Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a flexible conductive shielding film and a preparation method thereof.
The flexible conductive shielding film is formed by connecting a heating softening conductive layer or at least one side of the heating softening conductive layer with the conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
Further, the heating softening conductive layer is a thermoplastic matrix or a conductive shielding material formed by hot melt adhesive and conductive particles.
Further, the conductive shielding layer is a high-temperature softened conductive layer and is a conductive layer formed by a thermoplastic matrix or hot melt adhesive and conductive particles, and the softening temperature of the high-temperature softened conductive layer is higher than the softening temperature of the heated softened conductive layer. The thermoplastic matrix or the hot melt adhesive is subjected to a higher temperature to change the structure, and the softening temperature of the thermoplastic matrix or the hot melt adhesive is obviously different from that of the conductive layer softened by heating.
Further, the thermoplastic matrix is thermoplastic acrylic, thermoplastic polyurethane, polyester, polyurethane elastomer, polypropylene, polyethylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene, polymethyl methacrylate, polyoxymethylene, polyamide, polycarbonate or polyphenylene oxide. The thermoplastic matrix is softened after being heated, is easy to pull and keeps the structure unchanged after being restored to room temperature.
Further, the hot melt adhesive is a polyolefin hot melt adhesive, a polyester hot melt adhesive, a polyamide hot melt adhesive, a polyurethane hot melt adhesive, a styrene and block copolymer hot melt adhesive or a novel hot melt adhesive.
The said hot melt adhesive is one kind of plastic adhesive with its physical state changed with temperature, chemical characteristic unchanged, no toxicity and smell, and polyolefin hot melt adhesive, such as polyethylene hot melt adhesive, polypropylene hot melt adhesive, ethylene and its copolymer hot melt adhesive, such as ethylene-vinyl acetate copolymer (EVA) hot melt adhesive, etc.
Further, the conductive shielding layer is a thermosetting conductive layer and is a conductive shielding material formed by a bi-component resin and conductive particles. The two-component resin (comprising resin and curing agent) forms a firm three-dimensional network structure to bond the conductive particles together, and the structure is not destroyed and softened after heating.
The thermosetting matrix comprises epoxy resin, acrylic acid, polyurethane, unsaturated polyester, phenolic resin organic silicon resin, organic silicon rubber and the like.
Further, the conductive particles include gold powder, silver-coated copper powder, nickel powder, copper powder, carbon black, graphene, carbon nanotubes, or conductive fibers.
Further, the conductive shielding layer is a conductive cloth, a metal foil and a metal plating conductive film.
A method for preparing flexible conductive shielding film includes preparing heat softening conductive material and conductive shielding material separately, overlapping at least one side of heat softening material with conductive shielding material, heating and pressing to form flexible conductive shielding film.
Further, the heating temperature is 60-200 ℃.
When the flexible conductive shielding film is used, the flexible conductive shielding film is placed at the temperature of 60-200 ℃ to be baked, the conductive layer is softened by heating and softening, but the conductive shielding layer is not softened, the flexible conductive shielding film is immediately attached to a flexible circuit board, the region of the conductive layer is attached to a folding position by heating and softening, the conductive shielding layer is attached to a non-folding position, and the conventional structure is maintained after cooling.
The invention has the advantages that the flexible conductive shielding film is a composite film with a folding part capable of being heated and softened, is attached to the folding part of an electronic product after being softened, does not have tensile stress on a leg line, keeps the softened state unchanged after being restored to room temperature, and the like, and meanwhile, other non-heating softened parts of the composite film can have higher conductive shielding performance. The flexible shielding film is simple in preparation process, convenient to prepare, capable of being heated and pressed, and suitable for industrial mass production.
Detailed Description
The invention will be further described with reference to examples, but the scope of the invention is not limited to the following:
Example 1
The flexible conductive shielding film is formed by connecting a heating softening conductive layer and a conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
The heating softening conductive layer is a conductive shielding material formed by hot melt adhesive and conductive particle graphene, and the hot melt adhesive is polyethylene hot melt adhesive.
The conductive shielding layer is a high-temperature softening conductive layer and is formed by thermoplastic matrix acrylonitrile-butadiene-styrene and conductive fibers.
A preparation method of a flexible conductive shielding film comprises the steps of respectively preparing a heating softening conductive material and a conductive shielding material, overlapping one side of the heating softening material with one quarter of the area of the conductive shielding material, and heating and pressing to form the flexible conductive shielding film, wherein the heating temperature is 120-160 ℃.
Example 2:
A flexible conductive shielding film that is a heat softened conductive layer.
The heating softening conductive layer is a conductive shielding material formed by a thermoplastic matrix and conductive particles.
The thermoplastic matrix is thermoplastic acrylic acid, and the conductive particles are gold powder.
A method for preparing flexible conductive shielding film includes such steps as heating to soften conductive material, heating thermoplastic matrix, adding gold powder, and coating it to become film.
Example 3:
a flexible conductive shielding film is formed by connecting a heating softening conductive layer and a conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
The heating softening conductive layer is a conductive shielding material formed by hot melt adhesive vinyl acetate and conductive particle silver coated copper powder;
the conductive shielding layer is a high-temperature softened conductive layer and is a conductive layer formed by hot melt adhesive SBS and conductive particle carbon black, and the softening temperature of the high-temperature softened conductive layer is higher than that of the heated softened conductive layer.
The conductive shielding layer is a conductive cloth, a metal foil and a metal plating conductive film.
A preparation method of a flexible conductive shielding film comprises the steps of respectively preparing a heating softening conductive material and a conductive shielding material, coating the heating softening conductive material and the conductive shielding material into a film, overlapping one side of the heating softening material with one half of the area of the conductive shielding material, and heating and pressing to form the flexible conductive shielding film, wherein the heating temperature is 80-140 ℃.
Example 4
The flexible conductive shielding film is formed by connecting the left side and the right side of a heating softening conductive layer with a conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
The heating softening conductive layer is a conductive shielding material formed by hot melt adhesive polyester hot melt adhesive and conductive particle carbon nano tubes.
The conductive shielding layer comprises a high-temperature softened conductive layer, and is a conductive layer formed by hot melt adhesive styrene and conductive particle graphene, and the hot melt adhesive is subjected to higher temperature to change the structure, so that the softening temperature of the conductive layer is obviously different from the softening temperature of the conductive layer.
A preparation method of a flexible conductive shielding film comprises the steps of respectively preparing a heating softening conductive material and a conductive shielding material, respectively coating the heating softening conductive material and the conductive shielding material into films to form 3 layers of films, respectively overlapping the left side and the right side of the heating softening material with one third of the area of the 2 layers of conductive shielding material films, and heating and pressing the films to form the flexible conductive shielding film, wherein the heating temperature is 80-170 ℃.
Example 5:
The flexible conductive shielding film is formed by connecting the left side and the right side of a heating softening conductive layer with a conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
The heating softening conductive layer is a conductive shielding material formed by thermoplastic matrix polymethyl methacrylate and conductive particle gold powder.
The conductive shielding layer is a thermosetting conductive layer and is a conductive shielding material formed by bi-component resin and conductive particle nickel powder. The two-component resin (comprising resin and curing agent) forms a firm three-dimensional network structure to bond the conductive particles together, and the structure is not destroyed and softened after heating.
A preparation method of a flexible conductive shielding film comprises the steps of respectively preparing a heating softening conductive material and a conductive shielding material, respectively coating the heating softening conductive material and the conductive shielding material into films to form 3 layers of films, respectively overlapping the left side and the right side of the heating softening material with one quarter of the area of the 2 layers of conductive shielding material films, and heating and pressing the films to form the flexible conductive shielding film, wherein the heating temperature is 100-160 ℃.
Example 6:
The flexible conductive shielding film is formed by connecting the left side and the right side of a heating softening conductive layer with a conductive shielding layer, and the heating softening conductive layer is connected with the conductive shielding layer in an overlapping manner.
The heating softening conductive layer is a conductive shielding material formed by thermoplastic matrix polyurethane and conductive particle silver powder.
The conductive shielding layer is a metal-plated conductive film.
A preparation method of a flexible conductive shielding film comprises the steps of preparing a heating softening conductive material, coating the heating softening conductive material into a film, overlapping the left side and the right side of the heating softening material with one quarter of the area of a metal-plated conductive film respectively, and heating and pressing the heating softening conductive material to form the flexible conductive shielding film, wherein the heating temperature is 60-120 ℃.
Experimental example 1
A flexible conductive shielding film is provided with only one layer, as shown in figure 1, namely silver powder is added into acrylic hot melt adhesive according to the proportion of 2:1, 20% of butyl acetate solvent and 0.1% of organosilicon wetting leveling agent are added to form a filled conductive composite material, the conductive film is scraped and coated, the thickness of the conductive film is 40 mu m after drying, the sheet resistance is 100mΩ/≡c, the conductive film is baked at the high temperature of 120 ℃ after solidification, the conductive film is immediately attached to a flexible circuit board after softening, and still is firmly attached to the flexible circuit board after the conductive film returns to room temperature, and at the moment, the sheet resistance of the conductive film is consistent with that before softening treatment.
Experimental example 2
A flexible conductive shielding film is provided with two layers, as shown in figure 2, wherein after TPU is melted at high temperature, silver-coated copper powder is added into melted hot melt adhesive according to a certain proportion of 1:1 to form a conductive material 1, the conductive material 1 is coated into a film with the thickness of 50 mu m, the cured sheet resistance is 355 m omega/-18, one third of the width of the right side of the conductive material is built on a second copper foil (conductive material 2), the materials are connected together through hot pressing by a flat vulcanizing machine at the softening temperature of 100 ℃ and the pressure of 10Mpa of the hot melt adhesive, at the moment, the materials of the flexible conductive shielding film (namely the composite conductive film) from left to right are respectively conductive material 1, the joint of the conductive materials 1 and 2 and conductive material 2, the conductive performance of the composite material is measured at normal temperature, the thickness of the conductive film in a region 1 is reduced to 20 mu m, the sheet resistance is 115 m omega/-18, the conductive performance is improved by about 3 times, and the sheet resistance of the copper foil is unchanged. And (3) placing the composite conductive film on a heating plate and baking at a high temperature of 160 ℃, wherein the region of the conductive material 1 is softened (the state that the conductive material is drawn when the conductive material is slightly forced), the region of the conductive material 2 is not softened, bonding the region of the conductive material 1 on one surface and the folded position of the flexible circuit board, bonding the other surface of the flexible circuit board by the bonding positions of the conductive materials 1 and 2 and the copper foil, and keeping the sheet resistance of the conductive film of the region 1 which is recovered to the room temperature after the bonding is softened to be 115 m Ω/≡unchanged.
Experimental example 3
A flexible conductive shielding film is provided with three layers, as shown in figure 3, wherein graphite is added into thermoplastic polyurethane according to a ratio of 4:1, 25% of butyl acetate solvent, 0.1% of organosilicon wetting leveling agent and 1% of organosilicon defoaming agent are added to form conductive materials 1 and 3, the conductive materials are coated into films with certain thickness, the films are baked at 80 ℃, and the sheet resistance of the conductive materials 1 and 3 is 2.5 omega/≡after the conductive materials are restored to room temperature. And a second layer, namely adding graphite into thermoplastic polyurethane with lower softening temperature according to a certain ratio of 4:1, adding 0.1% of organosilicon wetting leveling agent and 1% of organosilicon defoaming agent to form a conductive material 2, coating the conductive material 2 into a film with a certain thickness, baking at a temperature of 40 ℃, and recovering the conductive material 2 to the room temperature to obtain a sheet resistance of 5.5 omega/≡. Arranging the conductive materials in the order of 1,2 and 3, spreading the conductive material 2 to the quarter of the conductive material 1, spreading the conductive material 3 to the quarter of the conductive material 2, compacting the three conductive materials by using a calender, and mutually adhering to form the multi-layer combined composite conductive film. And (3) baking the composite conductive film at the temperature of 100 ℃, wherein the area of the conductive material 2, namely the middle area, is softened, but the area 1 and the area 3 are not softened, the composite material is immediately attached to the flexible circuit board, the area of the conductive material 2 is attached to the folding part, the area of the conductive material 1 is attached to one side, the area of the conductive material 3 is attached to the other side, and the composite conductive film maintains the existing structure after being cooled.
Experimental example 4
A flexible conductive shielding film is provided with three layers, as shown in figure 3, wherein a sheet-shaped silver-coated copper powder is added into TPU with 20% of solid content in a ratio of 1:1, after 0.05% of organosilicon wetting leveling agent and 1% of organosilicon defoamer are added, a conductive material 2 is formed, the conductive material 2 is coated into a film with a thickness of 40 mu m, the film is baked at a temperature of 60 ℃, and the sheet resistance of the conductive material 2 is 710mΩ/≡after the conductive material is restored to room temperature. And the conductive materials 1 and 3 are conductive cloths commonly used in mobile phones. Arranging conductive materials on a release film according to the sequence of 1,2 and 3, wherein the conductive film 2 is an intermediate layer, the conductive material 2 is flatly paved to one quarter of the positions of the conductive materials 1 and 3, covering the upper part of the conductive material by the release film, placing the conductive material on a heating plate, heating at 160 ℃, lightly pressing the connecting position by hands after wearing a heat-proof glove, forming a multi-layer combined composite conductive film, cooling the composite conductive film in room temperature, keeping the adhesion structure unchanged, and keeping the sheet resistance of the intermediate layer, namely the conductive material 2, to be 710mΩ/, and keeping the thickness unchanged. When the composite conductive film is used, the composite conductive film is placed at 160 ℃ for baking, the area of the conductive material 2, namely the middle layer, is softened, but the areas 1 and 3 are not softened, the composite material is immediately attached to the flexible circuit board, the area of the conductive material 2 is attached to the folding part, the area of the conductive material 1 is attached to one side of the flexible circuit board, the area of the conductive material 3 is attached to the other side of the flexible circuit board, and the existing structure of the composite conductive film is maintained after the composite conductive film is cooled.
The flexible conductive shielding film provided by the invention can be designed into multiple layers, such as 5 layers, according to the product requirement, and the conductive shielding layer 1, the heating softening layer 1, the conductive shielding layer 2, the heating softening layer 2 and the conductive shielding layer 3 are sequentially arranged from left to right. The conductive shielding layer is arranged at the folding position of the product, and the conductive shielding layer is arranged at the non-folding position.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art who is skilled in the art to which the present invention pertains will appreciate that the technical scheme and the inventive concept according to the present invention are equally substituted or changed within the scope of the present invention.