Abstract:
An in-plane switching mode liquid crystal display device includes a lower substrate having pixels arranged thereon in a matrix, each pixel being defined and surrounded by a gate line and a pair of adjacent data lines crossing substantially normal to the gate line, a common line, an upper substrate having a black matrix and a color filter formed thereon, a spacer formed on the lower substrate including the region adjacent to the data lines, and a liquid crystal layer interposed between the lower substrate and the upper substrate.

Description:
This application claims the benefit of the Korean Application No. P2002-86636 filed on Dec. 30, 2002, which is hereby 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 an in-plane switching mode liquid crystal display device having a pattern of spacers. 
     2. Discussion of the Related Art 
     Generally, a liquid crystal display (LCD) device operates by optical anisotropy and polarization of a liquid crystal material therein. Since the liquid crystal material includes liquid crystal molecules, each having a thin and long structure, the liquid crystal material has a specific orientation according to the alignment direction of the liquid crystal molecules. Hence, the alignment direction of the liquid crystal molecules can be controlled by applying an external electric field to the liquid crystal. As the alignment of the liquid crystal molecules is changed by applying an electric field, light polarization caused by the optical anisotropy of the liquid crystal material is modulated to display image information. 
     One of the LCD devices widely used is a twisted nematic (TN) mode LCD device. The TN mode LCD device is configured in such a manner that an electrode is provided on each of the two substrates respectively. The direction of the liquid crystal molecules is arranged to be twisted at an angle of 90°. The TN LCD device operates such that the direction of the liquid crystal molecules is arranged by applying an electric field. However, the TN mode LCD device has a disadvantage of having a narrow viewing angle. 
     Therefore, various new methods have been actively developed and studied in order to solve the problem of the narrow viewing angle. An in-plane switching (IPS) mode and an optically compensated birefringence (OCB) mode are some examples of the results of the above study. 
     The IPS mode LCD device is configured such that two electrodes are provided on one common substrate, and liquid crystal molecules are rotated relative to the substrate with their long axes remaining substantially in parallel with the substrate. Then, an electric field is generated with respect to the substrate in parallel therewith by applying voltages between the two electrodes. That is, the major axis of the liquid crystal molecule does not rise with respect to the substrate. Therefore, since the birefringence change of the liquid crystal in the viewing direction is small, the viewing angle becomes much improved compared with that of the related art TN mode LCD device. 
       FIG. 1  is a plan view of a part of a lower substrate of an IPS mode LCD device. 
     Referring to  FIG. 1 , the lower substrate includes a plurality of gate lines  13  and common lines  54  substantially in parallel with each other and a plurality of data lines  15  substantially perpendicular to the gate lines  13  and common lines  54 . 
     Pixels  10  are defined in the lower substrate as the region surrounded by the gate lines  13 , the common lines  54 , and the data lines  15 ,  15 ′. 
     Further, a gate electrode  31  is formed at one side of the gate line  13 , and a source electrode  33  is formed at one side of the data line  15  adjacent to the gate electrode  31  and partially overlapping the gate electrode  31 . A drain electrode  35  is formed to face the source electrode  33  and is space from the source electrode  33  by an interval. Together, the gate electrode  31 , the source electrode  33  and the drain electrode  35  form a thin film transistor region (T). 
     Further, the common line  54  has a plurality of common electrodes  54   a  extending therefrom. The drain electrode  35  is connected to a lead interconnection line  37  from which pixel electrodes  37   a  extend. The common electrode  54   a  and the pixel electrode  37   a  are formed in an alternating manner. An image display region of the pixel  10  is formed by the plurality of the common electrodes  54   a  and the pixel electrodes  37   a.    
     A common voltage input from the common lines  54  is applied to the common electrodes  54   a  formed in the pixel  10 . Various levels of image signals are applied to the subpixel via the data line  15  when a gate voltage is applied via the gate line and gate electrode. 
     Therefore, a plane electric field is formed by the voltage applied to the pixel electrode  37   a  and the common electrode  54   a , and the alignment degree of the liquid crystal molecules can be varied depending on the intensity of such electric field so as to display images. 
     A block  39  refers to a region in which images are displayed by the pixel electrode  37   a  and the common electrode  54   a  according to the applied plane electric field. Each pixel  10  includes a plurality of the blocks  39 . As illustrated in  FIG. 1 , a four-block type in which four blocks  39  are formed in one pixel  10  is widely used. 
       FIG. 2  is a sectional view of a related art in-plane switching mode LCD device taken along the line I-I′ of FIG.  1 . 
     Referring to  FIG. 2 , the related art in-plane switching mode LCD device is configured such that a black matrix  8  and a color filter  6  are formed on an upper substrate  5 . A lower substrate  22  is provided with the pixels  10  as illustrated in  FIG. 1  arranged in a matrix. In addition, the liquid crystal  20  as described above is in a predetermined gap between the upper substrate  5  and the lower substrate  22 , and the two substrates are sealed by a sealant (not shown) deposited on the edges of the substrates. 
     Further, spacers (not shown) are disposed between the upper substrate  5  and the lower substrate  22  to maintain the predetermined gap between the substrates  5  and  22  so that the liquid crystal  20  can be injected therebetween or applied by dispensing. 
     Light does not penetrate the LCD device as illustrated in  FIGS. 1 and 2  except in the image display regions of the pixel  10 , i.e., the four blocks  39 . Therefore, penetration of unnecessary light is shielded in the region except for the four blocks  39  where the region corresponds to the black matrix  8  of the upper substrate  5 . 
     However, because the data lines  15 ,  15 ′ and the common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ are not included in the blocks  39 , they are shadowed by the black matrix  8 , as illustrated in FIG.  2 . Accordingly, even though the data lines  15 ,  15 ′ and the common electrodes  54   a ,  54   a ′ are shielded by the black matrix  8 , light leakage can occur where there is misalignment of the upper and lower substrates  5 ,  22  during manufacturing. 
     Particularly, as the substrate size becomes large, a misalignment of the upper and lower substrates  5 ,  22  becomes more serious. Therefore, it may be necessary to widen the width of the black matrix  8  of the upper substrate  5  sufficient to cover a part of the blocks  39 , as illustrated in  FIG. 2 , which results in the decrease of the final aperture ratio. 
     Further, as illustrated in  FIG. 2 , even though the width of the black matrix  8  is widened, the light leakage may also occur due to the refraction of light in that region. 
     Before the explanation of an in-plane switching mode LCD device of the present invention, a spacer formed between an upper substrate and a lower substrate is explained to maintain a space therebetween. 
     The spacer is distributed between the upper and lower substrates to maintain a cell gap uniform, and there are various types of spacers, such as a fiber-shaped spacer, an elastic ball-shaped spacer, or an adhesive spacer. 
     However, since the spacer particles are dispersed on the substrate randomly, the spacer is sometimes found to exist inside an effective pixel region, which causes a problem in that the spacer is seen, or incident light is scattered thereby decreasing the contrast of a liquid crystal panel. 
     Therefore, a method has been introduced for forming the spacer by using a photolithography process to solve the above problem. The method is performed by depositing a photoresist layer on the substrate, and illuminating ultraviolet rays through a mask before developing the substrate to form a dot or stripe-shaped spacer. The spacer is formed in a region other than an effective pixel region, and the cell gap can be controlling by the thickness of the photoresist layer, which provides advantages of controlling the width of the cell gap easily and increasing the precision. 
     As described above, spots may be seen on the image display of the related art in-plane switching mode LCD device due to light leakage. 
     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 advantage of the present invention is to provide an in-plane switching mode liquid crystal display device for preventing a light leakage phenomenon by forming a patterned spacer in a specific region of a lower substrate where liquid crystal material is not formed. 
     Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may 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 objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an in-plane switching mode liquid crystal display device comprises a first substrate having pixel areas, each pixel area being defined by a gate line and data lines; a thin film transistor having a drain electrode, each of the pixel areas including the thin film transistor a common line, a plurality of common electrodes extending from the common line, and a plurality of pixel electrodes; a lead interconnection line connected between the drain electrode of the thin film transistor and the pixel electrodes; a second substrate spaced from the first substrate by a gap; a pattern of spacers, each spacer over a region including a data line and a common electrode adjacent to the data line on the first substrate; and a liquid crystal layer between the first substrate and the second substrate. 
     In another aspect of the present invention, an in-plane switching mode liquid crystal display device, comprises a first substrate having pixel areas, each pixel area being defined by a gate line and data lines, each pixel area including a switching device, a common line, a plurality of common electrodes extending from the common line, and a plurality of pixel electrodes connected to a lead interconnection line between the switching device and the pixel electrodes; a second substrate spaced from the first substrate by a gap; first spacer and second spacer over a region including a data line, the data line being located substantially between the first and second spacers, the first spacer at least partially overlapping a common electrode adjacent the data line; and a liquid crystal layer between the first substrate and the second substrate. 
     In another aspect of the present invention, a method of manufacturing an in-plane switching mode liquid crystal display device, comprises forming a first substrate having pixel areas, each pixel area being defined by a gate line and data lines; forming a thin film transistor having a drain electrode, each of the pixel areas including the thin film transistor a common line, a plurality of common electrodes extending from the common line, and a plurality of pixel electrodes; forming a lead interconnection line connected between the drain electrode of the thin film transistor and the pixel electrodes; forming a pattern of spacers, each spacer over a region including a data line and a common electrode adjacent to the data line on the first substrate; and attaching a second substrate to the first substrate, the second substrate being spaced from the first substrate by a gap. 
     In another aspect of the present invention, an in-plane switching mode liquid crystal display device includes a lower substrate having pixels arranged thereon in a matrix, each pixel being defined and surrounded by a plurality of gate lines and data lines, each pixel including a thin film transistor, a common line, a plurality of common electrodes extending from the common lines, and a plurality of pixel electrodes extending from a lead interconnection line connected with a drain electrode of the thin film transistor; an upper substrate having a black matrix and a color filter thereon, the upper substrate facing the lower substrate and spaced apart from the lower substrate by a predetermined gap; a spacer over a region including the data lines and the common electrodes adjacent to the data lines on the lower substrate; and a liquid crystal layer between the lower substrate and the upper substrate. 
     Further, the black matrix formed on the upper substrate may be located over the region including the data lines and the common electrodes adjacent to the data lines on the lower substrate shield the light passing through the region including the data lines and the common electrodes. 
     In another aspect of the present invention, an in-plane switching mode liquid crystal display device includes a lower substrate having pixels aligned in a matrix, an upper substrate having a black matrix and a color filter, a liquid crystal layer between the lower substrate and the upper substrate, and a spacer formed by patterning over the lower substrate. 
     The structure and elements of the pixel are the same as those of the liquid crystal display device described before, but the location and the pattern configuration of the spacers are different. 
     Thus, the spacer formed by patterning in the present invention may be provided over just the region including the common electrodes adjacent to the data lines on the lower substrate. The pattern of spacers may be configured such that there are two separate spacers in the region including the data lines, and the liquid crystal may be included between the two separate spacers in the region. 
     In a further aspect of the present invention, an in-plane switching mode liquid crystal display device includes a lower substrate having pixels aligned in a matrix, each pixel being defined and surrounded by a gate line, a common line, and a pair of adjacent data lines crossing the gate line and the common line, an upper substrate having a black matrix and a color filter, a spacer formed on the lower substrate including a region adjacent to the data line, and a liquid crystal layer between the lower substrate and the upper substrate. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention 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. 1  is a plane view of a part of the lower substrate of a related art in-plane switching mode LCD; 
         FIG. 2  is a sectional view of the related art in-plane switching mode LCD device taken along the line I-I′ of  FIG. 1 ; 
         FIGS. 3A  to  3 D are sectional views to show the steps for manufacturing a spacer of an LCD device according to the present invention; 
         FIG. 4  is a sectional view of an in-plane switching mode LCD device according to one embodiment of the present invention; and 
         FIG. 5  is a sectional view of an in-plane switching mode LCD device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiments of the present invention, examples of which are 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. 
     A method for forming the spacer of the LCD device according to the present invention is illustrated with reference to  FIGS. 3A  to  3 D which provides sectional views of the method steps. 
     First, a photoresist layer  2  is deposited on a lower substrate  1  by using spin-coating method, for example, as illustrated in FIG.  3 A. The lower substrate  1  includes pixels arranged in a matrix. The photoresist material includes a photoresist with sufficient characteristics to act as a spacer for the liquid crystal display. For example, a photo acryl may be used. Moreover, the photo acryl may have a hardness of 3-4H, for example. 
     Then, as illustrated in  FIG. 3B , ultraviolet light is selectively illuminated on the photoresist layer  2  using a mask (not shown) to develop the photoresist to form a pattern in the photoresist layer  2 . 
     Referring to  FIG. 3C , a rubbing or other alignment treatment is performed on the lower substrate  1  having the pattern of the photoresist layer  2  formed thereon so that a desired alignment is achieved when liquid crystal is supplied between the substrates in a subsequent process. 
     Finally, as illustrated in  FIG. 3D , an upper substrate  3  is attached to the lower substrate  1 . Although not illustrated in the figures, liquid crystal may be dispensed onto one of the substrates before they are attached together with a sealant. 
     A detailed explanation according to the embodiments of the present invention will be made with reference to the attached drawings. 
       FIG. 4  is a sectional view of an in-plane switching mode LCD device according to one embodiment of the present invention. In particular,  FIG. 4  is a sectional view illustrating the region around one specific pixel on the lower substrate. Although there may be some variation, the lower substrate of the present invention has basically the same structure as that of the related art lower substrate of FIG.  1 . Therefore, similar reference numerals will be used for like elements also indicated in FIG.  1 . 
     Referring to  FIG. 4 , the in-plane switching mode LCD device according to one embodiment of the present invention includes an upper substrate  5 ′ having a black matrix  8 ′ and a color filter  6 ′ formed thereon, and a lower substrate  22  having pixels  10 , illustrated in  FIG. 1 , formed thereon in a matrix shape. A liquid crystal  20  as explained above is provided between the upper substrate  5 ′ and the lower substrate  22 , which are attached to each other by a deposited sealant (not shown) on their edges. 
     Further, a spacer  40  is formed between the upper substrate  5 ′ and the lower substrate  22 , for providing a space where the liquid crystal  20  is provided. 
     The spacer  40  is a patterned spacer which is formed by the method described with reference to  FIG. 3 , for example, and is formed over a region including data lines  15 ,  15 ′ and common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ on the lower substrate  22 . 
     Referring to  FIG. 4 , light does not penetrate through the pixel region illustrated in the figure except at an image display region corresponding to the region between the data electrodes  37   a  and the common electrodes  54   a ,  54   a ′ formed on the lower substrate  22 , that is, four blocks  39  illustrated in FIG.  1 . Accordingly, unnecessary light is blocked from passing through the upper substrate  5 ′ by the black matrix  8 ′. Here, the spacer  40  may also act as a light shielding element to further block undesired light. 
     In the related art case, the data lines  15 ,  15 ′ and the common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ as shown in  FIG. 2 , which do not belong to the block  39  region, are covered by the black matrix  8 . However, even if the region other than the region of the display blocks  39  is shielded by the black matrix  8 , light from a backlight unit (not shown) may be refracted by the liquid crystal  20  provided between the upper substrate  5  and the lower substrate  22 . Thus, light can penetrate into the region where the black matrix  8  is not formed, causing failure. Further, to solve this problem in the related art the black matrix  8  is formed rather wide to cover a part of the block  39  region, which decreases the aperture ratio. 
     In one embodiment of the present invention to solve the problem, the patterned spacer  40  is formed over the region including the data lines  15 ,  15 ′ and the common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ on the lower substrate  22  as illustrated in FIG.  4 . As described above, if the patterned spacer  40  is formed over the region including the data lines  15 ,  15 ′ and the common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ on the lower substrate  22 , the liquid crystal is not placed in the region. Thus, light from the lower back light cannot enter the region between the data lines  15 ,  15 ′ and the adjacent common electrodes  54 ,  54 ′ because the spacer occupies that region, even if the LCD device is in a normally black mode. 
     Therefore, even though the upper substrate  5 ′ and the lower substrate  22  are misaligned, a light leakage phenomenon can be prevented. 
     Accordingly, the present invention does not require the widening of the black matrix  8 ′ and as a result, the occurrence of the light leakage phenomenon is minimized and the aperture ratio of the image display region can be improved. 
     Moreover, the width of the black matrix  8 ′ may be reduced in the present invention because the spacer  40  acts to block the light leakage. For example, the black matrix  8 ′ need not extend up to the right/left most edge of the common electrode  54   a  and  54   a ′ (such as shown in FIG.  5 ). Thus, the black matrix  8 ′ may be reduced as much as about 5 μm, for example, at one side. 
     It should also be noted that the spacer  40  may be formed to extend short of the right/left most edge of the common electrode  54   a  and  54   a ′ in accordance with a tolerance level of the manufacturing process. For example, the end of the spacer  40  may be as much as about 5 μm or more short of the end of the common electrode  54   a  and  54   a ′, as long as the light leakage is prevented. 
       FIG. 5  is a sectional view of an in-plane switching mode LCD device according to another embodiment of the present invention. In particular,  FIG. 5  is a sectional view including a specific pixel region on a lower substrate, and the lower substrate of the present invention has basically the same structure as that of the related art lower substrate of FIG.  1 . Therefore, similar reference numerals will be used for like elements from FIG.  1 . 
     Referring to  FIG. 5 , the structure of the LCD device is similar to that of  FIG. 4 , except that the location of a patterned spacer  50  between a lower substrate  22  and an upper substrate  5 ′ is different from that of the embodiment shown in FIG.  4 . 
     In particular, the embodiment of the present invention illustrated in  FIG. 5  is especially useful in the case where the width of the data lines  15 ,  15 ′ aligned on the lower substrate  22  is wide, and the patterned spacer  50  is formed over the region including the common electrodes  54   a ,  54   a ′ adjacent to the data lines  15 ,  15 ′ on the lower substrate  22 . Here, the spacer  50  may or may not be partially over the data lines  15 ,  15 ′. 
     In other words, there may be two or more patterned spacers  50  in  FIG. 5  (although only two spacers are shown, for example) in the same or similar region where only one patterned spacer  40  exists in FIG.  4 . If two spacers  50  occupy this region, for example, then the two spacers may have a complete or partial gap between them. In the gap, liquid crystal  20  may exist. Thus, the liquid crystal  20  can be in the region over the data lines  15 ,  15 ′, and the spacers  50  may be separated by a gap with or without the liquid crystal  20 . Moreover, the gap may also act to receive overflow of liquid crystal such as when liquid crystal dispensing method is used to form the liquid crystal layer between the upper and lower substrates. 
     In this case, even though light is illuminated on the liquid crystal  20  located in the region over the data lines  15 ,  15 ′, the light is blocked by a black matrix  8 ′ and does not allow light leakage. 
     As shown in  FIG. 5 , there are two spacers  50  corresponding to one data line  15 , for example. Between the two spacers, there is a pocket of space to receive the liquid crystal. In this instance, this pocket of space may also be used to received extra or overflow liquid crystal when a liquid crystal dispensing method is used, for example. The pocket space may be formed the entire length of the cell gap or less than the cell gap such as a groove. 
     Accordingly, as described above, a spacer or spacers are formed on the lower substrate  22  at the region adjacent to the data lines  15 ,  15 ′ according to the embodiments of the present invention and a refraction of light by the liquid crystal does not occur. Moreover, a light leakage phenomenon is prevented. 
     Further, according to the present invention, it is not necessary to increase the width of the black matrix to prevent the light leakage phenomenon as in the related art case. Thus, the present invention has an advantage of improving the aperture ratio of the image display region. 
     As described above, according to the in-plane switching mode LCD device of the present invention, a light leakage phenomenon is prevented, and spots generated on a displayed image can be minimized. Furthermore, the aperture ratio is improved because the width of the black matrix formed on the upper substrate is minimized. 
     The present invention also contemplates using photoresist that is opaque enough to be used as a light shielding element. In this instance, the light shielding photoresist acts both as a spacer and a black matrix. Such photoresist may further block light in addition to the black matrix on the upper substrate or the black matrix on the upper substrate may not be needed. 
     Moreover, although the present invention has been explained with reference to four blocks in one pixel, different number of blocks may be used and is contemplated in the present invention. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in 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.