Abstract:
A film tray for fabricating a flexible display, the film tray preventing a flexible substrate or film from sagging. The film tray includes a support plate and at least one pair of clamps, each clamp of the at least one pair of clamps located along an opposite edge of the support plate to fix a flexible film. A first clamp of the at least one pair clamps is aligned with a second clamp of the least one pair of clamps. Each clamp includes an open-shut part adapted to be opened to receive the flexible substrate or film and adapted to be shut to fix the flexible substrate or film and a support part separated from the open-shut part by a predetermined space to support the flexible substrate or film at a predetermined level when the open-shut part is closed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2005-80995, filed on Aug. 31, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a film tray, and more specifically, to a film tray for fabricating a flexible display. 
     2. Discussion of Related Art 
     Recently, technology of flexible displays such as an Organic Light Emitting Diode Display have been actively researched and developed. An Organic Light Emitting Diode (OLED) is used for an OLED Display. The OLED includes an anode electrode, an emitting light layer and a cathode electrode. The anode electrode supplies a hole for an emitting light layer and the cathode electrode supplies the electron for the emitting light layer. The holes supplied by the anode electrode and the electron supplied from cathode electrode generate light after being combined in the emitting light layer. 
     The formation process of a thin film as part of a flexible display has typically been carried out by a deposition method using a mask. However, sagging of the flexible substrate or film may occur in the thin film forming processes, preventing accurate sputtering and patterning. Also, since sputtering is performed within a vacuum chamber, it becomes difficult to transfer the flexible substrate or film to the chamber without any defects affecting the flexible substrate or film. Thus, there is a need for a film tray for fabricating a flexible display capable of preventing the flexible substrate or film from sagging at the time of manufacturing. 
     SUMMARY OF THE INVENTION 
     A film tray is provided for fabricating a flexible display. In one exemplary embodiment, the film tray includes a support plate and a support plate and at least one pair of clamps, each clamp of the at least one pair of clamps being located at a perimeter of the support plate to fix a flexible medium. A first clamp of the at least one pair clamps is aligned with a second clamp of the least one pair of clamps. Each clamp includes an open-shut part adapted to open to receive the flexible medium and adapted to close to fix the flexible medium, an open-shut part adapted to open to receive the flexible medium and adapted to close to fix the flexible medium, and a support part adjacent to the open-shut part for providing a predetermined space to support the flexible medium at a predetermined level when the open-shut part is closed. An opening is formed in the central part of the support plate. The width of the support plate ranges from about 10 mm to about 50 mm. The support plate and clamps may be formed from a light metal like the aluminum or the synthetic resins such as a Carbon Fiber Reinforced Plastic. The support plate and clamps may be formed by the different metal bonding. 
     According to another exemplary embodiment of the present invention, a film tray is provided for flexible substrates attached to inflexible substrates. The film tray includes a support frame and a substrate support section formed within the perimeter of the support frame, the substrate support section providing a recess to support the flexible substrate attached to an inflexible substrate. The substrate support section corresponds to the size of the flexible substrate attached to an inflexible substrate. 
     According to yet another exemplary embodiment of the present invention, a method of forming a thin film as part of a flexible medium is provided. The method includes providing a film tray including a support plate and at least one pair of clamps, each clamp of the at least one pair of clamps being located at a perimeter of the support plate to fix a flexible medium, a first clamp of the at least one pair of clamps being aligned with a second clamp of the least one pair of clamps. The flexible medium is inserted into an open open-shut part of each clamp of the at least one pair of clamps and the open-shut part of each clamp of the least one pair of clamps is closed to fix the flexible medium. Finally, the thin film is deposited onto the flexible medium. 
     According to still another exemplary embodiment of the present invention, a method of forming an emission layer of an organic light emitting diode is provided. The method includes providing a film tray including a support plate and at least one pair of clamps, each clamp of the at least one pair of clamps being located at a perimeter of the support plate to fix a flexible medium, a first clamp of the at least one pair of clamps being aligned with a second clamp of the least one pair of clamps. A donor film is inserted into an open open-shut part of each clamp of the at least one pair of clamps, the donor film including a base substrate, a light to thermal conversion layer and a thermal image layer. The open-shut part of each clamp of the least one pair of clamps is closed to fix the donor film. The donor film is placed in contact with an upper section of a combination of an acceptor substrate, an anode electrode, a hole pouring layer and a hole transferring layer and the donor film is laser patterned through the support plate. Finally, the donor film is removed from the acceptor substrate such that the emission layer is formed only in the portion of the acceptor substrate contacted by a laser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a film tray for fabricating a flexible display according to one embodiment of the present invention. 
         FIG. 2  is a side cross-sectional view of the film tray of  FIG. 1  through section line A-A′. 
         FIGS. 3A ,  3 B and  3 C are cross-sectional views illustrating a method of fixing a flexible film to a film tray. 
         FIG. 4  is a top view of a film tray for fabricating a flexible display according to another embodiment of the present invention. 
         FIG. 5  is a top view of a film tray for fabricating a flexible, display according to yet another embodiment of the present invention. 
         FIG. 6A  is a partial cross-sectional view of the film tray of  FIG. 5 . 
         FIG. 6B  is a partial perspective view of the film tray of  FIG. 5 . 
         FIGS. 7A and 7B  show another embodiment of a film tray for fabricating a flexible display according to the present invention. 
         FIG. 8A  is the cross-sectional view that shows a thin film deposited onto a flexible film using the film tray of  FIG. 2 . 
         FIG. 8B  is a cross-sectional view showing fabrication of donor film using the film tray of  FIG. 2 . 
         FIGS. 9A ,  9 B,  9 C and  9 D are cross-sectional views showing the formation of an emission layer of an organic light emitting diode using the film tray of  FIG. 8B . 
         FIGS. 10A ,  10 B,  10 C,  10 D, and  10 E illustrate a film tray for fabricating a flexible display according to yet another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , the film tray  100  for fabricating a flexible display includes a support plate  110 , clamps  120  established along edges of an upper side of the support plate  110  and an opening  130  formed in the central part of the support plate  110 . 
     The support plate  110  is used to support the flexible film when the flexible film is fixed or transferred. The support plate  110  may be formed from light metals like Aluminum (Al) or synthetic resins such as Carbon Fiber Reinforced Plastic (CFRP). If the support plate  110  is made from aluminum, it is possible to combine the joint part (i.e., where the support plate and the clamps are joined to each other) of the support plate  110  and clamps  120  using steel. More specifically, the support plate  110  and the clamps  120  may have a partially heterogeneous structure between steel and aluminum. Alternatively, the support plate  110  and the clamps  120  may be made of aluminum and steel so their joint part may be achieved by a heterojunction. The support plate  110  is typically manufactured to have a width ranging between about 10 mm to about 50 mm. 
     The size and thickness of the support plate may be based on various sizes of the flexible film. For example, if the support plate  110  supports flexible film of 4-generation level (730×920 mm 2 ), the support plate may be manufactured to a width of 1240 mm, a length of 900 mm and a thickness of 15 mm, (1240×900×15 mm 3 ). A hole  140  may be formed on an edge of the support plate into which a pin for fixing (not shown) may be inserted. The pin for fixing serves to prevent the film tray  100  from moving when a thin film is deposited onto flexible film fixed on the film tray  100 . 
     The opening  130  is formed in order to reduce the weight of the support plate  110 . Also, the opening  130  serves to limit the areas of the film onto which materials may be deposited. 
     The clamps  120  serve to fix the flexible film. At least two clamps are formed symmetrical with each other on an edge of the upper side of the support plate  110 . In one embodiment of the present invention, the clamps  120  are formed to be symmetrical on all four edges of the upper side of the support plate  110  in order to stably fix the flexible film. Such clamps  120  may be manufactured from light metals like aluminum and synthetic resins such as CFRB. In addition, a square-shaped groove  125  may be formed in the clamps  120  to reduce the weight of the film tray. Although the groove  125  is described as square-shaped in this embodiment, the groove is not limited to this shape. 
     Referring to  FIG. 2 , the clamp  120  is established in a defined distance from the open-shut end  120   a  to fix the flexible film and to keep the film flat. The clamp  120  is adapted to be capable of opening and shutting at the open-shut end  120   a , such as by pivoting. A supporting part  120   b  is provided to fix and support the flexible film at a desired height. A step is formed on the interior of the open-shut end  120   a  to fix the flexible film. The exterior of the support part  120   b  is formed so as to be able to be combined with the step created on the interior of the open-shut end  120   a.    
     The film tray  100  may be used in a process chamber and then be transferred by a transferring robot (not shown) in a direction indicated in  FIG. 2 . 
     The film tray  100  may also be used in a laser-induced thermal imaging process using a donor film. For example, a Light-to-Heat Conversion Layer (LTHC), a transfer layer and the like may be formed while the base substrate of a flexible donor film is fixed on the support plate  110  and transferred to the deposition chamber. 
     Referring to  FIGS. 3A to 3C , the flexible film  210  is placed on the film tray  100  when the open-end part  120   a  is open. One side of the flexible film  210  is inserted into the open-shut part  120   a . An external deviation prevention device  220 , for example, a removable weighted block, fixes the flexible film  210  using pressure to prevent the flexible film  210  from folding or bending on the film tray  100 . The flexible film  210  described here is film formed by soft materials such as polyethyleneterephthalate (PET), polyethersulfone (PES) and polycarbonate (PC). (See  FIG. 3A ) 
     One side of the flexible film  210  is fixed by closing the open-end  120   a . After one side of the flexible film  210  has been fixed, the flexible film  210  is tensioned to prevent the flexible film  210  from sagging. Then the flexible film  210  may be sized with the cutter  230 . For example, the flexible film  210  may be sized such that the flexible film does not sag more than 20 mm. (See  FIG. 3B ) 
     A second side of the flexible film  210  is then fixed by another clamp  120  by inserting the flexible film into the open open-shut part  120   a  and closing the open-shut part adjacent to support part  120 B. (See  FIG. 3C ) 
     When the flexible film  210  is fixed using the above-described method, the shape of the flexible film is maintained even when a thin film is applied to the flexible film  210  or when the flexible film  210  is transferred. Therefore, it is possible to perform sputtering and patterning at the desired location and position, and it is possible to make the thin films uniform in the entire sputtering area. Also, the flexible film  210  may be conveniently transferred. 
     Referring to  FIG. 4 , the film tray for fabricating a flexible display  400  includes a support plate  410 , clamps  420  on the edges of the upper side of the support plate  410  and an opening  430  formed in the central part of the support plate  410 , according to another embodiment of the present invention. 
     A fixing hole  440  adapted to receive a fixing pin (not shown) is located on at least one corner portion of the support plate  410 . The support plate  410  and the clamps  420  include a plurality of four-sided grooves  450 ,  425  to make the support plate lighter. As the support plate  410 , clamps  420 , opening  430 , fixing hole  440  and grooves  450 ,  425  are previously described above, a more detailed explanation will not follow. 
     Referring to  FIG. 5 , the film tray for fabricating a flexible display  500  includes a support plate  510 , clamps  520  symmetrical with each other on two edges of an upper side of the support plate, an opening  530  formed in the central section of the support plate, and front side supporting sections  540  established to support the clamps  520 . 
     The front side support sections  540  are established to be symmetrical with each other and to securely fix the flexible film. As shown in  FIGS. 6A and 6B , the front side support sections  540  are established to jointly bond with the open-shut end  520   a  of the clamps  520  and to be located above the support part  520   b . Such front side section  540  is open and shut together with the open-shut part  520   a  to keep the flexible film  560  flat by keeping the flexible film  560  in tension. 
     The film tray  500  may further include a plurality of holes  570  in the front side support section  540  to further reduce the weight as shown in  FIG. 7A . The film tray  500  may also include a plurality of holes  570  in the support plate  510  and front side support section  540  as shown in  FIG. 7B . For example,  58  holes  570  with a diameter of about 30 mm may be formed in the film tray  500 . Generally, holes  570  are formed to have a diameter of between about 10 mm to about 50 mm, but they are not limited in size, number, or location. 
     Referring now to  FIG. 8A , the flexible film  830  (or flexible substrate) is fixed by clamps  820  on the support plate  810  having opening  810   a . A deposition substance is supplied to the flexible film  830  from a deposition source  840  located in the lower section of the support plate  810 . The deposition substance is deposited on the flexible film  830  (or flexible substrate) through the opening  810   a  of the support plate  810 . Thereby, a thin film  850  is formed which corresponds to the size of the opening  810   a  on the flexible film  830  (or flexible substrate). The opening  810   a  serve to limit the deposition area of the thin film  850 . The deposition of the thin film  850  may be performed by using various methods such as, for example, sputtering, thermal deposition or chemical vapor deposition. 
     A donor film may be manufactured by using a film tray for fabricating flexible display as described herein. Donor film may be used when the thin film is formed by a laser-induced thermal imaging method. For example, donor film may be used when the organic emission layer of an OLED is formed. In this case, the base substrate  835  of the flexible donor films as shown in  FIG. 8B  is transferred to a chamber (for example, to the deposition chamber) after the base substrate is fixed by clamps  820  and located in the lower section of the support plate  810 . The thin film  850  is formed in the base substrate  835  when supplied from the deposition source  840  located in the lower section of the base substrate  835 . A light to thermal conversion layer and thermal image layer may be formed as the thin film  850 . When the film tray is transferred to a chamber, a transferring robot(not shown) is used. 
     Referring to  FIGS. 9A to 9D , to form an emission layer, donor film  950  is located on an accepter substrate  910  wherein an anode electrode  920 , a hole injection layer  930  and a hole transfer layer  940  are formed. The donor film  950  here includes a base substrate  950   a , a light to thermal conversion layer  950   b  and a thermal image layer  950   c . The base substrate  950   a  works as a support substrate to support the donor film  950  and is made from a high molecular substance, for example, PET and so on. Such base substrate  950   a  is fixed to prevent the donor film  950  from sagging. 
     A light to thermal conversion layer  950   b  includes a radiation absorber for converting the absorbed laser to thermal energy. Namely, the light to thermal conversion layer  950   b  absorbs the laser radiation and then converts it to thermal energy. Such a light to thermal conversion layer  950   b  may include infrared rays such as carbon black, black lead, infrared dyes, pigment within oxide and sulfide, and so on. 
     A thermal image layer  950   c  is manufactured as a coating of organic thin film and includes a light emitting layer. A small amount of a substance, for example, a dopant, may be added to improve various characteristics of the light emitting layer. 
     The donor film  950  may be placed in contact with an upper section of the combination of accepter substrate  910 , anode electrode  920 , hole pouring layer  930  and hole transferring layer  940 . Patterning may be performed after optionally irradiating the laser in the area where the emission layer is to be formed. The laser can reach the donor film  950  through openings  810   a  formed in the support plate  810  of the film tray for fabricating flexible display. ( FIG. 9B ) 
     When the donor film  950  is removed from the accepter substrate  910 , the portion of the thermal image layers  950   c  which the laser contacted will adhere to the hole transfer layer  940  and then will be separated from the donor film  950 . ( FIG. 9C ). 
     Thus, when the donor film  950  is removed from the accepter substrate  910 , the light emitting layer  960  is formed only in the portion of the acceptor substrate  910  which was contacted by the laser. ( FIG. 9D ) 
     When a donor film  950  is manufactured by using the film tray for fabricating a flexible display shown in  FIG. 8B , the light to thermal conversion layer  950   b  and thermal image layer  950   c  may be formed on the base substrate  950   a  because the base substrate  950   a  remains flat even though it is flexible. Accordingly, it is possible to form a uniform light to thermal conversion layer  950   b  and thermal image layer  950   c  in the desired location on the base substrate  950   a.    
     Also, when the emission layer is formed on a donor film  950  that is held flat by the film tray for fabricating flexible display as shown in  FIG. 8B , the possibility of misalignment is reduced. 
       FIGS. 10A to 10E  show a film tray for fabricating a flexible display and its fixing method according to yet another embodiment of the present invention. The film tray  1100  of this embodiment may be used for a flexible substrate or a flexible film and includes a square-shaped support frame  1100   a , substrate support section  1100   b  to secure the flexible film, and opening  1110  through which sputtering may be performed. 
     Such film tray  1100  is used to fix a flexible film  1200  adhered to an inflexible substrate  1300 , such as a glass substrate. The film tray  1100  may be manufactured from the same materials and in substantially the same manner as the film trays described above. 
     The flexible film  1200  may be adhered to an inflexible substrate  1300  in order to prevent the flexible film  1200  from sagging during transferring and deposition. ( FIG. 10C ) 
     Then, the flexible film  1200  and the inflexible substrate  1300  are secured and settled within the film tray  1100 . The flexible film  1200  may be secured and settled within the substrate support section  1100   b  of the film tray. ( FIGS. 10D to 10E ). 
     Since the flexible film  1200  does not sag or bend when it is mounted on the film tray  1100 , it is possible to perform uniform sputtering and patterning of the thin film in the desired location on the flexible film  1200 . 
     According to the embodiments of the present invention as described above, a flexible substrate or flexible substrate, or film is able to be kept flat when a thin film is deposited onto the flexible substrate. Accordingly, it is possible to perform uniform sputtering and patterning in a desired location. Also, the flexible substrate or film can be conveniently transferred without deformation. Also, when a film tray for fabricating a flexible display of the present invention is used in a laser thermal image method using a donor film, the possibility of misalignment is reduced because the donor film can be kept flat.