Abstract:
An electrophoretic display (EPD) device adapted to prevent a dispensed fluid sealant from moving toward a non-active area is disclosed. The EPD device includes: a first substrate configured to include a flexible plate divided into an active area and a non-active area; a thin film transistor array formed on the active area of the plate; a second substrate opposite to the first substrate; an electrophoretic film, between the first and second substrates, configured to contain charged particles driven depending on electrophoresis; a sealant, between the first and second substrates, hardened from fluid state; a sealant block formed on a sealant formation region to prevent the fluid sealant from flowing into the non-active area before hardening of the fluid sealant, wherein the sealant block is configured to include a first dam, a second dam, and a furrow between the first and second dams.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2008-132730, filed on Dec. 23, 2008, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     This present invention relates to an electrophoretic display (EPD) device and a manufacturing method thereof, and more particularly to an electrophoretic display device adapted to prevent sealant from moving onto a non-active area, as well as a manufacturing method thereof. 
     2. Description of the Related Art 
     In general, electrophoretic display (EPD) devices are reflection type display devices which can repeatedly write and erase images and letters using electrophoresis. In other words, the EPDs allow charged particles scattered in a fluid substance to move according to an applied electric field, in order to display images or letters. 
     EPDs can be manufactured to be light weight and thin as well as to normally maintain display properties in a bent-state like paper. In addition, EPDs provide superior visual-perceptibility and portability compared to paper. In view of these points, EPDs have been highlighted as medium for paper substitution showing a yearly increment, and furthermore have been actively developed as flexible display devices. 
       FIG. 1A  is a cross-sectional view showing an EPD according to the related art. Referring to  FIG. 1A , a related art EPD includes a lower substrate  10  with a lower electrode (not shown), an upper substrate  12  with an upper electrode (not shown), and an electrophoretic film  14  interposed between the lower and upper substrates  10  and  12 . The electrophoretic film  14  includes electrophoretic suspension particles driven by a vertical electric field induced between the lower and upper electrodes. The lower and upper substrates  10  and  12  may be a flexible plate type of base substrate. 
     The EPD further includes a sealant  16  interposed between the lower and upper substrates  10  and  12 . The sealant  16  is formed to prevent moisture from intruding into the EPD. The sealant  16  is formed through a process of dispensing a fluid sealant on the lower substrate  10  using a dispenser  18  shown in  FIG. 1B , and allowing the fluid sealant  16   a  to flow along a direction D 1  by a tensile force between the electrophoretic film  14  and the upper substrate  12 . 
     However, the fluid sealant  16   a  dispensed on the flexible lower substrate  10  can flow not only along the positive direction D 1 , but also along a negative direction D 2 . The fluid sealant  16   a  flowing along the negative direction D 2  can reach a different area, such as a non-active area including a driver circuit loading region, beyond the sealant formation area. In this case, the fluid sealant  16   a  causes malfunction or breakdown for the driver circuit to be formed or installed on the driver circuit loading region. 
     To address the driver circuit malfunction or breakdown, a method of shifting the driver circuit toward the edge of the panel has been proposed. The shift of the driver circuit forces the panel to be enlarged. As the sealant is formed on an unnecessary area, the amount of the sealant also increases. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present embodiments are directed to an EPD that substantially obviates one or more problems due to the limitations and disadvantages of the related art, as well as a manufacturing method thereof. 
     An advantage of the embodiments is to provide an EPD that can prevent a dispensed fluid sealant from moving toward a non-active area, as well as a manufacturing method thereof. 
     Additional features and advantages of the embodiments will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the embodiments. The advantages of the embodiments will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     According to one general aspect of the present embodiment, an EPD includes: a first substrate configured to include a flexible plate divided into an active area and a non-active area; a thin film transistor array formed on the active area of the plate; a second substrate opposite to the first substrate; an electrophoretic film, between the first and second substrates, configured to contain charged particles driven depending on electrophoresis; a sealant, between the first and second substrates, hardened from fluid state; a sealant block formed on a sealant formation region to prevent the fluid sealant from flowing into the non-active area before hardening of the fluid sealant, wherein the sealant block is configured to include a first dam, a second dam, and a furrow between the first and second dams. 
     The sealant formation region is provided in the boundary portion between the active and non-active areas and the fluid sealant is dispensed on the sealant formation region adjacent to the active area. 
     The sealant block is formed on the sealant formation region adjacent to the non-active area. 
     An EPD manufacturing method according to another aspect of the present embodiment includes: preparing an lower plate divided into an active area and a non-active area; forming a gate electrode and a gate line on the active area of the lower plate; forming a gate insulation film on the entire surface of the lower plate including a sealant formation region and the active area; forming a semiconductor pattern and source/drain electrodes on the gate insulation film; forming a passivation film on the lower plate with the source/drain electrodes and patterning the passivation film, to provide a contact hole exposing the drain electrode; and forming a pixel electrode electrically connected to the drain electrode, wherein the passivation film is also formed on the sealant formation region, and the passivation film and the gate insulation film on the sealant formation region are patterned to provide first and second dams and a furrow during the patterning of the passivation film. 
     The first and second dams are provided on regions in which the passivation film and the gate insulation film remain after the patterning of the passivation film and the gate insulation film, and the furrow is provided on a region in which the passivation film and the gate insulation film are removed after the patterning of the passivation film and the gate insulation film. 
     The first and second dams are formed in a stacked layer of the gate insulation film and the passivation film. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. Nothing in this section should be taken as a limitation on those claims. Further aspects and advantages are discussed below in conjunction with the embodiments. It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the disclosure. In the drawings: 
         FIGS. 1A and 1B  are cross-sectional views showing an EPD according to the related art; 
         FIG. 2A  is a planar view showing an EPD according to an embodiment of the present disclosure; 
         FIG. 2B  is a cross-sectional view showing an EPD according to an embodiment of the present disclosure taken along the line I-I′ shown in  FIG. 2A ; 
         FIG. 2C  is a cross-sectional view showing an EPD according to another embodiment of the present disclosure taken along the line I-I′ shown in  FIG. 2A . 
         FIG. 3  is a cross-sectional view showing the state of a fluid sealant dispensed on an EPD according to an embodiment of the present disclosure; and 
         FIGS. 4A to 4C  are cross-sectional views showing the flowing state of a fluid sealant included in an EPD according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. These embodiments introduced hereinafter are provided as examples in order to convey their spirits to the ordinary skilled person in the art. Therefore, these embodiments might be embodied in a different shape, so are not limited to these embodiments described here. Also, the size and thickness of the device might be expressed to be exaggerated for the sake of convenience in the drawings. Wherever possible, the same reference numbers will be used throughout this disclosure including the drawings to refer to the same or like parts. 
     An EPD and a manufacturing method thereof according to an embodiment of the present disclosure will now be explained in detail referring to the attached drawings. 
       FIG. 2A  is a planar view showing an EPD according to an embodiment of the present disclosure.  FIG. 2B  is a cross-sectional view showing an EPD according to an embodiment of the present disclosure taken along the line I-I′ shown in  FIG. 2A .  FIG. 2C  is a cross-sectional view showing an EPD according to another embodiment of the present disclosure taken along the line I-I′ shown in  FIG. 2A . Referring to  FIGS. 2A and 2B , an EPD of the present embodiment includes a lower substrate  20 , an upper substrate  30 , and an electrophoretic film  90  interposed between the substrates  20  and  30 . The EPD is divided into an active area AA corresponding to part of the lower substrate  20  which overlaps the electrophoretic film  90 , and a non-active area NAA including the rest of the lower substrate  20 , except for a sealant formation region A. 
     The upper substrate  30  includes a common electrode  84  formed on an upper plate  82 . The upper plate  82  may be formed of a flexible material, such as a flexible plastic, an easily bendable base film, a flexible metal, and so on. 
     The electrophoretic film  90  is configured to include a plurality of capsules  92  each containing charged pigment particles, a lower protective layer  94  disposed under the capsules  92 , and an upper protective layer  96  on the capsules  92 . Each of the capsules  92  is configured to contain black pigment particles  92   a  reacting to a positive polarity voltage, white pigment particles  92   b  reacting to a negative polarity voltage, and solvent. The lower and upper protective layers  94  and  96  protect the capsules  92  and prevent them from moving. Such lower and upper protective layers  94  and  96  may be formed of either a flexible plastic, an easily bendable base film, or another similar material. 
     The lower substrate  20  includes gate and data lines (not shown) formed crossing each other in the center of a gate insulation film  44  on the active area of a lower plate  42 , a thin film transistor (TFT)  6  formed at an intersection of the gate and data lines, and a pixel electrode  18  formed on each pixel region which is defined by the crossing gate and data lines. The lower plate  42  may be formed of a flexible material, such as a flexible plastic, an easily bendable base film, a flexible metal, and the like. 
     The TFT  6  includes a gate electrode  8  receiving a gate voltage, a source electrode  10  connected the data line, a drain electrode  12  connected to the pixel electrode  18 , and an active layer overlapping the gate electrode  8  and forming a channel between the source and drain electrodes  10  and  12 . The active layer  14  is formed partially overlapping the source electrode  10  and the drain electrode  12  in order to form the channel. The TFT  6  further includes an ohmic contact layer  48  formed on the active layer  14 . The ohmic contact layer  48  comes in ohmic contact with the source electrode  10  and the drain electrode  12 . The ohmic contact layer  48  together with the active layer  14  may configure a semiconductor pattern  45 . 
     The pixel electrode  18  electrically contacts the drain electrode  12  through a contact hole  17 . The contact hole  17  penetrates through a passivation (or protective) film  50  and exposes the drain electrode  12 . The passivation film  50  protects the TFT  6 . 
     The lower substrate  20  formed in such a structure is combined with the electrophoretic film  90  by an adhesive. 
     The EPD further includes a sealant  100  interposed between the lower and upper substrates  20  and  30 , and a sealant block disposed on the sealant formation region, i.e., at the boundary portion between the active and non-active areas AA and NAA. The sealant  100  prevents moisture from intruding into the inside of the EPD. The sealant block controls the flowing of the sealant  100  during the sealant formation process. 
     The sealant  100  is formed through a dispensing process of dispensing a fluid sealant  100   a  at a designated location on the sealant formation region A of the lower substrate  20  using a dispenser  28  shown in  FIG. 3 , and a hardening process of curing the fluid sealant  100   a . The designated location on the sealant formation region A is designed to come more close to the active area AA, while the sealant block controlling the flowing of the fluid sealant  100   a  is formed closely to the non-active area NAA. 
     More specifically, the fluid sealant  100  prior to hardening can flow not only toward the active area AA but also toward the non-active area NAA due to the bending property of the lower plate  42  which is included in the lower substrate  20 . In order to prevent the fluid sealant  100   a  from flowing into the non-active area NAA, the sealant block is formed on the sealant formation region A close to the boundary portion of the non-active area NAA. Such a sealant block includes a first dam  102   a , a furrow  104 , and a second dam  102   b  which can be arranged in order as shown in  FIG. 3 . 
     To prevent the fluid sealant  100   a  from flowing into the non-active area NAA by the sealant block will now be explained in detail. 
     The fluid sealant  100   a  dispensed on the lower substrate  20  shown in  FIG. 3  flows toward the active area AA and the non-active area NAA, as shown in  FIGS. 4A to 4C . The fluid sealant  100   a  moving toward the active area AA fills an opening surrounded by the lower substrate  20 , the upper substrate  30 , and the electrophoretic film  90 . 
     Meanwhile, the fluid sealant  100   a  moving toward the non-active area NAA is primarily prevented from flowing into the furrow  104  due to tensile force generated on one edge of the first dam  102   a , as shown in  FIG. 4A . The fluid sealant  100   a  overflowing into the non-active area without being prevented by the first dam  102   a  is secondarily blocked from moving toward the second dam  102   b  due to tensile force generated in the other edge of the first dam  102   a , as shown in  FIG. 4B . Furthermore, the fluid sealant  100   a  moving toward the non-active area NAA despite the first dam  102   a  and the furrow  104  is thirdly blocked from flowing into the non-active area NAA due to tensile force generated on one edge of the second dam  102   b , as shown in  FIG. 4C . As such, the fluid sealant  100   a  is substantially prevented from flowing into the non-active area NAA by means of the first and second dams  102   a  and  102   b  and the furrow  104  formed on the sealant formation region A during the sealant formation process. 
     The first and second dams  102   a  and  102   b  and the furrow  104  prevent not only the fluid sealant  100   a  from moving toward the non-active area NAA, but also moisture from intruding into the active area AA. This results from the fact that the intrusion path of moisture into the active area AA passing the second dam  102   b , the furrow  104 , and the first dam  102   a  is longer than that of moisture intruding into the active area AA without passing the first and second dams  102   a  and  102   b  and the furrow  104 . In other words, the greater the length of the intrusion path of moisture, the more the intrusion probability of moisture is lowered, because external moisture can evaporate during intrusion. Accordingly, the first dam  102   a , the furrow  140 , and the second dam  102   b  can greatly prevent external moisture from intruding into the active area AA in comparison with a device without such barriers. 
     Method of manufacturing the lower and upper substrates  20  and  30  of the EPD in which such dams and furrow are formed will now be explained. The method will be described referring to  FIGS. 2B and 2C  below.  FIG. 2B  illustrates a lower substrate on which a double film dam is formed according to an embodiment of the present disclosure.  FIG. 2C  illustrates a lower substrate on which a single film dam is formed according to another embodiment of the present disclosure. 
     Firstly, a lower substrate  20  includes a gate electrode  8  and a gate line (not shown) which are provided by forming and patterning a metal film for the gate electrode and the gate line on a lower plate  42 , as shown in  FIGS. 2B and 2C . A gate insulation film  44  is formed on the entire surface of the lower plate  42  including the gate electrode  8  and the gate line. The gate insulation film  44  is formed of an insulation material such as silicon nitride. At this time, the gate insulation film  44  is formed not only on an active area AA, but also on a sealant formation region A, as shown in  FIG. 2B . Alternatively, the gate insulation film  44  can be formed on only the active area AA without the sealant formation region A, as shown in  FIG. 2C . 
     On the lower plate  42  with the gate insulation film  44 , a semiconductor layer pattern  45  including a stacked active layer  14  and ohmic contact layer  48 , source/drain electrodes  10  and  12 , and a data line (not shown) is provided by forming and patterning an amorphous silicon film, an amorphous dopant-silicon film, and a metal film for a data line on the lower plate  42 . In this case, the formation of the semiconductor layer pattern  45  and the source/drain electrodes can be completed either by forming and patterning the metal film after patterning of the amorphous silicon/dopant-silicon films, or by a unified process of patterning the amorphous silicon/dopant-silicon films and the metal film all at once. 
     Sequentially, a passivation (or protective) film  50  is formed on the lower plate  42  including the source/drain electrodes  10  and  12  and the data line. The passivation film  50  is patterned to form a contact hole  17  which exposes the drain electrode  12 . Such a passivation film  50  is formed of an organic insulation material including a material such as photoacryl or BCB. 
     In addition, when the passivation film  50  is formed on the active area AA, it is simultaneously formed on the sealant formation region A, as shown in  FIG. 2B . In this case, the passivation film  50  on the sealant formation region A is formed on the gate insulation film  44 . Alternatively, the passivation film  50  can be formed directly on the substrate  42  corresponding to the sealant formation region A, as shown in  FIG. 2C . In other words, the gate insulation film  44  does not exist under the passivation film  50  on the sealant formation region A. 
     The passivation film  50  and the gate insulation film  44  on the sealant formation region A shown in  FIG. 2B  are patterned all at once when the contact hole  17  is formed by patterning the passivation film  50  on the active area AA, thereby forming first and second dams  102   a  and  102   b  and a first furrow  104   a . After the patterning process of the passivation film  50 , the remaining double-film (or stacked layer) patterns consisting of the gate insulation film  44  and passivation film  50  become the first and second dams  102   a  and  102   b . A region between the double-film patterns, in which the passivation and gate insulation films  44  and  50  do not remain, becomes the first furrow  104   a . The height of the first and second dams  102   a  and  102   b  corresponds to the total height of the gate insulation film  44  and the passivation film  50 , because they are formed by patterning the stacked gate insulation film  44  and passivation film  50 . 
     On the other hand, the passivation film  50  on the sealant formation region A shown in  FIG. 2C  are patterned when the contact hole  17  is formed by patterning the passivation film  50  on the active area AA, thereby forming third and fourth dams  102   c  and  102   d  and a second furrow  104   b . In other words, after the patterning process of the passivation film  50 , the remaining single-film patterns consisting of the passivation film  50  become the third and fourth dams  102   c  and  102   d . A region between the single-film patterns, in which the passivation film does not remain, becomes the second furrow  104   b . The height of the third and fourth dams  102   c  and  102   d  corresponds to the height of the passivation film  50 , because they are formed by patterning the passivation film  50 . 
     Next, a pixel electrode  18  is provided by forming and patterning a transparent conductive film on the lower plate  42  including the contact hole  17 . The pixel electrode  18  is electrically connected to the drain electrode  12  via the contact hole  17 . 
     In these ways, the dams can be formed to include either a double-film consisting of the gate insulation film  44  and the passivation film  50  stacked as shown in  FIG. 2B , or a single-film having only the passivation film  50  as shown in  FIG. 2C . Although it is explained the structure that the dams are formed of the gate insulation film and/or the passivation film, the EPD of the present embodiment is not limited to these. In other words, any films formed on the active area AA can be used in the formation of the dams, instead of the gate insulation film and/or the passivation film. 
     A method of manufacturing an upper substrate of the EPD and an electrophoretic film combined with the upper substrate will now be explained referring to  FIG. 2A . 
     An upper substrate  30  includes a common electrode  84  below an upper plate  82 . The common electrode  84  is provided by forming a transparent conductive film below the upper plate  82 . The common electrode  84  of the upper plate  82  is bonded with an electrophoretic film  90 . 
     The electrophoretic film  90  is provided by positioning a lower protective layer  94  and an upper protective layer  96  under and on a plurality of capsules  92 . Each of the capsules  92  contains charged pigment particles. 
     In this way, although the sealant block is implemented in the arrangement of the first dam  102   a , the furrow  104 , and the second dam  102   b , the EPD of the present embodiment is not limited to this. The sealant block may consist of more than two dams, together with furrows between every two dams. For example, an EPD of the present embodiment can include a sealant block having another arrangement in which the first dam  102   a , the furrow  104 , and the second dam  102   b  are repeated at least twice. 
     As described above, the EPD and the manufacturing method thereof form the sealant block on the sealant formation region and prevent the dispensed fluid sealant on the lower plate from flowing into the non-active area. As such, the fluid sealant is not formed on an undesired region (or area) so that process efficiency is improved. Also, since the fluid sealant does not flow into the driver circuit loading region, a defect and/or malfunction in the driver circuit to be formed or installed in the following process can be substantially prevented. Furthermore, it is unnecessary to shift the driver circuit toward the edge of the panel, and thus the size increment of the panel can be avoided. In addition, external moisture intruding into the active area can be more effectively blocked as well. 
     Although the present disclosure has been limitedly explained regarding only the embodiments described above, it should be understood by the ordinary skilled person in the art that the present disclosure is not limited to these embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the present disclosure. Accordingly, the scope of the present disclosure shall be determined only by the appended claims and their equivalents.