Foldable structural member, preparation method thereof and foldable electronic equipment

Abstract

The embodiment of the invention provides a foldable structural member, a preparation method thereof and foldable electronic equipment. The foldable structural member comprises a first middle frame and a second middle frame, a first protection layer and an injection molding layer are sequentially arranged in corresponding areas of the first middle frame and the second middle frame in a stacked mode, and an anti-corrosion layer is arranged between the injection molding layer and the first protection layer. According to the special anti-corrosion design, feasibility is provided for the magnesium alloy to serve as a metal body of a rotating open area in the foldable structural part, and therefore the structural part can be used for providing lighter and thinner foldable electronic equipment.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of electronic technology, and in particular to foldable structural parts and preparation methods thereof, and foldable electronic devices. Background Art

[0002] With the rapid development of electronic technology, consumers are increasingly pursuing the lightness and thinness of electronic devices such as mobile phones. Generally, manufacturers choose to assemble magnesium alloy middle frames in electronic devices to improve the lightness and thinness of electronic devices. However, for the currently popular foldable electronic devices that have higher requirements for lightness and thinness, the middle frame generally includes a first middle frame and a second middle frame connected by a rotating mechanism, which means that there must be a rotating open area on the middle frame (including an area where salt spray and water vapor can penetrate). If a full magnesium alloy middle frame is still used, the conventional magnesium alloy anti-corrosion design cannot meet the requirements. In a salt spray environment, galvanic corrosion will occur in the rotating open area, causing the rotating mechanism to get stuck and fail.

[0003] If the anti-corrosion solution of the magnesium alloy middle frame for straight-screen phones is simply applied to foldable structural parts, it will not solve the problem of galvanic corrosion between the magnesium alloy and the steel shaft in the shaft development area, which will cause the whole machine to fail the salt spray test and thus fail to meet the product requirements. Therefore, it is urgent to provide a foldable structural part with a new anti-corrosion design to realize the feasibility of using the full magnesium alloy middle frame in foldable electronic devices. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a foldable structural member and a method for preparing the same, and a foldable electronic device. The foldable structural member has a special anti-corrosion design, which provides feasibility for magnesium alloy to be used as the metal body of the rotating open area of ​​the foldable structural member.

[0005] A first aspect of an embodiment of the present application provides a foldable structural member, comprising a rotating mechanism, and a first middle frame and a second middle frame rotatably connected to the rotating mechanism;

[0006] The first middle frame includes a first back plate, the first back plate has a first surface; the second middle frame includes a second back plate, the second back plate has a second surface, and the rotating mechanism overlaps the first surface and the second surface;

[0007] defining a first area and a second area, wherein the first area includes a side edge of the first surface close to the rotating mechanism, and the second area includes a side edge of the second surface close to the rotating mechanism;

[0008] The first back plate and the second back plate both include a metal body, a first protective layer arranged on the surface of the metal body, an injection molding layer arranged on the surface of the first protective layer at least in the first area and the second area, and an anti-corrosion layer arranged between the injection molding layer and the first protective layer.

[0009] The metal body provides structural strength for the first middle frame and the second middle frame, and plays a certain protective role. When it is applied to electronic devices, it can also assist the heat dissipation of the processor of the electronic device. The first protective layer can protect the metal body and prevent the metal body from being corroded. In particular, the injection molding layer in the first area and the second area can have a good sealing effect, that is, it greatly reduces the risk of salt spray and water vapor penetrating into the interior of the structural parts, so that when the material of the metal body is a magnesium alloy, the risk of galvanic corrosion of the magnesium alloy body in the rotating open area can be fully reduced. The anti-corrosion layer can significantly enhance the interfacial bonding force between the first protective layer and the injection molding layer, and avoid the situation where the bonding force between the injection molding layer and the first protective layer is poor and delamination occurs, thereby significantly reducing the risk of galvanic corrosion of the metal body, thereby providing feasibility for the application of the magnesium alloy middle frame (including the first middle frame and the second middle frame) to foldable electronic devices.

[0010] In some embodiments of the present application, the first back plate has a third surface opposite to the first surface, and a fourth surface connecting the first surface and the third surface, and the fourth surface includes the anti-corrosion layer and the injection molding layer stacked in sequence on the surface of the first protective layer away from the metal body.

[0011] In some embodiments of the present application, the second back plate has a fifth surface opposite to the second surface, and a sixth surface connecting the second surface and the fifth surface, and the sixth surface includes the anti-corrosion layer and the injection molding layer stacked in sequence on the surface of the first protective layer away from the metal body.

[0012] In some embodiments of the present application, the first middle frame and the second middle frame further include a first frame fixed to the first back plate and a second frame fixed to the second back plate; the first frame, the first back plate, the second back plate and the second frame constitute a first receiving space; the first frame and the second frame are made by injection molding. In this way, not only can the anti-corrosion effect of the foldable structural parts be fully guaranteed, but also the display screen in the final electronic device has a limiting effect, and can also constitute the appearance of the final electronic device.

[0013] In some embodiments of the present application, the first frame is integrally formed with the injection molding layer, and the second frame is integrally formed with the injection molding layer. This is beneficial to improving the strength of the first middle frame and the second middle frame, and is also easy to manufacture.

[0014] In some embodiments of the present application, the thickness of the first protective layer is in the range of 15 μm-40 μm, so as to enhance the anti-corrosion effect of the first protective layer and further reduce the risk of galvanic corrosion of the metal body.

[0015] In some embodiments of the present application, the first protective layer is a porous structure, and the porosity of the first protective layer is ≤15%, and the pore size is ≤20μm. At this time, the first protective layer has a certain density, which can achieve a good anti-corrosion effect by itself, and can significantly improve the direct interface bonding force between the first protective layer and the anti-corrosion layer, thereby improving the anti-corrosion ability of the entire first middle frame and the second middle frame.

[0016] In some embodiments of the present application, the first protective layer is a ceramic layer formed by micro-arc oxidation. The ceramic layer obtained by micro-arc oxidation has high hardness, strong corrosion resistance and good insulation performance.

[0017] In some embodiments of the present application, the thickness of the injection molding layer is in the range of 0.15 mm to 0.35 mm. In this way, it can have good sealing performance, thereby improving the anti-corrosion effect of the entire electronic device, and can also help ensure that the final electronic device is relatively light and thin.

[0018] In some embodiments of the present application, the injection molding layer is an inorganic material reinforced resin layer. The inorganic material reinforced resin has good mechanical properties and good bonding strength with the material of the first protective layer.

[0019] In some embodiments of the present application, the anti-corrosion layer is a resin layer; the material of the resin layer includes a cured product of epoxy resin, polyester resin and silane coupling agent; the thickness of the anti-corrosion layer is in the range of 10 μm-40 μm. In this way, the anti-corrosion layer can achieve better anti-corrosion performance while taking into account the lightness and thinness of the final electronic device.

[0020] In some embodiments of the present application, the anti-corrosion layer includes a first resin layer and a second resin layer stacked, the first resin layer is in contact with the first protective layer; wherein the first resin layer includes a resin distributed with a first type of inorganic filler, the resin includes a material made of epoxy resin, polyester resin and silane coupling agent, the first type of inorganic filler includes at least one of hydrophobic silica, talcum powder and magnesium powder; the second resin layer includes a cured product of a first type of acrylic resin and isocyanate distributed with a second type of inorganic filler, the second type of inorganic filler includes at least one of silica, barium sulfate and titanium dioxide. In this way, the anti-corrosion performance of the anti-corrosion layer can be further improved.

[0021] In some embodiments of the present application, the thickness of the first resin layer is in the range of 2 μm-10 μm, and the thickness of the second resin layer is in the range of 10 μm-30 μm. In this way, the anti-corrosion layer can achieve better anti-corrosion performance.

[0022] In some embodiments of the present application, a transition layer is further provided between the first resin layer and the second resin layer, and the transition layer includes a second type of hydroxy acrylic resin; wherein the thickness of the first resin layer is in the range of 2μm-10μm; the thickness of the second resin layer is in the range of 2μm-10μm; and the thickness of the transition layer is in the range of 10μm-20μm. In this way, the anti-corrosion layer can achieve better anti-corrosion performance while taking into account the lightness and thinness of the final electronic device.

[0023] In some embodiments of the present application, on the first surface, the surface of the anti-corrosion layer not covered by the injection layer is further provided with a second protective layer in at least a portion of the area adjacent to the injection layer, so as to further enhance the anti-galvanic corrosion effect of the rotating open area.

[0024] In some embodiments of the present application, in the second surface, a second protective layer is provided on at least a portion of the surface of the anti-corrosion layer not covered by the injection layer and adjacent to the injection layer, so as to further enhance the anti-galvanic corrosion effect of the rotating open area.

[0025] In some embodiments of the present application, the second protective layer is connected to the injection molding layer.

[0026] In some embodiments of the present application, the second protective layer also covers the surface of the injection molding layer away from the anti-corrosion layer.

[0027] In some embodiments of the present application, the second protective layer includes a fluorine-containing resin, or the second protective layer includes a cured product of a third type of hydroxy acrylic resin and isocyanate. The fluorine-containing resin also has a certain hydrophobic property, and the cured product of the third type of hydroxy acrylic resin and isocyanate has good compactness.

[0028] In some embodiments of the present application, the thickness of the second protective layer is in the range of 5 μm-30 μm. In this way, both the anti-corrosion performance and the lightness and thinness of the final electronic device can be taken into account.

[0029] In some embodiments of the present application, screw holes are provided in the first area and the second area, and the screw holes are adapted for screws, and the screws are used to fix the rotating mechanism.

[0030] In some embodiments of the present application, the material of the metal body is a magnesium alloy. In this way, while ensuring the mechanical properties of the foldable structural member, its weight and thickness can be significantly reduced. When applied to electronic devices, the market competitiveness of the electronic devices can be greatly improved.

[0031] The second aspect of the present application provides a method for preparing the above-mentioned foldable structural member, comprising:

[0032] Providing a metal body, and forming the first protective layer on the surface of the metal body;

[0033] forming the anti-corrosion layer at least on the surface of the first protective layer in the first region and the second region;

[0034] The injection molding layer is formed at least on the surface of the anti-corrosion layer in the first region and the second region to prepare a foldable structural member.

[0035] The preparation method has simple steps and high production efficiency and is suitable for large-scale industrial production.

[0036] In some embodiments of the present application, the process of forming the first protective layer on the surface of the metal body includes:

[0037] The metal body is immersed in an electrolyte in an electrolytic cell, the metal body is used as an anode, the electrolytic cell is used as a cathode, an electric field is applied, and the metal body is subjected to micro-arc oxidation at a current density greater than 2A and less than or equal to 5A; wherein the electrolyte includes a solvent, a salt, and a nano-additive; the salt includes at least one of a silicate, a phosphate, and an aluminate. In this way, a first protective layer with a thickness of 15μm-40μm can be obtained.

[0038] A third aspect of the embodiments of the present application provides a foldable electronic device, comprising the foldable structural component provided by the first aspect of the embodiments of the present application.

[0039] In some embodiments of the present application, the above-mentioned foldable electronic devices include but are not limited to mobile phones, laptop computers, tablet computers, electronic watches and other wearable electronic devices.

[0040] In some embodiments of the present application, the foldable electronic device includes a first display screen and a second display screen;

[0041] The first display screen is arranged on the first surface of the first middle frame and the second surface of the second middle frame; the first display screen is a flexible display screen;

[0042] The second display screen is disposed on a surface of the first middle frame facing away from the first display screen, or the second display screen is disposed on a surface of the second middle frame facing away from the first display screen. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1A A schematic diagram of a foldable structural member in an unfolded state provided by an embodiment of the present application;

[0044] Figure 1B for Figure 1A A schematic diagram of the foldable structural member from another perspective;

[0045] Figure 1C for Figure 1B A schematic diagram of another form of the foldable structural member;

[0046] Figure 1D A schematic diagram of a first backplane provided in an embodiment of the present application at a viewing angle;

[0047] Figure 2A A schematic diagram of a first middle frame and a second middle frame of a foldable structural member provided by an embodiment of the present application in an unfolded state;

[0048] Figure 2B A schematic diagram of a first middle frame and a second middle frame of a foldable structural member provided by another embodiment of the present application in an unfolded state;

[0049] Figure 3A A partial enlarged view of a first area on a first surface of a first middle frame provided in an embodiment of the present application;

[0050] Figure 3B A partial enlarged view of a first area on a first surface of a first middle frame provided in another embodiment of the present application;

[0051] Figure 3C A partial enlarged view of a first area on a first surface of a first middle frame provided in another embodiment of the present application;

[0052] Figure 3D A partial enlarged view of a first area on a first surface of a first middle frame provided in yet another embodiment of the present application;

[0053] Figure 4A A schematic structural diagram of a cross section of a first middle frame provided in an embodiment of the present application;

[0054] Figure 4B A schematic structural diagram of a cross section of a first middle frame provided in yet another embodiment of the present application;

[0055] Figure 4C A schematic structural diagram of a cross section of a first middle frame provided in another embodiment of the present application.

[0056] Description of Figure Numbers

[0057] 100-foldable structural member; 10-first middle frame; 11-first back plate; 111-first surface; 112-third surface; 113-first area; 114-fourth surface; 12-first frame; 20-second middle frame; 21-second back plate; 211-second surface; 212-fifth surface; 213-second area; 22-second frame; 30-rotating mechanism; 40-metal body; 50-first protective layer; 60-anti-corrosion layer; 70-injection molding layer; 80-second protective layer. DETAILED DESCRIPTION

[0058] At present, in mainstream foldable electronic devices, two display screens can be set at the same time, and one of the display screens is a flexible screen, which can change accordingly as the electronic device is folded and unfolded. In order to achieve the above purpose, the middle frame of the electronic device needs to be set as a foldable structural member, which generally includes a first middle frame and a second middle frame connected by a steel rotating mechanism, and the folding and unfolding of the flexible display screen is achieved by rotating the first middle frame and the second middle frame around the rotating mechanism. To this end, the flexible display screen needs to be simultaneously attached to the surface of the first middle frame and the second middle frame, which makes it impossible for the folding electronic device to use the screen dispensing method like a straight-screen machine to achieve the seal between the middle frame and the screen (which can achieve the performance of resistance to salt spray and water vapor corrosion). Therefore, the middle frame of the foldable electronic device must have a rotation open area, which means that salt spray and water vapor can enter this area, thereby forming an electrolyte environment in the rotation open area.

[0059] In view of the great difference between the standard electrode potential of magnesium alloy (-2.37V) and the steel rotating mechanism (the potential of steel depends on the standard electrode potential of its main element Fe, which is about -0.44V), in the electrolyte environment, the magnesium alloy middle frame will form a primary battery circuit with the steel rotating mechanism, galvanic corrosion will occur, and the magnesium alloy will lose electrons as the anode, causing corrosion perforation of the magnesium alloy, local material shortage and other phenomena, causing the rotating mechanism to stagnate and fail. In order to avoid the above problems, the industry directly chooses aluminum alloy as the material for the rotating open area of ​​the middle frame, but this will reduce the lightness and thinness of the electronic device and cannot meet the market demand. In order to solve the above problems, the embodiment of the present application provides a foldable structural member, and its special anti-corrosion design can effectively solve the galvanic corrosion problem of magnesium alloy in the foldable structural member.

[0060] Please also see Figure 1A-Figure 3D The embodiment of the present application provides a foldable structure 100, including a rotating mechanism 30, and a first middle frame 10 and a second middle frame 20 rotatably connected to the rotating mechanism 30; during the unfolding and folding process of the foldable structure 100, the first middle frame 10 and the second middle frame 20 are centered along the rotating mechanism 30. Figure 1C When the foldable structure 100 is fully unfolded, as shown in FIG. Figure 1A and Figure 1B As shown, the first middle frame 10 and the second middle frame 20 are disposed on opposite sides of the rotating mechanism 30 .

[0061] The first middle frame 10 includes a first back plate 11, and the first back plate 11 includes a first surface 111; the second middle frame 20 includes a second back plate 21, and the second back plate 21 has a second surface 211, and the rotating mechanism 30 overlaps the first surface 111 and the second surface 211;

[0062] A first area 113 and a second area 213 are defined, wherein the first area 113 includes a side edge of the first surface 111 close to the rotating mechanism 30, and the second area 213 includes a side edge of the second surface 211 close to the rotating mechanism 30; specifically, see Figure 2A-2B , on the side of the first back plate 11 close to the rotating mechanism 30 (for convenience of description, the side is recorded as the first side of the first back plate 11), on the first surface 111 thereof, the area from the contour line of the first side toward away from the first side and covering the first width at the center of the first back plate 11 is the first area 113 (that is, from the contour line of the first side along Figure 2B The area with the first width W1 in the direction of the black dotted arrow in the middle is the first area 113); accordingly, on the side of the second back plate 21 close to the rotating mechanism 30 (for the convenience of description, the side is recorded as the A side of the second back plate 21), on the second surface 211, the area from the contour line of the above-mentioned A side of the second back plate 21 to the direction away from the A side and covering the second width toward the center of the second back plate 21 is the second area 213 (that is, from the contour line of the above-mentioned A side along the Figure 2BThe second width W2 area in the direction of the black dotted arrow at the second back plate 21 is the second area 213); wherein the values ​​of W1 and W2 can be adapted and adjusted according to the size of the foldable structure 100, for example, 0.5mm-2.0mm, so that the first area 113 and the second area 213 at least cover part of the rotation opening area. Specifically, the values ​​of W1 and W2 can be independently 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, etc. In addition, the first area 113 and the second area 213 can further extend toward the center position of the first back plate 11 and the second back plate 21 along the direction indicated by the black dotted arrow (that is, increase W1 and W2); or they can be reduced toward one side of the rotating mechanism 30 (that is, reduce toward the first side edge of the first back plate 11 and the A side edge of the second back plate 21 in the direction away from the black dotted arrow, reduce W1 and W2). In the embodiment of the present application, the values ​​of W1 and W2 can be the same or different. It can be understood that when the above-mentioned foldable structural member 100 is fully folded, the first area 113 is opposite to the second area 213.

[0063] Generally, in the foldable structure 100, in order to fix the rotating mechanism 30, screw holes are provided on the first back plate 11 and the second back plate 21, and the screw holes are adapted to screws, and the screws are used to fix the rotating mechanism 30. In some embodiments of the present application, see Figure 2B , the first area 113 extends to the side of the screw hole away from the first side of the first back plate 11, and the second area 213 extends to the side of the screw hole away from the A side of the second back plate 21. In other words, the screw holes are provided in both the first area 113 and the second area 213. In this way, the anti-galvanic corrosion effect of the rotating open area of ​​the foldable structural member 100 can be further improved, and the folding and unfolding of the foldable structural member 100 will not be affected.

[0064] See also Figure 3A-3C, the first back plate 11 and the second back plate 21 both include a metal body 40, a first protective layer 50 disposed on the surface of the metal body 40, an injection molding layer 70 disposed on the surface of the first protective layer 50 at least in the first area 113 and the second area 213, and an anti-corrosion layer 60 disposed between the injection molding layer 70 and the first protective layer 50. The metal body 40 provides structural strength for the first middle frame 10 and the second middle frame 20, and plays a certain protective role. When it is applied to electronic equipment, it can also play a role in assisting the heat dissipation of the processor of the electronic equipment. The first protective layer 50 can protect the metal body 40 and prevent the metal body 40 from being corroded. In particular, the injection molding layer 70 in the first area 113 and the second area 213 can have a good sealing effect, that is, greatly reduce the risk of salt spray water vapor and the like penetrating into the interior of the foldable structural member 100, so that when the material of the metal body 40 is a magnesium alloy, the risk of galvanic corrosion of the magnesium alloy in the rotating open area can be fully reduced. The anti-corrosion layer 60 can significantly improve the interfacial bonding strength between the first protective layer 50 and the injection molding layer 70, avoiding the delamination due to poor bonding between the injection molding layer 70 and the first protective layer 50, thereby significantly reducing the risk of galvanic corrosion of the metal body 40 and significantly improving its environmental stability, thereby providing feasibility for magnesium alloy to be used as the metal body of the rotating open area in the foldable structural member 100.

[0065] In the embodiment of the present application, the anti-corrosion layer 60 is provided between the injection molding layer 70 and the first protective layer 50, including but not limited to the following situations: the orthographic projection of the injection molding layer 70 on the first surface 111 on the metal body 40 falls inside the orthographic projection of the anti-corrosion layer 60 on the metal body 40, specifically, including but not limited to the following two situations: (1) Figure 3A As shown, the orthographic projection of the injection molding layer 70 on the first surface 111 on the metal body 40 completely overlaps with the orthographic projection of the anti-corrosion layer 60 on the metal body 40; the orthographic projection of the injection molding layer 70 on the second surface 211 on the metal body 40 completely overlaps with the orthographic projection of the anti-corrosion layer 60 on the metal body 40. (2) Figure 3B As shown, the orthographic projection of the injection molding layer 70 on the first surface 111 on the metal body 40 falls inside the orthographic projection of the anti-corrosion layer 60 on the metal body 40, and there is a surface of the anti-corrosion layer 60 that is not covered by the injection molding layer 70; the orthographic projection of the injection molding layer 70 on the second surface 211 on the metal body 40 falls inside the orthographic projection of the anti-corrosion layer 60 on the metal body 40, and there is a surface of the anti-corrosion layer 60 that is not covered by the injection molding layer 70.

[0066] In some embodiments of the present application, on the first surface 111 and / or the second surface 211, the orthographic projection of the injection molding layer 70 on the metal body 40 falls within the orthographic projection of the anti-corrosion layer 60 on the metal body 40 (that is, part of the surface of the anti-corrosion layer 60 is not covered by the injection molding layer 70). The following is a detailed description taking the first back plate 11 as an example: Figure 3B , the width of the first area 113 is W1, that is, on the first surface 111, from the contour line of the first side of the first back plate 11 toward the center of the first back plate 11 (that is, along the direction indicated by the black dotted arrow), the width of the injection molding layer 70 is W1, and the width of the anti-corrosion layer 60 is W1', W1'>W1. In this way, while meeting the anti-corrosion requirements of the metal body 40, the thickness of the central area of ​​the first back plate 11 can be further reduced, and more accommodation space can be reserved for the first middle frame 10 to accommodate other components such as the processor, thereby helping to reduce the total thickness of the final electronic device and further improve the lightweight degree of the electronic device. Furthermore, the value of the above W1'-W1 can be in the range of 0.03mm-20mm. Specifically, the value of W1'-W1 can be 0.03mm, 0.05mm, 0.10mm, 0.20mm, 0.50mm, 0.80mm, 1.00mm, 2.00mm, 5.00mm, 8.00mm, 10.00mm, 12.00mm, 15.00mm, 18.00mm, 20.00mm, etc. On the second surface 211 of the second back plate 21, from the contour line of the A side of the second back plate 21 toward the center of the second back plate 21, the width of the injection molding layer 70 is greater than the width of the anti-corrosion layer 60; specifically, the situation on the second back plate 21 can be adapted according to the above principles, which will not be repeated here. In some specific embodiments, on the first surface 111 of the first back plate 11, at least part of the first protective layer 50 is not covered by the anti-corrosion layer 60; and, on the second surface 211 of the second back plate 21, at least part of the first protective layer 50 is not covered by the anti-corrosion layer 60. In this way, while meeting the anti-corrosion requirements of the metal body 40, the total thickness of the final electronic device can be further reduced, the lightweight degree of the final electronic device can be further improved, and the production cost can be reduced. Of course, according to actual applications, the surface of the first protective layer 50 on the first surface 111 of the first back plate 11 can be fully covered by the anti-corrosion layer 60. Similarly, the surface of the first protective layer 50 on the second surface 211 of the second back plate 21 can also be fully covered by the anti-corrosion layer 60.

[0067] In some other embodiments of the present application, on the first surface 111 and / or the second surface 211, the orthographic projection of the injection molding layer 70 on the metal body 40 completely overlaps with the orthographic projection of the anti-corrosion layer 60 on the metal body 40. In this way, in the area where the injection molding layer 70 is not provided, the anti-corrosion layer 60 is also not provided, which is conducive to reducing production costs. It can be selected according to actual application needs.

[0068] In the embodiment of the present application, it should also be noted that a first protective layer 50 is provided on the surface of the metal body 40 , which specifically means that the entire surface of the metal body 40 is covered by the first protective layer 50 .

[0069] In some embodiments of the present application, the material of the metal body 40 is a magnesium alloy. The density of magnesium alloy is relatively low and the specific strength is high. The base metal is made of magnesium alloy, which can reduce the weight of the first back plate 11 and the second back plate 21 while ensuring their strength, which helps to improve the lightness and thinness of the electronic device. Among them, the magnesium alloy can be a profile magnesium alloy, a die-cast magnesium alloy, or a semi-solid magnesium alloy, but not limited to this. In some embodiments, the magnesium alloy can be a magnesium-aluminum alloy or a magnesium-lithium alloy, but not limited to this. Specifically, the magnesium alloy can be selected from at least one of AZ series magnesium alloys, AM series magnesium alloys, AE series magnesium alloys, and AS series magnesium and gold.

[0070] In some embodiments of the present application, the first back plate 11 has a third surface 112 opposite to the first surface 111, and a fourth surface 114 (eg, Figure 1D As shown), the fourth surface 114 includes an anti-corrosion layer 60 and an injection molding layer 70 which are sequentially stacked on the surface of the first protective layer 50 away from the metal body 40;

[0071] And / or, the second back plate 21 has a fifth surface 212 opposite to the second surface 211, and a sixth surface ( Figure 1D The sixth surface includes an anti-corrosion layer 60 and an injection molding layer 70 which are sequentially stacked on the surface of the first protective layer 50 away from the metal body 40. In this way, the anti-corrosion performance of the first middle frame 10 and the second middle frame 20 can be improved in all directions, so that the final foldable electronic device can pass the salt spray test.

[0072] The following is a detailed description using the first back panel 11 as an example. One end of the first side of the first back panel 11 is sequentially connected to the second side, the third side and the fourth side, wherein the fourth side is connected to the other end of the first side. The surfaces of the first side, the second side, the third side and the fourth side together constitute the fourth surface 114. It can be understood that in order to fully guarantee the anti-corrosion effect of the foldable structural member 100, the fourth surface 114 also needs to be treated with anti-corrosion. Therefore, the surface of the first protective layer 50 on the fourth surface 114 also includes an anti-corrosion layer 60 and an injection molding layer 70 stacked in sequence. Similarly, the second back panel also includes four sides, and the surfaces of the four sides together constitute the sixth surface. The specific situation can be adapted according to the above principles, which will not be repeated here.

[0073] In some specific embodiments, the fourth surface 114 of the first back plate 11 does not expose the metal body 40. In some specific embodiments, further, the anti-corrosion layer 60 and the injection molding layer 70 can also extend from the fourth surface 114 to the first surface 111 of the first back plate 11. Taking the second side as an example, the anti-corrosion layer 60 and the injection molding layer 70 extend from the fourth surface 114 to the edge area of ​​the first surface 111 close to the second side, and the width of the area on the first surface 111 can be determined according to the actual application needs. It should be noted that the injection molding layer 70 on the first side is connected to the injection molding layer 70 on the first area 113 to enhance the anti-corrosion effect; further, the injection molding layer 70 on the first side is seamlessly connected to the injection molding layer 70 on the first area 113. The anti-corrosion layer 60 on the first side is seamlessly connected to the anti-corrosion layer 60 on the first area 113. Similarly, the sixth surface of the second back plate does not expose the metal body 40 , and the anti-corrosion layer 60 and the injection molding layer 70 of the second back plate 21 can be adapted according to the above principles, which will not be described in detail here.

[0074] In some embodiments of the present application, the thickness of the injection molding layer 70 is in the range of 0.15 mm to 0.35 mm. In this way, the protective performance of the injection molding layer 70 and the thinness of the foldable structural member 100 can be taken into account. Specifically, the thickness of the injection molding layer 70 can be 0.15 mm, 0.18 mm, 0.20 mm, 0.22 mm, 0.25 mm, 0.28 mm, 0.30 mm, 0.32 mm, 0.35 mm, etc.

[0075] See also Figure 1B-Figure 1C as well as Figure 4AIn some embodiments of the present application, the first middle frame 10 further includes a first frame 12 fixed on the first back plate 11; the second middle frame 20 further includes a second frame 22 fixed on the second back plate 21; the first frame 12, the first back plate 11, the second back plate 21 and the second frame 22 constitute a first receiving space; the first frame 12 and the second frame 22 are made by injection molding. The first frame 12 and the second frame 22 extend toward the first surface 111 of the first back plate 11, and the extension direction thereof is perpendicular to the first surface 111; the second frame 22 extends toward the second surface 211 of the second back plate 21, and the extension direction thereof is perpendicular to the second surface 211. The first frame 12 and the second frame 22 have the function of limiting and protecting the outer edge of the display screen of the electronic device. Specifically, the first receiving space can be used to accommodate the first display module, the heat sink and other components. Among them, the first display module includes a first display screen, and the first display screen is a flexible screen. In addition, the first frame 12 and the second frame 22 also participate in forming the appearance surface of the foldable electronic device.

[0076] In some implementations of this application, please see Figure 4B , the first frame 12 also extends toward the third surface 112 of the first back panel 11, and its extension direction is also perpendicular to the third surface 112; the second frame 22 also extends toward the fifth surface 212 of the second back panel 21, and its extension direction is also perpendicular to the fifth surface 212. In this way, the first frame 12, the first back panel 11, the second frame 22 and the second back panel 21 also form a second receiving space, and the second receiving space can be used to receive battery components, etc. Among them, when the foldable structure 100 is fully unfolded, the second receiving space and the first receiving space are arranged opposite to each other. In some specific embodiments, a second display module is provided in the second receiving space. At this time, the second display module is located on the third surface 112 of the first back panel 11, or, on the fifth surface 212 of the second back panel 21. For further information, please refer to Figure 4C The anti-corrosion layer 60 and the injection layer 70 also extend to the third surface 112 of the first back plate 11, and / or the anti-corrosion layer 60 and the injection layer 70 also extend to the fifth surface 212 of the second back plate. Further, the second middle frame 20 can be adapted according to the above principles, which will not be described in detail here.

[0077] In some embodiments of the present application, the first frame 12 is integrally formed with the injection molding layer 70 on the first back plate 11, and the second frame 22 is integrally formed with the injection molding layer 70 on the second back plate 21. In this way, the structural strength of the first middle frame 10 and the second middle frame 20 is further improved. At this time, it can be understood that the surface of one side of the injection molding layer 70 close to the anti-corrosion layer 60 is a flat surface attached to the first back plate 11 and the second back plate 21, and the first frame 12 protrudes relative to the first back plate 11, which can achieve a limiting effect on the display screen. Similarly, the second frame 22 protrudes relative to the second back plate 21. The first frame 12 is seamlessly connected to the injection molding layer 70, and the second frame 22 is seamlessly connected to the injection molding layer 70.

[0078] In some embodiments, the material of the injection molding layer 70 is a resin reinforced by an inorganic material. In some embodiments of the present application, the material of the injection molding layer 70 is a resin reinforced by an inorganic fiber. Among them, the inorganic fiber includes but is not limited to glass fiber (GF). Among them, the resin includes but is not limited to at least one of polycarbonate (PC), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), and polyamide (PA). That is, the material of the injection molding layer 70 can be at least one of GF-reinforced PC, GF-reinforced PBT, GF-reinforced PPS, and GF-reinforced PA, but is not limited thereto. In this way, the anti-corrosion performance and strength of the injection molding layer 70 can be taken into account. In some specific embodiments, the mass percentage of inorganic fibers in the injection molding layer 70 is 10%-60%. Specifically, the mass percentage of the inorganic fiber in the injection layer 70 can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, etc. In this way, the injection layer 70 can have good toughness, good density and high strength.

[0079] In some embodiments of the present application, the material of the first frame 12 and the material of the second frame 22 are resins reinforced with inorganic materials. In this case, the first frame 12 and the second frame 22 not only have good strength, excellent anti-fall performance, and excellent sealing and anti-corrosion performance, but also, when the foldable structural member 100 is used in an electronic device, the antenna module of the electronic device can transmit electrical signals to the outside world through the first frame 12 and the second frame 22, and receive electrical signals from the outside world to realize the communication function of the electronic device. Moreover, at this time, a discontinuous coating technology (NCVM) system appearance can also be formed on the outer surface of the first frame 12 and the second frame 22 to enhance the appearance of the final foldable electronic device.

[0080] In some embodiments of the present application, the material of the first frame 12 and the material of the second frame 22 are independently selected from at least one of GF-reinforced PC, GF-reinforced PBT, GF-reinforced PPS and GF-reinforced PA, but are not limited thereto. In some specific embodiments, the material of the first frame 12, the material of the second frame 22 and the material of the injection molding layer 70 are the same. At this time, the mass percentage of the inorganic fiber in the first frame 12 and the mass percentage of the inorganic fiber in the second frame 22 can be the same or different; the above two and the mass percentage of the inorganic fiber in the injection molding layer 70 can be the same or different.

[0081] In some embodiments of the present application, the first protective layer 50 is a ceramic layer formed by micro-arc oxidation. Micro-arc oxidation can grow a uniform ceramic layer in situ on the surface of the metal body 40, and the formed ceramic layer has high hardness, strong corrosion resistance and good insulation performance. In some embodiments of the present application, the resistance of the first protective layer 50 is ≥3MΩ. In some embodiments of the present application, the material of the first protective layer 50 includes but is not limited to at least one of magnesium silicate, magnesium oxide, magnesium hydroxide and magnesium chlorate.

[0082] In some embodiments of the present application, the first protective layer 50 has a porous structure, the porosity of the first protective layer 50 is ≤15%, and the pore size of the porous structure is ≤20μm. That is, in some specific embodiments, the porosity of the ceramic layer formed by micro-arc oxidation is ≤15%, and the pore size is ≤20μm. Specifically, the above porosity can be but is not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. Specifically, the pore size of the porous structure may be, but is not limited to, 0.5 μm, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, 6.0 μm, 6.5 μm, 7.0 μm, 8.0 μm, 9.0 μm, 10.0 μm, 11.0 μm, 12.0 μm, 13.0 μm, 14.0 μm, 15.0 μm, 16.0 μm, 17.0 μm, 18.0 μm, 19.0 μm, 20.0 μm, etc. In some specific embodiments, the pore size of the plurality of pores in the first protective layer 50 is distributed in the range of 0.5 μm-20 μm, and further, may be distributed in the range of 6.6 μm-20 μm. Thus, on the one hand, the first protective layer 50 has a certain number of pores with relatively large pore sizes, which can significantly improve the interfacial bonding force between the anticorrosion layer 60 and the first protective layer 50. In particular, when the anticorrosion layer 60 is a resin layer, during the preparation process, the raw material of the resin layer can flow into the above-mentioned pores (more easily flow into pores with larger pore sizes, pores with pore sizes>5μm), and after curing, the bonding force between the anticorrosion layer 60 and the first protective layer 50 is significantly improved, and the above-mentioned pores can be sealed; on the other hand, the first protective layer 50 is distributed with pores with smaller pore sizes (pores with pore sizes ≤5μm), which can adjust the overall porosity of the first protective layer 50 within a suitable range, so that the first protective layer 50 also has a certain density, and salt spray water vapor is not easy to pass through the pores with smaller pore sizes, thereby further reducing the risk of fine droplets such as salt spray penetrating into the surface of the metal body 40 through the first protective layer 50, so that when the material of the metal body 40 is a magnesium alloy, galvanic corrosion can be further slowed down, and the environmental stability of the final foldable electronic device can be improved.

[0083] In some embodiments of the present application, the surface roughness of the first protective layer 50 is ≥32A. For example, the surface roughness of the first protective layer 50 is 32A-50A. This is conducive to improving the interface bonding force between the first protective layer 50 and the anti-corrosion layer 60, and further reducing galvanic corrosion in the rotating open area.

[0084] In some embodiments of the present application, the thickness of the first protective layer 50 is in the range of 15μm-40μm. In this way, the protective performance of the first protective layer 50 can be further improved, and salt spray and water vapor can be further prevented from penetrating the first protective layer 50. It can also ensure that the total thickness of the first middle frame 10 and the second middle frame 20 is small, thereby taking into account the degree of thinness of the final electronic device. It can be understood that when the first protective layer 50 has a porous structure, its pores are randomly arranged in the first protective layer 50 (the first protective layer 50 has a pore structure intricately distributed inside, and the pores on the surface of the first protective layer 50 are in a typical crater shape). When the thickness of the first protective layer 50 is within a suitable range, it can significantly increase the path that fine droplets such as salt spray need to take when penetrating the first protective layer 50, and more obstacles are set, thereby achieving a better protective effect. Specifically, the thickness of the first protective layer 50 may be 15 μm, 15.5 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 35 μm, 36 μm, 38 μm, 39 μm, etc. In some specific embodiments of the present application, the first protective layer 50 has a porous structure, the porosity of the first protective layer 50 is ≤15%, the pore size of the porous structure is ≤20 μm, and the thickness of the first protective layer 50 is in the range of 15 μm-40 μm.

[0085] In the embodiment of the present application, the anti-corrosion layer 60 may be a single-layer structure, a double-layer structure, or a three-layer structure, but is not limited thereto.

[0086] In some embodiments of the present application, the anti-corrosion layer 60 is a resin layer (ie, the anti-corrosion layer 60 is a single-layer structure). The material of the resin layer includes a cured product of epoxy resin, polyester resin and silane coupling agent. Thus, during the preparation process, the mixture of epoxy resin, polyester resin and silane coupling agent can be coated on the surface of the first protective layer 50, and the mixture can be impregnated in some pores of the first protective layer 50. Moreover, epoxy resin and polyester resin have strong van der Waals force. After the mixture is cured, the material of the anticorrosion layer 60 (that is, the resin layer) is also dispersed in the first protective layer 50, thereby improving the interface bonding force between the anticorrosion layer 60 and the first protective layer 50. Moreover, when the material of the injection molding layer 70 includes the resin reinforced by the inorganic material, the interface bonding force between the resin in the anticorrosion layer 60 and the resin in the injection molding layer 70 is good, so the anticorrosion layer 60 can bridge the first protective layer 50 and the injection molding layer 70, and form a firm anticorrosion and waterproof structure on the surface of the corresponding area of ​​the metal body 40, greatly reducing the risk of galvanic corrosion of the magnesium alloy body, and ensuring that the final electronic equipment meets the salt spray test requirements of the whole machine. In addition, the cured product of epoxy resin, polyester resin and silane coupling agent has good resistance to water boiling, high temperature and high humidity. At this time, in some embodiments of the present application, the thickness of the anti-corrosion layer 60 is in the range of 10 μm-40 μm. Specifically, the thickness of the anti-corrosion layer 60 can be, but is not limited to, 10 μm, 12 μm, 15 μm, 20 μm, 22 μm, 24 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, etc. Controlling the thickness of the anti-corrosion layer 60 within the above range can take into account both good anti-corrosion performance and high lightness and thinness.

[0087] In some specific embodiments of the present application, the resin layer is further distributed with a first type of inorganic filler, wherein the first type of inorganic filler includes but is not limited to at least one of hydrophobic silica, talcum powder and magnesium powder. The first type of inorganic filler can increase the hiding power of the resin layer during the preparation process, that is, reduce the particles caused by environmental dust during the spraying process, and improve the flatness and anti-corrosion performance of the resin layer (that is, the anti-corrosion layer 60); at the same time, the first type of inorganic filler can also make the anti-corrosion layer 60 form a hydrophobic nanostructure to improve its anti-corrosion performance.

[0088] In some embodiments of the present application, the anti-corrosion layer 60 includes a first resin layer and a second resin layer stacked (the anti-corrosion layer 60 is a double-layer structure, Figure 3A-3B(not shown in the figure), the first resin layer is in contact with the first protective layer 50; wherein the first resin layer includes a material made of epoxy resin, polyester resin and silane coupling agent; the second resin layer includes a cured product of a first type of acrylic resin and isocyanate. Wherein, the molar content of hydroxyl groups of the above-mentioned first type of acrylic resin is ≥1.0%. Similarly, the first resin layer can partially penetrate into the holes of the first protective layer 50 to achieve better bonding; and the second resin layer and the injection molding layer 70 can achieve better interface bonding, so the anti-corrosion layer 60 can cooperate with the first protective layer 50 and the injection molding layer 70 to form a stable anti-corrosion barrier. At this time, the thickness of the first resin layer is in the range of 2μm-10μm, and the thickness of the second resin layer is in the range of 10μm-30μm. Specifically, in the double-layer anti-corrosion layer 60, the thickness of the first resin layer can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc. Specifically, the content of the second resin layer may be 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, or the like.

[0089] In some specific embodiments of the present application, the first resin layer is also distributed with a first type of inorganic filler; the second resin layer is also distributed with a second type of inorganic filler; wherein the first type of inorganic filler includes but is not limited to at least one of hydrophobic silica, talcum powder and magnesium powder; the second type of inorganic filler includes but is not limited to at least one of silica, barium sulfate and titanium dioxide. That is, the first resin layer includes a resin distributed with a first type of inorganic filler, and the resin includes a material made of epoxy resin, polyester resin and silane coupling agent; the second resin layer includes a cured product of a first type of acrylic resin and isocyanate distributed with a second type of inorganic filler. Similarly, the first type of inorganic filler can increase its hiding power during the preparation of the resin layer, that is, reduce the particles caused by environmental dust during the spraying process, and improve the flatness and anti-corrosion performance of the resin layer (that is, the anti-corrosion layer 60); at the same time, the first type of inorganic filler can also form a hydrophobic nanostructure in the anti-corrosion layer 60 to improve its anti-corrosion performance. The second type of inorganic filler can increase the surface dyne value of the second resin layer, thereby improving the bonding force between the injection molding layer and the anti-corrosion layer 60, which is beneficial to the corrosion resistance of the final electronic device.

[0090] In some other embodiments of the present application, a transition layer (the anti-corrosion layer 60 is a three-layer structure) is further provided between the first resin layer and the second resin layer. Figure 3A-3B(not shown in the figure). That is, the anti-corrosion layer 60 includes a first resin layer, a transition layer and a second resin layer stacked in sequence, and the first resin layer is in contact with the first protective layer 50. At this time, the transition layer includes a second type of hydroxyl acrylic resin. Among them, the molar content of hydroxyl groups in the second type of acrylic resin is ≤1.0%. The transition layer plays a role in connecting the first resin layer and the second resin layer, further improving the stability of the three-layer anti-corrosion layer 60. In the three-layer structure, the thickness of the first resin layer is in the range of 2μm-10μm; the thickness of the second resin layer is in the range of 2μm-10μm; the thickness of the transition layer is in the range of 10μm-20μm. Specifically, in the three-layer anti-corrosion layer 60, the thickness of the first resin layer and the second resin layer can be independently 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, etc. Specifically, in the three-layer anti-corrosion layer 60 , the thickness of the transition layer may be 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc.

[0091] In the embodiment of the present application, the anti-corrosion layer 60 can be prepared by electrophoresis or by coating process.

[0092] In the embodiment of the present application, the adhesion between the anti-corrosion layer 60 and the first protective layer 50 is ≥4B. In the embodiment of the present application, the boiling water adhesion between the anti-corrosion layer 60 and the first protective layer 50 is ≥4B.

[0093] The injection molding process is to place the metal body 40 with the first protective layer 50 and the anti-corrosion layer 60 in the corresponding area in the injection molding cavity, and perform injection molding on the designated area under high temperature and high pressure environment. In some cases, cracks will appear in the area where the anti-corrosion layer 60 is adjacent to the injection molding layer 70, affecting the anti-corrosion performance of the anti-corrosion layer 60. In other words, when the injection molding layer 70 does not cover the entire surface of the anti-corrosion layer 60, cracks will appear on the surface of the anti-corrosion layer 60 adjacent to the edge of the injection molding layer 70. In some embodiments of the present application, please refer to Figure 3C , a second protective layer 80 is also provided on the first surface 111 of the first back plate 11. Specifically, on the first surface 111 of the first back plate 11, a second protective layer 80 is also provided on at least a portion of the surface of the anti-corrosion layer 60 not covered by the injection molding layer 70, adjacent to the injection molding layer 70. Similarly, on the second surface 211 of the second back plate 21, a second protective layer 80 is also provided on at least a portion of the surface of the anti-corrosion layer 60 not covered by the injection molding layer 70, adjacent to the injection molding layer 70. In this way, the second protective layer 80 can seal the gaps that appear on the exposed surface of the anti-corrosion layer 60 due to injection molding, prevent salt spray water vapor from penetrating into the anti-corrosion layer 60 through the gaps, greatly reduce the galvanic corrosion rate, and enable the final electronic device to meet the salt spray test requirements of the whole machine.

[0094] In some embodiments of the present application, the second protective layer 80 is connected to the injection molding layer 70 .

[0095] In some implementations of this application, please see Figure 3D , the second protective layer 80 also covers the surface of the injection molding layer 70 away from the anti-corrosion layer 60. It can be understood that at this time, the second protective layer 80 can better cover the exposed surface of the anti-corrosion layer 60 at the junction of the injection molding layer 70 and the anti-corrosion layer 60, thereby better preventing salt spray and water vapor from penetrating into the anti-corrosion layer 60 through the gap. Further, in some specific embodiments, the second protective layer 80 can also cover the surface of the injection molding layer 70 away from the anti-corrosion layer 60.

[0096] In some embodiments of the present application, the thickness of the second protective layer 80 is in the range of 5μm-30μm. Specifically, the thickness of the second protective layer 80 refers to the maximum cross-sectional dimension of the second protective layer 80, and the above cross-section refers to the surface obtained by cutting the first backplane 11 (or, the second backplane 21) with a plane perpendicular to the thickness direction of the first backplane 11 (or, the second backplane 21). Specifically, the thickness of the second protective layer 80 can be 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm, 40μm, etc. In this way, while fully improving the anti-corrosion effect, the thinness of the final electronic product can also be improved.

[0097] In some embodiments of the present application, the second protective layer 80 includes a fluorine-containing resin. The fluorine-containing resin not only has good compactness, but also has certain hydrophobic properties, which is beneficial to further improve the waterproof and anti-corrosion properties. Specifically, the fluorine-containing resin includes but is not limited to fluoroacrylates, fluorosilicone acrylates, fluorourethanes, perfluoropolyethers, perfluoropolyoxetanes, fluorotelomers, polytetrafluoroethylene, polyvinylidene fluoride, fluorosilicone, 1,1,1,2,3,4,5,5,5-monofluoro-4-methoxypent-2-ene and at least one of perfluorohexyl alcohol tridecafluorooctanol.

[0098] In some other embodiments of the present application, the second protective layer 80 includes a solidified product of a third type of hydroxyl acrylic resin and isocyanate. Among them, the molar content of hydroxyl groups in the third type of hydroxyl acrylic resin is ≥1.0 (hydroxyl value ≥33) to improve the cross-linking degree of the polymer chain in the second protective layer, form a dense macromolecular network structure, and improve the corrosion resistance. At this time, the second protective layer also has good density, and has good bonding properties with the material of the anti-corrosion layer 60 and the material of the injection molding layer 70. In some embodiments of the present application, the third type of hydroxyl acrylic resin is the same as the aforementioned first type of hydroxyl acrylic resin, and further, the material of the second protective layer 80 is the same as the material of the second resin layer in the aforementioned anti-corrosion layer 60.

[0099] In some embodiments of the present application, the rotating mechanism 30 includes but is not limited to a hinge.

[0100] Accordingly, the embodiment of the present application further provides a method for preparing the foldable structural member 100, comprising:

[0101] S01, providing a metal body, and forming a first protective layer on the surface of the metal body;

[0102] S02, forming an anti-corrosion layer on the surface of the first protective layer at least in the first region and the second region;

[0103] S03, forming the above-mentioned injection molding layer 70 on the surface of the anti-corrosion layer at least in the first area and the second area to prepare a foldable structural member.

[0104] In some embodiments of the present application, before step S01, the metal body is also pretreated. It can be understood that when the material of the metal body is a magnesium alloy, the corrosion resistance of the magnesium alloy is poor, so the manufacturer will form a film (for example, a phosphating layer of the magnesium alloy) on the surface of the magnesium alloy raw material, and thus, the pretreatment of the magnesium alloy includes degreasing, water washing, film removal, water washing, neutralization, and water washing in sequence.

[0105] In step S01, a first protective layer is formed on the surface of the pretreated metal body by a micro-arc oxidation process. Specifically, the pretreated metal body is placed in an electrolyte immersed in an electrolytic cell, the metal substrate is used as an anode, the electrolytic cell is used as a cathode, and an electric field is applied to perform micro-arc oxidation, so that the surface layer of the metal body is melted, and the obtained melt is contacted with the electrolyte to form a ceramic layer with high hardness, good corrosion resistance and good electrical insulation performance on the surface of the metal body. In some embodiments, the electrolyte includes a solvent, a salt and a nano-additive, wherein the salt includes but is not limited to at least one of a silicate, a phosphate and an aluminate. In some embodiments, the metal body is micro-arc oxidized at a current density of 1A-5A. Specifically, the current density can be 1.5A, 2.0A, 2.2A, 2.4A, 2.5A, 3.0A, 3.5A, 4.0A, 4.2A, 4.5A, 4.8A, 5.0A, etc. In some specific embodiments, the metal body is immersed in an electrolyte containing salt and nano-additives, and micro-arc oxidation is performed on the metal body at a current density of 2A-5A, so that a first protective layer with a thickness of 15μm-40μm can be formed on the surface of the metal body.

[0106] In some implementations of the present application, in step S01, the voltage of the electric field does not exceed 1000V.

[0107] In some embodiments of the present application, in step S01, the duty cycle of the micro-arc oxidation process is in the range of 5%-25%. The duty cycle refers to the ratio of the power-on time to the total time in one pulse cycle of the micro-arc oxidation. Specifically, the duty cycle of the micro-arc oxidation process can be 5%, 6%, 10%, 15%, 20%, 22%, 25%, etc.

[0108] In some embodiments of the present application, in step S01, the temperature of the electrolyte is in the range of 15° C. to 25° C. Specifically, the temperature of the electrolyte may be 15° C., 18° C., 20° C., 22° C., 25° C., etc.

[0109] In some implementations of the present application, in step S01, the pulse frequency used in micro-arc oxidation is 800 Hz-1000 Hz. Specifically, the pulse frequency used in micro-arc oxidation can be 800 Hz, 850 Hz, 900 Hz, 950 Hz, 980 Hz, etc.

[0110] In some implementations of the present application, in step S01, the duration of the micro-arc oxidation process is 20 minutes to 40 minutes. Specifically, the duration of the micro-arc oxidation process can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc.

[0111] In some implementations of the present application, in step S02, the anti-corrosion layer may be prepared by an electrophoresis process or by a coating process.

[0112] In some embodiments of the present application, when the anti-corrosion layer is a single-layer structure (the anti-corrosion layer is a resin layer), a first mixture is coated on the surface of the first protective layer in at least the first region and the second region, wherein the first mixture includes epoxy resin, polyester resin and silane coupling agent, and is placed at 80°C-120°C and baked for 15min-30min to obtain a cured product of epoxy resin, polyester resin and silane coupling agent to obtain an anti-corrosion layer. In some specific embodiments of the present application, the first type of inorganic filler is added to the first mixture.

[0113] In some embodiments of the present application, when the anti-corrosion layer is a double-layer structure, the first mixture is coated on the surface of the first protective layer in at least the first region and the second region, and baked at 80°C-120°C for 15-30 minutes to obtain a first resin layer, and the second mixture is coated on the surface of the first resin layer; wherein the second mixture includes a first type of hydroxy acrylic resin and an isocyanate curing agent, and is baked at 80°C-120°C for 30 minutes-40 minutes to allow the first type of hydroxy acrylic resin to react with the isocyanate curing agent to obtain a second resin layer, thereby obtaining an anti-corrosion layer with a double-layer structure. In some specific embodiments of the present application, the first type of inorganic filler is added to the first mixture; and the second type of inorganic filler is added to the second mixture, wherein the second type of inorganic filler includes but is not limited to at least one of fumed silica, barium sulfate and titanium dioxide.

[0114] In some embodiments of the present application, when the anti-corrosion layer has a three-layer structure, the first mixture is coated on the surface of the first protective layer in at least the first region and the second region, and baked at 80°C-120°C for 15-30 minutes to obtain a first resin layer, and a transition layer mixture is coated on the surface of the first resin layer; wherein the transition layer mixture includes a second type of hydroxy acrylic resin, and is baked at 80°C-120°C for 15 minutes to 30 minutes to obtain a transition layer; and then the second mixture is coated on the surface of the transition layer, and baked at 80°C-120°C for 30 minutes to 40 minutes to obtain a second resin layer, thereby obtaining an anti-corrosion layer with a three-layer structure.

[0115] In some embodiments of the present application, step S02 further includes forming an anti-corrosion layer on other areas of the surface of the first protective layer, so that on the first surface of the first back plate, the orthographic projection of the injection molded layer on the metal body falls within the orthographic projection of the anti-corrosion layer on the metal body, and the anti-corrosion layer has an area not covered by the injection molded layer. In some embodiments of the present application, further includes forming an anti-corrosion layer on other areas of the surface of the first protective layer, so that on the second surface of the second back plate, the orthographic projection of the injection molded layer on the metal body falls within the orthographic projection of the anti-corrosion layer on the metal body, and the anti-corrosion layer has an area not covered by the injection molded layer.

[0116] In some embodiments of the present application, step S02 further includes forming an anti-corrosion layer on the side wall of the metal body (i.e., the fourth surface of the first back plate and the sixth surface of the second back plate). Furthermore, the anti-corrosion layer on the first side wall is extended to the edge of the first surface of the first back plate; it should be noted that the edge of the first surface here does not contain the first area. Similarly, the situation of the second back plate can also be adapted according to the above situation.

[0117] In some embodiments of the present application, in step S03, the above-mentioned injection molding layer is formed on the surface of the anti-corrosion layer in at least the first region and the second region, including: the metal body obtained in step S02 is placed in the mold cavity of the injection molding equipment, and the injection molding is performed at a mold temperature of 90°C-120°C with an injection molding pressure of 200MPa, and the temperature of the injection molding raw material is controlled to be 290°C-320°C, so as to form an injection molding layer on the surface of the anti-corrosion layer in the first region and the second region. Wherein, the above-mentioned injection molding raw material includes but is not limited to inorganic fiber reinforced resin particles. In some embodiments of the present application, in step S03, it also includes forming an injection molding layer on the surface of the anti-corrosion layer of the side wall of the metal body (equivalent to the fourth surface of the first backplane and the sixth surface of the second backplane). Taking the first backplane as an example, an injection molding layer is formed on the anti-corrosion layer on the fourth surface of the first backplane. Furthermore, the injection molding layer on the fourth surface is also extended to the edge of the first surface of the first backplane; it should be noted that the edge of the first surface here does not contain the first region. Similarly, the injection-molded layer on the sixth surface is also extended to the edge of the second surface of the second back plate; it should be noted that the edge of the second surface here does not contain the second area.

[0118] In some embodiments of the present application, step S03 further includes forming a first frame and a second frame. In some specific embodiments, the first frame is integrally formed with the injection molding layer, and the second frame is integrally formed with the injection molding layer, so that the first frame is seamlessly connected to the injection molding layer, and the second frame is seamlessly connected to the injection molding layer. In this way, the overall structural strength of the first middle frame and the second middle frame is improved.

[0119] In some embodiments of the present application, step S03 is followed by step S04: forming a second protective layer on at least a portion of the surface of the anti-corrosion layer that is not covered by the injection molding layer and is adjacent to the injection molding layer. Further, the second protective layer is connected to the injection molding layer. Furthermore, the second protective layer is extended to the surface of the injection molding layer that is away from the anti-corrosion layer.

[0120] In some embodiments of the present application, in step S04, the process of forming the second protective layer includes: coating the fluorine-containing resin on the designated area, baking at 40°C-60°C for 20min-50min to obtain the second protective layer; or, coating the fluorine-containing resin on the designated area, leaving it at room temperature for more than 24h to obtain the second protective layer.

[0121] In some other embodiments of the present application, in step S04, the process of forming the second protective layer includes: coating the third type of hydroxyl acrylic resin and isocyanate on a designated area, and baking at 80°C-120°C for 15min-30min to obtain the second protective layer.

[0122] The preparation method has simple steps, strong process reliability and is suitable for large-scale industrial production.

[0123] The embodiment of the present application also provides a foldable electronic device, including the foldable structural member provided by the embodiment of the present application.

[0124] In some embodiments of the present application, the above-mentioned foldable electronic devices include but are not limited to mobile phones, laptop computers, tablet computers, electronic watches and other wearable electronic devices.

[0125] In some embodiments of the present application, the foldable electronic device is a mobile phone.

[0126] In some embodiments of the present application, the foldable electronic device includes a first display screen and a second display screen; the first display screen is provided on both the first surface of the first middle frame and the second surface of the second middle frame; the first display screen is a flexible display screen; the second display screen is provided on the surface of the first middle frame away from the first display screen (that is, the third surface), or the second display screen is provided on the surface of the second middle frame away from the first display screen (that is, the fifth surface). At this time, the first display screen can be folded and unfolded as the electronic device is folded and unfolded. It can be understood that a display screen back panel is also provided on the surface of the first display screen facing the first middle frame and the second middle frame.

[0127] In some embodiments of the present application, the second display screen is provided on the surface of the first middle frame away from the first display screen (that is, the aforementioned third surface), and in this case, a battery is provided on the surface of the second middle frame away from the first display screen (that is, the aforementioned fifth surface). In other embodiments, the second display screen is provided on the surface of the second middle frame away from the first display screen (that is, the aforementioned fifth surface), and in this case, a battery is provided on the surface of the first middle frame away from the first display screen (that is, the aforementioned third surface).

[0128] The above are exemplary embodiments of the present application. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A foldable structural member, characterized in that: It includes a rotating mechanism, and a first middle frame and a second middle frame rotatably connected to the rotating mechanism; The first middle frame includes a first back plate, the first back plate has a first surface; the second middle frame includes a second back plate, the second back plate has a second surface, and the rotating mechanism overlaps the first surface and the second surface; defining a first area and a second area, wherein the first area includes a side edge of the first surface close to the rotating mechanism, and the second area includes a side edge of the second surface close to the rotating mechanism; The first back plate and the second back plate both include a metal body, a first protective layer arranged on the surface of the metal body, an injection molding layer arranged on the surface of the first protective layer at least in the first area and the second area, and an anti-corrosion layer arranged between the injection molding layer and the first protective layer.

2. The foldable structural member according to claim 1, characterized in that: The first back plate has a third surface opposite to the first surface, and a fourth surface connecting the first surface and the third surface, wherein the fourth surface includes the anti-corrosion layer and the injection molding layer which are sequentially stacked on the surface of the first protective layer away from the metal body; And / or, the second back plate has a fifth surface opposite to the second surface, and a sixth surface connecting the second surface and the fifth surface, and the sixth surface includes the anti-corrosion layer and the injection molding layer stacked in sequence on the surface of the first protective layer away from the metal body.

3. The foldable structural member according to claim 1 or 2, characterized in that: The first middle frame and the second middle frame further include a first frame fixed to the first back plate and a second frame fixed to the second back plate respectively; The first frame, the first back plate, the second back plate and the second frame constitute a first receiving space; The first frame and the second frame are made by injection molding.

4. The foldable structural member according to claim 3, characterized in that: The first frame is integrally formed with the injection molding layer, and the second frame is integrally formed with the injection molding layer.

5. The foldable structural member according to any one of claims 1 to 4, characterized in that: The thickness of the first protective layer is in the range of 15 μm-40 μm.

6. The foldable structural member according to any one of claims 1 to 5, characterized in that: The first protective layer is a porous structure, the porosity of the first protective layer is ≤15%, and the pore size is ≤20 μm.

7. The foldable structural member according to any one of claims 1 to 6, characterized in that: The first protective layer is a ceramic layer formed by micro-arc oxidation.

8. The foldable structural member according to any one of claims 1 to 7, characterized in that: The thickness of the injection molding layer is in the range of 0.15 mm to 0.35 mm.

9. The foldable structural member according to any one of claims 1 to 8, characterized in that: The injection molding layer is an inorganic material reinforced resin layer.

10. The foldable structural member according to any one of claims 1 to 9, characterized in that: The anti-corrosion layer is a resin layer; the material of the resin layer includes a cured product of epoxy resin, polyester resin and a silane coupling agent; the thickness of the anti-corrosion layer is in the range of 10 μm-40 μm.

11. The foldable structural member according to any one of claims 1 to 9, characterized in that: The anti-corrosion layer includes a first resin layer and a second resin layer stacked together, and the first resin layer is in contact with the first protective layer; wherein the first resin layer includes a resin distributed with a first type of inorganic filler, and the resin includes a material made of epoxy resin, polyester resin and silane coupling agent, and the first type of inorganic filler includes at least one of hydrophobic silica, talcum powder and magnesium powder; the second resin layer includes a cured product of a first type of acrylic resin and isocyanate distributed with a second type of inorganic filler, and the second type of inorganic filler includes at least one of silica, barium sulfate and titanium dioxide.

12. The foldable structure according to claim 11, characterized in that: The thickness of the first resin layer is in the range of 2 μm-10 μm, and the thickness of the second resin layer is in the range of 10 μm-30 μm.

13. The foldable structure according to claim 11, characterized in that: A transition layer is further provided between the first resin layer and the second resin layer, and the transition layer comprises a second type of hydroxy acrylic resin; Wherein, the thickness of the first resin layer is in the range of 2 μm-10 μm; the thickness of the second resin layer is in the range of 2 μm-10 μm; and the thickness of the transition layer is in the range of 10 μm-20 μm.

14. The foldable structural member according to any one of claims 1 to 13, characterized in that: On the first surface, a second protective layer is further provided on at least a portion of the surface of the anti-corrosion layer not covered by the injection layer and adjacent to the injection layer; And / or, on the second surface, a second protective layer is further provided in at least a portion of the area adjacent to the injection molded layer on the surface of the anti-corrosion layer not covered by the injection molded layer.

15. The foldable structure according to claim 14, characterized in that: The second protective layer is connected to the injection molding layer.

16. The foldable structure according to claim 15, characterized in that: The second protective layer also covers the surface of the injection molding layer facing away from the anti-corrosion layer.

17. The foldable structural member according to any one of claims 14 to 16, characterized in that: The second protective layer includes a fluorine-containing resin, or the second protective layer includes a cured product of a third type of hydroxy acrylic resin and isocyanate.

18. The foldable structural member according to any one of claims 14 to 17, characterized in that: The thickness of the second protective layer is in the range of 5 μm-30 μm.

19. The foldable structural member according to any one of claims 1 to 18, characterized in that: The first area and the second area are provided with screw holes, the screw holes are adapted for screws, and the screws are used to fix the rotating mechanism.

20. The foldable structural member according to any one of claims 1 to 19, characterized in that: The material of the metal body is magnesium alloy.

21. The method for preparing a foldable structural member according to any one of claims 1 to 20, characterized in that: include: Providing a metal body, and forming the first protective layer on the surface of the metal body; forming the anti-corrosion layer at least on the surface of the first protective layer in the first region and the second region; The injection molding layer is formed at least on the surface of the anti-corrosion layer in the first region and the second region to prepare a foldable structural member.

22. The method for preparing a foldable structural member according to claim 20, characterized in that: The process of forming a first protective layer on the surface of the metal body comprises: The metal body is immersed in an electrolyte in an electrolytic cell, the metal body is used as an anode, the electrolytic cell is used as a cathode, an electric field is applied, and micro-arc oxidation is performed on the metal body at a current density greater than 2A and less than or equal to 5A; wherein the electrolyte includes a solvent, a salt and a nano-additive; the salt includes at least one of a silicate, a phosphate and an aluminate.

23. A foldable electronic device, characterized in that: It comprises a foldable structural member as described in any one of claims 1-19.

24. The foldable electronic device according to claim 23, characterized in that: It comprises a first display screen and a second display screen; wherein the first display screen is a flexible display screen; The first display screen is arranged on a first surface of the first middle frame and a second surface of the second middle frame; The second display screen is disposed on a surface of the first middle frame facing away from the first display screen, or the second display screen is disposed on a surface of the second middle frame facing away from the first display screen.

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