Patent Publication Number: US-7911138-B2

Title: Encapsulation cap and display device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 10-2006-0030061 filed on Apr. 3, 2006, the content of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     The present invention relates to an encapsulation cap and a display device including the same. Particularly, the present invention relates to an encapsulation cap having a structure which has a reinforced strength and is not modified although a thickness of a workpiece is decreased and a display device including the same. 
     2. Background 
     An organic light-emitting device, one of the display devices, is a device using organic electroluminescence. Organic electroluminescence is a phenomenon that excitons are formed in an (low molecular or high molecular) organic material thin film by re-combining holes injected through an anode with electrons injected through a cathode, and a light of specific wavelength is generated by energy of the formed excitons. 
     The organic light-emitting device using the above a phenomenon has the basic structure as illustrated in  FIG. 1 . The organic light-emitting device comprises a glass substrate  200 , an indium tin oxide film  102  disposed on the glass substrate  200  and acting as the anode electrode (hereinafter, referred to as “anode electrode”), an insulating layer and an organic light-emitting layer  103  disposed sequentially on the anode electrode and a metal layer  104  disposed on the organic light-emitting layer and acting as the cathode electrode (hereinafter, referred to as “cathode electrode”). 
       FIG. 2  is a plane view of the organic light-emitting device shown in  FIG. 1 , In  FIG. 2 , the organic light-emitting device to which a cap is not attached is illustrated. Also, in  FIG. 2 , an active area  100  consisting of the structural elements described above is shown in the shape of the box. 
     As shown in  FIG. 1  and  FIG. 2 , in a process of forming the anode electrodes  102  and the cathode electrodes  104 , data lines  111  and scan lines  110   a  and  110   b  are formed on a periphery of the active area  100  and connected to the anode electrodes  102  and the cathode electrode  104  in the active area  100 , respectively. 
     In  FIG. 1 , on the other hand, the reference numeral “ 108 ” which is not illustrated indicates a moisture absorbing material layer (hereinafter, referred to as “getter”) attached on an inner surface of the cap  106  through an adhesive  107 , and the reference numeral “W” indicates a wall formed for separating the cathode electrodes  104 . 
     Here, a cap  106  is attached on a cap-attaching region  112  of the substrate  200  defined as an outer region of the active area  100  through an adhesive  106 A (hereinafter, referred to as “sealant”). The cap  106  is used for isolating and protecting the structural elements in the active area  100  from an external environment such as moisture, light and the like and is mainly made from metal material. 
     An entire thickness (height) of the organic light-emitting device having the structure as described above includes a thickness of the substrate  200 , a thickness of the sealant  106 A applied on the substrate  200 , a thickness of the cap  106  and a thickness of a reflective film (not shown) attached on a lower surface of the substrate  200  which is opposed to a surface on which the structural elements are disposed. 
     For example, thicknesses of the members constituting the organic light-emitting device with a thickness of 1.83 mm are as follows: 
     Glass substrate ( 200 ): 0.7 mm 
     Sealant ( 106 A): 0.03 mm 
     Reflective film: 0.2 mm 
     Cap ( 106 ): 0.9 mm 
     (not a thickness of the workpiece, but an entire thickness of the cap) 
     In order to slim down the organic light-emitting device, the study has been conducted for reducing a thickness of each structural member, however, there are limitations to reduce a thickness of the sealant  106 A applied on the substrate for attaching the cap and a thickness of the reflective film due to the characteristics of the material thereof. 
     Accordingly, an entire thickness of the organic light-emitting device can be reduced by reducing thicknesses of the substrate  200  and the cap  106 . In particular, it is more effective to reduce a thickness of the cap  106  which has more room than the glass substrate  200  in terms of the dimension and the strength. 
       FIG. 3  is a sectional view of the cap according to the related art. For example, a cap  106 - 1  with an entire thickness T 1  of 0.9 mm is made from a metal workpiece having a thickness t 1  of 0.3 mm. A space S 1  having a height of approximately 0.6 mm is formed in the cap  106 - 1  due to a difference between a central portion C- 1  and an attaching portion B- 1  to be attached to an attaching region ( 112  in  FIG. 2 ) of the substrate. 
     If the cap  106 - 1  shown in  FIG. 3  is made from the metal workpiece having a thickness which is thin by approximately 0.1 mm, that is, having a thickness of 0.2 mm, an entire height T 1  of the cap  106 - 1  can be reduced by approximately 0.2 mm while the same height of the inner space S 1  is maintained. 
     On the other hand, there is a solution that a height of the inner space S 1  is reduced to reduce an entire height T 1  of the cap  106 - 1 . However, there is a limit to reduce a height of the inner space S 1  of the cap  106 - 1  if the special regard will be paid to the fact that a distance between the getter  108  (in  FIG. 1 ) attached to an inner surface of the central portion C 1  of the cap  106 - 1  and the structural element such as the wall W (in  FIG. 1 ) or the cathode electrode  104  should be maintained to some degree. 
       FIG. 4  is a sectional view of the cap having another structure, according to the related art. The cap  106 - 2  shown in  FIG. 4  has a first space S 2  formed on a central portion C- 2  and a second space S 2 - 1  formed on a central portion of the first space S 2 . The getter  108  (in  FIG. 1 ) is attached to the central portion C- 2  corresponding to the second space S 2 - 1 . Due to the second space S 2 - 1 , the cap  106 - 2  has a structure in which some region of the central portion C- 2  is protruded with a certain height. 
     If the cap  106 - 2  having the structure as described above is made from the metal workpiece having a thickness which is thin by approximately 0.1 mm, that is, having a thickness of 0.2 mm, an entire height T 2  of the cap  106 - 2  can be reduced by approximately 0.2 mm while the same height of the inner space S 1  and S 2  is maintained. 
     As described above, in order to reduce a thickness of the organic light-emitting area, that is, an entire thickness of the cap  106 - 1  or  106 - 2 , it is most preferred to reduce a thickness of the workpiece (for example, the metal sheet) used for manufacturing the cap. 
     However, if the cap  106 - 1  or  106 - 2  is made from the metal sheet having a reduced thickness, it is difficult to obtain a desired shape and a specification of the cap. That is, a deformation such as a deflection is generated on a large portion (that is, C- 1  in  FIG. 3  and C- 2  in  FIG. 4  to which the getter is attached) of the cap with a thin thickness. Accordingly, there is a strong possibility that the getter is contacted with the structural elements of the device. Such contact between the getter and the structural element increases the possibility that a line fail of the cathode electrodes is generated, consequently an inferiority of the organic light-emitting device is caused by the above contact 
     In particular, the metal cap  106 - 1  or  106 - 2  made from the thin metal sheet has a weak structural strength, and a distortion caused by a spring back phenomenon (an elastic back caused by removing a load after the plastic deformation and an elastic deformation generated after bending) is also generated on the cap, and so a function of the cap can undergo the serious influence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements. 
         FIG. 1  is a sectional view showing schematically a structure of an organic light-emitting device of the related art; 
         FIG. 2  is a plane view of the organic light-emitting device to which a cap is not attached, shown in  FIG. 1 ; 
         FIG. 3  and  FIG. 4  are detailed sectional views of a cap shown in  FIG. 1 ; 
         FIG. 5  is a plane view of a cap according to the first embodiment of the present invention; 
         FIG. 6  is a sectional view taken along the line A-A in  FIG. 5 ; 
         FIG. 7  is a plane view of a cap according to the second embodiment of the present invention; 
         FIG. 8  is a sectional view taken along the line B-B in  FIG. 7 ; 
         FIG. 9  is a plane view of a cap according to the third embodiment of the present invention; 
         FIG. 10  is a sectional view taken along the line C-C in  FIG. 9 ; 
         FIG. 11  is a plane view of a cap according to the fourth embodiment of the present invention; 
         FIG. 12  is a sectional view taken along the line D-D in  FIG. 11 ; and 
         FIG. 13  is a partial sectional view taken along the line E-E in  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An object of a present invention is to provide an encapsulation cap which can be solve the above mentioned problems caused by a thin workpiece and has the structure being capable of preventing a deformation caused by a workpiece with a thin thickness for miniaturizing the display device, and a display device comprising the same. 
     Hereinafter, the encapsulation cap and the display device comprising the same according to the embodiments of the present invention will be explained in more detail with reference to the accompanying drawings. On the other hand, the organic light-emitting devices will be explained for explanation purposes, however, the present invention is not limited to the organic light-emitting devices. 
     First Embodiment 
       FIG. 5  is a plane view of a cap according to the first embodiment of the present invention and  FIG. 6  is a sectional view taken along the line A-A in  FIG. 5 . In  FIG. 5  which is a plane view, beads which will be described below are indicated by the dotted line. Here, the term of “bead” used in this description and the claim means a groove with a certain length and depth formed on a workpiece. 
     The cap  310  according to this embodiment is manufactured through a machining process for a metal sheet with a certain thickness (for example, 0.2 mm). The cap  310  comprises an attaching part  311  hereinafter, referred to “first plane part”) to be attached to a cap attaching region of a substrate (not shown) by an adhesive (sealant) and a central part  312  hereinafter, referred to as “second plane part”) on which a moisture absorbing material layer (hereinafter, referred to as “getter”) is attached. Structural elements disposed on the substrate are received in a space part  313  formed due to a height difference between the first plane part  311  and the second plane part  312 . 
     The most important feature of the cap  310  according to this embodiment of the present invention is that at least one bead  314  and  314 - 1  are formed on an inner surface of the second plane part  312  for reinforcing a strength of the cap and preventing the cap from being deformed. A configuration, an arrangement and a function of the beads are more concretely illustrated below. 
     On a region of the cap  310  except the first plane part  311 , that is, on a periphery of an inner surface of the second plane part  312 , a plurality of beads  314  having a certain depth are formed along each side of the first plane part  311 . In particular, oblique beads  314 - 1  making a certain angle with the adjacent beads  314  are formed on each corner sections of the second plane part  312 . 
     A size (length, width and depth) of the beads  314  and  314 - 1  are not limited, and the beads  314  and  314 - 1  can be formed on any place except the region on which the getter is attached later. 
     Second Embodiment 
       FIG. 7  is a plane view of a cap according to the second embodiment of the present invention and  FIG. 8  is a sectional view taken along the line B-B in  FIG. 7 . In  FIG. 7  which is a plane view, beads which will be described below are illustrated by the dotted lines. 
     The cap  410  according to this embodiment has a structure which differs from that of the cap  310  shown in  FIG. 5 . That is, the cap  410  comprises a first plane part  411  to be attached to a cap attaching region of a substrate (not shown) and a second plane part  412 . A receiving part  412 - 1  is formed on an inner surface of the second plane part  412 . The receiving part  412 - 1  is a recess having a certain depth and a moisture absorbing material layer hereinafter, referred to as “getter”) is attached to the receiving part  412 - 1 . Although the getter receiving part  412 - 1  is formed on an inner surface of the second plane part  412 , the second plane part  412  has an outer flat surface. 
     On the other hand, structural elements disposed on the substrate are received in a space part  413  formed due to a height difference between the first plane part  411  and the second plane part  412 . 
     In addition t the getter receiving part  412 - 1 , the most important feature of the cap  410  according to this embodiment of the present invention is that at least one bead  414 - 1  and  414 - 2  are formed on an inner surface of the second plane part  412  for reinforcing a strength of the cap and preventing the cap from being deformed. A configuration, an arrangement and a function of the beads are more concretely illustrated below. 
     On a region of the cap  410  except the first plane part  411 , that is, on an outside of the getter receiving part  412 - 1  of the second plane part  412 , the first bead  414 - 1  is formed, and a second bead  414 - 2  is formed on a periphery of an inner surface of the second plane part  412 . 
     The first bead  414 - 1  is formed along the getter receiving part  412 - 1  such that the first bead forms a closed-loop shape and the second bead  414 - 2  is formed along the first bead  414 - 1  such that the second bead also forms a closed-loop shape. The first bead  414 - 1  and the second bead  414 - 2  have a certain width and depth and are spaced apart from each other. 
     Third Embodiment 
       FIG. 9  is a plane view of a cap according to the third embodiment of the present invention and  FIG. 10  is a sectional view taken along the line C-C in  FIG. 9 . In  FIG. 9  which is a plane view, beads which will be described below are illustrated by the dotted lines. 
     The cap  510  according to this embodiment has a structure which differs from that of the cap  410  shown in  FIG. 7 . 
     That is, the cap  510  comprises a first plane part  511  to be attached to a cap attaching region of a substrate (not shown) and a second plane part  512 . A receiving part  512 - 1  is formed on an inner surface of the second plane part  512 . The receiving part  512 - 1  is a recess having a certain depth and a moisture absorbing material layer (hereinafter, referred to as “getter”) is attached to the receiving part  512 - 1 . On the other hand, structural elements disposed on the substrate are received in a space part  513  formed due to a height difference between the first plane part  511  and the second plane part  512 . 
     In addition to the getter receiving part  512 - 1  having a certain depth, the most important feature of the cap  510  according to this embodiment of the present invention is that at least one bead  514 - 1  and  514 - 2  are formed on an inner surface of the second plane part  512  for reinforcing a strength of the cap and preventing the cap from being deformed. A configuration, an arrangement and a function of the beads are more concretely illustrated below. 
     On a region of the cap  510  except the first plane part  511 , that is, on an outside of the getter receiving part  512 - 1  of the second plane part  512 , the first bead  514 - 1  is formed, and the second bead  514 - 2  is formed on a periphery of the second plane part  512  (that is, an outside of the first bead  514 - 1 ). 
     The first bead  514 - 1  is formed along the getter receiving part  512 - 1  such that the first bead forms a closed-loop shape and the second bead  514 - 2  is formed along the first bead  514 - 1 . The second bead  514 - 2  is divided into a plurality of unit beads  514 - 2   a ,  514 - 2   b ,  514 - 2   c  and  514 - 2   d.    
     On the other hand, the cap  510  according to this embodiment further comprises a third plane part disposed between the first plane part  511  and the second plane part  512 . At least two third plane parts  521  and  522  are formed and disposed on the same plane. The unit beads  514 - 2   b  and  514 - 2   d  are formed on surfaces of the third plane parts  521  and  522 , respectively. 
     As shown in  FIG. 10 , due to the third plane parts  521 ,  522  disposed at both sides of the second plane part  512 , an entire surface of the cap  510  has a two-steps structure, and so a distortion of the cap  510  can be sufficiently prevented. 
     On the other hand, a process of attaching the cap to the substrate, a pusher is employed for making move upward the cap toward the substrate and pressurizing the cap. In order carry out the above function, a block of the pusher is contacted with a surface (plane surface) of the cap, and so a pressure exerted on the cap through the block of the pusher functions as one of the major causes by which a deformation of the cap is generated. 
     Accordingly, it is preferred that a contact area between the block of the pusher and the cap is minimized. In the cap  510  according to this embodiment, there is a height difference between the second plane part  512  and each of the third plane part  521 ,  522  disposed at both sides, and so it is difficult to utilize the block of the conventional pusher. That is, the block of the conventional pusher has a rectangular frame shape corresponding to and contacted with a surface of the cap, however, the block of the pusher should consist of two bars which correspond to the both third plane parts  521 ,  522  and are in parallel to each other so as to pressurize the cap  510  according to this embodiment. 
     Accordingly, in a state where two bars constituting the block of the pusher are contacted with both third plane parts  521 ,  522 , the cap  510  is moved upward and pressurized by the block of the pusher. And so, a contact area between the block of the pusher and the cap  510 , particularly, the second plane part  512  with relatively large surface can be remarkably reduced. Consequently, a deformation of the cap  510  caused by the pusher can be minimized. 
     Fourth Embodiment 
       FIG. 11  is a plane view of a cap according to the fourth embodiment of the present invention, and  FIG. 12  is a sectional view taken along the line D-D in  FIG. 11 . In  FIG. 11  which is a plane view, beads which will be described below are illustrated by the dotted lines. 
     The cap  610  according to the fourth embodiment comprises a first plane part  611  to be attached to a cap attaching region of a substrate (not shown) and a second plane part  612 . A receiving part  612 - 1  is formed on an inner surface of the second plane part  612 . The receiving part  612 - 1  is a recess having a certain depth and a moisture absorbing material layer (hereinafter, referred to as “getter”) is attached to the receiving part  612 - 1 . On the other hand, structural elements disposed on the substrate are received in a space part  613  formed due to a height difference between the first plane part  611  and the second plane part  612 . 
     In addition to the getter receiving part  612 - 1  having a certain depth, the most important feature of the cap  610  according to this embodiment of the present invention is that at least one bead  614 - 1  and  614 - 2  are formed on an inner surface of the second plane part  612  for reinforcing a strength of the cap and preventing the cap from being deformed. A configuration, an arrangement and a function of the beads are more concretely illustrated below. 
     On a region of the cap  610  except the first plane part  611 , that is, on an outside of the getter receiving part  612 - 1  of the second plane part  612 , the first bead  614 - 1  is formed, and the second bead  614 - 2  is formed on a periphery of the second plane part  612  (that is, an outside of the first bead  614 - 1 ). 
     The first bead  614 - 1  is formed along the getter receiving part  612 - 1  such that the first bead forms a closed-loop shape, and the second bead  614 - 2  is formed along the first bead  614 - 1 . The second bead  614 - 2  is divided into a plurality of unit beads  614 - 2   a  and  614 - 2   b.    
     As known from  FIG. 11  and  FIG. 13  which is a sectional view taken along the line E-E in  FIG. 11 , on the other hand, the cap  610  according to this embodiment further comprises third plane parts  620  formed corners thereof. Each of the third plane parts  620  is disposed between a corner of the first plane part  611  and a corner of the second plane part  612 , and the third plane part  620  differs from the second plane part  612  in a height. Also, the third plane parts  620  are disposed on a same plane. 
     The unit bead  614 - 2   b  is formed on a surface of each third plane part  620 . Accordingly, the second bead  614 - 2  consists of a plurality of unit beads  614 - 2   a  (four unit beads in  FIG. 11 ) corresponding to the sides of the first bead  614 - 1  and a plurality of unit beads  614 - 2   b  (four unit beads in  FIG. 11 ) formed on the third plane parts  620 . At this time, the unit beads  614 - 2   a  and  614 - 2   b  are spaced apart from the first bead  614 - 1  with a predetermined distance. 
     Each of the third plane parts  620  has a triangular shape, and each unit bead  614 - 2   b  formed on each third plane part  620  is aligned with the unit beads  614 - 2   a  adjacent thereto at a predetermined angle. On the other hand, due to the third plane parts  620  disposed at the corners of the second plane part  612 , an entire surface of the cap  610  has a two-steps structure, and so a distortion of the cap  610  can be sufficiently prevented. 
     As compared with the caps  106 - 1  and  106 - 2  shown in  FIG. 3  and  FIG. 4 , the caps  310 ,  410 ,  510  and  610  according to the embodiments of the present invention can have the advantages as follows. 
     First of all, in a case where the cap is made from a workpiece having a significant thin thickness (for example, 0.2 mm), the cap can secure the sufficient structural strength due to a plurality of beads. Also, a torsion of the cap and a deflection of the second plane part with a relatively area which can be caused by the thin workpiece are prevented, and so a surface planarization of the cap can be maintained. 
     Although the cap is made of the workpiece with a thin thickness, the present invention can reinforce the structural strength of the cap and can prevent a deformation of the cap from being generated, and so an entire thickness of the cap is remarkably reduced and a shape of the cap can be stably maintained. 
     In particular, as shown in  FIG. 11 , the third plane parts  620  having a triangular shape are disposed on the corners of the second plane part  612  and the bead  614 - 2   b  formed on the third plane part  620  is aligned with the adjacent beads, and so the torsion of the entire cap can be completely inhibited. 
     As shown in  FIG. 7 ,  FIG. 9  and  FIG. 11 , on the other hand, the getter receiving part  412 - 1  (and  512 - 1 ,  612 - 1 ) is formed on the second plane part of the cap  410  (and  510 ,  610 ) and the getter is attached on a surface of the getter receiving part  412 - 1  (and  512 - 1 ,  612 - 1 ). Due to this structure, accordingly, although a height of the space formed by a height difference between the first plane part and the second plane part is reduced, the getter received in the getter receiving part  412 - 1  (and  512 - 1 ,  612 - 1 ) does not contact with the structural elements of the device, and so a line fail of the electrode is nor occurred. 
     Here, the bead and the getter receiving part (that is, recess) having a certain depth can be formed by the mechanical machining as well as the chemical machining such as an etching. 
     An embodiment of the present invent on may be achieved in a whole or in part by a cap comprising a first plane part; and a second plane part having at least one bead thereon, and disposed in a plane different from a plane of the first plane part, wherein the second plane part is connected with the first plane part. 
     Another embodiment of the present invention be achieved in a whole or in part by a display device comprising a substrate; an active area disposed on the substrate; and a cap comprising a first plane part attached to the substrate, and a second plane part having at least one bead thereon and disposed to correspond to the active area in a plane different from a plane of the first plane part. 
     Any reference in this specification to “an embodiment,” “another embodiment,” “the first embodiment,” “the second embodiment,” “the third embodiment,” or “the fourth embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications  1  in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.