Abstract:
A method of delivering donor sheets to be subsequently processed in the process of making an organic light-emitting device including providing a roll of a flexible substrate which can either include organic layers or subsequently be coated with organic layers and unrolling a predetermined length of donor and cutting the donor sheet to a size suitable for subsequent use in depositing organic layers. The method also includes transferring the cut donor sheet into a sheet receiver onto a frame and securing the donor sheet to the sheet receiver and delivering the sheet receiver and the secured donor sheet to a position to be further processed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to the manufacture of framed donor sheets used for use in the manufacture of organic light-emitting diode (OLED) display devices.  
       BACKGROUND OF THE INVENTION  
       [0002]     OLED displays are one of the most recent flat panel display technologies and are predicted to overtake LCD display technology within the next decade. OLED displays offer brighter displays, significantly wider viewing angles, lower power requirements, and longer lifetimes than their LCD counterparts. OLED technology offers more display flexibility and alternatives to backlit LCD displays. For example, OLED displays can be made of thin, flexible materials that conform to any desired shape for specific applications. However, OLED displays and their components, known as OLED structures, which constitute subpixels of the display, are more difficult and costly to manufacture than LCD displays. It is a continuing focus of the industry to increase the throughput in an effort to lower the cost of OLED manufacturing.  
         [0003]     Conventional OLED display devices are built on glass substrates in a manner such that a two-dimensional OLED array for image manifestation is formed. The basic OLED cell structure includes a stack of thin organic layers sandwiched between an array of anodes and a common metallic cathode. The organic layers comprise a hole transport layer (HTL), an emissive layer (EL), and an electron transport layer (ETL). When an appropriate voltage is applied to the cell, the injected holes and electrons recombine in the EL near the EL-HTL interface to produce light (electroluminescence).  
         [0004]     The EL within a color OLED display device most commonly includes three different types of fluorescent molecules that are repeated through the EL. Red, green, and blue regions, or subpixels, are formed throughout the EL during the manufacturing process to provide a two-dimensional array of pixels. Each of the red, green, and blue subpixel sets undergoes a separate patterned deposition, for example, by evaporating a linear source through a shadow mask. Shadow masking is a well known technology, yet it is limited in the precision of its deposition pattern and in the pattern&#39;s fill factor or aperture ratio; thus, incorporating shadow masking into a manufacturing scheme limits the achievable sharpness and resolution of the resultant display. Laser thermal transfer promises a more precise deposition pattern and higher aperture ratio; however, it has proved challenging to adapt laser thermal transfer to a throughput manufacturing line, which is necessary to warrant its use in the manufacture of cost-effective OLED display devices.  
         [0005]     During laser thermal transfer, a donor sheet having the desired organic material is placed into close proximity to the OLED substrate within a vacuum chamber. A laser impinges through a clear support that provides physical integrity to the donor sheet and is absorbed within a light-absorbing layer contained atop the support. The conversion of the laser&#39;s energy to heat sublimates the organic material that forms the top layer of the donor sheet and thereby transfers the organic material in a desired subpixel pattern to the OLED substrate. The donor sheets are ideally fed automatically into the process such that the stoppages between depositions can be minimized.  
         [0006]     U.S. Pat. No. 6,485,884 provides a method for patterning oriented materials to make OLED display devices, and also provides donor sheets for use with the method, as well as methods for making the donor sheets. However, U.S. Pat. No. 6,485,884 fails to provide a continuous way to manufacture the donor sheets. Donor sheets must be cut from a sheet of fragile web prior to being coating with the organic material layer that is subsequently deposited on the OLED display via laser thermal transfer. To provide the ease of robotic handling necessary for a high throughput process, it is also desirable to provide a continuous way of mounting the donor sheets to frames.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an object of the present invention to provide an effective way of delivering cut donor sheets into a frame for use in OLED manufacturing.  
         [0008]     It is therefore another object of the invention to provide a high-throughput method for the cutting and framing of donor sheets from a roll of web for use in the manufacture of OLED display devices.  
         [0009]     The present invention is a high-throughput system for cutting and framing donor sheets from a roll of web for use in laser thermal transfer during the manufacture of OLED display devices.  
         [0010]     This object is achieved by a method of delivering donor sheets to be subsequently processed in the process of making an organic light-emitting device, comprising: 
        a) providing a roll of a flexible substrate which can either include organic layers or subsequently be coated with organic layers;     b) unrolling a predetermined length of donor and cutting the donor sheet to a size suitable for subsequent use in depositing organic layers;     c) transferring the cut donor sheet into a sheet receiver onto a frame and securing the donor sheet to the sheet receiver; and     d) delivering the sheet receiver and the secured donor sheet to a position to be further processed.        
 
       ADVANTAGES  
       [0015]     The present invention provides an improved way of delivering cut donor sheets into frames for use in subsequent OLED manufacturing. A particular feature of the present invention is the use of cassettes for receiving frames each with a corresponding cut sheet. The cassette is then used in the OLED manufacturing process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIGS. 1A and 1B  illustrate perspective and side views, respectively, of a donor sheet conversion apparatus in accordance with the present invention;  
         [0017]      FIG. 2  illustrates a manual frame-mounting scheme in accordance with the present invention;  
         [0018]      FIG. 3  illustrates a support platform that is included in the manual frame-mounting scheme;  
         [0019]      FIG. 4  illustrates an automatic frame-mounting apparatus in accordance with the present invention; and  
         [0020]      FIG. 5  illustrates another embodiment of the automatic frame-mounting apparatus of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]      FIGS. 1A and 1B  illustrate views of a donor sheet conversion apparatus  100  for converting a web roll  110  supported axially upon a motorized unwind spindle  116  into a plurality of donor sheets  114 . After a predetermined length of web is unrolled, donor sheets are cut from the web. Donor sheets  114  form the support for a subsequently deposited organic material layer that is later selectively transferred in an appropriate pattern via laser thermal transfer to provide the emissive material throughout a color group of subpixels within an OLED display device. It is understood that donor web  112  can be precoated with an organic material layer prior to processing on sheet donor conversion apparatus  100 . Web roll  110  is supplied in the form of a large roll of a donor web  112  that is, in one example, 3 mills thick, 22 inches wide, and hundreds of yards long. Web roll  110 , as well as donor sheet  114 , in one example includes a flexible substrate that is fabricated from high-temperature polymeric material such as a thermoplastic with an aromatic backbone and is precoated with a light-absorbing layer such as metallic chromium and an optional antireflecting layer such as silicon.  
         [0022]     Donor sheet conversion apparatus  100  further includes a drive roller  122  that pays out donor web  112  over a guide shoe  118 , a slack loop roller  120  that maintains an appropriate level of tension in donor web  112 , and a pinch roller  124  that helps to drive the forward motion of donor web  112 . Guide shoe  118  is a mechanical means of guiding donor web  112  such that donor web  112  does not run off its track while advancing. Donor sheet conversion apparatus  100  further includes a bed knife  128 , against which translates a slitter knife  132  (shown in  FIG. 1B ), which can rotate and is supported by a slitter knife cartridge  130  that is in turn translationally supported along a rail (not shown). A clamping mechanism  126  is provided for securing donor web  112  during the act of cutting.  
         [0023]     Donor sheet conversion apparatus  100  can further include a hopper  136  that collects donor sheets  114  upon their singulation. Hopper  136  includes a lift plate  134  that is mounted on an elevator mechanism (not shown) for stacking singulated donor sheets  114 .  
         [0024]     Donor sheet conversion apparatus  100  is assumed to further include an appropriate level of machine control electronics and software.  
         [0025]     In operation, donor sheet conversion apparatus  100  converts web roll  110  to a stack of singulated donor sheets  114 . Motorized spindle  116  mounts web roll  110  and pays out donor web  112 . Slack loop roller  120  is weighted and vertically positioned so as to provide an appropriate amount of tension in donor web  112 , and so as to control the rotation of spindle  116  and the payout rate of donor web  112 . Alternately, a vacuum box looper or vacuum drum can be substituted for slack loop roller  120  and would limit surface contact with precoated donor web  112 . Drive roller  122 , along with pinch roller  124 , serve as a drive assembly that advances donor web  112  a predetermined distance and subsequently halts the translation of donor web  112  to await cutting. The predetermined distance for advancing donor web  112  before halting its translation for singulation into donor sheets  114  can be accomplished, for example, using rotary encoder counts of the rotation of drive roller  122  or direct sensor detection of the lead edge of donor web  112 . Once the translation of donor web  112  is halted, clamping mechanism  126  secures donor web  112  while slitter knife cartridge  130  translates along a rail (not shown) that forms a line of contact between slitter knife  132  and bed knife  128 . As rotating slitter knife  132  translates across bed knife  128 , a cut is made on donor web  112  that forms donor sheet  114 . Slitter knife  132  can be translated along bed knife  128  in a number of ways, including manually or with the use of a pneumatic cylinder or a motor-driven lead screw. Other cutting assemblies can be substituted for bed knife  128  and slitter knife  132 , such as a point contact shear cutter (chopper) or a laser cutting assembly. Clamping mechanism  126  can be operated manually or by an actuator. As the cut is made, donor sheet  114  is formed. Donor sheet  114  is stacked atop previously formed donor sheets  114  in hopper  136  while lift plate  134  lowers an incremental vertical distance to accommodate the next donor sheet  114 .  
         [0026]     The next step in preparing uncoated donor sheets  114  for the subsequently deposited organic material layer is to mount donor sheets  114  to frames. Frames can be mounted to donor sheets  114  manually in a number of ways, such as by collecting a stack of donor sheets  114  in hopper  136 , as previously described, and subsequently providing loaded hopper  136  to an operator at a work table, at which time the operator manually mounts each donor sheet  114  to a frame and forms a stack of mounted donor sheets  114  in a cassette  218 .  FIG. 2  illustrates an alternate way to manually mount donor sheets  114  to frames.  
         [0027]      FIG. 2  illustrates a manual frame-mounting scheme  200  and includes an operator  210 , a frame hopper  212  that houses a plurality of rigid frames  214 , a frame-mounted donor sheet  216  that is formed by operator  210 , the cassette  218 , and a donor sheet conversion apparatus  220 . Cassette  218  is a transport vessel capable of being pumped down to achieve a desired vacuum condition and is docked to a subsequent coating apparatus or process station such as a deposition chamber. Donor sheet conversion apparatus  220  is identical to donor sheet conversion apparatus  100 , except that hopper  136  and lift plate  134  are replaced by a support platform  222 . Support platform  222  includes an indentation for housing a frame  214  and a plateau for positioning and aligning donor sheet  114  atop frame  214 , as illustrated in  FIG. 3 . Frame hopper  212  can include a lift plate connected to an elevator mechanism so as to maintain the position of frames  214  near the top of frame hopper  212  for ease of manual withdrawal.  
         [0028]     In operation, and in reference to  FIGS. 2 and 3 , the operator  210  is positioned in close proximity to the end of donor sheet conversion apparatus  220 . Operator  210  removes frame  214  from frame hopper  212  and fits frame  214  into an indented form on support platform  222 . The lead edge of donor web  112  is automatically cut, thereby forming donor sheet  114  that falls atop frame  214 . Operator  210  aligns donor sheet  114  to frame  214 , if necessary, and mounts the nearer edge of donor sheet  114  to frame  214  by any number of methods, such as by using glue, double-sided tape, clamps, clips, heat, etc. Operator  210  then rotates donor sheet  114 , along with frame  214 , 180° and mounts the opposite side of donor sheet  114  to frame  214 , thereby forming frame-mounted donor sheet  216 , which the operator places into cassette  218 . In an alternate embodiment, a second operator can be included in manual frame-mounting scheme  200  to achieve higher throughput. The second operator receives donor sheets  114  having one side mounted to frames  214  from operator  210 . The second operator then mounts the opposite side of donor sheets  114  to frames  214  and places frame-mounted donor sheets  216  into cassette  218 . A variety of mechanical approaches also exist for mounting donor sheets  114  to frames  214 , as are described in reference to  FIGS. 4 and 5 .  
         [0029]      FIG. 4  illustrates a frame-mounting apparatus  400  that includes an indexing dial  410 . The indexing dial  410  sequentially receives a cut sheet one at a time to a frame at the sheet receiving position on the indexing dial, and transferring each such cut donor sheet to a corresponding frame and securing each such cut donor sheet to its corresponding frame. The indexing dial  410  incrementally rotates and aligns donor sheets  114  with frames  214  to form a plurality of donor sheets with frames  416  and to subsequently form a plurality of frame-mounted donor sheets  418 . Frame-mounting apparatus  400  further includes a frame hopper  412  that houses a plurality of frames  214 , a hopper  414  that houses a plurality of donor sheets  114 , and cassette  218 . Hopper  414  can be similar or identical to hopper  136  or, alternately, can be a dual-stack hopper that houses two adjacent stacks of donor sheets  114  and enables a depleted stack to be replaced by the mechanical translation of the full stack into the depleted stack space. The empty half of hopper  414  can then be filled while donor sheets  114  are being fed into frame-mounting apparatus  400  from the non-depleted frame hopper  412  can be similar or identical to frame hopper  212  or, alternately, can be a dual-stack hopper that houses two adjacent stacks of frames  214  and enables a depleted stack to be replaced by the mechanical translation of the full stack into the depleted stack space. In such a way, increased throughput is realized by limiting the necessity for work stoppages. Frame-mounting apparatus  400  further includes an appropriate set of robotics (not shown) for transferring frames  214  into indexing dial  410 , an appropriate set of robotics (not shown) for transferring donor sheets  114  into indexing dial  410 , an appropriate set of robotics (not shown) for mounting donor sheets  114  to frames  214 , and an appropriate set of robotics (not shown) for transferring frame-mounted donor sheets  418  into cassette  218 .  
         [0030]     In operation, a set of robotics automatically transfers frame  214  from dual-stack frame hopper  412  into indexing dial  410 . Indexing dial  410  incrementally rotates, e.g., 90°, bringing frame  214  to a position at which a set of robotics automatically transfers donor sheet  114  from hopper  414  into indexing dial  410 , and appropriately aligns donor sheet  114  atop frame  214  to form donor sheet with frame  416 . Indexing dial  410  incrementally rotates again, bringing donor sheet with frame  416  to a position at which a set of robotics automatically mounts donor sheet  114  to frame  214 , e.g. by clamping, to form frame-mounted donor sheet  418 . Indexing dial  410  incrementally rotates again, transferring frame-mounted donor sheet  418  to a position at which a set of robotics automatically transfers frame-mounted donor sheet  418  from indexing dial  410  into cassette  218 . During each incremental stop of indexing dial  410 , a new frame  214  is robotically transferred from frame hopper  412  into indexing dial  410 , a new donor sheet  114  is robotically transferred from hopper  414  into indexing dial  410  and onto frame  214 , a new frame-mounted donor sheet  418  is formed from donor sheet with frame  416 , and a new frame-mounted donor sheet  418  is robotically unloaded from indexing dial  410  into cassette  218 . Once cassette  218  is filled with frame-mounted donor sheets  418 , cassette  218  is undocked from frame-mounting apparatus  400 , eventually to be pumped down to an appropriate level of vacuum and docked with a process chamber for organic material layer deposition. In an alternate embodiment, donor sheets  114  can be fed directly into indexing dial  410  from donor sheet conversion apparatus  100 , as described with reference to  FIG. 5 .  
         [0031]      FIG. 5  illustrates a frame-mounting apparatus  500  that includes a donor sheet conversion apparatus  510  that is identical to donor sheet conversion apparatus  100  in all respects, except that hopper  136  and lift plate  134  are replaced with a simple support platform (not shown) affixed to an indexing dial  512 . Indexing dial  512  is identical in all respects to indexing dial  410  except that the appropriate robotics for transferring donor sheets  114  from hopper  414  into frame-mounting apparatus  500  are replaced by functionality enabling an appropriate coupling between donor sheet conversion apparatus  510  and indexing dial  512 . Frame-mounting apparatus  500  further includes frame hopper  212 , frames  214 , frame-mounted donor sheets  418 , and cassette  218 . A cut line  514  is shown for illustrative purposes.  
         [0032]     The operation of frame-mounting apparatus  500  is similar in all respects to the operation of frame-mounting apparatus  400  except that the lead edge of donor web  112  pays out directly into indexing dial  512 , a cut is made along cut line  514 , and donor sheet  114  is laid atop frame  214 . Frame-mounted donor sheets  418  are formed from donor sheets  114  and frames  214  and are transferred into cassette  218  in a manner identical to that described in reference to frame-mounting apparatus  400 .  
         [0033]     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  
       [0000]    
       
           100  donor sheet conversion apparatus  
           110  web roll  
           112  donor web  
           114  donor sheet  
           116  motorized unwind spindle  
           118  guide shoe  
           120  slack loop roller  
           122  drive roller  
           124  pinch roller  
           126  clamping mechanism  
           128  bed knife  
           130  slitter knife cartridge  
           132  slitter knife  
           134  lift plate  
           136  hopper  
           200  manual frame-mounting scheme  
           210  operator  
           212  frame hopper  
           214  rigid frames  
           216  frame-mounted donor sheet  
           218  cassette  
           220  donor sheet conversion apparatus  
           222  support platform  
           400  frame-mounting apparatus  
           410  indexing dial  
           412  frame hopper  
           414  hopper  
           416  frames  
           418  frame-mounted donor sheets  
           500  frame-mounting apparatus  
           510  donor sheet conversion apparatus  
           512  indexing dial  
           514  cut line