Patent Publication Number: US-11037512-B2

Title: Flexible display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0165423, filed on Dec. 19, 2018, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Aspects of some example embodiments of the present disclosure herein relate to a display device, and for example, to a flexible display device that is bendable or foldable. 
     Various display devices for use in multimedia devices such as televisions, mobile phones, tablet computers, navigators, game machines, and the like are being developed. For example, flexible display devices that are variously deformable to be bent or folded have recently been developed. 
     Meanwhile, various research is being carried out to reduce power consumption of battery-powered electronic devices such as mobile phones, tablet computers, navigators, game machines, and the like. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background and therefore it may contain information that does not constitute prior art. 
     SUMMARY 
     Aspects of some example embodiments of the present disclosure include a flexible display device for reducing power consumption. 
     According to some example embodiments of the inventive concept, a display device includes: a display panel including a first display region having first pixels connected to a plurality of first data lines and a plurality of scan lines and a second display region having second pixels connected to a plurality of second data lines and the plurality of scan lines; a voltage generator configured to generate a first driving voltage; a driving controller configured to output a first switching signal and a second switching signal; and a switching circuit configured to provide the first driving voltage to the first pixels in response to the first switching signal and provide the first driving voltage to the second pixels in response to the second switching signal. The driving controller determines whether each of the first display region and the second display region is a visible region or a non-visible region, and outputs the first switching signal and the second switching signal corresponding to a determination result. 
     According to some example embodiments, the driving controller may generate the first switching signal and the second switching signal so as to provide the first driving voltage to the first pixels and not to provide the first driving voltage to the second pixels when the first display region is the visible region and the second display region is the non-visible region. 
     According to some example embodiments, the display device may further include: a light emitter configured to output a light ray signal; and a light receiver configured to activate a light detection signal when the light ray signal is received. The driving controller may deactivate either the first switching signal or the second switching signal when the light detection signal is activated. 
     According to some example embodiments, the switching circuit may include: a first switching transistor configured to transfer the first driving voltage to a first voltage line in response to the first switching signal; and a second switching transistor configured to transfer the first driving voltage to a second voltage line in response to the second switching signal. 
     According to some example embodiments, at least one of the first pixels may include: a light emitting diode including an anode and a cathode; a first transistor including a first electrode connected to the first voltage line, a second electrode electrically connected to the anode of the light emitting diode, and a gate electrode; a second transistor including a first electrode connected to a corresponding first data line among the plurality of first data lines, and a gate electrode connected to the first electrode of the first transistor and receiving a first scan signal; and a third transistor including a first electrode connected to the second electrode of the first transistor, a second electrode connected to the gate electrode of the second transistor, and a gate electrode connected to a second scan signal. 
     According to some example embodiments, at least one of the second pixels may include: a light emitting diode including an anode and a cathode; a first transistor including a first electrode connected to second first voltage line, a second electrode electrically connected to the anode of the light emitting diode, and a gate electrode; a second transistor including a first electrode connected to a corresponding second data line among the plurality of second data lines, and a gate electrode connected to the first electrode of the first transistor and receiving a first scan signal; and a third transistor including a first electrode connected to the second electrode of the first transistor, a second electrode connected to the gate electrode of the second transistor, and a gate electrode connected to a second scan signal. 
     According to some example embodiments, the display device may further include: a first data driving circuit configured to drive the first data lines; a second data driving circuit configured to drive the second data lines; and a scan driving circuit configured to drive the plurality of scan lines. 
     According to some example embodiments, the driving controller may further output a third switching signal and a fourth switching signal, and the display device may further include a data driving control circuit configured to selectively provide a second driving voltage to the first data driving circuit in response to the third switching signal and selectively provide the second driving voltage to the second data driving circuit in response to the fourth switching signal. 
     According to some example embodiments, the data driving control circuit may be located on the same circuit board as at least one of the driving controller and the voltage generator. 
     According to some example embodiments, the data driving control circuit may be on the same circuit board as at least one of the first data driving circuit and the second data driving circuit. 
     According to some example embodiments, the data driving control circuit may include: a third switching transistor configured to transfer the second driving voltage to the first data driving circuit in response to the third switching signal; and a fourth switching transistor configured to transfer the second driving voltage to the second data driving circuit in response to the fourth switching signal. 
     According to some example embodiments, the display panel may include a bending region and a non-bending region, and may include: a base layer; a pixel layer on the base layer; and a conductive layer in the bending region between the base layer and the pixel layer, wherein the display device may further include a resistance measurement circuit configured to measure a resistance of the conductive layer. 
     According to some example embodiments, the display panel may be bent about a bending axis, and the driving controller may output the first switching signal or the second switching signal at an inactive level when the measured resistance indicates that the display panel is bent. 
     According to some example embodiments of the inventive concept, a display device includes: a display panel including a first display region having first pixels connected to a plurality of first data lines and a plurality of first scan lines and a second display region having second pixels connected to a plurality of second data lines and a plurality of second scan lines; a driving controller configured to output a first start control signal and a second start control signal; a first scan driving circuit configured to drive the plurality of first scan lines in response to the first start control signal; and a second scan driving circuit configured to drive the plurality of second scan lines in response to the second start control signal. The driving controller may determine whether or not each of the first display region and the second display region is a visible region or a non-visible region, and outputs the first start control signal and the second start control signal corresponding to a determination result. 
     According to some example embodiments, the driving controller may provide the first start control signal to the first scan driving circuit and maintain the second start control signal at an inactive level when the first display region is the visible region and the second display region is the non-visible region. 
     According to some example embodiments, the display device may further include: a light emitter configured to output a light ray signal; and a light receiver configured to activate a light detection signal when the light ray signal is received, wherein the driving controller may maintain the first start control signal or the second start control signal at an inactive level when the light detection signal is activated. 
     According to some example embodiments, the display device may further include: a first light emission driving circuit configured to provide a first light emission control signal to the first pixels in synchronization with a first light emission start signal; and a second light emission driving circuit configured to provide a second light emission control signal to the second pixels in synchronization with a second light emission start signal, wherein the driving controller may further output the first light emission start signal and the second light emission start signal. 
     According to some example embodiments, the driving controller may provide the first light emission start signal to the first light emission driving circuit and maintain the second light emission start signal at an inactive level when the first display region is the visible region and the second display region is the non-visible region. 
     According to some example embodiments, the display panel may include a bending region and a non-bending region, and may include: a base layer; a pixel circuit layer on the base layer; and a conductive layer in the bending region between the base layer and the pixel circuit layer, wherein the display device may further include a resistance measurement circuit configured to measure a resistance of the conductive layer. 
     According to some example embodiments, the display panel may be bent about a bending axis, and the driving controller may output the corresponding first start control signal or second start control signal at an inactive level when the measured resistance indicates that the display panel is bent. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate aspects of some example embodiments of the inventive concept and, together with the description, serve to explain aspects of the inventive concept. In the drawings: 
         FIG. 1  is a perspective view illustrating a display device according to some example embodiments of the inventive concept; 
         FIGS. 2A and 2B  illustrate the display device of  FIG. 1  as being folded; 
         FIG. 3A  is a perspective view illustrating a lower surface of a display device according to some example embodiments of the inventive concept; 
         FIG. 3B  is a diagram illustrating a display device as being out-folded according to some example embodiments of the inventive concept; 
         FIG. 4  is a diagram illustrating a circuit configuration of a display device according to some example embodiments of the inventive concept; 
         FIG. 5  is an equivalent circuit diagram of a first pixel and a second pixel according to some example embodiments of the inventive concept; 
         FIG. 6  illustrates first and second pixels and first and second switching circuits according to some example embodiments of the inventive concept; 
         FIG. 7  illustrates first and second pixels and third and fourth switching circuits according to some example embodiments of the inventive concept; 
         FIG. 8  is a planar view illustrating a display device according to some example embodiments of the inventive concept; 
         FIG. 9  is a diagram illustrating an example connection relationship between partial circuits illustrated in  FIG. 8 ; 
         FIG. 10  is a planar view illustrating a display device according to some example embodiments of the inventive concept t; 
         FIG. 11  is a diagram illustrating an example connection relationship between partial circuits illustrated in  FIG. 10 ; 
         FIG. 12  is a diagram illustrating a circuit configuration of a display device according to some example embodiments of the inventive concept; 
         FIG. 13  is a timing diagram illustrating operation of the display device illustrated in  FIG. 12 ; 
         FIG. 14  is a perspective view of a display device according to some example embodiments of the inventive concept; 
         FIG. 15  is a schematic cross-sectional view of the display device taken along the line I-I′ of  FIG. 14 ; 
         FIG. 16  is a perspective view illustrating a folded state of the display device of  FIG. 14 ; 
         FIG. 17A  is a planar view illustrating a conductive layer and an insulating layer according to some example embodiments of the inventive concept of the display device illustrated in  FIG. 14 ; and 
         FIG. 17B  is a schematic cross-sectional view of the conductive layer and the insulating layer taken along the line II-II′ of  FIG. 17A . 
     
    
    
     DETAILED DESCRIPTION 
     It will be understood that when an element (or a region, layer, portion, or the like) is referred to as being “on”, “connected to”, or “coupled to” another element, it can be directly on or directly connected/coupled to the other element, or a third element may be present therebetween. 
     The same reference numerals refer to the same elements. In the drawings, the thicknesses, ratios, and dimensions of elements are exaggerated for clarity of illustration. 
     As used herein, the term “and/or” includes any combinations that can be defined by associated elements. 
     The terms “first”, “second” and the like may be used for describing various elements, but the elements should not be construed as being limited by the terms. Such terms are only used for distinguishing one element from other elements. For example, a first element could be termed a second element and vice versa without departing from the teachings of the present disclosure. The terms of a singular form may include plural forms unless otherwise specified. 
     Furthermore, the terms “under”, “lower side”, “on”, “upper side”, and the like are used to describe association relationships among elements illustrated in the drawings. The terms, which are relative concepts, are used on the basis of directions illustrated in the drawings. 
     All of the terms used herein (including technical and scientific terms) have the same meanings as understood by those skilled in the art, unless otherwise defined. Terms in common usage such as those defined in commonly used dictionaries should be interpreted to contextually match the meanings in the relevant art, and are explicitly defined herein unless interpreted in an idealized or overly formal sense. 
     It will be further understood that the terms “include”, “including”, “has”, “having”, and the like, when used in this specification, specify the presence of stated features, numbers, steps, operations, elements, components, or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, or combinations thereof. 
     Hereinafter, embodiments of the inventive concept will be described in more detail with reference to the accompanying drawings. 
       FIG. 1  is a perspective view illustrating a display device according to some example embodiments of the inventive concept. 
     Referring to  FIG. 1 , a display device  100  according to some example embodiments of the inventive concept includes a display surface DS on which an image IM is displayed, wherein the display surface DS is parallel to a plane defined by a first direction DR 1  and a second direction DR 2 . A normal direction of the display surface DS, i.e., a thickness direction of the display device  100 , is indicated by a third direction DR 3 . An upper surface (or front surface) and lower surface (or rear surface) of each member is differentiated by the third direction DR 3 . However, the directions indicated by the first to third directions DR 1  to DR 3  are relative concepts and thus may be changed to other directions. Hereinafter, first to third directions which are indicated by the first to third directions DR 1  to DR 3  referred to by the same reference symbols. The display device  100  according to some example embodiments of the inventive concept may be a flexible display device. The display device  100  according to some example embodiments of the inventive concept may be a foldable display device or a rollable display device, but embodiments are not particularly limited. The display device  100  according to some example embodiments of the inventive concept may be used in a large-size electronic device such as a television, a monitor, or the like, or a small- or medium-size electronic device such as a mobile phone, a tablet, a vehicle navigator, a game machine, a smart watch, or the like. 
     In the present disclosure, the term “flexible” represents a bendable characteristic without causing damage, and may encompass a structure that is bent to a level of several nanometers without being limited to a structure that is bent and completely folded. 
     As illustrated in  FIG. 1 , the display surface DS of the display device  100  may include a plurality of regions. The display device  100  includes a display region DA at which the image IM is displayed and a non-display region NDA adjacent to the display region DA. The non-display region NDA is one at which the image IM is not displayed.  FIG. 1  illustrates icons and a clock window as an example of the image IM. The display region DA may be rectangular. The non-display region NDA may surround the display region DA. However, embodiments of the inventive concept are not limited thereto, and thus a shape of the display region DA and a shape of the non-display region NDA may be relatively designed. 
     For example, the display device  100  may be an organic light emitting display device. For example, embodiments of the inventive concept are not limited thereto, and thus the display device  100  may be a liquid crystal display device, a plasma display device, an electrophoretic display device, a microelectromechanical system (MEMS) display device, an electrowetting display device, or the like. 
     According to some example embodiments, the display region DA may be divided into a first display region DA 1  and a second display region DA 2  with respect to a bending axis BX. The first display region DA 1  and the second display region DA 2  may have the same area in this embodiment, but may have different areas in other embodiments. Furthermore, the display region DA is divided into two regions in this embodiment, but may be divided into more than two regions. 
       FIGS. 2A and 2B  illustrate the display device of  FIG. 1  as being folded. 
     Referring to  FIGS. 1, 2A, and 2B , the display device  100  according to some example embodiments of the inventive concept may operate in a first mode in which at least a part of the display device  100  is bent or a second mode in which the display device  100  is unbent.  FIGS. 2A and 2B  illustrate an example in which the display device  100  is operating in the first mode, and  FIG. 1  illustrates an example in which the display device  100  is operating in the second mode. 
     Referring to  FIG. 2A , the display device  100  according to some example embodiments of the inventive concept may be in-folded with respect to the bending axis BX in the first mode. When the display device  100  is completely in-folded, the display surface DS is not exposed to the outside, but a lower surface NDS is exposed to the outside. Furthermore, referring to  FIG. 2B , the display device  100  according to some example embodiments of the inventive concept may be out-folded with respect to the bending axis BX in the first mode. 
       FIG. 3A  is a perspective view illustrating the lower surface of the display device.  FIG. 3B  is a diagram illustrating the display device as being out-folded. 
     Referring to  FIGS. 3A and 3B , a light emitter  110  and a light receiver  120  are arranged in the lower surface NDS of the display device  100 . The light emitter  110  and the light receiver  120  are spaced a distance (e.g., a predetermined distance) apart in the first direction with respect to the bending axis BX. 
     The light emitter  110  outputs a light ray signal. The light ray signal may be an infrared signal, but is not limited thereto. The light receiver  120  receives the light ray signal from the light emitter  110 . In the case where the light emitter  110  outputs an infrared signal, the light receiver  120  may be an infrared sensor. However, embodiments of the inventive concept are not limited thereto. 
     The light ray signal output from the light emitter  110  when the display device  100  is out-folded may be received by the light receiver  120 . The light receiver  120  may detect that the display device  100  is out-folded when a light quantity of the received light ray signal has at least a predetermined level. 
       FIG. 4  is a diagram illustrating a circuit configuration of a display device according to some example embodiments of the inventive concept. 
     Referring to  FIG. 4 , the display device  100  includes a pixel circuit  210 , a driving controller  220 , a scan driving circuit  230 , a first data driving circuit  240 , a second data driving circuit  250 , a light emission driving circuit  260 , a voltage generator  270 , and a switching circuit  280 . 
     The driving controller  220  receives an image signal RGB and a control signal CTRL, and converts a data format of the image signal RGB so that the image signal RGB is suitable for the pixel circuit  210 , so as to generate a first image data signal DATA 1  and a second image data signal DATA 2 . The driving controller  220  outputs a start control signal FLM, a light emission start signal ECTL, a first data control signal DCS 1 , a second data control signal DCS 2 , a folding detection control signal F_C, a first switching signal SW 1 , and a second switching signal SW 2 . Although  FIG. 4  illustrates that the driving controller  220  only provides the start control signal FLM to the scan driving circuit  230 , the driving controller  220  may further provide other signals to the scan driving circuit  230 . 
     The scan driving circuit  230  receives the start control signal FLM from the driving controller  220 . The scan driving circuit  230  generates a plurality of scan signals, and outputs the plurality of scan signals to scan lines SL 1  to SLn. 
     Although  FIG. 4  illustrates the plurality of scan signals as being output from one scan driving circuit  230 , embodiments of the inventive concept are not limited thereto. According to some example embodiments of the inventive concept, a plurality of scan driving circuits may divide and output the plurality of scan signals. 
     The light emission driving circuit  260  generates a plurality of light emission control signals in response to the light emission start signal ECTL, and outputs the light emission control signals to a plurality of light emission control lines EU to ELn. 
     Although  FIG. 4  illustrates the plurality of light emission control signals as being output from one light emission driving circuit  260 , embodiments of the inventive concept are not limited thereto. According to some example embodiments of the inventive concept, a plurality of light emission driving circuits may divide and output the plurality of light emission control signals. 
     According to some example embodiments of the inventive concept, the scan driving circuit  230  and the light emission driving circuit  260  are configured as independent circuits and arranged opposite to each other with the pixel circuit  210  therebetween. According to some example embodiments of the inventive concept, the scan driving circuit  230  and the light emission driving circuit  260  may be arranged adjacent to each other on one side of the pixel circuit  210 . Furthermore, according to some example embodiments of the inventive concept, the scan driving circuit  230  and the light emission driving circuit  260  may be configured as a single circuit and arranged on one side of the pixel circuit  210 . 
     The first data driving circuit  240  receives the first data control signal DCS 1  and the first image data signal DATA 1  from the driving controller  220 . The first data driving circuit  240  converts the first image data signal DATA 1  into first data signals, and outputs the first data signals to a plurality of first data lines DL 11  to DL 1   k . The first data signals are analog voltages corresponding to gradation values of the first image data signal DATA 1 . 
     The second data driving circuit  250  receives the second data control signal DCS 2  and the second image data signal DATA 2  from the driving controller  220 . The second data driving circuit  250  converts the second image data signal DATA 2  into second data signals, and outputs the second data signals to a plurality of second data lines DL 21  to DL 2   k . The second data signals are analog voltages corresponding to gradation values of the second image data signal DATA 2 . 
     The voltage generator  270  generates voltages required for operating the display device  100 . According to some example embodiments of the inventive concept, the voltage generator  270  generates a first driving voltage ELVDD, a second driving voltage ELVSS, and an initialization voltage Vint, but embodiments of the inventive concept are not limited thereto. For example, the voltage generator  270  may further generate an analog reference voltage required for generating gradation voltages of the first data driving circuit  240  and the second data driving circuit  250 . The second driving voltage ELVSS may have a lower level than that of the first driving voltage ELVDD. 
     The pixel circuit  210  includes a plurality of first pixels PX 1  and a plurality of second pixels PX 2 . Each of the plurality of first pixels PX 1  is connected to a corresponding first data line among the first data lines DL 11  to DL 1   k , and is connected to a corresponding scan line among the scan lines SL 1  to SLn. Each of the plurality of second pixels PX 2  is connected to a corresponding second data line among the second data lines DL 21  to DL 2   k , and is connected to a corresponding scan line among the scan lines SL 1  to SLn. 
     Each of the plurality of first pixels PX 1  and the plurality of second pixels PX 2  receives the first driving voltage ELVDD, the second driving voltage ELVSS, and the initialization voltage Vint. Each of the first pixels PX 1  is connected to a first voltage line VDL 1  to which the first driving voltage ELVDD is applied. Each of the second pixels PX 2  is connected to a second voltage line VDL 2  to which the first driving voltage ELVDD is applied. 
     Each of the first pixels PX 1  and the second pixels PX 2  may be electrically connected to two scan lines. As illustrated in  FIG. 4 , pixels of a second pixel row may be connected to the scan lines SL 1  and SL 2 . 
     The first pixels PX 1  may be arranged in the first display region DA 1  illustrated in  FIG. 1 , and the second pixels PX 2  may be arranged in the second display region DA 2 . 
     Although, it is illustrated and described that the first pixels PX 1  are connected to the first data driving circuit  240  via the first data lines DL 11  to DL 1   k , and the second pixels PX 2  are connected to the second data driving circuit  250  via the second data lines DL 21  to DL 2   k , embodiments of the inventive concept are not limited thereto. For example, the first data lines DL 11  to DL 1   k  and the second data lines DL 21  to DL 2   k  may be driven by a single data driving circuit. 
     The scan lines SL 1  to SLn, the light emission control lines EU to ELn, the first data lines DL 11  to DL 1   k , the second data lines DL 21  to DL 2   k , the first voltage line VDL 1 , the first pixels PX 1 , the second pixels PX 2 , and the scan driving circuit  230  may be formed on a base substrate through a photolithography process performed multiple times. 
     The switching circuit  280  provides the first driving voltage ELVDD to the first pixels PX 1  via the first voltage line VDL 1  in response to the first switching signal SW 1 , and provides the first driving voltage ELVDD to the second pixels PX 2  via the second voltage line VDL 2  in response to the second switching signals SW 2 . 
     The switching circuit  280  includes a first switching transistor ST 11  and a second switching transistor ST 12 . The first switching transistor ST 11  includes a first electrode for receiving the first driving voltage ELVDD, a second electrode connected to the first voltage line VDL 1 , and a gate electrode for receiving the first switching signal SW 1 . The second switching transistor ST 12  includes a first electrode for receiving the first driving voltage ELVDD, a second electrode connected to the second voltage line VDL 2 , and a gate electrode for receiving the second switching signal SW 2 . 
     The driving controller  220  outputs the folding detection control signal F_C to the light emitter  110 . For example, the driving controller  220  may periodically activate the folding detection control signal F_C during operation. 
     The light emitter  110  outputs the light ray signal in response to the folding detection control signal F_C. The light ray signal may be an infrared signal, but is not limited thereto. The light receiver  120  receives the light ray signal from the light emitter  110 . 
     As illustrated in  FIG. 3B , the light ray signal output from the light emitter  110  when the display device  100  is out-folded may be received by the light receiver  120 . The light receiver  120  outputs a folding detection signal F_S at an active level (e.g., a high level) when the light quantity of the received light ray signal has at least a predetermined level. This folding detection signal F_S is provided to the driving controller  220 . 
     The driving controller  220  regards the display device  100  as being out-folded when the folding detection signal F_S has an active level (e.g., a high level), and deactivates the first switching signal SW 1  or the second switching signal SW 2 . For example, the driving controller  220  may deactivate the first switching signal SW 1  when the folding detection signal F_S has an active level. When the first switching signal SW 1  is deactivated, the first pixels PX 1  may be turned off because the first driving voltage ELVDD is not provided to the first pixels PX 1 . 
     According to some example embodiments of the inventive concept, the display device  100  may further include a gyroscope sensor. The driving controller  220  may determine which one of the first display region DA 1  and the second display region DA 2  is an invisible (or non-visible, e.g., where images are not displayed) region on the basis of a detection signal from the gyroscope sensor when the folding detection signal F_S transitions to an active level. The driving controller  220  deactivates the first switching signal SW 1  when the first display region DA 1  is determined to be an invisible region, and deactivates the second switching signal SW 2  when the second display region DA 2  is determined to be an invisible region. 
     According to some example embodiments of the inventive concept, the driving controller  220  may regard a preset one among the first display region DA 1  and the second display region DA 2  as an invisible region when the folding detection signal F_S has an active level. 
     As described above, power consumption of the display device  100  may be reduced by turning off an invisible region when the display device  100  is out-folded. 
       FIG. 5  is an equivalent circuit diagram of a first pixel and a second circuit according to some example embodiments of the inventive concept. 
       FIG. 5  illustrates an example of a first pixel PX 1   ij  connected to an ith first data line DL 1   i  among the plurality of first data lines DL 11  to DL 1   k , a jth scan line SLj and (j−1)th scan line SLj−1 among the plurality of scan lines SL 1  to SLn, and a jth light emission control line ELj among the plurality of light emission control lines EL 1  to ELn, and a second pixel PX 2   ij  connected to an ith second data line DL 2   i  among the plurality of second data lines DL 21  to DL 2   k , a jth scan line SLj and (j−1)th scan line SLj−1 among the plurality of scan lines SL 1  to SLn, and a jth light emission control line ELj among the plurality of light emission control lines EL 1  to ELn. 
     Each of the plurality of first pixels PX 1  and the plurality of second pixels PX 2  illustrated in  FIG. 4  may have the same circuit configuration as the equivalent circuit diagram of the first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 5 . 
     According to some example embodiments of the inventive concept, the first pixel PX 1   ij  includes first to seventh transistors T 11  to T 17 , a capacitor Cst 1 , and at least one light emitting diode ED 1 . Each of the first to seventh transistors T 11  to T 17  is a P-type transistor having a low-temperatures polycrystalline silicon (LTPS) semiconductor layer. According to some example embodiments of the inventive concept, each of the first, second, fifth, sixth, and seventh transistors T 11 , T 12 , T 15 , T 16 , and T 17  may be a P-type transistor having an LTPS semiconductor layer, and each of the third and fourth transistors T 13  and T 14  may be an N-type transistor having an oxide semiconductor layer. However, embodiments of the inventive concept are not limited thereto, and thus at least one of the first to seventh transistors T 11  to T 17  may be an N-type transistor and the others may be P-type transistors. Furthermore, the circuit configuration of the first pixel PX 1   ij  according to some example embodiments of the inventive concept is not limited to that illustrated in  FIG. 5 . The first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 5  is merely an example, and thus the circuit configuration may be modified. 
     For convenience, the jth scan line SLj and the (j−1)th scan line SLj−1 are referred to as a first scan line SLj and a second scan line SLj−1. 
     The first scan line SLj and the second scan line SLj−1 may transfer scan signals Sj and Sj−1 respectively. 
     The light emission control line ELj may transfer a light emission control signal Ej for controlling light emission of the light emitting diode ED 1 . The light emission control signal Ej transferred through the light emission control line ELj may have a waveform different from waveforms of the scan signals Sj and Sj−1 transferred through the first scan line SLj and the second scan line SLj−1. The first data line DL 1   i  may transfer a first data signal D 1   i , and the first driving voltage line VDL 1  may transfer the first driving voltage ELVDD. The first data signal D 1   i  may have different voltage levels according to the first image data signal DATA 1 , and the first driving voltage ELVDD may have a substantially constant level. 
     The first transistor T 11  includes a first electrode connected to the first driving voltage line VDL 1  via the fifth transistor T 15 , a second electrode electrically connected to an anode of the light emitting diode ED 1  via the sixth transistor T 16 , and a gate electrode connected to one end of the capacitor Cst 1 . The first transistor T 11  may receive the first data signal D 1   i  transferred through the first data line DL 1   i  in response to a switching operation of the second transistor T 12  to supply a driving current Id to the light emitting diode ED 1 . The first transistor T 11  may be referred to as a driving transistor. 
     The second transistor T 12  includes a first electrode connected to the first data line DL 1   i , a second electrode connected to the first electrode of the first transistor T 11 , and a gate electrode connected to the first scan line SLj. The second transistor T 12  may be turned on in response to the scan signal Sj received through the first scan line SLj to transfer, to the first electrode of the first transistor T 11 , the first data signal D 1   i  transferred from the first data line DL 1   i.    
     The third transistor T 13  includes a first electrode connected to the gate electrode of the first transistor T 11 , a second electrode connected to the second electrode of the first transistor T 11 , and a gate electrode connected to the first scan line SLj. The third transistor T 13  may be turned on in response to the scan signal Sj received through the first scan line SLj to connect the gate electrode and the second electrode of the first transistor T 11  to each other so as to diode-connect the first transistor T 11 . 
     The fourth transistor T 14  includes a first electrode connected to the gate electrode of the first transistor T 11 , a second electrode receiving the initialization voltage Vint, and a gate electrode connected to the second scan line SLj−1. The fourth transistor T 14  is turned on in response to the scan signal Sj−1 received through the second scan line SLj−1, and transfers the initialization voltage Vint to the gate electrode of the first transistor T 11  to perform an initialization operation for initializing a voltage of the gate electrode of the first transistor T 11 . 
     The fifth transistor T 15  includes a first electrode connected to the first driving voltage line VDL 1 , a second electrode connected to the first electrode of the first transistor T 11 , and a gate electrode connected to the jth light emission control line ELj. 
     The sixth transistor T 16  includes a second electrode connected to the first electrode of the first transistor T 11 , a second electrode connected to the anode of the light emitting diode ED 1 , and a gate electrode connected to the jth light emission control line ELj. 
     The fifth transistor T 15  and the sixth transistor T 16  may be simultaneously turned on in response to the light emission control signal Ej received through the jth light emission control line ELj so that the first driving voltage ELVDD is compensated through the diode-connected first transistor T 11  and transferred to the light emitting diode ED 1 . 
     The seventh transistor T 17  includes a first electrode connected to the second electrode of the fourth transistor T 14 , a second electrode connected to the second electrode of the sixth transistor T 16 , and a gate electrode connected to the second scan line SLj−1. 
     One end of the capacitor Cst 1  is connected to the gate electrode of the first transistor T 11  as described above, and the other end is connected to the first driving voltage line VDL 1 . A cathode of the light emitting diode ED 1  may be connected to a terminal for transferring the second driving voltage ELVSS. A structure of the first pixel PX 1   ij  according to some example embodiments of the inventive concept is not limited to the structure illustrated in  FIG. 5 , and thus the number of transistors and the number of capacitors included in the first pixel PX 1   ij  and a connection relationship therebetween may be variously modified. 
     When the first switching signal SW 1  has an active level (e.g., a low level), the first switching transistor ST 11  may be turned on so that the first driving voltage line VDL 1  may receive the first driving voltage ELVDD. Therefore, the first pixel PX 1   ij  of the first display region DA 1  operates in response to the first data signal D 1   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the first switching signal SW 1  has an inactive level (e.g., a high level), the first switching transistor ST 11  may be turned off so that the first driving voltage line VDL 1  is unable to receive the first driving voltage ELVDD. Therefore, the first pixel PX 1   ij  of the first display region DA 1  does not emit light. 
     According to some example embodiments of the inventive concept, the second pixel PX 2   ij  includes first to seventh transistors T 21  to T 27 , a capacitor Cst 2 , and at least one light emitting diode ED 2 . Each of the first to seventh transistors T 21  to T 27  is a P-type transistor having an LTPS semiconductor layer. According to some example embodiments of the inventive concept, each of the first, second, fifth, sixth, and seventh transistors T 21 , T 22 , T 25 , T 26 , and T 27  may be a P-type transistor having an LTPS semiconductor layer, and each of the third and fourth transistors T 23  and T 24  may be an N-type transistor having an oxide semiconductor layer. However, embodiments of the inventive concept are not limited thereto, and thus at least one of the first to seventh transistors T 21  to T 27  may be an N-type transistor and the others may be P-type transistors. Furthermore, the circuit configuration of the second pixel PX 2   ij  according to some example embodiments of the inventive concept is not limited to that illustrated in  FIG. 5 . The first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 5  is merely an example, and thus the circuit configuration may be modified. 
     The connection relationship between the first to seventh transistors T 21  to T 27 , the capacitor Cst 2 , and the light emitting diode ED 2  of the second pixel PX 2   ij  and operations thereof are similar to the connection relationship between the first to seventh transistors T 11  to T 17 , the capacitor Cst 1 , and the light emitting diode ED 1  of the first pixel PX 1   ij  and operations thereof. Thus, overlapping descriptions are not provided below. 
     When the second switching signal SW 2  has an active level (e.g., a low level), the second switching transistor ST 12  may be turned on so that the second driving voltage line VDL 2  may receive the first driving voltage ELVDD. Therefore, the second pixel PX 2   ij  of the second display region DA 2  operates in response to the second data signal D 2   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the second switching signal SW 2  has an inactive level (e.g., a high level), the second switching transistor ST 12  may be turned off so that the second driving voltage line VDL 2  is unable to receive the first driving voltage ELVDD. Therefore, the second pixel PX 2   ij  of the second display region DA 2  does not emit light. 
     The first display region DA 1  or the second display region DA 2  is turned off since the first switching signal SW 1  or the second switching signal SW 2  transitions to an inactive level (e.g., a high level) when the display device  100  is out-folded. Power consumption of the display device  100  may be reduced by turning off an invisible region when the display device  100  is out-folded. 
       FIG. 6  illustrates first and second pixels and first and second switching circuits according to some example embodiments of the inventive concept. 
     The first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 6  may have the same circuit configuration as the first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 5 . 
     The display device  100  illustrated in  FIG. 4  may include a first switching circuit  281  and a second switching circuit  282  instead of the switching circuit  280 . 
     The first switching circuit  281  provides either the first driving voltage ELVDD or the second driving voltage ELVSS to the cathode of the light emitting diode ED 1  in the first pixel PX 1   ij  in response to the first switching signal SW 1 . 
     The first switching circuit  281  includes switching transistors ST 21  and ST 22 . The switching transistor ST 21  includes a first electrode connected to the first voltage line VDL 1 , a second electrode connected to the cathode of the light emitting diode ED 1 , and a control electrode for receiving the first switching signal SW 1 . The switching transistor ST 22  includes a first electrode connected to the cathode of the light emitting diode ED 1 , a second electrode connected to a terminal for transferring the second driving voltage ELVSS, and a control electrode for receiving the first switching signal SW 1 . The switching transistor ST 21  may be an N-type transistor, and the switching transistor ST 22  may be a P-type transistor. 
     When the first switching signal SW 1  has an active level (e.g., a low level), the switching transistor ST 21  is turned off and the switching transistor ST 22  is turned on so that the second driving voltage ELVSS is transferred to the cathode of the light emitting diode ED 1 . Therefore, the first pixel PX 1   ij  of the first display region DA 1  operates in response to the first data signal D 1   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the first switching signal SW 1  has an inactive level (e.g., a high level), the switching transistor ST 21  is turned on and the switching transistor ST 22  is turned off so that the first driving voltage ELVDD is transferred to the cathode of the light emitting diode ED 1 . Therefore, the first pixel PX 1   ij  of the first display region DA 1  does not emit light. 
     The second switching circuit  282  provides either the first driving voltage ELVDD or the second driving voltage ELVSS to the cathode of the light emitting diode ED 2  in the second pixel PX 2   ij  in response to the second switching signal SW 2 . 
     The second switching circuit  282  includes switching transistors ST 23  and ST 24 . The switching transistor ST 23  includes a first electrode connected to the second voltage line VDL 2 , a second electrode connected to the cathode of the light emitting diode ED 2 , and a control electrode for receiving the second switching signal SW 2 . The switching transistor ST 24  includes a first electrode connected to the cathode of the light emitting diode ED 2 , a second electrode connected to a terminal for transferring the second driving voltage ELVSS, and a control electrode for receiving the second switching signal SW 2 . The switching transistor ST 23  may be an N-type transistor, and the switching transistor ST 24  may be a P-type transistor. 
     When the second switching signal SW 2  has an active level (e.g., a low level), the switching transistor ST 23  is turned off and the switching transistor ST 24  is turned on so that the second driving voltage ELVSS is transferred to the cathode of the light emitting diode ED 2 . Therefore, the second pixel PX 2   ij  of the second display region DA 2  operates in response to the second data signal D 2   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the second switching signal SW 2  has an inactive level (e.g., a high level), the switching transistor ST 23  is turned on and the switching transistor ST 24  is turned off so that the first driving voltage ELVDD is transferred to the cathode of the light emitting diode ED 2 . Therefore, the second pixel PX 2   ij  of the second display region DA 2  does not emit light. 
       FIG. 7  illustrates first and second pixels and third and fourth switching circuits according to some example embodiments of the inventive concept. 
     The first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 7  may have the same circuit configuration as the first pixel PX 1   ij  and the second pixel PX 2   ij  illustrated in  FIG. 5 . 
     The display device  100  illustrated in  FIG. 4  may include a third switching circuit  283  and a fourth switching circuit  284  instead of the switching circuit  280 . 
     The third switching circuit  283  transfers the light emission control signal Ej to the first pixel PX 1   ij  in response to the first switching signal SW 1 . 
     The third switching circuit  283  includes a switching transistor ST 31 . The switching transistor ST 31  includes a first electrode for receiving the light emission control signal Ej, a second electrode connected to the gate electrode of each of the fifth and sixth transistors T 15  and T 16 , and a control electrode for receiving the first switching signal SW 1 . The switching transistor ST 31  may be a P-type transistor. 
     When the first switching signal SW 1  has an active level (e.g., a low level), the switching transistor ST 31  is turned on so that the light emission control signal Ej is transferred to the gate electrode of each of the fifth and sixth transistors T 15  and T 16 . Therefore, the first pixel PX 1   ij  of the first display region DA 1  operates in response to the first data signal D 1   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the first switching signal SW 1  has an inactive level (e.g., a high level), the switching transistor ST 31  is turned off so that the light emission control signal Ej is not transferred to the gate electrode of each of the fifth and sixth transistors T 15  and T 16 . Therefore, the first pixel PX 1   ij  of the first display region DA 1  does not emit light. 
     The fourth switching circuit  284  transfers the light emission control signal Ej to the second pixel PX 2   ij  in response to the second switching signal SW 2 . 
     The fourth switching circuit  284  includes a switching transistor ST 32 . The switching transistor ST 32  includes a first electrode for receiving the light emission control signal Ej, a second electrode connected to the gate electrode of each of the fifth and sixth transistors T 25  and T 26 , and a control electrode for receiving the second switching signal SW 2 . The switching transistor ST 32  may be a P-type transistor. 
     When the second switching signal SW 2  has an active level (e.g., a low level), the switching transistor ST 32  is turned on so that the light emission control signal Ej is transferred to the gate electrode of each of the fifth and sixth transistors T 25  and T 26 . Therefore, the second pixel PX 2   ij  of the second display region DA 2  operates in response to the second data signal D 2   i , the first scan signal Sj, the second scan signal Sj−1, and the light emission control signal Ej. 
     When the second switching signal SW 2  has an inactive level (e.g., a high level), the switching transistor ST 32  is turned off so that the light emission control signal Ej is not transferred to the gate electrode of each of the fifth and sixth transistors T 25  and T 26 . Therefore, the second pixel PX 2   ij  of the second display region DA 2  does not emit light. 
     The display device  100  includes a single bending axis according to some example embodiments of the inventive concept, but the display device  100  may include a plurality of bending axes. For example, the display device  100  including two bending axes may include at least one invisible region. Power consumption of the display device  100  may be reduced by turning off at least one invisible region when the folding detection signal F_S transitions to an active level. 
       FIG. 8  is a planar view illustrating a display device according to some example embodiments of the inventive concept. 
     Referring to  FIG. 8 , a display device  300  includes a pixel circuit  310 , a driving controller  320 , a scan driving circuit  330 , a first data driving circuit  351 , a second data driving circuit  352 , a light emission driving circuit  360 , a voltage generator  370 , and a switching circuit  380 . 
     The pixel circuit  310 , the scan driving circuit  330 , and the light emission driving circuit  360  may be formed on a display substrate  302 . 
     The driving controller  320 , the voltage generator  370 , and the switching circuit  380  may be mounted on a main substrate  304 . 
     Each of the first data driving circuit  351  and the second data driving circuit  352  may be configured as an independent integrated circuit (IC). Each of the first data driving circuit  351  and the second data driving circuit  352  may be mounted on a flexible circuit board  340 . The flexible circuit board  340  electrically connects the main substrate  304  and the display substrate  302 . 
       FIG. 8  illustrates an example chip-on-film (COF)-type first data driving circuit  351  and second data driving circuit  352 . According to some example embodiments of the inventive concept, the first data driving circuit  351  and the second data driving circuit  352  may be arranged on a non-display region NDA of the display substrate  302  using a chip-on-plastic (COP) method. 
       FIG. 9  is a diagram illustrating an example connection relationship between partial circuits illustrated in  FIG. 8 . 
     Referring to  FIG. 9 , the driving controller  320  receives the folding detection signal F_S, and outputs a third switching signal SW 3  and a fourth switching signal SW 4 . For example, when the folding detection signal F_S has an active level (e.g., a high level), the driving controller  320  deactivates the third switching signal SW 3  or the fourth switching signal SW 4 . 
     The voltage generator  370  generates a driving voltage VDD. The driving voltage VDD may be a power supply voltage of the first data driving circuit  351  and the second data driving circuit  352 , but is not limited thereto. For example, the driving voltage VDD may be an analog reference voltage required for generating a gradation voltage of each of the first data driving circuit  351  and the second data driving circuit  352 . 
     The switching circuit  380  may selectively provide the driving voltage VDD to the first data driving circuit  351  and the second data driving circuit  352  in response to the third switching signal SW 3  and the fourth switching signal SW 4 . 
     The switching circuit  380  includes a switching transistor ST 41  and a switching transistor ST 42 . The switching transistor ST 41  includes a first electrode for receiving the driving voltage VDD, a second electrode connected to the first data driving circuit  351 , and a gate electrode for receiving the third switching signal SW 3 . The switching transistor ST 42  includes a first electrode for receiving the driving voltage VDD, a second electrode connected to the second data driving circuit  352 , and a gate electrode for receiving the fourth switching signal SW 4 . 
       FIG. 10  is a planar view illustrating a display device according to some example embodiments of the inventive concept. 
     Referring to  FIG. 10 , a display device  400  includes a pixel circuit  410 , a driving controller  420 , a voltage generator  430 , a first data driving circuit  440 , a second data driving circuit  450 , and a switching circuit  460 . According to some example embodiments, the display device  400  may further include a scan driving circuit and a light emission driving circuit. 
     Each of the first data driving circuit  440  and the second data driving circuit  450  may be configured as an independent integrated circuit (IC). The first data driving circuit  440 , the second data driving circuit  450 , and the switching circuit  460  may be arranged on a non-display region NDA of a display substrate  402  using a chip-on-plastic (COP) method. 
     The driving controller  420  and the voltage generator  430  may be mounted on a main substrate  404 . A flexible circuit board  470  electrically connects the main substrate  404  and the display substrate  402 . 
       FIG. 11  is a diagram illustrating an example connection relationship between partial circuits illustrated in  FIG. 10 . 
     Referring to  FIG. 11 , the driving controller  420  receives the folding detection signal F_S, and outputs the third switching signal SW 3  and the fourth switching signal SW 4 . For example, when the folding detection signal F_S has an active level (e.g., a high level), the driving controller  420  deactivates at least one of the third switching signal SW 3  or the fourth switching signal SW 4 . 
     The voltage generator  430  generates a driving voltage VDD. The driving voltage VDD may be a power supply voltage of the first data driving circuit  440  and the second data driving circuit  450 , but is not limited thereto. For example, the driving voltage VDD may be an analog reference voltage required for generating a gradation voltage of each of the first data driving circuit  440  and the second data driving circuit  450 . 
     The switching circuit  460  may selectively provide the driving voltage VDD to the first data driving circuit  440  and the second data driving circuit  450  in response to the third switching signal SW 3  and the fourth switching signal SW 4 . 
     The switching circuit  460  includes a switching transistor ST 51  and a switching transistor ST 52 . The switching transistor ST 51  includes a first electrode for receiving the driving voltage VDD, a second electrode connected to the first data driving circuit  440 , and a gate electrode for receiving the third switching signal SW 3 . The switching transistor ST 52  includes a first electrode for receiving the driving voltage VDD, a second electrode connected to the second data driving circuit  450 , and a gate electrode for receiving the fourth switching signal SW 4 . 
       FIG. 12  is a diagram illustrating a circuit configuration of a display device according to some example embodiments of the inventive concept. 
     Referring to  FIG. 12 , a display device  500  includes the light emitter  110 , the light receiver  120 , a pixel circuit  510 , a driving controller  520 , a first light emission driving circuit  530 , a first scan driving circuit  540 , a second light emission driving circuit  550 , a second scan driving circuit  560 , a first data driving circuit  570 , a second data driving circuit  580 , and a voltage generator  590 . 
     The driving controller  520  receives the image signal RGB and the control signal CTRL, and converts a data format of the image signal RGB so that the image signal RGB is suitable for the pixel circuit  510 , so as to generate the first image data signal DATA 1  and the second image data signal DATA 2 . The driving controller  520  outputs a first start control signal FLM 1 , a second start control signal FLM 2 , a first light emission start signal ECTL 1 , a second light emission start signal ECTL 2 , the first data control signal DCS 1 , the second data control signal DCS 2 , and the folding detection control signal F_C. 
     The first light emission driving circuit  530  receives the first light emission start signal ECTL 1  from the driving controller  520 . The first light emission driving circuit  530  generates a plurality of light emission control signals in response to the first light emission start signal ECTL 1 , and outputs the light emission control signals to a plurality of first light emission control lines EL 11  to EL 1   n.    
     The first scan driving circuit  540  receives the first start control signal FLM 1  from the driving controller  520 . The first scan driving circuit  540  generates a plurality of scan signals, and outputs the plurality of scan signals to first scan lines SL 11  to SL 1   n.    
     The second light emission driving circuit  550  receives the second light emission start signal ECTL 2  from the driving controller  520 . The second light emission driving circuit  550  generates a plurality of light emission control signals in response to the second light emission start signal ECTL 2 , and outputs the light emission control signals to a plurality of second light emission control lines EL 21  to EL 2   n.    
     The second scan driving circuit  560  receives the second start control signal FLM 2  from the driving controller  520 . The second scan driving circuit  560  generates a plurality of scan signals, and outputs the plurality of scan signals to second scan lines SL 21  to SL 2   n.    
     The first data driving circuit  570  receives the first data control signal DCS 1  and the first image data signal DATA 1  from the driving controller  520 . The first data driving circuit  570  converts the first image data signal DATA 1  into first data signals, and outputs the first data signals to a plurality of first data lines DL 11  to DL 1   k . The first data signals are analog voltages corresponding to gradation values of the first image data signal DATA 1 . 
     The second data driving circuit  580  receives the second data control signal DCS 2  and the second image data signal DATA 2  from the driving controller  520 . The second data driving circuit  580  converts the second image data signal DATA 2  into second data signals, and outputs the second data signals to a plurality of second data lines DL 21  to DL 2   k . The second data signals are analog voltages corresponding to gradation values of the second image data signal DATA 2 . 
     The voltage generator  590  generates voltages required for operating the display device  500 . In this embodiment, the voltage generator  590  generates the first driving voltage ELVDD, the second driving voltage ELVSS, and the initialization voltage Vint, but embodiments of the inventive concept are not limited thereto. For example, the voltage generator  590  may further generate an analog reference voltage required for generating gradation voltages of the first data driving circuit  570  and the second data driving circuit  580 . The second driving voltage ELVSS may have a lower level than that of the first driving voltage ELVDD. 
     The pixel circuit  510  includes a plurality of first pixels PX 1  and a plurality of second pixels PX 2 . Each of the plurality of first pixels PX 1  is connected to a corresponding first data line among the plurality of first data lines DL 11  to DL 1   k , and is connected to a corresponding first scan line among the plurality of first scan lines SL 11  to SL 1   n . Each of the plurality of second pixels PX 2  is connected to a corresponding second data line among the plurality of the second data lines DL 21  to DL 2   k , and is connected to a corresponding second scan line among the plurality of second scan lines SL 21  to SL 2   n.    
     Each of the plurality of first pixels PX 1  and the plurality of second pixels PX 2  receives the first driving voltage ELVDD, the second driving voltage ELVSS, and the initialization voltage Vint. 
     Each of the first pixels PX 1  and the second pixels PX 2  may have the circuit configuration illustrated in  FIG. 5 . The first pixels PX 1  may be arranged in the first display region DA 1  illustrated in  FIG. 1 , and the second pixels PX 2  may be arranged in the second display region DA 2 . 
     Although it is illustrated and described that the first pixels PX 1  are connected to the first data driving circuit  570  via the first data lines DL 11  to DL 1   k , and the second pixels PX 2  are connected to the second data driving circuit  580  via the second data lines DL 21  to DL 2   k , embodiments of the inventive concept are not limited thereto. For example, the first data lines DL 11  to DL 1   k  and the second data lines DL 21  to DL 2   k  may be driven by a single data driving circuit. 
     The driving controller  520  outputs the folding detection control signal F_C to the light emitter  110 . For example, the driving controller  520  may periodically activate the folding detection control signal F_C during operation. 
     The light emitter  110  outputs the light ray signal in response to the folding detection control signal F_C. The light ray signal may be an infrared signal, but is not limited thereto. The light receiver  120  receives the light ray signal from the light emitter  110 . 
     As illustrated in  FIG. 3B , the light ray signal output from the light emitter  110  when the display device  100  is out-folded may be received by the light receiver  120 . The light receiver  120  outputs the folding detection signal F_S at an active level (e.g., a high level) when the light quantity of the received light ray signal has at least a predetermined level. This folding detection signal F_S is provided to the driving controller  520 . 
     The driving controller  520  regards the display device  500  as being out-folded when the folding detection signal F_S has an active level (e.g., a high level), and deactivates the first switching signal SW 1  or the second switching signal SW 2 . For example, the driving controller  520  may deactivate the first switching signal SW 1  when the folding detection signal F_S has an active level. When the first switching signal SW 1  is deactivated, the first pixels PX 1  may be turned off since the first driving voltage ELVDD is not provided to the first pixels PX 1 . 
     According to some example embodiments of the inventive concept, the display device  500  may further include a gyroscope sensor. The driving controller  520  may determine which one of the first display region DA 1  and the second display region DA 2  is an invisible region on the basis of a detection signal from the gyroscope sensor when the folding detection signal F_S transitions to an active level. The driving controller  520  deactivates the first switching signal SW 1  when the first display region DA 1  is determined to be an invisible region, and deactivates the second switching signal SW 2  when the second display region DA 2  is determined to be an invisible region. 
     According to some example embodiments of the inventive concept, the driving controller  520  may regard a preset one among the first display region DA 1  and the second display region DA 2  as an invisible region when the folding detection signal F_S has an active level. 
     The light emitter  110  outputs the light ray signal in response to the folding detection control signal F_C. The light ray signal may be an infrared signal, but is not limited thereto. The light receiver  120  receives the light ray signal from the light emitter  110 . 
     As illustrated in  FIG. 3B , the light ray signal output from the light emitter  110  when the display device  500  is out-folded may be received by the light receiver  120 . The light receiver  120  outputs the folding detection signal F_S at an active level (e.g., a high level) when the light quantity of the received light ray signal has at least a predetermined level. This folding detection signal F_S is provided to the driving controller  520 . 
       FIG. 13  is a timing diagram illustrating operation of the display device illustrated in  FIG. 12 . 
     Referring to  FIGS. 12 and 13 , the driving controller  520  provides the first start control signal FLM 1 , the first light emission start signal ECTL 1 , the second start control signal FLM 2 , and the second light emission start signal ECTL 2  of a normal mode to the first scan driving circuit  540 , the first light emission driving circuit  530 , the second scan driving circuit  560 , and the second light emission driving circuit  550  respectively while the folding detection signal F_S has an inactive level (e.g., a low level). 
     The driving controller  520  regards the display device  500  as being out-folded when the folding detection signal F_S has an active level (e.g., a high level), and maintains the first start control signal FLM 1  provided to the first scan driving circuit  540  at an inactive level (e.g., a low level). The first pixels PX 1  may be turned off because the first scan signals are not provided to the plurality of first scan lines SL 11  to SL 1   n  while the first start control signal FLM 1  is maintained at an inactive level. 
     Furthermore, when the folding detection signal F_S has an active level (e.g., a high level), the driving controller  520  maintains the first light emission start signal ECTL 1  provided to the first light emission driving circuit  530  at an inactive level (e.g., a low level). The first pixels PX 1  may be turned off since the first light emission control signals are not provided to the plurality of first light emission control lines EL 11  to EL 1   n  while the first light emission start signal ECTL 1  is maintained at an inactive level. 
     As described above, power consumption of the display device  500  may be reduced by turning off an invisible region when the display device  500  is out-folded. 
       FIG. 14  is a perspective view of a display device according to some example embodiments of the inventive concept.  FIG. 15  is a schematic cross-sectional view of the display device taken along line I-I′ of  FIG. 14 .  FIG. 16  is a perspective view illustrating a folded state of the display device of  FIG. 14 . 
     Referring to  FIG. 14 , a display device  600  according to some example embodiments of the inventive concept is a foldable display device. However, the flexible display device  600  according to embodiments is not limited to the illustrated shape, and thus the flexible display device  600  according to some example embodiments may include a display device having a part that is bent by tensile force or compressive force. 
     The flexible display device  600  may include a plurality of regions defined according to operation types. The flexible display device  600  according to some example embodiments may include the display panel including a bending region BA that is bent about a bending axis BX and a non-bending region NBA. The flexible display device  600  according to some example embodiments may include at least one bending region BA and at least one non-bending region NBA. Although  FIG. 14  illustrates one bending region BA and two non-bending regions NBA, embodiments of the inventive concept are not limited thereto. For example, the flexible display device  600  according to some example embodiments may include a plurality of bending regions BA. Furthermore, the flexible display device  600  according to some example embodiments may include three or more non-bending regions NBA. 
     In the flexible display device  600  according to some example embodiments, the bending region BA and the non-bending region NBA may be connected to each other. For example, the non-bending regions NBA may be arranged on both sides of the bending region BA according to some example embodiments as illustrated in  FIG. 14 . 
     As illustrated in  FIG. 14 , a display surface DS of the flexible display device  600  may include a plurality of regions. The flexible display device  600  includes a display region DA in which an image IM is displayed and a non-display region NDA adjacent to the display region DA. The non-display region NDA is one in which the image IM is not displayed. 
     Referring to  FIG. 15 , the display device  600  includes a base substrate BS, an insulating layer IL, a conductive layer ML, and a display substrate DP. The base substrate BS may include a plastic protection film. A material of the base substrate BS is not limited to plastic resins, and may include organic/inorganic composite materials. The base substrate BS may include a porous organic layer and an inorganic material filling pores of the organic material. The base substrate BS may further include a functional layer formed on a plastic film. According to some example embodiments of the inventive concept, the base substrate BS may not be provided. 
     The display substrate DP generates an image IM (see  FIG. 14 ) corresponding to input image data. The display substrate DP may further include a touch detection unit.  FIG. 15  illustrates an organic light emitting display substrate as a representative example of the display substrate DP. However, embodiments of the inventive concept are not limited thereto, and thus the display substrate DP may be a liquid crystal display substrate, a plasma display substrate, or an electrophoretic display substrate. According to some example embodiments, the display substrate DP may include a base layer, a pixel circuit layer located on the base layer, a light emitting element layer, and a thin-film encapsulation layer. 
     The insulating layer IL is located between the base substrate BS and the display substrate DP. The conductive layer ML is located between the base substrate BS and the display substrate DP. The insulating layer IL and the conductive layer ML may be positioned in the same layer. According to some example embodiments of the inventive concept, the insulating layer IL may cover an entire area of the conductive layer ML. 
     The conductive layer ML may include metals such as molybdenum, silver, titanium, copper, aluminum, or an alloy thereof. The conductive layer ML overlaps the bending region BA in a plan view. For example, a length MLL 1  of the conductive layer ML in the first direction DR 1  may be longer than the bending region BA. That is, the conductive layer ML may partially overlap the bending region BA in a plan view. 
     The display device  600  includes a resistance measurement circuit  610 . The resistance measurement circuit  610  is electrically connected to two end portions of the conductive layer ML, measures a resistance value of the conductive layer ML, and outputs a measured resistance value R. 
     Referring to  FIG. 16 , the display device  600  may be out-folded with respect to the bending axis BX. A radius of curvature BR of the bending region BA may be about 5 mm or less. For example, the radius of curvature BR may indicate a radius of curvature formed by an inner surface of the bending region BA in a bent or folded state. In detail, in the flexible display device  600  of an embodiment, the radius of curvature BR may be from about 1 mm to about 5 mm. 
     A length MLL 2  of the conductive layer ML in a state in which the display device  600  is out-folded may be larger than the length MLL 1  of the conductive layer ML in the first direction in a state in which the display device  600  is unfolded. Conductivity, i.e., resistance, of the conductive layer ML may vary since the conductive layer ML is stretched when the display device  600  is out-folded. 
     The display device  600  may detect a resistance change of the conductive layer ML when the length of the conductive layer ML changes from MLL 1  to MLL 2 , and may determine whether the display device  600  is out-folded according to the detected resistance value R. 
     Furthermore, the display device  600  may include the circuit elements illustrated in  FIGS. 4 to 12 . Power consumption of the display device  600  may be reduced by turning off an invisible region when the display device  600  is out-folded. 
       FIG. 17A  is a planar view illustrating a conductive layer and an insulating layer according to some example embodiments of the display device illustrated in  FIG. 14 .  FIG. 17B  is a schematic cross-sectional view of the conductive layer and the insulating layer taken along line II-II′ of  FIG. 17A . 
     Referring to  FIGS. 17A and 17B , the insulating layer IL is located between the base substrate BS and the display substrate DP. A conductive layer MML is located between the base substrate BS and the display substrate DP. The insulating layer IL and the conductive layer MML may be positioned in the same layer. According to some example embodiments of the inventive concept, the insulating layer IL may cover an entire area of the conductive layer MML. 
     The conductive layer MML may include metals such as molybdenum, silver, titanium, copper, aluminum, or an alloy thereof. The conductive layer MML includes a first conductive layer MLa and a second conductive layer MLb. The first conductive layer MLa and the second conductive layer MLb may be formed of the same material or different materials. 
     The first conductive layer MLa and the second conductive layer MLb may be arranged on the insulating layer IL in a lattice form. The first conductive layer MLa and the second conductive layer MLb arranged in a lattice form may be easily stretched when the display device  600  is out-folded. 
     The display device  600  may detect a resistance change of the conductive layer MML, and may determine whether the display device  600  is out-folded according to the detected resistance value R. 
     A display device configured as described above may reduce power consumption by turning off operation of an invisible region when the display device is folded. 
     Although aspects of some example embodiments of the present invention have been described, it is understood that the present invention should not be limited to these example embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as defined by the following claims and their equivalents.