Patent Publication Number: US-11037472-B2

Title: Rollable display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/794,288 filed on Oct. 26, 2017, which claims the priority benefit of Korean Patent Application No. 10-2016-0140353 filed on Oct. 26, 2016, all of which are hereby incorporated by reference in their entirety as if fully set forth herein. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to a display device, and more particularly, to a rollable display device. 
     Description of the Background 
     With the advancement of information technologies, the demands for display devices which enable a user to access information have increased. Accordingly, various types of the display devices are widely used, such as an electroluminescent display, a liquid crystal display (LCD), and a plasma display panel (PDP). 
     Since the electroluminescent display is a self-light emitting device, power consumption is lower than that of a liquid crystal display device requiring a backlight, and the electroluminescent display can be made thinner than the liquid crystal display device. In addition, the electroluminescent display has a wide viewing angle and a high response speed. The electroluminescent display is expanding the market while competing with the liquid crystal display device by developing process technology up to the level of large-screen mass production technology. 
     Pixels of the electroluminescent display include organic light emitting diodes (OLEDs) which are self light emitting elements. The electroluminescent display may be divided depending on kinds of light emitting materials, light emitting methods, light emitting structures, driving methods, and the like. Accordingly, the electroluminescent display may be divided into a fluorescent emission and a phosphorescent emission depending on a light emitting method and may be divided into a top emission structure and a bottom emission structure depending on a light emitting structure. In addition, the electroluminescent display may be divided into a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED) depending on a driving method. 
     Recently, a flexible display device has been commercialized. The flexible display device can reproduce input images on a screen of a display panel on which a plastic OLED is formed. The plastic OLED is formed on a flexible plastic substrate. The flexible display device can be implemented in various designs, and has advantages in portability and durability. The flexible display device can be implemented in various forms such as a bendable display device, a foldable display device, and a rollable display device. Such a flexible display device can be applied not only to a mobile device such as a smart phone and a tablet PC but also to a television (TV), an automobile display, and a wearable device, and the application field thereof is expanding. 
     A display panel of the rollable display device can be rolled or unrolled as needed. When a user desires to use the rollable display device, the display panel needs to be kept unrolled. Since a conventional rollable display device does not include a fixture for holding the display panel in the unrolled state, unlike the user&#39;s desire, the display panel can return to be the rolled state during the using. The absence of the fixture can degrade usability of the user and is problematic. 
     SUMMARY 
     Accordingly, the present disclosure is to provide a rollable display device including a structure capable of facilitating an operation of rolling and unrolling a display panel and capable of supporting the display panel. 
     In one aspect, a rollable display device comprises a display panel; a driving unit including a motion converting unit configured to linearly move in a width direction of the display panel in conjunction with a rotational motion of a motor; a lifting unit connected to one end of the display panel and the motion converting unit, and configured to move up and down the display panel in a longitudinal direction of the display panel in conjunction with a linear motion of the motion converting unit; and a panel roller unit connected to other end of the display panel, wherein the display panel is unrolled and rolled along a periphery of the panel roller unit corresponding to moving up and down of the display panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate aspects of the disclosure and together with the description serve to explain the principles of the disclosure. 
       In the drawings: 
         FIG. 1  is a schematic view of a rollable display device according to an aspect of the present disclosure; 
         FIG. 2  is a schematic view of a pixel shown in  FIG. 1 ; 
         FIG. 3  is a view illustrating a structure of a modular display panel; 
         FIGS. 4A and 4B  are views illustrating an example of use of a rollable display device according to an aspect of the disclosure; 
         FIG. 5  is a perspective view illustrating a rollable display device according to an aspect of the disclosure; 
         FIGS. 6A and 6B  are perspective views illustrating an operation state of a rollable display device according to an aspect of the present disclosure; 
         FIG. 7  is a view illustrating a driving unit of a support assembly; 
         FIGS. 8A and 8B  are views respectively illustrating a structure and an operation state of a motion converting unit; 
         FIG. 9  is a view illustrating a lifting unit of a support assembly; 
         FIGS. 10A, 10B and 11  are views illustrating a structure and an operation state of a motion converting unit; 
         FIG. 12  is a view illustrating an example of driving of a driving unit; 
         FIGS. 13A and 13B  are views illustrating a rollable display device according to another aspect of the present disclosure; and 
         FIGS. 14A and 14B  are views illustrating a rollable display device according to still another aspect of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE ASPECTS 
     Reference will now be made in detail to aspects of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. It will be paid attention that detailed description of known arts will be omitted if it is determined that the arts can mislead the aspects of the disclosure. In describing various aspects, the same components may be described at the outset and may be omitted in other aspects. 
     The terms “first”, “second”, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. 
     A display device according to an aspect of the disclosure may be implemented based on a display device such as a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an electroluminescent display, an electrophoresis display (EPD), a quantum dot display (QDD), or the like. Hereinafter, for convenience of explanation, a rollable display device including an organic light emitting diode (hereinafter, referred to as OLED) will be described as an example. 
       FIG. 1  is a schematic view of a rollable display device according to an aspect of the disclosure.  FIG. 2  is a schematic view of a pixel shown in  FIG. 1 .  FIG. 3  is a view illustrating a structure of a modular display panel. 
     Referring to  FIG. 1 , a rollable display device  10  according to an aspect of the disclosure includes a display driving circuit and a display panel  100 . 
     The display driving circuit includes a data driver  12 , a gate driver  14 , and a timing controller  16 , and writes a video data voltage of an input image to pixels of the display panel  100 . The data driver  12  converts digital video data RGB input from the timing controller  16  into an analog gamma compensation voltage to generate a data voltage. The data voltage output from the data driver  12  is supplied to data lines D 1  to Dm. The gate driver  14  sequentially supplies a gate signal synchronized with the data voltage to gate lines G 1  to Gn to select the pixels of the display panel  100  to which the data voltage is written. 
     The timing controller  16  receives a timing signal such as a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a data enable signal DE and a main clock MCLK, and the like input from a host system  19 , and synchronizes operation timing of the data driver  12  and the gate driver  14 . Data timing control signal for controlling the data driver  12  includes a source sampling clock SSC, a source output enable signal SOE, and the like. Gate timing control signal for controlling the gate driver  14  includes a gate start pulse GSP, a gate shift clock GSC, a gate output enable signal GOE, and the like. 
     The host system  19  may be implemented as one of a television system, a set-top box, a navigation system, a DVD player, a Blu-ray player, a personal computer (PC), a home theater system, and a phone system. The host system  19  includes a system on chip (SoC) with an embedded scaler to convert the digital video data RGB of the input image into a format suitable for displaying on the display panel  100 . The host system  19  transmits the timing signals Vsync, Hsync, DE, and MCLK together with the digital video data RGB to the timing controller  16 . 
     A pixel array of the display panel  100  includes pixels defined by the data lines (D 1  to Dm, where m is a positive integer) and the gate lines (G 1  to Gn, where n is a positive integer). Each of the pixels includes an OLED which is a self-light emitting element. 
     Referring further to  FIG. 2 , in the display panel  100 , a plurality of data lines D and a plurality of gate lines G intersect, and pixels are arranged in a matrix form in each of the intersecting regions. Each of the pixels includes an OLED, a driving thin film transistor (hereinafter, referred to as TFT) DT for controlling an amount of current flowing through the OLED, and a programming unit SC for setting a gate-source voltage of the driving TFT DT. 
     The programming unit SC may include at least one switching TFT and at least one storage capacitor. The switching TFT is turned on in response to a gate signal from the gate line G to apply a data voltage from the data line D to one electrode of the storage capacitor. The driving TFT DT controls the amount of current supplied to the OLED depending on a magnitude of a voltage charged in the storage capacitor to control an amount of light emitted from the OLED. The amount of light emitted from the OLED is proportional to the amount of current supplied from the driving TFT DT. Each of the pixels is connected to a high potential power source EVDD and a low potential power source EVSS, and are supplied with a high potential power supply voltage and a low potential power supply voltage from a power generator (not shown). TFTs constituting a pixel may be implemented as a p-type or an n-type. In addition, a semiconductor layer of the TFTs constituting the pixel may include amorphous silicon, polysilicon, or an oxide. The OLED includes an anode electrode ANO, a cathode electrode CAT, and an organic compound layer interposed between the anode electrode ANO and the cathode electrode CAT. The anode electrode ANO is connected to the driving TFT DT. 
     Referring further to  FIG. 3 , the display panel  100  is electrically connected to the timing controller  16  shown in  FIG. 1 , the data driver  12 , the gate driver  14 , and the like (the host system  19  shown in  FIG. 1  and the power generator not shown), and is modularized. 
     The gate driver  14  may be formed on the display panel  100  by a gate in panel (GIP) manner. That is, the gate driver  14  may be formed in a GIP manner on left, right, or both left and right sides of a display area AA, so that the display panel  100  can be easily rolled and unrolled. However, the aspect of the disclosure is not limited thereto. 
     A data printed circuit board (PCB)  20  is electrically connected to the display panel  100  through a first connection member  25 . The first connection member  25  may be a chip on film (COF) on which the data driver  12  is mounted, but is not limited thereto. For example, the first connection member  25  may be implemented by a tape carrier package (TCP) manner to electrically connect the data PCB  20  and the display panel  100 . 
     The data PCB  20  is connected to a control board  30  through a second connection member  35 . The second connection members  35  may be plural. The timing controller  16  and the like are mounted on the control board  30 . The second connection member  35  may be a flexible flat cable (FFC), but is not limited thereto. The control board  30  may be connected to the host system  19  shown in  FIG. 1 , the power generator, and the like through a connection cable. 
       FIGS. 4A and 4B  are views illustrating an example of use of a rollable display device according to an aspect of the disclosure. 
     Referring to  FIGS. 4A and 4B , a display panel  100  includes a display area in which an input image is reproduced. A user can recognize information output from the display panel  100  through the display area. A front surface of the display panel  100  refers to one surface of the display panel  100  in which the display area is defined. Conversely, a back surface of the display panel  100  refers to one surface of the display panel  100 , in a direction opposite to the front surface thereof, in which the user can not recognize the display area. However, the present disclosure is not limited thereto. If necessary, the display area can also be defined on the back surface of the display panel  100 . 
     The display panel  100  may be rolled and unrolled. That is, the display panel  100  may be easily and repeatedly subjected to rolling (or winding) operations or unrolling (or unwinding) operations by being given a predetermined flexibility. As shown in  FIG. 4B , the display panel  100  may be rolled (Inner rolling) in a front surface direction of the display panel  100  and may be rolled (Outer rolling) in a back surface direction of the display panel  100 . Hereinafter, for convenience of explanation, an instance of that the display panel  100  is rolled in the back surface direction will be described as an example, unless otherwise specified. 
     Hereinafter, referring to  FIGS. 5 to 12 , a rollable display device according to a first aspect of the disclosure will be described.  FIG. 5  is a perspective view illustrating a rollable display device according to an aspect of the disclosure.  FIGS. 6A and 6B  are perspective views illustrating an operation state of a rollable display device according to an aspect of the disclosure.  FIG. 7  is a view illustrating a driving unit of a support assembly.  FIGS. 8A and 8B  are views illustrating a structure and an operation state of a motion converting unit.  FIG. 9  is a view illustrating a lifting unit of a support assembly.  FIGS. 10A, 10B and 11  are views illustrating a structure and an operation state of a motion converting unit.  FIG. 12  is a view illustrating an example of driving of a driving unit. 
     Referring to  FIGS. 5, 6A and 6B , the rollable display device according to an aspect of the disclosure includes a display panel  100 , a support assembly  200 , and a panel roller unit  300 . 
     The display panel  100  may have a square or rectangular planar shape, but is not limited thereto. For example, the planar shape of the display panel  100  may be irregular shape (or a free form shape) including a circle. 
     Hereinafter, a width direction (for example, an x-axis direction) of the display panel  100  is defined as a first direction, a longitudinal direction (for example, a y-axis direction) of the display panel  100  is defined as a second direction, and a thickness direction (for example, a z-axis direction) of the display panel  100  is defined as a third direction. 
     The display panel  100  can be rolled or unrolled, and can maintain a first state ST 1  and a second state ST 2  as shown in  FIGS. 6A and 6B . The display panel  100  may be changed from the first state ST 1  to the second state ST 2  or from the second state ST 2  to the first state ST 1  as necessary. The first state ST 1  indicates a state in which the display panel  100  is rolled. Since a display area of the display panel  100  is not exposed to outside in the first state ST 1 , the first state ST 1  may be a state in which a user can not recognize the display area from outside. In the first state ST 1 , the rollable display device may be turned off so that no input image is displayed. 
     The second state ST 2  indicates a state in which the display panel  100  is unrolled. In the second state ST 2 , the display panel  100  can maintain a substantially flat shape. The second state ST 2  may be a state in which the user can recognize the display area of the display panel  100  from outside and be provided with necessary information. In the second state ST 2 , the rollable display device may be turned on so that the input image is displayed. 
     Although not shown, a back cover may be further provided on a back surface of the display panel  100 . The back cover supports the back surface of the display panel  100  and reinforces rigidity of the display panel  100 . That is, an aspect of the disclosure can improve physical durability of the display panel  100  by further including the back cover. The back cover may include a lightweight and high-strength material. For example, the back cover may be formed of one of glass fiber reinforced plastics (GFRP), carbon fiber reinforced plastics (CFRP), aluminum, and plastic. 
     The support assembly  200  includes a driving unit  250  and a lifting unit  270 . An aspect of the disclosure can support the unrolled display panel  100  on the back surface of display panel  100  and maintain a flat state of display panel  100  by having the support assembly  200 . Thus, there is an advantage that usability of the rollable display device can be improved. 
     Referring to  FIGS. 7, 8A and 8B , the driving unit  250  includes a motor  210  and a motion converting unit  230 . The motor  210  may be fixed at a predetermined position of a base member  510 . The motor  210  is connected to a power generator such as an external power source or an embedded battery and can receive power. The motor  210  generates a rotational force to provide a driving force (i.e., rotational force) to the motion converting unit  230 . 
     The motion converting unit  230  is connected to the motor  210  and is configured to convert a rotational motion of the motor  210  into a linear reciprocating motion in the first direction. For example, the motion converting unit  230  may be implemented as a shaft (or a screw)  231  and a ball screw including a nut (or a ball nut)  235  which is coupled to the shaft  231 . 
     The shaft  231  receives the rotational force from the motor  210  and performs a rotational motion with reference to a rotation axis extending along the first direction. The nut  235  coupled to the shaft  231  performs a linear reciprocating motion corresponding to a rotation direction of the shaft  231 . 
     One end of the shaft  231  is coupled to be rotatable to a shaft bracket  401  fixed on the base member  510 . Therefore, the movement of the shaft  231  other than the rotational motion with respect to the rotation axis can be restricted. That is, the shaft  231  has a degree of freedom in the rotation direction with respect to the rotation axis. A bearing may be further provided between the shaft bracket  401  and the shaft  231  so that the rotational motion of the shaft  231  can be facilitated. The movement of the nut  235  other than the linear reciprocating motion in the first direction can be restricted. That is, the nut  235  has a degree of freedom in the first direction. 
     For example, as shown in  FIGS. 8A and 8B , when the shaft  231  rotates in a forward direction ({circle around (1)}), the nut  235  can be linearly moved in +x-axis direction ({circle around (2)}). When the shaft  231  rotates in a reverse direction ({circle around (1)}′), the nut  235  can be linearly moved in −x-axis direction ({circle around (2)}′). The direction of linear motion of the nut  235  corresponding to the rotation direction of the shaft  231  can be determined depending on a direction in which a screw groove between the shaft  231  and the nut  235  is formed. 
     A limit sensor  630  (shown in  FIG. 5 ) capable of restricting the movement of the nut  235  may be further provided on the base member  510 . The limit sensor  630  is provided at a predetermined position and may restrict the movement of the nut  235  so that the nut  235  can move only within a predetermined interval. For example, a controller can control on/off of the motor  210  through a signal sensed through the limit sensor  630 . 
     Referring to  FIGS. 9 to 12 , the lifting unit  270  is configured to move up and down the display panel  100  in conjunction with the linear motion of the motion converting unit  230 . The lifting unit  270  is formed in a link structure and can repeatedly perform a folding or an unfolding operation by receiving a driving force from the motion converting unit  230 . When the display panel  100  is in the first state ST 1 , the lifting unit  270  maintains a folded state. In other words, when the display panel  100  is in the first state ST 1 , the lifting unit  270  has a lowest height. When the display panel  100  is in the second state ST 2 , the lifting unit  270  maintains an unfolded state. In other words, when the display panel  100  is in the second state ST 2 , the lifting unit  270  has a highest height. 
     The lifting unit  270  may be implemented as a scissor lift structure. That is, the lifting unit  270  includes a link portion LP. The link portion LP includes a first link LN 1  and a second link LN 2 . The first link LN 1  and the second link LN 2  intersect with each other to have scissor shape (or an ‘X’ shape) and are coupled to be rotatable via a first hinge HG 1 . 
     For example, the lifting unit  270  may include a first link portion LP 1  and a second link portion LP 2  arranged along a second direction. The first link portion LP 1  includes a 1-1 link LN 1 - 1  and a 1-2 link LN 1 - 2 . The 1-1 LN 1 - 1  and the 1-2 link LN 1 - 2  of the first link portion LP 1  intersect with each other in a scissor shape and are coupled to be rotatable via a 1-1 hinge HG 1 - 1 . 
     One end of the 1-1 link LN 1 - 1  is coupled to be rotatable to a hinge bracket  405  fixed on the base member  510 . The 1-1 link LN 1 - 1  has a degree of freedom in a rotation direction with respect to a rotation axis extending along the third direction. As shown in the figure, the hinge bracket  405  and the shaft bracket  401  may be formed as one body, but the aspect of the disclosure is not limited thereto. 
     One end of the 1-2 link LN 1 - 2  is provided so as to be movable in conjunction with the linear motion of the motion converting unit  230 . That is, the one end of the 1-2 link LN 1 - 2  may be coupled to be rotatable to the nut  235  of the ball screw. Accordingly, the 1-2 link LN 1 - 2  is rotatable with respect to a rotation axis extending along the third direction and is provided to be capable of linear reciprocating motion corresponding to the linear reciprocating motion of the nut  235 . A rotational motion of the nut  235  can be limited by a coupled structure with the 1-2 link LN 1 - 2 . Accordingly, the nut  235  can perform the linear reciprocating motion without rotating in conjunction with the rotational motion of the shaft  231 . 
     The second link portion LP 2  includes a 2-1 link LN 2 - 1  and a 2-2 link LN 2 - 2 . The 2-1 LN 2 - 1  and the 2-2 link LN 2 - 2  of the second link portion LP 2  intersect with each other in a scissor shape and are coupled to be rotatable via a 1-2 hinge HG 1 - 2 . 
     The first link LN 1  of the first link portion LP 1  and the second link LN 2  of the second link portion LP 2  are coupled to be rotatable via a second hinge HG 2 . The second link LN 2  of the first link portion LP 1  and the first link LN 1  of the second link portion LP 2  are coupled to be rotatable via a second hinge HG 2 . A rotation axis of the first hinge HG 1  and a rotation axis of the second hinge HG 2  are parallel to each other. 
     The second hinge HG 2  may be implemented as a spur gear. That is, the second hinge HG 2  may be implemented in such a manner that a first gear G 1  connected to the first link LN 1  and a second gear G 2  connected to the second link LN 2  are engaged with each other. The first gear G 1  and the second gear G 2  have different rotation axes, and the rotation axes are parallel to each other. In an aspect of the disclosure, the second hinge HG 2  is implemented in a form of the spur gear, so that driving stability and durability of the second hinge HG 2  can be secured more than when the second hinge HG 2  is implemented to have one rotation axis. 
     Other end of the 1-1 link LN 1 - 1  and one end of the 2-2 link LN 2 - 2  are coupled to be rotatable via a 2-1 hinge HG 2 - 1 , and other end of the 1-2 link LN 1 - 2  and one end of the 2-1 link LN 2 - 1  are coupled to be rotatable via a 2-2 hinge HG 2 - 2 . 
     Other end of the 2-2 link LN 2 - 2  is coupled to be rotatable to one end of the display panel  100 . The one end of the display panel  100  may be defined as an upper end of the display panel  100 . The link 2-2 LN 2 - 2  has a degree of freedom in a rotation direction with respect to a rotation axis extending along the third direction. 
     The display panel  100  may further include a head bar  600  (shown in  FIG. 5 ) at the one end of the display panel, and the other end of the 2-2 link LN 2 - 2  may be coupled to be rotatable to the head bar  600  fixed to the one end of the display panel  100 . The head bar  600  has a predetermined rigidity. When the 2-2 link LN 2 - 2  is directly coupled to the one end of the display panel  100 , an external force due to a movement of the 2-2 link LN 2 - 2  may be provided on the display panel  100  and damage may occur. An aspect of the disclosure further includes the head bar  600 , thereby alleviating the external force that can be provided on the display panel  100 , and minimizing damage to the display panel  100 . 
     The head bar  600  includes a slide rail  620 . The slide rail  620  has a predetermined tracking path extending in the first direction. The slide rail  620  determines a movement path of the 2-1 link LN 2 - 1  in the first direction. Other end of the 2-1 link LN 2 - 1  is coupled to be rotatable to the slide rail  620  and its movement is guided along the tracking path of the slide rail  620 . The other end of the 2-1 link LN 2 - 1  is coupled to a slider  625  to be movable along the slide rail  620  and can move along the tracking path of the slide rail  620 . 
     The lifting unit  270  can move up and down the display panel  100  in conjunction with the linear motion from the motion converting unit  230 . That is, the one end of the 1-1 link LN 1 - 1  is coupled to the hinge bracket  405  to fix the movement in the first direction, the one end of the 1-2 link LN 1 - 2 , which receives a driving force from the nut  235 , performs a linear reciprocating motion in the first direction corresponding to the linear reciprocating motion of the nut  235  in the first direction. Accordingly, in response to the linear reciprocating motion of the 1-2 link LN 1 - 2  in the first direction, the one end of the 1-1 link LN 1 - 1  and the one end of the 1-2 link LN 1 - 2  may be spaced apart from or adjacent to each other in the first direction. As the one end of the 1-1 link LN 1 - 1  and the one end of the 1-2 link LN 1 - 2  are disposed to be adjacent to each other, the lift unit  270  is unfolded. On the contrary, as the one end of the 1-1 link LN 1 - 1  and the one end of the 1-2 link LN 1 - 2  are spaced apart, the lift unit  270  is folded. The one end of the display panel  100  can ascend and descend in the second direction corresponding to a height change of the lift unit  270 . 
     Specifically, the one end of the 1-2 link LN 1 - 2  is moved in the +x-axis direction in conjunction with the nut  235  moving in the +x-axis direction ({circle around (1)}) and is disposed to be gradually adjacent to the one end of the 1-1 link LN 1 - 1 . Correspondingly, the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  are rotated via the 1-1 hinge HG 1 - 1 , and the other end of the 1-1 link LN 1 - 1  and the other end of the 1-2 link LN 1 - 2  are disposed to be gradually adjacent to each other. Correspondingly, the one end of the 2-2 link LN 2 - 2  coupled to the other end of the 1-1 link LN 1 - 1  and the one end of the 2-1 link LN 2 - 1  coupled to the other end of the 1-2 link LN 1 - 2  are disposed to be gradually adjacent to each other. Correspondingly, the 2-1 link LN 2 - 1  and the 2-2 link LN 2 - 2  are rotated via the 1-2 hinge HG 1 - 2 , and the other end of the 2-1 link LN 2 - 1  and the other end of the 2-2 link LN 2 - 2  are disposed to be gradually adjacent to each other. At this time, the other end of the 2-1 link LN 2 - 1  slides in the +x-axis direction along the tracking path of the slide rail  620  and is disposed to be gradually adjacent to the other end of the 2-2 link LN 2 - 2 . Accordingly, an overall height H 1  of the lifting unit  270  including the first link portion LP 1  and the second link portion LP 2  is increased ({circle around (2)}). The one end of the display panel  100  ascends corresponding to the height of the lifting unit  270 . 
     Conversely, the one end of the 1-2 link LN 1 - 2  is moved in the −x-axis direction in conjunction with the nut  235  moving in the −x-axis direction ({circle around (1)}′) and is gradually spaced apart from the one end of the 1-1 link LN 1 - 1 . Correspondingly, the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  are rotated via the 1-1 hinge HG 1 - 1 , and the other end of the 1-1 link LN 1 - 1  and the other end of the 1-2 link LN 1 - 2  are gradually spaced apart from each other. Correspondingly, the one end of the 2-2 link LN 2 - 2  coupled to the other end of the 1-1 link LN 1 - 1  and the one end of the 2-1 link LN 2 - 1  coupled to the other end of the 1-2 link LN 1 - 2  are gradually spaced apart from each other. Correspondingly, the 2-1 link LN 2 - 1  and the 2-2 link LN 2 - 2  are rotated via the 1-2 hinge HG 1 - 2 , and the other end of the 2-1 link LN 2 - 1  and the other end of the 2-2 link LN 2 - 2  are gradually spaced apart from each other. At this time, the other end of the 2-1 link LN 2 - 1  slides in the −x-axis direction along the tracking path of the slide rail  620  and is gradually spaced apart from the other end of the 2-2 link LN 2 - 2 . Accordingly, an overall height H 2  of the lifting unit  270  including the first link portion LP 1  and the second link portion LP 2  is decreased ({circle around (2)}′). The one end of the display panel  100  descends corresponding to the height of the lifting unit  270 . 
     An aspect of the disclosure uses a driving element such as a ball screw extending in the first direction to provide a driving force for driving the lifting unit  270 . In this instance, an area occupied by the driving element in the second direction can be minimized. Therefore, it is possible to minimize the area occupied by the driving element in a state in which the lifting unit  270  is folded. 
     Further, an aspect of the disclosure uses a driving element such as a ball screw that can convert the rotational motion of the motor  210  into a linear motion to provide a driving force to the lifting unit  270 . Accordingly, a relatively strong driving force can be generated even in a narrow space, and a load applied to the driving unit  250  can be minimized. Since it is possible to provide the driving force required for the lifting unit  270  with output of the relatively small motor  210 , noise and power consumption of the motor  210  for driving the lifting unit  270  can be reduced. Since the motor  210  having a relatively small size can be used, a compact design can be realized. 
     Although not shown, the lifting unit  270  may include only one link portion LP having a first link LN 1  and a second link LN 2 . In this instance, one end of the first link LN 1  is coupled to be rotatable to the hinge bracket  405 , other end of the first link LN 1  is coupled to be rotatable to the slide rail  620  so as to be guided along the tracking path of the slide rail  620 , one end of the second link LN 2  is coupled to be rotatable so as to be linearly movable corresponding to the linear reciprocating motion of the motion converting unit  230 , and other end of the second link LN 2  may be coupled to be rotatable to one end of the display panel  100 . 
     An aspect of the disclosure can minimize a driving force required to drive the lifting unit  270  by reducing the number of link portions LP constituting the lifting unit  270 . Since the motor  210  having a relatively small size can be used, a compact design can be realized. Power consumption for driving the lifting unit  270  can be reduced, and the relatively small motor  210  can be used, thereby realizing a compact design. 
     In addition, an aspect of the disclosure reduces the number of link portions LP constituting the lifting unit  270  so that an area in the second direction occupied by the lifting unit  270  can be reduced when the lifting unit  270  is folded. Therefore, it is possible to reduce the area occupied by the lifting unit  270  in a state in which the lifting unit  270  is folded. 
     Although not shown, one or more auxiliary link portions may be further provided between the first link portion LP 1  and the second link portion LP 2 . In this instance, the auxiliary link portion is arranged in order along the second direction between the first link portion LP 1  and the second link portion LP 2 , and may be coupled to be rotatable to a neighboring link portion LP and/or a neighboring other auxiliary link portion via the second hinge HG 2 . 
     The lifting unit  270  of the support assembly  200  supports the display panel  100  from the back side and restrains and restricts shaking and torsion in all directions of the unrolled display panel  100 . Thus, an unrolled portion of the display panel  100  can be maintained in a flat state unless a direct physical force is applied thereto. 
     Referring to  FIG. 12 , the lifting units  270   a  and  270   b  may be provided on the left and right sides of the display panel  100 , respectively. That is, an aspect of the disclosure may include a plurality of lifting units  270   a  and  270   b  as necessary. The lifting units  270   a  and  270   b  may be selectively provided at appropriate positions to avoid mechanical interference with other structures located on the back surface of the display panel  100 . That is, it means that the degree of design freedom can be improved unlike an instance when only one lifting unit  270  is provided, the lifting unit  270  must be disposed at a center of the display panel  100 . 
     In order to drive the lifting units  270 , it is necessary to provide a corresponding number of motion converting units  230 . That is, in order to drive a first lifting unit  270   a  and a second lifting unit  270   b  that respectively cover the left and right sides of the display panel  100 , a first motion converting unit  230   a  and a second motion converting unit  230   b  may be provided, respectively. 
     The first motion converting unit  230   a  and the second motion converting unit  230   b  may be driven by using one motor  210 . In an aspect of the disclosure, the first motion converting unit  230   a  and the second motion converting unit  230   b  are driven by using one motor  210  so that the first lifting unit  270   a  and the second lifting unit  270   b  can be synchronized with each other. That is, in an aspect of the disclosure, the first motion converting unit  230   a  and the second motion converting unit  230   b  are simultaneously driven by using one motor  210  so that it is possible to prevent a deviation in the moving positions of the first lifting unit  270   a  and the second lifting unit  270   b . Therefore, there is an advantage that driving stability and product reliability of the rollable display device can be secured. 
     A connection between the motion converting unit  230  and the motor  210  may be implemented as a bevel gear BV. That is, the shafts  231  of the first motion converting unit  230   a  and the second motion converting unit  230   b  can receive a driving force from the motor  210  using a structure of the bevel gear BV. Rotation axes of gears connected to the shaft  231  of the first motion converting unit  230   a  and the shaft  231  of the second motion converting unit  230   b  are parallel to each other, and gears connected to the motor  210  intersect with the rotation axes of the gears connected to the shafts  231 . 
     Since an aspect of the disclosure uses the motion converting unit  230  such as a ball screw, the driving force for driving the lifting unit  270  can be relatively reduced. Therefore, it is easy to drive a plurality of motion converting units  230  by using one motor  210 . 
     The panel roller unit  300  may be fixed to other end of the display panel  100 . The other end of the display panel  100  may be defined as a lower end of the display panel  100 . The panel roller unit  300  may be rotatable about a rotation axis extending in the first direction. Accordingly, the display panel  100  can be rolled and unrolled along a periphery of the panel roller portion  300 . 
     The panel roller unit  300  may have a cylindrical shape. That is, a cross-sectional shape of the panel roller unit  300  may be circular. However, an aspect of the disclosure is not limited thereto. The panel roller unit  300  may be formed in any shape as long as the display panel  100  can easily be rolled and unrolled. 
     The operation of rolling and unrolling the display panel  100  along the periphery of the panel roller unit  300  can be mechanically controlled. The control operation can be implemented by the support assembly  200 . That is, the display panel  100  can be rolled and unrolled along the periphery of the panel roller unit  300  in conjunction with the folding operation of the lifting unit  270 . 
     For example, when the lifting unit  270  of the support assembly  200  is unfolded, the display panel  100  is unrolled from the panel roller unit  300 . That is, one end of the display panel  100  rises when the lifting unit  270  is unfolded, and the display panel  100  is unrolled from the panel roller unit  300  correspondingly. The back surface of the unrolled display panel  100  is supported by the lifting unit  270  of the support assembly  200  to maintain its flat state. Conversely, when the lifting unit  270  is folded, the display panel  100  is rolled along the periphery of the panel roller unit  300 . That is, the one end of the display panel  100  is lowered when the lifting unit  270  is folded, the display panel  100  is rolled along the periphery of the panel roller unit  300  in response thereto. 
     Although not shown, an aspect of the disclosure may further include a torsion spring capable of applying a predetermined tension to the display panel  100  so that the display panel  100  is smoothly rolled and unrolled. The torsion spring can provide a restoring force to the panel roller unit  300  so that the panel roller unit  300  can be restored to the original state. 
     Although not shown, the panel roller unit  300  can be driven by a driving device such as a motor  210 . The driving device may be a tubular motor, and may be provided in the panel roller unit  300 . The driving device can convert electrical energy into mechanical energy in synchronization with a signal from a controller, and can supply the mechanical energy to the panel roller unit  300 . The driving device may be in conjunction with the driving unit  250  of the support assembly  200  in synchronization with a control signal from the controller. 
     An aspect of the disclosure may further include a housing  550  (shown in  FIG. 5 ). There is an internal space for accommodating the panel roller unit  300  inside the housing  550 . The housing  550  further includes a lead-in portion that opens the internal space. The display panel  100 , which is rolled and unrolled to the panel roller unit  300 , can be drawn in and out through the lead-in portion. A base member  510  having a support assembly  200  may be disposed on the housing  550 . The housing  550  and the base member  510  may be formed as one body, but are not limited thereto. 
       FIG. 13  is a view illustrating a rollable display device according to another aspect of the disclosure. 
     Referring to  FIG. 13A , in an aspect of the disclosure, there are two fixing points FIX 1  and FIX 2  at which one end of a lifting unit  270  and one end of the display panel  100  are coupled to each other. In this instance, one FIX 1  of the fixing points FIX 1  and FIX 2  needs to be provided to be slidable along a slide rail  620 . 
     Referring to  FIG. 13B , in another aspect of the disclosure, the rollable display device can be implemented as a simple structure in which the slide rail  620  is removed by reducing the number of the fixing point FIX 1  at which one end of the lifting unit  270  and one end of the display panel  100  are coupled to each other. For example, in another aspect of the disclosure, the slide rail  620  can be removed by not coupling the other end of a 2-1 link LN 2 - 1  to one end of the display panel  100  or removing the other end of the 2-1 link LN 2 - 1 . 
     Another aspect of the disclosure can implement the rollable display device with a simpler structure. Therefore, another aspect of the disclosure has an advantage that a more compact design can be implemented. Further, manufacturing cost and manufacturing time can be shortened, manufacturing defect can be reduced, and manufacturing yield can be improved. 
       FIGS. 14A and 14B  are views illustrating a rollable display device according to still another aspect of the present disclosure. 
     Referring to  FIG. 14A , when a second hinge HG 2  coupling a first link portion LP 1  and a second link portion LP 2  is implemented as a gear, there is a limit in folding the lifting unit  270  so that a 1-1 hinge HG 1 - 1  of the first link portion LP 1  and a 1-2 hinge HG 1 - 2  of the second link portion LP 2  are disposed adjacent to each other. Therefore, in a folded state of the lifting unit  270 , an area D 1  occupied by the lifting unit  270  in the second direction is relatively wide. 
     Referring to  FIG. 14B , still another aspect of the disclosure is characterized in that links LN 1  and LN 2  constituting the first link portion LP 1  and/or the second link portion LP 2  have a bent shape. The bending directions of the links LN 1  and LN 2  constituting each link portion LP are the same, and the bending directions of links LN 1 - 1  and LN 1 - 2  constituting the first link portion LP 1  and links LN 2 - 1  and LN 2 - 2  constituting the second link portion LP 2  are different. 
     A first link LN 1  and a second link LN 2  may include a first portion P 1  and a second portion P 2 , respectively. The first portion P 1  and the second portion P 2  each may be a portion extending in a reverse direction with respect to a first hinge HG 1 . The first portion P 1  and the second portion P 2  may have a predetermined angle. That is, the first link LN 1  and the second link LN 2  do not extend in parallel and may be bent at a predetermined angle. 
     For example, the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  of the first link portion LP 1  may be bent upward. In other words, the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  of the first link portion LP 1  may be bent upward convexly. The 2-1 link LN 2 - 1  and the 2-2 link LN 2 - 2  of the second link portion LP 2  may be bent downward. In other words, the 2-1 link LN 2 - 1  and the 2-2 link LN 2 - 2  of the second link portion LP 2  may be bent downward convexly. 
     In still another aspect of the disclosure, by bending the links LN 1  and LN 2  constituting the first link portion LP 1  and the second link portion LP 2  according to above-mentioned conditions, even when the second hinge HG 2  coupling the first link portion LP 1  and the second link portion LP 2  is implemented as a gear, the lifting unit  270  can be folded until the 1-1 hinge HG 1 - 1  of the first link portion LP 1  and the 1-2 hinge HG 1 - 2  of the second link portion LP 2  are disposed adjacent to each other. In this instance, an area D 2  occupied by the lifting unit  270  in the second direction can be minimized in the state in which the lifting unit  270  is folded. Therefore, it is possible to minimize the area occupied by the lifting unit  270  in the state in which the lifting unit  270  is folded. 
     On the other hand, since the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  of the first link portion LP 1  may be bent upward, the 1-1 link LN 1 - 1  and the 1-2 link LN 1 - 2  are not arranged in parallel along the first direction and have a predetermined angle α in the state in which the lifting unit  270  is completely folded. Accordingly, the lifting unit  270  can be smoothly unfolded by receiving a driving force in the first direction. That is, since the links LN 1 - 1  and LN 1 - 2  located at the lowermost end maintain a predetermined angle α even when the lifting unit  270  is completely folded, it can be easy to receive the driving force from the first direction and transmit it to the second direction. 
     Although aspects have been described with reference to a number of illustrative aspects thereof, it should be understood that numerous other modifications and aspects can be devised by those skilled in the art that will fall within the 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 in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.