Flexible circuit board and display device

Abstract

The invention discloses a flexible circuit board and a display device. The flexible circuit board comprises a base material layer and a first conductive layer, the base material layer comprises a first bonding pad area, a second bonding pad area and a transmission line area; the first conductive layer is located on the first side of the base material layer and comprises a first bonding pad structure, a second bonding pad structure and a plurality of signal transmission lines extending in the first direction. The first bonding pad structure is located in the first bonding pad area, the second bonding pad structure is located in the second bonding pad area, the signal transmission lines are located in the transmission line area, and the transmission line area comprises a first single-layer area and a first double-layer area which are arranged in the first direction; in the first single-layer area, a first conductive layer is arranged on the first side of the base material layer, a conductive structure is not arranged on the second side of the base material layer, in the first double-layer area, a first conductive layer is arranged on the first side of the base material layer, a second conductive layer is arranged on the second side of the base material layer, and the second side and the first side are two opposite sides of the base material layer. Therefore, the flexible circuit board has relatively strong anti-electromagnetic interference capability and electromagnetic compatibility.

Description

Flexible circuit board and display device Technical Field

[0001] Embodiments of the present disclosure relate to a flexible circuit board and a display device. Background Art

[0002] In a display device, in order to achieve a narrow bezel design, the driver circuit board of the display panel is usually set on the backlight side of the display panel, and then the binding area on the light-emitting side of the display panel is connected to the driver circuit board on the backlight side of the display panel through a bent flexible circuit board.

[0003] On the other hand, as the size and resolution of display devices continue to increase, the frequency of display signals is also getting higher and higher; therefore, it is necessary to use high-frequency signal transmission lines (such as LVDS / EDP transmission lines) to transmit display signals, and their clock frequencies usually range from tens to hundreds of MHz.

[0004] During high-frequency signal transmission, signals or electromagnetic waves must propagate along a transmission path with uniform impedance. Once the impedance mismatch or discontinuity of the transmission path occurs, part of the signal or electromagnetic wave will be reflected back to the transmitter, while the remaining part will continue to be transmitted to the receiver.

[0005] Summary of the Invention

[0006] The embodiments of the present disclosure provide a flexible circuit board and a display device. By providing a first single-layer region and a first double-layer region in the transmission line region, the flexible circuit board can be bent or curved in the first single-layer region, thereby having better bending performance and avoiding the generation of large stress or fracture in the first single-layer region. At the same time, the flexible circuit board can also use the second conductive layer in the first double-layer region to provide electromagnetic protection and impedance matching for the signal transmission line, thereby avoiding poor display caused by poor data transmission stability, and also improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board, thereby having a wider range of applications and application scenarios.

[0007] At least one embodiment of the present disclosure provides a flexible circuit board, comprising: a substrate layer, comprising a first pad area, a second pad area, and a transmission line area located between the first pad area and the second pad area; and a first conductive layer, located on a first side of the substrate layer, and comprising a first pad structure, a second pad structure, and a plurality of signal transmission lines extending along a first direction, wherein the first pad structure is located in the first pad area, the second pad structure is located in the second pad area, the plurality of signal transmission lines are located in the transmission line area, and the transmission line area comprises a first single-layer area and a first double-layer area arranged along the first direction; in the first single-layer area, the first side of the substrate layer is provided with the first conductive layer, and the second side of the substrate layer is not provided with a conductive structure; in the first double-layer area, the first side of the substrate layer is provided with the first conductive layer, and the second side of the substrate layer is provided with the second conductive layer, and the second side and the first side are opposite sides of the substrate layer.

[0008] For example, in the flexible circuit board provided in an embodiment of the present disclosure, at least a portion of the first single-layer area is a bending area, and at least a portion of the first double-layer area is a flat area.

[0009] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the transmission line area also includes: a second double-layer area, which is located on the side of the first single-layer area away from the first double-layer area in the first direction, and in the second double-layer area, the first side of the substrate layer is provided with the first conductive layer, and the second side of the substrate layer is provided with a third conductive layer.

[0010] For example, in a flexible circuit board provided in an embodiment of the present disclosure, the flexible circuit board is bent to form a U-shaped structure, and the U-shaped structure includes a first flat portion, a second flat portion, and a connecting portion located between the first flat portion and the second flat portion, and the connecting portion connects the first flat portion and the second flat portion to semi-enclose a accommodating space; at least part of the first double-layer area is located in the second flat portion, at least part of the first single-layer area and the second double-layer area are located in the connecting portion, at least part of the second double-layer area is located in the connecting portion away from the bottom of the accommodating space, and at least part of the first single-layer area is located between the bottom and the second flat portion.

[0011] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the third conductive layer includes a first interconnection line extending along a second direction intersecting with the first direction; the multiple signal transmission lines include a plurality of first signal transmission lines, and the multiple first signal transmission lines are configured to transmit the same electrical signal, and the multiple first signal transmission lines are electrically connected to the first interconnection lines respectively.

[0012] For example, in the flexible circuit board provided in an embodiment of the present disclosure, the first signal transmission line is configured to transmit a ground signal.

[0013] For example, in the flexible circuit board provided in an embodiment of the present disclosure, the second conductive layer and the third conductive layer are provided on the same layer.

[0014] For example, the flexible circuit board provided in one embodiment of the present disclosure further includes: a second single-layer area located between the second double-layer area and the first pad area; and a third single-layer area located between the first double-layer area and the second pad area.

[0015] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the multiple signal transmission lines include: a high-frequency signal transmission line, configured to transmit a high-frequency signal; and a plurality of first ground lines, wherein the high-frequency signal transmission line is provided with at least one first ground line on both sides thereof in a second direction intersecting with the first direction; in the first double-layer area, the second conductive layer is respectively connected to the first ground lines on both sides of the high-frequency signal transmission line through a first via hole passing through the substrate layer.

[0016] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the high-frequency signal transmission line includes: a first high-frequency signal sub-line; and a second high-frequency signal sub-line, and the polarity of the high-frequency signal on the first high-frequency signal sub-line and the polarity of the high-frequency signal on the second high-frequency signal sub-line are different.

[0017] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the transmission line area also includes: a third double-layer area, located between the first double-layer area and the second double-layer area, and passing through the first single-layer area to be connected to the first double-layer area and the second double-layer area respectively, the first single-layer area is also located on both sides of the third double-layer area in the second direction, the second direction intersects with the first direction, in the third double-layer area, the first conductive layer is provided on the first side of the substrate layer, and the fourth conductive layer is provided on the second side of the substrate layer, the second conductive layer and the third conductive layer are connected through the fourth conductive layer, and are provided on the same layer.

[0018] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the multiple signal transmission lines include: a high-frequency signal transmission line, configured to transmit a high-frequency signal; and a plurality of first ground lines, the high-frequency signal transmission line extending from the first double-layer area through the third double-layer area to the second double-layer area, and the high-frequency signal transmission line is provided with at least one first ground line on both sides of the second direction intersecting with the first direction; in the first double-layer area, the second conductive layer is respectively connected to the first ground lines on both sides of the high-frequency signal transmission line through a first via hole passing through the substrate layer, and in the third double-layer area, the fourth conductive layer is respectively connected to the first ground lines on both sides of the high-frequency signal transmission line through a second via hole passing through the substrate layer.

[0019] For example, the flexible circuit board provided by one embodiment of the present disclosure includes: a first protective layer, located in the transmission line area, and located on the side of the first conductive layer away from the substrate layer; a second protective layer, located in the first double-layer area, and located on the side of the second conductive layer away from the substrate layer; and a first exposure opening, located in the second protective layer, and configured to expose the second conductive layer.

[0020] For example, the flexible circuit board provided in one embodiment of the present disclosure also includes: a conductive tape, which is at least partially located on the side of the second protective layer away from the second conductive layer, and contacts the second conductive layer through the first exposed opening, and the conductive tape is configured to be connected to the ground terminal.

[0021] For example, in the flexible circuit board provided by an embodiment of the present disclosure, the first exposure opening is located at a side of the center of the first double-layer region close to the first single-layer region in the first direction.

[0022] For example, in the flexible circuit board provided by an embodiment of the present disclosure, the flexible circuit board includes a plurality of first exposure openings arranged along a second direction intersecting with the first direction.

[0023] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the multiple signal transmission lines include a second ground line, which is located at the outermost side of the multiple signal transmission lines; the first conductive layer also includes: a conductive grid, which is located on a side of the second ground line away from the center of the multiple signal transmission lines and is connected to the second ground line; and a protective line, which is located on a side of the conductive grid away from the second ground line.

[0024] For example, the flexible circuit board provided in one embodiment of the present disclosure also includes: a first protective layer, located in the transmission line area, and located on the side of the first conductive layer away from the substrate layer; a second protective layer, located in the first double-layer area, and located on the side of the second conductive layer away from the substrate layer; and a second exposure opening, located in the first protective layer, and configured to expose the first conductive layer, the orthographic projection of the second exposure opening on the substrate layer overlapping with the orthographic projection of the second ground line on the substrate layer and the orthographic projection of the conductive grid on the substrate layer, respectively.

[0025] For example, the flexible circuit board provided in one embodiment of the present disclosure further includes: a first electromagnetic shielding coating, located on a side of the first protective layer away from the first conductive layer, and arranged in contact with the second ground line and the conductive grid through the second exposure opening.

[0026] For example, in the flexible circuit board provided by an embodiment of the present disclosure, the first electromagnetic shielding coating is only located in the first double-layer area.

[0027] For example, the flexible circuit board provided in one embodiment of the present disclosure also includes: a third exposure opening, located in the second protective layer and configured to expose the second conductive layer; and a second electromagnetic shielding coating, located on a side of the second protective layer away from the second conductive layer, and arranged in contact with the second conductive layer through the third exposure opening.

[0028] For example, in the flexible circuit board provided in an embodiment of the present disclosure, the orthographic projection of the third exposure opening on the substrate layer overlaps with the orthographic projection of the second exposure opening on the substrate layer.

[0029] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the first pad structure includes M first conductive pads, and the second pad structure includes M second conductive pads; the multiple signal transmission lines include a second signal transmission line, the second signal transmission line includes a first end and a second end, the first end of the second signal transmission line includes P branches, and the second end of the second signal transmission line includes P branches; the P branches of the first end of the second signal transmission line are respectively connected to the P first conductive pads, and the P branches of the second end of the second signal transmission line are respectively connected to the P second conductive pads, where P is a positive integer greater than or equal to 2 and less than M.

[0030] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the first pad structure includes M first conductive pads, and the second pad structure includes N second conductive pads; the multiple signal transmission lines include a third signal transmission line, the third signal transmission line includes a first end and a second end, and the first end of the third signal transmission line includes P branches; the P branches of the first end of the third signal transmission line are respectively connected to P first conductive pads, and the second end of the third signal transmission line is connected to one second conductive pad, P is a positive integer greater than or equal to 2 and less than N, and M is greater than N.

[0031] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the first pad structure includes M first conductive pads, and the second pad structure includes Q second conductive pads; the multiple signal transmission lines include: a fourth signal transmission line, extending from the first pad area to the first double-layer area, the fourth signal transmission line includes a first end located in the first pad area and a second end located in the first double-layer area; and a fifth signal transmission line, extending from the first pad area through the first double-layer area to the second pad area, the fifth signal transmission line includes a first end located in the first pad area and a second end located in the second pad area, the second conductive layer also includes a lateral transmission line, the lateral transmission line is connected to the second end of the fourth signal transmission line through a third via passing through the substrate layer, and is connected to the fifth signal transmission line through a fourth via passing through the substrate layer.

[0032] For example, in the flexible circuit board provided in one embodiment of the present disclosure, the substrate layer is a flexible substrate layer.

[0033] For example, in the flexible circuit board provided in an embodiment of the present disclosure, the second conductive layer includes a conductive metal grid.

[0034] For example, in the flexible circuit board provided in an embodiment of the present disclosure, the material of the first conductive layer includes copper, and the material of the second conductive layer includes copper.

[0035] At least one embodiment of the present disclosure further provides a display device, comprising: a display panel; and any one of the flexible circuit boards described above.

[0036] For example, the display device provided by one embodiment of the present disclosure also includes: a backplane, located on one side of the display panel; and a driving circuit board, located on a side of the backplane away from the display panel, the display panel includes a binding area and a plurality of binding gaskets located in the binding area, the backplane includes a bottom frame, and the flexible circuit board is bent from the binding area to the side of the backplane away from the display panel; the first pad structure is connected to the multiple binding gaskets, and the second pad structure is connected to the driving circuit board.

[0037] For example, in a display device provided in an embodiment of the present disclosure, the first double-layer area is located on a side of the back plate away from the display panel, and at least part of the first single-layer area is a bending area surrounding the bottom frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure, rather than limiting the present disclosure.

[0039] FIG1 is a schematic diagram of a display device.

[0040] FIG2 is a plan view of a flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0041] FIG3A is a schematic cross-sectional view of a flexible circuit board provided by an embodiment of the present disclosure along line AB in FIG2 .

[0042] FIG3B is a schematic cross-sectional view of a flexible circuit board provided by an embodiment of the present disclosure along line CD in FIG2 .

[0043] FIG4A is a schematic diagram of a flexible circuit board applied to a display device according to an embodiment of the present disclosure.

[0044] FIG4B is a partial schematic diagram of a display device provided in accordance with an embodiment of the present disclosure.

[0045] FIG5 is a schematic cross-sectional view of another flexible circuit board provided by an embodiment of the present disclosure along line AB in FIG2 .

[0046] FIG6 is a layout diagram of a flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0047] FIG7 is a schematic diagram of a first conductive layer in a flexible circuit board provided by an embodiment of the present disclosure.

[0048] FIG8 is a schematic diagram of a second conductive layer in a flexible circuit board provided by an embodiment of the present disclosure.

[0049] FIG9 is a schematic diagram showing a flexible circuit board provided by an embodiment of the present disclosure in which a second conductive layer is connected to a first ground line through a first via hole.

[0050] FIG10 is a plan view of another flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0051] FIG11 is a schematic cross-sectional view of a flexible circuit board provided by one embodiment of the present disclosure along the center line EF of FIG10 .

[0052] FIG12 is a schematic diagram of the layout of a flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0053] FIG13A is a partial schematic diagram of a first pad structure in a flexible circuit board provided in an embodiment of the present disclosure.

[0054] FIG13B is a partial schematic diagram of a second pad structure in a flexible circuit board provided in an embodiment of the present disclosure.

[0055] FIG14A is a partial schematic diagram of a first pad structure in another flexible circuit board provided in an embodiment of the present disclosure.

[0056] FIG14B is a partial schematic diagram of a second pad structure in another flexible circuit board provided in an embodiment of the present disclosure.

[0057] FIG15 is a layout diagram of another flexible circuit board provided in an embodiment of the present disclosure.

[0058] FIG16 is a plan view of a flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0059] FIG17 is a schematic cross-sectional view of a flexible circuit board provided by one embodiment of the present disclosure along line GH in FIG16 .

[0060] FIG18 is a plan view of a flexible circuit board provided in accordance with an embodiment of the present disclosure.

[0061] FIG19 is a schematic cross-sectional view of a flexible circuit board provided by one embodiment of the present disclosure along line JK in FIG18 .

[0062] FIG20A is a schematic structural diagram of a display device provided in accordance with an embodiment of the present disclosure.

[0063] FIG20B is a partially enlarged view of a display device provided in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0064] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0065] Unless otherwise defined, the technical or scientific terms used in this disclosure should have the usual meanings understood by persons of ordinary skill in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "include" or "comprise" mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0066] Unless otherwise defined, the features such as “parallel”, “perpendicular” and “identical” used in the embodiments of the present disclosure include situations such as “parallel”, “perpendicular” and “identical” in a strict sense, as well as situations such as “approximately parallel”, “approximately perpendicular” and “approximately identical” that contain a certain error. For example, the above-mentioned “approximately” may mean that the difference between the compared objects is 10% of the average value of the compared objects, or within 5%. When the number of a component or element is not specifically indicated below in the embodiments of the present disclosure, it means that the component or element may be one or more, or may be understood as at least one. “At least one” refers to one or more, and “plurality” refers to at least two.

[0067] As the size and resolution of display devices continue to increase, the frequency of display signals is also getting higher and higher; therefore, it is necessary to use high-frequency signal transmission lines (such as LVDS / EDP transmission lines) to transmit display signals, and their clock frequencies usually range from tens to hundreds of MHz.

[0068] To ensure the accuracy of transmitted display data, high-frequency signal transmission lines require high stability, while also minimizing high-frequency signal reflections to improve the product's electromagnetic compatibility (EMC). In typical display devices, a single-layer flexible printed circuit board (FPC) is often used to connect the driver circuit board and display panel for optimal flexibility. This ultimately transmits display data from the host computer to the display panel. The FPC can also be bent to position the driver circuit board on the backlight side of the display panel, achieving a narrow-bezel design.

[0069] Figure 1 is a schematic diagram of a display device. As shown in Figure 1 , a host 10 transmits display data to a driver circuit board 20 via LVDS transmission lines. The driver circuit board 20 then transmits the display data to a display panel 40 via a flexible circuit board 30, thereby driving the display panel 40 to produce an illuminated display. It should be noted that the display panel 40 includes a display area 41 and a peripheral area 42 surrounding the display area 41. The peripheral area 42 includes a binding area 43. One end of the flexible circuit board 30 is connected to the driver circuit board 20, and the other end is connected to the binding area 43 of the display panel 40.

[0070] However, a single-layer flexible circuit board only includes a conductive layer for forming a signal transmission line, and cannot be provided with other shielding layers or impedance matching layers (such as copper layers). Therefore, it is impossible to control the impedance of the high-frequency signal transmission line, which can easily lead to impedance mismatch in the high-frequency signal transmission line. First, this impedance mismatch affects the stability of data transmission and causes display anomalies. Second, this impedance mismatch also easily causes high-frequency signals to reflect, resulting in poor performance of the flexible circuit board in both electromagnetic compatibility testing and electromagnetic interference resistance testing.

[0071] To address the aforementioned issues, a double-layer flexible circuit board (FPCB) comprising two conductive layers can be used to connect the driver circuit board and the display panel. However, due to the increased overall thickness of the FPCB, the FPCB exerts greater stress on the display panel after bonding. This can easily pull up the portion where the display panel is bonded to the FPCB, causing the backlight to leak from the raised position, resulting in defects such as light leakage and mura. Furthermore, the FPCB is also stiffer and more prone to breakage when bent.

[0072] The present disclosure provides a flexible circuit board. The flexible circuit board includes a substrate layer and a first conductive layer; the substrate layer includes a first pad area, a second pad area, and a transmission line area located between the first pad area and the second pad area; the first conductive layer is located on a first side of the substrate layer and includes a first pad structure, a second pad structure, and a plurality of signal transmission lines extending along a first direction; the first pad structure is located in the first pad area, the second pad structure is located in the second pad area, and the plurality of signal transmission lines are located in the transmission line area; the transmission line area includes a first single-layer area and a first double-layer area arranged along the first direction; in the first single-layer area, the first conductive layer is provided on the first side of the substrate layer, and no conductive structure is provided on the second side of the substrate layer; in the first double-layer area, the first conductive layer is provided on the first side of the substrate layer, and the second conductive layer is provided on the second side of the substrate layer, with the second side and the first side being opposite sides of the substrate layer. Thus, by providing the first single-layer area and the first double-layer area in the transmission line area, the flexible circuit board can be bent or folded in the first single-layer area, thereby having better bending performance and preventing the first single-layer area from generating large stress or fracture. At the same time, the flexible circuit board can also use the second conductive layer in the first double-layer area to perform electromagnetic protection and impedance matching on the signal transmission line, thereby avoiding poor display caused by poor data transmission stability, and can also improve the anti-electromagnetic interference ability and electromagnetic compatibility (EMC performance) of the flexible circuit board, thereby having a wider range of applications and application scenarios.

[0073] The present disclosure also provides a display device comprising a display panel and the aforementioned flexible circuit board. This device can avoid light leakage and other issues caused by high stress at the binding point between the flexible circuit board and the display panel, while also exhibiting strong electromagnetic compatibility and immunity to electromagnetic interference.

[0074] The flexible circuit board and the display device provided by the embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0075] One embodiment of the present disclosure provides a flexible circuit board. Figure 2 is a plan view of a flexible circuit board according to one embodiment of the present disclosure; Figure 3A is a cross-sectional view of a flexible circuit board according to one embodiment of the present disclosure taken along line AB in Figure 2; and Figure 3B is a cross-sectional view of a flexible circuit board according to one embodiment of the present disclosure taken along line CD in Figure 2.

[0076] As shown in Figures 2 and 3A, the flexible circuit board 100 includes a substrate layer 110 and a first conductive layer 120; the substrate layer 110 includes a first pad area 111, a second pad area 112 and a transmission line area 113 located between the first pad area 111 and the second pad area 112, and the first pad area 111, the transmission line area 113 and the second pad area 112 can be arranged along the first direction X; the first conductive layer 120 is located on the first side of the substrate layer 110, and includes a first pad structure 121, a second pad structure 122 and a plurality of signal transmission lines 130 extending along the first direction; the first pad structure 121 is located in the first pad area 111, the second pad structure 122 is located in the second pad area 112, and the plurality of signal transmission lines 130 are located in the transmission line area 113.

[0077] As shown in Figures 2 and 3A, the transmission line region 113 includes a first single-layer region 113A and a first double-layer region 113B arranged along a first direction X. In the first single-layer region 113A, a first conductive layer 120 is disposed on the first side of the substrate layer 110, and no conductive structure is disposed on the second side of the substrate layer 110. In the first double-layer region 113B, the first conductive layer 120 is disposed on the first side of the substrate layer 110, and a second conductive layer 140 is disposed on the second side of the substrate layer 110. The second side and the first side are opposite sides of the substrate layer 110. It can be seen that the "single-layer" or "double-layer" in the "single-layer region" and "double-layer region" in the embodiments of the present disclosure refers to the number of conductive layers contained in the corresponding region, and is not intended to limit the number of other non-conductive layers.

[0078] In the flexible circuit board provided in the embodiment of the present disclosure, the first single-layer area includes only a single conductive layer, and therefore has good bending performance and is not prone to breakage or excessive stress. Therefore, by providing the first single-layer area and the first double-layer area in the transmission line area, the flexible circuit board can be bent or curved in the first single-layer area, thereby having good bending performance and avoiding the generation of large stress or breakage in the first single-layer area. At the same time, the flexible circuit board can also use the second conductive layer in the first double-layer area to provide electromagnetic protection and impedance matching for the signal transmission line, thereby avoiding poor display caused by poor data transmission stability, and also improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board, thereby having a wider range of applications and application scenarios.

[0079] For example, the substrate layer can be a flexible substrate layer, and the material of the flexible substrate layer can be a flexible material such as polyimide. The material of the first conductive layer can be a conductive metal material such as copper, aluminum, silver, etc.; the material of the second conductive layer can also be a conductive metal material such as copper, aluminum, silver, etc.

[0080] In some examples, because the first single-layer region 113A includes only one conductive layer (i.e., the first conductive layer 120) and has good bending or curvature properties, at least a portion of the first single-layer region can serve as a bending region; that is, bending or curvature can be performed in the first single-layer region. The first double-layer region 113B, on the other hand, has two conductive layers (i.e., the first conductive layer and the second conductive layer), so at least a portion of the first double-layer region can serve as a flat region.

[0081] Figure 4A is a schematic diagram of a flexible circuit board according to one embodiment of the present disclosure, applied to a display device; Figure 4B is a partial schematic diagram of a display device according to one embodiment of the present disclosure. As shown in Figures 4A and 4B, a display device 500 includes a display panel 300, a driver circuit board 400, and the aforementioned flexible circuit board 100. The driver circuit board 400 is positioned on the backlight side of the display panel 300. One end of the flexible circuit board 100 is bonded to a bonding area of ​​the display panel 300 and then bent to connect to the driver circuit board 400 at the other end. This allows the driver circuit board 400 to transmit display data to the display panel 300 via the flexible circuit board 100, thereby driving the display panel 300 to produce an illuminated display. Furthermore, because the driver circuit board 400 is positioned on the backlight side of the display panel 300 and the flexible circuit board 100 is bent to connect the display panel 300 and driver circuit board 400, it does not occupy a large area, thus achieving a narrow bezel design.

[0082] As shown in Figures 4A and 4B , the first single-layer region 113A of the flexible circuit board 100 can serve as the bending portion of the flexible circuit board 100, while the first double-layer region 113B can serve as the flat portion of the flexible circuit board 100 located on the backlight side of the display panel 300. Thus, the flexible circuit board can be designed differently for the bending portion and the flat portion, namely, by using different numbers of conductive layers, to achieve both good bending performance and strong electromagnetic interference resistance and electromagnetic compatibility.

[0083] On the other hand, since the flexible circuit board 100 uses the first single-layer area 113A as the bending portion, the stress generated in the first single-layer area 113A is relatively small, and will not generate a large pulling force on the binding area of ​​the display panel 300, thereby preventing the backlight under the display panel 300 from being exposed, causing defects such as light leakage and mura.

[0084] It is noteworthy that the second conductive layer 140 of the first double-layer region 113B of the flexible circuit board 100 provided in the present embodiment can not only provide electromagnetic protection and impedance matching for the signal transmission lines 130, but can also be used to achieve other functions. For example, the second conductive layer 140 can be provided with a conductive structure to connect to some of the multiple signal transmission lines 130 to reduce resistance; or the second conductive layer 140 can be provided with a conductive structure to electrically connect signal transmission lines 130 that transmit the same signal among the multiple signal transmission lines 130 to improve the uniformity and stability of the signal.

[0085] In some examples, as shown in Figures 2 and 3A , the transmission line region 113 further includes a second double-layer region 113C. The second double-layer region 113C is located in the first direction on a side of the first single-layer region 113A away from the first double-layer region 113B. That is, the first single-layer region 113A is disposed between the first double-layer region 113B and the second double-layer region 113C. In the second double-layer region 113C, the first conductive layer 120 is disposed on the first side of the substrate layer 110, and the third conductive layer 140A is disposed on the second side of the substrate layer 110. Thus, the flexible circuit board 100 can utilize other relatively flat portions to provide the second double-layer region 113C. This allows the third conductive layer 140A in the second double-layer region 113C to provide electromagnetic shielding and impedance matching for the signal transmission line, thereby preventing display defects caused by poor data transmission stability and further improving the electromagnetic interference resistance and electromagnetic compatibility (EMC) performance of the flexible circuit board 100.

[0086] In some examples, the second conductive layer 140 and the third conductive layer 140A are provided in the same layer. That is, the second conductive layer 140 and the third conductive layer 140A can be formed by the same conductive material layer through the same patterning process. Of course, the embodiments of the present disclosure include but are not limited to this, and the second conductive layer 140 and the third conductive layer 140A can also be made of different materials and formed through different processes. It should be noted that even if the second conductive layer 140 and the third conductive layer 140A are made of different materials and formed through different processes, the second conductive layer 140 and the third conductive layer 140A can also be located on the side of the substrate layer 110 away from the first conductive layer 120, or on the surface of the substrate layer 110 away from the first conductive layer 120.

[0087] In some examples, as shown in Figures 4A and 4B, the flexible circuit board 100 is bent to form a U-shaped structure 200, and the U-shaped structure 200 includes a first flat portion 210, a second flat portion 220 and a connecting portion 230 located between the first flat portion 210 and the second flat portion 220. The connecting portion 230 connects the first flat portion 210 and the second flat portion 220 to semi-enclose a accommodating space 250; the accommodating space 250 can be used to set the back panel 510 and the backlight module 520; the backlight module 520 can adopt an edge-entry backlight module or a direct-down backlight module.

[0088] As shown in Figures 4A and 4B, at least a portion of the first double-layered region 113B is located on the second flat portion 220, at least a portion of the first single-layered region 113A and the second double-layered region 113C are located on the connecting portion 230, at least a portion of the second double-layered region 113C is located on the bottom 232 of the connecting portion 230 away from the accommodating space 250, and at least a portion of the first single-layered region 113A is located between the bottom 232 and the second flat portion 220. Thus, the flexible circuit board 100 can utilize the second flat portion 220 to define the first double-layered region 113B, utilize the bottom 232 of the connecting portion 230 to define the second double-layered region 113C, and utilize the first single-layered region 113A to bend or curve.

[0089] In some examples, as shown in Figures 2 and 3A, flexible circuit board 100 further includes a second single-layer region 113D and a third single-layer region 113E; second single-layer region 113D is located between second double-layer region 113C and first pad region 111; and third single-layer region 113E is located between first double-layer region 113B and second pad region 112. Second single-layer region 113D can serve as a bending region between bottom 232 of connecting portion 230 away from accommodating space 250 and second flat portion 220, while third single-layer region 113E can serve as a transition region between second pad region 112 and first double-layer region 113B.

[0090] In some examples, as shown in Figures 2 and 3A, the first pad area 111, the second single-layer area 113D, the second double-layer area 113C, the first single-layer area 113A, the first double-layer area 113B, and the third single-layer area 113E are arranged in sequence in the first direction. In this case, the size of the flexible circuit board in the first direction can be the sum of the sizes of the first pad area 111, the second single-layer area 113D, the second double-layer area 113C, the first single-layer area 113A, the first double-layer area 113B, and the third single-layer area 113E in the first direction.

[0091] It's worth noting that the aforementioned second double-layer region, a transition zone between the two bending zones, also provides support, preventing the flexible circuit board from bending excessively at sharp angles and potentially breaking the signal transmission lines. Furthermore, interconnects can be provided on the third conductive layer to connect signal transmission lines carrying the same signal in the first conductive layer, thereby improving signal uniformity across these lines.

[0092] In some examples, as shown in Figures 4A and 4B, the first pad area 111 is located at the first flat portion 210; the second single-layer area 113D can be located at the rounded connection portion between the first flat portion 210 and the connection portion 230, so that it has better bending performance and is not prone to breakage or generating large stress; the third single-layer area 113E can serve as a transition area between the second pad area 112 and the first double-layer area 113B.

[0093] For example, as shown in Figures 4A and 4B, the length of the flexible circuit board 100 is equal to the sum of the length of the first pad area 111, the length of the second single-layer area 113D, the length of the second double-layer area 113C, the length of the first single-layer area 113A, the length of the first double-layer area 113B, the length of the third single-layer area 113E, and the length of the second pad area 112. Generally speaking, the lengths of the first pad area and the second pad area are fixed values ​​depending on the type and model of the product.

[0094] For example, as shown in FIG. 4A and FIG. 4B , the second single-layer region 113D may be configured as a quarter arc, the radius of curvature of which is related to the shape of the back panel of the display device and is typically 0.6 to 0.8 mm.

[0095] For example, as shown in Figures 4A and 4B, the second double-layer area 113C can be a transition area between the curved second single-layer area 113D and the curved first single-layer area 113A, which can play a supporting role to prevent the flexible circuit board 100 from being excessively bent into a sharp angle and causing the signal transmission line (such as a copper wire) to break; at the same time, the second double-layer area 113 is a flat portion, and its length is equal to the linear length of the bottom of the backplane.

[0096] For example, as shown in FIG. 4A and FIG. 4B , the first single-layer region 113A may also be configured as an arc shape, the shape of which is similar to the rounded corner of the back plate, and the radius of curvature thereof is slightly larger than the radius of curvature of the rounded corner of the back plate.

[0097] For example, as shown in FIG. 4A and FIG. 4B , the first double-layer region 113B starts from where the rounded corner of the back plate ends and ends at the driving circuit board 400 .

[0098] In some examples, as shown in Figures 2 and 3A, the flexible circuit board 100 further includes a first protective layer 151, a second protective layer 152 and a first exposure opening 161; the first protective layer 151 is located in the transmission line area 113 and is located on the side of the first conductive layer 120 away from the substrate layer 110; the second protective layer 152 is located in the first double-layer area 113B and is located on the side of the second conductive layer 140 away from the substrate layer 110; the first exposure opening 161 is located in the second protective layer 152 and is configured to expose the second conductive layer 140, so that the second conductive layer 140 can be connected to an external conductive structure to provide voltage or electrical signals to various conductive structures in the second conductive layer 140.

[0099] 2 , the first exposure opening 161 is located in the first direction at the center of the first double-layer region 113B near the first single-layer region 113A. However, the present disclosure includes but is not limited to this, and the first exposure opening may also be located at other locations.

[0100] For example, the size of the first exposure opening 161 in the first direction X may be 2 mm, and the size of the first exposure opening 161 in the second direction Y may be 10 mm. Of course, the embodiments of the present disclosure include but are not limited to the above.

[0101] In some examples, as shown in FIG2 , the flexible circuit board 100 includes a plurality of first exposure openings 161 arranged along a second direction Y intersecting the first direction X. For example, the flexible circuit board 100 includes three first exposure openings 161 arranged at intervals along the second direction Y. Thus, the second conductive layer can have a more uniform potential.

[0102] In some examples, as shown in FIG3A , the flexible circuit board 100 may further include a first adhesive layer 171 and a second adhesive layer 172; the first adhesive layer 171 is located between the first conductive layer 120 and the first protective layer 151; and the second adhesive layer 172 is located between the second conductive layer 140 and the second protective layer 152. It should be noted that when the second adhesive layer 172 is provided, the first exposure opening 161 also penetrates the second adhesive layer 172 to expose the second conductive layer 140.

[0103] Figure 5 is a schematic cross-sectional view of another flexible circuit board provided by an embodiment of the present disclosure, taken along line AB in Figure 2. As shown in Figure 5, the flexible circuit board 100 further includes a conductive tape 270, at least partially located on a side of the second protective layer 152 away from the second conductive layer 140, and contacting the second conductive layer 140 through the first exposed opening 161. The conductive tape 270 is configured to be connected to a ground terminal. Thus, the flexible circuit board 100 can ground the second conductive layer 140 through the conductive tape 270 and the first exposed opening 161. It should be noted that when the flexible circuit board is used in a display device, the ground terminal can be a ground terminal on the display panel or a ground terminal on the driver circuit board.

[0104] Figure 6 is a layout diagram of a flexible circuit board provided in accordance with an embodiment of the present disclosure; Figure 7 is a schematic diagram of a first conductive layer in a flexible circuit board provided in accordance with an embodiment of the present disclosure; and Figure 8 is a schematic diagram of a second conductive layer in a flexible circuit board provided in accordance with an embodiment of the present disclosure. It should be noted that in the embodiments shown in Figures 6 to 8 , the second and third conductive layers are provided on the same layer and can be considered to be the same conductive layer.

[0105] As shown in Figures 6 to 8 , the third conductive layer 140A in the second double-layer region 113C of the flexible circuit board 100 includes first interconnects 141 extending along a second direction Y intersecting the first direction X. In this embodiment, the third conductive layer 140A and the second conductive layer 140 are co-located. The plurality of signal transmission lines 130 include a plurality of first signal transmission lines 131. The plurality of first signal transmission lines 131 are configured to transmit the same electrical signal and are electrically connected to the first interconnects 141. For example, the plurality of first signal transmission lines 131 may be connected to the first interconnects 141 through vias extending through the substrate layer 110. As a result, the flexible circuit board 100 can improve signal uniformity across the plurality of first signal transmission lines 131.

[0106] In some examples, the first signal transmission line 131 is configured to transmit a ground signal, that is, the first signal transmission line 131 is a ground line. In this configuration, since the second conductive layer 140 is typically grounded, the interconnection line is suitable for interconnecting multiple ground lines. It should be noted that the above-mentioned ground line may include the first ground line and the second ground line mentioned below. Of course, the embodiments of the present disclosure include but are not limited to this, and the first signal transmission line 131 may also be configured to transmit signals such as power supply voltage and common voltage.

[0107] In some examples, as shown in FIG. 6 to FIG. 8 , the second conductive layer 140 of the first double-layer region 113B may also include second interconnect lines 142 to connect the plurality of first signal transmission lines 131 , thereby further improving the uniformity of the signals on the plurality of first signal transmission lines 131 .

[0108] For example, as shown in Figures 6 to 8, the second interconnection line 142 and the first interconnection line 141 are arranged parallel to each other. Of course, the embodiments of the present disclosure include but are not limited to this. Due to the large area of ​​the first double-layer region 113B, the second interconnection line can also be selected to have different extension directions and types as needed.

[0109] In some examples, as shown in Figures 6 to 8, the plurality of signal transmission lines 130 include a high-frequency signal transmission line 132 and two first ground lines 133; the high-frequency signal transmission line 132 is configured to transmit a high-frequency signal; the two first ground lines 133 are located on both sides of the high-frequency signal transmission line 132 in a second direction Y intersecting the first direction X; in the first double-layer region 113B, the second conductive layer 140 is connected to the two first ground lines 133 respectively through first vias passing through the substrate layer 110. In other words, the plurality of signal transmission lines 130 include the high-frequency signal transmission line 132 and the plurality of first ground lines 133, and at least one first ground line 133 is provided on both sides of the high-frequency signal transmission line 132 in the second direction intersecting the first direction; in the first double-layer region 113B, the second conductive layer 140 is connected to the first ground lines 133 on both sides of the high-frequency signal transmission line 132 respectively through first vias passing through the substrate layer.

[0110] Thus, the first ground lines 133 and the second conductive layer 140 located on both sides of the high-frequency signal transmission line 132 can provide a stable electromagnetic environment for the high-frequency signal transmission line 132, and control the impedance of the high-frequency signal transmission line 132, thereby improving the stability of high-frequency signal transmission and avoiding reflection. Furthermore, the first ground lines 133 and the second conductive layer 140 located on both sides of the high-frequency signal transmission line 132 can also form a shielding structure, thereby improving electromagnetic interference resistance and electromagnetic compatibility.

[0111] Figure 9 is a schematic diagram illustrating a flexible circuit board according to one embodiment of the present disclosure, wherein a second conductive layer is connected to a first ground line via a first via. As shown in Figure 9, the second conductive layer 140 is connected to two first ground lines 133 via first vias H1 passing through the substrate layer 110. It should be noted that the connection of the second conductive layer to other signal transmission lines via vias passing through the substrate layer in this embodiment of the present disclosure can be seen in Figure 9 and the related description.

[0112] In some examples, as shown in Figures 6 to 8, the flexible circuit board 100 may include multiple high-frequency signal transmission lines 132, two first ground lines 133 are provided on both sides of each high-frequency signal transmission line 132, and two adjacent high-frequency signal transmission lines 132 may share one first ground line 133.

[0113] In some examples, as shown in FIG. 6 to FIG. 8 , a plurality of high-frequency signal transmission lines 132 and a plurality of first ground lines 133 are alternately arranged, and two first ground lines 133 are arranged on the outermost sides of the plurality of high-frequency signal transmission lines 132 .

[0114] In some examples, as shown in Figures 6 to 8, each high-frequency signal transmission line 132 includes a first high-frequency signal sub-line 132A and a second high-frequency signal sub-line 132B, and the polarity of the high-frequency signal on the first high-frequency signal sub-line 132A and the high-frequency signal on the second high-frequency signal sub-line 132B are different, thereby having better transmission performance for the high-frequency signal.

[0115] In some examples, as shown in FIG. 6 , the substrate layer 110 may further include a marking area 119 for forming various markings.

[0116] In some examples, as shown in Figures 2 and 3B, the transmission line region 113 also includes a third double-layer region 113F. The third double-layer region 113F is located between the first double-layer region 113B and the second double-layer region 113C, and passes through the first single-layer region 113A to be connected to the first double-layer region 113B and the second double-layer region 113C respectively. The first single-layer region 113A is also located on both sides of the third double-layer region 113F in the second direction, and the second direction intersects with the first direction. In the third double-layer region 113F, the first conductive layer 120 is provided on the first side of the substrate layer 110, and the fourth conductive layer 140B is provided on the second side of the substrate layer 110. The second conductive layer 140 and the third conductive layer 140A are connected through the fourth conductive layer 140B and are provided on the same layer. With this arrangement, the flexible circuit board 100 forms a third double-layer region 113F between the first double-layer region 113B and the second double-layer region 113C, thereby fully covering the high-frequency signal transmission line 132 in the first direction. Consequently, the third double-layer region 113F further provides a stable electromagnetic environment for the high-frequency signal transmission line 132, improving the stability of high-frequency signal transmission and preventing reflections. It should be noted that the third double-layer region is localized in the second direction, flanked by the first single-layer region. This ensures electromagnetic shielding for the high-frequency signal transmission line without compromising the flexible circuit board's bending performance and preventing the generation of significant stress.

[0117] In some examples, as shown in FIG6 to FIG8 , the orthographic projection of the high-frequency signal transmission line 132 on the substrate layer 110 overlaps with the first double-layer region 113B, the second double-layer region 113C, and the third double-layer region 113F, respectively.

[0118] In some examples, as shown in Figures 6 to 8, the multiple signal transmission lines 130 include a high-frequency signal transmission line 132 and two first ground lines 133; the high-frequency signal transmission line 132 is configured to transmit a high-frequency signal; the two first ground lines 133 are located on both sides of the high-frequency signal transmission line 132 in the second direction; the high-frequency signal transmission line 132 extends from the first double-layer region 113B through the third double-layer region 113F to the second double-layer region 113C; in the first double-layer region 113B, the second conductive layer 140 is respectively connected to the two first ground lines 133 through the first vias passing through the substrate layer 110, and in the third double-layer region 113F, the fourth conductive layer 140B is respectively connected to the two first ground lines 133 through the second vias passing through the substrate layer 110. That is to say, the multiple signal transmission lines 130 include a high-frequency signal transmission line 132 and a plurality of first ground lines 133. The high-frequency signal transmission line 132 extends from the first double-layer area 113B through the third double-layer area 113F to the second double-layer area 113C. The high-frequency signal transmission line 132 is provided with at least one first ground line 133 on both sides of the second direction intersecting with the first direction; in the first double-layer area 113B, the second conductive layer 140 is connected to the first ground lines 133 on both sides of the high-frequency signal transmission line 132 through the first via hole passing through the substrate layer 110, and in the third double-layer area 113F, the fourth conductive layer 140B is connected to the first ground lines 133 on both sides of the high-frequency signal transmission line 132 through the second via hole passing through the substrate layer 110.

[0119] Thus, the flexible circuit board can provide a continuous and stable electromagnetic environment for the high-frequency signal transmission line 132 through the first double-layer region 113B, the second double-layer region 113C, and the third double-layer region 113F, thereby further providing a stable electromagnetic environment for the high-frequency signal transmission line 132, improving the stability of high-frequency signal transmission and avoiding reflection. It should be noted that the above-mentioned second via hole can refer to the relevant arrangement of the first via hole in Figure 9.

[0120] In some examples, as shown in Figures 6 and 7, the plurality of signal transmission lines 130 include a second ground line 134 located at the outermost side of the plurality of signal transmission lines 130. The first conductive layer 120 also includes a conductive mesh 135 located on a side of the second ground line 134 away from the center of the plurality of signal transmission lines 130 and connected to the second ground line 134. The first conductive layer 120 also includes a protective wire 136 located on a side of the conductive mesh 135 away from the second ground line 134. This arrangement allows the conductive mesh 135 to be connected to the second ground line 134, thereby reducing the resistance of the second ground line 134 and fully utilizing the space on the flexible circuit board 100. The protective wire 136, located on the side of the conductive mesh 135 away from the second ground line 134, protects the conductive mesh 135 from tearing during the manufacturing and bending processes, thereby improving product yield.

[0121] In some examples, as shown in FIG6 and FIG7, the transmission line region 113 has a width-enlarged portion 113G, and the protection line 136 is located at the edge of the width-enlarged portion 113G, thereby preventing the conductive grid 135 from being torn during the manufacturing and bending process, thereby improving product yield.

[0122] 6 and 8 , the second conductive layer 140 may further include conductive blocks 144 and a conductive metal grid 146. The conductive blocks 144 are located in the first exposed openings 161 for connection to the conductive tape 270, while the conductive metal grid 146 is located in the first double-layer region 113B outside the first exposed openings 161.

[0123] Figure 10 is a schematic plan view of another flexible circuit board according to an embodiment of the present disclosure; Figure 11 is a schematic cross-sectional view of a flexible circuit board according to an embodiment of the present disclosure taken along line EF in Figure 10; and Figure 12 is a schematic layout view of a flexible circuit board according to an embodiment of the present disclosure. Figure 12 illustrates the locations of the second and third exposure openings.

[0124] In some examples, as shown in Figures 10 to 12, the flexible circuit board 100 further includes a first protective layer 151, a second protective layer 152, and a second exposure opening 162; the first protective layer 151 is located in the transmission line area 113 and on the side of the first conductive layer 120 away from the substrate layer 110; the second protective layer 152 is located in the first double-layer area 113B and on the side of the second conductive layer 140 away from the substrate layer 110; the second exposure opening 162 is located in the first protective layer 151 and is configured to expose the first conductive layer 120; the orthographic projection of the second exposure opening 162 on the substrate layer 110 overlaps with the orthographic projection of the second ground line 134 on the substrate layer 110 and the orthographic projection of the conductive grid on the substrate layer 110, respectively.

[0125] In some examples, as shown in Figures 10 to 12 , the flexible circuit board 100 further includes a first electromagnetic shielding coating 191, which is located on a side of the first protective layer 151 away from the first conductive layer 120 and is in contact with the second ground line 134 and the conductive grid through the second exposed opening 162. Thus, the first electromagnetic shielding coating 191 can further improve the electromagnetic interference resistance and electromagnetic compatibility of the flexible circuit board 100.

[0126] In some examples, as shown in FIG. 10 to FIG. 12 , the first electromagnetic shielding coating 191 is only located in the first double-layer region 113B, thereby avoiding affecting the bending performance of the flexible circuit board 100 .

[0127] In some examples, as shown in Figures 10 to 12 , the flexible circuit board 100 further includes a third exposure opening 163 and a second electromagnetic shielding coating 192. The third exposure opening 163 is located in the second protective layer 152 and is configured to expose the second conductive layer 140. The second electromagnetic shielding coating 192 is located on a side of the second protective layer 152 away from the second conductive layer 140 and is in contact with the second conductive layer 140 through the third exposure opening 163. Thus, the third exposure opening 163 and the second electromagnetic shielding coating 192 can further improve the electromagnetic interference resistance and electromagnetic compatibility of the flexible circuit board 100.

[0128] In some examples, as shown in Figures 10 to 12, the orthographic projection of the third exposure opening 163 on the substrate layer 110 overlaps with the orthographic projection of the second exposure opening 162 on the substrate layer 110, so that the first electromagnetic shielding coating 191 and the second electromagnetic shielding coating 192 can be electrically connected to each other, thereby further improving the anti-electromagnetic interference performance and electromagnetic compatibility of the flexible circuit board.

[0129] It should be noted that although the flexible circuit board 100 shown in FIG11 is provided with the above-mentioned first electromagnetic shielding coating 191 and second electromagnetic shielding coating 192 at the same time, the embodiments of the present disclosure include but are not limited to this, and the flexible circuit board may only be provided with the first electromagnetic shielding coating or the second electromagnetic shielding coating.

[0130] FIG13A is a partial schematic diagram of a first pad structure in a flexible circuit board provided in one embodiment of the present disclosure; FIG13B is a partial schematic diagram of a second pad structure in a flexible circuit board provided in one embodiment of the present disclosure.

[0131] As shown in Figures 13A and 13B, the first pad structure 121 includes M first conductive pads 1210; the second pad structure 122 includes M second conductive pads 1220; the multiple signal transmission lines 130 include a second signal transmission line 137, the second signal transmission line 137 includes a first end and a second end, the first end of the second signal transmission line 137 includes P branches 1371, and the second end of the second signal transmission line 137 includes P branches 1372; the P branches 1371 at the first end of the second signal transmission line 137 are respectively connected to the P first conductive pads 1210, and the P branches 1372 at the second end of the second signal transmission line 137 are respectively connected to the P second conductive pads 1220, where P is a positive integer greater than or equal to 2 and less than M. Therefore, the flexible circuit board 100 can reduce the number of signal transmission lines in the transmission line area 113 through the above structure, so that the signal transmission lines have a larger line width or increase the intervals between the signal transmission lines, thereby improving the stability of the flexible circuit board 100.

[0132] For example, as shown in Figures 13A and 13B, the value of P can be 2. In this case, the first end of the second signal transmission line 137 includes two branches 1371, and the second end of the second signal transmission line 137 includes two branches 1372. The two branches 1371 at the first end of the second signal transmission line 137 are respectively connected to the two first conductive pads 1210, and the two branches 1372 at the second end of the second signal transmission line 137 are respectively connected to the two second conductive pads 1220. Of course, the embodiments of the present disclosure include but are not limited to this, and the value of P can also be 3, 4, 5, 6, 7, 8, etc.

[0133] For example, the first conductive pad and the second conductive pad can also be called gold fingers. The width of the first conductive pad can be 0.09 mm, and the interval between adjacent first conductive pads is 0.09 mm; the width of the second conductive pad can be 0.15 mm, and the interval between adjacent second conductive pads is 0.15 mm.

[0134] FIG14A is a partial schematic diagram of a first pad structure in another flexible circuit board provided in one embodiment of the present disclosure; FIG14B is a partial schematic diagram of a second pad structure in another flexible circuit board provided in one embodiment of the present disclosure.

[0135] As shown in Figures 14A and 14B, the first pad structure 121 includes M first conductive pads 1210, and the second pad structure 122 includes N second conductive pads 1220. The plurality of signal transmission lines 130 include a third signal transmission line 138. The third signal transmission line 138 includes a first end and a second end. The first end of the third signal transmission line 138 includes P branches 1381. The P branches 1381 at the first end of the third signal transmission line 138 are respectively connected to the P first conductive pads 1210, and the second end of the third signal transmission line 138 is connected to one second conductive pad 1220. P is a positive integer greater than or equal to 2 and less than N, and M is greater than N. Thus, the flexible circuit board can reduce the number of signal transmission lines in the transmission line region 113 through the above structure, thereby increasing the signal transmission lines' line width or increasing the spacing between the signal transmission lines, thereby improving the stability of the flexible circuit board. Furthermore, the flexible circuit board can also reduce the number of second conductive pads in the second pad structure.

[0136] For example, as shown in Figures 13A and 13B , the value of P can be 2. In this case, the first end of the third signal transmission line 138 includes two branches 1381; the two branches 1381 of the first end of the third signal transmission line 138 are respectively connected to two first conductive pads 1210, and the second end of the third signal transmission line 138 is connected to a second conductive pad 1220. Of course, the embodiments of the present disclosure include but are not limited to this, and the value of P can also be 3, 4, 5, 6, 7, 8, etc.

[0137] FIG15 is a layout diagram of another flexible circuit board provided by an embodiment of the present disclosure. As shown in FIG15 , the first pad structure 121 includes M first conductive pads 1210, the second pad structure 122 includes Q second conductive pads 1220; the plurality of signal transmission lines 130 include a fourth signal transmission line 1391 and a fifth signal transmission line 1392; the fourth signal transmission line 1391 extends from the first pad area 111 to the first double-layer area 113B, and the fourth signal transmission line 1391 includes a first end located in the first pad area 111 and a second end located in the first double-layer area 113B; the fifth signal transmission line 1392 includes a first end located in the first pad area 111 and a second end located in the first double-layer area 113B; The transmission line 1392 extends from the first pad area 111 through the first double-layer area 113B to the second pad area 112. The fifth signal transmission line 1392 includes a first end located in the first pad area 111 and a second end located in the second pad area 112. The second conductive layer 140 also includes a transverse transmission line 147. The transverse transmission line 147 is connected to the second end of the fourth signal transmission line 1391 via a third via hole passing through the substrate layer 110, and is connected to the fifth signal transmission line 1392 via a fourth via hole passing through the substrate layer 110. With this arrangement, the flexible circuit board 100 can connect the fourth signal transmission line 1391 to the fifth signal transmission line 1392 via the fourth signal transmission line 1391 and the transverse transmission line 147, thereby reducing the number of signal transmission lines in the transmission line area 113, thereby allowing the signal transmission lines to have a larger line width or increasing the spacing between the signal transmission lines, thereby improving the stability of the flexible circuit board. It should be noted that, in the embodiment of the present disclosure, the situation in which the horizontal transmission line is connected to the fourth signal transmission line and the second signal transmission line through a via passing through the substrate layer can be seen in Figure 9 and its related description, and the specific structure and setting of the third via and the fourth via can be seen in the first via in Figure 9.

[0138] It should be noted that, in the absence of conflict, the method of reducing the number of signal transmission lines shown in Figures 13A-13B, the method of reducing the number of signal transmission lines shown in Figures 14A-14B, and the method of reducing the number of signal transmission lines shown in Figures 15A-15B can exist separately or be combined with each other, and the embodiments of the present disclosure are not limited thereto.

[0139] FIG16 is a plan view of a flexible circuit board provided in accordance with an embodiment of the present disclosure; FIG17 is a cross-sectional view of a flexible circuit board along line GH in FIG16 provided in accordance with an embodiment of the present disclosure.

[0140] As shown in Figures 16 and 17, the flexible circuit board 100 includes a substrate layer 110 and a first conductive layer 120; the substrate layer 110 includes a first pad area 111, a second pad area 112 and a transmission line area 113 located between the first pad area 111 and the second pad area 112, and the first pad area 111, the transmission line area 113 and the second pad area 112 can be arranged along the first direction X; the first conductive layer 120 is located on the first side of the substrate layer 110, and includes a first pad structure 121, a second pad structure 122 and a plurality of signal transmission lines 130 extending along the first direction; the first pad structure 121 is located in the first pad area 111, the second pad structure 122 is located in the second pad area 112, and the plurality of signal transmission lines 130 are located in the transmission line area 113.

[0141] As shown in Figures 16 and 17 , unlike the flexible circuit board shown in Figure 2 , the transmission line region 113 includes a second double-layer region 113C, a first single-layer region 113A, and a first double-layer region 113B arranged along a first direction X, but does not include a third double-layer region connecting the first and second double-layer regions. In the first single-layer region 113A, a first conductive layer 120 is disposed on the first side of the substrate layer 110, while no conductive structure is disposed on the second side of the substrate layer 110. In the first double-layer region 113B, the first conductive layer 120 is disposed on the first side of the substrate layer 110, while a second conductive layer 140 is disposed on the second side of the substrate layer 110. In the second double-layer region 113C, the first conductive layer 120 is disposed on the first side of the substrate layer 110, while a third conductive layer 140A is disposed on the second side of the substrate layer 110. The second and first sides are opposite sides of the substrate layer 110. It can be seen that the "single layer" or "double layer" in the "single layer area" and "double layer area" in the embodiments of the present disclosure refers to the number of conductive layers contained in the corresponding area, and is not used to limit the number of other non-conductive layers.

[0142] In the flexible circuit board provided in the embodiment of the present disclosure, the first single-layer area includes only a single conductive layer, and therefore has good bending performance and is not prone to breakage or excessive stress. Therefore, by providing the second double-layer area, the first single-layer area, and the first double-layer area in the transmission line area, the flexible circuit board can be bent or curved in the first single-layer area, thereby having good bending performance and avoiding the generation of large stress or breakage in the first single-layer area. At the same time, the flexible circuit board can also use the second conductive layer in the first double-layer area to provide electromagnetic protection and impedance matching for the signal transmission line, thereby avoiding poor display caused by poor data transmission stability, and also improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board, thereby having a wider range of applications and application scenarios. In addition, the flexible circuit board can also use the third conductive layer in the second double-layer area to provide electromagnetic protection and impedance matching for the signal transmission line, thereby further improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board.

[0143] In some examples, the second conductive layer 140 and the third conductive layer 140A are provided in the same layer. That is, the second conductive layer 140 and the third conductive layer 140A can be formed by the same conductive material layer through the same patterning process. Of course, the embodiments of the present disclosure include but are not limited to this, and the second conductive layer 140 and the third conductive layer 140A can also be made of different materials and formed through different processes. It should be noted that even if the second conductive layer 140 and the third conductive layer 140A are made of different materials and formed through different processes, the second conductive layer 140 and the third conductive layer 140A can also be located on the side of the substrate layer 110 away from the first conductive layer 120, or on the surface of the substrate layer 110 away from the first conductive layer 120.

[0144] For example, the substrate layer 110 may be a flexible substrate layer 110 , and the material of the flexible substrate layer 110 may be polyimide, etc. The material of the first conductive layer 120 may be a conductive metal material such as copper, aluminum, or silver; the material of the second conductive layer 140 may also be a conductive metal material such as copper, aluminum, or silver.

[0145] In some examples, because the first single-layer region 113A includes only one conductive layer (i.e., the first conductive layer 120) and has good bending or curvature properties, at least a portion of the first single-layer region can serve as a bending region; that is, bending or curvature can be performed within the first single layer. The first double-layer region 113B and the second double-layer region 113C, having two conductive layers, can serve as flat regions.

[0146] It is noteworthy that the second conductive layer 140 of the first double-layer region 113B of the flexible circuit board 100 provided in the present embodiment can not only provide electromagnetic protection and impedance matching for the signal transmission lines 130, but can also be used to achieve other functions. For example, the second conductive layer 140 can be provided with a conductive structure to connect to some of the multiple signal transmission lines 130 to reduce resistance; or the second conductive layer 140 can be provided with a conductive structure to electrically connect signal transmission lines 130 that transmit the same signal among the multiple signal transmission lines 130 to improve the uniformity and stability of the signal.

[0147] Similarly, the third conductive layer 140A of the second double-layer region 113C of the flexible circuit board 100 provided in the present embodiment can not only provide electromagnetic protection and impedance matching for the signal transmission lines 130, but can also be used to achieve other functions. For example, the third conductive layer 140A can be provided with a conductive structure to connect to some of the multiple signal transmission lines 130 to reduce resistance; or the third conductive layer 140A can be provided with a conductive structure to electrically connect the signal transmission lines 130 transmitting the same signal among the multiple signal transmission lines 130 to improve the uniformity and stability of the signal.

[0148] In some examples, the flexible circuit board can also be bent to form a U-shaped structure, which includes a first flat portion, a second flat portion, and a connecting portion located between the first flat portion and the second flat portion. The connecting portion connects the first flat portion and the second flat portion to semi-enclose a storage space; the storage space can be used to set the back panel and the backlight module; the backlight module can adopt a side-entry backlight module or a direct-type backlight module. The first double-layer area is located on the second flat portion, the first single-layer area and the second double-layer area are located on the connecting portion, the second double-layer area is located at the bottom of the connecting portion away from the storage space, and the first single-layer area is located between the bottom and the second flat portion. Thus, the flexible circuit board can use the first flat portion to set the above-mentioned first double-layer area, use the bottom of the connecting portion to set the above-mentioned second double-layer area, and use the first single-layer area to bend or bend. It should be noted that the specific setting of the above-mentioned U-shaped structure can refer to the relevant description of Figures 4A and 4B, which will not be repeated here.

[0149] In some examples, as shown in Figures 16 and 17 , flexible circuit board 100 further includes a second single-layer region 113D and a third single-layer region 113E. Second single-layer region 113D is located between second double-layer region 113C and first pad region 111, while third single-layer region 113E is located between first double-layer region 113B and second pad region 112. Second single-layer region 113D can serve as a bending region between bottom 232 of connecting portion 230 away from accommodating space 250 and second flat portion 220, while third single-layer region 113E can serve as a transition region between second pad region 112 and first double-layer region 113B.

[0150] In some examples, as shown in Figures 16 and 17, the first pad region 111, the second single-layer region 113D, the second double-layer region 113C, the first single-layer region 113A, the first double-layer region 113B and the third single-layer region 113E are sequentially arranged in the first direction.

[0151] It's worth noting that the aforementioned second double-layer region, a transition zone between the two bending zones, also provides support, preventing the flexible circuit board from bending excessively at sharp angles and potentially breaking the signal transmission lines. Furthermore, interconnects can be provided on the third conductive layer to connect signal transmission lines carrying the same signal in the first conductive layer, thereby improving signal uniformity across these lines.

[0152] In some examples, as shown in Figures 16 and 17, the flexible circuit board 100 also includes a first protective layer 151, a second protective layer 152 and a first exposure opening 161; the first protective layer 151 is located in the transmission line area 113 and is located on the side of the first conductive layer 120 away from the substrate layer 110; the second protective layer 152 is located in the first double-layer area 113B and is located on the side of the second conductive layer 140 away from the substrate layer 110; the first exposure opening 161 is located in the second protective layer 152 and is configured to expose the second conductive layer 140, so that the second conductive layer 140 can be connected to an external conductive structure to provide voltage or electrical signals to various conductive structures in the second conductive layer 140.

[0153] 16 and 17 , the first exposure opening 161 is located in the first direction at the center of the first double-layer region 113B near the first single-layer region 113A. However, the present disclosure includes but is not limited to this, and the first exposure opening may also be located at other locations.

[0154] In some examples, as shown in Figures 16 and 17 , the flexible circuit board 100 includes a plurality of first exposure openings 161 arranged along a second direction Y intersecting the first direction X. For example, the flexible circuit board 100 includes three first exposure openings 161 arranged at intervals along the second direction Y. Thus, the second conductive layer can have a more uniform potential.

[0155] In some examples, as shown in Figures 16 and 17 , the flexible circuit board 100 may further include a first adhesive layer 171 and a second adhesive layer 172; the first adhesive layer 171 is located between the first conductive layer 120 and the first protective layer 151; and the second adhesive layer 172 is located between the second conductive layer 140 and the second protective layer 152. It should be noted that when the second adhesive layer 172 is provided, the first exposure opening 161 also penetrates the second adhesive layer 172 to expose the second conductive layer 140.

[0156] In some examples, the flexible circuit board further includes a conductive tape that contacts the second conductive layer through the first exposed opening, thereby grounding the second conductive layer. It should be noted that the specific configuration of the conductive tape can be found in the description of FIG5 and will not be repeated here.

[0157] FIG18 is a plan view of a flexible circuit board provided in accordance with an embodiment of the present disclosure; FIG19 is a cross-sectional view of a flexible circuit board along line JK in FIG18 provided in accordance with an embodiment of the present disclosure.

[0158] As shown in Figures 18 and 19 , unlike the flexible circuit board shown in Figures 15 and 16 , this flexible circuit board does not have the aforementioned first exposure opening. The flexible circuit board 100 includes a substrate layer 110 and a first conductive layer 120 . The substrate layer 110 includes a first pad region 111, a second pad region 112, and a transmission line region 113 located between the first and second pad regions 111, 112. The first pad region 111, the transmission line region 113, and the second pad region 112 may be arranged along a first direction X. The first conductive layer 120 is located on a first side of the substrate layer 110 and includes a first pad structure 121, a second pad structure 122, and a plurality of signal transmission lines 130 extending along the first direction. The first pad structure 121 is located in the first pad region 111, the second pad structure 122 is located in the second pad region 112, and the plurality of signal transmission lines 130 are located in the transmission line region 113.

[0159] As shown in Figures 18 and 19, the transmission line region 113 includes a first single-layer region 113A and a first double-layer region 113B arranged along a first direction X. In the first single-layer region 113A, a first conductive layer 120 is disposed on the first side of the substrate layer 110, and no conductive structure is disposed on the second side of the substrate layer 110. In the first double-layer region 113B, the first conductive layer 120 is disposed on the first side of the substrate layer 110, and a second conductive layer 140 is disposed on the second side of the substrate layer 110. The second side and the first side are opposite sides of the substrate layer 110. It can be seen that the "single-layer" or "double-layer" in the "single-layer region" and "double-layer region" in the embodiments of the present disclosure refers to the number of conductive layers contained in the corresponding region, and is not intended to limit the number of other non-conductive layers.

[0160] In the flexible circuit board provided in the embodiment of the present disclosure, the first single-layer area includes only a single conductive layer, and therefore has good bending performance and is not prone to breakage or excessive stress. Therefore, by providing the second double-layer area, the first single-layer area, and the first double-layer area in the transmission line area, the flexible circuit board can be bent or curved in the first single-layer area, thereby having good bending performance and avoiding the generation of large stress or breakage in the first single-layer area. At the same time, the flexible circuit board can also use the second conductive layer in the first double-layer area to provide electromagnetic protection and impedance matching for the signal transmission line, thereby avoiding poor display caused by poor data transmission stability, and also improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board, thereby having a wider range of applications and application scenarios. In addition, the flexible circuit board can also use the third conductive layer in the second double-layer area to provide electromagnetic protection and impedance matching for the signal transmission line, thereby further improving the anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance) of the flexible circuit board.

[0161] In some examples, as shown in Figures 18 and 19, the transmission line region 113 further includes a second double-layer region 113C. This second double-layer region 113C is located in the first direction on a side of the first single-layer region 113A away from the first double-layer region 113B. In other words, the first single-layer region 113A is disposed between the first double-layer region 113B and the second double-layer region 113C. In the second double-layer region 113C, the first conductive layer 120 is disposed on the first side of the substrate layer 110, and the third conductive layer 140A is disposed on the second side of the substrate layer 110. Thus, the flexible circuit board 100 can utilize other relatively flat portions to form the second double-layer region 113C. This allows the third conductive layer 140A in the second double-layer region 113C to provide electromagnetic shielding and impedance matching for the signal transmission line, thereby preventing display defects caused by poor data transmission stability and further improving the electromagnetic interference resistance and electromagnetic compatibility (EMC) performance of the flexible circuit board 100.

[0162] In some examples, as shown in Figures 18 and 19, flexible circuit board 100 further includes a second single-layer region 113D and a third single-layer region 113E. Second single-layer region 113D is located between second double-layer region 113C and first pad region 111, while third single-layer region 113E is located between first double-layer region 113B and second pad region 112. Second single-layer region 113D can serve as a bending region between bottom 232 of connecting portion 230 away from accommodating space 250 and second flat portion 220, while third single-layer region 113E can serve as a transition region between second pad region 112 and first double-layer region 113B.

[0163] In some examples, as shown in Figures 18 and 19, the first pad region 111, the second single-layer region 113D, the second double-layer region 113C, the first single-layer region 113A, the first double-layer region 113B and the third single-layer region 113E are sequentially arranged in the first direction.

[0164] In some examples, as shown in Figures 18 and 19, the flexible circuit board 100 also includes a first protective layer 151, a second protective layer 152 and a first exposure opening 161; the first protective layer 151 is located in the transmission line area 113 and is located on the side of the first conductive layer 120 away from the substrate layer 110; the second protective layer 152 is located in the first double-layer area 113B and is located on the side of the second conductive layer 140 away from the substrate layer 110; the first exposure opening 161 is located in the second protective layer 152 and is configured to expose the second conductive layer 140, so that the second conductive layer 140 can be connected to an external conductive structure to provide voltage or electrical signals to various conductive structures in the second conductive layer 140.

[0165] In some examples, as shown in Figures 18 and 19 , the flexible circuit board 100 may further include a first adhesive layer 171 and a second adhesive layer 172; the first adhesive layer 171 is located between the first conductive layer 120 and the first protective layer 151; and the second adhesive layer 172 is located between the second conductive layer 140 and the second protective layer 152. It should be noted that when the second adhesive layer 172 is provided, the first exposure opening 161 also penetrates the second adhesive layer 172 to expose the second conductive layer 140.

[0166] At least one embodiment of the present disclosure further provides a display device 500. Figure 20A is a structural schematic diagram of a display device provided by an embodiment of the present disclosure; Figure 20B is a partially enlarged view of a display device provided by an embodiment of the present disclosure. As shown in Figures 20A and 20B, the display device 500 includes a display panel 300 and the above-mentioned flexible circuit board 100. Since the flexible circuit board has good bending performance and is not prone to breakage and excessive stress. Therefore, the display device using the flexible circuit board can achieve a narrow frame design while avoiding light leakage and Mura caused by excessive tension exerted by the flexible circuit board on the display panel. On the other hand, since the flexible circuit board has strong anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance), the display device using the flexible circuit board also has strong anti-electromagnetic interference capability and electromagnetic compatibility (EMC performance), thereby having a wider range of applications and application scenarios.

[0167] In some examples, the display device can be an electronic device with a display function, such as a mobile phone, a computer, a tablet computer, a television, an electronic picture frame, a navigation system, an in-vehicle display, or a medical display. It should be noted that because the display device also has strong electromagnetic interference resistance and electromagnetic compatibility (EMC) performance, it has strong stability when used as an in-vehicle display or a medical display.

[0168] In some examples, as shown in Figures 20A and 20B , the display device 500 further includes a backplane 510 and a driver circuit board 400. The backplane 510 is located on one side of the display panel 300. The driver circuit board 400 is located on a side of the backplane 510 away from the display panel 300. The display panel 300 includes a binding area 310 and a plurality of binding pads 312 located in the binding area 310. The backplane 510 includes a bottom frame 512. The flexible circuit board 100 is bent from the binding area to the side of the backplane 510 away from the display panel 300. The first pad structure 121 is connected to the plurality of binding pads 312, and the second pad structure 122 is connected to the driver circuit board 400. Thus, the driver circuit board 400 can transmit display data to the display panel 300 via the flexible circuit board 100 to drive the display panel 300 to emit light for display. Furthermore, since the driving circuit board 400 is located on the backlight side of the display panel 300 and the flexible circuit board 100 is bent to connect the display panel 300 and the driving circuit board 400, it does not occupy too much area, thereby achieving a narrow frame design.

[0169] In some examples, as shown in Figures 20A and 20B, at least a portion of the first double-layer region 113B is located on the side of the backplane away from the display panel 300, and at least a portion of the first single-layer region 113A is a bending region surrounding the bottom frame 512. With this arrangement, the first single-layer region 113A of the flexible circuit board 100 can serve as the bending portion of the flexible circuit board 100, while the first double-layer region 113B can be the flat portion of the flexible circuit board 100 located on the backlight side of the display panel 300. As a result, the display device can utilize this flexible circuit board, ensuring that the flexible circuit board has both good bending performance and strong electromagnetic interference resistance and electromagnetic compatibility.

[0170] On the other hand, since the flexible circuit board 100 uses the first single-layer area 113A as the bending portion, the stress generated in the first single-layer area 113A is relatively small, and will not generate a large pulling force on the binding area of ​​the display panel 300, thereby preventing the backlight under the display panel 300 from being exposed, causing defects such as light leakage and mura.

[0171] There are a few points to note:

[0172] (1) The drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure, and other structures may refer to conventional designs.

[0173] (2) Unless there is any conflict, the features of the same embodiment and different embodiments of the present disclosure may be combined with each other.

[0174] The above are merely specific embodiments of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein should be included within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A flexible circuit board, comprising: A substrate layer, comprising a first pad area, a second pad area and a transmission line area between the first pad area and the second pad area; as well as The first conductive layer is located on the first side of the substrate layer and includes a first pad structure, a second pad structure and a plurality of signal transmission lines extending along a first direction. Wherein, the first pad structure is located in the first pad area, the second pad structure is located in the second pad area, the plurality of signal transmission lines are located in the transmission line area, and the transmission line area includes a first single-layer area and a first double-layer area arranged along a first direction; In the first single-layer area, the first conductive layer is arranged on the first side of the substrate layer, and no conductive structure is arranged on the second side of the substrate layer. In the first double-layer area, the first conductive layer is arranged on the first side of the substrate layer, and a second conductive layer is arranged on the second side of the substrate layer. The second side and the first side are opposite sides of the substrate layer.

2. The flexible circuit board according to claim 1, wherein: At least a portion of the first single-layer region is a bending region, and at least a portion of the first double-layer region is a flat region.

3. The flexible circuit board according to claim 1, wherein: The transmission line region further includes: a second double-layer region, located on a side of the first single-layer region away from the first double-layer region in the first direction; Wherein, in the second double-layer region, the first side of the substrate layer is provided with the first conductive layer, and the second side of the substrate layer is provided with a third conductive layer.

4. The flexible circuit board according to claim 3, wherein: The flexible circuit board is bent to form a U-shaped structure, wherein the U-shaped structure includes a first flat portion, a second flat portion, and a connecting portion located between the first flat portion and the second flat portion, wherein the connecting portion connects the first flat portion and the second flat portion to semi-enclose an accommodating space; At least part of the first double-layer area is located in the second flat portion, at least part of the first single-layer area and at least part of the second double-layer area are located in the connecting portion, at least part of the second double-layer area is located in the connecting portion away from the bottom of the accommodating space, and at least part of the first single-layer area is located between the bottom and the second flat portion.

5. The flexible circuit board according to claim 3, wherein: The third conductive layer includes a first interconnection line extending along a second direction intersecting the first direction; The plurality of signal transmission lines include a plurality of first signal transmission lines, the plurality of first signal transmission lines are configured to transmit the same electrical signal, and the plurality of first signal transmission lines are electrically connected to the first interconnection lines, respectively.

6. The flexible circuit board according to claim 5, wherein: The first signal transmission line is configured to transmit a ground signal.

7. The flexible circuit board according to any one of claims 3 to 6, wherein: The second conductive layer and the third conductive layer are arranged on the same layer.

8. The flexible circuit board according to any one of claims 3 to 6, further comprising: a second single-layer region, located between the second double-layer region and the first pad region; as well as The third single-layer region is located between the first double-layer region and the second pad region.

9. The flexible circuit board according to any one of claims 1 to 8, wherein: The plurality of signal transmission lines include: a high-frequency signal transmission line configured to transmit a high-frequency signal; and Multiple first ground lines, Among them, at least one first ground wire is respectively arranged on both sides of the high-frequency signal transmission line in a second direction intersecting with the first direction, and in the first double-layer area, the second conductive layer is respectively connected to the first ground wires on both sides of the high-frequency signal transmission line through a first via hole passing through the substrate layer.

10. The flexible circuit board according to claim 9, wherein: The high-frequency signal transmission line comprises: a first high frequency signal sub-line; and The second high frequency signal sub-line, The polarity of the high-frequency signal on the first high-frequency signal sub-line is different from the polarity of the high-frequency signal on the second high-frequency signal sub-line.

11. The flexible circuit board according to any one of claims 3 to 6, wherein: The transmission line region further includes: a third double-layer region, located between the first double-layer region and the second double-layer region, and passing through the first single-layer region to be connected to the first double-layer region and the second double-layer region respectively, Wherein, the first single-layer region is also located on both sides of the third double-layer region in the second direction, and the second direction intersects with the first direction. In the third double-layer region, the first side of the substrate layer is provided with the first conductive layer, and the second side of the substrate layer is provided with a fourth conductive layer. The second conductive layer and the third conductive layer are connected through the fourth conductive layer and are arranged in the same layer.

12. The flexible circuit board according to claim 11, wherein: The plurality of signal transmission lines include: a high-frequency signal transmission line configured to transmit a high-frequency signal; and a plurality of first ground lines, Wherein, the high-frequency signal transmission line extends from the first double-layer area through the third double-layer area to the second double-layer area, and at least one first ground line is respectively arranged on both sides of the high-frequency signal transmission line in a second direction intersecting with the first direction; In the first double-layer area, the second conductive layer is connected to the first ground wires on both sides of the high-frequency signal transmission line through the first via holes passing through the substrate layer. In the third double-layer area, the fourth conductive layer is connected to the first ground wires on both sides of the high-frequency signal transmission line through the second via holes passing through the substrate layer.

13. The flexible circuit board according to any one of claims 1 to 12, further comprising: A first protective layer, located in the transmission line region and on a side of the first conductive layer away from the substrate layer; A second protective layer, located in the first double-layer region and located on a side of the second conductive layer away from the substrate layer; as well as The first exposure opening is located in the second protection layer and is configured to expose the second conductive layer.

14. The flexible circuit board according to claim 13, further comprising: a conductive tape, at least partially located on a side of the second protective layer away from the second conductive layer, and in contact with the second conductive layer through the first exposure opening, Wherein, the conductive tape is configured to be connected to the ground terminal.

15. The flexible circuit board according to claim 13, wherein: The first exposing opening is located at a side of the center of the first double-layer region close to the first single-layer region in the first direction.

16. The flexible circuit board according to claim 13, wherein: The flexible circuit board includes a plurality of the first exposure openings arranged along a second direction intersecting the first direction.

17. The flexible circuit board according to any one of claims 1 to 16, wherein: The plurality of signal transmission lines include a second ground line located at the outermost side of the plurality of signal transmission lines; The first conductive layer further comprises: A conductive grid is located on a side of the second ground line away from the center of the plurality of signal transmission lines, and connected to the second ground line; and The protection line is located at a side of the conductive grid away from the second ground line.

18. The flexible circuit board according to claim 17, further comprising: A first protective layer, located in the transmission line region and on a side of the first conductive layer away from the substrate layer; A second protective layer, located in the first double-layer region and located on a side of the second conductive layer away from the substrate layer; as well as a second exposure opening, located in the first protection layer and configured to expose the first conductive layer, The orthographic projection of the second exposure opening on the substrate layer overlaps with the orthographic projection of the second ground line on the substrate layer and the orthographic projection of the conductive grid on the substrate layer respectively.

19. The flexible circuit board according to claim 18, further comprising: The first electromagnetic shielding coating is located on a side of the first protective layer away from the first conductive layer and is disposed in contact with the second ground line and the conductive grid through the second exposed opening.

20. The flexible circuit board according to claim 19, wherein: The first electromagnetic shielding coating is only located in the first double-layer region.

21. The flexible circuit board according to claim 18, further comprising: a third exposure opening, located in the second protection layer and configured to expose the second conductive layer; as well as The second electromagnetic shielding coating is located on a side of the second protective layer away from the second conductive layer and is disposed in contact with the second conductive layer through the third exposure opening.

22. The flexible circuit board according to claim 21, wherein: An orthographic projection of the third exposure opening on the substrate layer overlaps with an orthographic projection of the second exposure opening on the substrate layer.

23. The flexible circuit board according to any one of claims 1 to 22, wherein: The first pad structure includes M first conductive pads, and the second pad structure includes M second conductive pads; The plurality of signal transmission lines include a second signal transmission line, the second signal transmission line includes a first end and a second end, the first end of the second signal transmission line includes P branches, and the second end of the second signal transmission line includes P branches; The P branches at the first end of the second signal transmission line are respectively connected to the P first conductive pads, and the P branches at the second end of the second signal transmission line are respectively connected to the P second conductive pads, where P is a positive integer greater than or equal to 2 and less than M.

24. The flexible circuit board according to any one of claims 1 to 22, wherein: The first pad structure includes M first conductive pads, and the second pad structure includes N second conductive pads; The plurality of signal transmission lines include a third signal transmission line, the third signal transmission line includes a first end and a second end, and the first end of the third signal transmission line includes P branches; The P branches at the first end of the third signal transmission line are respectively connected to P first conductive pads, and the second end of the third signal transmission line is connected to one second conductive pad. P is a positive integer greater than or equal to 2 and less than N, and M is greater than N.

25. The flexible circuit board according to any one of claims 1 to 22, wherein: The first pad structure includes M first conductive pads, and the second pad structure includes Q second conductive pads; The plurality of signal transmission lines include: a fourth signal transmission line extending from the first pad area to the first double-layer area, the fourth signal transmission line comprising a first end located in the first pad area and a second end located in the first double-layer area; and a fifth signal transmission line extending from the first pad area through the first double-layer area to the second pad area, the fifth signal transmission line comprising a first end located in the first pad area and a second end located in the second pad area, The second conductive layer further includes a transverse transmission line, which is connected to the second end of the fourth signal transmission line through a third via hole passing through the substrate layer, and is connected to the fifth signal transmission line through a fourth via hole passing through the substrate layer.

26. The flexible circuit board according to any one of claims 1 to 25, wherein the substrate layer is a flexible substrate layer.

27. The flexible circuit board according to any one of claims 1 to 25, wherein: The second conductive layer includes a conductive metal grid.

28. The flexible circuit board according to any one of claims 1 to 25, wherein: The material of the first conductive layer includes copper, and the material of the second conductive layer includes copper.

29. A display device comprising: Display panel; as well as A flexible circuit board according to any one of claims 1-28.

30. The display device according to claim 29, further comprising: A back panel, located on one side of the display panel; as well as A driving circuit board is located on a side of the back plate away from the display panel, Wherein, the display panel comprises a binding area and a plurality of binding pads located in the binding area, The back plate includes a bottom frame, and the flexible circuit board is bent from the binding area to a side of the back plate away from the display panel; The first pad structure is connected to the plurality of binding pads, and the second pad structure is connected to the driving circuit board.

31. The display device according to claim 30, wherein: At least part of the first double-layer area is located at a side of the back plate away from the display panel, and at least part of the first single-layer area is a bending area surrounding the bottom frame.

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