A covering film with wave absorbing function

Abstract

The utility model belongs to the technical field of wave-absorbing material structure, and specifically relates to a covering film with wave-absorbing function. The covering film with wave-absorbing function comprises a wave-absorbing layer, a first PI film is provided on one side of the wave-absorbing layer, a second PI film or a high-temperature resistant release film is provided on the other side of the wave-absorbing layer, an epoxy film layer is provided on the side of the first PI film away from the wave-absorbing layer, and a release paper is provided on the side of the epoxy film layer away from the first PI film. The covering film with wave-absorbing function can prevent electromagnetic interference of internal circuits, prevent external electromagnetic intrusion, and steal privacy and information; at the same time, the covering film with wave-absorbing function can not only meet the high temperature requirement of 260°C, but also provide good protection for the metal circuits on the FPC, and has good shielding performance.

Description

Technical Field

[0001] The utility model belongs to the technical field of wave-absorbing material structures, and in particular relates to a covering film with a wave-absorbing function. Background Art

[0002] NFC, short for Near Field Communication, allows two-way data exchange between electronic devices. The standard NFC communication frequency is 13.56MHz, and the data transmission distance is generally within 10cm, which has great advantages in many application scenarios. The working principle of NFC devices is to achieve data transmission through electromagnetic induction. When two NFC devices are close to each other, a magnetic field is generated between them, which causes the coil in the NFC device to generate current, thereby completing data transmission and interaction.

[0003] With the development of the times, flexible wearables are becoming more and more popular because of their lightness, thinness and convenience. Flexible wearables can also have NFC functions. The functional structure is composed of NFC chips and near-field coupling antennas. Since flexible wearable consumer products have high appearance requirements, the antenna generally needs to be built-in, but after the antenna is built-in, it must be close to the motherboard. The consequence is that the antenna will be affected by electromagnetic interference from other lines, affecting the sensitivity of interaction. Although electromagnetic interference can be solved by attaching an electromagnetic shielding film to the antenna, it will also lose its interactive function.

[0004] In the prior art, antennas are usually made by bonding magnetic films (such as those produced by TDK and other companies) to FPC. However, due to the high content of magnetic powder in the magnetic film, it is easy to cause poor temperature resistance and high water vapor permeability. In the subsequent reflow soldering process, it cannot meet the high temperature requirement of 260°C, and is prone to problems such as blistering, delamination, and bulging, which reduces the shielding performance or even loses the shielding performance. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of the utility model is to provide a covering film with good shielding properties and high temperature resistance.

[0006] To achieve this purpose, the technical solution adopted by the utility model is as follows:

[0007] A covering film with a wave-absorbing function comprises a wave-absorbing layer, a first PI film is arranged on one side of the wave-absorbing layer, a second PI film or a high-temperature-resistant release film is arranged on the other side of the wave-absorbing layer, an epoxy film layer is arranged on the side of the first PI film away from the wave-absorbing layer, and a release paper is arranged on the side of the epoxy film layer away from the first PI film.

[0008] Furthermore, the wave absorbing layer is obtained by curing the wave absorbing slurry at high temperature.

[0009] Furthermore, the absorbing slurry includes a resin matrix and absorbing powder dispersed in the resin matrix. The absorbing slurry has sufficient flexibility after curing, and the cured absorbing layer is very suitable for application on the absorbing functional cover film of the magnetic flexible substrate and can withstand high temperatures of 260°C.

[0010] Furthermore, the resin matrix is ​​one or a mixture of epoxy resin, modified epoxy resin, and polyurethane resin.

[0011] Furthermore, the absorbing powder is a flaky sendust powder with a D50 particle size of 80 μm to 200 μm. The absorbing powder is dispersed in a resin matrix and can form a dense and flat magnetic track layer after high-temperature pressing, which can achieve good absorbing and electromagnetic shielding effects.

[0012] Furthermore, the thickness of the PI film is 12 μm to 50 μm.

[0013] Furthermore, the color of the PI film is black or yellow.

[0014] Preferably, the PI film is a thermoplastic PI film. Since the absorbing layer is obtained by high-temperature curing of the absorbing slurry, and the thermoplastic PI film has a layer of thermoplastic coating on its surface, which is in a molten state at a high temperature of 200°C and can be well combined and cured with the absorbing slurry, the absorbing layer and the PI film layer are tightly combined, which has a good protection effect and shielding effect.

[0015] Furthermore, the raw materials for preparing the epoxy film layer include modified epoxy resin, liquid resin 128 or 818, carboxyl-modified nitrile rubber, and filler.

[0016] Furthermore, the filler is at least one of aluminum oxide and aluminum hydroxide.

[0017] Preferably, the modified epoxy resin is dicyclopentadiene modified epoxy resin.

[0018] Using dicyclopentadiene to modify epoxy resin can improve the water absorption rate of epoxy film; adding liquid resin 128 or 818 can increase the viscosity of epoxy film and strengthen its bonding force after curing; adding carboxyl-modified nitrile rubber can effectively toughen epoxy film and can well control the amount of glue overflow; adding fillers can control the glue overflow of the film. Since the epoxy film will form a three-dimensional network structure when it is cured, the added fillers will be filled in the three-dimensional network structure, which can well reduce the water vapor permeability.

[0019] In the present invention, there is no special restriction on the method for preparing the covering film with wave absorbing function. For example, the following method can be used:

[0020] S1. Applying an absorbing slurry on the second PI film or the high temperature resistant release film, and laminating and rolling up the absorbing slurry on one side of the first PI film;

[0021] S2. High temperature pressing of the three-layer structure product obtained in step S1;

[0022] S3. Apply epoxy glue on the release paper, and the epoxy glue is attached to the other side of the first PI film and rolled up.

[0023] In step S2, the temperature of the high temperature pressing is 200° C. The high temperature pressing can crosslink and solidify the absorbing slurry, tightly combine with the PI film and form a compact absorbing layer, which is beneficial to improving the absorbing and electromagnetic shielding effects.

[0024] The utility model has the following beneficial effects:

[0025] The covering film with absorbing function described in the utility model has good absorbing performance and electromagnetic shielding effect by combining PI film and absorbing layer, can block electromagnetic interference of internal circuits, prevent external electromagnetic intrusion, steal privacy and information, and meet the high temperature requirement of 260°C; an epoxy film layer is arranged under the absorbing layer to reduce the water vapor permeability; the arranged PI film, absorbing layer and epoxy film layer can provide good protection for the metal circuits on the FPC, and has obvious advantages in solving electromagnetic interference and maintaining shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of a covering film with a wave absorbing function according to the first embodiment of the utility model;

[0027] Figure 2 It is a schematic structural diagram of a covering film with a wave absorbing function according to the second embodiment of the utility model. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model. The methods involved in the utility model are all commonly used methods in the field unless otherwise specified; the reagents involved can be obtained from ordinary commercial channels unless otherwise specified.

[0029] Reference Figure 1, is the first embodiment of the covering film with absorbing function described in the utility model, which includes an absorbing layer 2, a first PI film 3 is provided on one side of the absorbing layer 2, a second PI film 1 is provided on the other side of the absorbing layer 2, an epoxy film layer 4 is provided on the side of the first PI film 3 away from the absorbing layer 2, and a release paper 5 is provided on the side of the epoxy film layer 4 away from the first PI film 3.

[0030] In one embodiment, the absorbing layer 2 is obtained by curing the absorbing slurry at high temperature.

[0031] In one embodiment, the microwave absorbing slurry includes a resin matrix and microwave absorbing powder dispersed in the resin matrix.

[0032] In one embodiment, the resin matrix is ​​one or a mixture of epoxy resin, modified epoxy resin, polyurethane resin.

[0033] In one embodiment, the absorbing powder is flaky Sendust powder with a D50 particle size of 80 μm to 200 μm.

[0034] In one embodiment, the thickness of the PI film is 12 μm to 50 μm.

[0035] In one embodiment, the color of the PI film is black or yellow.

[0036] In a preferred embodiment, the PI film is a thermoplastic PI film.

[0037] In one embodiment, the raw materials for preparing the epoxy film layer include modified epoxy resin, liquid resin 128 or 818, carboxyl-modified nitrile rubber, and filler.

[0038] In one embodiment, the filler is at least one of aluminum oxide and aluminum hydroxide.

[0039] In a preferred embodiment, the modified epoxy resin is dicyclopentadiene modified epoxy resin.

[0040] Reference Figure 2 , shows a covering film with absorbing function according to the second embodiment of the utility model, which includes an absorbing layer 2, a first PI film 3 is provided on one side of the absorbing layer 2, a high temperature resistant release film 6 is provided on the other side of the absorbing layer 2, an epoxy film layer 4 is provided on the side of the first PI film 3 away from the absorbing layer 2, and a release paper 5 is provided on the side of the epoxy film layer 4 away from the first PI film 3.

[0041] In one embodiment, a method for preparing a cover film having a wave absorbing function comprises the following steps:

[0042] S1. Applying an absorbing slurry on the second PI film or the high temperature resistant release film, and laminating and rolling up the absorbing slurry on one side of the first PI film;

[0043] S2. High temperature pressing of the three-layer structure product obtained in step S1;

[0044] S3. Apply epoxy glue on the release paper, and the epoxy glue is attached to the other side of the first PI film and rolled up.

[0045] In one embodiment, in the above step S2, the temperature of the high temperature pressing is 200°C.

[0046] The covering film with wave-absorbing function described in this embodiment can block electromagnetic interference of internal circuits, prevent external electromagnetic intrusion, and steal privacy and information; at the same time, the covering film with wave-absorbing function can not only meet the high temperature requirement of 260°C, but also provide good protection for the metal circuits on the FPC, and has good shielding performance.

[0047] The covering film with wave-absorbing function described in the utility model has good wave-absorbing performance and electromagnetic shielding effect by combining PI film and wave-absorbing layer, and can meet the high temperature requirement of 260°C; an epoxy film layer is arranged under the wave-absorbing layer to reduce the water vapor permeability; the arranged PI film, wave-absorbing layer and epoxy film layer can provide good protection for the metal circuits on the FPC, and has obvious advantages in solving electromagnetic interference and maintaining the shielding effect.

[0048] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0050] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A covering film with a wave absorbing function, characterized in that: It comprises an absorbing layer, a first PI film is arranged on one side of the absorbing layer, a second PI film or a high temperature resistant release film is arranged on the other side of the absorbing layer, an epoxy film layer is arranged on the side of the first PI film away from the absorbing layer, and a release paper is arranged on the side of the epoxy film layer away from the first PI film.

2. The cover film with wave absorbing function according to claim 1, characterized in that: The thickness of the PI film is 12 μm to 50 μm.

3. The cover film with wave absorbing function according to claim 1, characterized in that: The PI film is a thermoplastic PI film.

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