NFC Antenna for Mobile Phone and Preparation Method of Its Electromagnetic Wave Absorbing Material

Abstract

To provide an NFC antenna for a mobile phone and a preparation method of an electromagnetic wave absorbing material.SOLUTION: AN NFC antenna for a mobile phone, comprises: an NFC antenna main body; an electromagnetic wave absorbing material layer; and a metal bottom plate. The electromagnetic wave absorbing material layer is provided onto the metal bottom plate, the NFC antenna main body is provided onto the electromagnetic wave absorbing material layer. The electromagnetic wave absorbing material layer is a film or a sheet formed by the electromagnetic wave absorbing material. The electromagnetic wave absorbing material contains an electromagnetic wave absorption powder and a polymer elastomer. The electromagnetic wave absorption powder has a secondary sheet structure, is fixed into the polymer elastomer in plane. A mass ratio of the electromagnetic wave absorption powder and the polymer elastomer is 10 to 20:1 to 5. The NFC antenna for the mobile phone and a preparation method of the electromagnetic wave absorbing material provides the electromagnetic wave absorbing material layer between the NFC antenna main body and the metal bottom plate. The electromagnetic wave absorbing material layer has a thin thickness, a light weight, and a strong magnetic shield performance, and blocks an interference of a metal to the NFC antenna, and secures a signal quality of the NFC antenna.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and particularly to a NFC antenna for mobile phones and a method for preparing an electromagnetic wave absorbing material thereof.

Background Art

[0002] The NFC antenna for mobile phones is a passive antenna that realizes communication with other devices using the near-field communication technology (NFC). Generally, the NFC antenna uses a coil antenna composed of a conductor coil and a magnetic shielding material. The NFC antenna for mobile phones usually includes an NFC antenna body and a metal bottom plate. Since the metal reflects and absorbs radio waves and the metal bottom plate interferes with the NFC signal, the signal quality has been degraded. Therefore, in the prior art, a magnetic shielding material is combined with the NFC antenna for mobile phones to suppress metal interference.

[0003] In the prior art, many of the magnetic shielding materials use ferrite (metal oxide) or amorphous, nanocrystalline (soft magnetic alloy). In Patent Document 1, an antenna assembly includes an FPC substrate, a conducting wire, and a ferrite sheet. When in use, first, the conducting wire is placed in the etched groove at the upper end of the FPC substrate, then the ferrite sheet is placed on the upper end of the FPC substrate, and finally, the ferrite sheet is thermocompression bonded to complete the manufacture of a small-sized NFC antenna. Patent Document 2 discloses an NFC antenna and a tag including a PCB substrate, a metal bottom plate, a soft magnetic layer, and an NFC antenna body, wherein the metal bottom plate is provided on the PCB substrate, the soft magnetic layer is provided on the metal bottom plate, and the NFC antenna body is provided on the soft magnetic layer.

[0004] Currently, the problem with using ferrite (metal oxide) as a magnetic shielding material for the NFC antenna of a mobile phone is that ferrite (metal oxide) is relatively heavy, increasing the weight and volume of the mobile phone. The manufacturing method uses a sintering method, the temperature is 1100 °C or higher, the yield is low, and since the ferrite die-cutting contains scraps, it is necessary to cover it with a film on the top and bottom and to trim the edges, resulting in a relatively high cost.

[0005] Currently, the problem with using amorphous or nanocrystalline (soft magnetic alloy) as a magnetic shielding material for the NFC antenna of a mobile phone is that although the soft magnetic alloy, a typical magnetic loss absorption material, has advantages such as high saturation magnetization, good temperature stability, and low cost, its complex dielectric constant is large and the impedance matching is poor, making it difficult to meet the performance requirements of the electromagnetic wave absorption material for 5G communication.

[0006] Therefore, the object of the present invention is to provide a new radio wave absorption material for mobile phone NFC antennas that is thin, lightweight, has strong magnetic shielding performance, can effectively shield the interference of metals to the NFC antenna, guarantee the signal quality of the NFC antenna.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] To overcome the above-mentioned drawbacks, an object of the present invention is to provide an electromagnetic wave absorbing material layer that is thin, lightweight, has strong magnetic shielding performance between the NFC antenna body and the metal bottom plate, effectively shields the interference of the metal to the NFC antenna, and can guarantee the signal quality of the NFC antenna. By mixing the electromagnetic wave absorbing powder with the polymer elastomer in a method of spreading it flatly, a uniform particle size distribution is formed, which is easy to process into electromagnetic wave absorbing materials of various shapes, and realizes high magnetic permeability, good impedance matching, stability of electromagnetic wave absorption and high reliability. The present invention provides an NFC antenna for mobile phones and a method for preparing the electromagnetic wave absorbing material thereof.

Means for Solving the Problems

[0009] The object of the present invention is achieved by the following technical means.

[0010] An NFC antenna for a mobile phone, comprising an NFC antenna body, an electromagnetic wave absorbing material layer, and a metal bottom plate. The electromagnetic wave absorbing material layer is provided on the metal bottom plate, and the NFC antenna body is provided on the electromagnetic wave absorbing material layer. The electromagnetic wave absorbing material layer is a film or sheet made of an electromagnetic wave absorbing material. The electromagnetic wave absorbing material includes electromagnetic wave absorbing powder and a polymer elastomer. The electromagnetic wave absorbing powder is a soft magnetic alloy or a soft magnetic composite material and has a two-dimensional sheet-like structure, which is spread flatly in the polymer elastomer. The mass ratio of the electromagnetic wave absorbing powder to the polymer elastomer is 10-20:1-5.

[0011] Currently, many "magnetic shielding materials" use ferrite (metal oxide) or amorphous, nanocrystalline (soft magnetic alloy). However, the electromagnetic wave absorber used in the present invention is electromagnetic wave absorption powder in a two-dimensional sheet-like structure flattened on a polymer elastomer. The electromagnetic wave absorption powder has a high saturation magnetic induction intensity and a low coercive force, can effectively isolate electromagnetic interference and magnetic field interference, and can improve the magnetic shielding performance of the electromagnetic wave absorber layer. Compared with ferrite, the electromagnetic wave absorber has a smaller specific gravity, so it can significantly reduce the weight of the entire antenna structure and increase the weight ratio of the entire device. Compared with amorphous and nanocrystalline, the present invention forms a uniform particle size distribution by mixing with a polymer elastomer in a method of flattening the electromagnetic wave absorption powder, and is easy to process into electromagnetic wave absorbers of various shapes. The polymer elastomer can act as a filler and a binder in the electromagnetic wave absorber, and can not only uniformly disperse the electromagnetic wave absorption powder in the electromagnetic wave absorber to improve the magnetic shielding effect, but also tightly bond the electromagnetic wave absorption powder with the polymer elastomer to increase the mechanical strength and stability of the electromagnetic wave absorber.

[0012] Also, in the NFC antenna for mobile phones described above, the In the height direction powder thickness of the electromagnetic wave absorption powder is 0.5 to 1.5 μm, Median particle diameter in the width direction and the D50 range is 30 to 100 μm.

[0013] Also, in the NFC antenna for mobile phones described above, the soft magnetic alloy is at least one selected from iron-silicon-aluminum soft magnetic alloy, iron-silicon soft magnetic alloy, iron-nickel soft magnetic alloy, iron-nickel-molybdenum soft magnetic alloy, iron-aluminum soft magnetic alloy, iron-silicon-aluminum-nickel soft magnetic alloy, iron-chromium soft magnetic alloy, and iron-cobalt soft magnetic alloy.

[0014] Preferably, the soft magnetic alloy is an iron-silicon-aluminum soft magnetic alloy also known as Sendust alloy, and the main components are Fe9.6-Si5.4-Al.

[0015] In addition, in the NFC antenna for mobile phones, the soft magnetic composite material has a two-dimensional sheet-like multilayer structure including a soft magnetic alloy, an Al2O3 layer, and an amorphous carbon layer from the inside to the outside.

[0016] The soft magnetic composite material uses a two-dimensional sheet-like multilayer structure. An Al2O3 layer is provided between the soft magnetic alloy and the amorphous carbon layer, which not only prevents the generation of carbon nanomaterials on the surface of the soft magnetic composite material, but also introduces multiple scattering and reflection mechanisms to improve the microwave absorption characteristics. At the same time, this multilayer structure can also function as a barrier protection to improve the corrosion resistance of the soft magnetic composite material.

[0017] In addition, in the NFC antenna for mobile phones, the inductance value of the antenna coil of the NFC antenna body is 1.6 - 2.0 μH.

[0018] By setting the inductance value of the antenna coil of the NFC antenna body to 1.6 - 2.0 μH, it becomes easier to achieve capacitance matching.

[0019] Preferably, the metal bottom plate includes, but is not limited to, aluminum, copper, and stainless steel materials.

[0020] In addition, in the NFC antenna for mobile phones, the electromagnetic wave absorber is formed by laminating and flattening electromagnetic wave absorption powder with a two-dimensional sheet-like structure, and a polymer elastomer is interposed between the electromagnetic wave absorption powders to block, so that conduction of the electromagnetic wave absorption powder is not formed.

[0021] The communication frequency in the industry is 13.56 MHz. Due to the structural design of the electromagnetic wave absorber, it becomes suitable for a frequency of 13.56 MHz. When the electromagnetic wave absorption powder conducts, alloy flakes are formed, and the magnetic permeability at 13.56 MHz becomes very low, and the attenuation at 1 MHz is 50% or less.

[0022] In addition, in the NFC antenna for mobile phones, the polymer elastomer is at least one of polyurethane, acrylic acid, organosilicon, and epoxy resin.

[0023] Preferably, the polymer elastomer is polyurethane.

[0024] The present invention also relates to a method for preparing an electromagnetic wave absorbing material for the NFC antenna for mobile phones, including the following steps S1 to S5. S1 Raw material preparation: A step of uniformly mixing electromagnetic wave absorbing powder with a bulk density of 0.2 to 0.7 g / cm 3 and a tap density of 0.6 to 2.0 g / cm 3 to obtain a raw material mixture. S2 Slurry stirring: A step of adding the raw material mixture into a stirrer, then adding a solvent and an auxiliary component, mixing them according to a mass ratio of the solvent, the raw material mixture, and the auxiliary component of 40 to 80:10 to 50:0.5 to 2, and sufficiently stirring until uniform to produce a slurry with a viscosity of 1500 to 2000 mPa·s. S3 Slurry coating: A step of coating the slurry on a protective film, spreading it uniformly on the surface of the protective film with a scraper, setting the coating temperature at 50 to 120°C and the speed at 0.5 to 4 m / min, and obtaining a dried film after drying. S4 Dried film lamination: A step of putting the dried film after drying into a laminator, setting the temperature at 150 to 180°C and the pressure at 10 to 20 Mpa to make it dense and form an electromagnetic wave absorbing material, and S5 Die cutting: A step of cutting the laminated electromagnetic wave absorbing material according to the design requirements to obtain the required size and shape.

[0025] In the prior art, the method for preparing ferrite (metal oxide) used in the NFC antenna for mobile phones to prevent metal interference uses a sintering method, the temperature is 1100°C or higher, the yield is low, and the ferrite die cutting contains scraps, so it is necessary to cover it with a film on the top and bottom and perform edge trimming.

[0026] The preparation method of the electromagnetic wave absorbing material for the NFC antenna of the mobile phone of the present invention has a lower cost. Especially in the case of the electromagnetic wave absorbing material with a permeability of 150 and a thickness of 0.08 mm, the cost can be reduced by 20%.

[0027] The electromagnetic wave absorbing material manufactured by the above preparation method is a flexible product. Compared with ferrite and the like, it can be designed in various shapes, there is no falling of scraps, there is no need for edge trimming and double-sided coating, and the process and cost can be reduced. The above preparation method of the electromagnetic wave absorbing material is simple, can be prepared on a large scale, and has a wide range of application scenarios in the field of electromagnetic wave absorbing materials.

[0028] In addition, compared with the conventional manufacturing methods such as rolling and casting, due to the compatibility between the particles of the electromagnetic wave absorbing material and the polymer elastomer, there may be certain defects and gaps inside them. The present invention uses the dry film lamination method of hot press forming to help form an electromagnetic wave absorbing material with a uniform particle size distribution.

[0029] Preferably, the protective film is a PET film.

[0030] The above preparation method of the electromagnetic wave absorbing material is simple, can be prepared on a large scale, and has a wide range of application scenarios.

[0031] Also, in the preparation method of the electromagnetic wave absorbing material for the NFC antenna of the mobile phone, the solvent in the S2 is any one of methyl isopropyl ketone, acetone, cyclohexanone, and DMF, and the auxiliary agent component is at least one of a dispersant, an antifoaming agent, a leveling agent, and a surfactant.

[0032] Preferably, the solvent is methyl isopropyl ketone, and the auxiliary agent components include dispersant BYK-110, antifoaming agent BYK-141, leveling agent BYK-330, and SDBS. Methyl isopropyl ketone can effectively dissolve the polymer elastomer and the auxiliary agent and disperse them uniformly. The auxiliary agent can promote the contact between the polymer elastomer and the electromagnetic wave absorbing powder, improve the compatibility of the slurry, adjust the viscosity and fluidity, improve the slurry coating property, and enhance the stability of the slurry.

[0033] Also, in the method for preparing the electromagnetic wave absorbing material for the NFC antenna of the mobile phone, the electromagnetic wave absorbing powder is a soft magnetic composite material, and its preparation method includes the following steps S1 to S2: S1: Mix ammonium formate solution, soft magnetic alloy powder, and aluminum sulfate, and perform ultrasonic dispersion for 10 to 3 minutes to obtain a mixed solution. Heat the mixed solution in a water bath at 75 to 85 °C, maintain the temperature at that temperature, and react with stirring for 1 to 2 hours. After washing multiple times with ethanol and performing magnetic separation, dry in an oven at 40 to 50 °C for 1 to 3 days, and then anneal at 350 to 450 °C for 2 hours to obtain soft magnetic alloy powder coated with an Al2O3 layer, and S2: Spread the soft magnetic alloy powder coated with the Al2O3 layer flat in a quartz boat, then place it in a CVD rotary tube furnace. Under an argon protection atmosphere with a gas flow rate of 50 to 100 mL / min, heat it to 400 °C at a rate of 3 to 6 °C / min, then introduce acetylene gas at a flow rate of 20 to 30 mL / min and react for 0.5 to 1 hour. After the reaction is completed, stop the acetylene gas and slowly cool it to 25 °C, and take it out to obtain a soft magnetic composite material.

[0034] First, coat the surface of the soft magnetic alloy powder with an Al2O3 layer by the sol-gel method, and then introduce an amorphous carbon layer on the surface of the soft magnetic alloy by the CCDV method. The high-resistance amorphous carbon layer can reduce the dielectric constant of the magnetic metal, achieve good impedance matching between the absorbing material and free space, and improve the microwave absorption characteristics and corrosion resistance.

Advantages of the Invention

[0035] Compared with the prior art, the present invention has the following advantageous effects: (1) The NFC antenna for mobile phone disclosed by the present invention provides an electromagnetic wave absorbing material layer between the NFC antenna body and the metal bottom plate. The electromagnetic wave absorbing material layer has a thin thickness, is lightweight, and has strong magnetic shielding performance, which can effectively shield the interference of the metal to the NFC antenna and guarantee the signal quality of the NFC antenna. (2) The NFC antenna for mobile phone disclosed by the present invention forms a uniform particle size distribution by mixing electromagnetic wave absorbing powder with a polymer elastomer in a method of spreading it flat, and is easy to process into electromagnetic wave absorbing materials of various shapes. The polymer elastomer acts as a filler and a binder in the electromagnetic wave absorbing material, which can not only uniformly disperse the electromagnetic wave absorbing powder in the electromagnetic wave absorbing material to improve the magnetic shielding effect, but also tightly bond the electromagnetic wave absorbing powder with the polymer elastomer to increase the mechanical strength and stability of the electromagnetic wave absorbing material, realizing high magnetic permeability, good impedance matching, stability of electromagnetic wave absorption and high reliability. (3) The soft magnetic composite material of the NFC antenna for mobile phone disclosed by the present invention uses a two-dimensional sheet-like multilayer structure, and an Al2O3 layer is provided between the soft magnetic alloy and the amorphous carbon layer, which can not only prevent the generation of carbon nanomaterials on the surface of the soft magnetic composite material, but also introduce multiple scattering and reflection mechanisms to improve the microwave absorption characteristics. At the same time, this multilayer structure can also act as a shielding protection to improve the corrosion resistance of the soft magnetic composite material. (4) The preparation method of the electromagnetic wave absorbing material of the NFC antenna for mobile phone disclosed by the present invention has a lower cost than ferrite. The electromagnetic wave absorbing material manufactured by the above preparation method is a flexible product, which can be designed in various shapes, does not drop debris, does not require edging and double-sided coating, and can reduce the process and cost.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0037] Hereinafter, while referring to Example 1, Example 2, Comparative Example 1, Example 3, Example 4 and specific test data, FIGS. 1 to 4, the technical means in the examples of the present invention will be clearly and detailedly described. However, it goes without saying that the described examples are only some of the examples of the present invention and not all of the examples. Based on the examples in the present invention, all other examples obtained by those skilled in the art without creative activities belong to the protection scope of the present invention.

[0038] The following Example 1 and Example 2 provide electromagnetic wave absorbers, and the raw materials used in Example 1 and Example 2 are all commercially available raw materials generally used in industry.

[0039] (Example 1) The electromagnetic wave absorber of Example 1 contains a soft magnetic alloy and a polymer elastomer. Sendust alloy is used for the soft magnetic alloy, and polyurethane is used for the polymer elastomer. The adjustment method has the following steps. S1 Raw material preparation: A step of uniformly mixing Sendust alloy powder and polyurethane to obtain a raw material mixture with a mass ratio of Sendust alloy powder to polyurethane of 85:15. S2 Slurry stirring: Add the raw material mixture to a stirrer, and then add methyl isopropyl ketone, dispersant BYK-110, defoaming agent BYK-141, leveling agent BYK-330, and SDBS. Mix according to a mass ratio of 100:150:1:0.8:0.5:0.3:0.3 for the raw material mixture, methyl isopropyl ketone, dispersant BYK-110, defoaming agent BYK-141, leveling agent BYK-330, and SDBS, and stir sufficiently until uniform to produce a slurry. S3 Slurry Coating: Coating the slurry on the protective film, spreading it evenly on the surface of the protective film with a scraper, setting the temperature of the coating at 100 °C and the speed at 1 m / min, and obtaining a dried film after drying. S4 Dried Film Laminating: Putting the dried film after drying into a laminator, setting the temperature at 160 °C and the pressure at 15 Mpa, and making it dense to form an electromagnetic wave absorbing material, and S5 Die Cutting: Cutting the laminated electromagnetic wave absorbing material according to the design requirements to obtain the required size and shape.

[0040] (Example 2) The electromagnetic wave absorbing material of Example 2 includes a soft magnetic composite material and a polymer elastomer. Polyurethane is used for the polymer elastomer. The adjustment method has the following steps. S1 Preparation of Soft Magnetic Composite Material: Adding 12.612 g of ammonium formate powder to deionized aqueous solution per liter, adding formic acid solution after dispersion to adjust the pH to 4.4 to obtain an ammonium formate solution, mixing the ammonium formate solution, soft magnetic alloy powder, and aluminum sulfate in a mass ratio of 506:6:3, performing ultrasonic dispersion for 15 minutes to obtain a mixed solution, heating this mixed solution to 75 °C in a water bath, reacting at that temperature while stirring for 1.5 hours, washing multiple times with ethanol and performing magnetic separation, drying in an oven at 45 °C for 23 days, and then annealing at 380 °C for 2 hours to obtain soft magnetic alloy powder coated with an Al2O3 layer. The soft magnetic alloy powder coated with the Al2O3 layer is evenly spread in a quartz boat, then put into a CVD rotary tubular furnace, and under an argon protection atmosphere with a gas flow rate of 50 - 100 mL / min, after heating to 400 °C at a rate of 5 °C / min, introducing acetylene gas at a flow rate of 25 mL / min and reacting for 1 hour to generate an amorphous carbon layer. After the reaction is completed, stopping the acetylene gas and slowly cooling to 25 °C, taking it out to obtain a soft magnetic composite material. As shown in Figure 2, the soft magnetic composite material includes a soft magnetic alloy a, an Al2O3 layer b, and an amorphous carbon layer c from the inside to the outside. S2 Raw Material Blending: Uniformly mixing the soft magnetic composite material and polyurethane to obtain a raw material mixture with a mass ratio of the soft magnetic composite material to polyurethane of 88:12. S3 Slurry Stirring: Add the raw material mixture to a stirrer, then add methyl isopropyl ketone, dispersant BYK-110, defoamer BYK-141, leveling agent BYK-330, and SDBS, and mix them according to a mass ratio of 100:145:0.8:0.8:0.6:0.4:0.3 for the raw material mixture, methyl isopropyl ketone, dispersant BYK-110, defoamer BYK-141, leveling agent BYK-330, and SDBS. Stir well until uniform to produce a slurry. S4 Slurry Coating: Apply the slurry onto a protective film, spread it evenly on the surface of the protective film with a scraper, and set the coating temperature to 105°C and the speed to 1 m / min. S5 Dry Film Laminating: Put the dried dry film into a laminator, set the temperature to 165°C and the pressure to 15 Mpa, and rapidly dry it to form an electromagnetic wave absorber, and S6 Die Cutting: Cut the laminated electromagnetic wave absorber according to the design requirements to obtain the required size and shape.

[0041] Measurement of Electromagnetic Wave Absorption Characteristics: Measure the electromagnetic parameters of the Sendust alloy in Example 1 and the soft magnetic composite material in Example 2. The measuring instrument is a vector analyzer, and the measuring frequency band is 0.5 - 18 GHz.

[0042] During the measurement, the Sendust alloy in Example 1 and the soft magnetic composite material in Example 2 were measured in the form of coaxial rings. That is, paraffin and the Sendust alloy in Example 1 and the soft magnetic composite material in Example 2 were thoroughly mixed in a mass ratio of 1:1 until uniform, and a coaxial ring with a thickness of about 2.5 mm, an inner diameter of about 3.0 mm, and an outer diameter of about 7.0 mm was fabricated.

[0043] Measurement Results of Electromagnetic Wave Absorption Characteristics: Generally speaking, when RL < -10 dB, the material is considered to have an effective electromagnetic wave absorption bandwidth. In the frequency range of 0.5 to 18.0 GHz, the RL value of the Sendust alloy in Example 1 is less than -10 dB in a bandwidth of less than 0.2 GHz, indicating that the Sendust alloy in Example 1 has significant limitations in practical applications. The soft magnetic composite material in Example 2 had an RLmin of -23.9 dB at 6.8 GHz, and the effective electromagnetic wave absorption bandwidth was able to reach 3.4 GHz.

[0044] The above measurement results of electromagnetic wave absorption characteristics show that the two-dimensional sheet-like multilayer structure of the soft magnetic composite material synthesized by first coating Al2O3 by the sol-gel method and then coating the amorphous carbon layer by the CCDV method, compared with the Sendust alloy in Example 1 with a two-dimensional sheet-like single-layer structure, the minimum microwave loss value RLmin and the effective bandwidth have been significantly improved, indicating that the electromagnetic wave absorption characteristics of the electromagnetic wave absorption powder have been greatly improved.

[0045] SEM Characteristic Evaluation: SEM characteristic evaluation is carried out on the electromagnetic wave absorbing materials of Example 1 and Example 2. From Figures 3 and 4, it can be seen that the electromagnetic wave absorbing materials of Example 1 and Example 2 are both formed by laminating electromagnetic wave absorbing powders with a two-dimensional sheet-like structure and laying them flat, and a polymer elastomer is interposed between the electromagnetic wave absorbing powders to block, so that the conduction of the electromagnetic wave absorbing powders is not formed. The surface of the electromagnetic wave absorbing powders in the electromagnetic wave absorbing materials of Example 1 and Example 2 is smooth, and the shape is irregular and flaky, indicating that the wrapping effect of the soft magnetic composite material coated by the sol-gel method and the CCVD method is good, and the basic shape stability can be maintained.

[0046] Measurement of Permeability and Inductance Value: Referring to GB / T32596, the permeability and inductance value of the electromagnetic wave absorbing materials of Example 1 and Example 2 are measured, and the thicknesses are 0.1 mm or 0.08 mm respectively, and the measurement results are shown in Table 1.

[0047]

Table 1

[0048] From Table 1, when the thickness is about 0.08 mm, the magnetic permeabilities of Example 1 and Example 2 are 221.4 and 220.5 respectively, and the inductance values are 368 μH and 353 μH respectively. When the thickness is about 0.1 mm, the magnetic permeabilities of Example 1 and Example 2 are 151.2 and 150.7 respectively, and the inductance values are 365 μH and 352 μH respectively. It can be seen that this is the case.

[0049] Measurement of corrosion resistance: Electrochemical corrosion parameters were calculated using the electrochemical corrosion analysis method. The measuring device is an electrochemical workstation. In all measurement processes, a three-electrode system was used. The reference electrode is a silver chloride electrode, the auxiliary electrode is a platinum electrode, and samples 1 to 4 were placed on the copper foil to fabricate a working electrode. The measurement results are shown in Table 2.

[0050]

Table 2

[0051] From Table 2, for the electromagnetic wave absorber of Example 1, Sendust alloy was used as the electromagnetic wave absorption powder, and its natural corrosion potential E corr are -0.31 V and -0.33 V respectively, and the corrosion current density i corr are 5.12×10 ‐6 A / cm 2 , 5.12×10 ‐6 A / cm 2 respectively, and the polarization resistance Rp are 1.75×10 5 Ω / cm 2 , 1.97×10 5 Ω / cm2 respectively, and the corrosion rate CR are 1.87×10 ‐12 m / s and 2.03×10 ‐12 m / s respectively. It can be seen that this is the case. For the electromagnetic wave absorber of Example 2, Sendust alloy coated with an Al2O3 layer and an amorphous carbon layer was used as the electromagnetic wave absorption powder, and its natural corrosion potential E corr increased to -0.05 V and -0.04 V, and the corrosion current density i corr is 1.12×10 ‐6 A / cm2 、1.08×10 ‐6 A / cm 2 decreases to, and the polarization resistance Rp is 9.74×10 5 Ω / cm 2 、19.82×10 5 Ω / cm 2 increases to, and the corrosion rate CR is 2.98×10 ‐13 m / s, 3.01×10 ‐13 m / s decreases, indicating that the electromagnetic wave absorber of Example 2 has better corrosion resistance and can have a better service life in various environments.

[0052] The following Comparative Example 1, Example 3, Example 4, Example 4, and Example 5 provide NFC antennas for mobile phones. The materials used in Comparative Example 1, Example 3, Example 4, Example 4, and Example 5 were commercially available raw materials commonly used in industry.

[0053] (Comparative Example 1) The NFC antenna for mobile phones in Comparative Example 1 includes an NFC antenna body 1 and a metal bottom plate 3. The coil inductance value of the NFC antenna body 1 is 1.7 μH, and the sensing distance is 3.67 mm. The metal bottom plate 3 uses an aluminum foil material with a thickness of 0.05 mm (simulating a battery exterior material). By assembling the NFC antenna body 1 and the metal bottom plate 3, the NFC antenna for mobile phones in Comparative Example 1 was obtained.

[0054] (Example 3) As shown in FIG. 1, the NFC antenna for mobile phones in Example 3 includes an NFC antenna body 1, an electromagnetic wave absorber layer 2, and a metal bottom plate 3. The coil inductance value of the NFC antenna body 1 is 1.7 μH, and the sensing distance is 3.67 mm. The electromagnetic wave absorber layer 2 is made of the electromagnetic wave absorber of Example 1 and has a thickness of about 0.08 mm. The metal bottom plate 3 uses an aluminum foil material with a thickness of 0.05 mm. By assembling the NFC antenna body 1, the electromagnetic wave absorber layer 2, and the metal bottom plate 3 in sequence, the NFC antenna for mobile phones in Example 3 was obtained.

[0055] (Example 4) As shown in FIG. 1 , the NFC antenna for a mobile phone of Example 4 comprises an NFC antenna main body 1, an electromagnetic wave absorbing material layer 2, and a metal bottom plate 3, the coil inductance value of the NFC antenna main body 1 is 1.7 μH, the sensing distance is 3.67 mm, the electromagnetic wave absorbing material layer 2 is made of the electromagnetic wave absorbing material of Example 1 and has a thickness of about 0.1 mm, and the metal bottom plate 3 is made of aluminum foil material with a thickness of 0.05 mm, and the NFC antenna main body 1, the electromagnetic wave absorbing material layer 2, and the metal bottom plate 3 are assembled in this order to obtain the NFC antenna for a mobile phone of Example 4.

[0056] Example 5 As shown in FIG. 1 , the NFC antenna for a mobile phone of Example 5 comprises an NFC antenna main body 1, an electromagnetic wave absorbing material layer 2, and a metal bottom plate 3, the coil inductance value of the NFC antenna main body 1 is 1.7 μH, the sensing distance is 3.67 mm, the electromagnetic wave absorbing material layer 2 is made of the electromagnetic wave absorbing material of Example 2 and has a thickness of about 0.08 mm, and the metal bottom plate 3 is made of aluminum foil material with a thickness of 0.05 mm, and the NFC antenna main body 1, the electromagnetic wave absorbing material layer 2, and the metal bottom plate 3 are assembled in this order to obtain the NFC antenna for a mobile phone of Example 5.

[0057] Example 6 As shown in FIG. 1 , the NFC antenna for a mobile phone of Example 6 comprises an NFC antenna main body 1, an electromagnetic wave absorbing material layer 2, and a metal bottom plate 3, the coil inductance value of the NFC antenna main body 1 is 1.7 μH, the sensing distance is 3.67 mm, the electromagnetic wave absorbing material layer 2 is made of the electromagnetic wave absorbing material of Example 2 and has a thickness of about 0.1 mm, and the metal bottom plate 3 is made of aluminum foil material with a thickness of 0.05 mm, and the NFC antenna main body 1, the electromagnetic wave absorbing material layer 2, and the metal bottom plate 3 are assembled in this order to obtain the NFC antenna for a mobile phone of Example 6.

[0058] Antenna test: Refer to ISO / IEC14443, and use LCR100kHz for the digital bridge. The test results are shown in Table 3.

[0059] [Table 3]

[0060] The coil inductance value of the NFC antenna body 1 is 1.7 μH, and the sensing distance is 3.67 mm. As can be seen from Table 3, the NFC antenna body 1 and the metal bottom plate 3 are assembled (Comparative Example 1). Since the metal reflects and absorbs radio waves, the metal bottom plate 3 interferes with the NFC signal, the inductance value decreases to 1.58 μH, and the sensing distance decreases to 1.01 mm.

[0061] An electromagnetic wave absorbing material layer 2 is provided between the NFC antenna body 1 and the metal bottom plate 3 (Examples 3 to 5). In Examples 3 to 5, by effectively isolating the interference of the metal bottom plate 3 with respect to the NFC antenna body 1, the signal quality of the NFC antenna body 1 can be improved. In Example 5 using the electromagnetic wave absorbing material of Example 2 and Example 6, the inductance values are 1.71 μH and 1.73 μH respectively, which are close to the coil inductance value of the NFC antenna body 1, and the sensing distances are 3.56 mm and 3.52 mm respectively, which are close to the sensing distance of the NFC antenna body 1. This indicates that Examples 5 and 6 have better consistency between the NFC antenna body 1 and the metal bottom plate 3 and have better magnetic shielding and electromagnetic wave absorption effects.

[0062] The specific applications of the present invention are very numerous, and the above are only preferred embodiments of the present invention. It should be noted that the above examples are only used to interpret the present invention and are not intended to limit the protection scope of the present invention. Those skilled in the art can make some improvements without departing from the principle of the present invention, and these improvements should also be regarded as within the protection scope of the present invention.

Explanation of Reference Numerals

[0063] 1 NFC antenna body 2 Electromagnetic wave absorbing material layer 3 Metal bottom plate a Soft magnetic alloy b Al2O3 layer c Amorphous carbon layer

Claims

1. An NFC antenna for a mobile phone, comprising an NFC antenna body (1), an electromagnetic wave absorbing material layer (2), and a metal bottom plate (3), wherein the electromagnetic wave absorbing material layer (2) is provided on the metal bottom plate (3), the NFC antenna body (1) is provided on the electromagnetic wave absorbing material layer (2), the electromagnetic wave absorbing material layer (2) is a film or sheet made of an electromagnetic wave absorbing material, the electromagnetic wave absorbing material contains electromagnetic wave absorbing powder and a polymer elastomer, and has a two-dimensional sheet-like structure in which the electromagnetic wave absorbing powder is flattened and spread in the polymer elastomer, and the electromagnetic wave absorbing powder is a soft magnetic composite material, the mass ratio of the polymer elastomer is 10 to 20:1 to 5, and the soft magnetic composite material includes a soft magnetic alloy, an Al ２ O ３ layer, and an amorphous carbon layer, and is characterized by being an NFC antenna for a mobile phone.

2. The powder thickness of the electromagnetic wave absorbing powder in the height direction is 0.5 to 1.5 μm, and the median particle size D50 range in the width direction is 30 to 100 μm. The NFC antenna for mobile phone according to Claim 1, characterized in that.

3. The soft magnetic alloy is at least one selected from iron-silicon-aluminum soft magnetic alloy, iron-silicon soft magnetic alloy, iron-nickel soft magnetic alloy, iron-nickel-molybdenum soft magnetic alloy, iron-aluminum soft magnetic alloy, iron-silicon-aluminum-nickel soft magnetic alloy, iron-chromium soft magnetic alloy, iron-cobalt soft magnetic alloy. The NFC antenna for mobile phone according to Claim 1, characterized in that.

4. The inductance value of the antenna coil of the NFC antenna body (1) is 1.6 to 2.0 μH. The NFC antenna for mobile phone according to Claim 1, characterized in that.

5. The electromagnetic wave absorber is formed by laminating the electromagnetic wave absorbing powder in a two-dimensional sheet-like structure, laying it flat, and blocking it with the polymer elastomer interposed between the electromagnetic wave absorbing powders, so that the conduction of the electromagnetic wave absorbing powder is not formed. The NFC antenna for mobile phone according to Claim 1, characterized in that.

6. The polymer elastomer is at least one of polyurethane, acrylic acid, organosilicon, and epoxy resin. The NFC antenna for mobile phone according to Claim 1, characterized in that.

7. A method for preparing an electromagnetic wave absorber of the NFC antenna for mobile phone according to any one of Claims 1 to 6, Bulk density: 0.2 to 0.7 g / cm ３ , tap density: 0.6 to 2.0 g / cm ３ A raw material preparation step S1 of uniformly mixing an electromagnetic wave absorbing powder and a polymer elastomer with the above properties to obtain a raw material mixture, Adding the raw material mixture into a stirrer, then adding a solvent and an auxiliary component, mixing them according to a mass ratio of the solvent, the raw material mixture, and the auxiliary component of 40 to 80:10 to 50:0.5 to 2, and stirring sufficiently until it becomes uniform to produce a slurry with a viscosity of 1500 to 2000 mPa·s. The slurry stirring step S2; Coating the slurry on a protective film, spreading it uniformly on the surface of the protective film with a scraper, setting the coating temperature at 50 to 120 °C and the speed at 0.5 to 4 m / min, and obtaining a dried film after drying. The slurry coating step S3; Putting the dried film after drying into a laminator, setting the temperature at 150 to 180 °C and the pressure at 10 to 20 MPa, and densifying it to form an electromagnetic wave absorber. The dried film laminating step S4; A die-cutting step S5 of cutting the laminated electromagnetic wave absorber according to design requirements to obtain a required size and shape A method for preparing an electromagnetic wave absorber for an NFC antenna of a mobile phone, characterized by comprising the above steps.

8. The solvent in S2 is any one of methyl isopropyl ketone, acetone, cyclohexanone, and DMF, and the auxiliary component is at least one of a dispersant, an antifoaming agent, a leveling agent, and a surfactant. The method for preparing an electromagnetic wave absorber for an NFC antenna of a mobile phone according to claim 7.

9. The electromagnetic wave absorption powder is a soft magnetic composite material, and its preparation method is Mix ammonium formate solution, soft magnetic alloy powder, and aluminum sulfate, and ultrasonically disperse for 10 to more than 3 minutes to obtain a mixed solution. Heat the mixed solution in a water bath at 75 to 85 °C, maintain the temperature, and react with stirring for 1 to 2 hours. After washing multiple times with ethanol and magnetic separation, dry in an oven at 40 to 50 °C for 1 to 3 days, and then anneal at 350 to 450 °C for 2 hours to obtain soft magnetic alloy powder coated with an Al ２ O ３ layer in step S1. The above-mentioned Al ２ O ３ The soft magnetic alloy powder coated with the layer is evenly spread in a quartz boat, then placed in a CVD rotary tube furnace, heated to 400 °C at a rate of 3 - 6 °C / min under an argon protective atmosphere with a gas flow rate of 50 - 100 mL / min, then acetylene gas is introduced at a flow rate of 20 - 30 mL / min and reacted for 0.5 - 1 hour. After the reaction is completed, the acetylene gas is stopped and cooled slowly to 25 °C, and then taken out to obtain the soft magnetic composite material, which is step S2; A method for preparing an electromagnetic wave absorber for an NFC antenna of a mobile phone according to claim 7, characterized by comprising the above steps.

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