Abstract:
A thin film transistor array substrate and an electronic ink display device are provided. The thin film transistor includes a substrate, scan lines, data lines, thin film transistors, and pixel electrodes. The substrate has plural pixel regions, and the scan lines and the data lines are disposed on the substrate. Additionally, each pixel region has at least two thin film transistors therein, each thin film transistor only corresponds to one scan line and one data line, and each scan line and each data line is corresponded to at least one thin film transistor respectively. Furthermore, each pixel region has a pixel electrode therein, and the pixel electrode covers and is electrically connected to the thin film transistors in the same pixel region. The thin film transistor array substrate and the electronic ink display device can provide superior repairing functions to pixel defects for improving productive yield.

Description:
RELATED APPLICATIONS 
   The present application is based on, and claims priority from, Taiwan Application Serial Number 95106245, filed Feb. 24, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The present invention relates to an active device array substrate and a display device. More particularly, the present invention relates to a thin film transistor array substrate and an E-ink display device. 
   2. Description of Related Art 
   E-ink display device was initially developed in 1970&#39;s. It is featured by a charged small ball with white color on one side and black color on the other side. The charged small ball rotates up and down to show different colors when the electrical field applied to small ball is changed. The second generation E-ink display device, developed in 1990&#39;s, is featured by a microcapsule which substitutes the conventional charged ball. The microcapsule is filled by color oil and charged white particles. By varying external electrical field allows white particles to move up or down. White color will be illustrated when white particles are moving up (getting close to reader) and the color of oil will be illustrated when white particles are moving down (getting away from reader). 
   In general, commercial E-ink display device comprises a front plane laminate (FPL) and a thin film transistor array substrate. Front plane laminate usually comprises a transparent cover, a transparent electrode layer and an E-ink material layer. The E-ink material layer comprises E-ink and supporting liquid. When the electrical field between each pixel electrode of the thin film transistor array substrate and the transparent cover of the front plane laminate is changed, E-ink will flow up or down to change optical property of each pixel. 
   Problems such as broken circuit and short circuit caused by contaminated particles and unexpected residual material are possible in manufacturing process which lead to low quality E-ink display device with dot defect or line defect. Therefore, it is very necessary to avoid such problem in order to improve the quality of E-ink display device. 
   SUMMARY OF THE INVENTION 
   An aspect of the present invention is to provide a thin film transistor array substrate which overcome conventional problems and improve yield rate. 
   In accordance with the foregoing and another aspects of the present invention, an E-ink display device utilizing the thin film transistor substrate mentioned above is provided to avoid conventional problem and improve quality. 
   In accordance with the foregoing and other aspects of the present invention, a thin film transistor array substrate is used in an E-ink display device. The thin film transistor array substrate of the invention comprises a substrate, a plurality of scan lines and a plurality of data lines, a plurality of thin film transistors and a plurality of pixel electrodes. Wherein, the substrate also comprises a plurality of pixel areas formed thereon. Moreover, al least two thin film transistors are formed in each pixel area. Each of the thin film transistors only corresponds to one scan line and data line. Each of the scan line and data line, at least, corresponds to one thin film transistor. One pixel electrode is formed in each pixel area. The pixel electrode covers and connects to the thin film transistor in the same pixel area. 
   According to a preferred embodiment, each pixel area contains, at least, two thin film transistors corresponding to two scan lines. The thin film transistor array substrate can further comprise a plurality of connecting lines formed in the pixel area to connect scan lines in the same pixel area. 
   According to a preferred embodiment, each pixel area contains four thin film transistors corresponding to two scan lines and two data lines. Moreover, the thin film transistor array substrate of the invention can further comprise a plurality of connecting lines formed in the pixel area to connect scan lines or data lines in the same pixel area. 
   This invention provides an E-ink display device comprising the thin film transistor array substrate, an E-ink material layer, a transparent electrode layer and a transparent cover, wherein the E-ink material layer is formed on the pixel electrodes of the E-ink transistor array substrate and the transparent cover is formed on the E-ink material layer. Furthermore, the transparent electrode layer is formed between the transparent cover and the E-ink material layer. 
   Accordingly, several thin film transistors are formed in one pixel area. Once if any defect is found, the pixel repairing technique can be used to fix the problem or even an automatic recovery, the damaged thin film transistor can be substituted by the spare one, can be performed without using the pixel repairing technique. Furthermore, the E-ink display device featured by its displaying property allows the pixel area to be completely covered by pixel electrode, so to increase the number of thin film transistor or circuit below the pixel electrode doesn&#39;t change the aperture ratio of the pixel. 
   It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 

   
     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. In the drawings, 
       FIG. 1  is a cross-sectional view of an E-ink display device of this invention, 
       FIG. 2  is a layout of thin film transistor array substrate of this invention, according to one preferred embodiment of this invention, 
       FIG. 3  is a cross-sectional view along A-A′ in  FIG. 2 , 
       FIG. 4  is a layout of thin film transistor array substrate of this invention, according to another preferred embodiment of this invention, 
       FIG. 5  is a layout of thin film transistor array substrate of this invention, according to another preferred embodiment of this invention, and 
       FIG. 6  is a layout of thin film transistor array substrate of this invention, according to another preferred embodiment of this invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIG. 1 ,  FIG. 1  is a cross-sectional view of an E-ink display device of this invention, E-ink display device  100  comprises a thin film transistor array substrate  110 , a transparent cover  120 , an E-ink material layer  130  and a transparent electrode layer  140 . The material used in the transparent cover  120  is, for example, polyethylene terephthalate (PET) or other types of plastic material. The transparent electrode layer  140  made of indium zinc oxide (IZO) or other transparent conducting materials is formed on the transparent cover  120 . The E-ink material layer  130  is formed between the transparent electrode layer  140  and the pixel electrode  112  of the thin film transistor array substrate  110 . The optical property of each pixel in the E-ink display device may be modified by changing the electric field between the pixel electrode  112  and the transparent electrode layer  140   
   The solution provided by this invention to solve defect problem is to form more than two thin film transistors in one pixel area so the yield rate can be increased. The layout and pixel structure of thin film transistor in this invention will be disclosed and several preferred embodiments is also discussed. 
   Please refer to  FIG. 2  and  FIG. 3 ,  FIG. 2  is a layout of thin film transistor array substrate of this invention, according to one preferred embodiment of this invention, and  FIG. 3  is a cross-sectional view along A-A′ in  FIG. 2 . Referred is made to  FIG. 2 , a plurality of scan lines  212   a ,  212   b  and a plurality of data lines  214  are formed on substrate  210 . The substrate  210  is divided into several pixel areas  210   a  containing a first scan line  212   a , a second scan line  212   b  and a data line  214  passing through every pixel area  210   a.    
   A first thin film transistor  216   a  and a second thin film transistor  216   b  are formed on every pixel area  210   a . The first thin film transistor  216   a  is triggered by the first scan line  212   a , the second thin film transistor  216   b  is triggered by the second scan line  212   b . In this preferred embodiment, The first thin film transistor  216   a  and the second thin film transistor  216   b  are, for example, dual gate thin film transistors with minimum leakage current between source and drain so transistors  216   a ,  216   b  with good electric property can be expected. However, the first thin film transistor  216   a  and the second thin film transistor  216   b  may be other types of thin film transistors (for example, single gate thin film transistor) in other preferred embodiments. 
   Please refer to  FIG. 2  and  FIG. 3 , a pixel electrode  218  is formed on every pixel area  210   a  and connected downward to the first thin film transistor  216   a  and the second thin film transistor  216   b.    
   The pixel area  210   a  including the first thin film transistor  216   a  and the second thin film transistor  216   b  is completely covered by the pixel electrode  218 , so the aperture ratio of the pixel will not be influenced by the number of thin film transistor or circuit. In this preferred embodiment, the pixel electrode can be made of transparent conducting material or metallic material such as indium tin oxide (ITO) and indium zinc (IZO). 
   When the thin film transistor array substrate mentioned above is in operation. For example, same driving signal is transmitted to the first scan line  212   a  and the second scan line  212   b  in the same pixel to activate their corresponded first thin film transistor  216   a  and second thin film transistor  216   b , respectively. A displaying voltage from the data line  214  is then input into the pixel electrode  218  connected to transistors  216   a ,  216   b  through the data line, the first thin film transistor  216   a  and the second thin film transistor  216   b . Pigment of the E-ink material layer  230  is able to move in the direction of electric field between the pixel electrode  218  and the transparent electrode layer  240  of the transparent cover  220 . Therefore, colors can be displayed in each pixel of the E-ink display device by controlling the electric field. 
   Whatever has to be noticed is there are two thin film transistors  216   a ,  216   b  and two corresponding scan line  212   a ,  212   b  in every pixel area  210   a . Once if the two scan lines  212   a ,  212   b  or the two thin film transistors  216   a ,  216   b  are damaged, repairing technique such as laser cutting or laser welding can be used to fix the problem. Furthermore, if any of the two sets (thin film transistor  216   a  and scan line  212   a  or thin film transistor  216   a  and scan line  212   a ) is damaged, pixel still function normally without applying any conventional repairing to achieve automatic recovery results. 
   In addition, in order to obtain more efficient repairing, a connecting line  219  connected to the first scan line  212   a  and the second scan line  212   b  is formed in every pixel area  210   a  in this embodiment. Once if any of the scan lines  212   a ,  212   b  is broken, the scan line  212   a  and  212   b  of the next pixel can still receive driving signal. 
   In addition to the preferred embodiment mentioned above. More than two data lines can be formed in one pixel area. Different thin film transistors are connected to different data lines.  FIG. 4  is a layout of thin film transistor array substrate of this invention, according to another preferred embodiment of this invention. Structures similar to previously disclosed embodiment is not discussed again. 
   Referring is made to  FIG. 4 , in this preferred embodiment, every pixel area  410   a  is passed through by, for example, a scan line  412 , a first data line  414   a  and a second data line  314   b . A first thin film transistor  416   a  and a second thin film transistor  416   b  are formed in every pixel area  410   a . The first thin film transistor  416   a  and the second thin film transistor  416   b  are both activated by the scan line  412 . Similarly, the first thin film transistor  416   a  and the second thin film transistor  416   b  can be dual gate thin film transistor or other types of thin film transistors. 
   As illustrated in  FIG. 4 , a pixel electrode  418  connected to the first thin film transistor  416   a  and the second thin film transistor  416   b  is formed in every pixel area  410   a . The pixel area  410   a  is completely covered by the pixel electrode  418 . The pixel electrode can be made of transparent conducting material or metallic material such as indium tin oxide (ITO) and indium zinc (IZO). When the thin film transistor array substrate is in operation, driving signal is transmitted to the scan line  412  to activate the first thin film transistor  416   a  and the second thin film transistor  416   b , respectively. A displaying voltage from the first data line  414   a  or/and the second data line  414   b  is input into the pixel electrodes  418  through the first thin film transistor  416   a  or/and the second thin film transistor  416   b , respectively. 
   According to the preferred embodiment, the defects on the thin film transistors  416   a ,  416   b  and/or data lines  414   a ,  414   b  may be repaired by conventional repairing technique or may be automatically recovered. Furthermore, the first data line  414   a  and the second data line  414   b  in every pixel area  410   a  can be connected by a connecting line  419  to improve reliability of the thin film transistor array substrate. 
     FIG. 5  is a layout of thin film transistor array substrate of this invention, according to another preferred embodiment of this invention, more than two scan lines and more than two data lines are formed on the same pixel area in the preferred embodiment in order to repair any possible defect on the scan line, data line and thin film transistor. As illustrated in  FIG. 5 , each pixel area  510   a  comprises a first thin film transistor  516   a , a second thin film transistor  516   b , a first scan line  512   a , a second scan line  512   b , a first data line  514   a  and a second data line  514   b . The first thin film transistor  516   a  is activated by the first scan line  512   a  and the second thin film transistor  516   b  is activated by the second scan line  512   b . Furthermore, the first thin film transistor  516   a  and the second thin film transistor  516   b  can be, for example, dual gate thin film transistor or other types of thin film transistors. 
   Please refer to  FIG. 5 , a pixel electrode  518  connected to the first thin film transistor  516   a  and the second thin film transistor  516   b . The pixel area  510   a  is completely covered by the pixel electrode  518 . The pixel electrode can be made of transparent conducting material or metallic material such as indium tin oxide (ITO) and indium zinc (IZO). When the thin film transistor array substrate is in operation, same driving signal is transmitted from the first scan line  512   a  and the second scan line  512   b  to activate the first thin film transistor  516   a  and the second thin film transistor  516   b , respectively. A displaying voltage from the first data line  514   a  and/or the second data line  514   b  is input into the pixel electrode  518  through the first thin film transistor  516   a  and/or the second thin film transistor  516   b.    
   Similarly, connecting line (not illustrated in  FIG. 5 ) can also be formed on the pixel area  510   a  to connect scan lines  512   a ,  512   b  or data line  514   a ,  514   b  in this preferred embodiment. According to the preferred embodiment of the thin film transistor array substrate in this invention, the defects on the thin film transistors  516   a ,  516   b , scan lines  512   a ,  512   b  and/or data lines  514   a ,  514   b  may be repaired by conventional repairing technique or may be automatically recovered. 
   Whatever has to be noticed is that two sets of thin film transistors, scan lines or data lines are used to illustrate above preferred embodiments of this invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the number and arrangement of transistors, scan lines, data lines, connecting lines in order to reach the best layout. 
   For instance, this invention can be a layout of thin film transistor array substrate illustrated in  FIG. 6 . Four thin film transistors accompanied by two scan lines and two data lines can be formed on one pixel area to repair any possible defect on the scan lines, data lines and thin film transistors. As illustrated in  FIG. 6 , every pixel area  610   a  comprises a first thin film transistor  616   a , a second thin film transistor  616   b , a third thin film transistor  616   c , a forth thin film transistor  616   d , a first scan line  612   a , a second scan line  612   b , a first data line  614   a  and a second data line  614   b . The first thin film transistor  616   a  and the forth thin film transistor  616   d  are activated by the first scan line  612   a , the second thin film transistor  616   b  and the third thin film transistor  616   c  are activated by the second scan line  612   b . In addition, thin film transistors  616   a ˜ 616   d  can be dual gate thin film transistor or other types of thin film transistors. 
   Please refer to  FIG. 6 , a pixel electrode  618  connected to the thin film transistors  616   a ˜ 616   d , the pixel area  610   a  may be completely covered by the pixel electrode  618 . The pixel electrode can be made of transparent conducting material or metallic material such as indium tin oxide (ITO) and indium zinc (IZO). When the thin film transistor array substrate is in operation, same driving signal is transmitted from scan lines  612   a  and  612   b  to activate the thin film transistors  616   a ˜ 606   d , respectively. A displaying voltage from the data lines  614   a  and/or  614   b  is input into the pixel electrode  618  through the thin film transistors  616   a ,  616   b  and/or  616   c ,  606   d . Similarly, connecting line (not illustrated in  FIG. 5 ) can also be formed on the pixel area  610   a  to connect scan lines  612   a ,  612   b  or data line  614   a ,  614   b  in this preferred embodiment. 
   Accordingly, the thin film transistor of this invention has featuring characteristics and advantages: 
   1. Several thin film transistors, scan lines and data lines are formed in one pixel area. The repairing technique can be used to repair the defect or the defect can be automatically recovered once if any defect is found, so the yield rate can be improved. 
   2. Several scan lines and data lines in the same pixel can be connected to improve reliability. 
   3. The pixel area is completely covered by the pixel electrode, so the aperture ratio of the pixel will not be influenced by the number of thin film transistors or circuits underneath the electrode. Even the repairing technique can be applied to obtain better displaying quality. 
   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 invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.