Abstract:
This invention envisages having flexible wiring substrate terminals serving to connect with the wires for preventing dielectric breakdown caused by static electricity during the manufacturing process, and reducing the number of the flexible wiring substrate terminals. On a mother TFT substrate, signal lines extend over each liquid crystal cell in a manner flanking a scribe line between the adjacent liquid crystal cells. The signal lines of each liquid crystal cell are connected with connecting lines striding the scribe line. This reduces the number of static electricity countermeasure wires extending from the flexible wiring substrate terminals of each liquid crystal cell. Once completed, the individual liquid crystal cells are separated from one another, with no adverse effects caused by the connecting lines.

Description:
CLAIM OF PRIORITY 
       [0001]    The present application claims priority from Japanese Patent Application JP 2013-183795 filed on Sep. 5, 2013, the content of which is hereby incorporated by reference into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a display device. More particularly, the invention relates to a liquid crystal display device in whose manufacturing process the destruction of wiring and other parts by static electricity is effectively prevented. 
         [0004]    2. Description of the Related Art 
         [0005]    In the liquid crystal display device, a TFT substrate having pixel electrodes and thin film transistors (TFTs) formed in a matrix thereon is opposed to a counter substrate having color filters or overcoat films formed at the locations corresponding to the pixel electrodes of the TFT substrate, the TFT substrate and the counter substrate sandwiching a liquid crystal therebetween. The light transmission rate of liquid crystal molecules is controlled per pixel to form images. 
         [0006]    Because it is not efficient to manufacture individual liquid crystal display panels making up the liquid crystal display device, numerous liquid crystal cells are formed on a mother substrate that is later divided into individual liquid crystal cells. In particular, the TFT substrate has numerous TFTs, video signal lines, and scanning signal lines formed with a short spacing therebetween. Static electricity, if incurred during the manufacturing process, can lead to dielectric breakdown between wires or breakdown of TFTs. To prevent such eventualities, the signal lines are connected to a common line so that static electricity will not occur between wires during the manufacturing process. On the mother substrate, the common line is connected to ground wires formed between the individual liquid crystal display panels. 
         [0007]    JP-1999-84353-A describes a structure in which numerous liquid crystal display panels are formed on the mother substrate, the liquid crystal display panels being subjected to lighting inspection. The signal lines of the individual liquid crystal display panels are made common to each column for a single inspection. In this structure, the liquid crystal display panels arrayed in each row on the mother substrate are subjected to a single lighting inspection. 
       SUMMARY OF THE INVENTION 
       [0008]      FIG. 7  is a schematic plan view of a mother TFT board  1000 . In  FIG. 7 , liquid crystal cells  10  are formed in a matrix. Each liquid crystal cell  10  has a display area  11  and a terminal area  12 . Between the upper liquid crystal cell  10  and the lower liquid crystal cell  10  is a static electricity countermeasure element  21 . A static electricity countermeasure wire  20  connects the static electricity countermeasure element  21  with the terminal area  12  of the liquid crystal cell  10 . The individual static electricity countermeasure elements  21  are connected to a static electricity countermeasure common line  22 . 
         [0009]      FIG. 8  is a plan view showing a partial overall structure of a TFT substrate associated only with the liquid crystal cells indicated in  FIG. 7 . In  FIG. 8 , a gate circuit  30  is built in on the right of the display area  11 . Although an IC driver has yet to be mounted on the TFT substrate in its state shown in  FIG. 8 , the area delineated with dotted lines in the terminal area constitutes an IC drive mounting area  40 . The terminal area  12  is provided with a flexible wiring substrate terminal  70  to be connected to a flexible wiring substrate. 
         [0010]      FIG. 9  is an enlarged plan view of the vicinity of the flexible wiring substrate terminal  70  shown in  FIG. 8 . In  FIG. 9 , signal lines extending from the display area are connected to the flexible wiring substrate terminals  70  formed near a scribe line  90  constituting a product contour. A ground wire  51  provided outside the signal lines  50  is also connected to the flexible wiring substrate terminals  70 . 
         [0011]    In  FIG. 9 , the static electricity countermeasure wires  20  extend from the flexible wiring substrate terminals  70  beyond the scribe lines  90  making up the product contour. The static electricity countermeasure wires  20  are connected to the static electricity countermeasure elements  21  in a portion not shown in  FIG. 9 . A line output from the static electricity countermeasure elements  21  is connected to the static electricity countermeasure common line  22  as shown in  FIG. 7 . 
         [0012]      FIG. 10  shows a cross-section taken along line A-A in  FIG. 9 . This is a cross-sectional view showing the signal line  50 , flexible wiring substrate terminal  70 , and static electricity countermeasure wire  20  near the scribe line  90  constituting the product contour. In  FIG. 10 , a first insulating film  101  is formed over a glass substrate  100 , and connecting wires  60  are formed over the first insulating film  101 . In this case, the connecting wires  60  make up a semiconductor layer. A second insulating film  102  is formed in a manner covering the connecting wires  60 . Over the second insulating film  102 , the signal lines  50  or static electricity countermeasure wires  20  are formed. 
         [0013]    Through holes  105  are formed in the second insulating film  102 . The through holes  105  connect the signal lines  50  or static electricity countermeasure wires  20  to the connecting wires  60  typically formed with a semiconductor, so that the signal lines  50  and static electricity countermeasure wires  20  are interconnected. A third insulating film  103  is formed in a manner covering the signal lines  50  or static electricity countermeasure wires  20 . Terminal through holes  106  are formed in the third insulating film  103 . ITOs  110  are provided in these parts to form the flexible wiring substrate terminals  70 . 
         [0014]    The left-hand side of the scribe line  90  indicated with a dotted line in  FIG. 10 , i.e., the side where the signal lines  50  exist, is the side that will be left as the product. The right-hand side of the scribe line  90 , i.e., the side where the static electricity countermeasure wires  20  exit, is the side to be cut off from the liquid crystal cells and discarded when the liquid crystal cells are separated from the mother substrate. 
         [0015]    As shown in  FIGS. 9 and 10 , the static electricity countermeasure wires  20  are connected to the signal lines  50  via the flexible wiring substrate terminals  70 . This structure is not mandatory for the static electricity countermeasures. However, if there is provided a structure in which the static electricity countermeasure wires  20  are connected to the signal lines  50  via the flexible wiring substrate terminals  70  in some regions and not connected via the flexible wiring substrate terminals  70  in other regions, the reliability of the eventual products varies depending on where they were located. For this reason, the static electricity countermeasure wires  20  are connected to the signal lines  50  uniformly via the flexible wiring substrate terminals  70  in most cases. 
         [0016]    Meanwhile, the liquid crystal display device is required to offer a high-definition screen while maintaining the same external size. On the high-definition screen, there exist a growing number of signal lines  50 , which entails an increasing number of flexible wiring substrate terminals  70  connecting with the signal lines  50 . Hence the growing number of wires that require static electricity countermeasures resulting in the increasing number of flexible wiring substrate terminals  70 . All this adds up to the difficulty in securing a necessary area in the liquid crystal cells in which the flexible wiring substrate terminals  70  are to be installed. 
         [0017]    It is therefore an object of the present invention to make it possible to take static electricity countermeasures by way of flexible wiring substrate terminals during the production process even if there are numerous signal lines in liquid crystal cells so that liquid crystal display devices may be produced with constant reliability. 
         [0018]    To achieve the above and other objects of the present invention, there are provided specific means as follows: 
         [0019]    (1) A display device including a first side having a terminal area, a second side opposed to the terminal area, a third side located on the left of the first side and connecting the first side with the second side, and a fourth side located on the right of the first side and connecting the first side with the second side. A first wire extends in exposed fashion from a flexible wiring substrate terminal formed in the terminal area up to a flank of the first side. A second wire extends in exposed fashion from the flexible wiring substrate terminal up to a flank of the third side. A third wire extends in exposed fashion from the flexible wiring substrate terminal up to a flank of the fourth side. The first, the second, and the third wires are covered either with an insulating film or with wiring except over the flanks. 
         [0020]    (2) Preferably in the display device described in above item (1), there may exist a plurality of the second wires, part of the second wires being connected to the flexible wiring substrate terminals, the remaining second wires not being connected to the flexible wiring substrate terminals. There may also exist a plurality of the third wires, part of the third wires being connected to the flexible wiring substrate terminals, the remaining third wires not being connected to the flexible wiring substrate terminals. 
         [0021]    (3) Preferably in the display device described in above item (2), the second and the third wires may be formed with a semiconductor layer each. 
         [0022]    (4) Preferably in the display device described in above item (2), the part of the second wires may occupy half the number of the second wires. 
         [0023]    (5) Preferably in the display device described in above item (2), the part of the third wires may occupy half the number of the third wires. 
         [0024]    According to the present invention, there is provided a structure in which static electricity countermeasure wires are connected via flexible wiring substrate terminals to static electricity countermeasure elements formed outside liquid crystal cells. In this structure, the static electricity countermeasure wires of the adjacent liquid crystal cells on a mother TFT board are made common. This makes it possible to reduce the number of flexible wiring substrate terminals even as the number of signal lines increases in conjunction with the ever-higher resolution of the screen. That in turn can suppress the growing size of the liquid crystal cells resulting from the increasing number of the terminals. 
         [0025]    Also, with the terminal count reduced, it is possible to prevent the flexible wiring substrate from growing in size. Furthermore, because the static electricity countermeasure wires can be connected to the static electricity countermeasure elements outside the liquid crystal cells under the same conditions, the liquid crystal cells having stable reliability can be manufactured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Further objects and advantages of the present invention will become apparent upon a reading of the following description and appended drawings in which: 
           [0027]      FIG. 1  is a plan view showing a partial structure of a mother TFT substrate according to the present invention; 
           [0028]      FIG. 2  is a plan view showing a connecting wire striding a scribe line; 
           [0029]      FIG. 3  is a cross-sectional view taken along line B-B in  FIG. 2 ; 
           [0030]      FIG. 4  is a plan view showing a first embodiment of the invention; 
           [0031]      FIG. 5  is a plan view showing a second embodiment of the invention; 
           [0032]      FIG. 6  is a plan view showing a third embodiment of the invention; 
           [0033]      FIG. 7  is a plan view showing a typical ordinary mother TFT substrate; 
           [0034]      FIG. 8  is a plan view of a liquid crystal cell indicated in  FIG. 7 ; 
           [0035]      FIG. 9  is a plan view showing examples of ordinary flexible wiring substrate terminals and ordinary static electricity countermeasure wires; and 
           [0036]      FIG. 10  is a cross-sectional view taken along line A-A in  FIG. 9 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    The present invention will now be described in detail through the use of some embodiments. 
       First Embodiment 
       [0038]      FIG. 1  is a plan view showing two TFT substrates according to the present invention, the substrates being located on a mother TFT substrate. On the TFT substrate shown in  FIG. 1 , built-in gate circuits  30  are formed on both sides of a display area  11 . In  FIG. 1 , an IC driver amounting area  40  is formed in a terminal area  12 . Some of the wires from the gate circuits  30  extend to the IC driver mounting area  40 . Flexible wiring substrate terminals  70  are formed at the edge of the terminal area  12 . In an ordinary setup, static electricity countermeasure wires  20  extend from the flexible wiring substrate terminals  70  to the outside. 
         [0039]    In  FIG. 1 , the gate circuits  30  of the adjacent liquid crystal display panels are formed in a manner flanking a scribe line  60  that separates the liquid crystal cells from one another. To prevent dielectric breakdown caused by static electricity during the manufacturing process, the wires from the gate circuits  30  need to be connected via the static electricity countermeasure wires  20  to static electricity countermeasure elements, not shown, outside the liquid crystal cells. 
         [0040]    In  FIG. 1 , the wires extended from the adjacent gate circuits  30  are connected in a manner striding the scribe line  90 . A static electricity countermeasure wire from either of two liquid crystal cells is extended to the outside of the cells. The static electricity countermeasure wires  20  are allowed to extend outside the liquid crystal cells and not by way of the flexible wiring substrate terminals  70 . This structure reduces the number of static electricity countermeasure wires  20  extending from the liquid crystal cells. 
         [0041]    Also, because the static electricity countermeasure wires  20  extend outside the liquid crystal cells via the flexible wiring substrate terminals  70 , the number of flexible wiring substrate terminals  70  can be reduced. Since the widths of the terminals are greater than the wire widths, reducing the number of the terminals makes it possible to reduce correspondingly the size of the liquid crystal cells, and also to reduce the size of the flexible wiring substrates. In this specification, the term “signal lines” refers to gate wires, video signal lines, common lines, or ground wires. 
         [0042]      FIG. 2  is a plan view showing how adjacent signal lines are connected in a manner flanking the scribe line  90 . In  FIG. 2 , over two liquid crystal cells flanking the scribe line  90 , signal lines  50  extend from the gate circuits located above in the drawing but not shown. The signal lines  50  formed over the adjacent liquid crystal cells are connected with connecting wires  60 . The signal lines  50  and the connecting wires  60  are formed with separate layers with an insulating film interposed therebetween; these wires are interconnected via through holes  105 . 
         [0043]      FIG. 3  is a cross-sectional view taken along line B-B in  FIG. 2 . In  FIG. 3 , a first insulating film  101  is formed over a glass substrate  100 . The connecting wires  60  are formed over the first insulating film  101 . The connecting wires  60  in this case are formed with a semiconductor layer. The semiconductor layer has very large resistance but offers sufficient conductivity in terms of static electricity prevention. The semiconductor layer is chemically stable and, for this reason, is used as the connecting wires  60  that will be cut off along the scribe line  90  and exposed to the atmosphere at the flanks of the liquid crystal cells. If the stability at the flanks of the liquid crystal cells is ensured, the connecting wires  60  may be formed with a metal or an alloy. 
         [0044]    A second insulating film  102  is formed over the connecting wires  60  formed with a semiconductor layer. The signal lines  50  extend over the second insulating film  102 .  FIG. 3  illustrates a cross-section of the through holes  105  formed at spots where the signal lines  50  are located. The through holes  105  formed in the second insulating film  102  are covered with signal lines formed with a metal or an alloy and conduct electricity to the connecting wires  60 . The signal lines  50  and through holes  105  are covered with a third insulating film  103  for protection against the atmosphere. 
         [0045]      FIG. 4  illustrates examples of the signal lines  50 , connecting wires  60 , flexible wiring substrate terminals  70 , and static electricity countermeasure wires  20  making up the first embodiment. The terminals and wires of the adjacent liquid crystal cells are approximately arranged in axially symmetrical fashion across the scribe line  90 . Thus the liquid crystal cell on the left will be explained as a representative example. The signal lines  50  extended from the gate circuit, not shown, are connected to inspection terminals  80  via IC driver terminals  41  formed in the IC driver mounting area  40 . The wires extending from the inspection terminals  80  are connected to the flexible wiring substrate terminals  70 . Furthermore, the static electricity countermeasure wires  20  extend from the flexible wiring substrate terminals  70 . 
         [0046]    In  FIG. 4 , there exist four wires in the left-hand liquid crystal cell while there are two flexible wiring substrate terminals  70  and two static electricity countermeasure wires  20 . Also in  FIG. 4 , there exist four signal lines  50  in the right-hand liquid crystal cell while there are two flexible wiring substrate terminals  70  and two static electricity countermeasure wires  20 . The reason the number of flexible wiring substrate terminals  70  and that of static electricity countermeasure wires  20  can be reduced in this manner is that the connecting wires  60  striding the scribe line  90  connect with the signal lines  50  that are arranged in axial symmetrical fashion across the scribe line  90 . 
         [0047]    In  FIG. 4 , the wires corresponding to the inspection terminals A and C are connected to the flexible wiring substrate terminals  70  in the left-hand liquid crystal cell, and the wires corresponding to the inspection terminals B and D are connected to the flexible wiring substrate terminals  70  in the right-hand liquid crystal cell. That is, in each liquid crystal cell, there are half as many flexible wiring substrate terminals  70  as the inspection terminals  50 . The static electricity countermeasure wires  20  extending from the flexible wiring substrate terminals  70  beyond the scribe line  90  are connected via static electricity countermeasure elements, not shown, to a static electricity countermeasure common line, not shown, outside the liquid crystal cells. 
         [0048]    According to the first embodiment, there may be only half as many flexible wiring substrate terminals  70  connected to the static electricity countermeasure wires  20  as the signal lines  50  that need to be protected against static electricity. Furthermore, the flexible wiring substrate terminals  70  in the adjacent liquid crystal cells can be arranged in axially symmetrical fashion across the scribe line  90 . This makes it possible to arrange each liquid crystal cells and each flexible wiring substrate in such a manner that their centers can approximately coincide with one another. 
       Second Embodiment 
       [0049]      FIG. 5  illustrates examples of the signal lines  50 , connecting wires  60 , flexible wiring substrate terminals  70 , and static electricity countermeasure wires  20  making up the second embodiment. Also in  FIG. 5 , four wires from the gate circuit, not shown, in each liquid crystal cell are extended to the IC driver terminals  41  in the IC driver mounting area  40 . The second embodiment is different from the first embodiment in  FIG. 4  in that there are three flexible wiring substrate terminals  70  in the left-hand liquid crystal cell while there is one flexible wiring substrate terminal  70  in the right-hand liquid crystal cell. 
         [0050]    In  FIG. 5 , the wires leading up to the inspection terminals  80  are the same as those in the first embodiment of  FIG. 4 . The difference is that the wires from the inspection terminals  80  up to the flexible wiring substrate terminals  70  are made different between the left-hand and the right-hand liquid crystal cells. This entails there being different numbers of flexible wiring substrate terminals  70  between the left-hand and the right-hand liquid crystal cells. In the right-hand liquid crystal cell, the terminals on the right-hand edge are the same as in the left-hand liquid crystal cell in  FIG. 5 . Conversely, in the left-hand liquid crystal cell, the terminals on the left-hand edge are the same as in the right-hand liquid crystal cell. Thus the total number of terminals is the same between the left-hand and the right-hand terminals. 
         [0051]    That is, the structure in  FIG. 5  is characterized in that the flexible wiring substrate terminals  70  are arranged lopsidedly on the right in each liquid crystal cell. It also follows that the flexible wiring substrate connected to each liquid crystal cell is positioned lopsidedly on the right relative to the liquid crystal cell. The second embodiment is effective where, depending on the structure of the product in which the liquid crystal cells are housed, the flexible wiring substrate should preferably be connected off-center of each liquid crystal cell. 
       Third Embodiment 
       [0052]      FIG. 6  illustrates examples of the signal lines  50 , connecting wires  60 , flexible wiring substrate terminals  70 , and static electricity countermeasure wires  20  making up the third embodiment. Also in  FIG. 6 , four wires from the gate circuit, not shown, in each liquid crystal cell are extended to the IC driver terminals  41  in the IC driver mounting area  40 . The difference between the third embodiment and the first embodiment in  FIG. 4  is that the signal lines  50  in the left-hand liquid crystal cell are directly connected to the inspection terminals  80  without the intervention of the IC driver terminals  41  in the IC driver mounting area  40 . The signal lines  50  in the right-hand liquid crystal cell are connected, as in the first embodiment of  FIG. 4 , to the IC driver terminals  41  in the IC driver mounting area  40  before being connected to the inspection terminals  80 . 
         [0053]    In the structure shown in  FIG. 6  where the connections with the wires and terminals leading up to the flexible wiring substrate terminals  70  differ on both sides of the scribe line  90 , the signal lines  50  of the adjacent liquid crystal cells may be connected via the connecting lines  60  so as to reduce the number of the flexible wiring substrate terminals  70 . This makes it possible to prevent the liquid crystal cells as well as the flexible wiring substrate from growing in size, as with the first or the second embodiment. 
         [0054]    While the above embodiments have been described in conjunction with liquid crystal display devices, the present invention can also be applied to other display devices such as organic EL display devices that have flexible wiring substrate terminals and need to be protected against static electricity.