Patent Publication Number: US-2022240386-A1

Title: Flexible circuit board and display device

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application is a Section 371 National Stage Application of International Application No. PCT/CN2020/139459, filed on Dec. 25, 2020, entitled “FLEXIBLE CIRCUIT BOARD AND DISPLAY DEVICE”, the contents of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a field of display technology, and in particular, to a flexible circuit board and a display device. 
     BACKGROUND 
     Flexible Printed Circuit (FPC) is a highly reliable and flexible printed circuit board made of a base material such as a flexible film. The flexible circuit board has characteristics of high wiring density, light weight, thin thickness and good bendability and the like, and the flexible circuit board is widely used in various display devices such as a mobile phone, a computer and a monitor, and the like. 
     SUMMARY 
     In one aspect, a flexible circuit board is provided, including: 
     a body area including at least one driving device and a plurality of wirings; 
     a bonding area combined with a first side of the body area, and the bonding area includes a plurality of bonding pins; and 
     an extension area combined with a second side of the body area, and the first side and the second side are two opposite sides of the body area, 
     wherein the body area includes a first sub-body area and a second sub-body area, and the second sub-body area is located on a side of the first sub-body area close to the extension area; the plurality of wirings at least include a first wiring, a second wiring and a third wiring, each of the first wiring, the second wiring and the third wiring extends in the first sub-body area, and the first wiring and the second wiring extend in the second sub-body area; and 
     the first sub-body area includes a multi-layer board structure, the second sub-body area includes a single-layer board structure or a double-layer board structure, and a thickness of the second sub-body area is smaller than a thickness of the first sub-body area. 
     According to some exemplary embodiments, the first sub-body area includes a first size in a first direction, the first direction is perpendicular to a thickness direction of the flexible circuit board, and the first direction is directed from the bonding area to the extension area; and 
     the second sub-body area includes a second size in the first direction, a ratio of a sum of the first size and the second size to the first size of the first sub-body area is in a range of 1.5 to 5. 
     According to some exemplary embodiments, the first size is in a range of 5 to 10 mm; and/or, the sum of the first size and the second size is in a range of 7 to 20 mm. 
     According to some exemplary embodiments, the first sub-body area includes a four-layer board structure. 
     According to some exemplary embodiments, the first sub-body area includes a first sub-circuit board, a second sub-circuit board and a protective film, and each of the first sub-circuit board and the second sub-circuit board includes a base film and conductive films on opposite sides of the base film. 
     According to some exemplary embodiments, the first sub-body area includes a six-layer board structure. 
     According to some exemplary embodiments, the first sub-body area includes a first sub-circuit board, a second sub-circuit board, a third sub-circuit board and a protective film, and each of the first sub-circuit board, the second sub-circuit board and the third sub-circuit board includes a base film and conductive films on opposite sides of the base film. 
     According to some exemplary embodiments, the first sub-body area includes a first sub-circuit board, a second sub-circuit board, a third sub-circuit board, a fourth sub-circuit board and a protective film, each of the first sub-circuit board and the fourth sub-circuit board includes a base film and a conductive film on a side of the base film, each of the second sub-circuit board and the third sub-circuit board includes a base film and conductive films on opposite sides of the base film, and an adhesive layer is disposed between the first sub-circuit board and the second sub-circuit board, between the second sub-circuit board and the third sub-circuit board, and between the third sub-circuit board and the fourth sub-circuit board. 
     According to some exemplary embodiments, the second sub-body area includes the double-layer board structure, the double-layer board structure includes a double-layer sub-circuit board, and the double-layer sub-circuit board includes a base film and conductive films on opposite sides of the base film. 
     According to some exemplary embodiments, one of the first sub-circuit board, the second sub-circuit board and the third sub-circuit board extends continuously with the double-layer sub-circuit board. 
     According to some exemplary embodiments, the second sub-body area includes the double-layer board structure, the double-layer board structure includes a double-layer sub-circuit board, and the double-layer sub-circuit board includes a base film and conductive films on opposite sides of the base film. 
     According to some exemplary embodiments, one of the second sub-circuit board and the third sub-circuit board extends continuously with the double-layer sub-circuit board. 
     According to some exemplary embodiments, the second sub-body area includes the single-layer board structure, the single-layer board structure includes a single-layer sub-circuit board, and the single-layer sub-circuit board includes a base film and a conductive film on a side of the base film. 
     According to some exemplary embodiments, one of the first sub-circuit board and the fourth sub-circuit board extends continuously with the single-layer sub-circuit board. 
     According to some exemplary embodiments, the first sub-body area includes a third size in a second direction, the second sub-body area includes a fourth size in the second direction, the second direction is perpendicular to the thickness direction of the flexible circuit board, and the second direction is perpendicular to the first direction; and the third size is equal to the fourth size, or the third size is greater than the fourth size. 
     According to some exemplary embodiments, the extension area includes a double-layer board structure or a single-layer board structure. 
     According to some exemplary embodiments, the extension area and the second sub-body area extend continuously. 
     According to some exemplary embodiments, as the first size of the first sub-body area increases, an area of an orthographic projection of the second sub-body area in the thickness direction of the flexible circuit board becomes decreases. 
     According to some exemplary embodiments, the bonding area includes a double-layer board structure or a single-layer board structure. 
     According to some exemplary embodiments, the bonding area and the second sub-body area are extracted from one sub-circuit board of the first sub-body area. 
     According to some exemplary embodiments, the bonding area and the second sub-body area are extracted from different sub-circuit boards of the first sub-body area. 
     In another aspect, a display device is provided, including: a display panel; the flexible circuit board as described above; and a battery, wherein the bonding area of the flexible circuit board is connected to the display panel, and the flexible circuit board is located on a non-display side of the display panel; and the battery is located on a side of the flexible circuit board away from the display panel. 
     According to some exemplary embodiments, an orthographic projection of the battery on the display panel at least partially overlaps with an orthographic projection of the second sub-body area on the display panel. 
     According to some exemplary embodiments, the display device further includes a middle frame component, at least a part of the middle frame component is located on a side of the flexible circuit board away from the display panel, and an orthographic projection of the middle frame component on the display panel at least partially overlaps with an orthographic projection of the second sub-body area on the display panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe technical solutions more clearly in the embodiments of the present disclosure or the prior art, in the following, drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure. For those skilled in the art, other drawings may be obtained according to the drawings without creative work. 
         FIG. 1  illustrates a schematic diagram of a display device according to the embodiments of the present disclosure; 
         FIG. 2  is a partially exploded schematic diagram of a display device according to the embodiments of the disclosure; 
         FIGS. 3A and 3B  are schematic cross-sectional views of the display device taken along line I-I′ in  FIG. 2  according to the embodiments of the disclosure, respectively; 
         FIG. 4  is a schematic plan view of a flexible circuit board according to some exemplary embodiments of the present disclosure, which illustrates a connection of the flexible circuit board and a display panel; 
         FIG. 5  is a schematic plan view of a flexible circuit board according to some exemplary embodiments of the present disclosure; 
         FIG. 6  is a cross-sectional view of the flexible circuit board taken along line II-If in  FIG. 5  according to the embodiments of the present disclosure; 
         FIG. 7  is a cross-sectional view of a first sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a four-layer board structure of the first sub-body area; 
         FIG. 8  is a cross-sectional view of a first sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a six-layer board structure of the first sub-body area; 
         FIGS. 9A to 9F  are schematic diagrams of layered wirings of the six-layer board structure shown in  FIG. 8 ; 
         FIGS. 10A and 10B  are cross-sectional views of a first sub-body area included in a flexible circuit board according to other embodiments of the present disclosure, which schematically illustrate a six-layer board structure of the first sub-body area, respectively; 
         FIG. 11  is a cross-sectional view of a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the second sub-body area; 
         FIG. 12  is a cross-sectional view of a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the second sub-body area; 
         FIG. 13  is a schematic plan view of a flexible circuit board according to other embodiments of the present disclosure; 
         FIG. 14  is a cross-sectional view of an extension area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the extension area; 
         FIG. 15  is a cross-sectional view of an extension area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the extension area; 
         FIG. 16  is a cross-sectional view of a bonding area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the bonding area; 
         FIG. 17  is a cross-sectional view of a bonding area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the bonding area; 
         FIG. 18  is a partial enlarged view of the display device according to the embodiments of the present disclosure at part III in  FIG. 1 ; 
         FIG. 19  is a schematic plan view of the display device shown in  FIG. 18 ; 
         FIG. 20  is a partial plan view of the display device of the embodiments shown in  FIG. 13 ; 
         FIG. 21  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure; 
         FIG. 22  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure; 
         FIG. 23  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure; 
         FIG. 24  is a cross-sectional view of a body area and an extension area included in a flexible circuit board according to the embodiments of the present disclosure; 
         FIG. 25  is a cross-sectional view of a body area and an extension area included in a flexible circuit board according to the embodiments of the present disclosure; and 
         FIG. 26  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to some exemplary embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In order to make objectives, technical solutions, and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be described clearly and completely in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present disclosure. 
     Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have general meanings understood by those skilled in the art. The “first”, “second” and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. “Include” or “comprise” and other similar words refer to that an element or an item appearing before the word contains an element or an item and their equivalents listed after the word, but does not exclude other elements or items. “Connected” or “coupled” and other similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Up”, “down”, “left”, “right”, etc. are only used to indicate a relative positional relationship. When an absolute position of a described object changes, the relative position relationship may also change accordingly. 
     In the present disclosure, unless otherwise expressly stipulated and limited, the term “connected” shall be understood in a broad sense. For example, “connected” may be a fixed connection, a detachable connection or a whole; the “connected” may be directly connected or indirectly connected through an intermediary. 
     In the present disclosure, unless otherwise specified, the expressions “multi-layer board”, “multi-layer board structure” and the like refer to a board including a stacked structure of three or more layers. 
     In the present disclosure, unless otherwise expressly stipulated and limited, the term “extend continuously” refers to that one component extends from another component, or that the two components are formed as a whole. 
     The embodiments of the present disclosure provide a flexible circuit board, the flexible circuit board includes: 
     a body area, the body area includes at least one driving device and a plurality of wirings; 
     a bonding area, the bonding area is combined with a first side of the body area, and the bonding area includes a plurality of bonding pins; and 
     an extension area, the extension area is combined with a second side of the body area, and the first side and the second side are two opposite sides of the body area, 
     wherein the body area includes a first sub-body area and a second sub-body area, and the second sub-body area is located on a side of the first sub-body area close to the extension area; the plurality of wirings at least include a first wiring, a second wiring and a third wiring, each of the first wiring, the second wiring and the third wiring extends in the first sub-body area, and the first wiring and the second wiring extend in the second sub-body area; and 
     the first sub-body area includes a multi-layer board structure, the second sub-body area includes a single-layer board structure or a double-layer board structure, and a thickness of the second sub-body area is smaller than a thickness of the first sub-body area. 
     By designing a thinned part of the body area, an interference avoiding design may be achieved, so that components such as batteries and middle frame components, etc. may extend below the flexible circuit board. In this way, it is conducive to placing large-capacity batteries or performing interference avoiding on the components. 
     It should be understood that, a plurality of signal wirings may usually be integrated on the flexible circuit board, to transmit different types of signals. When there are many numbers and types of signal wirings on the flexible circuit board, for example, when the plurality of signal wirings for display signals, touch signals, fingerprint recognition signals, etc. are required at a same time, a wiring difficulty in the flexible circuit board will also be increased. In this way, at least a part of the flexible circuit board may be formed as a multi-layer wiring layer such as four-layer wiring layer or six-layer wiring layer, etc., so as to facilitate an arrangement of the plurality of wirings, so that the plurality of wirings may be distributed on different layers, thereby reducing mutual interference between different types of wirings. In addition, in the process of manufacturing the flexible circuit board with multi-layer wiring layers, it is also necessary to form an insulating layer (and a corresponding bonding layer) between adjacent wiring layers. In order to avoid a signal crosstalk between different wirings, it is also necessary to form a (electromagnetic signal) shielding layer between different wirings. 
     The embodiments of the present disclosure provide a display device, the type of the display device is not limited, and the display device may be a Liquid Crystal Display (LCD) or an electroluminescent display device. In the case that the display device is an electroluminescent display device, the electroluminescent display device may be an Organic Light-Emitting Diode (OLED) or a Quantum Dot Light Emitting Diodes (QLED). 
       FIG. 1  illustrates a schematic diagram of a display device. As shown in  FIG. 1 , a main structure of the display device includes a frame  1 , a cover plate  2 , a display panel  3 , a flexible circuit board  4  and other components. In a case that the display device is a liquid crystal display device, the display device further includes a backlight component. Here, the display panel  3  may be a flexible display panel or a rigid display panel. In the case that the display panel  3  is a flexible display panel, the display device is a flexible display device. 
     For example, an upper side of the display panel  3  shown in  FIG. 1  is a display side, and a lower side is a non-display side; while the flexible circuit board  4  is placed on the non-display side of the display panel  3  after being bonded. In an embodiment of the present disclosure, after the flexible circuit board  4  and the display panel  3  are bonded and connected, a bonding end of the display panel  3  is bent toward the non-display side, so that the flexible circuit board  4  is located on the non-display side of the display panel  3 , that is, the flexible circuit board  4  is located on a back surface of the display panel  3 , so as to achieve a narrow bezel design of a display screen. 
     For example, the display device provided by the embodiments of the present disclosure may be a product or component with any display function, such as a television, a digital camera, a mobile phone, a tablet computer and so on. 
     As shown in  FIG. 1 , a longitudinal section of the frame  1  is U-shaped, the display panel  3 , the flexible circuit board  4  and other components are all disposed in the frame  1 . The flexible circuit board  4  is placed under the display panel  3  (that is, located on the back surface away from a display surface of the display panel  3 ), and the cover plate  2  is disposed on a side of the display panel  3  away from the flexible circuit board  4 . In the case that the display is a liquid crystal display and the liquid crystal display includes the backlight component, the backlight component is disposed between the display panel  3  and the flexible circuit board  4 . 
     As shown in  FIG. 1 , the display panel  3  may include a display unit  31  and a touch layer  32 , the touch layer  32  may be disposed on a light emitting side of the display unit  31 . For example, in the case that the display panel  3  is an OLED display panel, the touch layer  32  may be disposed on an encapsulation layer of the OLED display panel (the touch layer  32  may be in direct contact with the encapsulation layer, or there may be other layers between the touch layer  32  and the encapsulation layer, such as a planarization layer, etc.). Wherein the encapsulation layer may be an encapsulation substrate or an encapsulation film; in the case that the display panel  3  is the liquid crystal display panel, the touch layer  32  may be embedded in a liquid crystal layer (that is, in cell); or the touch layer  32  may be disposed between a color filter substrate and an upper polarizer (that is, on cell). A position of the touch layer  32  is not limited to this, for example, the touch layer  32  may also be disposed on a side of the cover plate  2  close to the display panel  3 . 
       FIG. 2  is a partially exploded schematic diagram of a display device according to the embodiments of the present disclosure. Referring to  FIGS. 1 and 2  in combination, the display unit  31  may include a display area AA and a non-display area NA on at least one side of the display area AA.  FIG. 2  illustrates an example in which the non-display area NA surrounds the display area AA. The display area AA may be limited as an area in which an image is displayed, and the display area AA includes a plurality of sub-pixels for implementing an image. The non-display area NA may be limited as an area in which no image is displayed, and the non-display area NA is used for wiring. For example, a gate driving circuit may be disposed in the non-display area NA. 
     In the case that a display panel  3  includes a touch layer  32 , the touch layer  32  may be disposed on the display unit  31 . The touch layer  32  may acquire coordinate information from external input (for example, a touch of user&#39;s finger), that is, the touch layer  32  may be a touch panel that senses the touch of user; the touch layer  32  may also be a fingerprint sensing panel that acquires fingerprint information of user&#39;s finger. For example, the touch layer  32  may sense external input through a capacitive method. It should be noted that, the sensing method of the touch layer  32  in the embodiments of the present disclosure includes but is not limited to the above-mentioned embodiments, and other suitable sensing methods should fall within the protection scope of the embodiments of the present disclosure. 
       FIGS. 3A and 3B  are schematic cross-sectional views of the display device taken along line I-I′ in  FIG. 2  according to the embodiments of the present disclosure. In some embodiments, referring to  FIG. 3A , the touch layer  32  may be formed on the display unit  31  through a continuous process. Here, the expression “continuous process” may be understood as: the touch layer  32  may be formed directly above the display unit  31  after the display unit  31  is formed, instead of separately forming the display unit  31  and the touch layer  32 , and then disposing the touch layer  32  on the display unit  31  through a process such as attaching. Referring to  FIG. 3A , for example, when the touch layer  32  is formed in a electroluminescent display device, the touch layer  32  may be directly formed on an encapsulation layer  33 . In addition, in order to avoid damage to the encapsulation layer  33  when the touch layer  32  is formed on the encapsulation layer  33 , a buffer layer  34  may be formed on the encapsulation layer  33  before the touch layer  32  is formed on the encapsulation layer  33 . In other embodiments, referring to  FIG. 3B , the touch layer  32  may be formed as a separate element, and the touch layer  32  is attached to the display unit  31  through an adhesive layer  35 . In the case that the touch layer  32  is formed as a separate element (for example, a separate film layer), the touch layer  32  may also include a carrier film for carrying touch electrodes. For example, in the embodiment shown in  FIG. 3B , the touch layer  32  may include a touch electrode layer  321  and a carrier film  320  carrying the touch electrode layer. 
     For example, the carrier film  320  may be a resin film, a glass substrate, a composite film, etc.; the adhesive layer  35  may be a pressure sensitive adhesive (PSA), Optical Clear Adhesive (OCA), Optical Clear Resin (OCR), or the like. 
     It should be noted that, in the embodiment shown in  FIG. 2 , the display panel  3  may be rectangular in the plan view. The “rectangular” here includes not only a substantially rectangular shape, but also a shape similar to a rectangle in consideration of process conditions. On this basis, the display panel  3  includes a long side and a short side. In some embodiments, each intersection position (i.e, corner) of the long side and the short side of the display panel  3  is a right angle. In other embodiments, each corner of the display panel  3  is curved, that is, each corner is smooth. 
     In combination with the above embodiments, referring again to  FIG. 2 , the touch layer  32  may overlap with the display unit  31 . In some embodiments, the touch layer  32  may have substantially the same size as the display unit  31 . That is, as shown in  FIGS. 3A and 3B , a side of the touch layer  32  may be aligned with a side of the display unit  31 . However, the embodiments of the present disclosure are not limited to this. Optionally, the touch layer  32  may only overlap with a part of the display unit  31 , for example, the touch layer  32  at least partially overlaps with the display area AA of the display unit  31 . 
     It should be noted the touch layer  32  includes a touch area B 1  that is provided with a plurality of touch electrodes, and a peripheral area B 2  on a periphery of the touch area B 1 , and the peripheral area B 2  is provided with touch leads that are electrically connected to the touch electrodes. In the case that the touch layer  32  has substantially the same size as the display unit  31 , the touch area B 1  corresponds to the display area AA, and the peripheral area B 2  corresponds to the non-display area NA. 
     On this basis, as shown in  FIG. 2 , the cover plate  2  may include a light-transmitting area C 1  and a light-shielding area C 2 . The light-transmitting area C 1  may at least partially overlap with the display area AA of the display unit  31 , and the light-transmitting area C 1  may transmit light generated from the display unit  31  to outside, so that the light may be seen by human eyes. The light-shielding area C 2  may be disposed at a periphery of the light-transmitting area C 1 , and the light shielding area C 2  may at least partially overlap with the non-display area NA of the display unit  31 . 
       FIG. 4  is a schematic plan view of a flexible circuit board according to some exemplary embodiments of the present disclosure, which illustrates a connection of the flexible circuit board and a display panel.  FIG. 5  is a schematic plan view of a flexible circuit board according to some exemplary embodiments of the present disclosure. With reference to  FIGS. 2, 4 and 5  in combination, a part of the display panel may be bent in line AX toward the non-display side of the display panel  3 , so that the flexible circuit board  4  is located on the back surface of the display panel  3 . The flexible circuit board  4  may include a bonding area  41 , a body area  42  and an extension area  43 . The bonding area  41  and the extension area  43  are located on two sides of the body area  42 , respectively. 
     The bonding area  41  of the flexible circuit board  4  may include a plurality of bonding pins  411 . The non-display area NA of the display panel  3  may include a plurality of bonding pads. The plurality of bonding pins  411  are respectively bonded with the plurality of bonding pads, to achieve the bonding of the flexible circuit board  4  and the display panel  3 . 
     For example, in some embodiments, as shown in  FIG. 4 , the non-display area NA of the display panel  3  further includes a driving circuit IC  37 . Data signals sent by a main board is electrically connected to the driving circuit IC  37  through wirings (for example, collectively referred to as data signal control lines) of the flexible circuit board  4 , the data signals are processed by the driving circuit IC  37  and finally output to the display panel  3 , thereby the display panel  3  is driven for display. 
     The body area  42  of the flexible circuit board  4  may include one or more driving devices, such as a display driving device D 1  and/or a touch driving device D 2 . The body area  42  of the flexible circuit board  4  may also include one or more wirings, for example, the wirings may include a first wiring L 1 , a second wiring L 2  and a third wiring L 3 . Exemplarily, the first wiring L 1  may be a signal wiring used to transmit data required for display, the second wiring L 2  may be a power wiring L 2 , and the third wiring L 3  may be a touch wiring L 3 . The signal wiring L 1  may be electrically connected to the display driving device D 1 , and the touch wiring L 3  may be electrically connected to the touch driving device D 2 . 
     It should be noted that, in  FIG. 4 , a rectangular frame is used to schematically illustrate the display driving device D 1  and the touch driving device D 2 . However, this should not be regarded as a restriction on shapes of the display driving device D 1  and the touch driving device D 2 . In addition, in the embodiments of the present disclosure, only the display driving device D 1  and the touch driving device D 2  are taken as examples to describe the body area  42  of the flexible circuit board  4 , so as to illustrate that electronic elements and various wirings may be disposed in the body area  42 . It should be understood that, the electronic elements disposed in the body area  42  of the flexible circuit board  4  are not limited to the display driving device D 1  and the touch driving device D 2 . For example, in an area corresponding to the touch drive device D 2 , a touch IC, a touch driving element associated with the touch driving signals may be disposed, and other touch elements associated with the touch sensing signals may also be disposed. 
     For example, the driving device may include a driving IC chip. There are a plurality of methods (that is, the packaging method) to combine the driving IC chip to the flexible circuit board  4 , for example, Tape Carrier Package (TCP), Chip on Film (COF) packaging, etc. In the TCP method, the flexible circuit board includes a plurality of contact pads, a plurality of pins of the driving IC chip and the plurality of contact pads of the flexible circuit board are soldered in one-to-one correspondence (such as eutectic soldering) or are electrically connected in one-to-one correspondence through anisotropic conductive adhesive (ACF), and at least the soldering part is protected by, for example, epoxy resin; in order to increase a bendability of the flexible circuit board in the TCP method, a slit may be formed in an packaging part. In the COF packaging method, the flexible circuit board includes a plurality of contact pads, a plurality of pins of the driving IC chip are directly crimped on the plurality of contact pads of the flexible circuit board through ACF, so that the plurality of pins of the driving IC chip are electrically connected to the plurality of contact pads of the flexible circuit board in one-to-one correspondence. For example, sizes and arrangements of the contact pads used to combine the driver IC chip on the flexible circuit board may be adjusted according to different types of packaging methods or driver IC chips to be packaged. For example, the contact pads may be arranged in a strip shape or in a rectangular shape. The embodiments of the present disclosure do not limit the packaging method of the driver IC chip. 
     It should be noted that the number of each of the first wiring L 1 , the second wiring L 2  and the third wiring L 3  are not limited, and the number may be one or more. Here, the “more” may be at least two, for example. 
     Continuing to refer to  FIGS. 4 and 5 , the one or more wirings included in the body area  42  may extend to the extension area  43  and are electrically connected to the main board through the binding area or a golden finger included in the extension area  43 . For example, each of the first wiring L 1  and the second wiring L 2  may extend to the extension area  43 . In this way, the data signal, the power signal, etc. sent by the main board may be transmitted to the display panel  3  through the wirings of the flexible circuit board  4 . 
       FIG. 6  is a cross-sectional view of the flexible circuit board taken along line II-If in  FIG. 5  according to the embodiments of the present disclosure. With reference to  FIGS. 5 and 6  in combination, the body area  42  of the flexible circuit board  4  includes a first sub-body area  421  and a second sub-body area  422 . A thickness of the first sub-body area  421  is greater than a thickness of the second sub-body area  422 . 
     It should be noted that, in the present disclosure, unless otherwise specified and limited, the expression “thickness” refers to a size in a direction perpendicular to the display surface of the display panel. 
     In some embodiments, the first sub-body area  421  includes a multi-layer board structure, for example, the first sub-body area  421  includes a four-layer board structure or a six-layer board structure. The second sub-body area  422  includes a single-layer board structure or a double-layer board structure. It should be noted that the embodiments of the present disclosure do not limit the number of layers of the first sub-body area  421  and the second sub-body area  422 . In the embodiments of the present disclosure, the number of layers of the first sub-body area  421  is greater than the number of layers of the second sub-body area  422 . In this way, the second sub-body area  422  is formed as a thinned area relative to the first sub-body area  421 . 
       FIG. 7  is a cross-sectional view of a first sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a four-layer board structure of the first sub-body area. As shown in  FIG. 7 , the first sub-body area  421  may include a first sub-circuit board  51  and a second sub-circuit board  52 . For example, each sub-circuit board may be a copper clad laminate. The first sub-circuit board  51  may include a base film  511 , conductive films  512  on opposite sides of the base film  511  and an adhesive layer  513  on a side of the base film  511 . The second sub-circuit board  52  may include a base film  521  and conductive films  522  on opposite sides of the base film  521 . The adhesive layer  513  may be disposed between the first sub-circuit board  51  and the second sub-circuit board  52 . For example, the first sub-circuit board  51  may include an adhesive layer  513 , and the adhesive layer  513  may be disposed on a side of the first sub-circuit board  51  close to the second sub-circuit board  52 . Optionally, the adhesive layer may also be disposed on a side of the second sub-circuit board  52  close to the first sub-circuit board  51 . In this way, the first sub-circuit board and the second sub-circuit board are bonded together through the adhesive layer  513 . 
     Continuing to refer to  FIG. 7 , the first sub-circuit board  51  and the second sub-circuit board  52  may include an insulating film layer  59  and a protective film  53 , respectively. For example, the insulating film layer  59  of the first sub-circuit board  51  is disposed on a side away from the second sub-circuit board  52 , the insulating film layer  59  of the second sub-circuit board  52  is disposed on a side away from the first sub-circuit board  51 . For example, the protective films  53  of the first sub-circuit board  51  and the protective films  53  of the second sub-circuit board  52  may be respectively disposed on a side of each insulating film layer  59  away from the base film, so as to protect each film layer inside. 
     It should be noted that the embodiments of the present disclosure are not limited to the embodiment shown in  FIG. 7 . For example, in other embodiments, the protective film  53  may also be disposed between two sub-circuit boards according to actual application requirements. 
       FIG. 8  is a cross-sectional view of a first sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a six-layer board structure of the first sub-body area. As shown in  FIG. 8 , the first sub-body area  421  may include a first sub-circuit board  51 , a second sub-circuit board  52  and a third sub-circuit board  54 . For example, each sub-circuit board may be a copper clad laminate. The first sub-circuit board  51  may include a base film  511 , conductive films  512  on opposite sides of the base film  511  and an insulating film layer  59  on a side of the base film  511 . The second sub-circuit board  52  may include a base film  521 , conductive films  522  on opposite sides of the base film  521  and adhesive layers  523  on two sides of the base film  521 . The third sub-circuit board  54  may include a base film  541 , conductive films  542  on opposite sides of the base film  541  and an insulating film layer  59  on a side of the base film  541 . An adhesive layer  523  may be disposed between the first sub-circuit board  51  and the second sub-circuit board  52 , and another adhesive layer  523  may be disposed between the second sub-circuit board  52  and the third sub-circuit board  54 . In this way, the first sub-circuit board, the second sub-circuit board and the third sub-circuit board are bonded together through the adhesive layers  523 . 
     Continuing to refer to  FIG. 8 , the first sub-circuit board  51  and the third sub-circuit board  54  may include the insulating film layer  59  and a protective film  53 , respectively. For example, the insulating film layer  59  of the first sub-circuit board  51  is disposed on a side away from the second sub-circuit board  52 , the insulating film  59  of the third sub-circuit board  54  is disposed on a side away from the second sub-circuit board  52 . For example, the protective film  53  of the first sub-circuit board  51  and the protective film  53  of the third sub-circuit board  54  may be respectively disposed on a side of each insulating film layer  59  away from the base film, so as to protect each film layer inside. 
     It should be noted that the embodiments of the present disclosure are not limited to the embodiments shown in  FIG. 8 . For example, in other embodiments, the protective film  53  may also be disposed between two sub-circuit boards according to actual application requirements. 
     For example, the base film may adopt a flexible material such as polyimide or polyester, and the conductive film may adopt a conductive metal material such as copper. 
     In the present disclosure, unless otherwise specified and limited, the numbers of layers in the expressions “single-layer board”, “double-layer board”, “four-layer board”, “six-layer board”, etc. indicate the number of layers of the conductive films of the flexible circuit board. For example, the “single-layer board” is disposed with one conductive film, the “double-layer board” is disposed with two conductive films, the “four-layer board” is disposed with four conductive films, and the “six-layer board” is disposed with six conductive films. 
       FIGS. 9A to 9F  are schematic diagrams of layered wirings of the six-layer board structure shown in  FIG. 8 . With reference to  FIGS. 8 and 9  in combination, the six-layer board structure of the first sub-body area  421  may include six conductive films. For ease of description, in  FIG. 9 , the six conductive films are described as a first layer ALL a second layer AL 2 , a third layer AL 3 , a fourth layer AL 4 , a fifth layer AL 5  and a sixth layer AL 6 , respectively. 
     The first layer AL 1  includes driving devices D 1 , D 2  and device wirings electrically connected to the driving devices D 1 , D 2 . For example, the device wirings may be a part of the first wiring L 1  and a part of the third wiring L 3  described above. The second layer AL 2  includes the power wiring L 2 . The third layer AL 3  includes a part of the touch wiring and a part of the power wiring. For example, the third wiring L 3  may include an Rx wiring L 31  for touch function, and the Rx wiring L 31  is used to transmit signals to a touch receiving electrode. The part of the touch wiring here may include the Rx wiring L 31 . The fourth layer AL 4  and the fifth layer AL 5  may include other types of wiring L 4 . The sixth layer AL 6  includes a part of the touch wiring. For example, the third wiring L 3  may also include a Tx wiring L 32  for touch function, the Tx wiring L 32  is used to transmit signals to a touch sending electrode, and the part of the touch wiring here may include the Tx wiring L 32 . 
     It should be noted that the arrangements of the above-mentioned elements and wirings are only exemplary, and are not a limitation to the embodiments of the present disclosure. In other embodiments, the elements and wrings on each layer may be adjusted according to actual requirements. For example, some conductive layers may not be disposed with wirings. For example, the fourth layer AL 4  and the fifth layer AL 5  may not be disposed with wirings, but a shielding layer may be disposed in the fourth layer AL 4  and the fifth layer AL 5 . 
     For example, the bonding area  41  and the bonding pins  411  may be disposed in the second layer AL 2 . 
     The power wiring L 2 , the Rx wiring L 31  of the touch wiring L 3 , and the Tx wiring L 32  of the touch wiring L 3  are located in the second layer, the third layer and the sixth layer, respectively, and an orthographic projection of the power wiring L 2  on the base film intersects with an orthographic projection of the touch wiring L 3  on the base film. In the above embodiments, the shielding between the power wiring L 2  and the touch wiring L 3  is achieved by the shielding layer of the fourth layer AL 4  and the shielding layer of the fifth layer AL 5 . For example, the shielding layer of the fourth layer AL 4  and the shielding layer of the fifth layer AL 5  may include a metal material, the shielding layer may be suspended, or configured to be electrically connected to a grounding wiring. In this way, signal interference between the power wiring L 2  and the touch wiring L 3  may be avoided. In practical applications, the shielding layer may be adjusted accordingly according to the number of layers of the flexible circuit board and the actual wiring layout. 
     Referring back to  FIG. 8 , the six-layer board structure of the first sub-body area  421  includes three sub-circuit boards, each sub-circuit board includes 2 layers of conductive film, that is, the six-layer board structure of the first sub-body area  421  has a combination of “2 layers+2 layers+2 layers”. 
     Optionally, the six-layer board structure of the first sub-body area  421  may have a combination of “1 layer+2 layers+2 layers+1 layer”.  FIG. 10A  is a cross-sectional view of a first sub-body area included in a flexible circuit board according to other embodiments of the present disclosure, which schematically illustrates a six-layer board structure of the first sub-body area. As shown in  FIG. 10A , the first sub-body area  421  may include a first sub-circuit board  51 , a second sub-circuit board  52 , a third sub-circuit board  54  and a fourth sub-circuit board  55 . For example, each sub-circuit board may be a copper clad laminate. The first sub-circuit board  51  may include a base film  511 , a conductive film  512  on a side of the base film  511  and an adhesive layer  513  on a side of the conductive film  512  away from the base film  511 . The second sub-circuit board  52  may include a base film  521 , conductive films  522  on opposite sides of the base film  521  and an adhesive layer  523  on a side of a lower conductive film  522  away from the base film  521 . The third sub-circuit board  54  may include a base film  541  and conductive films  542  on opposite sides of the base film  541 . The fourth sub-circuit board  55  may include a base film  551 , a conductive film  552  on a side of the base film  551  and an adhesive layer  553  on a side of the conductive film  552  away from the base film  551 . The adhesive layer  513  may be disposed between the first sub-circuit board  51  and the second sub-circuit board  52 , and the adhesive layer  523  may be disposed between the second sub-circuit board  52  and the third sub-circuit board  54 . For example, the adhesive layer  513  of the first sub-circuit board may be disposed on a side close to the second sub-circuit board  52 , the adhesive layer  523  of the second sub-circuit board may be disposed on a side close to the third sub-circuit board  54 , and the adhesive layer  553  of the fourth sub-circuit board may be disposed on a side close to the third sub-circuit board  54 . In this way, the first sub-circuit board, the second sub-circuit board, the third sub-circuit board and the fourth sub-circuit board are bonded together through the adhesive layers  513 ,  523 , and  553 . 
     Continuing to refer to  FIG. 10A , the first sub-circuit board  51  and the fourth sub-circuit board  55  may include a protective film  53 , respectively. For example, the protective film  53  of the first sub-circuit board  51  is disposed on a side away from the second sub-circuit board  52 , the protective film  53  of the fourth sub-circuit board  55  is disposed on a side away from the third sub-circuit board  54 . 
     It should be noted that the embodiments of the present disclosure are not limited to the embodiment shown in  FIG. 10A . For example, in other embodiments, the protective film  53  may also be disposed between two sub-circuit boards according to actual application requirements. For example, referring to  FIG. 10B , a protective film  53  may be respectively disposed between a first sub-circuit board  51  and a second sub-circuit board  52 , between the second sub-circuit board  52  and the third sub-circuit board  54 , and between the third sub-circuit board  54  and the fourth sub-circuit board  55 . 
       FIG. 11  is a cross-sectional view of a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the second sub-body area. As shown in  FIG. 11 , the second sub-body area  422  includes the double-layer board structure, and the double-layer board structure may include a double-layer sub-circuit board  56 . For example, the double-layer sub-circuit board  56  may be a copper clad laminate. The double-layer sub-circuit board  56  may include a base film  561 , conductive films  562  on opposite sides of the base film  561  and adhesive layers  563  on two sides of the conductive film  562  away from the base film  561 . 
       FIG. 21  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure. With reference to  FIGS. 8, 11 and 21  in combination, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “2 layer+2 layer+2 layer”, a double-layer sub-circuit board  56  of the second sub-body area  422  may be extracted from one of the first sub-circuit board  51 , the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 8 . That is, the double-layer sub-circuit board  56  of the second sub-body area  422  extends continuously with one of the first sub-circuit board  51 , the second sub-circuit board  52 , and the third sub-circuit board  54  in  FIG. 8 . For example, in the embodiment shown in  FIG. 21 , each of film layers  561 ,  562 , and  563  in the double-layer sub-circuit board  56  respectively extends from each of film layers  521 ,  522 , and  523  in the second sub-circuit board  52 . In this way, a process of forming the body area may be simplified. 
       FIG. 22  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure. With reference to  FIGS. 10A, 11, and 22  in combination, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, a double-layer sub-circuit board  56  of the second sub-body area  422  may be extracted from one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . That is, the double-layer sub-circuit board  56  of the second sub-body area  422  extends continuously with one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . For example, in the embodiment shown in  FIG. 22 , each of film layers  561  and  562  in the double-layer sub-circuit board  56  extend from each of film layers  541  and  542  in the third sub-circuit board  54  respectively. The adhesive layer  563  may extend from the adhesive layers  523  and  553  on two sides of the third sub-circuit board  54 . In this way, a process of forming the body area may be simplified. 
     In some exemplary embodiments, the conductive film  562  on an upper side of the double-layer sub-circuit board  56  forms a first conductive layer, and the conductive film  562  on a lower side of the double-layer sub-circuit board  56  forms a second conductive layer. For example, the first conductive layer may include a signal wiring and a power wiring, that is, the first wiring L 1  and second wiring L 2  described above. The second conductive layer may also include a signal wiring and a power wiring, that is, the first wiring L 1  and second wiring L 2  described above. Optionally, the second conductive layer may include a shielding layer. For example, the shielding layer may include a metal material, and the shielding layer may be suspended, or configured to be electrically connected to a grounding wiring. 
       FIG. 12  is a cross-sectional view of a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the second sub-body area. As shown in  FIG. 12 , the second sub-body area  422  includes the single-layer board structure, and the single-layer board structure may include a single-layer sub-circuit board  57 . For example, the single-layer sub-circuit board  57  may be a copper clad laminate. The single-layer sub-circuit board  57  may include a base film  571 , a conductive film  572  on a side of the base film  571 , and an adhesive layer  573  on a side of the conductive film  572  away from the base film  571 . 
       FIG. 23  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to the embodiments of the present disclosure. With reference to  FIGS. 10A, 12, and 23  in combination, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, a single-layer sub-circuit board  57  of the second sub-body area  422  may be extracted from one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . That is, the single-layer sub-circuit board  57  of the second sub-body area  422  extends continuously with one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . For example, in the embodiment shown in  FIG. 23 , each of film layers  571 ,  572 , and  573  in the single-layer sub-circuit board  57  extends from each of film layers  511 ,  512 , and  513  in the first sub-circuit board  51 , respectively. In this way, a process of forming the body area may be simplified. 
     In some exemplary embodiments, the conductive film  572  of the single-layer sub-circuit board  57  may include a signal wiring and a power wiring, that is, the first wiring L 1  and second wiring L 2  described above. 
     Referring back to  FIG. 5 , an orthographic projection of the combination of the first sub-body area  421  and the second sub-body area  422  (that is, the entire body area  42 ) on the display panel or the base film has a rectangular shape. The “rectangular” here includes not only a substantially rectangular shape, but also a shape similar to a rectangle in consideration of process conditions. On this basis, the body area  42  includes a long side and a short side. In some embodiments, each intersection position (i.e, corner) of the long side and the short side of the body area  42  has a right angle. In other embodiments, each corner of the body area  42  is curved, that is, each corner is smooth. 
     As shown in  FIG. 5 , a direction in which the short side of the body area  42  extends is defined as a first direction A 1 , and a direction in which the long side extends is defined as a second direction A 2 . A size of the body area  42  in the first direction A 1  is H, a size of the first sub-body area  421  in the first direction A 1  is H 1 , and a size of the second sub-body area  422  in the first direction A 1  is H 2 . A size of the first sub-body area  421  in the second direction A 2  is W 1 , and a size of the second sub-body area  422  in the second direction A 2  is W 2 . 
     In the embodiments of the present disclosure, an area of an orthographic projection of the body area  42  on the display panel or the base film is associated with an area of an orthographic projection of the first sub-body area  421  on the display panel or the base film. For example, as an area of the first sub-body area  421  decreases, an area of the body area  42  needs to be increased. That is, when an area of the first sub-body area  421  with the six-layer board structure is decreased, the area of the entire body area  42  needs to be increased, that is, an area of the second sub-body area  422  needs to be increased. In this way, it is still ensured that there is sufficient wiring area to arrange the plurality of wirings. 
     In some embodiments, the size H of the body area  42  is associated with the size H 1  of the first sub-body area  421 . For example, as the size H 1  of the first sub-body area  421  decreases, the size H of the body area  42  needs to be increased. For example, a ratio of the size H of the body area  42  to the size H 1  of the first sub-body area  421  may be between 1.5 to 5. For example, the size H 1  of the first sub-body area  421  may be within 5-10 mm, for example, about 7 mm; the size H of the body area  42  may be in a range of 7 to 20 mm, for example, about 12 mm. 
     It should be noted that a minimum value of the size H 1  of the first sub-body area  421  needs to meet a signal shielding requirement. In the above exemplary embodiments, the minimum value of the size H 1  of the first sub-body area  421  is set to about 5 mm to be able to meet the signal shielding requirement. 
     Continuing to refer to  FIG. 5 , the size W 1  of the first sub-body area  421  is substantially equal to the size W 2  of the second sub-body area  422 . That is, an orthographic projection of each of the first sub-body area  421  and the second sub-body area  422  on the display panel or the base film has a rectangular shape. By designing such the regular shape, it is advantageous to achieve the process of forming the first sub-body area and the second sub-body area. 
     In the embodiments of the present disclosure, the shape and the position of the second sub-body area  422  may be designed according to actual avoidance requirements.  FIG. 13  is a schematic plan view of a flexible circuit board according to other embodiments of the present disclosure. As shown in  FIG. 13 , the size W 2  of the second sub-body area  422  is smaller than the size W 1  of the first sub-body area  421 . For example, the size W 2  of the second sub-body area  422  may be less than or equal to half of the size W 1  of the first sub-body area  421 . 
     For example, the orthographic projection of the body area  42  on the display panel or the base film has a rectangular shape, the orthographic projection of the first sub-body area  421  on the display panel or the base film has an inverted L shape, and the orthographic projection of the second sub-body area  422  on the display panel or the base film has a rectangular shape. 
     In the embodiments of the present disclosure, the extension area  43  of the flexible circuit board  4  may include a double-layer board structure or a single-layer board structure. For example, the extension area  43  of the flexible circuit board  4  and the second sub-body area  422  of the flexible circuit board may extend continuously. 
     For example,  FIG. 14  is a cross-sectional view of an extension area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the extension area. As shown in  FIG. 14 , the extension area  43  includes the double-layer plate structure, the double-layer board structure may include a double-layer sub-circuit board  431 . For example, the double-layer sub-circuit board  431  may be a copper clad laminate. The double-layer sub-circuit board  431  may include a base film  4311 , conductive films  4312  on opposite sides of the base film  4311  and adhesive layers  4313  on two sides of the conductive film  4312  away from the base film  4311 . 
     The double-layer sub-circuit board  431  and the double-layer sub-circuit board  56  may be continuously extended. For example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “2 layers+2 layers+2 layers”, the double-layer sub-circuit board  431  may be extracted from one of the first sub-circuit board  51 , the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 8 . That is, the double-layer sub-circuit board  431  extends continuously with one of the first sub-circuit board  51 , the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 8 . For another example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, the double-layer sub-circuit board  431  may be extracted from one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . That is, the double-layer sub-circuit board  431  extends continuously with one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . In this way, the process of forming the body area may be simplified. 
       FIG. 24  is a cross-sectional view of a body area and an extension area included in a flexible circuit board according to the embodiments of the present disclosure. Referring to  FIG. 24 , the double-layer sub-circuit board  431  may be extracted from the second sub-circuit board  52  in  FIG. 10A . That is, each of film layers  4311 ,  4312 ,  4313  in the double-layer sub-circuit board  431  extend from each of film layers  521 ,  522 , and  523  in the second sub-circuit board  52 , respectively. 
     In some exemplary embodiments, the conductive film  4312  on an upper side of the double-layer sub-circuit board  431  forms a first conductive layer, and the conductive film  4312  on a lower side of the double-layer sub-circuit board  431  forms a second conductive layer. For example, the first conductive layer may include a signal wiring and a power wiring, that is, the first wiring L 1  and the second wiring L 2  described above. The second conductive layer may also include the signal wiring and the power wiring, that is, the first wiring L 1  and the second wiring L 2  described above. Optionally, the second conductive layer may include a shielding layer, For example, the shielding layer may include a metal material, and the shielding layer may be suspended, or configured to be electrically connected to a grounding wiring. 
       FIG. 15  is a cross-sectional view of an extension area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the extension area. As shown in  FIG. 15 , the extension area  43  includes the single-layer board structure, and the single-layer board structure may include a single-layer sub-circuit board  432 . For example, the single-layer sub-circuit board  432  may be a copper clad laminate. The single-layer sub-circuit board  432  may include a base film  4321 , a conductive film  4322  on a side of the base film  4321 , and an adhesive layer  4323  on a side of the conductive film  4322  away from the base film  4321 . 
     The single-layer sub-circuit board  432  and the single-layer sub-circuit board  57  may extend continuously. For example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, the single-layer sub-circuit board  432  may be extracted from one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . That is, the single-layer sub-circuit board  432  continuously extends with one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . In this way, the process of forming the extension area may be simplified. 
       FIG. 25  is a cross-sectional view of a body area and an extension area included in a flexible circuit board according to the embodiments of the present disclosure. Referring to  FIG. 25 , the single-layer sub-circuit board  432  may be extracted from the first sub-circuit board  51  in  FIG. 10A . That is, each of film layers  4321 ,  4322 ,  4323  in the single-layer sub-circuit board  432  extend from each of film layers  511 ,  512 , and  513  in the first sub-circuit board  51 , respectively. 
     In some exemplary embodiments, the conductive film  4322  of the single-layer sub-circuit board  432  may include a signal wiring and a power wiring, that is, the first wiring L 1  and the second wiring L 2  described above. 
     In the above embodiments, the extension area of the flexible circuit board is designed to include the double-layer board structure or the single-layer board structure. In this way, it is convenient for the flexible circuit board to be bent in the extension area, and it is beneficial to bend the flexible circuit board to the back surface of the display panel to be electrically connected to the main board. 
     In some embodiments, an electromagnetic shielding layer  435  is disposed on a side (for example, a side away from the display panel) of the second sub-body area  422  and the extension area  43  of the flexible circuit board  4 , as shown in  FIG. 18 . For example, the electromagnetic shielding layer  435  may be one or more of conductive rubber, conductive cloth, conductive foam and conductive shielding adhesive. By providing the electromagnetic shielding layer, the interference of external signals on signals transmitted by the wirings on the flexible circuit board may be shielded. 
       FIG. 26  is a cross-sectional view of a first sub-body area and a second sub-body area included in a flexible circuit board according to some exemplary embodiments of the present disclosure. Referring to  FIG. 26 , a left part corresponds to the first sub-body area, and a right part corresponds to the second sub-body area. The first sub-body area includes base films  511 ,  521 ,  531  and  541 , a conductive film  512  is disposed on a side surface (upper surface) of the base film  511 , conductive films  522  are respectively disposed on two sides of the base film  521 , conductive films  532  are respectively disposed on two sides of the base film  531 , a conductive film  542  is disposed on a side surface (lower surface) of the base film  541 . That is, the first sub-body area includes six conductive films and has a combination of “1 layer+2 layers+2 layers+1 layer”. The second sub-body area includes a base film  561 , and conductive films  562  are respectively disposed on two sides of the base film  561 . That is, the second sub-body area includes two conductive films. 
     In this embodiment, the second sub-body area extends continuously with the first sub-body area. Referring to  FIG. 26 , the base film  561  extends from the base film  531 , and the conductive films  562  extend from the conductive films  532 . 
     For example, a copper clad layer TL is disposed on at least one of the conductive films. Each of the wirings described above may be formed in the copper clad layer TL. That is, each wiring is formed by forming the copper clad layer TL on the conductive film and through patterning process such as a composition process. 
     It should be noted that in the embodiment shown in  FIG. 26 , only the conductive film  512 , one conductive film  522 , one conductive film  532 / 562  and the conductive film  542  are disposed with the copper clad layer TL, and the copper clad layer TL is not disposed on the other conductive film  522  and the other conductive film  532 / 562 . Such arrangement is exemplary, and is not intended to limit the embodiments of the present disclosure. The conductive film corresponding to the copper clad layer may be determined according to the actual requirements of the wiring layout. 
     Continuing to refer to  FIG. 26 , the first sub-body area and the second sub-body area may further include an electromagnetic shielding layer EMI, the electromagnetic shielding layer EMI is used to protect electronic elements and wirings in the first sub-body area and the second sub-body area from external electromagnetic interference. 
     For example, adhesive layers  513 ,  523 ,  533 , and  563  may also be disposed between the film layers. In the second sub-body area, a protective film  53  may be further disposed between the adhesive layer  563  and the electromagnetic shielding layer EMI. 
     For example, in the first sub-body area, a protective layer PTL may be disposed on a side of the adhesive layer  513  away from the base film. An insulating film layer  59  may also be disposed between the copper clad layer TL and the electromagnetic shielding layer EMI. 
     In the embodiments of the present disclosure, the bonding area  41  of the flexible circuit board  4  may include a double-layer board structure or a single-layer board structure. For example, the bonding area  41  of the flexible circuit board  4  may be extracted from one sub-circuit board of the six-layer board structure of the first sub-body area  421 . 
     In some embodiments, extracting layers of the bonding area  41 , the second sub-body area  422  and the extension area  43  of the flexible circuit board  4  may be the same. That is, the bonding area  41 , the second sub-body area  422  and the extension area  43  are all extracted from the same sub-circuit board of the six-layer board structure of the first sub-body area  421 . In this way, when the each wiring described above extends from one area to another area, the each wiring may extend in the same layer without extending to other layers through via holes, which is beneficial to reduce a impedance of the wiring. 
     For example,  FIG. 16  is a cross-sectional view of a bonding area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a double-layer board structure of the bonding area. As shown in  FIG. 16 , the bonding area  41  includes the double-layer board structure, and the double-layer board structure may include a double-layer sub-circuit board  411 . For example, the double-layer sub-circuit board  411  may be a copper clad laminate. The two-layer sub-circuit board  411  may include a base film  4111 , conductive films  4112  on opposite sides of the base film  4111  and adhesive layers  4113  on a side of the conductive film  4112  away from the base film  4111 , respectively. 
     The double-layer sub-circuit board  411  and the double-layer sub-circuit board  56  may extend continuously. For example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “2 layers+2 layers+2 layers”, the double-layer sub-circuit board  411  may be extracted from one of the first sub-circuit board  51 , the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 8 . That is, the double-layer sub-circuit board  411  extends continuously with one of the first sub-circuit board  51 , the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 8 . For another example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, the double-layer sub-circuit board  411  may be extracted from one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . That is, the double-layer sub-circuit board  411  extends continuously with one of the second sub-circuit board  52  and the third sub-circuit board  54  in  FIG. 10A . 
       FIG. 17  is a cross-sectional view of a bonding area included in a flexible circuit board according to the embodiments of the present disclosure, which schematically illustrates a single-layer board structure of the bonding area. As shown in  FIG. 17 , the bonding area  41  includes a single-layer board structure, and the single-layer board structure may include a single-layer sub-circuit board  412 . For example, the single-layer sub-circuit board  412  may be a copper clad laminate. The single-layer sub-circuit board  412  may include a base film  4121 , a conductive film  4122  on a side of the base film  4121 , and an adhesive layer  4123  on a side of the conductive film  4122  away from the base film  4121 . 
     The single-layer sub-circuit board  412  and the single-layer sub-circuit board  57  described above may extend continuously. For example, in the case that the six-layer board structure of the first sub-body area  421  adopts the layout of “1 layer+2 layers+2 layers+1 layer”, the single-layer sub-circuit board  412  may be extracted from one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . That is, the single-layer sub-circuit board  412  extends continuously with one of the first sub-circuit board  51  and the fourth sub-circuit board  55  in  FIG. 10A . 
     In some embodiments, extracting layers of the bonding area  41  and the second sub-body area  422  of the flexible circuit board  4  may be different. For example, the bonding area  41  may be extracted from the second layer AL 2  of the six-layer board structure of the first sub-body area  421 , and the second sub-body area  422  may be extracted from the sixth layer AL 6  of the six-layer board structure of the first sub-body area  421 . In this embodiment, it may be ensured that the extension area of the flexible circuit board extends flatly from the first sub-body area, which is beneficial to the formation of the extension area. 
       FIG. 18  is a partial enlarged view of the display device at part III in  FIG. 1  according to the embodiments of the present disclosure.  FIG. 19  is a schematic plan view of the display device shown in  FIG. 18 . With reference to  FIGS. 1, 2, 18 and 19 , the display device may also include a battery  6 . It should be noted that the expression “battery” herein may include any form of power storage components, including but not limited to lithium batteries, battery compartments with protective shells and the like. 
     An orthographic projection of the battery  6  on the display panel  3  do not overlap with the orthographic projection of the first sub-body area  421  on the display panel  3 . The first sub-body area  421  includes a thicker six-layer board structure, and the battery  6  or a middle frame component  7  does not extend below the first sub-body area  421 . 
     The orthographic projection of the battery  6  on the display panel  3  at least partially overlaps with the orthographic projection of the body area  42  on the display panel  3 . For example, the orthographic projection of the battery  6  on the display panel  3  at least partially overlaps with the orthographic projection of the second sub-body area  422  on the display panel  3 . 
     In the embodiments of the present disclosure, by designing the second sub-body area  422  thinner than the first sub-body area  421 , the battery  6  may extend below the second sub-body area  422 . In this way, an area of the battery  6  equipped in the display device may be increased, and accordingly, a capacity of the battery  6  may be increased. 
     It should be noted that, the embodiments of the present disclosure are not limited to an interference avoiding of the battery  6 . By designing the thinned second sub-body area  422 , other components of the display device (for example, the middle frame component) may extend below the second sub-body area, so as to achieve the purpose of interference avoiding. For example,  FIG. 20  is a partial plan view of the display device of the embodiment shown in  FIG. 13 . As shown in  FIG. 20 , the display device includes a middle frame component  7 , the middle frame component  7  may extend below the second sub-body area  422 . That is, an orthographic projection of the middle frame component  7  on the display panel  3  at least partially overlaps with the orthographic projection of the second sub-body area  422  on the display panel  3 . Therefore, through such design, components such as the battery, the middle frame component, etc. may be avoided from interference. When the display device is a small-sized display device such as a mobile phone, such design of interference avoiding is particularly advantageous. 
     In the specific implementation process, the flexible circuit board  4  may be bent to the back surface of the display panel to achieve the narrow bezel design of the display device. The display device provided by the embodiments of the present disclosure may be any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a laptop computer, a digital photo frame, a navigator and the like. Other indispensable components of the display device are understood by those skilled in the art, which will not be repeated here, and should not be used as a limitation to the embodiments of the present disclosure. 
     The descriptions above are only specific implementations of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Within the technical scope disclosed in the present disclosure, any changes or substitutions that may be easily conceived by those skilled in the art should fall within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.