Patent Publication Number: US-8537105-B2

Title: Electro-phoretic display apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 99136006, filed Oct. 21, 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 generally relates to an electro-phoretic display apparatus. 
     2. Description of Related Art 
     With the increasing advancements in electronic technologies nowadays, the electronic paper has emerged as a next generational product popular for enabling a user to have a convenient reading experience. By using electronic paper technology, people no longer have to carry heavy and voluminous books or magazines in order to peruse a large quantity of information. Among the electronic paper technologies, the electro-phoretic display apparatus is a common and popular implementation. 
     Please refer to  FIG. 1 , which schematically illustrates a conventional electro-phoretic display apparatus  100 . The electro-phoretic display apparatus  100  includes a plurality of pixel units  110 - 140 , and the pixel units are arranged in an array between the scan lines GL 1 -GL 4  and the data lines DL 1 -DL 5 . The scan lines GL 1 -GL 4  and the data lines DL 1 -DL 5  are arranged perpendicular to each other. In addition to being connected to the corresponding scan lines and data lines, the pixel units  110 - 140  respectively receives an alternating current (AC) common voltage VCOM through the transferring lines TL 1 -TL 4  and TA 1 . On a panel layout of the conventional electro-phoretic display apparatus  100  where the pixel units  110  and  120  are connected to the first scan line GL 1 , only the common voltage VCOM correspondingly connected to the pixel units  110  and  120  is directly connected to a power source device (not drawn) providing the common voltage VCOM. On the other hand, the pixel units  130 - 140  connected to other scan lines GL 2  and GL 4  are connected with the power source device through a transparent conductive film (e.g., an indium tin oxide (ITO) film) from a farther distance. Accordingly, timing delays exist between the common voltage VCOM connected to the pixel units on each of the scan lines. 
     Please refer to  FIG. 2 , which illustrates a relational diagram of a pixel voltage of a pixel unit and the common voltage of the conventional electro-phoretic display apparatus. The pixel voltage on the pixel units of the first line Line 1  is synchronous with the common voltage VCOM, and the pixel voltage on the pixel units of the last line LineN has a timing delay with the common voltage VCOM, such as the timing delay shown in a region D 1  (when the display image remains the same). Moreover, since a turn on time tON and a turn off time tOFF for the electro-phoretic display apparatus are not the same, after successive appearances of the timing differences in the region D 1 , an image fading phenomenon is generated. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention is directed to an electro-phoretic display apparatus capable of effectively lowering the image fading phenomenon generated due to the delays of different pixel unit lines receiving the common voltage. 
     An embodiment of the invention provides an electro-phoretic display apparatus, including a plurality of pixel unit lines, a plurality of common voltage transferring lines, and a common voltage generator. The common voltage transferring lines respectively connects to the pixel unit lines, and the common voltage transferring lines extend and connect to a common line segment directly along a layout direction. The common voltage generator generates an alternating current (AC) common voltage, and provides the common voltage for directly electrically connecting to a connection point on the common line segment. Moreover, the transfer timing delays of transferring the common voltage from the connection point to the first common voltage transferring line and the last common voltage transferring line are the same. 
     According to an embodiment of the invention, the connection point is a center point of the common line segment. 
     According to an embodiment of the invention, the common voltage transferring lines are formed by using a transparent conductive film such as indium tin oxide (ITO). 
     According to an embodiment of the invention, each of the pixel unit lines includes a plurality of pixel units. 
     According to an embodiment of the invention, each of the pixel units includes a thin film transistor, a storage capacitor, and a display capacitor. The thin film transistor has a control terminal connected to a scan line, and a first terminal connected to a data line. The storage capacitor is serially connected between a second terminal of the thin film transistor and one of the common voltage transferring lines. The display capacitor is parallel connected with the storage capacitor. 
     In summary, according to an embodiment of the invention, the common voltage is directly provided to the pixel unit line disposed at the center of the layout, and the common voltage is transferred to different pixel unit lines through a plurality of common voltage transferring lines. Accordingly, the delay of the common voltage received by each of the pixel unit lines is evenly distributed, thereby effectively lowering the generation of the image fading phenomenon. 
     In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the 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 view of a conventional electro-phoretic display apparatus. 
         FIG. 2  is a relational diagram of a pixel voltage of a pixel unit and a common voltage of the conventional electro-phoretic display apparatus. 
         FIG. 3  is a schematic view of an electro-phoretic display apparatus according to an embodiment of the invention. 
         FIG. 3A  is a schematic view of a pixel unit according to an embodiment of the invention. 
         FIG. 4  is a waveform diagram of an electro-phoretic display apparatus according to an embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Please refer to  FIG. 3 , which is a schematic view of an electro-phoretic display apparatus  300  according to an embodiment of the invention. The electro-phoretic display apparatus  300  includes a plurality of pixel unit lines  10 - 40 , a plurality of common voltage transferring lines TL 1 -TL 4 , a common line segment TA 1 , and a common voltage generator  360 . The pixel unit lines  10 - 40  respectively includes a plurality of pixel units. (e.g., using the pixel unit line  10  for example, the pixel unit line  10  includes pixel units  310 - 320 , etc.) The common voltage transferring lines TL 1 -TL 4  are respectively connected to the pixel unit lines  10 - 40  and used for transferring an alternating current (AC) common voltage VCOM. The pixel unit lines  10 - 40  are respectively connected to the scan lines GL 1 -GL 4  and jointly connected to the data lines DL 1 -DL 5 . The data lines DL 1 -DL 5  are respectively connected to each of the pixel units (e.g., pixel units  310 - 330 ) in each of the pixel unit lines  10 - 40 . 
     Moreover, the common voltage transferring lines TL 1 -TL 4  extend and connect to the common line segment TA 1  directly along a layout direction TA 1 . Moreover, the common line segment TA 1  may also be used as a conductive transferring line to transfer the common voltage VCOM. 
     The common voltage generator  360  is used for generating the common voltage VCOM. Moreover, the common voltage generator  360  provides the common voltage VCOM for directly electrically connecting to a connection point MPT on the common line segment TA 1 . 
     It should be noted that, the afore-described common voltage transferring lines TL 1 -TL 4  and the common line segment TA 1  may be formed by using transparent conductive film materials, such that a display aperture ratio of the electro-phoretic display apparatus  300  is not affected, and the common voltage VCOM is effectively transferred. Therefore, the common voltage transferring lines TL 1 -TL 4  and the common line segment TA 1  have a non-negligible resistance value thereon. In other words, when the common voltage VCOM is being transferred on the common voltage transferring lines TL 1 -TL 4  and the common line segment TA 1 , a specific degree of timing delay occurs due to the resistance values thereon. 
     The connection point MPT is chosen so that a transferring timing delay DE 1  needed for transferring the common voltage VCOM from the connection point MPT to the first common voltage transferring line TL 1  can be the same as a transferring timing delay DE 2  needed for transferring the common voltage VCOM from the connection point MPT to the last common voltage transferring line TL 4 . Under the condition that the resistance values provided by each unit length of the common line segment TA 1  are the same (e.g., in other words, the common line segment TA 1  is a transferring line having uniform width and density), the connection point MPT is equal to a center point of the common line segment TA 1 . 
     From another perspective, when the common line segment TA 1  is not a transferring line having uniform width and density, then the resistance values provided by each unit length of the common line segment TA 1  are not the same. Accordingly, the connection point may not be chosen at the center point of the common line segment TA 1 . Rather, the most suitable connection point MPT may be obtained according a practical calculation, such that the transfer timing delays of transferring the common voltage VCOM from the connection point MPT to the first common voltage transferring line TL 1  and the last common voltage transferring line TL 4  are the same. 
     The common line segment TA 1  according to the present embodiment of the invention does not necessarily have to be a straight line as illustrated by  FIG. 3 . The common line segment TA 1  may also be bent according to a layout requirement of the display panel of the electro-phoretic display apparatus  300 , with emphasis on the common voltage VCOM being directly provided to the connection point MPT matching the above description. 
     Moreover, the common voltage generator  360  is used to generate the common voltage VCOM. Since the common voltage generator  360  of the present embodiment generates an AC common voltage VCOM, therefore, the common voltage generator  360  must rely on the scan timing of the electro-phoretic display apparatus  300  to provide a transition point of the common voltage VCOM. The implementation details of the common voltage generator  360  are well known to persons having ordinary skills in the art, and thus the description thereof are omitted herein. 
     Please refer to  FIG. 3A , which is a schematic view of the pixel unit  310  according to an embodiment of the invention. The pixel unit  310  includes a thin film transistor TFT 1 , a storage capacitor CS, and a display capacitor CD. The thin film transistor TFT 1  has a control terminal connected to the scan line G 1 , and a first terminal connected to the data line DL 1 . The storage capacitor CS is serially connected between a second terminal of the thin film transistor TFT 1  and the common voltage transferring line TL 1 . The display capacitor CD is parallel connected with the storage capacitor CS. 
     Please refer to  FIG. 4 , which is a waveform diagram of the electro-phoretic display apparatus  300  according to an embodiment of the invention. Since the common voltage VCOM is directly provided to the connection point MPT, where the transfer timing delays of transferring the common voltage VCOM from the connection point MPT to the first common voltage transferring line TL 1  and the last common voltage transferring line TL 4  are the same, therefore, the AC common voltage VCOM is evenly distributed on each of the pixel unit lines  310 - 340  due to the timing delays generated in transfer. The magnitude of a region D 2  of the timing delay D 2  of a pixel voltage V 310  on the pixel unit line  310  and the common voltage VCOM is the same as the magnitude of a region D 3  of the timing delay D 3  of a pixel voltage V 340  on the pixel unit line  340  and the common voltage VCOM. Moreover, the magnitude of the regions D 2  and D 3  is half of the region D 1  depicted in  FIG. 2 . 
     In view of the foregoing, according to an embodiment of the invention, the common voltage is directly provided to the connection point, where the transfer timing delays of transferring the common voltage from the connection point to the first common voltage transferring line and the last common voltage transferring line are the same. Accordingly, the AC common voltage is evenly distributed to each of the pixel unit lines due to the transfer timing delays generated on each of the transferring lines, thereby effectively reducing the effect the transfer timing delays have on the electro-phoretic display apparatus, and further lowering the occurrence of an image fading phenomenon. 
     Although the invention has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed descriptions.