Patent Publication Number: US-2023164248-A1

Title: Flexible display device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a portable device including a flexible display, in which the overall size of the device is variable while two bodies of the device slide relative to each other. 
     BACKGROUND ART 
     T With the development of a flexible display that is bendable while displaying image information, research and development has come to be conducted on a foldable-type device in which a flexible display is applied to a device having two bodies and a folding structure (e.g., a hinge). In this device, since the flexible display may be disposed over both of the two bodies across the folding structure, a large-screen display may be implemented in the device. 
     As another device using a flexible display, development and research has come to be conducted on a rollable type device having a structure in which a display is wound. In this device, when the flexible device is rolled, the size or area of the entire display may decrease, and when the flexible display is unrolled, the size or area of the entire display may increase. 
     Another device using a flexible display has been introduced in which, when two bodies slide relative to each other, the flexible display that forms a U-shape by being bent in the middle portion is deformable, so that the area of the display visible from one side is variable. 
     As a document of prior art using a flexible display related thereto, Korean Patent Registration No. 1107127 (hereinafter, “prior art document”) discloses a mobile terminal which includes a terminal body, a sliding member, a flexible display, and a rotating shaft. 
     The mobile terminal according to the prior art document is configured such that a sliding member is in surface contact with the terminal body in a state in which the sliding member is not drawn out from the terminal body. While the sliding member is drawn out from the terminal body, both the terminal body and the sliding member move relative to each other while maintaining surface contact, and when the drawing-out is completed, a display having a relatively large screen is provided. 
     In a device in which a flexible display is transformed while two bodies (in the case of the prior art document, the terminal body and the sliding member) move relative to each other, it is necessary for the two bodies to stably operate while minimizing the frictional force generated therebetween for easy operation. 
     Smartphones, which occupy a significant market proportion among mobile phones, are configured to have various functions. For this purpose, the smartphones include a battery, various sensors including a touch sensor, cameras, and the like. Recently, various smartphones including a flexible display have also been introduced. 
     Accordingly, in the device in which the flexible display is transformed while two bodies move relative to each other, it is required to develop a device capable of securing a space in which various components are accommodated while having a configuration necessary for the relative movement of the two bodies. 
     A flexible display device may be stored for a relatively long period of time in a state in which the middle portion of a flexible display forms a U-shape. In this case, when the flexible display device is transformed, the middle portion of the flexible display forming the U-shape may not be completely flattened, and the flat portion of the flexible display may not form a complete U-shape. These phenomena may occur due to plastic deformation and springback, which occur in a portion of the flexible display, and/or elasticity of the flexible display. 
     Therefore, even in consideration of these properties according to the transformation of the flexible display, there is a need to develop a flexible display device that ensures stable and accurate operation. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     One problem to be solved by the present disclosure is to provide a flexible display device in which, when a flexible display is transformed while two bodies move relative to each other, point contact is made at the portion where a relative movement occurs so that a frictional force generated during the movement can be reduced and a movement in an unintended direction can be prevented. 
     Another problem to be solved by the present disclosure is to provide a flexible display device in which a flexible display is transformed while the two bodies move relative to each other, in which, while a structure configured to guide the relative movement of two bodies is provided in a rim side of the device, the exposure of the structure to the outside of the device can be minimized. 
     Still another problem to be solved by the present disclosure is to provide a flexible display device in which a flexible display is transformed while two bodies move relative to each other, in which each body can be accurately placed at an intended position. 
     Solution to Problem 
     A flexible display device according to an exemplary embodiment of the present disclosure is configured to be carried and held by a user. 
     The flexible display device includes a first body, a second body, and a flexible display. 
     The second body is configured to reciprocate between a first position and a second position in a first direction relative to the first body. The first position is a relative position of the second body relative to the first body, and the second position is also a relative position of the second body with respect to the first body. 
     When the second body is located at the first position relative to the first body, the state of the flexible display device corresponds to a first state, and when the second body is located at the second position relative to the first body, the state of the flexible display device correspond to a second state. Accordingly, in the description of the present disclosure, the term “first position” may be used in the same meaning as the “first state of the flexible display device”, and the term “second position” may have the same meaning as the “second state of the flexible display device”. 
     The second body may be provided with a support. 
     The support may form a curved surface around a center line of curvature parallel to a second direction orthogonal to the first direction. 
     The flexible display may include a first region and a second region. 
     A portion of the second region is bent in a semicircular shape, and the bent position of the second region is changed according to the movement of the second body. 
     The second region may include a first connection region and a second connection region. 
     The first region may be fixed in front of the first body and directed forward. The first region may configure the front surface of the flexible display device. The first region may be provided as a flat surface. 
     The first connection region extends from the first region. 
     The second connection region extends from the first connection region. 
     At the first position, the first connection region may be bent to form a curved surface, and the second connection region may be provided to be parallel to the first region. 
     At the first position, the first connection region may be placed on the support to form a curved surface. 
     At the second position, the first connection region is coplanar with the first region, and a portion of the second connection region is bent to form a curved surface. 
     At the second position, a portion of the second connection region may be placed on the support to form a curved surface. 
     The flexible display device includes a plurality of rolling balls and at least one rolling recess. 
     When the rolling balls are coupled to the first body, the rolling recess is provided in the second body, and when the rolling balls are coupled to the second body, the rolling recess is provided in the first body. 
     That is, the rolling balls are coupled to one of the first body and the second body, and the rolling recess is provided in the other one of the first body and the second body. 
     The plurality of the rolling balls are spaced apart from each other and arranged in the first direction. Each of the rolling balls may be rotatably coupled to the first body or the second body. 
     The rolling recess is elongated in the first direction and is provided in the form of concave grooves with a constant cross section in the first direction. The rolling balls are in contact with the rolling recess, and in this state, the rolling balls and the rolling recess move relative to each other. 
     The rolling balls may move relative to the rolling recess while rolling in contact with the rolling recess. 
     The rolling balls and the rolling recess may be combined with each other, and may be respectively provided on opposite sides of the flexible display device. 
     The first body may include inner edges. The rolling recess may be provided in the inner edges. 
     The inner edges include a first inner edge and a second inner edge. The first inner edge and the second inner edge may configure opposite rims of the first body and may be elongated in the first direction. 
     Of the rolling recesses, a first rolling recess is provided in the first inner edge. 
     Of the rolling recesses, a second rolling recess opposite to the first rolling edge is provided in the second inner edge. 
     The second body may include outer edges. The outer edges may be located outside the inner edges, respectively, and the rolling balls may be coupled to the outer edges. 
     The outer edges include a first outer edge and a second outer edge. The first outer edge and the second outer edge may configure opposite rims of the second body and may be elongated in the first direction. 
     The first outer edge may be located outside the first inner edge, and among the rolling balls, first rolling balls moving along the first rolling recess may be coupled to the first outer edge. 
     The second outer edge may be located outside the second inner edge, and among the rolling balls, second rolling balls moving along the second rolling recess may be coupled to the second outer edge. 
     The flexible display device may include a first support frame and a second support frame. 
     The first support frame is located between and spaced apart from an outer surface of the first inner edge and an inner surface of the first outer edge, and is fixed to the second body. First holes, which have a diameter smaller than the diameter of the first rolling balls, and into which the first rolling balls are fitted to protrude therefrom, respectively, are repeatedly provided in the first support frame in the first direction. 
     The second support frame is located between and spaced apart from an outer surface of the second inner edge and an inner surface of the second outer edge, and is fixed to the second body. Second holes, which have a diameter smaller than the diameter of the second rolling balls, and into which the second rolling balls are fitted to protrude therefrom, respectively, are repeatedly provided in the second support frame in the first direction. 
     The first rolling recess may be configured to be in point contact with the first rolling balls. The first rolling recess may be configured in the form of a curved or angled groove. 
     The second rolling recess may be configured to be in point contact with the second rolling balls. The second rolling recess may be configured in the form of a curved or angled groove. 
     Concave first support grooves may be provided on an inner surface of the first outer edge. 
     The first support grooves may be configured to be in point contact with the first rolling balls, respectively. The first support grooves may be provided in the form of a curved or angled groove. 
     Concave second support grooves may be provided on an inner surface of the second outer edge. The second support grooves may be configured to be in point contact with the second rolling balls, respectively. The second support grooves may be provided in the form of a curved or angled groove. 
     The second body may include a first rear guide groove, a first front guide groove, a first connection guide groove, a second rear guide groove, a second front guide groove, and a second connection guide groove. 
     The first rear guide groove provides a space inside the first outer edge, wherein the first rear guide may have a constant cross section in the first direction and may open inward from the rear side of the first outer edge. 
     The first front guide groove provides a space inside the first outer edge, wherein the first front guide groove may have a constant cross section in the first direction and may open inward from the front side of the first outer edge. The first front guide groove may be symmetric to the first rear guide groove. 
     The first connection guide groove may be provided to interconnect the first rear guide groove and the first front guide groove while providing a semicircular space inside the second body. 
     The second rear guide groove provides a space inside the second outer edge, wherein the second rear guide groove may have a constant cross section in the first direction and may open inward from the rear side of the second outer edge. 
     The second front guide groove provides a space inside the second outer edge, wherein the second front guide may have a constant cross section in the first direction and may open inward from the front side of the second outer edge. The second front guide groove may be symmetric to the second rear guide groove. 
     The second connection guide groove may be provided to interconnect the second rear guide groove and the second front guide groove while providing a semicircular space inside the second body. 
     The flexible display device may include a plurality of support bars. 
     Each of the support bars is configured to support the first connection region or the second connection region from the inside, and the plurality of the support bars are sequentially arranged along the first connection region and the second connection region. 
     Each support bar may include a first support slider, a second support slider, and a connection arm. 
     The first support slider is inserted into and moved in the first rear guide groove, the first connection guide groove, and the first front guide groove. 
     The second support slider is inserted into and moved in the second rear guide groove, the second connection guide groove, and the second front guide groove. 
     The connection arm interconnects the first support slider and the second support slider, supports the inner surface of the flexible display, and helps the first connection region and the second connection region to maintain a stable flat or curved state. 
     The first body may include a support plate. The support plate is configured to support the first region from the inside. The support plate may be flat, and may have the same size as the first region. 
     The front surface of the connection arm and the front surface of the support plate may be coplanar with each other. 
     One of the first body and the second body may be provided with a first magnet and a second magnet, and the other may be provided with a first stopper. 
     The first magnet and the second magnet are spaced apart from each other in the first direction. 
     The first stopper is configured to be in contact with or approach the first magnet at the first position so that an attractive force acts between the first stopper and the first magnet, and to be in contact with or approaches at the second position so that an attractive force acts between the first stopper and the second magnet. 
     The first magnet and the second magnet may be coupled to the inner edges, may be located to be spaced apart from each other and to be respectively adjacent to opposite ends of the rolling recess. 
     The first stopper may be coupled to the outer edge. 
     The rolling recess, the first magnet, and the second magnet may be formed on the same line along the first direction. 
     The first stopper may have a spherical shape and may be configured to be inserted into the rolling recess to move along the rolling recess. 
     The first magnet and the second magnet, which are spaced apart from each other, may be coupled to one of the first inner edge and the first outer edge, and the other of the first inner edge and the first outer edge may be provided with a first stopper configured such that, depending on the movement of the second body, an attractive force acts between the first magnet and the first stopper or between the second magnet and the first stopper. 
     The third magnet and the fourth magnet, which are spaced apart from each other, may be coupled to one of the second inner edge and the second outer edge, and the other of the second inner edge and the second outer edge may be provided with a second stopper configured such that, depending on the movement of the second body, an attractive force acts between the third magnet and the second stopper or between the fourth magnet and the stopper. 
     Each of the first magnet, the second magnet, and the first stopper may be symmetric with each of the third magnet, the fourth magnet, and the second stopper. 
     A stopping ball may be coupled to one of the first body and the second body, and a plurality of Hall sensors configured to detect the stopping ball may be arranged on the other of the first body and the second body in the first direction. 
     The flexible display device may include a controller configured to control the flexible display according to position information of the stopping ball detected by the Hall sensors. 
     One of the first body and the second body is provided with a first stopping groove and a second stopping groove, and a ball plunger may be coupled to the other of the first body and the second body. 
     The first stopping groove and the second stopping groove have a concave groove shape. 
     The ball plunger includes a stopping ball. The stopping ball of the ball plunger is inserted into the first stopping groove at the first position and inserted into the second stopping groove at the second position. 
     The first stopping groove and the second stopping groove may be provided on the inner edge, and may be spaced apart from each other and respectively provided adjacent to opposite ends of the rolling recess. 
     The ball plunger may be coupled to the outer edge. 
     The ball plunger may include a stopping ball, a cylinder in which the stopping ball is accommodated to protrude, and a spring accommodated in the cylinder to elastically support the stopping ball. 
     One of the first inner edge and the first outer edge may be provided with a first stopping groove and a second stopping groove in the form of a concave groove to be spaced apart from each other, and a first ball plunger including a first stopping ball configured to be inserted into the first stopping groove or the second stopping groove depending on the movement of the second body may be coupled to the other of the first inner edge and the first outer edge. 
     One of the second inner edge and the second outer edge may be provided with a third stopping groove and a fourth stopping groove in the form of a concave groove to be spaced apart from each other, and a second ball plunger including a second stopping ball configured to be inserted into the third stopping groove or the fourth stopping groove depending on the movement of the second body may be coupled to the other of the second inner edge and the second outer edge. 
     Each of the first stopping groove, the second stopping groove, and the first ball plunger may symmetric with each of the third stopping groove, the fourth stopping groove, and the second ball plunger. 
     The ball plungers may be coupled to the inner edges. 
     The first stopping groove and the second stopping groove may be provided in the outer edge. When the rolling balls are provided in the outer edge, the first stopping groove and the second stopping groove may be respectively located on opposite sides with reference to a series of the rolling balls. 
     The second body may include a first moving surface, a first inclined surface, and a second inclined surface. 
     The first moving surface is configured to provide a path on which the stopping ball moves between the first stopping groove and the second stopping groove. 
     The first inclined surface interconnects the first stoppling groove and the first moving surface and is configured to provide an inclined surface that approaches the outer edge as it goes toward the first stopping groove. 
     The second inclined surface interconnects the second stoppling groove and the first moving surface and is configured to provide an inclined surface that approaches the outer edge as it goes toward the second stopping groove. 
     Advantageous Effects of Invention 
     In the flexible display device according to an exemplary embodiment of the present disclosure, a plurality of spherical rolling balls, which are arranged in a first direction, are coupled to one of the first body and the second body, and the other of the first body and the second body is provided with a rolling recess in the form of a concave groove having a constant cross section in the first direction so that the rolling balls move in point contact with the rolling recess. When the flexible display is transformed while the second body moves relative to the first body, the rolling balls move along the rolling recess while being in point contact with the rolling recess. This makes it possible to reduce a frictional force when the flexible display device is transformed, and to prevent the flexible display from moving in an unintended direction in the flexible display device. 
     In the flexible display device according to an exemplary embodiment of the present disclosure, the first body may include a first inner edge which is provided with a first rolling recess and a second inner edge which is provided with a second rolling recess, and the second body may include a first outer edge to which the first rolling balls are coupled, and a second outer edge to which the second rolling balls are coupled. The first rolling balls, the second rolling balls, the first rolling recess, and the second rolling recess, which guide the relative movement between the first body and the second body may be provided on opposite side rims of the flexible display device, and when the second body is transformed from the first position to the second position relative to the first body, only the first rolling recess and the second rolling recess are exposed to the outside. 
     The flexible display device according to an exemplary embodiment of the present disclosure includes a magnet and a Hall sensor. In addition, the flexible display device may include a controller configured to control the flexible display according to position information of the magnet detected by the Hall sensor. This makes it possible to identify whether the second body is disposed at the first position, at the second position, or between the first position and the second position relative to the first body. According to each position of the second body, it is possible to perform control of an image such that an image is displayed on the flexible display, an image is not displayed, or an image to be displayed is changed. 
     The flexible display device according to an exemplary embodiment of the present disclosure may include a first stopping groove, a second stopping groove, and a first ball plunger. In addition, the flexible display device may include a third stopping groove, a fourth stopping groove, and a second ball plunger. At the first position, the first stopping ball is inserted into the first stopping groove and the second stopping ball is inserted into the third stopping groove. At the second position, the first stopping ball is inserted into the second stopping groove and the second stopping ball is inserted into the fourth stopping groove. This makes it possible to cause the second body to be placed at an intended correct position relative to the first body and to stably operate. 
     A flexible display device according to an exemplary embodiment of the present disclosure includes a first magnet, a second magnet, and a first stopper. In addition, the flexible display device includes a third magnet, a fourth magnet, and a second stopper. This makes it possible to cause the second body to be placed at an intended correct position relative to the first body and to stably operate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a block diagram for describing a flexible display device. 
         FIG.  2 A  is a perspective view illustrating a first state of the flexible display device, and  FIG.  2 B  is a perspective view illustrating a second state in which the flexible display device illustrated in  FIG.  2 A  is transformed. 
         FIG.  3 A  is a rear view illustrating the flexible display device of  FIG.  2 A , and  FIG.  3 B  is a rear view illustrating the flexible display device illustrated in  FIG.  2 B . 
         FIG.  4 A  is a perspective view illustrating the flexible display separated from the flexible display device in the first state, and  FIG.  4 B  is a perspective view illustrating a transformed state (the second state) of the flexible display of  FIG.  4 A . 
         FIGS.  5 A and  5 B  are views for describing a coupling relationship between rolling balls and rolling recesses, in which the state of the inside of the flexible display device is schematically illustrated.  FIG.  5 A  illustrates a first state, and  FIG.  5 B  illustrates a second state. 
         FIG.  6    is a cross-sectional view taken along line A-A′ in  FIG.  2 A , and  FIGS.  7 A and  7 B  are cross-sectional views each illustrating a portion of the flexible display device according to another exemplary embodiments. 
         FIGS.  8 A and  8 B  are side views each illustrating the flexible display device of  FIG.  2 B . 
         FIG.  9    is a cross-sectional view taken along line B-B′ of  FIG.  2 A . 
         FIG.  10 A  is a cross-sectional view taken along line C-C′ in  FIG.  2 A .  FIG.  10 B  is a cross-sectional view illustrating the inner surface side of a first outer edge and a second edge, and  FIG.  10 C  is a cross-sectional view illustrating the inner surface side of a second outer edge and a second edge. 
         FIG.  11 A  is a cross-sectional view taken along line D-D′ in  FIG.  2 A .  FIG.  11 B  is a cross-sectional view illustrating a transformed state of the flexible display device of  FIG.  11 A . 
         FIG.  12 A  is a cross-sectional view illustrating the flexible display of  FIG.  11 A  in the separated state, and  FIG.  12 B  is a cross-sectional view illustrating the flexible display of  FIG.  11 B  in the separated state. 
         FIGS.  13 A and  13 B  are views for describing the relationship between first and second magnets and a first stopper, and the relationship between third and fourth magnets and a second stopper, in which the states of the inside of a portion of the flexible display device are illustrated. 
         FIGS.  14 A and  14 B  are views for describing the relationship of ball plungers, stopping grooves, and Hall sensors; in which the states of the inside of the flexible display device are schematically illustrated. 
         FIGS.  15 A and  15 B  are views for describing the relationship between the stopping grooves and the ball plungers, in which the states of the inside of the flexible display device are schematically illustrated. 
         FIG.  16    is a rear view schematically illustrating a flexible display device. 
         FIG.  17    is a view illustrating a tension generator. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, exemplary embodiments disclosed herein will be described in detail with reference to the accompanying drawings, and like reference numerals designate like elements, and redundant description thereof will be omitted. Suffixes “module” and “unit or portion” for elements used in the following description are merely provided for facilitation of preparing this specification, and thus they are not granted a specific meaning or function. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the following description, known functions or structures, which may confuse the substance of the present disclosure, are not explained. The accompanying drawings are used to help easily explain 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. 
     Although the terms first, second, and the like, may be used herein to describe various elements, these elements should not be limited by these terms. These terms are generally only used to distinguish one element from another. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. 
     The singular expressions include plural expressions unless the context clearly dictates otherwise. 
     It should be understood that the terms “comprises,” “comprising,” “includes,” “including,” “containing,” “has,” “having” or any other variation thereof specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components. 
     A flexible display device (also referred to as a ‘display device’) described in the present specification may include a mobile terminal such as a portable phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation, a slate PC, a tablet PC, an ultra-book, a wearable device, a smart watch, a smart glass, a head mounted display (HMD), and the like. 
     It will be apparent to those skilled in the art that the configuration according to the embodiment disclosed in the present specification may be applied to a fixed terminal such as a digital TV, a desktop computer, a digital signage except for an example that is applied only to a mobile terminal. Hereinafter, in the present disclosure, for the convenience of description, the mobile terminal will be first described as an example of the display device. 
       FIG.  1    is a block diagram for explaining a mobile terminal  100  according to the present disclosure. 
     The mobile terminal  100  may include, for example, a wireless transceiver  110 , an input interface  120 , a sensor  140 , an output interface  150 , an interface  160 , a memory  170 , a controller  180 , and a power supply  190 . The components shown in  FIG.  1    are not essential to implement the mobile terminal, and the mobile terminal described in the present disclosure may include more or fewer components than the components described above. 
     More specifically, the wireless transceiver  110  may include one or more modules that enable wireless communication between the mobile terminal  100  and a wireless communication system, between the mobile terminal  100  and another mobile terminal  100 , or between the mobile terminal  100  and an external server. Further, the wireless transceiver  110  may include one or more modules that connect the mobile terminal  100  to one or more networks. 
     The wireless transceiver  110  may include at least one of a broadcast receiving module  111 , a mobile communication module  112 , a wireless internet module  113 , a near field communication module  114 , or a position information module  115 . 
     The input interface  120  may include a camera  121  or an image input interface that inputs an image signal, a microphone  122  or an audio input interface that inputs an audio signal, and a user input interface  123  (for example, a touch key or a mechanical key) that receives information from a user. Voice data or image data collected by the input interface  120  may be analyzed and processed as a control command of the user. 
     The sensor  140  may include one or more sensors that sense at least one of information in the mobile terminal, surrounding environment information around the mobile terminal, or user information. For example, the sensor  140  may include at least one of a proximity sensor  141 , an illumination sensor  142 , a touch sensor, an acceleration sensor, a magnetic sensor, a G-sensor, a gyroscope sensor, a motion sensor, an RGB sensor, an infrared (IR) sensor, a finger scan sensor, an ultrasonic sensor, an optical sensor (for example, a camera  121 ), a microphone  122 , a battery gauge, an environment sensor (for example, a barometer, a hygrometer, a thermometer, a radiation sensor, a thermal sensor, a gas sensor, etc.), or a chemical sensor (for example, an electronic nose, a healthcare sensor, and a biometric sensor). Further, the mobile terminal disclosed in the present specification may combine and utilize information sensed by at least two sensors from the above-mentioned sensors. 
     The output interface  150  generates outputs related to visual, auditory, or tactile senses, and may include at least one of a display  151 , a sound output interface  152 , a haptic module  153 , or an optical output interface  154 . The display  151  forms a mutual layered structure with a touch sensor, or is formed integrally to be implemented as a touch screen. The touch screen simultaneously may serve as a user input interface  123  that provides an input interface between the mobile terminal  100  and the user while providing an output interface between the mobile terminal  100  and the user. 
     The interface  160  serves as a passage between the mobile terminal  100  and various types of external devices that are connected to the mobile terminal  100 . The interface  160  may include at least one of a wired/wireless headset port, an external charger port, a wired/wireless data port, a memory card port, a port for connecting a device equipped with an identification module, an audio input/output (I/O) port, a video input/output (I/O) port, or an earphone port. As the external device is connected to the interface  160 , the mobile terminal  100  may perform appropriate control on the connected external device. 
     Further, the memory  170  may store data that supports various functions of the mobile terminal  100 . The memory  170  may store a plurality of application programs (or applications) driven in the mobile terminal, and data and commands for operations of the mobile terminal  100 . At least some of the application programs may be downloaded from an external server through wireless communication. Further, at least some of the application programs for the basic functions of the mobile terminal  100  (for example, functions for receiving and making calls and receiving and sending messages) may be provided in the mobile terminal  100  from the time of manufacture. The application programs may be stored in the memory  170 , and may be installed on the mobile terminal  100  so as to be driven by the controller  180  to perform operations (or functions) of the mobile terminal. 
     In addition to the operations related to the application programs, the controller  180  may generally control overall operation of the mobile terminal  100 . The controller  180  may process a signal, data, or information that is inputted or outputted through the above-described components or drive the application programs stored in the memory  170  to provide or process appropriate information or functions to the user. 
     Further, in order to drive the application programs stored in the memory  170 , the controller  180  may control at least some of components described with reference to  FIG.  1   . Moreover, the controller  180  may combine and operate at least two of components included in the mobile terminal  100  to drive the application programs. 
     Under the control of the controller  180 , the power supply  190  may be supplied with external power or internal power, and supply power to each component included in the mobile terminal  100 . The power supply  190  includes a battery, which may be a built-in battery or a replaceable battery. 
     At least some of the above-described components may operate in cooperation with each other to implement the operation, the control, or the control method of the mobile terminal according to various embodiments which will be described below. Further, the operation, the control, or the control method of the mobile terminal may be implemented on the mobile terminal by driving at least one application program stored in the memory  170 . 
     Hereinafter, prior to describing various embodiments implemented by the mobile terminal  100  described above, the above-mentioned components will be described in more detail with reference to  FIG.  1   . 
     The broadcast receiving module  111  of the wireless transceiver  110  receives a broadcast signal and/or broadcast-related information from an external broadcast management server through a broadcast channel. The broadcast channel may include a satellite channel and a ground wave channel. Two or more broadcast receiving modules for simultaneous broadcast reception or broadcast channel switching for at least two broadcast channels may be provided to the mobile terminal  100 . 
     The broadcast management sever may refer to a server that generates and transmits a broadcast signal and/or broadcast-related information or a server that is supplied with the previously generated broadcast signal and/or broadcast-related information to transmit the broadcast signal and/or the broadcast-related information to the terminal. The broadcast signal may include not only a TV broadcast signal, a radio broadcast signal, and a data broadcast signal, but also a broadcast signal obtained by combining the TV broadcast signal or the radio broadcast signal with the data broadcast signal. 
     The broadcast signal may be encoded according to at least one of technical standards (or broadcast schemes, for example, ISO, IEC, DVB, or ATSC) for transmitting and receiving a digital broadcast signal, and the broadcast receiving module  111  may receive the digital broadcast signal using an appropriate method for the technical specification defined by the technical standards. 
     The broadcast-related information may refer to information related to a broadcast channel, a broadcast program, or a broadcast service provider. The broadcast-related information may also be provided over the mobile communication network. In this case, the broadcast-related information may be received by the mobile communication module  112 . 
     The broadcast-related information may exist in various types, such as an electronic program guide (EPG) of a digital multimedia broadcast (DMB) or an electronic service guide (ESG) of a digital video broadcast-handheld (DVB-H). The broadcast signal and/or the broadcast-related information received by the broadcast receiving module  111  may be stored in the memory  170 . 
     The mobile communication module  112  may transmit/receive a wireless signal to/from at least one of a base station, an external terminal, or a server over a mobile communication network established according to the technical standards or communication methods for mobile communication (for example, Global System for Mobile communication (GSM), Code Division Multi Access (CDMA), Code Division Multi Access 2000 (CDMA2000), Enhanced Voice-Data Optimized or Enhanced Voice-Data Only (EV-DO), Wideband CDMA (WCDMA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), and Long Term Evolution-Advanced (LTE-A)). 
     The wireless signal may include a voice call signal, a video call signal, or various types of data in accordance with transmission or reception of a text/multimedia message. 
     The wireless internet module  113  refers to a module for wireless internet connection, and may be embodied in the mobile terminal  100  or installed at the outside of the mobile terminal  100 . The wireless internet module  113  may be configured to transmit/receive a wireless signal over a communication network according to wireless internet technologies. 
     The wireless internet technologies include, for example, wireless LAN (WLAN), wireless fidelity (Wi-Fi), Wi-Fi direct, digital living network alliance (DLNA), wireless broadband (WiBro), world interoperability for microwave access (WiMAX), high speed downlink packet access (HSDPA), high speed uplink packet access (HSUPA), long term evolution (LTE), and long term evolution-advanced (LTE-A). The wireless internet module  113  may transmit or receive data in accordance with at least one wireless internet technology within a range including internet technology that have not been described above. 
     From the viewpoint that the wireless internet connection through, for example, WiBro, HSDPA, HSUPA, GSM, CDMA, WCDMA, LTE, and LTE-A is performed over the mobile communication network, the wireless internet module  113  that performs the wireless internet connection over the mobile communication network may be understood as a type of the mobile communication module  112 . 
     The near field communication module  114  is for short range communication, and may support the short range communication using at least one of BluetoothlM, radio frequency identification (RFID), infrared data association (IrDA), ultra-wideband (UWB), ZigBee, Near Field Communication (NFC), wireless fidelity (Wi-Fi), Wi-Fi Direct, or Wireless Universal Serial Bus (Wireless USB). The near field communication module  114  may support wireless communication between the mobile terminal  100  and the wireless communication system, between the mobile terminal  100  and the other mobile terminal  100 , or between the mobile terminal  100  and a network in which the other mobile terminal  100  (or external server) is located, over the wireless local area network. The wireless local area network may be a wireless personal area network. 
     Here, the other mobile terminal  100  may be a wearable device (for example, a smart watch, a smart glass, or a head mounted display (HMD)) that is capable of exchanging data (or interworking) with the mobile terminal  100  according to the present disclosure. The near field communication module  114  may detect (or recognize) the wearable device that is capable of communicating with the mobile terminal  100 , in the vicinity of the mobile terminal  100 . Moreover, when the detected wearable device is authenticated to communicate with the mobile terminal  100  according to the present disclosure, the controller  180  may transmit at least a portion of data processed in the mobile terminal  100  to the wearable device through the near field communication module  114 . Therefore, the user of the wearable device may use the data processed in the mobile terminal  100 , through the wearable device. For example, according to this, when a phone call is received by the mobile terminal  100 , the user may make a phone call through the wearable device, or when a message is received by the mobile terminal  100 , the user may check the received message through the wearable device. 
     The position information module  115  is a module for obtaining a position (or a current position) of a mobile terminal, and its representative examples include a global positioning system (GPS) module or a wireless fidelity (Wi-Fi) module. For example, when the GPS module is utilized, the mobile terminal may obtain the position of the mobile terminal using a signal transmitted from the GPS satellite. As another example, when the Wi-Fi module is utilized, the mobile terminal may obtain the position of the mobile terminal based on information on a wireless access point (AP) that transmits and receives wireless signals with the Wi-Fi module. If necessary, the position information module  115  may alternatively or additionally perform a function of another module of the wireless transceiver  110  to obtain data on the position of the mobile terminal. The position information module  115  is a module used to obtain the position (or the current position) of the mobile terminal, and is not limited to a module that directly calculates or obtains the position of the mobile terminal. 
     Next, the input interface  120  is for inputting video information (or signal), audio information (or signal), data, or information inputted by the user, and the mobile terminal  100  may include one or a plurality of cameras  121  to input the video information. The camera  121  processes an image frame such as a still or moving image obtained by an image sensor in a video call mode or a photographing mode. The processed image frame may be displayed on the display  151  or stored in the memory  170 . Further, the plurality of cameras  121  included in the mobile terminal  100  may be arranged to form a matrix structure, and a plurality of pieces of image information having various angles or focal points may be inputted to the mobile terminal  100  through the cameras  121  that form the matrix structure. Further, the plurality of cameras  121  may be arranged to form a stereo structure to obtain left and right images used to implement a stereoscopic image. 
     The microphone  122  processes an external sound signal as electrical speech data. The processed voice data may be utilized in various manners in accordance with the function (or an application program that is being executed) that is being performed by the mobile terminal  100 . Various noise removal algorithms for removing noise generated during the process of receiving the external sound signal may be implemented in the microphone  122 . 
     The user input interface  123  is for receiving information from the user, and when the information is inputted through the user input interface  123 , the controller  180  may control the operation of the mobile terminal  100  so as to correspond to the inputted information. The user input interface  123  may include a mechanical input interface (or a mechanical key, for example, a button located on a front, rear, or side surface of the mobile terminal  100 , a dome switch, a jog wheel, a jog switch, etc.) and a touch type input interface. For example, the touch type input interface may be formed as a virtual key, a soft key, or a visual key that is displayed on the touch screen through a software process, or a touch key that is disposed on a part other than the touch screen. The virtual key or visual key may be displayed on the touch screen in various shapes, and, for example, may be formed as graphics, text, icons, video, or a combination thereof. 
     The sensor  140  senses at least one of information in the mobile terminal, surrounding environment information around the mobile terminal, or user information, and generates a sensing signal corresponding to the information. The controller  180  may control the driving or the operation of the mobile terminal  100  or perform data processing, functions, or operations related to the application program installed in the mobile terminal  100 , based on the sensing signal. Representative sensors among various sensors that may be included in the sensor  140  will be described in more detail below. 
     First, the proximity sensor  141  refers to a sensor that senses the presence of an object approaching a predetermined sensing surface or nearby objects, using an electromagnetic field force or infrared ray without any mechanical contact. The proximity sensor  141  may be disposed in an internal area of the mobile terminal that is enclosed by the above-described touch screen or in the vicinity of the touch screen. 
     Examples of the proximity sensor  141  may include, for example, a transmission type photoelectric sensor, a direct reflection type photoelectric sensor, a mirror reflection type photoelectric sensor, a high frequency oscillation type proximity sensor, a capacitive proximity sensor, a magnetic proximity sensor, and an infrared proximity sensor. When the touch screen is a capacitive type, the proximity sensor  141  may be configured to detect the proximity of an object with a change in the electric field in accordance with the proximity of the object having conductivity. In this case, the touch screen (or the touch sensor) itself may be classified as a proximity sensor. 
     For convenience of description, when the object approaches the touch screen without contacting the touch screen, and it is recognized that the object is located over the touch screen, it is referred to as a “proximity touch”. When the object actually touches the touch screen, it is referred to as a “contact touch”. A position at which the object proximately touches the touch screen refers to a position at which the object vertically corresponds to the touch screen when the object proximately touches the touch screen. The proximity sensor  141  may sense the proximity touch and a proximity touch pattern (for example, a proximate touch distance, a proximate touch direction, a proximate touch speed, a proximate touch time, a proximate touch position, and a proximate touch movement state). As described above, the controller  180  may process data (or information) corresponding to the proximate touch operation and the proximate touch pattern sensed by the proximity sensor  141 , and may further display visual information corresponding to the processed data on the touch screen. Furthermore, the controller  180  may control the mobile terminal  100  to process different operations or data (or information) depending on whether the touch on the same point on the touch screen is the proximity touch or the contact touch. 
     The touch sensor senses a touch (or a touch input) applied to the touch screen (or the display  151 ) using at least one of various touch types such as a resistive film type, a capacitive type, an infrared type, an ultrasonic type, and a magnetic field type. 
     For example, the touch sensor may be configured to convert a change in a pressure applied to a specific portion of the touch screen, or a capacitance generated in a specific portion, into an electrical input signal. The touch sensor may be configured to detect a position and area where a touch subject that applies a touch onto the touch screen is touched on the touch sensor, and a pressure and capacitance at the time of the touch. Here, the touch subject is an object that applies a touch to the touch sensor, and may include, for example, a finger, a touch pen, a stylus pen, and a pointer. 
     As described above, when there is the touch input to the touch sensor, corresponding signal(s) is transmitted to a touch controller. The touch controller processes the signal(s) and then transmits corresponding data to the controller  180 . By doing this, the controller  180  may confirm which area of the display  151  is touched. Here, the touch controller may be a separate component from the controller  180 , or may be the controller  180  itself. 
     The controller  180  may perform different control or the same control depending on a type of a touch subject that touches the touch screen (or a touch key provided other than the touch screen). Whether to perform the different or the same control depending on the type of touch subject may be determined in accordance with an operating state of the current mobile terminal  100  or an application program that is being executed. 
     The touch sensor and the proximity sensor that are described above may, independently or in combination, sense various types of touches on the touch screen, such as a short (or tap) touch, a long touch, a multi touch, a drag touch, a flick touch, a pinch-in touch, a pinch-out touch, a swipe touch, or a hovering touch. 
     The ultrasonic sensor may recognize position information on a sensing object using an ultrasonic wave. The controller  180  may calculate a position of a wave generating source by using information sensed by the optical sensor and the plurality of ultrasonic sensors. The position of the wave generating source may be calculated using the property that light is much faster than the ultrasonic wave, that is, the time in which light reaches the optical sensor is much faster than the time in which the ultrasonic wave reaches the ultrasonic sensor. More specifically, the position of the wave generating source may be calculated using a time difference of the time of arrival of the ultrasonic wave with respect to light that serves as a reference signal. 
     As seen from the configuration of the input interface  120 , the camera  121  includes at least one of a camera sensor (for example, a CCD and a CMOS), a photo sensor (or an image sensor), or a laser sensor. 
     The camera  121  and the laser sensor may be combined to sense a touch of a sensing object for a three-dimensional stereoscopic image. The photo sensor, which may be stacked on a display element, is configured to scan a motion of the sensing object proximate to the touch screen. More specifically, the photo sensor includes photo diodes and transistors (TR) in rows/columns so as to scan contents disposed on the photo sensor by using an electrical signal that changes in accordance with an amount of light applied to the photo diode. That is, the photo sensor calculates coordinates of the sensing object in accordance with a changed amount of light, and position information on the sensing object may be obtained through the coordinates. 
     The display  151  displays (outputs) information processed in the mobile terminal  100 . For example, the display  151  may display execution screen information on an application program driven in the mobile terminal  100  and user interface (UI), or graphic user interface (GUI) information in accordance with the execution screen information. 
     Further, the display  151  may be configured as a stereoscopic display that displays a stereoscopic image. 
     A three-dimensional display type such as a stereoscopic type (a glass type), an autostereoscopic type (a glass-free type), and a projection type (a holographic type) may be applied to the stereoscopic display. 
     The sound output interface  152  may output audio data received from the wireless transceiver  110  or stored in the memory  170  in, for example, a call signal reception mode, a phone-call mode, a recording mode, a voice recognition mode, and a broadcasting reception mode. The sound output interface  152  may also output a sound signal (for example, a call signal reception sound and a message reception sound) related to a function performed in the mobile terminal  100 . Such a sound output interface  152  may include, for example, a receiver, a speaker, and a buzzer. 
     The haptic module  153  may generate various tactile effects that the user may feel. A representative example of the tactile effect generated by the haptic module  153  may be vibration. For example, an intensity and pattern of the vibration generated in the haptic module  153  may be controlled by the selection of the user or a setting of the controller  180 . For example, the haptic module  153  may compose different vibrations to output the composed vibrations, or sequentially output the different vibrations. 
     In addition to the vibration, the haptic module  153  may generate various tactile effects, such as effects by, for example, a pin arrangement that vertically moves to a contact skin surface, an injection force or a suction force of air through an injection port or a suction port, grazing on a skin surface, electrode contact, and stimulation of an electrostatic force or effects of reproducing a cold or hot sensation using a heat absorbing or heat emitting element. 
     The haptic module  153  may not only transmit a tactile effect by means of direct contact, but may also be implemented to allow the user to feel a tactile effect by muscular sensation of a finger or an arm. Two or more haptic modules  153  may be provided in accordance with a configuration aspect of the mobile terminal  100 . 
     The optical output interface  154  outputs a signal for notifying occurrence of an event by using light from a light source of the mobile terminal  100 . Examples of events generated in the mobile terminal  100  may include message reception, call signal reception, missed call, alarm, schedule notification, email reception, and information reception through an application. 
     The signal outputted from the optical output interface  154  is implemented as the mobile terminal emits single color or a plurality of color light on a front surface or a rear surface. When the mobile terminal senses the event confirmation of the user, the signal output may be completed. 
     The interface  160  serves as a passage with all external devices that are connected to the mobile terminal  100 . The interface  160  receives data from the external device or is supplied with power from the external device to supply power to each component in the mobile terminal  100 , or transmits data in the mobile terminal  100  to the external device. For example, the interface  160  may include, for example, a wired/wireless headset port, an external charger port, a wired/wireless data port, a memory card port, a port that connects a device equipped with an identification module, an audio input/output (I/O) port, a video input/output (I/O) port, and an earphone port. 
     The identification module is a chip in which various pieces of information for authenticating a usage right of the mobile terminal  100  is stored, and may include, for example, a user identity module (UIM), a subscriber identity module (SIM), and a universal subscriber identity module (USIM). A device (hereinafter, referred to as “identification device”) equipped with the identification module may be manufactured as a smart card. Therefore, the identification device may be connected to the terminal  100  through the interface  160 . 
     When the mobile terminal  100  is connected to an external cradle, the interface  160  may serve as a passage through which power is supplied from the cradle to the mobile terminal  100  or a passage through which various command signals inputted to the cradle by a user are transmitted to the mobile terminal  100 . Various command signals or power inputted from the cradle may operate a signal for recognizing that the mobile terminal  100  is precisely mounted in the cradle. 
     The memory  170  may store a program for an operation of the controller  180 , or temporarily store inputted/outputted data (for example, a phone book, a message, a still image, and a moving image). The memory  170  may store data related to vibrations or sounds of various patterns outputted when the touch is inputted onto the touch screen. 
     The memory  170  may include at least one type of storage medium of a flash memory type, a hard disk type, a solid state disk (SSD) type, a silicon disk drive (SDD) type, a multimedia card micro type, and card type memories (for example, SD or XD memory), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read only memory (PROM), a magnetic memory, a magnetic disk, or an optical disk. The mobile terminal  100  may operate in association with a web storage that performs a storage function of the memory  170  on the Internet. 
     As described above, the controller  180  may control an operation related to the application program and an overall operation of the mobile terminal  100 . For example, when the state of the mobile terminal satisfies a predetermined condition, the controller  180  may execute or release a locking state that restricts an input of a control command of a user regarding the applications. 
     Further, the controller  180  may perform control and processing related to, for example, voice call, data communication, and video call, or may perform a pattern recognition process that may recognize a handwriting input or a picture drawing input performed on the touch screen as a text or an image, respectively. Moreover, the controller  180  may control any one or a combination of a plurality of components described above to implement various embodiments which will be described below, in the mobile terminal  100  according to the present disclosure. 
     Under the control of the controller  180 , the power supply  190  is supplied with an external power or an internal power, and supplies power required for operating the components. The power supply  190  includes a battery, and the battery may be a chargeable embedded battery and be detachably coupled to a terminal body to be charged. 
     Further, the power supply  190  may include a connection port, and the connection port may be configured as one example of an interface  160  to which an external charger which supplies power to charge a battery is electrically connected. 
     As another example, the power supply  190  may be configured to wirelessly charge the battery without using the connection port. In this case, the power supply  190  may receive power from an external wireless power transmission device by using one or more of an inductive coupling scheme based on a self-induction phenomenon or a magnetic resonance coupling scheme based on an electromagnetic resonance phenomenon. 
     Various embodiments below may be implemented in a recording medium readable by a computer or a similar device using hardware, software, or a combination thereof, for example. 
     The display  151  displays (outputs) information processed in the mobile terminal  100 . For example, the display  151  may display execution screen information on an application program driven in the mobile terminal  100  and user interface (UI), or graphic user interface (GUI) information in accordance with the execution screen information. 
     The display  151  may include at least one of a liquid crystal display (LCD), a thin film transistor liquid crystal display (TFT LCD), an organic light emitting diode (OLED), a flexible display, a three-dimensional display (3D display), or an electronic ink display (e-ink display). 
     Further, two or more displays  151  may be provided in accordance with an implementation type of the mobile terminal  100 . In this case, a plurality of displays may be disposed to be spaced apart from each other or integrally disposed on one surface of the mobile terminal  100  or may be disposed on different surfaces. 
     The display  151  may include a touch sensor that senses a touch on the display  151  so as to receive the control command by the touch method. Therefore, when the touch is made on the display  151 , the touch sensor senses the touch, and based on the touch, the controller  180  may generate a control command corresponding to the touch. Contents inputted by the touch method may be, for example, letters or numbers, or instructions or designated menu items in various modes. 
     The microphone  122  is configured to receive a voice of the user, or other sounds. The microphone  122  may be provided in a plurality of locations to receive stereo sounds. 
     The interface  160  serves as a passage through which the mobile terminal  100  is connected to the external device. For example, the interface  160  may be at least one of a connection terminal for connection with other devices (for example, an earphone or an external speaker), a port for near field communication (for example, an infrared port (IrDA port), a Bluetooth port, and a wireless LAN port) or a power supply terminal for supplying power to the mobile terminal  100 . The interface  160  may be implemented as a socket type which accommodates an external card, such as a subscriber identity module (SIM), a user identity module (UIM), and a memory card for information storage. 
     At least one antenna for wireless communication may be provided in a terminal body. The antenna may be embedded in the terminal body or formed in a case. For example, the antenna which forms a part of the broadcast receiving module  111  (see  FIG.  1   ) may be configured to be withdrawn from the terminal body. Alternatively, the antenna may be formed to be a film type to be attached onto an inner surface of a housing, or a case including a conductive material may serve as an antenna. 
     The terminal body includes the power supply  190  (see  FIG.  1   ) which supplies power to the mobile terminal  100 . The power supply  190  may be embedded in the terminal body, or may include a battery  191  which is configured to be detachable at the outside of the terminal body. 
     The battery  191  may be configured to be supplied with power through a power cable connected to the interface  160 . Further, the battery  191  may be configured to be wirelessly chargeable by a wireless charging device. The wireless charging may be implemented by a self-induction scheme or a resonance scheme (magnetic resonance scheme). 
     An accessory which protects an outer appearance of the mobile terminal  100  or supports or extends the function thereof may be added to the mobile terminal  100 . An example of the accessory may include a cover or a pouch which covers at least one surface of the mobile terminal  100  or accommodates the mobile terminal  100 . The cover or the pouch may interwork with the display  151  to extend the function of the mobile terminal  100 . Another example of the accessory may include a touch pen which supports or extends a touch input on the touch screen. 
     The display device  1  according to the embodiment of the present disclosure includes a flexible display  300  which is transformable by an external force. 
     The transformation may be at least one of warping, bending, folding, twisting, rolling, and spreading of the display module. The transformable display module may be referred to as a “flexible display”. Here, the flexible display  300  may include a general flexible display, an electronic paper (e-paper), and a combination thereof. 
     A general flexible display  300  refers to a durable display which maintains characteristics of existing flat panel displays, and is manufactured on a thin and flexible substrate which can be warped, bent, folded, twisted, rolled, and spread like paper, is light in weight, and is not easily broken. 
     Further, electronic paper is a display technique to which characteristic of general ink are applied, but uses reflection light, which is different from existing flat panel displays. The electronic paper may change information using a twist ball or electrophoresis using a capsule. 
     Information displayed on the flexible display  300  may include visual information that is outputted on a curved surface. The visual information is implemented by independently controlling the light emission of unit pixels (sub pixels) disposed in a matrix. A unit pixel refers to a minimum unit which implements one color. 
     A part of the flexible display  300  may be not flat but may be bent. In this case, when an external force is applied to the flexible display  300 , a part of the flexible display  300  may be deformed into a flat state, or a less bent state or a more bent state. 
     The flexible display  300  may be combined with a touch sensor to implement a flexible touch screen. When a touch is made on the flexible touch screen, the controller  180  (see  FIG.  1   ) performs control corresponding to the touch input. The flexible touch screen is formed such that the touch input is sensed while a part of the flexible display  300  is spread or bent. 
     The display device  1  according to the modified example may include a deformation sensing means which senses deformation of the flexible display  300 . The deformation sensing means may be included in the sensor  140  (see  FIG.  1   ). 
     The deformation sensing means may be provided in the flexible display  300  or the body  200 , and may sense information related to the deformation of the flexible display  300 . Here, the information related to the deformation may be information on a deformation direction of the flexible display  300 , information on how much the flexible display  300  is deformed, information on the position of the deformation, information on the time of the deformation, information on an acceleration at which the deformed flexible display  300  is restored, and the like. In addition to the above information, various other types of information which can be sensed due to the bending of the flexible display  300  may also be included. 
     Further, the controller  180  (see  FIG.  1   ) may change information disposed on the flexible display  300  or generate a control signal for controlling a function of the display device  1 , based on the information related to the deformation of the flexible display  300  sensed by the deformation sensing means. 
     The deformation of the state of the flexible display  300  is not limited to the deformation by the external force. For example, when a part of the flexible display  300  is unfolded, the part may be deformed to be bent by the command of the user or an application. 
       FIG.  2 A  is a perspective view illustrating a first state of a flexible display device  1 , and  FIG.  2 B  is a perspective view illustrating a second state in which the flexible display device  1  illustrated in  FIG.  2 A  is transformed. 
       FIG.  3 A  is a rear view illustrating the flexible display device  1  of  FIG.  2 A , and  FIG.  3 B  is a rear view illustrating the flexible display device  1  illustrated in  FIG.  2 B . In  FIGS.  3 A and  3 B , a flexible display  300  is indicated by dotted lines. 
     The flexible display device  1  includes a body  200  and a flexible display  300 . The body  200  may include a first body  200   a,  a second body  200   b,  and a support  240 . 
     In describing embodiments of the present disclosure, the first direction (the X direction), the second direction (the Y direction), and the third direction (the Z direction) indicated in the drawings are directions orthogonal to each other, respectively. 
     The flexible display device  1  may include two surfaces  1   a  and  1   b  opposite to each other. The flexible display device  1  may include a first surface  1   a  and a second surface  1   b,  and the direction in which the first surface  1   a  is oriented (the direction perpendicular to or substantially perpendicular to the first surface  1   a ) and the direction in which the second surface  1   b  is oriented (the direction perpendicular to or substantially perpendicular to the second surface  1   b ) are opposite to each other. The flexible display device  1  may be placed such that the first surface  1   a  is oriented in the third direction (the Z direction), and the second surface  1   b  is oriented in the opposite direction to the third direction (the Z direction). Assuming that the first surface  1   a  is the front surface of the flexible display device  1 , the second surface  1   b  becomes the rear surface of the flexible display device  1 . 
     Hereinafter, unless otherwise particularly specified, the forward direction of the flexible display apparatus  1  will be referred to as the third direction (the Z direction) and the rear side of the flexible display device  1  will be referred to as the opposite direction to the third direction (the Z direction). 
     The body  200  may form the overall shape of the display device  1 . The body  200  may be configured as a frame of the display device  1 . The body  200  may be made of a relatively hard material, and may include, for example, plastic, carbon fiber, metal, or a combination thereof. Other components of the display device  1  may be coupled to the body  200 . 
     The body  200  may take various shapes capable of supporting the other components coupled thereto. 
     The body  200  may have a flat shape as a whole, or may have a curved shape such as a curved surface. The body  200  may be in a form in which the interior thereof is entirely filled, or may be in a form in which a portion of the interior thereof is not filled. 
     For example, when viewed from the front side (in the Z direction), the body  200  may be generally flat while having a generally rectangular shape. 
     The body  200  may be divided into two or more parts. The body  200  may include a first body  200   a  and a second body  200   b,  and the first body  200   a  and the second body  200   b  may be configured to move relative to each other (see  FIGS.  2 A,  2 B,  3 A,  3 B ). 
     The second body  200   b  may be configured to slide and reciprocate relative to the first body  200   a.  Accordingly, the second body  200   b  may be configured to make the total area, which is occupied by the body  200  when viewed from the front side (in the Z direction), variable. 
     The second body  200   b  may be configured to reciprocate between a first position and a second position relative to the first body  200   a.    
     When viewed from the front side (in the Z direction), at the first position, the total area occupied by the body  200  (the area of the body  200  projected in the Z direction) is the smallest (see  FIGS.  2 A and  3 A ), and at the second position, the total area occupied by the body  200  (the area of the body  200  projected in the Z direction) may be the largest (see  FIGS.  2 B and  3 B ). 
     When viewed from the front side (in the Z direction), at the first position, the area in which the first body  200   a  and the second body  200   b  overlap each other may be the largest (see  FIGS.  2 A and  3 A  or the like), and at the second position, the area in which the first body  200   a  and the second body  200   b  overlap each other may be the smallest (see  FIGS.  2 B and  3 B  or the like). 
     The moving direction of the second body  200   b  relative to the first body  200   a  may be parallel to the first direction (the X direction). 
     The first body  200   a  may have a predetermined length in the first direction (the X direction) and may have a predetermined length in the second direction (the Y direction) orthogonal to the first direction. The first body  200   a  may have a predetermined length in the third direction (the Z direction) orthogonal to the first and second directions, but the length in the third direction may be sufficiently smaller than the lengths in the first and second directions. Accordingly, the first body  200   a  may be generally flat in the first and second directions, or may have a flat shape in the first and second directions. 
     The first body  200   a  may have a plate shape. 
     The second body  200   b  is formed to have predetermined lengths in the first direction and the second direction. The second body  200   b  may have a predetermined length in the third direction, but the length in the third direction may be sufficiently smaller than the lengths in the first and second directions. Accordingly, the second body  200   b  may be generally flat in the first and second directions, or may have a flat shape in the first and second directions. 
     The second body  200   a  may have a plate shape. 
     The first body  200   a  and the second body  200   b  may be configured in plate shapes parallel to each other. 
     The support  240  may be coupled to, provided on, or fixed to the second body  200   b.  The supporter  240  moves together with the second body  200   b  relative to the first body  200   a  (see  FIGS.  10 A,  11 A, and  11 B ). 
     The support  240  may be provided inside the flexible display device  1 . 
     The support  240  allows the flexible display  300  to be bent to change its direction. That is, the flexible display  300  provided in the first direction may be bent while forming a curved surface on the support  240  and may extend in the opposite direction to the first direction while passing through the support  240 . 
     The support  240  may provide a U-shaped or C-shaped path on which the flexible display  300  moves, or may support the inner surface of the flexible display  300 . 
     When the support may be configured to support the inner surface of the flexible display  300 , the support  240  may be elongated in the second direction (the Y direction). 
     At least a portion of the support  240  may have a constant cross section in the second direction (the Y direction). An outer peripheral surface of the support  240  that faces or is in contact with the flexible display  300  may provide a curved surface, and the supporter  240  may have a circular cross section, a semicircular cross section, or the like. 
     In an exemplary embodiment, the support  240  may have a cylindrical shape with a constant cross section in the second direction (the Y direction). In addition, the support  240  may be configured in the form of a roller rotatable in both directions about a central axis  241  parallel to the second direction. That is, the support  240  may be coupled to the second body  200   b  to be rotatable using the central axis  241  as a rotating axis (see  FIG.  10 A ). 
       FIG.  4 A  is a perspective view illustrating the flexible display  300  separated from the flexible display device  1  in the first state, and  FIG.  4 B  is a perspective view illustrating the flexible display  300  of  FIG.  4 A  in a transformed state (in the second state). 
       FIG.  4 A  may correspond to the state at the first position described above, and each of  FIGS.  4 B and  4 C  may correspond to the state at the second position described above. 
     The flexible display  300  is made in the form of a thin film, and includes an outer surface and an inner surface. The outer surface of the flexible display  300  is a surface directed outward of the flexible display device  1 , and an inner surface of the flexible display  300  is a surface directed inward of the flexible display device  1 . An image is displayed on at least a portion of the outer surface of the flexible display  300 . 
     The flexible display  300  configured to be at least partially bent is configured such that its shape is transformed when the second body  200   b  moves relative to the first body  200   a.  When transformation is performed from the first position to the second position, the flexible display  300  may be deformed in shape as the middle portion thereof is placed on the support  240  and pushed by the support  240 . 
     The flexible display  300  may include a first region  310  and a second region  320 , which are connected to each other. 
     The flexible display  300  may include a first region  310 , a second region  320 , and a third region  330 , which are sequentially connected to each other. 
     When the flexible display  300  is not coupled to the body  200  and spreads to be flat as a whole, all of the first region  310 , the second region  320 , and the third region  330  may be coplanar with each other. 
     In  FIG.  2 B , dotted lines are imaginary lines indicating the boundary between the first region  310  and the second region  320  (a first connection region  321 ), the boundary between the first region  310  and a fourth region  340 , and the boundary between a first connection region  321  and a second connection region  322 . 
     The first region  310  may have a predetermined area and may be coupled to the body  200  from one side of the body  200 . The first region  310  may be coupled to the first body  200   a  and fixed to the first body  200   a.  That is, the first region  310  may be configured such that there is no relative movement relative to the first body  200   a.    
     The first region  310  may be parallel to the first direction and the second direction. The first region  310  may be fixed in front of the first body  200   a.  The first region  310  may be fixed in front of the first body  200   a  in the third direction. The first region  310  and the first body  200   a  may be coupled to be parallel to each other. 
     In an exemplary embodiment of the present disclosure, the first region  310  may have a generally curved surface. At this time, the curvature of the first region  310  may be smaller than the curvature of the first connection region  321  to be described later, and the radius of curvature of the first region  310  may be greater than the radius of curvature of the first connection region  321 . The radius of curvature of the first region  310  may be sufficiently larger than the radius of curvature of the first connection region  321 . For example, when the radius of curvature of the first connection region  321  is a, the radius of curvature of the first region  310  may be  10 *a or more. 
     In another exemplary embodiment of the present disclosure, the first region  310  may be provided as a flat surface as a whole. The first region  310  may form a planar outer surface and may be disposed on the front surface of the body  200 . The first region  310  may have a constant cross section in the first direction and the second direction. 
     Hereinafter, in the flexible display device  1 , the first region  310  will be described on the assumption that the first region is provided as a flat surface. 
     A direction in which the first region  310  is oriented (a direction in which an outer surface of the first region  310  is oriented) may be the third direction. The first region  310  may form all or part of the first surface  1   a  of the flexible display device  1 . 
     The flexible display  300  may further include a fourth area  340 . 
     The fourth region  340  may extend from the first region  310  as an end portion of the flexible display  300 . The fourth region  340  may have a constant cross section in the second direction and may form a curved surface, and an image may be displayed on the fourth region  340 . 
     The second region  320  extends from the first region  310 , and a portion thereof is placed on the support  240  to be bent. The second region  320  may have a constant cross section in the second direction. 
     A portion of the second region  320  is bent in a semicircular shape, and the bent position of the second region  320  is changed according to the movement of the second body  200   b.  At the first position, the first connection region  321  is curved in a semicircular shape, and at the second position, a portion of the second connection region  322  is curved in a semicircular shape. 
     The second region  320  may include a first connection region  321  and a second connection region  322 . 
     The first connection region  321  may be directly connected to the first region  310 , and the second connection region  322  may be directly connected to the first connection region  321  and the third region  330 . 
     At the first position, the first connection region  321  is placed along the outer peripheral surface of the support  240  to form a curved surface. At the first position, the first connection region  321  may form a curved outer surface about a center line of curvature L 1 . The center line of curvature L 1  is an imaginary straight line forming the center of curvature of the first connection region  321  at the first position, and is parallel to the second direction. 
     At the first position, the first connection region  321  may form a semicircular shape in cross section. 
     The center line of curvature L 1  may coincide with the central axis  241  of the support  240 . 
     At the second position, the center line of curvature L 1  may be the center of curvature of the second connection region  322  forming a curved surface. 
     An image may be displayed on the first connection region  321  and the first region  310 . 
     The area of the first region  310  may be larger than that of the first connection region  321 . 
     At the first position, the second connection region  322  may form the outer surface, which is the opposite surface of the first region  310 . That is, when the first region  310  is oriented in the third direction (the Z direction) at the first position, the second connection region  322  may be oriented in the opposite direction to the third direction (the Z direction). An image may be displayed on the second connection region  322 . 
     The second connection region  322  may have a constant cross section in the second direction. At the first position, the second connection region  322  may have a constant cross section in the first direction. 
     The flexible display  300  is configured to be connected in the order of the first region  310 , the first connection region  321 , and the second connection region  322 , and at the first position, the first region  310 , the first connection region  321 , and the second connection region  322  may form a U-shape as a whole. 
     In an exemplary embodiment of the present disclosure, at the first position, the second connection region  322  may form a curved surface as a whole. At this time, the curvature of the second region  322  may be smaller than the curvature of the first connection region  321 , and the radius of curvature of the second region  322  may be greater than the radius of curvature of the first connection region  321 . The radius of curvature of the second connection region  322  may be sufficiently larger than the radius of curvature of the first connection region  321 . For example, when the radius of curvature of the first connection region  321  is a, the radius of curvature of the second connection region  322  may be 10*a or more. 
     In another exemplary embodiment of the present disclosure, at the first position, the second connection region  322  may be provided as a flat surface as a whole. In addition, the second connection region  322  may be parallel to the first region  310 . The following description will be made in the assumption that, in the flexible display device  1 , at the first position, the second connection region  322  is provided a flat surface and is parallel to the first region  310 . 
     The third region  330  extends from the second region  320  at the opposite side to the first region  310 . The third region  330  may extend from the second connection region  322  as an end portion of the flexible display  300 . 
     In the flexible display  300 , the first region  310 , the second region  320 , and the fourth area  340  may be configured to display an image on the surfaces thereof, and the third region  330  may be configured such that no image is displayed on the surface thereof. In the flexible display  300 , the third region  330  may configure an extension portion of the display substrate, and may configure a dummy portion on which no image is displayed. 
     The third region  330  may be configured separately from the flexible display  300  and then coupled to the flexible display  300 , or may be configured integrally with the flexible display  300  during the manufacturing process of the flexible display  300 . The third region  330  may be configured with a substrate of the flexible display  300 . 
     The third region  330  may be fabricated in the form of a plastic film, and may be configured to be flexibly bent. 
     The camera  121  is fixed to the rear surface of the body  200 . The camera  121  may be coupled to the body  200  to be oriented in the opposite direction to the third direction (the Z direction). 
     The camera  121  may be fixed to the rear surface of the first body  200   a.    
     The camera  121  may be fixed to the body  200  on the side facing away from the support  240 . That is, when the support  240  is coupled to the body  200  to be biased toward the lower side of the flexible display device  1 , the camera  121  is coupled to the body  200  to be biased toward the upper side of the flexible display device  1 . 
     The camera  121  may be fixed adjacent to the edge of the first body  200   a  that is furthest from the support  240 . 
     Two or more cameras  121  may be provided and arranged in the second direction. 
     The first body  200   a  may include a first edge  205 . 
     The first edge  205  is one rim of the flexible display device  1 . The first edge  205  may form one side of the flexible display device  1  having a rectangular shape. 
     When inner edges (a first inner edge  210  and a second inner edge  220 ) form the left and right rims of the first body  200   a,  the first edge  205  may form an upper rim of the first body  200   a.    
     The first edge  205  is fixed to the first body  200   a.  The first edge  205  may be configured integrally with the first body  200   a  or may be configured separately from the first body  200   a  and fixed to the first body  200   a.    
     The first edge  205  is elongated in the second direction (the Y direction). 
     At least a portion of the first edge  205  may have a constant cross section in the second direction (the Y direction). The first edge  205  may have a convexly curved outer surface, and the cross section thereof may have a semicircular shape or the like. 
     The fourth region  340  may be fixed to the first edge  205 . 
     The second body  200   b  may include a second edge  206 . 
     The second edge  206  configures a rim of the flexible display device  1  at the opposite side to the first edge  205 . When the first edge  205  configures the upper rim of the flexible display device  1 , the second edge  206  configures a lower rim. 
     The second edge  206  is disposed outside the support  240 . 
     A gap  207  is provided between the second edge  206  and the support  240 , and the flexible display  300  forming a curved surface moves through the gap  207  (see  FIGS.  11 A and  11 B ). 
     When the flexible display device  1  includes a support bar  370 , a connection arm  373  of the support bar  370  may move through the gap  207 . 
     The second edge  206  is fixed to the second body  200   b.  The second edge  206  may be configured integrally with the second body  200   b  or may be configured separately from the second body  200   b  and fixed to the second body  200   b.    
     The second edge  206  is elongated in the second direction (the Y direction). 
     At least a portion of the second edge  206  may have a constant cross section in the second direction (the Y direction). The second edge  206  may have a convexly curved outer surface, and the cross section thereof may have a semicircular shape or the like. 
       FIGS.  5 A and  5 B  are views for describing a coupling relationship between rolling balls  510  and  520  and rolling recesses  211  and  221 , in which internal features of the flexible display device  1  are illustrated.  FIG.  5 A  illustrates a first state, and FIG.  5 B illustrates a second state. 
       FIG.  6    is a cross-sectional view taken along line A-A′ of  FIG.  2 A , and  FIGS.  7 A and  7 B  are cross-sectional views each illustrating a portion of the flexible display device  1  according to another exemplary embodiment. 
       FIGS.  8 A and  8 B  are side views each illustrating the flexible display device  1  of  FIG.  2 B . 
     The flexible display device  1  includes a plurality of rolling balls and rolling recesses. 
     The rolling balls and the rolling recesses are combined with each other. In this case, one rolling recess and a plurality of rolling balls are combined with each other. 
     When the rolling balls is coupled to the first body  200   a,  rolling recesses are provided in the second body  200   b,  and when the rolling balls are coupled to the second body  200   b,  the rolling recesses are formed in the first body  200   a.    
     That is, the rolling balls are coupled to one of the first body  200   a  and the second body  200   b  and the rolling recesses are provided in the other one of the first body  200   a  and the second body  200   b.    
     The rolling balls  510  and  520  are configured to be rollable. The rolling balls  510  and  520  may have a spherical shape, and are spaced apart from each other and arranged in the first direction. Each of the rolling balls  510  and  520  may be rotatably coupled to the first body  200   a  or the second body  200   b.  The rolling balls  510  and  520  may have the same size and shape as each other. 
     The rolling recesses  211  and  221  are may be elongated in the first direction, and may be provided in the form of a concave groove and having a constant cross section in the first direction. The rolling balls  510  and  520  are partially inserted into and come into contact with the rolling recesses  211  and  221 , and in this state, the rolling balls  510  and  520  and the rolling recesses  211  and  221  move relative to each other. 
     The rolling balls  510  and  520  may move relative to the rolling recesses  211  and  221  while rolling in contact with the rolling recesses  211  and  221 . 
     The rolling balls and the rolling recesses may be respectively provided on opposite sides of the flexible display device  1 . That is, the rolling balls  510  and the rolling recess  211  forming one combination are provided on one side (e.g., the left side) of the flexible display device  1 , and the rolling balls  520  and the rolling recess  221  forming the other combination is formed on the other side (e.g., the right side) of the flexible display device  1 . In this case, the rolling balls includes first rolling balls  510  and second rolling balls  520 , and the rolling recesses includes a first rolling recess  211  and a second rolling recess  221 . 
     The first body  200   a  may include inner edges  210  and  220 . The inner edges  210  and  220  form rims of the first body  200   a.  The rolling recesses  211  and  221  may be provided in the inner edges  210  and  220 . 
     The inner edges includes a first inner edge  210  and a second inner edge  220 . The first inner edge  210  and the second inner edge  220  may form opposite side rims of the first body  200   a  and be elongated in the first direction. The first inner edge  210  may be provided over the entire section of one side rim of the first body  200   a,  or may be provided in a partial section of the first body  200   a.  The second inner edge  220  may be provided over the entire section of one side rim of the first body  200   a,  or may be provided in a partial section of the first body  200   a.    
     The first inner edge  210  and the second inner edge  220  may be parallel to the first direction and may have a constant cross section in the first direction. When the first inner edge  210  forms the left rim of the first body  200   a,  the second inner edge  220  forms the right rim of the first body  200   a.    
     A first rolling recess  211  is provided in the first inner edge  210 . The first rolling recess  211  is provided in the outer surface of the first inner edge  210 . The first rolling recess  211  may be provided in the entire section of the first inner edge  210  or may be provided in a partial section of the first inner edge  210 . 
     A second rolling recess  221  opposite to the first rolling recess  211  is provided in the second inner edge  220 . The second rolling recess  221  is provided in the outer surface of the second inner edge  220 . The second rolling recess  221  may be provided in the entire section of the second inner edge  220  or may be provided in a partial section of the second inner edge  220 . 
     When the first rolling recess  211  is provided on the left side surface of the first body  200   a,  the second rolling recess  221  may be provided on the right side surface of the first body  200   a,  and the first rolling recess  211  and the second rolling recess  221  are exposed to face away from each other. 
     The second body  200   b  may include outer edges  250  and  260 . The outer edges  250  and  260  form rims of the second body  200   b.  The outer edges  250  and  260  may be located outside the inner edges  210  and  220 , and the rolling balls  510  and  520  may be coupled to the outer edges  250  and  260 . 
     The outer edges include a first outer edge  250  and a second outer edge  260 . The first outer edges  250  and the second outer edges  260  form opposite side rims of the second body  200   b  and may be elongated in the first direction. The first outer edge  250  and the second outer edge  260  may be parallel to the first direction and may have a constant cross section in the first direction. 
     The first outer edge  250  may be located outside the first inner edge  210 , and among the rolling balls  510  and  520 , the first rolling balls  510  may be coupled to the first outer edge  250 . The first rolling balls  510  are configured to move along the first rolling recess  211 . 
     The plurality of first rolling balls  510  may be provided in the entire section of the first outer edge  250 , or may be provided in a partial section of the first outer edge  250 . 
     The second outer edge  260  may be located outside the second inner edge  220 , and among the rolling balls  510  and  520 , the second rolling balls  520  may be coupled to the second outer edge  260 . The second rolling balls  520  are configured to move along the second rolling recess  221 . 
     The plurality of second rolling balls  520  may be provided in the entire section of the second outer edge  260 , or may be provided in a partial section of the second outer edge  260 . 
     The flexible display device  1  may include a first support frame  530  and a second support frame  540 . 
     The first support frame  530  supports the first rolling balls  510  so that the first rolling balls  510  are each rollable at a fixed position of the first outer edge  250 . 
     The first support frame  530  is provided, in the first direction, with first holes  531  having a diameter d 2  smaller than the diameter d 1  of the first rolling balls  510 , wherein the first rolling balls  510  are inserted into the first holes  531  to protrude from the first holes  531 , respectively. The first holes  531  may be spaced apart from each other at the same interval. 
     The first support frame  530  is located between and spaced apart from the outer surface of the first inner edge  210  and the inner surface of the first outer edge  250  and is fixed to the second body  200   b.    
     The second support frame  540  supports the second rolling balls  520  so that the second rolling balls  520  are each rollable at a fixed position of the second outer edge  260 . 
     The second support frame  540  is provided, in the first direction, with second holes  541  having a diameter d 2  smaller than the diameter d 1  of the second rolling balls  520 , wherein the second rolling balls  520  are inserted into the second holes  541  to protrude from the second holes  541 , respectively. The second holes  541  may be spaced apart from each other at the same interval. 
     The second support frame  540  is located between and spaced apart from the outer surface of the second inner edge  220  and the inner surface of the second outer edge  260  and is fixed to the second body  200   b.    
     The first support frame  530  and the second support frame  540  may be configured integrally with each other. 
     The first rolling recess  211  may have a constant cross section in the first direction. The first rolling recess  211  may be configured to be in point contact with the first rolling balls  510 , and the first rolling recess  211  may be provided in the form of a curved or angled groove. The first rolling balls  510  and the first rolling recess  211  may be in one-point contact, two-point contact, or three-point contact with each other. 
     The second rolling recess  221  may have a constant cross section in the first direction. The second rolling recess  221  may be configured to be in point contact with the second rolling balls  520 , and the second rolling recess  221  may be provided in the form of a curved or angled groove. The second rolling balls  520  and the second rolling recess  221  may be in one-point contact, two-point contact, or three-point contact with each other. 
     A concave first support groove  251  may be provided in an inner surface of the first outer edge  250 . 
     In an exemplary embodiment, one first support groove  251  may be elongated in the first direction, and may have a constant cross section in the first direction. In this case, the plurality of first rolling balls  510  may be inserted into the first support groove  251  to be spaced apart from each other. 
     In another exemplary embodiment, a plurality of first support grooves  251  may be provided on the first outer edge  250 . In this case, the first support grooves  251  are not elongated in the first direction, but may only be provided at specific points, respectively, in the form of a concave groove. The number of first support grooves  251  may be the same as the number of first rolling balls  510 , in which one first rolling ball  510  is inserted and brought into contact with each first support groove  251  (see  FIGS.  5 A and  5 B ). 
     A portion of the first rolling ball  510  is inserted and brought into contact with the first support groove  251 , and the corresponding first rolling ball  510  is supported by the first support frame  530  to prevent the corresponding first rolling ball  510  from being separated from the corresponding first support groove  251 . 
     The first support frame  530  supports the first rolling balls  510  such that respective first rolling balls  510  are located at specific points of the first outer edge  250 . 
     The first support grooves  251  may be configured to be in point contact with the first rolling balls  510 , respectively, and may be provided in the form of a curved or angled groove (see  FIGS.  7 A and  7 B ). 
     A concave second support groove  261  may be provided in an inner surface of the second outer edge  260 . 
     In an exemplary embodiment, one second support groove  261  may be elongated in the first direction, and may have a constant cross section in the first direction. In this case, the plurality of second rolling balls  520  may be inserted into the second support groove  261  to be spaced apart from each other. 
     In another exemplary embodiment, a plurality of second support grooves  261  may be provided on the first outer edge  250 . In this case, the second support grooves  261  are not elongated in the first direction, but may only be provided at specific points, respectively, in the form of a concave groove. The number of second support grooves  261  may be the same as the number of second rolling balls  520 , in which one second rolling ball  520  is inserted and brought into contact with each second support groove  261  (see  FIGS.  5 A and  5 B ). 
     A portion of the second rolling ball  520  is inserted and brought into contact with the second support groove  261 , and the corresponding second rolling ball  520  is supported by the second support frame  540  to prevent the corresponding second rolling ball  520  from coming off from the corresponding second support groove  261 . 
     The second support frame  540  supports the second rolling balls  520  such that respective second rolling balls  520  are located at specific points of the second outer edge  260 . 
     The second support grooves  261  may be configured to be in point contact with the second rolling balls  520 , respectively, and may be provided in the form of a curved or angled groove (see  FIGS.  7 A and  7 B ). 
     As described above, when the flexible display  300  is transformed while the second body  200   b  moves relative to the first body  200   a,  the first rolling balls  510  move along the first rolling recess  211 , and the second rolling balls  520  move along the second rolling recess  221 , wherein the rolling balls  510  and  520  and the rolling recesses  211  and  221 are in point contact with each other. The first rolling balls  510  are prevented from moving in a direction other than the longitudinal direction of the first rolling recess  211  (the first direction), and the second rolling balls  520  are prevented from moving in a direction other than the longitudinal direction of the second rolling recess  221  (the first direction). This makes it possible to reduce a frictional force generated when the flexible display device  1  is transformed between the first position and the second position, and to prevent a movement in an unintended direction in the flexible display device  1 . 
       FIG.  9    is a cross-sectional view taken along line B-B′ of  FIG.  2 A . 
       FIG.  10 A  is a cross-sectional view taken along line C-C′ in  FIG.  2 A .  FIG.  10 B  is a cross-sectional view illustrating the inner surface side of the first outer edge  250  and the second edge  206 , and  FIG.  10 C  is a cross-sectional view illustrating the inner surface side of the second outer edge  260  and the second edge  206 . 
     The second body  200   b  may include a first rear guide groove  252 , a first front guide groove  253 , a first connection guide groove  254 , a second rear guide groove  262 , a second front guide groove  263 , and a second connection guide groove  264  may be included. 
     The first rear guide groove  252  and the first front guide groove  253  may be provided on the first outer edge  250 , the second rear guide groove  262  and the second front guide groove  263  may be provided on the second outer edge  260 , and the first connection guide groove  254  and the second connection guide groove  264  may be provided on the second edge  206 . 
     The first rear guide groove  252  may provide a space inside the first outer edge  250 , may have a constant cross section in the first direction, and may open inward from the rear side of the first outer edge  250 . 
     The first front guide groove  253  may provide a space inside the first outer edge  250 , may have a constant cross section in the first direction, and may open inward from the front side of the first outer edge  250 . The first front guide groove  253  may be symmetric with the first rear guide groove  252 . 
     The first connection guide groove  254  may interconnect the first rear guide groove  252  and the first front guide groove  253  while providing a semicircular space inside the second edge  206  of the second body  200   b.    
     The first rear guide groove  252 , the first connection guide groove  254 , and the first front guide groove  253  are combined with each other to provide a U-shaped space, wherein these guide groves function as a rail while providing a movement path for support bars  370  (especially, first support sliders  371 ) to be described later. 
     The second rear guide groove  262  may provide a space inside the second outer edge  260 , may have a constant cross section in the first direction, and may open inward from the rear side of the second outer edge  260 . 
     The second front guide groove  263  may provide a space inside the second outer edge  260 , may have a constant cross section in the first direction, and may open inward from the front side of the second outer edge  260 . The second front guide groove  263  may be symmetric with the second rear guide groove  262 . 
     The second connection guide groove  264  may interconnect the second rear guide groove  262  and the second front guide groove  263  while providing a semicircular space inside the second edge  206  of the second body  200   b.    
     The second rear guide groove  262 , the second connection guide groove  264 , and the second front guide groove  263  are combined with each other to provide a U-shaped space, wherein these guide groves function as a rail while providing a movement path for support bars  370  (especially, second support sliders  372 ) to be described later. 
     The first rear guide groove  252 , the first front guide groove  253 , and the first connection guide groove  254  may be symmetric with the second rear guide groove  262 , the second front guide groove  263 , and the second connection guide  264 . 
       FIG.  11 A  is a cross-sectional view taken along line D-D′ in  FIG.  2 A .  FIG.  11 B  is a cross-sectional view illustrating a transformed state of the flexible display device  1  of  FIG.  11 A . 
       FIG.  12 A  is a cross-sectional view illustrating the flexible display  300  of  FIG.  11 A  in the separated state, and  FIG.  12 B  is a cross-sectional view illustrating the flexible display  300  of  FIG.  11 B  in the separated state. 
     The first body  200   a  may include a support plate  230 . 
     The support plate  230  may have be flat, and may have the same or similar size as the first region. The first region may be stacked on the outside (front side) of the support plate  230 , and the support plate  230  is configured to support the first region from the inside. 
     The flexible display device  1  according to an exemplary embodiment of the present disclosure may include a plurality of support bars  370 . 
     Each of the support bars  370  is configured to support the first connection region  321  or the second connection region  322  from the inside, and the plurality of support bars  370  are sequentially arranged along the first connection region  321  and the second connection region  322 . 
     The support bars  370  are made of a relatively hard material to support the flexible display  300 , and may be made of a material such as plastic or metal. 
     The support bars  370  may have a trapezoidal cross section (a shape in which the width is narrowed in a direction away from the rear surface of the flexible display  300 ). 
     The support bars  370  are elongated in the second direction (the Y direction) and may each include a first support slider  371 , a second support slider  372 , and a connection arm  373 . 
     The first support sliders  371  are provided as end portions of the support bars  370 , respectively, at one side. 
     The first support sliders  371  are inserted into the first rear guide groove  252 , the first connection guide groove  254 , and the first front guide groove  253 , and are configured to move along the space (path) provided by the first rear guide groove  252 , the first connection guide groove  254 , and the first front guide groove  253 . 
     The second support sliders  372  are provided as end portions of the support bars  370 , respectively, at the opposite side to the first support sliders  371 . 
     The second support sliders  372  are inserted into the second rear guide groove  262 , the second connection guide groove  264 , and the second front guide groove  263 , and are configured to move along the space (path) provided by the second rear guide groove  262 , the second connection guide groove  264 , and the second front guide groove  263 . 
     The connection arms  373  may have a constant cross section in the second direction (the Y direction). 
     The connection arms  373  interconnect the first support sliders  371  and the second support sliders  372 , respectively, support the inner surface of the flexible display  300 , and help the first connection region  321  and the second connection region  322  to maintain a stable flat or curved state. 
     The support bars  370  may have a predetermined thickness so that, when the plurality of successively arranged support bars  370  provide a plane parallel to the first region  310 , the second region  320  supported by the support bars  370  is stably maintained like the first region  310 . 
     The front surfaces of the connection arms  373  and the front surface of the support plate  230  may be coplanar with each other. 
     The support bars  370  are able to maintain the second region  320  in a stable state. In particular, when the second region  320  is made of a touch screen and a touch input is performed thereon, the second region  320  is stably supported by the support bar  370 . 
     The second body  200   b  may include a back cover  280 . The back cover  280  may be provided as the rear surface of the second body  200   b.  The back cover  280  may be fixed to the second body  200   b,  or may be detachably coupled to the second body  200   b.  The back cover  280  may be made transparent or may be made opaque. 
     A portion of the flexible display  300  is located inside the back cover  280 . At the first position, the second connection region  322  is located inside the back cover  280 . 
     When the back cover  280  is made transparent, the second connection region  322  is visible from the back through the back cover  280 . 
       FIGS.  13 A and  13 B  are views for describing the relationship between first and second magnets  571  and  572  and a first stopper  573 , and the relationship between third and fourth magnets  574  and  575  and a second stopper  576 , in which the state of the inside of a portion of the flexible display device  1  is illustrated.  FIG.  13 A  illustrates the first state, and  FIG.  13 B  illustrates the second state. 
     One of the first body  200   a  and the second body  200   b  may include the first magnet  571  and the second magnet  572 , and the other may include the first stopper  573 . 
     The first magnet  571  and the second magnet  572  may be coupled to one of the first inner edge  210  and the first outer edge  250 , and the first stopper  573  may be provided on the other of the first inner edge  210  and the first outer edge  250 . 
     The first magnet  571  and the second magnet  572  may be made of an electromagnet or a permanent magnet. 
     The first magnet  571  and the second magnet  572  are spaced apart from each other in the first direction. 
     The first stopper  573  is configured to apply an attractive force to each of the first magnet  571  and the second magnet  572 . The first stopper  573  may be made of a metal or a permanent magnet. 
     The first stopper  573  may be configured to come into contact with or approach the first magnet  571  to apply an attractive force to the first magnet  571  at the first position, and the first stopper  573  may be configured to come into contact with or approach the second magnet  572  to apply an attractive force to the second magnet  572  at the second position. 
     Each of the first magnet  571  and the second magnet  572  may be coupled to the first inner edge  210 , wherein the first magnet  571  and the second magnet  572  may be located adjacent to opposite ends of the first rolling recess  211 , respectively, while being spaced apart from each other. When the first magnet  571  is located relatively upward, the second magnet  572  may be located relatively downward. 
     The first stopper  573  may be coupled to the first outer edge  250 . 
     The first rolling recess  211 , the first magnet  571 , and the second magnet  572  may be arranged on the same line in the first direction. The first magnet  571  and the second magnet  572  may each configure a portion of the surface of the first rolling recess  211 . In addition, the first stopper  573 , which has a spherical shape, is inserted into the first rolling recess  211  to move along the first rolling recess  211 . 
     The first stopper  573  may have the same size and shape as the first rolling balls  510 . 
     The flexible display device  1  may further include a first auxiliary stopper  573   a.  The first auxiliary stopper  573   a  may be coupled to the first outer edge  250 . The first auxiliary stopper  573   a  may have a spherical shape, and may be inserted into the first rolling recess  211  to move along the first rolling recess  211 . 
     The first auxiliary stopper  573   a  may be configured to approach or contact with the second magnet  572  when the first stopper  573  approaches or comes into contact with the first magnet  571 . 
     The flexible display device  1  may include a third magnet  574 , a fourth magnet  575 , and a second stopper  576 . 
     One of the first body  200   a  and the second body  200   b  may include the third magnet  574  and the fourth magnet  575 , and the other may include the second stopper  576 . 
     The third magnet  574  and the fourth magnet  575  may be coupled to one of the second inner edge  220  and the second outer edge  260 , and the second stopper  576  may be provided on the other of the second inner edge  210  and the second outer edge  260 . 
     Each of the third magnet  574  and the fourth magnet  575  may be an electromagnet or a permanent magnet. 
     The third magnet  574  and the fourth magnet  575  are spaced apart from each other in the first direction. 
     The second stopper  576  is configured to apply an attractive force to each of the third magnet  574  and the fourth magnet  575 . The second stopper  576  may be made of a metal or a permanent magnet. 
     The second stopper  576  may be configured to come into contact with or approach the third magnet  574  to apply an attractive force to the third magnet  574  at the first position, and the fourth stopper  575  may be configured to come into contact with or approach the fourth magnet  575  to apply an attractive force to the fourth magnet  575  at the second position. 
     Each of the third magnet  574  and the fourth magnet  575  may be coupled to the second inner edge  220 , wherein the third magnet  571  and the fourth magnet  572  may be located adjacent to opposite ends of the second rolling recess  221 , respectively, while being spaced apart from each other. When the third magnet  574  is located relatively upward, the fourth magnet  575  may be located relatively downward. 
     The second stopper  576  may be coupled to the second outer edge  260 . 
     The second rolling recess  221 , the third magnet  574 , and the fourth magnet  575  may be arranged on the same line in the first direction. The third magnet  574  and the fourth magnet  575  may each configure a portion of the surface of the second rolling recess  221 . In addition, the second stopper  576 , which has a ball shape, is inserted into the second rolling recess  221  to move along the second rolling recess  221 . 
     The second stopper  576  may have the same size and shape as the second rolling balls  520 . 
     The flexible display device  1  may further include a second auxiliary stopper  576   a.  The second auxiliary stopper  576   a  may be coupled to the second outer edge  260 . The second auxiliary stopper  576   a  may have a ball shape, and may be inserted into the second rolling recess  221  to move along the second rolling recess  221 . 
     The second auxiliary stopper  576   a  may be configured to approach or contact with the fourth magnet  575  when the second stopper  576  approaches or comes into contact with the third magnet  574 . 
     Each of the first magnet  571 , the second magnet  572 , and the first stopper  573  may be symmetrical with each of the third magnet  574 , the fourth magnet  575 , and the second stop  576  (e.g., left-right symmetry). 
     As described above, the flexible display device  1  according to an exemplary embodiment of the present disclosure includes a first magnet  571 , a second magnet  572 , and a first stopper  573 , and further includes a third magnet  574 , a fourth magnet  575 , and a second stopper  576 . As a result, the second body  200   b  may be placed at an intended correct position relative to the first body  200   a  and operates stably. 
     In addition, the first stopper  573  is configured to move along the first rolling recess  211 , and the second stopper  576  is configured to move along the second rolling recess  221 . It is possible to minimize a separate space to be secured due to the addition of the first magnet  571 , the second magnet  572 , the first stopper  573 , the third magnet  574 , the fourth magnet  575 , and the second stopper  576 . 
     This makes it possible to secure a sufficient internal space  200   c  inside the flexible display device  1 . 
     In an exemplary embodiment of the present disclosure, the first rolling balls  510  and the second rolling balls  520  may be made of a non-magnetic material. This makes it possible to prevent the first magnet  571  or the second magnet  572  from applying an attractive force to the first rolling balls  510  when the first rolling balls  510  move along the first rolling recess  211 , and further makes it possible to prevent the third magnet  574  or the fourth magnet  575  from applying an attractive force to the second rolling balls  520  when the second rolling balls  520  move along the second rolling recess  221 . 
       FIGS.  14 A and  14 B  are views for describing the relationship of ball plungers  550  and  560 , stopping grooves  271 ,  272 ,  273 , and  274 , and Hall sensors  578  and  579  of the flexible display device  1 , in which the states of the inside of the flexible display device  1  is schematically illustrated.  FIG.  14 A  illustrates the first state, and  FIG.  14 B  illustrates the second state. 
     One of the first body  200   a  and the second body  200   b  may be provided with a stopping groove  271 ,  272 ,  273 , or  274 , a ball plunger  550  or  560  may be coupled to the other of the first body  200   a  and the second body  200   b.    
     The stopping groove  271 ,  272 ,  273 , or  274  is provided in the form of a concave groove. The stopping groove  271 ,  272 ,  273 , or  274  may be provided in the form of a circular groove. 
     The ball plunger  550  or  560  may include a stopping ball, a cylinder, and a spring. 
     The stopping ball  551  or  561  may have a ball shape. The stopping ball is configured to be partially inserted into the stopping groove. The stopping ball may be made of a magnetic material or may include a magnetic material. The stopping ball may be made of a permanent magnet or may include a permanent magnet. 
     The spring  553  or  563  may be formed in various elastically deformable shapes. The spring may be configured in the form of a coil spring. 
     The cylinder  552  or  562  includes an inner space open to one side, and the stopping ball and the spring are accommodated in the inner space of the cylinder. 
     The stopping ball accommodated in the inner space of the cylinder is urged outward while being elastically supported by the spring, and partially protrudes to the outside of the cylinder. The cylinder may have an inlet slightly smaller than the diameter of the stopping ball to prevent the stopping ball from coming off. 
     When the first body  200   a  is provided with the stopping groove  271 ,  272 ,  273 , or  274 , the ball plunger  550  or  560  is fixed to the second body  200   b  (see  FIGS.  14 A and  14 B ). Alternatively, when the second body  200   b  is provided with the stopping groove, the ball plunger may be fixed to the first body  200   a.    
     Depending on the relative position between the first body  200   a  and the second body  200   b,  the stopping ball of the ball plunger may be inserted into or come out from the stopping groove. 
     When the stopping ball is inserted into the stopping groove, unless a separate external force is applied, the engagement between the stopping ball and the stopping groove are maintained, and the relative movement between the first body  200   a  and the second body  200   b  is prevented. For example, when the stopping ball is inserted into the stopping groove, the first state or the second state is maintained unless a separate external force is applied. 
     When the second body  200   b  is moved in parallel to the first direction relative to the first body  200   a  in the state in which the stopping ball is inserted into the stopping groove, the spring is compressed and the stopping ball comes off from the stopping groove so that the engagement between the ball plunger and the stopping groove is released, and a relative movement is allowed between the first body  200   a  and the second body  200   b.    
     A plurality of stopping grooves may be provided, and a plurality of ball plungers may also be provided. 
     When a plurality of stopping grooves are provided, the stopping grooves may include a first stopping groove  271  and a second stopping groove  272 . The first stopping groove  271  and the second stopping groove  272  are spaced apart from each other in the first direction. 
     Of the ball plungers, a first ball plunger  550  may include a first stopping ball  551 , a first cylinder  552 , and a first spring  553 . Each of the first stopping ball  551 , the first cylinder  552 , and the first spring  553  may be configured like the above-described stopping ball, cylinder, and spring. 
     The first stopping ball  551  of the first ball plunger  550  may be inserted into the first stopping groove  271  at the first position and inserted into the second stopping groove  272  at the second position. 
     In an exemplary embodiment, the first stopping groove  271  and the second stopping groove  272  may be provided on the first inner edge  210  and may be disposed to be spaced apart from each other in the first direction. In this case, the first ball plunger  550  may be coupled to the first outer edge  250 . 
     The stopping groove may include a third stopping groove  273  and a fourth stopping groove  274 . The third stopping groove  273  and the fourth stopping groove  274  are spaced apart from each other in the first direction. 
     Of the ball plungers, a second ball plunger  560  may include a second stopping ball  561 , a second cylinder  562 , and a second spring  563 . Each of the second stopping ball  561 , the second cylinder  562 , and the second spring  563  may be configured like the above-described stopping ball, cylinder, and spring. 
     The second stopping ball  561  of the first ball plunger  560  may be inserted into the third stopping groove  273  at the first position and inserted into the fourth stopping groove  274  at the second position. 
     In an exemplary embodiment, the third stopping groove  273  and the fourth stopping groove  274  may be provided on the first inner edge  220  and may be disposed to be spaced apart from each other in the first direction. In this case, the second ball plunger  560  may be coupled to the second outer edge  260 . 
     The flexible display device  1  may include a Hall sensor (Hall IC)  578  or  579 . A plurality of Hall sensors  578  and  579  may be provided and arranged in the first direction. The Hall sensors  578  and  579  may be coupled to sensor boards  701  and  702 . 
     Some of the Hall sensors  578  and  579  may be disposed at the same position as stopping grooves. 
     The Hall sensors  578  and  579  may be configured to detect a magnetic field generated from the stopping balls. According to a change in the relative position between respective Hall sensors  578  and  579  and the stopping balls, it is possible to identify the relative position between the first body  200   a  and the second body  200   b,  and further it is possible to identify the state of the flexible display  300 . 
     The flexible display device  1  may include a controller  180  configured to control the flexible display  300  according to the position information of the stopping balls detected by the Hall sensors  578  and  579  (see  FIG.  1   ). 
     When the stopping balls are coupled to the first body  200   a,  the Hall sensors  578  and  579  may be coupled to the second body  200   b.    
     When the stopping balls are coupled to the second body  200   b,  the hall sensors  578  and  579  may be coupled to the first body  200   a  (see  FIGS.  14 A and  14 B ). 
     The Hall sensors  578  and  579  may include a first Hall sensor  578  and a second Hall sensor  579 . 
     The first Hall sensor  578  may be coupled to the first inner edge  210 , and the first stopping ball  551  may be coupled to the first outer edge  250 . The first Hall sensor  578  may be configured to detect the magnetic field of the first stopping ball  551  and to transmit position information of the first stopping ball  551  to the controller  180 . 
     A plurality of first Hall sensors  578  may be provided and arranged to be spaced apart from each other in the first direction. 
     The second Hall sensor  579  may be coupled to the second inner edge  220 , and the second stopping ball  561  may be coupled to the second outer edge  260 . The second Hall sensor  579  may be configured to detect the magnetic field of the second stopping ball  561  and to transmit position information of the second stopping ball  561  to the controller  180 . 
     A plurality of second Hall sensors  579  may be provided and arranged to be spaced apart from each other in the first direction. 
     In an exemplary embodiment, when the first state is switched into the second state, i.e., the screen is expanded on the front side of the flexible display  300 , respective Hall sensors  578  and  579  mounted on the first body  200   a  are capable of recognizing the positional movement of respective stopping balls mounted on the second body  200   b,  thereby recognizing the transformation from the first state to the second state. 
     When the plurality of Hall sensors  578  and  579  are arranged in the first direction on the first body  200   a,  the flexible display  300  is configured to be variable while the stopping balls are moving. 
     The controller  180  may be configured to control the above-described haptic module  153  according to the position information of the stopping balls detected by the Hall sensors  578  and  579 . That is, as the second body  200   b  moves relative to the first body  200   a,  the intensity and pattern of vibration generated by the haptic module  153  may be controlled by the controller  180 . 
       FIGS.  15 A and  15 B  are views for describing the relationship between the stopping grooves and the ball plungers, in which the states of the inside of the flexible display device  1  are schematically illustrated.  FIG.  15 A  illustrates the first state, and  FIG.  15 B  illustrates the second state. 
     In an exemplary embodiment, the first stopping groove  271  and the second stopping groove  272  may be provided on the first outer edge  250  and may be disposed to be spaced apart from each other in the first direction. In this case, the first ball plunger  550  may be coupled to the first inner edge  210 . 
     The flexible display device  1  may further include a first auxiliary ball plunger  550   a.    
     The first auxiliary ball plunger  550   a  may be configured to be the same as the above-described ball plungers. When the first stopping ball  551  of the first ball plunger  550  is inserted into the first stopping groove  271 , the stopping ball of the first auxiliary ball plunger  550   a  may be inserted into the second stopping groove  272 . 
     When the first rolling recess  211  is provided on the first inner edge  210  and the first rolling ball  510  is provided on the first outer edge  250 , the first stopping groove  271  and the second stopping groove  272  may be provided on the first outer edge  250  and the first ball plunger  550  and the first auxiliary ball plunger  550   a  may be provided on the first inner edge  210 . 
     The first stopping groove  271  and the second stopping groove  272  may be located to be spaced apart from each other in the first direction and to be respectively adjacent to opposite ends of a series of first rolling balls  510 . The first ball plunger  550  and the first auxiliary ball plunger  550   a  may be located to be spaced apart from each other in the first direction and to be respectively adjacent to opposite ends of the first rolling recess  211 . 
     In an exemplary embodiment, the third stopping groove  273  and the fourth stopping groove  274  may be provided on the second outer edge  260  and may be disposed to be spaced apart from each other in the first direction. In this case, the second ball plunger  560  may be coupled to the second inner edge  220 . 
     The flexible display device  1  may further include a second auxiliary ball plunger  560   a.    
     The second auxiliary ball plunger  560   a  may be configured to be the same as the above-described ball plungers. When the second stopping ball  561  of the second ball plunger  560  is inserted into the third stopping groove  273 , the stopping ball of the second auxiliary ball plunger  560   a  may be inserted into the fourth stopping groove  274 . 
     When the second rolling recess  221  is provided on the second inner edge  220  and the second rolling ball  520  is provided on the second outer edge  260 , the third stopping groove  273  and the fourth stopping groove  274  may be provided on the second outer edge  260  and the second ball plunger  560  and the second auxiliary ball plunger  560   a  may be provided on the second inner edge  220 . 
     The third stopping groove  273  and the fourth stopping groove  274  may be located to be spaced apart from each other in the first direction and to be respectively adjacent to opposite ends of a series of second rolling balls  520 . The second ball plunger  560  and the second auxiliary ball plunger  560   a  may be located to be spaced apart from each other in the first direction and to be respectively adjacent to opposite ends of the second rolling recess  221 . 
     The flexible display device  1  may include auxiliary magnets, and in this case, the stopping balls may be disposed such that an attractive force acts between the stopping ball and the auxiliary magnets. 
     The auxiliary magnets may be electromagnets or permanent magnets. 
     The auxiliary magnets are fixed inside the stopping grooves, respectively. 
     The auxiliary magnets may include a first auxiliary magnet  581 , a second auxiliary magnet  582 , a third auxiliary magnet  583 , and a fourth auxiliary magnet  584 . 
     The first auxiliary magnet  581  is fixed inside the first stopping groove  271 , the second auxiliary magnet  582  is fixed inside the second stopping groove  272 , and the third auxiliary magnet  583  may be fixed in the third stopping groove  273 , and the fourth auxiliary magnet  584  may be fixed inside the fourth stopping groove  274 . 
     When the stopping balls are inserted into the stopping grooves, respectively, unless a separate external force acts, the engagement between the stopping balls and the stopping grooves is maintained, and the attractive force acts between the auxiliary magnets and the stopping balls, so that the relative movement between the first body  200   a  and the second body  200   b  is prevented more stably. 
     In addition, even if the depth of each stopping groove is relatively low, it is possible to prevent an unintended relative movement between the first body  200   a  and the second body  200   b,  and it is possible to reduce the frictional force generated in the state in which the stopping balls come off from the stopping grooves. 
     The flexible display device  1  may further include a first moving surface  255 , a first inclined surface  256 , and a second inclined surface  257 . 
     When the first stopping groove  271  is provided in the first body  200   a,  the first moving surface  255 , the first inclined surface  256 , and the second inclined surface  257  are also provided in the first body  200   a,  and when the first stopping groove  271  is provided in the second body  200   b,  the first moving surface  255 , the first inclined surface  256 , and the second inclined surface  257  are also provided in the second body  200   b.    
     In an exemplary embodiment, when the first stopping groove  271  and the second stopping groove  272  are provided on the first outer edge  250 , the first moving surface  255 , the first inclined surface  256 , and the second inclined surface  257  are provided on the first outer edge  250 . 
     The first moving surface  255  provides a path on which the first stopping ball  551  moves between the first stopping groove  271  and the second stopping groove  272 . The first moving surface  255  may have a constant cross section in the first direction. 
     The first inclined surface  256  interconnects the first stopping groove  271  and the first moving surface  255  and is configured to provide an inclined surface that is closer to the first inner edge  210  as it goes toward the first stopping groove  271 . 
     The second inclined surface  257  interconnects the second stopping groove  272  and the first moving surface  255  and is configured to provide an inclined surface that is closer to the first inner edge  210  as it goes toward the second stopping groove  272 . 
     When a first rolling ball  510  is located on the first moving surface  255 , the first rolling ball  510  may not be in contact with the first moving surface  255 . Meanwhile, the compressive deformation of the first spring  553  when the first rolling ball  510  is located on the first moving surface  255  may be smaller than the compressive deformation of the first spring  553  when the first rolling ball  510  is located on the first stopping groove  271  or the second stopping groove  272 . Accordingly, when the first rolling ball  510  is located on the first moving surface  255 , no friction may occur between the first rolling ball  510  and the first moving surface  255  or the frictional force generated between the first rolling ball  510  and the first moving surface  255  may be minimized. 
     When the first rolling ball  510 , the first moving surface  255 , the first stopping groove  271  and the second stopping groove  272  are provided on the first outer edge  250 , the first rolling ball  510  may be disposed at a position different from those of the first moving surface  255 , the first stopping groove  271 , and the second stopping groove  272  in the third direction (the Z direction). In addition, in the third direction (the Z direction), the first rolling ball  510  is disposed at a position different from those of the first ball plunger  550  and the first stopping ball  551 , so that, when transformation is performed between the first position and the second position, the first rolling ball  510  does not interfere with the first ball plunger  550  and the first stopping ball  551 . 
     The flexible display device  1  may further include a second moving surface  265 , a third inclined surface  266 , and a fourth inclined surface  267 . 
     When the third stopping groove  273  is provided in the first body  200   a,  the second moving surface  265 , the third inclined surface  266 , and the fourth inclined surface  267  are also provided in the first body  200   a,  and when the third stopping groove  273  is provided in the second body  200   b,  the second moving surface  265 , the third inclined surface  266 , and the fourth inclined surface  267  are also provided in the second body  200   b.    
     In an exemplary embodiment, when the third stopping groove  273  and the fourth stopping groove  274  are provided on the second outer edge  260 , the second moving surface  265 , the third inclined surface  266 , and the fourth inclined surface  267  are provided on the second outer edge  260 . 
     The second moving surface  265  forms a path on which the second stopping ball  561  moves between the third stopping groove  273  and the fourth stopping groove  274 . The second moving surface  265  may have a constant cross section in the first direction. 
     The third inclined surface  266  interconnects the third stopping groove  273  and the second moving surface  265  and is configured to provide an inclined surface that is closer to the second inner edge  220  as it goes toward the third stopping groove  273 . 
     The fourth inclined surface  267  interconnects the fourth stopping groove  274  and the second moving surface  265  and is configured to provide an inclined surface that is closer to the second inner edge  220  as it goes toward the fourth stopping groove  274 . 
     When a second rolling ball  520  is located on the second moving surface  265 , the second rolling ball  520  may not be in contact with the second moving surface  265 . Meanwhile, the compressive deformation of the second spring  563  when the second rolling ball  520  is located on the second moving surface  265  may be smaller than the compressive deformation of the second spring  563  when the second rolling ball  520  is located on the third stopping groove  273  or the fourth stopping groove  274 . Accordingly, when the second rolling ball  520  is located on the second moving surface  265 , no friction may occur between the second rolling ball  520  and the second moving surface  265  or the frictional force generated between the second rolling ball  520  and the second moving surface  255  may be minimized. 
     When the second rolling ball  520 , the second moving surface  265 , the third stopping groove  273 , and the fourth stopping groove  274  are provided on the second outer edge  260 , the second rolling ball  520  may be disposed at a position different from those of the second moving surface  265 , the third stopping groove  273 , and the fourth stopping groove  274  in the third direction (the Z direction). In addition, in the third direction (the Z direction), the second rolling ball  520  is disposed at a position different from those of the second ball plunger  560  and the second stopping ball  561 , so that during the transformation between the first position and the second position, the second rolling ball  520  does not interfere with the second ball plunger  560  and the second stopping ball  561 . 
       FIG.  16    is a rear view schematically illustrating a flexible display device  1 . 
       FIG.  17    is an exploded perspective view illustrating tension generators  400 ,  400   a,  and  400   b.    
     The flexible display device  1  may include a tension generator  400 . 
     The tension generator  400  may be configured to pull the flexible display  300  and cause a tensile force to be generated in the flexible display  300 . 
     The tension generator  400  may be coupled to the body  200  and connected to the second region  320  or the third region  330  of the flexible display  300 , and may be configured to increase the tension applied to the flexible display  300  during the transformation from the first position to the second position. 
     In an exemplary embodiment, the tension generator  400  may include a spring. 
     When the flexible display  300  includes the third region  330 , the tension generator  400  may be configured to interconnect the first body  200   a  and the third region  330 , and when the third region  330  approaches the support  240  in the first direction, the tension generator  400  may apply an external force to the flexible display  300  so that the third region  330  moves away from the support  240 . That is, the tension generator  400  may be configured to pull the third region  330  so that the third region  330  approaches the camera  121  in the first direction. 
     When the flexible display  300  includes the third region  330 , the tension generator  400  may be configured to interconnect the second body  200   b  and the third region  330 , and when the third region  330  approaches the support  240  in the first direction, the tension generator  400  may apply an external force to the flexible display  300  so that the third region  330  moves away from the support  240 . That is, the tension generator  400  may be configured to pull the third region  330  so that the third region  330  approaches the camera  121  in the first direction. 
     In the flexible display device  1 , the tension generator  400  may include a first tension generator  400   a  and a second tension generator  400   b.  Each of the first tension generator  400   a  and the second tension generator  400   b  may be configured like the above-described tension generator  400 . 
     The first tension generator  400   a  may be configured to interconnect the second body  200   b  and the third region  330  and apply a tensile force to the flexible display  300  at the second position. 
     The second tension generator  400   b  may connect the second body  200   b  and the third region  330  and apply a tensile force to the flexible display  300  at the second position. 
     Each of the tension generator  400 , the first tension generator  400   a,  and the second tension generator  400   b  may include a tension body  410 , a spool  420 , a spiral spring  430 , and a wire  440 . 
     In addition, each of the tension generator  400 , the first tension generator  400   a,  and the second tension generator  400   b  may include a tension housing  450  in which the spiral spring  430  is accommodated. 
     In addition, each of the tension generator  400 , the first tension generator  400   a,  and the second tension generator  400   b  may include a pulley  460  on which the wire  440  is applied to change the direction of the wire 
     The tension body  410  may be fixed to the second body  200   b  so as not to rotate relative to the second body  200   b.    
     The spool  420  is rotatably coupled to the tension body  410  relative to the rotating shaft  401 , and is configured such that the wire  440  is wound around the rim thereof. 
     The spiral spring  430  may be accommodated in the tension housing  450 , wherein one end portion  431  may be fixed to the tension body  410  and the other end portion  432  may be fixed to the spool  420 . Accordingly, the spool  420  is elastically supported relative to the tension body  410 . That is, when an external force is applied to rotate the spool  420  relative to the tension body  410 , the spiral spring  430  stores elastic energy while being elastically deformed, and when the external force is released, the spool  420  is reversely rotated relative to the tension body  410 . 
     On end portion  441  of the wire  440  is fixed to the spool  420  so that the wire is wound, and the other end portion  442  is connected (fixed) to the third region  330 . The wire  440  of the first tension generator  400   a  and the wire  440  of the second tension generator  400   b  are connected to the third region  330  at points spaced apart from each other. 
     When an external force is applied to the flexible display device  1  such that the flexible display device  1  is transformed from the first position to the second position, the third region  330  approaches the support  240  in the first direction and as the wire  440  is unwound from the spool  420 , the spiral spring  430  stores elastic energy while being elastically deformed. Accordingly, a predetermined tension is applied to the flexible display  300 . 
     When the external force applied to the flexible display device  1  is removed, the wire  440  is wound around the spool  420  again by the elastic restoring force of the spiral spring  430 , and accordingly, the tension generator  400 ,  400   a,  or  400   b  pulls the third region  330  so that the third region  330  approaches the camera  121  in the first direction. 
     Although specific embodiments of the present disclosure have been described above and illustrated in the figures, it will be understood that the present disclosure is not limited to the described embodiments, and various modifications and changes can be made as other specific embodiments by a person ordinarily skilled in the art without departing from the spirit and scope of the present disclosure. Accordingly, the scope of the present disclosure should not be defined by the described embodiments, but should be defined by the technical idea described in the claims. 
     INDUSTRIAL APPLICABILITY 
     The flexible display device according to an exemplary embodiment of the present disclosure is remarkable in industrial applicability in that, when transformation is performed between the first position and the second position, the movement of the second body is facilitated due to the point contact between the rolling balls and the rolling recesses, and the external exposure of the components for the sliding movement of the second body is minimized.