Patent Publication Number: US-2022212434-A1

Title: Flexible display panel

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Taiwan Application Serial Number 110100260, filed Jan. 5, 2021, which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a display. More particularly, the present disclosure relates to a flexible display panel. 
     Description of Related Art 
     The existing display technology has developed a flexible display panel, in which the flexible display panel can be bent repeatedly many times. However, the existing flexible display panel is usually damaged after certain times of bending. Thus, many manufacturers are studying how to enhance the tolerant strength of the flexible display panel, so as to increase the times of bending that the flexible display panel can withstand, thereby improving the lifetime of the flexible display panel. 
     SUMMARY 
     At least one embodiment of the disclosure provides a flexible display panel including an accommodating structure that can enhance the tolerant strength of the flexible display panel, so as to increase the times of bending that the flexible display panel can withstand. 
     A flexible display panel according to at least one embodiment of the disclosure can be bent around an axis and includes a flexible substrate and an accommodating structure. The accommodating structure is disposed on the flexible substrate and includes a plurality of polygonal microcups connected to each other, in which the polygonal microcups are arranged regularly, and the abovementioned axis is not substantially parallel to any sidewall of each of the polygonal microcups. 
     A flexible display panel according to at least one embodiment of the disclosure can be bent around an axis and includes a flexible substrate and an accommodating structure. The accommodating structure is disposed on the flexible substrate and includes a plurality of polygonal microcups connected to each other, in which the polygonal microcups are arranged regularly. Each of the polygonal microcups has a width and a thickness, where a ratio value of the width to the thickness ranges between 5 and 80. 
     Based on the above, under the condition that the abovementioned axis is not substantially parallel to any sidewall of each polygonal microcup, the accommodating structure can enhance the tolerant strength of the flexible display panel, so as to increase the times of bending that the flexible display panel can withstand, thereby improving the, thereby improving the lifetime of the flexible display panel. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the disclosure as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1A  is a schematic perspective view of a flexible display panel according to at least one embodiment of the disclosure. 
         FIG. 1B  is a schematic cross-sectional view of the flexible display panel in  FIG. 1A . 
         FIG. 1C  is a schematic perspective view of the accommodating structure in  FIG. 1B . 
         FIG. 1D  is a schematic top view of the accommodating structure in  FIG. 1C . 
         FIG. 1E  is a schematic line chart of the variation in the shear strength of the accommodating structure in  FIG. 1D  with different directions. 
         FIG. 1F  is a schematic line chart measured by a stress fatigue testing of the accommodating structure in  FIG. 1D  in two different directions. 
         FIG. 1G  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 1C  at a particular ratio value of the width to the thickness. 
         FIG. 2A  is a schematic perspective view of a flexible display panel according to another embodiment of the disclosure. 
         FIG. 2B  is a schematic top view of the flexible display panel in  FIG. 2A . 
         FIG. 2C  is a schematic cross-sectional view along a line  2 C- 2 C shown in  FIG. 2B . 
         FIG. 3  is a schematic top view of an accommodating structure according to another embodiment of the disclosure. 
         FIG. 4A  is a schematic top view of a flexible display panel according to another embodiment of the disclosure. 
         FIG. 4B  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 4A . 
         FIG. 5A  is a schematic top view of a flexible display panel according to another embodiment of the disclosure. 
         FIG. 5B  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 5A . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     In the following description, in order to clearly present the technical features of the present disclosure, the dimensions (such as length, width, thickness, and depth) of elements (such as layers, films, substrates, and areas) in the drawings will be enlarged in unusual proportions. Accordingly, the description and explanation of the following embodiments are not limited to the sizes and shapes of the elements presented in the drawings, but should cover the sizes, shapes, and deviations of the two due to actual manufacturing processes and/or tolerances. For example, the flat surface shown in the drawings may have rough and/or non-linear characteristics, and the acute angle shown in the drawings may be round. Therefore, the elements presented in the drawings in this case which are mainly for illustration are intended neither to accurately depict the actual shape of the elements nor to limit the scope of patent applications in this case. 
       FIG. 1A  is a schematic perspective view of a flexible display panel according to at least one embodiment of the disclosure. Referring to  FIG. 1A , a flexible display panel  100  in the embodiment can be bent around an axis A 1 , where the term “bent” herein includes “rolled” and “folded”. Taking  FIG. 1A  for example, the flexible display panel  100  can be rolled around the axis A 1  into a tube, and the flexible display panel  100  further can be rolled around the axis A 1  repeatedly many times. 
       FIG. 1B  is a schematic cross-sectional view of the flexible display panel in  FIG. 1A . Referring to  FIG. 1B , the flexible display panel  100  includes a flexible substrate  110  and an accommodating structure  120 , in which the accommodating structure  120  is disposed on the surface  112  of the flexible substrate  110 . The material of the accommodating structure  120  can be selected from one of or the group consisting of epoxy acrylate, monomer, urethane ebecryl, polymethyl-methacrylate, photoinitiator, cationic photoinitiator, and acetone. That is, the accommodating structure  120  can be made of at least one of the abovementioned epoxy acrylate, monomer, urethane ebecryl, polymethyl-methacrylate, photoinitiator, cationic photoinitiator, and acetone. 
     The flexible substrate  110  can have circuitry (not shown), which can include a plurality of control components, in which the control component may be a transistor or a diode. Specifically, the flexible display panel  100  can be an active display panel or a passive display panel. When the flexible display panel  100  is the active display panel, the control components of the flexible substrate  110  can be transistors, such as thin-film transistors (TFTs). When the flexible display panel  100  is the passive display panel, the control components of the flexible substrate  110  can be diodes. 
     The flexible display panel  100  can further include two protective layers  131 ,  132 , and a functional layer  140 . Both of the protective layers  131  and  132  are disposed on the accommodating structure  120  and the flexible substrate  110 , in which the accommodating structure  120  and the flexible substrate  110  are located between both of the protective layers  131  and  132 . Accordingly, the protective layers  131  and  132  can protect the accommodating structure  120  and the flexible substrate  110 . The functional layer  140  can be disposed on the protective layer  131  and provide additional function. For example, the functional layer  140  can be a touch sensing layer, so that the flexible display panel  100  can have the function of touch sensing. Alternatively, the functional layer  140  can be an anti-reflective (AR) layer, so as to reduce the light reflecting off the flexible display panel  100 , thereby improving the image quality. 
       FIG. 1C  is a schematic perspective view of the accommodating structure in  FIG. 1B , and  FIG. 1D  is a schematic top view of the accommodating structure in  FIG. 1C . Referring to  FIGS. 1C and 1D , the accommodating structure  120  includes a plurality of polygonal microcups  121  which are connected to each other and arranged regularly. In the embodiment, the polygonal microcup  121  can be a hexagonal microcup, and the polygonal microcups  121  can be arranged in a honeycomb. Hence, each of the polygonal microcups  121  basically takes the shape of a hexagonal prism and has a hole  121   h,  where the accommodating space of the hole  121   h  also can take the shape of a hexagonal prism basically. In addition, the heights of the polygonal microcups  121  relative to the surface  112  are substantially equal to each other. 
     Each of the polygonal microcups  121  includes two first sidewalls S 1  and a plurality of second sidewalls S 2 , in which the first sidewalls S 1  are opposite to and substantially parallel to each other, and both shapes of the first sidewall S 1  and the second sidewall S 2  are substantially the same. Hence, the first sidewalls S 1  can substantially lie in a plurality of reference planes R 1  that are substantially parallel to each other, where all of the reference planes R 1  are virtual plane. The second sidewalls S 2  are connected to the first sidewalls S 1 , in which two first sidewalls S 1  and four second sidewalls S 2  can form a polygonal microcup  121 , i.e., a hexagonal microcup, and surround a hole  121   h,  as shown in  FIG. 1D . In addition, two polygonal microcups  121  connected to each other can share one first sidewall S 1  or one second sidewall S 2 . 
     The hole  121   h  of each of the polygonal microcups  121  can accommodate image-display ink (not shown), in which the image-display ink may be electrophoretic ink used in an electrophoretic display (EPD) panel. The circuitry of the flexible substrate  110  (referring to  FIG. 1B ) can further include a plurality of the electrodes (not shown), in which the electrodes electrically connected to the control components may be located at the bottoms of the holes  121   h,  so that the control components can generate electric fields in the holes  121   h  via the electrodes. Thus, the control components of the flexible substrate  110  can control the image-display ink in the holes  121   h,  so that the flexible display panel  100  can display images. 
     The flexible display panel  100  can be bent (e.g., rolled) around the axis A 1 , in which the axis A 1  is not substantially parallel to any sidewall of each of the polygonal microcups  121 , i.e., not parallel to the first sidewall S 1  and the second sidewall S 2 . For example, under the condition that each of the polygonal microcups  121  substantially takes the shape of a regular hexagonal prism, the angle of each of the polygonal microcups  121 , that is, the included angle between two adjacent sidewalls (e.g., both of the first sidewall S 1  and the second sidewall S 2 , or two adjacent second sidewalls S 2 ) is substantially 120°. 
     Each of the polygonal microcups  121  has a width  121   w  and a thickness  121   t.  Since each of the polygonal microcups  121  substantially takes the shape of a regular hexagonal prism, the width  121   w  can be equivalent to a distance between two opposite first sidewalls S 1  or a distance between two opposite second sidewalls S 2  in the same polygonal microcup  121 . In addition, in the embodiment, the ration value of the width  121   w  to the thickness  121   t  can range between 0.5 and 1.5. 
     Under the condition that the angle of each of the polygonal microcups  121  is substantially 120°, the axis A 1  is not substantially parallel to any one of the first sidewalls S 1  and the second sidewalls S 2  of each of the polygonal microcups  121  when the included angle θ 1  between the axis A 1  and the reference plane R 1  (equivalent to the first sidewall S 1 ) is larger than 60°, and less than or equal to 90°. In addition, in the embodiment shown in  FIG. 1D , the included angle θ 1  is substantially equal to 90°, so that the axis A 1  is substantially perpendicular to the reference planes R 1 , that is, the axis A 1  is substantially perpendicular to the first sidewall S 1  and not substantially parallel to any one of the first sidewalls S 1  and the second sidewalls S 2 . 
       FIG. 1E  is a schematic line chart of the variation in the shear strength of the accommodating structure in  FIG. 1D  with different directions, in which the “shear strength” shown in the vertical axis of  FIG. 1E  is measured by applying stress to the accommodating structure  120  in a direction parallel to the direction D 1  in  FIG. 1D , and the unit of the shear strength is megapascals (MPa). The “angle” shown in the horizontal axis of  FIG. 1E  is the angle θ 2  between the direction D 1  and the reference plane R 1  in  FIG. 1D , so that the “angle” shown in the horizontal axis of  FIG. 1E  represents the direction of stress. In addition, the direction D 1  is substantially parallel to the surface  112  of the flexible substrate  110 , so that the stress used for measuring the shear strength is applied to the accommodating structure  120  along the surface  112  basically. 
     When the angle shown in the horizontal axis of  FIG. 1E  (i.e., included angle θ 2 ) is 0°, it means that the stress is substantially applied to the accommodating structure  120  in the direction parallel to the reference plane R 1  (equivalent to the first sidewall S 1 ) and the surface  112 . When the angle shown in the horizontal axis of  FIG. 1E  (i.e., included angle θ 2 ) is 90°, it means that the stress is substantially applied to the accommodating structure  120  in the direction perpendicular to the reference plane R 1 . 
     As seen from the line E 1  shown in  FIG. 1E , when the included angle θ 2  is 0°, the accommodating structure  120  has the strongest shear strength. In other words, the accommodating structure  120  has the best shear strength (about larger than 6.5 MPa) in the direction parallel to the reference plane R 1  (equivalent to the first sidewall S 1 ) and the surface  112 , so that the accommodating structure  120  is capable of withstanding the stress in the direction parallel to the reference plane R 1  and the surface  112 . 
     Conversely, when the included angle θ 2  is 90°, the accommodating structure  120  has a weak shear strength (about 3.5 MPa), so that the accommodating structure  120  has a bad shear strength in the direction perpendicular to the reference plane R 1 . That is to say, the accommodating structure  120  is not capable of withstanding the stress in the direction perpendicular to the reference plane R 1 . Moreover, it can be known from the line E 1  shown in  FIG. 1E  that when the included angle θ 2  is larger than 60° and close to 70°, the accommodating structure  120  has the weakest shear strength, which is equal to about 3.5 MPa. 
     When the flexible display panel  100  is bent around the axis A 1  without limiting the included angle θ 1 , the accommodating structure  120  can generate the stress in the direction perpendicular to the axis A 1 . For example, when the flexible display panel  100  is bent around the axis A 1  that is substantially perpendicular to the reference plane R 1  (i.e., the included angle θ 1  is substantially equal to 90°), the accommodating structure  120  can generate the stress in the direction substantially parallel to the reference plane R 1  and the surface  112 , where the stress is substantially perpendicular to the axis A 1  and parallel to the direction D 1  when the included angle θ 2  is 0°. 
     Since the accommodating structure  120  has the best shear strength in the direction parallel to the reference plane R 1  and the surface  112 , and is capable of withstanding the stress in the direction parallel to the reference plane R 1  and the surface  112 , under the condition that the axis A 1  is substantially perpendicular to the reference plane R 1 , in contrast to the existing flexible display panel, the flexible display panel  100  which can be bent around the axis A 1  can withstand more times of bending, thereby having longer lifetime. 
     In addition, as seen from the line E 1  shown in  FIG. 1E , in the range of the included angle θ 2  less than 30°, the accommodating structure  120  still has a good shear strength. Thus, in the range of the included angle θ 1  formed between the axis A 1  and the reference plane R 1  larger than 60°, and less than or equal to 90° range, that is, under the condition that the axis A 1  is not substantially parallel to any one of the first sidewalls S 1  and the second sidewalls S 2  of each of the polygonal microcups  121 , in contrast to the existing flexible display panel, the flexible display panel  100  which can be bent around the axis A 1  still can withstand more times of bending. 
       FIG. 1F  is a schematic line chart measured by a stress fatigue testing of the accommodating structure in  FIG. 1D  in two different directions, in which the “stress amplitude” in the vertical axis of  FIG. 1F  is the magnitude of the stress applied to the accommodating structure  120  in unit of megapascal (MPa), whereas the “number of cycles to failure” in the horizontal axis of  FIG. 1F  means the necessary times of applying the stress to the accommodating structure  120  in order to break the accommodating structure  120 . The line L 1  in  FIG. 1F  represents the stress applied in the direction parallel to the reference plane R 1  and the surface  112 , whereas the line L 2  represents the stress applied in the direction perpendicular to the reference plane R 1 . 
     Referring to  FIGS. 1D and 1F , it can be seen from  FIG. 1F  that under the condition that the stress applied to the accommodating structure  120  has the constant magnitude, the stress applied in the direction parallel to the reference plane R 1  and the surface  112  requires more times to be applied for breaking the accommodating structure  120 , but the stress applied to the accommodating structure  120  few times in the direction perpendicular to the reference plane R 1  can break the accommodating structure  120 . Hence, under the condition that the axis A 1  is substantially perpendicular to the reference plane R 1 , the flexible display panel  100  bent around the axis A 1  can withstand more times of bending, indeed. 
       FIG. 1G  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 1C  at a particular ratio value of the width to the thickness, in which the “strain” shown in the vertical axis of  FIG. 1G  is calculated by applying the stress to the accommodating structure  120  in the direction parallel to the direction D 1  in  FIG. 1D , whereas the “angle” shown in the horizontal axis of  FIG. 1G  is the included angle θ 2  (referring to  FIG. 1D ). In addition, the line in  FIG. 1G  is obtained by a simulation calculation at a ratio value of the width  121   w  to the thickness  121   t  ranging between 5 and 80. 
     Referring to  FIGS. 1C and 1G , when the ratio value of the width  121   w  to the thickness  121   t  ranges between 5 and 80, the accommodating structure  120  has the minimum strain in the direction at the angles θ 2  of 0° and 60°. In other words, when the included angle θ 2  is 0° or 60°, the accommodating structure  120  has very good structural strength. Accordingly, under the condition that he ratio value of the width  121   w  to the thickness  121   t  ranges between 5 and 80, the flexible display panel  100  can be bent (e.g., rolled or folded) around the axis A 1  at the included angle θ 1  of 90° or 30° repeatedly many times, that is, the axis A 1  can be still not substantially parallel to any first sidewall S 1  and second sidewall S 2  of each of the polygonal microcups  121 , or can be substantially parallel to at least one of the second sidewalls S 2  of each of the polygonal microcups  121 . For example, the axis A 1  can be substantially parallel to two of the second sidewalls S 2  of the polygonal microcup  121 . 
       FIG. 2A  is a schematic perspective view of a flexible display panel according to another embodiment of the disclosure. Referring to  FIG. 2A , the flexible display panel  200  of the embodiment can be bent around the axis A 2 , and can be folded around the axis A 2  repeatedly many times. The flexible display panel  200  has a bendable section  201  and two rigid sections  202 , where the bendable section  201  located between the rigid sections  202  is connected to the rigid sections  202 . The bendable section  201  can be bent, e.g., folded, so that the axis A 2  is located in the bendable section  201 , but the rigid sections  202  is rigid and hard to bend. 
       FIG. 2B  is a schematic top view of the flexible display panel in  FIG. 2A , and  FIG. 2C  is a schematic cross-sectional view along a line  2 C- 2 C shown in  FIG. 2B . Referring to  FIGS. 2B and 2C , the flexible display panel  200  includes an accommodating structure  220 , in which the accommodating structure  220  is similar to the accommodating structure  120  in the previous embodiment. 
     For example, the accommodating structure  220  also includes a plurality of polygonal microcups  221  which are connected to each other and arranged regularly, and each of the polygonal microcups  221  takes the shape of a hexagonal prism basically and has a hole  221   h,  where the accommodating space of the hole  221   h  also can take the shape of a hexagonal prism basically and accommodate the image-display ink (not shown), such as electrophoretic ink. In other words, all of the polygonal microcups  221  are hexagonal microcups and can be arranged in a honeycomb. 
     Unlike the previous embodiment, in the embodiment, the heights of the polygonal microcups  221  are not equal. Specifically, the height H 1  of the polygonal microcups  221  in the bendable section  201  is lower than the height H 2  of the polygonal microcups  221  in the rigid sections  202 , in which the variation in height of the polygonal microcups  221  in the bendable section  201  increases from the axis A 2  to the rigid section  202 . In other words, the polygonal microcups  221  near the axis A 2  have a low height H 1 , and the polygonal microcups  221  far away from the axis A 2  have a high height H 1 . Hence, it is advantageous to bend the bendable section  201  so that the flexible display panel  200  is easily folded along the axis A 2 . 
     Moreover, each of the polygonal microcups  221  can include a bottom layer  221   b,  a chamfer part  221   c,  a plurality of first sidewalls S 1  (as shown in  FIG. 2B , not shown in  FIG. 2C ), and a plurality of second sidewalls S 2 . Both the first sidewalls S 1  and the second sidewalls S 2  are connected to the bottom layer  221   b  and extend from the bottom layer  221   b  and in a direction away from the flexible substrate  110 . The chamfer part  221   c  is connected to the first sidewalls S 1 , the second sidewalls S 2 , and the bottom layer  221   b,  and the chamfer part  221   c  is located at the junction between the bottom layer  221   b  and both of the first sidewalls S 1  and the second sidewalls S 2 . By using the chamfer part  221   c,  the cracks between the bottom layer  221   b  and both of the first sidewall S 1  and the second sidewall S 2  caused by stress can be reduced, so as to reduce the chance of both the first sidewall S 1  and the second sidewall S 2  breaking from the bottom layer  221   b.    
     It is worth mentioning that the chamfer part  221   c  in the embodiment can be applied to the flexible display panel  100  in the previous embodiment. In other words, in the preceding accommodating structure  120 , each of the polygonal microcups  121  further includes a bottom layer (not shown), and the chamfer parts  221   c  can be formed at the junctions between the bottom layer and both of the first sidewalls S 1  and the second sidewalls S 2  in the polygonal microcups  121 . Hence, the chamfer part  221   c  is not limited to being in the polygonal microcup  221 . 
       FIG. 3  is a schematic top view of an accommodating structure according to another embodiment of the disclosure. Referring to  FIG. 3 , the accommodating structure  320  is similar to the previous accommodating structure  120 . The accommodating structure  320  can be applied to the flexible display panels  100  and  200  in the previous embodiments, and can be bent around the axis A 3 . Hence, each of the accommodating structures  120  and  220  in the previous embodiments can be replaced by the accommodating structure  320 . 
     Unlike the accommodating structure  120  of the previous embodiment, the accommodating structure  320  shown by the embodiment in  FIG. 3  includes a plurality of polygonal microcups  321  which are connected to each other and arranged in a honeycomb, and each of the polygonal microcups  321  includes a plurality of first sidewalls S 31  and a plurality of second sidewalls S 32 . The first sidewalls S 31  are connected to the second sidewalls S 32 , and a round angle TH 3  can be formed between the first sidewall S 31  and the second sidewall S 32  which are connected to and adjacent to each other. In addition, two second sidewalls S 32  that are connected to and adjacent to each other respectively have two curved surfaces (not shown) connected to each other, and an acute angle TH 4  is formed between two curved surfaces, as shown in  FIG. 3 . 
       FIG. 4A  is a schematic top view of a flexible display panel according to another embodiment of the disclosure. Referring to  FIG. 4A , the flexible display panel  400  of the embodiment includes a flexible substrate  110  and an accommodating structure  420 , in which the accommodating structure  420  is disposed on the surface  112  of the flexible substrate  110 , and the material of the accommodating structure  420  can be the same as the material of the accommodating structure  120 . In addition, the accommodating structure  420  also includes a plurality of polygonal microcups  421  which are connected to each other and arranged regularly. 
     Unlike the previous embodiment, each of the polygonal microcups  421  can be a quadrilateral microcup, and the quadrilateral microcups can be arranged in a matrix. Each of the polygonal microcups  421  includes two first sidewalls S 41  and two second sidewalls S 42 , in which the second sidewalls S 42  is connected to the first sidewalls S 41 . Both of the first sidewalls S 41  are opposite to and substantially parallel to each other, and both of the second sidewalls S 42  are opposite to and substantially parallel to each other, where the included angle θ 1  between the axis A 1  and the first sidewall S 41  can be larger than 60°, and less than or equal to 90°. For example, the included angle θ 1  can be equal to 45°. 
     The widths W 41  and W 42  of both of the first sidewalls S 41  and the second sidewalls S 42  are equal to each other, that is, any two of the sidewalls (i.e., first sidewall S 41  or second sidewall S 42 ) of each of the polygonal microcups  421  have the equal widths (i.e., widths W 41  and W 42 ). Moreover, the first sidewall S 41  and the second sidewall S 42  connected to each other are perpendicular to each other. Thus, the polygonal microcup  421  can be a square microcup. 
       FIG. 4B  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 4A , where the “strain” shown in the vertical axis of  FIG. 4B  is calculated by applying the stress to the accommodating structure  420  in the direction parallel to the direction D 1  in  FIG. 4A , whereas the “angle” shown in the horizontal axis of  FIG. 4B  is the included angle θ 2  in  FIG. 4A . In addition, the line in  FIG. 4B  is obtained by a simulation calculation. 
     Referring to  FIGS. 4A and 4B , it can be known from  FIG. 4B  that the accommodating structure  420  has the minimum strain in the direction at the angles θ 2  of 45°. In other words, when the included angle θ 2  is 45°, the accommodating structure  420  has very good structural strength. Accordingly, the flexible display panel  400  can be bent (e.g., rolled or folded) around the axis A 1  at the included angle θ 1  of 45° repeatedly many times, that is, the axis A 1  is not substantially parallel to any one of the first sidewalls S 41   s  and the second sidewalls S 42  of each of the polygonal microcups  421 . 
       FIG. 5A  is a schematic top view of a flexible display panel according to another embodiment of the disclosure. Referring to  FIG. 5A , the flexible display panel  500  of the embodiment is similar to the flexible display panel  400 . For example, the flexible display panel  500  of the embodiment includes the flexible substrate  110  and an accommodating structure  520 , in which the accommodating structure  520  is disposed on the surface  112  of the flexible substrate  110 , and the material of the accommodating structure  520  can be the same as the material of the accommodating structure  120 . In addition, the accommodating structure  520  also includes a plurality of polygonal microcups  521  which are connected to each other and arranged regularly, and each of the polygonal microcups  521  can be a quadrilateral microcup. 
     However, unlike the polygonal microcup  521  in the previous embodiment, each of the polygonal microcups  521  can be a rhombic microcup, not the square microcup. Specifically, each of the polygonal microcups  521  includes two first sidewalls S 51  and two second sidewalls S 52 , in which the second sidewalls S 52  are connected to the first sidewalls S 51 . Both of the first sidewalls S 51  are opposite to and substantially parallel to each other, and both of the second sidewalls S 52  are opposite to and substantially parallel to each other. 
     The widths W 51  and W 52  of both of the first sidewalls S 51  and the second sidewalls S 52  are equal to each other, and the first sidewall S 51  and the second sidewall S 52  connected to each other are not perpendicular to each other, so that each of the polygonal microcups  521  can be the rhombic microcup, not the square microcup. Moreover, the included angle θ 1  between the axis A 1  and the first sidewall S 51  can be larger than 60°, and less than or equal to 90°. 
       FIG. 5B  is a schematic line chart of the equivalent strain of the accommodating structure in  FIG. 5A , in which the “strain” shown in the vertical axis of  FIG. 5B  is calculated by applying the stress to the accommodating structure  520  in the direction parallel to the direction D 1  in  FIG. 5A , whereas the “angle” shown in the horizontal axis of  FIG. 5B  is the included angle θ 2  in  FIG. 5A . In addition, the line in  FIG. 5B  is obtained by a simulation calculation. 
     Referring to  FIGS. 5A and 5B , it can be known from  FIG. 5B  that the accommodating structure  520  has the minimum strain in the direction at the angles θ 2  of 0°. In other words, when the included angle θ 2  is 0°, the accommodating structure  520  has very good structural strength. Accordingly, the flexible display panel  500  can be bent (e.g., rolled or folded) around the axis A 1  at the included angle θ 1  of 90° repeatedly many times, that is, the axis A 1  is not substantially parallel to any one of the first sidewalls S 51  and the second sidewalls S 52  of each of the polygonal microcups  521 , and can be perpendicular to the first sidewall S 51 . 
     Consequently, under the condition that the axis is not substantially parallel to any sidewall (e.g., first sidewall S 1  or second sidewall S 2 ) of each of the polygonal microcups, the accommodating structure has good or the best shear strength, so that the flexible display panel disclosed by at least one embodiment of the disclosure can be bent (e.g., rolled or folded) around the axis repeatedly many times. Accordingly, the accommodating structure can enhance the tolerant strength of the flexible display panel. In contrast to the existing flexible display panel, the flexible display panel bent around the axis can withstand more times of bending, thereby having a longer lifetime. 
     In addition, although the accommodating structure may be made of a low-cost material of slightly poor quality, the accommodating structure also can enhance the tolerant strength of the flexible display panel by the above accommodating structure and the axis not parallel to any sidewall of the polygonal microcups, so that the flexible display panel is able to withstand certain times of bending. In other words, in order to maintain or improve the times of bending which the flexible display panel can withstand, the material costs of the accommodating structure can be reduced, thereby enabling the costs of the flexible display panel to decrease. 
     Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.