Patent Publication Number: US-2023147918-A1

Title: Rollable device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 17/369,975, filed on Jul. 8, 2021. The content of the application is incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure generally relates to an electronic device, in particular to a rollable device. 
     2. Description of the Prior Art 
     In recent years, an electronic device or a deformable electronic device has become one of the focuses of the new generation of the electronic technology. Therefore, the demands for a flexible display device which may be incorporated into an electronic device have also been increasing accordingly, such as a rollable display device. 
     When the battery system board in the rollable display device is working, it generates heat and becomes a heat source. If the heat generated by the battery system board is not quickly dissipated due to the structural design, the resultantly formed hot spot may affect heat-sensitive components and increase the probability of display abnormalities, thereby reducing the reliability of the display device. Because consumers have higher and higher requirements for flexible display devices, it is one of the important issues for manufacturers to develop display devices of higher reliability. rollable device 
     SUMMARY OF THE DISCLOSURE 
     In view of this, the present disclosure proposes a rollable device with a novel thermal conductive structure. The novel thermal conductive structure may improve the thermal conductivity of the rollable device, or may increase the reliability of the rollable device. 
     According to some embodiments of the present disclosure, there is provided a rollable device including a rollable panel, a heat dissipation sheet and a supporting plate. The rollable panel has two surfaces opposed to each other. The heat dissipation sheet is disposed on one of the two surfaces of the rollable panel. The supporting plate is disposed between the rollable panel and the heat dissipation sheet. The heat dissipation sheet has a thermal conductivity greater than 200 W/mK. 
     According to the rollable device of the embodiments of the present disclosure, by adjusting the shapes, structures and/or thermal conductivity of the heat dissipation sheet, the heat generated by the heat source in the rollable device may be uniformly dispersed, thereby reducing the temperature of the hot spot. In such a way, the heat dissipation quality of the rollable device may be improved, or the reliability of the rollable display may be enhanced. 
     These and other objectives of the present disclosure will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of the display device according to the first embodiment of the present disclosure in an unrolled state or a partially rolled state. 
         FIG.  2    is a schematic top view of the display device according to the first embodiment of the present disclosure after being fully unrolled. 
         FIG.  3    is a schematic side view corresponding to  FIG.  2   . 
         FIG.  4    is a schematic side view of a variant embodiment corresponding to  FIG.  2   . 
         FIG.  5    is a schematic diagram of the display device in a partially rolled state according to the second embodiment of the present disclosure. 
         FIG.  6    is a schematic side view of an implementation corresponding to  FIG.  2   . 
         FIG.  7    is a schematic side view of another variant implementation corresponding to  FIG.  2   . 
         FIG.  8    is a schematic side view of another variant implementation corresponding to  FIG.  2   . 
         FIG.  9    is a schematic bottom view according to an implementation of the present disclosure. 
         FIG.  10    is a schematic bottom view according to an implementation of the present disclosure. 
         FIG.  11    is a schematic bottom view according to an implementation of the present disclosure. 
         FIG.  12    illustrates a schematic side view according to a variant implementation of the heat dissipation sheet of the present disclosure. 
         FIG.  13    illustrates a schematic side view according to a variant implementation of the heat dissipation sheet of the present disclosure. 
         FIG.  14    illustrates a schematic side view according to a variant implementation of the heat dissipation sheet of the present disclosure. 
         FIG.  15    is a schematic side view of the display device according to the third embodiment of the present disclosure. 
         FIG.  16    is a schematic diagram of the display device in an unrolled state according to the fourth embodiment of the present disclosure. 
         FIG.  17    is a schematic diagram of a variant embodiment of the display device according to the fourth embodiment of the present disclosure. 
         FIG.  18    is a schematic diagram of another variant embodiment of the display device according to the fourth embodiment of the present disclosure. 
         FIG.  19    is a schematic top view of the display device according to the fifth embodiment of the present disclosure corresponding to  FIG.  1   . 
         FIG.  20    is a schematic side view of a display device according to a variant embodiment of the fifth embodiment of the present disclosure. 
         FIG.  21    is a schematic top view of the display device corresponding to  FIG.  20    when it is unrolled. 
         FIG.  22    is a schematic side view of the display device corresponding to  FIG.  21    when it is rolled. 
         FIG.  23    is a schematic bottom view corresponding to the implementations of  FIG.  20    or of  FIG.  22   . 
         FIG.  24    is a schematic diagram corresponding to the implementations of  FIG.  20    or of  FIG.  22   . 
         FIG.  25    is a schematic partial cross-sectional side view of the display device according to the sixth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as described below. It is noted that, for purposes of illustrative clarity and being easily understood by the readers, various drawings of this disclosure show a portion of the touch display device, and certain elements in various drawings may not be drawn to scale. In addition, the number and dimension of each device shown in drawings are only illustrative and are not intended to limit the scope of the present disclosure. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. 
     In the following description and in the claims, the terms “include”, “comprise” and “have” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to”. 
     When a component or a film layer is referred to as “disposed on another component or another film layer” or “electrically connected to another component or another film layer”, it may mean that the component or film layer is directly disposed on another component or film layer, or directly connected to another component or film layer, or there may be other components or film layers in between. In contrast, when a component is said to be “directly disposed on another component or film” or “directly connected to another component or film”, there is no component or film which inserts between the two. 
     Although terms such as first, second, third, etc., may be used to describe diverse constituent elements, such constituent elements are not limited by the terms. The terms are used only to discriminate a constituent element from other constituent elements in the specification. The claims may not use the same terms, but instead may use the terms first, second, third, etc. with respect to the order in which an element is claimed. Accordingly, in the following description, a first constituent element may be a second constituent element in a claim. 
     The technical features in different embodiments described in the following may be replaced, recombined, or mixed with one another to constitute another embodiment without departing from the spirit of the present disclosure. 
       FIG.  1    is a schematic diagram of the display device  100  according to the first embodiment of the present disclosure in an unrolled state or a partially rolled state. Please refer to  FIG.  1   , the display device  100 , a rollable display panel  110 , an optional supporting plate  120  disposed under the rollable display panel  110 , and a heat dissipation sheet  140 . In some embodiments, the display device  100  may also optionally include an electronic system  130  physically and/or electrically connected to the rollable display panel  110 , for example, to provide the rollable display panel  110  with power, or with display information, or with signals, but the present disclosure is not limited thereto. The rollable display panel  110  has two surfaces which are opposite to each other, such as a first surface  111  and a second surface  112  (please see  FIG.  3   ). As shown in  FIG.  1    and in  FIG.  3   , the first surface  111  may be the display side of the rollable display panel  110 , and the second surface  112  may be the back side of the rollable display panel  110 . The heat dissipation sheet  140  may be disposed on one of the two surfaces of the rollable display panel  110 , for example, on a side of the second surface  112 , and may be rolled together with the rollable display panel  110 . 
     The rollable display panel  110  may include a flexible substrate  117  (please see  FIG.  3   ) and a display layer  118  (please see  FIG.  3   ) disposed on the flexible substrate. The flexible substrate may be a transparent or an opaque organic polymeric material, for example, may include polyimide (PI), polycarbonate (PC), polyethylene terephthalate (PET), or a combination of the above, but the present disclosure is not limited thereto. The flexible substrate may also include, for example, thin glass, or any suitable material. The display layer may include any type of display medium, of electronic elements and/or of light-emitting elements. For example, the display medium may include a liquid crystal, fluorescence, phosphor, a light-emitting diode, other suitable display media, or a combination of the above, but the present disclosure is not limited thereto. Electronic components may include (but are not limited to) transistors, capacitors, and/or wires. The light-emitting element may be an organic light-emitting diode (OLED), a micro light-emitting diode (micro-LED), a sub-millimeter light-emitting diode (mini-LED), a quantum dot light-emitting diode (quantum dot LED, QDLED), a nano wire light-emitting diode (nano wire LED) or a bar type LED, but the present disclosure is not limited thereto. The types of the light-emitting diodes are not limited. For example, it may be a flip chip type light-emitting diode or a vertical type light-emitting diode, but the present disclosure is not limited thereto. The rollable display panel  110  may generate heat when the display device  100  is in use. 
     The display device  100  of the present disclosure may be a flexible electronic device, and may be rolled with respect to a rolling axis (not shown) as the axis  109 . The display device  100  of the present disclosure may also have a rolling radius R in the rolled state, as shown in  FIG.  1   . The term “flexible” here refers to an electronic device which may be curved, bent, fold, rolled, flexible, stretch and/or other similar deformations, hereinafter “rollable” is used to represent the above-mentioned deformations. The display device  100  may further include an antenna device, a sensing device or a tiling device, but the present disclosure is not limited thereto. The antenna device may be, for example, a liquid crystal antenna. The tiling device may be, for example, a display tiling device or an antenna tiling device. It should be noted that the electronic device may be any combination of the above, but the present disclosure is not limited thereto. 
     The optional supporting plate  120  may be disposed on the second surface  112  of the rollable display panel  110 , and may be used to support the rollable display panel  110  when necessary. The supporting plate  120  may be a plate which has a thickness, such as an organic supporting plate material or an inorganic supporting plate material. The organic supporting plate material may include polyimide, and the inorganic supporting plate material may include a metal or an alloy, such as a stainless steel plate, but the present disclosure is not limited thereto. 
     The electronic system  130  may include one or more electronic components or computing units, for example may include a battery, a system board, a printed circuit board (PCB), a COF (chip on film), and a flexible printed circuit assembly, FPCA) or a combination of the above, but the present disclosure is not limited thereto. In the embodiment in  FIG.  1   , the electronic system  130  includes the flexible board module  1301  as an example, but the present disclosure is not limited thereto. The electronic system  130  may be the signal input terminal of the display device  100  to the rollable display panel  110 , and may generate heat when the display device  100  is in use and becomes a heat source. 
     According to some embodiments, the heat dissipation sheet  140  may have different designs according to different portions of the rollable display panel  110 . For example, as shown in  FIG.  1   , the rollable display panel  110  may include a first region  113  and a second region  114 . The rollable display panel  110  in the first region  113  and in the second region  114  may have different properties. The first region  113  and the second region  114  may be different portions, and the second region  114  may be a part outside of the first region  113 . According to some embodiments, as shown in  FIG.  1   , the first region  113  may be closer to the electronic system  130 , and the second region  114  may be farther away from the electronic system  130 . According to some embodiments, compared to the second region  114 , the first region  113  may be a portion with a higher temperature in the display device  100 , and have higher requirements for the heat dissipation. According to some embodiments, the first region  113  may be closer to the axis  109 , and the second region  114  may be farther away from the axis  109 . 
       FIG.  1    illustrates that at least a portion of the display device  100  is unrolled. As shown in  FIG.  1   , a region of the rollable display panel  110  surrounds the electronic system  130  by rolling. In this case, the first region  113  of the rollable display panel  110  may be a portion of the rollable display panel  110  surrounding the electronic system  130 , and may be an inner circle or a first circle. The second region  114  of the rollable display panel  110  may be a portion other than the first region  113 , and may be an outer circle or a second circle, surrounding the first region  113  (the inner circle). Because the electronic system  130  generates heat, the first region  113  of the rollable display panel  110  surrounding the electronic system  130  is directly affected by the heat to have influences on the performance of the panel. According to some embodiments, a heat dissipation sheet may be provided on some place of the first region  113  of the rollable display panel  110  to be able to improve the heat dissipation efficacy of the electronic system  130 , so that the rollable display panel  110  is less affected by the heat source of the electronic system  130 . According to some embodiments, a heat dissipation sheet is provided in at least some region of the first region  113  of the rollable display panel  110 . 
       FIG.  2    is a schematic top view of the display device  100  according to the first embodiment of the present disclosure after being fully unrolled, and  FIG.  3    is a schematic side view corresponding to  FIG.  2   . Please refer to  FIG.  2   , the rollable display panel  110  may include a bonding pad  150 . The flexible board module  1301  of the electronic system  130  of the display device  100  may be physically connected to the rollable display panel  110 , or the flexible board module  1301  may also be electrically connected to the rollable display panel  110  via the bonding pad  150 . According to some embodiments, the rollable display panel  110  may include a peripheral area  115  and an active area  116 . According to some embodiments, the peripheral area  115  may be located outside of the active area  116 , for example, the peripheral area  115  may surround the active area  116 . According to some embodiments, a part of the peripheral area  115  (the part  115 A of the peripheral area as shown in  FIG.  2   ) may be disposed between the active area  116  and the electronic system  130 , or a part  115 A of the peripheral area  115  may be closer to the electronic system  130  than the active area  116 . As shown in  FIG.  2   , the first region  113  of the rollable display panel  110  may be closer to the part  115 A of the peripheral area of the electronic system  130 , and the second region  114  may be a portion other than the first region  113 . For example, the second region  114  may include the active area  116  and a part  115 B of the peripheral area farther away from the electronic system  130 . 
     Please refer to  FIG.  3   , which is a schematic side view of the display device  100  in an unrolled state. The rollable display panel  110  may include a flexible substrate  117  and a display layer  118  disposed on the flexible substrate  117 . As shown in  FIG.  3   , according to some embodiments, the heat dissipation sheet  140  may include a first portion  141  and a second portion  142 . The bonding pad  150  may be disposed closer to the first portion  141  and farther away from the second portion  142 . In other words, the bonding pad  150  may be disposed closer to the first portion  141  than the second portion  142 . The first portion  141  may have a better heat dissipation characteristic, for example, have a better heat dissipation characteristic than the second portion  142 , but the present disclosure is not limited thereto. The better heat dissipation characteristic of the first portion  141  may be performed by means of a larger thickness, or performed by means of a material with a larger thermal conductivity, or performed by means of the two. Optionally, the first portion  141  and the second portion  142  of the heat dissipation sheet  140  may be interchanged. For example, the second portion  142  may be closer to the bonding pad  150  than the first portion  141 . 
     According to some embodiments, as shown in  FIG.  3   , the first portion  141  of the heat dissipation sheet  140  may be disposed corresponding to the first region  113  of the rollable display panel  110 , and the second portion  142  of the heat dissipation sheet  140  may be disposed corresponding to the second region  114  of the rollable display panel  110 , but the present disclosure is not limited thereto. For example, the first region  113  is closer to the electronic system  130  than the second region  114 , and the first portion  141  may also be closer to the electronic system  130  than the second portion  142 . According to some embodiments, the first region  113  is closer to the axis  109  for rolling than the second region  114 , and the first portion  141  may be closer to the axis  109  than the second portion  142  (shown in  FIG.  1   ). According to some embodiments, as shown in  FIG.  1   , the first region  113  may be an inner circle so the first portion  141  also corresponds to the inner circle, and the second region  114  is an outer circle so the second portion  142  may also correspond to the outer circle. According to some embodiments, compared to the second region  114 , the first region  113  may be closer to the heat source, and is a portion with higher heat dissipation requirements than the second region  114 . For example, the heat source may include the electronic system  130 . According to some embodiments, the first region  113  may be a fixed rolling region, and the second region  114  may be a re-rollable region (a to-and-fro rolling region). According to some embodiments, the rollable display panel  110  within the first region  113  may be fixedly accommodated in a housing, and the rollable display panel  110  within the second region  114  may be pulled out of the housing. The following embodiments respectively describe implementations of the first region  113  and of the second region  114 , and implementations of the first portion  141  and of the second portion  142  of the heat dissipation sheet  140 . 
     According to some embodiments, please refer to  FIG.  3   , the first region  113  may be a fixed rolling region, and the second region  114  may be a to-and-fro rolling region. The first portion  141  of the heat dissipation sheet  140  may be disposed corresponding to the first region  113 , and the second portion  142  may be disposed corresponding to the second region  114 . The design of the first portion  141  of the heat dissipation sheet  140  having a larger thickness than the second portion  142  may provide the fixed rolling region with a better heat dissipation characteristic. 
     According to some embodiments, the boundary between the first portion  141  and the second portion  142  of the heat dissipation sheet  140  may be the same as the boundary between the first region  113  and the second region  114  of the rollable display panel  110 . Or alternatively, according to some embodiments, the boundary between the first portion  141  and the second portion  142  of the heat dissipation sheet  140  may be different from the boundary between the first region  113  and the second region  114  of the rollable display panel  110 . According to some embodiments, the first portion  141  of the heat dissipation sheet  140  corresponds to the first region  113  of the rollable display panel  110 , and the second portion  142  of the heat dissipation sheet  140  corresponds to the second region  114  of the rollable display panel  110 . Specifically speaking, the first region  113  of the rollable display panel  110  may be an inner circle. For example, as shown in  FIG.  3   , at least some portion of the first portion  141  of the heat dissipation sheet  140  is disposed within the first region  113  (the inner circle) of the rollable display panel  110 , and at least some portion of the second portion  142  of the heat dissipation sheet  140  is disposed within the second region  114  (the outer circle) of the display panel  110 . As shown in  FIG.  3   , some portion of the first portion  141  of the heat dissipation sheet  140  is disposed within the first region  113  (the inner circle) of the rollable display panel  110 , and other portion of the first portion  141  of the heat dissipation sheet  140  may be disposed within the second region  114 . Although not shown in the figure, according to some embodiments, the entire of the first portion  141  of the heat dissipation sheet  140  may be disposed within the first region  113 . At least some portion of the second portion  142  of the heat dissipation sheet  140  may be disposed within the second region  114 , and other portion of the second portion  142  may be disposed within the first region  113 . 
     According to some embodiments, the better heat dissipation characteristic of the first portion  141  may be performed by means of the larger thickness T 1  of the first portion  141 . For example, the first region  113  of the rollable display panel  110  is closer to the electronic system  130  and may be a region requiring high heat dissipation ability.  FIG.  3    illustrates that the first portion  141  may correspond to the region requiring high heat dissipation ability (the first region  113 ), and the thickness T 1  of the first portion  141  may be greater than the thickness T 2  of the second portion  142 . For example, the thickness T 1  of the first portion  141  is larger than the thickness T 2  so that the first portion  141  disposed on the heat dissipation sheet  140  has a better heat dissipation characteristic. The larger thickness T 1  of the first portion  141  is beneficial to quickly dissipate the heat of the electronic system  130  to the entire first portion  141  and then to the second portion  142 . The thickness T 1  of the first portion  141  is thicker so that sufficient heat energy may be smoothly transferred to the heat dissipation sheet  140  to make the heat dissipation sheet  140  have better utilization efficiency. 
     According to some embodiments, a better heat dissipation characteristic of the first portion  141  may be performed by means of a material of the first portion  141  with a greater thermal conductivity. For example, the thermal conductivity of a material of the first portion  141  may be greater than the thermal conductivity of a material of the second portion  142 . Optionally, the thickness of the first portion  141  and of the second portion  142  may be the same or different as needed.  FIG.  4    is a schematic side view of a variant embodiment corresponding to  FIG.  2   . The heat dissipation sheet  140  may have a thermal conductivity greater than 200 W/mK.  FIG.  4    illustrates that the first portion  141  may correspond to a portion requiring high heat dissipation ability (the first region  113 ), and the thermal conductivity of the first portion  141  may be greater than the thermal conductivity of the second portion  142 . The suitable materials of the heat dissipation sheet  140  may include diamond, silver, copper, gold, aluminum, graphite, and a combination thereof, but the present disclosure is not limited thereto. If the first portion  141  of the heat dissipation sheet  140  uses a material with a greater thermal conductivity, it may be beneficial to quickly dissipate the heat of the electronic system  130  to the first portion  141 . According to some embodiments, if the heat dissipation sheet  140  includes a composite material, the thermal conductivity of the heat dissipation sheet  140  may reside in the thermal conductivity of the material with the greatest thermal conductivity. The thermal conductivity may be measured by looking up the tables to obtain the thermal conductivity corresponding to each component (or element) after analyzing the various components (or elements) of a heat dissipation sheet. Or alternatively, it may also be obtained by measuring a heat dissipation sheet with a thermal conductivity analyzer. According to some embodiments, the better heat dissipation characteristic of the first portion  141  may also be performed by means of the greater thermal conductivity of the first portion  141  to go with a larger thickness T 1  together. 
     Please refer to  FIG.  4    again. In addition to the electronic system  130  physically connected to the rollable display panel  110 , the electronic system  130  may also be physically connected to the heat dissipation sheet  140  by means of extension. For example, the electronic system  130  may also be bent backwards extending toward the back side of the rollable display panel  110  by rolling so that the two end points of the electronic system  130  may be respectively physically connected to the rollable display panel  110  and to the first portion  141  of the heat dissipation sheet  140 . Such a configuration is beneficial to dissipate the heat of the electronic system  130  directly and quickly to the first portion  141 . 
       FIG.  5    is a schematic diagram of the display device  100  in a partially rolled state according to the second embodiment of the present disclosure. According to the display device  100  of the second embodiment of the present disclosure, in a rolled state or a half-rolled state, it is possible that a second circle  113 ′ rolls to surround the first region  113  serving as the first circle. A rolled state may be a state which has curvature of most of the rollable display panel  110  or of the heat dissipation sheet  140 . The region of the rollable display panel  110  closer to the axis  109  may be referred to as a fixed rolling region of the rollable display panel  110 . In some embodiments, a fixed rolling region may be, for example, the first region  113  corresponding to the rollable display panel  110 . Whether it is in a rolled state or in an unrolled state, the fixed rolling region is kept rolled, that is, to form the first circle surrounding the electronic system  130 . The fixed rolling region may not have a display function or provide no display. The region other than the fixed rolling region of the rollable display panel  110  may be referred to as a to-and-fro rolling region of the rollable display panel  110 . The to-and-fro rolling region may, for example, include the second circle  113 ′ and correspond to the second region  114 . When the rollable display panel  110  is in an unrolled state, the to-and-fro rolling region is generally unrolled to become a plane (as shown in  FIG.  1   ). 
       FIG.  6    is a schematic side view of an implementation corresponding to  FIG.  2   . According to some embodiments, the active area  116  of the rollable display panel  110  may be designed in some region after the first circle. In details, the second region  114  of the rollable display panel  110  may include the active area  116 , and the first region  113  of the rollable display panel  110  may include a part  115 A of the peripheral area close to the electronic system  130 . As shown in  FIG.  6   , the first portion  141  of the heat dissipation sheet  140  corresponds to the first region  113  of the rollable display panel  110 , and the second portion  142  of the heat dissipation sheet  140  corresponds to the second region  114  of the rollable display panel  110 . For example, at least some portion of the first portion  141  of the heat dissipation sheet  140  may be disposed within the first region  113 , and at least some portion of the second portion  142  of the heat dissipation sheet  140  may be disposed within the second region  114  (the active region  116 ). Such a design is beneficial to reduce the probability of display abnormality of the display device  100  due to heat, and thus may increase the reliability of the rollable display device  100 . Specifically speaking, the first region  113  of the rollable display panel  110  may be the part  115 A of the peripheral area close to the electronic system  130 . For example, as shown in  FIG.  6   , according to some embodiments, all of the first portion  141  of the heat dissipation sheet  140  may be disposed within the first region  113  (the part  115 A of the peripheral area). At least some portion of the second portion  142  of the heat dissipation sheet  140  may be disposed within the second region  114  (the active area  116 ), and other portion of the second portion  142  may be disposed within the first region  113 . Although not shown in the figure, according to some embodiments, a portion of the first portion  141  of the heat dissipation sheet  140  is disposed within the first region  113  (the part  115 A of the peripheral area) of the rollable display panel  110 , and other portion of the first portion  141  is disposed within the second region  114  (the active area  116 ) of the rollable display panel  110 , and all of the second portion  142  of the heat dissipation sheet  140  is disposed within the second region  114  (the active area  116 ) of the rollable display panel  110 . 
     According to some embodiments, the surface of the heat dissipation sheet  140  may be provided with an opening  240 . The opening  240  may be a recess and/or a trench.  FIG.  7    is a schematic side view of another variant implementation corresponding to  FIG.  2   . The thickness of the heat dissipation sheet  140  in the fixed rolling region (the first region  113 ) may be T 3 , and the thickness of the heat dissipation sheet  140  in the to-and-fro rolling region (the second region  114 ) has a smaller thickness. The heat dissipation sheet  140  may include at least one recess  143  so that a protrusion  145  of the heat dissipation sheet  140  may be formed between the recesses  143 . The recess  143  may be recessed into the surface  140 S of the heat dissipation sheet  140 , but the recess  143  may not expose the rollable display panel  110  or the supporting plate  120  on the other side of the heat dissipation sheet  140 . In other words, the recess  143  may not penetrate the heat dissipation sheet  140 . By providing at least one recess  143  on the heat dissipation sheet  140 , the average thickness of the heat dissipation sheet  140  may be reduced. The heat-dissipating surface area of the heat dissipation sheet  140  may also be increased, and/or the flexibility of the to-and-fro rolling region may also be increased to facilitate to increase the reliability of the rollable display panel  110  in the to-and-fro rolling region (the second region  114 ). The calculation method of the average thickness is shown in  FIG.  9    and in the corresponding descriptions below. 
       FIG.  8    is a schematic side view of another variant implementation corresponding to  FIG.  2   . The heat dissipation sheet  140  may include at least one opening  240  (a trench  144 ). The trench  144  may be recessed into the surface  140 S of the heat dissipation sheet  140 , and the bottom of the trench  144  may also expose some part of the rollable display panel  110  or of the supporting plate  120 .  FIG.  8    illustrates that the trench  144  may expose some part of the supporting plate  120 . In other words, the trench  144  may penetrate the heat dissipation sheet  140  so that a protrusion  145  of the heat dissipation sheet  140  may be formed between the trenches  144 . With the design of the opening  240 , the average thickness of the heat dissipation sheet  140  may be reduced. In addition, the heat-dissipating surface area of the heat dissipation sheet  140  may also be increased, and/or the flexibility of the to-and-fro rolling region may also be increased, to more beneficially increase the reliability of the rollable display panel  110  in the to-and-fro rolling region. 
       FIG.  9    is a schematic bottom view according to an implementation of the present disclosure. According to some embodiments, as shown in  FIG.  9   , the heat dissipation sheet  140  may include a plurality of openings  240 . The opening  240  may be a recess  143 , a trench  144 , or a combination thereof. The extending direction D 11  of the recess  143  or of the trench  144  may be perpendicular to the unrolling direction D 2  of the display device  100 . As shown in  FIG.  10   , the extending direction D 12  of the recess  143  or of the trench  144  may be designed to be parallel to the unrolling direction D 2  of the display device  100 . The calculation method of the average thickness of the heat dissipation sheet  140  is as follows. Please refer to the method shown in  FIG.  9   . For example, the width of the heat dissipation sheet  140  is W, and the width W may be the width in the direction perpendicular to the unrolling direction D 2  of the display device  100 . The width of the heat dissipation sheet  140  may be divided into four quarters, such as 0.25 W, 0.5 W, 0.75 W are taken, and the total thicknesses of 10 points along each horizontal line are respectively measured and then averaged to get the average thickness of the heat dissipation sheet  140 , but the present disclosure is not limited thereto. If the designs of the first portion  141  are different from the designs of the second portion  142  of the heat dissipation sheet  140 , the average thicknesses of the first portion  141  and of the second portion  142  may be calculated separately. According to some embodiments, the first portion  141  of the heat dissipation sheet  140  may be provided corresponding to the first region  113 , and the second portion  142  may be provided corresponding to the second region  114 . The thickness of the first portion  141  in the first region  113  may be measured, and the thickness of the second portion  142  in the second region  114  may be measured. The thicknesses of the first portion  141  and of the second portion  142  of the heat dissipation sheet  140  in the first region  113  and in the second region  114  may be respectively measured by referring to the above-mentioned method of dividing the width of the heat dissipation sheet  140  into four quarters. For every 10 points taken in a portion, the distance between two adjacent points may be equal. In other words, there may be 10 points of the same pitch. However, the measurement of the average thickness is not limited thereto. According to some embodiments, two points in one portion may also be taken for the thickness measurement. According to some embodiments, samples of the heat dissipation sheet  140  of the same size, for example, a sample of 1 cm 2 , may be taken respectively out of the first region  113  and out of the second region  114  of the rollable display panel  110  to be subjected to the measurement of the thickness. According to some embodiments, the thickness of the heat dissipation sheet  140  may not be limited to the average thickness, and may also be the thickness at a specific location. 
       FIG.  11    is a schematic bottom view of an implementation according to the present disclosure. In another implementation of the present disclosure, as shown in  FIG.  11   , the recesses  143  or the trenches  144  may form an uneven distribution along the unrolling direction D 2  of the display device  100 , so that the average thickness of different portions may be different. For example, if the flexibility requirement of the first region  113  is greater than that of the second region  114 , the region closer to the first region  113  of the electronic system  130  may be optionally provided with more recesses  143  or trenches  144  as needed, that is, the distribution density of the recesses  143  or of the trenches  144  may be larger, where the distribution density may represent the number of the recesses  143  or of the trenches  144  per unit area of the heat dissipation sheet  140 , or the area occupied by the recesses  143  or by the trenches  144  per unit area of the heat dissipation sheet  140 , but the present disclosure is not limited thereto. 
       FIG.  12    illustrates a schematic side view of a variant implementation of the heat dissipation sheet  140 . The heat dissipation sheet  140  may have one or more protrusions  145 . For example, the heat dissipation sheet  140  may include a first portion  141  and a second portion  142 , and a plurality of protrusions  145  may be provided in the to-and-fro rolling region corresponding to the second portion  142 . The density of the protrusions  145  may be optionally different, but the present disclosure is not limited thereto. The protruding portion  145  may increase the heat-dissipating surface area of the heat dissipation sheet  140 , or may also increase the flexibility of the to-and-fro rolling region, thereby facilitating to increase the reliability of the rollable display panel  110  in the to-and-fro rolling region. The density of the protrusions  145  may adjust the rolling radius R of the rollable display panel  110 . 
       FIG.  13    is a schematic side view of a variant implementation of the heat dissipation sheet  140 . The thickness T 5  of the first portion  141  of the heat dissipation sheet  140  may be greater than the thickness T 6  of the second portion  142 . The first portion  141  and the second portion  142  may be evenly provided with the protrusions  145  and with the openings  240 , but the present disclosure is not limited thereto. The greater thickness of the fixed rolling region may make sufficient heat energy smoothly dissipated to all the protrusions  145 , so that all the protrusions  145  are most efficiently used. 
       FIG.  14    is a schematic side view of a variant implementation of the heat dissipation sheet  140 . One or more protrusions  145  and openings  240  may be evenly provided in the second portion  142  of the heat dissipation sheet  140 . The thickness T 5  of the first portion  141  of the heat dissipation sheet  140  may be greater than the thickness T 6  of the second portion  142 , but the present disclosure is not limited thereto. The thickness design of this variant implementation reduces from the first portion  141  which is closer to the electronic system to the second portion  142 , so that the heat dissipation sheet  140  may absorb enough heat from the electronic system part to quickly dissipate it to the surrounding thinner portion. 
       FIG.  15    is a schematic side view of the display device  100  according to the third embodiment of the present disclosure. If it is needed to increase the heat dissipation characteristic of the display device  100 , it may also be performed by means of deepening a trench  121  of the heat dissipation sheet  140  into the optional supporting plate  120 . For example, the heat dissipation sheet  140  may include a first portion  141  disposed in the first region  113  and a second portion  142  disposed in the second region  114 . There may be at least one trench  121  in the optional supporting plate  120 . At least one trench  121  of the supporting plate  120  may be recessed into the surface  120 S of the supporting plate  120 , and the trench  121  may further expose a region of the rollable display panel  110 . The trench  121  goes deep into the surface  120 S of the supporting plate  120 , or the supporting plate  120  may also be designed to be thinner to increase the flexibility of the to-and-fro rolling region when being frequent rolled, and to be beneficial to increase the reliability of the rollable display panel  110  in the to-and-fro rolling region. The location of the trench  144  of the heat dissipation sheet  140  may coincide with the location of the hole of the trench  121  of the supporting plate  120  to reduce the risk of peeling off of the two layers when the rollable display panel  110  is rolled to maintain the adhesion between the two layers. According to some embodiments, an auxiliary heat dissipation material  122  may also be used to fill the trench  121  and/or the trench  144 . For example, the auxiliary heat dissipation material  122  may fill some of the trenches  121  and/or of the trenches  144 , or the auxiliary heat dissipation material  122  may partially fill the trenches  124  and/or the trenches  144  without filling up the trenches  121  and/or trenches  144 , but the present disclosure is not limited thereto. The auxiliary heat dissipation material  122  may be thermal grease, thermal gel, or a combination thereof, but the present disclosure is not limited thereto. 
       FIG.  16    is a schematic diagram of the display device  100  in an unrolled state according to the fourth embodiment of the present disclosure. According to some embodiments, in  FIG.  16   , at least some of the rollable display panel  110  is unrolled. The display device  100  of the fourth embodiment of the present disclosure may further include a housing  160 . In a rolled state, the housing  160  may accommodate the rollable display panel  110  and the heat dissipation sheet  140 . According to some embodiments, the housing  160  may accommodate the rollable display panel  110 , the supporting plate  120 , and an electronic system (not shown). When the housing  160  rotates in the D 3  direction, the rollable display panel  110  may be pulled out from the housing  160  together with the heat dissipation sheet  140  to obtain the unrolled state of the display device  100 . Please refer to the above, an electronic system (not shown) and/or the rollable display panel  110  may generate heat when the display device  100  is in use. According to the display device  100  of the fourth embodiment of the present disclosure, the display device  100  includes a housing  160 , and at least some of the heat generated by the rollable display panel  110  may be dissipated by the housing  160  via the heat dissipation sheet  140 . In other words, according to some embodiments, the heat-dissipating direction of the heat generated by the rollable display panel  110  may be: first through the heat dissipation sheet, and then through the housing. Theoretically, the direction of heat transfer is from high temperature to low temperature. Therefore, by respectively detecting the surface temperatures of the rollable display panel  110 , of the heat dissipation sheet  140 , and of the housing  160 , the heat transfer direction may be identified from the temperature gradient. According to some embodiments, the detection location of the surface temperature of the rollable display panel  110  may be a location closer to the bonding pad  150 . According to some embodiments, the detection location of the surface temperature of the rollable display panel  110  may be a location closer to the rolling axis. According to some embodiments, the detection location of the surface temperature of the rollable display panel  110  may be the first portion of the rollable display panel  110 . According to some embodiments, the detection location of the surface temperature of the rollable display panel  110  may be a location corresponding to the first portion  141  of the heat dissipation sheet  140 . According to some embodiments, the detection location of the surface temperature of the rollable display panel  110  may correspond to a location closer to the first portion  141  of the heat dissipation sheet  140 . 
     Please refer to  FIG.  3    together with  FIG.  16   .  FIG.  3    shows the rollable display panel  110  in a fully unrolled state, and  FIG.  16    shows some region of the rollable display panel  110  in a rolled state. Some region of the rollable display panel  110  may be rolled to be accommodated in a housing  160 . According to some embodiments, the first region  113  of the rollable display panel  110  may be an interior housing region, that is, the second region  114  may be an exterior housing region. The first portion  141  of the heat dissipation sheet  140  may be disposed corresponding to the first region  113 , and the second portion  142  may be disposed corresponding to the second region  114 . In other words, the interior housing region may be the portion of the heat dissipation sheet  140  which is accommodated in the housing  160  when the display device  100  is in the fully unrolled state, and the exterior housing region may be the portion of the heat dissipation sheet  140  which is not accommodated in the housing  160  when the display device  100  is in the fully unrolled state. Compared with the exterior housing region, the interior housing region may have a better heat dissipation characteristic. The better heat dissipation of the interior housing region may be performed by means of a larger thickness T 1  of the heat dissipation sheet  140  in the interior housing region (the first region  113 ). For example, the thickness T 1  of the interior housing region may be greater than the thickness T 2  of the exterior housing region (the second region  114 ). Please refer to the aforementioned descriptions for the details of the heat dissipation sheet  140  with a larger thickness T 1  in the interior housing region. 
       FIG.  17    is a schematic diagram of a variant embodiment of the display device  100  according to the fourth embodiment of the present disclosure. As shown in  FIG.  16    or in  FIG.  17   , ventilation holes  163  may be provided in the housing  160  to increase the heat dissipation ability of the housing. The ventilation holes  163  on the housing  160  may include a plurality of holes as shown in  FIG.  16   , or concentric rings as shown in  FIG.  17   , but the present disclosure is not limited thereto. 
       FIG.  18    is a schematic diagram of another variant embodiment of the display device  100  according to the fourth embodiment of the present disclosure. According to some embodiments, ventilation blades  164  may be provided in the housing  160  to increase the heat dissipation ability of the housing  160 . For example, the ventilation blades  164  in the housing  160  may facilitate to generate air turbulence to increase the heat dissipation ability of the housing  160  when the heat dissipation sheet  140  is retracted into the housing  160  or pulled out of the housing  160  to rotate in the D 3  direction, but the present disclosure is not limited thereto. 
       FIG.  19    is a schematic top view of the display device  100  according to the fifth embodiment of the present disclosure corresponding to  FIG.  1   .  FIG.  19    shows the heat dissipation sheet  140  of the display device  100  to correspond to the size of the rolling radius R in the rolled state of  FIG.  1   . For example, according to some embodiments, the width of the heat dissipation sheet  140  may be greater than 0.5 W if the width of the rollable display panel  110  is W, but the present disclosure is not limited thereto. The length of the heat dissipation sheet  140  may be greater than 2πR when the rolling radius of the heat dissipation sheet  140  in the rolled state is R. A portion of the heat dissipation sheet  140  may still be exposed to the outside when the heat dissipation sheet  140  is in the rolled state corresponding to  FIG.  1    as the length of the heat dissipation sheet  140  is greater than 2πR to facilitate to increase the heat dissipation ability of the heat dissipation sheet  140 . 
       FIG.  20    is a schematic side view of a display device  101  according to a variant embodiment of the fifth embodiment of the present disclosure. According to some embodiments, as shown in  FIG.  20   , the display device  100  may have more than one rollable portion, such as a first rollable portion  105  and a second rollable portion  106 , and the first rollable portion  105  and the second rollable portion  106  may be respectively disposed on the opposite sides of the rollable display panel  110 . The first rollable portion  105  and the second rollable portion  106  may respectively have a rolling radius R in a rolled state. Disposed between the first rollable portion  105  and the second rollable portion  106 , there may be a display portion  107  of the rollable display panel  110 . At least one of the first rollable portion  105  and the second rollable portion  106  may include one or more electronic components or computing units, for example include a bonding pad (not shown), a battery (not shown), a system board (not shown), a printed circuit board (PCB), a chip on film (COF), a flexible printed circuit assembly (FPCA) (not shown) or a combination of the above, but the present disclosure is not limited thereto. At least one of the first rollable portion  105  and the second rollable portion  106  may include an electronic system (not shown) of the display device  100 , and a heat dissipation sheet  140  may be provided between the electronic system (not shown) and the rollable display panel  110 , but the present disclosure is not limited thereto. In this variant embodiment, the electronic system  130  may also be provided in the display portion  107  to be physically and/or electrically connected to the heat dissipation sheet  140  in the display portion  107 . Therefore, the electronic system  130  is still exposed when the rollable display panel  110  is rolled to facilitate to improve the heat dissipation of the rollable display device  100 . That is to say, the electronic system  130  physically and/or electrically connected to the heat dissipation sheet  140  in the display portion may quickly dissipate heat to everywhere through the heat dissipation sheet  140  whether the rollable display panel  110  is rolled or unrolled, for example, to quickly dissipate heat to the rollable display panel  110  in the display portion  107  and/or to quickly dissipate heat to at least one of the first rollable portion  105  and the second rollable portion  106  to facilitate the display device  100  to have a better heat dissipation characteristic, but the present disclosure is not limited thereto. 
       FIG.  21    is a schematic top view of the display device  101  corresponding to  FIG.  20    when it is unrolled. The width of the heat dissipation sheet  140  may be greater than 0.5 W if the width of the rollable display panel  110  is W, but the present disclosure is not limited thereto. The length of the heat dissipation sheet  140  may be greater than L if the length of the rollable display panel  110  in the display portion is L, so that the heat dissipation sheet  140  may extend into at least one of the first rollable portion  105  and the second rollable portion  106  to facilitate to increase the heat dissipation ability of the heat dissipation sheet  140 . 
       FIG.  22    is a schematic side view of the display device  101  corresponding to  FIG.  21    when it is rolled. The heat dissipation sheet  140  in at least one of the first rollable portion  105  and the second rollable portion  106  may include at least one of the recess  143  and the trench  144 , and the quantity of the recess  143  and the trench  144  may be optional as needed. Please refer to the aforementioned descriptions for the details and advantages of the recess  143  and the trench  144 .  FIG.  22    illustrates that the first rollable portion  105  and the second rollable portion  106  may include recesses  143  and the trenches  144 , but the present disclosure is not limited thereto. 
       FIG.  23    is a schematic bottom view corresponding to the implementations of  FIG.  20    or of  FIG.  22   . The heat dissipation sheet  140  may include a recess  143  and a trench  144 , and the recess  143  and the trench  144  may be disposed in at least one of the first rollable portion  105 , the second rollable portion  106  and the display portion  107 .  FIG.  23    shows that the recesses  143  and the trenches  144  may be provided in the first rollable portion  105 , in the second rollable portion  106  and in the display portion  107 , but the present disclosure is not limited thereto. 
       FIG.  24    is a schematic diagram corresponding to the implementations of  FIG.  20    or of  FIG.  22   . The electronic system  130  may be provided under the rollable display panel  110 , and the electronic system  130  may also be provided between the first rollable portion  105  and the second rollable portion  106 , but the electronic system  130  is exposed to facilitate to increase the heat dissipation ability of the display device  101 . 
       FIG.  25    is a schematic partial cross-sectional side view of the display device  100  according to the sixth embodiment of the present disclosure. The display device  100  of the sixth embodiment of the present disclosure may include a heat dissipation frame  170  to facilitate the heat dissipation along the planar direction and homogenizes hot spots. For example, the heat dissipation frame  170  may be disposed under the heat dissipation sheet  140 , so that the heat dissipation sheet  140  may be disposed between the heat dissipation frame  170  and the rollable display panel  110  or the optional supporting plate  120 . For example, the heat dissipation frame  170  may be disposed in the first region  113  or disposed adjacent to the axis  109 , but the present disclosure is not limited thereto. For example, according to some embodiments, the heat dissipation frame  170  may not be rolled out together with the heat dissipation sheet  140  and not with the rollable display panel  110  when the heat dissipation sheet  140  is rolled out together with the rollable display panel  110 . For example, taking  FIG.  16    as an example, the heat dissipation frame (not shown) may not be rolled out together with the heat dissipation sheet  140  and not with the rollable display panel  110  to be accommodated in the housing  160 , but the present disclosure is not limited thereto. The heat dissipation frame  170  may include a strong material, such as glass or plastic, or a material with a high thermal conductivity, such as a metal or an alloy, for example an aluminum-magnesium alloy, but the present disclosure is not limited thereto. 
     According to the rollable display device of the embodiments of the present disclosure, the installation of the heat dissipation sheet facilitates the thermal conduction and/or dissipation of the heat generated by the rollable display panel, thereby improving the heat dissipation quality of the rollable display device to enhance the reliability of the rollable display device. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the disclosure. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.