Abstract:
A step of forming graphical symbols in an electroluminescent display device is performed by applying laser beams to a metal layer that is formed as a part of internal component formation of the display device. Powdery substances generated during the graphical symbol formation do not reach the internal components of the display device because they are sealed at the time of the graphical symbol formation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to an electroluminescent display device manufacturing method, particularly to an electroluminescent display device manufacturing method including a step of forming letters or symbols on a device substrate by applying laser beams.  
           [0003]    2. Description of the Related Art  
           [0004]    In recent years, electroluminescent (hereafter, referred to as EL) display devices with EL elements have been receiving an attention as a display device substituting for a CRT and an LCD.  
           [0005]    Hereafter, there is described an example of a structure of a pixel of an organic EL display device.  
           [0006]    [0006]FIG. 6 is a plane view showing a pixel of an organic EL display device. FIG. 7A is a cross-sectional view along A-A line of FIG. 6 and FIG. 7B is a cross-sectional view along B-B line of FIG. 6.  
           [0007]    As shown in FIG. 6, and FIGS. 7A and 7B, a pixel  115  is formed in a region enclosed with a gate signal line  51  and a drain signal line  52 . A plurality of the pixels  115  are disposed in a matrix.  
           [0008]    There are disposed in the pixel  115  an organic EL element  60  as a self-emission device, a switching TFT (thin film transistor)  30  for controlling a timing of supplying an electric current to the organic EL element  60 , a driving TFT  40  for supplying an electric current to the organic EL element  60  and a storage capacitor. The organic EL element  60  is formed of an anode  61 , an emissive made of an emission material, and a cathode  63 .  
           [0009]    The switching TFT  30  is provided in a periphery of a point of intersection of the both signal lines  51  and  52 . A source  33   s  of the switching TFT  30  serves as a capacitor electrode  55  for forming a capacitor with a storage capacitor electrode line  54  and is connected to a gate electrode  41  of the driving TFT  40 . A source  43   s  of the driving TFT  40  is connected to the anode  61  of the organic EL element  60 , while a drain  43   d  is connected to a driving source line  53  as a current source to be supplied to the organic EL element  60 .  
           [0010]    The storage capacitor electrode line  54  is disposed in parallel with the gate signal line  51 . The storage capacitor electrode line  54  is made of Cr (chromium) or the like and forms a capacitor by storing an electric charge with the capacitor electrode  55  connected to the source  33   s  of the TFT through a gate insulating film  12 . A storage capacitor  56  is provided for storing voltage applied to the gate electrode  41  of the driving TFT  40 .  
           [0011]    As shown in FIGS. 7A and 7B, the organic EL display device is formed by laminating the TFTs and the organic EL element sequentially on a substrate  10  such as a substrate made of a glass or a synthetic resin, a conductive substrate, or a semiconductor substrate. When using a conductive substrate or a semiconductor substrate as the substrate  10 , however, an insulating film such as SiO 2  or SiN x  is formed on the substrate  10 , and then the switching TFT  30 , the driving TFT  40  and the organic EL element  60  are formed thereon. Each of the two TFTs has a so-called top gate structure in which a gate electrode is disposed above an active layer with a gate insulating film being interposed therebetween.  
           [0012]    There will be described the switching TFT  30  first. As shown in FIG. 7A, an amorphous silicon film (hereafter, referred to as an a-Si film) is formed on the insulating substrate  10  made of a silica glass, a non-alkali glass or the like by a CVD method etc. The a-Si film is irradiated with laser beams for melting and recrystalizing to form a polysilicon film (hereafter, referred to as a p-Si film) as an active layer  33 . On the active layer  33 , a single-layer or a multi-layer of an SiO 2  film and an SiN x  film is formed as the gate insulating film  12 . There are disposed on the gate insulating film  12  the gate signal line  51  made of metal having a high melting point such as Cr and Mo (molybdenum) and also serving as a gate electrode  31 , the drain signal line  52  made of Al (aluminum), and the driving source line  53  made of Al and serving as a driving source of the organic EL element.  
           [0013]    An interlayer insulating film  15  laminated with an SiO 2  film, an SiN x  film and an SiO 2  film sequentially is formed on whole surfaces of the gate insulating film  12  and the active layer  33 . There is provided a drain electrode  36  by filling metal such as Al in a contact hole provided correspondingly to a drain  33   d . Furthermore, a planarization insulation film  17  for planarizing a surface which is made of organic resin is formed on the whole surface.  
           [0014]    Next, there will be described the driving TFT  40  of the organic EL element. As shown in FIG. 7B, an active layer  43  formed by poly-crystalizing an a-Si film by applying laser beams thereto, the gate insulating film  12 , and the gate electrode  41  made of metal having a high melting point such as Cr or Mo are formed sequentially on the insulating substrate  10  made of a silica glass, a non-alkali glass or the like. There are provided in the active layer  43  a channel  43   c , and a source  43   s  and a drain  43   d  on both sides of the channel  43   c.    
           [0015]    The interlayer insulating film  15  laminated with an SiO 2  film, an SiN x  film and an SiO 2  film sequentially is formed on the whole surface of the gate insulating film  12  and the active layer  43 . There is disposed the driving source line  53  connected to a driving source by filling metal such as Al in a contact hole provided correspondingly to a drain  43   d . Furthermore, a planarization insulation film  17  for planarizing the surface, which is made of, for example, an organic resin is formed on a whole surface.  
           [0016]    A contact hole is formed in a position corresponding to a source  43   s  in the planarization insulation film  17 . There is formed on the planarization insulation film  17  a transparent electrode made of ITO (indium tin oxide) and contacting to the source  43   s  through the contact hole, i.e., the anode  61  of the organic EL element. The anode  61  is formed in each of the pixels, being isolated as an island.  
           [0017]    The organic EL element  60  includes the anode  61  made of a transparent electrode such as ITO, a first hole transport layer made of MTDATA (4,4-bis (3-methylphenylphenylamino) biphenyl), a hole transport layer  62  made of a second hole transport layer made of TPD (4,4,4-tris (3-methylphenylphenylamino) triphenylanine), an emissive  63  made of Bebq 2  (bis(10-hydroxybenzo[h]quinolinato)beryllium) containing a quinacridone derivative, an electron transport layer  64  made of Bebq 2 , and a cathode  65  made of magnesium-indium alloy, aluminum or aluminum alloy.  
           [0018]    In the organic EL element  60 , a hole injected from the anode  61  and an electron injected from the cathode  65  are recombined in the emissive and an exciton is formed by exciting an organic module forming the emissive  63 . Light is emitted from the emissive  63  in a process of relaxation of the exciton and then released outside after going through the transparent anode  61  and the transparent insulating substrate  10 .  
           [0019]    In the organic EL display device having the above-described structure, for example, as shown in FIG. 8, a plurality of organic EL display units  201  are formed in a matrix at predetermined intervals on a glass substrate  200  called a mother glass. In the example of FIG. 8, four by four pieces of the organic EL display units  201  are formed. There is formed adjacent each of the organic EL display units  201 , a numbering region  202  for forming letters, symbols, or the like (referred to as graphical symbols, hereinafter) which represent manufacturing information such as a manufacturing number or a lot number of the organic EL display unit  201 .  
           [0020]    [0020]FIG. 9 shows a method of forming graphical symbols on the numbering region  202  and corresponds to a cross-sectional view along A-A line in FIG. 8. There is formed on the glass substrate  200  the numbering region  202  made of Cr layer with an insulating film  120  interposed therebetween.  
           [0021]    The insulating film  120  and the numbering region  202  are formed by utilizing a part of a manufacturing step of the above-described organic EL display unit  201 . For example, the insulating film  120  is formed in a step of forming the gate insulating film  12  of the TFTs  30  and  40 , and the numbering region  202  is formed in a step of forming the gate electrodes  31  and  41  of the TFTs  30  and  40 .  
           [0022]    Graphical symbols are formed on the numbering region  202  by scratching a surface of the numbering region  202  by applying laser beams  300  thereto.  
           [0023]    After subsequent manufacturing steps, the organic EL display units  201  are completed forming on the glass substrate  200 . The glass substrate  200  is then attached to a sealing substrate (not shown) with a sealing resin interposed between the substrates. Furthermore, the attached glass substrate  200  and sealing substrate are cut off to be divided in into individual organic EL panels.  
           [0024]    In the step of forming graphical symbols on the numbering region  202  by the application of the laser beams  300 , however, powders substances scattered by the irradiating laser beams adhere to the surface of the glass substrate  200  on which the device elements such as the TFTs and the organic EL elements are formed. This results in failure of the completed EL display device.  
         SUMMARY OF THE INVENTION  
         [0025]    The invention provides a manufacturing method of an electroluminescent display device. The method includes forming an organic electroluminescent display unit on a device substrate, attaching the device substrate having the organic electroluminescent display unit thereon to a sealing substrate using a sealing resin so that the organic electroluminescent display unit is sealed in a space formed by the device substrate, the sealing substrate and the sealing resin, and forming a graphic symbol by applying a laser to a layer disposed on the device substrate after the attaching of the device substrate and the sealing substrate.  
           [0026]    The invention also provides another manufacturing method of an electroluminescent display device. The method includes forming an organic electroluminescent display unit on a device substrate, and attaching the device substrate having the organic electroluminescent display unit thereon to a sealing substrate using a sealing resin so that the organic electroluminescent display unit is sealed in a space formed by the device substrate, the sealing substrate and the sealing resin. The method also includes cutting a portion of the sealing substrate attached to the device substrate to expose a portion of the device substrate that is outside the sealed space, and forming a graphic symbol by applying a laser to a layer disposed on the exposed portion of the device substrate. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 is a cross-sectional view of a sealed device intermediate according to a first embodiment of the invention.  
         [0028]    [0028]FIG. 2 is a plan view of an organic EL panel cut out from the device intermediate of FIG. 1.  
         [0029]    [0029]FIG. 3 is a cross-sectional view of the organic EL panel along line B-B of FIG. 2.  
         [0030]    [0030]FIG. 4 is a partially expanded sectional view of FIG. 3 at the time of graphical symbol formation.  
         [0031]    [0031]FIG. 5 is a cross-sectional view of an organic EL display device of a second embodiment of the invention at the time of graphical symbol formation.  
         [0032]    [0032]FIG. 6 is a plan view of a pixel of a conventional organic EL display device.  
         [0033]    [0033]FIGS. 7A and 7B are cross-sectional views of the organic EL display device of FIG. 6.  
         [0034]    [0034]FIG. 8 is a plan view of the organic EL display units of the conventional display device formed on a mother glass substrate.  
         [0035]    [0035]FIG. 9 is a cross-sectional view along line A-A line of FIG. 8 at the time of graphical symbol formation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    There will be described in detail a manufacturing method of an electroluminescent display device according to an embodiment of the invention with reference to the drawings.  
         [0037]    [0037]FIG. 1 is a cross-sectional view showing a sealed device structure. In FIG. 1, a reference number  210  is a mother glass substrate, which is also referred to as a device substrate. On a surface of the mother glass substrate  210 , organic EL panels provided with organic EL display units  211  are formed at predetermined intervals. Each of the organic EL display units  211  formed on the device substrate  210  includes pixels arranged in a matrix configuration, which have the structure shown in FIGS.  6 - 7 B.  
         [0038]    This device substrate  210  is attached to a sealing substrate  230  with a sealing resin  220  interposed therebetween. The sealing resin  220  is made of, for example, an epoxy resin, and coated so as to surround the organic EL display units  211 .  
         [0039]    Next, the device substrate  210  attached to the sealing substrate  230  is cut to be divided into individual organic EL panels. FIG. 2 is a plane view showing one of such organic EL panels. FIG. 3 is a cross-sectional view along line B-B of FIG. 2.  
         [0040]    The divided device substrate  210  is attached to the sealing substrate  230  at its edges with the sealing resin  220 . The organic EL display unit  211  is sealed in a space defined by the two substrates and the sealing resin. Then, an edge of the sealing substrate  230  is cut off to expose the corresponding edge of the device substrate  210 .  
         [0041]    Accordingly, there is formed on the exposed edge of the device substrate  210  a numbering region  213  for forming graphical symbols representing manufacturing information such as a manufacturing number or a lot number of the organic EL display unit  211 . Furthermore, the wiring of the organic EL display unit  211  extends to the exposed edge of the device substrate  210 , and a plurality of electrodes for outside connection  212  are formed thereon. An FPC (flexible printed circuit) which is not shown is connected to the electrodes for outside connection  212 .  
         [0042]    There will be described a numbering step with reference to FIG. 4 hereafter. FIG. 4 is an enlarged view of a region enclosed by a broken line in FIG. 3. There is formed on a surface of the device substrate  210  an insulating film  214  made of a multi-layer of SiN x  and SiO 2 , and a numbering region  213  made of Cr (chromium) layer is formed thereon.  
         [0043]    The insulating film  214  is formed, for example, in a step of forming a gate insulating film of TFTs of the organic EL display unit  211 , and the numbering region  213  is formed in a step of forming gate electrodes of the TFTs.  
         [0044]    Graphical symbols are formed on the numbering region  213  by scratching a surface of the numbering region  213  by applying laser beams  300  thereto. The graphical symbols may be, for example, P1X048-06, which represents a manufacturing number. These graphical symbols are selected arbitrarily.  
         [0045]    Although powdery substances  301  (such as powders of Cr) are scattered by the application of the laser beams, the organic EL display unit  211  is already sealed and blocked by the sealing resin  220  and the sealing substrate  230  covering the organic EL display unit  211 . Therefore, device failure due to the adhesion of the scattered powders to the organic EL display unit  211  is eliminated.  
         [0046]    [0046]FIG. 5 is shows a second embodiment of this invention. In the above embodiment, the laser beams are applied to the edge of the device substrate  210  which is exposed by cutting off the edge of the sealing substrate  230 . However, the graphical symbols may be formed by applying the laser beams without cutting off the edge of the sealing substrate  230 , i.e., with the corresponding edge of the sealing substrate  230  covering the numbering region  213 .  
         [0047]    The laser beams  300  may be applied to the numbering region  213  through the sealing substrate  230  if the sealing substrate  230  is made of a glass. The powders scattered by the irradiating laser beams are blocked by the sealing resin  220  and the sealing substrate  230  covering the organic EL display unit  211 .  
         [0048]    Although the gate insulating film  214  of the TFTs is provided below the numbering region  213  in the two embodiments above, any of the suitable layers that are formed during the formation of the organic EL display device may be used to form the numbering region thereon.