minute electric fields is much smaller than an intensity of the first horizontal electric field between the common electrodes  305   a - 305   c  and the pixel electrodes  307   a  and  307   b . Accordingly, the minute electric fields between the data lines  340  and the black matrix  332  do not distort the first horizontal electric field. The minute electric fields between the data lines  340  and the black matrix  332  may prevent an electric field from being generated between the data lines  304  and the pixel electrodes  307   a  and  307   b , thereby preventing a distortion of the first horizontal electric field between the common electrodes  305   a - 305   c  and the pixel electrodes  307   a  and  307   b  and preventing cross talk in the vertical direction. Further, a width of the common electrodes  305   a  and  305   c  arranged close to the data lines  304  may be reduced, thereby improving an aperture ratio of the IPS mode liquid crystal display device. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the in-plane switching mode liquid crystal display device of the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Technology Category: 3