Electromagnetic shielding film and preparation method thereof

Abstract

The invention relates to an electromagnetic shielding film and a preparation method thereof. The method comprises the following steps: preparing a transfer film layer in advance; a sacrificial layer is arranged on the transfer film layer, and the sacrificial layer has the characteristic of being infiltrated in an acid solution to be dissolved or decomposed; and sequentially arranging an insulating layer, a metal layer and a conductive adhesive layer on the sacrificial layer to obtain the electromagnetic shielding film. The problems that in the prior art, when the transfer film is peeled off, due to the fact that the binding force between the transfer film and the insulating layer is high, a large number of openings are punched in the peeling process, breakage and other abnormalities are prone to occurring in the peeling process, and efficiency is difficult to improve no matter manual operation or machine operation is conducted can be solved.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to an electromagnetic shielding film and its preparation method. Background Technology

[0002] Electromagnetic shielding film is one of the common functional materials in the fabrication of FPC (Flexible Printed Circuit). With the rapid popularization of wireless communication technology and the rapid development of electronic devices, the demand for high-frequency signal transmission in various industries is increasing, and electromagnetic shielding film has gradually become one of the most important components in FPC.

[0003] In the manufacturing of FPCs, the assembly of electromagnetic shielding films is exceptionally complex. To protect the insulating layer of the electromagnetic shielding film from damage during the manufacturing process, a transfer film is typically loaded onto its surface, and this transfer film needs to be peeled off after lamination. However, due to the strong adhesion between the transfer film and the insulating layer, and the numerous openings punched during peeling, breakage and other abnormalities are highly likely to occur during the peeling process, making it difficult to improve efficiency whether done manually or by machine. Summary of the Invention

[0004] This invention provides an electromagnetic shielding film and its preparation method, which can solve the problem that in traditional technology, when peeling off the transfer film, the strong bonding force between the transfer film and the insulating layer, as well as the large number of openings punched out during peeling, makes it easy for abnormalities such as breakage to occur during the peeling process, making it difficult to improve efficiency whether operated manually or by machine.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing an electromagnetic shielding film, comprising: Prepare the transfer membrane layer in advance; A sacrificial layer is disposed on the transfer film layer, the sacrificial layer having the property of being wetted, dissolved or decomposed in an acidic solution; An insulating layer, a metal layer, and a conductive adhesive layer are sequentially disposed on the sacrificial layer to obtain an electromagnetic shielding film.

[0006] Optionally, the sacrificial layer is formed from a polymer resin and functional fillers; The polymer resin is obtained by polymerization of at least two polymer monomers (M1, M2, ..., Mn); The polymer resin has a 5% thermal weight loss temperature greater than 100℃ and a thermal decomposition temperature greater than 200℃.

[0007] Optionally, the polymer resin comprises at least one soluble monomer M1 and at least one auxiliary monomer M2; The soluble monomer M1 has a functional group R1, which has protonation capability under acidic conditions; the auxiliary monomer M2 has a functional group R2, which has a strong conjugated structure or strong polarity.

[0008] Optionally, the polymer resin is obtained by polymerizing the soluble monomer M1 and the auxiliary monomer M2 in a preset ratio; Wherein, the soluble monomer M1 is N-vinylpyrrolidone or 2-vinylpyridine; the auxiliary monomer M2 is styrene or vinyl alcohol.

[0009] Optionally, the polymer resin is an N-vinylpyrrolidone-styrene copolymer, or an N-vinylpyrrolidone-vinyl alcohol copolymer, or a 2-vinylpyridine-n-butyl methacrylate copolymer.

[0010] Optionally, the provision of a sacrificial layer on the transfer film layer includes: Prepare high molecular weight polymer resins and functional fillers; The polymer resin and the functional filler are stirred to obtain a mixed coating; The mixed coating is spin-coated onto the surface of the transfer film layer and fully cured to form a sacrificial layer.

[0011] Optionally, the content of the functional filler is 5% to 15%, its size is 1 μm to 5 μm, and its thermal decomposition temperature is greater than 200°C.

[0012] Optionally, the functional filler is calcium carbonate filler or alumina filler.

[0013] Optionally, the thickness of the sacrificial layer is greater than 5 μm.

[0014] In addition, the present invention also proposes an electromagnetic shielding film, which is prepared by the electromagnetic shielding film preparation method described above.

[0015] The beneficial effects of the technical solution provided by this invention include: In the process of making an electromagnetic shielding film, a transfer film layer can be prepared first to protect the insulating layer of the electromagnetic shielding film from being damaged during the manufacturing process. A sacrificial layer that can be wetted, dissolved or decomposed in an acidic solution is then set on the transfer film layer. An insulating layer, a metal layer and a conductive adhesive layer are then set on the sacrificial layer from bottom to top to form an electromagnetic shielding film.

[0016] In the production of FPCs, the electromagnetic shielding film can be pressed onto a flexible substrate with the transfer film layer on the outer side. When it is necessary to remove the transfer film layer from the electromagnetic shielding film, it can be fully immersed in an acidic solution to dissolve or decompose the sacrificial layer of the electromagnetic shielding film. This allows the transfer film layer on the sacrificial layer to detach automatically, preventing abnormal situations such as breakage of the electromagnetic shielding film during the peeling process. This not only ensures product quality but also greatly improves production efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a simplified schematic diagram illustrating the steps of the method for preparing the electromagnetic shielding film according to an embodiment of the present invention; Figure 2 This is a simplified structural diagram of the electromagnetic shielding film described in an embodiment of the present invention; Figure 3 This is a simplified schematic diagram of the sacrificial layer structure of the electromagnetic shielding film according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the molecular structure of the polymer resin of the sacrificial layer described in an embodiment of the present invention; Figure 5 This is a schematic diagram of the molecular structure of the polymer resin described in this embodiment of the invention when it is an N-vinylpyrrolidone-styrene copolymer; Figure 6 This is a schematic diagram illustrating the structural changes in which the sacrificial layer of the electromagnetic shielding film described in this embodiment of the invention dissolves in an acidic solution, causing the transfer film layer to detach. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the manufacturing of FPCs, the assembly of electromagnetic shielding films is exceptionally cumbersome. To protect the insulating layer of the electromagnetic shielding film from damage during the manufacturing process, a transfer film is typically loaded onto its surface, and this transfer film needs to be peeled off after lamination. In traditional techniques, due to the strong adhesion between the transfer film and the insulating layer, and the numerous openings punched during peeling, breakage and other abnormalities are highly likely to occur, making it difficult to improve efficiency whether done manually or by machine. To solve the above technical problems, this invention proposes an electromagnetic shielding film and its preparation method.

[0021] like Figure 1 As shown, the present invention proposes a method for preparing an electromagnetic shielding film 10, which may specifically include the following steps: S100, prepare a 500-layer transfer film in advance; S200, A sacrificial layer 400 is disposed on the transfer film layer 500, the sacrificial layer 400 having the property of being wetted and dissolved or decomposed in an acidic solution; S300, an insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 are sequentially disposed on the sacrificial layer 400 to obtain an electromagnetic shielding film 10.

[0022] In the process of manufacturing the electromagnetic shielding film 10, a transfer film layer 500 can be prepared first to protect the insulating layer 300 of the electromagnetic shielding film 10 from being damaged during the manufacturing process. A sacrificial layer 400 that can be wetted, dissolved, or decomposed in an acidic solution is then placed on the transfer film layer 500. Finally, an insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 are sequentially placed on the sacrificial layer 400 from bottom to top, thereby forming the electromagnetic shielding film 10 (e.g., ...). Figure 2 (As shown).

[0023] In the manufacturing of FPCs, the electromagnetic shielding film 10 can be pressed onto the flexible substrate through a conductive adhesive layer 100, with the transfer film layer 500 positioned on the outer side. For example... Figure 6 As shown, when it is necessary to remove the transfer film layer 500 on the electromagnetic shielding film 10, it can be fully immersed in an acidic solution to dissolve or decompose the sacrificial layer 400 of the electromagnetic shielding film 10. This will allow the transfer film layer 500 on the sacrificial layer 400 to detach automatically, thus preventing abnormal situations such as breakage of the electromagnetic shielding film 10 during the peeling process. This not only ensures product quality but also greatly improves production efficiency.

[0024] Further, in step S100, the pre-preparation of the transfer film layer 500 may include: S110, Prepare the transfer membrane.

[0025] The transfer film is mainly made of high-temperature resistant polymer films such as polyester film (PET), polyimide (PI, the same as the FPC substrate), or polypropylene (PP); its thickness can be 10~100μm, balancing strength and flexibility. In this embodiment, polyester film (PET) can be used to make the transfer film.

[0026] Moreover, the preparation process of the transfer membrane mainly includes: selection and treatment of the carrier membrane, preparation of the release layer, preparation of the functional layer, preparation of the adhesive layer (optional), and multilayer composite to obtain the transfer membrane.

[0027] S120. The transfer membrane is made into a transfer membrane layer 500.

[0028] The transfer film layer 500 is the basic carrier layer of the electromagnetic shielding film 10, located below the insulating layer 300, and provides temporary support and transfer function for the entire electromagnetic shielding film 10. After the transfer film is made, the whole transfer film can be cut into the required transfer film layers 500 as needed, or the whole transfer film can be used directly as the basic carrier layer (i.e., transfer film layer 500) of the electromagnetic shielding film 10.

[0029] Furthermore, in step S200, a sacrificial layer 400 is formed on the transfer film layer 500, which may include the following steps: A sacrificial layer 400, formed of a polymer resin 410 and a functional filler 420, is disposed on the transfer film layer 500. Because the sacrificial layer 400 has the property of dissolving or decomposing upon wetting in an acidic solution, it can be completely dissolved or decomposed after being fully wetted in an acidic solution (such as hydrochloric acid). This allows the transfer film layer 500, which connects to the insulating layer 300 of the electromagnetic shielding film 10 via the sacrificial layer 400, to automatically detach without the need for additional peeling. Furthermore, the pH value of the acidic solution can be less than or equal to 3, giving it good dissolving properties.

[0030] Furthermore, depositing a sacrificial layer 400, formed of a polymer resin 410 and a functional filler 420, on the transfer film layer 500 may include the following steps: S210, Prepare high molecular polymer resin 410 and prepare functional filler 420.

[0031] A polymer resin 410 that can be dissolved or decomposed in an acidic solution is prepared, and a functional filler 420 is prepared that can help improve the dissolution or decomposition of the polymer resin 410 under the action of an acidic solution. Moreover, the functional filler 420 also helps to improve the thermal stability and mechanical properties of the polymer resin 410 in the undissolved state, which is beneficial to the processing of the electromagnetic shielding film 10 and the FPC bonded to the electromagnetic shielding film 10.

[0032] S220. The polymer resin 410 and the functional filler 420 are stirred to obtain a mixed coating.

[0033] After obtaining the liquid polymer resin 410 and the functional filler 420, the functional filler 420 can be mixed into the liquid polymer resin 410 according to a preset mixing ratio. The two are stirred thoroughly so that the functional filler 420 is evenly distributed in the polymer resin 410, thereby obtaining a mixed coating that can form a sacrificial layer 400.

[0034] For example, polymer resin 410 can be added to a solvent and stirred until completely dissolved to obtain a resin solution. The resin solution is then added to a high-speed disperser, and functional filler 420 is added to the resin solution at a low speed (e.g., 500 rpm) to pre-disperse the functional filler 420 for a first preset time (e.g., 5 min). Then, the functional filler 420 is dispersed at a high speed (e.g., 1500-3000 rpm) to obtain a mixed coating. Dispersing the functional filler 420 into the resin solution using a high-speed disperser ensures that the system is free of visible particles, resulting in a smooth and uniformly glossy surface after the sacrificial layer 400 is fabricated. Furthermore, the dispersion process promotes solvent evaporation (or, with the aid of vacuum degassing), reducing air bubbles in the mixed coating and preventing pinholes and craters from appearing in the sacrificial layer 400.

[0035] In addition, the mixed coating can be further ground using a sand mill to achieve high dispersion precision and eliminate particles.

[0036] S230. Spin-coat the mixed coating onto the surface of the transfer film layer 500, and after full curing, form the sacrificial layer 400.

[0037] A liquid mixed coating, formed by mixing a polymer resin 410 and a functional filler 420, can be applied to the surface of the transfer film layer 500, and then cured to form a solid sacrificial layer 400 on the surface of the transfer film layer 500. Furthermore, the thickness of the sacrificial layer 400 can be greater than 5 μm. In this embodiment, the thickness of the sacrificial layer 400 can be set to 10 μm.

[0038] Further, in step S210, the preparation of the polymer resin 410 may further include: The polymer resin 410 can be obtained by polymerizing at least two polymer monomers (M1, M2, ..., Mn). Polymer monomers refer to small molecule compounds containing polymerizable active functional groups that can be linked to form polymer chains through polymerization reactions (such as free radical polymerization, cationic polymerization, etc.). Their core characteristics are "polymerizability" and "small molecule properties." The polymer resin 410 obtained by polymerizing at least two polymer monomers possesses the ability to dissolve in acidic solutions and exhibits glass transition properties. It also possesses good mechanical properties under normal conditions for easy processing, while being able to melt or decompose in acidic solutions to facilitate removal from the transfer film layer 500. In this embodiment, after immersion in an acidic environment for 30 seconds, the solid mass of the polymer resin 410 can be reduced by more than 90%.

[0039] Furthermore, the 5% thermogravimetric temperature (T5%) of the polymer resin 410 is greater than 100°C, and its thermal decomposition temperature is greater than 200°C. The 5% T5% T5% is the most commonly used thermal stability evaluation index in thermogravimetric analysis (TGA), referring to the temperature at which the mass loss reaches 5% of the initial mass. A higher 5% T ...

[0040] Furthermore, thermal decomposition temperature refers to the critical temperature at which a material undergoes irreversible chemical decomposition (breakage of chemical bonds) and generates small molecule products (such as gases and oligomers) under heating conditions. By ensuring that the thermal decomposition temperature of the polymer resin 410 is greater than 200°C, it is less prone to thermal damage during processing.

[0041] In this embodiment, as Figure 3 As shown, the polymer resin 410 may contain at least one soluble monomer M1 and at least one auxiliary monomer M2. The soluble monomer M1 has a functional group R1, which is protonated under acidic conditions. By enabling the functional group R1 of the soluble monomer M1 to be protonated under acidic conditions, the solid mass of the homopolymerized polymer resin 410 can gradually decrease until it is completely dissolved or decomposed after immersion in an acidic solution. For example, after immersing the polymer resin 410 containing the soluble monomer M1 in an acidic solution for 30 seconds, the solid mass can be reduced by more than 90%. Furthermore, the auxiliary monomer M2 has a functional group R2, which has a strongly conjugated structure or strong polarity. By enabling the functional group R2 of the auxiliary monomer M2 to have a strongly conjugated structure or strong polarity, the glass transition temperature of the homopolymerized polymer resin 410 is greater than 100°C.

[0042] Furthermore, the polymer resin 410 is obtained by polymerizing soluble monomer M1 and auxiliary monomer M2 in a preset ratio. The glass transition temperature, solubility and dissolution rate in acidic solutions, and mechanical properties of the polymer resin 410 can be affected by adjusting the preset ratio. Specifically, the preset ratio can be (60~80):(40~20), which ensures that the preset ratio of soluble monomer M1 to auxiliary monomer M2 is between 60:40 and 80:20.

[0043] In this embodiment, the soluble monomer M1 can be N-vinylpyrrolidone or 2-vinylpyridine; the auxiliary monomer M2 can be styrene or vinyl alcohol. Both N-vinylpyrrolidone and 2-vinylpyridine are highly reactive vinyl monomers. N-vinylpyrrolidone focuses on water solubility, biocompatibility, film-forming flexibility, and complexing properties, while 2-vinylpyridine focuses on basic functional groups, weather resistance, high adhesion, and copolymerization modification. Styrene focuses on rigidity, processability, and low cost, while vinyl alcohol focuses on water solubility, environmental friendliness, and adhesiveness.

[0044] Further, the polymer resin 410 may be an N-vinylpyrrolidone-styrene copolymer, or an N-vinylpyrrolidone-vinyl alcohol copolymer, or a 2-vinylpyridine-n-butyl methacrylate copolymer. Preferably, such as Figure 5 As shown, the polymer resin 410 can be an N-vinylpyrrolidone-styrene copolymer, which has good water solubility, film-forming flexibility, as well as good rigidity and processability.

[0045] Furthermore, the content of functional filler 420 is 5%~15%, its size is 1um~5um, and its thermal decomposition temperature is greater than 200℃. This functional filler 420 can have the following functions: it can completely react or dissolve after being immersed in an aqueous environment (including acidic solutions) for 30 seconds without producing precipitates or toxic substances; it can accelerate the dissolution or decomposition of the above-mentioned polymer resin 410 in an aqueous environment (including acidic solutions) through catalysis, gas release, etc.; and it can improve the thermal stability and mechanical properties of the sacrificial layer 400.

[0046] Furthermore, the functional filler 420 is either calcium carbonate filler or alumina filler. Both calcium carbonate and alumina fillers can enhance the overall performance of the mixed coating and sacrificial layer 400, reduce costs, or impart special functions through synergistic effects with the polymer resin 410. For example, calcium carbonate filler can improve the mechanical properties (hardness, abrasion resistance) of the mixed coating and sacrificial layer 400, improve corrosion resistance and stability, and also has characteristics such as low cost, environmental friendliness, and easy dispersibility. Alumina filler has wear resistance, high temperature resistance, high hardness, and special functions (thermal conductivity, insulation). In this embodiment, the functional filler 420 is preferably calcium carbonate filler, which has low cost, balanced basic properties, and is easily dispersed in liquid polymer resin 410.

[0047] Furthermore, in this embodiment, the thickness of the sacrificial layer 400 can be greater than 5 μm. By setting an appropriate thickness, the sacrificial layer 400 can maintain good thermal stability and mechanical properties (such as rigidity, processability, toughness, etc.) even if it dissolves or decomposes.

[0048] Furthermore, step S230 above may further include the following steps: S232. Pretreatment of the mixed coating, including viscosity adjustment, filtration to remove impurities, and defoaming treatment of the mixed coating.

[0049] Specifically, when adjusting the viscosity of the mixed coating, the core principle is to achieve a viscosity suitable for spin coating. This is done by diluting with solvents or adjusting with thickeners to ensure that the coating spreads evenly during spin coating without sagging due to excessively low viscosity or uneven film thickness due to excessively high viscosity. Furthermore, solvents compatible with the mixed coating should be selected, and it is also necessary to prevent the precipitation of the high molecular weight polymer resin 410 from the mixed coating.

[0050] When filtering and removing impurities from mixed coatings, use a 100-200 mesh nylon filter (laboratory grade) or a cartridge filter (industrial grade) 1-2 times to remove undispersed particles and impurities (such as agglomerates of functional filler 420 and dust) from the mixed coating, thus preventing pitting on the film surface after spin coating. Furthermore, avoid excessive pressure during filtration to prevent filter damage, and seal the filter promptly after filtration to prevent solvent evaporation.

[0051] When degassing mixed coatings, vacuum degassing can be performed at a pressure of -0.08 to -0.1 MPa and a degassing time of 10-20 minutes (suitable for coatings without volatile solvents or thermosetting coatings); alternatively, high-speed centrifugal degassing can be performed at a speed of 3000-5000 rpm and a degassing time of 5-10 minutes (suitable for solvent-based coatings, to avoid excessive solvent evaporation). Degassing eliminates air bubbles in the mixed coating, preventing pinholes and craters from appearing on the film surface after spin coating. Furthermore, the mixed coating should be used within 30 minutes after degassing to prevent secondary bubble formation.

[0052] S234. Pre-treat the surface of the transfer film layer 500.

[0053] Pre-treating the surface of the transfer film layer 500 can improve the adhesion of the mixed coating and prevent delamination. For example, for the transfer film layer 500 made of polyester film (PET), anhydrous ethanol or isopropanol can be used to wipe the surface of the transfer film layer 500 to remove oil and dust; plasma treatment or corona treatment can also be performed on the surface of the transfer film layer 500. This ensures that the surface of the transfer film layer 500 is free of visible impurities and that the mixed coating can be wetted and spread on the surface of the transfer film layer 500.

[0054] S236. The pretreated mixed coating is spin-coated onto the surface of the pretreated transfer film layer 500 using a spin coating equipment to form a coating film layer.

[0055] During the spin coating process, the transfer film layer 500 is first fixed by laying the pre-treated transfer film layer 500 flat on the suction cup of the spin coating equipment and vacuum adsorbing and fixing the transfer film layer 500 to ensure that the transfer film layer 500 is free of wrinkles and bubbles (the edges can be fixed with tape to prevent it from falling off during high-speed rotation).

[0056] Then, the mixed coating is dropped onto the fixed transfer film layer 500. For example, the mixed coating can be drawn up with a pipette or dropper and then dropped onto the center of the transfer film layer 500. The amount of coating can be calculated based on the area of ​​the transfer film layer 500 and the target film thickness.

[0057] Then, the mixed coating is spin-coated using a spin coating device: during the start-up phase, the mixed coating is evenly spread on the surface of the transfer film layer 500 at a low speed, covering the entire surface area and avoiding localized missing coating; after spreading the mixed coating on the entire surface of the transfer film layer 500, the mixed coating is homogenized at a medium to high speed to ensure uniform thickness distribution of the mixed coating on the entire surface of the transfer film layer 500; then, the mixed coating on the surface of the transfer film layer 500 is treated with a high speed to remove excess mixed coating at the film edges, avoid edge accumulation (sagging), and improve film thickness uniformity.

[0058] After spin coating is completed, vacuum adsorption can be turned off to stop fixing the transfer film layer 500, and then the transfer film layer 500 and the mixed coating on it can be removed.

[0059] S238. The coating film on the surface of the transfer film layer 500 is cured to form the sacrificial layer 400.

[0060] This allows the solvent in the coating film to evaporate, solidify, and dry. During this process, it is necessary to control the drying temperature gradient. That is, the coating film is first pre-dried at a low temperature and then heated to the target temperature to dry the coating film, in order to prevent the rapid evaporation of the solvent from causing pinholes on the coating film surface.

[0061] Furthermore, after the coating film is dried and cured, it can be heated and cured again to cure the polymer resin 410 in the coating film. The curing temperature must not exceed the heat resistance limit of the film.

[0062] Furthermore, in step S300, an insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 can be sequentially deposited on the sacrificial layer 400 using conventional processes to obtain the electromagnetic shielding film 10. Details will not be elaborated further here.

[0063] In addition, such as Figure 2 As shown, the present invention also proposes an electromagnetic shielding film 10, which is prepared by the method described above. The electromagnetic shielding film 10 prepared by this method, after being punched and pressed onto an FPC to form an FPC product, allows the sacrificial layer 400 of the electromagnetic shielding film 10 to be melted or decomposed by immersing the FPC product in an acidic solution, thereby causing the transfer film layer 500 of the electromagnetic shielding film 10 to detach (e.g., ...). Figure 6 (As shown). Compared with the traditional method of mechanically peeling off the transfer film layer 500 of the electromagnetic shielding film 10, this method does not damage the main structure of the electromagnetic shielding film 10 and the FPC, and the peeling speed is also very fast.

[0064] Example 1 1. N-vinylpyrrolidone was selected as the soluble monomer M1, and styrene was selected as the auxiliary monomer M2. N-vinylpyrrolidone and styrene were polymerized in a ratio of 80:20 to form a high molecular weight polymer resin 410. Calcium carbonate filler with a D50 (D50 is the median particle size distribution, also called "50% particle size") of less than 2 μm was used as the functional filler 420, and the content of calcium carbonate filler was 10%.

[0065] 2. After thoroughly mixing the polymer resin 410 and the functional filler 420, spin-coat the mixture onto the surface of the PET transfer film layer 500 and allow it to fully cure to form a sacrificial layer 400 with a thickness of 10µm. 3. An insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 are prepared on the surface of the sacrificial layer 400 according to conventional processes to obtain an implementation sample-1 of the electromagnetic shielding film 10.

[0066] Example 2 1. N-vinylpyrrolidone was selected as the soluble monomer M1, and styrene was selected as the auxiliary monomer M2. N-vinylpyrrolidone and styrene were polymerized in a ratio of 60:40 to form a high molecular weight polymer resin 410. Calcium carbonate filler with a D50 of less than 2 μm was used as the functional filler 420, and the content of calcium carbonate filler was 10%.

[0067] 2. After thoroughly mixing the polymer resin 410 and the functional filler 420, spin-coat the mixture onto the surface of the PET transfer film layer 500 and allow it to fully cure to form a sacrificial layer 400 with a thickness of 10µm. 3. An insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 are prepared on the surface of the sacrificial layer 400 according to conventional processes to obtain an implementation sample-2 of the electromagnetic shielding film 10.

[0068] Example 3 1. N-vinylpyrrolidone was selected as the soluble monomer M1, and styrene was selected as the auxiliary monomer M2. N-vinylpyrrolidone and styrene were polymerized in a ratio of 60:40 to form a high molecular weight polymer resin 410.

[0069] 2. Spin-coat the polymer resin 410 onto the surface of the PET transfer film layer 500 and allow it to fully cure to form a sacrificial layer 400 with a thickness of 10µm. 3. An insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 are prepared on the surface of the sacrificial layer 400 according to conventional processes to obtain the implementation sample-3 of the electromagnetic shielding film 10.

[0070] Comparative Example 1 A release agent was coated on the surface of the PET transfer film layer 500 using conventional processes, and an insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 were prepared to obtain a comparative sample-1 of the electromagnetic shielding film 10.

[0071] Comparative Example 2 1. Select N-vinylpyrrolidone homopolymer resin 410 to form a high molecular weight polymer.

[0072] 2. Spin-coat the polymer resin 410 onto the surface of the PET transfer film layer 500 and allow it to fully cure to form a sacrificial layer 400 with a thickness of 10µm. 3. An insulating layer 300, a metal layer 200, and a conductive adhesive layer 100 were prepared on the surface of the sacrificial layer 400 according to conventional processes to obtain a comparative sample-2 of the electromagnetic shielding film 10.

[0073] The self-peeling properties of the transfer film layer 500 of the electromagnetic shielding film 10 prepared in the above embodiments and comparative examples are compared as follows: Following the standard FPC preparation process, the electromagnetic shielding film 10, including sample-1, sample-2, sample-3, control sample-1, and control sample-2, were punched and pressed onto the FPC surface, and the appearance of each sample was observed. Each sample was then placed in an acidic solution (such as HCl solution) with a pH of 3 and stirred thoroughly at room temperature. The peeling time of the transfer film layer 500 for each sample was observed and recorded. After stirring for 30 seconds, each sample was removed and thoroughly rinsed with DI (Deionized Water), and the appearance of the insulating layer 300 of each sample was observed. A detailed comparison table is shown below. As can be seen from the table above, the electromagnetic shielding film prepared by the method of the present invention not only has a good bonding effect with FPC, but also has a good effect on the shedding of its transfer film layer in acidic solution, and also has a good protective effect on the insulating layer.

[0074] The electromagnetic shielding film and its preparation method proposed in this invention can achieve the self-detachment of the transfer film layer after being immersed in an acidic solution for a certain period of time, thereby avoiding common problems such as transfer film rupture and residue in the FPC process, reducing personnel requirements, lowering process costs, and improving production efficiency.

[0075] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0076] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A method for producing an electromagnetic shielding film, characterized by, The application relates to a preparation method of an electromagnetic shielding film. The application comprises the following steps: preparing a transfer film layer in advance; arranging a sacrificial layer on the transfer film layer, wherein the sacrificial layer has the characteristics of being dissolved or decomposed by being soaked in an acid solution; 2. The method for producing an electromagnetic shielding film according to claim 1, wherein arranging an insulating layer, a metal layer and a conductive adhesive layer on the sacrificial layer in sequence to obtain the electromagnetic shielding film. The sacrificial layer is prepared from a high-molecular polymer resin and functional fillers. The high-molecular polymer resin is obtained by polymerization of at least two polymer monomers (M1, M2,..., Mn).

3. The method for producing an electromagnetic shielding film according to claim 2, wherein The 5% thermal weight loss temperature of the high-molecular polymer resin is greater than 100 DEG C, and the thermal decomposition temperature is greater than 200 DEG C. The high-molecular polymer resin comprises at least one soluble monomer M1 and at least one auxiliary monomer M2.

4. The method for producing an electromagnetic shielding film according to claim 3, wherein The soluble monomer M1 has a functional group R1 which has protonation capacity under acid conditions; and the auxiliary monomer M2 has a functional group R2 which has a strong conjugated structure or strong polarity. The high-molecular polymer resin is obtained by polymerization of the soluble monomer M1 and the auxiliary monomer M2 in a preset ratio.

5. The method of producing an electromagnetic shielding film according to claim 4, wherein The soluble monomer M1 is N-vinyl pyrrolidone or 2-vinyl pyridine; and the auxiliary monomer M2 is styrene or ethylene alcohol.

6. The method of producing an electromagnetic shielding film according to claim 2, wherein The high-molecular polymer resin is N-vinyl pyrrolidone-styrene copolymer, N-vinyl pyrrolidone-ethylene alcohol copolymer or 2-vinyl pyridine-n-butyl methacrylate copolymer. The arrangement of the sacrificial layer on the transfer film layer comprises the following steps: preparing a high-molecular polymer resin and preparing functional fillers; stirring the high-molecular polymer resin and the functional fillers to obtain a mixed coating; 7. The method of producing an electromagnetic shielding film according to claim 2, wherein spinning the mixed coating to the surface of the transfer film layer to form the sacrificial layer after sufficient solidification.

8. The method of producing an electromagnetic shielding film according to claim 2, wherein The content of the functional fillers is 5% to 15%, the size is 1 um to 5 um, and the thermal decomposition temperature is greater than 200 DEG C.

9. The method of producing an electromagnetic shielding film according to claim 1, wherein The functional fillers are calcium carbonate fillers or alumina fillers.

10. An electromagnetic shielding film, characterized by, The thickness of the sacrificial layer is greater than 5 um. The electromagnetic shielding film is prepared by the preparation method of the electromagnetic shielding film according to any one of claims 1 to 9.

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