Patent Publication Number: US-2021195766-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/585,246 filed on Sep. 27, 2019, which is a divisional of U.S. patent application Ser. No. 15/626,311 filed Jun. 19, 2017, now U.S. Pat. No. 10,455,710 issued on Oct. 22, 2019, which claims priority under 35 U.S.C. § 119 to Korean Patent Application No. 10-2016-0084846 filed in the Korean Intellectual Property Office on Jul. 5, 2016 the disclosures of which are incorporated by reference herein their entireties. 
    
    
     TECHNICAL FIELD 
     The present inventive concept relates to display device. 
     (b) Description of the Related Art 
     There are a variety of known display devices, which include a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED) display, a field effect display (FED), an electrophoretic display, and the like. 
     For example, the OLED display includes two electrodes and an organic emission layer interposed therebetween. Electrons injected from one electrode and holes injected from the other electrode are combined in the organic emission layer to generate excitons. The generated excitons release energy to emit light. 
     The OLED display may be light-weight and thin. In addition, the OLED display has high quality characteristics such as low power consumption, high luminance, arid high response speed. 
     Currently, foldable display devices that can be folded or unfolded and rollable display devices that can be rolled are being developed. To increase the lifetime of the foldable display devices or the rollable display devices, the amount of stress applied to the display panels thereof can be minimized. 
     SUMMARY 
     An exemplary embodiment of the present inventive concept provides a display device including: a display panel configured to display an image; and a winder configured to fix a first end portion of the display panel thereinto, wherein the winder may include a first fixing portion including a first external surface which is curved, and a second fixing portion that includes a second external surface which is curved and that faces the first external surface, wherein the first end portion of the display panel may be interposed between the first external surface and the second external surface. 
     The first external surface may include a first curved surface convexly protruded in a first direction, and a second curved surface that is adjacent to the first curved surface and that is concavely protruded in a second direction. 
     A curvature radius of the first curved surface may be the same as that of the second curved surface. 
     A curvature radius of the first curved surface may be different from that of the second curved surface. 
     The second external surface may include a third curved surface that faces the first curved surface, and a fourth curved surface that is adjacent to the third curved surface, and faces the second curved surface. 
     A curvature radius of the third curved surface may be the same as that of the fourth curved surface. 
     A curvature radius of the third curved surface may be different from that of the fourth curved surface. 
     A curvature radius of the first curved surface may be the same as that of the third curved surface. 
     A curvature radius of the second curved surface may be the same as that of the fourth curved surface. 
     The winder may have a cylindrical shape. 
     The first end portion of the display panel may be wound on the winder. 
     An adhesive layer may be interposed between the display panel and the first external surface or between the display panel and the second external surface. 
     The display panel may include a display area for displaying an image and a peripheral area positioned at a periphery of the display area, and the peripheral area of the display panel may be inserted in and fixed to the winder. 
     The display device may further include a fastening portion that fixes the first fixing portion and the second fixing portion to each other. 
     The fastening portion may include a bolt passing through the first fixing portion and the second fixing portion, and a nut for engaging with the bolt. 
     The fastening portion may include a first protrusion disposed at a first end portion of the first fixing portion, a second protrusion disposed at a second end portion of the second fixing portion, and a case configured to receive the first protrusion and the second protrusion. 
     The first fixing portion and the second fixing portion may be respectively made of stainless steel (SUS), Invar, nickel, cobalt, aluminum, titanium, an alloy thereof, an acryl, or wood. 
     An exemplary embodiment of the present inventive concept provides a display device including: a display panel configured to display an image; and a winder configured to be connected with a first end portion of the display panel, wherein the winder includes a cut-out groove in which the first end portion of the display panel is inserted and fixed. 
     The cut-out groove may include a first exposed surface and a second exposed surface facing each other, the first exposed surface may be curved, and the second exposed surface may be curved. 
     The first exposed surface may include a first curved surface convexly protruded in a first direction, and a second curved surface that is adjacent to the first curved surface and is concavely protruded in a second direction. 
     A curvature radius of the first curved surface may be the same as that of the second curved surface. 
     A curvature radius of the first curved surface play be different from that of the second curved surface. 
     The second exposed surface may include a third curved surface that faces the first curved surface, and a fourth curved surface that is adjacent to the third curved surface, and faces the second curved surface. 
     A curvature radius of the third curved surface may be the same as that of the fourth curved surface. 
     A curvature radius of h third curved surface may be different from that of the fourth curved surface. A curvature radius of the first curved surface may be the same as that of the third curved surface. 
     A curvature radius of the second curved surface may be the same as that of the fourth curved surface. 
     An exemplary embodiment of the present inventive concept provides a display device including a display panel including a display area and a peripheral area; and a winder that includes a first portion and a second portion, the first portion having a first curved surface facing a second curved surface of the second portion, wherein the winder is configured to secure a portion of the peripheral area between the first and second curved surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side view of a display device according to an exemplary embodiment of the present inventive concept. 
         FIG. 2  illustrates a perspective view enlarging a display panel and a winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept. 
         FIG. 3  illustrates an exploded view of the display panel and the winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept. 
         FIG. 4  illustrates a side view enlarging the display panel and the winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept. 
         FIG. 5  illustrates a schematic view of the display panel of  FIG. 4  according to an exemplary embodiment of the present inventive concept. 
         FIG. 6  consists of schematic views illustrating processes in which respective films are deformed when stacked films are bent. 
         FIG. 7  illustrates a perspective view in which a fastening portion is coupled with a display device of an exemplary embodiment of the present inventive concept. 
         FIG. 8  illustrates a cross-sectional view taken along line VIII-VIII of  FIG. 7  according to an exemplary embodiment of the present inventive concept. 
         FIG. 9  illustrates a variation of the fastening portion of  FIG. 7  according to an exemplary embodiment of the present inventive concept. 
         FIG. 10  illustrates a side view of a display device of  FIG. 9  according to air exemplary embodiment of the present inventive concept. 
         FIG. 11  illustrates a side view of a display device according to an exemplary embodiment of the present inventive concept. 
         FIG. 12  illustrates a state before a display panel is fixed to a winder of  FIG. 11  according to an exemplary embodiment of the present inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present inventive concept will be described more fully hereinafter with reference to the accompanying drawings. As those skilled in the art would realize, the described embodiments may be modified in various different ways, and thus, should not be limited to the embodiments set forth herein. Like reference numerals may designate like elements throughout the specification. 
     In the drawings, the thickness of layers, films, panels, regions, etc., may be exaggerated for clarity. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. 
     Hereinafter, a display device according to an exemplary embodiment of the present inventive concept will be described with reference to  FIG. 1  to  FIG. 5 . 
       FIG. 1  illustrates a side view of a display device according to an exemplary embodiment of the present inventive concept, and  FIG. 2  illustrates a perspective view enlarging a display panel and a winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept.  FIG. 3  illustrates an exploded view of the display panel and the winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept,  FIG. 4  illustrates a side view enlarging the display panel and the winder of  FIG. 1  according to an exemplary embodiment of the present inventive concept, and  FIG. 5  illustrates a schematic view of the display panel of  FIG. 4  according to an exemplary embodiment of the present inventive concept. 
     Referring to  FIG. 1  to  FIG. 4 , a display device of the present exemplary embodiment may include a display panel  100 , a first winder  300 , and a second winder  500 . In the present exemplary embodiment, opposite end portions of the display panel  100  may be respectively fixed to the insides of the first winder  300  and the second winder  500 . For example, a first end portion of the display panel  100  may be connected to the first winder  300  and a second end portion of the display panel  100  may be connected to the second winder  500 . In this case, in the first winder  300  and the second winder  500 , by respectively forming external circumferential surfaces of a first fixing portion  310  and a second fixing portion  330  to have a curved surface shape, the display panel  100  interposed between the first fixing portion  310  and the second fixing portion  330  may be fixed in a curved surface shape. As shown in  FIGS. 1-4 , the external circumferential surfaces of the first and second fixing portions  310  and  330  face each other. 
     The display panel  100  may display an image by emitting light. For example, the display panel  100  may be a display panel used in a liquid crystal display (LCD), a plasma display panel (PDP), a field effect display (FED), an electrophoretic display, or the like. In addition, the display panel  100  may be a display panel of an organic light emitting device (OLED). 
     The display panel  100  may be divided into a display area DA and a peripheral area PA. An image may be displayed in the display area DA. In addition, a plurality of pixels may be disposed in the display area DA. 
     The peripheral area PA corresponds to an area excluding the display area DA. A driving signal line, and a driver, etc. for driving the display area DA may be disposed in the peripheral area PA. In the present exemplary embodiment, the peripheral area PA of the display panel  100  may be inserted in and fixed to the first winder  300  and the second winder  500 . 
     For example, when the peripheral area PA is fixed to the first winder  300  and the second winder  500 , and when the first winder  300  and/or the second winder  500  are/is rotated, some of the display area DA as well as the peripheral area PA may be wound on the first winder  300  and/or the second winder  500 . 
     In the present exemplary embodiment, the peripheral area. PA may be disposed at opposite sides of the display area DA. However, the present inventive concept is not limited thereto, and the peripheral area PA may be disposed only at one side of the display area DA. When the peripheral area PA is disposed only at one side of the display area DA, only the first winder  300  may be combined with the display panel  100 . Since the second winder  500  applied to the present exemplary embodiment has a structure that is symmetrical with the first winder  300 , a detailed description of the second winder  500  will be omitted. 
     Referring to  FIG. 3  and  FIG. 4 , the first winder  300  may be combined with the peripheral area PA of the display panel  100 . For example, the peripheral area PA of the display panel  100  may be inserted in and fixed to the first winder  300 . 
     In the present exemplary embodiment, the first winder  300  include the first fixing portion  310  and the second fixing portion  330 . In this case, the first winder  300  may be a cylindrical member that has a cross-section of a third curvature radius R 3 . The first fixing portion  310  and the second fixing portion  330  may respectively correspond to portions of a cylindrical-shaped member that are cut and divided along a length direction of the first winder  300 . 
     The first fixing portion  310  may include a first external circumferential surface  350 . In this case, the first external circumferential surface  350  corresponds to a surface facing the second fixing portion  330 , and it may have a curved surface shape. 
     For example, the first external circumferential surface  350  may include a first curved surface  351  and a second curved surface  353  that are adjacent to each other. 
     The first curved surface  351  may have a convexly curved shape protruded toward the second fixing portion  330 . In this case, the first curved surface  351  may be curved with a first curvature radius R 1 . Herein, a cross-section of the first curved surface  351  cut in a direction perpendicular to a rotation axis of the first winder  300  may have a semi-circular shape with the first curvature radius R 1 . 
     The second curved surface  353  is adjacent to the first curved surface  351 , and it may have a concavely curved shape protruded toward the first fixing portion  310  away from the second fixing portion  330 . In this case, the second curved surface  353  may be curved with a second curvature radius R 2 . Herein, a cross-section of the second curved surface  353  cut in a direction perpendicular to a rotation axis of the first winder  300  may have a semi-circular shape with the second curvature radius R 2 . 
     As such, the first curved surface  351  and the second curved surface  353  adjacent to each other are respectively formed to have a convex shape and a concave shape. Thus, the cross-section of the first external circumferential surface  350  cut in the direction perpendicular to the rotation axis of the first winder  300  may be similar to a sinusoidal wave shape. 
     The second fixing portion  330  facing the first fixing portion  310  may include a second external circumferential surface  370 . The first external circumferential surface  350  of the first fixing portion  310  and the second external circumferential surface  370  of the second fixing portion  330  may face each other. In this case, the second external circumferential surface  370  may have a curved surface corresponding to the first external circumferential surface  350 . 
     For example, the second external circumferential surface  370  may include a third curved surface  371  and a fourth curved surface  373  that are adjacent to each other. 
     The third curved surface  371  may be a curved surface that faces the first curved surface  351  of the first fixing portion  310  and corresponds to the first curved surface  351 . For example, the third curved surface  371  may be formed with a shape opposite to that of the first curved surface  351 . In other words, the third curved surface  371  may have a concavely curved shape protruded toward the second fixing portion  330  away from the first fixing portion  310 . In this case, the third curved surface  371  may be curved with the first curvature radius R 1  like the first curved surface  351 . Similar to the first curved surface  351 , a cross-section of the third curved surface  371  cut in a direction perpendicular to the rotation axis of the first winder  300  may have a semi-circular shape with the first curvature radius R 1 . 
     The fourth curved surface  373  may be a curved surface that is adjacent to the third curved surface  371  and corresponds to the second curved surface  353 . For example, the fourth curved surface  373  may be formed with a shape opposite to that of the second curved surface  353 . In other words, the fourth curved surface  373  may have a convexly curved shape protruded toward the first fixing portion  310  away from the second fixing portion  330 . In this case, the fourth curved surface  373  may be curved with the second curvature radius R 2  like the second curved surface  353 . Similar to the second curved surface  353 , a cross-section of the fourth curved surface  373  cut in a direction perpendicular to the rotation axis of the first winder  300  may have a semi-circular shape with the second curvature radius R 2 . 
     In this case, the third curved surface  371  and the fourth curved surface  373  adjacent to each other are respectively formed to have a concave shape and a convex shape. Thus, a cross-section of the second external circumferential surface  370  cut in a direction perpendicular to the rotation axis of the first winder  300  may be similar to a sinusoidal wave shape and symmetrical to the first external circumferential surface  350 . 
     In the present exemplary embodiment, the first curvature radius R 1  and the second curvature radius R 2  may be the same. Accordingly, the first curved surface  351  and the second curved surface  353  may have the same size curved surface. The first curved surface  351  and the second curved surface  353  may also be convexly and concavely disposed in different directions, respectively. In addition, the third curved surface  371  and the fourth curved surface  373  may have the same size curved surface. The third curved surface  371  and the fourth curved surface  373  may be convexly and concavely disposed in different directions, respectively. 
     However, the present inventive concept is not limited thereto, and the first curvature radius R 1  and the second curvature radius R 2  may be different. For example, the first curvature radius R 1  may be greater than the second curvature radius R 2 , or the first curvature radius R 1  may be less than the second curvature radius R 2 . 
     In this case, the first external circumferential surface  350  of the first fixing portion  310  and the second external circumferential surface  370  of the second fixing portion  330  correspond to each other. In addition, the first external circumferential surface  350  and the second external circumferential surface  370  may closely contact each other. 
     Accordingly, in the present exemplary embodiment, by interposing the peripheral area PA of the display panel  100  between the first fixing portion  310  and the second fixing portion  330  facing each other, the peripheral area PA of the display panel  100  can be fixed in the first winder  300 . In other words, by interposing the peripheral area PA of the display panel  100  between the first external circumferential surface  350  and the second external circumferential surface  370 , and then, by bringing the first external circumferential surface  350  and the second external circumferential surface  370  to each other such that they contact or almost contact, the peripheral area PA of the display panel  100  can be tightly fixed in the first winder  300 . 
     Referring to  FIG. 5 , the peripheral area PA of the display panel  100  may correspond to the first external circumferential surface  350  (refer to  FIG. 3 ) and the second external circumferential surface  370  (refer to  FIG. 3 ) of the first winder  300  (refer to  FIG. 3 ). For example, the peripheral area PA of the display panel  100  may have not only a convexly curved surface protruded toward the second fixing portion  330  (refer to  FIG. 4 ) away from the first fixing portion  310  (refer to  FIG. 4 ) but also a convexly curved surface protruded toward the first fixing portion  310  (refer to  FIG. 4 ) away from the second fixing portion  330  (refer to  FIG. 4 ). 
     As such, since all of the surfaces of the peripheral area PA of the display panel  100  are convexly curved in different directions, the peripheral area PA can reduce stress in the display panel  100  of the rollable display device. 
     Hereinafter, when all of the surfaces of the peripheral area PA of the display panel  100  are convexly curved in different directions, a process in which stress in the display panel  100  is reduced will be described with reference to  FIG. 6 . 
       FIG. 6  consists of schematic views illustrating processes in which respective films are deformed when stacked films are bent. 
     As shown in  FIG. 6(A) , it is assumed that the display panel applied to the rollable display device has a structure in which a first substrate Layer 1 , an adhesive layer PSA, and the second substrate Layer 2  are stacked. In other words, a first layer is disposed at lower portion of the adhesive layer PSA and a second layer is disposed at a lower portion of the adhesive layer PSA. In this case, it is assumed that each length of the first substrate Layer 1 , the adhesive layer PSI, and the second substrate Layer 2  is a length L 1 . The first substrate Layer 1  and the second substrate Layer 2  may be a thin film transistor (TFT) layer, an emission layer, a touch screen panel (TSP) layer, a polarization layer, etc. that are positioned in the display panel. 
     As shown in  FIG. 6(B) , when the display panel of  FIG. 6(A)  is bent with a predetermined curvature, the first substrate Layer 1  the adhesive layer PSA, and the second substrate Layer 2  may be convexly bent in one direction. In this case, when the display panel is bent with the predetermined curvature, lengths of respective upper and lower surfaces of the first substrate Layer 1  and the second substrate Layer 2  excluding the adhesive layer PSI may kept the same. For example, each length of the upper and lower surfaces of the first substrate Layer 1  may still be identical to the length L 1 . The length shown in  FIG. 6(B)  represents an arc length. The length of the lower surface of the adhesive layer PSA contacting the upper surface of the first substrate Layer 1  may be the length L 1 ; however, the length of the upper surface of the adhesive layer PSA may be a length L 2  shorter than the length L 1 . Unlike the first substrate Layer 1  and the second substrate Layer 2 , since the adhesive layer PSA is made of a relatively soft adhesive material, when it is bent, the lengths of the upper and lower surfaces of the adhesive layer PSA may be different. For a closer visual of the differences in the lengths of the upper and lower surfaces of the adhesive layer PSA, refer to the slant in the sides of the adhesive layer PSA in  FIG. 6(B) . 
     In addition, the length of the lower surface of the second substrate Layer 2  positioned on the upper surface of the adhesive layer PSA may be the length L 2 . In other words, the length of the lower surface of the second substrate Layer 2  may be the same as the length of the upper surface of the second substrate Layer 2 . 
     In other words, when the first substrate Layer 1 , the adhesive layer PSA, and the second substrate Layer 2  are convexly bent in one direction, the length L 2  of the second substrate Layer 2  may be shorter than the length L 1  of the first substrate Layer 1 . Since the adhesive layer PSA is disposed between the first substrate Layer 1  and the second substrate Layer 2 , the second substrate Layer 2  positioned on the adhesive layer PSA may become shorter than the length L 1  before being bent. 
     Accordingly, a compressive force is applied to the display panel in the arrow direction shown in  FIG. 6(B) . In other words, when the sequentially stacked structure is bent, the compressive force may be applied to the display panel due to the adhesive layer PSA. Therefore, a stress is applied to the display panel including the adhesive layer PSA. 
     However, when the display panel of  FIG. 6(A)  in which the first substrate Layer 1  the adhesive layer PSA, and the second substrate Layer 2  are sequentially stacked is bent in different directions, the compressive force applied to the display panel may be offset. 
     Accordingly, in an exemplary embodiment of the present inventive concept, when the peripheral area PA of the display panel  100  is provided with the surfaces convexly curved in different directions, it is possible to reduce or disperse stress occurring in the display panel  100 . 
     In addition, since the first fixing portion  310  and the second fixing portion  330  closely contact each other, the first, fixing portion  310  and the second fixing portion  330  may be made of a hard material so that the display panel  100  is not separated therefrom. For example, the first fixing portion  310  and the second fixing portion  330  may be respectively made of at least one of stainless steel (SUS), Invar, nickel, cobalt, aluminum, titanium, an alloy thereof, an acryl, and wood. 
     Referring to  FIG. 7  to  FIG. 10 , a fastening portion  700  that closely and fixedly connects the first fixing portion  310  and the second fixing portion  330  may be combined with the first winder  300 . The fastening portion  700  closely fixes the first fixing portion  310  and the second fixing portion  330  to be able to fix the display panel  100  interposed therebetween. 
     In the present exemplary embodiment, referring to  FIG. 7  and  FIG. 8 , the fastening portion  700  may include a bolt  710  and a nut  730 . The bolt  710  may pass through the first fixing portion  310  and the second fixing portion  330 . The nut  730  may be engaged with the bolt  710  passing through the first fixing portion  310  and the second fixing portion  330 . As such, when the bolt  710  and the nut  730  are engaged, the first fixing portion  310  and the second fixing portion  330  closely and tightly contact each other such that the display panel  100  may be disposed within and fixed to the first winder  300 . 
     In this case, the bolt  710  and the nut  730  may be positioned at opposite sides of end portions of the first winder  300 . In other words, by positioning the bolt  710  and the nut  730  at opposite sides of the end portions of the first winder  300 , the first fixing portion  310  and the second fixing portion  330  can be secured to each other. However, the present inventive concept is not limited thereto, and the bolt  710  and the nut  730  may be positioned at another portion of the first winder  300 , for example, a central portion of the first winder  300 . 
       FIG. 9  and  FIG. 10  illustrate exemplary variations of the fastening portion  700  shown in  FIG. 7  and  FIG. 8 . For example, the fastening portion  700  may include a first protrusion  751 , a second protrusion  753 , and a cover  770 . 
     The first protrusion  751  is positioned at one end portion of the first fixing portion  310 , and protrudes in a length direction of the first fixing portion  310 . The second protrusion  753  may be positioned at one end portion of the second fixing portion  330  and protrude in a length direction of the second fixing portion  330 . In this case, the first protrusion  751  and the second protrusion  753  may be adjacent to each other. The second protrusion  753  is formed to have a shape corresponding to the first protrusion  751 . 
     The first protrusion  751  and the second protrusion  753  may be fitted into the cover  770 . External circumferential surfaces of the first protrusion  751  and the second protrusion  753  form a single cylindrical shape. Thus, an interior circumferential surface of the cover  770  may have a cylindrical shape corresponding to the external circumferential surfaces of the first protrusion  751  and the second protrusion  753 . In other words, external circumferential surfaces of the first protrusion  751  and the second protrusion  753  may be fitted into the interior circumferential surface of the cover  770 . 
     An adhesive layer may be interposed between the display panel  100  and the first fixing portion  310  and the second fixing portion  330  so that the display panel  100  may be tightly fixed between the first fixing portion  310  and the second fixing portion  330 . For example, an adhesive layer may be interposed between the display panel  100  and the first external circumferential surface  350  of the first fixing portion  310 , and an adhesive layer may be interposed between the display panel  100  and the second external circumferential surface  370  of the second fixing portion  330 . Further, adhesive layers may be provided at opposite sides of the display panel  100 . 
     Hereinafter, a display device according to an exemplary embodiment of the present inventive concept will be described with reference to  FIG. 11  and  FIG. 12 . In describing the present exemplary embodiment, a detailed description of the same components as those already described above will be omitted. 
       FIG. 11  illustrates a side view of a display device according to an exemplary embodiment of the present inventive concept, and  FIG. 12  illustrates a state before a display panel is fixed to a winder of  FIG. 11  according to an exemplary embodiment of the present inventive concept. 
     Referring to  FIG. 11  and  FIG. 12 , the display device of the present exemplary embodiment may include the display panel  100  and a third winder  600 . In the present exemplary embodiment, a cut-out groove  650  is formed in the third winder  600 , and the peripheral area (PA; refer to  FIG. 3 ) of the display panel  100  may be inserted into and fixed in the cut-out groove  650 . This is different from the display panel  100  of  FIG. 3  which fixes the peripheral area (PA; refer to  FIG. 3 ) of the display panel  100  between the first fixing portion  310  and the second fixing portion  330 , while the first fixing portion  310  and the second fixing portion  330  are separated from each other. For example, in this embodiment the display panel  100  is fixed in the single cut-out groove  650  that does not split the third winder  600  completely apart. 
     In the present exemplary embodiment, the cut-out groove  650  of the third winder  600  may be formed by a third external circumferential surface  610  and a fourth external circumferential surface  630  facing each other. In this case, the third external circumferential surface  610  and the fourth external circumferential surface  630  may have a curved surface, and the shapes of the third external circumferential surface  610  and the fourth external circumferential surface  630  may correspond to each other. 
     For example, the third external circumferential surface  610  may include a fifth curved surface  611  and a sixth curved surface  613  adjacent to each other. 
     The fifth curved surface  611  may have a convexly curved shape protruded toward the fourth external circumferential surface  630 . In this case, the fifth curved surface  611  may be curved with a fourth curvature radius R 4 . Herein, a cross-section of the fifth curved surface  611  cut in a direction perpendicular to the rotation axis of the third winder  600  may have a semi-circular shape with the fourth curvature radius R 4 . 
     The sixth curved surface  613  is adjacent to the fifth curved surface  611 , and it may be formed to have a concavely curved shape protruded toward the third external circumferential surface  610  away from the fourth external circumferential surface  630 . In this case, the sixth curved surface  613  may be curved with a fifth curvature radius R 5 . Herein, a cross-section of the sixth curved surface  613  cut in a direction perpendicular to the rotation axis of the third winder  600  may have a semi-circular shape with the fifth curvature radius R 5 . 
     As such, the fifth curved surface  611  and the sixth curved surface  613  adjacent to each other respectively have a convex shape and a concave shape. In addition, a cross-section of the third external circumferential surface  610  cut in a direction perpendicular to the rotation axis of the third winder  600  may be similar to a sinusoidal wave shape. 
     The fourth external circumferential surface  630  may include a seventh curved surface  631  and an eighth curved surface  633  adjacent to each other. 
     The seventh curved surface  631  may be a curved surface that faces the fifth curved surface  611  of the third external circumferential surface  610  and corresponds to the fifth curved surface  611 . For example, the seventh curved surface  631  may have a shape opposite to that of the fifth curved surface  611 . In other words, the seventh curved surface  631  may be concavely curved toward the fourth external circumferential surface  630  and protruded away from the third external circumferential surface  610 . In this case, the seventh curved surface  631  may be curved with the fourth curvature radius R 4  like the fifth curved surface  611 . Similar to the fifth curved surface  611 , a cross-section of the seventh curved surface  631  cut in a direction perpendicular to the rotation axis of the third winder  600  may have a semi-circular shape with the fourth curvature radius R 4 . 
     The eighth curved surface  633  may be a curved surface that is adjacent to the seventh curved surface  631  and corresponds to the sixth curved surface  613 . For example, the eighth curved surface  633  may have a shape opposite to that of the sixth curved surface  613 . In other words, the eighth curved surface  633  may have a convexly curved shape protruded toward the third external circumferential surface  610  and away from the fourth external circumferential surface  630 . In this case, the eighth curved surface  633  may be curved with the fifth curvature radius R 5  like the sixth curved surface  613  that faces the eighth curved surface  633 . Similar to the sixth curved surface  613 , a cross-section of the eighth curved surface  633  cut in a direction perpendicular to the rotation axis of the third winder  600  may have a semi-circular shape with the fifth curvature radius R 5 . 
     In this case, the seventh curved surface  631  and the eighth curved surface  633  adjacent to each other respectively have a concave shape and a convex shape. In addition, a cross-section of the fourth external circumferential surface  630  cut in a direction perpendicular to the rotation axis of the third winder  600  may be similar to a sinusoidal wave shape symmetrical to the third external circumferential surface  610 . 
     In the present exemplary embodiment, the fourth curvature radius R 4  and the fifth curvature radius R 5  may be the same. Accordingly, the fifth curved surface  611  and the sixth curved surface  613  may be formed with curved surfaces of the same size, and may be convexly and concavely disposed in different directions, respectively. In addition, the seventh curved surface  631  and the eighth curved surface  633  may be formed with curved surfaces of the same size, and may be concavely and convexly disposed in different directions, respectively. 
     However, the present inventive concept is not limited thereto, and the fourth curvature radius R 4  and the fifth curvature radius R 5  may be different. For example, fourth curvature radius R 4  may be greater than the fifth curvature radius R 5 , or the fourth curvature radius R 4  may be less than the fifth curvature radius R 5 . 
     In this case, the third external circumferential surface  610  and the fourth external circumferential surface  630  correspond to each other. Thus, the third external circumferential surface  610  and the fourth external circumferential surface  630  may closely contact each other. Accordingly, in the present exemplary embodiment, by disposing the peripheral area PA of the display panel  100  in the cut-out groove  650  formed by the third external circumferential surface  610  and the fourth external circumferential surface  630 , it is possible to fix the peripheral area PA of the display panel  100  in the third winder  600 . 
     According to an exemplary embodiment of the present inventive concept, it is possible to prevent a display panel of a display device from being broken due to stress. 
     While the present inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims.