Abstract:
A method for encapsulating one or more OLED devices with an transparent encapsulation cover, including placing an OLED device onto an alignment fixture; after the OLED device is aligned on the alignment fixture removing the aligned OLED device and placing the OLED device at an adhesive receiving position; using an adhesive dispenser to dispense adhesive at the adhesive receiving position at one or more predetermined locations on the OLED device; removing the adhesive containing OLED device from the adhesive dispenser and placing the adhesive containing OLED device in an encapsulation device; removing an transparent encapsulation cover from a storage cassette and positioning the transparent encapsulation cover in the alignment fixture; and moving the transparent encapsulation cover into an engaging relationship with the adhesive on the OLED device to secure the transparent encapsulation cover onto the OLED device.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the encapsulation of OLED devices. 
     BACKGROUND OF INVENTION 
     In making organic light emitting devices (OLED) there are steps in which organic layers are deposited on or over a substrate. Organic light emitting devices are sensitive to moisture and contact damage and are commonly adhesively sealed in an inert atmosphere along with an encapsulation cover containing a desiccant material. The encapsulation cover is a transparent encapsulation cover similar in size to the OLED device glass having a strategically placed etched pocket or pockets containing desiccant. The transparent encapsulation cover has to be properly positioned with the OLED device. Another problem with sealing the transparent encapsulation cover to the OLED device is an over pressure condition caused when gases are compressed within the sealed region of the encapsulated OLED device requiring a vacuum controlled atmosphere. The transparent encapsulation cover and OLED devices are transported using robots. Previous art typically uses an encapsulation method having individual metal encapsulation covers individually located and sealed simultaneously to the OLED device. Another problem was the previous encapsulation device was limited to (1) device design and the use of metal encapsulation covers requiring a larger device format to accommodate the encapsulation cover. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved way of encapsulating OLED devices having the ability to encapsulate many device design formats and a single piece transparent encapsulation cover similar in size to the OLED device glass. 
     This object is achieved by a method for encapsulating one or more OLED devices with an transparent encapsulation cover, comprising the steps of: 
     (a) placing an OLED device onto an alignment fixture; 
     (b) after the OLED device is aligned on the alignment fixture removing the aligned OLED device and placing the OLED device at an adhesive receiving position; 
     (c) using an adhesive dispenser to dispense adhesive at the adhesive receiving position at one or more predetermined locations on the OLED device; 
     (d) removing the adhesive containing OLED device from the adhesive dispenser and placing the adhesive containing OLED device in an encapsulation device; 
     (e) removing an transparent encapsulation cover from a storage cassette and positioning the transparent encapsulation cover in the alignment fixture; and 
     (f) moving the transparent encapsulation cover into an engaging relationship with the adhesive on the OLED device to secure the transparent encapsulation cover onto the OLED device. 
     It is an advantage of the present invention to provide for encapsulation of an OLED device and in the process of encapsulation capture an inert atmosphere. 
     It is a further advantage of the present invention to provide an encapsulation method which can accurately position the transparent encapsulation cover on an OLED device. This encapsulation process can be provided by an automated process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an assembly drawing of an apparatus for practicing the present invention; 
         FIG. 2  is a top view of an encapsulation device shown in  FIG. 1  for encapsulation in accordance with the present invention; 
         FIG. 3  is a cross-sectional view taken along lines  3 — 3  of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view taken along lines  4 — 4  of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view taken along lines  5 — 5  of  FIG. 2 ; 
         FIG. 6  is a cross-sectional view taken along lines  6 — 6  of  FIG. 2 ; and 
         FIG. 7  is a cross-sectional view taken along lines  7 — 7  of FIG.  2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is an assembly drawing of apparatus that includes an encapsulation device  10 . A description of the process practiced by this apparatus is described in sequence. An OLED device  34  is transported from a handling position by a robotic arm  76  using a vacuum operated pick-up tool  82  to a alignment fixture  78 . The OLED device  34  is positioned in the alignment fixture  78  and released by the pick-up tool  82 . The robotic arm  76  moves the pick-up tool  82  away from the OLED device  34 . The alignment fixture  78  aligns the OLED devise  34  to a fixed location. The robotic arm  76  and the pick-up tool  82  return to the OLED device  34 . The OLED device  34  is removed from the alignment fixture  78  by the pick-up tool  82  and transported to an adhesive receiving position adjacent to an adhesive dispenser  72  and adhesive  36  is dispensed at the adhesive receiving position on the OLED device  34  at one or more predetermined locations. 
     The OLED device  34  with adhesive  36  applied is transported to the encapsulation device  10  (see FIG.  2 ). The OLED device  34  is positioned on a lower vacuum plate  22  inside encapsulation device  10  having the adhesive  36  facing up. The vacuum plate  22  applies a hold down vacuum to position the transparent encapsulation cover  32  relative to the adhesive bearing OLED device  34 . The robotic arm  76  with the pick-up tool  82  exits encapsulation device  10  and move to a storage cassette  74 . The pick-up tool  82  then removes a transparent encapsulation cover  32  from the storage cassette  74  and moves such transparent encapsulation cover  32  to the alignment fixture  78 . The transparent encapsulation cover  32  is located in the alignment fixture  78  and is released by the pick-up tool  82 . The transparent encapsulation cover  32  now is aligned to a fixed location. Thereafter, the transparent encapsulation cover  32  is removed from the alignment fixture  78  by pick-up tool  82  and transported to the encapsulation device  10 . The transparent encapsulation cover  32  is then positioned in a predetermined location on a transparent upper vacuum plate  20  located in encapsulation device  10 . 
     The pick-up tool  82  releases the transparent encapsulation cover  32  and exits encapsulation device  10 . The encapsulation device  10  with the OLED device  34  and the transparent encapsulation cover  32  located in position are ready for the encapsulation process to begin. The encapsulation device  10  is hermetically sealed facilitated by a door cylinder  86  so the interior of the encapsulation device  10  can be subject to a vacuum. The encapsulation device  10  is transported by a transport conveyor  80  to an adhesive cure station  70 . Preferably, ultraviolet light is applied at the adhesive curing station  70  to an encapsulated OLED device  84  which cures the adhesive  36 . The transparent encapsulation cover  32  is now sealed to the OLED device  34 . 
     At the completion of the curing process the encapsulation device  10  returns to its initial position adjacent to the storage cassette  74 . The hermetic seal of encapsulation device  10  is opened and the encapsulated OLED device  84  is removed from the encapsulation device  10  using the robotic arm  76  and the pickup tool  82  and transported to the encapsulation cover and encapsulated OLED device storage cassette  74 . The encapsulation process is now complete. 
     The encapsulation process of encapsulation device  10  will now be discussed. The encapsulation has three basic process positions. 
     A first process position  88  (see  FIGS. 3 and 4 ) is the loading and unloading position where OLED device  34  and transparent encapsulation cover  32  are loaded into the encapsulation device  10 . The encapsulated OLED devices  84  are unloaded after encapsulation is completed. 
     In a second process position  90  (see  FIGS. 5 and 6 ) the encapsulation device  10  is hermetically sealed and vacuum is introduced in the form of an inert gas. The OLED device  34  and the transparent encapsulation cover  32  are located in close proximity but not in contact. 
     In a third process position  92  ( FIG. 7 ) the OLED device  34  with adhesive  36  is pressed against the transparent encapsulation cover  32  compressing the adhesive  36  and trapping inert gas in a vacuum state between the OLED device  34  and the transparent encapsulation cover  32 . The adhesive  36  is cured with ultra violet light using adhesive cure station  70 . 
     The encapsulation process is now complete and the encapsulation device  10  returns to the first process position  88  repeating the process steps in reverse order and the encapsulated OLED device  84  is removed from the encapsulation device  10 . 
       FIG. 3  depicts a front cross-sectional view taken along lines  3 - 3  of  FIG. 2  of the encapsulation device  10 . The encapsulation device  10  is depicted in the first process position  88  the loading and unloading position. The encapsulation device  10  having a transport cylinder  24  retracted and a encapsulation cylinder  26  retracted. The OLED device  34  is located in position on a lower vacuum plate  22  having adhesive  36  previously applied at the adhesive dispenser  72 . The OLED device  34  and the adhesive  36  are depicted larger than scale for clarity of illustration. 
     A transparent encapsulation cover  32  is located in position and held in place by vacuum on a transparent upper vacuum plate  20 . The transparent encapsulation cover  32  is depicted larger than scale for clarity of illustration. Also depicted in  FIG. 3  are a base plate  42 , a left hand side plate  44 , a right hand side plate  46 , and a vacuum plate frame  48  that form the framework of the encapsulation device  10 . Also shown is a lower platen  38  that is raised and lowered during the encapsulation process by the transport cylinder  24  and guided and positioned by two die pins  28 . The lower platen  38  when raised by the transport cylinder  24  is stopped at a fixed location when contacting two lower platen stops  40 . Mounted to the top surface of the lower platen  38  are two lower vacuum plate supports  60 , four guide pins  62  only two of which are shown, and the encapsulation cylinder  26 . The operating sequence will be described in detail in following figures. 
       FIG. 4  is a side cross-sectional view taken along lines  4 — 4  of  FIG. 2  of the encapsulation device  10 . The encapsulation device  10  is depicted in the first process position  88  having the transport cylinder  24  retracted and the encapsulation cylinder  26  retracted. A front cover  50  and a rear cover  52  are depicted and are fastened to the base plate  42 , the vacuum plate frame  48 , the left hand side plate  44 , and the right hand side plate  46  using fasteners  58  represented in only one location for clarity of illustration. A door  56  is attached to the front cover  50 . The door  56  is depicted in the open position. The encapsulation device  10  is enclosed on all four sides, and the top and bottom. The encapsulation device  10  preferably is hermetically sealed when the door  56  is closed. 
     The OLED device  34  and the transparent encapsulation cover  32  are oriented in the encapsulation device  10  through the door  56  in the open position. The encapsulated OLED device  84  is then removed through the door  56  in the open position. Three spring plungers  54  two of which are shown in three locations mounted to the lower vacuum plate  22 . The spring plunger  54  is a threaded device. The spring plungers  54  are fastened to vacuum plate  22  in threaded holes located on vacuum plate  22 . The function of the spring plungers  54  will be explained in detail FIG.  6 . Also depicted in  FIG. 4  a pressure transducer  30  positioned on the bottom side of vacuum plate  22 . The function of the pressure transducer  30  will be described in detail in FIG.  7 . 
       FIG. 5  is a front cross-sectional view taken along lines  5 — 5  of  FIG. 2  of the encapsulation device  10 . This figure depicts the second process position  90  with the transport cylinder  24  actuated in the up position. The lower platen  38  guided by die pins  28  is raised to the lower platen stops  40 . The transport cylinder  24  remains actuated applying continuous pressure to the lower platen  38  located against lower platen stops  40 . 
       FIG. 6  is a side cross-sectional view taken along lines  6 — 6  of  FIG. 2  of the encapsulation device  10  is depicted in the second process position  90 . The door  56  is closed hermetically sealing the interior of the encapsulation device  10  and can be subjected to inert atmosphere under vacuum conditions. The lower vacuum platen  38  is depicted in the raised position against lower platen stops  40 . The spring plungers  54  is partially compressed and in contact with vacuum plate frame  48 . The spring plungers  54  establishes an equal gap between the lower vacuum platen  22  and the transparent upper vacuum plate  20 . This prevents the OLED device  34  with the adhesive  36  from contacting the transparent encapsulation cover  32  prior to encapsulation. 
       FIG. 7  is a cross-section view taken along lines  7 — 7  of  FIG. 2  of the encapsulation device  10  is depicted in a third process position  92 , the encapsulation position. The lower platen  38  stopped at lower platen stops  40 . The encapsulation cylinder  26  is extended raising the lower platen  38  mounted on the lower vacuum supports  60  upward on the guide pins  62 . The OLED device  34  with the adhesive  36  is raised and contacts the transparent encapsulation cover  32 . The adhesive  36  is compressed and the vacuum allows the gases trapped between the OLED device  34  and the transparent encapsulation cover  32  to equalize preventing an over pressure condition within the encapsulated OLED device  84 . The encapsulated OLED device  84  is then subjected to ultra violet light provided by the adhesive cure station  70  of FIG.  1 . The encapsulated OLED device  84  is exposed to the ultra violet light through the transparent upper vacuum plate  20 . 
     The encapsulation device  10  returns to the first process position  88  and the encapsulated OLED device  84  is removed using robotic arm  76  and placed in the storage cassette  74  of FIG.  1 . 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
     
         
           10  encapsulation device 
           20  transparent upper vacuum plate 
           22  lower vacuum plate 
           24  transport cylinder 
           26  encapsulation cylinder 
           28  die pin 
           30  pressure transducer 
           32  transparent encapsulation cover 
           34  OLED device 
           36  adhesive 
           38  lower platen 
           40  lower platen stop 
           42  base plate 
           44  left hand side plate 
           46  right hand side plate 
           48  vacuum plate frame 
           50  front cover 
           52  rear cover 
           54  spring plungers 
           56  door 
           58  fastener 
           60  lower vacuum support 
           62  guide pin 
           70  adhesive cure station 
           72  adhesive dispenser 
           74  storage cassette 
           76  robotic arm 
           78  alignment fixture 
           80  transport conveyor 
           82  pick-up tool 
           84  encapsulated OLED device 
           86  door cylinder 
           88  first process position 
           90  second process position 
           92  third process position