Abstract:
An organic EL display device and a method for fabricating the same are disclosed, wherein an organic luminescence layer is formed at a crossing region of first and second electrodes using a shadow mask on which a plurality of holes are connected by bridges.

Description:
This application is a Continuation of U.S. patent application Ser. No. 10/185,012, filed Jul. 1, 2002, now U.S. Pat. No. 6,884,139, and claims the benefit of the Korean Application No. 2001-0039542 filed on Jul. 3, 2001, which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a display device, and more particularly, to an organic electroluminescence (EL) display device and a method for fabricating the same. 
     2. Discussion of the Related Art 
     A method of using a shadow mask as shown in  FIG. 1  is the most efficient method to improve the luminescence efficiency among methods of forming R, G, and B pixels in fabricating a full-color organic EL display device. 
       FIGS. 1A to 1D  are diagrams showing a related art shadow mask and a full-color organic EL display device according to a pixel array method. 
     As shown in  FIG. 1A , an first electrode  2  is formed on a transparent substrate  1  and barriers  7  are additionally formed on the same to separate between an insulating film  3  and a second electrode. 
     Also, using a shadow mask  6 , a common luminescence layer  5  of R, G, and B, and each of organic luminescence layers  5 - 1  to  5 - 3  of R, G, and B is formed at a corresponding pixel on the insulating film  3 . 
     Then, the second electrode is formed on the entire surface. 
     There are three different types (i.e. a strip type as shown in  FIG. 1B , a delta type as shown in  FIG. 1C , and an array type as shown in  FIG. 1D ) in forming an organic luminescence layer using a shadow mask depending on the array method of a pixel. In the array type, the size of R pixel is designed to be larger than G or B pixel to supplement the luminescence efficiency of the R pixel. 
     The strip type is best among the above three pixel array types in terms of the aperture ratio and first electrode resistance. In other words, because first electrodes are formed in the form of strips, the device can be driven with low driving voltage. 
     On the other hand, in the strip type, the shadow mask  6  should also be made in a strip form as shown in  FIG. 1 . In this instance, problems such as the transformation or droop of the shadow mask  6  are caused in a large degree because of an external pulling strength. Accordingly, in the process of deposition, colors spread not only on the intended pixel region but also on other areas because of shadow effect. 
     To obviate the above-mentioned problems, as shown in  FIG. 2 , a shadow mask on which mask holes are made in turns while having the same pixel array structure as that of the strip type of  FIG. 1B  is applied. 
       FIGS. 2A to 2D  are deposition process diagrams of an organic luminescence layer of a full-color organic EL display device using the related art shadow mask structure. 
     In this method, however, each organic luminescence layer displaying one of R, G, and B colors should be formed by carrying out alignment and deposition twice respectively. That is, to form three layers of R, G, and B, the deposition should be carried out six times in all after the alignment being carried out six times as well. 
     In other words, to form organic luminescence layers of R, G, and B, in case of using the shadow mask  6  of  FIGS. 1B to 1D , the shadow mask is aligned and deposited three times respectively. In case of using a shadow mask shown in  FIG. 2 , however, the shadow mask should be deposited 6 times. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an organic EL display device and method for fabricating the same that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a full-color organic EL display device and a method for fabricating the same, in which an improved shadow mask structure is provided to prevent a mask pattern from being transformed, thereby obtaining high luminescence efficiency. 
     Another object of the present invention is to provide a full-color organic EL display device and a method for fabricating the same which has a shadow mask structure that provides a predetermined number of bridges formed over a long strip-shaped holes so as to prevent transformation and droop caused by a pulling strength from occurring, thereby obtaining high aperture ratio and low driving voltage. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a full-color organic EL display device of the present invention includes organic luminescence layers of R, G, and B formed in a strip shape at a plurality of pixels, which are defined by a crossing region of first and second electrodes, on a transparent substrate using a mask which has a plurality of strip-shaped holes and a plurality of bridges crossing the holes. 
     In the preferred embodiment of the present invention, thin metal that act as bridges is formed over long strip-shaped holes of a shadow mask so as to prevent the shadow mask from being transformed or drooped because of the pulling strength. The organic luminescence layers of R, G, and B are alternately arranged in rows by three times&#39; alignments of the shadow mask. 
     To further achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a mask for fabricating a display device that includes a plate having a plurality of holes, and a plurality of bridges connecting the holes, wherein the bridges are formed on the same or different plane as the plate. 
     To further achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a mask for fabricating a display device that includes a plate having a plurality of holes, and a plurality of bridges connecting the holes, wherein the bridges are formed on the same or different plane as the plate and thicker than the plate. 
     To further achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a mask for fabricating a display device that includes a plate having a plurality of holes, and a plurality of bridges connecting the holes, wherein the bridges are formed on the same or different plane as the plate and at the same thickness from that of the plate. 
     To further achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a mask for fabricating a display device that includes a plate having a plurality of holes, and a plurality of bridges formed between the adjacent holes, wherein the bridges are formed on the same or different plane as the plate and thicker than the plate. 
     To further achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a mask for fabricating a display device that includes a plate having a plurality of holes, and a plurality of bridges formed between the adjacent holes, wherein the bridges are formed on the same or different plane as the plate and at the same thickness from that of the plate. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention 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 principle of the invention. In the drawings: 
         FIGS. 1A to 1D  illustrate diagrams showing full-color organic EL display devices in accordance with pixel array types and related art shadow masks; 
         FIGS. 2A to 2D  illustrate deposition process diagrams of an organic luminescence layer of a full-color organic EL display device using a shadow mask structure of a related art; 
         FIGS. 3A to 3D  illustrate deposition process diagrams of an organic luminescence layer of a full-color organic EL display device using a shadow mask structure of the present invention; 
         FIG. 4  illustrates a plane view of a shadow mask in accordance with the present invention; and 
         FIGS. 5A to 5C  are detailed diagrams showing a part ‘A’ of the shadow mask of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIGS. 3A to 3D  illustrate deposition process diagrams of an organic luminescence layer of a full-color organic EL display device using a shadow mask structure of the present invention. 
     Referring to  FIG. 3A , a first electrode  20  of a transparent electrode material is formed on a transparent substrate  10 . A supplementary electrode may be applied to reduce the resistance of the first electrode  20 . The substrate includes at least thin film transistors. 
     Metals which have relatively lower resistance than the resistance of the first electrode  20 , such as Cr, Al, Cu, W, Au, Ni, and Ag, can be used as the supplementary electrode. 
     An insulating film  30  is formed on the first electrode  20 . Any insulators, regardless of inorganic materials or organic materials, can be used as the insulating film  30 . 
     A barrier  70  is formed on the insulating film  30  to insulate intervals of each second electrode (not shown). 
     As shown in  FIG. 4 , a shadow mask  60  is used to form each organic luminescence layer of R, G, and B and a common organic luminescence layer of the same at a plurality of pixels on the transparent substrate  10 . The pixels are defined by a region crossed by the first and second electrodes. 
       FIG. 4  is a plane view of the shadow mask  60  in accordance of the present invention. The shadow mask  60  has a plurality of strip-shaped holes and a plurality of bridges  60 - 1  which connect the holes. 
     The transformation of the shadow mask  60  is prevented by the bridges  60 - 1  which connect the holes. 
     Referring to  FIG. 3A , one bridge  60 - 1  for each pixel is formed, but the bridge  60 - 1  is not necessarily formed at every pixel. In consideration of the transformation of the shadow mask  60 , the bridge may be formed between every two or three pixels. 
     Preferably, the bridge  60 - 1  has its width ‘a’ and thickness ‘b’ in the range of 1˜1000 μm. 
       FIGS. 5A to 5C  illustrate a detailed view of the part ‘A’ of the shadow mask of  FIG. 4 . The bridge  60 - 1  can be formed either on the same plane and at the same thickness as the shadow mask  60  as shown in  FIG. 5A , or on a different plane and at a different thickness from the shadow mask  60  as shown in  FIG. 5B . Alternatively, the bridge  60 - 1  can also be formed on the same or different plane as or from the shadow mask at a different thickness from the shadow mask  60  as shown in  FIG. 5C . 
     A common luminescence layer of R, G, and B (not shown) is deposited on the transparent substrate  10  at a time using a blank mask which can deposit all the entire luminescence region. 
     Subsequently, each organic luminescence layer of R, G, and B is alternately arranged in rows at the pixel by three times aligning the shadow mask  60 . 
     The common luminescence layer of R, G, and B may also be formed at each pixel of R, G, and B using the shadow mask  60 , not being deposited on the entire luminescence region. 
     Subsequently, the second electrode (not shown) is formed by forming a second electrode (Mg—Ag alloy, or Al, or other conductive materials) using the blank shadow mask. 
     Then, passivation layers (oxygen adsorption layer, moisture adsorption layer, and moisture-proof layer) are formed on the second electrode and encapsulation is carried out. 
     The full-color organic EL display device in accordance with the present invention has the following advantages. 
     By forming mask holes in the form of a bridge, the transformation and droop of the shadow mask caused by the pulling strength is prevented. Thus, efficiency of the full-color organic EL display device is maximized. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.