Patent Publication Number: US-2022238048-A1

Title: Display panel and display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The application claims the priority benefits of the patent application No. 202110119640.4 filed with the Patent Office of China on Jan. 28, 2021, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present application relates to the field of display technologies, especially to a display panel and a display device. 
     BACKGROUND 
     With the development of display technologies, flexible display modules have become more and more widely used. For example, due to the advantages of OLED flexible display elements, display devices with a full screen, a narrow bezel and a curved screen have a lot of room for development. The process of fabricating a typical OLED flexible display panel includes depositing a barrier layer, an insulating layer, a gate array control switch elements, a metal electrode, and the like on a flexible substrate, and then evaporating a light emitting material on the surface of a pixel circuit. In order to realize a narrow bezel, the edge of a flexible display panel is usually designed to be a curved edge with a certain curvature, which involves a process of bending an edge region of a flexible substrate layer including the pixel circuit. However, in a fabricated flexible display panel, damage to the wiring in the flexible substrate layer often occurs, which affects the yield of the flexible display panel. 
     SUMMARY 
     An embodiment of the present disclosure provides a display panel comprising a base substrate and a flexible substrate layer on the base substrate. The base substrate comprises a flat portion and a curved portion extending from the flat portion and curved towards a side of the base substrate facing away from a display surface of the display panel, and the flexible substrate layer comprises a first portion on a side of the base substrate facing the display surface of the display panel and a second portion on a side of the base substrate facing away from the display surface. The first portion of the flexible substrate layer comprises a pixel circuit for driving pixels of the display panel, and the second portion of the flexible substrate layer comprises a signal line electrically connected to the pixel circuit. The display panel further comprises a support structure fixed to the curved portion of the base substrate, the support structure comprises a support surface facing away from the display surface of the display panel, the second portion of the flexible substrate layer is coupled to the support surface to be supported by the support surface, and a plane of the support surface intersects a plane of the flat portion of the base substrate. 
     According to some embodiments of the disclosure, the support structure comprises a support adhesive layer, the support adhesive layer is fixed to a surface of the curved portion of the base substrate facing away from the display surface of the display panel, a flat surface of the support adhesive layer facing away from the display surface of the display panel forms the support surface, the display panel further comprises a first protective layer between the support surface and the second portion of the flexible substrate layer. 
     According to some embodiments of the disclosure, the support adhesive layer extends to the flat portion of the base substrate and comes into contact with a portion of a surface of the flat portion facing away from the display surface of the display panel. 
     According to some embodiments of the disclosure, the display panel further comprises a second protective layer on a surface of the second portion of the flexible substrate layer facing away from the support adhesive layer. 
     According to some embodiments of the disclosure, a material of the support adhesive layer comprises foamed rubber. 
     According to some embodiments of the disclosure, a thickness and a modulus of the first protective layer are respectively equal to a thickness and a modulus of the second protective layer. 
     According to some embodiments of the disclosure, the base substrate further comprises a reversely bent portion extending from the curved portion and bending towards the flat portion of the base substrate, the reversely bent portion forms the support structure, and an end of the reversely bent portion is in contact with a surface of one of the flat portion and the curved portion of the base substrate facing away from the display surface of the display panel. 
     According to some embodiments of the disclosure, the display panel further comprises a first adhesive layer and a first protective layer between the second portion of the flexible substrate layer and the reversely bent portion, and the second portion of the flexible substrate layer and the first protective layer are fixed to the reversely bent portion via the first adhesive layer. 
     According to some embodiments of the disclosure, the display panel further comprises a second protective layer on a surface of the second portion of the flexible substrate layer facing away from the reversely bent portion. 
     According to some embodiments of the disclosure, the first portion of the flexible substrate layer extends along the flat portion and the curved portion of the base substrate, the flexible substrate layer further reversely bends and extends from the first portion toward the flat portion of the base substrate beyond the curved portion of the base substrate, thereby forming the second portion and an arc-shaped portion connecting the second portion and the first portion, the display panel further comprises a third protective layer on a surface of the arc-shaped portion facing away from the base substrate. 
     According to some embodiments of the disclosure, the display panel further comprises a fourth protective layer between the base substrate and the flexible substrate layer, the fourth protective layer extends along the flat portion and the curved portion of the base substrate without going beyond an end of the curved portion of the base substrate. 
     According to some embodiments of the disclosure, the display panel further comprises a light emitting layer, a polarizing layer and a cover plate on a side of the flexible substrate layer facing away from the base substrate. 
     Another embodiment of the disclosure provides a display device comprising the display panel according to any one of the foregoing embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       By referring to the detailed description of non-limiting embodiments with reference to the following drawings, other features, purposes and advantages of the application will become more apparent. 
         FIG. 1  illustrates a partial sectional view of a display panel according to an embodiment of the disclosure, in which the second portion of the flexible substrate layer is in an unbent state; 
         FIG. 2  illustrates a state where the second portion of the flexible substrate layer in the display panel shown in  FIG. 1  is bent; 
         FIG. 3  illustrates a partial sectional view of a display panel according to another embodiment of the disclosure, in which the second portion of the flexible substrate layer is in an unbent state; 
         FIG. 4  illustrates a state where the second portion of the flexible substrate layer in the display panel shown in  FIG. 3  is bent; 
         FIG. 5  illustrates a partial sectional view of a display panel according to another embodiment of the disclosure, in which the second portion of the flexible substrate layer is in an unbent state; 
         FIG. 6  illustrates a state where the second portion of the flexible substrate layer in the display panel shown in  FIG. 5  is bent; 
         FIG. 7  illustrates a partial sectional view of a display panel according to another embodiment of the disclosure, in which the second portion of the flexible substrate layer is in an unbent state; 
         FIG. 8  illustrates a state where the second portion of the flexible substrate layer in the display panel shown in  FIG. 7  is bent; 
         FIG. 9  illustrates a partial sectional view of a display panel according to yet another embodiment of the disclosure, in which the second portion of the flexible substrate layer is in an unbent state; 
         FIG. 10  illustrates a state where the second portion of the flexible substrate layer in the display panel shown in  FIG. 9  is bent. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings and examples. It can be understood that specific embodiments described herein are only for explaining the present disclosure, rather than to limit the protection scope of the present application. In addition, it is to be further noted that, to facilitate description, only the components and elements related to the technical solutions of the embodiments of the disclosure are shown in the drawings. 
     The terms such as “first”, “second” and similar words in the application do not indicate any order, quantity or importance, but are only used to distinguish different elements or portions. The wording such as “include” or “comprise” means that an element before the wording covers elements listed after the wording, which does not exclude the possibility of covering other elements as well. “Upper”, “lower”, “left”, “right”, “inner”, “outer”, “top”, “bottom”, etc. are only used to indicate a relative positional relationship. When the absolute position of an object is changed, the relative positional relationship may be changed accordingly. 
     A display panel according to an embodiment of the disclosure comprises a base substrate and a flexible substrate layer on the base substrate. The base substrate comprises a flat portion and a curved portion extending from the flat portion and curved towards a side of the base substrate facing away from a display surface of the display panel. The flexible substrate layer comprises a first portion on a side of the base substrate facing the display surface of the display panel and a second portion on a side of the base substrate facing away from the display surface. The first portion of the flexible substrate layer comprises a pixel circuit for driving pixels of the display panel, and the second portion of the flexible substrate comprises a signal line electrically connected to the pixel circuit. The display panel further comprises a support structure fixed to the curved portion of the base substrate. The support structure comprises a support surface facing away from the display surface of the display panel, and the second portion of the flexible substrate layer is coupled to the support surface to be supported by the support surface, and a plane of the support surface intersects a plane of the flat portion of the base substrate. 
     The specific form of the support surface of the support structure is not limited herein. The support surface may be a flat surface or a curved surface, and the support surface may be a rough surface or a smooth surface. In the case where the support surface is a curved surface, the radius of curvature of the support surface may be greater than the radius of curvature of the curved portion of the base substrate. During the process of fabricating the display panel provided by the embodiment of the disclosure, especially in the process of fabricating a curved portion of the display panel (e.g., the curved portion of the flexible substrate layer, that is, the second portion described above), the second portion of the flexible substrate layer will be subjected to the pressure from the indenter of an external mechanical apparatus, and the support structure with the support surface can provide supporting force for the second portion of the flexible substrate layer to buffer the pressure of the indenter of the mechanical apparatus on the second portion of the flexible substrate layer and reduce the risk of breakage and failure of the signal line in the flexible substrate layer, thereby improving the reliability of the fabricated display panel. In addition, the second portion of the flexible substrate layer may be connected to an integrated circuit chip, for example, a source driver chip, so that the signal line in the second portion can perform signal transmission with the source driver to achieve image display. 
     The display panel provided by the embodiment will be further illustrated below by way of examples.  FIGS. 2, 4, 6 and 8  illustrate partial sectional views of display panels in a bent state according to different examples, and  FIGS. 1, 3, 5 and 7  illustrate the states of display panels to which the display panels shown in  FIGS. 2, 4, 6 and 8  correspond respectively prior to being subjected to the pressure of the indenter of an external mechanical apparatus. As shown in  FIGS. 1 and 2 , the display panel comprises a base substrate  60  and a flexible substrate layer  40  on the base substrate  60 . The base substrate  60  includes a flat portion  60 A and a curved portion  60 B extending from the flat portion  60 A and curved towards a side of the base substrate  60  facing away from a display surface S of the display panel. The flexible substrate layer  40  comprises a first portion  40 A on a side of the base substrate  60  facing the display surface S of the display panel and a second portion  40 B on a side of the base substrate  60  facing away from the display surface S. The first portion  40 A of the flexible substrate layer  40  comprises a pixel circuit (not shown) for driving pixels of the display panel, and the second portion  40 B of the flexible substrate layer comprises a signal line (not shown) electrically connected to the pixel circuit. A support structure fixed to the curved portion  60 B of the base substrate  60  comprises a support adhesive layer  70  comprising a support surface P facing away from the display surface S of the display panel, and the second portion  40 B of the flexible substrate layer  40  is coupled to the support surface P to be supported by the support surface P, and the plane of the support surface P intersects and the plane of the flat portion  60 A of the base substrate  60 . 
     The bending process performed for the display panel will be briefly described below with reference to  FIGS. 1 and 2 . As shown in  FIG. 1 , before the flexible substrate layer  40  of the display panel is subjected to the bending process, the second portion  40 B of the flexible substrate layer  40  may be in a horizontal state. An indenter  400  of an external apparatus moves downwards from a position above the second portion  40 B of the flexible substrate layer  40  and then comes into contact with the second portion  40 B of the flexible substrate layer  40 . The second portion  40 B of the flexible substrate layer  40  bends under the pressure of the indenter  400 , gradually approaches the support adhesive layer  70 , and is bonded and fixed to the support adhesive layer  70  (other protective structures may be provided between the second portion  40 B and the support adhesive layer  70 , for example, a protective layer  50  to be described below). As the indenter  400  continues to apply pressure, the support adhesive layer  70  achieves a tight connection with the flexible substrate layer  40  during the process of providing a reaction force to the second portion  40 B of the flexible substrate layer  40 , as shown in  FIG. 2 . In this embodiment, during the process of performing the bending process for the display panel with the indenter  400 , the surface of the indenter  400  facing the display panel may be kept parallel to the support surface P of the support adhesive layer  70 . 
     In the example of  FIG. 2 , the support adhesive layer  70  is fixed to a surface P 1  of the curved portion  60 B of the base substrate  60  facing away from the display surface S of the display panel, and a flat surface of the support adhesive layer  70  facing away from the display surface S of the display panel forms the support surface P. That is, in this embodiment, the support surface P is a flat surface. The display panel further comprises a first protective layer  50  between the support surface P and the second portion  40 B of the flexible substrate layer. As shown in  FIG. 1 , the first protective layer  50  may be pre-formed on the second portion  40 B of the flexible substrate layer  40 . In this way, during the process of performing the bending process for the flexible substrate layer  40  with the indenter  400  of an external mechanical apparatus, the first protective layer  50  can provide additional protection for signal lines or other devices in the second portion  40 B of the flexible substrate layer  40 . According to some embodiments of the disclosure, the material of the support adhesive layer  70  includes a foamed rubber, and the material of the first protective layer  50  may include polyimide. 
     In the examples of  FIGS. 2 and 4 , the support adhesive layer  70  is directly fixed to a surface of the curved portion of the base substrate, and the support adhesive layer  70  directly acts as a support structure, thereby eliminating the necessity of arranging an auxiliary support device. The base substrate  60  may be made of a rigid material. For example, the base substrate may include a metal material such as stainless steel. Compared to the base substrate, the support adhesive layer  70  may have some elasticity. In this way, the support adhesive layer  70  is supported by the rigid base substrate  60 , which can decrease a required thickness of the support adhesive layer  70  to thereby reduce the amount of deformation of the support adhesive layer  70  when subjected to an external force, and can provide support for the second portion  40 B of the flexible substrate layer  40  during the process of performing the bending process for the display panel, further reducing the risk of damage to signal lines in the second portion  40 B of the flexible substrate layer  40  during the bending process. 
     As shown in  FIGS. 1 to 4 , according to some embodiments of the disclosure, the support adhesive layer  70  extends to the flat portion  60 A of the base substrate  60  and comes into contact with a portion of the surface of the flat portion  60 A facing away from the display surface S of the display panel. Thus, the support adhesive layer  70  is simultaneously fixed to the flat portion  60 A and the curved portion  60 B of the base substrate, which enhances the reliability and stability of the support adhesive layer  70 . 
     As shown in  FIG. 4 , in some embodiments, the display panel further comprises a second protective layer  90  on a surface of the second portion  40 B of the flexible substrate layer  40  facing away from the support adhesive layer  70 . The second protective layer  90  may include polyimide, which may be pre-formed on the second portion  40 B of the flexible substrate layer  40 , as shown in  FIG. 3 . With the second protective layer  90 , the second portion of the flexible substrate layer  40  is able to serve as a stress-neutral layer. When the bending process is performed for the flexible substrate layer  40  with the indenter  400 , it is possible to buffer the pressure received by the second portion  40 B of the flexible substrate layer  40 , and meanwhile prevent the indenter  400  from causing damage to the second portion  40 B of the flexible substrate layer  40 . 
     As shown in  FIGS. 3 and 4 , the thickness and modulus of the first protective layer  50  are equal to those of the second protective layer  90 , respectively. The first protective layer  50  and the second protective layer  90  both include polyimide. In some embodiments, the first protective layer and the second protective layer both have a thickness of 50 μm±25 μm and a modulus of about 3.5±1 GPa. In this way, the two opposite surfaces of the second portion  40 B of the flexible substrate layer  40  are covered with a protective layer of the same material and the same thickness, which can be better protected during the bending process of the display panel. 
     According to some embodiments of the disclosure, as shown in  FIG. 6  or  FIG. 8 , the base substrate  60  further comprises a reversely bent portion  60 C extending from the curved portion  60 B and bending towards the flat portion  60 A of the base substrate  60 . The reversely bent portion  60 C forms the support structure, and an end of the reversely bent portion  60 C is in contact with the surface of one of the flat portion  60 A and the curved portion  60 B of the base substrate  60  that faces away from the display surface S of the display panel. In the example of  FIGS. 6 and 8 , the end of the reversely bent portion  60 C is in contact with the surface of the curved portion  60 B of the base substrate  60  that faces away from the display surface S of the display panel. In another embodiment, the reversely bent portion  60 C may extend to the flat portion of the base substrate  60 , so that the end of the bent portion  60 C is in contact with the surface of the flat portion of the base substrate that faces away from the display surface S of the display panel. In this embodiment, the surface of the reversely bent portion  60 C facing away from the display surface S of the display panel is namely the support surface of the support structure described above. In this embodiment, the reversely bent portion  60 C is easy to provide a flat support surface, which can provide a uniform support force for the second portion  40 B of the flexible substrate layer  40 , and further reduce the risk of damage to signal lines in the second portion  40 B of the flexible substrate layer  40  during the bending process. Moreover, the end of the reversely bent portion  60 C abuts against the surface of the base substrate facing away from the display surface of the display panel. In the bending process for the display panel, when an external indenter applies pressure to the display panel, the reversely bent portion  60 C will maintain a stable state without moving relative to the flat portion  60 A or the curved portion  60 B, so as to prevent damage to signal lines in the second portion  40 B of the flexible substrate layer  40  resulting from unstable forces received by its different parts during the pressurizing process. 
     As shown in  FIG. 6 or 8 , in some embodiments, the display panel further comprises a first adhesive layer  100  and a first protective layer  50  between the second portion  40 B of the flexible substrate layer  40  and the reversely bent portion  60 C, and the second portion  40  of the flexible substrate layer and the first protective layer  50  are fixed to the reversely bent portion  60 C via the first adhesive layer  100 . The first adhesive layer  100  here may include the same material as the support adhesive layer  70  described above. Further, as shown in  FIG. 8 , the display panel further comprises a second protective layer  90  on a surface of the second portion  40 B of the flexible substrate layer  40  facing away from the reversely bent portion  60 C. 
     According to some embodiments of the disclosure, as shown in  FIGS. 2, 4, 6 and 8 , the first portion  40 A of the flexible substrate layer  40  extends along the flat portion  60 A and the curved portion  60 B of the base substrate  60 , and the flexible substrate layer  40  further reversely bends and extends from the first portion  40 A towards the flat portion  60 A of the base substrate  60  beyond the curved portion  60 B of the base substrate, thereby forming the second portion  40 B and an arc-shaped portion  40 C connecting the second portion  40 B and the first portion  40 A. The display panel further comprises a third protective layer  80  on a surface of the arc-shaped portion  40 C facing away from the base substrate  60 . The third protective layer  80  may include an ultraviolet curing glue. The third protective layer  80  can provide good protection for signal lines in the arc-shaped portion  40 C during the bending process for the display panel. 
     Further, as shown in  FIGS. 2, 4, 6 and 8 , the display panel further comprises a fourth protective layer  50 ′ between the base substrate  60  and the flexible substrate layer  40 , and the fourth protective layer  50 ′ extends along the flat portion  60 A and the curved portion  60 B of the base substrate without going beyond the end of the curved portion  60 B of the base substrate. The fourth protective layer  50 ′ and the first protective layer  50  described above may be formed of the same material. In some embodiments, the fourth protective layer  50 ′ and the first protective layer  50  may be formed in the same patterning process, that is, the fourth protective layer  50 ′ and the first protective layer  50  form a protective pattern, and the protective pattern includes an opening corresponding to the arc-shaped portion  40 C of the flexible substrate layer  40 . As such, this can facilitate the bending process for the flexible substrate layer  40 , and meanwhile provide comprehensive protection for the flexible substrate layer  40 . 
     As shown in  FIGS. 1 to 8 , in some embodiments, the display panel further comprises a light emitting layer  30 , a polarizing layer  20  and a cover plate  10  on a side of the flexible substrate layer  40  facing away from the base substrate  60 . In the examples of  FIGS. 1 to 8 , when the display panel is operating to display images, the viewing surface of the display panel on which a user views the displayed images is a surface of the cover plate  10  facing away from the base substrate  60 , and this surface acts as the display surface S of the display panel. The cover plate  10  may include glass, i.e., the cover plate  10  may be a glass cover plate. In some embodiments, the light emitting layer  30  may comprise a touch structure, for example, the light emitting layer  30  is an OLED touch display layer. 
     According to another embodiment of the application, as shown in  FIG. 10 , the display panel comprises a base substrate  60  and a flexible substrate layer  40  on the base substrate  60 . The base substrate  60  comprises a flat portion  60 A and a curved portion  60 B extending from the flat portion  60 A and curved towards a side of the base substrate  60  facing away from the display surface S of the display panel. The flexible substrate layer  40  comprises a first portion  40 A on a side of the base substrate  60  facing the display surface S of the display panel and a second portion  40 B on a side of the base substrate  60  facing away from the display surface S. The first portion  40 A of the flexible substrate layer  40  comprises a pixel circuit (not shown) for driving pixels of the display panel, and the second portion  40 B of the flexible substrate comprises a signal line (not shown) electrically connected to the pixel circuit. The second portion  40 B of the flexible substrate layer  40  bends and extends along a curved surface CS of the curved portion  60 B of the base substrate facing away from the display surface, and the second portion  40 B is coupled to the curved surface CS of the curved portion  60 B to be supported by the curved portion  60 B. The display panel further comprises a second protective layer  90  on a surface of the second portion  40 B facing away from the curved portion  60 B. 
     In some embodiments, the second protective layer  90  may include polyimide, which may be pre-formed on the second portion  40 B of the flexible substrate layer  40 , as shown in  FIG. 9 . By disposing the second protective layer  90 , the second portion of the flexible substrate layer  40  is able to be a stress-neutral layer. When the bending process is performed for the flexible substrate layer  40  with the indenter  400 , it is possible to buffer the pressure received by the second portion  40 B of the flexible substrate layer  40 , and meanwhile prevent the indenter  400  from causing damage to the second portion  40 B of the flexible substrate layer  40 . In addition, during the process of applying the bending process on the display panel, in this embodiment, the second protective layer  90  may be bent along with the second portion  40 B of the flexible substrate layer, so that the second protective layer  90  forms a curved structure. The second protective layer  90 , the second portion  40 B of the flexible substrate layer, and the curved portion  60 B of the base substrate may have the same curvature. 
     As shown in  FIG. 10 , in some embodiments, the display panel further comprises a first protective layer  50  and a support adhesive layer  70  between the second portion  40 B of the flexible substrate layer and the curved surface CS of the base substrate  60 . The second portion  40 B of the flexible substrate layer and the first protective layer  50  are fixed to the curved surface CS of the curved portion via the support adhesive layer  70 . The support adhesive layer  70 , the first protective layer  50 , the second portion, and the curved portion of the base substrate have a same curvature. Therefore, in this embodiment, the curved portion  60 B of the base substrate, the support adhesive layer  70 , the first protective layer  50 , and the second portion  40 B of the flexible substrate layer form multilayer curved structures stacked in sequence, and these is no gap between different layers of the multilayer curved structures. 
     As shown in  FIG. 10 , the first portion  40 A of the flexible substrate layer  40  extends along the flat portion  60 A and the curved portion  60 B of the base substrate  60 , and the flexible substrate layer  40  further reversely bends and extends from the first portion  40 A toward the flat portion  60 A of the base substrate beyond the curved portion  60 B of the base substrate, thereby forming the second portion  40 B and an arc-shaped portion  40 C connecting the second portion  40 B and the first portion  40 A. The display panel further comprises a third protective layer  80  on a surface of the arc-shaped portion  40 C facing away from the base substrate  60 . The third protective layer  80  may include ultraviolet curing glue. The third protective layer  80  can provide good protection for signal lines in the arc-shaped portion  40 C during the bending process for the display panel. 
     Further, as shown in  FIG. 10 , similar to the foregoing embodiment, the display panel further comprises a fourth protective layer  50 ′ between the base substrate  60  and the flexible substrate layer  40 , and the fourth protective layer  50 ′ extends along the flat portion  60 A and the curved portion  60 B of the base substrate without going beyond the end of the curved portion  60 B of the base substrate. The fourth protective layer  50 ′ and the first protective layer  50  are formed of the same material. Furthermore, the display panel further comprises a light emitting layer  30 , a polarizing layer  20  and a cover plate  10  on a side of the flexible substrate layer  40  facing away from the base substrate  60 . 
     Another embodiment of the disclosure provides a display device comprising the display panel described in any one of the foregoing embodiments. The display device may be any electronic device having a display function, including but not limited to a mobile phone, a tablet computer, a watch, a navigation apparatus, and the like. 
     What have been described are only some embodiments of the disclosure and explanations of the related technical principles. Those skilled in the art should understand that the scope involved in the disclosure is not limited to technical solutions formed by specific combinations of the described technical features, and should also encompass other technical solutions formed by any combinations of the described technical features or their equivalent features without departing from the inventive concept, for example, technical solutions formed by replacing the above features and technical features having similar functions as those disclosed in the present disclosure (but not limited to) with each other.