Abstract:
A flat panel display and method of fabricating the same are disclosed. The flat panel display includes a first substrate having a pixel region; a light-emitting element located on the pixel region; a second substrate located opposite the first substrate; and a sealant located between the first and second substrates to cover the light-emitting element. At least one of the first and second substrates includes a groove formed around at least a portion of the circumference surrounding the pixel region. When the first and second substrates are pressed together with the sealant between them, the sealant spreads, covering the light-emitting element, and at least partially filling the groove.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 11/100,137, filed Apr. 5, 2005, which claims priority to and the benefit of Korean Patent Application No. 2004-23893, filed Apr. 7, 2004, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a flat panel display and method of fabricating the same and, more particularly, to a flat panel display and method of fabricating the same including a sealant covering a light-emitting element. 
       BACKGROUND OF THE INVENTION 
       [0003]    An electroluminescence display, being a type of flat panel display, is an emissive display and has advantages of a wide viewing angle, good contrast and fast response speed. For these reasons, electroluminescence displays have attracted attention as the next generation of displays. An electroluminescence display includes a light-emitting element having an anode, a cathode, and an emission layer interposed between the anode and the cathode, and is classified as either an inorganic electroluminescence display or an organic electroluminescence display according to the type of the emission layer. 
         [0004]    In the organic electroluminescence display, the light-emitting element is susceptible to being damaged by exterior moisture. Therefore, in order to protect the light-emitting element from exterior moisture, various techniques for encapsulating the light-emitting element using an encapsulating substrate have been developed. One of the encapsulating technologies is a method of applying a sealant on a circumference of a region in which the light-emitting element is formed, and bonding the encapsulating substrate using the sealant as a bonding medium. However, since the sealant has a defined width, it is difficult to fully prevent moisture or oxygen from the exterior environment from penetrating the sealant. In order to improve this, a technique has been developed by which sealant is applied to the entire region in which the light-emitting element is formed. 
         [0005]      FIGS. 1   a  and  1   b  are cross-sectional views illustrating conventional methods of encapsulating an organic electroluminescence display. 
         [0006]    Referring to  FIG. 1A , a mother substrate  10  including a plurality of cell regions  10   a  and scribing lanes  10   b  defined by the cell regions  10   a  is provided. Each of the cell regions  10   a  includes a pixel region  10   aa  and a pad region (not shown) located in a predetermined region of the periphery of the pixel region  10   aa.  Then, light-emitting elements  25  are formed in the pixel regions  10   aa,  respectively. 
         [0007]    Meanwhile, an encapsulating substrate  50  is provided, and a sealant  40  is applied on a predetermined region of the encapsulating substrate  50 . The region where the sealant  40  is applied corresponds to the pixel region  10   aa  of the mother substrate  10 . Then, the encapsulating substrate  50  is disposed in a way such that the surface of the encapsulating substrate  50  to which the sealant has been applied faces the mother substrate  10 . 
         [0008]    Referring to  FIG. 1B , the encapsulating substrate  50  and the mother substrate  10  are bonded together by applying pressure. At this time, the sealant  40  may be squeezed out up to the circumference of the pixel region  10   aa,  as defined by the scribing lane  10   b  and the pad region by the pressure. 
         [0009]    Subsequently, the scribing lane  10   b  is scribed to separate the respective cells  10   a,  thereby manufacturing the organic electroluminescence display. In the scribing process, the sealant  40  squeezed out to the scribing lane  10   b  between adjacent cells  10   a  may cause adjacent cells to attach to each other, thereby causing a separation defect, i.e., a scribing defect between cells  10   a  adjacent to each other. In addition, an additional process step is required in order to remove the sealant  40  squeezed out to the pad region, i.e., the sealant  40  incorrectly formed on the pad region. 
         [0010]    In order to solve the problem, Korean Patent Application No. 2002-28714 discloses “Method of encapsulating OLED and OLED panel using the same.” According to the Korean Patent, the method of encapsulating OLED includes forming a partition wall by applying a first sealant to a region of an encapsulating substrate, wherein the region face a region enclosing a selected OLED of a plurality of OLEDs formed on a substrate, filling a second sealant in an opened space formed by the first sealant, bonding the encapsulating substrate and the substrate using the first and second sealants as mediums by applying pressure, and curing the first and second sealants to encapsulate the OLED. However, although the first sealant is formed of a high viscosity material, the method has a problem in that the first sealant may be squeezed out up to an outer periphery by the pressure for bonding the substrate and the encapsulating substrate. Therefore, the aforementioned problems may still occur. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention provides a method of encapsulating a flat panel display and flat panel display manufactured thereby, which is capable of readily controlling the region in which the sealant is formed. 
         [0012]    In an exemplary embodiment of the present invention, a flat panel display includes: a first substrate having a pixel region; a light-emitting element located on the pixel region; a second substrate opposite to the first substrate; and a sealant located between the first and second substrates to cover the light-emitting element. At least one substrate of the first and second substrates is provided with a groove formed along a circumference of the sealant for containing excess sealant. 
         [0013]    The second substrate may be a glass substrate or a plastic substrate. 
         [0014]    The groove may be formed along an entire circumference of the sealant. In one embodiment of the invention, the groove has a depth of between about 20 and about 500 μm. In another embodiment of the invention, the groove has a width of between about 0.1 and about 5 mm. 
         [0015]    The light-emitting element may include a first electrode, an emission layer and a second electrode, which are sequentially stacked on the substrate. The second electrode may be a transparent electrode. In addition, the sealant may be a transparent sealant. Furthermore, the sealant may be a thermosetting sealant or a UV light curing sealant. 
         [0016]    In one embodiment of the invention, the flat panel display also includes an optional moisture-absorbing layer located between the sealant and the second substrate. The moisture-absorbing layer may be a layer formed using an alkaline earth metal oxide. 
         [0017]    In another exemplary embodiment according to the present invention, a method of fabricating a flat panel display includes: providing a first substrate and a second substrate each having a pixel region; forming a light-emitting element on the pixel region of the first substrate; forming a first groove surrounding the pixel region of the first substrate and/or a second groove surrounding the pixel region of the second substrate; applying a sealant in a region defined by the groove of the second substrate; disposing the second substrate to direct the applied sealant toward the first substrate; and bonding the first and second substrates together by applying pressure. 
         [0018]    Forming the groove may be performed using methods such as etching, sandblasting or molding. 
         [0019]    In one embodiment, the method further includes, after bonding the first and second substrates, irradiating heat or UV light to the sealant through the first and/or second substrates in order to cure the sealant. Furthermore, the method may further include, after forming the light-emitting element, forming a passivation layer covering the light-emitting element on the first substrate. Meanwhile, the method may further include, before applying the sealant on the second substrate, forming a moisture-absorbing layer on the second substrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0020]    The above and other features of the present invention will be described in reference to certain exemplary embodiments thereof with reference to the attached drawings in which: 
           [0021]      FIGS. 1A and 1B  are cross-sectional views illustrating a conventional method of encapsulating an organic electroluminescence display; and 
           [0022]      FIGS. 2A to 2C  are cross-sectional views illustrating a method of fabricating a flat panel display in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0023]    Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
         [0024]      FIGS. 2A to 2C  are cross-sectional views illustrating a method of fabricating a flat panel display in accordance with an embodiment of the present invention. 
         [0025]    Referring to  FIG. 2A , a first substrate  100  having cell regions  100   c  and scribing lanes  100   s  located between the cell regions  100   c  is provided. Each of the cell regions  100   c  includes a pixel region  100   ca  and a pad region (not shown) located at a periphery of the pixel region  100   ca.  The first substrate  100  may be a glass, quartz or plastic substrate. 
         [0026]    At least one light-emitting element E is made on the respective pixel regions  100   ca.  The light-emitting element E is made by forming a first electrode  120  on the first substrate  100 , forming an emission layer  125  on the first electrode  120 , and then forming a second electrode  130  on the emission layer  125 . The emission layer  125  is preferably formed of an organic light-emitting material. In this case, before forming the emission layer  125 , a first charge injection layer and/or a first charge transport layer may be formed on the first electrode  120 . Furthermore, before forming the second electrode  130 , a second charge injection layer and/or a second charge transport layer may be formed on the emission layer  125 . Either or both of the first and second electrodes  120  and  130  may be formed of a transparent electrode. Optionally, one of the first and second electrodes is formed of a reflective electrode. 
         [0027]    Preferably, a passivation layer  140  covering the light-emitting element E is formed on the light-emitting element E. The passivation layer  140  may protect the light-emitting element E from physical or chemical stimulation of the exterior, and may be formed of an organic layer, an inorganic layer, or a composite layer thereof. 
         [0028]    While forming the first electrode  120  and/or the second electrode  130 , a pad electrode is formed on the pad region. The pad electrode is a terminal to be electrically connected to FPC (Flexible Printed Circuit film), COG (Chip On Glass) or COF (Chip On Film). 
         [0029]    Subsequently, a second substrate  150  is provided. The second substrate  150  may be a glass or plastic substrate. Grooves G are formed on predetermined regions of the first and second substrates  100 ,  150 . It should be noted that while grooves G are shown on both the first and second substrates  100 ,  150 , in other embodiments, a groove G may be formed on just a predetermined region of the first substrate  100 , or on just a predetermined region of the second substrate  150 . When the groove G is formed on the first substrate  100 , the groove G is formed in a region surrounding the pixel region  100   ca.  Similarly, when the groove G is formed on the second substrate  150 , the groove G is formed on a region corresponding to the region surrounding the pixel region  100   ca.  Preferably, the groove G is formed to fully surround the pixel region  100   ca.  The groove G may be formed using an etching, sandblasting, or molding method, but its formation is not limited to such methods. Furthermore, in one embodiment, the groove G is preferably formed to have a depth D between about 20 and about 500 μm. In another embodiment, the groove G is preferably formed to have a width W between about 0.1 and about 5 mm. 
         [0030]    A sealant  165  is applied to a region of the second substrate that corresponds to the pixel region  100   ca  of the first substrate  100 . For this embodiment, the region is also defined by the groove G of the second substrate  150 . Examples of suitable sealants  165  include thermosetting or UV light curing types of sealants. In one embodiment, the sealant  165  is a transparent sealant. Therefore, light emitted from the light-emitting element may be emitted to the exterior through the second substrate  150 . That is, a top emission flat panel display may be implemented. However, not limited thereto, it is also possible to implement a bottom emission type emitting light through the first substrate  100  or a double sided emission type emitting light through both the first and second substrates  100  and  150 . 
         [0031]    Before applying the sealant  165  on the second substrate  150 , in one embodiment, a moisture-absorbing layer  161  may be formed on the second substrate  150 . In yet another embodiment, the sealant  165  may contain a moisture-absorbing material. According to this embodiment, the moisture-absorbing material may be contained in the sealant  165  in a distributed manner, and the sealant  165  may function as a binder for the moisture-absorbing material. 
         [0032]    Examples of suitable materials for the moisture-absorbing layer  161  include alkaline earth metal oxides. Examples of alkaline earth metal oxides include calcium oxide and barium oxide. 
         [0033]    Referring to  FIG. 2B , the second substrate  150 , on which the sealant  165  is applied, is disposed to direct the applied sealant  165  toward the first substrate  100  when the first and second substrates  100  and  150  are pressed together, thereby bonding the first and second substrates  100  and  150  using the sealant  165  as a medium. At this time, the light-emitting element E of the pixel region  100   ca  is buried into the sealant  165 . That is, the sealant  165  covers the light-emitting element E. At the same time, the sealant  165  is squeezed out of the pixel region  100   ca  by the pressure. However, the squeezed sealant  165  meets the groove G to stop its outward movement as the excess sealant fills the groove G. Therefore, it is possible to prevent the sealant  165  from extending past the scribing lane  100   s  or the pad region. In other words, the flow of the sealant  165  may be readily controlled by the groove G. Therefore, the need for removing sealant incorrectly formed on the pad region may be omitted, and it is possible to prevent scribing defects from occurring due to the sealant incorrectly forming on the scribing lane  100   s.    
         [0034]    According to one embodiment, the groove G is located along at least a portion of a circumference of the sealant  165 . Preferably, the groove G is located along the entire circumference of the sealant  165 . Forming the groove G along the entire circumference of the sealant  165  may be implemented by forming the groove G to entirely surround the pixel region  100   ca.    
         [0035]    In one embodiment, the pressing of the second and first substrates  150  and  100  is performed in vacuum or inert gas atmosphere. This helps to prevent oxygen or moisture from penetrating into the light-emitting element E. 
         [0036]    Subsequently, the sealant  165  may be cured such as by irradiating heat or UV light to the first and second substrates  100  and  150 . 
         [0037]    Referring to  FIG. 2C , the cells are separated by applying physical force to the scribing lanes  100   s  of the first and second substrates  100  and  150 . Each of the separated cells is defined as one flat panel display. 
         [0038]    As can be seen from the foregoing, in a method of fabricating a flat panel display, the flow of sealant during the sealing process is readily controlled using one or more grooves formed on a predetermined region or regions of one or both of the first and second substrates to contain excess sealant. 
         [0039]    Although the present invention has been described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that a variety of modifications and variations may be made to the present invention without departing from the spirit or scope of the present invention defined in the appended claims, and their equivalents.