Patent Publication Number: US-2010117531-A1

Title: Organic light emitting device and manufacturing method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2008-0112913, filed on Nov. 13, 2008, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an organic light emitting device (“OLED”) and a manufacturing method thereof. 
     2. Discussion of the Background 
     An OLED is a self-emissive display device using a light emitting layer. 
     If a light emitting layer of the OLED is exposed to moisture and/or oxides, however, the light emitting characteristics thereof may deteriorate. Accordingly, after forming a thin film structure including the light emitting layer and a thin film transistor (“TFT”), the thin film structure is usually covered by an encapsulation layer such as a metal enclosure or a glass substrate to close and seal the space to reduce exposure to moisture and/or oxides. A passivation layer may alternatively be used to protect the thin film structure. 
     However, the conventional encapsulation layer and the method for encapsulating the light emitting layer may not effectively keep moisture and oxygen out of the light emitting layer, and also may be difficult to apply to a larger substrate. 
     A method has been proposed in which a sealant is directly formed on the thin film structure, or the thin film structure is covered with the passivation layer and sealed by the sealant. However, the sealant that has been used may not effectively prevent moisture penetration, and moisture penetration may occur through a defective portion of the passivation layer if the passivation layer has a poor uniformity. 
     SUMMARY OF THE INVENTION 
     The present invention provides an OLED with an enhanced seal, and a simplified sealing method thereof. 
     Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. 
     The present invention discloses an OLED that includes: a first substrate, a thin film structure disposed on the first substrate, a second substrate comprising an inner surface and an outer surface, a first sealing member disposed between the first substrate and the second substrate, the first sealing member comprising an inner surface and an outer surface, and a second sealing member disposed on the outer surface of the second substrate. 
     The present invention also discloses a method for manufacturing an OLED that includes forming a thin film structure on a first substrate, arranging a second substrate to face the first substrate, the second substrate comprising an inner surface and an outer surface, forming a first sealing member between the first substrate and the second substrate, the first sealing member comprising an inner surface and an outer surface, and forming a second sealing member on the outer surface of the second substrate. 
     It is to be understood that both the foregoing general description and the following detailed description 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 specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a plan view of an OLED according to an exemplary embodiment of the present invention. 
         FIG. 2A  is a cross-sectional view of the OLED shown in  FIG. 1 , taken along line I-I′ according to an exemplary embodiment of the present invention. 
         FIG. 2B  is a cross-sectional view of the OLED shown in  FIG. 1 , taken along line I-I′ according to an exemplary embodiment of the present invention. 
         FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E , and  FIG. 3F  are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
         FIG. 4  is a plan view of an OLED according to another exemplary embodiment of the present invention. 
         FIG. 5  is a cross-sectional view of the OLED shown in  FIG. 4 , taken along line I-I′. 
         FIG. 6A ,  FIG. 6B , and  FIG. 6C  are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
         FIG. 7  is a plan view of an OLED according to another exemplary embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of the OLED shown in  FIG. 7 , taken along line I-I′. 
         FIG. 9A ,  FIG. 9B ,  FIG. 9C , and  FIG. 9D  are cross-sectional views of showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of a thin film structure according to an exemplary embodiment of the present invention. 
         FIG. 11  is a cross-sectional view of a thin film structure according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. 
     It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, it can be directly on or directly connected to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present. 
     An OLED according to exemplary embodiments of the present invention will be described with reference to  FIG. 1 ,  FIG. 2 ,  FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E ,  FIG. 3F ,  FIG. 10 , and  FIG. 11 . 
       FIG. 1  is a plan view of an OLED according to an exemplary embodiment of the present invention.  FIG. 2A  is a cross-sectional view of the OLED shown in  FIG. 1 , taken along line I-I′ according to an exemplary embodiment of the present invention.  FIG. 2B  is a cross-sectional view of the OLED shown in  FIG. 1 , taken along line I-I′ according to an exemplary embodiment of the present invention.  FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E , and  FIG. 3F  are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention.  FIG. 10  is a cross-sectional view of a thin film structure according to an exemplary embodiment of the present invention.  FIG. 11  is a cross-sectional view of a thin film structure according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 1  and  FIG. 2A , an OLED according to an exemplary embodiment includes a thin film structure  100 , a display substrate  200 , a cover substrate  300 , a first sealing member  410 , a second sealing member  420 , a driving unit  600 , a flexible printed circuit board (“FPCB”),  610  and wires (not shown) to transmit signals and power among the driving unit  600 , the FPCB  610 , and the thin film structure  100 . 
     The display substrate  200  and the cover substrate  300  may be made of transparent material, such as glass or plastic. The display substrate  200  may be larger than the cover substrate  300 . Therefore, the cover substrate may be is disposed on the inside of the display substrate  200 , and the display substrate  200  includes exposed regions  201 A,  201 B,  201 C and  201 D that are not covered by the cover substrate  300 . 
     As shown in  FIG. 10 , the thin film structure  100  may be disposed on the display substrate  200 . The thin film structure  100  may include a switching TFT Qs, a driving TFT Qd, a first insulating layer  110 A, a red color filter layer  160 R, a green color filter layer  160 G, a blue color filter layer  160 B, a second insulating layer  110 B, a pixel electrode  120 , a wall  130 , a light emitting layer  140 , a common electrode  150 , and a contact hole  170 . The driving TFT Qd is exposed by the contact hole  170  and is connected to the pixel electrode  120  through the contact hole  170 . 
     Alternatively, as shown in  FIG. 11 , the thin film structure  100  may include light emitting layers  140 R,  140 G, and  140 B that emit light having different colors, such as red, green, and blue, respectively, instead of the red color filter layer  160 R, the green color filter layer  160 G, and the blue color filter layer  160 B. 
     Also, as shown in  FIG. 11 , the thin film structure  100  may include a switching TFT Qs, a driving TFT Qd, an insulating layer  110 , a pixel electrode  120 , a wall  130 , a common electrode  150 , and a contact hole  170 . The driving TFT Qd is exposed by the contact hole  170  and is connected to the pixel electrode  120  through the contact hole  170 . 
     Referring back to  FIG. 1  and  FIG. 2A , the driving unit  600  is connected to the FPCB  610 , and the FPCB  610  is connected to the thin film structure  100  through the wires (not shown) disposed on the display substrate  200 . Therefore, the driving unit  600  and the thin film structure  100  may be connected. 
     The first sealing member  410  seals the display substrate  200  and the cover substrate  300  and is disposed on an inner surface of the cover substrate  300 . The first sealing member  410  may include a light hardening resin or a thermal hardening resin. 
     For example, the light hardening resin may include a urethane based resin, epoxy based resin, or acryl based resin. The light hardening resin may include a ultraviolet ray (“UV”) hardening resin including 1,6-hexanediol-diacrylate (HDDA) or bis(hydroxyethyl)bisphenol-A dimethacrylate (HEBDM). 
     For example, the thermal hardening resin may include phenolic resin, silicone resin, or polyimide. 
     The second sealing member  420  may be disposed on an outer surface of the first sealing member  410  and on the exposed regions  201 A,  201 B,  201 C, and  201 D, to enclose an edge portion of the cover substrate  300 . The second sealing member  420  may also be disposed on a portion of the FPCB  610 . 
     The second sealing member  420  may include a light hardening resin or a thermal hardening resin and may include the same material as the first sealing member  410 . 
     Also, as shown in  FIG. 2B , the OLED may include a passivation layer  500  disposed between the display substrate  200  and the cover substrate  300 . 
     The passivation layer  500  may be a transparent material, and may have a hygroscopic property or a dehumidifying property. The passivation layer  500  may be made by forming a thin sheet on the thin film structure  100  through a lamination process. 
     The passivation layer  500  may partially or completely fill the space enclosed by the cover substrate  300 , the display substrate  200 , and the first sealing member  410 . 
     As described above, since the OLED includes the second sealing member  420  disposed on the outside surface of the first sealing member  410 , introduction of moisture or oxygen may be more effectively reduced without additional equipment during the manufacturing process. 
     Therefore, the OLED may be better sealed. 
     Next, a manufacturing method for forming an OLED according to an exemplary embodiment of the present invention will be described, with reference to  FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E , and  FIG. 3F . 
       FIG. 3A ,  FIG. 3B ,  FIG. 3C ,  FIG. 3D ,  FIG. 3E , and  3 F are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 3A , the thin film structure  100  and the wires (not shown) are formed on the display substrate  200 . The thin film structure may not cover the display substrate  200  completely, and the exposed regions  201 A,  201 B,  201 C, and  201 D may be exposed on the display substrate  200 . A method for forming the thin film structure  100  and the wires may include forming a switching TFT, a driving TFT, and a light emitting layer. A method for forming the switching TFT, the driving TFT, and the light emitting layer may be substantially similar or identical to a method for forming a TFT and an organic light emitting layer in general, and thus detailed descriptions of those methods will be omitted. Also, as shown in  FIG. 2B , the passivation layer  500  may be formed on the thin film structure  100 , such as through a lamination process. 
     Next, as shown in  FIG. 3B , the first sealing member  410  is coated on the edge portion of the cover substrate  300 . As described above, the first sealing member  410  may be formed by using the UV hardening resin or the thermal hardening resin. 
     Next, as shown in  FIG. 3C  and  FIG. 3D , the display substrate  200  and the cover substrate  300  are attached to each other. Attaching the display substrate  200  and the cover substrate  300  may include one or more steps for accurately aligning the display substrate  200  and the cover substrate  300 , and one or more steps for transporting, pressurizing, and attaching the display substrate  200  and the cover substrate  300 . 
     Next, as shown in  FIG. 3D , the first sealing member  410  may be cured. A thermal hardening technique or an UV hardening technique may be used if the first sealing member  410  is formed by using the thermal hardening resin or the UV hardening resin, respectively. That is, the first sealing member  410  is cured by irradiating the first sealing member  410  with UV light or heating the first sealing member  410  while the display substrate  200  and the cover substrate  300  are attached together. A mask  700  may be used to prevent the UV light or the heat from damaging the thin film structure  100 , and may be arranged on the cover substrate  300  corresponding to the thin film structure  100 . 
     Next, as shown in  FIG. 3E , an assembling step to connect the driving unit  600  and the FPCB  610  to the display substrate  200  is performed. The driving unit  600  is connected to the display substrate  200  through FPCB  610  and the wires (not shown). 
     Next, as shown in  FIG. 3F , the second sealing member  420  may be formed by coating and curing the UV hardening resin or the thermal hardening resin on the outside surface of the first sealing member  410  and the cover substrate  300 . Curing the UV hardening resin or the thermal hardening resin may be performed by irradiating UV light or heat, respectively. The second sealing member  420  may cover the exposed regions  201 A,  201 B,  201 C, and  201 D that are not covered by the cover substrate  300 . 
     While irradiating UV light or heat to cure the second sealing member  420 , the mask  700  used to prevent the UV light or the heat from damaging the thin film structure  100  may be arranged on the cover substrate  300  corresponding to the thin film structure  100 . 
     Next, an OLED according to exemplary embodiments of the present invention will be described with reference to  FIG. 4 ,  FIG. 5 ,  FIG. 6A ,  FIG. 6B , and  FIG. 6C . 
       FIG. 4  is a plan view of an OLED according to an exemplary embodiment of the present invention.  FIG. 5  is a cross-sectional view of the OLED taken along line I-I′ according to the exemplary embodiment of the present invention.  FIG. 6A ,  FIG. 6B , and  FIG. 6C  are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 4  and  FIG. 5 , an OLED according to an exemplary embodiment includes a thin film structure  100 , a display substrate  200 , a cover substrate  300 , a first sealing member  410 , a second sealing member  420 , a driving unit  600 , a FPCB  610 , and wires (not shown). Although not shown, a passivation layer may be formed on the thin film structure  100 , and may partially or completely fill the space enclosed by the cover substrate  300 , the display substrate  200 , and the first sealing member  410 . 
     Unlike as shown in  FIG. 1 , the second sealing member  420  does not contact the FPCB  610  in the exemplary embodiment shown in  FIG. 4  and  FIG. 5 . Therefore, as shown in  FIG. 5 , a portion of exposed region  201 A remains exposed even after the second sealing member  420  has been arranged on the display substrate  200 . 
     Next, the manufacturing method for forming an OLED according to an exemplary embodiment of the present invention will be described, with reference to  FIG. 6A ,  FIG. 6B , and  FIG. 6C . 
     As shown in  FIG. 6A , the display substrate  200  including the thin film structure  100  and the cover substrate  300  including the first sealing member  410  are attached to each other and the first sealing member  410  is cured, similar to  FIG. 3A ,  FIG. 3B ,  FIG. 3C , and  FIG. 3D . 
     Next, as shown in  FIG. 6B , the second sealing member  420  may be formed by coating and curing the UV hardening resin or the thermal hardening resin on the outside surface of the first sealing member  410  and the cover substrate  300 . Curing the UV hardening resin or the thermal hardening resin may be performed by irradiating UV light or heat, respectively. 
     Next, as shown in  FIG. 6C , an assembling step of connecting the driving unit  600  and the FPCB  610  to the display substrate  200  is performed. The driving unit  600  is connected to the display substrate  200  through the FPCB  610  and the wires (not shown). 
     Therefore, the manufacturing method for forming an OLED according to exemplary embodiments of the present invention with reference to  FIG. 4 ,  FIG. 5 ,  FIG. 6A ,  FIG. 6B , and  FIG. 6C  may form the second sealing member  420  before the assembling step of connecting the driving unit  600  to the display substrate  200  through the FPCB  610  and the wires. Also, in the present exemplary embodiment, the second sealing member  410  does not contact FPCB  610 . 
     Next, an OLED according to exemplary embodiments of the present invention will be described with reference to  FIG. 7 ,  FIG. 8 ,  FIG. 9A ,  FIG. 9B , and  FIG. 9C . 
       FIG. 7  is a plan view of an OLED according to an exemplary embodiment of the present invention.  FIG. 8  is a cross-sectional view of the OLED taken along line I-I′ according to an embodiment of the present invention.  FIG. 9A ,  FIG. 9B ,  FIG. 9C , and  FIG. 9D  are cross-sectional views showing a method for manufacturing an OLED according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 7  and  FIG. 8 , an OLED according to this exemplary embodiment includes a thin film structure  100 , a display substrate  200 , a cover substrate  300 , a first sealing member  410 , a second sealing member  420 , a driving unit  600 , a FPCB  610 , and wires (not shown). Although not shown, a passivation layer may be formed on the thin film structure  100 , and may partially or completely fill the space enclosed by the cover substrate  300 , the display substrate  200 , and the first sealing member  410 . 
     Unlike as shown in  FIG. 1 , the size of the display substrate  200 , except for the exposed part  201 A, is substantially equal to the size of the cover substrate  300  in this exemplary embodiment. Thus, the display substrate  200  includes only exposed region  201 A, on which FPCB  610  is disposed, and not exposed regions  201 B,  201 C, and  201 D. 
     Also, as shown in  FIG. 8 , the second sealing member  420  may be disposed on an outer surface of the cover substrate  300  and three edges of the display substrate  200  to enclose the cover substrate  300  and the display substrate  200 . The second sealing member  420  may be disposed on the exposed part  201 A, and may contact FPCB  610 . 
     Next, the method for forming an OLED according to an exemplary embodiment will be described, with reference to  FIG. 9A ,  FIG. 9B ,  FIG. 9C , and  FIG. 9D . 
     As shown in  FIG. 9A , the display substrate  200  including the thin film structure  100  and the cover substrate  300  including the first sealing member  410  are attached to each other, and the first sealing member  410  is cured, similar to  FIG. 3A ,  FIG. 3B ,  FIG. 3C , and  FIG. 3D . 
     Next, as shown in  FIG. 9B , the second sealing member  420  is formed by coating and curing the UV hardening resin or the thermal hardening resin on the outer surface of the cover substrate  300  and three edges of the display substrate  200  to enclose the display substrate  200  and the cover substrate  300 . The curing of the UV hardening resin or the thermal hardening resin may be performed by irradiating UV light or heat, respectively. 
     Next, as shown in  FIG. 9C , an assembling step connecting the driving unit  600  and the FPCB  610  to the display substrate  200  is performed. The driving unit  600  is connected to the display substrate  200  through the FPCB  610  and the wires (not shown). 
     Next, as shown in  FIG. 9D , the second sealing member  420  is formed by coating and curing the UV hardening resin or the thermal hardening resin on the exposed part  201 A. The curing of the UV hardening resin or the thermal hardening resin may be performed by irradiating UV light or heat, respectively. 
     Although not shown, in a method for manufacturing an OLED according to an alternate exemplary embodiment, the second sealing member  420  may not contact the FPCB  610 . Therefore, the assembling step shown in  FIG. 9C  and the coating and curing step shown in  FIG. 9D  may be performed in a different order. In this alternate exemplary embodiment, a portion of exposed region  201 A remains exposed even after the second sealing member  420  has been arranged on the display substrate  200 . After the second sealing member  420  has been coated on a portion of exposed region  201 A and cured, the driving unit  600  may be connected to the display substrate  200  through FPCB  610  and the wires. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.