Patent Publication Number: US-2022232716-A1

Title: Electronic device including slide-out display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/KR2021/005484 designating the United States, filed on Apr. 29, 2021, in the Korean Intellectual Property Receiving Office and claiming priority to Korean Patent Application No. 10-2020-0060146, filed on May 20, 2020, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Field 
     The disclosure relates to an electronic device including a slide-out display. 
     Description of Related Art 
     With the development of digital technologies, electronic devices are being provided in various forms such as a smartphone, a tablet personal computer (PC), and a personal digital assistant (PDA). Electronic devices are being designed to provide a larger screen while having a portable size that does not cause inconvenience to a user&#39;s hand. 
     An electronic device may be implemented to be capable of extending a screen, for example, in a slide manner. For example, a portion of a flexible display is pulled out from the inner space of the electronic device in a slide manner, whereby the screen can be expanded. However, a non-smooth screen may be provided due to lifting due to elasticity of the flexible display in the state in which the screen is expanded. In order to prevent and/or reduce this, a tension structure for the flexible display may be provided, but it may be difficult to assemble electrical mechanical elements in the electronic device while maintaining the tension, and it may also be difficult to maintain the tension due to the repetition of the slide operation. 
     SUMMARY 
     Embodiments of the disclosure provide an electronic device including a slide-out display that maintains tension on a flexible display and enables a smooth slide operation. 
     According to an example embodiment of the disclosure, an electronic device may include: a housing, a sliding plate configured to slide-out from the housing, a flexible display including a first section coupled to overlap the sliding plate, and a bendable section extending from the first section and configured to be pulled out from an inner space of the housing during the slide-out, a support sheet disposed on a rear surface of the flexible display, a first curved portion located inside the housing and corresponding to the bendable section, a belt connecting the support sheet and the sliding plate to each other, and a second curved portion located inside the housing corresponding to the belt and spaced apart from the first curved portion in a slide-out direction. 
     According to various example embodiments of the disclosure, since a smooth screen is provided by maintaining tension on the flexible display and a smooth slide operation is enabled, reliability of an electronic device including a slide-out display can be improved. 
     In addition, effects that can be obtained by various example embodiments of the disclosure will be directly or implicitly disclosed in the detailed description of the embodiments of the disclosure. For example, various effects according to various example embodiments of the disclosure will be disclosed in the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and advantages of certain embodiments of the present disclosure will be more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a front perspective view illustrating a slidable electronic device in a closed state according to various embodiments; 
         FIG. 1B  is a rear perspective view illustrating a slidable electronic device in the closed state according to various embodiments; 
         FIG. 2A  is a front perspective view illustrating a slidable electronic device in an open state according to various embodiments; 
         FIG. 2B  is a rear perspective view illustrating a slidable electronic device in the open state according to various embodiments; 
         FIG. 3  is an exploded perspective view of the slidable electronic device of  FIG. 1A  according to various embodiments; 
         FIG. 4  is a cross-sectional view of the electronic device of  FIG. 1A  in the closed state taken along line A-A′ according to various embodiments; 
         FIG. 5  is a cross-sectional view of the electronic device of  FIG. 2A  in the open state taken along line B-B′ according to various embodiments; 
         FIG. 6  is an exploded perspective view of a display assembly according to various embodiments; 
         FIG. 7A  is a diagram illustrating the front surface of the display assembly of  FIG. 6  when the display assembly is in an unfolded state according to various embodiments; 
         FIG. 7B  is a diagram illustrating the rear surface of the display assembly of  FIG. 6  when the display assembly is in the unfolded state according to various embodiments; 
         FIG. 8  is a diagram illustrating the rear surface of the display assembly of  FIG. 6  when the display assembly is in the unfolded state according to various embodiments; 
         FIG. 9  is a diagram illustrating the rear surface of the display assembly of  FIG. 6  when the display assembly is in the unfolded state according to various embodiments; 
         FIG. 10  is a diagram illustrating the rear surface of the display assembly of  FIG. 6  when the display assembly is in the unfolded state according to various embodiments; 
         FIG. 11  is a perspective view of a portion of an electronic device according to various embodiments 
         FIG. 12  is a diagram illustrating a first belt of  FIG. 11  according to various embodiments; 
         FIG. 13A  is a diagram illustrating a first fastening part of  FIG. 11  according to various embodiments; 
         FIG. 13B  is a cross-sectional view of the first fastening part of  FIG. 13A  taken along line C-C′ according to various embodiments; 
         FIG. 13C  is a perspective view illustrating a state in which the first fastening part and the first belt are connected to each other according to various embodiments; 
         FIG. 14  is a perspective view illustrating a tension adjusting device for a first belt according to various embodiments; 
         FIG. 15A  is a diagram illustrating a portion of an electronic device including a tension adjusting device according to various embodiments; 
         FIG. 15B  is a partial perspective view illustrating the portion indicated by reference numeral “D” of the electronic device of  FIG. 15A  according to various embodiments; 
         FIG. 15C  is a diagram illustrating a belt included in the electronic device of  FIG. 15A  according to various embodiments; 
         FIGS. 16A and 16B  are diagrams illustrating an electronic device according to various embodiments; 
         FIG. 17A  is a partial perspective view illustrating a portion of the electronic device of  FIG. 16A  according to various embodiments; and 
         FIG. 17B  is a partial perspective view illustrating a portion of the electronic device of  FIG. 16A  according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, various example embodiments of the disclosure will be described with reference to the accompanying drawings. 
     It should be understood that various embodiments of the disclosure and terms for describing the embodiments are not intended to limit the technical features disclosed herein to specific embodiments, and that the embodiments include various modifications, equivalents, and/or substitutions of the corresponding embodiments. In connection with the description of the drawings, similar or related components may be denoted by similar reference numerals. The singular form of a noun corresponding to an item may include one or more of the items unless the context clearly indicates otherwise. Herein, each of phrases, such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B, or C”, “at least one of A, B, and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase or all possible combinations of the items. Terms such as “1 st ”, “2 nd ”, “first”, or “second” may be used simply to distinguish corresponding components from other components, and the components are not limited in other respects (e.g., importance or order). 
     An electronic device according to various embodiments disclosed herein may be any of various types of devices. The electronic device may include, for example, a portable communication device (e.g., a smartphone), a computer device, a portable multimedia device, a portable medical device, a camera, a wearable device, a home appliance, or the like. The electronic device according to an embodiment disclosed herein is not limited to the above-described devices. 
       FIG. 1A  is a front perspective view illustrating a slidable electronic device  100  in a closed state according to various embodiments.  FIG. 1B  is a rear perspective view illustrating the slidable electronic device  100  in the closed state according to various embodiments.  FIG. 2A  is a front perspective view illustrating the slidable electronic device  100  in an open state according to various embodiments.  FIG. 2B  is a rear perspective view illustrating the slidable electronic device  100  in the open state according to various embodiments. 
     Referring to  FIGS. 1A, 1B, 2A, and 2B , in an embodiment, the electronic device  100  may be implemented to expand a screen in a sliding manner.  FIGS. 1A and 1B  illustrate the electronic device  100  in a state in which the screen is not expanded, and  FIGS. 2A and 2B  show the electronic device  100  in a state in which the screen is expanded. The state in which the screen is not expanded is a state in which a sliding plate  120  for a sliding motion of a display  130  is not slid-out, and may be referred to as a “closed state” below. The state in which the screen is expanded is a maximally expanded state in which the screen is not expanded any more due to the slide-out of the sliding plate  120 , which may be referred to as an “open state” below. According to various embodiments, the open state may be referred to as a state in which the screen is expanded compared to the closed state, and the screens may be provided in various sizes depending on the moving position of the sliding plate  120 . The screen is an active area of the flexible display  130  that is visible to output an image, and the electronic device  100  is capable of adjusting the active area depending on the movement of the sliding plate  120  or the movement of the flexible display  130 . In the following description, the open state may refer to a state in which the screen is maximally expanded. In various embodiments, the flexible display  130 , which is disposed to be slidable in the electronic device  100  of  FIG. 1A  to provide a screen, may be referred to as a “slide-out display” or an “expandable display”. In various embodiments, the electronic device  100  may be referred to as a “rollable” electronic device. 
     According to an embodiment, the electronic device  100  may include a sliding structure based on an elastic structure connected to (or associated with) the flexible display  130 . When the flexible display  130  is moved to a set distance by an external force, the flexible display  130  may be switched from the closed state to the open state or from the open state to the closed state without any further external force due to an elastic structure (e.g., a semi-automatic slide operation). 
     According to various embodiments, when a signal is generated via an input device included in the electronic device  100 , the electronic device  100  may be switched from the closed state to the open state or from the open state to the closed state due to a driving device such as a motor connected to the flexible display  130 . For example, when a signal is generated via a hardware button or a software button provided through the screen, the electronic device  100  may be switched from the closed state to the open state or from the open state to the closed state. 
     According to various embodiments, when a signal is generated from various sensors such as a pressure sensor, the electronic device  100  may be switched from the closed state to the open state or from the open state to the closed state. For example, when carrying or grasping the electronic device  100  by hand, a squeeze gesture in which a portion of the hand (e.g., the palm or fingers) presses a portion within a predetermined section of the electronic device  100  may be detected by a sensor, and in response thereto, the electronic device  100  may be switched from the closed state to the open state or from the open state to the closed state. 
     According to an embodiment, the flexible display  130  may include a first bendable section  133  (see  FIG. 2A ). The first bendable section  133  may provide an expanded portion of the screen when the electronic device  100  is switched from the closed state to the open state. When the electronic device  100  is switched from the closed state to the open state, the first bendable section  133  is pulled out from the inner space of the electronic device  100  in a sliding manner, and thus the screen can be expanded. When the electronic device  100  is switched from the open state to the closed state, the first bendable section  133  is introduced into the inner space of the electronic device  100  in a sliding manner, and thus the screen can be contracted. When the electronic device  100  is switched from the open state to the closed state, the first bendable section  133  may be bent and moved into the inner space of the electronic device  100 . The display  130  may be implemented using a flexible display based on a flexible substrate (e.g., a plastic substrate) formed of a polymer material including polyimide (PI) or polyester (PET (polyester)), and may be referred to as a flexible display below. 
     According to an embodiment, the electronic device  100  may include a housing  110 , a sliding plate  120 , and/or a flexible display  130 . 
     The housing (or a case)  110  may include, for example, a back cover  112 , a first side cover  113 , and/or a second side cover  114 . The back cover  112 , the first side cover  113 , and/or the second side cover  114  may be connected to a support member (not illustrated) located inside the electronic device  100 , and may define at least a portion of the external appearance of the electronic device  100 . 
     The back cover  112  may define, for example, at least a portion of the rear surface  100 B of the electronic device  100 . The back cover  112  may be substantially opaque. The back cover  112  may be made of coated or colored glass, ceramic, polymer, metal (e.g., aluminum, stainless steel (STS), or magnesium), or a combination of at least two of these materials. According to various embodiments, at least a partial area of the back cover  112  may be transparent or may include an opening, and an image output from the flexible display  130  in the closed state of  FIG. 1B  may be visible through the partial area. 
     According to an embodiment, the back cover  112  may include a flat portion  112   a  and curved portions  112   b  and  112   c  located opposite to each other with the flat portion  112   a  interposed therebetween. The curved portions  112   b  and  112   c  may be disposed adjacent to opposite long edges (not illustrated) of the back cover  112 , respectively, and may be bent and extend seamlessly toward the screen located opposite to the back cover  112 . According to various embodiments, the back cover  112  may include one of the curved portions  112   b  and  112   c  or may be implemented without the curved portions  112   b  and  112   c.    
     According to an embodiment, the first side cover  113  and the second side cover  114  may be located opposite to each other. The first side cover  113  may define a first side surface  113   a  of the electronic device  100 , and the second side cover  114  may define a second side surface  114   a  of the electronic device  100  that faces away from the first side cover  113   a . The first side cover  113  may include a first peripheral portion (or a first rim)  113   b  extending from an edge of the first side surface  113   a , and the first peripheral portion  113   b  may provide at least a portion of one side bezel of the electronic device  100 . The second side cover  114  may include a second peripheral portion (or a second rim)  114   b  extending from an edge of the second side surface  114   a , and the second peripheral portion  114   b  may provide at least a portion of the other side bezel of the electronic device  100 . 
     According to an embodiment, the sliding plate  120  may be slidable on a support member (not illustrated) located inside the electronic device  100 . The flexible display  130  may be disposed on the sliding plate  120 , and the closed state of  FIG. 1A  or the open state of  FIG. 2A  may be formed based on the position of the sliding plate  120  on the support member. According to an embodiment, the flexible display  130  may be attached to the sliding plate  120  via an adhesive member (not illustrated) such as a double-sided tape. According to an embodiment, the adhesive member may include a thermally reactive adhesive member, a photoreactive adhesive member, an ordinary adhesive, and/or a double-sided tape. According to various embodiments, the flexible display  130  may be inserted into a recess provided at the sliding plate  120  in a sliding manner to be disposed on and fixed to the sliding plate  120 . The sliding plate  120  may include a third peripheral portion  120   b  that defines an outer surface of the electronic device  100 , and the third peripheral portion  120   b  may provide a bezel around the screen together with the first peripheral portion  113   b  and the second peripheral portion  114   b  in the closed state of  FIG. 1A . In the closed state of  FIG. 1A , the surface (not illustrated) of the third peripheral portion  120   b  may be smoothly connected to the surface (not illustrated) of the first peripheral portion  113   b  and/or the surface of the second peripheral portion  114   b.    
     The flexible display  130  may define, for example, a screen located opposite to the back cover  112 . According to an embodiment, the flexible display  130  may include a first bendable section  133 , which can be pulled out from the inner space of the housing  110 . Due to the slide-out of the sliding plate  120 , at least a portion of the first bendable section  133  comes out from the inside of the electronic device  100  so that the screen can be provided in the expanded state (e.g., the open state) as illustrated in  FIG. 2A . 
     According to an embodiment, in the closed state of  FIG. 1A , the screen may include a flat portion  130   a , and a first curved portion  130   b  and a second curved portion  130   c  located opposite to each other with the flat portion  130   a  interposed therebetween. For example, the first curved portion  130   b  and the second curved portion  130   c  may be substantially symmetrical to each other with the flat portion  130   a  interposed therebetween. In the closed state of  FIG. 1A , the first curved portion  130   b  and the second curved portion  130   c  may be located to correspond to the curved portions  112   b  and  112   c  of the back cover  112 , respectively, and may be curved toward the back cover  112 . When the electronic device  100  is switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A , the flat portion  130   a  may be expanded. For example, a partial area of the first bendable section  133  that forms the first curved portion  130   b  in the closed state of  FIG. 1A  may be included in the flat portion  130   a  expanded when the electronic device  100  is switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A  and may be formed as another area of the first bendable section  133 . According to an embodiment, the electronic device  100  may include an opening (not illustrated) for introducing or pulling-out of the first bendable section  133 , and a pulley (not illustrated) located in the opening. The pulley may be located to correspond to the first bendable section  133 , and the movement and the direction of movement of the first bendable section  133  may be guided through the rotation of the pulley during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . The first curved portion  130   b  may be provided by a portion corresponding to the curved surface of the pulley in the first bendable section  133 . The second curved portion  130   c  may be provided to correspond to a curved surface provided on one surface of the sliding plate  120 . The second curved portion  130   c  may be located opposite to the first curved portion  130   b  in the closed state or the open state of the electronic device  100  to improve the aesthetics of the screen. According to various embodiments, the flat portion  130   a  may be implemented in the expanded form without the second curved portion  130   c.    
     According to an embodiment, the flexible display  130  may further include a touch detection circuit (e.g., a touch sensor). The touch detection circuit may be implemented as a transparent conductive layer (or a film) based on various conductive materials such as indium tin oxide (ITO). For example, the touch detection circuit may be located between an optical layer (e.g., a layer for improving image quality or outdoor visibility of a screen, such as a polarization layer) and a light-emitting layer (e.g., a layer including a plurality of pixels implemented by light-emitting elements, such as OLEDs, and at least one thin film transistor (TFT) for controlling the same) of the flexible display  130  (e.g., an on-cell type). As another example, the touch detection circuit may be located between a transparent cover (e.g., a cover made of a material, such as polyimide or ultra-thin glass (UTG), and exposed to the outside) and the optical layer (e.g., a polarization layer) (e.g., an add-on type). As another example, the light-emitting layer may include a touch detection circuit or a touch sensing function (e.g., an in-cell type). According to various embodiments (not illustrated), the flexible display  130  may be coupled to or disposed adjacent to a pressure sensor capable of measuring the intensity (pressure) of a touch, and/or a digitizer configured to detect a magnetic field-type pen input device (e.g., a stylus pen). For example, the digitizer may include a coil member disposed on a dielectric substrate to detect an electromagnetically induced resonance frequency applied from a pen input device. 
     According to an embodiment, the electronic device  100  may include a microphone hole  151 , a speaker hole  152 , a connector hole  153 , a camera device (or a camera module)  154 , or a flash  155 . According to various embodiments, at least one of the components may be omitted from the electronic device  100  or other components may be additionally included in the electronic device  100 . 
     The microphone hole  151  may be provided, for example, in at least a portion of the second side surface  114   a  to correspond to a microphone (not illustrated) located inside the electronic device  100 . The position of the microphone hole  151  is not limited to the embodiment of  FIG. 1A  and may vary. According to various embodiments, the electronic device  100  may include a plurality of microphones capable of detecting the direction of sound. 
     The speaker hole  152  may be provided, for example, in at least a portion of the second side surface  114   a  to correspond to a speaker located inside the electronic device  100 . The position of the speaker hole  152  is not limited to the embodiment of  FIG. 1A  and may vary. According to various embodiments, the electronic device  100  may include a receiver hole for a call. In various embodiments, the microphone hole  151  and the speaker hole  152  may be implemented as one hole, or the speaker hole  152  may be omitted like a piezo speaker. 
     The connector hole  153  may be provided, for example, in at least a portion of the second side surface  114   a  to correspond to a connector (e.g., a USB connector) located inside the electronic device  100 . The electronic device  100  may transmit and/or receive power and/or data to/from an external electronic device electrically connected to the connector through the connector hole  153 . The position of the connector hole  153  is not limited to the embodiment of  FIG. 1A  and may vary. 
     The camera device  154  and the flash  155  may be located, for example, on the rear surface  100 B of the electronic device  100 . The camera device  154  may include one or more lenses, an image sensor, and/or an image signal processor. The flash  155  may include, for example, a light-emitting diode or a xenon lamp. In various embodiments, two or more lenses (e.g., an infrared camera lens, a wide-angle lens, and a telephoto lens) and image sensors may be located on one surface of the electronic device  100 . According to various embodiments, without being limited to the embodiment of  FIG. 1B  or  FIG. 2B , the electronic device  100  may include a plurality of camera devices (or a plurality of camera modules). The camera device  154  may be one of the plurality of camera devices. For example, the electronic device  100  may include a plurality of camera devices (e.g., a dual camera or a triple camera) having different properties (e.g., angles of view) or functions, respectively. For example, a plurality of camera devices (e.g., the camera device  154 ) including lenses having different angles of view may be configured, and the electronic device  100  may be configured to control the camera devices to perform change of angles of view implemented therein based on a user&#39;s selection. In addition, the plurality of camera devices may include at least one of a wide-angle camera, a telephoto camera, a color camera, a monochrome camera, or an infrared (IR) camera (e.g., a time of flight (TOF) camera or a structured light camera). According to an embodiment, the IR camera may be operated as at least a part of a sensor module (not illustrated). According to various embodiments (not illustrated), the electronic device  100  may further include a camera device (e.g., a front camera) that generates an image signal based on light received through the front surface (not illustrated) of the electronic device  100  placed in a direction in which the screen is oriented. For example, the camera device  154  is not limited to the embodiment of  FIG. 1B  or  FIG. 2B , and may be located inside the housing  110  to be aligned with an opening (e.g., a through hole, or a notch) provided in the flexible display  130 . The camera device  154  may receive light through the opening and a partial area of a transparent cover overlapping the opening to generate an image signal. The transparent cover may be formed of a material such as polyimide or ultrathin glass (UTG) to protect the flexible display  130  from the outside. 
     According to various embodiments, without being limited to the embodiment of  FIG. 1B  or  FIG. 2B , in the electronic device  100 , the camera device  154  may be disposed at the lower end of at least a portion of the screen of the flexible display  130  to perform related functions (e.g., image capturing) in the state in which the position thereof is not visually distinguished (or exposed). For example, the camera device  154  is disposed to overlap at least a portion of the screen when viewed from above the screen (e.g., when viewed in the −z-axis direction) so that the camera device  154  can acquire an image of an external subject without being exposed to the outside. 
     According to various embodiments (not illustrated), the electronic device  100  may further include a key input device. The key input device may be located, for example, on the first side surface  113   a  of the electronic device  100  that is provided by the first side cover  113 . In various embodiments (not illustrated), the key input device may include at least one sensor module. 
     According to various embodiments (not illustrated), the electronic device  100  may include various sensor modules. A sensor module may generate electrical signals or data values corresponding to the internal operating states or the external environmental states of the electronic device  100 . For example (not illustrated), the sensor module may include a proximity sensor that generates a signal regarding proximity of an external object based on light received through the front surface (not illustrated) of the electronic device  100  placed in a direction in which the screen is oriented. As another example (not illustrated), the sensor module may include various biometric sensors, such as a fingerprint sensor and an HRM sensor, for detecting biometric information based on light received through the front or rear surface  100 B of the electronic device. The electronic device  100  may include at least one of various other sensor modules, such as a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor. 
       FIG. 3  is an exploded perspective view of the electronic device  100  of  FIG. 1A  according to various embodiments. 
     Referring to  FIG. 3 , in an embodiment, the electronic device  100  may include a back cover  112 , a first side cover  113 , a second side cover  114 , a support member assembly  300 , a first pulley  360 , sliding plate  120 , flexible display  130 , a support sheet  370 , a multi-bar structure (or a multi-bar assembly)  380 , a printed circuit board  390  (e.g., a printed circuit board (PCB), a flexible PCB (FPCB), or a rigid-flexible PCB (RFPCB)), a first belt  410 , a second belt  420 , a third belt  430 , a second pulley  440 , a third pulley  450 , and/or a fourth pulley  460 . A redundant description of some of the reference numerals in  FIG. 3  may not be repeated here. 
     According to an embodiment, the support member assembly (or a support structure)  300  is a frame structure capable of withstanding a load, and may contribute to durability or rigidity of the electronic device  100 . At least a portion of the support member assembly  300  may include a non-metal material (e.g., polymer) and/or a metal material. The housing  110  (see  FIG. 1A ) including the back cover  112 , the first side cover  113 , or the second side cover  114 , the first pulley  360 , the sliding plate  120 , and the flexible display  130 , the support sheet  370 , the multi-bar structure  380 , the printed circuit board  390 , the first belt  410 , the second belt  420 , the third belt  430 , the second pulley  440 , the third pulley  450 , or the fourth pulley  460  may be disposed on the support member assembly  300 . 
     According to an embodiment, the support member assembly  300  may include a first support member  310 , a second support member  320 , a third support member  330 , a fourth support member  340 , or a fifth support member  350 . 
     The first support member (or a first bracket)  310  may be, for example, in the form of a plate, and the sliding plate  120  may be disposed on one surface  310   a  of the first support member  310 . The second support member (or a second bracket)  320  may be, for example, in the form of a plate overlapping the first support member  310  and may be coupled to the first support member  310  and/or the third support member  330 . The third support member  330  may be coupled to the first support member  310  and/or the second support member  320  with the second support member  320  interposed therebetween. The printed circuit board  390  may be disposed on the second support member  320  between the first support member  310  and the second support member  320 . The fourth support member  340  may be coupled to one side of an assembly (not illustrated) in which the first support member  310 , the second support member  320 , and the third support member  330  are coupled to each other. The fifth support member  350  may be coupled to the other side of the assembly (not illustrated) in which the first support member  310 , the second support member  320 , and the third support member  330  are coupled to each other, and may be located opposite to the fourth support member  340 . The first side cover  113  may be coupled to the support member assembly  300  from the side of the fourth support member  340 . The second side cover  114  may be coupled to the support member assembly  300  from the side of the fifth support member  350 . The back cover  112  may be coupled to the support member assembly  300  from the side of the third support member  330 . At least a portion of the first support member  310 , the second support member  320 , the third support member  330 , the fourth support member  340 , or the fifth support member  350  may include a metallic material and/or a non-metallic material (e.g., polymer). According to various embodiments, at least two or more of the first support member  310 , the second support member  320 , the third support member  330 , the fourth support member  340 , and the fifth support member  350  may be integrally implemented. According to various embodiments, the support member assembly  300  may refer to a structure including at least some of the first support member  310 , the second support member  320 , the third support member  330 , the fourth support member  340 , and the fifth support member  350 . 
     The first support member  310  may include, for example, a first side surface (not illustrated) facing the fourth support member  340 , a second side surface  310   c  facing the fifth support member  350  and located opposite to the first side surface, a third side surface (not illustrated) interconnecting one end of the first side surface and one end of the second side surface  310   c , or a fourth side surface  310   d  interconnecting the other end of the first side surface and the other end of the second side  310   c  and located opposite to the third side surface. According to an embodiment, the first pulley  360  may be located near the third side surface of the first support member  310 . The first pulley  360  may include a cylindrical roller  361  extending in a direction (e.g., +y-axis direction) from the fifth support member  350  to the fourth support member  340 . The first pulley  360  may include a first rotation shaft (not illustrated) and a second rotation shaft  363  connected to the roller  361 , and the first rotation shaft and the second rotation shaft  363  may be located opposite to each other with the roller  361  interposed therebetween. The first rotation shaft may be located between the roller  361  and the first side cover  113 , and may be connected to the fourth support member  340 . The second rotation shaft  363  may be located between the roller  361  and the second side cover  114 , and may be connected to the fifth support member  350 . The fourth support member  340  may include a first through hole  341  into which the first rotation shaft is inserted, and the fifth support member  350  may include a second through hole  351  into which the second rotation shaft  363  is inserted. The roller  361  may be rotatable based on the first rotation shaft disposed on the fourth support member  340  and the second rotation shaft  363  disposed on the fifth support member  350 . 
     According to an embodiment, the sliding plate  120  may be disposed on the support member assembly  300  to be slidable on the first support member  310 . For example, a sliding structure for supporting and guiding the coupling and the movement of the sliding plate  120  may be provided between the first support member  310  and the sliding plate  120 . According to an embodiment, the sliding structure may include at least one elastic structure  490 . When the sliding plate  120  is moved by a set distance by an external force, due to the at least one elastic structure  490 , the electronic device  100  may be switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A  or from the open state to the closed state without a further external force. The at least one elastic structure  490  may be implemented based on various elastic members such as torsion springs. For example, a torsion spring as the resilient structure  490  may include one end connected to the sliding plate  120 , the other end connected to the first support member  310 , and a spring portion between the one end and the other end. When the sliding plate  120  is moved by an external force by a set distance in a first direction in which the sliding plate  120  slides out, the position of the one end relative to the other end is changed so that the sliding plate  220  can be moved in the first direction due to the elastic force of the spring portion without a further external force, and thus the electronic device  100  can be switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A . When the sliding plate  120  is moved by an external force by a set distance in a second direction opposite to the first direction, the position of the one end relative to the other end is changed so that the sliding plate  120  can be moved in the second direction due to the elastic force of the spring portion without a further external force, and thus the electronic device  100  can be switched from the open state of  FIG. 2A  to the closed state of  FIG. 2A . 
     According to an embodiment, the flexible display  130  may include a first section  131  extending from the first bendable section  133 . The first section  131  may be disposed on the sliding plate  120 . When the electronic device  100  is switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A , due to the movement of the sliding plate  120 , the first bendable section  133  connected to the first section  131  moves out of the electronic device  100  in a sliding manner so that the screen can be expanded. When the electronic device  100  is switched from the closed state to the open state, due to the movement of the sliding plate  120 , at least a portion of the first bendable section  133  is introduced into the electronic device  100  so that the screen can be contracted. The support member assembly  300  may include an opening (not illustrated) for introducing or pulling-out of the first bendable section  133 , and the first pulley  360  may be located in the opening. The opening may include a gap on one side between the first support member  310  and the third support member  330 , and a portion  331  of the third support member  330  that is located adjacent to the opening may have a curved shape corresponding to the curved surface of the roller  361 . The first pulley  360  may be located to correspond to the first bendable section  133 , and the movement and the direction of movement of the first bendable section  133  during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A  may be guided based on the rotation of the first pulley  360 . 
     According to an embodiment, the support sheet  370  may be attached to the rear surface of the flexible display  130 . The rear surface of the flexible display  130  may refer to the surface located opposite to the surface from which light from a light-emitting layer (or a display panel) including a plurality of pixels is emitted. For example, the support sheet  370  may include a second section (not illustrated) that is disposed at least partially along the first section  131 , a second bendable section (not illustrated) that is disposed along the first bendable section  133 , or a third section (not illustrated) that is spaced apart from the second section with the second bendable section interposed therebetween and does not overlap the flexible display  130 . According to various embodiments, at least a portion of the second section or at least a portion of the third section may be omitted. The support sheet  370  may contribute to durability of the flexible display  130 . The support sheet  370  may reduce the influence of a load or stress that may occur during switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A , on the flexible display  130 . The support sheet  370  may prevent and/or reduce the flexible display  130  from being damaged by a force transmitted from the sliding plate  120  when the sliding plate  120  is moved. Although not illustrated, the flexible display  130  may include a first layer including a plurality of pixels and a second layer coupled to the first layer. The first layer may include, for example, a light-emitting layer including a plurality of pixels implemented with light-emitting elements, such as organic light-emitting diodes (OLEDs) or micro light-emitting diodes (LEDs), and various other layers (e.g., an optical layer for improving the image quality of outdoor visibility of the screen, such as a polarization layer). According to various embodiments, the plurality of pixels may not be disposed in a partial area of the flexible display  130  that at least partially overlaps at least one electronic component (e.g., a camera module or a sensor module) included in the electronic device  100  when viewed from above the screen (e.g., in the −z-axis direction). According to various embodiments, the partial area of the flexible display  130  that at least partially overlaps at least one electronic component (e.g., a camera module or a sensor module) included in the electronic device  100  when viewed from above the screen may include a pixel structure and/or a wiring structure different from those of other areas. For example, the partial area of the flexible display  130  that at least partially overlaps at least one electronic component (e.g., a camera module or a sensor module) may have a pixel density different from that of other areas. For example, the partial area of the flexible display  130  that at least partially overlaps at least one electronic component (e.g., a camera module or a sensor module) may be implemented as a substantially transparent area formed by changing the pixel structure and/or the wiring structure even if the partial area does not include an opening. The second layer may include various layers for supporting and protecting the first layer (e.g., a cushioning member), blocking light, absorbing or blocking electromagnetic waves, or diffusing, dissipating, or radiating heat. According to an embodiment, at least a portion of the second layer is a conductive member (e.g., a metal plate), which may be helpful for reinforcing the rigidity of the electronic device  100 , and may be used in order to block ambient noise and to dissipate heat emitted from surrounding heat-emitting components (e.g., a display driving circuit). According to an embodiment, the conductive member may include at least one of copper (Cu), aluminum (Al), stainless steel (SUS), or a CLAD (e.g., a stacked member in which SUS and Al are alternately disposed). The support sheet  370  may cover at least a portion of the second layer of the flexible display  130  and may be attached to the rear surface of the second layer. The support sheet  370  may be formed of various metallic materials and/or non-metallic materials (e.g., polymer). According to an embodiment, the support sheet  370  may include stainless steel. According to various embodiments, the support sheet  370  may include engineering plastic. According to various embodiments, the support sheet  370  may be implemented integrally with the flexible display  130 . 
     According to an embodiment, the multi-bar structure  380  may be connected to the sliding plate  120 , and may include a first surface  381  facing the support sheet  370  and a second surface  382  located opposite to the first surface  381 . The second surface  382  may be spaced apart from the support sheet  370  with the first surface  381  interposed therebetween. When the sliding plate  120  is moved, the movement and the direction of movement of the multi-bar structure  380  may be guided by the roller  361  rotating in friction with the second surface  382 . According to an embodiment, the second surface  382  may include a form in which a plurality of bars (not illustrated) extending in a direction (e.g., +y-axis direction) from the second rotational axis  363  of the first pulley  360  to the first rotational axis (not illustrated) are arranged. The multi-bar structure  380  may be bent at portions having a relatively small thickness between the plurality of bars. In various embodiments, this multi-bar structure  380  may be referred to as various other terms, such as a “flexible track” or a “hinge rail”. According to various embodiments, various other types of flexible members substantially serving the same role as the multi-bar structure  380  may be substituted for the multi-bar structure  380 . 
     According to an embodiment, in the closed state of  FIG. 1A  or the open state of  FIG. 2A , at least a portion of the multi-bar structure  380  can be located on the screen side to support the first bendable section  133  of the flexible display  130  such that the first bendable section  133  can maintain a form smoothly connected to the first section  131  of the flexible display  130  without lifting. The multi-bar structure  380  may contribute to enabling the first bendable section  133  to be moved while maintaining the form smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . 
     According to an embodiment, the support sheet  370  may substantially prevent and/or reduce elements positioned inside the electronic device  100  (e.g., the multi-bar structure  380 ) from being visible through the flexible display  130 . 
     According to an embodiment, the first belt  410  may interconnect the sliding plate  120  and the support sheet  370 , and the second pulley  440  may be located on the first support member  310  to correspond to the first belt  410 . The second pulley  440  may include a rotation shaft (not illustrated) parallel to the rotation shaft of the first pulley  360  and may be located to be spaced apart from the first pulley  360 . The first support member  310  may include an opening (not illustrated) penetrating one surface facing the sliding plate  120  and the other surface facing the second support member  320 , and the second pulley  440  may be disposed in the opening. The first belt  410  may be disposed through the opening, wherein one end  411  of the first belt  410  may be connected to the sliding plate  120 , and the other end  412  may be connected to the support sheet  370 . The second pulley  440  connected to the first belt  410  may guide the movement and the direction of movement of the first belt  410 . The second belt  420  and the third pulley  450  located to correspond to the same interconnect the sliding plate  120  and the support sheet  370  at different positions, and may be implemented in substantially the same manner as the first belt  410  and the second pulley  440  located to correspond to the same. The third pulley  450  connected to the second belt  420  may guide the movement and the direction of movement of the second belt  420 . The third belt  430  and the fourth pulley  460  located to correspond to the same interconnect the sliding plate  120  and the support sheet  370  at different positions, and may be implemented in substantially the same manner as the first belt  410  and the second pulley  440  located to correspond to the same. The fourth pulley  460  connected to the third belt  410  may guide the movement and the direction of movement of the third belt  410 . According to various embodiments, the number or positions of the belts or the corresponding pulleys may vary without being limited to the embodiment of  FIG. 3 . 
     According to an embodiment, the sliding plate  120 , the multi-bar structure  380 , the flexible display  130 , the support sheet  370 , the first belt  410 , the second belt  420 , the third belt  430 , the first pulley  360 , the second pulley  440 , the third pulley  450 , and the fourth pulley  460  may transfer a motion or force during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . For example, the force for moving the sliding plate  120  on the first support member  310  may cause the movement of the flexible display  130 , the movement of the first belt  410 , the movement of the second belt  420 , and the movement of the third belt  430 , the rotation of the first pulley  360 , the rotation of the second pulley  440 , the rotation of the third pulley  450 , and the rotation of the fourth pulley  460 . When the sliding plate  120  is moved by a set distance by an external force, due to at least one elastic structure  490 , the electronic device  100  may be switched from the closed state of  FIG. 1A  to the open state of  FIG. 2A  from the open state to the closed state without a further external force. The force for moving the sliding plate  120  on the first support member  310  may include the external force or a force generated by the elastic structure  490 . 
     According to an embodiment, the first bendable section  133  of the flexible display  130 , the second bendable section (e.g., see reference numeral  373  in  FIG. 6 ) of the support sheet  370  that corresponds to the first bendable section  133 , and the multi-bar structure  380  may be connected to the first pulley  360 . The movement and the direction of movement of the first bendable section  133 , the second bendable section, and the multi-bar structure  380  may be guided by the first pulley  360 . The multi-bar structure  380  may be in face-to-face contact with the roller  361  of the first pulley  360 . The second bendable section of the support sheet  370  may be located between the multi-bar structure  380  and the first bendable section  133  of the flexible display  130 . The second bendable section of the support sheet  370  is not in direct face-to-face contact with the first pulley  360 , but is moved based on the rotation of the first pulley  360  in a driving relationship with the first pulley  360  to correspond to the multi-bar structure  380 . Thus, in the following description, the second bendable section may be described as being in a connected state (or a drivingly connected state) with the first pulley  360 . The first bendable section  133  is not in direct face-to-face contact with the first pulley  360 , but is moved based on the rotation of the first pulley  360  in a driving relationship with the first pulley  360  to correspond to the multi-bar structure  380  and the second bendable section of the support sheet  370 . Thus, in the following description, the first bendable section  133  may be described as being in a connected state (or a drivingly connected state) with the first pulley  360 . 
     According to an embodiment, the first belt  410  may be connected to the second pulley  440  located opposite to the first pulley  360 , which is in the drivingly connected state with the first bendable section  133 , to provide a tension to the flexible display  130  and the support sheet  370 . The second belt  420  may be connected to the third pulley  450  located opposite to the first pulley  360 , which is in the drivingly connected state with the first bendable section  133 , to provide a tension to the flexible display  130  and the support sheet  370 . The third belt  430  may be connected to the fourth pulley  460  located opposite to the first pulley  360 , which is in the drivingly connected state with the first bendable section  133 , to provide a tension to the flexible display  130  and the support sheet  370 . The tension of the first belt  410 , the tension of the second belt  420 , and/or the tension of the third belt  430  may contribute to forming a screen in which the first bendable section  133  is smoothly connected to the first section  131  without lifting. The tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430  may contribute to enabling the first bendable section  133  to be smoothly connected to the first section without lifting with respect to the elasticity of the flexible display  130  and/or the elasticity of the support sheet  370 . 
     According to an embodiment, the third pulley  450  may be located between the second pulley  440  and the fourth pulley  460 . The second pulley  440 , the third pulley  450 , and the fourth pulley  460  may be arranged in a direction (e.g., the +y-axis direction) from the second side cover  114  to the first side cover  113 . A distance by which the third pulley  450  is spaced apart from the second pulley  440  in the +y-axis direction may be substantially the same as a distance by which the third pulley  450  is spaced apart from the fourth pulley  460  in the −y-axis direction. According to an embodiment, the third pulley  450  may be located to correspond to the center of the first section  131  or the center of the screen in the y-axis direction. A distance by which the third pulley  450  is spaced apart from the fourth support member  340  in the −y-axis direction may be substantially the same as a distance by which the third pulley  450  is spaced apart from the fifth support member  350  in the +y-axis direction. The second pulley  440 , the third pulley  450 , and the fourth pulley  460  may be located to be spaced apart from the first pulley  360  by a substantially equal distance. The positions or numbers of the belts or other pulleys located to be spaced apart from the first pulley  360  corresponding to the belt are not limited to the embodiment of  FIG. 3  and may vary. 
     According to various embodiments (not illustrated), one pulley replacing the second pulley  440 , the third pulley  450 , and the fourth pulley  460  may be implemented. In this case, the pulley may include a groove formed in a circumferential surface thereof for locating the first belt  410 , the second belt  420 , or the third belt  430 . 
     According to various embodiments, one belt replacing the first belt  410 , the second belt  420 , and the third belt  430  may be implemented. In this case, one belt and one pulley located to correspond the belt and to be spaced apart from the first pulley  360  may be located to correspond to the center of the first section  131  or the center of the screen in the +y-axis direction. 
     According to various embodiments, belts or other pulleys located to correspond to the belts and to be spaced apart from the first pulley  360  may be provided in an even number. The plurality of pulleys provided in the even number may be symmetrically arranged with respect to the center of the first section  131  or the center of the screen in the y-axis direction. According to various embodiments, the plurality of pulleys provided in the even number may be arranged at a constant interval in the y-axis direction. According to various embodiments, a distance by which a pulley at one side closest to the fifth support member  350  among the plurality of pulleys provided in the even number is spaced apart from the fifth support member  350  in the +y-axis direction may be substantially the same as a distance by which a pulley at the other side closest to the fourth support member  340  among the plurality of pulleys provided in the even number is spaced apart from the fourth support members  340  in the −y-axis direction. 
     According to an embodiment, one surface  310   a  of the first support member  310  may include a first recess  310   c  between the first pulley  360  and the second pulley  440 , a second recess  310   d  between the first pulley  360  and the third pulley  450 , or a third recess  310   e  between the first pulley  360  and the fourth pulley  460 . A portion (not illustrated) between one end  411  and the second pulley  440  in the first belt  410  may be disposed in the first recess  310   c . A portion of the second belt  420  may be disposed in the second recess  310   d  like the first belt  410 . A portion of the third belt  430  may be disposed in the third recess  320   e  like the first belt  410 . 
     According to an embodiment, on the printed circuit board  390 , a processor, a memory, and/or an interface may be mounted. The processor may include one or more of, for example, a central processing unit, an application processor, a graphics processor, an image signal processor, a sensor hub processor, or a communication processor. The memory may include, for example, a volatile memory or a nonvolatile memory. The interface may include, for example, a high-definition multimedia interface (HDMI), a universal serial bus (USB) interface, an SD card interface, and/or an audio interface. The interface may electrically or physically connect, for example, the electronic device  100  to an external electronic device and may include a USB connector, an SD card/an MMC connector, or an audio connector. The electronic device  100  may include various other elements disposed on the printed circuit board  390  or electrically connected to the printed circuit board  390 . For example, the electronic device  100  may include a battery (not illustrated) located between the first support member  310  and the second support member  320  or between the second support member  320  and the back cover  112 . A battery (not illustrated) is a device for supplying power to at least one component of the electronic device  100  and may include, for example, a non-rechargeable primary battery, a rechargeable secondary battery, or a fuel cell. The battery (not illustrated) may be integrally disposed inside the electronic device  100 , or may be detachably disposed on the electronic device  100 . According to an embodiment, the electronic device  100  may include an antenna (not illustrated) located between the first support member  310  and the second support member  320  or between the second support member  320  and the back cover  112 . The antenna (not illustrated) may include, for example, a near field communication (NFC) antenna, a wireless charging antenna, and/or a magnetic secure transmission (MST) antenna. The antenna (not illustrated) may perform short-range communication with, for example, an external electronic device, or may transmit/receive power required for charging to/from the external device in a wireless manner. In another embodiment, an antenna structure may be provided by a portion of the first side cover  113  and/or the second side cover  114  or a combination thereof. 
     According to an embodiment, the electronic device  100  may include a flexible printed circuit board (FPCB)  135  that electrically connects the flexible display  130  and the printed circuit board  390  to each other. For example, the flexible printed circuit board  135  may be electrically connected to the printed circuit board  390  through an opening (not illustrated) provided in the sliding plate  120  and an opening (not illustrated) provided in the first support member  310 . 
       FIG. 4  is a cross-sectional view of the electronic device  100  in the closed state taken along line A-A′ of  FIG. 1A  according to various embodiments.  FIG. 5  is a cross-sectional view of the electronic device  100  taken along line B-B′ of  FIG. 2A  in the open state according to various embodiments. 
     Referring to  FIGS. 4 and 5 , in an embodiment, the electronic device  100  may include a back cover  112 , a first support member  310 , a second support member  320 , a third support member  330 , and sliding plate  120 , a flexible display  130 , a support sheet  370 , a multi-bar structure  380 , a printed circuit board  390 , a first pulley  360 , a second pulley  440 , and/or a first belt  410 . Redundant descriptions of some of the reference numerals of  FIG. 4 or 5  may not be repeated here. 
     According to an embodiment, the sliding plate  120  may be disposed on the first support member  310  to be capable of sliding out. The flexible display  130  may include a first section  131  overlappingly coupled to the sliding plate  120 . The flexible display  130  may include a first bendable section  133  extending from the first section  131 , and the first bendable section  133  may be pulled out from the inner space of the electronic device  100  at the time of sliding out of the sliding plate  120 . The support sheet  370  may be disposed on the rear surface of the flexible display  130 . According to various embodiments, the support sheet  370  may be included in the flexible display  130 . The first pulley  360  may be located inside the electronic device  100  and may be connected to the first bendable section  133  of the flexible display  130 . The first belt  410  may interconnect the support sheet  370  and the sliding plate  120 . For example, one end  411  of the first belt  410  may be connected to the sliding plate  120  between the first support member  310  and the sliding plate  120 . The support sheet  370  may include a second section (not illustrated) that is disposed at least partially along the first section  131 , a second bendable section (not illustrated) that is disposed along the first bendable section  133 , or a third section (not illustrated) that is spaced apart from the second section with the second bendable section interposed therebetween and does not overlap the flexible display  130 . The other end  412  of the first belt  410  may be connected to the third section of the support sheet  370 . According to an embodiment, the first belt  410  may be connected to the sliding plate  120  through various methods such as bolting, welding, or hook jointing. According to various embodiments, a device capable of adjusting a connection position between the first belt  410  and the support sheet  370  may be implemented. The tension of the first belt  410  may vary depending on the connection position between the first belt  410  and the support sheet  370 . According to various embodiments, a device capable of adjusting a connection position between the first belt  410  and the sliding plate  120  may be implemented. The tension of the first belt  410  may vary depending on the connection position between the first belt  410  and the sliding plate  120 . The second pulley  440  may have a rotation shaft parallel to the first pulley  360  and may be disposed inside the electronic device  100  to be spaced apart from the first pulley  360  in the slide-out direction (e.g., the +x-axis direction). The second pulley  440  may be connected to the first belt  410 . The multi-bar structure  380  may extend from the sliding plate  120  to the space between the support sheet  370  and the first pulley  360 . The multi-bar structure  380  may contribute to enabling the first bendable section  133  to be moved while maintaining the form smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . In the closed state of  FIG. 4  or the open state of  FIG. 5 , a portion of the first bendable section  133  may form a first curved portion  130   b  of the screen, and the first curved portion  130   b  may be supported by the multi-bar structure  380  between the first pulley  360  and the first bendable section  133  to be smoothly connected to the first section without lifting. In the open state of  FIG. 5 , a portion of the first bendable section  133  may form a partial flat portion  130   d  of the screen, and the flat portion  130   d  may be supported by the multi-bar structure  380  between one surface  310   b  of the first support member  310  (e.g., the area around the first recess  310   c  in the one surface  310   a  in  FIG. 3 ) and the first bendable section  133  to be smoothly connected to the first section  131  without lifting. 
     According to an embodiment, when the sliding plate  120  is moved, the motion or force may be transferred via the flexible display  130 , the support sheet  370 , the multi-bar structure  380 , the first pulley  360 , the first belt  410 , and the second pulley  440 . For example, the force for moving the sliding plate  120  on the first support member  310  may cause the movement of the flexible display  130 , the movement of the first belt  410 , the rotation of the first pulley  360 , and the rotation of the second pulley  440 . 
     According to an embodiment, in the closed state of  FIG. 4  or the open state of  FIG. 5 , the tensile forces (the tensions of the belt) generated at opposite sides of the first belt  410  with respect to the second pulley  440  are substantially the same. The tensile force T 1  of the first belt  410  in the closed state of  FIG. 4  or the tensile force T 2  of the first belt  410  in the open state of  FIG. 5  may contribute to enabling the first bendable section  133  to form a screen smoothly connected to the first section  131  without lifting. 
     According to an embodiment, the first belt  410  may contribute to enabling the first bendable section  133  to be moved while maintaining the form smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . 
     For example, when the electronic device  100  is switched from the closed state of  FIG. 4  to the open state of  FIG. 5 , the sliding plate  120  may move on the first support member  310  in the +x-axis direction. With reference to the second pulley  440 , a relaxation-side tension T 3  may be generated at one side of the first belt  410  connected to the sliding plate  120 , and a tension-side tension (or tensile-side tension) T 4  may be generated at the other side of the first belt  410  connected to the support sheet  370 . According to an embodiment, the relaxation-side tension T 3  and the tension-side tension T 4  may be generated to minimize and/or reduce the load applied to the rotation shaft C 1  of the first pulley  360  and the rotation shaft C 2  of the second pulley  440  while making the first bendable section  133  movable while maintaining the shape smoothly connected to the first section  131  without lifting. 
     For example, when the electronic device  100  is switched from the open state of  FIG. 5  to the closed state of  FIG. 4 , the sliding plate  120  may move on the first support member  310  in the −x-axis direction. With reference to the second pulley  440 , a tension-side tension T 5  may be generated at one side of the first belt  410  connected to the sliding plate  120 , and a relaxation-side tension T 6  may be generated at the other side of the first belt  410  connected to the support sheet  370 . According to an embodiment, the tension-side tension T 5  and the relaxation-side tension T 6  may be generated to minimize and/or reduce the load applied to the rotation shaft C 1  of the first pulley  360  and the rotation shaft C 2  of the second pulley  440  while making the first bendable section  133  movable while maintaining the shape smoothly connected to the first section  131  without lifting. 
     According to an embodiment, the stress acting on the first belt  410  may include stress due to tension (tensile stress) or stress due to bending (bending stress). The tensile stress may be, for example, proportional to the tensile force acting on the first belt  410  and inversely proportional to the cross-sectional area of the first belt  410 . The bending stress may be proportional to, for example, the vertical elastic coefficient (the degree of resistance to tension or compression) of the first belt  410  and/or the thickness of the first belt  410  and may be inversely proportional to the diameter of the second pulley  440 . In order to prevent and/or reduce breakage of the first belt  410  during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 , the shape or material of the first belt  410  may be selected in consideration of such tensile stress or bending stress. According to an embodiment, the first belt  410  may include stainless steel and may be implemented in the form of a thin belt. 
     According to various embodiments, the second belt  420  or the third belt  430  of  FIG. 3  may be implemented substantially the same as the first belt  410 . The third pulley  450  or the fourth pulley  460  of  FIG. 3  may be implemented substantially the same as the second pulley  420 . The interactive operation between the second belt  420  and the third pulley  450  and the interactive operation between the third belt  430  and the fourth pulley  460  may be made to be substantially the same as the interactive operation between the first belt  410  and the second pulley  440 . 
     According to various embodiments (not illustrated), a first curved member including a first curved portion with which the multi-bar structure  380  comes into contact may be disposed in place of the first pulley  360 . For example, during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 , the multi-bar structure  380  may be slid relative to the first curved portion. According to various embodiments, in order to reduce the frictional force between the first curved portion and the multi-bar structure  380 , the surface of the first curved portion or the surface of the multi-bar structure  380  may be surface-treated. According to various embodiments, the first curved member may be connected to the support structure  300  of  FIG. 3 . According to various embodiments, the first pulley  360  may include a first curved member implemented to be rotatable based on friction with the multi-bar structure  380 . According to various embodiments (not illustrated), a rail portion (not illustrated) for guiding the movement of the multi-bar structure  380  may be implemented by replacing the first curved member or by being formed along the curved portion of the first curved member. The rail portion may be formed in, for example, the housing  110  of  FIG. 1A  or the support member structure  300  of  FIG. 3 . According to an embodiment, the fourth support member  340  may include a first rail portion for guiding the movement of the multi-bar structure  380  by inserting one side portion of the multi-bar structure  380  into the first rail portion. The fifth support member  350  may include a second rail portion for guiding the movement of the multi-bar structure  380  by inserting the other side portion of the multi-bar structure  380  into the second rail portion. 
     According to various embodiments (not illustrated), a second curved member including a second curved portion with which the first belt  410  comes into contact may be disposed in place of the second pulley  440 . For example, during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 , the first belt  410  may be slid relative to the second curved portion. According to various embodiments, in order to reduce the frictional force between the second curved portion and the first belt  380 , the surface of the second curved portion or the surface of the multi-bar structure  380  may be surface-treated. According to various embodiments, the second curved member may be connected to the support structure  300  of  FIG. 3 . According to various embodiments, the second pulley  440  may include the second curved member implemented to be rotatable based on friction with the first belt  440 . 
     According to various embodiments, a third curved member with which the second belt  420  comes into contact may be disposed in place of the third pulley  450  of  FIG. 3 . The third curved member may be connected to the support structure  300  of  FIG. 3 . According to various embodiments, the third pulley  440  may include the third curved member implemented to be rotatable based on friction with the second belt  450 . 
     According to various embodiments, a fourth curved member with which the third belt  430  comes into contact may be disposed in place of the fourth pulley  460  of  FIG. 4 . The fourth curved member may be connected to the support structure  300  of  FIG. 4 . According to various embodiments, the fourth pulley  460  may include the fourth curved member implemented to be rotatable based on friction with the third belt  460 . 
       FIG. 6  is an exploded perspective view of a display assembly  600  according to various embodiments.  FIG. 7A  is a diagram illustrating the front surface of the display assembly  600  of  FIG. 6  when the display assembly  600  is in the unfolded state according to various embodiments.  FIG. 7B  is a diagram illustrating the rear surface of the display assembly  600  when the display assembly  600  of  FIG. 6  is in the unfolded state according to various embodiments. 
     Referring to  FIG. 6 , in an embodiment, the display assembly  600  may include a flexible display  130 , a support sheet  370  disposed on the flexible display  130 , and/or a flexible printed circuit board  135  electrically interconnecting the flexible display  130  and the printed circuit board  390  of  FIG. 3 . 
     According to an embodiment, the flexible display  130  may be implemented based on a substrate (e.g., a plastic substrate)  610  formed of a flexible material such as polyimide. Various layers such as a light-emitting layer and an optical layer may be disposed on the substrate  610  through a series of processes such as deposition, patterning, and etching. The substrate  610  may be referred to as a “backplane” or a “backplane substrate”. A portion  620  of the substrate  610  may extend to the outside of the screen and may be electrically connected to the flexible printed circuit board  135 . For example, the flexible printed circuit board  135  may be electrically connected to an extension  620  of the substrate  610  based on anisotropic conductive film (ACF) bonding. The flexible printed circuit board  135  may be electrically connected to the extension  620  of the substrate  610  through various other methods (e.g., connection between connectors). One end (not illustrated) of the flexible printed circuit board  135  may be electrically connected to the extension  620  of the substrate  610 , and the other end (not illustrated) of the flexible printed circuit board  135  may be electrically connected to the printed circuit board  390  illustrated in  FIG. 3, 4 or 5 . The flexible printed circuit board  135  may include a connector  135   a  for electrically connecting the flexible printed circuit board  135  to the printed circuit board  390 . 
     According to an embodiment, a display drive circuit (e.g., a display drive integrated circuit (DDI))  135   b  electrically connected to the light-emitting layer may be disposed on the flexible printed circuit board  135 . A processor (e.g., an application processor (AP)) may be disposed on the printed circuit board  390  of  FIG. 3, 4 , or  5 , and a signal commanded by the processor may be transmitted to the display drive circuit  135   b  via the flexible printed circuit board  135 . 
     According to an embodiment, the flexible display  130  may be based on OLEDs, and may include an encapsulation layer disposed between the light-emitting layer and the optical layer (e.g., a circular polarization layer). The encapsulation layer may seal the light-emitting layer such that oxygen and/or moisture do not penetrate into the OLEDs. The encapsulation layer may be implemented as, for example, thin-film encapsulation (TFE). According to various embodiments, the flexible display  130  may include a conductive pattern such as a metal mesh (e.g., an aluminum metal mesh) as a touch-sensitive circuit disposed on the encapsulation layer between the encapsulation layer and the optical layer. For example, in response to the bending of the flexible display  130 , the metal mesh may have greater durability than a transparent conductive layer made of ITO. 
     According to an embodiment, the flexible display  130  may include a first section  131  and a first bendable section  133  extending from the first section  131 . The support sheet  370  may include a second section  371 , a third section  372 , and/or a second bendable section  373 . The second section  371  may be at least partially disposed along the first section  131 . The second bendable section  373  may be at least partially disposed along the first bendable section  133 . The third section  372  may not overlap the flexible display  130  by being spaced apart from the second section  371  with the second bendable section  373  interposed therebetween. 
     According to an embodiment, the display assembly  600  may include a first fastening part  710 , a second fastening part  720 , and/or a third fastening part  730  disposed in the third section  372 . The first fastening part  710  may be connected to the first belt  410  of  FIG. 3 . The second fastening part  720  may be connected to the second belt  420  of  FIG. 3 , and may be located between the first fastening part  710  and the third fastening part  730 . The third fastening part  730  may be connected to the third belt  430  of  FIG. 3 . Referring to  FIG. 7B , the support sheet  370  may include a first edge  370   a , a second edge  370   b , a third edge  370   c , and/or a fourth edge  370   d . The second edge  370   b  may extend opposite to the first edge  370   a  and may be substantially parallel to the first edge  370   a . The third edge  370   c  may interconnect one end of the first edge  370   a  and one end of the second edge  370   b . The fourth edge  370   d  may interconnect the other end of the first edge  370   a  and the other end of the second edge  370   b , and may be substantially parallel to the third edge  370   c . The first fastening part  710 , the second fastening part  720 , and the third fastening part  730  may be located adjacent to the second edge  370   b . According to an embodiment, the distance between the first fastening part  710  and the second fastening part  720  may be substantially the same as the distance between the second fastening part  720  and the third fastening part  730 . 
     According to various embodiments, the connection position between the support sheet  370  and the first belt  410  of  FIG. 3  is adjustable. The connection position between the support sheet  370  and the second belt  420  of  FIG. 3  is adjustable. The connection position between the support sheet  370  and the third belt  430  of  FIG. 3  is adjustable. The connection position between the support sheet  370  and a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) is adjustable such that the tension applied to the support sheet  370  is within a threshold range. When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the first bendable section  133  can be maintained in a shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 1A  or the open state of  FIG. 2A . When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the first bendable section  133  can be moved while maintaining the shape smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the slide operation can be smoothly performed during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . 
     For example, due to the connection position between the support sheet  370  and a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ), the tension applied to the flexible display  130  and the attached support sheet  370  may be lower than the threshold range. In this case, due to the elasticity of the flexible display  130  and/or the elasticity of the support sheet  370 , the first bendable section  133  may lift or may not be smoothly connected to the first section  131 . 
     As another example, due to the connection position between the support sheet  370  and a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ), the tension applied to the flexible display  130  and the attached support sheet  370  may be higher than the threshold range. In this case, the first bendable section  133  may be smoothly connected to the first section  131  without lifting, but it may be difficult to smoothly perform the slide operation during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . When the tension applied to the flexible display  130  and the attached support sheet  370  is higher than the threshold range, the load applied to the rotation shaft of a pulley (e.g., the first pulley  360 , the second pulley  440 , the third pulley  450 , or the sixth pulley  460 ) may exceed a threshold value and may increase the resistance to rotation of the pulley, thereby making it difficult to perform a smooth and gentle slide operation. 
     According to an embodiment, the second bendable section  373  may include a lattice structure  702  including a plurality of openings (or a plurality of slits)  701  (see  FIG. 7B ). For example, the plurality of openings  701  may be provided periodically, may have substantially the same shape, and may be repeatedly arranged at regular intervals. The second bendable section  373  may be more flexible than the second section  371  or the third section  372  due to the lattice structure  702 . The lattice structure  702  may contribute to the flexibility of the second bendable section  373 . The lattice structure  702  of the second bendable section  373  is not limited to the embodiment of  FIG. 7B  and may be implemented in various other forms. According to various embodiments, the support sheet  470  may include a recess pattern (not illustrated) including a plurality of recesses in place of the lattice structure  702 , wherein the recess pattern may contribute to flexibility of the flexible display  130 . According to various embodiments (not illustrated), the lattice structure  702  or the recess pattern may further extend to at least a portion of the second section  371 . 
     According to an embodiment, the support sheet  370  may make elements located inside the electronic device  100  substantially invisible through the flexible display  130  of  FIG. 4  or  FIG. 5 . For example, the lattice structure  702  of the second bendable section  373  includes a plurality of openings  701 , but is capable of transmitting light at a level at which the multi-bar structure  380  is substantially invisible through the flexible display  130 . According to various embodiments, the lattice structure  702  of the second bendable structure  373  includes a plurality of openings  701 , but is also capable of preventing and/or reducing a phenomenon in which the plurality of bars of the multi-bar structure  380  are seen as protruding through the flexible display  130 . 
     According to an embodiment, the display assembly  600  may include a support  740  (see  FIG. 7B ) connected to the first fastening part  710 , the second fastening part  720 , and the third fastening part  730 . The support  740  may be disposed adjacent to the second edge  370   b  of the support sheet  370  and may extend along the second edge  370   b . According to an embodiment, the support  740  may be a reinforcing substrate having rigidity, and the tension of the first belt  410  (see  FIG. 3 ) connected to the first fastening part  710  may be distributed without being concentrated in a local area of the support sheet  370  due to the support  740  (see reference numeral “ 761 ”). The tension of the second belt  420  (see  FIG. 3 ) connected to the second fastening part  720  may be distributed without being concentrated in a local area of the support sheet  370  due to the support  740  (see reference numeral “ 762 ”). The tension of the third belt  430  (see  FIG. 3 ) connected to the third fastening part  730  may be distributed without being concentrated in a local area of the support sheet  370  due to the support  740  (see reference numeral “ 763 ”). 
     According to various embodiments, the support  740  may be integrated with the first fastening part  710 , the second fastening part  720 , and the third fastening part  730 , and the support and the fastening parts may include the same material as each other. According to various embodiments, the support  740  may be integrated with the support sheet  370  and the support and the support sheet may include the same material. According to various embodiments, the support  740  may be implemented as a portion of the support sheet  370 . For example, the support  740  may be implemented in a structure (e.g., a hemming structure) in which a portion of the support sheet  370  is folded. 
     Referring to  FIGS. 6 and 7A , in an embodiment, the flexible display  130  may include a bezel area  137  provided adjacent to and along the edge  136  of the flexible display  130 . The bezel area  137  may not include pixels implemented with light emitting elements such as OLEDs, and may include, for example, black or a black-based material having a relatively low light transmittance. The bezel area  137  may be formed through various methods such as coating or printing a light shielding material on the transparent cover forming the front surface of the flexible display  130 . Referring to the open state of  FIG. 2A , the bezel area  137  may be placed between a screen and a mechanical structure in a slide-out state around the screen to contribute to the aesthetics of the electronic device  100 . In an embodiment, referring to the closed state of  FIG. 1A , a bezel area may not be present at the opening (not illustrated) side for introducing or pulling-out of the first bendable section  133 , but in various embodiments, a bezel area may be implemented at the boundary between the first section  131  and the first bendable section  133  in a software manner. The software-type bezel area may be implemented by, for example, not activating a partial area of the flexible display  130  or using an image displayed on a partial area of the flexible display  130 . According to various embodiments, the flexible display  130  may be implemented such that the bezel area  137  is minimized or there is substantially no bezel area  137 . In this case, the mechanical structure around the screen may be implemented in a slim form factor that can slide out without degrading aesthetics, or in some cases, the bezel area may be implemented in a software manner for the closed state of  FIG. 1A  or the open state of  FIG. 2A . According to various embodiments, a signal line of the flexible display  130  and/or a touch screen panel (TSP) electrode may be disposed in the bezel area  137 . 
       FIG. 8  is a diagram illustrating the rear surface of the display assembly  600  of  FIG. 6  when the display assembly  600  is in the unfolded state according to various embodiments. 
     Referring to  FIG. 8 , in an embodiment, the display assembly  600  may include a first reinforcing sheet  810 , a second reinforcing sheet  820 , and/or a third reinforcing sheet  830  attached to the support sheet  370  and extending from the second section  371  to the third section  372  across the second bendable section  373 . A redundant description of some of the reference numerals in  FIG. 8  may not be repeated here. When a tensile force is applied to the support sheet  370 , the second section  371  or the third section  373  is not stretched, but the second bendable section  373  may be stretched due to the lattice structure  702  of  FIG. 7B . According to an embodiment, the first reinforcing sheet  810 , the second reinforcing sheet  820 , and the third reinforcing sheet  830  may prevent and/or reduce the second bendable section  373  from stretching. The first reinforcing sheet  810 , the second reinforcing sheet  820 , and the third reinforcing sheet  830  may prevent and/or reduce the second bendable section  373  from stretching due to the lattice structure  702  of  FIG. 7B  so that the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430  are not reduced. For this reason, the first bendable section  133  of  FIG. 4 or 5  may be maintained in a shape smoothly connected to the first section  131  without lifting. 
     According to an embodiment, the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may be bonded to the second section  371  and/or the third section  372  in at least a portion through a method such as welding. According to various embodiments, the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may be additionally bonded to the second bendable section  373 . According to various embodiments, in order to reduce a degradation in flexibility of the second bendable section  373 , the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may not be bonded to the second bendable section  373  or may be bonded in a manner of minimizing and/or reducing the bonding area. 
     The first reinforcing sheet  810  may extend, for example, from the second section  371  to the third section  372  across the second bendable section  373  between the first fastening part  710  and the second section  371 . According to various embodiments, the first reinforcing sheet  810  may be connected to the support  740 . The first reinforcing sheet  810  may prevent and/or reduce the stretching of the second bendable section  373  by providing a bearing force (e.g., tensile stress) resisting the tension of the first belt  410  (see  FIG. 3 ) connected to the first fastening part  710 , to the second bendable section  373 . 
     The second reinforcing sheet  820  may extend, for example, from the second section  371  to the third section  372  across the second bendable section  373  between the second fastening part  720  and the second section  371 . According to various embodiments, the second reinforcing sheet  820  may be connected to the support  740 . The second reinforcing sheet  820  may prevent and/or reduce the stretching of the second bendable section  373  by providing a bearing force (e.g., tensile stress) resisting the tension of the second belt  420  (see  FIG. 3 ) connected to the second fastening part  720 , to the second bendable section  373 . 
     The third reinforcing sheet  830  may extend, for example, from the second section  371  to the third section  372  across the second bendable section  373  between the third fastening part  730  and the second section  371 . According to various embodiments, the third reinforcing sheet  830  may be connected to the support  740 . The third reinforcing sheet  830  may prevent and/or reduce the stretching of the second bendable section  373  by providing a bearing force (e.g., tensile stress) resisting the tension of the third belt  430  (see  FIG. 3 ) connected to the third fastening part  730 , to the second bendable section  373 . 
     According to an embodiment, the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may be implemented to support smooth bending of the first bendable section  133  (see  FIG. 4 or 5 ) of the flexible display  130  and smooth bending of the second bendable section  373  of the support sheet  370  based on the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 , as well as to have durability to resist the tensions. For example, the first reinforcing sheet  810 , the second reinforcing sheet  820 , and the third reinforcing sheet  830  may not substantially stretch due to the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 . 
     According to an embodiment, when a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) interconnecting the sliding plate  120  of  FIG. 3  coupled to the second section  371  of the support sheet  370  and a fastening part (e.g., the first fastening part  710 , the second fastening part  720 , or the third fastening part  730 ) of the support sheet  370  provides a tension in a threshold range, the first reinforcing sheet  810 , the second reinforcing sheet  820  and/or the third reinforcing sheet  830  may contribute to preventing and/or reducing the tension from being lost in the second bendable section  373  between the second section  371  and the third section  372 . The tension in the threshold range is capable of making the first bendable section  133  maintain a shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 4  or the open state of  FIG. 5 . The tension in the threshold range is capable of making the first bendable section  133  move while maintaining a shape smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . The tension in the threshold range is capable of contributing to a smooth and gentle slide motion during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . 
     According to an embodiment, the width (W 1 , W 2 , or W 3 ) and/or the thickness (not illustrated) of each reinforcing sheet (e.g., the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830 ) may be determined such that the elasticity of the reinforcing sheet does not interfere with making the first bendable section  133  ( FIG. 4 or 5 ) smoothly connected to the first section  131  ( FIG. 4 or 5 ) without lifting. According to an embodiment, the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may include stainless steel and may have a thickness of about 0.01 mm to about 0.2 mm (not illustrated). For example, the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may have a thickness of about 0.05 mm or about 0.1 mm. The first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  may be implemented with various other materials (e.g., engineering plastics) or in various other forms. 
       FIG. 9  is a diagram illustrating the rear surface of the display assembly  600  of  FIG. 6  when the display assembly  600  is in the unfolded state according to various embodiments. 
     A redundant description of some of the reference numerals in  FIG. 9  may not be repeated here. Referring to  FIG. 9 , in an embodiment, in place of the first reinforcing sheet  810  of  FIG. 8 , the support sheet  370  may include a first area  910  extending from the second section  371  to the third section  372  across the second bendable section  373 . In place of the second reinforcing sheet  820  of  FIG. 8 , the support sheet  370  may include a second area  920  extending from the second section  371  to the third section  372  across the second bendable section  373 . In place of the third reinforcing sheet  830  of  FIG. 8 , the support sheet  370  may include a third area  930  extending from the second section  371  to the third section  372  across the second bendable section  373 . The first area  910 , the second area  920 , and the third area  930  may not include an opening or a lattice structure. When the tension of the first belt  410  (see  FIG. 3 ) connected to the first fastening part  710  acts on the support sheet  370 , the first area  910  may prevent and/or reduce the stretching of the second bendable section  373 . When the tension of the second belt  420  (see  FIG. 3 ) connected to the second fastening part  720  acts on the support sheet  370 , the second area  920  may prevent and/or reduce the stretching of the second bendable section  373 . When the tension of the third belt  430  (see  FIG. 3 ) connected to the third fastening part  730  acts on the support sheet  370 , the third area  930  may prevent and/or reduce the stretching of the second bendable section  373 . The first area  910 , the second area  920 , and the third area  930  may prevent and/or reduce the stretching of the second bendable section  373  so that the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430  are not reduced. For this reason, the first bendable section  133  of  FIG. 4 or 5  may be maintained in a shape smoothly connected to the first section  131  without lifting. The first area  910 , the second area  920 , and the third area  930  may prevent and/or reduce the stretching of the second bendable section  373  by providing a bearing strength (e.g., tensile stress) resisting the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 , to the second bendable section  373 . 
     According to an embodiment, the first area  910 , the second area  920 , or the third area  930  may be implemented to support smooth bending of the first bendable section  133  (see  FIG. 4 or 5 ) of the flexible display  130  and smooth bending of the second bendable section  373  of the support sheet  370  based on the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 , as well as to have durability to resist the tensions. For example, the first area  910 , the second area  920 , and the area  930  may not substantially stretch due to the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 . For example, the width (W 4 , W 5 , or W 6 ) and/or the thickness (not illustrated) of the first area  910 , the second area  920 , or the third area  930  may be determined such that the elasticity of the areas does not interfere with making the first bendable section  133  ( FIG. 4 or 5 ) smoothly connected to the first section  131  ( FIG. 4 or 5 ) without lifting. 
     According to an embodiment, when a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) interconnecting the sliding plate  120  of  FIG. 3  coupled to the second section  371  of the support sheet  370  and a fastening part (e.g., the first fastening part  710 , the second fastening part  720 , or the third fastening part  730 ) of the support sheet  370  provides a tension in a threshold range, the first area  910 , the second area  920 , and/or the third are  930  may contribute to preventing and/or reducing the tension from being lost in the second bendable section  373  between the second section  371  and the third section  372 . The tension in the threshold range is capable of making the first bendable section  133  maintain a shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 4  or the open state of  FIG. 5 . The tension in the threshold range is capable of making the first bendable section  133  move while maintaining a shape smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . The tension in the threshold range is capable of contributing to a smooth and gentle slide motion during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . 
       FIG. 10  is a diagram illustrating the rear surface of the display assembly  600  of  FIG. 6  when the display assembly  600  is in the unfolded state according to various embodiments. 
     A redundant description of some of the reference numerals in  FIG. 10  may not be repeated here. Referring to  FIG. 10 , in an embodiment, in place of the first reinforcing sheet  810  of  FIG. 8 , the support sheet  370  may be implemented to have a first lattice structure  1010  in which some openings between the first fastening part  710  and the second section  371  are omitted. In place of the second reinforcing sheet  820  of  FIG. 8 , the support sheet  370  may be implemented to have a second lattice structure  1020  in which some openings between the second fastening part  720  and the second section  371  are omitted. In place of the third reinforcing sheet  830  of  FIG. 8 , the support sheet  370  may be implemented to have a third lattice structure  1030  in which some openings between the third fastening part  730  and the second section  371  are omitted. When the tension of the first belt  410  (see  FIG. 3 ) connected to the first fastening part  710  acts on the support sheet  370 , the first lattice structure  1010  may reduce the stretching of the second bendable section  373 . When the tension of the second belt  420  (see  FIG. 3 ) connected to the second fastening part  720  acts on the support sheet  370 , the second lattice structure  1020  may reduce the stretching of the second bendable section  373 . When the tension of the third belt  430  (see  FIG. 3 ) connected to the third fastening part  730  acts on the support sheet  370 , the third lattice structure  1030  may reduce the stretching of the second bendable section  373 . The first lattice structure  1010 , the second lattice structure  1020 , and the third lattice structure  1030  may reduce the stretching of the second bendable section  373  so that the reduction of the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430  can be suppressed. For this reason, the first bendable section  133  of  FIG. 4 or 5  may be maintained in a shape smoothly connected to the first section  131  without lifting. The first area  910 , the second area  920 , and the third area  930  may provide a bearing strength (e.g., tensile stress) resisting the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 , to the second bendable section  373 . 
     According to an embodiment, the first lattice structure  1010 , the second lattice structure  1020 , or the third lattice structure  1030  may support smooth bending of the first bendable section  133  (see  FIG. 4 or 5 ) of the flexible display  130  and smooth bending of the second bendable section  373  of the support sheet  370  based on the tension of the first belt  410 , the tension of the second belt  420 , and the tension of the third belt  430 , as well as may provide a bearing force resisting the tensions. 
     According to an embodiment, when a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) interconnecting the sliding plate  120  of  FIG. 3  coupled to the second section  371  of the support sheet  370  and a fastening part (e.g., the first fastening part  710 , the second fastening part  720 , or the third fastening part  730 ) of the support sheet  370  provides a tension in a threshold range, the first lattice structure  1010 , the second lattice structure  1020  and/or the third lattice structure  1030  may contribute to preventing and/or reducing the tension from being lost in the second bendable section  373  between the second section  371  and the third section  372 . The tension in the threshold range is capable of making the first bendable section  133  maintain a shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 4  or the open state of  FIG. 5 . The tension in the threshold range is capable of making the first bendable section  133  move while maintaining a shape smoothly connected to the first section  131  without lifting during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . The tension in the threshold range is capable of contributing to a smooth and gentle slide motion during the switching between the closed state of  FIG. 4  and the open state of  FIG. 5 . 
       FIG. 11  is a perspective view illustrating a portion of an electronic device  100  according to various embodiments. 
     Referring to  FIG. 11 , in an embodiment, the electronic device  100  may include a first support member  310 , a third support member  330 , a flexible display  130 , a support sheet  370 , and a first fastening part  710 , a second fastening part  720 , a third fastening part  730 , a support  740 , a first belt  410 , a second belt  420 , a third belt  430 , a second pulley  440 , a third pulley  450 , a fourth pulley  460 , a camera device  154 , and/or a flash  155 . A redundant description of some of the reference numerals in  FIG. 11  may not be repeated here. 
     According to an embodiment, the first support member  310  may include a first opening  1101 , and the second pulley  440  may be disposed in the first opening  1101 . The first belt  410  may be disposed through the first opening  1101 , wherein one end (not illustrated) of the first belt  410  may be connected to the sliding plate  120  of  FIG. 3 , and the other end  412  may be connected to the first fastening part  710 . The second pulley  440  connected to the first belt  410  may guide the movement and the direction of movement of the first belt  410 . 
     According to an embodiment, the first support member  310  may include a second opening  1102 , and the third pulley  450  may be disposed in the second opening  1102 . The second belt  420  may be disposed through the second opening  1102 , wherein one end (not illustrated) of the second belt  420  may be connected to the sliding plate  120  of  FIG. 3 , and the other end  422  may be connected to the second fastening part  720 . The third pulley  450  connected to the second belt  420  may guide the movement and the direction of movement of the second belt  420 . 
     According to an embodiment, the first support member  310  may include a third opening  1103 , and the fourth pulley  460  may be disposed in the third opening  1103 . The third belt  430  may be disposed through the third opening  1103 , wherein one end (not illustrated) of the third belt  430  may be connected to the sliding plate  120  of  FIG. 3 , and the other end  432  may be connected to the third fastening part  730 . The fourth pulley  460  connected to the third belt  430  may guide the movement and the direction of movement of the third belt  430 . 
     According to an embodiment, a connection position between the first fastening part  710  and the first belt  410 , a connection position between the second fastening part  720  and the second belt  420 , and/or a connection position between the third fastening part  730  and the third belt  430  may be adjustable. The tension of the first belt  410  may vary depending on the connection position between the first fastening part  710  and the first belt  410 . The tension of the second belt  420  may vary depending on the connection position between the second fastening part  720  and the second belt  420 . The tension of the third belt  430  may vary depending on the connection position between the third fastening part  730  and the third belt  430 . 
       FIG. 12  is a diagram illustrating the first belt  410  of  FIG. 11  according to various embodiments. 
     Referring to  FIG. 12 , in an embodiment, one end  411  of the first belt  410  may be connected to the sliding plate  120  of  FIG. 3  and may include, for example, a through hole  1210  used for fastening with the sliding plate  120 . The other end  412  of the first belt  410  may be connected to the first fastening part  710  of  FIG. 11 , and may include, for example, a plurality of fastening holes  1220  used for fastening with the first fastening part  710 . The plurality of fastening holes  1220  may be arranged in the longitudinal direction of the first belt  410 . 
     The first belt  410  may be implemented, for example, in the form of a thin belt. The second belt  420  or the third belt  430  of  FIG. 11  may be implemented to be substantially the same as or similar to the first belt  410 . According to various embodiments (not illustrated), the first belt  410 , the second belt  420 , or the third belt  430  may be implemented as a wire type or a chain type. The first belt  410 , the second belt  420 , or the third belt  430  may be implemented in various other forms. 
       FIG. 13A  is a diagram illustrating the first fastening part  710  of  FIG. 11  according to various embodiments.  FIG. 13B  is a cross-sectional view of the first fastening part  710  of  FIG. 13A  taken along line C-C′ according to various embodiments.  FIG. 13C  is a perspective view illustrating a state in which the first fastening part  710  and the first belt  410  are connected to each other according to various embodiments. 
     Referring to  FIGS. 13A, 13B, and 13C , in an embodiment, the first fastening part  710  may be connected to the support  740 . The first fastening part  710  may include a structure  1310  including a through portion  1311  into which the first belt  410  of  FIG. 12  can be inserted. The structure  1310  may include a hook  1320 . After inserting the first belt  410  into the through portion  1311  as indicated by reference numeral “ 1301 ”, a connection between the first fastening part  710  and the first belt  410  and a connection position thereof may be determined through a method of fastening the hook  1320  to one of the plurality of fastening holes  1220  (see  FIG. 12 ). The tension of the first belt  410  may vary depending on the connection position between the first fastening part  710  and the first belt  410 . The connection method between the second fastening part  720  and the second belt  420  of  FIG. 11  may be substantially the same as the connection method between the first fastening part  710  and the first belt  410 . The connection method between the third fastening part  730  and the third belt  430  of  FIG. 11  may be substantially the same as the connection method between the first fastening part  710  and the first belt  410 . 
     Referring to  FIGS. 3 and 11 , the connection position between the first belt  410  and the first fastening part  710 , the connection position between the second belt  420  and the second fastening part  720 , and the connection position between the third belt  430  and the third fastening part  730  may be adjusted such that the tension applied to the support sheet  370  is within a threshold range. When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the first bendable section  133  can be maintained in a shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 1A  or the open state of  FIG. 2A . When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the first bendable section  133  can be moved while maintaining the shape smoothly connected to the first section  131  without lifting in the closed state of  FIG. 1A  and the open state of  FIG. 2A . When the tension applied to the flexible display  130  and the attached support sheet  370  is in the threshold range, the slide operation can be smoothly performed during the switching between the closed state of  FIG. 1A  and the open state of  FIG. 2A . A device for adjusting the tension of a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) (hereinafter, referred to as a “tension adjusting device”) may be implemented in various other methods. According to various embodiments, the number of belts or other pulleys positioned to be spaced apart from the first pulley  360  to correspond to the belts may vary without being limited to the embodiment of  FIG. 3 or 11 , and the number of tension adjusting devices provided to correspond thereto may also vary. For example, the pulleys corresponding to the belts may be provided in an even number, and the tension adjusting devices corresponding to the pulleys may also be implemented in an even number. A state in which the tension of at least one of the first belt  410 , the second belt  420 , and the third belt  430  is out of a threshold range, and thus the first bendable section  133  lifts or is not smoothly connected to the first section  131  or a state in which the sliding operation is not smooth may occur. In this case, a measure of adjusting the tension of the first belt  410 , the second belt  420 , or the third belt  430  using a tension adjusting device may be executed. According to an embodiment, it may be identified whether or not tension adjustment of the first belt  410  is required based on a position at which the hook  1320  is fastened among the plurality of fastening holes  1220  (see  FIG. 12 ). It may also be identified whether or not tension adjustment is required for the second belt  420  or the third belt  430  in the same manner. According to various embodiments (not illustrated), a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ) may include a gradation, wherein it may be confirmed whether or not tension adjustment is required by identifying the position at which the belt is fastened to the support sheet  370  or the sliding plate  120  of  FIG. 3  through the gradation. According to various embodiments (not illustrated), the electronic device  100  of  FIG. 1A  may include a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430 ), a support sheet  470 , or at least one sensor (e.g., a tension sensor or a strain gauge) for detecting tension in the first bendable section  133  of the flexible display  130 . The electronic device  100  may detect the tension of the first belt  410 , the second belt  420 , or the third belt  430  based on a sensor value acquired through the at least one sensor. The electronic device  100  may be implemented to identify a belt requiring tension adjustment and to output an identified result via the flexible display  130  or other various output devices (e.g., a speaker). 
       FIG. 14  is a perspective view illustrating a tension adjusting device  1400  for the first belt  410  according to various embodiments. 
     Referring to  FIG. 14 , in an embodiment, the tension adjusting device  1400  may further include a first moving member  1411 , a second moving member  1412 , a first screw  1421 , and/or a second screw  1422 . A redundant description of some of the reference numerals in  FIG. 14  may not be repeated here. The first moving member  1411  and the second moving member  1412  may be located on the first support member  310  to be spaced apart from each other with the second pulley  440  interposed therebetween. The first moving member  1411  may be connected to one rotation shaft (not illustrated) of the second pulley  440 , and the second moving member  1412  may be connected to the other rotation shaft of the second pulley  440  (not illustrated). The first support member  310  may include a first opening  1431  and a second opening  1432  provided in the fourth side surface  310   d . The first screw  1421  may be connected to the first moving member  1411  through the first opening  1431 . The second screw  1422  may be connected to the second moving member  1412  through the second opening  1432 . When the first screw  1421  is rotated, the moving direction and the moving distance of the first moving member  1411  may be adjusted based on the rotating direction and the number of revolutions of the first screw  1421 . When the second screw  1422  is rotated, the moving direction and the moving distance of the second moving member  1412  may be adjusted based on the rotating direction and the number of revolutions of the second screw  1422 . The tension of the first belt  410  connected to the second pulley  440  may be adjusted depending on the moving direction  1411   a  of the first moving member  1411  connected to the second pulley  440  and/or the moving direction  1412   a  of the second moving member  1412 . According to various embodiments, the rotation shafts of the second pulley  440  may be tilted depending on the position of the first moving member  1411  and the position of the second moving member  1412 . 
     According to various embodiments, the tension adjusting device for the second belt  420  or the third belt  430  of  FIG. 11  may be implemented to be substantially the same as the tension adjusting device  1400  according to the embodiment of  FIG. 14 . 
       FIG. 15A  is a diagram illustrating a portion of an electronic device  1500  including a tension adjusting device according to various embodiments.  FIG. 15B  is a partial perspective view illustrating the portion indicated by reference numeral “D” of the electronic device  1500  of  FIG. 15A  according to various embodiments.  FIG. 15C  is a diagram illustrating a belt  1530  included in the electronic device  1500  of  FIG. 15A  according to various embodiments. 
     The electronic device  1500  of  FIG. 15A  may be implemented to include at least one of the components of the electronic device  100  of  FIG. 3 , or may be implemented by replacing at least one of the components of the electronic device  100  of  FIG. 3  with another component. 
     Referring to  FIG. 15A , in an embodiment, the electronic device  1500  may include a sliding plate  1510 , a flexible display  1520 , a support sheet  1530 , a first belt  1541 , a second belt  1542 , a first tension adjusting device  1550  and/or a second tension adjusting device  1560 . The sliding plate  1510  may include, for example, the sliding plate  120  of  FIG. 3 . The sliding plate  1510  may slide out in the +x-axis direction. The flexible display  1520  may include, for example, the flexible display  130  of  FIG. 3 . The support sheet  1530  may include, for example, the support sheet  370  of  FIG. 3 . 
     Referring to  FIGS. 15A and 15B , in an embodiment, the first tension adjusting device  1550  may include a first curved member  1551 , a first moving plate  1552 , a first holder  1553 , or a first gear  1554 . The first holder  1553  may be coupled to the support sheet  1530  (e.g., the third section  372  of the support sheet  370  in  FIG. 3 ). The first moving plate  1552  may be disposed in the first holder  1553  to be movable in the first holder  1553 . The first holder  1553  may include an opening (not illustrated), and the first moving plate  1552  may be inserted into a groove  1553   b  provided in the inner surface of the opening in a sliding manner, so that the first holder  1553  is movable on the first moving plate  1552 . Referring to  FIGS. 15B and 15C , in an embodiment, the first belt  1541  may include one end  1541   a  connected to the first moving plate  1552  and the other end  1541   b  connected to the sliding plate  1510 . The first gear  1554  may include first teeth  1554   b  having the same interval on the disk-shaped rotating body. The rotation shaft  1554   a  of the first gear  1554  may be rotatably connected to the moving plate  1552 . One end  1541   a  of the first belt  1541  may be disposed between the moving plate  1552  and the first gear  1554 , and a through hole  1541   c  provided in the one end  1541   a  of the first belt  1541  may be penetrated by the rotation shaft  1541   a  of the first gear  1541 . The first holder  1553  may include second teeth  1553   a  provided on a straight line of one side edge of the opening. When the first gear  1541  is rotated, due to the engagement between the first teeth  1554   b  of the first gear  1541  and the second teeth  1553   a  of the first holder  1553 , the first gear  1541  can be rectilinearly moved. The tension of the first belt  1541 , which is in face-to-face contact with the first curved member  1551 , may be adjusted depending on the moving direction and the moving distance of the first gear  1541 . According to various embodiments, the first curved member  1551  may include a pulley rotatably coupled to the support member  1570  (e.g., the support member assembly  300  in  FIG. 3 ). The second tension adjusting device  1560  may include a second curved member  1561 , a second moving plate  1562 , a second holder  1563 , and/or a second gear  1564 . The second tension adjusting device  1560  may be implemented in substantially the same manner as the first tension adjusting device  1550 . The first tension adjusting device  1550  and the second tension adjusting device  1560  may be symmetrical to each other with respect to the center line  1501  of the electronic device  1500  in the y-axis direction (e.g., the center line of the screen in the y-axis direction). According to various embodiments, the first holder  1553  and the second holder  1563  may be implemented as an integral holder, wherein the integral holder may extend from the first tensioning device  1550  to the second tensioning device  1560 . According to various embodiments, the number or positions of the tension adjusting devices may vary without being limited to the embodiment of  FIG. 15A . The tension adjusting device according to the embodiment of  FIG. 15A  may be applied to the electronic device  100  of  FIG. 3  such that the tension of the first belt  410 , the tension of the second belt  420 , or the tension of the third belt  430  can be adjusted. A variety of other tension adjusting devices may be implemented. 
       FIGS. 16A and 16B  are diagrams illustrating an electronic device  1600  according to various embodiments. 
     In an embodiment, the electronic device  1600  may be implemented such that the screen thereof is expandable to both sides.  FIG. 16A  is a diagram illustrating the electronic device  1600  in a state in which the screen is not expanded (hereinafter, referred to as a “closed state”).  FIG. 16B  is a diagram illustrating the electronic device  1600  in a state in which the screen is expanded to both sides (e.g., a “both side open state”). Although not illustrated, the electronic device  1600  may be in a state in which the screen is expanded to one side (e.g., a “one side open state”). 
     Referring to  FIGS. 16A and 16B , the electronic device  1600  may include a housing  1610 , a first sliding plate  1621  that is capable of sliding out from the housing  1610  in the +x-axis direction, and/or a second sliding plate  1622  capable of being slid out from the housing  1610  in the −x-axis direction. The flexible display  1630  may include a first bendable section  1631  pulled out from the inner space of the housing  1610  when the first sliding plate  1621  slides out. The first sliding plate  1621  may support the first bendable section  1631  when sliding out. The flexible display  1630  may include a second bendable section  1632  pulled out from the inner space of the housing  1610  when the second sliding plate  1622  slides out. The second sliding plate  1622  may support the second bendable section  1632  when sliding out. The flexible display  1630  may include a flat section  1633  between the first bendable section  1631  and the second bendable section  1632 . 
     According to an embodiment, the electronic device  1600  may include at least one elastic structure (e.g., the elastic structure  490  in  FIG. 3 ) for the first sliding plate  1621 . When the first sliding plate  1621  is moved by a set distance by an external force, the electronic device  1600  may be switched from the closed state to the open state or from the open state to the closed state without any further external force due to the at least one elastic structure. 
     According to an embodiment, the electronic device  1600  may include at least one elastic structure (e.g., the elastic structure  490  in  FIG. 3 ) for the second sliding plate  1622 . When the second sliding plate  1622  is moved by a set distance by an external force, the electronic device  1600  may be switched from the closed state to the open state or from the open state to the closed state without any further external force due to the at least one elastic structure. 
     According to an embodiment, the electronic device may include various elements that make the first bendable section  1631  maintained in a shape smoothly connected to the flat section  1633  of the flexible display  1630  without lifting when the screen is expanded or contracted. This will be described in greater detail below with reference to  FIG. 17A or 17B . 
       FIG. 17A  is a diagram illustrating a portion of the electronic device  1600  of  FIG. 16A  according to various embodiments. 
     Referring to  FIG. 17A , in an embodiment, the electronic device  1700  may include a flexible display  1630 , a support sheet  1710 , a support member  1720 , a first pulley  1721 , a second pulley  1722 , a third pulley  1723 , a fourth pulley  1724 , a first belt  1731 , and/or a second belt  1732 . 
     According to an embodiment, the support sheet  1710  may be disposed on the rear surface of the flexible display  1630  or may be included in the flexible display  1630 . The support sheet  1710  may include a first lattice structure (e.g., the lattice structure  702  in  FIG. 7B ) provided to correspond to the first bendable section  1631  in  FIG. 16B . The first lattice structure may contribute to flexibility of a corresponding portion of the support sheet  1710  that corresponds to the first bendable section  1631 . The support sheet  1710  may include a second lattice structure (e.g., the lattice structure  702  in  FIG. 7B ) provided to correspond to the second bendable section  1632  of  FIG. 16B . The second lattice structure may contribute to flexibility of a corresponding portion of the support sheet  1710  that corresponds to the second bendable section  1632 . The support sheet  1710  may reduce the effect of a load or stress that may occur when the screen is expanded or contracted, on the flexible display  1630 . 
     According to an embodiment, the support member  1720  may be located inside the housing  1610  of  FIG. 16A or 16B  to contribute to durability or rigidity of the electronic device  1600 . The first sliding plate  1621  and/or the second sliding plate  1622  of  FIG. 16B  may be slidably disposed on the support member  1720 . 
     According to an embodiment, the first pulley  1721  may be connected to the first bendable section  1631  of  FIG. 16B . The first pulley  1721  may be connected to the first sliding plate  1621  of  FIG. 16B  to be moved together with the first sliding plate  1621 . The second pulley  1722  may be connected to the second sliding plate  1622  of  FIG. 16B  to be moved together with the second sliding plate  1622 . 
     According to an embodiment, the third pulley  1723  may have a rotation shaft parallel to the first pulley  1721 , and may be located on the support member  1720  to be spaced apart from the first pulley  1721  in the direction opposite to the direction in which the first sliding plate  1621  of  FIG. 16B  slides out. The fourth pulley  1724  may have a rotation shaft parallel to the second pulley  1722 , and may be located on the support member  1720  to be spaced apart from the second pulley  1722  in the direction opposite to the direction in which the second sliding plate  1622  of  FIG. 16B  slides out. According to an embodiment, the rotation shaft of the third pulley  1723  and the rotation shaft of the fourth pulley  1724  may be placed on a straight line. 
     According to an embodiment, one end (not illustrated) of the first belt  1731  may be connected to the support sheet  1710 , and the other end (not illustrated) of the first belt  1731  may be connected to the first sliding plate  1621  of  FIG. 16B . The third pulley  1723  may be connected to the first belt  1731 . During the switching between the open state and the closed state, the force for moving the first sliding plate  1621  on the support member  1720  may cause the movement of the first bendable section  1631 , the movement of the first belt  1731 , the rotation of the first pulley  1721 , and the rotation of the third pulley  1723 . The number or positions of the third pulleys  1723  and the first belts  1731  connected thereto, or the number or positions of the fourth pulleys  1724  and the second belts  1732  connected thereto is not limited to the embodiment of  FIG. 17A  and may vary. 
     According to an embodiment, one end (not illustrated) of the second belt  1732  may be connected to the support sheet  1710 , and the other end (not illustrated) of the second belt  1732  may be connected to the second sliding plate  1622  of  FIG. 16B . The fourth pulley  1724  may be connected to the second belt  1732 . During the switching between the open state and the closed state, the force for moving the second sliding plate  1622  on the support member  1720  may cause the movement of the second bendable section  1632 , the movement of the second belt  1732 , the rotation of the second pulley  1722 , and the rotation of the fourth pulley  1724 . According to an embodiment, the tension of the first belt  1731  and the tension of the second belt  1732  may contribute to making the first bendable section  1631  and the second bendable section  1632  maintain a shape smoothly connected to the flat section  1633  without lifting. The tension of the first belt  1731  or the tension of the second belt  1732  may be adjusted through various tension adjusting devices as in the embodiment of  FIG. 13C . 
     According to various embodiments, a reinforcing sheet (e.g., the reinforcing sheet  810 ,  820 , or  830  in  FIG. 8 ) may be attached to the first lattice structure of the support sheet  1710  that corresponds to the first bendable section  1631  of  FIG. 16B  so that stretching of the first lattice structure can be prevented or reduced, and the tension of the first belt  1731  can be maintained. According to various embodiments, the support sheet  1710  may be implemented by applying the embodiment of  FIG. 9  or the embodiment of  FIG. 10  in order to prevent and/or reduce stretching of the first lattice structure. By also preventing and/or reducing the second lattice structure of the support sheet  1710  that corresponds to the first bendable section  1631  of  FIG. 16B  from stretching based on the embodiment of  FIG. 8 , the embodiment of  FIG. 9 , or the embodiment of  FIG. 10 , the tension of the second belt  1732  can be maintained. 
     According to various embodiments, the electronic device  1700  may include a first multi-bar structure (e.g., the multi-bar structure  380  in  FIG. 3 ) extending between the support sheet  1710  and the first pulley  1721  from the first sliding plate  1621  of  FIG. 16B . The electronic device  1700  may include a second multi-bar structure (e.g., the multi-bar structure  380  in  FIG. 3 ) extending between the support sheet  1710  and the second pulley  1722  from the second sliding plate  1621  of  FIG. 16B . The first multi-bar structure and the second multi-bar structure may make the first bendable section  1631  and the second bendable section  1631  of  FIG. 16B  maintain a shape smoothly connected to the flat section  1633  in the closed state or the open state of the electronic device  1700 , or during the switching of the electronic device  1700  between the closed state and the open state. 
       FIG. 17B  is a diagram illustrating a portion of the electronic device  1600  of  FIG. 16A  according to various embodiments. 
     Referring to  FIG. 17B , in various embodiments, the third pulley  1723  and the fourth pulley  1724  may be located adjacent to each other. Due to this, the tension of the first belt  1731  connected to the third pulley  1723  and the tension of the second belt  1732  connected to the fourth pulley  1724  may be concentrated. 
     According to an example embodiment of the disclosure, an electronic device (e.g., the electronic device  100  in  FIG. 3 ) may include: a housing (e.g., the housing  110  in  FIG. 1A ), and a sliding plate (e.g., the sliding plate  120  of  FIG. 3, 4 , or  5 ) capable of sliding out of the housing. The electronic device may include a flexible display (e.g., the flexible display  130  in  FIG. 3, 4 , or  4 ). The flexible display may include a first section (e.g., the first section  131  of  FIG. 3, 4 , or  5 ) overlappingly coupled to the sliding plate, and a bendable section (e.g., the first bendable section  133  in  FIG. 3, 4 , or  5 ) extending from the first section and configured to be pulled out of the inner space of the housing during the slide-out. The electronic device may include a support sheet (e.g., the support sheet  370  in  FIG. 3, 4 , or  5 ) disposed on the rear surface of the flexible display. The electronic device may include a first curved portion (e.g., the first pulley  360  in  FIG. 3, 4 , or  5 ) located inside the housing corresponding to the bendable section. The electronic device may include a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430  in  FIG. 3 ) interconnecting the support sheet and the sliding plate. The electronic device may include a second curved portion (e.g., the second pulley  440 , the third pulley  450 , or the fourth pulley  460  in  FIG. 3 ). The second curved member may be located inside the housing corresponding to the belt, and may be spaced apart from the first curved portion in the slide-out direction. 
     According to an example embodiment of the disclosure, the first curved portion or the second curved portion may include a pulley. For example, the first curved portion may include the first pulley  360  of  FIG. 3 . For example, the second curved portion may include the second pulley  440 , the third pulley  450 , or the fourth pulley  460  in  FIG. 3 . 
     According to an example embodiment of the disclosure, the support sheet (e.g., the support sheet  370  of  FIG. 3, 4 , or  5 ) may include a lattice structure (e.g., the lattice structure  702  in  FIG. 7B ) including a plurality openings (e.g., the plurality of openings  701  in  FIG. 7B ) corresponding to the bendable section (e.g., the first bendable section  133  in  FIG. 6 ). 
     According to an example embodiment of the disclosure, the support sheet (e.g., the support sheet  370  in  FIG. 7B ) may include a second section (e.g., the second section  371  in  FIG. 7B ) and a third section (e.g., the third section  372  in  FIG. 7B ) arranged with the lattice structure (e.g., the lattice structure  702  of  FIG. 7B ) interposed therebetween. The second section may be connected to the sliding plate (e.g., the sliding plate  120  in  FIG. 3, 4 , or  5 ). The third section may be connected to the belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430  in  FIG. 3 ). 
     According to an example embodiment of the disclosure, the electronic device (e.g., the electronic device  100  of  FIG. 1A ) may further include at least one reinforcing sheet (e.g., the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  in  FIG. 8 ). The at least one reinforcing sheet may be attached to the support sheet (e.g., the support sheet  370  in  FIG. 8 ) and may interconnect the second section (e.g., the second section  371  in  FIG. 8 ) and the third section (e.g., the third section  372  in  FIG. 8 ) across the lattice structure (e.g., the lattice structure  702  in  FIG. 7B ). 
     According to an example embodiment of the disclosure, the reinforcing sheet (e.g., the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  of  FIG. 8 ) may include stainless steel. 
     According to an example embodiment of the disclosure, the lattice structure may include at least one first area and at least one second area (e.g., the first lattice structure  1010 , the second lattice structure  1020 , or third lattice structure  1030  in  FIG. 10 ). The at least one first area and the at least one area may extend across the second section (e.g., the second section  371  in  FIG. 10 ) and the third section (e.g., the third section  372  in  FIG. 10 ). The at least one second area including a smaller number of openings than the at least one first area. 
     According to an example embodiment of the disclosure, the lattice structure may not be provided in at least one area (e.g., the first area  910 , the second area  920 , or third area  930  in  FIG. 9 ) extending across the second section (e.g., the second section  371  in  FIG. 9 ) and the third section (e.g., the third section  372  in  FIG. 9 ). 
     According to an example embodiment of the disclosure, the support sheet (e.g., the support sheet  370  in  FIG. 3, 4, 5, 6, 7B, 8, 9 , or  10 ) may include stainless steel. 
     According to an example embodiment of the disclosure, the support sheet (e.g., the support sheet  370  in  FIG. 3, 4, 5, 6, 7B, 8, 9 , or  10 ) may include engineering plastic. 
     According to an example embodiment of the disclosure, the electronic device (e.g., the electronic device  100  of  FIG. 1A ) may further include a tension adjusting device configured to adjust the tension of the belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430  in  FIG. 3 ). 
     According to an example embodiment of the disclosure, the tension adjusting device may include a plurality of fastening holes (e.g., the plurality of fastening holes  1220  in  FIG. 12 ) provided in the belt (e.g., the first belt  410  in  FIG. 12 ) and arranged in the longitudinal direction of the belt. The tension adjusting device may include a hook (e.g., the hook  1320  in  FIG. 13A or 13B ) disposed on the support sheet (e.g., the support  740  included in the support sheet  370  of  FIG. 11 ) and capable of being fastened to the plurality of fastening holes. The tension may be changed depending on a position at which the hook is fastened to the plurality of fastening holes. 
     According to an example embodiment of the disclosure, the tension adjusting device may include a moving portion (e.g., the first moving member  1411  or the second moving member  1412 ) connected to the second curved member (e.g., the second pulley  440  in  FIG. 14 ), and a screw (e.g., the first screw  1421  or the second screw  1422  in  FIG. 14 ) connected to the moving portion. The second curved member may be moved together with the moving portion based on the rotation of the screw, and the tension may be changed depending on the position of the second curved member. 
     According to an example embodiment of the disclosure, the electronic device (e.g., the electronic device  100  of  FIG. 3, 4 , or  5 ) may further include a multi-bar support (e.g., the multi-bar structure  380  of  FIG. 3, 4 , or  5 ) extending from the sliding plate (e.g., the sliding plate  120  in  FIG. 3, 4 , or  5 ) to the space between the support sheet (e.g., the support sheet  370  in  FIG. 3, 4 , or  5 ) and the first curved member (e.g., the first pulley  360  of  FIG. 3, 4 , or  5 ). 
     According to an example embodiment of the disclosure, the electronic device (e.g., the electronic device  100  of  FIG. 3 ) may further include an elastic structure (e.g., the elastic structure  490  in  FIG. 3 ) comprising an elastic material disposed between the housing (e.g., the housing  110  in  FIG. 1A ) and the sliding plate (e.g., the sliding plate  120  in  FIG. 1A ). The elastic structure may be configured to provide a force for moving the sliding plate. 
     According to various example embodiments of the disclosure, an electronic device (e.g., the electronic device  100  in  FIG. 1A ) may include: a housing (e.g., the housing  110  in  FIG. 1A ), and a sliding plate (e.g., the sliding plate  120  of  FIG. 3, 4 , or  5 ) capable of sliding out of the housing. The electronic device may include a flexible display (e.g., the flexible display  130  in  FIG. 3, 4 , or  5 ). The flexible display may include a first section (e.g., the first section  131  of  FIG. 3, 4 , or  5 ) overlappingly coupled to the sliding plate, and a bendable section (e.g., the first bendable section  133  in  FIG. 3, 4 , or  5 ) extending from the first section and configured to be pulled out of the inner space of the housing during the slide-out. The electronic device may include a support sheet (e.g., the support sheet  370  of  FIG. 3, 4 , or  5 ). The support sheet may be disposed on the rear surface of the flexible display or may be included in the flexible display. The electronic device may include a first pulley (e.g., the first pulley  360  in  FIG. 3, 4 , or  5 ) located inside the housing corresponding to the bendable section. The electronic device may include a belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430  in  FIG. 3 ) interconnecting the support sheet and the sliding plate. The electronic device may include a second pulley (e.g., the second pulley  430 , the third pulley  440 , or the fourth pulley  460  in  FIG. 3 ) including a rotation shaft parallel to the first pulley, spaced apart from the first pulley in the slide-out direction, and located inside the housing, and connected to the belt. 
     According to various example embodiments of the disclosure, the support sheet (e.g., the support sheet  370  in  FIG. 7B ) may include a lattice structure (e.g., the lattice structure  720  in  FIG. 7B ) including a plurality openings (e.g., the plurality of openings  701  in  FIG. 7B ) corresponding to the bendable section (e.g., the first bendable section  133  in  FIG. 6 ). 
     According to various example embodiments of the disclosure, the support sheet (e.g., the support sheet  370  in  FIG. 7B ) may include a second section (e.g., the second section  371  in  FIG. 7B ) and a third section (e.g., the third section in  FIG. 7B ) arranged with the lattice structure (e.g., the lattice structure  702  of  FIG. 7B ) interposed therebetween. The second section may be connected to the sliding plate (e.g., the sliding plate  120  in  FIG. 3, 4 , or  5 ). The third section may be connected to the belt (e.g., the first belt  410 , the second belt  420 , or the third belt  430  in  FIG. 3 ). 
     According to various example embodiments of the disclosure, the electronic device (e.g., the electronic device  100  of  FIG. 1A ) may further include at least one reinforcing sheet (e.g., the first reinforcing sheet  810 , the second reinforcing sheet  820 , or the third reinforcing sheet  830  in  FIG. 8 ). The at least one reinforcing sheet may be attached to the support sheet (e.g., the support sheet  370  in  FIG. 8 ) and may interconnect the second section (e.g., the second section  371  in  FIG. 8 ) and the third section (e.g., the third section  372  in  FIG. 8 ) across the lattice structure (e.g., the lattice structure  702  in  FIG. 7B ). 
     According to various example embodiments of the disclosure, the belt (e.g., the first belt  410 , the belt  420 , or the third belt  430  of  FIG. 3 ) may include stainless steel. 
     While the disclosure has been illustrated and described with reference to various example embodiments, it will be understood that the various example embodiments are intended to be illustrative, not limiting. It will be further understood by those skilled in the art that various changes in form and detail may be made without departing from the true spirit and full scope of the disclosure, including the appended claims and their equivalents. It will also be understood that any of the embodiment(s) described herein may be used in conjunction with any other embodiment(s) described herein.