Abstract:
An organic light emitting display device includes a first substrate, a second substrate, and an array of organic light emitting elements formed over the first substrate and interposed between the first and second substrate. The array comprises a pixel defining layer. The organic light emitting display device further includes a recess formed into the pixel defining layer, a sealing member, and a reinforcing member. The sealing member is formed along the edges of the first and second substrates and interconnects the first and second substrates. The reinforcing member comprises a first portion positioned in the recess and a second portion projected outside the recess toward the second substrate such that the second portion of the reinforcing member is capable of supporting the second substrate when the second substrate is pressed toward the first substrate by an external force.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0142584, filed on Nov. 22, 2013, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference in their entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to an organic light emitting display device and a method of manufacturing the same. 
         [0004]    2. Description of the Related Art 
         [0005]    An organic light emitting display device a flat panel display device in which an organic emission layer is positioned between electrodes facing each other. Electrons injected from one electrode and holes injected from the other electrode are combined in the organic emission layer to excite luminescent molecules of the organic emission layer, and as the excited molecules are subsequently returned to a ground state, energy is released to emit light. 
         [0006]    Because organic light emitting display devices have excellent visibility, are devised to be lighter and thinner, and are driven with a low voltage, they are promising candidates as next-generation display devices. 
         [0007]    However, organic light emitting display devices have characteristics of being degraded by ambient oxygen and moisture infiltration. 
         [0008]    In order to address such a problem, an organic light emitting element tends to be sealed by using an inorganic sealant such as frit. In such a frit encapsulation structure, a substrate and a sealing substrate may be completely sealed by curing molten frit, and thus, the organic light emitting element may be more effectively protected without having to use a moisture absorbent material. 
         [0009]    Meanwhile, due to the brittleness of the frit material used in the frit encapsulation structure, when external impact is applied, stress is concentrated on a bonding surface between the frit and the substrate to cause cracks to be generated in the bonding surface and spread to the entire substrate. 
       SUMMARY 
       [0010]    An embodiment of the present invention relates to an organic light emitting display device and a method of manufacturing the same, capable of increasing mechanical strength and effectively blocking ambient oxygen and moisture. 
         [0011]    An organic light emitting display device according to an embodiment of the present invention may include a first substrate, a second substrate, and an array of organic light emitting elements formed over the first substrate and interposed between the first and second substrate. The array may comprise a pixel defining layer. The organic light emitting display device may further include a recess formed into the pixel defining layer, a sealing member, and a reinforcing member. The sealing member may be formed along the edges of the first and second substrates and interconnect the first and second substrates. The reinforcing member may comprise a first portion positioned in the recess and a second portion projected outside the recess toward the second substrate such that the second portion of the reinforcing member is capable of supporting the second substrate when the second substrate is pressed toward the first substrate by an external force. 
         [0012]    An organic light emitting display device according to an embodiment of the present invention includes: a substrate having at least one thin film transistor (TFT); an organic light emitting element having a first electrode electrically connected to the TFT, a pixel defining layer formed on the first electrode and having an opening partially exposing the first electrode, an organic emission layer formed on the first electrode, and a second electrode formed on the organic emission layer; a sealing unit sealing the organic light emitting element along the edges of the substrate; and a reinforcing unit positioned within a hole partially formed in the pixel defining layer and enhancing strength of the substrate. 
         [0013]    The reinforcing unit may be formed of a material identical to that of the sealing unit. 
         [0014]    The reinforcing unit and the sealing unit may be formed of glass frit. 
         [0015]    The second electrode may include an opening formed in a portion corresponding to the reinforcing unit. 
         [0016]    The reinforcing unit may be formed in a non-light emitting region of the substrate on the pixel defining layer. 
         [0017]    Two or more reinforcing units may be formed to be spaced apart from one another at a predetermined interval on the pixel defining layer. 
         [0018]    The reinforcing unit may be formed to be applied to the interior of the hole of the pixel defining layer through a printing method. 
         [0019]    The pixel defining layer may be an organic layer. 
         [0020]    A method of making an organic light emitting display device according to an embodiment of the present invention may include: providing an intermediate device comprising a first substrate, a second substrate, and an array of organic light emitting elements formed over the first substrate and interposed between the first and second substrates, the array comprising a pixel defining layer and a recess formed into the pixel defining layer; forming a reinforcing member comprising a first portion and a second portion such that the first portion is received in the recess and the second portion projects outside the recess toward the second substrate; and forming a sealing member along edges of the first and second substrates to interconnect the first and second substrates. 
         [0021]    A method for manufacturing an organic light emitting display device according to another embodiment of the present invention, includes: providing a substrate including a thin film transistor (TFT); forming a first electrode electrically connected to the TFT; forming a pixel defining layer on the first electrode and having an opening partially exposing the first electrode; forming an emission layer and a second electrode on the first electrode; partially forming a hole in the pixel defining layer; and forming a sealing unit sealing an organic light emitting element having the emission layer along edges of the substrate and simultaneously forming a reinforcing unit formed of glass frit in the hole. 
         [0022]    The method may further include: a melting operation to irradiate laser to the sealing unit and the reinforcing unit. 
         [0023]    The reinforcing unit may be formed of a material identical to that of the sealing unit. 
         [0024]    The sealing unit may be formed of glass frit. 
         [0025]    The second electrode may be patterned to include an opening formed in a portion corresponding to the reinforcing unit. 
         [0026]    The reinforcing unit may be formed in a non-light emitting region of the substrate on the pixel defining layer. 
         [0027]    Two or more reinforcing units may be formed to be spaced apart from one another at a predetermined interval on the pixel defining layer. 
         [0028]    The reinforcing unit may be formed to be applied to the interior of the hole of the pixel defining layer through a printing method. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the example embodiments to those skilled in the art. 
           [0030]    In the drawing figures, dimensions may be exaggerated for clarity of illustration. It will be understood that when an element is referred to as being “between” two elements, it may be the only element between the two elements, or one or more intervening elements may also be present. Like reference numerals refer to like elements throughout. 
           [0031]      FIG. 1  is a view schematically illustrating an organic light emitting display device according to an embodiment of the present invention. 
           [0032]      FIG. 2  is a cross-sectional view of the organic light emitting display device of  FIG. 1  taken along line A-A′ in  FIG. 1 . 
           [0033]      FIGS. 3A through 3G  are cross-sectional views sequentially illustrating a process of manufacturing the organic light emitting display device of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    Details of embodiments are included in detailed descriptions and drawings. 
         [0035]    The advantages and features of the present disclosure and methods for achieving these will be clarified in detail through embodiments described hereinafter in conjunction with the accompanying drawings. 
         [0036]    However, embodiments of the present invention may, however, be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art and are defined by the claim coverage of the present invention. Throughout the specification, the same reference numerals will be used to designate the same or like components. 
         [0037]    In order to clarify the present invention, parts that are not connected with the description will be omitted, and since sizes and thickness of respective components are arbitrarily shown for the description purpose, the present invention is not necessarily limited to the illustration. 
         [0038]    In the drawings, the thickness of layers, films, regions, etc. are exaggerated for clarity. Also, in the drawings, the thickness of some layers and regions are exaggerated for the sake of brevity. 
         [0039]    It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it may be directly on the other element or intervening elements may also be present. 
         [0040]      FIG. 1  is a view schematically illustrating an organic light emitting display device according to an embodiment of the present invention, and  FIG. 2  is a cross-sectional view of the organic light emitting display device of  FIG. 1  taken along line A-A′ in  FIG. 1 . 
         [0041]    Hereinafter, an organic light emitting element provided in a substrate and characteristics of first and second seals will be described with reference to  FIGS. 1 and 2 . In the present disclosure, an active matrix organic light emitting display device using a top gate type driving transistor will be described as an example, but the present disclosure is not limited thereto. 
         [0042]    Referring to  FIGS. 1 and 2 , an organic light emitting display device according to an embodiment of the present invention includes a first substrate  100  including a display region  101  and a non-display region  102  and a second substrate  200  facing the first substrate  100 . 
         [0043]    The first substrate  100  includes a plurality of pixel units P composed of a light emitting unit  150   b  configured to generate light within the display region  101  and a non-light emitting unit  150   a  in which driving elements (a thin film transistor, a capacitor, and the like) providing electrical signals to the light emitting unit  150   b  are formed. 
         [0044]    The first and second substrates  100  and  200  may be glass substrates, but the present disclosure is not limited thereto and the first and second substrates  100  and  200  may be substrates formed of metal or plastic. 
         [0045]    The second substrate  200  may be smaller than the first substrate  100 , and thus, a portion of the first substrate  100  may be exposed. A driving unit  250  such as an integrated circuit (IC), or the like, may be provided in the non-display region  102  as an exposed portion of the first substrate  100 . 
         [0046]    The first substrate  100  includes a buffer layer  110 , a semiconductor layer  112  formed on the buffer layer  110  and including an active layer  112   a  and source and drain regions  112   b  and  112   c,  a gate insulating layer  113  formed on the semiconductor layer  112 , a gate electrode  114  formed in one region of the gate insulating layer  113  and having a size corresponding to a width of the active layer  112   a , an interlayer insulating layer  115  formed on the gate electrode  114 , source and drain electrodes  116   a  and  116   b  formed on the interlayer insulating layer  115 , and a planarization layer  117  formed on the source and drain electrodes  116   a  and  116   b.    
         [0047]    Also, the first substrate  100  further includes a first electrode  118  formed on the planarization layer  117 , a pixel defining layer  125  having an opening exposing a region of the first electrode  118 , an organic emission layer  119  formed on the pixel defining layer  125 , and a second electrode  120  formed on the pixel defining layer  125  and the organic emission layer  119 . 
         [0048]    Here, the first and second electrodes  118  and  120  and the organic emission layer  119  formed therebetween constitute an organic light emitting element E. 
         [0049]    The pixel defining layer  125  is patterned on the planarization layer  117  to have a hole h having a predetermined depth in a particular region excluding the opening exposing the first electrode  118 . In one example, the hole h and the organic light emitting element E (or the recessed area thereof) do not overlap. The hole h of the pixel defining layer  125  is formed in a region that corresponds to the non-light emitting unit  150   a  of the display region  101 . 
         [0050]    The second electrode  120  of the organic light emitting element E is patterned to expose the hole h of the pixel defining layer  125  and formed on the first substrate  100 . 
         [0051]    Meanwhile, the organic light emitting display device according to an embodiment of the present invention further includes a first seal  300  for sealing the first and second substrates  100  and  200  and a second seal  400  formed in the display region  101  to enhance the mechanical strength of the first and second substrates  100  and  200 . Although the term “second seal” is used in the present disclosure, the term may be replaced with a support, a spacer, or any other term that may be appropriate for describing an element configured to provide support to the first and second substrates  100  and  200 . 
         [0052]    The first seal  300  may be formed of frit made of a transparent material to block an introduction of moisture and oxygen from the outside and forms a rectangular closed loop surrounding the display region  101  of the first substrate  100 . 
         [0053]    Frit originally refers to a powder type glass material including an additive; however, since frit may also generally refer to glass formed by melting frit in a glass technical field, the term as used herein covers both concepts. 
         [0054]    The second seal  400  may also be formed of frit, like the first seal  300 . The second seal  400  is formed in the non-light emitting unit  150   a  of the display region  101  of the first substrate  100  to serve to enhance mechanical strength of the first and second substrates  100  and  200 . As a result, better blocking of the introduction of moisture and oxygen from the outside may be achieved. 
         [0055]    The second seal  400  is inserted into the hole h formed in the pixel defining layer  125  through a printing method, or the like, to support the first and second substrates  100  and  200 , and at least two or more holes h may be formed in the display region  101  of the first substrate  100 . The second seal  400  may be formed in the hole h formed in the pixel defining layer  125  through a photolithography process using a half-tone mask. 
         [0056]    Since the second seal  400  is inserted in the hole h formed in the pixel defining layer  125  to support the first and second substrates  100  and  200 , the bonding surface between the first seal  300  and the first and second substrates  100  and  200  is less likely to be damaged, and the introduction of oxygen and moisture to the organic light emitting element E from the outside may be more effectively blocked. 
         [0057]    In addition, the second seal  400  lessens the external impact applied to the first and second substrates  100  and  200  to a degree, enhancing the mechanical strength of the first and second substrates  100  and  200 . 
         [0058]    Hereinafter, a method for manufacturing an organic light emitting display device according to an embodiment of the present invention will be described in detail. 
         [0059]      FIGS. 3A through 3G  are cross-sectional views sequentially illustrating a process of manufacturing the organic light emitting display device of  FIG. 2 . 
         [0060]    Referring to  FIG. 3A , the buffer layer  110  is formed on the first substrate  100 , and the semiconductor layer  112  is formed in one region of the buffer layer  110 . The semiconductor layer  112  includes the active layer  112   a  and the source and drain regions  112   b  and  112   c,  and is formed by performing an ion doping process in a predetermined region of the buffer layer  110 . 
         [0061]    A material having excellent mechanical strength or dimensional stability may be used to form the first substrate  100 . The first substrate  100  may comprise, for example, a glass plate, a metal plate, a ceramic plate, plastic (a polycarbonate resin, an acrylic resin, a polyvinyl chloride, a polyethyleneterephthalate resin, a polyimide resin, a polyester resin, an epoxy resin, a silicon resin, a fluoride resin, and the like), and the like, but the present disclosure is not limited thereto. 
         [0062]    The buffer layer  110  may be formed to protect the driving elements formed in a follow-up process from impurities such as an alkali ion, or the like, effused from the first substrate  100 , and may be omitted depending on the material of the first substrate  100 . 
         [0063]    Subsequently, as illustrated in  FIG. 3B , the gate insulating layer  113  is formed on the first substrate  100 , and the gate electrode  114  is formed in a region of the gate insulating layer  113  corresponding to the active layer  112   a.    
         [0064]    The gate insulating layer  113  is formed as a silicon oxide film (SiOx), a silicon nitride film (SiNx), or a dual-layer including the silicon oxide film (SiOx) and the silicon nitride film (SiNx), and serves to insulate the gate electrode  114  and the semiconductor layer  112  positioned in lower and upper portions thereof. 
         [0065]    The gate electrode  114  may be formed of a type of material selected from the group consisting of aluminum (Al), an aluminum alloy, tungsten (W), molybdenum (Mo), chromium (Cr), titanium (Ti), and the like, as a conductive metal. 
         [0066]    Subsequently, as illustrated in  FIG. 3C , the interlayer insulating layer  115  is formed on the gate insulating layer  113  and the gate electrode  114 , and through holes are formed in at least one region of the gate insulating layer  113  and the interlayer insulating layer  115 . The source and drain electrodes  116   a  and  116   b  connected to the source and drain regions  112   b  and  112   c  are formed in the through holes. 
         [0067]    The source and drain electrodes  116   a  and  116   b  may be formed of one or more types of material selected from the group consisting of chromium (Cr), molybdenum (Mo), tungsten (W), molybdenum-tungsten (MoW), titanium (Ti), aluminum (Al), an aluminum alloy, and the like. 
         [0068]    Subsequently, as illustrated in  FIG. 3D , the planarization layer  117  serving as a protective film protecting the source and drain electrodes  116   a  and  116   b  is formed on the first substrate  100  over the source and the drain electrodes  116   a  and  116   b  formed thereon. The planarization layer  117  may include an inorganic protective film formed as at least one of a silicon nitride film (SiNx) and a silicon oxide film (SiOx). 
         [0069]    The first electrode  118  electrically connected to the drain electrode  116   b  is formed on the first substrate  100  over the planarization layer  117  formed thereon. The first electrode  118  refers to an anode electrode of the organic light emitting element (E in  FIG. 2 ) and may be formed of an inorganic film material. 
         [0070]    The pixel defining layer  125  is formed on the planarization layer  117  over the first electrode  118  formed thereon. The pixel defining layer  125  includes an opening through which a partial region is exposed through a photolithography process. 
         [0071]    Preferably, the pixel defining layer  125  is formed of an organic film material selected from the group consisting of a polyacrylic resin, an epoxy resin, a phenol resin, a polyamide-based resin, a polyimide-based resin, an unsaturated polyester-based resin, a polyphenylenether-based resin, a polyphenylenesulfide-based resin, and benzocyclobutene. 
         [0072]    Subsequently, as illustrated in  FIG. 3E , the organic emission layer  119  is formed on the opening of the pixel defining layer  125 , and the second electrode  120  is formed on the organic emission layer  119 . 
         [0073]    A low molecular or high molecular organic film may be used as the organic emission layer  119 . In the case of using a low molecular organic film, a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), and the like, may be stacked to form a single or complex structure. 
         [0074]    The second electrode  120  serves as a cathode electrode. The polarities of the first and second electrodes  118  and  120  may be reversed. 
         [0075]    In case of a bottom emission type display device in which an image is implemented in a direction of the first substrate  100 , the first electrode  118  may be a transparent electrode and the second electrode  120  may be a reflective electrode. In this case, the first electrode  118  may be formed of ITO, IZO, ZnO, In 2 O 3 , or the like, having a high work function, and the second electrode  120  may include a reflective film formed of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, and a compound thereof having a small work function and ITO, IZO, ZnO, In 2 O 3 , and the like, having a high work function. Also, the transparent electrode as the second electrode  120  may be formed by depositing a metal having a small work function, namely, Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, and a compound thereof and forming an auxiliary electrode layer or a bus electrode line formed of a transparent conductive material such as ITO, IZO, ZnO, and In 2 O 3  thereon. 
         [0076]    In case of a dual-type display device, both the first and second electrodes  118  and  120  may be formed as transparent electrodes. 
         [0077]    The first and second electrodes  118  and  120  may not necessarily be formed of the foregoing materials, and may be formed of a conductive paste including a conductive organic material or conductive particles such as Ag, Mg, Cu, and the like. In the case of using a conductive paste, the conductive paste may be printed by using an inkjet printing method, and after the printing operation, the paste may be sintered to form an electrode. 
         [0078]    The second electrode  120  in the first substrate  100  may be patterned to include an opening exposing a portion of the pixel defining layer  125 . The opening of the second electrode  120  refers to a portion corresponding to the second seal  400  to be subsequently formed in the hole h of the pixel defining layer  125  in a follow-up process. 
         [0079]    Subsequently, as illustrated in  FIG. 3F , the hole h is formed in the pixel defining layer  125  in the first substrate  100  with the second electrode  120  patterned such that a portion thereof is open. The hole h of the pixel defining layer  125  is positioned in a region corresponding to the opening of the second electrode  120  and has a predetermined depth. 
         [0080]    Subsequently, as illustrated in  FIG. 3G  the first seal  300  is formed on the edge of the first substrate  100  and seals the first and second substrates  100  and  200 , and at the same time, the second seal  400  formed of the same material as that of the first seal  300  is inserted into the hole h of the pixel defining layer  125  and supports the first and second substrates  100  and  200 . 
         [0081]    The second seal  400  may be formed of frit. More than one second seal  400  may be formed, for example, by using a photolithography process using a half-tone mask, a printing method, and the like, and the number of the second seals  400  formed may correspond to the number of holes h provided in the pixel defining layer  125 . In one embodiment, the number of the second seals  400  equals the number of the organic light emitting elements E formed in the display region  101 . In another embodiment, one second seal  400  is formed for each organic light emitting elements E. In yet another embodiment, more than one second seal  400  is formed for each organic light emitting elements E. 
         [0082]    In this case, a shape and size of the second seal  400  and an interval therebetween may be determined according to a structure of an organic light emitting display device. 
         [0083]    As described above, in embodiments of the present invention, by forming the first and second seals  300  and  400  formed of frit between the two substrates  100  and  200 , moisture, oxygen, and the like, which may be introduced from the outside, may be effectively blocked and impact applied from the outside may be reduced or eliminated, enhancing the mechanical strength of the substrates  100  and  200 . 
         [0084]    By way of summation and review, in the case of the organic light emitting display device and the method of manufacturing the same according to embodiments of the present invention, introduction of oxygen and moisture from the outside may be completely blocked and impact applied to the substrates may be reduced or eliminated to thus enhance the mechanical strength of the substrates. 
         [0085]    Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.