Abstract:
An electrophoretic display device is disclosed. The electrophoretic display device includes a plurality of gate lines and a plurality of data lines formed to cross each other on a substrate and define a plurality of pixel regions, a plurality of thin film transistors connected to the respective gate lines and the respective data line on the substrate, an electrophoretic film disposed on the substrate and configured to contain charged particles which are driven in an electrophoresis, color filter patterns disposed on the electrophoretic film and used to realize colors, a protective film adhered with the electrophoretic film by an adhesive material and configured to protect the electrophoretic film, and a sealant formed by dispensing and hardening in a fluid phase on edges of the substrate. The protective film is configured to include an outwardly exposed portion from edges of the electrophoretic film, and a step coverage formed on the exposed portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. 119 to Korean Patent Application No. 10-2009-0070526, filed on Jul. 31, 2009, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Disclosure 
         [0003]    This disclosure relates to an electrophoretic display device, and more particularly to an electrophoretic display device adapted to provide a step coverage in a part of a protective film which is adhered with electrophoretic film using an adhesive material, thereby minimizing a defect where sealant is not injected during a side sealing process. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, electrophoretic display devices (EPDs) are flat display devices, which can display images using electrophoresis. These devices have features such as superior flexibility and portability as well as light weight. The electrophoresis allows charged particles within an electric field to move toward an anode or a cathode. 
         [0006]    EPDs include a thin film transistor array formed on a thin base film which can be bent like paper and plastic. The EPDs drive electrophoretic drift particles using a vertical electric field between pixel and common electrodes within the thin film transistor array. Such EPDs have been anticipated as electric paper of the next generation. 
         [0007]      FIGS. 1A and 1B  are cross-sectional views showing schematically a part of a related art EPD. 
         [0008]    As shown in  FIG. 1A , a related art EPD includes a lower substrate  10  provided with a lower electrode (not shown), an upper substrate  12  provided with an upper electrode (not shown), and an electrophoretic film  14  provided with electrophoretic drift particles (not shown) and interposed between the lower and upper substrates  10  and  12 . The electrophoretic drift particles are driven by an electric field induced between the lower and upper electrodes. 
         [0009]    The EPDs further includes a sealant  16  formed between the lower and upper substrates  10  and  12 . The sealant  16  prevents moisture from intruding into the electrophoretic film  14 . The sealant  16  is formed through a process of dispensing a fluid sealant  16   a  on the lower substrate  10  using a dispenser shown in  FIG. 1B , and allowing the fluid sealant  16   a  to flow along a positive direction D 1  by a tensile force between the electrophoretic film  14  and the upper substrate  12 . 
         [0010]    The electrophoretic film  14  is configured to include a plurality of capsules (not shown) each containing charged pigment particles (not shown). Each of the capsules is configured to contain black pigment particles (not shown) reacting to a positive polarity voltage, white pigment particles (not shown) reacting to a negative polarity voltage, and solvent (not shown). 
         [0011]    Moreover, the EPD can include a protective film  20  attached to the electrophoretic film  14  using an adhesive material. The protective film  20  protects the spheric capsules within the electrophoretic film  14  and prevents them from moving. A total thickness of the electrophoretic film  14  and the adhesive material may correspond to about 196 μm. 
         [0012]    Such a related art EPD applies voltages to the lower and upper electrodes opposite to each other and induces a voltage difference between these electrodes. In accordance therewith, charged black and white pigment particles move toward opposite polarity electrodes, so that an image colored in black and white is viewed from users. 
         [0013]    Recently, EPDs employ a color filter array so as to realize a variety of colors. More specifically, EPDs with the color filter array is configured to further include color filter patterns formed on the electrophoretic film  14 . 
         [0014]    The electrophoretic film of the color EPD can be formed to have the same thickness as that of the normal EPD without the color filter patterns. In this case, a displacement difference (or deviation) is generated between the black and white particles included in the electrophoretic film when the black and white particles are driven. The displacement difference (or deviation) can cause an undesired image to be viewed from an user at the side direction of the EPD. 
         [0015]    To address the generation of the displacement difference, the electrophoretic film included in the color EPD is formed to have a minimized thickness. Actually, the electrophoretic film of the color EPD has a thickness of about 60 μm. The color EPD with the electrophoretic film of such a thickness can prevent the generation of the above displacement difference (or deviation). 
         [0016]    However, the thinned electrophoretic film causes step coverage in a protective film or a substrate, which is adhered to it, to be lowered. Moreover, the step coverage in the protective film or the substrate can lose uniformity due to fine alien substances attached to the protective film or the substrate. As such, a non-injection defect of sealant is caused during a process of forming a seal pattern on the outer-circumferential surface of the electrophoretic film. 
       BRIEF SUMMARY 
       [0017]    Accordingly, the present embodiments are directed to an EPD that substantially obviates one or more of problems due to the limitations and disadvantages of the related art. 
         [0018]    An object of the present embodiments is to provide an EPD that is adapted to include color filter patterns and realize desired images. 
         [0019]    Another object of the present embodiments is to provide an EPD that is adapted to provide a step coverage in a part of the protective film which is adhered with electrophoretic film using an adhesive material, thereby minimizing a defect where sealant is not injected during a side sealing process. 
         [0020]    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. 
         [0021]    According to one general aspect of the present embodiment, an EPD includes: a plurality of gate lines and a plurality of data lines formed to cross each other on a substrate and define a plurality of pixel regions; a plurality of thin film transistors connected to the respective gate lines and the respective data line on the substrate; an electrophoretic film disposed on the substrate and configured to contain charged particles which are driven in an electrophoresis; color filter patterns disposed on the electrophoretic film and used to realize colors; a protective film adhered with the electrophoretic film by an adhesive material and configured to protect the electrophoretic film; and a sealant formed by dispensing and hardening in a fluid phase on edges of the substrate. The protective film is configured to include an outwardly exposed portion from edges of the electrophoretic film, and a step coverage formed on the exposed portion. 
         [0022]    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 
         [0023]    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. 
           [0000]    In the drawings: 
           [0024]      FIGS. 1A and 1B  are cross-sectional views showing schematically a part of a related art EPD; 
           [0025]      FIG. 2  is a planar view showing schematically an EPD according to an embodiment of the present disclosure; 
           [0026]      FIG. 3  is a cross-sectional view showing an EPD taken along a line I-I′ of  FIG. 2 ; and 
           [0027]      FIG. 4  is a cross-sectional view showing protective and electrophoretic films adhered by an adhesive material shown in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    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. 
         [0029]      FIG. 2  is a planar view showing schematically an EPD according to an embodiment of the present disclosure.  FIG. 3  is a cross-sectional view showing an EPD taken along a line I-I′ of  FIG. 2 . Referring to  FIGS. 2 and 3 , an EPD according to an embodiment of the present disclosure includes a lower array unit  160  and an upper array unit  180 . 
         [0030]    The lower array unit  160  includes gate and data lines (not shown) formed to cross each other in the center of a gate insulation film  113  on a lower substrate  110 , a thin film transistor TFT formed at each intersection of the gate and data lines, and a pixel electrode  121  formed on each cell region which is defined by the crossing gate and data lines. The lower substrate  110  may be formed of one material among a flexible plastic, an easily bendable base film, a flexible metal, and the like. 
         [0031]    The thin film transistor TFT includes a gate electrode  111  receiving a gate voltage, a source electrode  117  connected to the data line, a drain electrode  119  connected to the pixel electrode  121 , and an active layer  115   a  formed to overlap the gate electrode  111  and form a channel between the source and drain electrodes  117  and  119 . The active layer  115   a  is formed to partially overlap the source electrode  117  and the drain electrode  119  in order to form the channel. The thin film transistor TFT further includes an ohmic contact layer  115   b  formed on the active layer  115   a . The ohmic contact layer  115   b  comes in ohmic contact with the source electrode  117  and the drain electrode  119 . The ohmic contact layer  115   b  together with the active layer  115   a  may configure a commercial semiconductor pattern  115 . 
         [0032]    The pixel electrode  121  electrically contacts the drain electrode  119  through a contact hole. The contact hole penetrates through a passivation (or protective) layer  131  and exposes the drain electrode  119 . The passivation layer  131  protects the thin film transistor TFT. 
         [0033]    The upper array unit  180  includes color filter patterns  127  and a protective film  120  formed on lower surfaces of the color filter patterns  127 , and an electrophoretic film  114  disposed under the protective film  120 . The upper array unit  180  can further include a common electrode (not shown). 
         [0034]    The electrophoretic film  114  is configured to include a plurality of capsules (not shown) each containing charged pigment particles. Each of the capsules is configured to contain black pigment particles (not shown) reacting to a positive polarity voltage, white pigment particles (not shown) reacting to a negative polarity voltage, and solvent (not shown). 
         [0035]    The protective film  120  protects the spheric capsules and prevents them from moving. Also, the protective film  120  is adhered with the electrophoretic film  114  by an adhesive material  123 . Furthermore, the protective film  120  includes a step coverage  129  formed on an outwardly exposed portion from the outer-circumferential surface of the electrophoretic film  114 . 
         [0036]    The EPD further includes a sealant  116  interposed between the lower and upper array units  160  and  180 . The sealant  116  prevents moisture from intruding into the inside of the EPD. The sealant  116  is formed through a dispensing process of dispensing a fluid sealant  116   a  at a designated location (i.e., the edges) on the sealant formation region of the lower array unit  160  using a dispenser, and a hardening process of curing the fluid sealant. 
         [0037]    The EPD with such a configuration applies voltages to the pixel electrode  121  and the common electrode (not shown) opposite to each other and induces a voltage difference between these electrodes. In accordance therewith, charged pigment particles move toward opposite polarity electrodes, so that an color image is viewed from users. 
         [0038]    The electrophoretic film  114  is adhered with the protective film  120  by the adhesive material  123 , as described above. The protective film  120  is larger than the electrophoretic film  114 . As such, the protective film  120  is exposed outwardly from the left and/or right outer-circumferential surface of the electrophoretic film  114 . The protective film  120  is configured to include a step coverage  129  formed on the exposed portion. The exposed portion of the protective film  120  provided with the step coverage has a thickness different from that of the rest protective film  120 . More specifically, the exposed portion of the protective film  120  provided with the step coverage  129  has a smaller thickness compared to the rest of the protective film  120  without the step coverage  129 . The step coverage  129  can be formed by mold-pressing the exposed portion of the protective film  120  which extends outwardly from the left and/or right outer-circumferential surface of the electrophoretic film  114 . In accordance therewith, the sealant  116  is formed on the exposed portion of the protective film  120  with the step coverage  129 . 
         [0039]      FIG. 4  is a cross-sectional view showing protective and electrophoretic films adhered by an adhesive material shown in  FIG. 3 . 
         [0040]    As shown in  FIGS. 3 and 4 , the protective film  120  adhered with the electrophoretic film by the adhesive material  123  provided with the step coverage  129  is formed on the outwardly exposed portion A from the right outer-circumferential surface of the electrophoretic film  114 . The step coverage  129  can be formed by partially cutting off both the adhesive material  123  and the protective film  120  through a mold press process. 
         [0041]    The EPD of the present embodiment realizes a variety of colors. As such, the thickness of the electrophoretic film  114  becomes thinner than that of the electrophoretic film included in the related art EPD which is unable to implement a color image. For example, if an electrophoretic film of the related art has a thickness of about 171 μm, the electrophoretic film  114  of the present embodiment may be made with a thickness D 1  of about 60 μm. 
         [0042]    The thinner electrophoretic film  114  prevents the generation of a displacement difference (or deviation) when a color image is displayed. As such, the picture quality of the EPD can be enhanced. On the other hand, a non-injection defect of a sealant to the outer-circumferential surface is caused. 
         [0043]    To address this matter, the step coverage  129  is formed on the outwardly exposed portion A of the protective film  120  from the right outer-circumferential surface of the electrophoretic film  114 , thereby preventing the sealant from not being injected to the right outer-circumferential surface of the electrophoretic film  114 . In this case, the adhesive material  123  is not coated on the exposed portion A of the protective film  120 . Moreover, the step coverage  129  can be formed in an inwardly recessed shape or in an inwardly inclined shape which goes from the right outer-circumferential surface of the electrophoretic film  114  to the inner side of the protective film  120 . 
         [0044]    The exposed portion A of the protective film  120  which is lowered inwardly in a thickness direction due to the step coverage  129  has a thickness D 3  of about 255 μm. The thickness D 2  of the rest B of the protective film  120  without the exposed portion A becomes about 280 μm. The thickness of the adhesive material  123  is about 25 μm. Accordingly, the height D 4  of the step coverage  129  becomes about 50 μm corresponding to a sum value which adds the thickness of the adhesive material  123  to a subtraction value which subtracts the thickness D 3  of the exposed portion A from the thickness D 2  of the rest B of the protective film  120 . Moreover, the thickness of the adhesive material  123  and the thickness of the exposed portion A of the protective film  120  can be adjusted according to the design specifications of the EDD. As such, the step coverage  129  can be formed to have a height range of about 40˜140 μm. 
         [0045]    A distance between the exposed portion A of the protective film  120  and the lower array unit ( 160  in  FIG. 3 ) which is placed under the electrophoretic film  114  becomes about 110 μm. The exposed portion A of the protective film  120  which is extended to the right direction of the electrophoretic film  114  has a width of about 0.7˜1.4 mm. As such, a top portion of the sealant  116  side-sealed on the exposed portion A of the protective film  120  also has a width of about 0.7˜1.4 mm. 
         [0046]    If the distance between the lower array unit  160  and the protective film  120  with the step coverage, i.e., the height of the side-sealed sealant  116 , becomes 100 μm or more, the non-injection defect of the sealant  116  formed on the exposed portion A of the protective film  120  can be prevented. More specifically, the distance between the lower array unit  160  and the protective film  120  with the step coverage is above 100 μm, the process of side-sealing the sealant  116  is not affected by alien substances attached on the protective film  120  and the lower array unit  160 . Accordingly, the non-injection defect of the sealant  116  can be prevented. 
         [0047]    As described above, the EPD according to an embodiment of the present disclosure, which includes color filter patterns for realizing colors, is provided with a constant step coverage in a part of the protective film extending outwardly from the edges of the electrophoretic film, thereby allowing the exposed portion of the protective film to become thinner. As such, the distance between the protective film and the lower array unit is enlarged in above 100 μm. Therefore, the non-injection defect of a sealant caused in the side-sealing process of forming the seal pattern on the exposed portion of the protective film can be prevented (or minimized). As a result, the reliability of the EPD can be enhanced. 
         [0048]    Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
         [0049]    Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.