Patent Publication Number: US-2022232712-A1

Title: Electronic apparatus having flexible display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 17/105,918, filed on Nov. 27, 2020, which is a continuation of U.S. application Ser. No. 16/535,463, filed on Aug. 8, 2019, which has issued as U.S. Pat. No. 10,888,005 on Jan. 5, 2021, which is a continuation of U.S. application Ser. No. 15/747,584, filed on Jan. 25, 2018, which has issued as U.S. Pat. No. 10,420,227 on Sep. 17, 2019, and was the National Stage of International application PCT/KR2016/003501 filed on Apr. 5, 2016, which claimed the benefit under 35 U.S.C. § 119(a) of a Korean patent application number 10-2015-0110659, filed on Aug. 5, 2015, in the Korean Intellectual Property Office, the entire disclosure of each of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to electronic devices, and more particularly, to structures in which flexible displays are extendable out of or retractable into electronic devices. 
     BACKGROUND ART 
     Currently, display devices are regarded as essential electronic products. Electronic devices are required to be of compact size but many customers also desire large screens. Therefore, research and development are being actively conducted on flexible displays which are foldable or rollable into electronic devices. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
     Provided are electronic devices capable of minimizing damage to flexible displays when the flexible displays extend out of or retract into the electronic devices. 
     Technical Solution 
     According to an aspect of an embodiment, an electronic device includes a housing having an opening, a roll mounted in the housing, a flexible display wound on the roll and being extendable and retractable through the opening based on a rotation direction of the roll, and a roll guide configured to guide the roll to move in a direction capable of maintaining a proceeding direction of the flexible display toward the opening in the housing, based on a variation in a wound length of the flexible display on the roll. 
     The electronic device may further include a central shaft serving as an axis of rotation of the roll, and the roll guide may guide the central shaft. 
     The electronic device may further include a winding member configured to provide elastic force in a direction capable of winding the flexible display on the roll. 
     The electronic device may further include a locking unit configured to lock the roll so as not to rotate in a direction of the elastic force of the winding member. 
     The locking unit may include a stopper projection provided on the roll, and a stopper lever having a release location where interference with the stopper projection is released, and a contact location where the stopper lever is obstructed by the stopper projection to stop rotation of the roll. 
     The roll guide may guide the roll to move in a direction perpendicular to the proceeding direction of the flexible display toward the opening in the housing. 
     The roll guide may guide the roll to move diagonally to a direction perpendicular to the proceeding direction of the flexible display toward the opening. 
     The electronic device may further include a display guide having a supporting surface configured to support the flexible display and guide the flexible display unwound from the roll, toward the opening. 
     The electronic device may further include a guide member configured to guide the flexible display at a side opposite to the display guide with respect to the flexible display interposed between the guide member and the display guide. 
     The guide member may guide the flexible display to proceed in a horizontal direction after passing through the opening. 
     The electronic device may further include a push member configured to push the roll toward the display guide in such a manner that the flexible display wound on the roll contacts the supporting surface. 
     The electronic device may further include an elastic member configured to provide elastic force to push the push member toward the display guide. 
     The push member may include a roller rotating in contact with the flexible display. 
     The push member may include a roll spring supported by the roll guide and pushing the roll toward the display guide. 
     The electronic device may further include a pinion gear rotating together with the roll, and a rack gear connected to the pinion gear and extending in an extension direction of the roll guide. 
     The electronic device may further include one or more reduction gears interposed between the pinion gear and the rack gear. 
     According to another aspect of an embodiment, an electronic device includes a housing having an opening, a roll mounted in the housing, and a flexible display having an end connected to the roll, wound on the roll, and being extendable and retractable through the opening based on a rotation direction of the roll, wherein the roll moves to constantly maintain a proceeding angle of the flexible display toward the opening in the housing. 
     The electronic device may further include a central shaft serving as an axis of rotation of the roll, and a roll guide configured to guide the central shaft in a direction capable of constantly maintaining the proceeding angle. 
     The roll guide may guide the roll to move in a direction perpendicular to a proceeding direction of the flexible display toward the opening in the housing. 
     The roll guide may guide the roll to move diagonally to a direction perpendicular to a proceeding direction of the flexible display toward the opening. 
     According to another aspect of an embodiment, an electronic device includes a housing having an opening, a roll mounted in the housing, a flexible display wound on the roll and being extendable and retractable through the opening based on a rotation direction of the roll, a supporting surface configured to support the flexible display wound on the roll, and a roll guide configured to guide the roll to move toward the supporting surface as the flexible display is unwound from the roll. 
     The supporting surface may extend toward the opening to guide the flexible display unwound from the roll, toward the opening. 
     The electronic device may further include a push member configured to push the roll toward the supporting surface. 
     The electronic device may further include an elastic member configured to provide elastic force to push the push member toward the supporting surface. 
     The push member may include a roller rotating in contact with the flexible display wound on the roll. 
     The electronic device may further include a guide member configured to guide the flexible display toward the opening at a side opposite to the supporting surface. 
     The electronic device may further include a pinion gear rotating together with the roll, and a rack gear connected to the pinion gear and extending in an extension direction of the roll guide. 
     The electronic device may further include one or more reduction gears interposed between the pinion gear and the rack gear. 
     Advantageous Effects of the Invention 
     According to an embodiment, when a flexible display extends out of an electronic device, a roll having the flexible display wound thereon may move to reduce a load applied to the flexible display. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a network environment including an electronic device according to an embodiment. 
         FIG. 2  is a perspective view of an electronic device according to an embodiment. 
         FIG. 3  is a perspective view of a roll included in an electronic device, and a flexible display wound on the roll, according to an embodiment. 
         FIG. 4  is a side cross-sectional view showing that a flexible display is wound or unwound when a roll rotates at a fixed location. 
         FIGS. 5 and 6  are side cross-sectional views of an electronic device according to an embodiment. 
         FIG. 7  is a side cross-sectional view showing that a roll of an electronic device moves toward an opening, according to an embodiment. 
         FIG. 8  is a side cross-sectional view of an electronic device including a display guide, according to embodiment. 
         FIG. 9  is a side cross-sectional view of an electronic device including a push member, according to embodiment. 
         FIGS. 10 and 11  are side cross-sectional views of an electronic device including a winding member, according to embodiment. 
         FIG. 12  is a structural view of a locking unit according to an embodiment. 
         FIGS. 13 and 14  are side cross-sectional views of an electronic device including a roll spring, according to an embodiment. 
         FIGS. 15 and 16  are side cross-sectional views of an electronic device including a pinion gear and a rack gear, according to an embodiment. 
         FIGS. 17 and 18  are structural views of a reduction gear(s) of an electronic device, according to embodiments. 
         FIGS. 19 and 20  are perspective views showing that a flexible display extends out of an electronic device, according to embodiments. 
     
    
    
     MODE OF THE INVENTION 
     Hereinafter, various embodiments of the present disclosure are described in detail with reference to the accompanying drawings. However, this description is not intended to limit the present disclosure to the described embodiments and it should be understood that the present disclosure covers all modifications, equivalents, and/or alternatives thereof. In the drawings, like reference numerals denotes like elements. 
     As used herein, terms such as “have,” “may have,” “include,” “may include,” “comprise,” and “may comprise” specify the presence of stated features (e.g., values, functions, operations, or elements), but do not preclude the presence or addition of one or more other features. 
     The expressions “A or B,” “at least one of A or/and B,” or “one or more of A or/and B” used herein include any and all combinations of one or more of the listed items. For example, “A or B,” “at least one of A and B,” or “at least one of A or B” means (1) including at least one A, (2) including at least one B, or (3) including both at least one A and at least one B. 
     Terms such as “1st,” “2nd,” “first,” and “second” may be used herein to describe various elements regardless of order and/or priority thereof, but these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, “a first user device” and “a second user device” may indicate different user devices regardless of order and/or priority thereof. For example, a first element could be termed a second element and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure. 
     It will be understood that when an element (e.g., first element) is referred to as being “(operatively or communicatively) coupled with/to” or “connected to” another element (e.g., second element), the element can be directly coupled or connected to the other element or an intervening element (e.g., third element) may be present. Conversely, when an element (e.g., first element) is referred to as being “directly coupled” or “directly connected” to another element (e.g., second element), there is no intervening element (e.g., third element) present. 
     The expression “configured to” may be interchangeably used with “suitable for,” “having the capacity to,” “designed to,” “adapted to,” “made to,” or “capable of” according to the context. The expression “configured to” does not necessarily mean “specifically designed to” in terms of hardware. Instead, the expression “a device configured to . . . ” may mean that the device is “capable of . . . ” along with other devices or parts in a certain situation. For example, “a processor configured to perform A, B, and C” may mean a dedicated processor (e.g., an embedded processor) for performing the operations or a generic-purpose processor (e.g., a central processing unit (CPU) or application processor) for performing the operations by executing at least one software program stored in a memory device. 
     Terms used herein are used merely to describe certain embodiments and do not limit the scope of the present disclosure. Singular forms may include plural forms as well unless the context explicitly indicates otherwise. Unless defined differently, all terms used in the description including technical and scientific terms have the same meaning as generally understood by one of ordinary skill in the art. Terms as defined in a commonly used dictionary should be construed as having the same meaning as in an associated technical context, and unless defined in the description, the terms are not ideally or excessively construed as having formal meaning. In any case, even the terms defined in this specification cannot be interpreted as excluding embodiments of the present disclosure. 
     Electronic devices described herein according to various embodiments may include at least one of, for example, smartphones, tablet personal computers (PCs), mobile phones, video phones, electronic book (e-book) readers, desktop PCs, laptop PCs, netbook computers, workstations, servers, personal digital assistants (PDAs), portable multimedia player (PMPs), MP3 players, mobile medical devices, cameras, and wearable devices. According to various embodiments, the wearable devices may include at least one of accessory type wearable devices (e.g., watches, rings, bracelets, ankle bracelets, necklaces, glasses, and head-mounted-devices (HMDs)), textile/clothing type wearable devices (e.g., electronic apparel), body-attached wearable devices (e.g., skin pads and tattoos), and body-implantable wearable devices (e.g., implantable circuits). 
     In some embodiments, the electronic devices may be home appliances. The home appliances may include at least one of, for example, televisions (TVs), digital versatile disc (DVD) players, audio players, refrigerators, air conditioners, cleaners, washing machines, air cleaners, set-top boxes, home automation control panels, security control panels, TV boxes (e.g., Samsung HomeSync™, Apple TV™, and Google TV™), game consoles (e.g., Xbox™ and PlayStation™), electronic dictionaries, electronic keys, camcorders, and electronic picture frames. 
     In other embodiments, the electronic devices may include at least one of various medical devices (e.g., various portable medical measurement devices such as blood glucose meters, heart rate meters, blood pressure meters, and thermometers, magnetic resonance angiography (MRA) devices, magnetic resonance imaging (MRI) devices, computed tomography (CT) devices, scanners, and ultrasonic devices), navigation devices, global navigation satellite systems (GNSSs), event data recorders (EDRs), flight data recorders (FDRs), vehicle infotainment devices, electronic equipment for vessels (e.g., vessel navigation systems and gyrocompasses), avionics, security devices, vehicle head units, industrial or home robots, automatic teller machines (ATMs), point of sales (POS) devices, and Internet of Things (IoT) devices (e.g., lamps, various sensors, electricity or gas meters, sprinklers, fire alarms, thermostats, streetlamps, toasters, exercise equipment, hot water tanks, heaters, and boilers). 
     According to an embodiment, the electronic devices may include at least one of parts of furniture or buildings/structures, electronic boards, electronic signature receiving devices, projectors, or various measuring instruments (e.g., water meters, electricity meters, gas meters, and radio wave meters). In various embodiments, the electronic device may be one or a combination of two or more of the above-mentioned devices. The electronic device according to an embodiment may be a flexible electronic device. However, the electronic devices according to embodiments are not limited to the above-mentioned devices, but may include new electronic devices to be developed. 
       FIG. 1  is a block diagram of a network environment  100  including an electronic device  101  according to various embodiments. 
     Referring to  FIG. 1 , the electronic device  101  may include a bus  110 , a processor  120 , a memory  130 , an input/output interface  140 , and a display  150 . 
     The bus  110  may be a circuit for interconnecting the above-mentioned elements and transmitting communication data (e.g., control messages) between the above-mentioned elements. 
     The processor  120  may, e.g., receive instructions from the above-mentioned other elements (e.g., the memory  130 , the input/output interface  140 , the display  150 , and a communication interface  160 ) through the bus  110 , interpret the received instructions, and perform calculation or data processing based on the interpreted instructions. 
     The memory  130  may store instructions or data received from the processor  120  or the other elements (e.g., the input/output interface  140 , the display  150 , and the communication interface  160 ) or generated by the processor  120  or the other elements. The memory  130  may include programming modules, e.g., a kernel  131 , middleware  132 , an application programming interface (API)  133 , and applications  134 . Each of the above-mentioned programming modules may be configured as software, firmware, hardware, or a combination of two or more thereof. 
     The kernel  131  may control or manage system resources (e.g., the bus  110 , the processor  120 , or the memory  130 ) which are used to perform operations or functions implemented in the other programming modules, e.g., the middleware  132 , the API  133 , or the applications  134 . In addition, the kernel  131  may provide an interface for allowing the middleware  132 , the API  133 , or the applications  134  to access and control or manage each element of the electronic device  101 . 
     The middleware  132  may serve as a relay for allowing the API  133  or the applications  134  to communicate and exchange data with the kernel  131 . In addition, the middleware  132  may control (e.g., schedule or load-balance) operation requests received from the applications  134  by, for example, giving a priority of using the system resources (e.g., the bus  110 , the processor  120 , or the memory  130 ) of the electronic device  101  to at least one of the applications  134 . 
     The API  133  may be an interface for allowing the applications  134  to control a function provided by the kernel  131  or the middleware  132 , and may include at least one interface or function (e.g., an instruction) for, for example, file control, window control, image processing, or text control. 
     According to various embodiments, the applications  134  may include a short message service (SMS)/multimedia message service (MMS) application, an e-mail application, a calendar application, an alarm application, a healthcare application (e.g., an application for measuring a workrate or a blood glucose level), and an environmental information application (e.g., an application for providing information about atmospheric pressure, humidity, or temperature). Additionally or alternatively, the applications  134  may be applications related to information exchange between the electronic device  101  and an external electronic device (e.g., an electronic device  104 ). The application related to information exchange may include, for example, a notification relay application for transmitting certain information to the external electronic device or a device management application for managing the external electronic device. 
     For example, the notification relay application may include a function for transmitting notification information generated from the other application of the electronic device  101  (e.g., the SMS/MMS application, the e-mail application, the health management application, or the environmental information application), to the external electronic device (e.g., the electronic device  104 ). Additionally or alternatively, the notification relay application may receive notification information from, for example, the external electronic device (e.g., the electronic device  104 ) and provide the received notification information to a user. The device management application may manage (e.g., install, delete, or update), for example, functions related to at least a part of the external electronic device (e.g., the electronic device  104 ) communicating with the electronic device  101  (e.g., functions for turning on/off the external electronic device (or some parts thereof) or adjusting brightness (or resolution) of a display), and applications operating in the external electronic device or services provided by the external electronic device (e.g., a call service or a message service). 
     According to various embodiments, the applications  134  may include an application that is designated based on properties (e.g., the type) of the external electronic device (e.g., the electronic device  104 ). For example, when the external electronic device is an MP3 player, the applications  134  may include an application related to reproduction of music. Similarly, when the external electronic device is a mobile medical device, the applications  134  may include an application related to healthcare. According to an embodiment, the applications  134  may include at least one of an application designated for the electronic device  101  and an application received from an external electronic device (e.g., a server  106  or the electronic device  104 ). 
     The input/output interface  140  may transmit an instruction or data input from the user through an input/output device (e.g., a sensor, a keyboard, or a touchscreen) to the processor  120 , the memory  130 , or the communication interface  160  through, for example, the bus  110 . For example, the input/output interface  140  may provide, to the processor  120 , data about the user&#39;s touch input through the touchscreen. In addition, the input/output interface  140  may output, through an input/output device (e.g., a speaker or a display), an instruction or data received from the processor  120 , the memory  130 , or the communication interface  160  through, for example, the bus  110 . For example, the input/output interface  140  may output voice data processed by the processor  120 , to the user through the speaker. 
     The display  150  may display various types of information (e.g., multimedia data and text data) to the user. The display  150  may include, for example, a liquid crystal display (LCD), a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, a microelectromechanical system (MEMS) display, an electronic paper display, or a flexible display. The display  150  may, for example, display various contents (e.g., text, images, videos, icons, and symbols) to the user. The display  150  may include a touchscreen and may receive, for example, touches, gestures, proximity touches, or hovering inputs using an electronic pen or a body part of the user. 
     The electronic device  101  may further include the communication interface  160 . The communication interface  160  may establish a communication connection between the electronic device  101  and the external device (e.g., the electronic device  104  or the server  106 ). For example, the communication interface  160  may be connected to a network  162  through wireless or wired communication to communicate with the external device. The wireless communication technology may include at least one of, for example, wireless fidelity (Wi-Fi), Bluetooth (BT), near field communication (NFC), global positioning system (GPS), and cellular communication (e.g., long term evolution (LTE), LTE-advanced (LTE-A), code division multiple access (CDMA), wideband CDMA (WCDMA), universal mobile telecommunication system (UNITS), wireless-broadband (WiBro), and global system for mobile communications (GSM)). The wired communication technology may include at least one of, for example, universal serial bus (USB), high definition multimedia interface (HDMI), recommended standard 232 (RS-232), and plain old telephone service (POTS). 
     According to an embodiment, the network  162  may be a telecommunications network. The telecommunications network may include at least one of a computer network, the Internet, the Internet of things, or a telephone network. According to an embodiment, a protocol (e.g., a transport layer protocol, a data link layer protocol, or a physical layer protocol) for communication between the electronic device  101  and the external device may be supported by at least one of the applications  134 , the API  133 , the middleware  132 , the kernel  131 , and the communication interface  160 . 
       FIG. 2  is a perspective view of the electronic device  101  according to an embodiment.  FIG. 3  is a perspective view of a roll  300  included in the electronic device  101 , and a flexible display  310  wound on the roll  300 . 
     Referring to  FIGS. 2 and 3 , the electronic device  101  may include a housing  200 , the roll  300  on which the flexible display  310  is wound, and the flexible display  310  wound on the roll  300  to retract into the housing  200  or unwound from the roll  300  to extend out of the housing  200 . 
     The electronic device  101  has a structure capable of accommodating the flexible display  310  in the housing  200  in a wound state, and of extending and spreading the display  310  out of the housing  200  as necessary to provide information to a user. 
     To this end, an opening  400  is provided in a surface or at a side of the housing  200 . The flexible display  310  may be unwound from the roll  300  and may extend out of the electronic device  101  through the opening  400  of the housing  200 . When wound on the roll  300 , the flexible display  310  may retract into the housing  200  through the opening  400 . 
     An end of the flexible display  310  is connected to the roll  300 . The flexible display  310  may be connected to the roll  300  directly or through a medium for transmitting signals between the flexible display  310  and the electronic device  101 . 
     The roll  300  may rotate in the housing  200  to wind the flexible display  310  on a body of the roll  300 . A handle  210  holdable by the user to extend the flexible display  310  out of the housing  200  may be provided at the other end of the flexible display  310 . 
     A side protector  320  is provided at a width-direction side and the other width-direction side of the flexible display  310 . The side protector  320  may protect the flexible display  310  from external impact. The side protector  320  may be thicker than the flexible display  310 . 
     Referring to  FIG. 3 , when the flexible display  310  is wound on the roll  300  in a multilayer structure, a distance between an inner layer  311  and an outer layer  312  may be constantly maintained such that an outer surface of the inner layer  311  may not contact an inner surface of the outer layer  312 . As such, wear and damage of the surface of the flexible display  310 , i.e., a display surface on which an image is displayed, may be reduced. 
     A central shaft  330  of the roll  300  is rotatably supported in the housing  200 . The roll  300  rotates with respect to the central shaft  330  of the roll  300  in the housing  200 . The electronic device  101  may further include a winder  220  for rotating the roll  300 . The winder  220  may be connected from outside the housing  200  to the central shaft  330  directly or through a motive power transmission device such as a gear, but is not limited thereto. The flexible display  310  may be wound on the roll  300  by rotating the roll  300  by using the winder  220 . 
     When the roll  300  rotates, the flexible display  310  connected to the roll  300  is wound on or unwound from the roll  300 . For example, when the user pulls the handle  210 , the roll  300  rotates in a counterclockwise direction and the flexible display  310  is unwound from the roll  300  and extends out of the housing  200 . When the user rotates the winder  220  connected to the central shaft  330  of the roll  300 , the roll  300  rotates in a clockwise direction. Then, the flexible display  310  is wound on the roll  300  and retracts into the housing  200 . 
     A stopper  350  may be mounted on a region of the flexible display  310  or on a region of the side protector  320 . An area of the flexible display  310  extending out of the housing  200  may be determined based on a location of the stopper  350 . For example, referring to  FIG. 3 , the stopper  350  may be mounted adjacent to the end of the flexible display  310  connected to the roll  300 . As such, the flexible display  310  may extend outside only to where the stopper  350  is mounted. 
     In the electronic device  101  according to an embodiment, a part from where the stopper  350  is mounted to where the handle  210  is provided may be configured as the flexible display  310  and a part from where the flexible display  310  is connected to the roll  300  to where the stopper  350  is mounted may be configured as a component for transmitting electronic signals between the processor  120  and the flexible display  310  of the electronic device  101 . In other words, in the flexible display  310 , a region from where the stopper  350  is mounted to the other end where the handle  210  is provided may be an image display area for displaying an image, and a region from the end connected to the roll  300  to where the stopper  350  is mounted may be a signal transmission area on which a flexible printed circuit board (FPCB) or the like is provided to transmit/receive signals to/from the processor  120 . 
     When the flexible display  310  is wound on or unwound from the roll  300 , a distance from a center of the roll  300  to the flexible display  310  wound on the roll  300 , i.e., an outer diameter of the roll  300 , is increased or reduced. As such, although not shown in  FIGS. 2 and 3 , the flexible display  310  moves in a direction almost perpendicular to a direction in which the flexible display  310  is unwound from or wound on the roll  300 , i.e., a radius direction of the roll  300 . The movement of the flexible display  310  in the radius direction may cause shaking of a screen. 
       FIG. 4  is a side cross-sectional view showing that the flexible display  310  is wound or unwound when the roll  300  rotates at a fixed location. As illustrated in  FIG. 4 , when the opening  400  of the housing  200  does not have a sufficient height, a proceeding direction of the flexible display  310  with respect to the opening  400  in the housing  200  may be continuously changed and thus the opening  400  may be damaged. 
     In a first state in which the flexible display  310  is completely wound on the roll  300  as indicated by a solid line in  FIG. 4 , the flexible display  310  passes through the opening  400  in an almost horizontal direction. However, in a second state in which the flexible display  310  is completely unwound from the roll  300  as indicated by a two-dot chain line in  FIG. 4 , the flexible display  310  passes through the opening  400  in a direction inclined with respect to the direction of the first state by an angle α. Since the flexible display  310  is repeatedly bent while extending/retracting, fatigue may be accumulated and thus the flexible display  310  may be damaged. 
     A method capable of reducing repeated bending of the flexible display  310  in a direction perpendicular to a direction of the flexible display  310  that enters and exits the housing  200  through the opening  400 , and of constantly maintaining a proceeding direction of the flexible display  310  with respect to the opening  400  in the housing  200  may be considered. 
     As an example of the method, the roll  300  may be supported in the housing  200  to move in a direction capable of compensating for a variation in the outer diameter thereof. For example, the roll  300  may be guided by a roll guide  340  provided in the housing  200 . The roll guide  340  may have, for example, a slot shape, and two ends of the central shaft  330  of the roll  300  are inserted into a pair of roll guides  340 . Due to the above-described configuration, the roll  300  may move along the roll guide  340  in accordance with the variation in the outer diameter thereof. The movement of the roll  300  may occur simultaneously with rotation of the roll  300 . 
     Embodiments of a structure in which the roll  300  moves in accordance with a variation in a wound length of the flexible display  310  on the roll  300  will now be described. 
       FIGS. 5 and 6  are side cross-sectional views of the electronic device  101  according to an embodiment.  FIG. 5  shows a state in which the flexible display  310  is completely wound on the roll  300 , and  FIG. 6  shows a state in which the flexible display  310  is completely unwound from the roll  300 . 
     Referring to  FIG. 5 , an end of the flexible display  310  is connected to the roll  300  and the other end thereof is connected to the handle  210 . The flexible display  310  is wound on the roll  300  and is positioned in the housing  200 . When the flexible display  310  extends out of the housing  200 , the roll  300  and the central shaft  330  rotate together. In this case, the roll  300  may rotate with respect to the central shaft  330 , and the central shaft  330  may be supported by the housing  200  to move along the roll guide  340 . Referring to  FIG. 6 , the flexible display  310  is unwound from the roll  300  and extends out of the housing  200 . 
     When the flexible display  310  extends out of the housing  200 , an outer diameter of the roll  300  varies. When the outer diameter of the roll  300  in  FIG. 5  is D1, the outer diameter of the roll  300  in  FIG. 6  is D2 less than D1. The roll guide  340  guides the roll  300  in such a manner that the roll  300  moves to compensate for a variation (D1−D2) in the outer diameter of the roll  300 . Herein, each of the outer diameters D1 and D2 refers to a total outer diameter including the flexible display  310  wound on the roll  300 . 
     In  FIGS. 5 and 6 , the roll guide  340  guides the central shaft  330  in such a manner that the roll  300  moves downward as the flexible display  310  extends from the housing  200 . In the current embodiment, a display guide  920  is positioned under the roll  300  in the direction of gravity, and supports the flexible display  310  wound on the roll  300 . The display guide  920  extends toward the opening  400  in a direction equal to a direction in which the flexible display  310  extends out of the housing  200 . The display guide  920  is provided adjacent to the opening  400 . 
     Although the display guide  920  is positioned at a lower side in the direction of gravity in the following description for convenience of explanation, the electronic device  101  may be used in a state in which the central shaft  330  of  FIGS. 5 and 6  stands upright in the direction of gravity. In this case, the location of the display guide  920  is not under the roll  300  in the direction of gravity, and the display guide  920  may extend toward the opening  400  in a direction equal to a direction in which the flexible display  310  extends out of the housing  200 . 
     When the flexible display  310  extends or retracts, the display guide  920  may contact the surface of the flexible display  310  or the side protector  320  of the flexible display  310  to reduce shaking of the flexible display  310 . Therefore, as the flexible display  310  is unwound from the roll  300 , the roll  300  is guided by the roll guide  340  to move downward and a movement distance thereof is limited by the display guide  920 . 
     The display guide  920  guides the flexible display  310  toward the opening  400 . The display guide  920  of the current embodiment guides the flexible display  310  to pass through the opening  400  in a horizontal direction. To this end, a supporting surface  921  of the display guide  920 , which supports the flexible display  310 , extends toward the opening  400 . 
     As such, a proceeding direction of a part of the flexible display  310  positioned in the housing  200 , i.e., a part of the flexible display  310  between the roll  300  and the opening  400 , may be constantly maintained as a certain direction, e.g., a horizontal direction. Although not shown in  FIGS. 5 and 6 , when the electronic device  101  is used in a state in which the central shaft  330  stands upright in the direction of gravity, the proceeding direction of the flexible display  310  may be constantly maintained as a vertical direction. 
     The roll guide  340  extends in the direction of gravity, i.e., a direction almost perpendicular to a proceeding direction of the flexible display  320  unwound from the roll  300  and proceeding toward the opening  400  in the housing  200 , in  FIGS. 5 and 6 , but is not limited thereto. The roll guide  340  may have various shapes capable of compensating for the variation (D1-D2) in the outer diameter of the roll  300 . 
       FIG. 7  is a side cross-sectional view of the electronic device  101  according to an embodiment. 
     Referring to  FIG. 7 , the roll guide  340  is inclined downward with respect to the direction of gravity. In other words, the roll guide  340  is inclined with respect to a proceeding direction of the flexible display  320  unwound from the roll  300  and proceeding toward the opening  400  in the housing  200 . In this case, the inclined direction of the roll guide  340  may be a direction toward the opening  400 . As such, a distance between the roll  300  and the opening  400  may be reduced and thus a length of an effective image display area of the flexible display  310  may be increased. 
     Since the roll  300  rotates and moves as described above, the flexible display  310  unwound from the roll  300  may always proceed toward the opening  400  in the same direction. That is, a part of the flexible display  310  between the roll  300  and the opening  400  may constantly maintain the same proceeding direction toward the opening  400  in a state in which the flexible display  310  is positioned in the housing  200 , a state in which a part of the flexible display  310  extends out of the housing  200 , and a state in which an extendable area of the flexible display  310  completely extends out of the housing  200 . 
     The proceeding direction of the flexible display  310  for interconnecting the roll  300  and the opening  400  may not be a horizontal direction.  FIG. 8  is a side cross-sectional view of the electronic device  101  according to embodiment. 
     Referring to  FIG. 8 , the display guide  920  includes a supporting surface  922  inclined with respect to a horizontal direction. For example, in the current embodiment, the supporting surface  922  is inclined downward toward the opening  400 . Due to the above-described configuration, as the flexible display  310  is unwound from the roll  300 , the roll  300  may be naturally guided by the roll guide  340  to move downward, and the flexible display  310  unwound from the roll  300  may be guided along the supporting surface  922  to extend out of the housing  200  through the opening  400 . 
     Therefore, a proceeding direction of a part of the flexible display  310  between the roll  300  and the opening  400  may be constantly maintained. A guide member  800  for guiding the proceeding direction of the flexible display  310  passing through the opening  400  may be provided at an upper side of the opening  400  with respect to a direction in which the flexible display  310  is unwound. 
     The guide member  800  guides the flexible display  310  at a side opposite to the display guide  920  with respect to the flexible display  310  interposed between the guide member  800  and the display guide  920 . The guide member  800  may, for example, guide the flexible display  310  to proceed in a horizontal direction after passing through the opening  400 . 
     Inclination of the guide member  800  may be designed in consideration of a curvature by which the flexible display  310  is bendable. That is, the inclination of the guide member  800  may be designed to have a curvature greater than the maximum curvature of the flexible display  310 . As such, even when the flexible display  310  bent by a certain curvature by the guide member  800  passes through the opening  400 , fatigue due to the bending may not accumulated in the flexible display  310 . 
       FIG. 9  is a side cross-sectional view of the electronic device  101  according to an embodiment. 
     Referring to  FIG. 9 , a push member  900  is illustrated. The roll  300  is positioned between the display guide  920  and the push member  900 . The push member  900  pushes the roll  300  toward the display guide  920  in such a manner that the flexible display  310  wound on the roll  300  contacts the supporting surface  921 . 
     In  FIG. 9 , the push member  900  pushes the flexible display  310  wound on the roll  300 . The push member  900  may contact the flexible display  310  or the side protector  320 . The push member  900  may be provided in the form of a roller that rotates as the roll  300  rotates, to reduce frictional contact with the flexible display  310  or the side protector  320  (see  FIG. 3 ). 
     The push member  900  may push the roll  300  toward the display guide  920  due to a self weight thereof. As illustrated in  FIG. 9 , an elastic member  910  for applying elastic force to the push member  900  in a direction capable of pushing the roll  300  toward the display guide  920  may be further provided. 
     The display guide  920  supports the flexible display  310  wound on the roll  300 , and guides the flexible display  310  unwound from the roll  300 , toward the opening  400 . 
     The flexible display  310  may be pushed by the push member  900  and supported by the display guide  920  and thus may be stably held in a wound state on the roll  300 . In addition, even when the flexible display  310  is wound on or unwound from the roll  300 , the push member  900  aids stable extension and retraction of the flexible display  310  by reducing movement of the roll  300  in directions other than a direction in which the roll  300  is rolled or unrolled. 
     A structure in which the roll  300  is pushed toward the display guide  920  by using the push member  900  and the elastic member  910  may be applied to the embodiment of  FIG. 8  such that the flexible display  310  wound on the roll  300  may be pushed toward the supporting surface  922  of the display guide  920 . 
       FIGS. 10 and 11  are side cross-sectional views of the electronic device  101  according to an embodiment. The electronic device  101  of the current embodiment may include a winding member for providing elastic force to the roll  300  in such a manner that the roll  300  rotates in a direction capable of winding the flexible display  310  thereon. Referring to  FIGS. 10 and 11 , the winding member may be implemented by, for example, a spiral spring  1000 . 
     An end of the spiral spring  1000  may be connected to the roll  300 , and the other end thereof may be connected to the housing  200 . Alternatively, the end of the spiral spring  1000  may be connected to the roll  300  and the other end thereof may be connected to the central shaft  330 . In this case, the roll  300  has a structure rotatable with respect to the central shaft  330 , and the central shaft  330  does not rotate with respect to the housing  200  but is merely supported by the housing  200  to move along the roll guide  340 . In the current embodiment, the other end of the spiral spring  1000  is connected to the central shaft  330 . 
     Referring to  FIG. 11 , when the flexible display  310  starts to extend out of the housing  200 , the roll  300  rotates in a counterclockwise direction. The spiral spring  1000  accumulates elastic force as the roll  300  rotates. The elastic force accumulated by the spiral spring  1000  is used to retract the flexible display  310  extended out of the housing  200 , into the housing  200  to wind the flexible display  310  on the roll  300 . 
     The electronic device  101 , which retracts the flexible display  310  into the housing  200  by using the spiral spring  1000 , may include a locking unit capable of holding the flexible display  310  in an extended state.  FIG. 12  is a structural view of a locking unit according to an embodiment. 
     Referring to  FIG. 12 , the locking unit may be implemented by a stopper projection  1200  and a stopper lever  1210 . The stopper projection  1200  is provided on the roll  300 . The stopper projection  1200  may be provided at a side or two sides of the roll  300 . As necessary, a plurality of stopper projections  1200  may be provided in a rotation direction of the roll  300 . The number of stopper projections  1200  may be determined in consideration of a diameter of the roll  300  or a length of the flexible display  310 . For example, when the plurality of stopper projections  1200  are provided, a length of the flexible display  310  extending out of the housing  200  may be adjusted in multiple stages. 
     The stopper lever  1210  may be provided on the housing  200 . Alternatively, in a structure in which the central shaft  330  is supported by the housing  200  and the roll  300  rotates with respect to the central shaft  330 , the stopper lever  1210  may be provided on the central shaft  330 . In the current embodiment, the stopper lever  1210  is provided on the central shaft  330 . 
     An end of the stopper lever  1210  is rotatably supported by the central shaft  330 . The stopper lever  1210  may rotate to a contact location (indicated by a solid line in  FIG. 12 ) at which the other end of the stopper lever  1210  contacts the stopper projection  1200 , and a release location (indicated by a two-dot chain line in  FIG. 12 ) at which the other end of the stopper lever  1210  is released from the stopper projection  1200 . The spring  1220  provides elastic force to the stopper lever  1210  in a direction capable of holding the stopper lever  1210  at the contact location. 
     Referring to  FIG. 12 , when the roll  300  rotates in a counterclockwise direction to extend the flexible display  310  out of the housing  200 , the stopper projection  1200  contacts the stopper lever  1210  mounted on the central shaft  330 . In this state, when the roll  300  further rotates in the counterclockwise direction, the stopper lever  1210  is pushed by the stopper projection  1200  and rotates in a direction opposite to a direction of the elastic force of the spring  1220 . 
     As the stopper lever  1210  is pushed by the stopper projection  1200  and rotates, a length of a superposed part between the stopper lever  1210  and the stopper projection  1200  is gradually reduced. When the roll  300  further rotates in the counterclockwise direction, the stopper lever  1210  is positioned at the release location, the stopper projection  1200  is released from the stopper lever  1210 , and the roll  300  may continuously rotate in the counterclockwise direction. The stopper lever  1210  returns to the contact location due to the elastic force of the spring  1220 . 
     When the roll  300  stops rotating in the counterclockwise direction, the roll  300  rotates in a clockwise direction due to the elastic force of the spiral spring  1000 . As the roll  300  rotates in the clockwise direction, the stopper projection  1200  contacts the stopper lever  1210 . The stopper lever  1210  may rotate from the contact location to the release location, but is restricted so as not to rotate beyond the contact location. A restriction member for the restriction may be implemented by, for example, a restriction slot  1230  provided in the central shaft  330 , and a restriction protrusion  1240  provided on the stopper lever  1210  and inserted into the restriction slot  1230 . Accordingly, when the stopper projection  1200  rotates in the clockwise direction and contacts the stopper lever  1210  positioned at the contact location, the roll  300  may no more rotate in the clockwise direction and the display  310  is held in an extended state. 
     The electronic device  101  needs to release a locked state of the stopper lever  1210  and the stopper projection  1200  to retract the held display  310  into the housing  200 . For example, the electronic device  101  may rotate the stopper lever  1210  to the release location. To this end, although not shown in  FIG. 12 , to allow a user to manually manipulate and rotate the stopper lever  1210  to the release location, a part of the stopper lever  1210  may be exposed outside the housing  200 . In addition, although not shown in  FIG. 12 , a release lever for manually manipulating and rotating the stopper lever  1210  exposed outside the housing  200 , to the release location may be further provided. 
       FIGS. 13 and 14  are side cross-sectional views of the electronic device  101  according to an embodiment. 
     Referring to  FIGS. 13 and 14 , the push member  900  may be implemented by a roll spring  1300 . The roll spring  1300  is supported by the roll guide  340  and pushes the roll  300  toward the display guide  920 . The roll spring  1300  pushes the central shaft  330 . 
     The flexible display  310  wound on the roll  300  is held in contact with the display guide  920 , by the roll spring  1300 . Therefore, the flexible display  310  may be held in a wound state on the roll  300 . In addition, as the flexible display  310  is unwound from the roll  300 , the roll  300  may more easily move downward and the flexible display  310  may be held in contact with the display guide  920 . 
     The push member  900  and the elastic member  910  of  FIG. 9  may be applied to the electronic device  101  illustrated in  FIGS. 13 and 14 . As such, the flexible display  310  may be more stably held in a wound state on the roll  300 . 
     The electronic device  101  illustrated in  FIGS. 13 and 14  may include a spiral spring (not shown) between the roll  300  and the central shaft  330 . The spiral spring may be provided at the same location as and may perform the same function as the spiral spring  1000  described above in relation to  FIGS. 10 and 11 . 
     The electronic device  101 , which retracts the flexible display  310  into the housing  200  by using the spiral spring  1000 , may include a locking unit capable of holding the flexible display  310  in an extended state. The locking unit may hold the extended flexible display  310 . The locking unit may be implemented by the stopper projection  1200  and the stopper lever  1210  described above in relation to  FIG. 12 . 
     When the flexible display  310  enters and exits the housing  200  through the opening  400 , a certain relationship may be established between rotation of the roll  300  and movement of the roll  300  along the roll guide  340 . 
     Referring to  FIG. 15 , a pinion gear  1500  is illustrated. The pinion gear  1500  may be provided on, for example, the roll  300 . In a structure in which the central shaft  330  rotates together with the roll  300 , the pinion gear  1500  may be provided on the central shaft  330 . In the current embodiment, the pinion gear  1500  is provided on the central shaft  330 . The pinion gear  1500  engages with a rack gear  1510  extending in a movement direction of the roll  300 , i.e., an extension direction of the roll guide  340 . The rack gear  1510  is positioned at a fixed location. For example, the rack gear  1510  may be provided on the housing  200 . As the flexible display  310  is wound on or unwound from the roll  300 , the pinion gear  1500  may move along the rack gear  1510  in an extension direction of the rack gear  1510 . 
     The pinion gear  1500  may be designed to move along the rack gear  1510  by a variation in an outer diameter of the roll  300  including the flexible display  310 , when the flexible display  310  is wound on the roll  300  in a multilayer structure. That is, when the flexible display  310  wound on the roll  300  is unwound or further wound by a layer, the roll  300  may move along the roll guide  340  by a thickness of the flexible display  310  such that a proceeding direction of the flexible display  310  with respect to the opening  400  may be constantly maintained. 
     When a diameter of the pinion gear  1500  is Dp, the number of turns of the pinion gear  1500  is Np, and a movement distance of the pinion gear  1500  along the rack gear  1510  is L, 
         L=Dp*π*Np   Equation (1)
 
     is satisfied. 
     Referring to  FIG. 16 , the pinion gear  1500  moves along the rack gear  1510  and is positioned at a location under the location of  FIG. 15 , and the flexible display  310  is in an extended state. As described above, the pinion gear  1500  may move by an increase or a reduction in the thickness of the flexible display  310  wound on or unwound from the roll  300 . Therefore, while the roll  300  is moving together with the pinion gear  1500 , a proceeding direction of the flexible display  310  toward the opening  400  may be constantly maintained. 
     The electronic device  101  according to the current embodiment may include a display guide (not shown), a push member (not shown), and an elastic member (not shown) for appropriate extension and retraction of the flexible display  310 . The display guide, the push member, and the elastic member of the current embodiment may be provided at the same locations as and may perform the same functions as the display guide  920 , the push member  900 , and the elastic member  910  described above in relation to  FIG. 9 . 
     The electronic device  101  according to the current embodiment may include a spiral spring (not shown) for interconnecting the roll  300  and the central shaft  330 . The spiral spring of the current embodiment may be provided at the same location as and may perform the same function as the spiral spring  1000  described above in relation to  FIGS. 10 and 11 . 
     The electronic device  101 , which retracts the flexible display  310  into the housing  200  by using the spiral spring  1000 , may include a locking unit capable of holding the flexible display  310  in an extended state. The locking unit may hold the extended flexible display  310 . The locking unit may employ a structure of the stopper projection  1200  and the stopper lever  1210  described above in relation to  FIG. 12 . 
     In a structure including only the rack gear  1510  and the pinion gear  1500 , the diameter of the pinion gear  1500  is reduced in proportion to the thickness of the flexible display  310 . Therefore, in consideration of production errors and durability of the pinion gear  1500 , a gear reduction structure may be interposed between the rack gear  1510  and the pinion gear  1500 . 
       FIG. 17  is a structural view of a reduction structure according to an embodiment. 
     Referring to  FIG. 17 , a reduction gear  1720  is interposed between the pinion gear  1500  and the roll  300 . 
     The reduction gear  1720  is a double gear including a first gear part  1721  engaging with the pinion gear  1500 , and a second gear part  1722  engaging with the rack gear  1510 . A diameter of the first gear part  1721  is greater than a diameter of the second gear part  1722 . Although not shown in  FIG. 17 , the reduction gear  1720  may be provided on a bracket (not shown) for rotatably supporting the roll  300 . The bracket is supported by the housing  200  to move together with the roll  300 . 
     When the diameter of the first gear part  1721  is D1 and the diameter of the second gear part  1722  is D2, the pinion gear  1500  is connected to the rack gear  1510  at a reduction gear ratio of D2/D1. Therefore, when a diameter of the pinion gear  1500  is Dp1, a movement distance of the roll  300  is L1, and the number of turns of the pinion gear  1500  is Np, 
         L 1= Dp 1*( D 2/ D 1)* Np*π   Equation (2)
 
     is satisfied. 
     Herein, if L of Equation (1) equals L1 of Equation (2), the diameter Dp1 of the pinion gear  1500  satisfies 
     Dp1=(D1/D2)*Dp. Since D1&gt;D2, Dp1&gt;Dp is satisfied. Therefore, since the diameter of the pinion gear  1500  may be increased by (D1/D2) times, the pinion gear  1500  having a size appropriate for production may be employed by appropriately selecting the diameters of the first and second gear parts  1721  and  1722 , and durability of the pinion gear  1500  may be increased. 
     As necessary, two or more reduction gears may be employed.  FIG. 18  is a structural view of a reduction structure according to an embodiment. Referring to  FIG. 18 , first and second reduction gears  1820  and  1830  are interposed between the pinion gear  1500  and the rack gear  1510 . 
     The first reduction gear  1820  is a double gear including first and second gear parts  1821  and  1822 . The second reduction gear  1830  is a double gear including third and fourth gear parts  1831  and  1832 . The first gear part  1821  engages with the pinion gear  1500 . The second gear part  1822  engages with the third gear part  1831 . The fourth gear part  1832  engages with the rack gear  1510 . 
     A diameter of the first gear part  1821  is greater than a diameter of the second gear part  1822 . A diameter of the third gear part  1831  is greater than a diameter of the fourth gear part  1832 . Although not shown in  FIG. 18 , the first and second reduction gears  1820  and  1830  may be provided on a bracket (not shown) for rotatably supporting the roll  300 . The bracket is supported by the housing  200  to move together with the roll  300 . 
     When the diameters of the first, second, third, and fourth gear parts  1821 ,  1822 ,  1831 , and  1832  are D1, D2, D3, and D4, respectively, the pinion gear  1500  is connected to the rack gear  1510  at a reduction gear ratio of (D2/D1)*(D4/D3). Therefore, when a diameter of the pinion gear  1500  is Dp2, a movement distance of the roll  300  is L2, and the number of turns of the pinion gear  1500  is Np, 
         L 2= Dp 2*( D 2/ D 1)*( D 4/ D 3)* Np*π   Equation (3)
 
     is satisfied. 
     Herein, if L of Equation (1) equals L2 of Equation (3), the diameter Dp1 of the pinion gear  1500  satisfies Dp2=(D1/D2)*(D3/D4)*Dp. Since D1&gt;D2 and D3&gt;D4, Dp2&gt;Dp is satisfied. Therefore, since the diameter of the pinion gear  1500  may be increased by (D1/D2)*(D3/D4) times, the pinion gear  1500  having a size appropriate for production may be employed by appropriately selecting the diameters of the first to fourth gear parts  1821 ,  1822 ,  1831 , and  1832 , and durability of the pinion gear  1500  may be increased. In addition, since gear reduction occurs twice, when Dp1 equals Dp2, the first and second reduction gears  1820  and  1830  may have sizes less than a size of the reduction gear  1720  and thus a compact gear reduction structure applicable to a small space may be implemented. 
       FIG. 19  includes perspective views showing usage of the electronic device  101  using the afore-described structures. Herein, the electronic device  101  may be, for example, a rollable TV or screen. 
     Referring to  FIG. 19( a ) , the electronic device  101  may be fixed to a wall in such a manner that the opening  400  faces downward. The flexible display  310  is completely wound on the roll  300  and accommodated in the housing  200 . The roll  300  is positioned, for example, at a rear end of the roll guide  340 . A user may extend the flexible display  310  out of the housing  200  by holding and pulling downward the handle  210  positioned at a front end of the flexible display  310 . 
       FIG. 19( b )  shows that the flexible display  310  partially extends downward through the opening  400  of the housing  200 .  FIG. 19( c )  shows that the flexible display  310  mostly extends downward through the opening  400  of the housing  200 . As illustrated in  FIGS. 19( b ) and 19( c ) , the roll  300  moves forward along the roll guide  340  as the flexible display  310  is unwound from the roll  300  and extends through the opening  400 , and reaches a front end of the roll guide  340  when the flexible display  310  completely extends. When the flexible display  310  is wound on the roll  300 , a wound length of the flexible display  310  on the roll  300  is increased and the roll  300  moves backward along the roll guide  340 . Therefore, even when the wound length of the flexible display  310  on the roll  300  varies, a proceeding direction of the flexible display  310  with respect to the opening  400  in the housing  200  may be constantly maintained. 
       FIG. 20  includes perspective views of the electronic device  101  according to an embodiment. Referring to  FIG. 20 , the electronic device  101  includes a pair of housings  200  and  200 ′, and rolls  300  and  300 ′ are provided in the housings  200  and  200 ′, respectively. An end of the flexible display  310  is fixed to the roll  300  and the other end thereof is fixed to the roll  300 ′. The flexible display  310  is wound on the rolls  300  and  300 ′ and accommodated in the housings  200  and  200 ′. Openings  400  and  400 ′ through which the flexible display  310  enters and exits are provided in the housings  200  and  200 ′, respectively. The housings  200  and  200 ′ are positioned in such a manner that the openings  400  and  400 ′ face each other. Roll guides  340  and  340 ′ for guiding the rolls  300  and  300 ′ are provided in the housings  200  and  200 ′, respectively. Due to the above-described configuration, the flexible display  310  may extend out of/retract into the housings  200  and  200 ′ by pulling/pushing the housings  200  and  200 ′ away from/toward each other. 
       FIG. 20( a )  shows that the flexible display  310  is accommodated in the housings  200  and  200 ′. The housings  200  and  200 ′ closely contact each other. In this state, when the housings  200  and  200 ′ are pulled away from each other, as illustrated in  FIG. 20( b ) , the flexible display  310  is unwound from the rolls  300  and  300 ′, extends through the openings  400  and  400 ′, and is spread between the housings  200  and  200 ′. When the housings  200  and  200 ′ are pulled away from each other by the maximum distance, as illustrated in  FIG. 20( c ) , the flexible display  310  is completely unwound from the rolls  300  and  300 ′ and spread between the housings  200  and  200 ′, thereby ensuring the widest image display area. 
     The roll guides  340  and  340 ′ extend in a vertical direction. The rolls  300  and  300 ′ move downward along the roll guides  340  and  340 ′ as the flexible display  310  is unwound from the rolls  300  and  300 ′, and are positioned at lower ends of the roll guides  340  and  340 ′ when the flexible display  310  is completely spread. When the housings  200  and  200 ′ are pushed toward each other, the rolls  300  and  300 ′ rotate in directions for winding the flexible display  310  thereon due to, for example, elastic force of the spiral spring  1000 . When a wound length of the flexible display  310  on the rolls  300  and  300 ′ is increased, the rolls  300  and  300 ′ move upward along the roll guides  340  and  340 ′. Therefore, even when the wound length of the flexible display  310  on the rolls  300  and  300 ′ varies, proceeding directions of the flexible display  310  with respect to the openings  400  and  400 ′ in the housings  200  and  200 ′ may be constantly maintained. 
     Each of the above-described elements of the electronic device according to various embodiments may include one or more components, and the names of the elements may vary depending on the type of the electronic device. The electronic device according to various embodiments may include at least one of the above-described elements and may not include some elements or may further include additional elements. Furthermore, some of the elements of the electronic device according to various embodiments may be combined to configure a single entity, and the single entity may equally perform functions of the combined elements.