Abstract:
An organic electroluminescence structure comprises a first substrate, an organic electroluminescence device, and a control device. Forming either a lifting layer under the control device or a recess under the organic electroluminescence device, or forming both of them, creates a difference between their tops, in order to reduce the dark spots and promote the yield of the end product. The lifting layer preferably has a thickness greater than about 0.5 micro meters and the recess has a depth ranges of about 0.1 micro meters to about 100 micro meters. Alternatively, the height difference between the upper surfaces of the control device and the organic electroluminescence device is controlled to be greater than about 2 micro meters or substantially equal to 2 micro meters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims priority to U.S. patent application Ser. No. 11/581,726, filed 16 Oct. 2006, the entire contents of which are incorporated herein by reference, which also claims the benefit of Taiwan Patent Application No. 095121486, filed Jun. 15, 2006, the contents of which are herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an organic electroluminescence structure, more particularly, to the organic electroluminescence structure which may reduce or eliminate dark spots occurring thereon. 
         [0004]    2. Descriptions of the Related Art 
         [0005]    The basic structure of an organic electroluminescence device (OELD) is schematically shown in  FIG. 1 . The OLED structure comprises a plurality of signal lines formed on a substrate. Commonly, the signal lines are constituted by a plurality of scan lines  15  and data lines  17 , thereby defining a plurality of pixel areas  10  on the substrate. Each of the pixel areas  10  has a thin-film-transistor (TFT) and an OELD  13  disposed thereon. The scan lines  15  and the data lines  17  are utilized to control the image display of the pixel areas  10 . 
         [0006]    In comparison with liquid crystal displays (LCDs), an OELD display is capable of self-luminescence, and can perform higher contrast, and a wider viewing angle. The OLED is more compact in size and light in weight. It also performs a shorter response time. All of these advantages are brought from the structure without backlight module. On current trends, the OELD is going to be the most potential key technology in the field of the display. 
         [0007]    However, OELD displays may encounter problems due to the failures in its manufacturing processes. For example, because the first and second substrates (usually named “a cover substrate”) are disposed very close to each other, they may bend to be in contact with each other due to external forces or self-weights during manufacturing processes. Once there are particles existing between the substrates, the aforementioned contact is more likely to damage the OELD layer. The luminescence structure of the pixel areas would tend to be damaged, whereby occurring dark spots on the product. 
         [0008]      FIG. 2  is a cross-sectional view illustrating the pixel area  10  between the first substrate  21  and the second substrate  23 . Apparently, the pixel area  10  comprises a non-luminescence portion (i.e. where the TFT and the control device are located) and a luminescence portion (i.e. light penetrable area), wherein the non-luminescence portion is formed with a height relevant to the luminescence portion. When an impurities or a particle  25  is attached onto the upper surface of the non-luminescence portion, it is very possible that the second substrate  23  exerts a force to the particle  25  and produces stresses onto an OELD layer  24 . If the stresses transit down to the luminescence portion, the OELD  13  at the luminescence portion would likely be damaged. The flaw as presented for the luminescence function is usually called a “dark spot.” 
         [0009]    In convention, increasing the thickness of each layer on the non-luminescence portion that results in the TFT  11  having a greater height is considered. The greater height of the TFT  11  may acquire a delay of the damage to the OELD layer  24 . However, it would give rise to altering numerous manufacturing processes, influencing the yields, and increasing manufacturing costs. The way is not preferably exercised in the industry. 
         [0010]    Given the above, providing an organic electroluminescence structure for promoting yields and reliabilities of products needs to be developed in this field. 
       SUMMARY OF THE INVENTION 
       [0011]    The primary objective of the present invention is to provide an organic electroluminescence structure which can effectively eliminate or reduce dark spots. The present invention is to increase the height difference between upper surfaces of the control device and the organic electroluminescence device, in order to relieve the destructive stresses transiting from the non-luminescence portion to the luminescence portion, and therefore reduce the probability of failure on the organic electroluminescence device on the luminescence portion. 
         [0012]    Another objective of the present invention is to provide an organic electroluminescence structure. Through the aforesaid arrangements, damages from particles, which are compressed by a mask, to break the organic electroluminescence device in an evaporation process can be reduced. After an encapsulation process, the similar damages caused by the desiccant layer which is disposed on the cover can also be reduced. 
         [0013]    To achieve the aforementioned objectives, the organic electroluminescence structure of the present invention comprises a first substrate, an organic electroluminescence device, and at least one control device. The first substrate has a plurality of pixel areas, and each pixel area includes a luminescence portion and a non-luminescence portion adjacent to the luminescence portion. The organic electroluminescence device is disposed on the luminescence portion while the control device is disposed on the non-luminescence portion and electrically connects with the organic electroluminescence device. Each of the organic electroluminescence device and the control device respectively has an upper surface. Particularly, the height difference formed between the upper surfaces is greater than or equal to about 2 micro meters. 
         [0014]    The organic electroluminescence structure of the present invention can also comprise a lifting layer formed on the non-luminescence portion. The lifting layer has a thickness greater than about 0.5 micro meters. 
         [0015]    The organic electroluminescence structure of the present invention can also comprise a recess formed on the luminescence portion. The recess has a surface and the non-luminescence portion defines an upper surface as well. The upper surface of the recess and the upper surface of the non-luminescence portion form a height difference of about 0.1 micro meters to about 100 micro meters. 
         [0016]    Other objectives, features, and advantages of the present invention will become apparent from the following detailed description of the preferred but non-limiting embodiments. The following description is made with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a plan view schematically illustrating a conventional OELD structure; 
           [0018]      FIG. 2  is a cross-sectional view illustrating each pixel area in  FIG. 1 ; 
           [0019]      FIG. 3  is a cross-sectional view illustrating each pixel area of the first embodiment of the present invention; 
           [0020]      FIG. 4  is a cross-sectional view illustrating each pixel area of the second embodiment of the present invention; 
           [0021]      FIG. 5  is a cross-sectional view illustrating each pixel area of the third embodiment of the present invention; and 
           [0022]      FIG. 6  is a schematic view illustrating the OELD display of the present invention after an encapsulation process. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    With reference to  FIG. 3 , an organic electroluminescence structure  3  of the present invention comprises a first substrate  30 , at least one control device  31 , and an organic electroluminescence device  33 . The first substrate  30  has a plurality of pixel areas. It is noted that only one pixel area  40  is illustrated in the figures for disclosing the present invention with clarity. The pixel area  40  includes a non-luminescence portion  41  and a luminescence portion  43 , in which the non-luminescence portion  41  is adjacent to the luminescence portion  43 . Moreover, the pixel area  40  further includes a connecting portion  45  for connecting the non-luminescence portion  41  and the luminescence portion  43 . 
         [0024]    Specifically, the control device  31  is disposed on the non-luminescence portion  41  while the organic electroluminescence device  33  is disposed on the luminescence portion  43 , and the control device  31  electrically connected to the organic electroluminescence device  33 . Referring to the figures, a connecting device  35  is disposed on the connecting portion  45  for connecting the organic electroluminescence device  33  and the control device  31 . 
         [0025]    It is noted that the control device  31  comprises a TFT, preferably. The embodiments of the present invention exemplify, but are not limited to, a top-gate type poly-silicon. The present invention can also be applied to a bottom-gate type or a dual gate type, which can be formed by poly-silicon, single crystal silicon, microcrystalline silicon, amorphous silicon, or the combination thereof. It can further applied to N-type, P-type, or the combination thereof. The organic electroluminescence device comprises an organic light emitting diode (OLED) or a polymer light emitting diode (PLED). In addition, the organic electroluminescence device can include, but not be limited to, a bottom emitting type, a top emitting type, or a dual emitting type. 
         [0026]    In this embodiment, an upper surface  311  of the control device  31  and an upper surface  331  of the organic electroluminescence device  33  form a height difference a greater than or equal to about 2 micro meters. More specifically, after an evaporation process, the mask will be removed and a second substrate  50  (as above-mentioned, namely a cover substrate) will be subsequently disposed thereon. Generally, a passivation layer (not shown in figures) covers the control device  31  and the organic electroluminescence device  33 . The height difference between the upper surfaces of the devices is greater than or equal to about 2 micro meters. 
         [0027]    The second embodiment of the present invention is shown in  FIG. 4 , which is another practical embodiment as shown in  FIG. 3 . The organic electroluminescence structure  3  further comprises a lifting layer  37  disposed between the control device  31  and the non-luminescence portion  41  of the first substrate  30 . The lifting layer  37  has a thickness b preferably greater than about 0.5 micro meters. The thickness b can associate with the aforesaid height difference between the control device  31  and the organic electroluminescence device  33 , as shown in  FIG. 2 , to get a total of height difference between the upper surface  311  of the control device  31  and the upper surface  331  of the organic electroluminescence device  33  to correspond to the predetermined height difference a, which is greater than or equal to about 2 micro meters. The aforementioned lifting layer  37  can comprise organic material, inorganic material, opaque material, light-penetrable material, or combinations thereof. 
         [0028]    The third embodiment of the present invention is shown in  FIG. 5 , which is another practical embodiment as shown in  FIG. 3 . The luminescence portion  43  of the organic electroluminescence structure  3  is formed with a recess  39  which has an upper surface  391 . Also, the non-luminescence portion  41  defines an upper surface  411 . The upper surface  391  of the recess  39  and the upper surface  411  of the non-luminescence portion  41  form a height difference c of about 0.1 micro meters to about 100 micro meters. The thickness c can associate with the aforesaid height difference between the control device  31  and the organic electroluminescence device  33 , as shown in  FIG. 2 , to get a total of the height difference between the upper surface  311  of the control device  31  and the upper surface  331  of the organic electroluminescence device  33  to correspond to the predetermined height difference a, which is greater than or equal to about 2 micro meters. 
         [0029]    It is understandable that the recess  39  disposed on the luminescence portion  43  in the aforesaid third embodiment can simultaneously be combined with the lifting layer  37  disposed on the non-luminescence portion  41  in the second embodiment, to form the predetermined height difference between the control device  31  on the non-luminescence portion  41  and the organic electroluminescence device  33  on the luminescence portion  43 . 
         [0030]    The above-mentioned recess and the lifting layer can be applied as desired but is not limited to the ways of the above disclosures. Any arrangement applicable to the present invention for achieving the similar effects is acceptable. For example, a predetermined expanded recess on all of the pixel areas  40  of the first substrate  30  can be formed in advance of starting the manufacturing processes. Soon after, the lifting layer  37  described in the second embodiment is applied to meet the needs of the height difference a. 
         [0031]    The aforementioned organic electroluminescence structure  3  can further comprise a signal line disposed on the non-luminescence portion  41 . More specifically, the signal line electrically connects to the control device  31 . With reference to  FIG. 1 , the signal line is formed by a plurality of scan lines  15  and data lines  17 . Thereby, the display signals are transferred to each control device  31  of the organic electroluminescence structure  3  and then drive the organic electroluminescence device  33  to operate on the luminescence portion  43  for luminescence. 
         [0032]    In the following encapsulation process, the above-mentioned organic electroluminescence structure  3  is assembled with a second substrate  50  which is opposite to the first substrate  30 . As shown in  FIG. 6 , sealants  60  are circumferentially applied between the first substrate  30  and the second substrate  50 . Furthermore, the second substrate  50  can protect the organic electroluminescence device  33  from ambient influence. It can further include other components such as a desiccant, water absorbent, oxygen absorbent layer, or the like, to enhance its reliability. Moreover, the second substrate  50  can be combined with other components such as the organic electroluminescence device  33  (to form a dual display), a color filter or color transformation layer (to form a multicolor display), a reflecting layer (to form a reflecting display), or a transflective layer (to form a transflective display). 
         [0033]    In the present invention, the connecting device  35 , which is disposed on the connecting portion  45  of the pixel area  40  of the first substrate, forms a path (i.e. the sloping surface as shown in the figures). The specifically large height difference a between the upper surface  311  of the control device  31  and the upper surface  331  of the organic electroluminescence device  33  creates the sloping surface to have a longer path. When the upper surface  311  of the control device  31  is stressed by the undesired particle  25  during the manufacturing process, the OELD layer  34  of the organic electroluminescence device  33  can have a better buffer on the connecting device  35  because it acquires a longer path that makes it difficult for the stress to transit into the luminescence portion  43 . In specific, even if the upper surface  311  of the control device  31  is subject to the sandwiched particle  25  and any damages due to stress are produced, the damages may not laterally diffuse to the luminescence portion  43 . Thus, the display capability on the luminescence portion and the overall display quality can be maintained. 
         [0034]    The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.