Patent Publication Number: US-2012043017-A1

Title: Joule Heat Encapsulating Apparatus and Encapsulating Method Using the Same

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on Aug. 18, 2010 and there duly assigned Serial No. 10-2010-0079851. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an encapsulating apparatus for encapsulating a display unit of a flat panel display device, and more particularly, to an encapsulating apparatus for performing encapsulation by using Joule heat. 
     2. Description of the Related Art 
     Flat panel display devices, e.g., an organic light-emitting display device, may be fabricated so as to be thin and flexible due to operating properties, and thus a variety of research is being conducted thereon. 
     However, such flat panel display devices have a property such that a display unit thereof is deteriorated by permeation of oxygen or moisture. Therefore, th flat panel display devices require an encapsulating structure for encapsulating and protecting a display unit by preventing permeation of oxygen or moisture. To form the encapsulating structure, an encapsulating apparatus is required for convenient formation of a stable encapsulating structure which prevents permeation of oxygen or moisture. 
     SUMMARY OF THE INVENTION 
     The present invention provides an encapsulating apparatus for convenient formation of a stable encapsulating structure which prevents permeation of oxygen or moisture, and an encapsulating method using the encapsulating apparatus. 
     According to an aspect of the present invention, a Joule heat encapsulating apparatus comprises: a stage to which a panel is mounted, the panel including a thermal-hardening type sealant for surrounding and sealing a display unit formed between a first substrate and a second substrate, a heat-generating wiring overlapping the thermal-hardening type sealant, and an electric current application wiring connected to the heat-generating wiring; a cap for forming a sealed space, in which the panel is arranged, between the stage and the cap; an exhaustion mechanism for exhausting air in the sealed space; and a power applying mechanism which is connected to the electric current application wiring, and which supplies a current to the heat-generating wiring. 
     The Joule heat encapsulating apparatus may further include a sealing member which is elastically pressed between the stage and the cap, and which maintains the sealed space airtight. 
     The sealing member may include a silicon O-ring or a cellular rubber O-ring. 
     The thermal-hardening type sealant may include frit. 
     The exhaustion mechanism may include an exhaustion hose connected to a via hole formed in the cap and a vacuum pump for sucking out the air via the exhaustion hose. 
     The power applying mechanism may include an electrode member which is attached to the cap so as to contact the electric current application wiring, and a power source connected to the electrode member. 
     A plurality of the electric current application wirings may be formed, and a plurality of electrode members may be formed in correspondence to the plurality of electric current application wirings. 
     A pressing unit for pressing the panel when the cap is adhered to the stage may be formed on the cap. 
     According to another aspect of the present invention, a Joule heat encapsulating method comprises: mounting a panel on a stage, the panel including a thermal-hardening type sealant for surrounding and sealing a display unit formed between a first substrate and a second substrate, a heat-generating wiring overlapping the thermal-hardening type sealant, and an electric current application wiring connected to the heat-generating wiring; forming a sealed space, in which the panel is arranged, between the stage and a cap by covering the stage with the cap; exhausting air in the sealed space; and hardening the thermal-hardening type sealant by supplying a current to the heat-generating wiring via the electric current application wiring. 
     The Joule heat encapsulating method may further include maintaining the sealed space airtight by interposing a sealing member which is elastically pressed between the stage and the cap. 
     The sealing member may include a silicon O-ring or a cellular rubber O-ring. 
     The Joule heat encapsulating method may further include pressing the panel when the cap is adhered to the stage by using a pressing unit formed on the cap. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is an exploded perspective view of a Joule heat encapsulating apparatus according to an embodiment of the present invention; 
         FIG. 2  is plan view of the Joule heat encapsulating apparatus of  FIG. 1 ; 
         FIG. 3  is a sectional view taken along a line A-A of  FIG. 2 ; 
         FIG. 4  is a plan view showing the structure of a display unit of the panel shown in  FIG. 1 ; and 
         FIG. 5  is a plan view showing a modified example of the panel shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present invention will be described in detail by explaining embodiments of the invention with reference to the attached drawings. 
     First, a Joule heat encapsulating apparatus according to the present invention is an apparatus for performing an encapsulating operation by using Joule heat generated when a current flows in a conductor, and it may have a structure as shown in  FIGS. 1  thru  3 , for example. 
       FIG. 1  is an exploded perspective view of a Joule heat encapsulating apparatus according to an embodiment of the present invention;  FIG. 2  is plan view of the Joule heat encapsulating apparatus of  FIG. 1 ; and  FIG. 3  is a sectional view taken along a line A-A of  FIG. 2 . 
     Referring to  FIGS. 1  thru  3 , the Joule heat encapsulating apparatus according to the present embodiment includes a stage  10  to which a panel  100  is mounted, and a cap  20  which covers the stage  10  so as to seal around the panel  100 . In other words, a sealed space S (refer to  FIG. 3 ) housing the panel  100  is formed by mounting the panel  100  on the stage  10  and covering the stage  10  with the cap  20 . 
     In  FIG. 2 , since a cap  20  and a second substrate  102  are formed of transparent materials, components therebelow may be seen therethrough. 
     Next, a sealing member  30  is adhered to the cap  20 . The sealing member  30  firmly maintains the sealed space S airtight by elastically compressing when the cap  20  covers the stage  10 . 
     The stage  10  and the cap  20  may be formed of an acrylic material. Furthermore, the sealing member  30  may be formed of a silicon O-ring or a cellular rubber O-ring. Here, since a cellular rubber O-ring has higher elasticity than a silicon O-ring, a cellular rubber O-ring may be used for smooth adherence between the cap  20  and the stage  10 . If a silicon O-ring with relatively low elasticity is used, the sealing member  30  may not absorb sufficient pressure when the cap  20  is adhered to the stage  10 , and thus the stage  10  may be bent. 
     An electrode member  41 , which is connected to a power source  42 , is attached to the cap  20  as a power applying mechanism  40  for supplying a current to the panel  100  so as to generate Joule heat. The electrode member  41  contacts an electric current application wiring  160  of the panel  100  when the cap  20  is attached to the stage  10  with the sealing member  30 . 
     Furthermore, an exhaustion hose  51  and a vacuum pump  52 , which are connected to a via hole  22  formed in the cap  20 , are formed as an exhaustion mechanism  50  for exhausting air in the sealed space S. Therefore, when the vacuum pump  52  operates, the air in the sealed space S is exhausted via the exhaustion hose  51 , and thus the sealed space S becomes nearly vacuum. 
     Detailed descriptions on operations of the Joule heat encapsulating apparatus will be given below. Here, the structure of the panel  100 , on which an encapsulating operation is performed, will be described. 
     The panel  100  is a component constituting a flat panel display device, such as an organic light-emitting display device, and includes a first substrate  101  and a second substrates  102  facing the first substrate  101 , a display unit  110  which is formed between the first substrate  101  and second substrate  102 , a thermal-hardening type sealant  170  which surrounds and seals the display unit  110 , a heat-generating wiring  150  which is arranged so as to overlap the thermal-hardening type sealant  170 , and the electric current application wiring  160 . Therefore, when a current flows in the heat-generating wiring  150  via the electric current application wiring  160 , Joule heat is generated and the thermal-hardening type sealant  170  is hardened. As a result, a space between the first and second substrates  101  and  102  is firmly sealed by the sealant  170 , and thus the display unit  110  is protected. 
     The first substrate  101  may be formed of an SiO 2 -based transparent glass material. However, the present invention is not limited thereto, and the first substrate  101  may also be formed of a transparent plastic material. In the latter case, the transparent plastic material for forming the first substrate  101  may be an organic insulation material selected from a group consisting of polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethyelene naphthalate (PEN), polyethyelene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), and cellulose acetate propionate (CAP). 
     Furthermore, the display unit  110  is arranged on the first substrate  101  as described above. The display unit  110  may be any of various types. Although the display unit  110  includes an organic light-emitting display device in the present embodiment, the present invention is not limited thereto, and the display unit  110  may include a liquid crystal display device. 
     The second substrate  102 , which is a sealing substrate, is arranged on the display unit  110 , and the thermal-hardening type sealant  170  is arranged between the first and second substrates  101  and  102 , respectively. The thermal-hardening type sealant  170  maybe formed so as to surround the display unit  110 . The thermal-hardening type sealant  170  may include frit. 
     Next, the heat-generating wiring  150  is formed so as to overlap the thermal-hardening type sealant  170 . In other words, the heat-generating wiring  150  is formed on the first substrate  101 , and the thermal-hardening type sealant  170  is formed on the heat-generating wiring  150  so as to overlap the heat-generating wiring  150 . 
     The heat-generating wiring  150  may be formed of any of various conductive materials. 
     The electric current application wiring  160  connected to the heat-generating wiring  150  is arranged on the first substrate  101 , and the electric current application wiring  160  may be formed of the same material as the heat-generating wiring  150 . 
     Here, the width W 1  ( FIG. 1 ) of the electric current application wiring  160  may be greater than the width W 2  of the heat-generating wiring  150 . As described above, a current flows to the heat-generating wiring  150  via the electric current application wiring  160 . Since a current flowing in the electric current application wiring  160  flows in a divided manner to the left side and the right side of the heat-generating wiring  150 , more load may be generated in the electric current application wiring  160  than in the heat-generating wiring  150 . For example, in the case where the width W 1  of the electric current application wiring  160  is the same as the width W 2  of the heat-generating wiring  150 , heat generated in the electric current application wiring  160  may be twice as much as heat generated in the heat-generating wiring  150 , and thus the electric current application wiring  160  may be damaged. Therefore, the width W 1  of the electric current application wiring  160  may be at least twice as much as the width W 2  of the heat-generating wiring  150  so as to prevent the electric current application wiring  160  from overheating. 
     In the present embodiment, each of two electric current application wirings  160  is formed at both ends of the heat-generating wiring  150  (see  FIG. 2 ). However, more than two electric current application wirings  160  may be arranged if necessary. When a current flows to the heat-generating wiring  150  via the electric current application wirings  160  and Joule heat is generated, the thermal-hardening type sealant  170  is hardened by the Joule heat. 
     The display unit  110  may be any of various types as stated above, and the present embodiment discloses the display unit  110  employing an organic light-emitting device. Detailed description of the display unit  110  will be given below with reference to  FIG. 4 . 
       FIG. 4  is a plan view showing the structure of a display unit of the panel shown in  FIG. 1 . 
     First, a buffer layer  111  is formed on the first substrate  101 . The buffer layer  111  provides a flat surface on the first substrate  101  and prevents permeation of moisture and impurities into the first substrate  101 . 
     An active layer  112  having a predetermined pattern is formed on the buffer layer  111 . The active layer  112  may be formed of an inorganic semiconductor, e.g., amorphous silicon or poly-silicon, or an organic semiconductor, and includes a source region, a drain region, and a channel region. 
     The source region and the drain region may be formed by doping the active layer  112 , which is formed of amorphous silicon or poly-silicon, with impurities. A p-type semiconductor may be formed by doping the active layer  112  with a Group III atom, e.g., boron (B), whereas an n-type semiconductor may be formed by doping the active layer  112  with a Group V atom, e.g., nitrogen (N). 
     A gate insulation layer  113  is formed on the active layer  112 , and a gate electrode  114  is formed in a predetermined region on the gate insulation layer  113 . The gate insulation layer  113  is a layer for insulating the active layer  112  from the gate electrode  114 , and may be formed of an organic material or an inorganic material, e.g., SiNx or SiO 2 . 
     The gate electrode  114  may be formed of a metal, such as Au, Ag, Cu, Ni, Pt, Pd, Al, or Mo, or a metal alloy, such as Al:Nd or Mo:W. However, the present invention is not limited thereto, and the gate electrode  114  may be formed of any of various materials in consideration of adherence, planarity, electric resistance, and manufacturability. The gate electrode  114  is connected to a gate line (not shown), by means of which an electric signal is applied. 
     An interlayer insulation layer  115  is formed on the gate electrode  114 . The interlayer insulation layer  115  and the gate insulation layer  113  expose the source region and the drain region of the active layer  112 , and a source electrode  116  and a drain electrode  117  are connected to the exposed source and drain regions, respectively, of the active layer  112 . 
     The source electrode  116  and the drain electrode  117  may be formed of a metal, such as Au, Pd, Pt, Ni, Rh, Ru, Ir, or Os, or an alloy of two or more metals, such as Al:Mo, Al:Nd, or MoW. However, the present invention is not limited thereto. 
     Next, a passivation layer  118  is formed so as to cover the source electrode  116  and the drain electrode  117 . The passivation layer  118  may be formed of an inorganic insulation layer and/or an organic insulation layer. The inorganic insulation layer may include SiO 2 , SiN x , SiON, Al 2 O 3 , TiO 2 , Ta 2 O 5 , HfO 2 , ZrO 2 , BST, or PZT, and the organic insulation layer may include a general-purpose polymer, such as poly (methyl methacrylate (PMMA) or polystyrene (PS), a polymer derivative containing a phenol group, an acrylic polymer, an imide-based polymer, an arylene-ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl-alcoholic polymer, or a blend thereof. The passivation layer  118  may also be formed as a composite stacked structure of an inorganic insulation layer and an organic insulation layer. 
     The passivation layer  118  exposes a portion of the drain electrode  117 , and an organic light-emitting device  120  is formed so as to be connected to the exposed portion of the drain electrode  117 . The organic light-emitting device  120  includes a first electrode  121 , a second electrode  122 , and an organic light-emitting layer  123 . In detail, the first electrode  121  and the drain electrode  117  contact each other. 
     The organic light-emitting layer  123  emits visible rays when voltages are applied thereto via the first electrode  121  and the second electrode  122 . 
     A pixel define layer (PDL)  119  is formed on the first electrode  121 , the PDL  119  being formed of an insulation material. A predetermined opening is formed in the PDL  119  so as to expose a portion of the first electrode  121 , and the organic light-emitting layer  123  is formed on the exposed portion of the first electrode  121 . Next, the second electrode  122  is formed so as to be connected to the organic light-emitting layer  123 . 
     The first electrode  121  and the second electrode  122  have polarities of an anode electrode and a cathode electrode, respectively. However, the polarities of the first electrode  121  and the second electrode  122  may be reversed. 
     Operations of encapsulating the panel  100  for sealing the display unit  110  from external air are performed as described below by using a Joule heat encapsulating apparatus according to the present embodiment. 
     First, the panel  100  is mounted on the stage  10 . 
     The panel  100  has a structure in which the display unit  110  is formed between the first and second substrates  101  and  102 , the heat-generating wiring  150  and the thermal-hardening type sealant  170 , which overlap each other, surround the display unit  110 , and the electric current application wiring  160  is connected to the heat-generating wiring  150 . Furthermore, the electric current application wiring  160  extends outside the second substrate  102  so that the electrode member  41  may contact the electric current application wiring  160  from above. 
     At this point, the cap  20  is adhered to the stage  10  so as to house the panel  100  in the sealed space S between the cap  20  and the stage  10 . Here, the electrode member  41  contacts and is electrically connected to the electric current application wiring  160 , and the sealing member  30  is elastically pressed so as to firmly maintain the sealed space S between the cap  20  and the stage  10  airtight. Furthermore, a pressing unit  21 , which is formed on the bottom surface of the cap  20 , presses the panel  100  as shown in  FIG. 3  so as to fix the panel  100  so that the panel  100  does not move. 
     Accordingly, when the cap  20  and the stage  10  are adhered to each other, the air in the sealed space S is exhausted to the outside via the exhaustion hose  51  by operating the vacuum pump  52 . As a result, the sealed space S is nearly vacuum, and thus the panel  100  is located in a vacuum chamber. 
     Next, a current is supplied by the power source  42  via the electrode member  41 , and a current flows to the heat-generating wiring  150  via the electric current application wiring  160 , and Joule heat is generated in the heat-generating wiring  150 . 
     As a result, the thermal-hardening type sealant  170 , which overlaps the heat-generating wiring  150 , is hardened and firmly seals the display unit  110  between the first and second substrates  101  and  102 , respectively. 
     Therefore, a sturdy encapsulation structure may be formed by simple operations, including mounting the panel  100  on the stage  10 , covering the panel  100  with the cap  20 , and applying a current thereto. 
       FIG. 5  is a plan view showing a modified example of the panel shown in  FIG. 1 . 
     Although the present embodiment discloses the case in which one display unit  110  is formed in the panel  100 , a plurality of display units  110  may be formed in a single panel  100  as shown in  FIG. 5 , and may be divided into individual units after encapsulation. Even in this case, since the heat-generating wirings  150  overlap with the thermal-hardening type sealant  170  of each of the display units  110 , which are all connected to the electric current application wiring  160 , the encapsulating operation, in which a current is supplied to the heat-generating wirings  150  via the electric current application wiring  160  so as to generate heat, may be performed as described above. Therefore, the present invention is not limited to the number of display units  110  included in the panel  100 . 
     Furthermore, although the stage  10  and the cap  20  have rectangular shapes in the present embodiment, the stage  10  and the cap  20  may have circular shapes or any of a variety of polygonal shapes. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.