Abstract:
Disclosed is a liquid crystal display device that has a narrower frame and that prevents a sealing member from entering a display region. The disclosed liquid crystal display device is provided with a first substrate and a second substrate arranged facing each another, a liquid crystal layer provided between the first and the second substrates, and a sealing member that bonds together the first and second substrates and that seals the liquid crystal layer therebetween. On the first substrate or the second substrate, a recess is made between the sealing member and the display region in the corner portion of the substrate.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a liquid crystal display device and a method of manufacturing same, and more particularly, to a reduction of the width of a bezel of a display panel. 
       BACKGROUND ART 
       [0002]    In a recent liquid crystal display device for a mobile device such as a mobile phone, a demand has been increased more than ever to reduce the width of a bezel region that is disposed around the display region and that is provided with a sealing member for sealing a liquid crystal layer, and the like, in order to make a display region that displays an image thereon larger. In other words, a demand for a slimmer bezel has been increasing. If a bezel of a display panel is made slimmer, space between a sealing member and a display region is narrowed, and in a corner portion of the bezel, in particular, because the sealing member is formed in a circular arc shape, it is possible that the sealing member enters the display region when panels are bonded and the sealing member is thereby pressed. Therefore, a structure for preventing this problem has been proposed. 
         [0003]    Patent Document 1 discloses a first substrate  40  that is provided with a protrusion  41  on a side region on one surface thereof so as to create a difference in level, thereby making a top surface in a corner region of the first substrate  40  lower, and a sealing member  42  is applied on the side and corner regions along the periphery of the first substrate  40  as shown in  FIG. 7 . When a second substrate is stacked on the first substrate  40 , the sealing member  42  applied thereon is pressed. However, because of the difference in level, it is possible to minimize the spread of an inner edge  44  of the sealing member in the corner region of a liquid crystal cell. 
         [0004]    Patent Document 2 discloses that, as shown in  FIG. 8 , by placing an end of a display region  51  so as to face a sealing pattern  52  through a wall pattern  53  near a corner portion of an inner periphery side wall of the sealing pattern, a sealing member provided near the corner portion of the sealing pattern  52  is prevented from entering the display region  51 . 
       RELATED ART DOCUMENTS 
     Patent Documents 
       [0000]    
       
         Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2000-193989 
         Patent Document 2: Japanese Patent Application Laid-Open Publication No. 2009-25355 
       
     
       SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
       [0007]    However, in Patent Document 1, because the sealing member  42  is formed lower in the corner region, when the second substrate is stacked on the first substrate  40 , the liquid crystal leaks to the outside from a region where the sealing member  42  is formed lower, which is problematic. In Patent Document 2, because the wall pattern  53  limits the spread of the sealing pattern  52 , the sealing pattern  52  is formed thick near the wall pattern  53 , thereby causing an uneven cell thickness, which is problematic. 
         [0008]    The present invention was made in view of such problems, and aims at eliminating a liquid crystal leak or an uneven cell thickness, preventing a sealing member from entering a display region, and reducing a bezel width of a liquid crystal display device. 
       Means for Solving the Problems 
       [0009]    A liquid crystal display device according to the present invention includes: a first substrate and a second substrate disposed to face each other; a liquid crystal layer disposed between the first substrate and the second substrate; and a sealing member that bonds the first substrate and the second substrate to each other and that seals the liquid crystal layer therebetween, wherein, on the first substrate or the second substrate, a recess is made between the sealing member and a display region in a corner portion of the substrate. 
         [0010]    A method of manufacturing a liquid crystal display device according to the present invention is a method of manufacturing a liquid crystal display device that includes: a first substrate and a second substrate disposed to face each other; a liquid crystal layer disposed between the first substrate and the second substrate; and a sealing member that bonds the first substrate and the second substrate to each other and seals the liquid crystal layer therebetween, the method including: forming a recess between a display region and the a location at which the sealing member is formed in a corner portion of the first substrate or the second substrate; forming the sealing member on an outside of the recess; providing a liquid crystal material on the first substrate or the second substrate; and stacking the first substrate and the second substrate, and bonding the first substrate and the second substrate such that a part of the sealing member flows into the recess. 
       EFFECTS OF THE INVENTION 
       [0011]    According to the present invention, in the corner portion of the first substrate or the second substrate, the recess is made between the sealing member and the display region. Therefore, the sealing member is stopped from reaching the display region beyond the recess, thereby preventing the sealing member from spreading into the display region. As a result, it becomes possible to provide a liquid crystal display device with a slimmer bezel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a plan view of a liquid crystal display device. 
           [0013]      FIG. 2  is a cross-sectional view of the liquid crystal display device. 
           [0014]      FIG. 3  is an enlarged plan view of a corner portion of a frame region. 
           [0015]      FIG. 4  is a cross-sectional view of the liquid crystal display device before bonding substrates thereof. 
           [0016]      FIG. 5  is an explanatory plan view showing how a sealing member spreads when a recess is not provided. 
           [0017]      FIG. 6  is an explanatory plan view showing how the sealing member spreads when the recess is provided. 
           [0018]      FIG. 7  is a plan view of a conventional liquid crystal display device. 
           [0019]      FIG. 8  is a plan view of the conventional liquid crystal display device. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0020]    An embodiment of the present invention will be described below in detail with reference to the figures. The present invention is not limited to the embodiment described below. 
         [0021]      FIG. 1  is a plan view showing a liquid crystal display device  100  of the present invention. The liquid crystal display device  100  is provided with a TFT substrate  20  used as a first substrate, a CF substrate (color filter substrate)  30  that is disposed to face the TFT substrate  20  and used as a second substrate, a liquid crystal layer (not shown) provided between the TFT substrate  20  and the CF substrate  30 , and a sealing member  24  formed in a frame shape to bond the TFT substrate  20  and the CF substrate  30  to each other and to seal the liquid crystal layer therebetween. On the liquid crystal display device  100 , a rectangular-shaped display region D for displaying an image and a frame-shaped bezel region F around the display region D, which has the sealing member  24  disposed thereon, are defined, respectively. 
         [0022]      FIG. 2  is a cross-sectional view of a corner portion of the liquid crystal display device  100  along the one-dot chain line A-A in  FIG. 1 . 
         [0023]    The TFT substrate  20  is provided with an insulating substrate  10   a , a plurality of gate lines (not shown) disposed on the insulating substrate  10   a  so as to extend in parallel with each other, a plurality of source lines (not shown) disposed so as to extend in parallel with each other in a direction orthogonal to the respective gate lines, a plurality of TFTs (not shown) disposed at respective intersections where the respective gate lines and the respective source lines orthogonally cross, an organic film  11   a  disposed so as to cover the respective TFTs, and a plurality of pixel electrodes (not shown) disposed on the organic film  11   a  in a matrix. On the organic film  11   a , columnar spacers  12  that define the thickness of a liquid crystal layer  23  are disposed. The thickness of the organic film  11   a  is 2 to 4 μm, for example. The height of the columnar spacer  12  is 5 μm, for example. 
         [0024]    The CF substrate  30  is provided with an insulating substrate  10   b , a black matrix  21 , and a color filter layer  22 . The black matrix  21  is disposed in a frame shape in the bezel region F on the insulating substrate  10   b , and is disposed in a grid pattern in the display region D, which is inside the frame. The color filter layer  22  includes red layers, green layers, and blue layers, which are respectively disposed in corresponding grids of the black matrix  21 . On the black matrix  21  and the color filter layer  22 , a common electrode (not shown) and an organic film  11   b  that serves as an overcoat layer are disposed. 
         [0025]    As shown in  FIGS. 1 and 2 , in a corner portion of the bezel region F of the CF substrate  30 , a recess  13  is formed between the display region D and an area where the sealing member  24  is to be formed by removing the organic film  11   b  through dry etching. The depth of the recess  13  is the same as the thickness of the organic film  11   b , which is 2 to 4 μm, for example. 
         [0026]      FIG. 3  shows enlarged schematic plan views of a portion around the recess  13 . As shown in  FIG. 3(   a ), the recess  13  is formed such that at least the inner side thereof is rectangular so as to be placed near the display region D. As shown in  FIG. 3(   b ), it is preferable that the recess  13  be made as large as possible by forming an outer side thereof in a circular arc shape that coincides with the curvature of an inner side of the sealing member  24  and by placing the recess  13  closer to both the display region D and the sealing member  24 . When the recess  13  is made large, even if the formed sealing member  24  becomes thick, it is possible to prevent the sealing member  24  from reaching the display region D beyond the recess  13  when the sealing member  24  is pressed. 
         [0027]      FIG. 4  is a cross-sectional view of a corner portion of the liquid crystal display device  100  along the one-dot chain line A-A in  FIG. 1 , showing a state before the TFT substrate  20  and the CF substrate  30  are bonded. 
         [0028]    On the organic film  11   b  in the bezel region F of the CF substrate  30 , the sealing member  24  made of a thermosetting resin or a UV-curable resin such as an epoxy-based adhesive, for example, is formed using a dispenser device. In the corner portion of the frame region F, the sealing member  24  is placed outside of the recess  13  so as not to overlap the recess  13 . By placing the sealing member  24  so as not to overlap the recess  13 , the height of the sealing member  24  that was formed can be even on the entire bezel region F, thereby preventing the liquid crystal layer  23  from leaking to the outside of the sealing member  24  when bonding the substrates. 
         [0029]    In the CF substrate  30  having the sealing member  24  formed thereon, the nematic liquid crystal material  23  having electrooptic characteristics is provided on the display region D by the dripping method or the like. After the liquid crystal material  23  is provided, the CF substrate  30  is stacked on the TFT substrate  20  having the columnar spacers  12  formed therein. As a result, as shown in  FIG. 1 , the liquid crystal display device  100  having the liquid crystal layer  23  sealed between the TFT substrate  20  and the CF substrate  30  by the sealing member  24  is formed. 
         [0030]      FIG. 5  is a schematic plan view showing how the sealing member  24  is pressed and thereby spreads outwardly when the TFT substrate  20  and the CF substrate  30  are stacked. The sealing member  24  is pressed between the TFT substrate  20  and the CF substrate  30 , and the width (W 2 ) of a sealing member  24   a  after bonding thereby becomes wider than the width (W 1 ) of the sealing member  24  at the time when the sealing member  24  was formed. The sealing member  24  in a side portion spreads differently compared to the sealing member  24  in a corner portion. The sealing member  24  in the side portion is pressed and spreads out evenly to both sides from the width W 1 , which is the width at the time of forming the sealing member  24 . The sealing member  24  in the corner portion, however, spreads in a direction to the center of the curvature in a more concentrated manner when pressed. Consequently, a spread width to the inside is increased, and therefore, the sealing member  24  in the corner portion tends to be closer to the display region D compared to the sealing member  24  in the side portion. Because of this, a location of the sealing member  24  formation needs to be determined by taking into account a shape of the sealing member  24   a  after bonding in the corner portion so as to ensure that the sealing member after bonding  24   a  does not enter the display region D. 
         [0031]    The respective shapes of the sealing member  24  in the corner portion before and after the substrates are bonded can be expressed by Formula 1. 
         [0000]      (Formula 1) 
         [0000]      ¼π( r 1 2   −r 2 2 )× h 1×(⅔)=¼π( r 1 2   −r 3 2 )× h 2  Formula 1
 
         [0032]    Here, “r 1 ” represents a curvature radius when the sealing member  24  is formed in the corner portion. When the center of r 1  is set to a reference point, “r 2 ” represents a location of an inner side of the sealing member immediately after the sealing member  24  is formed, and “r 3 ” represents a location of the inner side of the sealing member after the substrates are bonded. Further, “h 1 ” represents a height of the sealing member  24  immediately after the sealing member  24  is formed, and “h 2 ” represents the height of the sealing member after bonding  24   a.    
         [0033]    The location “r 3 ” of the inner side of the sealing member in the corner portion after the substrates are bonded can be derived from (Formula 2) that is transposed from Formula 1. 
         [0000]      (Formula 2) 
         [0000]        r 3=√{square root over ((1 /h 2)×( h 2 ×r 1 2 −( r 1 2   −r 2 2 )× h 1×(⅔))))}{square root over ((1 /h 2)×( h 2 ×r 1 2 −( r 1 2   −r 2 2 )× h 1×(⅔))))}{square root over ((1 /h 2)×( h 2 ×r 1 2 −( r 1 2   −r 2 2 )× h 1×(⅔))))}  Formula 2
 
         [0034]    In the conventional liquid crystal display device, when r 1 =500 μm, r 2 =400 μm, h 1 =20 μm, and h 2 =5 μm, for example, the location “r 3 ” of the inner side of the sealing member after the substrates are bonded is 100 μm, according to Formula 2. 
         [0035]    When the location of the sealing member  24  is determined such that the location “r 3 ” of the inner side of the sealing member derived as above comes to the closest point to the display region D before making contact therewith, a location “d 1 ” of the sealing member  24  formed in the side portion can be derived from Formula 3. 
         [0000]      (Formula 3) 
         [0000]        d 1 =r 1−( r 3/√{square root over (2)})  Formula 3
 
         [0036]    In the conventional liquid crystal display device, when r 1 =500 μm and r 3 =100 μm, for example, “d 1 ” is derived to be 430 μm. That is, when the location at which the sealing member  24  is to be formed is determined so as to ensure that the location “r 3 ” of the inner side of the sealing member in the corner portion after the substrates are bonded is not in contact with the display region D, the location of the sealing member  24  formation in the side portion needs to be at least 430 μm away from the display region D. 
         [0037]    On the other hand, a spread width “d 2 ” of the sealing member after bonding  24   a  in the side portion can be derived from Formula 4. 
         [0000]      (Formula 4) 
         [0000]        d 2=( W 1 ×h 1×(⅔))/ h 2/2  Formula 4
 
         [0038]    In the conventional liquid crystal display device, when the sealing member width (W 1 ) immediately after the sealing member is 200 μm, for example, the spread width “d 2 ” of the sealing member  24   a  is derived to be 260 μm. Therefore, when the location for forming the sealing member  24  (d 1 =430 μm) is determined with reference to the location “r 3 ” of the inner side of the sealing member in the corner portion, the location of the inner side of the sealing member after bonding  24   a  in the side portion is away from the display region D as much as d 3 =170 μm (d 3 =d 1 −d 2 ), and the bezel region F is at least 170 μm larger than the sealing member width. 
         [0039]      FIG. 6  is a schematic plan view showing how the sealing member  24  is pressed and spreads out when the TFT substrate  20  and the CF substrate  30  are stacked in the liquid crystal display device  100  of the present invention. In the liquid crystal display device  100  of the present invention, the recess  13  is formed inside of the location for forming the sealing member  24  in the corner portion, such that the pressed sealing member  24   a  flows into the recess  13  in the corner portion. The height (h 2 ) of the sealing member  24   a  after bonding is set to 5 μm except at the recess  13 . The height (h 2 ′) at the recess  13  is 8 μm when the depth of the recess  13  is 3 μm, for example. 
         [0040]    Therefore, compared with the conventional liquid crystal display device, the height of the sealing member  24   a  (h 2 ′) is increased to 8 μm, and because of this, the location “r 3 ′” of the inner side of the sealing member after bonding becomes 320 μm according to Formula 2. When the location for forming the sealing member  24  is determined with reference to the location “r 3 ′” of the inner side of the sealing member, a location “d 1 ′” of forming the sealing member  24  in the side portion is 270 μm according to Formula 3. 
         [0041]    Therefore, in the liquid crystal display device of the present invention, when the location for forming the sealing member  24  (d 1 ′=270 μm) is determined such that the sealing member  24  is not in contact with the display region D in the corner portion, it is possible to shorten the distance between the sealing member  24   a  and the display region D in the side portion to d 3 ′=10 μm (d 3 ′=d 1 ′−d 2 ). Therefore, it is possible to make the bezel region F smaller than that of the conventional liquid crystal display device. 
         [0042]    According to the liquid crystal display device  100  of the present invention, the recess  13  is made between the sealing member  24  and the display region D in the corner portion of the bezel region F. Therefore, the sealing member after bonding  24   a  is prevented from spreading to the inside and entering the display region D. Further, because the recess  13  is not made at the location at which the sealing member  24  is to be formed, the height of the sealing member  24  that was formed can be made uniform, thereby preventing the liquid crystal layer  23  from leaking to the outside. Furthermore, because the sealing member after bonding  24   a  stays inside of the recess  13 , and the cell at the corner portion does not become thick, the display quality can be improved. 
         [0043]    The present invention is not limited to the embodiment described above. It is also possible to make the recess  13  in the TFT substrate  20 , for example.