Patent Publication Number: US-10770520-B2

Title: Organic light emitting display device and method of manufacturing the same

Description:
This application is a continuation of U.S. patent application Ser. No. 15/918,164 filed on Mar. 12, 2018, which is a continuation of U.S. patent application Ser. No. 15/257,471, filed on Sep. 6, 2016, now U.S. Pat. No. 9,947,727, which claims the benefit of Korean Patent Application No. 10-2015-0126133, filed on Sep. 7, 2015, which are incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a display device, and more particularly, to an organic light emitting display device having slim profile and flexibility, and a method of manufacturing the same. 
     Discussion of the Related Art 
     Flat display devices include a liquid crystal display device (LCD), an organic light emitting diode (OLED) device, a plasma display panel (PDP) device, a quantum dot display device, a field emission display (FED) device, an electrophoretic display (EPD) device, etc. Each of these flat display devices typically includes a flat display panel for displaying an image in which a pair of transparent insulating substrates facing each other are bonded to each other, with an intrinsic light emitting layer, a polarizing layer or other optical material layers interposed therebetween. 
     As the demand for a flat display element having a small space occupation is increasing in accordance with the recent trend of large-sized display devices, an organic light emitting display device is considered as the next generation display device among these flat display devices. This is because the organic light emitting display device typically does not require a separate light source and a structure to assemble the light source to a display panel, and includes organic light emitting diodes spontaneously emitting light in the unit of pixels. 
     An organic light emitting diode typically comprises an anode, a cathode and an organic layer between the anode and the cathode. The organic light emitting diode emits light when pairs of electrons and holes, which are injected into the organic layer between an electron injection electrode (a cathode) and a hole injection electrode (an anode) and then are recombined in the organic layer, are transitioned from an excited state to a ground state. 
     Meanwhile, a touch panel, which can recognize a touch point contacted by a human hand or other input unit, is recently added and attached to an external surface of a display device. 
     Touch panels are divided into a resistive type, a capacitive type, and an infrared sensing type. Presently, the capacitive type touch panel is advantageous for small-sized display devices due to ease of fabrication and sensitivity. 
     Hereinafter, a conventional organic light emitting display device to which a touch panel is attached will be described with reference to the accompanying drawings. 
       FIG. 1  is a cross-sectional view illustrating a conventional organic light emitting display device to which a touch panel is attached. 
     As shown in  FIG. 1 , the conventional organic light emitting display device includes an organic light emitting display panel  10 , a touch panel  20  and a cover film  30  which are sequentially stacked. First and second adhesive layers  15  and  25  are provided between the light emitting display panel  10  and the touch panel  20  and between the touch panel  20  and the cover film  30 , respectively. 
     Herein, the organic light emitting display panel  10  includes a substrate, a thin film transistor array arranged on the substrate in a matrix, and organic light emitting diodes connected to respective thin film transistors of the thin film transistor array. An encapsulating substrate sealing the organic emitting diodes and a polarizing layer are further provided. In this case, the first adhesive layer  15  is disposed on the polarizing layer. The touch panel  20  includes a plurality of touch electrodes disposed on its touch substrate for detecting a user&#39;s touch. 
     The substrate of the organic light emitting display panel  10 , the encapsulating substrate, the touch substrate of the touch panel  20  and the cover film  30  are typically formed of a hard material such as glass. These substrates typically have a thickness of about 0.5 mm or more, and thus, it may be difficult to manufacture an organic light emitting display device to which a touch panel is attached with slim profile and desired flexibility. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to an organic light emitting display device and a method of manufacturing the same that substantially obviates one or more problems due to limitations and disadvantages of the related art. 
     An advantage of the present invention is to provide an organic light emitting display device having slimness and flexibility, and a method of manufacturing the same. 
     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, an organic light emitting display device, in which a plastic or glass support substrate used to form a touch electrode array is removed after forming the touch electrode array, is provided. As a result, an entire thickness of the organic light emitting display device can be decreased when the touch electrode array is disposed on an organic light emitting panel. In addition, a material causing visibility of reflected external light can be removed, thereby improving visibility of desired images. 
     In an aspect of the present invention, an organic light emitting display device including an organic light emitting panel includes a thin film transistor array on a base substrate, an organic light emitting diode array electrically connected to the thin transistor array, and an encapsulation layer covering the organic light emitting diode array, a first adhesive layer on the organic light emitting panel, a touch electrode array being in contact with the first adhesive layer, a separation layer on the touch electrode array, and a cover film on the separation layer. 
     The separation layer may have a thickness of 100 Å or less. 
     The separation layer may include a silicon material or a metal oxide layer. 
     The organic light emitting display device may further include a barrier layer in contact with the touch electrode array and a buffer layer in contact with the buffer layer, between the touch electrode array and the separation layer. 
     The barrier layer may include an inorganic layer having a thickness of 500 Å to 3,000 Å, and the buffer layer may include an organic layer having a thickness of 1 μm to 8 μm. 
     The barrier layer may include a single layer of an oxide layer or a nitride layer, multi-layers of an oxide layer or a nitride layer, or an alternately laminated layer of an oxide layer and a nitride layer. 
     The buffer layer may include at least one of an acrylic group, an epoxy group, a polyimide group, and a polyamide group. 
     The cover film may include a circular polarizing plate. 
     The circular polarizing plate may be in contact with the separation layer. 
     The organic light emitting display device may further include a second adhesive layer between the separation layer and the cover film. 
     The separation layer and the cover film may be in contact with a lower surface and an upper surface of the second adhesive layer, respectively. 
     The organic light emitting display device may further include a circular polarizing plate between the second adhesive layer and the cover film. 
     The touch electrode array may include a plurality of first and second touch electrodes intersecting each other; a protective layer covering the first and second touch electrodes; a plurality of touch pad electrodes corresponding to the first and second electrodes at an outside region of an active region, and a plurality of routing wires transmitting signals to the first and second touch electrodes at the touch pad electrodes, wherein, at least one of the first and second touch electrodes, the routing wires, and the touch pad electrodes may be in contact with the barrier layer, and the protective layer may be in contact with the first adhesive layer. 
     The organic light emitting display device may further include a light shielding layer between the barrier layer and the protective layer within the touch electrode array, and the light shielding layer including a color filter layer and a black matrix layer staked. 
     In accordance with another aspect of the present invention, there is provided a method of manufacturing an organic light emitting display device including providing an organic light emitting panel comprising a thin transistor array on a first base substrate, an organic light emitting diode array electrically connected to the thin transistor array, and an encapsulation layer covering the organic light emitting diode array, forming a separation layer and a touch electrode array on a second base substrate, attaching a first adhesive layer between the encapsulation layer and the touch electrode array which face each other, exposing the separation layer to remove the second base substrate, and attaching a cover film to the exposed separation layer through a second adhesive layer. 
     Removing the second base substrate may include irradiating a laser. 
     Optionally, removing the separation layer to a certain thickness may be added. 
     The remaining separation layer may have a thickness of 100 Å, or less after partially removing the separation layer. 
     Also, forming a buffer layer and a barrier layer on the separation layer may be added, after forming the separation layer and before forming the touch electrode array. 
     The second base substrate may include a plastic substrate or a glass substrate, or a stacked structure of a plurality of plastic substrates. 
     In accordance with another aspect of the present invention, there is provided a method of manufacturing an organic light emitting display device including providing an organic light emitting panel including a thin transistor array on a base substrate, an organic light emitting diode array electrically connected to the thin transistor array, and an encapsulation layer covering the organic light emitting diode array, sequentially forming a separation layer, a buffer layer, a barrier layer and a touch electrode array on a glass substrate, attaching a first adhesive layer between the encapsulation layer and the touch electrode array, which face each other, removing the glass substrate and the separation layer, and attaching a cover film to the exposed buffer layer through a second adhesive layer. 
    
    
     
       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: 
         FIG. 1  is a cross-sectional view illustrating a conventional organic light emitting display device to which a touch panel is attached; 
         FIG. 2  is a cross-sectional view illustrating an example of an organic light emitting display device employed as a flexible display; 
         FIG. 3  is a view illustrating an optical path of an external light incident on the organic light emitting display device of  FIG. 2 ; 
         FIG. 4  is a graph showing changes of birefringence depending on types of materials and thicknesses of the second flexible substrate of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view illustrating an organic light emitting display device according to an embodiment of the present invention; 
         FIG. 6  is a view illustrating an optical path of an external light incident on the organic light emitting display device of  FIG. 5 ; 
         FIGS. 7A to 7D  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a first embodiment of the present invention; 
         FIGS. 8A and 8B  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a second embodiment of the present invention; 
         FIGS. 9A to 9C  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a third embodiment of the present invention; 
         FIG. 10  show pictures capturing an upper surface of  FIG. 9C  using measurement equipment after removing the upper base substrate of the organic light emitting display device through the method of  FIGS. 9A to 9C ; 
         FIG. 11  is a graph measuring a laser energy density vs a Si ratio at the upper surface of  FIG. 9C  after removing the upper base substrate of the organic light emitting display device through the method of  FIGS. 9A to 9C . 
         FIG. 12  is a cross-sectional view illustrating an organic light emitting display device according to a first embodiment of the present invention; 
         FIG. 13  is a cross-sectional view specifically illustrating the organic light emitting display device according to the first embodiment of the present invention; 
         FIG. 14  is a cross-sectional view illustrating an organic light emitting display device according to a second embodiment of the present invention; 
         FIG. 15  is a cross-sectional view specifically illustrating the organic light emitting display device according to the second embodiment of the present invention; 
         FIG. 16  is an SEM of the organic light emitting display device according to the second embodiment of the present invention; 
         FIG. 17  is a cross-sectional view illustrating an organic light emitting display device according to a third embodiment of the present invention; 
         FIG. 18  show pictures of an organic light emitting display device when an upper material is maintained and removed, as viewed from an upper side, a profile side and a front side; and 
         FIG. 19  is a graph illustrating reflectivity changes with respect to wavelength changes when an upper material is maintained and removed. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     Reference will now be made in detail to embodiments of the 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. It will be paid attention that detailed description of known arts will be omitted if it is determined that the arts can mislead the embodiments of the invention. Names of components used in the following description may be selected in consideration of facility of specification preparation. Thus, the names of the components may be different from names of components used in a real product. 
       FIG. 2  is a cross-sectional view illustrating an example of an organic light emitting display device as a flexible display.  FIG. 3  is a view illustrating an optical path of an external light incident on the organic light emitting display device of  FIG. 2 . 
     Referring to  FIG. 2 , an organic light emitting display device according to an embodiment includes first and second plastic base substrates  41  and  52 , with which the substrate and the touch panel of the organic light emitting display including the attached touch panel of  FIG. 1  are replaced, and a circular polarizing plate  60 , with which the cover film of  FIG. 1  is replaced. 
     In this case, an organic light emitting display panel  40  disposed at a lower side includes the first plastic base substrate  41 , a thin film transistor array  42 , an organic light emitting array  43 , and an encapsulating layer  44 , which are sequentially stacked from below. A touch panel facing the organic light emitting display panel  40  includes the second plastic base substrate  52 , a touch electrode array  51  disposed on the second plastic base substrate  52 . 
     In addition, a first adhesive layer  45  is disposed between the organic light emitting display panel  40  and the touch panel  50 . A second adhesive layer  55  is disposed between the touch panel  50  and the circular polarizing plate  60 . 
     In this case, a polarizing plate is omitted in the organic light emitting display panel  40 . The circular polarizing plate  60  is disposed at the outmost side to reduce or prevent a reflection of external light while protecting a surface of the device. 
     As compared to the organic light emitting display device according to the related art, the thick glass material is replaced with the plastic substrates  41  and  52  and the circular polarizing plate  60  having a thickness of 25 μm or lower, and, as such, the thickness of the entire device can be decreased and the flexibility of the device can be increased. 
     Meanwhile, when the thin film transistor array  42  and the touch electrode array  52  are formed on the thin first and second plastic substrates  41  and  52 , the first and second plastic substrates  41  and  52  can be rolled. To this end, a support substrate such as a glass substrate is disposed on each of the lower sides of the first and second plastic substrates  41  and  52  to support the first and second plastic substrates  41  and  52 . After completing an array process and an bonding process in which the organic light emitting light panel  40  is attached to the touch panel  50 , the support substrates may be removed. 
     The organic light emitting display device of  FIG. 2  has an advantage in flexibility, but may have a reflective element in response to an external light, which will now be described in detail. 
     Referring to  FIG. 3 , after an external light is incident on the circular polarizing plate  60  along a certain axis, the circularly polarized light then passes through the second adhesive layer  55 , the touch panel  50 , the first adhesive layer  45 , and the organic light emitting display panel  40 . Herein, an optical path of the circular polarized light changes due to a birefringence at the second plastic substrate  52  of the touch panel  50 . In this case, after the circularly polarized light is reflected from a reflection electrode of the organic light emitting array  43  in the organic light emitting display panel  40 , the reflected light reaches the circular polarizing plate  60  through the first adhesive layer  45 , the touch panel  50 , and the second adhesive layer  55 . Herein, the reflected light includes an element crossing the certain axis of the circular polarizing plate  60  and an element twisted by the birefringence of the second plastic substrate  52 , which may result in a light leakage. 
     Hereinafter, in consideration of the principle of  FIG. 3 , changes of birefringence of the second flexible substrate  52  will be measured and discussed depending on materials and thicknesses employed. 
       FIG. 4  is a graph showing changes of birefringence depending on types of materials and thicknesses of the second flexible substrate  52  of  FIG. 2 . 
     The second plastic substrate  52 , as tested in  FIG. 4 , is a transparent polyimide group film. The second plastic substrate  52  has materials A to D which are different from one another. However,  FIG. 4  shows that regardless of the material A to D employed, as the thickness of the second plastic substrate  52  increases, the birefringence thereof increases. In addition, the visibility of the reflected light increases in proportion to an amount of birefringence of the second flexible substrate  52 . 
     When the second plastic substrate  52  has a thickness of about 5 μm to 20 μm, an amount of birefringence Rth is greater than 40 nm for all the materials of the second plastic substrates  52 , namely, A to D. In this case, although the circular polarizing plate  60  for birefringence is provided, it may not be easy to reduce or prevent reflection of external light due to the birefringence of the second plastic substrate  52 , which is used for a slim profile design of the organic light emitting display device. 
     To reduce or prevent the visibility of the reflected light caused by the birefringence of the second plastic substrate  52 , an optical compensation film such as a C+ plate may be further provided to compensate for the birefringence of the second plastic substrate  52 . However, since the optical compensation film typically has a thickness 150 μm or more, there may be a disadvantage in flexibility. 
     Hereinafter, an organic light emitting display device according to an embodiment will be described, which does not include an optical compensation film for slimness and flexibility. However, the present invention is not limited thereto, and an organic light emitting display device according to an embodiment of the present invention may include an optical compensation film. 
       FIG. 5  is a cross-sectional view illustrating an organic light emitting display device according to an embodiment of the present invention.  FIG. 6  is a view illustrating an optical path of an external light incident on the organic light emitting display device of  FIG. 5 . 
     Referring to  FIGS. 5 and 6 , the organic light emitting display device includes an organic light emitting panel  1000  including a thin film transistor array  110  disposed on a first plastic base substrate  100 , an organic light emitting diode array  120  electrically connected to the thin film transistor array  110 , and an encapsulation layer  130  covering the organic light emitting diode array  120 , a first adhesive layer  140  disposed on the organic light emitting panel  1000 , a touch electrode array  150  contacting the first adhesive layer  140 , a separation layer  225  disposed on the touch electrode array  150 , and a cover film  160  disposed on the separation layer  225 . 
     The separation layer  225  has a thickness of 100 Å or less. After a second plastic base substrate  210  (see  FIG. 7A ) is removed, the separation layer  225  is exposed. Namely, during a manufacture of the touch electrode array  150  using deposition and patterning processes, the second plastic base substrate  210  is maintained at a bottom side of the separation layer  225 . Then, after bonding the touch electrode array  150  to the organic light emitting panel  1000 , the second plastic base substrate  210  is removed. As a result, the visibility of external light due to the birefringence of the second plastic base substrate  210  can be reduced or prevented. 
     A surface of the separation layer  225  may not be flat. The separation layer  225  may have a non-uniform surface according to contained elements thereof. Alternatively, a part of the separation layer  225  may be removed at an upper surface of the touch electrode array  150  and the other part of the separation layer  225  may remain at the upper surface of the touch electrode array  150 . 
     Herein, the separation layer  225  may be formed of a single element such as amorphous silicon, or a silicon group compound such as silicon nitride (SiN x ) and/or silicon oxide (SiO x ). The separation layer  225  may be a metal oxide layer formed of Al 2 O 3 , MO x  and/or TiO 2 . 
     Furthermore, the separation layer  225  functions to protect the touch electrode array  150  when the second plastic base substrate  210  disposed at the upper side of the touch electrode array  150  is removed after bonding the organic light emitting panel  1000  and the touch electrode array  150 . Upon removal of the second plastic base substrate  210 , a part of the separation layer  225  adjacent to the second plastic base substrate  210  may be removed. The separation layer  225  is provided to reduce or prevent damage such as corrosion or oxidation of a metallic touch electrode when the touch electrode array  150  is directly exposed. 
     The second plastic base substrate  210  may be removed by a laser releasing process. At the same time, the silicon group material or metal oxide, namely, elements of the separation layer  225  which is adjacent to the second plastic base substrate  210  is partially removed. 
     Meanwhile, the encapsulation layer  130  may be a face seal or a barrier stack structure composed of alternately laminated inorganic and organic layers, in order to cover the organic light emitting diode array  120 . 
     The cover film  160  may basically include a circular polarizing plate. The cover film  160  may be a circular polarizing plate itself. In this case, the cover film may be directly coated on an exposed surface of the separation layer  225 , or may be added with a separate circular polarizing plate film in an attached manner. In the former case, a phase delay layer and a linear polarizing layer are formed on the surface of the separation layer  225  to form the cover film  160 . In the latter case, forming the cover film  160  includes preparing a circular polarizing plate having a film type, and directly laminating an adhesive surface of the circular polarizing plate on the separation layer  225  while a protection surface of the circular polarizing plate is exposed. Furthermore, in the case that the cover film  160  is a single circular polarizing plate, the circular polarizing plate functions to protect the organic light emitting display device from external impact. The cover film  160  has a thickness of 10 μm to 80 μm, which may be sufficient to flex the organic light emitting display device, emit light from the organic light emitting diode array  120  disposed below and reduce or prevent reflection of external light. 
     Alternatively, the cover film  160  may have a double-layered structure including a circular polarizing plate and a cover film. In this case, the cover film is disposed at outside corresponding to a viewed surface. The cover film is beneficially formed of a soft transparent film, not a hard material such as a glass. For example, the cover film may be formed of one selected from the group including a polyethylene group resin, a polypropylene group resin, a polyethylene terephthalate group resin, a polyvinyl alcohol group resin, a nylon group resin, a polyacrylonitrile group resin, and a polymethacrylic acid group resin. In this case, the cover film is disposed on a surface of the organic light emitting display device to protect the device from external impact. The circular polarizing plate disposed below the cover film optically functions to reduce or prevent visibility of external light. 
     When the cover film  160  includes a circular polarizing plate, as illustrated in  FIG. 6 , unpolarized external light passes through the circular polarizing plate  160  to be right-circularly polarized with respect to a transmission axis and is incident upon the touch electrode array  150 , the adhesive layer  140 , the encapsulation layer  130  and the organic light emitting diode array  120 . The incident light is reflected by a reflection electrode included in the organic light emitting diode array  120  to be left-circularly polarized. In this case, the reflected light is thus oriented along an absorption axis crossing the transmission axis of the circular polarizing plate, and, as such, the reflected light is reduced or prevented as it does not pass though the circular polarizing plate  160 . 
     Accordingly, the organic light emitting display device as illustrated in  FIG. 5  according to an embodiment of the present invention can reduce or prevent visibility of external light. In such a structure, the separation layer  225  contacting the touch electrode array  150  between the touch electrode array  150  and the cover film  160  has a thickness of 0.01 μm (=100 Å) or less, thereby reducing or preventing movement of the transmission axis. A movement of the transmission axis may occur when an incident light passes through a plastic film before or after reflection after an external light is incident upon the circular polarizing plate  160  in the organic light emitting display device. In addition, when the light is reflected by the reflection electrode of the organic light emitting diode array  120 , the reflected light may be blocked by the absorption axis of the circular polarizing plate  160 . 
     Hereinafter, a method of manufacturing an organic light emitting display device according to an embodiment of the present invention will be described in which a removal process of an upper base substrate such as a second plastic base substrate and/or a second glass substrate is employed. 
       FIGS. 7A to 7D  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a first embodiment of the present invention. 
     As illustrated in  FIG. 5A , a method of manufacturing an organic light emitting display device according to an embodiment of the present invention includes forming the organic light emitting panel  1000  including the thin film transistor array  110  disposed on the first plastic base substrate  100 , the organic light emitting diode array  120  connected to the thin film transistor array  110 , and the encapsulation layer  130  covering the organic light emitting diode array  120 . In this process, when the first plastic base substrate  100  has process tolerance sufficient to endure impact such as sputtering and a high temperature process such as crystallization, the thin film transistor array  110  can be directly formed thereon. If not, a first glass substrate  250  is provided below the first plastic base substrate  100 , as illustrated in  FIG. 7A , the thin film transistor array  110  and the organic light emitting diode array  120  can be formed and then the encapsulation layer  130  may be formed to cover an upper surface of the organic light emitting diode array  120  and a periphery thereof. 
     Sequentially, as illustrated in  FIG. 7A , a surface to be formed with the touch electrode array  150  may be the second plastic base substrate  210 . However, before forming the touch electrode array  150 , the separation layer  225  is provided to protect the touch electrode array  150  during removal of the second plastic base substrate  210 . The separation layer  225  is an inorganic layer having a thickness of 0.01 μm (=100 Å) or less. The separation layer  225  may be formed of a silicon group material or may be a metal oxide layer. When the thickness of the separation layer  225  is greater than 0.01 μm, a part of the separation layer  225  may be removed by adjusting laser energy density in laser releasing during removal of the second plastic base substrate  210  of  FIG. 7D , which will be described later. Furthermore, a second glass substrate  200  may be further provided below the second plastic base substrate  210  and, as such, the second plastic base substrate  210  may be sufficiently supported during formation of the first and second touch electrodes using a sputtering process. 
     Sequentially, the encapsulation layer  130  and the touch electrode array  150  are positioned to face each other, the first adhesive layer  140  (see  FIG. 5 ) is interposed therebetween, and the encapsulation layer  130  and the touch electrode array  150  are bonded to one another. 
     Meanwhile, each of the first and second glass substrates  250  and  200  has a thickness of 0.5 mm or more. This increases the thickness of the device, thereby decreasing the flexibility of the device. As such, the first and second glass substrates  250  and  200  are removed. First, the second glass substrate  200  is removed, and then the first glass substrate  250  is removed. This will be described later. 
     As illustrated in  FIGS. 7B and 7C , the second glass substrate  200  is first released and removed by irradiating a laser as illustrated in  FIG. 7C . 
     In succession, as illustrated in  FIG. 7D , the exposed second plastic base substrate  210  is removed up to the separation layer  225  as a boundary. The second plastic base substrate  210  is thin and transparent, and thus, the separation layer  225  may be stripped by raising a corner thereof. 
     After the second glass substrate  200  and the second plastic base substrate  210  are removed, the first glass substrate  250  disposed therebelow is removed using a laser, although not shown. 
     Meanwhile, an element of the removed second plastic base substrate  210  may include a polymer compound. The element may include at least one selected from the group consisting of polyester, copolymer including polyester, polyimide, copolymer including polyimide, olefin group copolymer, polyacrylic acid, copolymer including polyacrylic acid, polystyrene, copolymer including polystyrene, polysulfate, copolymer including polysulfate, polycarbonate, copolymer including polycarbonate, polyamic acid, copolymer including polyamic acid, polyamine, copolymer including polyamic acid, polyvinyl alcohol, polyallylamine. The removed second plastic base substrate  210  may have a thickness of about 20 μm to 100 μm. 
       FIGS. 8A and 8B  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a second embodiment of the present invention. 
     In the second embodiment, the second plastic base substrate  210  as illustrated in  FIG. 8A  is directly irradiated by a laser. As illustrated in  FIG. 8B , the second plastic base substrate  210  may be stripped by raising it from the separation layer  225 . 
     After removal of the second plastic base substrate  210 , because the separation layer  225  is very thin and transparent, the touch electrode array  150  may be visible through the naked eye. 
       FIGS. 9A to 9C  are cross-sectional views illustrating a method of removing an upper base substrate of an organic light emitting display device according to a third embodiment of the present invention. 
     In the third embodiment, the method of removing the upper base substrate of the organic light emitting display device, as illustrated in  FIG. 9A , includes sequentially forming a sacrificial layer  220  directly disposed on the second glass substrate  200 , a buffer layer  170 , and a barrier layer  165  without the second plastic base substrate  210 , and forming the touch electrode array  150 . Since the second plastic base substrate  210  is not used, the buffer layer  170  and the barrier layer  165  may be further provided to protect the touch electrode array  150 . 
     A removal process will be described in detail. The sacrificial layer  220  is formed of amorphous silicon, a silicon dielectric layer or a metal oxide layer. The buffer layer  170  is an organic layer having a thickness of 1 μm to 8 μm. The barrier layer  165  is an inorganic layer having a thickness of 500 Å to 3,000 Å. In this case, when the touch electrode array  150  is formed, at least one of the electrodes of the touch electrode array  150  is formed to directly contact the barrier layer  165 . 
     In addition, in the state that such a structure is maintained, the first glass substrate  250  may be bonded to the organic light emitting display device  1000  having the above structure. 
     In this case, as illustrated in  FIG. 9B , the second glass substrate  200  is irradiated with a laser. As illustrated in  FIG. 9C , the second glass substrate  200  and a part  220   a  of the sacrificial layer  220  are removed. During the removal process, as illustrated in  FIG. 9C , a part of the sacrificial layer  220  may remain at the separation layer  225 . The thickness of separation layer  225 , as described above, may be 100 Å or less. 
     In addition, since the separation layer  225  is very thin, the separation layer  225  may not have a flat surface. One region of the separation layer  225  may be removed to expose the buffer layer  170 , and the other region may remain to have a thin thickness. 
     Meanwhile, in a process of  FIG. 9C , the separation layer  225  may be completely removed. In this case, during removal of the separation layer  225 , a part of the buffer layer  170  may be removed and exposed. In this process, the buffer layer  170  functions to protect against physical impact such as radiation of laser. 
     In the third embodiment, since the plastic base substrate on the touch electrode array  150 , which generates birefringence, is omitted, the same effect as removal of the second plastic base substrate in the first and second embodiments may be obtained. 
     Furthermore, after removal of the upper base substrate of the first to third embodiments as described above, the first glass substrate  250  disposed below may be removed using a laser. The removal process of the first glass substrate  250  is similar to the removal process of the second glass substrate or the second plastic base substrate. 
     Meanwhile, after the separation layer  225  is exposed by removal of the second plastic base substrate  210  and/or the second glass substrate  200 , a second adhesive layer  320  (see  FIG. 10 ) may be disposed on the exposed separation layer  225  and the cover film  160  may be attached to the separation layer  225 . 
     Hereinafter, effectiveness of a method of manufacturing an organic light emitting display device according to an embodiment of the present invention will be described through composition analysis of a picture, which captures an exposed upper surface after removal of the second glass substrate or the second plastic base substrate used as a support substrate or a formation substrate of the touch electrode array in the organic light emitting display device. 
       FIG. 10  show pictures capturing the upper surface of  FIG. 9C  using a measurement equipment after removing the upper base substrate of the organic light emitting display device through the method of  FIGS. 9A to 9C .  FIG. 11  is a graph measuring a laser energy density vs a Si ratio at the upper surface of  FIG. 9C  after removing the upper base substrate of the organic light emitting display device through the method of  FIGS. 9A to 9C . 
     In particular,  FIG. 10  are image pictures of the composition of the exposed upper surface of the separation layer  225  after removal of the second plastic base substrate  210  and/or the second glass substrate  200  using a time of flight secondary mass spectrometer (ToF-SIMS). 
     In  FIG. 10 , the separation layer having a thickness of 100 Å is tested twice when each laser energy density is 220 mJ/cm and 180 mJ/cm. Results of the laser energy density of 220 mJ/cm are referred as to #1 and #2, and results of the laser energy density of 180 mJ/cm are referred as to #3 and #4. In addition,  FIG. 10  shows the composition of the measured elements. As the brightness of the image picture increases, an amount of the element increases. In other words, as the color of the image picture is gradually close to black, the amount of the element becomes smaller. 
     Herein, during removal of the upper base substrate, when the separation layer is very thin, the buffer layer is exposed by the partially removed separation layer. H, CH, and O are elements of the exposed buffer layer. 
     In addition, a single element such as Si or a silicon compound bonded to hydrogen such as SiH is an element of the separation layer. 
     Under the condition of #1 to #4, Si or SiH, namely, the element of the separation layer, is about 0.01% to 0.2% (169/967,379) in comparison with H, CH, or O, namely, the element of the buffer layer. It is noted that the amount of the element of the remaining separation layer is very small. Thus, this is not optically or electrically influenced to the other devices in the organic light emitting display device. 
       FIG. 11  illustrates composition between C—H (a main element of the buffer layer) versus Si (a main element of the separation layer) in the case of the separation layer having a thickness of 200 Å and in the case of the separation layer having a thickness of 500 Å. In the case of the thickness of 200 Å, the separation layer contains 0.1% Si. In the case of the thickness of 500 Å, the separation layer contains 1% Si. It is noted that the remaining amount of Si is proportional to the thickness of the separation layer. 
     The separation layer according to an embodiment of present invention is an inserted layer for removing the upper base substrate of the touch electrode array. In other words, the separation layer is not an optical or electrical layer in the device. Accordingly, the thickness of the separation layer is beneficially 100 Å or less to not influence the other functional layers in the device. 
     In addition, when the separation layer is formed of silicon or is a metal oxide layer, the separation layer may have semiconductive or conductive characteristics. Alternatively, the separation layer may be completely removed to drive a sensitive touch electrode array. In this case, although the separation layer is removed, the touch electrode array should be not exposed. To do so, as illustrated in  FIG. 9A , the barrier layer  165  and the buffer layer  170  are provided on the touch electrode array  150  to protect the touch electrode array  150  from external physical stress due to removal of the separation layer. 
     Hereinafter, various embodiments of an organic light emitting display device will be described. The organic light emitting display device which includes the structure of  FIG. 5  as the basic structure may be modified in the following various embodiments. 
       FIG. 12  is a cross-sectional view illustrating an organic light emitting display device according to a first embodiment of the present invention.  FIG. 13  is a cross-sectional view specifically illustrating the organic light emitting display device according to the first embodiment of the present invention. 
     As illustrated in  FIG. 12 , the organic light emitting display device according to the first embodiment of the present invention includes an organic light emitting panel  1000  including a thin film transistor array  110  disposed on a first plastic base substrate  100 , an organic light emitting diode array  120  electrically connected to the thin film transistor array  110 , and an encapsulation layer  130  covering the organic light emitting diode array  120 , a first adhesive layer  140  disposed on the organic light emitting panel  1000 , a touch electrode array  150  contacting the first adhesive layer  140 , a barrier layer  165 , a buffer layer  170  and a separation layer  225  sequentially disposed on the touch electrode array  150 , and a cover film  160  disposed on the separation layer  225 . 
     Herein, before bonding the organic light emitting panel  1000  and the touch electrode array  150 , the separation layer  225 , the buffer layer  170 , and the barrier layer  165  are from upside sequentially formed on a second glass substrate  200  (see,  FIG. 7A ) or a second plastic base substrate  210 . After removal of the second glass substrate  200  and the second plastic base substrate  210 , in the state that the separation layer  225  is exposed, the cover film  160  is attached to the separation layer  225  through a second adhesive layer  160 . In this case, the second adhesive layer  160  is disposed between the separation layer  225  and the cover film  160  such that the separation layer  225  and the cover film  160  are in contact with an upper surface and a lower surface of the second adhesive layer  320 , respectively. 
     A difference from the basic structure of  FIG. 5  is the addition of the buffer layer  170  and the barrier layer  165  to protect the touch electrode array  150 . 
     The barrier layer  165  is an inorganic layer having a thickness of 500 Å to 3000 Å. The buffer layer is an organic layer having a thickness of 1 μm to 8 μm. The organic buffer layer acting as a buffer against physical stress such as a laser is adjacent to the separation layer  225 . Furthermore, the barrier layer  165  directly contacts the touch electrode array  150 . The barrier layer  165  functions to reduce or prevent a touch electrode, a routing wire, or a touch pad electrode from being directly exposed during a removal process of the second plastic base substrate or the second glass substrate. The barrier layer  165  may be formed of the same material as an insulation layer constituting the touch electrode array. 
     In detail, the buffer layer  170  may include an organic layer formed of at least one of acrylic group, epoxy group, polyimide group, and polyamide. The barrier layer  165  may include a single layer such as an oxide layer or a nitride layer, or multiple layers of an oxide layer or a nitride layer, or alternately laminated layers of an oxide layer and a nitride layer. The buffer layer  170  and the barrier layer  165  are transparent and have a reflectivity of 5% or less. As a result, the buffer layer  170  and the barrier layer  165  may direct the light emitted from the organic light emitting diode array  120  without loss. As the buffer layer  170  has a thickness range from 1 μm to 8 μm, there may be no birefringence upon introduction of external light. Even if there is birefringence, an amount of birefringence may be maintained at an invisible level. 
     Meanwhile, according to the first embodiment, the cover film  160  is a circular polarizing plate itself. When an unpolarized external light is incident along a certain transmission axis of the circular polarizing plate, the light is left-circularly polarized or right-circularly polarized. Then, when the light is reflected at the first electrode  121  ( FIG. 13 ) of a reflective electrode element of the organic light emitting diode array  120 , the light is right-circularly polarized or left-circularly polarized to proceed to the circular polarizing plate in an opposite direction. Herein, the reflected light is blocked by the absorption axis to reduce or prevent reflection of external light. 
     In detail, internal constituents of the organic light emitting display device according to the first embodiment of the present invention in  FIG. 13  will now be described. 
     As illustrated in  FIG. 13 , a TFT buffer layer  105  including a plurality of inorganic layers may be further provided on the first plastic base substrate  100 . When wiring or an active layer is directly formed on the first plastic base substrate  100 , the TFT buffer layer  105  allows a surface of the wiring or active layer to be uniform. 
     The thin transistor array  110 , the organic light emitting diode array  120 , and the touch electrode array  150  in an active region are disposed at the same level as the thin transistor array  110 , the organic light emitting diode array  120 , and the touch electrode array  150  in a peripheral region. In addition, in a planar view, a plurality of pixels are arranged in a matrix in the active region. Each thin transistor array  110  includes gate lines and data lines, which cross each other. In this case, each pixel is disposed at every crossing point and includes at least one thin film transistor (TFT). The organic light emitting diode array  120  includes organic light emitting diodes (OLEDs). The touch electrode array  150  includes first touch electrodes  151  and second touch electrodes  152 , which cross each other. The crossing point of the first and second touch electrodes  151  and  152  may correspond to each pixel. Alternatively, an arrangement of the first and second touch electrodes  151  and  152  may be unrelated to an arrangement of the pixels. 
     Furthermore, a pad part is disposed in a peripheral region of the thin transistor array  110 . The touch electrode array  150  includes a touch pad part partially connected to the pad part of the thin film transistor array  110 . Herein, since the pad part of the thin film transistor array  110  is connected to the touch pad part, a separate a flexible printed circuit (FPC) connection may not be needed at the touch electrode array  150  side to receive a touch control signal from the thin transistor array  110 . As a result, the manufacturing process may be simplified and the FPC connection may be minimized. 
     The thin transistor (TFT) in the pixel of the thin pixel transistor array  110  includes an active layer  111  on the TFT buffer layer  105 , a gate dielectric layer  112  covering the active layer  111  while being formed on the TFT buffer layer  105 , a gate electrode  113  overlapping the active layer  111 , an interlayer dielectric  114  formed on the gate electrode  113  and the gate dielectric layer  112 , and a source electrode  115  and a drain electrode  116  passing through the interlayer dielectric  114  and the gate dielectric layer  112  to connect both ends of the active layer  112 , respectively. At least one touch auxiliary pad electrode  117  may be formed on a same layer with the source electrode  115  and the drain electrode  116 . On the interlayer dielectric  114 , a TFT protective layer  118  is formed to expose at least the drain electrode  117  and a part of the touch auxiliary pad electrode  117 . Herein, the gate electrode  113  may be disposed at the same level as the gate line. The source electrode  115  and the drain electrode  116  may be disposed at the same level as the data line. Also, a planarization film is formed on the TFT protective layer  118 , in at least an active area. 
     Pad electrodes for the gate line and the data line and a second electrode pad electrode grounding the second electrode of the organic light emitting diode array or applying a uniform voltage thereto are provided in the peripheral region of the thin film transistor array. Furthermore, as illustrated, a touch auxiliary electrode  117  connected to the touch pad electrode  155  of an upper surface of the touch pad electrode array  150  may be further provided. 
     The organic light emitting diode (OLED) includes a first electrode connected to the drain electrode  116 , an organic light emitting layer  123  formed in a bank  122   a  defining a light emitting region, and a second electrode  124  covering the organic light emitting layer  123 . 
     Optionally, spacers  112   b  having a certain thickness corresponding to a width of the bank  112   a  may be provided on the bank  122   a . When the organic light emitting layer  123  is formed, organic material is disposed at the first plastic base substrate  100  using a metal mask having an opening. In this case, the metal mask droops such that the bank  122   a  collapses or the light emitting region is influenced to an inner the emitting region. To this end, the spacers  112   b  are regularly provided on the bank  112   a . Meanwhile, the first electrode is a reflection electrode and the second electrode  124  is a transparent electrode. The external light is reflected at the first electrode  121  after passing through the organic light emitting diode (OLED). Then, the reflected light proceeds through the transparent second electrode  124 . 
     In addition, the encapsulation layer  130  is formed on the organic light emitting diode array  120  to cover the upper side and the profile side of the organic light emitting diode (OLED). 
     The touch electrode array  150  includes the first and second touch electrodes  151  and  152  which cross each other in the active region, a protective layer  156  covering the first and second touch electrodes  151  and  152 , a plurality of touch pad electrodes  155  corresponding to the first and second touch electrodes  151  and  152  in the peripheral region, and a routing wire  154  transferring signals from the touch pad electrodes  155  to the first and second touch electrodes  151  and  152 . 
     In the illustrated embodiment, the first and second touch electrodes  151  and  152 , the routing wire  154 , and the touch pad electrodes  155  include metal mash patterns  151   a ,  152   a ,  154   a , and  155   a  disposed at an upper side and transparent electrodes  151   b ,  152   b ,  154   b , and  155   b  disposed at a lower side, respectively. Each of the first and second touch electrodes  151  and  152 , the routing wire  154 , and the touch pad electrodes  155  has a double-layered electrode structure, thereby realizing a stable electric field and low resistance. However, the present invention is not limited by such an electrode structure including the metal mash patterns. An organic light emitting display device according to an embodiment of the present invention may include a single-layer electrode structure. 
     Furthermore, since the first touch electrodes  151  and the second touch electrodes  152  are disposed at the same level in order to reduce or prevent a short circuit between the first and second touch electrodes  151  and  152 , the first touch electrodes are connected to each other by a bridge pattern  151   c  disposed through a contact hole in the protective layer  140 . As a result, the first touch electrodes  151  are electrically isolated from the second touch electrodes  152 . 
     As illustrated in  FIG. 13 , the first and second touch electrodes  151  and  152 , the routing wire  154 , and the touch pad electrodes  155  are in contact with the barrier layer  165 . The protective layer  156  may be in contact with the first adhesive layer  140  for bonding the encapsulation layer  130  and the touch electrode array  150 . 
     The barrier layer  165  is in contact with the organic buffer layer  170 . The buffer layer  170  is in contact with the separation layer  225  formed of a silicon material or a metal oxide layer. The cover film  160  functioning as a circular polarizing plate is attached to the separation layer  225 . The second adhesive layer  320  may be disposed between the cover film  160  and the separation layer  225  or be omitted. In the latter case, the circular polarizing plate includes an adhesive surface corresponding to a surface of the separation layer  225 . 
     Meanwhile, in the peripheral region, a seal material  272  including a conductive bead  271  is provided. The conductive bead  271  is disposed at a part corresponding to the touch auxiliary pad electrode  117  through the TFT protective layer  118  to be vertically connected between the touch pad electrode  155  and the touch auxiliary pad electrode  117 . 
     In addition, the first plastic base substrate  100  may be formed of a polymer compound. The first plastic base substrate  100  may include at least one selected from the group including polyester, copolymer including polyester, polyimide, copolymer including polyimide, olefin group copolymer, polyacrylic acid, copolymer including polyacrylic acid, polystyrene, copolymer including polystyrene, polysulfate, copolymer including polysulfate, polycarbonate, copolymer including polycarbonate, polyamic acid, copolymer including polyamic acid, polyamine, copolymer including polyamic acid, polyvinyl alcohol, polyallylamine. The first plastic base substrate has relatively a high heat-resisting property in comparison with the second plastic base substrate  210 . The first plastic base substrate  100  may have a thickness of 5 μm to 100 μm. 
     In addition, a back cover film  190  is further provided below the first plastic base substrate  100  to protect the first plastic base substrate  100 . The back cover film  190  is thicker than the plastic base substrate  100  and has a higher hardness than the plastic base substrate  100 . 
       FIG. 14  is a cross-sectional view illustrating an organic light emitting display device according to a second embodiment of the present invention.  FIG. 15  is a cross-sectional view specifically illustrating the organic light emitting display device according to the second embodiment of the present invention.  FIG. 16  is an SEM of the organic light emitting display device according to the second embodiment of the present invention. 
     As illustrated in  FIGS. 14 and 15 , the organic light emitting display device according to the second embodiment of the present invention includes an external light shielding pattern  159  including a color filter layer  159   a  and a black matrix layer  159   b  disposed at the touch electrode array  150  side, rather than the circular polarizing plate disposed at an outmost side in comparison with the first embodiment. As a result, visibility of external light can be reduced or prevented. In this case, the external light shielding pattern  159  is disposed at an entire active region and a part of the peripheral region excluding the touch pad part. A cover film  230  is provided to protect the outside surface of the device. The cover film  230  may be a transparent protective film. Herein, the color filter layer  159   a  may include a red color filter, a green color filter, and a blue color filter according to desired colors of the organic light emitting layer of the organic light emitting diode array  120 . 
     Meanwhile, in the second embodiment of the present invention, the routing wire  154  and the pad electrode  155  are in contact with the barrier layer  165 . The external light shielding pattern  159  is inserted between the first and second touch electrodes  151  and  152  and the barrier layer  165 . Such a disposition of the external light shielding pattern  159  is merely an example. The first and second touch electrodes  151  and  152  may be in contact with the barrier layer  165 , and the external light shielding pattern  159  may be disposed farther from the barrier layer  165 . The color filter  159   a  and the black matrix layer  159   b  of the external light shielding pattern  159  may be dividedly disposed at different layers in an inserted manner, similar to the disposition of the first and second touch electrodes  151  and  152 . 
     Elements in  FIG. 15  of the same reference numerals used in  FIG. 13  have the identical functions. As such, the duplicative description thereof will be omitted. 
       FIG. 16  shows the exposed separation layer  225  after removal of the upper base substrate in the organic light emitting display device according to the second embodiment of the invention. The real separation layer  225  has a thickness of 1/50 to 1/20 as thin as the buffer layer  170  or the color filter layer  159   a  of the touch electrode array  150 . The upper base substrate is removed up to the separation layer  225  used as a boundary, thereby protecting the touch electrode array  150 . 
     In the second embodiment, the upper base substrate is removed to reduce or prevent birefringence caused by the upper base substrate. As a result, visibility of external light is decreased, and optical characteristics may be improved. Since a total thickness of the device is reduced by, for example, 20 μm to 100 μm due to removal of the upper base substrate, the organic light emitting display device can have a slimmer profile. 
       FIG. 17  is a cross-sectional view illustrating an organic light emitting display device according to a third embodiment of the present invention. 
     As illustrated in  FIG. 17 , the organic light emitting panel  1000 , the first adhesive  140 , and the touch electrode array  150  as described in the first embodiment are employed to the organic light emitting display device according to the third embodiment of the present invention. The barrier layer  165 , the buffer layer  170 , and the separation layer  225  are sequentially provided on the touch electrode array  150  and a circular polarizing plate  1600  and the cover film  230  are sequentially provided on the separation layer  225 . 
     The circular polarizing plate  1600 , as described above, has a function of reducing or preventing visibility of external light. The circular polarizing plate  1600  may be formed by attaching a film or by sequentially coating a phase delay layer and a linear polarizing layer. 
     The cover film  230  is a flexible transparent film and has a function of protection of a surface of the device from the outside. For example, the cover film  230  may be selected from the group including a polyethylene group resin, a polypropylene group resin, a polyethylene terephthalate group resin, a polyvinyl alcohol group resin, a nylon group resin, a polyacrylonitrile group resin, and a polymethacrylic acid group resin. 
       FIG. 18  show pictures of an organic light emitting display device with or without an upper base substrate, as viewed from an upper side, a profile side and a front side. 
     As illustrated in  FIG. 18 , when the second plastic base substrate used as a formation surface of the touch electrode array is maintained, the reflected light may be visible at a black state. When the second plastic base substrate or the second glass substrate is removed according to embodiments of the present invention, reflection of external light, which can be seen by an observer, can be reduced or prevented. 
       FIG. 19  is a graph illustrating reflectivity changes with respect to wavelength changes when an upper material is maintained and removed. 
     As shown in  FIG. 19 , between 400 nm to 700 nm, that is, wavelengths of visible light, there is a difference of reflectivity depending whether the upper base substrate is removed or not. Particularly, in a red wavelength, the reflectivity difference is large. When the upper base substrate is maintained, reflectivity is high at a specific wavelength. As a result, reflection of external light may be visible by the observer. According to an embodiment of the present invention, reflectivity is 4% or less in entire wavelengths of the visible light due to removal of the upper base substrate, and, as such, the observer recognizes little or no reflection of external light. 
     As is apparent from the above description, there are the following advantages according to an embodiment of the present invention. 
     First, an organic light emitting display device includes a circular polarizing plate. When an unpolarized external light is incident along a certain transmission axis of the circular polarizing plate, the light is left-circularly polarized or right-circularly polarized. Then, the light is reflected to be right-circularly polarized or left-circularly polarized in an opposite direction. Herein, the reflected light is blocked by an absorption axis of the circular polarizing plate to reduce or prevent visibility of external light. Plastic base substrates of the organic emitting panel disposed at below and the touch panel disposed at upper are provided to have flexibility of the device. When the thin transistor array/organic emitting diode array and the touch electrode array are formed, birefringence may occur at the upper plastic base substrate along the optical path. As a result, reflected external light may not be completely blocked by the absorption axis of the circular polarizing plate due to its twisted optical path. According to an embodiment of the present invention, the upper plastic base substrate is removed to expose the thin separation layer and the cover film, or the circular polarizing plate is directly attached to the separation layer. Namely, unintended birefringence and reflection caused by an upper plastic and/or glass base substrate in the device may be reduced or prevented, and luminousness may be improved due to reduced visibility of reflected external light. 
     Second, the thick upper plastic base substrate is removed from the organic light emitting diode array, and flexibility and sliminess of the flexible display device can thus be improved. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. 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.