Patent Publication Number: US-10777102-B2

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2018-0076894 filed on Jul. 3, 2018, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference, in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a display device, and more particularly, to a rollable display device with a driving assembly and a lifting assembly for manipulating a display panel between a rolled configuration and an unrolled configuration. 
     Description of the Related Art 
     Organic light emitting display (OLED) devices are known for use as computer monitors, televisions, or cellular phones. OLED devices are a self-emitting device and thus produce images without a separate light source, unlike liquid crystal display (LCD) devices and other types of display devices. 
     Over time, an applicable range of display devices has been diversified to personal digital assistants as well as monitors of computers and televisions, including display devices with a large display area, a reduced volume, and a reduced weight. 
     Recently in the field of display devices, rollable display devices with a display panel and a wiring line on a flexible substrate are gaining interest as a next generation display device. Specifically, devices are of interest that are capable of displaying images even when the display device is in a rolled configuration. However, known display devices are unable to be precisely controlled between rolled and unrolled configurations. Moreover, known display devices include drive mechanisms for rolling and unrolling the display device that are inefficient, occupy a relatively large amount of space, and include additional components, which decrease efficiency of repair and replacement and increase the cost of the overall display device. 
     BRIEF SUMMARY 
     In various embodiments, the present disclosure provides a display device which precisely winds or unwinds a rollable display panel by precisely controlling a roller. 
     In various embodiments, the present disclosure provides a display device with a simplified structure in which forces from a driving assembly and a lifting assembly are directly transmitted to a roller and a link, respectively, to roll or unroll the rollable display panel without using an intermediate medium. 
     In one embodiment, the present disclosure provides a display device which reduces a volume of a motor configuration which winds or unwinds a display panel. 
     In one embodiment, the present disclosure provides a display device which increases a degree of freedom of design of a driving assembly and a lifting assembly by disposing a driving assembly and a lifting assembly outside of a display panel and a roller. 
     In one embodiment, the present disclosure provides a display device which adjusts a degree of flatness of at least a part of a display panel which is unwound from a roller. 
     The present disclosure is not limited to the above-mentioned examples, and other embodiments, which are not mentioned above, can be clearly understood by those skilled in the art from the following description. 
     According to one or more embodiments of the present disclosure, a display device includes: a display panel having a first edge and a second edge, a roller coupled to the first edge of the display panel, a plurality of links having a first end opposite a second end, each of the second ends of the plurality of links coupled to the display panel proximate the second edge of the display panel, a driving assembly disposed outside of the roller and configured to rotate the roller, and an elastic member coupled to the first end of each of the plurality of links, the elastic member disposed outside of the roller. Accordingly, a force generated by the driving unit is directly transmitted to the roller and a force generated by the elastic member is directly transmitted to the plurality of links, such that the configuration of the driving mechanism of the display device is simplified. 
     According to one or more embodiments of the present disclosure, a rollable display device includes: a roller, a display panel fixed to the roller, a plurality of links coupled to the display panel, the plurality of links configured to support the display panel in a flat and planar configuration, a driving unit mechanically coupled to the roller, and a lifting assembly configured to apply a force to the plurality of links, wherein during operation the driving unit rotates the roller to wind the display panel about the roller, and wherein during operation, the lifting unit acts with the force on the plurality of links to unfold the plurality of links. Accordingly, in order to wind the display panel around the roller, only the driving unit controls the roller, such that it is possible to more precisely control the roller. 
     Further details of the embodiments are included in the detailed description and the drawings. 
     According to the present disclosure, a display device in which a driving assembly directly rotates a roller to precisely control the roller is provided. 
     According to the present disclosure, in order to wind or unwind the rollable display panel, a driving assembly directly transmits a torque to a roller and a lifting assembly directly transmits a force to a plurality of links, which together simplify the configuration of the driving mechanism of the display device. 
     According to the present disclosure, a simplified driving unit is disposed to reduce an amount of space occupied by the driving unit. 
     According to the present disclosure, the driving assembly and the lifting assembly are disposed outside of, or exterior to, the roller, so that the driving assembly and the lifting assembly are easily accessible for repairs, replacement, and rearrangement, which increases a degree of freedom of design of the driving assembly and the lifting assembly. 
     According to the present disclosure, a degree of flatness of the display panel may be adjusted by adjusting a modulus of elasticity of an elastic member. 
     The embodiments of the present disclosure are not limited to the examples above, and more features of the embodiments are included in the present specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other embodiments, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a display device in a fully unrolled configuration according to an embodiment of the present disclosure; 
         FIG. 2  is a perspective view of the display device of  FIG. 1  in a fully rolled configuration according to the present disclosure; 
         FIG. 3  is an exploded perspective view of the display device of  FIG. 1  according to the present disclosure; 
         FIG. 4  is an enlarged perspective view of a portion of the display device of  FIG. 1  according to the present disclosure; 
         FIG. 5  is a rear view of the display device of  FIG. 1  in a fully rolled configuration according to the present disclosure; 
         FIGS. 6A and 6B  are schematic views for explaining operation of a driving assembly and an elastic member of the display device of  FIG. 1  for manipulating the display device between the rolled and unrolled configurations; 
         FIG. 7  is a rear view of the display device of  FIG. 1  in a fully unrolled configuration according to the present disclosure; 
         FIGS. 8A and 8B  are schematic views for explaining the driving assembly and the elastic member of the display device of  FIG. 1  for manipulating the display device between the unrolled and rolled configurations; and 
         FIG. 9  is an enlarged perspective view for explaining a driving assembly, a roller, an elastic member, and a link of a display device according to an alternative embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Advantages and characteristics of the present disclosure and a method of achieving the advantages and characteristics will be clear by referring to embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed herein but can be implemented in various forms. The embodiments are provided by way of example only so that those skilled in the art can fully understand the embodiments of the present disclosure and the scope of the present disclosure. Therefore, the present disclosure is not limited to the disclosed embodiments, but will be defined only by the scope of the appended claims. 
     The shapes, sizes, ratios, angles, numbers, and the like illustrated in the accompanying drawings for describing the exemplary embodiments of the present disclosure are merely examples, and the present disclosure is not limited thereto. Like reference numerals generally denote like elements throughout the specification, unless the context dictates otherwise. Further, in the following description of the present disclosure, a detailed explanation of known related technologies may be omitted to avoid unnecessarily obscuring the embodiments of the present disclosure. Terms such as “including,” “having,” and “consist of” used herein are generally intended to allow other components to be added unless the terms are used with the term “only.” Any references to singular may include plural unless expressly stated otherwise. 
     Components are interpreted to include an ordinary error range even if not expressly stated. 
     When the relationship between two parts is described using the terms such as “on,” “above,” “below,” and “next,” one or more parts may be positioned between the two parts unless the terms are used with the term “immediately” or “directly.” 
     When an element or layer is disposed “on” another element or layer, another layer or another element may be interposed directly on the other element or there between. 
     Although the terms “first,” “second,” and the like are used for describing various components, these components are not confined by these terms. These terms are merely used for distinguishing one component from the other components. Therefore, a first component mentioned below may be a second component in accordance with the present disclosure. 
     A size and a thickness of each component illustrated in the drawings is provided only for convenience of description and understanding the illustrated embodiments, and the present disclosure is not limited to the size and the thickness of the component illustrated. 
     The features of various embodiments of the present disclosure can be partially or entirely adhered to or combined with each other and can be interlocked and operated in various ways, and the embodiments can be carried out independently of or in association with each other. 
     Hereinafter, embodiments of the present disclosure will be described in detail with reference to accompanying drawings. 
       FIG. 1  is a perspective view of a display device  100  in a fully unrolled configuration according to one embodiment of the present disclosure.  FIG. 2  is a perspective view of the display device  100  in a fully rolled configuration according to one embodiment of the present disclosure. Referring to  FIGS. 1 and 2 , the display device  100  includes a display panel DP and a housing HP (which may be referred to herein as a housing unit HP), wherein the display panel DP is coupled to the housing unit HP, as described herein, and stored in the housing unit HP when not in use. When the display panel DP is in use, the display panel DP extends from the housing unit HP. 
     As an initial matter, the display device  100  described herein may be a display device  100  with a rollable or flexible display panel DP which is capable of displaying images in the rolled configuration. The display panel DP of the display device  100  may have a high flexibility as compared with a general display panel or device of the related art. Because of the flexibility and configurability of the rollable display panel DP described herein, a size and shape of the rollable display panel DP may be freely selected. Further, when the display device  100  is not in use, the display device  100 , and more particularly the display panel DP, is manipulated from the unrolled configuration to the rolled configuration to be stored with a reduced volume relative to other known devices. In contrast, when the display device  100  is manipulated from a storage configuration to a use configuration (e.g. when the display device  100  is in use), the display panel DP of the display device  100  is manipulated from the rolled configured to the unrolled configuration. 
     The display panel DP displays images to a user. For example, in one embodiment, the display panel DP includes a display element, a circuit, a wiring line, and a component for driving the display element. In such an embodiment, since the display panel DP of the display device  100  is a rollable display panel DP, the display panel DP is configured to be manipulated between the rolled and unrolled configurations. For example, the display panel DP may be formed of a display panel and a back cover each having flexibility such that they can be manipulated between the rolled and unrolled configurations. 
     The display panel is a panel for displaying images to the user. The display panel may include a display element which displays images, a driving element which drives the display element, and wiring lines which transmit various signals to the display element and the driving element. The display element may be defined in different ways depending on a type of the display panel. For example, when the display panel is an organic light emitting display panel, the display element may be an organic light emitting diode which includes an anode, an organic light emitting layer, and a cathode. In an alternative embodiment, the display panel is a liquid crystal display panel, in which case the display element may be a liquid crystal display element. 
     A back cover is disposed on a rear surface of the display panel to support the display panel. The back cover may protect the display panel from damage or from debris or other materials from coming into contact with electronic components of the display panel and shorting the electronic components, such as the anode and cathode of an OLED display panel. In general, the back cover protects the display panel from harmful outside forces. The back cover is formed of a material that has a rigidity to support the display panel, but also that is flexible enough to be manipulated between the rolled and unrolled configurations with the display panel DP. 
     The housing unit HP is a case in which the display panel DP is accommodated when not in use. As will be described in further detail below, the housing unit HP further includes various electronic and mechanical components for manipulating the display panel DP between rolled and unrolled configurations. When the display device  100  and display panel DP are not in use, (e.g. when the display panel DP is in the rolled configuration), the display panel DP is received or accommodated in the housing unit HP. When in the use, the display panel DP is manipulated to the unrolled configuration such that the display panel DP extends from the housing unit HP. In other words, in the unrolled configuration, the display panel DP extends from the housing unit HP such that the display panel DP is positioned outside the housing unit HP. 
     The housing unit HP further includes an opening HPO. The opening HPO is preferably centrally disposed with respect to a top surface of the housing unit HP. The display panel DP moves between the rolled and unrolled configurations (e.g. from being positioned in the inside to the outside of the housing unit HP) through the opening HPO, as indicated by arrow A in  FIG. 1 . In one embodiment, the display panel DP moves in a vertical direction through the opening HPO of the housing unit HP between the rolled and unrolled configurations. 
     As will be described in further detail herein, the display panel DP of the display device  100  may be manipulated from a fully unrolled configuration as in  FIG. 1  to a fully rolled configuration as in  FIG. 2 , or from a fully rolled configuration to a fully unrolled configuration. 
       FIG. 1  illustrates the fully unrolled configuration of the display panel DP of the display device  100 . In the fully unrolled configuration, the display panel DP of the display device  100  extends from the housing unit HP such that the display panel DP is positioned outside of the housing unit HP. The fully unrolled configuration is defined as a state in which the display panel DP is unrolled and positioned outside of the housing unit HP to a maximum amount, such that it cannot be further unrolled any further without uncoupling from the housing unit HP. When the user activates the display device  100  such that images appear on the display panel DP, the display panel DP may be manipulated to the fully unrolled configuration, in which the display panel DP is flat and planar and preferably arranged vertically with respect to the housing unit HP, which is preferably arranged horizontal, or substantially horizontal. Moreover, the display panel DP extends from the housing unit HP such that the display panel DP is outside of the housing unit HP. 
       FIG. 2  illustrates the fully rolled configuration of the display panel DP of the display device  100 . In the fully rolled configuration, the display panel DP of the display device  100  is received in the housing unit HP. The fully rolled configuration is fined as a state in which the display panel DP is rolled and received in the housing unit HP to a maximum amount, such that it cannot be further rolled without damaging one or more components of the display device  100 . When the display device  100  is not in use (e.g. the user is not watching images on the display unit DP, it is advantageous from an aesthetic standpoint that the display panel DP is received in the housing unit HP and not positioned outside of the housing unit HP. Therefore, the display device  100 , and more particularly the display panel DP, may be manipulated to the fully rolled configuration, in which the display panel DP is rolled to be accommodated in the housing unit HP. Further, when the display panel DP is in the fully rolled configuration and accommodated in the housing unit HP, a volume of the display unit DP (and the display device  100  generally) is reduced, such that the display device  100  maintains a pleasing aesthetic as well as a form factor that may easily be carried, transported, or stored. 
       FIGS. 3 and 4  provide further details of embodiments of driving mechanisms and components for manipulating the display panel DP between the fully rolled configuration and the fully unrolled configuration. For example,  FIGS. 3 and 4  describe a roller unit  110  and a driving assembly  140  (which may be referred to hereinafter as a driving unit  140 ) for rolling and unrolling the display panel DP, which are both disposed or received in the housing unit HP. A lifting assembly  150  (which may be hereinafter referred to as a lifting unit) which lifts the display panel DP is also disposed or received in the housing unit HP. A link unit  120  which connects the display panel DP and the lifting unit  150  is on a rear surface  104  of the display panel DP. 
     Hereinafter, the roller unit  110 , the link unit  120 , a head bar  130 , the driving unit  140 , and the lifting unit  150  will be described in detail with reference to  FIGS. 3 and 4 . 
       FIG. 3  is an exploded perspective view of the display device  100 .  FIG. 4  is an enlarged perspective view of a portion of the display device  100 . Specifically,  FIG. 4  is an enlarged view of the driving unit  140  and the lifting unit  150  on the rear surface  104  of the display device  100  in order to explain a connection relationship of the link unit  120  and the lifting unit  150  of the display device  100  and a connection relationship of the roller unit  110  and the driving unit  140 . In  FIG. 4 , for the convenience of description, a roller support unit  112  and a link support unit  123  are illustrated with a dotted line to avoid obscuring features that are normally located behind the roller support unit  112  and the link support unit  123  in the orientation shown in  FIG. 4 . 
     Referring to  FIGS. 3 and 4 , the display device  100  according includes the display panel DP, which includes a front or display surface  102  opposite the rear surface, the housing unit HP, the roller unit  110 , the link unit  120 , the head bar  130 , the driving unit  140 , and the lifting unit  150 . In one embodiment, the front surface  102  of the display panel DP is referred to as a first surface of the display panel DP and the rear surface  104  is referred to as a second surface of the display panel DP. 
     The roller unit  110  rotates in a clockwise direction or a counterclockwise direction to roll or unroll the display panel DP, respectively. In one embodiment, rotation of the roller unit  110  in the clockwise direction manipulates the display panel DP from the unrolled configuration to the rolled configuration, while in other embodiments, rotation of the roller unit  110  in the counterclockwise direction manipulates the display panel DP from the rolled configuration to the unrolled configuration. The roller unit  110  includes a roller  111 , a roller support unit  112 , and a roller shaft  113 , which is received in a longitudinal bore of the roller  111 . In other words, the roller shaft  113  is positioned in the roller  111  and extends beyond outer edges of the roller  111  to couple to the roller support unit  112 . 
     The roller  111  is a member around which the display panel DP is wound or rolled. The roller  111  rotates in a clockwise direction or a counterclockwise direction to roll or unroll, respectively, or vice versa, the display panel DP, which is fixedly coupled to the roller  111 . The roller  111  may be, for example, formed to have a cylindrical shape. However, other shapes are specifically contemplated in embodiments of the present disclosure, such as triangular, ovular, square, or rectangular, among other geometric shapes. In embodiments where the roller  111  has edges, such as if the roller  111  is square, it is preferable that such edges are rounded to avoid damage to the display panel DP. 
     As noted above, the display panel DP is fixed to the roller  111 . For example, a lower edge  103  of the display panel DP may be fixed to the roller  111 . In an embodiment, the lower edge  103  is a first edge or simply, an edge of the display panel DP. When the roller  111  rotates in a clockwise direction, the display panel DP is wound around the roller  111 . When the roller  111  rotates in a counterclockwise direction, the display panel DP, which is wound around the roller  111 , is unwound from the roller  111 . However, the winding and unwinding of the display panel DP in accordance with the rotating direction of the roller  111  may vary depending on an arrangement or relationship of the roller  111  and the display panel DP. For example, the winding and unwinding may depend on whether a surface of the display panel DP which is in contact with an outer circumferential surface of the roller  111  is the front surface  102  of the display panel DP or the rear surface  104  of the display panel DP. It is to be appreciated that rotation of the roller  111  to wind or unwind the display panel DP according to the rotation can be selected. 
     The roller support unit  112  preferably includes two support units  112 , one disposed at end of the roller  111 . The roller  111  is rotatably coupled to the roller support unit  112 . Specifically, the roller shaft  113  protruding from both ends of the roller  111  is rotatably coupled to the roller support unit  112 . The roller support unit  112  is disposed on a bottom surface HPF of the housing unit HP, as in  FIG. 4 . A side upper end of the roller support unit  112  is coupled to the roller shaft  113  protruding from both ends of the roller  111 . Therefore, the roller support units  112  may support the roller  111  in spaced relationship relative to the bottom surface HPF of the housing unit HP. Therefore, when the roller  111  rotates, the roller  111  and the display panel DP wound to, and rolled about, the roller  111  do not interfere with, or contact, the bottom surface HPF of the housing unit HP, even when the display panel DP is in the fully rolled configuration. 
     The link unit  120  supports the display panel DP. Specifically, the link unit  120  supports the display panel DP in the unrolled configuration from the roller  111  in a flat and planar orientation. Preferably, the link unit  120  supports the display panel DP in a vertical orientation relative to the housing unit HP. The link unit  120  includes a plurality of links  121  coupled to each other, a link connecting unit  122  coupled between pairs of links  121 , a link support unit  123  coupled to one of the plurality of links, and a support shaft  124  coupled to one of the plurality of links. 
     Each of the plurality of links  121  is connected to an upper side of the display panel DP. For example, one end of each of the plurality of links  121  is connected to both sides of an upper edge  105  of the display panel DP to support the display panel DP in a flat and planar orientation when the display panel DP is in the unrolled configuration. 
     Each of the plurality of links  121  includes an upper link  121 U and a lower link  121 D. The upper link  121 U may be referred to as a first link and the lower link  121 D may be referred to as a second link. The upper link  121 U and the lower link  121 D are rotatably coupled to each other to be folded or unfolded. That is, the upper link  121 U and the lower link  121 D rotate in a direction to be proximate each other when in a folded configuration. The upper link  121 U and the lower link  121 D rotate in a direction away from each other when manipulated from the folder configuration to an unfolded configuration. 
     One end of the upper link  121 U is rotatably coupled to both ends of the upper edge  105  of the display panel DP. Specifically, one end of the upper link  121 U is rotatably coupled to the head bar  130 , which is fixed to the upper edge  105  of the display panel DP. 
     The head bar  130  is a member for connecting the display panel DP and the upper link  121 U. In one embodiment, the head bar  130  is fixed to the upper edge  105  of the display panel DP. The upper link  121 U may be rotatably coupled to the head bar  130  and the head bar  130  may move in a vertical direction in accordance with the rotation of the upper link  121 U. Because the display panel DP is preferably fixed to the head bar  130 , the display panel DP may also move in a vertical direction together with the head bar  130 . 
     The other end of the upper link  121 U is rotatably coupled to one end of the lower link  121 D. A gear  121 UG may be further disposed at the other end of the upper link  121 U so that the other end of the upper link  121 U is rotatably coupled to one end of the lower link  121 D. For example, the gear  121 UG disposed at the other end of the upper link  121 U may have a shape of a spur gear, but is not limited thereto. The gear  121 UG includes a plurality of teeth, splines, ribs, or like structures, such that the gear  121 UG can be mechanically coupled or intermeshed a gear  121 DG, as described herein. 
     One end of the lower link  121 D is rotatably coupled to the other end of the upper link  121 U. Similar to the other end of the upper link  121 U, the gear  121 DG may be further disposed at one end of the lower link  121 D. Further, similar to the gear  121 UG disposed at the other end of the upper link  121 U, the gear  121 DG disposed at one end of the lower link  121 D may be formed to have a shape of a spur gear, but is not limited thereto. In other words, the gear  121 DG includes a plurality of teeth, splines, ribs, or like structures such that the gear  121 DG is mechanically coupled to the gear  121 UG in an intermeshed configuration. 
     The link connecting unit  122  is disposed at the other end of the upper link  121 U and one end of the lower link  121 D. A shaft of the gear  121 UG at the other end of the upper link  121 U and a shaft of the gear  121 DG at one end of the lower link  121 D are connected to the link connecting unit  122 . Therefore, the gear  121 UG at the other end of the upper link  121 U rotates around the shaft connected to the link connecting unit  122 . The gear  121 DG at one end of the lower link  121 D rotates around the shaft connected to the link connecting unit  122 . Teeth of the gear  121 UG at the other end of the upper link  121 U and teeth of the gear  121 DG at one end of the lower link  121 D are engaged with each other so that the upper link  121 U also rotates in accordance with the rotation of the lower link  121 D and the lower link  121 D also rotates in accordance with the rotation of the upper link  121 U. 
     The other end of the lower link  121 D is coupled to the lifting unit  150 . Specifically, since the other end of the lower link  121 D is coupled to the lifting unit  150 , the other end of the lower link  121 D may rotate via the lifting unit  150 , as described herein. 
     The lower link  121 D is rotatably coupled to the support shaft  124  of the link support unit  123  at a point between one end and the other end of the lower link  121 D. Therefore, the lower link  121 D may rotate relative to the support shaft  124  via torque or force generated by the lifting unit  150 . Specifically, the lifting unit  150  rotates the other end of the lower link  121 D around the support shaft  124  to lift the lower link  121 D, which will be described below in detail with reference to  FIGS. 6A and 6B . 
     The support shaft  124  protrudes near an upper end of one surface of the link support unit  123 . The support shaft  124  is in spaced relationship with the bottom surface HPF of the housing unit HP. When the other end of the lower link  121 D rotates by the lifting unit  150 , the support shaft  124  is spaced apart from the bottom surface HPF of the housing unit HP so that the other end of the lower link  121 D and the bottom surface HPF of the housing unit HP do not interfere with each other. 
     In one embodiment, the plurality of links  121  includes two links  121 . Each of the links  121  includes the upper link  121 U, which may be referred to as a first link, and the lower link  121 D, which may be referred to as a second link. The upper link  121 U includes opposing first and second ends, wherein the first end is coupled to the head bar  130  and the second end is rotatably coupled to the lower link  121 D, as shown in  FIG. 3 . The lower link  121 D similarly includes opposing first and second ends, wherein the first end is coupled to the upper link  121 U and the second end is coupled to the lifting unit  150  and the elastic member  151  via the link support unit  123 . The head bar  130 , and thus the upper link  121 U is attached to the upper edge  105  of the display panel PD and the lower link  121 D is coupled to the lifting unit  150  proximate the lower edge  103  of the display panel PD. As shown in  FIG. 3 , the second end of the upper link  121 U and the first end of the lower link  121 D include gears  121 UG,  121 DG, respectively, which are mechanically coupled to each other in an intermeshed or interlocked configuration via the link connecting unit  122 . In other words, the link connecting unit  122  is coupled to each of the links  121 U,  121 D to secure the links  121 U,  121 D in a relationship wherein the links  121 U,  121 D can rotate relative to each other. 
     When the display panel DP is manipulated from the rolled configuration to the unrolled configuration, the lifting unit  150  acts with a force on the second end of the lower link  121 D to pull the second end of the lower link  121 D towards a center of the display panel DP, which causes rotation of the first and second links  121 U,  121 D towards vertical alignment in an unfolded configuration. Further, when the display panel DP is manipulated from the rolled configuration to the unrolled configuration, the lifting unit  150  acts with a similar force to maintain the links  121 U,  121 D in the unfolded configuration, which is opposite to the force provided by the driving unit  140  to manipulate the display panel DP to the rolled configuration. As such, when the display panel DP is in any configuration (e.g. rolled, unrolled, or anywhere in between), the lifting unit  150  and the links  121  provide a force that tends to keep the display panel DP in a flat and planar orientation that is preferably vertical relative to the bottom surface HPF of the housing unit HP. 
     Referring to  FIG. 4 , the lifting unit  150  is connected to the plurality of links  121  to apply a force or a torque to the plurality of links  121  to be lifted. The lifting unit  150  includes an elastic member  151  and an elastic member fixing unit  152 . 
     The elastic member  151  of the lifting unit  150  is disposed at the outside of the roller  111  to be connected to the plurality of links  121 . The elastic member  151  is a member having an elastic force and is connected to the plurality of links  121  to transfer the elastic force to the plurality of links  121  to lift the links  121 . In other words, the elastic member  151  applies the elastic force to the plurality of links  121  to unfold the links  121  so that the lower link  121 D rotates in a direction in which the lower link  121 D is disposed to be vertical relative to the lower edge  103  and the upper edge  105  of the display panel DP. The elastic member  151  may be, for example, a spring. However, as long as a member applies a force to the lower link  121 D to rotate the other end of the lower link  121 D, the elastic member is not limited to a spring, but rather, may be another type of elastic material or device with elastic properties. 
     The elastic member  151  is positioned closer to a center area of the display panel DP than the other end of the lower link  121 D. That is, the elastic member  151  may be disposed between the other end of the lower link  121 D of the link  121  disposed to be adjacent to one side  107  of the display panel DP and the other end of the lower link  121 D of the link  121  disposed to be adjacent to the other side  109  of the display panel DP. 
     As described above, one end of the elastic member  151  is connected to the other end of the lower link  121 D. Specifically, one end of the elastic member  151  may be rotatably coupled to the other end of the lower link  121 D. For example, one end of the elastic member  151  is inserted into a hole  121 DH formed in and extending through the other end of the lower link  121 D so that the other end of the lower link  121 D may rotate by the elastic force of the elastic member  151 . 
     The other end of the elastic member  151  is connected to the elastic member fixing unit  152 . Specifically, the elastic member fixing unit  152  is fixedly coupled to the bottom surface HPF of the housing unit HP and the other end of the elastic member  151  may be connected to the elastic member fixing unit  152 . The elastic member  151  may be contracted or expanded with respect to the elastic member fixing unit  152 . In other words, the elastic member  151  translates along its axis while the elastic member fixing unit  152  remains fixed in location. The other end of the lower link  121 D connected to one end of the elastic member  151  also rotates in accordance with contraction and expansion of the elastic member  151 . The elastic member  151  may be contracted or expanded by the rotation of the other end of the lower link  121 D. It is to be appreciated that the length, and other properties, of the elastic member  151  may be selected according to the preferred elastic force to be generated by the elastic member  151 . 
     The driving unit  140  is disposed proximate the roller  111  to rotate the roller  111 . In one embodiment, the driving unit  140  is adjacent to at least one of the ends of the roller  111  and is connected to the roller  111 . The driving unit  140  may rotate the roller  111  in a clockwise direction or a counterclockwise direction and the display panel DP may be wound or unwound around the rotating roller  111  accordingly, as described herein. 
     The driving unit  140  may generate a torque sufficient to rotate the roller  111  about its axis. Because the driving unit  140  is coupled mechanically and physically to the roller  111 , as described herein, the generated torque is applied to the roller  111  to rotate the roller  111 . The driving unit  140  includes a motor  141 , a worm gear  142 , a worm gear support unit  143 , and a worm wheel  144 . 
     The motor  141  applies a torque to the roller  111  to rotate the roller  111 . The motor  141  applies the torque to the roller  111  to rotate the roller  111  in a clockwise direction or applies the torque to the roller  111  to rotate the roller  111  in a counterclockwise direction, which can be selected according to applications of the motor  141  and the display device  100 . In this embodiment, the motor  141  is arranged vertically with respect to the bottom surface HPF of the housing unit HP. 
     In order to transmit the torque from the motor  141  to the roller  111 , the worm gear  142  and the worm wheel  144  are disposed between the motor  141  and the roller  111  and mechanically coupled to each other. The worm gear  142  and the worm wheel  144  are transmission members which transmit the torque generated in the motor  141  to the roller  111  and rotate the roller  111  in a clockwise direction or a counterclockwise direction via the torque supplied by the motor  141 . 
     Saw teeth are formed on outer circumferential surfaces of each of the worm gear  142  and the worm wheel  144 . The worm gear  142  and the worm wheel  144  are disposed such that the saw teeth of the worm gear  142  and the saw teeth of the worm wheel  144  are engaged with each other in an intermeshed or interconnected mechanical relationship. The worm gear  142  may rotate around a shaft of the worm gear  142  in a clockwise direction or a counterclockwise direction by the torque generated from the motor  141 . The worm wheel  144 , whose saw teeth are engaged with the saw teeth of the worm gear  142 , accordingly rotates around a shaft of the worm wheel  144  in a clockwise direction or a counterclockwise direction. 
     The worm gear support unit  143  is arranged on both ends of the worm gear  142 . The worm gear  142  is coupled to the worm gear support unit  143  to enable rotation of both ends of the worm gear  142 . The worm gear  142  is arranged or positioned at a lower portion of the worm wheel  144  to transmit the torque from the motor  141  to the worm wheel  144 . In one embodiment, the worm gear  142  may be supported by the worm gear support unit  143  in spaced relationship relative to the bottom surface HPF of the housing unit HP. Therefore, when the worm gear  142  rotates by the torque from the motor  141 , the worm gear  142  does not interfere with the bottom surface HPF of the housing unit HP. 
     The worm wheel  144  is fixedly coupled to the roller shaft  113 . For example, the worm wheel  144  and the roller shaft  113  may be integrally formed or the worm wheel  144  and the roller shaft  113  may be separately formed, and fixed together. Therefore, the roller  111  also rotates in a clockwise direction or a counterclockwise direction in accordance with the rotation of the worm wheel  144 . 
     Although it is described in  FIG. 4  that the driving unit  140  includes the motor  141 , the worm gear  142 , the worm gear support unit  143 , and the worm wheel  144 , configurations of the driving unit  140  are not limited thereto. Rather, other configurations are specifically contemplated that include the driving unit  140  rotating the roller  111  in the clockwise direction or the counterclockwise direction. For example, in order to transmit the torque of the motor  141  to the roller  111 , instead of the worm gear  142  and the worm wheel  144 , a member such as a chain or a belt may be used, or a geared motor may be directly connected to the roller  111 . 
     Although  FIG. 4  illustrates that the driving unit  140  is disposed at any one of the ends of the roller  111 , the driving unit  140  may be disposed on both ends of the roller  111  to rotate the roller  111 , and is therefore not limited thereto to the arrangement shown in  FIGS. 3 and 4 . 
     Accordingly, the display panel DP may be wound around the roller  111 , which rotates by the driving unit  140 . 
     The display panel DP may be unwound by the roller  111  via the driving unit  140  and the plurality of links  121 , which are unfolded by the elastic member  151 . In this case, the elastic member  151  unfolds the plurality of links  121  to support the display panel DP such that the display panel DP is maintained in a flat, planar, and preferably vertical orientation relative to the housing unit HP via the plurality of links  121 . 
     Hereinafter, a driving operation for manipulating the display panel DP from the fully rolled configuration to the unrolled configuration will be described in detail with reference to  FIGS. 5 to 6B . 
       FIG. 5  is a rear view of a display device  100 , and more specifically, the display panel DP, in the fully rolled configuration.  FIGS. 6A and 6B  are schematic views for explaining operation of the driving unit  140  and the elastic member  151  for manipulating the display unit DP. Specifically,  FIG. 6A  is an enlarged side view of a portion of the display device  100  illustrating the motor and the roller  111  in more detail.  FIG. 6B  is an enlarged rear view of the display device  100  illustrating the elastic member  151  in more detail. In  FIGS. 5 to 6B , the bottom surface HPF of the housing unit HP is illustrated in order to more clearly describe the roller unit  110 , the driving unit  140 , and the lifting unit  150  disposed in the housing unit HP. 
     Referring to  FIG. 5 , the display panel DP is in the fully rolled configuration, wherein the display panel DP is fully wound around the roller  111 . 
     In the fully rolled configuration, the plurality of links  121  are folded such that the upper link  121 U and the lower link  121 D overlap each other. Specifically, one pair of the upper links  121 U and the lower link  121 Ds of the plurality of links  121 , which are proximate or adjacent to one side  107  of the display panel DP, are folded to overlap each other. The upper link  121 U and the lower link  121 D of a second pair of links of the plurality of links  121 , which are adjacent to the other side  109  of the display panel DP are folded to overlap each other. 
     Further, the plurality of links  121  are disposed to be horizontal to the upper edge  105  and the lower edge  103  of the display panel DP. In the plurality of links  121 , the other end of the lower link  121 D may be disposed to be farther from the center area of the display panel DP than one end of the lower link  121 D. In the plurality of links  121 , the other end of the upper link  121 U may be disposed to be closer to the center area of the display panel DP than one end of the upper link  121 U. 
     In one embodiment, even though the force of the lifting unit  150  is applied to the plurality of links  121  in a fully wound state, which force acts to lift the plurality of links  121 , the plurality of links  121  may maintain a folded state via the driving unit  140 . In other words, in the fully wound state or the fully rolled configuration, the driving unit  140  fixes the roller  111  so that the display panel DP is preventing from unrolling. As such, the plurality of links  121  will similarly be maintained in the folded state. The display panel DP will also remain in the fully rolled configuration around the roller  111  via the driving unit  140 , which is locked in place. The plurality of links  121  connected to the head bar  130  at the upper edge of the display panel DP also remain in the folded state without being lifted. Therefore, the driving unit  140  may maintain the fixed state of the roller  111  so as not to rotate the roller  111 , such that the display panel DP maintains the fully rolled or wound configuration around the roller  111  and the plurality of links  121  connected to the head bar  130  also remain in the folded state. 
     Hereinafter, a driving operation of the driving unit  140  and the lifting unit  150  to manipulate the display panel DP from the fully rolled configuration around the roller  111  to the unrolled configuration will be described with reference to  FIGS. 6A and 6B . 
     Referring to  FIG. 6A , the driving unit  140  rotates the roller  111  in a counterclockwise direction. Specifically, the motor  141  rotates the worm gear  142  in a clockwise direction or a counterclockwise direction in accordance with an engagement state of saw teeth of the worm gear  142  and the worm wheel  144 . The worm wheel  144 , whose saw teeth are engaged with the saw teeth of the worm gear  142 , rotates in a counterclockwise direction in accordance with the rotation of the worm gear  142 . Therefore, the driving unit  140  rotates the roller  111  in a counterclockwise direction to unwind the display panel DP, which is illustrated wound around the roller  111 , from the roller  111 . Put another way, during operation, operation of the driving unit  140  rotates the roller  111 , which manipulates the display panel DP from the fully folded or wound configuration to the unfolded configuration. 
     Referring to  FIG. 6B , the display panel DP is unwound from the roller  111  by the driving unit  140  and the elastic member  151  of the lifting unit  150 , which applies an elastic force to the plurality of links  121  so as to lift the links  121 . 
     First, in the fully rolled configuration, the driving unit  140  fixes the roller  111  so as to prevent the roller  111  from rotating, as above. By preventing rotation of the roller  111  via the driving unit  140 , the plurality of links  121  are also maintained in the folded state. 
     When the display panel DP is to be unwound from the roller  111 , the driving unit  140  releases, such that the driving unit  140  may rotate the roller  111 . The release of the force from the driving unit  140  which maintains the plurality of links  121  in the folded state enables the plurality of links  121  to be unfolded from the folded state by the elastic member  151 . 
     In one embodiment, a length from one end of the elastic member  151  to the other end is a first length D 1  when the display panel DP is in the fully rolled configuration. Specifically, in the fully rolled configuration, the elastic member  151  may be expanded to a maximum amount of expansion without damaging the elastic member  151 . Therefore, in this embodiment, the first length D 1  is a maximum length of the elastic member  151 . 
     The other end of the elastic member  151  is fixed to the elastic member fixing unit  152  and one end of the elastic member  151  may move in accordance with the rotation of the lower link  121 D. In this case, as described above, in the fully rolled configuration of the display panel DP, the driving unit  140  may fix the roller  111  so as prevent rotation of the roller and the plurality of links  121  connected to the head bar  130  display panel. In other words, fixing the driving unit  140  prevents movement of the links  121  and the head bar  130 , which prevents the display panel DP from unrolling. In this case, the other end of the lower link  121 D is disposed farthest from the center area of the display panel DP as compared with other parts. One end of the elastic member  151  connected to the other end of the lower link  121 D also moves away from the center area of the display panel DP. Therefore, the elastic member  151  is expanded. Until the driving unit  140  releases the fixing force on the roller  111 , the elastic member  151  maintains the maximum expansion state due to the force of the driving unit  140 , wherein the elastic member  151  has the maximum first length D 1 . 
     When the driving unit  140  releases the fixing force on the roller  111  (e.g. when the driving unit  140  is an operational state) and rotates the roller  111  to unwind the display panel DP, the fixing force from the driving unit  140  on the elastic member  151  is also released, such that the elastic member  151  contracts from the maximum first length D 1  to its original state. Therefore, one end of the elastic member  151  may move toward the elastic member fixing unit  152  with respect to the other end of the elastic member  151  and the elastic member fixing unit  152 . In other words, one end of the elastic member  151  may move to be closer to the center area of the display panel DP relative to its position in the maximum first length D 1 . 
     Therefore, as the display panel DP is unrolled, the elastic member  151  may rotate the other end of the lower link  121 D of the plurality of links  121  so that the plurality of folded links  121  unfolds. That is, the elastic member  151  may rotate the other end of the lower link  121 D to lift the plurality of links  121  by the elastic force of the elastic member  151  from its maximum expanded state to its original or resting state. 
     The other end of the lower link  121 D rotates so as to be closer to the center area of the display panel DP by the elastic member  151 . The lower link  121 D rotates with respect to the support shaft  124  by the rotation of the other end of the lower link  121 D. For example, the lower link  121 D rotates in a direction that is vertical to the bottom surface HPF of the housing unit HP. 
     Therefore, when the display panel DP is to be unrolled, the driving unit  140  rotates the roller  111  to initiate unrolling of the display panel DP from the roller  111  and the force of the driving unit  140  applied to the elastic member  151  is released. Therefore, the elastic member  151  may be contracted. As the elastic member  151  is contracted, one end of the elastic member  151  may move closer to the center area of the display panel DP and the other end of the lower link  121 D connected to one end of the elastic member  151  also rotates to be closer to the center area of the display panel DP. As a result, the lower link  121 D and the upper link  121 U connected to the lower link  121 D are lifted, which raises the display panel DP. 
     Hereinafter, a driving operation corresponding to manipulating the display panel DP from the fully unrolled configuration to the fully rolled configuration will be described in detail with reference to  FIGS. 7 to 8B . 
       FIG. 7  is a rear view of the display device  100  in a fully unrolled configuration.  FIGS. 8A and 8B  are schematic views for explaining operation of the driving unit  140  and the elastic member  151  when the display device  100  is wound or rolled from the unrolled configuration to the rolled configuration. Specifically,  FIG. 8A  is an enlarged side view of a portion of the display device  100  illustrating the driving unit in more detail.  FIG. 8B  is an enlarged rear view of a portion of the display device  100  illustrating the elastic member  151  in more detail. In  FIGS. 8A to 8B , only the bottom surface HPF or a bottom portion of the housing unit HP is illustrated in order to clearly describe the roller unit  110 , the driving unit  140 , and the lifting unit  150  disposed proximate the bottom surface HPF in the housing unit HP. 
     Referring to  FIG. 7 , the display panel DP is in the fully unrolled configuration, where in the display panel DP is fully unwound from the roller  111 . 
     In the fully unrolled configuration, the upper link  121 U and the lower link  121 D of each of the plurality of links are fully unfolded. Specifically, the upper link  121 U and the lower link  121 D of the link  121  which is adjacent to one side  107  of the display unit DP are unfolded as close as possible to vertical (e.g. the links  121 U,  121 D are aligned in a straight line). The upper link  121 U and the lower link  121 D of the link  121  which is adjacent to the other side  109  of the display panel DP are similarly unfolded as close as possible to vertical (e.g. the links  121 U,  121 D are aligned in a straight line). For example, the upper link  121 U and the lower link  121 D are unfolded to a maximum rotation, in which an angle between the upper link  121 U and the lower link  121 D is an obtuse angle which is larger than 90 degrees and smaller than 180 degrees. In other embodiments, the angle is 180 degrees, or greater than 180 degrees. As such, the present disclosure is not limited by the angle between the links  121 U,  121 D. 
     The plurality of links  121  are disposed to be vertical relative to the upper edge  105  and the lower edge  103  of the display panel DP. In each of the plurality of links  121 , the other end of the lower link  121 D may be disposed to be closer to the lower edge  103  of the display panel DP, the roller  111 , and the bottom surface HPF of the housing unit HP than one end of the lower link  121 D. In each of the plurality of links  121 , the other end of the upper link  121 U may be disposed to be closer to the lower edge  103  of the display panel DP, the roller  111 , and the bottom surface HPF of the housing unit HP than one end of the upper link  121 U. 
     The plurality of links  121  are maintained in the unfolded state by the driving unit  140  and the lifting unit  150 . In the fully unrolled configuration of the display panel DP, the driving unit  140  applies a force to fix the roller  111  so that the roller  111  cannot be rotated, and as such, the display panel DP is not wound around the roller  111 . That is, the display panel DP is maintained in the fully unrolled configuration by the driving unit  140 . The plurality of links  121  connected to the head bar  130  at the upper edge  105  of the display panel DP remain in the unfolded state due to the fixing force applied to the roller  111 , which prevents the lifting unit  150  from lowering the links  121  and the head bar  130 . In this case, the lifting unit  150  continuously applies a force to unfold the plurality of links  121  regardless of the winding or unwinding of the display panel DP due to the force exerted by the elastic member  151 . Therefore, the lifting unit  150  applies the force to the plurality of links  121  such that the plurality of links  121  remain unfolded via the lifting unit  150 . Therefore, the head bar  130  and the display panel DP connected to the plurality of links  121  may remain in the unrolled configuration by the lifting unit  150  and the driving unit  140 . 
     Further, when manipulating the display panel DP from the fully rolled configuration to the fully unrolled configuration or vice versa, the plurality of links  121  may remain unfolded all the time to support a part of the display panel DP which is not wound around the roller  111  in a flat and planar orientation. In other words, regardless of the configuration of the display panel DP (e.g. rolled or unrolled), a portion of the display panel DP may remain unrolled, in which case, the plurality of links  121  and the lifting unit  150  support the portion of the display panel DP in the unrolled configuration. 
     In the embodiment shown in  FIG. 8A , the driving unit  140  rotates the roller  111  in a clockwise direction. Specifically, the motor  141  rotates the worm gear  142  in the counterclockwise direction or the clockwise direction and the worm wheel  144  rotates in the clockwise or counterclockwise direction in accordance with the rotation of the worm gear  142 . Therefore, the driving unit  140  rotates the roller  111  in a clockwise direction to wind the display panel DP around the roller  111 . In other words, the driving unit  140  rotates the roller  111  to which the display panel DP is fixed, which manipulates the display panel DP from the unrolled configuration to the rolled configuration. 
     Referring to  FIG. 8B , the display panel DP is wound around the roller  111  by the driving unit  140  via rotation of the roller  111  by the driving unit  140 . However, when the display panel DP is wound around the roller  111  by the driving unit  140 , the elastic member  151  of the lifting unit  150  applies an elastic force to the plurality of links  121  so as to lift the plurality of links. In one embodiment, the force applied by the driving unit  140  is greater than the force applied to the links  121  by the lifting unit  150 , and as such, the driving unit  140  causes the display panel DP to be wound around the roller  111  while also folding the links  121  and expanding the elastic member  151 , as described herein. However, more preferably, the force applied by the driving unit  140  is less than the force applied to the links  121  by the lifting unit  150 , but because of the arrangement of the links  121  and the support shaft  124 , greater torque is generated by the driving unit  140  as compared to the lifting unit  150 , as described herein. 
     First, in the fully unrolled configuration, the driving unit  140  fixes the roller  111  so as to prevent the roller  111  from rotating and the lifting unit  150  applies a force to the plurality of links  121  so as maintain the links  121  in the unfolded state. When the display panel DP is wound around the roller  111 , the driving unit  140  rotates the roller  111  and the lifting unit  150  applies a force to the plurality of links  121  to maintain the links  121  in the unfolded state. Because the torque generated by the driving unit  140  is greater than the torque applied by the lifting unit  150 , the plurality of links  121  are folded by the force of the driving unit  140  despite the contrary force provided by the lifting unit  150 . 
     In this embodiment, the force of the driving unit  140  is less than the force of the lifting unit  150 . Specifically, the motor  141  of the driving unit  140  winds the display panel DP around the roller  111  to lower the display panel DP to the rolled configuration. The upper link  121 U connected to the head bar  130  at the upper edge of the display panel DP is also lowered by the force of the driving unit  140 , which lowers the display panel DP together with the links  121 . That is, the driving unit  140  applies force to the head bar  130 , the upper link  121 U, and one end of the lower link  121 D connected to the upper link  121 U. The driving unit  140  applies the force to one end of the lower link  121 D to rotate the lower link  121 D with respect to the support shaft  124 , thereby lowering the lower link  121 D and the upper link  121 U. 
     Further, the lifting unit  150  causes rotation of the other end of the lower link  121 D with respect to the support shaft  124  that tends to lift the lower link  121 D and the upper link  121 U. The head bar  130  and the display panel DP connected to the lower link  121 D and the upper link  121 U may also be lifted by the force of the lifting unit  150 . That is, the lifting unit  150  applies the force to the other end of the lower link  121 D to rotate the lower link  121 D with respect to the support shaft  124 , which lifts the upper link  121 U and the lower link  121 D connected to the upper link  121 U. 
     In summary, when the display panel DP is wound or manipulated to the rolled configuration, the driving unit  140  applies force to one end of the lower link  121 D so that one end of the lower link  121 D rotates with respect to the support shaft  124 , folding in the process. The lifting unit  150  applies force to the other end of the lower link  121 D such that the other end of the lower link  121 D rotates with respect to the support shaft  124  towards the unfolded configuration. 
     In this case, a length from one end of the lower link  121 D proximate the top edge  105  of the display panel DP to the support shaft  124  may be longer than a length from the other end of the lower link  121 D proximate bottom edge  103  of the display panel DP to the support shaft  124 . Further, it is known that the farther a point where the force is applied is with respect to another point, such as the support shaft  124 , the smaller the force is needed to generate the same torque and rotate the lower link  121 D. Specifically, the lower link  121 D is a body of rotation which rotates with respect to the support shaft  124  by torque. The torque may be determined by multiplying the length from the support shaft  124  to the point where the force is applied by a magnitude of the applied force. Therefore, the longer the length between the point where the force is applied and the support shaft  124 , the larger the torque. Because the length from the top edge  105  of the display panel DP to the support shaft  124  is greater than the length from the bottom edge  103  of the display panel to the support shaft  124 , a smaller force applied by the driving unit  140  to the top edge  105  of the display panel DP generates more torque than a large force applied by the elastic member  151  to the bottom edge  103  of the display panel DP and as such, the display panel DP is wound around the roller  111  and the links  121  are manipulated to the folded configuration. 
     For example, the length from one end of the lower link  121 D to the support shaft  124  is larger than the length from the other end of the lower link  121 D to the support shaft  124 . Therefore, even though the force of the driving unit  140  which is applied to one end of the lower link  121 D is smaller than the force of the lifting unit  150  applied to the other end of the lower link  121 D, the torque at the one end of the lower link  121 D may be stronger, as above. As such, even though the force of the driving unit  140  is smaller than the force of the lifting unit  150 , the driving unit  140  manipulates the lower link  121 D to the folded state. Therefore, when the display panel DP is manipulated to the folded configuration, the driving unit  140  applies the force so as to lower the lower link  121 D and the lifting unit  150  applies the force to lift the lower link  121 D, which is opposite to the driving unit  140 . Because the torque applied by the driving unit  140  to one end of the lower link  121 D is larger than the torque applied to the other end of the lower link  121 D by the lifting unit, the lower link  121 D is lowered together with the display panel DP. 
     Therefore, the force of the driving unit  140  and the force of the lifting unit  150  and the elastic member may be selected in consideration of a length from the support shaft  124  to one end of the lower link  121 D and the length from the support shaft  124  to the other end of the lower link  121 D. 
     In one embodiment, in the fully unrolled configuration, a length from one end of the elastic member  151  to the other end of the elastic member  151  is a second length D 2 . Specifically, in the fully unrolled configuration, the elastic member  151  is contracted a maximum amount. Therefore, the second length D 2  is a minimum length of the elastic member  151 . 
     Specifically, in the fully unrolled configuration, the elastic member  151  is contracted by the driving unit  140  and the lifting unit  150 . The other end of the elastic member  151  is fixed to the elastic member fixing unit  152  and one end of the elastic member  151  may move in accordance with the rotation of the lower link  121 D. In this case, as described above, in the fully unrolled configuration, the driving unit  140  fixes the roller  111  so as to prevent rotation of the roller  111 , which prevents the display panel DP from winding around the roller  111  and lowering the display panel DP. Further, the force from the driving unit  140  is not applied to the plurality of links  121 , which prevents the links  121  from being manipulated to the folded state by the driving unit  140 . Therefore, the plurality of links  121  remain the unfolded state to the maximum by the lifting unit  150 , which exerts a lifting force on the links due to the contraction of the elastic element  151  and its tendency to return to its uncontracted state. In this case, the other end of the lower link  121 D rotates with respect to the support shaft  124  so as to be closer to the center area of the display panel DP, which the lower link  121 D vertical with respect to the bottom surface HPF of the housing unit HP. One end of the elastic member  151  connected to the other end of the lower link  121 D may also move closer to the center area of the display panel DP, which contracts the elastic member  151 . Therefore, before the driving unit  140  applies the force to lower the display panel DP, the elastic member  151  is not expanded by the driving unit  140 , but rather, is contracted to be back to its original state so that the elastic member  151  has the second length D 2 , which is the minimum length. 
     In one embodiment, when the driving unit  140  rotates the roller  111  to wind the display panel DP again, the elastic member  151 , which is contracted to the maximum in the fully unrolled configuration, is expanded again by the force of the driving unit  140  applied to the elastic member  151 . Therefore, one end of the elastic member  151  may move away from the elastic member fixing unit  152  with respect to the other end of the elastic member  151  fixed to the elastic member fixing unit  152 . In other words, one end of the elastic member  151  may move away from the center area of the display panel DP. 
     Therefore, when the display panel DP is wound, the driving unit  140  rotates the other end of the lower link  121 D of the plurality of links  121  so that the plurality of unfolded links  121  are folded. That is, the driving unit  140  rotates the other end of the lower link  121 D to lower the plurality of links  121 . 
     The other end of the lower link  121 D rotates away from the center area of the display panel DP via the force applied by the driving unit  140 . Further, the lower link  121 D rotates with respect to the support shaft  124  by the rotation of the other end of the lower link  121 D and for example, in one embodiment, the lower link  121 D rotates until the lower link  121 D is horizontal relative to the bottom surface HPF of the housing unit HP. 
     Therefore, when the display panel DP is wound around the roller  111 , the driving unit  140  rotates the roller  111  to wind the display panel DP around the roller  111  and the elastic member  151  is expanded by the force of the driving unit  140  which rotates the lower link  121 D away from the center of the display panel DP. As the elastic member  151  expands, one end of the elastic member  151  moves away from the center area of the display panel DP and the other end of the lower link  121 D connected to one end of the elastic member  151  also rotates away from the center area of the display panel DP. Therefore, the lower link  121 D and the upper link  121 U connected to the lower link  121 D are lowered. 
     The display device  100  according to the exemplary embodiment of the present disclosure includes the driving unit  140 . The driving unit  140  directly rotates the roller  111  to precisely control the roller  111 . Specifically, the display device  100  according to the embodiments of the present disclosure includes the driving unit  140  coupled to any one of both ends of the roller  111  at the outside of the roller  111 . The driving unit  140  is a member which generates a torque and the torque generated in the driving unit  140  may rotate the roller  111  in either the clockwise or counterclockwise directions. In this case, the display panel DP fixed to the roller  111  may be wound or unwound around the roller  111  in accordance with the rotating direction of the roller  111 . The driving unit  140  display panel controls a speed or rate at which the display panel DP is wound around the roller  111  or unwound from the roller  111  by precisely controlling rotation of the roller  111 . The lifting unit  150  is also connected to an upper portion of the display panel DP to apply the force so as to lift the display panel DP while maintaining the display panel DP in a flat and planar configuration. However, operation of the lifting unit  150  is dependent on whether the driving unit  140  fixes the roller  111  or rotates the roller  111 . That is, even though the force is applied from the lifting unit  150  to lift the display panel DP, the driving unit  140  rotates the roller  111  to wind and lower the display panel DP. Therefore, even though the force from the lifting unit  150  is applied to the display panel DP and the plurality of links  121 , the display device  100  according to the exemplary embodiment of the present disclosure may sufficiently rotate the roller  111  in both directions or may fix the roller  111  with the force of the driving unit  140  and control the display panel DP and the plurality of links  121 . Put another way, the fixing force applied by the driving unit  140  controls operation of the lifting unit  150 , as the fixing force holds the links in the unfolded or folded state, which results in the display panel DP remaining the unrolled or rolled configurations, respectively. When the display panel DP is manipulated to the unrolled configuration, the force exerted by the lifting unit  150  assists in raising the display panel DP. 
     The display device  100  according to the exemplary embodiment of the present disclosure includes the lifting unit  150  which is connected to the upper edge  105  of the display panel DP via the links  121  and which maintains the display panel DP in a flat and planar configuration when the display panel DP is in the unrolled configuration. Specifically, the elastic member  151  of the lifting unit  150  is connected to the other end of the lower link  121 D at each of the plurality of links  121  to apply force such that the lower link  121 D rotates with respect to the support shaft  124 . The other end of the lower link  121 D rotates with respect to the support shaft  124  via force applied by the elastic member  151  to lift the lower link  121 D, in which case, the upper link  121 U connected to the lower link  121 D is also lifted. Therefore, the head bar  130  connected to the plurality of links  121  is also lifted to lift the display panel DP whose upper edge  105  is fixed to the head bar  130 . In this case, while winding or unwinding the display panel DP which display panel is fixed to the roller  111 , at least a part including the lower edge of the display panel DP may be wound around the roller  111 . In a state in which a lower portion of the display panel DP is fixed to the roller  111  or wound around the roller  111  to be lowered, or unwound from the roller  111 , the upper edge of the display panel DP is lifted by the lifting unit  150  at all times. Therefore, at least a part of the display panel DP which is unwound from the roller  111  is lifted by the lifting unit  150  and maintained in a flat and planar state. 
     A degree of flatness of the display panel DP may be selected by adjusting the lifting unit  150  and the degree of flatness of the display panel DP may be selected by adjusting the force of the lifting unit  150 . For example, when the elastic member  151  of the lifting unit  150  is a spring, the degree of flatness of the display panel DP may be adjusted only by selecting a constant or other characteristics of the spring. Therefore, the lifting unit  150  of the display device  100  according to the exemplary embodiment of the present disclosure applies force so as to continuously lift at least a part of the display panel DP which is unwound from the roller  111  to maintain the flat state of the display panel DP. Moreover, embodiments of the present disclose enable selectively adjusting the force of the lifting unit  150  to adjust the degree of flatness of the display panel DP by selecting a different elastic element  151 . 
     The display device  100  according to the present disclosure simplifies a configuration for winding or unwinding the display panel DP to reduce the volume of the display device  100 . Specifically, the display device  100  includes the roller  111  and the plurality of links  121 , which assist with winding and unwinding (or rolling and unrolling) of the display panel DP and which support the display panel DP in a flat and planar state. The roller  111  and the plurality of links  121  are members to which force is applied in order to be operated. In this case, force is applied to the roller  111  from the driving unit  140  to rotate the roller  111  and wind or unwind the display panel DP. Further, force is applied to the plurality of links  121  from the lifting unit  150  to lift the plurality of links  121  and support the display panel DP in the flat and planar state when the display panel DP is in any configuration, rolled or unrolled. In this case, the driving unit  140  is directly connected to the roller  111  so that the force of the driving unit  140  is directly applied to the roller  111  without using an intermediate medium which transmits the force from the driving unit  140 . The lifting unit  150  is directly connected to the plurality of links  121  so that the force of the lifting unit  150  is directly applied to the plurality of links  121  without using an intermediate medium which transmits the force from the lifting unit  150 . Therefore, the driving unit  140  directly applies the force to the roller  111  and the lifting unit  150  directly applies the force to the plurality of links  121  so that the intermediate medium which transmits the force may be omitted. Therefore, the display device  100  according to the present disclosure simplifies the configuration of the display device  100 , which reduces the number of parts or components, which reduces cost and also reduces the volume occupied by the display device  100 . 
     The display device  100  according to the embodiments of the present disclosure disposes the driving unit  140  and the lifting unit  150  at the outside of the roller  111  to increase the degree of freedom of design of the driving unit  140  and the lifting unit  150 . In the related art, the elastic member is disposed in the roller so that the size of the elastic member is restricted and it is not easy to repair or replace the elastic member. In contrast, in the display device  100  according to the embodiments of the present disclosure, the driving unit  140  is connected to the roller  111  at the outside of the roller  111  and the lifting unit  150  is connected to the plurality of links  121  at the outside of the roller  111 . Therefore, the size of the roller  111  is not limited and the driving unit  140  may be easily replaced with another driving unit  140  without dissembling the roller  111  or changing its position. The lifting unit  150  is not limited by the size of the roller  111  and the lifting unit  150  may be easily replaced with another lifting unit  150  without dissembling the roller  111  and the plurality of links  121  or move their position. Therefore, in the display device  100  according to the embodiments of the present disclosure, the driving unit  140  and the lifting unit  150  are disposed at the outside of the roller  111  such that the driving unit and the lifting unit can be easily repaired, rearranged, or replaced. Further, because of the reduction in complexity and number of components, design changes to the display device  100  are easier to implement. More specifically, changing the design of the display device  100 , such as a size or a curvature of the housing unit HP, the display device  100  may still be implemented with minimum modification, thereby increasing the degree of freedom of design. 
       FIG. 9  is an enlarged perspective view for explaining a driving assembly, a roller, an elastic member, and a link of a display device according to alternative embodiment of the present disclosure. The configuration of the display device  900  of  FIG. 9  is the same as that of the display device  100  of  FIGS. 1 to 8B  except for the differences described below, such as the arrangement of a motor  941  of a driving assembly  940  (which may be referred to hereinafter as a driving unit  940 ). As such, redundant description has been omitted. 
     Referring to  FIG. 9 , the driving unit  940  is disposed at the outside of the roller  111  and connected to the roller  111 . Specifically, in one embodiment, the driving unit  940  is positioned adjacent to any one of both ends of the roller  111  and connected to the roller  111 . 
     A motor  941  of the driving unit  940  is not vertically erected from the bottom surface HPF of the housing unit HP, but is positioned on the bottom surface HPF of the housing unit HP. For example, the motor  941  rotates toward the bottom surface HPF of the housing unit HP with respect to the worm gear  142  so that the side of the motor  941  is opposite to the bottom surface HPF of the housing unit HP. Since the motor  941  is positioned on the bottom surface HPF, a height of the motor  941  from the bottom surface HPF of the housing unit HP is reduced. 
     In the display device  900 , the arrangement of the driving unit  940  is modified to lower a height of the housing unit HP and to reduce a volume of the housing unit HP. Specifically, the display device  900  according to one embodiment of the present disclosure does not arrange the motor  941  of the driving unit  940  erected, but rather, the motor  941  is laid on the bottom surface HPF of the housing unit HP. Therefore, the height of the motor  941  from the bottom surface HPF of the housing unit HP is lowered. Therefore, the height of the housing unit HP which is designed in consideration of the height of the motor  941  is also reduced and thus the volume of the housing unit HP is also reduced. Therefore, the display device  900  according to one embodiment of the present disclosure includes a design of the driving unit  940  to reduce the volume of the display device  900 . 
     Further, the display device  900  according to the present disclosure includes various designs, arrangements, and orientations of the driving unit  940 . In one embodiment, the driving unit  940  is disposed at the outside of the roller  111  and connected to the roller  111 . Therefore, in order to change the design of the driving unit  940 , the driving unit  940  may be modified without changing the size of the roller  111  or the arrangement of the roller  111 . For example, the driving unit  940  may be arranged erected or laid on the bottom surface HPF. Because the driving unit  940  is outside of the roller  111 , the driving unit  940  may be easily repaired and replaced regardless of the roller  111  and the remaining components of the display device  900 , which increases design freedom for the device  900 . In sum, the embodiments of the present disclosure can be described as follows: 
     According to one or more embodiments of the present disclosure, there is provided a display device. The display device includes a display panel, a roller to which a lower edge of the display panel is fixed, a plurality of links having one end connected to an upper edge of the display panel, a driving unit which is disposed at the outside of the roller to rotate the roller, and an elastic member which is connected to the other end of each of the plurality of links to be disposed at the outside of the roller. 
     The driving unit may be connected to at least one of both ends of the roller to rotate the roller in a clockwise direction or a counterclockwise direction. 
     Each of the plurality of links may be connected to the upper edge of the display panel through a head bar. 
     Each of the plurality of links may include a lower link having the other end coupled to the elastic member, and an upper link having one end rotatably coupled to the upper edge of the display panel and the other end rotatably coupled to one end of the lower link. 
     The lower link may be rotatably coupled to a support shaft, and the elastic member may rotate the other end of the lower link around the support shaft to lift the lower link. 
     One end of the elastic member may be rotatably coupled to the other end of the lower link, and a length of the elastic member in a fully wound state of the display panel may be longer than a length of the elastic member in a fully unwound state of the display panel. 
     The elastic member may have an elastic force which rotates the other end of the lower link to lift each of the plurality of links. 
     In a fully unwound state of the display panel, the plurality of links may be disposed to be vertical to the upper edge of the display panel, the other end of the lower link may be disposed to be closer to the lower edge of the display panel than the one end of the lower link, and the other end of the upper link may be disposed to be closer to the lower edge of the display panel than one end of the upper link. 
     In a fully wound state of the display panel, the plurality of links may be disposed to be horizontal to the upper edge of the display panel, the other end of the lower link may be disposed to be farther from a center area of the display panel than the one end of the lower link, and the other end of the upper link may be disposed to be closer to the center area of the display panel than one end of the upper link. 
     The length from the support shaft to the other end of the lower link may be shorter than the length from the support shaft to the one end of the lower link. 
     While winding the display panel, the driving unit may rotate the roller with a force smaller than a force of the elastic member which lifts the plurality of links. 
     While winding the display panel, the driving unit may rotate the one end of the lower link around the support shaft to lower the lower link. 
     According to another embodiment of the present disclosure, there is provided a rollable display device. The rollable display device includes a roller, a display panel fixed to the roller, a plurality of links which supports the display panel to be flat, a driving unit which rotates the roller and a lifting unit which applies a force to the plurality of links. The display panel is wound by the roller which rotates by the driving unit and is unwound by the roller which rotates by the driving unit and the plurality of links which is unfolded by the lifting unit. 
     Each of the plurality of links may include a lower link having the other end applied with a force from the lifting unit and an upper link whose the other end is rotatably coupled to one end of the lower link to transmit the force from the driving unit to one end of the lower link, and the lower link may rotate around a support shaft. A length from the support shaft to the one end of the lower link may be longer than a length from the support shaft to the other end of the lower link. 
     While winding the display panel, a force of the driving unit may be smaller than a force of the lifting unit and a torque applied to the one end of the lower link may be larger than a torque applied to the other end of the lower link. 
     While winding the display panel, the driving unit may apply the force so as to lower the display panel and the lifting unit may apply the force to lift the display panel, and while unwinding the display panel, the driving unit and the lifting unit may apply the force to lift the display panel. 
     Although the exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto and may be embodied in many different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only but not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above-described embodiments are illustrative and do not limit the present disclosure. The protective scope of the present disclosure should be construed based on the following claims, and all the technical concepts in the equivalent scope thereof should be construed as falling within the scope of the present disclosure. 
     The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. The embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments. 
     These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.