Patent Publication Number: US-9411188-B2

Title: Liquid crystal display

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0002979 filed in the Korean Intellectual Property Office on Jan. 8, 2015, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (a) Field 
     The present inventive concept relates to a liquid crystal display. 
     (b) Description of the Related Art 
     A liquid crystal display is one of flat panel displays that have been most widely used, includes two substrates on which electrodes are formed, respectively, and a liquid crystal layer inserted into the substrate, and adjusts the amount of light passing through the liquid crystal by applying signals to the electrodes to rearrange liquid crystal molecules of the liquid crystal layer. 
     A thin film transistor (TFT) substrate as one of the two substrates included in liquid crystal display is used for independently driving each pixel in a liquid crystal display or an organic light emitting diode (OLED). 
     A liquid crystal display includes a gate line for transmitting a gate signal and a data line for transmitting a data signal, which are formed to cross each other on the thin film transistor substrate, a thin film transistor connected to the gate line and the data line, and a pixel electrode connected to the thin film transistor. 
     When wirings of the liquid crystal display are undesirably disconnected or short-circuited, a corresponding pixel is determined to be a defective pixel and needs to be repaired. Pixel repair includes short-circuit or disconnection processes using a laser, and in this case metal debris may be generated. The metal debris causes short-circuit between a common electrode and a pixel electrode or a common electrode and a data line which degrades image quality. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present inventive concept has been made in an effort to provide a liquid crystal display having advantages of minimizing short circuit due to impurity generated from a laser process. 
     An exemplary embodiment of the present inventive concept provides liquid crystal display including a first insulation substrate, a gate line and a data line that are positioned to cross each other on the first insulation substrate, a thin film transistor including a gate electrode connected to the gate line, a semiconductor layer positioned to overlap the gate electrode, and source and drain electrodes connected to the semiconductor layer, a pixel electrode connected to the thin film transistor, a second insulation substrate facing the first insulation substrate, a light blocking member disposed on the second insulation substrate, and a common electrode disposed on the light blocking member, and a short-circuiting prevention insulating layer disposed on the common electrode in a region corresponding to a repair region. 
     The repair region may include any one of a first region in which a data line and a first source electrode are connected, a second region in which a first drain electrode and a first subpixel electrode are connected, and a third region in which a second drain electrode and a second subpixel electrode are connected. 
     The light blocking member may include a recess portion formed in a region corresponding to the repair region. 
     The recess portion may have a depth equal to or more than 0.2 μm. 
     The liquid crystal display may further include a planarization layer formed on the light blocking member. 
     The liquid crystal display may further include a planarization layer formed on the light blocking member 
     The recess portion may include a light blocking member, a planarization layer, a common electrode, and a short-circuiting prevention insulating layer that are sequentially positioned below a second insulation substrate. 
     A thickness of a planarization layer positioned in the recess portion may be thicker than a planarization layer disposed in a region other than the recess portion. 
     A region other than the recess portion may not include a short-circuiting prevention insulating layer. 
     The short-circuiting prevention insulating layer may be formed of an insulating material. 
     The short-circuiting prevention insulating layer may be formed to a thickness between about 0.03 μm and about 1 μm. 
     The liquid crystal display may further include a column spacer disposed in a region other than the recess portion for maintaining a cell gap between the first insulation substrate and the second insulation substrate on the second insulation substrate. 
     The short-circuiting prevention insulating layer may be formed of the same material as the column spacer. 
     The short-circuiting prevention insulating layer may be formed of an organic material. 
     An exemplary embodiment of the present inventive concept provides liquid crystal display including a first insulation substrate, a gate line and a data line that are positioned to cross each other on the first insulation substrate, a thin film transistor including a gate electrode connected to the gate line, a semiconductor layer positioned to overlap the gate electrode, and source and drain electrodes connected to the semiconductor layer, a pixel electrode connected to the thin film transistor, a second insulation substrate facing the first insulation substrate, a light blocking member disposed on the second insulation substrate, a common electrode disposed on the light blocking member. The light blocking member may include a recess portion formed in a region corresponding to a repair region of an electrode included in the thin film transistor. 
     The liquid crystal display may further include a short-circuiting prevention insulating layer disposed on the common electrode in a region corresponding to the repair region. 
     A height of the surface of the short-circuiting prevention insulating layer may be equal to or higher that of the pixel electrode. 
     It is to be understood that both the foregoing general description and the following detailed description of the present inventive concept are exemplary and explanatory and are intended to provide further explanation of the inventive concept as claimed. 
     According to the aforementioned exemplary embodiment of the present inventive concept, the following effects may be achieved. 
     According to an embodiment of the present inventive concept, a recess portion including a short-circuiting prevention insulating layer may be formed on a second insulation substrate that overlaps a repair region so as to prevent a common electrode and a pixel electrode from being short circuited due to impurities, thereby minimizing potential distortion. 
     According to an embodiment of the present inventive concept, a recess portion may be formed at a higher level than a region other than the recess portion based on a first insulation substrate, thereby preventing a pixel electrode and a common electrode from being short-circuited due to metal debris. 
     According to an embodiment of the present inventive concept, a liquid crystal display may be configured in such a way that a short-circuiting insulating layer included in a recess portion may be formed of the same material via the same manufacturing process as a column spacer, thereby reducing manufacturing costs. 
     In addition, according to exemplary embodiments of the present inventive concept, other features and advantages may be newly recognized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of liquid crystal display according to an exemplary embodiment of the present inventive concept. 
         FIG. 2  is a cross-sectional view taken along a line II-II of  FIG. 1 . 
         FIG. 3  is a cross-sectional view taken along a line III-III of  FIG. 1 . 
         FIG. 4  is a cross-sectional view taken along a line IV-IV of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, the present inventive concept will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the inventive concept are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present inventive concept. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. When an element, such as a layer, a region, or a substrate, is referred to as being “on”, “connected to” or “coupled to” another element, it may be directly on, connected or coupled to the other element or intervening elements may be present between the element and the another element. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. 
     Hereinafter, a liquid crystal display according to an exemplary embodiment of the present inventive concept will be described in detail with reference to the attached drawings. 
       FIG. 1  is a top plan view of liquid crystal display according to an exemplary embodiment of the present inventive concept,  FIG. 2  is a cross-sectional view taken along a line II-II of  FIG. 1 ,  FIG. 3  is a cross-sectional view taken along a line III-III of  FIG. 1 , and  FIG. 4  is a cross-sectional view taken along a line IV-IV of  FIG. 1 . 
     Referring to  FIGS. 1 to 4 , the liquid crystal display according to an exemplary embodiment of the present inventive concept includes a lower display panel  100  and an upper display panel  200  that face each other, and a liquid crystal layer  3  interposed between the two display panels. 
     First, the lower display panel  100  will be described below. 
     A plurality of gate lines including a first gate line  121   a  and a second gate line  121   b  and a plurality of gate conductors including a plurality of storage electrode lines  131  are formed on a first insulation substrate  110  including a pixel area. 
     The gate lines  121   a  and  121   b  mainly extend in a horizontal direction and transmit a gate signal. The first gate line  121   a  includes a first gate electrode  124   a  and a second gate electrode  124   b  that protrude upward and downward, and the second gate line  121   b  includes a third gate electrode  124   c  that protrudes upward. The first gate electrode  124   a  and the second gate electrode  124   b  are connected to each other to constitute one protrusion. 
     A storage electrode line  131  also mainly extends in a horizontal direction and transmits a predetermined voltage such as a common voltage Vcom. The storage electrode line  131  includes a storage electrode  129  that protrude upward and downward, a pair of vertical portions  134  that extend downward to be substantially perpendicular to the gate lines  121   a  and  121   b , and a horizontal portion  127  for connecting ends of the pair of vertical portions  134  to each other. The horizontal portion  127  includes a capacitor electrode  137  that extends downward. 
     A gate insulating layer  140  is formed on gate conductors  121   a ,  121   b , and  131 . 
     A plurality of semiconductor stripes  151  are formed of amorphous or crystalline silicon on the gate insulating layer  140 . A semiconductor stripe mainly extends in a vertical direction and includes first and second semiconductors  154   a  and  154   b  that extend toward first and second gate electrodes  124   a  and  124   b  and are connected to each other, and a third semiconductor  154   c  positioned on the third gate electrode  124   c.    
     A plurality of pairs of ohmic contacts (not shown) are formed on the semiconductors  154   a ,  154   b , and  154   c . The ohmic contact may be formed of a material such as silicide or n+ hydrogenated amorphous silicon doped with high concentration of n-type impurity. 
     A data conductor including a plurality of data lines  171 , a plurality of first drain electrodes  175   a , a plurality of second drain electrodes  175   b , and a plurality of third drain electrodes  175   c  is formed on the ohmic contact. 
     The data lines  171  transmit a data signal and mainly extend in a vertical direction to cross the gate lines  121   a  and  121   b . Each of the data lines  171  includes a first source electrode  173   a  and a second source electrode  173   b  that extend toward the first gate electrode  124   a  and the second gate electrode  124   b  and are connected to each other. 
     A first drain electrode  175   a , a second drain electrode  175   b , and a third drain electrode  175   c  include one wide end portion and the other end portion with a rod shape. The rod type other end portion of each of the first drain electrode  175   a  and the second drain electrode  175   b  is partially surrounded by the first source electrode  173   a  and the second source electrode  173   b . The wide one end portion of the first drain electrode  175   a  extends to constitute the third source electrode  173   c  with a curved shape of ‘U’. A wide end portion  177   c  of a third drain electrode  175   c  overlaps the capacitor electrode  137  to form a step-down capacitor Cstd and the rod type end portion is partially surrounded by the third source electrode  173   c.    
     The first gate electrode  124   a , the first source electrode  173   a , and the first drain electrode  175   a  form a first thin film transistor Qa together with the first semiconductor  154   a , the second gate electrode  124   b , the second source electrode  173   b , and the second drain electrode  175   b  form a second thin film transistor Qb together with the second semiconductor  154   b , the third gate electrode  124   c , the third source electrode  173   c , and the third drain electrode  175   c  form a third thin film transistor Qc together with the third semiconductor  154   c.    
     A semiconductor stripe including the first semiconductor  154   a , the second semiconductor  154   b , and the third semiconductor  154   c  may have substantially the same planar shape as data conductors  171 ,  173   a ,  173   b ,  173   c ,  175   a ,  175   b , and  175   c  and ohmic contacts disposed therebelow except for a channel region between source electrodes  173   a ,  173   b , and  173   c  and drain electrodes  175   a ,  175   b , and  175   c.    
     The first semiconductor  154   a  has an exposed portion that is not covered by the first source electrode  173   a  and the first drain electrode  175   a  between the first source electrode  173   a  and the first drain electrode  175   a , the second semiconductor  154   b  has an exposed portion that is not covered by the second source electrode  173   b  and the second drain electrode  175   b  between the second source electrode  173   b  and the second drain electrode  175   b , and the third semiconductor  154   c  has an exposed portion that is not covered by the third source electrode  173   c  and the third drain electrode  175   c  between the third source electrode  173   c  and the third drain electrode  175   c.    
     A passivation layer  180   a  formed of an inorganic insulator such as silicon nitride or silicon oxide is formed on the data conductors  171 ,  173   a ,  173   b ,  173   c ,  175   a ,  175   b , and  175   c  and the exposed portions of the semiconductors  154   a ,  154   b , and  154   c.    
     A plurality of color filters  230  are formed on the passivation layer  180   a . The plurality of color filters  230  include a red color filter, a green color filter, and a blue color filter that are arranged in parallel to each other. The plurality of color filters  230  are formed in parallel to each other in a horizontal direction, or alternatively, may be formed in a stripe form in a vertical direction. 
     A second passivation layer  180   b  may be positioned on the plurality of color filters  230 . The second passivation layer  180   b  may be formed as an organic layer or an inorganic layer. According to another exemplary embodiment of the present inventive concept, the second passivation layer  180   b  may be omitted. 
     A pixel electrode  191  including a first subpixel electrode  191   a  and a second subpixel electrode  191   b  is formed on the second passivation layer  180   b . The first subpixel electrode  191   a  and a second subpixel electrode  191   b  are separated from each other across the first gate line  121   a  and the second gate line  121   b  and are disposed above and below the first gate line  121   a  and the second gate line  121   b  to be adjacent to each other in a column direction, respectively. An area of the second subpixel electrode  191   b  may be greater than an area of the first subpixel electrode  191   a  and may be about 1 to 3 times the area of the first subpixel electrode  191   a.    
     An overall shape of each of the first subpixel electrode  191   a  and the second subpixel electrode  191   b  is a quadrangle, and each of the first subpixel electrode  191   a  and the second subpixel electrode  191   b  includes a cross stem portion including horizontal stem portions  193   a  and  193   b , and vertical stem portions  192   a  and  192   b  that cross the horizontal stem portions  193   a  and  193   b . In addition, each of the first subpixel electrode  191   a  and the second subpixel electrode  191   b  includes a plurality of fine branch portions  194   a  and  194   b . The first subpixel electrode  191   a  includes a lower protrusion  197   a  and the second subpixel electrode  191   b  includes an upper protrusion  197   b.    
     The first subpixel electrode  191   a  and the second subpixel electrode  191   b  are divided into four subregions by the horizontal stem portions  193   a  and  193   b  and the vertical stem portions  192   a  and  192   b , respectively. The fine branch portions  194   a  and  194   b  may diagonally extend from the horizontal stem portions  193   a  and  193   b  and the vertical stem portions  192   a  and  192   b , and an inclination direction may make an angle of about 45 or 135 degrees with respect to the gate lines  121   a  and  121   b  or the horizontal stem portions  193   a  and  193   b . In addition, the fine branch portions  194   a  and  194   b  of two neighboring subregions may be perpendicular to each other. 
     According to the present exemplary embodiment, the first subpixel electrode  191   a  further includes a contour branch portion surrounding a contour thereof, and the second subpixel electrode  191   b  further includes upper and lower horizontal portions and right and left vertical portions  198  positioned on the right and left of the first subpixel electrode  191   a . The right and left vertical portions  198  may prevent capacitive-coupling between the data lines  171  and the first subpixel electrode  191   a . The right and left vertical portions  198  may be omitted. 
     A plurality of first contact holes  185   a  and a plurality of second contact holes  185   b  through which the wide end portion of the first drain electrode  175   a  and the wide end portion of the second drain electrode  175   b  are exposed, respectively, are formed on the first passivation layer  180   a , a color filter  230 , and the second passivation layer  180   b . The first contact hole  185   a  may connect the second subpixel electrode  191   b  and the third drain electrode  175   c  to each other, and the second contact hole  185   b  may connect the first subpixel electrode  191   a  and the second drain electrode  175   b.    
     In this case, wirings and electrodes included in the lower display panel  100  may include fine lines with a width of several to several tens of μm. Accordingly, during manufacturing of the lower display panel  100 , wirings and electrodes with a fine line width may be disconnected. When wirings and electrodes with a fine line width are disconnected, a corresponding pixel is determined as a defective pixel and needs to be repaired. 
     In the case of a defective pixel, a repair process for disconnecting an electrode included in a thin film transistor using a laser is performed in the manufacturing method. In this case, the repair process is performed in repair regions A 1 , A 2 , and A 3  including any one of a first region A 1  in which the first pixel electrode  191   a  is connected, a second region A 2  in which the data line  171  and the second source electrode  173   b  are connected, and a third region A 3  in which the first drain electrode  175   a  and the first contact hole  185   a  are connected. 
     That is, in the case of a defective first subpixel, the first pixel electrode  191   a  positioned in the first region A 1  may be disconnected using a laser so as to block a data voltage transmitted to the first pixel electrode  191   a . A line connecting the data line  171  and the second source electrode  173   b  may be disconnected using a laser so as to block a data voltage transmitted to the pixel electrode  191   a  and  191   b . A line connecting the first drain electrode  175   a  and the first contact hole  185   a  may be disconnected using a laser so as to block a data voltage transmitted to the second subpixel electrode  191   b  using a laser so as to effectively block a data voltage transmitted to the second subpixel electrode  191   b.    
     A separate reference number is not denoted to a repair region, but for convenience of description, the first region A 1 , the second region A 2 , and the third region A 3  are collectively referred to as the repair regions A 1 , A 2 , and A 3 . 
     According to an exemplary embodiment of the present inventive concept, the repair region may include a region in which wirings and electrodes are disconnected. The first region A 1 , the second region A 2 , and the third region A 3  are only examples of the repair region. 
     Hereinafter, the upper display panel  200  will be described. 
     The upper display panel  200  is configured in such a way that a light blocking member  220  is positioned on a transparent second insulation substrate  210 . The light blocking member  220  is used to prevent light leakage and is formed to correspond to upper portions of the gate line  121 , the data lines  171 , the storage electrode line  131 , and the thin film transistor. 
     The light blocking member  220  may be positioned between pixels that are adjacent to each other in a row direction or between pixels that are adjacent to each other in a column direction. That is, the light blocking member  220  may be positioned in a direction in which a gate line or a data line of a thin film transistor extends. 
     A planarization layer  240  may be disposed on the light blocking member  220 . 
     The planarization layer  240  may be formed of an organic or inorganic material, particularly, an organic material with excellent planarization characteristic, for example, benzocyclobutene (BCB) and acryl resin. 
     A common electrode  270  is formed on the planarization layer  240 . 
     The common electrode  270  is formed of transparent metal such as indium tin oxide (ITO) or indium zinc oxide (IZO) and transmits a common voltage. 
     A column spacer (CS) may be formed on the common electrode  270 . 
     The column spacer CS may be positioned in a region in which the light blocking member  220  is formed. 
     Particularly, the column spacer CS may be formed in a region other than a recess portion DA. 
     The column spacer CS is formed to protrude from the common electrode  270  with a shape such as an approximate cylinder, truncated circular cone and hemisphere on the second insulation substrate  210  and maintains an interval with the first insulation substrate  110 . 
     The column spacer CS may be formed of a material with elastic force, such as thermoset resin, for example, acryl. 
     An upper alignment layer (not shown) may be formed on the common electrode  270 . 
     In this case, the upper display panel  200  includes the recess portion DA. 
     The recess portion DA may be formed on the second insulation substrate  210  to overlap the repair regions A 1 , A 2 , and A 3 . 
     A distance between the first substrate  110  and the recess portion DA may be longer than that between the first substrate  110  and a region other than the recess portion DA. 
     In this case, in the case of defective pixel, when any one of the source electrode  173 , the drain electrode  175 , and the pixel electrode  191  positioned in the repair regions A 1 , A 2 , and A 3  is disconnected using a laser, metal debris may be generated. The metal debris may be separated from a conductor, and thus the common electrode  270  and the pixel electrode  191  are short-circuited to degrade image quality. 
     That is, according to an exemplary embodiment of the present inventive concept, the distance between the first insulation substrate  110  and the recess portion DA may be longer than that between the first insulation substrate  110  and a region other than the recess portion DA so as to prevent the pixel electrode  191  and the common electrode  270  from being short-circuited due to metal debris, thereby minimizing potential distortion. 
     The recess portion DA may be formed in the light blocking member  220  to have a depth of the recess to be about 0.2 μm or more. 
     The recess portion DA may include the light blocking member  220 , the planarization layer  240 , the common electrode  270 , and a short-circuiting prevention insulating layer  280  that are formed on the second insulation substrate  210 . 
     To increase the distance between the first insulation substrate  110  and the recess portion DA, the light blocking member  220  positioned in the recess portion DA may be formed with a smaller thickness than that of the light blocking member  220  positioned in a region other than the recess portion DA. 
     In addition, in order to increase the distance between the first insulation substrate  110  and the recess portion DA, the planarization layer  240  positioned in the recess portion DA may be thicker than that of the planarization layer  240  positioned in a region other than the recess portion DA. 
     The recess portion DA may include the short-circuiting prevention insulating layer  280 . The short-circuiting prevention insulating layer  280  may be formed of an insulating material in order to prevent the pixel electrode  191  and the common electrode  270  from being short-circuited. 
     In addition, the short-circuiting prevention insulating layer  280  may be formed of the same material via the same manufacturing process as the column spacer CS. The short-circuiting prevention insulating layer  280  may be formed of an organic material such as acryl. 
     In addition, the short-circuiting prevention insulating layer  280  may prevent the pixel electrode  191  and the common electrode  270  from being short-circuited and may be formed to a thickness between 300 Å and 1 μm in order to maintain a predetermined distance to the recess portion DA from the first insulation substrate  110 . 
     A liquid crystal display according to an exemplary embodiment of the present Inventive concept may be configured in such a way that the short-circuiting prevention insulating layer  280  included in the recess portion DA is formed of the same material via the same manufacturing process as the column spacer CS, thereby reducing manufacturing costs. 
     The liquid crystal layer  3  has negative dielectric anisotropy, and liquid crystal molecules of the liquid crystal layer  3  are aligned such that a major axis of the liquid crystal molecules are perpendicular to surfaces of the two display panels  100  and  200  in a state in which an electric field is not present. The liquid crystal layer  3  may include an aligning aid agent including reactive mesogen such that major axis of liquid crystal molecules may have a pretilt in approximately parallel to a length direction of the fine branch portions  194   a  and  194   b  of the pixel electrode  191 . The aligning aid agent may be included in an alignment layer instead of a liquid crystal layer. 
     While this inventive concept has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the inventive concept is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.