Patent Publication Number: US-2012026072-A1

Title: Active device array substrate, display panel and repair method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 99125127, filed on Jul. 29, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an active device array substrate, a display panel, and a repair method. More particularly, the invention relates to an active device array substrate, a display panel, and a repair method capable of reducing resistance-capacitance (RC) loading during signal transmission and preventing short circuit caused by metallic particles. 
     2. Description of Related Art 
     In normal displays, bottom gate thin film transistors (TFT) have high parasitic capacitance (C gd  and C gs ), and therefore significant RC loading is often generated during signal transmission if the bottom gate TFT serves as the TFT in a driving circuit. 
     In most cases, the bottom gate TFT in the driving circuit is disposed on a coating path of a sealant. Hence, when the sealant is cured by ultraviolet light, the sealant cannot be completely cured due to the metal gate in the bottom gate TFT. 
     Besides, in the process of forming the driving circuit (including the bottom gate TFT), metallic particles are very much likely to be formed. If the metallic particles fall between the source and the drain, then the short circuit occurs. As such, devices cannot be fully or partially operated. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an active device array substrate capable of effectively reducing RC loading when signals are transmitted by a driving circuit. 
     The invention is further directed to a display panel capable of resolving an issue of incompletely curing a sealant caused by a metal gate in a driving circuit. 
     The invention is further directed to a repair method capable of removing short circuit phenomenon caused by metallic particles falling between a source and a drain of a driving circuit. 
     The invention provides an active device array substrate having a display region. The active device array substrate includes a substrate, a plurality of first signal lines, a plurality of second signal lines, a plurality of active devices, a plurality of pixel electrodes, a bus line, and a switch device. The first signal lines and the second signal lines are arranged on the substrate and interlaced with each other to define a plurality of pixel regions in the display region. The active devices are respectively disposed corresponding to the pixel regions and coupled to the first signal lines and the second signal lines. The pixel electrodes are respectively disposed in the pixel regions and coupled to the active devices. The bus line is disposed outside the display region. The switch device is disposed outside the display region. Besides, the switch device has a gate, a first electrode, and a second electrode. The gate is coupled to the bus line, and the first and second electrodes are located above the gate. The first electrode is coupled to a signal source, and the second electrode is coupled to one of the first signal lines. The first and second electrodes are comb-shaped, respectively. The first electrode includes a plurality of first fingers parallel to one another and a first connection portion connecting the first fingers. The second electrode includes a plurality of second fingers parallel to one another and a second connection portion connecting the second fingers. The first fingers and the second fingers are alternately arranged, and a portion of the first electrode is located outside the gate. 
     According to an embodiment of the invention, the first connection portion is, for example, located outside the gate. Each of the first fingers has a first end contiguously connected to the first connection portion, and the first ends are located outside the gate. 
     According to an embodiment of the invention, the second connection portion is, for example, located outside the gate. Each of the second fingers has a second end contiguously connected to the second connection portion, and the second ends are located outside the gate. 
     According to an embodiment of the invention, a portion of the second electrode is, for example, located outside the gate. 
     According to an embodiment of the invention, the bus line has a plurality of slits, for instance. 
     According to an embodiment of the invention, the slits are arranged along an extending direction of the bus line, for instance. 
     According to an embodiment of the invention, the first fingers are parallel to the second fingers. 
     The invention further provides a display panel including an active device array substrate, an opposite substrate, and a display medium layer. The active device array substrate has a display region. Besides, the active device array substrate includes a substrate, a plurality of active devices, a plurality of pixel electrodes, a bus line, and a switch device. The active devices are disposed in the display region. The pixel electrodes are disposed in the display region and respectively coupled to the active devices. The bus line is disposed outside the display region. The switch device is disposed outside the display region. Besides, the switch device has a gate, a first electrode, and a second electrode. The gate is coupled to the bus line, and the first and second electrodes are located above the gate. The first electrode is coupled to a signal source, and the second electrode is coupled to one of the active devices. The first and second electrodes are comb-shaped, respectively. The first electrode includes a plurality of first fingers parallel to one another and a first connection portion connecting the first fingers. The second electrode includes a plurality of second fingers parallel to one another and a second connection portion connecting the second fingers. The first fingers and the second fingers are alternately arranged, and a portion of the first electrode is located outside the gate. The opposite substrate is disposed opposite to the active device array substrate. The display medium layer is disposed between the active device array substrate and the opposite substrate. 
     According to an embodiment of the invention, the first connection portion is, for example, located outside the gate. Each of the first fingers has a first end contiguously connected to the first connection portion, and the first ends are located outside the gate. 
     According to an embodiment of the invention, the second connection portion is, for example, located outside the gate. Each of the second fingers has a second end contiguously connected to the second connection portion, and the second ends are located outside the gate. 
     According to an embodiment of the invention, a portion of the second electrode is, for example, located outside the gate. 
     According to an embodiment of the invention, the bus line has a plurality of slits, for instance. 
     According to an embodiment of the invention, the display panel further includes a sealant. At least one portion of the sealant is disposed on the bus line and located between the active device array substrate and the opposite substrate. 
     According to an embodiment of the invention, the slits are arranged along an extending direction of the bus line, for instance. 
     According to an embodiment of the invention, the first fingers are parallel to the second fingers. 
     The invention further provides a repair method for repairing an active device array substrate or a display panel having the active device array substrate. The active device array substrate has a display region. Besides, the active device array substrate includes a substrate, a plurality of first signal lines, a plurality of second signal lines, a plurality of active devices, a plurality of pixel electrodes, a bus line, and a switch device. The first signal lines and the second signal lines are arranged on the substrate and interlaced with each other to define a plurality of pixel regions in the display region. The active devices are respectively disposed corresponding to the pixel regions and coupled to the first signal lines and the second signal lines. The pixel electrodes are respectively disposed in the pixel regions and coupled to the active devices. The bus line is disposed outside the display region. The switch device is disposed outside the display region. Besides, the switch device has a gate, a first electrode, and a second electrode. The gate is coupled to the bus line, and the first and second electrodes are located above the gate. The first electrode is coupled to a signal source, and the second electrode is coupled to one of the first signal lines. The first and second electrodes are comb-shaped, respectively. The first electrode includes a plurality of first fingers parallel to one another and a first connection portion connecting the first fingers. The second electrode includes a plurality of second fingers parallel to one another and a second connection portion connecting the second fingers. The first fingers and the second fingers are alternately arranged. The first connection portion is located outside the gate. Each of the first fingers has a first end contiguously connected to the first connection portion, and the first ends are located outside the gate. In the repair method, when short circuit occurs between one of the first fingers and a corresponding one of the second fingers, the first end of the first finger encountering the short circuit is cut, such that the rest of the first finger encountering the short circuit is electrically insulated from the first connection portion and the other first fingers. 
     According to an embodiment of the invention, the second connection portion is located outside the gate, for example. Each of the second fingers has a second end contiguously connected to the second connection portion, and the second ends are located outside the gate. When the short circuit occurs between one of the first fingers and the corresponding one of the second fingers, the second end of the second finger encountering the short circuit is cut, such that the rest of the second finger encountering the short circuit is electrically insulated from the second connection portion and the other second fingers. 
     Based on the above, the first electrode and the second electrode of the switch device are comb-shaped in the invention. Besides, the first fingers of the first electrode and the second fingers of the second electrode are alternately arranged, such that the switch device of the driving circuit is considered to be constituted by a plurality of small TFTs connected in parallel. Therefore, when the metallic particles fall between the first and second electrodes and the short circuit occurs, the first end of the first finger and/or the second end of the second finger that encounters the short circuit can be cut to resolve the short circuit issue. 
     In addition, according to this invention, the bus line has a plurality of slits, and therefore RC loading between switch pulse (SW pulse) signals and other data signals can be mitigated effectively. 
     Moreover, since the bus line of the invention has a plurality of slits, the sealant can be cured by ultraviolet light passing through the slits. As such, the bus line and the switch device no longer make a great impact on curing the sealant, and the issue of incompletely curing the sealant can be resolved. 
     It is to be understood that both the foregoing general descriptions and the following detailed embodiments are exemplary and are, together with the accompanying drawings, intended to provide further explanation of technical features and advantages of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a schematic diagram illustrating circuits in an active device array substrate according to an embodiment of the invention. 
         FIG. 2  is a schematic top view illustrating a bus line and a switch device depicted in  FIG. 1 . 
         FIG. 3  is a schematic diagram illustrating circuits in the switch device depicted in  FIG. 2 . 
         FIG. 4  is a schematic cross-sectional view illustrating a display panel according to an embodiment of the invention. 
         FIG. 5  is a schematic top view of repairing the switch device depicted in  FIG. 2 . 
         FIG. 6  is a schematic diagram of repairing circuits in the switch device depicted in  FIG. 2 . 
         FIG. 7  is a schematic diagram illustrating circuits in an active device array substrate according to another embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a schematic diagram illustrating circuits in an active device array substrate according to an embodiment of the invention. For illustrative and descriptive purposes, only one scan line is depicted in  FIG. 1 , while there are actually a plurality of scan lines in the active device array substrate. As indicated in  FIG. 1 , the active device array substrate has a display region  100 . Besides, the active device array substrate includes a substrate, first signal lines, second signal lines, active devices  106 , pixel electrodes (not shown), a bus line  108 , and a switch device  110 . The substrate is depicted in  FIG. 2  and will be described later. In this embodiment, the first signal lines are scan lines  102 , and the second signal lines are data lines  104 . 
     The scan lines  102  and the data lines  104  are arranged on the substrate and interlaced with each other to define a plurality of pixel regions  100   a  in the display region  100 . The active devices  106  are disposed corresponding to the pixel regions  100   a  and coupled to the scan lines  102  and the data lines  104 . The pixel electrodes are respectively disposed in the pixel regions  100   a  and coupled to the active devices  106 . To be more specific, the active devices  106  are the well-known TFTs, for instance. The gates of the TFTs are coupled to the scan lines  102 . The sources of the TFTs are coupled to the data lines  104 . The drains of the TFTs are coupled to the pixel electrodes. In addition, the pixel electrodes in the active device array substrate, the common electrode in the opposite substrate, and the display medium layer sandwiched between the active device array substrate and the opposite substrate together form the capacitor C. The opposite substrate and the display medium layer are described later with reference to  FIG. 4 . 
     The bus line  108  and the switch device  110  are disposed outside the display region  100 . Here, the bus line  108  and the switch device  110  together form the driving circuit for driving the active devices  106 . In  FIG. 1 , three bus lines  108  are depicted, which should not be construed as a limitation to this invention. 
     The bus line  108  and the switch device  110  are elaborated hereinafter with reference to  FIG. 2 . 
       FIG. 2  is a schematic top view illustrating the bus line and the switch device depicted in  FIG. 1 . As indicated in  FIG. 2 , the switch device  110  is disposed on the substrate  10 . The substrate  10  is, for example, a glass substrate. The switch device  110  has a gate  112 , a first electrode  114 , and a second electrode  116 . The gate  112  is coupled to the bus line  108 . In this embodiment, the gate  112  and the bus line  108  are in the same metal layer. The first electrode  114  and the second electrode  116  respectively acting as the source and the drain are located above the gate  112 . In an alternative embodiment, the first electrode  114  and the second electrode  116  can also serve as the drain and the source, respectively. An active layer  118  acting as a channel is located between the gate  112  and the first and second electrodes  114  and  116 . The first electrode  114  is coupled to an external signal source (not shown), and the second electrode  116  is coupled to the data lines  104 . 
     The first and second electrodes  114  and  116  are comb-shaped, respectively. In particular, the first electrode  114  includes first fingers  114   a  parallel to one another and a first connection portion  114   b  connected to the first fingers  114   a . The second electrode  116  includes second fingers  116   a  parallel to one another and a second connection portion  116   b  connected to the second fingers  116   a . The first fingers  114   a  and the second fingers  116   a  are alternately arranged. In this embodiment, the first fingers  114   a  are, for instance, parallel to the second fingers  116   a , and a portion of the first electrode  114  is located outside the gate  112 . Namely, the projection of the first electrode  114  on the substrate  10  is partially located outside the projection of the gate  112  on the substrate  10 . In detail, the first connection portion  114   b  is located outside the gate  112 . Additionally, each of the first fingers  114   a  has a first end  114   c  contiguously connected to the first connection portion  114   b , and the first ends  114   c  are located outside the gate  112 . 
     In this embodiment, the first ends  114   c  and the first connection portion  114   b  of the first electrode  114  are located outside the gate  112 , and the second ends  116   c  and the second connection portion  116   b  of the second electrode  116  are located above the gate  112 . However, in other embodiments of the invention, the second connection portion  116   b  of the second electrode  116  and the second ends  116   c  (contiguously connected to the second connection portion  116   b ) of the second fingers  116   a  can be located outside the gate  112 , while the first ends  114   c  and the first connection portion  114   b  of the first electrode  114  are located above the gate  112 . Alternatively, the first connection portion  114   b  of the first electrode  114 , the first ends  114   c , the second connection portion  116   b  of the second electrode  116 , and the second ends  116   c  are all located outside the gate  112 . 
     In this embodiment, the first and second electrodes  114  and  116  are comb-shaped, respectively, and the first fingers  114   a  of the first electrode  114  and the second fingers  116   a  of the second electrode  116  are alternately arranged. Hence, the switch device  110  of the driving circuit can be deemed as a plurality of small TFTs  110   a  connected in parallel.  FIG. 3  is a schematic diagram illustrating circuits in the switch device depicted in  FIG. 2 . As indicated in  FIG. 3 , the TFTs  110   a  are connected in parallel, so as to form the switch device  110 , and the gates of the TFTs  110   a , i.e. a portion of the gate  112 , are coupled to the bus line  108 . 
     Besides, the bus line  108  in this embodiment has a plurality of slits  108   a . The slits  108   a  are arranged along an extending direction of the bus line  108 , for instance. Since the bus line  108  has the slits  108   a , RC loading between SW pulse signals and other data signals can be effectively reduced. In other words, the bus line  108  having the slits  108   a  mitigates the RC loading during signal transmission. 
     Furthermore, the bus line  108  has the slits  108   a . Hence, even though the bus line  108  and the switch device  110  are located on the coating path of the sealant, the sealant can be cured by ultraviolet light passing through the slits  108   a . As such, the bus line  108  and the switch device  110  make the least impact on curing the sealant, and the issue of incompletely curing the sealant can be resolved. 
     According to the previous embodiment, the second electrode  116  of the switch device  110  is coupled to the data lines  104 . The second electrode  116  of the switch device  110  can also be coupled to the scan lines  102  in another embodiment of the invention, as indicated in  FIG. 7 . 
     A display panel having the active device array substrate depicted in  FIG. 1  is discussed below. 
       FIG. 4  is a schematic cross-sectional view illustrating a display panel according to an embodiment of the invention. As shown in  FIG. 4 , the display panel  40  includes an active device array substrate  400 , an opposite substrate  402 , and a display medium layer  404 . The active device array substrate  400  is identical to the active device array substrate depicted in  FIG. 1 . The active device array substrate  400  includes a substrate  400   a , an active device layer  400   b  located on the substrate  400   a , and pixel electrodes  400   c  located on the active device layer  400   b . The substrate  400   a  is, for example, a glass substrate. Besides, the bus line  108  and the switch device  110  as shown in  FIG. 1 ,  FIG. 2 , and  FIG. 3  are located on the substrate  400   a . The active device layer  400   b  includes the scan lines  102 , the data lines  104 , and the active devices  106  as indicated in  FIG. 1 ,  FIG. 2 , and  FIG. 3 . The opposite substrate  402  is disposed opposite to the active device array substrate  400 . Besides, the opposite substrate  402  is, for example, a color filter substrate and includes a substrate  402   a , a color filter layer  402   b  located on the substrate  402   a , and a common electrode  402   c  located on the color filter layer  402   b . The substrate  402   a  is, for example, a glass substrate. The display medium layer  404  is disposed between the opposite substrate  402  and the active device array substrate  400 . Here, the display medium layer  404  is, for instance, a liquid crystal layer, a plasma layer, an electro-phoretic display layer, or an organic light emitting device layer. The display panel  40  having the different display medium layer  404  can also be in different types, e.g. a liquid crystal display panel, a plasma display panel, an electro-phoretic display panel, or an organic light emitting display panel. 
     It should be mentioned that metallic particles are apt to be formed during fabrication of the driving circuit (including the bus line  108  and the switch device  110 ), and the metallic particles result in short circuit when falling between the source and the drain (i.e. the first electrode  114  and the second electrode  116 ). To resolve the short circuit issue, the first electrode  114  and the second electrode  116  need to be repaired. 
     The repair method of this invention is described hereinafter by taking the switch device of  FIG. 2  as an example. 
       FIG. 5  is a schematic top view of repairing the switch device depicted in  FIG. 2 .  FIG. 6  is a schematic diagram of repairing circuits in the switch device depicted in  FIG. 2 . With reference to  FIG. 5  and  FIG. 6 , when the metallic particles fall between the first and second electrodes  114  and  116 , short circuit occurs. In this embodiment, the metallic particles  600  fall between one of the first fingers  114   a  and a corresponding one of the second fingers  116   a , and therefore short circuit arises between the first and second electrodes  114  and  116 . At this time, the first end  114   c  of the first finger  114   a  encountering the short circuit is cut, such that the first finger  114   a  having the metallic particles  600  is separated (i.e. electrically insulated) from the first connection portion  114   b  and the other first fingers  114   a . Thereby, the short circuit issue between the first and second electrodes  114  and  116  can be resolved. The first end  114   c  is cut by performing a laser cutting process, for instance. 
     In this embodiment, metallic particles  600  are only located in one place between the first and second electrodes  114  and  116 , and thus only one first end  114   c  needs to be cut. However, in other embodiments of the invention, if the metallic particles  600  are in more than one places between the first and second electrodes  114  and  116 , the first ends  114   c  corresponding to the metallic particles  600  should be cut. 
     In another embodiment of the invention, if the second connection portion  116   b  of the second electrode  116  and the second ends  116   c  are located outside the gate  112 , and if the metallic particles  600  result in short circuit when falling between the first and second electrodes  114  and  116 , the second ends  116   c  are cut, such that the second fingers  116   a  having the metallic particles  600  are separated from the second connection portion  116   b  and the other second fingers  116   a.    
     In still another embodiment of the invention, if the first connection portion  114   b  of the first electrode  114 , the first ends  114   c , the second connection portion  116   b  of the second electrode  116 , and the second ends  116   c  are all located outside the gate  112 , and if the metallic particles  600  result in short circuit when falling between the first and second electrodes  114  and  116 , the first ends  114   c , the second ends  116   c , or both the first and second ends  114   c  and  116   c  can be cut. 
     That is to say, the switch device  110  is deemed to be formed by a plurality of small TFTs  110   a  connected in parallel in the above-mentioned repair process. Accordingly, when one of the TFTs  110   a  encounters short circuit, the TFT  110   a  encountering the short circuit is electrically insulated from the other TFTs  110   a  through performing the cutting process. Thereby, the short circuit issue can be resolved, and the other TFTs  110   a  can continue to operate. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the present invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of the present invention provided they fall within the scope of the following claims and their equivalents.