Electromagnetic shielding film and its preparation method and application

Abstract

The present invention relates to an electromagnetic shielding film and a preparation method and application thereof, belonging to the field of electromagnetic shielding technology. The electromagnetic shielding film comprises a heat-adhesive elastomer film and a metal conductive layer, a surface of the heat-adhesive elastomer film is provided with grooves, and the metal conductive layer is filled in the grooves. The present invention uses the heat-adhesive elastomer film as the substrate of the electromagnetic shielding film, so that the metal conductive layer can be directly arranged in the groove of the heat-adhesive elastomer film without the need for bonding with an adhesive, which not only avoids the introduction of an insulating adhesive layer to affect the electromagnetic shielding effect of the electromagnetic shielding film, but also enables the electromagnetic shielding film to have good ductility, heat adhesion and visible light transparency at the same time, and is suitable for preparing various products with electromagnetic shielding functions.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic shielding technology, and in particular to an electromagnetic shielding film and a preparation method and application thereof. Background Art

[0002] As integrated circuits develop towards high density, high frequency, high power, and thinness, the electromagnetic interference of electronic devices is becoming more and more serious. Electromagnetic shielding materials are one of the important means to solve the electromagnetic interference problem and meet electromagnetic compatibility design. Electromagnetic shielding film is an important type of electromagnetic shielding material with the characteristics of being thin, light, and soft.

[0003] At present, the commonly used electromagnetic shielding film materials in the market include copper foil, aluminum foil, metal sputtering PI / PET film, ITO sputtering PET film, metal mesh film (Metal Mesh), etc. These materials have high electromagnetic shielding efficiency and have certain flexibility (bendable or foldable), but they are not ductile (stretchable) and do not have adhesiveness. In actual use, mechanical anchoring or adhesive backing (a technology of applying adhesive glue on the surface) is required to make the shielding film fit and fix to the substrate, and to ground or build a "Faraday cage" to achieve electromagnetic shielding function. The use of mechanical anchoring to fit the electromagnetic shielding film is suitable for application scenarios with larger space sizes. For fine devices and small spaces such as fine printed circuits (FPC) or high-density integrated circuits (PCB), mechanical anchoring conditions are often not available, so adhesive backing is often used to make shielding films such as metal copper foil have the ability to attach. Even so, since the glue itself does not have good conductivity, an insulating glue layer is added between the shielding film and the attached substrate, which reduces the actual shielding effect of the shielding film. In addition, the shielding film with adhesive on the back still has no ductility and is not suitable for use in complex and irregular structure electronic devices and flexible and stretchable electronic devices.

[0004] Filling conductive fillers into a specific polymer matrix to prepare a conductive polymer composite film can simultaneously achieve electromagnetic shielding and bonding functions. For example: The patent published by Tozda Wire Co., Ltd. with the publication number CN 113853839 B uses an electromagnetic shielding film containing conductive particles and a conductive adhesive layer of a bonding resin composition, which can be used for electromagnetic shielding of FPC by hot pressing at 150°C, 2MPa, and 30min. Under normal circumstances, the filling amount of the conductive filler needs to reach above its percolation threshold to have conductive and electromagnetic shielding properties, and the higher the filling amount, the better the electromagnetic shielding effect of the shielding film, but the adhesion is weakened. High filling amount will undoubtedly bring high cost and high weight. In addition, it is difficult for the filled electromagnetic shielding film to obtain the characteristic of being transparent to visible light, which limits its use in certain specific occasions. The preparation of electromagnetic shielding film materials that have ductility, thermal adhesion and light transmittance at the same time is still a challenge. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an electromagnetic shielding film and a preparation method and application thereof. The electromagnetic shielding film provided by the present invention uses a thermal adhesive elastomer film as the substrate of the electromagnetic shielding film, so that the metal conductive layer can be directly arranged in the groove of the thermal adhesive elastomer film without the need for bonding with an adhesive. This not only avoids the introduction of an insulating adhesive layer to affect the electromagnetic shielding effect of the electromagnetic shielding film, but also enables the electromagnetic shielding film to have good ductility, thermal adhesion and visible light transparency, and is suitable for preparing various products with electromagnetic shielding functions.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present invention provides an electromagnetic shielding film, comprising a thermal adhesive elastic film and a metal conductive layer, wherein grooves are distributed on a surface of the thermal adhesive elastic film, and the metal conductive layer is filled in the grooves.

[0008] The present invention uses a heat-adhesive elastomer film as the substrate of the electromagnetic shielding film, so that the metal conductive layer can be directly set in the groove of the heat-adhesive elastomer film without bonding with an adhesive. This not only avoids the introduction of an insulating adhesive layer to affect the electromagnetic shielding effect of the electromagnetic shielding film, but also enables the electromagnetic shielding film to have good ductility and heat adhesion.

[0009] The present invention optimizes the material of the heat-adhesive elastic film, the size and shape of the groove, and the size of the metal conductive layer, so that the electromagnetic shielding film has good visible light transparency while having ductility and heat-adhesiveness.

[0010] As a preferred embodiment of the present invention, the heat-adhesive elastic film includes any one of a thermoplastic elastomer film and a modified thermoplastic elastomer film.

[0011] Furthermore, the thermoplastic elastomer film is any one of a thermoplastic polyurethane elastomer film, a styrene-based thermoplastic elastomer film, a thermoplastic polyolefin-based elastomer film, a thermoplastic polyester-based elastomer film, a thermoplastic polyamide-based elastomer film, a thermoplastic ethylene-vinyl acetate copolymer (EVA) film, and a thermoplastic silicone-based elastomer film. The above-mentioned thermoplastic elastomer film has good ductility and thermal adhesion.

[0012] In the present invention, the styrene-based thermoplastic elastomer film includes any one of SBS film, SIS film, SEBS film, and SEPS film, the thermoplastic polyolefin elastomer film includes any one of TPO film and TPV film, the thermoplastic polyester elastomer film is TPEE film, and the thermoplastic polyamide elastomer film is TPAE film.

[0013] Furthermore, the modified thermoplastic elastomer film includes any one of epoxy modified thermoplastic elastomer film and vulcanized thermoplastic elastomer film, such as TPSiV film and EPU film. The modified thermoplastic elastomer film has better ductility and thermal adhesion.

[0014] As a preferred embodiment of the present invention, the groove on the thermal adhesive elastic film is processed by any one of the following methods (A) to (C):

[0015] (A) Dissolving thermally adhesive elastomer particles in a solvent to obtain a polymer solution; applying the obtained polymer solution to the convex surface of a template, drying to form a film, and then peeling off the template.

[0016] (B) hot pressing a heat-adhesive elastic film onto the convex surface of the template, and peeling off the template after cooling;

[0017] (C) Grooves are formed on the surface of the thermo-adhesive elastic film by mechanical processing, wherein the mechanical processing method is any one of laser etching, soft lithography, and electron beam lithography.

[0018] As a preferred embodiment of the present invention, the heat-adhesive elastomer film is an epoxy-modified thermoplastic elastomer film, and the epoxy-modified thermoplastic elastomer film includes the following raw material components in parts by weight: 100 parts of epoxidized thermoplastic elastomer, 20-50 parts of epoxy resin, 10-20 parts of curing agent, 1-5 parts of auxiliary agent and 300-500 parts of solvent.

[0019] Furthermore, the epoxy-modified thermoplastic elastomer film comprises the following raw material components by weight: 100 parts of epoxidized thermoplastic elastomer, 30-40 parts of epoxy resin, 12-15 parts of curing agent, 1-5 parts of auxiliary agent and 300-500 parts of solvent.

[0020] In actual application, the epoxy-modified thermoplastic elastomer film is coated on the surface of the substrate by hot pressing. The curing agent, epoxidized thermoplastic elastomer and epoxy resin contained in the epoxy-modified thermoplastic elastomer film undergo a chemical cross-linking reaction under hot pressing, and the interface is firmly bonded. At the same time, the metal conductive layer of the shielding film can be grounded to achieve electrical connectivity, forming a "Faraday cage" and playing an electromagnetic shielding role.

[0021] Further, at least one of the following (I) to (IV):

[0022] (I) the epoxy resin comprises at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin and aliphatic epoxy resin;

[0023] (II) the curing agent includes at least one of an anhydride curing agent, an amine curing agent, an imidazole curing agent, a polyamide curing agent, and a cationic curing agent;

[0024] (III) The auxiliary agent includes at least one of a defoaming agent, a leveling agent, a thixotropic agent, a accelerator, and an antioxidant;

[0025] (IV) The solvent includes at least one of cyclohexanone, acetone, butanone, ethylene glycol methyl ether, propylene glycol methyl ether, toluene, xylene, and N,N-dimethylformamide.

[0026] In the present invention, further, the epoxy resin is preferably bisphenol A epoxy resin Epikote 828. Further, the epoxy resin is composed of at least one of bisphenol A epoxy resin E-44 and bisphenol F epoxy resin jER 807 and bisphenol A epoxy resin Epikote 828; the ratio of the bisphenol A epoxy resin Epikote 828 to the total weight of the epoxy resin is (1-3):3; the curing agent is preferably a polyamide curing agent. When this condition is met, the present invention can improve the elongation and interfacial adhesion of the elastomeric film while ensuring the light transmittance and electromagnetic shielding effect of the electromagnetic shielding film, that is, improve the ductility and adhesion of the elastomeric film.

[0027] Furthermore, the preparation method of the epoxidized thermoplastic elastomer comprises the following steps: dissolving thermoplastic elastomer powder in an organic solvent, adding formic acid and hydrogen peroxide solution, reacting at 40-80° C. for 1-8 hours, condensing with ethanol, washing and drying to obtain an epoxidized thermoplastic elastomer; the thermoplastic elastomer comprises at least one of SBS, TPU, TPO, and SIS; the weight ratio of the formic acid to the thermoplastic elastomer powder is 1:(2-6), the weight ratio of the hydrogen peroxide solution to the thermoplastic elastomer powder is 1:(1.25-3.75), the organic solvent is cyclohexane or toluene, the weight ratio of the thermoplastic elastomer powder to the organic solvent is (1-3):10, and the volume concentration of hydrogen peroxide in the hydrogen peroxide solution is 30%.

[0028] The invention utilizes formic acid and hydrogen peroxide to modify the thermoplastic elastomer, so that epoxy functional groups are grafted onto the chemical structure of the thermoplastic elastomer, and the grafting amount of the epoxy functional groups can be adjusted by controlling the reaction conditions.

[0029] Furthermore, the preparation method of the epoxy-modified thermoplastic elastomer film comprises the following steps:

[0030] After dissolving the epoxidized thermoplastic elastomer in a solvent, epoxy resin, curing agent and auxiliary agent are added and mixed to obtain a polymer solution; the obtained polymer solution is coated on the convex surface of the template, and after drying to form a film, the template is peeled off to obtain an epoxy-modified thermoplastic elastomer film.

[0031] In the present invention, the coating method includes any one of coating, pouring, spin coating, scraping, spraying and drip coating.

[0032] In the present invention, the material of the template is any one of silicon, metal, and ceramic; protrusions corresponding to the grooves are distributed on the template, and the protrusions are formed on one surface of the template by any one of laser etching, soft lithography, screen printing, electron beam lithography, and filament weaving.

[0033] As a preferred embodiment of the present invention, the grooves are distributed in a continuous network; each groove has a width of 5 to 1000 μm and a depth of 5 to 250 μm, and the total opening area of ​​the grooves is 10 to 90% (more preferably 50 to 70%) of the corresponding surface area of ​​the thermal adhesive elastomer film.

[0034] It can be understood that the cross-sectional shape of the groove is a regular shape or an irregular shape, and the regular shape includes but is not limited to at least one of a square, a rhombus, a regular hexagon, a circle, and a ring.

[0035] As a preferred embodiment of the present invention, the thickness of the metal conductive layer is 0.2-50 μm, and the thickness of the metal conductive layer is not greater than the depth of the groove structure; the material of the metal conductive layer is at least one of silver and copper.

[0036] In a second aspect, the present invention provides a method for preparing the electromagnetic shielding film as described in the first aspect, comprising the following steps:

[0037] (1) performing surface modification treatment on the groove surface of the polymer film substrate;

[0038] (2) Injecting the metal complex solution into the groove after the surface modification treatment, and then heating the groove to obtain an electromagnetic shielding film.

[0039] The present invention uses grooves to hold liquid. Under heating conditions, metal ion complexes in the solution are reduced in situ to generate metal particles, thereby achieving gridding of the conductive layer on the surface of the film. The prepared electromagnetic shielding film not only has electrical connection and electromagnetic shielding functions, but also has strong interface bonding function.

[0040] As a preferred embodiment of the present invention, the surface modification method in step (1) includes any one of the following methods:

[0041] (a) Plasma surface treatment;

[0042] (b) coating with a surface modifier, wherein the surface modifier comprises at least one of perfluorosilane, perfluoropolyether, perfluoropolyether alcohol, perfluoropolyester, and anti-fingerprint liquid, and the coating method is any one of dip coating, spray coating, spin coating, and scraping coating.

[0043] As a preferred embodiment of the present invention, the metal complex solution in step (2) includes at least one of an aqueous silver metal organic decomposition solution, an organic solvent type silver metal organic decomposition solution, an aqueous copper metal organic decomposition solution, and an organic solvent type copper metal organic decomposition solution.

[0044] As a preferred embodiment of the present invention, in step (2), the metal complex solution is injected into the groove after surface modification treatment in N times, N≥1, N is an integer, and heating treatment is performed after each injection; the injection method is any one of syringe injection, dropper injection, and peristaltic pump injection.

[0045] As a preferred embodiment of the present invention, in step (2), the heating treatment is carried out in an inert atmosphere, the temperature is increased to 100-300°C at a rate of 1-20°C / min, kept at this temperature for 10-120 min, and then cooled to room temperature.

[0046] In a third aspect, the present invention provides a use of the electromagnetic shielding film as described in the first aspect in the preparation of an electromagnetic shielding product.

[0047] As a preferred embodiment of the present invention, the application comprises the following steps: hot pressing the electromagnetic shielding film onto the surface of a substrate to obtain an electromagnetic shielding product.

[0048] Furthermore, the substrate includes any one of a glass substrate, a stainless steel substrate, a copper substrate, a gold substrate, a PI film, a PCB board, a flexible circuit board (FPC), a system-in-package module (SiP), and a board-level printed circuit board assembly (PCBA).

[0049] The electromagnetic shielding film of the present invention has an adhesive force of not less than 3.0 N / cm on the surface of the substrate, an electromagnetic shielding efficiency of 20 to 80 dB, and is firmly bonded, and can achieve grounding and electromagnetic shielding functions.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The present invention uses a heat-adhesive elastomer film as the substrate of the electromagnetic shielding film, so that the metal conductive layer can be directly arranged in the groove of the heat-adhesive elastomer film without bonding through an adhesive. This not only avoids the introduction of an insulating adhesive layer to affect the electromagnetic shielding effect of the electromagnetic shielding film, but also enables the electromagnetic shielding film to have good ductility, heat adhesion, electromagnetic shielding efficiency and visible light transparency. While ensuring that the elongation of the substrate is not less than 500%, the adhesion of the substrate is not less than 3.0 N / cm, the transmittance is not less than 30%, and the electromagnetic shielding efficiency is 20 to 80 dB. It can not only be firmly bonded to the surface of the substrate, but also can achieve grounding and electromagnetic shielding functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A flow chart of the preparation of an electromagnetic shielding film provided by an embodiment of the present invention;

[0053] Figure 2 A schematic diagram of the structure of the test piece provided by the present invention;

[0054] Figure 3 for Figure 2 A magnified schematic diagram of part A;

[0055] Figure 4 A schematic diagram of the distribution of the grooves provided by the present invention on the electromagnetic shielding film;

[0056] Figure 5 Another schematic diagram of the distribution of grooves on the electromagnetic shielding film provided by the present invention. DETAILED DESCRIPTION

[0057] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0058] The sources of raw materials in the following examples and comparative examples are as follows:

[0059] Epoxidized thermoplastic elastomer 1: epoxidized SBS, the preparation method of which is as follows: dissolving SBS in cyclohexane, adding formic acid and hydrogen peroxide solution, reacting at 60°C for 4 hours, condensing with ethanol, washing, and drying to obtain epoxidized SBS, the weight ratio of formic acid to SBS is 1:4, the weight ratio of hydrogen peroxide solution to SBS is 1:2, the volume concentration of hydrogen peroxide in the hydrogen peroxide solution is 30%, the manufacturer of SBS is Baling Petrochemical, and the model is 1401;

[0060] Epoxidized thermoplastic elastomer 2: Japan Daicel, model: EPOFRIEND AT501;

[0061] Epoxidized thermoplastic elastomer 3: Epoxidized SIS, the preparation method of which is as follows: dissolving SIS in toluene organic solvent, adding formic acid and hydrogen peroxide solution, reacting at 50°C for 4 hours, condensing with ethanol, washing, and drying to obtain epoxidized SIS. The weight ratio of formic acid to SIS is 1:4, the weight ratio of hydrogen peroxide solution to SIS is 1:2, the volume concentration of hydrogen peroxide in the hydrogen peroxide solution is 30%, and the manufacturer of SIS is Kraton, USA, and the model is D1114P;

[0062] Epoxy resin 1: bisphenol A epoxy resin, manufactured by Hanson, USA, model number Epikote 828;

[0063] Epoxy resin 2: bisphenol A epoxy resin, manufactured by Baling Petrochemical, model E-44;

[0064] Epoxy resin 3: bisphenol F epoxy resin, manufactured by Mitsubishi Chemical of Japan, model number jER 807;

[0065] Curing agent 1: polyamide curing agent, manufactured by Gabriel, USA, model Versamid 140;

[0066] Curing agent 2: anhydride curing agent, the manufacturer is Shanghai Guoyao, the model is methyl hexahydrophthalic anhydride;

[0067] Curing agent 3: Imidazole curing agent, manufactured by Japan Shikoku Chemical, model 2MZ-A;

[0068] Leveling agent: manufacturer is Evonik, model is TEGO GLIDE 432;

[0069] Defoaming agent: manufacturer is BYK, model is BYK-A530;

[0070] Thixotropic agent: manufacturer is Evonik, model is AEROSIL R 8200;

[0071] Antioxidant: manufacturer is MERCK, model is 2,6-di-tert-butyl-4-methylphenol;

[0072] Silver MOD solution: prepared by the following method:

[0073] (1) 20 g of oxalic acid and 200 mL of deionized water were mixed, and magnetic stirring was performed at a speed of 400 r / min for 1 min to fully dissolve the oxalic acid, and then 10 g of silver nitrate was added and the stirring was continued. During the stirring process, a large amount of white precipitate was generated. After the precipitate was fully reacted, it was filtered using a suction filtration bottle, and the filtrate was placed in a vacuum drying oven and dried at 27° C. for 24 h to obtain white silver oxalate particles, which were stored away from light;

[0074] (2) 2.175 mL of ethylenediamine was mixed with 2 mL of deionized water, and magnetic stirring was performed at a speed of 200 r / min for 5 min. The prepared silver oxalate particles were slowly added, and stirring was continued. After sufficient reaction, a yellow-black solution was formed, and 30 mL of isopropanol was added as a precipitant. After filtering, the silver oxalate-ethylenediamine complex was obtained, and stored in a refrigerator at 3° C. away from light;

[0075] (3) 3 g of silver oxalate-ethylenediamine complex was added to 4.5 mL of deionized water and stirred thoroughly. Then, 1.2 mL of isopropanol was added as an auxiliary reducing agent. Finally, the mixture was filtered using a syringe filter to obtain a silver MOD solution.

[0076] Examples 1 to 22

[0077] An electromagnetic shielding film comprises a heat-adhesive elastomer film and a metal conductive layer. One surface of the heat-adhesive elastomer film has grooves uniformly distributed in a mesh shape. The metal conductive layer is filled in the grooves. The cross-section of the grooves is square. The width of the grooves is 200 μm and the depth is 300 μm. The total opening area of ​​the grooves is 70% of the corresponding surface area of ​​the heat-adhesive elastomer film. The heat-adhesive elastomer film is an epoxy-modified thermoplastic elastomer film.

[0078] The preparation method of the electromagnetic shielding film has the following process: Figure 1 As shown, the following steps are included:

[0079] (1) using laser etching to make a protrusion matching the groove on a polytetrafluoroethylene plate;

[0080] (2) weighing the raw materials of the epoxy-modified thermoplastic elastomer film according to Table 1, dissolving the epoxidized thermoplastic elastomer in a solvent, adding epoxy resin, curing agent, leveling agent, defoaming agent, thixotropic agent and antioxidant, and mixing to obtain a polymer solution; pouring the polymer solution onto the convex surface of the template obtained in step (1), drying at 80° C. to remove the solvent, and then cooling to room temperature, peeling off the mold, and obtaining an epoxy-modified thermoplastic elastomer film with a thickness of 1000 μm;

[0081] (3) using a plasma cleaning machine to perform plasma surface treatment on the film obtained in step (2) for 10 minutes to enhance its surface hydrophilicity;

[0082] (4) using a syringe to fill the silver MOD solution into the film groove treated in step (3), and then heating the film to 150° C. at a rate of 10° C. / min under nitrogen protection, and heat-treating the film for 30 min.

[0083] The above step (4) is repeated twice to obtain an electromagnetic shielding film.

[0084] Table 1 Formula of epoxy modified thermoplastic elastomer film (unit: weight parts)

[0085]

[0086]

[0087] Comparative Example 1

[0088] This comparative example provides an electromagnetic shielding film and a preparation method thereof. The difference between this comparative example and Example 2 is that the weight proportion of epoxy resin 1 in the formula of the epoxy-modified thermoplastic elastomer film of this comparative example is 15 parts.

[0089] Comparative Example 2

[0090] This comparative example provides an electromagnetic shielding film and a preparation method thereof. The difference between this comparative example and Example 2 is that the weight proportion of epoxy resin 1 in the formula of the epoxy-modified thermoplastic elastomer film of this comparative example is 60 parts.

[0091] Comparative Example 3

[0092] This comparative example provides an electromagnetic shielding film and a preparation method thereof. The difference between this comparative example and Example 2 is that this comparative example does not use the epoxidized thermoplastic elastomer 1, but uses an equal amount of SBS instead.

[0093] Comparative Example 4

[0094] This comparative example provides an electromagnetic shielding film and a preparation method thereof. The difference between this comparative example and Example 10 is that this comparative example does not use the epoxidized thermoplastic elastomer 2, but uses an equal amount of TPU instead.

[0095] Embodiment 23

[0096] The present embodiment provides an electromagnetic shielding film and a method for preparing the same. The difference between the present embodiment and embodiment 2 is that, in the present embodiment, the width of the groove is 5 μm and the depth is 5 μm, and the total opening area of ​​the groove is 90% of the corresponding surface area of ​​the thermal adhesive elastomer film; step (4) is carried out under nitrogen protection, heating to 100°C at a rate of 1°C / min, and heat treatment is performed for 10 minutes. Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0097] Embodiment 24

[0098] The present embodiment provides an electromagnetic shielding film and a method for preparing the same. The difference between the present embodiment and embodiment 2 is that, in the present embodiment, the width of the groove is 100 μm, the depth is 100 μm, and the total opening area of ​​the groove is 50% of the corresponding surface area of ​​the thermal adhesive elastomer film; step (4) is carried out under nitrogen protection, heating to 150°C at a rate of 5°C / min, and heat treatment is carried out for 20 minutes. Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0099] Embodiment 25

[0100] The present embodiment provides an electromagnetic shielding film and a method for preparing the same. The difference between the present embodiment and embodiment 2 is that, in the present embodiment, the width of the groove is 500 μm and the depth is 200 μm, and the total opening area of ​​the groove is 30% of the corresponding surface area of ​​the thermal adhesive elastomer film; step (4) is carried out under nitrogen protection, heating to 150°C at a rate of 10°C / min, and heat treatment is carried out for 60 minutes. Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0101] Embodiment 26

[0102] The present embodiment provides an electromagnetic shielding film and a method for preparing the same. The difference between the present embodiment and embodiment 2 is that, in the present embodiment, the width of the groove is 1000 μm and the depth is 250 μm, and the total opening area of ​​the groove is 10% of the corresponding surface area of ​​the thermal adhesive elastomer film; step (4) is carried out under nitrogen protection, heating to 300°C at a rate of 20°C / min, and heat treatment is performed for 120 minutes. Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0103] Comparative Example 5

[0104] This comparative example provides an electromagnetic shielding film and a preparation method thereof. The difference between this comparative example and Example 2 is that in step (3) of this comparative example, perfluorosilane is sprayed on the side of the film obtained in step (2) where the groove is provided, and step (4) is repeated twice to obtain an electromagnetic shielding film.

[0105] Embodiment 27

[0106] The present embodiment provides an electromagnetic shielding film, including a thermal adhesive elastomer film and a metal conductive layer, wherein one surface of the thermal adhesive elastomer film has grooves uniformly distributed in a mesh shape, the metal conductive layer is filled in the grooves, the cross-section of the grooves is square, the width of the grooves is 200 μm, the depth is 200 μm, and the total opening area of ​​the grooves is 70% of the corresponding surface area of ​​the thermal adhesive elastomer film; the thermal adhesive elastomer film is a thermoplastic polyurethane elastomer film.

[0107] The preparation method of the electromagnetic shielding film has the following process: Figure 1 As shown, the following steps are included:

[0108] (1) Protrusions are made on a polytetrafluoroethylene plate by a mechanical processing method. The protrusions are distributed in a mesh shape, the cross section of the protrusions is a square, the width of the protrusions is 200 μm, the height is 200 μm, and the spacing between any two adjacent protrusions is 500 μm;

[0109] (2) dissolving thermoplastic polyurethane particles in N,N-dimethylformamide to prepare a polymer solution, wherein the mass concentration of the thermoplastic polyurethane in the polymer solution is 25 wt %, pouring the polymer solution onto the convex surface of the template obtained in step (1), drying with air at 100° C. for 2 h to completely evaporate the solvent, then cooling to room temperature, peeling off the mold, and obtaining a thermoplastic polyurethane elastomer film with a thickness of 1000 μm;

[0110] (3) using a plasma cleaning machine to perform plasma surface treatment on the film obtained in step (2) for 10 minutes to enhance its surface hydrophilicity;

[0111] (4) using a syringe to fill the silver MOD solution into the film groove treated in step (3), and then under nitrogen protection, heating to 150° C. at a rate of 10° C. / min, and heat-treating for 30 min;

[0112] Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0113] Embodiment 28

[0114] The present embodiment provides an electromagnetic shielding film, including a thermo-adhesive elastomer film and a metal conductive layer, wherein one surface of the thermo-adhesive elastomer film has grooves uniformly distributed in a mesh shape, the metal conductive layer is filled in the grooves, the cross-section of the grooves is rectangular, the width of the grooves is 120 μm, the depth is 240 μm, and the total opening area of ​​the grooves is 60% of the corresponding surface area of ​​the thermo-adhesive elastomer film; the thermo-adhesive elastomer film is an SBS film.

[0115] The method for preparing the electromagnetic shielding film comprises the following steps:

[0116] (1) A stainless steel mesh is selected as a template, wherein the thickness of the stainless steel mesh is 240 μm, the mesh wire width is 120 μm, the mesh shape is rectangular, the mesh length is 480 μm, and the mesh width is 380 μm;

[0117] (2) hot pressing a 1000 μm thick SBS film onto a stainless steel mesh, and peeling off the stainless steel mesh after cooling;

[0118] (3) using a plasma cleaning machine to perform plasma surface treatment on the film obtained in step (2) for 10 minutes to enhance its surface hydrophilicity;

[0119] (4) using a syringe to fill the groove of the film treated in step (3) with the silver MOD solution, and then heating the film to 150° C. at a rate of 10° C. / min under nitrogen protection, and heat-treating the film for 30 min;

[0120] Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0121] Embodiment 29

[0122] The present embodiment provides an electromagnetic shielding film, including a thermo-adhesive elastomer film and a metal conductive layer, wherein one surface of the thermo-adhesive elastomer film has grooves uniformly distributed in a mesh shape, the metal conductive layer is filled in the grooves, the cross-section of the grooves is square, the width of the grooves is 20 μm, the depth is 15 μm, the total opening area of ​​the grooves is 70% of the corresponding surface area of ​​the thermo-adhesive elastomer film, and the thermo-adhesive elastomer film is a thermoplastic polyurethane film.

[0123] The method for preparing the electromagnetic shielding film comprises the following steps:

[0124] (1) A laser etching method is used to etch grooves in a continuous network distribution on the surface of a thermoplastic polyurethane film with a thickness of 1000 μm;

[0125] (2) using a plasma cleaning machine to perform plasma surface treatment on the thermal adhesive elastomer film obtained in step (1) for 10 minutes to enhance its surface hydrophilicity;

[0126] (4) using a peristaltic pump to fill the groove of the film treated in step (2) with the silver MOD solution, and then heating the film to 150° C. at a rate of 10° C. / min under nitrogen protection, and heat-treating the film for 30 min;

[0127] Step (4) is repeated twice to obtain an electromagnetic shielding film.

[0128] Effect Example 1

[0129] The products obtained in the above embodiments and comparative examples were used as film samples and the following performance tests were performed:

[0130] (1) The thickness test method of the metal conductive layer is: using laser confocal microscopy and scanning electron microscopy;

[0131] (2) The electromagnetic shielding effectiveness test method is as follows: the electromagnetic shielding effectiveness adopts the coaxial method and the waveguide method, and the test frequency range is 30MHz to 18GHz;

[0132] (3) Tensile property test method: according to GB / T 528-1998 method, elongation rate: 50 mm / min;

[0133] (4) Light transmittance test method: The transmittance of light with a wavelength of 400 nm to 700 nm was tested by UV-vis spectrophotometry, and the average transmittance was calculated. The average transmittance is the transmittance in Table 2.

[0134] (5) Figures 2-3 As shown, the PCB board 1 is provided with a radiation chip 2 and an electrical component 3, and a film sample is hot pressed on the surface of the PCB board 1, the radiation chip 2 and the electrical component 3 to form an electromagnetic shielding film 4. The hot pressing temperature is 180°C, the pressure is 2MPa, and the time is 10min. A test piece is obtained. The electromagnetic shielding film is bonded to the surface of the PCB board 1, the radiation chip 2 and the electrical component 3 through a thermal adhesive elastomer film 6. The metal conductive layer 5 serves as the electrical connection area of ​​the test piece. The adhesion of the electromagnetic shielding film on the test piece is tested. The test method is: GB / T 2792-2014 90° peel test (N / cm).

[0135] The test results are shown in Table 2.

[0136] Table 2

[0137]

[0138]

[0139] It can be seen from Table 2 that the shielding effectiveness has nothing to do with the elastic matrix, but is only related to the thickness, width, material (silver or copper) of the metal layer. The metal layers of Examples 1 to 22 are of the same material and specification, so the average electromagnetic shielding performance is maintained at around 60 dB.

[0140] The content of epoxy resin has a great influence on the elongation and interfacial adhesion of the elastomeric film. It can be seen from Examples 1 to 4 and Comparative Examples 1 to 2 that with the increase in the amount of epoxy resin, the interfacial adhesion of the elastomeric film increases, but the elongation decreases. When the amount of epoxy resin is 30 to 40 parts, the comprehensive performance of the interfacial adhesion and elongation of the elastomeric film is better. It can be seen from Examples 2, 12 to 13 and 16 to 20 that the comprehensive performance of the electromagnetic shielding film obtained in Examples 2 and 16 to 19 is better, which shows that the use of a single bisphenol A epoxy resin Epikote 828, or the use of at least one of bisphenol A epoxy resin E-44 and bisphenol F epoxy resin jER 807 and bisphenol A epoxy resin Epikote 828 in a certain weight ratio can ensure the light transmittance and electromagnetic shielding effect of the electromagnetic shielding film while improving the elongation and interfacial adhesion of the elastomeric film.

[0141] The amount of curing agent has an effect on the interfacial adhesion and elongation of the elastomer film. As can be seen from Examples 2 and 5 to 7, with the increase in the amount of curing agent, the elongation of the elastomer film decreases slightly, while the interfacial adhesion shows a trend of increasing first and then decreasing, and the curing agent does not help much to improve the interfacial adhesion after increasing to a certain amount (≥12 parts), therefore, the amount of curing agent is preferably 12 to 15 parts. Compared with Examples 14 to 15, Example 2 uses a polyamide curing agent, and the elastomer film can maintain a higher elongation and improve the interfacial adhesion of the elastomer film, therefore, the present invention preferably uses a polyamide curing agent.

[0142] Compared with Example 2 and Examples 10-11, the interfacial adhesion and elongation of the elastomer films of Comparative Examples 3-4 are significantly deteriorated, which indicates that the addition of the epoxidized thermoplastic elastomer of the present invention can more effectively improve the interfacial adhesion and elongation of the elastomer films.

[0143] In Comparative Example 5, perfluorosilane is sprayed on the side of the film obtained in step (2) where the groove is provided, which is not conducive to filling the MOD in the groove, so an effective conductive network cannot be formed and the film does not have electromagnetic shielding performance.

[0144] In Example 27, protrusions are made on a polytetrafluoroethylene plate by a mechanical processing method. The protrusions are distributed in a grid pattern, the cross-section of the protrusions is square, the width of the protrusions is 200 μm, the height is 200 μm, the spacing between any two adjacent protrusions is 500 μm, and the thermal adhesive elastomer film is a thermoplastic polyurethane elastomer film, without epoxy resin and curing agent, resulting in a significant decrease in the interface adhesion to 3.2 N / cm, and no significant change in the electromagnetic shielding performance, which is 62 dB.

[0145] Example 28 uses a stainless steel mesh as a template with a thickness of 240μm, a mesh wire width of 120μm, a rectangular mesh shape, a mesh length of 480μm, a mesh width of 380μm, and a thermal adhesive elastomer film of SBS film, without epoxy resin and curing agent, resulting in a significant decrease in interface adhesion to 3.0N / cm, and an electromagnetic shielding performance of 63dB.

[0146] Example 29 uses laser etching to etch grooves with a width of 20 μm and a depth of 15 μm on the surface of a thermoplastic polyurethane film with a thickness of 1000 μm. The total opening area of ​​the grooves is 70% of the corresponding surface area of ​​the thermal adhesive elastomer film. The thermal adhesive elastomer film is a thermoplastic polyurethane film without epoxy resin and curing agent, which results in a significant decrease in the interfacial adhesion to 3.1 N / cm and a significant increase in the electromagnetic shielding performance to 73 dB.

[0147] It should be noted that the cross-sectional shape of the groove of the present invention is not limited to the shape described in the above embodiment, and the cross-sectional shape of the groove can be regular or irregular. The regular shape includes but is not limited to a square (such as Figure 4 ), rhombus, regular hexagon, circle (as shown in Figure 5 as shown), or at least one of a ring shape.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. An electromagnetic shielding film, characterized in that: The invention comprises a heat-adhesive elastomer film and a metal conductive layer, wherein a groove is distributed on one surface of the heat-adhesive elastomer film, and the metal conductive layer is filled in the groove; the heat-adhesive elastomer film is an epoxy-modified thermoplastic elastomer film, and the epoxy-modified thermoplastic elastomer film is composed of the following raw material components in parts by weight: 100 parts of epoxidized thermoplastic elastomer, 30-40 parts of epoxy resin, 12-15 parts of curing agent, 1-5 parts of auxiliary agent and 300-500 parts of solvent; the epoxy resin is bisphenol A type epoxy resin Epikote 828, or is compounded with at least one of bisphenol A type epoxy resin E-44 and bisphenol F type epoxy resin jER 807 and bisphenol A type epoxy resin Epikote 828, and the bisphenol A type epoxy resin Epikote The weight ratio of 828 to the total weight of the epoxy resin is (1-3):3; the curing agent is a polyamide curing agent; the auxiliary agent includes at least one of a defoaming agent, a leveling agent, a thixotropic agent, a accelerator, and an antioxidant.

2. The electromagnetic shielding film according to claim 1, characterized in that: The solvent includes at least one of cyclohexanone, acetone, butanone, ethylene glycol methyl ether, propylene glycol methyl ether, toluene, xylene, and N,N-dimethylformamide.

3. The electromagnetic shielding film according to claim 1, characterized in that: The preparation method of the epoxy-modified thermoplastic elastomer film comprises the following steps: After dissolving the epoxidized thermoplastic elastomer in a solvent, epoxy resin, curing agent and auxiliary agent are added and mixed to obtain a polymer solution; the obtained polymer solution is coated on the convex surface of the template, and after low-temperature drying to form a film, the template is peeled off to obtain an epoxy-modified thermoplastic elastomer film.

4. The electromagnetic shielding film according to claim 1, characterized in that The width of the groove structure is 5 to 1000 μm, and the depth is 5 to 250 μm. The groove structure occupies 10 to 90% of the plane area of ​​the thermal adhesive elastic film.

5. The electromagnetic shielding film according to claim 1, characterized in that: The thickness of the metal conductive layer is 0.2-50 μm, and the thickness of the metal conductive layer is not greater than the depth of the groove structure; the material of the metal conductive layer is at least one of silver and copper.

6. A method for preparing an electromagnetic shielding film according to any one of claims 1 to 5, characterized in that: The steps include: (1) performing surface modification treatment on the groove surface of the polymer film substrate; (2) injecting a metal complex solution into the groove after the surface modification treatment, and then performing a heating treatment; (3) Repeat step (2) at least once to obtain an electromagnetic shielding film.

7. Use of the electromagnetic shielding film according to any one of claims 1 to 5 in the preparation of electromagnetic shielding products.

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