Patent Publication Number: US-11665837-B2

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/891,878, filed on Jun. 3, 2020, which claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2019-0070939, filed on Jun. 14, 2019, the contents of which are hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a display device. 
     Description of the Related Art 
     With the development of the information society, various demands for display devices are increasing. Various display devices, such as liquid crystal displays (LCDs), plasma display panels (PDPs), electroluminescent displays (ELDs), and vacuum fluorescent displays (VFDs), have been recently studied and used in response to the various demands for the display devices. 
     Among the various display devices, a display device using an organic light emitting diode (OLED) is advantageous in that it has better luminance characteristic and better viewing angle characteristic than a liquid crystal display, and has a ultra-thin profile because it does not require a backlight unit. 
     A flexible display can be bent or rolled on a roller. A display device rolled or unrolled from the roller using the flexible display can be implemented, if necessary or desired. 
     Recently, a structural study on the flexible display has been actively carried out. 
     SUMMARY OF THE INVENTION 
     An object of the present disclosure is to address the above-described and other problems. 
     Another object of the present disclosure is to reduce a noise that may occur when a display device is driven. 
     Another object of the present disclosure is to reduce a vibration that may occur when a display device is driven. 
     Another object of the present disclosure is to improve durability of a display device. To achieve the above-described and other objects, in one aspect of the present disclosure, there is provided a display device comprising a housing; a roller disposed inside the housing; a display unit configured to be rolled around the roller; a first arm and a second arm, wherein one end of the first arm is rotatably coupled to the display unit and another end of the first arm is rotatably coupled to the second arm; a lead screw disposed inside the housing; a slider configured to move along the lead screw according to a rotation of the lead screw; and a rod comprising one end rotatably coupled to the slider and another end rotatably coupled to the second arm such that the second arm is raised and lowered based on movement of the slider along the lead screw; wherein the rod and the second arm are rotatably coupled via at least a first connection member and a first intermediate member, wherein the first connection member is configured to pass through the second arm and the rod and the first intermediate member is configured to surround a portion of the first connection member which passes through the second arm. 
     According to another aspect of the present disclosure, wherein the rod and the slider are rotatably coupled via at least a second connection member and a second intermediate member, wherein the second connection member is configured to pass through the rod and a portion of the slider and the second intermediate member is configured to surround a portion of the second connection member which passes through the portion of the slider. 
     According to another aspect of the present disclosure, wherein the first connection member comprises a body configured to pass through an opening at the second arm and a first opening at the rod; and a head connected to the body and having a diameter greater than a diameter of the body, wherein the first intermediate member has a ring shape, wherein an inner circumferential surface of the first intermediate member contacts an outer circumferential surface of the body of the first connection member, and wherein an outer circumferential surface of the first intermediate member contacts an inner circumferential surface of the opening at the second arm. 
     According to another aspect of the present disclosure, wherein the first intermediate member comprises a first flange positioned between the second arm and the rod; and a first groove formed at the outer circumferential surface and positioned to face the inner circumferential surface of the opening at the second arm. 
     According to another aspect of the present disclosure, wherein the first groove is configured to accommodate a lubricant. 
     According to another aspect of the present disclosure, wherein the first flange is accommodated within the opening at the second arm. 
     According to another aspect of the present disclosure, the display device may further comprise a first fixing member configured to pass through an end of the body of the first connection member opposite the head. 
     According to another aspect of the present disclosure, wherein the portion of the slider is a rod mount extending from a body of the slider, wherein the second connection member comprises a second connection member body configured to pass through a second opening at the rod and an opening at the rod mount; and a second connection member head connected to the second connection member body and having a diameter greater than a diameter of the second connection member body, wherein the second intermediate member has a ring shape, wherein an inner circumferential surface of the second intermediate member contacts an outer circumferential surface of the second connection member body, and wherein an outer circumferential surface of the second intermediate member contacts an inner circumferential surface of the opening at the rod mount. 
     According to another aspect of the present disclosure, wherein the second intermediate member comprises a second flange positioned at an end of the second intermediate member away from the second connection member head and the rod; and a second groove formed at the outer circumferential surface of the second intermediate member and positioned to face the inner circumferential surface of the opening at the rod mount. 
     According to another aspect of the present disclosure, wherein the second groove is configured to accommodate a lubricant. 
     According to another aspect of the present disclosure, wherein the second flange is accommodated within the opening at the rod mount. 
     According to another aspect of the present disclosure, the display device may further comprise a second fixing member configured to pass through an end of the second connection member body opposite the second connection member head. 
     Effects of a display device according to the present disclosure are described as follows. 
     According to at least one aspect of the present disclosure, the present disclosure can reduce a noise that may occur when a display device is driven. 
     According to at least one aspect of the present disclosure, the present disclosure can reduce a vibration that may occur when a display device is driven. 
     According to at least one aspect of the present disclosure, the present disclosure can improve durability of a display device. 
     Further scope of applicability of the present disclosure will become apparent from the detailed description given blow. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, that may be included to provide a further understanding of the disclosure and are incorporated in and constitute a part of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain various principles of the disclosure. 
         FIGS.  1  to  17 K  illustrate configuration of a display device related to the present disclosure. 
         FIGS.  18  to  29    illustrate a display device according to an embodiment of the disclosure. 
         FIGS.  30  to  34    illustrate a display device according to another embodiment of the disclosure. 
         FIGS.  35  to  64    illustrate a display device according to another embodiment of the disclosure. 
         FIGS.  65  to  70    illustrate a display device according to another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to embodiments 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. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the disclosure, and the suffix itself is not intended to give any special meaning or function. It will be noted that a detailed description of known arts will be omitted if it is determined that the detailed description of the known arts can obscure the embodiments of the disclosure. The accompanying drawings are used to help easily understand various technical features, and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. 
     Hereinafter, embodiments of the disclosure are described using an organic light emitting diode (OLED) display panel as an example of a display panel. However, embodiments of the disclosure are not limited thereto. For example, a liquid crystal display (LCD) panel, a plasma display panel (PDP), and a field emission display (FED) panel may be used. 
       FIGS.  1  to  17 K  illustrate configuration of a display device related to the present disclosure. 
     As shown in  FIG.  1   , it is described below that a display panel  10  may include a first long side LS 1 , a second long side LS 2  opposite the first long side LS 1 , a first short side SS 1  adjacent to the first long side LS 1  and the second long side LS 2 , and a second short side SS 2  opposite the first short side SS 1 . 
     In embodiments disclosed herein, the first short side SS 1  may be referred to as a first side area; the second short side SS 2  may be referred to as a second side area opposite the first side area; the first long side LS 1  may be referred to as a third side area which is adjacent to the first side area and the second side area and is positioned between the first side area and the second side area; and the second long side LS 2  may be referred to as a fourth side area which is adjacent to the first side area and the second side area, is positioned between the first side area and the second side area, and is opposite to the third side area. 
     Embodiments of the disclosure illustrate and describe that lengths of the first and second long sides LS 1  and LS 2  are longer than lengths of the first and second short sides SS 1  and SS 2  for convenience of explanation. However, the lengths of the first and second long sides LS 1  and LS 2  may be almost equal to the lengths of the first and second short sides SS 1  and SS 2 . 
     It is described below that a first direction DR 1  may be a direction parallel to the long sides LS 1  and LS 2  of the display panel  10 , and a second direction DR 2  may be a direction parallel to the short sides SS 1  and SS 2  of the display panel  10 . 
     A third direction DR 3  may be a direction vertical to the first direction DR 1  and/or the second direction DR 2 . 
     In embodiments disclosed herein, the first direction DR 1  and the second direction DR 2  may be commonly referred to as a horizontal direction. Further, the third direction DR 3  may be referred to as a vertical direction. 
     In addition, a side or a surface, on which a display device  100  displays an image, may be referred to as a front side or a front surface. When the display device  100  displays the image, a side or a surface, at which the image cannot be observed, may be referred to as a rear side or a rear surface. When the display device  100  is observed at the front side or the front surface, the first long side LS 1  may be referred to as an upper side or an upper surface. In the same manner as the first long side LS 1 , the second long side LS 2  may be referred to as a lower side or a lower surface. Further, the first short side SS 1  may be referred to as a left side or a left surface, and the second short side SS 2  may be referred to as a right side or a right surface. 
     The first long side LS 1 , the second long side LS 2 , the first short side SS 1 , and the second short side SS 2  may be referred to as edges of the display device  100 . Positions where the first long side LS 1 , the second long side LS 2 , the first short side SS 1 , and the second short side SS 2  meet one another may be referred to as corners. For example, a position where the first long side LS 1  and the first short side SS 1  meet each other may be referred to as a first corner C 1 ; a position where the first long side LS 1  and the second short side SS 2  meet each other may be referred to as a second corner C 2 ; a position where the second short side SS 2  and the second long side LS 2  meet each other may be referred to as a third corner C 3 ; and a position where the second long side LS 2  and the first short side SS 1  meet each other may be referred to as a fourth corner C 4 . 
     In embodiments disclosed herein, a direction from the first short side SS 1  to the second short side SS 2  or a direction from the second short side SS 2  to the first short side SS 1  may be referred to as a left-right direction LR. A direction from the first long side LS 1  to the second long side LS 2  or from the second long side LS 2  to the first long side LS 1  may be referred to as an up-down direction UD. 
     +x-axis direction may be referred to as a right direction, and −x-axis direction may be referred to as a left direction. +y-axis direction may be referred to as an upward direction, and −y-axis direction may be referred to as a downward direction. +z-axis direction may be referred to as a frontward direction, and −z-axis direction may be referred to as a rearward direction. 
     The x-axis direction may be a direction parallel to the first direction. The y-axis direction may be a direction parallel to the second direction. The z-axis direction may be a direction parallel to the third direction. 
     Referring to  FIG.  2   , the display device  100  according to the present disclosure may include a display unit  20  and a housing  30 . 
     The display unit  20  may include the display panel  10  and a module cover  15 . The display panel  10  may be provided on a front surface of the display device  100  and may display an image. The display panel  10  may divide an image into a plurality of pixels and output the image by controlling the light emission in accordance with color, brightness, and chroma of each pixel. The display panel  10  may be divided into an active area on which an image is displayed, and an inactive area in which no image is displayed. 
     If the display panel  10  has flexibility, the display panel  10  may be referred to as a flexible display panel  10 . 
     The display panel  10  may have a rectangular shape. However, embodiments of the disclosure are not limited thereto. For example, the display panel  10  may have a shape which has a predetermined curvature at an edge. The display panel  10  may be an OLED display panel. Other display panels may be used. For example, a liquid crystal display panel may be used. 
     The module cover  15  may be provided on a rear surface of the display panel  10 . The module cover  15  may be directly attached to the display panel  10 . A size of the module cover  15  may be equal to or greater than a size of the display panel  10 . 
     The module cover  15  may support the rear surface of the display panel  10 . Hence, the module cover  15  may include a lightweight material with high rigidity. For example, the module cover  15  may include aluminum or include stainless material. 
     The housing  30  may be provided on a rear surface of the display unit  20 . Namely, the housing  30  may be provided on a rear surface of the module cover  15 . The housing  30  may shield at least one printed circuit board (PCB). Namely, the housing  30  may cover at least one PCB attached to the rear surface of the module cover  15 . A coupling structure and a coupling method of at least one PCB are described in detail below. 
     The housing  30  may receive electromagnetic waves emitted from at least one PCB. Hence, although not shown, the housing  30  may include an inner housing made of a conductive material and an outer housing covering the inner housing. However, embodiments of the disclosure are not limited thereto. For example, the housing  30  may be formed as one body made of a conductive material. 
     Referring to  FIG.  3   , in the display device  100  according to the embodiment of the disclosure, the housing  30  may be positioned under the display unit  20 . More specifically, the housing  30  may have a shape surrounding a lower part of the display unit  20 . Namely, the housing  30  may be configured not to expose various driving devices or driving circuits positioned inside the housing  30  to the outside. 
     A width of the housing  30  in the first and third directions may be greater than a width of the display unit  20  in the first and third directions in order to protect the display unit  20  therein. A width of the housing  30  in the second direction may be less than a width of the display unit  20  in the second direction. 
     In the display device  100  according to the present disclosure, the housing  30  may not be positioned in the active area of the display unit  20 . 
     Referring to  FIG.  4   , the display device  100  according to the embodiment of the disclosure may be in a first state, in which the active area of the display unit  20  is positioned inside the housing  30 , or a second state in which the active area of the display unit  20  is exposed to the outside of the housing  30 . 
     When the display device  100  is in the first state, the active area of the display unit  20  may be positioned inside the housing  30 . Namely, the display unit  20  may be shielded by the housing  30  in the first state. 
     When the display device  100  is in the second state, the active area of the display unit  20  may be exposed to the outside of the housing  30 . Namely, at least a portion of the display unit  20  may protrude to an upper part of the housing  30  in the second state. 
     Although not shown, the display unit  20  may change from the first state to the second state by a roller positioned inside the housing  30 . More specifically, the display unit  20  may change from the first state, in which the display unit  20  is rolled on the roller, to the second state in which the display unit  20  is unrolled from the roller and is exposed to the outside. On the contrary, the display unit  20  may change from the second state to the first state when the display unit  20  is rolled on the roller. A structure and an operation method of the roller and the display unit  20  are described in detail below. 
     The display unit  20  of the display device  100  according to the present disclosure may be in the first state or the second state. Hence, only when the display device  100  is used, the display unit  20  can be exposed to the outside of the housing  30 , thereby saving the space. 
     Referring to  FIG.  5   , a panel roller  143  may be connected to one end of the display panel  10 . The panel roller  143  may roll or unroll the display panel  10  so that the display panel  10  is in the first state or the second state. The panel roller  143  may be referred to as a roller  143 . 
     In the display device according to the present disclosure, at least one source PCB  120  may be positioned on at least a portion of a front surface of the display panel  10 . For example, a plurality of source PCBs  120  may be positioned to be spaced apart from one another. 
     Signal lines may be positioned on at least one source PCB  120  and may transmit digital video data and timing control signals received from a timing controller board  105 . The source PCB  120  may be connected to the display panel  10  by a source chip-on film (COF)  123 . The source COF  123  connected to one side of the source PCB  120  may be extended to the active area of the display panel  10  and connected to the display panel  10 . 
     A seating portion  379  may be positioned on an outer circumference of the panel roller  143 . The seating portion  379  may form an accommodation space B as a portion of the outer circumference of the panel roller  143  is stepped. The seating portion  379  may be positioned at a contact portion between the source PCB  120  and the panel roller  143  while the panel roller  143  is rolled or unrolled. The seating portion  379  may have a shape in which at least a portion of the outer circumference of the panel roller  143  is recessed. 
     When the panel roller  143  is rolled, the source PCB  120  may be accommodated in the accommodation space B of the seating portion  379 . Hence, even if the panel roller  143  is rolled, the source PCB  120  cannot be damaged. 
     The timing controller board  105  may be mounted inside the panel roller  143 . A flexible flat cable (FFC)  117  may electrically connect the timing controller board  105  to the source PCB  120 . 
     The panel roller  143  may include an upper panel roller  331  and a lower panel roller  337 . The upper panel roller  331  and the lower panel roller  337  may be coupled to each other by a screw. The timing controller board  105  may be mounted between the upper panel roller  331  and the lower panel roller  337 . The screw may mutually couple the upper panel roller  331 , the lower panel roller  337 , and the timing controller board  105 . The FFC  117  may be connected to the timing controller board  105  and the source PCB  120  through a hole  331   a  positioned in the upper panel roller  331 . 
     Because the timing controller board  105  rotates together with the panel roller  143 , the FFC  117  may not be twisted. Further, the space can be saved because the timing controller board  105  is mounted inside the panel roller  143 . 
     Referring to  FIG.  6   , with respect to the center of the housing  30  in which the display panel moves up and down, the timing controller board  105  may be mounted on the panel roller  143  at one side of the housing  30 , and a power supply board  107  and a main board  109  may be positioned at other side of the housing  30 . 
     The timing controller board  105  may be connected to the power supply board  107  and the main board  109 . The timing controller board  105  may be connected to the power supply board  107  and the main board  109  through a wiring electrode. The wiring electrode may include a first wiring electrode  307  connecting the timing controller board  105  to the power supply board  107  and a second wiring electrode  309  connecting the timing controller board  105  to the main board  109 . 
     For example, a plurality of first wiring electrodes  307  may be disposed. The first wiring electrode  307  may be in a circular shape. The first wiring electrode  307  may connect the timing controller board  105  to the power supply  107  through an opening in the center of a rotation axis of the panel roller  143 . 
     The second wiring electrode  309  may use the FFC  117  connected to the timing controller board  105  and the source PCB  120 . The second wiring electrode  309  may connect the timing controller board  105  to the main board  109  through an opening in the center of the rotation axis of the panel roller  143 . 
     The first wiring electrode  307  and the second wiring electrode  309  may be positioned on the opposite sides of the timing controller board  105 . An opening through which the first wiring electrode  307  passes and an opening through which the second wiring electrode  309  passes may be positioned on the opposite sides. 
     In the display device according to the present disclosure, the timing controller board  105  may be mounted on the panel roller  143 , and the power supply board  107  and the main board  109  may be positioned on the opposite sides of the display panel. Hence, an inner space of the housing  30  can be saved. 
     Referring to  FIG.  7   , the display device according to the present disclosure may include the panel roller  143 , a motor assembly  137 , and a link  73  inside the housing  30 . 
     The link  73  may be referred to as a supporter  73 . 
     The module cover  15  may include a plurality of segments  15   a . The segment  15   a  may be referred to as an apron. 
     The panel roller  143  may be positioned in front of a portion of the housing  30  in which the display unit  20  moves up and down. The panel roller  143  may simultaneously roll and unroll the display panel  10  and the module cover  15 . 
     The link  73  may be installed in the housing  30 . The link  73  may perform a support function so that the display panel  10  and the module cover  15  can move up or down. The link  73  may move up or down an upper bar  75  (see  FIG.  9 A ) coupled to the upper parts of the module cover  15  and the display panel  10 . 
     An upper end of the display unit  20  may be connected to the upper bar, and a lower end of the display unit  20  may be connected to the panel roller  143 . A portion between the upper end and the lower end of the display unit  20  may easily bend. The link  73  may support the module cover  15  at the rear surface of the module cover  15  so that the module cover  15  does not bend. 
     A motor assembly  137  may be positioned in a portion to which the link  73  is connected. The motor assembly  137  may be driven so that the link  73  moves up or down. The motor assembly  137  may receive an electrical signal and convert the electrical signal into a physical force. The motor assembly  137  may transfer rotation energy to the link  73  and changes form the first state to the second state. A structure and a driving principle of the motor assembly  137  are described in detail below. 
     A guide bar  234  may be positioned at an entrance  30   a  at which the link  73  moves up and down inside the housing  30 . The guide bar  234  may include first and second guide bars  234   a  and  234   b . The entrance  30   a  of the housing  30  may be formed between the first and second guide bars  234   a  and  234   b . The first and second guide bars  234   a  and  234   b  may face each other with the link  73  interposed therebetween. For example, the first guide bar  234   a  may be positioned behind the link  73 , and the second guide bar  234   b  may be positioned in front of the link  73 . 
     The display device according to the present disclosure can simultaneously roll and unroll the display panel  10  and the module cover  15  using one roller. Hence, a thickness of the housing  30  can decrease. 
     Referring to  FIG.  8   , the segments  15   a  may have a rectangular shape. The respective segments  15   a  may be spaced apart from each other in the y-axis direction and attached to the rear surface of the display panel  10 . The module cover  15  may consist of the plurality of segments  15   a  and may be rolled or unrolled by the roller. The module cover  15  may include a plastic material or an aluminum material. Hence, the module cover  15  can protect the display panel  10  from an external impact. 
     The display panel  10  and the module cover  15  may be coupled to each other through adhesive layers  70 . The adhesive layer  70  may be a double-sided tape. The display panel  10  and the module cover  15  may be rolled or unrolled together by the adhesive layers  70 . The adhesive layer  70  may be positioned on each segment  15   a  and attached to the display panel  10 . The adhesive layers  70  may be spaced apart from one another. Hence, the shape of the adhesive layers  70  may easily change when the module cover  15  is rolled or unrolled by the roller. As a width of the adhesive layer  70  in the second direction decreases, the display panel  10  can be naturally rolled or unrolled from the panel roller  143  (see  FIG.  7   ) without being wrinkled. 
     As a width of the segment  15   a  in the second direction increases, the segments  15   a  can stably support the display panel  10  because rigidity of the segment  15   a  is improved. 
     When the width of the adhesive layer  70  in the second direction is equal to or less than 30% of the width of the segment  15   a  in the second direction, wrinkle in the display screen can decrease because less external force is transferred to the display panel  10 . 
     Further, when the width of the adhesive layer  70  in the second direction is equal to or greater than 15% of the width of the segment  15   a  in the second direction, wrinkle in the display panel  10  can greatly decrease because the rigidity of the display panel  10  is improved. 
     As a width of the adhesive layer  70  in the third direction increases, the deformation of the display panel  10  against an external force can decrease. More specifically, as the width of the adhesive layer  70  in the third direction increases, the adhesive layer  70  can stably attach the display panel  10  and the module cover  15  because the flexibility of the adhesive layer  70  is good. 
     Further, as a width of the segment  15   a  in the third direction decreases, wrinkle of the display panel  10  can decrease. More specifically, as the width of the segment  15   a  in the third direction decreases, the segments  15   a  can decrease the wrinkle of the display panel  10  because the rigidity is improved. 
     Hence, when the width of the adhesive layer  70  in the third direction is equal to or greater than 3% of the width of the segment  15   a  in the third direction, the rigidity of the display panel  10  can be improved and the wrinkle of the display panel  10  can greatly decrease. 
     Further, when the width of the adhesive layer  70  in the third direction is equal to or less than 6% of the width of the segment  15   a  in the third direction, the rigidity of the display panel  10  can be improved and the wrinkle of the display panel  10  can greatly decrease. 
     In the display device according to the present disclosure, the module cover  15  may include the plurality of segments  15   a , and the adhesive layer  70  may be positioned on each segment  15   a.    
     Referring to  FIGS.  9 A and  9 B , the module cover  15  and the display panel  10  may be fastened to an upper bar  75 . The module cover  15 , the display panel  10 , and the upper bar  75  may be fastened to each other by screws  115   a  and  115   b.    
     The screws  115   a  and  115   b  may allow the module cover  15 , the display panel  10 , and the upper bar  75  to move up and down together. The screw  115   a  may fasten the upper bar  75  to the module cover  15 . Alternatively, the screw  115   b  may fasten the upper bar  75  to the display panel  10 . However, embodiments of the disclosure are not limited thereto. For example, at least one screw ( 115   a ,  115   b ) may fasten the module cover  15 , the display panel  10 , and the upper bar  75  together. 
     An upper part of the module cover  15  may have a shape suitable for being coupled to the upper bar  75 . An upper segment  15   t  may be a segment positioned at the top of the module cover  15 . The upper segment  15   t  may have a different shape from other segment  15   a . The upper segment  15   t  may be referred to as an upper module cover  15   t.    
     The upper segment  15   t  may include a first body  15   ta  connected to the other segment  15   a  and a second body  15   tb  coupled to the upper bar  75 . A lower end of the first body  15   ta  may be connected to the other segment  15   a , and the second body  15   tb  may be formed on the first body  15   ta.    
     The upper bar  75  may include a groove  75   a  formed in the +y-axis direction. The second body  15   tb  may be inserted into the groove  75   a . The screw  115   a  may pass through the second body  15   tb  in the z-axis direction. 
     A z-axis direction thickness of the first body  15   ta  may be greater than a z-axis direction thickness of the second body  15   tb.    
     Referring to  FIG.  9 B , a top case  167  may cover the upper bar  75 , the module cover  15 , and the display panel  10 . The upper bar  75 , the module cover  15 , and the display panel  10  may not be exposed to the outside by the top case  167 . Hence, an appearance of the display device can be neat. 
     The top case  167  may be fastened to the upper bar  75 , the module cover  15 , or the display panel  10  by the screw. 
     Referring to  FIG.  10 A , the display device according to the present disclosure may be in a shape in which both sides of the upper bar  75  are supported by the link  73 . The upper bar  75  may be moved up and down by the link  73 . The link  73  may include a first arm  73   a  and a second arm  73   b.    
     The first arm  73   a  may be referred to as an upper link  73   a . The second arm  73   b  may be referred to as a lower link  73   b.    
     The first arm  73   a  and the second arm  73   b  may be connected by an arm joint  152 . The arm joint  152  may be referred to as a hinge  152  or a joint  152 . 
     An upper end of the first arm  73   a  may be fastened to the upper bar  75 , and a lower end of the first arm  73   a  may be fastened to the arm joint  152 . An upper end of the second arm  73   b  may be fastened to the motor assembly, and a lower end of the second arm  73   b  may be fastened to the arm joint  152 . 
     The guide bar  234  may be positioned at the entrance  30   a  at which the link  73  moves up and down inside the housing  30 . The guide bar  234  may include the first and second guide bars  234   a  and  234   b . The entrance  30   a  of the housing  30  may be formed between the first and second guide bars  234   a  and  234   b . The first and second guide bars  234   a  and  234   b  may face each other with the link  73  interposed therebetween. For example, the first guide bar  234   a  may be positioned behind the link  73 , and the second guide bar  234   b  may be positioned in front of the link  73 . 
     The panel roller  143  may be positioned in front of the link  73 . A base  31  of the housing  30  may include a plurality of brackets  221 . The base  31  may be referred to as a bottom surface  31 . 
     The plurality of brackets  221  may be formed under the panel roller  143 . The plurality of brackets  221  may be spaced along a longitudinal direction of the panel roller  143 . Alternatively, the plurality of brackets  221  may be spaced along a longitudinal direction of the base  31 . Each bracket  221  may be fixed to the base  31  through a screw. 
     Referring to  FIG.  10 B , the display device according to the present disclosure may be in a gear shape in which other side of the first arm  73   a  and one side of the second arm  73   b  that are positioned inside the arm joint  152  are engaged with each other. The arm joint  152  may be referred to as a connection portion  152 . The first arm  73   a  may be referred to as an upper support link  73   a . The second arm  73   b  may be referred to as a lower support link  73   b.    
     The first arm  73   a  may be rotatably connected to an upper part of the arm joint  152 . The second arm  73   b  may be rotatably connected to a lower part of the arm joint  152 . 
     A lower part of the first arm  73   a  may be provided with a gear st 1 . An upper part of the second arm  73   b  may be provided with a gear st 2 . The gear st 1  of the first arm  73   a  and the gear st 2  of the second arm  73   b  may be engaged with each other. 
     An angle HRA 1  of the first arm  73   a  from the ground and an angle HRA 2  of the second arm  73   b  from the ground may be equal to each other because the first arm  73   a  and the second arm  73   b  are engaged with each other to form a gear shape. Further, an angle between the first arm  73   a  and the second arm  73   b  may be the same on both sides because the first arm  73   a  and the second arm  73   b  are engaged with each other to form the gear shape. Hence, both sides of the upper bar  75  can move up or down while not being inclined and maintaining level. That is, the angle between the first arm  73   a  and the second arm  73   b  of each link  73  can be equal regardless of a height of the upper bar  75  from the ground. 
     Referring to  FIG.  11   , the display device according to the present disclosure may further include a module cover roller  141  as well as the panel roller  143  inside the housing  30 . The module cover roller  141  may be referred to as an apron roller  141 . 
     The panel roller  143  may be positioned in front of the link  73 , and the module cover roller  141  may be positioned behind the link  73 . That is, the panel roller  143  and the module cover roller  141  may face each other based on the link  73 . 
     The panel roller  143  may roll and unroll the display panel  10 , and the module cover roller  141  may roll and unroll the module cover  15 . 
     The module cover  15  may be thicker than the display panel  10 . The module cover roller  141  on which the module cover  15  is rolled may occupy a larger space inside the housing  30  than the panel roller  143  on which the display panel  10  is rolled. Thus, the motor assembly  137  may be positioned in front of the link  73  relatively having a margin of space. However, embodiments of the disclosure are not limited thereto. For example, the motor assembly  137  may be positioned behind the link  73 . 
     Because the display panel  10  and the module cover  15  are dividedly rolled and unrolled inside the housing  30 , a rolling force required for the panel roller  143  to roll the display panel  10  may be greater than an adhesive force between the display panel  10  and the module cover  15 . Further, a rolling force required for the module cover roller  141  to roll the module cover  15  may be greater than the adhesive force between the display panel  10  and the module cover  15 . 
     The present disclosure can roll and unroll the display panel  10  and the module cover  15  using two rollers, respectively. Hence, less weight can be loaded on each of two rollers respectively rolling the display panel  10  and the module cover  15  than one roller rolling both the display panel  10  and the module cover  15 . As a result, the display panel  10  rolled on the panel roller  143  can be prevented from sagging, and the module cover  15  rolled on the module cover roller  141  can be prevented from sagging. 
     Referring to  FIG.  12   , the panel roller  143  and the module cover roller  141  may be positioned on the same side with respect to the link  73 . For example, the panel roller  143  and the module cover roller  141  may be positioned behind the link  73 . However, embodiments of the disclosure are not limited thereto. For example, the panel roller  143  and the module cover roller  141  may be positioned in front of the link  73 . 
     The module cover roller  141  may be positioned under the panel roller  143 . The module cover roller  141  on which the module cover  15  is rolled and the panel roller  143  on which the display panel  10  is rolled may interfere with each other. Thus, as the module cover roller  141  and the panel roller  143  are spaced apart from each other by a first distance PGD, interference between them can be prevented. 
     The first distance PGD may be a distance capable of preventing interference between the display panel  10  rolled on the panel roller  143  and the module cover  15  rolled on the module cover roller  141 . 
     A guide roller  145  may be positioned under the panel roller  143 . The guide roller  145  may guide a location of the module cover  15  so that the module cover  15  does not interfere with the panel roller  143 . 
     Referring to  FIG.  13   , a pressure roller  147  may be positioned under the panel roller  143 . The pressure roller  147  may press the module cover  15  so that the module cover  15  contacts the link  73 . Hence, the module cover  15  can be prevented from sagging or bending. The pressure roller  147  may be positioned adjacent to the link  73 . The pressure roller  147  may guide the module cover  15  so that the module cover  15  and the display panel  10  do not interfere with each other. 
     Referring to  FIG.  14   , a guide roller  145  and a pressure roller  147  may be positioned under the panel roller  143 . The guide roller  145  may guide a location of the module cover  15  so that the module cover  15  does not interfere with the panel roller  143 . The pressure roller  147  may press the module cover  15  so that the module cover  15  contacts the link  73 . 
     Hence, malfunction of the display device due to the sagging or bending of the module cover  15  can be prevented. Further, malfunction of the display device due to interference between the module cover  15  and the display panel  10  can be prevented. 
     Referring to  FIG.  15   , in the display device according to the present disclosure, segments  15   c  on both sides of the module cover  15  may be attached to the display panel  10 . The segment  15   c  may be referred to as a third module cover  15   c.    
     A magnet  64  may be attached to a front surface of the segment  15   c . The magnet  64  may be attached to the segment  15   c  through a double-sided tape. Each segment  15   c  may be provided with the magnet  64 . 
     The display panel  10  may include a metal material. Thus, the display panel  10  and the magnet  64  may be attached to each other by a magnetic force. Further, the display panel  10  and the segment  15   c  may be attached to each other by the magnet  64 . 
     The rear surface of the display panel  10  may include Fe—Ni Invar alloy. Thus, the display panel  10  can be strongly attached to the magnet  64 . 
     Because the display panel  10  and the module cover  15  are attached by the magnets  64  positioned only on both sides of the module cover  15 , a large number of magnets  64  are not needed. As a result, the manufacturing cost of the display device can be reduced. 
     Referring to  FIG.  16   , in the display device according to the present disclosure, the magnet  64  may be positioned in a groove  118  of the segment  15   c.    
     The groove  118  may be positioned on a surface of the segment  15   c  facing the display panel  10 . The groove  118  may be positioned on a front surface of each segment  15   c . Because the magnet  64  is accommodated in the groove  118 , the magnet  64  may not protrude to the outside of the segment  15   c . Thus, even if the display panel  10  contacts the segment  15   c , the display panel  10  does not wrinkle and can be flat. 
     As the magnet  64  is accommodated in the groove  118 , a thickness of the segment  15   c  can be reduced. Hence, a thickness of the display device can be reduced. 
     Referring to  FIGS.  17 A to  17 C , as the display device according to the present disclosure changes from the first state to the second state, the upper bar  75  may move up. The upper bar  75  may move up and down by the links  73  connected to both sides of the upper bar  75 . 
     As shown in  FIG.  17 A , when the display device is in the first state, an angle HRA between the first arm  73   a  and the second arm  73   b  may be very small. Hence, the upper bar  75  may not move up. Further, the display panel  10  and the module cover  15  may be rolled on the panel roller  143 . 
     As shown in  FIG.  17 B , the angle HRA between the first arm  73   a  and the second arm  73   b  may increase while the motor assembly  137  rotates. While the angle HRA between the first arm  73   a  and the second arm  73   b  increases, the upper bar  75  may move up. Hence, the display panel  10  and the module cover  15  that have been rolled on the panel roller  143  may be gradually unrolled. 
     As shown in  FIG.  17 C , when the display device is in the second state, the first arm  73   a  and the second arm  73   b  may be positioned on a straight line. Namely, the angle HRA between the first arm  73   a  and the second arm  73   b  may be 180 degrees. Thus, the upper bar  75  may move up to a maximum height. Further, the display panel  10  and the module cover  15  may be unrolled from the panel roller  143 . 
     Referring to  FIG.  17 D , in the display device according to the present disclosure, a plurality of first arms  73   a  and a plurality of second arms  73   b  may be used. 
     More specifically, the first arm  73   a  may include a first upper arm  73 Ca and a second upper arm  73 Fa. Further, the second arm  73   b  may include a first lower arm  73 Cb and a second lower arm  73 Fb. 
     The first upper arm  73 Ca may be referred to as a first upper link  73 Ca, and the second upper arm  73 Fa may be referred to as a second upper link  73 Fa. The first lower arm  73 Cb may be referred to as a first lower link  73 Cb, and a second lower arm  73 Fb may be referred to as a second lower link  73 Fb. 
     The first arm  73   a  may be rotatably connected to the upper part of the arm joint  152 . The second arm  73   b  may be rotatably connected to the lower part of the arm joint  152 . 
     More specifically, the second upper arm  73 Fa may be connected to an upper side above the first upper arm  73 Ca. The second lower arm  73 Fb may be connected to a lower side below the first lower arm  73 Cb. 
     A lower part of the first upper arm  73 Ca may be provided with a gear st 3 . An upper part of the first lower arm  73 Cb may be provided with a gear st 4 . The gear st 3  of the first upper arm  73 Ca and the gear st 4  of the first lower arm  73 Cb may be engaged with each other. 
     An angle HRA 1  of the first upper arm  73 Ca from the ground and an angle HRA 2  of first lower arm  73 Cb from the ground may be equal to each other because the first upper arm  73 Ca and the first lower arm  73 Cb are engaged with each other. Further, an angle between the first upper arm  73 Ca and the first lower arm  73 Cb may be the same on both sides because the first upper arm  73 Ca and the first lower arm  73 Cb are engaged with each other. Hence, the upper bar  75  can move up or down while not being inclined and maintaining level. That is, the angle between the first upper arm  73 Ca and the first lower arm  73 Cb can be the same on both sides regardless of the height of the upper bar  75  from the ground. 
     The second upper arm  73 Fa and the second lower arm  73 Fb may not be provided with a gear. An angle between the second upper arm  73 Fa and the second lower arm  73 Fb may be equal to the angle between the first upper arm  73 Ca and the first lower arm  73 Cb. 
     As shown in  FIG.  17 E , in a related art display device, upper and lower arms  73   a  and  73   b  may be formed as one arm. Hence, when an external force F is applied to one side, an angle HLA between the upper and lower arms  73   a  and  73   b  may be different on both sides. In this case, the display panel may be inclined to one side. 
     Unlike  FIG.  17 E , as shown in  FIG.  17 F , when the gear st 3  of the first upper arm  73 Ca and the gear st 4  of the first lower arm  73 Cb are engaged with each other, an angle HLA between the upper and lower arms  73   a  and  73   b  may not change even if an external force F is applied to one side of the display device. Hence, a damage of the display panel due to the inclination can be prevented. 
     Referring to  FIG.  17 G , one side of each of the first upper and lower arms  73 Ca and  73 Cb may be extended in a direction toward the second upper and lower arms  73 Fa and  73 Fb. That is, a width of each of the first upper and lower arms  73 Ca and  73 Cb may further increase. Hence, the first upper and lower arms  73 Ca and  73 Cb can shield the second upper and lower arms  73 Fa and  73 Fb at the front when viewing the link  73  from the front of the display device. Alternatively, the first upper arm  73 Ca and the second upper arm  73 Fa may overlap each other. Alternatively, the first lower arm  73 Cb and the second lower arm  73 Fb may overlap each other. 
     A rotation axis of the first upper arm  73 Ca, a rotation axis of the second upper arm  73 Fa, a rotation axis of the first lower arm  73 Cb, and a rotation axis of the second lower arm  73 Fb may be spaced apart from each other. 
     A vertical height of a portion of the arm joint  152  connected to the first upper and lower arms  73 Ca and  73 Cb may be different from a vertical height of a portion of the arm joint  152  connected to the second upper and lower arms  73 Fa and  73 Fb. 
     Although not shown, one side of each of the second upper and lower arms  73 Fa and  73 Fb may also be extended in a direction toward the first upper and lower arms  73 Ca and  73 Cb. That is, a width of each of the second upper and lower arms  73 Fa and  73 Fb may further increase when viewed from the rear surface. Hence, the second upper and lower arms  73 Fa and  73 Fb can shield the first upper and lower arms  73 Ca and  73 Cb at the front. 
     As shown in  FIG.  17 H , in the first state, a width of at least a portion of the first upper and lower arms  73 Ca and  73 Cb may overlap the second upper and lower arms  73 Fa and  73 Fb. For example, the first upper and lower arms  73 Ca and  73 Cb may be spaced apart from the second upper and lower arms  73 Fa and  73 Fb by a predetermined distance SLB and may overlap the second upper and lower arms  73 Fa and  73 Fb. Hence, an entire width HLW of the first arm  73   a  may be greater than a width of the second upper arm  73 Fa or a width CLW of the first upper arm  73 Ca. 
     Unlike  FIG.  17 H , as shown in  FIG.  17 I , in the second state, an entire width of the first upper and lower arms  73 Ca and  73 Cb may overlap the second upper and lower arms  73 Fa and  73 Fb. Hence, an entire width HLW of the first arm  73   a  may be equal to a width of the second upper arm  73 Fa or a width CLW of the first upper arm  73 Ca. 
     As shown in  FIG.  17 J , when one side of the first upper arm  73 Ca is not extended, there may occur a predetermined gap (or distance) LD between the first upper arm  73 Ca and the second upper arm  73 Fa with the change from the second state to the first state. As the change to the first state proceeds, the distance LD between the first upper arm  73 Ca and the second upper arm  73 Fa may further increase. 
     In this case, there is a problem that the user&#39;s hand may be caught between the first upper arm  73 Ca and the second upper arm  73 Fa during the change from the first state to the second state. 
     Unlike  FIG.  17 J , as shown in  FIG.  17 K , when one side of the first upper arm  73 Ca is extended and overlaps the second upper arm  73 Fa, the gap between the first upper arm  73 Ca and the second upper arm  73 Fa may not be still exposed even during the change from the second state to the first state. Hence, the present disclosure can prevent the user&#39;s hand from being caught between the first upper arm  73 Ca and the second upper arm  73 Fa during the change from the first state to the second state. 
     Referring to  FIG.  18   , a plurality of magnets  64  may be positioned on the link  73 . For example, at least one magnet  64  may be positioned on the first arm  73   a , and at least one magnet  64  may be positioned on the second arm  73   b . The plurality of magnets  64  may be spaced apart from each other. 
     The display unit may include a metal material. The display unit may be in close contact with the link  73  by the magnet  64 . Even if a magnetic force of one of the plurality of magnets  64  weakens, it can be maintained that the display panel and the module cover are in close contact with the link  73  by a magnetic force of the remaining magnets  64 . 
     Referring to  FIG.  19   , one magnet  64  may be positioned on each of the first arm  73   a  and the second arm  73   b . In this case, the magnet  64  may have a shape extending in a long side direction of the first arm  73   a  and the second arm  73   b.    
     Because the magnet  64  has the shape extending in the long side direction of the first arm  73   a  and the second arm  73   b , an area of a portion where the link  73  is in close contact with the display panel and the module cover can be increased. Hence, an adhesive strength between the link  73  and the display panel and the module cover can increase. 
     Referring to  FIG.  20   , the magnet  64  may be positioned in a recess  321  formed on the link  73 . The recess  321  may have a shape recessed to the inside of the link  73 . The magnet  64  may be coupled to the link  73  through at least one screw  187 . 
     A width LHW of the recess  321  recessed to the inside of the link  73  may be equal to or greater than a thickness MGW of the magnet  64 . If the thickness MGW of the magnet  64  is greater than the width LHW of the recess  321 , the display panel  10  and the module cover  15  may not be in close contact with the link  73 . In this case, the display panel  10  may be wrinkled or may not be flat. 
     A panel protection portion  97  may be disposed on the rear surface of the display panel  10 . The panel protection portion  97  can prevent an impact that the display panel  10  receives due to a friction with the module cover  15 . The panel protection portion  97  may include a metal material. The panel protection portion  97  may have a very thin thickness. For example, the panel protection portion  97  may be about 0.1 mm thick. 
     Because the panel protection portion  97  includes a metal material, a mutual attraction may act between the panel protection portion  97  and the magnet  64 . Even if the module cover  15  between the panel protection portion  97  and the link  73  does not include a metal material, the module cover  15  may be in close contact with the magnet  64 . 
     Referring to  FIG.  21   , when a magnet is not provided on the link  73 , the module cover  15  may be in close contact with the link  73  by the upper bar  75  on the upper side and the guide bar  234  (see  FIG.  10   ) on the lower side. A portion of the link  73  between the upper bar  75  and the guide bar  234  may not be in close contact with the module cover  15 . Alternatively, a central portion of the link  73  may not be in close contact with the module cover  15 . The central portion of the link  73  may be around the arm joint  152 . In this case, distances APRD 1  and APLD 2  between the module cover  15  and the link  73  may not be constant. In this case, the display panel  10  may bend. 
     Referring to  FIG.  22   , when the magnet  64  is positioned on the recess  321  of the link  73 , the magnet  64  may be in close contact with both the module cover  15  and the panel protection portion  97  at the same time because the magnet  64  pulls the panel protection portion  97 . That is, the central portion of the link  73  may be in close contact with the module cover  15 . 
     Referring to  FIGS.  23 A and  23 B , both ends of the module cover  15  may bend in the +z-axis direction. The display panel  10  may be attached to a non-bent portion of the module cover  15 . A bent length in the +z-axis direction on both ends of the module cover  15  may be greater than a sum of thicknesses of the display panel  10  and the adhesive layer  70 . That is, a bent portion of the module cover  15  may protrude from the display panel  10  by a predetermined distance AD 1  in the +z-axis direction. Hence, the display panel  10  can be shielded when viewing the module cover  15  in the x-axis direction. 
     Referring to  FIG.  23 A , the adhesive layer  70  may be disposed between the display panel  10  and the module cover  15 . The adhesive layer  70  may be disposed to elongate along the x-axis direction. The whole of the display panel  10  may be attached to the module cover  15 . In this case, because an adhesive strength between the module cover  15  and the display panel  10  may be very strong, the module cover  15  and the display panel  10  may not be easily detached from each other. 
     Referring to  FIG.  23 B , the adhesive layer  70  may be disposed between the display panel  10  and the module cover  15 . The adhesive layer  70  may be partially disposed between the display panel  10  and the module cover  15 . For example, the adhesive layers  70  may be respectively disposed at one end and other end of the display panel  10 . In this case, a smaller amount of the adhesive layer  70  may be used than when the adhesive layer  70  is disposed to elongate along the x-axis direction. Thus, the manufacturing cost of the display device can be reduced. 
     The present disclosure is not limited to the case where the adhesive layer  70  is used to attach the display panel  10  and the module cover  15 . For example, the magnet may be used to attach the display panel  10  and the module cover  15 . 
     Referring to  FIG.  24   , a bead  136  may be formed on an upper surface of a segment  15   b . The bead  136  may have a shape recessed to the inside of the segment  15   b . The bead  136  may have a shape recessed in the −y-axis direction. A plurality of beads  136  may be formed on the segment  15   b . The plurality of beads  136  may be spaced apart from each other. The beads  136  can improve rigidity of the segment  15   b . For example, the bead  136  can prevent the shape of the segment  15   b  from being deformed by an external impact. 
     Referring to  FIG.  25   , the source PCB  120  may be positioned on the upper side of the module cover  15 . When the first state changes to the second state, a location of the source PCB  120  may change depending on the movement of the module cover  15 . 
     The FFC  231  may be positioned in the center of the module cover  15  with respect to the first direction. However, embodiments of the invention are not limited thereto. For example, the FFC  231  may be positioned at both ends of the module cover  15  with respect to the first direction. 
     Referring to  FIG.  26   , a segment  15   d  may include a recess  425  that is recessed in the −z-axis direction. The recess  425  may form a space between the display panel  10  and the module cover  15 . The FFC  231  may be accommodated in the space formed by the recess  425 . The recess  425  can improve the rigidity of the segment  15   d.    
     The bead  136  may be positioned on the segment  15   d  except a formation portion of the recess  425 . The bead  136  may not be positioned in the formation portion of the recess  425  because a thickness of the segment  15   d  in the third direction decreases. However, embodiments of the invention are not limited thereto. For example, the bead  136  may be positioned in the formation portion of the recess  425 . 
     Referring to  FIG.  27   , a segment  15   e  may have a through portion  437  positioned in the center with respect to the first direction. The through portion  437  may pass through a central portion of the segment  15   e  in the second direction. Namely, the through portion  437  may be a hole positioned in the segment  15   e . The through portion  437  may be a portion in which the FFC  231  is positioned. Because the through portion  437  is formed inside the segment  15   e , a thickness of the segment  15   e  can further decrease compared to when the FFC  231  is positioned in the recess  425 . 
     The bead  136  may be positioned on the segment  15   e  except a formation portion of the through portion  437 . The bead  136  may not be positioned in the formation portion of the through portion  437  because the thickness of the segment  15   e  in the third direction decreases. However, embodiments of the invention are not limited thereto. For example, the bead  136  may be positioned in the formation portion of the through portion  437 . 
     Referring to  FIG.  28   , in the display device according to the present disclosure, the top case  167  may shield the source PCB  120  and the upper bar  75  as well as the display panel  10  and the module cover  15 . Hence, the appearance of the display device can be neat because the source PCB  120  is not exposed to the outside. 
     One surface of the upper bar  75  may be coupled to the rear surface of the module cover  15 , and other surface of the upper bar  75  may be coupled to the source PCB  120 . The upper bar  75  may be fixed to the module cover  15  and may support the source PCB  120 . 
     A lower end of the FFC  231  may be connected to the timing controller board  105  (see  FIG.  29   ) inside the panel roller  143  (see  FIG.  29   ). The FFC  231  and the display unit  20  may be rolled and unrolled from the panel roller  143 . 
     A portion of the FFC  231  may be positioned between the display panel  10  and the module cover  15 . The portion of the FFC  231  that is positioned between the display panel  10  and the module cover  15  may be referred to as a first portion  231   a . The first portion  231   a  may be positioned in the recess  425  in which the plurality of segments  15   d  is formed. Alternatively, the first portion  231   a  may be accommodated in the recess  425  in which the plurality of segments  15   d  is formed. 
     A portion of the FFC  231  may pass through a segment  15   f . The portion of the FFC  231  that passes through the segment  15   f  may be referred to as a second portion  231   b . The segment  15   f  may include a first hole  521   a  formed at a front surface and a second hole  521   b  formed at a rear surface. The first hole  521   a  and the second hole  521   b  may be connected to each other to form one hole  521 . The hole  521  may pass through the segment  15   f  in the third direction. The second portion  231   b  may pass through the hole  521 . The hole  521  may be referred to as a connection hole  521 . 
     An upper end of the FFC  231  may be electrically connected to the source PCB  120 . A portion of the FFC  231  may be positioned on the rear surface of the module cover  15 . The portion of the FFC  231  that is positioned on the rear surface of the module cover  15  may be referred to as a third portion  231   c . The third portion  231   c  may be electrically connected to the source PCB  120 . 
     The third portion  231   c  may be shielded by the top case  167 . Hence, the third portion  231   c  may not be exposed to the outside. 
     Referring to  FIG.  29   , in the display device according to the present disclosure, the FFC  231  may be connected to the timing controller board  105  mounted on the panel roller  143 . A through hole  615  may be positioned in the panel roller  143 , and the FFC  231  may be connected to one side of the timing controller board  105  through the through hole  615 . 
     The through hole  615  may be positioned on one side of the panel roller  143  and may pass through an outer circumferential portion of the panel roller  143 . The FFC  231  may be connected to one side of the timing controller board  105  through the through hole  615 . 
     In the display device according to the present disclosure, even if the FFC  231  is positioned on the outer circumference of the panel roller  143 , the connection between the FFC  231  and the timing controller board  105  can be maintained by the through hole  615 . Hence, the FFC  231  rotates together with the panel roller  143  and cannot be twisted. 
     A portion of the FFC  231  may be rolled on the panel roller  143 . The portion of the FFC  231  rolled on the panel roller  143  may be referred to as a fourth portion  231   d . The fourth portion  231   d  may contact an outer circumferential surface of the panel roller  143 . 
     A portion of the FFC  231  may pass through the through hole  615 . The portion of the FFC  231  that passes through the through hole  615  may be referred to as a fifth portion  231   e.    
     The lower end of the FFC  231  may be electrically connected to the timing controller board  105 . A portion of the FFC  231  may be positioned inside the panel roller  143 . The portion of the FFC  231  that is positioned inside the panel roller  143  may be referred to as a sixth portion  231   f  The sixth portion  231   f  may be electrically connected to the timing controller board  105 . 
     Referring to  FIG.  30   , the first arm  73   a  may be connected to both ends of the upper bar  75 . The first arm  73   a  may be rotatably connected to a link bracket  277  through a coupling hole  77  positioned in the first arm  73   a . The link bracket  277  may be coupled to a connection portion  275  of the upper bar  75 . The link bracket  277  may be separated from the top case  167  downwardly (in −y-axis direction). The link bracket  277  may couple the first arm  73   a  to the connection portion  275  through at least one screw. 
     The small-sized display device can be implemented by coupling the module cover  15 , the source PCB  120 , and the first link  73   a  to the upper bar  75 . 
     Referring to  FIGS.  31 A and  31 B , an auxiliary roller  556  may be spaced apart from the panel roller  143 . The auxiliary roller  556  may be connected to a protective sheet  472 . One end of the protective sheet  472  may be connected to the auxiliary roller  556 , and other end of the protective sheet  472  may be connected to the display panel  10 . The auxiliary roller  556  may roll or unroll the protective sheet  472 . The protective sheet  472  may include a nonwoven fabric. 
     The auxiliary roller  556  may be positioned adjacent to a portion in which the panel roller  143  rolls and unrolls. The auxiliary roller  556  may rotate in the opposite direction of a rotation direction of the panel roller  143 . Namely, when the panel roller  143  unrolls the display panel  10 , the auxiliary roller  556  may roll the protective sheet  472 . Further, when the panel roller  143  rolls the display panel  10 , the auxiliary roller  556  may unroll the protective sheet  472 . 
     Referring to  FIG.  31 A , if the protective sheet  472  is not included, the module cover  15  and the display panel  10  may rub against each other when the panel roller  143  rolls and unrolls the module cover  15  and the display panel  10 . The display panel  10  may be damaged by friction with the module cover  15 . 
     Referring to  FIG.  31 B , the display panel  10 , the module cover  15 , and the protective sheet  472  may be together rolled and unrolled from the panel roller  143 . If the display panel  10 , the module cover  15 , and the protective sheet  472  are rolled on the panel roller  143 , the protective sheet  472  may be positioned between the display panel  10  and the module cover  15 . The protective sheet  472  can prevent friction between the display panel  10  and the module cover  15 . The protective sheet  472  can prevent a damage of the display panel  10  by preventing the friction between the display panel  10  and the module cover  15 . 
     Referring to  FIG.  32   , the auxiliary roller  556  may include a fixed cap  521 , a rotating cap  523 , a shaft  547 , a coil spring  573 , and a roller cover  582 . 
     The coil spring  573  may be disposed inside the auxiliary roller  556 . A longitudinal direction of the coil spring  573  may be parallel to a longitudinal direction of the auxiliary roller  556 . 
     The fixed cap  521  may be positioned at one end of the auxiliary roller  556 . The fixed cap  521  may be coupled to one end of the coil spring  573 . The fixed cap  521  may be fixed regardless of a rotation of the roller cover  582 . The fixed cap  521  may not rotate. 
     The rotating cap  523  may be positioned at other end of the auxiliary roller  556 . The rotating cap  523  may be coupled to other end of the coil spring  573 . When the roller cover  582  rotates, the rotating cap  523  may rotate together with the roller cover  582 . 
     When the roller cover  582  rotates, the fixed cap  521  at one side may not rotate, the rotating cap  523  may rotate together with the roller cover  582 , and the coil spring  573  may be elastically deformed. The coil spring  573  may store energy during the elastic deformation and apply a restoring force to the rotating cap  523 . The restoring force of the coil spring  573  may act in the opposite direction of a rotation direction of the rotating cap  523 . 
     Hence, as the protective sheet  472  is unrolled from the auxiliary roller  556 , a force of rolling again the protective sheet  472  on the auxiliary roller  556  may act on the auxiliary roller  556 . That is, when the display panel is unrolled from the panel roller, the protective sheet  472  may be rolled on the auxiliary roller  556 . 
     As the protective sheet  472  is rolled on the auxiliary roller  556 , a force of unrolling again the protective sheet  472  from the auxiliary roller  556  may act on the auxiliary roller  556 . That is, when the display panel is rolled on the panel roller, the protective sheet  472  may be unrolled from the auxiliary roller  556 . 
     The shaft  547  may be a central axis of the auxiliary roller  556 . The shaft  547  may be connected to the fixed cap  521 . The coil spring  573  may be inserted into the shaft  547 . The shaft  547  may assist so that the coil spring  573  is stably positioned inside the auxiliary roller  556 . 
     The roller cover  582  may form an appearance of the auxiliary roller  556 . The roller cover  582  may accommodate the fixed cap  521 , the rotating cap  523 , the shaft  547 , and the coil spring  573 . The roller cover  582  may be connected to one end of the protective sheet  472 . That is, the protective sheet  472  may be rolled on the roller cover  582 . 
     Referring to  FIG.  33   , a radius formed by the panel roller  143  and the display panel  10  rolled on the panel roller  143  may be denoted as R 1 . A value of R 1  may vary depending on a rolling degree of the display panel  10  on the panel roller  143 . A radius of the panel roller  143  may be denoted as R 2 . 
     The panel roller  143  may be fixed inside the housing  30  (see  FIG.  7   ). Further, the entrance  30   a  (see  FIG.  7   ) of the housing  30  through which the display panel  10  passes may be fixed. Thus, an angle formed by the display panel  10  unrolled from the panel roller  143  inside the housing  30  and the base  31  (see  FIG.  10 A ) may vary depending on Rt. 
     When the display panel  10  is sufficiently unrolled from the panel roller  143 , the radius formed by the panel roller  143  and the display panel  10  rolled on the panel roller  143  is the radius R 2  of the panel roller  143 . In this instance, the display panel  10  may be inclined to the base  31  by an angle A 1 . When the display panel  10  may be inclined to the base  31 , the moving up and down of the display panel  10  may be unstable. 
     Referring to  FIG.  34   , a guide assembly  731  may be coupled to the auxiliary roller  556 . 
     The auxiliary roller  556  can prevent the display panel  10  from being inclined to the base  31  (see  FIG.  10 A ). The auxiliary roller  556  can stably guide the display panel  10  unrolled from the panel roller  143 . However, the radius formed by the panel roller  143  and the display panel  10  rolled on the panel roller  143  may vary depending on a rolling degree of the protective sheet  472  on the auxiliary roller  556 . 
     The guide assembly  731  may be coupled to the auxiliary roller  556  and may adjust a location of the auxiliary roller  556  depending on a rolling degree of the protective sheet  472  on the auxiliary roller  556 . Hence, the auxiliary roller  556  can stably guide the display panel  10  unrolled from the panel roller  143  even if the radius formed by the auxiliary roller  556  and the protective sheet  472  rolled on the auxiliary roller  556  varies. 
     The guide assembly  731  may include a guide arm  752 , a pin bolt  761 , a tension spring  764 , and a supporter  772 . One end of the guide arm  752  may be connected to the auxiliary roller  556 , and other end of the guide arm  752  may be connected to the tension spring  764 . The guide arm  752  may rotate around the pin bolt  761 . The pin bolt  761  may be fixed to the housing. The auxiliary roller  556  may be connected to the guide arm  752  and may rotate around the pin bolt  761 . 
     One end of the tension spring  764  may be connected to the guide arm  762 , and the other end of the tension spring  764  may be connected to the supporter  772 . The supporter  772  may be fixed to the housing  30 . 
     When the display panel  10  is unrolled from the panel roller  143 , the auxiliary roller  556  may roll the protective sheet  472 , and the radius formed by the auxiliary roller  556  and the protective sheet  472  rolled on the auxiliary roller  556  may increase. In addition, the auxiliary roller  556  may rotate counterclockwise around the pin bolt  761 . In this instance, the tension spring  764  may apply a force to rotate the guide arm  752  clockwise. The tension spring  764  can prevent the auxiliary roller  556  from excessively rotating counterclockwise around the pin bolt  761 . 
     When the display panel  10  is rolled on the panel roller  143 , the protective sheet  472  may be unrolled from the auxiliary roller  556 , and the radius formed by the auxiliary roller  556  and the protective sheet  472  rolled on the auxiliary roller  556  may decrease. In addition, the auxiliary roller  556  may rotate clockwise around the pin bolt  761 . 
     The tension spring  764  can prevent the auxiliary roller  556  from rotating counterclockwise around the pin bolt  761 . 
     The following description will be given focusing on different configurations and actions from the embodiments described above, and the description of configurations equivalent to or similar to the embodiments described above is omitted to avoid the duplicate description. 
     Referring to  FIG.  35   , a motor assembly  810  may be installed on the base  31 . The base  31  may be the bottom of the housing  30  (see  FIG.  19   ). Drive shafts may be formed on both sides of the motor assembly  810 . A right drive shaft and a left drive shaft of the motor assembly  810  may rotate in the same direction. Alternatively, the right drive shaft and the left drive shaft of the motor assembly  810  may rotate in opposite directions. 
     The motor assembly  810  may include a plurality of motors. The plurality of motors may be connected in series with each other. The plurality of motors may be arranged in order of a first motor  811 , a second motor  812 , a third motor  813 , and a fourth motor  814  from right to left. The right drive shaft of the motor assembly  810  may be formed in the first motor  811 , and the left drive shaft of the motor assembly  810  may be formed in the fourth motor  814 . The motor assembly  810  can output a high torque by connecting the plurality of motors in series. 
     The motor assembly  810  may be connected to lead screws  840   a  and  840   b . The lead screws  840   a  and  840   b  may include a right lead screw  840   a  connected to the right side of the motor assembly  810  and a left lead screw  840   b  connected to the left side of the motor assembly  810 . The right lead screw  840   a  may be referred to as a first lead screw  840   a , and the left lead screw  840   b  may be referred to as a second lead screw  840   b.    
     The right drive shaft of the motor assembly  810  may be connected to the right lead screw  840   a . Alternatively, the right drive shaft of the motor assembly  810  and the right lead screw  840   a  may be connected to each other through a right coupling  820   a . Alternatively, a drive shaft of the first motor  811  may be connected to the right lead screw  840   a . Alternatively, the drive shaft of the first motor  811  and the right lead screw  840   a  may be connected to each other through the right coupling  820   a . The right drive shaft may be referred to as a first drive shaft, and the left drive shaft may be referred to as a second drive shaft. 
     The left drive shaft of the motor assembly  810  may be connected to the left lead screw  840   b . Alternatively, the left drive shaft of the motor assembly  810  and the left lead screw  840   b  may be connected to each other through a left coupling  820   b . Alternatively, a drive shaft of the fourth motor  814  may be connected to the left lead screw  840   b . Alternatively, the drive shaft of the fourth motor  814  and the left lead screw  840   b  may be connected to each other through the left coupling  820   b.    
     The couplings  820   a  and  820   b  may include the right coupling  820   a  connecting the right drive shaft of the motor assembly  810  to the right lead screw  840   a , and the left coupling  820   b  connecting the left drive shaft of the motor assembly  810  to the left lead screw  840   b.    
     Each of the lead screws  840   a  and  840   b  may be formed with a screw thread in the longitudinal direction. A direction of the screw thread of the right lead screw  840   a  and a direction of the screw thread of the left lead screw  840   b  may be opposite to each other. Alternatively, the direction of the screw thread of the right lead screw  840   a  and the direction of the screw thread of the left lead screw  840   b  may be the same. 
     Bearings  830   a ,  830   b ,  830   c  and  830   d  may be installed on the base  31 . The plurality of bearings  830   a ,  830   b ,  830   c  and  830   d  may be formed along a longitudinal direction of the base  31 . The bearings  830   a ,  830   b ,  830   c  and  830   d  may include right bearings  830   a  and  830   b  on the right side of the motor assembly  810  and left bearings  830   c  and  830   d  on the left side of the motor assembly  810 . 
     The bearings  830   a ,  830   b ,  830   c  and  830   d  may support the lead screws  840   a  and  840   b . The lead screws  840   a  and  840   b  may be connected to the drive shafts of the motor assembly  810  and may rotate. The bearings  830   a ,  830   b ,  830   c  and  830   d  may support the lead screws  840   a  and  840   b  without disturbing the rotation of the lead screws  840   a  and  840   b.    
     The right bearings  830   a  and  830   b  may support the right lead screw  840   a . The right bearings  830   a  and  830   b  may include a first right bearing  830   a  supporting the right side of the right lead screw  840   a , and a second right bearing  830   b  supporting the left side of the right lead screw  840   a . The first right bearing  830   a  may be referred to as a first bearing  830   a , and the second right bearing  830   b  may be referred to as a second bearing  830   b.    
     The left bearings  830   c  and  830   d  may support the left lead screw  840   b . The left bearings  830   c  and  830   d  may include a first left bearing  830   c  supporting the right side of the left lead screw  840   b , and a second left bearing  830   d  supporting the left side of the left lead screw  840   b.    
     The bearings  830   a ,  830   b ,  830   c  and  830   d , the couplings  820   a  and  820   b , and the motor assembly  810  may be arranged in order of the first right bearing  830   a , the second right bearing  830   b , the right coupling  820   a , the motor assembly  810 , the left coupling  820   b , the first left bearing  830   c , and the second left bearing  830   d  from right to left. 
     Referring to  FIGS.  36  and  37   , the display device may further include sliders  860   a  and  860   b . The sliders  860   a  and  860   b  may be coupled to the lead screws  840   a  and  840   b , and the lead screws  840   a  and  840   b  may be disposed to pass through the sliders  860   a  and  860 . The plurality of sliders  860   a  and  860   b  may be used. The sliders  860   a  and  860   b  may include a right slider  860   a  coupled to the right lead screw  840   a , and a left slider  860   b  coupled to the left lead screw  840   b . The right slider  860   a  may be referred to as a first slider  860   a , and the left slider  860   b  may be referred to as a second slider  860   b.    
     A screw thread SS (see  FIG.  43   ) may be formed on an inner perimeter surface of each of the sliders  860   a  and  860   b . The screw threads SS on the inner perimeter surface of each of the sliders  860   a  and  860   b  may be engaged with screw threads RS and LS on the lead screws  840   a  and  840   b . The sliders  860   a  and  860   b  may move back and forth in the longitudinal direction of the lead screws  840   a  and  840   b  according to the rotation of the lead screws  840   a  and  840   b.    
     The right slider  860   a  may be engaged with the right lead screw  840   a . The right slider  860   a  may move back and forth between the first right bearing  830   a  and the second right bearing  830   b  according to the rotation of the right lead screw  840   a.    
     The left slider  860   b  may be engaged with the left lead screw  840   b . The left slider  860   b  may move back and forth between the first left bearing  830   c  and the second left bearing  830   d  according to the rotation of the left lead screw  840   b.    
     The right slider  860   a  may be spaced apart from a symmetry axis ys of the motor assembly  810  by a distance RD 1 . The left slider  860   b  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 1 . The distance RD 1  and the distance LD 1  may be set to the same length. That is, the right slider  860   a  and the left slider  860   b  may be symmetrical to each other with respect to the symmetry axis ys of the motor assembly  810 . 
     The motor assembly  810  may be configured such that a rotation direction of the right drive shaft and a rotation direction of the left drive shaft are equally output. A direction of the screw thread RS of the right lead screw  840   a  and a direction of the screw thread LS of the left lead screw  840   b  may be opposite to each other. Hence, when the right slider  860   a  moves in the +x-axis direction according to the rotation of the right drive shaft, the left slider  860   b  may move in the −x-axis direction according to the rotation of the left drive shaft. Alternatively, when the right slider  860   a  moves in the −x-axis direction according to the rotation of the right drive shaft, the left slider  860   b  may move in the +x-axis direction according to the rotation of the left drive shaft. 
     Referring to  FIG.  38   , a direction of the screw thread RS of the right lead screw  840   a  and a direction of the screw thread LS of the left lead screw  840   b  may be opposite to each other. The right lead screw  840   a  may have a pitch PR, and the left lead screw  840   b  may have a pitch PL. The pitch PR of the right lead screw  840   a  and the pitch PL of the left lead screw  840   b  may be set to the same length. 
     The motor assembly  810  may be configured such that an output of the right drive shaft and an output of the left drive shaft are equally output. A rotation direction Ra of the right drive shaft and a rotation direction Ra of the left drive shaft may be the same as each other. The number of revolutions per unit time in the right drive shaft and the number of revolutions per unit time in the left drive shaft may be the same as each other. A direction of torque of the right drive shaft and a direction of torque of the left drive shaft may be the same as each other. A magnitude of torque of the right drive shaft and a magnitude of torque of the left drive shaft may be the same as each other. 
     The right slider  860   a  may move in the +x-axis direction according to the rotation of the right drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 1 . When the right drive shaft rotates n times, the right slider  860   a  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 2 . In this case, the distance RD 1  and the distance RD 2  may have a difference of (the number n of revolutions)*(pitch PR of the right slider  860   a ). 
     The left slider  860   b  may move in the −x-axis direction according to the rotation of the left drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 1 . When the left drive shaft rotates n times, the left slider  860   b  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 2 . In this case, the distance LD 1  and the distance LD 2  may have a difference of (the number n of revolutions)*(pitch PL of the left slider  860   b ). 
     That is, when the pitch PR of the right slider  860   a  and the pitch PL of the left slider  860   b  are the same as each other, a displacement of the right slider  860   a  and a displacement of the left slider  860   b  may have the same magnitude and opposite directions. 
     When initial locations of the right slider  860   a  and the left slider  860   b  are symmetrical with respect to the symmetry axis ys of the motor assembly  810 , the right slider  860   a  and the left slider  860   b  may be far from each other while maintaining the symmetry with respect to the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  39   , the right slider  860   a  may move in the −x-axis direction according to the rotation of the right drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 2 . A rotation direction Rb of the right drive shaft and a rotation direction Rb of the left drive shaft may be the same as each other. When the right drive shaft rotates n times, the right slider  860   a  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 1 . In this case, the distance RD 1  and the distance RD 2  may have a difference of (the number n of revolutions)*(pitch PR of the right slider  860   a ). 
     The left slider  860   b  may move in the +x-axis direction according to the rotation of the left drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 2 . When the left drive shaft rotates n times, the left slider  860   b  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 1 . In this case, the distance LD 1  and the distance LD 2  may have a difference of (the number n of revolutions)*(pitch PL of the left slider  860   b ). 
     That is, when the pitch PR of the right slider  860   a  and the pitch PL of the left slider  860   b  are the same as each other, a displacement of the right slider  860   a  and a displacement of the left slider  860   b  may have the same magnitude and opposite directions. 
     When initial locations of the right slider  860   a  and the left slider  860   b  are symmetrical with respect to the symmetry axis ys of the motor assembly  810 , the right slider  860   a  and the left slider  860   b  may be close to each other while maintaining the symmetry with respect to the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  40   , the motor assembly  810  may be configured such that a rotation direction Ra of the right drive shaft and a rotation direction Rb of the left drive shaft are output in opposite directions. A direction of the screw thread RS of the right lead screw  840   a  and a direction of the screw thread LS of the left lead screw  840   b  may be the same. Hence, when the right slider  860   a  moves in the +x-axis direction according to the rotation of the right drive shaft, the left slider  860   b  may move in the −x-axis direction according to the rotation of the left drive shaft. Alternatively, when the right slider  860   a  moves in the −x-axis direction according to the rotation of the right drive shaft, the left slider  860   b  may move in the +x-axis direction according to the rotation of the left drive shaft. 
     The right lead screw  840   a  may have a pitch PR, and the left lead screw  840   b  may have a pitch PL. The pitch PR of the right lead screw  840   a  and the pitch PL of the left lead screw  840   b  may be set to the same length. 
     The motor assembly  810  may be configured such that an output of the right drive shaft and an output of the left drive shaft are equally output. A rotation direction of the right drive shaft and a rotation direction of the left drive shaft may be opposite to each other. The number of revolutions per unit time in the right drive shaft and the number of revolutions per unit time in the left drive shaft may be the same as each other. A direction of torque of the right drive shaft and a direction of torque of the left drive shaft may be opposite to each other. A magnitude of torque of the right drive shaft and a magnitude of torque of the left drive shaft may be the same as each other. 
     The right slider  860   a  may move in the +x-axis direction according to the rotation of the right drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 1 . When the right drive shaft rotates n times, the right slider  860   a  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 2 . In this case, the distance RD 1  and the distance RD 2  may have a difference of (the number n of revolutions)*(pitch PR of the right slider  860   a ). 
     The left slider  860   b  may move in the −x-axis direction according to the rotation of the left drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 1 . When the left drive shaft rotates n times, the left slider  860   b  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 2 . In this case, the distance LD 1  and the distance LD 2  may have a difference of (the number n of revolutions)*(pitch PL of the left slider  860   b ). 
     That is, when the pitch PR of the right slider  860   a  and the pitch PL of the left slider  860   b  are the same as each other, a displacement of the right slider  860   a  and a displacement of the left slider  860   b  may have the same magnitude and opposite directions. 
     When initial locations of the right slider  860   a  and the left slider  860   b  are symmetrical with respect to the symmetry axis ys of the motor assembly  810 , the right slider  860   a  and the left slider  860   b  may be far from each other while maintaining the symmetry with respect to the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  41   , the motor assembly  810  may be configured such that a rotation direction Rb of the right drive shaft and a rotation direction Ra of the left drive shaft are output in opposite directions. The right slider  860   a  may move in the −x-axis direction according to the rotation of the right drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 2 . When the right drive shaft rotates n times, the right slider  860   a  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance RD 1 . In this case, the distance RD 1  and the distance RD 2  may have a difference of (the number n of revolutions)*(pitch PR of the right slider  860   a ). 
     The left slider  860   b  may move in the +x-axis direction according to the rotation of the left drive shaft at a location that is spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 2 . When the left drive shaft rotates n times, the left slider  860   b  may be spaced apart from the symmetry axis ys of the motor assembly  810  by a distance LD 1 . In this case, the distance LD 1  and the distance LD 2  may have a difference of (the number n of revolutions)*(pitch PL of the left slider  860   b ). 
     That is, when the pitch PR of the right slider  860   a  and the pitch PL of the left slider  860   b  are the same as each other, a displacement of the right slider  860   a  and a displacement of the left slider  860   b  may have the same magnitude and opposite directions. 
     When initial locations of the right slider  860   a  and the left slider  860   b  are symmetrical with respect to the symmetry axis ys of the motor assembly  810 , the right slider  860   a  and the left slider  860   b  may be close to each other while maintaining the symmetry with respect to the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIGS.  42 ,  43 ,  44 A and  44 B , link mounts  920   a  and  920   b  may be installed on the base  31 . The link mounts  920   a  and  920   b  may include a right link mount  920   a  that is spaced apart from the first right bearing  830   a  toward the right side, and a left link mount  920   b  that is spaced apart from the second left bearing  830   d  toward the left side. 
     Links  910   a  and  910   b  may be connected to the link mounts  920   a  and  920   b . The links  910   a  and  910   b  may include a right link  910   a  connected to the right link mount  920   a  and a left link  910   b  connected to the left link mount  920   b.    
     The right link  910   a  may be referred to as a first link, and the left link  910   b  may be referred to as a second link. The right link mount  920   a  may be referred to as a first link mount  920   a , and the left link mount  920   b  may be referred to as a second link mount  920   b.    
     The links  910   a  and  910   b  may include first arms  911   a  and  911   b , second arms  912   a  and  912   b , and arm joints  913   a  and  913   b . One sides of the second arms  912   a  and  912   b  may be rotatably connected to the link mounts  920   a  and  920   b , and other sides of the second arms  912   a  and  912   b  may be rotatably connected to the arm joints  913   a  and  913   b . One sides of the first arms  911   a  and  911   b  may be rotatably connected to the arm joints  913   a  and  913   b , and other sides of the first arms  911   a  and  911   b  may be rotatably connected to link brackets  951   a  and  951   b.    
     The link brackets  951   a  and  951   b  may include a right link bracket  951   a  connected to the first arm  911   a  of the right link  910   a  and a left link bracket  951   b  connected to the first arm  911   b  of the left link  910   b . The link brackets  951   a  and  951   b  may be connected to an upper bar  950 . 
     The upper bar  950  may connect the right link bracket  951   a  to the left link bracket  951   b.    
     Rods  870   a  and  870   b  may connect the sliders  860   a  and  860   b  to the links  910   a  and  910   b . One sides of the rods  870   a  and  870   b  may be rotatably connected to the sliders  860   a  and  860   b , and other sides of the rods  870   a  and  870   b  may be rotatably connected to the second arms  912   a  and  912   b . The rods  870   a  and  870   b  may include a right rod  870   a  connecting the right slider  860   a  to the second arm  912   a  of the right link  910   a  and a left rod  870   b  connecting the left slider  860   b  to the second arm  912   b  of the left link  910   b . The right rod  870   a  may be referred to as a first rod  870   a , and the left rod  870   b  may be referred to as a second rod  870   b.    
     More specifically, a structure formed by the right lead screw  840   a , the right slider  860   a , the right rod  870   a , and the right link  910   a  is described. The right slider  860   a  may include a body  861   a  and a load mount  862   a . A screw thread SS may be formed on an inner perimeter surface of the body  861   a . The screw thread SS of the body  861   a  may be engaged with the screw thread RS of the right lead screw  840   a . The right lead screw  840   a  may pass through the body  861   a.    
     The load mount  862   a  may be formed on the right side of the body  861   a . The rod mount  862   a  may be rotatably connected to one side of the right rod  870   a . The rod mount  862   a  may include a first rod mount  862   a   1  and a second rod mount  862   a   2 . The first rod mount  862   a   1  may be disposed in front of the right lead screw  840   a , and the second rod mount  862   a   2  may be disposed behind the right lead screw  840   a . The first rod mount  862   a   1  and the second rod mount  862   a   2  may be spaced apart from each other. The second rod mount  862   a   2  may be spaced apart from the first rod mount  862   a   1  in the −z-axis direction. The right lead screw  840   a  may be positioned between the first rod mount  862   a   1  and the second rod mount  862   a   2 . 
     The rod mount  862   a  may be rotatably connected to one side of the right rod  870   a  through a connection member C 1 . The connection member C 1  may pass through the rod mount  862   a  and the right rod  870   a.    
     The right rod  870   a  may be rotatably connected to the second arm  912   a  through a connection member C 2 . The connection member C 2  may pass through the second arm  912   a  and the right rod  870   a.    
     The right rod  870   a  may include a transfer portion  871   a  connected to the second arm  912   a  of the right link  910   a  and a cover  872   a  connected to the rod mount  862   a  of the right slider  860   a . The transfer portion  871   a  may transfer, to the right link  910   a , a force generated when the right slider  860   a  moves back and forth along the right lead screw  840   a.    
     The cover  872   a  may include a first plate  873   a  disposed in front of the right lead screw  840   a . The first plate  873   a  may be disposed perpendicular to the base  31 . Alternatively, the first plate  873   a  may face the right lead screw  840   a.    
     The cover  872   a  may include a second plate  874   a  disposed behind the right lead screw  840   a . The second plate  874   a  may be disposed perpendicular to the base  31 . Alternatively, the second plate  874   a  may face the right lead screw  840   a . Alternatively, the second plate  874   a  may be spaced apart from the first plate  873   a . The right lead screw  840   a  may be positioned between the first plate  873   a  and the second plate  874   a.    
     The cover  872   a  may include a third plate  875   a  connecting the first plate  873   a  to the second plate  874   a . The third plate  875   a  may be connected to the transfer portion. The third plate  875   a  may be positioned on an upper side of the right lead screw  840   a.    
     The cover  872   a  may include a fourth plate  876   a  connecting the first plate  873   a  to the second plate  874   a . The fourth plate  876   a  may be connected to the third plate  875   a . The fourth plate  876   a  may be positioned on the upper side of the right lead screw  840   a.    
     One side of the first plate  873   a  may be connected to the first rod mount  862   a   1 . The first plate  873   a  and the first rod mount  862   a   1  may be connected through a connection member C 1 ′. Other side of the first plate  873   a  may be connected to the third plate  875   a.    
     One side of the second plate  874   a  may be connected to the second rod mount  862   a   2 . The second plate  874   a  and the second rod mount  862   a   2  may be connected through a connection member C 1 . Other side of the second plate  874   a  may be connected to the third plate  875   a.    
     When the right slider  860   a  moves to close to the motor assembly  810 , the right lead screw  840   a  and the right rod  870   a  may contact each other. When the right lead screw  840   a  and the right rod  870   a  contact each other, a mutual interference may occur, and a movement of the right slider  860   a  may be restricted. 
     The cover  872   a  may provide a space S 1  therein. The first plate  873   a , the second plate  874   a , the third plate  875   a , and the fourth plate  876   a  may form the space S 1 . When the right slider  860   a  moves to close to the motor assembly  810 , the right lead screw  840   a  may be accommodated or escaped in the space S 1  provided by the cover  872   a . The right slider  860   a  may move closer to the motor assembly  810  than when there is no cover  872   a , due to the space S 1  provided by the cover  872   a . That is, the cover  872   a  can increase a movable range of the right slider  860   a  by providing the space S 1  therein. In addition, there is an advantage in that the size of the housing  30  (see  FIG.  2   ) can be reduced by accommodating the right lead screw  840   a  in the cover  872   a.    
     The cover  872   a  may limit a minimum value of an angle θS formed by the second arm  912   a  and the base  31 . When the angle θS is sufficiently small, the third plate  875   a  of the cover  872   a  may contact the second arm  912   a  and support the second arm  912   a . The third plate  875   a  can limit the minimum value of the angle θS and prevent the sagging of the second arm  912   a  by supporting the second arm  912   a . That is, the cover  872   a  may serve as a stopper preventing the sagging of the second arm  912   a . Further, the third plate  875   a  can reduce an initial load of standing up the second arm  912   a  by limiting the minimum value of the angle θS. 
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , a load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, the third plate  875   a  can reduce the load on the motor assembly  810  in order to stand up the second arms  912   a  and  912   b  by limiting the minimum value of the angle θS. 
     A structure formed by the left lead screw  840   b , the left slider  860   b , the left rod  870   b , and the left link  910   b  may be symmetrical to the above-described structure formed by the right lead screw  840   a , the right slider  860   a , the right rod  870   a , and the right link  910   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     With reference to  FIGS.  45  and  46   , a connection of the right rod  870   a  to a protrusion  914   a  is shown. The protrusion  914   a  may be referred to as a connection portion  914   a.    
     An angle formed by the right rod  870   a  and the base  31  may vary depending on a location of the connection portion. An angle formed by the second arm  912   a  and the base  31  may be denoted as an angle θS. When the right slider  860   a  is positioned closest to the motor assembly  810  within a movable range, the second arm  912   a  may lie completely on the base  31 . When the second arm  912   a  lies completely on the base  31 , the angle θS may have a minimum value. For example, when the second arm  912   a  lies completely on the base  31 , the angle θS may have a value close to 0°. 
     When the right slider  860   a  moves in the +x-axis direction, the angle θS may gradually increase. Alternatively, when the right slider  860   a  moves in the +x-axis direction, the second arm  912   a  may stand up with respect to the base  31 . Alternatively, when the angle θS gradually increases, the second arm  912   a  may stand up with respect to the base  31 . 
     When the right slider  860   a  is positioned farthest from the motor assembly  810  within a movable range, the second arm  912   a  may completely stand up with respect to the base  31 . When the second arm  912   a  completely stands up with respect to the base  31 , the angle θS may have a maximum value. For example, when the second arm  912   a  completely stands up with respect to the base  31 , the second arm  912   a  may be positioned perpendicular to the base  31 . Alternatively, when the second arm  912   a  completely stands up with respect to the base  31 , an angle formed by the second arm  912   a  and the base  31  may have a value close to 90°. 
     A direction in which an angle (angle θS) between the second arm  912   a  of the right link  910   a  and the base  31  increases may be referred to as a standing direction S. Alternatively, a direction in which an angle between the second arm  912   b  of the left link  910   b  and the base  31  increases may be referred to as a standing direction S. 
     When a rod mount  862   a ″ is positioned on an upper side of the body  861   a , an angle formed by a right rod  870   a ″ and the base  31  may be denoted as OA, and a minimum force required for the right rod  870   a ″ to stand up the second arm  912   a  may be denoted as Fa. 
     When a rod mount  862   a ′ is positioned at a middle height of the body  861   a , an angle formed by a right rod  870   a ′ and the base  31  may be denoted as OB, and a minimum force required for the right rod  870   a ′ to stand up the second arm  912   a  may be denoted as Fb. 
     When a rod mount  862   a  is positioned on a lower side of the body  861   a , an angle formed by a right rod  870   a  and the base  31  may be denoted as OC, and a minimum force required for the right rod  870   a  to stand up the second arm  912   a  may be denoted as Fc. 
     In this case, a relationship of θA&lt;θB&lt;θC may be established for the same angle θS. Further, a relationship of Fc&lt;Fb&lt;Fa may be established for the same angle θS. 
     That is, if an angle formed by the second arm  912   a  and the base  31  is the same, a force required to stand up the second arm  912   a  may decrease as the angle formed by the right rod  870   a  and the base  31  increases. 
     The cover  872   a  (see  FIG.  43   ) of the right rod  870   a  provides a space S 1  (see  FIG.  43   ) capable of accommodating the right lead screw  840   a  and thus can allow the load mount  862   a  to be coupled close to a lower side of a body  861   b  or the right lead screw  840   a.    
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , a load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, the load on the motor assembly  810  in order to stand up the second arm  912   a  can decrease by increasing the angle formed by the right rod  870   a  and the base  31 . 
     A structure formed by the left lead screw  840   b , the left slider  860   b , the left rod  870   b , and the second arm  912   b  may be symmetrical to the structure formed by the right lead screw  840   a , the right slider  860   a , the right rod  870   a , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIGS.  47  to  49   , the second arm  912   a  may include a bar  915   a  and a protrusion  914   a .  FIG.  47    illustrates that the right rod  870   a  is connected to the bar  915   a , and  FIG.  48    illustrates that the right rod  870   a  is connected to the protrusion  914   a . The protrusion  914   a  may be referred to as a connection portion  914   a.    
     An angle formed by the second arm  912   a  and the base  31  may be denoted as θS. When the right slider  860   a  is positioned closest to the motor assembly  810  within a movable range, the second arm  912   a  may lie completely on the base  31 . When the second arm  912   a  lies completely on the base  31 , the angle θS may have a minimum value. For example, when the second arm  912   a  lies completely on the base  31 , the angle θS may have a value close to 0°. 
     When the right slider  860   a  moves in the +x-axis direction, the angle θS may gradually increase. Alternatively, when the right slider  860   a  moves in the +x-axis direction, the second arm  912   a  may stand up with respect to the base  31 . Alternatively, when the angle θS gradually increases, the second arm  912   a  may stand up with respect to the base  31 . 
     When the right slider  860   a  is positioned farthest from the motor assembly  810  within a movable range, the second arm  912   a  may completely stand up with respect to the base  31 . When the second arm  912   a  completely stands up with respect to the base  31 , the angle θS may have a maximum value. For example, when the second arm  912   a  completely stands up with respect to the base  31 , the second arm  912   a  may be positioned perpendicular to the base  31 . Alternatively, when the second arm  912   a  completely stands up with respect to the base  31 , an angle formed by the second arm  912   a  and the base  31  may have a value close to 90°. 
     A direction in which an angle (angle θS) between the second arm  912   a  of the right link  910   a  and the base  31  increases may be referred to as a standing direction S. Alternatively, a direction in which an angle between the second arm  912   b  of the left link  910   b  and the base  31  increases may be referred to as a standing direction S. 
     Referring to  FIG.  47   , an angle formed by the right rod  870   a  and the right lead screw  840   a  may be denoted as θ 1 . When the second arm  912   a  lies completely on the base  31 , the angle θ 1  may have a minimum value. 
     To stand up the second arm  912   a , the motor assembly  810  may drive the drive shaft. When the drive shaft rotates, the right slider  860   a  may move in the +x-axis direction. The right slider  860   a  may apply a force to the right rod  870   a , and the rod  870   a  may transfer the force to the bar  915   a  of the second arm  912   a . The second arm  912   a  may receive the force from the right rod  870   a  and rotate in the standing direction S. When the right link  910   a  stands up, the angles θS and θ 1  may increase. 
     When the second arm  912   a  lies completely on the base  31 , a minimum force for standing up the second arm  912   a  may be denoted as F 1 . That is, the F 1  may mean a minimum force that the right rod  870   a  has to transfer to the bar  915   a  of the second arm  912   a  in order to stand up the second arm  912   a.    
     Referring to  FIG.  48   , an angle formed by the right rod  870   a  and the right lead screw  840   a  may be denoted as θ 2 . When the second arm  912   a  lies completely on the base  31 , the angle θ 2  may have a minimum value. 
     To stand up the second arm  912   a , the motor assembly  810  may drive the drive shaft. When the drive shaft rotates, the right slider  860   a  may move in the +x-axis direction, and the left slider  860   b  may move in the −x-axis direction. The sliders  860   a  and  860   b  may apply a force to the rods  870   a  and  870   b , and the rods  870   a  and  870   b  may transfer the force to the bar  915   a  of the second arm  912   a . The second arm  912   a  may receive the force from the rods  870   a  and  870   b  and rotate in the standing direction S. When the links  910   a  and  910   b  stand up, the angles θS and θ 2  may increase. 
     When the second arm  912   a  lies completely on the base  31 , a minimum force for standing up the second arm  912   a  may be denoted as F 2 . That is, the F 2  may mean a minimum force that the right rod  870   a  has to transfer to the bar  915   a  of the second arm  912   a  in order to stand up the second arm  912   a.    
     With reference to  FIGS.  47  and  48   , in preparation for the case where the right rod  870   a  is connected to the bar  915   a  of the second arm  912   a  and the case where the right rod  870   a  is connected to the protrusion  914   a  of the second arm  912   a , when an angle θS formed by the second arm  912   a  and the base  31  is the same, an angle θ 2  formed by the right rod  870   a  connected to the protrusion  914   a  of the second arm  912   a  and the right lead screw  840   a  may be greater than an angle θ 1  formed by the right rod  870   a  connected to the bar  915   a  of the second arm  912   a  and the right lead screw  840   a.    
     Further, when the angle θS formed by the second arm  912   a  and the base  31  is the same, the force F 1  required to stand up the second arm  912   a  when the right rod  870   a  is connected to the bar  915   a  of the second arm  912   a  may be greater than the force F 2  required to stand up the second arm  912   a  when the right rod  870   a  is connected to the protrusion  914   a  of the second arm  912   a.    
     That is, if an angle formed by the second arm  912   a  and the base  31  is the same, a force required to stand up the second arm  912   a  may decrease as an angle formed by the right rod  870   a  and the right lead screw  840   a  increases. Alternatively, the second arm  912   a  can stand up by less force than the force required when the right rod  870   a  is connected to the bar  915   a , by connecting the right rod  870   a  to the protrusion  914   a.    
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , a load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, by connecting the right rod  870   a  to the protrusion  914   a  of the second arm  912   a , an angle formed by the right rod  870   a  and the base  31  may increase, and the load on the motor assembly  810  in order to stand up the second arm  912   a  can decrease. 
     A structure formed by the left lead screw  840   b , the left slider  860   b , the left rod  870   b , and the second arm  912   b  may be symmetrical to the structure formed by the right lead screw  840   a , the right slider  860   a , the right rod  870   a , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     With reference to  FIGS.  50  and  51   , a connection of the right rod  870   a  to the protrusion  914   a  is shown. The protrusion  914   a  may be referred to as a connection portion  914   a.    
     An angle formed by the right rod  870   a  and the base  31  may vary depending on a connection location of the protrusion  914   a  and the right rod  870   a . An angle formed by the second arm  912   a  and the base  31  may be denoted as θS. When the right slider  860   a  is positioned closest to the motor assembly  810  within a movable range, the second arm  912   a  may lie completely on the base  31 . When the second arm  912   a  lies completely on the base  31 , the angle θS may have a minimum value. For example, when the second arm  912   a  lies completely on the base  31 , the angle θS may have a value close to 0°. 
     When the right slider  860   a  moves in the +x-axis direction, the angle θS may gradually increase. Alternatively, when the right slider  860   a  moves in the +x-axis direction, the second arm  912   a  may stand up with respect to the base  31 . Alternatively, when the angle θS gradually increases, the second arm  912   a  may stand up with respect to the base  31 . 
     When the right slider  860   a  is positioned farthest from the motor assembly  810  within a movable range, the second arm  912   a  may completely stand up with respect to the base  31 . When the second arm  912   a  completely stands up with respect to the base  31 , the angle θS may have a maximum value. For example, when the second arm  912   a  completely stands up with respect to the base  31 , the second arm  912   a  may be positioned perpendicular to the base  31 . Alternatively, when the second arm  912   a  completely stands up with respect to the base  31 , an angle formed by the second arm  912   a  and the base  31  may have a value close to 90°. 
     A direction in which an angle (angle θS) between the second arm  912   a  of the right link  910   a  and the base  31  increases may be referred to as a standing direction S. Alternatively, a direction in which an angle between the second arm  912   b  of the left link  910   b  and the base  31  increases may be referred to as a standing direction S. 
     When a right rod  870   a   1  and the protrusion  914   a  are fastened to be spaced apart from a central axis CR of the second arm  912   a  by a distance r, an angle formed by the right rod  870   a   1  and the base  31  may be denoted as θ 2 , and a minimum force required for the right rod  870   a   1  to stand up the second arm  912   a  may be denoted as F 3 . 
     When a right rod  870   a   2  and the protrusion  914   a  are fastened to be spaced apart from the central axis CR of the second arm  912   a  by a distance r′, an angle formed by the right rod  870   a   2  and the base  31  may be denoted as θ 2 ′, and a minimum force required for the right rod  870   a   2  to stand up the second arm  912   a  may be denoted as F 4 . 
     When a right rod  870   a   3  and the protrusion  914   a  are fastened to be spaced apart from the central axis CR of the second arm  912   a  by a distance r″, an angle formed by the right rod  870   a   3  and the base  31  may be denoted as θ 2 ″, and a minimum force required for the right rod  870   a   3  to stand up the second arm  912   a  may be denoted as F 5 . 
     In this case, a relationship of θ 2 &lt;θ 2 ′&lt;θ 2 ″ may be established for the same angle θS. Further, a relationship of F 5 &lt;F 4 &lt;F 3  may be established for the same angle θS. 
     That is, if an angle formed by the second arm  912   a  and the base  31  is the same, a force required to stand up the second arm  912   a  may decrease as the angle formed by the right rod  870   a  and the base  31  increases. 
     A structure formed by the left lead screw  840   b , the left slider  860   b , the left rod  870   b , and the second arm  912   b  may be symmetrical to the structure formed by the right lead screw  840   a , the right slider  860   a , the right rod  870   a , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  52   , guides  850   a ,  850   b ,  850   c  and  850   d  may be connected to bearings  830   a ,  830   b ,  830   c  and  830   d . The guides  850   a ,  850   b ,  850   c  and  850   d  may include right guides  850   a  and  850   b  disposed on the right side of the motor assembly  810  and left guides  850   c  and  850   d  disposed on the left side of the motor assembly  810 . 
     One sides of the right guides  850   a  and  850   b  may be connected to the first right bearing  830   a , and other sides of the right guides  850   a  and  850   b  may be connected to the second right bearing  830   b . The right guides  850   a  and  850   b  may be positioned parallel to the right lead screw  840   a . Alternatively, the right guides  850   a  and  850   b  may be spaced apart from the right lead screw  840   a.    
     The right guides  850   a  and  850   b  may include a first right guide  850   a  and a second right guide  850   b . The first right guide  850   a  and the second right guide  850   b  may be spaced apart from each other. The right lead screw  840   a  may be positioned between the first right guide  850   a  and the second right guide  850   b.    
     The right slider  860   a  may include a protrusion. Alternatively, the display device may include a protrusion formed in the right slider  860   a . The protrusion may be formed on the body of the slider. The protrusion may include a front protrusion (not shown) that protrudes from the body  861   a  of the right slider  860   a  in the +z-axis direction, and a rear protrusion  865   a  that protrudes from the body of the slider in the −z-axis direction. 
     The first right guide  850   a  may pass through the rear protrusion  865   a . Alternatively, a first hole  863   a  may be formed in the rear protrusion  865   a , and the first right guide  850   a  may pass through the first hole  863   a . The first hole  863   a  may be formed in the x-axis direction. The first hole  863   a  may be referred to as a hole  863   a.    
     The second right guide  850   b  may pass through the front protrusion (not shown). Alternatively, a second hole (not shown) may be formed in the front protrusion (not shown), and the second right guide  850   b  may pass through the second hole. The second hole may be formed in the x-axis direction. 
     The right guides  850   a  and  850   b  may guide the right slider  860   a  to move more stably when the right slider  860   a  moves back and forth along the right lead screw  840   a . Since the right guides  850   a  and  850   b  stably guide the right slider  860   a , the right slider  860   a  does not rotate about the right lead screw  840   a  and may move back and forth along the right lead screw  840   a.    
     A structure formed by the left guides  850   c  and  850   d , the left bearings  830   a ,  830   b ,  830   c  and  830   d , the left slider  860   b , and the left lead screw  840   b  may be symmetrical to the above-described structure formed by the right guides  850   a  and  850   b , the right bearings  830   a ,  830   b ,  830   c  and  830   d , the right slider  860   a , and the right lead screw  840   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  53   , first springs  841   a  and  841   b  may be inserted into the lead screws  840   a  and  840   b . Alternatively, the lead screws  840   a  and  840   b  may pass through the first springs  841   a  and  841   b . The first springs  841   a  and  841   b  may include a first right spring  841   a  disposed on the right side of the motor assembly  810  and a first left spring  841   b  disposed on the left side of the motor assembly  810 . 
     The first right spring  841   a  may be disposed between the right slider  860   a  and the second right bearing  830   b . One end of the first right spring  841   a  may contact or be separated from the right slider  860   a , and other end of the first right spring  841   a  may contact or be separated from the second right bearing  830   b.    
     When the second arm  912   a  lies completely on the base  31 , a distance between the right slider  860   a  and the second right bearing  830   b  may be denoted as RD 3 . The first right spring  841   a  may have a length greater than the distance RD 3  in a non-compressed or non-tensioned state. Thus, when the second arm  912   a  lies completely on the base  31 , the first right spring  841   a  may be compressed between the right slider  860   a  and the second right bearing  830   b . Further, the first right spring  841   a  may provide a restoring force of the +x-axis direction to the right slider  860   a.    
     When the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the restoring force provided by the first right spring  841   a  may assist the second arm  912   a  to stand up. The first right spring  841   a  assists the second arm  912   a  to stand up, and thus the load of the motor assembly  810  can be reduced. 
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , a load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, the first right spring  841   a  can assist the second arm  912   a  to stand up, thereby reducing the load of the motor assembly  810  and reducing the load on the motor assembly  810  in order to stand up the second arm  912   a.    
     Alternatively, when the second arm  912   a  changes from a state of standing up with respect to the base  31  to a state of lying completely on the base  31 , the restoring force provided by the first right spring  841   a  can alleviate an impact generated when the second arm  912   a  lies on the base  31 . That is, the first right spring  841   a  may serve as a damper when the second arm  912   a  lies on the base  31 . The first right spring  841   a  serves as the damper, and thus the load of the motor assembly  810  can be reduced. 
     A structure formed by the first left spring  841   b , the left bearings  830   a ,  830   b ,  830   c  and  830   d , the left slider  860   b , the left lead screw  840   b , and the second arm  912   a  may be symmetrical to the above-described structure formed by the first right spring  841   a , the right bearings  830   a ,  830   b ,  830   c  and  830   d , the right slider  860   a , the right lead screw  840   a , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  54   , second springs  851   a  and  851   b  may be inserted into the guides  850   a ,  850   b ,  850   c  and  850   d . Alternatively, the guides  850   a ,  850   b ,  850   c  and  850   d  may pass through the second springs  851   a  and  851   b . The second springs  851   a  and  851   b  may include a second right spring  851   a  disposed on the right side of the motor assembly  810  and a second left spring  851   b  disposed on the left side of the motor assembly  810 . 
     The second right spring  851   a  may be provided as a plurality of springs. The second right spring  851   a  may include springs  940   a  and  940   b  inserted into the first right guide  850   a  and springs  940   a  and  940   b  inserted into the second right guide  850   b . Alternatively, the second right spring  851   a  may include springs  940   a  and  940   b  through which the first right guide  850   a  passes, and springs  940   a  and  940   b  through which the second right guide  850   b  passes. 
     The guides  850   a ,  850   b ,  850   c  and  850   d  may include locking jaws  852   a  and  852   b . The locking jaws  852   a  and  852   b  may include a right locking jaw  852   a  disposed on the right side of the motor assembly  810  and a left locking jaw  852   b  disposed on the left side of the motor assembly  810 . 
     The right locking jaw  852   a  may be disposed between the right slider  860   a  and the second right bearing  830   b . The second right spring  851   a  may be disposed between the right slider  860   a  and the second right bearing  830   b . One end of the second right spring  851   a  may contact or be separated from the right slider  860   a , and other end of the second right spring  851   a  may contact or be separated from the right locking jaw  852   a.    
     When the second arm  912   a  lies completely on the base  31 , a distance between the right slider  860   a  and the right locking jaw  852   a  may be denoted as RD 4 . The second right spring  851   a  may have a length greater than the distance RD 4  in a non-compressed or non-tensioned state. Thus, when the second arm  912   a  lies completely on the base  31 , the second right spring  851   a  may be compressed between the right slider  860   a  and the right locking jaw  852   a . Further, the second right spring  851   a  may provide a restoring force of the +x-axis direction to the right slider  860   a.    
     When the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the restoring force provided by the second right spring  851   a  may assist the second arm  912   a  to stand up. The second right spring  851   a  assists the second arm  912   a  to stand up, and thus the load of the motor assembly  810  can be reduced. 
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , a load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, the second right spring  851   a  assists the second arm  912   a  to stand up and thus can reduce the load of the motor assembly  810  and reduce the load on the motor assembly  810  in order to stand up the second arm  912   a.    
     Alternatively, when the second arm  912   a  changes from a state of standing up with respect to the base  31  to a state of lying completely on the base  31 , the restoring force provided by the second right spring  851   a  can alleviate an impact generated when the second arm  912   a  lies on the base  31 . That is, the second right spring  851   a  may serve as a damper when the second arm  912   a  lies on the base  31 . The second right spring  851   a  serves as the damper, and thus the load of the motor assembly  810  can be reduced. 
     A structure formed by the second left spring  851   b , the left locking jaw  852   b , the left slider  860   b , the left guides  850   c  and  850   d , and the second arm  912   a  may be symmetrical to the above-described structure formed by the second right spring  851   a , the right locking jaw  852   a , the right slider  860   a , the right guides  850   a  and  850   b , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIGS.  55  to  57   , the second arm  912   a  may receive the restoring force from the first right spring  841   a  and the second right spring  851   a  and may stand up. 
     An angle formed by the second arm  912   a  and the base  31  may be denoted as θS. An angle formed by the right rod  870   a  and the base  31  may be denoted as θT. A force required for the motor assembly  810  to move the right slider  860   a  in the +x-axis direction may be denoted as FA. A force that the first right spring  841   a  applies to the right slider  860   a  may be denoted as FB. A force that the second right spring  851   a  applies to the right slider  860   a  may be denoted as FC. A force that the right rod  870   a  transfers to the second arm  912   a  may be denoted as FT. 
     When the second arm  912   a  lies completely on the base  31 , the angles θS and θT may have a minimum value. When the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the angles θS and θT may gradually increase. 
     When the second arm  912   a  lies completely on the base  31 , the first right spring  841   a  may be compressed. The compressed first right spring  841   a  may provide a restoring force FB to the right slider  860   a . The restoring force FB may act in the +x-axis direction. When the second arm  912   a  lies completely on the base  31 , a compression displacement amount of the first right spring  841   a  may have a maximum value, and a magnitude of the restoring force FB may have a maximum value. When the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the compression displacement amount of the first right spring  841   a  may gradually decrease, and the magnitude of the restoring force FB may gradually decrease. 
     When the second arm  912   a  lies completely on the base  31 , the second right spring  851   a  may be compressed. The compressed second right spring  851   a  may provide a restoring force FC to the right slider  860   a . The restoring force FC may act in the +x-axis direction. When the second arm  912   a  lies completely on the base  31 , a compression displacement amount of the second right spring  851   a  may have a maximum value, and a magnitude of the restoring force FC may have a maximum value. When the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the compression displacement amount of the second right spring  851   a  may gradually decrease, and the magnitude of the restoring force FC may gradually decrease. 
     The force FT that the right rod  870   a  transfers to the second arm  912   a  may be a sum of the force FA required for the motor assembly  810  to move the right slider  860   a  in the +x-axis direction, the restoring force FB of the first right spring  841   a , and the restoring force FC of the second right spring  851   a.    
     When the second arm  912   a  starts to stand up with respect to the base  31  in the state of lying completely on the base  31 , the load of the motor assembly  810  may be a maximum load. In this instance, the restoring force FB provided by the first right spring  841   a  may have a maximum magnitude, and the restoring force FC provided by the second springs  851   a  and  851   b  may have a maximum magnitude. 
     When the second arm  912   a  changes from the state of lying completely on the base  31  to the state of standing up with respect to the base  31 , the restoring forces provided by the first right spring  841   a  and the second right spring  851   a  may assist the second arm  912   a  to stand up. The first right spring  841   a  and the second right spring  851   a  assist the second arm  912   a  to stand up, and thus the load of the motor assembly  810  can be reduced. 
     The first right spring  841   a  and the second right spring  851   a  may simultaneously provide a restoring force (a sum of the restoring force FB and the restoring force FC) to the right slider  860   a . The restoring force (a sum of the restoring force FB and the restoring force FC) may be provided to the right slider  860   a  until a distance RD 5  between the right slider  860   a  and the right locking jaw  852   a  is equal to a length of the second right spring  851   a.    
     When the distance RD 5  between the right slider  860   a  and the right locking jaw  852   a  is equal to the length of the second right spring  851   a , the compression displacement amount of the second right spring  851   a  may be zero. When the compression displacement amount of the second right spring  851   a  is zero, the restoring force FC that the second right spring  851   a  provides to the right slider  860   a  may be zero. 
     When the distance RD 5  between the right slider  860   a  and the right locking jaw  852   a  is greater than the length of the second right spring  851   a , only the first right spring  841   a  may provide the restoring force FB to the right slider  860   a . The restoring force FB may be provided to the right slider  860   a  until a distance RD 6  between the right slider  860   a  and the second right bearing  830   b  is equal to a length of the first right spring  841   a.    
     When the distance RD 6  between the right slider  860   a  and the second right bearing  830   b  is equal to the length of the first right spring  841   a , the compression displacement amount of the first right spring  841   a  may be zero. When the compression displacement amount of the first right spring  841   a  is zero, the restoring force FB that the first right spring  841   a  provides to the right slider  860   a  may be zero. 
     When the distance RD 6  between the right slider  860   a  and the second right bearing  830   b  is greater than the length of the first right spring  841   a , the motor assembly  810  does not receive the restoring force from the first right spring  841   a  or the second right spring  851   a  and can stand up the second arm  912   a.    
     A structure formed by the first left spring  841   b , the second left spring  851   b , the left locking jaw  852   b , the left slider  860   b , the left guides  850   c  and  850   d , the left lead screw  840   b , the left rod  870   b , and the second arm  912   a  may be symmetrical to the above-described structure formed by the first right spring  841   a , the second right spring  851   a , the right locking jaw  852   a , the right slider  860   a , the right guides  850   a  and  850   b , the right lead screw  840   a , the right rod  870   a , and the second arm  912   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIG.  58   , pushers  930   a  and  930   b  may be connected to the link mounts  920   a  and  920   b . The pushers  930   a  and  930   b  may include a right pusher  930   a  disposed on the right side of the motor assembly  810  and a left pusher  930   b  disposed on the left side of the motor assembly  810 . 
     The link mounts  920   a  and  920   b  may form an accommodation space A. The accommodation space A may accommodate the springs  940   a  and  940   b  and the pushers  930   a  and  930   b . The springs  940   a  and  940   b  may include a right spring  940   a  disposed on the right side of the motor assembly  810  and a left spring  940   b  disposed on the left side of the motor assembly  810 . The accommodation space A may be referred to an inner space A. 
     The link mounts  920   a  and  920   b  may include a first hole  922   a  connecting the accommodation space A and an outer space (first hole corresponding to the link mount  920   b  is not shown). The first hole  922   a  may be formed in the upper surfaces of the link mounts  920   a  and  920   b . The first hole  922   a  may be referred to as a hole  922   a.    
     The pushers  930   a  and  930   b  may be positioned perpendicular to the base  31 . Alternatively, the pushers  930   a  and  930   b  may be disposed parallel to the y-axis. The springs  940   a  and  940   b  may be positioned perpendicular to the base  31 . Alternatively, the springs  940   a  and  940   b  may be disposed parallel to the y-axis. 
     The pushers  930   a  and  930   b  may include first parts  931   a  and  931   b  and second parts  932   a  and  932   b . The second parts  932   a  and  932   b  may be connected to lower sides of the first parts  931   a  and  931   b . Lower ends of the second parts  932   a  and  932   b  may be connected to the springs  940   a  and  940   b . The second parts  932   a  and  932   b  may be entirely or partially accommodated in the accommodation space A formed by the link mounts  920   a  and  920   b . The second parts  932   a  and  932   b  may have a diameter equal to a diameter of the first hole  922   a  or a diameter less than the diameter of the first hole  922   a . The second parts  932   a  and  932   b  may pass through the first hole  922   a.    
     The first parts  931   a  and  931   b  may be positioned outside the link mounts  920   a  and  920   b . Alternatively, the first parts  931   a  and  931   b  may be positioned outside the accommodation space A of the link mounts  920   a  and  920   b . The first parts  931   a  and  931   b  may have a diameter greater than the diameter of the first hole  922   a.    
     The first parts  931   a  and  931   b  may contact or be separated from the link brackets  951   a  and  951   b . For example, when the second arms  912   a  and  912   b  lie completely on the base  31 , the first parts  931   a  and  931   b  may contact the link brackets  951   a  and  951   b . Alternatively, when the second arms  912   a  and  912   b  completely stand up with respect to the base  31 , the first parts  931   a  and  931   b  may be spaced apart from the link brackets  951   a  and  951   b.    
     When the first parts  931   a  and  931   b  contact the link brackets  951   a  and  951   b , the pushers  930   a  and  930   b  may receive a force from the link brackets  951   a  and  951   b . The force received by the pushers  930   a  and  930   b  may be in a downward direction. Alternatively, the force received by the pushers  930   a  and  930   b  may be in the −y-axis direction. Alternatively, the link brackets  951   a  and  951   b  may pressurize the pushers  930   a  and  930   b . A direction in which the link brackets  951   a  and  951   b  pressurize the pushers  930   a  and  930   b  may be a downward direction. Alternatively, a direction in which the link brackets  951   a  and  951   b  pressurize the pushers  930   a  and  930   b  may be the −y-axis direction. 
     When the first parts  931   a  and  931   b  receive a force, the springs  940   a  and  940   b  may be compressed. The compressed springs  940   a  and  940   b  may provide a restoring force to the pushers  930   a  and  930   b . The restoring force may be in a direction opposite to a direction of the force applied to the first parts  931   a  and  931   b . Alternatively, the restoring force may act in the +y-axis direction. 
     The link mounts  920   a  and  920   b  may include a second hole  921   a  (second hole corresponding to the link mount  920   b  is not shown). The second hole  921   a  may communicate the accommodation space A with an outer space. The springs  940   a  and  940   b  may be entirely or partially exposed to the outside through the second hole  921   a . The pushers  930   a  and  930   b  may be entirely or partially exposed to the outside through the second hole  921   a . During maintenance or repair of the display device, a service provider may check operation states of the pushers  930   a  and  930   b  through the second hole  921   a . The second hole  921   a  may provide the convenience of maintenance or repair to the service provider. 
     Referring to  FIGS.  59  to  61   , the right link  910   a  may receive a restoring force from the right pusher  930   a  and stand up. The following description is given based on the right link  910   a.    
     An angle formed by the second arm  912   a  and the base  31  may be denoted as θS. A force that the right rod  870   a  transfers to the second arm  912   a  may be denoted as FT. A force that the right pusher  930   a  transfers to the right link bracket  951   a  may be denoted as FP. 
     Referring to  FIG.  59   , when the second arm  912   a  lies completely on the base  31 , the angle θS may have a minimum value. The right spring  940   a  connected to the right pusher  930   a  may be compressed to the maximum, and a magnitude of the restoring force FP may have a maximum value. The compressed right spring  940   a  may provide the restoring force FP to the right pusher  930   a . The right pusher  930   a  may transfer the restoring force FP to the right link bracket  951   a . The restoring force FP may act in the +y-axis direction. 
     When the second arm  912   a  lies completely on the base  31 , a distance HL from the base  31  to an upper end of the right pusher  930   a  may have a minimum value. The first part  931   a  of the right pusher  930   a  may protrude to the outside of the right link mount  920   a , and the second part  932   a  of the right pusher  930   a  may be entirely accommodated in an accommodation space  923   a  of the right link mount  920   a.    
     Referring to  FIG.  60   , when the second arm  912   a  changes from a state of lying completely on the base  31  to a state of standing up with respect to the base  31 , the angle θS may gradually increase. In addition, a compression displacement amount of the right spring  940   a  may gradually decrease, and a magnitude of the restoring force FP may gradually decrease. 
     As the angle θS gradually increases, at least a portion of the second part  932   a  of the right pusher  930   a  may protrude to the outside of the right link mount  920   a . A length of the second part  932   a  of the right pusher  930   a  protruding to the outside of the right link mount  920   a  may be denoted as HP. The distance HL from the base  31  to the upper end of the right pusher  930   a  may be increased by HP, compared to when the second arm  912   a  lies completely on the base  31 . 
     Referring to  FIG.  61   , when the standing up of the second arm  912   a  with respect to the base  31  is performed, the right pusher  930   a  and the right link bracket  951   a  may be separated from each other. A compression displacement amount of the right spring  940   a  may be zero. When the compression displacement amount of the right spring  940   a  is zero, the restoring force FP that the right pusher  930   a  provides to the right link bracket  951   a  may be zero. 
     Further, the length HP of the second part  932   a  of the right pusher  930   a  protruding to the outside of the right link mount  920   a  may have a maximum value. The distance HL from the base  31  to the upper end of the right pusher  930   a  may have a maximum value. 
     That is, the right pusher  930   a  applies the restoring force to the right link bracket  951   a  while contacting the right link bracket  951   a , and thus can assist the second arm  912   a  to stand up and reduce the load of the motor assembly  810 . 
     The lead screws  840   a  and  840   b  may be driven by one motor assembly  810 . The second arms  912   a  and  912   b  may stand up while being symmetrical to each other by driving the lead screws  840   a  and  840   b  by one motor assembly  810 . However, when the lead screws  840   a  and  840   b  are driven by one motor assembly  810 , the load on the motor assembly  810  may excessively increase to stand up the second arms  912   a  and  912   b . In this instance, the right pusher  930   a  applies the restoring force to the right link bracket  951   a  and thus can assist the second arm  912   a  to stand up and reduce the load of the motor assembly  810 . 
     Alternatively, when the second arm  912   a  changes from a state of standing up with respect to the base  31  to a state of lying completely on the base  31 , the restoring force that the right pusher  930   a  provides to the right link bracket  951   a  can alleviate an impact generated when the link  910   a  lies on the base  31 . That is, that the right pusher  930   a  providing the restoring force to the right link bracket  951   a  may serve as a damper when the link  910   a  lies on the base  31 . The right pusher  930   a  serves as the damper, and thus the load of the motor assembly  810  can be reduced. 
     A structure formed by the left pusher  930   b , the left spring  940   b , the left link bracket  951   b , the left link mount  920   b , and the left rod  870   b  may be symmetrical to the above-described structure formed by the right pusher  930   a , the right spring  940   a , the right link bracket  951   a , the right link mount  920   a , and the right rod  870   a . In this instance, a symmetry axis may be the symmetry axis ys of the motor assembly  810 . 
     Referring to  FIGS.  62  to  64   , the panel roller  143  may be installed on the base  31 . The panel roller  143  may be installed in front of the lead screws  840   a  and  840   b . Alternatively, the panel roller  143  may be disposed parallel to the longitudinal direction of the lead screws  840   a  and  840   b . Alternatively, the panel roller  143  may be spaced apart from the lead screws  840   a  and  840   b.    
     The display unit  20  may include the display panel  10  and the module cover  15 . The lower side of the display unit  20  may be connected to the panel roller  143 , and the upper side of the display unit  20  may be connected to the upper bar  75 . The display unit  20  may be rolled or unrolled from the panel roller  143 . 
     A distance from the symmetry axis ys of the motor assembly  810  to the right slider  860   a  may be denoted as RD. A distance from the symmetry axis ys of the motor assembly  810  to the left slider  860   b  may be denoted as LD. A distance between the right slider  860   a  and the left slider  860   b  may be denoted as SD. The distance SD may be a sum of the distance RD and the distance LD. A distance from the base  31  to the upper end of the display unit  20  may be denoted as HD. 
     Referring to  FIG.  62   , when the second arms  912   a  and  912   b  lie completely on the base  31 , the distance SD between the right slider  860   a  and the left slider  860   b  may have a minimum value. The distance RD from the symmetry axis ys of the motor assembly  810  to the right slider  860   a  and the distance LD from the symmetry axis ys of the motor assembly  810  to the left slider  860   b  may be equal to each other. 
     When the second arms  912   a  and  912   b  lie completely on the base  31 , the distance HD from the base  31  to the upper end of the display unit  20  may have a minimum value. 
     When the second arms  912   a  and  912   b  lie completely on the base  31 , the first springs  841   a  and  841   b  may contact the sliders  860   a  and  860   b . Further, the second springs  851   a  and  851   b  may contact the sliders  860   a  and  860   b , and the pushers  930   a  and  930   b  may contact the link brackets  951   a  and  951   b.    
     When the second arms  912   a  and  912   b  lie completely on the base  31 , an amount of compression of the first springs  841   a  and  841   b  may have a maximum value, and a magnitude of a restoring force that the first springs  841   a  and  841   b  provide to the sliders  860   a  and  860   b  may have a maximum value. 
     When the second arms  912   a  and  912   b  lie completely on the base  31 , an amount of compression of the second springs  851   a  and  851   b  may have a maximum value, and a magnitude of a restoring force that the second springs  851   a  and  851   b  provide to the sliders  860   a  and  860   b  may have a maximum value. 
     When the second arms  912   a  and  912   b  lie completely on the base  31 , an amount of compression of the springs  940   a  and  940   b  may have a maximum value, and a magnitude of a restoring force that the springs  940   a  and  940   b  provide to the pushers  930   a  and  930   b  may have a maximum value. 
     When the second arms  912   a  and  912   b  start to stand up with respect to the base  31 , the second arms  912   a  and  912   b  may receive the restoring force from the first springs  841   a  and  841   b , the second springs  851   a  and  851   b , and the springs  940   a  and  940   b  to stand up. Hence, a load on the motor assembly  810  can be reduced. 
     Referring to  FIG.  63   , as the standing up of the second arms  912   a  and  912   b  with respect to the base  31  is performed, the distance SD between the right slider  860   a  and the left slider  860   b  may gradually increase. Even if the distance SD increases, the distance RD and the distance LD can be equal to each other. That is, the right slider  860   a  and the left slider  860   b  may be positioned to be symmetrical to each other with respect to the symmetry axis ys of the motor assembly  810 . Further, a degree to which the second arms  912   a  and  912   b  of the right link  910   a  stand up with respect to the base  31  and a degree to which the second arms  912   a  and  912   b  of the left link  910   b  stand up with respect to the base  31  may be the same as each other. 
     As the standing up of the second arms  912   a  and  912   b  with respect to the base  31  is performed, the distance HD from the base  31  to the upper end of the display unit  20  may gradually increase. The display unit  20  may be unrolled from the panel roller  143 . Alternatively, the display unit  20  may be deployed from the panel roller  143 . 
     When the second arms  912   a  and  912   b  sufficiently stand up with respect to the base  31 , the first springs  841   a  and  841   b  may be separated from the sliders  860   a  and  860   b . Further, when the second arms  912   a  and  912   b  sufficiently stand up with respect to the base  31 , the second springs  851   a  and  851   b  may be separated from the sliders  860   a  and  860   b . Further, when the second arms  912   a  and  912   b  sufficiently stand up with respect to the base  31 , the pushers  930   a  and  930   b  may be separated from the link brackets  951   a  and  951   b.    
     The separation of the first springs  841   a  and  841   b  from the sliders  860   a  and  860   b , the separation of the second springs  851   a  and  851   b  from the sliders  860   a  and  860   b , and the separation of the pushers  930   a  and  930   b  from the link brackets  951   a  and  951   b  may be performed independently of each other. That is, the order of the separation of the first springs  841   a  and  841   b  from the sliders  860   a  and  860   b , the separation of the second springs  851   a  and  851   b  from the sliders  860   a  and  860   b , and the separation of the pushers  930   a  and  930   b  from the link brackets  951   a  and  951   b  may be mutually variable. 
     An angle formed by an axis xs 1  parallel to the base  31  and the second arm  912   a  may be denoted as θR, and an angle formed by the axis xs 1  parallel to the base  31  and the first arm  911   a  may be denoted as θR′. The axis xs 1  may be parallel to the x-axis. 
     When the second arm  912   a  lies completely on the base  31 , or while the second arm  912   a  stands up with respect to the base  31 , or when the standing up of the second arm  912   a  with respect to the base  31  is completed, the angle θR and the angle θR′ may be maintained to be the same. 
     An angle formed by an axis xs 2  parallel to the base  31  and the second arm  912   b  may be denoted as θL, and an angle formed by the axis xs 2  parallel to the base  31  and the first arm  911   b  may be denoted as θL′. The axis xs 2  may be parallel to the x-axis. 
     When the second arm  912   b  lies completely on the base  31 , or while the second arm  912   b  stands up with respect to the base  31 , or when the standing up of the second arm  912   b  with respect to the base  31  is completed, the angle θL and the angle θL′ may be maintained to be the same. 
     The axis xs 1  and the axis xs 2  may be the same axis. 
     Referring to  FIG.  64   , when the second arms  912   a  and  912   b  completely stand up with respect to the base  31 , the distance SD between the right slider  860   a  and the left slider  860   b  may have a maximum value. Even if the distance SD has the maximum value, the distance RD and the distance LD can be equal to each other. 
     When the second arms  912   a  and  912   b  completely stand up with respect to the base  31 , the distance HD from the base  31  to the upper end of the display unit  20  may have a maximum value. 
     Referring to  FIGS.  65  to  67   , the connection portion  914   a  of the second arm  912   a  may be pivotally connected to the right rod  870   a . The connection portion  914   a  of the second arm  912   a  may include a hole  914 H, and the right rod  870   a  may include a hole  870 H at a location corresponding to the hole  914 H of the connection portion  914   a . Diameters D 1 , D 2  and D 3  of the hole  914 H of the connection portion  914   a  of the second arm  912   a  may be greater than a diameter dl of the hole  870 H of the right rod  870   a.    
     A connection member C may be inserted into the hole  914 H of the connection portion  914   a  of the second arm  912   a  and the hole  870 H of the right rod  870   a . For example, the connection member C may be a pin. The connection member C may include a body CB and a head CH, and a diameter DH of the head CH may be greater than a diameter DB of the body CB. 
     The diameter D 1  of the hole  914 H corresponding to the head CH of the connection member C may be greater than the diameter D 2  of the hole  914 H corresponding to the body CB of the connection member C. The diameter DH of the head CH of the connection member C may be substantially equal to the diameter D 1  of the hole  914 H. A gap may be positioned between the body CB of the connection member C and the hole  914 H. For example, the gap may entirely have a ring shape. The diameter DB of the body CB of the connection member C may be substantially equal to the diameter dl of the hole  870 H of the right rod  870   a.    
     A fixing member CL may be inserted into a portion of the connection member C protruding to the outside of the right rod  870   a . For example, the fixing member CL may be a clip. 
     The connection member C to which the connection portion  914   a  of the second arm  912   a  and the right rod  870   a  are pivotally connected may be subjected to a high load during a pivot drive. In addition, the connection portion  914   a  of the second arm  912   a  and the right rod  870   a  may be made of different kinds of materials. Hence, abrasion of the material or noise may occur when the connection portion  914   a  of the second arm  912   a  and the right rod  870   a  are pivotally driven. 
     An intermediate member  1000  may surround an outer diameter of the body CB of the connection member C. The intermediate member  1000  may have a ring shape, and the body CB of the connection member C may be inserted into the intermediate member  1000 . An inner diameter of the intermediate member  1000  may be substantially equal to or greater than the outer diameter of the body CB of the connection member C, and an outer diameter of the intermediate member  1000  may be substantially equal to or less than the diameter D 2  of the hole  914 H. The intermediate member  1000  may include a flange  1001 . The flange  1001  of the intermediate member  1000  may be positioned between the connection portion  914   a  of the second arm  912   a  and the right rod  870   a . The intermediate member  1000  may include a groove  1003  at its outer diameter. The groove  1003  of the intermediate member  1000  may have a ring shape formed by recessing an outer surface of the intermediate member  1000 . A lubricant may be accommodated in the groove  1003  of the intermediate member  1000 . Hence, the lubricant may not require intermediate refueling. 
     Accordingly, the present disclosure can reduce and prevent abrasion of the material or noise generated when the connection portion  914   a  of the second arm  912   a  and the right rod  870   a  are pivotally driven. 
     Referring to  FIGS.  68  to  70   , the cover  872   a  of the right rod  870   a  may be pivotally connected to the slider  860   a . The first plate  873   a  of the cover  872   a  may be pivotally connected to the first rod mount  862   a   1  of the slider  860   a , and the second plate  874   a  of the cover  872   a  may be pivotally connected to the second rod mount  862   a   2  of the slider  860   a.    
     A connection member C 1 ′ may be inserted into a pivot connection portion of the first plate  873   a  of the cover  872   a  and the first rod mount  862   a   1  of the slider  860   a . A connection member C 1  may be inserted into a pivot connection portion of the second plate  874   a  of the cover  872   a  and the second rod mount  862   a   2  of the slider  860   a.    
     The connection members C 1  and C 1 ′ may be subjected to a high load during a pivot drive. In addition, the first plate  873   a  of the cover  872   a  and the first rod mount  862   a   1  of the slider  860   a  may be made of different kinds of materials. Further, the second plate  874   a  of the cover  872   a  and the second rod mount  862   a   2  of the slider  860   a  may be made of different kinds of materials. Hence, abrasion or noise may occur in the pivot connection portion or the connection members C 1  and C 1 ′ during the pivot drive. 
     The connection member C 1  may include a body C 1   b  and a head C 1   h . A diameter Dh of the head C 1   h  may be greater than a diameter Db of the body C 1   b . A diameter D 11  of a hole  874 H of the second plate  874   a  of the cover  872   a  may be slightly greater than or substantially equal to the diameter Db of the body C 1   b  of the connection member C 1 . A diameter D 22  of a hole  862 H of the second rod mount  862   a   2  may be greater than the diameter Db of the body C 1   b  of the connection member C 1 . A gap may be formed between the body C 1   b  of the connection member C 1  and the hole  862 H of the second rod mount  862   a   2 . The gap may have entirely a ring-shape. 
     An intermediate member  1000  may be inserted into the gap between the second rod mount  862   a   2  and the body C 1   b  of the connection member C 1 . The intermediate member  1000  may entirely have a ring shape. An inner diameter of the intermediate member  1000  may be slightly greater than or substantially equal to an outer diameter of the body C 1   b  of the connection member C 1 . An outer diameter of the intermediate member  1000  may be slightly less than or substantially equal to an inner diameter of the hole  862 H of the second rod mount  862   a   2 . 
     The intermediate member  1000  may include a flange  1005 . The flange  1005  of the intermediate member  1000  may be inserted into the second rod mount  862   a   2 . An outer diameter of the flange  1005  may be slightly less than or substantially equal to the diameter of the hole  862 H of the second rod mount  862   a   2 . 
     A fixing member CL may be inserted into a portion of the connection member C 1  protruding to the outside. For example, the fixing member CL may be a clip. 
     The intermediate member  1000  may include a groove  1007  at its outer diameter. The groove  1007  of the intermediate member  1000  may have a ring shape formed by recessing an outer surface of the intermediate member  1000 . A lubricant may be accommodated in the groove  1007  of the intermediate member  1000 . Hence, the lubricant may not require intermediate refueling. 
     Accordingly, the present disclosure can reduce and prevent abrasion of the material or noise generated when the rod mounts  862   a   1  and  862   a   2  of the slider  860   a  and the plates  873   a  and  874   a  of the cover  872   a  are pivotally driven. 
     Embodiments of the disclosure described above are not mutually exclusive or distinct from each other. Configurations or functions of embodiments of the disclosure described above may be used together or combined with each other. 
     Embodiments of the disclosure described and illustrated the structure of the display device in which the display unit is rolled up from the inside of the housing, but are not limited thereto. Embodiments of the disclosure can be applied to a structure of the display device in which the display unit is rolled down from the inside of the housing. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope of the principles of the 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.