Patent Publication Number: US-11042195-B1

Title: Mobile terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     Pursuant to 35 U.S.C. § 119 (a), this application claims the benefit of an earlier filing date and right of priority to International Application No. PCT/KR2020/004795 filed on Apr. 9, 2020, the contents of which are hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     Field 
     The present disclosure relates to a mobile terminal, and more particularly, to a mobile terminal that has a flexible display and is capable of extending a size of a screen while the display is scrolled and slid at the same time. 
     Discussion of the Related Art 
     Terminals may be generally classified as mobile/portable terminals or stationary terminals according to their mobility. Mobile terminals may also be classified as handheld terminals or vehicle mounted terminals according to whether or not a user can directly carry the terminal. 
     A display device is a device having a function of receiving, processing, and displaying a video that a user may watch. For example, the display device receives a broadcast selected by the user from broadcast signals transmitted from a broadcasting station, separates a video signal from the received signals, and displays the separated video signal on a display. 
     In recent years, because of a development of a broadcasting technology and a network technology, functions of the display device have also been considerably diversified, and a performance of the device has been improved accordingly. That is, the display device has been developed to provide not only broadcast contents but also various other contents to the user. For example, the display device may provide game play, music listening, internet shopping, user customized information, and the like using various applications as well as programs received from the broadcasting station. In order to perform such extended functions, the display device may be basically connected to other devices or networks using various communication protocols, and may provide the user with a ubiquitous computing environment. In other words, the display device has evolved into a smart device that enables connectivity to a network and continuous computing. 
     Recently, a flexible display having sufficient elasticity and capable of large deformation has been developed. The size of a mobile terminal can be varied using the deformable nature of the flexible display. For the mobile terminal having such a variable structure, changing the size of the mobile terminal should be stably performed, and there is a need for a structure to support the extended display unit to maintain a flat state of the display unit. 
     SUMMARY 
     One purpose of the present disclosure is to provide a mobile terminal that may improve durability of a flexible display unit by not restricting a point where the flexible display unit is bent to a specific position. 
     Another purpose of the present disclosure is to provide a mobile terminal including a support structure of a flexible display unit that may stably support the flexible display unit when the flexible display unit is extended. 
     One aspect of the present disclosure proposes a mobile terminal able to be switched from a first state to a second state by expanding in a first direction including a first frame, a second frame movable in a sliding manner from the first frame in the first direction or in a second direction opposite to the first direction, a slide frame movable in the first direction or in the second direction with respect to the second frame, a roller coupled to one side of the second frame in a manner of being rotatable in a third direction perpendicular to the first direction, a flexible display unit including a first region coupled to the first frame, a second region coupled to the slide frame, and a third region positioned between the first region and the second region and bent while surrounding the second frame, and a rolling plate having one surface, wherein the flexible display unit is attached to said one surface of the rolling plate, wherein the roller contains a high friction material. 
     In one implementation, the roller may have a high surface roughness. 
     In one implementation, the roller may contain a thermoplastic polyurethane (TPU) or a thermoplastic polyester elastomer (TPEE). 
     In one implementation, the roller may include an inner high-strength plastic portion and a high-friction outer cover. 
     In one implementation, the rolling plate may contain a metal material, wherein the roller may include an inner magnetic roller and a high-friction outer cover. 
     In one implementation, the magnetic roller may be composed of circumferential series of magnetic portions having alternately arranged opposite polarities. 
     In one implementation, the magnetic roller may have a cylindrical shape combining a plurality of sintered magnets of a shape of a fan-shaped column with each other, wherein a portion in a direction of an outer surface and a portion in a rotation axis of the sintered magnet of the shape of the fan-shaped column may have opposite poles. 
     In one implementation, the roller may further include a roller shaft inserted into a shaft hole extending in the third direction, and each roller bearing fitted on the roller shaft and disposed on each of both sides of the roller shaft, wherein the second frame may include a seating portion, wherein the roller bearing is seated on the seating portion. 
     In one implementation, the roller may include each mini roller having a radius smaller than a radius of curvature of a curved face of the display unit bent while surrounding the roller. 
     In one implementation, each mini roller may include a plurality of mini rollers respectively arranged at a start point, an end point, and a middle portion of the curved face of the display unit. 
     In one implementation, at least one of the mini rollers may contain a high friction material, wherein at least one of the others of the mini rollers may contain a magnet. 
     In one implementation, the mobile terminal may further include a support link having one end hingeably coupled to the first frame and the other end hingeably coupled to the second frame, wherein a length of the support link varies, wherein the support link may be disposed to be adjacent to the roller in the first state. 
     In one implementation, the roller may include a plurality of rollers arranged in the third direction. 
     In one implementation, the rolling plate may include a plurality of support bars extending in the third direction perpendicular to the first direction and arranged side by side in the first direction, wherein the support bar may include a curved face having a curvature corresponding to a curvature of the roller. 
     In one implementation, the rolling plate may further include a magnetic force shielding sheet having one surface attached with the support bars and the other surface coupled to the flexible display unit. 
     The mobile terminal of the present disclosure may adjust a size of a screen as needed, so that both portability and usability may be satisfied. 
     In addition, a phenomenon in which the flexible display unit is lifted when the second frame moves may be prevented, thereby maintaining the display unit in a flat state. 
     In addition, when the flexible display unit expands or contracts, the flexible display unit may stably move. 
     In addition, space utilization may be increased by the mini roller and adhesion between the roller and the rolling plate may be easily adjusted. 
     Further scope of applicability of the present disclosure will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the disclosure, are given by illustration only, since various changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a block diagram of a mobile terminal in accordance with the present disclosure; 
         FIG. 2  is a front view of a first state and a second state of the mobile terminal in accordance with an embodiment; 
         FIG. 3  is a rear view of the first state and the second state of the mobile terminal in accordance with an embodiment; 
         FIGS. 4 and 5  are exploded perspective views of the mobile terminal in accordance with an embodiment; 
         FIG. 6  is a side view of the mobile terminal as viewed from a third direction; 
         FIG. 7  is a view showing a driving unit of the mobile terminal in accordance with an embodiment; 
         FIG. 8  is a cross-sectional view taken along lines A-A and B-B in  FIG. 2 ; 
         FIG. 9  is a view illustrating a display unit and a rolling plate of the mobile terminal in accordance with an embodiment; 
         FIG. 10  is a view illustrating an issue raised in an extendable mobile terminal; 
         FIG. 11  is a cross-sectional view taken along lines C-C and D-D in  FIG. 2 ; 
         FIG. 12  is a cross-sectional view taken along lines E-E and F-F in  FIG. 11 ; 
         FIG. 13  is a view showing an expanded side portion and a guide hook of the mobile terminal in accordance with an embodiment; 
         FIG. 14  is a view showing a rolling plate of the mobile terminal in accordance with an embodiment; 
         FIG. 15  is a view showing a slide frame and a second frame of the mobile terminal; 
         FIGS. 16 and 17  are views showing a magnetic roller coupled to the second frame of the mobile terminal; 
         FIG. 18  is a view showing another embodiment of a roller of the present disclosure; 
         FIG. 19  is a cross-sectional view showing a magnetic roller and a rolling plate in accordance with an embodiment; 
         FIGS. 20 and 21  are views illustrating magnetic force applied to the rolling plate according to the number of poles of the magnetic roller; 
         FIG. 22  is a view showing a magnetic roller and a rolling plate in accordance with another embodiment; 
         FIG. 23  is a view showing another embodiment of a roller of a mobile terminal; 
         FIG. 24  is a view showing another embodiment of a roller of a mobile terminal; and 
         FIG. 25  is a view showing a first state and a second state of a mobile terminal in a state in which front surface components of the mobile terminal are removed. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Description will now be given in detail according to exemplary embodiments disclosed herein, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components may be provided with the same reference numbers, and description thereof will not be repeated. In general, a suffix such as “module” and “unit” may be used to refer to elements or components. Use of such a suffix herein is merely intended to facilitate description of the specification, and the suffix itself is not intended to give any special meaning or function. In the present disclosure, that which is well-known to one of ordinary skill in the relevant art has generally been omitted for the sake of brevity. The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. 
     It will be understood that although the terms first, second, etc. 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. 
     It will be understood that when an element is referred to as being “connected with” another element, the element may be directly connected with the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly connected with” another element, there are no intervening elements present. 
     A singular representation may include a plural representation unless it represents a definitely different meaning from the context. 
     Terms such as “include” or “has” are used herein and should be understood that they are intended to indicate an existence of several components, functions or steps, disclosed in the specification, and it is also understood that greater or fewer components, functions, or steps may likewise be utilized. 
       FIG. 1  is a block diagram of a mobile terminal in accordance with the present disclosure. 
     The mobile terminal  100  is shown having components such as a wireless communication unit  110 , an input unit  120 , a sensing unit  140 , an output unit  150 , an interface unit  160 , a memory  170 , a controller  180 , and a power supply unit  190 . Referring now to  FIG. 1 , the mobile terminal  100  is shown having wireless communication unit  110  configured with several commonly implemented components. It is understood that implementing all of the illustrated components is not a requirement, and that greater or fewer components may alternatively be implemented. 
     More specifically, the wireless communication unit  110  typically includes one or more modules which permit communications such as wireless communications between the mobile terminal  100  and a wireless communication system, communications between the mobile terminal  100  and another mobile terminal, communications between the mobile terminal  100  and an external server. Further, the wireless communication unit  110  typically includes one or more modules which connect the mobile terminal  100  to one or more networks. 
     To facilitate such communications, the wireless communication unit  110  includes one or more of a broadcast receiving module  111 , a mobile communication module  112 , a wireless Internet module  113 , a short-range communication module  114 , and a location information module  115 . 
     Regarding the wireless communication unit  110 , the broadcast receiving module  111  is typically configured to receive a broadcast signal and/or broadcast associated information from an external broadcast managing entity via a broadcast channel. The broadcast channel may include a satellite channel, a terrestrial channel, or both. In some embodiments, two or more broadcast receiving modules  111  may be utilized to facilitate simultaneously receiving of two or more broadcast channels, or to support switching among broadcast channels. 
     The mobile communication module  112  may transmit and/or receive wireless signals to and from one or more network entities. Typical examples of a network entity include a base station, an external mobile terminal, a server, and the like. Such network entities form part of a mobile communication network, which is constructed according to technical standards or communication methods for mobile communications (for example, Global System for Mobile Communication (GSM), Code Division Multi Access (CDMA), CDMA2000 (Code Division Multi Access 2000), EV-DO (Enhanced Voice-Data Optimized or Enhanced Voice-Data Only), Wideband CDMA (WCDMA), High Speed Downlink Packet access (HSDPA), HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like). 
     Examples of wireless signals transmitted and/or received via the mobile communication module  112  include audio call signals, video (telephony) call signals, or various formats of data to support communication of text and multimedia messages. 
     The wireless Internet module  113  is configured to facilitate wireless Internet access. This module may be internally or externally coupled to the mobile terminal  100 . The wireless Internet module  113  may transmit and/or receive wireless signals via communication networks according to wireless Internet technologies. 
     Examples of such wireless Internet access include Wireless LAN (WLAN), Wireless Fidelity (Wi-Fi), Wi-Fi Direct, Digital Living Network Alliance (DLNA), Wireless Broadband (WiBro), Worldwide Interoperability for Microwave Access (WiMAX), High Speed Downlink Packet Access (HSDPA), HSUPA (High Speed Uplink Packet Access), Long Term Evolution (LTE), LTE-A (Long Term Evolution-Advanced), and the like. The wireless Internet module  113  may transmit/receive data according to one or more of such wireless Internet technologies, and other Internet technologies as well. 
     In some embodiments, when the wireless Internet access is implemented according to, for example, WiBro, HSDPA, HSUPA, GSM, CDMA, WCDMA, LTE, LTE-A and the like, as part of a mobile communication network, the wireless Internet module  113  performs such wireless Internet access. As such, the Internet module  113  may cooperate with, or function as, the mobile communication module  112 . 
     The short-range communication module  114  is configured to facilitate short-range communications. Suitable technologies for implementing such short-range communications include BLUETOOTH™, Radio Frequency Identification (RFID), Infrared Data Association (IrDA), Ultra-WideBand (UWB), ZigBee, Near Field Communication (NFC), Wireless-Fidelity (Wi-Fi), Wi-Fi Direct, Wireless USB (Wireless Universal Serial Bus), and the like. The short-range communication module  114  in general supports wireless communications between the mobile terminal  100  and a wireless communication system, communications between the mobile terminal  100  and another mobile terminal  100 , or communications between the mobile terminal and a network where another mobile terminal  100  (or an external server) is located, via wireless area networks. One example of the wireless area networks is a wireless personal area networks. 
     The location information module  115  is generally configured to detect, calculate, derive or otherwise identify a position of the mobile terminal. As an example, the location information module  115  includes a Global Position System (GPS) module, a Wi-Fi module, or both. If desired, the location information module  115  may alternatively or additionally function with any of the other modules of the wireless communication unit  110  to obtain data related to the position of the mobile terminal. As one example, when the mobile terminal uses a GPS module, a position of the mobile terminal may be acquired using a signal sent from a GPS satellite. As another example, when the mobile terminal uses the Wi-Fi module, a position of the mobile terminal may be acquired based on information related to a wireless access point (AP) which transmits or receives a wireless signal to or from the Wi-Fi module. 
     The input unit  120  includes a camera  121  for obtaining images or video, a microphone  122 , which is one type of audio input device for inputting an audio signal, and a user input unit  123  (for example, a touch key, a push key, a mechanical key, a soft key, and the like) for allowing a user to input information. Data (for example, audio, video, image, and the like) is obtained by the input unit  120  and may be analyzed and processed by controller  180  according to device parameters, user commands, and combinations thereof. 
     Such cameras  121  may process image frames of still pictures or video obtained by image sensors in a video or image capture mode. The processed image frames may be displayed on the display unit  151  or stored in memory  170 . In some cases, the cameras  121  may be arranged in a matrix configuration to permit a plurality of images having various angles or focal points to be input to the mobile terminal  100 . As another example, the cameras  121  may be located in a stereoscopic arrangement to acquire left and right images for implementing a stereoscopic image. 
     The microphone  122  is generally implemented to permit audio input to the mobile terminal  100 . The audio input may be processed in various manners according to a function being executed in the mobile terminal  100 . If desired, the microphone  122  may include assorted noise removing algorithms to remove unwanted noise generated in the course of receiving the external audio. 
     The user input unit  123  is a component that permits input by a user. Such user input may enable the controller  180  to control operation of the mobile terminal  100 . The user input unit  123  may include one or more of a mechanical input element (for example, a key, a button located on a front and/or rear surface or a side surface of the mobile terminal  100 , a dome switch, a jog wheel, a jog switch, and the like), or a touch-sensitive input, among others. As one example, the touch-sensitive input may be a virtual key or a soft key, which is displayed on a touch screen through software processing, or a touch key which is located on the mobile terminal at a location that is other than the touch screen. On the other hand, the virtual key or the visual key may be displayed on the touch screen in various shapes, for example, graphic, text, icon, video, or a combination thereof. 
     The sensing unit  140  is typically implemented using one or more sensors configured to sense internal information of the mobile terminal, the surrounding environment of the mobile terminal, user information, and the like. For example, the sensing unit  140  may alternatively or additionally include other types of sensors or devices, such as a proximity sensor  141  and 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, a ultrasonic sensor, an optical sensor (for example, camera  121 ), a microphone  122 , a battery gauge, an environment sensor (for example, a barometer, a hygrometer, a thermometer, a radiation detection sensor, a thermal sensor, and a gas sensor, among others), and a chemical sensor (for example, an electronic nose, a health care sensor, a biometric sensor, and the like), to name a few. The mobile terminal  100  may be configured to utilize information obtained from sensing unit  140 , and in particular, information obtained from one or more sensors of the sensing unit  140 , and combinations thereof. 
     The output unit  150  is typically configured to output various types of information, such as audio, video, tactile output, and the like. The output unit  150  is shown having a display unit  151 , an audio output module  152 , a haptic module  153 , and an optical output module  154 . The display unit  151  may have an inter-layered structure or an integrated structure with a touch sensor in order to facilitate a touch screen. The touch screen may provide an output interface between the mobile terminal  100  and a user, as well as function as the user input unit  123  which provides an input interface between the mobile terminal  100  and the user. 
     The audio output module  152  is generally configured to output audio data. Such audio data may be obtained from any of a number of different sources, such that the audio data may be received from the wireless communication unit  110  or may have been stored in the memory  170 . The audio data may be output during modes such as a signal reception mode, a call mode, a record mode, a voice recognition mode, a broadcast reception mode, and the like. The audio output module  152  may provide audible output related to a particular function (e.g., a call signal reception sound, a message reception sound, etc.) performed by the mobile terminal  100 . The audio output module  152  may also be implemented as a receiver, a speaker, a buzzer, or the like. 
     A haptic module  153  may be configured to generate various tactile effects that a user feels, perceive, or otherwise experience. A typical example of a tactile effect generated by the haptic module  153  is vibration. The strength, pattern and the like of the vibration generated by the haptic module  153  may be controlled by user selection or setting by the controller. For example, the haptic module  153  may output different vibrations in a combining manner or a sequential manner. 
     An optical output module  154  may output a signal for indicating an event generation using light of a light source. Examples of events generated in the mobile terminal  100  may include message reception, call signal reception, a missed call, an alarm, a schedule notice, an email reception, information reception through an application, and the like. 
     The interface unit  160  serves as an interface with various types of external devices that may be coupled to the mobile terminal  100 . The interface unit  160 , for example, may include any of wired or wireless ports, external power supply ports, wired or wireless data ports, memory card ports, ports for connecting a device having an identification module, audio input/output (I/O) ports, video I/O ports, earphone ports, and the like. In some cases, the mobile terminal  100  may perform assorted control functions associated with a connected external device, in response to the external device being connected to the interface unit  160 . 
     The memory  170  is typically implemented to store data to support various functions or features of the mobile terminal  100 . For instance, the memory  170  may be configured to store application programs executed in the mobile terminal  100 , data or instructions for operations of the mobile terminal  100 , and the like. Some of these application programs may be downloaded from an external server via wireless communication. Other application programs may be installed within the mobile terminal  100  at time of manufacturing or shipping, which is typically the case for basic functions of the mobile terminal  100  (for example, receiving a call, placing a call, receiving a message, sending a message, and the like). It is common for application programs to be stored in the memory  170 , installed in the mobile terminal  100 , and executed by the controller  180  to perform an operation (or function) for the mobile terminal  100 . 
     The controller  180  typically functions to control overall operation of the mobile terminal  100 , in addition to the operations associated with the application programs. The controller  180  may provide or process information or functions appropriate for a user by processing signals, data, information and the like, which are input or output, or activating application programs stored in the memory  170 . 
     To drive the application programs stored in the memory  170 , the controller  180  may be implemented to control a predetermined number of the components mentioned above in reference with  FIG. 1 . Moreover, the controller  180  may be implemented to combinedly operate two or more of the components provided in the mobile terminal  100  to drive the application programs. 
     The power supply unit  190  may be configured to receive external power or provide internal power in order to supply appropriate power required for operating elements and components included in the mobile terminal  100 . The power supply unit  190  may include a battery, and the battery may be configured to be embedded in the terminal body, or configured to be detachable from the terminal body. 
     Some or more of the components may be operated cooperatively to embody an operation, control or a control method of the mobile terminal in accordance with embodiments of the present disclosure. Also, the operation, control or control method of the mobile terminal may be realized on the mobile terminal by driving of one or more application problems stored in the memory  170 . 
       FIG. 2  is a front view of a first state and a second state of the mobile terminal in accordance with an embodiment, and  FIG. 3  is a rear view of the first state and the second state of the mobile terminal in accordance with an embodiment.  FIGS. 2( a ) and 3( a )  are views showing the first state in which the mobile terminal is contracted, and  FIGS. 2( b ) and 3( b )  are views showing the second state in which the mobile terminal is extended. 
     As shown in the figures, the mobile terminal  100  in the first state is in a contracted position, and has a smaller size than the mobile terminal  100  in the second state. In addition, the size of the display unit  151  positioned on the front of the mobile terminal  100  is also smaller than in the second state. The mobile terminal  100  in the first state may be extended in a first direction D 1  to switch to the second state. In the second state, as shown in  FIG. 2( b ) , the size of the mobile terminal  100  and the size of the display unit  151  positioned on the front of the mobile terminal  100  are larger than in the first state, while the size of the display unit  151  positioned on the rear of the mobile terminal  100  is reduced as shown in  FIG. 3( b ) . That is, a part of the display units  151  positioned on the rear of the mobile terminal  100  in the first state moves to the front of the mobile terminal  100  in the second state. 
     In the following description, the direction in which the mobile terminal  100  and the display unit  151  thereof are extended or enlarged is defined as a first direction D 1 , and the direction in which the mobile terminal contracts or retracts or is reduced to switch from the second state to the first state is defined as a second direction D 2 . A direction perpendicular to the first and second directions D 1  and D 2  is defined as a third direction. Description will be made on the assumption that the first and second directions are horizontal directions and the third direction is a vertical direction. However, depending on the arrangement of the mobile terminal  100 , the first and second directions may be vertical directions and the third direction may be a horizontal direction. 
     As such, a flexible display unit  151  which is bendable may be used as the display unit such that the position of the display unit may be varied. The flexible display unit  151  may be a display unit capable of maintaining a flat state like a conventional flat panel display and capable of warping, bending, folding, twisting, or rolling like paper. The flexible display unit  151  refers to a display which is manufactured on a thin and flexible substrate and is thus lightweight and robust as not to be easily broken. The flexible display unit according the present disclosure may be bent in a specific direction, and may be arranged such that the curvature thereof may change in the first direction. 
     In addition, electronic paper is a display technology to which properties of general ink are applied. The electronic paper may be different from the conventional flat panel display in using reflected light. The electronic paper may change information using a twisted ball or electrophoresis using a capsule. 
     In a state in which the flexible display unit  151  is not deformed (e.g., a state of having an infinite curvature radius, hereinafter referred to as a basic state), a display region of the flexible display unit  151  becomes flat. In a state in which the flexible display unit  151  is deformed by an external force from the basic state (e.g., a state of having a finite radius of curvature, hereinafter referred to as a deformed state), the display region may become a curved face. As shown, information displayed in the deformation state may be visual information output on the curved face. Such visual information is implemented by independently controlling light emission of sub-pixels arranged in a matrix. The sub-pixel refers to a minimum unit for implementing one color. When external force is applied to the flexible display unit  151 , the flexible display unit  151  may be deformed to switch from the default state, which is the flat state, to a bent state, which is not the flat state. 
     The flexible display unit  151  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 ) may perform control corresponding to such touch input. The flexible touch screen may be configured to detect the touch input in the deformed state as well as in the basic state. 
     The touch sensor detects the touch (or touch input) applied on the touch screen using at least one of various touch schemes such as a resistive film scheme, a capacitance scheme, an infrared scheme, an ultrasonic wave scheme, a magnetic field scheme, and the like. 
     As an example, the touch sensor may be configured to convert a change in pressure applied on a specific portion of the touch screen, capacitance generated at the specific portion, or the like into an electrical input signal. The touch sensor may be configured such that a touch object applying a touch on the touch screen may detect touched position and area on the touch sensor, a pressure during the touch, a capacitance during the touch, and the like. 
     Further, the mobile terminal  100  may have a deformation detection means for detecting the deformation of the flexible display unit  151 . Such deformation detection means may be included in the sensing unit  140  (see  FIG. 1 ). 
     The deformation detection means may be disposed in the flexible display unit  151  or a case (first to second frames  101  to  102  to be described later) to detect information related to the deformation of the flexible display unit  151 . In this connection, the information related to the deformation may include a direction in which the flexible display unit  151  is deformed, a degree of the deformation, a deformed position, a deformed time, an acceleration at which the deformed flexible display unit  151  is restored, and the like. In addition, the information related to the deformation may include various kinds of information that may be detected due to the bending of the flexible display unit  151 . 
     In addition, the controller  180  may change information displayed on the flexible display unit  151  or generate a control signal for controlling a function of the mobile terminal  100  based on the information related to the deformation of the flexible display unit  151  detected by the deformation detection means. 
     The deformation of the flexible display unit  151  may vary depending on the positions of the first frame  101  and the second frame  102 . As shown in  FIG. 2 , since the bending position on the flexible display unit  151  is determined according to the positions of the first frame and the second frame, the bending deformation position of the flexible display unit  151  and the area thereof positioned on the front may be calculated based on the positions of the first frame  101  and the first frame  102  in place of the deformation detection means of the flexible display unit  151 . 
     The state conversion (first or second state) of the flexible display unit  151 , i.e., the size change at the front and rear faces of the mobile terminal  100  of the display unit  151  based on the size change of the mobile terminal  100  may be performed manually by a force applied by the user, but may be not limited to such manual scheme. For example, when the mobile terminal  100  or the flexible display unit  151  is in the first state, the mobile terminal  100  or the flexible display unit  151  may be converted into the second state by the user or an application command without the external force applied by the user. As such, in order for the flexible display unit  151  to be automatically deformed without the external force, the mobile terminal  100  may include a driving unit  200 , which will be described later. 
     The flexible display unit  151  of the present disclosure is bent 180 degrees by rolling around a side portion of the mobile terminal  100  facing in the first direction. Accordingly, based on the side portion of the mobile terminal  100 , a part of the flexible display unit  151  is disposed on the front of the mobile terminal  100 , and the other part of the flexible display unit  151  is disposed on the rear of the mobile terminal  100 . For simplicity, the part of the flexible display unit  151  positioned on the front is called a front face, and the other part of the flexible display unit  151  positioned on the rear is called a rear face. As illustrated in  FIG. 2 , the mobile terminal may extend in the first direction or contract in the second direction opposite to the first direction. In this case, the area of the flexible display unit  151  positioned on the front changes. That is, the sizes of the front face and the rear face may be changed according to a change in the state of the mobile terminal. 
     The part of the flexible display unit  151  positioned on the front of the mobile terminal  100  may be immovably fixed to the front surface of the first frame  101 , and the other part thereof positioned on the rear of the mobile terminal  100  may be movably arranged on the rear of the mobile terminal  100 . 
     In addition, the flexible display unit  151  may be rolled on or released at the side portion in the first direction of mobile terminal. Accordingly, the rear face of the display unit  151  moves, so that the size of the front face of the display unit  151  may be adjusted. Since the size of the flexible display unit  151  is determined and the flexible display unit  151  is formed of one continuous body, an area of the rear face of the display unit  151  decreases as an area of the front face of the display unit  151  increases. Such a display unit  151  may be rolled in a second frame  102 , which is movable relative to a first frame  101  to be described later, more correctly, on one of sides of the second frame  102 . The display unit  151  may be withdrawn or pulled out from or inserted or pushed into the second frame  102  while being rolled in the second frame  102  along a moving direction of the second frame  102  to adjust the area of the display unit  151  on the front face of the mobile terminal  100 . Such operation will be described in more detail below along with other relevant components of the mobile terminal  100 . 
     Typically, an antenna is disposed in the case or the housing of the mobile terminal  100 , but a portion where the antenna is installed in the case or the housing may be limited because of the flexible display unit  151  that covers not only the front face of the mobile terminal  100  but also the rear face thereof. For this reason, the antenna may be implemented on the flexible display unit  151 . An antenna on display (AOD) is an antenna in which a transparent film is formed by stacking an electrode layer and a dielectric layer that have patterns engraved thereon, respectively. The antenna on display may be implemented thinner than an antenna implemented using a laser direct structuring (LDS) technology using a conventional copper nickel plating scheme, so that the antenna on display may not be exposed to the outside without affecting a thickness. In addition, the antenna on display may transmit and receive a signal directly to or from the display unit  151 . Accordingly, the antenna on display may be used in the mobile terminal  100  in which the display unit  151  is located on the both faces of the mobile terminal  100  as in the present disclosure. 
       FIGS. 4 and 5  are exploded perspective views of the mobile terminal in accordance with an embodiment.  FIG. 4  is an exploded perspective view of the mobile terminal as viewed from the front side, and  FIG. 5  is an exploded perspective view of the mobile terminal as viewed from the rear side. 
     The mobile terminal  100  of the present disclosure includes frames  101  and  102  in which components are mounted, and the frames  101  and  102  of the present disclosure may vary in size in the first direction as shown in  FIG. 2 . One or more frames  101  and  102  move relative to each other, and sizes thereof may vary in the first direction. Electronic components are mounted in the frames  101  and  102 , and the flexible display unit  151  is located out of the frames  101  and  102 . 
     Since the mobile terminal  100  of the present disclosure includes the flexible display unit  151 , the flexible display unit  151  may be combined in a form surrounding front faces and rear faces of the frames  101  and  102 . The frame may include the first frame  101  and the second frame  102  moving in the first direction with respect to the first frame  101 . The first frame  101  and the second frame  102  include front portions, a rear portions, and side portions, respectively, and are coupled to each other. 
     First, the first frame  101  corresponds to a main body of the mobile terminal  100 , and may have a space between the first front portion  1011  and the first rear portion  1012  therein for accommodating various components. In addition, the first frame  101  may accommodate the second frame  102  movably coupled to the first frame  101  in such a space. More specifically, as shown in  FIGS. 2 and 5 , the first frame  101  may include a first front portion  1011  disposed at a front portion of the mobile terminal  100  and supporting the front face of the display unit  151  and a first rear portion  1012  disposed at a rear portion of the mobile terminal and on which various components are mounted. A front deco  1016  may cover front edges of the first area  151   a  to protect the edges of the first area  151   a.    
     The first front portion  1011  and the first rear portion  1012  may be spaced apart from each other at a predetermined spacing to define a predetermined space therebetween, and may be connected to each other by a first side portion  1013 . The first side portion  1013  may be integrally formed with the first rear portion  1012  or the first front portion  1011 . The camera  121 , the audio output module  152 , and the input/output terminal, the controller  180 , and the power supply unit  190  may be accommodated as components of the mobile terminal  100  in the space in the first frame  101 . For example, the controller  180  may be a circuit board  181  including a processor and an electronic circuit for controlling the operation of the mobile terminal, and the power supply unit  190  may be a battery  191  and related components. In addition, the driving unit  200  that controls the slide movement of the second frame  102 , which will be described later, may also be accommodated in the first frame  101 . 
     As described above, the display unit  151  has the continuous body, and thus, may be disposed on both the front face and the rear face of the mobile terminal  100  while being rolled in the mobile terminal  100 . The display unit  151  may include the front face positioned at the front face of the mobile terminal  100 , the rear face positioned at the rear face of the mobile terminal  100 , and the side face positioned between the front face and the rear face thereof and surrounding the side face of the mobile terminal. The front face and the rear face of the display unit  151  are flat, and the side face of the display unit  151  may form a curved face. The flexible display unit  151  may be damaged when being bent at an angle. Thus, the flexible display unit  151  may be formed to be bent with a predetermined curvature at the side face. 
     The display unit  151  may be divided into a fixed portion  151   a  and  151   b  and a variable portion  151   c . The fixed portion  151   a  and  151   b  means a portion fixed to the frame. Because of being fixed to the frame, the fixed portion  151   a  and  151   b  maintains a constant shape without changing a bending degree. On the other hand, the variable portion  151   c  means a portion in which a bending angle or a position of the bent portion changes. The variable portion  151   c  in which the position or bending angle of the bent portion changes requires a structure for supporting a rear face of the variable portion  151   c  in response to the change. 
     The fixed portion  151   a ,  151   b  is coupled to the first frame of the display unit and is always positioned on the front face of the display unit to form a portion of the front face of the display unit. The variable portion  151   c  includes a side face located at a side portion of the mobile terminal, and a position of the side face varies depending on the position of the second frame. Based on a side face, an area of a portion disposed on the front face of the display unit and an area of a portion disposed on the rear face of the display unit vary. That is, a portion of the variable portion  151   c  may be the front face and another portion of the variable portion  151   c  may be the rear face based on the first and second states. The variable portion  151   c  is positioned in the first direction with respect to the fixed portion  151   a ,  151   b  relative to the mobile terminal, and an end of the variable portion  151   c  is bent toward the rear face of the mobile terminal and slides on the rear face of the second frame. 
     The end of the variable portion of the display unit is coupled with a slide frame that guides the variable portion to slide move on the rear face of the second frame, and the slide frame moves in the first direction at the same time as the second frame moves in the first direction. As a result, a moving distance of the slide frame with respect to the first frame is twice as a moving distance of the second frame with respect to the first frame. Further, as shown in  FIG. 3 , the first rear portion  1012  of the mobile terminal  100  includes an exposed rear portion  1015  that is exposed to the outside without being covered by the display unit  151  even in the first state. The physical input unit  120  for the manipulation of the mobile terminal  100  such as various buttons, switches, the camera  121 , and a flash, and the sensing unit  140  such as the proximity sensor  141  or a fingerprint sensor may be arranged on the exposed rear portion  1015 . The first rear portion  1012  except for the exposed rear portion  1015  may be covered by the display unit  151  in the first state as shown in  FIG. 3( a ) , and may be exposed rearward in the second state as shown in  FIG. 3( b ) . 
     In a conventional bar-shaped terminal, a display unit is provided only on a front face of the terminal. Therefore, a main camera is placed on a rear face of the terminal in order for the user to capture an object at an opposite side while looking through the display unit. On the other hand, an additional auxiliary camera is required to be disposed on the front face of the terminal in order for the user to photograph himself or herself while viewing himself or herself through the display unit. 
     In the mobile terminal  100  of the present disclosure, on the other hand, the display unit  151  is arranged on both the front and rear of the mobile terminal  100 . Accordingly, when a user photographs himself, a portion of the display unit  151  positioned on the same surface as the camera  121 , that is, the rear face of the display unit  151  may be used. When the user takes a photograph of an object around the user, a portion of the display unit  151  on the side facing away from the camera  121 , that is, the front face of the display unit  151  may be used. For this reason, the mobile terminal  100  may take a photograph of the user or an object located around the user using one camera  121 . The camera may include a plurality of cameras having different angles of view, such as wide angle, ultra wide angle, and telephoto angle. Not only the camera but also a proximity sensor and an audio output unit may be disposed on the exposed rear portion  1015 , and an antenna may be installed on the rear portion  1015 . A rear portion  1015  may be used to protect the camera, the sensor, or the like on the exposed rear portion  1015  and not to deteriorate the exterior design. A portion of the rear portion  1015  corresponding to the camera  121  or the sensor  140  may be configured to be transparent, and the other portion thereof may have a predetermined pattern or color in consideration of design aspects without exposing internal parts. 
     The first side portion  1013  may extend along the edges of the first front portion  1011  and the first rear portion  1012  to surround the circumference of the first frame  101  and may define the appearance of the mobile terminal  100 . However, as mentioned above, the second frame  102  is accommodated in and movably coupled to the first frame  101 , and therefore a portion of the first frame  101  needs to be open to allow movement of the second frame  102  relative to the first frame  101 . As an example, as best shown in  FIG. 2 , the second frame  102  may be movably coupled to a side of the first frame  101  facing in the first direction, and accordingly the first side portion  1013  may not be formed on the lateral surface facing in the first direction such that the lateral surface is open. Since the first side portion  1013  is exposed to the outside of the mobile terminal  100 , the interface unit  160  for connecting a power port or an ear jack or the user input unit  120 , such as a volume control button, may be disposed on the first side portion  1013 . When the first side portion  1013  contains a metal material, the first side portion  1013  may serve as an antenna. 
     The second frame  102  may include a second front portion  1021  disposed at the front portion of the mobile terminal  100  and a second rear portion  1022  disposed at the rear portion of the mobile terminal  100 . Like the first front portion  1011  and the first rear portion  1012  of the first frame  101 , the second front portion  1021  and the second rear portion  1022  may be formed of plate-shaped members that are generally flat. In addition, the second frame  102  also accommodates various components, and must not interfere with the components accommodated in the first frame  101  during the movement. Accordingly, the second front portion  1021  and the second rear portion  1022  may be coupled to each other in a state of being spaced apart from each other to define a predetermined space therebetween, and may have shapes that do not interfere with the components in the first frame  101 . 
       FIG. 6  is a side view of the mobile terminal as viewed from a third direction.  FIG. 6  shows the first side portion  1013  of the first frame  101  and a second side portion  1023  of the second frame  102 . Since the flexible display unit  151  is positioned at an end of the second frame  102  facing in the first direction, the end of the second frame  102  facing in the first direction should not be exposed to the outside. An end of the second frame  102  facing in the second direction should be open so as not to interfere with the first frame  101 . In the first state, the second side portion  1023  of the second frame  102 , which is positioned on the side facing in the third direction (which refers to the upward or downward direction in the drawing or may include both the upward and downward directions), may not be exposed to the outside because it overlaps the first side portion  1013  of the first frame. However, in the second state, it may be exposed to the outside because the second frame  102  is drawn out. 
     In addition, the display unit  151  may be bent 180 degrees while being rolled in the second frame  102  to be disposed on both the front face and the rear face of the mobile terminal  100 . For such an arrangement of the display unit  151 , the second frame  102  may include a roller  210  rotatably disposed therein. The roller  210  may be disposed at any position inside the second frame  102 . However, the display unit  151  should be spread flat on the front face and the rear face of the mobile terminal  100  to provide a good quality screen to the user. Further, for such spread, a proper tension must be provided on the display unit  151 . In order to provide the proper tension, the roller  210  may be disposed at a first directional end of the second frame  102 . The roller  210  may extend in the third direction, and may be rotatably coupled to the second frame  102 . 
     The display unit  151  may be rolled around the roller  210  while being gently bent with a predetermined curvature. The flexible display unit  151  may include a first face on which a video is output and exposed to the outside and an inner face facing the frame at the opposite side. The roller  210  may be installed to rotate freely in the second frame  102  while being in contact with the inner face of the display unit  151 . Accordingly, the roller  210  may actually move the display unit  151  in a lateral direction of the mobile terminal  100 , that is, in a direction perpendicular to a longitudinal direction. As will be described later, when the second frame  102  slides, because of the tension applied by the second frame  102 , the display unit  151  moves to the front face or the rear face of the mobile terminal  100  in different directions (i.e., the first direction D 1  or the second direction D 2 ) relative to the second frame  102 . The roller  210  may guide such movement while rotating. 
     The roller  210  may be disposed adjacent to the end of the second frame  102  that faces in the first direction. A side frame  1024  may be disposed at the end of the second frame  102  facing in the first direction to prevent damage to the display unit  151  rolled around the roller  210 . 
     The side frame  1024  may extend in the longitudinal direction (the third direction) of the second frame  102  to cover the side portion facing in the first direction, thereby protecting the roller  210  and the display unit  151  rolled therearound. 
     The side frame  1024  may substantially define the appearance of the mobile terminal  100  in cooperation with the first side portion  1013  of the first frame  101 . In addition, the side portion of the second frame  102  that faces in the second direction may be omitted to minimize interference with the components arranged in the first frame  101  during movement. 
     During the expansion and the contraction in such first and second directions D 1  and D 2 , the second frame  102  may overlap the first frame  101 , more precisely, the first front portion  1011  and the first rear portion  1012  thereof so as not to interfere with the first frame  101 . More specifically, the display unit  151  may be coupled to and supported by the first front portion  1011  of the first frame  101 , as described above. Accordingly, the display unit  151  does not need to be additionally supported by the second front portion  1021  of the second frame  102 . Rather, when the second front portion  1021  is interposed between the first front portion  1011  and the display unit  151 , the display unit  151  may be deformed or damaged because of friction with the second front portion  1021 , which is repeatedly moved. Thus, the second front portion  1021  may be disposed below the first front portion  1011 , or may be interposed between two first front portions  1011 . The second rear portion  1022  of the second frame  102  may be disposed rearward of the first rear portion  1012  of the first frame  101 . That is, the front face of the second rear portion  1022  may face the rear face of the first rear portion  1012 . In addition, the rear face of the first rear portion  1012  may be in contact with the front face of the second rear portion  1022  to stably support the movement of the second frame  102 . Because of such arrangement, the second rear portion  1022  may be exposed to the outside of the first frame, more precisely, of the first rear portion  1012 , and may be coupled to the display unit  151 . 
     In addition, the second frame  102  may extend and contract in the first and second directions D 1  and D 2  to change the size of the mobile terminal  100 , particularly, to extend or contract the front face of the mobile terminal  100 . Thus, the display unit  151  must move by such extended or reduced front face size to obtain the intended first and second states. However, when being fixed to the second frame  102 , the display unit  151  may not be moved smoothly to be adapted for the front face of the mobile terminal  100  that is extended or contracted. For this reason, the display unit  151  may be movably coupled to the second frame  102 . 
     More specifically, the display unit  151  may include a first region  151   a  disposed on the front of the mobile terminal  100 , a second region  151   b  coupled to a slide frame  103  positioned on the rear of the mobile terminal  100 , and a third region  151   c  located between the first region  151   a  and the second region  151   b  and bent around the roller  210 . The third region  151   c  may move to the front or the rear according to change in the state of the mobile terminal  100 . The slide frame  103  may be formed of a plate-shaped member extending in the longitudinal direction (the third direction) of the mobile terminal  100 , and may be coupled to the second rear portion  1022  so as to be movable in the first and second directions D 1  and D 2 . 
     The first to third regions  151   a ,  151   b , and  151   c  may be connected to each other, and may form a continuous body of the display unit  151 . In addition, as described above, for the movement of the third region  151   c  toward the front face or the rear face of the mobile terminal  100  depending on the moving direction of the second frame  102 , the first region  151   a  may be fixed so as not to move to the front face of the mobile terminal  100 , and the second region  151   b  may be provided to be movable on the rear face of the mobile terminal. Such configuration of the display unit  151  will be described in more detail below. 
     The first region  151   a  may be disposed on the front face of the mobile terminal  100 , more specifically, the first frame  101 , that is, on the front face of the first front portion  1011 . The first region  151   a  is fixed to the first frame  101 , that is, the front face of the first front portion  1011  so as not to be moved during the movement of the second frame  102 , and thus, the first region  151   a  may always be exposed to the front face of the mobile terminal  100 . 
     The third region  151   c  may be adjacent to the first region  151   a  in the first direction and rolled on the roller  210 . The third region  151   c  may partially cover the second frame  102 , that is, the rear face of the second rear portion  1022 . Further, the second frame  102 , that is, the second rear portion  1022 , is adjacent to the first frame  101 , namely the first rear portion  1012  and together forms the rear case of the mobile terminal  100 . Accordingly, it may be described that the third region  151   c  is also disposed on the rear face of the first frame  101 . 
     The second region  151   b  may be adjacent to the third region  151   c  and may be disposed on the rear face of the mobile terminal  100 , more specifically, on the second frame  102 , that is, the rear face of the second rear portion  1022  thereof. The second region  151   b  may be coupled to the slide frame  103  without being directly coupled to the second frame  102 . 
     As a result, the first region  151   a  may be disposed on the front face of the mobile terminal  100  and may be always exposed to the front face regardless of the movement of the second frame  102 , and the second region  151   b  may be disposed on the rear face of the mobile terminal  100  and may be always exposed to the rear face regardless of the movement of the second frame  102 . In addition, the third region  151   c  may be disposed between the first and second regions  151   a  and  151   b , and may be selectively placed on the front face or the rear face of the mobile terminal  100  depending on the moving directions D 1  and D 2  of the second frame  102 . 
     Because of such selective placement of the third region  151   c , the first rear portion  1012  of the first frame  101  may be exposed to the outside of the mobile terminal  100  because the first rear portion  1012  is covered by the second and third regions  151   b  and  151   c  and the second rear portion  1022  of the display unit  151  in the first state, but, in the second state, the third region  151   c  moves to the front face of the mobile terminal  100  and the second rear portion  1022  also moves in the first direction D 1 . In addition, the second front portion  1021  of the second frame  102  is hidden by the first front portion  1011  of the first frame  101  in the first state, but, in the second state, moves out of the first frame  101  to support the third region  151   c  of the display unit  151  disposed on the front face of the mobile terminal  100 . 
     In order to prevent the second front portion  1021  from affecting the internal components during the slide movement, a separating plate  1017  may be further disposed rearward of the second front portion  1021  and fastened with the first front portion  1011 . The second front portion  1021  may move between the first front portion  1011  and the separating plate  1017  based on the slide movement of the second frame. 
     However, the third region  151   c  may be rolled on the roller  210  and bent in the second frame  102 . When converting from the first state to the second state, the third region  151   c  may extend from the second frame  102  to the front face of the mobile terminal  100  while being rolled on the roller  210  in one direction. On the other hand, when converting from the second state to the first state, the third region  151   c  may be retracted from the front face of the mobile terminal  100  to the second frame  102  while being rolled on the roller  210  in the opposite direction, and at the same time, may return to the rear face of the mobile terminal  100  from the second frame  102 . 
     A specific location of the foldable mobile terminal in a form of being spread like a book is easily damaged because only the specific location is folded repeatedly. On the other hand, the deformed portion of the flexible display unit  151 , that is, a portion rolled on the roller  210 , may vary based on the first and second states of the mobile terminal  100 , that is, the movement of the second frame  102 . Accordingly, the mobile terminal  100  of the present disclosure may significantly reduce deformation and fatigue repeatedly applied to a specific portion of the display unit  151 , thereby preventing damage to the display unit  151 . 
     Based on the above-described configuration, overall operations of the mobile terminal  100  will be described as follows. As an example, the state conversion may be performed manually by the user, and an operation of the mobile terminal  100  during such manual state conversion will be described. However, operations of the first to third frames  101  to  103  and the display unit  151 , which will be described below, may be performed in the same manner when a power source other than a user&#39;s force is used, for example, when the driving unit  200  to be described below is applied. 
     A rear face cover  1025  may be further disposed on a rear face of the second rear portion  1022  such that the rear face of the display unit positioned on the rear face of the mobile terminal  100  is not exposed to the outside. The rear face of the display unit may be used in the first state when the rear face cover  1025  uses a transparent material, and the rear face of the display unit may be covered such that the movement of the slide frame  103  is not exposed when the rear face cover  1025  uses an opaque material. That is, the second region and the third region of the slide frame  103  and the display unit  151  may move in the first direction and in the second direction in a space between the second rear portion  1022  and the rear face cover  1025 . 
       FIG. 7  is a view showing a driving unit  200  of the mobile terminal  100  in accordance with an embodiment. The mobile terminal  100  of the present disclosure may be switched between the states in a manner in which a user manually pulls the second frame  102  in the first direction or pushes the same in the second direction with respect to the first frame  101 . However, in the manual method, applying excessive force to the body of the mobile terminal  100  may damage the mobile terminal  100 . Accordingly, a driving unit  200  employing a motor  201  may be further provided to allow the second frame  102  to stably move without distortion. 
     As the motor  201 , a motor  201  configured to provide rotational force as shown in  FIG. 7 , or a linear motor  201  configured to make linear motion may be used. The motor  201  configured to provide the rotational force may need to have a large diameter to provide large force. However, in order to provide driving force of a predetermined magnitude or more in the limited space of the mobile terminal  100  without increasing the thickness, two motors  201  may be used as shown in  FIG. 7 . 
     If the second frame  102  is moved excessively fast, damage or malfunction may occur. Accordingly, a planetary gear configured to decrease the speed of the motor  201  to ensure movement at a stable speed may be further provided. The planetary gear  202  serves to amplify or attenuate the number of revolutions of the motor  201  using a plurality of disc gears having different numbers of teeth. The motor  201  may be fixed to the first frame  101  as shown in  FIG. 7( a ) . The position of the motor  201  is fixed even when the second frame  102  moves in the first direction to switch the mobile terminal  100  to the second state, as shown in  FIG. 7( b ) . 
     Since the second frame  102  linearly moves with respect to the first frame  101  in the first direction or the second direction, rack and pinion gears configured to convert the rotational force of the motor  201  into linear motion may be used. A pinion gear to receive the rotational force of the motor  201  may be arranged to engage with a rack gear  205  composed of teeth continuously arranged in the first direction. The pinion gear may be fixed to the first frame  101  together with the motor  201  and the rack gear  205  may be positioned on the second frame  102 . Alternatively, the rack gear  205  may be positioned on the first frame  101 , and the motor  201  and the pinion gear may be arranged on the second frame  102 . Since the motor  201  holds the pinion gear such that the pinion gear does not rotate, the second frame  102  may maintain the first state and the second state. However, when large external force is applied, the second frame  102  may be displaced as the pinion gear rotates. 
     A stopper (not shown) configured to fix the positions of the second frame  102  or the rack gear  205  and the first frame  101  may be further provided to fix the mobile terminal  100  in the first state or the second state. When electric current flows through the motor  201  to drive the motor  201 , the stopper may be released to allow the movement of the second frame  102 . When power is not applied to the motor  201  and thus the motor  201  does not rotate, the first frame  101  and the second frame  102  may be fastened such that the positions thereof are fixed. 
     When a pair of driving units  200  is symmetrically disposed in the vertical direction (the third direction), stable movement may be made. However, to arrange a battery or the like, the driving unit  200  should be arranged biased to one side in consideration of the limited mounting space of the mobile terminal  100  as shown in  FIG. 7( a ) . According to such asymmetric arrangement of the driving unit  200 , the second frame  102  may be distorted during movement due to a difference in movement speed between the upper end portion and the lower end portion. To address this issue, a linear guide  230  may be further provided. 
     The linear guide  230  may be disposed at both ends of the mobile terminal  100  facing in the third direction, that is, on the upper and lower sides of the mobile terminal  100 , in order to supplement the function of one driving unit  200  biased to one side in the third direction. The linear guide  230  may include a guide rail  231  extending in the first direction and a guide block  232  configured to move along the guide rail  231 . The guide rail  231  may be disposed on the first frame  101  and the guide block  232  may be disposed on the second frame  102 , or vice versa. In this embodiment, the guide rail  231  may be disposed on the second frame  102  to cover the upper and lower sides of the extended portion of the second frame  102  in the second state. 
     After the guide block  232  is coupled to the first frame  101  and the guide rail  231  is coupled to the second frame  102 , the guide block  232  and the guide rail  231  may be slidably fastened to each other. However, for convenience of the fastening, the guide block  232  and the guide rail  231  fastened to each other. Then, the guide block  232  may be first fixed to the first frame  101 , and then the second frame  102  may be coupled to the guide rail  231 . 
     The guide block  232  may be provided with a guide groove into which the guide rail  231  is inserted. Alternatively, the guide rail  231  may be provided with a rail groove into which a portion of the guide block  232  is inserted. The fastening portions of the guide rail  231  and the guide block  232  may be formed to be bumpy. Accordingly, movement in the first direction or the second direction may be made without displacement in the thickness direction of the mobile terminal  100 . In order to reduce friction between the guide block  232  and the guide rail  231 , a self-lubricating member having high wear resistance and low friction resistance, such as a bearing or polyoxymethylene (POM), may be added to the inside of the guide groove. 
       FIG. 8  is a cross-sectional view taken along lines A-A and B-B in  FIG. 2 . As illustrated in  FIG. 2 , when the second frame  102  switches to the second state by moving in the first direction, the third region  151   c  positioned on the rear side moves to the front, and thus a structure to support the rear surface of the third region  151   c  moved to the front is required. The second front portion  1021  positioned on the front surface of the second frame  102  may be positioned on the rear surface of the third region  151   c  in the second state. However, in the first state, the second front portion  1021  is disposed to overlap the first front portion  1011  of the first frame  101 , and accordingly the first front portion  1011  and the second front portion  1021  form a step. A boundary is formed between the first region  151   a  and the third region  151   c  of the flexible display unit  151  by the step formed by the first front portion  1011  and the second front portion  1021 . A rolling plate  104  may be used as a support structure to fill the gap between the second front portion  1021  and the third region  151   c  of the flexible display unit  151 . 
     The rolling plate  104  may be positioned on the rear surface of the flexible display unit  151 , and have a thickness corresponding to the gap between the second front portion  1021  and the flexible display unit  151  in the second state. As shown in  FIG. 8( a ) , in the first state, the rolling plate  104  is rolled around the roller  210  and is positioned on the lateral side and rear side of the mobile terminal  100 . The flexible display unit  151  and the rolling plate  104  may be positioned between the second rear portion of the second frame  102  and a rear cover  1025  provided to cover the rear face of the display unit  151 . As shown in  FIG. 8( b ) , when switch to the second state occurs, the rolling plate  104  may move to the front and the rolling plate  104  may be positioned on the front portion of the second frame  102 . 
     The third region  151   c  of the display unit  151  in which the rolling plate  104  is positioned is a portion where bending deformation occurs when switch from the first state to the second state occurs. Accordingly, the rolling plate  104  may be deformed according to deformation of the third region  151   c . Here, the rolling plate  104  is required to have a predetermined stiffness to maintain the flat state when the flexible display unit  151  is positioned on the front or rear of the mobile terminal. That is, the rolling plate  104  needs a structure capable of maintaining the flat state in the third direction and performing bending deformation in the first direction. 
       FIG. 9  is a view illustrating a display unit  151  and a rolling plate  104  of the mobile terminal  100  in accordance with an embodiment. The rolling plate  104  may include multiple support bars  1041  extending in the third direction. The multiple support bars  1041  may be arranged side by side in the first direction and spaced apart from each other by a predetermined distance. Accordingly, even when the flexible display unit  151  is rolled around the roller  210  and is thus bent, interference between the support bars  1041  may be avoided. The support bars  1041  may be implemented with an injection molding material having a predetermined thickness for stiffness, and may include a metallic material such as SUS. 
     The multiple support bars  1041  may be directly attached to the rear surface of the display unit  15 . However, this operation may take a long time and produce a lot of defects, resulting in poor productivity. In addition, directly processing the display unit  151  is highly likely to damage the display unit  151 . Therefore, a rolling sheet  1045  to fix the multiple support bars  1041  may be further provided. The rolling sheet  1045  may include a metal material, and may employ a superelastic material that is bending-deformable and capable of recovering the flat state after the bending deformation. For example, a superelastic metal sheet such as a thin STS sheet of 0.05 mm or less may be used. An adhesive tape may be attached to both surfaces of the rolling sheet  1045  to bond the rolling sheet  1045  to the support bars  1041  and bond the rear surface of the display unit  151  to the rolling sheet  1045 . 
     The rolling sheet  1045  may be provided with a kerf pattern in which multiple grooves extending in the third direction are formed in the first direction. The grooves in the kerf pattern may be formed between the multiple support bars  1041 . The grooves may be formed on a surface of the rolling sheet  1045  to which the support bars  1041  are bonded. The kerf pattern may be formed in a wedge shape so as to be gradually narrowed from the surface portion of the rolling sheet  1045 . 
     Instead of the rolling sheet  1045 , an elastic material such as silicone may be disposed between the support bars  1041  to join neighboring support bars  1041 . In this case, the angle between the support bars  1041  may be varied. The elastic connector may be bent at a position corresponding to the roller  210 . When positioned on the front or rear of the mobile terminal, the elastic connector may be unfolded such that the support bars  1041  are disposed forming a flat surface. 
     The support bars  1041  may form a flat surface corresponding to the rear surface of the display unit  151 . Alternatively, as shown in  FIG. 8( b ) , the support bars  1041  may be formed in a shape having a predetermined curvature. The curved support bars  1041  may closely contact the curved surface of the roller  210  when the rolling plate  104  is rolled around the roller  210 . Alternatively, one surface of the support bars  1041  in contact with the display unit  151  maintains a flat state, and the other surface thereof on the opposite side may include a curved surface corresponding to the curvature of the roller  210 . In this case, the support bars  1041  may be thick at the ends thereof facing in the first and second directions and have the thinnest portion in the middle thereof. 
     The rolling plate  104  may be disposed at a position corresponding to the third region  151   c  and is rolled and bent around the roller  210 . Thus, the rolling plate  104  may span over the front and rear surfaces. The rolling plate  104  is connected to the first front portion  1011  of the first frame  101  on the front side and connected to the slide frame  103  on the rear side. In order for the flexible display unit  151  to form a continuous surface without a step, the first front portion  1011  of the first frame  101  positioned on the rear surface of the first region  151   a , the slide frame  103  positioned on the rear surface of the second region  151   b , and the rolling plate  104  positioned on the rear surface of the third region  151   c  may be arranged such that the surfaces thereof in contact with the display unit  151  are at the same height. In particular, since the slide frame  103  moves on the rear of the mobile terminal  100  and moves in the same space as the rolling plate  104 , the rolling plate  104  may have a thickness corresponding to the thickness of the slide frame  103 . 
       FIG. 10  is a view illustrating an issue raised in an extendable mobile terminal  100 . The figure shows the end of the second frame  102  facing in the third direction when the second frame  102  positioned overlapping the first frame  101  is extended as switching from the first state to the second state occurs. Since the display unit  151  contains a flexible material, the display unit  151  may be bent at a position corresponding to the roller  210 . However, when the display unit  151  is positioned on the front of the mobile terminal  100  in the second state, it should be maintained in a flat state. Since the rolling plate  104  is not fixed to the second frame  102 , the display unit  151  may sag downward as shown in  FIG. 10( a )  or rise upward as shown in  FIG. 10( b ) . 
     The sagging issue of the display unit  151  (in  FIG. 10( a ) ) may be addressed when the support bars  1041  of the rolling plate  104  described above support the rear surface of the third region  151   c  of the display unit  151  and the front portion of the second frame  102  supports the support bars  1041 . However, in order to address an issue that the display unit  151  moved to the front is not arranged flat but is separated from the second frame  102  as shown in  FIG. 10( b ) , the rolling plate  104  and the second frame  102  may further include a slide structure  1043 ,  1027 . The slide structures  1043  and  1027  may fasten the rolling plate  104  (the display unit  151 ) so as not to be separated from the second frame  102  in the thickness direction of the mobile terminal  100  while allowing the movement thereof only in the first direction or the second direction. 
       FIGS. 11 to 13  are views showing the slide structures  1043  and  1027  provided on the rolling plate  104  and the second frame  102 .  FIG. 11  is a cross-sectional view taken along lines C-C and D-D in  FIG. 2 ,  FIG. 12  is a cross-sectional view taken along lines E-E and F-F in  FIG. 11 , and  FIG. 13  is a view showing an expanded side portion  1042  and a guide hook  1043  of the mobile terminal  100  in accordance with an embodiment. 
     As shown in  FIG. 13 , the rolling plate  104  may include a slide hook  1043  protruding toward the second side portion  1023  positioned on the side of the second frame  102  facing in the third direction. As shown in  FIG. 11 , the second side portion  1023  of the second frame  102  may include a slide rail  1027  into which the slide hook  1043  is movably inserted.  FIG. 11  shows the slide rail  1027  formed on the second side portion  1023  of the second frame  102 . The slide rail  1027  may include a pair of horizontal portions  1027   a  and  1027   b  arranged side by side in a thickness direction and a curved portion  1027   c  connecting ends of the horizontal portions  1027   a  and  1027   b  facing in the first direction. The pair of horizontal portions  1027   a  and  1027   b  and the curved portion  1027   c  may form a U shape, and the slide hook  1043  may move along the slide rail  1027 . 
     In the first state, the slide hook  1043  may be positioned in the horizontal portion  1027   a ,  1027   b  positioned on the rear side, as shown in  FIG. 11( a ) . In the second state, the slide hook  1043  may be moved to the horizontal portion  1027   a ,  1027   b  positioned on the front side, as shown in  FIG. 11( b ) . When moved from the rear horizontal portion  1027   a ,  1027   b  to the front horizontal portion  1027   a ,  1027   b , the slide hook  1043  may pass through the curved portion  1027   c . When the slide hooks  1043  pass through the curved portion  1027   c , the rolling plate  104  may be bent and the space between the slide hooks  1043  may be narrowed. 
     The slide rail  1041  along which the slide hook  1043  moves may guide the movement of the slide hook  1043  and the movement of the slide frame  103  simultaneously. Since the slide frame  103  is also disposed adjacent to the support bars, a slide hook  1033  protruding from the slide frame  103  may be further provided. 
       FIG. 12( a )  shows the second frame  102  in the first state in which the first frame  101  and the second frame  102  overlap each other, and  FIG. 12( b )  shows the second frame  102  moved from the first frame  101  in the first direction in the second state. As shown in  FIG. 12( a ) , the support bars  1041  and the slide hooks  1043  are positioned on the rear in the first state. In the second state, as shown in  FIG. 12( b ) , the support bars  1041  and the slide hooks  1043  are positioned on the front. The distance from the front face of the display unit  151  to the front horizontal portions  1027   a  and  1027   b  may be equal to the distance from the rear face of the display unit  151  to the rear horizontal portions  1027   a  and  1027   b.    
     When large friction occurs during movement of the slide hooks  1043  along the slide rail  1027 , a large load may be applied to the driving unit  200 , thereby generating frictional noise or affecting the durability of the product. A self-lubricating member having high abrasion resistance and low friction resistance, such as polyoxymethylene (POM), may be used to facilitate the movement of the slide hooks  1043  on the slide rail  1027 . By forming the slide hooks  1043  in a cylindrical shape, the area thereof in contact with the slide rail  1027  may be minimized. 
     As illustrated in  FIG. 13 , a slide roller  1044  fitted onto the slide hook  1043  may be further provided. The slide roller  1044  may be fitted onto the cylindrical slide hook  1043  to rotate about an axis extending in a direction in which the slide hook  1043  protrudes. The slide roller  1044  may rotate when the slide hook  1043  moves along the slide rail  1027 , thereby reducing friction generated between the slide roller  1044  and the slide rail  1027 . 
     A bearing structure may help to reduce the friction, but it may increase the overall size. For this reason, a simple ring-shaped slide roller  1044  may be used. A fastening groove  1043   a  and a fastening protrusion  1044   a  may be further provided to prevent the slide roller  1044  from being separated from the slide hook  1043 . When the fastening protrusion  1044   a  is inserted into the fastening groove  1043   a , the fastening groove  1043   a  formed on the outer circumferential surface of the slide hook  1043  in a ring shape and the ring-shaped fastening protrusion  1044   a  protruding from the inner surface of the slide roller  1044  are fastened to each other. 
     The second side portion  1023  of the second frame  102  is disposed overlapping the first side portion  1013  of the first frame  101  in the first state, and is exposed to the outside in the second state. Since the second side portion  1023  is positioned inside the first side portion  1013  of the first frame  101  in the first state, it may be difficult to connect the interface unit  160 , the user input unit  123 , the audio output unit  152 , the antenna, and the like, which are positioned on the first side portion  1013 , to the printed circuit board  181 , which is positioned inside. 
     The second side portion  1023  may include an opening  1023   a  formed by omitting at least a part of the second side portion  1023  to connect the components positioned on the first side portion  1013  to the printed circuit board  181  positioned inside the first frame  101 . Through the opening  1023   a , a connector may be arranged between the components positioned on the first side portion  1013  and the printed circuit board. The opening  1023   a  may have a shape elongated in the first direction to prevent interference between the connector and the second side portion  1023  of the second frame  102  even when the second frame  102  is moved. 
     However, in order to prevent the inside of the mobile terminal  100  from being exposed through the opening  1023   a  in the second state, an expanded side portion  1042  may be formed at an end of the support bar  1041  to cover the opening  1023   a  in the second state. The expanded side portion  1042  may have a larger area than the cross section of the support bar  1041  at the end of the support bar  1041 . The slide hook  1043  may be formed on a first expanded side portion  1042   a  extending in a direction away from the display unit  151 . When the slide hook  1043  is disposed parallel to the support bar  1041 , the second side portion  1023  of the second frame  102  should be extended adjacent to the display unit  151 , which may make it difficult to form the opening  1023   a . Accordingly, the slide hooks  1043  may be formed at positions spaced apart from the display unit  151  by a predetermined distance. The first expanded side portion  1042   a  may be formed in a fan shape to have a width that is reduced as the first expanded side portion  1042   a  extends in a direction away from the display unit  151 .  FIG. 13  is a view showing an embodiment of the rolling plate  104  of the mobile terminal  100 . Since the rolling plates at positions on the curved portion  1027   c  of the slide rail  1027  spaced apart from the display portion  151  are disposed adjacent to each other, the first expanded side portion  1042   a  may be formed in a fan shape to prevent the rolling plates from overlapping each other. 
     The expanded side portion  1042  may also extend in the left-right direction, and may thus cover a space between neighboring support bars  1041 . The expanded side portion  1042  may further include a second expanded side portion  1042   b  forming a step with respect to the first expanded side portion  1042   a  as shown in  FIG. 13 . The second extension side portion  1042   b  may be disposed to overlap the first expanded side portion  1042   a  adjacent thereto to cover the space between the support bars  1041 . The second expanded side portion  1042   b  may have a size corresponding to the thickness-wise size of the opening  1023   a  formed in the second side portion  1023  of the second frame  102 . The second expanded side portion  1042   b  may be formed to be shorter than the first expanded side portion  1042   a  on the side spaced apart from the display unit  151 . The second expanded side portion  1042   b  may be formed to be shorter than the first expanded side portion  1042   a  to prevent the second expanded side portions  1042   b  from overlapping each other when the rolling plates pass through the curved portion  1027   c  of the slide rail  1027 . The second expanded side portion  1042   b  may be formed to have a size corresponding to the size of the opening  1023   a  to cover the space between the first expanded side portions  1042   a  to prevent the inside of the second frame  102  from being exposed to the outside. 
     As shown in  FIG. 14 , the second expanded side portion  1042   b  may have any shape as long as the shape ensures that the second expanded side portions  1042   b  do not interfere with each other, and allows the second expanded side portion  1042   b  to cover the space between the first expanded side portions  1042   a  and to cover the opening  1023   a  of the second side portion  1023  of the frame  102 . It may have a rectangular shape as shown in  FIG. 14( a )  or a semicircular shape as shown in  FIG. 14( b ) . 
       FIG. 15  is a view showing the slide frame  103  and the second frame  102  of the mobile terminal  100 . Like the rolling plate  104 , the slide frame  103  is positioned on the rear surface of the display unit  151  and moves together with the display unit  151 . The rolling plate  104  moves to the back and front of the mobile terminal  100 , but the slide frame  103  moves only on the back of the mobile terminal  100 , that is, on the second rear portion  1022  of the second frame  102 . A structure to guide the slide frame  103  to linearly move in the first direction or the second direction without distortion is needed. A guide slot extending in the first direction may be formed in the rear surface of the second frame  102  and the slide frame  103  may be configured to move along the guide slot. 
     However, since the second side portion  1023  of the second frame  102  includes the slide rail  1027  extending in the first direction as described above, the movement of the slide frame  103  may be guided through the slide rail  1027 , into which the slide hook  1043  of the rolling plate  104  is inserted, without forming a separate guide rail. As shown in  FIG. 15 , slide hooks  1033  may be formed at both ends of the slide frame  103  to guide the slide frame  103  to move along the slide rail  1027 . The slide hooks  1033  of the slide frame  103  may have a shape similar to that of the slide hook  1043  of the rolling plate  104 . The slide hooks  1033  protrude from the display unit  151  in a direction away from the display unit  151 . However, since the slide hooks  1033  of the slide frame  103  do not move to the front, they move only on a first horizontal portion. 
     Since the slide frame  103  and the rolling plate  104  move along the slide rail  1027 , movement in the first direction and movement in the second direction may be guided stably, and the issue of separation of the display unit  151  from the second frame  102  may be addressed. However, since the slide rail  1027  is positioned at the end facing in the third direction, the middle portion of the slide frame  103  in the third direction may be separated from the second frame  102 . To prevent the separation at the middle portion of the slide frame  103  while both ends of the slide frame  103  are fixed to the frame  102 , a magnetic material may be used. 
       FIGS. 16 and 17  are diagrams illustrating a magnetic roller  211  coupled to the second frame  102  of the mobile terminal  100 . The roller  210  is a member of a cylindrical shape rotating about an axis extending in the third direction. When the roller  210  is formed to have a great length corresponding to a length in the third direction of the mobile terminal, a rigidity of the roller  210  may be weakened and a large mounting space may be required. 
     In order to solve the above problems, as shown in  FIG. 17 , the roller  210  may include a plurality of rollers  210  with a small length. As shown in  FIG. 17 , in order to avoid interference with the driving unit  200  located at the top or to secure a mounting space of other parts, the rollers  210  may be omitted at some positions. 
     The roller  210  requires a shaft  212  to be rotatably coupled to the second frame  102 . When the shaft  212  protrudes, the protruding shaft  212  may be broken. Thus, as shown in  FIG. 16( b ) , a shaft hole  210   h  may be defined in a rotation axis direction in the roller  210  and the shaft  212  may be inserted into the shaft hole  210   h . The shaft  212  may be made of a metal material for a rigidity. 
     The shaft  212  may be formed to be longer than the roller  210 , and roller bearings  213  may be respectively fastened to both ends of the shaft  212  respectively protruding from both ends of the roller  210 . The roller bearing  213  may minimize friction generated when the roller  210  is rotated through an inner ring, an outer ring, and a ball located between the inner ring and the outer ring. The inner ring is fixed to the shaft  212  and the outer ring is fixed to the second frame  102 , so that the outer ring may not rotate when a state of the mobile terminal  100  changes, but only the inner ring may rotate. In order to fix the roller bearing  213  on a seating portion formed on the second frame  102 , a fastener  216  of the bearing  213  may be further included. 
       FIG. 18  is a view showing another embodiment of the roller  210  of the present disclosure. The roller  210  provides, to the third region  151   c  of the display unit  151 , a force to move from the rear surface to the front surface or vice versa while rotating. When the display unit  151  slides on the roller  210 , a driving force of the roller  210  is not properly transmitted to the display unit  151 , so that the movement of the display unit  151  may not be smoothly performed. In addition, when the display unit  151  is not in close contact with the roller  210 , the display unit  151  may be lifted. 
     Therefore, a surface frictional force of the roller  210  may be increased such that the display unit  151  is able to be driven in close contact with the roller  210 . A surface of the roller  210  may contain a high friction material. Thermoplastic poly urethane (TPU), a thermoplastic polyester elastomer (TPEE), or the like may be an example of the high friction material. Alternatively, laser processing and the like may be performed on a circumferential surface of the roller  210  to increase a surface roughness, thereby increasing the friction. 
     As shown in  FIG. 18( a ) , the high friction material may be used for an entirety of the roller  210 , but the high friction material has a problem of low strength or low hardness. In order to increase adhesion with the display unit  151  while securing the strength and the hardness of the roller  210 , a high-strength plastic may be used for an inner portion of the roller  210  and a high-friction outer cover  2102  may be formed as an outer portion of the roller  210 . An inner roller  2101  containing the high-strength and high-hardness plastic and the high-friction outer cover  2102  may be attached to each other in a dissimilar joining scheme or may be manufactured in a double injection scheme to rotate together. 
     When a cross-section of the support bar  1041  forms a straight line as shown in  FIG. 18( a ) , there is an advantage that the display unit  151  may be remained in a flat state and drivability is good, but adhesion between the rolling plate  104  and the roller  210  is weak because a contact area between the plate  104  and the roller  210  is small as described above. 
     When the cross-section of the support bar  1041  is formed as a curved face to have a curvature corresponding to a curvature of the roller  210  as shown in  FIG. 18( b ) , the frictional force between the roller  210  and the rolling plate  104  may be increased. However, because of the curved face of the support bar  1041 , uneven irregularities may occur on the display unit  151 . 
     In the embodiment of  FIG. 18( a ) , when it is difficult to increase the contact area of the rolling plate  104 , a surface roughness of the support bar  1041  of the rolling plate  104  may also be increased to increase the frictional force of the rolling plate  104 . The frictional force may be increased by forming irregularities on a surface of the support bar  1041  in contact with the roller  210 . The laser processing scheme may be exemplified as a processing scheme for forming the fine irregularities on the support bar  1041 . 
     In order for the display unit  151  to move in close contact with the roller  210 , a magnetic material may be used in addition to the method using the high friction material on the roller  210 . The magnetic roller  211  containing the magnetic material provides a magnetic force to pull a metal material of the rolling plate  104 , so that the rolling plate  104  may move in close contact with the roller  210 . 
     A magnetic shielding sheet can be used as the rolling sheet  1045  so that the magnetic force of the roller  210  does not affect the outside of the mobile terminal  100  and only affects the support bars  1041 . 
       FIG. 19  is a cross-sectional view showing a magnetic roller  211  and a rolling plate  104  in accordance with an embodiment. A magnet cannot consist of only one pole. The N-pole and the S-pole are arranged on one side and the opposite side of the magnet to face in different directions. In general, the poles of a cylindrical magnet are divided in the longitudinal direction of the cylindrical body of the magnet. On the other hand, the magnet roller  211  exhibits strong magnetic force at both ends thereof, while exhibiting weak magnetic force in the circumferential direction. Accordingly, the pulling force that the magnetic roller  211  exerts on the rolling plate  104  is weak. 
     Accordingly, in the present disclosure, the magnetic roller  211  having a cylindrical shape may be configured such that different poles are arranged along the outer circumference of the magnetic roller  211 . As shown in  FIG. 19 , the magnet roller  211  may be divided into 2n sectors along the outer circumference thereof to dispose n S-poles and n N-poles. If the magnetic roller  211  consists of one N-pole and one S-pole, the rolling plate  104  may not be pulled uniformly during rotation. For this reason, n may be a number greater than 1. 
       FIGS. 20 and 21  are views illustrating magnetic force applied to the rolling plate  104  according to the number of poles of the magnetic roller.  FIG. 20  is a view showing the arrangement of the rolling plate  104  and the magnetic roller  211  in the case where the magnetic roller  211  consists of one N-pole and one S-pole. A magnet having two poles exhibits large magnetic force at a position most distant from the other pole of another magnet, and weak magnetic force at a position adjacent to the other pole of the other magnet. When the poles of the magnet roller are arranged in the vertical direction as shown in  FIG. 20( b ) , the two parts of the magnet exhibits strong magnetic force. However, when the poles of the magnet are arranged in the horizontal direction as shown in  FIG. 20( a )  or  20 ( c ), only one part of the magnetic roller  211  that exhibits strong magnetic force contacts and overlaps the rolling plate  104 , and accordingly the magnetic force of the magnetic roller  211  to pull the rolling plate  104  is weak. 
     Therefore, the magnet may be divided into more poles. When the magnet has six poles as shown in  FIG. 19( a ) , the N-poles and the S-poles may be configured by combining three fan-shaped column magnets  211   u  each having an N-pole and an S-pole adjacent to each other. 
       FIG. 21  illustrates magnetic force applied by the magnetic roller  211  to the rolling plate  104  when a magnet having a shape as shown in  FIG. 21( a )  is used. In the case of  FIGS. 21( a ) to 21( c ) , at least three parts of the magnetic roller that exhibit strong magnetic force overlap the rolling plate  104 . Accordingly, the rolling plate  104  may be pulled with sufficient magnetic force, and thus the display unit  151  may be maintained in the flat state. 
       FIG. 22  is a view showing a magnetic roller and a rolling plate in accordance with another embodiment. As shown in  FIG. 22( a ) , the magnetic roller may be divided into four sectors along the outer circumference thereof to dispose two S-poles and two N-poles. This embodiment may be configured by attaching four fan-shaped sintered column magnets  211   u  each having opposite poles arranged on the inner and outer sides, as shown in  FIG. 22( b ) . 
     The three fan-shaped column magnets  211   u  of  FIG. 19  may have the same shape. For this magnet configuration, two types of magnets are needed. That is, a fan-shaped sintered column magnet  211   a  having the S-pole on the inner side and the N-pole on the outer side, and a fan-shaped sintered column magnet  211   b  having the N-pole on the inner side and the S-pole on the outer side are needed. Since these fan-shaped sintered column magnets  211   a  and  211   b  each have opposite poles arranged on the inner side (facing the shaft  211 ) and the outer side (facing the outer circumference), the magnetic field may be formed in a direction toward the shaft  212 , that is, a radial direction of the magnetic roller  211 , they may readily pull the rolling plate  104  flat. 
       FIG. 23  is a view showing another embodiment of the roller  210  of the mobile terminal. The inner portion in  FIG. 18( b )  is formed by the magnetic roller  211  described above and the high-friction outer cover  2102  is formed to further increase the friction between the roller  210  and the rolling plate  104 . 
     Portions of the magnetic roller  211  located inside may have different poles in an axial direction as shown in  FIG. 23( a )  and may have different poles in a circumferential direction as shown in  FIG. 23( b ) . As described above, when a S pole is located, an N pole is always located on the opposite side of the magnet, so that the magnetic roller  210  in which fan-shaped sintered magnets are arranged in the circumferential direction such that poles of outer portions of the sintered magnets are different from each other may be used as shown in  FIG. 23( c ) . 
     The above-described roller  210  has a problem in that a mounting space of the roller  210  occupies a significant portion in the mobile terminal. As shown in  FIG. 17 , an area occupied by the roller  210  may be reduced in the axial direction of the roller  210  using the short rollers  210 . In addition, as shown in  FIG. 24 , a size occupied by the roller  210  in a radial direction may be reduced using mini rollers  2103 . 
       FIG. 24  is a view showing another embodiment of the roller  210  of the mobile terminal. In addition,  FIG. 25  is a view showing the first state and the second state of the mobile terminal  100  in a state in which front surface components of the mobile terminal are removed. 
     The roller  210  of the present embodiment includes the mini rollers  2103  having a small diameter. The above-described roller  210  used a roller  210  having a curvature corresponding to a bending curvature of the display unit  151 . However, the roller  210  of the present embodiment may use the mini roller  2103  having a radius smaller than radii of curvature of the display unit  151  and the rolling plate  104 . 
     As shown in  FIG. 24( a ) , a curved face of the display unit  151  may be maintained using the plurality of mini rollers  2103 . The plurality of mini rollers  2103  may be arranged at start and end points and a middle portion therebetween of the curved face of the display unit  151 , so that the same effect as a roller  210  of a large diameter may be obtained. 
     In order to fix the plurality of mini rollers  2103  in positions, a roller fixing plate  2104  to which the plurality of mini rollers  2103  are fastened may be formed at each of both ends of the mini rollers  2103 . The roller fixing plate  2104  may have a shape corresponding to the curvature of the rolling plate  104 , as shown in  FIG. 24( b ) . Because the roller fixing plate  2104  does not rotate, a material having a small frictional force may be used such that the rolling plate  104  may slide well. 
     Because the mini roller  2103  has a small surface in contact with the rolling plate  104 , a high friction material or a magnet may be used to increase the adhesion between the rolling plate  104  and the mini roller  2103 . Some of the plurality of mini rollers  2103  may be arranged as mini rollers  2103  of the high friction material and the others may be arranged as mini rollers  2103  of the magnetic material. Because the size of the magnet is small, the mini roller  2103  has an advantage in that it is easier for the mini roller  2103  to adjust the magnetic force and the friction than the magnetic roller  210  of the large size. 
     The mini roller  2103  may save a space represented in a dotted line as shown in  FIG. 24( a )  than the above-described roller  210  with the large diameter, so that the corresponding space may be further utilized. For example, as shown in  FIG. 25 , when the second frame  102  is extended by moving in the first direction, a support link receiving space for supporting the expanded portion may be provided. 
     One end of a support link  240  may be coupled to the first frame  101  and the other end thereof may be coupled to the second frame  102 , and a length of the support link  240  may vary. In a first state, the length of the support link  240  is reduced and the support link  240  is disposed in parallel with the third direction as shown in  FIG. 25( a ) . In addition, in a second state, the support link  240  is disposed diagonally as the length thereof increases as shown in  FIG. 25( b ) . The support link  140  disposed obliquely in the second state may support the extended display unit  151  and the second front portion  1021  of the second frame  102 . 
     In the first state, a storage space for the support link  240  is required. Some of the plurality of rollers  210  may be omitted to provide the space in which the support link  240  is disposed. Alternatively, when using the roller  210  composed of the mini rollers  2103  in  FIG. 24 , because the mini rollers  2103  are smaller in size, the support link  240  may be stored in the secured space. 
     The above-described various types of rollers  210  may constitute some of the plurality of rollers  210  arranged in the third direction. That is, some of the rollers  210  arranged in the third direction may use the rollers  210  of the high friction material and the others may use the magnetic rollers  210 . 
     Alternatively, because the rollers  210  including the mini rollers  2103  in  FIG. 24  may be partially used, the rollers  210  may be formed in various combinations. Through the combination of the rollers  210 , the frictional force between the rolling plate  104  and the roller  210  may be adjusted to a desired level. 
     As described above, the mobile terminal of the present disclosure may adjust the size of the screen as needed, so that both the portability and the usability may be satisfied. 
     In addition, the display unit  151  may be prevented from being lifted when the second frame moves, so that the display unit  151  may be maintained in the flat state. 
     In addition, when the flexible display unit  151  expands or contracts, the flexible display unit  151  may stably move. 
     In addition, the space utilization may be increased using the mini roller and the adhesion between the roller and the rolling plate  104  may be easily adjusted. 
     The detailed description is to be considered in all aspects as illustrative and not restrictive. The scope of protection sought by the present disclosure should be determined by the appended claims and their equivalents, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.