Abstract:
An organic light-emitting diode. The diode structure includes a substrate having edges, and a sealing layer formed on the edges thereof, wherein at least a breach is formed at a corner of the sealing layer. A method of fabricating the OLED is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optoelectrical element, and more specifically to an organic light-emitting diode and method of fabrication the same. 
   2. Description of the Related Art 
   Moisture may permeate an OLED device after extended use, due to the deterioration of seal performance, with moisture reacting with highly activated metal electrodes inside the OLED, finally resulting in cleavage of materials or dark spots, reducing the active lifetime of the device. 
   A related OLED device is disclosed in U.S. Pat. No. 5,882,761, and illustrated in  FIG. 1   a . The OLED device comprises a glass substrate  2 , a lamination body  6  comprising an ITO electrode (i.e. In 2 O 3  :Sn film electrode)  3 , an organic luminescent material layer  4  and a cathode  5 , a glass sealing case  7 , a drying substance  8 , a sealing agent  9 , and a glass substrate  10  The sealing agent  9  comprises a UV-cured resin applied to the edges thereof to bind a sealing case  7 , forming an airtight space  11  therebetween. 
   In the process, a breach  12  is formed at a midway position of coating route  13 , and its two end points  12   a  and  12   b  extend toward the exterior, as shown in  FIG. 1   b . Thus, after pressing, as shown in  FIG. 1   c , the connection point  14  of the coating route  13  may thicken due to original sealing agent conformation and interior gas pressure, possibly resulting in sealing agent outflow. 
   Additionally, breach size is difficult to control, because the diffusion rate of the sealing agent in the midway position may be influenced by gas pressure, during pressing. If the breach is too wide, the subsequently formed connection point may thin, and if too narrow, the sealing layer may be penetrated, due to the increase in interior pressure. Both conditions threaten OLED seal performance. 
   SUMMARY OF THE INVENTION 
   In order to solve the conventional problems, an object of the invention is to provide a conformation in which a breach is formed at a corner position of a coating route, to improve the seal performance and protect interior elements from moisture. 
   The OLED structure provided in the invention includes a substrate having edges and a sealing layer formed on the edges thereof, wherein at least a breach is formed at a corner of the sealing layer. 
   Proper breach size is provided in the present invention, because effects of interior gas pressure are reduced in the corner position. Additionally, the present method provides a larger breach size than the related art to release interior gas pressure more rapidly. 
   Another object of the invention is to provide a method of fabricating an OLED, including the following steps. A first substrate having edges is provided, and an illuminative element is installed on the inner surface thereof. Subsequently, a sealing layer is formed along the edges of the first substrate, with at least a breach formed at a corner thereof. Finally, a second substrate is provided, bound to the first substrate by the sealing layer to form an airtight space containing the illuminative element. 
   Compared to the related art&#39;s control of numerous starting points and terminal points of various breaches, the present invention merely notes the terminal point of the coating route, because the breach is situated at the corner position, whereby the invention provides a convenient and rapid method for applying the sealing layer. 
   A detailed description is given in the following embodiments with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
       FIG. 1   a  is a cross section of an OLED in U.S. Pat. No. 5,882,761. 
       FIG. 1   b  is a top view of a related coating, route. 
       FIG. 1   c  is an enlarged view of the part of the related seal behavior. 
       FIG. 2  is a cross section of the method of fabricating an OLED in the embodiment of the invention. 
       FIG. 3  is a top view of a coating route in the embodiment of the invention. 
       FIGS. 4˜5  are enlarged views of the part of the corner position shown in  FIG. 3  in the embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  is a cross section of the method of fabricating the OLED according to the embodiment of the invention. First, referring to  FIG. 2 , a substrate  22  having edges is provided. The substrate  22  comprises glass, polymer, ceramic, or plastic, wherein the plastic substrate comprises polyethyleneterephthalate, polyester, polycarbonates, polyimide, arton, polyacrylates, or polystyrene. 
   Next, a first electrode  25  is formed on the substrate  22 . The first electrode  25  is a transparent electrode, and may comprise indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), or zinc oxide (ZnO). 
   Subsequently, an organic light-emitting structural layer is formed on the first electrode  25 , comprising an electron-transport layer (not shown), an organic light-emitting layer  27 , and a hole-transport layer (not shown) in order. The organic light-emitting layer  27  comprises a single or multiple organic illuminative layers. The organic illuminative materials comprise micromolecules or macromolecules of fluorescent or phosphorescent materials, wherein the micromolecule organic illuminative materials covering the first electrode  25  are formed by vacuum evaporation, and the macromolecule organic illuminative materials are formed by spin-on coating, injection, or screen printing. 
   Next, a second electrode  29  is formed on the organic light-emitting layer  27 . The second electrode  29  may be a single or multiple metal electrode layers, and may comprise Li, Mg, Ca, Al, Ag, In, Au, Ni, Pt, or combinations thereof. 
   Subsequently, a coating route  24  is formed by screen printing or optical coating method along the edges of the substrate  22 , as shown in  FIG. 3 . The sealing agent may comprise a UV-cured resin, and the width of the coating route  24  is about 5˜10 mm, preferably 8 mm. Additionally, the coating route  24  is square, rectangular, or polygonal, varying with display region shape  36 . 
   Referring to  FIG. 3 , during coating of the sealing layer, a breach  34  serving as a pressure release point is formed at a corner position  30 . The number of breaches  34  is altered with display region size  36 . If the display region size is larger, more breaches  34  are required, and if smaller, fewer. Additionally, as the breach count increases, individual sizes decreases, or the inverse, wherein the distance from the breach center  34 ′ to the coating route  24  is about 3˜7 mm, preferably 5 mm. 
   The diffusion paths and rates of the sealing agent at the corner position  30  can be precisely estimated due to immunity to interior gas pressure, thus a proper breach size can be formed. 
   Additionally, a larger breach size is formed in the present invention, because the diffusion rate of the sealing agent at the corner position  30  is faster than other positions. As it releases interior pressure more rapidly to protect the sealing layer from cracks, the gas outflow efficiency exceeds 50%. 
   Compared to the related art&#39;s control of numerous starting points and terminal points of various breaches, the present invention merely notes the terminal point of the coating route  24 , because the breach  34  is situated at the corner position  30 , whereby the invention provides a convenient and rapid method for applying the sealing layer. 
   Finally, Referring to  FIG. 2 , a sealing case  26  is provided, bound to the edges of the substrate  22  by the sealing agent  24 , and an airtight space containing the first electrode  25 , an organic light-emitting layer  27 , and the second electrode  29  is formed therebetween. The sealing case  26  may have a plane or concave substrate, and comprise glass, polymer, ceramic, or metal. 
   Referring to  FIGS. 4 and 5 , when pressing is performed, the sealing agent proceeds in various directions, as shown in  FIG. 4 , whereby improved pressing performance is generated, for example, where uniform width of the coating route  24 , especially at the connection point  38 , as shown in  FIG. 5 . 
   Additionally, a drying layer  32  may be installed on the inner surface of the sealing case  26 . The drying layer  32  may comprise metal oxide (e.g. alkaline metal oxide or alkaline-earth metal oxide), metal sulfide, metal halide, metal perchlorate, or highly active metal (e.g. alkaline metal or alkaline-earth metal), at a thickness of less than 10 μm. 
   While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.