Abstract:
A display device including: a substrate with a display area having a plurality of organic EL devices and a peripheral area having a driving circuit for the organic EL devices and surrounding the display area on the substrate; an organic insulating film covering at least the driving circuit; and a groove in the organic insulating film along a line between the display area and the peripheral area, an inorganic but not an not the organic insulating film being present in an outermost portion of the peripheral area spaced apart from the groove.

Description:
RELATED APPLICATION DATA 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/298,960, filed Nov. 17, 2011, which is a continuation of Ser. No.11/193,864, filed Jul. 29, 2005, now U.S. Pat. No. 8,080,936 issued on Dec. 20, 2011, the entireties of which are incorporated herein by reference to the extent permitted by law. The present application claims priority to Japanese Patent JP2004-235125 filed in the Japanese Patent Office on Aug. 12, 2004, the entirety of which also is incorporated by reference herein to the extent permitted by law. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a display device and particularly relates to a display device suitable for the application to an organic EL display device. 
         [0004]    2. Description of the Related Art 
         [0005]    An organic EL device containing an organic material, electroluminescence (called EL hereinafter), is now popular as a light-emitting device, which can emit high intensity light through low-voltage direct-current driving. However, in such a device including organic EL devices (that is, an organic EL display device), moisture may deteriorate an organic layer of the device, which may lower the intensity of emitted light in each of the devices and/or may cause unstable light emission. 
         [0006]    Conventionally as shown in  FIG. 6 , the organic EL devices on the substrate  101  are sealed by a cover member  102  and a sealant  103 . Also, a rigid carbon film may be further provided at the outside of the sealant  103 . Thus, the organic EL devices on the substrate  101  can be shielded from the outside, especially from moisture and oxygen which may cause the oxidization of the organic EL devices and prompt the deterioration of the devices (see Patent Document 1 below). 
         [0007]    In  FIG. 7 , the cover member  102  is bonded via an adhesive  105  onto a device side  101   a  of the substrate  101  having organic EL devices and/or a circuit. 
         [0008]    Patent Document 1: JP-A-2002-93576 
       SUMMARY OF THE INVENTION 
       [0009]    However, in such devices, the spread of the moisture remaining within the display device is not completely prevented. 
         [0010]    In particular, an inter-layer insulating film covering a driving circuit is made of an organic photo-sensitive material and allows water to pass through easily. Therefore, the moisture left within the display device easily spread via the inter-layer insulating film. 
         [0011]    Accordingly, it is desirable to propose a display device which can prevent the deterioration of organic EL devices due to the spread of moisture remaining within the display device for higher long-term reliability. 
         [0012]    According to an embodiment of the present invention, there is provided a display device including, a display area having a plurality of organic EL devices on a substrate; a peripheral area having a driving circuit for the organic EL devices and surrounding the display area on the substrate; and an organic insulating film covering at least the driving circuit, the organic insulating film has a separating groove which divides itself into the inner part and outer part at the periphery of the display area. 
         [0013]    In such a device, the separating groove divides the organic insulating film into the inner part and outer part. Therefore, the deterioration of the organic EL devices due to moisture in the display area can be reduced by preventing moisture in the outer part of the organic insulating film from moving into the inner part of the organic insulating film. The separating groove is preferably provided between the display area and the peripheral area, so that the moisture in the peripheral area is prevented from moving into the display area through the organic insulating film. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIGS. 1A and 1B  are diagrams showing a construction of a display device of a first embodiment; 
           [0015]      FIGS. 2A and 2B  are main part enlarged section views showing a construction of the display device of the first embodiment; 
           [0016]      FIGS. 3A and 3B  are main part enlarged section views showing a construction of a display device of a second embodiment; 
           [0017]      FIGS. 4A and 4B  are diagrams showing a construction of a display device of a third embodiment; 
           [0018]      FIG. 5  is a schematic section view showing a construction of a display device of a fourth embodiment; 
           [0019]      FIG. 6  is a schematic section view showing a construction of a display device in the past; and 
           [0020]      FIG. 7  is a schematic section diagram showing another construction of a display device in the past. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Embodiments of a display device of the invention will be described below in detail with reference to drawings. 
       First Embodiment 
       [0022]      FIG. 1A  is a plan view showing a construction of a display device of a first embodiment, and  FIG. 1B  is a schematic section view taken at Line A-A′ in  FIG. 1A . 
         [0023]    First of all, as shown in the plan view in  FIG. 1A , a display device  1  is an organic EL display device including organic EL devices EL serving as light emitting elements. On a substrate (which is a supporting substrate here)  2 , the display device  1  includes a display area  3 , a peripheral area  4  surrounding the display area  3 , and an implemented area  5 . The substrate  2  is made of a transparent material such as glass. The display area  3  has a plurality of organic EL devices EL. An IC chip and/or a circuit substrate are implemented on the implemented area  5 . 
         [0024]    In the display area  3 , each of pixels on the supporting substrate  2  has an organic EL device EL. When the display device  1  is an active-matrix display device, each pixel has an organic EL device and a pixel circuit (not shown) for driving the organic EL device. Each of the pixel circuits has a thin-film transistor serving as a switching element. 
         [0025]    The peripheral area  4  surrounding the display area  3  has driving circuits (not shown) for transmitting a scan signal and/or a data signal to the organic EL devices EL. Each of the driving circuits includes a thin-film transistor. The driving circuits in the peripheral area  4  are connected to each other. 
         [0026]    The implemented area  5  may have an array of terminals  6  for inputting an external signal to the driving circuits in the peripheral area  4 , for example. 
         [0027]    The display device  1  including the display area  3 , peripheral area  4  and implemented area  5  as described above has the construction as shown in  FIGS. 1A and 1B . In other words, a circuit-formed layer  11  (shown in the section view only) is provided on the supporting substrate  2 . The circuit-formed layer  11  has the pixel circuits in the display area  3  and driving circuits in the peripheral area  4 . An organic insulating film  12  covers the circuit-formed layer  11  on the supporting substrate  2 . Here, the organic insulating film  12  serves as a flattening insulating film. 
         [0028]    An EL layer  13  (shown in the section view only) is provided on the surface flattened by the organic insulating film  12 . The EL layer  13  has a plurality of organic EL devices EL. An inorganic insulating film  14  (shown in the section view only) covers the organic EL devices EL (that is, EL layer  13 ) in the display area  3  and peripheral area  4 . Notably, the implemented area  5  does not have the inorganic insulating film  14 . 
         [0029]    The display area  3  and peripheral area  4  covered by the inorganic insulating film  14  further have an adhesive layer  15  (shown in the section view only). The supporting substrate  2  is bonded to an opposite substrate  17  through the adhesive layer  15  so that the organic EL devices EL in the display area  3  can be sealed. The adhesive layer  15  contains an extremely low pervious material. 
         [0030]    In the plan view in  FIG. 1A , a part of the organic insulating film  12  and opposite substrate  17  is cut out for easy description. 
         [0031]    In the display device  1  of the first embodiment having this layer structure as described above, the organic insulating film  12  has a separating groove a. The separating groove a separates the organic insulating film  12  into an inner part  12   a  and outer part  12   b.    
         [0032]    The separating groove a is a groove-shaped part resulting from the complete removal of the organic insulating film  12  and at least surrounds a part of the display area  3  and preferably surrounds the entire circumference of the display area  3 . The separating groove a is further preferably provided between the display area  3  and the peripheral area  4  as shown in  FIG. 1A . 
         [0033]      FIG. 2A  shows an enlarged section view of Part B in the schematic section diagram in  FIG. 1B , and  FIG. 2B  shows an enlarged section view of Part B′ in the schematic section view in  FIG. 1B . Note that Parts B and B′ overlap one another in the depth direction in  FIG. 1B . Detailed layer structures of the separating groove a and the surrounding will be described with reference to  FIGS. 1A and 1B  and based on the enlarged section views in  FIGS. 2A and 2B . 
         [0034]    As shown in  FIG. 2A , the display area  3  and peripheral area  4  on the supporting substrate  2  have thin-film transistors Tr included in the pixel circuit and driving circuits, and an inorganic insulating film  21  covers the thin-film transistors Tr therein. A wiring  25  is provided on the inorganic insulating film  21 . The wiring  25  is connected to a semiconductor layer included in the sources and drains of the thin-film transistors Tr through connection holes  21   a  in the inorganic insulating film  21 . The thin-film transistors Tr and wiring  25  are included in the pixel circuits of the display area  3  and the driving circuits of the peripheral area  4 . These components described up to this point are included in the circuit-formed layer  11  described with reference to  FIG. 1B . 
         [0035]    A first organic insulating film  27  covers the wiring  25  on the inorganic insulating film  21 . The first organic insulating film  27  contains a photo-sensitive compound and is coated as a flattening insulating film. The first organic insulating film  27  has a separating groove al between the display area  3  and the peripheral area  4  so that the display area  3  is surrounded. The separating groove al is formed by lithography processing. 
         [0036]    The display area  3  on the first organic insulating film  27  has a plurality of organic EL devices EL. The organic EL devices EL have a lower electrode  31  connecting to the wiring  25  through a connection hole  27   a  in the first organic insulating film  27 . The lower electrode  31  is to be used as an anode (or cathode) and is patterned as a pixel electrode. The periphery of the lower electrode  31  is covered by a second organic insulating film  33  and is widely exposed at the center part only. The second organic insulating film  33  may contain a photo-sensitive compound, for example. Lithography processing is used to form an opening above the lower electrode  31  and a separating groove a 2  over the separating groove al of the first organic insulating film  27 . 
         [0037]    Thus, according to the first embodiment, the first organic insulating film  27  and the second organic insulating film  33  are included in the organic insulating film  12  described with reference to  FIGS. 1A and 1B . The separating groove a 1  in the first organic insulating film  27  and the separating groove a 2  in the second organic insulating film  33  form the separating groove a described with reference to  FIGS. 1A and 1B . 
         [0038]    An organic layer  35  including a light-emitting layer at least is patterned and stacked on the lower electrodes  31  exposing from the second organic insulating film  33 . The light-emitting layer in the organic layer  35  contains an organic material, which emits light in response to the re-coupling of positive holes and electrons implanted to the light-emitting layer. An upper electrode  37  is provided on the patterned organic layer  35  and the second organic insulating film  33 . Here, the upper electrode  37  is isolated from the lower electrode  31 . The upper electrode  37  is to be used as a cathode (or anode), is provided as an electrode common to the organic EL devices EL and covers the display area  3 . 
         [0039]    Here, the EL layer  13  described with reference to  FIG. 1B  is the layer having a plurality of organic EL devices EL in the construction as described above. 
         [0040]    The inorganic insulating film  14  and adhesive layer  15  cover the organic insulating film  12  and organic EL devices EL, and the opposite substrate  17  is provided thereon. 
         [0041]    As shown in  FIG. 2B , the upper electrode  37  for the organic EL devices EL has an end extending as an upper electrode wiring  37   a  in the peripheral area  4  and connecting, at predetermined positions, to the driving circuits in the peripheral area  4 . Thus, the upper electrode wiring  37   a  extends to the peripheral area  4  across the separating groove a surrounding the display area  3 . Therefore, securing an enough thickness of the organic insulating film  12  (that is, the first organic insulating film  27 ) is important for maintaining isolation between the wiring  25  in the display area  3  and the peripheral area  4  and the upper electrode wiring  37   a.    
         [0042]    At place where the upper electrode wiring  37   a  crosses the separating groove a, the wiring  25  in the display area  3  and the wiring  25  in the peripheral area  4  are connected through a connection wiring below the inorganic insulating film  21 . In this case, for example, the semiconductor layer part of the same layer as the semiconductor layer  23  included in the thin-film transistors Tr may be a connection wiring  23   a  so that the connection wiring  23   a  can connect the wiring  25  in the display area  3  and the wiring  25  in the peripheral area  4 . Thus, the wiring  25  in the display area  3  and the wiring  25  in the peripheral area  4  can be connected each other without a short circuit with respect to the electrode wiring  37   a.    
         [0043]    In display device  1 , the separating groove a in the organic insulating film  12  surrounding the display area  3  divides the organic insulating film  12  into the inner part  12   a  and the outer part  12   b,  as described with reference to  FIGS. 1A and 1B  and  2 A and  2 B. Thus, the moisture existing in the part corresponding to the outer part  12   b  of the organic insulating film  12  does not enter into the inner part  12   a  through the organic insulating film  12 . Therefore, the deterioration of the organic EL devices EL due to moisture can be prevented in the display area  3  positioned at the part covered by the inner part  12   a.    
         [0044]    In particular, the separating groove a surrounding the display area  3  and between the display area  3  and the peripheral area  4  can prevent the entry of the moisture existing in the peripheral area  4  having the driving circuits into the display area  3  through the organic insulating film  12 . Therefore, even when moisture is absorbed to a foreign material (such as dust) caused in a process of manufacturing the driving circuits in the peripheral area  4 , the entry of the moisture into the display area  3  can be prevented, which can further prevent the deterioration of the organic EL devices more effectively. Preferably, the separating groove a is provided surrounding the display area  3  as closely as possible to the display area  3 . Thus, the volume of the inner part  12   a  of the organic insulating film  12  can be reduced, and the amount of moisture that reaches to the organic EL devices EL through the part can be therefore reduced. 
         [0045]    As a result, the long-term reliability of the display device  1  can be achieved since the deterioration of the organic EL devices EL due to moisture can be prevented. 
       Second Embodiment 
       [0046]      FIGS. 3A and 3B  are main part enlarged section views showing features in a display device according to a second embodiment.  FIG. 3A  shows an enlarged section view corresponding to Part B in the schematic section view in  FIG. 1B , and  FIG. 3B  shows an enlarged section view corresponding to Part B′ in the schematic section view in  FIG. 1B . A display device  1   a  according to the second embodiment shown in  FIGS. 3A and 3B  is different from the display device according to the first embodiment in that an inorganic layer  41  is provided at the bottom of the separating groove a for alleviating the degree of the level change due to the separating groove a. The other construction of the second embodiment is the same. 
         [0047]    The inorganic layer  41  has a width W 1 , which is wider enough than the width W of the opening at the bottom of the separating groove a. The bottom of the separating groove a is configured to securely position on the inorganic layer  41  only so that the degree of the level change due to the separating groove a can be evenly alleviated. The inorganic layer  41  may be formed by patterning the same layer as that of the wiring  25  in the display area  3  and peripheral area  4 . In this case, the inorganic layer  41  may be patterned with sufficient isolation from the wiring  25 . 
         [0048]    In particular, as shown in  FIG. 3B , the upper electrode wiring  37   a  is connected and wired to the inorganic layer  41  containing the same material as that of the wirings  25  in the part where the upper electrode wiring  37   a  extending from the upper electrode  37  for the organic EL devices EL crosses the separating groove a. 
         [0049]    Note that the inorganic layer  41  may contain an insulating material. Also in this case, the inorganic layer  41  has the width W 1 , which is wider enough than the width W of the opening at the bottom of the separating groove a, and the bottom of the separating groove a is configured to securely position on the inorganic layer  41  only. 
         [0050]    Since the separating groove a of the organic insulating film  12  is provided between the display area  3  and peripheral area  4  also in this construction, the deterioration of the organic EL devices EL due to moisture in the display area  3  can be prevented like the first embodiment. 
         [0051]    Furthermore, this embodiment has the inorganic layer  41  at the bottom of the separating groove a so that the degree of the level change due to the separating groove a can be alleviated. Thus, the stress on the part covering the level change due to the separating groove a can be alleviated in the inorganic insulating film  14  on the organic insulating film  12 . Therefore, the occurrence of a crack due to the stress can be prevented, which can prevent the entry of moisture through the crack. 
         [0052]    The alleviation of the degree of the level change due to the separating groove a can easily secure the thickness of the upper electrode wiring  37   a  extending to the peripheral area  4  across the separating groove a. Thus, the increase in resistant value and/or break of the upper electrode wiring  37   a  can be prevented in the side walls of the separating groove a. 
         [0053]    Notably, the inorganic layer  41  for alleviating the degree of the level change due to the separating groove a can be provided without any increase in number of steps when the inorganic layer  41  is formed by patterning the same layer as that of the wiring  25  in the display area  3  and peripheral area  4 . 
       Third Embodiment 
       [0054]      FIG. 4A  is a plan view showing a construction of a display device according to a third embodiment, and  FIG. 4B  is a schematic section view taken at Line A-A′ in  FIG. 4A . A display device  1   b  shown in  FIGS. 4A and 4B  is different from the display devices of the embodiments above in that a sealed area  45  resulting from the removal of the organic insulating film  12  is provided in the outermost circumference of the part having the opposite substrate  17  over the supporting substrate  2 , and the other construction is the same. 
         [0055]    In other words, in the display device  1   b,  the separating groove a resulting from the removal of the organic insulating film  12  is provided between the display area  3  and the peripheral area  4  so that the display area  3  is surrounded. The sealed area  45  resulting from the removal of the organic insulating film  12  is provided surrounding the separating groove a and the perimeter of the peripheral area  4 . The sealed area  45  is the outermost periphery of the part having the opposite substrate  17  over the supporting substrate  2  as described above. The outer part  12   b  of the organic insulating film  12  separated by the separating groove a has the both side walls and top face completely covered by the inorganic insulating film  14  (shown in the section view only) on the organic insulating film  12  and are sealed by the adhesive layer (shown in the section view only). In other words, the organic insulating film  12  is not exposed to the outside in the part between the supporting substrate  2  and the opposite substrate  17 . 
         [0056]    In display device  1   b,  the deterioration of the organic EL devices EL due to moisture in the display area  3  can be prevented like the first embodiment since the separating groove a of the organic insulating film  12  is provided between the display area  3  and the peripheral area  4 . 
         [0057]    Furthermore, in the display device  1   b  of the third embodiment, the sealed area  45  resulting from the removal of the organic insulating film  12  and being provided at the outer edges of the supporting substrate  2  and opposite substrate  17  can prevent the entry of moisture from the outside of the display device  1   b.  Thus, the deterioration of the organic EL devices EL due to moisture in the display area  3  can be more securely prevented, and the corrosion of a metallic material due to moisture, for example, can be also prevented in the peripheral area  4 . 
       Fourth Embodiment 
       [0058]      FIG. 5  is a schematic section view showing a construction of a display device according to a fourth embodiment. A display device  1   c  in  FIG. 5  is different from the display device of the third embodiment in that a hollow part exists between the supporting substrate  2  and the opposite substrate  17 , and the other construction is the same. 
         [0059]    In other words, in the display device  1   c,  an adhesive sealant  47  is provided between the supporting substrate  2  and the opposite substrate  17  surrounding the separating groove a between the display area  3  and the peripheral area  4  and the perimeter of the peripheral area  4 , resulting from the removal of the organic insulating film  12 . The sealant  47  bonds the opposite substrate  17  to the supporting substrate  2  and seals the hollow part between the supporting substrate  2  and the opposite substrate  17 . 
         [0060]    Also in the display device  1   c  of the fourth embodiment, the deterioration of the organic EL devices EL due to moisture in the display area  3  can be prevented, and the reliability can be improved since the separating groove a of the organic insulating film  12  is provided between the display area  3  and the peripheral area  4 . 
         [0061]    It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.