Abstract:
A flexible display device includes a display panel including a plastic substrate where an organic light emitting diode and a thin film transistor are formed; a circuit portion applying a power signal and a data signal, which are supplied from an external portion, to the display panel; and a support member coupled to the plastic substrate, wherein the display panel and the circuit portion are bent around the support member.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the priority benefit of Korean Patent Application No. 10-2013-0085412 filed in Republic of Korea on Jul. 19, 2013, which is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field of the Disclosure 
         [0003]    The present disclosure relates to a flexible display device and a method of fabricating the same. 
         [0004]    2. Discussion of the Prior Art 
         [0005]    Recently, flexible display devices using organic light emitting diodes (OLEDs) have been widely developed. 
         [0006]    In more detail, categories of OLEDs include a passive matrix type and an active matrix type according to a driving method. 
         [0007]    Further, OLEDs may be categorized into a top emission type emitting light to a top surface, a bottom emission type emitting light to a substrate where a thin film transistor (TFT) is formed (e.g., to a bottom surface), and a dual emission type emitting light to both the top surface and the bottom surface. 
         [0008]    The flexible display device generally includes a plastic substrate that is flexible and capable of being bent, an OLED element, and a passivation element that can endure bending. 
         [0009]    Further, the flexible display device is designed to have a structure that can endure a specific bending radius according to the purpose of application and the field of application. 
         [0010]    The bending radius is a radius of a bent surface when bending the flexible display device, and as the bending radius becomes smaller, the fields of application are various and the quality of the flexible display device increases. However, currently, the OLED element, the passivation element, and the materials thereof are limited, and thus reliability is reduced. 
         [0011]      FIG. 1  is a cross-sectional view illustrating a flexible display device  10  according to the prior art. 
         [0012]    Referring to  FIG. 1 , the flexible display device  10  includes a plastic substrate  11 , a TFT and OLED element layer  12  formed on the plastic substrate  11 , an encapsulation portion  13  protecting the TFT and OLED element layer  12 , a circuit portion  14  applying a power signal and a data signal, which are supplied from an external portion, to the element layer  12 , and a bottom film  15  protecting a bottom of the plastic substrate  11 . 
         [0013]    The circuit portion  14  includes an IC (integrated circuit) pad portion  14   a  of a COF (chip on film) type or a COG (chip on glass) type, which is formed on the plastic substrate  11 , a resin layer  14   b  protecting the IC pad portion  14   a,  and a flexible printed circuit substrate  14   c  connected to the IC pad portion  14   a.    
         [0014]    An upper peripheral area A1 and a circuit portion area A2 of the flexible display device  10  are generally in a non-luminous area, and the non-luminous areas A1 and A2 are bent to achieve a thin profile and miniaturization of the display device. 
         [0015]    However, a bending stress is applied to the non-luminous area A1 and A2 in the bending process, and thus the circuit portion  14 , the plastic substrate  11 , or the OLED element layer  12  is destroyed. 
         [0016]    Further, in the bending process, the bent area does not maintain a constant bending radius. 
       SUMMARY OF THE INVENTION 
       [0017]    Accordingly, the present invention is directed to a flexible display device including a support member capable of easily bending a plastic substrate, and a method of fabricating the same. 
         [0018]    Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims herein as well as the appended drawings. 
         [0019]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, a flexible display device includes a display panel including a plastic substrate where an organic light emitting diode and a thin film transistor are formed; a circuit portion applying a power signal and a data signal, which are supplied from an external portion, to the display panel; and a support member coupled to the plastic substrate, wherein the display panel and the circuit portion are bent around the support member. 
         [0020]    In another aspect, a method of fabricating a flexible display device includes preparing a display panel including a plastic substrate on which an organic light emitting diode and a thin film transistor are formed; preparing a support member; coupling the display panel to the support member; and bending the display panel along a side surface of the support member. 
         [0021]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
           [0023]      FIG. 1  is a cross-sectional view illustrating a flexible display device according to the prior art; 
           [0024]      FIGS. 2 and 3  are a plan view and a cross-sectional view, respectively, illustrating a flexible display device before the device is bent according to an embodiment of the present invention, respectively; 
           [0025]      FIGS. 4A to 4D  are cross-sectional views illustrating various examples of a support member according to an embodiment of the present invention; 
           [0026]      FIG. 5  is a cross-sectional view illustrating the flexible display device after the device is bent according to an embodiment of the present invention; 
           [0027]      FIG. 6  is a schematic flow chart illustrating a method of fabricating the flexible display device according to an embodiment of the present invention; 
           [0028]      FIGS. 7A to 7F  are views illustrating a method of fabricating the flexible display device according to an embodiment of the present invention; 
           [0029]      FIGS. 8 and 9  are a plan view and a cross-sectional view, respectively, illustrating a flexible display device before the device is bent according to another embodiment of the present invention; 
           [0030]      FIG. 10  is a cross-sectional view illustrating the support member according to another embodiment of the present invention; and 
           [0031]      FIG. 11  is a cross-sectional view illustrating the flexible display device after the device is bent according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Reference will now be made in detail to exemplary embodiments, which are illustrated in the accompanying drawings. 
         [0033]      FIGS. 2 and 3  are a plan view and a cross-sectional view, respectively, illustrating a flexible display device  100  before the device is bent according to an embodiment of the present invention, respectively.  FIG. 4  is a cross-sectional view illustrating various examples of a support member according to an embodiment of the present invention, and  FIG. 5  is a cross-sectional view illustrating the flexible display device  100  after the device is bent according to an embodiment of the present invention. 
         [0034]    As shown in the drawings, the flexible display device  100  includes a display panel  110 , a circuit portion  120 , and a support member  130 . The display panel  110  and the circuit portion  120  are bent around the support member  130  to make the flexible display panel  100 . 
         [0035]    In more detail, the display panel  110  is formed of a plastic substrate where an OLED and a TFT are formed, and non-luminous areas such as non-active areas N/A, N/A1, and N/A2 may be formed at peripheral areas of the display panel  110 . 
         [0036]    The circuit portion  120  is for applying a power signal and a data signal, which are supplied from the external portion, to the display panel  110 . 
         [0037]    The circuit portion  120  may be formed as a COF, and an IC element may be formed on the COF. 
         [0038]    In more detail, referring to  FIG. 3 , the circuit portion  120  includes a COF  121  electrically connected to the display panel  110 , an IC element  122  coupled to the COF  121  on a surface of the COF  121 , and a FPCB (flexible printed circuit board)  123  supplied with the power signal and the data signal from the external portion. 
         [0039]    The IC element  122  may be a drive-IC (D-IC) element. 
         [0040]    The support member  130  is coupled to the plastic substrate that forms the display panel  110 . 
         [0041]    In more detail, referring to  FIG. 3 , the support member  130  includes a flat surface  131  coupled to the plastic substrate, an outer rounded surface such as a side surface  132  having a constant bending radius R, and an accommodation portion  133   a  accommodating the IC element  122 . 
         [0042]    The support member  130  may be made of stainless steel (SUS), magnesium (Mg), rubber, graphene, Teflon, PDMS (polydimethylsiloxane), urethane, or PVC (polyvinyl chloride) films, for example. 
         [0043]    The ratio of the bending radius R to the thickness t of the support member  130  may be between 0.2 and 0.8, and preferably 0.5. 
         [0044]    For example, if the thickness t of the support member  130  is 100 μm (micrometers), the radius R may be 0.05 mm (millimeters). 
         [0045]    The support member  130  may be formed in various forms, as shown in  FIG. 4 . 
         [0046]    In more detail, referring to  FIG. 4A , the accommodation portion  133   a  of the support member  130   a  may be formed in a groove shape to accommodate the IC element  122 . 
         [0047]    Alternatively, referring to  FIG. 4B , the accommodation portion  133   b  of the support member  130   b  may be formed in a hole shape to accommodate the IC element  122 . 
         [0048]    Alternatively, referring to  FIG. 4C , an insulator  134  may be coupled to the inner surface of the accommodation portion  133   a  formed in the groove shape. 
         [0049]    Alternatively, referring to  FIG. 4D , an insulator  134  may be coupled to the accommodation portion  133   b  formed in the hole shape. 
         [0050]    Accordingly, referring to  FIGS. 4A-4D  and  5 , the insulator  134  may be coupled to the accommodation portion  133  ( 133   a  or  133   b ) in the support member  130  ( 130   a  or  130   b ) to advantageously prevent transfer of electromagnetic waves from the IC element  122  to the support member  130  when the IC element  122  is inserted into the accommodation portion  133 . 
         [0051]      FIG. 6  is a schematic flow chart illustrating a method of fabricating the flexible display device according to an embodiment of the present invention, and  FIGS. 7A to 7F  are views illustrating the method of fabricating the flexible display device according to an embodiment of the present invention. 
         [0052]    The flexible display device  100  may be fabricated with four steps (S 1  to S 4 ). 
         [0053]    First, the display panel  110 , including the plastic substrate where the OLED and TFT are formed, is prepared (step S 1 ). 
         [0054]    Then, the support member  130  having the side surface  132  of the constant bending radius R is prepared (step S 2 ). 
         [0055]    Then, the display panel  110  is coupled to the support member  130  (step S 3 ). 
         [0056]    Then, the non-active areas N/A, N/A1, and N/A2 of the display panel  110  may be selectively bent around the side surface  132  of the support member  130  (step S 4 ). 
         [0057]    In this regard, at least one area of the non-display areas N/A, N/A1, and N/A2 may be selectively bent. 
         [0058]    In more detail, the step S 2  of preparing the support member  130  is as follows. 
         [0059]    First, referring to  FIG. 7A , a base support member  330  that becomes the support member  130  having the constant bending radius R at the side surface  132  later is prepared. 
         [0060]    A first optically transparent adhesive  136  is coated on a surface of the base support member  330 , and a second optically transparent adhesive  137  is coated on an opposite surface of the base support member  330 . 
         [0061]    The first optically transparent adhesive  136  may have an adhesion strength higher than the second optically transparent adhesive  137  so that the first optically transparent adhesive  136  is coupled to the display panel  110 . The first and second optically transparent adhesives  136  and  137  may be made of OCA (optical clear adhesive). 
         [0062]    Then, protective films  138   a  and  138   b  are attached to the first and second optically transparent adhesives  136  and  137 , respectively. 
         [0063]    Then, referring to  FIGS. 7B and 7C , the constant bending radius is formed at the side surface of the base support member  330 . 
         [0064]    In more detail, the side surface of the base support member  330  is cut round such that the area of the base support member  330  corresponds to a luminous area (i.e., an active area A/A) of the display panel  110 . To do this, a platen die cutting apparatus C may be used, which selectively cuts films. 
         [0065]    In other words, referring to  FIG. 7B , the area of the base support member  330  may correspond to the area of the display panel  110  except for the non-active areas N/A1 and N/A2. 
         [0066]    Further, the support member  130  may extend to the direction of the non-active area N/A2 where the circuit portion  120  is formed. 
         [0067]    Accordingly, the support member  130  may cover a part of the non-active area N/A2 for the circuit  120 . 
         [0068]    Referring to  FIG. 7C , the cutting apparatus C makes round cuts along the cutting lines C/L in order to form the constant bending radius at the side surface of the base support member  330 . 
         [0069]    The above explanation relates to bending the non-active areas N/A1 and N/A2 located at the top and bottom side of the flexible display device  100 . Alternatively, as shown in  FIG. 7D , other non-active areas N/A may be bent in a similar manner. 
         [0070]    Then, referring to  FIG. 7E , after cutting the side surface of the base support member  330 , the protective film  138   a  attached to the first optically transparent adhesive  136  and the protective film  138   b  attached to the second optically transparent adhesive  137  are removed. 
         [0071]    Accordingly, the support member  130  having the constant bending radius R at the side surface  132  is prepared. 
         [0072]    The step S 3  of coupling the display panel  110  and the support member  130  is finished by coupling the display panel  110  and the circuit portion  120  to the first optically transparent adhesive  136 . 
         [0073]    Then, referring to  FIG. 7E , when coupling the display panel  110  to the support member  130  is finished, an optically polarizing member  113  is coupled to the display panel  110 . 
         [0074]    A vacuum auto roller VR, on the surface of which vacuum holes are formed, is coupled to the display panel  110 , and then the display panel  110  is bent around the side surface having the bending radius R of the support member  130 . 
         [0075]    Accordingly, referring to  FIGS. 2 and 7F , the non-active areas N/A1 and N/A2 of the display panel  110  may be selectively bent. 
         [0076]    Besides the non-active areas N/A1 and N/A2, other non-active areas N/A of the display panel  110  shown in  FIGS. 2 and 7D  may be also bent. 
         [0077]    A flexible display device according to another embodiment is explained as below, and explanations of parts similar to parts of the previous embodiment may be omitted. 
         [0078]      FIGS. 8 and 9  are a plan view and a cross-sectional view illustrating a flexible display device  200  before the device is bent according to another embodiment of the present invention. 
         [0079]    As shown in the drawings, the flexible display device  200  includes a display panel  110 , a circuit portion  220 , and a support member  230 . The display panel  110  and the circuit portion  220  are bent around the support member  230  so that the flexible display device  100  can be realized. 
         [0080]    In more detail, the display panel  110  may be formed of a plastic substrate where an OLED and a TFT are formed, and non-luminous areas such as non-active areas N/A, N/A3, and N/A4 may be formed at a peripheral area of the display panel  110 . 
         [0081]    The circuit portion  220  applies a power signal and a data signal, which are supplied from the external portion, to the display panel  110 . 
         [0082]    The circuit portion  220  may be formed as a COG, and an IC element may be formed at the COG. 
         [0083]    In more detail, referring to  FIG. 9 , the circuit portion  220  includes an IC element  221  coupled to the COG on a surface of the COG and a FPCB  223  supplied with the power signal and the data signal from the external portion. 
         [0084]    The IC element  221  may be a drive-IC (D-IC) element. 
         [0085]    Referring to  FIG. 10 , which is a cross-sectional view illustrating the support member  230  according to another embodiment of the present invention, the support member  230  is coupled to the plastic substrate that forms the display panel  110 . 
         [0086]    In more detail, the support member  230  includes a flat surface  231  coupled to the plastic substrate of the display panel  110  and a side surface  232  having a bending radius R at an outer rounded surface. 
         [0087]    The display device  200  may be fabricated using the method described above with reference to  FIGS. 7A to 7F , and at least one of the non-active areas N/A, N/A3 and N/A4 of the display panel  110  may be selectively bent. 
         [0088]    Accordingly, referring to  FIG. 11 , which is a cross-sectional view illustrating the flexible display device  200  after the device is bent according to another embodiment of the present invention, the non-active area N/A4 formed by the circuit portion  220  and the non-active area N/A3 formed at the top portion of the display panel  110  can be bent. 
         [0089]    Besides the non-active areas N/A3 and N/A4, other non-display areas N/A of the display panel  110  may also be bent, similarly to  FIG. 8 . 
         [0090]    As described above, in the flexible display device of the present invention, the plastic substrate is bent around the outer rounded surface of the support member, which advantageously prevents destruction of the bent portion. 
         [0091]    Further, bending the non-active area (e.g., the bezel area) of the display device advantageously obtains a zero-bezel display device (i.e., a display device with substantially no bezel). 
         [0092]    Further, since the non-active area (e.g., a bezel area) of the display device is bent, there is an advantage of miniaturizing the display device. 
         [0093]    It will be apparent to those skilled in the art that various modifications and variations can be made in a display device of the present disclosure without departing from the sprit or scope of the invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.