ELECTROMAGNETIC SHIELDING FILM AND METHOD FOR MAKING SAME

Abstract

An electromagnetic shielding film and a method for making the same. The method includes: dispersing a conductive agent and a magnetic nanomaterial in sodium alginate solutions to form an electrically conductive shielding solution and a magnetic field shielding solution, respectively; applying the electrically conductive and magnetic field shielding solutions onto two opposite surfaces of a transparent substrate to form an electrically conductive shielding layer and a magnetic field shielding layer, respectively, so that an electromagnetic shielding film precursor of a sandwich structure is obtained; and placing the film precursor in a calcium chloride solution to perform a crosslinking process to cure the layers, so as to obtain an electromagnetic shielding film product after being rinsed and dried. The electric and magnetic fields shielding layers of the film can each have a uniform thickness and cooperate to provide an improved shielding effect and superior performances for the film.

Claims

1. A method for making an electromagnetic shielding film, comprising steps of: S1: dispersing a conductive agent and a magnetic nanomaterial in sodium alginate solutions to form an electrically conductive shielding solution and a magnetic field shielding solution, respectively; S2: applying the electrically conductive and magnetic field shielding solutions onto two opposite surfaces of a transparent substrate to form an electrically conductive shielding layer and a magnetic field shielding layer, respectively, so that an electromagnetic shielding film precursor of a sandwich structure is obtained; and S3: placing the film precursor obtained in the step S2 in a calcium chloride solution to perform a crosslinking process to cure the layers, so as to obtain an electromagnetic shielding film product after being rinsed and dried.

2. The method according to claim 1, wherein, in the step S1, the mass ratio of the sodium alginate to the conductive agent in the electrically conductive shielding solution is in the range of 3 to 100.

3. The method according to claim 1 or claim 2, wherein, the conductive agent is one or more of carbon nanotubes, graphene, silver nanowires, copper nanowires, polythiophene, and polypyrrole.

4. The method according to claim 3, wherein, the conductive agent has a one-dimensional nano-structure.

5. The method according to claim 4, wherein, the conductive agent is one or more of carbon nanotubes, silver nanowires, and copper nanowires.

6. The method according to claim 1, wherein, in the step S1, the mass ratio of the sodium alginate to the magnetic nanomaterial in the magnetic field shielding solution is in the range of 1 to 50.

7. The method according to claim 1, wherein, the magnetic nanomaterial used in the step S1 is one or more of nickel, cobalt, and ferrosoferric oxide.

8. The method according to claim 1, wherein, the magnetic nanomaterial used in the step S1 is one or more of nanowires, nanochains, nanoparticles, nanorods and nanosheets, formed of metal or metal alloy.

9. The method according to claim 8, wherein, the metal or metal alloy nanowire comprises one or more of nickel, cobalt, ferrosoferric oxide, and magnetic alloy nanowires.

10. The method according to claim 9, wherein, the magnetic alloy comprises at least two of nickel, cobalt, and ferrosoferric oxide.

11. The method according to claim 1, wherein, the transparent substrate used in the step S2 is made of polyethylene terephthalate (PET), polymethylmethacrylate (PMMA), polycarbonate (PC), polyethylene (PE), polystyrene (PS), polyimide (PI) or polyvinyl alcohol (PVA); and wherein, the transparent substrate has a thickness of 10 to 500 m.

12. The method according to claim 1, wherein, the electrically conductive shielding layer in the step S2 has a thickness of 0.02 to 1 mm; and wherein, the magnetic field shielding layer in the step S2 has a thickness of 0.02 to 1 mm.

13. The method according to claim 1, wherein, the calcium chloride solution used in the step S3 has a CaCl.sub.2 concentration of 1 to 10 wt. %.

14. An electromagnetic shielding film made by the method according to claim 1.

15. The method according to claim 2, wherein, the conductive agent is one or more of carbon nanotubes, graphene, silver nanowires, copper nanowires, polythiophene, and polypyrrole.

16. The method according to claim 15, wherein, the conductive agent has a one-dimensional nano-structure.

17. The method according to claim 16, wherein, the conductive agent is one or more of carbon nanotubes, silver nanowires, and copper nanowires.

18. The method according to claim 6, wherein, the magnetic nanomaterial used in the step S1 is one or more of nickel, cobalt, and ferrosoferric oxide.

19. An electromagnetic shielding film made by the method according to claim 2.

20. An electromagnetic shielding film made by the method according to claim 3.

Description

DETAILED DESCRIPTION

[0044] Embodiments of the present disclosure will now be further described below with reference to examples. It should be understood, however, that the examplary embodiments are provided to further illustrate the present disclosure and not to be taken as limiting the scope of the disclosure. Reaction conditions not indicated in the following examplary embodiments can be conventional or can be carried out following the manufacturer's recommendations. Reagents, starting materials, and the like used in the examplary embodiments without specified manufacturers can be any commercially available ones. Any changes or modifications made by those skilled in the art under the spirit and principles of the disclosure shall fall within the scope of the disclosure.

EXAMPLE 1

[0045] An electromagnetic shielding film, composed of a transparent substrate, an electrically conductive shielding layer applied on one surface of the substrate, and a magnetic field shielding layer applied on the other surface of the substrate, was made as follows.

[0046] A polyethylene terephthalate (PET) film with a thickness of 50 m was used as the above transparent substrate, and was rinsed with deionized water before use.

[0047] An electrically conductive shielding solution, composed of a carbon nanotube (a conductive agent), sodium alginate, and water with a mass ratio of 3:10:1000, was applied onto one surface of the PET substrate to form thereon an electrically conductive shielding layer having a thickness of 50 m.

[0048] A magnetic field shielding solution, composed of a magnetic cobalt nanowire, sodium alginate, and water with a mass ratio of 20:60:1000, was applied onto the other surface of the PET substrate without the electrically conductive shielding layer, to form thereon a magnetic field shielding layer having a thickness of 50 m.

[0049] The resulting film precursor of the sandwich structure was then placed in a calcium chloride solution with a concentration of 5 wt. % to perform a crosslinking process. Thereafter, the film was rinsed with deionized water, and dried at 50 C. for 30 minutes to obtain an electromagnetic shielding film product.

EXAMPLE 2

[0050] An electromagnetic shielding film, composed of a transparent substrate, an electrically conductive shielding layer applied on one surface of the substrate, and a magnetic field shielding layer applied on the other surface of the substrate, was made as follows.

[0051] A polyimide (PI) film with a thickness of 60 m was used as the above transparent substrate, and was rinsed with deionized water before use.

[0052] An electrically conductive shielding solution, composed of a silver nanowire (a conductive agent), sodium alginate, and water with a mass ratio of 3:10:1000, was applied onto one surface of the PI substrate to form thereon an electrically conductive shielding layer having a thickness of 50 m.

[0053] A magnetic field shielding solution, composed of a magnetic nickel nanowire, sodium alginate, and water with a mass ratio of 20:60:1000, was applied onto the other surface of the PI substrate without the electrically conductive shielding layer, to form thereon a magnetic field shielding layer having a thickness of 100 m.

[0054] The resulting film precursor of the sandwich structure was then placed in a calcium chloride solution with a concentration of 3 wt. % to perform a crosslinking process. Thereafter, the film was rinsed with deionized water, and dried at 80 C. for 30 minutes to obtain an electromagnetic shielding film product.

EXAMPLE 3

[0055] An electromagnetic shielding film, composed of a transparent substrate, an electrically conductive shielding layer applied on one surface of the substrate, and a magnetic field shielding layer applied on the other surface of the substrate, was made as follows.

[0056] A polyethylene (PE) film with a thickness of 30 m was used as the above transparent substrate, and was rinsed with deionized water before use.

[0057] An electrically conductive shielding solution, composed of a copper nanowire (a conductive agent), sodium alginate, and water with a mass ratio of 6:75:1000, was applied onto one surface of the PE substrate to form thereon an electrically conductive shielding layer having a thickness of 100 m.

[0058] A magnetic field shielding solution, composed of a magnetic ferrosoferric oxide nanowire, sodium alginate, and water with a mass ratio of 25:50:1000, was applied onto the other surface of the PE substrate without the electrically conductive shielding layer, to form thereon a magnetic field shielding layer having a thickness of 150 m.

[0059] The resulting film precursor of the sandwich structure was then placed in a calcium chloride solution with a concentration of 3 wt. % to perform a crosslinking process. Thereafter, the film was rinsed with deionized water, and dried at 80 C. for 30 minutes to obtain an electromagnetic shielding film product.

EXAMPLE 4

[0060] An electromagnetic shielding film, composed of a transparent substrate, an electrically conductive shielding layer applied on one surface of the substrate, and a magnetic field shielding layer applied on the other surface of the substrate, was made as follows.

[0061] A polyethylene terephthalate (PET) film with a thickness of 50 m was used as the above transparent substrate, and was rinsed with deionized water before use.

[0062] An electrically conductive shielding solution, composed of a carbon nanotube (a conductive agent), sodium alginate, and water with a mass ratio of 6:75:1000, was applied onto one surface of the PET substrate to form thereon an electrically conductive shielding layer having a thickness of 100 m.

[0063] A magnetic field shielding solution, composed of a magnetic cobalt nanowire, sodium alginate, and water with a mass ratio of 1:50:1000, was applied onto the other surface of the PET substrate without the electrically conductive shielding layer, to form thereon a magnetic field shielding layer having a thickness of 150 m.

[0064] The resulting film precursor of the sandwich structure was then placed in a calcium chloride solution with a concentration of 5 wt. % to perform a crosslinking process. Thereafter, the film was rinsed with deionized water, and dried at 50 C. for 30 minutes to obtain an electromagnetic shielding film product.

EXAMPLE 5

[0065] An electromagnetic shielding film, composed of a transparent substrate, an electrically conductive shielding layer applied on one surface of the substrate, and a magnetic field shielding layer applied on the other surface of the substrate, was made as follows.

[0066] A polyethylene terephthalate (PET) film with a thickness of 50 m was used as the above transparent substrate, and was rinsed with deionized water before use.

[0067] An electrically conductive shielding solution, composed of a carbon nanotube (a conductive agent), sodium alginate, and water with a mass ratio of 3:10:1000, was applied onto one surface of the PET substrate to form thereon an electrically conductive shielding layer having a thickness of 100 m.

[0068] A magnetic field shielding solution, composed of a magnetic cobalt nanowire, sodium alginate, and water with a mass ratio of 20:60:1000, was applied onto the other surface of the PET substrate without the electrically conductive shielding layer, to form thereon a magnetic field shielding layer having a thickness of 50 m.

[0069] The resulting film precursor of the sandwich structure was then placed in a calcium chloride solution with a concentration of 5 wt. % to perform a crosslinking process. Thereafter, the film was rinsed with deionized water, and dried at 50 C. for 30 minutes to obtain an electromagnetic shielding film product.

COMPARATIVE EXAMPLE 1

[0070] An electromagnetic shielding film was made in the same manner as in Example 1 expect that the electrically conductive shielding solution and the magnetic field shielding solution contained no sodium alginate, and that the film precursor resulting from applying the solutions onto respective surfaces of the substrate was not subjected to the crosslinking process in the calcium chloride solution and also not subjected to the drying.

[0071] The electromagnetic shielding films made in Examples 1 to 5 and in Comparative Example 1 were tested for tensile property and surface resistance. Additionally, their electromagnetic shielding performance was measured in decibels over a range of GHz frequencies following the method of standard test GB/T12190-2006. The results of these tests are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Test Results Magnetic shielding factor after Surface Magnetic the film samples resistivity shielding being bent for Trans- (m/sq) factor (dB) 1000 times (dB) parency Haze Ex. 1 220 35 33 90 3.5 Ex. 2 208 40 40 88 3.8 Ex. 3 145 43 41 89 4.3 Ex. 4 143 37 36 89 4.0 Ex. 5 148 38 37 91 3.6 Comp 235 35 12 92 3.1 Ex. 1

[0072] From the results of Table 1, it can be seen that Examples 1-5 of the present disclosure had good shielding performance for both electric fields and magnetic fields. Also, the examples had strong adhesion, high transparency and conductivity, and low haze. The conductivity, transparency, and haze of the electromagnetic shielding film of the present disclosure can be changed depending on the intended use of the film by varying the conditions for making the same. In particular, the electric field shielding layer of Example 1 had a different thickness from that of Example 5, and the magnetic field shielding layer of Example 1 had a different thickness from that of Example 2; the results of the three examples showed that as the thickness of the electric or magnetic field shielding layer increased, the electromagnetic shielding effect and the haze were increased, and the transparency was lowered. Comparison between Example 3 and Example 4 indicates that an increase in amount of the magnetic nanomaterial in the magnetic field shielding layer can improve the electromagnetic shielding effect of the film. Moreover, comparison between Example 1 and Comparative Example 1 indicates that addition of sodium alginate can prevent flaking off of the electric and magnetic fields shielding layers from the substrate surfaces during bending of the film samples, even after many repetitions of flexion.

[0073] Therefore, the electric and magnetic fields shielding layers of the electromagnetic fielding film, made by the present method, can have a uniform thickness, and they cooperate to provide an improved shielding effect and superior performances for the film. Each of these two functional layers has a good adhesive property and is resistant to cracking, flaking, and oxidizing. The solution of the present disclosure complies with the future development trends of the electromagnetic shielding materials and thus gives very broad development prospects.

[0074] Finally, it is noted that the above examplary embodiments are provided merely for purposes of illustration and are not intended to limit the scope of the disclosure. Various substitutions or variations providing the same performances or functions, made by those skilled in the art without departing from the concept of the present disclosure, fall within the protection scope of the present disclosure.